JP2000205004A - Control device for cylinder injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce NOx while improving an acceleration performance and a combustibility during deceleration. SOLUTION: This control device has an EGR valve basic control quantity setting means 59 as a means for controlling an EGR quantity, an EGR valve control quantity computing means 60, and an EGR valve control means 61. The EGR valve basic control quantity setting means 59 sets the basic control quantity of an EGR valve 38 according to a running mode. The EGR valve control quantity computing means 60 detects an accelerating stage or a decelerating stage from a change rate of an accelerator opening, and sets a correction factor so as to reduce and correct the basic control quantity given by the EGR valve basic control quantity setting means 59. When a running mode is stoichiometric, the last control quantity is computed by applying the correction factor to the basic control quantity. The EGR valve control means 61 controls the lift quantity of the EGR valve 38 by outputting a control signal proportional to the last control quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an engine provided with an exhaust gas recirculation means for introducing a part of exhaust gas back into an intake system. In particular, the invention provides an injector for directly injecting fuel into a combustion chamber. The present invention relates to a control device for a direct injection engine.

[0002]

2. Description of the Related Art Conventionally, there is known an engine provided with an exhaust gas recirculation means for introducing a part of exhaust gas into an intake system again in order to reduce NOx emission.

In recent years, in particular, an injector for directly injecting fuel into the combustion chamber has been provided, and when the load is low, the fuel is injected from the injector late in the compression stroke, whereby stratified charge combustion is performed in a state where the air-fuel mixture is unevenly distributed around the ignition plug. In this way, while maintaining combustion stability, the air-fuel ratio is made lean to improve fuel efficiency, and at high load, the fuel is diffused by injecting fuel in the intake stroke to perform uniform combustion, thereby increasing the air-fuel ratio. An in-cylinder injection spark ignition engine (hereinafter, referred to as an in-cylinder injection engine) has been developed in which a high stoichiometric air-fuel ratio or rich engine output is obtained, and this type of engine also employs an exhaust gas recirculation means. In some cases, a part of the exhaust gas is introduced again into the intake system. For example, Japanese Patent Application Laid-Open No. 9-32651 discloses an engine in which part of exhaust gas is again introduced into an intake system in a stoichiometric region and a stratified combustion region of uniform combustion.

[0004]

In this type of engine provided with exhaust gas recirculation means, the recirculation amount of exhaust gas (generally, based on the engine speed and the actual intake air amount) is obtained from a map prepared in advance. (EGR amount) is determined, but recently, the transient state of the engine, that is, the time of acceleration and deceleration is detected, and the EGR amount is suppressed in the transient state to improve the acceleration performance and the combustion performance at the time of deceleration. It is considered to improve.

That is, at the time of acceleration, there is a time lag from when the accelerator pedal is depressed until the intake air charge reaches the target value. As a result, the increase in torque in the initial stage of acceleration is slow, and it is difficult to obtain smooth acceleration. However, when the amount of EGR during acceleration is reduced as described above, the proportion of fresh air in the intake gas introduced into the combustion chamber increases, whereby a rapid increase in torque can be expected. On the other hand, at the time of deceleration, the throttle valve is closed and the intake charge decreases, so that the already recirculated exhaust gas tends to stay in the combustion chamber, and the exhaust gas is further recirculated and the fresh air in the combustion chamber is regenerated. A so-called over-EGR in which the ratio is remarkably reduced is likely to cause poor combustion such as misfire. However, if the amount of EGR during deceleration is reduced as described above, over EGR
Therefore, it is possible to expect prevention of deterioration of combustibility such as misfire during deceleration.

Accordingly, even in the above-described in-cylinder injection type engine, the transient state of the engine is similarly detected, and the EGR amount during the transient state is reduced, thereby improving the acceleration performance and the combustion property during the deceleration. It is conceivable to aim for.

However, since the combustion state of the in-cylinder injection engine is switched between stratified combustion and uniform combustion as described above, if the EGR amount is uniformly suppressed during a transition, it will be described in detail in an embodiment of the invention. In some cases, the effect of reducing NOx is simply impaired and not always effective.
Therefore, in the cylinder injection engine, while improving the acceleration performance and the combustion performance during deceleration as described above,
It is necessary to adjust the EGR amount so that the emission of NOx can be reduced as much as possible.

The present invention relates to a direct injection type engine.
NOx while improving acceleration and combustion during deceleration
It is an object of the present invention to provide an engine control device capable of satisfactorily reducing the engine speed.

