JP4985111B2 - DIESEL ENGINE CONTROL DEVICE AND STOP CONTROL METHOD - Google Patents

Description

  The present invention relates to control of a diesel engine, and more particularly to control for preventing occurrence of engine vibration when the engine is stopped.

  A diesel engine has a problem that a large engine vibration is generated when the engine is stopped, and the entire vehicle body vibrates greatly. This engine vibration is caused by the fact that air continues to be sent into the combustion chamber after the fuel supply is stopped after the key-off until the engine stops, so that the internal pressure of the combustion chamber increases when the piston rises, and the engine speed decreases. It is known to occur when the engine passes through a resonance point on the way.

Patent Document 1 discloses a technical means for reducing the generation of engine noise by suppressing the increase in internal pressure of the combustion chamber by blocking the introduction of air by closing the intake shutter valve in the engine stop mode after key-off. Has been.
Japanese Patent No. 3846109

  By the way, in the case of a diesel engine, control for introducing a large amount of exhaust gas recirculation gas (hereinafter referred to as EGR gas) is generally performed in an idle operation state in order to improve exhaust performance and sound vibration performance. In general, the EGR valve that adjusts the amount of EGR gas introduced remains at the opening degree during idling after key-off.

  Therefore, even if the introduction of air is blocked by the intake shutter as in Patent Document 1, air is introduced from the exhaust system to the combustion chamber via the EGR valve, so that the combustion chamber is not in a suffocation state, The generation of the engine vibration described above cannot be suppressed.

  In particular, in a large displacement diesel engine having a large inertia of a flywheel or a crankshaft, the time until the engine stops after key-off becomes longer. The influence of air from the EGR valve becomes large, and the generation of engine vibration cannot be suppressed.

  Therefore, an object of the present invention is to suppress engine vibration, which is a main cause of vibration of the vehicle body when the engine is stopped, even in a diesel engine that introduces a large amount of EGR gas during idling.

The control device for a diesel engine according to the present invention includes an intake throttle valve that adjusts an intake air amount, an EGR passage that recirculates a part of exhaust gas to an intake passage downstream of the intake throttle valve, and opens and closes the EGR passage. In a diesel engine control device comprising: an EGR valve that fully closes the EGR passage at the time of the valve; stop request detection means for detecting an engine stop request; and stop of fuel injection in response to a detection signal of the stop request detection means And stop control means for closing the intake throttle valve, and stop determination means for determining whether or not the engine has stopped. The stop control means closes the intake throttle valve. prior to substantially the same time or it Noto, closed the EGR valve, the stop control means, after opening the EGR valve if it is determined that the engine has been stopped by the stop determining means, said EGR There stop system for left engine control of the valve opening state.

  According to the present invention, since both the intake passage and the EGR passage are shut off until the engine stops after the key-off, the combustion chamber is in a suffocation state without air flowing in. Therefore, an increase in the internal pressure of the combustion chamber due to the piston rising can be suppressed, and as a result, engine vibration when the engine is stopped can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram of a system configuration to which this embodiment is applied. 1 is a diesel engine (hereinafter simply referred to as an engine), 2 is an intake passage, 3 is a collector tank, 4 is an intake shutter valve (intake throttle valve), 5 is an exhaust passage, and 6 is an exhaust recirculation passage (hereinafter referred to as an EGR passage). ), 7 is an exhaust gas recirculation amount adjustment valve (hereinafter referred to as an EGR valve), 8 is a piston, 9 is an intake valve, 10 is an exhaust valve, 11 is a fuel injection valve, and 12 is for preheating when starting the engine. Glow plug, 13 is an engine control unit (hereinafter referred to as ECU) (stop control means, stop determination means), 14 is a water temperature sensor, 15 is a crank angle sensor, and 16 is a key position detection sensor (stop request detection means). .

  A piston 8 is housed in the engine 1 so as to be able to reciprocate. The intake passage 2 opens so as to face the combustion chamber 1 a of the engine 1, and the opening is opened and closed by an intake valve 9. Similarly, the exhaust passage 5 opens into the combustion chamber 1 a and the opening is opened and closed by an exhaust valve 10. The fuel injection valve 11 and the glow plug 12 are also arranged so as to face the combustion chamber 1a.

  An intake shutter valve 4 for adjusting the intake air amount is disposed in the intake passage 2, and a collector tank 3 that connects the intake passage 2 of each cylinder is disposed downstream of the intake shutter valve 4.

  The exhaust passage 5 and the collector tank 3 communicate with each other through an EGR passage 6. The EGR passage 6 is provided with an EGR valve 7 that adjusts the flow area. Thus, if the EGR valve 7 is opened during engine operation, a part of the exhaust gas flowing through the exhaust passage 5 returns to the collector tank 3 as EGR gas due to the pressure difference between the exhaust passage 5 and the collector tank 3. The EGR valve 7 is an EGR valve 6 that can fully close the flow path of the EGR passage 6, for example, an on / off valve.

