The PC200-5 Hitachi excavator deviates in the same direction during forward and backward. During troubleshooting, the connecting hoses of the left and right traveling motors and the central swivel can be exchanged first to observe whether the deviation direction changes. If there is no change, there is a problem with the hydraulic motor. Repair the hydraulic motor. If the deviation direction changes, there is a problem with the hydraulic oil circuit. The outlet hoses of the front and rear hydraulic pumps shall be exchanged again. If the deviation direction does not change, it indicates that the hydraulic pump has no fault; If the deviation direction changes after the exchange, it indicates that the hydraulic system on the deviation side needs to be adjusted. After exchanging the outlet hoses of the front and rear hydraulic pumps, if the walking deviation direction does not change, the following inspection shall be carried out:
(1) Check whether the outlet pressure of PPC valve (pilot operated valve) is normal. If the outlet pressure of PPC valve does not reach 3.2 + 0.4MPa, it indicates that PPC valve is faulty; If the outlet pressure of PPC valve is within the specified range, check whether the traveling valve core of the main control valve acts stably, and whether there is jamming or serious wear.
(2) If the traveling valve core of the main control valve is normal, the deviation direction shall not be changed after exchanging the left and right hoses between the main control valve and the central swivel.
(3) If the deviation direction changes, it indicates that the main operating valve is still faulty, which can be eliminated by repairing or replacing the main operating valve; If the deviation direction has not changed, exchange the left and right hoses at the outlet of the central swivel and observe whether the deviation direction has changed. If the deviation direction changes, the oil seal of the central swivel is damaged. The fault can be eliminated after replacing the oil seal; If the original deviation direction is changed after the outlet hoses of the front and rear hydraulic pumps are exchanged, the following inspection and adjustment shall be made.
(1) If it deviates to the right, adjust the stroke of the servo piston of the front hydraulic pump. The specific method is: loosen the upper end cover at the top of the servo piston of the front hydraulic pump and add an adjusting gasket. The maximum thickness of the gasket is 0.3mm. For PC200-5 Hitachi excavator, increased flow (L / min) = 25 × Thickness of adjusting piece (mm); If it deviates to the left, the stroke of the servo piston of the rear hydraulic pump can be adjusted in the same way.
(2) If the fault is still not eliminated after the deviation adjustment, check whether the overflow pressure of the main overflow valve is normal (when the engine runs at high speed and no-load, the traveling overflow pressure is 32.5 ~ 36.5mpa; during operation, the overflow pressure is 31.0 ~ 34.0mpa).
(3) If the overflow pressure is not within the specified range, the main overflow valve is faulty; If the overflow pressure is normal, check whether the output pressure of NC valve (reverse control valve) is normal (when the engine runs at high speed and no-load and the track rotates freely or runs normally, the output pressure of NC valve must be the same as that of TVC valve; when the control lever is in the middle position, the maximum output pressure of NC valve is 0.55mpa).
If the output pressure of NC valve is abnormal, further check whether the differential pressure of jet sensor is normal (when the control lever is in the middle position, the differential pressure is 1.3 ~ 1.9mpa; when the control lever is at the end of stroke, the maximum differential pressure is 0.2MPa).
(4) If the differential pressure of the jet sensor is normal, it indicates that the action of the NC valve is abnormal. After adjusting, repairing or replacing the NC valve, it can return to normal state.
(5) If the differential pressure of the jet sensor is abnormal, it indicates that the set pressure of the overflow valve of the jet sensor decreases, and the pressure of the valve can be adjusted (when the engine is running at high speed and no-load, the maximum differential pressure when operating the control lever is 0.2MPa). If the pressure of the overflow valve of the jet sensor does not return to the normal state after adjusting, it indicates that the orifice of the jet sensor is faulty and should be cleaned or replaced.
(6) If the overflow pressure of the main overflow valve is normal and the output pressure of the maintenance C valve of Hitachi excavator is also normal, check whether the stroke of the servo piston of the hydraulic pump is normal (the standard stroke is about 7.2mm). If the stroke of the servo piston is within the specified range, it indicates that the internal leakage of the hydraulic pump is serious; If the stroke of the servo piston is not within the specified range, the servo valve does not operate normally.
