Sharp AL-800, AL-840, Digital Copier service manual Paper Transfer roller

Step 3 (Development):

Doctor

Developing roller

Toner is attached to the latent electrostatic images formed on the OPC drum.

:Toner (Negative charge)

Toner supply roller

100V

At that time, the potential of the OPC drum surface where there is no charge by exposure of laser beams is higher than the developing roller potential. On the other hand, there are negative charges in the OPC drum surface area which is not exposed to laser beams. When that area is brought into contact with the developing roller, if toner is attached to the OPC drum,. toner is moved to the developing roller which is in a high potential than the OPC drum.

As a result, unnecessary toner and paper dust on the OPC drum are collected in the developing unit.

In this operation, toner is moved from the OPC drum to the develop- ing roller.

In cleaning operation mode, DC +200V is applied to the developing roller and cleaning capacity is further increased.

Step 4 (Transfer): Visible images of toner on the OPC drum are transferred to the paper.

OPC drum
Exposure area
(Exposed by	Earth sheet
laser beams.)

Non-exposure area (Not exposed by laser beams.)

	DC	DC
Aluminum layer	+200V	-310V
	CGL
(Drum base)

CTL

Toner enters between the developing roller and the doctor, and a thin layer of toner (a certain fixed amount) is formed on the developing roller by a pressure applied to the doctor.

Toner is negatively charged by friction when passing between the developing roller and the doctor.

When the OPC drum surface area where there is no charges be- cause of exposure of laser beams is brought into contact with the developing roller, toner is moved from the developing roller to the OPC drum surface. The principle of the process is as follows:

A bias voltage of –310V is applied to the developing roller. Toner which is charged by potential difference between the bias voltage and the OPC drum surface potential is attracted to the OPC drum surface (positively charged).

Aluminum surface (Drum base)

CGL

OPC drum

CTL

Paper

Transfer roller

DC+3500V

AC600V(P-P)

DC –850V

A high voltage of AC60V (P-P) is applied to DC+350V and applied to the transfer roller, generating electric discharge between the roller and the OPC drum, generating positive and negative charges.

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