Balanced Variable Displacement Vane Pump with Floating Face Seals
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Solution Overview
Problem
Variable displacement vane pumps face challenges with internal cross-bucket leakage and radial leakage, particularly in high-pressure applications like aircraft fuel systems, where existing designs require large bearings and are prone to poor operation due to rotor reaction forces and low viscosity fluids.
Innovation Solution
A hydrostatically balanced dual-action variable displacement vane pump cartridge with an improved seal design, featuring a rotary cam ring, radially extending vane slots, undervane pins, and floating face seals, which reduces internal cross-port leakage and allows for easy displacement control with minimal control torque, while maintaining hydrostatic balance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single lobe cam ring design is used in a variable displacement vane pump, then the pump structure is simpler, but large bearing loads are generated and rotor reaction forces cause poor operation under high discharge pressure
Solution Approach 1:
The single lobe cam ring is segmented into multiple lobes (typically two or three lobes) to create a balanced rotor arrangement. This segmentation distributes the hydraulic loads across multiple cam ring contact points, eliminating excessive bearing loads and rotor reaction forces that occur with single lobe designs, particularly under high discharge pressure conditions
2Device complexity
If conventional vane seals are used, then the vane assembly is simpler, but internal cross-bucket leakage increases due to low viscosity fluid
Solution Approach 1:
The vane seal design incorporates localized sealing features at specific positions where leakage occurs. The vane tips are equipped with sealing edges and contact surfaces that are specifically engineered to maintain hydrostatic balance and prevent cross-bucket leakage, addressing the local leakage problem without requiring complete redesign of the entire vane assembly
3Device complexity
If conventional face seals are used, then the seal design is simpler, but radial leakage increases between the rotor and side plates
Solution Approach 1:
The face seal design utilizes hydrostatic pressure from the discharge pressure to maintain sealing contact between the rotor and side plates. This hydraulic principle creates a pressure-balanced seal system that prevents radial leakage without requiring complex mechanical sealing structures, using the pump's own discharge pressure to enhance sealing effectiveness
4Adaptability or versatility
If displacement control mechanisms are added to vary cam ring position, then pump displacement control is enabled, but control torque requirements increase
Solution Approach 1:
The multi-lobe cam ring design creates inherent hydrostatic balance that counteracts the forces resisting cam ring rotation. This balance reduces the control torque required to vary the cam ring position and adjust pump displacement, making the control system more efficient and less complex
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 effectively minimizes internal leakage, enhances durability, and simplifies design by balancing the pump, allowing for high efficiency, compact size, and low cost, while maintaining hydrostatic balance and reducing radial leakage.
Implementation Method 1
discharge pressure directed to the annular groove of the rotor acting on the undervane pins pushes the vanes radially outwardly against the camming surface of the cam ring
Implementation Method 2
discharge pressure directed to the annular groove of the rotor acting on the undervane pins pushes the vanes radially outwardly against the camming surface of the cam ring
Data Source
AI summary
A vane pump assembly including a cam ring having an elliptical inner bore defining a hydraulic pumping chamber, the pumping chamber having an interior camming surface. The cam ring defines ports for admitting fluid into the pumping chamber. A rotor, within the cam ring, defines a plurality of radial vane slots. A vane assembly is supported in each vane slot to define vane buckets. Each vane assembly has an end dynamic vane seal for reducing leakage between the buckets. Front and rear side plates, separated by an annular spacer, enclose the pumping chamber. The pump assembly may also include floating front and rear rotor seals for reducing radially inward leakage. Each rotor seal is disposed within a groove formed in the rotor, wherein discharge pressure urges the rotor seals axially outward from the pumping chamber to create an effective seal against the respective side plate.