Roller Bearing Inner Ring Hardening and Ceramic Elements
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Solution Overview
Problem
Roller bearings experience premature failures, especially under extreme stress situations, leading to high repair and downtime costs in applications like offshore wind turbines, necessitating a solution for extended service life and reduced failure risk.
Innovation Solution
A method for producing roller bearings with an inner ring made of steel subjected to heat treatment, strain hardening, and burnishing to create residual compressive stresses, combined with ceramic rolling elements to reduce friction, wear, and hydrogen penetration, along with thermal post-treatment to stabilize the microstructure, and a high-temperature plastic cage for reduced mass and improved tribological behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional steel rolling elements are used, then the bearing can support high loads, but the friction and energy losses increase and the service life is reduced due to steel-to-steel contact and hydrogen penetration
Solution Approach 1:
The patent applies composite materials by combining ceramic rolling elements (silicon nitride or zirconium oxide) with steel raceways. The ceramic material provides low friction and high stiffness while the steel provides structural strength. This composite approach resolves the contradiction by reducing friction losses and energy consumption while maintaining load-bearing capacity and extending service life through hydrogen barrier properties of the ceramic material.
Solution Approach 2:
The patent changes the material parameter of the rolling elements from steel to ceramic materials with specific properties (low density, high stiffness, hydrogen barrier). This parameter change reduces the friction coefficient and prevents hydrogen penetration into the steel raceway, thereby reducing energy losses and extending service life simultaneously.
2Strength
If the inner ring is hardened to increase surface strength, then mechanical damage resistance improves, but crack formation sensitivity increases due to residual tensile stresses
Solution Approach 1:
The patent applies preliminary anti-action by introducing residual compressive stresses through strain hardening and burnishing processes before the bearing enters service. These pre-induced compressive stresses counteract the tensile stresses that would otherwise develop during operation, preventing crack initiation and propagation. This resolves the contradiction by maintaining surface hardness while eliminating crack formation sensitivity.
Solution Approach 2:
The patent converts the potentially harmful residual tensile stresses from hardening into beneficial residual compressive stresses through subsequent strain hardening and burnishing processes. The compressive stresses mask the harmful effects of hardening-induced tensile stresses, allowing the bearing to achieve both high surface strength and high crack resistance.
3Reliability
If strain hardening is applied to create residual compressive stresses, then crack resistance improves, but surface roughness increases requiring additional finishing operations
Solution Approach 1:
The patent merges multiple surface treatment processes (strain hardening, burnishing, and optionally honing or grinding) into an integrated surface preparation sequence. The strain hardening creates beneficial compressive stresses, while the subsequent burnishing process simultaneously improves surface finish by cold welding and smoothing the surface. This combined approach resolves the contradiction by achieving both crack resistance and acceptable surface roughness in a unified manufacturing flow.
4Reliability
If multiple heat treatment and surface treatment steps are applied, then material properties and service life are optimized, but manufacturing complexity and production time increase
Solution Approach 1:
The patent applies preliminary action by performing heat treatment and surface treatments (strain hardening, burnishing) on the inner ring before final assembly. The heat treatment establishes the base material properties, followed by strain hardening and burnishing to create residual compressive stresses and improve surface finish. This sequential preliminary preparation resolves the contradiction by optimizing material properties in advance, allowing simpler final assembly processes.
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 method significantly extends the service life of roller bearings by reducing crack sensitivity, friction, and mechanical damage, enabling operation under extreme conditions with reduced energy losses and increased reliability, particularly in wind turbine gearboxes.
Implementation Method 1
heat treatment is used for hardening which is completed with the performance of a final heat treatment step at a predetermined temperature
Implementation Method 2
residual compressive stresses are formed in a surface layer, which extends to a minimum depth below the surface of the inner ring raceway, by strain hardening in the area of the inner ring raceway
Implementation Method 3
After strain hardening, the inner ring is burnished
Implementation Method 4
thermal post-treatment to stabilize the microstructure
Data Source
Figure 1
Figure 2~3
AI summary
The method involves subjecting the inner ring (1) to a heat treatment to harden it, in which the heat treatment is concluded with the performance of final heat treatment step at a predetermined temperature, and forming compressive residual stresses in the outer layer of the inner ring by subjecting the inner ring to cold working in the region of the inner-ring raceway (2). After the cold working, the inner ring is subjected to bluing treatment, and the rolling elements (5) manufactured from ceramic material are arranged between inner-ring raceway and outer-ring raceway (4). An independent claim is included for a rolling bearing.