Driving force transmission device

Abstract

This driving force transmission device includes an input shaft (11) to which a rotational drive force (F) from a drive source (2) is inputted, a first joint (20) that is connected to the input shaft (11), an output shaft (12) to which the rotational drive force (F) is outputted, a second joint (30) that is connected to the output shaft (12), and an intermediate shaft (13) that connects the first joint (20) and the second joint (30). A drive force transmission path (14) is provided with a plurality of fitting parts including a spline shaft part (16) having a plurality of spline teeth (16a), and a spline groove part (17) having a plurality of fitting grooves (17a) fitted to the plurality of spline teeth (16a). The plurality of fitting parts include a first fitting part (15A) and a second fitting part (15B) in which the plurality of spline teeth (16a) are twisted with respect to rotation axis lines (L1, L2), and the twisting directions of the plurality of spline teeth (16a) are different between the first fitting part (15A) and the second fitting part (15B).

Description

Drive force transmission device

[0001] The present disclosure relates to a driving force transmission device.

[0002] Japanese Patent Application Laid-Open Publication No. 2003-144992 discloses a vehicle drive shaft, which is one such driving force transmission device. The driving force transmission path of this vehicle drive shaft is provided with two joints and four fitting portions. Depending on the fitting, a torsion angle may be provided in the spline teeth of the spline shaft to improve assembly ease and suppress rotational backlash. Providing a torsion angle in the spline teeth of the spline shaft results in different torsional rigidity depending on the direction of rotation. That is, in a rotation direction in which the spline teeth of the spline shaft abut against the wall surfaces of the spline grooves from their root portions, the torsional rigidity is relatively high. In contrast, in a rotation direction in which the spline teeth of the spline shaft abut against the wall surfaces of the spline grooves from their tip portions, the torsional rigidity is relatively low.

[0003] Japanese Patent Application Laid-Open No. 2020-153460

[0004] In electric and hybrid vehicles, kinetic energy is converted into electrical energy by an electric motor during regenerative braking, and the recovered electrical energy is then used to drive the electric motor while the vehicle is moving. This allows for higher energy efficiency than braking using friction brakes (mechanical brakes). Regenerative torque is generated in the drivetrain during regenerative braking, but if the components of the drivetrain have low torsional rigidity, torsional vibrations that occur when a large torque is transmitted, such as during starting, tend to be difficult to suppress, which can result in a poor ride.

[0005] To solve these problems, the design of this type of driving force transmission device requires increasing the torsional rigidity of the components of the driving force transmission path. Therefore, one solution to this requirement is to increase the diameter of the intermediate shaft that constitutes the driving force transmission path. This makes it possible to increase the lower torsional rigidity even in cases where the torsional rigidity varies depending on the direction of rotation, such as the vehicle drive shaft described in Patent Document 1. However, increasing the diameter of the intermediate shaft increases costs, which is disadvantageous in that it makes it difficult to reduce the cost of the driving force transmission device.

[0006] The present disclosure seeks to provide a driving force transmission device that can increase torsional rigidity without increasing the diameter of components in the driving force transmission path.

[0007] One aspect of the present disclosure is a driving force transmission device comprising: an input shaft to which a rotational driving force from a driving source is input; a first joint connected to the input shaft; an output shaft to which the rotational driving force is output; a second joint connected to the output shaft; and an intermediate shaft connecting the first joint and the second joint; a driving force transmission path between the input shaft and the output shaft is provided with a plurality of fitting portions each including a spline shaft portion having a plurality of spline teeth and a spline groove portion having a plurality of fitting grooves that fit with the plurality of spline teeth; the plurality of fitting portions include a first fitting portion and a second fitting portion in which the plurality of spline teeth are twisted with respect to the rotation axis; and the twist direction of the plurality of spline teeth differs between the first fitting portion and the second fitting portion.

