JPH09158767A - Fuel supply control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of the exhaust characteristic and the operability by smoothly switching the combustion mode between the stratified charge combustion mode and the homogeneous charge combustion mode. SOLUTION: When the request A/F>30 (to be judged in S104), the fuel injection timing is in the intake stroke (to be set in S105) so as to achieve the stratified charge combustion mode and when the request A/F<=30, the fuel is injected also in the compression stroke (to be set in S108). Because the combustion mode is gradually shifted from the stratified charge combustion to the homogeneous charge combustion, the combustion step associated with the switching of the combustion mode can be suppressed to a minimum, and at the same time, the torque step with the same air volume can be suppressed, the operability can also be improved, and deterioration of the fuel consumption, the exhaust performance, etc., can be suppressed to a minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving a fuel supply control device for an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional fuel supply control device for an internal combustion engine, there is, for example, one disclosed in JP-A-4-231645 (see FIGS. 8 and 9). In order to supply high-quality HC to the lean NOx catalyst and to raise the NOx purification rate over a wide range, this one causes the auxiliary fuel injection to be performed separately from the main fuel injection, and the injection timing of the auxiliary fuel injection is When the exhaust temperature is low, it is set within the period from the intake stroke to the initial stage of the compression stroke, and when the exhaust temperature is high, it is set within the period from the latter half of the combustion period to the early stage of the exhaust stroke. As a result, a large amount of low boiling point HC can be supplied at a low temperature, while a large amount of high boiling point HC can be supplied at a high temperature. → 2CO ₂ + H ₂ O + N ₂ )
The characteristics can be optimized according to the exhaust gas temperature, and the NOx purification rate of the lean NOx catalyst can be increased over a wide range.

[0003]

However, in the device described in Japanese Patent Laid-Open No. 4-231645, reduction of exhaust emission (particularly NOx) during stratified combustion (for example, during lean combustion). The main purpose is to fix the main fuel injection timing and change the sub fuel injection timing according to the exhaust gas temperature. Note that stratified (also referred to as stratified) combustion is a form of combustion that is effective when performing lean combustion at light loads, etc., and gives a concentration distribution that changes stratified in the combustion chamber mixture gas, and the concentration that changes to this stratified This is a combustion mode in which the combustible mixture layer region of the distribution is guided to the vicinity of the ignition plug and ignited, and combustion is advanced to the entire mixture. According to the stratified combustion, the combustible mixture layer region may be locally formed, so that the air-fuel ratio (hereinafter, also referred to as A / F) can be made extremely lean as the entire mixture.

However, for example, engine output (high load)
In the region, from the viewpoint of improving the soot emission amount and the air utilization rate, the combustion mode (hereinafter also referred to as the combustion state) is changed from stratified combustion to homogeneous combustion of a relatively rich air-fuel mixture (the entire air-fuel mixture has a uniform air-fuel ratio). It is necessary to switch to a combustion mode in which it is formed and burned. At that time, since there is a difference between the air-fuel ratio required for homogeneous combustion and the air-fuel ratio required for stratified combustion described above, the air-fuel ratio characteristics that do not match the combustion mode will be obtained during switching of the combustion mode. There is a fear that combustion will deteriorate, and a torque step may occur even if the amount of air is the same.

The present invention has been made in view of such a conventional situation, and even if the combustion mode is switched between stratified combustion and homogeneous combustion depending on the operation region, the combustion step extension due to the switching of the combustion mode is not extended. An object of the present invention is to provide a fuel supply control device for an internal combustion engine, which can suppress a torque step and maintain high exhaust characteristics and drivability.

[0006]

For this reason, the fuel supply control apparatus for an internal combustion engine according to the invention described in claim 1 is as follows.
In the fuel supply control device for the internal combustion engine, which selectively switches fuel supply timings set at different times in one cycle to achieve a combustion state according to the operating state, as shown in FIG. So that the combustion state can be achieved, the first fuel supply means for supplying fuel by selecting one fuel supply timing according to the operating state, and at least the first fuel so that the combustion state is gradually changed. During the transition from the operating state in which one fuel supply timing is selected by the supply means to the operating state in which another fuel supply timing is selected, the fuel is distributed and supplied at a predetermined sharing rate at both fuel supply timings. And a second fuel supply means.

