Patent ID: 7634216

Claim:
An image forming device, comprising: an image carrier configured to carry an electrostatic latent image; a rotary type developing unit having a plurality of developing machines being configured to store toner in the interior thereof and to develop the electrostatic latent image by providing toner on the image carrier; and a control unit being configured to execute a toner discharge process to discharge a portion of the toner in the interior of the at least one of the plurality of developing machines after rotating the developing unit during a time of not forming an image and after a single color image formation using only one of the plurality of developing machines, the control unit including a determination unit configured to determine whether the toner discharge process should be executed, and a discharge process execution unit configured to control the developing unit and to execute the toner discharge process; and a printing rate calculation unit configured to calculate the printing rates of images developed by one of the plurality of developing machines, the determination unit being configured to determine whether the toner discharge process should be executed based on the printing rate, and that the toner discharge process should be executed when the printing rate is equal to or less than a predetermined value.