Service manual

Chapter 8
8-3
a level 15 deg C/59 deg F lower than paper passage control temperature target.
- Paper Passage Temperature Control
While printing is taking place, the fixing heater temperature is controlled so that it is ientical with the paper passage
control temperature target.
- Sheet-to-Sheet Temperature Control
To prevent overheating of areas not covered by paper (between sheets), the fixing heater temperature is controlled to
a level relatively lower than the paper passage control temperature target.
- Rest Heating Temperature Control
While the machine is at rest, the fixing pressure roller is heated so that the toner collecting on it is melted and moved
to the fixing film, thereby ridding the roller of toner.
The rest heating control mechanism is used to control the temperature of the fixing heater to a level lower than the
paper passage target level when LTR or larger paper is used for printing.
The control temperature targets are switched in reference to the following 4 conditions:
- paper type (as indicated by a command during printing)
- type of control (cover paper or between sheets)
- change in fixing temperature control (OFF -> start-up -> paper passage, etc.)
- count of prints in continuous mode
8.2.2 Controlling the Fixing File Bias Temperature
8.2.2.1 Controlling the Fixing Film Bias 0006-4144
The machine is equipped with a fixing film bias control mechanism which is controlled by the CPU on the DC
controller PCB. The fixing film bias is used to prevent displacement of toner deposits; i.e., when the primary
charging roller DC bias is applied, a bias of the same polarity as the toner is applied to the fixing film so as to create
a magnetic field between the paper and the film.
F-8-4
Primary
charging
roller
CPU
DC controller PCB
Superposition
J205
Primary charging
roller
DC bias drive circuit
Primary charging
roller
AC bias drive circuit
J206
Fixing film
Photosensitive
drum