Liquid injection apparatus

A method of adjusting the resonance frequency of an injection unit in a liquid injection apparatus, the liquid injection apparatus having

• an injection unit including a liquid ejection nozzle one end of which is exposed to a liquid injection space, a chamber communicating with the other end of the liquid ejection nozzle and one end of a first liquid supply pipe, a lower electrode formed on a wall surface of the chamber, an upper electrode formed opposite to the lower electrode, and a piezoelectric/electrostrictive element formed between the lower electrode and the upper electrode,
• drive voltage generating means for providing a drive voltage signal having a predetermined frequency across the upper electrode and the lower electrode to thereby give an electric field to the piezoelectric/electrostrictive element, for causing vibration of the wall of the chamber by actuating the piezoelectric/electrostrictive element, and
• pressurizing means having an ejection section to which is connected the other end of the first liquid supply pipe and also having an introduction section communicating with a liquid storage tank, for pressurizing liquid in the liquid storage tank introduced from the introduction section to eject the liquid from the ejection section, to thereby inject the liquid into the liquid injection space via the liquid ejection nozzle of the injection unit,
• wherein liquid injected from the liquid ejection nozzle is atomized by the operation of the piezoelectric/electrostrictive element,
• characterized in that trimming part of the upper electrode to change a region of the piezoelectric/electrostrictive element to which the electric field is applied by the upper electrode and the lower electrode, and thereby adjusting the resonance frequency of the injection unit to be substantially equal to a frequency in the vicinity of the frequency of the drive voltage signal.