JPH11236845A - Intake control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform regulation of torque to a value as demanded corresponding to a target load even during lean operation by adding an influence on improvement of thermal efficiency by a lean state, in an intake control device for an engine to control an intake air amount of an engine based on a target load set according to an operation state. SOLUTION: An intake control device for an engine comprises a target air- fuel ratio setting means for controlling an intake air amount; a means to determine virtual filling efficiency matching with a target load when a state to be operated in a theoretical air-fuel ratio is supposed; a target filling efficiency computing means 55 to determine target filling efficiency by adding an air excess factor content of a target air-fuel ratio and a fuel improvement effect content by a lean state from the virtual filling efficiency; and a throttle opening computing means 56 to compute the opening of a throttle valve to regulate an intake air amount according to the target filling efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an engine that controls an intake air amount based on a target load set according to an operation state.

[0002]

2. Description of the Related Art Conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 8-313396, a plurality of operation modes having different air-fuel ratios are selected according to an operation state, and a value corresponding to a load target value is obtained. A control device that sets a target air-fuel ratio and the like and controls an intake air amount according to the target value and the operation mode is known.

That is, the engine disclosed in the above publication is a direct injection type spark ignition type engine, which has an injector for directly injecting fuel into a combustion chamber, and has an intake air amount corresponding to a change in air-fuel ratio. For control, a large-diameter bypass passage that bypasses the throttle valve in the intake passage is provided with a valve for adjusting the amount of intake air.This engine control device significantly reduces the air-fuel ratio by stratified combustion by compression stroke injection. It is possible to select a plurality of operation modes such as a mode for setting a state, a mode for setting a lean state with uniform combustion by intake stroke injection, and a mode for setting a stoichiometric air-fuel ratio. Then, a target average effective pressure (net average effective pressure or indicated average effective pressure) corresponding to the target value of the load is obtained from the intake pipe pressure, the throttle opening, and the like, and the target air-fuel ratio and the like are calculated according to the target average effective pressure. In addition, during stratified charge combustion, the opening degree of the valve is increased to increase the intake air amount in order to secure the target average effective pressure while keeping the air-fuel ratio lean.

[0004]

In this type of conventional apparatus, when the target air-fuel ratio is made lean, the air is taken in by an amount corresponding to the excess air ratio (the ratio between the target air-fuel ratio and the stoichiometric air-fuel ratio). Only the air amount is controlled to be increased, and the effect of improving the fuel economy by leaning is not reflected in the control of the intake air amount, so that there is room for improvement.

That is, when setting the control conditions such as the intake air amount, the target air-fuel ratio is made lean on the basis of a control state in which a torque characteristic corresponding to the target load is obtained at the stoichiometric air-fuel ratio. In addition, compared to the reference control state at the above stoichiometric air-fuel ratio, the intake air amount is increased by an amount corresponding to the excess air ratio (the ratio between the target air-fuel ratio and the stoichiometric air-fuel ratio) to secure the same fuel injection amount It is controlled to make it happen. However, when the air-fuel ratio is made lean by stratified combustion, etc., the fuel efficiency is greatly improved by increasing the thermal efficiency.Therefore, as described above, the intake air amount is increased by the amount corresponding to the leaning and the fuel injection amount is made equal. Then, the engine torque is increased by the fuel efficiency improvement effect (thermal efficiency improvement). Therefore, there may be a case where the required torque characteristic corresponding to the target load cannot always be obtained in a low load region or the like.

The present invention has been made in view of the above circumstances, and when the air-fuel ratio is lean, by controlling the intake air amount while taking into account the effect of improving the thermal efficiency, the torque can be adjusted as required corresponding to the target load. It is an object of the present invention to provide an intake control device for an engine capable of performing the following.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention sets a target load according to an operation state and controls an intake air amount of the engine based on the target load. An intake air amount adjusting means for adjusting an intake air amount; an accelerator operation amount detecting means for detecting an accelerator operation amount or a value corresponding thereto; a rotational speed detecting means for detecting an engine rotational speed; The target air-fuel ratio setting means for setting the target air-fuel ratio according to the operation state so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio in the region, and the target load in the case where the operation at the stoichiometric air-fuel ratio is assumed. Virtual value calculating means for obtaining a charging efficiency or a value corresponding to the charging efficiency as a virtual value of the intake charging state; and calculating the excess air ratio of the target air-fuel ratio and the target air-fuel ratio from the virtual value of the intake charging state. Target value calculating means for obtaining the intake charge state target value in consideration of the fuel efficiency improvement effect with respect to the stoichiometric air-fuel ratio at the time, and means for controlling the intake air amount adjusting means according to the intake charge state target value. It is provided with.

[0008] According to this intake control device, in an operating region in which the target air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the charging efficiency corresponding to the target load or the filling efficiency corresponding to the target load when operating at the stoichiometric air-fuel ratio is assumed. The intake air charge state target value that takes into account the excess air ratio of the target air-fuel ratio and the fuel efficiency improvement effect due to leaning is determined based on the target air-fuel ratio. The intake air amount is adjusted so as to meet the requirements. Therefore, the intake air amount is appropriately controlled so that the load in the state where the thermal efficiency is improved in the lean operation corresponds to the target load assuming the state of operating at the stoichiometric air-fuel ratio.

As an example of the virtual value calculating means and the target value calculating means in the apparatus of the present invention, the virtual value calculating means is a virtual charging efficiency which is a charging efficiency corresponding to a target load when a standard operation state at a stoichiometric air-fuel ratio is assumed. And the target value calculating means obtains a target charging efficiency as an intake charging state target value from the virtual charging efficiency. In this case, the target value calculating means calculates the target charging efficiency by multiplying the virtual charging efficiency by a coefficient corresponding to the fuel efficiency improvement ratio with respect to the stoichiometric air-fuel ratio and the excess air ratio of the target air-fuel ratio. It is good.

With this configuration, when the target charging efficiency during the lean operation is calculated from the virtual charging efficiency corresponding to the target load in a state where the operation is performed at the stoichiometric air-fuel ratio, the fuel efficiency improvement rate is reduced. By being reflected, the target filling efficiency is properly obtained.

In the apparatus of the present invention, the means for controlling the intake air amount adjusting means obtains the target volume efficiency based on the target charging efficiency, taking into account a correction corresponding to the intake density, and calculates the intake air amount in accordance with the target volume efficiency. Preferably, the control amount of the adjusting means is determined. In this way, even when the intake air density changes due to a change in the atmospheric pressure or the intake air temperature, the intake air amount is properly controlled.

Further, the means for controlling the intake air amount adjusting means is adapted to change the control amount of the intake air amount adjusting means determined according to the intake charge state target value when the exhaust gas recirculation device for returning exhaust gas to the intake system is operated. It is preferable to change according to the stop time. With this configuration, when the exhaust gas is being recirculated, the amount of intake air is adjusted accordingly in response to the fact that this influences the inflow of intake air.

[0013] In addition to the target air-fuel ratio setting means for controlling the intake air amount, a target air-fuel ratio setting means for controlling the fuel injection amount is provided, and the target air-fuel ratio setting means for controlling the fuel injection amount is set. Means for controlling the amount of fuel injected from the injector in accordance with the target air-fuel ratio and the actual charging efficiency.The target air-fuel ratio setting means for controlling the intake air amount is calculated based on the air-fuel ratio leaner than the stoichiometric air-fuel ratio. The target air-fuel ratio is set in the range up to the air-fuel ratio according to the operating condition, and the target air-fuel ratio setting means for controlling the fuel injection amount operates the target air-fuel ratio in the range from the lean side to the rich side of the stoichiometric air-fuel ratio. It is desirable that the setting be made according to the state.

