JP4888379B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with a particulate collection filter and a three-way catalyst in an exhaust passage.

Conventionally, fine particles (particulate matter (PM), that is, nano fine particles such as SOF and Soot) discharged from a diesel engine are collected by a fine particle collecting filter (particulate filter) disposed in an exhaust passage. In addition, there is known a control device for an internal combustion engine that regenerates the particulate collection filter by burning the particulate collected by the particulate collection filter when a predetermined condition is satisfied. One of such conventional control devices detects the upstream air-fuel ratio and the downstream air-fuel ratio of the particulate collection filter, and the particulate collection filter is being regenerated by the detected air-fuel ratio. (Whether or not the collected particulates are in a burning state) and the operation mode of the engine is switched based on the determination result (for example, Patent Document 1). See).
JP-A-2005-240719

  By the way, in order to burn the particulates collected by the particulate collection filter, it is necessary that the particulate collection filter is at a high temperature and that oxygen is supplied to the particulate collection filter. The conventional control device is applied to a diesel engine in which the air-fuel ratio of the supplied air-fuel mixture is very lean. Accordingly, the particulate collection filter is sufficiently supplied with oxygen for burning the particulates. Therefore, the conventional control device raises the temperature of the particulate collection filter by executing the delay of the fuel injection timing, the increase of the fuel injection amount, the decrease of the intake amount by the intake throttle valve, etc. The collected fine particles are burned.

  By the way, in recent years, in order to reduce the amount of fine particles discharged from a gasoline engine, it has been studied to arrange a fine particle collecting filter in an exhaust passage of the gasoline engine. On the other hand, in general gasoline engines, there are three exhaust passages in the exhaust passage for the purpose of reducing the amount of unburned substances (HC, CO, etc.) emitted into the atmosphere and nitrogen oxide (NOx) into the atmosphere. An original catalyst is provided, and the amount of fuel is controlled so that the air-fuel ratio of the air-fuel mixture supplied to the engine (hereinafter also referred to as “engine air-fuel ratio”) becomes an air-fuel ratio in the vicinity of the theoretical air-fuel ratio.

  As described above, in order to regenerate the particulate collection filter (burn the particulates), oxygen must be supplied to the particulate collection filter. However, when the air-fuel ratio of the engine is controlled to be close to the stoichiometric air-fuel ratio, oxygen is hardly supplied to the particulate collection filter. In particular, when an upstream catalyst that is a three-way catalyst is provided upstream of the particulate collection filter, oxygen is consumed and stored by the upstream catalyst, so the amount of oxygen flowing into the particulate collection filter is extremely small. . Therefore, in order to regenerate the particulate collection filter in the gasoline engine, the air-fuel ratio of the engine is controlled to an air-fuel ratio leaner than the stoichiometric air-fuel ratio (hereinafter also referred to as “lean air-fuel ratio for filter regeneration control”). By doing so, oxygen must be supplied to the particulate collection filter. However, if the air-fuel ratio of the engine is simply set to the lean air-fuel ratio for filter regeneration control in order to regenerate the particulate collection filter, a large amount of nitrogen oxides discharged from the engine when the air-fuel ratio of the engine is the lean air-fuel ratio. There arises a case where the matter cannot be purified by the three-way catalyst, and a problem arises that a large amount of nitrogen oxides are discharged into the atmosphere.

  Therefore, an object of the present invention is a control device for an internal combustion engine (gasoline engine) provided with a particulate collection filter and a three-way catalyst in an exhaust passage, and the particulate collection is performed without increasing the amount of nitrogen oxide emission. An object of the present invention is to provide a control device capable of regenerating a filter (burning particulates collected by a particulate collection filter).

  In order to achieve the above object, a control apparatus for a multi-cylinder internal combustion engine according to the present invention comprises a main exhaust passage constituent part, a particulate collection filter, a downstream catalyst, a bypass passage constituent part, and an air-fuel ratio control means. I have.

  The main exhaust passage constituting portion includes a first branch portion connected to an exhaust port of a part of a plurality of cylinders included in the multi-cylinder internal combustion engine, and a collecting portion in which the first branch portions are gathered, A main passage portion connected to the collecting portion, and a main exhaust passage for passing the exhaust gas exhausted through the exhaust ports of some of the cylinders (for exhaust gas being discharged into the atmosphere). Yes. The part of the cylinders may be at least one cylinder and less than the total number of the plurality of cylinders.

  For example, a normal exhaust manifold includes a plurality of branches, each of which is connected to an exhaust port of each cylinder. In this case, the first branch portion corresponds to a branch portion connected to the exhaust ports of the some cylinders among the plurality of branch portions of the exhaust manifold. The exhaust hold has a collecting portion, and is connected to the exhaust pipe at the collecting portion. In this case, the exhaust pipe corresponds to the main passage portion.

The particulate collection filter is a filter that collects particulates (nanoparticulates, particulate matter) contained in exhaust gas, and is disposed (intervened) in the main passage portion of the main exhaust passage.
The downstream catalyst is a three-way catalyst disposed in a position downstream of the particulate collection filter in the main passage portion of the main exhaust passage.
The bypass passage constituting section causes the exhaust gas exhausted through an exhaust port of “another cylinder”, which is a “cylinder other than the part of the cylinders” among the plurality of cylinders, to “pass the particulate collection filter”. And a bypass passage "directly flowing into the downstream catalyst".

  The air-fuel ratio control means is defined as “an average of the air-fuel ratios of the air-fuel mixture supplied to the some cylinders (hereinafter also simply referred to as“ partial cylinder air-fuel ratio average ”) leaner than the stoichiometric air-fuel ratio. And the average of the air-fuel ratios of the air-fuel mixture supplied to the other cylinders (hereinafter also simply referred to as “other cylinder air-fuel ratio average”). Filter regeneration control is executed to control to an air-fuel ratio richer than the stoichiometric air-fuel ratio (hereinafter also simply referred to as “rich air-fuel ratio” or “rich air-fuel ratio for filter regeneration control”).

  According to this, in the filter regeneration control, “excess oxidation component (for example, oxygen) generated by the air-fuel mixture set to the filter regeneration control lean air-fuel ratio combusting in the part of the cylinders”. The exhaust gas containing "is supplied to the particulate collection filter through the main exhaust passage (the first branch portion, the collecting portion, and the main passage portion). Accordingly, the particulates collected by the particulate collection filter burn. As a result, the particulate collection filter is regenerated. Further, nitrogen oxide (hereinafter also referred to as “NOx”) generated in a large amount in the partial cylinder flows into the downstream side catalyst through the main exhaust passage.

  At this time, “exhaust gas containing excess reducing components (unburned matter such as HC and CO)” generated by combustion of the air-fuel mixture set to the rich air-fuel ratio for filter regeneration control in the other cylinders. Is directly supplied to the downstream catalyst through the bypass passage (without passing through the particulate collection filter). Accordingly, nitrogen oxide flows into the downstream catalyst through the main exhaust passage, and a reducing component that reduces the nitrogen oxide flows through the bypass passage. Therefore, nitrogen oxide is purified (reduced) in the downstream catalyst. As a result, the present control device can regenerate the particulate collection filter while reducing the discharge amount of nitrogen oxides.

  In this case, during the execution of the filter regeneration control, the air-fuel ratio control means averages the air-fuel ratio of the air-fuel mixture comprising the air-fuel mixture supplied to the some cylinders and the air-fuel mixture supplied to the other cylinders. Supply the air-fuel ratio of the air-fuel mixture supplied to the some cylinders and the other cylinders so that the (temporal average value) becomes “the air-fuel ratio within a predetermined air-fuel ratio range including the theoretical air-fuel ratio” It is preferable that the air-fuel ratio of the air-fuel mixture is controlled. Here, the “predetermined air-fuel ratio range including the stoichiometric air-fuel ratio” means that the downstream catalyst (three-way catalyst) simultaneously purifies both unburned matter and nitrogen oxides at a high purification rate. It can be a so-called “window”. Hereinafter, this “air-fuel ratio within a predetermined air-fuel ratio range including the stoichiometric air-fuel ratio” is also simply referred to as “the stoichiometric air-fuel ratio air-fuel ratio”.

  According to this, since the average of the air-fuel ratio of the gas flowing into the downstream side catalyst becomes “the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio in the window”, the downstream side catalyst purifies unburned matter and nitrogen oxides with high efficiency. (Reduction). As a result, the amount of nitrogen oxide emission during the execution of the filter regeneration control can be made extremely small.

The main exhaust passage constituent part includes a second branch part connected to the exhaust port of the other cylinder and connected to the collective part,
The bypass passage constituting portion has one end connected to the second branch portion and the other end connected to the main passage portion at a position between the particulate collection filter and the downstream catalyst. An on-off valve comprising a bypass passage forming member constituting the bypass passage and shutting and opening the bypass passage in response to an instruction;
The air-fuel ratio control means executes the filter regeneration control by giving an instruction to open the bypass passage to the on-off valve when executing the filter regeneration control, and performs the filter regeneration control when not executing the filter regeneration control. An instruction to shut off the bypass passage is given to the air-fuel ratio, and the average of the overall air-fuel ratio of the mixture supplied to each of the plurality of cylinders is controlled to an air-fuel ratio within a predetermined air-fuel ratio range including the theoretical air-fuel ratio. Suitably configured to perform control.

  According to this, when the filter regeneration control is being executed, the “exhaust gas containing excessive oxidation components” discharged from the some cylinders is transferred to the main exhaust passage (the first branch portion, the collecting portion, and the In addition to being supplied to the particulate collection filter through the main passage portion), nitrogen oxides discharged from the some cylinders are supplied to the downstream catalyst through the main exhaust passage and the particulate collection filter. At this time, the “exhaust gas containing excessive reducing components” discharged from the other cylinders is the bypass passage (the second branch portion, the bypass passage forming member and the on-off valve connected to the second branch portion). To the downstream catalyst. Accordingly, nitrogen oxide flows into the downstream catalyst through the main exhaust passage, and a reducing component that reduces the nitrogen oxide flows through the bypass passage. In addition, in this case, the overall average of the air-fuel ratio of the air-fuel mixture supplied to the engine is made to coincide with the air-fuel ratio in the vicinity of the theoretical air-fuel ratio. Therefore, the downstream catalyst can purify nitrogen oxide at a relatively high purification rate. As a result, the present control device can regenerate the particulate collection filter while reducing the discharge amount of nitrogen oxides.

  On the other hand, when the filter regeneration control is not executed, the bypass passage is blocked by the on-off valve, and the average of the entire air-fuel ratio of the air-fuel mixture supplied to each of the plurality of cylinders includes the theoretical air-fuel ratio. The air-fuel ratio is made to coincide with the air-fuel ratio within the predetermined air-fuel ratio range (the air-fuel ratio close to the theoretical air-fuel ratio). That is, normal control is executed. As a result, the exhaust gas discharged from some cylinders flows through the first branch portion to the collecting portion and the main passage portion. Exhaust gas discharged from other cylinders flows through the second branch portion to the collecting portion and the main passage portion. As a result, exhaust gas having an air-fuel ratio in the vicinity of the theoretical air-fuel ratio flows into the downstream catalyst. Therefore, unburned matter and nitrogen oxides are purified at a high purification rate.

  In this case, it is desirable that the present control device includes an upstream catalyst that is a three-way catalyst that is the main passage portion or the collecting portion and is disposed upstream of the particulate collection filter. According to this, when normal control is executed, unburned matter and nitrogen oxides are purified at a very high purification rate by both the upstream catalyst and the downstream catalyst.

Such a control device
Reduction state determination means for determining whether or not the downstream catalyst has reached a reduction state capable of purifying a predetermined amount of nitrogen oxides,
It is preferable that the air-fuel ratio control unit is configured to permit the execution of the filter regeneration control when it is determined that the downstream catalyst has reached the reduction state during the execution of the normal control. . Here, “permit execution of the filter regeneration control” includes starting execution of the filter regeneration control when a condition for regeneration of the particulate collection filter is satisfied.

  When the above-described filter regeneration control is started, oxygen is supplied to the particulate collection filter, and the air-fuel ratio of the gas flowing into the downstream catalyst becomes the above-mentioned stoichiometric air-fuel ratio. However, if the operation state immediately before is a state where a large amount of oxygen is supplied to the downstream catalyst as in the fuel cut operation state, for example, the oxygen storage amount of the downstream catalyst is close to the maximum oxygen storage amount of the downstream catalyst. It is a value. Therefore, when the filter regeneration control is started immediately, the downstream catalyst immediately purifies a large amount of nitrogen oxides at a high purification rate even when the gas in the vicinity of the theoretical air-fuel ratio flows into the downstream catalyst. May not be possible.

  On the other hand, according to the above configuration, when it is determined that the downstream catalyst has reached the reduction state during execution of the normal control, the filter regeneration control is permitted (starts if other conditions are met). ) Therefore, at the start of filter regeneration control, the downstream catalyst has a certain degree of high reduction ability, so even if nitrogen oxide flows into the downstream catalyst, the nitrogen oxide is purified with high efficiency. It becomes possible to do.

  The control device of the present invention configured to execute the filter regeneration control and the normal control when the operation state of the engine becomes a predetermined fuel cut operation state (when a predetermined fuel cut condition is satisfied). There may be provided fuel cut means for stopping the supply of fuel to the engine.

In this case, the air-fuel ratio control means is
(A1) The average air-fuel ratio of the air-fuel mixture supplied to each of the plurality of cylinders in the normal control is an air-fuel ratio within the predetermined air-fuel ratio range including the stoichiometric air-fuel ratio, and is richer than the stoichiometric air-fuel ratio. To a “weakly rich air-fuel ratio” that is the air-fuel ratio of
(A2) The configuration is such that the execution of the normal control is started from “the fuel cut return time when fuel has started to be supplied again to the engine” after the “fuel supply stop to the engine by the fuel cut means” is canceled. And
The reduction state determination means includes
(B1) “Excessive reduction component”, which is an amount obtained by subtracting “amount of oxidation component” discharged from the engine that oxidizes the reduction component from “amount of reduction component” that is unburned material discharged from the engine. The “first amount” is obtained by “accumulating the amount” from the fuel cut return time point, and
(B2) It is preferable that the downstream catalyst is determined to have reached the reduction state when the first integrated value is equal to or greater than a first predetermined value.

  According to this, during normal control, the average of the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to “weakly rich air-fuel ratio”. The weak rich air-fuel ratio is an air-fuel ratio within the range of the window, and is slightly richer than the stoichiometric air-fuel ratio. In this way, the average of the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to be a rich rich air-fuel ratio because the “purification rate of unburned matter” of the three-way catalyst such as the downstream catalyst and the upstream catalyst is Although the air-fuel ratio of the engine slightly decreases even if it shifts slightly to the rich side of the window, the “nitrogen oxide purification rate” of the three-way catalyst shows that the engine air-fuel ratio is slightly leaner than the window. This is because when it shifts to the side, it rapidly decreases.

  When the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to a weak rich air-fuel ratio in this way, excessive reducing components are discharged from the plurality of cylinders (the some cylinders and the other cylinders). Since the weakly rich air-fuel ratio is the air-fuel ratio in the window, unburnt substances and nitrogen oxides are purified by the catalytic function of the downstream catalyst.

  In addition, according to the above configuration, the normal control is started from the fuel cut return time. Therefore, the state of the downstream side catalyst in the oxidation state (the oxygen storage amount matches the maximum oxygen storage amount or is very close to the maximum oxygen storage amount) during the fuel cut control is the fuel cut state. Due to an excessive reduction component discharged from the engine in the normal control from the time of return, it changes toward the “reduction state”.

  At this time, the reduction state determination means obtains the first integrated value by “integrating the excess amount of the reducing component from the fuel cut return time point”. Therefore, the first integrated value is an amount corresponding to the excess amount of the reducing component flowing into the downstream catalyst (if an upstream catalyst is provided, the total amount of excess reducing component flowing out from the engine after returning from the fuel cut) To the amount obtained by subtracting the amount of the reducing component consumed by the upstream catalyst). Therefore, by determining whether or not the first integrated value is equal to or greater than the first predetermined value, it is easily determined whether or not the downstream catalyst has reached the reduction state after returning from the fuel cut. be able to.

On the other hand, the control device of the present invention configured to execute the filter regeneration control and the normal control further includes a downstream air conditioner for detecting an air fuel ratio of the gas flowing into the fuel cut means and the downstream catalyst. And a fuel ratio sensor,
The air-fuel ratio control means includes
(C1) The average of the air-fuel ratios of the air-fuel mixture supplied to each of the plurality of cylinders in the normal control is expressed as “the air-fuel ratio within the predetermined air-fuel ratio range including the stoichiometric air-fuel ratio and richer than the stoichiometric air-fuel ratio. To the “weak rich air-fuel ratio” that is the “side air-fuel ratio”, and
(C2) It is configured to start execution of the normal control from a fuel cut return time point when the fuel cut by the fuel cut means is released and fuel is started to be supplied again to the engine.
The reduction state determination means includes
(D1) “Reduction component excess”, which is an amount obtained by subtracting “amount of oxidation component discharged from the engine that oxidizes the reduction component” from “amount of reduction component that is unburned material discharged from the engine” The “rich reversal point” when the detected air-fuel ratio detected by the downstream air-fuel ratio sensor is changed to a richer air-fuel ratio than the stoichiometric air-fuel ratio (the detected air-fuel ratio is theoretical The first integrated value is obtained by integrating from the air-fuel ratio leaner than the air-fuel ratio to the air-fuel ratio richer than the stoichiometric air-fuel ratio).
(D2) It is preferable that the downstream catalyst is determined to have reached the reduction state when the first integrated value is equal to or greater than a first predetermined value.

  According to this, during normal control, the average air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to the “weakly rich air-fuel ratio”. Thereby, the discharge | emission amount of the nitrogen oxide and unburned substance in normal control can be reduced. Further, since normal control is started from the fuel cut return time point, the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to a weak rich air-fuel ratio. As a result, the plurality of cylinders (the some cylinders and the other cylinders) are controlled. Excess reducing components are discharged from the cylinder. Therefore, the state of the downstream side catalyst in the oxidation state (the oxygen storage amount matches the maximum oxygen storage amount or is very close to the maximum oxygen storage amount) during the fuel cut control is the fuel cut state. Due to an excessive reduction component discharged from the engine in the normal control from the time of return, it changes toward the “reduction state”.

  By the way, even if the normal control is started after the fuel cut is restored, an excessive reducing component does not immediately flow into the downstream catalyst. In other words, after a predetermined time has elapsed since the fuel cut was restored, excess reducing components begin to flow into the downstream catalyst. This time varies depending on the intake air amount of the engine, the engine speed, and the like. Further, when the upstream catalyst is provided, the excessive reducing component is consumed by the upstream catalyst whose oxygen storage amount reaches the maximum oxygen storage amount or an amount close to the maximum oxygen storage amount during fuel cut. The downstream catalyst reaches the downstream catalyst after the oxygen storage amount of the upstream catalyst becomes substantially “0”. Therefore, the point in time when the excessive reducing component starts to flow into the downstream catalyst varies depending on the maximum oxygen storage amount of the upstream catalyst.

  Therefore, in the above configuration, from the “rich inversion time” when the detected air-fuel ratio detected by the downstream air-fuel ratio sensor after the fuel cut return time has changed to an air-fuel ratio richer than the stoichiometric air-fuel ratio, Excess reducing components are integrated, thereby obtaining a “first integrated value”. This rich inversion time coincides accurately with the time when excessive reducing components begin to flow into the downstream catalyst, regardless of the intake air amount of the engine, the engine rotational speed, the maximum oxygen storage amount of the upstream catalyst, and the like. Therefore, the first integrated value accurately represents the retention amount of the reducing component of the downstream catalyst (the amount of decrease in the oxygen storage amount of the downstream catalyst or the reduction ability capable of purifying the nitrogen oxides of the downstream catalyst). Therefore, by determining whether or not the first integrated value is equal to or greater than the first predetermined value, it is possible to further accurately determine whether or not the downstream catalyst has reached the reduction state after returning from the fuel cut. Can be judged well.

  The control device according to the present invention described above and the control device according to the present invention to be described later are the three-way catalyst disposed at a position upstream of the particulate collection filter in the main passage portion or the collecting portion. It is desirable to provide an upstream catalyst. According to this, it is possible to maintain the discharge amount of unburned matter and the discharge amount of nitrogen oxide at extremely small values, particularly during normal control.

Furthermore, in the control apparatus for an internal combustion engine according to the present invention,
The air-fuel ratio control means acquires (estimates) a particulate collection amount that is the amount of particulates collected by the particulate collection filter, and acquires the particulate collection obtained when the filter regeneration control is executed. It is preferable that the larger the amount, the more the air-fuel ratio of the air-fuel mixture supplied to the some cylinders is controlled to a leaner air-fuel ratio. At this time, the average air-fuel ratio of the gas flowing into the downstream catalyst during the filter regeneration control (that is, the air-fuel mixture composed of the air-fuel mixture supplied to the some cylinders and the air-fuel mixture supplied to the other cylinders) The air / fuel ratio of the air-fuel mixture supplied to the some cylinders and the other cylinders are supplied so that the average of the air / fuel ratios of the air / fuel ratio is equal to “the air / fuel ratio within a predetermined air / fuel ratio range including the stoichiometric air / fuel ratio”. When the air-fuel ratio of the air-fuel mixture is controlled, the average air-fuel ratio of the air-fuel mixture supplied to the other cylinders is controlled to the richer air-fuel ratio as the acquired particulate collection amount increases. It will be.

  The filter regeneration control is control that prevents part of the exhaust gas from passing through the particulate collection filter. Therefore, there is a high possibility that the fine particles contained in a part of the exhaust gas are released into the atmosphere. Further, the filter regeneration control is control for making the air-fuel ratio of the air-fuel mixture supplied to some cylinders different from the air-fuel ratio of the air-fuel mixture supplied to other cylinders. Therefore, the generated torque differs between the cylinders, and vibration may occur. In addition, when the upstream catalyst is provided, the filter regeneration control is a control for allowing a lean air-fuel ratio gas to flow into the upstream catalyst, and therefore the upstream catalyst cannot particularly purify nitrogen oxides. That is, the filter regeneration control is a control necessary for regenerating the particulate filter, but is not a preferable control as the air-fuel ratio control of the engine. From the above, it is desirable that the filter regeneration control is finished within a short time.

  Therefore, as in the above configuration, when the filter regeneration control is executed, the average of the air-fuel ratio of the air-fuel mixture supplied to the some cylinders becomes the leaner air-fuel ratio as the acquired particulate collection amount increases. To control. As a result, the larger the amount of particulates collected in the particulate collection filter, the larger the amount of oxygen flowing into the particulate collection filter per unit time, so the amount of particulates combusted per unit time also increases. . As a result, the filter regeneration control can be completed within a short time (regeneration of the particulate collection filter is completed) regardless of the amount of collected particulates.

  In any one of the control devices according to the present invention described above, the air-fuel ratio control unit acquires a filter temperature related value that increases as the temperature of the particulate collection filter increases, and the acquired filter temperature related value. It is preferable that the filter regeneration control is prohibited when the temperature is higher than the high-side filter threshold temperature.

  When filter regeneration control is executed when the temperature of the particulate collection filter is very high and heat is generated by burning the particulates in the particulate collection filter, the temperature of the particulate collection filter becomes excessively high. As a result, the particulate collection filter may be damaged by overheating. Thus, if the filter regeneration control is prohibited when the filter temperature relation value is higher than the high-side filter threshold temperature as in the above configuration, the possibility of such a particulate collection filter being damaged due to overheating can be reduced. it can.

  In this case, when the acquired filter temperature related value is lower than the high-side filter threshold temperature, the air-fuel ratio control means is supplied to the some cylinders when the filter regeneration control is executed. The average air-fuel ratio of the air-fuel mixture becomes closer to the same high-side filter threshold temperature as “the air-fuel ratio leaner than the stoichiometric air-fuel ratio, but the richer air-fuel ratio (more stoichiometric air-fuel ratio). It is preferable to be configured to control to “close air / fuel ratio)”. That is, the average of the air-fuel ratios of the air-fuel mixture supplied to the some cylinders when the filter regeneration control is executed is the leaner side of the stoichiometric air-fuel ratio as the filter temperature-related value decreases from the high-side filter threshold temperature. The air-fuel ratio is controlled so as to increase the difference from the stoichiometric air-fuel ratio.

  Even if the temperature of the particulate collection filter is equal to or lower than the high-side filter threshold temperature, if an excessive amount of particulates burns, a large amount of heat is generated, and the temperature of the particulate collection filter may become excessively high. Therefore, as the filter temperature-related value approaches the high-side filter threshold temperature as in the above configuration, the average of the air-fuel ratio of the air-fuel mixture supplied to some cylinders is expressed as “lean than the theoretical air-fuel ratio, The air-fuel ratio on the rich side (the air-fuel ratio closer to the theoretical air-fuel ratio) is controlled. As a result, as the temperature of the particulate collection filter increases, the amount of oxygen supplied to the particulate collection filter decreases, and accordingly, the amount of particulates burned per unit time (the amount of heat generated) decreases. The collecting filter can be protected from the above-described damage due to overheating.

  In addition, in any one of the control devices according to the present invention described above, the air-fuel ratio control unit acquires (estimates) a filter temperature related value that increases as the temperature of the particulate collection filter increases, and the acquired It is preferable that the filter regeneration control is prohibited from being executed when the filter temperature related value is lower than the low-side filter threshold temperature.

  As described above, when the temperature of the particulate collection filter is low, the particulate does not burn even if oxygen is supplied to the particulate collection filter. Further, as described above, the filter regeneration control is a control necessary for the particulate filter regeneration, but it is not a preferable control as the air-fuel ratio control of the engine. Therefore, as in the above configuration, when oxygen cannot be expected even if oxygen is supplied to the particulate collection filter, that is, when the filter temperature relation value is lower than the low-side filter threshold temperature, the filter By prohibiting the execution of the regeneration control, it is possible to avoid performing the filter regeneration control wastefully.

  In this case, when the acquired filter temperature related value is higher than the low-side filter threshold temperature, the air-fuel ratio control means is supplied to the some cylinders when the filter regeneration control is executed. The average air-fuel ratio of the air-fuel mixture becomes closer to the same low-side filter threshold temperature as “the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, but the richer air-fuel ratio (more stoichiometric air-fuel ratio). It is preferable to be configured to control to “close air / fuel ratio)”. That is, the average of the air-fuel ratios of the air-fuel mixture supplied to the some cylinders when the filter regeneration control is executed is the leaner side of the stoichiometric air-fuel ratio as the filter temperature-related value increases from the lower filter threshold temperature. The air-fuel ratio is controlled so as to increase the difference from the stoichiometric air-fuel ratio.

  If the temperature of the particulate collection filter is equal to or higher than the low-side filter threshold temperature, the particulates burn. However, the closer the temperature of the particulate collection filter is to the lower filter threshold temperature, the more difficult the particulates will burn (the burning of the particulates becomes slower). Therefore, in such a case, much oxygen is wasted even if a large amount of oxygen is supplied. On the other hand, supplying a large amount of oxygen means that the air-fuel ratio of the cylinders is set to a lean air-fuel ratio that is greatly deviated from the stoichiometric air-fuel ratio. In that case, a large amount of nitrogen oxide is discharged from the cylinders.

  Therefore, as in the above configuration, if the filter temperature-related value is closer to the same low-side filter threshold temperature, it is controlled to “richer air-fuel ratio (an air-fuel ratio closer to the theoretical air-fuel ratio)”. The amount of nitrogen oxides discharged from the some cylinders can be reduced without being supplied to the collection filter. As a result, the amount of nitrogen oxide that passes through the downstream catalyst without being purified (blows through the downstream catalyst) can be reduced, so that the amount of nitrogen oxide discharged from the engine into the atmosphere can be reduced. it can.

  Further, the air-fuel ratio control means acquires (estimates) a downstream catalyst temperature related value that increases as the temperature of the downstream catalyst increases, and the acquired downstream catalyst temperature related value is low. It is preferable that the filter regeneration control is prohibited from being executed when the temperature is lower than the threshold temperature.

  A three-way catalyst such as a downstream catalyst cannot exert its original purification function unless it reaches an activation temperature. Therefore, as described above, when the downstream catalyst temperature-related value is lower than the low-side downstream catalyst threshold temperature, if the execution of filter regeneration control is prohibited, nitrogen oxides are not purified by the downstream catalyst in the atmosphere. It is possible to avoid being discharged.

A control device according to the present invention comprises:
An upstream catalyst disposed in a position upstream of the particulate collection filter in the main passage portion;
An upstream air-fuel ratio that is disposed at a position upstream of the upstream catalyst and that is an output value corresponding to the air-fuel ratio of the gas flowing through the portion disposed in the main passage portion or the collecting portion. A sensor,
A downstream side of the main passage portion that is disposed at a position between the particulate collection filter and the downstream catalyst and outputs an output value corresponding to the air-fuel ratio of the gas flowing through the disposed portion. An air-fuel ratio sensor;
Whether the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled according to a predetermined mode and whether the upstream catalyst has deteriorated based on the output value of the upstream air-fuel ratio sensor and the output value of the downstream air-fuel ratio sensor Deterioration determination means for executing deterioration determination control (catalyst deterioration determination control) (when a predetermined catalyst deterioration determination condition is satisfied);
If you have
The air-fuel ratio control means includes
It is preferable that the deterioration determination unit is configured to prohibit the execution of the filter regeneration control when the deterioration determination control is being executed.

