In high-end equipment fields such as industrial automation, aerospace, and heavy machinery, the control requirements for power transmission have reached an almost stringent level - not only requiring enormous force, but also precise, fast, and intelligent adjustment. The core component for achieving this goal is the liquid servo valve, known as the "nerve center" of the hydraulic system. 
It is a precision hydraulic component that continuously and accurately controls the direction, flow rate, and pressure of high-pressure fluid flow through electrical signal instructions. It amplifies weak electrical signals into powerful hydraulic power output, achieving the ultimate "electro-hydraulic" conversion, and is one of the cutting-edge technologies in the field of modern precision engineering control. 
1、 Core working principle: The exquisite dance steps of the torque motor 
The working principle of liquid servo valve can be regarded as a model of electromechanical hydraulic integration, and its core lies in the two-stage amplification mechanism: 
one 
Electromechanical conversion (first stage amplification): 
When the control system emits a weak electrical signal, the torque motor (or electro-mechanical converter) inside the servo valve will act first. The electromagnetic force generated by this signal will drive the armature inside the motor to undergo extremely small deflection. This step converts the microampere level current signal into mechanical displacement. 
two 
Hydraulic amplification (second stage amplification): 
The small mechanical displacement generated by the first stage will manipulate a precise pilot stage (usually a nozzle baffle or slide valve). The pilot stage controls the flow of a small amount of pilot hydraulic oil, which drives the movement of the main spool valve core. The movement of the main valve core directly determines the state of the main oil circuit from the oil pump to the actuator (such as the oil cylinder or hydraulic motor). Through this design of "small flow control large flow", the secondary amplification of power was ultimately achieved, allowing tiny electrical signals to accurately control hydraulic power of hundreds or thousands of horsepower. 
2、 Distinctive features from ordinary valves 
Compared with ordinary on-off valves or proportional valves, servo valves have outstanding performance advantages: 
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High precision and high resolution: capable of extremely smooth and continuous proportional control of output flow and pressure, with almost no "step" feeling. 
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Fast dynamic response: The response frequency is extremely high, reaching hundreds of hertz or more, and can quickly keep up with the rapid changes in control signals, which is crucial for systems that require high-speed motion. 
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High reliability: Due to its design for continuous modulation control, it exhibits longer lifespan and stability under frequent start stop and commutation conditions. 
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The foundation of closed-loop control: Servo valves are the core of building closed-loop hydraulic servo systems. The system detects the actual output of the actuator (such as position and speed) through sensors, compares it with the target value, and adjusts the electrical signal input to the servo valve in real time to form a closed-loop feedback, thereby eliminating errors and achieving precise control.