Transfer - Brother HL-5240 Service Manual

CHAPTER 2 THEORY OF OPERATION
3. The laser beams reflected by the reflection mirror go straight toward the exposure drum
below it, then expose the exposure drum.
The area exposed to the laser beam is the image to be printed. The surface potential of the
exposed area is reduced, forming the electrostatic image to be printed.
Surface
potential (V)
Drum
sleeve
3.5.3

Transfer

(1) Transfer process
After the drum has been charged and exposed, and has received a developed image, the
toner formed is transferred onto the paper by applying a negative charge to the back of
the paper. The negative charge applied to the paper causes the positively charged toner
to leave the drum, and adhere to the paper. As a result, the image is visible on the paper.
(2) Cleaning process of transfer roller
If the toner is not transferred onto the paper perfectly it is possible that there may be
residual toner on the drum which will adhere to the transfer roller. The transfer roller
voltage changes to a positive voltage during non-printing rotation of the drum. Therefore
the transfer roller is cleaned by returning the positively charged toner adhering to the
transfer roller onto the exposure drum.
1 Cycle of drum
1 2
(a)
+900
+400
(b)
+100
0
3
Primary charging
1
2 Laser beam exposure and developing
(a) Unexposed area
(b) Exposed area
Transfer the image to paper
3
Time
Fig. 2-19
2-22
(Non image area)
(Image area)
Confidential