Potential Of The Drum; Measuring The Dark Area Potential Attenuation; Controlling The Environment; Contrast Potential - Canon 1130 Service Manual

3. Measuring the Dark Area Potential Attenuation

The operation referred to as "dark area potential attenuation measurement" consists in
measuring the rate of attenuation to prevent fogging and carrier adhesion. (The potential created on
the photosensitive drum by primary charging tends to decrease if left alone in a dark area.)
In practice, the degree of decrease of the potential created by primary charging is detected at
the point of development, and the result is used as feedback when controlling the developing bias
and grid bias.
The grid bias (Vg) of the primary charging assembly is set to -500 and -700 V, and the dark
area potential (VD1, VD2) occurring when the laser is off and the light area potential (VL1, VL2)
occurring when the laser is on are measured by the potential sensor (as when measuring the surface

potential of the drum).

The measurements taken during the first rotation (VD1, VD2, VL1, VL2) and the
measurements taken during the second rotation (VD3, VD4, VL3, VL4) are compared, and the
differences (= VD1 - VD3, = VL1 - VL3, = VD2 - VD4, = VL4 - VL6) are used to determine the
rate of attenuation.
Dark area potential attenuation measurement is executed when the power switch is turned on
while the temperature of the upper fixing roller is 130°C or less, during initial multiple rotation
following jam removal and once every two hours thereafter, or when FUNCTION>DPC>DPC is
initiated in service mode.
While dark area potential attenuation measurement is being executed, the surface potential
(Vd5) occurring when the post-cleaning charging assembly is operated with the pre-exposure lamp
kept off is measured to check the output of the high voltage after cleaning; further, the surface
potential (VL5) occurring when the potential of the area (VD5) has been eliminated by the pre-
exposure lamp is measured to check the operation of the pre-exposure lamp.
4. Controlling the Environment Contrast Potential
The operation referred to as "environment contrast potential control" consists in measuring the
environment (temperature/humidity) around the developing assembly to determine the target

contrast potential.

Changes in the environment around the developing assembly change the characteristics of
developing agents and, consequently, affect the image density. To make up for such changes, the
environment (temperature/humidity) around the developing assembly is measured by the
environment sensor to determine the target contrast potential.
Figure 6-203 shows the relationship between changes in the environment and the target
contrast potential.
Target contrast
potential
COPYRIGHT © 2002 CANON INC.
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Figure 6-203
CANON CLC1100/1130/1150/1160/1180 REV.1 JAN. 2000 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 6 IMAGE FORMATION SYSTEM
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