In the hydraulic system, the high-pressure servo valve is the key element to control the motion accuracy and response speed of the actuator, and its performance directly affects the stability and control accuracy of the system. Especially in the servo system running under high pressure, the pressure bearing capacity of servo valve becomes an important basis for design and selection. Therefore, it is of great significance to accurately calculate the pressure-bearing capacity of the high-pressure servo valve to ensure the safe and reliable operation of the system.
First, the basic structure and working principle of high pressure servo valve
Servo valve is a kind of hydraulic control valve which can accurately control the flow and pressure output according to the input signal (usually electrical signal). Its core structure includes torque motor, nozzle baffle mechanism, slide valve and feedback mechanism. When the system works, the servo valve should bear the high-pressure oil from the hydraulic pump and control the action of the actuator (such as hydraulic cylinder or hydraulic motor). Under high pressure, the servo valve must not only ensure good control performance, but also have enough structural strength to withstand system pressure.
Second, the basic principle of pressure calculation of high pressure servo valve
1. Determine the system working pressure and peak pressure.
Before calculating the bearing capacity of the servo valve, the working pressure range of the system and the possible peak pressure should be defined first. For example, the working pressure of the system is 21 MPa, but when the load changes suddenly or commutates, the pressure may rise to 30 MPa or even higher instantly.
2. Material strength and structural stress analysis
Servo valves are usually made of high-strength alloy steel or stainless steel, and the yield limit and tensile strength of their materials are the basis for judging the bearing capacity. Through finite element analysis (FEA) and other methods, the stress distribution of the key components of the servo valve (such as valve body, spool, spring, etc.) can be analyzed and calculated under the maximum working pressure.
3. Selection of safety factor
In practical design, a safety factor (usually 1.5~2.5) must be introduced to cope with unpredictable impact, fatigue load and temperature difference stress in the system. Ultimate design bearing capacity = material yield strength/safety factor.
4. Pressure check of seal and connection parts
The sealing ring, flange connection, threaded interface and other parts in the servo valve are also weak points, so it is necessary to evaluate the bearing capacity separately to ensure the sealing and strength of the whole structure meet the requirements.
Iii. Calculation example of bearing capacity
Assuming that a servo valve is designed to be used in a system with a working pressure of 30 MPa, the material is 40CrNiMoA, its yield strength is about 900 MPa, and the safety factor is 2.0, then:
-Maximum allowable stress of valve body = 900 MPa/2 = 450 MPa
-if the diameter of the inner cavity of the valve body is 20 mm, the inner wall area is about 314 mm²
-maximum bearing load = pressure× area = 30mpa× 314mm = 9420n.
Through the above calculation, it can be judged whether the valve body meets the structural strength requirements, and the material selection or structural size can be optimized accordingly.
IV. Matters needing attention in practical application
-Dynamic pressure shock: Due to the fast response speed of the servo valve, high-frequency pressure pulsation may occur in the system, so dynamic pressure test is needed.
-Temperature influence: high temperature will reduce the strength and sealing performance of materials, and heat-resistant materials should be selected in high temperature environment.
-Fatigue life: Long-term working under high pressure will lead to material fatigue, which will affect the service life, so durability test is needed.
tag
To sum up, the pressure calculation of high-pressure servo valve involves many knowledge such as material mechanics, fluid mechanics and system engineering. In practical application, not only theoretical calculation is needed, but also simulation analysis and experimental verification should be combined to ensure the reliability and safety of servo valve in high pressure environment. With the continuous development of hydraulic technology, the requirements for the pressure-bearing performance of servo valves will be continuously improved, and the future design will pay more attention to the unity of intelligence, lightweight and high efficiency.