Created on:2021-10-07 10:13

Automobile hydraulic fault diagnosis and maintenance_ Failure of Steyr heavy truck steering power hydraulic pump

Automobile hydraulic fault diagnosis and maintenance_ Failure of Steyr heavy truck steering power hydraulic pump

Steering hydraulic pump is the power pump of automobile hydraulic power steering, which can also be said to be the "heart" of power steering system. The vehicle adopts hydraulic power steering, which is conducive to reducing the labor intensity of the driver and reducing the occurrence of driving accidents. Steyr adopts hydraulic power steering system. Only by understanding its performance and working principle can we ensure the normal operation of hydraulic power steering, prolong the service life of steering power hydraulic pump, play the role of safety protection and increase benefits for enterprises.

(1) Working principle

The ZF vane pump of ZF company in Germany is adopted as the steering power hydraulic pump of Steyr heavy-duty truck. After localization, zf7672 and zf7673 vane pumps produced by Sichuan automobile factory with imported technology are adopted. The former is used for road vehicles and the latter is used for off-road vehicles. It is composed of a pump body with double arc curve inner cavity, grooved rotor, blade and other parts. It is installed on the engine timing gear chamber and driven by camshaft timing gear. When the engine is running, it drives the power assisted hydraulic pump to rotate, and the blade moves outward along the blade groove under the action of centrifugal force, close to the inner wall of the double arc of the pump body. In the process of rotor rotation, the volume enclosed between blades increases and decreases continuously to complete the process of oil absorption and pressure. The rotor completes oil suction and oil pressure twice every revolution. A safety valve is installed in the pump body to limit the maximum pressure. When the external load of the steering system increases, resulting in the oil pressure rising to 13Mpa, the safety valve opens to unload the load. A throttle valve and are also installed in the pump body to ensure that the displacement of the pump is basically constant.

(2) Precautions for use and maintenance

① Correct selection of hydraulic oil is the key to ensure the efficiency and prolong the service life of the steering power hydraulic pump. N32 low temperature hydraulic oil is used in the hydraulic power steering system of Steyr heavy truck.

② The added hydraulic oil must be kept clean, and the oil level shall be checked regularly. If it is insufficient, it shall be supplemented in time. It is better to clean the filter element in the oil storage tank once every level of maintenance, and clean it with alcohol.

③ During use, the hydraulic pump shall be frequently checked for leakage, normal operation, impact or abnormal noise.

④ The hydraulic oil and filter element shall be replaced after one year of vehicle operation. The oil change method is as follows: A. support the front axle with a jack to keep the wheel off the ground; b. Remove the oil storage tank cover, oil return pipe and steering gear drain plug; c. Start the engine and run at high speed for about 10s to discharge the hydraulic oil in the oil storage tank, hydraulic pump and steering gear; d. Stop the engine, turn the steering gear left and right to the limit position, and discharge all the residual hydraulic oil; e. Replace the filter element, assemble, add oil to the specified height, and exhaust the air in the hydraulic system.

(3) Troubleshooting

If the steering power hydraulic pump is not inspected and maintained in time, the following faults are easy to occur.

① The pump does not suck oil or sucks oil, but there is no pressure on the pump output oil. This fault is mainly caused by the following reasons: a. the filter element is blocked and the oil pipeline is blocked due to rubber's non oil corrosion resistance; b. There is leakage at the connecting part of the pipeline and air enters; c. The pump parts are worn, the clearance is too large, so the leakage is large, and the pump oil has no pressure; d. The oil does not meet the requirements, the viscosity is too large, and the blade sliding resistance is large; e. The oil level in the oil storage tank is too low. The above faults can be eliminated by the following methods: A. clean the filter element with alcohol, replace the pipeline and change the oil; b. Check and fasten all connecting parts to prevent air from entering; c. Repair the booster hydraulic pump and replace the severely worn parts; d. Replace the specified hydraulic oil; e. Add oil to the specified oil level.

② Excessive noise. Excessive noise is mainly caused by the following reasons: A. air enters the pump; b. The pressure impact is too large, the safety valve is damaged or inoperative, or the pressure is adjusted too high; c. Large oil absorption resistance; d. The pump is excessively worn. Abnormal noise or excessive noise of the steering power hydraulic pump can be eliminated by the following methods: A. check the fastening of each joint to prevent empty; get into; b. For maintenance of safety valve, the maximum pressure shall be adjusted to 13Mpa; c. Replace the oil suction pipe; d. Disassemble and inspect the booster hydraulic pump and replace the severely worn parts.

③ The steering pump shaft is broken. If the steering hydraulic pump is killed in one direction during use and stays for a long time, it will cause excessive pressure and lead to shaft suffocation. Therefore, when using the vehicle, the driver should pay attention not to kill the direction and stay for too long.

④ Serious hydraulic oil leakage. If the liquid level of the oil storage tank drops rapidly and the hydraulic oil is replenished more, great attention should be paid. If the replenishment of hydraulic oil is too large, the causes should be found from the following aspects: a. the connecting oil pipes of each part are damaged, the joints are not fastened, and there is leakage; b. Oil tank damage and hydraulic oil leakage; c. The steering gear oil seal is damaged and the hydraulic oil leakage is large; d. The steering hydraulic pump oil seal is damaged and the hydraulic oil flows into the engine crankcase. In case of such faults, stop the engine immediately to prevent the hydraulic oil from mixing into the engine oil, resulting in deterioration of the engine oil and failure of the engine bearing bush.

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