JP5958404B2 - Diesel engine control device - Google Patents

Description

  The present invention relates to a control device for a diesel engine.

  2. Description of the Related Art Conventionally, in a diesel engine control device, exhaust gas recirculation (EGR) is performed to recirculate a part of exhaust gas to an intake passage in order to reduce NOx emission. However, if the EGR gas recirculated by EGR in this manner remains in the cylinder when the engine is stopped, sulfuric acid is generated when the engine temperature is lowered, and the cylinder inner wall and the fuel injection nozzle hole may be corroded.

  Further, if a large amount of air remains in the cylinder when the engine speed is reduced due to the engine being stopped, the rotational fluctuation may occur due to the reaction force when the air is compressed and expanded, and the engine may vibrate.

In the control device described in Patent Document 1, the following control is executed in order to eliminate these disadvantages.
The control device first closes the EGR control valve when the driver performs an engine stop operation. In this state, the EGR gas remaining in the cylinder is scavenged by maintaining the engine in an operating state for a predetermined time. When the EGR gas is scavenged, the throttle valve is then closed. Then, fuel injection is continued until the pressure in the intake manifold sufficiently decreases. This reduces the amount of air remaining in the cylinder and suppresses vibrations that occur when the engine is stopped. And after performing these controls, fuel injection is stopped and the engine is stopped.

Japanese Utility Model Publication No. 61-152741

  By the way, in the control device described in Patent Document 1 described above, the engine speed does not decrease for a while even though the driver has stopped the engine, and therefore the driver feels that the engine does not stop quickly after the stop operation. There is a risk of feeling a so-called run-on.

  The present invention has been made in view of such circumstances, and its purpose is to scavenge EGR gas remaining in the cylinder and suppress vibration generated when the engine is stopped, and to reduce the run-on feeling felt by the driver. It is an object of the present invention to provide a diesel engine control device.

A control device for a diesel engine for solving the above problems closes an EGR control valve and a throttle valve in order before the diesel engine is stopped by a stop operation of the diesel engine. Then, the control apparatus of the diesel engine, the first fuel injection amount have less than the fuel injection amount immediately before the stop operation of the fuel injection amount when the stop operation is performed, the fuel injection amount immediately before the subsequent stop operation When the second fuel injection amount is less than the first fuel injection amount and the fuel injection amount is the first fuel injection amount, the opening of the throttle valve is maintained at the opening just before the stop operation. Then, after the fuel injection amount is set to the second fuel injection amount, the throttle valve is closed .

  In the above configuration, the EGR control valve is closed before the engine is stopped by the engine stop operation, and then the throttle valve is closed. Therefore, the EGR gas remaining in the cylinder can be scavenged before the engine is stopped. Further, since the fuel injection is continued even after the throttle valve is closed, the pressure in the intake manifold can be reduced before the engine is stopped, and the air in the cylinder can be reduced.

  Further, since the fuel injection amount is made smaller than the fuel injection amount immediately before the stop operation when the engine stop operation is performed, the engine speed decreases almost simultaneously with the engine stop operation. For this reason, the driver can feel that the engine is shifting to the stopped state after the stop operation of the engine, and can reduce the run-on feeling felt by the driver.

In the above control device, if the first fuel injection amount is set to zero, the degree of decrease in the engine speed when the stop operation is performed increases. Therefore, according to such a structure, the run-on feeling felt by the driver can be reduced. If the engine speed is excessively reduced, engine vibration may occur. In this regard, in the above control device, if the execution time in which the fuel injection amount is the first fuel injection amount is changed according to the engine speed when the fuel injection amount is the first fuel injection amount , the engine speed The fuel injection amount can be set to the second fuel injection amount before the vibration due to the decrease in the pressure increases. Further, for example, even when the degree of decrease in the engine speed when the fuel injection amount is set to the first fuel injection amount is different due to the influence of friction, the fuel injection amount is set to the second fuel at an appropriate time according to the decrease degree. The injection amount can be set.

