Patent ID: 7979006

Claim:
An image forming apparatus, comprising: a main body; an electrostatic latent image bearing member having a surface on which an electrostatic latent image is formed; a toner cartridge that contains toner; a developing member that supplies the toner from the toner cartridge onto the surface of the electrostatic latent image bearing member, thereby developing the electrostatic latent image into a toner image; a transfer member that transfers the toner image from the surface of the electrostatic latent image bearing member to a recording medium; a developing device, to which the toner cartridge is removably coupled and which incorporates the developing member; a circulating member configured to operate while the toner cartridge remains coupled to the developing device; a driving force output unit disposed in the main body to output a drive force; a first driving force input unit disposed on the toner cartridge and that is configured to receive the drive force and transmit the drive force to the circulating member; a second driving force input unit disposed on the developing device and that is configured to receive the drive force and transmit the drive force to the developing member; a switching unit that switches a transmission of the driving force outputted from the driving force output unit to either the first driving force input unit or both of the first driving force input unit and the second driving force input unit; and an operation control unit that operates the switching unit, wherein the circulating member comprises: an agitator provided in the toner cartridge and configured to supply the toner from the toner cartridge to the developing device and configured to agitate the toner in the toner cartridge; and a returning member provided in the developing device and configured to return the toner from the developing device into the toner cartridge, wherein the toner cartridge comprises a toner cartridge-side drive-force output unit that is configured to output the drive force inputted to the first drive-force input unit, to the returning member, wherein the developing member is a developing roller, and the developing device comprises the developing roller and a supplying roller that supplies the toner to the developing roller, and wherein, after the toner cartridge is coupled to the developing device, the operation control unit operates the switching unit to transmit the drive force to the first driving force input unit while not to transmit the drive force to the second driving force input unit, thereby mixing the toner remaining in the developing device and the toner supplied from the toner cartridge.