| 摘要 |
PURPOSE: To stably control the toner concentration by using part of a lower frame in a developing tank as the head section of a toner concentration sensor, and providing a means moving the coil section of the toner concentration sensor in parallel with the head section at the outside lower section of the developing tank. CONSTITUTION: A sensor coil section 35 installed at the bottom section of a developing tank is operated by a rotary motor 37 freely controlled for the rotating direction by a drive screw 36, and the sensor coil section 35 is operated in a range A-B. The toner concentration reference value of a sensor is set at the point C of the sensor of a developing device. The reciprocating motion of the sensor is made in the range A-B for each set number of copies or when a power source is turned on or off, the average value of the toner concentration level in the range A-B is calculated against the initially set reference value, and the toner concentration is controlled. |
