Servo Valve Spool Geometry for Precise Nozzle Flow Control
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Solution Overview
Problem
Existing servo valves in aerospace applications face challenges in precise control of fluid flow due to complex calibration requirements and potential inaccuracies caused by friction and 'slip-stick' errors, which affect the precise axial movement of the member within the valve housing.
Innovation Solution
A servo valve design featuring a member with angled transition sections and a concave portion, combined with a piezoelectric actuator, allows for precise control of nozzle openings by varying the axial and radial positions, enabling finer calibration of fluid flow through the use of a non-circular cross-section and rotational alignment of the member within the valve housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flapper is deflected by an armature connected to an electric motor to control fluid flow, then the servo valve can control actuator movement, but friction and slip-stick errors cause inaccuracies in axial movement
Solution Approach 1:
The patent replaces the traditional electric motor-driven armature-flapper mechanical system with a direct-acting spool valve mechanism. The spool is directly actuated by an electromagnetic coil, eliminating the intermediate mechanical components (armature, flapper, nozzles) that generate friction and slip-stick errors. This substitution of the mechanical control system with a more direct actuation mechanism resolves the accuracy issues caused by friction in the original system.
2Measurement precision
If complex calibration procedures are used to achieve precise fluid flow control, then measurement precision improves, but device complexity and calibration time increase
Solution Approach 1:
The spool valve design incorporates self-aligning features where the spool automatically centers itself in the valve body bore through balanced forces and geometric constraints. The lands on the spool automatically align with the ports during operation, eliminating the need for complex external calibration procedures. The valve self-regulates its position based on fluid pressure balance and mechanical constraints, providing precise fluid flow control without requiring complex calibration equipment or procedures.
3Ease of manufacture
If the spool valve uses a simple cylindrical spool design, then manufacturing is easier, but sealing effectiveness and contamination resistance are reduced
Solution Approach 1:
The spool valve employs different geometric features at different locations along the spool length. The central portion of the spool has a reduced diameter creating an annular sealing surface, while the ends maintain the full diameter for structural support and alignment. This localized variation in spool geometry provides enhanced sealing at the critical annular interface without compromising the overall structural integrity or manufacturability of the spool component.
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
This design enhances the precision and accuracy of fluid flow control by reducing calibration complexities and minimizing inaccuracies, providing a simplified construction that effectively manages fluid flow through multiple ports with improved sealing and reduced risk of contamination.
Implementation Method 1
a piezoelectric actuator configured to move the member relative to the valve housing, between said first and second axial positions
Data Source
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AI summary
A servo valve (10) comprises a member (18) disposed in a cavity (16) and axially-moveable therein. The member (18) includes first and second sections (32, 34), a central section (36) located between the first and second sections (32, 34) and first and second transition sections (33, 35) respectively between the first and second sections (32, 34) and the central section (36), forming respective first and second outer surfaces (33a, 35a) angled relative to the axis (X). At least one of the transition sections (33, 35) comprises a non-circular cross-section having a concave portion (46) forming at least part of the respective first and second surfaces (33a, 35a)and being at least partially aligned with and facing the respective first or second nozzle opening (52A, 52B) such that rotating the member (18) in said cavity (16) varies the level of obstruction of the first or second nozzle openings (52A, 52C) by the first or second outer surfaces (33a, 35a).