Operations - Canon CP660 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
B.

Operations

In response to the print signal (PRNT*) from the printer board*
PCB drives the photosensitive drum, primary charging roller, developing rotary assembly,
intermediate transfer drum, secondary transfer belt, and ITD cleaning roller.
At the same time, it turns on the LEDs of the pre-exposure LED assembly to remove
the residual charges from the surface of the photosensitive drum. The primary charging
roller then charges the surface of the photosensitive drum to a uniform negative poten-
tial; the laser diode directs a laser beam modulated by video data signals to the surface
of the photosensitive drum to form a latent static image.
The latent static image formed on the surface of the photosensitive drum is turned
into a visible image by toner from the toner cartridge, and is transferred (primary trans-
fer) to the intermediate transfer drum.
1. Full-Color Prints
First, Y (yellow) video data is used to form a latent static image on the photosensitive
drum, and the color developing cylinder is positioned against the photosensitive drum by
rotating the developing rotary to develop the Y toner. After development, the toner is
transferred to the intermediate transfer drum by the positive bias applied to the interme-
diate transfer drum to end the primary transfer process for Y toner.
The developing rotary is then rotated once again to position the M (magenta) devel-
oping cylinder against the photosensitive drum. A latent static image is then formed on
the photosensitive drum using M video data, and is developed and transferred (primary)
as in the case of Y toner.
The same sequence of operations is performed for C (cyan) toner to complete the
development processes, upon which the developing rotary is rotated. At this time, each
color developing cylinder is stopped where it will not face the photosensitive drum in
preparation for black development. (See Reference.)
Since the black developing cylinder is positioned always to face the photosensitive
drum, mere application of a bias starts development unlike color toners. When each color
has been developed and primary transfer has been performed four times in sequence, as
many as four color toners exist on the intermediate transfer drum to complete a series of
primary transfer processes for full-color printing.
2. Mono-Color Printing
In the case of mono-color toner, the toner is deposited on the intermediate transfer
drum when the foregoing processes have been performed once, thereby completing the
primary transfer processes.
To increase the efficiency of toner from intermediate transfer drum to paper (sec-
ondary transfer), the secondary pre-transfer charging assembly makes the charges of
toner even. When paper is moved to the intermediate transfer drum, the secondary trans-
fer belt is pushed up so that the paper is brought into contact with the intermediate trans-
fer drum.
The toner on the intermediate transfer drum is transferred to print paper by the work
of the positive bias applied to the secondary transfer belt to complete the secondary
transfer processes.
The paper is then separated from the secondary transfer belt and sent to the fixing
assembly.
1
*
Reader controller PCB (when making prints with the reader unit installed).
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COPYRIGHT © 1999 CANON INC.
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CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
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, the DC controller