RU2846865C2 - Lightweight cardan joint, splined conjugated pair and drive shaft - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: present application discloses a lightweight cardan joint, a splined conjugated pair and a drive shaft and relates to automotive drive shafts. Lightweight cardan includes a ball coupling, a ball head and a straight shaft, the ball coupling is a thin-walled structure, the ball coupling is no longer used to transmit the drive torque; ball head is hinged in ball coupling; ball head has driving punch; straight shaft passes through driving punch; both ends of ball coupling are connected to fixed bearing surfaces, and fixed bearing surface has carrying hole and driving key. Lightweight splined conjugated pair consists of splined shaft and splined bushing, wherein splined shaft and splined bushing have thin-wall structure. Light-weight drive shaft includes a light-weight cardan and/or a light-weight splined conjugated pair.

EFFECT: reduced weight of the part.

23 cl, 32 dwg

Description

Field of technology

The present application relates to the field of automotive drive shafts, and more specifically to a lightweight cardan shaft, a splined mating pair, and a drive shaft.

State of the art

This application is a further optimization and improvement based on Chinese Patent Technology CN 202021793026.3. Filing date: 2020-08-20, Publication number: CN 213176523 U. This improvement is made to adapt to the requirements of the automobile industry for the lightweighting of the drive shaft. To achieve the lightweighting of the drive shafts of the prior art, lightweight materials such as aluminum alloy and carbon fiber are generally used to achieve the goal of reducing the weight of the drive shaft. However, such lightweight materials are generally expensive, which increases the cost of the drive shaft and also increases the difficulty of production. The technological process is complex, and there are still technical shortcomings. There is also a quality risk in the connection between carbon fiber and steel. Delamination phenomenon easily occurs between different materials, thereby reducing the strength of the product and causing quality failures. Compared with the traditional spider-type drive shaft, Chinese patent technology CN 202021793026.3, although the weight is reduced, the processing technology of the ball coupling is complex, the processing efficiency is low, the processing cost is high, and it is difficult to realize standardization. Since the ball coupling is the key power component that bears the function of transmitting torque, the overall stress is relatively large, and it requires high structural strength. It is difficult to further reduce the wall thickness and weight of the parts. The weight is heavy, and it cannot adapt to the mass production and lightweight requirements of automobile drive shafts. The huge torque absorbed by the ball coupling easily leads to the deformation of the main structure of the ball coupling, which further affects the fit accuracy of the DSE. There is a need for further structural optimization to achieve the purpose of reducing weight, simplifying the process technology, improving production efficiency and the stability of processing quality, improving product performance, and reducing product costs. At the same time, the production process of the spline mating pair - spline sleeve and spline shaft of the existing drive shaft technology is also more complex and the weight is heavy, so there is a need for improvement.

The essence of the invention

The main objective of this application is to provide a lightweight cardan shaft, a spline mating pair and a drive shaft to adapt to the requirements of the automobile industry for the lightweighting and standardization of drive shafts, and at the same time solve the problems of high cost, complex processing technology, low processing efficiency, and the inability to adapt to the mass production requirements of automobile drive shafts, etc., which exist in CN Patent 202021793026.3; and at the same time, optimize the force state and function of the cardan shaft and the ball coupling, so that the main structure of the ball coupling no longer transmits torque, but mainly adopts the function of sealing the lubricating oil, so as to reduce the deformation of the ball coupling due to stress, improve the manufacturability of the structure of the ball coupling, reduce the manufacturing complexity, improve the processing efficiency of the ball coupling, reduce the weight of the ball coupling and the processing cost; Optimize the manufacturability of the splined sleeve and splined shaft design, optimize material distribution due to a large diameter and thin wall thickness, and maximize material yield. This improves spline load-bearing capacity, reduces spline stress and sliding friction, reduces spline wear, extends spline service life, reduces the weight of the mating spline pair, simplifies the spline mating pair manufacturing process, improves production efficiency, reduces product costs, and improves product quality.

To address the aforementioned problems existing in existing drive shaft technologies, this application provides a lightweight cardan shaft comprising a ball coupling, a ball head, and a straight shaft, characterized in that: the ball coupling is a thin-walled structure, the ball coupling is no longer used to transmit torque, the ball head is rotationally mounted in the ball coupling, the ball head has a leading punch, and the straight shaft passes through the leading punch and passes through the center of the ball of the ball head. Both ends of the ball coupling are connected to fixed bearing surfaces, and the fixed bearing surface has a bearing hole and a leading key.

In this application, the main structure of the ball coupling no longer transmits the drive torque, but rather serves primarily to provide a closed lubricating space for other drive components in the ball coupling. This completely improves the stress state of the cardan shaft and solves the technical problem that the main structure of the ball coupling of traditional cardan shafts in the prior art must be used to transmit torque. The overall stress on the ball coupling is relatively large, and a large torque can cause deformation of the ball coupling structure. Furthermore, by connecting with external components through a fixed bearing surface, when the connection size of the external components changes, it can be adapted by changing the fixed bearing surface. Therefore, the change in the size of the external connection no longer affects the design of the ball coupling. Thus, the ball coupling, as the main DSU, can be realized for standardized mass production, thereby adapting to the requirements of high-volume automobiles.

More preferably, the ball coupling is a monolithic, integrally molded thin-walled structure or a split thin-walled structure.

More preferably, it further includes a rolling body, the rolling body is mounted on both ends of the straight shaft, both ends of the leading punch are provided with rolling raceway surfaces, the outer surface of the rolling body interacts with the rolling raceway surfaces of the leading punch and thus transmits torque, the rolling body is capable of rotating around the axis of the straight shaft and is capable of rolling on the rolling raceway surface of the leading punch.

More preferably, the outer surface of the rolling element is a conical surface, the conical surface of the rolling element interacts with the surface of the rolling raceway of the driving punch, the contact reference lines of both are straight, and the continuation line of the contact reference lines passes through the center of the ball of the ball head.

More preferably, it further includes a limiting mechanism, wherein the limiting mechanism is used to axially limit the rolling element.

More preferably, it further includes an axial support mechanism that is used to axially support and position the straight shaft.

More preferably, the axial support mechanism is a steel ball or friction linings.

More preferably, the ball coupling is a monolithic, integrally molded, thin-walled structure, two plug sockets are symmetrically located on the ball coupling, the fixed bearing surface is provided with plug sockets, the plug sockets are inserted into the plug sockets, and the straight shaft is rotationally supported on the bearing hole of the fixed bearing surface.

More preferably, the ball coupling is a one-piece injection molded structure.

