Patent ID: 8291822

Claim:
An image forming apparatus comprising: a body casing; at least two rollers in the body casing; an endless belt looped around the at least two rollers, the belt having an outer surface and an inner surface; a cleaning unit disposed outside the loop of the belt, the cleaning unit including a case, a cleaning mechanism disposed within the case, and at least one cam, the cleaning mechanism including a cleaning member that is positioned to face the outer surface of the belt; a backup member that is positioned to face the inner surface of the belt; one pressure force applying mechanism comprising a first arm coupled to the backup member and a first urging member configured to urge the first arm, the one pressure force applying mechanism being configured to apply one pressure force to the backup member such that the belt is in contact with and held between the backup member and the cleaning member by the one pressure force; another pressure force applying mechanism comprising a second arm having a cam follower and a second urging member configured to urge the second arm, the other pressure force applying mechanism being configured to apply another pressure force to the first arm of the one pressure force applying mechanism when the second arm contacts the first arm; and a pressure force adjusting mechanism configured to move the second arm of the other pressure force applying mechanism by rotation of the cam so as to change a state of the backup member and the cleaning member from a first state in which the cam moves the cam follower of the second arm such that the second arm is spaced from the first arm and the backup member is urged by the one pressure force applying mechanism, to a second state in which the cam moves the cam follower of the second arm such that the second arm contacts the first arm and the backup member is urged by both the one pressure force applying mechanism and the other pressure force applying mechanism.