According to the above construction, the fuel supply timings set at different timings in one cycle are selectively switched, and the combustion mode (combustion state) corresponding to the operating state (engine speed, load, target air-fuel ratio, etc.) is selected. ), When switching the combustion mode, one fuel supply timing (combustion mode) to the other fuel supply timing (combustion mode)
It is possible to gradually shift the fuel to the fuel supply timing in both fuel supply timings in a manner that the fuel is shared at a predetermined sharing ratio and supplied.
As a result, it is possible to minimize the combustion step due to the switching of the combustion mode, thereby suppressing the torque step with the same air amount, improving the drivability, and minimizing the deterioration of fuel consumption, exhaust performance, etc. It can be suppressed to the limit.

According to the second aspect of the present invention, the combustion state according to the operating state is configured to be a homogeneous combustion mode or a stratified combustion mode corresponding to the target air-fuel ratio set according to the operating range. That is, the switching of the combustion mode between the homogeneous combustion mode and the stratified combustion mode in a gasoline engine has a large combustion step and a large degree of deterioration of exhaust characteristics and drivability, but according to the present invention, this can be smoothly performed. It will be. In other words, in this case, the action and effect of the present invention are maximized.

According to a third aspect of the present invention, the internal combustion engine is an internal combustion engine having a fuel supply device for directly supplying fuel into the cylinder. In the invention according to claim 4, the fuel supply timing in the homogeneous combustion mode is set during the intake stroke, and the fuel supply timing in the stratified combustion mode is set during the compression stroke.

In the fifth aspect of the present invention, the first fuel supply means selects the fuel supply timing during the compression stroke in the low load region to supply fuel, while the fuel is in the intake stroke during the high load region. The fuel is supplied by selecting the supply time, and the second fuel supply means is arranged in the medium load region.
The fuel is supplied at both fuel supply timings during the intake stroke and the compression stroke.

The structures of claims 3, 4 and 5 are as follows:
With a relatively simple configuration, it is possible to switch the combustion mode between the homogeneous combustion mode and the stratified combustion mode in a gasoline engine, and it is highly possible to mount it on an actual vehicle. Deterioration and the like are likely to become a problem, and the utilization of the present invention is most expected.

In the invention according to claim 6, when the second fuel supply means cannot secure the minimum fuel supply amount at one fuel supply timing, regardless of the predetermined share ratio, The minimum fuel supply amount securing means for supplying all fuel at the fuel supply timing on the side capable of securing the minimum fuel supply amount is included.

Thus, for example, it is possible to avoid the situation where the fuel supply device (for example, the fuel injection valve) has to supply the fuel with a fuel supply amount smaller than the minimum fuel supply amount with which the fuel can be stably supplied. Therefore, the control of the fuel supply amount can always be made highly accurate. In the invention according to claim 7, in the state where the first fuel supply means sets the fuel supply timing to a later one of different timings in one cycle, the fuel supply at the previous fuel supply timing is performed. After the end, if there is a predetermined acceleration request by the later fuel supply timing, the fuel supply during acceleration is compulsorily supplied at the later fuel supply timing so as to meet the predetermined acceleration request. It is configured to include means.

Thus, for example, when a predetermined acceleration request (for example, a rapid acceleration request) is made before the intake valve is closed after the fuel is supplied during the intake stroke which is the previous fuel supply timing, At the time of fuel supply during the compression stroke, which is the fuel supply timing of, it is possible to immediately supply the fuel amount corresponding to the acceleration request, and therefore it is possible to improve the acceleration response. If the required fuel amount cannot be covered by the fuel supply amount during the intake stroke while the acceleration request is being continued, the fuel shortage amount may be supplemented by the fuel supply during the compression stroke. This is also possible, and the capacity of the fuel supply device and the like can be reduced.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
It will be described with reference to the accompanying drawings. As shown in FIG. 2, an air cleaner 3 is provided upstream of an intake passage 4 of an internal combustion engine (in-line four-cylinder Gaazoline engine) 1 according to the first embodiment of the present invention.
Is provided. The downstream side of the intake passage 4 is connected to the surge tank 2.

