Silicon Nitride Piston Ring for Low-Friction Pump Wear
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Solution Overview
Problem
Traditional piston rings made of tool steel for piston pumps are heavy and dense, posing challenges in applications where weight is a consideration, and there is a need for a highly wear-resistant, lighter material.
Innovation Solution
The use of silicon nitride piston rings combined with a tool steel cylinder barrel, which reduces friction and maintains a low coefficient of friction even under wear, along with a design that maintains bore diameter throughout the life of the cylinder barrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tool steel piston rings are used, then wear resistance is improved, but weight and density increase
Solution Approach 1:
The patent changes the material parameter from traditional tool steel to silicon nitride ceramic, fundamentally altering the physical and chemical properties of the piston ring to achieve both weight reduction and wear resistance
Solution Approach 2:
The patent employs composite material strategy by combining silicon nitride ceramic with appropriate bonding materials or coatings, creating a composite structure that leverages the high wear resistance of ceramic while managing mechanical properties and weight
2Reliability
If tungsten carbide cylinder barrels are used, then wear resistance is improved, but density and weight increase
Solution Approach 1:
The patent changes the material parameter from dense tungsten carbide to tool steel for the cylinder barrel, adjusting the material properties to reduce density while maintaining adequate wear resistance through the complementary silicon nitride piston rings
Solution Approach 2:
The patent applies local quality by using different materials for different components - tool steel for the cylinder barrel and silicon nitride for the piston rings - optimizing the overall system performance rather than using a single material throughout
3Reliability
If traditional materials are used, then wear resistance is achieved, but friction coefficient remains high
Solution Approach 1:
The patent changes the surface property parameter by introducing silicon nitride ceramic material, which inherently possesses lower friction characteristics and higher lubricity compared to traditional metal materials
Solution Approach 2:
The patent substitutes the mechanical interaction between metal surfaces with a ceramic-metal interface, where the silicon nitride piston ring interacts with the tool steel cylinder barrel, reducing direct metal-to-metal contact and associated friction
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 combination of silicon nitride piston rings with tool steel cylinder barrels results in a lighter, more lubricious, and less dense pump system with reduced friction, extending the service life and reducing wear, thus enhancing the operational efficiency and durability of the pump.
Implementation Method 1
a friction coefficient between the piston ring and the inner surface of the bore can be about 0.11 when hydrodynamically lubricated
Data Source
Figure 1~2
Figure 3~5
AI summary
In accordance with at least one aspect of this disclosure, a pump system for an aircraft includes, a cylinder barrel (108) configured to rotate within a pump housing (104) of a pump (102), and a plurality of pistons (110) seated within a respective bore (116) defined in the cylinder barrel. Each piston further includes a piston ring (118) disposed at an end thereof configured to form a hydrodynamic seal with an inner surface (122) of the respective bore. Each respective piston ring is of silicon nitride. In embodiments, the piston ring can include a chamfer on at least a leading edge of the piston ring. In embodiments, the piston ring can include a cut therethrough configured to allow for thermal expansion of the piston ring.