Patent ID: 7177569

Claim:
An image forming apparatus, comprising: an endless belt configured to be rotatably driven; a plurality of image carriers disposed in a moving direction of the endless belt; a plurality of charging units, a charging unit provided for each image carrier of the plurality of image carriers and configured to uniformly charge a surface of an associated image carrier; a plurality of exposing units, each exposing unit configured to expose an associated image carrier of the plurality of image carriers charged by the associated charging unit to form an electrostatic latent image on each image carrier of the plurality of image carriers; and a plurality of developing units, a developing unit provided for each image carrier of the plurality of image carriers and configured to develop the electrostatic latent image on an associated image carrier with a developer of different color to form a developer image, wherein the endless belt is configured to transfer the developer image formed on each image carrier of the plurality of image carriers to form a color image, the developing unit provided at a most upstream position with respect to the moving direction of the endless belt forms the developer image with a developer of black color, and the each developing unit is configured to be separable from the associated image carrier and detachable from the image forming apparatus, each developing unit comprising a developer supplying unit disposed to be in contact with a developer carrier and supplies onto the developer carrier while charging the developer, and the developer of black color contains more charge control agent than developers of other colors so that the developer of black color is more chargeable than the developers of other colors.