JP2001173473A - Control device for internal combustion engine - Google Patents

Abstract

(57) Abstract: In a control device for an internal combustion engine, the startability of the engine is improved by stopping the engine at a desired crank angle. SOLUTION: When a stop condition of an engine 11 is satisfied, a lean air-fuel ratio injection mode is selected to increase the intake pressure as a compression lean, and then the engine 11 is stopped after a predetermined time elapses. By stopping in the vicinity of the BTDC, the engine ignition and the start of combustion at the next start of the engine 11 are accelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control for stopping the internal combustion engine.

[0002]

2. Description of the Related Art As a method of reducing exhaust gas and improving fuel efficiency,
There have been proposed various techniques for automatically stopping an engine when a vehicle is stopped in an idle state at a traffic light and automatically restarting the vehicle when the vehicle starts to smoothly start the vehicle. In this case, if it takes a long time to restart the engine, the response to the driver's intention to start is delayed and drivability deteriorates. Therefore, it is important how the engine is restarted quickly and smoothly. Further, in a hybrid vehicle having an engine and a motor, even when starting the engine, it is important to start the engine promptly in order to lower the battery capacity and improve the acceleration. Further, even when the engine is started by an ignition key, it is important to start the engine promptly in order to improve drivability.

[0003] As an improvement in the startability of such an engine, for example, there is one disclosed in Japanese Patent Application Laid-Open No. H11-107793. The `` stop position control device for the internal combustion engine '' disclosed in this publication, when the ignition switch is turned off, to specify the last combustion cylinder to be burned last according to the engine speed and the intake pipe pressure, By stopping the engine by controlling fuel supply and ignition, the crankshaft is always stopped at the top dead center position of the intake stroke, thereby improving the exhaust gas characteristics at the time of starting the engine without impairing the startability. Is what you can do.

[0004]

However, the stop position of the crankshaft is greatly affected by the amount of fuel supplied, the ignition timing, and the cylinder pressure. When the internal pressure changes, the crankshaft may not stop at a desired position. And
If the fuel supply and the ignition are controlled with high precision in order to stop the crankshaft at a desired position, the cost is increased due to an increase in the number of matching steps and complicated control.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a control device for an internal combustion engine in which the engine is stopped at a desired crank angle to improve the engine startability. .

[0006]

In order to achieve the above object, in the control apparatus for an internal combustion engine according to the present invention, when the engine stop condition determining means determines that the engine stop condition is satisfied, the intake pressure is controlled. The intake pressure is increased by the increasing means, and then the engine is stopped by the engine stopping means. Therefore, by increasing the intake pressure before the engine is stopped, the compression pressure of the engine is increased, and the engine can be stopped at a desired crank angle. As a result, the engine startability is improved.

In the control device for an internal combustion engine according to a second aspect of the present invention, the engine has a stoichiometric air-fuel ratio injection mode and a lean air-fuel ratio injection mode, and the intake pressure increasing means selects the lean air-fuel ratio injection mode. By doing so, the intake pressure is increased. Therefore, it is possible to easily increase the intake pressure before the engine is stopped without separately adding a device for increasing the intake pressure.

The intake pressure increasing means is executed by increasing the intake air amount by retarding the ignition timing, increasing the EGR amount or increasing the throttle opening in addition to the lean air-fuel ratio injection mode. Is also good.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration of a control apparatus for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a flowchart of control by the control apparatus for an internal combustion engine according to the present embodiment, and FIG. FIG. 4 is a graph showing the position frequency, and FIG. 4 is a graph showing the engine starting characteristics at different crank angle positions.

