Bearing Ring Form-Coupling for Weight Reduction
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Solution Overview
Problem
The motorcar industry faces a challenge in achieving weight reduction in vehicle components while maintaining strength and safety, particularly in vehicle wheel bearings, where conventional steel is used for raceways to withstand rolling contact stresses, and integrating lightweight materials poses a risk of relative displacement between different material portions.
Innovation Solution
A form-coupling arrangement is implemented between a radially inner core of bearing grade steel and a radially outer lightweight body, utilizing a dovetail joint with undercuts and radial notches to prevent relative displacement, ensuring effective interlocking and resistance to various forces and thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a lightweight material such as aluminium alloy is used for the outer body of the bearing ring, then the weight of the bearing ring is reduced, but the risk of relative displacement between the core and outer body increases
Solution Approach 1:
The bearing ring is divided into two distinct segments: an inner core made of bearing grade steel and an outer body made of lightweight material. This segmentation allows each part to be optimized for its specific function while maintaining overall structural integrity through the form-coupling arrangement.
Solution Approach 2:
The form-coupling arrangement employs asymmetric geometric features including undercuts and radial notches that create an interlocking profile. This asymmetric design prevents relative displacement between the core and outer body by creating mechanical interference that resists axial, radial, and circumferential forces.
Solution Approach 3:
The form-coupling arrangement extends the coupling interface into the axial dimension through undercuts and radial notches, creating a three-dimensional interlocking structure. This multi-dimensional coupling provides resistance to relative displacement in all directions, not just along the radial interface.
2Strength
If conventional bearing grade steel is used for the entire bearing ring, then strength and safety are maintained, but weight reduction cannot be achieved
Solution Approach 1:
Different regions of the bearing ring are assigned different material qualities: the inner core uses high-strength bearing grade steel to withstand rolling contact stresses, while the outer body uses lightweight material for weight reduction. The form-coupling arrangement ensures that the interface between these different material zones can withstand all applied loads.
Solution Approach 2:
The bearing ring employs a composite structure combining two different materials (bearing grade steel and lightweight alloy) in a single integrated component. This composite approach allows the structure to leverage the high strength of steel where needed while utilizing the low density of lightweight materials in non-critical regions.
3Weight of moving object
If the bearing ring is made of two different materials joined together, then weight reduction is achieved, but the coupling reliability under thermal expansion differences is challenged
Solution Approach 1:
The form-coupling arrangement with undercuts and radial notches creates a pre-engineered mechanical interlock that anticipates and compensates for thermal expansion differences between materials. The geometric features provide mechanical constraints that maintain coupling integrity even when thermal expansion causes dimensional changes.
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 provides a compact, reliable, and effective coupling that resists relative displacement and maintains structural integrity under diverse working conditions, enhancing the bearing ring's strength and safety while allowing for weight reduction.
Implementation Method 1
a form-coupling arrangement at the interface between the inner core and the outer body, in the shape of a dovetail joint, for opposing any combination of forces and stresses
Implementation Method 2
The raceways must be made of a material hard enough to resist the stresses of rolling contact. Conventional bearing grade steel is still widely used. The raceways are heat treated so as to attain a level of hardness and microstructure homogeneity adequate to withstand the stresses caused by rolling Hertzian contacts.
Data Source
Figure 1~2
Figure 3~4
AI summary
A bearing ring (10) has a tubular steel core (15) around which is formed an outer body (16) of lightweight material. The outer surface of the core forms a circumferential shoulder (26), having two axially opposite sides: - a first side, subjected to a turning finishing process, which provides an undercut surface (23) defining part of an annular groove (22); and - a second side, not subjected to a turning finishing process, which has a non-circular portion (29) with radial recesses (28) that act as anti-rotation means cooperating with complementary portions formed by the outer body (16).