JPS5929870B

PURPOSE:To make the developing device of easy developer changing smaller and lighter by forming the permanent magnetic poles for developer conveying by the specific magnets and making the magnetic fluz densities of a rotary sleeve at the specific values thereby achieving the reduction in the friction force by the developer. CONSTITUTION:A magnetic brush ear end length defining member 33 of a crest shape is made removable from the bottom face of a housing 30 and the exchanging of the developer is readily accomplished. The magnetic flux density produced by the magnetic polse for conveying the developer by isotropic barium ferrite magnets or plastic magnets 23, 21, 24, 25 comprising dispersing magnetic powder in synthetic resins becomes smaller than the magnetic flux density produced when the anisotropic magnet 22 formed to the non-magnetic revolving sleeve 20 opposing to said member 33 is let magnetic pole for developing electrostatic latent images. By this small density magnetic flux, the friction force by the developer between the sleeve 20 and the bottom of the housing 30 is reduced and the sleeve 20 may be revolved at small torgue, thus the developing device may be made smaller and lighter.