Patent ID: 9715193
Date: 2017-07-25
CPC Classifications: G03G

Claim:
1. An image forming apparatus comprising: an image bearing member configured to bear a toner image; an intermediary transfer member configured to carry the toner image transferred from the image bearing member at a primary-transfer position; a transfer member provided contactable to an outer peripheral surface of the intermediary transfer member and configured to transfer the toner image from the intermediary transfer member onto a recording material at a secondary-transfer position; a constant-voltage element electrically connected between the intermediary transfer member and a ground potential and configured to form a predetermined voltage by passing of a current therethrough, said constant-voltage element comprising a Zener diode or a varistor; wherein the predetermined voltage is a breakdown voltage of the constant-voltage element, a power source to form both of a secondary transfer electric field at the secondary-transfer position and a primary-transfer electric field at the primary-transfer position by applying a voltage to the transfer member to pass the current through the constant-voltage element; a detecting portion configured to detect the current passing through the transfer member; an executing portion configured to execute a test mode in which a test voltage is applied to the transfer member by the power source to detect the current by the detecting portion when no recording material exists at the secondary-transfer position; and a controller configured to control a voltage to be applied to the transfer member by the power source when the recording material exists at the secondary-transfer position on the basis of the current detected by the detecting portion in the test mode, wherein the controller controls the test voltage applied by the power source so that the current passes through the constant-voltage element in a period of the test mode.