Patent ID: 7486901

Claim:
An image forming apparatus comprising: an image retainer; an electrostatic latent image forming unit that forms an electrostatic latent image on the image retainer; a developing unit that forms a toner image by developing the electrostatic image; an intermediate image transfer member; a primary image transfer unit that transfers the toner image on the image retainer to the intermediate image transfer member; a secondary image transfer unit that transfers the toner image on the intermediate image transfer member to a recording material; a toner density sensor that detects the density of the toner image on the intermediate image transfer member; a pre-transfer discharging unit having a scorotron charger including a discharging electrode and a grid electrode that discharges the intermediate image transfer member before the image transfer by the secondary image transfer unit, the grid electrode being provided opposite to the surface of the intermediate image transfer member with a gap and between the discharging electrode and the intermediate image transfer member, wherein a voltage with a polarity opposite to the potential on the toner image is applied to the discharging electrode, and a voltage with the same polarity as the potential on the toner image is applied to the grid electrode; and a control unit that controls a voltage applied to the discharging electrode; wherein a toner image is formed on the image retainer by the electrostatic latent image forming unit and the developing unit under prescribed conditions, the toner image is transferred to the intermediate image transfer member by the primary image transfer unit, the density of the toner image on the intermediate image transfer member is detected, and the control unit controls the voltage applied to the discharging electrode corresponding to toner charge obtained from a toner density of the toner image on the intermediate image transfer member after transferring by the secondary image transfer unit so that an electric potential of the toner image is set to a predetermined level.