Wheel Bearing Shoulder Relief Surface Design
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Solution Overview
Problem
Wheel bearing apparatuses face issues with shoulder overriding of the contact ellipse, leading to edge load generation, noise, and reduced durability due to the contact ellipse being pushed out beyond the raceway surfaces, which increases manufacturing costs and reduces sealability when attempting to address these issues.
Innovation Solution
The wheel bearing apparatus incorporates a relief surface on the outer member's shoulder portion, formed as a straight line tangent to the outer raceway surfaces with a chamfered circular arc, and a second relief surface with a specific inclined angle, both designed to prevent shoulder overriding and edge load generation, while maintaining efficient grinding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the contact angle is increased to improve bearing rigidity, then the bearing rigidity is improved, but the contact ellipse is pushed out to the auxiliary raceway surfaces causing shoulder overriding and edge load generation
Solution Approach 1:
The patent introduces a new spatial dimension by adding a relief surface at the corner of the shoulder portion, extending the load distribution path from the traditional raceway surface into the corner region. This dimensional extension allows the contact ellipse to be redistributed onto the relief surface, preventing shoulder overriding while maintaining the necessary contact angle for bearing rigidity.
Solution Approach 2:
The relief surface acts as an intermediary element between the raceway surface and the shoulder corner. It provides a transition zone that redistributes the contact stress, preventing the contact ellipse from directly overriding the shoulder while maintaining proper load distribution. The relief surface mediates the conflict between high contact angle requirements and shoulder protection needs.
2Strength
If auxiliary raceway surfaces are added to prevent edge load generation, then edge load generation is reduced, but the contact ellipse is pushed out beyond the original raceway surfaces
Solution Approach 1:
The patent segments the load-bearing surface into distinct functional zones: the original raceway surface for primary contact, the auxiliary raceway surface for load distribution, and the relief surface at the corner for preventing shoulder overriding. This segmentation allows each zone to perform its specific function, preventing the contact ellipse from being pushed out beyond the intended boundaries.
Solution Approach 2:
The relief surface is specifically located at the corner of the shoulder portion where the critical transition occurs. By applying this local modification only where needed (at the corner rather than throughout the entire raceway), the patent prevents shoulder overriding without affecting the overall contact ellipse position on the main raceway surfaces.
3Reliability
If the shoulder height is increased to prevent contact ellipse overriding, then shoulder overriding is prevented, but the sealability is reduced and manufacturing cost increases
Solution Approach 1:
Instead of changing the shoulder height parameter, the patent changes the surface geometry parameters by introducing the relief surface with specific curvature radius and inclination angle. This parameter change approach prevents shoulder overriding through geometric redistribution of contact stress rather than through increased dimensional parameters, thereby maintaining sealability and reducing manufacturing complexity.
Data Source
AI summary
A wheel bearing apparatus has a double row angular contact ball bearing. A height of a shoulder of a shoulder portion (18) of an outer member (12) with respect to a ball diameter of a double ball (14) row is set in a range of 0.35 to 0.50 mm. A corner (19) of the shoulder portion (18) has a relief surface (19a) and a chamfered portion (19b). The relief surface is on a straight line that is on a tangent line of an outer raceway surface (12a). The chamfered portion (19b) is round in a circular arc with a predetermined radius of curvature r. The corner (19) is formed simultaneously by a formed grinding wheel forming the double row outer raceway surface (12a). The corner is formed smoothly continuous from each outer raceway surface (12a). A length in the radial direction of the relief surface (19a) is set greater than or equal to 0.2 mm.