In this way, the actual air-fuel ratio is controlled from the lean side to the rich side from the stoichiometric air-fuel ratio by controlling the fuel injection amount according to the target air-fuel ratio for controlling the fuel injection amount and the actual charging efficiency. Although the target air-fuel ratio for controlling the intake air amount is not made richer than the stoichiometric air-fuel ratio, the intake air amount becomes richer in the high-load range where the air-fuel ratio is made richer. Inappropriate control, such as reduction due to optimizing, is reliably prevented.

Further, the apparatus of the present invention includes an injector for directly injecting fuel into the combustion chamber, and is in a stratified combustion state in which fuel is injected from the injector in a compression stroke at least in a low-load low-speed range. Preferably, the present invention is applied to an engine in which the air-fuel ratio is set leaner than the stoichiometric air-fuel ratio in the state.

[0016] In this case, the stratified combustion state can be attained at least in the low-load low-speed range, so that a great lean operation can be achieved. In addition, the intake air amount is controlled in consideration of the fuel consumption effect. In addition, the intake air amount is appropriately controlled such that the actual load corresponds to the target load even under the influence of the fuel efficiency improvement effect while obtaining a large fuel efficiency improvement effect.

[0017]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the overall structure of an in-cylinder injection spark ignition type engine in which the intake control device of the present invention is applied. In this figure, the engine body 1
0 has a plurality of cylinders 12, each of which has a combustion chamber 15 above a piston 14 inserted into its cylinder bore.
An intake port and an exhaust port are opened in the combustion chamber 15, and these ports are opened and closed by an intake valve 17 and an exhaust valve 18, respectively.

At the center of the combustion chamber 15 is a spark plug 2
0 is disposed, and the plug tip faces the combustion chamber 15. Further, the injector 2 is inserted into the combustion chamber 15 from the side.
2 comes to the front, and the injector 22
5 is directly injected with fuel. A fuel circuit including a high-pressure fuel pump, a pressure regulator, and the like (not shown) is connected to the injector 22. Fuel is supplied to the injector 22 of each cylinder, and the fuel pressure is higher than the in-cylinder pressure in the compression stroke. The fuel circuit is configured such that

An intake passage 24 and an exhaust passage 34 are connected to the engine body 10. In the intake passage 24, an air cleaner 25, an air flow sensor 26, a throttle valve 28 and a surge tank 30 driven by a motor 27 are provided in this order from the upstream side, and the throttle valve 28 and a motor 27 for driving the throttle valve 28 and the surge tank 30 are provided. Constitutes the intake air amount adjusting means. Surge tank 30
A separate intake passage for each cylinder is provided downstream of the cylinder, and each independent intake passage communicates with an intake port. In this embodiment,
The downstream portion of each independent intake passage is the first and second passages 31.
a, 31b, two downstream intake ports open to the combustion chamber, and a swirl control valve 32 (hereinafter referred to as an S valve 32) is provided in the second passage 31b.
Is provided.

The S-valve 32 is opened and closed by being driven by an actuator 33. When the S-valve 32 closes the second passage 31b, the S-valve 32 enters the combustion chamber 15 by intake air passing through the first passage 31a. A swirl is generated,
The swirl is weakened as the S valve 32 is opened.

The exhaust passage 34 is provided with a catalyst 35 for purifying exhaust gas. The catalyst 35 provided in the engine of the present embodiment has NOx purification performance even in the lean operation state. For example, the catalyst 35 stores NOx in the exhaust gas in the lean operation state and converts the NOx to the stoichiometric air-fuel ratio or higher. A NOx storage catalyst that reduces when an operation state with a rich air-fuel ratio is established is used.

Further, an EGR passage 37 for recirculating exhaust gas is formed between the exhaust passage 34 and the intake passage 24, and an EGR valve 38 is provided in the EGR passage 37.

In addition to the air flow sensor 26, the engine has a boost sensor 40 for detecting a negative pressure of intake air in the surge tank 30, a throttle opening sensor 41 for detecting a throttle opening, and a rotation speed for detecting an engine rotation speed. A sensor 42, an accelerator opening sensor 43 for detecting an accelerator opening (accelerator operation amount), an intake air temperature sensor 44 for detecting an intake air temperature, an atmospheric pressure sensor 45 for detecting an atmospheric pressure, a water temperature sensor 46 for detecting an engine cooling water temperature, An O ₂ sensor 47 for detecting an air-fuel ratio by detecting an oxygen concentration in exhaust gas;
EGR valve lift sensor 4 for detecting the amount of lift of the EGR valve
8. Sensors such as a fuel pressure sensor 49 for detecting the fuel pressure of the fuel supplied to the injector 22 are provided, and output signals (detection signals) of these sensors are input to an ECU (control unit) 50.

The ECU 50 controls the amount and timing of fuel injection from the injector 22 and
The control of the throttle valve 28 is performed by outputting a control signal to the motor 27 that drives the throttle valve 28, the ignition timing is controlled by outputting the control signal to the ignition circuit 21, and the control signal is transmitted to the actuator 33. Is also output to control the S valve 32. In addition, the ECU 50 also controls the EGR valve 38 and the like.

As basic control of the direct injection engine of the present embodiment, various operation modes in which the fuel injection form from the injector 22 and the air-fuel ratio are different can be selected, and the operation mode is changed depending on the operation region. It is supposed to be.

More specifically, as will be described later, a predetermined region on the low-load low-rotation side is a stratified combustion region, and the other region is a uniform combustion region (see FIG. 8). In the stratified combustion region, the fuel is injected in the compression stroke from the injector 22 to set a stratified combustion mode in which combustion is performed in a stratified state in which the air-fuel mixture is unevenly distributed in the vicinity of the ignition plug 20. By increasing the opening degree of the throttle valve 28 and increasing the amount of intake air, the air-fuel ratio of the entire combustion chamber is set to a large lean state (for example, 30 or more). On the other hand, in the uniform combustion region, the fuel is injected from the injector 22 in the first half of the intake stroke, so that the combustion is performed in a state in which the air-fuel mixture is uniformly diffused throughout the combustion chamber 15. In the region of relatively low load and low rotation speed (region adjacent to the stratified combustion region) in the uniform combustion region, the excess air ratio λ is λ> 1, that is, the air-fuel ratio leaner than the stoichiometric air-fuel ratio (for example, 20 to 20). 2
5), and λ =
1, that is, the stoichiometric air-fuel ratio (A / F = 14.7).
The air-fuel ratio may be set to be richer than the stoichiometric air-fuel ratio (λ <1) in the full-open region of the accelerator or in the high-load region and the high-speed region in the vicinity thereof.

FIG. 2 shows the structure of the means functionally included in the ECU 50. The ECU 50 has an intake density state detecting means 51 for detecting an intake density state based on signals from the intake air temperature sensor 44 and the atmospheric pressure sensor 45, and outputs signals from the accelerator opening sensor 43 and the engine speed sensor 42. A target load setting means 52 for setting a value corresponding to the target load based on the intake air density state based on the intake air density state.

As shown in FIG. 3, the target load setting means 52 includes a virtual volume efficiency calculating means 52a, a virtual filling efficiency calculating means 52b, a smoothing processing means 52c, a target indicated mean effective pressure calculating means 52d and an idling load correction. Means 5
2e.