[0009]

In order to solve the above-mentioned problems, the present invention comprises an injector for directly injecting fuel into a combustion chamber, and a stratified combustion state in which fuel is injected during a compression stroke to perform stratified combustion. An exhaust gas recirculation means for recirculating exhaust gas from the exhaust system of the engine to the intake system, and an exhaust system, wherein the combustion state can be switched to a uniform combustion state in which fuel is injected during the intake stroke to perform uniform combustion. In a control device for a direct injection type engine having a recirculation amount adjusting means capable of adjusting a gas recirculation amount, a recirculation amount setting means for setting a recirculation amount of exhaust gas according to an operation state of the engine, and a combustion state. Determining means for determining whether stratified combustion or uniform combustion;
Only when the combustion state is in a uniform combustion state and the operation state is in a transient state, based on the transient state detecting means for detecting the transient state of the operating state and the detection result of the determining means and the detection result of the transient state detecting means. Correction means for reducing the reflux amount set by the reflux amount setting means, and reflux control means for controlling the reflux amount adjusting means based on the reflux amount set by the reflux amount setting means or the reflux amount corrected by the correction means. (Claim 1).

According to this engine control device, the exhaust gas is basically recirculated based on the recirculation amount set by the recirculation amount setting means. The amount of recirculation set by the setting means is reduced and corrected. However, even when the operating state is in a transitional state, when the combustion state is a stratified combustion state, the reduction of the recirculation amount is not performed, and only when the combustion state is a uniform combustion state, the reduction of the recirculation amount is performed.

In the above configuration, the correction means may be configured to correct the amount of recirculation set by the recirculation amount setting means when the acceleration is detected as the transient time. Item 2) The correction means may be configured to correct the amount of recirculation set by the recirculation amount setting means to decrease the amount of recirculation when the time of deceleration is detected as the transient time (claim 3).

With respect to the setting of the recirculation amount of the exhaust gas by the recirculation amount setting means, the intake air amount changes according to the engine load in the uniform combustion state, but the intake air amount changes according to the engine load in the stratified combustion state. However, the recirculation amount of the exhaust gas is set based on the engine speed and the intake air amount when the combustion state is the uniform combustion state, and is related to the engine speed and the accelerator opening when the stratified combustion state is performed. The recirculation amount of the exhaust gas may be set based on the information (claim 4).

If the intake air amount control means for increasing the intake air amount during stratified combustion compared to the intake air amount during uniform combustion is provided, combustion can be performed in a state where the air-fuel ratio is satisfactorily lean during the stratified combustion. It can be performed (claim 5). In this case, the intake air amount control means can be configured to control the intake air amount so that the intake air pressure at the time of stratified combustion becomes a pressure at substantially the full load of the engine (claim 6). The intake air amount control means can be configured to control the throttle valve to an opening degree corresponding to the engine speed so that the intake pressure becomes a pressure at substantially full load of the engine.

In particular, during stratified charge combustion, combustion is performed with the air-fuel ratio leaner than the stoichiometric air-fuel ratio, and during uniform combustion, combustion is performed with the air-fuel ratio substantially at the stoichiometric air-fuel ratio. (Claim 8) Acceleration performance can be favorably improved at the time of uniform combustion, and the combustibility at the time of deceleration can be effectively improved. Further, the emission of NOx can be reduced as much as possible.

[0015]

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

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

An intake passage 24 and an exhaust passage 34 are connected to the engine body 10. The intake passage 24 is provided with an air cleaner 25, an air flow sensor 26, a throttle valve 28 driven by a motor 27, and a surge tank 30 in this order from the upstream side. An independent intake passage for each cylinder is provided downstream of the surge tank 30, and each independent intake passage communicates with an intake port. In this embodiment, the downstream portion of each of the independent intake passages is the first and second portions.
Into two passages 31a and 31b, two intake ports downstream thereof open to the combustion chamber, and the second passage 31b
The control valve 32 for swirl generation (hereinafter referred to as S valve 3)
2).

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

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

Further, an EGR passage 37 for recirculating exhaust gas is formed between the exhaust passage 34 and the intake passage 24, and the amount of exhaust gas recirculation (EGR amount) is adjusted in the EGR passage 37. An EGR valve 38 is provided. That is, the EGR passage 37 and the like constitute exhaust gas recirculation means of the present invention, and the EGR valve 38 constitutes recirculation amount adjusting means of the present invention.

In addition to the air flow sensor 26, the engine further includes a boost sensor 40 for detecting the intake negative pressure in the surge tank 30, a throttle opening sensor 41 for detecting the throttle opening, and a rotation for detecting the engine speed. Number sensor 42, accelerator opening sensor 43 for detecting accelerator opening (accelerator operation amount), intake air temperature sensor 44 for detecting intake air temperature, atmospheric pressure sensor 45 for detecting atmospheric pressure, water temperature sensor 46 for detecting engine cooling water temperature , EGR valve lift sensor 48 for detecting the lift amount of the O ₂ sensor 47, EGR valve for detecting the air-fuel ratio by detecting the oxygen concentration in the exhaust gas, such as fuel pressure sensor 49 for detecting the fuel pressure of fuel supplied to the injector 22 Sensors are provided, and output signals (detection signals) of these sensors are transmitted to an ECU (control unit) 50. It has been input.

