G147 6-22 SM
6.6.2 CHARGE ROLLER VOLTAGE CORRECTION
Correction for Environmental Conditions
The voltage transferred from roller to drum could vary with the temperature and humidity
around the drum charge roller. The lower the temperature or humidity, the higher the applied
voltage required.
The ID sensor measures the effects of ambient conditions, and any small change in drum
potential caused by changes in temperature/humidity is reflected in the amount of toner
transferred to the drum.
This measurement is done immediately after the ID sensor pattern for toner density control.
After creating ID sensor pattern [A], another pattern [B] is made. To do this, the LD switches
off, the charge roller voltage drops, and the drum potential is reduced to –600 V. At the same
time, development bias returns to –550 V. The drum potential is now slightly higher than the
development bias, so only a very small amount of toner transfers to the drum. The ID sensor
measures the density of pattern [B], and Vsdp, the output voltage, is compared with Vsg
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