Quasi Constant Velocity Joint

At present there are three types of universal joints mainly used in the market

1. Duplex universal joint

The duplex universal joint (Figure 4-3) is composed of two cross-axis universal joints. In order to ensure that the working speeds of the shafts connected by the two universal joints tend to be equal, there is an indexing mechanism for speed regulation. The eccentric cross-shaft duplex -joint universal joint eliminates the indexing mechanism and can also ensure that the output shaft and the input shaft are close to the same speed. The duplex - universal joint with five index rods is widely used in the steering drive axle of military off-road vehicles. It adopts the method that the center of the king pin deviates from the center of the universal joint by 1.0 to 3.5 mm, so that the working speed of the two universal joints is nearly equal. The main advantage of the duplex universal joint is that it allows a large included angle between the two shafts (generally up to 50°, and the eccentric cross shaft duplex universal joint can reach 60°), and the bearing has good sealing performance and high efficiency, reliable work and convenient manufacturing. The disadvantage is that the structure is more complicated, the external dimension is larger, and the number of parts is more. Because of the axial size of the duplex universal joint is larger used in the steering drive axle, in order to make the extension line of the kingpin axis deviate little from the intersection point of the ground to the center of tire’s grounding mark, the kingpin with a larger inclination angle is required, 

2. Convex block type universal joint

For the convex block type universal joint (Figure 4-4), its motion pair is also a duplex -type universal joint. It is mainly composed of two universal joint forks 1 and 4, and two special shaped convex blocks 2 and 3. These two convex blocks are equivalent to the intermediate shaft and two cross pins with two universal joint forks located on the same plane at both ends of the duplex universal joint device, so that the input shaft and the output shaft can be guaranteed to have approximately equal speed. The universal joint of this structure is reliable in work, simple in processing, and the allowable universal joint angle is larger (up to 50°). However, since the working surface is all sliding friction, the efficiency is low, the friction surface is easy to wear, and the sealing and lubrication requirements are higher. It is mainly used for steering drive axles of medium-sized and above off-road vehicles. 

3. Three pin axles universal joint 

Three pin axles universal joint (Picture 4-5) is evolved from the duplex universal joint. It is mainly composed of two eccentric shaft forks, two three-pin shafts and six needle bearings. The three-pin shaft universal joint allows the maximum angle of the two connected shafts to be 45°, which is easy to seal. However, its external dimensions are relatively large, the shape of the parts is more complicated, and the blank needs to be accurately forged. Due to the relative axial sliding between the three pin shafts during work, the two shafts of the universal joint are subjected to additional bending moments and axial forces, so an axial thrust bearing must be installed on one side of the driving shaft. The universal joint of this structure is currently used in the steering drive axle of heavy off-road vehicles.