| 摘要 |
PURPOSE:To stabilize image formation using high resistivity magnetic toner both in normal and reversal development and to prevent uneven density or the like, by changing the gap between a developing sleeve surface and a photreceptor surface at the times of normal development and reversal development. CONSTITUTION:Development gap control disc 7 larger by h1 than the inside radius of photoreceptor 3 is fixed to the driving shaft of receptor 3 in order to control the gap between the surface of developing sleeve 1 having magnetic roller 2 and the surface of receptor 3. Developing sleeve 1 is provided with gap control cam 6 and magnetic brush height control plate 8, energized to be pressed in the direction (g). Cam 6 is fixed so as not to rotate in developing, but at the time of change-over of normal development and reversal development, cam 6 is turned by 180 deg. in synchronism to developing bias change-over switch 4 to make the gap h1+h2 and the brush height h3, thus permitting the gap and the height to become smaller (h1+h2), (h3) in the normal development using a magnetic toner of 10<12>-1013OMEGA.cm resistivity, and both to be made larger in the reversal development, and good copy images to be formed in both the development. |
