Bearing Assembly Thermal Expansion Decoupling
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Solution Overview
Problem
Previous electrical generators face reliability issues due to fretting corrosion caused by mismatched thermal expansion rates between aluminum or magnesium frames and hardened steel bearing liners, leading to increased clearance and reduced bearing system reliability.
Innovation Solution
A bearing support assembly with a frame made from a first material and a bearing liner made from a second material with a dissimilar thermal expansion rate, where a non-metallic ring surrounds the bearing liner to decouple thermal expansion and maintain clearance, thereby mitigating fretting corrosion and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardened steel bearing liners are shrunk fit or cast into aluminum or magnesium frames, then the frame provides a low-wear surface to mate with the bearing outer ring, but the mismatched thermal expansion rates cause the liner to expand away from the bearing outer ring, increasing clearance and leading to fretting corrosion
Solution Approach 1:
A non-metallic ring (intermediary component) is introduced between the bearing liner and the frame. This ring has a thermal expansion rate that is intermediate between the aluminum/magnesium frame and the steel bearing liner, thereby compensating for the thermal expansion mismatch and maintaining proper clearance between the liner and bearing outer ring during temperature changes, preventing fretting corrosion
Solution Approach 2:
The invention changes the thermal expansion parameter by selecting a non-metallic ring material whose thermal expansion coefficient is specifically chosen to be between that of the aluminum/magnesium frame and the steel bearing liner. This parameter adjustment allows the assembly to accommodate thermal expansion differences without causing harmful clearance variations
2Strength
If hardened steel bearing liners are shrunk fit or cast into aluminum or magnesium frames, then the frame provides structural support, but the combined thermal expansion rate of the frame and liner is greater than that of the steel bearing outer ring, causing increased clearance
Solution Approach 1:
The non-metallic ring acts as an intermediary that decouples the thermal expansion behavior of the frame from the bearing liner. This allows the frame to maintain its structural support function while the ring compensates for differential thermal expansion, thereby maintaining precise clearance control between the liner and bearing outer ring
Solution Approach 2:
The bearing support assembly is segmented into distinct components (frame, non-metallic ring, bearing liner) that can independently accommodate thermal expansion. This segmentation allows each component to be optimized for its specific function while the non-metallic ring bridges the thermal expansion gap between the frame and liner
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 effectively manages thermal expansion differences, reducing fretting corrosion and improving bearing system reliability by maintaining proper clearance and concentricity, thus enhancing the overall performance of electrical generators.
Implementation Method 1
the combined thermal expansion rate of the aluminum or magnesium frame and steel bearing liner is greater than the thermal expansion rate of the steel bearing outer ring. Therefore the liner expands away from the bearing outer ring which increases the clearance between the liner and the bearing outer ring
Data Source
Figure 1
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Figure 4
AI summary
A bearing assembly for an electrical generator includes a frame (102), a bearing liner (104) and a ring (106). The frame (102) is configured to connect with a housing of an electrical generator. The frame (102) includes a frame opening (114) and is made from a first material. The bearing liner (104) connects with the frame (102). The bearing liner (104) is made from a second material, which is dissimilar from the first material. At least a portion of the bearing liner (104) passes through the frame opening (114). The ring (106) surrounds the bearing liner (104). The ring (106) contacts the frame (102) and the bearing liner (104) and maintains a clearance between the portion of the bearing liner (104) passing through the frame opening (114) and the frame (102).