| 摘要 |
PROBLEM TO BE SOLVED: To quicken a use interruption time by reducing the ratio of UCR in accordance with the residual amount of black developer. SOLUTION: Photoreceptor drums 1BK, 1Y, 1M and 1C for respective colors black, yellow, magenta and cyan are driven by a driving means, and uniformly electrified to specified potential by roller electrifiers 2BK, 2Y, 2M and 2C. The photoreceptor drum is scanned with light by a signal in accordance with an image pattern in each color conducted to a desired input image 4 by a toner image conducting part 31 so as to form a latent image by exposure devices 5BK, 5Y, 5M and 5C and the toner image on the photoreceptor drum is developed by a developing device. A K toner residual amount detection part 11 detects that the residual amount of the black developer becomes the specified one of several stages. The conducting part 31 sets the ratio of UCR in accordance with the residual amount detected by the detection part 11. |
