Image forming apparatus

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;
• a driving roller configured to move the intermediate transfer belt and arranged downstream to all primary transfer nip portions and upstream of the secondary transfer nip portion in a moving direction of the intermediate transfer belt;
• and
• a speed control unit configured to control a conveying speed of the transferring material,
• wherein the speed control unit is capable of controlling a loop amount of a loop of the transferring material at a position between the secondary transfer nip portion and the fixing nip portion, and
• wherein, when a first loop amount is created in a case where a primary transfer portion is defined only by a primary transfer member facing a most downstream image bearing member in the moving direction of the intermediate transfer member and a second loop amount is created in a case where primary transfer nip portions are defined by all of the image bearing members and all of the primary transfer members, the first loop amount is larger than the second loop amount.