JPH1136926A - Cylinder injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively carry out the regulation of torque in a cylinder injection type engine by appropriately and precisely controlling the fuel consumption in each of stratified and homogenous combustion ranges so as to restrain the difference in torque between both ranges. SOLUTION: An injector 22 directly injects fuel into a combustion chamber so that the fuel is injected during compression stroke in a stratified combustion range, but it is injected during suction stroke during a homogeneous combustion range. Further, a throttle opening degree control means 52 carries out control such that a throttle degree is set to be substantially constant even though the load to the engine varies in the stratified combustion range, but it is changed in accordance with a variation in the load in the homogeneous combustion range while a desired air-fuel ratio setting means 56 sets a desired air-fuel ratio in accordance with an engine speed and a desired torque in the stratified combustion range, but sets the same in accordance with an engine and a change volume of intake air in the homogenous combustion range, and a fuel oil consumption control means 57 controls the fuel oil consumption in accordance with the desired air-fuel ratio and the change volume of intake air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder provided with an injector for directly injecting fuel into a combustion chamber, in which stratified combustion is performed in some operation regions and uniform combustion is performed in another operation region. The present invention relates to an internal injection engine.

[0002]

2. Description of the Related Art Conventionally, an injector for directly injecting fuel into a combustion chamber has been provided, and stratified combustion has been performed in a significantly lean state in a specific operation region in order to improve fuel efficiency.
In-cylinder injection engines designed to perform uniform combustion in other operating regions are generally known. That is, as a control of the combustion state of the engine, in the predetermined operation region on the low-load low-rotation side, the fuel is injected from the injector in the compression stroke, so that the combustion chamber as a whole is substantially lean and mixed around the spark plug. The stratified combustion is performed by unevenly distributing the air, and the fuel is injected in the intake stroke from the injector in the high load side and the high rotation side regions, so that the fuel is diffused throughout the combustion chamber to perform uniform combustion. I have to. Also, in the relatively low load side and the low rotation side operation region adjacent to the stratified combustion region in the region where uniform combustion is performed, the air-fuel ratio is generally leaner than the stoichiometric air-fuel ratio, and according to the operation state. It is set to change the air-fuel ratio.

As a general method of controlling the fuel injection amount in such an engine, in a uniform combustion region, a target air-fuel ratio is set according to an operating state, and a fuel is set based on the target air-fuel ratio and the intake air amount. In the stratified combustion region, on the other hand, in the stratified combustion region, the throttle opening is almost fully opened and the amount of intake air is increased to adjust the torque with the fuel amount. It can be calculated from the map.

In the apparatus disclosed in Japanese Patent Application Laid-Open No. 7-301139, a target torque is obtained from an accelerator opening and an engine speed in both a stratified combustion region and a uniform combustion region. In addition to obtaining the target air-fuel ratio from the map according to the above, the intake air amount is obtained from the engine speed and the boost, and the fuel injection amount is calculated from the target rotational speed and the intake air amount.

[0005]

According to the control which can be considered as a general method described above, the fuel injection amount is directly calculated from a map in the stratified combustion region, and based on the target air-fuel ratio and the intake air amount in the uniform combustion region. The fuel injection method is remarkably different in each operation region, such as calculating the fuel injection amount. Even if a map of the target air-fuel ratio in the uniform combustion region is set, if the intake air density changes due to changes in the intake air temperature or atmospheric pressure, and this affects the intake air amount, the torque step between the two operation regions will And adversely affect driving performance and driver's feeling.

In the apparatus disclosed in the above publication, the amount of intake air is obtained from the engine speed and the boost, and the fuel injection amount is calculated based on this and the target air-fuel ratio.
It is difficult to accurately determine the weight of intake air per cycle, and errors due to changes in intake air temperature and atmospheric pressure are likely to occur. In addition, in both the stratified combustion region and the uniform combustion region, a map is set in which the target air-fuel ratio corresponds to the target torque. It is necessary to adjust the output by controlling the target air-fuel ratio with high accuracy, and the relationship between the target torque and the target air-fuel ratio is set on a map in advance by bench tests etc. so as to satisfy the driving performance under a constant environment. Even so, if the intake air temperature or the atmospheric pressure changes during operation, the intake charge changes, so that the relationship between the actual torque and the target air-fuel ratio is shifted.

