JPH11270372A - Stopping device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent injection of excessive fuel and generation of knocking at the time of stopping a diesel engine. SOLUTION: It is possible to speedily stop an engine 11 and to reduce vibration at the time of stopping it by totally closing an air intake throttle valve 55 provided on an air intake system at the time of stopping the diesel engine 11. An electronic control unit(ECU) provided on the engine 11 guards an upper limit of fuel injection quantity to be excessively increased due to lowering of engine speed at the time when there is sudden lowering of the engine speed in accordance with total closing of the air intake throttle valve 55 at the time of stopping the engine 11. Additionally, the ECU guards target fuel injection timing to be corrected to the spark advance side excessively in accordance with lowering of its air intake pressure about the spark advance side at the time when there is sudden lowering of the air intake pressure in accordance with total closing of the air intake throttle valve 55 at the time of stopping the engine 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine stop device for imparting engine rotational resistance by controlling an intake throttle valve to reduce an intake air amount at the start of engine stop.

[0002]

2. Description of the Related Art In general, for example, in a vehicle-mounted diesel engine, a fuel injection amount and a fuel injection timing are obtained based on an operation state of the engine such as an accelerator pedal depression amount, an engine speed and an intake pressure. When the fuel injection amount and the fuel injection timing are obtained in this way, an amount of fuel corresponding to the obtained fuel injection amount is injected into the combustion chamber of the diesel engine at a time corresponding to the obtained fuel injection timing. Under the condition that the accelerator depression amount is “0”, the fuel injection amount obtained becomes larger as the engine speed becomes lower. In addition, the fuel injection timing obtained becomes a value on the advance side as the engine speed increases under the condition that the accelerator depression amount is constant.

[0003] Further, the fuel injection timing is corrected to the advanced side in order to achieve good fuel combustion in the combustion chamber when the atmospheric pressure becomes low such as at high altitude and the intake pressure becomes low.
That is, when the intake pressure decreases and the amount of oxygen drawn into the combustion chamber decreases, ignition of fuel in the combustion chamber is delayed,
Misfire or white smoke is generated in the diesel engine due to the ignition delay. However, by advancing the fuel injection timing as described above, it is possible to prevent ignition delay to the fuel in the combustion chamber and obtain good combustion without generating misfire or white smoke.

[0004] On the other hand, in such a diesel engine, there is a case where an engine rotation resistance is applied in order to reduce vibration when the engine is stopped. As a method of giving the engine rotational resistance in this way, it is conceivable to provide an intake throttle valve in an intake passage of a diesel engine and close the intake throttle valve when the engine stops. An example of such an intake throttle valve is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-13133.
No. 9 is known. When the intake throttle valve described in the above publication is adopted for a diesel engine, the intake throttle valve is closed at the start of the stop of the engine, and the amount of intake air is reduced. Then, by increasing the pumping loss of the diesel engine due to the decrease in the intake air amount, the stop of the engine is completed promptly, thereby reducing the vibration when the engine is stopped.

[0005]

By the way, when the diesel engine is stopped, it is better to stop the fuel injection after a predetermined time has elapsed than to stop the fuel injection immediately, rather than immediately stop the fuel injection. It is known that vibrations are reduced. However, when the fuel injection stop is delayed as described above, if the accelerator depression amount is set to “0” at the start of the stop of the diesel engine and the intake throttle valve is closed, the engine speed of the engine is rapidly increased. Therefore, the required fuel injection amount increases rapidly, and extra fuel is injected into the combustion chamber. If the stop of the diesel engine is completed in a state where the excess fuel is injected into the combustion chamber in this way, the next time the engine is started, smoke will be generated due to the remaining unburned fuel.

[0006] These problems are not limited to the case where an intake throttle valve is employed as means for imparting engine rotational resistance.
For example, this is also common in a case where an exhaust throttle valve is provided in an exhaust passage of a diesel engine, and when the engine is stopped, the exhaust throttle valve is closed to impart engine rotation resistance.

On the other hand, when the intake throttle valve is closed at the start of the stop of the diesel engine, the intake air amount is reduced, the intake pressure is reduced, and the required fuel injection timing is corrected to the advanced side. When the fuel injection timing of the diesel engine is advanced in this manner, knocking occurs in the engine, and the knocking noise is not negligible.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a diesel engine stopping device capable of preventing injection of excess fuel at the time of stopping. .

Another object of the present invention is to provide a diesel engine stopping device capable of preventing occurrence of knocking at the time of stopping.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, an amount of fuel required to be injected into a combustion chamber on the basis of an operating state of the engine is supplied, and when the engine is stopped, the engine rotational resistance is reduced. The diesel engine stopping device according to claim 1, further comprising an injection amount guard means for guarding an upper limit of a fuel injection amount obtained based on the engine operating state when the diesel engine starts to stop.

When the engine rotation resistance is applied at the start of the stop of the diesel engine, the engine speed suddenly decreases based on the application of the engine rotation resistance. However, according to this configuration, the upper limit of the fuel injection amount obtained based on the engine operating state such as the engine speed is guarded. Therefore, the fuel injection amount is not excessively increased due to the sudden decrease in the engine rotation speed based on the application of the engine rotation resistance, and the excess fuel injection into the combustion chamber based on the excessive increase in the fuel injection amount is prevented. Is prevented.

According to a second aspect of the present invention, in the first aspect of the invention, the guard value of the fuel injection amount is equal to or less than the fuel injection amount at the start of stopping the diesel engine.

According to this configuration, after the start of the stop of the diesel engine, the fuel injection amount does not increase even if the engine rotation resistance is applied and the engine speed suddenly decreases, so that the fuel injection amount increases excessively. Excessive fuel injection into the combustion chamber due to this is preferably prevented.

According to a third aspect of the present invention, in the first aspect of the invention, the guard value of the fuel injection amount is equal to or less than the idle injection amount. According to the configuration, for example, when the diesel engine is stopped immediately after the engine is idled, the fuel injection amount increased based on the idleness is guarded to be equal to or less than the idle injection amount.
That is, the fuel injection amount after the start of the stop is equal to or less than the idle injection amount, and excess fuel injection into the combustion chamber due to excessive increase in the fuel injection amount is suitably prevented.

