Drive shaft for vehicle

Abstract

To provide a drive shaft for a vehicle capable of making right and left parts common while equalizing torsional rigidity on the right and left sides.SOLUTION: Any one of the outer circumferential surface spline teeth formed at both ends of the intermediate shaft and the inner circumferential surface spline teeth formed at the first joint and the second joint has a helix angle. The torsion angle is formed such that the inclination direction is opposite between the power source side and the drive wheel side. Accordingly, in a case where the vehicle drive shaft has common specifications on the left and right sides, the substantial axial length for transmitting power is likely to be equal on the left and right sides, and thus the torsional rigidity of the vehicle drive shaft is likely to be equal on the left and right sides. Therefore, in the vehicle drive shaft, it is possible to achieve commonality of components on the left and right sides while making the torsional rigidity equal on the left and right sides.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle drive shaft in which joints are spline-fitted to both ends of an intermediate shaft. [Background technology]

[0002] A well-known vehicle driveshaft includes an intermediate shaft that transmits power from a power source to drive wheels, a first joint connected by spline fitting to the power source end of the intermediate shaft, and a second joint connected by spline fitting to the drive wheel end of the intermediate shaft. Patent Document 1 (Patent Document 1) describes an example of such a vehicle driveshaft. Patent Document 1 discloses that the spline teeth formed on the intermediate shaft have a helix angle inclined at a predetermined angle with respect to the rotational axis of the intermediate shaft, thereby suppressing circumferential backlash at the spline-fitted portion. Patent Document 1 also discloses that the effective axial length for transmitting power can be changed by changing the direction of the helix angle, thereby adjusting the torsional rigidity of the vehicle driveshaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-153460 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vehicle driveshaft disclosed in Patent Document 1, the spline teeth formed on the intermediate shaft have a helix angle inclined in the same direction at both ends. On the other hand, if the length of the vehicle driveshaft in the rotational axis direction is the same on both sides relative to the forward direction of the vehicle when mounted on the vehicle, it is desirable to have a common specification for both left and right vehicle driveshafts. However, if the helix angles at both ends of the intermediate shaft are formed in the same direction, the effective axial lengths will be different on the left and right, which may result in a difference in torsional rigidity between the left and right vehicle driveshafts.

[0005] The present invention has been made against the background of the above circumstances, and its object is to provide a vehicle drive shaft that has equal torsional rigidity on the left and right sides while allowing for standardization of left and right parts. [Means for solving the problem]

[0006] The gist of a first invention is a vehicle drive shaft including: (a) an intermediate shaft that transmits power from a power source to drive wheels; a first joint connected by spline fitting to an end of the intermediate shaft on the power source side; and a second joint connected by spline fitting to an end of the intermediate shaft on the drive wheel side; (b) at a fitting portion where the spline fitting is performed, either one of outer peripheral surface spline teeth formed on an outer peripheral surface of the power source side end of the intermediate shaft and an outer peripheral surface of the drive wheel side end of the intermediate shaft, or inner peripheral surface spline teeth formed on an inner peripheral surface of the first joint and an inner peripheral surface of the second joint, at the fitting portion, forms a helix angle inclined at a predetermined angle with respect to a rotation axis of the intermediate shaft; and (c) the helix angle is formed in opposite directions on the power source side and the drive wheel side. [Effects of the Invention]

