Rolling Bearing Nitrogen Enriched Layer Hardness Gradient
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Solution Overview
Problem
Rolling bearings without cages face issues with surface damage and separation due to high-speed and high-load conditions, leading to reduced life and difficulties in caulking processes, especially under harsh engine conditions.
Innovation Solution
A rolling bearing structure with a nitrogen-enriched layer and controlled austenite grain size, hardness, and microstructure, including high-frequency quenching and carbonitriding treatments, to enhance surface durability and facilitate caulking, while maintaining suitable hardness for end portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rolling contact surface is made hard to resist surface damage, then surface durability is improved, but caulking formation at end portions becomes difficult
Solution Approach 1:
The invention applies different hardness levels to different regions of the shaft. The rolling contact surface has high hardness (HV653 or more) to resist surface damage, while the end portion has low hardness (HV300 or less) to facilitate caulking formation. This is achieved through selective heat treatment processes such as high-frequency quenching applied only to the rolling contact surface, or through controlled carbonitriding treatment that creates a hardness gradient from the surface to the end portion.
2Productivity
If high-speed and high-load conditions are operated, then productivity is improved, but surface damage and separation occur reducing reliability
Solution Approach 1:
The invention changes the physical parameters of the shaft surface through controlled heat treatment. By regulating the hardness of the rolling contact surface to be HV653 or more and controlling the austenite grain size to be No. 11 or larger, the surface gains enhanced resistance to surface damage and separation. The nitrogen enriched layer and specific grain size control modify the material properties to withstand high-speed and high-load operating conditions without suffering from surface damage or separation.
3Reliability
If the rolling contact surface is hardened to prevent surface damage, then reliability is improved, but the end portion becomes too hard for caulking processes
Solution Approach 1:
The invention segments the shaft into functionally distinct regions with different hardness requirements. The rolling contact surface is treated separately from the end portion, allowing each region to have optimized properties. The rolling contact surface receives hardening treatment (high-frequency quenching or controlled carbonitriding) to achieve HV653 or more, while the end portion is either excluded from hardening treatment or receives minimal treatment to maintain hardness at HV300 or less, ensuring caulking processability.
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 effectively suppresses surface damage and internally originating separation, achieving extended life and facilitating caulking processes, even under high-speed and high-load conditions.
Implementation Method 1
At least one member of the outer member and the inner member has a nitrogen enriched layer
Implementation Method 2
austenite grain size of a surface portion of an area in a rolling contact surface where the rolling element rolls is No. 11 or larger
Implementation Method 3
austenite grain size of a surface portion of an area in a rolling contact surface where the rolling element rolls is No. 11 or larger
Implementation Method 4
carbonitriding treatments, to enhance surface durability
Implementation Method 5
an end portion of that member has hardness of at most HV (Vickers hardness) 300
Data Source
AI summary
A rolling bearing that attains long life against surface damage such as surface-originating separation or internally originating separation and allows caulking of its shaft end face, a cam-follower with roller employing the rolling bearing, and a cam are obtained. The rolling bearing includes an outer-roller, a roller shaft located inside the outer-roller, and a rolling element interposed between the outer-roller and the roller shaft. At least one member of the outer-roller and the roller shaft has a nitrogen enriched layer. A surface portion of an area in a rolling contact surface where the rolling element rolls has austenite grain size of No. 11 or larger. The end portion has hardness of not larger than HV300.