Sharp MX 3501N - Color Laser - Copier, Service Manual

Page: 413 / 448

MX3500N FUSING SECTION N – 2
2. Operational descriptions
A. Fusing unit drive
To drive the fusing unit, the drive power is transmitted from the
drive motor (FUM) through the connection gear to the upper heat
roller gear.
The drive motor (stepping motor) is driven according to the control
signal sent from the PCU.
B. Heater lamp drive
The surface temperature of the heat roller detected by the ther-
mistor is sent to the PCU. When the temperature is lower than the
specified level, the heater lamp lighting signal is sent from the PCU
to the heater lamp drive circuit in the sub power PWB.
The power triac in the heater lamp drive circuit is turned on, and the
AC power is supplied to the heater lamp, lighting the lamp and
heating the heat roller.
To prepare for an abnormally high temperature of the heat roller,
the thermostat is provided for safety.
When the thermostat is opened, power supply (AC line) to the
heater lamp is cut off.
C. Fusing operation
Color toner of YMCK on paper is heated and pressed by the heat
rollers to be fused on paper.
At that time, color toner of YMCK is mixed to reproduce nearly
actual colors of document images.
The heater lamp is provided in the upper and lower heat rollers and
the sub roller. It heats paper up and down.
This is because it is necessary to heat four layers of toner from
above and below and right and left to fuse it on paper.
The upper and lower heat rollers are of silicon rubber.
This is because of the following reasons:
1)
To provide a greater nip quantity and a higher heating capacity
for paper.
2) The soft, flexible rollers press multi-layer toner without defor-
mation to fuse on paper.
3) An even pressure is applied to an uneven surface of multi-
layer toner.
The sub roller has the following functions.
1)
Helps fusing and keeps the fusing temperature under special
conditions.
2) Remove and clean paper dust and toner from the upper heat
roller.
Signal name Name Function/Operation
TH_UM Upper thermistor C (Non-contact) Controls the surface temperature of the upper heat roller.
TH_LM Lower thermistor Controls the surface temperature of the lower heat roller.
HLOUT_UM Upper thermostat main Shuts conduction to the heater lamp when the temperature rises abnormally. [For the upper heat roller]
HLOUT_LM Lower thermostat Shuts conduction to the heater lamp when the temperature rises abnormally. [For the lower heat roller]
HL_UM Heater lamp upper main Heats the upper heat roller.
HL_US Heater lamp upper sub Heats the sub roller.
TH_E Upper thermistor sub Controls the surface temperature of the sub roller.
HLOUT_US Upper thermostat sub Shuts conduction to the heater lamp when the temperature rises abnormally. [For the sub roller]
HL_LM Heater lamp lower main Heats the lower heat roller.
FUM Fusing motor Drives the fusing unit.
WEB-END Web roller end detection Detects presence of cleaning paper.
WEB-INL Web roller initial detection Detects installation of the web unit.
TH_US Upper thermistor sub Controls the surface temperature of the upper heat roller. (For supplementary use)
WEBM Fusing web cleaning motor Drives the fusing web cleaning paper.
No. Name Function/Operation
1 Upper heat roller Heat and presses toner on paper to fuse it on paper.
2 Upper separation pawl Paper which was not separated naturally from the upper heat roller is mechanically separated.
3 Lower heat roller Heat and presses toner on paper to fuse it on paper.
4 Transport roller 9 (Drive) Transports paper from the heat roller to the paper exit roller 1.
5 Web roller Cleans the upper heat roller.
6 Lower separation pawl Mechanically separates paper which was not naturally separated from the lower heat roller.
7 Sub roller Helps temperature control of the upper heat roller.
FUM PCU