| 摘要 |
PURPOSE:To detect the concentration of a toner at high responsiveness by providing a magnetic shield plate within an extent to which a magnetic field caused by a magnet extends between a cylindrical sleeve and a toner concentration detector. CONSTITUTION:A block 3 of magnet is fixed to form odd numbers, for instance 3, of magnetic poles at the inside of the cylindrical rotary sleeve 1, and adjoining magnetic poles 2 are made reverse to each other. That is, N poles and S poles are arranged to face the inner face of the rotary sleeve 1 alternately. The magnetic shield plate 9 is placed between the rotary sleeve 1 and toner concentration detector 8 below a separator 7 and within the reach of a magnetic field caused by the magnet. Consequently, influences of magnetic flux hardly occur within an extent in which the toner that completed developing flows to the toner concentration detector 8 by the nonmagnetic separator 7. Accordingly, by interposition of the magnetic shield plate 9, the toner concentration detector 8 can be brought close to the rotary sleeve 1. |
