Sharp Z-21 Service Manual page 13

Step 6. Separation
The paper is negatively charged (About –3KV) by the discharge pin to
neutralize the potential, separating the paper from the drum.
Step 7. Cleaning
The residual toner remaining on the drum is collected by the cleaning
blade and carried into the toner collection unit.
Cleaning blabe
Toner
collection
unit
Residual toner
Step 7. (same as step 1)
<Transition in the drum surface potential at each step>
-600
Black image area
White image
area
-150V
-150
Canceled by
-100
developing bias
Residual potential (-80~100V)
0
Charge Exposure
Because of the developing bias, toner is not attracted to the non-
image areas of the drum surface. If, for any reason, the developing
bias fails, the toner will be attracted to the residual charge on the
drum producing background in the non-image areas.
Toner attract
potential
Charge
Developing Transfer
Discharge
Time
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