Cryocooler Compressor Seal and Alignment Using Magnetic Axial Stiffness
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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 reduced thermodynamic performance, as well as difficulties in maintaining proper alignment and minimizing off-axis disturbances.
Innovation Solution
A small-scale compressor design utilizing magnetic axial stiffness and a bellows seal system, eliminating the need for mechanical springs and simplifying construction, while providing high radial stiffness and effective sealing, allowing for operation in a very small package volume.
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 too complex and difficult to scale down
Solution Approach 1:
The patent replaces complex mechanical flexure systems with a magnetic field-based alignment mechanism. Magnets embedded in the piston and corresponding magnets in the cylinder wall create magnetic attraction forces that automatically center the piston without requiring complex mechanical flexures, thereby reducing system complexity while maintaining alignment precision.
Solution Approach 2:
The patent changes the physical parameters of the sealing system by using magnetic field strength and gradient as the controlling parameter instead of mechanical flexure geometry. By adjusting magnet strength, spacing, and arrangement, the alignment characteristics can be optimized without increasing mechanical complexity.
2Reliability
If traditional clearance gap seals are used in small-scale compressors, then sealing is provided, but friction and seal blow-by increase reducing thermodynamic performance
Solution Approach 1:
The patent replaces traditional mechanical clearance gap seals with a magnetic field-based sealing mechanism. The magnetic attraction between pist on magnets and cylinder wall magnets creates a sealing force that prevents gas leakage without requiring physical contact, thereby eliminating friction losses and improving thermodynamic performance.
Solution Approach 2:
The patent uses the magnetic field as a non-contact force field analogous to pneumatic or hydraulic systems. The magnetic pressure distribution created by the magnet arrangement provides sealing force similar to how gas pressure provides sealing force in traditional systems, but without the harmful friction associated with mechanical contact.
3Stability of the object's composition
If mechanical springs are used for axial stiffness, then alignment is maintained, but the device size increases and construction becomes more complex
Solution Approach 1:
The patent replaces mechanical springs with magnetic field-based axial stiffness provision. Magnets arranged in alternating polarity patterns along the axial direction create magnetic restoring forces that provide axial stiffness without requiring physical spring components, thereby simplifying construction and reducing device size.
4Manufacturing precision
If mechanical springs or flexures are used for suspension, then alignment is maintained, but the system cannot be scaled down to small sizes
Solution Approach 1:
The patent replaces mechanical suspension systems with magnetic field-based suspension. The magnetic attraction forces between pist on magnets and cylinder wall magnets provide the necessary suspension and alignment functions without requiring large mechanical components, enabling scaling down to small compressor sizes while maintaining alignment precision.
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 resonant frequencies, long operational lifetimes, and efficient gas compression with minimal leakage, overcoming the limitations of traditional clearance gap seals in small-scale compressors by leveraging magnetic stiffness and bellows seals.
Implementation Method 1
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 effective length of the gap between the stationary coil assembly and the moving assembly so as to provide magnetic axial stiffness resisting motion of the moving assembly
Data Source
AI summary
In one 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.