JP2013231407A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably improve output performance and exhaust performance of an internal combustion engine when fresh air blow-by occurs from an intake passage to an exhaust passage via a combustion chamber, with regard to a control device for the internal combustion engine.SOLUTION: An internal combustion engine includes a turbocharger 20 and an in-cylinder injection valve 32. When the scavenge ratio (AFM passing flow rate/air amount charged in a cylinder) is higher than the air-fuel ratio (theoretical air-fuel ratio/output air-fuel ratio), a first amount Qin of fuel is injected during an intake step, the first amount of fuel being required so that an air-fuel ratio in a cylinder specified in relation to the air amount charged in a cylinder is the output air-fuel ratio. When the scavenge ratio is higher than the air-fuel ratio, a second amount Qex of fuel required so that an exhaust air-fuel ratio is a theoretical air-fuel ratio is injected besides the first amount Qin of fuel, in a predetermined timing during opening of an exhaust valve as a second timing when an injected fuel is not charged in the cylinder.

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device suitable for controlling an internal combustion engine with a supercharger.

  Conventionally, for example, Patent Document 1 discloses a control device for a spark ignition type cylinder injection type internal combustion engine. This conventional internal combustion engine includes a variable valve timing mechanism capable of adjusting a valve overlap period and a turbocharger. In this conventional control device, in order to achieve both exhaust performance improvement and torque improvement, the valve overlap is used in order to make the air-fuel ratio in the exhaust pipe the stoichiometric air-fuel ratio while controlling the in-cylinder air-fuel ratio to the output air-fuel ratio. The amount of scavenging (the amount of air blown from the intake passage to the exhaust passage through the combustion chamber) is adjusted by adjusting the period.

JP 2007-009768 A JP 2006-183553 A JP 2008-101540 A JP 2006-322335 A

  When performing the control as described in Patent Document 1, if the scavenging amount becomes too large and the in-cylinder air-fuel ratio becomes richer than the output air-fuel ratio, the set amount of the valve overlap period is limited. Therefore, there is a concern that the torque that can be generated by the internal combustion engine is limited.

  The present invention has been made in order to solve the above-described problems. In a situation where fresh air is blown from the intake passage to the exhaust passage through the combustion chamber, the output performance of the internal combustion engine is reduced and the fuel consumption is reduced. It is an object of the present invention to provide a control device for an internal combustion engine that can control the air-fuel ratio of exhaust gas to a target air-fuel ratio while suppressing the decrease of the exhaust gas.

1st invention is the control apparatus of the internal combustion engine which comprises a supercharger,
The air-fuel ratio of the exhaust gas during the execution of the scavenge control in which a part of the air flowing into the cylinder from the intake passage is discharged to the exhaust passage by overlapping the valve opening period of the intake valve and the valve opening period of the exhaust valve When the amount of fuel that will be the target air-fuel ratio is supplied into the cylinder and the air-fuel ratio in the cylinder becomes smaller than the output air-fuel ratio, the fuel in the cylinder is set so that the air-fuel ratio in the cylinder becomes the output air-fuel ratio. And a second fuel injection different from the first fuel injection for supplying fuel into the exhaust gas so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio. It is characterized by.

The second invention is the first invention, wherein
A catalyst for purifying a specific component in the exhaust gas is provided in the exhaust passage, and when the air-fuel ratio of the exhaust gas flowing into the catalyst is a specific air-fuel ratio, the purification rate is higher than a predetermined purification rate. The target air-fuel ratio is set to the specific air-fuel ratio.

The third invention is the first or second invention, wherein
When the amount of air blown from the intake passage to the exhaust passage through the cylinder during the execution of the scavenge control is referred to as the blow-off air amount, the air-fuel ratio in the cylinder is set as the target air-fuel ratio during the non-execution of the scavenge control. When the amount of fuel is injected during the execution of scavenge control, the upper limit value of the blow-through air amount that is allowed to maintain the air-fuel ratio in the cylinder at or above the output air-fuel ratio is between the target air-fuel ratio and the output air-fuel ratio. It is calculated as an allowable blow-by air amount based on the relationship, and it is determined that the air-fuel ratio in the cylinder is smaller than the output air-fuel ratio when the actual blow-through air amount during execution of the scavenge control is larger than the allowable blow-through air amount. It is characterized by that.

Moreover, 4th invention is set in 3rd invention,
An in-cylinder inflow air amount sensor that detects an in-cylinder inflow air amount that is the amount of air that flows into the cylinder, and an in-cylinder pressure sensor that detects in-cylinder pressure, and further detected by the in-cylinder inflow air amount sensor. The blow-through air amount is calculated by subtracting the in-cylinder charged air amount calculated based on the in-cylinder pressure detected by the in-cylinder pressure sensor from the in-cylinder inflow air amount.

The fifth invention is the fourth invention, wherein
Based on the sum of the calculated in-cylinder charged air amount and the calculated blow-through air amount, the amount of fuel necessary to make the air-fuel ratio of the exhaust gas the target air-fuel ratio is calculated as the total fuel injection amount, During the execution of scavenge control, the total fuel injection amount of fuel is injected by the first fuel injection and the second fuel injection.