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

As basic control of the direct injection engine of this embodiment, various operation modes in which the fuel injection form (injection timing, air-fuel ratio, etc.) from the injector 22 is different can be selected, and depending on the operation region. The operation mode is changed.

More specifically, as will be described later, a predetermined region on the low-load, low-rotation side is a stratified combustion region, and the other region is a uniform combustion region (see FIG. 4). In the stratified combustion region, fuel is injected from the injector 22 at a later stage of the compression stroke, so that a stratified combustion mode is set such that combustion is performed in a stratified state in which the air-fuel mixture is unevenly distributed near the ignition plug 20. In this case, the opening degree of the throttle valve 28 is increased and the amount of intake air is increased, so that the air-fuel ratio of the entire combustion chamber is significantly lean (for example, 3).
0 or more). On the other hand, in the uniform combustion region, the fuel is injected from the injector 22 in the first half of the intake stroke, so that the combustion is performed in a state in which the air-fuel mixture is uniformly diffused throughout the combustion chamber 15. In this uniform combustion region, the excess air ratio λ is λ = 1, that is, the stoichiometric air-fuel ratio (A / F = 14.7). As shown by the hatched lines in FIG. 3, in the uniform combustion region, the air-fuel ratio is made richer than the stoichiometric air-fuel ratio (λ <1) in the full-load region of the accelerator and in the high-load region and high-speed region near the accelerator region. An enriched region to be set may be provided.

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

The target load setting means 52 calculates the virtual volume efficiency from a map set in advance according to the accelerator opening accel and the engine speed ne, and calculates the virtual volume efficiency by the intake density state detecting means 51. The virtual charging efficiency is determined by taking into account the density of the intake air obtained. As a result, the charging efficiency corresponding to the required engine torque assuming the standard operating condition for maintaining the air-fuel ratio at the stoichiometric air-fuel ratio is obtained as the virtual charging efficiency.

The virtual volume efficiency is determined by opening the accelerator so that the required output performance can be obtained beforehand under standard atmospheric conditions by bench tests or the like and under standard operating conditions in which the air-fuel ratio is maintained at the stoichiometric air-fuel ratio. The correspondence between the degree accel and the engine speed ne and the virtual volume efficiency is determined, and the correspondence is stored in a memory in the ECU 50 as a map, and the actual accelerator opening degree accel is obtained from this memory.
And a virtual volume efficiency corresponding to the engine speed ne is required.

The target load setting means 52 further comprises:
From the virtual charging efficiency, a target indicated average effective pressure, which is a value corresponding thereto, is obtained, and this is set as a target load. In this case, the first target indicated mean effective pressure Piob is calculated from the virtual filling efficiency.
On the other hand, while j is obtained, an averaging process is performed on the virtual filling efficiency, and a second target indicated mean effective pressure Piobjd is obtained from the virtual filling efficiency after the averaging process.

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

The operation mode setting means 53 sets a basic operation mode mods according to the first target indicated mean effective pressure Piobj and the engine speed ne. That is, as shown in FIG. 4, the first target indicated mean effective pressure Piobj is lower than the predetermined low-load-side threshold and the engine speed is low (stratified combustion region), and the stratified combustion mode is set. In the region (uniform combustion region), a uniform combustion operation mode with λ = 1 (hereinafter referred to as a stoichiometric mode) is set.

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

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

More specifically, as means for controlling the intake air amount (that is, the intake amount control means of the present invention), the target air-fuel ratio setting means 54 and the target charging efficiency calculating means 55 are used.
And a throttle opening calculating means 56. The target air-fuel ratio setting means 54 sets the target air-fuel ratio afwb for controlling the intake air amount for each operation mode set by the operation mode setting means 53. In the stratified combustion mode, the first target indicated average value Effective pressure Piobj and engine speed ne
In accordance with the target air-fuel ratio af
In the stoichiometric mode, the target air-fuel ratio afwb is set to the stoichiometric air-fuel ratio (λ = 1).

