Patent ID: 7370925
Filing Date: 2008-05-13
Classification: B41J

Abstract:
1. A method for driving the piezoelectric ink jet head composed of: a pressure chamber filled with an ink; a nozzle that communicates with the pressure chamber and has an ink meniscus formed therein from the ink that fills the pressure chamber; a piezoelectric element that deforms when subjected to a drive voltage applied thereto; and an oscillator plate that is stacked on the piezoelectric element so as to constitute a drive section and deflects so as to decrease the volume of the pressure chamber as the piezoelectric element deforms when a voltage is applied thereto, so as to pressurize the ink in the pressure chamber and discharge an ink droplet from the tip of the nozzle, and wherein the piezoelectric ink jet head is operated by combining (A) the step of applying the drive voltage to the piezoelectric element so that the piezoelectric element deforms and the oscillator plate deflects, thereby decreasing the volume of the pressure chamber, and (B) the step of removing the drive voltage applied to the piezoelectric element so that the deformation of the piezoelectric element is canceled and consequently the deflection of the oscillator plate is canceled, thereby increasing the volume of the pressure chamber, thereby to discharge an ink droplet from the tip of the nozzle, characterized in that the piezoelectric element is driven with a drive voltage waveform of which pulse width T wherein the piezoelectric ink jet head is also operated as follows, a constant drive voltage is continuously applied to the piezoelectric element during a period of standby so that the piezoelectric element is kept deformed and the oscillator plate continues to deflect, thereby to maintain the pressure chamber in a state of decreased volume and, during a period of forming a dot, (1) the drive voltage is removed immediately before forming the dot so as to cancel the deformation of the piezoelectric element and relieve the oscillator plate of deflection, thereby increasing the volume of the pressure chamber and pulling the ink meniscus in the nozzle back toward the pressure chamber, then (2) the drive voltage is applied again so as to cause the piezoelectric element to deform and the oscillator plate to deflect, thereby decreasing the volume of the pressure chamber and discharge an ink droplet through the tip of the nozzle, and (3) pulse width T