| 摘要 |
PURPOSE:To increase remarkably the number of sheets to be processed under maintenance free status by forming a cleaning member driving means for receiving a cleaning signal from an electrostatic discharge line dirt detecting means and driving a discharge line cleaning member. CONSTITUTION:A light emitting element 17 and a light sensitive element 18 which are opposed through a filter 16 detect the degree of dirt due to the adsorption of attachment from the discharge line by the filter, and when light emitted from the element 17 can not be transmitted through the filter 16, a filter dirt sensor 19 sends a signal to an arithmetic part 26. Consequently, a control part 27 displays the dirty state of the filter 16 on a display part 29 as a message and the operator knows the necessity of replacement of the filter 16 by observing the displayed message. The surface of the discharge line 7 is always cleaned and the attachment can be removed by repeating said control. Consequently, influence due to the dirt of the discharge line is not generated on an image, maintenance free can be attained and the number of sheets resisting against the dirt of the discharge line can be remarkably increased as compared to the current case.
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