  In the above configuration, the piston 8 is connected to a crankshaft (not shown), and reciprocates as the crankshaft rotates. The intake valve 9 and the exhaust valve 10 are driven to open and close by an intake camshaft and an exhaust camshaft that rotate in synchronization with a crankshaft (not shown) by hanging a chain or the like. That is, the intake valve 9 and the exhaust valve 10 are driven to open and close in synchronization with the reciprocation of the piston 8.

  Specifically, when the piston 8 is lowered, the intake valve 9 is opened and the exhaust valve 10 is closed, whereby air flows into the combustion chamber 1a (intake stroke). The intake valve 9 is closed when the piston 8 is near the bottom dead center, and the intake valve 9 and the exhaust valve 10 are kept closed while the piston 8 is raised, so that the intake valve 9 flows into the combustion chamber 1a. The compressed air is compressed (compression process). When the piston 8 rises and is near the top dead center, combustion starts by performing fuel injection from a fuel injection valve 11 described later, and the piston 8 is pushed down by the combustion pressure. At this time, the intake valve 9 and the exhaust valve 10 are kept closed (expansion stroke). When the piston 8 descends to near the bottom dead center, the exhaust valve 10 is opened while the intake valve 9 is closed. As a result, the burned gas is discharged into the exhaust passage 5 as the piston 8 rises (exhaust stroke). The above four steps are repeated as one cycle.

  The fuel injection from the fuel injection valve 11 is performed at the fuel injection timing and the injection amount based on the signal from the ECU 13. The ECU 13 calculates the engine speed based on the detected value of the crank angle sensor 15, and calculates the engine load based on detected values of an accelerator opening sensor, an air flow sensor, etc. (not shown). Then, the fuel injection amount and the fuel injection timing are set based on the engine speed and the engine load. Further, the fuel injection amount and the fuel injection timing may be corrected in accordance with detection values of the water temperature sensor 14, an intake air temperature sensor (not shown), an atmospheric pressure sensor, or the like.

  Incidentally, the ECU 13 receives a signal from the key position detection sensor 16. The key position detection sensor 16 is a sensor that detects whether an ignition key (not shown) is in an on position or an off position.

  When the ignition key is turned off during engine operation, the ECU 13 starts control for stopping the engine.

  Here, the control for stopping the engine will be described with reference to FIGS. FIG. 2 is a flowchart showing a control routine executed by the ECU 13 during engine operation. This control routine is repeatedly executed at regular intervals, for example, every 10 ms.

  In step S10 (stop request detection stage), it is determined based on the detection signal of the key position detection sensor 16 whether or not the ignition key has been turned off. If it is not in the OFF position, the process proceeds to step S30, and control for normal operation is continued. The normal operation control sets the fuel injection timing, the fuel injection amount, and the opening degree of the intake shutter valve 4 in accordance with the engine load, the rotational speed, etc., as in the case of a general engine, and will not be described.

  If the ignition key is in the OFF position, the process proceeds to step S20, and stop control is executed. FIG. 3 is a flowchart showing a control routine of the stop control executed in step S20.

  In step S110 (fuel injection stop stage), fuel cut is performed. As a result, combustion is not performed in the combustion chamber 1a, and the engine speed starts to decrease.

  If the fuel cut is performed in step S110, the process proceeds to step S120 and step S130.

  In step S120 (EGR cutoff stage), the EGR valve 7 is closed, and in step S130 (intake cutoff stage), the intake shutter valve 4 is closed. Note that steps S120 and S130 are performed substantially simultaneously.

  As a result, the intake air from an air cleaner (not shown) can be blocked, and the introduction of air from the EGR passage 6 to the collector tank 3 can also be blocked.

  In step S140, based on the detection value of the crank angle sensor 15, it is determined whether or not the engine speed Ne has become zero, that is, whether or not the engine 1 has stopped. In addition, you may determine with the engine 1 having stopped, not only when an engine speed becomes zero but when it reduces to the speed close | similar to zero.

  If it is determined in step S140 (stop determination stage) that the engine 1 has stopped, the process proceeds to step S150, and the engine control system is stopped.

  As described above, when the intake shutter valve 4 and the EGR valve 7 are closed after the fuel cut is performed, air is not introduced into the combustion chamber 1a. Therefore, the combustion chamber 1a is in a suffocated state until the engine 1 is stopped.

