Patent ID: 8219019

Claim:
An image forming apparatus comprising: a rotatable intermediate transfer belt; a plurality of image bearing members arranged in a rotation direction of the intermediate transfer belt and configured to bear toner images; a plurality of primary transfer members respectively facing the plurality of image bearing members with the intermediate transfer belt interposed therebetween and being capable of defining primary transfer nip portions with the corresponding image bearing members facing the primary transfer members; a secondary transfer member configured to transfer the toner images transferred on the intermediate transfer belt by the primary transfer members onto a transferring material at a secondary transfer nip portion; a fixing portion configured to fix the toner images transferred by the secondary transfer member to the transferring material at a fixing nip portion; and a speed control unit configured to control a conveying speed of the transferring material at the secondary transfer nip portion and a conveying speed of the transferring material at the fixing nip portion, wherein a first image formation mode and a second image formation mode are executable, in the first image formation mode, image formation being performed while all of the image bearing members define the primary transfer nip portions with the corresponding primary transfer members respectively facing the image bearing members, in the second image formation mode, image formation being performed while at least one of the image bearing members does not define the primary transfer nip portion with the corresponding primary transfer member facing the image bearing member, and wherein the speed control unit controls the conveying speed of the transferring material at the secondary transfer nip portion and the conveying speed of the transferring material at the fixing nip portion such that a loop amount of a loop of the transferring material at a position between the secondary transfer nip portion and the fixing nip portion when the second image formation mode is executed is larger than a loop amount of a loop of the transferring material at the position between the secondary transfer nip portion and the fixing nip portion when the first image formation mode is executed.