Reasons of electrohydraulic servo valve failure and its solution

In the process of production practice, I found that the production of glass automatic press stamping cylinder in the process of shaking phenomenon, and the trembling action is strong and weak, but basically able to complete all the actions. Control system uses OILGEAR's SC-VP series of electro-hydraulic servo valve, the structure of the permanent magnetic force anti-debt two-stage servo valve. Working pressure is 9MPa. Analysis of the reasons According to the fault phenomenon for the hydraulic cylinder bad action to determine the servo valve spool in the action of shaking action, the reason can be divided into two major parts of the electrical and mechanical. Electrical failure due to faster, as soon as possible maintenance, so from the beginning of electrical treatment. 1, the electrical part is set to the electrical part of the failure, it is possible for the control signal crosstalk signal, loose terminals. Bad connection. Signal loop hardware failure, servo amplifier loop hardware failure and other reasons. After checking, the control signal can be excluded from the AC signal may be string, the terminal firmly without loosening, connection without bad, replace the signal generating circuit hardware module and the servo amplifier loop hardware module, the fault still exists, the use of oscilloscope measurements, the signal is normal . At this point, the basic elimination of electrical failure. 2, the hydraulic part of the order in order to eliminate the possibility of the following failures: hydraulic pipe and cylinder air, hydraulic oil pollution, cylinder leakage serious control of the oil and the main oil pressure instability. Finally, the servo valve is identified as the main fault. Replace the pilot part of the servo valve. Boot normally. After disassembling and inspecting, it is found that there are many metal shavings in the gap between the magnet and the armature of the torque motor, which is equivalent to reducing the length g of each air gap in the middle of the armature. According to the analysis of the "hydraulic control system", the armature is always unstable when | x / g |> 1/3 (x is the offset of the center of the armature). Therefore, it is considered that the metal shavings in the hydraulic system are adsorbed on the permanent magnet, reducing the air gap length g and destroying the original static characteristics of the torque motor. This is the root cause of this fault. Maintenance Measures In response to the reasons for this failure, as well as other possible analysis, the following measures have been taken: 1, regular replacement of oil filter, cleaning up deterioration of oil due to the fault caused by metal contamination of hydraulic oil, so regularly replace the oil in the system Of the filter, let go of the filter oil, prevent dirt from entering the servo valve, effectively prevent failure, extend the running time of the servo valve. The torque motor and pilot valve are completely immersed in the oil that is communicated with the oil return, and the position is at the blind end of the pipeline. Therefore, the oil there is almost no flow and is easily oxidized and deteriorated. Therefore, the deteriorated hydraulic oil needs to be discharged periodically. 2, regular replacement of hydraulic oil, to strengthen the management of hydraulic oil Hydraulic oil coking in the long-term work, and the hydraulic system of the pump. Valve, cylinder and other wear and tear, will produce some metal shavings, they will reduce the quality of hydraulic oil, causing failure. According to hydraulic oil life cycle and oil test results in recent years, every 10 months to replace the hydraulic oil, to ensure unplanned downtime equipment. 3, the regular replacement of the servo valve The direct cause of the fault is the torque motor is contaminated lead to poor performance servo valve, so regular cleaning, replacement of torque motor and pilot valve to prevent pollution, thereby eliminating the occurrence of the fault. Servo valve assembly and disassembly should be carried out in the environment as clean as possible, the operation should first remove the electrical signal to the servo valve, and then remove the hydraulic system pressure, and then remove the servo valve. Clean all parts in a clean, compatible, commercial solvent. Parts can be air dried or air-dried with a clean, dry air hose. After cleaning the servo valve, can be used as spare parts, reducing costs. 4, regular replacement of electrical signals, tighten the terminals to prevent loosening, check the connection, to prevent poor contact Servo valve is precision manufacturing of electromechanical products, high precision, very sensitive to pollution, it is in the maintenance, cleaning and The understanding of the importance of maintaining the work and other aspects of the requirements are very high, in actual use must give sufficient attention.

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