  FIG. 4 is a time chart when the above control is executed. For comparison, FIG. 5 shows a time chart when the EGR valve 7 is not closed during engine stop control (hereinafter referred to as conventional control). Further, in both FIG. 4 and FIG. 5, the waveform of the intake shutter valve 4 is omitted. This is because the intake shutter valve 4 is closed when the ignition key is in the OFF position in both the present embodiment and the conventional control, and there is no difference.

  As shown in FIG. 4, when the ignition key is turned off at t1, the EGR valve 7 is closed. Although not shown in FIG. 4, when the ignition key is turned off at t1, the fuel cut is started. Further, strictly speaking, the valve closing start timing of the EGR valve 7 is delayed from the time t1 by the calculation time, but for simplicity, it is shown as almost the same period in FIG.

  At t2, the engine speed starts to decrease. The reason why there is a delay time from t1 to t2 is that the engine speed before fuel cut is maintained by the inertial force of a flywheel and a crankshaft (not shown). The longer the engine, the longer the delay time. Then, it is determined that the engine has stopped at t3 when the engine speed has decreased to a value close to zero. Thereafter, the engine control system is stopped.

  That is, the EGR valve 7 starts the valve closing operation at t1, and after being fully closed, the EGR valve 7 remains closed until the engine is stopped. Similarly, the intake shutter valve 4 is closed. Therefore, no new air flows into the combustion chamber 1a during the intake stroke while the engine speed is decreasing. That is, the combustion chamber 1a is suffocated.

  On the other hand, in FIG. 5, after the ignition key is turned off at t1, the engine speed decreases as in FIG. 4, but the EGR valve 7 is determined to have stopped at t3. It remains open until the engine control system stops. That is, the EGR valve 7 remains open from t2 to t3 when the engine speed decreases.

  Therefore, during the intake stroke while the engine speed is decreasing, air newly flows from the EGR passage 6 into the combustion chamber 1a due to the negative pressure generated when the piston 8 descends.

  Due to such a difference, there is a difference in vibration acceleration of the engine 1 from when the ignition key is turned to the off position until the engine is stopped. 6 and 7 are time charts of the vibration acceleration of the vehicle body when the control of this embodiment is executed and when the conventional control is executed, respectively.

  Before t1, that is, during engine operation, there is no difference in vibration acceleration between FIG. 6 and FIG. However, after the ignition key is turned off at t1, the maximum value of the vibration acceleration is larger in the conventional control than in the present embodiment. Also, before and after the time when the maximum value is reached (the portion surrounded by a circle in the figure), the conventional control has a greater vibration acceleration over a longer period.

  This is because, in the conventional control, air flows into the combustion chamber 1a from the EGR passage 6 while the engine speed decreases, and the internal pressure of the combustion chamber 1a rises due to the rise of the piston 8, thereby vibrating at the resonance point of the engine 1. This is because acceleration increases. On the other hand, in this embodiment, since the combustion chamber 1a is in a suffocation state, an increase in internal pressure due to an increase in the piston 8 can be suppressed.

  As described above, in the present embodiment, the following effects can be obtained.

  In a diesel engine control device including the intake shutter valve 4, the EGR passage 6, and the EGR valve 7, an ECU 13 that stops fuel injection and closes the intake shutter valve 4 in response to a detection signal of the key position sensor 16. The ECU 13 closes the EGR valve 7 substantially simultaneously with or before the intake shutter valve 4 is closed, so that the combustion chamber 1a is in a suffocated state until the engine 1 is stopped. . For this reason, since the increase in the internal pressure of the combustion chamber 1a when the piston 8 is raised is suppressed, engine vibration can be suppressed.

  Since the EGR valve 7 can fully close the EGR passage 6, it is possible to reliably block the inflow of EGR gas from the EGR passage 6. Therefore, engine vibration can be more reliably suppressed.

  A second embodiment will be described.

  In this embodiment, the system configuration is the same as that of the first embodiment, but the control routine for the stop control is different. In this embodiment, the control routine shown in the flowchart of FIG. 8 is executed.

  When the ignition key is in the OFF position, fuel cut is started in step S210, and at the same time, the EGR valve 7 is closed in step S220.

  Next, in step S230, the intake shutter valve 4 is closed.

  Hereinafter, steps 240 and S250 are the same as steps S140 and S150 in FIG.

  Thus, even if the intake shutter valve 4 is closed after the fuel cut and the EGR valve 7 are closed at the same time, the combustion chamber 1a may be suffocated while the engine speed is reduced. it can. Therefore, the same effect as that of the first embodiment can be obtained.

  A third embodiment will be described.

  In this embodiment, the system configuration is the same as that of the first embodiment, but the control routine for the stop control is different. In this embodiment, the control routine shown in the flowchart of FIG. 9 is executed.

  When the ignition key is in the off position, fuel cut is started in step S310.

