Method Of Detecting Remaining Ink - Canon BJ-W3000 Service Manual

CHAPTER 2. BASIC OPERATION

2. Method of detecting remaining ink

The ink remaining in the ink chamber is detected by the remaining ink sensor (PS3) installed
on the purge unit, in the order of yellow, magenta, cyan, and black when the carriage returns to
the home position. The remaining ink sensor (PS3) uses a reflective prism. The light from the
sensor is reflected back by the prism in the bottom of the ink tank, and returns to the light receiv-
ing unit. When there is ink in the chamber, the light is absorbed by the ink and does not reflect
back to the light receiving unit, and the remaining ink signal (INK1_IN) is "1". When there is no
ink in the chamber, the light is reflected back by the prism to the light receiving unit, and the
remaining ink signal (INK1_IN) changes from "1" to "0". When the ink tank is not installed,
there is no prism, the light is not returned to the light receiving unit, and the remaining ink signal
(INK1_IN) is "1".
When the ink in the chamber is exhausted, remaining ink is calculated by counting dots. The
number of ink dots discharged from the head are counted by the gate array on the engine control-
ler and the counted value is sent to the CPU for each band. The CPU adds the dot counts sent to
it and the number of suction times (number of sucked dots) and the total is stored in the
EEPROM. When the total number of ink dots reaches a specified value (the amount of ink held
by the sponge), the indication of the ink status on the message display is changed.
Fig. 2-213 is a flow chart of the ink tank detection and remaining ink detection process.
Ink tank detection/remaining ink detection flow chart
2–36
ink chamber
Figure 2-212