Tapered Roller Bearing with Logarithmic Crowning for Lower Contact Pressure
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Solution Overview
Problem
Tapered roller bearings face challenges in suppressing contact surface pressure while maintaining a long lifetime, especially when strong interference fitting is used, as increased crowning drop amounts can lead to a shallower heat-treated hardened layer, affecting the bearing's longevity and increasing manufacturing costs.
Innovation Solution
The solution involves forming logarithmic crowning only on the rolling surfaces of the tapered rollers and using carburized steel for the raceway rings and rollers, with the raceway surfaces having a straight generating line shape, and the rollers made of high carbon chromium bearing steel, ensuring appropriate contact surface pressure and extended lifetime at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a large crowning drop amount is formed in the rolling surfaces of the tapered rollers, then the contact surface pressure is suppressed and bearing lifetime is extended, but the heat-treated hardened layer becomes shallower and manufacturing cost increases
Solution Approach 1:
The invention applies different crowning configurations to different components: logarithmic crowning is formed only in the rolling surfaces of the tapered rollers, while the raceway surfaces of the inner and outer rings maintain a straight generating line shape. This localized application of crowning to where it is most needed (the rollers) achieves contact pressure suppression without requiring costly crowning processing on all components.
Solution Approach 2:
The invention specifies precise parameter ranges for the crowning drop amount (Dr) relative to roller diameter (Dw), where 0.003 ≤ Dr/Dw ≤ 0.03. This parameter optimization ensures sufficient contact pressure distribution while limiting the crowning magnitude to preserve an appropriate hardened layer depth and control manufacturing complexity.
2Strength
If carburized steel is used for raceway rings with strong interference fitting, then the bearing can handle large loads, but the hardened layer becomes shallower when large crowning is applied
Solution Approach 1:
The invention maintains straight generating line shapes (no crowning) in the raceway surfaces of the carburized steel inner and outer rings, preserving the full depth and effectiveness of the heat-treated hardened layer in these high-strength components. Meanwhile, logarithmic crowning is applied only to the rollers, achieving contact pressure control without compromising the hardened layer integrity of the raceway rings.
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 cost-effective manufacturing process, with the ratio of crowning drop amount to roller diameter optimized between 0.003 and 0.03 for optimal performance.
Implementation Method 1
the inner ring and the outer ring are each made of carburized steel
Implementation Method 2
a heat-treated hardened layer for a top layer which is applied to attain a long lifetime
Data Source
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AI summary
Provided is a tapered roller bearing (1) for an automobile, including: an inner ring (12) including a raceway surface (12a) having a tapered shape on an outer periphery; an outer ring (13) including a raceway surface (13a) having a tapered shape on an inner periphery; a plurality of tapered rollers (14) incorporated into a space defined between the raceway surfaces (12a, 13a); and a retainer (15) configured to receive the tapered rollers (14), wherein the inner ring (12) and the outer ring (13) are each made of carburized steel, wherein the raceway surfaces (12a, 13a) of the inner ring (12) and the outer ring (13) each have a straight generating line shape, wherein the tapered rollers (14) each are made of high carbon chromium bearing steel, wherein the tapered rollers (14) each have a rolling surface (16) including: a straight portion (16a), which is formed at a center portion in an axial direction; and crowning portions (16b, 16c), which extend from the straight portion (16a) to both end portions, and wherein the crowning portions (16b, 16c) are each formed of logarithmic crowning.