[0007] According to the first aspect of the present invention, either the outer peripheral spline teeth formed on each end of the intermediate shaft or the inner peripheral spline teeth formed on each of the first and second joints has a helix angle. The helix angle is inclined in opposite directions on the power source side and the drive wheel side. This makes it easier to make the effective axial length for transmitting power equal on the left and right sides when the left and right vehicle drive shafts are made to have the same specifications, which makes it easier to make the torsional rigidity of the left and right vehicle drive shafts equal. Therefore, it is possible to make the torsional rigidity equal on the left and right sides of the vehicle drive shaft and to standardize the left and right parts. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a part of a main part of a vehicle drive shaft to which the present invention is applied. [Figure 2] 2 is an enlarged view showing a main part of a fitting portion where spline fitting is performed in a vehicle drive shaft. FIG. [Figure 3] 1 is a diagram illustrating an example of a vehicle drive shaft according to an embodiment of the present invention. [Figure 4] 2 is a diagram illustrating a state in which a vehicle drive shaft is mounted on a vehicle, different from that shown in FIG. 1. FIG. [Figure 5] 10A and 10B are diagrams illustrating a reference example for reducing the difference in torsional rigidity between the left and right sides of a vehicle drive shaft. [Figure 6] FIG. 10 is a diagram illustrating an example of a vehicle drive shaft in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] FIG. 1 is a cross-sectional view showing a portion of a main part of a vehicle drive shaft 10 (hereinafter referred to as drive shaft 10) to which the present invention is applied. In FIG. 1, drive shaft 10 is provided on the left and right sides when mounted on vehicle 8. When mounted on vehicle 8, drive shaft 10 is a power transmission member provided between a power unit 12 (see dashed line) and drive wheels 14 (see dashed line), which are provided on the left and right sides, respectively. The "left and right" mentioned above refer to the left and right sides in the forward direction of vehicle 8. The drive shaft 10, power unit 12, etc. basically have the same specifications on the left and right sides. Common specifications mean, for example, that the external dimensions such as the overall length are the same, and that the structure, function, etc. are also the same, and are synonymous with the same part.

[0011] The power unit 12 includes, for example, an electric motor MG as a power source, a transmission mechanism (not shown) that transmits power from the electric motor MG to the drive shaft 10, etc. Arrow A in Fig. 1 indicates the transmission direction of power output from the power unit 12. Arrow B in Fig. 1 indicates the rotation direction of the drive shaft 10, and indicates the forward direction of the vehicle 8.

[0012] The drive shaft 10 includes an intermediate shaft 20, a first joint 22, and a second joint 24. The intermediate shaft 20 is a power transmission shaft that transmits power from the power unit 12, i.e., the electric motor MG, to the drive wheels 14. The first joint 22 is an inboard joint that is connected by spline fitting to an end 20a of the intermediate shaft 20 on the input side, i.e., the electric motor MG side. The second joint 24 is an outboard joint that is connected by spline fitting to an end 20b of the intermediate shaft 20 on the output side, i.e., the drive wheels 14 side.

[0013] The intermediate shaft 20 has spline teeth 60 formed on a first fitting portion 50 serving as a fitting portion where the intermediate shaft 20 and the first joint 22 are spline-fitted together. The spline teeth 60 are outer peripheral spline teeth formed on the outer peripheral surface of the end portion 20a on the electric motor MG side. The intermediate shaft 20 has spline teeth 62 formed on a second fitting portion 52 serving as a fitting portion where the intermediate shaft 20 and the second joint 24 are spline-fitted together. The spline teeth 62 are outer peripheral spline teeth formed on the outer peripheral surface of the end portion 20b on the drive wheel 14 side.

[0014] The first joint 22 is a constant velocity universal joint, such as a tripod-type sliding constant velocity universal joint. The first joint 22 includes an inner ring 22a fitted onto the end 20a of the intermediate shaft 20, and an outer ring 22c having a housing chamber 22b formed therein. The inner ring 22a is housed in the housing chamber 22b. The outer ring 22c includes a first shaft portion 30 disposed to protrude in the direction of the rotation axis C1 of the outer ring 22c. The first shaft portion 30 is connected to an output rotating member of the transmission mechanism of the power unit 12.

[0015] The inner ring 22a has projections 22d formed on its outer periphery at equal intervals, protruding outward in the circumferential direction. The projections 22d are configured to support a plurality of rollers 22e. The inner circumferential surface of the outer ring 22c is provided with guide grooves 22f that receive the rollers 22e and guide them in a direction parallel to the rotation axis C1. This allows the inner ring 22a to move relative to the outer ring 22c in the direction of the rotation axis C1 but not to rotate relative to it. The outer ring 22c is permitted to move in an arc within a predetermined range starting from the end 20a of the intermediate shaft 20. Spline teeth 64 are formed on the inner circumferential surface of the inner ring 22a, which serves as the inner circumferential surface of the first joint 22. The spline teeth 64 are inner circumferential surface spline teeth that are spline-fitted with the spline teeth 60 at the first fitting portion 50.

