Multipoint Contact Ball Bearing Inner Raceway Curvature
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Solution Overview
Problem
Four-point contact ball bearings face durability issues when subjected to large radial loads, as the rolling surfaces of the balls can come into contact with unfinished rough surfaces or relief grooves, leading to damage and reduced fatigue life, especially in applications like automobile transmissions where gear reaction forces generate significant radial forces.
Innovation Solution
The multipoint contact ball bearing design features an inner raceway bottom section with a concave curved surface having a radius of curvature between 39% to 48% of the ball diameter, which is smoothly continuous with the side surface sections, and an outer raceway with a radius of curvature between 51% to 55% of the ball diameter, allowing for finishing and reducing surface pressure, thus preventing damage and maintaining load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the inner raceway bottom section and outer raceway bottom section are constructed with large curvature (small radius of curvature) or relief grooves, then it is difficult to bring a finishing grindstone into contact with these portions, but this causes rough surfaces that lead to damage of rolling surfaces and reduced durability
Solution Approach 1:
The invention changes the geometric parameters of the raceway bottom sections by specifying a radius of curvature that is 0.05 to 0.15 times the ball diameter, which is large enough to allow finishing grindstone contact while maintaining the structural function of the bottom sections. This parameter optimization enables both manufacturability and durability.
Solution Approach 2:
The invention applies different finishing qualities to different regions of the raceway. The side surface sections are finished to high precision for normal rolling contact, while the bottom sections are designed with specific curvature parameters that enable finishing access. This localized quality differentiation ensures that critical contact areas have superior surface quality while maintaining overall manufacturability.
2Manufacturing precision
If the radius of curvature of the inner raceway bottom section is made large (0.05 to 0.15 times ball diameter), then finishing can be performed, but this may affect the load distribution and contact characteristics
Solution Approach 1:
The invention carefully selects the radius of curvature parameter within the range of 0.05 to 0.15 times the ball diameter. This specific range is large enough to permit finishing grindstone contact and achieve high surface quality, yet small enough to maintain proper load distribution and contact characteristics during operation.
Solution Approach 2:
The invention applies finishing treatment to the bottom sections even though these areas are not the primary contact zones during normal operation. This partial finishing action ensures that if balls do contact the bottom sections (under certain operating conditions), the surfaces will be smooth and damage-free, providing a margin of safety beyond the primary contact areas.
Data Source
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AI summary
The present invention achieves construction of a multipoint contact ball bearing that is able to prevent the rolling surfaces of the balls 4 from becoming damaged and can keep the durability of the bearing from decreasing while maintaining the radial load capacity even when large radial loads act and the rolling surfaces of the balls 4 coming in contact with the inner raceway bottom section 8a. The inner raceway 5a is complex curved surface that comprises a pair of inner raceway side surface sections having a generating line shape with a radius of curvature that is larger than 50% the diameter of the balls 4, and an inner raceway bottom section 8a that connects the edges of the inside end in the width direction of the pair of inner raceway side surface sections 7a; with the inner raceway bottom section 8a big a concave curved surface having a generating line shape with a radius of curvature R8 that is less than 50% the diameter of the balls 4. The edges of both sides in the width direction of the inner raceway bottom section 8a and the edges of the inside ends in the width direction of the pair of inner raceway side surfaces sections 7a are smoothly continuous, and finishing is also performed on the inner raceway bottom section 8a in addition to the pair of inner raceway side surfaces sections 7a.