JP3702862B2 - Control method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control method for an internal combustion engine in which the opening / closing timing and lift amount of an intake / exhaust valve of an engine are controlled by an engine operating state, and in particular, a control method for assisting braking force using an engine brake. It is about.
[0002]
[Prior art]
Conventionally, when a vehicle is decelerated, a braking force by a brake device and a braking assist force by an engine brake have been used. When the brake pedal is operated, the engine brake is released from the accelerator pedal. Therefore, the throttle valve that controls the amount of air taken into the engine closes and the combustion chamber becomes negative pressure, causing pump loss. Due to However, in recent years, a non-throttle engine having no throttle valve has been considered as a system for reducing engine loss in order to improve fuel efficiency.
[0003]
[Problems to be solved by the invention]
In a non-throttle engine, there is a problem that the engine brake becomes weak because the combustion chamber does not have a negative pressure and pump loss hardly occurs.
[0004]
In view of the above circumstances, the present invention effectively generates a pump loss by using a variable valve mechanism that can arbitrarily control the opening / closing timing of the intake valve and the exhaust valve and the lift amount thereof, and assists the braking force during vehicle deceleration. It is an object of the present invention to provide a control method for an internal combustion engine capable of performing the above.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a valve mechanism including an intake valve and an exhaust valve combined with a cylinder of the internal combustion engine, a valve mechanism control means for controlling the valve mechanism, and an operation state detection for detecting the operation state of the internal combustion engine And a brake pedal force detection means for detecting a brake pedal force, and a control method for an internal combustion engine mounted on a vehicle provided with an anti-lock brake system for preventing a side slip of the vehicle during sudden braking. When the operation of the antilock brake system is detected, either the intake valve or the exhaust valve is closed, and the piston that is not closing the intake valve or the exhaust valve is lowered from the top dead center. Provided is a control method for an internal combustion engine, characterized in that the valve is opened once per rotation, that is, once per rotation, and the lift amount is controlled to a predetermined value.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0007]
An internal combustion engine (hereinafter referred to as an engine) 1 shown in FIG. 1 includes a crank mechanism including a connecting rod 4 and a crankshaft 5, and a combustion chamber 3 is formed by a piston 2 connected to the crank mechanism and an engine head 8 of the engine 1. ing. The combustion chamber 3 is sealed by an intake valve 10, an exhaust valve 11, a spark plug 12, and a fuel injection valve 13 mounted on the engine head 8. The intake valve 10 and the exhaust valve 11 are operated by variable valve mechanisms 30 and 40. The variable valve mechanisms 30 and 40, for example, attract the mover fixed to the valve by electromagnetic force generated when an electric current is passed through the coil, act on the upper and lower coils and the spring, and repeat the operation. A valve mechanism configured to perform the opening / closing operation is desirable. The engine 1 sucks air necessary for combustion into the combustion chamber 3 by the reciprocating motion of the piston 2. In the air taken into the engine 1, dust contained in the air is removed by the air cleaner 14, and the intake air amount that is a basis for calculating the fuel injection amount is measured by the air amount sensor 15. The control unit 50 that controls the engine 1 controls the operation of the operating state detection means 51 that detects the operating state of the engine 1 based on signals from various sensors, and the variable valve mechanisms 30 and 40 that are mounted on the engine 1. A variable valve control means 54 that controls the fuel amount injected from the fuel injection valve 13 and a fuel injection control means 53 that controls the injection timing, and an ignition control means 52 that controls the ignition timing at the spark plug 12. Further, a control signal from the variable valve control means 54 is sent to the variable valve drive circuit 57, and the operations of the intake and exhaust valves 10 and 11 are controlled by operating the variable valve mechanisms 30 and 40. When the intake / exhaust valves 10 and 11 are closed, current is supplied to the coils 30a and 40a to attract the mover. When the intake / exhaust valves 10 and 11 are opened, current is supplied to the coils 30b and 40b to attract the mover. A control signal from the fuel injection control means 53 is sent to the fuel injection valve drive circuit 56 to control the fuel injection valve 13. A control signal from the ignition control means 52 is sent to the ignition coil 55 and an ignition operation is performed by the spark plug 12.
