Servo valve is a key control element in hydraulic system, which is widely used in high-precision and high-response automatic control systems, such as aerospace, construction machinery, industrial automation and other fields. According to different control stages, servo valves can be divided into single-stage servo valves, second-stage servo valves and third-stage servo valves. Among them, the three-stage servo valve is often used in situations that require high system performance because of its complex structure and high control accuracy. This paper will focus on the classification principle and structural characteristics of three-stage servo valve.
First, the basic classification principle of servo valve
The “series” of the servo valve refers to the amplification series that its internal control signal passes from input to final driving of the main spool. Generally speaking:
-First-stage servo valve: there is no pre-stage, and the main spool is directly driven by the torque motor, with fast response speed but small control force;
-Two-stage servo valve: a pre-stage (such as nozzle baffle or jet pipe) amplifies the signal and drives the main valve core;
-Three-stage servo valve: an intermediate amplifier stage is added on the basis of the second stage to form a three-stage amplifier link, which is suitable for large flow and high pressure occasions.
Structure and working principle of second and third stage servo valve
Three-stage servo valve usually consists of the following three parts:
1. The first stage (pilot stage): nozzle baffle or jet pipe structure is usually adopted to receive the electric signal from the controller and convert it into hydraulic signal;
2. The second stage (intermediate amplification stage): the hydraulic signal output by the first stage is further amplified to control the position of the third stage main spool;
3. The third stage (main control stage): The main spool is controlled by the second stage, which is responsible for finally controlling the flow and pressure of the hydraulic system and driving the actuator.
The design of this three-stage structure enables the servo valve to drive a larger flow of hydraulic oil while maintaining a high response speed, thus meeting the needs of large equipment.
Advantages and application of three-stage and three-stage servo valves
Compared with the first and second-stage servo valves, the third-stage servo valve has the following advantages:
-Higher control accuracy: multi-stage amplification mechanism improves the stability of signal transmission;
-Stronger driving ability: it can control large-flow and high-pressure liquid flow, which is suitable for heavy-duty working conditions;
-Better dynamic response: Although the structure is complex, the overall response performance is excellent due to the cooperation of all parts.
Therefore, the three-stage servo valve is widely used in aircraft flight control system, heavy machinery, test-bed equipment, robots and other fields, especially in high-end hydraulic systems that need precise control and high power output.
Fourth, summary
The three-stage servo valve realizes high-precision and large-flow control of the hydraulic system through the three-stage amplification mechanism, and performs well under complex working conditions. Its hierarchical design not only improves the stability and response speed of the control system, but also broadens the application range of servo valves in industrial and military fields. With the development of intelligent manufacturing and automation technology, the three-stage servo valve will play a key role in more high-performance hydraulic systems.