JP2000282915A - Control device for direct injection engine of spark ignition type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote refreshing of a catalyst while suppressing deterioration of the fuel consumption in a spark ignition type direct injection engine provided with a catalyst of NOx absorbing type in an exhaust passage, being operated by changing-over between the stratified combustion mode and uniform combustion mode, and switched to the rich operation forcedly, when the NOx absorbing amount of the catalyst increases. SOLUTION: When an engine 1 is switched forcedly into rich operation, the closing motion of a throttle valve, in association with changing-over from the stratified combustion mode to the uniform combustion mode, is delayed to temporarily generate a condition in which the oxygen concentration in the exhaust gas is low and the flow rate of the exhaust gas is sufficiently high (SA15 and 16). The amount of fuel injection is increased, so that the excess air ratio in the combustion chamber does not become λ=1 to 1.3. Similar control is conducted for promoting the release of NOx from the catalyst, when the engine is in acceleration operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of disposing an NOx absorbing catalyst for absorbing nitrogen oxides (NOx) in exhaust gas in an oxygen-excess atmosphere in an exhaust passage of an engine. The present invention relates to a control apparatus for a spark ignition type direct injection engine capable of removing NOx.

[0002]

2. Description of the Related Art Conventionally, this type of engine has been controlled by controlling the air-fuel ratio of a combustion chamber to a predetermined lean state (for example, A / F ≧ 20) when the engine is in a low load range. At the same time, the NOx in the exhaust gas, which becomes an oxygen-excess atmosphere, is absorbed and removed by the NOx absorption catalyst, while the NOx absorption amount of the NOx absorption catalyst becomes excessive and the absorption performance is reduced. The air-fuel ratio of the combustion chamber of the engine is forcibly switched to a substantially stoichiometric air-fuel ratio or a state richer than the stoichiometric air-fuel ratio.
(Hereinafter, also referred to as catalyst refresh) is known.

[0003] Further, in the system disclosed in Japanese Patent Application Laid-Open No. 10-274085, the above NOx absorption catalyst oxidizes NOx in exhaust gas in an oxygen-excess atmosphere and absorbs it as nitrate. And reacts the absorbed nitrate with carbon monoxide (CO) in the exhaust gas to replace NO.
Focusing on the property of releasing x, NOx
When releasing NOx from the absorption catalyst, the CO concentration in the exhaust gas is increased by lowering the oxygen concentration in the exhaust gas and injecting additional fuel in the expansion stroke and the exhaust stroke of the cylinder to re-burn, thereby increasing the NOx concentration in the exhaust gas. To promote the emission and reduction purification.

[0004]

However, according to the conventional control device, the oxygen concentration in the exhaust gas is reduced,
Even though the CO concentration can be increased, there is a problem that the refresh of the catalyst cannot be sufficiently promoted because the flow rate of the exhaust gas flowing through the NOx absorption catalyst itself is small. That is, in the case of a general vehicle-mounted engine, for example, when the air-fuel ratio is forcibly changed to the rich side in order to refresh the NOx absorption catalyst in a low load region where the air-fuel ratio of the combustion chamber is lean, Since it is necessary to close the throttle valve and reduce the amount of intake air in order to suppress an increase in engine output, the exhaust flow rate is considerably reduced.

In consideration of the general traffic situation in Japan, the time during which the on-vehicle engine is in an operation state of medium to high load or higher is short. At this time, although the opening of the throttle valve becomes sufficiently large, the engine speed is increased. Does not become so high, and eventually the amount of exhaust gas flowing through the catalyst does not increase.

That is, when the conventional control device is applied to an on-vehicle engine, the air-fuel ratio of the combustion chamber is made rich and the exhaust gas flow cannot be sufficiently ensured during operation of the engine. In order to effectively promote this, it is necessary to increase the refresh frequency or control the air-fuel ratio at the time of refreshing to an excessively rich state, which causes a problem that fuel efficiency is deteriorated.

Further, the conventional example (Japanese Patent Laid-Open No. 10-2740)
No. 85, the additional fuel is injected during the expansion stroke and the exhaust stroke of the cylinder, since the additional fuel hardly contributes to the output of the engine.
There is a possibility that fuel efficiency may be significantly deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to pay attention to the importance of ensuring a sufficient exhaust flow rate at the time of refreshing a NOx absorption catalyst, and to examine the combustion of an engine. It is an object of the present invention to devise a control procedure for switching the air-fuel ratio of a chamber from a lean state to a rich state so as to promote catalyst refreshing while suppressing deterioration of fuel efficiency.

[0009]

According to a first aspect of the present invention, an air-fuel ratio of a combustion chamber of an engine is switched from a lean state to a rich state in order to refresh the NOx absorption catalyst. Sometimes, the intake charge of the combustion chamber of the engine is reduced more slowly than usual.

Specifically, according to the first aspect of the present invention, as shown in FIG. 1, fuel is directly supplied to the in-cylinder combustion chamber 4 of the engine 1.
A fuel injection valve 7 for injecting and supplying is arranged in an exhaust passage 22 communicating with the combustion chamber 4, and absorbs NOx in an oxygen-excess atmosphere in which the oxygen concentration in the exhaust gas is high, while reducing the absorbed NOx by decreasing the oxygen concentration. NOx absorption catalyst 2 that releases CO2
5 and controlling the air-fuel ratio of the combustion chamber 4 in accordance with the operating state of the engine 1 such that the air-fuel ratio becomes a lean state with an excess air ratio of 1.3 or more or a rich state richer than that. At the same time, N
When releasing Ox, it is assumed that the control device A of the spark ignition type direct injection engine includes the air-fuel ratio control means 40a for forcibly switching the air-fuel ratio of the combustion chamber 4 to the rich state.

A charge amount adjusting means 13 for adjusting an intake charge amount of the combustion chamber 4 is provided, and the air-fuel ratio control means 40a operates when the air-fuel ratio of the combustion chamber 4 is switched from a lean state to a rich state. And a filling amount control means 40b for controlling the filling amount adjusting means 13 so that the intake filling amount of the combustion chamber 4 is reduced.
When the air-fuel ratio of the combustion chamber 4 is forcibly switched to the rich state by the air-fuel ratio control means 40a, the operation of the charge amount adjusting means 13 is delayed.

With the above configuration, the combustion chamber 4 of the engine 1
When the air-fuel ratio of the engine 1 is switched from the lean state to the rich state according to the operating state of the engine 1, the charge control means 40b controls the charge control means 13 so that the charge of the intake air in the combustion chamber 4 is rapidly reduced. Therefore, fluctuations in engine output due to switching of the air-fuel ratio can be suppressed. on the other hand,
When the air-fuel ratio is forcibly switched to the rich state in order to refresh the NOx absorption catalyst 25, the operation of the charging amount adjusting means 13 is delayed. The state is temporarily switched to the rich state, and the state where the oxygen concentration in the exhaust is low and the exhaust flow rate is large is created. This effectively promotes the release of NOx from the NOx absorption catalyst.

In other words, the transition of the engine 1 from the lean operation state to the rich operation state can be utilized to effectively promote the catalyst refreshing, so that the catalyst refreshing frequency can be reduced accordingly. The period can be shortened, so that the catalyst can be refreshed while suppressing the deterioration of the fuel efficiency.

According to a second aspect of the present invention, when the air-fuel ratio of the combustion chamber of the engine is controlled to a lean state by the air-fuel ratio control means of the first aspect, the fuel is injected into the stratified combustion state by the fuel injection valve. Injection timing control means for injecting during the compression stroke of the cylinder as described above, the air-fuel ratio control means,
When the operating time of the engine in the stratified combustion state exceeds a set time, the air-fuel ratio of the combustion chamber is forcibly switched to a rich state.

As a result, if the operation of the engine in the stratified combustion state continues for a long time, the NOx absorption amount of the NOx absorption catalyst becomes excessive and its absorption performance decreases. By forcibly switching the air-fuel ratio of the combustion chamber to the rich state, the NOx absorption catalyst can be refreshed. Therefore, the NOx absorption performance of the catalyst can be stably maintained.

According to a third aspect of the present invention, when the air-fuel ratio of the combustion chamber of the engine is forcibly switched to a rich state, the air-fuel ratio control means according to the first or second aspect of the invention is provided. Injection amount control means for increasing the fuel injection amount so that the excess air ratio becomes smaller than 1.1, and when the fuel injection amount is increased by the injection amount control means, the ignition timing is delayed. A configuration is provided in which ignition timing correction means for correcting the corner side is provided.

With this configuration, when the air-fuel ratio of the combustion chamber of the engine is forcibly switched to the rich state for refreshing the NOx absorption catalyst, the fuel injection amount is increased by the injection amount control means, so that the lean state is maintained. The excess air ratio of the combustion chamber, which is 1.3 or more, can be immediately reduced to a state of less than 1.1. As a result, while the exhaust gas flow rate is sufficiently high, the oxygen concentration in the exhaust gas is reduced,
Refreshing of the x-absorbing catalyst can be sufficiently promoted. In addition, it is possible to avoid that the air-fuel ratio of the combustion chamber becomes an active state of NOx generation. Furthermore, the ignition timing is corrected by the ignition timing correction means to the retard side, and the increase in the engine output due to the increase in the fuel is offset, so that the fluctuation in the engine output can be reduced.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the charging amount control means operates the charging amount adjusting means when the excess air ratio λ of the combustion chamber of the engine is 1.1 <λ <1.3. Is controlled to be faster than when λ <1.1. As a result, when the excess air ratio λ of the combustion chamber of the engine is λ> 1.1, the operation of the charging amount adjusting means is relatively accelerated, and the generation of NOx accompanying the combustion is suppressed as in the third aspect. Is done. In addition, fuel consumption deterioration due to the fuel increase correction and the ignition timing retard correction is reduced.

According to a fifth aspect of the present invention, the air-fuel ratio control means in the first aspect of the present invention sets the air-fuel ratio of the combustion chamber of the engine to A / F =
It is assumed that the control is made to be 15 to 16. And
Exhaust recirculation means for recirculating a part of the exhaust gas to the intake system of the engine, and, when the air-fuel ratio of the combustion chamber of the engine is in a lean state, the exhaust gas recirculation means recirculates the exhaust gas. And an exhaust gas recirculation control means for recirculating exhaust gas so that the exhaust gas recirculation rate at this time is equal to or higher than the exhaust gas recirculation rate in the lean state.

With this configuration, even when the air-fuel ratio of the combustion chamber of the engine is forcibly made rich to release NOx, the air-fuel ratio is slightly leaner than the stoichiometric air-fuel ratio. Is reduced. At this time, by controlling the exhaust gas recirculation control means, a large amount of exhaust gas is recirculated so that the exhaust gas recirculation rate becomes higher than that in the lean state, whereby the generation of NOx can be sufficiently suppressed. As a result, the concentration ratio of the reducing agent component such as CO in the exhaust gas to NOx is increased, and the NOx is reduced even in the above-described slightly lean state.
Refreshing of the absorption catalyst can be promoted.

According to a sixth aspect of the present invention, the exhaust gas recirculation means according to the fifth aspect of the present invention comprises an exhaust gas recirculation passage communicating the intake passage and the exhaust gas passage of the engine, and an exhaust gas recirculation amount for adjusting the exhaust gas recirculation amount of the exhaust gas recirculation passage. The exhaust gas recirculation control means comprises an adjustment valve, and when the air-fuel ratio of the combustion chamber of the engine is forcibly switched to the rich state, the exhaust gas recirculation control means keeps the opening of the exhaust gas recirculation amount adjustment valve. This makes it possible to easily recirculate the exhaust gas in the forced rich state for releasing NOx so that the exhaust gas recirculation rate becomes higher than that in the lean state.

Next, according to the second solution of the present invention, when the engine is operated by switching between the stratified combustion state and the uniform combustion state, the intake charge of the combustion chamber of the engine becomes considerably large in the stratified combustion state. Focusing on this, when shifting from the stratified combustion state to the uniform combustion state, by reducing the intake charge of the combustion chamber of the engine more slowly than usual, the exhaust gas flow rate is sufficiently ensured and the catalyst is refreshed. I urged it.

More specifically, according to the invention of claim 7, a fuel injection valve for directly injecting fuel into the in-cylinder combustion chamber of the engine and an exhaust passage communicating with the combustion chamber are provided. While absorbing NOx in an oxygen-rich atmosphere having a high concentration, a NOx absorption catalyst that releases the absorbed NOx by decreasing the oxygen concentration,
When the engine is in a predetermined low load region, injection is performed in the compression stroke of the cylinder so as to be in a stratified combustion state, while injection is performed in the intake stroke of the cylinder so as to be in a uniform combustion state on a higher load side than the low load region. And a control device for a spark ignition type direct injection engine including an injection timing control means for causing the control to be performed.

The charge amount adjusting means for adjusting the charge amount of the intake air in the combustion chamber, and the air-fuel ratio of the combustion chamber of the engine are adjusted so that the excess air ratio is in a lean state of 1.3 or more in the stratified combustion state. On the other hand, in the uniform combustion state, air-fuel ratio control means for switching and controlling such that the excess air ratio becomes a rich state of 1 or less, and NOx from the NOx absorption catalyst
Determination means for determining whether or not the vehicle is in a state of promoting emission; and wherein the air-fuel ratio control means reduces the amount of intake air charged into the combustion chamber when the engine shifts from the stratified combustion state to the uniform combustion state. And a filling amount control means for controlling the filling amount adjusting means. When the judging means judges that the NOx release is promoted, the filling amount control means makes the filling amount larger than the non-promoted state. The operation of the adjusting means shall be delayed.