[0008]
The operation amount of the brake pedal 61 operated by the driver 60 of the vehicle on which the engine 1 is mounted is converted into an electric signal by the brake depression force detecting means 62 and input to the driving state detecting means 51 in the control unit 50. Other signals that are input to the operating state detection means 51 include, for example, rotation signals from the crank angle sensors 6 and 7 mounted on the crankshaft 5, the intake air amount from the air amount sensor 15 described above, and mounting in the exhaust pipe. The air-fuel ratio from the air-fuel ratio sensor 21, the catalyst temperature from the temperature sensor 23 that detects the temperature of the exhaust catalyst 22, the pressure in the combustion chamber 3 from the pressure sensor 18 attached to the combustion chamber 3, There is a knocking signal. The variable valve control means 54 outputs a control signal to the variable valve mechanisms 30 a and 30 b that operate the intake valve 10 based on the signal from the operating state detection means 51, and adjusts the amount of air taken into the engine 1. The fuel injection control means 53 outputs a control signal to the fuel injection valve 13 based on the signal from the operating state detection means 51, and adjusts the fuel injection amount and the injection timing. The ignition control means 52 outputs a control signal to the ignition coil 55 based on the signal from the operating state detection means 51 to adjust the ignition timing. Since the engine 1 does not include a throttle valve for adjusting the amount of intake air in the intake port 16, the intake air density is sucked into the combustion chamber 3 without being throttled. Therefore, it is desirable that the engine 1 be an in-cylinder injection engine capable of super lean burn operation with an air-fuel ratio of 40 or more.
[0009]
FIG. 2 shows the relationship between the opening / closing behavior of the intake and exhaust valves 10 and 11 and the in-cylinder pressure waveform. The on-off valve timings of the intake / exhaust valves 10 and 11 are shown in the case of normal operation. The pressure diagram 70P represents the combustion cycle when the intake valve 10 is operated with the lift 70IN and the exhaust valve 11 is operated with the lift 70EX. Since the intake valve 10 is opened to the vicinity of the maximum lift, the intake air enters the combustion chamber 3 without being throttled, so that the in-cylinder pressure during the intake stroke is close to the atmospheric pressure 75 and there is almost no pump loss. It is in a state. When the fuel supply is stopped from this state and combustion is stopped, the engine 1 rotates by inertia, and after a while, the rotational speed decreases due to friction between the piston 2 and the cylinder and friction loss of the bearing, and finally the engine 1 stops. This phenomenon is generally used as an engine brake. However, when the intake valve 10 is in the vicinity of the maximum lift, there is no pump loss during the intake stroke, so the engine brake is weak and it takes a long time to stop the engine. Therefore, if the lift amount of the intake valve 10 is reduced to 71IN, 72IN, and 73IN, the opening area of the intake valve 10 is reduced during the intake stroke, and the intake air is throttled. It becomes like 73P. That is, the negative pressure is generated in the combustion chamber 3 during the intake stroke, and pump loss occurs. Thus, the pump loss, that is, the strength of the engine brake is controlled by changing the lift amount of the intake valve 10.
[0010]
FIG. 3 shows the relationship between the intake valve lift amount and the engine brake strength. The case where the maximum lift amount is 8 mm is shown. Even when the intake valve lift amount is 8 mm, the engine brake is slightly applied due to engine friction loss. As the lift amount is reduced, the engine brake becomes stronger as indicated by a solid line 75.
[0011]
Another embodiment of the present invention is shown in FIG. When the intake / exhaust valves 10 and 11 are always closed like 76IN and 77EX, respectively, the air in the combustion chamber 3 is compressed near the top dead center (TDC in the figure) and near the bottom dead center (BDC in the figure). It expands to a pressure diagram 76P. In this state, the work for compression and the work for expansion are offset, and the engine braking effect is small. The pressure diagram when the intake valve opens at 77IN, that is, immediately after top dead center and closes at bottom dead center, is 77P, and high compression pressure is obtained near top dead center. . Immediately thereafter, the intake valve 10 is opened, so that the compressed air in the combustion chamber 3 is discharged to the intake port 16 side, and the in-cylinder pressure immediately decreases. The air discharged to the intake port 16 side is again sucked into the combustion chamber 3 by the downward movement of the piston 2, but almost no pump loss occurs when the lift amount of the intake valve 10 is near the maximum. When the intake valve 10 is closed near the bottom dead center, the air in the combustion chamber 3 is compressed again. At this time, a work loss for compressing air is generated in the engine 1, so that the engine brake works. Furthermore, in this embodiment, since the compression action works once during one revolution of the engine, a strong engine brake can be expected. FIG. 4 shows an example in which the intake valve 10 is opened and the exhaust valve 11 is always closed. However, the same effect can be obtained if the exhaust valve 11 is opened and the intake valve 10 is always closed. Can be expected. FIG. 5 shows the strength of the engine brake of this embodiment as a point 78. A solid line 75 represents the strength of the engine brake when a pumping loss is generated during the intake stroke. When the compression action is used, the engine brake is about twice as strong.