According to a fourth aspect of the present invention, in the invention of any one of the first to third aspects, the amount of air taken into the combustion chamber is reduced to provide engine rotation resistance at the start of stopping the diesel engine. An intake throttle valve to be controlled, injection timing control means for performing fuel injection at a fuel injection timing corrected based on the intake pressure of the engine, and when the diesel engine is started to stop, the fuel injection timing is advanced. And a fuel injection timing guard for guarding the side of the diesel engine.

According to this configuration, when the intake throttle valve is controlled to decrease the intake air amount at the start of stopping the diesel engine, the intake pressure decreases, and the fuel injection timing is corrected to the advance angle side. Since the fuel injection timing is guarded on the advance side, knocking based on excessive advance of the fuel injection timing is prevented.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the guard value of the fuel injection timing is the same as the fuel injection timing at the start of stopping the diesel engine.

According to this configuration, after the start of the stop of the diesel engine, the fuel injection timing is not advanced even if the intake pressure is reduced by controlling the intake throttle valve to the intake air amount decreasing side. Knocking based on excessively advanced angle is preferably prevented.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the amount of intake air to the combustion chamber is reduced to provide an engine rotation resistance at the start of stopping the diesel engine. Controlling the intake throttle valve and causing the fuel injection to be performed at the fuel injection timing corrected based on the intake pressure of the engine, and at the start of the stop of the diesel engine, at a timing delayed from the corrected fuel injection timing. And an injection timing control means for performing fuel injection.

According to this configuration, the fuel injection timing at the start of stopping the diesel engine is retarded from the fuel injection timing corrected based on the intake pressure, and is set to a value that can suppress the generation of smoke. become able to. Therefore, it is possible to prevent the occurrence of smoke due to excessive retardation of the fuel injection timing while preventing knocking due to excessive advance of the fuel injection timing.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the cylinder block 11a of the diesel engine 11
Is provided with a piston 12 so as to be able to reciprocate.
The piston 12 is connected via a connecting rod 13 to a crankshaft (output shaft) 14 provided below the diesel engine 11. And piston 1
The two reciprocating movements are converted into rotation of the crankshaft 14 by the connecting rod 13. Such a diesel engine 11 is provided with a starter 51 for forcibly rotating the crankshaft 14 at the time of starting. The starter 51 is driven by operating an ignition switch 52 provided in the interior of the vehicle.

On the other hand, one projection 15a is provided on the outer peripheral surface of the crankshaft 14, and a crank position sensor 16 for detecting the projection 15a and outputting a detection signal is provided on the side of the crankshaft 14. And
When the crankshaft 14 rotates and the protrusion 15a passes by the crank position sensor 16 at predetermined intervals, a detection signal is output from the sensor 16 at predetermined intervals.

The cylinder block 11a is provided with a water temperature sensor 11b for detecting a cooling water temperature of the diesel engine 11. Also, cylinder block 1
A cylinder head 17 is provided at the upper end of 1a.
Further, a combustion chamber 18 is provided between the cylinder head 17 and the piston 12. The cylinder head 17 is provided with an injection nozzle 18 a for injecting fuel into the combustion chamber 18, and an intake port 19 and an exhaust port 20 are provided so as to communicate with the combustion chamber 18. The intake port 19 and the exhaust port 20 have an intake valve 21 and an exhaust valve 22 respectively.
Is provided.

The cylinder head 17 has an intake valve 21
An intake camshaft 23 and an exhaust camshaft 24 for opening and closing the exhaust valve 22 are rotatably supported. These intake and exhaust camshafts 23, 24
Is connected to the crankshaft 14 via a timing belt (not shown), and the rotation of the crankshaft 14 is transmitted to the intake and exhaust camshafts 23 and 24 by the belt. When the intake camshaft 23 rotates, the intake valve 21 is driven to open and close,
The communication between the intake port 19 and the combustion chamber 18 is interrupted. Further, when the exhaust camshaft 24 rotates, the exhaust valve 22 is driven to open and close, so that the exhaust port 20 and the combustion chamber 18 are communicated and shut off.

An intake pipe 30 and an exhaust pipe 31 are connected to the intake port 19 and the exhaust port 20, respectively. The inside of the intake pipe 30 and the inside of the intake port 19 form an intake passage 32, and the inside of the exhaust pipe 31 and the inside of the exhaust port 20 form an exhaust passage 33.

The intake passage 32 is provided with a throttle valve 34 whose opening is adjusted based on the amount of depression of an accelerator pedal 34a provided in the cabin of the automobile. The depression amount of the accelerator pedal 34a (acceleration depression amount) is detected by an accelerator position sensor 27,
7 outputs a detection signal corresponding to the detected accelerator depression amount. The opening of the throttle valve 34 (throttle opening) is determined by the throttle position sensor 28.
The sensor 28 outputs a detection signal corresponding to the detected throttle opening. Furthermore,
In the intake pipe 30, a pressure sensor 30a is provided downstream of the throttle valve. The pressure sensor 30a detects a pressure in the intake passage 32 located downstream of the throttle valve 34, and outputs a detection signal corresponding to the detected pressure.

An exhaust gas recirculation (E) for recirculating a part of the exhaust gas of the diesel engine 11 to the intake gas passage 32 downstream of the throttle valve 34 in the intake gas passage 32 is provided.
(GR) communicates with an exhaust passage 33 through a passage 35.
When the exhaust gas is recirculated to the intake passage 32 by the EGR passage 35, the combustion temperature in the combustion chamber 18 of the diesel engine 11 is reduced, so that the generation of nitrogen oxides (NOx) is suppressed, and the emission is reduced. become.