An electromagnetic fuel injection valve 5 for directly injecting fuel into each cylinder (so-called direct injection type) is provided so as to face each cylinder. The fuel injection valve 5 receives a drive signal set in accordance with an operating state from a control unit 20 described later and is driven to open at a predetermined time for a predetermined time, so that the fuel metered to a predetermined amount is supplied to the cylinder. It is designed to be able to intermittently supply and inject.

By the way, in the present embodiment, the branch pipes 15 are connected to each of the fuel injection valves 5, and each branch pipe 15 is pressure-fed and supplied by the high-pressure fuel pump 8 driven by the engine 1. High-pressure fuel is passed through the high-pressure fuel passage 9
It is connected to a high-pressure fuel surge tank 7 which is guided and stored via. The high-pressure fuel pump 8 sucks fuel from the fuel tank 10 via the check valve 11 and the fuel filter 12.

A high-pressure regulator and a low-pressure regulator are connected to the high-pressure fuel surge tank 7 so that the fuel pressure in the high-pressure fuel surge tank 7 can be maintained at a desired level. The fuel that has become is returned to the fuel tank 10. As a result, the fuel injection valve 5 can inject high-pressure fuel adjusted so as to be directly injected into the cylinder.

By the way, an ignition plug 6 is provided facing each cylinder so that the air-fuel mixture in the cylinder is ignited and ignited and burned. The ignition timing of the spark plug 6 is set by the control unit 20 according to the operating state. In the exhaust passage 70, an exhaust purification catalyst 71 (three-way catalyst, lean NOx catalyst,
Alternatively, an oxidation catalyst or the like) is interposed.

The control unit 20 comprises a digital computer and comprises a ROM 22, a RAM 24, an input port 25 and an output port 26 which are connected to each other by a bidirectional bus 21. A crank angle signal 29 and a cylinder discrimination signal 31 detected by a crank angle sensor (not shown) are input to the control unit 20 via the input port 25.

Further, an accelerator opening signal (output voltage) 30 from an accelerator opening sensor (not shown) which generates an output voltage according to an operation amount of an accelerator pedal (not shown) is
After being digitally converted through the A / D converter 31, it is inputted through the input port 25.
By the way, each fuel injection valve 5 is connected to the output port 26 via each drive circuit 34 and each counter 35,
Each spark plug 6 is connected to the output port 26 via each drive circuit 36 and each counter 37.

The present embodiment having the above-described structure has the following operation. That is, in the engine output (high load) region where a relatively rich air-fuel ratio is required, when combustion is performed in stratified combustion (a combustion mode that matches lean combustion) that is highly effective in reducing fuel consumption and exhaust emission (particularly NOx), A rich air-fuel mixture is locally formed and the air utilization rate drops, and combustion is rather deactivated, which increases the emission of soot (black smoke, etc.) and unburned components (HC), etc. Therefore, it is advantageous to carry out homogeneous combustion in which the air-fuel ratio can be made uniform in the entire air-fuel mixture to increase the air utilization rate.

On the other hand, in the light load region, since the fuel injection amount is originally small, the deterioration of the air utilization rate does not pose a problem so much. Therefore, rather than performing homogeneous combustion, the air-fuel ratio is diluted as much as possible to improve fuel economy and exhaust emission. Combustion by stratified combustion, which is highly effective in reducing (particularly NOx), is advantageous. When trying to make both of them compatible, in the stratified charge combustion region shown in FIG. 4, there is a demand for leaning of the air-fuel ratio, so that the throttle opening (in other words, detected by an air flow meter) like the conventional homogeneous combustion. It prevents the intake air flow rate Q) and the output (in other words, the fuel injection amount [= k · Q / Ne, k is a constant, Ne is the engine speed]) from becoming unresponsive and giving the driver a feeling of strangeness. Therefore, in order to obtain the load required by the driver, the load required by the driver can be read from the accelerator opening (operation amount), and the target air-fuel ratio (for example, A / F> 30) can be achieved. Thus, the throttle opening (in other words, the cross-sectional area of the intake passage and thus the intake air flow rate Q) and the fuel injection amount are corrected.

