| 摘要 |
PURPOSE:To improve the efficiency of electrostatic charging and to uniform the electrostatic charging by employing such a simple constitution that an insulator is only fitted partially to the internal surface surface of the shield case of an electrostatic charger. CONSTITUTION:The entire internal surface of the side wall of the shield case 321 on the downstream side in the rotational direction of a photosensitive drum 31 is covered with an insulator 323 and the internal surface of the inner wall 325 viewed from the opening part of the shield case 321 is also covered with an insulator 324 on the downstream side in the rotational direction of the photosensitive drum. The insulator 323 prevents the efficiency of the electrostatic charging from decreasing owing to the side wall and straightens an ionic wind due to corona discharge and the rotation of the photosensitive drum 31 to some extent. Further, the insulator 324 is recessed arcuately on the upstream side in the moving direction of the photosensitive drum 31 to expose the shield case 321 which operates as a counter electrode more at the center part of a discharge wire 322 and less at both end parts. Therefore, an ionic wind is straightened effectively and the quantity of electrostatic charging is suppressed by the shield case 321 which is exposed more at the center part where the quantity of electrostatic charging tends to increase. Thus, the efficiency of electrostatic charging is improved and the electrostatic charging is uniformed. |
