| 摘要 |
PURPOSE:To oscillate a diaphragm while keeping it flat and to prevent the occurrence of resonance frequency by providing plural driving sources to drive the diaphragm. CONSTITUTION:A bottom plate 2 is provided at the inside of a cylindrical frame 1 made of such as synthetic resin, on the bottom plate 2, the metal diaphragm 6 whose central part is cut off in circle is disposed so that it 6 is not brought into contact with the frame 1, and its lower end part is fixed with an adhesive 9. Two pieces of piezoelectric elements 5 having donut shape that are thin plate are placed on the upper surface of the diaphragm 6, and electrode plates 8 in similar shape are also disposed. A damper 3 is fixed with the adhesive through oscillation bars 7 on the electrode plates 8. When n-pieces of the same element are used instead of the two piezoelectric elements 5 as the driving source, the elements are preferably arranged at each apex of an n-regular polygon.
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