[0016] The second joint 24 is a constant velocity universal joint, such as a Rzeppa-type fixed constant velocity universal joint. The second joint 24 includes an inner ring 24a fitted onto the end 20b of the intermediate shaft 20, and an outer ring 24c having a housing chamber 24b formed therein. The inner ring 24a is housed in the housing chamber 24b. The outer ring 24c includes a second shaft portion 32 disposed to protrude in the direction of the rotation axis C2 of the outer ring 24c. A hub bearing 40 connected to the drive wheel 14 is fitted onto the second shaft portion 32 by spline fitting. The second shaft portion 32 is connected to the drive wheel 14 via the hub bearing 40.

[0017] A substantially cylindrical cage 24d and a plurality of balls 24e are provided between the inner ring 24a and the outer ring 24c. The balls 24e are held in a plurality of retaining holes formed in the cage 24d. A plurality of guide grooves 24f corresponding to the balls 24e are formed in the outer peripheral surface of the inner ring 24a and the inner peripheral surface of the outer ring 24c, respectively, in the direction of the rotation axis C2. As a result, the balls 24e are fitted into and guided in the guide grooves 24f. The outer ring 24c is allowed to move in an arc within a predetermined range starting from the end 20b of the intermediate shaft 20. Spline teeth 66 are formed on the inner peripheral surface of the inner ring 24a, which serves as the inner peripheral surface of the second joint 24. The spline teeth 66 are inner peripheral spline teeth that are spline-fitted with the spline teeth 62 at the second fitting portion 52.

[0018] The opening between the intermediate shaft 20 and the outer ring 22c is covered by a bellows-shaped boot 34 made of a soft resin material. The large diameter end of the boot 34 is fitted around the outer ring 22c and the small diameter end is fitted to the intermediate shaft 20. The boot 34 is filled with lubricating grease. The opening between the intermediate shaft 20 and the outer ring 24c is covered by a bellows-shaped boot 36 made of a soft resin material. The large diameter end of the boot 36 is fitted around the outer ring 24c and the small diameter end is fitted to the intermediate shaft 20. The boot 36 is filled with lubricating grease.

[0019] The first joint 22 is provided between the power unit 12 and the intermediate shaft 20 and transmits rotation at a constant speed regardless of the intersecting angle between the rotational axis C1 of the first shaft unit 30 and the rotational axis C of the intermediate shaft 20. The second joint 24 is provided between the drive wheels 14 and the intermediate shaft 20 and transmits rotation at a constant speed regardless of the intersecting angle between the rotational axis C2 of the second shaft unit 32 and the rotational axis C of the intermediate shaft 20. In the drive shaft 10, power output from the power unit 12 is transmitted in the direction indicated by arrow A. The power output from the power unit 12 is transmitted to the intermediate shaft 20 via the first joint 22, from the intermediate shaft 20 via the second joint 24 to the hub bearing 40, and from the hub bearing 40 to the drive wheels 14. Note that FIG. 1 shows a state in which the first shaft unit 30, the intermediate shaft 20, and the second shaft unit 32 are all concentric.

[0020] FIG. 2 is an enlarged view of a main portion of the fitting portion of the drive shaft 10 where spline fitting is performed. FIG. 2 is an enlarged view of the first fitting portion 50 (or the second fitting portion 52). That is, FIG. 2 shows the fitting state between the spline teeth 60 formed on the end portion 20a of the intermediate shaft 20 and the spline teeth 64 formed on the inner ring 22a of the first joint 22. FIG. 2 also shows the fitting state between the spline teeth 62 formed on the end portion 20b of the intermediate shaft 20 and the spline teeth 66 formed on the inner ring 24a of the second joint 24. FIG. 2(a) is a diagram illustrating right-handed twisting. FIG. 2(b) is a diagram illustrating left-handed twisting.

