A Kobelco excavator operations and S K70SR during walking , the load is small movement abnormalities , mainly in the following three kinds of anomalies : one arm extended at normal speed , but stick recovered 90 ° ( ie, over load hour ) pause 5s, continue to touch the ground recovery ( load large ) , the arm speed immediately returned to normal. Second, the bucket cylinder rod is fully recovered , outwardly very slow , but the bucket encounter resistance when the normal speed . Third, the excavator uphill speed is normal, but when you stop and go downhill .
The machine uses Kawasaki K3S P36B controlled variable piston pump of this type of fuel for the working device , which separate a gear pump to provide power for the pilot system . Based on the above analysis of failure phenomena , if the variable displacement pump variable mechanism fails, it can lead to its output flow instability . But it by adjusting the variable displacement mechanism to increase after the test machine , the fault still exists.
Detection of the variable displacement pump starting pressure of 0 , overflow pressure 30MP a. Thus suspect that the variable displacement pump starting pressure is too low , causing the failure. Thus by adjusting the minimum tilt angle limit screw , the pressure will start to adjust to 3MPa, test machine failure remains .
The variable pump disassembled found that the swash plate bearing ball badly worn , the swash plate ball bearing ball has been rubbed off 6mm, fault position should be in here . Replace the swash plate and the supporting ball after the test machine , the fault disappears.
Analysts believe that the swash plate and the swash plate bearing ball bearing ball badly worn , the swash plate cylinder and core spring valve plate thrust decreases. At this point the cylinder and valve plate gap increases , the hydraulic pump internal leakage increases, flow decreases , resulting Stick recycling pause. But when a sudden encounter resistance when working device , the hydraulic pump increases, resulting in valve plate cylinder for increased pressure to the cylinder and valve disc space decreases. Cylinder and valve plate gap decreases , the hydraulic pump discharge volume decreases, the flow rate increases , excavator working device can be returned to normal operation .