Basic knowledge of the hottest transmission shaft

Basic knowledge of transmission shaft

I. Introduction to transmission shaft assembly (combined with specific assembly drawing)

transmission shaft, English propeller (driving) shift. The power is transmitted between the two shafts of different axes, and even between the two shafts whose relative positions are constantly changing during the working process

transmission shafts can be classified differently according to their important components - universal joints. According to whether 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. 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 function of cushioning and vibration reduction. Rigid universal joints can be divided into non constant velocity universal joints (such as cross axle universal joints), quasi constant velocity universal joints (such as duplex universal joints, three pin shaft universal joints) and constant velocity universal joints (such as ball cage universal joints, ball fork universal joints). Constant speed and unequal speed refer to whether the rotational angular rates of the driven shaft and the driven shaft are equal when they rotate with the driving shaft. Of course, the average rotational speeds of the driving shaft and the driven shaft are equal

a universal joint whose angular velocity of the driving and driven shafts is still equal when the included 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 of steering drive axle, disconnected drive axle, etc., and are mainly used for power transmission in cars. When the car is rear wheel drive, the cross axle universal joint transmission shaft is often used, and some high-end cars also use constant velocity ball joints; When the car is front wheel drive, constant velocity universal joint is often used - constant velocity universal joint is also a kind of transmission shaft, but the appellation is different

on the vehicle with front rear wheel drive (or all wheel drive) of the engine, due to the deformation of the suspension during the movement of the vehicle, there is often relative movement between the input shaft of the main reducer of the drive shaft and the output shaft of the transmission (or transfer box). In addition, in order to effectively avoid some mechanisms or devices (unable to realize linear transmission), there must be a device to realize the normal transmission of power, so universal joint transmission appears. Universal joint transmission must have the following characteristics: A. ensure that the relative position of the connected two shafts can reliably transmit power when it changes within the expected range; b. Ensure that the two shafts connected can run evenly. The additional load, vibration and noise caused by the included angle of the universal joint shall be within the allowable range; c. High transmission efficiency, long service life, simple structure, convenient manufacture and easy maintenance. For automobiles, since the output shaft of a cross shaft universal joint rotates at an unequal speed relative to the input shaft (with a certain included angle), double universal joints (or multiple universal joints) must be used for transmission, and the two universal joint forks connected with the transmission shaft are arranged on the same plane, so that the included angles of the 20000 direction joints are equal. This is very important. The included angle of the universal joint should be minimized in the design

the imbalance of the transmission shaft assembly is the main reason for the bending vibration of the transmission system. The vibration and noise caused by it is obvious with the rapid development of new energy vehicles. In addition, the axial movement of the universal joint spider, the gap in the sliding spline of the transmission shaft, the positioning 4 of the connection at both ends of the transmission shaft assembly: the abnormal centering accuracy of the hammer return, the elastic deformation of the transmission shaft during high-speed rotation, and the thermal influence factors during the spot welding of the balance sheet on the transmission shaft can change the imbalance of the transmission shaft assembly. Reducing the imbalance of the transmission shaft is extremely important for cars, especially high-speed cars such as cars, otherwise it will cause many related faults or abnormal damage

the transmission shaft of cross shaft rigid universal joint is the most widely used and has the longest history in the automotive transmission system. The transmission shaft usually refers to the transmission shaft of cross shaft rigid universal joint. The spider type rigid universal joint is mainly used to transmit the change of angle. It is generally composed of flange fork, spider with needle bearing assembly, universal joint fork or sliding fork, intermediate connecting fork or spline shaft fork, axial fastener of needle bearing, etc. The flange fork is generally connected with the gearbox, drive axle or other transmission shafts. Flange fork is a fork shaped part with flange, which is generally forged with medium carbon steel or medium carbon alloy steel, and also with ball 1. It has good comprehensive performance, high impact strength, chemical stability and electrical performance; Sand castings of graphite iron and precision castings of medium carbon steel or medium carbon high-quality alloy steel. Flange forks generally have a flat flange, but also have a trapezoidal tooth flange with an end face. The spider with needle roller bearing assembly generally 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 (some with a skeleton). In some needle roller bearings, there is also a circular gasket with oil groove, including nylon, copper or other materials, which is mainly used to reduce the axial clearance of the universal joint and improve the dynamic balance quality of the transmission shaft. The universal joint fork is a fork shaped part, which is generally forged with medium carbon steel or medium carbon alloy steel, and there are also precision castings with medium carbon steel. The axial fixings of needle roller bearings are generally circlips (internal and external snap type) for holes (or shafts), or bearing pressure plates, locks, bolts, etc

