Purchasing MOOG servo valves from the United States to sell D633 series

At the end of World War II, servo valves were single-stage open-loop control valves that were directly driven by a solenoid to move the valve core. With the maturity of control theory and the need for military applications, the research and development of servo valves have achieved great success. In 1946, Tinsie from the UK obtained a two-stage valve; Raytheon and Bell Aviation invented a two-stage valve with feedback; MIT replaced the solenoid with a torque motor, resulting in lower power consumption and better linearity of the motor. In 1950, W.C. Moog was the first to invent a single nozzle two-stage servo valve. Between 1953 and 1955, T.H. Carson invented a mechanical feedback two-stage servo valve; W. C. Moog invented a dual nozzle two-stage servo valve; Wolpin invented a dry torque motor, eliminating the reliability issues caused by oil contamination in torque motors that were previously immersed in oil. In 1957, R. Atchley developed a two-stage jet tube servo valve using the Askania jet tube principle. And in 1959, a three-level electric feedback servo valve was developed.

In February 1959, a foreign hydraulic and pneumatic magazine published a 12 page report on the situation of servo valves at that time, showing the flourishing development of servo valves at that time. At that time, there were over 20 manufacturers producing various types of servo valves. Various manufacturers have engaged in fierce competition for the dominant position in servo valve production. Looking back at history, it can be seen that the few manufacturers that ultimately won, most of which produced two-stage servo valves with feedback and torque motors. We can see that servo valves from 1960 already have many characteristics of modern servo valves. For example, the second level forms a closed-loop control by providing feedback to the first level; Adopting a dry torque motor; The pressure recovery of the front-end to the power stage can usually reach 50%; The first level of mechanical symmetry reduces the impact of temperature and pressure changes on the zero position. Meanwhile, the direct acting two-stage closed-loop control servo valve, which evolved from the early direct acting open-loop control valve, has also emerged. At that time, servo valves were mainly used in the military field. With the arrival of the space age, servo valves were widely used in the aerospace field, and high reliability redundant servo valves and other products were developed.

The main manufacturers of servo valves in China include: the 69th Research Institute of Aviation Industry Corporation, the 618th Research Institute of Aviation Industry Corporation, Beijing Machine Tool Research Institute, the 18th Research Institute of China Academy of Launch Vehicle Technology, Shanghai Aerospace Control Engineering Research Institute, Jiujiang CSIC Instrument Co., Ltd. (Factory 441), and the 74th Research Institute of China Shipbuilding Industry Corporation. The main foreign manufacturers of servo valves include Moog Company from the United States, Dowty Company from the United Kingdom, Team Company from the United States, the "Homeland" Design Bureau from Russia, and the Voskhod factory. In addition, Park Company from the United States, Eaton Vickers Company from Germany, Bosch Company from Germany, Rexroth Company, and others also have their own servo valve products.

　　Purchasing MOOG servo valves from the United States to sell D633 seriesGenerally, torque motors are divided into two types: moving coil type and permanent magnet type. Most traditional servo valves use permanent magnet torque motors, which can be divided into two categories: nozzle baffle type and jet type. Most domestic manufacturers of servo valves mainly use nozzle baffle type. The only companies that have formed a scale and series of production of jet tube servo valves are Jiujiang CSIC Instrument Co., Ltd. (Factory 441) and China Shipbuilding Industry Corporation's 704 Research Institute. The situation abroad is also similar. Abex, a manufacturer specializing in the production of jet tube servo valves in the United States, has been acquired by Park Corporation. However, due to the characteristics of good anti pollution performance, high reliability, and high resolution of jet tube servo valves. Some manufacturers are also developing or have launched their own jet tube products, such as the 69th Research Institute of the Aviation Industry Corporation, the 18th Research Institute of the China Academy of Launch Vehicle Technology, Moog Corporation in the United States, and relevant manufacturers in Russia. Moog Company in the United States also held a product promotion meeting in July 2006 and launched the D660 series of jet tube products, believing that this product represents the future development trend of servo valves.

