| 摘要 |
PURPOSE:To shield a toner concentration detecting part from a magnetic field, by providing a magnetic shielding member which has combined >=2 platelike magnetic substances through a nonmagnetic substance, between a magnetic roll and the toner concentration detecting part. CONSTITUTION:A magnetic shielding member 5 formed by combining a platelike magnetic substance 51 and 53 through a nonmagnetic substance 52 is placed between a magnetic roll and a toner concentration detecting part. When a sleeve 10 is turned clockwise, a developer scraped by a doctor 2 flows down through on a guide plate 3, and its concentration is detected by a sensor 4. According to this constitution, since the shielding member 5 is provided, lines of magnetic force of magnets 11, 12 are led into the magnetic substance 51, the line of magnetic force of the magnetic substance 51 is led into the magnetic substance 53, and the line of magnetic force of the magnetic substance 53 enters the sensor partially, but it is weakened enough. In this way, the magnetic field does not operate on the detecting part substantially, and the toner concentration is detected exactly. |
