Sliding Spline Surface Layers to Prevent Torque-Induced Stick-Slip
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Solution Overview
Problem
Conventional sliding spline shaft devices experience stick-slip vibrations due to the increase in static friction force when torque is applied, leading to significant vibrations.
Innovation Solution
A sliding spline shaft device with a surface processed layer comprising an undercoat layer formed by nitriding, an intermediate phosphate layer, and a topcoat layer containing solid lubricant, which increases the surface hardness to reduce microscopic deformation and real contact area, thereby suppressing the increase in static friction force.
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 dynamic friction is reduced, but stick-slip vibrations occur when torque increases and static friction force increases
Solution Approach 1:
The invention applies a composite surface processed layer comprising multiple functional layers: a base material layer, an intermediate layer containing phosphate, and a topcoat layer containing solid lubricant. This composite structure combines the load-bearing capability of the base material with the low-friction properties of the solid lubricant, resolving the contradiction between maintaining smooth sliding and preventing stick-slip vibrations under torque
Solution Approach 2:
The surface processed layer creates local quality differentiation by providing a hard, wear-resistant base layer for structural integrity and a soft, lubricious topcoat layer for low friction. This local differentiation allows the sliding surface to simultaneously withstand torque loads and maintain low static friction coefficient, preventing stick-slip vibrations
2Reliability
If surface hardness is increased to reduce microscopic deformation, then static friction increase is suppressed, but manufacturing complexity increases due to multiple coating layers
Solution Approach 1:
The surface processed layer is formed as a preliminary structure on the sliding spline shaft before use. The multiple layers are pre-applied and cured to create a stable, friction-resistant surface that will maintain its properties throughout operation, eliminating the need for complex real-time control systems
Solution Approach 2:
The invention changes the physical and chemical parameters of the sliding surface by applying layers with different compositions and properties. The phosphate intermediate layer provides chemical bonding, while the solid lubricant topcoat provides low friction, creating a surface with optimized friction characteristics without requiring complex mechanical structures
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 reduces the occurrence of stick-slip vibrations even under high torque conditions by minimizing static friction and maintaining low dynamic friction, enhancing the durability and wear resistance of the sliding surface.
Implementation Method 1
an undercoat layer formed by nitriding
Implementation Method 2
an intermediate layer containing phosphate, and a topcoat layer containing solid lubricant
Implementation Method 3
a topcoat layer containing solid lubricant
Data Source
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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.