Drive shaft

Abstract

To propose a drive shaft having high strength and allowing an increase in torque transmission capacity with ease, in a structure where a fixed type constant velocity universal joint and a sliding type constant velocity universal joint are mounted on both ends of a hollow intermediate shaft.SOLUTION: The intermediate shaft is hollow over its entire length. A shaft portion is coaxially and integrally formed with the inner race of the fixed type constant velocity universal joint, and an end opening of the intermediate shaft is solid-phase bonded to the shaft portion. A shaft portion is coaxially and integrally formed with the tripod of the sliding type constant velocity universal joint, and the other end opening of the intermediate shaft is solid-phase bonded to the shaft portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drive shaft having constant velocity universal joints attached to both ends of a hollow shaft. [Background technology]

[0002] Drive shafts used in automotive drive trains generally have a structure in which a fixed constant velocity universal joint and a sliding constant velocity universal joint are attached to both ends of an intermediate shaft. Recently, intermediate shafts have been made hollow to reduce weight and rotational inertia (for example, Patent Document 1).

[0003] A conventional driveshaft using an integrated hollow intermediate shaft will be described in detail with reference to Figure 5. This driveshaft 101 is a driveshaft for the front wheels, and is connected to a sliding-type constant velocity universal joint 103 on the inboard side and a fixed-type constant velocity universal joint 104 on the outboard side. The sliding-type constant velocity universal joint 103 is a tripod-type constant velocity universal joint, and the fixed-type constant velocity universal joint 104 is a Rzeppa-type constant velocity universal joint using eight balls. The sliding-type constant velocity universal joint 103 comprises an outer joint member 105, a tripod member 106 as an inner joint member, and rollers 107, and the rollers 107 are rotatably fitted to three trunnions 108 formed on the tripod member 106. The rollers 107 are rollably received in track grooves 109 formed in the outer joint member 105.

[0004] The tripod member 106 and one end of the hollow shaft 102 are fitted together by a spline 130 (which also includes serrations; the same applies hereinafter), and are fixed in the axial direction by a retaining ring 111. Both ends of a boot 120 are attached to the outer periphery of the outer joint member 105 and the outer periphery of the hollow shaft 102, sealing the inside of the joint. Grease is enclosed inside the joint as a lubricant.

[0005] On the other hand, the fixed type constant velocity universal joint 104 comprises an outer joint member 112, an inner joint member 113, balls 114, and a cage 115. Eight track grooves 116 curved in the axial direction are formed on a spherical inner peripheral surface 118 of the outer joint member 112. Track grooves 117 facing the track grooves 116 of the outer joint member 112 are formed on a spherical outer peripheral surface 119 of the inner joint member 113, and balls 114 are arranged between the track grooves 116, 117.

[0006] The balls 114 are housed in a cage 115, and the inner and outer peripheral surfaces of the cage 115 are fitted into a spherical outer peripheral surface 119 of the inner joint member (inner race) 113 and a spherical inner peripheral surface 118 of the outer joint member 112, respectively. The other end of the hollow shaft 102 is fitted into the inner joint member 113 by a spline 131 and is fixed in the axial direction by a retaining ring 122. Both ends of a boot 121 are attached to the outer periphery of the outer joint member 112 and the outer periphery of the hollow shaft 102, sealing the inside of the joint. It has also been proposed to divide a long hollow shaft into two and join them at the center by solid-state welding (friction welding) to ensure the formability of the long shaft. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-315463 Summary of the Invention [Problem to be solved by the invention]

[0008] However, because a large-diameter opening is provided in the inner joint member (inner race) 113 or the tripod member 106, and the hollow shaft 102 fits into the opening (a so-called internal fitting), it is necessary to ensure a large wall thickness (thick in the radial direction) around the opening for strength reasons. If this thickness is not sufficient, this area is likely to become the weakest point. Furthermore, due to the relationship between the opening and the peripheral wall thickness, it is difficult to reduce the weight and size of the inner race or tripod. Furthermore, increasing the torque transmission capacity requires increasing the diameter of the hollow shaft 102, which, however, requires increasing the diameter of the opening, which is in conflict with ensuring sufficient wall thickness around the opening, making it difficult to increase the diameter.

[0009] In view of the above-mentioned problems, the present invention aims to provide a drive shaft that is strong and has an easily increased torque transmission capacity, in a structure in which a fixed constant velocity universal joint and a sliding constant velocity universal joint are attached to both ends of a hollow intermediate shaft. [Means for solving the problem]

[0010] In order to solve the above problems, in the drive shaft of the present invention, a shaft portion is coaxially formed integrally with an inner race of a fixed type constant velocity universal joint, and one end opening of an intermediate shaft is joined to the shaft portion by solid-state welding, and a shaft portion is coaxially formed integrally with a tripod of a sliding type constant velocity universal joint, and the other end opening of the intermediate shaft is joined to the shaft portion by solid-state welding. Furthermore, it is preferable that the intermediate shaft is hollow throughout. [Effects of the Invention]

[0011] According to the present invention, since the shaft portion is integrated with the inner race and the shaft portion is integrated with the tripod, and the intermediate shaft is directly and coaxially joined to each shaft portion by solid-state welding, it is possible to provide a drive shaft that ensures the strength of the joints, is lightweight, and easily increases the torque transmission capacity. If the intermediate shaft is hollow throughout, further weight reduction can be achieved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a front view of a drive shaft according to a first embodiment of the present invention. FIG. [Figure 2] 1 is a front cross-sectional view of a drive shaft according to a first embodiment of the present invention. [Figure 3] FIG. 1 is a perspective view of a tripod according to a first embodiment of the present invention. [Figure 4] 1 is a perspective view of an inner race according to a first embodiment of the present invention. FIG. [Figure 5] FIG. 1 is a cross-sectional view of a conventional drive shaft. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will now be described with reference to FIGS.

