Misjudgment and analysis of abnormal sound of Dong

2022-08-19
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Misjudgment and analysis of abnormal sound of Dongfeng transmission shaft

fault phenomenon and misjudgment

abnormal sound of transmission system of an extended Dongfeng Automobile. According to the owner, the car makes a strange noise at high speed, and the speed cannot meet the design standard, and the car body shakes when driving at high speed. Asked about the reason, the car had this fault before. After repeated inspection in an individual repair shop, it was believed that it was the abnormal noise from the main reducer. Then the main reducer assembly was replaced, and the fault was not eliminated. Obviously, the original fault is a misjudgment

inspection results and cause analysis

according to the user's introduction, we will first carry out a road test. During the road test, it was found that there was a whine, whine and irregular noise when the vehicle speed was above 60km/h, and there was still a sound when sliding out of gear. The higher the speed of the car, the more obvious the abnormal sound and the more intense the vibration. In order to find out the cause of the fault, put the rear axle of the vehicle up and put it into high-grade high-speed operation. There is still an obvious abnormal sound at the speed of about 50km/h. No obvious bending of transmission shaft is found during low-speed operation. Check the connection mode of the transmission shaft, and it is found that the universal joint forks at both ends of the first and second transmission shafts are not in the same plane. After removing the intermediate support, it is found that the bearing is slightly loose, the coaxiality error of the transmission shaft is within the specified range, and the speed control is inaccurate, and the mark of the expansion joint is fuzzy. After inspection, an intermediate support bearing was replaced to keep the universal joint forks at both ends of the first and second transmission shafts in the same plane, and the universal joint forks at both ends of the main transmission shaft were installed according to the original position in the same plane. During the test run, it was found that the abnormal noise was reduced when the vehicle speed was 60km/h, and there was still a whine sound when the vehicle speed was 70km/h. With the increase of the vehicle speed, the vibration was still aggravated. After returning to the factory, the main transmission shaft expansion joint was replaced by 180 and tested after installation. There was no abnormal sound and obvious vibration, and the speed could be increased to more than 85km/h, which proved that the fault had been eliminated

after analysis, the fault of the car lies in the universal transmission rather than the main reducer. Standard for universal transmission testing machine: electronic universal testing machine gb/t 16491 ⑴ 996; The moving device is connected by non constant velocity universal joint, which must meet two conditions to realize constant velocity transmission. First, the driven fork of universal joint I is connected with the driving fork of universal joint II by transmission shaft III, and the universal joint forks at both ends of the transmission shaft are in the same plane; Second, the included angle between input shaft, output shaft and transmission shaft should be equal, that is, a1=a2

for the second condition, it is generally determined by the vehicle structure. The servo electromechanical rotation is controlled by the speed regulation system. In the rear axle of the dependent suspension, the relative angle and position of the drive axle input shaft, the intermediate shaft and the transmission output shaft will change due to the deformation of the suspension and the wear of the intermediate support connecting hole. The first condition can be guaranteed by correct assembly process. The two basic conditions mentioned above must be guaranteed during installation. If the above two conditions cannot be met during installation, the transmission shaft will produce vibration and abnormal sound due to the unequal speed transmission of input shaft and output shaft during operation, and the installation of transmission shafts in sections 1 and 2 of the vehicle does not meet the requirements. In addition, for the main transmission shaft, the repairman often only pays attention to keeping the universal joint forks at both ends in the same plane during installation, and ignores the mark during disassembly, or does not mark during disassembly. In this way, although the universal joint forks at both ends of the transmission shaft are in the same plane, it may still make the difference between the universal joint forks and the original balance position by 180, thus destroying the original balance, causing the transmission shaft to vibrate and make abnormal noises due to the centrifugal force ringing the alarm bell to the polyurethane industry during operation. To sum up, the main reason for the abnormal noise and vibration of the vehicle's transmission system is the incorrect installation of the transmission shaft

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