EHA Accumulator Refill Spool for Automatic Hydraulic Replenishment
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Solution Overview
Problem
Electrohydrostatic actuators (EHAs) require large accumulators to compensate for fluid leakages over their long lifespan, which adds weight, size, and cost, and conventional refilling systems are complex, bulky, and require downtime.
Innovation Solution
An accumulator assembly with a refill arrangement that automatically refills the accumulator by using a spool mechanism and a ramped piston surface to control fluid flow, eliminating the need for external solenoids, pressure sensors, and fill valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the accumulator is made very large to compensate for leakages over the whole life of the EHA, then the accumulator can provide sufficient fluid volume, but the weight and size of the system increase significantly
Solution Approach 1:
The system performs preliminary action by providing a refilling capability that activates when fluid levels drop, eliminating the need to pre-size the accumulator for the entire operational lifetime. The accumulator can be smaller since it will be periodically refilled from the aircraft hydraulic supply through the automated refilling system.
2Ease of operation
If conventional refilling systems with solenoid valves and pressure sensors are used, then the accumulator can be refilled in situ, but the complexity, cost, and weight of components increase
Solution Approach 1:
The invention extracts and eliminates the complex external refilling components (solenoid valves, pressure sensors, fill valves) by integrating the refilling function directly into the accumulator piston assembly. The piston itself becomes the control element through the spool mechanism, removing the need for separate sensing and actuation components.
Solution Approach 2:
The invention merges multiple functions into the accumulator piston: it serves as both the fluid displacement element and the control valve actuator. The spool mechanism integrated into the piston combines the functions of level detection, valve actuation, and flow control into a single integrated assembly, dramatically reducing system complexity.
3Reliability
If conventional refilling systems with external piping are used, then the accumulator can be refilled, but the risk of damage to pipes and components or leakage increases
Solution Approach 1:
The refilling connection is merged with the accumulator housing and piston assembly, creating an integrated refilling path that eliminates external piping. The fluid line connects directly to the accumulator chamber through the spool mechanism, removing vulnerable external pipe connections and reducing leakage risks.
4Weight of stationary object
If the accumulator is made smaller to reduce weight and size, then the system becomes more compact, but the accumulator cannot compensate for leakages over the long term
Solution Approach 1:
The refilling system ensures continuity of useful action by automatically replenishing the accumulator when fluid levels drop, allowing the system to maintain its hydraulic fluid volume indefinitely. This continuous refilling capability enables a smaller accumulator to provide long-term reliability equivalent to a much larger non-refillable accumulator.
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 components, minimizing downtime, and maintaining the actuator's long-term functionality without the weight and size penalties of large accumulators.
Implementation Method 1
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
AI summary
An accumulator assembly for providing hydraulic fluid to an electrohydrostatic actuator includes an accumulator 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 includes an accumulator refill arrangement fluidly connected to a supply of hydraulic fluid for refilling the accumulator via a fluid line when a level of fluid in the accumulator is below a predetermined value. The accumulator includes a cylinder defining a fluid chamber and an accumulator piston moveable within the cylinder relative to the chamber responsive to the fluid pressure. The refill arrangement includes a spool moveable across the fluid line between an open position, wherein fluid can flow along the fluid line from the supply to the chamber, and a closed position, wherein the spool blocks the flow of fluid from the supply to the chamber.