Failure analysis of asphalt concrete paver hydraulic system
An imported asphalt concrete paver for many years has gradually been nationalized because of the deterioration of the hydraulic system. Among them, the hydraulic control valve of the automatic leveling system is made of home-made valves instead of the leveling cylinder. The use of the paver is not long, then it is found that the right leveling system is not working properly. When the leveling control switch is placed in the manual neutral position, the leveling oil cylinder and the piston rod can be automatically retracted, so that the traction point of the ironing drawing arm is automatically ascending. Moreover, this phenomenon is sometimes absent, fast, slow, big and small when traveling, and there is no obvious law.
According to the control principle of leveling system, it can be concluded that the piston rod of leveling cylinder is automatically retracted when no pressure oil is supplied. The most likely reason is that the oil cylinder is leaking or the hydraulic control check valve is invalid. However, taking into account the leveling cylinder working condition, the axial force is small, and the stroke usually change little, so if the two failure reason, the piston rod to recover more slowly, and the little trip. This is inconsistent with the aforementioned fault phenomena. If the three - bit four - way solenoid valve can not reliably return to the middle, there may be the above-mentioned fault phenomenon. That is when the power solenoid valve, the valve spool if sometimes in a slightly open state, and open range, along with the mechanical vibration, the spool is likely to return to the closed state, and from time to close the continuation of its range, it is entirely possible failure of the above phenomenon. Judging from this, the cause of the fault may be that the solenoid valve is stuck, and the return spring sometimes can not make the spool fully return to the middle position.
Subsequently, in the case of no boot, manually push the spool with the tool, and indeed found that the spool at the corresponding end of the back stroke is very small, so the solenoid valve is removed, the disintegration of the inspection.
Inspection results did not find the spool or armature stuck phenomenon, but when cleaning, found in the corresponding solenoid valve armature side of a circular arc of about 1cm of nylon nylon shape. Then, after the cleaning, the solenoid valve is installed. To put back in situ before tool push spool, find the fault phenomenon remains the same. So the valve will be broken again and carefully examined, it is found that the electromagnetic back on both sides of the spring seat hole depth difference of about 3cm.
According to the analysis, when the valve is not affected by electromagnetic force, in the two ends of the spring force, the spool is not in place, of course, will cause the fault phenomenon, at the construction site by conditions, for the two spring seat gasket into deep hole. Then install the valve and return it to the original position. After starting the test, the malfunction is completely eliminated.
