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How Servo Valves Work


How Servo Valves Work
The hydraulic control servo valve mainly refers to the electro-hydraulic servo valve, which outputs the modulated flow and pressure correspondingly after receiving the electrical analog signal. It is not only an electro-hydraulic conversion element, but also a power amplifying element, which can convert a weak electrical input signal of low power into a hydraulic energy output of high power.

How Servo Valves Work

A typical servo valve consists of a permanent magnet torque motor, nozzle, baffle, valve core, valve sleeve and control cavity. When the input coil passes current, the baffle plate moves to the right, which strengthens the throttling effect of the right nozzle, reduces the flow, and increases the back pressure on the right side; at the same time, reduces the throttling effect of the left nozzle, increases the flow rate, and decreases the back pressure on the left side. . The forces at both ends of the spool are out of balance, and the spool moves to the left. The high pressure oil flows from S to C2 and is sent to the load. The load return oil flows through the return oil port through C1 and enters the fuel tank. The displacement of the spool is proportional to the input current of the torque motor, and the hydraulic pressure acting on the spool is balanced with the spring force. Therefore, in a balanced state, the differential current of the torque motor is proportional to the displacement of the spool. If the incoming current is reversed, the flow is also reversed. The table shows the classification of servo valves.
Servo valves are mainly used as actuators in electro-hydraulic servo systems. In the servo system, compared with the electrical and pneumatic actuators, the hydraulic actuator has the characteristics of good rapidity, large output power per unit weight, stable transmission, and strong anti-interference ability. On the other hand, many electrical components are used to transmit signals and correct characteristics in servo systems. Therefore, modern high-performance servo systems also use electro-hydraulic methods, and servo valves are essential components of such systems.
The structure of the servo valve is complex, the cost is high, and the quality and cleanliness of the oil are high. New servo valves are trying to overcome these shortcomings, such as servo valves using electrostrictive elements, which greatly simplify the structure. Another direction is to develop special working oil. This kind of working oil can change the viscosity coefficient under the action of electromagnetism. Using this property, the oil flow can be directly controlled by electrical signals.
The above is the whole content of the working principle of the servo valve shared with you today, I hope it will be helpful to you.


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