| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing device for a multi-color image forming device by which color mixture is prevented by surely preventing developer from coming through even by durable use for a long period. SOLUTION: This developing device is provided with a developing roller 2 by which developer is sucked and fed on a sleeve surface by rotating a hollow cylindrical sleeve 2a around the outer periphery of a magnetic roller 2b, a layer thickness regulating member 3 to regulate the thickness of the developer and a developer cutting off member 4 which is switchable to attach/detach to/from the sleeve surface and by which the sticking of the developer to the sleeve surface is stopped by abutting on the sleeve surface, and a magnetic pattern at a magnetic pole opposed to the developer cutting off member 4 is set so as to deteriorate the come-through property of the developer for the developer cutting off member 4. For instance, it is desirable that magnetic force in a normal direction is set to be a maximum value and that in a tangent direction is set to be a minimum value in the vicinity of a position opposed to the developer cutting off member 4. Also, it is desirable that the magnetic force in the normal direction is set to be the minimum value and that in the tangent direction is set to be the maximum in the vicinity of the position opposed to the layer thickness regulating member 3.
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