Patent ID: 8364063

Claim:
An image forming apparatus comprising: a transfer-sheet conveying unit that is rotated to convey a transfer sheet; a first image forming unit that directly transfers a single-color image onto the transfer sheet that is in a process of being conveyed; an intermediate transfer unit that is rotated while an image to be transferred onto the transfer sheet that is in the process of being conveyed is transferred thereon, the intermediate transfer unit having an identical length in a circumferential direction to a length of the transfer-sheet conveying unit in a circumferential direction; a second image forming unit that transfers, onto the intermediate transfer unit, an image in a plurality of colors except for a color of the image directly transferred by the first image forming unit; a secondary transfer unit that transfers the image transferred onto the intermediate transfer unit onto the transfer sheet that is in the process of being conveyed; a measuring unit that measures surface speeds of the transfer-sheet conveying unit and the intermediate transfer unit for a predetermined number of cycles; and a control unit that controls rotation of at least one of the transfer-sheet conveying unit and the intermediate transfer unit so as to match phases of fluctuation of the measured surface speed of the transfer-sheet conveying unit and fluctuation of the measured surface speed of the intermediate transfer unit.