JP2001012281A - Internal combustion engine control device and cylinder excess air ratio estimation device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To recirculate as much exhaust gas as possible while making it possible to accurately and easily estimate an in-cylinder excess air ratio and to perform a stable lean operation without an engine misfiring. It is ensured that NO _X can be reduced. SOLUTION: In a control device for an internal combustion engine provided in a vehicle having an exhaust gas recirculation device and capable of performing a lean operation with an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the in-cylinder excess air ratio estimating means 23 includes an exhaust gas recirculation device. The in-cylinder excess air ratio is estimated based on the amount of exhaust gas recirculated by the device and the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio during steady operation. The amount of exhaust gas to be recirculated by the exhaust gas recirculation device is controlled based on the in-cylinder excess air ratio estimated by the means 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for an internal combustion engine and an apparatus for estimating an excess in-cylinder air ratio which are used in an internal combustion engine capable of performing a lean operation, provided with an exhaust gas recirculation apparatus.

[0002]

2. Description of the Related Art Conventionally, an internal combustion engine (engine) capable of performing a lean operation has been developed in order to improve fuel efficiency. In such an internal combustion engine that can perform lean operation, NO
_{Since X} emissions becomes more generally exhaust gas recirculation device for recirculating exhaust gas to the intake passage to reduce the NO _X (EGR device) is provided.

[0003]

In an internal combustion engine in which the fuel injection amount is set based on, for example, the amount of air passing through a throttle valve, when the exhaust gas is recirculated by the EGR device, the in-cylinder air-fuel ratio becomes the target. In some cases, the air-fuel ratio deviates from the air-fuel ratio and stable combustion is not performed.

For this reason, the in-cylinder air-fuel ratio is estimated from the exhaust gas air-fuel ratio obtained by analyzing the exhaust gas components, and the fuel injection control is performed so that the in-cylinder air-fuel ratio matches the target air-fuel ratio. I have. For example, JP-A-8-611
No. 12 discloses a technique of performing fuel injection control to match the in-cylinder air-fuel ratio to a target air-fuel ratio. However, simply performing fuel injection control to make the in-cylinder air-fuel ratio equal to the target air-fuel ratio does not make it possible to reliably reduce NO _X discharged during lean operation even if misfire can be prevented.

[0005] Here, the NO _X generated during lean operation more in order to reduce, it is necessary to recycle as much exhaust gas and thus is recycled too many exhaust gas, combustion instability And easily misfires. For this reason, it is desired to reliably reduce NO _X by recirculating as much exhaust gas as possible while performing stable lean operation without causing the engine to misfire.

[0006] To achieve this, it is necessary to accurately control the amount of exhaust gas (EGR amount) to be recirculated into the intake passage. As described above, in order to accurately control the EGR amount, it is important to accurately estimate the in-cylinder air-fuel ratio or the in-cylinder excess ratio. At this time, it is also desirable to easily estimate the in-cylinder air-fuel ratio or the in-cylinder excess ratio. For example, the cylinder air-fuel ratio or the cylinder excess air ratio can be more easily estimated when various settings are made in the engine development stage, or when the above-described fuel injection control or EGR control is performed while the vehicle is running. I want to be able to easily estimate the internal air-fuel ratio or the cylinder excess air ratio.

Further, for example, Japanese Patent Application Laid-Open No. Hei 8-61112
In the technology disclosed in the above publication, an O ₂ sensor is provided, and the in-cylinder air-fuel ratio is obtained based on the oxygen concentration detected by the O ₂ sensor. _{In addition to the two} sensors, it is necessary to provide a full-range O ₂ sensor (air-fuel ratio sensor) capable of detecting the oxygen concentration in a wider air-fuel ratio range, which leads to an increase in the number of parts and an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is possible to accurately and easily estimate an in-cylinder excess air rate so that an engine can be stably operated without a misfire. , and to provide as much of the exhaust gas was to be able to be recirculated to reliably reduce the NO _X to the controller and the in-cylinder air excess ratio estimation apparatus for an internal combustion engine.

In addition, the in-cylinder excess air ratio is accurately and simply estimated, and the EGR amount (EGR ratio) can be accurately controlled based on the estimated excess air ratio. It is another object of the present invention to provide a control device for an internal combustion engine, which is capable of preventing a decrease or a rapid increase in the engine speed. It is another object of the present invention to provide an in-cylinder excess air ratio estimating device capable of estimating the in-cylinder excess air ratio without increasing the number of parts and cost.

[0010]

Therefore, in the control apparatus for an internal combustion engine according to the first aspect of the present invention, the in-cylinder air-fuel ratio estimating means includes an exhaust gas recirculation device and an exhaust gas recirculation device. The in-cylinder excess air ratio is estimated based on the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio, and the exhaust gas recirculation amount control means recirculates by the exhaust gas recirculation device based on the estimated in-cylinder excess air ratio. Control the amount of exhaust gas.

