Image forming apparatus that searches for toner cartridges in need of replacement

摘要

In an image forming apparatus, a rotary developing device or revolver has a plurality of developing sections each storing a developer of particular color thereinside. The revolver is rotatable to sequentially move the developing sections to a preselected developing position so as to develop toner images sequentially formed on an image carrier. Toner cartridges are each removably mounted to the respective developing section. Only one of the cartridges located at a preselected replacing position can be pulled out and replaced. A toner cartridge is prevented from being accidentally mounted to the developing section located at the replacing position and whose cartridge has already been replaced.