Hydraulic Actuator End-Stroke Damping Valve for Bottoming Protection
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Solution Overview
Problem
Hydraulic actuators in aircraft face damage due to 'bottoming out' of the piston when unpressurized, caused by external forces like wind gusts, which existing solutions attempt to mitigate with complex mode valves.
Innovation Solution
A stroke end damping valve with a selectively varying damping orifice, activated by the piston as it approaches the cylinder end, increases damping in the final stages of its stroke to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mode valve with damping orifice is incorporated to prevent piston bottoming out, then the actuator reliability is improved, but the device complexity increases
Solution Approach 1:
The damping valve is integrated directly into the existing hydraulic fluid flow passage of the actuator, merging the damping function with the existing hydraulic system rather than adding a separate mode valve assembly. This reduces device complexity while maintaining reliability
Solution Approach 2:
The damping valve automatically activates when the piston approaches the cylinder end, using the piston's own motion to engage the valve element and close the damping orifice. This self-activating mechanism eliminates the need for external control systems, reducing complexity while ensuring reliable operation
2Reliability
If damping is provided throughout the entire stroke, then the piston bottoming out is prevented, but the actuator productivity decreases
Solution Approach 1:
The damping orifice area is dynamically adjusted during the piston stroke. The valve element remains retracted during most of the stroke, providing full flow area for high productivity. As the piston approaches the cylinder end, the valve element is engaged by the piston and progressively closes the damping orifice, providing damping only in the final portion of the stroke to prevent bottoming out while maintaining high speed during the majority of 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 effectively reduces the likelihood and impact of piston damage by dissipating kinetic energy through controlled damping, simplifying the actuator design by eliminating the need for additional mode valves.
Implementation Method 1
The stroke end damping valve comprises a damping orifice and a valve element for selectively varying the area of the damping orifice and thereby changing the damping provided by the orifice
Data Source
AI summary
A hydraulic actuator includes a piston and a cylinder. The piston is axially movable within the cylinder. A stroke end damping valve is provided in a hydraulic fluid flow passage of the actuator and adjacent an end of the cylinder. The stroke end damping valve comprises a damping orifice and a valve element for selectively varying the area of the damping orifice and thereby changing the damping provided by the orifice. The valve element projects from a wall of the cylinder into the cylinder and is engageable by the piston as the piston moves towards the end of the cylinder. This reduces the area of the damping orifice and thereby increases the damping effect on the piston towards the end of its stroke in the cylinder.