Hydraulic Actuator Stroke-End Damping to Prevent Piston Bottoming
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Solution Overview
Problem
Hydraulic actuators in aircraft applications face damage due to 'bottoming out' of the piston when unpressurized, caused by external forces like wind gusts, which existing solutions like mode valves or damping mechanisms with frustoconical seats and plugs may complicate.
Innovation Solution
A stroke end damping valve is integrated into the hydraulic actuator, featuring a damping orifice with a selectively varying valve element that increases damping as the piston approaches the end of its stroke, reducing the risk of damage by controlling the flow of hydraulic fluid and dissipating kinetic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mode valve is incorporated to connect chambers through a damping orifice, then piston bottoming is prevented, but device complexity increases
Solution Approach 1:
The invention extracts the damping function from a complex mode valve system and implements it through a simple damping orifice with a valve element that is directly engageable by the piston. This removes the need for complicated mode valve mechanisms while retaining the essential damping functionality to prevent piston bottoming.
Solution Approach 2:
The valve element is designed to be automatically engaged by the piston itself during its stroke, eliminating the need for external control systems or complex actuation mechanisms. The piston's own motion triggers the damping action through direct engagement with the valve element, simplifying the overall system.
2Reliability
If damping means with frustoconical seat and plug is used, then piston motion is damped, but device complexity increases
Solution Approach 1:
The invention extracts the essential damping function from complex frustoconical seat and plug mechanisms and implements it through a simple damping orifice with a valve element. This maintains the damping effect while removing unnecessary structural complexity.
Solution Approach 2:
The damping action is localized to a specific region through the damping orifice and valve element arrangement, providing targeted damping where needed (at the end of the piston stroke) without requiring complex damping mechanisms throughout the entire actuator system.
3Reliability
If damping orifice area is reduced selectively, then damping effect increases, but flow restriction increases
Solution Approach 1:
The damping orifice area is made dynamic through the valve element that can be selectively engaged by the piston. The orifice area changes from open to restricted based on the piston's position and velocity, providing high damping when needed (during bottoming prevention) while maintaining normal flow during regular operation, thus minimizing unnecessary energy loss.
Solution Approach 2:
The damping action occurs periodically only during the critical phases when the piston approaches the end of its stroke, rather than continuously. The valve element is engaged only when needed to prevent bottoming, allowing full flow during normal operation and restricted flow only during the damping phase, reducing overall energy loss.
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 prevents or mitigates piston damage by selectively increasing damping in the final stages of the piston's stroke, reducing the likelihood and impact of 'bottoming out' without the complexity of additional mode valves, thus enhancing the reliability and simplicity of the actuator design.
Implementation Method 1
A stroke end damping valve is provided in a hydraulic fluid flow passage of the actuator
Implementation Method 2
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
Implementation Method 3
The plug supports a compression spring which extends from the plug and towards the piston
Implementation Method 4
The seat is configured to allow hydraulic fluid to be pushed out of the cylinder, through the seat and into a channel that carries the hydraulic fluid back to a reservoir
Data Source
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AI summary
The present disclosure provides a hydraulic actuator (2) comprising a piston (4) and a cylinder (6). The piston (4) is axially movable within the cylinder (6). A stroke end damping valve (32) is provided in a hydraulic fluid flow passage (40) of the actuator (2) and adjacent an end (10) of the cylinder (6). The stroke end damping valve (32) comprises a damping orifice (34) and a valve element (36) for selectively varying the area of the damping orifice (34) and thereby changing the damping provided by the orifice (34). The valve element (36) projects from a wall (8) of the cylinder (6) into the cylinder (6) and is engageable by the piston (4) as the piston (4) moves towards the end (10) of the cylinder (6). This reduces the area of the damping orifice (34) and thereby increases the damping effect on the piston (4) towards the end of its stroke in the cylinder (6).