The drive shaft is composed of a shaft tube, a telescopic sleeve and a universal joint. The telescopic sleeve automatically adjusts the distance between the transmission and the transaxle. The universal joint is to ensure the change of the Angle between the two axes of the transmission output shaft and the drive axle input shaft, and to achieve the equal angular speed transmission of the two axes.

The universal joint is the key component of the automobile drive shaft. On front-engine rear-wheel drive vehicles, the universal-joint drive shaft is installed between the transmission output shaft and the drive axle main reducer input shaft; The front-engine front-wheel drive vehicle omits the drive shaft, and the universal joint is installed between the front axle axle and the wheel, which is responsible for both driving and steering

一，Fault cause

 The drive shaft is slender, the supporting points at both ends are far away, the stiffness is not large, after long-term use (or after overhaul), under the action of self-weight, the middle of the drive shaft will produce a trace bending deformation, so that the mass center of the drive shaft and the rotating center line are offset: due to the existence of the offset, the centrifugal force is generated in the operation, and the centrifugal force intensifies the bending of the shaft. When the transmission shaft rotates at high speed, its own vibration period and external force action period resonate at the same time, which causes torsional vibration and noise at high speed.

After long-term use, often because the rotating center of the shaft does not coincide with its center line, or the material mass distribution is not uniform (pipe wall thickness is different), and the installation is not correct or the flat block falls off, the imbalance will produce a great centrifugal force, which can cause the shaft to bend. When the speed increases to a certain value, the bending deformation of the shaft will be close to infinity, causing the drive shaft to break, and the speed at this time is "dangerous speed". "Dangerous speed" is the most dangerous state of the drive shaft, and some people also call "dangerous speed" "critical speed".

Due to the high speed of the drive shaft, its rotation time is changing, the imbalance produces a large centrifugal force that changes in size and direction, the light will produce vibration, the heavy will cause bending and torsional deformation, so that the drive shaft spline, intermediate bearings, universal joint cross shaft journal wear intensification, serious will make the body tremble, the drive shaft will also produce strong noise, the steering wheel will tremble, and the steering wheel will be weak. Making it impossible for vehicles to travel at high speeds.

The wear, deformation or improper installation of each part of the drive shaft assembly will increase the radial runout of the drive shaft, and the drive shaft will produce jitter and abnormal sound. If it is not eliminated in time, it will cause a broken shaft accident.

The rotating center line of the drive shaft does not coincide with the axis of the drive shaft itself. The reason is that the center of the cross axis produces error; The end face of each journal is not centered; The bearing and journal have a large amount of slack, and the cross shaft wobbles, causing the axis line of the drive shaft to offset the rotating center line. Therefore, the cross shaft should be replaced in time after it is loose.

Universal joint damage: The damage of the universal joint parts makes the cross shaft swing and axial flapping with the loose, which not only makes a crash sound in the work, but also weakens the bending strength of the drive shaft: the center of mass of the drive shaft is more deviated from the rotation axis, thus enhancing the jitter and abnormal sound.

二，Fault diagnosis

When the car starts, the body shakes and there is a crash sound of "rolla, rolla", which is more obvious when changing the speed, especially when slowing down.

1.The main problems are: the connection of the transmission axon edge is loose; Universal-joint bearing wear loose or needle roller break; Spline wear loose; Expansion joints wear loose; Drive axle positioning bolt loose; The fixing bolt of the middle support bracket is loose or the tightness is improperly adjusted; Intermediate bearing wear or lack of oil.
Elimination method: tighten the bolts, replace the worn parts, and replenish the grease.

2.When the vehicle starts, it is no different, and there is sound in the driving.
Mainly: the cross shaft universal joint at both ends of the drive shaft is not in the same plane; Equiangular velocity and unequal angular velocity universals are improperly assembled or too tight; Poor lubrication of bearings everywhere; Improper installation of intermediate bearings; Intermediate bearing damaged. Elimination method: due to improper assembly, it should be reassembled; Damaged parts should be replaced and greased.

3.When the car is driving, it hears a periodic sound, the faster the speed, the louder the sound, and the body shakes seriously.
The main ones are: drive shaft bending; The transmission uranium flange and shaft tube welding skew; Drive shaft unbalance; The fixing bolts of the middle hanger are loose or the eye holes are tilted.

4.Vibration occurs when the vehicle is stopped or slow, which is caused by the loosening of the universal joint. The maintenance method is to tighten or replace the universal joint.

5.Noise at low speed or variable speed is generally caused by wear and loose parts. Turn the drive shaft forward and backward by hand, and feel it if it is loose. If the sliding fork splines, cross shaft and needle roller bearings are seriously worn, the entire drive shaft should be replaced. The drive shaft is subjected to a strict dynamic balance test, so it cannot be decomposed at will.

6.When the vehicle is driving, the drive shaft has abnormal sound and oscillates at the same time.
The drive shaft is bent and deformed, and the shaft tube is dented and damaged. The drive shaft balance block falls off or is not installed according to the assembly mark; The center of rotation of the universal joint is not on the axis of the drive shaft; Poor engine fixing; Other components of the universal transmission are not balanced; The intermediate bearing bracket is loose or skewed, and the drive shaft should be replaced if the dynamic balance is seriously damaged. Adjust the installation of the universal joint, tighten the engine, adjust the intermediate support.

