| 摘要 |
PURPOSE:To correctly detect the residual amount of the developer by providing a light emitting element and a photodetector within the range where the magnetic force of a magnet acts from the developing sleeve surface, near the opening part of a hopper for supplying developing powder to the developing sleeve. CONSTITUTION:The developing powder 6 in a hopper 5 is supplied from the opening part 5a in the lower part of a hopper 5 onto the developing sleeve surface. The developing powder 6 is attracted on the rotating sleeve by the magnetic force of the magnet 2 in the sleeve 1, and the amount of its pickup is regulated by the tip of a partition plate 3a. The developing powder on the sleeve 1 contacts the photosensitive drum surface in the position where the sleeve 1 approaches the nearest the photosensitive drum 4, thereby developing the electrostatic latent image on the photoreceptor. When the developing powder 6 in the hopper decreases gradually upon repetition of development, the developing powder which had fallen in the recess 3c of the back plate 3b is swept to the sleeve side by the magnetic force of the approaching magnetic pole and the quantity of the light from the light emitting element 9 crossing this recess increases as well and is captured as a change in current by the photodetector 9, whereby the residual amount of the developing powder is detected. |