  It is an important control item to determine whether or not the upstream catalyst has deteriorated. However, when determining the deterioration of the upstream catalyst, the air-fuel ratio is controlled according to a predetermined mode. For example, when the maximum oxygen storage amount of the upstream catalyst is used as an index value for determining deterioration, the air-fuel ratio of the air-fuel mixture supplied to the engine is forced to be higher than the stoichiometric air-fuel ratio in order to obtain the maximum oxygen storage amount. The lean first air-fuel ratio, the second air-fuel ratio richer than the stoichiometric air-fuel ratio, and then the third air-fuel ratio leaner than the stoichiometric air-fuel ratio (or the fourth air-fuel ratio richer than the stoichiometric air-fuel ratio, the stoichiometric air-fuel ratio The fifth air-fuel ratio leaner than the fuel ratio, and then the sixth air-fuel ratio richer than the stoichiometric air-fuel ratio. The maximum oxygen storage amount of the upstream catalyst is acquired based on the output value of the upstream air-fuel ratio sensor and the output value of the downstream air-fuel ratio at the time of such air-fuel ratio control. Alternatively, when the deterioration determination of the upstream catalyst is performed based on the comparison of the locus length of the output value of the upstream air-fuel ratio sensor and the locus length of the output value of the downstream air-fuel ratio, the mixture of the mixture supplied to the engine The air-fuel ratio is adjusted by feedback control in which the stoichiometric air-fuel ratio (or the air-fuel ratio near the stoichiometric air-fuel ratio) is the target air-fuel ratio. In other words, since the control mode of the air-fuel ratio during the filter regeneration control and the control mode of the air-fuel ratio in the case of performing the deterioration determination of the upstream catalyst are different, it is not possible to determine the deterioration of the upstream catalyst during the filter regeneration control. Have difficulty.

  Therefore, as in the configuration described above, when the deterioration determination unit is executing the deterioration determination control, the execution of the filter regeneration control is prohibited. Thereby, since the deterioration determination of the upstream catalyst and the filter regeneration control are executed at different timings, it is possible to make these controls compatible.

  In addition, the air-fuel ratio control means acquires an intake air amount related value that increases as the intake air amount of the engine increases, and when the acquired intake air amount related value is greater than an intake air amount threshold, the filter It is preferable to be configured to prohibit execution of the reproduction control.

  When the filter regeneration control is executed when the intake air amount of the engine is large at the time of acceleration or high load, the amount of nitrogen oxide generated per unit time becomes very large. Therefore, even if the average air-fuel ratio of the gas flowing into the downstream catalyst during the filter regeneration control is a value close to the stoichiometric air-fuel ratio (the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio), the nitrogen oxide remains unpurified by the downstream catalyst. There is a case where it is released into the atmosphere (nitrogen oxide blows through the downstream catalyst).

  Thus, if the filter regeneration control is prohibited when the intake air amount related value is larger than the intake air amount threshold as in the above configuration, the amount of nitrogen oxides released into the atmosphere by the filter regeneration control is reduced. Can do.

  In this case, the air-fuel ratio control means acquires (estimates) the maximum oxygen storage amount of the downstream catalyst, and the intake air amount threshold value increases as the acquired maximum oxygen storage amount increases. It is preferable to set an air amount threshold value.

  A large maximum oxygen storage amount of the downstream catalyst means that the downstream catalyst has not deteriorated, and therefore the downstream catalyst can purify more nitrogen oxides per unit time. Therefore, as described above, the filter regeneration control is executed while setting the intake air amount threshold value to be larger as the maximum oxygen storage amount of the downstream catalyst is larger, so that nitrogen oxides are not released into the atmosphere. Opportunities can be increased.

Further, the present control device is configured to prohibit the execution of filter regeneration control when the intake air amount related value is larger than the intake air amount threshold, and in the main passage portion or the collecting portion, the particulate collection control When equipped with an upstream catalyst that is a three-way catalyst disposed upstream of the filter,
The air-fuel ratio control means is configured to provide the on-off valve for a predetermined period from the time when the filter regeneration control is stopped due to the intake air amount related value becoming larger than the intake air amount threshold during the execution of the filter regeneration control. The air-fuel ratio average of the air-fuel mixture supplied to the plurality of cylinders is richer than the average air-fuel ratio of the air-fuel mixture supplied to the plurality of cylinders during the normal control. It is preferable that the control is performed so that the air-fuel ratio becomes the same, and then the execution of the normal control is started.

  During the filter regeneration control, a large amount of oxygen flows into the upstream catalyst. Therefore, the oxygen storage amount of the upstream catalyst reaches the maximum oxygen storage amount of the upstream catalyst or an amount close thereto. In such a state, when the filter regeneration control is stopped by increasing the intake air amount, the upstream catalyst cannot effectively purify nitrogen oxides immediately after that. As a result, nitrogen oxides may pass through (blow through) the upstream catalyst and the downstream catalyst without being purified.

  Therefore, as in the above-described configuration, the plurality of the plurality of the plurality of the intake air amount-related values during execution of the filter regeneration control for a predetermined period from when the execution of the filter regeneration control is stopped due to being greater than the intake air amount threshold. If the average of the air-fuel ratio of the air-fuel mixture supplied to the cylinder is controlled so that it becomes a richer air-fuel ratio than the average of the air-fuel ratio of the air-fuel mixture supplied to the plurality of cylinders during normal control, the upstream side catalyst The oxygen storage amount of can be quickly reduced. As a result, the upstream catalyst is in a state in which more nitrogen oxides can be purified within a short period after stopping the filter regeneration control. Therefore, the amount of nitrogen oxides blown through the upstream catalyst and the downstream catalyst (the amount of nitrogen oxides discharged from the engine into the atmosphere) can be reduced.

  By the way, when executing fuel cut control, a large amount of oxygen is discharged from the engine. Therefore, the particulate collection filter can be regenerated by flowing the oxygen into the particulate collection filter.

  More specifically, the control device according to the present invention includes an upstream side catalyst which is the three-way catalyst disposed at a position upstream of the particulate collection filter in the main passage portion or the collecting portion. In this case, it is preferable that the main exhaust passage configuration portion, the bypass passage configuration portion, and the air-fuel ratio control means are configured as follows.

The main exhaust passage constituting part includes a second branch part connected to the exhaust port of the other cylinder and connected to the collecting part.
The bypass passage component is
One end of the bypass passage is configured by one end being connected to the second branch portion and the other end being connected to the main passage portion at a position between the particulate collection filter and the downstream catalyst. A tubular section;
A first end is connected to the second branch portion and the other end forms a passage (air introduction passage) connected to the main passage portion at a position between the upstream catalyst and the particulate collection filter. Two tubular parts;
Passage switching means;
Is provided.

At this time, the passage switching means
A first state in which only the second branch portion and the main passage portion at a position between the particulate collection filter and the downstream catalyst are communicated (via the first tubular portion);
A second state in which only the second branch portion and the main passage portion at a position between the upstream catalyst and the particulate collection filter communicate (via the second tubular portion); and
A third state in which communication between the second branch portion and the main passage (via the first tubular portion and the second tubular portion) is interrupted;
Any one of these states is configured to be selectively achieved in response to an instruction.

Further, the air-fuel ratio control means includes:
Executing the filter regeneration control by giving an instruction to the passage switching means to achieve the first state when the filter regeneration control is performed;
When the operation state of the engine becomes a predetermined fuel cut operation state, the fuel cut control is performed by stopping the supply of fuel to the engine and giving an instruction to achieve the second state to the passage switching means,
When neither the filter regeneration control nor the fuel cut control is executed, the average of the air-fuel ratio of the air-fuel mixture supplied to each of the plurality of cylinders is the air-fuel ratio within the predetermined air-fuel ratio range including the theoretical air-fuel ratio. And a normal control is executed by giving an instruction to achieve the third state to the passage switching means.

  According to this, when the filter regeneration control is executed, the exhaust port of the other cylinder is communicated with the main passage portion at a position between the particulate collection filter and the downstream catalyst, and the filter regeneration described above is performed. Filter regeneration control similar to the control is executed.

  When neither filter regeneration control nor fuel cut control is executed, all of the gas discharged from the plurality of cylinders passes through the main passage portion, and normal control similar to the normal control described above is executed. Is done.

  Further, when performing fuel cut control, the second branch portion communicating with the exhaust port of the other cylinder, the main passage portion at a position between the upstream catalyst and the particulate collection filter, , Can be communicated. Therefore, since the air containing a large amount of oxygen discharged from the other cylinders is supplied to the particulate collection filter, the particulate collection filter is regenerated.

  Hereinafter, embodiments of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a spark ignition type multi-cylinder (4 cylinders in this example) internal combustion engine (gasoline engine) 10 as an internal combustion engine control apparatus (hereinafter also referred to as “first control apparatus”) according to the first embodiment. The schematic configuration of the applied system is shown. The internal combustion engine 10 includes a cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and a gasoline mixture to the cylinder block portion 20. An intake system 40 for supplying and an exhaust system 50 for releasing exhaust gas from the cylinder block unit 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 that communicates with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake cam shaft that drives the intake valve 32, and continuously changes the phase angle of the intake cam shaft. A variable intake timing device 33, an actuator 33a of the variable intake timing device 33, an exhaust port 34 communicating with the combustion chamber 25, an exhaust valve 35 for opening and closing the exhaust port 34, an exhaust camshaft 36 for driving the exhaust valve 35, an ignition plug 37, An igniter 38 including an ignition coil for generating a high voltage to be applied to the spark plug 37 and an injector (fuel injection means) 39 for injecting fuel into the intake port 31 are provided. An injector 39 as fuel injection means is configured to inject fuel of the indicated injection amount included in the injection instruction signal in response to the injection instruction signal.

  The intake system 40 includes an intake manifold 41, an intake pipe (intake duct) 42, an air filter 43, a throttle valve 44, and a throttle valve actuator 44a.

  The intake manifold 41 is connected to the intake port 31 of the combustion chamber 25 of each cylinder. More specifically, as shown in FIG. 2, the intake manifold 41 includes a plurality of branch portions 41a connected to each intake port, and a surge tank portion 41b in which those branch portions 41a are assembled. As shown in FIGS. 1 and 2, the intake pipe 42 is connected to the surge tank 41b. The intake manifold 41 and the intake pipe 42 constitute an intake passage. The air filter 43 shown in FIG. 1 is provided at the end of the intake pipe 42. The throttle valve 44 is rotatably provided in the intake pipe 42, and changes the opening cross-sectional area of the intake passage formed by the intake pipe 42 by rotating. The throttle valve actuator (throttle valve drive means) 44a is formed of a DC motor, and rotates the throttle valve 44 in response to an instruction signal.

  The exhaust system 50 includes an exhaust manifold 51, an exhaust pipe (exhaust pipe) 52, an upstream side catalyst 53, a particulate collection filter 54, a downstream side catalyst 55, a bypass passage forming member 56, and an on-off valve 57.

  As shown in FIG. 1, the exhaust manifold 51 is connected to the exhaust port 34 of the combustion chamber 25 of each cylinder. More specifically, as shown in FIG. 2, the exhaust manifold 51 includes a plurality of branch portions 51 a 1 to 51 a 4 and one aggregate portion 51 b that is a portion where the plurality of branch portions are aggregated. .

One end of the branch portion 51a1 is connected to the exhaust port of the first cylinder # 1, and the other end of the branch portion 51a1 is connected to the collecting portion 51b.
One end of the branch portion 51a2 is connected to the exhaust port of the second cylinder # 2, and the other end of the branch portion 51a2 is connected to the collecting portion 51b.
One end of the branch portion 51a3 is connected to the exhaust port of the third cylinder # 3, and the other end of the branch portion 51a3 is connected to the collecting portion 51b.
One end of the branch portion 51a4 is connected to the exhaust port of the fourth cylinder # 4, and the other end of the branch portion 51a4 is connected to the collecting portion 51b.
The exhaust pipe 52 is connected to the collective portion 51 b of the exhaust manifold 51.

  Here, for convenience of explanation, the second cylinder # 2, the third cylinder # 3, and the fourth cylinder # 4 are referred to as “partial cylinders” of the plurality of cylinders included in the multi-cylinder internal combustion engine 10, The first cylinder # 1 is referred to as “another cylinder” other than the part of the plurality of cylinders. Furthermore, for convenience of explanation, the branch part 51a2, the branch part 51a3, and the branch part 51a4 are referred to as “first branch part” for convenience. According to this naming method, it can be expressed as “the first branch is connected to the exhaust ports of some of the cylinders included in the multi-cylinder internal combustion engine 10”. Further, the branch part 51a1 is referred to as a “second branch part” for convenience. In this case, it can be expressed as “the second branch portion is connected to an exhaust port of another cylinder among a plurality of cylinders included in the multi-cylinder internal combustion engine 10”.

  In addition, the exhaust pipe 52 can also be expressed as constituting a main passage portion connected to the collecting portion 51b together with the collecting portion 51b. Further, the first branch portion, the collecting portion, and the main passage portion are expressed as a “main exhaust passage constituting portion” that constitutes a “main exhaust passage through which the exhaust gas discharged through the exhaust ports of the some cylinders passes”. You can also

  The upstream side catalyst 53 supports “noble metal as catalyst material” and “ceria (CeO2)” on a support made of ceramic and has an oxygen storage / release function (simply “oxygen storage function” or “O2 storage function”). It is also referred to as a three-way catalyst. The upstream catalyst 53 is disposed (intervened) in the exhaust pipe 52 downstream of the exhaust passage collection portion (the collection portion 51b of the exhaust manifold 51). The upstream catalyst 53 is also referred to as a start catalytic converter (SC) or a first catalyst.

  The particulate collection filter 54 is a known particulate filter made of ceramic and collects particulates discharged from the engine 10. The particulate collection filter 54 is also referred to as a particulate matter filter (PMF). The particulate collection filter 54 is disposed (intervened) in the exhaust passage (exhaust pipe 52) at a position downstream of the upstream side catalyst 53. In other words, the particulate collection filter 54 is disposed in the main passage portion at a position downstream of the upstream catalyst 53. Further, the upstream catalyst 53 is disposed at a position upstream of the particulate collection filter 54 in the main passage portion or the collecting portion.

  Similarly to the upstream catalyst 53, the downstream catalyst 55 is a three-way catalyst having a precious metal and ceria supported on a ceramic support and having an oxygen storage function. The downstream catalyst 55 is disposed (intervened) in the exhaust pipe 52 at a position downstream of the particulate collection filter 54. In other words, the downstream catalyst 55 is disposed at a position downstream of the particulate collection filter 54 in the main passage portion. That is, in the main passage portion of the main exhaust passage, the upstream catalyst 53, the particulate collection filter 54, and the downstream catalyst 55 are arranged in series in order from upstream to downstream. Since the downstream catalyst 55 is disposed below the floor of the vehicle, it is also referred to as an under-floor catalytic converter (UFC) or a second catalyst.

  As shown in FIG. 3, the three-way catalyst constituting the upstream catalyst 53 and the downstream catalyst 55 is not burned when the air-fuel ratio of the gas flowing into the three-way catalyst is within a so-called “window W” range. By oxidizing substances (HC, CO, etc.) and reducing nitrogen oxides (NOx), it has a characteristic (catalytic function) that purifies these harmful components with high efficiency.

  Further, the three-way catalyst can purify HC, CO and NOx even if the air-fuel ratio shifts from the stoichiometric air-fuel ratio to a certain extent due to the oxygen storage function. That is, if the air-fuel ratio of the engine is leaner than the stoichiometric air-fuel ratio and the gas flowing into the three-way catalyst contains a large amount of NOx, the catalyst deprives the NOx of oxygen molecules (reduces NOx). ), Occlude the lost oxygen molecules. Such a state can also be expressed as “a state in which the three-way catalyst substantially holds a reducing agent (reducing component)”. In addition, when the air-fuel ratio of the engine becomes richer than the stoichiometric air-fuel ratio and the gas flowing into the three-way catalyst contains a large amount of unburned substances (reducing components) such as HC and CO, the three-way catalyst Gives the stored oxygen molecules to these unburned materials and oxidizes (purifies) these components. Such a state can also be expressed as “a state in which the three-way catalyst substantially holds the oxidizing agent (oxidizing component)”.

  Referring to FIGS. 1 and 2 again, the bypass passage forming member 56 is formed of a tubular member. One end of the bypass passage forming member 56 is connected to a branch portion 51a1 connected to the exhaust port of the first cylinder # 1, as shown in FIG. The other end of the bypass passage forming member 56 is connected to the exhaust pipe 52 at a position between the particulate collection filter 54 and the downstream catalyst 55. That is, the bypass passage forming member 56 removes the exhaust gas discharged through the exhaust port of the other cylinder (first cylinder # 1), which is a cylinder other than the part of the plurality of cylinders, from the particulate collection filter. This corresponds to a “bypass passage constituting portion” that constitutes a bypass passage that directly flows into the downstream catalyst 55 in cooperation with the branch portion 51a1 without passing through the branch portion 51a1. Further, the bypass passage constituting part is “one end is connected to the second branch part (branch part 51a1) and the other end is located at a position between the particulate collection filter 54 and the downstream catalyst 55. It can also be expressed as “a bypass passage forming member that constitutes the bypass passage by being connected to the main passage portion”.

  The on-off valve 57 is an electromagnetic on-off valve, and shuts off and opens the bypass passage of the bypass passage forming member 56 in response to an instruction (drive signal, instruction signal). When the bypass passage is blocked by closing the on-off valve 57, the gas flow in the bypass passage is stopped. When the on-off valve 57 is opened and the bypass passage is opened, the exhaust gas discharged from the first cylinder # 1 passes through the bypass passage forming member 56 and the on-off valve 57, and is the exhaust pipe 52 and the particulate collection filter 54. And the downstream catalyst 55.

  Further, as shown in FIGS. 1 and 2, this system includes a hot-wire air flow meter 61, a throttle position sensor 62, a cam position sensor 63, a crank position sensor 64, a water temperature sensor 65, an upstream air-fuel ratio sensor 66, a downstream side. A side air-fuel ratio sensor 67 and an accelerator opening sensor 68 are provided.

The hot-wire air flow meter 61 detects the mass flow rate of the intake air flowing through the intake pipe 42 and outputs a signal indicating the mass flow rate (intake air amount / intake air flow rate per unit time of the engine 10) Ga. It has become. Hereinafter, Ga is referred to as “intake air amount Ga”.
The throttle position sensor 62 detects the opening of the throttle valve 44 and outputs a signal representing the throttle valve opening TA.

The cam position sensor 63 outputs one pulse every time the intake camshaft rotates 90 degrees, 90 degrees, and 180 degrees from a predetermined angle. This signal is also referred to as a G2 signal.
The crank position sensor 64 has a narrow pulse every time the crankshaft 24 rotates 10 ° and outputs a signal having a wide pulse every time the crankshaft 24 rotates 360 °. A pulse output from the crank position sensor 64 is converted into a signal representing the engine rotational speed NE by an electric control device 70 described later. Further, the electric control device 70 acquires the crank angle (absolute crank angle) of the engine 10 based on signals from the cam position sensor 63 and the crank position sensor 64.
The water temperature sensor 65 detects the temperature of the cooling water of the internal combustion engine 10 and outputs a signal representing the cooling water temperature THW.

  As shown in FIG. 2, the upstream air-fuel ratio sensor 66 is disposed between the exhaust manifold 51 and the exhaust pipe 52 at a position between the collection portion 51 b (exhaust passage collection portion) of the exhaust manifold 51 and the upstream catalyst 53. It is arranged. In other words, the upstream air-fuel ratio sensor 66 is disposed at a position upstream of the upstream catalyst 53 in the main passage portion or the collecting portion. The upstream air-fuel ratio sensor 66 outputs an output value corresponding to the air-fuel ratio of exhaust gas flowing through a portion in the exhaust passage where the upstream air-fuel ratio sensor 66 is disposed (detected gas that is exhaust gas flowing into the upstream catalyst 53). Is output.

  More specifically, the upstream air-fuel ratio sensor 66 is a limiting current type oxygen concentration sensor. As shown in FIG. 4, the upstream air-fuel ratio sensor 66 outputs an output value Vabyfs that is a voltage corresponding to the air-fuel ratio A / F of the detected gas (and hence the air-fuel ratio of the air-fuel mixture supplied to the engine). It is supposed to be. This output value Vabyfs matches the value Vstoich when the air-fuel ratio of the detected gas is the stoichiometric air-fuel ratio. The output value Vabyfs increases as the air-fuel ratio of the gas to be detected increases (lean).

  The electric control device 70 described later stores the table (map) Mapabyfs shown in FIG. 4 and detects the air-fuel ratio by applying the actual output value Vabyfs to the table (acquires the detected air-fuel ratio). It is like that. However, the upstream air-fuel ratio sensor 66 gradually changes the output value Vabyfs even if the air-fuel ratio of the gas (that is, the gas to be detected) reaching the upstream air-fuel ratio sensor 66 is stepped on the time axis. It has a detection response delay characteristic. More specifically, the air-fuel ratio value of the gas reaching the upstream air-fuel ratio sensor 66 is used as an input signal, and the air-fuel ratio obtained based on the output value Vabyfs of the upstream air-fuel ratio sensor 66 and the table Mapabyfs. When the value is an output signal, the output signal is a signal very similar to a signal obtained by subjecting the input signal to low-pass filter processing (for example, primary delay processing including so-called “smoothing processing” and secondary delay processing). Become.

  As shown in FIG. 2, the downstream air-fuel ratio sensor 67 is disposed in the exhaust pipe 52 (main passage portion) at a position between the particulate collection filter 54 and the downstream catalyst 55. More specifically, the downstream side air-fuel ratio sensor 67 is connected to the exhaust pipe 52 (main exhaust) at a position between the connection portion (joining position) between the bypass passage forming member 56 and the exhaust pipe 52 and the downstream side catalyst 55. It is disposed in the main passage portion of the passage. The downstream air-fuel ratio sensor 67 corresponds to the air-fuel ratio of the exhaust gas flowing through the portion in the exhaust passage where the downstream air-fuel ratio sensor 67 is disposed (that is, the detected gas that is exhaust gas flowing into the downstream catalyst 55). Output value is output.

  More specifically, the downstream air-fuel ratio sensor 67 is an electromotive force type (concentration cell type) oxygen concentration sensor. Accordingly, the downstream air-fuel ratio sensor 67 is also referred to as an oxygen concentration sensor. As shown in FIG. 5, the downstream air-fuel ratio sensor 67 outputs an output value Voxs that is a voltage that changes suddenly in the vicinity of the theoretical air-fuel ratio. That is, the downstream side air-fuel ratio sensor 67 is approximately 0.1 (V) when the air-fuel ratio of the detected gas is larger than the stoichiometric air-fuel ratio and is on the lean side, and the air-fuel ratio of the detected gas is the stoichiometric air-fuel ratio. When the air-fuel ratio is larger and richer than about 0.9 (V), and when the air-fuel ratio is the stoichiometric air-fuel ratio, a voltage of 0.5 (V) is output. Further, the downstream air-fuel ratio sensor 67 detects the gas to be detected when the air-fuel ratio of the gas to be detected is an air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio (the air-fuel ratio substantially corresponding to the above-described three-way catalyst window W). A voltage that suddenly decreases (changes from approximately 0.9 (V) to approximately 0.1 (V)) as the air-fuel ratio of the engine changes from rich to lean is output. Note that the downstream air-fuel ratio afdown obtained based on the output value Voxs of the downstream air-fuel ratio sensor 67 is expressed as follows when the function representing the relationship between the output value Voxs and the downstream air-fuel ratio afdown shown in FIG. It is calculated | required by afdown = f (Voxs).

  Referring to FIG. 1 again, the accelerator opening sensor 68 detects the operation amount of the accelerator pedal 81 operated by the driver, and outputs a signal indicating the operation amount Accp of the accelerator pedal 81.

  The electric control device 70 includes a CPU 71 connected by a bus, a routine (program) executed by the CPU 71, a ROM 72 pre-stored with tables (look-up tables, maps), constants, and the like, and the CPU 71 temporarily stores data as necessary. The microcomputer 73 includes a RAM 73 that stores data, a backup RAM 74 that stores data while the power is on, and retains the stored data even when the power is shut off, and an interface 75 that includes an AD converter.

  The interface 75 is connected to the sensors 61 to 68, supplies signals from the sensors 61 to 68 to the CPU 71, and in response to instructions from the CPU 71, the actuator 33a, the igniter 38, the injector 39, and the throttle valve of the variable intake timing device 33. A drive signal (instruction signal) is sent to the actuator 44a, the on-off valve 57, and the like.

(Operation)
Next, an overview of air-fuel ratio control by the first control device configured as described above will be described. The first control device executes normal control and particulate collection filter regeneration control (filter regeneration control) using main feedback control, sub-feedback control, and the like.

  The CPU 71 of the first control device performs the various controls described above according to the procedure shown by the schematic flowchart shown in FIG. The CPU 71 is configured to repeat the procedure shown in FIG. 6 every elapse of a predetermined time. In the following description, it is assumed that both the upstream air-fuel ratio sensor 66 and the downstream air-fuel ratio sensor 67 are activated.

  The CPU 71 starts processing from step 600 and proceeds to step 610 to determine whether or not the value of the filter regeneration request flag XPM is “1”. The value of the filter regeneration request flag XPM is set to “1” when a request to regenerate the particulate collection filter 54 (filter regeneration request) is generated, and when it is not necessary to regenerate the particulate collection filter 54 “ 0 "is set. The operation of the filter regeneration request flag XPM will be described later (see FIG. 7).

  Assume that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 determines “No” in step 610, proceeds to step 620, gives an instruction to close the on-off valve 57 to the on-off valve 57, and shuts off the bypass passage of the bypass passage forming member 56.

  Next, the CPU 71 proceeds to step 630 to execute “normal control”. In this normal control, the average air-fuel ratio of the air-fuel mixture supplied to each of the first to fourth cylinders (all of the plurality of cylinders) is substantially equal to the stoichiometric air-fuel ratio (the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio). Thus, the air-fuel ratio (fuel injection amount for each cylinder) of the air-fuel mixture supplied to each cylinder is controlled.

  Note that “controlling the air-fuel ratio of the air-fuel mixture supplied to a certain cylinder” is achieved by “controlling fuel injection from the injector 39 provided corresponding to that cylinder”. The air-fuel ratio near the stoichiometric air-fuel ratio here is the air-fuel ratio in the window W of the upstream catalyst 53 and the downstream catalyst 55, and the air-fuel ratio on the rich side by a predetermined value ΔAF slightly smaller than the stoichiometric air-fuel ratio. (Weak rich air-fuel ratio AFR).

  More specifically, in step 630, the CPU 71 executes both “main feedback control” and “sub feedback control” which will be described in detail later. In this case, the upstream target air-fuel ratio abyfr in the main feedback control is set to the stoichiometric air-fuel ratio stoich, and the downstream target value Voxsref in the sub-feedback control is set to a value Vrich corresponding to the weak rich air-fuel ratio AFR. The main feedback control is feedback control in which the upstream air-fuel ratio abyfs obtained based on the output value Vabyfs of the upstream air-fuel ratio sensor 66 matches the upstream target air-fuel ratio abyfr (main feedback control target air-fuel ratio abyfrtgt). The sub-feedback control is feedback control that makes the output value Voxs of the downstream air-fuel ratio sensor 67 coincide with the downstream target value Voxsref. Thereafter, the CPU 71 proceeds to step 695 to end the present routine tentatively.

  By this normal control, the air-fuel ratio of the gas flowing into the upstream catalyst 53 and the downstream catalyst 55 becomes the stoichiometric air-fuel ratio near the stoichiometric air-fuel ratio within the window W, so that unburned substances (HC, CO, etc.) and nitrogen oxidation Things (NOx) are purified at a high purification rate.

  On the other hand, the CPU 71 executes the filter regeneration request flag operation routine shown in the flowchart of FIG. 7 every elapse of a predetermined time. Accordingly, the CPU 71 starts the process from step 700 at a predetermined timing, proceeds to step 710, and the “integrated value SGa of the intake air amount Ga after the end of the previous filter regeneration control” is a predetermined threshold (filter regeneration). It is determined whether or not the control execution threshold value) is greater than SGath.

  The integrated value SGa is updated by an intake air amount integrating routine (not shown) that is executed every elapse of the predetermined time Δts. That is, the CPU 71 updates the integrated value SGa by adding the intake air amount Ga detected by the air flow meter 61 at that time to the integrated value SGa at that time every elapse of the predetermined time Δts. The integrated value SGa is stored in the backup RAM 74. Since the amount of fine particles generated by the operation of the engine 10 increases as the intake air amount Ga increases, the integrated value SGa is an amount representing the amount of fine particles collected by the fine particle collection filter 54. The integrated value SGa is set (cleared) to “0” by the intake air amount integrating routine when the execution of the filter regeneration control is completed.