In the middle of the EGR passage 35, an EGR valve 36 is provided. The EGR valve 36 includes a case 36c in which a negative pressure chamber 36b is defined by a diaphragm 36a, and a rod 36d connected to the diaphragm 36a and protruding outside the case 36c.
And a valve element 36e attached to the tip of the rod 36d. The rod 36d is urged in a direction protruding from the case 36c by a coil spring 36f in the case 36c. In this state, the valve element 36e is closed and the amount of exhaust gas passing through the EGR passage 35 becomes "0".

The negative pressure chamber 36b is provided with a negative pressure passage 37 and an electric vacuum regulating valve (E).
VRV) 38, and is connected to a vacuum pump 59 driven by rotation of the crankshaft 14. The EVRV 38 is provided with an electromagnetic solenoid (not shown), and the duty of the voltage application to the electromagnetic solenoid is controlled.
The amount of air sucked through the negative pressure passage 37 is adjusted. The adjustment of the suction air amount changes the amount of protrusion of the rod 36d from the case 36c, and adjusts the opening of the valve element 36e attached to the rod 36d. By adjusting the opening degree of the EGR valve 36, the amount of exhaust gas recirculated to the intake passage 32 via the exhaust passage 33 is adjusted.

The intake pipe 30 has a bypass passage 5 which bypasses the throttle valve 34 and communicates with the intake passage 32.
3 are provided. The bypass passage 53 has an intake throttle valve 5 that opens and closes when driven by an actuator 54.
5 are provided. The actuator 54 includes two diaphragms 55a and 55b that define two negative pressure chambers 56a and 56b in a case 54a, and the case 54a is connected to the diaphragms 55a and 55b.
Rod 6 projecting out of the cylinder and connected to intake throttle valve 55
0. The rod 60 is fixed to the case 5 by the coil springs 60a and 60b in the case 54a.
4a.

The two negative pressure chambers 56a and 56b are connected to the vacuum pump 59 via negative pressure passages 57a and 57b and vacuum switching valves (VSV) 58a and 58b, respectively. VSV58a, 5
8b includes an electromagnetic solenoid (not shown), and when the electromagnetic solenoid is in a demagnetized state, the negative pressure passages 57a and 57b are provided.
b is opened to the atmosphere, and the electromagnetic pressure is applied to the vacuum pumps 59a and 57b by exciting the electromagnetic solenoid.
To communicate with

When the negative pressure passages 57a and 57b and the vacuum pump 59 communicate with each other, the air in the negative pressure chambers 56a and 56b is sucked out by the driving of the pump 59, and the negative pressure is supplied into the negative pressure chambers 56a and 56b. Will occur. Due to this negative pressure, the rod 60 and the diaphragms 55a, 55
b moves against the coil springs 60a and 60b in a direction in which the rod 60 enters the case 54a, and the intake throttle valve 55 is controlled to the closed side.

The closing control of the intake throttle valve 55 is performed, for example, when the diesel engine 11 is stopped.
1 is intended to reduce the vibration. That is, when the intake throttle valve 55 is closed when the diesel engine 11 is stopped,
The pumping loss of the engine 11 increases, and the engine rotation resistance is given. Due to the engine rotation resistance, the rotation of the engine 11 is promptly reduced and stopped, thereby reducing vibration when the engine is stopped.

Further, the intake throttle valve 55 is used for fine adjustment of the exhaust gas recirculation amount (EGR amount). That is, since the EGR amount changes depending on the pressure difference between the exhaust passage 33 and the intake passage 32, the opening degree of the intake throttle valve 55 is controlled to change the pressure of the intake passage 32 on the downstream side of the throttle valve 34, whereby The EGR amount can be finely adjusted by adjusting the pressure difference.

In the exhaust passage 33 of the diesel engine 11, downstream of the EGR passage 35, an exhaust throttle valve 4 that opens and closes by being driven by an actuator 45.
6 are provided. The actuator 45 includes a diaphragm 45c for partitioning and forming a negative pressure chamber 45b in a case 45a, and a rod 45d protruding outside the case 45a and connected to an exhaust throttle valve 46 while being connected to the diaphragm 45c. I have. The rod 45d is urged by a coil spring 45e in the case 45a in a direction protruding from the case 45a. And
In this state, the exhaust throttle valve 46 is closed.

The negative pressure chamber 45b has a negative pressure passage 47 and an electric vacuum regulating valve (E).
(VRV) 48 and connected to the vacuum pump 59. The EVRV 48 includes an electromagnetic solenoid (not shown), and the amount of air sucked from the negative pressure chamber 45b through the negative pressure passage 47 by the vacuum pump 59 is adjusted by duty control of voltage application to the electromagnetic solenoid. Is done. By adjusting the suction air amount, the rod 4
The protrusion amount of the 5d with respect to the case 45a changes, and the opening degree of the exhaust throttle valve 46 attached to the rod 45d is adjusted. Such adjustment of the opening degree of the intake throttle valve 46 is performed, for example, by
During the idle operation of the diesel engine 11 in a state where the engine temperature is low, the exhaust throttle valve 46 is controlled to the closed side in order to quickly warm up the engine 11.

The pressure of the exhaust passage 33 on the upstream side of the exhaust throttle valve 46 is finely adjusted by controlling the opening degree of the exhaust throttle valve 46, and the pressure difference between the exhaust passage 33 and the intake passage 32 is adjusted to an appropriate value.
Fine adjustment is made to a value at which the GR amount is obtained. And so on.

On the other hand, the crankshaft 14 of the diesel engine 11 is connected to the drive shaft 41a of the fuel injection pump 41. This fuel injection pump 41
Is connected to the injection nozzle 18a of the cylinder head 17 via a fuel line 42. Then, the fuel injection pump 41 is driven by the rotation of the crankshaft 14 being transmitted to the drive shaft 41a, and draws fuel from a fuel tank (not shown) of the automobile and directs the fuel toward the injection nozzle 18a. Discharge. The injection nozzle 18a operates by the pressure of the fuel sent from the fuel injection pump 41, and injects the fuel into the combustion chamber 18.

