Detecting And Controlling The Level Of Toner - Canon NP7160 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
B. Detecting and Controlling the Level of Toner
The toner inside the developing assembly is monitored by the toner sensor (TS1).
The toner sensor uses a piezoelectric oscillator which oscillates in the absence of toner over
the sensor at several kHz and sends an oscillation signal (TNEMP) to the DC controller PCB. In
the presence of toner over the sensor, on the other hand, the weight will prevent oscillation.
The copier detects the absence of toner in two stages.
The DC controller PCB monitors the output of the toner sensor at all times as long as the
main motor is rotating. If the sum of periods of the toner absent signal is 70 sec (consecutive two
periods), it will identify the condition as a condition preceding the absence of toner and will flash
the Toner indicator on the control panel.
Thereafter, if the period of the toner absent signal reaches 180 sec or more, the DC controller
PCB will assume the condition to be the absence of toner, and will stop flashing the Toner
indicator to keep it on. At this time, the copy being made is processed as would a normal copy
and discharged, and then the operation will be stopped.
Sequence
Toner sensor (TS1)
Toner indication
Flashing
On
Note:
When the DC controller identifies a condition preceding the absence of toner, there is
likely to be as much as 10 g of toner inside the developing assembly. In terms of A4
copies, about 200 copies may be made without the addition of toner.
4–16
COPYRIGHT © 1998 CANON INC.
AMP
Piezoelectric oscillator
Figure 4-203
T1
Toner absent
Figure 4-204
Conditions
(T1+T2) or (T2+T1)
T1 or T2
Table 4-201
CANON NP7161/NP7160 REV.0 AUG. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
Output
Integration
circuit TNEMP
T2 T1
= >
70sec
= >
180sec
T2 T1
Copying
Possible
No possible