Patent ID: 8260179

Claim:
An image forming apparatus, comprising: a first belt unit rotatably suspended by at least two first rollers; at least one first image bearer arranged opposite a front surface of the first belt unit and configured to bear a first image; a first image forming device configured to form the first image on the first image bearer; a primary transfer device configured to primarily transfer the first image from the first image bearer onto the first belt unit at a primary transfer position; a secondary transfer device configured to secondarily transfer the first image from the first belt unit onto a printing medium at a secondary transfer position; a second image bearer configured to bear a second image other than the first image; a second image forming device configured to form the second image on the second image bearer; a direct transfer device configured to directly transfer the second image from the second image bearer onto the printing medium at a direct transfer position; and a second belt unit rotatably suspended by at least two second rollers and configured to carry and convey the printing medium through the direct transfer position and the secondary transfer position, and a conveyance roller rotatably contacting one of the front surface of the first belt unit and the second image bearer and configured to convey the printing medium through the direct transfer position and the secondary transfer position, wherein a size of an interval between the direct transfer position and the secondary transfer position is a multiple of a circumference of one of the at least two second rollers causing a velocity of the second belt unit and the conveyance roller to fluctuate, and the multiple is obtained by multiplying the circumference of the one of the at least two second rollers by a prescribed natural number.