[0021] As shown in FIG. 2(a), in the first fitted portion 50, the spline teeth 60 are formed with a right-hand helix angle θr, which is inclined at a predetermined angle θf with respect to the rotation axis C of the intermediate shaft 20. In other words, the end 20a of the intermediate shaft 20 has, on its outer circumferential surface, spline teeth 60 formed with a right-hand helix angle θr, which is a helix angle θ rotating clockwise toward the drive wheels 14. The right-hand helix angle θr is a right-hand helix angle θ when viewed from the first joint 22 (inboard joint) side. In the first fitted portion 50, the spline teeth 64 are formed parallel to the rotation axis C of the intermediate shaft 20. In addition, in the second fitted portion 52, the spline teeth 62 are formed with a right-hand helix angle θr, which is inclined at a predetermined angle θf with respect to the rotation axis C of the intermediate shaft 20. In other words, the end 20b of the intermediate shaft 20 has, on its outer circumferential surface, spline teeth 62 formed with a right-hand helix angle θr. In the second fitting portion 52, the spline teeth 66 are formed parallel to the rotation axis C of the intermediate shaft 20. The predetermined angle θf is an acute angle formed with respect to the rotation axis C of the intermediate shaft 20.

[0022] As shown in FIG. 2(b), in the first fitted portion 50, the spline teeth 60 are formed with a left helix angle θl, which is inclined at a predetermined angle θf with respect to the rotation axis C of the intermediate shaft 20. In other words, the end 20a of the intermediate shaft 20 has, on its outer circumferential surface, spline teeth 60 formed with a left helix angle θl, which is a helix angle θ in a counterclockwise direction toward the drive wheels 14. The left helix angle θl is a left-handed helix angle θ when viewed from the first joint 22 (inboard joint) side. In the first fitted portion 50, the spline teeth 64 are formed parallel to the rotation axis C of the intermediate shaft 20. In addition, in the second fitted portion 52, the spline teeth 62 are formed with a left helix angle θl, which is inclined at a predetermined angle θf with respect to the rotation axis C of the intermediate shaft 20. In other words, the end 20b of the intermediate shaft 20 has, on its outer circumferential surface, spline teeth 62 formed with a left helix angle θl. In the second fitting portion 52 , the spline teeth 66 are formed parallel to the rotation axis C of the intermediate shaft 20 .

[0023] In the first fitting portion 50, the spline teeth 60 having a helix angle θ formed therein are press-fitted with the spline teeth 64. This reduces or eliminates circumferential backlash in the first fitting portion 50. In the second fitting portion 52, the spline teeth 62 having a helix angle θ formed therein are press-fitted with the spline teeth 66. This reduces or eliminates circumferential backlash in the second fitting portion 52. The predetermined angle θf is, for example, a predetermined angle at which circumferential backlash in the fitting portions (50, 52) is reduced or eliminated while spline fitting is performed in the fitting portions (50, 52).

[0024] Fig. 6 is a diagram illustrating an example of a vehicle drive shaft 100 (hereinafter referred to as drive shaft 100) in a comparative example. Fig. 6(a) is a diagram illustrating an example of a torsion angle θ formed in an intermediate shaft 110 in the drive shaft 100. Fig. 6(b) is a diagram illustrating the torsional rigidity of the drive shaft 100.

[0025] 6(a), the intermediate shaft 110 has spline teeth 120, 122 on its outer circumferential surface, each of which has a helix angle θ inclined in the same direction at both ends, for example, a right helix angle θr. The left and right intermediate shafts 110 have the same specifications.

[0026] 6(b), when the vehicle is traveling forward, the first joint 22 and the intermediate shaft 110 are related in such a way that the first joint 22 is on the driving side that transmits power, and the intermediate shaft 110 is on the driven side to which power is transmitted. When the vehicle is traveling forward, power is transmitted from the spline teeth 64 on the driving side to the spline teeth 120 on the driven side (see transmission point P1). Transmission point P1 is on the power unit 12 side for the left drive shaft 100, and on the drive wheel 14 side for the right drive shaft 100.

[0027] 6(b), when the vehicle is traveling forward, the relationship between the second joint 24 and the intermediate shaft 110 is such that the intermediate shaft 110 is on the driving side that transmits power, and the second joint 24 is on the driven side to which power is transmitted. When the vehicle is traveling forward, power is transmitted from the spline teeth 122 on the driving side to the spline teeth 66 on the driven side (see transmission point P2). Transmission point P2 is on the driving wheel 14 side for the left drive shaft 100, and on the power unit 12 side for the right drive shaft 100.

