Universal joint encyclopedia
I. Overview
A universal joint is a universal joint. The English name universal joint, refers to a machine that uses spherical connections to realize the power transfer of different shafts and is used to change the position of the drive shaft line. It is the "joint" part of the universal drive device of the automobile drive system. Universal joint and drive shaft combination, called universal joint transmission device.
II. Location of use
On the vehicle driven by the rear wheel of the front engine, the universal joint drive device is installed between the output shaft of the transmission and the input shaft of the main reducer of the drive axle; The front wheel drive vehicle omits the drive shaft and the universal joint is installed between the front axle half shaft and the wheel which is responsible for driving and steering.
III. Classification and characteristics
It can be divided into rigid universal joint and flexible universal joint according to whether there is obvious elasticity in torsional direction of universal joint.
The rigid universal joint can be divided into three kinds: constant speed universal joint (such as ball cage universal joint), unequal speed universal joint (commonly used as cross shaft type), and quasi equal speed universal joint (such as double joint universal joint).
1. Constant velocity universal joint
The constant speed universal joint (: CV Joint (Constant Velocity Joint) is a universal joint with the same rotational speed (angular velocity) of the drive shaft and the follower shaft.
There are many kinds of constant speed universal joints used in cars, among which ball cage constant speed universal joints and tripod constant speed universal joints are the most used.
Main composition: sliding sleeve, three axis, drive shaft, star sleeve, cage, bell shell, etc.
The advantages of the constant speed universal joint are large deflection angle and uniform angular velocity, but the disadvantages are that the structure is more complicated, the manufacturing process is precise and the cost is higher, so it can not completely replace the common universal joint.
Principle of action: the position of the point of transmission is always on the flat plane of the angle between the two axes, thus ensuring the isokinetic motion.
2. Unequal universal joint
The non-constant speed universal joint widely used in automobile is cross-axle rigid universal joint. The cross shaft rigid universal joint has the advantages of simple structure and high transmission efficiency, but it has strict requirements for the angle between the two axes (zero), otherwise it cannot transfer the isometric rotation.
3. Quasi-isokinetic universal joint
The common quasi-isokinetic universal joints are two kinds of double-coupling and three-pin shafts.
1) dual:
Principle: according to the double cross shaft universal joint to realize the principle of equal speed transmission. When two universal joint forks produce an angle relative to each other and satisfy their swing within a certain angle range, the double joint fork also deflects the corresponding angle, so that the angle difference between the central line of the two axes and the axis of the two universal joint forks is very small. In order to ensure that the angular velocity of two axes is close to equal, the dual universal joint has quasi-isokinetic speed in the range of the difference.
Advantages: allow large shaft angle, simple structure, easy to manufacture, reliable work, maximum angle up to 50
Dual universal joint can be used for steering drive axle without indexing mechanism, but the center of double joint must be located at the intersection point between the main pin axis and half shaft axis in order to ensure the constant speed transmission.
2) Tri-pin universal joint:
Evolved from a dual universal joint.
Advantages: allow two adjacent axles to have a larger angle, up to 45, in the steering drive axle can allow the car to obtain a smaller turning radius, improve vehicle mobility.
Disadvantages: large amount of space.