Ultrasonic Transducer Structure for Below-Resonance Directivity Control
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Solution Overview
Problem
Existing ultrasonic transducers with parallel piezoelectric elements face challenges in controlling directivity due to dispersion in resonance frequencies, making precise phase control difficult, especially when driving frequencies are set below the resonance frequency.
Innovation Solution
The ultrasonic transducer design includes a rigid supporting plate with cavity portions and waveguides, a flexible resin film, and piezoelectric elements arranged to overlap with the cavity portions, suppressing transmission of frequencies near resonance while allowing transmission of driving frequencies, thereby enhancing sound pressure and directivity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the driving frequency is set below the resonance frequency of the piezoelectric element, then the vibrational amplitude can be secured, but the directivity control of the sonic wave becomes difficult due to frequency components near resonance
Solution Approach 1:
The patent introduces a flexible resin film as an intermediary layer between the piezoelectric element and the rigid substrate. This film acts as a mechanical filter that suppresses transmission of frequency components near the resonance frequency while allowing the driving frequency to pass through, thereby resolving the contradiction between maintaining vibrational amplitude and controlling directivity
Solution Approach 2:
The patent changes the mechanical parameters of the coupling structure by using a flexible resin film with specific viscoelastic properties. This modifies the frequency transmission characteristics of the system, enabling suppression of resonance frequency components while maintaining transmission of the driving frequency, thus improving directivity control
2Adaptability or versatility
If multiple piezoelectric elements are arranged in parallel for phased array operation, then the detection range is expanded, but uniformization of resonance frequencies among elements becomes extremely difficult
Solution Approach 1:
The patent applies local quality by providing individual cavity portions for each piezoelectric element through which the flexible resin film passes. Each element thus has its own localized mechanical filtering structure, allowing independent optimization of frequency characteristics for each element while maintaining overall array functionality
Solution Approach 2:
The patent changes the mechanical boundary conditions for each piezoelectric element by introducing individual cavities and flexible film passages. This modifies the resonance characteristics of each element locally, making it easier to uniformize frequencies across the array by adjusting cavity dimensions or film properties
3Stability of the object's composition
If a rigid substrate is used to support the piezoelectric elements, then structural stability is improved, but the control of sonic wave directivity deteriorates when driving frequency is below resonance frequency
Solution Approach 1:
The patent introduces the flexible resin film as an intermediary layer between the rigid substrate and the piezoelectric elements. This film decouples the rigid substrate from direct mechanical interaction with the piezoelectric elements, allowing the substrate to provide structural stability while the film controls the mechanical transmission of vibrational frequencies, thereby improving directivity control
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
This configuration ensures sufficient vibration amplitude and precise phase control of sonic waves, even at driving frequencies below resonance, improving directivity and sound pressure output.
Implementation Method 1
a plurality of piezoelectric elements functioning as vibrating bodies are arranged in parallel
Implementation Method 2
The cavity portion and the waveguide are configured to have a shape and size set so as to suppress transmittance of the sonic wave, which has the frequency within ±1.5% of the resonance frequency of the piezoelectric element
Implementation Method 3
a flexible resin film that is fixed to the first surface of the supporting plate so as to cover the plurality of cavity portions
Data Source
AI summary
An ultrasonic transducer of this invention includes a supporting plate having plural cavity portions and waveguides opened to first and second surfaces, respectively, a flexible resin film fixed to the supporting plate, and plural piezoelectric elements fixed to the flexible resin film so that, in a plan view, their center regions overlap with the corresponding cavity portions and their peripheral regions overlap with the supporting plate, the cavity portion and the waveguide portion being set to have a shape and size set so as to suppress transmittance of the sonic wave, which has the frequency within ±1.5% of the resonance frequency of the piezoelectric element.