For this reason, when the operating region changes and the stratified charge combustion mode is switched to the homogeneous combustion state, if the stratified charge combustion mode is switched to the homogeneous combustion state at the same throttle opening state as the stratified charge combustion mode, the air-fuel ratio becomes the homogeneous combustion mode. However, since the homogeneous combustion mode has a different combustion mode from the stratified combustion mode, the lean limit of the air-fuel ratio is narrower than that of the stratified combustion mode, and the combustion itself deteriorates. (For example, a misfire etc.), and there is a possibility that the operability and the exhaust characteristics are deteriorated more than the deterioration of the operability and the exhaust characteristics due to the normal air-fuel ratio step (when the combustion mode is not changed). . That is, in the present embodiment, when switching the combustion mode, the air-fuel ratio is switched, but one air-fuel ratio is gradually approached to the other air-fuel ratio so as to suppress this air-fuel ratio step. Even if control is performed, there is a combustion step (change) factor in the switching of the combustion mode itself, and if this cannot be solved, the drivability, exhaust characteristics, etc. cannot be effectively improved.

Therefore, in this embodiment, the method of injecting fuel from the fuel injection valve 5 is optimally controlled in order to improve the deterioration of drivability and exhaust characteristics due to the switching of the air-fuel ratio and thus the combustion mode. By doing so, both combustion modes are smoothly connected. Here, the fuel supply control (combustion mode switching control) performed by the control unit 20 in the present embodiment will be described with reference to the flowchart of FIG. The control unit 20
However, the software has the functions of the first fuel supply means, the second fuel supply means, and the minimum fuel supply amount securing means according to the present invention.

In step (denoted by S in the figure, the same applies hereinafter) 100, the engine speed (speed) Ne and the accelerator opening degree are read. In step 101, step 1
The required torque Te is calculated based on the information read at 00. In step 102, the calculated required torque T
Based on e and the engine speed Ne, the required A / F is calculated by referring to the required A / F map as shown in FIG.

In step 103, the calculated request A /
The required fuel injection amount (injection pulse width) TP is calculated based on F, the engine rotation speed Ne, and the intake air flow rate Q detected by an air flow meter (not shown). In step 104, for example, it is determined whether or not the request A / F> 30. If YES, it is determined to be in the stratified combustion region (see the request A / F map in FIG. 4), and step 10
Go to 5. If NO, it is determined that the combustion area is other, and the routine proceeds to step 106.

In step 105, since it is in the stratified charge combustion region, fuel injection in the intake stroke (hereinafter, also referred to as intake stroke injection) is stopped, and only fuel injection in the compression stroke (hereinafter, also referred to as compression stroke injection) is performed. To perform. That is, in the injection pulse width TP2 of the compression stroke injection,
Finally, the required fuel injection pulse width TP with which the required A / F obtained in 03 is obtained (injection stroke injection injection pulse width TP1 = 0), that is, fuel injection is performed in the state of FIG. Then, the flow is finished.

On the other hand, when the process proceeds to step 106, it is not in the stratified charge combustion region, so in step 106, the injection pulse width TP2 of the compression stroke injection is A / F = 30 T.
P'is set, and the difference between TP required to obtain the required A / F (the required fuel injection pulse width TP obtained in step 103) and TP 'set in TP2 is set to the injection pulse width of the intake stroke injection. Set it to TP1 (= TP-TP2). That is, the process proceeds to step 107 in consideration of supplementing the insufficient fuel injection amount with the intake stroke injection while suppressing the change in the fuel injection amount in the compression stroke injection (in other words, the rapid change of the combustion form) as much as possible. .

