JP3577979B2 - Stop control device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stop control device for an internal combustion engine, and particularly to a stop control device for an internal combustion engine suitable for use in an internal combustion engine that starts / stops separately from a start / stop operation of a driver, such as a hybrid electric vehicle or an automatic idle stop vehicle. It relates to a control device.
[0002]
[Prior art]
A vehicle that stops the engine (internal combustion engine) separately from the driver's stop operation, for example, a hybrid electric vehicle (hybrid vehicle) driven by the engine and an electric motor, or an automatic vehicle that automatically stops the engine when the vehicle is stopped and idling The problem with idle stop vehicles is to reduce the shock associated with stopping the engine.
In other words, in these vehicles, the engine is stopped regardless of the driver's intention, so that the shock accompanying the engine stop is unexpectedly transmitted to the driver. For this reason, the driver may feel strongly uncomfortable.
[0003]
Accordingly, the present applicant has increased the engine rotation speed, reduced the amount of intake air, and increased the magnitude of the negative pressure in the intake pipe, and then stopped the engine, thereby reducing the work from the compression stroke to the expansion stroke of the engine. A patent application has been filed for a technique for reducing the change to reduce the shock when the engine is stopped (Japanese Patent Application No. 11-42875).
[0004]
[Problems to be solved by the invention]
However, in the above-described technology (Japanese Patent Application No. 11-42875), a difference occurs in the magnitude of the intake pressure in the intake pipe depending on the elapsed time from the stop of the engine. That is, as shown in FIG. 4, when the engine is stopped, the negative pressure of the intake air is increased by increasing the engine speed immediately before the stop and reducing the amount of intake air. Eventually, the negative pressure of the intake gradually decreases and eventually recovers to the atmospheric pressure.
[0005]
Such a difference in the intake pressure due to the elapsed time makes it difficult to manage the air-fuel ratio when the engine is restarted. That is, when the engine is restarted at the time point B shown in FIG. 4, the intake pressure has already recovered to the atmospheric pressure as shown by the thick solid line, but when the engine is restarted at the time point A, the intake pressure has not yet been restored as shown by the thin solid line. The negative pressure is large, and the intake air amount in the intake pipe at the time point A is smaller than the intake air amount at the time point B. For this reason, when the same amount of fuel is injected at the time point A as at the time point B, the air-fuel ratio drops significantly from the target value. In FIG. 4, a portion where the characteristic line overlaps between the restart at the time point A and the restart at the time point B is indicated by a thin solid line before the start and by a thick solid line after the start.
[0006]
As described above, in a vehicle in which the engine is started / stopped separately from the driver's stop operation, the possibility of restarting immediately after the engine is stopped is lower than in a vehicle in which the engine is started / stopped by the driver's operation. The problem that the air-fuel ratio fluctuates depending on the time from engine stop to restart cannot be ignored.
[0007]
As described above, the above-described technology (Japanese Patent Application No. 11-42875) can reduce the shock when the engine is stopped, but cannot manage the air-fuel ratio due to the time change of the intake pressure after the engine is stopped. Therefore, there is a problem that the startability of the engine is deteriorated.
[0008]
The present invention has been made in view of such a problem, and provides a stop control device for an internal combustion engine that reduces shock at the time of engine stop and prevents deterioration of startability at restart. The purpose is to:
[0009]
[Means for Solving the Problems]
To achieve the above object, in the stop control equipment of an internal combustion engine of the present invention, it includes a the judging means and the stop means intake pressure control means, apart from stop condition is satisfied and the operation of a driver by judging means Is determined, the intake pressure of the internal combustion engine is reduced by the intake pressure control means prior to the stop of the internal combustion engine by the stop means, and the intake pressure is increased again by the intake pressure control means after the stop of the internal combustion engine by the stop means. .
As a result, the vibration at the time of stopping the internal combustion engine is suppressed, and the variation in the intake air amount at the time of restart is reduced, so that the startability is improved.