[0008] In the driving force transmission device of the above aspect, the multiple fitting portions provided in the driving force transmission path between the input shaft and the output shaft include a first fitting portion and a second fitting portion. The torsional directions of the spline teeth of the spline shaft portion are different in the first fitting portion and the second fitting portion. This allows the difference in torsional rigidity between the first fitting portion and the second fitting portion due to the rotational direction to be canceled out. That is, the difference in torsional rigidity can be kept small even when the rotational direction is changed. Furthermore, for a rotational direction in which torsional rigidity is low, the torsional rigidity in that rotational direction can be increased. This prevents a decrease in torsional rigidity regardless of the rotational direction. This makes it easier to suppress torsional vibrations that occur when transmitting large torque, such as during starting, and improves the ride comfort of the vehicle. According to the above aspect, the degree to which components of the driving force transmission path need to be enlarged to increase torsional rigidity can be minimized, thereby reducing the cost required for the driving force transmission device.

[0009] According to the above-described aspect, it is possible to provide a driving force transmission device that can increase the torsional rigidity without increasing the diameter of components of the driving force transmission path.

[0010] Note that the symbols in parentheses in the claims indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present disclosure.

[0011] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a longitudinal sectional view of a driving force transmission device according to a first embodiment, Fig. 2 is a schematic view of a main portion of a first fitting portion in Fig. 1 as viewed from the radially outer side, Fig. 3 is a schematic view of a main portion of a second fitting portion in Fig. 1 as viewed from the radially outer side, Fig. 4 is a schematic view of a main portion of a third fitting portion in Fig. 1 as viewed from the radially outer side, Fig. 5 is a schematic view of a main portion of a fourth fitting portion in Fig. 1 as viewed from the radially outer side, and Fig. 6 is a schematic view of a main portion of a spline shaft portion in Fig. 2 as viewed from the radially outer side when the spline shaft portion rotates in a first rotation direction through the first fitting portion in Fig. 2. 7 is a schematic diagram showing the second fitted portion of FIG. 3 in a state where the spline shaft portion rotates in a first rotation direction, FIG. 8 is a schematic diagram showing the first fitted portion of FIG. 2 in a state where the spline shaft portion rotates in a second rotation direction, FIG. 9 is a schematic diagram showing the second fitted portion of FIG. 3 in a state where the spline shaft portion rotates in the second rotation direction, and FIG. 10 is a diagram for comparing and explaining the torsional rigidity of the first embodiment and the comparative example.

[0012] Hereinafter, a driving force transmission device according to one embodiment of the above aspect will be described with reference to the drawings.

[0013] (First embodiment) 1. Overall structure of driving force transmission device 1 The driving force transmission device 1 of the first embodiment shown in Fig. 1 corresponds to a vehicle drive shaft. This driving force transmission device 1 includes an input shaft 11, an output shaft 12, an intermediate shaft 13, a first joint 20, and a second joint 30.

[0014] A rotational driving force F from the driving source 2 is input to the input shaft 11 via the differential mechanism 3. The input shaft 11 is connected to the differential mechanism 3, which is an input-side member, and a fourth fitting portion 15D is provided at this connection portion. The input shaft 11 is also connected to a first joint 20. In this embodiment, the driving source 2 is an electric motor.

[0015] The rotational driving force F from the driving source 2 is output at the output shaft 12. The output shaft 12 is connected to a hub bearing 4, which is an output-side member that rotates integrally with the driving wheels 5, and a first fitting portion 15A is provided at this connection portion. The output shaft 12 is also connected to a second joint 30. The intermediate shaft 13 is provided to connect the first joint 20 and the second joint 30. A third fitting portion 15C is provided at the connection portion between the first joint 20 and one end 13a (left end in FIG. 1 ) of the intermediate shaft 13. A second fitting portion 15B is provided at the connection portion between the second joint 30 and the other end 13b (right end in FIG. 1 ) of the intermediate shaft 13.

[0016] The input shaft 11 is disposed on a rotational axis L3. The output shaft 12 is disposed on a rotational axis L1. The intermediate shaft 13 is disposed on a rotational axis L2. Four fitting portions 15A, 15B, 15C, and 15D are provided in a driving force transmission path 14 between the input shaft 11 and the output shaft 12. In this embodiment, one first fitting portion 15A and one second fitting portion 15B are provided (i.e., the same number).

[0017] 1 , in this embodiment, when the vehicle is traveling forward, the forward rotation direction in which the input shaft 11, the intermediate shaft 13, and the output shaft 12 all rotate about their respective rotation axes is defined as a first rotation direction A1. When the vehicle is traveling backward, the reverse rotation direction is defined as a second rotation direction A2. The direction in which the rotational driving force F and driving torque from the driving source 2 are transmitted through the intermediate shaft 13 is indicated by arrow B1, and the direction in which regenerative torque is transmitted through the intermediate shaft 13 is indicated by arrow B2.

