B. Detecting the Level of Toner and Controlling the Supply
The level of toner inside the developing assembly is monitored by the toner sensor
(TS1) of a piezoelectric oscillator type which generates the toner absent signal (TEP*=0)
when the level drops below a specific value.
The DC controller turns on the hopper motor (M4) to start toner supply when it has
detected TEP*=0 for 1 sec or more continuously.
The hopper motor drive signal (HMD*) is generated so that it is ‘1’ for 1 sec and ‘0’
for 4 sec; this cycle of 5 sec is repeated as necessary.
The hopper motor (M4) is stopped when the toner absent signal (TEP*) goes ‘1’.
If the toner absent signal (TEP*) does not go 25 sec after the start of toner supply,
the DC controller PCB assumes the absence of toner inside the hopper and lights the
“Add Toner indicator” after copying operation (max : 100 sheets of paper).
Reference:
The detecting unit of the toner sensor used inside the developing assembly is of a
piezoelectric oscillator type; it vibrates at several kHz in the absence of toner with
its output ‘1’, and stops vibrating because of the weight of toner in the presence of
toner with its output going ‘1’.
Figure 4-202
CHAPTER 4 IMAGE FORMATION SYSTEM
COPYRIGHT © 1997 CANON INC. CANON NP6330 REV.0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
4-23
Amplifier (R)
circuit
Phase detec-
tion circuit
Digital
processor
circuit
Oscillator
circuit
Sensor
Output
circuit
TEP*
