Piezoelectric Actuator Protective Assembly for Long-Stroke Stability
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Solution Overview
Problem
Piezoelectric actuators are prone to fracture due to tangential forces, reduced stiffness, and external excitation, especially in longer-stroke conditions, leading to instability and reduced resonant frequency.
Innovation Solution
Incorporating a protective assembly with limiting members and adapters between the housing and piezoelectric assembly, utilizing self-lubricated materials to reduce friction and guide movement, and dividing the piezoelectric assembly into multiple short struts to enhance stability and guide axial movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a longer piezoelectric stack is used to achieve longer stroke, then the stroke length is improved, but the overall stiffness of the ceramic stack is reduced causing it to be more prone to fracture
Solution Approach 1:
The patent introduces intermediate support structures (such as ceramic rings or metal inserts) at regular intervals along the length of the piezoelectric stack. These segmentation elements divide the long stack into multiple shorter segments, each providing local stiffness support while allowing the overall stack to maintain its extended length for long stroke operation.
Solution Approach 2:
The patent employs composite structures by combining piezoelectric ceramic materials with supporting materials having different mechanical properties. The composite design includes ceramic rings or metal inserts positioned within the stack, creating a multi-material structure that maintains both the long stroke capability and adequate stiffness through the synergistic properties of different materials.
2Length of moving object
If a longer piezoelectric stack is used to achieve longer stroke, then the stroke length is improved, but the resonant frequency of the ceramic stack is reduced making it more susceptible to external excitation
Solution Approach 1:
By introducing intermediate support structures that segment the long piezoelectric stack into shorter effective lengths, the patent increases the resonant frequency of each segment. This segmentation approach allows the overall stack to maintain long stroke capability while each shorter segment contributes to higher resonant frequency, reducing susceptibility to external excitation.
Solution Approach 2:
The composite material structure with ceramic rings or metal inserts positioned at specific locations along the stack creates a multi-material system that modifies the vibrational characteristics. The supporting materials have different density and stiffness properties that raise the resonant frequency of the composite structure compared to a uniform long ceramic stack.
3Force
If the piezoelectric stack is subjected to tangential force during use, then the actuator operates under load, but the low stiffness stack generates large strain in radial direction causing fracture
Solution Approach 1:
The intermediate support structures segment the stack into shorter segments along its length, creating multiple load-bearing paths. This segmentation distributes the tangential force and radial strain across multiple shorter segments rather than allowing a single long stack to experience concentrated strain, thereby preventing fracture while maintaining load capacity.
Solution Approach 2:
The composite structure with supporting materials having different mechanical properties creates a multi-material system that better resists radial strain. The supporting ceramic rings or metal inserts provide additional structural reinforcement that distributes and mitigates the effects of tangential forces, preventing the piezoelectric ceramic from fracturing under 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
The solution prevents fracture, ensures smooth movement, and increases the stroke length of the piezoelectric actuator while maintaining high stability and reliability.
Implementation Method 1
when a certain voltage is applied to a piezoelectric ceramic stack, the piezoelectric ceramic stack deforms in an axial direction due to an inverse piezoelectric effect of piezoelectric material, so as to output displacement
Implementation Method 2
the limiting member has at least one lubricated surface, and the lubricated surface is at least arranged on the non-fixed side of the limiting member
Data Source
AI summary
Provided is a piezoelectric actuator and a moving device. The piezoelectric actuator includes: a housing assembly internally provided with an accommodating chamber having an open at an end; a piezoelectric assembly arranged in the accommodating chamber and including a plurality of piezoelectric elements, where the piezoelectric elements are stacked sequentially in an axial direction; and at least one protective assembly arranged in the accommodating chamber and at least a part of the protective assembly is arranged between an inner wall of the housing assembly and an outer wall of the piezoelectric assembly. When two or more protective assemblies are arranged, a plurality of protective assemblies are spaced one above another Through the piezoelectric actuator provided in the present disclosure, the problem that a ceramic stack of a prior piezoelectric actuator is prone to fracture is solved.