Acoustic matching member, ultrasound transducer, ultrasonic flowmeter and method for manufacturing the same

An ultrasonic transducer that transmits and receives ultrasonic waves, comprising an acoustic matching member and a piezoelectric member,

• wherein the acoustic matching member comprises at least two layers including a first layer and a second layer that have different acoustic impedance values from each other,
• the first layer is made of a composite material of a porous member and a filling material supported by void portions of the porous member, the second layer is made of the filling material or the porous member, and the first layer and the second layer are present in this stated order,
• wherein the porous member is a sintered porous member of ceramic or a mixture of ceramic and glass, and
• the piezoelectric member is disposed on a side of the first layer of the acoustic matching member.

An ultrasonic flowmeter comprising ultrasonic tranducers that transmit and receive ultrasonic waves, each of the ultrasonic transducers comprising an acoustic matching member and a piezoelectric member, wherein

• the acoustic matching member comprises at least two layers including a first layer and a second layer that have different acoustic impedance values from each other,
• the first layer is made of a composite material of a porous member and a filling material supported by void portions of the porous member, the second layer is made of the filling material or the porous member, and the first layer and the second layer are present in this stated order,
• wherein the porous member is a sintered porous member of ceramic or a mixture of ceramic and glass, and
• the piezoelectric member is disposed on a side of the first layer of the acoustic matching member to form each ultrasonic transducer, and
• the ultrasonic flowmeter further comprising:
• a measurement tube comprising a flow path through which fluid to be measured flows, a pair of the ultrasonic transducers being disposed in the measurement tube on an upstream side and a downstream side relative to the flow of the fluid to be measured so as to oppose each other;
• a transmission circuit for causing the ultrasonic transducers to transmit ultrasonic waves;
• a reception circuit for processing ultrasonic waves received by the ultrasonic transducers;
• a transmission/reception switching circuit for switching between transmission and reception of the pair of ultrasonic transducers;
• a circuit for measuring a time for ultrasonic waves to propagate between the pair of ultrasonic transducers;
• and
• a calculation unit that converts the propagation time into a flow rate of the fluid to be measured.