Two-Stage Electrohydraulic Servovalve with Transfer Link
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Solution Overview
Problem
Existing electrohydraulic servovalves face challenges in achieving precise control and reduced leakage, with limitations in motion amplification and susceptibility to misalignment and friction, particularly in multi-stage designs.
Innovation Solution
A two-stage electrohydraulic servovalve design featuring a rotary brushless DC toroid motor with a torsional spring bias mechanism, a transfer link system, and symmetrical rotor configuration, which allows for efficient motion transfer between stages with reduced friction and binding, utilizing a transfer link with rounded ends to engage slots and minimize misalignment, and a stator design with opposing coil windings to minimize torque ripple and eddy current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-stage valve design is used to achieve motion amplification, then control precision is improved, but susceptibility to misalignment and friction increases
Solution Approach 1:
The patent introduces a transfer link as an intermediary component between the pilot stage valve spool and the main stage valve spool. This transfer link translates the small motion of the pilot stage into amplified motion of the main stage while maintaining mechanical coupling. The rounded ends of the transfer link engage with slots in the valve spools, providing a mediator that reduces direct friction and misalignment issues between stages.
Solution Approach 2:
The transfer link features rounded ends that engage with slots in the valve spools. This curved/spheroidal geometry allows for smoother motion transfer, reduces binding, and accommodates minor misalignments between components. The rounded configuration minimizes point contact friction compared to sharp-edged connections.
2Measurement precision
If a two-stage valve design is used to reduce leakage, then flow control precision is improved, but device complexity increases
Solution Approach 1:
The valve is divided into two functional stages: a pilot stage with a small spool for precise control and a main stage with a larger spool for high-flow control. Each stage has its own valve spool, chamber, and port configuration. This segmentation allows the pilot stage to control leakage and flow precision while the main stage handles bulk flow, achieving both precision and reduced leakage.
Solution Approach 2:
The pilot stage is effectively nested within the overall valve structure, with the pilot valve spool operating in a smaller chamber that is part of the main valve body. The transfer link connects the two stages, allowing the smaller pilot stage to control the larger main stage, creating a nested configuration that achieves complex functionality without proportionally increasing external dimensions.
3Productivity
If direct mechanical coupling is used between valve stages, then motion transfer efficiency is improved, but friction and binding increase
Solution Approach 1:
The transfer link serves as a mechanical intermediary between the pilot stage valve spool and the main stage valve spool. It translates and transmits motion while reducing direct friction through its rounded end geometry that engages with slots. This intermediary approach maintains motion transfer efficiency while minimizing binding and friction compared to direct rigid coupling.
Solution Approach 2:
The rounded ends of the transfer link provide curved contact surfaces that engage with the slots in the valve spools. This curvature allows for smoother relative motion, reduces point contact stress, and minimizes friction and binding compared to flat or sharp-edged mechanical couplings.
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 design achieves precise control, reduced leakage, and enhanced motion amplification between stages, with improved stability and resistance to external forces, allowing for efficient fluid flow management and reduced motor size requirements.
Implementation Method 1
a stator design with opposing coil windings to minimize torque ripple and eddy current losses
Implementation Method 2
a rotary brushless DC toroid motor with a torsional spring bias mechanism
Implementation Method 3
The transfer link may be configured and arranged to move the first valve member from the first null position to the first off-null position with selective rotation about the second connection
Implementation Method 4
the second valve member may be adapted to be moved from the first position to the second position along the second valve axis as a function of a hydraulic pressure differential between the first sub-chamber and the second sub-chamber
Data Source
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AI summary
A servovalve (15) comprising a motor (16), a motor bias mechanism (20), a first stage valve member (22) adapted to be moved from a first position to a first off-null position, a second stage member (29) adapted to be moved from a first position to a second position with movement of the first valve member (22), a transfer link (34) acting between the first (22) and second (29) valve members, an eccentric drive member (35) acting between the motor (16) and transfer link (34), the transfer link (34) and drive member (35) configured such that selective movement of the motor (16) causes the transfer link (34) to move the first valve member (22), movement of the first valve member (22) causes the second valve member (29) to move, and movement of the second valve member (29) causes the transfer link (34) to move the first valve member (22) from the first off-null position back to the null position.