JP4710815B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  Conventionally, as an exhaust purification device applied to an internal combustion engine such as a vehicle-mounted diesel engine, an exhaust system provided with a filter for collecting particulate matter (PM) that contains soot as a main component is known. ing. In such an exhaust purification device, the filter is clogged due to the accumulation of PM, which may lead to a decrease in the PM collection ability of the filter or a decrease in engine output. Filter regeneration is performed to eliminate clogging of the filter by burning.

Specifically, filter regeneration is performed as follows.
When the PM accumulation amount in the filter rises to the allowable upper limit value, the main fuel injection, which is the fuel injection for engine operation from the fuel injection valve to the combustion chamber, is performed, and then the fuel component is supplied to the exhaust system catalyst. Post-injection, which is fuel injection from the fuel injection valve, is performed. When fuel components are supplied to the exhaust system catalyst through this post injection, components such as hydrocarbons (HC) and carbon monoxide (CO) are oxidized in the exhaust and on the catalyst, and the heat generated by the oxidation reaction is generated. The filter is placed in a high temperature environment. Thereby, PM accumulated on the filter is burned and removed, and clogging due to PM of the filter is eliminated.

  By the way, when the vehicle equipped with the internal combustion engine is in a place with a low atmospheric pressure such as a high altitude, in other words, in a place where the density of air is low, if post injection is performed to perform filter regeneration, the filter temperature will rise excessively. There is a fear. This is related to the fact that the density of air is lower in places where atmospheric pressure is lower than in places where standard atmospheric pressure is present. That is, when the density of air decreases, the mass of air sucked per unit time (intake air amount) in the internal combustion engine decreases, and changes from, for example, the state indicated by the solid line L1 to the state indicated by the solid line L2 in FIG. To do. As a result, the air-fuel ratio of the gas in the combustion chamber after fuel injection into the combustion chamber becomes rich, and the temperature of the exhaust gas sent to the exhaust system after fuel combustion in the combustion chamber becomes high. This causes an excessive increase in the filter temperature during post injection at a low atmospheric pressure.

In consideration of the above, as shown in Patent Document 1, a filter temperature is predicted based on the atmospheric oxygen concentration obtained by a pressure sensor or an air density sensor, and the filter temperature is postponed when the filter temperature is higher than a predetermined temperature. It is conceivable to reduce the injection amount. In this case, it is possible to detect an increase in the filter temperature due to a decrease in atmospheric pressure, and it is possible to suppress an excessive increase in the filter temperature through a decrease in the post injection amount.
JP 2004-218440 A (paragraphs [0080] and [0085])

  As shown in Patent Document 1, the filter temperature is predicted based on the oxygen concentration in the atmosphere, and the post-injection amount is reduced when the filter temperature exceeds a predetermined temperature. An excessive increase in the filter temperature during regeneration can be suppressed. However, when post-injection for filter regeneration is performed in a state where the atmospheric pressure is low, the temperature of the portion upstream of the catalyst in the exhaust system also rises. For example, the state shown by the solid line L4 from the state shown by the solid line L3 in FIG. Change to state.

  Here, it has been confirmed that the temperature of the portion upstream of the catalyst in the exhaust system also rises higher than the filter temperature through post-injection during filter regeneration at a low atmospheric pressure. The reason why such a phenomenon occurs is presumed to be the reason shown in the following [1] and [2].

  [1] When fuel is injected into the combustion chamber by post injection, it is inevitable that a part of the fuel burns in the combustion chamber in a high temperature environment. When the atmospheric pressure decreases and the intake air amount of the internal combustion engine decreases, the air-fuel ratio of the gas existing in the combustion chamber immediately after the post-injection becomes rich, and the fuel injected into the combustion chamber by the post-injection becomes the same in the combustion chamber. It becomes easy to burn at. As a result, of the fuel injected into the combustion chamber by post injection, the amount of fuel combusted in the combustion chamber increases, the temperature of the exhaust immediately after being discharged from the combustion chamber rises, and the exhaust in the exhaust system becomes a catalyst. The upstream portion is heated.