More preferably, the ball coupling is a split structure consisting of a ball coupling I and a ball coupling II, the ball coupling I and the ball coupling II are integrally molded thin-walled structures, the ball coupling I and the ball coupling II are connected to each other and arranged symmetrically.

More preferably, the ball coupling I and the ball coupling II have an inner spherical surface, a bearing hole and a mounting cylinder, the fixed bearing surface is connected to the mounting cylinder through the bearing hole, and the straight shaft is rotationally supported on the bearing hole.

More preferably, the ball coupling I and the ball coupling II are respectively provided with a sealing stationary surface, and the sealing stationary surface is further provided with a sealing groove with a sealing ring to implement a hermetically sealed connection between the ball coupling I and the ball coupling II.

Preferably, the wall thickness of the ball coupling is 0.2-5 mm. Preferably, the diameter of the ball coupling shell is smaller than the diameter of the ball head.

More preferably, a locking ball surface is provided in the middle portion of the straight shaft, and a limiting surface is provided in the middle portion of the leading punch of the ball head, wherein the locking ball surface is limited in the limiting surface of the leading punch.

The present application also provides a lightweight splined mating pair including a splined shaft and a splined sleeve, characterized in that the splined shaft and the splined sleeve have a thin-walled structure, and that the splined shaft and the splined sleeve are formed into a sliding splined mating pair by a spline fit.

The mating spline pair of existing technology typically has a small diameter and large wall thickness. By appropriately increasing the spline pitch circle diameter and intelligently reducing the wall thickness, the diameter and wall thickness of the spline shaft and spline sleeve are intelligently optimized, material distribution is optimized, material utilization is reduced, and material yield is maximized. A large diameter and thin wall thickness improves spline load-bearing capacity, reduces spline stress and sliding friction, reduces spline wear, increases spline service life, improves spline performance, and is better suited for advanced cold forming and chipless machining, reducing machining costs and improving product quality.

More preferably, one end of the splined shaft is provided with an internal spline, through which the splined shaft is fixedly connected to an external spline corresponding to the shank of the ball head at one end of the drive shaft; an external spline is also provided on the outer side of the splined shaft, the external spline on the splined shaft has a sliding fit with an internal spline provided at one end of the splined sleeve, and the other end of the splined sleeve is fixedly connected to an external spline corresponding to the shank of the ball head at the other end of the drive shaft through its internal spline.

More preferably, it further includes a splined oil reservoir, wherein the splined oil reservoir is located in an internal cavity of the splined shaft to form an oil storage cavity, wherein the splined shaft is provided with a number of oil distribution holes, wherein the oil distribution holes are in communication with the oil storage cavity.

More preferably, the internal and external splines of the splined shaft and splined sleeve are involute splines, or straight-sided splines, or staggered splines.

The present application also provides a lightweight drive shaft including a cardan shaft and/or a splined mating pair, characterized in that the cardan shaft is the above-mentioned lightweight cardan shaft and/or the lightweight splined mating pair is the above-mentioned lightweight splined mating pair.

More preferably, a sealing hole is provided on the ball coupling of the lightweight cardan shaft, the sealing hole is connected to the dust cover, one end of the dust cover is connected to the sealing hole, and the other end is connected to the shank of the ball head or to the splined sleeve of the cardan shaft.

More preferably, the ball coupling and dust cover are monolithic, integrally molded structures.

More preferably, the dust cover is also provided with a filter at the end where it is connected to the spline sleeve or shank of the ball head, and the ball head is provided with an exhaust hole, and the internal cavity of the dust cover is connected to the central cavity of the spline mating pair through the exhaust hole, so that external air can enter the internal cavity of the dust cover after being filtered by the filter.

This application has the following beneficial effects:

1. The ball coupling and splined mating pair are integrally molded thin-walled structures, realizing chipless or machining, which not only significantly improves production efficiency and quality stability, reduces weight by about 40-70%, saves a large amount of steel, and adapts to the requirements for the development of lightweight automotive parts, but also significantly improves product performance and reduces vibration and noise of the drive shaft.

2. The ball coupling is connected with the external parts through a fixed bearing surface. When the connection size of the external parts changes, it can be adapted by changing the fixed bearing surface, so that the change in the external connection size no longer affects the design of the ball coupling, so that the ball coupling can be realized for standardized mass production, thus adapting to the requirements of large-volume automobiles.

3. Through the structural optimization of the design, the stress state of the cardan shaft has been completely improved, so that the torque transmission is basically completed through the fixed bearing surface, bearing, straight shaft, rolling element and ball head. So that the main structure of the ball coupling is no longer responsible for torque transmission, and the ball coupling mainly has the function of oil storage and sealing, which fundamentally and substantially reduces the load of the ball coupling. So that the ball coupling can be introduced into die casting or stamping and other light structural structures, which saves the amount of material used and improves the performance and quality of the product, reducing the cost.

4. The ball coupling adopts die casting and the spline mating pair adopts cold forming process, eliminating the original complex chipless machining operation, which not only improves the machining quality of the parts, but also saves a lot of processing costs and prolongs the service life of the product.

5. The design of the spline oil reservoir lubrication structure allows the oil to be evenly distributed on the inner surface of the spline portion of the spline shaft, making the oil more evenly and reliably distributed on the sliding surface of the spline mating pair due to centrifugal force, and at the same time preventing the oil from gathering in a pile or shifting to one side caused by eccentricity, which may adversely affect the dynamic balance of the drive shaft, and improving the oil utilization efficiency.

6. Due to the interaction between the positioning ball surface of the straight shaft and the limiting surface in the middle part of the leading punch of the ball head, the axial breakaway force of the ball head acts on the positioning ball surface of the straight shaft through the limiting surface, which effectively reduces the centering load on the ball coupling, allows the cardan to withstand a greater breakaway force of the ball head, enhances the centering ability, effectively protects the ball coupling and increases the service life of the ball coupling.

7. The installation of the rolling element limiting mechanism allows the axial force of the rolling element to be transmitted to the straight shaft, and due to the symmetrical arrangement of the rolling elements, the axial force becomes a pair of equal-sized and opposite-direction equilibrium forces acting on the straight shaft to avoid damaging this force to other DSEs, so that the force on the overall cardan structure is more balanced and reasonable.

8. The axial support mechanism installed at both ends of the straight shaft can realize axial support for the straight shaft, and then through the rolling element of the ball head, play the role of axial support and centering, while simultaneously taking the supporting force of the ball coupling on the ball head, improving the vibration and wear resistance of the cardan.

9. This application can solve the problem of high cost, complicated process and hidden quality problems of high-end aluminum alloy/carbon fiber drive shafts and other existing technology.