In a hybrid vehicle to which the control apparatus for an internal combustion engine of the present embodiment is applied, as shown in FIG. 1, an engine 11 mounted is, for example, a direct injection spark ignition gasoline engine, Spark plug 1 for each cylinder
2 and an injector 13 are mounted, and the injector 13 is provided in a combustion chamber 15 formed above a piston 14.
Are opened so that the fuel is directly injected into the combustion chamber 15. An intake port 16 and an exhaust port 17 facing the combustion chamber 15 are formed in the cylinder head. The intake port 16 is opened and closed by an intake valve 18, and the exhaust port 17 is opened and closed by an exhaust valve 19. The engine 11 is provided with a crank angle sensor 20 that outputs a crank angle signal at a predetermined crank position of each cylinder. The crank angle sensor 20 can detect the engine speed. Further, an intake pipe 21 is provided in the intake port 16.
An electronically controlled throttle valve 23 and a throttle position sensor 24 are mounted on the intake pipe 21. An air flow sensor 25 is mounted on the upstream side of the throttle valve 23. Have been. Exhaust pipe 2 is connected to exhaust port 17
6 are connected.

Although not shown, the engine 11 has an E
A GR passage is provided, and in a predetermined engine operating state, exhaust gas can be introduced into the intake system, and an exhaust gas circulation amount can be adjusted by an EGR valve provided in the EGR passage. .

The crankshaft 27 of the engine 11 thus configured is connected to an electric motor 29 via a transmission clutch 28.
The transmission clutch 28 can be driven by an actuator 31 operated by a hydraulic drive device (not shown). The electric motor 29 is drivable by receiving power supply from the battery 32, and is capable of charging the battery 32 by generating power by receiving driving force from the engine 11.

The output shaft 30 of the electric motor 29 is connected to a CVT 33 as a continuously variable transmission. This CVT
33, an endless steel belt is wound around a pair of variable V-shaped pulleys (not shown), the rotation shaft of one variable V-type pulley is connected to the output shaft 30 on the input side, and the other
The rotary shaft of the pulley is connected to an output shaft 34 on the output side. The width of each variable V-type pulley is changed by supply and discharge of hydraulic pressure to change the pulley ratio, so that the engine 11 and the electric motor The rotational force transmitted from the output shaft 29 can be transmitted to the output shaft 34 by adjusting the torque continuously through a pair of variable V-shaped pulleys and a steel belt. And CVT33
The output shaft 34 is connected to a differential gear 36 via a starting clutch 35.
Is an actuator 3 operated by a hydraulic drive (not shown)
6 enables the amount of torque transmitted from the output shaft 34 to the left and right drive wheels 38 to be adjusted.

The vehicle includes an electronic control unit (E) for controlling the engine 11, the electric motor 29, the CVT 33, and the like.
The ECU 39 includes an input / output device, a storage device for storing a control program, a control map, and the like, a central processing unit, and a timer and a counter. Eleven comprehensive controls are performed. That is, in addition to the crank angle sensor 20, the throttle position sensor 24, and the air flow sensor 25, detection information of various sensors such as an accelerator pedal position sensor 40 depressed by a driver, and a signal of an ignition key switch 42 are provided by the ECU 3.
9, the ECU 39 determines the fuel injection mode, the fuel injection amount, the ignition timing, etc. based on the detection information of the various sensors, and the ignition plug 12, the driver of the injector 18, the drive motor of the throttle valve 23, the EGR valve Drive control of opening and the like.

A charging capacity of the battery 32 detected by a battery capacity sensor (not shown) is input to the ECU 39, and the electric motor 2 is controlled according to the charging capacity of the battery 32.
9 is controlled. Further, as described above, the CVT 33 has a hydraulic drive circuit for changing the width of the pair of variable V-type pulleys, and the ECU 39 controls the hydraulic drive circuit to change the pulley ratio and change the gear ratio. To change the settings. The control of the actuators 31 and 37 of the transmission clutch 28 and the starting clutch 35 is also performed by the ECU.
39 is to do.

The starting characteristics of the engine 11 are greatly affected by the crank angle position at the time of starting the engine (at the time of the previous stop). The graph shown in FIG. 4 shows the starting characteristics at three different crank angle positions when the engine is started under acceleration conditions and the like when the hybrid vehicle is running using only the driving force of the motor. . In this graph, when the engine is started at a crank angle of 60 ° BTDC, the solid line is
When the engine is started at the crank angle of 12
This is the case where the engine is started at 0 ° BTDC. As can be seen from this graph, in particular, the engine torque, the motor torque, and the engine speed are delayed by a predetermined time at a crank angle of 90 ° BTDC or at a crank angle of 120 ° BTDC compared to a crank angle of 60 ° BTDC. Therefore, it can be understood that it is best to start the engine at a crank angle of 60 ° BTDC in terms of the acceleration and the quickness of starting of the vehicle.

