Patent ID: 8831452

Claim:
An image forming apparatus comprising: a photosensitive member; a charging member configured to charge said photosensitive member; an exposure member configured to expose to light said photosensitive member to form an electrostatic latent image; a developing member configured to develop the electrostatic latent image into a toner image, the toner image being developed to an area of an image portion potential and not being developed to an area of a non-image portion potential; a transfer roller configured to form a transfer portion at which the toner image to be transferred onto a recording material is transferred from said photosensitive member onto a transfer belt; a power supply configured to apply a transfer voltage to be applied to said transfer roller so that a current passing through said transfer roller is constant; a voltage detecting member configured to detect the transfer voltage applied to said transfer roller; a test mode executing portion configured to execute an operation in a test mode in which the toner image does not pass through the transfer portion, the power supply passes a predetermined current through the transfer roller to detect a voltage by said voltage detecting member; and an image formation executing portion configured to execute an image forming operation in an image forming mode in which the toner image to be transferred onto the recording material passes through the transfer portion, wherein an absolute value of the current passing through said transfer roller during the image forming mode is set to a smaller value when a ratio of a potential difference between the image portion potential and the transfer voltage detected in the operation in the test mode by said voltage detecting member to a potential difference between the non-image portion potential and the transfer voltage detected in the operation in the test mode by said voltage detecting member is a larger value that exceeds a desired value.