Valve timing adjusting apparatus

Abstract

A valve timing adjusting apparatus includes a driving-side rotor, a driven-side rotor, and a directional control valve. The driven-side rotor is rotated in the advance direction when the advance and retard output ports communicate with the intake port and the retard drain port respectively, and the advance and retard output ports are disconnected from the advance drain port. The driven-side rotor is rotated in the retard direction when the advance and retard output ports communicate with the advance drain port and the intake port respectively, and the advance and retard output ports are disconnected from the retard drain port. A relay passage is provided at an exterior of the directional control valve for communication with the advance and retard drain ports. The drain relay passage closes the advance and retard drain ports relative to the exterior.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is based on and incorporates herein by reference Japanese Patent Application No. 2008-84525 filed on Mar. 27, 2008.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a valve timing control apparatus for controlling valve timing of a valve that is opened and closed by a camshaft through torque transmitted from a crankshaft in an internal combustion engine.[0004]2. Description of Related Art[0005]A conventional fluid-actuated valve timing adjusting apparatus is commonly known to includes a housing and a vane rotor. The housing serves as a driving-side rotor that is rotatable synchronously with a crankshaft, and the vane rotor serves as a driven-side rotor that is rotatable synchronously with a camshaft. For example, JP-A-2002-235513 (FIGS. 9, 10) corresponding to US2002 / 0088413 (FIGS. 8, 9) discloses an apparatus that defines an advance chamber and a retard chamber arranged in a ...

AI Technical Summary

Benefits of technology

[0013]To achieve the objective of the present invention, there is provided a valve timing adjusting apparatus for adjusting valve timing of a valve that is opened and closed by a camshaft through torque transmission from a crankshaft of an internal combustion engine, the valve timing adjusting apparatus including a driving-side rotor, a driven-side rotor, and a control unit. The driving-side rotor is rotatable synchronously with the crankshaft. The driven-side rotor is rotatable synchronously with the camshaft. The driven-side rotor and the driving-side rotor define therebetween an advance chamber and a retard chamber arranged one after another in a rotational direction. When working fluid is supplied to the advance chamber or the retard chamber, the driven-side rotor is rotated relative to the driving-side rotor in an advance direction or a retard direction. The control unit controls supply of working fluid to the advance chamber and the retard chamber. The control unit includes a directional control valve, an advance communication passage, an advance check valve, a retard communication passage, a retard check valve, and a drain relay passage. The directional control valve includes an intake port, an advance output port, a retard output port, an advance drain port, and a retard drain port. The directional control valve receives working fluid from an external fluid input source through the intake port. The directional control valve outputs working fluid to the advance chamber through the advance output port. The directional control valve outputs working fluid to the retard chamber through the retard output port. The directional control valve drains working fluid through the advance drain port. The directional control valve drains working fluid through the retard drain port. The driven-side rotor is rotated relative to the driving-side rotor in the advance direction when the followings are satisfied; the directional control valve provides communication between the advance output port and the intake port, the directional control valve provides communication

Problems solved by technology

As a result, flow of the drained fluid into the relay passage is limited.

Generally, when the vane rotor is rotated in the advance direction, fluid in the retard chamber is required to be drained However, the fluid in the advance chamber is drained disadvantageously if the positive torque is applied to the vane rotor in the retard direction even while the vane rotor is rotated in the advance direction.

Thus, the backflow of fluid to the retard chamber is limited as above, and thereby the unwanted rotation of the vane rotor relative to the housing in the retard direction is limited.

As a result, pressure drop of working fluid that flows through the opened check valve is substantially enhanced, and thereby the timing advance responsivity and the timing retard responsivity may deteriorate disadvantageously.

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