| 摘要 |
PURPOSE:To prevent vibration modes from coupling with each other and, as a result, facilitate high efficiency operation by a method wherein a first elastic element, first piezoelectric elements and second piezoelectric elements which excite standing waves of two directions which are approximately perpendicular to each other in the first elastic unit and a second elastic unit which is bonded to the first elastic element by compression are provided. CONSTITUTION:To the upper surface of an elastic unit 21 which has a rectangular square column shape, first piezoelectric elements 41-44 which are divided into four are attached to excite a bending vibration in the elastic unit 21. Further, to the lower surface of the elastic element 21, first piezoelectric elements 45-48 which are divided into four are attached to excite a bending vibration in the elastic unit 21. Electrodes 51-58 are connected to the first piezoelectric elements 41-48 respectively and the electrodes 51-58 are connected to an AC power supply 60 in parallel with each other through switches S1-S8. When the elastic unit 21 has variation in its shape along a direction of an arrow Z and the thickness of the +Z direction is larger than the the thickness of the -Z direction, if the switches S1 and S5 which correspond to the piezoelectric elements 41 and 45 are cut off, the variation in the shape of the elastic unit 21 is balanced with a distribution of excitation force and only the required bending vibration can be excited. |
