Sliding Surface Dimple Processing for Wide-Range Fluid Lubrication
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Solution Overview
Problem
Existing sliding components face challenges in achieving both improved sliding characteristics across a wide range of bearing characteristic numbers and generating a predetermined dynamic pressure while maintaining effective sealing and lubrication, as previous methods either focus on temperature stability or liquid lubricity without considering a broad range of bearing characteristics.
Innovation Solution
A method involving a sliding component with randomly distributed dimples on its surface, each with a shallow groove depth of 0.05 µm to 10 µm and a bottom surface roughness of 1/10 or less, and an opening diameter of 10 to 500 µm, processed using an ultrashort pulse laser with a repetition frequency of 5 kHz or higher and pulse width less than 10 picoseconds, to reduce friction and enhance lubrication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If dimples are formed on sliding face to improve liquid lubricity, then friction reduction is achieved, but sliding characteristics in wide range of bearing characteristic numbers cannot be improved and predetermined dynamic pressure cannot be generated
Solution Approach 1:
The patent applies local quality by creating dimples with specific local characteristics (depth 0.05-10μm, diameter 10-500μm, roughness Ra≤1/10 of depth) in specific regions of the sliding face. This localized structuring optimizes fluid pressure generation in specific zones while maintaining overall sliding surface functionality, resolving the contradiction between friction reduction and reliable sliding performance across bearing characteristic numbers.
Solution Approach 2:
The patent changes physical parameters of the dimples (depth, diameter, roughness, distribution pattern) to optimize performance. By controlling depth within 0.05-10μm and roughness Ra to be 1/10 or less of processing depth, the dimples generate appropriate fluid pressure without excessive friction, improving sliding characteristics across a wide range of bearing characteristic numbers.
2Reliability
If dimples with larger depth are formed to generate dynamic pressure, then sealing performance improves, but heat effect during processing increases causing undulations on sliding face
Solution Approach 1:
The patent optimizes the depth parameter within a specific range (0.05-10μm) and controls roughness Ra to be 1/10 or less of the processing depth. This parameter optimization generates sufficient fluid pressure for sealing while minimizing heat-affected zone and preventing undulations on the sliding face, resolving the contradiction between sealing performance and manufacturing precision.
3Productivity
If conventional laser processing is used to form dimples, then processing speed is achieved, but heat effect causes undulations and reduces sealing performance
Solution Approach 1:
The patent employs ultrashort pulse laser processing which delivers energy in extremely short periodic pulses (picosecond to femtosecond range). This periodic action allows material removal through ablation without significant heat diffusion to surrounding areas, achieving high processing speed while maintaining dimple accuracy and preventing undulations that would compromise sealing performance.
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 approach effectively reduces friction across a wide range of bearing characteristic numbers, improves lubrication, and maintains good sealing performance by generating a fluid film with accurate positive-pressure grooves, minimizing heat effects and protuberances, thus providing superior sliding characteristics and sealing.
Implementation Method 1
processed using an ultrashort pulse laser with a repetition frequency of 5 kHz or higher and pulse width less than 10 picoseconds
Implementation Method 2
load capacity due to a fluid bearing pressure produced in fluid interposed between the sliding face and an opposing sliding face during sliding
Implementation Method 3
friction reduction by interposing fluid between sliding faces
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
Sliding characteristics are improved in a wide range of bearing characteristic numbers on a sliding face, and a predetermined dynamic pressure is generated by dimples processed accurately. In a sliding component including a plurality of dimples 10 disposed on at least one of sliding faces S of a pair of sliding parts 3 and 5 relatively sliding on each other, the plurality of dimples 10 is provided mutually independently of the other dimples and disposed in a randomly distributed manner, each of the dimples 10 is formed by irradiation with an ultrashort pulse laser, constituting a shallow groove with a depth in a range of 0.05 µm to 5 µm, and the dimples have a bottom surface whose roughness Ra is 1/10 or less of a processing depth.