The virtual volume efficiency calculating means 52a calculates a virtual volume efficiency veimg according to the accelerator opening accel and the engine speed ne. In this case, the accelerator is opened so that the required output performance can be obtained under standard atmospheric conditions by a bench test or the like and under standard operating conditions in which the air-fuel ratio is maintained at a predetermined value (specifically, the stoichiometric air-fuel ratio). The correspondence between the degree accel and the engine speed ne and the virtual volumetric efficiency veimg is determined, and the correspondence is stored as a map in a memory in the ECU 50, and the actual accelerator opening accel and the engine speed ne are stored from this memory. The virtual volume efficiency veimg according to is required.

The correspondence between the accelerator opening accel and the engine speed ne and the virtual volume efficiency veimg is as shown in FIG. 7, for example. That is, the virtual volume efficiency Veimg is set so as to increase as the accelerator opening accel increases, and to increase as the engine speed decreases.

In FIG. 3, the virtual filling efficiency calculating means 52b calculates the virtual filling efficiency ceimg by adding the intake air density obtained by the intake air density state detecting means 51 to the virtual volume efficiency veimg. As a result, the charging efficiency corresponding to the required engine torque assuming the standard operating condition for maintaining the air-fuel ratio at the stoichiometric air-fuel ratio is obtained as the virtual charging efficiency ceimg.

The smoothing means 52c smoothes the virtual filling efficiency ceimg by primary delay correction as shown in the following equation.

[0033]

Ceimgd = (1−α) · ceimg + α · ceimgd [i-1] where ceimgd [i-1] is the previous value of ceimgd, and α is the coefficient (0 <
α <1).

The target indicated mean effective pressure calculating means 52
As for d, a target indicated average effective pressure, which is a value corresponding thereto, is obtained from the virtual filling efficiency, and is set as a target load. In this case, the first target indicated mean effective pressure Piobj from the virtual filling efficiency ceimg that has not been annealed, and the second target indicated mean effective pressure Piobjd from the virtual filling efficiency ceimgd that has been annealed, are as follows. Is calculated.

[0035]

## EQU2 ## Piobjd = K1.times.ceimg + K2 Piobjd = K1.times.ceimgd + K2 The idling load correction means 52e calculates an idling load correction value to increase the engine torque to an extent commensurate with an external load such as an air conditioner during idling operation. The virtual filling efficiency ceimg and ceimgd are corrected prior to the calculation of the target indicated mean effective pressure.

The ECU 50 shown in FIG. 2 further includes an operation mode setting means 53 for setting basic operation mode mods.
have.

The operation mode setting means 53 sets a basic operation mode mods according to the first target indicated mean effective pressure Piobj and the engine speed ne. That is, as shown in FIG. 8, the first target indicated average effective pressure Piobj is lower than the predetermined low load side threshold and the engine speed is low (stratified combustion region), and the stratified combustion mode is set. In the region (uniform combustion region), the first target indicated mean effective pressure Piobj is lower than a predetermined high-load-side threshold, and in regions other than the high engine speed region, a uniform combustion mode (hereinafter, uniform lean) of λ> 1 In the region where the first target indicated mean effective pressure Piobj is higher than the high-load-side threshold and the engine high-speed region, the uniform combustion operation mode (hereinafter referred to as stoichiometric mode) with λ = 1 is set.

Further, the ECU 50 has control means for determining the values of various control parameters related to the engine output. In this embodiment, the intake air amount adjusted by the throttle valve 28 and the EGR adjusted by the EGR valve 38 are used. Quantity, S valve 3
The swirl, the fuel injection amount from the injector 22, the fuel injection timing, and the ignition timing of the ignition plug 20, which are adjusted in 2, are used as control parameters, and the values of these control parameters are determined according to the target load, the engine speed ne, and the like. You. In this case, the first target indicated mean effective pressure Piobj is used as the target load for determining the control value of the low-speed response system among the control parameters, and is used as the target load for determining the control value of the high-speed response system. Is the second target indicated mean effective pressure
Piobjd is used.

That is, among the above control parameters, the intake air amount, the EGR amount and the swirl are low-speed response systems having relatively low responsiveness to the operation of the throttle valve 28, the EGR valve 38 and the S valve 32, respectively. Throttle opening tvoobj, which is the control amount of EGR valve 38
robj and the opening of the S valve 32 are the first target indicated mean effective pressure
It is determined according to Piobj and the engine speed ne. On the other hand, the fuel injection amount, the fuel injection timing, and the ignition timing are a high-speed response system that quickly responds to the control signal, and the fuel injection amount, the fuel injection timing, and the ignition timing are the second target indicated average effective pressure Piobjd and the engine. It is determined according to the rotation speed ne and the like.

More specifically, as means for controlling the intake air amount, target air-fuel ratio setting means 54, target charging efficiency calculating means 55 (target value calculating means), and throttle opening degree calculating means 56 (intake charging state target means). (Means for controlling the intake air amount adjusting means in accordance with the value). The target air-fuel ratio setting means 54 includes a target air-fuel ratio afwb for controlling the intake air amount.
Is set for each operation mode set by the operation mode setting means 53. As shown in FIG.
In the stratified combustion mode and the uniform lean mode, the target air-fuel ratio afwb is obtained from a map prepared in advance according to the first target indicated mean effective pressure Piobj and the engine speed ne. In the stoichiometric mode, the target air-fuel ratio afwb is theoretically calculated. Air-fuel ratio (λ =
1).

The target charging efficiency calculating means 55 calculates the target charging efficiency ceobj from the virtual charging efficiency ceimg and the target air-fuel ratio afwb, for example, by the following equation (8).

As shown in FIG. 4, the throttle opening calculating means 56 has a target volume efficiency calculating means 56a and a throttle opening determining means 56b. Then, as described later in detail, a target volume efficiency veobj is calculated from the target charging efficiency ceobj by taking into account the intake air density correction.
Throttle opening tvoobj according to bj and engine speed ne
At this time, the throttle opening degree tvoobj is obtained from a different map depending on whether the EGR is performed or not, according to the determination of the EGR determining means 56c.

Further, in the example shown in FIG. 4, the correction according to the burned gas volume ratio when EGR is performed is performed.
That is, when the EGR is performed in a state where the air-fuel ratio is lean as in the stratified combustion mode, not only the burned gas but also a large amount of air (oxygen) is present in the EGR gas. Because it affects the amount of air that is inhaled,
The burned gas volume ratio is calculated by the burned gas volume ratio calculating means 57, and is calculated by the intake air amount / EGR correcting means 58.
The throttle opening is corrected based on a comparison between the burned gas volume ratio and its target value and a comparison between the actual volume efficiency ve and the target volume efficiency veobj obtained based on the output of the air flow sensor 26. The correction of the EGR valve control amount is also performed in association with the above. As for the target value of the burned gas volume ratio, a map (not shown) similar to a map of the EGR valve basic control amount described later is created in advance and read from this map.

As means for controlling the EGR amount, EGR
A valve basic control amount setting means 59 and an EGR valve control amount calculating means 60 are provided. EGR valve basic control amount setting means 5
7 sets the basic control amount pbase of the EGR valve 38 for each operation mode mods set by the operation mode setting means 53. As shown in FIG. 9B, the first target is set in the stratified combustion mode. According to the indicated mean effective pressure Piobj and the engine speed ne, a basic control amount pbase is obtained from a map created in advance, and in the uniform lean mode, the basic control amount pba
se is set to “0”, and in the stoichiometric mode, the basic control amount is obtained from a previously created map in accordance with the actual charging efficiency ce and the engine speed ne obtained based on the output of the air flow sensor 26. I have.

The EGR valve control amount calculating means 60 adds the intake air amount / EGR correcting means 58 to the basic control amount pbase to obtain a final EGR valve control amount.
egrobj is obtained (see FIG. 4).