[0018] 1-1. Structure of the first joint 20 As shown in Fig. 1, the first joint 20 is an inboard joint provided on the input shaft 11 side. This first joint 20 is what is called a tripod-type constant velocity joint. This first joint 20 includes an outer ring 21, a tripod 22, and three roller units 25.

[0019] The outer ring 21 is formed in a cylindrical shape with a bottom, having an opening 21a at one end (right side in FIG. 1) in the axial direction along the rotation axis L3. Three raceway grooves 21b are formed on the inner peripheral surface of the outer ring 21 at equal intervals in the circumferential direction, extending axially from the opening 21a of the outer ring 21 toward the rear side (left side in FIG. 1).

[0020] The tripods 22 are movable in the axial direction and tiltable relative to the outer ring 21. The tripods 22 include a boss 23 to which one end 13a of the intermediate shaft 13 is connected, and three tripod shaft portions 24 extending radially outward from the boss 23. The outer peripheral surface of each tripod shaft portion 24 is formed in a spherical convex shape. In other words, the axial cross section of the outer peripheral surface of each tripod shaft portion 24 is formed in an arc-convex shape.

[0021] The roller unit 25 is formed in an annular shape. The roller unit 25 is rotatable on the outer periphery of each of the three tripod-shaft portions 24, slidable in the axial direction of each of the three tripod-shaft portions 24, and supported so as to be tiltable relative to each of the three tripod-shaft portions 24. Furthermore, each of the three roller units 25 is disposed so as to be rollable along each of the three raceway grooves 21b. Therefore, the three roller units 25 are configured to roll while maintaining their posture relative to the three raceway grooves 21b.

[0022] A boot 26 is provided on the opening 21a side of the outer ring 21. The boot 26 is formed in a bendable bellows-like shape and is expandable and contractible in the axial direction. The boot 26 closes the opening 21a side of the outer ring 21, thereby sealing the grease contained in the internal region of the outer ring 21 to prevent leakage.

[0023] 1-2. Structure of the Second Joint 30 As shown in FIG. 1, the second joint 30 is an outboard joint provided on the output shaft 12 side. This second joint 30 is what is called a ball-type constant velocity joint. For example, a Rzeppa-type fixed constant velocity joint is used. This second joint 30 includes an inner ring 31 to which the other end 13b of the intermediate shaft 13 is connected, and an outer ring 32 having an accommodation chamber 32a formed therein. The inner ring 31 is accommodated in the accommodation chamber 32a of the outer ring 32. The outer ring 32 is formed in a bottomed cylindrical shape having an opening 32b at one end (left side in FIG. 1) in the axial direction along the rotation axis L1.

[0024] A substantially cylindrical cage 33 and a plurality of balls 34 are provided between the inner ring 31 and the outer ring 32 of the second joint 30. The plurality of balls 34 are held in a plurality of retaining holes formed in the cage 33. A plurality of guide grooves 35a corresponding to the plurality of balls 34 are provided on the outer peripheral surface of the inner ring 31, and a plurality of guide grooves 35b corresponding to the plurality of balls 34 are provided on the inner peripheral surface of the outer ring 32. The plurality of balls 34 are guided while fitted into the guide grooves 35a, 35b of the inner ring 31 and the outer ring 32. This allows the outer ring 32 to move in an arc within a predetermined range starting from the other end 13b of the intermediate shaft 13.

[0025] A boot 36 is provided on the opening 32b side of the outer ring 32. The boot 36 is formed in a bendable bellows-like shape and is expandable and contractible in the axial direction. The boot 36 closes the opening 32b side of the outer ring 32, thereby sealing the grease contained in the inner region of the outer ring 32 to prevent leakage.

[0026] For further detailed structures of the first joint 20 and the second joint 30 of the driving force transmission device 1, reference may be made to, for example, the structure of a vehicle drive shaft 10 described in Japanese Patent Application Laid-Open No. 2020-153460.

[0027] 2, the first fitting portion 15A is one of the four fitting portions 15A, 15B, 15C, and 15D. The first fitting portion 15A includes a spline shaft portion 16 and a spline groove portion 17.