According to a second aspect of the present invention, there is provided an in-cylinder excess air ratio estimating device for an internal combustion engine which includes an exhaust gas recirculation device and is capable of performing lean operation with an air-fuel ratio leaner than the stoichiometric air-fuel ratio. Is used to estimate the excess air ratio in the cylinder based on the amount of exhaust gas recirculated by the exhaust gas recirculation device and the exhaust gas air-fuel ratio.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. A control device for an internal combustion engine and a cylinder excess air ratio estimating device according to an embodiment of the present invention will be described with reference to FIGS. The internal combustion engine according to the present embodiment is a lean-burn internal combustion engine of a four-cycle engine, and is a spark-ignition type direct injection type internal combustion engine (direct injection engine) that directly injects fuel into a combustion chamber.
Is configured as

An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1 so that they can communicate with each other. The communication between the intake passage 2 and the combustion chamber 1 is controlled by an intake valve 4.
The communication between the exhaust passage 3 and the combustion chamber 1 is controlled by an exhaust valve 5. The intake passage 2 is provided with an air cleaner 6 and a throttle valve 7 in order from the upstream side, and the exhaust passage 3 is provided with an exhaust gas purifying catalytic converter 9 and a muffler (not shown) in order from the upstream side. Is provided. Note that a surge tank 2a is provided in the intake passage 2.

Further, the engine in order to reduce NO _X, the exhaust gas recirculation device for recirculating part of exhaust gases to the intake passage (hereinafter, EGR device hereinafter) 10 is disposed.
The EGR device 10 includes a surge tank 2a in the intake passage 2.
It comprises an exhaust gas recirculation passage (EGR passage) 10b provided to connect the portion and the upstream side of the exhaust gas passage 3 and an EGR valve 10a attached to the exhaust gas recirculation passage 10b.

The flow rate of the exhaust gas from the exhaust passage 3 to the intake passage 2 can be controlled by the EGR valve 10a. The control of the EGR valve 10a is performed according to the operating state of the engine. The opening of the throttle valve 7 changes in accordance with the amount of depression of an accelerator pedal (not shown), whereby the amount of air introduced into the combustion chamber 1 is adjusted. Reference numeral 12 denotes an air bypass valve (ABV), which is provided in a bypass passage 12A that bypasses a portion of the intake passage 2 where the throttle valve 7 is installed, and is driven to open and close by a drive device (not shown) such as a stepper motor or a linear solenoid. The air-fuel ratio can be adjusted by adjusting the intake air amount separately from the valve 7.

An injector (fuel injection valve) 8 is arranged so that its opening faces the combustion chamber 1 so as to directly inject fuel toward the combustion chamber 1 in the cylinder. With such a configuration, the air sucked through the air cleaner 6 according to the opening degree of the throttle valve 7 and the ABV 12 causes the intake valve 4
Is opened, the air is sucked into the combustion chamber 1, and the sucked air and the fuel directly injected from the injector 8 are mixed in the combustion chamber 1, and the ignition plug 13 is ignited in the combustion chamber 1 at an appropriate timing. by, are burned, after which caused the engine torque, is discharged to the exhaust passage 3 as an exhaust gas from the combustion chamber 1, CO in the exhaust gas in the catalytic converter 9, HC, 3 one adverse of the NO _x After the components are purified, they are muffled by mufflers and released to the atmosphere.

Here, in the present engine, as a mode of fuel injection, operation (super lean) in an extremely lean state of the fuel (that is, the air-fuel ratio is much larger than the stoichiometric air-fuel ratio) due to the stratified combustion by the compression stroke fuel injection. A compression lean operation mode for performing combustion operation), and an intake lean operation mode for performing a premix combustion operation in a fuel-lean state (that is, the air-fuel ratio is larger than the stoichiometric air-fuel ratio) although not as much as the compression lean operation mode. A stoichiometric operation mode (stoichiometric feedback operation mode) in which a premix combustion operation is performed by feedback control based on O ₂ sensor information or the like so that the air-fuel ratio becomes the stoichiometric air-fuel ratio, and a fuel rich state (that is, an air-fuel ratio) Operating mode (open loop mode) in which premix combustion operation is performed by open loop control with open loop control at stoichiometric air-fuel ratio) It is provided.

The engine is provided with various sensors, and detection signals from these sensors are supplied to the ECU.
20. For example, detection signals are transmitted from an air flow sensor (AFS) 11 for detecting an intake air amount, a potentiometer type throttle position sensor (TPS) 14 for detecting a throttle opening, a crank angle sensor 15 for detecting a crank angle, and the like. It has become so. Since the engine speed (engine speed) can be calculated based on the crank angle sensor 15, the crank angle sensor 15 is referred to as an engine speed sensor (engine speed sensor) for convenience.