[0007] Due to these causes, even with the device disclosed in the above-mentioned publication, there are problems that the torque step between the two operating regions cannot be sufficiently suppressed, and that the operating performance and the like cannot be obtained as required. .

In view of the above circumstances, the present invention appropriately and accurately controls the fuel injection amount in each of the stratified combustion region and the uniform combustion region, suppresses the torque step between both operation regions, and adjusts the torque. It is an object of the present invention to provide a direct injection type engine capable of effectively performing the following.

[0009]

In order to achieve the above object, the present invention comprises an injector for directly injecting fuel into a combustion chamber, wherein a part of an operation region is a stratified combustion region and another operation region is a uniform combustion region. In the stratified combustion region, a fuel is injected in the compression stroke from the injector to perform stratified combustion, and in the uniform combustion region, fuel is injected from the injector in the intake stroke to perform uniform combustion. In the injection type engine, a throttle opening control means for controlling the throttle opening to be substantially constant with respect to a change in load in the stratified combustion region, and changing the throttle opening in accordance with the change in load in the uniform combustion region, and a target air-fuel ratio. In the stratified combustion region, set according to the target torque or accelerator opening,
In the uniform combustion region, the air conditioner includes target air-fuel ratio setting means that is set in accordance with the intake air charge, and fuel injection amount control means that calculates a fuel injection amount from the injector based on the target air-fuel ratio and the intake air charge. It is a thing.

According to this configuration, in both the stratified combustion region and the uniform combustion region, the target air-fuel ratio is set and the fuel injection amount is calculated in accordance with the target air-fuel ratio and the intake charge amount. Even when the intake air density changes due to a change in the atmospheric pressure, the influence of the change on the calculation of the fuel injection amount becomes equal in the two operation regions, and the occurrence of a torque step between the two operation regions is prevented.

In addition, in the stratified combustion region where the throttle opening is substantially constant with respect to a change in load, the target air-fuel ratio is set in accordance with the target torque or the accelerator opening. In the uniform combustion region where the intake air charge changes due to the change, the target air-fuel ratio is set according to the intake air charge, so that the correspondence between the actual operating state and the target air-fuel ratio is properly maintained. It is.

[0012] The engine of the present invention is provided with arithmetic means for calculating the intake air charge from the output of the air flow sensor for detecting the intake air flow, calculating the target torque from the accelerator opening and the engine speed, and controlling the throttle opening. The means sets the throttle opening based on the engine speed and the target torque, and the air-fuel ratio setting means sets the target air-fuel ratio based on the engine speed and the target torque in the stratified combustion region, while in the uniform combustion region. The target air-fuel ratio is set based on the engine speed and the intake charge, and the fuel injection amount control means calculates the fuel injection amount based on the target air-fuel ratio, the intake charge and the engine speed. Is preferred.

With this configuration, the amount of intake air can be accurately obtained from the output of the air flow sensor, and the target torque, the throttle opening, and the target air-fuel ratio can be properly obtained.

[0014] In the uniform combustion region, a specific operation region adjacent to the stratified combustion region is a uniform lean region in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. The target air-fuel ratio setting means and the fuel injection amount control means so as to set an air-fuel ratio and calculate a fuel injection amount based on a target air-fuel ratio, an intake charge amount and an engine speed in a uniform lean region and a stratified combustion region. It is preferable to configure

With this arrangement, the correspondence between the intake air charge and the target air-fuel ratio is properly maintained, particularly in the uniform lean region.

Further, the fuel injection timing from the injector controlled by the fuel injection timing control means and the ignition timing of the engine controlled by the ignition timing control means also correspond to the target torque or the accelerator opening in the stratified combustion region. What is necessary is just to set and set it according to the intake air filling amount in a uniform combustion area. Furthermore, in the case where a control valve for swirl generation is provided in the intake passage, the opening of the control valve controlled by the control valve control means is also set in accordance with the target torque or the accelerator opening in the stratified combustion region, and is uniform. In the combustion region, it may be set in accordance with the intake charge amount.

