| 摘要 |
PURPOSE:To prevent a developer from entering a magnetic roll securely, by providing an annular permanent magnet which is greater than the external diameter of a seal member to the driven-side flange member of a developing sleeve and producing a magnetic field. CONSTITUTION:An oil seal 90 for preventing the developer from entering a bearing 89 is provided on an end surface of the flange member 86 of the developing roll 8. The annular permanent magnet 92 is fixed coaxially with a shaft 83 on the opposite side of a member 86 to a side plate 1b. The permanent magnet 92 has an internal diameter greater than the external diameter of the oil seal 90 and is magnetized in its thickness direction. Therefore, a line of magnetic flux from the N pole of the permanent magnet 92 flows to the S pole, so a magnetic field in a circumferential direction is formed in the gap (d) between the member 86 and a stopper member 91 to the outside of the seal 90. Then, if the developer enters the gap (d), it is cut off by the magnetic field to prevent the entrance of the developer into the seal 90. |