Moreover, 6th invention is either 1st-5th invention,
A fuel injection valve for directly injecting fuel into the cylinder; fuel supply to the cylinder by the first fuel injection is realized by fuel injection from the fuel injection valve; and in the exhaust gas by the second fuel injection The fuel is supplied to the fuel by the fuel injection from the fuel injection valve during the opening period of the exhaust valve.

In addition, a seventh invention is any one of the first to fifth inventions,
A fuel injection valve for injecting fuel into the intake passage, and the supply of fuel into the cylinder by the first fuel injection is realized by fuel injection from the fuel injection valve during a valve opening period of the intake valve; The fuel supply to the exhaust gas by the fuel injection is realized by the fuel injection from the fuel injection valve in a period in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap. To do.

  According to the first invention, the air-fuel ratio in the cylinder becomes smaller than the output air-fuel ratio during execution of the scavenge control, and as a result, the air-fuel ratio in the cylinder is reduced under a situation where the output performance and fuel consumption of the internal combustion engine are reduced. Since the fuel ratio is controlled to the output air-fuel ratio, the reduction in output performance and fuel consumption of the internal combustion engine are suppressed, and fuel is supplied into the exhaust gas so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio. Therefore, the air-fuel ratio of the exhaust gas is controlled to the target air-fuel ratio.

  According to the second invention, since the air-fuel ratio of the exhaust gas is controlled to an air-fuel ratio (that is, a specific air-fuel ratio) at which the purification rate of the catalyst is higher than a predetermined purification rate, high purification of the catalyst. Rate is obtained.

  According to the third aspect of the invention, if the relationship between the target air-fuel ratio and the output air-fuel ratio is used, the allowable blow-through air amount for determining whether the in-cylinder air-fuel ratio is smaller than the output air-fuel ratio is accurately determined. Since it is calculated, it is accurately determined whether or not the air-fuel ratio in the cylinder is smaller than the output air-fuel ratio.

  According to the fourth aspect of the invention, specific means for calculating the amount of blown air is provided.

  According to the fifth invention, specific means for realizing the first fuel injection and the second fuel injection are provided.

  According to the sixth invention, when the internal combustion engine includes a fuel injection valve that directly injects fuel into the cylinder, specific means for realizing the first fuel injection and the second fuel injection are provided.

  According to the seventh aspect, when the internal combustion engine includes a fuel injection valve for injecting fuel into the intake passage, specific means for realizing the first fuel injection and the second fuel injection are provided.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the relationship between a scavenge rate (AFM passage flow volume / cylinder filling air amount) and the torque of an internal combustion engine. It is a figure showing the relationship between a torque, (theoretical air fuel ratio / cylinder air fuel ratio), and a scavenge rate. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 is assumed to be a gasoline engine as an example. An intake passage 12 and an exhaust passage 14 communicate with the combustion chamber of the internal combustion engine 10.

  An air cleaner 16 is disposed in the vicinity of the inlet of the intake passage 12. An air flow meter 18 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 12 is provided in the intake passage 12 on the downstream side of the air cleaner 16. A compressor 20 a of the turbocharger 20 is disposed in the intake passage 12 on the downstream side of the air flow meter 18.

  An intercooler 22 that cools the air compressed by the compressor 20a is disposed in the intake passage 12 on the downstream side of the compressor 20a. An electronically controlled throttle valve 24 is provided in the intake passage 12 downstream of the intercooler 22. An air bypass passage 26 for bypassing the compressor 20a is connected to the intake passage 12. An air bypass valve (ABV) 28 for controlling the flow rate of air flowing through the air bypass passage 26 is disposed in the middle of the air bypass passage 26. An intake pressure sensor 30 for detecting the intake pressure at this portion is attached to the intake passage 12 (surge tank) on the downstream side of the throttle valve 24.

  Each cylinder of the internal combustion engine 10 is provided with an in-cylinder injection valve 32 for directly injecting fuel into the combustion chamber (inside the cylinder) and an ignition plug 34 for igniting the air-fuel mixture. Each cylinder of the internal combustion engine 10 is provided with an in-cylinder pressure sensor 36 for detecting the in-cylinder pressure.

  The internal combustion engine 10 includes an intake variable valve mechanism 38 that continuously varies the opening / closing timing of an intake valve (not shown), and an exhaust variable operation that continuously varies the opening / closing timing of an exhaust valve (not shown). And a valve mechanism 40.

  A turbine 20 b of the turbocharger 20 is disposed in the exhaust passage 14. In the exhaust passage 14 downstream of the turbine 20b, a catalyst (three-way catalyst) 42 and the like are disposed as an exhaust purification catalyst for purifying exhaust gas. In the exhaust passage 14 on the upstream side of the catalyst 42, an A / F sensor 44 that emits a substantially linear output with respect to the air-fuel ratio of the exhaust gas flowing into the catalyst 42 (exhaust gas discharged from each cylinder) is disposed. Yes.