  If the integrated value SGa is greater than or equal to the threshold value SGath at this time, the CPU 71 proceeds from step 710 to step 720, sets the value of the filter regeneration request flag XPM to “1”, and proceeds to step 730. On the other hand, when the integrated value SGa is smaller than the threshold value SGath, the CPU 71 proceeds directly from step 710 to step 730.

  As will be described later, instead of the integrated value SGa, the integrated amount (particulate collection amount) SPM of the particulates collected by the particulate collection filter 54 is estimated with higher accuracy than the integrated value SGa, and step 710 is performed. You may change to the step which determines "whether the estimated particulate collection amount SPM is more than threshold value SPMth" (refer step 1510 thru | or step 1525 of FIG. 15 mentioned later).

  In step 730, the CPU 71 starts a predetermined time Tsth (filter regeneration control execution time Tsth) from the start time of filter regeneration control (in this case, when the value of the filter regeneration request flag XPM changes from “0” to “1”). It is determined whether or not elapses. When a predetermined time Tsth (filter regeneration control execution time Tsth) has elapsed since the start of filter regeneration control, the CPU 71 makes a “Yes” determination at step 730 to proceed to step 740, where the filter regeneration request flag XPM Is set to “0”. Thereafter, the CPU 71 proceeds to step 795 to end the present routine tentatively. On the other hand, if the predetermined time Tsth has not elapsed since the filter regeneration control start time, the CPU 71 makes a “No” determination at step 730 to directly proceed to step 795 to end the present routine tentatively.

  Thus, the filter regeneration request flag XPM is set to “1” when the integrated value SGa of the intake air amount Ga after the end of the previous filter regeneration control is equal to or greater than the threshold value SGath, and the filter regeneration request flag XPM is “ When a predetermined time Tsth elapses from “0” to “1”, it is set to “0”. Accordingly, when the total execution period of the normal control in step 620 and step 630 in FIG. 6 is equal to or longer than the predetermined period, the value of the integrated value SGa becomes equal to or greater than the threshold value SGath, and therefore the value of the filter regeneration request flag XPM is set to “1”. Is done.

  At this time, when the CPU 71 executes the processing of step 610 in FIG. 6, the CPU 71 determines “Yes” in step 610, proceeds to step 640, gives an instruction to open the on-off valve 57 to the on-off valve 57, and forms a bypass passage The bypass passage of the member 56 is opened (a state in which gas can flow is set).

  Next, the CPU 71 proceeds to step 650 and executes “filter regeneration control”. In this filter regeneration control, the average of the air-fuel ratio of the air-fuel mixture supplied to the first cylinder is set to an air-fuel ratio richer than the stoichiometric air-fuel ratio, and each of the second, third, and fourth cylinders is set. The average air-fuel ratio of the supplied air-fuel mixture is set to an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. However, the average of the overall air-fuel ratio of the air-fuel mixture supplied to each of the first to fourth cylinders (that is, all cylinders) is the stoichiometric air-fuel ratio or the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio (in this example, weak The air-fuel ratio of the air-fuel mixture supplied to the first cylinder and the air-fuel ratio of the air-fuel mixture supplied to the second to fourth cylinders are controlled so that the rich air-fuel ratio AFR) is obtained.

  More specifically, in step 650, the CPU 71 increases the fuel injection amount for the first cylinder more than the fuel injection amounts for the second to fourth cylinders. For example, if the fuel injection amount per cylinder required to maintain the overall air-fuel ratio of the air-fuel mixture supplied to each cylinder at the weak rich air-fuel ratio AFR is Fi, the fuel injection amount of the first cylinder Is set to Fi · (1 + 3a), and the fuel injection amounts of the second to fourth cylinders are set to Fi (1-a). Here, the value a is a number greater than 0 and less than 1. That is, as a whole, fuel of 4 · Fi (average value = Fi for each cylinder) is injected per cycle of the engine 10 (crank angle 720 degrees). At this time, the CPU 71 stops the main feedback control and executes only the sub feedback control. The downstream target value Voxsref of the sub feedback control is set to a value Vrich corresponding to the weak rich air-fuel ratio AFR (see FIG. 5).

  By this filter regeneration control, the air-fuel mixture leaner than the stoichiometric air-fuel ratio (lean air-fuel ratio for filter regeneration control) is supplied to the second to fourth cylinders (a part of the plurality of cylinders). Therefore, “exhaust gas containing excess oxygen” is discharged from the second to fourth cylinders through the exhaust ports of the cylinders. The exhaust gas flows through the branch part 51a2, the branch part 51a3, and the branch part 51a4 (that is, the “first branch part”) communicating with the second cylinder, the third cylinder, and the fourth cylinder, respectively, to the collecting part 51b. Passes through the exhaust pipe 52. Accordingly, the oxygen storage amount OSA1 of the upstream catalyst 53 gradually increases. When the oxygen storage amount OSA1 substantially coincides with the maximum oxygen storage amount Cmax1 of the upstream catalyst 53, oxygen flows out of the upstream catalyst 53 and flows into the particulate collection filter. As a result, the particulates collected by the particulate collection filter 54 are combusted, and the regeneration of the particulate collection filter 54 is started.

  That is, in the filter regeneration control, the “excess oxidation component (generated by the combustion of the air-fuel mixture set to the filter regeneration control lean air-fuel ratio) in the partial cylinders (second to fourth cylinders)”. For example, exhaust gas containing oxygen) is supplied to the particulate collection filter 54 through the main exhaust passage (the first branch portion, the collecting portion, and the main passage portion). Accordingly, the particulates collected by the particulate collection filter 54 are burned. As a result, the particulate collection filter 54 starts to be regenerated. At this time, nitrogen oxide (NOx) generated in a large amount in the part of the cylinders is hardly purified by the upstream catalyst 53 and flows into the downstream catalyst 55.

  On the other hand, since the air-fuel mixture richer than the stoichiometric air-fuel ratio (rich air-fuel ratio for filter regeneration control) is supplied to the first cylinder (the other cylinder among the plurality of cylinders), the first cylinder “Exhaust gas containing excessive reducing components (unburned substances HC, CO)” is discharged through the exhaust port of one cylinder. The exhaust gas passes through a bypass passage (bypass passage constituent portion) composed of a part of the branch portion 51a1 and the bypass passage forming member 56 (without passing through the upstream catalyst 53 and the particulate collection filter 54). It flows directly into 55.

  Accordingly, nitrogen oxide flows into the downstream catalyst 55 through the main exhaust passage, and a reducing component that reduces the nitrogen oxide flows through the bypass passage. Accordingly, the nitrogen oxide is purified (reduced) in the downstream catalyst 55. As a result, the first control device can regenerate the particulate collection filter 54 while reducing the discharge amount of nitrogen oxides.

  Even during the filter regeneration control, the average air-fuel ratio of the air-fuel mixture supplied to each of the first to fourth cylinders (ie, all cylinders) is the stoichiometric air-fuel ratio or the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio. (In this example, the control is performed so that the air-fuel ratio is slightly rich AFR.) Therefore, the exhaust gas having the air-fuel ratio near the stoichiometric air-fuel ratio within the window W also flows into the downstream catalyst 55. Therefore, the downstream catalyst 55 can purify (reducing) nitrogen oxides with high efficiency. As a result, the amount of nitrogen oxide discharged during filter regeneration control can be made extremely small.

  When this filter regeneration control continues for a predetermined time Tsth or longer and the CPU 71 executes the process of step 730 in FIG. 7, the CPU 71 proceeds from step 730 to step 740 and sets the value of the filter regeneration request flag XPM to “0”. To do. As a result, the CPU 71 makes a “No” determination at step 610 in FIG. 6 to proceed to step 620 and step 630 to execute normal control again.

(Details of normal control)
Here, the main feedback control and the sub feedback control executed in step 630 will be described.

<Outline of main feedback control>
As described above, in the normal control, the first control device sets the upstream air-fuel ratio abyfs acquired based on the output value Vabyfs of the upstream air-fuel ratio sensor 66 to the upstream target air-fuel ratio abyfr (main feedback target value). Feedback control (main feedback control) is performed on the air-fuel ratio of the air-fuel mixture supplied to the engine so as to match. The upstream target air-fuel ratio abyfr is set to the stoichiometric air-fuel ratio during normal control. In other cases (for example, when the engine is warming up and when catalyst overheating is prevented), the upstream target air-fuel ratio abyfr may be set to a richer air-fuel ratio than the stoichiometric air-fuel ratio.

<Outline of sub feedback control>
As described above, in the first control device, in the normal control and the filter regeneration control, the output value Voxs of the downstream air-fuel ratio sensor 67 matches the downstream target value Voxsref that is a value corresponding to the downstream target air-fuel ratio. Thus, the air-fuel ratio of the air-fuel mixture supplied to the engine is feedback controlled (sub-feedback control). As shown in FIG. 5, the downstream target value Voxsref is a predetermined value ΔAF where the air-fuel ratio of the gas (detected gas) passing through the position where the downstream air-fuel ratio sensor 67 is disposed is slightly smaller than the stoichiometric air-fuel ratio. Only when the air-fuel ratio is equivalent to the rich air-fuel ratio (weak rich air-fuel ratio AFR), the value to be output by the downstream air-fuel ratio sensor 67 (for example, Voxsref = Vrich = 0.55 V) is set.

  Thus, the overall air-fuel ratio of the air-fuel mixture supplied to the engine 10, that is, the average (center, median) of the air-fuel ratio of the gas flowing into the downstream catalyst 55 is slightly richer than the stoichiometric air-fuel ratio. It is made to coincide with the fuel ratio (weak rich air-fuel ratio AFR). As shown in FIG. 3, the weak rich air-fuel ratio AFR is an air-fuel ratio that is slightly richer than the stoichiometric air-fuel ratio within the window W range.

  Incidentally, since the upstream catalyst 53 has an oxygen storage function, the air-fuel ratio change upstream of the upstream catalyst 53 appears as the air-fuel ratio change downstream of the upstream catalyst 53 after a predetermined delay time has elapsed. Therefore, it is difficult to suppress the transient air-fuel ratio fluctuation only by the sub feedback control. Therefore, the first control device executes the main feedback control to suppress transient air-fuel ratio fluctuations. At this time, the first control device uses a plurality of means shown in FIG. 8 which is a functional block diagram to prevent the occurrence of control interference between the main feedback control and the sub feedback control. Execute control. Hereinafter, a description will be given with reference to FIG. However, the following description is performed according to the modes of main feedback control and sub feedback control in normal control (control in which the fuel injection amount supplied to each cylinder does not differ between cylinders).

<Calculation of corrected basic fuel injection amount>
The cylinder intake air amount calculation means A1 includes an intake air amount Ga measured by the air flow meter 61, an engine speed NE obtained based on the output of the crank position sensor 64, and a table MapMc stored in the ROM 72. Based on the above, the in-cylinder intake air amount Mc (k) that is the intake air amount of the cylinder that reaches the current intake stroke is obtained. Here, the subscript (k) indicates a value for the current intake stroke. The in-cylinder intake air amount Mc (k) is stored in the RAM 73 while corresponding to the intake stroke of each cylinder. The in-cylinder intake air amount Mc (k) may be obtained using a known air amount estimation model (air model) that models the behavior of air in the intake passage of the engine 10.

  The upstream target air-fuel ratio setting (determination) means A2 sets the upstream target air-fuel ratio abyfr (k) to the theoretical air-fuel ratio. Since the upstream target air-fuel ratio abyfr (k) may be changed as described below, it is stored in the RAM 73 while corresponding to the intake stroke of each cylinder. That is, the upstream target air-fuel ratio setting (determining) means A2 is based on the engine speed NE, which is the operating state of the internal combustion engine 10, the accelerator pedal operation amount Accp (engine load), etc., and the upstream target air-fuel ratio abyfr (k ) May be determined.

The pre-correction basic fuel injection amount calculation means A3 uses the in-cylinder intake air amount Mc (k) obtained by the in-cylinder intake air amount calculation means A1 as shown in the following equation (1). By dividing by the upstream target air-fuel ratio abyfr (k) set by the setting means A2, the basic fuel injection amount Fbaseb for the current intake stroke for setting the air-fuel ratio of the engine to the upstream target air-fuel ratio abyfr (k) Find (k). The basic fuel injection amount Fbaseb (k) is also referred to as a pre-correction basic fuel injection amount Fbaseb (k) because it is a basic fuel injection amount before correction by a basic correction value KF, which will be described later. The uncorrected basic fuel injection amount Fbaseb (k) is stored in the RAM 73 while corresponding to the intake stroke of each cylinder.
Fbaseb (k) = Mc (k) / abyfr (k) (1)

  The post-correction basic fuel injection amount calculation means A4 is obtained by the basic correction value calculation means A16, which will be described later, based on the current pre-correction basic fuel injection quantity Fbaseb (k) obtained by the pre-correction basic fuel injection quantity calculation means A3. A corrected basic fuel injection amount Fbase (k) (= KF · Fbaseb (k)) is obtained by multiplying the basic correction value KF stored in the RAM 74. The basic correction value calculation means A16 for calculating the basic correction value KF will be described in detail later.

  As described above, the first control device includes the cylinder intake air amount calculation unit A1, the upstream target air-fuel ratio setting unit A2, the uncorrected basic fuel injection amount calculation unit A3, the corrected basic fuel injection amount calculation unit A4, and the basic correction. The corrected basic fuel injection amount Fbase (k) is obtained using the value calculation means A16.

<Calculation of final fuel injection amount>
As shown by the following equation (2), the final fuel injection amount calculating means A5 is a main feedback correction value updating means A15 which will be described later in the corrected basic fuel injection amount Fbase (k) (= KF · Fbaseb (k)). Is multiplied by the main feedback correction value KFmain obtained by the above, and the product (= Fbase (k) · KFmain) is added with a sub feedback correction value Fisub obtained by the PID controller A9, which will be described later. Find Fi (k). The final fuel injection amount Fi (k) is stored in the RAM 73 while corresponding to the intake stroke of each cylinder.
Fi (k) = (KF · Fbaseb (k)) · KFmain + Fisub = Fbase (k) · KFmain + Fisub (2)

  As described above, the first control apparatus corrects the corrected basic fuel injection amount Fbase (k) based on the main feedback correction value KFmain and the sub feedback correction value Fisub by the final fuel injection amount calculation means A5. The fuel injection amount Fi (k) is obtained. Further, the first control device sends an injection instruction signal to the injector 39 so that the fuel of the final fuel injection amount Fi (k) is injected from the injector 39 of the cylinder that reaches the current intake stroke. . In other words, the injection instruction signal includes information on the final fuel injection amount Fi (k) as the instruction injection amount.

<Calculation of sub feedback correction value>
The downstream target value setting means A6 outputs the downstream target value Voxsref. The downstream target value Voxsref is set to a value Vrich (for example, 0.55 (V)) corresponding to the above-described weak rich air-fuel ratio AFR. The downstream target value setting means A6 is based on the engine speed NE, which is the operating state of the internal combustion engine 10, the accelerator pedal operation amount Accp (engine load), and the like, similar to the upstream target air-fuel ratio setting means A2. And may be configured to change the downstream target value Voxsref.

The output deviation amount calculation means A7 is based on the following equation (3), at the current time set by the downstream target value setting means A6 (specifically, the current Fi (k) injection instruction start time). The output deviation amount DVoxs is obtained by subtracting the current output value Voxs of the downstream air-fuel ratio sensor 67 from the downstream target value Voxsref. The output deviation amount calculation means A7 outputs the obtained output deviation amount DVoxs to the low-pass filter A8.
DVoxs = Voxsref−Voxs (3)

The low-pass filter A8 is a primary digital filter. A transfer function A8 (s) representing the characteristics of the low-pass filter A8 is expressed by the following equation (4). In the equation (4), s is a Laplace operator, and τ1 is a time constant. The low-pass filter A8 substantially prohibits the passage of high-frequency components having a frequency (1 / τ1) or higher. The low-pass filter A8 inputs the value of the output deviation amount DVoxs and outputs the output deviation amount DVoxslow after passing through the low-pass filter, which is a value after low-pass filtering the output deviation amount DVoxs, to the PID controller A9.
A8 (s) = 1 / (1 + τ1 · s) (4)

The PID controller A9 performs proportional / integral / derivative processing (PID processing) on the output deviation amount DVoxslow after passing through the low-pass filter based on the following equation (5) to obtain a sub feedback correction value Fisub.
Fisub = Kp · DVoxslow + Ki · SDVoxslow + Kd · DDVoxslow… (5)

  In the above equation (5), Kp is a preset proportional gain (proportional constant), Ki is a preset integral gain (integral constant), and Kd is a preset differential gain (differential constant). SDVoxslow is a time integral value of the output deviation amount DVoxslow after passing through the low-pass filter, and DDVoxslow is a time differential value of the output deviation amount DVoxslow after passing through the low-pass filter. Thus, the sub feedback correction value Fisub is obtained.

  As is apparent from the above, the downstream target value setting means A6, the output deviation amount calculation means A7, the low-pass filter A8, and the PID controller A9 constitute sub feedback correction value calculation means.

<Main feedback control and calculation of main feedback correction value>
As described above, the upstream catalyst 53 has a catalytic function and an oxygen storage function. Therefore, in the fluctuation of the air-fuel ratio of the exhaust gas upstream of the upstream catalyst 53, “high frequency component having a relatively high frequency (high frequency component having the frequency of 1 / τ1 or more)” and “relatively low frequency and relatively low amplitude. A small low frequency component (a low frequency component that fluctuates at a frequency equal to or less than the frequency 1 / τ1 and has a relatively small deviation from the theoretical air-fuel ratio) is absorbed by the catalytic function and oxygen storage function of the upstream catalyst 53. Therefore, it is difficult to appear as a change in the air-fuel ratio of the exhaust gas downstream of the upstream side catalyst 53.

  Therefore, for example, compensation for “sudden change in air-fuel ratio in a transient operation state” in which the air-fuel ratio of exhaust gas greatly fluctuates at a high frequency equal to or higher than the frequency (1 / τ1) cannot be performed by sub-feedback control. Therefore, in order to reliably perform the compensation for “the sudden change in the air-fuel ratio in the transient operation state”, it is necessary to perform the main feedback control based on the output value Vabyfs of the upstream air-fuel ratio sensor 66.

  On the other hand, in the fluctuation of the air-fuel ratio of the exhaust gas upstream of the upstream side catalyst 53, “a low-frequency component having a relatively low frequency and a relatively large amplitude (for example, the frequency fluctuates below the frequency (1 / τ1) and the theoretical sky). The low-frequency component having a relatively large deviation from the fuel ratio) cannot be absorbed by the upstream catalyst 53. Therefore, such a variation in the air-fuel ratio upstream of the upstream catalyst 53 appears as a variation in the air-fuel ratio of the downstream exhaust gas with a predetermined delay. As a result, the output value Vabyfs of the upstream air-fuel ratio sensor 66 and the output value Voxs of the downstream air-fuel ratio sensor 67 become values indicating the air-fuel ratio shifted in the opposite directions with respect to the air-fuel ratio near the stoichiometric air-fuel ratio. There are cases. In this case, since the main feedback control and the sub-feedback control try to correct the air-fuel ratio of the air-fuel mixture supplied to the engine in opposite directions, interference in the air-fuel ratio control may occur between these controls.

  From the above, the first control device is a predetermined frequency component that can appear as a variation in the air-fuel ratio downstream of the upstream catalyst 53 among the frequency components in the variation in the output value Vabyfs of the upstream air-fuel ratio sensor 66. A value obtained by removing a low frequency component equal to or lower than the frequency (in this example, the frequency (1 / τ1)) from the output value Vabyfs of the upstream air-fuel ratio sensor 66 is used for the main feedback control. In this example, the value corresponding to the output value Vabyfs of the upstream air-fuel ratio sensor 66 used for the main feedback control is “the target air-fuel ratio for main feedback control abyfrtgt and the output value Vabyfs ( The deviation Daf from the upstream air-fuel ratio (detected air-fuel ratio) abyfs (k) based on k) is “a value DafHi subjected to high-pass filter processing”. As a result of executing the main feedback control based on this value DafHi, it is possible to avoid the occurrence of the above-described interference in air-fuel ratio control. More specifically, the main feedback correction value obtained as a result of the main feedback control is obtained as described below.

  Based on the output value Vabyfs of the upstream air-fuel ratio sensor 66 and the table Mapabyfs representing the relationship between the upstream air-fuel ratio sensor output value Vabyfs and the air-fuel ratio A / F shown in FIG. The present detected air-fuel ratio abyfs (k) detected by the upstream air-fuel ratio sensor 66 is obtained.

  The target air-fuel ratio delay means A11 is determined by the upstream target air-fuel ratio setting means A2 and, from among the upstream target air-fuel ratio abyfr stored in the RAM 73 while corresponding to the intake stroke of each cylinder, N stroke from the present time The upstream target air-fuel ratio abyfr at the time point before (N intake strokes) is read from the RAM 73 and set as the upstream target air-fuel ratio abyfr (kN). Here, the subscript (kN) indicates a value relative to the intake stroke before the N stroke (N · 180 ° CA, CA: crank angle in a four-cylinder engine) from the current intake stroke. . The upstream target air-fuel ratio abyfr (kN) is used to calculate the pre-correction basic fuel injection amount Fbaseb (kN) (= Mc (kN) / abyfr (kN)) of the cylinder that has reached the intake stroke N strokes before the present time. (See the above formula (1)).

  Here, the value N differs depending on the displacement of the internal combustion engine 10, the distance from the combustion chamber 25 to the upstream air-fuel ratio sensor 66, and the like. Thus, the upstream target air-fuel ratio abyfr (kN) N strokes before the current stroke is used for calculating the main feedback correction value because the fuel containing the fuel injected from the injector 39 and mixed in the combustion chamber 25 is used. This is because a dead time L1 corresponding to the N stroke is required until the air reaches the upstream air-fuel ratio sensor 66. The value N is desirably changed so as to decrease as the engine rotational speed NE increases and to decrease as the engine load (for example, the cylinder intake air amount Mc) increases.

  The low-pass filter A12 performs a low-pass filter process on the upstream target air-fuel ratio abyfr (kN) N strokes before the current time output from the target air-fuel ratio delay unit A11, and the target air-fuel ratio for main feedback control (upstream feedback) Control target air-fuel ratio) abyfrtgt (k) is calculated. Hereinafter, the main feedback control target air-fuel ratio abyfrtgt (k) is also simply referred to as “MFB target air-fuel ratio abyfrtgt (k)”. Thus, the MFB target air-fuel ratio abyfrtgt (k) is a value (based on) according to the upstream upstream target air-fuel ratio abyfr (kN) determined by the upstream target air-fuel ratio setting means A2. is there.

This low-pass filter A12 is a primary digital filter. The transfer characteristic A12 (s) of the low-pass filter A12 is expressed by the following equation (6). In equation (6), s is a Laplace operator, and τ is a time constant (a parameter related to responsiveness). This characteristic substantially prohibits the passage of high frequency components having a frequency (1 / τ) or higher.
A12 (s) = 1 / (1 + τ · s) (6)

  As described above, the air-fuel ratio value of the gas reaching the upstream air-fuel ratio sensor 66 is used as the input signal, and the air-fuel ratio value obtained based on the output value Vabyfs of the upstream air-fuel ratio sensor 66 is used as the output signal. In this case, the output signal is a signal very similar to a signal obtained by subjecting the input signal to a low-pass filter process (for example, a first-order lag process and a second-order lag process including so-called “smoothing process”). As a result, the MFB target air-fuel ratio abyfrtgt (k) generated by the low-pass filter A12 reaches the upstream air-fuel ratio sensor 66 with the exhaust gas having a desired air-fuel ratio corresponding to the upstream target air-fuel ratio abyfr (k−N). Is the value that the upstream air-fuel ratio sensor 66 will actually output.

Based on the following equation (7), the upstream air-fuel ratio deviation calculating means A13 detects “the current detection obtained by the table converting means A10 from the“ MFB target air-fuel ratio abyfrtgt (k) output from the low-pass filter A12 ”. The air-fuel ratio deviation Daf is obtained by subtracting the “air-fuel ratio abyfs (k)”. This air-fuel ratio deviation Daf is an amount representing a deviation from the target air-fuel ratio of the air-fuel ratio of the air-fuel mixture supplied into the cylinder at a time point before the N stroke.
Daf = abyfrtgt (k) −abyfs (k) (7)

The high-pass filter A14 is a primary filter. A transfer function A14 (s) representing the characteristics of the high-pass filter A14 is expressed by the equation (8). In the equation (8), s is a Laplace operator, and τ1 is a time constant. The time constant τ1 is the same time constant as the time constant τ1 of the low-pass filter A8. The high-pass filter A14 substantially prohibits the passage of low-frequency components having a frequency of (1 / τ1) or less.
A14 (s) = {1-1 / (1 + τ1 · s)} (8)

  The high-pass filter A14 receives the air-fuel ratio deviation Daf obtained by the upstream-side air-fuel ratio deviation calculating means A13, and after high-pass filtering the air-fuel ratio deviation Daf according to the characteristic expression expressed by the above equation (8). The main feedback control deviation DafHi, which is a value, is output.

  The main feedback correction value updating means A15 performs proportional processing on the main feedback control deviation DafHi, which is the output value of the high-pass filter A14. That is, the main feedback correction value updating unit A15 obtains the main feedback correction value KFmain by multiplying the main feedback control deviation DafHi by the proportional gain GpHi. The main feedback correction value KFmain is used when determining the final fuel injection amount Fi (k) as shown by the equation (2).

The main feedback correction value updating unit A15 performs main feedback correction by performing proportional / integral processing (PI processing) on the main feedback control deviation DafHi, which is an output value of the high-pass filter A14, based on the following equation (9). The value KFmain may be obtained.
KFmain = (Gphi · DafHi + Gihi · SDafHi) · KFB (9)

  In the above equation (9), Gphi is a preset proportional gain (proportional constant), and Gihi is a preset integral gain (integral constant). SDafHi is a time integral value of the deviation DafHi for main feedback control. The coefficient KFB is “1” in this example. However, the coefficient KFB may be variable depending on the engine speed NE, the cylinder intake air amount Mc, and the like.

  As is apparent from the above, the upstream target air-fuel ratio setting means A2, table conversion means A10, target air-fuel ratio delay means A11, low-pass filter A12, upstream air-fuel ratio deviation calculating means A13, high-pass filter A14, and main feedback correction value update The means A15 constitutes a main feedback correction value calculation means.

  As described above, the first control device connects the main feedback control system and the sub feedback control system in parallel and independently to the calculation system of the pre-correction basic fuel injection amount Fbaseb. That is, the first control device performs sub-feedback correction on the product of the main feedback control by multiplying the corrected basic fuel injection amount Fbase by the main feedback correction value KFmain and the corrected basic fuel injection amount Fbase and the main feedback correction value KFmain. The sub-feedback control by adding the value Fisub is executed independently. Further, as described above, the main feedback control deviation DafHi is a value obtained by subjecting the air-fuel ratio deviation Daf to the high-pass filter processing by the high-pass filter A14 and reflects the air-fuel ratio fluctuation that does not appear downstream of the upstream side catalyst 53. Value. Therefore, the main feedback correction value KFmain and the sub feedback correction value Fisub do not correct the air / fuel ratio fluctuations of the air-fuel mixture supplied to the engine so as to interfere with each other. In addition, sudden change of the air-fuel ratio in the transient operation state is suppressed by the main feedback control, and “gradual air-fuel ratio shift appearing as fluctuation of the air-fuel ratio downstream of the upstream catalyst 53” is eliminated by the sub-feedback control. Further, the sub-feedback control supplies the engine with “detection error with respect to the average of the air-fuel ratio” caused by “the characteristic deviation of the upstream air-fuel ratio sensor 66”, “the arrangement position of the upstream air-fuel ratio sensor 66”, and the like. It can be avoided that the “average of the air-fuel ratio of the air-fuel mixture” deviates from the window W.

<Calculation of basic correction value>
As described above, the sub-feedback correction value Fisub is calculated by performing proportional / integral / derivative processing on the output deviation amount DVoxslow after passing through the low-pass filter by the PID controller A9. However, the change in the air-fuel ratio of the engine 10 is slightly delayed due to the influence of the oxygen storage function of the upstream catalyst 53 and the like, and appears as a change in the air-fuel ratio of the exhaust gas downstream of the upstream catalyst 53. Therefore, if the steady-state error due to the detection accuracy of the air flow meter or the estimation accuracy of the air amount estimation model increases relatively rapidly due to a sudden change in the operation region, etc., the excess fuel injection amount due to the error will increase. The shortage cannot be compensated immediately by sub-feedback control alone.

