| 摘要 |
PROBLEM TO BE SOLVED: To always obtain a stable high-quality image without fluctuating toner concentration in a developing device by the change of the linear velocity of a photoreceptor. SOLUTION: In this image forming device where the linear velocity of the photoreceptor (electrostatic latent image carrier) 1 is variable and the linear velocity of a developing roller 8 in the developing device 4 is changed over in accordance with the linear velocity of the photoreceptor 1 so as to keep the ratio of the linear velocity of the roller 8 to that of the photoreceptor 1 constant, the toner concentration in the device 4 is detected by a toner concentration detection means (magnetic permeability sensor) 9 and the detected value is compared with a threshold so as to control the toner concentration in the device 4, and the threshold to the detected value by the detection means 9 is changed in accordance with the change of the linear velocity of the photoreceptor 1. |