  [2] In the above [1], when a portion upstream of the catalyst in the exhaust system is heated by exhaust, the low temperature exhaust gas from which heat has been removed by the portion reaches the filter. Further, as shown in [1] above, when the amount of fuel combusted in the combustion chamber among the fuel injected into the combustion chamber by post injection increases, the amount of fuel reaching the catalyst correspondingly increases. Since the heat generated by the oxidation reaction of the fuel component on the catalyst is reduced, the transmission of the heat to the filter is also reduced. As a result, the increase in the filter temperature becomes dull.

  As described above, when the temperature of the upstream portion of the exhaust system with respect to the catalyst increases through the post-injection during filter regeneration at a low atmospheric pressure, the filter temperature becomes a predetermined temperature and the post-injection. There is a high possibility that the temperature of the portion upstream of the catalyst in the exhaust system reaches the allowable upper limit before the amount is reduced. In this case, even if the temperature of the portion upstream of the catalyst in the exhaust system exceeds the allowable upper limit value, the post injection amount is not reduced because the filter temperature does not reach the predetermined temperature. The part may not be lowered and may be damaged by heat.

  The present invention has been made in view of such circumstances, and its purpose is to provide a portion upstream of the catalyst in the exhaust system when post-injection for filter regeneration is performed at a low atmospheric pressure. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can suppress the occurrence of damage due to heat.

In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a filter provided in an exhaust system of the internal combustion engine for collecting particulate matter in the exhaust, from the fuel injection valve for engine operation to the combustion chamber. A fuel component is supplied to the exhaust system catalyst through post-injection, which is fuel injection from the fuel injection valve performed after the fuel injection, and the filter temperature is raised by oxidation heat of the fuel component in the catalyst. In an exhaust gas purification apparatus for an internal combustion engine that performs filter regeneration for burning and removing particulate matter accumulated on the filter, the post injection amount that is the amount of fuel injected from the fuel injection valve during the post injection is guarded Guard means for performing an upper limit guard using a value, and setting means for variably setting the guard value to be smaller when the atmospheric pressure is low than when the atmospheric pressure is high. The setting means is such that when the atmospheric pressure is low, the guard value is reduced to a value that can suppress an excessive increase in temperature of the portion upstream of the catalyst in the exhaust system due to the post injection. It was.

  According to the above configuration, the upper limit guard based on the guard value of the post-injection amount is performed during filter regeneration, and when the atmospheric pressure is low, the guard value is higher than the catalyst in the exhaust system by the post-injection. The value is reduced to a value that can suppress an excessive increase in temperature. Therefore, when the atmospheric pressure is low, the post-injection prevents the temperature of the portion upstream of the catalyst in the exhaust system from being excessively raised, and the portion is prevented from being damaged by heat.

  According to a second aspect of the present invention, in the first aspect of the present invention, the post-injection amount is set so that the filter temperature reaches a target temperature that is a value at which particulate matter deposited on the filter can burn. The guard means is configured to guard the post-injection amount corrected by the feedback correction value by using the guard value as an upper limit.

  According to the above configuration, when the filter is being regenerated at a low atmospheric pressure and the filter temperature is lower than the target temperature, the feedback correction value is increased until the filter temperature reaches the target temperature. The post-injection amount increase correction based on the feedback correction value will increase. Under such circumstances, the temperature of the portion upstream of the catalyst in the exhaust system tends to rise, and the portion is easily damaged by heat. However, since the post-injection amount after correction by the feedback correction value is guarded at the upper limit using the guard value that is reduced as described above when the atmospheric pressure is low, the upstream side is more upstream than the catalyst in the exhaust system. It becomes possible to accurately suppress the damage caused by the heat of the part.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the post injection amount is determined based on an engine load and an engine speed, and the setting means includes the engine load, the engine speed. The guard value is variably set based on the atmospheric pressure.

