PVD-Coated Ball Socket Geometry for Low-Friction Sliding
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Solution Overview
Problem
The formation of recessed portions for lubricating oil collection in ball socket structures increases the coefficient of friction due to a reduced effective sliding surface area, leading to insufficient lubrication and higher friction coefficients, especially at small tilt angles.
Innovation Solution
A ball socket structure with a socket portion featuring a PVD coating layer on a concave spherical surface with a specific depth-to-radius ratio (0.05 to 0.70) and optional chamfered edges, through holes, and DLC coating to enhance lubricity and reduce friction without recessed portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a recessed portion for collecting lubricating oil is formed in the sliding surface, then lubricating oil can be collected and drawn up into the space between sliding surfaces, but the effective area of the sliding surface is reduced, leading to an increase in the coefficient of friction
Solution Approach 1:
The invention extracts the harmful recessed portion from the sliding surface while maintaining the lubrication function through a different mechanism. The PVD coating layer provides lubrication without requiring recessed areas, thus preserving the full sliding surface area while still ensuring adequate lubricating oil supply.
Solution Approach 2:
The invention changes the surface parameters by applying a PVD coating layer with specific properties (low friction coefficient, appropriate roughness) that enables effective lubrication without the need for recessed portions. This parameter change allows the sliding surface to maintain both full area contact and adequate lubrication.
2Area of stationary object
If the sliding surface is made very shallow to increase effective area, then the coefficient of friction decreases, but the PVD coating layer cannot be formed uniformly on deep regions
Solution Approach 1:
The invention optimizes the depth-to-radius ratio parameter to a specific range (0.05 to 0.70) that balances two requirements: maintaining sufficient sliding surface area for low friction while ensuring the geometry allows uniform PVD coating deposition. This parameter optimization resolves the contradiction between area and coating quality.
3Reliability
If the sliding surface is made deep to improve lubrication oil collection, then oil can be retained better, but the effective sliding area is reduced and coating uniformity is compromised
Solution Approach 1:
The invention removes the recessed portion structure entirely, replacing it with a PVD coating layer that provides lubrication through its material properties rather than through geometric oil retention features. This extraction eliminates the trade-off between depth and area.
Solution Approach 2:
The invention uses a composite structure consisting of the base socket portion material combined with a PVD coating layer. The coating layer provides both the lubrication function and the low-friction surface, eliminating the need for deep recesses while maintaining full sliding surface area.
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 reduces the coefficient of friction and ensures uniform PVD coating adhesion and film thickness, maintaining effective sliding performance without the need for recessed oil collection areas.
Implementation Method 1
the sliding surface of the socket portion includes a PVD coating layer
Data Source
AI summary
A ball socket structure is provided, which includes a ball portion and a socket portion, the ball portion and the socket portion being configured to slide against one another, in which the socket portion includes a sliding surface including a PVD coating layer, the sliding surface of the socket portion is a concave spherical surface, and a value (Ds/Rs) of a ratio between a depth Ds of the sliding surface and a radius of curvature Rs of the sliding surface is from 0.05 to 0.70.