In this embodiment, in order to perform EGR control and ABV control, an ECU (controller, electronic control unit) 20 includes an EGR rate estimating means (recirculating exhaust gas rate estimating means) as shown in FIG. ) 2
1, an exhaust gas excess ratio estimating unit 22, an in-cylinder excess ratio estimating unit 23, an EGR control unit (exhaust gas recirculation amount control unit) 24, and an ABV control unit (air bypass valve control unit, intake air amount control unit). ) 25 are provided.
Hereinafter, in order to make the description easy to understand, the description may be made using the air-fuel ratio instead of the excess air ratio.

Here, the EGR rate estimating means 21 determines the EGR rate R based on the detection information from the air flow sensor 11, the engine speed sensor 15 and the EGR valve opening degree information.
_It estimates _egr . That is, the EGR rate estimating means 21 determines the throttle valve 7 and the ABV 12 based on the airflow sensor 11 and the engine rotational speed sensor 15.
And function of estimating the amount of intake air G _in passing (intake air quantity estimating means), EGR based on the EGR valve opening information
Gas amount (that is, the amount of exhaust gas recirculated into the intake passage 2)
A function of estimating G _egr (EGR amount estimating means). Then, the EGR gas amount (EG) with respect to the intake air amount (intake air weight flow rate) G _in passing through the throttle valve 7.
The EGR rate R _egr is estimated from the following equation (1) as the ratio of the R gas weight flow rate) G _egr . For this reason, the EGR rate estimating means 21 is also called an EGR meter.

R _egr = G _egr / G _in (1) The EGR rate estimating means 21 relates, for example, to the amount of intake air passing through the throttle valve 7 and the ABV 12 in the compression lean operation mode and the amount of EGR gas. EGR attached
The EGR rate _Regr may be determined from the rate estimation map. In this way, by setting the EGR rate R _egr based on the intake air amount and the EGR gas amount, the EGR rate R _egr can be estimated without providing a separate full-range O ₂ sensor for detecting the oxygen concentration. ing.

The exhaust gas excess ratio estimating unit (control air excess ratio estimating unit) 22 estimates the exhaust gas excess ratio λ _e . Since the exhaust gas excess ratio λ _e is the excess air ratio of the exhaust gas discharged after performing combustion by performing the air-fuel ratio control, the excess air ratio λ _e (control λ)
Also called. Here, the exhaust gas excess ratio λ _e is the ratio of the exhaust gas air-fuel ratio to the stoichiometric air-fuel ratio (stoichiometric A / F), and is expressed by the following equation (2).

The lambda _e = exhaust gas air-fuel ratio / theoretical air-fuel ratio (2) As described above, the exhaust gas excess air rate estimating means 22, the exhaust gas air-fuel ratio when determining the exhaust gas excess air ratio lambda _e (exhaust A /
Since F) is also estimated, it also functions as exhaust gas air-fuel ratio estimating means for estimating the exhaust gas air-fuel ratio. Here, the exhaust gas excess ratio estimating means 22 calculates the intake air-fuel ratio (intake A / F), the exhaust gas air-fuel ratio (exhaust gas A / F), and
Since the EGR gas air-fuel ratio (EGR gas A / F) is considered to be equal to each other, the exhaust gas air-fuel ratio is estimated from the intake air-fuel ratio (intake A / F). _e is estimated. Since the fuel injection amount is set with respect to the intake air amount so as to reach the target air-fuel ratio, the intake air-fuel ratio can be considered as the target air-fuel ratio.

Here, the reason why the intake air-fuel ratio, the exhaust gas air-fuel ratio, and the EGR gas air-fuel ratio are considered to be equal during steady operation is as follows. Referring to FIG. 3, the intake air-fuel ratio (intake A / F) which is the air-fuel ratio with respect to the intake fresh air amount.
The in-cylinder air-fuel ratio (in-cylinder A / F), which is the air-fuel ratio with respect to the in-cylinder air amount, and the exhaust gas air-fuel ratio (exhaust gas A / F), which is the air-fuel ratio calculated from the exhaust gas composition, will be described.

First, the intake air-fuel ratio is determined by the throttle valve 7
And the intake air amount (new air amount) passing through the ABV 12_in
And the fuel amount (fuel weight) to be injected is G_fAs the following
It is represented by equation (3). Intake air-fuel ratio = G_in/ G_f ... (3) The in-cylinder air-fuel ratio passes through the throttle valve 7 and ABV12.
G is the amount of intake air _inAnd the amount of fuel injected is G_f
And the amount of air in EGR gas (the weight of air in EGR gas)
G_aegrIs represented by the following equation (4). EG
R gas air volume G_aegrTake into account especially the lean operation
This is because air is contained in the EGR gas.

