Brother International HL-1660E Service Manual - Page 25

3.2.3 Transfer stage In the transfer stage, the toner image is transferred from the drum surface to the paper. Step 4 Transfer Photosensitive drum Paper Transfer charging roller Figure 2.13 A positive charge applied to the back of the paper attracts the negatively charged toner particles to the paper. The printer accomplishes transfer by using the charging roller method. Advantages compared with the corona transfer method are as follows: • Low transfer voltage that is less than half that for corona transfer. • Less ozone generation. • The paper is supported by the transfer charging roller and photosensitive drum, so feed is more stable. Reference: If the image on the photosensitive drum is not completely transferred to the paper due to jamming, etc., the toner may adhere to the transfer charging roller. The printer removes the toner from the transfer charging roller by switching the transfer voltage between positive and negative in sequence. During wait, initial rotation, and last rotation, the printer sets the primary DC voltage to zero, and sets the charge on the drum to zero. In this case, the transfer voltage is made negative to remove the negatively-charged toner on the transfer charging roller to the drum. The transfer charging roller is thus cleaned. Step 5 Separation Photosensitive drum Paper Static charge eliminator Transfer charging roller Figure 2.14 The stiffness of the paper causes it to separate from the drum. (Curvature separation) To stabilize the paper feed and prevent small white circles from appearing in the printed image at low temperature and humidity, the charge on the back of the paper is reduced by the static charge eliminator after transfer. II - 9