Abstract: An image forming apparatus includes a belt conveyance device that corrects leaning of an endless belt member, the belt conveyance device being detachably attachable to an apparatus body of the image forming apparatus; a first guiding portion that supports a first guided portion provided in a frame member supporting rotatably a first roller on which the belt member is laid under tension and guides the belt conveyance device being attached to or detached from the apparatus body; and a second guiding portion that supports a second guided portion provided in a steering unit supporting rotatably a second roller on which the belt member is laid under tension, releases the second guided portion at an attachment position of the belt conveyance device to the apparatus body, and guides the belt conveyance device being attached to or detached from the apparatus body.

Abstract: A cartridge unit includes a first drum cartridge, a first cover member, a stopper, and a first cover erroneous insertion blocking portion. The first cover member is removably attached with the first drum cartridge and configured to be compatible in shape with a first holding portion of a first apparatus body so that the first cover member is guided and held by the first holding portion. The first cover erroneous insertion blocking portion is configured to permit the first cover member to be guided by the first holding portion by a first distance from a first insertion slot portion and to block a second cover member, which is removably attached with a second drum cartridge functionally different from the first drum cartridge, to be guided by the first holding portion in a range exceeding a second distance shorter than the first distance from the first insertion slot portion.

Abstract: A cartridge unit includes a first drum cartridge, a first cover member, a stopper, and a first cover erroneous insertion blocking portion. The first cover member is removably attached with the first drum cartridge and configured to be compatible in shape with a first holding portion of a first apparatus body so that the first cover member is guided and held by the first holding portion. The first cover erroneous insertion blocking portion is configured to permit the first cover member to be guided by the first holding portion by a first distance from a first insertion slot portion and to block a second cover member, which is removably attached with a second drum cartridge functionally different from the first drum cartridge, to be guided by the first holding portion in a range exceeding a second distance shorter than the first distance from the first insertion slot portion.

Abstract: An image forming apparatus includes: a belt conveyance device that corrects leaning of an endless belt member, the belt conveyance device being detachably attachable to an apparatus body of the image forming apparatus; a first guiding portion that supports a first guided portion provided in a frame member supporting rotatably a first roller on which the belt member is laid under tension and guides the belt conveyance device attached to or detached from the apparatus body; and a second guiding portion that supports a second guided portion provided in a steering unit supporting rotatably a second roller on which the belt member is laid under tension, releases the second guided portion at an attachment position of the belt conveyance device to the apparatus body, and guides the belt conveyance device attached to or detached from the apparatus body.