JPH09310643A - Controller for direct injection gasoline engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct injection gasoline engine with an exhaust gas reflux device and vaporized fuel treating device wherein exhaust gas reflux and canister purging are concurrently carried out so that accuracy in controlling air-fuel ratio is prevented from lowering. SOLUTION: Though demand for canister purging is generated (S1) during exhausting gas reflux(EGR) being carried out (S2), canister purge is inhibited from carrying out and is stood by (S4), then the canister purging is carried out after stopping of the exhaust gas reflux (S3). Similarly, though demand for the exhausting gas reflux is generated (S6) during the canister purging being carried out (S7), the exhausting gas reflux is inhibited from carrying out and is stood by (S9), then the exhausting gas reflux is carried out after stopping of the canister purging (S8).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a direct injection gasoline engine, and more particularly to control of exhaust gas recirculation and canister purge in a direct injection gasoline engine.

[0002]

2. Description of the Related Art Conventionally, there has been known a direct injection gasoline engine configured to inject fuel directly into a combustion chamber of each cylinder. In the direct-injection gasoline engine, for example, by injecting the fuel in the latter stage of the compression stroke, it is possible to suppress the dispersion of the fuel and form a rich air-fuel mixture in the vicinity of the spark plug, which is sufficiently rich for ignition, and the stratified air supply reduces the lean air-fuel mixture. Stable combustion can be performed even with a mixture having an air-fuel ratio (for example, air-fuel ratio = 40) (see Japanese Patent Laid-Open No. 30420/1985).

[0003]

By the way, the above direct injection gasoline engine is provided with an exhaust gas recirculation device for reducing the combustion temperature by recirculating a part of the exhaust gas to the intake passage, thereby reducing NOx, and In the case where an evaporative fuel processing apparatus is provided which adsorbs and collects the evaporative fuel generated from the fuel tank on the canister and purges the evaporative fuel adsorbed and collected on the canister into the intake passage to burn it, the following problems occur. There was a fear that it would occur.

That is, when the exhaust gas recirculation and the canister purge are performed at the same time, they mutually affect the suction negative pressure. Therefore, especially when large-volume exhaust gas recirculation and canister purge are performed, the suction negative pressure is performed. In some cases, the target exhaust gas recirculation amount and purge air amount could not be obtained due to the decrease of the. Further, in the state of burning with a lean air-fuel ratio, the exhaust gas contains a large amount of air (oxygen) used for combustion,
When performing exhaust gas recirculation, unless the fuel injection amount is controlled in consideration of the amount of air (oxygen) contained in the recirculated exhaust gas, it becomes impossible to form a desired air-fuel mixture. . Similarly, when performing canister purging, unless the fuel injection amount is controlled in consideration of the purge air amount and the fuel amount contained in the purge air, it is not possible to form a desired air-fuel mixture. Will end up.

In a lean burn state of a direct injection gasoline engine, high air-fuel ratio control accuracy is required to maintain stable combustion and good exhaust properties, so the exhaust gas recirculation,
It is necessary to accurately control the injection amount considering the canister purge, but if exhaust gas recirculation and canister purge are performed at the same time, the exhaust gas recirculation amount and the purge air amount will be affected because they mutually influence the suction negative pressure. The amount becomes unstable, and the amount of intake air from the outside air becomes unstable due to fluctuations in the intake negative pressure, so it is not possible to control the injection amount with high precision, which impairs combustion stability and exhaust properties. There was a fear.

The present invention has been made in view of the above problems, and ensures that the target exhaust gas recirculation amount and purge air amount are obtained, and that the air-fuel ratio control accuracy is sufficiently reduced by the exhaust gas recirculation and canister purge. The purpose is to be able to deter.

[0007]

Therefore, the invention according to claim 1 is constructed as shown in FIG. In FIG. 1, a direct injection gasoline engine is an engine configured to directly inject fuel into a combustion chamber of each cylinder, and the direct injection gasoline engine includes an exhaust gas recirculation device and an evaporated fuel processing device. There is.

