| 摘要 |
PROBLEM TO BE SOLVED: To prevent developer from leaking outside, by forming a high-attraction developer magnetic brush along a line of magnetic force between a magnetic member, or a magnet and a developer carrier, at the end part of a developer carrier. SOLUTION: In a phase R at almost the central part of a repulsive magnetic field of a developing sleeve 10, the magnet 25 is arranged so that the inside end part 25a in the axial direction may be arranged on the inner side in the axial direction from a position where the axial magnetic flux density is reversed from an N-polarity to an S-polarity at the end part 10b of the developing sleeve. And the developing sleeve 10 and the magnetic plate 21 are correlated with each other so that the magnetic flux density L at a position facing the magnetic plate 21 may be >=50G and the reversed maximum magnetic flux density M is <50G, as for the magnetic flux density distribution of the phase R. By setting the ratio of M to L to be <=100% in such a way, the magnetic force line which is formed by the magnet 25 and the sleeve 10 near the magnetic plate 21 becomes stronger and more dominant than the axial magnetic force line formed on the surface of the end part of the sleeve 10, then, the high-attraction developer magnetic brush is formed between the magnet 25 and the sleeve 10 in the repulsive magnetic field. |