In step 107, the injection pulse width TP1 of the intake stroke injection set in step 106 is the minimum injection pulse width T with which the intake stroke injection can be satisfactorily performed.
It is determined whether it is shorter than Pmin. If yes,
It is judged that the injection pulse width TP1 of the intake stroke injection is too short, for example, stable fuel injection cannot be performed, and the process proceeds to step 105, and the TP set at step 106 is set.
The relationship of 2 = TP ', TP1 = TP-TP2 is canceled, and the required fuel injection pulse width TP at which the required A / F obtained in step 103 is obtained is finally set in TP2 (intake stroke injection Injection pulse width TP1 = 0),
That is, the fuel injection is performed in the state of FIG. 5, and this flow ends.

On the other hand, if NO, it is judged that the injection pulse width TP1 of the intake stroke injection is not too short, and the intake stroke injection can be satisfactorily performed, and the routine proceeds to step 108. In Step 108, Step 10
TP2 = TP ', TP1 = TP-T set in 6
The relationship of P2 is finalized as it is, that is, the fuel injection is performed in the state of (or) in FIG. 5, and this flow is ended.

In the state of FIG. 5 (or), since the compression stroke injection is performed and the rich mixture exists around the spark plug 6, the combustion mode is the stratified combustion mode, but the intake stroke injection is performed. By also performing the above, it is possible to allow a homogeneous air-fuel mixture to exist even in the region that is originally lean in the normal stratified charge combustion mode (the region where the concentration distribution in the cylinder is lean), so combustion that begins in the rich region Can be slowly advanced to a lean region, and combustion can be made to occur in substantially the entire region of the cylinder.

That is, when the fuel injection amount is increased (the air-fuel ratio is made rich) in accordance with the output increase request in the normal stratified charge combustion mode, the rich air-fuel mixture is locally in the rich air-fuel mixture state. Since it is burned, the combustion itself is deactivated, and since the combustion does not proceed satisfactorily throughout the cylinder thereafter, it is not possible to use the air in the cylinder effectively.
As a result, combustion is inactivated and soot, emissions, and drivability are deteriorated. However, according to the present embodiment, even if the fuel injection amount is increased according to the output increase request (the air-fuel ratio is made richer However, although the combustion form is a stratified combustion form by compression stroke injection, by causing the intake stroke injection to be performed together, as described above, the combustion starting in the rich region,
Since it can be slowly advanced to the lean region, and by extension, combustion can be performed in almost the entire region of the cylinder,
The air utilization rate can be maximized, and soot, emissions, and deterioration of drivability can be markedly improved.

In the output required region (A / F <14), the proportion of intake stroke injection becomes extremely high, and homogeneous combustion can be achieved. However, when more complete homogeneous combustion is desired to be achieved. In addition, after the execution of this flow, the injection mode may be switched so that only the intake stroke injection is performed when the operating state is stable. As a result, complete homogeneous combustion can be achieved as compared with the case where fuel is injected in both the compression stroke and the intake stroke, so it is possible to further promote the increase in output and the reduction in soot.

As described above, in the present embodiment, when the combustion mode (combustion state) is switched by switching the fuel supply timings set at different times in one cycle, the switching of the combustion mode is performed. , It is possible to gradually shift from one fuel supply timing (combustion mode) to the other fuel supply timing (combustion mode) through a mode in which the fuel is supplied in a predetermined sharing ratio at both fuel supply times. As a result, it is possible to minimize the combustion step due to the switching of the combustion mode, and it is possible to suppress the torque step at the same air amount, improve the drivability, and minimize the deterioration of fuel consumption, exhaust performance, etc. It can be suppressed to the limit.

Next, a second embodiment of the present invention will be described. The system configuration of the second embodiment is the first
Is similar to the case of the embodiment (FIG. 2), and the fuel supply (combustion mode switching) performed by the control unit 20 is performed.
As for control, as shown in the flowchart of FIG. 6, steps 100 to 107 are steps 100 to 1 of the flowchart of FIG. 3 of the first embodiment.
Since it is similar to 07, the description thereof will be omitted, and different steps 109 to 111 will be described in detail.

