| 摘要 |
In a timing chain drive unit the tooth pitch of a driven sprocket from which a tension span of the chain travels toward a driving sprocket varies cyclically around the circumference of the driven sprocket and cyclically increases and decreases the length of the tension span in synchronism with load variations imparted to the driven sprocket by a valve-operating camshaft. If the driven sprocket has the varying tooth pitch, then in use the tooth pitch at the disengagement point on the driven sprocket is at a minimum when the load reaches its peak. If the driving sprocket has the varying tooth pitch, then in use the tooth pitch at the engagement point on the driving sprocket is at a maximum when the load reaches its peak. Preferably the driving sprocket is on an engine crankshaft, the driven sprocket is on an engine valve-operating camshaft and the cyclic load variation is imparted to the chain by engine valves through the camshaft and the driven sprocket. |
