Ricoh Aficio Color 4006, Service Manual

Page: 137 / 487

TRANSFER BELT UNIT 24 February, 1999
2-88
Paper Transfer Bias
In this machine, paper transfer voltage is applied using a bias roller and constant
current. The high voltage supply board – T2, D [A] applies bias voltage to the paper
transfer bias roller [B] and the paper separation corona unit [C].
The bias terminal [D] moves up and down while the transfer unit repeats the
contact/release operations, so it always remains connected.
The machine changes the paper transfer current, depending on the following six
parameters:
1. Absolute humidity
Under low temperature/low humidity conditions, the current depends on the
absolute humidity. The temperature and humidity sensors at the rear of the
machine (see the diagram on the next page) measure absolute humidity.
2. Paper size
Since a constant-current system is used to generate the paper transfer bias,
the current is adjusted according to the paper size to compensate for the leak
of current around the edges of the paper.
3. At the leading and trailing edges of the paper
To prevent poor paper transfer at the leading and trailing paper edges, there
are SP modes to change the current that is used within about 15 mm from the
edges.
A259D411.WMF
[A]
[B]
[C]
[D]