This paper introduces the composition of transmission shaft: shaft tube, telescopic sleeve and universal joint transmission shaft; Transmission characteristics: high transmission efficiency and long service life; The function of telescopic sleeve: welding spline sleeve and flange fork together; Function, structure, universal joint, telescopic sleeve, shaft sleeve, type, elasticity, angular velocity, power performance, use and maintenance, fault maintenance, wear and balance, and work transmission shaft are important parts of automobile transmission system to transmit power. Its function is to transfer the power of the engine to the wheels together with the gearbox and drive axle, so that the car can generate driving force. The purpose of the transmission shaft The transmission shaft for special purpose vehicles is mainly used for tankers, fuel trucks, sprinklers, sewage suction vehicles, dung suction vehicles, fire engines, high-pressure cleaning vehicles, road wreckers, aerial work vehicles, garbage trucks and other vehicles. The structural transmission shaft consists of shaft tube, telescopic sleeve and universal joint. The telescopic sleeve can automatically adjust the change of the distance between the transmission and the drive axle. Universal joint is to ensure the change of the included angle between the transmission output shaft and the drive axle input shaft, and realize the equal angular velocity transmission of the two shafts. Universal joint universal joint is the key component of automobile transmission shaft. A car is a moving object. In a rear-drive car, the engine, clutch and transmission are installed on the frame as a whole, while the drive axle is connected with the frame through an elastic suspension, and there is a distance between them, so they need to be connected. When the car is driving, the uneven road surface jumps. Universal universal joint consists of spider, spider bearing and flange fork. Universal joint is the key component of automobile transmission shaft. On vehicles with front engine and rear wheel drive, the universal joint transmission shaft is installed between the output shaft of the transmission and the input shaft of the main reducer of the drive axle; Vehicles with front engine and front wheel drive omit the transmission shaft, and a universal joint is installed between the front axle and the wheel, which is responsible for both driving and steering. When the vehicle is running, the included angle and distance between the output shaft of the transmission and the input shaft of the main reducer of the drive axle will change due to uneven road surface, load change or different installation positions of the two assemblies. Therefore, a "variable strain" device is needed to solve this problem, so there is a universal joint. In the automobile with front engine and rear wheel drive (or all-wheel drive), there is often relative motion between the input shaft of the main reducer of the transmission shaft and the output shaft of the transmission (or transfer case) due to the deformation of the suspension during the movement of the automobile. In addition, in order to effectively avoid some mechanisms or devices (which can not realize linear transmission), there must be a device to realize the normal transmission of power, so universal joint transmission appeared. Universal joint drive must have the following characteristics: a, ensure that the relative position of two connecting shafts changes within the expected range and can transmit power reliably; B, ensure that the two connected shafts can run evenly. The additional load, vibration and noise caused by the included angle of the universal joint should be within the allowable range; C, high transmission efficiency, long service life, simple structure, convenient manufacture and easy maintenance. For automobiles, because the output shaft of a spider universal joint does not rotate at the same speed relative to the input shaft (with a certain angle), it is necessary to use double universal joints (or multi-universal joints) for transmission, arrange the two universal joint forks connected with the transmission shaft on the same plane, and make the angles of the two universal joints equal. This is very important. The included angle of the universal joint should be minimized in the design. Telescopic sleeve In the traditional structure, the telescopic sleeve of the transmission shaft is welded together with the spline sleeve and the flange fork, and the spline shaft is welded on the transmission shaft tube. The new transmission shaft changes the traditional structure, welding the spline sleeve and the transmission shaft tube into a whole, and making the spline shaft and the flange fork into a whole. Changing rectangular spline into involute short spline with large pressure angle not only increases strength, but also facilitates extrusion forming, which meets the needs of high torque working conditions. The tooth surfaces of the telescopic sleeve and the spline shaft are integrally coated with a layer of nylon material, which not only improves the wear resistance and self-lubrication, but also reduces the damage of impact load to the transmission shaft and improves the buffering capacity. A tubular sealing protective sleeve is added outside the spline shaft of the transmission shaft flange, and two polyurethane rubber oil seals are arranged at the end of the protective sleeve, so that a completely sealed space is formed in the telescopic sleeve, and the telescopic spline shaft is not corroded by external dust, which is dustproof and antirust. Therefore, when assembling, the spline shaft and the sleeve are coated with grease at one time, which can completely meet the use requirements, without lubrication of the oiler, and the maintenance content is reduced. The design of the shaft sleeve is to reduce the friction and wear when the shaft moves. Its basic use is the same as that of bearings, and its relative cost is relatively low, but its friction resistance is large, so it will only be used in some parts. Bushings are mostly made of copper, but there are also plastic bushings. Most of the shaft sleeves are placed in the shaft and supporting structure, and they are very close to the supporting structure. Only the shaft can rotate on the shaft sleeve. When assembling the shaft and sleeve, lubricant will be added between them to reduce the friction generated when they rotate. The types of transmission shafts can be classified according to their important components-universal joints. According to whether the universal joint has obvious elasticity in the torsion direction, it can be divided into rigid universal joint transmission shaft and flexible universal joint transmission shaft. 