[0010]
Further, the reduction control of the intake pressure is performed by reduction the amount of intake air with increasing the rotational speed of the internal combustion engine, the increase control of the intake pressure intends line by extending the amount of intake air.
This makes it possible to further advance the timing at which the intake pressure becomes constant after the internal combustion engine is stopped.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIGS. 1 to 3 show an internal combustion engine stop control device according to an embodiment of the present invention. Here, a case where the internal combustion engine stop control device of the present invention is applied to a parallel type hybrid vehicle is shown. I have.
[0012]
FIG. 1 shows a drive system of a hybrid vehicle to which the present invention is applied. As shown in FIG. 1, the drive system of the hybrid vehicle is configured by combining an engine (internal combustion engine) 1, an electric motor 2, and a transmission 3, and a clutch 4 is provided between the engine 1 and the electric motor 2. Is provided. The clutch 4 connects and disconnects between the output shaft 1a of the engine 1 and the output shaft 2a of the electric motor 2. When the clutch 4 is connected, rotation of the engine 1 causes the output shaft of the electric motor 2 via the clutch 4 to rotate. The transmission is transmitted to the transmission 3 from the output shaft 2 a of the electric motor 2. Then, the Oite appropriately shift the transmission 3 is transmitted to the drive wheels 5 via a differential in the transmission 3.
[0013]
The ECU 20 controls the operation of the engine 1 and the electric motor 2 and the connection and disconnection of the clutch 4 in the hybrid vehicle. The ECU 20 selects an appropriate traveling mode based on the traveling state of the vehicle, and controls the engine 1, the electric motor 2, and the clutch 4 according to the selected traveling mode.
For example, when a large output is required, such as during acceleration, a mode in which the vehicle travels using only the engine 1 or a combination of the engine 1 and the electric motor 2 is selected. Then, the clutch 1 is connected, the engine 1 is started using the electric motor 2 as a starter, and the output of the engine 1 is input to the transmission 3. When the engine is started in a stopped state, the starting clutch (not shown) of the transmission 3 is disengaged. On the other hand, when the load is low, such as during steady running, a mode in which the vehicle runs by the electric motor 2 is selected. In this case, the engine 1 is stopped, the clutch 4 is released so that the engine 1 does not become a load on the electric motor 2, and only the electric motor 2 is operated.
[0014]
As described above, in the present hybrid vehicle, the start / stop of the engine 1 and the electric motor 2 is frequently performed according to the running state. The start / stop control is automatically performed by the ECU 20 regardless of the driver's intention. At this time, if vibration occurs due to the stop of the engine 1 or the startability at the time of restart becomes unstable, the driver I feel uncomfortable. Therefore, in the ECU 20, a special stop control is performed by the stop control device 21 in order to prevent such vibration at the time of stop and deterioration of the startability at the time of restart.
[0015]
The stop control device 21 includes a determination unit 22, a stop unit 23, and an intake pressure control unit 24. First, the determination means 22 is a means for determining whether or not a stop condition of the engine 1 is satisfied separately from a stop operation of the driver (for example, an operation of turning off an ignition key). The establishment of the stop condition corresponds to a traveling mode selected according to the traveling state, and it is determined that the stop condition is established when the ECU 20 issues a command to stop the engine 1.
[0016]
The stop unit 23 is a unit that stops the engine 1 when the determination unit 22 determines that the stop condition is satisfied. Here, the engine 1 is stopped by closing the throttle valve 11 and stopping the fuel supply to the injector 10 to gradually reduce the rotation speed of the engine 1. In addition to stopping the fuel supply, it is also possible to stop the engine 1 by stopping the ignition of the spark plug.
[0017]
The intake pressure control means 24 is means for controlling the intake pressure in the intake pipe of the engine 1. The intake pressure control means 24 controls the intake pressure by controlling the opening of the throttle valve 11. If the determination means 22 determines that the stop condition is satisfied, the stop means 23 stops the engine 1. The intake pressure is decreased before the engine 1 is stopped, and the intake pressure is increased again after the engine 1 is stopped.
