Patent ID: 9568854
Date: 2017-02-14
CPC Classifications: G03G

Claim:
1. An image forming apparatus comprising: an image bearing member disposed rotatably and configured to bear a latent image; a first developer bearing member disposed rotatably and bearing developer on its surface to develop the latent image formed on the image bearing member; a second developer bearing member disposed rotatably in a same direction as the first developer bearing member and disposed at a downstream side of the first developer bearing member in a rotary direction of the image bearing member to develop the latent image developed by the first developer bearing member; a power supply configured to apply a developing bias to the first developer bearing member and the second developer bearing member; and a controller configured to execute a control mode including both a first mode and a second mode to drive the first developer bearing member and the second developer bearing member during a non-image forming period, wherein the controller is configured to control a drive of the first developer bearing member and the second developer bearing member so that the first developer bearing member and the second developer bearing member are driven in the first mode and configured to control the developing bias and a potential of the image bearing member in the first mode so that a sign of a value of a DC component of the developing bias in the first mode minus a potential of the image bearing member in the first mode and a sign of a value of the DC component of the developing bias in an image forming period minus the potential of the image bearing member at a non-image forming area in the image forming period are the same, and so that a first potential difference between the DC component of the developing bias in the first mode and the potential of the image bearing member in the first mode is larger than a second potential difference between the DC component of the developing bias in the image forming period and the potential of the image bearing member at a non-image forming area in the image forming period, wherein the controller is configured to control a drive of the first developer bearing member and the second developer bearing member in the second mode so that the first developer bearing member rotates at a circumferential velocity faster than a circumferential velocity of the second developer bearing member, and the controller is configured to control a potential difference between the DC component of the developing bias in the second mode and a potential of the image bearing member in the second mode so as to be zero.