With the above configuration, when the engine shifts from the low load region in the stratified combustion state to the higher load region, the combustion state of the engine is switched from the stratified combustion state to the uniform combustion state, and the combustion state is changed. The air-fuel ratio of the chamber is switched from the lean state to the rich state by the air-fuel ratio control means. At this time, usually, the amount of intake air in the combustion chamber is rapidly reduced by the control of the charge amount adjusting means by the charge amount control means, so that fluctuations in the engine output due to switching of the combustion state and the air-fuel ratio are suppressed.

On the other hand, if the determination means determines that the NOx emission promoting state is in effect, the operation of the charge amount adjusting means is delayed, so that the air-fuel ratio becomes rich before the intake charge amount of the combustion chamber decreases so much. The state is temporarily switched to a state where the oxygen concentration in the exhaust gas is low and the exhaust gas flow rate is large, and the release of NOx from the NOx absorption catalyst is effectively promoted. That is, when the engine shifts from the low-load region to the middle-high load region, a state where the exhaust gas flow rate is increased transiently can be created, and the refresh of the catalyst can be effectively promoted.

Further, since a change in the operating state of the engine is used to create a state in which the exhaust flow rate is large when shifting to the high load range, even if the engine output fluctuates accordingly, The driving feeling does not deteriorate significantly.

According to an eighth aspect of the present invention, the air-fuel ratio control means in the seventh aspect of the present invention determines when the determination means determines that the NOx release is promoted, and when the engine shifts from the stratified combustion state to the uniform combustion state. It is assumed that the vehicle has an injection amount control means for increasing the fuel injection amount from the fuel injection valve so that the air-fuel ratio of the combustion chamber of the engine becomes rich.

With this configuration, when the engine shifts from the stratified combustion state to the uniform combustion state, if the NOx release from the NOx absorption catalyst is promoted, the fuel injection amount is increased by the injection amount control means. The excess air ratio in the combustion chamber of the engine is immediately changed from a lean state of 1.3 or more to a rich state of 1 or less. As a result, while the exhaust gas flow rate is sufficiently large, the oxygen concentration in the exhaust gas is reduced, and NOx
Refreshing of the absorption catalyst can be sufficiently promoted, and the air-fuel ratio of the combustion chamber can be prevented from becoming active in the generation of NOx.

According to a ninth aspect of the present invention, the injection amount control means in the eighth aspect of the present invention increases the fuel injection amount before the excess air ratio in the combustion chamber becomes smaller than 1.3 due to a decrease in the intake charge. It shall be. That is, in general, the generation of NOx due to combustion is most active when the excess air ratio is in the range of λ = 1 to 1.3. Therefore, according to the present invention, the excess air ratio in the combustion chamber of the engine is smaller than 1.3. The fuel injection amount is increased before switching to a rich state, so that the fuel injection amount is switched to a rich state.
The effect of the invention of the invention can be sufficiently obtained.

According to a tenth aspect of the present invention, the air-fuel ratio control means according to the seventh aspect of the present invention is arranged such that when the engine shifts from the stratified combustion state to the uniform combustion state, the air-fuel ratio of the combustion chamber of the engine becomes rich. The injection amount control means increases the fuel injection amount from the fuel injection valve. When the determination means determines that the NOx release is promoted, the fuel injection control is performed earlier than the non-promotion state. The amount is increased.

In this configuration, when the engine shifts from the stratified combustion state to the uniform combustion state, if the NOx release from the NOx absorption catalyst is promoted, the fuel injection amount is increased relatively quickly by the injection amount control means. Therefore, similarly to the invention of claim 8, the generation of NOx accompanying combustion is suppressed,
In addition, refreshing of the NOx absorption catalyst can be sufficiently promoted. On the other hand, if the emission of NOx is not promoted, the increase in the fuel injection amount is relatively delayed, so that the air-fuel ratio of the combustion chamber is switched to the rich state after the intake charge decreases. Thus, it is possible to reduce fluctuations in output and deterioration in fuel efficiency due to switching of the combustion state of the engine.

In the eleventh aspect of the present invention, the injection amount control means in the tenth aspect of the present invention provides an excess air ratio of 1.3 in the combustion chamber of the engine when the determination means determines that the NOx release is promoted. In this case, the fuel injection amount is increased when the fuel injection amount is increased, and when the non-promotion state is determined, the fuel injection amount is increased when the excess air ratio becomes 1.2. According to this configuration, the function and effect of the tenth aspect can be sufficiently obtained.

According to a twelfth aspect of the present invention, in any one of the eighth to eleventh aspects, when the fuel injection amount is increased by the injection amount control means, the ignition timing is corrected to the retard side. A means is provided. With this configuration, the ignition timing is corrected to the retard side by the ignition timing correction means, so that the increase in the engine output due to the increase in the fuel is offset, and the fluctuation in the engine output can be reduced.

According to a thirteenth aspect of the present invention, the injection timing control means in the seventh aspect of the present invention determines that the NOx emission promoting state is determined by the determining means and that the engine shifts from the stratified combustion state to the uniform combustion state. The fuel injection valve injects the fuel in two parts: early injection from the intake stroke to the compression stroke of the cylinder, and late injection in the compression stroke.

With this configuration, when the engine shifts from the stratified combustion state to the uniform combustion state, if the release of NOx from the NOx absorption catalyst is promoted, the fuel is compressed from the intake stroke by the control of the injection timing control means. The injection is divided into two parts, an early injection during the stroke and a late injection during the compression stroke. The fuel thus injected in two parts forms a rich air-fuel mixture around the spark plug in the combustion chamber of the engine and a lean air-fuel mixture around the spark plug. Intermediate combustion state (hereinafter,
Combustion in a weakly stratified state). In this weakly stratified combustion, the amount of CO emission greatly increases.
Refreshing of the x-absorbing catalyst can be further promoted.

According to a fourteenth aspect of the present invention, the determination means according to the seventh aspect of the present invention determines that when the engine is in a rapid acceleration state equal to or greater than a predetermined value, it is determined that the NOx release catalyst is accelerating the release of NOx. I do. As a result, the engine output rapidly increases during the rapid acceleration operation of the engine. If the NOx release from the NOx absorption catalyst is promoted at this time, the engine output will be increased during the transition from the stratified combustion state to the uniform combustion state. Even if it fluctuates, the adverse effect on the driving feeling can be relatively reduced.

According to a fifteenth aspect of the present invention, the exhaust gas recirculation means for recirculating a part of the exhaust gas to the intake system of the engine according to the seventh aspect of the present invention, and Exhaust recirculation control means for recirculating exhaust gas by the exhaust gas recirculation means when the engine is in the predetermined medium load area, wherein the fuel injection valve controls fuel injection by the fuel injection valve when the engine is in the medium load area. Is divided into two during the intake stroke of the cylinder and the injection is performed, and the determination means determines that the time when the engine shifts from the low load region to the medium load region is a state of promoting NOx release from the NOx absorption catalyst. I do.

With this configuration, when the engine is in a low load region in a stratified combustion state or in a predetermined medium load region following the low load region, that is, when the engine is in a normal operation region of the vehicle-mounted engine, the exhaust gas recirculation control means is provided. The exhaust gas is recirculated by the control of (1), and NOx generation accompanying combustion is suppressed. In particular, in the medium load region, the fuel is injected in two parts during the intake stroke of the cylinder under the control of the injection timing control means, so that the degree of uniformity of the air-fuel mixture is increased and the combustion stability is improved. Even if relatively high, a sufficient amount of exhaust gas can be recirculated.

When the engine shifts from the low-load region to the medium-load region, the exhaust gas naturally continues to recirculate during the shift, and the NOx concentration in the exhaust gas decreases. NOx emission can be further enhanced.

According to a sixteenth aspect of the present invention, the exhaust gas recirculation control means according to the fifteenth aspect of the present invention provides the exhaust gas recirculation rate of 3 when the engine shifts from a stratified combustion state to a uniform combustion state.
The exhaust gas recirculation means is controlled so as to be 0% or more.

As described above, by controlling the exhaust gas recirculation control means, a large amount of exhaust gas is recirculated so that the recirculation rate of the exhaust gas becomes 30% or more.
The generation of Ox can be sufficiently suppressed, and the concentrations of CO and HC in the exhaust gas can be increased. Therefore, the function and effect of the invention of claim 15 can be sufficiently obtained. The recirculation rate of the exhaust gas is represented by the following equation based on the concentration of carbon dioxide (CO2).

[0043]

(Equation 1)

According to a seventeenth aspect of the present invention, the determination means according to the seventh aspect of the present invention determines whether the engine is in an idling operation state and an acceleration operation state by the NOx absorption catalyst from the NOx absorption catalyst.
It shall be determined that the release is promoted. As a result, when the engine is accelerated from the idling operation state, the operation state of the engine is frequently switched to the uniform combustion state.
By promoting NOx release from the Ox absorption catalyst,
Refreshing of the catalyst can be sufficiently promoted.

According to an eighteenth aspect of the present invention, in the invention of the seventh aspect, a transition predicting means for predicting a transition from a stratified combustion state to a uniform combustion state based on a change in the load state of the engine, and Is predicted to shift to a uniform combustion state, and when the determination means determines that the NOx emission is not promoted, the charging amount adjustment means reduces the intake charge of the combustion chamber before the engine shifts to the uniform combustion state. And a filling amount correction control means to be provided.

That is, generally, the adjustment of the amount of intake air in the combustion chamber by the charge amount adjusting means involves a large response delay due to the flow of intake air into the combustion chamber. Therefore, when the engine shifts from the stratified combustion state to the uniform combustion state, the amount of intake air in the combustion chamber cannot be reduced immediately, and there is a problem that the engine output tends to fluctuate.
Therefore, according to the present invention, when NOx emission from the NOx absorption catalyst is not promoted, the transition predicting means predicts that the engine will transition from the stratified combustion state to the uniform combustion state, and the engine actually transitions to the uniform combustion state. By reducing the amount of intake air in the combustion chamber beforehand, fluctuations in engine output due to a response delay in intake air amount control can be reduced.

According to a nineteenth aspect of the present invention, the charging amount adjusting means in any one of the first and seventh aspects is a throttle valve disposed in an intake passage of the engine, and the charging amount controlling means is at least When the engine is in a steady operation state, the opening of the throttle valve is controlled according to the accelerator operation amount and the engine speed.
Thus, the configurations of the filling amount adjusting unit and the filling amount controlling unit are embodied.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Overall Configuration of Control Apparatus) FIG. 2 shows the overall configuration of a control apparatus A for a spark ignition type direct injection engine according to Embodiment 1 of the present invention. It is a cylinder engine. The engine 1 has a plurality of cylinders 2, 2,... (Only one is shown), and a piston 3 is inserted into each cylinder 2 in a reciprocating manner, and the piston 3 burns into the cylinder 2. Room 4 is partitioned. An ignition plug 6 connected to an ignition circuit 5 is attached to a position on the cylinder axis on the upper wall of the combustion chamber 4 so as to face the combustion chamber 4. In addition, the side wall of the combustion chamber 4 is provided at a position where it does not interfere with the moving piston 3.
(Fuel injection valve) 7 is mounted so as to directly inject and supply fuel to the fuel cell.

Although not shown, the injector 7
A high-pressure fuel pump, a fuel supply circuit having a pressure regulator and the like are connected, and while the fuel from the fuel tank is adjusted to an appropriate pressure by the fuel supply circuit,
The power is supplied to the injector 7. Further, a fuel pressure sensor 8 for detecting the fuel pressure is provided.
When fuel is injected by the injector 7 after the middle stage of the compression stroke of the cylinder 2, the fuel spray is trapped in a cavity (not shown) formed in the top surface of the piston 3, A relatively thick mixture is formed. On the other hand, when fuel is injected by the injector 7 in the intake stroke of the cylinder 2, the fuel spray diffuses into the combustion chamber 4 and mixes with the intake air (air) to form a uniform mixture in the combustion chamber 4. You.

The combustion chamber 4 is connected to an intake passage 10 via an intake valve 9 through an intake port (not shown).
The intake passage 10 supplies the intake air filtered by the air cleaner 11 to the combustion chamber 4 of the engine 1, and detects the amount of intake air taken into the engine 1 in order from the upstream side to the downstream side. A wire type air flow sensor 12, an electric throttle valve (filling amount adjusting means) 13 for restricting the intake passage 10, and a surge tank 14 are provided. The electric throttle valve 13 is not mechanically connected to an accelerator pedal (not shown),
It is opened and closed by being driven by a motor 15. Further, a throttle opening sensor 16 for detecting the opening of the throttle valve 13 and an intake pressure sensor 17 for detecting the intake pressure in the surge tank 14 are provided.

The intake passage 10 on the downstream side of the surge tank 14 is an independent passage branching for each cylinder 2, and the downstream end of each independent passage is further branched into two and connected to the intake ports. The swirl control valve 18 is provided on one of the branches. The swirl control valve 18 is driven by an actuator 19 to open and close. When the swirl control valve 18 is closed, intake air is supplied to the combustion chamber 4 only from the other branch passage, and strong intake air is supplied to the combustion chamber 4. While swirl is generated, intake swirl is reduced as the swirl control valve 18 opens. A swirl control valve opening sensor 2 for detecting the opening of the swirl control valve 18
0 is provided.

