For a loader, there was a failure inside the gearbox. The customer overhauled the gearbox in a local repair shop. During the test run, the machine could only reverse but not move forward. The specific performance is: when the Engine is started, the machine reverses when reverse gear or neutral gear is engaged, and the machine does not move when the first or second gear is engaged.
The loader gearbox is a planetary power shift gearbox. The planetary gears, sun gear and inner ring gear are in constant meshing state. The power transmission is driven by variable speed pressure oil to push the pistons of each gear to compress the master and driven friction plates. To achieve. In the event of the above failure phenomenon, you should first check the change of the transmission oil pressure. Observe the variable speed pressure gauge, the pressure indicator at idling speed is about 1.3Mpa. When the gear is shifted, the pressure gauge pointer drops and quickly returns to the normal value, indicating that the pressure oil has entered the oil cylinders of each gear, and the sealing performance of the oil cylinders of each gear is good. The reason for the gearbox oil supply system can be ruled out.
It can be analyzed that the reason why the loader has only reverse gear and also reverses in neutral gear may be that the reverse gear mechanism is always combined. Because when the first and second gears are engaged, despite the action of the pressure oil, the piston pushes the friction plates of the first and second gears to be normally combined. If the reverse gear mechanism cannot be separated, the forward and reverse powers will cancel each other out. Although the Torque Converter can output torque, the machine will not move forward or backward.
The main reasons why the reverse gear mechanism cannot be separated are as follows:
1) The reverse clutch brakes the reverse planetary carrier, and the reverse planetary carrier is supported on the intermediate input shaft of the overrunning clutch through bearings. The overrunning clutch is supported on the gearbox housing and the torque converter through two bearings. Between the shells, there is a spacer between the reverse planetary carrier and the overrunning clutch. If this spacer is missing, the reverse planetary carrier will move backwards to top the reverse piston, so the reverse planetary carrier is not installed. When the piston is pushed, braking may occur;
2) If the thickness of the reverse gear friction plate exceeds the requirement, the free gap between the reverse gear piston and the friction plate disappears, and the reverse gear friction plate can always be combined together;
3) Fracture or sintering of the reverse gear friction plate can also cause this type of failure, but the possibility of this occurrence in the newly repaired gearbox is very small.
The reason for this failure must be inside the gearbox. The gearbox was disassembled and inspected. It was found that the spacer between the reverse gear carrier and the overrunning clutch was not missing, and the friction plate did not appear to be broken or sintered. Measure the thickness of the friction plate Both of them exceed the requirements of 3.85mm for the driving plate and 3mm for the driven plate required by the process, so that the reverse gear can not be guaranteed after the friction plate is assembled. The quality loader attachments look for the public number and the smart manufacturing. The last one is the driving plate to the friction plate isolation frame The distance of the joint surface is between 0.9-2.8mm, which causes the reverse gear to always be combined and cannot be separated. After replacing the standard friction plate, the installation and test run are normal.
