Bearing Seal Sliding Surface Roughness for Lower Friction Torque
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Solution Overview
Problem
Existing seal assemblies in bearings, such as automobile wheel bearings, increase rotational frictional torque due to high friction losses, which is a mechanical energy loss, and existing solutions do not effectively reduce this while maintaining the seal's performance.
Innovation Solution
The seal assembly features a sliding surface with an arithmetic mean roughness between 0.15 μm and 0.5 μm and a roughness ratio greater than or equal to one, achieved through shot blasting and polishing to create a smooth and lubricated surface, reducing frictional torque and wear, and is filled with grease of specific kinematic viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sliding surface has high roughness (Ra ≥ 0.5 μm) to create valleys for lubricant retention, then the seal can maintain good lubrication, but the frictional torque increases significantly
Solution Approach 1:
The invention changes the surface roughness parameters from conventional high roughness (Ra ≥ 0.5 μm) to a controlled range (0.05 μm ≤ Ra < 0.5 μm) with specific valley depth requirements. This parameter optimization allows the surface to retain lubricant effectively while reducing frictional torque, resolving the contradiction between seal performance and energy loss.
Solution Approach 2:
The invention creates localized valleys with specific depth characteristics on the sliding surface while maintaining overall smoothness. The valleys are strategically formed to retain lubricant only where needed, rather than making the entire surface rough. This local modification approach preserves lubrication functionality while minimizing overall friction.
2Loss of energy
If the sliding surface is made very smooth to reduce friction, then frictional torque decreases, but the seal performance deteriorates due to insufficient lubricant retention
Solution Approach 1:
The invention optimizes surface roughness parameters to a specific range (0.05 μm ≤ Ra < 0.5 μm) with controlled valley depth, rather than making the surface extremely smooth. This controlled roughness allows the surface to retain lubricant in the valleys while maintaining low overall friction, resolving the contradiction between friction reduction and seal performance.
Solution Approach 2:
The valleys are pre-formed on the sliding surface during manufacturing to ensure lubricant retention capability before operation. This preliminary structuring of the surface ensures that lubricant is retained where needed from the start, preventing seal performance deterioration while maintaining low friction during operation.
3Loss of energy
If conventional surface treatments are used to reduce friction, then frictional torque decreases, but the wear of the seal and contact surfaces increases
Solution Approach 1:
The invention changes the surface roughness parameters to an optimized range (0.05 μm ≤ Ra < 0.5 μm) with controlled valley depth, rather than using conventional high roughness treatments. This optimized surface structure reduces frictional torque while preventing excessive wear, thereby extending seal life.
Solution Approach 2:
The invention converts what would normally be considered surface imperfections (valleys) into beneficial features for lubricant retention. These controlled valleys, rather than being defects, become functional elements that reduce wear by ensuring proper lubrication while maintaining low friction, thus extending component life.
4Reliability
If the sliding surface roughness is increased to ensure seal retention, then seal performance improves, but the frictional torque and wear increase
Solution Approach 1:
The invention optimizes surface roughness parameters to a specific range (0.05 μm ≤ Ra < 0.5 μm) with controlled valley depth, rather than simply increasing roughness. This precise parameter control ensures adequate seal retention through lubricant-filled valleys while minimizing friction and wear.
Solution Approach 2:
The invention creates localized valleys with specific depth characteristics only where needed for lubricant retention, rather than making the entire surface rough. This local modification approach ensures seal retention functionality while keeping the overall surface smooth enough to minimize friction and wear.
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 significantly reduces frictional torque, maintains seal performance, and increases the life of the seal assembly by ensuring the sliding surface is smooth and well-lubricated, resulting in consistent and repeatable performance across multiple parts.
Implementation Method 1
the sliding surface is treated by the following substeps: a) a shot blasting substep for forming valleys on the sliding surface and removing peaks from the sliding surface
Implementation Method 2
b) a polishing substep for smoothing the sliding surface and for removing at least a part of the peaks from the sliding surface
Implementation Method 3
the sliding surface has an arithmetic mean roughness (Ra) greater than or equal to 0.15 μm and less than 0.5 μm; and the sliding surface has a roughness ratio (R) greater than or equal to one... the sliding surface is sufficiently smooth and lubricated to avoid abrasion of the seal
Data Source
AI summary
The seal assembly comprising a fixed element, a rotating element, and a seal member comprising a stiff annular reinforcement and a seal of an elastic material and in contact with a sliding surface. The sliding surface has an arithmetic mean roughness greater than or equal to 0.15 μm and less than 0.5 μm. The sliding surface has a roughness ratio greater than or equal to one. The roughness ratio is the ratio of a first parameter corresponding to a quantity of valleys to a second parameter corresponding to a quantity of peaks over the sliding surface.