The fuel injection pump 41 is provided with an electromagnetic spill valve 43 for adjusting the amount of fuel discharged toward the injection nozzle 18a, and a timer device 44 for adjusting the fuel discharge start timing. And the fuel injection pump 41
The electromagnetic spill valve 43 and the timer device 4 determine the discharge amount and discharge timing of the fuel discharged from the nozzle toward the injection nozzle 18a.
By adjusting at 4, the injection amount and the injection timing of the fuel injected from the injection nozzle 18a to the combustion chamber 18 are adjusted. Further, the fuel injection pump 41 is provided with a rotation speed sensor 45 for detecting the rotation speed of the diesel engine 11. The rotation speed sensor 45 outputs a detection signal corresponding to the rotation of the drive shaft 41a.

In the diesel engine 11, air is drawn into the combustion chamber 18 through the intake passage 32 as the piston 12 descends during the intake stroke.
Thereafter, in the compression stroke, the injection nozzle 1 is moved in a state where the air in the combustion chamber 18 is compressed by the rise of the piston 12.
From 8a, an amount of fuel corresponding to the depression amount of the accelerator pedal 34a is injected toward the combustion chamber 18. as a result,
The fuel injected into the high-pressure air in the combustion chamber 18 self-ignites and burns, and the combustion energy lowers the piston 12 to move to an explosion stroke. This explosion stroke causes the engine 11 to obtain a driving force. The exhaust gas generated by the combustion of the fuel in the combustion chamber 18 is supplied to the engine 1
In the first exhaust stroke, the piston 12 is discharged to the exhaust passage 33 by the rise of the piston 12. Then, part of the exhaust gas in the exhaust passage 33 is recirculated to the intake passage 32 via the EGR passage 35.

Next, the electrical configuration of the engine stop device according to the present embodiment will be described with reference to FIG. The stop device includes an electronic control unit (hereinafter, referred to as “ECU”) 92 for controlling the operation state of the engine 11 such as fuel injection timing control, fuel injection amount control, and intake throttle valve control. The ECU 92 includes a ROM 93, a CPU 94,
The logic operation circuit includes a RAM 95, a backup RAM 96, and the like.

The ROM 93 is a memory that stores various control programs and maps and the like that are referred to when executing the various control programs.
The arithmetic processing is executed based on various control programs and maps stored in the OM 93. The RAM 95 is a CPU
94 is a memory for temporarily storing the calculation result at 94, data input from each sensor, and the like.
Reference numeral 6 denotes a nonvolatile memory for storing data to be stored when the engine 11 is stopped. And ROM93, CP
The U 94, the RAM 95, and the backup RAM 96 are connected to each other via a bus 97, and are also connected to an external input circuit 98 and an external output circuit 99.

The external input circuit 98 includes a water temperature sensor 11
b, a crank position sensor 16, an accelerator position sensor 27, a throttle position sensor 28, a pressure sensor 30a, a rotation speed sensor 45, an ignition switch 52, and the like. On the other hand, the external output circuit 9
9 includes an electromagnetic spill valve 43, a timer device 44, and a VSV.
58a, 58b, etc. are connected.

The ECU 92 configured as described above determines whether or not the accelerator depression amount is "0" based on the detection signal from the accelerator position sensor 27, that is, whether or not the vehicle is idling. The ECU 92 is provided with the water temperature sensor 11.
Based on the detection signal from b, it is determined whether or not the cooling water temperature is, for example, 70 ° C. or higher, that is, whether or not the diesel engine 11 is in a warm-up completed state. Further, the ECU 92 determines, based on a signal from the ignition switch 52, whether or not the diesel engine 11 has started stopping.

When it is determined that the diesel engine 11 is performing an idling operation in a cold state, the ECU
Reference numeral 92 denotes a state in which the electromagnetic solenoids of the VSVs 58a and 58b are both in a demagnetized state, so that the inside of the negative pressure chambers 56a and 56b is at atmospheric pressure. In this state, the coil spring 60
The rods 60 of the actuator 54 project most from the case 54a by the urging forces of a and 60b, and the intake throttle valve 55 is fully opened by the rod 60. By fully opening the intake throttle valve 55 in this manner, the intake air amount of the diesel engine 11 is sufficiently ensured.

If it is determined that the diesel engine 11 is idling with the engine warmed up, the EC
U92 excites the electromagnetic solenoid of the VSV 58a and demagnetizes the electromagnetic solenoid of the VSV 58b, so that air is sucked only from the negative pressure chamber 56a. In this state, the negative pressure in the negative pressure chamber 56a causes the rod 60 of the actuator 54 to be positioned at an intermediate position between the most immersed position and the most protruded position with respect to the case 54a. The throttle valve 55 is opened halfway. By half-opening the intake throttle valve 55 in this manner, vibration and noise during idle operation can be reduced.

Further, when it is determined that the diesel engine 11 is in a state where the stop has been started, the ECU 92 sets the VSV
By exciting both of the electronic solenoids 58a and 58b, air is sucked out of the negative pressure chambers 56a and 56b of the actuator 54. In this state, the negative pressure chamber 56
The rod 60 of the actuator 54 is most immersed in the case 54a due to the negative pressure in the a and 56b, and the intake throttle valve 55 is fully closed by the rod 60. By fully closing the intake throttle valve 55 in this manner, an engine rotation resistance is given to the diesel engine 11, and the resistance allows the engine 11 to be quickly stopped, thereby reducing the stop vibration.

Next, a procedure for calculating the fuel injection amount Q will be described with reference to FIG. FIG. 4 is a flowchart showing a fuel injection amount calculation routine for calculating the fuel injection amount Q. This fuel injection amount calculation routine is executed by the ECU 9
2 through, for example, a time interruption every predetermined time.

In the fuel injection amount calculation routine, the ECU
A step 92 obtains the engine speed NE based on the detection signal from the rotation speed sensor 45 and obtains the accelerator pedal depression amount based on the detection signal from the accelerator position sensor 27 as the process of step S101. Further, the ECU 9
2 performs a map calculation of the fuel injection amount Q based on the engine speed NE and the accelerator pedal depression amount with reference to a known map. The fuel injection amount Q thus map-calculated becomes smaller as the engine speed NE increases, under the condition that the accelerator depression amount is constant. Further, under the condition that the engine speed NE is constant, the fuel injection amount Q becomes larger as the accelerator pedal depression amount becomes larger.

