PURPOSE: To set the error of the angle to be formed by the line connecting the timing mark to the center and the line connecting the knock hole and the center in the prescribed range when the difference between the pitch of the helical spline of the body pulley and the pitch of the outer tooth of the timing pulley is two times or more as large as the upper limit witin the prescribed standard range of error.

CONSTITUTION: A plurality of knock grooves 71, 72 where knock pins fixed to a body pulley 31 are inserted are formed in a timing pulley 16. As a result, the error can be set in the prescribed standard range.