| 摘要 |
PURPOSE:To perform good-quality copying which does not form any solid black image in the margin part of recording paper other than normal sizes by controlling the change-over period of developing bias and cleaning bias to be impressed to a developing electrode according to the sizes of recording paper. CONSTITUTION:The recording paper size detected with a recording paper size detector 1 is stored in a memory device 2. The stored content and the image size corresponding to a scale-down magnification CM by a normal size deciding circuit 4 are compared by a comparator 5, and when the margin part of recording paper is calculated, a switch circuit 3 is controlled based on the result of the operation. According to the size of the recording paper, the periods of impression of the developing bias and cleaning bias in the developing device part are controlled, and the developing bias is impressed to the developing electrode until the trailing end part of the recording paper passes the developing electrode. Hence, no solid black images are formed in the margin part of the recording paper, and the copying of good quality in which the margin is left as it is is carried out. |
