Tapered Roller Bearing Crowning for Lower Contact Pressure

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Solution Overview

Problem

Tapered roller bearings used in automobiles face challenges in suppressing contact surface pressure while maintaining a long lifetime, particularly when strong interference fitting is involved, as increased crowning drop amounts lead to shallower heat-treated hardened layers, affecting their longevity and increasing manufacturing costs.

Innovation Solution

A tapered roller bearing design featuring logarithmic crowning only on the rolling surfaces of the rollers, with the inner and outer rings having straight generating line shapes made of carburized steel, and rollers made of high carbon chromium bearing steel, which balances contact surface pressure and extends the bearing's lifetime at a lower cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If logarithmic crowning with large drop amount is formed in the rolling surfaces of the tapered rollers, then contact surface pressure is suppressed and bearing lifetime is extended, but the heat-treated hardened layer becomes shallower and manufacturing cost increases

Engineering Contradiction:

Improvebearing lifetimeVSAvoidmanufacturing cost and hardened layer depth

Core Design Contradiction:

Duration of action of stationary objectVSEase of manufacture

Solution Approach 1:

The invention applies different surface profiles to different components: logarithmic crowning is applied only to the rolling surfaces of the tapered rollers where contact stress occurs, while the raceway surfaces of the inner and outer rings maintain straight generating line shapes. This localized application of crowning achieves contact surface pressure suppression at the roller-raceway interface without requiring expensive large-drop crowning processing on all components, thereby extending bearing lifetime while controlling manufacturing cost and preserving hardened layer depth on the raceway rings

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention segments the crowning application by component type: tapered rollers receive logarithmic crowning on their rolling surfaces to handle contact stress, while inner and outer rings maintain straight raceway surfaces. This segmentation allows each component to be optimized independently - rollers get the stress-distributing crowning profile where needed, while raceway rings maintain simple straight profiles for ease of manufacturing and adequate hardened layer depth

Inventive Principle:

Principle #1Segmentation

2Stress or pressure

If single-curve crowning or logarithmic crowning with large drop amount is formed in the rolling surfaces of the tapered rollers, then contact surface pressure is suppressed, but grinding amount increases and heat-treated hardened layer becomes shallower

Engineering Contradiction:

Improvecontact surface pressureVSAvoidgrinding amount and hardened layer depth

Core Design Contradiction:

Stress or pressureVSManufacturing precision

Solution Approach 1:

Logarithmic crowning is applied locally only to the rolling surfaces of the tapered rollers where contact stress between rolling elements and raceways occurs, rather than applying large-drop crowning to all components. This localized approach suppresses contact surface pressure at the critical interface while minimizing unnecessary grinding on other components, preserving hardened layer depth and reducing overall manufacturing complexity

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of applying crowning to the raceway surfaces of the inner and outer rings as traditionally done, the invention inverts the approach by applying logarithmic crowning only to the tapered rollers while keeping the raceway surfaces straight. This inversion achieves contact pressure suppression through the roller profile rather than the raceway profile, reducing the grinding amount required on the more expensive-to-process ring components

Inventive Principle:

Principle #13The other way round (Inversion)

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

This configuration effectively suppresses contact surface pressure and increases the lifetime of the tapered roller bearing while maintaining a low manufacturing cost, ensuring the bearing's functionality under strong interference fitting conditions.

Implementation Method 1

the inner ring and the outer ring are each made of carburized steel

Methodology Applied

Scientific EffectCarburizing: Carburizing

Implementation Method 2

the crowning portions are each formed of logarithmic crowning

Methodology Applied

Scientific EffectLogarithmic crowning:

Data Source

PatentUS11268571B2Tapered roller bearing for automobile

Publication Date: 2022.03.08 NTN CORP

AI summary

A tapered roller bearing for an automobile includes an inner ring including a raceway surface having a tapered shape on an outer periphery, an outer ring including a raceway surface having a tapered shape on an inner periphery, a plurality of tapered rollers incorporated into a space defined between the raceway surfaces, and a retainer configured to receive the tapered rollers. The inner and outer rings are each made of carburized steel, and the raceway surfaces of the inner and outer rings each have a straight generating line shape. The tapered rollers each are made of high carbon chromium bearing steel, and each have a rolling surface including a straight portion, which is formed at a center portion in an axial direction, and crowning portions, which extend from the straight portion to both end portions. The crowning portions are each formed of logarithmic crowning.