| 摘要 |
PURPOSE:To realize stable toner concentration control in any copying mode by respectively providing developer concentration detecting means at both ends in a thrust direction in a developer container and controlling the concentration of two-component developer based on the detection output of at least one of the detecting means. CONSTITUTION:Toner concentration detecting means are installed at two spots in the thrust direction in the developer container. Namely, the toner concentration detecting means(sensor) 7a on this side and a sensor 7b on the inside are installed in a developer returning member 1. Since the toner concentration of the developer in a stirring chamber 17 is reflected in the sensor 7b on the inside and the toner concentration obtained by consuming the toner in a developing chamber 16 is reflected in the sensor 7a on this side, the toner concentration value shown by the sensor 7b is higher. By utilizing such characteristic, the detection output showing the excessive supply of the toner is detected also by the sensor 7b. Thus, the excessive supply of the toner is detected at an early stage in comparison with the conventional device, and the overshooting of the toner concentration control is eliminated. |
