The hydraulic mechanical transmission system of a forklift is an important part of the entire vehicle. After long-term use, some internal combustion forklifts may experience common faults in the hydraulic mechanical transmission system, such as insufficient output power, difficult starting, and slow shifting response; Excessive oil temperature and malfunctioning hydraulic torque converter.
Fault Analysis
If it is found that the forklift has insufficient power, difficulty climbing, slow gear shifting response, but the load lifting work is normal during use, the first thing to do is to use a pressure gauge to detect the system pressure. If the specified pressure value cannot be reached, the reason may be that the gears and pump body of the compensation pump are excessively worn, causing excessive wear of the gears and pump body of the compensation pump and increasing internal leakage of the compensation pump; Poor oil cleanliness can cause blockage in the oil circuit, leading to compensation suction.
If the oil temperature is too high, the usual reason is that the oil circuit is blocked, causing insufficient oil supply from the compensating pump, resulting in dry friction of the clutch and high oil temperature; The oil pressure inside the torque converter is lower than the adjustment pressure of the main pressure valve, causing the outlet pressure of the torque converter to be too low; The oil grade is incorrect; The internal components of the torque converter are damaged, causing only a small portion of the engine's power to be transmitted to the turbine, resulting in excessive reactive power and a sharp increase in oil temperature.
If it is observed from the observation hole of the hydraulic torque converter that the hydraulic torque converter is not working, the inlet and return oil of the hydraulic torque converter should be checked first. If there is no return oil and the forklift is driving normally in cold mode but difficult in hot mode, the cause of the fault is severe wear or damage to the compensation pump; If the torque converter has no power output and works intermittently, the cause of the fault is blockage in the oil circuit, damage to the inner sleeve of the guide wheel seat, or loosening of the guide wheel seat nut.
Fault handling
From the above analysis, it can be seen that the main faults in the hydraulic mechanical transmission system of forklifts are the oil circuit, hydraulic torque converter, and compensating pump. Therefore, when troubleshooting, the first consideration should be to clean the oil circuit, replace the oil and filter as required; Then check the three links of hydraulic torque converter and compensating pump. Therefore, when troubleshooting, the first consideration should be to clean the oil circuit, replace the oil and filter as required; Then check whether the guide wheel, guide wheel seat, and overrunning clutch of the hydraulic torque converter are damaged; Finally, check the compensation pump for wear and repair or replace damaged components. It is also necessary to clean the dust and dirt on the surface of the oil radiator. After the above processing, the fault can generally be effectively eliminated.
When repairing the transmission system, the following checks should be noted:; The coaxiality error of the engine flywheel, torque converter, and torque converter housing should not exceed 0.2mm; the dynamic unbalance of the connecting plate should be less than 30g · cm; The end runout of the engine flywheel housing end face and the torque converter housing end face relative to their axis should not exceed 50UM; there should be a gap of 1.0-1.5mm between the torque converter fork and the compensating pump gear end face.