As means for controlling the S-valve opening, an S-valve opening setting means 61 is provided. This S valve opening setting means 6
1 sets the S-valve opening so as to obtain the swirl required in each mode for each operation mode mods set by the operation mode setting means 53, as shown in FIG. 9 (c). In the stratified combustion mode and the uniform lean mode, the first target indicated mean effective pressure Piobj and the engine speed ne are set.
In accordance with the above, the S valve opening scvo
bj is determined, and in the stoichiometric mode, the S-valve opening scvobj is determined from a previously created map according to the actual charging efficiency ce and the engine speed ne.

The means for controlling the fuel injection from the injector 22 includes a target air-fuel ratio creating means 62, an operation mode setting means 63, a split ratio setting means 64, and an injection amount calculating means 6.
5, an injection timing setting means 66 and an injection control means 67 are provided.

The target air-fuel ratio creating means 62 determines the target air-fuel ratio used for controlling the fuel injection amount and the like. More specifically, as shown in FIG. Target air-fuel ratio calculating means 6 for calculating afw0
2a and target air-fuel ratio afwbd mainly used during steady state
Target air-fuel ratio setting means 62b for setting the target air-fuel ratio afwb for controlling the intake air amount for detecting a transient state and means 62c for calculating a deviation dafwb between the target air-fuel ratio afw0 calculated by the calculating means 62a. Means 62d for determining the final target air-fuel ratio afw.

The target air-fuel ratio calculating means 62a calculates the target air-fuel ratio afw0 from the second target indicated mean effective pressure Piobjd or the virtual charging efficiency ceimgd corresponding thereto and the actual charging efficiency ce as follows: .

[0050]

[Equation 3] afw0 = 14.7 × K1 × ce / {K4 × (Piobjd−K2)}
−K3 [= 14.7 × ce / (K4 × ceimgd) −K3] This arithmetic expression is based on the stoichiometric air-fuel ratio, the actual charging efficiency ce, and the second target average effective pressure Piobjd (or the virtual charging efficiency ceimg).
d) and the coefficients K3 and K taking into account the above-described fuel economy improvement effect.
4, the air-fuel ratio is determined so that a torque corresponding to the target load can be obtained under the actual charging efficiency.

The setting means 62b determines whether the target air-fuel ratio
afwbd is set for each operation mode modf set by the operation mode setting means 63. As shown in FIG. 12A, in the stratified combustion mode and the uniform lean mode, the second
According to the target indicated average effective pressure Piobjd and the engine speed ne, the target air-fuel ratio afwbd
In the stoichiometric mode, the target air-fuel ratio afwbd is set to the stoichiometric air-fuel ratio (λ = 1). If necessary, the target air-fuel ratio afwbd may be set to be richer than the stoichiometric air-fuel ratio in the stoichiometric mode particularly at a high load and a high rotation speed. In this case, the mode is a mode of λ ≦ 1. Become.

Means 62d for determining final target air-fuel ratio afw
In the transient state when the deviation dafwb becomes large,
The target air-fuel ratio afw0 calculated in 2a is used as the final target air-fuel ratio.
afw, when the deviation dafwb is small and steady, the setting means 6
The target air-fuel ratio afwbd set in 2b is set as the final target air-fuel ratio afw.

The reason why the target air-fuel ratio creating means 62 is configured in this way is to satisfy the demand for output and the emission as described later. However, as a simpler structure, the setting means 62b and The deviation calculation means 62c may be omitted, and the target air-fuel ratio afw0 always calculated by the calculation means 62a may be used as the final target air-fuel ratio for controlling the fuel injection amount.

In FIG. 5, reference numeral 80 denotes a means for calculating the air-fuel ratio deviations dafwbd and dafw0 for correcting the ignition timing at the time of transition as described later. The mode set by the operation mode setting means 63 is the stoichiometric mode. If not, dafwbd = afwbd-a
fw is calculated, and in the stoichiometric mode, dafw0 = afw0-a
fw is calculated.

The operation mode setting means 63 sets the operation mode modf used to determine the control parameters of the high-speed system,
Target air-fuel ratio afw0 and engine speed for controlling fuel injection amount, etc.
Set according to ne. That is, as shown in FIG. 11, when the target air-fuel ratio afw0 calculated by the calculation means 62a is smaller than the uniform lean lower limit side reference value (for example, about 18), the stoichiometric mode is set, and the target air-fuel ratio is set.
When afw0 is a value between the uniform lean lower limit reference value and the uniform lean upper limit reference value larger than this, the uniform lean mode is set, and the target air-fuel ratio afw0 is set to a value larger than the uniform lean upper limit reference value. When this happens, the stratified combustion mode is set.

Note that, when the operation mode modf is changed between the uniform lean mode and the stratified combustion mode, the split injection mode is temporarily selected near the uniform lean upper limit reference value (hatched portion). Is also good. In the split injection mode, the fuel injection is performed by dividing the fuel injection into an intake stroke and a compression stroke, and the mode is changed from the stratified combustion mode of the compression stroke injection to the uniform lean mode of the intake stroke injection, and vice versa. If the mode change is performed, the combustion state can be abruptly changed by passing through the split injection mode.

The split ratio setting means 64 sets the split ratio between the intake stroke injection and the compression stroke injection according to the operation mode modf set by the operation mode setting means 63. In the stratified combustion mode, the intake stroke injection is performed. Ratio rqbasep is 0
% In the uniform lean mode and the stoichiometric mode, the intake stroke injection ratio rqbasep is set to 100%. When the split injection mode is selected, the split ratio may be set according to the target air-fuel ratio afw and the engine speed ne.

The injection amount calculating means 65 is set by the filling efficiency ce obtained from the output of the air flow sensor 26, the target air-fuel ratio afw obtained by the target air-fuel ratio creating means 62, and the split ratio setting means 64. The fuel injection amount is calculated based on the injection ratio rqbasep. Specifically, the basic injection amounts qbasep, qbased of the intake stroke injection and the compression stroke injection are calculated from these values and the conversion coefficient KGKF.

[0059]

[Mathematical formula-see original document] qbasep = KGKF * (ce / afw) * rqbasep qbased = KGKF * ce (i) / afw (i-1) -qbasep (i-1), and further, intake stroke injection according to fuel pressure , Each correction value cdpfp, cdpfd of compression stroke injection and other various correction values ct
Taking into account otal, the final injection amounts qinjp and qinjd of the intake stroke injection and compression stroke injection

[0060]

[Mathematical formula-see original document] qinjp = qbasep * cdpfp * (1 + ctotal) qinjd = qbased * cdpfd * (1 + ctotal (i-1)), and an injection pulse width Ti proportional to the final fuel injection amounts qinjp and qinjd is obtained. Note that c in the equation for the basic injection amount qbased and the final injection amount qinjd of the compression stroke injection.
e (i) means the current value of the charging efficiency (a value based on the detected value of the intake air amount immediately before the injection in the compression stroke), and afw (i-1) and qbasep (i-
1) and ctotal (i-1) mean the target air-fuel ratio, the intake stroke basic injection amount, and the previous value of the correction value (a value based on the detection immediately before the intake stroke injection), respectively. The reason why the previous value is used as the target air-fuel ratio or the like in the calculation of the compression stroke injection is that if the current value (the value based on the detection value immediately before the compression stroke injection) is used as the target air-fuel ratio, This is because the operation mode, the air-fuel ratio, and the like may fluctuate between the time of the compression stroke injection and the time of the injection during the compression stroke, making it impossible to obtain consistency.

