Tapered Roller Bearing End-Face Geometry for Lower Friction Torque
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Solution Overview
Problem
Tapered roller bearings experience significant torque loss and heat generation due to sliding friction, especially in high-speed, high-load applications like differential gears, leading to insufficient fuel economy and potential oil film breakdown.
Innovation Solution
A tapered roller bearing design featuring a nitrogen-enriched layer on the outer and inner rings and rollers, combined with a crowning profile expressed by a logarithmic function, which optimizes the contact pressure distribution and reduces friction, incorporating specific carbon, silicon, manganese, and chromium content in the steel composition to enhance durability and rolling fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the bearing size is reduced to enhance fuel economy, then the bearing can be made smaller and fit in limited space, but the bearing must bear higher loads and experience greater misalignment
Solution Approach 1:
The patent applies different surface treatments to different parts of the bearing components. A nitrogen enriched layer is formed on the rolling surfaces through nitriding treatment, while the core material maintains its original properties. This local modification enhances surface hardness and wear resistance where contact occurs, without changing the overall bearing size or core structure.
Solution Approach 2:
The bearing components consist of a composite structure with a steel base material and a nitrogen-enriched surface layer. This composite construction combines the high strength and toughness of the steel core with the enhanced surface hardness and wear resistance of the nitrided layer, allowing the bearing to withstand higher loads and misalignment while maintaining a compact size.
2Force
If the tapered roller bearing is used in high-speed, high-load applications, then the bearing can handle the load, but friction torque and heat generation increase due to sliding friction
Solution Approach 1:
The patent changes the surface properties of the bearing components by forming a nitrogen enriched layer through nitriding treatment. This surface modification increases surface hardness and alters the friction characteristics, reducing the coefficient of friction between contacting surfaces. The hardened surface also generates less heat during sliding contact, thereby reducing energy loss while maintaining load bearing capacity.
3Force
If the bearing operates under high temperature due to friction heat, then the bearing can sustain high loads, but the lubricating oil viscosity decreases and oil film becomes insufficient
Solution Approach 1:
The patent converts the harmful effect of sliding friction into a beneficial outcome through surface hardening. By forming a nitrogen enriched layer, the surface hardness is increased, which reduces the coefficient of friction and consequently the heat generation. The hardened surface acts as a protective barrier that maintains lower operating temperatures, preserving lubricant viscosity and oil film integrity even under high load conditions.
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 significantly reduces torque loss and heat generation, shortens the running-in period, and enhances the durability and rolling fatigue life of the bearing, ensuring improved fuel economy and reduced wear, even under conditions of misalignment and low lubrication.
Implementation Method 1
a nitrogen enriched layer which is formed on a surface layer of the outer-ring raceway surface, the inner-ring raceway surface, or the rolling surface
Implementation Method 2
The rolling surface of the tapered roller is provided with a crowning profile. A sum of drops of the crowning profiles is expressed in a y-z coordinate system
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A suitable tapered roller bearing which is less in torque loss and heat generation caused by friction and shorter in running-in period is provided. The tapered roller bearing comprises an outer ring including an outer-ring raceway surface around an inner circumferential surface; an inner ring arranged on a radially inner side relative to the outer ring. The inner ring includes an inner-ring raceway surface around an outer circumferential surface and a larger flange surface arranged on a larger diameter side relative to the inner-ring raceway surface. A plurality of tapered rollers is disposed between the outer-ring raceway surface and the inner-ring raceway surface. The tapered roller includes a rolling surface in contact with the outer-ring raceway surface and the inner-ring raceway surface and a larger end face in contact with the larger flange surface. The rolling surface of the tapered roller is provided with a crowning profile. A chamfered portion is provided between the larger end face and the crowning profile. A recess is provided in a central portion of the larger end face. A projection is provided in an outer circumferential portion of the larger end face, the projection having an inner circumferential end of projection connected to the recess and an outer circumferential end connected to a chamfered portion, in a cross section along a rolling axis of the tapered roller. The large end face includes points C1 and C4 connecting the outer circumferential end of the projection and the chamfered portion, points C2 and C3 connecting the inner circumferential end of the projection and the recess, an intermediate point P5 between the point C1 and the point C2 on the large end face, and an intermediate point P6 between the point C3 and the point C4 on the large end face. A value of R/RBASE is not smaller than 0.75 and not greater than 0.87, with R representing a reference radius of curvature of a single arc which passes through the point C1, the intermediate point P5, the intermediate point P6, and the point C4 in the cross section and RBASE representing a distance from an apex of a cone angle of the tapered roller to the larger flange surface of the inner ring.