Patent ID: 8213846

Claim:
An image forming apparatus comprising: a first image bearing member which bears a toner image; a second image bearing member which bears a toner image; a rotatable belt member; a first transfer member which is arranged in an inner side of the belt member, presses the belt member so that the belt member makes contact with the first image bearing member, and transfers the toner image on the first image bearing member onto the belt member; a second transfer member which is arranged in an inner side of the belt member, presses the belt member so that the belt member makes contact with the second image bearing member, and transfers the toner image on the second image bearing member onto the belt member; a detection member which contacts an edge of an end of the belt member in a width direction thereof and detects a position of the belt member in the width direction thereof in a position downstream and adjacent to a contact position of the belt member with the second image bearing member in a rotation direction of the belt member; an adjustment mechanism which adjusts the position of the belt member in the width direction thereof based on an output of the detection member; an execution portion which executes a first image formation mode, where the belt member is in contact with the first image bearing member and the second image bearing member and an image is formed on the belt member by being transferred from the first and second image bearing members, and a second image formation mode, where the first transfer member is spaced from the belt member so that the belt member is spaced from the first image bearing member, and, at the same time, the belt member is in contact with the second image bearing member and so that an image is formed on the belt member by being transferred from the second image bearing member; and a pressing member which presses, from a side of the first image bearing member, an end of the belt member which is in a region moved from a position in the first image formation mode so that the belt member is spaced from the first image bearing member, at least in the second image formation mode.