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Cause analysis and diagnosis of torsional vibration jitter of transmission shaft
  • Automotive

The drive shaft is used to connect the output shaft of the transmission and the driving shaft of the main transmission on the farm transporter. In the course of farm transporter, the transmission shaft must bear a lot of torque and impact load. At the same time, with the high speed rotation, with the constant vibration, its lubrication condition is poor, it is easy to produce wear, deformation and damage, and there will be torsional vibration jitter and other faults. The failure of the transmission shaft is caused by the loss of dynamic balance of the transmission shaft. Therefore, when the speed reaches a certain speed, it will generate resonance. There are many hazards in the vibration of the transmission shaft, which will produce noise, reduce the transmission efficiency, produce coordination loosening, and even make the component break, resulting in the occurrence of the accident. 1. the transmission shaft is long and long, the supporting points of the two ends are far away from the stiffness. After long term use (or after overhaul), the central part of the transmission shaft will produce a little bending deformation under the action of self weight, which makes the center of the transmission shaft deviate from the center line of rotation: centrifugal force and centrifugal force are produced in operation due to the existence of the offset. It also aggravates the bending of the shaft. When the drive shaft rotates at high speed, the vibration cycle and the external force cycle are resonating at the same time, which causes the torsional vibration phenomenon at high speed, and is accompanied by noise. 2. long term use, often because the axis of the center of rotation does not coincide with the heart line, or the material quality distribution is not uniform (the tube wall thickness is not uniform), and the installation is not correct or the plane block shedding causes, the imbalance will produce large centrifugal force, this centrifugal force can cause the axis to bend. When the speed increases to a certain value, the bending deformation of the shaft will be close to infinity, causing the shaft to break and the rotational speed at that time is "dangerous rotational speed". "Dangerous speed" is the most dangerous state of the transmission shaft. Some people also call the dangerous speed "critical speed". 3. because the speed of the drive shaft is very high, its rotation time is changing, the imbalance produces large centrifugal force in the size and direction, the light produces vibration, and the weight will cause the bending and torsion deformation, which makes the wear bond, the middle bearing, the universal joint of the universal joint and so on. The transmission shaft will also generate strong noise, and the steering wheel will tremble, so that the vehicle will not be able to drive at high speed. 4. the wear, deformation or improper installation of the parts of the drive shaft assembly will increase the radial runout of the transmission shaft, and the shaft will produce jitter and abnormal sound. If it is not eliminated in time, it will cause a broken shaft accident. 5. the rotation centerline of the transmission shaft does not coincide with the axis of the transmission shaft itself. The reason is the error of the center of the cross shaft; the end of the neck of each axis is not positive to the center; the bearing and the journal have a large amount of loose and open, the cross axis sloshing, causing the axis of the shaft and the rotation center line offset. Therefore, the cross axis should be replaced in time. 6. universal joint damage: the damage of the part of the universal joint causes the swing and axial movement of the cross shaft in combination with the loose and loose. It not only sends out the sound of the impact in the work, but also weakens the bending strength of the transmission shaft: the mass center of the transmission shaft is more deviated from the axis of rotation, thus enhancing the jitter and the abnormal sound. At the start of the 1. car, the body trembled and heard the click of a crash. When the speed was changed, especially when the speed was slow, the noise became more pronounced. Mainly: the loosening of the connection of the driving shaft flange; the wear loose or needle roller fracture of the universal joint bearing; the loose and loose spline of the spline; the loosening of the expansion joints; the loosening of the positioning bolt of the driving bridge; the loosening or loosening of the fixed bolt of the middle support bracket; the wear of the middle bearing or the lack of oil. Troubleshooting: fastening bolts, changing worn parts and filling grease. 2. vehicles start without noise. There is sound in traffic. The main points are: the universal joints at both ends of the transmission shaft are not in the same plane; the isometric and unequal angular velocity universal joints are unsuitable or too tight; the bearings in various places are not lubricated; the intermediate bearings are not installed; the intermediate bearings are damaged. Method of elimination: because of improper assembly, it should be reassembled; damaged parts should be replaced and grease filled. When the 3. cars are running, they hear a cyclical noise. The faster the speed is, the louder the sound is, and the body trembles when it is serious. The main parts are: the transmission shaft is bent; the transmission flange of the uranium is skewed with the axle tube; the transmission shaft is not balanced; the anchor bolts of the middle hanger are loose or the hole position is deflected. 4. the vibration occurs when the vehicle stops or at a slow speed because of the loosening of the universal joint. The repair method is to fasten or replace the universal joint. 5. noise at low speed or variable speed is usually caused by loose parts. If you use your hands to rotate the drive shaft, you can feel it if you loose. If the sliding fork spline, cross shaft and needle roller bearings are seriously worn, the entire transmission shaft should be replaced. The transmission shaft is subjected to strict dynamic balance test, so it can not be decomposed at will. 6. the driving shaft of the vehicle has abnormal sound while vibrating. The transmission shaft is bent and deformed, the shaft pipe is broken, the shaft balance block falls off or is not installed according to the assembly mark; the rotary center of the universal joint is not on the axis of the transmission shaft; the engine is not fixed; the other parts of the universal transmission device are not balanced; the positioning of the middle bearing support is loose or skewed, and the dynamic balance damage should be seriously replaced by the transmission shaft. Adjust the installation of universal joint, tighten the engine and adjust the middle support. 7. there is a cyclical noise at high speed. When the accelerator is throttle, there is a crash of "laleng and Lun". When the speed and stability of the throttle is shivering, when the steering wheel has numbness, the rear axle of the vehicle can be stopped and the engine hangs high speed to look at the shimmy of the drive shaft, especially when the speed drops, which is caused by the unbalance of the drive shaft and should be overhauled seriously. The side of the rear wheel is erected, the wheel is rotated, the drive shaft is rotated, and the shaft is bent with a chalk bracket or a pin. In addition, the technical status of the cardan fork and the intermediate shaft support should also be checked, such as the loosening of the wear and tear of the cross shaft and the needle roller because of the disassembly of the shaft and the wear of the needle, so that the shaft assembly will lose balance and should be repaired or replaced.