Development apparatus having a plurality of rolls rotated at particular speeds

摘要

The present invention provides a development apparatus capable of improving the development pole of a plurality of development rolls and the rotation speed thereof, thus obtaining stable printing quality. A first development roll rotatable in the opposite direction to the moving direction of photosensitive body is disposed in the upstream of it, whereas a group of second development rolls are disposed in the down stream, which development rolls are rotatable in the same direction as the moving direction of photoconductive body and have magnets of the same polarity. The first development roll and the photoconductive body define a peripheral speed ratio ranging from 0.5 to 1.5, while allowing the second development roll and the photoconductive body to define a peripheral speed ratio ranging from 0.6 to 1.5. A development control member is provided between the first development roll and the group of second development rolls. A toner density detector is provided in the downstream of the last one of the group of second development rolls which is disposed in the most significant downstream. A cross mixer and a carrier member are also provided under the first development roll and the group of second development rolls.