Piezoelectric Transducer Shim Connector for Robust Electrical Connection
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Solution Overview
Problem
Ultrasonic flow meters face challenges in maintaining robust electrical connections to piezoelectric elements due to thermal and mechanical stresses, particularly at varying temperatures, which can lead to electrode separation and increased electrical resistance over time.
Innovation Solution
A piezoelectric assembly with a shim connector attached to the electrode, where the shim connector is made of a material with a coefficient of thermal expansion similar to the piezoelectric element, providing a larger attachment surface area and reducing stress concentrations, and using conductive epoxy to secure the wires to the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wire is soldered directly to the piezoelectric electrode, then the electrical connection is simple and direct, but the connection becomes vulnerable to thermal stress and electrode separation due to mismatched coefficients of thermal expansion
Solution Approach 1:
The patent introduces a shim connector as an intermediary component between the wire and the piezoelectric electrode. This shim connector is bonded to the electrode and provides a larger attachment surface area, acting as a stress-distributing mediator that protects the wire-electrode connection from thermal stress and mechanical damage.
Solution Approach 2:
The shim connector is pre-bonded to the piezoelectric electrode before the wire is attached. This preliminary action creates a robust foundation that distributes thermal and mechanical stresses across a larger area, preventing electrode separation and connection failure during subsequent thermal cycling and operation.
2Ease of manufacture
If the electrical connection uses a small attachment area, then the connection is simple to make, but stress concentrations increase leading to connection failure
Solution Approach 1:
The shim connector transitions the connection from a point-contact or line-contact geometry to a distributed areal contact. By bonding the wire to the shim connector's surface rather than directly to the electrode, the stress is distributed across a two-dimensional area, dramatically reducing stress concentration while maintaining manufacturing simplicity.
3Reliability
If epoxy is used to encapsulate the piezoelectric crystal and wires, then acoustical performance and corrosion protection are improved, but the mismatched coefficient of thermal expansion causes stress on the electrical connections
Solution Approach 1:
The shim connector serves as a mediator between the epoxy-encapsulated electrode and the wire. It absorbs and distributes the thermal expansion stress generated by the epoxy, preventing this stress from concentrating at the wire-electrode connection point while maintaining the protective encapsulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the robustness of the electrical connection, reducing the risk of failure due to thermal and mechanical stresses, and maintains the acoustic performance of the transducer over a broad temperature range.
Implementation Method 1
When an alternating current is applied to the piezoelectric element of the first transducer assembly of the pair, the piezoelectric element responds by radiating an ultrasonic wave through the fluid flowing through the flow meter
Implementation Method 2
When the wave is incident upon the piezoelectric element of the second transducer assembly of the pair, the second transducer assembly responds by generating an electric signal
Implementation Method 3
Temperature changes can exert stress on the electrode connections through differences in the coefficients of thermal expansion (CTEs) of the various materials making up the transducer
Data Source
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AI summary
An embodiment of a piezoelectric assembly for an ultrasonic flow meter comprises a piezoelectric element including a first face and a second face. In addition, the piezoelectric assembly comprises a first electrode engaging the first face. Further, the piezoelectric assembly comprises a second electrode engaging the second face. Still further, the piezoelectric assembly comprises an electrically conductive shim connector attached to the first electrode. Moreover, the piezoelectric assembly comprises a first wire electrically coupled to the shim connector.