Inspection for the excavator's weak right travel: the fault phenomenon was found when Caterpillar built the ex90 hydraulic excavator, and the right travel was weak during operation; When walking on a level road, it deviates to the right obviously; It is normal to turn to the right. When turning to the left, the engine must run at high speed and turn very slowly.
Cause of failure:
According to the driving power transmission sequence of the excavator, the following inspections are carried out according to the sequence:
1. Check that the right travel motor of the excavator hydraulic pump is supplied with oil by the hydraulic pump. In addition to the travel driving device, the hydraulic pump also supplies oil to the bucket cylinder. Since the bucket cylinder works normally, it can be determined that the pump is OK.
2. The symptoms of the control valve failure of the excavator control valve generally include: the travel valve stem cannot be pushed or the stroke is small; The fitting clearance between the valve rod and the valve hole is large and there is leakage; Relief valve pressure decreases. All of the above faults will lead to weak right travel.
3. The inspection shows that the valve rod stroke of the left and right travel operating valves is the same, indicating that the valve rod operation is no problem, but it is difficult to determine whether there is internal leakage and whether the pressure value of the safety valve is reduced. The verification method is to exchange the left and right traveling oil pipes, but it is very difficult to disassemble some oil pipes, so it is doubtful whether the control valve has fault for the time being, so it is not necessary to disassemble and check it first.
4. Check the traveling motor of the excavator. Since the noise is relatively large when the excavator is traveling, it is very inconvenient and unsafe to measure and touch the traveling motor and oil pipe. Therefore, use the bucket to support the right travel crawler, slowly operate the right travel control lever under the engine idle speed, and you can hear the "hissing" sound of the right travel motor before the driving wheel is turned. Touch the oil inlet and return pipes with your hand, and feel that there is oil flow in the oil return pipe; When the control lever continues to move, the track starts to rotate but very slowly; When the engine accelerates, the "hissing" sound also increases. When the left travel is operated in the same way, there is no above abnormal phenomenon, which indicates that the internal leakage of the right travel motor connects the oil inlet and return circuits, resulting in the reduction of the pressure at the oil inlet of the travel motor and the reduction of the motor output torque. Therefore, the right travel motor needs to be disassembled for inspection.
5. Check that the hydraulic oil of the rotary joint of the excavator is transferred from the upper part of the excavator to the lower traveling driving device, which must pass through the rotary joint. If there is leakage in the rotary joint, a certain amount of high-pressure oil flows to the oil return pipe, which will also lead to weak walking. However, it is difficult to judge whether there is leakage inside without disassembly, so this part can only be regarded as a doubtful point.
6. Check that the power transmission between the traveling motor and the traveling driving wheel of the excavator traveling reducer is normal without abnormal noise. In addition, the oil temperature, oil quality and oil level in the reducer are normal, so the traveling reducer can be eliminated. Based on the above analysis and inspection results, it is decided to remove and repair the right travel motor first. After the overhaul and disassembly of the right travel motor, it was found that a piece of the valve sleeve had fallen off at the separation between the high and low pressure oil passages, making the inlet and return oil connected, thus reducing the output torque of the right travel motor and making the travel weak, which was consistent with the inspection and listening results. As it was difficult to repair the shaft sleeve, it was decided to replace the right travel motor, and the right travel motor returned to normal after installation.