In FIG. 2, reference numeral 22 denotes an exhaust passage for discharging combustion gas from the combustion chamber 4. The upstream end of the exhaust passage 22 branches off for each cylinder 2 and is connected to the combustion chamber via an exhaust valve (not shown) through an exhaust valve 23. 4 is connected. An O 2 sensor 24 for detecting the oxygen concentration in the exhaust gas and a catalyst 25 for purifying the exhaust gas are arranged in this exhaust passage 22 in order from the upstream side to the downstream side.
Reference numeral 4 is used to detect the air-fuel ratio based on the oxygen concentration in the exhaust gas, and a so-called lambda O2 sensor whose output is inverted in a stepwise manner at the stoichiometric air-fuel ratio is used. Further, the catalyst 25 absorbs NOx in an oxygen-excess atmosphere in which the oxygen concentration in the exhaust gas is high (for example, 4% or more), and releases the NOx absorbed by the decrease in the oxygen concentration and reduces and purifies the NOx. Particularly, in the vicinity of the stoichiometric air-fuel ratio, it exhibits high exhaust gas purification performance similar to that of a so-called three-way catalyst.

As shown in FIG. 3, the catalyst 25 has a cordierite honeycomb carrier 25a, and the inner catalyst layer 2 is provided on the wall surface of each through hole formed in the carrier 25a.
5b and an outer catalyst layer 25c formed thereon. Platinum P is applied to the inner catalyst layer 25b.
A noble metal such as t and barium Ba as a NOx absorbent are supported on a porous material such as alumina or ceria as a support material. On the other hand, in the outer catalyst layer 25c, Pt as a catalyst metal and rhodium Rh and Ba are supported as a support material with zeolite as a porous material.

In place of the barium, at least one of other alkaline earth metals, alkali metals such as sodium Na, and rare earth metals may be used. Further, zeolite may be used as a support material of the inner catalyst layer 25b, and in that case, alumina or ceria may be used as a support material of the outer catalyst layer 25c. Further, as the catalyst 25, although not shown, a catalyst layer in which alumina or ceria is supported as a support material is formed on a wall surface of the support, and the support material includes a noble metal such as platinum Pt, rhodium Rh, and palladium Pd.
A one-layer coat type supporting an alkali metal such as potassium K or an alkaline earth metal such as barium Ba may be used.

An upstream end of an EGR passage (exhaust gas recirculation passage) 26 is branched and connected to the exhaust passage 22 upstream of the O 2 sensor 24, and a downstream end of the EGR passage 26 is connected to the throttle valve 13 and the surge tank 14. Intake passage 1 between
0, and a part of the exhaust gas is returned to the intake system. An EGR valve (exhaust gas recirculation amount adjusting valve) 27 whose opening can be adjusted is disposed near the downstream end of the EGR passage 26, and the amount of exhaust gas recirculated by the EGR passage 26 (hereinafter, also referred to as EGR amount). ) To adjust. The EGR passage 26 and the EGR valve 27 constitute an exhaust gas recirculation means.
A lift sensor 28 for detecting a lift amount of the valve 27 is provided.

The ignition circuit 5 of the ignition plug 6, the injector 7, the drive motor 15 for the electric throttle valve 13, the actuator 19 for the swirl control valve 18, the electric EGR
The operation of the valve 27 and the like is controlled by a control unit 40 (hereinafter, referred to as an ECU). On the other hand, the ECU 40 includes the air flow sensor 12,
The output signals of the throttle opening sensor 16, the intake pressure sensor 17, the swirl control valve opening sensor 20, the O2 sensor 24, and the lift sensor 28 of the EGR valve 27 are input, and in addition, the cooling water temperature of the engine 1 ( Engine water temperature)
, An intake air temperature sensor 31 for detecting the intake air temperature, an atmospheric pressure sensor 32 for detecting the atmospheric pressure, a rotational speed sensor 33 for detecting the engine speed, and an accelerator opening for detecting the opening of the accelerator pedal Each output signal of the sensor 34 is input.

(Outline of Engine Control) The engine 1 according to this embodiment has an injector 7 according to the operating state.
, The fuel injection timing and the air-fuel ratio are switched to operate in different combustion states. That is, as shown in FIG. 4, in the warm state of the engine 1, the predetermined region (a) on the low-load low-rotation side is a stratified combustion region, and the injector 7 injects fuel after the middle stage of the compression stroke,
The combustion mode is a combustion mode in which the mixture is burned in a stratified state in which the air-fuel mixture is unevenly distributed in the vicinity of the ignition plug 6. In the stratified combustion mode, the throttle valve 1 is used to reduce the pump loss of the engine 1.
3, the average air-fuel ratio of the combustion chamber 4 becomes significantly lean (for example, A / F = about 30).

On the other hand, other operating regions (b) and (c)
(D) and (e) are all defined as a uniform combustion region, in which fuel is injected by the injector 7 in the intake stroke and sufficiently mixed with the intake air to form a uniform mixture in the combustion chamber 4 before combustion. The combustion mode is set. Area of this (b)
(C) In (d), the fuel injection amount and the throttle opening are controlled so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 4 becomes substantially the stoichiometric air-fuel ratio (A / F = 14.7, λ = 1). In particular, in a medium-load medium rotation region (C) of the engine 1, fuel is split into two in the first half and the second half of the intake stroke by the injector 7 so as to be injected.

In the high-load or high-speed operation region (e) in the uniform combustion region, the air-fuel ratio is made richer than the stoichiometric air-fuel ratio (for example, A / F = 13 to 14) to increase the high output. (Hereinafter referred to as enrichment mode). Note that, when the engine is cold, although not shown, the entire operation region of the engine 1 is set to a uniform combustion region in order to secure combustion stability.

Further, in the region indicated by hatching in the figure, the EGR valve 27 is opened to recirculate a part of the exhaust gas to the intake passage 10 through the EGR passage 26. The exhaust gas recirculation rate in (a) is set to about 40% at the maximum. Due to this large amount of exhaust gas recirculation, the heat capacity of the combustion chamber 4 increases, and the generation of NOx due to combustion is sufficiently suppressed. Further, in the region (c), since the fuel-intake mixing is improved by the divided injection of the fuel and the combustion stability is improved, the engine load is higher than that in the region (a). Also, a sufficient amount of exhaust gas can be recirculated.

FIG. 5 is a functional block diagram showing basic processing of engine control in the ECU 40. That is, the ECU 40 includes the intake density state detecting means 41 for detecting the intake density state based on the signals from the intake air temperature sensor 31 and the atmospheric pressure sensor 32, and converts the signals from the rotation speed sensor 33 and the accelerator opening sensor 34 into signals. Based on
Further, a target load setting means 42 for setting a target load of the engine 1 in consideration of the intake air density state is provided.

In the target load setting means 42, as shown in FIG. 6, first, the virtual volume efficiency calculating section 42a calculates the virtual volume efficiency veimg based on the accelerator opening accel and the engine speed ne. Specifically, the accelerator opening degree accel and the engine speed ne are determined by a bench test or the like in advance so that the required output performance can be obtained under standard operating conditions in which the air-fuel ratio is kept at the stoichiometric air-fuel ratio under standard atmospheric conditions. A correspondence relationship with the virtual volume efficiency veimg is obtained, and this correspondence relationship is stored in the memory of the ECU 40 as a map. From this map, the virtual volumetric efficiency v corresponding to the actual accelerator opening degree accel and the engine speed ne is obtained.
eimg is read. The correspondence between the accelerator opening accel and the engine speed ne and the virtual volumetric efficiency veimg is, for example, as shown in FIG. It increases as the accelerator opening accel increases, and increases as the engine speed ne decreases.

Subsequently, the virtual filling efficiency calculating section 42b calculates the virtual filling efficiency ceimg by adding the virtual volume efficiency veimg determined as described above to the intake density determined by the intake density state detecting means 41. I do. The virtual charging efficiency ceimg is a charging efficiency (intake charging amount) corresponding to the output required of the engine 1 under the standard operating conditions. , The following temporary delay correction is performed.
That is, delay processing is performed on the virtual filling efficiency ceimg.

[0064]

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).

Then, based on the virtual filling efficiency ceimg calculated by the virtual filling efficiency calculating section 42b or the virtual filling efficiency ceimgd delayed by the smoothing processing section 42c, the target load calculating section 42d determines the respective values. The corresponding indicated average effective pressure (Pi) is calculated as the target load. That is, the virtual filling efficiency that has not been annealed
A first target load Piobjd is calculated based on ceimg, and a second target load Piobjd is calculated based on the simulated virtual filling efficiency ceimgd.

[0066]

## EQU3 ## Piobjd = K1.times.ceimg + K2 Piobjd = K1.times.ceimgd + K2 When the external load such as an air conditioner is applied to the target load setting means 42 during the idling operation of the engine 1, the external load is reduced. In order to increase the engine output to an appropriate degree, an idling load correction unit 42e that corrects the virtual filling efficiency ceimg, ceimgd prior to the calculation of the target load is provided.

Further, the target load setting means 42 includes:
A switching prediction unit (transition prediction unit) for predicting that the operation mode will be changed from the stratified combustion mode to the uniform combustion mode during the acceleration operation of the engine;
When the switching of the operation mode is predicted by f, the correction unit 42g that corrects the first target load Piobj to the value after the switching to the uniform combustion mode before the switching.
Are provided. Although details of the control by the switching prediction unit 42f and the correction unit 42g will be described later, the operation mode of the engine 1 is actually switched to the uniform combustion mode by correcting the first target load Piobj by the correction unit 42g. Before the replacement, the throttle opening tvoobj is reduced, and the charging efficiency of the combustion chamber 4 is reduced. That is, the correction unit 42g corresponds to a filling amount correction control unit.

The ECU 40 sets an operation mode setting means 4 for setting a basic operation mode mods based on the first target load Piobj and the engine speed ne obtained as described above.
3 is provided. That is, for example, when the engine is warm, as shown in the map of FIG.
In the operation region (a) where j is lower than the predetermined low load side threshold value Piobj * and the engine speed ne is low, the stratified combustion mode is set, and in the other operation regions, the uniform combustion mode is set. According to the load Piobj and the engine speed ne, either the stoichiometric mode (b) (c) (d) or the enrichment mode (e) is set.

The ECU 40 determines the values of various control parameters related to the engine output. More specifically, the ECU 40 adjusts the intake air amount adjusted by the throttle valve 13 and the EGR valve 27. EGR amount,
The intake swirl intensity adjusted by the swirl control valve 18, the fuel injection amount by the injector 7, the injection timing, and the ignition timing by the spark plug 6 are used as control parameters.
The values of these control parameters are changed to the first and second target loads Pi.
It is determined according to obj, Piobjd and the engine speed ne.

Here, the intake air amount, the EGR amount, and the swirl strength of the control parameters are low-speed response systems having relatively low responsiveness to the operation of the throttle valve 13, the EGR valve 27, and the swirl control valve 18, respectively. These control amounts such as throttle opening tvoobj, EGR valve opening,
The swirl control valve opening is determined according to the first target load Piobj and the engine speed ne. On the other hand, since the fuel injection amount, the injection timing, and the ignition timing are all of a high-speed response system that responds quickly to the control signal, they are determined according to the second target load Piobjd after the delay processing and the engine speed ne. .

(Throttle Control) Specifically, the ECU
Reference numeral 40 denotes a first target air-fuel ratio setting unit 44, a target filling efficiency calculation unit, which controls the throttle valve 13 in accordance with the first target load Piobj set by the target load setting unit 42 (filling amount control unit). Means 45 and a throttle opening calculating means 46. The first target air-fuel ratio setting means 44 provides a target air-fuel ratio af for controlling the intake air amount.
wb is set for each of the operation modes set by the above-described operation mode setting means 43. As shown in FIG. 10, in the stratified combustion mode or the enrichment mode, according to the first target load Piobj and the engine speed ne. The target air-fuel ratio afwb is obtained from a map created in advance, and the target air-fuel ratio afwb is set to the stoichiometric air-fuel ratio in the stoichiometric mode.

The target filling efficiency calculating means 45
The first target load Piobj or the virtual filling efficiency cei corresponding thereto
Based on mg and the target air-fuel ratio afwb, the target charging efficiency ceobj is calculated according to, for example, the following equation.

[0073]

Ceobj = ceimg × ｛(afwb + K3) /14.7｝ × K4 The equation of this (Formula 4) is obtained from the virtual charging efficiency ceimg by the excess air ratio of the target air-fuel ratio when operating in the lean state ( afwb / 14.7) and the fuel efficiency improvement effect are taken into account to calculate the target charging efficiency ceobj, and the coefficients K3 and K4 are values that reduce the target charging efficiency to an extent commensurate with the fuel efficiency improvement effect. It has been.

That is, since the virtual charging efficiency ceimg is a value corresponding to the target load when the engine 1 is operated under the standard operating conditions, the above-described air injection is necessary to ensure the same fuel injection amount during the lean operation. Although it is necessary to take into account the excess ratio, if the fuel injection amount is secured in the same manner as in the case of the stoichiometric air-fuel ratio, the engine output will increase due to high thermal efficiency during lean operation (this Fuel efficiency improvement effect). Therefore, in order to obtain the engine output corresponding to the target load, in addition to taking into account the excess air ratio as described above, the fuel consumption improvement effect is also taken into account.

From the above (Equation 3), ceimg = (Piobj
−K2) / K1, so that this may be substituted into (Equation 4) to determine the target charging efficiency ceobj from the first target load Piobj.

In the throttle opening calculating means 46, as shown in FIG. 7, the target charging efficiency ceob obtained as described above is obtained.
j is corrected by the target volume efficiency calculation unit 46a in accordance with the intake air density to obtain a target volume efficiency veobj, and a target throttle opening degree tvoobj is calculated in accordance with the target volume efficiency veobj and the engine speed ne. At this time, since the correspondence between the volumetric efficiency and the engine speed and the throttle opening differs depending on the presence or absence of the EGR, a map showing the correspondence is prepared in advance for each case, and the presence or absence of the EGR by the EGR determination unit 46c is determined. Target volume efficiency veobj and engine speed n
The throttle opening tvoobj corresponding to e is read.