The exhaust gas recirculation device is a device for recirculating a part of the exhaust gas to the intake passage, and the evaporated fuel processing device adsorbs and collects the evaporated fuel generated from the fuel tank in the canister and in the canister. It is a device for purging the vaporized fuel thus formed into the intake passage. Here, the selecting means selectively executes only one of the exhaust gas recirculation by the exhaust gas recirculation device and the canister purge by the evaporated fuel processing device.

The direct-injection gasoline engine is an engine which enables combustion at a lean air-fuel ratio of, for example, an air-fuel ratio of about 40 by so-called stratified charge. Further, both the exhaust gas recirculation device and the evaporated fuel processing device utilize the negative suction pressure of the engine to supply a part of the exhaust gas or purge air to the intake passage of the engine.

The canister purge means supplying the evaporated fuel adsorbed in the canister together with the purge air to the intake passage, and specifically, means the open control of the valve interposed in the purge passage. Exhaust gas recirculation (hereinafter, also referred to as EGR) means that a part of the exhaust gas is recirculated to the intake passage through the exhaust gas recirculation passage, and specifically, the valve provided in the exhaust gas recirculation passage is opened. Show control.

[0011] And, even if both execution requests overlap, only one of the selection means is arranged so that exhaust gas recirculation by the exhaust gas recirculation device and canister purge by the evaporated fuel processing device are not performed at the same time. Select and execute. Note that, for example, even when the initially set leakage amount occurs in the fully closed control state of the purge valve interposed in the purge passage, this is regarded as a stopped state, and similarly, the exhaust gas recirculation Even if there is a leak amount in the stop control state, this is regarded as the stop state.

According to another aspect of the present invention, the selection means executes the execution corresponding to the other execution request in the execution state of one of the exhaust gas recirculation by the exhaust gas recirculation device and the canister purge by the evaporated fuel processing device. Is configured to be forced to stop. That is, the one that has been started first is prioritized, and even if the other execution request occurs in the middle, the other that is being executed first is kept waiting until the other one is completed.

According to a third aspect of the invention, the selecting means sets a priority in advance between the exhaust gas recirculation by the exhaust gas recirculation device and the canister purge by the evaporated fuel processing device, and a higher priority one is prioritized. It is configured to be executed automatically. For example, if both execution requests occur at the same time, the one with the higher priority is executed, and the other with the lower priority is made to wait until the execution of the higher priority is completed, and the higher priority is executed. Let it run after the other person finishes. Also, when the one with the lower priority is running,
When the execution request with the higher priority is issued, the execution with the lower priority is stopped, and the execution with the higher priority is executed instead. Conversely, when the higher priority execution is being executed, even if an execution request with a lower priority occurs, the execution corresponding to that request is not executed and the execution with a higher priority is waited for. To run.

According to a fourth aspect of the present invention, the exhaust gas is exhausted when the selection means issues both an exhaust gas recirculation execution request by the exhaust gas recirculation device and a canister purge execution request by the evaporated fuel processing device. The exhaust gas recirculation by the recirculation device and the canister purge by the evaporative fuel treatment device are alternately performed in a time division manner. If both the exhaust gas recirculation execution request and the canister purge execution request are generated and the other is executed after waiting for the end of one of them, the execution opportunity of the other may be lost. Therefore, after the exhaust gas recirculation is performed for a predetermined time, the canister purge is then performed for a predetermined time so that the execution request is satisfied alternately.

[0015]

According to the first aspect of the present invention, it is possible to prevent the exhaust gas recirculation and the canister purge from being performed at the same time, so that the required exhaust gas recirculation amount and purge air amount can be secured respectively. At the same time, there is an effect that it becomes possible to maintain the accuracy of injection control in consideration of exhaust gas recirculation and supply of purge air.

According to the second aspect of the present invention, when the execution requests are generated in time series, the exhaust gas recirculation and the canister purge are performed simultaneously by giving priority to the execution request first. The effect is that it can be avoided. According to the invention described in claim 3, when the request for exhaust gas recirculation and the request for canister purge overlap, the one to be preferentially executed can be executed, and the adverse effect caused by executing only one of them. The effect is that it can be suppressed.

