1. Fault analysis and exclusion of bucket cylinders and left lines
A Hitachi Excavator, after the work 8500h, the bucket cylinder and the left line take the motor work weakness, but the rotation action and right travel are normal, and the rest is slightly slow.
1. Possible causes of flexible failure of bucket cylinders
(1) Control the pilot oil passage of the bucket has faults.
(2) Control the valve valve core card death or severe wear.
(3) The fuel valve card of the bucket loop die.
(4) The bucket, the piston or oil seal is severely damaged.
(5) The main shift valve is killed.
(6) After the pump or its control system is faulty.
2. Possible causes of the left line to walk in power failure
(1) Controlling the leading oil path of the left walking has faults.
(2) Control the valve valve core card death or severe wear.
(3) The walking motor is faulty.
(4) The center rotary joint is serious.
(5) The main shift valve is killed.
(6) After the pump or its control system is faulty.
According to the principle of hydraulic system of the machine, it is known that the bucket cylinder and the left walking motor are separately filled by the rear pump, so that the bucket cylinder and the left line take the motor at the same time, the reason is the most likely that the main shift valve is Or after the pump and its control system. So the front pump, the high pressure tube of the front pump is exchanged, and when the test is detected, the bucket cylinder and the left line take the motor have been working properly. In contrast, the rotary motor and the right line take the motor but work weak. This shows that the bucket cylinder and the left line take the motor and its control system are normal, and the fault should be on the post-oil supply of the bucket and the left line to oil or its control system thereof.
3. Check the post-pump control system and analyze the results
(1) Since the preadensing pump is working properly, the pre-pump is proved, the pump shared by the post pump and the TVC valve are normal.
(2) A routine is 6MPa in the NC valve outlet, and the oil pressure is measured as p, (due to the pressure of the CO valve outlet pressure, the Qo valve adjustment bolt is adjusted 2 to 4 turns, It is found that P, value rises, then adjust the adjustment bolt to the original position, p; decreased to the original value. The detection result complies with the working characteristics of the CO valve, indicating that the CO valve is working properly.
(3) When adjusting the NC valve adjustment bolt, when the bolts are adjusted, the P; the value is rising, and the adjustment bolt is adjusted back to the original position, p; falls to the original value. The detection result complies with NC valve working characteristics, indicating that the NC valve is working properly.
(4) After the demolition servo institution, it is understood that the return spring is not broken and the elasticity is good, and the connecting rod mechanism does not fall off, and the valve core has no cardicular and wear, whereby the servo mechanism is working properly.
By the above inspection results, the post-pump control system works fine, the bucket and the left line take the motor work can only be caused by the failure of the pump itself.
Remove the hydraulic pump assembly, the residual examination found that each hydraulic element of the front pump is intact, the post-pump is damaged, and there are several deeper trenches at the distribution plate sealing oil. The remaining hydraulic components have no obvious wear. Obviously, the rear pump does not work properly because the contact surface of the plunger cylinder and the distribution plate is severely worn, resulting in severe leakage of hydraulic oil, causing oil pressure to create, resulting in a bucket cylinder and left line to walk the motor work weakness.
4. Troubleshooting
In view of the case where the plunger end face damage is not large and the distribution disk is seriously damaged, the maintenance scheme of the grinding piston cylinder and the update distribution disk is employed. That is, the wear end surface of the piston cylinder is first used in the plane grinding machine, and then polished with chromium oxide. Finally, the grinding cylinder cylinder and the distribution tray were used to ensure that its contact area was more than 95%.
