| 摘要 |
PURPOSE:To easily form electrodes by forming the areas of the driving electrodes per unit length in the longitudinal direction of respective surfaces of the electrodes by directing the areas from a center to both end parts to make the area into the gradually narrowing one and forming the areas of the damping electrodes per unit length in the longitudinal direction by directing the areas from both end parts to the center to make the areas into the gradually narrowing one. CONSTITUTION:By impressing an AC power source E which is concerned in a resonance frequency, a piezo-electric vibrator 10 emits an ultrasonic wave from a radiation surface Us upward and from a surface which is confronted with the radiation surface Us downward. In such a case, a piezo-electric vibrator 10 operates in such a way that it is strongly damped on both end parts and is strongly driven as approaching towards the center with directing the longitudinal direction, since the directional characteristic of an ultrasonic wave indicates that the damping electrodes 20a and 20b, and 22a and 22b of same potential exist with facing each other on the side of both end parts in the longitudinal direction of the piezo-electric vibrator 10. |
