Control device of an internal combustion engine

Details Control device of an internal combustion engine Control device of an internal combustion engine

2000-05-08

2001-12-18

Lo, Wellun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090160, C123S090170, C123S090190

Reexamination Certificate

active

06330869

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a control device of an internal combustion engine which is provided with a valve moving apparatus having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic such as lift of a suction valve or an exhaust valve and a hydraulic valve phase variable mechanism for altering phase of the suction valve or the exhaust valve. According to the control device, when the valve operation characteristic is changed, a map storing control amounts for controlling combustion condition of the engine such as amount of injected fuel is changed at a timing reflecting property of a working oil such as viscosity of the working oil supplied to the valve characteristic changing mechanism.
An internal combustion engine provided with a valve moving apparatus having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic by driving a suction valve and an exhaust valve with a cam for low speed of small lift and small valve opening time on a low rotational speed of the engine and with a cam for high speed of large lift and large valve opening time on a high rotational speed of the engine has been known (Japanese Patent Publication No. 2619696).
The above valve characteristic changing mechanism has connecting pins provided on respective rocker arms of the suction valve and the exhaust valve, and an oil pressure changing valve. The connecting pins are moved by pressure of oil which is changed over by the oil pressure changing valve, to connect or disconnect the rocker arms, so that the rocker arms, therefore the suction valve and the exhaust valve, are driven by the cam for low speed or the cam for high speed.
When the valve operation characteristic is changed, a map of fuel injection amount and a map of ignition time are changed into maps for low speed or maps for high speed corresponding to the valve operation characteristic, to carry out fuel injection amount control and ignition time control. In that case, a delay time required for changing actions of the valve characteristic changing mechanism of all cylinders to be completed by the oil pressure changed by the oil pressure changing valve is previously set in a timer, and change of the maps is carried out after the delay time elapses for the fuel injection amount control and the ignition time control adapted to the valve operation characteristic.
However, in the above-mentioned prior art, as the delay time to be set in the timer, a fixed value decided from a viewpoint of prevention of engine stall and prevention of deterioration of drive ability is adopted, so that the delay time does not correspond to change of property of the working oil of the valve characteristic changing mechanism. Therefore, sometimes, notwithstanding that actually valve characteristic changing mechanisms of all cylinders have been already changed into high speed side (or low speed side), maps for fuel injection amount ad ignition time remain in maps for low speed (or for high speed), because the oil property (oil viscosity susceptible to temperature, for example) is altered influenced by operational condition of the engine to alter operation response of the valve characteristic changing mechanism. And, in a short period when a suction air amount, a fuel injection amount and an ignition time are not adapted to each other due to a time lag between a valve operation characteristic changing time point and a map changing time point, air-fuel ratio or ignition time deviates from an optimum value to produce undesirable results regarding engine performance other than the prevention of engine stall and the prevention of deterioration of drive ability, especially regarding exhaust emission.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the foregoing, and a subject of the invention is to further improve performance of the internal combustion engine by that property of the working oil in the hydraulic valve characteristic changing mechanism of the valve moving apparatus is detected, and the delay time deciding a change timing of a control amount holding means which folds control amounts for controlling combustion condition of the internal combustion engine is altered in accordance with the detected property of the working oil, to make a change of the valve operation characteristic coincide with the change of the control amount holding means.
The present invention provides a control device of an internal combustion engine, comprising an operational condition detecting means for detecting an operational condition of the internal combustion engine; a valve moving apparatus provided with a first valve control mechanism having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic of at least one of a suction valve and a exhaust valve of said engine, and an oil pressure changing valve for changing pressure of a working oil supplied to said valve characteristic changing mechanism from an oil pressure source; a first valve operation control means for controlling operation of said oil pressure changing valve in accordance with the operational condition detected by said operational condition detecting means; control amount holding means corresponding to said respective valve operation characteristic which hold control amounts to control combustion condition of said engine; a combustion control means operated based on said control amount of said control amount holding means; a working oil pressure detecting means for detecting property of said working oil; a delay time setting means for setting a delay time between change of oil pressure by said oil pressure changing valve and completion of change of valve operation characteristic by said valve characteristic changing mechanism based on property of said working oil detected by said working oil property detecting means; and changing means for changing said control amount holding means to a control amount holding means corresponding to a changed valve operation characteristic when said delay time elapses after said oil pressure to be supplies to said valve characteristic changing mechanism is changed by said oil pressure changing valve.
According to this invention, after the delay time set based on property of the working oil of the valve characteristic changing mechanism elapses, the changing means changes the control amount holding means from a control amount holding means corresponding to a valve operation characteristic before the valve moving mechanism is changed to a control amount holding means corresponding to a valve operation characteristic after the valve moving mechanism is changed. And the combustion control means controls combustion of the engine based on a control amount held in the changed control amount holding means. Since the delay time can be set in accordance with change of property of the working oil which is influenced by operational condition of the engine, in a wide operation range of the engine, change timing of the valve operation characteristic and change timing of the control amount holding means can be made coincide with each other to control combustion of the engine with a control amount most suitable for the valve operation characteristic, so that performance of the engine can be more improved.
The said valve moving apparatus may further comprise a hydraulic valve phase variable mechanism for altering phase of open-close period of at least one of said suction valve and said exhaust valve, and a second valve control mechanism having an oil pressure control valve for controlling pressure of a working oil supplied to said valve phase variable mechanism from said oil pressure source. Further, operation of said oil control valve may be controlled by a second valve operation control means in accordance with the operational condition detected by said operational condition detecting means, and said working oil property detecting means may detect property of said working oil based on behavior of said second valve cont

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