Patent ID: 8099032

Claim:
An image forming apparatus comprising: an image carrier configured to carry a toner image on a surface thereof; an endless belt member configured to move while being wound around plural belt support members and to form a transfer nip by having a front surface thereof contact the image carrier; and a transfer roller configured to be rotated while contacting a back surface of the endless belt member at a region corresponding to the transfer nip, and to receive a transfer bias, wherein: at the transfer nip, the toner image on the image carrier is transferred onto the front surface of the endless belt member or onto a recording material held by the endless belt member; the transfer roller is made of metal, and is configured to slidably rotate in bearings supporting a shaft of the transfer roller; and F 1 >F 3 and F 2 >F 4 are satisfied, where F 1 is a maximum static friction between the transfer roller and the endless belt member, F 2 is a dynamic friction between the transfer roller and the endless belt member, F 3 is a maximum static friction between the shaft of the transfer roller and slide parts of the bearings in which the shaft slidably rotates, and F 4 is a dynamic friction between the shaft of the transfer roller and the slide parts of the bearings in which the shaft slidably rotates, wherein: end members having a higher friction coefficient than that of a surface of the transfer roller are provided at end portions of the transfer roller.