10. This application overcomes the limitations of the existing technology in the structure and production process, undermines the design ideas and technological routes of the drive shaft of the existing technology, and opens up a new design concept and development idea of the drive shaft.

Brief description of the drawings

Fig. 1 is a top view of a first embodiment of the lightweight cardan shaft of the present application;

Fig. 2 is a sectional view E-E in Fig. 1;

Fig. 3 is a structural diagram of the cap of Fig. 2 with an equivalent replacement of the retaining ring and steel ball;

Fig. 4 is a structural diagram of the limiting mechanism of Fig. 2 with the equivalent replacement of the locking ring with a bolt;

Fig. 5 is a sectional view F-F of Fig. 1;

Fig. 6 is an exaggerated view of place A in Fig. 1;

Fig. 7 is a three-dimensional schematic view of a ball head with a slot on the ball head shank;

Fig. 8 is a schematic view of the assembly of the three-dimensional structure of the lightweight cardan shaft of Fig. 1;

Fig. 9 is a schematic view of a three-dimensional structure of the ball coupling in Fig. 1, where (a) is a three-dimensional front view of the ball coupling in the view, and (b) is a three-dimensional rear view of the ball coupling;

Fig. 10 is a schematic view of a three-dimensional structure of the fixed bearing surface of Fig. 1, where (a) is a three-dimensional top view of the fixed bearing surface, and (b) is a three-dimensional bottom view of the fixed bearing surface;

Fig. 11 is a design diagram of a second example of the implementation of a lightweight cardan;

Fig. 12 is a sectional view B-B of Fig. 11;

Fig. 13 is a structural diagram of a friction lining as an axial support mechanism;

Fig. 14 is a structural diagram of a bolt as a limiting mechanism;

Fig. 15 is a sectional view C-C of Fig. 11;

Fig. 16 is a sectional view D-D of Fig. 11;

Fig. 17 is a diagram of a three-dimensional structure of the ball coupling of Fig. 11, where (a) is a three-dimensional view of the ball coupling from above, and (b) is a three-dimensional view of the ball coupling from below;

Fig. 18 is a diagram of a three-dimensional structure of the fixed bearing surface of Fig. 11, where (a) is a three-dimensional top view of the fixed bearing surface, and (b) is a three-dimensional bottom view of the fixed bearing surface;

Fig. 19 is a diagram of the three-dimensional structure of the lightweight cardan shaft of Fig. 11, where the fixed bearing surface is not shown;

Fig. 20 is a design diagram of a third example of the implementation of a lightweight cardan;

Fig. 21 is a sectional view H-H of Fig. 20;

Fig. 22 is a three-dimensional schematic view of the splined shaft and the splined sleeve, where (a) is a three-dimensional schematic view of the splined shaft, and (b) is a three-dimensional schematic view of the splined sleeve;

Fig. 23 is a three-dimensional schematic view II of a splined shaft and a splined sleeve, where (a) is a three-dimensional schematic view of the splined shaft, and (b) is a three-dimensional schematic view of the splined sleeve;

Fig. 24 is a structural diagram of a first example of the implementation of a drive shaft;

Fig. 25 is a structural diagram of a second embodiment of a drive shaft;

Fig. 26 is a sectional view Q-Q of Fig. 24, where the spline shaft and spline sleeve are the spline shaft and spline sleeve shown in Fig. 22;

Fig. 27 is a sectional view J-J of Fig. 24;

Fig. 28 is a sectional view K-K of Fig. 25, where the spline shaft and spline sleeve are the spline shaft and spline sleeve shown in Fig. 23;

Fig. 29 is a sectional view L-L of Fig. 28;

Fig. 30 is a structural diagram of a third embodiment of a drive shaft;

Fig. 31 is a three-dimensional schematic view of a splined shaft and a splined sleeve, where (a) is a three-dimensional schematic view of the splined shaft, and (b) is a three-dimensional schematic view of the splined sleeve;

Fig. 32 is a structural diagram of a fourth embodiment of a drive shaft.

Examples of the invention

This application will be described in detail below with reference to the accompanying drawings.

Example of implementation First:

As shown in Fig. 1, 11 and 20, the lightweight cardan of the present application includes a ball coupling 3, a ball head 1 and a straight shaft 2, the ball coupling 3 is a thin-walled structure, the ball head 1 is rotationally mounted in the ball coupling 3, the ball head 1 has a leading punch, the straight shaft 2 passes through the leading punch, both ends of the ball coupling 3 are connected to fixed bearing surfaces (8). As shown in Fig. 10, the fixed bearing surface 8 has a bearing hole 8-1 and a leading key 8-2.

In particular, the ball head 1 is rotationally mounted in the ball coupling 3 and rotationally mounted on the straight shaft 2 through a driving punch, the ball coupling has an inner spherical surface Q, the outer surface of the ball head 1 is concentrically rotationally mated with the inner spherical surface Q of the ball coupling 3, and the ball coupling 3 is provided with one fixed bearing surface 8 at each end, wherein the driving key 8-2 on the fixed bearing surface 8 is connected to the input or output opening of the transmission system. The fixed bearing surface 8 receives the torque transmitted from the end of the straight shaft and transmits it to the transmission system connected to it through the driving key 8-2, or the fixed bearing surface 8 receives the torque transmitted from the transmission system connected to it through the driving key 8-2, then transmits it to the end of the straight shaft and transmits the torque to the head 1 through the straight shaft, thus implementing the transmission of cardan power. In this power transmission method, the main structure of the ball coupling 3 no longer transmits the drive torque, but rather serves primarily to provide a closed lubricating space for other drive components in the ball coupling 3. Therefore, by installing fixed bearing surfaces for transmitting torque at both ends of the ball coupling 3, this solves the technical problem that the main structure of the ball coupling of the traditional cardan joints in the prior art must be used for transmitting torque. The overall stress on the ball coupling 3 is relatively large, and a large torque may cause deformation of the ball coupling structure, thereby completely improving the stress state of the cardan joint. Furthermore, by connecting with external parts through a fixed bearing surface, when the connection size of the external parts changes, it can be adapted by changing the fixed bearing surface. Therefore, the change in the size of the external connection no longer affects the structure of the ball coupling. Thus, the ball coupling as the main DSU can be realized for standardized mass production, thereby adapting to the requirements of high-volume automobiles.

