Epson STYLUS 4001968 Service Manual page 29

STYLUS 800 Service Manual
Principles
of the Printing Operation
The operation of the printhead to inject ink from each nozzle is:
(1) Normal state
No electrical charge is applied to the MLP (Multi-Layer Piezoelectric) element attached to the back
of the cavity, and pressure inside the cavity is kept at constant level.
(2) Injecting state
The head data signal is applied to the specific nozzle control line to select the active nozzle for
printing, and the MLP element is gradually charged by the drive voltage. By charging the MLP
element, the vibration plate is bent to compress the cavity. Then, ink is injected from the nozzle.
Figure 2-3. Principles of the Printing Operation
When the ink charge or printhead cleaning operation is performed, the ink in the cavity is
vacuumed out with the pump mechanism.
simultaneously supplied from the ink
change of volume in the cavity.
A thermistor is attached to the printhead drive board to monitor the temperature, because the
viscosity of the ink varies, depending on the temperature. The detected temperature level is fed
back to the printhead drive voltage control circuit to regulate the drive voltage to a proper level.
Rev. A
During printing, on the other hand, the ink is
injected from the nozzle, according to the
cartridge and
Operating Principles
2-3