| 摘要 |
An image forming apparatus gets information on the thickness of the photosensitive layer by using the image transfer power source and transfer brush, and controls the contact position of the transfer brush on the paper carrying belt based on the thickness information, so that in case the photosensitive layer wears thin partially due to the long-term use, the apparatus increases in compensation the impedance of the carrying belt in its section from the image transfer zone to the contact position of the transfer brush. The apparatus may be designed to use selectively multiple transfer brushes having different impedances, instead of the position control of one transfer brush. Consequently, the apparatus can retain the difference of impedance between the toner image portion and non-toner image portion in the transfer zone of the photosensitive layer and thus can retain the unevenness of transfer electric field distribution across the transfer zone in the same degree as with a new photosensitive layer, whereby it performs high-quality image formation without the occurrence of dropout throughout the long-term use. For a multi-color image forming apparatus, the image forming unit for black color that is most sensitive to the print quality implements the impedance control.
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