The target charging efficiency calculating means 55 calculates the excess air ratio (afwb / 14...) Of the target air-fuel ratio in the lean operation from the first target indicated average effective pressure Piobj or the virtual charging efficiency corresponding thereto. The target filling efficiency is obtained by taking into account 7) and the fuel efficiency improvement effect. In other words, the virtual charging efficiency is a value corresponding to a target load assuming a state of operating at the stoichiometric air-fuel ratio. On the other hand, in order to secure the same fuel injection amount during the lean operation, the above-described excess air ratio is required. Although it is necessary to take this into account, securing the same fuel injection amount as in the case of the stoichiometric air-fuel ratio in this way increases the thermal efficiency during lean operation and improves fuel efficiency. Will be higher than in the case of. Therefore,
In order to obtain a torque corresponding to the target load, in addition to the above-mentioned excess air ratio, the fuel efficiency improvement effect is also taken into account. When taking into account the fuel efficiency improvement effect, the target filling efficiency is corrected in the decreasing direction to an extent commensurate with the fuel efficiency improvement effect.

The throttle opening calculating means 56 obtains a target volume efficiency by performing a correction according to the intake density from the target charging efficiency, and obtains the target volume efficiency and the engine speed ne.
The throttle opening is determined according to. In this case, the throttle opening may be determined in the stratified combustion mode so that the intake pressure always becomes the pressure when the engine is fully loaded.

As means for controlling the EGR amount, EGR
It has a basic valve control amount setting means 59, an EGR valve control amount calculating means 60, and an EGR valve control means 61.

The EGR valve basic control amount setting means 59 includes:
The basic control amount pbase of the EGR valve 38 (that is, the basic value of the EGR amount) is set for each operation mode mods set by the operation mode setting means 53. In the stratified charge combustion mode, the first target indicated average effective pressure is set. A basic control amount pbase is obtained from a map prepared in advance according to Piobj (information related to the accelerator opening) and the engine speed ne. In the stoichiometric mode, an actual intake air amount obtained based on an output of the air flow sensor 26 And the engine speed ne,
A basic control amount pbase is obtained from a map created in advance. That is, the EGR valve basic control amount setting means 59 constitutes the recirculation amount setting means of the present invention.

The EGR valve control amount calculating means 60 calculates the final control amount pt of the EGR valve 38. As shown in FIG. 3, the EGR feedback coefficient calculating means 60a and the EG
R valve final control amount calculating means 60b.

EGR feedback coefficient calculating means 60a
Determines the operation mode mods, and when the operation mode mods is the stratified combustion mode, the control amount pt of the EGR valve 38 based on the actual intake air amount so that the actual intake air amount becomes the target intake air amount.
To obtain a target intake air amount from the first target indicated mean effective pressure Piobj and the target air-fuel ratio afwb,
An EGR feedback coefficient ptfb is calculated based on a difference between the actual intake air amount obtained based on the output of the air flow sensor 26 and the target intake air amount.

The EGR valve final control amount calculating means 60b detects the transient state of the operating state, that is, the acceleration or deceleration, from the rate of change of the accelerator opening accel. When the operating state is in the transient state, the EGR valve basic control amount is calculated. A correction coefficient is set so that the basic control amount pbase obtained by the setting means 59 is corrected to be reduced. In this case, as a correction coefficient suitable for a transient state, an acceleration decrease correction coefficient pacc is set during acceleration, and a deceleration decrease correction coefficient pdec is set during deceleration. Then, the operation mode mods is determined. If the operation mode mods is the stratified charge combustion mode, the EGR feedback correction coefficient pbase is added to the basic control amount pbase obtained by the EGR valve basic control amount setting means 59.
A final control amount pt of the EGR valve 38 is calculated in consideration of tfb,
On the other hand, when the operation mode mods is the stoichiometric mode,
A final control amount pt of the EGR valve 38 is calculated by adding the EGR feedback correction coefficient ptfb and the above-mentioned decrease correction coefficient pacc or pdec to the basic control amount pbase obtained by the EGR valve basic control amount setting means 59. That is, the EGR valve control amount calculating means constitutes the determining means, the transient detecting means and the correcting means of the present invention.

The EGR valve control means 61 constitutes the recirculation control means of the present invention. The EGR valve control means 61 outputs a control signal proportional to the control amount pt obtained by the EGR valve control amount calculating means 60 to output the EGR valve 38. Control.

As means for controlling the S-valve opening, an S-valve opening setting means 62 is provided. This S valve opening setting means 6
2 sets the S valve opening for each operation mode mods set by the operation mode setting means 53 so as to obtain the swirl required in each mode. In the stratified combustion mode, the first target diagram is set. According to the average effective pressure Piobj and the engine speed ne, the S-valve opening is obtained from a map created in advance, and in the stoichiometric mode, from the map created in advance according to the actual charging efficiency ce and the engine speed ne. The S valve opening is determined.

The means for controlling the fuel injection from the injector 22 includes a target air-fuel ratio creating means 63, an operation mode setting means 64, a split ratio setting means 65, and an injection amount calculating means 6.
6, an injection timing setting means 67 and an injection control means 68 are provided.