That is, in step 107, step 106
It is determined whether or not the injection pulse width TP1 of the intake stroke injection set in step 1 is shorter than the minimum injection pulse width TPmin with which the intake stroke injection can be satisfactorily performed. If YES, the injection pulse width TP1 of the intake stroke injection is determined. Is too short,
For example, it is determined that stable fuel injection cannot be performed, and the routine proceeds to step 105, where the fuel injection is performed in the state shown in FIG. 5 as in the first embodiment, and this flow ends.

On the other hand, if NO, it is judged that the injection pulse width TP1 of the intake stroke injection is not too short and the intake stroke injection can be performed favorably, and the routine proceeds to step 109. At step 109, the request A / F <
It is determined whether it is 14. If YES, the process proceeds to step 110, and if NO, the process proceeds to step 111.

In step 110, it is judged that the required A / F <14 and the output is in the required output region, the fuel injection in the compression stroke (stratified combustion mode) is stopped, and the fuel injection only in the intake stroke (homogeneous) is performed. Combustion mode). This is because, in the output request region (for example, the request A / F <14), the combustion form is switched to a completely homogeneous combustion form so that the combustion form matches the output request region, and the intake stroke injection is performed. While the intake valve is open, the fuel hits the intake air to promote vaporization and the latent heat of vaporization of the fuel can be used to lower the intake air temperature to improve the air filling efficiency. This is because even if a certain torque step is sacrificed to some extent, further improvement in output can be expected with good responsiveness.

In step 111, the output improvement request and the responsiveness request are not so strong, so that the top priority is to reduce the torque shock when switching the combustion mode, TP2 = TP 'set in step 106, TP1 =
The relationship of TP-TP2 is made final as it is, that is, the fuel injection is performed in the state of (or) in FIG. 5, and this flow is ended.

As described above, in the state of FIG. 5 (or), since the compression stroke injection is performed and the rich mixture exists around the spark plug 6, the combustion mode is the stratified combustion mode. However, since the intake stroke injection is also performed, a homogeneous air-fuel mixture can be made to exist even in the region that is normally lean in the normal stratified charge combustion mode (the region where the concentration distribution in the cylinder is lean). The combustion that starts in the rich region can be slowly advanced to the lean region, and by extension, the combustion can be performed in substantially the entire region of the cylinder.

As described above, in the second embodiment, it is possible to reduce the torque shock due to the combustion step due to the switching of the combustion mode, and also the output required region (for example, A / F <1.
In 4), the combustion mode can be switched to a completely homogeneous combustion mode. Therefore, when the driver has a demand for increasing the output, the demand for increasing the output can be responded with good responsiveness. It becomes possible to give top priority to the output increase request of.

Next, the third embodiment will be described. The system configuration of the third embodiment is similar to that of the first embodiment (FIG. 2), and the fuel supply (combustion mode switching) control performed by the control unit 20 is shown in the flowchart of FIG. As shown, steps 100 to 107 are steps 100 to 107 in the flowchart of FIG. 3 of the first embodiment.
Since it is similar to the above, the description is omitted and a different step 11
2 to step 116 will be described in detail. The control unit 20 in the third embodiment has the function of the fuel supply means for acceleration according to the present invention.

That is, in step 107, step 106
It is determined whether or not the injection pulse width TP1 of the intake stroke injection set in step 1 is shorter than the minimum injection pulse width TPmin with which the intake stroke injection can be satisfactorily performed. If YES, the injection pulse width TP1 of the intake stroke injection is determined. Is too short,
For example, it is determined that stable fuel injection cannot be performed, and the routine proceeds to step 105, where the fuel injection is performed in the state shown in FIG. 5 as in the first embodiment, and this flow ends.

On the other hand, if NO, it is judged that the injection pulse width TP1 of the intake stroke injection is not too short, and the intake stroke injection can be satisfactorily performed, and the routine proceeds to step 112. At step 112, the request A / F <
It is determined whether it is 14. If YES, the process proceeds to step 113, and if NO, the process proceeds to step 116.