1. Rigid universal joint: Power is transmitted through the articulation of parts. 2. Flexible universal joint: the power is transmitted by elastic parts, which has the function of cushioning and vibration reduction. Rigid universal joints can be divided into non-constant velocity universal joints (such as spider universal joints), quasi-constant velocity universal joints (such as double universal joints and three-pin universal joints) and constant velocity universal joints (such as ball cage universal joints and ball fork universal joints) according to angular velocity. Constant speed and unequal speed refer to whether the rotational angular velocity of the driven shaft is equal when it rotates with the driving shaft. Of course, the average rotational speeds of the driving shaft and the driven shaft are equal. 1. Constant velocity universal joint: When the included angle between the two shafts changes, the universal joint whose angular velocity of the driving shaft and the driven shaft is still equal is called constant velocity universal joint or constant angular velocity universal joint. Mainly used for steering drive axle, disconnecting drive axle and other wheel transmission devices, mainly used for power transmission in automobiles. 2. Non-constant velocity universal joint: When the included angle between the two shafts changes, the angular velocity of the driving shaft and the driven shaft is not equal, which is called non-constant velocity universal joint, also called cross shaft universal joint. Cross-shaft rigid universal joint transmission shaft is widely used in automobile transmission system and has the longest history. When driving the rear wheel of an automobile, the cross-shaft universal joint transmission shaft is often used, and for some high-end cars, the constant velocity ball head is also used; Constant velocity joint (CV joint) is often used in front-wheel drive of automobiles-CV joint is also a kind of transmission shaft, but its name is different. The transmission shaft usually refers to the transmission shaft of the cross shaft rigid universal joint. The rigid universal joint of cross shaft is mainly used to transmit the change of angle, and generally consists of flange fork, cross shaft bearing assembly with needle roller, universal joint fork or sliding fork, intermediate connecting fork or splined shaft fork, axial fixing parts of needle roller bearing, etc. Flange fork is a forked part with flange. Generally, forgings of medium carbon steel or medium carbon alloy steel, sand castings of nodular cast iron and precision castings of medium carbon steel or medium carbon high quality alloy steel are used. Flange forks generally have flat flanges, and some ends have trapezoidal tooth flanges. The spider bearing assembly with needle roller usually includes four needle roller bearings, a spider and a grease nozzle. Needle roller bearings are generally composed of several needles, a bearing bowl and a multi-blade rubber oil seal (partially with a skeleton). In some needle bearings, there is also a circular gasket with oil groove, which is made of nylon, copper or other materials and is mainly used to reduce the axial clearance of universal joint and improve the dynamic balance quality of transmission shaft. Universal joint fork is a fork, which is generally made of forgings of medium carbon steel or medium carbon alloy steel and precision castings of medium carbon steel. The axial fixing parts of needle roller bearings are generally elastic retaining rings of holes (or shafts), or bearing pressure plates, locking plates, bolts, etc. In the process of car trading, we must carry out a road test. However, the power of the vehicle must be considered during the road test. So, what is the driving force of the car? The dynamic performance of an automobile refers to the process of the automobile running in a straight line on a good road surface, and the corresponding driving performance can be determined by the longitudinal external force, which can meet the requirements of the average driving speed. From this definition, it can be seen that for roads, it must be a good road surface, horizontal or inclined, and the movement mode can take the process of driving in a straight line. For external factors, the basis of movement can be determined by longitudinal external forces, so that it can reach a certain ability. For sports ability, there are three main indicators, such as the maximum speed of the car, acceleration time and maximum climbing degree. If a car can reach the maximum speed when driving on a good level road, we call it the maximum speed. For the acceleration time, it is usually the acceleration time of starting in place and the acceleration time of overtaking, which shows the acceleration ability of the car. "T" means the time to start in the same place, usually starting in the first or second gear and gradually shifting gears. If you drive to a predetermined distance, the time it takes to speed up. It's time to start from the same place. The acceleration time of overtaking can also be expressed by "t". On some expressways with a speed of about 30 or 4, it takes time for some cars with the largest secondary gear to accelerate completely. Use and maintenance In order to ensure the normal operation of the transmission shaft and prolong its service life, attention should be paid to: 1. It is forbidden to start the car in high gear. 2. It is forbidden to slam on the clutch pedal. 3. Overloading and speeding are strictly prohibited. 4. Be sure to check the working condition of the transmission shaft. 5. Always check the fastening of the transmission shaft hanger, whether the supporting rubber is damaged, whether the connection part of the transmission shaft is loose, and whether the transmission shaft is deformed. 