[0028] The axial length DL of the left drive shaft 100 is longer than the axial length DR of the right drive shaft 100. The axial length D is the actual axial length dimension for transmitting power in a vehicle drive shaft. The axial length D represents, for example, the distance in the direction of the rotation axis C between transmission points P1 and P2.

[0029] When the axial length D of a vehicle drive shaft is relatively long, the torsional rigidity is made smaller than when the axial length D is relatively short. Therefore, the torsional rigidity of the left drive shaft 100 is made smaller than the torsional rigidity of the right drive shaft 100. By reducing the torsional rigidity of the vehicle drive shaft, the occurrence of booming noise is likely to be reduced, and by increasing the torsional rigidity of the vehicle drive shaft, the stability of driving operation is likely to be improved.

[0030] If drive shafts 100 in which both ends of intermediate shaft 110 are inclined in the same direction at a torsion angle θ are used on both the left and right sides of a vehicle, there is a risk that a difference in torsional rigidity will occur between the left and right sides of drive shaft 100.

[0031] Therefore, in the drive shaft 10 of this embodiment, the torsion angle θ of the spline teeth 60, 62 of the intermediate shaft 20 is formed so that the inclination direction is opposite between the electric motor MG side and the drive wheel 14 side (see FIG. 1).

[0032] 3A and 3B are diagrams illustrating an example of the drive shaft 10 in this embodiment. Fig. 3A is a diagram illustrating an example of the torsion angle θ formed in the intermediate shaft 20 of the drive shaft 10. Fig. 3B is a diagram illustrating the torsional rigidity of the drive shaft 10.

[0033] 3(a), the intermediate shaft 20 has spline teeth 60, 62 on its outer circumferential surface, with the helix angles θ inclined in opposite directions at both ends. For example, the spline teeth 60 have a right-hand helix angle θr, while the spline teeth 62 have a left-hand helix angle θl. The left and right intermediate shafts 20 have the same specifications.

[0034] 3(b), when the vehicle is traveling forward, the first joint 22 and the intermediate shaft 20 are related in such a way that the first joint 22 is on the driving side that transmits power, and the intermediate shaft 20 is on the driven side to which power is transmitted. When the vehicle is traveling forward, power is transmitted from the spline teeth 64 on the driving side to the spline teeth 60 on the driven side (see transmission point P1). Transmission point P1 is on the power unit 12 side for the left drive shaft 10, and on the drive wheel 14 side for the right drive shaft 10.

[0035] 3(b), when the vehicle is traveling forward, in the relationship between the second joint 24 and the intermediate shaft 20, the intermediate shaft 20 is on the driving side that transmits power, and the second joint 24 is on the driven side to which power is transmitted. When the vehicle is traveling forward, power is transmitted from the spline teeth 62 on the driving side to the spline teeth 66 on the driven side (see transmission point P2). Transmission point P2 is on the power unit 12 side for the left drive shaft 10, and on the drive wheel 14 side for the right drive shaft 10.

[0036] The axial length DL of the left drive shaft 10, which is the axial length D, and the axial length DR of the right drive shaft 10, which is the axial length D, are set to be the same. Therefore, the torsional rigidity of the left and right drive shafts 10 is set to be the same. Whether the drive shaft 10, which has a torsion angle θ inclined in opposite directions at both ends of the intermediate shaft 20, is used on the left or right, the torsional rigidity of the left and right drive shafts 10 is set to be the same.

[0037] As described above, according to this embodiment, the spline teeth 60, 62 formed on each end of the intermediate shaft 20 are inclined at a predetermined angle θf with respect to the rotational axis C of the intermediate shaft 20, forming a helix angle θ. The helix angle θ is inclined in opposite directions on the electric motor MG side and the drive wheel 14 side. This makes it easier to make the axial length D equal on the left and right sides when the drive shafts 10 are made to have the same specifications, which makes it easier to make the torsional rigidity of the drive shafts 10 equal on the left and right sides. Therefore, the torsional rigidity of the drive shafts 10 can be made equal on the left and right sides while also allowing for left and right component standardization.