In step 113, it is determined whether or not there is an acceleration determination (acceleration request) after the injection in the intake stroke and before the injection in the compression stroke in the same cycle. If YES, the process proceeds to step 114, and if NO, the process proceeds to step 115. The acceleration determination can be made based on a change in accelerator opening, a change in TP, a change in intake air flow rate, or the like.

In step 114, TPol referred to in the intake stroke is TPol so that the acceleration request is immediately reflected in the compression stroke injection performed immediately after in the same cycle.
Then, TP referred to in the compression stroke is TPnew, and the difference (= TPnew-TPold) is injected in the compression stroke. That is, the fuel injection is performed in the state of FIG. 5, and this flow ends.

On the other hand, in step 115, since there is no acceleration request after the injection in the intake stroke and before the injection in the compression stroke in the same cycle, the request A / F <14.
The fuel injection in the compression stroke (stratified combustion mode) in the same manner as described in the second embodiment so as to meet the required output region of
Is stopped and fuel injection (homogeneous combustion mode) is performed only in the intake stroke.

At step 116, the output improvement request and the responsiveness request are not so strong. Therefore, in order to give the highest priority to reducing the torque shock when switching the combustion mode, TP2 = TP set at step 106 is set. ',
The relationship of TP1 = TP-TP2 is finalized as it is, that is, the fuel injection is performed in the state of (or) in FIG. 5, and this flow is ended.

As described above, according to the third embodiment, it is possible to reduce the torque shock due to the combustion step due to the change of the combustion mode, and when the output increase request is made, the output increase request is responded with good responsiveness. You can, of course,
Conventionally, even if there is an acceleration request, fuel injection that follows the acceleration request can be performed only from the time of fuel injection in the next cycle or in another cylinder, and it has not been possible to quickly respond to the acceleration request. Since the acceleration request can be immediately reflected in the compression stroke injection in the same cycle, leaning of the air-fuel ratio can be suppressed and the acceleration request can be responded with good response. That is, it is possible to eliminate the need for phase control and pre-correction of air metering at the time of transition for improving the response to the acceleration request.

When the acceleration request is continued,
Even when the required fuel amount cannot be covered by the fuel supply amount during the intake stroke, it is possible to make up for the fuel shortage with the fuel supply during the compression stroke, thus reducing the capacity of the fuel supply device, etc. It can also be achieved. By the way, the sharing of the intake stroke injection and the compression stroke injection is not limited to the example described in each of the above-described embodiments, and if both combustion modes can be smoothly connected, the sharing degree can be gradually increased at another predetermined sharing rate. It is also possible to change.

In each of the above-described embodiments, during stratified combustion, fuel is injected in the compression stroke (a state in which the air flow in the cylinder is attenuated) to suppress vaporization and diffusion of the fuel, and a rich air-fuel mixture near the spark plug 6. In order to achieve stratified charge combustion, the air flow in the cylinder is changed during the intake stroke, for example, via a swirl control valve. May be. And
During homogeneous combustion, by injecting fuel in the intake stroke (a state where the air flow in the cylinder is promoted), the injected fuel is placed on the intake flow to promote vaporization and diffusion of the fuel, and a uniform mixture is created in the entire cylinder. Although it is formed to achieve uniform combustion, at this time, for example, the air flow in the cylinder may be changed via the swirl control valve or the like with respect to the stratified charge combustion.

The present invention is of course applicable to a gasoline engine in which the combustion mode (combustion state) can be changed by changing the fuel supply method (for example, fuel injection timing). For example, even in a diesel engine or the like, when injecting fuel or the like in multiple times during one cycle (for example, in the case of injecting fuel in multiple times to reduce the initial injection rate, etc., NOx
It can also be applied to the case where water injection for reduction is performed), and it is also applicable to the case where both combustion states are smoothly connected by gradually changing the sharing ratio of each fuel injection. Is what you can do.

