JP4952654B2 - Internal combustion engine control system - Google Patents

Description

  The present invention relates to a control system for an internal combustion engine provided with an EGR device that introduces part of exhaust gas into an intake passage of the internal combustion engine as EGR gas.

  Conventionally, an EGR passage having one end connected to an exhaust passage and the other end connected to an intake passage and an EGR valve provided in the EGR passage is introduced into the intake passage as EGR gas through the EGR passage. EGR devices are known. In such an EGR device, the amount of EGR gas introduced into the intake passage via the EGR passage is controlled by changing the opening of the EGR valve, and as a result, the amount of EGR gas flowing into the internal combustion engine. Is controlled.

  When the operation state of the internal combustion engine is a deceleration operation, the throttle valve provided in the intake passage is controlled in the valve closing direction so as to reduce the intake air amount. At this time, the EGR valve is also controlled in the valve closing direction so as to decrease the amount of EGR gas in accordance with the decrease in the intake air amount.

  Here, in the intake passage of the internal combustion engine, a throttle valve may be provided upstream of the surge tank, and the other end of the EGR passage may be connected downstream of the surge tank. In this case, if the amount of EGR gas is decreased in accordance with the decrease in the intake air amount as described above, the change in the amount of EGR gas in the cylinder of the internal combustion engine (hereinafter referred to as the in-cylinder EGR gas amount) changes. It becomes slower than the change in the amount of air in the cylinder of the internal combustion engine (hereinafter referred to as in-cylinder air amount) (the change in the in-cylinder EGR gas amount has a larger response delay than the change in the in-cylinder air amount). For this reason, during the deceleration operation, the EGR rate of the gas in the cylinder (hereinafter referred to as the in-cylinder EGR rate) becomes excessively high, and as a result, there is a risk of causing misfire and a reduction in torque.

  Patent Document 1 discloses a technique for increasing the supply of auxiliary air by increasing the opening of an ISC valve than in a normal state when a sudden deceleration state in which the engine load rapidly decreases occurs. Further, Patent Document 1 also discloses a technique for retarding the ignition timing in accordance with the amount of auxiliary air in order to cancel the output change accompanying the increase in auxiliary air.

  Patent Document 2 discloses a technique for limiting the upper limit value of the target EGR control value according to the target throttle valve opening when the throttle valve is operated in the valve closing direction during deceleration. .

Patent Document 3 discloses a correction for a pumping loss change accompanying a change in the EGR rate caused by changing the opening of the EGR valve, and a correction for a change in combustion state due to a change in the EGR rate. A technique is disclosed that is performed at different timings with respect to the opening of the valve.
JP-A-9-209798 JP 2004-1000046 A JP 2001-152916 A

  The present invention suppresses the occurrence of misfiring during deceleration operation and more preferably provides torque during deceleration operation in an internal combustion engine equipped with an EGR device that introduces part of the exhaust gas as EGR gas into the intake passage of the internal combustion engine. An object is to provide a technique that can be controlled.

  In the present invention, in an internal combustion engine equipped with an EGR device, when the operating state of the internal combustion engine becomes a deceleration operation, the opening degree of the EGR valve is first decreased, and then the in-cylinder EGR gas amount becomes equal to or less than a predetermined amount. After that, decrease the opening of the air amount control valve. Further, during deceleration operation, the ignition timing in the internal combustion engine is retarded from MBT (Minimum advance for best torque).

More specifically, the control system for an internal combustion engine according to the present invention is:
The EGR passage has one end connected to the exhaust passage and the other end connected to the downstream side of the surge tank in the intake passage, and the EGR valve provided in the EGR passage, and exhaust gas is discharged through the EGR passage to the EGR gas. EGR device to be introduced into the intake system as
An air amount control valve that is provided upstream of the surge tank in the intake passage and controls the intake air amount of the internal combustion engine;
EGR valve control means for controlling the opening of the EGR valve;
An air amount control valve control means for controlling the opening of the air amount control valve;
Ignition timing control means for controlling the ignition timing in the internal combustion engine;
In-cylinder EGR gas amount estimation means for estimating an in-cylinder EGR gas amount that is the amount of EGR gas in the cylinder of the internal combustion engine;
A decelerating target torque calculating means for calculating a decelerating target torque that is a target value of the torque of the internal combustion engine when the operating state of the internal combustion engine is during decelerating operation,
When the operating state of the internal combustion engine becomes a decelerating operation state, the EGR valve control means decreases the opening of the EGR valve, and then the in-cylinder EGR gas amount decreases to a predetermined amount or less before the air amount. Reducing the opening of the air amount control valve by the control valve control means; and
When the operating state of the internal combustion engine is in a decelerating operation, the ignition timing control means retards the ignition timing in the internal combustion engine from the MBT so that the torque of the internal combustion engine becomes a target torque during deceleration. .

  Here, the predetermined amount may be a value equal to or less than the upper limit value of the in-cylinder EGR gas amount that can be combusted in the cylinder after the deceleration operation is completed. The predetermined amount may be an in-cylinder EGR gas amount corresponding to the target value of the in-cylinder EGR rate after the deceleration operation is completed.

  In the present invention, during the deceleration operation, after the opening degree of the EGR valve is reduced, the opening degree of the air amount control valve is reduced after the in-cylinder EGR gas amount is sufficiently reduced. Therefore, it is possible to suppress the in-cylinder EGR rate from becoming excessively high during the deceleration operation.

  In the present invention, during deceleration operation, the internal combustion engine torque is controlled to the target torque during deceleration by retarding the ignition timing in the internal combustion engine from MBT. As a result, the torque of the internal combustion engine can be reduced even before the opening of the air amount control valve is reduced.