Moreover, in the said control apparatus, after setting it as the 2nd fuel injection amount, it is preferable to reduce the fuel injection amount gradually.
According to the above configuration, after the second fuel injection amount is set, the engine speed gradually decreases as the fuel injection amount gradually decreases. For this reason, the driver can easily recognize that the engine has shifted to the stopped state, and the run-on feeling can be further reduced.

The block diagram which shows schematic structure of the control apparatus of a diesel engine. (A)-(f) is a timing chart which shows an example of the engine stop control performed by the control apparatus of a diesel engine. (A), (b) is a timing chart which shows another example of engine stop control. (A), (b) is a timing chart which shows the other example of engine stop control.

Hereinafter, an embodiment of a control device for a diesel engine will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, a vehicle equipped with a diesel engine is provided with a control device 1 that comprehensively controls the diesel engine. Signals are input to the control device 1 from various sensors mounted on the vehicle. As such sensors, for example, a key switch 2 provided in the driver's seat of the vehicle, a rotational speed sensor 3 for detecting the engine rotational speed, a pressure sensor 4 for detecting the pressure in the intake manifold, and the like are provided. Yes.

  The control device 1 executes various controls based on signals input from these various sensors. For example, when the key switch 2 is switched from the “OFF” position to the “ON” position, the fuel injection from the fuel injection valve 5 is started and the engine start control is executed, while the key switch 2 is “ON”. When the position is switched to the “OFF” position, stop control for stopping the engine is executed. In addition, EGR control for adjusting the recirculation amount of the EGR gas by adjusting the opening of the EGR control valve 6, pressure control for controlling the pressure in the intake manifold by adjusting the opening of the throttle valve 7, etc. are also executed.

  Next, the engine stop control described above will be described in detail with reference to the time chart of FIG. In the following, stop control when the diesel engine is in an idle operation state will be described as an example.

  As shown in FIG. 2A, when the key switch 2 is switched from the “ON” position to the “OFF” position by the driver, that is, when a stop operation is performed (timing T1), the control device 1 As shown in b), the EGR control valve 6 is closed and, as shown in FIG. 2D, fuel cut is started. For this reason, at the timing T1, the EGR is stopped and the engine speed gradually decreases from the idle speed Ni as indicated by the solid line in FIG.

  Then, as shown in FIGS. 2 (d) and 2 (e), when the engine speed decreases and becomes equal to or lower than the predetermined speed Na (timing T2), the control device 1 ends the fuel cut and performs fuel injection. To resume. Note that the fuel injection amount when restarting the fuel injection is smaller than the fuel injection amount immediately before the stop operation, that is, during idle operation. Then, after restarting the fuel injection, the fuel injection amount is gradually decreased. As a result, after the timing T2, the engine speed decreases as the fuel injection amount decreases. However, the degree of decrease is smaller than the degree of decrease in engine speed during execution of fuel cut (timing T1 to T2).

  On the other hand, as shown in FIGS. 2C to 2F, the control device 1 closes the throttle valve 7 after the EGR control valve 6 is closed (timing T3). Then, the fuel injection is stopped after the throttle valve 7 is closed (timing T5). Thus, fuel injection is continued even after the throttle valve 7 is closed, the engine is maintained in an operating state, and the pressure in the intake manifold gradually decreases. Thereafter, after the pressure in the intake manifold has sufficiently decreased to a predetermined pressure and the air in the cylinder has decreased, fuel injection is stopped and the engine speed is set to “0”, that is, the engine is stopped. Note that the timing T5 at which the fuel injection is stopped is set in advance in consideration of the pressure decrease rate in the intake manifold after the throttle valve is closed.

