Head Overheat Protection - Canon QY8-1360-000 Service Manual

Part 4: Technical Reference

2.5 Head Overheat Protection

If the temperature of the print heads of the BJ cartridges is allowed to rise beyond a set
temperature, not only is there a risk of burns in the event that the heads are touched,
but it becomes increasingly difficult to achieve optimum print quality. The printer is
therefore equipped with an overheat protection function that uses thermal sensors in
the heads to prevent the temperature rising above the set temperature.
Print head temperature detection is effected by independent sensors in the black head,
optimizer head, color head, and photo head.
Protection level 1:
This protection level prevents the operator from touching the metal plate of a hot print
head when changing the BJ cartridge. If, when replacing a head, the head
temperature is higher than the temperature at which replacement is prevented, the
printer displays a BJ cartridge overheat warning (and the beeper sounds 4 times).
While the protection function is operating, the printer temporarily will not allow BJ
cartridge or ink tank replacement.
Protection level 2:
The carriage returns to the home position after printing each line and waits for a
maximum of 3 seconds to allow the print head to cool. This overheat protection
mechanism continues for a minimum of 20 seconds.
Protection level 3:
If the head temperature continues to rise, the printer stops printing; the carriage
continues to move and the paper is fed through the printer. The printer then discards
any further data sent from the host PC, and performs cleaning operations, ink-out
detection, and checks for failure of the head temperature sensor. If the printer
determines that the ink or ink optimizer has run out, it displays an ink-out error
when data is next received from the host PC. If the head temperature sensor is found
to be faulty, the printer displays a BJ cartridge overheat error.
If the BJ cartridge head temperature sensor is faulty, the above overheat
protection controls may not function correctly.
If it detects a fault in the head temperature sensor, the BJC-7100 printer
displays other hardware error messages (the head temperature sensor
error message may not be displayed correctly).
If the printer cannot recover from the overheat protection control
operations to normal printing, or if other hardware error messages are
displayed, replace the BJ cartridge. For details of how to recover from the
respective error states, see Part 5, Section 6, "TROUBLESHOOTING" (page 5-
13) .
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BJC-7100