The target air-fuel ratio creating means 63 calculates the target air-fuel ratio used for controlling the fuel injection amount and the like, and calculates the target air-fuel ratio afw0 mainly used during a transient state, and is mainly used during a steady state. Target air-fuel ratio afwbd
Ask for.

The target air-fuel ratio afw0 used during the transition is determined by the second target indicated mean effective pressure Piobjd or the virtual charging efficiency corresponding thereto so that a torque corresponding to the target load can be obtained under the actual charging efficiency. Based on the actual filling efficiency ce, it is determined in consideration of the fuel efficiency improvement effect. On the other hand, the target air-fuel ratio afwbd used in the steady state is the second in the stratified combustion mode.
The target indicated average effective pressure Piobjd and the engine speed ne are obtained from a map created in advance, and in the stoichiometric mode, the target air-fuel ratio afwbd is calculated based on the stoichiometric air-fuel ratio (λ =
1).

The target air-fuel ratio creating means 63 calculates a deviation dafwb between the target air-fuel ratio afwb for controlling the intake air amount and the target air-fuel ratio afw0 obtained as described above, and calculates a deviation daf.
The target air-fuel ratio afw0 is set to the final target air-fuel ratio afw during a transition when wb increases, and the target air-fuel ratio afwbd is set to the final target air-fuel ratio afw during steady state when the deviation dafwb is small.

The operation mode setting means 64 sets the operation mode modf used to determine the control parameters of the high-speed system,
The target air-fuel ratio afw0 for controlling the fuel injection amount and the like is set according to the engine speed ne. That is, as shown in FIG. 5, when the target air-fuel ratio afw0 is larger than the stoichiometric upper limit reference value, the stratified charge combustion mode is set, and when the target air-fuel ratio afw0 is smaller than the stoichiometric upper limit reference value, the stoichiometric mode is set.

When the operation mode modf is changed between the stoichiometric mode and the stratified combustion mode, the split injection mode is temporarily selected near the stoichiometric upper limit reference value (the hatched portion in FIG. 5). It may be. In the split injection mode, the fuel injection is performed by dividing the fuel injection into an intake stroke and a compression stroke, and the mode is changed from the stratified combustion mode of the compression stroke injection to the stoichiometric mode of the intake stroke injection, and vice versa. If the mode change is performed, the combustion state can be abruptly changed by passing through the split injection mode.

The split ratio setting means 65 sets the split ratio between the intake stroke injection and the compression stroke injection according to the operation mode modf set by the operation mode setting means 64. In the stratified combustion mode, the intake stroke injection is performed. The ratio is 0%,
In the stoichiometric mode, the intake stroke injection ratio is set to 100%. When the split injection mode is selected, the split ratio may be set according to the target air-fuel ratio afw and the engine speed ne.

The injection amount calculating means 66 calculates the actual charging efficiency ce determined from the output of the air flow sensor 26, the target air-fuel ratio afw determined by the target air-fuel ratio creating means 62,
The fuel injection amount is calculated based on the injection ratio set by the split ratio setting means 65. In this case, each basic injection amount of the intake stroke injection and the compression stroke injection is calculated, and further, the intake stroke injection and the compression stroke injection are corrected by taking into account the correction values of the intake stroke injection and the compression stroke injection according to the fuel pressure and other correction values. The final injection amount of the compression stroke injection is calculated, and an injection pulse Ti proportional to this final injection amount is obtained.

The injection timing setting means 67 determines the fuel injection timing th
tinj is set for each operation mode set by the operation mode setting means 64. In the stratified combustion mode, tinj
The injection timing for the compression stroke injection is obtained from a map created in advance in accordance with the target indicated average effective pressure Piobjd and the engine speed ne, and in the stoichiometric mode, the engine speed is calculated.
The injection timing for the intake stroke injection is obtained from a table created in advance according to ne. When the split injection mode is set, the data in the stratified combustion mode is used as the injection timing for the compression stroke injection, and the target air-fuel ratio af
An injection timing for intake stroke injection is obtained from a map created in advance according to w and the engine speed ne.

The injection control means 68 operates the injector 22 at the injection timing set by the injection timing setting means 67 for a time corresponding to the injection pulse width Ti calculated by the injection amount calculation means 66. Injection pulse
Output Ti.

As means for controlling the ignition timing,
A setting means 69 for setting a basic ignition timing and a correction amount, and an ignition timing calculating means 70 are provided.

The setting means 69 sets the basic ignition timing and various ignition timing correction values for each operation mode set by the operation mode setting means 64, and sets the ignition timing calculation means 70.
Is to determine the ignition timing from the basic injection amount set by the setting means 69 and various correction values.