[0018]
More specifically, when the stop condition is satisfied in the determination unit 22, the intake pressure control unit 24 first increases the intake air amount by opening the throttle valve 11 , increases the rotation speed of the engine 1, and increases the suction capacity. It has become. Then, after the rotation speed has increased to a predetermined value, the throttle valve 11 is operated in the closing direction to narrow the intake air amount. As a result, the amount of intake air during one cycle is reduced, and the intake pressure is reduced.
[0019]
Thereafter, when the engine 1 is stopped by a stop operation of the stop means 23, the intake pressure control means 24 opens the throttle valve 11 to a predetermined opening. As a result, air at atmospheric pressure is introduced into the intake pipe, and the intake pressure increases. The engine 1 is stopped when the engine speed Ne is calculated based on a signal from the crank angle sensor 12 and the engine 1 is judged to have stopped when the calculated engine speed Ne becomes equal to or lower than a sufficiently low predetermined speed No. It has become.
[0020]
The stop control device for an internal combustion engine as one embodiment of the present invention is configured as described above. When the engine 1 is stopped separately from the operation of the driver and restarted, the following operation is performed. To control the engine 1 to stop. Hereinafter, the stop control of the engine 1 by the present stop control device will be specifically described with reference to FIGS. FIG. 2 is a time chart showing the state of the stop control, and FIG. 3 is a flowchart of the stop control.
[0021]
First, in the stop control device 21, the determination unit 22 determines whether the stop condition of the engine 1 is satisfied separately from the driver's stop operation (step S100). If the stop condition is satisfied, the intake pressure control unit 24 opens the throttle valve 11 to increase the amount of intake air, thereby increasing the rotation speed of the engine 1 (step S110). Then, when the rotation speed has increased to the predetermined rotation speed, the throttle valve 11 is operated in the closing direction to narrow the intake air amount (step S120). As a result, the intake air amount during one cycle is reduced, and the intake pressure is reduced (that is, the negative pressure is increased).
[0022]
Thereafter, when a predetermined time has elapsed since the rotation speed of the engine 1 was increased to the predetermined rotation speed (time point X in FIG. 2), the fuel supply is stopped, and the throttle valve 11 is fully closed to stop the engine 1 ( Step S130). At this time, since the intake pressure is largely negative, the work change in the compression stroke and the expansion stroke of the engine 1 is reduced, and the vibration of the engine 1 caused by the rotation fluctuation is suppressed.
[0023]
Next, the stop control device 21 determines whether or not the engine 1 has stopped, that is, whether or not the engine rotational speed Ne has become equal to or lower than the sufficiently low predetermined rotational speed No (step S140). When this happens (Y point in FIG. 2), the intake pressure control means 24 opens the throttle valve 11 to a predetermined opening for a predetermined time (step S150). This opening operation is performed only for a predetermined time Th, which is a minimum necessary for the air at the atmospheric pressure to be introduced into the intake pipe and the intake pressure to be restored to the atmospheric pressure.
By recovering the intake pressure to the atmospheric pressure immediately after the engine 1 is stopped in this way, even when the engine 1 is restarted immediately after the stop, the engine 1 can be started at the atmospheric pressure. The variation in the amount is reduced (at time Z in FIG. 2).
[0024]
As described above, according to the internal combustion engine stop control device, when the stop condition of the engine 1 is satisfied and the engine 1 is stopped separately from the stop operation of the driver, the negative pressure of the intake air is increased by the intake pressure control means 24. After the engine 1 is stopped, the engine 1 is stopped by the stopping means 23, so that the work change in the compression stroke and the expansion stroke of the engine 1 is reduced, and the vibration of the engine 1 at the time of stop caused by the rotation fluctuation is suppressed. be able to. As a result, vibration when the engine 1 is stopped separately from the operation of the driver can be reduced, and there is no possibility that the driver will feel uncomfortable.
