JP3678095B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine, and more particularly to stop control for an internal combustion engine.
[0002]
[Prior art]
Various techniques to prevent exhaust gas and improve fuel efficiency include a technology that automatically stops the engine when the vehicle is stopped in an idle state with a signal and automatically restarts the vehicle when starting Proposed. In this case, if it takes time to restart the engine, a response is delayed with respect to the driver's intention to start, and drivability deteriorates. Therefore, it is important how quickly and smoothly the engine is restarted. Further, in a hybrid vehicle having an engine and a motor, even when the engine is started, it is important to start the engine promptly in order to reduce battery capacity or improve acceleration. Furthermore, it is important to start the engine promptly in order to improve drivability even if the engine is started by an ignition key.
[0003]
For example, Japanese Patent Laid-Open No. 11-107793 discloses an engine that improves the startability of the engine. The “stop position control device for an internal combustion engine” disclosed in this publication specifies the final combustion cylinder to be burned last according to the engine speed and the intake pipe pressure when the ignition switch is turned off. By controlling the fuel supply and ignition to stop the engine, the crankshaft is always stopped at the position where the intake stroke is at the top dead center position, and the exhaust gas characteristics at the time of starting the engine are improved without impairing the startability. It is something that can be done.
[0004]
[Problems to be solved by the invention]
However, the stop position of the crankshaft is greatly influenced by the in-cylinder pressure in addition to the fuel supply amount and the ignition timing. In this conventional "internal combustion engine stop position control device", when the in-cylinder pressure changes due to disturbance, There is a risk of not stopping at a desired position. If it is attempted to control the fuel supply and ignition with high precision in order to stop the crankshaft at a desired position, the cost increases due to an increase in matching man-hours and complicated control.
[0005]
The present invention solves such problems, and an object of the present invention is to provide a control device for an internal combustion engine that improves engine startability by stopping the engine at a desired crank angle.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the control apparatus for an internal combustion engine according to the first aspect of the present invention, when the engine stop condition determining means determines that the engine stop condition is satisfied, the intake pressure increasing means causes the crank angle when the engine is stopped. The intake pressure is increased so that the position is in the vicinity of 60 ° BTDC , and then the engine is stopped by the engine stop means. Therefore, by increasing the intake pressure before stopping the engine, the compression pressure of the engine increases, and the engine can be stopped at a desired crank angle. As a result, the engine startability is improved.
[0007]
Further, in the above control device of the internal combustion engine, the engine, and a stoichiometric air-fuel ratio injection mode and lean air-fuel ratio injection mode, the intake pressure increasing means may increase the intake pressure by selecting a lean air-fuel ratio injection mode I try to let them. Therefore, it is possible to easily increase the intake pressure before stopping the engine without separately adding a device for increasing the intake pressure.
[0008]
In addition to the lean air-fuel ratio injection mode, the intake pressure increasing means may be executed by retarding the ignition timing, or increasing the intake air amount by increasing the EGR amount or the throttle opening.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 shows a schematic configuration of an internal combustion engine control apparatus according to an embodiment of the present invention, FIG. 2 shows a flowchart of control by the internal combustion engine control apparatus of the present embodiment, and FIG. 3 shows engine stop position frequencies at different in-cylinder pressures. FIG. 4 shows a graph representing engine start characteristics at different crank angle positions.
[0011]
In the hybrid vehicle to which the control device for an internal combustion engine of the present embodiment is applied, as shown in FIG. 1, the mounted engine 11 is, for example, an in-cylinder injection type spark ignition gasoline engine, for each cylinder. A spark plug 12 and an injector 13 are attached, and an injection port of the injector 13 is opened in a combustion chamber 15 formed above the piston 14 so that fuel is directly injected into the combustion chamber 15. Further, 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 rotation speed. Further, an intake pipe 21 is connected to the intake port 16, and an air cleaner 22 is attached to the air intake port. An electronically controlled throttle valve 23 and a throttle position sensor 24 are attached to the intake pipe 21, and the throttle valve An air flow sensor 25 is attached to the upstream side. An exhaust pipe 26 is connected to the exhaust port 17.
[0012]
Although not shown, the engine 11 is provided with an EGR passage, and in a predetermined engine operating state, exhaust gas can be introduced into the intake system, and exhaust gas can be discharged by an EGR valve provided in the EGR passage. The amount of gas circulation can be adjusted.
[0013]
The crankshaft 27 of the engine 11 configured as described above can be connected to and disconnected from the output shaft 30 of the electric motor 29 via the transmission clutch 28. The transmission clutch 28 is an actuator 31 that is operated by a hydraulic drive device (not shown). It can be driven by. The electric motor 29 can be driven by receiving electric power from the battery 32 and can generate electric power by receiving driving force from the engine 11 to charge the battery 32 with electric power.