  On the other hand, in the main feedback control without the influence of the delay due to the oxygen storage function, the high-pass filter process by the high-pass filter A14 is a process that achieves a function equivalent to the differentiation process (D process). Therefore, in the main feedback control in which the value after passing through the high-pass filter A14 is the input value of the main feedback correction value updating unit A15, the main feedback correction value is updated by the main feedback correction value updating unit A15 performing integration processing. Even if it is configured to obtain KFmain, the main feedback correction value KFmain including a substantial integral term cannot be calculated. Therefore, the main feedback control cannot compensate for a steady error in the fuel injection amount due to the detection accuracy of the air flow meter and the estimation accuracy of the air amount estimation model. As a result, there is a possibility that the emission amount of emissions such as HC, CO and NOx temporarily increases when the operation region changes.

From the above, the first control device obtains the “basic correction value KF for correcting the uncorrected basic fuel injection amount Fbaseb” expressed by the following equation (10), and the corrected basic fuel injection amount based on the basic correction value KF. Fbase (k) is obtained, and the corrected basic fuel injection amount Fbase (k) is further corrected by the main feedback correction value KFmain and the sub feedback correction value Fisub (see the above formula (2)).

In the above equation (10), Fbaset is a true command injection amount necessary for obtaining the target air-fuel ratio, and can be said to be a basic fuel injection amount that does not include an error. Hereinafter, Fbaset is referred to as “true basic fuel injection amount”. This true basic fuel injection amount Fbaset (kN) is calculated by the following equation (11).

  The above formula (11) will be further described. As described above, the detected air-fuel ratio abyfs (k) at the present time is the air-fuel ratio brought about by the injected fuel based on the final fuel injection amount Fi (k−N). Therefore, abyfs (k) · Fi (k−N) of the numerator on the right side in the equation (11) represents the in-cylinder air amount when the final fuel injection amount Fi (k−N) is determined. Therefore, as shown in the equation (11), the in-cylinder air amount (abyfs (k) · Fi (kN)) at the time when the final fuel injection amount Fi (kN) is determined is determined as the final fuel injection amount Fi (kN ) Is divided by the upstream target air-fuel ratio abyfr (kN) at the time of determination, the true basic fuel injection amount Fbaset (kN) is calculated.

On the other hand, the pre-correction basic fuel injection amount Fbaseb (k) used in the above equation (10) is obtained based on the above equation (1) described again below.
Fbaseb (k) = Mc (k) / abyfr (k) (1)

Therefore, the first control device obtains the basic correction value KF based on the following equation (12) obtained from the equations (1), (10), and (11), and uses the obtained basic correction value KF as the basic correction. The value KF is stored in the memory (backup RAM 74) in correspondence with the operation region when the value KF is calculated. This operating region is partitioned by, for example, the in-cylinder intake air amount Mc.

  Hereinafter, an actual calculation method of the basic correction value KF will be described with reference to FIG. 9 which is a detailed functional block diagram of the basic correction value calculation means A16. The basic correction value calculation means A16 includes each means A16a to A16f.

  The final fuel injection amount delay means A16a obtains the final fuel injection amount Fi (k−N) N strokes before the present time by delaying the current final fuel injection amount Fi (k). Actually, the final fuel injection amount delay means A 16 a reads the final fuel injection amount Fi (k−N) from the RAM 73.

  The target air-fuel ratio delay unit A16b obtains the upstream target air-fuel ratio abyfr (k−N) N strokes before the current time by delaying the current upstream target air-fuel ratio abyfr (k). Actually, the target air-fuel ratio delay unit A16b reads the upstream target air-fuel ratio abyfr (k−N) from the RAM 73.

  The true basic fuel injection amount calculation means A16c is the true basic fuel injection N strokes before the present time according to the above equation (11) (Fbaset (kN) = (abyfs (k) · Fi (kN) / abyfr (kN)) Find the quantity Fbaset (kN).

  The pre-correction basic fuel injection amount delay means A16d obtains the pre-correction basic fuel injection amount Fbaseb (k−N) N strokes before the present time by delaying the current pre-correction basic fuel injection amount Fbaseb (k). In practice, the pre-correction basic fuel injection amount delay means A16d reads the pre-correction basic fuel injection amount Fbaseb (k−N) from the RAM 73.

  The pre-filter basic correction value calculation means A16e calculates the true basic fuel injection amount Fbaset (kN) before correction according to the equation (KFbf = Fbaset (kN) / Fbaseb (kN)) based on the equation (12) described above. By dividing by the amount Fbaseb (kN), the pre-filter basic correction value KFbf is calculated.

  The low-pass filter A16f calculates a basic correction value KF by performing a low-pass filter process on the pre-filter basic correction value KFbf. This low-pass filter process is performed to stabilize the basic correction value KF (to remove the noise component superimposed on the pre-filter basic correction value KFbf). The basic correction value KF obtained in this way is stored and stored in the RAM 73 and the backup RAM 74 while being associated with the operation region to which the operation state N strokes before belongs. Note that the operation region in which the basic correction value KF is stored is divided by the load of the engine 10 (in-cylinder intake air amount Mc, accelerator pedal operation amount Accp, etc.), for example, as shown in FIG. This operating region may be divided by the engine speed NE and the engine load.

  As described above, the basic correction value calculation means A16 updates the basic correction value KF by using the means A16a to A16f each time the final fuel injection amount Fi (k) is calculated. Then, as shown in FIG. 8, the basic correction value calculation means A16 backs up the basic correction value KF stored in the operating region to which the operating state of the engine 10 belongs when calculating the final fuel injection amount Fi (k). The basic correction value KF read from the RAM 74 is provided to the corrected basic fuel injection amount calculation means A4. As a result, a steady error of the fuel injection amount (basic fuel injection amount before correction) is quickly compensated.

(Details of filter regeneration control)
Next, details of the filter regeneration control executed in step 650 will be described. In this case, the main feedback control is stopped. However, the CPU 71 obtains the in-cylinder intake air amount Mc (k) by the in-cylinder intake air amount calculation means A1. Then, the CPU 71 divides the in-cylinder intake air amount Mc (k) by the filter regeneration control rich air-fuel ratio TR set for the first cylinder, and the fuel injection amount Fib (k) # 1 for the first cylinder. Ask for.

Further, the CPU 71 divides the in-cylinder intake air amount Mc (k) by the filter regeneration control lean air-fuel ratio TL set for the second cylinder to the fourth cylinder, and the second cylinder, the third cylinder, and the fourth cylinder. Cylinder fuel injection amounts Fib (k) # 2, Fib (k) # 3, and Fib (k) # 4 are obtained. Note that the filter regeneration control rich air-fuel ratio TR and the filter regeneration control lean air-fuel ratio TL are determined in advance so that the following expression (13) is satisfied, and stored in the ROM 72. That is, the CPU 71 reads out the filter regeneration control rich air-fuel ratio TR and the filter regeneration control lean air-fuel ratio TL from the ROM 72. In the equation (13), ST is the stoichiometric air fuel ratio. The denominator “3” on the left side of (13) is a value obtained by subtracting “1” from the number of cylinders of the engine 10 (n = 4). The expression (13) indicates that “the excess per one cylinder from the stoichiometric air-fuel ratio generated by the air-fuel mixture supplied to the first cylinder” represented by the left side is represented by “second to fourth”. This means that the fuel shortage per cylinder from the stoichiometric air-fuel ratio generated by the air-fuel mixture supplied to the cylinders is equal.

Then, the CPU 71 obtains the “sub feedback correction value Fisub” using the downstream target value setting means A6, the output deviation amount calculating means A7, the low pass filter A8 and the PID controller A9, and according to the following equation (14), A final fuel injection amount Fi (k) #N is calculated. #N represents a cylinder. That is, for example, Fi (k) # 1 indicates the current fuel injection amount for the first cylinder.
Fi (k) # N = Fib (k) # N + Fisub (14)

(Actual operation)
Next, the actual operation of the first control device will be described. Hereinafter, for convenience of explanation, “MapX (a1, a2,...)” Represents a table for obtaining a value X having a1, a2,. If the argument value is a sensor detection value, the current value is applied to the argument value.

<Calculation of final fuel injection amount Fi (k)>
The CPU 71 performs the routine for calculating the final fuel injection amount Fi and the injection instruction shown in the flowchart of FIG. 11 according to a predetermined crank angle (for example, BTDC 90 ° CA) before the intake top dead center of each cylinder. Each time it becomes, it is executed repeatedly. Therefore, when the crank angle of an arbitrary cylinder reaches the predetermined crank angle, the CPU 71 starts processing from step 1100 and proceeds to step 1105, and whether or not the current operating state satisfies the fuel cut condition (deceleration fuel cut condition). Determine whether.

  The fuel cut condition is satisfied, for example, when the accelerator pedal operation amount Accp is “0” and the engine speed NE is equal to or higher than the fuel cut speed NEFC. This fuel cut condition is not satisfied when the accelerator pedal operation amount Accp is not "0" during the fuel cut (when the fuel cut condition is satisfied) or when the engine speed NE is equal to or lower than the fuel cut return speed NEFK. Thus, the fuel cut return condition is satisfied. The fuel cut return rotational speed NEFK is smaller than the fuel cut rotational speed NEFC. The completion of the fuel cut control and the resumption of fuel injection is also referred to as “fuel cut return”.

  If the fuel cut condition is satisfied, the CPU 71 makes a “Yes” determination at step 1105 to directly proceed to step 1195 to end the present routine tentatively. Accordingly, since step 1150 for instructing fuel injection is not executed, fuel injection is stopped (fuel cut control is executed).

  On the other hand, if the fuel cut condition is not satisfied at the time of determination in step 1105, the CPU 71 determines “No” in step 1105, proceeds to step 1110, and based on the table MapMc (NE, Ga), the current intake stroke. The in-cylinder intake air amount Mc (k) this time taken into the cylinder (hereinafter also referred to as “fuel injection cylinder”) is estimated and determined. Next, the CPU proceeds to step 1115 to determine whether or not the value of the filter regeneration request flag XPM is “1”.

  Now, the description will be continued assuming that a request for regenerating the particulate collection filter 54 has not occurred, and therefore the value of the filter regeneration request flag XPM is “0”. The value of the filter regeneration request flag XPM is changed by a filter regeneration request flag XPM operation routine of FIG.

In this case, the CPU 71 sequentially performs the processing from step 1120 to step 1150 described below, proceeds to step 1195, and once ends this routine.
Step 1120: The CPU 71 gives an instruction to close the on-off valve 57 to the on-off valve 57, and shuts off the bypass passage of the bypass passage forming member 56. Thereby, all the exhaust gas discharged from the engine 10 passes through the collecting portion 51b and the exhaust pipe 52 (that is, the main passage portion).
Step 1125: The CPU 71 sets the theoretical air fuel ratio ST to the upstream target air fuel ratio abyfr (k).
Step 1130: The CPU 71 calculates a basic correction value KF stored in the operation region to which the current operation state belongs, out of the basic correction values KF calculated for each operation region in the backup RAM 74 and calculated by a routine described later. Is read. Further, the CPU 71 reads a main feedback correction value KFmain obtained by a routine described later.

Step 1135: The CPU 71 calculates the uncorrected basic fuel injection amount Fbaseb (k) by dividing the in-cylinder intake air amount Mc (k) obtained in step 1110 by the upstream target air-fuel ratio abyfr (k). To do. The uncorrected basic fuel injection amount Fbaseb (k) is stored in the RAM 73 while corresponding to the intake stroke of each cylinder.
Step 1140: The CPU 71 sets a value obtained by multiplying the basic fuel injection amount Fbaseb (k) before correction by the basic correction value KF as the corrected basic fuel injection amount Fbase.

Step 1145: The CPU 71 adds the sub-feedback correction value Fisub to the product of the corrected basic fuel injection amount Fbase and the main feedback correction value KFmain according to the above equation (2) (and the above equation (14)), and this final fuel for this time Obtain the injection amount Fi (k).
Step 1150: The CPU 71 issues an injection instruction to the injector 39 so that fuel of the final fuel injection amount Fi (k) is injected from the injector 39 for the fuel injection cylinder.

  Through the above processing, when the value of the filter regeneration request flag XPM is “0”, the fuel injection amount Fi determined with the theoretical air-fuel ratio ST as the upstream target air-fuel ratio abyfr (k) for all the cylinders. (k) fuel is injected. In this way, when the value of the filter regeneration request flag XPM is “0”, the above-described normal control is executed.

  Next, processing when the value of the filter regeneration request flag XPM is changed to “1” will be described. In this case, the CPU 71 determines “Yes” at step 1115 and proceeds to step 1155 to give an instruction to close the on-off valve 57 to the on-off valve 57, thereby blocking the bypass passage of the bypass passage forming member 56. Next, the CPU 71 proceeds to step 1160 to determine whether or not the fuel injection cylinder is the first cylinder.

  Assuming that the fuel injection cylinder is the first cylinder, the CPU 71 determines “Yes” in step 1160 and proceeds to step 1165 to set the rich air-fuel ratio TR for filter regeneration control to the upstream target air-fuel ratio abyfr (k). Set. As described above, the filter regeneration control rich air-fuel ratio TR is a predetermined air-fuel ratio richer than the theoretical air-fuel ratio ST. Next, the CPU 71 proceeds to step 1170 to set the basic correction value KF to “1” and the main feedback correction value KFmain to “1”. After that, the CPU 71 performs the processing from step 1135 to step 1150 described above, proceeds to step 1195, and once ends this routine.

  With the above processing, when the value of the filter regeneration request flag XPM is “1”, the air-fuel ratio of the air-fuel mixture supplied to the first cylinder is controlled to the rich air-fuel ratio TR for filter regeneration control.

  On the other hand, when the CPU 71 proceeds to step 1160, if the fuel injection cylinder is a cylinder other than the first cylinder (second to fourth cylinders), the CPU 71 determines “No” in step 1160 and proceeds to step 1175. Then, the lean air-fuel ratio TL for filter regeneration control is set to the upstream target air-fuel ratio abyfr (k). As described above, the lean air-fuel ratio TL for filter regeneration control is an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio ST, and the above equation (13) is established with the rich air-fuel ratio TR for filter regeneration control. It is predetermined. Then, the CPU 71 performs processing of step 1170 and steps 1135 to 1150, proceeds to step 1195, and once ends this routine.

  With the above processing, when the value of the filter regeneration request flag XPM is “1”, the air-fuel ratio of the air-fuel mixture supplied to the second to fourth cylinders is controlled to the lean air-fuel ratio TL for filter regeneration control. In this way, when the value of the filter regeneration request flag XPM is “1”, the above-described filter regeneration control is executed.

<Calculation of main feedback correction value>
Next, the operation for calculating the main feedback correction value KFmain will be described. The CPU 71 is configured to repeatedly execute the routine shown in the flowchart of FIG. 12 at every elapse of the execution cycle Δt (constant). Accordingly, the CPU 71 starts processing from step 1200 at a predetermined timing, sequentially performs the processing of steps 1205 and 1210 described below, and then proceeds to step 1215. The execution period Δt is set to a time shorter than the generation time interval between two consecutive injection instructions when the engine speed NE is the maximum engine speed assumed, for example.

  Step 1205: The CPU 71 obtains the MFB target air-fuel ratio abyfrtgt (k) according to the simple low-pass filter equation (abyfrtgt (k) = α · abyfrtgtold + (1−α) · abyfr (k−N)) described in step 1205. . This process corresponds to the process of the target air-fuel ratio delay unit A11 and the low-pass filter A12 described above. Here, α is a constant larger than 0 and smaller than 1, and is set according to the time constant τ of the low-pass filter A12. abyfrtgtold is “the target air-fuel ratio for MFB abyfrtgt calculated when this routine was executed last time” set in the next step 1210. abyfrtgtold is referred to as the previous MFB target air-fuel ratio (previous main feedback control target air-fuel ratio). abyfr (k−N) is the upstream target air-fuel ratio N strokes before the current time. However, in this example, the main feedback control is executed only when the value of the filter regeneration request flag XPM is “0” and normal control is executed (see step 1215 described later). The upstream target air-fuel ratio abyfr in the normal control is the theoretical air-fuel ratio ST (see step 1125 in FIG. 11 described above). Therefore, the process of step 1205 can be replaced with a process of setting the MFB target air-fuel ratio abyfrtgt (k) to the theoretical air-fuel ratio ST.

  Step 1210: The CPU 71 stores the MFB target air-fuel ratio abyfrtgt (k) calculated in step 1205 in the previous MFB target air-fuel ratio abyfrtgtold for the next execution of this routine.

  Next, the CPU 71 proceeds to step 1215 to determine whether or not the value of the main feedback control condition satisfaction flag XmainFB is “1”. The value of the main feedback control condition satisfaction flag XmainFB is set to “1” when the main feedback control condition is satisfied, and is set to “0” when the main feedback control condition is not satisfied. Further, the value of the main feedback control condition satisfaction flag XmainFB is set to “0” in an initial routine executed when an ignition key switch (not shown) is changed from the off position to the on position. The main feedback control condition is satisfied when, for example, all of the following conditions J1 to J3 are satisfied.

J1: The upstream air-fuel ratio sensor 66 is activated.
J2: The fuel cut condition is not established.
J3: The value of the filter regeneration request flag XPM is “0”.

  Now, assuming that the value of the main feedback control condition satisfaction flag XmainFB is “1”, the CPU 71 determines “Yes” in step 1215, sequentially performs the processing of steps 1220 to 1235 described below, Proceeding to 1295, the present routine is ended once.

Step 1220: The CPU 71 obtains the current detected air-fuel ratio abyfs (k) by converting the current output value Vabyfs of the upstream air-fuel ratio sensor 66 based on the table Mapabyfs (Vabyfs) shown in FIG.
Step 1225: The CPU 71 subtracts the current detected air-fuel ratio abyfs (k) from the MFB target air-fuel ratio abyfrtgt (k) according to the equation described in step 1225, which is the above equation (7), to thereby obtain the air-fuel ratio deviation Daf. Ask.

Step 1230: The CPU 71 obtains a main feedback control deviation DafHi by applying a high-pass filter process having the characteristic expressed by the above equation (8) to the air-fuel ratio deviation Daf. This processing corresponds to the processing by the high-pass filter A14 described above.
Step 1235: The CPU 71 obtains a main feedback correction value KFmain by adding a value “1” to the product obtained by multiplying the main feedback control deviation DafHi by the proportional gain GpHi.

On the other hand, if the value of the main feedback control condition satisfaction flag XmainFB is “0”, the CPU 71 determines “No” in step 1215, performs the processes of step 1240 and step 1245 described below in order, Proceeding to 1295, the present routine is ended once.
Step 1240: The CPU 71 sets the main feedback correction value KFmain to “1”.
Step 1245: The CPU 71 sets the basic correction value KF to “1”.

  Thus, when the main feedback control condition is not satisfied (XmainFB = 0), the update of the main feedback correction value KFmain is stopped and the value of the main feedback correction value KFmain is set to “1”. The control is stopped (reflecting the main feedback correction value KFmain to the final fuel injection amount Fi is stopped). When the main feedback control condition is not satisfied, the basic correction value KF is set to “1”, and the reflection of the basic correction value KF to the final fuel injection amount Fi is stopped.

<Calculation of sub feedback correction value>
Next, an operation for calculating the sub feedback correction value Fisub will be described. The CPU 71 repeatedly executes the routine shown in the flowchart of FIG. 13 every time a predetermined time elapses. Therefore, when the predetermined timing comes, the CPU 71 starts processing from step 1300 and proceeds to step 1305 to determine whether or not the value of the sub feedback control condition satisfaction flag XsubFB is “1”.

  The value of the sub feedback control condition satisfaction flag XsubFB is set to “1” when the sub feedback control condition is satisfied, and is set to “0” when the sub feedback control condition is not satisfied. Further, the value of the sub-feedback control condition satisfaction flag XsubFB is set to “0” in the initial routine (not shown). The sub feedback control condition is satisfied when, for example, all of the following conditions K1 and K2 are satisfied.

K1: The downstream air-fuel ratio sensor 67 is activated.
K2: The fuel cut condition is not established.
The sub feedback control condition does not include that the value of the filter regeneration request flag XPM is “0”. In other words, the sub feedback control condition is executed in both the normal control and the filter regeneration control as described above.

  Now, assuming that the value of the sub-feedback control condition satisfaction flag XsubFB is “1”, the CPU 71 determines “Yes” in step 1305, performs the processing of steps 1310 to 1335 described below in order, Proceed to 1395 to end the present routine tentatively.

Step 1310: The CPU 71 reduces the output deviation amount DVoxs by subtracting the current output value Voxs of the downstream air-fuel ratio sensor 67 from the downstream target value Voxsref according to the equation described in step 1310, which is the above equation (3). Ask. As described above, the downstream target value Voxsref is set to Vrich corresponding to the weak rich air-fuel ratio AFR.
Step 1315: The CPU 71 calculates the output deviation amount DVoxslow after passing through the low-pass filter by performing low-pass filter processing having the characteristic expressed by the above equation (4) on the output deviation amount DVoxs.

Step 1320: The CPU 71 obtains a differential value DDVoxslow of the output deviation amount DVoxslow after passing through the low-pass filter based on the following equation (13). In the equation (13), DVoxslow1 is the previous value of “the output deviation amount DVoxslow after passing through the low-pass filter” updated in step 1335 (described later) at the previous execution of this routine. Δt is the time from the time when this routine was executed last time to the time when this routine was executed this time.
DDVoxslow = (DVoxslow-DVoxslow1) / Δt (13)

Step 1325: The CPU 71 obtains the sub feedback correction value Fisub according to the equation shown in step 1325 which is the equation (5).
Step 1330: The CPU 71 adds the output deviation amount DVoxslow after passing through the low-pass filter obtained in the above step 1315 to the integrated value SDVoxslow of the output deviation amount DVoxslow after passing through the low-pass filter at that time, to thereby obtain a new output deviation amount after passing through the low-pass filter Find the integrated value SDVoxslow of DVoxslow.
Step 1335: The CPU 71 stores the output deviation amount DVoxslow after passing through the low-pass filter obtained in step 1315 in the previous value DVoxslow1 of the output deviation amount DVoxslow after passing through the low-pass filter.

  On the other hand, if the value of the sub feedback control condition satisfaction flag XsubFB is “0” at the time of determination in step 1305, the CPU 71 determines “No” in step 1305 and proceeds to step 1340 to execute the sub feedback correction value Fisub. Is set to “0”, and in step 1345, the integrated value SDVoxslow of the output deviation DVoxslow after passing through the low-pass filter is set to “0”. Then, the process proceeds to step 1395 to end the present routine tentatively.

  Thus, when the sub-feedback control condition is not satisfied (XsubFB = 0), the sub-feedback correction value Fisub is set to “0”, so the air-fuel ratio corresponding to the output value Voxs of the downstream air-fuel ratio sensor 67 is reduced. Feedback control is not performed. Note that immediately after the value of the filter regeneration request flag XPM changes from “0” to “1” and / or immediately after the value of the filter regeneration request flag XPM changes from “1” to “0”, sub-feedback is performed. The correction value Fisub may be set to “0” and the integral value SDVoxslow may be set to “0”.

<Calculation, storage and storage of basic correction values>
The CPU 71 is configured to repeatedly execute the routine shown in the flowchart of FIG. 14 prior to the execution of the routine shown in FIG. Therefore, the CPU 71 starts processing from step 1400 at a predetermined timing, and proceeds to step 1405 to determine whether or not both the values of the main feedback control condition satisfaction flag XmainFB and the sub feedback control condition satisfaction flag XsubFB are “1”. judge. Now, assuming that both of these flags are “1”, the CPU 71 sequentially performs the processing from step 1410 to step 1430 described below, proceeds to step 1495, and once ends this routine.

  Step 1410: The CPU 71 calculates the product of the detected air-fuel ratio abyfs (k) at the current time and the final fuel injection amount Fi (kN) N strokes before the current time according to the equation described in Step 1410 which is the above equation (11). By dividing by the upstream target air-fuel ratio abyfr (kN) N strokes before the current time, the true basic fuel injection amount Fbaset (kN) N strokes before the current time is calculated. Note that the final fuel injection amount Fi (k−N) N strokes before the current time and the upstream target air-fuel ratio abyfr (k−N) N strokes before the current time are both read from the RAM 73.

  Step 1415: The CPU 71 calculates the true basic fuel injection amount Fbaset (kN) N strokes before the current time calculated in step 1410 based on the equation described in step 1415, which is the same equation as the above equation (12). Is divided by the pre-correction basic fuel injection amount Fbaseb (kN) before N strokes to calculate the current value KFnew (pre-filter basic correction value KFbf) that is the basis of the basic correction value KF. The uncorrected basic fuel injection amount Fbaseb (k−N) N strokes before the current time is read from the RAM 73.

Step 1420: The CPU 71 reads out from the backup RAM 74 the basic correction value KF stored in the backup RAM 74 corresponding to the operating region to which the operating state of the engine 10 at the time N strokes before the current time belongs. The read basic correction value KF is a past basic correction value KFold.
Step 1425: The CPU 71 calculates a new basic correction value KF (final basic correction value KF) according to the simple low-pass filter equation (KF = β · KFold + (1−β) · KFnew) described in Step 1425. Here, β is a constant larger than 0 and smaller than 1.

Step 1430: The CPU 71 stores and stores the basic correction value KF obtained in step 1425 in a storage area in the backup RAM 74 corresponding to the operation area to which the operation state of the engine 10 at the time point N strokes before the current time point belongs. .
In this way, when the value of the main feedback control condition satisfaction flag XmainFB is “1”, the basic correction value KF is updated and stored.

  On the other hand, if any of the value of the main feedback control condition satisfaction flag XmainFB and the value of the sub feedback control condition satisfaction flag XsubFM is “0”, the CPU 71 determines “No” in step 1405 and directly goes to step 1495. Proceed to end this routine. In this case, updating of the basic correction value KF and storage / storage processing of the basic correction value KF in the backup RAM 74 are not executed.

<Operation of filter regeneration request flag>
Next, an operation for operating the filter regeneration request flag XPM will be described. The CPU 71 is configured to execute the routine shown by the flowchart in FIG. Accordingly, the CPU 71 proceeds to step 1505 at a predetermined timing, and determines whether or not the value of the filter regeneration request flag XPM is currently set to “1”. The value of the filter regeneration request flag XPM is set to “0” in the above-described initial routine.

  The description will be continued assuming that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 makes a “No” determination at step 1505, executes the processing of steps 1510 and 1515 described below, and then proceeds to step 1520.

  Step 1510: A coefficient k1 is obtained based on the current detected air-fuel ratio abyfs obtained based on the current output value Vabyfs of the upstream air-fuel ratio sensor 66 and the map shown in Step 1510. According to this map, the coefficient k1 increases as the detected air-fuel ratio abyfs becomes farther from the theoretical air-fuel ratio ST. In particular, when the detected air-fuel ratio abyfs moves away from the stoichiometric air-fuel ratio ST in the region on the rich side of the stoichiometric air-fuel ratio ST, the coefficient is larger than when the detected air-fuel ratio abyfs moves away from the stoichiometric air-fuel ratio ST in the region on the lean side of the stoichiometric air-fuel ratio ST. k1 becomes larger. The coefficient k1 is determined in this way because even if the intake air amount Ga is constant, the more the air-fuel ratio of the air-fuel mixture supplied to the engine 10 deviates from the stoichiometric air-fuel ratio ST, the fine particles generated from the engine 10 Rely on the increase in quantity.

  Step 1515: The CPU 71 measures the coefficient k1 and the current air flow meter 61 at the current particle collection amount SPM (estimated value of the amount (total amount) of particles collected by the particle collection filter 54) at the current time. A value obtained by adding the product (k1 · Ga) to the intake air amount Ga is set as a new particulate collection amount SPM. This particulate collection amount SPM is stored in the backup RAM 74.

  Next, the CPU 71 proceeds to step 1520 to determine whether or not the particulate collection amount SPM updated (estimated) in step 1515 is equal to or greater than a threshold value SPMth. At this time, if the particulate collection amount SPM is smaller than the threshold value SPMth, the CPU 71 makes a “No” determination at step 1520 to directly proceed to step 1595 to end the present routine tentatively.

  Thereafter, when the engine 10 is operated, the value of the particulate collection amount SPM gradually increases and becomes equal to or greater than the threshold value SPMth. At this time, when the CPU 71 proceeds to step 1520, the CPU 71 determines “Yes” in step 1520, proceeds to step 1525, and sets the value of the filter regeneration request flag XPM to “1”. Then, the CPU 71 proceeds to step 1595 to end the present routine tentatively. As a result, the CPU 71 determines “Yes” in step 1115 of FIG. 11 and executes filter regeneration control. Accordingly, the regeneration of the particulate collection filter 54 starts.

  Next, when the CPU 71 proceeds to step 1505 in FIG. 15, the CPU 71 determines “Yes” at step 1505 and proceeds to step 1530 to continue the filter regeneration control duration (that is, the value of the filter regeneration request flag XPM is It is determined whether or not the elapsed time (Ts after the change from “0” to “1”) Ts is equal to or longer than a predetermined time Tsth (filter regeneration control execution time Tsth).

  The present time is immediately after the value of the filter regeneration request flag XPM is changed from “0” to “1”. Therefore, the filter regeneration control duration Ts does not reach the predetermined time Tsth. Therefore, the CPU 71 makes a “No” determination at step 1530 to directly proceed to step 1595 to end the present routine tentatively.

