Color image forming apparatus comprising a regular mode and a high speed mode

摘要

PCT No. PCT/JP97/03349 Sec. 371 Date Mar. 19, 1998 Sec. 102(e) Date Mar. 19, 1998 PCT Filed Sep. 22, 1997 PCT Pub. No. WO98/13732 PCT Pub. Date Apr. 2, 1998In a color image forming apparatus, a plurality of image forming units 3Y, 3M, 3C and 3K, which correspond to a plurality of colors and with each unit including a developing device and a photosensitive drum, are retained so as to define a cylinder. The color image forming apparatus includes: a conveying apparatus for conveying the plurality of image forming units around the main axis of the cylinder between an image forming position and a waiting position by simultaneously rotating all image forming units; an exposing device 6 for exposure of the photosensitive drum of the image forming unit that is in the image forming position 10; a transfer apparatus 5, which contacts a transfer belt 50 with the photosensitive drum 30 of the image forming unit that is in the image forming position, and when the image forming unit that is in the image forming position is switched, successively transcribes the toner images of all colors formed on the photosensitive drums onto the transfer belt, superimposes the toner images of all colors and forms a colored toner image on the transfer belt; and a transfer belt driving apparatus for driving the transfer belt at a constant speed. When a second color image is formed after a first color image, the first toner image color of the second color image is formed on the transfer belt by using the image forming unit of the last color added to the first color image. The exposing device includes a light source accommodated by the inner portion of the cylinder defined by the image forming units.