Variable valve timing control apparatus with supplementary oil pump

Abstract

A variable valve timing control apparatus includes: a relative rotational phase adjusting mechanism capable of adjusting a relative rotational phase between a drive-side rotational member and a driven-side rotational member between the most advanced angle phase and the most retarded angle phase; and a lock mechanism capable of locking the relative rotational phase at an intermediate phase between the most advanced angle phase and the most retarded angle phase; a first pump operated by a driving force of an engine; and an electrically driven second pump operated as an electrically driven pump. Hydraulic fluid is supplied from at least one of the first pump and the second pump, and the second pump is capable of operating even if the first pump is inoperative when the engine is not running.

Description

TECHNICAL FILED[0001]This invention generally relates to a variable valve timing control apparatus which controls opening and closing timings of one of, or both of, an intake valve and an exhaust valve, in response to running conditions of an engine mounted for example on a vehicle.BACKGROUND ART[0002]This type of variable valve timing control apparatus is mainly configured with a variable valve timing control unit and a relative rotational phase adjusting mechanism. The variable valve timing control unit incorporates, therein, a drive-side rotational member, which rotates in synchronization with a crankshaft; a driven-side rotational member, which is positioned coaxially with the drive-side rotational member and rotates integrally with a camshaft; at least one fluid pressure chamber defined in at least one of the drive-side rotational member and the driven-side rotational member; at least one vane dividing the fluid pressure chamber into an advanced angle chamber and a retarded ang...

AI Technical Summary

Benefits of technology

[0010]According to an aspect of the present invention, a variable valve timing control apparatus includes: a drive-side rotational member rotatable in synchronization with a crankshaft; a driven-side rotational member positioned coaxially with the drive-side rotational member and being rotatable integrally with a camshaft; at least one fluid pressure chamber defined at least one of the drive-side rotational member and the driven-side rotational member; at least one vane diving the fluid pressure chamber into an advanced angle chamber and a retarded angle chamber; a relative rotational phase adjusting mechanism capable of changing a position of the at least one vane relative to the fluid pressure chamber by supplying hydraulic fluid to or draining hydraulic fluid from at least one of the advanced angle chamber and the retarded angle chamber, the relative rotational phase adjusting mechanism being capable of adjusting a relative rotational phase between the drive-side rotational member and the driven-side rotational member between the most advanced angle phase, in which a volume of the advanced angle chamber reaches maximum, and the most retarded angle phase, in which a volume of the retarded angle chamber reaches maximum; a lock mechanism capable of locking the relative rotational phase at an intermediate phase between the most advanced angle phase and the most retarded angle phase; a first pump operated by a driving force of an engine; and an electrically driven second pump. Hydraulic fluid is supplied from at least one of the first pump and the second pump, and the second pump is capable of operating when the engine is stopped (i.e. when the engine is not running).

Problems solved by technology

In such a case, it is not possible to control opening and closing timings of valves when the engine is not running.

Therefore, there is no guarantee that a reliable lock condition can be achieved.

Therefore, the engine start-up could possibly be delayed by the time required for an engine start-up lock, and moreover, it is also possible that a reliable lock may not be achieved.

Here, if the engine is stopped and is started again in a relatively short period of time at the lock phase set by the lock mechanism, cranking of the engine would require more work than required for the actual compression ratio necessary for stable combustion, thus requiring higher input voltage to a motor for cranking possibly with increased vibration of the motor.

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