Patent ID: 8238773

Claim:
An image forming apparatus comprising: an image carrier on which a toner image is formed; an intermediate transfer member onto which the toner image formed on the image carrier is transferred; a primary transfer member disposed facing the image carrier via the intermediate transfer member, to transfer the toner image formed on the image carrier onto the intermediate transfer member; a power supply unit, operatively connected to the primary transfer member, to form a primary-transfer electric-field between the image carrier and the primary transfer member by applying a primary transfer current to the primary transfer member by performing constant-current control; and to detect a change in a primary transfer voltage in a sub-scanning direction that is applied to the primary transfer member from the power supply unit in the sub-scanning direction; a conductive member to sandwich a recording medium with the intermediate transfer member; a secondary transfer member, disposed facing the conductive member via the intermediate transfer member, to transfer the toner image formed on the intermediate transfer member onto the recording medium; a secondary-transfer electric-field forming member to form a secondary-transfer electric-field between the conductive member and the secondary transfer member and apply a secondary transfer current to the secondary transfer member or the conductive member; and a control device, operatively connected to the secondary-transfer electric-field forming member, to control the secondary transfer current applied to the secondary transfer member or the conductive member in accordance with the change in the primary transfer voltage in the sub-scanning direction detected by the power supply unit.