Ceramic Piston Rings and Sleeves for Lightweight Wear Resistance
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Solution Overview
Problem
Traditional positive displacement piston pumps used in aerospace applications face challenges due to the weight and wear characteristics of materials like Tungsten Carbide, which are not optimal for reduced weight and improved wear resistance.
Innovation Solution
The pump assembly incorporates a cylinder block made of tool steel, with sleeves and piston rings made of ceramic materials such as partially stabilized zirconias (PSZs) or silicon nitride (Si3N4), which provide improved wear resistance and reduced weight compared to traditional WC-based pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Tungsten Carbide is used for cylinder barrels, then wear resistance is improved, but weight increases
Solution Approach 1:
The cylinder barrel is divided into two functional segments: a non-wearing structural portion made of lighter aluminum alloy and a wearing portion lined with Tungsten Carbide. This segmentation allows the heavy WC material to be used only where wear resistance is needed, while the majority of the barrel structure uses lightweight material.
Solution Approach 2:
Different materials are applied to different regions of the cylinder barrel based on functional requirements. The structural portions use aluminum alloy for lightweight, while the wearing portions contactin g pistons use Tungsten Carbide for wear resistance. This local quality approach optimizes the weight-strength-wear resistance balance.
2Reliability
If tool steel is used for piston wearing portions, then wear resistance is improved, but weight increases
Solution Approach 1:
The piston is segmented into a structural body made of lightweight aluminum alloy and separate wearing portions (piston rings) made of tool steel. This allows the heavy steel material to be used only for the small contact surfaces that require wear resistance.
Solution Approach 2:
Tool steel is applied locally only to the piston rings and contact surfaces that require wear resistance, while the main piston body remains aluminum alloy. This localized application of heavy material minimizes weight increase while maintaining wear resistance where needed.
3Weight of moving object
If ceramic materials are used for sleeves and piston rings, then weight is reduced and wear resistance is maintained, but material compatibility challenges arise
Solution Approach 1:
The invention uses composite material combinations: aluminum alloy structural components paired with ceramic wearing surfaces. This composite approach allows the lightweight aluminum to form the bulk structure while thin ceramic coatings or liners provide the wear resistance, achieving both weight reduction and durability.
Solution Approach 2:
The patent addresses material compatibility challenges by using intermediate bonding layers or transition materials between the aluminum alloy substrate and ceramic wearing surfaces. This intermediary layer ensures proper adhesion and thermal expansion compatibility between dissimilar materials.
Data Source
AI summary
A pump assembly includes a cylinder block defining a piston bore therein extending in an axial direction. A sleeve lines the piston bore. A piston is included in the piston bore, configured to reciprocate along a stroke in the axial direction within the sleeve. A piston ring is engaged circumferentially about the piston. The piston ring is fixed to the piston and is slidingly engaged to an inner surface of the sleeve.