In-cylinder air-fuel ratio = (G _in + G _aegr ) / G _f (4) The exhaust gas air-fuel ratio is calculated from, for example, the composition ratio of the exhaust gas using an exhaust gas analyzer, and CO, CO ₂ , THC ( The total concentration (HC) is expressed as the gas concentration (%) by the following equation (5). Exhaust gas air-fuel ratio = [208.8-3.05 THC] / (THC + CO + CO ₂ ) -1.8 CO / (CO + CO ₂ ) +0.96 (5) When calculated by an analyzer, the exhaust gas air-fuel ratio is called an analyzer air-fuel ratio (analyzer A / F), and the excess air ratio calculated in accordance with this is called an analyzer excess air ratio. Further, here, the essential error of the above-described calculation formula (5) for calculating the exhaust gas air-fuel ratio and the error of the air-fuel ratio calculation due to the difference in the amount of NO _X generated during the large EGR are ignored.

Here, the relationship between the intake air-fuel ratio and the exhaust gas air-fuel ratio during EGR is as shown in FIG. The exhaust gas air-fuel ratio is calculated from the composition ratio of exhaust gas (mixture) discharged when fuel, fresh air, and EGR gas are mixed and burned. In this case, for simplicity, it is considered that only fresh air and fuel injected corresponding thereto contribute to combustion, and the EGR gas returned from the exhaust passage 3 does not react at the time of combustion and is discharged as it is. .

In consideration of the above, during steady operation, the composition of the exhaust gas (corresponding to intake) discharged when fresh air and injected fuel are burned is equal to the EGR gas composition of the EGR gas which has recirculated the exhaust gas. Therefore, the composition of the mixture of the exhaust gas corresponding to the intake air and the EGR gas becomes equal,
The following relationship holds. Exhaust gas (corresponding to intake air) composition = EGR gas composition = Exhaust gas (mixed) composition For this reason, during steady operation, exhaust gas (mixed) discharged from the cylinder when fresh air, fuel, and EGR gas are mixed and burned Is the same as the composition of exhaust gas (corresponding to intake air) discharged from the cylinder when fresh air and fuel are burned, regardless of whether EGR gas is introduced or not.

If the exhaust gas composition is equal, the air-fuel ratio of the exhaust gas is also
During steady-state operation, the
The gas air-fuel ratio can be considered to be the same as the intake air-fuel ratio.
Wear. For this reason, the exhaust gas excess ratio estimating means 22
From the intake air-fuel ratio, which is considered to be the same as the gas air-fuel ratio,
The excess air ratio λ can be estimated. In this way, intake air-fuel
Excess gas air ratio λ by ratio_eConfigured to estimate
This allows the ECU 20 mounted on the vehicle to travel while the vehicle is running.
Excess air ratio λ _eCan be estimated.

The concentration of exhaust gas components is analyzed by an exhaust gas analyzer, and the excess air ratio λ _e calculated based on this is stored in a map in association with the intake air-fuel ratio (or target air-fuel ratio). The exhaust gas excess ratio estimating means 22 may be configured to obtain the exhaust gas excess ratio λ _e according to the intake air-fuel ratio (or the target air-fuel ratio) using this map.

By the way, during the lean operation, the EGR device 10
When the exhaust gas is recirculated, the in-cylinder air-fuel ratio deviates from the target air-fuel ratio. That is, since the amount of air contained in the EGR gas is large during the lean operation, the in-cylinder air-fuel ratio becomes lean with respect to the intake air-fuel ratio by the excess air in the EGR gas, as shown in FIG. In particular, if a large amount of exhaust gas is recirculated during the super-lean operation, the degree of leanness of the in-cylinder air-fuel ratio increases.

Therefore, during the lean operation, the EGR device 1
When the exhaust gas is recirculated at 0, the exhaust gas air-fuel ratio and the intake air-fuel ratio are considered to be the same during steady-state operation as described above, but the in-cylinder air-fuel ratio becomes lean, and the in-cylinder air-fuel ratio becomes the target air-fuel ratio. Will be deviated. Accordingly, in the present embodiment, the in-cylinder excess air ratio λ _c (in-cylinder λ) which is the ratio of the in-cylinder air-fuel ratio to the stoichiometric air-fuel ratio is estimated, and EGR control and ABV control are performed based on the in-cylinder excess air ratio λ _c.
Control is performed.

For this purpose, the ECU 20 is also provided with an in-cylinder excess air ratio estimating means 23 as shown in FIG.
Cylinder excess air rate estimating means 23, as shown in FIG. 1, to estimate the cylinder air excess ratio lambda _c on the basis of the detection information from the EGR rate estimation means 21 and the exhaust gas excess air rate estimating means 22 described above It is. The in-cylinder excess air ratio estimating means 2
3 is also called an in-cylinder excess air rate meter and an in-cylinder excess air rate estimation device.

The in-cylinder excess air ratio estimating means 23
The in-cylinder air-fuel ratio is determined based on the EGR gas amount estimated by the EGR amount estimating unit provided in the GR rate estimating unit 21 and the exhaust gas air-fuel ratio estimated by the exhaust gas excess ratio estimating unit as the exhaust gas air-fuel ratio estimating unit. Since it can be considered to be estimated, the in-cylinder excess ratio estimating means 23 is also referred to as in-cylinder air-fuel ratio estimating means.

