重型载货汽车根据驱动形式的不同选择不同型式的传动轴。一般来讲4×2驱动形式的汽车仅有一根主传动轴。6×4驱动形式的汽车有中间传动轴、主传动轴和中、后桥传动轴。6×6驱动形式的汽车不仅有中间传动轴、主传动轴和中、后桥传动轴，而且还有前桥驱动传动轴。在长轴距车辆的中间传动轴一般设有传动轴中间支承．它是由支承架、轴承和橡胶支承组成。

　　The drive shaft is composed of a shaft tube, a telescopic sleeve and a universal joint.The telescopic sleeve can automatically adjust the distance between the transmission and the drive axle.The universal joint guarantees the change of the angle between the output shaft of the transmission and the input shaft of the drive axle, and realizes the constant angular speed transmission of the two shafts.Generally, it is composed of universal joint cross shaft, cross bearing and flange fork.The universal joint of the drive shaft used in the Steyr series of heavy-duty vehicles adopts roller cross shaft bearings, combined with a short and thick cross shaft, which can transmit a larger torque.A butterfly spring is provided on the end face of the bearing to compress the roller.A reinforced nylon gasket with spiral grooves is added to the end of the cross shaft to prevent sintering when the power is transmitted with a large angle or a large torque.

　　In the traditional structure of the transmission shaft telescopic sleeve, the spline sleeve and the flange fork are welded together, and the spline shaft is welded to the transmission shaft tube.The transmission shaft of GWB Company changed the traditional structure, welded the spline sleeve and the transmission shaft tube into one body, and made the spline shaft and the flange fork into one body.The rectangular tooth spline is changed to a large pressure angle involute short tooth spline, which not only increases the strength but also facilitates the extrusion forming, and meets the needs of high torque working conditions.The tooth surface of the telescopic sleeve and spline shaft is coated with a layer of nylon material, which not only increases the wear resistance and self-lubricity, but also reduces the impact load on the drive shaft and improves the cushioning capacity.

　　This type of transmission shaft adds a tube-shaped sealing protective sleeve outside the flange spline shaft. Two polyurethane rubber oil seals are set at the end of the protective sleeve to form a completely sealed space in the factory to make the telescopic spline The shaft is not corroded by external sand and dust, not only dustproof but also rustproof.Therefore, when assembling, applying grease to the spline shaft and the sleeve at one time can fully meet the requirements of use, and there is no need to install a grease nipple for lubrication, which reduces the maintenance content.

　　The drive shaft is a rotating body with high speed and less support, so its dynamic balance is very important.Generally, the drive shaft must undergo a dynamic balance test before leaving the factory and be adjusted on a balance machine.Therefore, a set of drive shafts are delivered as a complete set, so special attention should be paid to them during use.
Transmission shaft classification [Edit this paragraph] 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 drive shaft and flexible universal joint drive shaft.The former relies on the hinged connection of parts to transmit power, while the latter relies on elastic parts to transmit power, and has the effect of buffering and damping.Rigid universal joints can be divided into unequal velocity universal joints (such as cross-shaft universal joints), quasi-constant velocity universal joints (such as duplex universal joints, three-pin shaft universal joints) and constant velocity universal joints. Universal joints (such as ball cage universal joints, ball fork universal joints).Constant speed and unequal speed refer to whether the rotational angular velocity of the driven shaft is equal when the driven shaft rotates with the driving shaft. Of course, the average speed of the driving shaft and the driven shaft are equal.A universal joint whose angular velocity of the main and driven shafts is still equal when the angle between the two shafts changes is called a constant velocity universal joint or a constant angular velocity universal joint.They are mainly used in wheel transmission devices such as steering drive axles and disconnected drive axles, and are mainly used for power transmission in cars.When the car is rear-wheel drive, the cross-shaft universal joint drive shaft is often used. For some high-end cars, constant velocity ball joints are also used; when the car is front-wheel drive, constant velocity universal joints are often used-etc. Speed ​​universal joint is also a kind of transmission shaft, but the title is different.
Important parts of the drive shaft [Edit this paragraph] Universal joint is the key part of the car drive shaft.On the front-engine rear-wheel drive vehicle, the universal joint drive shaft is installed between the transmission output shaft and the drive axle final drive input shaft; while the front-engine front-wheel drive vehicle omits the drive shaft, and the universal joint is installed Between the front axle half shaft and the wheels, which are responsible for both driving and steering.The car is a moving object.In a rear-drive car, the engine, clutch, and transmission are installed on the frame as a whole, and the drive axle is connected to the frame through an elastic suspension. There is a distance between the two, which needs to be connected.During the operation of the car, uneven road surface bounces, load changes or differences in the installation positions of the two assemblies will cause the angle and distance between the transmission output shaft and the input shaft of the drive axle final reducer to change. Therefore, it is necessary to use a "to change the strain". "" device to solve this problem, so there is a universal joint.