Next, the operation of the control device 1 for the diesel engine according to the present embodiment will be described.
In the control device 1 of the present embodiment, before the engine is stopped by the key switch 2 being switched to the “OFF” position, the EGR control valve 6 is closed and the EGR control valve 6 is closed. Since the valve 7 is closed, the EGR gas remaining in the cylinder is scavenged. Further, since the fuel injection is continued even after the throttle valve 7 is closed, the pressure in the intake manifold is lowered before the engine is stopped, and the air in the cylinder is reduced.

  Further, as indicated by a one-dot chain line in FIGS. 2D and 2E, the fuel injection is stopped after a predetermined time Ts has elapsed after the key switch 2 is switched to the “OFF” position (timing T4). In this case, it takes a long time from when the key switch 2 is switched to the “OFF” position until the engine speed starts to decrease.

  On the other hand, in the present embodiment, since the fuel cut is started at the timing T1 when the key switch 2 is switched to the “OFF” position, the engine speed decreases almost simultaneously with the engine stop operation. For this reason, the driver can feel that the engine is shifting to the stop state after the engine stop operation.

  Further, when the engine rotational speed becomes equal to or lower than the predetermined rotational speed Na (timing T2), the fuel cut is finished and the fuel injection is restarted. That is, the fuel cut execution time is changed according to the engine speed during the fuel cut. For this reason, fuel injection is restarted before the vibration caused by the decrease in engine speed increases. Further, for example, even when the degree of decrease in engine speed during execution of fuel cut differs due to the influence of friction, fuel injection is restarted at an appropriate time according to the degree of decrease.

Further, since the fuel injection amount when the fuel injection is resumed is made smaller than the fuel injection amount during the idling operation, the engine speed is suppressed from being increased when the fuel injection is resumed.
Further, after the timing T2 at which the fuel injection is restarted, the fuel injection amount is gradually decreased, and accordingly, the engine speed is also gradually decreased. For this reason, it becomes easy for the driver to recognize that the engine has shifted to the stopped state.

According to the embodiment described above, the following effects can be obtained.
(1) Since the fuel cut is executed when the key switch 2 is switched to the “OFF” position, the driver can feel that the engine is shifting to the stop state after the engine stop operation, The run-on feeling felt by the driver can be reduced. Further, it is possible to scavenge EGR gas remaining in the cylinder and to suppress vibration generated when the engine is stopped.

  (2) Since the fuel cut is terminated when the engine speed becomes equal to or lower than the predetermined speed Na and fuel injection is resumed with a fuel injection amount smaller than the fuel injection amount during idle operation, the engine speed The fuel injection can be resumed before the vibration due to the decrease in the pressure increases. Further, for example, even when the degree of decrease in engine speed during execution of fuel cut differs due to the influence of friction, fuel injection can be restarted at an appropriate time according to the degree of decrease.

  (3) After restarting the fuel injection, the fuel injection amount is gradually decreased, so that the driver can easily recognize that the engine has stopped and the run-on feeling can be further eased. .

In addition, the said embodiment can also be changed and implemented as follows. It should be noted that the above embodiment and the following modification examples can be combined as appropriate.
In the above embodiment, the fuel injection amount is gradually decreased after the fuel injection is restarted. However, for example, the fuel injection amount may be changed as described below.

  As shown in FIG. 3A, the control device 1 starts fuel cut at the timing T1 when the key switch 2 is switched to the “OFF” position. Then, as shown in FIG. 3B, when the engine speed decreases and becomes equal to or lower than the predetermined speed Na, fuel injection is resumed. At this time, the fuel injection amount is set to an amount smaller than the fuel injection amount during idle operation. Thereafter, the fuel injection amount is kept constant, and the fuel injection is stopped at timing T5. In such control, the engine speed decreases after fuel injection is stopped at timing T5. Even with such a configuration, the same effects as in the above (1) and (2) can be obtained.

  In each of the above embodiments, the fuel injection amount may be decreased stepwise after restarting the fuel injection. Even with such a configuration, the same effects as in the above (1) and (2) can be obtained.