The ball coupling of the present application has a thin-wall structure, and the ball coupling of the thin-wall structure is manufactured by chipless processing such as die casting, stamping, or stretch molding, which simplifies production. The basic structure of the ball coupling of a traditional universal joint requires a large wall thickness to ensure its structural strength due to the need to transmit torque, and the processing cost of a traditional ball coupling is high. This application makes it possible to reduce the wall thickness of the ball coupling and significantly reduce the weight of the universal joint. Through structural optimization of the design, the lightweight universal joint of the present application completely improves the stress state of the universal joint, so that torque is transmitted mainly through the fixed bearing surface, bearing, straight shaft, rolling element, and ball head, and the ball coupling mainly performs the function of oil storage and sealing, which fundamentally and significantly reduces the load of the ball coupling. This allows for a light and thin structure of the ball coupling, saving material, improving the performance and quality of the product, and reducing the cost.

More preferably, as shown in Fig. 1, 11 and 20, the cardan of the present application further includes a rolling body 7, the rolling body 7 has a conical surface 7-2 and a fixed surface 7-1, the leading punches of the ball head 1 pass through the ball head and are symmetrically located along the central plane of the ball head C-C, F-F and N-N, the axis of the leading punch passes through the center of the ball of the ball head 1, the two ends of the leading punch are the surfaces of the rolling raceways 1-1, and the rolling body 7 is symmetrically coaxially assembled on the straight shaft 2, the conical surface 7-2 of the rolling body 7 interacts with the surface of the rolling raceway 1-1 of the leading punch 1, the contact reference lines M of both are straight, and the continuation line of the contact reference lines M passes through the center of the ball R of the ball head 1, and the rolling body 7 can roll around the center of the ball of the ball head 1 along the surface of the rolling raceway 1-1 leading punching; symmetrically located both rolling elements 7 are used as the inner ring of bearings simultaneously, which respectively interact with bearings 9 of both ends of the straight shaft through their fixed surfaces 7-1, and are then fixed by bearings 9 in bearing seats G of ball coupling 3 or in bearing holes of a fixed bearing surface, wherein ball coupling 3 is cooperatively wrapped around the outer spherical surface of ball head 1 by means of its inner spherical surface Q.

More preferably, as shown in Fig. 1, 11 and 20, the ball coupling 3 is also provided with a sealing hole T. One end of the dust cover 11 is connected to the sealing hole T of the ball coupling 3, and the other end is fixedly wrapped around the shank portion of the ball head 1 (including an extension portion such as a shaft pipe, etc., which is fixedly connected to the ball head 1) or a splined sleeve, so that a sealed space is formed between the dust cover and the ball coupling, and the head portion of the ball head 1, the rolling element and the straight shaft, the bearing are wrapped and sealed together and added with grease.

More preferably, as shown in Fig. 2-4, 12-14, a limiting mechanism is also provided at both ends of the straight shaft, which is used to axially limit the rolling element 7.

Fig. 2-3, 12-13 show an embodiment of the limiting mechanism, wherein the limiting mechanism includes grooves of the locking ring and a locking ring 5, wherein the grooves of the locking ring are located at the ends of the straight shaft 2, and the locking ring 5 snaps into these grooves of the locking ring.

More preferably, the snap ring is an open elastic snap ring which, after assembly, is clamped in the snap ring groove of the straight shaft by the elastic locking of the snap ring itself.

More preferably, as shown in Fig. 8, for the convenience of assembly, the retaining ring 5 is an open semi-ring structure, the paired use of the retaining ring 5 can form a complete annular retaining ring, which is clamped in the grooves of the retaining ring at both ends of the straight shaft 2, and the paired use of two semi-ring retaining rings 5 can be tightly clamped together by a tightening device that prevents the retaining ring 5 from coming out of the grooves of the retaining ring of the straight shaft 2. In Fig. 1 and 8, the tightening device is shown in the form of a cap 24, the cap 24 is installed on the end of the straight shaft and holds the paired used semi-rings 5 in the cylindrical inner cavity of the cap 24, and the tightening device shown in Fig. 11-13 and 19, is a spring retaining ring 6, the retaining ring 5 has an annular groove on the outer cylindrical surface of the retaining ring 5, and the spring retaining ring 6 can be installed inside the annular groove of the retaining ring 5 to tightly fasten two semi-annular retaining rings 5 used in pairs. Similarly, the spring retaining ring 6 can be replaced by a wire, with the help of which two semi-annular retaining rings 5 used in pairs are wound and pulled together. The cap 24 can also have a tubular structure with holes at both ends, which is not described in detail in this document. The limiting structure holds the rolling element 7 symmetrically located between the retaining rings 5 at both ends of the straight shaft 2, limits the outward movement of the rolling element 7 along the axis of the straight shaft and receives the axial force in the direction of the axis of the straight shaft, which occurs when the rolling element is transmitted. Of course, the retaining ring 5 can be equivalently replaced by other structures, such as a retaining post, a retaining plate, or the like.

In Fig. 4 and 14 another embodiment of the limiting mechanism is shown, wherein the limiting mechanism includes a bolt X and an internal thread open at both ends of the straight shaft 2, wherein the bolt X is fastened to both ends of the straight shaft 2 by means of an internal thread, or, the limiting mechanism includes a nut and an external thread open at both ends of the straight shaft 2, wherein the nut is fastened to both ends of the straight shaft 2 by means of an external thread. In particular, an internal or external thread is provided at both ends of the straight shaft 2, and bolts or nuts are screwed on and fastened on the thread at both ends of the straight shaft in order to retain symmetrically located rolling elements 7 between the bolts or nuts at both ends of the straight shaft, to limit the outward movement of the rolling element 7 along the axis of the straight shaft and to perceive the axial force in the direction of the axis of the straight shaft, arising during the transmission of the rolling element.

The installation of a limiting mechanism can transfer the axial force generated by the rolling element transmission to the straight shaft. Thanks to the symmetrical arrangement of the rolling elements, the axial force becomes a pair of equal-sized, opposite-direction equilibrium forces acting on the straight shaft. This prevents this force from affecting other joints, resulting in a more balanced and reasonable force on the overall cardan structure. After the straight shaft is subjected to the above-mentioned axial tensile force, its ability to withstand bending and torsion can be improved, and its stress state can be improved.

More preferably, as shown in Fig. 5 and 15, a shell K is provided on the ball coupling 3, the diameter of which is smaller than the diameter of the ball of the ball head.

Preferably, the wall thickness of the ball coupling is 0.2-5 mm.