With this configuration, the fuel injection timing, the ignition timing, and the opening of the control valve are set in accordance with the operating range, as in the case of the target air-fuel ratio. Is controlled.

[0018]

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 according to an embodiment of the present invention.
In this figure, an engine body 10 has a plurality of cylinders 12, and each of the cylinders 12 has a combustion chamber 15 formed 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. An ignition circuit 21 capable of controlling ignition timing is electrically connected to the ignition plug 20. In addition, the tip of the injector 22 faces the combustion chamber 15 from the side,
Fuel is directly injected into the combustion chamber 15 from the injector 22.

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 second passage 31b is closed by the S-valve 32, 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. Further, the exhaust passage 34
An EGR passage 37 for recirculating exhaust gas is formed between the EGR passage 37 and the intake passage 24.
An R valve 38 is provided.

In addition to the air flow sensor 26, the engine has a throttle opening sensor 41 for detecting a throttle opening and a rotation speed sensor 4 for detecting an engine speed.
2. an accelerator opening sensor 43 for detecting an accelerator opening (accelerator pedal depression amount), an intake air temperature sensor 44 for detecting intake air temperature, a pressure sensor 45 for detecting atmospheric pressure, a water temperature sensor 46 for detecting engine cooling water temperature, O ₂ sensor 4 for detecting the air-fuel ratio by detecting the oxygen concentration in the exhaust gas
Sensors such as 7 are provided, and output signals (detection signals) of these sensors are input to an ECU (control unit) 50.

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

The basic control of the in-cylinder injection type engine according to the present embodiment is as shown in FIG.
2, the fuel injection mode and the air-fuel ratio are changed depending on the operating range.

That is, the region on the low-load, low-rotation side is a stratified combustion region. In this region, fuel is injected from the injector 22 in the latter stage of the compression stroke, so that the air-fuel mixture is unevenly distributed near the ignition plug 20. Combustion is performed in a stratified state. In this case, the opening degree of the throttle valve 28 is increased and the intake air amount is increased, so that the air-fuel ratio of the entire combustion chamber is set to a large lean state (for example, 40 or more).

The region other than the stratified combustion region is a uniform combustion region. In this region, the injector 22
By injecting fuel in the first half of the intake stroke, combustion is performed in a state where the air-fuel mixture is uniformly diffused throughout the combustion chamber 15. In the region of relatively low load and low rotation speed in the uniform combustion region, the excess air ratio λ is λ> 1, that is, the air-fuel ratio leaner than the stoichiometric air-fuel ratio (for example, about 20). In the high rotation speed region, λ = 1, that is, the stoichiometric air-fuel ratio (A / F = 14.7). The operating region (uniform lean region) in which the air-fuel ratio is lean in the uniform combustion region is adjacent to the stratified combustion region. The air-fuel ratio may be set to be richer than the stoichiometric air-fuel ratio (λ <1) in the full-open region of the accelerator or in the high-load region and the high-speed region in the vicinity thereof.

FIG. 3 shows the structure of the means functionally included in the ECU 50. The ECU 50 determines the intake charge amount c based on the output (intake amount) afs of the air flow sensor 26.
On the other hand, the target torque calculating means 52 calculates the accelerator opening acc and the engine speed at that time from a map in which the target torque trqob is set in advance in association with the accelerator opening acc and the engine speed ne. The target torque trqob according to ne is calculated. The map of the target torque and various maps described later are stored in a memory in the ECU 50.

The ECU 50 has throttle opening control means 53, target air-fuel ratio setting means 56, fuel injection amount control means 57, fuel injection timing control means 60, ignition timing control means 62, and control valve control means 65. I have.

The throttle opening control means 53 includes a throttle opening calculating means 54 and an actual throttle opening tvo.
And a throttle control signal output means 55 for outputting a control signal to the motor 27 so that the value calculated by the throttle opening calculation means 54 is obtained.

