Conical Spool Servo Valve for Precise Flow Area Control
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Solution Overview
Problem
Existing servo valve designs, such as the flapper and nozzle arrangement, face challenges in achieving precise control, require tight tolerances, and are heavy, complex to manufacture and operate, with limitations in operational pressures and frequencies.
Innovation Solution
A servo valve assembly featuring a spool with conical blocking and cavity surfaces, moveable along a central axis to vary fluid flow areas, supported by retaining and guiding lands, and biased by electromagnetic forces for precise fluid pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flapper and nozzle arrangement is used for servo valve control, then fluid flow can be controlled, but tight tolerances are required for spacing and calibration
Solution Approach 1:
The patent replaces the flapper and nozzle mechanical arrangement with a spool valve mechanism. The spool valve uses a different mechanical principle where a spool moves axially within a valve body to control fluid flow paths, eliminating the need for tight spacing tolerances between flapper and nozzle components. This substitution fundamentally changes the control mechanism from gap-based flow control to port-based flow control.
Solution Approach 2:
The invention changes the critical control parameter from spacing distance (in flapper-nozzle systems) to axial position (in spool valve systems). The spool valve controls flow based on the axial position of the spool relative to the valve body ports, which is a more easily manufacturable and calibratable parameter than maintaining tight radial spacing tolerances between moving and stationary components.
2Measurement precision
If flapper and nozzle spacing is reduced for better control, then control precision improves, but manufacturing complexity and cost increase
Solution Approach 1:
The spool valve mechanism replaces the flapper-nozzle system, fundamentally changing how control precision is achieved. Instead of relying on tight spacing between components, the spool valve achieves precision through the axial positioning of the spool relative to precisely machined ports in the valve body. This port-based approach is inherently simpler to manufacture with standard tolerances compared to gap-based control.
Solution Approach 2:
The spool valve divides the fluid control into distinct segments or zones defined by the spool positions relative to different ports. The spool can be at different axial positions to control different fluid paths independently, allowing for simpler manufacturing of each port and the spool itself, rather than requiring precise overall spacing between all components.
3Reliability
If traditional servo valve designs are used, then fluid control is achieved, but weight and structural complexity are high
Solution Approach 1:
The spool valve mechanism is inherently lighter than the flapper-nozzle assembly because it eliminates the need for a flapper component and its supporting structure. The spool is a single moving element that directly controls multiple fluid paths, reducing the overall moving mass while maintaining reliable fluid control functionality.
Solution Approach 2:
The spool valve design allows a single moving component (the spool) to control multiple fluid paths and functions simultaneously. By positioning the spool at different axial locations, different combinations of ports are opened or closed, enabling the valve to perform multiple functions with fewer moving parts, thereby reducing weight while maintaining reliability.
4Productivity
If flapper and nozzle arrangements are used, then servo control is achieved, but operational pressure and frequency limitations exist
Solution Approach 1:
The spool valve mechanism is better suited for high-pressure and high-frequency operation compared to flapper-nozzle systems. The spool's axial movement creates more direct and efficient fluid path changes, allowing for faster response times. Additionally, the spool valve can handle higher pressures because the sealing surfaces are typically more robust and the fluid paths are more direct, avoiding the pressure losses and limitations inherent in gap-based flow control.
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 precision, reduces weight and complexity, and improves operational pressures and frequencies by allowing more precise adjustment of fluid flow characteristics and simplifying the manufacturing process.
Implementation Method 1
an electromagnet 205 surrounding an armature 202. The electromagnet 205 includes coils (not shown) that surround the armature 202 and a set of permanent magnets (not shown) that surround the coils. When a current is applied to the coils from the electrical input, magnetic flux acting on the ends of the armature 202 is developed.
Implementation Method 2
When a current is applied to the coils from the electrical input, magnetic flux acting on the ends of the armature 202 is developed. The direction of the magnetic flux (force) depends on the sign (direction) of the current.
Implementation Method 3
The magnetic flux will cause the armature tips 202a, 202b to be attracted to the electromagnet 205 (current direction determines which magnetic pole is attracting and which one is repelling) thus varying the size of the spaces 203a, 203b, 203c, 203d. This magnetic force creates an applied torque on the flapper 201, which is proportional to applied current.
Data Source
AI summary
A servo valve assembly includes a housing defining a cylindrical cavity having a central axis, and a spool disposed in the cavity and co-axially aligned with the central axis. A pair of transition portions define opposing conical cavity surfaces each connect a respective one of first and second cylindrical cavity portions with a third cylindrical cavity portion. The spool comprises a pair of blocking members projecting radially, and each of the blocking members defines a conical blocking surface opposing a respective one of the conical cavity surfaces to define a fluid flow passage therebetween. A cone angle of each conical blocking surface relative to the central is equal to a cone angle of the opposing conical cavity surface relative to the central axis. The spool is moveable along the central axis to vary a flow area of the flow passages between the conical blocking surfaces and the conical cavity surfaces.