WO2013054410A1

WO2013054410A1 - Control device for internal combustion engine

Info

Publication number: WO2013054410A1
Application number: PCT/JP2011/073503
Authority: WO
Inventors: 真介青柳
Original assignee: トヨタ自動車株式会社
Priority date: 2011-10-13
Filing date: 2011-10-13
Publication date: 2013-04-18

Abstract

The present invention relates to a control device for an internal combustion engine, the control device being provided with an intake air quantity detection means (35), a fuel supply means (21), an air-fuel ratio detection means (43), and an exhaust gas recirculation means (50). In the present invention, when a first accuracy (A1) calculated on the basis of the detection accuracy (Aafm) of the intake air quantity detection means and the fuel supply accuracy (Ainj) of the fuel supply means is higher than a second accuracy (A2) calculated on the basis of the detection accuracy (Aafs, Aaft) of the air-fuel ratio detection means, the quantity of exhaust gas to be introduced into a combustion chamber by the exhaust gas recirculation means is controlled such that the intake air quantity detected by the intake air quantity detection means matches the target value thereof. Meanwhile, in the present invention, when the first accuracy is equal to or lower than the second accuracy, the quantity of the exhaust gas to be introduced into the combustion chamber by the exhaust gas recirculation means is controlled such that the air-fuel ratio detected by the air-fuel ratio detection means matches the target value thereof.

Description

Control device for internal combustion engine

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

The control object of the internal combustion engine is described in Patent Document 1. An internal combustion engine described in Patent Document 1 is an exhaust gas recirculation device that introduces a part of exhaust gas discharged from a combustion chamber into an exhaust passage into the combustion chamber via an intake passage (hereinafter, this device is referred to as an “EGR device”). And an oxygen concentration sensor for detecting the oxygen concentration in the exhaust gas discharged from the combustion chamber into the exhaust passage. And the control apparatus of patent document 1 controls the operation | movement of an EGR apparatus so that the oxygen concentration detected by the oxygen concentration sensor may converge on the target value, and the exhaust gas introduce | transduced into a combustion chamber by the said EGR apparatus Control the amount of gas.

Japanese Patent Laid-Open No. 2002-138907 JP 2007-262946 A JP 2009-103062 A

By the way, when the response delay of the oxygen concentration sensor is relatively small, the followability of the oxygen concentration with respect to the target value (hereinafter referred to as “target value followability”) is relatively high. However, the response delay of the oxygen concentration sensor changes depending on the engine operating state (that is, the operating state of the internal combustion engine). Therefore, depending on the engine operating state, the response delay of the oxygen concentration sensor may be relatively large. At this time, the target value followability is relatively low, and thus the emission performance in the exhaust gas is degraded. This is because the air-fuel ratio detected by the air-fuel ratio sensor in an internal combustion engine having an air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas discharged from the combustion chamber into the exhaust passage instead of the oxygen concentration sensor is The same applies to controlling the amount of exhaust gas introduced into the combustion chamber by the EGR device by controlling the operation of the EGR device so as to converge to the target value.

Therefore, an object of the present invention is to maintain a high target value followability regardless of the engine operating state and to maintain a high emission performance in the exhaust gas.

The present invention includes an intake air amount detecting means for detecting an intake air amount that is an amount of air sucked into the combustion chamber, a fuel supply means for supplying fuel to the combustion chamber, and an exhaust passage discharged from the combustion chamber. A control apparatus for an internal combustion engine, comprising: an air-fuel ratio detection means for detecting an air-fuel ratio of exhaust gas; and an exhaust gas recirculation means for introducing the exhaust gas discharged from the combustion chamber into the exhaust passage into the combustion chamber via the intake passage. About. In the present invention, the first accuracy calculated based on the detection accuracy of the intake air amount detection means and the fuel supply accuracy of the fuel supply means is calculated based on the detection accuracy of the air-fuel ratio detection means. When the accuracy is higher than two, the amount of exhaust gas introduced into the combustion chamber is controlled by the exhaust gas recirculation unit so that the intake air amount detected by the intake air amount detection unit matches the target value. On the other hand, in the present invention, when the first accuracy is less than or equal to the second accuracy, the exhaust gas recirculation means introduces the air into the combustion chamber so that the air-fuel ratio detected by the air-fuel ratio detection means matches the target value. The amount of exhaust gas emitted is controlled.

According to the present invention, the following effects can be obtained. That is, the detection accuracy of the intake air amount detection means, the fuel supply accuracy of the fuel supply means, and the detection accuracy of the air-fuel ratio detection means vary depending on the engine operating state (that is, the operating state of the internal combustion engine).

Here, in the present invention, when the first accuracy is higher than the second accuracy, that is, the accuracy of the intake air amount detected by the intake air amount detection unit than the accuracy of the air-fuel ratio detected by the air-fuel ratio detection unit, and When the accuracy of the amount of fuel supplied to the combustion chamber by the fuel supply means is higher, the amount of exhaust gas introduced into the combustion chamber is not controlled based on the air-fuel ratio detected by the air-fuel ratio detection means. The amount of exhaust gas introduced into the combustion chamber is controlled based on the intake air amount detected by the intake air amount detection means. That is, at this time, the amount of exhaust gas introduced into the combustion chamber is controlled based on a parameter with higher accuracy. For this reason, the followability of the intake air amount with respect to the target value is high, and thus the emission performance in the exhaust gas is maintained high.

