Maintenance of hydraulic pump - Troubleshooting of hydraulic cylinder

2020-05-14 14:07:26

The fault phenomenon of the system is that the return speed of the hydraulic cylinder is slow and there is no limit return speed.

After checking and debugging the system, it is found that the fast forward and working movement of the hydraulic cylinder are normal, but it is not normal when the hydraulic cylinder moves backward. Check the one-way valve and it works normally. When the hydraulic cylinder returns, there is no working load. At this time, the system pressure is relatively low. The outlet flow of the hydraulic pump is all transmitted to the hydraulic cylinder with a rod chamber, which should make the hydraulic cylinder produce a higher speed. But it is found that the return speed of hydraulic cylinder is not only slow, but also the system pressure is very high.

It is found that the return spring of the reversing valve is not only lack of elasticity, but also skew, which causes the valve core of the reversing valve not to return to the original position after power failure, so the opening of the slide valve is too small, which restrains the oil passing through the reversing valve. Most of the pressure oil output by the hydraulic pump overflows back to the oil tank by the relief valve. At this time, the pressure in front of the reversing valve has reached the set pressure of the relief valve, which is the reason why the pressure increases when the hydraulic cylinder returns. When the pressure oil overflows back to the oil tank, there will be less oil entering the rod cavity of the hydraulic cylinder through the reversing valve, so there is no limit speed for the return of the hydraulic cylinder.

This method of eliminating howling is: the slide valve cannot return to its original position, which is caused by the spring. The qualified spring should be replaced. In case of radial clamping due to poor accuracy of slide valve, the slide valve shall be grinded or reconstituted. Generally, the tolerance of roundness and taper of wing core is 0.003-0.005mm. The valve core has a slight taper (which can be a quarter of the minimum clearance), and the large end of the valve core is on the side of the low-pressure chamber, so that the eccentricity can be automatically reduced, and the friction force can be reduced, so as to reduce or avoid the radial clamping force.

The reasons for the increase of the return resistance of the valve core may also be: it is difficult for the valve core to move due to the dirt entering into the gap of the slide valve; the space between the valve core and the valve hole is too small, so that the valve expands and gets stuck when the oil temperature rises, the resistance at the sealing position of the electromagnet push rod is too large, and the valve hole is deformed when the solenoid valve is installed and tightened. As long as we can find out the real cause of the clamping, the corresponding elimination method will be easier