7.There is a periodic sound at high speed, and there is a "clanging, clanging" crash sound when the throttle is sharply closed.
When the body shakes when the accelerator is stabilized at high speed, when the steering wheel is numb, the vehicle can stop and set up the rear axle of the vehicle, start the engine to hang the high-speed gear to see the swing vibration of the drive shaft, especially when the swing vibration is significantly increased when the speed is decreased, that is, the drive shaft is caused by imbalance, and should be repaired in serious cases. Set up one side of the rear wheel, turn the wheel to rotate the drive shaft, use a bracket with chalk or a marker to check whether the drive shaft is bent, if bent, it should be straightened. In addition, it should also check the technical status of the universal joint fork and intermediate shaft support, such as due to installation requirements, cross shaft and needle roller wear and fracture caused by loose, so that the drive shaft assembly out of balance, should be repaired or replaced.

Driving shaft

DriveShaft (DriveShaft) connecting or assembling various accessories, and can move or turn the round object accessories, generally made of light and torsion-resistant alloy steel pipe. For front-engined rear-wheel drive cars, this is the shaft that transmits the rotation of the transmission to the main reducer, which can be several joints connected by universals. It is a rotating body with high speed and little support, so its dynamic balance is crucial. Generally, the drive shaft should be tested for action balance before leaving the factory, and adjusted on the balancing machine.

effect
The drive shaft is an important part of the transmission of power in the automobile transmission system, and its role is to transmit the power of the engine to the wheels together with the gearbox and the drive axle, so that the car can produce driving force.

Purpose:
Special automobile transmission shaft is mainly used in tank trucks, refueling trucks, sprinklers, suction trucks, suction trucks, fire trucks, high-pressure cleaning vehicles, road wreckers, aerial work vehicles,

structure
The drive shaft is composed of a shaft tube, a telescopic sleeve and a universal joint. The telescopic sleeve automatically adjusts the distance between the transmission and the transaxle. The universal joint ensures the change of the Angle between the two axes of the transmission output shaft and the drive axle input shaft, and realizes the equiangular speed transmission of the two axes [1]. Universal joint The universal joint is the key component of the automobile drive shaft. A car is a moving object. On the rear-drive car, the engine, clutch and transmission are mounted on the frame as a whole, while the drive axle is connected to the frame by elastic suspension, with a distance between the two, which needs to be connected. The uneven road surface in the running of the car produces a jump.

1. Function:

The general universal joint is composed of a cross shaft, a cross bearing and a flange fork. The universal joint is the key component of the automobile drive shaft. On front-engine rear-wheel drive vehicles, the universal-joint drive shaft is installed between the transmission output shaft and the drive axle main reducer input shaft; The front-engine front-wheel drive vehicle omits the drive shaft, and the universal joint is installed between the front axle axle and the wheel, which is responsible for both driving and steering. The uneven road surface of the vehicle in operation produces a jump, the load changes or the difference in the installation position of the two assemblies, which will make the Angle and distance between the transmission output shaft and the drive axle main reducer input shaft change, so a "variable strain" device is used to solve this problem, so there is a universal joint.

2. Transmission features:
In the front and rear wheel drive (or all-wheel drive) car, due to the suspension deformation of the car during movement, the drive shaft main reducer input shaft and the transmission (or transfer box) output shaft often have relative motion, in addition, in order to effectively avoid some mechanisms or devices (can not achieve linear transmission), there must be a device to achieve the normal transmission of power. Thus came the universal-joint drive. Universal joint drive must have the following characteristics:

a, ensure that the relative position of the connected two axes change within the expected range, can reliably transmit power;

b, ensure that the connected two axes 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, long service life, simple structure, convenient manufacturing, easy maintenance. For the automobile, because the output shaft of a cross shaft universal joint is not rotating at the same speed relative to the input shaft (with a certain Angle), it is necessary to use double universal joint (or more than universal joint) transmission, and the two universal joint forks connected with the drive shaft are arranged in the same plane, and the Angle of the two universal joints is equal. This is very important. The Angle of the universal joint should be minimized in the design.

Telescopic sleeve

The traditional structure of the drive shaft expansion sleeve is spline sleeve and flange fork welded together, the spline shaft welded on the drive shaft tube. The new drive shaft changes the traditional structure, the spline sleeve and the drive shaft tube are welded into one.

The spline shaft is integrated with the flange fork. The rectangular spline is changed into a short spline with a large pressure Angle involute, which not only increases the strength but also facilitates extrusion forming and ADAPTS to the needs of high torque 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-lubrication, but also reduces the impact load damage to the drive shaft and improves the buffering capacity.

The drive shaft adds a tubular seal protective sleeve outside the flange spline shaft, and two PU rubber oil seals are arranged at the end of the protective sleeve, so that a completely sealed space is formed in the telescopic sleeve, so that the telescopic spline shaft is not corroded by external dust, not only dust and rust prevention. Therefore, in the assembly of the spline shaft and the sleeve one-time grease, it can fully meet the requirements of use, do not need to install oil nozzle lubrication, reduce the maintenance content.

