Variable valve timing control apparatus of internal combustion engine

Abstract

A variable valve timing control apparatus of an internal combustion engine, has a housing having a plurality of shoes and a vane member having a plurality of vanes dividing each working fluid chamber formed between adjacent two shoes into advance and retard oil chambers. The vane member rotates to an advanced angle side and to a retarded angle side relative to the housing by selectively supplying or exhausting hydraulic pressure in or from the advance oil chamber and the retard oil chamber. A most-advanced angle position and a most-retarded angle position are limited by the fact that one vane touches one shoe from a circumferential direction. Radius of curvature of one of both corners of a base part of the one shoe, which is a corner located at a side where the one vane does not touch, is set to be greater than those of corners of the other shoes.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a variable valve timing control apparatus of an internal combustion engine, which variably controls open and closing timing of an intake valve and / or an exhaust valve of the engine in accordance with an engine operating condition.[0002]As one of generally used variable valve timing control apparatuses, a vane type variable valve timing control apparatus disclosed in Japanese Patent Provisional Publication No. 2002-295212 (hereinafter is referred to as “JP2002-295212”) is known.[0003]This vane type variable valve timing control apparatus has a housing to which a turning force is transmitted from an engine crankshaft and a vane member which is rotatably housed in the housing and is secured to an end portion of a camshaft. Further, a plurality of shoes are formed on an inner peripheral surface of the housing so as to protrude in a radially inward direction. Advance oil chambers and retard oil chambers are defined between...

AI Technical Summary

Benefits of technology

The present invention provides a variable valve timing control apparatus for an internal combustion engine that can ensure the strength of shoes while securing a large relative rotational angle between the housing and the vane member. This is achieved by limiting the most-advanced angle rotational position and the most-retarded angle rotational position based on the fact that one certain vane touches one certain shoe from a circumferential direction with the one certain vane pressed against the one certain shoe. Additionally, a thick portion is provided on the base part of the one certain shoe to further enhance the strength of the shoe.

Problems solved by technology

However, if the thickness of each shoe is formed thin, its strength decreases.

Because of this, the shoe might be bent and deformed when the vane is pressed against the shoe from the circumferential direction, and there is a possibility that a desired relative rotational angle will not be obtained.

However, there is a trade-off between an increase in the thickness of the shoe and an increase in the relative rotational angle between the housing and the vane.

Thus, if the thickness of the shoe is thicken, it is difficult to obtain the large relative rotational angle between the housing and the vane.

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