Wheel Hub Hardened Layer Design for Bearing Caulking

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Solution Overview

Problem

Existing wheel bearing apparatuses face issues with durability and anti-creep properties, particularly during the caulking process, leading to increased rotational torque, fuel consumption, and reduced bearing life due to deformation and excessive contact pressure.

Innovation Solution

A wheel bearing apparatus with a double row taper roller bearing design, featuring a hardened layer on the wheel hub and inner ring, where the inner ring is secured via a caulked portion with a predetermined interference fit, and an annular recess to minimize radial expansion and stress concentration, ensuring smooth roller guidance and reduced contact pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the inner ring is secured to the wheel hub by caulking the cylindrical portion, then the inner ring is firmly fixed, but the end of the cylindrical portion radially expands causing deformation of the inner ring and excessive contact pressure

Engineering Contradiction:

Improvefixing strength of inner ringVSAvoiddeformation of inner ring

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The cylindrical portion is segmented into two functional zones: a hardened layer portion (with hardened layer) and a caulked portion (without hardened layer). This segmentation allows the caulked portion to deform radially for securing the inner ring while the hardened layer portion maintains dimensional stability and prevents excessive radial expansion, thereby resolving the contradiction between fixing strength and manufacturing precision

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hardened layer is applied locally to only a portion of the cylindrical portion (the hardened layer portion) rather than the entire surface. This local quality approach allows the caulked portion to remain soft and deformable for effective radial expansion during caulking, while the hardened layer portion provides structural support to limit excessive expansion and prevent inner ring deformation

Inventive Principle:

Principle #3Local quality

2Strength

If a hardened layer is formed on the wheel hub to increase rigidity, then the rigidity of the wheel mounting flange improves, but the inner ring fitting surface may experience excessive contact pressure during caulking

Engineering Contradiction:

Improverigidity of wheel mounting flangeVSAvoidcontact pressure on inner ring fitting surface

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The hardened layer is applied selectively to the hardened layer portion of the cylindrical portion, excluding the caulked portion. This local quality approach ensures that the wheel mounting flange and most of the cylindrical portion have high rigidity to support heavy loads, while the caulked portion remains softer to allow controlled radial expansion during caulking without generating excessive contact pressure on the inner ring fitting surface

Inventive Principle:

Principle #3Local quality

3Reliability

If the hardened layer extends to the end of the cylindrical portion, then the anti-creep properties improve, but the caulking process becomes difficult and inner ring deformation increases

Engineering Contradiction:

Improveanti-creep properties of inner ring fitting surfaceVSAvoidcaulking processability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The cylindrical portion is divided into a hardened layer portion and a caulked portion. The hardened layer portion provides excellent anti-creep properties for the inner ring fitting surface, while the caulked portion (deprived of hardened layer) remains soft and formable, enabling easy caulking process without excessive force and preventing inner ring deformation during the securing operation

Inventive Principle:

Principle #1Segmentation

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 enhances the durability of the wheel hub and inner ring, suppresses fretting wear, and extends the life of the bearing by maintaining structural integrity and reducing deformations during the caulking process, thereby improving the overall performance and longevity of the wheel bearing apparatus.

Implementation Method 1

A predetermined hardened layer is formed by high frequency induction hardening over a range from a base of the wheel mounting flange to the cylindrical portion

Methodology Applied

Scientific EffectHigh frequency induction hardening: Induction Heating

Data Source

PatentUS7618196B2Wheel bearing apparatus

Publication Date: 2009.11.17 NTN CORP

AI summary

A wheel bearing apparatus is formed as a unit of a wheel hub and a double row taper roller bearing. An outer member is formed with double row tapered outer raceway surfaces, each opened axially outward, on its inner circumference. An inner member, including the wheel hub, has a wheel mounting flange integrally formed at one end of the wheel hub. On its larger outer diameter side, the inner ring has a larger flange portion to guide the tapered rollers. The at least one inner ring is secured on the wheel hub by a caulked portion. A predetermined hardened layer is formed by high frequency induction hardening over a range from the base of the wheel mounting flange to the cylindrical portion. A position of the inner side end of the hardened layer is set within a range from an edge of a chamfered portion at the caulked side of the inner ring to a position corresponding to a root of the larger flange portion.