Here, the relationship between the volumetric efficiency, the engine speed and the throttle opening is, for example, as shown by a solid line in FIG. 11 when EGR is not performed.
When GR is performed, it is indicated by a broken line in FIG. That is, the throttle opening tvoobj is equal to the target volumetric efficiency.
The larger the veobj, the larger the engine speed ne
Is higher when the EGR is higher, and is made larger than when there is no EGR.

As will be described later in detail, as a characteristic part of the present invention, when the operation mode of the engine 1 is switched from the stratified combustion mode to the stoichiometric mode, the throttle valve is used to promote the release of NOx from the catalyst 25. In order to delay the closing operation of the throttle valve 13, a tvoobj correction unit 46d that performs a smoothing process (delay correction) on the throttle opening degree tvoobj is provided.

In the stratified charge combustion mode, the exhaust gas has an extremely lean air-fuel ratio, so that not only the burned gas but also a large amount of air (oxygen) is contained in the EGR gas. Therefore, if there is EGR, the burned gas volume ratio in the EGR gas is obtained, and the throttle opening tvoobj and the EGR valve control amount are corrected according to the result.

(EGR Control) The ECU 40
EG as a means for R control (exhaust gas recirculation control means)
An R valve basic control amount setting means 62 and an EGR valve control amount calculating means 63 are provided. The EGR valve basic control amount setting means 62 sets the basic control amount of the EGR valve 27 for each operation mode. In the stratified charge combustion mode, the EGR valve basic control amount setting means 62 is prepared in advance in accordance with the first target load Piobj and the engine speed ne. On the other hand, in the stoichiometric mode, the basic control amount is read from a map created in advance in accordance with the actual charging efficiency ce and the engine speed ne obtained based on the output of the airflow sensor 12. Read. Then, the EGR valve control amount calculating means 63 corrects the basic control amount according to the burned gas volume ratio in the EGR gas to obtain a target EGR valve control amount, and outputs an output signal from the lift sensor 28. Actual E required according to
The EGR valve 27 is controlled so that the GR valve control amount matches the target EGR valve control amount.

(Fuel Injection Control) The ECU 40 includes second target air-fuel ratio setting means 47 for setting a target air-fuel ratio according to a target load and an operating state of the engine 1, and controls fuel injection by the injector 7. As means for this, an operation mode setting means 48, a division ratio setting means 49, an injection amount calculating means 50, an injection timing setting means 51 and an injection control means 52 are provided. The operation mode setting means 48,
The division ratio setting means 49, the injection timing setting means 51 and the injection control means 52 constitute an injection timing control means.
The injection amount control means is constituted by the injection amount calculation means 50 and the injection control means 52. Further, an air-fuel ratio control unit is constituted by the injection amount control unit, the exhaust gas recirculation control unit, and the charging amount control unit.

The second target air-fuel ratio setting means 47 obtains a target air-fuel ratio used for controlling the fuel injection amount and the like. More specifically, as shown in FIG.
Based on objd or the virtual charging efficiency ceimgd corresponding thereto and the actual charging efficiency (intake charging amount) ce, the calculation unit 47a calculates the target air-fuel ratio afw0 mainly used during the transient operation of the engine 1.

[0083]

Afw0 = 14.7 × K1 × ce / ｛K4 × (Piobjd−K2)｝ − K3 [= 14.7 × ce / (K4 × ceimgd) −K3] The equation of (Formula 5) is the theoretical air-fuel ratio. And the actual charging efficiency ce, the second target load Piobjd (or the virtual charging efficiency ceimgd), and the coefficients K3 and K4 that take into account the above-described fuel efficiency improvement effect.
The air-fuel ratio is determined so that the engine torque corresponding to the target load can be obtained under the actual charging efficiency.

The setting mode 47 sets the target air-fuel ratio afwbd, which is mainly used during steady operation of the engine 1, by the operation mode setting means 48.
Set for each modf. In other words, as shown in FIG. 13A, in the stratified combustion mode or the enrichment mode, the target air-fuel ratio afwbd is read from a previously created map based on the second target load Piobjd and the engine speed ne. In the stoichiometric mode, the target air-fuel ratio afwbd is set to the stoichiometric air-fuel ratio.

The deviation da between the target air-fuel ratio afwb for controlling the intake air amount set by the first target air-fuel ratio setting means 44 and the target air-fuel ratio afw0 calculated by the calculator 47a.
fwb is calculated by the deviation calculation unit 47c, and this deviation dafwb is calculated.
When the engine 1 is in a transient operation, the target air-fuel ratio afw0 calculated by the calculation unit 47a is set as the final target air-fuel ratio afw, while the engine 1 whose deviation dafwb is small.
During the steady operation, the target air-fuel ratio afwbd set by the setting unit 47b is set as the final target air-fuel ratio afw.

The second target air-fuel ratio setting means 47 is configured in this way in order to simultaneously satisfy the demands on engine output and the emission. The unit 47b and the deviation calculation unit 47c may be omitted, and the target air-fuel ratio afw0 always obtained by the calculation unit 47a may be set as the final target air-fuel ratio afw in the fuel injection control.

In FIG. 8, reference numeral 60 denotes a means for calculating air-fuel ratio deviations dafwbd and dafw0 for correcting the ignition timing at the time of transition as described later. The stratified combustion mode and enrich mode are set by the operation mode setting means 48. When the stoichiometric mode is set, dafwbd = afwbd−afw is calculated, while dafw0 = afw0−afw is calculated.

The operation mode setting means 48 is used to determine the operation mode used to determine the control parameters of the high-speed response system.
modf is set based on the target air-fuel ratio afw0 for controlling the fuel injection amount and the engine speed ne. That is, as shown in FIG. 12, the target air-fuel ratio af calculated by the calculation unit 47a.
When w0 is smaller than the lower limit reference value afw0 * of the stratified combustion mode, the stoichiometric mode is set, and the target air-fuel ratio is further set.
When afw0 becomes a predetermined value afw0 ** smaller than the stoichiometric air-fuel ratio, the enrichment mode is set. Conversely, if the target air-fuel ratio afw0 is equal to or more than the lower limit reference value afw0 *, the stratified combustion mode is set. By switching the operation mode modf, the fuel injection mode is switched, and the operation mode of the engine 1 is finally switched.

The split ratio setting means 49 sets the fuel 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 48. In the stratified combustion mode, Intake stroke injection ratio is 0
%, While in the stoichiometric mode or the enriched mode, the intake stroke injection ratio is set to 100%.

The injection amount calculating means 50 mainly calculates the actual charging efficiency ce obtained from the output of the air flow sensor 12 and the target air-fuel ratio set by the second target air-fuel ratio setting means 47.
The fuel injection amount is calculated based on afw and the injection ratio set by the split ratio setting means 49. Specifically, based on these values and the conversion coefficient KGKF, each basic injection amount of the intake stroke injection and the compression stroke injection
Calculate qbasep and qbased respectively.

[0091]

Qbasep = KGKF × (ce / afw) × rqbasep qbased = KGKF × ce [i] / afw [i-1] −qbasecp [i-1] where rqbasep is injection rate and ce [i] is filling Efficiency current value (value based on detected value of intake air amount immediately before compression stroke injection)
Afw [i-1], qbasep [i-1], ctotal [i-1] are the target air-fuel ratio, intake stroke injection basic injection amount, and the previous value of the correction value, respectively (for detection immediately before the intake stroke injection, Based value). 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 as described above is that if the current value (the value immediately before the compression stroke injection) is used as the target air-fuel ratio, the operation is performed in the intake stroke injection and the compression stroke injection. This is because the mode, the air-fuel ratio, and the like may fluctuate, making it impossible to obtain consistency.

Then, each of the basic injection quantities qbasep, qbased
On the other hand, each correction amount cdpfp, cdpfd of the intake stroke injection and the compression stroke injection according to the fuel pressure, and other various correction values c
The final injection amounts qinjp and qinjd of the intake stroke injection and the compression stroke injection are calculated in consideration of the total, and this final injection amount qinj
An injection pulse width Ti proportional to p and qinjd is obtained.

[0093]

[Mathematical formula-see original document] qinjp = qbasep * cdpfp * (1 + ctotal) qinjd = qbased * cdpfd * (1 + ctotal [i-1]) The injection timing setting means 51 sets the fuel injection timing by the operation mode setting means 48. In the stratified combustion mode, the second target load Piobjd and the engine speed are set as shown in FIG.
While the injection timing thtinjd for the compression stroke injection is obtained from a map prepared in advance according to ne, the injection timing thtinjp for the intake stroke injection is obtained from the map preset according to the engine speed ne in the uniform combustion mode. Ask for.

For the convenience of the arithmetic 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%). In the stoichiometric mode or the enriched mode, the injection timing thtinjp for the intake stroke injection is given by a map, and the injection timing thtinjd for the compression stroke injection is set to a fixed value (for example, a constant time at the beginning of the compression stroke). Injection only is used for additional injection when the fuel injection amount is insufficient. In particular, in the region (c) in the stoichiometric mode, the intake stroke injection amount qinjp is divided into two equal portions to obtain first and second injection amounts qinjp1 and qinjp2, and the injection timing th for the intake stroke injection is set.
While injecting the first injection amount qinjp1 fuel into tinjp,
After a predetermined interval after the end of this injection, the second injection amount qinjp2
The fuel is injected.

The injection control means 52 operates the injector 7 at the injection timing set by the injection timing setting means 51 for a time corresponding to the injection pulse width Ti calculated by the injection amount calculation means 50. , And outputs a pulse signal to the injector 7.

(Ignition Timing Control) The ECU 40 includes, as means for controlling the ignition timing of the engine 1, a setting means (ignition timing correction means) 53 for setting a basic ignition timing and a correction value, and an ignition timing calculation means 54 And The setting means 53 sets the basic ignition timing thtigb and various ignition timing correction values for each of the operation modes modf set by the operation mode setting means 48. Specifically, FIG.
As shown in (c), in the stratified charge combustion mode, the basic ignition timing thtigb is obtained from a map prepared in advance according to the second target load Piobjd and the engine speed ne, and the target air-fuel ratio deviation dafwbd described above. Correction value thtigw according to
d is obtained from a table created in advance. The correction according to the target air-fuel ratio deviation dafwbd is based on the basic ignition timing thtigb
Is determined in accordance with the second target load Piobjd and the engine speed ne corresponding to the target air-fuel ratio afwbd at the time of steady operation, whereas in the transient state, afw0 is set as the final target air-fuel ratio afw, Since the deviation of the air-fuel ratio occurs, the ignition timing is adjusted to match the deviation.

Further, in the stoichiometric mode or the enriched 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 executing the EGR is calculated as the charging efficiency ce. And a correction value tht according to the target air-fuel ratio deviation dafw0 obtained from a map created in advance according to
Cold correction value thtigwc according to igwd and engine water temperature thw
Are obtained from tables created in advance. The correction according to the target air-fuel ratio deviation dafw0 (= afw0-afw)
As will be described later, when the target air-fuel ratio afw0 becomes equal to or less than a predetermined value on the lean side of the stoichiometric air-fuel ratio, the final target air-fuel ratio is increased in order to prevent the NOx generation amount from passing through the air-fuel ratio.
When afw is the stoichiometric air-fuel ratio, the ignition timing is adjusted to match the change in the air-fuel ratio.

Further, when the operation mode modf is changed from the stratified combustion mode to the uniform combustion mode in accordance with the acceleration operation of the engine 1, a predetermined period is reduced in order to reduce the fluctuation of the engine output due to the change of the operation mode modf. Only the ignition timing is retard-corrected, and the retard correction value thtigwf for that is preset as a map in accordance with the change state of the target air-fuel ratio afw and the like. When performing the split injection, the basic ignition timing may be obtained from a table prepared in advance according to the target air-fuel ratio afw.

In this way, based on the basic ignition timing thtigb and various correction values set by the setting means 53, the ignition timing calculation means 54 calculates the ignition timing thtig as follows.

[0100]

[Equation 8] thtig = thtigb− (thtigwd + thtigwe + thtigwc
+ Thtigwf) When the ignition timing becomes thtig for each cylinder 2, a control signal is output to the ignition circuit 5 and ignition is performed by the ignition plug 6.

In the spark-ignition direct-injection engine 1 of the present embodiment equipped with the control device A as described above, one of the stratified combustion mode, the stoichiometric mode, and the enriched mode is set according to the operating state. In the combustion mode, stratified charge combustion is performed in a state where the air-fuel ratio is significantly leaner than the stoichiometric air-fuel ratio, so that fuel efficiency is greatly improved. On the other hand, in the enrich mode, the output of the engine 1 is increased by increasing the amount of fuel, and the combustion chamber 4 is appropriately cooled to reduce the heat load.

In the stratified combustion mode, for example, in order to increase the throttle opening and increase the intake air amount in order to increase the air-fuel ratio while ensuring the required torque, the operation mode and the target The intake air amount is controlled based on the load and the like, and the fuel injection amount, the injection timing, the ignition timing, and the like are controlled. In addition, the EGR valve 27 and the swirl control valve 18 are also controlled. The control parameters are appropriately controlled in consideration of each control response.

That is, as for the control of the intake air amount, the target charging efficiency ceobj is obtained based on the target air-fuel ratio afwb for intake air amount control set according to the target load and the like. Target volumetric efficiency veobj by correction
Is calculated, and the calculation of the throttle opening is performed based on the calculated value. As a result, the throttle opening is accurately controlled. On the other hand, based on the air-fuel ratio for controlling the injection amount obtained from the target load and the actual charging efficiency by the second target air-fuel ratio setting unit 47, the operation mode setting by the operation mode setting unit 48 and the fuel injection amount, injection timing, Control of the ignition timing and the like is performed, whereby the operation mode, the air-fuel ratio, and the like are appropriately controlled even during the transient operation of the engine in which the charging efficiency changes.

