Metal Ring Nitriding for CVT Belt Fatigue and Abrasion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing methods for metal rings in steel belt-type continuously variable transmissions face challenges in balancing fatigue resistance and abrasion resistance, particularly at the end surfaces where high nitrided layer thickness can lead to fatigue fracture and reduced surface hardness.
Innovation Solution
A manufacturing method involving the formation of a concentrated nitrogen-affinitive metal layer on the main surfaces and exposing a bulk layer on the end surfaces, followed by nitriding, which results in a thin but hard second nitrided layer on the end surfaces, enhancing both fatigue resistance and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the nitrided layer in the end part is increased to improve fatigue strength, then compressive residual stress is enhanced, but surface hardness is reduced and abrasion resistance deteriorates
Solution Approach 1:
The patent applies different nitrided layer thicknesses to different regions of the metal ring: the end surfaces have a thinner nitrided layer (5-20 μm) to maintain surface hardness and abrasion resistance, while the main surfaces have a thicker nitrided layer (15-30 μm) to provide compressive residual stress and improve fatigue strength. This regional differentiation resolves the contradiction by optimizing each surface for its specific functional requirements.
2Strength
If a nitriding inhibition film is formed on the end surface to reduce nitrided layer thickness and prevent fatigue fracture, then fatigue strength is improved, but surface hardness is reduced and abrasion resistance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the steel material by adding specific elements (Al: 0.01-0.05 wt%, Ti: 0.01-0.05 wt%, Nb: 0.01-0.05 wt%, V: 0.01-0.05 wt%) that have high affinity for nitrogen. These compositional changes enable the formation of a thin but hard nitrided layer on the end surfaces through controlled nitriding, achieving both fatigue strength improvement and abrasion resistance maintenance.
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 method effectively restrains fatigue fracture and maintains high abrasion resistance at the end surfaces while allowing for a thinner nitrided layer, improving the overall durability and performance of the metal rings.
Implementation Method 1
nitriding is performed for giving compressive residual stress to surfaces of the metal rings
Implementation Method 2
forming a concentrated layer in a main surface of a material of the metal ring, in which nitrogen-affinitive metal is concentrated in the concentrated layer
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided is a metal ring for a transmission belt of a belt-type continuously variable transmission. A first nitrided layer formed in a main surface of the metal ring, and a second nitrided layer formed in an end surface of the metal ring are included. A thickness of the second nitrided layer is smaller than a thickness of the first nitrided layer, and surface hardness of the end surface is higher than surface hardness of the main surface. Even though the second nitrided layer in the end part is thin, the surface hardness of the end surface is high.