Views:14 Author:Industrial Cardan Shaft Publish Time: 2019-03-06 Origin:Cardan Shaft Factory
This article is about vehicle drive shaft. If there is an error in the article, please leave a message so that we can correct it, thanks in advance.
Drive shaft is the shaft that transmits power in universal joint. It is a high-speed, low-supported rotating body, so its dynamic balance is crucial. Generally, drive shaft must be tested for dynamic balance before leaving factory and adjusted on the balancer. For front-engine rear-wheel drive car, rotation of transmission is transmitted to main reducer shaft, which can be several sections, and joints can be connected by a universal joint.
Drive shaft consists of a shaft tube, a telescopic sleeve and a universal joint.
Circular object fittings that are connected or assembled with various shafts and that can be moved or rotated are generally made of alloy steel tubes that are light and torsionally resistant. For front-engine rear-wheel drive car, rotation of transmission is transmitted to main reducer shaft, which can be connected by a universal joint for several sections. It is a high-speed, low-supported rotating body, so its dynamic balance is crucial. Generally, drive shaft must be tested for dynamic balance before leaving factory and adjusted on the balancer.
The transmission shaft is an important component of transmission power in vehicle drive train. Its function is to transmit power of engine to wheels together with gearbox and drive axle, so that vehicle generates driving force.
Special-purpose vehicle transmission shafts are mainly used in tank trucks, fuel trucks, sprinklers, suction trucks, suction trucks, fire trucks, high-pressure cleaning vehicles, road wreckers, aerial work vehicles, garbage trucks and other vehicles.
Drive shaft consists of a shaft tube, a telescopic sleeve and a universal joint. Telescopic sleeve automatically adjusts for changes in distance between transmission and transaxle. Universal joint is to ensure change of angle between transmission output shaft and input shaft of transaxle, and realize two-axis isometric transmission.
Universal joint is a key component on axle of car. In a rear-drive car, engine, clutch and transmission are mounted as a unit on frame, and transaxle is connected to frame via a flexible suspension with a distance between them that needs to be connected.
The universal joint is composed of a cross shaft, a cross bearing, and a flange fork. Universal joint is a key component on axle of car. On front-engine rear-wheel drive vehicles, universal joint drive shaft is mounted between transmission output shaft and transaxle final drive input shaft; front-engine front-wheel drive vehicle omits drive shaft, and universal joint is mounted between front axle axle and wheel that are both responsible for driving and steering. When vehicle is running unevenly, road surface is uneven, load changes or difference between two assembly installation positions changes angle and distance between transmission output shaft and input shaft of transaxle final drive. Therefore, a "change" is used. The strained device solves this problem, so there is a universal joint.
2. Transmission characteristics
In engine front-wheel drive (or all-wheel drive), there is often relative movement between drive shaft final drive input shaft and transmission (or transfer case) output shaft due to suspension deformation of car during motion. In addition, in order to effectively avoid certain mechanisms or devices (inability to achieve straight-line transmission), there must be a device to achieve normal power transmission, so a universal joint transmission occurs. The universal joint drive must include following features:
A. It can ensure reliable transmission of power when relative position of two shafts connected is within expected range.
B. Ensure that two shafts connected can operate evenly. Additional loads, vibrations, and noise included angle of joint should be within allowable range;
C. Transmission efficiency is high, service life is long, structure is simple, manufacture is convenient, and maintenance is easy. For a car, since output shaft of a cross-axis universal joint rotates at a constant speed with respect to input shaft (with a certain angle), a double universal joint (or multi-directional joint) transmission must be used for this purpose. And two universal joint forks connected to transmission shaft are arranged in the same plane, and angles of two universal joints are equal. This is very important. Angle of universal joint should be minimized during design.
Conventional transmission shaft sleeve is welded with spline sleeve and flange fork, and spline shaft is welded to transmission shaft tube. New drive shaft differs from conventional structure in that it integrates spline sleeve with drive shaft tube and integrates spline shaft with flange fork. Rectangular tooth spline is changed into a large pressure angle involute short tooth spline, which not only increases strength but also facilitates extrusion forming, and adapts to needs of large torque working condition. Surface of teeth of telescopic sleeve and spline shaft is entirely coated with a layer of nylon material, which not only increases wear resistance and self-lubricity, but also reduces damage of impact shaft to drive shaft and improves buffering capacity.
Transmission shaft adds a tubular sealing protective sleeve outside flange spline shaft, and two urethane rubber oil seals are arranged at the end of protective sleeve to form a completely sealed space in telescopic sleeve, so that telescopic spline shaft protected from dust and dust, it is not only dust-proof but also rust-proof. Therefore, it is necessary to apply grease to spline shaft and sleeve at the time of assembly, which can fully meet requirements of use, without lubrication of nozzle, and reduce maintenance content.