  Therefore, according to the present invention, it is possible to suppress the occurrence of misfire during deceleration operation, and it is possible to more suitably control the torque during deceleration operation.

  In the present invention, in-cylinder air amount estimation means, post-deceleration torque calculation means, post-deceleration EGR rate calculation means, target EGR valve opening calculation means, target air amount control valve opening calculation means, decelerating EGR rate estimation means, An MBT torque estimating unit during deceleration and a retard amount calculating unit may be further provided.

The cylinder air amount estimation means estimates the cylinder air amount. The post-deceleration torque calculation means calculates post-deceleration torque, which is a target value of the torque of the internal combustion engine after completion of the deceleration operation, when the operation state of the internal combustion engine becomes a deceleration operation. The post-deceleration EGR rate calculating means calculates an after-deceleration EGR rate that is an in-cylinder EGR rate corresponding to the post-deceleration torque when the operating state of the internal combustion engine is reduced. The target EGR valve opening degree calculation means calculates the opening degree of the EGR valve corresponding to the post-deceleration EGR rate when the operating state of the internal combustion engine becomes a deceleration operation. The target air amount control valve opening degree calculation means calculates a target air amount control valve opening degree that is an opening amount of the air amount control valve corresponding to the post-deceleration torque when the operation state of the internal combustion engine is a deceleration operation. .

  Further, the deceleration EGR rate estimation means estimates the deceleration EGR rate that is the in-cylinder EGR rate during the deceleration operation based on the in-cylinder air amount and the in-cylinder EGR gas amount. The decelerating MBT torque estimating means calculates the MBT torque during deceleration, which is the torque when the ignition timing in the internal combustion engine is MBT when the operating state of the internal combustion engine is in decelerating operation, the in-cylinder air amount and the EGR rate during deceleration Estimate based on The retard amount calculation means calculates the retard amount from the MBT of the ignition timing during the deceleration operation based on the difference between the target torque during deceleration and the MBT torque during deceleration.

  And when this invention is provided with said each means, when the driving | running state of an internal combustion engine turns into deceleration driving | operation, the opening degree of an EGR valve is controlled to a target EGR valve opening degree, and after that, in-cylinder EGR gas After the amount decreases to a predetermined amount or less, the opening degree of the air amount control valve is controlled to the target air amount control valve opening degree. Further, when the operating state of the internal combustion engine is decelerating, the ignition timing control means retards the ignition timing in the internal combustion engine by the retard amount calculated by the retard amount calculating means from the MBT.

  Based on the above, the retard amount from the MBT of the ignition timing during the deceleration operation is calculated based on the difference between the target torque during deceleration and the MBT torque during deceleration. Thereby, the torque during the deceleration operation can be controlled to the target torque during deceleration with higher accuracy.

  In the present invention, a post-deceleration air amount calculation unit may be provided instead of the post-deceleration torque calculation unit. The post-deceleration air amount calculation means calculates a post-deceleration air amount that is a target value of the intake air amount of the internal combustion engine after the end of the decelerating operation when the operating state of the internal combustion engine becomes a decelerating operation. In this case, the post-deceleration EGR rate calculating means calculates the post-deceleration EGR rate as an EGR rate corresponding to the post-deceleration air amount when the operating state of the internal combustion engine is a decelerating operation. The target air amount control valve opening calculating means calculates the target air amount control valve opening as the opening of the air amount control valve corresponding to the post-deceleration air amount.

  Even in such a configuration, during the deceleration operation, the opening degree of the EGR valve, the opening degree of the air amount control valve, and the ignition timing in the internal combustion engine are controlled as described above. Thereby, the effect similar to the above can be acquired.

  In the present invention, the MBT torque estimating means during deceleration may include reference combustion work calculation means, reference pump loss calculation means, combustion work correction means, pump loss correction means, and indicated torque calculation means.

  The combustion work calculation means calculates a reference combustion work, which is a reference value of the sum of work during the compression stroke and the expansion stroke when the ignition timing in the internal combustion engine is MBT, based on at least the in-cylinder air amount. The pump loss calculating means calculates a reference pump loss, which is a reference value of the pump loss during the intake stroke and the expansion stroke, based on at least the in-cylinder air amount. The combustion work correction means corrects the reference combustion work estimated by the combustion work estimation means based on the EGR rate during deceleration. The pump loss correcting unit corrects the reference pump loss estimated by the pump loss estimating unit based on the EGR rate during deceleration. The indicated torque calculating means calculates the indicated torque based on a value obtained by subtracting the pump loss corrected by the pump loss correcting means from the combustion work corrected by the combustion work correcting means.

  In this case, the deceleration MBT torque estimation means estimates the deceleration MBT torque based on the indicated torque calculated by the indicated torque calculation means.

Both the combustion work and the pump loss change as the in-cylinder EGR rate changes. However,
The manner of change of the combustion work and the pump loss with respect to the in-cylinder EGR rate is different. In the above, the reference combustion work and the reference pump loss are corrected separately based on the EGR rate during deceleration. Then, the indicated torque is calculated based on the corrected values, and the torque during the deceleration operation is estimated based on the indicated torque. Therefore, the MBT torque during deceleration can be estimated more efficiently and with higher accuracy.

  According to the present invention, in an internal combustion engine equipped with an EGR device that introduces a portion of exhaust gas into the intake passage of the internal combustion engine as EGR gas, the occurrence of misfire during deceleration operation is suppressed, and torque during deceleration operation is further increased. It can control suitably.

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

<Example 1>
(Schematic configuration of internal combustion engine and its intake and exhaust system)
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. The internal combustion engine 1 is a gasoline engine for driving a vehicle having four cylinders 2. A fuel injection valve (not shown) is provided at the intake port of each cylinder 2. Each cylinder 2 is provided with a spark plug 3 that ignites the air-fuel mixture supplied into the cylinder 2.

