Patent ID: 7130549

Claim:
An image forming apparatus comprising: a first developing unit which contains predetermined color developer, supplies developer to a first latent image, and forms a first developer image; a second developing unit which contains predetermined color developer, supplies developer to a second latent image, and forms a second developer image; a photoconductor having a circumference surface is moved at a constant speed, and which holds electrostatic latent image developed with at least one of said first and second developing units; an intermediate transfer body having a circumference surface which holds the electrostatic latent image formed on the circumference of the photoconductor by at least one of said developing units; a transfer unit which transfers said developer image held on the intermediate transfer body to a transfer medium; a fixing unit which fixes the developer image to the transfer medium; a first sensor which detects the timing for supplying the transfer medium to said transfer unit; a second sensor which detects the timing for forming the electrostatic latent images on the photoconductor; a medium feeding unit which feeds the transfer medium toward the transfer position at a timing said first sensor is detected a predetermined times pass through the at least one of the developer image; and a speed control unit which can control independently a speed of moving the circumference of the photoconductor, a speed of moving a belt surface of the intermediate transfer body, and a speed of moving a circumference of the fixing unit, according to an overlaying condition of said plurality of developer images or a thickness or material of the transfer medium, when the fixing unit fixes said plurality of developer images in an overlaid state to the transfer medium.