In a car with front-engine rear-wheel drive (or all-wheel drive), due to the deformation of the suspension during the movement of the car, there is often relative movement between the input shaft of the drive shaft final drive and the output shaft of the transmission (or transfer case). In addition, in order to effectively avoid certain mechanisms or devices (which cannot achieve linear transmission), there must be a device to achieve the normal transmission of power, so universal joint transmission appears.The universal joint drive must have the following characteristics: a. Ensure that the relative position of the two connected shafts changes within the expected range, and can reliably transmit power; b. Ensure that the two connected shafts can run evenly.The additional load, vibration and noise caused by the angle of the universal joint should be within the allowable range; c. The transmission efficiency should be high, the service life is long, the structure is simple, the manufacturing is convenient, and the maintenance is easy.For automobiles, since the output shaft of a cross-shaft universal joint rotates at unequal speeds relative to the input shaft (with a certain included angle), a double universal joint (or multiple universal joint) transmission must be adopted for this purpose. The two universal joint forks connected with the drive shaft are arranged on the same plane, and the angles of the two universal joints are equal.This is very important.In the design, the angle of the universal joint should be minimized.
Commonly used types [Edit this paragraph] Cross-shaft rigid universal joint drive shafts are the most widely used in automobile drive trains and have the longest history.The drive shaft usually refers to the cross shaft type rigid universal joint drive shaft.Cross-shaft rigid universal joints are mainly used to transfer angle changes, generally by flange fork, cross shaft with needle roller bearing assembly, universal joint fork or sliding fork, intermediate connecting fork or spline shaft fork, needle bearing The axial fixed parts and so on.The flange fork is generally connected with a gearbox, drive axle, or other drive shafts.The flange fork is a fork-shaped part with a flange, generally forging parts of medium carbon steel or medium carbon alloy steel, sand casting parts of nodular cast iron and precision casting parts of medium carbon steel or medium carbon high-quality alloy steel.The flange fork generally has a flat flange, but also has a trapezoidal tooth flange on the end face.The cross shaft with needle roller bearing assembly generally includes four needle roller bearings, a cross shaft, and a grease nipple.Needle roller bearings are generally composed of several needle rollers, a bearing bowl, and a multi-blade rubber oil seal (partly with a skeleton).In some needle roller bearings, there is also a circular gasket with an oil groove, which is made of nylon, copper or other materials, which is mainly used to reduce the axial gap of the universal joint and improve the quality of the dynamic balance of the drive shaft. .The universal joint fork is a fork-shaped part, generally forged parts 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 (internal and external clamping type) for holes (or shafts), or bearing pressure plates, lock plates, bolts, etc.

