IMAGE FORMING APPARATUS CONTROLLING LIGHT EXPOSURE BASED ON APPLIED BIAS

摘要

When a toner image formed on the surface of a photosensitive drum is transferred onto an intermediate transfer belt, a transfer bias is applied to a primary transfer portion. When a patch formed in an upstream image forming station and transferred onto the intermediate transfer belt and a patch formed on the surface of the photosensitive drum pass through the primary transfer portion, a passing bias different from the transfer bias is applied to the primary transfer portion. A control section controls a laser beam scanner as an exposure member not to expose the surface of the photosensitive drum to which the passing bias is applied.

主权项

1. An image forming apparatus comprising:
a rotating intermediate transfer member; a first image forming unit and a second image forming unit lined up in the rotational direction of the intermediate transfer member, wherein the second image forming unit is arranged downstream of the first image forming unit in the rotational direction of the intermediate transfer member, and each of the first image forming unit and the second image forming unit includes a rotating photosensitive member, a charging member for charging a surface of the photosensitive member, an exposure member for exposing the charged photosensitive member to form an electrostatic latent image, a developing member for developing, with toner, the electrostatic latent image formed on the surface of the photosensitive member, and a transfer member for transferring a toner image formed on the surface of the photosensitive member onto the intermediate transfer member at a transfer portion; a first detection member arranged downstream of the first image forming unit and the second image forming unit in the rotational direction of the intermediate transfer member to detect an adjusting toner image formed on the surface of the intermediate transfer member; a second detection member provided in the second image forming unit to detect an adjusting toner image formed on the surface of the photosensitive member in the second image forming unit; a bias application member for applying a transfer bias to the transfer member of the second image forming unit when the toner image formed on the surface of the photosensitive member in the second image forming unit is transferred onto the intermediate transfer member, and applying a passing bias different from the transfer bias to the transfer member of the second image forming unit when a first adjusting toner image formed in the first image forming unit and transferred onto the intermediate transfer member and a second adjusting toner image formed on the surface of the photosensitive member in the second image forming unit passes through the transfer portion of the second image forming unit; and a control portion for controlling the exposure member in the second image forming unit to expose a region except for a region of the photosensitive member passing through the transfer portion in a condition that the passing bias is applied.