According to the fourth aspect of the invention, even if only one of the exhaust gas recirculation and the canister purge is executed, it is possible to secure the opportunity to execute each control.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a system configuration of the embodiment. A fuel injection valve 2 is provided so as to face each combustion chamber of the engine 1. The fuel injection valve 2 is intermittently driven to open by an injection pulse signal, and directly injects fuel (gasoline) into the combustion chamber to perform stratified combustion by a direct injection method into the combustion chamber. It is possible to burn. That is, the engine 1 is a so-called direct injection gasoline engine.

Air conditioned by a throttle valve 4 provided in an intake passage 3 is sucked into the engine 1 and a mixture is formed by the fuel injected from the fuel injection valve 2. The air-fuel mixture is ignited and burned by spark ignition by a spark plug 5, and the combustion exhaust is discharged through an exhaust passage 6. An exhaust gas recirculation passage 7 that connects the exhaust passage 6 and the intake passage 3 downstream of the throttle valve 4 is provided, and an exhaust gas recirculation control valve 8 is interposed in the exhaust gas recirculation passage 7. The exhaust gas recirculation control valve 8 constitutes an exhaust gas recirculation device.

Further, the engine 1 is provided with an evaporated fuel processing device 10 for the fuel tank 9. The vaporized fuel processing device 10 causes the adsorbent such as activated carbon filled in the canister 11 to adsorb and collect the vaporized fuel generated in the fuel tank 9, and purges the fuel adsorbed by the adsorbent. The purge air is supplied to the intake passage 3 downstream of the throttle valve 4 via the purge passage 12.

Evaporated fuel in the fuel tank 9 is introduced into the canister 11 through an evaporated fuel passage 14 in which a check valve 13 that opens when the pressure in the fuel tank 9 exceeds a predetermined value is interposed. A purge valve 15 is provided in the purge passage 12. The canister 11, the purge passage 12, the check valve 13, the evaporated fuel passage 14, and the purge valve 15 constitute an evaporated fuel processing device.

The fuel injection by the fuel injection valve 2 and the ignition timing by the spark plug 5 are controlled, exhaust gas recirculation by the exhaust gas recirculation device (opening and closing of the exhaust gas recirculation control valve 8) and canister purge in the evaporated fuel processing device 10 ( The control unit 16 that controls the opening and closing of the purge valve 15)
It is configured to include a microcomputer and performs various controls based on signals from various sensors described later.

The various sensors are provided as follows. The air flow meter 17 detects the intake air amount from the outside air on the upstream side of the throttle valve 4. The crank angle sensor 18 generates a unit angle signal and a reference angle signal for each unit crank angle. Here, the engine rotation speed Ne can be detected by measuring the number of generations of the unit angle signal per unit time or by measuring the generation cycle of the reference angle signal.

The water temperature sensor 19 detects the cooling water temperature Tw of the engine 1. The air-fuel ratio sensor 20 is a sensor that detects the oxygen concentration in the exhaust gas that has a correlation with the air-fuel ratio of the combustion mixture to detect the air-fuel ratio. The control unit 16 is
While calculating the basic fuel injection amount based on the intake air amount detected by the air flow meter 17 and the engine rotation speed,
Various correction coefficient CO, air-fuel ratio sensor according to cooling water temperature etc.
The air-fuel ratio feedback correction coefficient α based on the detection result of 20 and the voltage correction amount Ts corresponding to the battery voltage are calculated to calculate the basic fuel injection amount Tp by the various correction coefficients CO,
The final injection amount Ti is calculated by making corrections using the air-fuel ratio feedback correction coefficient α, the voltage correction amount Ts, and the like. Then, the fuel injection valve 2 is driven to open at a predetermined timing according to the injection amount Ti.