  An intake manifold 5 and an exhaust manifold 7 are connected to the internal combustion engine 1. One end of an intake passage 4 is connected to the intake manifold 5. One end of an exhaust passage 6 is connected to the exhaust manifold 7.

  A compressor housing 8 a of a turbocharger 8 is installed in the intake passage 4. A turbine housing 8 b of a turbocharger 8 is installed in the exhaust passage 6.

  A throttle valve 9 is provided in the intake passage 4 downstream of the compressor housing 8 a and upstream of the surge tank 13. A three-way catalyst 10 is provided in the exhaust passage 6 on the downstream side of the turbine housing 8b.

  An air flow meter 11 is provided in the intake passage 4 upstream of the compressor housing 8a. The intake manifold 5 is provided with a pressure sensor 12 for detecting intake pressure.

  The internal combustion engine 1 according to this embodiment includes an EGR device 14 that introduces a part of exhaust gas into the intake system as EGR gas. The EGR device 14 has an EGR passage 15 and an EGR valve 16. The EGR passage 15 has one end connected to the exhaust manifold 7 and the other end connected to the intake manifold 5. The EGR valve 16 is provided in the EGR passage 15. With such a configuration, EGR gas is introduced from the exhaust manifold 7 to the intake manifold 5 via the EGR passage 15. Further, the amount of EGR gas introduced into the intake manifold 5 is controlled by changing the opening degree of the EGR valve 16.

The internal combustion engine 1 is provided with an electronic control unit (ECU) 20. The ECU 20 is a unit that controls the operating state of the internal combustion engine 1 and the like. An air flow meter 11, a pressure sensor 12, an air-fuel ratio sensor 13, a crank position sensor 21, and an accelerator opening sensor 22 are electrically connected to the ECU 20. The crank position sensor 21 detects the crank angle of the internal combustion engine 1. The accelerator opening sensor 22 detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. Output signals from the sensors are input to the ECU 20.

  The ECU 20 derives the engine speed of the internal combustion engine 1 based on the detected value of the crank position sensor 21. Further, the ECU 20 derives the engine load of the internal combustion engine 1 based on the detection value of the accelerator opening sensor 22.

  Further, the ECU 20 is electrically connected to the fuel injection valve of each cylinder 2, each spark plug 3, the throttle valve 9 and the EGR valve 16. These are controlled by the ECU 20.

(Control during deceleration operation)
In this embodiment, the EGR gas is introduced into the intake manifold 5 by the EGR device 14, so that the EGR gas is supplied to the internal combustion engine 1 together with the intake air. Thereby, the amount of NOx discharged from the internal combustion engine 1 is suppressed.

  When the accelerator opening of the vehicle equipped with the internal combustion engine 1 is decreased and the operation state of the internal combustion engine 1 is decelerated, the throttle valve 9 is controlled in the valve closing direction so as to reduce the intake air amount. The EGR valve 16 is also controlled in the valve closing direction in order to reduce the amount of internal EGR gas. At this time, the change in the in-cylinder EGR gas amount has a larger response delay than the change in the in-cylinder air amount. Therefore, when the throttle valve 9 and the EGR valve 16 are controlled at the same timing, the in-cylinder EGR rate becomes excessively high, and as a result, there is a possibility of causing misfire and a decrease in torque.

  Therefore, in this embodiment, when the operating state of the internal combustion engine 1 is decelerating to suppress an excessive increase in the in-cylinder EGR rate during the deceleration operation, first, the opening degree of the EGR valve 16 is set. After that, after the in-cylinder EGR rate is sufficiently reduced, the opening degree of the throttle valve 9 is reduced.

  Hereinafter, the opening degree of the throttle valve 9, the opening degree of the EGR valve 16, and the ignition timing by the ignition plug 3 during the deceleration operation according to the present embodiment will be described with reference to FIG. FIG. 2 shows the accelerator opening, the target torque, the opening of the EGR valve 16, the in-cylinder EGR gas amount, the opening of the throttle valve 9, the in-cylinder air amount, and the ignition timing by the spark plug 3 during the deceleration operation as MBT. 6 is a time chart showing transitions of estimated torque (hereinafter referred to as MBT torque) and ignition timing (hereinafter simply referred to as ignition timing) by the spark plug 3 in a case where the ignition is performed.

  In FIG. 2, the accelerator opening decreases at the time point (1). At this time, the ECU 20 calculates a post-deceleration torque Tta, which is a target value of the torque of the internal combustion engine 1 after completion of the deceleration operation, based on the reduced accelerator opening Accelela. Further, the ECU 20 calculates a post-deceleration air amount Qairta that is an in-cylinder air amount corresponding to the post-deceleration torque Ttta. Further, the ECU 20 calculates a target throttle valve opening degree Vsta that is the opening degree of the throttle valve 9 corresponding to the post-deceleration torque Ttta, and a post-deceleration EGR rate Regrta that is the in-cylinder EGR rate corresponding to the post-deceleration torque Trta. Further, the ECU 20 calculates a target EGR valve opening degree Vegrta that is an opening degree of the EGR valve 16 corresponding to the post-deceleration EGR rate Regrta.

  In the present embodiment, first, at the time point (1), the opening degree of the EGR valve 16 is controlled to the target EGR valve opening degree Vegrta. In the opening control of the EGR valve 16, there is a slight response delay until the actual opening reaches the value after the command value reaches the target EGR valve opening Vegrta.

