In the hydraulic system, the four-way servo valve is a key control element, which is widely used in the hydraulic servo system with high precision and high response. Its main function is to accurately control the movement direction, speed and torque of hydraulic actuators (such as hydraulic cylinders or hydraulic motors) according to the magnitude and direction of input signals. Among them, the principle and mechanism of four-way servo valve switching oil circuit is the core content to understand its working process.
First, the structure principle of four-way servo valve
Four-way servo valve usually consists of electromagnetic part and hydraulic part. The electromagnetic part receives the electric signal (usually analog voltage or current) and controls the position of the valve core through the torque motor or proportional electromagnet. The hydraulic part is composed of main spool and pilot valve, which is responsible for regulating the flow direction and flow rate of hydraulic oil.
The four-way servo valve has four oil ports: pressure oil port (P), oil return port (T) and two working oil ports (A and B). Through the movement of the valve core, the connection state between ports A and B and ports P and T can be switched, thus controlling the running state of the actuator.
Second, the basic way of oil circuit switching
When the servo valve receives the control signal, the electromagnetic part generates corresponding magnetic force, which makes the spool move left or right. The change of spool position changes the flow path of hydraulic oil and realizes the switching of oil circuit.
1. Forward switching: when the spool moves to the right, the pressure oil port P is communicated with the working oil port B, and the working oil port A is communicated with the oil return port T.. At this time, the hydraulic oil enters the B cavity from P, pushing the piston to move to the left.
2. Reverse switching: when the spool moves to the left, the pressure oil port P is communicated with the working oil port A, and the working oil port B is communicated with the oil return port T.. Hydraulic oil flows into cavity A, pushing the piston to move to the right.
3. Neutral state: When the valve core is in the neutral state, all oil ports are mutually closed, the actuator stops moving, and the system is in the pressure maintaining state.
Third, the characteristics of servo valve switching oil circuit
1. Fast dynamic response: Because the servo valve adopts closed-loop feedback control technology, the displacement of the spool is proportional to the input signal, which can realize fast and accurate oil circuit switching.
2. High control precision: the servo valve can realize micron-level flow control through a high-precision electronic control system to meet the needs of precision hydraulic systems.
3. Continuous control can be realized: Different from the common directional valve, the servo valve can not only switch between “on” and “off”, but also change the valve opening according to the signal size, thus realizing the continuous adjustment of the actuator.
Fourth, application examples
In industrial automation, aerospace, precision machine tools, robots and other fields, four-way servo valves are widely used to control the movement of hydraulic cylinders or motors. For example, in a CNC machine tool, the servo valve can accurately control the moving direction and speed of the workbench according to the instructions of the CNC system; In the aircraft flight control system, the servo valve is used to adjust the deflection angle of the rudder surface to realize the stability and adjustment of the aircraft attitude.
V. Conclusion
To sum up, the four-way servo valve realizes the efficient control of the direction and flow of the oil circuit in the hydraulic system through the accurate positioning of the spool. Its oil circuit switching process is not only fast and accurate, but also highly adjustable, and it is an indispensable and important component in modern hydraulic servo system. With the continuous development of electro-hydraulic control technology, four-way servo valve will play an important role in more high-precision and high-performance applications.