| 摘要 |
PURPOSE:To increase the surface magnetic force and improve the developing agent carrying force of a developing member so as to obtain a sufficient magnetic force with the developing member even if the member is small in size, by providing a cylindrical body, magnetic field generating means positioned in the cylindrical body, means which supports the cylindrical body and magnetic field generating means under a condition where they can rotate relatively to each other, and magnetic fluid enclosed between the cylindrical body and magnetic field generating means. CONSTITUTION:Bearings 55 are housed in both ends of a cylindrical developing sleeve 1 made of a magnetic substance, namely, cylindrical body and the rotary shaft 6 which is made integrally with a magnet roller 2 of a magnetism generating means housed in developing sleeve 1 is inserted in the sealed bearings 5. Therefore, the developing sleeve 1 and magnet roller 2 can rotate against each other. A magnetic fluid 3 is put in the space between the sleeve 1 and roller 2 at regular intervals in the circumferential direction over the full length of the roller. The locations where the magnetic fluid 3 is put are the ones where the densities of the magnetic fluxes of magnets 7 and 8 are large and magnetic poles of the magnets 7 and 8 exist. In the spaces 9 between the magnetic fluids 3, where densities of magnetic fluxes are small, a nonmagnetic substance 4 having a smaller magnetic permeability than the magnetic fluid has, such as air, silicon compound, etc., is enclosed.
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