  According to the above configuration, the guard value is an optimum value for suppressing an excessive increase in the filter temperature based on the engine load and the engine rotation speed, corresponding to the post injection amount determined based on the engine load and the engine rotation speed. In such a state that the atmospheric pressure is low, the guard value can be set to a value that can limit the post-injection amount so that the temperature of the portion upstream of the catalyst in the exhaust system does not rise excessively.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
FIG. 1 shows a configuration of an internal combustion engine 1 to which the exhaust emission control device of the present embodiment is applied. The internal combustion engine 1 is a diesel engine including a common rail fuel injection device and a turbocharger.

An intake passage 3 and an exhaust passage 4 are connected to each combustion chamber 2 of the internal combustion engine 1.
In the intake passage 3, an air flow meter 5, a compressor 6 a of a turbocharger 6, an intercooler 7, and an intake throttle valve 8 are arranged in order from the upstream portion to the downstream side. The intake passage 3 is branched corresponding to each cylinder at an intake manifold 9 provided on the downstream side of the intake throttle valve 8.

  On the other hand, the exhaust passage 4 is gathered together from a state branched for each cylinder by an exhaust manifold 10 connected to the combustion chamber 2 of each cylinder, and the exhaust turbine of the turbocharger 6 is downstream of the exhaust manifold 10. 6b. A first oxidation catalyst 11, a second oxidation catalyst 12, a filter 13, and an exhaust throttle valve 14 are disposed downstream from the exhaust turbine 6 b in the exhaust passage 4 in order from the upstream side. The first oxidation catalyst 11 and the second oxidation catalyst 12 oxidize and purify hydrocarbon (HC) and carbon monoxide (CO) in the exhaust gas. The filter 13 is made of a porous material and collects particulate matter (PM) mainly composed of soot in the exhaust gas.

  Note that, on the upstream side and the downstream side of the second oxidation catalyst 12 in the exhaust passage 4, a first exhaust temperature sensor 15 that detects the temperature of the exhaust gas flowing into the second oxidation catalyst 12, and the temperature of the exhaust gas that flows into the filter 13. A second exhaust temperature sensor 16 is provided for detecting the above. Further, a pressure sensor 17 that detects the pressure on the upstream side of the filter 13 is disposed between the second oxidation catalyst 12 and the filter 13 in the exhaust passage 4.

  Further, the internal combustion engine 1 is provided with an exhaust gas recirculation (hereinafter referred to as EGR) device that recirculates a part of the exhaust gas to the air in the intake passage 3. The EGR device includes an EGR passage 18 that allows the exhaust passage 4 and the intake passage 3 to communicate with each other. The most upstream part of the EGR passage 18 is connected to the exhaust upstream side of the exhaust turbine 6 b of the exhaust passage 4. An EGR cooler 19 that cools the recirculated exhaust gas and an EGR valve 20 that adjusts the flow rate of the exhaust gas are sequentially arranged in the EGR passage 18 from the upstream side. The most downstream portion of the EGR passage 18 is connected to the downstream side of the intake throttle valve 8 in the intake passage 3.

  On the other hand, a fuel injection valve 21 for injecting fuel to be used for combustion in the combustion chamber 2 is disposed in the combustion chamber 2 of each cylinder of the internal combustion engine 1. The fuel injection valve 21 of each cylinder is connected to a common rail 22, and high pressure fuel is supplied to the common rail 22 through a high pressure pump 23. The pressure of the high-pressure fuel in the common rail 22 is detected by a rail pressure sensor 24 attached to the common rail 22.

  Various controls of the internal combustion engine 1 are performed by the control device 25. The control device 25 is a CPU that executes various arithmetic processes related to engine control, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores CPU calculation results, and signals externally. An input / output port for input / output is provided.