The control of the intake air amount having a low response speed to the control signal uses the first target load piobj, whereas the control of the fuel injection amount or the like having a high response speed to the control signal uses the first target load piobj. By using the second target load piobjd based on the virtual filling efficiency ceimgd, the operation timing of each control parameter can be appropriately adjusted.

In other words, in a general gasoline engine in which the throttle opening changes in accordance with the accelerator operation amount while maintaining the standard operating condition where the air-fuel ratio is the stoichiometric air-fuel ratio in most of the operating range, For example, even if the accelerator operation amount and the throttle opening corresponding to it suddenly change during the acceleration operation of the engine, the change in the intake air amount has a delay, and the change in the engine output corresponds to the change in the intake air amount. become. Therefore, if the output control simulating such a general gasoline engine is to be performed, the second target load Piob based on the simulated virtual filling efficiency ceimgd is obtained.
It is appropriate to consider jd as the actual target load.

Therefore, the control of the fuel injection amount or the like, which is a high-speed response system, is performed by the second target load Piobjd regarded as the actual target load.
Based on the above, torque characteristics similar to those of a general engine can be obtained, and a good engine feel can be secured. On the other hand, regarding the control of the throttle opening and the like, which is a low-speed response system, since the change in the intake air amount and the like has a certain large delay and the change tends to be slow, the virtual filling without smoothing process is performed. By controlling the opening of the throttle valve 13 and the like according to the first target load Piobj based on the efficiency ceimg, it is possible to reduce a control response delay.

(Forced Rich Control for Catalyst Refresh) As described above, in this embodiment, the engine 1 is set to the stratified charge combustion mode in a low load range so as to greatly improve the fuel efficiency. As described above, a so-called absorption-reduction type catalyst 25 is employed so that when the air-fuel ratio is made extremely lean, NOx can be removed from the exhaust gas in an oxygen-excess atmosphere. And this catalyst 2
In order to stably exhibit the purification performance of NOx 5, if the amount of NOx absorbed by the catalyst 25 increases to some extent, the NO
x is released for reduction purification (refreshing of the catalyst).

That is, if the operation of the engine 1 in the stratified combustion mode continues for a long time and the amount of NOx absorbed by the catalyst 25 becomes excessive, the emptying of the combustion chamber 4 of the engine 1 is prevented in order to prevent a decrease in the NOx absorption performance due to this. The fuel ratio is forcibly controlled to be near the stoichiometric air-fuel ratio (forcible rich operation) to refresh the catalyst 25. As a first characteristic of the present invention, when the air-fuel ratio is changed to the rich side in such a manner, the closing operation of the throttle valve 13 is delayed so that the actual charging efficiency ce of the combustion chamber 4 is made slower than usual. By increasing the fuel injection amount and temporarily increasing the exhaust flow rate and lowering the oxygen concentration in the exhaust gas, the release of NOx from the catalyst 25 is promoted.

Next, the specific processing procedure of the above-mentioned forced rich control will be described with reference to the flowchart shown in FIG. 14. First, in step SA1 after the start,
Air flow sensor 12, O2 sensor 24, water temperature sensor 3
It accepts various sensor signals such as 0, a rotation speed sensor 33, an accelerator opening sensor 34, etc., and inputs various data from a memory of the ECU 40. Subsequently, step SA2
, The value TLean of the lean operation counter for accumulating the time during which the engine 1 is operated in the stratified combustion mode is read, and it is determined whether or not the accumulated value is smaller than the first set value T1. The first set value T1 is set such that the NOx absorption amount of the catalyst 25 becomes excessive due to the lean operation of the engine 1,
If the determination result is NO, the catalyst 2 is set to correspond to the time until the absorption performance decreases.
It is determined that it is time to release NOx from step 5, and the process proceeds to step SA13. If the determination result is YES,
Proceed to step SA3.

In this step SA3, this time, the value Trich of the rich operation counter for integrating the time of the forced rich operation and the time during which the engine 1 is operated in the stoichiometric mode or the enrich mode is read, and the value is set to the second value. It is determined whether it is smaller than the set value T2. If the determination result is YES, it means that the release of NOx from the catalyst 25 is insufficient, and in this case, the process proceeds to Step SA6. On the other hand, if the determination result is NO, it is determined that the catalyst 25 has sufficiently released NOx, and the process proceeds to Step SA4 to set the forced rich flag Fr to an off state (Fr = 0). This forced rich flag Fr indicates that the catalyst 2
5 indicates that the forced rich operation is performed for the refresh of No. 5. Subsequently, in step SA5, the rich operation counter is reset (Trich = 0), and step S5 is performed.
Proceed to A6.

In step SA6 following step SA3 or step SA5, it is determined whether or not the forced rich flag Fr is in an off state.
(r = 1), it is determined that the forced rich operation is to be continued, and the process proceeds to step SA19 to be described later. If YES in the off state (Fr = 0), it is determined that the forced rich operation does not need to be performed, and step SA7 is determined. Proceed to. In step SA7, the current operation mode modf set by the operation mode setting means 48 is read (operation mode determination), and in step SA8, it is determined whether the current operation mode of the engine 1 is the stratified combustion mode. Determine.

If the result of this determination is YES, step S
Proceeding to A9, the engine 1 is operated in the stratified combustion mode,
In the following step SA10, the value Tlean of the lean operation counter is set.
And returns after a while. On the other hand, if the decision result is NO, the process proceeds to Step SA11 and
Operating the engine 1 in a stoichiometric mode or an enriched mode (λ ≦ 1) depending on its load state and rotational speed state,
In the following step SA12, the value Tri of the rich operation counter is set.
Count up ch and return after a while.

That is, if it is not necessary to perform the forced rich operation for refreshing the catalyst 25, the engine 1 is operated in one of the combustion modes corresponding to the operation state, and when the engine 1 is operated in the stratified combustion mode, the lean operation counter is operated. On the other hand, when operating in the stoichiometric mode or the enriched mode, the operating time is integrated by the rich operation counter.

On the other hand, in step SA13, in which it is determined in step SA2 that it is time to release NOx from the catalyst 25, the forced rich flag Fr is turned on (Fr = 1). Reset the operation counter value Tlean (Tlean =
0). Subsequently, at step SA15, the delay timer Tde corresponding to the period for intentionally increasing the exhaust flow rate is set.
Set the lay. Subsequently, at step SA16, the throttle opening degree tvoo calculated according to the target volumetric efficiency veobj and the engine speed ne by normal throttle control.
bj is smoothed by the tvoobj correction unit 46d (FIG. 7).
), The closing operation of the throttle valve 13 is delayed.

Next, at step SA17, the ignition timing is retarded (retarded) so as to alleviate the fluctuation of the engine output due to the delay of the throttle control. At the next step SA18, the ignition timing of the combustion chamber 4 of the engine 1 is reduced. The fuel injection amount is increased so that the air-fuel ratio is slightly leaner than the stoichiometric air-fuel ratio (1 <λ <1.1). More specifically, the fuel injection amount is obtained based on the actual charging efficiency ce calculated from the output value of the air flow sensor 12 and the target air-fuel ratio (A / F = 15 to 16), and the injection pulse corresponding to the fuel injection amount is obtained. Set the width. Then, the fuel is injected at once in the first half of the intake stroke of the cylinder by the injector 7 to bring the engine 1 into a uniform combustion state.
The value Trich of the rich operation counter is counted up, and then the process returns.

That is, when the catalyst 25 is refreshed, the operation mode of the engine 1 is forcibly switched to the uniform combustion mode, and the air-fuel ratio of the combustion chamber 4 is controlled to be close to the stoichiometric air-fuel ratio. When the operation mode is switched, the closing operation of the throttle valve 13 is delayed, and the amount of fuel injection is increased to change the air-fuel ratio of the combustion chamber 4 to the rich side. It can create a condition where the oxygen concentration inside is low.

In step SA18, the fuel is injected by the injector 7 all at once in the first half of the intake stroke of the cylinder. However, the invention is not limited to this. May be injected. In this way, a relatively rich air-fuel mixture is formed around the ignition plug 6 in the combustion chamber 4 of the engine 1, and the combustion is performed in a weakly stratified state.
The concentration is greatly increased, which can further promote the refresh of the catalyst 25.

Further, in step SA6, the forced rich flag Fr is turned on (Fr =
1), in step SA19, in which it is determined that forced rich operation is to be continued, it is determined whether the value of the delay timer Tdelay has become zero. If the determination result is NO, the process proceeds to step SA16, where the throttle valve 13
On the other hand, if the determination result is YES (Tdelay = 0), the process proceeds to step SA18, after which the forced rich operation is performed until the forced rich flag Fr is cleared.

That is, when the engine 1 shifts from the stratified combustion mode to the uniform combustion mode, the delay timer Tde
Until the predetermined time set in lay elapses, the closing operation of the throttle valve 13 is delayed, and after the predetermined time elapses, the same control as in the normal uniform combustion mode is performed.

Step SA shown in the flow of FIG.
In each step of 9, SA11 and SA18, the air-fuel ratio of the combustion chamber 4 is set to λ
Control is performed by switching to a lean state of ≧ 1.3 or a rich state richer than that.
When releasing NOx from the catalyst 25, it corresponds to the control of the air-fuel ratio control means of forcibly switching the air-fuel ratio of the combustion chamber 4 to a rich state. According to this control, when the integrated value of the operation time of the engine 1 in the stratified combustion mode exceeds the set time, the air-fuel ratio of the combustion chamber 4 is forcibly changed to the rich side ( Step S
A2).

Further, steps SA15, SA16
However, when the air-fuel ratio of the combustion chamber 4 is forcibly switched to the rich state in order to release NOx from the catalyst 25, the closing operation of the throttle valve 13 is delayed more than otherwise. Control means).

Further, in step SA18, when the air-fuel ratio of the combustion chamber 4 of the engine 1 is forcibly switched to the rich state, the fuel is set so that the excess air ratio λ of the combustion chamber 4 becomes λ <1.1. The step SA17 corresponds to the control of the ignition timing correcting means for correcting the ignition timing to the retard side at that time.

Therefore, according to the control device A of this embodiment, first, as shown in FIG. 4, the engine 1 is operated in the stratified combustion mode in the low load side region (a). NOx in the exhaust gas is absorbed and removed by the catalyst 25. When the integrated value Tlean of the operation time in this state exceeds the first set value T1, the forced rich flag Fr is turned on (F = 1), and the engine is turned on as shown in steps SA15 to SA18 in the flow. The forced rich control for forcibly changing the air-fuel ratio of the first combustion chamber 4 to the rich side and releasing NOx from the catalyst 25 is performed.

That is, the throttle valve 13 is closed to reduce the amount of intake air, the amount of fuel injected by the injector 7 is increased, and the air-fuel ratio of the combustion chamber 4 of the engine 1 is in the range of λ = 1 to 1.1. Will be controlled to be. In addition, since the closing operation of the throttle valve 13 is delayed at the time of the switching of the operation state, the air-fuel ratio of the combustion chamber 4 is switched to a rich state before the intake charging efficiency ce decreases so much. This not only lowers the oxygen concentration in the exhaust gas, but also makes it possible to increase the flow rate of the exhaust gas, even temporarily, so that the release of NOx from the catalyst 25 can be effectively promoted. .

That is, by utilizing the transient state in which the engine 1 switches from the stratified combustion state to the uniform combustion state, the catalyst 25
Can be effectively promoted, so that the frequency of the catalyst 25 refresh can be reduced, the air-fuel ratio at the time of refresh can be controlled to the lean side, and the refresh period can be shortened accordingly. Thus, the refresh of the catalyst 25 can be promoted while suppressing the deterioration of the fuel efficiency.

At this time, as described above, while the intake air charging efficiency ce of the combustion chamber 4 is high, the excess air ratio λ of the combustion chamber becomes λ <λ.
By increasing the fuel injection amount to 1.1, the oxygen concentration in the exhaust gas can be reduced in a state where the exhaust gas flow rate is considerably large, and the refresh effect of the catalyst 25 can be further enhanced. Moreover, the air-fuel ratio of the combustion chamber 4 of the engine 1 is an intermediate air-fuel ratio (λ = 1 to 1.3) where NOx is actively generated.
Therefore, the refresh of the catalyst 25 is not hindered by the increase in the NOx concentration in the exhaust gas. In addition, despite the high intake air charging efficiency ce of the combustion chamber 4, the ignition timing can be retarded to reduce fluctuations in engine output.

Then, by the aforementioned forced rich operation, N
The catalyst 25 is refreshed before the Ox absorption performance decreases, and the NOx purification performance of the catalyst 25 is stably maintained.

(Control During Acceleration Operation) As a second feature of the present invention, in the engine control device A according to this embodiment, the engine 1 shifts from a stratified combustion state to a uniform combustion state during, for example, an acceleration operation. Sometimes NO from the catalyst 25
When promoting the release of x, the closing operation of the throttle valve 13 is delayed and the fuel injection amount is increased as in the above-described forced rich operation.

Next, during acceleration operation of the engine 1, the catalyst 25
The processing procedure for promoting the refresh will be specifically described with reference to the flowcharts shown in FIGS.

In the step SB0 after the start in the flow shown in FIG. 15, the air flow sensor 12, O2
It accepts various sensor signals from the sensor 24, the water temperature sensor 30, the rotation speed sensor 33, the accelerator opening sensor 34, and the like, and inputs various data from the memory of the ECU 40. Subsequently, at step SB1, the NO of the catalyst 25 is determined.
It is determined whether the x absorption amount StNO is smaller than a first absorption amount St1 set in advance. The NOx absorption amount StNO may be estimated based on, for example, the travel distance after the last release of NOx from the catalyst 25 and the total amount of fuel consumed during that time. The first absorption amount St1 is set to such an amount that the catalyst 25 is not in the state of excessively absorbing NOx, but it is preferable to release NOx in order to maintain the absorption performance.