Bushing is designed to reduce friction and wear during shaft movement. Basic use is the same as that of bearing, and relative cost is relatively low, but frictional resistance is large, so it will only be used on some parts. Most of bushings are made of copper, but there are also plastic bushings. Bushings are often placed in shaft and support structure, and are very close to support structure, and only shaft can rotate on bushing. When assembling shaft and bushing, a lubricant is added between two to reduce friction generated when it rotates.
Classified by elasticity
Drive shaft can be classified according to its important part_ universal joint. If universal joint has obvious elasticity in direction of twisting, it can be divided into a rigid universal joint drive shaft and a flexible universal joint drive shaft.
1. Rigid joints: Power is transmitted by hinged connection of parts.
2. Stretching universal joint: transmitting power by elastic parts and having buffer damping effect.
Classified by angular rate
Rigid joints can be divided into non-equal joints (such as cross-shaft universal joints), quasi-constant joints (such as double joints, three-pin joints) and constant speed. Universal joints (such as ball cage joints, ball fork joints). Constant speed and non-equal speed refer to whether driven shaft has the same angular velocity of rotation when main shaft rotates. Of course, average rotational speeds of driven shaft and driven shaft are equal.
1.Constant velocity joint
Angular velocity of main and driven axes is still equal when angle between two axes changes, and is called a constant velocity joint or an equal angular joint. They are mainly used in wheel transmissions such as steering axles, disconnected drive axles, etc., and are mainly used for power transmission in cars.
2. Unequal joint
Angular velocity at which angular velocity of main and driven axes is not equal when angle between two axes changes is called a non-equal velocity joint, which is also called a cross-axis universal joint.
Cross-shaft rigid universal joint drive shaft is the most widely used in automotive transmission system and has longest history. When car is driven by rear wheel, cross shaft type universal joint drive shaft is often used. For some high-end cars, the same speed ball head is also used. When car is driven by front wheel, constant velocity joint is often used. The constant velocity joint is also a kind of drive shaft, but title is different. Generally speaking, transmission shaft generally refers to a cross-shaft rigid universal joint transmission shaft. The cross-shaft rigid universal joint is mainly used for change of transmission angle, generally consisting of a flange fork, a cross-shaft needle roller bearing assembly, a universal joint fork or a sliding fork, an intermediate connecting fork or a spline shaft fork, and a needle bearing.
Flange fork is a flanged fork-shaped part, generally made of forged carbon steel or medium carbon alloy steel, sand casting with ductile iron and precision casting of medium carbon steel or medium carbon high quality alloy steel. The flange fork usually has a flat flange and also has a trapezoidal tooth flange. Cross shaft needle roller bearing assembly generally includes four needle bearings, a cross shaft, and a grease nipple. Needle roller bearings generally consist of several needle rollers, a bearing bowl, and a multi-edge rubber seal (partially with a skeleton). In some needle bearings, there is also a circular gasket with oil groove, which is made of nylon or copper or other materials. It is mainly used to reduce axial clearance of the universal joint and improve dynamic balance quality of transmission shaft. Universal joint fork is a fork-shaped part, generally made of forged parts of medium carbon steel or medium carbon alloy steel, and precision casting parts made of medium carbon steel. Axial fixing members of needle bearing are generally circlips for holes (or shafts) (inner and outer cards), or bearing plates, lock plates, bolts, and so on.
Classified by transmission torque
Miniature vehicle drive shaft
Light vehicle drive shaft
Medium-sized vehicle drive shaft
Heavy duty vehicle drive shaft
Engineering vehicle drive shaft
Use and maintenance
In order to ensure normal operation of drive shaft and prolong its service life, it should be noted in use:
1. It is strictly forbidden to start with high speed gear.
2. Do not lift the clutch pedal rudely.
3. It is strictly forbidden to overload the car and speed it.
4. Always check the working condition of drive shaft.
5. Always check the tightening of drive shaft hanger, whether supporting rubber is damaged, whether connection parts of drive shaft are loose, and whether drive shaft is deformed.
6. In order to ensure dynamic balance of drive shaft, always pay attention to whether the balance soldering piece is desoldered. New drive shaft assembly is provided. When loading new drive shaft, pay attention to assembly mark of telescopic sleeve, and ensure that flange fork is in one plane. When repairing and disassembling drive shaft, assembly marks shall be printed on telescopic sleeve and flange shaft in order to maintain original assembly relationship during reassembly.
