Created on:2022-10-14 13:22

Use and maintenance of MOOG E760Y electrohydraulic servo valve

Use and maintenance of MOOG E760Y electrohydraulic servo valve

Moog E760Y series electro-hydraulic servo valve is a high-performance, double nozzle, force feedback flow control valve, which has

It has the advantages of compact structure, stable and reliable working performance, high dynamic response, wide flow range, small volume and so on.

1. Working principle

Figure 2 is the structural schematic diagram of MOOG E760Y series electrohydraulic servo valve, which is composed of electromagnetic part and hydraulic part. In the electromagnetic part, the armature is connected with the baffle and supported by the spring tube fixed on the valve seat E. The baffle is inserted between the two nozzles to form two variable throttling ports. The feedback rod extends from the inside of the baffle, and its small ball is inserted into the small groove in the middle of the spool valve core. The permanent magnet and the conducting magnet form a fixed magnetic field. When there is no current in the coil, the magnetic flux in the four air gaps between the magnet and the armature is port g, and the armature is in the middle position. At this time, the hydraulic oil from the oil supply chamber P passes through the internal filter and two fixed orifices, and then flows back to the oil chamber T through the variable orifice formed by the nozzle baffle.


When there is a control current input, the magnetic flux in one group of diagonal direction breath increases, while the magnetic flux in the other group of direction breath decreases, so the armature overcomes the elastic reaction force of the spring tube and deflects an angle under the action of this force, and deflects until the torque generated by the magnetic force and the torque generated by the elastic reaction force balance. At the same time, the baffle deflects due to the deflection of the armature, which leads to the change of the gap between the two nozzles and the baffle. The variable throttle area on one side decreases and the variable throttle area on the other side increases, resulting in the pressure difference in the nozzle cavity, acting on the end face of the spool valve core, making the spool valve core move a certain distance in the corresponding direction, and the pressure oil flows to the hydraulic cylinder through the opening of the spool valve. When the slide valve moves, the ball head of the baffle feedback rod moves with it, generating a torque on the baffle assembly, deflecting the armature in the corresponding direction, and reducing the offset of the baffle between the two nozzles, which is the feedback effect. The result of feedback is to reduce the differential pressure at both ends of the spool valve. When the hydraulic force on the slide valve and the elastic reaction force generated by the movement of the baffle ball head reach balance, the slide valve will no longer move and remain at this opening. In other words, the valve core moves until the feedback torque generated by the bending of the feedback rod is balanced with the torque generated by the control current. At this time, the baffle is basically in the middle.

2. Use and maintenance

Moog E760Y series electro-hydraulic servo valves have high requirements for hydraulic systems. The stability of the working performance of the servo valve largely depends on the quality of the medium in the hydraulic system. The particle cleanliness of the medium shall not be lower than nas6. In addition to a filter with a nominal filtration accuracy of 3 µ m installed at the outlet of the pump of the hydraulic pump station, a 3 µ m secondary protection filter is also installed in front of the inlet of the servo valve.

According to the use and maintenance experience, the following aspects should be paid attention to in the use and maintenance of this servo valve:

1) Regularly take samples to test the particle pollution degree of hydraulic media, and formulate a reasonable replacement cycle of oil products and filter elements according to the test results, so as to ensure that the particle pollution degree of media is not lower than nas6 level.

2) The oil tank temperature of the hydraulic system pump station should not be too high and should be controlled below 50 ℃.

3) When the valve is used in places with high ambient humidity, a dehumidifiable respirator should be installed on the oil tank to ensure that the water content of the medium does not exceed 0.006%.

4) When replacing other components of the hydraulic system (such as seals and valves), it is necessary to ensure cleanliness during operation to prevent pollution to the hydraulic system.

5) Generally, the replaced servo valve can be reused after repair, but it is better to send it to a professional manufacturer for maintenance to ensure the reliable performance of the servo valve.

6) Before the failure of servo valve, its working state can often be judged according to many ways. Therefore, predictive replacement can better ensure the working stability of the whole system than passive replacement.

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