When the opening degree of the EGR valve 16 is controlled to the target EGR valve opening degree Vegrta, the in-cylinder EGR gas amount decreases. There is also a response delay from when the opening of the EGR valve 16 starts to decrease until the in-cylinder EGR gas amount starts to decrease.

  When the in-cylinder EGR gas amount reaches the predetermined EGR gas amount Qegr0 (time (2) in FIG. 2), the opening degree of the throttle valve 9 is controlled to the target throttle valve opening degree Vsta. Here, the predetermined EGR gas amount Qegr0 is an upper limit value of the in-cylinder EGR gas amount that can be combusted in the cylinder 2 after the deceleration operation is completed. Even in the opening control of the throttle valve 9, there is a slight response delay until the actual opening reaches that value after the command value reaches the target throttle valve opening Vsta.

  Alternatively, the predetermined EGR gas amount Qegr0 may be an in-cylinder EGR gas amount corresponding to the post-deceleration EGR rate Regra.

  Here, from the time point (1) in FIG. 2 to the time point (2), the opening of the throttle valve 9 is maintained in a state before the deceleration operation. Therefore, when the ignition timing is kept at MBT, the torque of the internal combustion engine 1 does not decrease like the deceleration target torque Trtde that is the target torque during the reduction operation. Therefore, in this embodiment, the torque of the internal combustion engine 1 is reduced by retarding the ignition timing with respect to MBT.

  At this time, during the period from the time point (1) to the time point (2), the retard amount Δtli from the MBT of the ignition timing is gradually increased to reduce the torque of the internal combustion engine 1 to the target torque Trtde during deceleration. Decrease gradually.

  When the opening degree of the throttle valve 9 is controlled to the target throttle valve opening degree Vsta at the time point (2) in FIG. 2, the in-cylinder air amount gradually decreases. As the in-cylinder air amount decreases, the MBT torque also gradually decreases. Therefore, after the time point (2), the retard amount Δtli from the MBT of the ignition timing is gradually decreased according to the decrease in the in-cylinder air amount. Thus, when the in-cylinder air amount reaches the post-deceleration air amount Qairta (time (3) in FIG. 2), the ignition timing is controlled to MBT.

  In the control as described above, after the opening degree of the EGR valve 16 is reduced during the deceleration operation, the opening degree of the throttle valve 9 is reduced after the in-cylinder EGR gas amount is sufficiently reduced. Therefore, it is possible to suppress the in-cylinder EGR rate from becoming excessively high during the deceleration operation.

  During deceleration operation, the torque of the internal combustion engine 1 is controlled to the target torque during deceleration by retarding the ignition timing in the internal combustion engine 1 from the MBT. Thereby, the torque of the internal combustion engine 1 can be reduced even before the opening of the throttle valve 9 is decreased.

  Therefore, according to the present embodiment, the occurrence of misfire during deceleration operation can be suppressed, and the torque during deceleration operation can be more suitably controlled.

(Control flow during deceleration operation)
Next, the control flow during the deceleration operation according to the present embodiment will be described based on the flowchart shown in FIG. This flow is stored in advance in the ECU 20 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1.

In this flow, first, in step S101, the ECU 20 determines whether or not the accelerator opening has decreased based on the detected value of the accelerator opening sensor 22. That is, it is determined whether or not the operating state of the internal combustion engine 1 is a deceleration operation. If an affirmative determination is made in step S101, the ECU 20 proceeds to step S102, and if a negative determination is made, the ECU 20 once ends the execution of this flow.

  In step S102, the ECU 20 calculates the post-deceleration torque Ttta based on the reduced accelerator opening Accelela.

  Next, the ECU 20 proceeds to S103 and calculates a post-deceleration air amount Qairta corresponding to the post-deceleration torque Ttta.

  Next, the ECU 20 proceeds to step S104 and calculates a target throttle valve opening degree Vsta corresponding to the post-deceleration torque Trta.

  Next, the ECU 20 proceeds to step S105, and calculates a post-deceleration EGR rate Regrta corresponding to the post-deceleration torque Trta.

  Next, the ECU 20 proceeds to step S106, and calculates a target EGR valve opening degree Vegrta corresponding to the post-deceleration EGR rate Regrta.

  Next, the ECU 20 proceeds to step S107, controls the EGR valve 16 in the valve closing direction, and controls the opening degree Vegr to the target EGR valve opening degree Vegrta.

  Next, the ECU 20 proceeds to step S108, and estimates the in-cylinder EGR gas amount Qegr. The in-cylinder EGR gas amount Qegr at this time is estimated based on the elapsed time since the opening degree Vegr of the EGR valve 16 is controlled to the target EGR valve opening degree Vegrta, the detected value of the air flow meter 11, the engine speed, and the like. I can do it.

  Next, the ECU 20 proceeds to step S109 and estimates the in-cylinder air amount Qair. The in-cylinder air amount Qair at this time can be estimated based on the detected value of the air flow meter 11, the engine speed, and the like.

  Next, the ECU 20 proceeds to step S110, and based on the in-cylinder EGR gas amount Qegr estimated in step S108 and the in-cylinder air amount Qair estimated in step S109, the current in-cylinder EGR rate, that is, the in-deceleration EGR Estimate the rate Regrde.

  Next, the ECU 20 proceeds to step S111, and based on the current engine speed, the in-cylinder air amount Qair estimated in step S109, and the decelerating EGR rate Regrde estimated in step S110, the current MBT torque, that is, The MBT torque Trmbde during deceleration is estimated. The method for estimating the MBT torque Trmbde during deceleration will be described later in detail.

  Next, the ECU 20 proceeds to step S112, and calculates the current target torque, that is, the deceleration target torque Trtde. The deceleration target torque Trtde at this time can be calculated based on the elapsed time since the post-deceleration torque Tta and the accelerator opening are reduced.