The injection timing setting means 66 sets the fuel injection timing for each of the operation modes set by the operation mode setting means 63. As shown in FIG. The injection timing thtinjd for the compression stroke injection is obtained from a map created in advance according to the target indicated average effective pressure Piobjd and the engine speed ne.In the uniform lean mode, the injection timing thtinjd is created in advance according to the charging efficiency and the engine speed. Injection map for intake stroke injection
Find thtinjp, and in stoichio mode, engine speed n
The injection timing thtinjp for the intake stroke injection is obtained from a table created in advance according to e.

For convenience of calculation processing, some value is always given to both thtinjd and thtinjp as the injection timing data. In the stratified combustion mode, the injection timing thtinjd for the compression stroke injection is given by a map. A fixed value is set for the injection timing thtinjp for the intake stroke injection (however, the intake stroke injection is not actually performed because the intake stroke injection ratio rqbasep is 0%). Injection timing for intake stroke injection in uniform lean mode or stoichiometric mode
Thtinjp is given by a map or a table, and a fixed value (for example, a fixed time at the beginning of the compression stroke) is set to the injection timing thtinjd for the compression stroke, which is used at the time of additional injection.

In the case of the split injection mode, the data in the stratified combustion mode is used as the injection timing thtinjd for the compression stroke injection, and the injection timing is prepared in advance in accordance with the target air-fuel ratio afw and the engine speed ne. The injection timing thtinjp for the intake stroke injection is obtained from the map.

The injection control means 67 operates the injector 22 at the injection timing set by the injection timing setting means 66 for a time corresponding to the injection pulse width Ti calculated by the injection amount calculation means. Outputs injection pulse.

As means for controlling the ignition timing,
A setting means 68 for setting a basic ignition timing and a correction amount, and an ignition timing calculating means 69 are provided.

The setting means 68 calculates the basic ignition timing for each operation mode modf set by the operation mode setting means 63.
Set thtigb and various ignition timing correction values.

The setting by the setting means 68 will be specifically described. As shown in FIG. 12C, in the stratified combustion mode, the setting is made in advance in accordance with the second target indicated mean effective pressure Piobjd and the engine speed ne. The basic air-fuel ratio deviation dafw
A correction value thtigwd corresponding to bd is obtained from a table created in advance. Target air-fuel ratio deviation dafwbd (= afwbd-afw)
Correction according to the target indicated average effective pressure Piobj at the target air-fuel ratio afwbd during steady-state operation in advance
While it is determined according to d and the engine speed ne, during transition, afw0 is set as the final target air-fuel ratio afw, and there is a difference in air-fuel ratio from the steady state.Therefore, the ignition timing must be adjusted accordingly. It is to adjust.

In the uniform lean mode, the basic ignition timing thtigb is obtained from a map prepared in advance according to the charging efficiency ce and the engine speed ne, and a correction value thtigwd corresponding to the target air-fuel ratio deviation dafwbd is prepared in advance. Ask from the table that is.

In the stoichiometric mode, the basic ignition timing thtigb is obtained from a map prepared in advance according to the charging efficiency ce and the engine speed ne, and the correction value thtigwe at the time of EGR is calculated based on the charging efficiency ce and the engine speed ne. The correction value thtigwd corresponding to the target air-fuel ratio deviation dafw0 and the cold-time correction value thtigwc corresponding to the engine coolant temperature thw are obtained from a table prepared in advance. Target air-fuel ratio deviation dafw0 (= afw
0-afw) is corrected by the target air-fuel ratio afw0 as described later.
Is smaller than a predetermined value on the lean side of the stoichiometric air-fuel ratio, N
When the final target air-fuel ratio afw is set to the stoichiometric air-fuel ratio in order to avoid passing through the air-fuel ratio in which the amount of generated Ox increases,
The ignition timing is adjusted to match the change in the air-fuel ratio.

When the split injection mode is set, the basic injection timing thtigb is obtained from a table prepared in advance according to the target air-fuel ratio afw.

The ignition timing calculating means 69 calculates the ignition timing thtig from the basic injection amount thtigb set by the setting means 68 and various correction values as in the following equation.

[0072]

## EQU00006 ## thtig = thtigb- (thtigwd + thtigwe + thtigwc) FIG. 6 is a flowchart showing processing mainly related to the control of the intake air amount, among the processing such as various calculations and control performed by the ECU 50.

When the flowchart starts, first, in step S1, detected data of the accelerator opening, the engine speed, the intake air temperature, and the atmospheric pressure are read. Subsequently, in step S2, the virtual volume efficiency veimg is obtained from the map in which the correspondence is determined as shown in FIG. 7, for example, as described above, according to the accelerator opening and the engine speed.

Next, in step S3, the virtual volume efficiency ve
Based on the img, the virtual filling efficiency ceim is corrected by performing correction according to the intake air density obtained from the intake air temperature and atmospheric pressure.
g is required. In the case where an idling load due to the air conditioner or the like is applied as described above, a correction may be made to add the idling load correction value to the virtual filling efficiency.

Further, in step S4, the virtual filling efficiency ceim
g (If necessary, add idling load correction)
Is subjected to the following conversion to obtain the target indicated mean effective pressure Piobj.

[0076]

[Mathematical formula-see original document] Piobj = K1 * ceimg + K2 where K1 and K2 are conversion coefficients.

Next, at step S5, a target air-fuel ratio afwb for controlling the intake air amount is calculated. That is, the operation mode is set from the map of the operation mode mods shown in FIG. 8 according to the target indicated mean effective pressure Piobj and the engine speed ne. Based on the operation mode, the stratified combustion mode and the stratified combustion mode are set as shown in FIG. In the uniform lean mode, the target indicated average effective pressure Pi
The target air-fuel ratio afwb is obtained from the map according to obj and the engine speed ne, and the target air-fuel ratio af
wb is the stoichiometric air-fuel ratio.

In step S6, the target charging efficiency ceobj is calculated from the virtual charging efficiency ceimg and the target air-fuel ratio afwb as follows.

[0079]

[Mathematical formula-see original document] ceobj = ceimg * {(afwb + K3) /14.7} * K4 This operation expression is, as described later in detail, the virtual filling efficiency ceim.
The target charging efficiency ceobj is obtained from g (virtual value of the intake charging state) by taking into account the excess air ratio (afwb / 14.7) of the target air-fuel ratio and the fuel efficiency improvement effect when the engine is operated lean. K3 and K4 are coefficients for taking into account the fuel efficiency improvement effect. In order to correct the target charging efficiency in a decreasing direction to an extent commensurate with the fuel efficiency improvement effect, coefficients K3 and K4 are set in advance.
3, K4 are set. In the above equation, a value corresponding to the virtual filling efficiency ceimg may be used instead of the virtual filling efficiency ceimg. For example, the first target indicated mean effective pressure Piob
Using j, the target filling efficiency is calculated by an arithmetic expression obtained by substituting ceimg = (Piobj−K1) / K2 from the expression of Expression 7 into the expression of Expression 8 above.
ceobj may be obtained.

In step S7 following step S6, a target volume efficiency veobj is calculated by performing a correction based on the target charging efficiency ceimg in accordance with the intake air density and the intake air density obtained from the atmospheric pressure.

Further, at step S8, it is determined whether or not EGR is being performed. Based on the determination result, the target throttle opening tvoobj is obtained from either the map with EGR or the map without EGR. (Steps S9 and S10). That is, since the correspondence relationship between the volumetric efficiency and the engine speed and the throttle opening differs depending on the presence or absence of EGR, a map showing the correspondence relationship in each case is created in advance, and the EGR determination means 56c determines whether or not EGR exists. The target throttle opening tvoobj corresponding to the target volumetric efficiency veobj is obtained from one of the maps according to the following.