On the other hand, if the compression pressure is high before the engine stops, the piston receives a downward reaction force and cannot stop over the top dead center and stops immediately before the top dead center. Significantly affected by pressure. The graph shown in FIG. 3 shows the frequency of the stop position of the crankshaft for three different intake pressures when the engine stops.
FIG. 3A shows a case in which the throttle is fully opened and the intake pressure (manifold pressure) is 0 mmHg (atmospheric pressure), and the crankshaft frequently stops at a crank angle of 60 ° BTDC. FIG. 3B shows that the intake pressure (manifold pressure) is -200.
mmHg, and the crankshaft has a crank angle of 50 °
Stops frequently at BTDC. This is because the crank angle at which the inertial force of the piston or the like and the compression pressure balance with the compression pressure shifts to the TDC side as the compression pressure decreases.
It is considered that the piston stops at a position slightly shifted to the TDC side from (a). Further, FIG. 3C shows a case where the intake pressure (manifold pressure) is -400 mmHg, and the crankshaft frequently stops at a crank angle of 150 ° BTDC or more. This is because the piston stops after the inertial force of the piston or the like overcomes the compression pressure and passes over the TDC, and it is considered that the piston is not affected by the compression pressure. Therefore, it can be seen that when the intake pressure is about -200 mmHg or more, the frequency at which the crankshaft stops near the crank angle of 60 ° BTDC is high.

Accordingly, in the control apparatus for an internal combustion engine according to the present embodiment, the ECU 39 determines whether or not a stop condition of the engine 11 is satisfied (engine stop condition determining means). When the condition is satisfied, the intake pressure is increased (intake pressure increasing means).
(Engine stop means). Here, since the engine 11 has a stoichiometric air-fuel ratio injection mode in which fuel is injected near the stoichiometric air-fuel ratio and a lean air-fuel ratio injection mode in which fuel is injected at a lean air-fuel ratio,
The intake pressure is increased by selecting the lean air-fuel ratio injection mode.

Here, the control of the ECU 39 in the control device for an internal combustion engine according to the above-described embodiment will be described in detail with reference to the flowchart of FIG.

As shown in FIG. 2, in step S11,
It is determined whether or not the stop condition of the engine 11 is satisfied. The stop of the engine 11 includes a manual stop by an operation of turning off an ignition key switch by a driver, an automatic stop by an idle stop, a battery power and a driving state in a hybrid vehicle. In the case of an automatic stop by an idle stop, a preset stop condition, for example, a neutral position of the shift lever, a vehicle speed of 0
The stop condition of the engine is, for example, the continuation of the state for a fixed time, the turning on of a brake switch, and the like.

If such a condition for stopping the engine 11 is satisfied in step S11, the process proceeds to step S11.
At 12, the ECU 39 selects the lean air-fuel ratio injection mode of the engine 11 and operates at the compression lean, thereby increasing the intake pressure and increasing the compression pressure. And step S
At 13, after a predetermined time has elapsed from the increase of the intake pressure, it is determined that the compression pressure has increased until a reaction force capable of stopping the piston at the predetermined position can be obtained, and the engine 11 is started at step S 14. Stop.

When the condition for stopping the engine 11 is satisfied, the lean air-fuel ratio injection mode is selected and the intake air pressure is increased as a compression lean state.
By stopping the engine 1, the compression pressure of the engine 11 is increased before the engine stops, and the piston receives a downward reaction force so that the piston cannot cross the top dead center. The probability of stopping near 60 ° BTDC increases.
Therefore, at the next start of the engine 11, the engine ignition and the start of combustion are advanced, and as shown by the solid line in FIG.
The engine torque, the motor torque, the engine speed, and the like increase early, and the acceleration and the quick start of the vehicle are improved.