Next, the ECU 20 proceeds to step S113, and based on the difference between the deceleration MBT torque Trmbde estimated in step S111 and the deceleration target torque Trtde calculated in step S112, the retard amount Δtli of the ignition timing from the MBT. Is calculated. This retard amount Δtli is calculated as a value at which the torque of the internal combustion engine 1 becomes the target torque Trtde during deceleration, assuming that the ignition timing is retarded from the MBT by the retard amount Δtli. The difference between the MBT torque Trmbde during deceleration and the target torque Trtde during deceleration and the retard amount Δ of the ignition timing
The relationship with tli can be obtained based on experiments or the like, and in this embodiment, these relationships are stored in advance in the ECU 20 as a map.

  Next, the ECU 20 proceeds to step S114 and executes a retard of the ignition timing. That is, the ignition timing is controlled at a timing retarded from the retard amount Δtli MBT calculated in step S113. Thereby, even if the opening degree of the throttle valve 9 is maintained at the opening degree before the deceleration operation, the torque of the internal combustion engine 1 can be reduced to the target torque Trtde during the deceleration.

  Next, the ECU 20 proceeds to step S115 and determines whether or not the in-cylinder EGR amount Qger has decreased to a predetermined in-cylinder EGR amount Qegr0 or less. If an affirmative determination is made in step S115, the ECU 20 proceeds to step S116, and if a negative determination is made, the ECU 20 returns to step S108.

  In S116, the ECU 20 controls the throttle valve 9 in the valve closing direction, and controls the opening Vs of the opening to the target throttle valve opening Vsta calculated in Step S104.

  Next, the ECU 20 proceeds to step S117, and the ECU 20 estimates the in-cylinder EGR gas amount Qegr by the same method as in step S108.

  Next, the ECU 20 proceeds to S118 and estimates the in-cylinder air amount Qair. The in-cylinder air amount Qair at this time can be estimated based on the elapsed time since the opening of the throttle valve 9 is controlled to the target throttle valve opening Vsta, the detected value of the air flow meter 11, the engine speed, and the like. I can do it.

  Next, the ECU 20 proceeds to step S119, and estimates the EGR rate Regrde during deceleration based on the in-cylinder EGR gas amount Qegr estimated in step S117 and the in-cylinder air amount Qair estimated in step S118.

  Next, the ECU 20 proceeds to step S120, and based on the current engine speed, the in-cylinder air amount Qair estimated in step S118, and the in-deceleration EGR rate Regrde estimated in step S119, the same method as in step S111. To estimate the MBT torque Trmbde during the deceleration.

  Next, the ECU 20 proceeds to step S121, and calculates the current deceleration target torque Trtde by the same method as step S112.

  Next, the ECU 20 proceeds to step S122, and based on the difference between the deceleration MBT torque Trmbtde estimated in step S120 and the deceleration target torque Trtde calculated in step S121, ignition is performed in the same manner as in step S113. A retardation amount Δtli from the MBT of the time is calculated.

  Next, the ECU 20 proceeds to step S123 and executes a retard of the ignition timing. That is, the ignition timing is controlled at a timing retarded from the retard amount Δtli amount MBT calculated in step S122. Thus, the torque of the internal combustion engine 1 can be reduced to the target torque Trtde during deceleration while the in-cylinder air amount Qair does not reach the post-deceleration target air amount Qairta.

Next, the ECU 20 proceeds to step S124, and determines whether or not the in-cylinder air amount air has reached the post-deceleration target air amount Qairta. When the in-cylinder air amount air reaches the post-deceleration target air amount Qairta, the MBT torque is the post-deceleration torque Ttta, and the ignition timing is MBT. If an affirmative determination is made in step S124, the ECU 20 once ends the execution of this flow, and if a negative determination is made, the ECU 20 returns to step S117.

  According to the control flow during the deceleration operation, the retard amount Δtli of the ignition timing from the MBT during the deceleration operation is calculated based on the difference between the deceleration target torque Trtde and the deceleration MBT torque Trmbde. As a result, the torque during deceleration operation can be controlled to the target torque Trtde during deceleration with higher accuracy.

  In the control flow during the deceleration operation, the post-deceleration EGR rate Regrta and the target EGR valve opening degree Vegrta are calculated as values corresponding to the post-deceleration torque Trta, but these values are calculated based on the post-deceleration air amount Qairta. You can also

(Method for estimating MBT torque during deceleration)
Here, the calculation method of the MBT torque Trmbde during deceleration in steps S111 and S120 of the control flow during the deceleration operation will be described. In this embodiment, the ECU 20 estimates the MBT torque Trmbde during deceleration based on the indicated torque. The indicated torque is calculated as follows.

  FIG. 4 is a PV diagram of the internal combustion engine 1 according to the present embodiment. In FIG. 4, point (a) represents the intake stroke top dead center (-360 °: compression stroke top dead center is 0 °, and so on), and point (b) represents the intake stroke bottom dead center ( Compression stroke bottom dead center: -180 °), points (c) and (d) indicate compression stroke top dead center (expansion stroke top dead center: 0 °), and point (e) indicates expansion. The stroke bottom dead center (exhaust stroke bottom dead center: + 180 °) is represented, and the point (f) represents the exhaust stroke top dead center (+ 360 °).

  In FIG. 4, the area of the region A surrounded by the points (b), (c), (d), and (e) represents the combustion work that is the sum of work during the compression stroke and the expansion stroke. In FIG. 4, the area of the region B surrounded by the points (a), (b), (e), and (f) represents the pump loss during the intake stroke and the expansion stroke. The indicated torque can be calculated by converting the value obtained by subtracting the pump loss from the combustion work expressed in this way into torque.