The throttle opening calculating means 54 calculates the throttle opening tvo according to the operating state at that time. In this case, as shown in FIG. 4A, in the stratified combustion region and the uniform lean region, respectively, the engine speed is previously determined.
throttle opening tvo corresponding to ne and target torque trqob
Is calculated from the maps M11 and M12 in which the engine speed ne and the target torque trqob at that time are set. In the uniform combustion region where λ = 1, the throttle opening tvo is set to be proportional to the accelerator opening acc.

The throttle opening tvo set in the map M11 in the above-described stratified combustion region is set relatively large so as to obtain a large lean state, but is set so as not to fully open the throttle. Then, in response to a change in the target torque (a change in load) in the stratified combustion region, the throttle opening is set so that the intake pressure downstream of the throttle valve is substantially constant (approximately atmospheric pressure or a pressure slightly lower than the atmospheric pressure). Is set substantially constant, and with respect to a change in the engine speed, the throttle opening is set to increase as the engine speed increases.

In the uniform lean region, the map M
The throttle opening degree tvo set at 12 is close to that of the engine having the stoichiometric air-fuel ratio in this region, and changes according to the load, that is, the target torque trqo.
It is set to increase as b increases.

The target air-fuel ratio setting means 56 calculates a target air-fuel ratio afw corresponding to the operating state at that time. In this case, as shown in FIG. 4 (b), in the stratified combustion region, a map M21 in which the target air-fuel ratio afw is set in advance in association with the engine speed ne and the target torque trqob is used. The target air-fuel ratio afw according to ne and the target torque trqob is calculated. In the uniform lean region, a map M22 in which the target air-fuel ratio afw is set in advance in association with the engine speed ne and the intake charge amount ce is used to obtain a target air-fuel ratio corresponding to the engine speed ne and the intake charge amount ce at that time. afw is calculated. In the uniform combustion region where λ = 1, the target air-fuel ratio is set to 14.7.

The fuel injection control amount means 57 comprises a fuel injection amount calculation means 58 and an injector control signal output means 59. The fuel injection timing control means 60 comprises an injection timing calculation means 61 and the injector control signal output means. 59
It is composed of

The fuel injection amount calculation means 58 calculates the target air-fuel ratio afw calculated by the target air-fuel ratio calculation means 58 and the intake air charge calculated from the output of the air flow sensor 26 and the like.
Based on ce, the fuel injection amount is calculated by a calculation process as shown in a flowchart described later. The injector control signal output means 59 outputs an injection pulse having a pulse width corresponding to the fuel injection amount calculated by the fuel injection amount calculation means 58 to the injector 22 at the timing calculated by the injection timing calculation means. It has become.

The injection timing calculating means 61 calculates the fuel injection timing according to the operating state at that time. In this case, FIG.
As shown in (c), in the stratified combustion region, the map M31 in which the injection timing is set in advance in association with the engine speed ne and the target torque trqob, corresponds to the engine speed ne and the target torque trqob at that time. The calculated injection timing is calculated. In the uniform lean region, an injection timing corresponding to the engine speed ne and the intake charge ce at that time is calculated from a map M32 in which the injection timing is set in advance in association with the engine speed ne and the intake charge ce. You. In the map M31, the injection timing is set in the latter half of the compression stroke, and in the map M32, the injection timing is set in the first half of the intake stroke. In the uniform combustion region where λ = 1, the injection timing is set so as to linearly change in accordance with the engine speed.

The ignition timing control means 62 includes an ignition timing calculation means 63, an ignition timing control signal output means 64 for outputting an ignition timing control signal corresponding to the calculation result by the ignition timing calculation means 63 to the ignition circuit 21. It has. Further, the control valve control means 65 outputs a control signal to the actuator 33 so that the actual opening of the S valve 32 becomes a value calculated by the S valve opening calculation means 66. S-valve control signal output means 67 is provided.

