Pressure Sensor Case Projections for Stress Distribution
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Solution Overview
Problem
Conventional pressure sensors face issues with stress concentration at the edges of the piezoelectric device, leading to cracking and reduced sensitivity due to the large size of the thick-walled case, which results in decreased reliability under repeated stress.
Innovation Solution
A pressure sensor design featuring a laminated piezoelectric device housed in a case with inwardly projected first and second projections, where the first projection's end face abuts the piezoelectric device to distribute stress evenly, reducing the likelihood of cracking, and the second projection helps in distributing external forces uniformly, while the resin between the case and the piezoelectric device further reduces stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the case wall thickness is increased to transmit force effectively, then force transmission is improved, but stress concentration occurs at the piezoelectric device edges leading to cracking
Solution Approach 1:
The case features localized thickening through inward projections at specific contact points with the piezoelectric device, rather than uniformly increasing wall thickness throughout. This localized quality change allows effective force transmission at contact points while avoiding stress concentration in other areas, resolving the contradiction between force transmission and crack resistance
Solution Approach 2:
The case wall is segmented into different thickness zones: thicker regions at inward projections for force transmission and thinner regions elsewhere to reduce overall stress. This segmentation allows the structure to optimize both force transmission capability and resistance to cracking by distributing wall thickness non-uniformly
2Measurement precision
If a thin-walled case is used to maintain high sensitivity output, then measurement sensitivity is improved, but the case becomes too weak to protect the piezoelectric device from stress concentration
Solution Approach 1:
The case employs local quality enhancement through inward projections that create localized thickened regions only where force transmission and stress distribution are needed. The majority of the case wall remains thin to maintain high measurement sensitivity, while the localized thickening provides the necessary strength and crack resistance
Solution Approach 2:
The inward projections act as intermediary structures between the external environment and the piezoelectric device. These projections distribute external forces uniformly across the piezoelectric device surface before transmission, preventing stress concentration while allowing the thin-walled case to maintain its sensitivity advantage
3Productivity
If the case is made compact for effective force transmission, then force transmission efficiency is improved, but stress concentration at piezoelectric device edges increases
Solution Approach 1:
The case structure uses local quality variation with inward projections creating localized thickened contact points. These projections concentrate force transmission capability at specific locations while distributing stress away from the piezoelectric device edges, achieving both efficient force transmission and reduced stress concentration
Solution Approach 2:
The case wall thickness is segmented into discrete zones: thickened regions at inward projections for force transmission and thinner regions elsewhere. This segmentation allows the compact structure to maintain force transmission efficiency while avoiding edge stress concentration through strategic thickness distribution
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 design enhances the durability and reliability of the pressure sensor by reducing stress concentration and preventing crack propagation, maintaining sensitivity over repeated use and increasing the sensor's durability.
Implementation Method 1
a pressure sensor that utilizes a laminated piezoelectric device
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
A pressure sensor (1) of the present disclosure includes a laminated piezoelectric device (2) including a stacked body (23) in which piezoelectric layers (21) and internal electrodes (22) are alternately laminated; and a case (3) which encloses the laminated piezoelectric device (2), the case (3) including a case main body (31) and a first projection (32) protruding inwardly from the case main body (31), the first projection (32) including an end face (32a) which abuts on an end face in a stacking direction of the stacked body (23), and is located inside an outer periphery of the end face of the stacked body (23) .