  Here, even during the deceleration operation, the combustion work and the pump loss as described above can be calculated based on the engine speed and the in-cylinder air amount. Therefore, the indicated torque can be calculated from these values even during the deceleration operation. However, even if the in-cylinder air amount is the same, if the in-cylinder EGR rate changes, the combustion work and the pump loss change accordingly, so the indicated torque also changes. At this time, changes in combustion work and pump loss with respect to changes in the in-cylinder EGR rate are different. Therefore, when the indicated torque value is to be corrected according to the in-cylinder EGR rate, the correction method may be complicated.

  Therefore, in the present embodiment, when estimating the MBT torque Trmbde during deceleration, first, reference values of combustion work and pump loss when the ignition timing is assumed to be MBT (hereinafter referred to as reference combustion work and reference pump loss, respectively). Are calculated based on the engine speed and the in-cylinder air amount. Next, the reference combustion work and the reference pump loss are separately corrected based on the in-cylinder EGR rate during deceleration. Then, the indicated torque is calculated by subtracting the corrected pump loss (referred to as corrected pump loss) from the corrected combustion work (hereinafter referred to as corrected combustion work).

According to this, the indicated torque when the ignition timing during the deceleration operation is assumed to be MBT can be calculated more efficiently and with higher accuracy. As a result, it is possible to estimate the MBT torque Trmbde during deceleration more efficiently and with higher accuracy.

(MBT torque calculation flow during deceleration)
Hereinafter, the calculation flow of the MBT torque during deceleration according to the present embodiment will be described based on the flowchart shown in FIG. In this embodiment, this calculation flow is stored in advance in the ECU 20. Then, this calculation flow is executed in steps S111 and S120 of the control flow during the deceleration operation.

  In this flow, first, in step S201, the ECU 20 calculates a reference combustion work Wcbase based on the current in-cylinder air amount Qairde and the engine speed. In the present embodiment, the relationship between the in-cylinder air amount Qairde, the engine speed, and the reference combustion work Wcbase is obtained through experiments or the like, and these relationships are stored in advance in the ECU 20 as a map.

  Next, the ECU 20 proceeds to step S202, and calculates a reference pump loss Wpbase based on the current in-cylinder air amount Qairde and the engine speed. In this embodiment, the relationship between the in-cylinder air amount Qairde, the engine speed, and the reference pump loss Wpbase is obtained based on experiments and the like, and these relationships are stored in advance in the ECU 20 as a map.

  Next, the ECU 20 proceeds to step S203, and corrects the reference combustion work Wcbase calculated in step S201 based on the current deceleration EGR rate Regrde, thereby calculating the corrected combustion work Wcc.

  Next, the ECU 20 proceeds to step S204, and corrects the reference pump loss Wpbase calculated in step S202 based on the current deceleration EGR rate Regrde, thereby calculating a corrected pump loss Wpc.

  In the present embodiment, the relationship between the EGR rate Regrde during deceleration and the corrected combustion work Wcc and the relationship between the EGR rate Regrde during deceleration and the corrected pump loss Wpc are separately determined based on experiments, etc. Are previously stored in the ECU 20 as separate maps.

  Next, the ECU 20 proceeds to step S205, subtracts the corrected pumping loss Wpc calculated in step S204 from the corrected combustion work Wcc calculated in step S203, and converts the subtracted value into torque, thereby igniting at the present time. The indicated torque Tri when the time is assumed to be MBT is calculated.

  Next, the ECU 20 proceeds to step S206, and estimates the decelerating MBT torque Trmbde based on the indicated torque Tri calculated in step S205. Thereafter, the ECU 20 once ends this flow.

  In the above calculation flow of MBT torque during deceleration, the reference combustion work Wcbase and the reference pump loss Wpbase are calculated based on the in-cylinder air amount Qairde and the engine speed, but other factors are also taken into consideration. May be calculated. For example, when the internal combustion engine 1 includes a variable valve mechanism that varies the valve characteristics of the intake valve and / or the exhaust valve, the lift amount and / or the opening / closing timing of the intake valve and / or the exhaust valve is also taken into consideration. The reference combustion work Wcbase and the reference pump loss Wpbase may be calculated.

  Further, a “map showing the relationship between the difference between the MBT torque Trmbde during deceleration and the target torque Trtde during deceleration and the retard amount Δtli of the ignition timing” used in steps S113 and S122 in the control flow during the deceleration operation is created. In this case, the illustrated torque calculation method in the MBT torque calculation flow during deceleration may be used. In this case, the indicated torque when the ignition timing is assumed to be retarded from the MBT is calculated for a plurality of retard amounts. At this time, the reference combustion work is corrected based on the retarded EGR rate and the retard amount from the MBT of the ignition timing. Then, the indicated torque corresponding to each retardation amount is calculated by subtracting a value obtained by correcting the reference pump loss based on the EGR rate during deceleration from the correction value. Based on this, the relationship between the difference between the MBT torque Trmbde during deceleration and the target torque Trtde during deceleration and the retard amount Δtli of the ignition timing is obtained.

  In this embodiment, the ignition timing in the internal combustion engine 1 is calculated as a retard amount from the MBT. However, if the ignition timing in one combustion cycle can be specified, the ignition timing can be calculated based on a timing other than the MBT. good.

(Relationship between Example and Components of the Present Invention)
In this embodiment, the throttle valve 9 corresponds to an air amount control valve according to the present invention. If an ISC valve is provided, the ISC valve may be used as an air amount control valve according to the present invention.

  In this embodiment, the ECU 20 for controlling the opening degree of the EGR valve 16, the ECU 20 for controlling the opening degree of the throttle valve 9, and the ECU 20 for controlling the ignition timing by the spark plug 3 are the EGR valve control means according to the present invention. It corresponds to air quantity control valve control means and ignition timing control means.

