Valve timing control system for internal combustion engine

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

2000-08-03

2001-12-11

Lo, Weilun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C074S56800M

Reexamination Certificate

active

06328008

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve timing control system for varying valve timing of intake and exhaust valves of an internal combustion engine for a motor vehicle according to a vehicle driving condition.
2. Description of the Related Art
Various valve timing control systems have been proposed and in practical use for the purpose of further improving performance of internal combustion engines. Japanese Patent Unexamined Publication No. 5(1993)-1514 discloses a typical valve timing control system which employs a pair of spring clutches and a selector for switching operation of the spring clutches. This conventional valve timing system is arranged to vary the valve timing by controlling a phase varying device installed between a sprocket and a camshaft. The phase varying device for preferably varying the valve timing into an advanced state or retarded state as shown in
FIG. 30
has a pair of spring clutches coaxial with the camshaft and a clutch switching mechanism for controlling holding states of the spring clutches.
Japanese Patent Unexamined Publication No. 9(1997)-250309 discloses another conventional valve timing control system which comprises a rotational phase controlling device constituted by a solenoid clutch and a sun-and-planet gear set. This conventional valve timing control system keeps a stationary holding state between a sprocket and a camshaft by applying a biasing force of a plate spring to the solenoid clutch.
SUMMARY OF THE INVENTION
Although the former conventional system has many outstanding features such as a simplicity of overall constitution, a small size and a light weight, it is yet required to further stably keep the holding state between the sprocket and the camshaft against alternating torque applied from the engine valves to the camshaft. On the other hand, although the latter conventional system can ensure a sufficient holding force by increasing the biasing force of the plate spring, this change of the plate spring requires the solenoid clutch to generate a larger force against the increased biasing force of the plate spring. However, this improvement requires the latter system to become larger in size.
It is, therefore, an object of the present invention to provide an improved valve timing control system for an internal combustion engine which preferably executes the holding of a rotational phase of the camshaft to the sprocket by stabilizing holding condition by means of a clutch and preventing the alternating torque from decreasing the clutch's tightening force.
There is provided a valve timing control system for an internal combustion engine according to the present invention. This valve timing control system comprises; a rotor rotated by a crankshaft of the internal combustion engine; a camshaft rotated according to the rotation of the rotor to open and close an intake valve and an exhaust valve of the internal combustion engine; and a rotational phase controller for variably controlling a rotational phase of the camshaft relative to the rotor. The rotational phase controller is disposed between the rotor and the camshaft. The rotational phase controller comprises; a clutch selectably put in one of a holding state for forbidding a relative rotation between the rotor and the camshaft in at least one of rotational directions and a releasing state for allowing the relative rotation; and a generator for generating a holding toque directing to the rotational direction forbidden by the clutch and applying the holding torque to the clutch when the clutch is put in the holding state.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.


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patent: 6129061 (2000-10-01), Okuda et al.
patent: 5-1514 (1993-01-01), None
patent: 6-10977 (1994-01-01), None
patent: 6-66328 (1994-03-01), None
patent: 7-91459 (1995-04-01), None
patent: 7-332385 (1995-12-01), None
patent: 9-250309 (1997-09-01), None

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