Patent ID: 7917060

Claim:
An image forming apparatus, comprising: an image forming unit configured to form a toner image on an image bearing member; an endless belt configured to transfer and carry the toner image thereon; a transfer unit configured to transfer the toner image carried by the endless belt onto a recording sheet; a sensing unit configured to sense the toner image transferred onto the endless belt; a blocking unit mounted between the sensing unit and the endless belt and configured to block the sensing unit; a contact and separation unit configured to cause the transfer unit to reciprocally contact and separate from the endless belt, and a cam in contact with a surface of the blocking unit and the contact and separation unit, wherein the blocking unit and the contact and separation unit configured to be in driven contact with a common drive source, wherein the blocking unit is slidably movable along a longitudinal axis of a roller opposite the sensing unit and the cam is in driven contact with the common drive source and rotatable about a shaft, the cam including a tip projecting from a side wall of the cam in a direction parallel to the shaft and the tip engages the blocking unit.