Cam-Profile Servo Valve for High-Flow Low-Torque Control
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Solution Overview
Problem
Conventional single-stage flapper servo valves face challenges in handling large fluid flows effectively at high operation frequencies due to high motor torque requirements and limited control range, especially when dealing with high pressures and temperatures, leading to inefficiencies and power consumption issues.
Innovation Solution
A servo valve assembly utilizing a cylindrical drive element with a cam profile, rotated by a stepper or micro brushless DC motor, which varies the flow through nozzles by altering the distance between them, allowing for precise control and reduced motor torque, enabling efficient handling of large fluid flows and high-pressure applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional single-stage flapper servo valves are used to handle large fluid flows, then the valve orifice area must be increased, but the motor torque requirements become excessively high and control range is limited
Solution Approach 1:
The valve is divided into a first stage (pilot stage) and a second stage (main stage). The first stage valve member controls fluid flow to actuate the second stage valve member, which in turn controls the main fluid flow to the actuator. This segmentation allows the motor to control a small pilot flow that amplifies to control large main flows, reducing motor torque requirements while maintaining high flow capacity.
Solution Approach 2:
A pilot fluid acts as an intermediary between the motor and the main fluid flow. The motor controls the first stage valve member which modulates pilot fluid flow, and this pilot fluid then acts on the second stage valve member to control the main fluid flow. This intermediary mechanism provides flow amplification, allowing small motor torques to control large fluid flows.
2Quantity of substance
If larger valve orifices are used to increase fluid flow capacity, then high pressure and temperature handling is improved, but the motor torque requirements increase and power consumption rises
Solution Approach 1:
The two-stage valve structure segments the control function so that the motor only needs to control the small first stage valve member, not the large second stage valve member directly. This allows high flow capacity and pressure handling through large orifices in the second stage while the motor consumes less power by only actuating the small first stage.
Solution Approach 2:
The system changes the pressure parameter by using high pressure pilot fluid from the first stage to actuate the second stage. This pressure amplification allows the main valve to handle high flow and pressure requirements while the motor operates at lower power levels by controlling only the pilot stage.
3Speed
If conventional flapper valve designs are used for high operation frequency, then response speed is improved, but motor torque becomes very high due to flow forces acting in the direction of flapper movement
Solution Approach 1:
The segmentation into pilot stage and main stage allows the first stage valve member to operate at high frequency with small dimensions, while the second stage valve member handles the large flows. The motor only drives the small first stage valve member, maintaining high operation frequency capability without excessive torque requirements.
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 servo valve assembly achieves accurate control and maintains stop positions of actuators with low pressure and fluid capacity loss, reducing motor torque and enabling operation in high-pressure environments while allowing for variable control and independent nozzle management.
Implementation Method 1
a drive assembly such as a motor controlled by a control current
Implementation Method 2
obtain pressurised fluid from a high pressure source which is transmitted through the valve from which the fluid is output as a control fluid
Data Source
Figure 1~2
Figure 3~4
Figure 5~10
AI summary
A servo valve comprising: a fluid transfer valve assembly comprising a valve body having a supply port (10) and a control port (C); the valve body (20) comprising first and second nozzles (2A, 2B) and a drive member (12, 6) therebetween, arranged to regulate flow of fluid from the supply port (10) to the control port in response to a control signal; wherein the drive member comprises an elongate member (12) arranged to rotate in response to the control signal, and a cylindrical disk (6) mounted on, and arranged to rotate with, the elongate member, between the first and second nozzles, the cylindrical disk (6) having a cam profile such as to vary the spacing (A, B) between the disk and at least one of the nozzles as the cylindrical disk rotates relative to the first and second nozzles