[0025]
Further, immediately after the stopping of the engine 1 by the stopping means 23, the negative pressure of the intake air is reduced by the intake pressure control means 24. Similarly, the intake air in the cylinder becomes the atmospheric pressure, and the variation in the intake air amount in the cylinder at the time of fuel injection is reduced. As a result, the air-fuel ratio at the time of starting can always be kept at a substantially constant value, and starting stability at the time of restarting is ensured.
[0026]
As described above, the stop control device for the internal combustion engine as one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and may be variously modified without departing from the gist of the present invention. be able to.
For example, in the above-described embodiment, the throttle valve 11 is closed after the rotation speed of the engine 1 is increased. However, the engine 1 bypasses the throttle valve 11 or the EGR which recirculates exhaust gas to the intake system. When a secondary air supply valve such as a valve is provided, if these valves are closed in accordance with the closing operation of the throttle valve, the amount of intake air per cycle can be further reduced, and the engine 1 is stopped. The vibration at the time can be further reduced.
[0027]
Similarly, when the throttle valve 11 is opened after the engine 1 is stopped, the secondary air supply valve, such as a bypass valve or an EGR valve, can be opened in response to the opening operation of the throttle valve 11 to further speed up the operation. The intake pressure in the cylinder can be raised to the atmospheric pressure, and even if the engine is restarted immediately after stopping, it is possible to keep the intake air amount in the cylinder constant to ensure starting stability. .
[0028]
Further, in the above-described embodiment, an example is described in which the present invention is applied to a parallel type hybrid vehicle that uses both the output of the engine 1 and the output of the electric motor 2. Vehicles that start / stop the engine separately from the driver's operation, such as a series-type hybrid car that generates electric power that is used as the power source for the electric motor by the engine, or an automatic idle stop car that detects the stop state and stops the engine. If so, it is of course possible to apply the present invention to engine stop control.
[0029]
【The invention's effect】
As described in detail above, according to the internal combustion engine stop control device of the present invention, when the internal combustion engine stop condition is satisfied separately from the driver's stop operation, the intake pressure of the internal combustion engine is reduced prior to the stop of the internal combustion engine. After stopping the internal combustion engine, the intake pressure is increased again, so that the vibration at the time of stopping the internal combustion engine is suppressed so that the driver does not feel uncomfortable, and the variation in the amount of intake air at the time of restarting. Therefore, there is an advantage that the startability can be improved by reducing the pressure.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a hybrid vehicle to which an internal combustion engine stop control device as one embodiment of the present invention is applied.
FIG. 2 is a time chart showing a stop control situation according to the stop control device for the internal combustion engine as one embodiment of the present invention.
FIG. 3 is a flowchart showing a flow of stop control according to the internal combustion engine stop control device as one embodiment of the present invention.
FIG. 4 is a time chart for explaining a problem in the prior art.
[Explanation of symbols]
1 engine (internal combustion engine)
2 Electric motor 3 Transmission 4 Clutch 11 Throttle valve 12 Crank angle sensor 20 ECU
21 Stop control device 22 Judgment means 23 Stop means 24 Intake pressure control means

Claims (1)

Determining means for determining whether or not a stop condition of the internal combustion engine is satisfied separately from a driver's stop operation;
Stopping means for stopping the internal combustion engine when the determination means determines that the stop condition is satisfied;
When the determining means determines that the stop condition has been satisfied, the intake pressure of the internal combustion engine is reduced prior to the stop of the internal combustion engine, and the intake pressure is increased after the internal combustion engine is stopped. Well ,
The intake pressure decrease control is performed by increasing the rotational speed of the internal combustion engine and decreasing the intake air amount, and the intake pressure increase control is performed by increasing the intake air amount. , An internal combustion engine stop control device.

Images