Spool Valve Servo Chamber Balancing for Low-Power Actuation
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Solution Overview
Problem
In spool valves with large spool diameters, high-power electric motors are required for precise control due to the significant 'flow force' from fluid pressure, leading to increased costs and size.
Innovation Solution
A spool valve design incorporating a servo chamber with a sleeve dividing it into two pressure chambers, where the piston shifts to balance fluid pressures, allowing the electric motor to control the spool position precisely without being affected by fluid forces, even with a low-power motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a large-diameter spool is used, then the flow control capability is improved, but the flow force increases requiring a high-power electric motor
Solution Approach 1:
The patent introduces a servo mechanism as an intermediary between the electric motor and the spool. The servo motor drives a piston that moves within a servo chamber, and this piston movement controls pressure distribution to shift the spool. This intermediary mechanism allows the electric motor to control the spool position indirectly, overcoming the direct flow force resistance with much lower power requirements.
Solution Approach 2:
The patent replaces the direct mechanical connection between the electric motor and spool with a fluid pressure-based control system. Instead of the motor directly overcoming flow force through mechanical transmission, it uses hydraulic pressure generated in the servo chamber to move the spool, substituting a mechanical force system with a fluid pressure system that requires much less input power.
2Measurement precision
If a high-power electric motor is used, then the spool position control precision is improved, but the device size and cost increase
Solution Approach 1:
The servo mechanism acts as a precision intermediary that amplifies the control capability of the low-power motor. The piston's precise movement within the servo chamber creates controlled pressure changes that accurately position the spool, achieving high control precision without requiring a large, expensive motor.
Solution Approach 2:
The patent uses hydraulic pressure in the servo chamber to achieve precise spool positioning. The pressure-generated force from the piston provides smooth, controllable movement of the spool, enabling high positioning precision while keeping the motor size small, as hydraulic systems provide high force multiplication with minimal input power.
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 control of the spool position using a low-power electric motor, reducing costs and size by isolating fluid forces from the motor's operation.
Implementation Method 1
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, are balanced
Implementation Method 2
a screw shaft screwed with the nut; and an electric motor that rotates the screw shaft
Data Source
AI summary
A spool is slidably located in a slide hole of a first housing. A second housing forms a servo chamber that is coaxial with the slide hole. A sleeve is slidably located in the servo chamber. A nut is fixed to a piston that is slidably fitted in the sleeve. An electric motor rotates a screw shaft screwed with the nut. The second housing includes an input port and a drain port. A first pressure chamber communicates with the input port. In a balanced state where forces applied to the sleeve from both sides are balanced, a second pressure chamber is blocked from the input port and the drain port by the piston. From the balanced state, when the piston shifts, the second pressure chamber comes into communication with the input port or the drain port.