Valve operating control system for internal combustion engine

Details Valve operating control system for internal combustion engine Valve operating control system for internal combustion engine

2000-02-04

2001-03-20

Lo, Wellun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090160, C123S090170

Reexamination Certificate

active

06202610

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve operating control system for an internal combustion engine, including a cam switching type, first valve operating characteristic changing mechanism, and a cam-phase changing type, second valve operating characteristic changing mechanism.
2. Description of the Prior Art
An internal combustion engine is known from Japanese Patent Publication No. 5-43847, which includes a cam switching type valve operating characteristic changing mechanism for stepwise controlling the valve lift and the opening angle of an intake valve or an exhaust valve for an internal combustion engine, and a cam-phase changing type, valve operating characteristic changing mechanism for continuously controlling the timing of the opening and closing of the valve.
When the cam-phase changing type, valve operating characteristic changing mechanism is mounted in an internal combustion engine including a cam switching type, valve operating characteristic changing mechanism, it is desirable that a common oil pump be used for both of the valve operating characteristic changing mechanisms and the capacity or displacement of the oil pump is suppressed to the minimum, in order to reduce the number of parts and to simplify the structure.
In general, however, the cam switching type valve operating characteristic changing mechanism is constructed to establish a high-speed valve timing by supplying hydraulic pressure from the oil pump, and to establish a low-speed valve timing by cutting-off the supplying of that hydraulic pressure. The cam-phase changing type, valve operating characteristic changing mechanism is constructed to change the cam phase by supplying hydraulic pressure selectively to the advancing chamber or the retarding chamber. If the cam phase is intended to be changed when high-speed valve timing has been established, or if the high-speed valve timing is intended to be established when the cam phase has been changed, there is a possibility that the hydraulic pressure supplied from the oil pump may be insufficient, resulting in a reduction in responsiveness and reliability of the valve operating characteristic changing control.
SUMMARY OF THE INVENTION
The present invention has been accomplished with the above circumstance in view, and it is an object of the present invention to provide a valve operating control system for an internal combustion engine including a cam switching type, valve operating characteristic changing mechanism, and a cam-phase changing type, valve operating characteristic changing mechanism, wherein the responsiveness and the reliability of the valve operating characteristic changing control can be guaranteed, while suppressing the capacity of the oil pump used commonly for both of the valve operating characteristic changing mechanisms.
To achieve the above object, there is provided a valve operating control system for an internal combustion engine, comprising a cam switching type, first valve operating characteristic changing mechanism to which hydraulic pressure is supplied from an oil pump through a first hydraulic pressure control valve, and a cam-phase changing type, second valve operating characteristic changing mechanism to which the hydraulic pressure is supplied from the oil pump through a second hydraulic pressure control valve, the first valve operating characteristic changing mechanism being adapted to select a low-speed cam to establish a low-speed valve timing, when no hydraulic pressure is supplied from the first hydraulic pressure control valve, and to select a high-speed cam to establish a high-speed valve timing, when the hydraulic pressure is supplied. The second valve operating characteristic changing mechanism includes an advancing chamber and a retarding chamber, and is adapted to change the cam phase, when hydraulic pressure is supplied selectively to the advancing chamber or the retarding chamber. When the first valve operating characteristic changing mechanism establishes the high-speed valve timing and the second valve operating characteristic changing mechanism sets the cam phase in a most-displaced basic position, the second hydraulic pressure control valve closes both of the advancing chamber and the retarding chamber, and is maintained in a neutral position in which it cuts off the hydraulic pressure supplied from the oil pump.
With the above arrangement, when the high-speed valve timing is established by supplying hydraulic pressure from the oil pump through the first hydraulic pressure control valve to the cam switching type, first valve operating characteristic changing mechanism, and the cam phase is set in the most-displaced basic position by the cam-phase changing type, second valve operating characteristic changing mechanism, the second hydraulic pressure control valve cuts off the hydraulic pressure supplied from the oil pump to close the advancing chamber and the retarding chamber in the second valve operating characteristic changing mechanism, thereby maintaining the cam phase in the most-displaced basic position. Thus, it is possible to set the cam phase in the most-displaced basic position without consumption of hydraulic pressure supplied from the oil pump by the leakage in the second valve operating characteristic changing mechanism, and to ensure the hydraulic pressure enough for the first valve operating characteristic changing mechanism to establish the high-speed valve timing with the minimum capacity or displacement of the oil pump, thereby guaranteeing the reliability of the valve operating characteristic changing control. Moreover, the second hydraulic pressure control valve is maintained in the neutral position in which it closes the advancing chamber and the retarding chamber in the second valve operating characteristic changing mechanism. Therefore, in changing the cam phase from the most-displaced basic position to an opposite position, the hydraulic pressure supplied to the advancing chamber or the retarding chamber in the second valve operating characteristic changing mechanism can be immediately raised to enhance the responsiveness.


REFERENCES:
patent: 5031583 (1991-07-01), Konno
patent: 5497737 (1996-03-01), Nakamura
patent: 5531193 (1996-07-01), Nakamura
patent: 5-43847 (1993-07-01), None

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