More preferably, as shown in Fig. 1, 6 and 11, in the middle portion of the straight shaft 2 there is a locking ball surface 2-1, and in the middle portion of the leading punch of the ball head there is a limiting surface 1-2 provided, and after the straight shaft 2 penetrates through the leading punch of the ball head, its locking ball surface 2-1 interacts with the limiting surface 1-2 of the leading punch, and the limiting surface 1-2 limits the position of the locking ball surface 2-1. As shown in Fig. 6, the locking ball surface 2-1 is a spherical surface protruding from the outer surface of the straight shaft 2.

The interaction between the locking ball surface 2-1 of the straight shaft and the limiting surface 1-2 in the middle part of the leading punch of the ball head allows the straight shaft to directly absorb the breaking force of the ball head, enhances the centering ability, effectively protects the ball coupling, and increases the service life of the ball coupling.

More preferably, as shown in Fig. 20-21, a hinge pin Y may also be provided, the middle portion of the straight shaft 2 is provided with a hinge hole 2-2, and the axis of the hinge hole 2-2 perpendicularly intersects with the axis of the straight shaft 2; the ball head 1 is provided with a fastening hole 1-3, and the axis of the fastening hole 1-3 passes through the center of the ball R of the ball head 1 and is perpendicular to the central plane C-C of the ball head, the hinge pin Y passes through the fastening hole 1-3 of the ball head and is pivotally connected with the hinge hole 2-2 of the straight shaft, and the straight shaft can swing around the axis of the hinge pin Y in the leading punch of the ball head. The structural installation of the hinge pin further enhances the centering effect.

More preferably, an axial support mechanism is provided at both ends of the straight shaft 2. As shown in Fig. 2-4, 11-14, the axial support mechanism is a cap 24, a steel ball or a friction lining P. Note: when the axial support mechanism is a cap 24, the cap 24 is used both as a tightening device for the semi-circular retaining ring 5 and as an axial support mechanism. In particular, a steel ball or a friction lining P is provided between the end of the straight shaft 2 and the bottom of the bearing seat G, as described in Fig. 11-14, or, as shown in Fig. 2-4, a steel ball or a friction lining P is provided between the end of the straight shaft 2 and the upper part of the inner cavity of the fixed bearing surface 8 for axial support of the straight shaft.

The axial support mechanism installed at both ends of the straight shaft, that is, the steel ball 4 or the friction lining P, can realize the effect of axial support for the straight shaft, and also play the role of axial support and centering for the ball head through the rolling element, and at the same time divide the supporting force of the ball coupling to the ball head, so as to improve the ability of the cardan to resist vibration and abrasion.

The locking ball surface 2-1 of the straight shaft and the axial support mechanism, the limiting mechanism and the rolling element 7 provided at the two ends of the straight shaft 2 can jointly hold and position the ball head to keep the ball head in a correct seating position.

Example of implementation Second:

As shown in Fig. 11-17, Fig. 19, the ball coupling 3 is a detachable thin-walled structure divided into two parts: the ball coupling I 31 and the ball coupling II 32. The ball coupling I 31 and the ball coupling II 32 are symmetrically arranged, hermetically connected, and combined to form a space including the head portion of the ball head 1 and the straight shaft 2, the rolling element 7 and the bearing, and the ball coupling I 31 and the ball coupling II 32 have an internal spherical surface Q, a bearing seat G and a mounting cylinder S, and the fixed bearing surface 8 embraces and clamps the mounting cylinder S corresponding to the ball coupling through the bearing hole 8-1, and transmits the drive torque through the mounting cylinder S, so that the main structure of the ball coupling no longer performs the function of transmitting torque.

Preferably, the ball coupling I 31 and the ball coupling II 32 are integrally molded thin-walled elements and are symmetrically located along the central plane C-C of the ball head. As shown in Fig. 17, the ball coupling I 31 and the ball coupling II 32 have a sealing and locking surface 12, by means of which the ball coupling I 31 and the ball coupling II 32 are fixedly connected, forming a monolithic ball coupling. In one embodiment of the invention, the sealing fixing surface 12 is also provided with a sealing groove 14, and the sealing groove 14 is an annular groove concave from the surface of the sealing fixing surface, after the sealing fixing surfaces 12 of the ball coupling I 31 and the ball coupling II 32 are fastened and fixed together, the sealing groove 14 of the ball coupling I 31 and the ball coupling II 32 can be combined to form a sealing cavity, and a sealing ring 15 is placed in the sealing cavity, and the sealing ring 15 is subjected to compression of the sealing groove 14 of the ball coupling I 31 and the ball coupling II 32, thereby forming a seal between the sealing fixed surfaces of the ball coupling 131 and the ball coupling II 32, and forming a complete sealing structure of the cardan together with the dust cover 11. Of course, it is also possible to use a concave-convex sealing fit (for example, on one sealing fixing surface there is a tubercle, on the other sealing fixing surface there is a groove, and the tubercle and the groove are sealing fits), a flat sealing fit (for example, between two sealing fixing surfaces there is a sealing gasket covered with a sealant), etc. between the sealing fixing surfaces of the ball coupling I 31 and the ball coupling II 32.

Preferably, the method of fixedly connecting the sealing fixing surfaces of the ball coupling I 31 and the ball coupling II 32 can be connected by rivets 13, bolts, welding, etc., depending on the need.

Example of implementation Third:

As shown in Fig. 1-5 and Fig. 8-9, the ball coupling 3 is a monolithic, integrally molded, thin-walled structure, i.e. The main structure of the ball coupling is a monolithic integrally molded thin-walled structure, the plug holes 3-1 are symmetrically arranged at the two ends of the ball coupling 3, and the plug sockets 8-3 are also arranged on the fixed bearing surface 8, and the plug sockets 8-3 of the fixed bearing surface 8 are hermetically inserted into the plug holes 3-1 of the ball coupling, and, preferably, an oil seal groove is provided at the entrance of the plug hole 3-1, the sealing ring 27 is compressed and placed between the oil seal groove and the plug hole to form a reliable seal (as shown in Fig. 1), and the bearing hole 8-1 of the fixed bearing surface 8 is used to support the fixed bearing 9.

The main unit of the ball coupling 3 can be integrally molded from a thin steel plate, or non-metallic materials such as resin, nylon, plastic, etc. can be used.

When the material of the ball coupling 3 is an elastic material, a portion of the plug hole 3-1 of the ball coupling 3 can be pre-embedded in a steel frame, so that when the main structure of the ball coupling 3 is integrally molded from an elastic material, it is connected with the steel frame to form a single part, so that the plug hole 3-1 has rigidity, and then is inserted with tension with the plug sockets 8-3 of the fixed bearing surface 8, so as to improve the sealing and reliability of the connection. In addition, the plug hole 3-1 of the ball coupling 3 should be tightly inserted into the plug sockets 8-3 of the fixed bearing surface 8 and fixed with a clamp or the like.