[0014]
The output shaft 30 of the electric motor 29 is connected to a CVT 33 as a continuously variable transmission. This CVT 33 hangs an endless steel belt between a pair of variable V-shaped pulleys (not shown), connects the rotating shaft of one variable V-shaped pulley to the output shaft 30 on the input side, and the other variable V-shaped pulley. The rotation shaft is connected to the output shaft 34 on the output side. By changing the pulley ratio by changing the width of each variable V-type pulley by supplying and discharging hydraulic pressure, the engine 11 and the electric motor 29 The transmitted rotational force can be adjusted steplessly and transmitted to the output shaft 34 via a pair of variable V-shaped pulleys and a steel belt. The output shaft 34 of the CVT 33 is connected to a differential gear 36 via a start clutch 35. The start clutch 35 can be driven by an actuator 36 that is operated by a hydraulic drive device (not shown). The amount of torque transmitted to the left and right drive wheels 38 can be adjusted.
[0015]
Further, the vehicle is provided with an electronic control unit (ECU) 39 that controls the engine 11, the electric motor 29, the CVT 33, and the like. The ECU 39 stores a storage device that stores an input / output device, a control program, a control map, and the like. A central processing unit, timers and counters are provided, and the ECU 39 performs comprehensive control of the in-cylinder injection engine 11. That is, in addition to the crank angle sensor 20, the throttle position sensor 24, and the airflow sensor 25 described above, detection information of various sensors such as an accelerator pedal position sensor 40 that the driver steps on, and a signal of the ignition key switch 42 are input to the ECU 39, The ECU 39 determines the fuel injection mode, fuel injection amount, ignition timing, etc. based on the detection information of various sensors, and drives the spark plug 12, the injector 18 driver, the drive motor for the throttle valve 23, the EGR valve opening degree, etc. Control.
[0016]
Further, the charging capacity of the battery 32 detected by a battery capacity sensor (not shown) is input to the ECU 39, and the electric motor 29 is controlled according to this battery charging capacity. Further, as described above, the CVT 33 has a hydraulic drive circuit for changing the width of the pair of variable V-shaped pulleys, and the ECU 39 controls the hydraulic drive circuit to change the pulley ratio to change the gear ratio. The setting is changed. The ECU 39 also controls the actuators 31 and 37 of the transmission clutch 28 and the starting clutch 35.
[0017]
By the way, the starting characteristic of the engine 11 is greatly influenced by the crank angle position at the time of engine start (at the time of the previous stop). The graph shown in FIG. 4 represents the starting characteristics at three different crank angle positions when an acceleration condition or the like is satisfied and the engine is started when the hybrid vehicle is running with the driving force of only the motor. . In this graph, a solid line indicates a case where the engine is started at a crank angle of 60 ° BTDC, a dotted line indicates a case where the engine is started at a crank angle of 90 ° BTDC, and a one-dot chain line indicates a case where the engine is started at a crank angle of 120 ° 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 and a crank angle of 120 ° BTDC as compared with a crank angle of 60 ° BTDC. Therefore, it can be seen that it is best to start the engine at a crank angle of 60 ° BTDC in terms of vehicle acceleration and quick start.
[0018]
On the other hand, if the compression pressure is high before the engine is stopped, the piston will receive a reaction force downward and stop before top dead center and stop before that. Affected. The graph shown in FIG. 3 represents the frequency of the stop position of the crankshaft with respect to three different intake pressures when the engine is stopped. FIG. 3A shows a case where 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 a case where the intake pressure (manifold pressure) is −200 mmHg, and the crankshaft frequently stops at a crank angle of 50 ° BTDC. This is because as the compression pressure decreases, the crank angle at which the inertial force of the piston or the like balances the compression pressure shifts to the TDC side, and the piston is shifted slightly to the TDC side from the above-described FIG. Is thought to stop. Further, FIG. 3C shows a case where the intake pressure (manifold pressure) is set to −400 mmHg, and the crankshaft is frequently stopped at a crank angle of 150 ° BTDC or more. This is because the piston stops after the inertial force of the piston overcomes the compression pressure and overcomes the TDC, and is considered not to be affected by the compression pressure. Therefore, it can be seen that when the intake pressure is about −200 mmHg or higher, the crankshaft frequently stops at a crank angle of about 60 ° BTDC.
