Ultrasonic Sensor Piezoelectric Element Segmentation
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Solution Overview
Problem
Conventional ultrasonic sensors face efficiency issues due to low deformation in the film thickness direction, leading to reduced transmission and reception efficiency and poor workability, as the shape of the opening portion must match the active portion of the piezoelectric element, which limits the size and aspect ratio of the opening portion.
Innovation Solution
The ultrasonic sensor design includes a substrate with a high aspect ratio opening portion, a vibration plate, and a piezoelectric element with active portions and suppressing portions to enhance deformation in the film thickness direction, allowing for significant deformation and improved transmission and reception efficiency, while maintaining a larger opening portion size for enhanced productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the shape of the opening portion is made to match the active portion of the piezoelectric element with a low aspect ratio, then significant deformation in the film thickness direction is achieved, but the size of the opening portion becomes excessively small and workability deteriorates
Solution Approach 1:
The piezoelectric element is divided into multiple active portions (first active portion and second active portion) arranged in different directions. This segmentation allows the opening portion to have a larger overall size while each active portion maintains the low aspect ratio needed for significant film thickness deformation, thus resolving the contradiction between deformation efficiency and workability
Solution Approach 2:
Different regions of the piezoelectric element are designed with different functions: the active portions are optimized for deformation (low aspect ratio) while the overall opening portion is optimized for workability (larger size). The suppressing portions are strategically placed to control vibration patterns locally, ensuring that each region contributes to the overall performance without compromising the other
2Ease of manufacture
If the opening portion size is increased for better workability, then manufacturing becomes easier, but partitions forming the opening portion inhibit ultrasonic wave propagation and transmission efficiency decreases
Solution Approach 1:
The piezoelectric element is segmented into multiple active portions that can be independently optimized. This allows the opening portion to be larger for better workability while the active portions maintain the low aspect ratio needed for efficient ultrasonic wave generation, preventing the trade-off between size and efficiency
Solution Approach 2:
Suppressing portions are introduced as intermediary structures between the active portions and the opening partitions. These suppressing portions control the vibration patterns and reduce the inhibitory effect of partitions on ultrasonic wave propagation, thereby maintaining transmission efficiency even with a larger opening portion
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 significantly enhances the efficiency of ultrasonic wave transmission and reception by limiting vibration scope and reducing wave attenuation, resulting in a high-efficiency and mass-producible ultrasonic sensor with improved productivity.
Implementation Method 1
a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode that are stacked on an opposite side of the opening portion of the vibration plate
Implementation Method 2
The efficiency of transmission and reception of the ultrasonic sensor depends on the deformation distribution in the ultrasonic sensor
Implementation Method 3
a suppressing portion that suppresses vibrations of the vibration plate is provided between the adjacent active portions. If the scope of the vibration of the vibration plate is limited by the suppressing portion, the deformation of the piezoelectric element in the film thickness direction in the active portion becomes significant
Implementation Method 4
Examples of a structure of the ultrasonic sensor include a structure in which transmission and reception are performed on an opening portion side
Implementation Method 5
reflection of the ultrasonic waves can be decreased by the partitions forming the opening portion
Implementation Method 6
it is possible to decrease attenuation of ultrasonic waves caused by interference between ultrasonic waves reflected on the partitions and other ultrasonic waves
Data Source
AI summary
An ultrasonic sensor includes a substrate in which an opening is formed; a vibration plate that is provided on the substrate so as to block the opening; and a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode that are stacked on an opposite side of the opening of the vibration plate, in which when a direction in which the first electrode, the piezoelectric layer, and the second electrode are stacked is a Z direction, and a portion that is completely overlapped by the first electrode, the piezoelectric layer, and the second electrode in the Z direction is an active portion, a plurality of active portions are provided so as to face the each opening, and a columnar member is provided between the adjacent active portions.