Patent ID: 7100754

Claim:
A pulley unit mounted around a shaft having a free end and a base end, the shaft extending, at the base end, in an axial direction from an alternator, the pulley unit when mounted on the shaft has a free end side near the free end of the shaft and a base end side near the base end of the shaft, the pulley unit comprising: inner and outer concentric ring bodies that define an annular space there between; a roller bearing located in the annular space at the free end side adjacent the free end of the shaft; a ball bearing located in the annular space at the base end side adjacent the base end of the shaft, the roller bearing having a comparatively large load carrying capacity as compared to the ball bearing, the ball bearing having a comparatively small load carrying capacity; a one-way clutch located in the annular space between the inner and outer ring bodies and between the roller bearing and the ball bearing, the one-way clutch including a cam face defined on the outer surface of the inner ring body; a holder defining a pocket, the holder being positioned on the cam face; and a roller with a movable surface and an elastic member positioned in the pocket so that the movable surface is in rolling contact with the inner surface of the outer concentric ring body and the outer surface of the inner concentric ring body, the roller locking the one-way clutch when the outer concentric ring body is rotated faster than the inner concentric ring body and the roller unlocking the one-way clutch and engaging the elastic member when the outer concentric ring body is rotated slower that the inner concentric ring body; the roller bearing being having a cylinder in rolling contact with the outer surface of the inner ring body, axial movement of the holder of the one-way clutch being restricted by the inner ring body adjacent to the ball bearing, and a belt engaging the outer ring body at the free end side in a region including only the roller bearing and the one-way clutch.