[0028] In the first fitting portion 15A, the spline shaft portion 16 is provided on the output shaft 12 (see FIG. 1) and has a plurality of spline teeth 16a. The plurality of spline teeth 16a protrude radially outward from the outer surface of the output shaft 12 and are arranged at intervals around the circumferential direction of the output shaft 12. The plurality of spline teeth 16a have the same twist direction and are twisted at the same twist angle θ1 with respect to the rotation axis L1.

[0029] In the first fitting portion 15A, the spline groove portion 17 is provided in the hub bearing 4 (see FIG. 1), and has a plurality of fitting grooves 17a that are press-fitted to fit with a plurality of spline teeth 16a of the spline shaft portion 16. In this first fitting portion 15A, when the spline shaft portion 16 is assembled to the spline groove portion 17, each spline tooth 16a comes into contact with the wall surface 17b of the spline groove portion 17 at both a contact point C1 on the base side and a contact point C2 on the tip side.

[0030] 3, the second fitting portion 15B is one of the four fitting portions 15A, 15B, 15C, and 15D. Similar to the first fitting portion 15A, the second fitting portion 15B includes a spline shaft portion 16 and a spline groove portion 17.

[0031] In the second fitting portion 15B, the spline shaft portion 16 is provided on the other end 13b (see FIG. 1) of the intermediate shaft 13 and has a plurality of spline teeth 16a. The plurality of spline teeth 16a protrude radially outward from the outer surface of the other end 13b of the intermediate shaft 13 and are arranged at intervals around the circumferential direction of the intermediate shaft 13. All of these plurality of spline teeth 16a have the same twist direction and are twisted at the same twist angle θ1 with respect to the rotation axis L2. All of these plurality of spline teeth 16a have the same twist direction and are twisted at the same twist angle θ2 with respect to the rotation axis L2.

[0032] In the second fitting portion 15B, the spline groove portion 17 is provided in the inner ring 31 (see FIG. 1) of the second joint 30, and has a plurality of fitting grooves 17a that are press-fitted to the plurality of spline teeth 16a of the spline shaft portion 16. In this second fitting portion 15B, when the spline shaft portion 16 is assembled to the spline groove portion 17, each spline tooth 16a comes into contact with the wall surface 17b of the spline groove portion 17 at both a contact point D1 on the base side and a contact point D2 on the tip side.

[0033] 2 and 3, in this embodiment, the torsion directions of the spline teeth 16a of the spline shaft portion 16 are different between the first fitting portion 15A and the second fitting portion 15B. That is, in FIGS. 2 and 3, when the direction of the rotation axes is taken as the left-right direction, the spline teeth 16a of the first fitting portion 15A extend downward to the right from the base toward the tip. In contrast, the spline teeth 16a of the second fitting portion 15B extend upward to the right from the base toward the tip. In other words, when the direction perpendicular to the rotation axis is taken as the up-down direction, the spline teeth 16a of the second fitting portion 15B are arranged so that the spline teeth 16a of the first fitting portion 15A are upside down.

[0034] 4, the third fitting portion 15C is one of the four fitting portions 15A, 15B, 15C, and 15D. Similar to the first fitting portion 15A, the third fitting portion 15C includes a spline shaft portion 16 and a spline groove portion 17.

[0035] In the third fitting portion 15C, the spline shaft portion 16 is provided on one end 13a of the intermediate shaft 13 (see FIG. 1) and has a plurality of spline teeth 16a. Each of the spline teeth 16a is configured to protrude radially outward from the outer surface of the one end 13a of the intermediate shaft 13. However, unlike the spline teeth 16a in the first fitting portion 15A, these spline teeth 16a extend linearly along the rotation axis L2. In this third fitting portion 15C, the spline groove portion 17 is provided on the boss 23 (see FIG. 1) of the tripod 22 of the first joint 20 and has a plurality of fitting grooves 17a that are press-fitted to the spline teeth 16a of the spline shaft portion 16. In this third fitting portion 15C, when the spline shaft portion 16 is assembled to the spline groove portion 17, each spline tooth 16a contacts the wall surface 17b of the spline groove portion 17 on both sides in the rotational direction.

[0036] 5, the fourth fitting portion 15D is one of the four fitting portions 15A, 15B, 15C, and 15D. The fourth fitting portion 15D includes a spline shaft portion 16 and a spline groove portion 17, similar to the first fitting portion 15A.