Thereafter, the filter regeneration control is continuously executed, so that the filter regeneration control duration Ts reaches a predetermined time Tsth. At this time, the CPU 71 makes a “Yes” determination at step 1530 following step 1505, performs the processing of step 1535 and step 1540 described below in order, proceeds to step 1595, and once ends this routine.
Step 1535: The value of the particulate collection amount SPM is set to “0” (cleared).
Step 1540: The value of the filter regeneration request flag XPM is set to “0”.

  As a result, the CPU 71 determines “No” in step 1115 of FIG. 11 and resumes normal control. Further, the CPU 71 makes a “No” determination at step 1505 in FIG. 15, and starts updating the particulate collection amount SPM again.

  As described above, the first control device controls the air-fuel ratio of the air-fuel mixture supplied to all of the cylinders to be close to the theoretical air-fuel ratio when the value of the filter regeneration request flag XPM is “0”. At the same time, exhaust gas discharged from all cylinders is discharged to the atmosphere through the upstream catalyst 53, the particulate collection filter 54, and the downstream catalyst 55. Therefore, the discharge amount of unburned matter, nitrogen oxides and fine particles can be extremely reduced. Further, when the value of the filter regeneration request flag XPM is changed to “1”, the first control device controls the air-fuel ratio of the air-fuel mixture supplied to the first cylinder for filter regeneration control over a predetermined period (Tsth). The rich air-fuel ratio TR is set, the air-fuel ratio of the second to fourth cylinders is set to the filter regeneration control lean air-fuel ratio TL, and the exhaust gas discharged from the first cylinder is sent to the downstream catalyst 55 via the bypass passage. The exhaust gas that is directly supplied and discharged from the second to fourth cylinders is supplied to the upstream catalyst 53, the particulate collection filter 54, and the downstream catalyst 55. As a result, since oxygen is supplied to the particulate collection filter, the particulate collection filter 54 is regenerated. Furthermore, since the average of the air-fuel ratio of the gas flowing into the downstream catalyst 55 becomes substantially the stoichiometric air-fuel ratio, the nitrogen oxide flowing into the downstream catalyst 55 can be purified by the downstream catalyst 55.

(Second Embodiment)
Next, a control device for an internal combustion engine according to a second embodiment of the present invention (hereinafter also referred to as “second control device”) will be described. The second control device includes reduction state determination means for determining whether or not the downstream catalyst 55 has reached a “reduction state in which a predetermined amount of nitrogen oxides can be purified”. When it is determined that the side catalyst 55 has reached the “reduced state”, the execution of the filter regeneration control is permitted (starts if there is a filter regeneration request). Is different. Therefore, the following description will be made with this difference as the center.

  More specifically, even if a filter regeneration request is generated, the second control device integrates the intake air amount after the previous (immediately preceding) fuel cut control is stopped (after the fuel cut is restored). Normal control is performed until the value (cumulative intake air amount after fuel cut return) tGaS becomes equal to or greater than the threshold Gth, and filter regeneration control is performed over a predetermined period from the time when the accumulated value tGaS becomes equal to or greater than the threshold Gth. This intake air amount integrated value tGaS is obtained when the average of the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is set to the weak rich air-fuel ratio AFR by normal control, so that “the excess reducing component is discharged” Since it is the “integrated value of the intake air amount Ga”, the “amount of oxidized component discharged from the engine 10 that oxidizes the reduced component” is subtracted from the “amount of reduced component that is unburned material discharged from the engine 10”. This is an integrated value of the “excess amount of reducing component” that is the amount (hereinafter referred to as “first integrated value”).

  Hereinafter, the actual operation of the second control device will be described. The CPU 71 of the second control device performs the above-described control according to the procedure shown in the schematic flowchart shown in FIG. The CPU 71 is configured to repeat the procedure shown in FIG. 16 every elapse of a predetermined time. In FIG. 16, steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as those given for such steps in FIG. 6. A detailed description of these steps is omitted.

  The CPU 71 starts processing from step 1600 at a predetermined timing, proceeds to step 1610, and determines whether or not the current operation state satisfies the fuel cut condition (deceleration fuel cut condition). Step 1610 is a step for performing the same processing as step 1105 of FIG. 11 described above. At this time, if the fuel cut condition is satisfied, the CPU 71 proceeds directly from step 1610 to step 1695 to end the present routine tentatively. Thereby, fuel injection is not performed but fuel cut control is performed.

  On the other hand, if the fuel cut condition is not satisfied, the CPU 71 determines “No” in step 1610 and proceeds to step 610 to determine whether or not the value of the filter regeneration request flag XPM is “1”. The value of the filter regeneration request flag XPM is set by a filter regeneration request flag operation routine shown in FIG.

  Assume that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 makes a “No” determination at step 610, proceeds to step 620 to close the on-off valve 57, and executes normal control at step 630. Accordingly, the average of the air-fuel ratios of the air-fuel mixture supplied to each of the first to fourth cylinders (all of the plurality of cylinders) becomes the “weakly rich air-fuel ratio AFR” that is the air-fuel ratio near the stoichiometric air-fuel ratio. The air-fuel ratio (fuel injection amount for each cylinder) of the air-fuel mixture supplied to each cylinder is controlled.

  Next, the CPU 71 proceeds to step 1630 to set the value of the regeneration execution flag (filter regeneration control execution flag) XJ to “0”. The regeneration execution flag XJ is set to “1” when the filter regeneration control is being executed (see step 1640 described later), and “0” in other cases (during normal control and fuel cut control, etc.). "Is set.

  On the other hand, the CPU 71 executes the filter regeneration request flag XPM operation routine shown by the flowchart in FIG. 17 every elapse of a predetermined time. In FIG. 17, steps for performing the same processing as the steps shown in FIG. 15 are given the same reference numerals as those assigned to such steps in FIG. 15. A detailed description of these steps is omitted.

  The CPU 71 starts processing from step 1700 at a predetermined timing. In step 1505, the CPU 71 determines whether or not the value of the filter regeneration request flag XPM is currently set to “1”. The value of the filter regeneration request flag XPM is set to “0” in the above-described initial routine.

  The description will be continued assuming that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 makes a “No” determination at step 1505 to execute the processes of steps 1510 to 1520 described above. Further, when the CPU 71 determines “Yes” in step 1520, the CPU 71 executes the process of step 1525 described above. As a result, when the value of the particulate collection amount SPM reaches the threshold value SPMth by operating the engine 10 for a predetermined period or longer, the value of the filter regeneration request flag XPM is set to “1”.

  At this time, the CPU 71 determines “No” in step 1610 of FIG. 16 and also determines “Yes” in step 610. The process proceeds to step 1620, where the integrated value tGaS of the intake air amount after returning from the fuel cut is obtained. It is determined whether or not the threshold value Gth is exceeded.

  The integrated value tGaS of the intake air amount is calculated by an integrated gas amount calculation routine shown in FIG. Specifically, the CPU 71 starts processing from step 1800 in FIG. 18 every elapse of the predetermined time Δt1 and proceeds to step 1810 to determine whether or not the current time is under fuel cut control. If the present time is during the fuel cut control, the CPU 71 determines “Yes” in step 1810 and proceeds to step 1820 to set the integrated value tGaS of the intake air amount to “0”. Thereafter, the CPU 71 proceeds to step 1895 to end the present routine tentatively.

  On the other hand, when the CPU 71 proceeds to step 1810 and the fuel cut control is not in progress, the CPU 71 makes a “No” determination at step 1810, performs the processing of step 1830 and step 1840 described below in order, and proceeds to step 1895. This routine is finished once.

Step 1830: The CPU 71 increases the integrated value tGaS of the intake air amount by a value (Ga · Δt1) obtained by multiplying the intake air amount Ga detected by the air flow meter 61 at that time by a predetermined time Δt1.
Step 1840: The CPU 71 limits the value of the intake air amount integrated value tGaS so that the integrated value tGaS of the intake air amount does not exceed a predetermined maximum value tGaSm.

  Through the above processing, the integrated value tGaS of the intake air amount becomes a value (first integrated value) obtained by integrating the intake air amount Ga from the fuel cut return time point. In other words, the integrated value tGaS of the intake air amount is set to “0” during the fuel cut, and the average of the air-fuel ratio of the air-fuel mixture that is executed after the fuel cut is restored and supplied to the engine 10 is set to the weak rich air-fuel ratio AFR. This is the integrated value of the intake air amount Ga in the normal control to be set. In normal control, an amount obtained by subtracting “amount of oxidized component discharged from engine 10” that oxidizes the reduced component from “amount of reduced component that is unburned material discharged from engine 10” per unit time. A certain “excessive amount of reducing component” is proportional to the intake air flow rate Ga. Accordingly, the integrated value tGaS of the intake air amount is a value (first integrated value) obtained by integrating the excessive amount of the reducing component from the fuel cut return time point.

  Assuming that the predetermined time has not elapsed since the fuel cut return time at present, the integrated value tGaS of the intake air amount is not equal to or greater than the threshold value Gth. That is, it can be determined that the first integrated value has not reached the threshold value, and the downstream catalyst 55 has not reached the “reduced state capable of purifying a predetermined amount of nitrogen oxides”. Accordingly, the CPU 71 makes a “No” determination at step 1620 to proceed to step 620, step 630, and step 1630, and thus normal control is executed.

  When a predetermined time elapses from the fuel cut return time and the integrated value tGaS of the intake air amount becomes equal to or greater than the threshold value Gth, the CPU 71 determines “Yes” in step 1620 and proceeds to step 640 to turn on the on-off valve 57. In step 650, filter regeneration control is executed. Therefore, the average of the air-fuel ratio of the air-fuel mixture supplied to the first cylinder matches the rich air-fuel ratio TR for filter regeneration control, and the average of the air-fuel ratio of the air-fuel mixture supplied to the second to fourth cylinders is controlled by filter regeneration control. The air-fuel ratio (fuel injection amount for each cylinder) of the air-fuel mixture supplied to each cylinder is controlled so as to match the lean air-fuel ratio TL.

  Next, the CPU 71 proceeds to step 1640, sets the value of the reproduction execution flag XJ to “1”, proceeds to step 1695, and once ends this routine. With the above processing, regeneration of the particulate collection filter 54 is started.

  At this point, when the CPU 71 starts processing from step 1700 in FIG. 17, the CPU 71 determines “Yes” in step 1505 and “determines whether the value of the reproduction execution flag XJ is“ 1 ”. In step 1710 ”,“ Yes ”is determined, and the process proceeds to step 1530. The continuation time of the filter regeneration control (ie, the elapsed time since the value of the regeneration execution flag XJ is changed from“ 0 ”to“ 1 ”) ) It is determined whether Ts is equal to or longer than a predetermined time Tsth (filter regeneration control execution time Tsth).

  The present time is immediately after the value of the playback execution flag XJ is changed from “0” to “1”. Therefore, the duration of the filter regeneration control has not reached the predetermined time Tsth. Therefore, the CPU 71 makes a “No” determination at step 1530 to directly proceed to step 1595 to end the present routine tentatively.

  Thereafter, the filter regeneration control is continuously executed, so that the filter regeneration control duration Ts reaches a predetermined time Tsth. At this time, the CPU 71 determines “Yes” in step 1530 following step 1505 and step 1710 in FIG. 17, and sequentially performs the processing in steps 1535 and 1540 described above.

  As a result, the CPU 71 determines “No” in step 610 of FIG. 16 and resumes normal control. Furthermore, the CPU 71 makes a “No” determination at step 1505 in FIG. 17 and starts updating the particulate collection amount SPM again. In other words, when it is determined “No” in 1710, the CPU 71 proceeds directly from step 1710 to step 1795.

  As described above, the second control device determines whether or not the downstream catalyst 55 has reached a reduction state that can purify a predetermined amount of nitrogen oxides (step 1620, FIG. 18), when it is determined that the downstream catalyst 55 has reached the reduction state during execution of the normal control, the execution of the filter regeneration control is permitted (step 610, step 1620, step 640 and step 650) or started ( Step 1620, Step 640 and Step 650) are provided.

  When the filter regeneration control is started, oxygen is supplied to the particulate collection filter 54, and the air-fuel ratio of the gas flowing into the downstream catalyst 55 becomes the stoichiometric air-fuel ratio vicinity air-fuel ratio (weak rich air-fuel ratio AFR). However, if the operation state immediately before is a state where a large amount of oxygen is supplied to the downstream catalyst 55 as in the fuel cut operation state, for example, the oxygen storage amount OSA2 of the downstream catalyst 55 is the maximum oxygen storage amount of the downstream catalyst. The value is in the vicinity of the amount Cmax2. Therefore, when the filter regeneration control is immediately started when the regeneration request for the particulate collection filter 54 is generated immediately after the fuel cut operation state, the air-fuel ratio gas near the stoichiometric air-fuel ratio flows into the downstream catalyst 55. Even so, the downstream catalyst 55 cannot immediately purify a large amount of nitrogen oxide at a high purification rate.

  Therefore, the second control device permits the filter regeneration control when it is determined that the downstream catalyst 55 has reached the reduction state during execution of the normal control, and performs the filter regeneration control when there is a regeneration request for the particulate collection filter 54. Start. Therefore, at the start of the filter regeneration control, the downstream catalyst 55 has a certain degree of high reduction ability (capability of purifying a predetermined amount or more of nitrogen oxide). Even if it flows, the nitrogen oxide can be purified with high efficiency.

  Further, the second control device is a fuel cut means for stopping the fuel supply to the engine 10 when the operation state of the engine 10 becomes a predetermined fuel cut operation state (flow from step 1610 to step 1695 in FIG. 16). For example).

in addition,
(A1) The second control device calculates an average of the air-fuel ratios of the air-fuel mixture supplied to each of the plurality of cylinders in the normal control by an air-fuel ratio within a predetermined air-fuel ratio range (window W) including the theoretical air-fuel ratio. The air-fuel ratio is controlled to be a rich air-fuel ratio AFR that is richer than the stoichiometric air-fuel ratio (see step 630 in FIG. 16), and
(A2) If the second controller determines “Yes” in step 1610 and determines “No” in step 1610 from the state in which the fuel cut operation is performed, and proceeds to step 610, filter regeneration Even if the value of the request flag XPM is “1”, the integrated value tGaS of the intake air amount is smaller than the threshold value Gth, so the normal control of Step 620 and Step 630 is executed. That is, the second control device starts execution of the normal control from the fuel cut return time point when the fuel cut to the engine 10 by the fuel cut means is released and the fuel is started to be supplied to the engine 10 again. It is configured. Therefore, the state of the downstream side catalyst 55 in the oxidation state (the state where the oxygen storage amount OSA2 coincides with the maximum oxygen storage amount Cmax2 or is very close to the maximum oxygen storage amount Cmax2) during the fuel cut control. Changes toward the “reduced state” due to excessive reducing components discharged from the engine in normal control.

And the second control device
(B1) “Excessive reduction component”, which is an amount obtained by subtracting “amount of oxidation component” discharged from the engine that oxidizes the reduction component from “amount of reduction component” that is unburned material discharged from the engine 10 By accumulating the “quantity” from the fuel cut return time point (see FIG. 18), the “first accumulated value tGaS” is obtained.
(B2) When the first integrated value tGaS becomes equal to or greater than the first predetermined value Gth, it is determined that the downstream catalyst 55 has reached the reduction state (see step 1620 in FIG. 16). . As described above, the first integrated value tGaS is an amount corresponding to the excessive amount of the reducing component flowing into the downstream catalyst 55. That is, the first integrated value tGaS is the amount of reducing component consumed (absorbed) by the upstream catalyst 53 from the total amount of excess reducing components flowing out from the engine after returning from the fuel cut (the maximum oxygen storage of the upstream catalyst 53). The amount obtained by subtracting the amount corresponding to the amount Cmax1). Accordingly, the second control device determines whether or not the downstream catalyst 55 has reached the reduction state after returning from the fuel cut by determining whether or not the first integrated value tGaS is equal to or greater than the first predetermined value Gth. “No” can be easily determined. The second control device acquires the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 using a known method, and increases the first predetermined value Gth as the acquired maximum oxygen storage amount Cmax1 increases. You may be comprised so that it may set to.

(Third embodiment)
Next, a control device for an internal combustion engine according to a third embodiment of the present invention (hereinafter also referred to as “third control device”) will be described. The third control device sets the integration start time of the “integrated value of the intake air amount Ga (first integrated value) tGaS” used in the second control device, not the “fuel cut return time”, but the downstream air-fuel ratio sensor. This is different from the second control device only in that the downstream air-fuel ratio afdown detected at 67 is set to the “rich inversion time” at which the air-fuel ratio on the richer side than the stoichiometric air-fuel ratio is changed. Therefore, the following description will be made with this difference as the center.

  The CPU 71 of the third control device executes an integrated gas amount calculation routine shown in FIG. 19 instead of the integrated gas amount calculation routine shown in FIG. 18 executed by the CPU 71 of the second control device. That is, the CPU 71 of the third control device executes the routines shown in FIGS. In FIG. 19, steps for performing the same processing as the steps shown in FIG. 18 are denoted by the same reference numerals as those given for such steps in FIG. 18.

  The CPU 71 starts the processing from step 1900 of FIG. 19 every elapse of the predetermined time Δt1, proceeds to step 1810, and determines whether or not the current time is under fuel cut control. If the present time is during the fuel cut control, the CPU 71 determines “Yes” in step 1810 and proceeds to step 1820 to set the integrated value tGaS of the intake air amount to “0”. Thereafter, the CPU 71 proceeds to step 1895 to end the present routine tentatively.

  On the other hand, when the CPU 71 proceeds to step 1810 and the fuel cut control is not in progress, the CPU 71 determines “No” in step 1810 and proceeds to step 1910 to output the downstream air-fuel ratio sensor 67 after returning from the fuel cut. The value Voxs is smaller than the value corresponding to the stoichiometric air-fuel ratio (0.5 (V)) (the value on the lean side of the value corresponding to the stoichiometric air-fuel ratio), and larger than the value corresponding to the stoichiometric air-fuel ratio (theoretical). It is determined whether or not the value has changed (reversed) to a value that is richer than the value corresponding to the air-fuel ratio. That is, it is determined whether or not the output value Voxs of the downstream side air-fuel ratio sensor has “rich-reversed” to a value from the time when the immediately preceding fuel cut control is completed to the current time.

  Assume now that the fuel cut has just been returned. During the fuel cut control, a large amount of oxygen is supplied to the upstream catalyst 53, so that the oxygen storage amount OSA1 of the upstream catalyst 53 substantially reaches the maximum oxygen storage amount Cmax1 of the upstream catalyst 53. Therefore, immediately after the fuel cut is restored, the reducing component (unburned material) is consumed in the upstream catalyst 53, so that the reducing component does not flow out from the upstream catalyst 53. Therefore, the output value Voxs of the downstream air-fuel ratio sensor 6 becomes a leaner value than the value corresponding to the theoretical air-fuel ratio. Therefore, the CPU 71 makes a “No” determination at step 1910 to proceed to step 1820 to set the integrated value tGaS of the intake air amount to “0”. That is, the CPU 71 does not start integrating the intake air amount integrated value (first integrated value) tGaS.

  As a result, when the CPU 71 executes the routine shown in FIG. 16, even if the value of the filter regeneration request flag XPM is set to “1”, the CPU 71 determines “No” in step 1620. Step 620 and Step 630 are executed. That is, normal control is executed. As a result, excessive reducing components continue to flow out of the engine 10, so that the oxygen storage amount OSA1 of the upstream catalyst 53 substantially reaches “0” after a predetermined time has elapsed. Then, since that time, the reducing component starts to flow out from the upstream side catalyst 53, so that the output value Voxs of the downstream side air-fuel ratio sensor 67 is "rich-reversed".

  At this time, when the CPU 71 executes the routine shown in FIG. 19, the CPU 71 determines “Yes” in step 1910 following step 1810, and executes the processes of steps 1830 and 1840 described above. That is, in order to calculate the integrated value tGaS of the intake air amount Ga, the integration of the intake air amount Ga is started. Further, after this time (rich inversion time), the CPU 71 continues to integrate the intake air amount Ga (update the integrated value tGaS).

  Therefore, when the predetermined time has elapsed, the integrated value tGaS of the intake air amount reaches the threshold value Gth. Therefore, when the CPU 71 proceeds to step 1620 in FIG. 16, it determines “Yes” in step 1620, and step 640. And the process of step 650 comes to be performed. That is, the CPU 71 starts filter regeneration control. When the filter regeneration control execution time Tsth has elapsed from the start of the filter regeneration control, the CPU 71 sets the value of the filter regeneration request flag XPM to “0” in step 1540 of FIG. As a result, the CPU 71 determines “No” in step 610 of FIG. 16 and executes normal control again.

As described above, the third control device
(C1) In normal control, the average of the air-fuel ratios of the air-fuel mixture supplied to all the cylinders (the plurality of cylinders) of the engine is calculated as the air in the predetermined air-fuel ratio range (window W) including the theoretical air-fuel ratio. AFR is controlled to a slightly rich air-fuel ratio that is an air-fuel ratio that is richer than the stoichiometric air-fuel ratio (see step 630), and
(C2) The normal control is executed from the fuel cut return time point when the fuel cut to the engine by the fuel cut means is released and fuel is started to be supplied to the engine again. (See steps 1910 and 1820 in FIG. 19 and steps 1620, 620 and 630 in FIG. 16.)

Furthermore, the third control device
(D1) An air-fuel ratio in which the detected air-fuel ratio detected by the downstream air-fuel ratio sensor 67 after the “fuel cut return time” is richer than the stoichiometric air-fuel ratio is an excess amount of the reducing component discharged from the engine The first integrated value (intake air amount integrated value tGaS) is obtained by integrating from the “rich inversion time” changed to (see Step 1910, Steps 1830 and 1840 in FIG. 19), and
(D2) When the first integrated value tGaS becomes equal to or greater than the first predetermined value Gth, it is determined that “the downstream catalyst 55 has reached the reduction state” (see step 1620 in FIG. 16), and a filter regeneration request is made. If there is, the filter regeneration control is executed (see step 610, step 640 and step 650 in FIG. 16).

  Thus, since normal control is started from the fuel cut return time point, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is controlled to the weak rich air-fuel ratio AFR. As a result, the plurality of cylinders (the part of the cylinders) are controlled. Excess reducing components are discharged from the cylinder and the other cylinders). However, even if the normal control is started after the fuel cut is restored, an excessive reducing component does not immediately flow into the downstream catalyst 55. In other words, after a predetermined time has elapsed after the fuel cut is restored, excess reducing components start to flow into the downstream catalyst 55. This time varies depending on the intake air amount of the engine, the engine speed, and the like. Further, since the third control device includes the upstream catalyst 53, excess reducing components are consumed by the upstream catalyst 53 after the fuel cut is restored, and the oxygen storage amount OSA1 of the upstream catalyst 53 is substantially reduced. After reaching “0”, the downstream catalyst 55 is reached. Therefore, the point in time when an excessive reducing component starts to flow into the downstream catalyst 55 changes depending on the maximum oxygen storage amount Cmax1 of the upstream catalyst 53.

  Therefore, in the third control device, the excess reducing component (intake air amount Ga) is accumulated from the “rich inversion time” after the fuel cut return time, thereby obtaining the “first accumulated value tGaS”. . This rich inversion time coincides accurately with the time when excessive reducing components begin to flow into the downstream catalyst 55 regardless of the intake air amount of the engine, the engine rotational speed, the maximum oxygen storage amount Cmax1 of the upstream catalyst 53, and the like. ing. Therefore, the first integrated value tGaS indicates the retention amount of the reducing component of the downstream catalyst 55 (the reduction amount of the oxygen storage amount of the downstream catalyst 55 or the reduction ability capable of purifying the nitrogen oxides of the downstream catalyst 55). Express accurately. Then, the third control device determines whether or not the first integrated value tGaS is equal to or greater than the first predetermined value Gth, so that the downstream side catalyst 55 returns to the “reduction state has been reached or not after the fuel cut is restored. Is determined. Therefore, the third control device can determine with higher accuracy whether or not the downstream catalyst 55 has reached the “reduction state”.

(Fourth embodiment)
Next, a control device for an internal combustion engine according to a fourth embodiment of the present invention (hereinafter also referred to as “fourth control device”) will be described. The fourth control device acquires (estimates) the fine particle amount SPM that is the amount of the fine particles collected by the fine particle collecting filter 54, and the more the fine particle amount SPM acquired when the filter regeneration control is executed, The average air-fuel ratio of the air-fuel mixture supplied to some cylinders (second cylinder to fourth cylinder) is controlled to a leaner air-fuel ratio (the air-fuel mixture supplied to the first cylinder which is the other cylinder) The average of the air-fuel ratio is controlled to a richer air-fuel ratio).

  Hereinafter, the operation of the fourth control device will be described in accordance with the routines shown in the flowcharts of FIGS. In addition, the code | symbol same as the code | symbol attached | subjected to the already demonstrated step is provided to the step for performing the process same as the step already demonstrated in these figures.

  The CPU 71 of the fourth control apparatus repeats the routine shown in the schematic flowchart shown in FIG. 20 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU 71 starts processing from step 2000 and proceeds to step 2010 to determine whether or not the value of the filter regeneration request flag XPM1 is “1”. The value of the filter regeneration request flag XPM1 is set to “1” when a request to regenerate the particulate collection filter 54 (filter regeneration request) is generated, similar to the filter regeneration request flag XPM described above. Set to “0” when the filter 54 need not be regenerated. The operation of the filter regeneration request flag XPM1 will be described later (see FIG. 21).

  Assume that the value of the filter regeneration request flag XPM1 is “0”. In this case, the CPU 71 makes a “No” determination at step 2010, proceeds to step 620 and step 630, and executes the above-described normal control. That is, the CPU 71 closes the on-off valve 57 to block the bypass passage of the bypass passage forming member 56 and to empty the mixture supplied to each of the first to fourth cylinders (all of the plurality of cylinders). The air-fuel ratio (fuel injection amount for each cylinder) of the air-fuel mixture supplied to each cylinder is controlled so that the average of the fuel ratio is substantially the stoichiometric air-fuel ratio vicinity air-fuel ratio (weak rich air-fuel ratio AFR).

  On the other hand, the CPU 71 executes the filter regeneration request flag operation routine shown by the flowchart in FIG. 21 every elapse of a predetermined time. Accordingly, the CPU 71 starts processing from step 2100 at a predetermined timing, proceeds to step 2110, and “the integrated value Ste of the operating time te of the engine 10 after the previous filter regeneration control is ended” is a predetermined threshold ( It is determined whether or not the filter regeneration control execution threshold value) is greater than or equal to Step. The integrated value Ste of the operating time te of the engine 10 is updated by a routine not shown. The integrated value Ste of the operating time te is stored in the backup RAM 74. Since the amount of fine particles generated by the operation of the engine 10 increases as the operation time of the engine 10 becomes longer, the integrated value SGa is an amount related to the amount of fine particles collected by the fine particle collection filter 54. Note that the integrated value Ste of the operating time te is set (cleared) to “0” in step 2150 described later when the execution of the filter regeneration control is completed.

  If the integrated value Ste of the operating time te is equal to or greater than the threshold value Steth, the CPU 71 proceeds from step 2110 to step 2120, sets the value of the filter regeneration request flag XPM1 to “1”, and proceeds to step 2130. On the other hand, when the integrated value Ste of the operation time te is smaller than the threshold value Step 71, the CPU 71 proceeds directly from step 2110 to step 2130.

  The CPU 71 determines that the predetermined time Tsth (filter regeneration control execution time Tsth) from the time when the value of the filter regeneration request flag XPM1 changes from “0” to “1” in Step 2130 (that is, the start time of the filter regeneration control). It is determined whether or not it has elapsed. If the predetermined time Tsth (filter regeneration control execution time Tsth) has elapsed since the value of the filter regeneration request flag XPM1 changed from “0” to “1”, the CPU 71 determines “Yes” in step 2130. And the processing of step 2140 to step 2160 described below is executed, and the process proceeds to step 2195 to end the present routine tentatively. If the predetermined time Tsth has not elapsed since the value of the filter regeneration request flag XPM1 changed from “0” to “1”, the CPU 71 proceeds directly from step 2130 to step 2195 to end the present routine tentatively. To do.

Step 2140: The CPU 71 sets the value of the filter regeneration request flag XPM1 to “0”.
Step 2150: The CPU 71 sets (clears) the value of the integrated value Ste of the operating time te of the engine 10 to “0”.
Step 2160: The CPU 71 sets (clears) the value of the particulate collection amount SPM calculated separately by a routine shown in FIG.

  By the way, immediately after the value of the filter regeneration request flag XPM1 is set to “1” in step 2120, when the CPU 71 executes the process of step 2010 in FIG. 20, the CPU 71 determines “Yes” in step 2010, Proceeding to step 640, an instruction to open the on-off valve 57 is given to the on-off valve 57, and the bypass passage of the bypass passage forming member 56 is opened (set to a state where gas can flow).