On the other hand, in the present invention, when the second accuracy is equal to or higher than the first accuracy, that is, the accuracy of the intake air amount detected by the intake air amount detection means and the accuracy of the amount of fuel supplied to the combustion chamber by the fuel supply means. When the accuracy of the air-fuel ratio detected by the air-fuel ratio detection unit is higher than the amount of exhaust gas introduced into the combustion chamber based on the intake air amount detected by the intake air amount detection unit Instead, the amount of exhaust gas introduced into the combustion chamber is controlled based on the air-fuel ratio detected by the air-fuel ratio detection means. That is, also at this time, the amount of exhaust gas introduced into the combustion chamber is controlled based on a parameter with higher accuracy. For this reason, the followability of the air-fuel ratio with respect to the target value is high, and thus the emission performance in the exhaust gas is maintained high.

Therefore, according to the present invention, the target value followability can be maintained high regardless of the engine operating state, and the emission performance in the exhaust gas can be maintained high.

In the above invention, the detection accuracy of the intake air amount detection means when the intake air amount is in a steady state can be adopted as the detection accuracy of the intake air amount detection means.

In this case, the following effects can be obtained. That is, the detection accuracy of the intake air amount detection means when the intake air amount is in a steady state is higher than the detection accuracy of the intake air amount detection means when the intake air amount is in a transient state. This greatly affects the detection accuracy. Therefore, when the detection accuracy of the intake air amount detection means when the intake air amount is in a steady state is adopted as the detection accuracy of the intake air amount detection means, the target value followability is maintained higher, and the emission in the exhaust gas The effect that performance can be maintained higher is acquired.

In the above invention, the fuel supply accuracy of the combustion supply means when the amount of fuel supplied to the combustion chamber by the fuel supply means is in a steady state can be adopted as the fuel supply accuracy of the fuel supply means. .

In this case, the following effects can be obtained. That is, the amount of fuel supplied to the combustion chamber by the fuel supply means (hereinafter referred to as “fuel supply amount”) is in a steady state rather than the fuel supply accuracy of the fuel supply means when in a transient state. The fuel supply accuracy of the fuel supply unit when the fuel supply unit is in the above condition greatly affects the fuel supply accuracy of the fuel supply unit. Therefore, when the fuel supply accuracy of the fuel supply means when the fuel supply amount is in a steady state is adopted as the fuel supply accuracy of the fuel supply means, the target value followability is maintained higher and the emission performance in the exhaust gas is improved. The effect that it can maintain more highly is acquired.

In the above invention, as the detection accuracy of the air-fuel ratio detection means, the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio of the exhaust gas discharged from the combustion chamber to the exhaust passage is in a steady state and the exhaust passage from the combustion chamber The detection accuracy of the air-fuel ratio detection means when the air-fuel ratio of the exhaust gas exhausted in a transient state can be employed.

In this case, the following effects can be obtained. That is, the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio is in a steady state and the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio is in a transient state are equal, greatly affecting the detection accuracy of the air-fuel ratio detection means. To do. Therefore, when the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio is in a steady state and the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio is in a transient state are adopted as the detection accuracy of the air-fuel ratio detection means, The effect that the target value followability can be maintained higher and the emission performance in the exhaust gas can be maintained higher can be obtained.

It is the figure which showed the internal combustion engine to which the control apparatus of this invention was applied. (A) is the figure which showed the map used in order to acquire the reference | standard fuel injection amount, (B) is the figure which showed the map used in order to acquire the reference | standard throttle valve opening degree, (C) FIG. 4 is a diagram showing a map used for obtaining a reference EGR rate. (A) is the figure which showed the map used in order to acquire the reference | standard intake air amount, (B) is the figure which showed the map used in order to acquire a reference | standard air-fuel ratio. (A) is a diagram showing an example of a routine for executing control of a fuel injection valve, and (B) is a diagram showing an example of a routine for executing setting of a target fuel injection amount. (A) is a diagram showing an example of a routine for executing control of a throttle valve, and (B) is a diagram showing an example of a routine for executing setting of a target throttle valve opening degree. It is the figure which showed an example of the routine which performs control of an EGR control valve. It is the figure which showed an example of the routine which performs the setting of the target EGR rate.

Hereinafter, embodiments of the present invention will be described. FIG. 1 shows an internal combustion engine to which the control device of the present invention is applied. The internal combustion engine shown in FIG. 1 is a compression ignition type internal combustion engine (so-called diesel engine). In FIG. 1, 10 is an internal combustion engine, 20 is a main body of the

internal combustion engine

10, 21 is a fuel injection valve, 22 is a fuel pump, 23 is a fuel supply passage, 30 is an intake passage, 31 is an intake manifold, 32 is an intake pipe, 33 , Throttle valve, 34 intercooler, 35 air flow meter, 36 air cleaner, 37 intake pressure sensor, 40 exhaust passage, 41 exhaust manifold, 42 exhaust pipe, 43 air-fuel ratio sensor, 50 exhaust recirculation 70, an accelerator pedal, 71 an accelerator pedal depression amount sensor, 72 a crank position sensor, and 80 an electronic control device. The intake passage 30 includes an intake manifold 31 and an intake pipe 32. The exhaust passage 40 includes an exhaust manifold 41 and an exhaust pipe 42.

The electronic control device 80 is composed of a microcomputer. The electronic control unit 80 includes a CPU (microprocessor) 81, a ROM (read only memory) 82, a RAM (random access memory) 83, a backup RAM 84, and an interface 85. The CPU 81, ROM 82, RAM 83, backup RAM 84, and interface 85 are connected to each other by a bidirectional bus.

