According to whether the universal drive shaft has significant ductility in the twisting direction, it can be divided into a rigid universal drive shaft and a flexible universal drive shaft. The rigidity universal transmission shaft can be divided into a non-constant speed universal transmission shaft (commonly a cross shaft type), a quasi-constant speed universal transmission shaft (such as a double-connected universal transmission shaft) and a constant speed universal transmission shaft (such as Ball cage type universal drive shaft) three types.

1. Unequal speed universal drive shaft

The cross shaft type universal transmission shaft is a universally variable speed universal transmission shaft commonly used in vehicles, and allows a larger intersection angle between the adjacent two shafts to be 15 ゜ ～ 20 ゜. The cross shaft universal drive shaft is composed of a cross shaft, 2 universal drive shaft forks and four cylindrical roller bearings. The holes on the two universal drive shaft forks 1 and 3 are sleeved on the two pairs of motor shafts of the cross shaft 2 respectively. In this way, when the driving shaft rotates, the driven shaft can not only follow the rotation, but also oscillate in a random direction around the cross-axis management center, so it incorporates the necessity of another transformation of the intersection angle and the spacing. A cylindrical roller bearing 5 is arranged between the cross shaft motor shaft and the universal drive shaft fork hole, and the outer side of the cylindrical roller bearing is accurately positioned radially by the snap ring. In order to lubricate the rolling bearings, a fuel injector is generally installed on the cross shaft and a fuel pipe leads to the motor shaft. Grease can be injected from the injector to the cylindrical roller bearing of the cross shaft motor shaft.

The cross shaft stiffness universal transmission shaft has the advantages of simple and clear structure and high efficiency of the transmission system, but it cannot transmit constant angular speed rotation under the condition that the intersection angle α of the two shafts is not zero.

When considering the following two standards, it is possible to maintain an equal angular speed transmission system from the output shaft of the gearbox to the input shaft of the drive:

1) The universal drive shaft forks on both sides of the drive shaft are in the same plan;

2) The intersection angle α1 of the two helical gears of the first universal drive shaft is the same as the intersection angle α2 of the two helical gears of the second universal drive shaft.

Since the drive should be relatively trembling relative to the gearbox during driving, it is unlikely that α1 = α2 will always be the case. In fact, there is only a similar constant speed transmission system that guarantees the gearbox to the drive.

In the left and right gear transmission, the greater the angle α of the helical gear, the more uneven the rotation of the transmission shaft, the greater the additional alternating load, the worse the service life of the parts, and the higher the efficiency of the transmission system. The overall layout should minimize this helical gear angle.

2. Quasi constant velocity universal drive shaft

Common quasi-constant universal drive shafts have two types: double-connected type and three-axis pin type. Their principle is the same as that of the double cross-shaft type universal drive shaft to maintain the constant speed drive system.

The double-connected universal drive shaft is in fact a set of double cross shaft universal drive shafts with constant speed gear transmission that reduces the length of the drive shaft to a minimum. The double-connected fork is equal to the drive shaft and the universal drive shaft on both sides on the same plan cross. When the angle of intersection between the output shaft and the input shaft is smaller than the clock, the intersection of the centerlines of the two shafts on the arc is very close to the vertical line, which makes the difference between α1 and α2 small, so that the angular velocity of the two shafts is close to the same The double-connected universal drive shaft is called a standard constant velocity universal drive shaft.

3. Constant velocity universal drive shaft

The common constant velocity universal drive shaft at this stage is a ball cage universal drive shaft, and the ball fork universal drive shaft or the optional three-pivot universal drive shaft is also selected. The inner spline shaft of the star-shaped sleeve 7 is connected with the driving shaft 1, and there are six arc-shaped concaves on the surface layer, which generates an inner dovetail guide rail. The inner surface layer of the spherical shell 8 has opposite six arc-shaped concave shapes, resulting in an outer dovetail rail. The six bearing steel balls 6 are respectively installed in the indoor space facing by the six sets of inner and outer dovetail guide rails, and are restricted by the cage 4 in the same plan. The driving force is transmitted from the driving shaft 1 (and star sleeve) to the spherical shell 8 through the bearing steel ball 6 and output.