  Next, the CPU 71 proceeds to step 2020 and reads the particulate collection amount SPM calculated by the particulate collection amount SPM calculation routine of FIG. Here, the particulate collection amount SPM calculation routine of FIG. 22 will be briefly described. The CPU 71 repeatedly executes the routine shown in FIG. 22 every elapse of a predetermined time. Accordingly, when the predetermined timing comes, the CPU 71 starts processing from step 2200 and proceeds to step 1510 described above to determine the coefficient k1. Next, the CPU 71 proceeds to step 1515 described above, and the product (k1 · Ga) of the coefficient k1 and the intake air amount Ga currently measured by the airflow meter 61 is added to the particulate collection amount SPM estimated at the present time. ) Is set as a new particulate collection amount SPM. This particulate collection amount SPM is stored in the backup RAM 74.

  Referring to FIG. 20 again, the CPU 71 proceeds to step 2030 following step 2020 and executes “filter regeneration control”. In this filter regeneration control, the average of the air-fuel ratio of the air-fuel mixture supplied to the first cylinder (other cylinders) is increased as the particulate collection amount SPM increases in accordance with the map shown in the block of step 2030. It is set to be the fuel ratio TR (the rich air-fuel ratio TR for filter regeneration control). This air-fuel ratio TR is an air-fuel ratio richer than the stoichiometric air-fuel ratio. In addition, the average air-fuel ratio of the air-fuel mixture supplied to each of the second cylinder, the third cylinder, and the fourth cylinder (a part of the cylinders) is determined according to the map shown in the block of step 2030. Is set so that the leaner the air-fuel ratio TL (lean air-fuel ratio for filter regeneration control TL) becomes, the larger the is. This air-fuel ratio TL is an air-fuel ratio leaner than the stoichiometric air-fuel ratio.

  However, the rich air-fuel ratio TR for filter regeneration control and the lean air-fuel ratio TL for filter regeneration control are set so that the relationship of the above equation (13) is established, that is, the first to fourth cylinders (that is, all cylinders). ) Is determined in advance so that the average of the air-fuel ratios of the entire air-fuel mixture supplied to each of the air-fuel ratios becomes the stoichiometric air-fuel ratio or the air-fuel ratio close to the stoichiometric air-fuel ratio (in this example, the weak rich air-fuel ratio AFR). Thereafter, the CPU 71 proceeds to step 2095 to end the present routine tentatively.

  As described above, the fourth control apparatus acquires (estimates) the fine particle amount SPM that is the amount of the fine particles collected by the fine particle collecting filter 54 (see FIG. 22). Further, the fourth control device, when executing the filter regeneration control, “mixing supplied to the some cylinders (second to fourth cylinders) as the acquired fine particle amount (fine particle collection amount) SPM increases. The average air-fuel ratio of the air is controlled to a leaner air-fuel ratio (lean air-fuel ratio for filter regeneration control TL) ”(see step 2030 in FIG. 20).

  Accordingly, the larger the amount of particulates collected by the particulate collection filter 54, the larger the amount of oxygen flowing into the particulate collection filter per unit time. Therefore, the particulate collection filter 54 burns per unit time. The amount of fine particles to be increased also increases. Further, since the temperature of the particulate collection filter 54 is increased by this combustion, the particulates are combusted with higher efficiency. As a result, the filter regeneration control can be completed within a short time (regeneration of the particulate collection filter is completed) regardless of the amount SPM of the collected particulates. In other words, since the period of normal control in which the exhaust gas can be purified by both the upstream catalyst 53 and the downstream catalyst 55 can be increased, the emission can be maintained better.

(Fifth embodiment)
Next, a control device for an internal combustion engine according to a fifth embodiment of the present invention (hereinafter also referred to as “fifth control device”) will be described. The fifth control device acquires a filter temperature related value (particulate collection filter temperature TempPMF) that increases as the temperature of the particulate collection filter 54 increases, and the filter temperature related value (particulate collection filter temperature TempPMF) increases. It is configured to prohibit the execution of filter regeneration control when it is higher than the side filter threshold temperature THith and when the filter temperature related value (particulate collection filter temperature TempPMF) is lower than the low side filter threshold temperature TLoth. Only in the first control device. Therefore, the following description will be made with this difference as the center.

  The CPU 71 of the fifth control apparatus estimates the routine shown in the flowchart of FIG. 23 instead of FIG. 6, the filter regeneration request flag operation routine shown in FIG. 7, and the filter temperature related value (particulate collection filter temperature TempPMF) (not shown). The routine is executed every time a predetermined time elapses. In FIG. 23, steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as those given for such steps in FIG. 6. A detailed description of these steps is omitted.

  The CPU 71 starts processing from step 2300 in FIG. 23 at a predetermined timing, proceeds to step 610, and determines whether or not the value of the filter regeneration request flag XPM changed by the routine shown in FIG. 7 is “1”. Determine.

  Assume that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 makes a “No” determination at step 610, proceeds to step 620 to close the on-off valve 57, and executes normal control at step 630. Accordingly, the average of the air-fuel ratios of the air-fuel mixture supplied to each of the first to fourth cylinders (all of the plurality of cylinders) becomes the “weakly rich air-fuel ratio AFR” that is the air-fuel ratio near the stoichiometric air-fuel ratio. The air-fuel ratio (fuel injection amount for each cylinder) of the air-fuel mixture supplied to each cylinder is controlled.

  Thereafter, the value of the filter regeneration request flag XPM is set to “1” as the integrated value SGa of the intake air amount Ga after the end of the previous filter regeneration control becomes equal to or greater than the threshold value SGath (step 710 in FIG. 7). And step 720). In this case, the CPU 71 determines “Yes” in step 610 of FIG. 23 and proceeds to step 2310 to determine whether the separately estimated (acquired) particulate collection filter temperature TempPMF is equal to or higher than the low-side filter threshold temperature TLoth. Determine whether. If the particulate collection filter temperature TempPMF is lower than the low-side filter threshold temperature TLoth, the CPU 71 makes a “No” determination at step 2310 to proceed to step 620 and step 630 to continue normal control. That is, even when the value of the filter regeneration request flag XPM is “1”, the execution of the filter regeneration control is prohibited.

  On the other hand, if the particulate collection filter temperature TempPMF is equal to or higher than the low-side filter threshold temperature TLoth, the CPU 71 determines “Yes” in step 2310 and proceeds to step 2320, where the particulate collection filter temperature TempPMF is the high-side filter threshold temperature. Judge whether it is below THith. If the particulate collection filter temperature TempPMF is higher than the high-side filter threshold temperature THith, the CPU 71 makes a “No” determination at step 2320 to proceed to step 620 and step 630 to continue normal control. That is, even when the value of the filter regeneration request flag XPM is “1”, the execution of the filter regeneration control is prohibited.

  On the other hand, if the particulate collection filter temperature TempPMF is equal to or lower than the high-side filter threshold temperature THith, the CPU 71 determines “Yes” in step 2320 and performs the processing in steps 640 and 2330 described below to perform the filter. Perform playback control.

Step 640: The CPU 71 gives an instruction to open the on-off valve 57 to the on-off valve 57 to open the bypass passage of the bypass passage forming member 56 (set to a state in which gas can flow).
Step 2330: The CPU 71 sets the air-fuel ratio average of the air-fuel mixture supplied to the first cylinder (other cylinders) to the rich air-fuel ratio TR for filter regeneration control according to the map shown in the block of Step 2330. Further, the CPU 71 sets the average of the air-fuel ratio of the air-fuel mixture supplied to the second to fourth cylinders (other cylinders) to the filter regeneration control lean air-fuel ratio TL according to the map shown in the block of step 2330. .

More specifically, in step 2330, the filter regeneration control rich air-fuel ratio TR is (1) an air-fuel ratio richer than the stoichiometric air-fuel ratio, and
(2) The particulate filter temperature TempPMF is equal to or higher than the low-side filter threshold temperature TLoth, but leaner toward the low-side filter threshold temperature TLoth in the low temperature region closer to the low-side filter threshold temperature TLoth than the high-side filter threshold temperature THith. Side air-fuel ratio (an air-fuel ratio closer to the theoretical air-fuel ratio), and
(3) In the high temperature region where the particulate collection filter temperature TempPMF is equal to or lower than the high-side filter threshold temperature THith but is closer to the high-side filter threshold temperature THith than the low-side filter threshold temperature TLoth, the leaner the closer to the high-side filter threshold temperature THith The air-fuel ratio on the side (the air-fuel ratio closer to the theoretical air-fuel ratio) is determined.

In step 2330, the filter regeneration control lean air-fuel ratio TL is
(5) The air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and
(5) The air-fuel ratio on the rich side (the air-fuel ratio closer to the theoretical air-fuel ratio) becomes closer to the low-side filter threshold temperature TLoth in the low temperature region where the particulate collection filter temperature TempPMF is equal to or higher than the low-side filter threshold temperature TLoth, and ,
(6) The air-fuel ratio on the rich side (the air-fuel ratio closer to the theoretical air-fuel ratio) becomes closer to the high-side filter threshold temperature THith in the high temperature region where the particulate collection filter temperature TempPMF is equal to or lower than the high-side filter threshold temperature THith. It is determined.

  Further, the lean air-fuel ratio TL for filter regeneration control and the rich air-fuel ratio TR for filter regeneration control are determined in advance so that the above equation (13) is established. Then, the CPU 71 proceeds from step 2330 to step 2395 to end the present routine tentatively. The filter regeneration control executed in this way is continued until the predetermined time Tsth has elapsed from the start of the filter regeneration control by Step 730, Step 740 in FIG. 7 and Step 610 in FIG. Control is executed.

In a filter temperature related value (particulate collection filter temperature TempPMF) estimation routine (not shown), the CPU 71 estimates the particulate collection filter temperature TempPMF as follows.
Step 1: The CPU 71 performs engine rotation speed NE, in-cylinder intake air amount Mc (k), detected air-fuel ratio abyfs (k) detected by the upstream air-fuel ratio sensor 66, and table MapTempPMFt (NE) at predetermined time intervals. , Mc (k), abyfs (k)), the instantaneous temperature TempPMFt of the particulate collection filter 54 is determined. The table MapTempPMFt (NE, Mc (k), abyfs (k)) is obtained when a certain engine speed NE, a certain cylinder intake air amount Mc (k), and a certain detected air-fuel ratio abyfs (k) continue constantly. 10 is a table that defines the relationship between these variables and the convergence temperature TempPMFt of the particulate collection filter 54. This table is acquired in advance by experiments and stored in the ROM 72.

Step 2: The CPU 71 obtains the particulate collection filter temperature TempPMF by filtering (integrating) the obtained instantaneous temperature TempPMFt according to the following equation (14). In the equation (14), γ is a constant larger than 0 and smaller than 1, and TempPMFold is the particulate collection filter temperature TempPMF estimated when the filter temperature related value estimation routine was executed last time.
TempPMF = γ ・ TempPMFold + (1−γ) ・ TempPMFt (14)

  The fifth control device is provided with a “particulate collection filter temperature sensor” that directly detects the temperature of the particulate collection filter 54, and the output value of the particulate collection filter temperature sensor. May be configured to obtain the particulate collection filter temperature TempPMF.

  As described above, the fifth control device is configured to prohibit the execution of the filter regeneration control when the filter temperature related value (the particulate collection filter temperature TempPMF) is higher than the high-side filter threshold temperature THith. As a result, when the temperature of the particulate collection filter is very high, the filter regeneration control is executed, so that the particulates are burned, and the temperature of the particulate collection filter 54 is prevented from becoming excessively high due to the heat generated thereby. can do. That is, the fifth control device can reduce the possibility that the particulate collection filter 54 is damaged due to overheating due to the filter regeneration control.

  Further, the fifth control device calculates an average of the air-fuel ratio of the air-fuel mixture supplied to the partial cylinders (second to fourth cylinders) when executing the filter regeneration control, as a filter temperature related value (particulate collection filter). As the temperature TempPMF) approaches the high-side filter threshold temperature THith in the high temperature region, the air-fuel ratio is controlled to be “richer-side air-fuel ratio (an air-fuel ratio closer to the theoretical air-fuel ratio)” (see step 2330). ).

  Accordingly, as the temperature of the particulate collection filter 54 increases, the amount of oxygen supplied to the particulate collection filter 54 decreases, so the amount of particulates to burn (the amount of heat generated) decreases. As a result, the particulate collection filter 54 can be protected from damage due to overheating described above.

  In addition, the fifth control device is configured to prohibit the execution of the filter regeneration control when the filter temperature related value (the particulate collection filter temperature TempPMF) is lower than the low-side filter threshold temperature TLoth. This makes it unnecessary to regenerate the filter when the filter temperature-related value (particulate collection filter temperature TempPMF) is lower than the low-side filter threshold temperature TLoth so that the particulates do not burn even when oxygen is supplied to the particulate collection filter. Execution of control can be avoided.

  Further, the fifth control device calculates an average of the air-fuel ratio of the air-fuel mixture supplied to the some cylinders (second to fourth cylinders) when the filter regeneration control is executed, as the filter temperature related value (fine particle As the collection filter temperature (TempPMF) approaches the low-side filter threshold temperature TLoth in the low temperature region, the air-fuel ratio on the richer side (the air-fuel ratio closer to the stoichiometric air-fuel ratio) is controlled (step 2330). See).

  If the temperature of the particulate collection filter 54 is equal to or higher than the low-side filter threshold temperature TLoth, the particulates burn in the particulate collection filter 54. However, the closer the temperature of the particulate collection filter 54 is to the lower filter threshold temperature TLoth, the more difficult the particulates will burn (the burning of the particulates becomes slower). Therefore, in such a case, even if a large amount of oxygen is supplied to the particulate collection filter 54, a lot of oxygen is wasted. On the other hand, supplying a large amount of oxygen to the particulate collection filter 54 means that the air-fuel ratio of the some cylinders is set to an air-fuel ratio greatly deviating from the stoichiometric air-fuel ratio toward the lean side. In that case, a large amount of nitrogen oxide is discharged from the cylinders.

  Therefore, the fifth control device controls to a “richer air-fuel ratio (an air-fuel ratio closer to the theoretical air-fuel ratio)” as the filter temperature-related value (particulate collection filter temperature TempPMF) approaches the lower filter threshold temperature TLoth. To do. As a result, wasteful oxygen is not supplied to the particulate collection filter 54, and the amount of nitrogen oxides discharged from the partial cylinders can be reduced. Therefore, since the amount of nitrogen oxides discharged from the engine 10 can be reduced, the amount of nitrogen oxides discharged into the atmosphere without being purified by the downstream catalyst 55 (by blowing through the downstream catalyst 55) is reduced. Can be reduced.

(Sixth embodiment)
Next, a control device for an internal combustion engine according to a sixth embodiment of the present invention (hereinafter also referred to as “sixth control device”) will be described. The sixth control device acquires (estimates) a downstream catalyst temperature related value (downstream catalyst temperature TempUF) that increases as the temperature of the downstream catalyst 55 increases, and also acquires the acquired downstream catalyst temperature related value (downstream). When the side catalyst temperature TempUF) is lower than the low-side downstream catalyst threshold temperature TLoUFth (the activation temperature of the downstream catalyst 55), the execution of the filter regeneration control is prohibited.

  Further, the sixth control device controls the air-fuel ratio of the air-fuel mixture supplied to the engine 10 according to a predetermined mode, and adjusts the output value Vabyfs of the upstream air-fuel ratio sensor 66 and the output value Voxs of the downstream air-fuel ratio sensor 67. And a deterioration determination means (catalyst deterioration determination means) for executing deterioration determination control for determining whether or not the upstream catalyst 53 has deteriorated based on the filter, and the filter when the deterioration determination means is executing the deterioration determination control. The reproduction control is prohibited from being executed.

  The CPU 71 of the sixth control unit performs the routine shown in the flowchart of FIG. 24 instead of FIG. 6, the filter regeneration request flag operation routine shown in FIG. 7, and the downstream catalyst temperature related value (downstream catalyst temperature TempUF) not shown. The estimation routine is executed every elapse of a predetermined time. In FIG. 24, steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as those given for such steps in FIG. A detailed description of these steps is omitted.

  The CPU 71 starts processing from step 2400 in FIG. 24 at a predetermined timing, proceeds to step 610, and determines whether or not the value of the filter regeneration request flag XPM changed by the routine shown in FIG. 7 is “1”. Determine.

  Assume that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 makes a “No” determination at step 610, proceeds to step 620 to close the on-off valve 57, and executes normal control at step 630. Accordingly, the average of the air-fuel ratios of the air-fuel mixture supplied to each of the first to fourth cylinders (all of the plurality of cylinders) becomes the “weakly rich air-fuel ratio AFR” that is the air-fuel ratio near the stoichiometric air-fuel ratio. The air-fuel ratio (fuel injection amount for each cylinder) of the air-fuel mixture supplied to each cylinder is controlled.

  Thereafter, the value of the filter regeneration request flag XPM is set to “1” when the integrated value SGa of the intake air amount Ga after the end of the previous filter regeneration control becomes equal to or greater than the threshold value SGath. In this case, the CPU 71 determines “Yes” in step 610 of FIG. 24 and proceeds to step 2410 to check whether the separately estimated (acquired) downstream catalyst temperature TempUF is equal to or lower than the low downstream catalyst threshold temperature TLoUFth. Determine whether or not.

  The downstream catalyst temperature TempUF is estimated in the same manner as the particulate collection filter temperature TempPMF. That is, the CPU 71 detects the engine speed NE, the in-cylinder intake air amount Mc (k), and the detected airflow detected by the upstream air-fuel ratio sensor 66 at predetermined time intervals in a downstream catalyst temperature related value estimation routine (not shown). Based on the fuel ratio abyfs (k) and the table MapTempUFt (NE, Mc (k), abyfs (k)), the instantaneous temperature TempUFt of the downstream catalyst 55 is determined. The table MapTempPMFt (NE, Mc (k), abyfs (k)) is obtained when a certain engine speed NE, a certain cylinder intake air amount Mc (k), and a certain detected air-fuel ratio abyfs (k) continue constantly. 4 is a table that defines the relationship between these variables and the convergence temperature TempUFt of the downstream catalyst 55. This table is acquired in advance by experiments and stored in the ROM 72.

  Further, the CPU 71 sets the obtained instantaneous temperature TempUFt to an expression similar to the above expression (14) (that is, TempUF = ψ · TempUFold + (1−ψ) · TempUFt, ψ is a constant larger than 0 and smaller than 1, TempUFold Is the downstream catalyst temperature TempUF estimated at the time when this downstream side catalyst temperature related value estimation routine was executed last time.) To obtain the downstream catalyst temperature TempUF. The sixth control device is provided with a “downstream catalyst temperature sensor” for directly detecting the temperature of the downstream catalyst 55 for the downstream catalyst 55, and the downstream side based on the output value of the downstream catalyst temperature sensor. It may be configured to obtain the side catalyst TempPUF.

  If the downstream catalyst temperature TempUF is equal to or lower than the low downstream catalyst threshold temperature TLoUFth, the CPU 71 makes a “Yes” determination at step 2410 to proceed to step 620 and step 630 to continue normal control. That is, even when the value of the filter regeneration request flag XPM is “1”, the execution of the filter regeneration control is prohibited. When the downstream catalyst temperature TempUF is equal to or lower than the low downstream catalyst threshold temperature TLoUFth, the ignition timing is retarded from the ignition timing during normal control, and warming up of the upstream catalyst 53 and the downstream catalyst 55 is promoted. The catalyst warm-up control is also executed.

  On the other hand, when the downstream catalyst temperature TempUF is higher than the low downstream catalyst threshold temperature TLoUFth, the CPU 71 makes a “No” determination at step 2410 to proceed to step 2420, where the value of the catalyst deterioration determination request flag XHN is “1”. It is determined whether or not. The value of the catalyst deterioration determination request flag XHN is changed by a catalyst deterioration determination request flag operation routine (not shown). In the catalyst deterioration determination request flag operation routine, the value of the catalyst deterioration determination request flag XHN indicates that the total operation time of the engine 10 after execution of the previous catalyst deterioration determination control is a predetermined time or more (or execution of the previous catalyst deterioration determination control). It is set to “1” when the integrated value of the intake air amount Ga later becomes equal to or greater than a predetermined amount), and is set to “0” when the catalyst deterioration determination control is executed.

  If the value of the catalyst deterioration determination request flag XHN is “1”, the CPU 71 determines “Yes” in step 2420 and proceeds to step 2430 to execute the catalyst deterioration determination control. That is, even if the value of the filter regeneration request flag XPM is “1” (and the downstream side catalyst temperature TempUF is higher than the low side downstream catalyst threshold temperature TLoUFth), the value of the catalyst deterioration determination request flag XHN is “ If “1”, the execution of the filter regeneration control is prohibited.

  On the other hand, when the CPU 71 proceeds to step 2420 and the value of the catalyst deterioration determination request flag XHN is “0”, the CPU 71 determines “No” in step 2420 and proceeds to step 640 and step 650 to perform filter regeneration. Execute control. Then, the CPU 71 proceeds from step 650 to step 2495, and once ends this routine. The filter regeneration control executed in this way is continued until the predetermined time Tsth has elapsed from the start of the filter regeneration control by Step 730, Step 740 in FIG. 7 and Step 610 in FIG. Control is executed.

  Here, the catalyst deterioration determination control in step 2430 will be briefly described. In this catalyst deterioration control, the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 is acquired. At this time, the CPU 71 executes, for example, a well-known control called “active control” to obtain the maximum oxygen storage amount Cmax1 (Japanese Patent Laid-Open No. 2005-194981, Japanese Patent Laid-Open No. 2006-057461, Japanese Patent Laid-Open No. 2005-207286). (See No. Gazette, etc.).

  Briefly describing the active control, the CPU 71 sets the air-fuel ratio of the air-fuel mixture supplied to the engine 10 to a richer air-fuel ratio than the stoichiometric air-fuel ratio, and the output value Voxs of the downstream air-fuel ratio sensor 67 is the theoretical air-fuel ratio. It is determined whether a value corresponding to the air-fuel ratio richer than the fuel ratio has been reached. Thereafter, when the output value Voxs of the downstream air-fuel ratio sensor 67 changes to a value indicating an air-fuel ratio richer than the stoichiometric air-fuel ratio, the CPU 71 sets the air-fuel ratio of the air-fuel mixture supplied to the engine to be lower than the stoichiometric air-fuel ratio. The lean air-fuel ratio is set, and it is monitored whether the output value Voxs of the downstream air-fuel ratio sensor 67 has changed to a value corresponding to the lean air-fuel ratio from the stoichiometric air-fuel ratio.

When it is detected that the output value Voxs of the downstream air-fuel ratio sensor 67 has changed to a value corresponding to the air-fuel ratio leaner than the stoichiometric air-fuel ratio (time ta), the air-fuel mixture supplied to the engine 10 The air-fuel ratio is set again to the rich-side air-fuel ratio. Then, until the time point (time tb) at which the output value Voxs of the downstream air-fuel ratio sensor 67 changes again to a value corresponding to the air-fuel ratio richer than the stoichiometric air-fuel ratio, The change amount ΔO2 is calculated every elapse of a predetermined time (calculation cycle tsample), and the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 is calculated by integrating the change amount ΔO2 based on the following equation (16).
ΔO2 = 0.23 · mfr · (stoich
-Abyfrr) (15)
Cmax1 = ΣΔO2 (section t = ta to tb) (16)

  In the above equation (15), the value “0.23” is the weight ratio of oxygen contained in the atmosphere. mfr is the total amount of the fuel injection amount Fi within a predetermined time (calculation cycle tsample). stoich is the stoichiometric air-fuel ratio (for example, 14.7). abyfrr is an air-fuel ratio measured by the upstream air-fuel ratio sensor 66 at a predetermined time tsample. Note that abyfrr may be an average value of the air-fuel ratio detected by the upstream air-fuel ratio sensor 66 within the predetermined time tsample.

  Further, the CPU 71 determines that the upstream catalyst 53 has not deteriorated if the obtained maximum oxygen storage amount Cmax1 of the upstream catalyst 53 is equal to or greater than the deterioration determination threshold CmaxR, and determines the maximum oxygen storage amount Cmax1 of the upstream catalyst 53. Is smaller than the deterioration determination threshold value CmaxR, it is determined that the upstream catalyst 53 has deteriorated.

  The CPU 71 executes normal control in step 630 instead of step 2430, and compares the locus length of the upstream air-fuel ratio sensor output value Vabyfs and the locus length of the downstream air-fuel ratio output value Voxs in a predetermined time. Based on the above, it may be determined whether or not the upstream catalyst 53 has deteriorated.

  As described above, the deterioration determination of the upstream catalyst 53 controls the air-fuel ratio of the air-fuel mixture supplied to the engine 10 according to a “predetermined aspect” different from the aspect in the filter regeneration control, and the upstream air-fuel ratio sensor 66. This is performed based on the output value Vabyfs and the output value Voxs of the downstream air-fuel ratio sensor 67.

  As described above, the sixth control device acquires (estimates) the downstream-side catalyst temperature related value (downstream-side catalyst temperature TempUF) that increases as the temperature of the downstream-side catalyst 55 increases. When the side catalyst temperature related value is lower than the low-side downstream catalyst threshold temperature TLoUFth, the filter regeneration control is prohibited from being executed (see step 2410, step 620, and step 630 in FIG. 24). Therefore, it is possible to prevent a large amount of nitrogen oxide from flowing into the downstream catalyst 55 that cannot reach its original purification function because it has reached the activation temperature due to the filter regeneration control. As a result, it can be avoided that a large amount of nitrogen oxides is discharged into the atmosphere without being purified by the downstream catalyst 55.

  Furthermore, the sixth control device prohibits the execution of the filter regeneration control when the deterioration determination unit is executing the deterioration determination control (see step 2420 and step 2430 in FIG. 24). Thereby, since the deterioration determination of the upstream catalyst 53 and the filter regeneration control are executed at different timings, it is possible to make these controls compatible.

  Note that the sixth control device does not change the value of the catalyst deterioration determination request flag XHN from “0” to “1” regardless of whether or not the value of the filter regeneration request flag XPM is “1”. Thus, the deterioration determination control may be executed. In this case, the value of the filter regeneration request flag XPM is changed from “0” to “1” while the deterioration determination control is being executed, and the downstream catalyst temperature related value is the low downstream catalyst threshold temperature TLoUFth. Even in this case, the filter regeneration control is prohibited from being executed.

(Seventh embodiment)
Next, a control device for an internal combustion engine according to a seventh embodiment of the present invention (hereinafter also referred to as “seventh control device”) will be described. The seventh controller differs from the first controller only in that it is configured to learn the sub-feedback correction value Fisub during normal control and stop learning the sub-feedback correction value Fisub during filter regeneration control. ing.

  The CPU 71 of the first control device executes the routines shown in FIGS. On the other hand, the CPU 71 of the seventh control device executes the routines shown in FIG. 11, FIG. 12, FIG. 25 instead of FIG. 13, FIG. 14, and FIG. That is, only the “routine for calculating the sub feedback correction amount” among the plurality of routines executed by the CPU 71 of the seventh control device is different from the plurality of routines executed by the CPU 71 of the first control device. Therefore, the operation based on the routine shown in FIG. 25 will be mainly described below. In FIG. 25, steps for performing the same processing as the steps shown in FIG. 13 are denoted by the same reference numerals as those given for such steps in FIG. A detailed description of these steps is omitted.

  The CPU 71 starts processing from step 2500 in FIG. 25 at a predetermined timing, determines whether the sub feedback control condition satisfaction flag XsubFB is “1” in step 1305, and sets the value of the sub feedback control condition satisfaction flag XsubFB When “0” is “0”, the process proceeds to step 1340 and step 1345 described above. Thereby, the sub feedback control is stopped.

  On the other hand, if the value of the sub feedback control condition satisfaction flag XsubFB is “1”, the CPU 71 determines “Yes” in step 1305 and proceeds to step 2510, where the sub feedback control condition satisfaction flag XsubFB is “0”. It is determined whether it is immediately after changing from “1” to “1” (immediately after the sub feedback control is started).

  If the sub feedback control condition satisfaction flag XsubFB has just changed from “0” to “1”, the CPU 71 proceeds to step 2520 and sets the learning value (sub feedback learning value) GKFisub to the sub feedback correction value Fisub. Thereafter, the process proceeds to Step 1310. The learning value GKFisub is stored in the backup RAM 74 as will be described later. On the other hand, if the sub feedback control condition satisfaction flag XsubFB is not immediately after the change from “0” to “1”, the CPU 71 proceeds directly from step 2510 to step 1310. With the above processing, when the sub feedback control is started, the learning value GKFisub is set as the sub feedback correction value Fisub.

  Next, the CPU 71 executes the processing from step 1310 to step 1335 to update (calculate) the sub feedback correction value Fisub. Subsequently, the CPU 71 proceeds to step 2530 to determine whether or not the filter regeneration control is being executed. When the filter regeneration control is not being executed (that is, when the normal control is being executed), the CPU 71 determines “No” in step 2530 and sequentially performs the processing of step 2540 and step 2550 described below, Proceed to step 2595 to end the present routine tentatively.

