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Cartridge Valve System Failure Analysis and Processing Methods
The system found many problems in the course of use, such as reverse large cone valve leakage, cone mouth seal is not strict, the valve sleeve deformation, the valve core is easy to wear and be stuck, easy to seal the basic plug-cut, handling difficulties, the control cover shuttle Valve seal is not strict, can not guarantee the main spool in the absence of a signal is reliably closed in the system caused by leakage, actuator instability and so on. The main reason for these problems is the processing accuracy of less than the requirements of material heat treatment, however off. The system has also appeared in the course of walking beam down when the valve block abnormal noise, the valve frame violent vibration, accompanied by screams, walking beam can only be intermittent decline, and the speed is very slow. The three proportional pressure valve test point pressure test, M1p, M3p point pressure within the normal range, but M2p pressure value swinging at 2.0 ~ 5.0MPa. However, the proportional valve reference voltage and feedback voltage test values ​​are within the set parameters, no abnormalities were found. Then the logical cone valve 1 control panel drain port P open observation, walking beam down, the drain should be immediately drain, but when the M2p pressure fluctuations, the drain is intermittent drain. Accordingly, it can be judged that the logic cone valve 1 has internal leakage and unbalanced dynamic balance causes malfunction. From the disintegration of the situation also found that a serious logic valve poppet valve core 1 serious wear and tear, valve cone and valve sleeve contact surface diameter increases. The picture shows the logic cone valve 1 matrix plug. Its function is to control the opening and closing of the logic cone valve by controlling the electromagnet M2 on the cover to lose the electricity. When M2 is out of power, the logic cone valve spool is closed by the control oil and the main spool spring to prevent pressure oil from entering into port A through port B. When M2 is energized, the control oil is blocked, and the pressure oil in the main valve spring oil chamber Ap is drained back to the fuel tank via the solenoid valve. At this moment, if the horizontal force of the pressure oil on the main valve bores A and B can overcome the spring force and the back pressure of the spring oil chamber Ap, the main valve core is opened and the pressure oil of the B port enters into the A port. As can be seen from the figure, when the walking beam rises, the logic cone valve 1 is closed; when the walking beam is lowered, the cone valve 1 is opened, so the reason for the failure can be analyzed from the static equilibrium condition of the logic cone valve 1 in the open state. When the valve is open, the force balance equation of the valve poppet acting on the poppet valve is: PBAB + PAAA = K (L + δ) + PXAAP If we omit the spool's own weight, frictional force and hydrodynamic influence, , PB, PA for the port B, A pressure value; PX for the spring oil chamber back pressure value; K is the main valve spring stiffness; L is the main valve spring pre-compression; δ main valve opening degree; AA, AB A, B for the effective area; AAP is the effective area of ​​the spring oil AP. From (1) can be seen, the main valve opening and the main port B, A pressure value and its effective area, the spring back pressure chamber and so on. For pre-made basic plug-ins, the main spool spring stiffness and pre-compression unchanged. Therefore, when the spool and sleeve due to wear and tear caused by the spool B pressure oil into the spring oil chamber AP, PX increases, so that the main valve opening δ smaller. When the valve sleeve with a small cone wear, resulting in the effective role of Port B, A change in the allocation of the area, that AA value increases, AB value decreases. However, PA is the system back pressure, the pressure relative to PB is very small, so PBAB and PAAA can not be balanced, resulting in the valve spool moving to the right, reducing the opening of the valve spool. At this time, the pressure of port B increases and the valve spool moves to the left mobile. In this way, the valve core in the valve sleeve repeatedly oscillating process caused by uneven pressure changes caused by screams and vibration. Machining and assembly causes the spool and sleeve to fit in the axial direction with varying clearances, creating an imbalanced radial hydrodynamic force that, if unbalanced, creates a significant frictional resistance when the spool moves Spool moving difficult. Therefore, a balancing groove is formed on the surface of the valve core, and if the surface of the valve core is worn, the balancing groove will lose its function and cause the valve core to malfunction. In addition, the length of the oil seal is too long, resulting in sleepy oil shocks, but also can not be ignored reason. In summary, the logical cone valve failure causes are: (1) valve wear caused by internal leakage balance tank lost; (2) into and out of the effective role of the oil distribution changes in the area caused by the basic plug-pressure to reduce the opening; (3) machining error And the assembly level of less than technical requirements. Troubleshooting From the scene of the disintegration of the situation, single-sided valve spool wear, spool and valve sleeve contact surface almost to the maximum diameter, the effective area of ​​Port B is almost non-existent. Therefore, to deal with the failure of the valve, the effective area of ​​port B must first be restored to the set value. As can be seen from Figure 2, there is a small cone in the sleeve that shortens it so that AB will increase, but machining is more difficult and inconvenient to measure. So in the actual process did not use this method. In the actual process, the spool made double cone, AA: AAP = 1: 1.12, the maximum contact surface diameter of 37.5mm, can basically reach the set value. 6 Conclusion Through the improvement of the valve spool, eliminating the fault. As a result of the double cone valve spool, the effective area of ​​the oil ports A, B is distributed on two different conical surfaces, and the effective area does not interfere with each other when the conical surfaces wear. Improved valve reliability.