  Connected to the exhaust passage 14 is an exhaust bypass passage 46 that bypasses the turbine 20b and connects the inlet side and the outlet side of the turbine 20b. A waste gate valve (WGV) 48 that opens and closes the exhaust bypass passage 46 is installed in the middle of the exhaust bypass passage 46.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. In addition to the air flow meter 18, the intake pressure sensor 30, the in-cylinder pressure sensor 36, and the A / F sensor 44, an internal combustion engine such as a crank angle sensor 52 for detecting a crank angle and an engine speed is included in the input portion of the ECU 50. Various sensors for detecting 10 operating states are connected. Further, the output portion of the ECU 50 includes various kinds of control for controlling the operation of the internal combustion engine 10 such as the throttle valve 24, the ABV 28, the in-cylinder injection valve 32, the ignition plug 34, the variable valve mechanisms 38 and 40, and the WGV 48. Actuator is connected. The ECU 50 controls the operating state of the internal combustion engine 10 by driving the various actuators according to a predetermined program based on the sensor outputs.

(Scavenging effect by blowing new air through the combustion chamber from the intake passage to the exhaust passage)
According to the variable valve mechanisms 38 and 40 having the above-described configuration, the intake valve opening / closing timing is changed by changing at least one of the advance value of the intake valve opening / closing timing and the retard value of the exhaust valve opening / closing timing. The valve overlap period in which the valve period and the exhaust valve opening period overlap can be increased or decreased.

  In the internal combustion engine 10 of the present embodiment including the turbocharger 20, the intake pressure (upstream of the intake valve) is higher than the exhaust pressure (downstream of the exhaust valve) due to supercharging by the turbocharger 20 in the high load region. Get higher. When the valve overlap period is set (by control by the variable valve mechanism 38 or the like or by a preset valve timing of the intake / exhaust valve) in a high load region where such a pressure condition is satisfied, A phenomenon occurs in which (intake air) blows through the combustion chamber from the intake passage 12 toward the exhaust passage 14. When such a blow-through of fresh air occurs, the residual gas in the cylinder, which normally has at least the clearance volume of the combustion chamber, is pushed out by using fresh air from the intake passage 12. It can be scavenged and replaced with fresh air (scavenging effect). Thereby, effects, such as a torque improvement of the internal combustion engine 10, can be acquired.

[Control of Embodiment 1]
In a situation where fresh air is blown out, a part of the amount of air flowing into the cylinder (hereinafter referred to as “in-cylinder inflow air amount”) remains (fills) in the cylinder and burns. The remainder is blown through the exhaust passage 14 without being combusted. Therefore, the in-cylinder inflow air amount (that is, the intake air amount (AFM passage flow rate) measured by the air flow meter 18) is the amount of air charged in the cylinder (in-cylinder charged air amount) and the amount of air blown through the cylinder. It is the sum of (blow-through air amount). In the exhaust passage 14, the in-cylinder charged air and the blow-through air merge, so the flow rate of the exhaust gas flowing through the exhaust passage 14 becomes equal to the in-cylinder inflow air amount (AFM passage flow rate).

  When the in-cylinder air-fuel ratio is controlled so that the stoichiometric air-fuel ratio (stoichiometric) is obtained in the high load region where fresh air is blown out, the air-fuel ratio (hereinafter simply referred to as “exhaust air”) of the exhaust gas flowing upstream of the catalyst 42 is controlled. The "fuel ratio" is abbreviated leaner than the stoichiometric air-fuel ratio. As a result, the exhaust performance deteriorates. Therefore, in the present embodiment, the fuel injection amount is controlled so that the exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio in order to suitably secure the exhaust gas purification performance by the catalyst 42 and the like during the occurrence of fresh air blow-through. It is like that. When the ratio of the amount of fresh air blown in the in-cylinder inflow air amount (hereinafter referred to as “scavenge rate”) increases during the execution of such control, the in-cylinder charged air amount in the in-cylinder inflow air amount This decreases the ratio, so that the in-cylinder air-fuel ratio becomes rich. When the in-cylinder air-fuel ratio becomes richer than the output air-fuel ratio (about 12.5 for a gasoline engine) due to an increase in the amount of blown air, the torque of the internal combustion engine 10 decreases. Hereinafter, it will be described in more detail with reference to FIG.

  FIG. 2 is a diagram for explaining the relationship between the scavenging rate (AFM passage flow rate / cylinder charge air amount) and the torque of the internal combustion engine 10. More specifically, FIG. 2 shows a change in torque with respect to a change in scavenging rate under the condition that the cylinder air charge amount is constant and the exhaust air-fuel ratio is controlled to the stoichiometric air-fuel ratio. Is. Here, the scavenging rate is defined as a value obtained by dividing the in-cylinder inflow air amount (AFM passage flow rate) by the in-cylinder charged air amount.

  As shown in FIG. 2C, an increase in the scavenge rate when the cylinder air charge amount is constant means that the AFM passage flow rate increases. In this case, as shown in FIG. 2B, when the exhaust air / fuel ratio, which is the air / fuel ratio of the exhaust gas having a flow rate equal to the AFM passage flow rate, is maintained at the stoichiometric air / fuel ratio, the in-cylinder air / fuel ratio increases the scavenging rate. As the value increases, the value becomes richer. In the internal combustion engine 10, the torque becomes maximum at an output air-fuel ratio richer than the theoretical air-fuel ratio (around 14.7 for gasoline engines) (around 12.5 for gasoline engines). Therefore, as shown in FIGS. 2A and 2B, when the in-cylinder air-fuel ratio becomes rich due to the increase in scavenging rate, the torque increases until the in-cylinder air-fuel ratio reaches the output air-fuel ratio. To go. However, when the in-cylinder air-fuel ratio becomes richer than the output air-fuel ratio, the torque decreases.