6. In order to ensure the dynamic balance of the transmission shaft, always pay attention to whether the balanced weldments are off-welded. The new drive shaft assembly is provided as a complete set. When installing a new transmission shaft, pay attention to the assembly mark of the telescopic sleeve to ensure that the flange fork is in a plane. When repairing and disassembling the transmission shaft, assembly marks should be printed on the telescopic sleeve and flange shaft, so as to keep the original assembly relationship unchanged when reassembling. 7. The universal joint spider must be filled with grease, with No.3 lithium-based grease in summer and No.2 lithium-based grease in winter. Failure, maintenance and wear of the transmission shaft, damage, wear, deformation and loss of dynamic balance of the transmission shaft parts will cause abnormal sound and vibration when the car is driving, and even lead to damage of related components in serious cases. When the car is driving, it will make a "Gordon" sound when it starts or accelerates rapidly, which obviously shows the feeling of loose parts. If the driving gear of the drive axle is not loose, it is obviously that the parts of the drive shaft are loose. Loose parts are nothing more than universal joint cross shaft or steel bowl and flange fork, spline shaft and spline sleeve of telescopic sleeve. Generally speaking, the clearance between the diameter of the cross shaft and the bearing should not exceed 0. 13mm, and the meshing clearance between the telescopic spline shaft and the spline sleeve should not be greater than 0.3 mm. If it exceeds the service limit, it should be repaired or replaced. If the chassis hums when the car is driving, and the higher the driving speed, the louder the sound. This is generally due to the wear and tear of the universal joint spider and bearing, the wear and tear of the intermediate bearing of the transmission shaft, the damage of the intermediate rubber bearing or the looseness of the hanger, or the wrong fixed position of the hanger. 1) the traditional methods of transmission shaft wear in China are generally repair welding, sleeve insertion and pitting corrosion. However, when the important official 45 # steel (quenched and tempered) is manufactured, if only surfacing treatment is used, welding internal stress will occur, and cracks or even fractures may occur in the shoulder under heavy load or high speed operation. If stress-relieving annealing is adopted, the operation is difficult, the processing cycle is long and the maintenance cost is high. When the material of important officials is HT200, it is not ideal to use cast iron for welding. Some enterprises with high maintenance technology will adopt brush plating, laser welding, micro-arc welding and even cold welding. These maintenance techniques are often demanding and costly. 2) The latest maintenance methods of the above repair technologies are not common in enterprises in Europe, America, Japan and South Korea. In developed countries, polymer composite technology and nanotechnology are generally adopted. Polymer technology can be operated on site, which can effectively improve maintenance efficiency and reduce maintenance cost and intensity, among which Meijiahua technology system is the most widely used. Compared with the traditional technology, polymer composites not only have the strength and hardness required by metals, but also have the concession (variable relationship) that metals do not have. Through the processes of "mold repair", "component matching" and "machining", the size matching between the repaired parts and the matching parts is ensured to the maximum extent; At the same time, the comprehensive advantages of composite materials such as compression resistance, bending resistance and ductility can effectively absorb the impact of external forces, greatly resolve and offset the radial impact of bearings on the shaft, and avoid the possibility of gaps, which also avoids the secondary wear of equipment due to the increase of gaps. Symptom diagnosis of the balance problem: When the 6×4 car is under heavy load, especially when it bumps, it is necessary to check whether the balance shaft of the middle and rear axle is displaced or not and whether it interferes with the transmission shaft. If the noise increases with the increase of vehicle speed, accompanied by jitter, it is generally because the transmission shaft is unbalanced. This vibration is most obvious in the cab. The unbalance of the dynamic balance of the transmission shaft should be less than100 g.cm. Serious failure of dynamic balance of transmission shaft will lead to damage of related components. The most common are the cracks in the clutch housing and the fatigue damage of the intermediate rubber bearing. Solution: plug the front wheel of the car with a wedge, and lift the middle and rear drive axles on one side of the car with a jack; Start the engine, shift to high gear and observe the shimmy of the transmission shaft. When observing, it should be noted that if the shimmy increases obviously when the speed decreases, it means that the transmission shaft is bent or the flange is skewed. The bending of the transmission shaft is the bending of the shaft tube, which is mostly caused by the overload of the car. Due to the overload and overhang of coal transport vehicles, there are many bending and fracture faults of transmission shafts. If some cars and trailers haul more than 60 tons of coal, the transmission shaft is seriously damaged due to overload and over-hanging. Although the middle support of the transmission shaft is strengthened and the strength of the flange fork is strengthened, the failure of fracture and damage still occurs from time to time. After replacing the transmission shaft parts and straightening them, check the balance, and the unbalance should meet the standard requirements. The technical conditions of universal joint fork and transmission shaft hanger should also be inspected in detail. If the installation does not meet the requirements, the spider and roller will be damaged, resulting in looseness and vibration, which will also make the transmission shaft out of balance.