Patent ID: 7848687

Claim:
An image forming device in which a plurality of image carriers are installed in a tandem manner, images of different colors are formed on the image carriers and combined to form a color image, the image forming device including a main controller unit controlling the image forming device, a motor controller unit controlling individually rotational speeds of a plurality of motors rotating the image carriers respectively, and a deviation detection unit detecting a deviation of the color image, the main controller unit comprising: a speed signal transmitting unit transmitting a speed signal, indicating a target rotational speed for correcting the deviation detected by the deviation detection unit, to the motor controller unit; and an enabling-signal transmitting unit transmitting, to the motor controller unit, a speed-change enabling signal that enables the motor controller unit to start a speed change of a rotational speed of one of the motors, after passing of a predetermined time from a time an imaging reference signal, which is indicative of a start and an end of an image region of each color, indicates an end of a corresponding image region immediately after transmission of the speed signal, wherein said predetermined time is calculated from a rotation angle between an exposure position and a transfer position of the image carrier relative to a center of rotation of the image carrier, and a rotation speed of the image carrier.