If the determination in step SB1 is YES, the amount of NOx absorbed by the catalyst 25 is not large, so the process proceeds to step SB2.
Since the Ox absorption amount is large, the process proceeds to step SB3,
A NOx emission promotion flag F indicating that the change of the operating state of the engine 1 is used to promote the refresh of the catalyst 25.
s is turned on (Fs = 1), and the process proceeds to step SB7. On the other hand, in step SB2, the catalyst 25
Is the second absorption amount St2 (S
It is determined whether or not t2 <St1). The second absorption amount St2 is set to such an amount that the NOx absorption performance of the catalyst 25 has a sufficient margin. This judgment is YE
If S, the process proceeds to step SB5, whereas if the determination is NO and there is sufficient room for the NOx absorption performance of the catalyst 25, the process proceeds to step SB4, where the NOx release promotion flag Fs is cleared (Fs = 0). Proceed to SB5.

Following steps SB2, SB3, and SB4, in step SB5, the current operating range of the engine 1 is determined based on the load state and the number of revolutions of the engine 1, and in step SB6, the engine is operated. It is determined whether or not the current operating state of No. 1 is in the area (a) (see FIG. 4). If the result of this determination is YES, the process proceeds to step SB10 shown in FIG. 16, in which the engine 1 is operated in the stratified combustion mode.
Proceeding to B7, it is determined whether or not the current operating state of the engine 1 is in the region (C) in the same manner as described above. If the result of this determination is YES, step SB1 shown in FIG.
On the other hand, if the result of the determination is NO, the process proceeds to step SB8, and it is determined whether or not the current operating state of the engine 1 is in the region (b) as described above. If the result of this determination is NO
If so, the process proceeds to step SB21 in FIG. 16 to operate the engine 1 in the uniform combustion mode, while the determination result is YES.
If so, the process proceeds to Step SB9, and it is determined whether or not the NOx release promotion flag Fs is on. If the result of this determination is YES, the process proceeds to step SB16,
If the determination result is NO, the process proceeds to step SB21.

Following step SB6 in FIG. 15, in step SB10 in FIG. 16, first, the first target load Piobj set by the target load setting means 42 (see FIG. 5) of the ECU 40 is read out. The change amount ΔPi of the target load is calculated by subtracting the previous value Piobj [i−1] from the current value Piobj [i] of the load Piobj. Subsequently, in step SB11, the target load change amount ΔPi is compared with a predetermined determination reference value C1, and whether or not the operation mode of the engine 1 is switched is predicted based on the comparison result. That is, the target load change amount ΔPi is larger than the determination reference value C1.
Since (ΔPi> C1) means that the target load of the engine 1 is rapidly increasing, the operation mode is predicted to be switched from the stratified combustion mode to the uniform combustion mode, and the process proceeds to step SB12. On the other hand, if the target load change amount ΔPi is not NO (ΔPi ≦ C1) not larger than the determination reference value C1, it is predicted that the operation mode will not be switched, and step S
Proceed to B14.

In step SB12, it is determined whether or not the NOx release promotion flag Fs is in an off state. If the result of the determination is NO, the process proceeds to step SB14, while if the result of the determination is YES, the process proceeds to step SB13, and the engine 1
When the operation mode is switched to the uniform combustion mode, the first target load Piobj (= Piobj *) in the uniform combustion mode immediately after the switching is read from the map, and this value is set again as the first target load Piobj. I do. That is, if it is predicted that the engine 1 in the stratified combustion mode will switch to the uniform combustion mode, and if the NOx emission promotion flag Fs is in the off state, then the first target is set before the operation mode is actually switched. The load Piobj is corrected to a value immediately after switching to the uniform combustion mode.

Subsequently, in step SB14, the engine 1 is operated in the stratified combustion mode. At this time, since the throttle opening tvoobj is calculated based on the newly set first target load Piobj, the throttle valve 13 is closed so as to be in the target opening state in the uniform combustion mode. Then, in the following step SB15, the current operating region of the engine 1 is stored in the memory of the ECU 40, and thereafter, the routine returns.

That is, if it is not necessary to promote the refreshing of the catalyst 25, when the engine 1 is operating in the stratified combustion mode and the transition to the uniform combustion mode is predicted, the engine 1 actually transitions to the uniform combustion mode. The throttle valve 13 is closed beforehand.

On the other hand, in step SB16, in which it is determined that the engine 1 is not in the region (A) (not in the stratified combustion mode) in the flow of FIG. 15, the engine 1 is stored in the previous control cycle. The previous operation area is read from the memory of the ECU 40, and it is determined whether or not the previous operation area is the area (a). If this determination is NO, the process proceeds to step SB22, while if the determination is YES,
Since the operation mode of the engine 1 has just been switched from the stratified combustion mode to the uniform combustion mode, the following step SB17
Sets the delay timer Tdelay. Subsequently, at step SB18, the throttle opening tvoobj (FIG. 7B)
(See the solid line in FIG. 7) by the tvoobj correction unit 46d (see the broken line in FIG. 7B) to correct the delay so that the closing operation of the throttle valve 13 is delayed.

Subsequently, in step SB19, the actual filling efficiency calculated from the output value of the air flow sensor 12 and the like
Based on the ce, the fuel injection amount by the injector 7 is corrected so that the air-fuel ratio of the combustion chamber 4 becomes substantially the stoichiometric air-fuel ratio. In the next step SB20, the engine delay associated with the delay of the throttle control and the correction of the fuel injection amount is described. The ignition timing is retarded (retarded) so as to reduce the output fluctuation. Then, in the subsequent step SB21, the engine 1 is operated in the stoichiometric mode or the enriched mode (operating at λ ≦ 1) so as to correspond to the region after the operation mode switching, and the routine proceeds to step SB15, where the current After the operation area of the ECU 40 is stored in the memory of the ECU 40, the process returns.

That is, when the engine 1 shifts from the stratified combustion state region (a) to the uniform combustion state region (c),
Alternatively, when the operation mode is switched from the stratified combustion state region (a) to the uniform combustion state region (b) and the NOx emission promotion flag Fs is on, the operation mode is switched. In addition, the closing operation of the throttle valve 13 is delayed for a predetermined time, and the air-fuel ratio of the combustion chamber 4 is changed to the rich side by increasing the fuel injection amount. A state where the exhaust gas flow rate is high and the oxygen concentration in the exhaust gas is low is created, and the catalyst 2
5 can be sufficiently promoted. In addition, since the air-fuel ratio of the combustion chamber 4 of the engine 1 can be switched from a very lean state to the stoichiometric air-fuel ratio at a stretch, the intermediate air-fuel ratio (λ = 1 to 1.3) that actively generates NOx does not occur.

The closing operation of the throttle valve 13 may be delayed as described above, and the fuel may be injected by the injector 7 in a plurality of times from the intake stroke to the compression stroke of the cylinder. Since the CO concentration in the exhaust gas is greatly increased by the combustion in the stratified state, the refresh of the catalyst 25 can be further promoted.

On the other hand, in step SB16, in which the previous operation area of the engine 1 was determined to be NO which is not the area (A) in step SB16, the process proceeds to step SB22, in which it is determined whether or not the value of the delay timer Tdelay has become zero. If NO, the process proceeds to step SB18 to continue the control such as delay correction of the throttle valve 13. On the other hand, if the answer is YES with the delay timer Tdelay = 0, the process proceeds to step SB21.
Then, normal control in each area after the operation mode switching is performed (step SB21), and step S21 is performed.
At B15, the current operation area is stored, and thereafter, the routine returns.

That is, when the engine 1 shifts from the stratified combustion mode to the uniform combustion mode due to acceleration operation or the like, the closing operation of the throttle valve 13 is delayed until a predetermined time set in the delay timer Tdelay has elapsed. While the exhaust gas flow rate is sufficiently ensured, the normal uniform combustion mode control is performed after the predetermined time has elapsed.

Step SB1 shown in the flow of FIG.
Steps 4 and SB21 are performed by the injector 7 when the engine 1 is in the low load side region (a).
Injection of fuel in the compression stroke of (1) to make the stratified combustion mode, while the region on the higher load side (b) (c) (d)
(E) corresponds to the control of the injection timing control means for injecting fuel in the intake stroke of the cylinder 2 to set the uniform combustion mode. In each of these steps, the air-fuel ratio of the combustion chamber 4 of the engine 1 is controlled in the stratified combustion mode so that the excess air ratio λ is in a lean state of λ ≧ 1.3, while in the uniform combustion mode, λ ≦ 1. It also corresponds to the control of the air-fuel ratio control means for controlling by switching so as to be rich.

The steps SB1 to SB4 and SB7 to SB9 of the flow shown in FIG.
When the engine 1 shifts from the stratified combustion mode to the uniform combustion mode, a determination unit 64 is configured to determine whether or not the state is such that the release of NOx from the catalyst 25 is promoted. The determination means 64 determines whether or not the NOx release is promoted based on the NOx absorption amount of the catalyst 25, and when the engine 1 is shifted from the stratified combustion mode region (a) to the middle load side. Is shifted to the region (c) of NOx, regardless of the NOx absorption amount of the catalyst 25,
It is configured to determine that the release is promoted.

The steps SB17, SB17 in FIG.
B18 is a tvoobj correction unit 46d that delays the closing operation of the throttle valve 13 more than the non-promotion state when the determination unit 64 determines that the NOx release is promoted.
(Filling amount control means).

In step SB19, when the determination means 64 determines that NOx emission is promoted and the engine 1 shifts from the stratified combustion mode to the uniform combustion mode, the air-fuel ratio of the combustion chamber 4 of the engine 1 is determined. Corresponds to the control of the injection amount control means for increasing the fuel injection amount so as to become approximately the stoichiometric air-fuel ratio.
Reference numeral 20 corresponds to the control of the ignition timing correction means for correcting the ignition timing to the retard side at that time. The injection amount control means is configured to increase the fuel injection amount before the excess air ratio λ becomes λ ≦ 1.3 due to a decrease in the intake air charging efficiency ce of the combustion chamber 4.

In each of the steps SB10 and SB11, the transition from the stratified combustion mode to the uniform combustion mode accompanying the acceleration operation of the engine 1 is performed by the first target load Piob.
Step SB13 corresponds to a transition prediction unit (switching prediction unit) 42f that predicts based on the change state of j.
The transition predicting section 42f predicts the transition of the engine 1 to the uniform combustion mode, and the determination section 64 determines NOx.
When it is determined that the emission is not promoted, the first target load Piobj is set before the engine 1 actually shifts to the uniform combustion mode.
The correction unit 42 that closes the throttle valve 13 to reduce the intake charging efficiency ce of the combustion chamber 4 by correcting
g (filling amount correction control means).

FIG. 17 is a time chart showing how the air-fuel ratio of the combustion chamber 4 of the engine 1 changes from the stratified combustion mode to the uniform combustion mode by the control during the acceleration operation. This will be described with reference to FIG.

First, the case where the NOx absorption amount of the catalyst 25 has a margin and the NOx release promotion flag Fs is in the off state will be described. In this case, when the accelerator opening accel increases in response to the driver's access operation when the engine 1 is accelerating, the first target load Piobj set by the target load setting means 42 of the ECU 40 and the first target load Piobj The throttle opening tvoobj calculated based on the target load Piobj increases as shown in FIGS. 7A and 7B (t = t1). And the actual throttle valve 1
Slightly after the opening operation of No. 3, the charging efficiency ce of each cylinder increases as shown in FIG. 3C, and the air-fuel ratio of the combustion chamber 4 increases as shown in FIG. Gradually changes to the rich side.

At this time, as shown in steps SB10 to SB14 of the flow of FIG. 16, the first target load Pi
When the switching of the operation mode is predicted based on the degree of change of obj (t = t2), as shown by a dashed line in FIG. 17A, immediately after the first target load Piobj is switched to the uniform combustion mode. The value is corrected to the value, the basic operation mode mods for controlling the throttle and the like is switched to the uniform combustion mode, and the throttle opening tvoobj is rapidly reduced as shown by the dashed line in FIG. Then, when the throttle valve 13 is closed, as shown by a dashed line in FIG.
Before the charging efficiency ce of each cylinder 2 becomes too large, it starts to decrease.

The actual filling efficiency ce and the second target load
When the final operation mode modf is switched based on Piobjd, the fuel injection by the injector 7
And the air-fuel ratio is set to the stoichiometric air-fuel ratio as indicated by the one-dot chain line in FIG.
= T3), the engine 1 is operated in the uniform combustion mode.

Here, if it is assumed that the above-mentioned operation mode switching is not predicted, after the throttle opening degree tvoobj becomes considerably large as shown by the solid line in FIG. Will be switched to (t
= T4) At that time, as shown by the solid line in FIG. 9C, the charging efficiency ce of each cylinder 2 is considerably large, and there is a possibility that the engine output may fluctuate greatly.

On the other hand, according to the control of this embodiment, the fluctuation of the charging efficiency ce can be made extremely small by closing the throttle valve 13 before switching the operation mode of the engine 1 as described above. Thereby, the fluctuation of the engine output as described above can be prevented.

On the other hand, when the NOx release promotion flag Fs is in the ON state, the prediction of the operation mode switching and the control corresponding thereto are not performed as described above. The first target load Piobj increases in response to the accelerator operation, and accordingly, the throttle opening tvoobj increases until the basic operation mode mods for controlling the throttle or the like is switched (t = t3).

