On the other hand, in the latter case, as a preferable shape of the shim, the flatness of the sliding surface relative to the cam is less than or equal to 0.5 ??m-5 ??m and the maximum height of the crowning of a contact surface relative to a mounting part such as a lifter, on which it is mounted and which is in contact with it is preferably 5 ??m-50 ??m.