In the in-cylinder excess air ratio estimating means 23, E
EGR rate R estimated by GR rate estimating means 21
_{The egr} and the exhaust gas excess air ratio λ _e estimated by the exhaust gas excess air ratio estimating means 22 are substituted into the following quadratic equation (6).
_It asks for _c . λ _c ² −λ _e (1 + R _egr ) λ _c + λ _e R _egr = 0 (6) λ _c = λ _e (1 + R _egr ) / 2 + [{λ _e (1 + R _egr )} ² -4λ _e R _egr] ^1/2 / 2 where, above quadratic equation (6) is derived as follows.

[0036] That is, the intake air amount detected by the air flow sensor 11 and G _in the air volume of the EGR gas amount is calculated based on the EGR valve opening information G
_{Assuming aegr} , the in-cylinder air amount (in-cylinder air weight) G _a is represented by the following equation (7). G _a = G _in + G _aegr (7) The EGR gas air amount G _aegr is represented by the following equation (8), where the in-cylinder excess air rate λ _c and the EGR rate R _egr are given. .

[0037] _{G aegr = R egr × G in} × (λ c -1) / λ c ··· (8) Equation (3), (4), the air quantity G _a is cylindrical, the following equation (9) Is represented by G _a = G _in × [1 + R _egr × (λ _c −1) / λ _c ] (9) Here, the fuel amount (fuel weight) G _f is represented by the following equation (10). G _f = G _in / (λ _e × 14.7) (10) Accordingly, the in-cylinder excess air factor λ _c is represented by the following equation (11).

Λ_c= G_a/ (G_f× 14.7) = λ_e[1 + R_egr× (λ_c-1) / λ_c] (11) Then, from this equation (11), the above-mentioned quadratic equation (6)
Is led. By the way, in the present embodiment, the engine is lost.
Reduce fuel injection as much as possible while avoiding fire
In order to be able to drive in a lean state,
As shown in FIG.
Estimated cylinder excess air ratio λ _cEGR valve based on
Opening control and ABV opening control are performed.
You.

Therefore, when the amount of intake air is increased,
Know the limit air amount (lean limit) that will cause a fire in case
There is a need. This lean limit can be described by the excess air ratio.
You. Here, FIG. 6 shows the excess air ratio λ and the compression lean.
FIG. 7 is a diagram showing a correlation with a power limit. In FIG.
The excess air ratio λ_eIs the EGR rate R_egrMany
6, the solid line B in FIG.
, The excess air ratio in the cylinder λ_cIs the EGR rate R_egrTo
Regardless, it is constant. Therefore, the in-cylinder excess air ratio λ _cTo
Based on this, it is possible to further increase the lean limit.
Wear. In addition, the cylinder excess air ratio λ_cIs the EGR rate R_egrAbout
The air excess ratio λ_cThis Lee
Limit cylinder excess air ratio λ_cFeed to match
Back control can be performed.
There is no need to provide a tap, and control becomes easier.

For this purpose, the ECU 20 is provided with EGR control means 24. The EGR control means 24 controls the EGR valve 10a to adjust the amount of exhaust gas to be recirculated into the intake passage 2. The EGR control unit 24, and performs the opening degree control of the EGR valve 10a on the basis of the cylinder air excess ratio lambda _c estimated by the cylinder air excess ratio estimating means 23.

Specifically, when the in-cylinder air-fuel ratio (in-cylinder A / F) is smaller than the target air-fuel ratio (target A / F), the EGR control means 24 sets the in-cylinder air-fuel ratio to the target air-fuel ratio. The amount of air required for matching is calculated as a required increased air amount (required increased air weight), and the target EGR opening is calculated so that the required increased air amount is supplied. Then, the EG is set so that the EGR opening matches the target EGR opening.
The opening of the R valve 10a is controlled.

On the other hand, if the in-cylinder air-fuel ratio is larger than the target air-fuel ratio, the amount of air required to make the in-cylinder air-fuel ratio equal to the target air-fuel ratio is calculated as the required reduced air amount. Is calculated such that the target EGR opening is supplied. The opening of the EGR valve 10a is controlled so that the EGR opening matches the target EGR opening.

[0043] Here, FIG. 7, EGR rate (%) and a control characteristic diagram of cylinder air excess ratio lambda _c based on the exhaust gas excess air factor lambda _e. As shown in FIG.
_c (in-cylinder λ) is set so as to increase as the exhaust gas excess ratio λ _e increases. Further, the cylinder air excess ratio lambda _c is set to be larger as the EGR rate R _egr becomes larger. When the excess exhaust gas air ratio λ _e is 1.0, it indicates that the in-cylinder air-fuel ratio is the stoichiometric air-fuel ratio.

