Knowledge of universal joints

Knowledge of universal joints (three-pin shaft type, cross shaft type, ball cage type)

There is a very important part on the car called the universal joint. The combination of the universal joint and the drive shaft is called a universal joint transmission. Universal joint, also known as universal joint, is a mechanism that realizes variable-angle power transmission and is used for positions where the direction of the transmission axis needs to be changed. On a vehicle with front-engine rear-wheel drive, the universal joint drive is installed between the transmission output shaft and the input shaft of the drive axle final reducer; while the vehicle with front-engine front-wheel drive omits the drive shaft, and the universal joint is installed Between the front axle half-shafts, which are responsible for both driving and steering, and the wheels.

Universal transmission

The working principle of the universal joint is easy to understand. It can be imagined that a finger on each hand is interlocked with each other, and it can swing in a plane without affecting the transmission of axial torque. In practice this is increased to two claws or more. The function is to prevent deformation caused by lateral vibration during the operation of the drive shaft.

Cross shaft universal joint

Ordinary cross shaft universal joints are generally composed of two universal joints crossed and their connected cross shafts, needle roller bearings and their axial positioning parts and oil seals. The cross shaft journal is installed in the hole of the universal joint fork by cooperating with the needle roller bearing. In order to prevent the needle roller bearing from moving in the axial direction, the axial positioning measures of the bearing should be taken when designing the structural scheme. At present, the common axial positioning methods of needle rollers include cover plate type, snap ring type, plastic ring positioning type and tile cover fixed type.

Three-pin shaft universal joint

The three-pin shaft universal joint is evolved from the double-joint universal joint. It is mainly composed of two eccentric shaft forks, two three-pin shafts and six needle roller bearings. The three-pin shaft universal joint allows the maximum angle between the two shafts to be connected to be 45°, which is easy to seal. However, its external size is large, the shape of the parts is more complex, and the blank needs to be precisely forged. Due to the relative axial sliding between the three-pin shafts during operation, the two shafts of the universal joint are subjected to additional bending moments and axial forces, so an axial thrust bearing needs to be installed on one side of the driving shaft. This structure is currently used in the steering drive axle of individual medium and heavy off-road vehicles.

Ball cage universal joint

The ball cage joint is the most widely used constant velocity joint.