Image forming apparatus

First Embodiment

A schematic configuration of the image forming apparatus according to the present embodiment is illustrated in FIG. 1. According to the present embodiment, the image forming apparatus includes a drum-shaped electrophotographic photosensitive body, i.e. a photosensitive drum 1, acting as an image bearing member. The photosensitive drum 1 can be rotated by a drive unit.

A charge roller 2, an exposure unit 3, a rotary developing unit 4A and a cleaning blade 6 are placed around the photosensitive drum 1. A laser beam emitted from the exposure unit 3 is irradiated on the photosensitive drum 1.

The rotary developing unit 4A can rotate by supporting developing devices 4Y, 4M, 4C, and 4Bk containing yellow toner, magenta toner, cyan toner and black toner, respectively. The developing devices 4Y, 4M, 4C and 4Bk have the same internal configuration. Thus, names of the developing devices are not distinguished and will be referred to as the developing device(s) 4 when the tonners con