| 摘要 |
PURPOSE:To stabilize the detection output of a sensor by arranging the sensor, which detects the density of a developer, a certain gap apart from a sleeve so that this sensor faces the part between magnetic poles especially and keeping alwyas the quantity of the developer passing the sensor constant. CONSTITUTION:A sensor 20 which detects the toner concentration of a developer 2 is arranged to face the part betwen pones S1 and N2 of a magnet 11. This sensor 20 is attached to an upper cover 18 of a developing tank 19 and is attached a considerable length apart from a sleeve 10 so that the center of the sensor 20 coincides with the approximate middle between poles S1 and N2 of the magnet 11. If the sensor 20 detects that the toner concentration is lower than a reference value, a tone supply roll 8 is rotated to supply a toner 7 into the developing tank 19, and the supplied toner is agitated sufficiently with the developer 2 by an agitating roll 4 and is sent to a developing roll 3. Thus, the toner concentration of the developer is raised gradually; and when the sensor 20 detects that the toner concentration is a certain value, the rotation of the toner supply roll 8 is stoped to stop the supply of the toner. |
