By flexibility

       Drive shafts can be classified into different categories 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.

       1. Rigid universal joint: the power is transmitted by the hinged connection of the parts.

       2. Torsion universal joint: Relying on elastic parts to transmit power, and has the function of buffering and damping.

       According to angular rate

       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.

       1. Constant velocity universal joint:

       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.

       2. Variable speed universal joint:

       Universal joints whose angular velocities of the main and driven shafts are not equal when the included angle between the two shafts are changed are called unequal-velocity universal joints, also known as cross-shaft universal joints. The cross-shaft rigid universal joint drive shaft is the most widely used in the automobile transmission system and has the longest history. 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. 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 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.