[0038] Furthermore, according to this embodiment, when the drive shaft 10 is mounted on the vehicle 8, it is provided on the left and right sides in the forward direction of the vehicle 8, and the same specifications are used for both the left and right sides. This allows the torsional rigidity of the drive shaft 10 to be equal on the left and right sides, while also allowing for the use of standardized left and right parts.

[0039] Furthermore, according to this embodiment, the predetermined angle θf is a predetermined angle for suppressing or eliminating circumferential backlash at the fitting portions (50, 52) while achieving spline fit at the fitting portions (50, 52). As a result, appropriate press-fit connection is achieved at the fitting portions (50, 52), and appropriate suppression or elimination of circumferential backlash at the fitting portions (50, 52).

[0040] Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments will be given the same reference numerals and the description thereof will be omitted. [Example]

[0041] FIG. 4 is a diagram illustrating a state in which the drive shaft 10 is mounted on a vehicle 80, different from FIG. 1. In FIG. 4, the left and right drive shafts 10 are mounted on the vehicle 80 and are respectively disposed between a transmission 82 (see dashed line) and left and right drive wheels 14 (see dashed line). The transmission 82 transmits power output from a power source 84 (see dashed line) provided on the vehicle 80 to the left and right drive shafts 10. The transmission 82 is provided with a differential gear 86 (see dashed line) at the center of the vehicle 80 in the vehicle width direction (left and right direction). The first shaft portions 30 of the left and right drive shafts 10 are respectively connected to the differential gear 86. If the vehicle 80 has the differential gear 86 disposed at the center of the vehicle width direction, a common drive shaft 10 can be used for both the left and right.

[0042] As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained.

[0043] Figure 5 is a diagram illustrating a reference example for reducing the difference in torsional rigidity between the left and right sides of a vehicle drive shaft 92 (hereinafter referred to as drive shaft 92). Figure 5(a) is a diagram illustrating the state in which the drive shaft 92 is mounted on a vehicle 90. Figure 5(b) is a diagram illustrating an example of the torsion angle θ formed in the intermediate shaft 94 of the drive shaft 92. Figure 5(c) is a diagram illustrating the torsional rigidity of the drive shaft 92.

[0044] In FIG. 5A, the drive shaft 92 includes a left drive shaft 92l and a right drive shaft 92r. The drive shaft 92l includes a left intermediate shaft 94l as an intermediate shaft 94. The drive shaft 92r includes a right intermediate shaft 94r as an intermediate shaft 94. When mounted on the vehicle 90, the left and right drive shafts 92 are respectively disposed between a transaxle 96 and the left and right drive wheels 14. The transaxle 96 transmits power output from an engine 98, which serves as a power source provided in the vehicle 90, to the left and right drive shafts 92. In the transaxle 96, a differential gear (not shown) is disposed to the left of the center of the vehicle 90 in the vehicle width direction. Therefore, the axial length LL of the intermediate shaft 94l is shorter than the axial length LR of the intermediate shaft 94r.

[0045] 5(b), the left intermediate shaft 94l has spline teeth 94ls1 and 94ls2 on its outer circumferential surface, each of which has a helix angle θ inclined in the same direction at both ends, e.g., a right-hand helix angle θr. The right intermediate shaft 94r has spline teeth 94rs1 and 94rs2 on its outer circumferential surface, each of which has a helix angle θ inclined in the same direction at both ends, e.g., a right-hand helix angle θr.

[0046] 5(c), when the vehicle travels forward, the first joint 22 and the intermediate shaft 94 are related in such a way that the first joint 22 is on the driving side that transmits power, and the intermediate shaft 94 is on the driven side to which power is transmitted. When the vehicle travels forward, power is transmitted from the spline teeth 64 on the driving side to the spline teeth 94ls1 and 94rs1 on the driven side (see transmission point P1). Transmission point P1 is on the engine 98 side for the left drive shaft 92l, and on the drive wheels 14 side for the right drive shaft 92r.

[0047] 5(c), when the vehicle travels forward, the relationship between the second joint 24 and the intermediate shaft 94 is such that the intermediate shaft 94 is on the driving side that transmits power, and the second joint 24 is on the driven side to which power is transmitted. When the vehicle travels forward, power is transmitted from the drive-side spline teeth 94ls2, 94rs2 to the driven-side spline teeth 66 (see transmission point P2). Transmission point P2 is on the drive wheel 14 side for the left drive shaft 92l, and on the engine 98 side for the right drive shaft 92r.

