| 摘要 |
PURPOSE:To properly control image density by detecting the transition current value of a developer transited from a development device, and controlling an image formation condition, depending upon the result of the detection. CONSTITUTION:A development device 20 has a development sleeve 4 placed in such a way as facing a photosensitive drum 1 in a development vessel 7 containing toner T as a negatively charged unary nonmagnetic developer. The development sleeve 4 is made of a conductive material such as aluminum, and the surface thereof is roughened by sand blasting or the like. In this case, the rotation and exposure of the photosensitive drum 1 are turned on, with all supply voltage turned off, and the predetermined value of development bias is applied. When a development bias supply 6 is turned on, toner on the development sleeve 4 is developed on the drum 1 and toner current as drum transition current flows. The value of the current is detected by a current detection circuit 10 as a detection means, and an image formation condition is changed by an image formation condition control circuit 11, depending upon the current value. Image density is thereby adjusted automatically. |
