Image Forming Apparatus

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 the 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, if a single color printing is executed by the first developing roller, to 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.