[0054]

As described above, according to the fuel supply control device for the internal combustion engine of the first aspect, the fuel supply timings set at different timings in one cycle are selectively switched, and the combustion mode ( When the combustion state is switched, when switching the combustion mode, one fuel supply timing (combustion mode) to another fuel supply timing (combustion mode)
Since the fuel can be gradually transferred through a mode in which the fuel is shared and supplied at a predetermined sharing rate in both fuel supply timings, the combustion step difference due to the switching of the combustion modes can be suppressed to the minimum. As a result, it is possible to suppress a torque step with the same air amount, improve drivability, and suppress deterioration of fuel consumption, exhaust performance, etc. to a minimum.

Claims 2, Claim 3, Claim 4, and Claim 5
If the present invention is applied to the above configuration, it is expected that the effects of the present invention can be maximized. According to the invention described in claim 6, it is possible to always control the fuel supply amount with high accuracy. According to the invention described in claim 7, the acceleration performance can be improved, and the capacity of the fuel supply device and the like can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an overall configuration diagram of a first embodiment of the present invention.

FIG. 3 is a control unit 2 according to the embodiment.
The flowchart for demonstrating the fuel supply control which 0 performs.

FIG. 4 is an example of a request A / F map in the embodiment.

FIG. 5 is a time chart for explaining a generation state of a fuel injection pulse for each area in the above embodiment.

FIG. 6 is a flowchart for explaining fuel supply control performed by a control unit 20 according to the second embodiment of the present invention.

FIG. 7 is a flowchart for explaining fuel supply control performed by a control unit 20 according to the third embodiment of the present invention.

FIG. 8 is an overall configuration diagram of a conventional device.

FIG. 9 is a flowchart for explaining fuel supply control of a conventional device.

[Explanation of symbols]

 1 Internal combustion engine 5 Fuel injection valve 20 Control unit 29 Crank angle signal 30 Accelerator opening signal

Claims (7)

[Claims] 1. A fuel supply control device for an internal combustion engine, wherein a fuel supply timing set at different times in one cycle is selectively switched to achieve a combustion state according to an operating state. A first fuel supply means for supplying fuel by selecting one fuel supply timing in accordance with the operating state so that the combustion state can be achieved, and at least the first fuel so that the combustion state is gradually changed. During the transition from the operating state in which one fuel supply timing is selected by the supply means to the operating state in which another fuel supply timing is selected, the fuel is distributed and supplied at a predetermined sharing rate at both fuel supply timings. A fuel supply control device for an internal combustion engine, comprising: a second fuel supply means. 2. The internal combustion engine according to claim 1, wherein the combustion state according to the operating state is a homogeneous combustion mode or a stratified combustion mode corresponding to a target air-fuel ratio set according to an operating range. Fuel supply control device. 3. The fuel supply control device for an internal combustion engine according to claim 1, wherein the internal combustion engine is an internal combustion engine equipped with a fuel supply device for directly supplying fuel into a cylinder. . 4. The fuel supply timing in the homogeneous combustion mode is set during an intake stroke, and the fuel supply timing in the stratified combustion mode is set during a compression stroke. Fuel supply control device for internal combustion engine. 5. The first fuel supply means selects the fuel supply timing during the compression stroke in the low load range to supply fuel, while selecting the fuel supply timing during the intake stroke in the high load range to select the fuel supply timing. The supply is performed, and the second fuel supply means is configured to supply the fuel at a fuel supply timing during both the intake stroke and the compression stroke in the medium load region. Fuel control device for internal combustion engine. 6. The second fuel supply means can secure the minimum fuel supply amount regardless of the predetermined share rate when the fuel supply amount at one fuel supply timing cannot secure the minimum fuel supply amount. 6. The fuel supply control device for an internal combustion engine according to claim 1, further comprising a minimum fuel supply amount securing means for supplying all fuel at a fuel supply timing on the side. . 7. The first fuel supply means, in a state in which the fuel supply timing is set to an earlier one of different timings in one cycle, after the fuel supply at the previous fuel supply timing is completed, and thereafter. If a predetermined acceleration request is made by the fuel supply timing of, the acceleration fuel supply means for forcibly supplying fuel at a later fuel supply time is included so as to meet the predetermined acceleration request. The fuel supply control device for an internal combustion engine according to any one of claims 1 to 6, which is configured.