  In each of the above embodiments, the fuel cut is terminated when the engine speed becomes equal to or lower than the predetermined engine speed Na. For example, a basic execution time for fuel cut is set in advance, and this basic execution time is set to You may make it correct | amend according to the fall degree of an engine speed. In this case, the fuel injection may be restarted earlier by shortening the fuel cut execution time by correction as the degree of decrease in the engine speed is larger. Even with such a configuration, the same effects as the above (1) and (2) can be obtained.

  In each of the above embodiments, the fuel cut execution time is changed according to the engine speed, but the fuel cut may be executed for a predetermined time. Even with such a configuration, the effect described in (1) above can be obtained.

  In each of the above embodiments, the fuel cut is started when the key switch 2 is switched to the “OFF” position, and then the fuel injection is restarted. For example, the fuel injection amount is changed as described below. Also good.

  As shown in FIG. 4A, at the timing T1 when the key switch 2 is switched to the “OFF” position, the fuel injection amount is set to a first fuel injection amount that is smaller than the fuel injection amount during idle operation. After that, the fuel injection amount is kept constant, and when the engine speed becomes equal to or lower than the predetermined rotation speed Na as shown in FIG. 4B, the fuel injection amount is larger than the first injection amount and during idle operation. The second injection amount is smaller than the fuel injection amount. After the timing T6 when the fuel injection amount is the second injection amount, the fuel injection amount is gradually decreased. Even with this configuration, the same effect as described in (1) can be obtained.

-The fuel injection amount may be gradually decreased from when the stop operation is performed. Even with such a configuration, the same effect as the above (1) can be obtained.
In each of the above embodiments, the EGR control valve is closed at the timing T1 when the key switch 2 is switched to the “OFF” position. However, the EGR control valve may be closed slightly after the timing T1. .

  In each of the above embodiments, the operation of switching the key switch 2 to the “OFF” position is exemplified as the stop operation, but the stop operation is not limited to this. For example, a button may be provided in the driver's seat, and the stop operation may be performed by operating this button.

  In each of the above embodiments, the stop control when the diesel engine is in the idle operation state has been described as an example, but the above-described control is applied even when the stop operation is performed in a state other than the idle operation state. I can.

  In each of the above embodiments, the fuel injection stop timing T5 is set in advance. For example, the pressure in the intake manifold is monitored each time, and the fuel injection stop timing is set based on the detection result. Also good. In short, the fuel injection stop timing may be set so that the fuel injection is stopped after the pressure in the intake manifold has sufficiently decreased.

  DESCRIPTION OF SYMBOLS 1 ... Control apparatus, 2 ... Key switch, 3 ... Speed sensor, 4 ... Pressure sensor, 5 ... Fuel injection valve, 6 ... EGR control valve, 7 ... Throttle valve.

Claims (4)

In a diesel engine control device that sequentially closes an EGR control valve and a throttle valve before stopping the diesel engine by a stop operation of the diesel engine,
The stop operation of the fuel injection amount of the stop operation when the has been made immediately before the first fuel injection amount have less than the fuel injection amount, then the stop operation immediately before the fuel injection amount less the first than the The second fuel injection amount is larger than the fuel injection amount,
When the fuel injection amount is the first fuel injection amount, the opening of the throttle valve is maintained at the opening immediately before the stop operation, and the fuel injection amount is set to the second fuel injection amount. A control device for a diesel engine, characterized by closing a throttle valve . The control device for a diesel engine according to claim 1, wherein the first fuel injection amount is zero . The execution time in which the fuel injection amount is the first fuel injection amount is changed according to the engine speed when the fuel injection amount is the first fuel injection amount.
The control apparatus of the diesel engine of Claim 1 or Claim 2 . The control device for a diesel engine according to claim 3, wherein after the second fuel injection amount is set, the fuel injection amount is gradually decreased.