  In addition to the above-described sensors, the input port of the control device 25 includes an accelerator sensor 26 that detects an accelerator operation amount, an engine rotation speed sensor 27 that detects an engine rotation speed, an atmospheric pressure sensor 28 that detects atmospheric pressure, and an intake air. A throttle valve sensor 29 and the like for detecting the opening degree of the throttle valve 8 are connected. The output port of the control device 25 is connected to drive circuits such as the intake throttle valve 8, the exhaust throttle valve 14, the EGR valve 20, the fuel injection valve 21, and the high-pressure pump 23.

  The control device 25 outputs a command signal to the drive circuit of each device connected to the output port according to the engine operating state grasped from the detection signal input from each sensor. Thus, the opening control of the intake throttle valve 8, the opening control of the exhaust throttle valve 14, the EGR control based on the opening control of the EGR valve 20, the fuel injection control of the fuel injection valve 21, and the discharge of the high pressure pump 23 Various controls such as pressure control are performed by the control device 25.

  In the present embodiment configured as described above, in order to prevent clogging of the filter 13 due to PM, filter regeneration is performed in which PM accumulated on the filter 13 is burned and purified. In order to perform such filter regeneration, it is necessary to sufficiently raise the temperature of the filter. For this reason, when filter regeneration is performed, fuel components are supplied to the first oxidation catalyst 11 and the second oxidation catalyst 12, and the temperature of the filter 13 is increased to a value (for example, 600 to 700 ° C.) necessary for PM combustion. Is done.

  The filter regeneration is started when the PM accumulation amount in the filter 13 during the non-filter regeneration estimated based on the detection signal of the pressure sensor 17 becomes equal to or greater than the allowable upper limit value. Note that the PM accumulation amount can be estimated based on the detection signal of the pressure sensor 17, and the pressure increases as the PM accumulation amount increases between the PM accumulation amount and the pressure detected by the pressure sensor 17. This is because of the relationship. When the filter regeneration is started, the fuel component is supplied to the first oxidation catalyst 11 and the second oxidation catalyst 12, and the temperature of the filter 13 becomes the above PM due to the oxidation heat accompanying the oxidation of the fuel in the catalysts 11 and 12. Raised to the value required for combustion.

  Specifically, after the main fuel injection, which is fuel injection for engine operation from the fuel injection valve 21 to the combustion chamber 2, is performed, the fuel component is supplied to the first oxidation catalyst 11 and the second oxidation catalyst 12. Therefore, post injection that is fuel injection from the fuel injection valve 21 is executed. Such post injection is realized by driving and controlling the fuel injection valve 21 so that the post injection amount Qp calculated based on the engine operating state is injected from the fuel injection valve 21 after the main fuel injection.

  The fuel injected from the fuel injection valve 21 by post injection is sent to the exhaust passage 4 and reaches the first oxidation catalyst 11. When the fuel component reaches the first oxidation catalyst 11, components such as hydrocarbon (HC) and carbon monoxide (CO) are oxidized in the exhaust or on the catalyst, and the exhaust temperature rises due to heat generated by the oxidation reaction. . Further, the temperature of the second oxidation catalyst 12 is raised by the action of increasing the exhaust temperature, and thereby the activation of the second oxidation catalyst 12 is promoted. Further, when the fuel component that has passed without being oxidized by the first oxidation catalyst 11 reaches the second oxidation catalyst 12, the oxidation reaction of the fuel component is also performed in the second oxidation catalyst 12, and the exhaust gas temperature is generated due to the accompanying heat generation. Rises. The exhaust gas whose temperature has been increased as described above flows into the filter 13, whereby the temperature of the filter 13 is increased to a value at which the PM can be combusted.

  By performing such filter regeneration, PM deposited on the filter 13 is burned, and the amount of PM deposited on the filter 13 decreases. The PM deposition amount on the filter 13 after the filter regeneration is started, in other words, the PM deposition amount during the filter regeneration is expressed by the equation “(PM deposition amount PMsm during filter regeneration) = (PM deposition amount PMsm at the start of filter regeneration). ) + PM emission amount PMe−PM oxidation amount PMc (1) ”.

