Brother International HL-1660E Service Manual - Page 21

3. IMAGE FORMATION SYSTEM 3.1 Outline The image formation system is the main part of the printer. The print information, after input from the video controller circuit into the engine controller circuit as a TVDO signal, forms a toner image on the photosensitive drum. Then the toner image is transferred onto the paper by the transfer charging roller. The image formation system is composed of the photosensitive drum the charging unit, the developing unit and the cleaning unit. 3.2 Printing Process The major part of the image formation system is contained in the cartridge, as shown in Figure 2.5. Laser beam Cartridge Primary charging roller Blade Cleaning blade Photosensitive drum Developing cylinder Paper Transfer charging roller Static charge eliminator Figure 2.5 The cartridge used by the printer has a seamless photosensitive drum with the structure shown in Figure 2.6. The outer layer of the drum consists of an organic photoconductor (OPC); the base is aluminum. The printing process can be divided into five major stages: Figure 2.6 1. Electrostatic latent image formation stage Step 1 Primary charge (-) Step 2 Scanning exposure 2. Developing stage Step 3 Development Photoconductive layer Base II - 5