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31 December 1992
4.
DEVELOPMENT
4.1 OVERVIEW
[C]
[A]
When the development motor turns on, the paddle roller [A] and development
roller [B] start turning. The paddle roller picks up developer in its paddles and
transports it to the development roller. Internal magnets in the development
roller attract the developer to the development roller sleeve.
The turning sleeve of the development roller then carries the developer past
the doctor blade [C]. The doctor blade trims the developer to the desired
thickness and creates backspill to the cross-mixing mechanism.
The development roller continues to turn, carrying the developer to the OPC
drum. When the developer brush contacts the drum surface, the negatively
charged areas of the drum surface attracts and holds the positively charged
toner. In this way, the latent image is developed.
Negative bias is applied to the development roller to prevent toner from being
attracted to non-image areas on the drum that may have residual positive
charge. The bias also controls image density.
After turning about 100 degrees more, the development roller releases the
developer into the developer tank. The developer is agitated by the paddle
roller and the cross-mixing mechanism.
Also, in this machine, rotation of the paddle roller and development roller tend
to cause air pressure inside the unit to become higher than the air pressure
around the development unit. Therefore, a hole fitted with a filter, has been
added to the top of the unit to relieve air pressure and to minimize toner
scattering.
The toner density sensor [D] is mounted on the upper side of the
development unit to detect the density of toner in the developer.
[D]
2-17
DEVELOPMENT
[B]
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