Cryocooler Compressor Bellows Seal With Magnetic Alignment
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Solution Overview
Problem
Small-scale cryocooler compressors face challenges in achieving long-life seals and alignment due to the inability to scale down large-scale flexure systems, leading to increased friction, seal blow-by, and premature degradation, which affects thermodynamic performance and generates particulate debris.
Innovation Solution
A small-scale compressor design utilizing a magnetic motor assembly with a bellows seal and guide rod, eliminating the need for mechanical springs, providing high axial stiffness and effective sealing, and allowing for efficient gas compression with minimal leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large-scale flexure systems are used in small-scale compressors, then alignment and centering are improved, but the system becomes inadequate for small-scale applications due to scaling issues
Solution Approach 1:
The patent replaces mechanical flexure systems with magnetic fields generated by coil assemblies to achieve alignment and centering functions. The stationary coil assembly and moving coil assembly create magnetic forces that automatically center the moving assembly within the housing, eliminating the need for mechanical flexures and enabling scalability to small-scale compressors while maintaining precise alignment.
2Reliability
If mechanical springs are used for suspension, then sealing is improved, but friction and debris generation increase reducing operational lifetime
Solution Approach 1:
The patent eliminates mechanical springs and contacts by using magnetic suspension through coil assemblies. The moving assembly is suspended magnetically within the compression volume, providing sealing without mechanical friction or wear. This contactless suspension system prevents debris generation and extends operational lifetime while maintaining effective sealing.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary between the moving assembly and housing to achieve suspension and sealing functions. The magnetic field acts as a non-contacting mediator that provides the necessary forces for centering and sealing without direct mechanical contact, thereby eliminating friction and wear associated with traditional mechanical spring systems.
3Loss of substance
If clearance gap seals are used, then gas leakage is reduced, but seal blow-by increases in small-scale applications
Solution Approach 1:
The patent replaces clearance gap seals with magnetic field-based sealing through coil assemblies. The stationary and moving coil assemblies create magnetic forces that maintain optimal gaps and prevent gas leakage without the blow-by issues encountered in small-scale clearance gap seals. This magnetic sealing mechanism provides superior performance in compact configurations.
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 achieves high radial stiffness, extended operational lifetime, and resonant frequencies exceeding those of large-scale compressors, while simplifying packaging and reducing friction and debris generation.
Implementation Method 1
The magnetic motor assembly includes a moving assembly with one or more magnets and a stationary coil assembly. The moving assembly is configured to reciprocally move between top-stroke and bottom-stroke positions while each time passing through a mid-stroke position, the moving assembly forming gaps between the moving assembly and the stationary coil assembly that are at a minimum in the mid-stroke position and are at a maximum in the top-stroke position and the bottom-stroke position such that the increased gaps result in a magnetic restoring force that urges the moving assembly toward the mid-stroke position.
Implementation Method 2
A bellows seal is interposed between a top surface of the moving assembly and a top inside surface of the housing at least partially defining the compression volume
Data Source
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AI summary
In one embodiment, a compressor includes a moving assembly configured to compress a gas within a compression volume; a guide rod connected to the moving assembly which reciprocates axially with the moving assembly; and a bellows seal positioned between the moving assembly and a stationary housing which at least partially defining the compression volume. In another embodiment, a compressor includes a motor assembly configured to compress a gas within a compression volume, the motor assembly including: a stationary coil assembly; a moving assembly having at least one magnet, and a gap located between the stationary coil assembly and the moving assembly; wherein the moving assembly is configured to reciprocate axially with respect to the stationary coil assembly when electrical current is applied to the stationary coil assembly, and to change the width of the gap between the stationary coil assembly and the moving assembly so as to provide magnetic axial stiffness against motion of the moving assembly. One or more embodiments may be used in a cryocooler assembly.