Two-Stage Electrohydraulic Servovalve with Eccentric Drive
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Solution Overview
Problem
Existing electrohydraulic servovalves face challenges in efficiently controlling fluid flow and pressure equilibrium across multiple stages, leading to inefficiencies and potential jamming due to misalignment and friction, particularly in high-pressure applications.
Innovation Solution
A two-stage electrohydraulic servovalve design featuring a rotary brushless DC toroid motor, a torsional spring bias mechanism, and an eccentric drive member with a transfer link, which allows for precise movement of valve spools and pistons, maintaining pressure equilibrium and minimizing friction through spherical end portions and dynamic adjustment, enabling efficient fluid flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-stage valve design is used to control fluid flow and pressure, then flow control precision is improved, but device complexity and potential for misalignment increase
Solution Approach 1:
The patent implements a nested valve structure where a first valve spool is positioned within a second valve spool, creating a compact multi-stage arrangement. The first valve member is received within the second valve member, allowing both valves to be integrated in a space-efficient manner while maintaining independent control functions for each stage.
Solution Approach 2:
The patent combines multiple valve stages and control mechanisms into a single integrated assembly. The first and second valve spools are merged within a common cylindrical bore, sharing hydraulic passages and control mechanisms, thereby reducing overall device complexity while achieving precise multi-stage flow control.
2Measurement precision
If valve spools are made to move precisely for flow control, then flow metering accuracy is improved, but friction and jamming risks increase
Solution Approach 1:
The patent incorporates spherical end portions on the valve spools that engage with corresponding spherical seats. This spherical geometry allows for smooth, frictionless movement of the spools while maintaining precise positioning. The curved surfaces reduce contact friction compared to flat surfaces, enabling accurate flow metering without increased jamming risks.
Solution Approach 2:
The patent uses hydraulic pressure differentials to actuate the valve spools, eliminating the need for mechanical linkages that would increase friction. The first and second valve spools are moved by hydraulic forces applied through controlled pressure differences, providing smooth, precise, and reliable movement without mechanical friction or jamming.
3Stability of the object's composition
If pressure equilibrium is maintained across stages, then system stability is improved, but control responsiveness may be reduced
Solution Approach 1:
The patent divides the pressure control system into separate stages with independent valve spools. The first valve spool controls pressure for the second stage, while the second valve spool independently controls the final output. This segmentation allows each stage to respond independently to control signals, maintaining system stability through pressure equilibrium while preserving fast control responsiveness through decentralized actuation.
Solution Approach 2:
The patent implements a feedback mechanism where the position of the valve spools is continuously monitored and used to adjust hydraulic pressure distribution. This feedback ensures pressure equilibrium across stages for stability while allowing rapid corrective actions to maintain responsiveness to changing control requirements.
4Reliability
If spherical end portions are used on valve spools, then friction is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies spherical end portions with a diameter of 0.030 inches and spherical seats with a diameter of 0.060 inches. These standardized spherical dimensions provide a balance between achieving low-friction movement and maintaining manufacturability. The spherical geometry is achieved through conventional machining processes, avoiding excessive manufacturing complexity while ensuring smooth spool movement and reduced friction.
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 enhances fluid flow control and pressure management across stages, reducing friction and misalignment issues, resulting in improved efficiency and reliability in high-pressure applications without the need for large motors or additional electronics.
Implementation Method 1
a rotary brushless DC toroid motor having a stator and a rotor and configured and arranged to rotate about a motor axis under the effect of a magnetic field generated by the stator
Implementation Method 2
a bias mechanism configured and arranged to bias the rotor to the rotor null position
Implementation Method 3
adapted to be moved from a first null position to a first off-null position along the first chamber axis to selectively meter fluid flow from at least one port defined between the first valve member and the first chamber
Implementation Method 4
minimizing friction through spherical end portions and dynamic adjustment
Data Source
AI summary
A servovalve comprising a motor, a motor bias mechanism, a first stage valve having a first position, a second stage valve movable with movement of the first valve, a reference member in fluid communication with the second valve, a transfer link acting between the first valve and the reference member, an eccentric drive acting between the motor and transfer link, wherein movement of the motor causes the transfer link to move the first valve, movement of the first valve causes the second valve member to move, movement of the second valve applies on the reference member a pressure differential from a load, the pressure differential on the reference member causes movement of the reference member, and movement of the reference member causes the transfer link to move the first valve back to the first position.