Epson EPL-N1600 Service Manual page 38

EPSON EPL-N1600
Step Process
1 Charging In this process, electric discharge from the BCR (Bias Charge Roll) generates a uniform negative charge on the surface of the OPC (Organic
Photconductor) drum located within the Imaging Cartridge.The BCR is a conductive roller positioned in contact with the OPC drum, The HVPS ASSY
applies a bias voltage (a negative DC bias voltage superposed on an AC voltage) to the BCR. The AC voltage is controlled by constant-current regulation
and the current level is apporx. 800µA (850Hz). This AC component evens out the residual charge left on the OPC drum during the previous print cycle,
so that a uniform negative charge corresponding to the DC bias voltage level (approx. -400VDC) is generated over the entire drum surface.
2 Exposure In this process, the ROS (Raster Output Scanner) ASSY generates the latent image onto the OPC drum surface by scanning the drum with the laser. The
scanner motor rotates the polygon mirror within the ROS ASSY. The mirror reflects the laser beam produced by the laser diode so that the beam scans
across the drum surface. The OPC drum surface consists of a photoconductive layer covering an aluminum (conductor) base. As the beam strikes the
surface it generates electrons and holes within the photoconductive layer. The electrons are pulled by the electric field into the conductor base, while the
holes move to the outside surface of the photocondutor layer (the outside of the drum), combining with the surface electrons and reducing the surface
charge (increasing the potential). This action occurs only at the areas illuminated by the beam. The result is that the negative charge at the illuminated
areas is lower than the negative charge at the non-illuminated areas. This charge differential constitutes the latent image. The SOS (Start of Scan)
sensor attached at the side of MIRROR M1 detects the scan start position (by detecting the laser illumination at the scan start area).
3 Development This process applies toner to the drum surface to generate the visible image. This printer utilizes non-conductive dry single-component magnetic toner.
Toner adheres to a surface of the MAG ROLL by magnetic force, while the narrow gap between the CM (Charging and Metering) blade keeps this toner
coating extremely thin and uniform. The friction between the CM blade and the MAG ROLL generates a negative charge on the toner. A negative DC
voltage (approx. -315VDC) superposed on an AC voltage (approx. 1.8KVp-p at 3.0KHz) is applied to a thin semiconductive sleeve that covers the MAG
ROLL, as a developing bias (DB). The DC component of the bias keeps the MAG ROLL at negative potential with respect to the OPC drum's conductive
layer and the AC component of the development bias serves to facilitate the transfer of the toner on the MAG ROLL. As a consequence, the parts of the
drum surface that were not hit by the laser beam (the areas where the negative charge was not reduced) will have lower potential than the MAG ROLL,
while the parts that were hit by the laser beam will have higher potential. Because the toner on the MAG ROLL is negatively charged, it will transfer to the
OPC drum only at those areas where the potential on the drum is higher than the potential on the MAG ROLL, thereby forming the visible image.
4 Transfer This process transfers the visible image formed by a toner on the OPC drum surface, to the paper. This printer utilizes a BTR (Bias Transfer Roller) to
effect the transfer. The BTR is a conductive roller that is in positioned in contact with the OPC drum. When the paper moves be tween the OPC drum and
the BTR, the BTR applies an HVPS-generated positive charge (+700VDC) to the back side of the paper. This pulls the toner image off the drum surface
and onto the paper.
5 Separation In the separation process, the action of the negatively charged DETACH SAW neutralizes a positive charge remained on the paper which causes the
paper to stick to the drum surface, so that the paper comes free of the drum. Specifically, an HVPS-generated negative voltage (-2.0KVDC) is applied to
the DETACH SAW.
6 Fusing This process fuses the toner image (the image transferred onto the paper in the transfer process) to the paper. This printer uses a HEAT ROLL to fuse
the image to the paper. The HEAT ROLL is heated by an internal heater lamp. A PRESSURE ROLL is positioned in contact with the HEAT ROLL. When
paper passes between the HEAT ROLL and PRESSURE ROLL, the application of heat and pressure fuses the toner to the paper.
7 Cleaning In this process, a cleaning plate attached to the OPC drum scrapes residual toner (the toner that not transfered to the paper) off the drum surface. The
toner scraped off from the drum surface is collected in the waste-toner compartment within the Imaging Cartridge.
In addition to the above explained cleaning operation, the BTR surface is also cleaned electrically. At the initialization cycle of the printer operation or
before starting a print job, a negative charge (approx. -600VDC) is applied to the BTR and the toner sticking on the BTR surface is transferred from the
BTR to the drum by this voltage.
Rev. A
Table 2-1. Electrophotographic Printing Process
Explanation
Chapter 2 Operating Principles
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