Service manual

Chapter 8
8-3
8.2 Various Control Mechanisms
8.2.1 Controlling the Speed of the Fixing Film
8.2.1.1 Controlling the Fixing Film Speed
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iR2016J / iR2016 / iR2020 / / iR2016i / iR2020i
The rotation cycle is measured with reference to the mark provided at the end of the fixing film to rotate the fixing drive motor at the optimum speed, thus keeping
the paper feed speed constant. Measurement of the cycle of each rotation (excluding the initial rotation and post-rotation) of the fixing drive motor starts when 1
second lapses after the motor starts rotating and ends when the trailing edge of the last sheet has passed through the fixing nipper.
F-8-3
[1] Film rotation detection signal (FILM_SENS): Set to 1 and 0 alternately when the fixing film is rotating.
[2] Rotation cycle measurement mark
8.2.2 Controlling the Fixing Film Temperature
8.2.2.1 Outline
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iR2016J / iR2016 / iR2020 / / iR2016i / iR2020i
The surface temperature of the fixing heater is detected to control the fixing heater drive signal so that the fixing heater temperature becomes the target temperature.
The temperature of the fixing heater is detected by the thermistor (TH1/TH2) provided on the fixing heater. If the surface temperature rises, the resistance of the
thermistor lowers and the voltage of the fixing heater temperature detection signal (M_TH/S_TH) also lowers.
The CPU on the DC controller monitors the voltage of the M_TH/S_TH signal to control the fixing heater 1 drive signal (H1DRV) and fixing heater 2 drive signal
(H2DRV). These two voltages are generated based on the zero crossing detection signal which is output from the heater control circuit. The CPU controls these two
signals to adjust the fixing heater temperature to the prescribed value.
8.2.2.2 Controlling the Fixing Film Temperature
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iR2016J / iR2016 / iR2020 / / iR2016i / iR2020i
This machine performs fixing temperature control according to the fixing heater temperature as mentioned below.
1) Warm-up temperature control
Upon receipt of a print command from the DC controller, the fixing heater heats to the temperature below the target paper-present section temperature.
2) Paper-present section temperature control
The fixing heater temperature is adjusted to the target paper-present section temperature according to the combination of the paper size, number of sheets fed,
fixing mode, and temperature detected by the fixing main thermistor.
3) Sheet-to-sheet temperature control
The fixing heater temperature is held relatively below the target paper-present section temperature to prevent the paper-absent section temperature from rising
between sheets.
4) Down sequence
The temperature may detect an abnormally high temperature during continuous printing. If the sub-thermistor detects a temperature equal to or higher than 275
deg C, the sheet-to-sheet distance is increased to prevent the paper-absent section temperature from rising. If the sub-thermistor detects a temperature equal to
or lower than 220 deg C in the down sequence, normal control resumes.
5) Cooling mode
If printing is performed using wider sheets (*1) after printing is performed using narrower sheets in the continuous print mode, fixing offset may occur due to
the difference in temperature between the edge and center. If the sub-thermistor detects a temperature equal to or higher than 130 deg C, paper feed and printing
stop to prevent the temperature from rising at the edge. If the sub-thermistor detects a temperature equal to or lower than 130 deg C or two or more minutes lapse,
normal control resumes.
*1: The large size is a paper of which the width is 10 mm larger than the previous job.
DC Controller PCB
[1] FILM_SENS
[2]
J217