Ultrasonic Sensor Elastic Layer Layout for Stable Resonance
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Solution Overview
Problem
Existing ultrasonic sensors face issues with varying resonance frequencies due to non-uniform elastic layer thicknesses, leading to decreased transmission and reception sensitivity.
Innovation Solution
The ultrasonic sensor design includes a substrate with a uniform elastic layer thickness equal to or greater than half the substrate thickness, arranged to overlap active portions uniformly, and uses a spatula to form a uniform elastic layer by reciprocating along the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a longitudinal opening with multiple piezoelectric elements is used, then the active area is increased, but the elastic layer thickness becomes non-uniform causing resonance frequency variation
Solution Approach 1:
The elastic layer is designed with different thickness characteristics in different regions: a first elastic layer portion with thickness t1 and a second elastic layer portion with thickness t2, where t1 > t2. This local quality differentiation allows the layer to accommodate multiple piezoelectric elements while maintaining uniform thickness in critical active portions, resolving the contradiction between increased active area and thickness uniformity.
Solution Approach 2:
The elastic layer is segmented into multiple portions (first elastic layer portion and second elastic layer portion) with different thickness characteristics. This segmentation enables the structure to simultaneously support multiple piezoelectric elements across a longitudinal opening while maintaining uniform thickness in the active regions, thus preventing resonance frequency variation.
2Measurement precision
If the elastic layer thickness is reduced to improve resolution, then the resonance frequency varies more, but transmission and reception sensitivity decreases
Solution Approach 1:
The elastic layer employs local quality differentiation with a first portion having thickness t1 and a second portion having thickness t2, where t1 > t2. This allows the structure to achieve fine resolution through the thinner second portion while maintaining sufficient thickness in the first portion to preserve uniform resonance frequency and transmission/reception sensitivity across multiple active portions.
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 design stabilizes resonance frequencies, ensuring uniform frequency output and reception sensitivity, enhancing transmission and reception efficiency while simplifying manufacturing.
Implementation Method 1
a piezoelectric element provided at a surface of the vibration plate opposite from the opening
Implementation Method 2
a surface of the elastic layer is curved so that an ultrasonic wave incident from an opening end side is refracted by the curved surface and is input to a position of the piezoelectric element
Implementation Method 3
an ultrasonic sensor which transmits ultrasonic waves by vibrating a vibration plate
Data Source
AI summary
An ultrasonic sensor includes: a substrate having a first surface and a second surface at an opposite side from the first surface, the substrate having an opening penetrating the substrate from the first surface to the second surface; a vibration plate covering a first surface side of the opening; piezoelectric elements provided at a surface of the vibration plate at an opposite side from the opening and each including a first electrode, a piezoelectric layer, and a second electrode; and an elastic layer in contact with the vibration plate in the opening, in which a portion in which the first electrode, the piezoelectric layer, and the second electrode overlap is defined as an active portion, and a plurality of the active portions face the one opening, and a thickness of the elastic layer is equal to or larger than half a thickness of the substrate and less than the thickness of the substrate, and the thickness of the elastic layer in each of the active portions is uniform.