In FIG. 7, point A is the cylinder excess air ratio λ _c (= approximately 3.3) in the normal compression lean operation state.
9, the air-fuel ratio is about 49.8). In this case, the excess exhaust gas air ratio λ _e is about 2.38 (the air-fuel ratio is about 35), and EG
The R rate R _egr is about 60%. Here, the target cylinder to cylinder air excess ratio lambda _c excess air ratio (target value, for example lambda _e = 4.
Consider the case of controlling to 0).

First, when controlling only the EGR valve opening,
In this case, as shown by an arrow X in FIG.
Air volume) is reduced, and as a result
λ_eIs slightly reduced. Also, the target in-cylinder excess air ratio
(Target value, for example, λ_e= 4.0)
Increase. When controlling only the ABV opening,
Is the EGR rate R as shown by the arrow Y in FIG._egrIs low
I will drop it. In addition, the target in-cylinder excess air ratio (target value,
For example, λ _e= 4.0), the control amount increases.

On the other hand, when controlling both of these,
In FIG. 7, as indicated by the arrow Z, a small amount of control is required to approach the target in-cylinder excess air ratio (target value, for example, λ _e = 4.0). This is because the current EGR valve opening and AB
This is because the difference between the control amount of the V opening and the control amounts of the EGR valve opening and the ABV opening of the target cylinder excess air ratio is small. As a result, the EGR rate _Regr does not decrease or increase sharply.

[0047] Therefore, in this embodiment, when controlling to match the cylinder air excess ratio lambda _c to the target cylinder air excess ratio, in addition to the control of the EGR valve 10a, ABV1
2, the opening degree control is also performed. Therefore, E
The CU 20 is also provided with ABV control means (air bypass valve control means) 25. Here, the EGR valve 1
The reason why the ABV opening control is performed in addition to the control of 0a is as follows. That is, for example, if the exhaust gas is recirculated by the EGR device during the lean operation, the in-cylinder air-fuel ratio becomes larger than the target air-fuel ratio, which may cause a misfire. To close. In engine control that focuses on the normal intake air amount, when the throttle valve is closed, the fuel injection amount decreases accordingly, and the engine output decreases. Therefore, in order to control the in-cylinder air-fuel ratio without changing the fuel injection amount, EG
The R amount and the intake amount are controlled at the same time.

The ABV control means 25 is connected to the bypass passage 12
The ABV 12 is controlled to adjust the amount of air supplied from A. The ABV control means 25 controls the in-cylinder excess air ratio λ estimated by the in-cylinder excess air
The opening degree control of the ABV 12 is performed based on _c . Specifically, when the in-cylinder air-fuel ratio is smaller than the target air-fuel ratio, the ABV control means 25 calculates the amount of air required to make the in-cylinder air-fuel ratio equal to the target air-fuel ratio as the required increased air amount. The target ABV opening is calculated so that the required increased air amount is supplied. And AB
The opening of the ABV 12 is controlled so that the V opening matches the target ABV opening. As a result, control is performed so that the in-cylinder air-fuel ratio matches the target air-fuel ratio.

On the other hand, if the in-cylinder air-fuel ratio is larger than the target air-fuel ratio, the amount of air required to make the in-cylinder air-fuel ratio equal to the target air-fuel ratio is calculated as the required reduced air amount. Is calculated so that the target ABV opening is supplied. The ABV opening is controlled so that the ABV opening matches the target ABV opening.

Since the control device for an internal combustion engine as one embodiment of the present invention is configured as described above, the operation by this device is performed as follows. That is, as shown in FIG. 8, in step S10, the EGR rate R _egr is estimated by the EGR rate estimating means 21, and in step S20, the excess exhaust gas air rate λ _{e is obtained} by the exhaust gas excess rate estimating means 22.
And proceeds to step S30.

In step S30, the EGR rate estimating means 2
And EGR rate R _egr estimated by 1, the exhaust gas excess air rate estimated by the exhaust gas excess air rate estimating means 22 lambda _e
Estimates the cylinder air excess ratio lambda _c by the cylinder air excess ratio estimating means 23 based on the bets, the process proceeds to step S40. At step S40, the EGR control unit 24 and the ABV control unit 25 determines whether the in-cylinder excess air ratio lambda _c is smaller than the target value (target air excess ratio), the result of the determination, the cylinder air excess If rate lambda _c is determined to be smaller than the target value, in step S50, to calculate the required increase air volume as cylinder air excess ratio lambda _c is equal to the target value, the process proceeds to step S60.

In step S60, the EGR control means 24 calculates the target EGR opening in accordance with the required increased air amount, and the ABV control means 25 calculates the target ABV opening in accordance with the required increased air amount. Proceeding to step S70, the EGR control means 24 performs feedback control so that the opening of the EGR valve 10a matches the target EGR opening, and the ABV control means 25
The feedback control is performed so that the opening of No. 2 matches the target ABV opening, and the routine returns.

