Patent ID: 8165484

Claim:
An image forming apparatus comprising: a belt member; a first image bearing member; a first transfer member configured to transfer a toner image from the first image bearing member to the belt member; a second image bearing member; a second transfer member configured to transfer a toner image from the second image bearing member to the belt member; a first sensing portion configured to sense a current passing through the first transfer member when a voltage is applied to the first transfer member; a second sensing portion configured to sense a current passing through the second transfer member when a voltage is applied to the second transfer member; and a controller configured to execute a first mode in which an image can be formed when the belt member is in contact with the first and second image bearing members and a second mode in which an image can be formed when the belt member is separated from the first image bearing member and is in contact with the second image bearing member, the controller further configured to set a voltage to be applied to the first transfer member during execution of the first mode based on an output of the second sensing portion during execution of the second mode.