PURPOSE: To obtain always a constant granulation characteristic for an ink jet head by a method in which a tiered portion is provided in the liquid chamber of an ink jet head, and a vibrator is driven at a frequency between two or more resonance points.
CONSTITUTION: A tiered portion 3 is provided in the in chamber of an ink jet head. When an ink 1 in the chamber 4 is vibrated by a vibrator 5 if the length of the liquid chamber from the front of a vibrating plate 6 to the rear step of the orifice of a nozzle 7 is l1 and the distance from the front of the vibrating plate 6 to the tiered face 3 is l2, the ink 1 is resonated at different resonance frequencies f1 and f2 corresponding to the distances l1 and l2. Then, the pressure of ink in the nozzle portion 7 in the frequency region between the frequencies f1 and f2 becomes almost constant. Thus, if the vibrator 5 is driven at the frequency fa for a constant pressure section of ink, ink can be always constantly gradulated even when ambient temperature and the viscosity of ink are varied.
KAKEFU SADAO
NARUSE OSAMU