[0012]
FIG. 6 shows the relationship between the operation amount of the accelerator pedal and the brake pedal, the engine output, and the engine brake torque. The intention of the driver 60 to move the vehicle such as starting and acceleration appears in the amount of operation (depression) of the accelerator pedal. When the amount of depression of the accelerator pedal is large, a large engine torque is required when starting a stopped vehicle or during acceleration, etc. When the amount of depression is small, the load during steady driving is small, and the engine This is a region that does not require much torque. Therefore, the relationship between the accelerator opening (depression amount) and the required engine torque has a tendency as shown by a solid line 80. Since the inclination of this straight line changes depending on the engine speed, the operating state detecting means 51 detects and corrects the engine speed. When decelerating, the amount of depression of the accelerator pedal is 0, and the brake pedal is depressed. The amount of operation of the brake pedal is detected by a brake pedal force detection means 62 that detects the pedal force. The brake pedaling force represents the driver's intention to decelerate, and the braking force corresponding to the pedaling force is transmitted to the brake device. According to the present invention, the engine generates engine brake torque according to the brake pedaling force to assist the braking force. A solid line 84 shows the relationship between the brake pedal force and the engine brake torque, and the engine brake is generated by reducing the lift amount of the intake valve. When the driver has a strong intention to decelerate, such as during sudden braking, the braking force increases, and the vehicle enters an area 85 where the antilock brake system (ABS) installed in the vehicle operates. At this time, the engine applies a powerful engine brake such as a solid line 86 to assist the braking force. At this time, the engine brake torque is generated by utilizing the compression action. Further, as a state where neither the accelerator pedal nor the brake pedal is depressed, the engine is stopped 82, the vehicle is stopped but the engine is rotating (ie, idling state) 81, and the vehicle is running. There is a state 83 in which the vehicle is decelerated due to inertia. In the state 81, the engine generates a slight engine torque for rotating against the friction loss. In state 83, the fuel supply is stopped and no engine torque is generated due to combustion explosion. Therefore, a slight engine brake corresponding to the frictional resistance of the engine is generated.
[0013]
FIG. 7 shows a flowchart of this embodiment. The driving state detection means 51 detects depression of the accelerator pedal in block 91. If the accelerator pedal is depressed, it determines that the engine brake is unnecessary and ends the processing. If the accelerator pedal is not depressed, it is determined in block 92 whether the brake pedal 61 is depressed. Here, when the brake pedal 61 is not depressed, the vehicle speed is detected at block 93 to determine whether or not the vehicle is traveling. If the vehicle speed is 0, it is determined that the vehicle is stopped, and the process is terminated. If the vehicle speed is not zero in block 93, the vehicle is coasting. At this time, as a deceleration mode at block 94, the lift amount of the intake valve is set to a predetermined value with a maximum lift amount (for example, 0.7 times), and negative pressure is generated in the combustion chamber 3 to cause engine braking due to pump loss. Act. As a result, the vehicle speed gradually decreases. In block 95, the depression of the brake pedal 61 is detected again. If the brake pedal 61 is not depressed, the process returns to the first block 91. If it is determined in block 95 or 92 that the brake pedal 61 is depressed, as shown in FIG. 8, the brake pedal force detecting means 62 determines the pedal force of the brake pedal. Determine if the system is operating. When it is determined that the ABS is not in operation, the lift amount of the intake valve 10 is determined by the engine brake strength determining means in block 96 so that the engine brake corresponding to the brake pedal force is applied, and a control signal is output. If it is determined that the engine is in the ABS operation region, the lift operation and the opening / closing valve timing of the intake valve 1 or the exhaust valve 11 are determined so as to apply a powerful engine brake due to the compression action in block 98, and a control signal is output. To do. The control signal from the block 96 or 98 is sent to the variable valve control means 54, and the intake / exhaust valves 10 and 11 are operated by the variable valve drive circuit 57.