  The PM emission amount PMe in the formula (1) is the amount of PM discharged from the internal combustion engine 1 to the exhaust passage 4, and is based on the engine rotational speed NE and the engine load with reference to a map set in advance through experiments or the like. Desired. As the engine load used here, the fuel injection amount Qfin at the time of main fuel injection from the fuel injection valve 21 is used. Further, the PM oxidation amount PMc in the equation (1) is the combustion amount of PM deposited on the filter 13 and is obtained based on the filter temperature Tf and the intake air amount GA with reference to a map set in advance through experiments or the like. . The filter temperature Tf used here is obtained based on the detection signal of the second exhaust temperature sensor 16, and the intake air amount GA is obtained based on the detection signal of the air flow meter 5.

  Then, when the PM accumulation amount estimated based on the formula (1) is sufficiently reduced by executing the filter regeneration, for example, when the amount of PM accumulation is reduced to be substantially “0”, it is determined that the filter regeneration is completed, and the post injection is stopped. Is done. The filter regeneration is completed through the stop of the post injection.

  Here, the calculation procedure of the post injection amount Qp used when performing the post injection for filter regeneration will be described with reference to the flowchart of FIG. 2 showing the post injection amount calculation routine. This post injection amount calculation routine is periodically executed through the control device 25, for example, with a time interruption every predetermined time.

  In this routine, the calculation of the basic injection amount Qpb (S101) and the calculation of the feedback correction value H (S102) are performed in order, and the basic injection amount Qpb and the feedback correction value H are used in accordance with the following equation (2). The post injection amount Qp is calculated (S103).

Qp = Qpb + H (2)
Qp: Post injection amount
Qpb: Basic injection amount
H: Feedback correction value The basic injection amount Qpb is a base value of the post injection amount Qp, and is calculated based on the fuel injection amount Qfin and the engine speed NE in step S101. The basic injection amount Qpb calculated in this way is set to a smaller value as the fuel injection amount Qfin increases under a condition where the engine speed NE is constant. This is because the exhaust temperature of the internal combustion engine 1 increases as the fuel injection amount Qfin increases, and the filter temperature Tf can be increased with a small amount of post injection. Further, the calculated basic injection amount Qpb has a general tendency to increase as the engine speed NE increases. This is because as the engine rotational speed NE increases, the time during which the exhaust gas passes through the filter 13, in other words, the time during which heat is transferred from the exhaust gas to the filter 13 is shortened, and the filter temperature Tf is less likely to increase. is there.

  The feedback correction value H is used to correct the post injection amount so that the filter temperature Tf becomes the target temperature Tt. In step S102, the feedback correction value H increases or decreases the filter temperature Tf with respect to the target temperature Tt. Calculated according to the amount of deviation. More specifically, regarding the feedback correction value H, when the filter temperature Tf is higher than the target temperature Tt, the larger the deviation amount of the filter temperature Tf from the target temperature Tt, the smaller the value, and the filter temperature Tf is lower than the target temperature Tt. Sometimes, the larger the deviation amount of the filter temperature Tf from the target temperature Tt, the larger the value. As the target temperature Tt, a value capable of reducing the PM accumulation amount in the filter 13 by burning PM accumulated in the filter 13 is adopted.

  By the way, when post-injection for filter regeneration is performed in a state where the atmospheric pressure is low, the temperature of the filter temperature Tf is likely to increase as compared with the case where the atmospheric pressure is normal. Further, the temperature of the portion located upstream of the first oxidation catalyst 11 and the second oxidation catalyst 12 in the exhaust system of the internal combustion engine 1 such as the exhaust manifold 10 is likely to increase further than the filter temperature Tf. As described in the [Problems to be solved by the invention] column. More specifically, the temperature T4 of the collective portion S of the exhaust passage 4 in the exhaust manifold 10 is more likely to rise than the filter temperature Tf. Therefore, when post injection is performed in a state where the atmospheric pressure is low, the temperature T4 of the collective portion S in the exhaust manifold 10 is excessively increased, and the collective portion S may be damaged by heat.