　　Purchasing MOOG servo valves from the United States to sell D633 seriesAt present, although a certain scale has been formed in the research, production, and use of servo valves in China. However, the products produced are mainly used in aviation, aerospace, shipbuilding and other fields, and are not widely used in civilian products. At the same time, due to the fact that each production unit is fighting independently, lacks cooperation, and has dispersed strength, it is not conducive to the further development of servo valves and cannot form a competitive edge to compete with foreign products. Currently, the largest foreign product market is Moog Company, whose products occupy the vast majority of the domestic civilian market.

1. Piezoelectric components

The characteristic of piezoelectric components is the "piezoelectric effect": under the action of a certain electric field, the external dimensions will change, and within a certain range, the deformation is proportional to the strength of the electric field. The main materials of piezoelectric elements are piezoelectric ceramics (PZT), electrostrictive materials (PMN), etc. Typical piezoelectric ceramic materials include stacked piezoelectric stretchable ceramics from Japan's TOKIN company. The principle of PZT direct acting servo valve is to connect two multi-layer piezoelectric components at both ends of the valve core through steel balls. By utilizing the piezoelectric effect, the piezoelectric material generates a stretching and driving force to move the valve core. Realize electromechanical conversion. The PMN nozzle baffle servo valve is equipped with a baffle fixedly connected to the piezoelectric stack at the nozzle. The gap between the baffle and the nozzle is increased or decreased by the extension and contraction of the piezoelectric stack, which creates a pressure difference at both ends of the valve core and drives it to move. The development of piezoelectric electromechanical converters is relatively mature and has been widely applied. It has the characteristic of fast frequency response, and the bandwidth of servo valves can even reach thousands of hertz. However, it also has disadvantages such as large hysteresis and easy drift, which restrict the further application of piezoelectric components in electro-hydraulic servo valves.

2. Giant magnetostrictive materials

Compared with traditional magnetostrictive materials, giant magnetostrictive materials (GMM) can produce much larger length or volume changes under the action of a magnetic field. The direct acting servo valve developed using GMM converter is connected to the valve core, and the current of the driving coil is controlled to drive the expansion and contraction of GMM, which drives the displacement of the valve core and controls the output flow of the servo valve. Compared with traditional servo valves, this valve not only has the characteristics of high frequency response, but also has the advantages of high precision and compact structure. In terms of the development and application of GMM, countries such as the United States, Sweden, and Japan are at a high level. Zhejiang University in China has conducted structural design and characteristic research on high-speed and powerful solenoid valves for pneumatic nozzle baffle valves and internal combustion engine fuel injection systems using GMM technology. Compared with piezoelectric materials and traditional magnetostrictive materials, GMM materials have the characteristics of large strain, high energy density, fast response speed, and high output force. Countries around the world attach great importance to the research of GMM electromechanical converters and related technologies. The level of GMM technology is rapidly developing and has gradually entered the market development stage from the laboratory research stage. In the future, it is necessary to address issues related to the thermal deformation, magnetic crystal anisotropy, material corrosiveness, manufacturing process, and parameter matching of GMM in order to facilitate its widespread application in high-tech fields.

3. Shape memory alloy

The characteristic of shape memory alloy (SMA) is its shape memory effect. After shaping it at high temperature, cool it to a low temperature state and apply external force to it. Generally, metals will deform beyond their elastic deformation, while SMA will restore its original shape at high temperatures after being heated above a certain temperature. The servo valve developed using its characteristics is equipped with a set of SMA actuators wound with shape memory alloy at both ends of the valve core. The SMA actuators are driven by heating and cooling methods to extend or contract the shape memory alloy at both ends of the valve core, driving the valve core to move. At the same time, position feedback is added to improve the control performance of the servo valve. From the situation of this valve, although SMA has a large deformation, its response speed is slow and the deformation is discontinuous, which also limits its application range.