Flexure Bearing Leaf Spring Design for Cryocooler Horizontal Stiffness
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Solution Overview
Problem
The existing flexure bearings in cryocoolers, particularly those with spiral leaf spring structures, face issues with horizontal stiffness and repeated contact or collision between moving parts, which affect the long-term reliability of linear compressors and cryocoolers.
Innovation Solution
A flexure bearing design featuring leaf springs with arm portions that linearly extend in a direction perpendicular to the oscillating direction, having an increasing arm width from an intermediate portion towards fixation points, and incorporating inner and outer spacers to alleviate stress concentration and enhance horizontal stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spring length is increased to improve stroke and fatigue resistance, then the reliability is improved, but the horizontal stiffness decreases causing displacement and inclination
Solution Approach 1:
The arm portion of the leaf spring is designed with variable thickness, being thicker at the inner and outer ends and thinner at the intermediate portion. This local variation in quality allows the spring to have sufficient stiffness at the fixation points while maintaining flexibility and fatigue resistance in the intermediate regions, thereby resolving the contradiction between reliability and horizontal stiffness.
2Length of moving object
If the spring length is increased to allow longer stroke, then the oscillating range is improved, but the movable member is likely to be displaced or inclined
Solution Approach 1:
By making the arm portion thicker at its ends and thinner at the intermediate portion, the leaf spring achieves optimal balance between allowing sufficient stroke length and maintaining positional stability. The thicker end portions provide stiffness to prevent displacement and inclination, while the thinner intermediate portion allows for the required oscillating range.
3Strength
If the arm width is increased to improve horizontal stiffness, then the stability is improved, but the stress concentration increases at the fixation portions
Solution Approach 1:
The leaf spring is designed with non-uniform thickness where the arm portion is thicker at the inner and outer ends and thinner at the intermediate portion. This local variation allows the fixation portions to have sufficient thickness for horizontal stiffness while the intermediate portion has reduced thickness to lower stress concentration, thereby resolving the contradiction between stiffness and stress concentration.
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 design improves the horizontal stiffness and reduces stress concentration, thereby enhancing the long-term reliability and reducing the likelihood of contact or collision between moving parts in cryocoolers, ensuring stable operation over extended periods.
Implementation Method 1
a flexure bearing that includes at least one leaf spring, which is disposed in a plane perpendicular to the oscillating direction and connects the oscillating body to the support body
Data Source
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AI summary
There are provided a flexure bearing (38) that improves the reliability of a linear compressor (12) and a cryocooler (10) that has such a flexure bearing (38) . The flexure bearing (38) that includes at least one leaf spring (40), which is disposed in a plane perpendicular to an oscillating direction of an oscillating body and connects the oscillating body to a support body. The leaf spring (40) includes an inner fixation portion (42) that is fixed to one of the oscillating body and the support body, an outer fixation portion (44) that is fixed to the other one of the oscillating body and the support body, an arm portion (46) that connects the inner fixation portion (42) and the outer fixation portion (44) to each other, linearly extends in an arm longitudinal direction intersecting a radial direction of the leaf spring (40) in the plane, and has an arm width in a direction perpendicular to the arm longitudinal direction in the plane, which increases from an intermediate portion (46c) of the arm portion (46) to each of the inner fixation portion (42) and the outer fixation portion (44).