  Next, in step S320, the EGR valve 7 is closed. In step S330, the intake shutter valve 4 is closed.

  Steps S340 and S350 are the same as steps S140 and S150 in FIG.

  As described above, even if the fuel cut, the EGR valve 7 and the intake shutter valve 4 are sequentially performed, the combustion chamber 1a can be suffocated while the engine speed is reduced. The same effect as in the first embodiment can be obtained.

  A fourth embodiment will be described.

  In this embodiment, the system configuration is the same as that of the first embodiment, but the control routine for the stop control is different. In the present embodiment, a control routine as shown in the flowchart of FIG. 10 is executed.

  Steps S410 to S440 in FIG. 10 are the same as steps S310 to S340 in FIG.

  If it is determined in step S440 (stop determination stage) that the engine 1 has stopped, the EGR valve 7 is opened in step S450 (EGR valve opening stage). In step S460, the engine control system is stopped.

  As described above, the EGR valve 7 is opened after the engine is stopped, and then the engine control system is stopped, so that the EGR valve can be used at the next start, particularly when an early start is required, such as during a hot restart. An appropriate amount of EGR gas can be secured immediately without waiting for the valve 7 to open.

  As described above, according to the present embodiment, in addition to the same effects as those of the first embodiment, the EGR valve 7 is opened after the engine is stopped, so that an appropriate amount of EGR gas can be secured immediately at the next start. The effect is obtained.

  In step S450, the intake shutter valve 4 may be opened simultaneously with the opening of the EGR valve 7. According to this, an appropriate intake amount can be secured immediately without waiting for the intake shutter valve 4 to open at the next start.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

1 is a schematic configuration diagram of a system to which a first embodiment is applied. It is a flowchart showing a control routine during engine operation. It is a flowchart showing the control routine of the engine stop control (first embodiment). It is a time chart at the time of performing control for stop of a 1st embodiment. It is a time chart at the time of performing the conventional control for a stop. It is a time chart of the vibration acceleration of the vehicle body when the control for stop of the first embodiment is executed. It is a time chart of the vibration acceleration of the vehicle body when the conventional stop control is executed. It is a flowchart showing the control routine of control for engine stop (2nd Embodiment). It is a flowchart showing the control routine of control for engine stop (3rd Embodiment). It is a flowchart showing the control routine of control for engine stop (4th Embodiment).

Explanation of symbols

1 Diesel engine (engine)
2 Intake passage 3 Collector tank 4 Intake shutter valve 5 Exhaust passage 6 Exhaust recirculation passage (EGR passage)
7 Exhaust gas recirculation control valve (EGR valve)
8 Piston 9 Intake valve 10 Exhaust valve 11 Fuel injection valve 12 Glow plug 13 Engine control unit (ECU)
14 Water temperature sensor 15 Crank angle sensor 16 Key position detection sensor

Claims (4)

An intake throttle valve for adjusting the amount of intake air;
An EGR passage for returning a part of the exhaust to the intake passage downstream of the intake throttle valve;
An EGR valve that opens and closes the EGR passage and closes the EGR passage when the valve is closed ;
In a diesel engine control device comprising:
A stop request detecting means for detecting an engine stop request;
Stop control means for stopping fuel injection and closing the intake throttle valve in response to a detection signal of the stop request detection means;
Stop determination means for determining whether or not the engine has stopped;
Have
The stop control means closes the EGR valve substantially simultaneously with or before the intake throttle valve is closed ,
When the stop control means determines that the engine has been stopped by the stop determination means, after opening the EGR valve,
A control system for a diesel engine, wherein the engine control system is stopped while the EGR valve is open . 2. The diesel engine control device according to claim 1, wherein the stop control unit opens the intake throttle valve when the determination unit determines that the engine is stopped. 3. An intake throttle valve for adjusting the amount of intake air;
An EGR passage for returning a part of the exhaust to the intake passage downstream of the intake throttle valve;
An EGR valve that opens and closes the EGR passage and closes the EGR passage when the valve is closed ;
In a control method for stopping a diesel engine comprising:
A stop request detection stage for detecting an engine stop request;
A fuel injection stop stage for stopping fuel injection after the engine stop request is detected;
An intake shut-off stage for closing the intake throttle valve;
An EGR gas shut-off step for closing the EGR valve simultaneously with or before the intake shut-off step;
A stop determination stage for determining whether or not the engine has stopped;
An EGR valve opening stage for opening the EGR valve when it is determined that the engine has stopped;
A system stop stage for stopping the engine control system while the EGR valve is open;
A control method for stopping a diesel engine, comprising: 4. The control method for stopping a diesel engine according to claim 3, further comprising an intake throttle valve opening step of opening the intake throttle valve when it is determined that the engine has stopped.

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