  Therefore, in the present embodiment, the post injection amount Qp calculated based on the equation (2) is used as a guard value in order to suppress an excessive increase in the filter temperature Tf and an excessive increase in the temperature T4 of the collective portion S of the exhaust manifold 10. Guard the upper limit using G. Specifically, the guard value G is variably set with reference to a map based on the fuel injection amount Qfin, the engine speed NE, and the atmospheric pressure Pa (S104), and the post injection amount Qp calculated based on the equation (2). The post-injection amount Qp is guarded so that does not become larger than the guard value G (S105).

  The guard value G corresponds to the post injection amount Qp (basic injection amount Qpb) determined based on the fuel injection amount Qfin and the engine rotational speed NE, and the filter temperature Tf is determined based on the fuel injection amount Qfin and the engine rotational speed NE. In order to suppress the excessive increase, it is made variable so as to be an optimum value. Further, the guard value G is variably set to be smaller when the atmospheric pressure Pa is lower than the standard atmospheric pressure compared to when the atmospheric pressure Pa is the standard atmospheric pressure. Specifically, when the exhaust gas temperature of the internal combustion engine 1 is high, that is, in a high load region as shown by hatching in FIG. 3, when the atmospheric pressure Pa is lower than the standard atmospheric pressure, The guard value G is variably set based on the atmospheric pressure Pa so as to reduce the guard value G to a value that can suppress the temperature T4 of the collective portion S below the allowable upper limit value and suppress an excessive increase in the temperature T4. .

  By performing the upper limit guard of the post injection amount Qp using the guard value G variably set in this way, the filter temperature Tf is excessively increased due to the post injection by the post injection amount Qp, and the atmospheric pressure It becomes possible to prevent the temperature T4 of the collecting portion S in the exhaust manifold 10 from excessively rising due to the post injection when the temperature becomes low.

According to the embodiment described in detail above, the following effects can be obtained.
(1) By using the guard value G variably set according to the atmospheric pressure Pa, the upper limit of the post injection amount Qp is guarded, so that the temperature T4 of the collective portion S of the exhaust manifold 10 at the time of post injection at a low atmospheric pressure. Can be prevented from rising above the allowable upper limit (over rise), and the assembly portion S can be prevented from being damaged by heat.

  (2) During post-injection with a low atmospheric pressure, when the filter temperature Tf is lower than the target temperature Tt, the feedback correction value H is increased until the filter temperature Tf reaches the target temperature Tt. Therefore, the increase correction of the post injection amount Qp by the feedback correction value H increases. Under such circumstances, the temperature T4 of the collective portion S in the exhaust manifold 10 is likely to increase, and the collective portion S is easily damaged by heat. However, since the post-injection amount Qp after the correction by the feedback correction value H is guarded at the upper limit using the guard value G, the above-described damage due to heat of the collective portion S can be accurately suppressed.

  (3) The guard value G is variably set as described above based on the fuel injection amount Qfin, the engine speed NE, and the atmospheric pressure Pa. Accordingly, the guard value G is used to suppress an excessive increase in the filter temperature Tf based on the fuel injection amount Qfin and the engine rotational speed NE in correspondence with the post injection amount Qp determined based on the fuel injection amount Qfin and the engine rotational speed NE. While being variable so as to be an optimum value, the guard value G can be set to a value that can suppress an excessive increase in the temperature T4 when the atmospheric pressure is low.

In addition, the said embodiment can also be changed as follows, for example.
Although the variable setting of the guard value G is performed with reference to the map, the guard value G may be calculated and set by a predetermined calculation formula instead.