Further, the control unit 16 determines the ignition timing of the spark plug 5 based on the engine load, the engine speed, etc. detected by the various sensors, while the exhaust gas recirculation (exhaust gas recirculation) by the exhaust gas recirculation device is performed. The opening / closing of the control valve 8) and the canister purge (opening / closing of the purge valve 15) by the evaporated fuel processing device 10 are controlled. Further, the control unit 16 is adapted to perform exhaust gas recirculation control and canister purge control as shown in the flowchart of FIG.

In the flowchart of FIG. 3, in step 1 (denoted as S1 in the figure; the same applies hereinafter), it is determined whether or not a request to execute canister purge has been issued. The canister purge and the exhaust gas recirculation are performed under preset operating conditions, and the execution request indicates that the current operating condition corresponds to the operating condition under which the canister purge or the exhaust gas recirculation should be performed. I shall.

If it is determined in step 1 that a canister purge execution request has been issued, the process proceeds to step 2 to determine whether exhaust gas recirculation (EGR) is being executed. If it is determined that the exhaust gas recirculation is not performed, the exhaust gas recirculation and the canister purge are not performed at the same time, so the process proceeds to step 3 to execute the canister purge.

On the other hand, when it is determined in step 2 that the exhaust gas recirculation is being performed, the process proceeds to step 4, and the canister purge is not performed in order to avoid the simultaneous execution, and the standby state is set. Therefore, when the canister purge execution request is issued during the exhaust gas recirculation, the canister purge is executed after waiting for the exhaust gas recirculation.

If it is determined in step 1 that the canister purge execution request has not been issued, the operation proceeds to step 5, where the execution of the canister purge is stopped, and then the operation proceeds to step 6. In step 6, it is determined whether or not an execution request for exhaust gas recirculation has been issued. When the exhaust gas recirculation execution request is generated, the process proceeds to step 7 and it is determined whether or not the canister purge is being executed.

When the canister purge is not executed, the exhaust gas recirculation is not executed at the same time, so the routine proceeds to step 8 and the exhaust gas recirculation is executed. On the other hand, when the canister purge is being executed, the routine proceeds to step 9, where the exhaust gas recirculation is not executed in order to avoid the simultaneous execution and the standby state is set.
Therefore, when the execution request of the exhaust gas recirculation is generated during the canister purge, the exhaust gas recirculation is executed after waiting for the end of the canister purge.

If it is judged in step 6 that the exhaust gas recirculation execution request has not been issued, the routine proceeds to step 10, and if the exhaust gas recirculation is being executed, it is stopped. in this way,
If only one of the exhaust gas recirculation and the canister purge is executed, even if each control has a relatively large capacity, it is possible to avoid having a great influence on the suction negative pressure due to simultaneous execution. The exhaust gas recirculation amount and the purge air amount are secured. Further, if only one of exhaust gas recirculation and canister purge is executed, control corresponding to the amount of air supplied by exhaust gas recirculation and control corresponding to purge air and evaporated fuel supplied by canister purge. Can be performed individually with high accuracy, and the air-fuel ratio control accuracy can be maintained in combination with the stabilization of the suction negative pressure.

By the way, in the control shown in the flow chart of FIG. 3, the one executed first is prioritized. For example, the exhaust gas recirculation and the canister purge are prioritized. However, if the exhaust gas recirculation is performed first, the canister purge cannot be executed until the exhaust gas recirculation ends.

Therefore, when either one of them is to be preferentially executed, it is preferable that either one of the exhaust gas recirculation and the canister purge is executed in accordance with the priority order. Such a second embodiment Is shown in the flowchart of FIG. In the following, the case where the canister purge is preferentially executed as compared with the exhaust gas recirculation is shown, but the reverse relationship may be applied.

In step 21, it is judged whether or not there is a canister purge execution request, and when a purge request is made, the routine proceeds to step 22. In step 22, it is determined whether or not there is a request for execution of exhaust gas recirculation. Here, when there is no request for execution of exhaust gas recirculation,
Proceed to step 23, stop exhaust gas recirculation, and proceed to the next step.
At 24, canister purge is executed.

