Displacer Resin Thickness Layout for Cryogenic Refrigerator Reliability
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Solution Overview
Problem
Conventional cryogenic refrigerators face issues with resin peeling and reliability due to temperature differences between the high-temperature and low-temperature sides, leading to potential contact with the cylinder and decreased performance during reverse rotation temperature increase.
Innovation Solution
A two-stage Gifford-McMahon cryogenic refrigerator with a displacer featuring a resin coating where the resin thickness is thinner on the high-temperature side than the low-temperature side, preventing thermal expansion and peeling by maintaining a thicker resin film on the low-temperature side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform thickness resin is formed on the whole outer circumferential surface of the displacer, then the sealing characteristic is improved, but the resin peels off during reverse rotation temperature increase
Solution Approach 1:
The resin thickness is made non-uniform, with a first thickness on the high-temperature side and a second thickness on the low-temperature side. This local variation in resin quality allows the displacer to accommodate thermal expansion during reverse rotation while maintaining sealing effectiveness, preventing resin peeling by providing extra material where thermal stress occurs.
2Stability of the object's composition
If the resin thickness is increased to prevent peeling, then the resin peeling is prevented, but the displacer contacts the cylinder during normal operation
Solution Approach 1:
Instead of uniformly increasing resin thickness, the invention applies thicker resin only where needed (on the high-temperature side where thermal expansion occurs during reverse rotation). This localized approach prevents peeling without causing excessive radial expansion that would lead to displacer-cylinder contact during normal cooling operation.
Solution Approach 2:
The resin coating is segmented into regions with different thicknesses based on thermal expansion requirements. The first region (high-temperature side) has greater thickness to accommodate expansion, while the second region (low-temperature side) has lesser thickness to maintain proper clearance during cooling, avoiding contact with the cylinder.
3Reliability
If the resin thickness is decreased to avoid contact with the cylinder, then the contact with cylinder is avoided, but the resin peels off during reverse rotation
Solution Approach 1:
The invention strategically places thicker resin only on the high-temperature side where thermal expansion occurs during reverse rotation, rather than uniformly thinning the resin. This localized thickness variation maintains adequate clearance during normal operation while providing sufficient material reserve to prevent peeling during thermal expansion events.
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 enhances the reliability of the cryogenic refrigerator and cryopump by preventing resin peeling and contact with the cylinder, ensuring consistent performance across temperature changes.
Implementation Method 1
A thickness of the resin is thinner on the high-temperature side than on the low-temperature side, preventing thermal expansion and peeling
Data Source
AI summary
A two-stage GM cryogenic refrigerator includes a displacer having a low-temperature side and a high-temperature side and a motor configured to drive the displacer. The motor is configured to be rotatable forward in cooling and backward in increasing a temperature. The cryogenic refrigerator further includes a resin provided on an outer circumferential surface of the displacer. A thickness of the resin is thinner on the high-temperature side than on the low-temperature side.