JPS54130134A - Developing bias control unit - Google Patents

Abstract

PURPOSE: To reduce unnecessary deposition of toner on photoreceptor and developing electrode and prevent bias leak, carrier deposition, etc. by fluctuating the developing bias voltage in correspondence to the surface potentials of the latent image regions on a photoreceptor after developing of latent images.

CONSTITUTION: The surface potential of a photoreceptor drum 1 is detected by a detecting part 7 immediately before the developing part and the developing bias voltage according to the detection value thereof is applied to the sleeve 13 of a developing device 3. At the developing of the latent images, a timing circuit 14 turns OFF a switch 12 and the constant developing bias voltage corresponding to the ground potential is applied from a bias power source 11 to a sleeve 13. Next, when developing of the latent images is completed, the timing circuit 14 turns ON a switch 15 and the bias power source 11 fluctuates the developing bias voltage according to the output of an analog delay line 10, thus minimizing the potential differences between the high potential and low potential portions outside the latent image regions on the photosensitive drum 1 and the developing electrode.

COPYRIGHT: (C)1979,JPO&Japio