Patent ID: 9134641
Filing Date: 2015-09-15
Classification: G03G

Abstract:
1. An image forming apparatus comprising: a plurality of image bearing members, provided in parallel with each other, each for forming a toner image; a transfer unit detachably mountable to a main assembly of said image forming apparatus and including a first intermediary transfer member and a second intermediary transfer member, wherein said first intermediary transfer member forms a primary transfer portion between itself and each of said plurality of image bearing members, wherein the toner images formed on said plurality of image bearing members are to be primary-transferred onto said first intermediary transfer member, and wherein the toner images are to be secondary-transferred from said first intermediary transfer member onto said second intermediary transfer member; a transfer member for tertiary-transferring the toner images from said second intermediary transfer member onto a recording material, wherein said first intermediary transfer member includes a rotatable belt and a plurality of stretching rollers for stretching the belt, wherein said transfer unit is mountable in and demountable from the main assembly with respect to a direction parallel to a rotational direction of the belt, and wherein said first intermediary transfer member and said second intermediary transfer member are arranged in a mounting and demounting direction of said transfer unit, and further comprising an apparatus main assembly frame forming the main assembly of said image forming apparatus, wherein said apparatus main assembly frame comprises a positioning portion for positioning said transfer unit relative to said apparatus main assembly, wherein said transfer unit comprises a transfer frame on both sides thereof with respect to a direction perpendicular to the rotational direction of the belt, and wherein the positioning portion is engageable with each of bearing portions of the stretching rollers and said second intermediary transfer member.