  In this embodiment, the ECU 20 that executes steps S108 and S117 in the control flow during the deceleration operation corresponds to the in-cylinder EGR gas amount estimating means according to the present invention. In the present embodiment, the ECU 20 that executes steps S112 and S121 in the control flow during the deceleration operation corresponds to the deceleration target torque calculation means according to the present invention.

  In the present embodiment, the ECU 20 that executes steps S109 and S118 in the control flow during the deceleration operation corresponds to the in-cylinder air amount estimating means according to the present invention. In this embodiment, the ECU 20 that executes step S102 in the control flow during the deceleration operation corresponds to the post-deceleration torque calculation means according to the present invention. In this embodiment, the ECU 20 that executes step S105 in the control flow during the deceleration operation corresponds to the post-deceleration EGR rate calculation means according to the present invention. In this embodiment, the ECU 20 that executes step S106 in the control flow during the deceleration operation corresponds to the target EGR valve opening degree calculation means according to the present invention. In the present embodiment, the ECU 20 that executes step S104 in the control flow during the deceleration operation corresponds to the target air amount control valve opening calculation means according to the present invention.

  In this embodiment, the ECU 20 that executes steps S110 and S119 in the control flow during the deceleration operation corresponds to the EGR rate estimating means during deceleration according to the present invention. In this embodiment, the ECU 20 that executes steps S110 and S119 in the control flow during the deceleration operation corresponds to the deceleration EGR rate estimating means according to the present invention. In this embodiment, the ECU 20 that executes steps S111 and S120 in the control flow during the deceleration operation corresponds to the MBT torque estimating means during deceleration according to the present invention. In this embodiment, the ECU 20 that executes steps S113 and S122 in the control flow during the deceleration operation corresponds to the retard amount calculation means according to the present invention.

In the present embodiment, the step S103 is executed in the control flow during the deceleration operation.
The CU 20 corresponds to the post-deceleration air amount calculation means according to the present invention.

  In this embodiment, the ECU 20 that executes step S201 in the MBT torque calculation flow during deceleration corresponds to the reference combustion work calculation means according to the present invention. In this embodiment, the ECU 20 that executes step S202 in the deceleration MBT torque calculation flow corresponds to the reference pump loss calculation means according to the present invention. In this embodiment, the ECU 20 that executes step S203 in the MBT torque calculation flow during deceleration corresponds to the combustion work correction means according to the present invention. In the present embodiment, the ECU 20 that executes step S204 in the MBT torque calculation flow during deceleration corresponds to the pump loss correcting means according to the present invention. In the present embodiment, the ECU 20 that executes step S205 in the MBT torque calculation flow during deceleration corresponds to the indicated torque calculation means according to the present invention.

The figure which shows schematic structure of the internal combustion engine which concerns on an Example, and its intake / exhaust system. When the accelerator opening, the target torque, the opening of the EGR valve, the in-cylinder EGR gas amount, the opening of the throttle valve, the in-cylinder air amount, and the ignition timing by the spark plug are set to MBT during deceleration operation according to the embodiment The time chart which shows transition of the estimated torque of this and the ignition timing by a spark plug. The PV diagram of the internal combustion engine which concerns on an Example. The flowchart which shows the control flow at the time of the deceleration driving | operation which concerns on an Example. The flowchart which shows the calculation flow of MBT torque during deceleration which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Spark plug 4 ... Intake passage 5 ... Intake manifold 6 ... Exhaust passage 7 ... Exhaust manifold 9 ... Throttle valve 10 ... Three-way catalyst 11, Air flow meter 12, Pressure sensor 13, Surge tank 14, EGR device 15, EGR passage 16, EGR valve 20, ECU
21 ・ ・ Crank position sensor 22 ・ ・ Accelerator position sensor

Claims (3)

