System for controlling valve shift timing of an engine.

摘要

An intake valve or an exhaust valve is lifted through a swingable cam by the rotation of a rotatable cam formed in the cam shaft. A surface at which the swingable cam abuts with the rotatable cam is tapered in the axial direction in which said cam shaft extends, and the valve shift timing is changed by transferring the cam shaft, that is, the rotatable cam in the axial direction in which said cam shaft extends. The power transmitting member such as a helical gear to be rotated with the output shaft of the engine is engaged with the cam shaft through a helical spline. The power transmitting member is so arranged as to be unmovable in the axial direction in which said cam shaft extends. The rotational phase of the rotatable cam relative to the output shaft of the engine is changed by displacement of the cam shaft relative to the power transmitting member in the axial direction in which said cam shaft extends.