Tapered Roller Bearing Torque Reduction via Crowning and Sealing

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Solution Overview

Problem

Tapered roller bearings in differentials experience high running torque due to rolling viscous resistance and oil agitation loss, with existing solutions failing to effectively reduce torque across all rotational speed ranges, particularly in low rotational speeds.

Innovation Solution

A tapered roller bearing design with optimized roller dimensions, crowning parameters, and a lubricating oil inflow restricting unit, which includes a labyrinth seal, to reduce rolling viscous resistance and oil agitation loss, while maintaining a high roller filling rate and controlling the rib angle to minimize contact stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If roller diameter is increased to reduce oil agitation loss, then oil agitation loss is reduced, but running torque increases in low rotational speed range

Engineering Contradiction:

Improveoil agitation lossVSAvoidrunning torque

Core Design Contradiction:

Loss of energyVSForce

Solution Approach 1:

The patent optimizes the roller length to roller diameter ratio (LWR/DW) within the range of 1.1 to 1.7, and controls the roller filling rate (z·DW/(π·dm)) between 0.7 to 0.92. These parameter adjustments allow the bearing to achieve reduced running torque in low rotational speed range while maintaining effective reduction in oil agitation loss, resolving the contradiction between these two energy loss mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If crowning amount is increased to reduce rolling viscous resistance, then rolling viscous resistance is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improverolling viscous resistanceVSAvoidcrowning application

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The patent specifies precise crowning parameters: outer ring crowning parameter (RCO/LRO) of 30 to 150, and inner ring crowning parameter (RCI/LRI) of 50 to 260. By defining these quantitative ranges, the patent standardizes the crowning application process, making it more controllable and manufacturable while still achieving the goal of reducing rolling viscous resistance through optimized crowning amounts.

Inventive Principle:

Principle #35Parameter changes

3Force

If roller length to roller diameter ratio is reduced to reduce running torque, then running torque is reduced, but load capacity decreases

Engineering Contradiction:

Improverunning torqueVSAvoidload capacity

Core Design Contradiction:

ForceVSStrength

Solution Approach 1:

The patent optimizes the roller length to roller diameter ratio (LWR/DW) within the specific range of 1.1 to 1.7 and maintains the roller filling rate (z·DW/(π·dm)) between 0.7 to 0.92. This coordinated parameter optimization ensures that the bearing achieves reduced running torque while maintaining sufficient load capacity, as the optimized ratio prevents excessive reduction in roller dimensions that would compromise strength.

Inventive Principle:

Principle #35Parameter changes

4Stress or pressure

If rib angle is decreased to reduce contact stress, then contact stress is reduced, but structural strength decreases

Engineering Contradiction:

Improvecontact stressVSAvoidrib structural strength

Core Design Contradiction:

Stress or pressureVSStrength

Solution Approach 1:

The patent optimizes the rib angle parameter within the range of α−0.87γ−0.334≦BK≦α−0.87γ−0.167, where α is the outer ring raceway angle and γ is the roller angle. This optimized rib angle reduces contact stress between the roller and rib surface, preventing edge loads and improving bearing life, while maintaining sufficient structural strength through the lower bound of the range.

Inventive Principle:

Principle #35Parameter 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 design effectively reduces running torque in the low rotational speed range by optimizing roller dimensions, crowning parameters, and incorporating a labyrinth seal, maintaining torque reduction while preventing interference and edge loads, thus enhancing bearing life.

Implementation Method 1

a lubricating oil inflow restricting unit which restricts an inflow of a lubricating oil into the bearing

Methodology Applied

Scientific EffectLabyrinth seal:

Implementation Method 2

the rolling viscous resistance of tapered rollers

Methodology Applied

Scientific EffectRolling contact:

Data Source

PatentUS7871201B2Tapered roller bearing, tapered roller bearing apparatus, and automotive pinion shaft supporting apparatus utilizing same tapered roller bearing apparatus

Publication Date: 2011.01.18 JTEKT CORP

AI summary

In a tapered roller bearing, LWR/DW is in the range of 1.1 to 1.7 where LWR represents a roller effective length of tapered rollers and DW represents a roller mean diameter of tapered rollers. RCO/LRO is 30 to 150, and RCI/LRI is 50 to 260 where RCO represents a crowning radius of an outer ring, LRO represents a raceway length of the outer ring, RCI represents a crowning radius of an inner ring and LRI represents a raceway length of the inner ring. The following expressions are satisfied: 20°≦α≦30°, and α−0.87γ−0.334≦BK≦α−0.87γ−0.167, where α represents a raceway angle of the outer ring, γ represents a roller angle of the tapered rollers, and BK represents a rib angle of a large rib portion of the inner ring.