When the throttle opening tvoobj is reduced by the switching of the basic operation mode mods, this time, steps SB16 to SB16 in the flow of FIG.
According to the control procedure shown in FIG. 20, the throttle opening tvoobj is smoothed as shown by the broken line in FIG. 17B, and the closing operation of the throttle valve 13 is delayed. As shown by the broken line in FIG. The charging efficiency ce of each cylinder 2 becomes extremely large. At this time, the fuel injection amount is increased and corrected, and the air-fuel ratio of the combustion chamber 4 is switched to the stoichiometric air-fuel ratio as shown by a broken line in FIG. Furthermore, the engine 1 temporarily enters a state in which the oxygen concentration in the exhaust gas is low and the exhaust gas flow rate is extremely large.

At this time, as shown in FIG. 17E, the EGR control is performed so that the exhaust gas recirculation amount is increased from the time when the switching of the operation mode is predicted (t = t2). By the time the oxygen concentration in the exhaust gas is low and the exhaust gas flow rate is extremely high, the exhaust gas recirculation rate (EGR
Therefore, in the combustion chamber 4 of the engine 1, the generation of NOx accompanying the combustion is sufficiently suppressed, and the slowing of the combustion increases the concentrations of CO and HC in the exhaust gas.

Therefore, according to the control at the time of the acceleration operation, when the engine 1 shifts from the stratified combustion mode to the uniform combustion mode at the time of the acceleration operation or the like, a state in which the exhaust gas flow rate is transiently considerably large can be created. At this time, by controlling the fuel injection amount to lower the oxygen concentration in the exhaust gas and recirculating a large amount of exhaust gas, NOx
Since the concentration can be reduced and the concentrations of the reducing agent components HC and CO can be increased, the refresh of the catalyst 25 can be promoted very effectively.

In addition, since the engine output changes greatly during the acceleration operation, even if the engine output fluctuates due to the switching of the operation mode, the adverse effect on the driving feeling can be relatively small. Furthermore, fluctuations in the engine output can be reduced by correcting the ignition timing to the retard side and slowing down the combustion by a large amount of exhaust gas recirculation.

Further, in this embodiment, when the engine 1 shifts from the stratified combustion mode region (a) to the medium load / medium rotation region (c), regardless of the NOx absorption state of the catalyst 25, the catalyst 25 NOx emission is promoted. This is because, in the region (c), the combustion stability is enhanced by dividing the fuel injection so that a large amount of exhaust gas is recirculated, whereby the operating state of the engine 1 is reduced in the region (a). When the operation shifts from (c) to (c), a large amount of exhaust gas is recirculated in both regions, so that a large amount of exhaust gas recirculation naturally continues during the transition of the operating state. Even if the operation responsiveness is low, a large amount of exhaust gas recirculation as described above can be easily realized when the operation mode of the engine 1 is switched.

(Embodiment 2) FIG. 18 shows a flow of forced rich control by a control device A of a spark ignition type direct injection engine according to Embodiment 2 of the present invention.
First, it is determined that it is time to release NOx from the catalyst 25 based on the estimated value of the NOx absorption amount of the catalyst 25. Further, during forced rich operation, the exhaust gas recirculation rate becomes stratified. The EGR control is performed so as to be longer than in the combustion mode. Furthermore, even when the engine 1 shifts to the forced rich operation, the closing operation of the throttle valve 13 is not delayed when the excess air ratio λ of the combustion chamber 4 is 1.1 <λ <1.3. It is. Since the overall configuration of the control device A according to the second embodiment is the same as that of the first embodiment (see FIG. 1), the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. I do.

Specifically, in step SC1 of the flow shown in FIG. 18, various data are input as in the first embodiment, and in subsequent step SC2, it is determined whether or not the catalyst 2 has an excessive amount of NOx absorption. That is, the NOx absorption amount of the catalyst 25 is estimated in the same manner as in the first embodiment,
When the estimated absorption amount exceeds a predetermined value, it may be determined that the NOx absorption state is excessive. If the determination is YES, the process proceeds to step SC10 to turn on the forced rich flag Fr (Fr = 1), while if the determination is NO, the process proceeds to step SC3.

In step SC3, it is similarly determined whether or not the release of NOx from the catalyst 25 has been completed. If the determination is YES, the flow advances to step SC4 to clear the forced rich flag Fr (Fr = 0). On the other hand, if the determination is NO, the process directly proceeds to step SC5. In step SC5, it is determined whether or not the forcible rich flag Fr is in an off state.
1) While the process proceeds to step SC17, if YES in the off state (Fr = 0), the process proceeds to step SC6, and in each of the steps SC6 to SC9, the engine 1 is set to the operating state as in the first embodiment. Operate in different combustion modes accordingly.

On the other hand, in step SC2, NOx
If it is determined that the state is excessive absorption and the forced rich flag Fr is turned on in step SC10, the process proceeds to step S10.
At C11, a delay timer Tdelay is set in the same manner as in the first embodiment.
It is determined whether the air-fuel ratio of the combustion chamber 4 is λ <1.1 at the excess air ratio λ. This determination may be made based on the excess air ratio obtained from the output of the airflow sensor and the actual fuel injection amount. If this determination is YES, step S
Proceeding to C13 and SC14, the closing operation of the throttle valve 13 is delayed and the ignition timing is retarded in the same manner as in the first embodiment, and the process proceeds to step SC15. Then, the process proceeds to step SC15.

That is, when the engine 1 is switched to the forced rich operation in order to release NOx from the catalyst 25,
When the excess air ratio λ of the combustion chamber 4 is λ ≧ 1.1, the throttle valve 13 is quickly closed to make NO
The generation of x is made to pass through the active state as fast as possible.

At step SC15 following steps SC12 and SC14, the opening of the EGR valve 27 is maintained as it is (EGR valve hold), and the process proceeds to step SC16. The state is switched to (forcible rich operation), and then the operation returns. That is, by keeping the opening of the EGR valve 27 the same as in the stratified combustion mode, the exhaust gas recirculation rate naturally increases with the closing operation of the throttle valve 13.

Step SC shown in the flow of FIG.
Steps 8, SC9 and SC16 correspond to the control of the air-fuel ratio control means, and the steps SC11 to SC13 correspond to the control of the tvoobj correction unit 46d (filling amount control means). Further, step SC1
4 is for controlling the ignition timing correction means, and in step SC1.
Numeral 5 corresponds to the control of the exhaust gas recirculation control means.

Therefore, according to the second embodiment, the same operation and effect as those of the first embodiment can be obtained.
When the engine 1 is switched to the forced rich operation in order to refresh the catalyst 25, the fuel consumption is not significantly deteriorated by not performing the large increase correction of the fuel, and the ignition timing is retarded. Since only a small amount is required, deterioration of fuel economy can be reduced.

(Other Embodiments) The present invention is not limited to the above-described embodiments, but includes other various embodiments. That is, in each of the above embodiments, as the determination means 64 for determining whether to promote the refresh of the catalyst 25, the NOx absorption amount of the catalyst 25 is equal to or more than the set amount, or the engine 1 is shifted from the region (A) to the region (C).
When shifting to, it is determined that the NOx release is promoted, but the present invention is not limited to this.

For example, when the engine 1 shifts from the idling operation state in the stratified charge combustion mode to the acceleration operation state, the N
It may be determined that the state is such that the Ox release is promoted. In this case, the engine 1 is accelerated from the idling operation state.
Since the frequency of shifting to the uniform combustion mode is high, if NOx emission from the catalyst 25 is promoted at this time,
The refresh frequency of the catalyst 25 can be naturally increased.

Further, when the engine 1 is in a sudden acceleration operation state equal to or higher than a predetermined value, it may be determined that the NOx emission is promoted. In this case, the engine output naturally increases rapidly during the rapid acceleration operation of the engine 1, so that
At this time, if the release of NOx from the catalyst 25 is promoted, even if the engine output fluctuates accordingly, the deterioration of the driving feeling due to this can be relatively small.

Furthermore, in each of the above embodiments, NOx
When the engine 1 shifts from the stratified combustion mode to the uniform combustion mode in the accelerated release state, the fuel injection amount from the injector 7 is immediately corrected for increase. However, the present invention is not limited to this. The correction may be performed earlier than in the non-promotion state.

That is, in the NOx emission promotion state, the fuel injection amount is increased when, for example, the excess air ratio of the combustion chamber 4 of the engine 1 becomes λ = 1.3. May be increased when λ = 1.2. In this case, in the non-promoting state of NOx release, the air-fuel ratio is reduced after the charging efficiency ce of the combustion chamber 4 is reduced. The state can be switched to the rich state, and the fluctuation of the engine output can be further suppressed.

[0173]

As described above, according to the control apparatus for a spark ignition type direct injection engine according to the first aspect of the present invention, when the air-fuel ratio of the combustion chamber is switched from the lean state to the rich state according to the operating state of the engine. When the air-fuel ratio is forcibly switched to a rich state for refreshing the NOx absorption catalyst, while controlling the charging amount control means, the amount of intake air in the combustion chamber can be rapidly reduced to suppress fluctuations in engine output. By delaying the operation of the charging amount adjusting means, it is possible to temporarily create a state in which the oxygen concentration in the exhaust gas is low and the exhaust gas flow rate is large, thereby effectively promoting the release of NOx from the NOx absorption catalyst. As a result, the frequency of the catalyst refresh can be reduced or the period can be shortened. Therefore, the catalyst refresh can be promoted while suppressing the deterioration of the fuel efficiency.

According to the second aspect of the present invention, when the operation time of the engine in the stratified combustion state exceeds the set time, the air-fuel ratio of the combustion chamber is forcibly switched to the rich state, so that N
The NOx absorption catalyst can be refreshed before the Ox absorption performance decreases, so that the NOx absorption performance of the catalyst can be stably maintained.

According to the third aspect of the invention, when the air-fuel ratio of the combustion chamber of the engine is forcibly switched to the rich state, the fuel injection amount is adjusted so that the excess air ratio of the combustion chamber becomes smaller than 1.1. By increasing the amount, the oxygen concentration in the exhaust gas is reduced while the exhaust gas flow rate is sufficiently large, so that the refreshing of the NOx absorption catalyst can be sufficiently promoted. In addition, the air-fuel ratio of the combustion chamber becomes a state where NOx generation is active. Can be avoided. At this time, by correcting the ignition timing to the retard side, fluctuations in the engine output can be reduced.

According to the fourth aspect of the invention, the operation of the charge amount adjusting means is delayed according to the excess air ratio of the combustion chamber of the engine, so that the same effect as that of the third aspect of the invention can be obtained, and the fuel consumption can be reduced. Deterioration can be further reduced.

According to the fifth aspect of the present invention, the fuel consumption is reduced by controlling the air-fuel ratio of the combustion chamber of the engine to A / F = 15 to 16 in the forced rich state for NOx release. It is planned. Also, by recirculating a large amount of exhaust at that time, the generation of NOx can be sufficiently suppressed and the CO concentration in the exhaust can be increased, thereby promoting the refresh of the catalyst.

According to the invention of claim 6, the effect of the invention of claim 5 can be easily obtained.

According to the control apparatus for a spark ignition type direct injection engine according to the seventh aspect of the present invention, the engine shifts from a low load region in a stratified combustion state to a region on a higher load side in a stratified combustion state, and a uniform combustion state is obtained. When the state is switched to the normal state, the amount of intake air in the combustion chamber can usually be quickly reduced to suppress fluctuations in the engine output. By delaying the operation of the adjusting means, temporarily creating a state where the oxygen concentration in the exhaust is low and the exhaust flow rate is high,
The release of NOx from the NOx absorption catalyst can be effectively promoted. Therefore, using the change in the operating state of the engine, without causing a significant deterioration in driving feeling,
A state where the exhaust gas flow rate is increased transiently can be created, and the catalyst refresh can be effectively promoted.

According to the eighth aspect of the present invention, similarly to the third aspect of the present invention, the refreshing of the NOx absorbing catalyst can be sufficiently promoted, and the air-fuel ratio of the combustion chamber can be prevented from becoming an active state of NOx generation. it can. According to the ninth aspect of the present invention, the effect can be sufficiently obtained.

According to the tenth aspect, the same effects as those of the eighth aspect can be obtained. In addition, when the emission of NOx is not promoted, the fluctuation of the output and the deterioration of the fuel efficiency accompanying the switching of the combustion state of the engine are achieved. Can be reduced. According to the eleventh aspect, the effect can be sufficiently obtained.

According to the twelfth aspect, fluctuations in engine output can be reduced by retarding the ignition timing.

According to the thirteenth aspect of the present invention, the combustion in a weakly stratified state is achieved by dividing the fuel injection, so that the concentration of CO and the like in the exhaust gas can be increased, and the catalyst can be further refreshed.

According to the fourteenth aspect of the present invention, by promoting the refresh of the catalyst in the state of rapid acceleration operation of the engine,
Deterioration of the driving feeling accompanying the transition of the combustion state can be reduced.

According to the fifteenth aspect, in the normal operation range of the vehicle-mounted engine, the N in the exhaust gas due to the recirculation of the exhaust gas.
Since the Ox concentration can be reduced and the exhaust gas recirculation is continued when the engine shifts from the low load region to the predetermined medium load region, the catalyst can be further refreshed at this time. Further, according to the sixteenth aspect, the operation and effect of the fifteenth aspect can be sufficiently obtained.

According to the seventeenth aspect of the invention, when the engine is in the idling state and in the acceleration state, the refresh of the catalyst is promoted, so that the frequency of the refresh can be increased.

According to the eighteenth aspect of the present invention, when NOx release from the NOx absorption catalyst is not promoted, the intake air filling amount of the combustion chamber is reduced before the engine is accelerated to shift to the uniform combustion state. Fluctuations in the engine output due to a response delay in the charge control can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of a control device for a spark ignition type direct injection engine according to the present invention.

