| 摘要 |
PURPOSE:To eliminate measurement errors owing to fluctuations of developer volume and perform accurate detection of toner concentation by letting the developer to be measured flow down in constant volume at a constant rate through a discharge port of a small diameter. CONSTITUTION:The developer 2 having developed electrostatic latent images by making contact to the surface of a photosensitive drum 12 is scraped off by a scraping plate 13 and is recovered into a developer vessel 1. Part of the developer enters the sensor part 14 of a toner concentation detector and flows down therein in constant volume at a constant rate and is then recovered in the developer vessel 1. Arrangement is so made that the oscillation fequency of an oscillating circuit 18 changes with the levels of the toner concentrations passing the sensor part 14, by which a driving circuit 21 is operated to control the toner replenishment from a toner replenishing device 22 to the developer vessel 1. |
