Patent ID: 8452200

Claim:
An image forming apparatus comprising: first and second photosensitive members which are arranged in a row, and are configured to form an electrostatic latent image thereon; an endless belt having a belt surface which faces the first and second photosensitive members and configured to rotate so that the belt surface moves in a traveling direction from the first photosensitive member to the second photosensitive member; first and second developing rollers configured to respectively supply, to the first and second photosensitive members, developer of different colors which is charged to a first polarity; first and second cleaning rollers provided so as to be adjacent respectively to the first and second photosensitive members for recovering developer adhering to the first and second photosensitive members; a separating mechanism configured to separate the second developing roller from the second photosensitive member; and a control unit configured to, if a single color printing is executed by the first developing roller, control the separating mechanism so as to separate the second developing roller from the second photosensitive member, wherein if a multi-color printing is executed, the control unit applies a cleaning bias whose polarity is a second polarity opposite to the first polarity and which holds a first electric potential to each of the first and second cleaning rollers, and wherein, if the single color printing is executed, the control unit executes a bias reduction control in which a cleaning bias applied to the second cleaning roller is given the second polarity and is made to hold a second electric potential whose absolute value is smaller than that of the first electric potential.