[0014] 1 and 2 show a front view and a cross-sectional view of the entire drive shaft 1. An intermediate shaft 2 that is hollow over its entire length is disposed in the center, and a fixed constant velocity universal joint 3 is attached to an end 13 on the right hand side of the figure, and a sliding constant velocity universal joint 8 is attached to an end 14 on the left hand side of the figure, thereby constituting the drive shaft 1. From the viewpoint of reducing weight and rotating mass, it is preferable that the intermediate shaft 2 is hollow over its entire length, but it may also have a structure that combines hollow and solid parts, or a solid structure over its entire length.

[0015] The inner race 6, which is a key part of the fixed type constant velocity universal joint 3, will be described with reference to Figure 4. Six track grooves 31 are formed in a barrel-shaped body portion 32, and balls 5 roll in each of the track grooves 31. Similarly, the balls 5 also roll in track grooves (not shown) provided on the inside of the outer joint member 4. The movement of each ball 5 is controlled by a cage 7. A hollow shaft portion 30, which serves as a mounting shaft, is formed coaxially with the body portion 32. In other words, the body portion 32 does not have a conventional fitting opening.

[0016] The end face of the shaft portion 30 is solid-state welded to the end face of the end portion 13 of the intermediate shaft 2 (an example of one end opening of the intermediate shaft 2) while in contact with it, forming a joining surface 15. Some burrs are formed inside and outside the joining surface 15, but these are removed or left as appropriate. Solid-state welding is a general term for a group of welding methods that combine metals in a solid state by applying heat and pressure, and is also called solid-state welding. While friction welding is used as the specific method in this embodiment, other solid-state welding methods may also be used. The structure other than the shaft portion 30 follows that of a conventional fixed-type constant velocity universal joint. To integrally form the shaft portion coaxially with the barrel of the inner race, a closed-circuit forging method is preferably used.

[0017] Next, the tripod 10, which is a main part of the sliding type constant velocity universal joint 8, will be described with reference to Figure 3. Three legs 21 extend radially from a barrel-shaped body 22. Rollers 12 (not shown) are rotatably attached to the legs 21. The rollers 12 slide within track grooves 11 on the inner surface of the outer component member 9. A hollow shaft 20, which serves as an attachment shaft, is formed coaxially with the body 22. In other words, the body 22 does not have a conventional fitting opening.

[0018] The end face of the shaft portion 20 is solid-state welded to the end face of the end portion 14 of the intermediate shaft 2 (an example of the other end opening of the intermediate shaft 2) in abutting contact therewith, thereby forming a welded surface 16. The solid-state welding to be applied is as described above. Note that the structure other than the shaft portion 20 follows that of a conventional Zepper type constant velocity universal joint. To integrally form the shaft portion 20 coaxially with the trunk portion 22 of the tripod 10, a closed die forging method may be used.

[0019] As described above, the drive shaft 1 is constructed by coaxially solid-state welding the ends 13, 14 of the intermediate shaft 2 to the axial portions 20, 30 of the inner race 6 and the tripods 10, respectively. In this drive shaft 1, the inner race 6 and the tripods 10 do not have openings as in conventional drive shafts, eliminating the concern that the areas around the mating portions will be the weakest points. Furthermore, the intermediate shaft 2, the inner race 6, and the tripods 10 are directly and coaxially joined by solid-state welding, making it easy to reduce the weight and size of the inner race 6, the tripods 10, and the entire joint while maintaining their strength and transmission torque capacity. It is also easy to increase the diameters of the axial portions and the intermediate shaft 2 in order to increase the transmission torque capacity. Of course, the intermediate shaft 2 can be hollow throughout, ensuring a lighter weight.

[0020] The ends of the shaft portion 30 of the inner race 6 and the shaft portion 20 of the tripod 10 may be solid instead of hollow. In that case, solid-state welding is performed between each solid shaft portion and the hollow intermediate shaft 2. The lengths of the shaft portions 20 and 30 may be determined in accordance with other requirements within the range in which solid-state welding is possible, and the shaft portions may have a shape with the shortest length.

[0021] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and even if there are modifications in the scope that deviate from the spirit of the present invention, they are still included in the present invention. [Explanation of symbols]

[0022] 1 drive shaft 2 intermediate shaft 3 Fixed constant velocity universal joint 6 Inner lace 8 Sliding constant velocity universal joint 10 Tripod 15, 16 Joint surface 20, 30 shaft 22, 32 Torso

Claims

1. In a drive shaft in which a fixed type constant velocity universal joint and a sliding type constant velocity universal joint are attached to both ends of an intermediate shaft, a shaft portion is integrally formed coaxially with the inner race of the fixed type constant velocity universal joint, and one end opening of the intermediate shaft is joined to the shaft portion by solid-state welding; a shaft portion is integrally formed coaxially with the tripod of the sliding type constant velocity universal joint, and the other end opening of the intermediate shaft is joined to the shaft portion by solid-state welding; A drive shaft characterized by:

2. The intermediate shaft is hollow throughout. The drive shaft according to claim 1 .

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