FIG. 3 is a sectional view showing a schematic configuration of a catalyst.

FIG. 4 is a diagram illustrating an example of a control map in which respective operation regions of a stratified combustion mode, a stoichiometric mode, and an enriched mode of the engine are set.

FIG. 5 is a functional block diagram of an ECU.

6 is a functional block diagram showing a specific configuration of a target load setting unit in FIG.

FIG. 7 is a functional block diagram showing a specific configuration of a throttle opening calculating means in FIG. 5;

8 is a functional block diagram showing a specific configuration of a second target air-fuel ratio setting means in FIG.

FIG. 9 is a diagram showing a correspondence relationship between an accelerator operation amount, an engine speed, and virtual volume efficiency.

FIG. 10 is a diagram showing a map in which a target air-fuel ratio for controlling an intake air amount is set for each operation mode.

FIG. 11 is a diagram showing a correspondence relationship between a target volume efficiency and a throttle opening.

FIG. 12 is a diagram showing setting of an operation mode used for calculation of a fuel injection amount and the like.

FIG. 13 is a diagram showing a map in which a target air-fuel ratio (a), an injection timing (b), and an ignition timing (c) for controlling a fuel injection amount and the like are set for each operation mode.

FIG. 14 is a flowchart illustrating a processing procedure of forced rich control for catalyst refresh.

FIG. 15 is a flowchart illustrating a first half of a control procedure during control of the engine during an acceleration operation.

FIG. 16 is a flowchart showing a latter half of a control procedure during control of the engine during acceleration operation.

FIG. 17 is a time chart illustrating a first target load, a throttle opening, an actual charging efficiency, an air-fuel ratio, and the like that change during an acceleration operation of the engine.

FIG. 18 is a diagram corresponding to FIG. 14 according to the second embodiment.

[Explanation of symbols]

A Control device for spark-ignition direct injection engine 1 Engine 2 Cylinder 4 Combustion chamber 7 Injector (fuel injection valve) 13 Throttle valve 40 Control unit (ECU) 42f Switch prediction unit (transition prediction unit) 42g Correction unit (Charge correction control) Means) 44 target air-fuel ratio setting means (filling quantity control means) 45 target filling efficiency calculating means (filling quantity control means) 46 throttle opening calculating means (filling quantity control means) 46d tvoobj correction unit (filling quantity control means) 48 operation Mode setting means (injection timing control means) 49 Split ratio setting means (injection timing control means) 50 Injection amount calculation means (injection amount control means) 51 Injection timing setting means (injection timing control means) 52 Injection control means (injection timing control) Means, injection amount control means) 53 setting means (ignition timing correction means) 62 EGR valve basic control amount setting means (exhaust gas return) Control means) 63 EGR valve control amount calculation means 64 determining means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/02 325 F02D 41/02 325E 41/34 41/34 H 43/00 301 43/00 301E 301N 301B F02P 5/15 F02P 5/15 BF F term (reference) 3G022 AA07 AA08 AA09 AA10 BA01 CA00 CA03 CA04 CA09 DA02 EA00 EA07 FA03 GA00 GA05 GA06 GA07 GA08 3G084 AA04 BA05 BA09 BA13 BA15 BA17 BA20 CA00 CA03 DA04 EB02 EC02 EC03 FA08 FA10 FA13 FA18 FA26 FA33 3G092 AA01 AA06 AA09 AA10 AA17 BA01 BA04 BA09 BB01 BB06 BB13 DC03 DC09 DC15 DE03S DG08 EA01 EA02 EA04 EA05 EA07 EA08 EA11 FA04 GA05 FA06 HA06X HA06Z HA11Z HB01Z HB03Z HC00X HD05X HD05Z HD07X HD07Z HE01Z HE08Z HF08Z 3G301 HA01 HA04 HA13 HA16 HA1 7 HA18 JA02 JA04 JA25 JA33 KA08 KA09 KA11 KA13 KA14 KA21 LA00 LA03 LB04 LC03 MA01 MA11 MA19 MA23 MA26 MA27 NA08 NB02 NB06 NB11 ND01 NE00 NE01 NE06 NE13 NE14 NE15 NE22 NE23 PA04Z PA07Z PA09Z PA10Z PA11Z PDBZZZZ PE08Z PF03Z PF11Z

Claims (19)

[Claims] A fuel is directly injected into a combustion chamber in a cylinder of an engine.
A fuel injection valve for injecting and supplying, disposed in an exhaust passage communicating with the combustion chamber, and absorbing NOx in an oxygen-excess atmosphere where the oxygen concentration in the exhaust gas is high,
A NOx absorption catalyst that releases the absorbed NOx due to a decrease in oxygen concentration, and an air-fuel ratio of the combustion chamber according to an operating state of the engine, a lean state where the excess air ratio is 1.3 or more, or a rich state that is richer than the lean state. And an air-fuel ratio control means for forcibly switching the air-fuel ratio of the combustion chamber to a rich state when releasing NOx from the NOx absorption catalyst. In a control device for a direct injection engine, a charge amount adjusting means for adjusting an intake charge amount of the combustion chamber is provided, and the air-fuel ratio control means is provided when the air-fuel ratio of the combustion chamber is switched from a lean state to a rich state. And a charge amount control means for controlling the charge amount adjusting means such that the charge amount of the intake air in the combustion chamber is reduced, wherein the charge amount control means is the air-fuel ratio control means. A control device for a spark-ignition direct injection engine, characterized in that when the air-fuel ratio of the combustion chamber is forcibly switched to a rich state, the operation of the charging amount adjusting means is delayed. 2. The fuel injection valve according to claim 1, wherein when the air-fuel ratio of the engine is controlled to a lean state by the air-fuel ratio control means, the fuel is injected by the fuel injection valve.
Injection timing control means for injecting in a compression stroke of a cylinder so as to be in a stratified combustion state, wherein the air-fuel ratio control means, when the operating time of the engine in the stratified combustion state exceeds a set time, the combustion chamber A control device for a spark ignition type direct injection engine, wherein the air-fuel ratio is forcibly switched to a rich state. 3. The air-fuel ratio control means according to claim 1, wherein the air-fuel ratio of the combustion chamber of the engine is set to 1.% when the air-fuel ratio of the combustion chamber of the engine is forcibly switched to a rich state. An injection amount control means for increasing the fuel injection amount so as to be smaller than 1; and an ignition timing correction means for correcting the ignition timing to a retard side when the fuel injection amount is increased by the injection amount control means. A control device for a spark ignition type direct injection engine, comprising: 4. The charge control means according to claim 1, wherein the charge control means controls the operation of the charge control means when the excess air ratio λ of the combustion chamber of the engine is 1.1 <λ <1.3.
A control apparatus for a spark ignition type direct injection engine, wherein the control is performed so as to be faster than when λ <1.1. 5. The air-fuel ratio control device according to claim 1, wherein the air-fuel ratio control means sets the air-fuel ratio of the combustion chamber of the engine to A / F = 15 as a forced rich state for NOx release.
And an exhaust gas recirculation unit that recirculates a part of the exhaust gas to the intake system of the engine. When the air-fuel ratio of the combustion chamber of the engine is in a lean state, the exhaust gas recirculation unit exhausts the exhaust gas. Exhaust recirculation control means for recirculating the exhaust gas so that the exhaust gas recirculation rate at that time even in the forced rich state is equal to or higher than the exhaust gas recirculation rate in the lean state. Control device for spark-ignition direct injection engine. 6. The exhaust gas recirculation means according to claim 5, wherein the exhaust gas recirculation means comprises an exhaust gas recirculation passage communicating the intake passage and the exhaust gas passage of the engine, and an exhaust gas recirculation amount adjusting valve for adjusting an exhaust gas recirculation amount of the exhaust gas recirculation passage. The exhaust gas recirculation control means is configured to maintain the opening of the exhaust gas recirculation amount adjusting valve when the air-fuel ratio of the combustion chamber of the engine is forcibly switched to a rich state. Control unit for direct injection engine. 7. Fuel is directly supplied to a combustion chamber in a cylinder of an engine.
A fuel injection valve for injecting and supplying, disposed in an exhaust passage communicating with the combustion chamber, and absorbing NOx in an oxygen-excess atmosphere where the oxygen concentration in the exhaust gas is high,
A NOx absorption catalyst that releases the absorbed NOx due to a decrease in oxygen concentration, and fuel is injected by the fuel injection valve in a compression stroke of the cylinder so as to be in a stratified combustion state when the engine is in a predetermined low load region. On the other hand, in a control device for a spark ignition type direct injection engine, comprising: an injection timing control means for injecting in a cylinder intake stroke so as to be in a uniform combustion state on a higher load side than the low load region. A filling amount adjusting means for adjusting the filling amount; and controlling the air-fuel ratio of the combustion chamber of the engine such that the excess air ratio becomes a lean state with the excess air ratio of 1.3 or more in the above-mentioned stratified combustion state. An air-fuel ratio control means for switching and controlling the rate so as to be a rich state of 1 or less, and a determining means for determining whether or not the state is such that NOx release from the NOx absorption catalyst is promoted. And a charge amount controlling the charge amount adjusting means such that when the engine shifts from the stratified combustion state to the uniform combustion state, the intake charge amount of the combustion chamber is reduced. Control means, wherein the filling amount control means is configured to delay the operation of the filling amount adjusting means more than the non-promotion state when the determination means determines that the NOx release is promoted. A control device for a spark ignition type direct injection engine. 8. The air-fuel ratio control means according to claim 7, wherein the air-fuel ratio control means determines that the NOx release is promoted by the determination means and that the air-fuel ratio in the combustion chamber of the engine changes from a stratified combustion state to a uniform combustion state. A control device for a spark ignition type direct injection engine, comprising: an injection amount control means for increasing an amount of fuel injection from a fuel injection valve so that a fuel ratio becomes a rich state. 9. The injection amount control means according to claim 8, wherein the injection amount control means is configured to increase the fuel injection amount before the excess air ratio of the combustion chamber becomes smaller than 1.3 due to a decrease in the intake charge amount. A control device for a spark ignition type direct injection engine. 10. The air-fuel ratio control means according to claim 7, wherein when the engine shifts from a stratified combustion state to a uniform combustion state, the air-fuel ratio from the fuel injection valve is set so that the air-fuel ratio of the combustion chamber of the engine becomes rich. An injection amount control unit configured to increase a fuel injection amount, wherein the injection amount control unit increases the fuel injection amount earlier than the non-promotion state when the determination unit determines that the NOx release is promoted. A control device for a spark ignition type direct injection engine. 11. The fuel injection control device according to claim 10, wherein the injection amount control means determines that the excess amount of air in the combustion chamber of the engine is 1.3 when the determination means determines that the NOx release is promoted. While increasing
When it is determined that the vehicle is in the non-promotion state, the excess air ratio is 1.2
A control device for a spark-ignition direct injection engine, wherein the control unit is configured to increase the fuel injection amount when the engine is turned on. 12. An ignition timing correction means according to claim 8, wherein the ignition timing is corrected to a retard side when the fuel injection amount is increased by the injection amount control means. A control device for a spark ignition type direct injection engine. 13. The fuel injection valve according to claim 7, wherein the fuel injection valve controls the fuel injection valve when the determination means determines that the NOx release is promoted and the engine shifts from the stratified combustion state to the uniform combustion state. ,
A control device for a spark ignition type direct injection engine, wherein the injection is divided into two parts: an early injection from an intake stroke to a compression stroke of a cylinder and a late injection in a compression stroke. 14. The method according to claim 7, wherein the determination means is configured to determine when the engine is in a rapid acceleration operation state equal to or greater than a predetermined state as a state in which NOx release from the NOx absorption catalyst is promoted. Control device for spark ignition type direct injection engine. 15. An exhaust gas recirculation means for recirculating a part of exhaust gas to an intake system of an engine, wherein the engine is in a low load region in a stratified combustion state or a predetermined medium load region continuous with the low load region. At one time, there is provided exhaust gas recirculation control means for recirculating exhaust gas by the exhaust gas recirculation means. When the engine is in the medium load range, the injection timing control means supplies fuel by the fuel injection valve during the intake stroke of the cylinder. Injection is performed in two parts, and the determination means is configured to determine when the engine shifts from the low load region to the medium load region as a state of promoting NOx release from the NOx absorption catalyst. A control device for a spark ignition type direct injection engine. 16. The exhaust gas recirculation means according to claim 15, wherein the exhaust gas recirculation means controls the exhaust gas recirculation means so that the exhaust gas recirculation rate becomes 30% or more when the engine shifts from the stratified combustion state to the uniform combustion state. A control device for a spark ignition type direct injection engine. 17. The method according to claim 7, wherein the determination means is configured to determine when the engine enters an acceleration operation state in an idle operation state as a state in which NOx release from the NOx absorption catalyst is promoted. Control device for spark ignition type direct injection engine. 18. A transition prediction means for predicting a transition from a stratified combustion state to a uniform combustion state based on a change in a load state of an engine, and a transition of the engine to a uniform combustion state by the transition prediction means. A charge correction control means for reducing the intake charge of the combustion chamber by the charge adjustment means before the engine shifts to the uniform combustion state when the prediction is made and the determination means determines that the NOx emission is not promoted; A control device for a spark ignition type direct injection engine, comprising: 19. The charging amount adjusting means according to claim 1, wherein the charging amount adjusting means is a throttle valve disposed in an intake passage of the engine, and the charging amount controlling means is provided when at least the engine is in a steady operation state. And controlling the opening of the throttle valve according to the accelerator operation amount and the engine speed.