Patent ID: 8818219

Claim:
An image forming apparatus, comprising: a developer containing part to contain a two-component developer including a toner and a carrier; a developer mixer that is provided in the developer containing part, agitates the two-component developer and charges the toner and the carrier; a mixer drive motor to drive the developer mixer; a magnetic sleeve that is provided in the developer containing part and supplies the charged toner to an oppositely arranged photoreceptor; a sleeve drive motor to drive the magnetic sleeve; a mixer rotation speed determination part to determine a mixer rotation speed of the mixer drive motor according to a supply amount of the toner supplied to the developer containing part from a toner cartridge by driving of a toner supply motor; a motor drive controller that independently performs rotation control of the sleeve drive motor and the mixer drive motor, and rotates and controls the mixer drive motor at the mixer rotation speed determined by the mixer rotation speed determination part; and printing ratio calculation part to count the number of pixels per unit number of printed sheets and to calculate a printing ratio, wherein the mixer rotation speed determination part calculates the supply amount of the toner according to the printing ratio calculated by the printing ratio calculation part, and determines the mixer rotation speed of the mixer drive motor.