When calculating the post injection amount Qp, the post injection amount Qp is corrected by the feedback correction value H, but such correction is not necessarily performed.
The post injection performed after the main fuel injection may be divided into a plurality of times such as twice or three times. In this case, the fuel injection valve 21 is driven and controlled so that the total value of the post injection amounts in the divided post injection becomes the post injection amount Qp, and the guard value with respect to the post injection amount Qp (total value). An upper limit guard is applied so as not to exceed G.

  The present invention may be applied to an exhaust purification device that raises the filter temperature Tf by carrying an oxidation catalyst on the filter 13 and oxidizing the fuel component on the filter 13. In this case, the first oxidation catalyst 11 and the second oxidation catalyst 12 may be omitted.

1 is a schematic diagram showing an internal combustion engine to which an exhaust emission control device of this embodiment is applied and its peripheral structure. The flowchart which shows the calculation procedure of post injection quantity. Explanatory drawing which shows the engine operation area | region where a guard value is made small when it exists in the state where atmospheric pressure is low. The graph which shows the difference by atmospheric pressure about the change of the amount of intake air with respect to the change of an engine speed. The graph which shows the difference by the atmospheric pressure about the change of the temperature of the part upstream from the catalyst in an exhaust system with respect to the change of an engine speed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Combustion chamber, 3 ... Intake passage, 4 ... Exhaust passage, 5 ... Air flow meter, 6 ... Turbocharger, 6a ... Compressor, 6b ... Exhaust turbine, 7 ... Intercooler, 8 ... Intake throttle valve, DESCRIPTION OF SYMBOLS 9 ... Intake manifold, 10 ... Exhaust manifold, 11 ... 1st oxidation catalyst, 12 ... 2nd oxidation catalyst, 13 ... Filter, 14 ... Exhaust throttle valve, 15 ... 1st exhaust temperature sensor, 16 ... 2nd exhaust temperature sensor, DESCRIPTION OF SYMBOLS 17 ... Pressure sensor, 18 ... EGR passage, 19 ... EGR cooler, 20 ... EGR valve, 21 ... Fuel injection valve, 22 ... Common rail, 23 ... High pressure pump, 24 ... Rail pressure sensor, 25 ... Control device (guard means, setting Means), 26 ... accelerator sensor, 27 ... engine rotational speed sensor, 28 ... atmospheric pressure sensor, 29 ... throttle valve sensor.

Claims (3)

Fuel injection from the fuel injection valve provided after the fuel injection from the fuel injection valve for engine operation to the combustion chamber is provided with a filter provided in the exhaust system of the internal combustion engine for collecting particulate matter in the exhaust The fuel component is supplied to the exhaust system catalyst through post-injection, and the filter temperature is increased by the oxidation heat of the fuel component in the catalyst, so that the particulate matter deposited on the filter is burned and removed. In an exhaust gas purification apparatus for an internal combustion engine that performs filter regeneration,
Guard means for guarding the upper limit of the post injection amount, which is the amount of fuel injected from the fuel injection valve during the post injection, using a guard value;
Setting means for variably setting the guard value to be smaller when the atmospheric pressure is low than when the atmospheric pressure is high;
With
When the atmospheric pressure is low, the setting means reduces the guard value to a value that can suppress an excessive increase in the temperature of the portion upstream of the catalyst in the exhaust system due to the post injection. An exhaust gas purification apparatus for an internal combustion engine characterized by the above. The post-injection amount is corrected by a feedback correction value that is increased or decreased based on the filter temperature and the target temperature so that the filter temperature reaches a target temperature that can burn the particulate matter deposited on the filter. And
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the guard means guards an upper limit of the post-injection amount corrected by the feedback correction value using the guard value. The post injection amount is determined based on the engine load and the engine speed,
The exhaust purification device for an internal combustion engine according to claim 1 or 2, wherein the setting means variably sets the guard value based on an engine load, an engine speed, and an atmospheric pressure.

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