Ultrasonic Sensor Piezoelectric Element Layer Segmentation
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Solution Overview
Problem
In ultrasonic sensors with multilayer piezoelectric elements, the number of layers affects both sound pressure and sensitivity in a reverse proportion, leading to folding issues during production when transmission and reception regions are adjacent, compromising sensor performance.
Innovation Solution
The ultrasonic sensor incorporates a piezoelectric element with distinct transmission and reception regions, separated by an isolation region, and includes float electrodes to prevent folding, allowing independent adjustment of sound pressure and sensitivity by varying the number of layers in each region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the number of layers in the piezoelectric element is increased, then sound pressure during transmission is improved, but sensitivity during reception deteriorates
Solution Approach 1:
The piezoelectric element is divided into multiple independent piezoelectric layers (first through fourth layers) with different numbers of layers dedicated to transmission and reception functions. The transmission region uses fewer layers (first and second layers) optimized for sound pressure generation, while the reception region uses more layers (third and fourth layers) optimized for sensitivity, resolving the contradiction between transmission performance and reception sensitivity
Solution Approach 2:
Different regions of the piezoelectric element are assigned different structural characteristics: the transmission region (first and second piezoelectric layers) has a structure optimized for generating sound pressure, while the reception region (third and fourth piezoelectric layers) has a structure optimized for detecting ultrasonic waves. This local differentiation allows each region to perform its function optimally without compromising the other
2Adaptability or versatility
If transmission and reception regions are formed adjacent to each other in the piezoelectric element, then independent adjustment of sound pressure and sensitivity is improved, but folding during production occurs
Solution Approach 1:
Electrode extensions are introduced as intermediary structures between the transmission and reception regions. These extensions physically separate the two functional regions and provide structural support that prevents the piezoelectric layers from folding during production, while still allowing the adjacent arrangement that enables independent adjustment of transmission and reception characteristics
Solution Approach 2:
The electrode extensions are formed in advance during the manufacturing process to prevent folding before it occurs. By pre-establishing these structural supports, the piezoelectric element maintains its integrity during subsequent production steps while preserving the adjacent transmission and reception region configuration
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 effectively suppresses folding, ensuring proper bonding and improved sensitivity and adhesive properties, enabling independent control of sound pressure and sensitivity during transmission and reception.
Implementation Method 1
a piezoelectric element bonded to an inner surface of the bottom portion and configured to undergo bending vibration together with the bottom portion
Data Source
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AI summary
A piezoelectric element of an ultrasonic sensor includes: a piezoelectric layer (40) including a transmission region (40N) and a reception region (40M); a common electrode (30); a transmission electrode (20); and a reception electrode (10). The transmission region and the reception region are adjacent to each other with an isolation region (40V) being interposed therebetween. The transmission region includes one or a plurality of first constituent piezoelectric layers, and the reception region includes one or a plurality of second constituent piezoelectric layers. The number of the one or the plurality of first constituent piezoelectric layers included in the transmission region is different from the number of the one or the plurality of second constituent piezoelectric layers included in the reception region, and a float electrode (70) is provided in one of the transmission region and the reception region, the one of the transmission region and the reception region having a smaller number of layers. This piezoelectric element can suppress occurrence of folding.