[0048] In the vehicle 90, the axial length LR of the intermediate shaft 94r is longer than the axial length LL of the intermediate shaft 94l, so the torsional rigidity of the right drive shaft 92r is smaller than the torsional rigidity of the left drive shaft 92l. To reduce this difference in torsional rigidity between the left and right sides, the diameter of the right intermediate shaft 94r is set to be larger than the diameter of the left intermediate shaft 94l. In addition to this setting, if the directions of the torsion angles θ of the spline teeth 94ls1, 94ls2 of the intermediate shaft 94l and the spline teeth 94rs1, 94rs2 of the intermediate shaft 94r are set as shown in Figures 5(b) and 5(c), the difference in torsional rigidity between the left and right sides can be further reduced.

[0049] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0050] For example, in the first and second embodiments described above, the spline teeth 60 of the intermediate shaft 20 may be formed parallel to the rotational axis C of the intermediate shaft 20 at the first fitted portion 50, and the spline teeth 64 of the first joint 22 may have a twist angle θ. In this case, the spline teeth 62 of the intermediate shaft 20 may be formed parallel to the rotational axis C of the intermediate shaft 20 at the second fitted portion 52, and the spline teeth 66 of the second joint 24 may have a twist angle θ. In short, the present invention can be applied to any drive shaft 10 in which either the outer peripheral surface spline teeth (60, 62) or the inner peripheral surface spline teeth (64, 66) have a twist angle θ and the other is formed parallel to the rotational axis C of the intermediate shaft 20. However, from the viewpoint of component machining, it is more useful if the outer peripheral surface spline teeth (60, 62) are formed with a helix angle θ and the inner peripheral surface spline teeth (64, 66) are formed parallel to the rotation axis C of the intermediate shaft 20.

[0051] The present invention can also be applied to drive shafts in engine vehicles that have an engine as a power source, hybrid vehicles that have an engine and an electric motor as power sources, and electric vehicles that have only an electric motor as a power source.

[0052] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0053] 8: Vehicle 10: Vehicle drive shaft 14: Drive wheel 20: Intermediate shaft 20a: End (end on the power source side) 20b: End (end on the drive wheel side) 22: First joint 24: Second joint 50: First mating portion (fitting portion) 52: Second mating portion (fitting portion) 60, 62: Spline teeth (outer peripheral surface spline teeth) 64, 66: Spline teeth (inner peripheral surface spline teeth) 80: Vehicle 84: Power source C: Rotation axis (rotation axis of intermediate shaft) MG: Electric motor (power source) θ: Twist angle θr: Right twist angle (twist angle) θl: Left twist angle (twist angle)

Claims

1. A vehicle drive shaft including: an intermediate shaft that transmits power from a power source to drive wheels; a first joint that is connected by spline fitting to an end of the intermediate shaft on the power source side; and a second joint that is connected by spline fitting to an end of the intermediate shaft on the drive wheel side, either one of outer peripheral spline teeth formed on an outer peripheral surface of the power source side end of the intermediate shaft and an outer peripheral surface of the drive wheel side end of the intermediate shaft at the fitting portion where the spline fitting is performed, or inner peripheral spline teeth formed on an inner peripheral surface of the first joint and an inner peripheral surface of the second joint at the fitting portion, has a helix angle inclined at a predetermined angle with respect to the rotation axis of the intermediate shaft, The torsion angle is formed such that the inclination direction is opposite between the power source side and the drive wheel side.

2. the outer peripheral surface spline teeth are formed with the helix angle, 2. The vehicle drive shaft according to claim 1, wherein the inner peripheral surface spline teeth are formed parallel to the rotation axis.

3. 3. The vehicle drive shaft according to claim 1, wherein, when mounted on a vehicle, the drive shaft is provided on both left and right sides relative to the forward direction of the vehicle, and the left and right sides have common specifications.

4. 2. The vehicle drive shaft according to claim 1, wherein the predetermined angle is a predetermined angle at which circumferential play in the fitting portion is suppressed or eliminated while the spline fitting is performed.

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