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Electronic technology and fluid power transmission (Part 1)

electronic technology and fluid power transmission (Part 1)

Yang Erzhuang, senior consultant of China Hydraulic and Pneumatic Seals Industry Association

in recent years, fluid power transmission technology has been developed and transplanted with the help of electronic technology, computer technology, automatic control technology, new materials and new processes. In recent years, new energy vehicles have achieved remarkable results with rapid development momentum. In particular, the integration of electronics, it technology and fluid transmission technology makes it more competitive with motor transmission and gain new vitality

1. Electrohydraulic servo valve products

1.1 American Moog company

a. direct acting high-frequency response electrohydraulic servo valve

the valve has a built-in linear permanent magnet force motor to drive the spool movement, the displacement of the spool is detected by the displacement sensor, and the built-in electronic amplifier controls the main spool in a closed loop. The characteristics of the valve are: low leakage, no pilot stage flow, low energy consumption; The driving force of the valve core is large, and the driving force of the permanent magnet force motor is twice that of the electromagnet, with strong anti pollution ability; Good dynamic response. Since the natural frequency of the force motor is 250Hz, the dynamic performance of the valve is good, and the frequency of the valve is independent of the system pressure; Low hysteresis, high resolution and high repetition precision; In case of power failure and emergency stop, the valve core can automatically return to the empty position to make the load in a safe state; In order to improve the service life and prevent the throttle edge of the valve element from wearing, the filtering accuracy is generally required to be 10 m( β 75)。

for example, the main parameters of MOOG d633/634 series direct acting electro-hydraulic servo valves are: flow range: 3.8 ~ 100l/min (7.0Mpa valve pressure drop); Maximum working pressure: 35MPa; Resolution 0.1%; Hysteresis 0.2%; Frequency response: 40 ~ 60Hz (± 100% input signal)

b. two stage electro-hydraulic servo valve with jet pipe as the pilot stage

the company's new production line for many years has more advantages in energy conservation and environmental protection. It has been producing nozzle baffle type two-stage electro-hydraulic servo valve. The valve has high frequency response, high precision and other properties when it is uniformly and stably introduced into the mold, but it has poor pollution resistance and requires high oil cleanliness. Recently, a two-stage electro-hydraulic servo valve with jet pipe as the pilot stage has been developed. The valve has good dynamic performance and strong pollution resistance. The position of the main valve core is electrically fed back by a displacement sensor, and the valve core is closed-loop controlled by a built-in electronic amplifier. It has a fail safe function. In case of unexpected power failure, the machine and equipment can be guaranteed to be in a safe position. The control pressure of the lowest pilot stage is 2.5MPa, which makes the valve applicable to low-pressure control systems such as steam turbines

c.d660 series servo proportional valve

the company's D660 series servo proportional valve can be used as a two-way, three-way, four-way and five way throttling flow control valve, which is suitable for electrohydraulic position, electrohydraulic speed, electrohydraulic pressure and electrohydraulic control system. It has high dynamic response characteristics and reliability, and is widely used in various injection molding machines, hollow molding machines, die-casting machines, pressure processing machinery, papermaking and wood processing industries. Its main performance: flow range: 30 ~ 1500l/min (1.0MPa valve pressure drop); The maximum working pressure is 35.0mpa; Resolution 0.2%; Hysteresis 1.0%; Response time 12 ~ 42ms; The working pressure is 21.0mpa

1.2 the direct acting electro-hydraulic servo valve of Japan Youyan company

the l5vhg series of the company's built-in amplifier direct acting electro-hydraulic servo valve can obtain high-precision hydraulic control only by inputting a 0 ~ ± 10V command signal from 24V power supply. The valve core is driven by a small powerful motor, the displacement of the valve core is detected by a differential transformer, and the built-in electronic amplifier controls the valve ring. The main performances of lsvhg-03eh type are: rated flow 180l/min, working pressure 35MPa, hysteresis dead zone 0.2%, frequency response 80 ~ 100Hz (± 25%v input, phase lag -900), fault indication signal (test results under 14MPa), strong pollution resistance (nas10)

1.3bosch Rexroth's electro-hydraulic servo valves

bosch Rexroth exhibited a full range of electro-hydraulic servo valves at ifpex2005 exhibition in Tokyo, Japan. The high-frequency response servo valve with built-in electronic circuit adopts linear electromagnet to drive the valve core. The valve core displacement is detected by differential transformer and controlled by electronic circuit to form a closed-loop system. 4wrpeh series direct acting servo valves include: 4wrpeh-6 with rated flow of 2 ~ 40l/min (six specifications in total), frequency response of 120Hz (at -900, ± 5% input, 31.5Mpa); 4wrpeh-10 has rated flow of 50, 10l/min and frequency response of 60Hz (at -900, ± 5% input and 31.5Mpa)

2. Proportional control valve product

proportional valve has the advantages of low price and strong pollution resistance. However, compared with servo valve, it has poor frequency response performance and is generally only used in open-loop system. In order to make it be used in closed-loop systems with high response and high precision, companies have developed high-frequency proportional control valves

The d680 series servo proportional valve produced by Moog company uses a high-performance direct acting servo valve as the pilot stage, which reduces the leakage of the pilot valve and improves the dynamic performance of the valve. The displacement of the main valve core is detected by a position sensor and a built-in electronic amplifier

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