(1) Impact caused by fluid flow reversing of Hitachi excavator
The control edge of the directional valve core can be cut into a cone angle of 1.5 ° ~ 4 ° (the original length depends on the length of the sealing edge) or an axial triangular buffer groove can be opened.
(2) Impact caused by failure of throttling buffer device
① The steel ball and valve seat in the hydraulic cylinder buffer device are poorly sealed, the paper pad at the end cover is damaged, the lock nut of the piston is loose, the matching clearance between the piston and the cylinder block hole is too large, etc.
Replace the steel ball, grind the joint of the valve seat, replace a new paper pad, tighten the lock nut or remake the piston (the fit clearance with the cylinder block hole is 0.03mm).
② The buffer plunger at the buffer piston end is provided with a triangular groove, and the oil is buffered when it returns through the triangular groove. When the outer edge of the buffer plunger and the inner hole of the end cover are worn and the matching clearance is too large, the triangular groove will not play a buffering role. The piston and buffer plunger can be remade according to the size of the inner hole of the end cover, or after the buffer plunger is rounded, a layer of hard inscription is plated on the surface, and then the clearance is matched according to the size of the inner hole of the end cover.
③ A throttle valve is arranged outside the buffer cylinder end. The throttle nut in the throttle valve is loose or improperly adjusted, resulting in hydraulic impact. The nut can be tightened or readjusted.
④ One way throttle valve (damper) is set at both ends of the hydraulic directional valve. If the throttle valve is improperly adjusted or the one-way valve is poorly sealed, the working device will have an impact during reversing. At this time, tighten the adjusting screw of the throttle valve and appropriately increase the buffer damping. If there is still impact, it can be judged that there is a problem with the sealing of the one-way valve, and then check the sealing of the one-way valve and its seat.
(3) There is air in the hydraulic system
There is a large amount of air in the hydraulic system. The air in the directional valve is sometimes compressed and sometimes released, resulting in hydraulic impact. Check the air inlet and take preventive measures to eliminate the air in the system.