In the above embodiment, the intake pressure is increased by operating the engine 11 in the lean air-fuel ratio injection mode as the intake pressure increasing means. However, the present invention is not limited to this method. For example, the intake air amount may be increased by increasing the throttle opening to compensate for the output that is reduced by retarding the ignition timing,
The intake amount may be increased by increasing the GR amount, or the intake pressure may be increased by simply increasing only the throttle opening.

However, if the engine output changes before and after the operation of the intake pressure increasing means when the engine is stopped, a shock accompanying the output change may occur at the time of engine stop and the drivability may be deteriorated. It is preferable that the engine output does not change before and after the operation of. Therefore, in the above-described embodiment, a change in the engine output is prevented by switching to the lean air-fuel ratio injection mode so that the same engine output is obtained. Also,
In the case of increasing the throttle opening, the engine output is kept constant by retarding the ignition timing.
In the case where the R amount is increased, if the engine output is made constant by retarding the ignition timing, it is possible to prevent the deterioration of drivability when the engine is stopped by keeping the engine output constant.

[0026]

As described above, according to the control apparatus for an internal combustion engine according to the first aspect of the present invention,
When it is determined that the engine stop condition is satisfied, the intake pressure is increased, and then the engine is stopped.
By increasing the compression pressure before stopping the engine, the engine can be stopped at a desired crank angle, ignition and combustion start at the time of starting the engine can be accelerated, and the speed of starting the engine can be improved. As a result, the acceleration of the vehicle can be improved.

According to the control apparatus for an internal combustion engine of the second aspect of the present invention, the engine has a stoichiometric air-fuel ratio injection mode and a lean air-fuel ratio injection mode, and the intake pressure is selected by selecting the lean air-fuel ratio injection mode. So that
The intake pressure can be easily increased before the engine is stopped without adding a separate device for increasing the intake pressure.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a flowchart of control by the control device for an internal combustion engine of the present embodiment.

FIG. 3 is a graph showing engine stop position frequencies at different in-cylinder pressures.

FIG. 4 is a graph showing engine starting characteristics at different in-cylinder pressures.

[Explanation of symbols]

11 engine 27 crankshaft 29 electric motor 33 CVT 39 electronic control unit, ECU (engine stop condition determining means, intake pressure increasing means, engine stopping means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02P 5/15 F02P 5/15 E (72) Inventor Nobuaki Murakami 5-33-8 Shiba 5-chome, Minato-ku, Tokyo Mitsubishi Motors Corporation F term (reference) 3G022 AA06 AA10 CA10 DA02 EA06 GA01 GA05 GA06 GA08 GA19 GA20 3G092 AA01 AA06 AA09 AA17 AC02 AC03 BA02 BA05 BA06 CA01 DC01 DC09 DG05 EA01 EA04 EA06 EA07 GA05 HA06Z HE01Z HE03Z HF08Z HF21Z HF26Z 3G093 AA06 AA07 AA16 BA00 BA22 CA00 CA02 CB06 DA01 DA06 DA07 DA09 DB05 DB15 EA09 EA13 EB08 EC04 3G301 HA00 HA01 HA04 HA13 JA00 KA04 KA12 KA28 LA01 PE01Z01 PA01 NE03Z

Claims (2)

[Claims] An engine stop condition determining means for determining whether an engine stop condition is satisfied, and an intake pressure increase for increasing the intake pressure when the engine stop condition determining means determines that the engine stop condition is satisfied. And an engine stopping means for stopping the engine after the intake pressure increasing means is operated. 2. A control device for an internal combustion engine according to claim 1, wherein said engine is a stoichiometric air-fuel ratio injection mode in which fuel is injected near a stoichiometric air-fuel ratio, and a lean air-fuel ratio injection mode in which fuel is injected at a lean air-fuel ratio. Wherein the intake pressure increasing means increases the intake pressure by selecting the lean air-fuel ratio injection mode.