FIG. 6 is a flowchart showing a process mainly related to the control of the EGR valve 38 among various processes performed by the ECU 50, such as various calculations and controls.

When this flowchart starts, first, in step S1, various signals of the rotation speed sensor 42, the accelerator opening sensor 43, etc. are read, and in step S2
A first target indicated mean effective pressure Piobj, which is a target load, is obtained based on the accelerator opening accel and the engine speed ne.

In step S3, it is determined whether or not the EGR execution condition is satisfied. If it is determined that the EGR execution condition is satisfied, the process further proceeds to step S4 to determine whether or not the operation mode mods is in the stratified combustion mode. I do. If it is determined that the engine is in the stratified combustion mode, the basic control amount pbase is obtained from the first target indicated mean effective pressure Piobj and the engine speed ne in step S5, and then the actual intake air amount and the target An EGR feedback coefficient ptfb is calculated based on the deviation from the intake air amount, and a final control amount pt is calculated in step S7 by adding the EGR feedback coefficient ptfb to the basic control amount pbase.

Then, in step S8, the final control amount pt
Is output to control the lift amount of the EGR valve 38, and thereafter, the process returns to step S1.

If it is determined in step S3 that the EGR execution condition is not satisfied, step S9 is executed.
Then, the final control amount pt is set to "0", and the process proceeds to step S9. In this case, the EGR valve 38 is fully closed controlled.

On the other hand, if it is determined in step S4 that the operation mode mods is not the stratified combustion mode, the basic control amount pbase is obtained from the actual intake air amount and the engine speed ne in step S10, and the operation is performed in step S11. It is determined whether the state is during acceleration. Here, when it is determined that the vehicle is accelerating, the acceleration decrease correction coefficient pacc is set in step S12, and the process proceeds to step S15. on the other hand,
If it is determined in step S11 that the operation state is not during acceleration, then it is determined whether or not the operation state is in deceleration in step S13. If it is determined that the operation state is in deceleration, the deceleration reduction correction coefficient is determined in step S14. pdec is set, and the routine goes to Step S15. In step S15, the calculation of the EGR feedback coefficient ptfb is stopped, and the EG immediately before the stop is stopped.
The R feedback coefficient ptfb is stored, and the routine goes to Step S7.

When the process proceeds to step S7 after steps S12 and S14, the EGR feedback coefficient ptfb stored as described above and the acceleration reduction coefficient pacc or Taking into account the deceleration and reduction correction coefficient pdec, the basic control amount pbase
, The final control amount pt is calculated.

In the in-cylinder injection engine of the present embodiment having the above-described control device, the stratified combustion mode and the stoichiometric mode are set as the operation modes according to the operation state. In the stratified combustion mode, stratified combustion is performed in a state in which the air-fuel ratio is significantly leaner than the stoichiometric air-fuel ratio, so that fuel efficiency is greatly improved.In the stoichiometric mode, the air-fuel ratio is substantially the stoichiometric air-fuel ratio. In this state, uniform combustion is performed by the intake stroke injection. In the above-described stratified combustion mode, the intake air amount is increased according to the target load for each operation mode, such as increasing the throttle opening to increase the intake air amount to make the air-fuel ratio lean while maintaining the required torque. In addition to the control, the fuel injection amount, the injection timing, the ignition timing, and the like are also controlled based on the target load, the operation mode, and the like.

The EGR valve 38 is controlled as follows.

That is, in the stratified charge combustion mode, the air-fuel mixture having an appropriate air-fuel ratio is unevenly distributed around the ignition plug due to the compression stroke injection, and a large amount of excess air exists around the mixture. Since the combustion stability is easily ensured, the control amount pt of the EGR valve 38 is calculated according to the target indicated average effective pressure Piobj and the engine speed ne in order to introduce a relatively large amount of EGR so as not to impair the combustion stability. Is done.

On the other hand, in the stoichiometric mode, the control amount of the EGR valve 38 is calculated according to the intake air amount and the engine speed ne in order to perform a certain amount of EGR while satisfying the demands on the output and the like. In this case, particularly when the operation state is in a transitional state, that is, during acceleration or deceleration, the EGR valve 3 is compared with the normal operation state as described in the flowchart of FIG.
The control amount pt of 8 is reduced, whereby the acceleration performance is improved, and the deterioration of the combustibility at the time of deceleration is prevented.

