| 摘要 |
PROBLEM TO BE SOLVED: To prevent a developer from being mixed from developing devices except one carrying out development by allowing a holding magnetic force and confining magnetic force between a fixed magnet roller and a movable magnet roller to completely intercept the horizontal magnetic force of the fixed magnet roller during bristle cutting. SOLUTION: After development, a rotary magnet 23 rotates and the S pole of it tops at an angle of 0 deg. in the position of a blade. At this time, between the S pole of the rotary magnet 23 and a first pole of a rotary sleeve 21, a magnetic shield by a repelling magnetic field is generated, so that developer on the rotary sleeve 21 is separated into a portion situated on the side of a developing position A and a portion situated further inside than the position of the blade with the magnetic field as a border between them. After the separation, a confining magnetic force from the S pole of the movable magnet 23 to a second pole of the rotary sleeve 21 is generated at the same time, and the developer further inside than the position of the blade is consequently confined between both the poles. Thus, because the shielding magnetic force and confining magnetic force intercept lines of the magnetic force between the second pole and first pole of the rotary sleeve 21, the developer is not carried on the rotary sleeve 21.
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