FIG. 3 is a graph showing the relationship between torque, (theoretical air / fuel ratio / in-cylinder air / fuel ratio), and scavenging rate.
From the relationship shown in FIGS. 2B and 2C, the relationship between (theoretical air / fuel ratio / in-cylinder air / fuel ratio) and the scavenge rate can be summarized as shown in FIG. 3 (B). When the in-cylinder air-fuel ratio becomes the stoichiometric air-fuel ratio under the condition that the exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio as the premise of the relationship of FIG. 2 above, the vertical axis of FIG. Since (theoretical air / fuel ratio / in-cylinder air / fuel ratio) is 1 and no fresh air is blown through, the scavenging rate, which is the horizontal axis in FIG. 3 (B), is zero. Under the above conditions, the in-cylinder air-fuel ratio decreases as the scavenge rate increases as shown in FIG. Therefore, between (theoretical air / fuel ratio / in-cylinder air / fuel ratio) and the scavenge rate, as shown in FIG. 3 (B), in proportion to the increase in the scavenge rate (theoretical air / fuel ratio / in-cylinder air / fuel ratio). The relationship that increases will be obtained.

  Therefore, when the scavenging rate is higher than (theoretical air / fuel ratio / output air / fuel ratio), as shown in FIGS. 3 (A) and 3 (B), the in-cylinder air / fuel ratio is a richer value than the output air / fuel ratio. Therefore, it becomes possible to grasp that the torque is in a decreasing state.

  Therefore, in this embodiment, the scavenging rate (AFM passage flow rate / cylinder filling air amount) obtained by dividing the in-cylinder inflow air amount (AFM passage flow rate) by the in-cylinder filling air amount is the stoichiometric air-fuel ratio. When the air-fuel ratio obtained by dividing by (theoretical air-fuel ratio / output air-fuel ratio) is higher, the in-cylinder air-fuel ratio specified in relation to the in-cylinder charged air amount becomes the output air-fuel ratio. Therefore, the fuel amount Qin (first fuel amount) necessary for injection is injected at the first timing when the injected fuel is filled in the cylinder. More specifically, in the present embodiment, a predetermined timing during the intake stroke after the exhaust valve is closed is used as the first timing. Note that a compression stroke may be used as such a first timing.

  Further, in the present embodiment, when the scavenging rate is higher than the air-fuel ratio, the fuel amount Qex (the second fuel amount required) other than the first fuel amount Qin is used to make the exhaust air-fuel ratio the stoichiometric air-fuel ratio. The amount of fuel) is injected at the second timing when the injected fuel is not filled into the cylinder. More specifically, in the present embodiment, as the second timing, the exhaust valve opening period (the expansion stroke after the exhaust valve is opened, the exhaust stroke, and the intake stroke before the exhaust valve is closed). The predetermined timing is used.

  FIG. 4 is a flowchart showing a control routine executed by ECU 50 in order to realize characteristic control in the first embodiment of the present invention. This routine is repeatedly executed every predetermined control cycle.

  In the routine shown in FIG. 4, it is first determined whether or not a condition that the scavenging rate is higher than the air-fuel ratio (theoretical air-fuel ratio / output air-fuel ratio) is satisfied (step 100). In step 100, the scavenge rate is calculated as (AFM passage flow rate / cylinder charged air amount) as described above. The in-cylinder charged air amount can be calculated, for example, as a value obtained by subtracting the blow-through air amount from the AFM passage flow rate (in-cylinder inflow air amount). The blow-by air amount itself is, for example, an AFM passage flow rate (in-cylinder inflow air amount), an intake air pressure (surge tank pressure), an exhaust pressure, a valve overlap amount, which is an air amount detected using the air flow meter 18. And the engine speed (opening time during the overlap period). In this case, the intake pressure can be acquired by using the intake pressure sensor 30, and the exhaust pressure is detected by, for example, a separately estimated turbine speed, the opening degree of the WGV 48, and the air flow meter 18. It can be acquired based on the amount of intake air. Accordingly, the above scavenge rate can be calculated based on these calculation results.

  When the determination in step 100 is satisfied, that is, when it can be determined that the in-cylinder air-fuel ratio is richer than the output air-fuel ratio, the output air-fuel ratio is obtained in relation to the in-cylinder charged air amount. The fuel of the first fuel amount Qin necessary for the injection is injected into the cylinder at a predetermined timing (first timing) during the intake stroke (after the end of the valve overlap period) (step 102).

