| 摘要 |
PURPOSE:To keep the picture quality at high quality through detection of the drop of concentration of only the toner contributing to the development and simultaneous detection of the degree of deterioration of the developer, by detecting the concentration of the developer in a wet type electrophotographic device between the electrodes for electrophoresis. CONSTITUTION:Electrodes 4a, 4b are opposedly provided across the flow of the developer. When an electric field is applied to the flow by means of these electrodes, the toner charged negatively is attracted by the positive electrode 4b to migrate. As a result, a difference is caused between the concentration detected by an upstream side detector 4c and that detected by a downstream side detector 4d. This concentration difference represents the degree of deterioration of the developer. By feeding the concentration difference found by the detector 4 into a comparator circuit 7 and operating a toner supply solenoid 6 depending on the output from the circuit 7, a constant picture image concentration may be always obtained. Since the rate of the toner not charged, i.e., the deterioration of the developer, is also detected at the same time, unevenness of picture image may be prevented, so that the picture quality may be maintained favorably. |