Step 2540: The CPU 71 substitutes the learning value GKFisub held in the backup RAM 74 at that time and the sub feedback correction value Fisub newly obtained in Step 1325 into the right side of the following equation (17). Thus, the learning value GKFisub is updated. In the equation (17), P1 is a predetermined constant larger than 0 and smaller than 1.
GKFisub = P1 · GKFisub + (1-P1) · Fisub (17)
Step 2550: The CPU 71 saves (stores / stores) the learning value GKFisub obtained in Step 2540 in the backup RAM 74.

  On the other hand, if the filter regeneration control is executed when the CPU 71 proceeds to step 2530, the CPU 71 determines “Yes” in step 2530 and proceeds directly to step 2595. That is, in this case, since the CPU 71 does not execute Step 2540 and Step 2550, learning of the sub feedback correction value Fisub (updating and storing the learning value GKFisub) is prohibited.

  As described above, the seventh control device is configured to stop (inhibit) learning of the sub feedback correction value Fisub during the filter regeneration control. The frequency at which the filter regeneration control is executed is extremely smaller than the frequency at which the normal control is executed. Further, in the filter regeneration control, part of the exhaust gas bypasses the upstream catalyst 53. Therefore, the learning value GKFisub at the time of normal control is not an appropriate value for the filter regeneration control, and when the learning value GKFisub is updated during the filter regeneration control, the learned value GKFisub is not an appropriate value for the normal control. Therefore, the seventh control device sets an appropriate learning value GKFisub at the start of the sub feedback control in the normal control by “stopping (prohibiting) learning of the sub feedback correction value Fisub during the filter regeneration control”. Can do. As a result, it is possible to avoid deterioration of emissions.

(Eighth embodiment)
Next, a control device for an internal combustion engine according to an eighth embodiment of the present invention (hereinafter also referred to as “eighth control device”) will be described. The eighth control device is the first control only in that the learning value of the sub feedback correction value Fisub during normal control and the learning value of the sub feedback correction value Fisub during filter regeneration control are separately provided. It is different from the control device.

  The CPU 71 of the first control device executes the routines shown in FIGS. On the other hand, the CPU 71 of the eighth control device executes the routines shown in FIGS. 11, 12, 14 and 15 and FIGS. 26 and 27 instead of FIG. Therefore, the operation based on the routine shown in FIGS. 26 and 27 will be mainly described below. In FIG. 26, steps for performing the same processing as the steps shown in FIGS. 13 and 25 are denoted by the same reference numerals as the steps given in FIGS. 13 and 25. . A detailed description of these steps is omitted.

  The CPU 71 starts processing from step 2600 of FIG. 26 at a predetermined timing, determines whether the sub feedback control condition satisfaction flag XsubFB is “1” in step 1305, and sets the value of the sub feedback control condition satisfaction flag XsubFB When “0” is “0”, the process proceeds to step 1340 and step 1345 described above. Thereby, the sub feedback control is stopped.

  On the other hand, if the value of the sub feedback control condition satisfaction flag XsubFB is “1”, the CPU 71 determines “Yes” in step 1305 and executes the processing of steps 1310 to 1335 to update the sub feedback correction value Fisub. (calculate. Subsequently, the CPU 71 proceeds to step 2530 to determine whether or not the filter regeneration control is being executed. When the filter regeneration control is not being executed (that is, when the normal control is being executed), the CPU 71 determines “No” in step 2530 and sequentially performs the processing of step 2610 and step 2620 described below. Proceed to step 2695 to end the present routine tentatively.

Step 2610: The CPU 71 sets the normal control learning value GKFisubN held in the backup RAM 74 at that time and the sub feedback correction value Fisub newly obtained in step 1325 to the right side of the following equation (18). By substituting, the learning value for normal control GKFisubN is updated. In the equation (18), P1 is a predetermined constant larger than 0 and smaller than 1.
GKFisubN = P1 · GKFisubN + (1-P1) · Fisub (18)
Step 2620: The CPU 71 stores (stores / stores) the normal control learning value GKFisubN obtained in Step 2610 in the backup RAM 74.

  On the other hand, if the filter regeneration control is being executed when the CPU 71 proceeds to step 2530, the CPU 71 determines “Yes” in step 2530, performs the processing of step 2630 and step 2640 described below in order, and step 2695. Proceed to to end the present routine.

Step 2630: The CPU 71 uses the filter regeneration control learning value GKFisubP held in the backup RAM 74 at that time and the sub feedback correction value Fisub newly obtained in step 1325 to the right side of the following equation (19) By substituting into, the learning value GKFisubP for filter regeneration control is updated. In the equation (19), P2 is a predetermined constant larger than 0 and smaller than 1.
GKFisubP = P2 · GKFisubP + (1-P2) · Fisub (19)
Step 2640: The CPU 71 stores (stores / stores) the filter regeneration control learning value GKFisubP obtained in Step 2630 in the backup RAM 74.

  As described above, the normal control learning value GKFisubN is updated and stored in the backup RAM 74 during normal control, and the filter regeneration control learning value GKFisubP is updated and stored in the backup RAM 74 during filter regeneration control.

  Further, the CPU 71 repeatedly executes the sub feedback learning value setting routine shown in FIG. 27 every elapse of a predetermined time. Therefore, when the predetermined timing is reached, the CPU 71 starts processing from step 2700, proceeds to step 2710, and determines whether or not the current time is immediately after the filter regeneration control is started. If the current time is immediately after the filter regeneration control is started, the CPU 71 makes a “Yes” determination at step 2710 to proceed to step 2720 to set the learning value GKFisubP for filter regeneration control to the sub feedback correction value Fisub. Go to step 2730. On the other hand, if the current time is not immediately after the filter regeneration control is started, the CPU 71 makes a “No” determination at step 2710 to directly proceed to step 2730.

  In step 2730, the CPU 71 determines whether or not the present time is immediately after the normal control is started. If the current time is immediately after the start of the normal control, the CPU 71 determines “Yes” in step 2730 and proceeds to step 2740 to set the normal control learning value GKFisubN as the sub feedback correction value Fisub. Proceed to 2795 to end the present routine tentatively. On the other hand, if the current time is not immediately after the normal control is started, the CPU 71 makes a “No” determination at step 2730 to directly proceed to step 2795 to end the present routine tentatively.

  As described above, the sub feedback correction value Fisub at the start of normal control is matched with the learning value GKFisubN for normal control, and the sub feedback correction value Fisub at the start of filter regeneration control is matched with the learning value GKFisubP for filter regeneration control. . Therefore, the sub feedback correction value Fisub becomes a value close to an appropriate value at the time of starting the filter regeneration control and at the time of starting the normal control, so that the emission can be improved.

(Ninth embodiment)
Next, a control device for an internal combustion engine according to a ninth embodiment of the present invention (hereinafter also referred to as “ninth control device”) will be described. The ninth control device acquires an intake air amount related value (intake air flow rate Ga) that increases as the intake air amount of the engine 10 increases, and the acquired intake air amount related value is greater than the intake air amount threshold GaPMth. It differs from the first control device only in that it is configured to prohibit the execution of the filter regeneration control. Therefore, the following description will be made with this difference as the center.

  The CPU 71 of the ninth control device repeatedly executes the routine processing shown in the flowcharts of FIGS. 28 and 7 instead of FIG. 6 every elapse of a predetermined time. Note that steps for performing the same processing as the steps already described in FIG. 28 are denoted by the same reference numerals as those given to such steps. Detailed description of these steps is omitted.

  When the predetermined timing comes, the CPU 71 starts processing from step 2800 of FIG. 28 and proceeds to step 610 to determine whether or not the value of the filter regeneration request flag XPM is “1”. The value of the filter regeneration request flag XPM is changed by the routine shown in FIG.

  Assume that the value of the filter regeneration request flag XPM is “0”. In this case, the CPU 71 makes a “No” determination at step 610 to proceed to step 620 and step 630 to execute the above-described normal control. The control content of the normal control is the same as the control content of the normal control by the first control device.

  In contrast, it is assumed that the value of the filter regeneration request flag XPM is “1”. In this case, the CPU 71 makes a “Yes” determination at step 610 to proceed to step 2810, and reads the intake air amount Ga detected by the air flow meter 61 at that time. Next, the CPU 71 proceeds to step 2820 and reads the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 separately calculated by a routine (not shown) (see the above-described equations (15) and (16)).

  Next, the CPU 71 proceeds to step 2830 and sets the maximum oxygen storage amount Cmax2 of the downstream catalyst 55 to the table shown in step 2830, the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 read in step 2820, and Estimate (acquire) based on This table is measured in advance by experiments and stored in the ROM 72. According to this table, the maximum oxygen storage amount Cmax2 increases as the maximum oxygen storage amount Cmax1 increases.

  Next, the CPU 71 proceeds to step 2840, and determines the intake air amount threshold value GaPMth based on the table shown in step 2840 and the maximum oxygen storage amount Cmax2 of the downstream catalyst 55 estimated in step 2830. . This table is determined in advance by experiments and stored in the ROM 72. According to this table, the larger the maximum oxygen storage amount Cmax2, the larger the intake air amount threshold GaPMth.

  Next, the CPU 71 proceeds to step 2850 to determine whether or not the intake air amount (intake air amount related value that increases as the intake air amount increases) Ga read in step 2810 is smaller than the intake air amount threshold GaPMth. To do. At this time, if the intake air amount Ga is smaller than the intake air amount threshold GaPMth, the CPU 71 determines “Yes” in step 2850 and proceeds to step 640 and step 650 to execute the above-described filter regeneration control. The control content of the filter regeneration control is the same as the control content of the filter regeneration control by the first control device.

  On the other hand, when the CPU 71 proceeds to step 2850, if the intake air amount Ga is equal to or greater than the intake air amount threshold GaPMth, the CPU 71 makes a “No” determination at step 2850 to proceed to step 620 and step 630. Execute control.

  When the filter regeneration control is executed when the intake air amount Ga of the engine 10 is large at the time of acceleration or high load, the amount of nitrogen oxides generated per unit time becomes very large. Therefore, even if the average of the air-fuel ratio of the gas flowing into the downstream side catalyst 55 during the filter regeneration control is controlled to a value close to the theoretical air-fuel ratio by the sub-feedback control (in this case, the weak rich air-fuel ratio AFR), In some cases, the product is released into the atmosphere without being purified by the downstream catalyst 55 (nitrogen oxide blows through the downstream catalyst 55).

  Therefore, the ninth control device prohibits execution of the filter regeneration control when the intake air amount related value (intake air amount Ga) is larger than the intake air amount threshold GaPMth. As a result, since the filter regeneration control is not executed in the operating state where the intake air amount Ga is large, the amount of nitrogen oxides released into the atmosphere can be reduced.

  Further, the ninth control device sets the intake air amount threshold GaPMth so that the intake air amount threshold GaPMth increases as the maximum oxygen storage amount Cmax2 of the downstream catalyst 55 increases (see step 2840).

  The fact that the maximum oxygen storage amount Cmax2 of the downstream catalyst 55 is large means that the deterioration of the downstream catalyst 55 has not progressed, and therefore the downstream catalyst 55 can purify more nitrogen oxides per unit time. Therefore, as in the ninth control device, the larger the maximum oxygen storage amount Cmax2 of the downstream side catalyst 55, the larger the intake air amount threshold GaPMth is set, thereby preventing the nitrogen oxide from being released into the atmosphere and the filter regeneration. Opportunities to perform control can be increased.

  The intake air amount related value may be replaced by the load KL (the value obtained by dividing the in-cylinder intake air amount Mc by the exhaust amount of each cylinder), the throttle valve opening TA, the operation amount Accp of the accelerator pedal 81, and the like. .

(10th Embodiment)
Next, a control device for an internal combustion engine according to a tenth embodiment of the present invention (hereinafter also referred to as “tenth control device”) will be described. In the tenth control device, during the filter regeneration control, the intake air amount related value (intake air amount Ga) is equal to or greater than the intake air amount threshold GaPMth, or the integrated value tGaSL of the intake air amount after the start of the filter regeneration control is “After the completion of the filter regeneration control, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 over a predetermined period is made to be higher than the stoichiometric air-fuel ratio. It is characterized in that the air-fuel ratio on the rich side (the air-fuel ratio on the rich side with respect to the above-described weak rich air-fuel ratio AFR at the time of normal control) is controlled, and then the control returns to normal control.

  The tenth control device is configured to execute the routines shown in the flowcharts of FIGS. 29 to 33 each time a predetermined time elapses. Hereinafter, the operation according to FIG. 29 will be described in order. These operations are performed after the engine 10 has been warmed up and is in a state where the main feedback control and the sub feedback control can be executed (a state where the engine has been warmed up). Further, the value of the normal control execution flag XSTOI is set to “1” when the main feedback control and the sub feedback control become executable.

<First flag operation>
The CPU 71 starts processing from step 2900 in FIG. 29 at a predetermined timing, and determines whether or not the value of the fuel cut execution flag XFC is “0”. Now, assuming that the value of the fuel cut execution flag XFC is “0”, the CPU 71 determines “Yes” in step 2910 and proceeds to step 2920 to determine whether or not the fuel cut condition is satisfied. judge. The fuel cut condition is the same condition (deceleration fuel cut condition) as the fuel cut condition in step 1105 of FIG.

  At this time, if the fuel cut condition is satisfied as the operating state of the engine 10 becomes a predetermined deceleration state, the CPU 71 determines “Yes” in step 2920 and proceeds to step 2930 to execute the fuel cut. The value of the flag XFC is set to “1”, and the values of other flags are set to “0”. Thereafter, the CPU 71 proceeds to step 2995 to end the present routine tentatively. Other flags are as follows: The values of these flags are changed by a routine described later. If the fuel cut condition is not satisfied, the CPU 71 makes a “No” determination at step 2920 to directly proceed to step 2995 to end the present routine tentatively.

  Filter regeneration control execution flag XPMFS: This flag is set to “1” when a condition for executing filter regeneration control is satisfied and when filter regeneration control is being executed, and to “0” in other cases. Yes (see step 3050 in FIG. 30).

  Rich control flag XLINE after normal end of filter regeneration control: This flag is hereinafter simply referred to as “rich control flag after normal end”. The post-normal end rich control flag XRINE is set to “1” when the integrated value tGaSL of the intake air amount after the start of the filter regeneration control becomes larger than the filter regeneration control end threshold GLth (step in FIG. 31). 3160). When the value of the rich control flag XLINE after the normal end is changed to “1”, the filter regeneration control is ended, and the air-fuel ratio of the engine is controlled to an air-fuel ratio richer than the air-fuel ratio in the normal control. That is, “rich control after normal termination” described later is executed.

  Filter regeneration control high Ga post-rich rich control flag XRIGA: This flag is hereinafter simply referred to as “high Ga post rich control flag”. The post-high Ga rich control flag XRIGA is set to “1” when the filter regeneration control is terminated because the intake air amount Ga becomes equal to or greater than the intake air amount threshold GaPMth during the execution of the filter regeneration control (FIG. 31). (See step 3130). When the value of the post-high Ga rich control flag XRIGA is changed to “1”, the filter regeneration control is terminated, and the air-fuel ratio of the engine is controlled to be richer than the air-fuel ratio in the normal control. That is, “rich control after returning to high Ga” is executed.

  Normal control execution flag XSTOI: The normal control execution flag XSTOI is set to “1” when normal control is to be performed and when normal control is being executed, and is set to “0” in other cases (FIG. 32). See). As described above, the value of the normal control execution flag XSTOI is set to “1” when the warm-up of the engine 10 is completed (when the main feedback control and the sub feedback control are executable). .

  Referring to FIG. 29 again, when executing the step 2910, if the value of the fuel cut execution flag XFC is “1”, the CPU 71 makes a “No” determination at step 2910 and proceeds to step 2940 to proceed to the fuel cut. It is determined whether the return condition is satisfied. This fuel cut return condition is also as described above.

  If the fuel cut return condition is satisfied, the CPU 71 determines “Yes” in step 2940 and proceeds to step 2950 to set the value of the normal control execution flag XSTOI to “1” and the values of other flags. Set to “0”. Thereafter, the CPU 71 proceeds to step 2995 to end the present routine tentatively. On the other hand, if the fuel cut return condition is not satisfied, the CPU 71 makes a “No” determination at step 2940 to directly proceed to step 2995 to end the present routine tentatively.

  As described above, the value of the fuel cut execution flag XFC is set to “1” when the fuel cut condition is satisfied, and is set to “0” when the fuel cut return condition is satisfied. Further, the value of the normal control execution flag XSTOI is set to “1” when the fuel cut return condition is satisfied.

<Second flag operation>
The CPU 71 starts processing from step 3000 in FIG. 30 at a predetermined timing, and performs processing from step 3010 to step 3050 described below.
Step 3010: The CPU 71 determines whether or not the value of the normal control execution flag XSTOI is “1”. If the value of the normal control execution flag XSTOI is “1”, the CPU 71 proceeds to step 3020, and proceeds to the normal control execution flag XSTOI. If the value of is not “1”, the process proceeds directly to step 3095 to end the present routine tentatively.

  Step 3020: The CPU 71 determines whether or not the value of the filter regeneration request flag XPM is “1”. If the value of the filter regeneration request flag XPM is “1”, the CPU 71 proceeds to step 3030 and performs the filter regeneration request flag XPM. If the value of is not “1”, the process proceeds directly to step 3095 to end the present routine tentatively. The value of the filter regeneration request flag XPM is set to “1” when it is determined by a routine (not shown) that a request to regenerate the particulate collection filter 54 (filter regeneration request) has occurred. For example, the value of the filter regeneration request flag XPM is “when the integrated value SGa of the intake air amount Ga since the end of the previous filter regeneration control” is greater than or equal to a predetermined threshold (filter regeneration control execution threshold) SGath. 1 ”. Further, the value of the filter regeneration request flag XPM is set to “0” when the necessity of regenerating the particulate collection filter 54 disappears as the filter regeneration control is completed (see step 3170 in FIG. 31). ).

  Step 3030: As in Step 1620 of FIG. 16, the CPU 71 determines that the integrated value of the intake air amount Ga after the fuel cut return time (accumulated intake air amount after fuel cut return) tGaS is obtained separately by a routine not shown. It is determined whether or not it is equal to or greater than Gth. If the integrated intake air amount tGaS after returning from the fuel cut is equal to or greater than the threshold value Gth, the process proceeds to step 3040. Otherwise, the process proceeds directly to step 3095, and this routine is temporarily terminated.

  Step 3040: The CPU 71 determines whether or not the intake air amount Ga detected by the air flow meter 61 at that time is smaller than the intake air amount threshold GaPMth, and if the intake air amount Ga is smaller than the intake air amount threshold GaPMth. Proceed to step 3050, otherwise proceed directly to step 3095 to end the present routine tentatively.

  Step 3050: The CPU 71 sets the value of the filter regeneration control execution flag XPMFS to “1” and the values of other flags to “0”, and proceeds to step 3095 to end this routine once.

As described above, the value of the filter regeneration control execution flag XPMFS is
The value of the normal control execution flag XSTOI is “1” (that is, normal control is being executed)
The value of the filter regeneration request flag XPM is “1” (that is, a filter regeneration request has occurred)
The integrated value tGaS of the intake air amount after returning from the fuel cut is equal to or greater than the threshold value Gth (that is, the downstream catalyst 55 has reached the reduction state), and
When the intake air amount Ga is smaller than the intake air amount threshold GaPMth (that is, the possibility that nitrogen oxides blow through the downstream catalyst 55 is small)
Set to “1”. As a result, filter regeneration control is executed as will be described later.

<Third flag operation>
The CPU 71 starts processing from step 3100 in FIG. 31 at a predetermined timing, proceeds to step 3110, and determines whether or not the value of the filter regeneration control execution flag XPMFS is “1”. That is, the CPU 71 determines in step 3110 whether or not filter regeneration control is being executed. Assuming that the value of the filter regeneration control execution flag XPMFS is not “1” (the filter regeneration control is not being executed), the CPU 71 makes a “No” determination at step 3110 and proceeds directly to step 3195 to temporarily execute this routine. finish.

  On the other hand, assuming that the value of the filter regeneration control execution flag XPMFS is “1” (filter regeneration control is being executed), the CPU 71 determines “Yes” in step 3110 and proceeds to step 3120. Then, it is determined whether or not the intake air amount Ga detected by the air flow meter 61 at that time is equal to or greater than the intake air amount threshold GaPMth. If the intake air amount Ga is equal to or greater than the intake air amount threshold GaPMth, the CPU 71 determines “Yes” in step 3120 and proceeds to step 3130 to set the value of the post-high Ga rich control flag XRIGA to “1”. The values of other flags are set to “0”. Next, the CPU 71 proceeds to step 3140 and subtracts “amount g (tGaSL) monotonically increasing with respect to the integrated value tGaSL of the intake air amount after the start of the filter regeneration control” from the separately estimated “particulate collection amount SPM”. Is stored as “new particulate collection amount SPM”. Thereafter, the CPU 71 proceeds to step 3195 to end the present routine tentatively.

  As described above, when the value of the filter regeneration control execution flag XPMFS is “1” (filter regeneration control is being executed), if the intake air amount Ga becomes equal to or greater than the intake air amount threshold GaPMth, the filter regeneration control execution flag XPMFS. Is changed to “0”, and the value of the post-high Ga rich control flag XRIGA is set to “1”. Thus, as will be described later, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 over a predetermined period is richer than the stoichiometric air-fuel ratio (air-fuel ratio richer than the weak rich air-fuel ratio AFR). To be controlled. Further, the step 3140 subtracts the amount of particulates burned by the filter regeneration control executed immediately before from the estimated particulate collection amount SPM, so that the “particulate collection amount SPM” at that time is more accurate. This is a good estimation step.

  On the other hand, when the value of the filter regeneration control execution flag XPMFS is “1” (filter regeneration control is being executed), if the intake air amount Ga does not exceed the intake air amount threshold GaPMth, the CPU 71 proceeds to step 3110. “Yes” is determined, “No” is determined in Step 3120, and the process proceeds to Step 3150. In step 3150, the CPU 71 determines whether or not the integrated value tGaSL of the intake air amount after the start of the filter regeneration control has become equal to or greater than the filter regeneration control end threshold GLth. At this time, if the integrated value tGaSL is smaller than the threshold value GLth, the CPU 71 proceeds directly to step 3195 to end the present routine tentatively. As a result, the value of the filter regeneration control execution flag XPMFS is maintained at “1”, so that the filter regeneration control is continuously executed.

  In this state, when a predetermined time elapses and the integrated value tGaSL of the intake air amount after the start of the filter regeneration control becomes equal to or greater than the filter regeneration control end threshold GLth, the CPU 71 proceeds to step 3150 following step 3110 and step 3120. Then, the process proceeds to step 3160, where the value of the rich control flag XLINE after normal termination is set to “1”, and the values of other flags are set to “0”. Next, the CPU 71 proceeds to step 3170, sets the value of the filter regeneration request flag XPM to “0”, sets the estimated particulate collection amount SPM to “0”, proceeds to step 3195, and proceeds to step 3195. The routine is temporarily terminated.

  As described above, when the value of the filter regeneration control execution flag XPMFS is “1” (filter regeneration control is being executed), after the filter regeneration control is started without the intake air amount Ga exceeding the intake air amount threshold GaPMth. When the integrated value tGaSL of the intake air amount becomes equal to or greater than the filter regeneration control end threshold GLth, the value of the filter regeneration control execution flag XPMFS is changed to “0” and the value of the rich control flag XLINE after the normal end is “1”. Set to Thus, as will be described later, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 over a predetermined period is richer than the stoichiometric air-fuel ratio (air-fuel ratio richer than the weak rich air-fuel ratio AFR). To be controlled. Further, in this case, since the filter regeneration control is sufficiently executed and the regeneration of the particulate collection filter 54 is completed, the value of the filter regeneration request flag XPM and the value of the particulate collection amount SPM are “in step 3170”. 0 "is set.

<Fourth flag operation>
The CPU 71 starts processing from step 3200 of FIG. 32 at a predetermined timing, executes processing of step 3210 to step 3230 described below, and then proceeds to step 3240.
Step 3210: The CPU 71 determines whether or not the value of the post-high Ga rich control flag XRIGA is “1”. If the value of the post-high Ga rich control flag XRIGA is “1”, the CPU 71 proceeds to step 3220, otherwise proceeds directly to step 3240.

Step 3220: The CPU 71 determines whether or not the first time TR1 has elapsed since the value of the post-high Ga rich control flag XRIGA was changed from “0” to “1”. If the first time TR1 has elapsed, the CPU 71 proceeds to step 3230, otherwise proceeds directly to step 3240.
Step 3230: The CPU 71 sets the value of the normal control execution flag XSTOI to “1” and the values of other flags to “0”.

  As described above, when the first time TR1 elapses after the value of the rich control flag XRIGA after the high Ga becomes “1”, the value of the rich control flag XRIGA after the high Ga is changed to “0”, and the normal control execution flag is set. The value of XSTOI is changed to “1”. As a result, as will be described later, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is controlled to a richer air-fuel ratio (weak rich air-fuel ratio AFR) than the stoichiometric air-fuel ratio.

Subsequently, the CPU 71 executes processing of step 3240 to step 3260 described below, and then proceeds to step 3295 to end the present routine tentatively.
Step 3240: The CPU 71 determines whether or not the value of the rich control flag XLINE after the normal end is “1”. If the value of the rich control flag XLINE is “1” after normal termination, the CPU 71 proceeds to step 3250, otherwise proceeds directly to step 3295 to end the present routine tentatively.

Step 3250: The CPU 71 determines whether or not the second time TR2 has elapsed since the value of the rich control flag XLINE after the normal end is changed from “0” to “1”. If the second time TR2 has elapsed, the CPU 71 proceeds to step 3260, otherwise proceeds directly to step 3295 to end the present routine tentatively.
Step 3260: The CPU 71 sets the value of the normal control execution flag XSTOI to “1” and the values of other flags to “0”.

  Thus, when the second time TR2 elapses after the value of the rich control flag XLINE after the normal end becomes “1”, the value of the rich control flag XLINE after the normal end is changed to “0”, and the normal control execution flag The value of XSTOI is changed to “1”. As a result, as will be described later, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is controlled to a richer air-fuel ratio (weak rich air-fuel ratio AFR) than the stoichiometric air-fuel ratio.

<Air-fuel ratio control>
Further, the CPU 71 executes a routine shown by a flowchart in FIG. 33 every elapse of a predetermined time. The following control is performed by the processing of this routine.
(1) When the value of the fuel cut execution flag XFC is “1”, the fuel cut control is executed and the on-off valve 57 is closed (see step 3305 and step 3310).
(2) When the value of the filter regeneration control execution flag XPMFS is “1”, the filter regeneration control is performed, and the on-off valve 57 is opened (see step 3315 and step 3320). The contents of this filter regeneration control are the same as the contents of control in step 640 and step 650 in FIG.

(3) When the value of the post-high Ga rich control flag XRIGA is “1”, rich control after the return of high Ga is executed, and the on-off valve 57 is closed (see step 3325 and step 3330). In the rich control after returning to high Ga, the "target forced air-fuel ratio abyfrich" is the air-fuel ratio on the upstream side of the main feedback control that is richer than the stoichiometric air-fuel ratio and richer than the weak rich air-fuel ratio AFR. And the main feedback control is executed. The sub feedback control is stopped. As a result, the average of the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is controlled to a richer air-fuel ratio than the above-described weak rich air-fuel ratio AFR. The forced rich air-fuel ratio abyfrich may be set to a richer air-fuel ratio as the integrated value GaSL of the intake air amount Ga during the previous filter regeneration control is larger.

(4) When the value of the rich control flag XLINE after the normal end is “1”, the rich control after the normal end (the rich control after the end of the normal regeneration) is executed, and the on-off valve 57 is closed (steps 3335 and 3340 are performed). reference.). In the rich control after the normal end, the upstream target air-fuel ratio abyfr of the main feedback control is set to the forced rich air-fuel ratio abyfrich, and the main feedback control is executed. The sub feedback control is stopped. As a result, the average of the air-fuel ratio of the air-fuel mixture supplied to the engine 10 is controlled to a richer air-fuel ratio than the above-described weak rich air-fuel ratio AFR. The forced rich air-fuel ratio abyfrich may be set to a richer air-fuel ratio as the integrated value GaSL of the intake air amount Ga during the previous filter regeneration control is larger.

(5) When any one of the fuel cut execution flag XFC, the filter regeneration control execution flag XPMFS, the high Ga post rich control flag XRIGA, and the normal end rich control flag XRINE is not “1” (the values of these flags are If it is “0”), the above-described normal control (the same control as the normal control in step 630 in FIG. 6) is executed, and the on-off valve 57 is closed.

  As described above, the tenth control device determines that the intake air amount related value (intake air amount Ga) is the intake air while the filter regeneration control is being executed (when the value of the filter regeneration control execution flag XPMFS is “1”). The bypass passage is connected to the on-off valve 57 during a predetermined period (first time TR1) from the time when the execution of the filter regeneration control is stopped by being larger than the amount threshold GaPMth (see Step 3120 and Step 3130 in FIG. 31). In addition to giving an instruction to shut off, the average of the air-fuel ratio of the mixture supplied to the plurality of cylinders of the engine 10 is richer than the “average of the air-fuel ratio of the mixture supplied to the plurality of cylinders during normal control” The air-fuel ratio is controlled to be abyfrich (refer to the rich control after returning to high Ga in step 3330 in FIG. 33), and then the execution of the normal control is started. It is configured urchin (see step 3220 and step 3230 of FIG. 32, and step 3345 of FIG. 33, a.).