[0014]
Another embodiment of the present invention will be described. When a vehicle equipped with the engine 1 equipped with the variable valve mechanisms 30 and 40 shown in FIG. 1 collides such that the airbag 67 mounted on the steering 65 operates, the fuel 17 injected into the combustion chamber 3 Remains uncombusted in the combustion chamber 3. Further, if the engine 1 is stopped and the exhaust valve 11 is left open, the fuel 17 remaining in the combustion chamber 3 may flow out to the exhaust pipe 24. Since the exhaust pipe 24 is constantly exposed to high-temperature exhaust gas and reaches a high temperature of about 300 ° C., if the fuel 17 leaks from the combustion chamber 3 to the exhaust pipe 24, there is a possibility of fire. is there. FIG. 9 shows a flowchart of this embodiment. When the vehicle collides, the driving state detection means 51 detects whether the airbag 67 mounted on the vehicle is activated in the block 106 by the airbag detection means 66. If the operation of the airbag 67 is detected, the airflow is detected in the block 107. In the bag operation mode, a control signal for closing the intake and exhaust valves 10 and 11 is output to the variable valve control means 54. The variable valve control means 54 causes a current to flow through the variable valve drive circuit 57 through the coils 30 a and 40 a on the valve closing side to close the intake and exhaust valves 10 and 11 to seal the combustion chamber 3. As a result, it is possible to prevent the fuel 17 remaining unburned in the combustion chamber 3 from flowing into the exhaust pipe 24 and causing a fire.
[0015]
【The invention's effect】
In the control method for an internal combustion engine of the present invention, the engine brake operation mode of the variable valve mechanism is controlled in association with the brake system mounted on the vehicle, and the braking force of the vehicle can be assisted. It has an excellent effect that can be simplified.
[Brief description of the drawings]
FIG. 1 is a system diagram in which the present invention is adopted.
FIG. 2 is a diagram showing a relationship between opening / closing behaviors of intake and exhaust valves and in-cylinder pressure waveforms.
FIG. 3 is a graph showing the relationship between intake valve lift and engine brake strength.
FIG. 4 is a diagram showing the relationship between the intake / exhaust valve opening / closing behavior and the in-cylinder pressure waveform in the ABS operation mode in another embodiment of the present invention.
FIG. 5 is a diagram showing the strength of engine braking in the ABS operation mode.
FIG. 6 is a diagram showing the relationship between accelerator and brake pedal operation amounts, engine output, and engine brake torque.
FIG. 7 is a flowchart of a braking force assist control method using engine braking.
FIG. 8 is a diagram showing a relationship between a brake pedal depression force and an intake valve lift amount.
FIG. 9 is a flowchart of another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Piston, 3 ... Combustion chamber, 4 ... Connecting rod, 5 ... Crankshaft, 8 ... Engine head, 10 ... Intake valve, 11 ... Exhaust valve, 12 ... Spark plug, 13 ... Fuel injection valve, 16 ... Intake port, 17 ... fuel, 18 ... pressure sensor, 19 ... knocking sensor, 21 ... air-fuel ratio sensor, 30, 40 ... variable valve mechanism, 50 ... control unit.

Claims (2)

A valve mechanism including an intake valve and an exhaust valve combined with a cylinder of the internal combustion engine;
Valve mechanism control means for controlling the valve mechanism;
Comprising an operating state detecting means for detecting an operating state of the internal combustion engine;
Brake pedal force detection means for detecting the brake pedal force;
In a method for controlling an internal combustion engine mounted on a vehicle equipped with an anti-lock brake system that prevents a side slip of the vehicle during sudden braking,
When the brake pedal force detection means detects the brake pedal force and detects the operation of the anti-lock brake system, at least one of the intake valve or the exhaust valve is closed, and the intake valve or the exhaust valve is not closed. While the piston moves from the top dead center to the bottom dead center, that is, once in one rotation, the lift amount is controlled to a predetermined value,
A control method for an internal combustion engine. A valve mechanism including an intake valve and an exhaust valve combined with a cylinder of the internal combustion engine;
Valve mechanism control means for controlling the valve mechanism;
In a control method of an internal combustion engine mounted on a vehicle equipped with
Brake state detection means for detecting the amount of brake operation is provided,
The lift amount of the intake valve is changed in accordance with the brake operation amount detected by the brake state detection means, and the intake air amount is controlled . When the brake state detection means detects the operation of the brake , the intake air amount is controlled. At least one of the valve and the exhaust valve is closed, and the valve that does not close the intake valve or the exhaust valve is opened while the piston moves from the top dead center to the bottom dead center, that is, once per rotation. And controlling the lift amount to a predetermined value according to the brake operation amount detected by the brake state detection means ,
A control method for an internal combustion engine.

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