Thermal bend actuated inkjet with pre-heat mode
View Patent ↗An inkjet printhead with thermal bend actuators for ejecting ink from the nozzle apertures and drive circuitry for operating each thermal bend actuator in a normal mode wherein drive signals to the actuator ejects ink from the chamber, or a pre-heat mode wherein drive signals to the actuator heats ink in the chamber but does not eject ink from the chamber. The invention uses the drive signal to the bend actuator to generate heat to raise the temperature of the ink in the chamber, but controls the signal so that the actuator will not respond in a manner that will eject ink. After a brief pre-heat cycle, the drive circuitry can switch to normal operating mode and the bend actuators will eject ink for printing. With the ink temperature and viscosity within normal operating range, the print quality is not compromised.
1. An inkjet printhead comprising:
an array of nozzles, each having a chamber for storing ink to be ejected, a nozzle aperture in one side of the chamber, a thermal bend actuator for ejecting ink from the chamber through the nozzle aperture, a MEMS temperature sensor and drive circuitry for operating the thermal bend actuator in:
a normal mode wherein drive signals to the actuator ejects ink from the chamber; and
when the MEMS temperature sensor senses that the ink temperature is below a predetermined threshold, a pre-heat mode wherein drive signals to the actuator heats ink in the chamber but does not eject ink from the chamber.
2. An inkjet printhead according to claim 1 wherein the drive signals to the thermal actuator during pre-heat mode are a series of pulses, each with a duration that is insufficient for the thermal bend actuator to eject ink from the chamber.
3. An inkjet printhead according to claim 1 wherein the drive circuitry operates in pre-heat mode after periods of printer inactivity.
4. An inkjet printhead according to claim 1 wherein the array of nozzles is pagewidth and self cooling such that heat generatod by the thermal bend actuator during normal operating mode is removed by the ejected ink drops.