The ignition timing calculating means 63 calculates the ignition timing according to the operating state at that time. In this case, FIG.
As shown in (d), in the stratified combustion region, the map M41 in which the ignition timing is set in advance in association with the engine speed ne and the target torque trqob, corresponds to the engine speed ne and the target torque trqob at that time. The calculated ignition timing is calculated. In the uniform lean region and the uniform combustion region of λ = 1, maps M42 and M4 in which the injection timing is set in advance in association with the engine speed ne and the intake charge amount ce, respectively.
From 3, the engine speed ne and the intake air charge ce at that time
Is calculated according to the injection timing.

The S-valve opening calculating means 66 calculates the S-valve opening according to the operating state at that time. Also in this case, FIG.
As shown in (e), in the stratified combustion region, from the map M51 in which the S valve opening is set in advance in association with the engine speed ne and the target torque trqob, the engine speed ne and the target torque trqob at that time are obtained. Is calculated in accordance with the following equation, and in the uniform lean region and the uniform combustion region of λ = 1, the map M52 in which the S valve opening is set in advance in association with the engine speed ne and the intake air charge ce, respectively. , M53
Then, the S-valve opening corresponding to the engine speed ne and the intake charge amount ce at that time is calculated.

A specific example of the control of the throttle opening and the fuel injection amount by the ECU 50 will be described with reference to the flowchart of FIG.

When the process shown in this flowchart is started, first, in step S1, various signals such as the engine speed ne, accelerator opening acc, intake air amount afs, intake air temperature tha, and atmospheric pressure atp are input. Next, in step S2, the intake air charging amount ce is calculated. In this case, the intake charge amount ce is the engine speed
ne and intake air amount (airflow sensor output) based on afs,
The filling amount ce is obtained as a function f of these values ne, afs, tha, and atp, taking into account the density correction based on the intake air temperature tha and the atmospheric pressure atp. Subsequently, in step S3, as a process corresponding to the function of the target torque calculating means 52, a target torque trqob is calculated from the map M in accordance with the accelerator opening acc and the engine speed ne at that time.

Next, at step S4, it is determined whether or not the operating state is in the uniform combustion region where λ = 1, and if not, it is further determined at step S5 whether or not it is in the uniform lean region. In accordance with these determinations, processing corresponding to the functions of the throttle opening calculating means 54 and the target air-fuel ratio setting means 58 is performed in steps S6 to S11.

That is, steps S4 and S5
Is NO, it means that the operating state is in the stratified combustion region. In this case, in step S6, the map 11 in FIG. 4A is used according to the engine speed ne and the target torque trqob at that time. And the target air-fuel ratio afw is calculated from the map 21 of FIG. 4B according to the engine speed ne and the target torque trqob at that time in step S7. If it is determined in step S5 that the engine is in the uniform lean region, then in step S8 the engine speed ne and the target torque tr at that time.
The throttle opening tvo is calculated from the map 12 of FIG. 4A in accordance with the qob, and in FIG. 4 in accordance with the engine speed ne and the intake air charging amount ce at step S9.
The target air-fuel ratio afw is calculated from the map 22 of (b).

If it is determined in step S4 that the operating state is in the uniform combustion region of λ = 1, step S1
The throttle opening tvo is calculated by multiplying the accelerator opening acc by a constant coefficient K1 at 0, and the target air-fuel ratio afw is set to 14.7, that is, the stoichiometric air-fuel ratio at step S11.

Subsequent to any of steps SS7, S9, and S11, processing corresponding to the function of the fuel injection amount control means 57 is performed in steps S12 to S15.

That is, in step S12, the basic fuel injection amount qbase is calculated from the target air-fuel ratio afw, the intake charge amount ce, and the constant coefficient K2 as follows.

[0048]

## EQU1 ## Subsequently, in step S13, the final fuel injection amount qfin is calculated as follows from the basic fuel injection amount qbase and a correction value ctotal obtained by totaling various corrections.

[0049]

Qfin = qbase × (1 + ctotal) Here, the correction value ctotal includes an air-fuel ratio feedback correction value based on the output of the O ₂ sensor 47 in a uniform combustion region of λ = 1. Include acceleration correction and enrichment correction.

