When the technical condition of the automobile drive shaft deteriorates, the amplitude of the bending vibration increases, the vibration is severe, and even causes the vehicle body to shake and emit obvious periodic noises, which are called shaking and abnormal noise. The drive shaft of an automobile is aggravated with the increase of vehicle speed. The main reasons for the vibration and abnormal noise of the drive shaft are as follows.
1. The drive shaft assembly is out of balance Excessive assembly errors of the drive shaft assembly, inaccurate parts size and wear and deformation in use, etc. will cause uneven mass distribution along the length of the drive shaft, resulting in unbalanced transmission.
An unbalanced drive shaft will generate additional bending moments during operation. The effect of the additional bending moments will not only make the mating parts impact, but also enhance the bending vibration of the drive shaft, making the vibration and abnormal noise of the drive shaft more obvious.
2. Universal joint damage The main damage of the universal joint in use is the wear of the cross shaft journal and end face, and the wear of the needle roller and the bearing seat hole.
The damage of the universal joint parts causes the cross shaft to oscillate and axially move due to the loose fit, which not only makes an impact sound during work, but also weakens the bending rigidity of the transmission shaft. The center of mass of the drive shaft deviates further from the axis of rotation, thereby enhancing vibration and abnormal noise.
3. Damage to propeller shafts and sliding fork
The bending of the propeller shafts tube, that is, increasing the amplitude of the bending vibration of the cardan shaft, can increase the centrifugal force, resulting in strong vibration and abnormal noise.
The key teeth of the drive shaft and the sliding fork keyway are worn out. Due to the loose fit, they will make a crashing sound during work, which will also weaken the flexural rigidity of the drive shaft and increase vibration and abnormal noise.
4. The installation position of both ends of the drive shaft is changed For unequal angular velocity universal joint drive shafts, in order to reduce the vibration of the drive shaft and ensure the uniform rotation of the drive axle gears, the following two conditions must be met:
1) The universal joint forks at both ends of the drive shaft should be in the same plane;
2) The angles between the input shaft, output shaft and drive shaft should be equal. When the drive shaft is in use, due to the wear of the drive shaft’s key teeth and sliding fork keyway, the loosening of the universal joint-cross shaft journal and the roller needle, etc.
The first condition will be destroyed; and the drive shaft is poorly installed and elastic suspension technology Changes in conditions, wear of the input shaft and output shaft of the drive shaft, and changes in the installation position, etc., will destroy the second condition.
With the destruction of the constant speed transmission conditions, the drive axle main reduction gear will have an impact, and cause unstable operation of the transmission shaft, and increase jitter and abnormal noise.
5. The critical speed of the drive shaft is reduced The maximum speed of the drive shaft is generally 0.7 times the critical speed.
However, due to the destruction of the dynamic balance of the transmission shaft, the damage of the universal joint and the looseness of the intermediate support bearing, etc., the critical speed of the transmission shaft will be reduced.
When the critical speed is reduced to the speed of the drive shaft, the drive shaft is prone to resonance during operation. When the drive shaft resonates, the amplitude is the largest, and the vibration is severe, which often causes the drive shaft to break.