| 摘要 |
PURPOSE:To make it possible to obtain a copy even if a film of bad quality is supplied by switching the driving speed of a photosensitive drum, a scanning optical system and a transfer paper carrying system at least to two steps and by controlling an electrostatic charger so that the electrostatic charging potential of the photosensitive drum is almost fixed independently of said switching. CONSTITUTION:A main motor M is constituted so that the driving speed can be switched to two steps, and glid bias voltage VG to be impressed to a screen glid of the charger 12 and sleeve bias voltage VB to be impressed to a developing sleeve 25 are changed in accordance with the change of the driving speed. If a microfilm of bad quality which can not be sufficiently copied at 90mm./sec driving speed, 600V bias voltage VG and 300V bias voltage VB is copied by switching the condition to 45mm./sec driving condition, 550V bias voltage VG and 400V bias voltage VB, a fine copy can be obtained. |
