| 摘要 |
PURPOSE:To prevent the inclusion of a floating toner into a casing and prevent detection errors by providng a magnetic member around the opening communicating with a developing device, forming a magnetic brush on the surface of said magnetic member and sealing the clearance between the opening and a probe. CONSTITUTION:A probe 16 consisting of a non magnetic member of aluminum or the like is provided freely rotatably within the casing 14 of a density detecting part 13, and a sealing member 31 is provided around an opening 12 which is the conducting part between the casing 14 and a developing device 11, and further a permanent magnet 32 is provided thereon. When the probe 16 slidingly contacts with a magnetic brush 17 formed by a magnetic roller 10 during developing, the toner sticks electrostatically on the probe 16. The developer 18 attracted to the magnet 32 forms a magnetic brushlike seal 33 on the magnet 32, thereby closing the gap between the probe 16 and the magnet 32. Thereby, the floating toner 30 in the device 11 is confined within the seal 33, and will not enter the inside of the casing 14, hence a detecting means 20 is prevented from being stained. |
