Variable speed gear for internal combustion engines

摘要

In a variable speed gear change mechanism (50) for an internal combustion engine, gear change operation is performed by rotating a star plate (54) fixed to a shift drum (9) by rotating a change spindle (51) and a stopper roller assembly (55) is pressed against and engaged with a recess on the outer periphery of the star plate. The center of rotation of the aforementioned stopper roller assembly is disposed on a straight line (X) connecting the center of rotation (A) of the aforementioned change spindle and the center of rotation (B) of the aforementioned shift drum, and a pressing force toward the center of rotation of the aforementioned shift drum is exerted on the stopper roller. The usage of a ball bearing at the portion rotatably supporting the shift drum is eliminated by equalizing the load generated during upshifting operation and the load generated during downshifting operation so that the sense of discomfort of the driver is eliminated.