Canon imageCLASS MF8450c, Service Manual

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Chapter 7
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7.4.3 ETB Cleaning
0019-8978
imageCLASS MF9170c / imageCLASS MF9150c / imageCLASS MF8450c
The ETB is used not only to transfer the toner on the photosensitive drum to the paper but also to write a pattern image for correction for image stabilization control.
If the toner which is not transferred to the paper remains on the ETB, it causes stain on the back of paper.
In this control, the ETB surface is cleaned by placing the residual toner on the ETB back to the photosensitive drum electrostatically.
The ETB cleaning is executed by the DC controller at the following timing.
- At power-on
- Before and after the execution of color displacement corrective control
- Before and after the execution of image gradation corrective control
- When the front cover is closed
- After printing is performed when the universal-size paper is specified
Negative charged toner and positive charged toner remain on the ETB.
When ETB cleaning starts, the DC controller sets the potential of the photosensitive drums for magenta (M) and yellow (Y) to 0, using the bias of the primary
charging roller. The photosensitive drums for cyan (C) and black (Bk) are changed negative.
For the transfer roller for each color, a positive or negative DC bias is applied as shown in the figure below.
Since potential difference occurs between each photosensitive drum and ETB, the residual toner is reverse-transferred to the photosensitive drum. The negative
charged toner is adhered to the photosensitive drums for magenta (M) and yellow (Y), and the positive charged toner is adhered to the photosensitive drums for
cyan (C) and black (Bk).
The toner adhered to the photosensitive drum is scraped by the cleaner blade and collected into the waste toner container.
F-7-26
Negative potential waste toner
Positive potential waste toner
M toner cartridge
C toner cartridge
Y toner cartridge
Bk toner cartridge
DC negative bias
DC positive bias
DC negative bias
DC