Another important part of the drive shaft is the sliding spline pair, which is composed of inner and outer splines (rectangular, involute), used to transmit changes in length.The swivel angle of the universal joint of the transmission shaft and the maximum expansion and contraction of the sliding spline pair are determined according to the check of the transmission shaft runout when the whole vehicle is arranged.The transmission shaft tube is generally made of electric welded steel pipe rolled by low carbon steel plate. For large-size shaft tubes, cold drawn seamless tubes are also used.The outer diameter and wall thickness (or inner diameter) of the shaft tube are determined according to conditions such as the maximum working torque and maximum working speed transmitted by the drive shaft.The hollow shaft tube has a smaller mass and can transmit a larger torque, and has the characteristics of a higher critical speed than a solid shaft with the same outer diameter.In general, the center distance between two universal joints is not more than 1.5m.When the distance is relatively close, it is generally composed of two universal joints and a sliding spline pair, and there is no shaft tube in the middle.When the distance is far and the length of the drive shaft exceeds 1.5m, it is often divided into two or three, three or four universal joints are used, and the last one has a sliding spline pair, and the rest have a structural type with intermediate support .A typical intermediate support generally consists of a cylindrical ball bearing, a bearing seat, two oil seals, a rubber pad, and a grease nipple.The intermediate transmission shaft is connected to the frame beam by an intermediate support bracket, and the axis of the intermediate transmission shaft is required to be perpendicular to the intermediate support plane.It is generally required that the intermediate support of the transmission shaft is arranged at the first-order critical speed node of the transmission shaft system.During use, maintenance is generally required on time.Where there are grease nipples such as universal joints, sliding spline pairs, intermediate supports, etc., the prescribed grease should be regularly filled in accordance with relevant regulations.There are also maintenance-free drive shafts. There are reserved grease in the universal joints and the bearings of the intermediate support, so there is no need to regularly add grease.　
Diagnosis and troubleshooting of common faults of the drive shaft [Edit this paragraph] The damage, wear, deformation and loss of dynamic balance of the drive shaft components will cause abnormal noise and vibration when the car is driving, and will cause damage to related parts in severe cases.When the car is running, it makes a "Gordon" sound when it starts or accelerates rapidly, and it clearly shows the feeling of loose parts. If it is not the loosening of the drive axle transmission gear, it is obviously the loosening of the drive shaft.The loose parts are nothing more than universal joint cross bearings or steel bowl and flange fork, the spline shaft and spline sleeve of the telescopic sleeve.Generally speaking, the cross shaft diameter and the bearing openness should not exceed 0.13mm, and the meshing gap between the telescopic spline shaft and the spline sleeve should not exceed 0.3mm.Exceeding the service limit should be repaired or replaced.

　　If the chassis makes a "humming" sound while the car is running, and the higher the running speed, the louder the sound.This is generally caused by the wear and tear of the universal joint cross shaft and the bearing, the middle bearing of the transmission shaft, the damage of the intermediate rubber support or the loosening of the hanger, or the fixed position of the hanger.

　　When a 6×4 car is under heavy load, especially when driving bumps, it occasionally makes a knocking sound. Pay attention to check whether the balance shaft of the middle and rear axle is displaced and interferes with the transmission shaft.If the noise increases with the increase of the vehicle speed during the operation of the car, and is accompanied by jitter, this is generally caused by the loss of balance of the transmission shaft.This kind of vibration is most noticeable in the cab.The unbalance of the dynamic balance of the drive shaft should be less than 100g.cm.

　　A serious failure of the dynamic balance of the drive shaft will cause damage to related components.The most common are the clutch shell cracks and the fatigue damage of the middle rubber support.

　　The installation of the intermediate hanger of the transmission shaft is very important in maintenance.If the hanger is installed in an improper position, it will increase the running resistance and noise of the drive shaft, resulting in early damage to the bearing.When reinstalling the hanger, first do not tighten the fixing bolts of the hanger, jack the car drive wheel off the ground, hang the low gear, slowly rotate the drive shaft to make the drive shaft and the hanger automatically align, and then fix the hanger Tighten the bolts.

　　The use and maintenance of the drive shaft [edit this paragraph]

　　In order to ensure the normal operation of the drive shaft and prolong its service life, pay attention to:

　　1.It is strictly forbidden for a car to start at a high gear.

　　2.It is strictly forbidden to lift the clutch pedal violently.

　　3.It is strictly forbidden to overload and speed vehicles.

　　4.The working condition of the drive shaft should be checked frequently.

　　5.Always check the tightness of the transmission shaft hanger, whether the supporting rubber is damaged, whether each 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 drive shaft, you should always pay attention to whether the balance pads are unsoldered.The new drive shaft assembly is provided as a complete set. When installing the new drive shaft, pay attention to the assembly mark of the telescopic sleeve and ensure that the flange fork is in a plane.When repairing and disassembling the drive shaft, the assembly mark should be printed on the telescopic sleeve and the flange shaft in order to keep the original assembly relationship unchanged during reassembly.

　　7.Grease should be frequently added to the universal joint cross bearing. In summer, No. 3 lithium grease should be injected, and in winter, No. 2 lithium grease should be injected.