Servo-Assisted Spool Valve for Low-Power Position Control
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Solution Overview
Problem
Existing spool valves require high-power electric motors for precise control of the spool position due to significant flow forces, leading to increased cost and size.
Innovation Solution
A spool valve design that includes a servo chamber divided into two pressure chambers, where a piston and sleeve mechanism balances hydraulic forces, allowing a low-power motor to control the spool position by adjusting pressure chamber communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-power electric motor is used to control the spool position against large flow forces, then the spool position control precision is improved, but the cost and size of the spool valve increase
Solution Approach 1:
A servo piston is introduced as an intermediary mechanism between the electric motor and the spool. The servo piston converts the small linear displacement from the motor into large pressure changes in the servo chambers, which then act on the spool to overcome large flow forces. This mediator amplifies the motor's effect, enabling precise spool control with low motor power.
Solution Approach 2:
The invention uses hydraulic pressure amplification through servo chambers filled with incompressible fluid. The electric motor's linear motion changes the volume of the servo chambers, creating pressure differences that act on the spool. This hydraulic transmission mechanism converts small mechanical displacements into large forces, resolving the contradiction between motor power and control precision.
2Measurement precision
If a high-power electric motor is used to control the spool position, then the spool position control precision is improved, but the size of the spool valve increases
Solution Approach 1:
The servo piston acts as a compact intermediary that provides mechanical advantage. Instead of using a large motor directly on the spool, the small-displacement piston amplifies the control force through pressure multiplication, achieving the same control precision with a much smaller overall valve size.
Solution Approach 2:
The invention changes the operating parameters by using pressure multiplication rather than direct force application. The servo system transforms the relationship between motor displacement and spool force, enabling precise control with compact dimensions by operating in the pressure domain rather than the force domain.
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
Enables precise spool position control using a low-power electric motor, reducing costs and size while maintaining control accuracy.
Implementation Method 1
a screw shaft screwed with the nut; and an electric motor that rotates the screw shaft
Implementation Method 2
a force that is applied to the sleeve by the hydraulic fluid in the first pressure chamber, and a force that is applied to the sleeve by the hydraulic fluid in the second pressure chamber
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A spool (3) is slidably located in a slide hole (21) of a first housing (2). A second housing (4) forms a servo chamber (41) that is coaxial with the slide hole (21). A sleeve (5) is slidably located in the servo chamber (41). A nut (71) is fixed to a piston (6) that is slidably fitted in the sleeve (5). An electric motor (74) rotates a screw shaft (72) screwed with the nut (71). The second housing (4) includes an input port (4a) and a drain port (4b). A first pressure chamber (42) communicates with the input port. In a balanced state where forces applied to the sleeve (5) from both sides are balanced, a second pressure chamber (43) is blocked from the input port (4a) and the drain port (4b) by the piston (6). From the balanced state, when the piston (6) shifts, the second pressure chamber (43) comes into communication with the input port (4a) or the drain port (4b).