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The DC controller detects the end of toner by monitoring the amount of time it takes for light
to pass through the cartridge during printing.
There is a memory controller PCB with light emitter (LED) and light receiver (PD) on the
back of the cartridge. When a print operation starts, the DC controller emits light from the
LED with TONER LEVEL DETECTION LED DRIVE signal (TONLED). The light enters the
toner container through the light guide attached to the cartridge. It passes through the
container and goes back through the light guide, when the light receiver detects the light.
Upon detection of light, the receiver sends the TONER LEVEL DETECTION signal
(TONSNS) to the DC controller.
Figure 5-42.
Toner level detection
When the toner level is high, the light is interrupted by the toner so it does not reach the light
receiver, and vice versa when the toner level is low. The DC controller detects the toner level
based on the light amount and notifies formatter of the detected toner level.
If no light is detected by the light receiver within a specified time during toner level detection,
the DC controller judges the “toner level sensor abnormal” and sends an error message to
the formatter.
NOTE
All color toner level is detected in full color print, and only K (BK) toner lever, in monochrome
print.
Developing cylinder engaging/disengaging control
This controls the disengagement of the developing cylinder from the photosensitive drum to
prevent toner from being developed on the drum during non-transferring time.
The developing cylinder is engaged/disengaged when the DC controller drives the
developing engaging clutch (CL3) under a specified condition such as when one print is
completed. (See
Figure 5-39. Developing engaging/disengaging unit.)
The following is the disengaging sequence.
162 Chapter 5 Theory of operation ENWW