The above-mentioned correspondence relationship is, for example, as shown by a solid line in FIG. 10 when EGR is not performed, and as a broken line in FIG. 10 when EGR is performed. In other words, the throttle opening degree tvoobj is increased as the target volumetric efficiency veobj is increased, and is increased as the engine speed is increased.In addition, the throttle opening tvoobj is increased with the EGR as compared with the case without the EGR. You. Although not shown in the flowchart, when the EGR is performed, in addition to obtaining the target throttle opening degree tvoobj from the map in the case where the EGR is performed, as described above, the total intake of the burned gas in the EGR is performed. It is desirable to obtain a volume ratio with respect to the air amount and correct the target throttle opening degree tvoobj according to the burned gas volume ratio.

After the target throttle opening tvoobj is obtained, a control signal corresponding to the target throttle opening tvoobj is output to the throttle valve driving motor 27 in step S11, so that the target throttle opening tvoobj is obtained. Thus, the throttle valve 28 is controlled.

According to the above-described apparatus, the operation mode is set according to the target indicated average effective pressure corresponding to the target load and the engine speed, and based on the target indicated average effective pressure or the virtual charging efficiency, etc. Control parameters such as the amount of intake air are controlled.

That is, in the in-cylinder injection engine of this embodiment, the stratified charge combustion mode, the uniform lean mode, and the stoichiometric mode are set according to the operation state. In the stratified charge combustion mode, the air-fuel ratio is equal to the stoichiometric air-fuel ratio. In contrast, when the mixture is substantially lean, the mixture is unevenly distributed around the spark plug by the compression stroke injection, and the stratified combustion is performed, so that the fuel efficiency is greatly improved. In the uniform lean mode, uniform combustion is performed by intake stroke injection, and the air-fuel ratio is made lean within a range where combustion in this state is possible. In the stratified combustion mode or the uniform lean mode, the throttle opening is increased to increase the intake air amount in order to make the air-fuel ratio lean while securing the required torque. The intake air amount and the like are controlled.

When the target load is obtained by the target load setting means 52, first, a virtual volume efficiency veimg assuming a stoichiometric air-fuel ratio state is obtained from a map according to the accelerator operation amount accel and the engine speed ne. The virtual filling efficiency ceimg is determined by performing a correction according to the intake density state, and the target indicated average effective pressure corresponding to the target load is determined from the virtual filling efficiency ceimg. , The calculation of the target load based on the accelerator operation amount and the like and the control according to the target load and the like are properly performed.

That is, the accelerator operation amount accel and the engine speed n, which were previously determined by a bench test or the like when the vehicle was in the standard intake density state, without performing the correction according to the intake density state.
By simply calculating the target load based on the correspondence between e and the target load, the engine output is limited because the target load does not change when the intake density increases, even though the engine output can be increased. Would. Further, when the intake air density becomes low, the engine load corresponding to the target load cannot be obtained when the throttle is fully opened, etc., and the actual load (engine torque) reaches a plateau in a region where the throttle opening is large, and the controllability is reduced. become worse.

On the other hand, if the target load (target indicated average effective pressure) is calculated from the virtual charging efficiency ceimg calculated in consideration of the intake density state as in this embodiment, when the intake density state changes, By adjusting the target load accordingly, control parameters related to the engine output are effectively controlled.

Further, if the target load setting means 52 performs the correction according to the load state at the time of idling by the idling load correction means 52e after the calculation of the virtual filling efficiency, the load of the air conditioner or the like is applied during the idling operation. When this occurs, the target average effective pressure is increased accordingly, and the engine output is adjusted to an extent commensurate with the idling load.

The intake air amount is controlled according to the target indicated mean effective pressure Piobj and the engine speed ne.
The target air-fuel ratio for controlling the intake air amount is set for each operation mode set by the operation mode setting means 53, and the fuel efficiency is improved with respect to the excess air ratio of the target air-fuel ratio and the stoichiometric air-fuel ratio based on the virtual charging efficiency ceimg. The target filling efficiency ceobj is calculated in consideration of the effect and the throttle opening is controlled based on the target charging efficiency ceobj, so even in the stratified combustion mode or the uniform lean mode where the target air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the suction The air amount is properly controlled according to the target load. This operation will be specifically described with reference to FIGS.

FIG. 13 shows the relationship between the air-fuel ratio and the fuel efficiency. As shown in FIG. 13, when the air-fuel ratio is made leaner than the stoichiometric air-fuel ratio, the thermal efficiency is improved. The fuel efficiency is improved, and the fuel efficiency is improved as the air-fuel ratio becomes leaner, as long as the combustion stability is not impaired. It is conventionally known that the fuel efficiency is improved by leaning.

FIG. 14 shows the relationship between the air-fuel ratio and the charging efficiency ce, the fuel flow rate, and the engine torque. In this figure, the solid line represents the case where the target air-fuel ratio afwb is set to be equal to or higher than the stoichiometric air-fuel ratio. This shows a case where the intake air amount is adjusted by taking only the excess air ratio into account. That is, the target air-fuel ratio
Virtual filling efficiency ceimg taking into account only the excess air rate of afwb
If the target filling efficiency ceobj ′ is obtained from

[0093]

[Equation 9] ceobj ′ = ceimg × afwb / 14.7. As the target air-fuel ratio afwb becomes lean, the charging efficiency increases at a rate corresponding to the excess air ratio, while the fuel injection amount does not change. However, the torque is increased by the fuel efficiency improvement effect as compared with the case of the stoichiometric air-fuel ratio. Δ in FIG.
T is the torque increase.

On the other hand, as shown in FIG. 15, the fuel flow coefficient CBI is set so as to be a linear function of the reciprocal of the target air-fuel ratio afwb so as to match the fuel efficiency improvement effect.
ceobj

[0095]

Assuming that ceobj = ceimg × (afwb / 14.7) × CBI, as shown by the broken line in FIG. 14, the rate of increase in the charging efficiency according to the leaning of the air-fuel ratio is larger than that of the solid line. And the fuel injection amount decreases with leaning. And, since the increase in torque due to the fuel efficiency improvement effect is offset by the decrease in the fuel injection amount, even when the air-fuel ratio is made lean, the torque is almost the same as at the stoichiometric air-fuel ratio, and from the stoichiometric air-fuel ratio to the lean air-fuel ratio, The torque can be controlled to correspond to the target load.

Although the fuel flow coefficient CBI in the above equation (10) changes according to the air-fuel ratio, the target air-fuel ratio af
Since it is a linear function of the reciprocal of wb,

[0097]

## EQU11 ## CBI = A × (B + 1 / afwb) can be replaced by the following equation.

[0098]

[Equation 12] ceobj = ceimg × (afwb / 14.7) × ｛A ×
(B + 1 / afwb)｝, and K3 = 1 / B and K4 = A × B,
Equation 12 becomes Equation 8 described above. That is, the arithmetic expression of Expression 8 is
The fuel flow coefficient CBI is converted into two constants K3 and K3.
K10 is replaced by K10.

In this manner, the target charging efficiency ceobj taking into account the fuel efficiency improvement effect is obtained. Further, in this embodiment, the target volume efficiency veobj is obtained from the target charging efficiency ceobj taking into account the correction corresponding to the intake air density. The throttle opening is controlled accordingly. Therefore, even when the intake air density changes due to a change in the intake air temperature or the atmospheric pressure, the throttle opening is adjusted so that the target charging efficiency ceobj is obtained.

