| 摘要 |
PURPOSE:To achieve a simplification of manufacture, a lower cost and a smaller size with a reduction in fluctuation in characteristics by applying an electric field between external electrodes and between internal and external electrodes to perform a polarization while a cylinder is made of piezo-electric ceramics. CONSTITUTION:A vibrator 12 which is formed into a cylinder from piezo-electric ceramics is subjected to a polarization radially from the inner to outer circumferential surface thereof and an internal electrode 16 is formed entirely on the inner circumferential surface thereof while external electrodes 18a, 18b and 18c are formed on the outer circumferential surface with the outer circumference thereof being divided in three. An electric field is applied between the electrodes 18a, 18b and 18c or between the electrode 16 and the electrodes 18a, 18b and 18c to polarize the vibrator 12 radially from the inner to outer circumferential surfaces. As a result, the vibrator 12 itself bends, eliminating the need for bonding a piezo-electric element and hence, there is no variation in adhesion parts wing to changes in atmospheric temperature thereby reducing fluctuation in characteristics. Coupled with a cylinder in shape of the sensor, a through hole is formed to facilitate working with a simple making of a die thereby achieving a lower cost and a smaller size. |