another important part of the transmission shaft is the sliding spline pair, which is composed of internal and external splines (rectangular and involute) to transmit the change of length

the swing 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 runout check of the transmission shaft during the layout of the whole vehicle

transmission shaft tubes are generally made of welded steel tubes rolled from low-carbon steel plates, and cold drawn seamless tubes are also used for large-size shaft tubes. The outer diameter and wall thickness (or inner diameter) of the shaft tube are determined according to the maximum working torque and maximum working speed transmitted by the transmission shaft. The hollow shaft tube has smaller mass and can transmit larger torque, and has higher critical speed than the solid shaft with the same outer diameter

generally, the center distance of 20000 direction nodes is not more than 1.5m. When the distance is close, it is generally composed of two universal joints and a sliding spline pair, with no shaft tube in the middle. When the distance is too far and the length of the transmission shaft exceeds 1.5m, it is often divided into two or three, three or four universal joints are used, and the last one is equipped with sliding spline pair, and the rest is equipped with intermediate support

a typical intermediate support is generally composed of a cylindrical ball bearing, a bearing seat, two oil seals, a rubber pad and a grease nozzle. The intermediate transmission shaft is connected to the frame beam by the intermediate support bracket, and the axis line of the intermediate transmission shaft is required to be perpendicular to the intermediate support plane. Generally, the intermediate support of the transmission shaft is required to be arranged on the first-order critical speed node of the transmission shaft system

in the process of use, it generally needs to be maintained on time. In places with grease nipples such as universal joints, sliding spline pairs, intermediate supports, etc., the specified grease shall be filled regularly according to relevant regulations. There are also maintenance free transmission shafts. There is reserved grease in the universal joint and the bearing of the intermediate support, so it is not necessary to fill the grease regularly

II. Introduction to universal joint

universal joint is a key component on the automobile transmission shaft whose market mentality gradually weakens. On vehicles with front engine 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; The front engine front wheel drive vehicle omits the transmission shaft, and the universal joint is installed between the front axle half shaft and the wheel, which is responsible for driving and steering

a car is a moving object. On the rear drive vehicle, 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 and they need to be connected. When the vehicle is running, the uneven road surface will produce runout, the load change or the installation position difference of the two assemblies will change the included angle and distance between the output shaft of the transmission and the input shaft of the main reducer of the drive axle. Therefore, a "variable strain" device should be used to solve this problem, so there is a universal joint

application of universal joint

in addition, this universal joint is required as a "joint" between the transmission and transfer gear of off-road vehicles, and between the steerable drive axle of front drive and the halfshaft. The structure and function of the universal joint is a bit like the joints on human limbs, which allows the included angle between the connected parts to change. However, it is different from the movement form of limb joints. It only allows the included angle to change within a certain range

universal joints include cross shaft rigid universal joints, quasi constant velocity universal joints (double shaft and three pin shaft), constant velocity universal joints (ball fork and ball cage), and disturbing universal joints. At present, the cross axle universal joint is the most widely used in rear drive vehicles

a single universal joint cannot make the instantaneous angular velocity of the output shaft equal to that of the input shaft, which is easy to cause vibration, aggravate the damage of parts, and produce great noise. Therefore, the universal joint transmission form of rear drive vehicles adopts double universal joints, that is, there is a universal joint at both ends of the transmission shaft, which is used to make the included angles at both ends of the transmission shaft equal and ensure that the instantaneous angular velocity of the output shaft and the shaft into the shaft is always equal

in order to meet the angle changes caused by power transmission, steering and the up and down runout of the vehicle during operation, the drive axle of the front drive vehicle, and the half axle and axle are also commonly connected with universal joints. Due to the limitation of axial size and large deflection angle, ordinary universal joints are not competent, so various constant velocity universal joints are widely used. In general front drive vehicles, each half axle uses two constant velocity universal joints. The universal joint near the transaxle is the inner universal joint of the half axle, and the outer universal joint near the axle is the outer universal joint of the half axle. Among all kinds of constant velocity universal joints, the common one is the ball cage universal joint, which uses six steel balls to transmit force. In the case of any intersection angle between the driving shaft and the driven shaft, the steel balls are located at the intersection of the two circles, that is, on the bisector of the intersection angle of the two shafts, so as to ensure the constant angular velocity transmission of the driving and driven shafts. (end)