Further, in step S14, an injection pulse width Ti corresponding to the final fuel injection amount qfin is calculated from a table in which the correspondence between the fuel injection amount and the injection pulse width is set based on the characteristics of the injector 22 previously checked. I do. In step S15, the fuel injection is performed by outputting the injection pulse having the pulse width Ti, that is, the fuel is injected from the injector 22 for a time corresponding to the pulse width Ti.

Although only the control of the throttle opening and the fuel injection amount is shown in the above flow chart, the control of the fuel injection timing, the ignition timing and the S-valve opening may be performed in accordance therewith. That is, based on the determination of the operating region as in steps S4 and S5 in the above-described flowchart, when the engine is in the stratified combustion region, the maps M31 and M in FIG.
The fuel injection timing, the ignition timing and the S-valve opening are calculated from 41 and M51, and when in the uniform lean region, the maps M32 and M42 in FIG. 4 according to the engine speed ne and the intake charge ce at that time. , M52, the fuel injection timing, the ignition timing, and the S-valve opening are calculated. Further, when the engine is in the uniform combustion region of λ = 1, the injection timing is calculated according to the engine speed ne from the correspondence between the engine speed ne and the injection timing shown in FIG. The ignition timing and the S-valve opening may be calculated from the maps M43 and M53 according to the intake charge amount ce.

According to the apparatus of the present embodiment as described above,
In the stratified combustion region on the low-load low-rotation side, the throttle opening tv
o is substantially constant with respect to a change in load, and the fuel is injected into the combustion chamber 15 from the injector 22 in the latter half of the compression stroke while the intake air amount is increased by being set to a large opening near full opening. The stratified combustion is performed in a state where the mixture is unevenly distributed around the ignition plug while the entire combustion chamber is largely lean, thereby improving the fuel efficiency.

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, whereby uniform combustion is performed in a state where the fuel is diffused in the entire combustion chamber 15. Relatively low load,
In the uniform lean region on the low rotation side, the target air-fuel ratio afw is made leaner than the stoichiometric air-fuel ratio, and the fuel efficiency is also improved in this region. Further, in the uniform combustion region, especially in the operation region on the high load side and the high rotation side, the air-fuel ratio is set to λ = 1 (or an air-fuel ratio richer than this), so that the output performance is ensured.

As described above, the combustion mode and the air-fuel ratio are changed depending on the operation region in order to improve the fuel efficiency and the like, and the air-fuel ratio changes suddenly at the boundary between the stratified combustion region and the uniform combustion region.
According to the control as shown in FIG. 4, the control of the fuel injection amount and the adjustment of the output in each operation region are performed appropriately and accurately, and the occurrence of a torque step at the boundary of the above-mentioned operation region where the air-fuel ratio changes abruptly is minimized. Is done.

More specifically, as described in the description of the related art, a map of the target air-fuel ratio is set in a uniform lean region where the intake air amount and the air-fuel ratio need to be adjusted according to the operating state. While calculating the fuel injection amount based on the target air-fuel ratio and the intake charge amount obtained from this map,
It is conceivable to set the fuel injection amount directly on the map in the stratified combustion region where the intake charge amount is substantially constant. However, in this case, a map of the fuel injection amount in the stratified combustion region and a map of the target air-fuel ratio in the uniform lean region are set in advance based on a bench test or the like so that a torque step does not occur at the boundary between both operation regions. However, when the intake air density changes due to changes in the intake air temperature or atmospheric pressure, the fuel injection amount changes with the change in the intake charge in the uniform lean region, whereas the fuel injection amount changes in the stratified combustion region. Since the fuel injection amount is obtained from the map irrespective of changes in the temperature and the atmospheric pressure, a difference in the fuel injection amount occurs at the boundary between the two operation regions, resulting in a torque step.

