Sharp UX-4000M Service Manual - Page 49

7-4. Functions and operations of major parts 2 3 11 1 10 4 9 5 8 7 6 1 Developing roller 2 Doctor 3 Toner stirring plate 4 Toner supply roller Fig. 10 5 Toner seal 9 Discharge brush 6 F Transfer roller Main charger 7 Separation brush G Toner seal electrode 8 OPC drum (1) OPC drum unit The OPC drum is charged and latent electrostatic images are formed on it and developed into visible toner images. a. OPC drum Latent electrostatic images are formed and developed into toner images on the OPC drum. Organic Photo Conductor is used. The OPC surface is charged negatively by the main charger brush. When the OPC is exposed to laser beam, the electric resistance of the exposed section falls and electric charge is generated in the OPC. As a result, electric charge on the OPC surface is removed. This principle is used to form latent electrostatic images. UX-4000MU FO-2950MU/C c. Toner seal The OPC drum unit is provided with two toner seals, which prevent leakage of toner remaining in the OPC drum unit. (2) Developing unit Latent electrostatic images formed by laser beam on the OPC drum are developed to visible images by the developing unit. Toner is filled in the developing unit. a. Developing roller The developing roller is made of urethane and has a high electric resistance. It is flexible and is in close contact with the OPC drum. Toner on the developing roller is attached to latent electrostatic images on the OPC drum to form visible images on the OPC drum. A voltage of DC-250V is applied the developing roller. b. Doctor The doctor is in close contact with the developing roller. It adjusts toner quantity on the developer roller surface. The doctor is made of conductive material. c. Toner supply roller Toner is supplied to the developing roller by the sponge roller which is connected to the developing roller. d. Toner stirring plate This plate stirs toner in the developing unit to transport it to the developing roller smoothly. e. Toner seal The toner seal prevents toner from leaking outside the developing unit. (3) Transfer charger roller The transfer charger roller is made of urethane and has a high electric resistance. It is flexible and is in close contact with the OPC drum. A high voltage of AC 600V (P-P) and DC +3500V are applied to charge. It positively charges paper transported from the paper feed section, which transfers negatively charged toner on the OPC drum onto the paper. (4) Separation electrode This electrode is connected to the drum ground. It discharges paper which was positively charged in the transfer section to reduce the potential difference with the OPC drum to reduce static electricity between the paper and the OPC drum, thus facilitating separation of paper. (5) High voltage unit (in the Printer PWB) A high voltage is generated by the invertor system, and is supplied to the main charger unit, the transfer charger unit, and the developing roller. OPC layer CTL (Charge transfer layer) CGL (Charge generation layer) Aluminum layer Fig. 11 b. Main charger brush The main charger brush charges the OPC drum surface. It is composed of brush fibre, and is in the shape of a roller. A high voltage of AC 600V (P-P) and DC-850V are applied to charge the brush. The main charger brush is in contact with the OPC drum. BY applying electric charge to the OPC drum, the OPC drum is charged to about 1kV. 3 - 6 manuals4you.com