Meanwhile, in step S40, when the cylinder air excess ratio lambda _c is determined to be equal to or greater than the target value, the process proceeds to step S80. Then, in step S80, to calculate the required reduction amount of air as cylinder air excess ratio lambda _c is equal to the target value, the process proceeds to step S90. Then, step S9
0, the EGR control means 24 calculates the target EGR opening in accordance with the required reduced air amount, and sets the ABV control means 25
Calculates the target ABV opening in accordance with the required reduced air amount, and proceeds to step S70. The EGR control means 24 performs feedback control so that the opening of the EGR valve 10a matches the target EGR opening, and performs ABV control. Means 25
Performs feedback control so that the opening of the ABV valve 12 matches the target ABV opening, and returns.

Therefore, according to the control apparatus for an internal combustion engine according to the present embodiment, the in-cylinder excess air ratio (cylinder excess) is determined in the engine ECU 20 based on the exhaust gas weight and the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio during steady operation. (Internal air-fuel ratio) can be accurately estimated, so that the opening control of the EGR valve 10a and the opening control of the ABV 12 can be accurately performed, whereby a stable lean operation can be performed without causing the engine to misfire. performed while, there is the advantage that as many exhaust gas can be recirculated to reliably reduce the NO _X to.

The control of the opening of the EGR valve 10a and the control of A
There is also an advantage that the control amount in the opening control of the BV 12 can be reduced as much as possible to prevent a decrease or a sudden increase in the EGR amount. Also, since the in-cylinder excess air ratio (in-cylinder air-fuel ratio) is estimated using the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio during steady-state operation, the oxygen concentration in a wide air-fuel ratio region as in the past is It is not necessary to provide a full-range O ₂ sensor capable of detecting, and there is an advantage that an increase in the number of parts and an increase in cost can be suppressed.

Further, there is an advantage that the estimation of the in-cylinder excess air ratio (in-cylinder air-fuel ratio) can be easily performed using a relatively simplified formula. For example, even when the above-described fuel injection control or EGR control is performed while the vehicle is running, the in-cylinder excess ratio (cylinder air-fuel ratio) can be more easily estimated. In addition,
In the above embodiment, the in-cylinder excess air ratio estimating device
Although it is constituted by the in-cylinder excess air ratio estimating means 23 of U20, the in-cylinder excess air amount estimating device is constituted by the EGR rate estimating means 21, the exhaust gas excess air amount estimating means 22 and the in-cylinder excess air amount estimating means 23 of the ECU 20. You may comprise.

The in-cylinder excess air ratio estimating apparatus is not limited to this. As shown in FIG. 9, data information (exhaust air-fuel ratio information (exhaust air-fuel ratio information) from an exhaust gas analyzer 31 used during engine development and the like is used. Exhaust gas excess ratio information) and EG
It may be configured as a cylinder air excess ratio meter 30 for estimating the cylinder air excess ratio lambda _c on the basis of the R ratio information]. in this case,
The in-cylinder excess air ratio estimating device 30 is configured to have the same function as the in-cylinder excess air ratio estimating unit 23 in the above-described embodiment, and is configured to receive information from the exhaust gas analyzer 31.

Here, the exhaust gas analyzer 31 is a CO ₂ meter 3
1a, CO meter 31b, HC meter 31c, O ₂ meter 31d, N
O _X meter 31e, based on the respective density detection information from the EGR-CO ₂ meter 31f, configured to calculate the exhaust gas air-fuel ratio (or exhaust gas excess air ratio) and the EGR rate. For example, these estimating units may be configured similarly to the EGR rate estimating unit 21 and the exhaust gas excess ratio estimating unit 22 in the above-described embodiment.

The in-cylinder excess air ratio estimating device 30
In-cylinder excess air data estimated by PC Laboratories Automation (PC Laboratories, P
LA) 32. The personal computer lab auto 32 also has a function of processing data from the exhaust gas analyzer 31. Further, the cylinder air excess ratio estimating device 30 is adapted to as to be able to display the in-cylinder excess air ratio lambda _c.

Since the in-cylinder excess ratio λ _c is the ratio of the in-cylinder air-fuel ratio to the stoichiometric air-fuel ratio, the in-cylinder excess ratio estimating device 30 is recirculated by the EGR rate estimating means via the EGR device. It can be considered as an in-cylinder air-fuel ratio estimating device (in-cylinder air-fuel ratio meter) for estimating the in-cylinder air-fuel ratio based on the exhaust gas amount and the exhaust gas air-fuel ratio input from the exhaust gas analyzer 31.

Accordingly, when the engine is developed based on the air-fuel ratio, the in-cylinder excess ratio λ _c can be accurately grasped by the in-cylinder excess ratio estimating device 30, so that the test accuracy at the time of engine development is improved. There is an advantage that can be. Further, since it calculates the cylinder air excess ratio lambda _c in a simple manner, for example, cylinder air excess ratio when performing various settings in the engine development phase (or in-cylinder air-fuel ratio)
Can be estimated more easily, and there is an advantage that man-hours can be reduced during engine development and the like.