The shaft sleeve is designed to reduce the friction and wear of the shaft movement, the basic purpose is the same as the bearing, and the relative cost is cheaper, but the friction resistance is larger, so it will only be used on some parts. Bushings are mostly made of copper, but there are also bushings made of plastic. The shaft sleeve is mostly placed in the shaft and support structure, and it is very close to the support structure, and only the shaft can be rotated on the shaft sleeve. When assembling the shaft and sleeve, a lubricant is added between them to reduce the friction generated during rotation.

Elastic fraction

The drive shaft can be classified differently according to its important parts - universal joints. If the universal joint has obvious elasticity in the direction of torsion, it can be divided into rigid universal joint drive shaft and flexible universal joint drive shaft.

1. Rigid universal joint: transmits power by hinge connection of parts.

2. Torsion universal joint: transfer power by elastic parts, and has a buffer reduction.

According to the angular rate, the rigid universal joint can be divided into unequal speed universal joints (such as cross shaft universal joints), quasi-constant speed universal joints (such as double universal joints, three-pin universal joints) and constant speed universal joints (such as ball cage universal joints, ball fork universal joints). Constant speed and unequal speed refer to whether the rotational angular rate of the driven shaft is equal when the driven shaft rotates with the drive shaft. Of course, the average rotational speed of the drive shaft and the driven shaft is equal.

1. Constant velocity universal joint:

The universal joint where the angular velocity of the main and driven axes is still equal when the Angle between the two axes changes is called the constant velocity universal joint or the constant angular velocity universal joint. They are mainly used in wheel transmission devices such as steering drive axle and broken drive axle, and are mainly used for power transmission in cars.

2. Unequal velocity universal joint:

The universal joint where the angular speed of the main and driven axes is not equal when the Angle between the two axes changes is called the unequal speed universal joint, also known as the cross-shaft universal joint.

The rigid universal-joint cross-shaft transmission shaft is the most widely used and has the longest history in the automobile transmission system. When the car is rear-wheel drive, the cross-shaft universal-joint drive shaft is often used, and some high-end cars also use the constant speed ball head; When the car is front-wheel drive, the constant speed universal joint is often used - the constant speed universal joint is also a transmission shaft, but the name is different. Usually said drive shaft generally refers to the cross shaft type rigid universal joint drive shaft. Cross shaft rigid universal joint is mainly used to transfer the change of Angle, generally by the flange fork, cross shaft with needle roller bearing assembly, universal joint fork or sliding fork, intermediate connection fork or spline shaft fork, needle roller bearing axial fixed parts.

Flanged fork is a fork shaped part with flange, generally using medium carbon steel or medium carbon alloy steel forging parts, there are also sand casting parts using ductile iron and medium carbon steel or medium carbon high-quality alloy steel precision casting parts. Flanged fork generally with a flat flange, also with a trapezoidal tooth flange. The needle roller bearing assembly generally includes four needle roller bearings, a cross shaft and a grease nozzle. Needle roller bearings are generally composed of a number of needle rollers, a bearing bowl, and a multi-edge rubber oil seal (part with a skeleton). In some needle bearings, there is a circular gasket with oil groove, nylon, and copper or other materials, mainly used to reduce the axial clearance of the universal joint and improve the dynamic balance quality of the drive shaft. The universal joint fork is a forked part, which is generally forged of medium carbon steel or medium carbon alloy steel, and is also precision cast of medium carbon steel. The axial fasteners of needle roller bearings are generally elastic stoppers (inside and outside clamps) for holes (or shafts), or bearing press plates, lock plates, bolts, etc.

According to the transfer torque: moment mini car drive shaft; Light vehicle drive shaft; Medium car drive shaft; Heavy truck drive shaft; Engineering vehicle drive shaft;

Dynamic property

In the process of car trading, we must carry out road tests, however, in the process of road testing must take into account the power of the vehicle, then, what is the power of the car?

The power of the car refers to the process of the car driving in a straight line on a good road surface, and the corresponding driving performance can be determined by the longitudinal external force, which is able to meet the requirements of the average driving speed. From this definition, we can see that for a road, it must be a good road surface, level or slope can be used, the mode of movement can take a straight line driving process, for external factors, the longitudinal external force can determine the basis of the movement, so that it can reach a certain capacity. For athletic ability, there are three main indicators, such as the car's maximum speed, acceleration time, and maximum climb. A vehicle driving on a good level road surface, if it can reach the highest speed, we call it the maximum speed. For acceleration time, it is usually the acceleration time of starting in place, and the acceleration time of overtaking, which indicates the acceleration ability of the car. "t" indicates the time to start in place, which is generally first or second gear to start, and gradually change gears, if you travel to a certain predetermined distance, the time required for the speed. It's time to start in place. The acceleration time of overtaking can also be expressed by "t", and some of the highest second-high gear cars, their speed is about 30 or 4, and the time taken to accelerate at full speed on some expressways is expressed.

Service and maintenance
In order to ensure the normal operation of the drive shaft and extend its service life, attention should be paid to: