Patent ID: 8295733

Claim:
An image forming apparatus for forming an image on a recording medium, comprising: a belt configured to travel rotationally, looped around at least two rotary support members; a driven rotary member disposed facing at least one of the rotary support members via the belt and configured to be driven to rotate by the belt; and a controller configured to minimize fluctuation in one of a travel velocity and a travel distance of the belt by controlling the travel of the belt based on one of a rotational angular displacement and a rotational angular velocity of each of the rotary support member and the driven rotary member, wherein the recording medium contacts the outer surface of the belt without passing through between the driven rotary member and the rotary support member, and wherein the controller is configured to determine both an inner surface travel velocity of the belt and an outer surface travel velocity of the belt based on said one of the rotational angular displacement and the rotational angular velocity of each of the rotary support member and the driven rotary member, calculate one of a belt travel velocity function and a belt travel distance function based on the inner surface travel velocity of the belt and the outer surface travel velocity of the belt, and control the travel of the belt to minimize fluctuation in said one of the belt travel velocity function and the belt travel distance function.