FIG. 3 shows how the calculated fuel injection amount Q changes with a change in the engine speed NE under the condition that the accelerator pedal depression amount is "0" (during idling operation). Is shown by a solid line. As is clear from the figure, the fuel injection amount Q during the idling operation increases as the engine speed NE decreases. Note that the target idle speed of the diesel engine 11 (for example, 700 r
pm) is an idle injection amount. During normal idling operation, an amount of fuel corresponding to the idle injection amount is injected from the injection nozzle 18a into the combustion chamber 18. Become.

The ECU 92 determines whether or not the switch 52 has been stopped based on the signal from the ignition switch 52 as the process of step S102.
When it is determined in step S102 that the ignition switch 52 has not been operated to stop,
The CU 92 temporarily ends the fuel injection amount calculation routine. When it is determined in step S102 that the ignition switch 52 has been stopped,
Proceed to step S103.

The ECU 92 drives the actuator 54 by exciting both of the electromagnetic solenoids of the VSVs 58a and 58b to fully close the intake throttle valve 55 as the process of step S103. By fully closing the intake throttle valve 55 in this manner, the amount of intake air of the diesel engine 11 is reduced and engine rotational resistance is imparted. Is achieved.

However, when the intake throttle valve 55 is fully closed and the engine speed NE decreases, the fuel injection amount Q calculated by the processing in step S101 based on the decrease in engine speed NE increases. I will. When the fuel injection is performed based on the fuel injection amount Q thus increased, excess fuel is injected into the combustion chamber 18 and the diesel engine 11 is stopped, and the fuel remains unburned the next time the diesel engine 11 starts. Smoke is generated due to the excess fuel. Subsequent step S1
04 and subsequent processes guard the fuel injection amount Q calculated by the process of step S101 from excessively increasing,
This is for preventing the generation of smoke when the diesel engine 11 is started next time.

The ECU 92 determines whether or not a predetermined time (0.2 seconds in the present embodiment) has elapsed since the ignition switch 52 was stopped in the process of step S104. Then, when it is determined that the answer is NO in the process of step S104, the process proceeds to step S105. As the process of step S105, the ECU 92 sets the previous fuel injection amount Q, that is, the fuel injection amount Q before increasing due to the intake throttle valve 55 fully closed, as a guard value QMX, and stores it in a predetermined area of the RAM 95. .

As a process of the subsequent step S106, the ECU 92 guards the upper limit of the fuel injection amount Q calculated in the step S101 with the guard value QMX, and then terminates the fuel injection amount calculation routine once. After calculating the fuel injection amount Q in this way, the ECU 92 controls the drive of the electromagnetic spill valve 43 based on the fuel injection amount Q according to another routine, and burns the fuel corresponding to the fuel injection amount Q from the injection nozzle 18a. It is injected into the chamber 18.

The fuel injection amount Q is determined in step S10.
By the upper limit guard process of 6, an excessive increase due to the full closing of the intake throttle valve 55 is prevented, so that no extra fuel is injected into the combustion chamber 18 when the stop of the diesel engine 11 is started. Therefore, when the diesel engine 11 is started next time, it is possible to prevent the generation of smoke due to the surplus fuel left unburned.

When the predetermined time (0.2 seconds) elapses after the ignition switch 52 is stopped, it is determined that the answer in step S104 is YES, and the process proceeds to step S107. ECU 9
2 sets the fuel injection amount Q to “0” as the process of step S107, and then temporarily ends the fuel injection amount calculation routine. When the fuel injection amount Q becomes “0”, E
The CU 92 controls the drive of the electromagnetic spill valve 43 by another routine to stop the fuel injection from the injection nozzle 18a into the combustion chamber 18.

According to the processing in steps S104 and S107 and the like, after the operation of stopping the ignition switch 52,
The fuel injection is stopped after a predetermined time (0.2 seconds) has elapsed. This is the ignition switch 52
This is because the vibration at the time of stopping the diesel engine 11 can be reduced by stopping the fuel injection after a predetermined time has elapsed from the stopping operation, rather than by stopping the fuel injection immediately after the stopping operation.

Next, the procedure for calculating the target fuel injection timing ATRG will be described with reference to FIG. FIG. 5 is a flowchart showing a fuel injection timing calculation routine for calculating the target fuel injection timing ATRG. This fuel injection timing calculation routine is executed by the ECU 92 by, for example, a time interruption at predetermined time intervals.

In the fuel injection timing calculation routine, EC
U92 calculates the target fuel injection timing ATRG by adding the atmospheric pressure correction amount APIM to the basic fuel injection timing ATRG as the process of step S201. The basic fuel injection timing ABSE is calculated from a known map based on the engine speed NE and the accelerator pedal depression amount. The calculated basic fuel injection timing ABSE becomes a value on the advance side as the engine speed NE increases and the accelerator depression amount increases.

When calculating the atmospheric pressure correction amount APIM, the intake pressure PM of the diesel engine 11 obtained based on the detection signal from the pressure sensor 30a is obtained. Then, a map calculation of the atmospheric pressure correction amount APIM is performed with reference to the map shown in FIG. 6 based on the intake pressure PM. The calculated atmospheric pressure correction amount APIM becomes a value on the advance side as the intake pressure PM is smaller, that is, as the atmospheric pressure is lower. Therefore, the atmospheric pressure correction amount API is added to the basic fuel injection timing ABSE.
The target fuel injection timing ATRG obtained by adding M is
The lower the atmospheric pressure is, the more the atmospheric pressure is corrected to the advance side by the atmospheric pressure correction amount APIM.

After calculating the target fuel injection amount ATRG as described above, the routine proceeds to step S202. The ECU 92 determines whether or not the ignition switch 52 has been stopped in the process of step S202. When it is determined in step S202 that the ignition switch 52 has not been stopped, the ECU 92 temporarily ends the fuel injection timing calculation routine. After calculating the target fuel injection timing ATRG in this way, the ECU 92
The target fuel injection timing ATR is calculated according to another routine.
Based on G, the timer device 44 is drive-controlled to bring the actual fuel injection timing closer to the target fuel injection timing ATRG.