  Next, it is determined whether or not the crank angle has reached the exhaust valve opening timing (EVO) (step 104). As a result, when it is determined that the EVO has arrived, the fuel of the second fuel amount Qex required other than the first fuel amount Qin in order to make the exhaust air-fuel ratio the stoichiometric air-fuel ratio is The fuel is injected into the cylinder at a predetermined timing (second timing) during the valve opening period (step 106). The second fuel amount Qex in this step 106 is used to obtain the theoretical air-fuel ratio in relation to the AFM passage flow rate (cylinder charged air amount + blow-through air amount) corresponding to the total air amount in one cycle (that is, It can be calculated as the remaining value obtained by subtracting the first fuel amount Qin from the required total injection amount Qall (to make the exhaust air-fuel ratio the stoichiometric air-fuel ratio).

  According to the routine shown in FIG. 4 described above, it is determined whether or not the scavenge rate is higher than the air-fuel ratio (theoretical air-fuel ratio / output air-fuel ratio). In the case of controlling to the stoichiometric air-fuel ratio, it becomes possible to determine whether or not the in-cylinder air-fuel ratio can be kept within a range from the output air-fuel ratio to the stoichiometric air-fuel ratio under the current scavenging rate. Then, according to the above routine, when it is determined that the in-cylinder air-fuel ratio becomes richer than the output air-fuel ratio because the scavenging rate is higher than the air-fuel ratio, the in-cylinder air-fuel ratio becomes the output air-fuel ratio. The second fuel amount Qex that compensates for the shortage of fuel to make the exhaust air-fuel ratio the stoichiometric air-fuel ratio while the first fuel amount Qin charged into the cylinder is adjusted is exhausted so as not to be filled in the cylinder. Injected during valve opening. As a result, the maximum amount of torque can be drawn in relation to the amount of air charged in the cylinder, and the second fuel amount Qex that does not contribute to combustion is supplied to the exhaust passage 14, whereby the exhaust passage 14 The exhaust air / fuel ratio can be controlled to the stoichiometric air / fuel ratio. Further, according to the control of the present embodiment, the cylinder air-fuel ratio and the exhaust air-fuel ratio can be controlled as described above without changing the valve overlap period. As described above, according to the control of the present embodiment, the output performance and the exhaust performance of the internal combustion engine 10 at the time of occurrence of blow-through of fresh air can be suitably made compatible.

  In the first embodiment described above, the ECU 50 acquires the AFM passage flow rate using the air flow meter 18, whereby the “in-cylinder inflow air amount acquisition means” in the first aspect of the invention is determined by the ECU 50. By executing the process, the “cylinder charged air amount obtaining means” in the first invention executes the process in step 102 when the ECU 50 makes the determination in step 100, so that the first invention is performed. The "first fuel injection control means" in the ECU 50 executes the processes in steps 104 and 106 when the determination in step 100 is satisfied, thereby providing the "second fuel injection control means" in the first invention. "Is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG.

  Also in the present embodiment, when a fresh air blown into the exhaust passage 14 occurs, basically the same control as in the first embodiment is performed. In the present embodiment, when such control is performed, the second fuel amount injected during the valve opening period of the exhaust valve based on the in-cylinder charged air amount Ga_cps calculated using the output of the in-cylinder pressure sensor 36. A further feature is in determining Qex ′.

  FIG. 5 is a flowchart showing a control routine executed by the ECU 50 in order to realize characteristic control in the second embodiment of the present invention. In FIG. 5, the same steps as those shown in FIG. 4 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 5, if it is determined in step 100 that the scavenging rate (AFM passage flow rate / cylinder charged air amount) is higher than the air / fuel ratio (theoretical air / fuel ratio / output air / fuel ratio). Then, the fuel of the first fuel amount Qin ′ necessary to obtain the output air-fuel ratio in relation to the expected in-cylinder charged air amount Ga_fwd is the intake air (after the end of the valve overlap period). The fuel is injected into the cylinder at a predetermined timing (first timing) during the stroke (step 200).

  The in-cylinder charged air amount Ga_fwd in step 200 is a predicted value of the in-cylinder charged air amount that is estimated at a timing before the cylinder is actually filled with air in each cycle of the internal combustion engine 10. A method for calculating such a value Ga_fwd is not particularly limited, and for example, the method described for Step 102 can be used.

  Next, it is determined whether or not the crank angle has reached the closing timing (IVC) of the intake valve (step 202). As a result, when it is determined that IVC has arrived, it is necessary to obtain the stoichiometric air-fuel ratio in relation to the total air amount in one cycle (that is, to make the exhaust air-fuel ratio the stoichiometric air-fuel ratio). A total injection amount Qall ′ is calculated (step 204). Specifically, the total injection amount Qall ′ is calculated as a value for setting the exhaust air-fuel ratio to the stoichiometric air-fuel ratio in relation to the total air amount that is the sum of the blow-through air amount Ga_scv and the in-cylinder charged air amount Ga_cps. The The blown air amount Ga_scv can be calculated based on the method described for step 100, for example. The in-cylinder charged air amount Ga_cps is calculated according to a predetermined relational expression based on the in-cylinder pressure detected by the in-cylinder pressure sensor 36 when the intake valve closing timing (IVC) comes.

  Next, when it is determined in step 104 that the crank angle has reached the opening timing (EVO) of the exhaust valve, the first fuel amount Qin ′ is then used to set the exhaust air / fuel ratio to the stoichiometric air / fuel ratio. In addition to this, the fuel of the required second fuel amount Qex ′ is injected into the cylinder at a predetermined timing (second timing) during the valve opening period of the exhaust valve (step 206). The second fuel amount Qex ′ in step 206 is calculated as the remaining value obtained by subtracting the first fuel amount Qin ′ calculated in step 200 from the total injection amount Qall ′ calculated in step 204. Is done.

