| 摘要 |
PURPOSE:To highly accurately form a desired magnetic force distribution pattern in a low cost, by providing recessed or projecting section over the longitudinal direction of a roll and controlling the magnetic force distribution by means of the recessed or projecting section. CONSTITUTION:The magnet roll M has a four-pole constitution and is formed by injection molding a resin (nylon 12) dispersing about 80pts.wt. of a magnetic substance (ferrite) and magnetization-oriented with the magnetic substance at the same time. Since projecting section 111 and recessed sections 121 are provided on the peripheral surface of the magnet roll M, a sharp distribution is obtained at the N1 pole and a magnetic force distribution which is asymmetrically reduced in intensity on the downstream side of a developing section is obtained at the S1 pole. Therefore, the toner layer on a sleeve stably becomes thinner and, since the magnetic force suddenly drops at the downstream side of the developing section, the sharpness of developing and fog-free pictures can be obtained. |
