Solutions to the problems of weak power in loaders and high oil temperature in torque converters

1. The problem of weak operation of the loader

Fault phenomenon: A 50-type loader is equipped with a ZF transmission and drive axle, and a CUMMINS diesel engine. The user has been mining sand and gravel materials in dry rivers for years. After over 1,800 hours of use, users have reported that the loader cannot move forward when the accelerator is lifted and the tires sometimes slip.

Fault analysis: Insufficient traction; It has a large traction force but insufficient adhesion to the ground. Tire wear; The work site is slippery. Poor quality or deterioration of transmission fluid, etc.

Fault diagnosis: First, inspect all systems of the vehicle. It was found that the oil level in the transmission was very high, and the oil was thin with many bubbles in it. Drain the oil to the required level. The tire pressure is 0.5MPa for the front wheels and 0.45MPa for the rear wheels. Deflate the front wheels to 0.32MPa and the rear wheels to 0.30MPa. And add an additional counterweight of 200 kilograms.

When the traction force was measured for the first time, it was only 116kN, and the diesel engine speed was 1790rpm during stall. Upon inspection, it was found that there was an aged crack of about 120mm on the intercooler of the diesel engine. After being repaired and welded at a repair shop and the traction force was measured again, it had reached 147kN. When the engine was stalling, the rotational speed was 2110rpm, but the fault phenomenon was not eliminated when working at the sand field.

Drain the transmission system oil and clean it. Replace it with new ZF box-specific oil in the required quantity. When the machine was tested at the construction site again, it was already working normally.

Summary and analysis: Water was mixed into the transmission, and due to the user's self-replacement with non-dedicated oil, the oil deteriorated and did not meet the ZF transmission requirements. During operation, bubbles formed in the transmission oil, causing the torque converter to be unable to continuously output the rated torque, resulting in weak overall operation of the machine.

2. The oil temperature of the ZF torque converter is high

Fault phenomenon: A ZL50C loader equipped with a ZF transmission reported that the oil temperature of the torque converter rose rapidly after two months of operation, reaching 1200 ° C in approximately half an hour. As it is a production operation site, various tests are not easy to carry out. We have replaced the gearbox, oil drain, oil in the gearbox, pipelines, etc., but the problem has not been solved. However, the temperature of the hydraulic oil and water has remained normal.

Fault analysis: The torque converter radiator is clogged. The heat dissipation oil pipe is clogged. There is a large leakage inside the torque converter. Low transmission oil pressure; Clutch slippage; Cooling system failure; The quality of the oil is poor and deteriorated. Continuous overload operation of loaders, etc.

Fault diagnosis: As all the components of the system have been replaced previously, it is planned to conduct the inspection from the dynamic operation of the loader. While operating in the cab, during the process of moving and digging, when operating the bucket collection rod, it was felt that the bucket moved slowly. Upon inspection, it was found that the lock nut at the position of the fixed flexible shaft in front of the distribution valve was loose. When the flexible shaft was pulled, the distribution valve moved with a delay. Tighten the nut and operate again. The oil temperature should be at the normal level.

Summary and analysis: When the torque converter is in a stall state, a large portion of the energy output by the engine will be converted into heat energy. Under the original heat dissipation conditions, the temperature rise rate of the torque converter oil will accelerate. Due to the loosening of the fixing nut of the flexible shaft of the distribution valve, the bucket cannot be retracted in time during the loading operation. Moreover, the driver often increases the throttle to move forward because of the operation reasons. The loader cannot move forward due to the obstruction of materials in front, and the torque converter is often in a stall state, which will inevitably cause the oil temperature to rise rapidly.