Common fault analysis of wheel excavator

[BONOVO]

The wheeled excavator suddenly failed to walk on the way back after finishing work at the steel slag loading and unloading site. Check that the tire is running well and the drive shaft is operating normally. Disassemble the pilot oil pipe that controls the high and low gear of the excavator , change the high and low gear positions, observe the strong oil output of the oil pipe, and eliminate the failure of the retaining valve and hydraulic oil circuit. The engine is turned off, the walking device is in the stop brake state, the transmission box is opened to observe the mouth cover, check the gear shift fork, the hand can feel the middle of the fork is broken, and it is separated from the slide sleeve, the preliminary judgment is the fork break fault.

1. Cause of failure

According to the breaking of the fork, the reason for the fault is analyzed: in the process of driving, the machine has not stopped completely, that is, the high and low gear switch. There is no synchronizer installed in the transmission box of the excavator . When the machine is moving, the internal transmission gear is running at high speed. If the gear is shifted at this time, the sliding gear sleeve of the shifting fork cannot engage with the gear, and the reaction force generated by the collision directly leads to the damage of the shifting fork. It was decided to replace the fork.

2. Disassemble the transmission box

The disassembly process is carried out in several steps: first, loosen the hydraulic tank cap and exhaust the hydraulic system, disconnect the hydraulic line connected to the transmission box and close the oil leakage point; Secondly, remove the front and rear transmission shaft, remove the hand brake hydraulic cylinder and the front axle drive hydraulic cylinder tubing; Thirdly, place the adjustable elevator in the disassembly position of the lower part of the transmission box, adjust the elevator to support the box, remove the 3 fixing bolts of the transmission box, and remove the transmission box from the frame. Due to the large weight of the transmission box, it is necessary to confirm that the elevator is fully contained and supported by the box before removing the fixing bolts. The decomposition steps of the transmission box: First, disassemble the transmission box cover, and remove the cylinder head lock nut, piston, O-ring, centering disc, compression spring, spring seat, pin, stop ring, shaft, fork and joystick in turn. Second, replace damaged joysticks, shifting forks and aging O-rings. Finally, the wear of the drive shaft and gear inside the transmission box is detected to confirm whether the state of each component is good.

3, assembly test machine

Assemble the disassembled parts one by one. Assembly is the reverse process of disassembly. After assembly, install the restored transmission box to the frame and connect the corresponding hydraulic lines. Finally, tighten the hydraulic fuel tank cover and start the engine, lift the bulldozer, respectively hang the high, low gear and reverse gear test machine, the fault disappeared.

In the process of testing, special attention should be paid to: do not rush to increase the accelerator after the operation of the gear, first light the accelerator pedal, feel the machine slight movement, when the gear in the transmission box is fully engaged, then increase the accelerator to drive, in order to prevent the gear mesh part offset and retreat.

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