On the other hand, if it is judged at step 22 that the exhaust gas recirculation execution request is generated, the routine proceeds to step 25, where it is judged if the exhaust gas recirculation is being executed. If the exhaust gas recirculation has not been executed, the process proceeds to step 27 and the canister purge is executed as it is, but if it is determined in step 25 that the exhaust gas recirculation has already been executed and the exhaust gas recirculation has already been executed, step 26 Then, the exhaust gas recirculation is stopped to proceed to step 27, and then the canister purge is executed to proceed to step 27.

That is, when the exhaust gas recirculation execution request and the canister purge execution request are simultaneously generated, the canister purge is preferentially executed, and the exhaust gas is exhausted before the canister purge execution request is generated. When a request for execution of recirculation has been issued and exhaust gas recirculation has already been executed, the exhaust gas recirculation is forcibly stopped in response to the occurrence of a request for execution of canister purge, and canister purge is executed instead.

As a result, when the canister purge execution request is issued, the canister purge can be surely executed. If it is determined in step 21 that there is no request to execute the canister purge, step
If the routine proceeds to 28, the canister purge is stopped if it is being executed, and in the next step 29, it is judged whether or not there is an execution request for exhaust gas recirculation.

If there is an execution request, the process proceeds to step 30 to execute the exhaust gas recirculation, and if there is no execution request, the process proceeds to step 31 to stop the exhaust gas recirculation. Therefore, when the canister purge execution request is not issued, the exhaust gas recirculation is controlled according to the execution request. By the way, in the case shown in the flow chart of FIG. 3, the other is not executed until the one being executed first ends, and in the case shown in the flow chart of FIG. 4, exhaust gas recirculation is performed during canister purge. You can't do it at all. Therefore, in the case where the execution requests of the exhaust gas recirculation and the canister purge are overlapped with each other, the respective configurations are alternately executed in a time-sharing manner so that the execution opportunity of each control can be secured. It is shown in the flowchart.

In step 41, it is judged whether or not there is a canister purge execution request. Then, when there is no execution request, in step 42, the canister purge is stopped,
In the next step 43, the timer tp for measuring the execution duration of the canister purge is reset to zero. Then, in step 44, it is judged whether or not there is a request for execution of exhaust gas recirculation, and if there is also no request for execution of exhaust gas recirculation, the process proceeds to step 45,
The exhaust gas recirculation is stopped, and in the next step 46, the timer te for measuring the execution duration of the exhaust gas recirculation is reset to zero.

On the other hand, if it is determined in step 41 that a canister purge execution request has been issued, the routine proceeds to step 47, where it is determined whether there is an exhaust gas recirculation execution request. here,
When both execution requests are overlapped, the routine proceeds to step 48, where it is determined whether the canister purge is continued for a predetermined time or longer by comparing the value of the timer tp with a predetermined value. To do.

If the value of the timer tp is less than the predetermined value, the routine proceeds to step 51, where canister purge is executed, and at the next step 52, the timer tp is counted up. Therefore, when both execution requests are generated at the same time when there is no execution request for both, the canister purge is first started and continued until the value of the timer tp becomes equal to or more than a predetermined value.

On the other hand, if it is determined that there is a canister purge execution request, but there is no exhaust gas recirculation execution request, the routine proceeds from step 47 to step 49, where the exhaust gas recirculation is stopped and the routine proceeds to step 50. The timer te is reset to zero. Therefore, when there is a canister purge execution request but no exhaust gas recirculation execution request, the canister purge is executed without any restriction while the exhaust gas recirculation is stopped, and the timer tp is incremented during that time.

Here, both execution requests occur at the same time,
Alternatively, if it is determined in step 48 that the exhaust gas recirculation execution request has been generated during execution of the canister purge and the value of the timer tp has exceeded the predetermined value, the process proceeds to step 53, and the canister purge is temporarily stopped. , In the next step 54,
Instead, start the execution of exhaust gas recirculation, and in step 55,
The timer te is incremented.