Generally, at high altitudes or the like, the atmospheric pressure (intake pressure PM)
When the intake air amount is reduced due to a decrease in the intake air amount, the amount of oxygen sucked into the combustion chamber 18 decreases, and the ignition of the fuel is delayed, causing misfire or white smoke in the diesel engine 11. . However, as described above, the atmospheric pressure (intake pressure P
By correcting the target fuel injection timing ATRG to the advanced side as M) becomes lower, it is possible to prevent ignition delay to fuel and prevent misfire and generation of white smoke.

Further, in the processing of step S202,
When it is determined that the ignition switch 52 has been stopped, the process proceeds to step S203. ECU 92
Are the VSVs 58a, 5 as the process of step S203.
The actuator 54 is driven by exciting both the electromagnetic solenoids 8b and the intake throttle valve 55 is fully closed. By fully closing the intake throttle valve 55 in this manner, the amount of intake air of the diesel engine 11 is reduced, so that the engine 11 is quickly stopped and vibration at the time of stop is reduced.

However, when the intake throttle valve 55 is fully closed and the intake pressure PM decreases, the target fuel injection timing ATRG calculated by the processing in step S201 is corrected to the advanced side. If the fuel injection is performed based on the target fuel injection timing ATRG corrected in this way, the fuel is ignited at an excessively early timing, and knocking occurs in the diesel engine 11. And the diesel engine 11
Knocking noise is generated when the vehicle stops. The processing after step S204 is for guarding the target fuel injection timing ATRG calculated by the processing of step S201 from being excessively advanced and preventing knocking when the diesel engine 11 is stopped. is there.

As the process of step S204, the ECU 92 sets the previous target fuel injection timing ATRG, that is, the target fuel injection timing ATRG before the advance correction is made due to the intake throttle valve 55 fully closed, as the guard value ATRGMX. , R
It is stored in a predetermined area of AM95. The ECU 92 sets the target fuel injection timing ATRG calculated in step S201 to the guard value A in the subsequent step S205.
After guarding the advance side with TRGMX, the fuel injection timing calculation routine is temporarily terminated. After calculating the target fuel injection timing ATRG in this manner, the ECU 92 controls the driving of the timer device 44 based on the target fuel injection timing ATRG by another routine to bring the actual fuel injection timing closer to the target fuel injection timing ATRG.

The target fuel injection timing ATRG is determined by the advance guard process at step S205.
Since the excessive advance due to the fully closed state of the fuel cell 5 is prevented, the fuel in the combustion chamber 18 is not ignited too early. Therefore, it is possible to prevent the occurrence of knocking due to excessively early fuel ignition at the start of stopping the diesel engine 11 and the occurrence of knocking noise.

Finally, the operation of the operation stop control of the engine 11 by the engine stop device of the present embodiment will be summarized with reference to the time chart of FIG. Note that, in the time chart of FIG. 7, (a) to (f) respectively indicate the negative pressure in the intake passage 32, the target fuel injection timing ATRG, the fuel injection amount Q, the engine speed NE, and the opening degree of the intake throttle valve 55. 3 shows the transition of the output signal of the ignition switch 52.

Before the start of the stop of the diesel engine 11, the accelerator depression amount is normally "0", and the fuel injection amount Q is set to the idle injection amount as shown in FIG.
The engine speed NE becomes the idle speed as shown in (d). In this state, when the ignition switch 52 is stopped from ON to OFF as shown in (f), the intake throttle valve 55 changes from the open state to the fully closed state as shown in (e). I do. When the intake throttle valve 55 is fully closed in this way, the amount of intake air is suddenly reduced and an engine rotation resistance is applied, and the engine speed NE is increased.
Decreases rapidly as shown in FIG.

When the engine speed NE suddenly decreases, the fuel injection amount Q calculated from a known map excessively increases. However, the fuel injection amount Q is determined in step S106 in the fuel injection amount calculation routine (FIG. 4). The upper limit is guarded by the processing. Therefore, even if the engine speed NE decreases as described above, the fuel injection amount Q does not increase excessively as indicated by the broken line in (c), and is indicated by the solid line even after the start of the stop of the diesel engine 11. Is maintained at the idle injection amount. By maintaining the fuel injection amount Q at the idle injection amount in this manner, no extra fuel is injected into the combustion chamber 18 when the diesel engine 11 is stopped, and the unburned fuel remains when the engine 11 is started next time. The generation of smoke due to the excess fuel is prevented.

When the intake throttle valve 55 is fully closed at the start of the stop of the diesel engine 11, the negative pressure in the intake passage 32 suddenly increases as shown in (a) (suddenly decreases as the intake pressure PM). Become. When the intake pressure PM suddenly decreases in this manner, the atmospheric pressure correction amount A calculated from the map of FIG.
PIM becomes a value on the advance side, and the target fuel injection timing ATRG
Is excessively corrected to the advanced angle side as shown by a broken line in FIG.

However, the target fuel injection timing ATRG is determined in step S2 in the fuel injection timing calculation routine (FIG. 5).
The lead angle is guarded by the process 05. Therefore, even if the intake pressure PM decreases as described above, the target fuel injection timing ATRG is not excessively corrected to the advanced side as indicated by the broken line in FIG. Thereafter, as shown by the solid line, the state before the start of the stop is maintained. By maintaining the target fuel injection timing ATRG in the state before the start of the stop in this way, the combustion chamber 18
The ignition of the fuel in the inside is not performed, and the knocking of the diesel engine 11 and the occurrence of knocking noise can be prevented.

According to the present embodiment in which the processing described in detail above is performed, the following effects can be obtained. (1) When the stop of the diesel engine 11 is started, even if the engine rotation resistance is imparted by fully closing the intake throttle valve 55 and the engine speed NE suddenly drops, the calculation is performed based on the engine speed NE and the like. Since the fuel injection amount Q to be performed is guarded at the upper limit, no extra fuel is injected into the combustion chamber 18. Therefore, when the diesel engine 11 is started next time, it is possible to prevent generation of smoke due to the surplus fuel left unburned.

