| 摘要 |
PURPOSE:To reduce an auxiliary vibration in an auxiliary pole compared to a main vibration in a main pole so as to improve a directional pattern in a wave transmitter, and to considerably boost a signal voltage generated from the main pole so as to improve a S/N in a wave receiver by forming a piezo electric board supplied to a piezoelectric transmitter-receiver so that its center can be made thick and gradually thin towards its periphery. CONSTITUTION:A conical surface 2 is formed on one side of a disklike piezoelectric rubber sheet 1 and a flat surface 3 on the other. Thus, the piezoelectric rubber sheet 1 thickened most in the center and gradually thinned toward the periphery. The piezo electric rubber sheet 1 is constituted in such a way that the conical surface 2 is surface-touched a reverse conical surface 6 and overlapped to unify the overlap thickness. A direct current power source 8 is connected to electrodes 4 and 7, and a voltage is impressed and polarized in the thickness direction. The impressed and polarized voltages on the piezoelectric rubber sheet 1 with respect to the unit thickness become equal in the surface direction.
|
