The wheel excavator suddenly couldn't walk on the way back after finishing the work at the steel slag loading and unloading site. Check the tire rotation is good, drive shaft transmission is normal. Disassemble the pilot oil pipeline that controls the excavator to walk in high and low gear, change the high and low gear positions, observe the oil out of the oil pipeline is strong and powerful, and the fault of the retaining valve and hydraulic oil pipeline can be eliminated. Turn off the engine, the walking device is in the stop braking state, open the transmission box observation mouth cover, check the gear fork, fork with hand can feel the middle of the fracture, and detached from the sliding sleeve, the preliminary judgment is fork fracture fault.
1, the cause of failure

According to the breaking condition of the fork, the reason for the fault is that the machine has not stopped completely in the process of driving, which is to switch between high and low gear. The transmission box of the excavator is not equipped with a synchronizer. When the machine is moving, the internal transmission gear runs at a high speed. If the gear is shifted at this time, the sliding gear sleeve moved by the fork cannot complete meshing with the gear, and the reaction force generated by the collision directly leads to the damage of the 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 oil box cover and exhaust the hydraulic system, disconnect the hydraulic pipeline connected with the transmission box and seal the oil leakage point; Secondly, remove the front and rear drive shafts, remove the hand brake hydraulic cylinder and the front axle drive hydraulic cylinder tubing; Again, the adjustable lifter placed in the lower part of the transmission box disassembly position, adjust the lifter to support the box, remove the three transmission box fixing bolts, the transmission box removed from the frame. Due to the large mass of the transmission box, it is necessary to confirm that the elevator is fully accommodating and supporting the box before removing the retaining bolts. Transmission box decomposition steps: first, open the transmission box cover, remove the cylinder head lock nut, piston, O ring, centering plate, compression spring, spring seat, pin, retaining ring, shaft, fork and lever. Second, replace damaged joysticks, forks, and worn O-rings. Finally, detect the wear of the transmission shaft and gear inside the transmission box to confirm whether the parts are in good condition.

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 on the frame and connect the corresponding hydraulic pipeline. Finally, tighten the hydraulic oil tank cover and start the engine, lift the bulldozer, respectively hang high, low gear and reverse gear test machine, the fault disappeared.

In the test process should pay special attention to: do not hurry to increase the throttle after the operation of gear, first gently throttle pedal, feel the machine micro-motion, to be fully engaged in the transmission box gear, and then increase the throttle driving, in order to prevent gear meshing parts offset.