On the other hand, in the apparatus of this embodiment, the target air-fuel ratio afw is set in both the stratified combustion region and the uniform lean region, and the fuel injection amount is calculated based on the target air-fuel ratio afw and the intake air charge amount ce. Therefore, even if the intake air temperature tha and the atmospheric pressure atp change, the fuel injection amount corresponding to the change in the intake charge amount ce changes equally in the above two operation regions, and there is no difference in the fuel injection amount. . In addition, since the intake air filling amount ce is obtained based on the output afs of the air flow sensor 28 that can accurately detect the weight of the intake air, the engine speed is determined as described in Japanese Patent Application Laid-Open No. 7-301139. And the intake air amount is obtained from the boost, the intake air filling amount (the weight of the intake air charged into the combustion chamber) can be obtained with higher accuracy, and the accuracy of the fuel injection amount can be increased accordingly. .

The map of the target air-fuel ratio is set in association with the engine speed ne and an element corresponding to the engine load. In the stratified combustion region, the intake air charge ce is substantially constant and corresponds to the engine load. Therefore, the map M21 is created so that the target air-fuel ratio afw is set in association with the engine speed ne and the target torque trqob.

On the other hand, in the uniform lean region, the target air-fuel ratio afw
Is set in association with the engine speed ne and the intake charge amount ce, the correspondence between the substantial operating state of the engine and the target air-fuel ratio is properly maintained.

That is, when performing uniform combustion at a lean air-fuel ratio, the intake air charge ce is a factor that determines the actual operating state (engine load, etc.), and the relationship between the intake air charge ce and the air-fuel ratio is the engine torque. However, if the target air-fuel ratio is set in association with the target torque even in the uniform lean region as described in Japanese Patent Application Laid-Open No. Hei 7-301139, the suction When the air temperature or the atmospheric pressure changes, the corresponding relationship between the actual operating state and the target air-fuel ratio shifts due to the change in the intake air charge. On the other hand, when a map M21 in which the target air-fuel ratio afw is set in association with the engine speed ne and the intake charge ce is used, when the intake charge ce changes due to a change in the intake air temperature tha or the atmospheric pressure atp, By determining the target air-fuel ratio afw in accordance therewith, the correspondence between the actual operating state and the target air-fuel ratio afw is properly maintained, and the driving performance is maintained satisfactorily.

As with the target air-fuel ratio afw, the maps M31, M41 set in association with the engine speed ne and the target torque trqob in the stratified combustion region, similarly to the target air-fuel ratio afw. , M51, while maps M32, M4 set in association with the engine speed ne and the intake air charge ce in the uniform lean region.
2, M52. Therefore, the fuel injection timing, the ignition timing, and the intake swirl are also adjusted so as to conform to the substantial operating state of the engine, and the control of these controls and the control of the fuel injection amount are matched, so that the torque and the engine torque of the engine are adjusted. The combustion state is properly adjusted.

In the above embodiment, the maps M11 and M12 of the throttle opening tvo in the stratified combustion region and the uniform lean region in FIG. 4A, and the target air-fuel ratio afw in the stratified combustion region in FIG. Map M21, FIG.
(C) Map M3 of the injection timing in the stratified combustion region in the middle
1. A map M41 of the ignition timing in the stratified combustion region in FIG. 4 (d) and a map M51 of the S valve opening in the stratified combustion region in FIG. 4 (e) respectively correspond to the engine speed ne and the target torque trqob. Although set in association with each other, the accelerator opening acc may be used instead of the target torque trqob.

[0062]

As described above, according to the present invention, in the direct injection type engine, the throttle opening is made substantially constant with respect to the change in load in the stratified combustion region, and is changed in accordance with the load change in the uniform combustion region. The target air-fuel ratio is set to correspond to the target torque or the accelerator opening in the stratified combustion region, and is set to correspond to the intake charge in the uniform combustion region, and based on the target air-fuel ratio and the intake charge. The fuel injection amount from the injector is calculated by using the above-described method. Therefore, even when the intake air density changes due to a change in the intake air temperature or the atmospheric pressure, it is possible to prevent a torque step from being generated between the two operation regions. . In addition, the fuel injection amount can be appropriately controlled in the stratified combustion region and the uniform combustion region in accordance with the operation state. In particular, in the uniform combustion region, the relationship between the intake air charge and the target air-fuel ratio is appropriately maintained, and the torque The adjustment can be performed effectively.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing an area setting for control of a combustion mode and an air-fuel ratio.

