As the core component of hydraulic control system, servo valve’s performance directly affects the control accuracy and response speed of the whole system. However, in practical application, the servo valve is easily affected by pollutants in the working medium, which leads to problems such as jamming, wear, slow response and even failure. Therefore, in the process of servo valve design, anti-pollution ability has become one of the key considerations.
I. Analysis of pollution sources
The pollutants in the working medium of servo valve mainly come from three aspects: first, the impurities brought in during the initial installation or maintenance of the system; The second is the metal particles produced by the wear of components during operation; The third is dust, moisture and other intrusions in the external environment. The particle size of these pollutants is often less than 5 microns, which is equivalent to the precise fit clearance inside the servo valve, and it is easy to cause throttle blockage or slide valve sticking.
Second, the anti-pollution design strategy
1. Structural optimization design
By optimizing the structural parameters such as the fit clearance between the valve core and the valve sleeve and the shape of the flow passage, the deposition and sticking of pollutants in key parts can be reduced. For example, the self-cleaning ability inside the valve body can be effectively improved by adopting asymmetric throttle, increasing the smoothness of the flow passage and setting up self-cleaning structure.
2. Materials and surface treatment technology
Selecting materials with high hardness and good wear resistance to make the valve core and valve sleeve, such as stainless steel and ceramic materials, can significantly improve the wear resistance; At the same time, the use of surface coatings (such as diamond-like carbon coating DLC, chromium coating, etc.) can also enhance the corrosion resistance and self-lubrication of the surface and reduce the probability of pollutant adhesion.
3. Integration of filtration and cleaning system
Setting high-efficiency filter in front of servo valve is an important means to prevent pollutants from entering. In modern servo system, multistage filtration is often used, such as setting a high-pressure filter at the outlet of hydraulic pump and adding a filter with a precision of 10μm or less at the inlet of servo valve, so as to ensure that the cleanliness of oil entering the servo valve reaches the standard of NAS 6 or above.
4. Dynamic response and fault-tolerant design
Intelligent control algorithm is used to improve the fault-tolerant ability of servo valve in polluted environment, such as introducing adaptive PID control, fault diagnosis and compensation mechanism, so that the system can still work normally under slight pollution and prolong the maintenance period.
Third, the future development direction
With the increasing demand of industrial automation and high-end equipment for the reliability of hydraulic system, the anti-pollution design of servo valve is developing towards intelligence and integration. Future servo valves may integrate online oil monitoring module, self-cleaning function and remote diagnosis system to realize a new operation and maintenance mode of “prevention first, maintenance second”.
In a word, the anti-pollution design of servo valve is a systematic project, which needs to be comprehensively considered from the aspects of structure, materials, supporting system and control strategy. Only by constantly improving its anti-pollution ability can we ensure the efficient and stable operation of the hydraulic system and meet the urgent demand of modern industry for high-performance hydraulic control.