The fuel injection valve 21 is attached to the main body 20 of the internal combustion engine. A fuel pump 22 is connected to the fuel injection valve 21 via a fuel supply passage 23. The fuel pump 22 supplies high-pressure fuel to the fuel injection valve 21 via the fuel supply passage 23. The fuel injection valve 21 is electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies a command signal for causing the fuel injection valve 21 to inject fuel to the fuel injection valve 21. The fuel pump 22 is also electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies the fuel pump 22 with a control signal for controlling the operation of the fuel pump 22 so that the pressure of the fuel supplied from the fuel pump 22 to the fuel injection valve 21 is maintained at a predetermined pressure. . The fuel injection valve 21 is attached to the main body 20 of the internal combustion engine so that its fuel injection hole is exposed in the combustion chamber. Therefore, when a command signal is supplied from the electronic control unit 80 to the fuel injection valve 21, the fuel injection valve 21 directly injects fuel into the combustion chamber.

The intake manifold 31 is branched into a plurality of pipes at one end thereof, and these branched pipes are connected to intake ports (not shown) formed respectively corresponding to the combustion chambers of the main body 20 of the internal combustion engine. Has been. The intake manifold 31 is connected to one end of the intake pipe 32 at the other end. The exhaust manifold 41 is branched into a plurality of pipes at one end thereof, and these branched pipes are connected to exhaust ports (not shown) formed respectively corresponding to the combustion chambers of the main body 20 of the internal combustion engine. Has been. The exhaust manifold 41 is connected to one end of the exhaust pipe 42 at the other end.

The throttle valve 33 is disposed in the intake pipe 32. When the opening of the throttle valve 33 (hereinafter, this opening is referred to as “throttle valve opening”) is changed, the flow path area in the intake pipe 32 in the region where the throttle valve 33 is disposed changes. As a result, the amount of air passing through the throttle valve 33 changes, and as a result, the amount of air taken into the combustion chamber changes. The throttle 33 is electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies a control signal for operating the throttle valve 33 to the throttle valve 33.

The intercooler 34 is disposed in the intake pipe 32 upstream of the throttle valve 33. The intercooler 34 cools the air flowing into the intercooler 34.

The air flow meter 35 is disposed in the intake pipe 32 upstream of the intercooler 34. The air flow meter 35 is electrically connected to the interface 85 of the electronic control device 80. The air flow meter 35 outputs an output value corresponding to the amount of air passing therethrough. This output value is input to the electronic control unit 80. Based on this output value, the electronic control unit 80 calculates the amount of air passing through the air flow meter 35, that is, the amount of air taken into the combustion chamber.

The intake pressure sensor 37 is disposed in the intake passage 30 (more specifically, the intake manifold 31) downstream of the throttle valve 33. The intake pressure sensor 37 is electrically connected to the interface 85 of the electronic control device 80. The intake pressure sensor 37 outputs an output value corresponding to the pressure of the surrounding gas (that is, the pressure of the gas in the intake manifold 31 and the pressure of the gas sucked into the combustion chamber). Based on this output value, the electronic control unit 80 calculates the pressure of the gas around the intake pressure sensor 37, that is, the pressure of the gas sucked into the combustion chamber (that is, the intake pressure).

The air-fuel ratio sensor 43 is disposed in the exhaust passage 40 (more specifically, the exhaust pipe 42). The air-fuel ratio sensor 43 is electrically connected to the interface 85 of the electronic control device 80. The air-fuel ratio sensor 43 outputs an output value corresponding to the oxygen concentration in the exhaust gas reaching there. Based on this output value, the electronic control unit 80 calculates the air-fuel ratio of the exhaust gas, that is, the air-fuel ratio of the air-fuel mixture formed in the combustion chamber.

Accelerator pedal depression amount sensor 71 is connected to accelerator pedal 70. The accelerator pedal depression amount sensor 71 is electrically connected to the interface 85 of the electronic control unit 80. The accelerator pedal depression amount sensor 71 outputs an output value corresponding to the depression amount of the accelerator pedal 70. This output value is input to the electronic control unit 80. The electronic control unit 80 calculates the amount of depression of the accelerator pedal 70 and thus the torque required for the internal combustion engine (hereinafter, this torque is referred to as “requested engine torque”) based on the output value.

The crank position sensor 72 is disposed in the vicinity of the crankshaft (not shown) of the internal combustion engine. The crank position sensor 72 is electrically connected to the interface 85 of the electronic control unit 80. The crank position sensor 72 outputs an output value corresponding to the rotational phase of the crankshaft. This output value is input to the electronic control unit 80. The electronic control unit 80 calculates the engine speed based on this output value.

The EGR device 50 includes an exhaust gas recirculation pipe (hereinafter referred to as “EGR pipe”) 51, an exhaust gas recirculation control valve (hereinafter referred to as “EGR control valve”) 52, and an exhaust gas recirculation cooler (hereinafter referred to as “EGR control valve”). This cooler is referred to as an “EGR cooler” 53. The EGR device 50 can introduce the exhaust gas discharged from the combustion chamber into the exhaust passage 40 into the intake passage 30 via the EGR pipe 51. The EGR pipe 51 is connected to the exhaust passage 40 (more specifically, the exhaust manifold 41) at one end, and connected to the intake passage 30 (more specifically, the intake manifold 31) at the other end. Yes. That is, the EGR pipe 51 connects the exhaust passage 40 to the intake passage 30.