  According to the routine shown in FIG. 5 described above, the cylinder charge air amount Ga_cps is calculated using the output of the cylinder pressure sensor 36, so that the cylinder is actually filled as compared with the case where the prediction method is used. The amount of air to be calculated can be calculated with high accuracy. In addition, according to the above routine, in order to set the exhaust air / fuel ratio to the stoichiometric air / fuel ratio in relation to the total air amount corresponding to the sum of the in-cylinder charged air amount Ga_cps and the blow-through air amount Ga_scv, the second timing is used. A second fuel amount Qex ′ to be injected is determined. Thereby, an error that can be included in the first fuel amount Qin ′ injected during the intake stroke can be corrected in the same cycle. For this reason, the control accuracy of the air-fuel ratio (exhaust air-fuel ratio) in the exhaust passage 14 can be improved. In addition, the same effects as those of the first embodiment are obtained.

  In the second embodiment described above, the ECU 50 executes the process of step 204, whereby the “blow-through air amount estimating means” and the “cylinder charged air amount acquiring means” in the second invention are replaced by the ECU 50. By executing the processing of step 206, the “second fuel amount calculating means” in the second aspect of the present invention is realized.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG. 6 and FIG.

[System Configuration of Embodiment 3]
FIG. 6 is a diagram for explaining a system configuration of the internal combustion engine 60 according to the third embodiment of the present invention. In FIG. 6, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The internal combustion engine 60 shown in FIG. 6 is described above except that it includes a port injection valve 62 for injecting fuel into the intake passage 12 (more specifically, the intake port) instead of the in-cylinder injection valve 32. The configuration is the same as that of the internal combustion engine 10.

  In the case where the in-cylinder injection valve 32 is not provided as in the internal combustion engine 60 of the present embodiment, the fuel injection performed during the opening period of the exhaust valve cannot inject fuel in a manner not filled in the cylinder. There is a case. Therefore, if priority is given to controlling the exhaust air / fuel ratio to the stoichiometric air / fuel ratio when a fresh air blow-off occurs, it is assumed that the scavenging rate exceeds the air / fuel ratio (theoretical air / fuel ratio / output air / fuel ratio) and a torque drop occurs. The

  Therefore, in this embodiment using the port injection valve 62, when the scavenging rate is higher than the air-fuel ratio, the valve overlap period comes after the execution of fuel injection with the first fuel amount Qin. In addition, in order to set the exhaust air-fuel ratio to the stoichiometric air-fuel ratio, fuel of a fuel amount Qovrp (second fuel amount) required in addition to the first fuel amount Qin is injected. That is, in the present embodiment, a predetermined timing during the valve overlap period corresponds to the second timing at which the injected fuel is not filled into the cylinder.

  FIG. 7 is a flowchart showing a control routine executed by the ECU 50 in order to realize characteristic control in the third embodiment of the present invention. In FIG. 7, the same steps as those shown in FIG. 4 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 7, if it is determined in step 100 that the scavenging rate (AFM passage flow rate / cylinder charged air amount) is higher than the air / fuel ratio (theoretical air / fuel ratio / output air / fuel ratio). Then, the fuel of the first fuel amount Qin required to obtain the output air-fuel ratio in relation to the cylinder air charge amount calculated in the same manner as in step 102 is a predetermined amount during the intake stroke. The fuel is injected into the intake port at the timing (first timing) (step 300). Since the port injection valve 62 is used in the present embodiment, more specifically, the fuel injection in this case is intake synchronous injection performed in synchronization with the intake stroke after the end of the valve overlap period.

  Next, it is determined whether or not the valve overlap period is in progress using the crank angle sensor 52 or the like (step 302). As a result, if it is determined that the valve overlap period has elapsed, the fuel of the second fuel amount Qovrp necessary in addition to the first fuel amount Qin in order to set the exhaust air-fuel ratio to the stoichiometric air-fuel ratio. Are injected at a predetermined timing (second timing) during the valve overlap period (step 304). The second fuel amount Qovrp in this step 304 is used to obtain the theoretical air-fuel ratio in relation to the AFM passage flow rate (cylinder charged air amount + blown air amount) corresponding to the total air amount in one cycle (that is, It can be calculated as the remaining value obtained by subtracting the first fuel amount Qin from the required total injection amount Qall (to make the exhaust air-fuel ratio the stoichiometric air-fuel ratio).

