Solid Lubricant Coating with Capillary Fluid Film for High Load Bearings
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Solution Overview
Problem
Existing lubrication methods for planetary roller screws and bearings, such as liquid lubricants and greases, fail to provide effective lubrication under high axial loads and slow movements, and solid lubricants are sensitive to thermal, climatic, and chemical conditions, making them unsuitable for applications like aviation.
Innovation Solution
A mechanical member with a coating of solid lubricant and retention and capillary distribution means that form a protective fluid film between moving parts, allowing temporary piercing for direct contact and protecting the solid lubricant from external attacks, using a fluid with low viscosity and high thermal conductivity to maintain the film and prevent consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid lubricant is used, then lubrication is provided under normal conditions, but lubrication effectiveness deteriorates under high axial loads and slow movements
Solution Approach 1:
The lubrication system is segmented into two distinct components: solid lubricant particles embedded in the coating for load-bearing contact zones, and liquid lubricant retained in reservoirs for general lubrication. This segmentation allows each lubricant type to perform its optimal function - solid lubricant handles high axial loads while liquid lubricant provides continuous lubrication film.
Solution Approach 2:
The solid lubricant particles act as intermediaries between the contacting surfaces in high-load zones, transferring load through rolling or sliding contact. The capillary channels serve as intermediaries to transport liquid lubricant from reservoirs to contact zones, enabling the liquid lubricant to reach areas where it is needed most.
2Reliability
If grease is used, then lubrication withstands higher axial loads and slower movements, but viscosity varies greatly with temperature causing freezing at low temperatures
Solution Approach 1:
The invention changes the physical state parameter of the lubricant from liquid/grease to solid particles for the load-bearing function. Solid lubricant particles maintain their lubricating properties across a wide temperature range, including cryogenic temperatures where greases would freeze. The solid state eliminates viscosity variation with temperature.
Solution Approach 2:
The coating is a composite material combining solid lubricant particles (such as PTFE, MoS2, or WS2) with a binder matrix. This composite structure provides both load-bearing capability through the solid particles and adhesion to the substrate, while maintaining performance across extreme temperature ranges from -50°C to +200°C.
3Reliability
If grease is used, then lubrication is provided, but grease is expelled from contact zones requiring regular refilling
Solution Approach 1:
The capillary channels are designed to automatically replenish liquid lubricant from the reservoirs to the contact zones based on demand. When lubricant is consumed or expelled from contact zones, capillary action and pressure differentials automatically draw more lubricant from the reservoirs, eliminating the need for external refilling operations.
Solution Approach 2:
The solid lubricant particles are embedded in the coating structure and are not easily expelled from contact zones. Even when particles wear or are displaced, the self-service liquid lubricant system continuously replenishes the contact zones, effectively recovering and reusing lubricant that would otherwise be lost.
4Reliability
If solid lubricant coating is applied, then lubrication withstands higher axial loads, but solid lubricant degrades in presence of water and chemical compounds
Solution Approach 1:
The coating is formulated as a composite material combining solid lubricant particles with chemically resistant binder materials. This composite structure maintains the load-bearing properties of the solid lubricant while the binder matrix provides resistance to water and chemical compounds, preventing degradation and aggressive reactions.
Solution Approach 2:
The liquid lubricant retained in the reservoirs and delivered via capillary channels acts as an intermediary protective layer between the solid lubricant particles and the external environment. This liquid film shields the solid lubricant from direct exposure to water and chemical compounds that would cause degradation.
5Reliability
If uniform oil film is formed, then lubrication is improved, but oil film formation is extremely difficult under high axial loads and slow movements
Solution Approach 1:
The lubrication system segments the lubrication function into solid lubricant particles for immediate contact zone lubrication and liquid lubricant reservoirs for continuous film formation. The solid particles provide instant lubrication under high load without requiring complex film formation processes, while the liquid reservoirs maintain a reservoir of lubricant for continuous supply.
Solution Approach 2:
The capillary channels are designed to automatically transport liquid lubricant from the reservoirs to the contact zones based on pressure differentials and capillary forces. This self-service mechanism eliminates the need for external pumping or complex control systems to maintain uniform oil film distribution across the contact surfaces.
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 provides robust and reliable lubrication with minimal maintenance, protecting the solid lubricant from environmental factors and reducing fluid consumption, while maintaining effective lubrication and thermal management.
Implementation Method 1
retention and capillary distribution means for distributing a fluid between the parts in such a manner as to form a film between said parts
Implementation Method 2
at least one of the parts including a coating of solid lubricant at least at contact zones between the first part and the second part
Data Source
AI summary
The invention relates to a mechanical member wherein a first part in contact with a second part movable relative to the first part, at least one of the parts including a coating of solid lubricant at least at contact zones between the first part and the second part, the solid lubricant being suitable on its own for lubricating the mechanical member. According to the invention, the mechanical member includes retention and capillary distribution means for distributing a fluid between the parts in such a manner as to form a film between said parts, which film can be pierced temporarily at each contact zone.