That is, there is a time lag from when the accelerator pedal is depressed to when the intake air charge amount ce reaches the target value, and the control amount of the EGR valve 38 in the initial stage of acceleration is changed to the normal operation state (that is, the stoichiometric mode). If the control is performed in the same manner as in the state other than during the transition, the torque slowly increases as shown in FIG. 7A, and it is difficult to obtain smooth acceleration. However, when the EGR amount during acceleration is reduced from that in the normal operation state, the proportion of fresh air in the intake gas introduced into the combustion chamber 15 increases, and as a result, the torque decreases as shown by the broken line in FIG. It will rise quickly. As a result, smooth acceleration can be expected, and the acceleration is improved. On the other hand, at the time of deceleration, the throttle valve 28 is closed and the flow of the intake air becomes slow, so that the already recirculated exhaust gas tends to stay in the combustion chamber. Therefore, when the control amount pt of the EGR valve 38 at the time of deceleration is controlled in the same manner as in the normal operation state, the so-called over EGR is achieved, in which the proportion of fresh air in the combustion chamber 15 is significantly reduced due to the recirculation of exhaust gas. However, when the vehicle is decelerated, a combustion failure such as a misfire may occur, and the torque may greatly decrease as shown by the solid line in FIG. However, if the amount of EGR at the time of deceleration is reduced as described above, over-EGR is unlikely to occur, and a decrease in flammability such as misfire at the time of deceleration is prevented. As a result, the torque drops as shown by the broken line in FIG. Disappears.

In the stratified charge combustion mode, the control amount of the EGR valve 38 is not reduced during the transition as in the stoichiometric mode, for the following reason.

That is, in the stratified charge combustion mode, since the intake air amount is increased by increasing the throttle opening to make the air-fuel ratio lean, as shown in FIG. The rise delay of ce is small, and the rise of torque is performed quickly. In the stratified combustion mode,
As described above, the air-fuel mixture having an appropriate air-fuel ratio is unevenly distributed around the ignition plug, and a large amount of excess air exists around the mixture, so that combustion stability is easily ensured even when the exhaust gas is recirculated. This means that the contribution to the improvement of the flammability is low even if the amount of recirculation is reduced. Therefore, in the stratified charge combustion mode, even when the control amount pt of the EGR valve 38 is actively reduced during acceleration or deceleration, a remarkable effect such as improvement in acceleration such as in the stoichiometric mode cannot be obtained. Reducing the amount only hinders NOx reduction.
Therefore, in the stratified combustion mode, the transient EGR
The control amount pt of the EGR valve 38 is set in the same manner as in the normal operation state without reducing the control amount pt of the valve 38.

Therefore, according to the in-cylinder injection engine equipped with the above-described control device, the acceleration performance can be improved or improved compared to the case where the control amount of the EGR valve 38 during the transition is reduced uniformly regardless of the combustion state. NO while improving flammability during deceleration
x can be favorably reduced.

The above-described in-cylinder injection engine is an example of an in-cylinder injection engine to which the engine control device according to the present invention is applied. However, the present invention can be appropriately changed without departing from the gist of the present invention.

For example, in the above-described embodiment, when the operation mode is the stoichiometric mode, the control amount pt of the EGR valve 38 is reduced as compared with the normal operation state during both acceleration and deceleration. Alternatively, the amount may be reduced only during acceleration or only during deceleration.

In the above embodiment, when the operation mode is the stratified charge combustion mode, the basic control amount pbase is calculated from a map prepared in advance according to the first target indicated mean effective pressure Piobj and the engine speed ne. Although it is obtained, it may be obtained directly from the accelerator opening and the engine speed ne.In short, if it is obtained based on information related to the engine speed ne and the accelerator opening, Good.

[0073]

As described above, the present invention comprises an injector for directly injecting fuel into a combustion chamber, and a stratified combustion state in which fuel is injected in a compression stroke by the injector to perform stratified combustion. A cylinder configured to be capable of switching a combustion state to a uniform combustion state in which the injected fuel is injected during an intake stroke to perform uniform combustion and to recirculate exhaust gas from an exhaust system to an intake system. In the control device of the internal injection type engine, when the combustion state is in a uniform combustion state and the operation state is in a transitional state, the set recirculation amount of the exhaust gas is corrected to be reduced. In the combustion state, the amount of fresh air introduced into the combustion chamber during the transition is increased, thereby improving the acceleration performance and improving the combustion performance during deceleration.
On the other hand, when the combustion state is stratified combustion, the above-mentioned reduction correction of the set recirculation amount is not performed, whereby a relatively large amount of exhaust gas is recirculated to the extent that combustion stability is not impaired, and NOx emissions are reduced. Is favorably reduced.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing an embodiment of an engine to which an engine control device of the present invention is applied.

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

FIG. 3 is a block diagram showing a specific configuration of an EGR valve control amount calculating means in FIG. 2;

FIG. 4 is an explanatory diagram showing an area setting of an operation mode.

FIG. 5 is an explanatory diagram showing setting of an operation mode used for calculation of a fuel injection amount and the like.

FIG. 6 is a flowchart showing control of an EGR valve.

