Image forming apparatus having preset developer unit replacement positions and a locking device

摘要

An image forming apparatus where during the image forming operation, the completion of development by one of development cartridges is followed by the rotation of a rotary for setting the next development cartridge to a development position. The rotational speed v of the rotary is increased linearly to the maximum speed vmax and, after that, is decreased linearly to stop the rotary when the next development cartridge reaches the development position. During replacement of the development cartridge, the rotary is rotated to set the development cartridge to be replaced to the replacement position. The rotational speed of the rotary is set to be a constant speed v₁ in a region other than a contact region where an input gear of the development side is in contact with a driving gear of the fixed side and a speed lower than the speed v₁ in the contact region (the minimum speed v₂).