Preferably, the sealing hole T of the ball coupling is fixedly connected to the dust-proof cover 11, and the ball coupling and the dust-proof cover can be divided into two parts for manufacturing separately, and then the sealing hole T of the ball coupling is fixedly connected to the connecting hole of the dust-proof cover 11 using a clamp or the like, and the dust-proof cover and the ball coupling can also be designed as a single integral part.

As shown in Fig. 20, when the ball coupling and the dust cover 11 are monolithic integrally molded thin-walled structures, and a soft elastic material is used as the material, the plug holes 3-1 of the ball coupling can be increased in rigidity of the bearing seat of the ball coupling by using embedded steel frames to facilitate assembly.

Example of implementation Fourth:

As shown in Fig. 22, 24, 26-27, the lightweight spline mating pair includes a spline shaft 16 and a spline sleeve 17, the spline shaft 16 and the spline sleeve 17 are thin-walled structures, the spline shaft 16 and the spline sleeve 17 are fastened to form a sliding spline mating pair by concave and convex shapes on the mating surfaces. By appropriately increasing the diameter of the pitch circle of the spline and reasonably reducing the wall thickness, the diameter and wall thickness of the spline shaft and the spline sleeve are optimized, the material distribution is optimized, so that the load-bearing capacity of the spline is increased, and the stress and sliding friction of the spline are reduced.

More preferably, there is a splined oil tank 22, the splined oil tank 22 is arranged in an inner cavity of the splined shaft 16, one end of the splined shaft is fixedly connected to the ball head, the other end is connected to one end of the splined oil tank for oil, and the other end of the splined oil tank is connected to the ball head to form an oil storage cavity 23 between the splined oil tank 22, the splined shaft 16 and the ball head, and a plurality of oil distribution holes 16-2 are arranged in the splined shaft 16, and the oil distribution holes 16-2 are connected to the oil storage cavity 23, and lubricating oil is stored in the oil storage cavity, and when the drive shaft rotates at a high speed, the lubricating oil in the oil storage cavity can reach the sliding mating surfaces of the splined shaft and the splined sleeve under the action of the rotating centrifugal force and lubricate the splined mating pair.

In particular, the spline shaft 16 and the spline sleeve 17 are thin-walled structures that use thin-walled round pipes subjected to cold drawing or stamping in such a way as to form a concave-convex wave spline structure on the surface of the round pipes to form a sliding spline mating pair, wherein one end of the spline mating pair mates with the spline of the ball head of the cardan shaft through the spline shaft and is welded to strengthen it, and the other end of the spline mating pair mates with the spline of the shank of the ball head of another cardan shaft through the spline sleeve and is welded to strengthen it, so that two cardans are connected by a spline mating pair. When the distance between the two cardans changes, the spline shaft of the spline mating pair can slide and be drawn into the spline sleeve to adapt to the change in the length of the drive shaft. In Fig. 7 shows the spline of the ball head shank, mating with the spline of the mating part of the corresponding spline shaft and spline sleeve, Fig. shows a conventional involute spline as an example.

The spline mating pair of the present application uses a one-piece molded thin-wall structure, on the one hand, it eliminates the initial complex cutting processing operation, not only improves the processing quality of the parts, but also saves a lot of processing costs, on the other hand, due to a significant reduction in weight, so that the spline mating pair can be used at a low cost to achieve the surface nitriding processing process, greatly improves the wear-resistant performance of the parts and increases the service life of the product.

In this application, the design of the lubricating structure of the spline oil reservoir allows the oil to be uniformly distributed on the inner surface of the spline portion of the spline shaft, can make the oil more uniformly and reliably distributed on the sliding surface of the spline mating pair due to centrifugal force, improve the oil utilization efficiency and lubricating effect, and at the same time can prevent the oil from gathering in a pile or shifting to one side caused by eccentricity, which can adversely affect the dynamic balance of the drive shaft.

As shown in Fig. 24, a dust cover 11 is also provided, one end of the dust cover 11 is fixedly connected to the sealing hole T of the main structure of the ball coupling, and the other end is connected to the splined sleeve 17.

The end of the dust-proof cover 11, connected to the splined sleeve 17, is also provided with a ventilation hole 25 and a filter 18, and an exhaust hole 16-1 is provided in the ball head, and the exhaust hole 16-1 is connected at one end to the internal cavity 26 of the dust-proof cover 11, and at the other end is connected to the central cavity 21 of the splined mating pair. The air in the central cavity 21 of the splined mating pair can be connected with the internal cavity 26 of the dust-proof cover 11 through the exhaust hole 16-1 provided on the ball head, and then connected to the filter 18 through the ventilation hole 25, through the filter 18, a respiratory exchange with the external air is achieved to balance the pressure change in the central cavity 21 of the splined mating pair, and the above is the breathing function of the splined mating pair.

Fig. 22 is a three-dimensional diagram of an arc spline shaft and a spline sleeve, the concave and convex shape of the spline surface is a curved surface consisting of positively and negatively alternating arc surfaces tangent to ends, and the cross-section of the spline has a checkerboard shape, as shown in Fig. 26-27; Fig. 23 is a three-dimensional diagram of a straight-sided spline shaft and a spline sleeve, the cross-sectional shape of the spline is a straight-sided spline; of course, the shape of the spline can have different types, such as a ladder spline, an involute spline, a triangular spline, and so on, which will not be fully listed here.

Additionally, the sliding surface of the splined pair can be coated with nylon. Once the splined shaft and/or splined sleeve are coated with nylon, the aforementioned splined oil reservoir lubrication method can be replaced, and self-lubrication can be achieved through the use of nylon, eliminating the need for structural components such as a splined oil reservoir, oil distribution holes, and so on.

Example of implementation Fifth:

Embodiment 5 is a modification of embodiment 4 as shown in Fig. 25, differing from embodiment 4 in that it further includes an oil storage plug 28, wherein the oil storage plug 28 is locked at one end of the splined oil reservoir 22, and an oil storage cavity 23 is formed between the splined oil reservoir 22, the oil storage plug 28 and the splined shaft 16, wherein the splined shaft 16 is provided with a number of oil distribution holes 16-2, wherein the oil distribution holes 16-2 communicate with the oil storage cavity 23.