  According to the routine shown in FIG. 7 described above, when the scavenging rate is higher than the air-fuel ratio, it can be determined that the in-cylinder air-fuel ratio becomes richer than the output air-fuel ratio. The second fuel amount Qovrp, which compensates for the shortage of fuel to make the exhaust air / fuel ratio the stoichiometric air / fuel ratio, is adjusted while the first fuel amount Qin charged into the cylinder is adjusted to become the fuel ratio. So that it is not injected during the valve overlap period. When fuel injection by the port injection valve 62 is performed during the valve overlap period, the fuel of the second fuel amount Qovrp is (first fuel amount) in synchronization with the fresh air blown through the combustion chamber into the exhaust passage 14. During the valve overlap period (which arrives at the end of the same cycle after the fuel injection at Qin is executed), the cylinder is not filled but introduced into the exhaust passage 14. As a result, by supplying the second fuel amount Qovrp that does not contribute to combustion to the exhaust passage 14 while allowing maximum torque to be drawn in relation to the amount of air charged in the cylinder, The exhaust air / fuel ratio can be controlled to the stoichiometric air / fuel ratio. For this reason, the same effects as those of the first embodiment can be obtained by the control of the present embodiment.

  In the above embodiment, the present invention is applied to an internal combustion engine in which the stoichiometric air-fuel ratio is the target air-fuel ratio. However, the present invention has an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. The present invention can also be applied to an internal combustion engine having a target air-fuel ratio, and is also applicable to an internal combustion engine having an air-fuel ratio richer than the stoichiometric air-fuel ratio and leaner than the output air-fuel ratio. Is also applicable.

  The three-way catalyst 42 of the first embodiment simultaneously purifies carbon monoxide, nitrogen oxides and unburned hydrocarbons in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into it is the stoichiometric air-fuel ratio. It is a catalyst that can be purified at a high rate. Therefore, although the above embodiment is an embodiment when the present invention is applied to an internal combustion engine having a three-way catalyst, the present invention is such that the air-fuel ratio of the inflowing exhaust gas is leaner than the stoichiometric air-fuel ratio. The present invention is also applicable to an internal combustion engine having a catalyst whose purification rate is higher than a predetermined purification rate at a specific air-fuel ratio, and the air-fuel ratio of the inflowing exhaust gas is richer than the stoichiometric air-fuel ratio. The present invention is also applicable to an internal combustion engine having a catalyst whose purification rate is higher than a predetermined purification rate at a specific air-fuel ratio. In these cases, in order to achieve a purification rate higher than a predetermined purification rate, the specific air-fuel ratio is set as the target air-fuel ratio.

  In the above embodiment, the in-cylinder charged air amount used for calculating the scavenge rate is calculated using, for example, the output of the in-cylinder pressure sensor 36.

  Further, the technical idea embodied as the above embodiment (hereinafter referred to as “first technical idea”) can be broadly expressed as an intake valve opening period in a control device for an internal combustion engine including a supercharger. The air-fuel ratio of the exhaust gas becomes the target air-fuel ratio during execution of scavenge control in which a part of the air flowing into the cylinder from the intake passage is discharged to the exhaust passage by overlapping the valve opening period of the exhaust valve When the amount of fuel is supplied into the cylinder and the air-fuel ratio in the cylinder becomes smaller than the output air-fuel ratio, the first fuel that supplies fuel into the cylinder so that the air-fuel ratio in the cylinder becomes the output air-fuel ratio It can be said that the second fuel injection different from the first fuel injection is performed while the injection is performed and the fuel is supplied into the exhaust gas so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio.

  Further, when the first technical idea is assumed, the more specific technical idea (hereinafter referred to as “second technical idea”) embodied as the above embodiment purifies a specific component in the exhaust gas. A catalyst is provided in the exhaust passage, and when the air-fuel ratio of the exhaust gas flowing into the catalyst is a specific air-fuel ratio, the purification rate is higher than a predetermined purification rate, and the target air-fuel ratio is It can be said that the specific air-fuel ratio is set.

  Further, on the premise of the first technical idea or the second technical idea, the more specific technical idea (hereinafter referred to as “third technical idea”) embodied as the above embodiment is the execution of scavenge control. When the amount of air blown from the intake passage through the cylinder into the exhaust passage is called the blow-through air amount, the amount of fuel that sets the air-fuel ratio in the cylinder to the target air-fuel ratio during non-execution of the scavenge control Based on the relationship between the target air-fuel ratio and the output air-fuel ratio, the upper limit value of the blow-through air amount allowed to maintain the in-cylinder air-fuel ratio equal to or higher than the output air-fuel ratio when injected during execution of scavenge control. It is calculated as the allowable blow-through air amount, and when the actual blow-through air amount during execution of the scavenge control is larger than the allowable blow-through air amount, it is determined that the air-fuel ratio in the cylinder is smaller than the output air-fuel ratio. It can be said.

  Further, assuming the third technical idea, the more specific technical idea (hereinafter referred to as “fourth technical idea”) embodied as the above embodiment is the amount of air flowing into the cylinder. A cylinder inflow air amount sensor for detecting a cylinder inflow air amount; and a cylinder pressure sensor for detecting a cylinder pressure, wherein the cylinder inflow from the cylinder inflow air amount detected by the cylinder inflow air amount sensor is provided. It can be said that the blow-by air amount is calculated by subtracting the in-cylinder charged air amount calculated based on the in-cylinder pressure detected by the internal pressure sensor.

  Further, on the premise of the fourth technical idea, a more specific technical idea embodied as the above embodiment (hereinafter referred to as “fifth technical idea”) includes the calculated in-cylinder charged air amount and Based on the sum of the calculated blow-through air amount, the amount of fuel necessary for setting the air-fuel ratio of the exhaust gas to the target air-fuel ratio is calculated as the total fuel injection amount, and during the execution of the scavenge control, the first fuel injection is performed. It can be said that the fuel of the total fuel injection amount is injected by the second fuel injection.

