Sliding Spline Shaft Coating for Stick-Slip Under High Torque
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Solution Overview
Problem
Conventional sliding spline shaft devices experience stick-slip vibrations due to the increased difference between static and dynamic friction forces when high torque is applied, leading to vibration issues.
Innovation Solution
A sliding spline shaft device with a surface processed layer comprising an undercoat layer of iron nitride, an intermediate phosphate layer, and a topcoat layer containing solid lubricant, which increases the surface hardness to reduce microscopic deformation and maintain a consistent friction coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film containing solid lubricant is provided to suppress increase in static friction coefficient, then stick-slip is reduced under normal conditions, but when large torque is applied, the difference between static and dynamic friction forces increases, resulting in large vibration due to stick-slip
Solution Approach 1:
The invention uses a composite surface processed layer comprising multiple functional layers: a base material, a diffusion layer containing nitrogen, an intermediate layer containing phosphate, and a topcoat layer containing solid lubricant. This composite structure combines the benefits of each layer to achieve both low friction and high hardness, resolving the contradiction between stick-slip suppression and vibration reduction under large torque.
Solution Approach 2:
The invention changes the physical and chemical parameters of the surface by forming a diffusion layer with nitrogen concentration gradient and controlling the hardness of the base material surface to be 500 HV or more. This parameter change maintains consistent friction characteristics even under large torque conditions, preventing the increase in friction force difference that causes vibration.
2Ease of operation
If the dynamic friction coefficient is kept low for smooth sliding, then sliding occurs easily, but fast sliding occurs when stress exceeds static friction force, causing stick-slip phenomenon
Solution Approach 1:
The invention modifies the friction parameters by forming a surface processed layer with controlled hardness (500 HV or more) and providing a topcoat layer with solid lubricant. This maintains a consistent friction coefficient that prevents the abrupt transition from static to dynamic friction, thereby suppressing stick-slip while ensuring smooth sliding.
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 stick-slip vibrations and maintains low friction forces even under high torque conditions, enhancing the durability and reducing vibration in the sliding spline shaft device.
Implementation Method 1
The undercoat layer includes a diffusion layer and a compound layer containing iron nitride
Implementation Method 2
increasing hardness of a surface of a base material to reduce microscopic deformation of a sliding surface
Implementation Method 3
a topcoat layer containing solid lubricant
Implementation Method 4
an intermediate layer containing phosphate
Data Source
AI summary
A sliding spline shaft device of the present invention includes a male spline and a female spline that is fitted to the male spline in an axially slidable manner, and at least one of the splines has a surface processed layer. The surface processed layer includes an undercoat layer, an intermediate layer containing phosphate, and a topcoat layer containing solid lubricant, in this order. The undercoat layer contains iron nitride and/or iron carbide. Thus, the surface of a base material has high hardness. As a result, microscopic deformation of the sliding surface is reduced, and increase in a real contact area is suppressed, whereby stick-slip is prevented.