The present application forms a closed oil storage cavity 23 between a splined oil reservoir 22, an oil storage plug 28 and an inner surface of a splined portion of a splined shaft, at the same time, a plurality of oil distribution holes 16-2 are provided on the outer surface of the splined portion of the splined shaft, the outer surface of the splined portion of the splined shaft communicates with the oil storage cavity 23 through the oil distribution holes 16-2, lubricating oil is stored in the oil storage cavity 23, and the splined shaft 16 and the splined sleeve 17 are installed together to form a spline mating pair by means of a spline mating set, and when the splined shaft 16 slides inside the splined sleeve 17, the lubricating oil in the oil storage cavity 23 can reach the sliding surface of the spline pair through the oil distribution holes 16-2 to lubricate the spline pair.

Preferably, one end of the splined oil reservoir 22 is provided with a funnel 22-1. When the splined oil reservoir 22 is coaxially inserted into the inner cavity of the splined shaft 16, the funnel 22-1 is used to block one end of the inner cavity of the splined portion of the splined shaft, and the other end of the splined oil reservoir 22 is connected to the oil storage plug 28, while the other end of the inner cavity of the splined portion of the splined shaft is sealed using the oil storage plug 28, thereby forming a closed oil storage cavity 23 between the splined oil reservoir, the oil storage plug and the inner surface of the splined portion of the splined shaft.

As shown in Fig. 25, a splined dust-proof sleeve 19 is also provided, one end of the splined dust-proof sleeve 19 is fixedly connected to the splined shaft 16, and the other end is connected to the splined sleeve 17.

As shown in Fig. 29, the end of the splined dust-proof sleeve 19, connected to the splined sleeve 17, is also provided with a ventilation hole 25 and a filter 18, and at the end of the splined shaft 16, remote from the splined sleeve 17, an exhaust hole 16-1 is provided, which is connected at one end to the internal cavity 20 of the splined dust-proof sleeve 19, and at the other end is connected to the central cavity 21 of the splined mating pair. The air in the central cavity 21 of the splined mating pair can be connected to the internal cavity 20 of the splined dust-proof sleeve 19 through the outlet hole 16-1 provided on the splined shaft 16, and then connected to the filter 18 through the ventilation holes 25 to provide respiratory exchange with the external air through the filter 18 to balance the change in pressure in the central cavity 21 of the splined mating pair, and the above is the respiratory function of the splined mating pair. Example of the Sixth Embodiment:

Embodiment 6 is another modification of embodiment 4, as shown in Fig. 30-31, a lightweight spline mating pair including a spline shaft 16 and a spline sleeve 17, the spline shaft 16 and the spline sleeve 17 have a thin-walled structure, the spline shaft 16 and the spline sleeve 17 are formed into a sliding spline mating pair by an involute spline fit, the spline shaft 16 and the spline sleeve 17 are involute splines. One end of the spline shaft 16 is provided with an internal spline, which is fixedly connected to an external spline (as shown in Fig. 7) located on the shank of the ball head at one end of the drive shaft, and is reinforced by welding; One end of the splined sleeve 17 is movably coupled with the external spline of the splined shaft 16 by means of an internal spline, and the other end of the splined sleeve 17 is fixedly connected with the external spline (as shown in Fig. 7) located on the shank of the ball head at the other end of the drive shaft by means of an internal spline, and is reinforced by welding. The splined shaft 16, the splined sleeve 17 and the shank of the ball head of the drive shaft are fixed by means of an internal and external spline, and then welded, which makes it possible to increase the strength of the connection between the splined shaft 16, the splined sleeve 17 and the shank of the ball head of the drive shaft.

Preferably, a dust protection cover 11 is also provided, one end of the dust protection cover 11 is fixedly connected to the sealing hole T of the main structure of the ball coupling, and the other end is connected to the splined sleeve 17. Or, a splined dust protection sleeve 19 is also provided, one end of the splined dust protection sleeve 19 is fixedly connected to the splined shaft 16, and the other end is connected to the splined sleeve 17.

Example of the implementation of the Seventh:

As shown in Fig. 24-25 and Fig. 30, the lightweight drive shaft includes a pair of lightweight cardan shafts and/or one lightweight spline mating pair, wherein the lightweight cardan shaft is the lightweight cardan shaft described in any of examples 1-3, and/or the lightweight spline mating pair is the lightweight spline mating pair described in any of examples 4-6.

The lightweight drive shaft of this application, its ball coupling, and splined mating pair are integrally molded thin-walled structures, ensuring chip-free or low-chip machining. This not only significantly improves production efficiency and quality stability, but also significantly reduces the weight of the parts and machining costs, reducing weight by approximately 40-70%. This not only saves a significant amount of steel and meets the requirements for the development of lightweight automotive parts, but also significantly improves product performance. The increased mating accuracy of the parts reduces vibration and noise of the drive shaft.

Example of the implementation of the Eighth:

The lightweight cardan in example 7 can be equivalently replaced by a cross-type cardan with a traditional design or a Rzeppa ball cardan, and we will not repeat this here.

Example of implementation Nine:

The lightweight spline pair in embodiment 7 can be equivalently replaced by a conventional spline shaft and spline sleeve, as shown in Fig. 32, and will not be repeated here. In this embodiment, the spline shaft 16 is integrally molded with the ball head 1, and the exhaust port 16-1 is formed on the spline shaft 16. Since the spline shaft 16 is integrally molded with the ball head 1, the shank of the ball head 1 is simultaneously not only a part of the ball head 1, but also a spline shaft, so that the exhaust port 16-1 provided on the ball head can also be described as an exhaust port 16-1 provided on the spline shaft 16. Preferably, the end of the spline sleeve 17, which is at a distance from the spline shaft 16, is connected to the other ball head 1 by means of an axial pipe.

In the description of this patented technology, it should also be noted that, unless otherwise expressly provided and limited, the terms "installation," "assembly," "connection," "combination," and "fixation" should be understood in a broad sense, for example, as a fixed connection, a detachable connection, or a one-piece connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium. This may be a connection within two elements. For a person of ordinary skill in the art, the specific meanings of the aforementioned terms in the field of this patented technology may be understood depending on the specific circumstances.

Of course, the foregoing are merely preferred embodiments of the present patented technology and should not be construed as limiting the scope of embodiments of the present patented technology. The present patented technology is not limited to the above examples, and changes and improvements made by a person of ordinary skill in the art within the scope of the present patented technology will fall within the scope of the patent for the present patented technology.