Further, when obtaining the target throttle opening tvoobj from the target volumetric efficiency veobj, the target throttle opening tvoobj is obtained from different maps when EGR is performed and when EGR is not performed. , EG
Adjustment is performed according to the influence of R, and the intake air amount is appropriately controlled.

In controlling various control parameters based on the target indicated average effective pressure and the like, the first target indicated average effective pressure is used for controlling the intake air amount, EGR, and swirl having a low response speed to a control signal. Although the pressure Piobj is used, the second target indicated mean effective pressure Piobjd based on the simulated virtual filling efficiency ceimgd is used for controlling the fuel injection amount, the injection timing, and the ignition timing having a high response speed to the control signal. Thereby, the operation timing of each control parameter is appropriately adjusted.

That is, in a general engine in which the throttle opening changes in accordance with the accelerator operation amount while maintaining the standard operating condition in which the air-fuel ratio is the stoichiometric air-fuel ratio in most of the operating range, the acceleration and the like are different. Even if the accelerator operation amount and the throttle opening corresponding to it suddenly change, there is a delay in the change in the amount of intake air, and the change in the engine output corresponds to the change in the amount of intake air. In order to perform simulated output control, the virtual filling efficiency ce
The second target indicated mean effective pressure Piobjd based on imgd corresponds to the target load actually required.

The fuel injection amount, injection timing, and ignition timing, which are the high-speed response system, are set based on the first target indicated mean effective pressure Piobj based on the virtual charging efficiency ceimg that has not been simulated.
If the control is performed according to the above, there is a concern that a drastic torque change which cannot be performed under the standard operation condition occurs, which leads to deterioration of drivability (driving feeling) and deterioration of reliability of the drive system. On the other hand, the throttle opening, the control amount of the EGR valve, and the opening of the S valve, which are low-speed response systems, have some delay in changes in the intake air amount, the EGR amount, and the swirl ratio with respect to changes in the target load. That is, there is a tendency that the change of the intake air amount or the like becomes slow with respect to the change of the virtual filling efficiency.

Therefore, the low-speed response system is controlled in accordance with the first target indicated mean effective pressure Piobj based on the virtual filling efficiency ceimg which is not smoothed, so that suction for the change in the target load actually required is performed. While the delay in the change of the air amount or the like is reduced, the high-speed response system uses the second target indicated average effective pressure Piobjd corresponding to the target load actually required.
, The operation timing of each control parameter is adjusted so as to obtain the same good drivability as when the vehicle is operated under the standard operation conditions.

Further, for the high-speed response system, the target air-fuel ratio for controlling the injection amount and the like is obtained by the target air-fuel ratio creating means 62, and the operation mode setting means 63 sets the operation mode modf according to the target air-fuel ratio. The fuel injection amount, the injection timing, and the ignition timing are appropriately controlled in accordance with the state of the actual charging efficiency or the like by performing the control based on the control.

That is, the operation mode setting means 5 shown in FIG.
In FIG. 3, the operation mode mods is the first mode as shown in FIG.
Is set in accordance with the target indicated average effective pressure Piobj and the engine speed ne. However, in the operation mode setting means 63 for controlling the high-speed response system, the target air-fuel ratio creating means 62 for controlling the injection amount and the like is used. The operation mode is set as shown in FIG. 11 according to the target air-fuel ratio afw0 calculated by the calculating means 62a.

In the steady operation state, the regions of the stratified combustion, uniform lean and stoichiometric modes in FIG. 11 correspond to the regions of the stratified combustion, uniform lean and stoichiometric modes in FIG. 8, respectively. In this case, the shift of the operation mode by the setting shown in FIG. 11 is shifted from the shift of the operation mode by the setting shown in FIG. 8 corresponding to the response delay of the change of the actual filling efficiency.

For example, when the target indicated mean effective pressure Piobj increases by operating the accelerator from a state in the stratified combustion region in FIG. 8 and exceeds this region, the low-speed response system operates in the stratified combustion mode in accordance with the setting in FIG. From control to control in uniform lean mode, target air-fuel ratio for intake air amount control
Although the throttle opening tvoobj is changed by changing afwb, there is a response delay in the change of the actual filling efficiency ce corresponding thereto. This actual filling efficiency ce and the target indicated average effective pressure
Based on Piobjd or the virtual filling efficiency ceimgd corresponding to this, the target air-fuel ratio af for controlling the fuel injection amount is adjusted so that the actual load efficiency ce satisfies the target load by the above equation (3).
By determining w0 and setting the operation mode as shown in FIG. 11 according to the target air-fuel ratio afw0, the mode transition according to this setting is performed according to the change in the actual charging efficiency ce.

The fuel injection amount, injection timing and ignition timing are shown in FIG.
The operation is performed based on the setting of the operation mode shown in FIG. 1, so that even if the target air-fuel ratio afwb for controlling the intake air amount is changed to the target air-fuel ratio in the uniform lean mode with the setting shown in FIG. Until the target air-fuel ratio afw0 for control approaches afwb, that is, until the actual charging efficiency ce approaches the target value,
While the fuel injection amount is adjusted according to the actual charging efficiency, the injection timing and the ignition timing are controlled in the stratified combustion mode, that is, stratified combustion by compression stroke injection is performed. Then, after the target air-fuel ratio afw0 for fuel injection amount control approaches afwb, that is, after the actual charging efficiency ce approaches the target value, the injection timing and the like are changed so as to shift to the substantially uniform lean mode. . In this way, the transition of the substantial operation mode is appropriately performed in response to the change in the actual filling efficiency ce.

The arithmetic expression of Equation 3 is obtained by replacing the target charging efficiency ceobj in Equation 8 with the actual charging efficiency ce and replacing afwb with afw0. Therefore, the target air-fuel ratio afw0 In the calculation of (1), the fuel efficiency improvement effect is also taken into account.

In the target air-fuel ratio creating means 62 for controlling the injection amount and the like, the target air-fuel ratio
If the setting means 62c of the target air-fuel ratio afwbd, the calculating means 62c of the deviation dafwb, and the determining means 62d of the final target air-fuel ratio afw are provided in addition to the calculating means 62a of afw0, control of the air-fuel ratio while avoiding an increase in NOx Is done properly.

More specifically, for example, when the mode shifts from the uniform lean mode to the stoichiometric mode, the target air-fuel ratio afw0 calculated by the calculating means 62a gradually becomes richer from the air-fuel ratio in the lean mode in accordance with the change in the charging efficiency. When the deviation dafwb is large in this case, the target air-fuel ratio afw0 is set to the final air-fuel ratio afw, but the target air-fuel ratio afw0 becomes a predetermined value (for example, about 17) or less, and the setting means 62c When the deviation dafwb from the target air-fuel ratio afwbd (stoichiometric air-fuel ratio) in the stoichiometric mode is reduced, the stoichiometric air-fuel ratio that is the target air-fuel ratio afwbd in the stoichiometric mode is set as the final air-fuel ratio.

Therefore, while the target air-fuel ratio for controlling the injection amount and the like is adjusted so that the torque changes as smoothly as possible in accordance with the target load as much as possible, the vehicle may pass through the air-fuel ratio (around 16) where the NOx generation amount increases. Thus, the amount of generated NOx is reduced and emission is kept good.

Note that the specific structure of the device of the present invention is not limited to the above embodiment, but can be variously modified.