[0037] In the fourth fitting portion 15D, the spline shaft portion 16 is provided on the input shaft 11 (see FIG. 1) and has a plurality of spline teeth 16a. Each of the plurality of spline teeth 16a is configured to protrude radially outward from the outer surface of the input shaft 11. Similar to the spline teeth 16a in the third fitting portion 15C, these plurality of spline teeth 16a extend linearly along the rotation axis L3. In this fourth fitting portion 15D, the spline groove portion 17 is provided on the differential mechanism 3 (see FIG. 1) and has a plurality of fitting grooves 17a that are press-fitted to the spline teeth 16a of the spline shaft portion 16. In this fourth fitting portion 15D, when the spline shaft portion 16 is assembled to the spline groove portion 17, each spline tooth 16a contacts the wall surface 17b of the spline groove portion 17 on both sides in the rotational direction.

[0038] 2. Operation of the Fitting Portions 15A and 15B Next, the operation of the fitting portions 15A and 15B configured as described above will be described.

[0039] 6, in the first fitting portion 15A, when the spline shaft portion 16 rotates in the first rotation direction A1, each spline tooth 16a is hardly deformed and maintains a state close to the initial state in which it contacts the wall surface 17b of the spline groove portion 17 at both the base side contact point C1 and the tip side contact point C2. This is because there is little area on the front side in the first rotation direction A1 where each spline tooth 16a can deform.

[0040] In contrast, as shown in FIG. 7 , in the second fitting portion 15B, a deformation allowance region Eb (a substantially triangular region indicated by a dashed line in FIG. 7 ) for each spline tooth 16 a exists on the front side in the first rotational direction A1. Therefore, in the second fitting portion 15B, when the spline shaft portion 16 rotates in the first rotational direction A1, each spline tooth 16 a can deform from the initial state indicated by the two-dot chain line to, for example, a state indicated by the solid line, with the tip-side contact point D2 as a fulcrum. At this time, each spline tooth 16 a releases contact with the wall surface 17 b at the base-side contact point D1. Therefore, the second fitting portion 15B has a larger deformation amount in the first rotational direction A1 and lower torsional rigidity than the first fitting portion 15A.

[0041] 2-2. Regarding the Second Rotational Direction A2 As shown in FIG. 8, in the first fitting portion 15A, a deformation allowance region Ea (a substantially triangular region indicated by a dashed line in FIG. 8) for each spline tooth 16a exists on the front side in the second rotational direction A2. Therefore, in the first fitting portion 15A, when the spline shaft portion 16 rotates in the second rotational direction A2, each spline tooth 16a can deform from the initial state indicated by the two-dot chain line to, for example, a state indicated by the solid line, with the tip side contact point C2 as a fulcrum. At this time, each spline tooth 16a releases contact with the wall surface 17b at the base side contact point C1.

[0042] 9, in the second fitting portion 15B, when the spline shaft portion 16 rotates in the second rotational direction A2, each spline tooth 16a is hardly deformed and maintains a state close to the initial state in which it contacts the wall surface 17b of the spline groove portion 17 at both the base contact point D1 and the tip contact point D2. This is because there is little area in front of the second rotational direction A2 where each spline tooth 16a can deform. Therefore, the second fitting portion 15B has a smaller amount of deformation in the second rotational direction A2 and higher torsional rigidity than the first fitting portion 15A.

[0043] In this embodiment, the twist angle θ1 of the spline teeth 16 a of the first fitting portion 15A may be the same as or different from the twist angle θ2 of the spline teeth 16 a of the second fitting portion 15B. By making the twist angle θ1 and the twist angle θ2 the same, the difference in torsional rigidity when the rotation direction is changed can be reduced. On the other hand, by making the twist angle θ1 and the twist angle θ2 different, a design can be implemented in which the torsional rigidity differs depending on the rotation direction.

