Piezoelectric Actuator Junction Stress Distribution
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Solution Overview
Problem
Piezoelectric actuators face disconnection issues due to concentrated tensile stress at welded junctions, leading to instability and potential failure over time.
Innovation Solution
Incorporating a flange portion with at least two bent portions and a ring-shaped portion between the flange and base body, which distributes stress concentration points and uses a different material for the ring-shaped portion to enhance stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the container is formed by welding members (base body and case) using laser welding or resistance welding, then the piezoelectric element can be enclosed with compressive load applied, but the junction (welded portion) is subjected to tensile stress and may disconnect due to repeated stress
Solution Approach 1:
The invention divides the single welded junction into multiple segments by introducing bent portions and a ring-shaped portion. Instead of having one continuous welded joint between the base body and case, the junction is segmented into multiple sections connected by bent portions that can deform elastically, distributing the tensile stress across multiple points rather than concentrating it at a single location.
Solution Approach 2:
The invention changes the geometric parameters of the junction by introducing bent portions with specific curvature radii and a ring-shaped portion with defined dimensions. These parameter changes allow the junction to accommodate tensile stress through elastic deformation of the bent portions, preventing stress concentration that would lead to disconnection.
2Device complexity
If stress is concentrated at a single place (bent portion) of the junction when viewed in cross section, then the structure is simple, but the junction may disconnect due to repeated tensile stress
Solution Approach 1:
The invention segments the junction structure by introducing multiple bent portions and a ring-shaped portion, transforming a simple single-point stress concentration into a distributed multi-point stress system. This segmentation maintains relative structural simplicity while significantly improving reliability by preventing disconnection through stress distribution.
3Reliability
If the case encloses the piezoelectric element with compressive load, then the piezoelectric element operates under optimal stress conditions, but the welded junction experiences tensile stress that can cause disconnection
Solution Approach 1:
The invention segments the load path at the junction by introducing bent portions that can deform elastically under tensile stress. This segmentation allows the piezoelectric element to maintain compressive load for optimal operation while the segmented junction absorbs tensile stress through elastic deformation, preventing stress concentration and disconnection.
Solution Approach 2:
The bent portions act as intermediary elements between the base body and case, mediating the stress transfer. These bent portions can deform elastically to absorb tensile stress, protecting the welded junction from disconnection while allowing the piezoelectric element to operate under compressive load.
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 junction disconnection due to tensile stress, enabling long-term stable operation of the piezoelectric actuator by distributing stress and preventing plastic deformation.
Implementation Method 1
a piezoelectric element (2)
Data Source
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Figure 2
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AI summary
[Problem] There is provided piezoelectric actuator capable of suppressing disconnection of a junction due to tensile stress. [Solution] A piezoelectric actuator of the invention includes a piezoelectric element, a base body (7) having an upper face on which a lower end of the piezoelectric element abuts, and a case (3) having an inner face on which an upper end of the piezoelectric element abuts, the case being configured to enclose the piezoelectric element, wherein the case (3) includes a flange portion (33) configured to be joined to the base body (7), and at least two bent portions (41) are present on an inner face that is formed from a lower face of the flange portion (33) of the case (3) to the upper face of the base body (7) on an enclosure space side of a junction between the case and the base body.