Patent ID: 8391756
Filing Date: 2013-03-05
Classification: G03G

Abstract:
1. An image forming apparatus comprising: a first intermediate transfer belt configured to carry a toner image; a first primary transfer unit configured to transfer a toner image from a first image forming unit configured to form a toner image to the first intermediate transfer belt; a second primary transfer unit arranged more downstream than the first primary transfer unit in a moving direction of the first intermediate transfer belt and configured to transfer a toner image from a second image forming unit configured to form a toner image to the first intermediate transfer belt; a second intermediate transfer belt configured to carry a toner image; a third primary transfer unit configured to transfer a toner image from a third image forming unit configured to form a toner image to the second intermediate transfer belt; a fourth primary transfer unit arranged more downstream than the third primary transfer unit in a moving direction of the second intermediate transfer belt and configured to transfer a toner image from a fourth image forming unit configured to form a toner image to the second intermediate transfer belt; a secondary transfer unit configured to transfer the toner image from the first intermediate transfer belt to the second intermediate transfer belt such that the toner image formed on the first intermediate transfer belt is superposed on the toner image formed on the second intermediate transfer belt; a tertiary transfer unit configured to collectively transfer toner images on the second intermediate transfer belt that has passed the secondary transfer unit from the second intermediate transfer belt onto a recording medium; a first drive roller configured to drive the first intermediate transfer belt, a perimeter of the first drive roller being an integral division of a distance from the first primary transfer unit to the second primary transfer unit in a moving direction of the first intermediate transfer belt and an integral division of a distance from the second primary transfer unit to the secondary transfer unit in the moving direction of the first intermediate transfer belt; a second drive roller configured to drive the second intermediate transfer belt, a perimeter of the second drive roller being an integral division of a distance from the third primary transfer unit to the fourth primary transfer unit in a moving direction of the second intermediate transfer belt and an integral division of a distance from the fourth primary transfer unit to the secondary transfer unit in the moving direction of the second intermediate transfer belt and equal to the perimeter of the first drive roller; a first stretch roller configured to stretch the first intermediate transfer belt with the first drive roller, and a second stretch roller configured to form the secondary transfer unit; and a third stretch roller configured to stretch the second intermediate transfer belt with the second drive roller and form the tertiary transfer unit, and a fourth stretch roller configured to form the secondary transfer unit, wherein, on a plane perpendicular to a rotation axis of the first drive roller, the first primary transfer unit is arranged at a position opposed to a first side of the first intermediate transfer belt stretched by the first stretch roller and the first drive roller, and the second primary transfer unit is arranged at a position opposed to a second side of the first intermediate transfer belt stretched by the first drive roller and the second stretch roller, and wherein, on a plane perpendicular to a rotation axis of the second drive roller, the third primary transfer unit is arranged at a position opposed to a third side of the second intermediate transfer belt stretched by the third stretch roller and the second drive roller, and the fourth primary transfer unit is arranged at a position opposed to a fourth side of the second intermediate transfer belt stretched by the second drive roller and the fourth stretch roller.