Fresa G024, Руководство по обслуживанию

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31 March, 1999 PROCESS CONTROL
2-5
Detailed
Descriptions
Step 4: Charge grid bias voltage adjustment
Adjusting the development bias V
B
controls the density of solid areas on the
printout, and adjusting the charge grid bias V
G
controls the density of low image
density (highlight) areas. These two biases maintain a consistent
γ
for the engine.
To adjust V
G
, the machine makes another pattern on the transfer belt. The ID
sensor detects the density of this pattern. Based on the result, the machine adjusts
the grid bias voltage.
The figure on the right shows the pattern formed on
the transfer belt during this process. The pattern is
20 mm (main scan) x 40 mm (sub scan), and
consists of a repeating pattern of two pixels made
with an LD intensity of 240 surrounded by pixels with
no LD intensity, as shown in the opposite diagram.
This is very pale, and suitable for calibrating the low
ID point of the engine’s gamma.
If the density of low image areas is not acceptable, adjust the target ID sensor
output for this sensor pattern with engine SP mode 12 (High-light adj). Then do a
forced process control (engine SP mode 7. Process Ctrl. – Normal, or Initialize).
Step 5: Y, C, M, and K bias fine adjustment
Steps 2 and 3 for determining V
B
are not done every process control (see the table
two pages ago). Because of this, the solid area density, based on the V
B
obtained
during initialization, may change as a result of changes inside the machine after a
period of use, or because of environmental changes. To suppress these
fluctuations, this step fine-tunes V
B
at regular intervals, or if the environmental
conditions change. The method is described below.
An ID sensor pattern is formed on the transfer belt based on the most recently
measured V
B
for each toner color. The ID sensor then reads the pattern formed.
V
B
changes in accordance with the difference between the ID sensor outputs in
this process and in the initial calibration.
The change in V
B
is restricted to a certain range, so that the density does not vary
widely after process control. However, this restriction does not apply to the process
control executed when fluctuations in the temperature/humidity sensor output are
detected (i.e., upon an environmental change).
Step 6: Resetting the process control interval counter
An internal counter in the MCU NV-RAM controls the process control interval. The
counter is reset at the end of process control. If power is shut down or if the cover
is opened during a process control operation, terminating the process control
operation, the process control restarts from the beginning upon recovery. The
counter is not reset when process control is performed for K-DTM replacement.
0 0 0
240 240 0
0 0 0