Claims (22)

1. A lightweight cardan shaft comprising a ball coupling (3), a ball head (1), a straight shaft (2), characterised in that the ball coupling (3) is a thin-walled structure, the ball coupling is no longer used to transmit drive torque; the ball head (1) is rotationally mounted in the ball coupling (3), the ball head (1) has a leading punch, the straight shaft (2) passes through the leading punch and passes through the centre of the ball (R) of the ball head, both ends of the ball coupling (3) are connected to fixed bearing surfaces (8), and the fixed bearing surface (8) has a bearing hole (8-1) and a leading key (8-2). 2. A lightweight cardan shaft according to paragraph 1, characterized in that the ball coupling (3) is a monolithic, integrally molded thin-walled structure or a detachable thin-walled structure. 3. A lightweight cardan shaft according to claim 2, characterized in that it additionally includes a rolling element (7), the rolling element (7) is mounted on both ends of the straight shaft (2), both ends of the driving punch are provided with surfaces of rolling tracks (1-1), the outer surface of the rolling element (7) interacts with the surfaces of the rolling tracks (1-1) of the driving punch and thus transmits torque, the rolling element (7) is capable of rotating around the axis of the straight shaft and is capable of rolling on the surface of the rolling track (1-1) of the driving punch. 4. A lightweight cardan shaft according to claim 3, characterized in that the outer surface of the rolling element (7) is a conical surface (7-2), the conical surface (7-2) of the rolling element (7) interacts with the surface of the rolling raceway (1-1) of the driving punch, the contact reference lines (M) of both are straight, and the continuation line of the contact reference lines (M) passes through the center of the ball (R) of the ball head (1). 5. A lightweight cardan shaft according to claim 4, characterized in that it additionally includes a limiting mechanism, wherein the limiting mechanism is used for axial limiting of the rolling element (7). 6. A lightweight cardan shaft according to paragraph 5, characterized in that it additionally includes an axial support mechanism, which is used for axial support and positioning of the straight shaft. 7. A lightweight cardan shaft according to paragraph 6, characterized in that the axial support mechanism is a steel ball (4) or friction linings (P). 8. A lightweight cardan shaft according to paragraph 5, characterized in that the ball coupling (3) is a monolithic, integrally molded, thin-walled structure, two plug holes (3-1) are symmetrically located on the ball coupling (3), the fixed bearing surface (8) is provided with plug sockets (8-3), the plug sockets (8-3) are inserted into the plug holes (3-1), and the straight shaft (2) is rotationally supported on the bearing hole (8-1) of the fixed bearing surface (8). 9. A lightweight cardan shaft according to paragraph 8, characterized in that the ball coupling (3) is a one-piece molded structure manufactured by injection molding. 10. A lightweight cardan shaft according to paragraph 5, characterized in that the ball coupling (3) is a detachable structure consisting of a ball coupling I (31) and a ball coupling II (32), the ball coupling I (31) and the ball coupling II (32) are integrally molded thin-walled structures, the ball coupling I (31) and the ball coupling II (32) are connected to each other and are located symmetrically. 11. A lightweight cardan shaft according to claim 10, characterized in that the ball coupling I (31) and the ball coupling II (32) have an internal spherical surface (Q), a bearing seat (G) and a mounting cylinder (S), the fixed bearing surface (8) is connected to the mounting cylinder (S) through a bearing hole (8-1), and the straight shaft (2) is rotationally supported on the bearing seat (G). 12. A lightweight cardan shaft according to paragraph 11, characterized in that the ball coupling I (31) and the ball coupling II (32) are respectively provided with a sealing stationary surface (12), and the sealing stationary surface (12) is additionally provided with a sealing groove (14) with a sealing ring (15) for implementing a hermetic connection between the ball coupling I (31) and the ball coupling II (32). 13. A lightweight cardan shaft according to any of paragraphs 1-12, characterized in that the wall thickness of the ball coupling is 0.2-5 mm. 14. A lightweight cardan shaft according to any one of paragraphs 1-12, characterized in that the diameter of the shell (K) of the ball coupling is less than the diameter of the ball of the ball head. 15. A lightweight cardan shaft according to any one of paragraphs 1-12, characterized in that a locking ball surface (2-1) is provided in the middle part of the straight shaft (2), and a limiting surface (1-2) is provided in the middle part of the leading punch of the ball head (1), wherein the locking ball surface (2-1) is limited in the limiting surface (1-2) of the leading punch. 16. A lightweight splined mating pair including a splined shaft (16) and a splined sleeve (17), characterized in that the splined shaft (16) and the splined sleeve (17) are thin-walled structures, and that the splined shaft (16) and the splined sleeve (17) are formed into a sliding splined mating pair by a spline fit; and the lightweight splined mating pair includes a splined oil reservoir (22), wherein the splined oil reservoir (22) is located in an internal cavity of the splined shaft (16) to form an oil storage cavity (23), wherein the splined shaft (16) is provided with a number of oil distribution holes (16-2), wherein the oil distribution holes (16-2) are in communication with the oil storage cavity (23). 17. A lightweight splined mating pair according to claim 16, characterized in that one end of the splined shaft is provided with an internal spline through which the splined shaft is fixedly connected to an external spline corresponding to the shank of a ball head at one end of the drive shaft; an external spline is also provided on the outside of the splined shaft, the external spline on the splined shaft has a sliding fit with an internal spline provided at one end of the splined sleeve, and the other end of the splined sleeve is fixedly connected to an external spline corresponding to the shank of a ball head at the other end of the drive shaft through its internal spline. 18. A lightweight splined mating pair according to any one of paragraphs 16, 17, characterized in that the internal and external splines of the splined shaft and splined sleeve are involute splines, or straight-sided splines, or staggered splines. 19. A lightweight drive shaft including a cardan shaft and/or a splined mating pair, characterized in that the cardan shaft is a lightweight cardan shaft according to any of paragraphs 1-15, and/or the lightweight splined mating pair is a lightweight splined mating pair according to any of paragraphs 16-18. 20. A lightweight drive shaft according to claim 19, characterized in that a sealing hole (T) is provided on the ball coupling of the lightweight cardan shaft, the sealing hole (T) is connected to a dust protection cover (11), one end of the dust protection cover (11) is connected to the sealing hole (T), and the other end is connected to the tail of the ball head (1) or to a splined sleeve of the cardan shaft. 21. A lightweight drive shaft according to item 20, characterized in that the ball coupling and dust cover (11) are a monolithic, integrally molded structure. 22. A lightweight drive shaft according to any one of paragraphs. 20, 21, characterized in that the dust protection cover (11) is also provided with a filter (18) at the end where it is connected to the splined sleeve (17) or the shank of the ball head, and the ball head is provided with an exhaust hole (16-1), and the internal cavity (26) of the dust protection cover (11) is connected to the central cavity (21) of the splined mating pair through the exhaust hole (16-1), so that external air can enter the internal cavity (26) of the dust protection cover (11) after filtering the filter (18).