[0019]
For this reason, in the control device for an internal combustion engine of the present embodiment, the ECU 39 determines whether or not the stop condition of the engine 11 is satisfied (engine stop condition determining means), and when the engine stop condition is satisfied, the intake air The pressure is increased (intake pressure increase means), and then the engine 11 is stopped (engine stop means). Here, the engine 11 has a stoichiometric air-fuel ratio injection mode in which fuel is injected in the vicinity of 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 mode.
[0020]
Here, the control of the ECU 39 in the control apparatus for an internal combustion engine of the present embodiment described above will be described in detail based on the flowchart of FIG.
[0021]
As shown in FIG. 2, it is determined in step S11 whether or not a stop condition of the engine 11 is satisfied. The engine 11 is stopped by manual stop by an ignition key switch OFF operation by the driver and idle stop. In the case of automatic stop, engine stop due to battery power or driving state in hybrid vehicle, in the case of automatic stop due to idle stop, preset stop conditions, for example, neutral position of shift lever, continuous vehicle speed 0 state for a certain period of time When the brake switch is turned on, the engine is stopped.
[0022]
When the stop condition of the engine 11 is established in step S11, the ECU 39 selects the lean air-fuel ratio injection mode of the engine 11 and operates in the compression lean state in step S12, so that the intake pressure is reduced. Increase to increase compression pressure. In step S13, when 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 a predetermined position can be obtained, and in step S14. The engine 11 is stopped.
[0023]
As described above, when the stop condition of the engine 11 is established, the lean air-fuel ratio injection mode is selected and the intake pressure is increased as the compression lean, and the engine 11 is stopped after a predetermined time has elapsed. When the compression pressure increases, the piston receives a reaction force in the downward direction and cannot overcome the top dead center, that is, the crankshaft is likely to stop before the crank angle of 60 ° BTDC. Therefore, when the next engine 11 is started, engine ignition and combustion start are accelerated, and as shown by a solid line in FIG. 4, the engine torque, the motor torque, the engine speed, etc. increase early, and the acceleration of the vehicle , Start-up speed is improved.
[0024]
In the above-described 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. In order to compensate for the output that decreases by retarding the timing, the intake amount is increased by increasing the throttle opening, the intake amount is increased by increasing the EGR amount, or only the throttle opening. May be increased to increase the intake pressure.
[0025]
However, if the engine output changes before and after the operation of the intake pressure increasing means when the engine is stopped, a shock may occur due to the output change when the engine is stopped and the drivability may be deteriorated. It is preferable to prevent the engine output from changing. Therefore, in the above-described embodiment, the engine output change is prevented by switching to the lean air-fuel ratio injection mode so that the same engine output is obtained. In the case of increasing the throttle opening, the engine output is made constant by retarding the ignition timing, and in the case of increasing the EGR amount, if the engine output is made constant by retarding the ignition timing, Deterioration of drivability when the engine is stopped can be prevented by keeping the engine output constant.
[0026]
【The invention's effect】
As described above in detail in the embodiment, according to the control apparatus for an internal combustion engine of the invention of claim 1, when it is determined that the engine stop condition is satisfied , the crank angle position at the time of engine stop is set to the vicinity of 60 ° BTDC. Since the intake pressure is increased as much as possible, and then the engine is stopped, the compression pressure is increased before the engine is stopped, so that the engine can be stopped at a desired crank angle, The start of combustion can be accelerated and the speed of starting the engine can be improved. As a result, the acceleration of the vehicle can be improved.
[0027]
Further, according to the above control device of the internal combustion engine, the engine has a theoretical air-fuel ratio injection mode and lean air-fuel ratio injection mode, since the increase the intake pressure by selecting a lean air-fuel ratio injection mode In addition, it is possible to easily increase the intake pressure before stopping the engine without adding a 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 frequency at different in-cylinder pressures.
FIG. 4 is a graph showing engine start 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 stop means)

Claims (1)

An engine stop condition determining means for determining whether or not the stop condition for the in-cylinder injection engine is satisfied, and if the engine stop condition determining means determines that the engine stop condition is satisfied , the crank angle position when the engine is stopped is set to 60 °. An intake pressure increasing means for increasing the intake pressure to be in the vicinity of BTDC; and an engine stop means for stopping the engine after the operation of the intake pressure increasing means. The engine injects fuel in the vicinity of the theoretical air-fuel ratio. An air-fuel ratio injection mode and a lean air-fuel ratio injection mode in which fuel is injected at a lean air-fuel ratio and operated in a compression lean state, and the intake pressure increasing means selects the lean air-fuel ratio injection mode to A control device for an internal combustion engine, characterized by increasing .

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