A developing device unit has a developing device unit main body which rotates about a rotary shaft. Plural developing devices are disposed on the developing device unit main body. The developing devices respectively have developing device main bodies, and developing agent cartridges containing four color developing agents are respectively loaded into the developing device main bodies. The developing agent cartridges are attached/detached in a direction substantially tangential to the rotating direction of the developing device unit main body when a grip section is gripped and operated by the operator in the case where the developing agent cartridges are at a location substantially opposite an image carrier with respect to the rotary shaft.

The present invention provides a highly-reliable image-forming apparatus. The image-forming apparatus includes an image carrier and a plurality of holders. A latent image is formed on the image carrier. The plurality of holders detachably hold a plurality of developing devices. The developing devices develop the latent image formed on the image carrier with toner of differing colors. The image carrier includes inspecting device capable of performing an inspection of whether or not the developing device is attached to the holder, and a nonvolatile rewritable storage region which stores detachment data for the developing device.

A replaceable developer roller apparatus is disclosed for a printing device. The apparatus includes a cylindrical developer roller having two opposed ends, and a drive assembly selectively and operatively engageable with one of the opposed ends of the developer roller. The drive assembly includes a shaft having two opposed regions; a gear rotationally fixed to one of the opposed regions of the shaft; and a drive member rotationally fixed to the other of the opposed regions of the shaft, and selectively, axially moveable between an engagement position and a disengagement position. A spindle assembly is engageable with the other of the opposed ends of the developer roller. The spindle assembly includes a spindle assembly shaft and an alignment member rotationally fixed to the spindle assembly shaft.

Provided are a developer cartridge and a developing apparatus using the developer cartridge, the developer cartridge making it possible to set the amount of developers that can be received to be large even when used in a miniaturized developing device and simplify the mechanism for opening/closing a supply outlet of the developer cartridge. As a result, the developer cartridge has no wasted space and thus can be miniaturized. In order to attain the above, the present invention provides a developer cartridge including a developer receiving portion that receives a new developer and has a section formed to have a shape that occupies a substantially entire space that is allocated to the developer cartridge to be attached.

A cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes a developing member for developing an electrostatic latent image formed on an electrophotografic photosensitive member, a developer accommodating portion for accommododating a developer to be used for developing an electrostatic latent image by the developing member, a cartridge locking portion for locking the cartridge with a main assembly locking portion provided in the main assembly of the apparatus to prevent the cartridge from disengaging from the main assembly of the apparatus when the cartridge is mounted to the main assembly of the apparatus, and a relasing member for releasing the cartridge locking portion to release the cartridge from the main assembly locking portion when the cartridge is to be removed from the main assembly of the apparatus.