The EGR passage has one end connected to the exhaust passage and the other end connected to the downstream side of the surge tank in the intake passage, and the EGR valve provided in the EGR passage, and exhaust gas is discharged through the EGR passage to the EGR gas. EGR device to be introduced into the intake system as
An air amount control valve that is provided upstream of the surge tank in the intake passage and controls the intake air amount of the internal combustion engine;
EGR valve control means for controlling the opening of the EGR valve;
An air amount control valve control means for controlling the opening of the air amount control valve;
Ignition timing control means for controlling the ignition timing in the internal combustion engine;
In-cylinder EGR gas amount estimation means for estimating an in-cylinder EGR gas amount that is the amount of EGR gas in the cylinder of the internal combustion engine;
Decelerating target torque calculating means for calculating a decelerating target torque that is a target value of the torque of the internal combustion engine when the operating state of the internal combustion engine is during decelerating operation;
In-cylinder air amount estimating means for estimating an in-cylinder air amount that is an air amount in a cylinder of the internal combustion engine;
A post-deceleration torque calculating means for calculating a post-deceleration torque that is a target value of the torque of the internal combustion engine after the end of the decelerating operation when the operating state of the internal combustion engine is a decelerating operation;
A post-deceleration EGR rate calculating means for calculating a post-deceleration EGR rate that is an EGR rate of gas in the cylinder of the internal combustion engine corresponding to the post-deceleration torque when the operation state of the internal combustion engine is a deceleration operation;
A target EGR valve opening calculation means for calculating a target EGR valve opening that is an opening of the EGR valve corresponding to the post-deceleration EGR rate when the operating state of the internal combustion engine is a deceleration operation;
A target air amount control valve opening calculating means for calculating a target air amount control valve opening that is an opening of the air amount control valve corresponding to the post-deceleration torque when the operation state of the internal combustion engine is a deceleration operation; ,
EGR rate estimation during deceleration for estimating an EGR rate during deceleration, which is an EGR rate of gas in the cylinder of the internal combustion engine when the operation state of the internal combustion engine is during deceleration operation, based on the in-cylinder air amount and the in-cylinder EGR gas amount Means,
MBT during deceleration that estimates the MBT torque during deceleration, which is the torque when the ignition timing in the internal combustion engine is assumed to be MBT when the operation state of the internal combustion engine is during deceleration operation, based on the in-cylinder air amount and the EGR rate during deceleration Torque estimation means;
A retard amount calculating means for calculating a retard amount from the MBT of the ignition timing during the deceleration operation based on a difference between the target torque during deceleration and the MBT torque during deceleration;
When the operation state of the internal combustion engine becomes a deceleration operation state, the opening degree of the EGR valve is decreased to the target EGR valve opening degree by the EGR valve control means, and then the in-cylinder EGR gas amount is reduced to a predetermined amount or less. The opening amount of the air amount control valve is decreased to the target air amount control valve opening degree by the air amount control valve control means after decreasing, and
When the operating state of the internal combustion engine is decelerating, the ignition timing control means calculates the ignition timing at the internal combustion engine from the MBT by the retard amount calculation means so that the torque of the internal combustion engine becomes the target torque during deceleration. A control system for an internal combustion engine, characterized by retarding by a retarded amount . The EGR passage has one end connected to the exhaust passage and the other end connected to the downstream side of the surge tank in the intake passage, and the EGR valve provided in the EGR passage, and exhaust gas is discharged through the EGR passage to the EGR gas. EGR device to be introduced into the intake system as
An air amount control valve that is provided upstream of the surge tank in the intake passage and controls the intake air amount of the internal combustion engine;
EGR valve control means for controlling the opening of the EGR valve;
An air amount control valve control means for controlling the opening of the air amount control valve;
Ignition timing control means for controlling the ignition timing in the internal combustion engine;
In-cylinder EGR gas amount estimation means for estimating an in-cylinder EGR gas amount that is the amount of EGR gas in the cylinder of the internal combustion engine;
Decelerating target torque calculating means for calculating a decelerating target torque that is a target value of the torque of the internal combustion engine when the operating state of the internal combustion engine is during decelerating operation;
In-cylinder air amount estimating means for estimating an in-cylinder air amount that is an air amount in a cylinder of the internal combustion engine;
A post-deceleration air amount calculation means for calculating a post-deceleration air amount that is a target value of the intake air amount of the internal combustion engine after the end of the deceleration operation when the operation state of the internal combustion engine is a deceleration operation;
A post-deceleration EGR rate calculating means for calculating a post-deceleration EGR rate that is an EGR rate of gas in the cylinder of the internal combustion engine corresponding to the post-deceleration air amount when the operating state of the internal combustion engine is a deceleration operation;
A target EGR valve opening degree calculation means for calculating a target EGR valve opening degree that is an opening degree of the EGR valve corresponding to the post-deceleration EGR rate when the operating state of the internal combustion engine is a deceleration operation;
Target air amount control valve opening calculating means for calculating a target air amount control valve opening that is an opening of the air amount control valve corresponding to the air amount after deceleration when the operation state of the internal combustion engine is a deceleration operation When,
EGR rate estimation during deceleration for estimating an EGR rate during deceleration, which is an EGR rate of gas in the cylinder of the internal combustion engine when the operating state of the internal combustion engine is during deceleration operation, based on the in-cylinder air amount and the in-cylinder EGR gas amount Means,
MBT during deceleration that estimates the MBT torque during deceleration, which is the torque when the ignition timing in the internal combustion engine is assumed to be MBT when the operation state of the internal combustion engine is during deceleration operation, based on the in-cylinder air amount and the EGR rate during deceleration Torque estimation means;
A retard amount calculating means for calculating a retard amount from the MBT of the ignition timing during the deceleration operation based on a difference between the target torque during deceleration and the MBT torque during deceleration ;
When the operation state of the internal combustion engine becomes a deceleration operation state, the opening degree of the EGR valve is decreased to the target EGR valve opening degree by the EGR valve control means, and then the in-cylinder EGR gas amount is reduced to a predetermined amount or less. The opening amount of the air amount control valve is decreased to the target air amount control valve opening degree by the air amount control valve control means after decreasing, and
When the operating state of the internal combustion engine is decelerating, the ignition timing control means calculates the ignition timing at the internal combustion engine from the MBT by the retard amount calculation means so that the torque of the internal combustion engine becomes the target torque during deceleration. A control system for an internal combustion engine, characterized by retarding by a retarded amount . The MBT torque estimating means during deceleration is
Reference combustion work calculation means for calculating a reference combustion work, which is a reference value of the sum of work during the compression stroke and the expansion stroke when the ignition timing in the internal combustion engine is MBT, based on at least the in-cylinder air amount;
A reference pump loss calculating means for calculating a reference pump loss that is a reference value of the pump loss between the intake stroke and the expansion stroke based on at least the in-cylinder air amount;
Combustion work correction means for correcting the reference combustion work calculated by the reference combustion work calculation means based on the EGR rate during deceleration;
Pump loss correction means for correcting the reference pump loss calculated by the reference pump loss calculation means based on the EGR rate during deceleration;
An indicated torque calculating means for calculating an indicated torque based on a value obtained by subtracting the pump loss corrected by the pump loss correcting means from the combustion work corrected by the combustion work correcting means,
3. The control system for an internal combustion engine according to claim 1, wherein the MBT torque during deceleration is estimated based on the indicated torque calculated by the indicated torque calculating means.

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