PURPOSE: To enable stable formation of a thin layer consisting of only the developer on a sleeve by selecting and disposing a magnet in a developer holding member in such a way that the restraining force by the magnetic force is larger than the conveying force by friction thereby restraining magnetic particles.
CONSTITUTION: A magnet 13 having an N pole 17 and an S pole 22 is fixed in a developer holding member 12. A mixture composed of magnetic particles 16 and a nonmagnetic developer 15 is supplied onto the member 12. A fine annular layer 18 is formed by the magnetic brush made by a magnetic pole 17 when the holding member is rotated toward an arrow (b) direction. If the magnetic force is adequately set on the downstream side of the pole 17, a static layer 20 is formed as the restraining force by the magnetic force of the particles 16, the effect of gravity and the conveying force by friction balance with each other. The particles 16 are thus restrained but the developer 15 is nonmagnetic and is therefore not restrained and passes the underside of the layer 20. The uniform thin layer consisting of only the developer is stably formed on the surface of a sleeve.
TAJIMA HATSUO
HOSOI ATSUSHI
TAKENOUCHI MASANORI
SAITOU TAKASHI
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