EHA Accumulator Refill Assembly With Piston-Actuated Spool Valve
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Solution Overview
Problem
Electrohydrostatic actuators (EHAs) require large accumulators to compensate for long-term fluid leakage, leading to increased weight, size, and maintenance costs, particularly in space-constrained applications like aircraft.
Innovation Solution
An accumulator assembly with a refill arrangement that automatically detects low fluid levels and refills the accumulator using a mechanical valve mechanism within the accumulator, eliminating the need for external solenoids, pressure sensors, and fill valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a large accumulator is used to compensate for long-term fluid leakage in EHAs, then the duration of action is improved, but the weight and volume increase
Solution Approach 1:
The accumulator is equipped with an automatic refilling mechanism that detects low fluid levels and activates a fill valve to refill from the aircraft hydraulic supply, eliminating the need for manual intervention and enabling long-term autonomous operation without requiring excessively large initial fluid capacity
Solution Approach 2:
The refilling system is pre-configured with detection mechanisms and fill pathways that activate automatically when needed, ensuring the accumulator can maintain operation over extended periods by proactively replenishing fluid before complete depletion occurs
2Duration of action of moving object
If a large accumulator is used to compensate for long-term fluid leakage in EHAs, then the duration of action is improved, but the size increases
Solution Approach 1:
The accumulator incorporates an automatic refilling system that enables it to sustain operation over its service life by replenishing lost fluid, thereby allowing a smaller initial volume to achieve the same effective duration of action that would otherwise require a much larger accumulator
Solution Approach 2:
The refilling capability is built into the accumulator design, allowing it to proactively maintain fluid levels and extend operational duration without requiring the volume that would be needed for a non-refillable accumulator to cover the entire service period
3Extent of automation
If external components such as solenoids, pressure sensors, and fill valves are used for accumulator refilling, then the extent of automation is improved, but the device complexity increases
Solution Approach 1:
The fill valve is integrated directly into the accumulator assembly, combining the refilling function with the existing accumulator structure and eliminating the need for separate external solenoids, pressure sensors, and fill valve components, thereby maintaining automation while reducing overall system complexity
Solution Approach 2:
The integrated fill valve serves multiple functions within the accumulator system, acting as both a refilling mechanism and a controlled flow pathway, thereby reducing the number of dedicated components needed and simplifying the overall device architecture while maintaining automatic operation
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 allows for efficient and automatic refilling of the accumulator, reducing the need for complex external components, thereby minimizing weight, size, and maintenance costs while ensuring long-term operation of EHAs.
Implementation Method 1
an accumulator piston moveable within the cylinder relative to the chamber responsive to the fluid pressure
Implementation Method 2
the piston comprises a ramped surface that engages the spool such that the contact force between the ramped surface and the spool varies as the piston moves relative to the chamber
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An accumulator assembly for providing hydraulic fluid to an electrohydrostatic actuator, EHA, the assembly comprising: accumulator (1) for containing a supply of hydraulic fluid, the accumulator having an exit port via which hydraulic fluid can flow, in use, to the actuator; the assembly further comprising an accumulator refill arrangement fluidly connected to a supply of hydraulic fluid for refilling the accumulator via a fluid line (15) when a level of fluid in the accumulator is below a predetermined value, wherein the accumulator comprises a cylinder (10) defining a fluid chamber (11) and an accumulator piston (12) moveable within the cylinder relative to the chamber responsive to the fluid pressure, the refill arrangement including a spool (60) moveable across the fluid line between an open position, wherein fluid can flow along the fluid line from the supply (2) to the chamber, and a closed position, wherein the spool blocks the flow of fluid from the supply to the chamber and also from the chamber to the supply, and wherein the piston is linked to, and moves, a ramped surface (111) that engages the spool such that the contact force between the ramped surface and the spool varies as the piston moves relative to the chamber, whereby when the chamber is in a full state, the contact force is such as to locate the spool in the closed position and when the level of fluid is less than the predetermined value, the contact force is such as to locate the spool in the open position.