Protection From Abnormally High Temperature; Ppm Control; Control For Preventing Roller Edge Temperature From Rising - Konica Minolta bizhub 164 Service Manual

Theory of Operation Ver. 1.1 Apr. 2010
19.3.4

Protection from abnormally high temperature

A. First approach: Thermistor protection (Software protection)
• The main body determines that there is a condition of an abnormally high temperature
when thermistor/1 continuously detects a predetermined temperature or more for a pre-
determined period of time or more. The main body then gives the following message:
"Trouble code C3751 (Fusing failure: abnormally high fusing temperature 1)".
• The main body determines that there is a condition of an abnormally high temperature
when thermistor/2 continuously detects a predetermined temperature or more for a pre-
determined period of time or more. The main body then gives the following message:
"Trouble code C3751 (Fusing failure: abnormally high fusing temperature 1)". The main
body prohibits the initiation of any new print cycle as soon as it displays the trouble code.
• When the trouble code is displayed, printing will be prohibited.
B. Second approach: Thermistor protection (Hardware protection)
• If either thermistor/1 or thermistor/2 detects an abnormally high temperature when the
CPU overruns to be unable to detect an abnormally high temperature trouble, the heater
relay of the DC power supply unit is turned OFF via the printer control board, thereby
shutting down power supplied to the fusing heater lamp.
• The power supplied to the fusing heater lamp can be shut down before the thermostat of
the third approach is activated. This inhibits damage to the fusing unit.
C. Third approach: Thermostat protection
• If the abnormally high temperature through the first and second approach cannot be
detected because of a faulty thermistor, the thermostat comes into play to shut down the
power supplied to the fusing heater lamp.
19.3.5

PPM Control

• To ensure good fusing characteristics of the image printed on the media, the number of
continuously prints is held low, thus preventing fusing characteristics during the multi-
print cycle from being degraded.
• When card 1/2 is selected, the main motor is deenergized to provide a delay of 4 sec-
onds in the paper feed start sequence regardless of the paper size.
Further, the PPM control (4-sec. delay in paper feed start sequence) is performed, if +2
or more is selected for the plain paper temperature choice in the FUSER TEMP menu of
SERVICE'S CHOICE.
19.3.6

Control for preventing roller edge temperature from rising

• If paper of a small size or card1/2 is used to run a multi-copy cycle, the temperature on
the edges of the heat roller tends to increase, so that the temperature of the heat roller
varies among different spots of the roller.
• A temperature increase prevention control is performed during a multi-print cycle to
thereby delay the paper feed operation, so that the temperature of the heat roller can be
controlled to achieve a uniform temperature of the roller.
• Thermistor/2 measures the temperature of the edges of the roller.
• When a predetermined temperature or more is detected from the edges of the roller, the
print cycle is temporarily stopped.
• The print cycle is resumed as soon as the temperature of the edges of the roller
decreases to reach the predetermined level. If the temperature does not decrease down
to the predetermined level even after the lapse of 30 seconds, the print cycle is resumed
regardless of whether the predetermined temperature is reached.
19. FUSING SECTION
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