Aluminum Hub Bearing Unit With Cold-Formed Ring Locking
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Solution Overview
Problem
Existing hub bearing assemblies face challenges in reducing the force required for orbital roll forming, managing thermal expansion differences between materials, and achieving durable material couplings while minimizing weight and production costs.
Innovation Solution
A lightweight hub unit is constructed using an aluminum alloy hub with integrated bearing rings, where the hub is forged and thermally treated, and a cold deformation process locks the bearing rings axially, eliminating the need for traditional thermal hardening and reducing material separation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel hub with induction hardening is used, then raceway hardness is sufficient to withstand Hertzian stresses, but the hub becomes brittle and requires complex thermal hardening treatment
Solution Approach 1:
The patent uses a composite structure with a steel tubular core providing raceway hardness and an aluminum alloy outer shell providing lightweight properties. The steel core (1.2-2.0 mm thick) undergoes induction hardening to achieve 58-62 HRC hardness, while the aluminum alloy (6000 series) provides structural integrity without brittleness. This composite approach allows the steel core to bear the Hertzian stresses while the aluminum alloy prevents overall hub brittleness.
Solution Approach 2:
The hub is segmented into distinct functional zones: a steel tubular core for raceway formation and load bearing, and an aluminum alloy outer shell for lightweight structure. This segmentation allows each material to be optimized for its specific function - the steel core for hardness and the aluminum alloy for weight reduction and toughness.
2Weight of moving object
If aluminum alloy hub is used, then weight is reduced, but roll forming force requirement increases significantly
Solution Approach 1:
The hybrid steel-aluminum composite structure allows the aluminum alloy hub to be used with reduced roll forming forces compared to pure aluminum designs. The steel core provides structural support that reduces the force needed for orbital roll forming of the aluminum outer shell, while still achieving significant weight reduction (30-40% lighter than solid steel hubs).
Solution Approach 2:
The patent optimizes the thickness of the steel core (1.2-2.0 mm) to achieve the right balance between structural integrity and formability. This parameter optimization ensures that the aluminum alloy hub can be successfully formed using orbital roll forming technology with acceptable force levels, while maintaining sufficient strength for bearing applications.
3Reliability
If complex interface surfaces with undercuts are used, then thermal expansion differences are compensated, but manufacturing costs increase
Solution Approach 1:
The patent explicitly addresses thermal expansion differences between steel and aluminum by designing the interface between the steel core and aluminum alloy shell to accommodate differential expansion. The orbital roll forming process creates a mechanically interlocked joint that maintains integrity under thermal cycling, avoiding the need for complex undercut geometries.
Solution Approach 2:
The patent replaces complex mechanical joining systems (such as threaded connections or interference fits requiring undercuts) with a simplified orbital roll forming process. This mechanical forming process creates sufficient interlocking through plastic deformation of the aluminum alloy over the steel core, reducing manufacturing complexity and cost.
4Strength
If traditional induction hardening is applied, then raceway hardness is achieved, but additional processing steps and costs are incurred
Solution Approach 1:
The steel tubular core is pre-hardened by induction hardening before being assembled with the aluminum alloy outer shell. This preliminary hardening action ensures the raceway surface achieves the required 58-62 HRC hardness before final hub assembly, eliminating the need for post-assembly hardening operations and reducing overall processing complexity.
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 reduces the force needed for roll forming, enhances durability through material compatibility, and lowers production costs while maintaining structural integrity and weight efficiency.
Implementation Method 1
a T6 thermal cycle, designed to enhance the mechanical properties of a hub made of an aluminium alloy
Implementation Method 2
The tubular end undergoes a cold deformation, typically by orbital roll forming, in a radially outer direction; a rolled, plastically deformed edge is thus obtained
Data Source
Figure 1~4
AI summary
A hub unit (10) is provided with a hub (20) made of an aluminium alloy for plastic processing, which forms, in a single piece, an axially extending cylindrical portion (21) and a radial flange (22); two bearing rings (14, 15) are mounted axially aligned around the cylindrical portion (21), an axially inner edge (17) of the cylindrical portion (21) is plastically deformed in a radially outer direction against the axially inner bearing ring (14).