FIG. 3 is a block diagram illustrating a functional configuration of an ECU.

FIGS. 4A to 4E are diagrams showing respective maps of a throttle opening, a target air-fuel ratio, a fuel injection timing, an ignition timing, and an S-valve opening.

FIG. 5 is a flowchart illustrating a specific example of control.

[Explanation of symbols]

 Reference Signs List 10 engine body 15 combustion chamber 22 injector 26 air flow sensor 27 motor for driving throttle valve 28 throttle valve 32 control valve 50 ECU 52 target torque calculating means 53 throttle opening control means 56 target air-fuel ratio setting means 57 fuel injection amount control means 60 Fuel injection timing control means 62 Ignition timing control means 65 Control valve control means

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI F02D 41/02 325 F02D 41/02 325A 41/14 310 41/14 310L 41/34 41/34 E (72) Inventor Kiyotaka Mamiya 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (6)

[Claims] An injector for directly injecting fuel into a combustion chamber is provided. A part of the operation region is a stratified combustion region, and another operation region is a uniform combustion region. In the stratified combustion region, fuel is injected from the injector in a compression stroke. In the cylinder injection type engine in which injection is performed to perform stratified combustion, and in the uniform combustion region, fuel is injected from the injector in an intake stroke to perform uniform combustion. Throttle opening control means to make it approximately constant with changes and to change according to load changes in the uniform combustion region, and set the target air-fuel ratio to correspond to the target torque or accelerator opening in the stratified combustion region And
In the uniform combustion region, the air conditioner includes target air-fuel ratio setting means for setting the amount of intake air corresponding to the amount of intake air, and fuel injection amount control means for controlling the amount of fuel injected from the injector based on the target air-fuel ratio and the amount of intake air. An in-cylinder injection engine. 2. An engine according to claim 1, further comprising an arithmetic unit for calculating an intake air charge from an output of an air flow sensor for detecting an intake air flow rate, and calculating a target torque from an accelerator opening and an engine speed. The throttle opening is set based on the engine speed and the target torque, and the air-fuel ratio setting means sets the target air-fuel ratio based on the engine speed and the target torque in the stratified combustion region, while the engine speed is set in the uniform combustion region. A target air-fuel ratio is set based on the intake air charge, and the fuel injection amount control means calculates the fuel injection amount based on the target air-fuel ratio, the intake air charge, and the engine speed. The in-cylinder injection engine according to claim 1. 3. A specific operation region in the uniform combustion region that is adjacent to the stratified combustion region is a uniform lean region where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and a target corresponding to the intake charge in the uniform lean region. The target air-fuel ratio setting means and the fuel injection amount control means so as to set an air-fuel ratio and calculate a fuel injection amount based on a target air-fuel ratio, an intake charge amount and an engine speed in a uniform lean region and a stratified combustion region. The in-cylinder injection engine according to claim 1 or 2, wherein: 4. A fuel injection timing control means for setting a fuel injection timing from an injector in accordance with a target torque or an accelerator opening in a stratified combustion region and setting in accordance with an intake air charge in a uniform combustion region. The in-cylinder injection engine according to any one of claims 1 to 3, characterized in that: 5. An engine ignition timing is set in a stratified combustion region in accordance with a target torque or an accelerator opening.
5. An apparatus according to claim 1, further comprising an ignition timing control means for setting the intake combustion amount in accordance with the amount of intake air in the uniform combustion region.
In-cylinder injection engine according to any one of the above. 6. A control valve for swirl generation is provided in an intake passage, and an opening of the control valve is set in accordance with a target torque or an accelerator opening in a stratified combustion region. The in-cylinder injection engine according to any one of claims 1 to 5, further comprising control valve control means for setting the value corresponding to (i).