In modern hydraulic control system, servo valve, as a key control element, is widely used in industrial automation, aerospace, heavy machinery and other fields. Among them, the three-way servo valve plays an important role in a specific hydraulic system because of its compact structure, fast response and high control accuracy. This paper will focus on the distribution principle, working mode and application points of the oil circuit of the three-way servo valve.
First, the basic structure of the three-way servo valve
Three-way servo valve usually has three main oil ports: pressure port (P), working port (A) and oil return port (T). Its core function is to control the flow and direction of hydraulic oil through electrical signals, so as to realize accurate control of executive components (such as hydraulic cylinders or hydraulic motors). Compared with four-way servo valve, three-way servo valve is suitable for single-acting actuator, such as single-acting hydraulic cylinder or hydraulic motor with spring reset.
Second, the basic principle of oil distribution
The oil distribution principle of the three-way servo valve mainly depends on the displacement control of the spool. The valve core moves slightly under the drive of the electromagnetic coil, thus changing the communication state between oil ports and controlling the flow direction and flow rate of hydraulic oil.
1. Forward control state: When the forward electric signal is input, the valve core moves to one side, which makes the pressure port (P) communicate with the working port (A) and cuts off the connection between the working port (A) and the oil return port (T). At this time, the hydraulic oil flows from port P to port A, pushing the actuator to act.
2. Reverse control state: When the reverse electric signal is input, the valve core moves to the other side, cutting off the connection between port P and port A, and connecting port A and port T.. At this time, the hydraulic oil in the cavity of the actuator returns to the oil tank, and the actuator returns to its original position under the action of external load or spring force.
3. Neutral state: When there is no control signal input, the valve core is in the middle position, and all oil ports are mutually closed or in a specific throttling state, so as to realize pressure maintenance or micro adjustment of the system.
Three, typical application and oil design points
Three-way servo valves are often used in hydraulic systems that need unidirectional control, such as spring-return hydraulic actuators. In the process of oil circuit design, special attention should be paid to the following points:
1. Stability of pressure source: In order to ensure the normal operation of servo valve, the system should be equipped with stable hydraulic pump and accumulator to reduce the influence of pressure fluctuation on control accuracy.
2. The oil return path is unobstructed: the oil return port (T) should be directly connected to the oil tank, and an appropriate oil filter and back pressure valve should be set to avoid the system pressure rising due to poor oil return.
3. Treatment of oil leakage: There is a slight internal leakage in the servo valve, so it is necessary to set a separate oil leakage port (L) to prevent the accumulation of oil leakage from affecting the movement of the valve core.
4. Accuracy of control signal: As servo valve is the key component of electro-hydraulic proportional control, the stability and accuracy of control signal directly affect the response performance of the system, so it is recommended to use high-precision controller and feedback device.
IV. Conclusion
To sum up, the three-way servo valve realizes the efficient and accurate driving of the hydraulic actuator by accurately controlling the oil passage between the three oil ports. Although its oil distribution mechanism is relatively simple, in practical application, many factors such as system pressure, oil return path and control signal need to be considered comprehensively in order to give full play to its advantages. With the continuous development of hydraulic technology, the three-way servo valve will continue to play an important role in the field of automatic control, providing reliable guarantee for various high-precision control systems.