| 摘要 |
PROBLEM TO BE SOLVED: To provide a piezoelectric sensor unit capable of reducing costs by forming a piezoelectric sensor and a level sensor out of one part, or one piezoelectric element, thereby reducing the number of parts and man-hours for assembly. SOLUTION: The piezoelectric element 21 is mounted on the ceiling wall of a fuel tank for vehicle. When the piezoelectric element 21 receives stress corresponding to the inner pressure of the fuel tank, the piezoelectric element 21 generates voltage corresponding to the stress, and the voltage generated at the piezoelectric element 21 is measured to measure the inner pressure of the fuel tank, thereby using it as a piezoelectric sensor. By applying AC voltage to the piezoelectric element 21, an ultrasonic wave is generated from the piezoelectric element 21, the wave level of the fluid fuel in the fuel tank can be measured by clocking the time until the ultrasonic wave is reflected on the fluid level of the fluid fuel in the fuel tank and returned to the piezoelectric element 21, thereby using it as a level sensor.
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