Davin J012, Service Manual

Page: 327 / 365

Transport Belt
This printer uses the BT (Belt Transfer) system to transport paper through the paper path.
A high voltage power supply pack (HVPS) [1] energizes the charge roller below the transport belt [2].
The charge roller applies a charge to the transport belt. This static charge attracts the paper to the transport
belt and holds it in place so it does not move during printing.
A temperature/humidity sensor below the transport belt monitors the temperature and humidity near the
charge roller and transport belt. The temperature/humidity readings of this sensor are matched with values
in lookup tables cross-indexed with combinations of temperature and humidity readings. The values read
from the tables are used to adjust the width of the bias (bias pitch) applied to the transport belt. This
operation, called belt charge control, operates within the following ranges of temperature and humidity:
Temperature: 0C to 35C (32F to 95F) Adjusted in 2.5C (4.5F) steps
Humidity: 0% to 100% Adjusted in 10% steps
The machine uses the feedback of the temperature/humidity sensor to reduce the width of the charge
applied to the transport belt below the print heads. This reduces the size of the electrical field to the smallest
size that can still provide the optimum charge to keep the paper on the belt at the leading edge, center,
and trailing edge of the paper without interfering with the operation of the print nozzles.
Belt charge control is done for every paper feed station (Tray 1, Tray 2, and bypass) and for every paper
type (normal paper, envelopes, thick paper, and OHP).
The sharp curvature of the paper path separates the paper from the transport belt at the time paper gets
fed out the paper exit.
6. Detailed Section Descriptions
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