| 摘要 |
PROBLEM TO BE SOLVED: To improve the contact reliability of a contact point and a shaft holding the developing roller of a developing device and to improve printing quality by improving the constitution to impress a bias voltage on the developing roller. SOLUTION: The contact point 12 fixed to a conductive permanent magnet 13 is pressed by a spring 11 to the shaft 6 holding the developing roller 5. The spring 11 and the contact point 12 are composed of a soft magnetic material in order to form a magnetic circuit. A conductive and magnetic fluid 5 is disposed between the contact point and shaft. The generation of arcs and the oxidation and corrosion of the surfaces of the contact point 12 and the shaft 6 are prevented by magnetic fluid 15 even if chattering arises when the bias voltage is impressed. |
