Brother International HL 1850 Service Manual - Page 99

HL-1850/1870N SERVICE MANUAL 2.4 2.4.1 Drum Unit Photosensitive drum Generates the latent electrostatic image and develops the image on the drum surface. 2.4.2 Primary charger Forms a uniform charge on the drum surface. (1) Corona wire Generates the ion charge on the drum. (2) Grid Spreads the ion charge evenly over the drum surface. 2.4.3 Transfer roller Transfers the toner image to the paper from the drum surface. 2.4.4 Cleaner Removes the paper dust or dirt on the surface of the photosensitive drum. 2.5 Toner Cartridge Develops the electrostatic latent image on the photosensitive drum with toner and forms the visible image. 2.6 Print Process 2.6.1 Charging The drum is charged to approximately 870V by an ion charge which is generated by the primary charger. The charge is generated by ionization of the corona wire, which has a DC bias from the high-voltage power supply applied to it. The flow of the ion charge is controlled by the grid to ensure it is distributed evenly on the drum surface. The aluminum drum sleeve in the photosensitive drum is grounded. Voltage Regulator + + + + 870V + + + + + - T- - -F - ++ + ++ \ \ Aluminum drum sleeve --I Photosensitive Organic Photoconductor layer 1 Drum Grid II HVPS \ \\ Corona wire Fig. 3-30 The primary charge uses a corona wire, but since the drum is positively charged, only less than 1/10 of the usual quantity of ozone is generated compared with the negatively charged drum. The level of ozone expelled from the printer is therefore not harmful to the human body. Applicable safety standards have been complied with. 3-27