FIG. 7 is an explanatory diagram showing a relationship among an accelerator opening, a throttle opening, an intake charge amount, an EGR valve lift amount, an actual EGR amount, and a torque in a uniform combustion mode and a stratified combustion mode.

[Explanation of symbols]

 Reference Signs List 10 engine body 15 combustion chamber 20 spark plug 22 injector 37 EGR passage 38 EGR valve 48 EGR valve lift sensor 50 ECU 59 EGR valve basic control amount setting means 60 EGR valve control amount calculation means 61 EGR valve control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 21/08 301 F02D 21/08 301A 41/04 310 41/04 310C 310F 43/00 301 43/00 301N 301K 301E F02M 25/07 550 F02M 25/07 550R 550D 550J 550K 570 570A (72) Inventor Kiyotaka Mamiya 3-1, Fuchu-cho, Shinchu, Aki-gun, Hiroshima Pref. Mazda Co., Ltd. F-term (reference) AD03 AD06 AE05 AG01 AG03 3G062 AA00 AA07 BA04 BA05 BA06 BA08 CA04 CA05 CA06 FA08 FA14 GA01 GA04 GA05 GA06 GA15 GA17 GA21 GA25 GA26 3G084 BA05 BA09 BA20 CA04 CA06 DA10 DA12 DA15 EB12 EB25 EC04 FA00 FA02 FA07 FA10 FA11 FA20 AA09 AA10 AA17 BA01 BA05 BA06 BA09 BB06 BB13 DC06 DC09 EA01 EA02 EA05 EA06 EA07 EC01 FA08 FA17 GA05 GA06 GA12 GA13 GA17 GA18 HA01X HA01Z HA04Z HA05Z HA06X HA06Z HC01Z HD05Z HD07X HD07Z HE01Z HE08Z HF09Z 3G301 HA01 HA04 HA13 HA16 PA03 NE06 KA11 PA01 NE12 PB08Z PD03Z PD15Z PE01Z PE08Z PF03Z

Claims (8)

[Claims] 1. A stratified combustion state comprising an injector for directly injecting fuel into a combustion chamber and injecting fuel in a compression stroke to perform stratified combustion, and a uniform combustion injecting fuel to an intake stroke to perform uniform combustion. And an exhaust gas recirculation means for recirculating exhaust gas from an exhaust system of the engine to an intake system, and a recirculation amount adjusting means capable of adjusting a recirculation amount of the exhaust gas. A control device for a direct injection engine, a recirculation amount setting means for setting a recirculation amount of exhaust gas in accordance with an operation state of the engine; a determination means for determining whether a combustion state is stratified combustion or uniform combustion; A transient state detecting means for detecting a transient state of the engine, and a combustion state in a uniform combustion state and an operating state in a transient state based on a result of the determination by the determining means and a result of the detection by the transient state detecting means. Only in the case where the recirculation amount set by the recirculation amount setting means is reduced and the recirculation amount adjusting means is adjusted based on the recirculation amount set by the recirculation amount setting means or the recirculation amount corrected by the correction means. A control device for an in-cylinder injection engine, comprising: a recirculation control means for controlling the recirculation control means. 2. The in-cylinder injection according to claim 1, wherein the correction means reduces the recirculation amount set by the recirculation amount setting means when the acceleration time is detected as the transient time. Control device for the expression engine. 3. The cylinder according to claim 1, wherein the correction means reduces the amount of recirculation set by the recirculation amount setting means when the deceleration time is detected as the transient state. Control device for internal injection engine. 4. The recirculation amount setting means sets the recirculation amount of the exhaust gas based on the engine speed and the intake air amount when the combustion state is a uniform combustion state, and sets the engine rotation speed when the combustion state is a stratified combustion state. 4. The control means for a direct injection engine according to claim 1, wherein the recirculation amount of the exhaust gas is set based on information relating to the accelerator opening. 5. The in-cylinder injection according to claim 1, further comprising an intake air amount control means for increasing an intake air amount during stratified combustion as compared with an intake air amount during uniform combustion. Control device for the expression engine. 6. The in-cylinder injection system according to claim 5, wherein the intake air amount control means controls the intake air amount so that the intake pressure during stratified combustion becomes a pressure at substantially full load of the engine. Engine control device. 7. The intake amount control means controls the throttle valve to an opening degree corresponding to the engine speed so that the intake pressure becomes a pressure at substantially full load of the engine. A control device for an in-cylinder injection engine according to the above description. 8. In stratified charge combustion, combustion is performed in a state where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. In uniform combustion, combustion is performed in a state where the air-fuel ratio is substantially equal to the stoichiometric air-fuel ratio. A control device for a direct injection engine according to any one of claims 1 to 7.