(2) Since the guard value QMX at the time of guarding the upper limit of the fuel injection amount Q is the same as the fuel injection amount Q at the start of the stop of the diesel engine 11, the fuel injection amount Q becomes smaller after the start of the stop. Does not increase. Therefore, excess fuel injection into the combustion chamber 18 based on an excessive increase in the fuel injection amount Q at the start of stopping the diesel engine 11 can be suitably prevented.

(3) Even when the intake throttle valve 55 is fully closed and the intake pressure PM decreases when the diesel engine 11 starts to stop, the target fuel injection timing whose advance is corrected based on the decrease in the intake pressure PM Since the ATRG is guarded on the advance side, the fuel in the combustion chamber 18 is not ignited too early. Therefore, it is possible to prevent knocking caused by the ignition of the fuel at an excessively early stage, and to prevent knocking noise caused by the knocking.

(4) Since the guard value ATRGMX at the time of advancing the target fuel injection timing ATRG is the same as the target fuel injection timing ATRG at the start of the stop of the diesel engine 11, the target fuel injection after the start of the stop is performed. Period A
TRG is not advanced. Therefore, it is possible to preferably prevent the occurrence of knocking based on the target fuel injection timing ATRG being excessively corrected to the advanced side at the start of stopping the diesel engine 11.

The present embodiment can be modified, for example, as follows. The guard value ATRGMX for advancing and guarding the target fuel injection timing ATRG may not be the same as the target fuel injection timing ATRG at the start of stopping the diesel engine 11, but may be determined in advance by experiments or the like. . In this case, for example, the target fuel injection timing ATRG advanced and guarded by the guard value ATRGMX is retarded from the target fuel injection timing ATRG that is advanced and corrected based on the intake pressure PM, and smoke is generated. It is preferable to set the value so that the occurrence can be suppressed. When such a guard value ATRGMX is employed, it is possible to prevent knocking due to excessive advance of the target fuel injection timing ATRG and to prevent generation of smoke due to excessive retardation of the target fuel injection timing ATRG.

The guard value QMX for guarding the upper limit of the fuel injection amount Q may not be the same as the fuel injection amount Q when the stop of the diesel engine 11 is started, but may be determined in advance by an experiment or the like. . In this case, for example, the guard value QMX is preferably set to the same value as the idle injection amount. When such a guard value QMX is adopted, for example, when the diesel engine 11 is stopped immediately after the engine 11 is stopped, the fuel injection amount Q increased based on the idle is set to the same value as the idle injection amount. The upper limit is guarded. That is, the diesel engine 11 as described above
In the operation state of the above, the fuel injection amount Q becomes equal to the idle injection amount, and it is possible to preferably prevent the excessive fuel injection into the combustion chamber 18 due to the excessive increase of the fuel injection amount Q.

At the start of stopping the diesel engine 11, it is not always necessary to control the intake throttle valve 55 to the closed side until it is fully closed. That is, when an actuator capable of adjusting the intake throttle valve 55 to an arbitrary opening degree is adopted, the actuator is set so that the intake throttle valve 55 has an opening degree near, for example, fully closed at the start of the stop of the diesel engine 11. Drive control may be performed.

When the guard values ATRGMX and QMX obtained by experiments and the like are employed as described above, the guard values ATRGMX and QMX do not necessarily have to be constant. For example, those guard values ATRGM
X and QMX may be variable based on the elapsed time from the start of stopping the diesel engine 11 and the operation (opening) of the intake throttle valve 55. In this case, the fuel injection amount Q and the target fuel injection timing A after the start of stopping the diesel engine 11
The TRG can be further optimized.

The fuel injection is stopped 0.2 seconds after the ignition switch 52 is stopped, but the time of 0.2 seconds may be appropriately changed. Even in this case, in order to stop the diesel engine 11 promptly, it is preferable that the time be within 1 second.

In the present embodiment, whether or not the diesel engine 11 has started to stop is determined based on whether or not the ignition switch 52 has been stopped, but the present invention is not limited to this. For example, when an emergency stop button or the like for forcibly stopping the diesel engine 11 at the time of failure or the like is employed, based on whether or not the emergency stop button has been operated in addition to the stop operation of the ignition switch 52 described above. It may be determined whether or not the engine 11 has started to stop. In this case, a signal from the emergency stop button is input to the ECU 92,
U92 determines whether the emergency stop button has been operated based on the signal.

In this embodiment, the diesel engine 1
1 as means for imparting engine rotation resistance to the intake throttle valve 55
When the engine 11 is stopped, the intake throttle valve 5
Although the engine rotation resistance was given by closing 5, the present invention is not limited to this. For example, the diesel engine 11
By controlling the exhaust throttle valve 46 to the closed side at the start of the stop of the operation, the engine 11 may be given an engine rotation resistance. Further, as a means for imparting the engine rotation resistance, a compressor of an air conditioner mounted on an automobile may be used. Such a compressor is connected to the crankshaft 14 of the diesel engine 11 via a clutch,
When the rotation of the crankshaft 14 is transmitted by connecting the clutch, the clutch is driven. Therefore, by engaging the clutch at the start of stopping the diesel engine 11, the compressor imparts engine rotation resistance to the engine 11. In these cases, the ECU 92 determines whether the diesel engine has been stopped and started
It controls the application of voltage to the electromagnetic solenoid of the VRV 48 and executes control of hydraulic pressure for driving the clutch.

Next, technical ideas other than the claims which can be grasped from the above embodiments will be described together with their effects. (1) Diesel equipped with an intake throttle valve that controls the amount of air taken into the combustion chamber to a reduced side at the start of stopping while supplying fuel into the combustion chamber at a fuel injection timing corrected based on the engine intake pressure. An engine stop device, comprising: an injection timing guard means for guarding the corrected fuel injection timing on the advance side when the diesel engine starts to stop.

