| 摘要 |
PURPOSE:To detect the density of a two-component developer surely with high accuracy and high reliability, by providing a toner weight detecting element so as to face a roll wherein a permanent magnet is used for a part of the outside circumferential surface. CONSTITUTION:A magnetic brush contacts a developer density sensor 9 before said brush contacts a photosensitive drum 1. A developer 3 in this stage is attracted by a permanent magnet 12 embedded in part of a roll 11 to form a magnetic brush. The magnetic brush rotates clockwise together with the roll 11 and contacts with a conductive member 13 applied with voltage on the roll 11. The toner in the electrostatically attracted carrier is attracted at this moment to the surface of the conductive member. When the voltage of a quartz oscillator 14 is applied, the natural frequency changes fe-f1 and since the (fe-f1) in this stage is proportional to the amt. of the attracted toner, the density of the developer is controlled in a specified range by controlling the same. |