In the above-described embodiment, the intake air amount is controlled by controlling the ABV 12. However, the control of the intake air amount is not limited to this. An electronically controlled throttle valve is configured to be electrically driven by a motor based on a signal, and the throttle valve 7 is electrically driven to change the opening degree, thereby reducing the amount of air introduced into the combustion chamber. It may be adjusted.

[0063]

As described above in detail, according to the control apparatus for an internal combustion engine of the present invention, the cylinder is controlled based on the exhaust gas amount and the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio during steady operation. Since the excess air ratio can be accurately and easily estimated,
It is possible to accurately control the amount of exhaust gases recirculated by this, while performing lean operation the engine stable not to misfire, be reduced reliably NO _X is recycled as much exhaust gas There is an advantage that control can be further simplified.
Further, since the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio during steady operation is used for estimating the in-cylinder excess air ratio, there is an advantage that an increase in the number of parts and an increase in cost can be suppressed.

According to the cylinder excess air ratio estimating apparatus of the present invention, the cylinder excess air ratio can be accurately and simply estimated based on the exhaust gas amount and the exhaust gas air-fuel ratio during engine development or the like. Further, there is an advantage that the test accuracy can be improved at the time of engine development and the like, and the man-hour at the time of engine development and the like can be reduced.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of an internal combustion engine according to one embodiment of the present invention.

FIG. 3 is a diagram for explaining estimation of an exhaust gas excess ratio in a control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 4 is a diagram for explaining an estimation of an exhaust gas excess ratio in the control device for the internal combustion engine according to one embodiment of the present invention.

FIG. 5 is a diagram for explaining estimation of an exhaust gas excess ratio in the control device for the internal combustion engine according to one embodiment of the present invention.

FIG. 6 is a diagram for explaining a correlation between an excess air ratio and a lean limit in a control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 7 is a diagram showing control characteristics of an in-cylinder excess air ratio in the control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 8 is a flowchart for explaining EGR control and ABV control in the control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 9 is a schematic diagram showing an in-cylinder excess air ratio estimating apparatus according to a modified example of one embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 Exhaust gas recirculation device (EGR device) 10 10a EGR valve 10b Exhaust gas recirculation passage (EGR passage) 11 Air flow sensor (AFS) 12 Air bypass valve (ABV) 15 Crank angle sensor (engine rotation speed sensor) 20 ECU (controller, electronic device) EGR rate estimating means (recirculation exhaust gas rate estimating means, E
GR amount estimating means) 22 Exhaust gas excess ratio estimating means (exhaust gas air-fuel ratio estimating means) 23 In-cylinder excess air rate estimating means (in-cylinder air-fuel ratio estimating means,
24 EGR control means (exhaust gas recirculation amount control means) 25 ABV control means (air bypass valve control means) 30 in-cylinder excess air rate estimation apparatus 31 exhaust gas analyzer

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) F02D 43/00 301 F02D 43/00 301T 301H 301L 45/00 368 45/00 368F F02M 25/07 550 F02M 25/07 550R 570 570A 580 580H (72) Inventor Nobuaki Murakami 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 3G062 AA06 BA03 BA06 ED09 GA01 GA04 GA06 GA21 3G084 AA04 BA06 BA09 BA20 CA05 DA10 DA25 EA11 EB08 EB16 EC03 EC07 FA10 FA26 FA28 FA29 FA33 FA37 FA38 3G092 AA01 AA06 AA09 AA17 BA01 BA04 DC03 DC04 DC09 EC01 FA17 FA50 HA01Z HA06Z HA10X HD07X HD07Z HE01Z HE03Z HF08Z 3G301 HA04 NA04 LC04 MA03 NA02 LC04 ND15 NE15 PA11Z PA15A PD01Z PD03A PD15A PD15Z PE01Z PE03Z PF03Z

Claims (2)

[Claims] A control device for an internal combustion engine provided in a vehicle having an exhaust gas recirculation device and capable of lean operation with an air-fuel ratio leaner than the stoichiometric air-fuel ratio, wherein the amount of exhaust gas recirculated by the exhaust gas recirculation device And an in-cylinder excess air ratio estimating means for estimating the in-cylinder excess air ratio based on the exhaust gas air-fuel ratio estimated from the intake air-fuel ratio during steady operation, and the in-cylinder air estimated by the in-cylinder excess air ratio estimating means. An exhaust gas recirculation amount control means for controlling an amount of exhaust gas to be recirculated by the exhaust gas recirculation device based on the excess ratio. 2. An in-cylinder excess air ratio estimating device that is provided with an exhaust gas recirculation device and that is used to estimate an in-cylinder excess air ratio of an internal combustion engine capable of lean operation with an air-fuel ratio leaner than the stoichiometric air-fuel ratio. An in-cylinder excess air ratio estimating device that estimates an in-cylinder excess air ratio based on an amount of exhaust gas recirculated by the exhaust gas recirculation device and an exhaust gas air-fuel ratio.