At the next step 56, the timer te is compared with a predetermined value, and if the timer te is less than the predetermined value, this routine is ended as it is. Therefore, the timer tp is not reset to zero until the timer te reaches a predetermined value or more, and as a result, the timer t is reset.
Until e becomes a predetermined value or more, the routine proceeds from step 48 to step 53, and exhaust gas recirculation is executed.

When it is determined that the exhaust gas recirculation has been continued for a predetermined time after the timer te has exceeded the predetermined value, the routine proceeds from step 56 to step 57, and the timers te and Tp are both reset to zero. Then, in the next step 58, the exhaust gas recirculation is stopped. As a result, in the next step 48, it is determined that the timer tp is equal to or less than the predetermined value,
The canister purge will be executed in step 51.

If it is determined in step 44 that an exhaust gas recirculation execution request has been issued, the routine proceeds to step 59, in which exhaust gas recirculation is executed, but if a canister purge execution request is generated during exhaust gas recirculation, there is no Since the condition is switched to the execution of the canister purge, in step 60, the timer te
Is held at zero. As described above, when the exhaust gas recirculation execution request and the canister purge execution request are simultaneously generated, the exhaust gas recirculation is executed on condition that the canister purge is continuously performed for a predetermined time or longer. Then, if exhaust gas recirculation is continued for a predetermined time or longer, execution of canister purge will be resumed, and while exhaust gas recirculation can be executed in a time division manner while giving priority to execution of canister purge, Opportunities for the return flow are also secured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the invention according to claim 1;

FIG. 2 is a system configuration diagram of a direct injection gasoline engine according to the embodiment.

FIG. 3 is a flow chart showing a first embodiment of exhaust gas recirculation and canister purge control.

FIG. 4 is a flowchart showing a second embodiment of exhaust gas recirculation and canister purge control.

FIG. 5 is a flowchart showing a third embodiment of exhaust gas recirculation and canister purge control.

[Explanation of symbols]

 1 engine 2 fuel injection valve 3 intake passage 4 throttle valve 5 spark plug 6 exhaust passage 7 exhaust gas recirculation passage 8 exhaust gas recirculation control valve 9 fuel tank 10 evaporative fuel processing device 11 canister 12 purge passage 13 check valve 14 evaporative fuel passage 15 purge valve 16 Control unit 17 Air flow meter 18 Crank angle sensor 19 Water temperature sensor 20 Air-fuel ratio sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location F02D 43/00 301 F02D 43/00 301H F02M 25/07 550 F02M 25/07 550R (72) Inventor Masayuki Yasuoka 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (4)

[Claims] 1. An exhaust gas recirculation device configured to directly inject fuel into a combustion chamber of each cylinder and recirculate a part of exhaust gas to an intake passage, and evaporative fuel generated from a fuel tank is adsorbed and collected by a canister. A direct injection gasoline engine control device comprising: an evaporative fuel treatment device that purges the evaporative fuel adsorbed and collected by the canister into an intake passage, wherein the exhaust gas recirculation device recirculates the exhaust gas and the evaporative fuel treatment device operates. A control device for a direct injection gasoline engine, comprising a selection means for selectively executing either one of the canister purge and the canister purge. 2. The selecting means forcibly stops the execution corresponding to the execution request of the other in the execution state of either one of the exhaust gas recirculation by the exhaust gas recirculation device and the canister purge by the evaporated fuel processing device. The control device for a direct injection gasoline engine according to claim 1, wherein: 3. The selecting means sets a priority in advance between exhaust gas recirculation by the exhaust gas recirculation device and canister purge by the evaporative fuel processing device, and preferentially executes the higher priority one. The controller for a direct injection gasoline engine according to claim 1. 4. The selecting means, when both an exhaust gas recirculation execution request by the exhaust gas recirculation device and a canister purge execution request by the evaporated fuel processing device are both generated,
2. The control device for a direct injection gasoline engine according to claim 1, wherein exhaust gas recirculation by the exhaust gas recirculation device and canister purge by the evaporated fuel processing device are alternately executed in a time division manner.