The EGR control valve 52 is disposed in the EGR pipe 51. When the opening degree of the EGR control valve 52 (hereinafter, this opening degree is referred to as “EGR control valve opening degree”) is changed, the amount of exhaust gas passing through the EGR control valve 52 is changed, and eventually introduced into the intake passage 30. The amount of exhaust gas is changed. The EGR control valve is electrically connected to the interface 85 of the electronic control unit 80. The electronic control unit 80 supplies a control signal for operating the EGR control valve 52 to the EGR control valve. The EGR cooler 53 is disposed in the EGR pipe 51. The EGR cooler 53 cools the exhaust gas flowing through the EGR pipe 51.

Next, control of the fuel injection valve of this embodiment will be described. In the following description, “fuel injection amount” means “amount of fuel injected from the fuel injection valve”. In the present embodiment, a command signal for injecting an amount of fuel corresponding to a target value of the fuel injection amount (hereinafter, this target value is referred to as “target fuel injection amount”) from the fuel injection valve is calculated by the electronic control unit. A signal is supplied from the electronic control unit to the fuel injector, which causes the fuel injector to operate.

Next, the setting of the target fuel injection amount of this embodiment will be described. In the present embodiment, in the internal combustion engine shown in FIG. 1, an appropriate fuel injection amount corresponding to the depression amount of the accelerator pedal is obtained in advance by experiments or the like. The obtained fuel injection amount is stored in the electronic control unit as a reference fuel injection amount Qb in the form of a map of a function of the accelerator pedal depression amount Dac as shown in FIG. Then, during engine operation, the reference fuel injection amount Qb corresponding to the accelerator pedal depression amount Dac at that time is acquired from the map of FIG. 2A, and the acquired reference fuel injection amount Qb becomes the target fuel injection amount. Is set. Note that, as shown in FIG. 2A, the reference fuel injection amount Qb increases as the accelerator pedal depression amount Dac increases.

Next, control of the throttle valve of this embodiment will be described. In the following description, “throttle valve opening” means “throttle valve opening”. In this embodiment, a control signal for operating the throttle valve is electronically controlled so that a throttle valve opening corresponding to a target value of the throttle valve opening (hereinafter, this target value is referred to as “target throttle valve opening”) is achieved. The control signal is calculated in the device, and this control signal is supplied from the electronic control device to the throttle valve, whereby the throttle valve is operated.

Next, the setting of the target throttle valve opening according to this embodiment will be described. In the present embodiment, an appropriate throttle valve opening corresponding to the engine operating state defined by the engine speed and the target fuel injection amount is obtained in advance by experiments or the like. The obtained throttle valve opening is electronically controlled as a reference throttle valve opening Dthb in the form of a function map of the engine speed NE and the target fuel injection amount Qt as shown in FIG. Stored in the device. During engine operation, the reference throttle valve opening degree Dthb corresponding to the current engine speed NE and the current target fuel injection amount Qt is acquired from the map of FIG. The acquired reference throttle valve opening Dthb is set to the target throttle valve opening. In the map of FIG. 2B, the reference throttle valve opening degree Dthb is larger as the engine speed NE is larger, and the reference throttle valve opening degree Dthb is larger as the target fuel injection amount Qt is larger.

Next, control of the EGR control valve of this embodiment will be described. In the following description, “EGR rate” means “ratio of the amount of exhaust gas sucked into the combustion chamber to the amount of gas sucked into the combustion chamber”. In the present embodiment, a control signal for operating the EGR control valve is calculated in the electronic control device so that the target value of the EGR rate (hereinafter, this target value is referred to as “target EGR rate”) is achieved. The EGR control valve is supplied from the control device, and thereby the EGR control valve is operated.

Next, the setting of the target EGR rate of this embodiment will be described. In the present embodiment, an appropriate EGR rate corresponding to the engine operating state defined by the engine speed and the target fuel injection amount is obtained in advance by experiments or the like. The obtained EGR rate is stored in the electronic control unit as a reference EGR rate Regrb in the form of a function map of the engine speed NE and the target fuel injection amount Qt as shown in FIG. ing. Then, during engine operation, the reference EGR rate Regrb corresponding to the current engine speed NE and the current target fuel injection amount Qt is acquired from the map of FIG.

On the other hand, in the present embodiment, an appropriate intake air amount corresponding to the engine operating state defined by the engine speed and the target fuel injection amount is obtained in advance by experiments or the like. Then, as shown in FIG. 3A, the obtained intake air amount is supplied to the electronic control unit as a reference intake air amount GAb in the form of a map of a function of the engine speed NE and the target fuel injection amount Qt. It is remembered. Furthermore, in the present embodiment, an appropriate air-fuel ratio corresponding to the engine operating state defined by the engine speed and the target fuel injection amount is obtained in advance by experiments or the like. The obtained air-fuel ratio is stored in the electronic control unit as a reference air-fuel ratio AFb in the form of a function map of the engine speed NE and the target fuel injection amount Qt as shown in FIG. 2C. ing.

An accuracy calculated based on the detection accuracy of the air flow meter and the fuel injection accuracy of the fuel injection valve (hereinafter referred to as “first accuracy”) is calculated based on the detection accuracy of the air-fuel ratio sensor ( Hereinafter, when this accuracy is higher than “second accuracy”), the reference intake air amount GAb corresponding to the engine speed NE at that time and the target fuel injection amount Qt at that time is acquired from the map of FIG. The acquired reference intake air amount GAb is set as the target intake air amount. Then, a deviation of the actual intake air amount (that is, the intake air amount detected by the air flow meter) with respect to the set target intake air amount (hereinafter, this deviation is referred to as “intake air amount deviation”) is calculated. Based on the calculated intake air amount deviation, a correction coefficient for correcting the current target EGR rate so that the EGR rate is changed so that the intake air amount deviation becomes zero (hereinafter referred to as this correction coefficient). (Referred to as “first correction coefficient”). Then, a value obtained by correcting the acquired reference EGR rate with the calculated first correction coefficient is set as the target EGR rate. That is, in this case, the EGR rate is controlled so that the actual intake air amount matches the target intake air amount.

