| 摘要 |
PURPOSE:To improve the controlling accuracy of toner concentration and to maintain stable picture density by using toner charged by a specific quantity when the toner is mixed with carrier in a fixed vessel and continuously agitated. CONSTITUTION:A developer 9 reaching a position free from influence of a magnetic field of a magnet roll 4 is dropped so as to be crumbled down in contact with the surface of a detecting sensor 8 and branched into two developer flows one of which is carried to a regulating member 7 and the other is dropped as it is. When the toner concentration in the developer 9 is comparatively high, the fluidity of the falling developer 9 is low, the contact resistance with the detecting surface of the detecting sensor 8 is high and the detecting signal of the sensor 8 remain on. When the toner concentration is reduced after repeating the developing cycle, the fluidity of the developer 9 becomes high and the detecting signal of the sensor 8 is turned off. The feeding operation of the toner 11 based upon a feed roll 10 is started by the OFF signal and stopped by the ON signal, so that the toner concentration in the developer 9 can be kept at a fixed level. |