7. Lubricated grease should always be added to universal joint cross bearing. In summer, No. 3 lithium grease should be injected, and in winter, No. 2 lithium grease should be injected.
Damage, wear, deformation and loss of dynamic balance of drive shaft will cause abnormal noise and vibration during driving, which may cause damage to related components. When car is driving, it emits a "Gerden" sound when starting or accelerating, and it clearly shows loose feeling of machine. If it is not drive axle transmission gear loose, it is obviously loose shaft of transmission shaft. Part of loose raft is nothing more than a universal joint cross bearing or a steel bowl and a flange fork, and a spline shaft and a spline sleeve of telescopic sleeve. Generally speaking, cross shaft diameter and bearing capacity should not exceed 0.13mm, and meshing clearance between telescopic spline shaft and spline sleeve should not exceed 0.3mm. It should be repaired or replaced beyond the limit of use.
If chassis is humming when car is running, the higher the running speed, the louder the sound. This is generally due to loose wear of universal joint cross shaft and bearing, wear of intermediate bearing of drive shaft, damage of intermediate rubber support or looseness of hanger, or incorrect position of hanger.
1. Traditional method
Domestically used for drive shaft wear is generally used for repair welding, bushing, pitting, etc. When material is 45 steel (tempering and tempering treatment), if only surfacing treatment is used, internal stress of welding will occur, and in the case of heavy load or high speed operation, cracks or breaks may occur at the shoulder. If stress relief annealing is used, it is difficult to operate, and the processing cycle is long and the maintenance cost is high; When the material of the shaft is HT200, it is not ideal to use cast iron. Some companies with higher maintenance techniques will use brush plating, laser welding, micro-arc welding or even cold welding. These maintenance techniques often require high requirements and high costs.
2. Latest maintenance method
For the above repair technology, it is not very common in Europe, America, Japan and South Korea. The developed countries generally use polymer composite technology and nanotechnology. Polymer technology can be operated on site, which effectively improves maintenance efficiency and reduces maintenance costs and maintenance intensity. Compared with traditional technology, polymer composite material has strength and hardness required by metal, and has concession (variable relationship) that metal does not have. Through the processes of "mold repair", "part correspondence", "machining", etc., size of repaired part and matching part can be ensured to utmost extent. At the same time, composite material itself has comprehensive advantages of compression resistance, bending resistance and elongation, which can effectively absorb impact of external force, greatly resolve and offset radial impact force of bearing on shaft, and avoid possibility of gap occurrence, it also avoids secondary wear caused by the increase of the gap.
Symptom diagnosis: 6×4 car occasionally emits a knocking sound during heavy load, especially in running bump. It should be checked whether balance axle of rear axle is displaced and interferes with transmission shaft. If vehicle increases in speed as vehicle speed increases, and there is jitter, this is generally caused by loss of balance of drive shaft. This vibration is most noticeable in cab. Unbalance of dynamic balance of drive shaft should be less than 100 g. cm.
Serious failure of drive shaft dynamic balance can result in damage to related components. The most common are fatigue damage of clutch shell crack and intermediate rubber bearing.
Plug front wheel of car with stud, and use middle and rear drive axles on the side of jack. Start engine and hang up high-speed gear to check vibration of transmission shaft. When observing the speed drop during observation, if vibration is significantly increased, drive shaft is bent or flange is skewed. Bending of drive shaft is bending of shaft tube, and most of it is caused by overload of car. Due to overloading and over-hanging of coal-carrying vehicles, there are many failures in bending and breaking of drive shaft.
Replace drive shaft assembly. After straightening, balance check should be carried out, and amount of unbalance should meet standard requirements. The technical condition of universal joint fork and drive shaft hanger should also be checked in detail. If installation is not satisfactory, cross shaft and roller damage cause looseness and vibration, and transmission shaft will be out of balance.
Welding of drive shaft
Because transmission shaft has to transmit a large torque, intermediate shaft is a pipe with a large wall thickness. Shaft fork and input shaft connected to both ends of intermediate shaft are welded by an automatic CO2 gas shielded welding or friction welding process. After drive shaft is subjected to dynamic balance test, dynamic balance piece is welded, and bump is machined on dynamic balance piece, and is welded to drive shaft by a projection welding process.
Drive shaft failure
A. Abnormal sound. If there is a crash when car starts, abnormal noise always exists during driving, and most of connection is loose. There is no abnormal noise when car starts, and abnormal noise occurs during driving, mostly caused by poor assembly or lubrication.
B. Vibration. Car has obvious vibration during driving, and some also have abnormal sound of transmission shaft, which is caused by dynamic balance damage of transmission shaft.