On the other hand, when the first accuracy is less than or equal to the second accuracy, the reference air-fuel ratio AFb corresponding to the engine speed NE at that time and the target fuel injection amount Qt at that time is acquired from the map of FIG. The set reference air-fuel ratio AFb is set to the target air-fuel ratio AFt. Then, a deviation of the actual air-fuel ratio (that is, the air-fuel ratio detected by the air-fuel ratio sensor) with respect to the set target air-fuel ratio (hereinafter, this deviation is referred to as “air-fuel ratio deviation”) is calculated. Then, based on the calculated air-fuel ratio deviation, a correction coefficient for correcting the current target EGR rate so that the EGR ratio is changed so that the air-fuel ratio deviation becomes zero (hereinafter, this correction coefficient is referred to as “first correction coefficient”). 2 correction coefficient ") is calculated. Then, a value obtained by correcting the acquired reference EGR rate by the calculated second correction coefficient is set as the target EGR rate. That is, in this case, the EGR rate is controlled so that the actual air-fuel ratio matches the target air-fuel ratio.

According to this embodiment, the following effects can be obtained. That is, the detection accuracy of the air flow meter, the fuel injection accuracy of the fuel injection valve, and the detection accuracy of the air-fuel ratio sensor vary according to the engine operating state.

Here, in the present embodiment, when the first accuracy is higher than the second accuracy, that is, the accuracy of the intake air amount detected by the air flow meter and the fuel injection than the accuracy of the air-fuel ratio detected by the air-fuel ratio sensor. When the accuracy of the amount of fuel injected from the valve is higher, the EGR rate is not controlled based on the air-fuel ratio detected by the air-fuel ratio sensor, but based on the intake air amount detected by the air flow meter. The rate is controlled, and consequently the air-fuel ratio is controlled to the target air-fuel ratio. That is, at this time, the EGR rate is controlled based on a parameter with higher accuracy, and thereby the air-fuel ratio is controlled to the target air-fuel ratio. For this reason, the followability of the intake air amount with respect to the target intake air amount is high, and accordingly, the followability of the air / fuel ratio with respect to the target air / fuel ratio is high, so that the emission performance in the exhaust gas is maintained high.

On the other hand, in the present embodiment, when the second accuracy is equal to or higher than the first accuracy, that is, the accuracy of the intake air amount detected by the air flow meter and the accuracy of the amount of fuel injected from the fuel injection valve, When the accuracy of the air-fuel ratio detected by the sensor is higher, the EGR rate is not controlled based on the intake air amount detected by the air flow meter, but based on the air-fuel ratio detected by the air-fuel ratio sensor. Thus, the air-fuel ratio is controlled to the target air-fuel ratio. That is, also at this time, the EGR rate is controlled based on a parameter with higher accuracy, and thereby the air-fuel ratio is controlled to the target air-fuel ratio. For this reason, the followability of the air-fuel ratio with respect to the target air-fuel ratio is high, and thus the emission performance in the exhaust gas is maintained high.

Therefore, according to the present embodiment, it is possible to obtain the effect that the air-fuel ratio followability with respect to the target air-fuel ratio can be kept high and the emission performance in the exhaust gas can be kept high regardless of the engine operating state.

The above-described embodiment is an embodiment in which the present invention is applied to an internal combustion engine having an air flow meter. However, the present invention is widely applied to an internal combustion engine having a means for detecting an intake air amount. Is possible. In addition, the above-described embodiment is an embodiment when the present invention is applied to an internal combustion engine including a fuel injection valve. However, the present invention broadly includes a fuel supply means for supplying fuel to the combustion chamber. Applicable to internal combustion engines. The above-described embodiment is an embodiment in which the present invention is applied to an internal combustion engine having an air-fuel ratio sensor. However, the present invention is broadly based on the exhaust gas exhausted from the combustion chamber into the exhaust passage. The present invention can be applied to an internal combustion engine having air-fuel ratio detection means for detecting the fuel ratio. In addition, the above-described embodiment is an embodiment in the case where the present invention is applied to an internal combustion engine having an EGR device. However, the present invention broadly relates to exhaust gas discharged from a combustion chamber into an exhaust passage. The present invention can be applied to an internal combustion engine having exhaust gas recirculation means introduced into the combustion chamber via the.

Next, an example of a routine for executing control of the fuel injection valve according to the above-described embodiment will be described. An example of this routine is shown in FIG. Note that this routine is started every time a predetermined crank angle arrives. When the routine of FIG. 4A is started, first, at step 10, the latest target fuel injection amount Qt set in the routine of FIG. 4B (details of this routine will be described later) is acquired. The Next, at step 11, a command signal Si to be supplied to the fuel injection valve is calculated based on the target fuel injection amount Qt acquired at step 10. Next, at step 12, the command signal Si calculated at step 12 is supplied to the fuel injection valve, and then the routine ends.

Next, an example of a routine for executing the setting of the target fuel injection amount according to the above-described embodiment will be described. An example of this routine is shown in FIG. This routine is started every time a predetermined crank angle comes when the routine is finished. When the routine of FIG. 4B is started, first, in step 15, the accelerator pedal depression amount Dac at that time is acquired. Next, at step 16, the reference fuel injection amount Qb corresponding to the accelerator pedal depression amount Dac acquired at step 15 is acquired from the map of FIG. Next, at step 17, the reference fuel injection amount Qb acquired at step 16 is set to the target fuel injection amount Qt, and then the routine ends.

Next, an example of a routine for executing control of the throttle valve of the above-described embodiment will be described. An example of this routine is shown in FIG. Note that this routine is started every time a predetermined crank angle arrives. When the routine of FIG. 5A is started, first, in step 20, the latest target throttle valve opening Dtht set in the routine of FIG. 5B (details of this routine will be described later) is acquired. Is done. Next, at step 21, a control signal Sth to be supplied to the throttle valve is calculated based on the target throttle valve opening degree Dtht acquired at step 20. Next, at step 22, the control signal Sth calculated at step 21 is supplied to the throttle valve, and then the routine ends.

Next, an example of a routine for executing the setting of the target throttle valve opening according to the above-described embodiment will be described. An example of this routine is shown in FIG. Note that this routine is started every time a predetermined crank angle arrives. When the routine of FIG. 5B starts, first, at step 25, the engine speed NE at that time and the target fuel injection amount Qt at that time are acquired. Next, at step 26, the reference throttle valve opening degree Dthb corresponding to the engine speed NE and the target fuel injection amount Qt acquired at step 25 is acquired from the map of FIG. Next, at step 27, the reference throttle valve opening degree Dthb acquired at step 26 is set to the target throttle valve opening degree Dtht, and then the routine ends.

Next, an example of a routine for executing control of the EGR control valve of the above-described embodiment will be described. An example of this routine is shown in FIG. Note that this routine is started every time a predetermined crank angle arrives. When the routine of FIG. 6 is started, first, at step 30, the latest target EGR rate Regrt set by the routine of FIG. 7 (details of this routine will be described later) is acquired. Next, at step 31, a control signal Segr to be supplied to the EGR control valve is calculated based on the target EGR rate Regrt acquired at step 30. Next, at step 32, the control signal Segr calculated at step 31 is supplied to the EGR control valve, and then the routine ends.

Next, an example of a routine for executing the setting of the target EGR rate according to the above-described embodiment will be described. An example of this routine is shown in FIG. Note that this routine is started every time a predetermined crank angle arrives. When the routine of FIG. 7 is started, first, at step 100, the engine speed NE at that time, the target fuel injection amount Qt at that time, the first accuracy A1 at that time, and the second accuracy A2 at that time are acquired. The Next, at step 101, the reference EGR rate Regrb corresponding to the engine speed NE and the target fuel injection amount Qt acquired at step 100 is acquired from the map of FIG. Next, in step 102, it is determined whether or not the first accuracy A1 acquired in step 100 is higher than the second accuracy A2 acquired in step 100 (A1> A2). When it is determined that A1> A2, the routine proceeds to step 103. On the other hand, when it is determined that A1> A2 is not satisfied, the routine proceeds to step 108.

In step 103, the intake air amount GA at that time is acquired. Next, at step 104, the reference intake air amount GAb corresponding to the engine speed NE and the target fuel injection amount Qt acquired at step 100 is acquired from the map of FIG. 3A, and the acquired reference intake air is obtained. The amount GAb is set to the target intake air amount GAt. Next, at step 105, the intake air amount deviation ΔGA is calculated based on the intake air amount GA acquired at step 103 and the target intake air amount GAt set at step 104. Next, at step 106, the first correction coefficient Kegr1 is calculated based on the intake air amount deviation ΔGA calculated at step 105. Next, in step 107, a value obtained by correcting the reference EGR rate Regrb acquired in step 101 with the first correction coefficient Kegr1 calculated in step 106 is set as the target EGR rate Regrt, and then the routine ends. To do.

In step 108, the air-fuel ratio AF at that time is acquired. Next, at step 109, the reference air-fuel ratio AFb corresponding to the engine speed NE and the target fuel injection amount Qt acquired at step 100 is acquired from the map of FIG. 3B, and this acquired reference air-fuel ratio AFb is acquired. Is set to the target air-fuel ratio AFt. Next, at step 110, the air-fuel ratio deviation ΔAF is calculated based on the air-fuel ratio AF acquired at step 108 and the target air-fuel ratio AFt set at step 109. Next, at step 111, the second correction coefficient Kegr2 is calculated based on the air-fuel ratio deviation ΔAF calculated at step 110. Next, in step 112, a value obtained by correcting the reference EGR rate Regrb obtained in step 101 with the second correction coefficient Kegr2 calculated in step 111 is set as the target EGR rate Regrt, and then the routine ends. To do.

In the above-described embodiment, the detection accuracy of the air flow meter may be any detection accuracy as long as it is the accuracy of the intake air amount detected by the air flow meter. For example, when the intake air amount is in a steady state (that is, It is preferable to employ detection accuracy (that is, static accuracy, for example, drawing tolerance) when the change in the intake air amount is zero or extremely small. Further, since the detection accuracy of the air flow meter is affected by the flow rate of air passing through the air flow meter and the pulsation of the gas around the air flow meter, the intake air amount detected by the air flow meter, the engine speed, and The detection accuracy of the air flow meter may be calculated based on any one or more of the target fuel injection amounts.

In the above-described embodiment, the fuel injection accuracy of the fuel injection valve may be any fuel injection accuracy as long as the amount of fuel injected from the fuel injection valve is accurate. For example, the fuel injection amount is in a steady state. It is preferable to employ the detection accuracy (that is, static accuracy, for example, drawing tolerance) when the time is changed (that is, when the change in the fuel injection amount is zero or extremely small). Further, since the fuel injection accuracy of the fuel injection valve is affected by the pressure of the fuel in the fuel supply passage and the pulsation of the fuel, the fuel pressure in the fuel supply passage, the engine speed, and the target fuel injection amount The fuel injection accuracy of the fuel injection valve may be calculated based on one or more of the above.

Further, when the first accuracy is represented by “A1”, the detection accuracy of the air flow meter is represented by “Aafm”, and the fuel injection accuracy of the fuel injection valve is represented by “Ainj”, the following equation 1 is obtained. In addition, the square root of the sum of the square of the detection accuracy of the air flow meter and the square of the fuel injection accuracy of the fuel injection valve can be employed as the first accuracy.

A1 = √ {(Aafm) ² + (Ainj) ² } (1)

In the above-described embodiment, the detection accuracy of the air-fuel ratio sensor may be any detection accuracy as long as the accuracy of the air-fuel ratio detected by the air-fuel ratio sensor. For example, when the air-fuel ratio is in a steady state (that is, When the air-fuel ratio change is zero or very small (ie, static accuracy, eg, drawing tolerance) and the air-fuel ratio is in a transient state (ie, the air-fuel ratio change is It is preferable to employ a detection accuracy that is the sum of the detection accuracy (that is, the dynamic accuracy) when the accuracy is relatively high. The static accuracy of the air-fuel ratio sensor is affected by the flow rate of exhaust gas passing through the air-fuel ratio sensor and the pressure of exhaust gas around the air-fuel ratio sensor, so the amount of intake air detected by the air flow meter (That is, the flow rate of exhaust gas passing through the air-fuel ratio sensor) and the pressure of exhaust gas around the air-fuel ratio sensor (this may be an actual measurement value or an estimated value) You may make it calculate based on one or both.

Further, when the second accuracy is represented by “A2”, the static accuracy of the air-fuel ratio sensor is represented by “Aafs”, and the dynamic accuracy of the air-fuel ratio sensor is represented by “Aaft”, the following equation 2 is obtained. As described above, the sum of the static accuracy of the air-fuel ratio sensor and the dynamic accuracy of the air-fuel ratio sensor can be adopted as the second accuracy. In addition, when the EGR control valve opening is changed stepwise while the engine speed and the fuel injection amount are kept constant, the time required for the actual air-fuel ratio to change by a predetermined amount (that is, the response) (Delay time) is referred to as “actual response delay time” and is expressed as “Tda”, and is empty when the EGR control valve opening is changed stepwise while the engine speed and the fuel injection amount are kept constant. The time required for the air-fuel ratio detected by the fuel-fuel ratio sensor to change by the predetermined amount (that is, the response delay time) is referred to as “detection response delay time” and is represented by “Tdd”. A coefficient for converting to the static accuracy of the air-fuel ratio sensor is referred to as a “conversion coefficient” and expressed as “β”, and as shown in the following expression 3, the detection response delay time is converted into the actual response delay time. Dividing by Thus obtained value (i.e., the ratio of the detection response delay time to the actual response delay time) can be employed a value obtained by multiplying the conversion factor as a dynamic accuracy of the air-fuel ratio sensor.

A2 = Aafs + Aaft (2)
Aaft = Tdd / Tda × β (3)

The predetermined amount used for acquiring the response delay time is, for example, the air-fuel ratio until the air-fuel ratio converges to a specific air-fuel ratio when the EGR control valve opening is changed stepwise. A change amount of 63% when the amount of change in the fuel ratio is taken as 100% can be adopted.

Further, when the ratio Tdd / Tda of the detected response delay time to the actual response delay time is referred to as “response delay ratio”, the closer the response delay ratio is to “1”, the higher the dynamic accuracy of the air-fuel ratio sensor and the response delay. The farther the ratio is from “1”, the lower the dynamic accuracy of the air-fuel ratio sensor.

Since the actual response delay time is affected by the flow rate of exhaust gas discharged from the combustion chamber into the exhaust passage and the pressure of exhaust gas in the exhaust passage, the intake air amount detected by the air flow meter (that is, combustion) The actual response delay time is determined in advance for each combination of the flow rate of the exhaust gas discharged from the chamber into the exhaust passage) and the pressure of the exhaust gas in the exhaust passage, and the obtained actual response delay time is calculated as the intake air amount. Is stored in the electronic control unit in the form of a map of the function of the exhaust gas pressure and the exhaust gas pressure. The actual response delay time corresponding to (or may be an estimated value) is acquired from the map, and the second accuracy may be calculated using the acquired actual response delay time. The detection response delay time is affected by the flow rate of the exhaust gas passing through the air-fuel ratio sensor and the pressure of the exhaust gas around the air-fuel ratio sensor, so the intake air amount detected by the air flow meter (that is, the air-fuel ratio sensor) For each combination of the exhaust gas flow rate passing through the air-fuel ratio sensor and the pressure of the exhaust gas around the air-fuel ratio sensor, a detection response delay time is obtained in advance by experiments or the like, and the obtained detection response delay time is calculated based on the intake air amount and the exhaust gas It is stored in the electronic control unit in the form of a function map with pressure, and during the operation of the engine, the amount of intake air at that time and the pressure of the exhaust gas at that time (this may be a measured value or estimated May be a value), and the second accuracy may be calculated using the acquired detection response delay time from the map.

Also, the conversion factor can be calculated by the following experiment, for example. That is, the EGR rate is controlled so that a plurality of different response delay ratios are achieved, and the emission performance in the exhaust gas for each response delay ratio (for example, the amount of nitrogen oxide (NOx) contained in the exhaust gas) , And the sensitivity of the change in the emission performance with respect to the change in the response delay ratio (hereinafter, this sensitivity is referred to as “sensitivity to the change in dynamic accuracy”) is calculated based on the acquired emission performance. On the other hand, a plurality of air-fuel ratio sensors with different static accuracy are prepared, the EGR rate is controlled using each air-fuel ratio sensor, and the emission performance in the exhaust gas for each air-fuel ratio sensor is obtained. Based on the emission performance, the sensitivity of the change in emission performance to the change in static accuracy of the air-fuel ratio sensor (hereinafter, this sensitivity is referred to as “sensitivity to change in static accuracy”) is calculated. Then, a coefficient to be multiplied by the sensitivity to the dynamic accuracy change is calculated in order to match the sensitivity to the dynamic accuracy change with the static accuracy change. The coefficient calculated here is a conversion coefficient. The absolute value is used for accuracy.

In the above-described embodiment, the reference intake air amount is set to the target intake air amount as it is. However, the appropriate intake air amount varies depending on the intake pressure, the intake temperature (that is, the temperature of the gas sucked into the combustion chamber), and the like. Therefore, in the above-described embodiment, a value obtained by correcting the reference intake air amount by one or both of the intake pressure at that time and the intake temperature at that time may be set as the target intake air amount. Also, the appropriate intake air amount is the cooling water temperature (that is, the temperature of the cooling water for cooling the internal combustion engine), the atmospheric pressure, the outside air temperature, and the fuel temperature (that is, the temperature of the fuel injected from the fuel injection valve). It depends on the situation. Therefore, in the above-described embodiment, the reference intake air amount is obtained by correcting the reference intake air temperature by one or more of the cooling water temperature at that time, the atmospheric pressure at that time, the outside air temperature at that time, and the fuel temperature at that time. The value may be set to the target intake air amount.

In the above-described embodiment, the reference intake air amount is determined based on the engine speed and the target fuel injection amount. However, instead of this, the target intake air amount that can achieve the target oxygen concentration (that is, the target value of the concentration of oxygen in the gas sucked into the combustion chamber) may be set as the target intake air amount. Good.

In the above-described embodiment, the first correction coefficient may be calculated by any method as long as it is a coefficient that corrects the EGR rate so that the intake air amount deviation becomes zero. As the first correction coefficient, for example, A coefficient calculated by PI control or PID control based on the intake air amount deviation can be employed. In the above-described embodiment, the second correction coefficient may be calculated by any method as long as it is a coefficient that corrects the EGR rate so that the air-fuel ratio deviation becomes zero. A coefficient calculated by PI control or PID control based on the fuel ratio deviation can be adopted.

In the above-described embodiment, an upper limit value and a lower limit value related to the first correction coefficient and the second correction coefficient may be provided in order to suppress the EGR rate from changing excessively.

Also, when the throttle valve opening is changed, the EGR rate changes. Therefore, in the above-described embodiment, the EGR rate may be controlled to the target EGR rate by changing the EGR control valve opening and the throttle valve opening.

The above-described embodiment is an embodiment in the case where the present invention is applied to an internal combustion engine that does not include a so-called supercharger. However, the present invention can also be applied to an internal combustion engine that includes a so-called supercharger. It is.

The above-described embodiment is an embodiment in which the present invention is applied to a compression ignition type internal combustion engine, but the present invention is also applicable to a spark ignition type internal combustion engine (so-called gasoline engine). .

Claims

Intake air amount detection means for detecting the intake air amount that is the amount of air sucked into the combustion chamber, fuel supply means for supplying fuel to the combustion chamber, and the air-fuel ratio of the exhaust gas discharged from the combustion chamber to the exhaust passage An internal combustion engine control device comprising: an air-fuel ratio detection means for detecting the exhaust gas; and an exhaust gas recirculation means for introducing exhaust gas discharged from the combustion chamber into the exhaust passage into the combustion chamber via the intake passage.
When the first accuracy calculated based on the detection accuracy of the intake air amount detection means and the fuel supply accuracy of the fuel supply means is higher than the second accuracy calculated based on the detection accuracy of the air-fuel ratio detection means Controlling the amount of exhaust gas introduced into the combustion chamber by the exhaust gas recirculation means so that the intake air quantity detected by the intake air quantity detection means matches the target value;
When the first accuracy is less than or equal to the second accuracy, the amount of exhaust gas introduced into the combustion chamber by the exhaust gas recirculation means so that the air fuel ratio detected by the air fuel ratio detection means matches the target value A control device for an internal combustion engine for controlling the engine.
The control apparatus for an internal combustion engine according to claim 1,
A control device for an internal combustion engine in which the detection accuracy of the intake air amount detection means when the intake air amount is in a steady state is adopted as the detection accuracy of the intake air amount detection means.
The control apparatus for an internal combustion engine according to claim 1 or 2,
A control apparatus for an internal combustion engine in which the fuel supply accuracy of the combustion supply means when the amount of fuel supplied to the combustion chamber by the fuel supply means is in a steady state is adopted as the fuel supply accuracy of the fuel supply means.
The control apparatus for an internal combustion engine according to any one of claims 1 to 3,
As the detection accuracy of the air-fuel ratio detection means, the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio of the exhaust gas discharged from the combustion chamber to the exhaust passage is in a steady state and the exhaust gas discharged from the combustion chamber to the exhaust passage A control apparatus for an internal combustion engine, which employs the detection accuracy of the air-fuel ratio detection means when the air-fuel ratio of the engine is in a transient state.