According to this configuration, when the intake throttle valve is controlled to decrease the intake air amount at the start of stopping the diesel engine, the intake pressure decreases and the fuel injection timing is obtained as a value on the advance side. Since the fuel injection timing is guarded on the advance side, knocking based on excessive advance of the fuel injection timing can be prevented.

(2) In the diesel engine stopping device described in (1), the guard value of the fuel injection timing is the same as the fuel injection timing at the start of stopping the diesel engine. Engine stop device.

According to this configuration, after the start of the stop of the diesel engine, the fuel injection timing is not advanced even if the intake pressure is reduced by controlling the intake throttle valve to the intake air amount decreasing side. Knocking based on excessively advanced angle can be suitably prevented.

(3) In the diesel engine stopping device according to the above (1), the fuel injection is performed at a fuel injection timing corrected based on the intake pressure of the diesel engine. A diesel engine stopping device further comprising an injection timing control means for performing fuel injection at a timing delayed from the fuel injection timing to be performed.

According to the above configuration, the fuel injection timing at the start of stopping the diesel engine can be set to a value that can suppress the generation of smoke while retarding the fuel injection timing obtained based on the intake pressure. Become like Accordingly, it is possible to prevent the occurrence of smoke due to the fuel injection timing being too retarded, while preventing the knocking due to the excessive advance of the fuel injection timing.

[0090]

According to the first aspect of the present invention, when the engine rotational resistance is applied at the start of the stop of the diesel engine, the engine rotational resistance is determined based on the engine operating state such as the engine speed which is reduced by the application of the engine rotational resistance. Since the upper limit of the fuel injection amount is guarded, it is possible to prevent unnecessary fuel injection into the combustion chamber due to an excessive increase in the fuel injection amount.

According to the second aspect of the present invention, after the start of the stop of the diesel engine, the fuel injection amount does not increase even if the engine rotation resistance is applied and the engine speed suddenly decreases. Excessive fuel injection into the combustion chamber due to excessive increase in the fuel consumption can be suitably prevented.

According to the third aspect of the invention, for example, when the diesel engine is stopped immediately after the engine is idled, the fuel injection amount increased based on the idleness becomes equal to or less than the idle injection amount. Guarded like that. That is, the fuel injection amount after the start of the stop becomes equal to or less than the idle injection amount, and it is possible to preferably prevent the excessive fuel injection into the combustion chamber due to the excessive increase in the fuel injection amount.

According to the fourth aspect of the invention, when the intake throttle valve is controlled to decrease the intake air amount at the start of stopping the diesel engine, the intake pressure decreases, and the fuel injection timing is corrected to the advance angle. However, since the fuel injection timing is guarded on the advance side, knocking based on excessive advance of the fuel injection timing can be prevented.

According to the fifth aspect of the invention, after the stop of the diesel engine, the fuel injection timing is not advanced even if the intake pressure is reduced by controlling the intake throttle valve to the intake air amount decreasing side. In addition, it is possible to preferably prevent knocking based on excessive advance of the fuel injection timing.

According to the sixth aspect of the present invention, the fuel injection timing at the start of stopping the diesel engine is retarded from the fuel injection timing corrected based on the intake pressure, and the value capable of suppressing the generation of smoke. And you will be able to Accordingly, it is possible to prevent the occurrence of smoke due to the fuel injection timing being too retarded, while preventing the knocking due to the excessive advance of the fuel injection timing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an entire diesel engine to which an engine stop device of the present invention is applied.

FIG. 2 is a block diagram showing an electrical configuration of the stopping device.

FIG. 3 is a graph showing a change in a fuel injection amount Q with respect to a change in engine speed under a condition of an accelerator depression amount of “0”.

FIG. 4 is a flowchart showing a procedure for calculating a fuel injection amount.

FIG. 5 is a flowchart showing a procedure for calculating a fuel injection timing.

FIG. 6 is a map referred to when calculating an atmospheric pressure correction amount.

FIG. 7 is a time chart showing changes in various parameters when the diesel engine is stopped.

[Explanation of symbols]

11: diesel engine, 18: combustion chamber, 27: accelerator position sensor, 30a: pressure sensor, 41: fuel injection pump, 43: electromagnetic spill valve, 44: timer device, 45: rotation speed sensor, 46: exhaust throttle valve, 52: an ignition switch; 55: an intake throttle valve; 92: an electronic control unit (ECU).

Claims (6)

[Claims] 1. A diesel engine stopping device for injecting and supplying an amount of fuel determined based on an engine operating state into a combustion chamber and applying an engine rotation resistance at the start of a stop. A diesel engine stopping device comprising an injection amount guard means for guarding an upper limit of a fuel injection amount obtained based on an engine operating state. 2. The diesel engine stopping device according to claim 1, wherein the guard value of the fuel injection amount is equal to or less than the fuel injection amount at the start of stopping the diesel engine. 3. The diesel engine stopping device according to claim 1, wherein the guard value of the fuel injection amount is a value equal to or less than an idle injection amount. 4. The diesel engine stopping device according to claim 1, wherein the amount of air taken into the combustion chamber is controlled to a reduced side so as to provide engine rotation resistance at the start of stopping the diesel engine. An intake throttle valve, an injection timing control means for performing fuel injection at a fuel injection timing corrected based on the intake pressure of the engine, and when the diesel engine is started to stop, the obtained fuel injection timing is advanced with respect to the advance side. A diesel engine stopping device further comprising an injection timing guard means for guarding. 5. The diesel engine stopping device according to claim 4, wherein the guard value of the fuel injection timing is the same value as the fuel injection timing at the start of stopping the diesel engine. 6. A diesel engine stopping device according to claim 1, wherein the amount of air taken into said combustion chamber is controlled to a reduced side so as to impart engine rotation resistance at the start of stopping the diesel engine. Fuel injection is performed at an intake throttle valve and at a fuel injection timing corrected based on the intake pressure of the engine. At the start of stopping the diesel engine, fuel injection is performed at a timing delayed from the corrected fuel injection timing. And a fuel injection timing control means for performing the following.