B. Operation - Canon CLBR 460ps Service Manual

B. Operation

1. Outline
When it receives a PRINT signal (/PRNT) from the video controller, the DC controller drives
motors to turn the photosensitive drum, developing rotary, primary charging roller, secondary
transfer roller, and intermediate transfer belt. The intermediate transfer belt is pressed against
the photosensitive drum to prepare for the transfer process.
The primary charging roller uniformly applies negative charge to the surface of the photo-
sensitive drum. Then the laser diode illuminates the laser beam modulated by the video data
signal (8 bits) to form the electrostatic latent image on the photosensitive drum. The latent
image formed on the photosensitive drum is changed to a visible image by the toner in the toner
cartridge and then transferred (primary transfer) to the intermediate transfer belt in the ITB
unit.
For full-color printing, the electrostatic latent image is first formed on the photosensitive
drum by the Bk (black) video data. Then the developing rotary turns and the developing cylin-
der faces the photosensitive drum and Bk toner is developed. The developed Bk toner is trans-
ferred to the intermediate transfer belt by the positive bias applied to the primary transfer roller
in the ITB unit. This completes the primary transfer process for Bk toner. When Bk develop-
ment ends, the developing rotary turns and the next developing cylinder (M:magenta) faces the
photosensitive drum. The electrostatic latent image is formed on the photosensitive drum by the
M video data. Like the Bk toner, the magenta toner is then developed and primarily transferred.
The C(cyan) and Y (yellow) toners are developed and transferred in the same way.
Four toners are transferred to the intermediate transfer belt by repeating development and
primary transfer four times, and the full-color primary transfer process is complete.
For mono-color printing, the mono-color toner is transferred to the intermediate transfer belt
by performing the process once and the primary transfer process is complete.
When a paper is fed to the intermediate transfer belt, the secondary transfer roller is lifted
and the paper is pressed against the intermediate transfer belt. The toners on the intermediate
belt are transferred to the paper by the positive bias applied to the secondary transfer roller. The
secondary transfer process is now complete.
The paper is separated from the intermediate transfer belt and transported to the fixing unit.
The residual toner on the photosensitive drum surface is scrapped down with the cleaning blade
and collected in the waste toner container in the drum cartridge. The potential on the drum is
made uniform by the primary charging roller for generation of a new latent image. The residual
toner on the intermediate transfer belt is charged by the ITB cleaning roller. The residual toner
on the intermediate transfer belt is then transferred to the photosensitive drum by applying the
cleaning bias to the photosensitive drum and collected in the waste toner container in the drum
cartridge.
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