Patent ID: 7773902

Claim:
An image forming apparatus comprising: an image bearing member which can rotate; a image forming unit which can form each color of toner image onto the image bearing member by means of different colors of toners having a negative polarity, the toner image to be formed on a recording material and a patch toner image for adjusting an image can be simultaneously formed on the image bearing member; a patch detecting unit which detects the patch toner image formed on the image bearing member; a controller which controls a toner image forming condition based on an output of the patch detecting unit; an intermediate transfer belt which bears the toner image transferred from the image bearing member; a transfer unit which forms a transfer portion transferring the toner image on the image bearing member onto the intermediate transfer belt; a voltage controller which controls a voltage to be applied to the transfer unit so that a first voltage is applied to the transfer unit when the toner image on the image bearing member is transferred onto the intermediate transfer belt and a second voltage that is lower than the first voltage is applied to the transfer unit when the patch toner image on the image bearing member passes through the transfer portion; and an executing unit which executes an adjusting mode by applying a first adjusting voltage to a first area to which the first voltage has been applied and applying a second adjusting voltage that is higher than the first adjusting voltage to a second area to which the second voltage has been applied while the intermediate transfer belt rotates once, the toner image to be formed on the recording material can be formed on a position which overlaps both the first area and the second area by the adjusting mode.