Patent ID: 6968145

Claim:
A rotary developing device comprising: a cylindrical rotary developing unit, a plurality of development members mounted around a periphery of said rotary developing unit, a rotary developing unit driving section for driving said rotary developing unit by a driving means, a driving power transmitting section for transmitting a driving power by said driving means to said development members at a developing position, a one-way clutch which is arranged between said driving means and the driving power transmitting section to couple or uncouple gears of a gear train, and a retaining means for retaining said rotary developing unit at a developing position, wherein: said rotary developing unit is driven by said driving means to bring one of said development members to the developing position facing a photoreceptor and subsequently the transmission of the driving power to said development member is conducted, in said driving power transmitting section, a driving direction of said development members is set to be the same as a driving direction of said rotary developing unit, and said retaining means retains said rotary developing unit at said developing position during a development member driving action and said driving means is energized to rotate in reverse at the end of the development member driving action and subsequently the retention of said rotary developing unit is cancelled.