  Further, assuming the first to fifth technical ideas, a more specific technical idea embodied as the embodiment includes a fuel injection valve that directly injects fuel into a cylinder, and The fuel supply into the cylinder by the first fuel injection is realized by the fuel injection from the fuel injection valve, and the fuel supply into the exhaust gas by the second fuel injection is the fuel injection during the valve opening period of the exhaust valve. It can be said that this is realized by fuel injection from the valve, or a fuel injection valve for injecting fuel into the intake passage is provided, and the supply of fuel into the cylinder by the first fuel injection is the opening of the intake valve A period in which the supply of fuel into the exhaust gas by the second fuel injection is overlapped with the valve opening period of the intake valve and the valve opening period of the exhaust valve. In the above fuel It can be said that is realized by the fuel injection from the event.

10, 60 Internal combustion engine 12 Intake passage 14 Exhaust passage 16 Air cleaner 18 Air flow meter 20 Turbocharger 20a Turbocharger compressor 20b Turbocharger turbine 22 Intercooler 24 Throttle valve 26 Air bypass passage 28 Air bypass valve ( ABV)
30 Intake pressure sensor 32 In-cylinder injection valve 34 Spark plug 36 In-cylinder pressure sensor 38 Intake variable valve mechanism 40 Exhaust variable valve mechanism 42 Catalyst 44 A / F sensor 46 Exhaust bypass passage 48 Waste gate valve (WGV)
50 ECU (Electronic Control Unit)
52 Crank angle sensor 62 Port injection valve

Claims (7)

In a control device for an internal combustion engine provided with a supercharger,
The air-fuel ratio of the exhaust gas during the execution of the scavenge control in which a part of the air flowing into the cylinder from the intake passage is discharged to the exhaust passage by overlapping the valve opening period of the intake valve and the valve opening period of the exhaust valve When the amount of fuel that will be the target air-fuel ratio is supplied into the cylinder and the air-fuel ratio in the cylinder becomes smaller than the output air-fuel ratio, the fuel in the cylinder is set so that the air-fuel ratio in the cylinder becomes the output air-fuel ratio. And a second fuel injection different from the first fuel injection for supplying fuel into the exhaust gas so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio. A control device for an internal combustion engine.   A catalyst for purifying a specific component in the exhaust gas is provided in the exhaust passage, and when the air-fuel ratio of the exhaust gas flowing into the catalyst is a specific air-fuel ratio, the purification rate is higher than a predetermined purification rate. The control apparatus for an internal combustion engine according to claim 1, wherein the target air-fuel ratio is set to the specific air-fuel ratio.   When the amount of air blown from the intake passage to the exhaust passage through the cylinder during the execution of the scavenge control is referred to as the blow-off air amount, the air-fuel ratio in the cylinder is set as the target air-fuel ratio during the non-execution of the scavenge control. When the amount of fuel is injected during the execution of scavenge control, the upper limit value of the blow-through air amount that is allowed to maintain the air-fuel ratio in the cylinder at or above the output air-fuel ratio is between the target air-fuel ratio and the output air-fuel ratio. It is calculated as an allowable blow-by air amount based on the relationship, and it is determined that the air-fuel ratio in the cylinder is smaller than the output air-fuel ratio when the actual blow-through air amount during execution of the scavenge control is larger than the allowable blow-through air amount. 3. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   An in-cylinder inflow air amount sensor that detects an in-cylinder inflow air amount that is the amount of air that flows into the cylinder, and an in-cylinder pressure sensor that detects in-cylinder pressure, and further detected by the in-cylinder inflow air amount sensor. The blow-through air amount is calculated by subtracting a cylinder air charge amount calculated based on a cylinder pressure detected by the cylinder pressure sensor from a cylinder inflow air amount. Control device for internal combustion engine.   Based on the sum of the calculated in-cylinder charged air amount and the calculated blow-through air amount, the amount of fuel necessary to make the air-fuel ratio of the exhaust gas the target air-fuel ratio is calculated as the total fuel injection amount, 5. The control apparatus for an internal combustion engine according to claim 4, wherein the total fuel injection amount of fuel is injected by the first fuel injection and the second fuel injection during execution of scavenge control.   A fuel injection valve for directly injecting fuel into the cylinder; fuel supply to the cylinder by the first fuel injection is realized by fuel injection from the fuel injection valve; and in the exhaust gas by the second fuel injection 6. The control apparatus for an internal combustion engine according to claim 1, wherein the supply of fuel to the engine is realized by fuel injection from the fuel injection valve during an exhaust valve opening period.   A fuel injection valve for injecting fuel into the intake passage, and the supply of fuel into the cylinder by the first fuel injection is realized by fuel injection from the fuel injection valve during a valve opening period of the intake valve; The fuel supply to the exhaust gas by the fuel injection is realized by the fuel injection from the fuel injection valve in a period in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap. The control apparatus for an internal combustion engine according to any one of claims 1 to 5.

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