The present invention relates to a valve-timing control apparatus for an internal combustion engine, in which opening and closing timings of intake valve and/or exhaust valve of the internal combustion engine are controlled.
Recently, a valve-timing control apparatus is proposed in which opening and closing timings of intake or exhaust valve are controlled by transmitting rotative force of an electric motor through a speed-reduction mechanism to a cam shaft and thereby varying a relative rotational phase of the cam shaft to a sprocket to which rotative force is transmitted from a crankshaft.
Japanese Patent Application Publication No. 2011-256798 discloses a previously-proposed valve-timing control apparatus. In this technique, an output shaft of the electric motor is formed in a tubular shape, and a bearing member such as a ball bearing is accommodated inside the tubular output shaft. Accordingly, an axial length of the entire valve-timing control apparatus can be shortened to attain a downsizing thereof. The bearing member is lubricated by supplying lubricating oil into the tubular output shaft.
Moreover, in the above previously-proposed valve-timing control apparatus, a brush is provided to a cover member located on a front end side of the electric motor whereas a slip ring is provided to the electric motor. By means of a contact between these brush and slip ring, electric power is supplied to the electric motor. A plug member is provided inside a tip portion of the tubular output shaft in order to prevent lubricating oil retained in the tubular output shaft from flowing out and adhering to the brush and the slip ring.
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