| 摘要 |
PURPOSE:To improve both transient and transmission/reception sensitive characteristics by setting the resonance frequency of a pasted piezoelectric element containing a diaphragm within a prescribed range. CONSTITUTION:A diaphragm 13 is attached at the center part of a pasted piezoelectric element 11, and the peripheral part of the diaphragm 13 is fixed to the inner side surface of a case 17 via a buffer 20 such as the elastic rubber, etc. In addition, a thin film 23 having opening parts 20, 20' and 20'' is provided at the front part of the diaphragm 13. The resonance frequency which is decided by each opening part of the film 23, the capacity between the film 23 and the diaphragm 13, etc. is set in a range between the resonance frequency of the element 11 and its antiresonance frequency. Thus both transient and transmission/reception sensitive characteristics can be improved by setting the resonance frequency within a prescribed range. |
