In the hydraulic control system, the servo valve is a key control element, which can accurately control the movement direction, speed and force of the hydraulic actuator according to the input signal. Among them, the pilot servo valve is widely used in high-performance hydraulic control system because of its high responsiveness, high precision and large flow output capacity. One of its core principles is amplification. This paper will introduce the amplification principle of pilot servo valve in detail.
First, the basic structure of pilot servo valve
Pilot servo valve consists of two parts: main stage valve and pilot stage valve. The main stage valve is responsible for controlling the high-pressure and large-flow hydraulic oil in the main oil circuit, while the pilot stage adjusts the action of the main stage valve through a low-power control signal (usually an electrical signal). This structural design of “controlling large with small” is the basis for the pilot servo valve to achieve amplification.
Second, the amplification principle is explained in detail
The core of the pilot servo valve is that it can amplify the tiny control signal into enough force or flow to drive the main stage spool to move. The amplification process can be divided into two stages:
1. Conversion from electric signal to hydraulic signal (primary amplification):
The pilot stage usually adopts nozzle baffle structure or torque motor structure, which converts the input tiny electrical signal into mechanical displacement, and then changes the gap between nozzle and baffle. This change will lead to the pressure change in the control chamber, thus forming a weak hydraulic differential pressure signal. At this stage, the conversion from electric signal to primary hydraulic signal is realized, which is the first amplification.
2. The primary hydraulic signal drives the main spool (secondary amplification):
The differential pressure signal of primary hydraulic pressure acts on the control cavity of the main spool, pushing the main spool to move, thus opening the main oil passage and making the high-pressure and large-flow hydraulic oil flow to the actuator. Because of the large area of the main valve core, even a small control pressure can generate a large driving force, thus achieving accurate control of the main oil circuit. This is the second amplification, and it is also the most critical amplification link in the whole system.
III. Advantages and Applications
Through the two-stage amplification mechanism, the pilot servo valve greatly improves the output ability and response speed of the system while ensuring the control accuracy. Compared with direct-acting servo valve, it is more suitable for high-flow and high-frequency response occasions, such as flight control systems, industrial robots, CNC machine tools and other fields.
Fourth, summary
To sum up, the working principle of the pilot servo valve is to convert the weak electrical signal into the primary hydraulic signal through the pilot stage, and further drive the main spool to act, so as to realize the efficient control of the main oil circuit. This “multi-stage amplification” mechanism not only improves the control accuracy and response speed of the system, but also provides reliable technical support for the realization of high-power hydraulic system. In the future, with the development of intelligence and automation technology, the application prospect of pilot servo valve will be broader.