  During the filter regeneration control, a large amount of oxygen flows into the upstream catalyst 53. Therefore, the oxygen storage amount OSA1 of the upstream catalyst 53 reaches the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 or an amount in the vicinity thereof. In such a state, if the filter regeneration control is stopped by increasing the intake air amount Ga, immediately after that, the upstream catalyst 53 cannot effectively purify the nitrogen oxides. As a result, nitrogen oxides may pass through (blow through) the upstream catalyst 53 and the downstream catalyst 55 without being purified.

  Therefore, the tenth control device performs a predetermined period TR1 from when the execution of the filter regeneration control is stopped when the intake air amount Ga becomes larger than the intake air amount threshold value GaPMth during the execution of the filter regeneration control. Control (control to make the air-fuel ratio of the air-fuel ratio supplied to the plurality of cylinders richer than the average air-fuel ratio of the air-fuel mixture supplied to the plurality of cylinders during normal control) To do. Thereby, the oxygen storage amount OSA1 of the upstream catalyst 53 can be rapidly reduced. As a result, the upstream catalyst 53 is in a state in which more nitrogen oxides can be purified within a short period after the filter regeneration control is stopped. Therefore, the amount of nitrogen oxide that blows through the upstream catalyst 53 and the downstream catalyst 55 can be reduced.

  Note that the tenth control device completes the normal termination until the second time TR2 elapses even when the integrated value tGaSL of the intake air amount after the start of the filter regeneration control becomes equal to or greater than the filter regeneration control end threshold GLth. Rear rich control (control in which the average of the air-fuel ratio of the air-fuel mixture supplied to the plurality of cylinders becomes a richer air-fuel ratio than the average of the air-fuel ratio of the air-fuel mixture supplied to the plurality of cylinders during normal control) Execute. Accordingly, the oxygen storage amount OSA1 of the flow side catalyst 53 after the filter regeneration control can be quickly reduced. As a result, the upstream catalyst 53 is in a state in which more nitrogen oxides can be purified within a short period after the filter regeneration control is stopped.

(Eleventh embodiment)
Next, a control device for an internal combustion engine according to an eleventh embodiment of the present invention (hereinafter also referred to as “eleventh control device”) will be described. The eleventh control device is configured to supply a part of the exhaust gas (in this case, the exhaust gas is air because the fuel cut is being executed) to the particulate collection filter 54 during the fuel cut control. However, it differs from a 1st control apparatus. Hereinafter, this difference will be mainly described.

  As shown in FIG. 34, the eleventh control device includes a first bypass passage forming member 56a, a second bypass passage forming member 56b, and a third bypass passage forming member 56c instead of the bypass passage forming member 56 shown in FIG. I have. Each of the first to third bypass passage forming members 56a to 56c is formed of a tubular member. Further, the eleventh control device includes a three-way valve (passage switching means, switching valve) 58 in place of the on-off valve 57 shown in FIG.

One end of the first bypass passage forming member 56a is connected to a branch portion 51a1 connected to the exhaust port of the first cylinder # 1. The other end of the first bypass passage forming member 56 a is connected to the inlet portion of the three-way valve 58.
One end of the second bypass passage forming member 56b is connected to one of the two outlet portions of the three-way valve 58 (hereinafter also referred to as “first outlet portion”). The other end of the second bypass passage forming member 56b is connected to the exhaust pipe 52 (the main passage portion) at a position between the particulate collection filter 54 and the downstream catalyst 55.

  That is, the branch portion 51a1, the first bypass passage forming member 56a, and the second bypass passage forming member 56b are cylinders other than some cylinders (second to fourth cylinders) of the plurality of cylinders of the engine 10. The gas exhausted through the exhaust port of the cylinder (first cylinder) of the first cylinder directly constitutes a bypass passage that allows the gas to flow directly into the downstream catalyst 55 without passing through the particulate collection filter 54 (and the upstream catalyst 53). Corresponding to “passage component”.

  One end of the third bypass passage forming member 56 c is connected to the other one of the two outlet portions of the three-way valve 58 (hereinafter also referred to as “second outlet portion”). The other end of the third bypass passage forming member 56c is connected to the exhaust pipe 52 (the main passage portion) at a position between the upstream catalyst 53 and the particulate collection filter 54.

  The three-way valve 58 is in a state in which one inlet and the first outlet are in communication with each other in response to an instruction signal from the CPU 71 of the electric control device 70, and in a state in which one inlet and the second outlet are in communication. One of the states in which one inlet portion does not communicate with any of the first outlet portion and the second outlet portion can be selected.

  Next, the operation of the eleventh control apparatus configured as described above will be described. The CPU 71 of the eleventh control device executes the routine shown in FIG. 35 every elapse of a predetermined time. In FIG. 35, steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as those assigned to such steps in FIG. A detailed description of such steps is omitted. Hereinafter, the cases will be described separately.

(Case 1) When the regeneration request for the particulate collection filter 54 is generated, the value of the filter regeneration request flag XPM is “1”, and the fuel cut condition is not satisfied.
In this case, the CPU 71 determines “Yes” in “Step 610 for determining whether or not the value of the filter regeneration request flag XPM is“ 1 ”” following Step 3500. Further, the CPU 71 determines “No” in the next “step 3510 for determining whether or not the fuel cut condition is satisfied”, and proceeds to step 3520.

  In step 3520, the CPU 71 sends an instruction signal “move the inlet and the first outlet” to the three-way valve 58. As a result, the gas discharged from the first cylinder is directly introduced into the downstream catalyst 55, bypassing the upstream catalyst 53 and the particulate collection filter 54. In the next step 650, the CPU 71 executes the “filter regeneration control” described above. Thereafter, the CPU 71 proceeds to step 3595 to end the present routine tentatively. This control state is the same as the control state during filter regeneration control by the first control device. Accordingly, the particulate collection filter 54 is regenerated while the discharge amount of nitrogen oxides is suppressed.

(Case 2) When the regeneration request for the particulate collection filter 54 is generated, the value of the filter regeneration request flag XPM is “1”, and the fuel cut condition is satisfied.
In this case, the CPU 71 determines “Yes” in step 610 following step 3500, and also determines “Yes” in the next step 3510 and proceeds to step 3530.

  In step 3530, the CPU 71 sends an instruction signal “move the inlet and the second outlet” to the three-way valve 58. Thereby, the gas discharged from the first cylinder bypasses the upstream catalyst 53 and is directly introduced into the particulate collection filter 54. In this case, since fuel cut control is executed as described later, the gas discharged from the first cylinder is air containing a large amount of oxygen. Next, the CPU 71 proceeds to step 3540 and executes fuel cut control for stopping fuel injection from all the injectors 39. As a result, since oxygen is supplied to the particulate collection filter 54, the particulates collected in the particulate collection filter 54 are burned, and the particulate collection filter 54 is regenerated. Thereafter, the CPU 71 proceeds to step 3595 to end the present routine tentatively.

(Case 3) When the regeneration request for the particulate collection filter 54 is not generated, the value of the filter regeneration request flag XPM is “0”, and the fuel cut condition is not satisfied.
In this case, the CPU 71 makes a “No” determination at step 610 following step 3500 to proceed to step 3550 to instruct the three-way valve 58 to “block communication between the inlet portion and the first outlet portion and the second outlet portion”. Send a signal. As a result, all of the gas discharged from the first cylinder flows to the collecting portion 51b together with the gas discharged from the second cylinder to the fourth cylinder, and then passes through the exhaust pipe 52.

  Next, the CPU 71 proceeds to step 3560 to determine whether or not the fuel cut condition is satisfied. In this case, the fuel cut condition is not satisfied. Accordingly, the CPU 71 makes a “No” determination at step 3560 to proceed to step 630 to execute the “normal control” described above. Thereafter, the CPU 71 proceeds to step 3595 to end the present routine tentatively. This control state is the same as the control state during normal control by the first control device. Therefore, unburned matter and nitrogen oxides are purified by the upstream catalyst 53 and the downstream catalyst 55, and the fine particles are collected by the fine particle collecting filter 54.

(Case 4) When the regeneration request for the particulate collection filter 54 is not generated, the value of the filter regeneration request flag XPM is “0”, and the fuel cut condition is satisfied.
In this case, the CPU 71 makes a “No” determination at step 610 following step 3500 to proceed to step 3550 to instruct the three-way valve 58 to “block communication between the inlet portion and the first outlet portion and the second outlet portion”. Send a signal. As a result, all of the gas discharged from the first cylinder flows to the collecting portion 51b together with the gas discharged from the second cylinder to the fourth cylinder, and then passes through the exhaust pipe 52.

  Next, the CPU 71 determines “Yes” in step 3560 and proceeds to step 3570 to execute fuel cut control. That is, the CPU 71 stops fuel injection from all the injectors 39, proceeds to step 3595, and once ends this routine.

  As described above, in the eleventh control apparatus, the “main exhaust passage constituting portion that constitutes the“ main exhaust passage through which the exhaust gas discharged through the exhaust ports of some cylinders (second to fourth cylinders) passes ”is formed. "Includes a second branch portion 51a1 connected to the exhaust port of another cylinder (first cylinder) and connected to the collecting portion 51b.

The bypass passage component is
A bypass passage having one end connected to the second branch portion 51a1 and the other end connected to the main passage portion (exhaust pipe 52) at a "position between the particulate collection filter 54 and the downstream catalyst 55". A first tubular portion (56a, 56b) constituting
One end is connected to the second branch portion 51a1 and the other end is connected to the main passage portion (exhaust pipe 52) at the “position between the upstream catalyst 53 and the particulate collection filter 54”. A second tubular portion (56a, 56c) to be configured;
A three-way valve 58 which is a passage switching means;
Is provided.

At this time, the passage switching means (three-way valve 58)
A first state in which only the second branch portion 51a1 communicates with the main passage portion (exhaust pipe 52) at a position between the particulate collection filter 54 and the downstream catalyst 55 (see step 3520). ),
A second state in which only the second branch portion 51a1 communicates with the main passage portion (exhaust pipe 52) at a position between the upstream catalyst 53 and the particulate collection filter 54 (see step 3530). ),as well as,
A third state in which “the communication between the second branch portion 51a1 and the main passage (exhaust pipe 52)” through the first tubular portion (56a, 56b) and the second tubular portion (56a, 56c) is blocked (step 3550). ),
Any one of the above states is selectively achieved according to an instruction.

And the eleventh control device
When executing the filter regeneration control, an instruction to achieve the first state is given to the passage switching means to execute the filter regeneration control (see Step 3520 and Step 650).
When the operation state of the engine becomes a predetermined fuel cut operation state, fuel supply to the engine is stopped and an instruction to achieve the second state is given to the passage switching means to execute fuel cut control ( See steps 3530 and 3540),
When neither the filter regeneration control nor the fuel cut control is executed, the average of the air-fuel ratio of the air-fuel mixture supplied to each of the plurality of cylinders is the air-fuel ratio within the predetermined air-fuel ratio range including the theoretical air-fuel ratio. And the normal control is executed by giving an instruction to the passage switching means to achieve the third state (see Step 3550 and Step 630).
It is configured as follows.

  Therefore, as in other control devices, when the fuel cut control is not executed, the filter regeneration control or the normal control is executed. Further, when fuel cut control is executed when there is a regeneration request for the particulate collection filter, the air discharged from the other cylinder (first cylinder) is located immediately before and upstream of the particulate collection filter 54. be introduced. Therefore, since air containing a large amount of oxygen is supplied to the particulate collection filter 54, the particulate collection filter 54 can be regenerated even during fuel cut control.

  Note that the eleventh control device gives an instruction to the passage switching means to achieve the third state when fuel cut control is executed when there is no regeneration request for the particulate collection filter. That is, all the gas discharged from all the cylinders flows into the upstream catalyst 53. Instead, the eleventh control device gives an instruction to the passage switching means to achieve the second state when the fuel cut control is executed when there is no regeneration request for the particulate collection filter. The exhaust gas (air) during fuel cut control may be supplied to the collecting filter 54.

  As described above, according to each embodiment of the present invention, oxygen is supplied to the particulate collection filter 54 in the filter regeneration control, and the average of the air-fuel ratio of the gas flowing into the downstream catalyst 55 is approximately theoretical. The air-fuel ratio can be controlled. Therefore, a control device for a gasoline engine, which can regenerate the particulate collection filter without increasing the emission amount of nitrogen oxides, is provided.

  The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, in each of the above embodiments, the duration of one filter regeneration control may be increased as the particulate collection amount SPM estimated at the time of starting the filter regeneration control increases. Furthermore, the duration of one filter regeneration control may be set longer as the maximum oxygen storage amount Cmax1 of the upstream catalyst 53 is larger.

  The sub-feedback control is performed by the upstream air-fuel ratio sensor 66 so that the output value Voxs of the downstream air-fuel ratio sensor 67 matches the downstream target value, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-278186. It may be a control that apparently corrects the detected air-fuel ratio. Alternatively, the sub-feedback control is created based on the output value Voxs of the downstream air-fuel ratio sensor 67 and based on the output value of the upstream air-fuel ratio sensor 66 as disclosed in Japanese Patent Laid-Open No. 06-010738. Alternatively, the control may be performed to change the air-fuel ratio correction coefficient.

  Furthermore, in each embodiment, between the connection position of the branch part 51a1 connected to the exhaust port of the first cylinder and the bypass passage forming member 56 (or the first bypass passage forming member 56a) and the collecting part 51b. The control device is configured to close the second on-off valve during the filter regeneration control and to open the second on-off valve during other normal control. May be. Further, the downstream target air-fuel ratio in the sub feedback control may be a stoichiometric air-fuel ratio instead of the weak rich air-fuel ratio.

1 is a schematic view of an internal combustion engine to which a control device (first control device) according to a first embodiment of the present invention is applied. It is a schematic block diagram of the internal combustion engine shown in FIG. It is the graph which showed the purification rate of the unburned component and the nitrogen oxide with respect to the air fuel ratio of the upstream catalyst and downstream catalyst shown in FIG. 2 is a graph showing the relationship between the output voltage of the upstream air-fuel ratio sensor shown in FIG. 1 and the air-fuel ratio. 2 is a graph showing the relationship between the output voltage of the downstream air-fuel ratio sensor shown in FIG. 1 and the air-fuel ratio. It is the flowchart which showed the routine which CPU of a 1st control apparatus performs. It is the flowchart which showed the routine which CPU of a 1st control apparatus performs. It is a functional block diagram at the time of a 1st control apparatus performing air-fuel ratio control. It is a functional block diagram of the basic correction value calculation means shown in FIG. It is the conceptual diagram which showed the driving | operation area | region which stores the basic correction value calculated by the basic correction value calculation means shown in FIG. It is the flowchart which showed the detailed routine for performing calculation of the fuel injection amount, and the injection instruction which CPU of a 1st control apparatus performs. It is the flowchart which showed the routine for calculating the main feedback correction value which CPU of the 1st control device performs. It is the flowchart which showed the routine for calculating the sub feedback correction value which CPU of the 1st control unit executes. It is the flowchart which showed the routine for calculating the basic correction value which CPU of the 1st control unit executes. It is the flowchart which showed the routine for changing the value of the filter regeneration request flag which CPU of the 1st control unit executes. It is the flowchart which showed the routine which CPU of the control apparatus (2nd control apparatus) concerning 2nd Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of a 2nd control apparatus performs. It is the flowchart which showed the routine which CPU of a 2nd control apparatus performs. It is the flowchart which showed the routine which CPU of the control apparatus (3rd control apparatus) concerning 3rd Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus (4th control apparatus) which concerns on 4th Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the 4th control unit performs. It is the flowchart which showed the routine which CPU of the 4th control unit performs. It is the flowchart which showed the routine which CPU of the control apparatus (5th control apparatus) which concerns on 5th Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus (6th control apparatus) concerning 6th Embodiment of this invention performs. It is a flowchart which showed the routine which CPU of the control apparatus (7th control apparatus) concerning 7th Embodiment of this invention performs. It is a flowchart which showed the routine which CPU of the control apparatus (8th control apparatus) concerning 8th Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the 8th control unit executes. It is the flowchart which showed the routine which CPU of the control device (9th control device) which relates to 9th execution form of this invention executes. It is a flowchart which showed the routine which CPU of the control apparatus (10th control apparatus) which concerns on 10th Embodiment of this invention performs. It is a flowchart which showed the routine which CPU of 10th control apparatus performs. It is a flowchart which showed the routine which CPU of 10th control apparatus performs. It is a flowchart which showed the routine which CPU of 10th control apparatus performs. It is a flowchart which showed the routine which CPU of 10th control apparatus performs. It is a schematic block diagram of the internal combustion engine to which the control apparatus (11th control apparatus) concerning 11th Embodiment of this invention is applied. It is the flowchart which showed the routine which CPU of the 11th control unit performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Multi-cylinder internal combustion engine (gasoline engine), 21 ... Cylinder, 22 ... Piston, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 34 ... Exhaust port, 35 ... Exhaust valve, 39 ... Injector, 40 ... Intake system, 44 ... throttle valve, 50 ... exhaust system, 51 ... exhaust manifold, 51a1 ... branch, 51a2 ... branch, 51a3 ... branch, 51a4 ... branch, 51b ... collecting part, 52 ... exhaust pipe, 53 ... Upstream catalyst, 54 ... particulate collection filter, 55 ... downstream catalyst, 56 ... bypass passage forming member, 57 ... open / close valve, 58 ... three-way valve, 61 ... hot-wire air flow meter, 66 ... upstream air-fuel ratio sensor, 67 ... downstream air-fuel ratio sensor, 70 ... electric control device, 71 ... CPU, 74 ... backup RAM.

Claims (18)

A first branch portion connected to an exhaust port of a part of a plurality of cylinders included in the multi-cylinder internal combustion engine, a collecting portion where the first branch portions are gathered, and a main passage portion connected to the collecting portion. A main exhaust passage constituting part that constitutes a main exhaust passage through which exhaust gas discharged through the exhaust port of the cylinder of the same part is passed,
A particulate collection filter disposed in the main passage,
A downstream catalyst that is a three-way catalyst disposed in a position downstream of the particulate collection filter in the main passage portion;
A bypass passage through which exhaust gas discharged through an exhaust port of another cylinder other than the part of the plurality of cylinders directly flows into the downstream catalyst without passing through the particulate collection filter; A bypass passage component to be configured; and
The average air-fuel ratio of the air-fuel mixture supplied to the some cylinders is controlled to an air-fuel ratio leaner than the stoichiometric air-fuel ratio, and the average air-fuel ratio of the air-fuel mixture supplied to the other cylinders is the stoichiometric air-fuel ratio. Air-fuel ratio control means for performing filter regeneration control for controlling the air-fuel ratio on the richer side,
The control apparatus of the internal combustion engine provided with. The control apparatus for an internal combustion engine according to claim 1,
The air-fuel ratio control means includes
During execution of the filter regeneration control, a predetermined air-fuel ratio in which the average of the air-fuel ratio of the air-fuel mixture consisting of the air-fuel mixture supplied to the some cylinders and the air-fuel mixture supplied to the other cylinders includes the stoichiometric air-fuel ratio A control device configured to control an air-fuel ratio of an air-fuel mixture supplied to the some cylinders and an air-fuel ratio of an air-fuel mixture supplied to the other cylinders so that the air-fuel ratio is within a range. A control device for an internal combustion engine according to claim 2,
The main exhaust passage constituent part includes a second branch part connected to the exhaust port of the other cylinder and connected to the collective part,
The bypass passage constituting portion has one end connected to the second branch portion and the other end connected to the main passage portion at a position between the particulate collection filter and the downstream catalyst. An on-off valve comprising a bypass passage forming member constituting the bypass passage and shutting and opening the bypass passage in response to an instruction;
The air-fuel ratio control means executes the filter regeneration control by giving an instruction to open the bypass passage to the on-off valve when executing the filter regeneration control, and performs the filter regeneration control when not executing the filter regeneration control. An instruction to shut off the bypass passage is given to the air-fuel ratio, and the average of the entire air-fuel ratio supplied to each of the plurality of cylinders is controlled to an air-fuel ratio within the predetermined air-fuel ratio range including the stoichiometric air-fuel ratio. A control device configured to perform control. A control device for an internal combustion engine according to claim 3,
Reduction state determination means for determining whether or not the downstream catalyst has reached a reduction state capable of purifying a predetermined amount of nitrogen oxides,
The air-fuel ratio control unit is configured to permit execution of the filter regeneration control when it is determined that the downstream catalyst has reached the reduction state during execution of the normal control. A control device for an internal combustion engine according to claim 4,
Fuel cut means for stopping the supply of fuel to the engine when the operating state of the engine becomes a predetermined fuel cut operating state;
The air-fuel ratio control means is an air-fuel ratio within the predetermined air-fuel ratio range including the stoichiometric air-fuel ratio, wherein the average of the air-fuel ratios of the air-fuel mixture supplied to each of the plurality of cylinders in the normal control is the stoichiometric air-fuel ratio. The fuel cut return time when the fuel cut to the engine is released and the fuel cut to the engine is released from the stop of the fuel supply by the fuel cut means is released. Is configured to start execution of the normal control from
The reduction state determination means is an excess amount of a reducing component that is an amount obtained by subtracting an amount of an oxidizing component discharged from the engine that oxidizes the reducing component from an amount of a reducing component that is an unburned matter discharged from the engine. So as to determine that the downstream catalyst has reached the reduction state when the first integrated value is equal to or greater than a first predetermined value. Configured control device. A control device for an internal combustion engine according to claim 4,
Fuel cut means for stopping the supply of fuel to the engine when the operation state of the engine becomes a predetermined fuel cut operation state;
A downstream air-fuel ratio sensor for detecting an air-fuel ratio of the gas flowing into the downstream catalyst;
With
The air-fuel ratio control means is an air-fuel ratio within the predetermined air-fuel ratio range including the stoichiometric air-fuel ratio, wherein the average of the air-fuel ratios of the air-fuel mixture supplied to each of the plurality of cylinders in the normal control is the stoichiometric air-fuel ratio. The fuel cut return time when the fuel cut to the engine is released and the fuel cut to the engine is released from the stop of the fuel supply by the fuel cut means is released. Is configured to start execution of the normal control from
The reduction state determination means is an excess amount of a reducing component that is an amount obtained by subtracting an amount of an oxidizing component discharged from the engine that oxidizes the reducing component from an amount of a reducing component that is an unburned matter discharged from the engine. Is integrated from the rich inversion time after the fuel cut return time and the detected air-fuel ratio detected by the downstream air-fuel ratio sensor has changed to the air-fuel ratio richer than the stoichiometric air-fuel ratio. And a control device configured to determine that the downstream catalyst has reached the reduction state when the first integrated value is equal to or greater than a first predetermined value. A control device for an internal combustion engine according to any one of claims 1 to 6,
A control apparatus comprising an upstream side catalyst that is a three-way catalyst disposed in a position upstream of the particulate collection filter in the main passage part or the collecting part. The control device for an internal combustion engine according to any one of claims 1 to 7,
The air-fuel ratio control means obtains a particulate collection amount that is the amount of particulates collected by the particulate collection filter, and the obtained particulate collection amount is large when the filter regeneration control is executed. A control device configured to control the average air-fuel ratio of the air-fuel mixture supplied to the some cylinders to a leaner air-fuel ratio. A control device for an internal combustion engine according to any one of claims 1 to 8,
The air-fuel ratio control means acquires a filter temperature related value that increases as the temperature of the particulate collection filter increases, and when the acquired filter temperature related value is higher than a high-side filter threshold temperature, the filter regeneration control A control device configured to prohibit execution. A control device for an internal combustion engine according to claim 9,
When the acquired filter temperature related value is lower than the high-side filter threshold temperature, the air-fuel ratio control means is configured to reduce the mixture gas supplied to the some cylinders when the filter regeneration control is executed. A control device configured to control the air-fuel ratio to a richer-side air-fuel ratio as the filter temperature-related value approaches the higher-side filter threshold temperature. A control device for an internal combustion engine according to any one of claims 1 to 8,
The air-fuel ratio control means acquires a filter temperature-related value that increases as the temperature of the particulate collection filter increases. When the acquired filter temperature-related value is lower than a low-side filter threshold temperature, the filter regeneration control A control device configured to prohibit execution. The control apparatus for an internal combustion engine according to claim 11,
When the acquired filter temperature-related value is higher than the low-side filter threshold temperature, the air-fuel ratio control means is configured to reduce the mixture gas supplied to the some cylinders when the filter regeneration control is executed. A control device configured to control the air-fuel ratio to a richer air-fuel ratio as the filter temperature-related value approaches the lower-side filter threshold temperature. The control apparatus for an internal combustion engine according to claim 3,
The air-fuel ratio control means acquires a downstream catalyst temperature related value that increases as the temperature of the downstream catalyst increases, and when the acquired downstream catalyst temperature related value is lower than a low downstream catalyst threshold temperature A control device configured to prohibit execution of the filter regeneration control. The control apparatus for an internal combustion engine according to claim 3,
An upstream catalyst disposed in a position upstream of the particulate collection filter in the main passage portion or the collecting portion;
An upstream air-fuel ratio that is disposed at a position upstream of the upstream catalyst and that is an output value corresponding to the air-fuel ratio of the gas flowing through the portion disposed in the main passage portion or the collecting portion. A sensor,
A downstream side of the main passage portion that is disposed at a position between the particulate collection filter and the downstream catalyst and outputs an output value corresponding to the air-fuel ratio of the gas flowing through the disposed portion. An air-fuel ratio sensor;
Whether the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled according to a predetermined mode and whether the upstream catalyst has deteriorated based on the output value of the upstream air-fuel ratio sensor and the output value of the downstream air-fuel ratio sensor Deterioration determination means for executing deterioration determination control for determining whether or not
With
The air-fuel ratio control means includes
A control device configured to prohibit execution of the filter regeneration control when the deterioration determination means is executing the deterioration determination control. The control apparatus for an internal combustion engine according to claim 3,
The air-fuel ratio control means acquires an intake air amount related value that increases as the intake air amount of the engine increases, and when the acquired intake air amount related value is greater than an intake air amount threshold, the filter regeneration control A control device configured to prohibit execution. The control apparatus for an internal combustion engine according to claim 15,
The air-fuel ratio control means acquires the maximum oxygen storage amount of the downstream catalyst, and sets the intake air amount threshold value so that the intake air amount threshold value increases as the acquired maximum oxygen storage amount increases. Control device. The control apparatus for an internal combustion engine according to claim 15 or 16,
An upstream catalyst that is a three-way catalyst disposed in a position upstream of the particulate collection filter in the main passage portion or the collecting portion;
The air-fuel ratio control means is configured to provide the on-off valve for a predetermined period from the time when the filter regeneration control is stopped due to the intake air amount related value becoming larger than the intake air amount threshold during the execution of the filter regeneration control. The air-fuel ratio average of the air-fuel mixture supplied to the plurality of cylinders is richer than the average air-fuel ratio of the air-fuel mixture supplied to the plurality of cylinders during the normal control. A control device configured to perform control so that the air-fuel ratio becomes the same, and then to start execution of the normal control. A control device for an internal combustion engine according to claim 2,
An upstream catalyst that is a three-way catalyst disposed in a position upstream of the particulate collection filter in the main passage portion or the collecting portion;
The main exhaust passage component is
A second branch connected to the exhaust port of the other cylinder and connected to the collecting portion;
The bypass passage component is
One end of the bypass passage is configured by one end being connected to the second branch portion and the other end being connected to the main passage portion at a position between the particulate collection filter and the downstream catalyst. A tubular section;
A second tubular portion having one end connected to the second branch portion and the other end constituting a passage connected to the main passage portion at a position between the upstream catalyst and the particulate collection filter;
Passage switching means;
With
The passage switching means is
A first state in which only the second branch portion and the main passage portion at a position between the particulate collection filter and the downstream catalyst are communicated;
A second state in which only the second branch portion communicates with the main passage portion at a position between the upstream catalyst and the particulate collection filter; and
A third state in which communication between the second branch portion and the main passage is blocked;
Is configured to selectively achieve any of the states according to instructions,
The air-fuel ratio control means includes
Executing the filter regeneration control by giving an instruction to the passage switching means to achieve the first state when the filter regeneration control is performed;
When the operation state of the engine becomes a predetermined fuel cut operation state, the fuel cut control is performed by stopping the supply of fuel to the engine and giving an instruction to achieve the second state to the passage switching means,
When neither the filter regeneration control nor the fuel cut control is executed, the average of the air-fuel ratio of the air-fuel mixture supplied to each of the plurality of cylinders is the air-fuel ratio within the predetermined air-fuel ratio range including the theoretical air-fuel ratio. And performing normal control by giving an instruction to achieve the third state to the passage switching means.
A control device configured as described above.

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