For example, FIG. 11 for controlling a high-speed response system
In the setting of the operation mode modf shown in, the stoichiometric mode is set as shown in parentheses in FIG.
In the rich mode, the target air-fuel ratio afwdb set by the setting means 62b is changed from the stoichiometric air-fuel ratio to the rich side as shown in parentheses in FIG. In particular, the air-fuel ratio may be richer than the stoichiometric air-fuel ratio particularly on the high load side and the high rotation side. However, also in this case, it is more convenient for the control in the target air-fuel ratio setting means 54 for controlling the intake air amount to keep the lower limit (rich side limit) of the target air-fuel ratio afwb to the stoichiometric air-fuel ratio.

That is, the target air-fuel ratio for controlling the intake air amount af
When wb is made rich on the high load side, the throttle opening obtained by the above-described calculation based on this is made small to reduce the intake air amount by the amount of the enrichment, and control contrary to the demand to increase the torque is performed. Will be done,
The target air-fuel ratio for controlling the intake air amount is limited to the stoichiometric air-fuel ratio. And even in this case, if the target air-fuel ratio afw0 for controlling the injection amount or the like is made rich, the actual air-fuel ratio is controlled by controlling the fuel injection amount according to the target air-fuel ratio afw0 and the actual charging efficiency ce. Can be rich.

In the above embodiment, the present invention is applied to a direct injection type engine. However, in addition to this, for example, an engine having an injector at an intake port may generate lean swirl while generating swirl at low speed and low load. The present invention can also be applied to a configuration in which the target load is set and the throttle opening, the fuel injection amount, and the like are controlled based on the target load.

In the above embodiment, the motor 27 is used as intake air amount adjusting means which is operated to control the intake air amount in accordance with the operation mode set based on the target load and the target air-fuel ratio. Although the throttle valve 28 is used, while the throttle valve is mechanically linked to the accelerator pedal, a control valve for adjusting the amount of intake air is provided in a bypass passage that bypasses the throttle valve to control this. Is also good. In such a case, a throttle opening sensor that detects the opening of a throttle valve that is mechanically linked to an accelerator pedal is used instead of the accelerator opening sensor 43 as a means for detecting a value corresponding to the accelerator operation amount. It may be.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing an embodiment of the apparatus of the present invention.

FIG. 2 is a block diagram showing a functional configuration of an ECU.

FIG. 3 is a block diagram showing a specific configuration of target load setting means in FIG. 2;

FIG. 4 is a block diagram showing a specific configuration of a throttle opening calculating means and the like in FIG. 2;

FIG. 5 is a block diagram showing a specific configuration of target air-fuel ratio creating means for controlling an injection amount or the like in FIG. 2;

FIG. 6 is a flowchart showing a specific example of control.

FIG. 7 is an explanatory diagram showing a correspondence relationship between an accelerator operation amount, an engine speed, and virtual volume efficiency.

FIG. 8 is an explanatory diagram showing an area setting of an operation mode.

FIGS. 9A, 9B, and 9C are diagrams showing maps and the like set for each operation mode for each of the target air-fuel ratio for controlling the intake air amount, the basic control amount of the EGR valve, and the opening of the S valve. is there.

FIG. 10 is an explanatory diagram showing a correspondence relationship between a target volume efficiency and a throttle opening.

FIG. 11 is an explanatory diagram showing a setting of an operation mode used for calculating a fuel injection amount and the like.

FIGS. 12A, 12B, and 12C are diagrams showing maps and the like set for each operation mode for each of a target air-fuel ratio, an injection timing, and an ignition timing for controlling a fuel injection amount and the like.

FIG. 13 is an explanatory diagram showing a relationship between an air-fuel ratio and fuel efficiency.

FIG. 14 is an explanatory diagram showing the relationship among the air-fuel ratio, the charging efficiency, the fuel injection amount, and the torque when the intake air amount is controlled according to the target air-fuel ratio.

FIG. 15 is an explanatory diagram showing a relationship between a target air-fuel ratio and a fuel flow coefficient.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Engine main body 15 Combustion chamber 22 Injector 28 Throttle valve 50 ECU 52 Target load setting means 53 Operation mode setting means 54 Target air-fuel ratio setting means for intake air amount control 55 Target filling efficiency calculation means 56 Throttle opening degree calculation means 62 Injection amount Target air-fuel ratio creation means for equal control 63 Operation mode setting means 65 Injection amount calculation means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Tetsuno 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Kiyotaka Mamiya 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Shares Inside the company (72) Inventor Hirofumi Nishimura 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (7)

[Claims] An intake air control device for an engine for setting a target load according to an operation state and controlling an intake air amount of the engine based on the target load, wherein the intake air amount adjusting means adjusts an intake air amount. And an accelerator operation amount detecting means for detecting an accelerator operation amount or a value corresponding thereto, a rotational speed detecting means for detecting an engine rotational speed, and a method for making the air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operation region. Target air-fuel ratio setting means for setting a target air-fuel ratio according to the operating state, and a charging efficiency or a value corresponding to the target load corresponding to the target load assuming a state of operating at the stoichiometric air-fuel ratio as an intake charging state virtual value. From the virtual value calculating means to be determined and the intake air filling state virtual value, the excess air ratio of the target air-fuel ratio and the fuel efficiency improvement effect with respect to the stoichiometric air-fuel ratio when the target air-fuel ratio is lean are calculated. An intake control device for an engine, comprising: target value calculating means for obtaining an intake charge state target value in consideration of the target value; and means for controlling the intake air amount adjusting means according to the intake charge state target value. 2. The virtual value calculating means obtains a virtual charging efficiency which is a charging efficiency corresponding to a target load when a standard operation state at a stoichiometric air-fuel ratio is assumed. 2. The intake control system for an engine according to claim 1, wherein a target charging efficiency as a state target value is obtained. 3. The target value calculation means calculates a target charging efficiency by multiplying the virtual charging efficiency by an excess air ratio of a target air-fuel ratio and a coefficient corresponding to a fuel efficiency improvement ratio with respect to a stoichiometric air-fuel ratio. 3. The intake control device for an engine according to claim 2, wherein: 4. The means for controlling the intake air amount adjusting means includes:
A target volume efficiency is calculated based on a target charging efficiency by taking into account a correction according to an intake density, and a control amount of intake air amount adjusting means is determined according to the target volume efficiency. Item 4. An intake control device for an engine according to item 2 or 3. 5. The means for controlling the intake air amount adjusting means includes:
The control amount of the intake air amount adjusting means determined according to the intake charge state target value is changed according to the operation time and the stop time of the exhaust gas recirculation device that recirculates exhaust gas to the intake system. The intake control device for an engine according to any one of claims 1 to 4. 6. A target air-fuel ratio setting means for controlling a fuel injection amount, separately from a target air-fuel ratio setting means for controlling an intake air amount, and set by the target air-fuel ratio setting means for controlling a fuel injection amount. Means for controlling the amount of fuel injected from the injector in accordance with the target air-fuel ratio and the actual charging efficiency.The target air-fuel ratio setting means for controlling the intake air amount is calculated based on the air-fuel ratio leaner than the stoichiometric air-fuel ratio. The target air-fuel ratio is set in the range up to the air-fuel ratio according to the operating condition, and the target air-fuel ratio setting means for controlling the fuel injection amount operates the target air-fuel ratio in the range from the lean side to the rich side of the stoichiometric air-fuel ratio. The engine intake control device according to any one of claims 1 to 5, wherein the setting is made in accordance with a state. 7. A stratified combustion state in which an injector for directly injecting fuel into a combustion chamber is provided and fuel is injected from the injector in a compression stroke at least in a low-load low-speed range, and an air-fuel ratio is theoretically in this stratified combustion state. 7. The intake control device for an engine according to claim 1, wherein the air-fuel ratio is set to be leaner than the air-fuel ratio.