[0044] In this embodiment, the product of the twist angle θ1 of the spline teeth 16a of the first fitting portion 15A and its fitting length can be made to match the product of the twist angle θ2 of the spline teeth 16a of the second fitting portion 15B and its fitting length. Here, the fitting length of the spline teeth 16a refers to the dimension in the press-fit direction of the fitting portion of the spline teeth 16a that are press-fitted into the fitting grooves 17a and that actually fit into the fitting grooves 17a. This makes the deformation allowance region Ea (see FIG. 8) for the spline teeth 16a of the first fitting portion 15A and the deformation allowance region Eb (see FIG. 7) for the spline teeth 16a of the second fitting portion 15B the same. This allows the amount of deformation of the larger spline teeth 16a to be approximately the same between the first fitting portion 15A and the second fitting portion 15B, regardless of the rotation direction.

[0045] Here, the torsional rigidity of the first embodiment and the comparative example will be compared in the first rotation direction and the second rotation direction with reference to Fig. 10. As shown in Fig. 10, the torsional rigidity is expressed as a correlation between the torque and the rotation angle of the spline shaft portion 16.

[0046] The structure of the comparative example is based on the assumption that the twist direction of each spline tooth 16a of the spline shaft portion 16 of each of the two fitting portions 15A, 15B is the direction shown in Fig. 2. Therefore, the spline teeth 16a of both of the two fitting portions 15A, 15B of the comparative example operate in the first rotation direction A1 in the same manner as described using Fig. 6, and operate in the second rotation direction A2 in the same manner as described using Fig. 8.

[0047] In the comparative example, the amount of deformation in the first rotational direction A1 of each of the spline teeth 16a of the two fitting portions 15A, 15B is small (see FIG. 6). In contrast, in the first embodiment, the amount of deformation in the first rotational direction A1 of each of the spline teeth 16a of the first fitting portion 15A is small (see FIG. 6), but the amount of deformation in the first rotational direction A1 of each of the spline teeth 16a of the second fitting portion 15B is large (see FIG. 7). Therefore, in terms of the torque at the same rotation angle in the first rotational direction A1, the comparative example exceeds that of the first embodiment.

[0048] In the comparative example, the amount of deformation in the second rotational direction A2 of each spline tooth 16a of the two fitting portions 15A and 15B is large (see FIG. 8). In contrast, in the first embodiment, the amount of deformation in the second rotational direction A2 of each spline tooth 16a of the first fitting portion 15A is large (see FIG. 8), but the amount of deformation in the second rotational direction A2 of each spline tooth 16a of the second fitting portion 15B is small (see FIG. 9). In terms of the torque in the second rotational direction A2 at the same rotation angle, the first embodiment exceeds the comparative example. In other words, when the structure of the first embodiment is adopted, the value of the torsional rigidity on the vehicle reverse traveling side of the comparative example can be improved. In this case, the difference between the torsional rigidity on the vehicle forward traveling side and the torsional rigidity on the vehicle reverse traveling side is smaller than that of the comparative example.

[0049] 3. Effects and Advantages The effects and advantages of the first embodiment will be described below.

[0050] In the driving force transmission device 1 of the first embodiment, the multiple fitting portions provided in the driving force transmission path 14 between the input shaft 11 and the output shaft 12 include a first fitting portion 15A and a second fitting portion 15B. The torsional directions of the spline teeth 16a of the spline shaft portion 16 are different in the first fitting portion 15A and the second fitting portion 15B. This allows the difference in torsional rigidity between the first fitting portion 15A and the second fitting portion 15B to be canceled out depending on the rotational direction. That is, the difference in torsional rigidity can be minimized even when the rotational direction is changed. Furthermore, for rotational directions in which torsional rigidity is low, the torsional rigidity in the rotational direction can be increased. This prevents a decrease in torsional rigidity regardless of the rotational direction. This effect can be particularly enhanced by having the same number of first fitting portions 15A and second fitting portions 15B. In this case, torsional vibrations that occur when a large torque is transmitted, such as when starting, are more easily suppressed, improving the ride comfort of the vehicle. According to the first embodiment, the degree to which the diameter of components of the driving force transmission path 14 (e.g., the intermediate shaft 13) that are required to increase the torsional rigidity can be minimized, thereby reducing the cost required for the driving force transmission device 1.

[0051] According to the first embodiment, it is possible to provide a driving force transmission device 1 that can increase the torsional rigidity without increasing the diameter of the components of the driving force transmission path 14 .

[0052] Although the present disclosure has been described based on the above-described embodiments, it is understood that the present disclosure is not limited to these embodiments or structures. The present disclosure also encompasses various modifications and equivalent variations. In addition, various combinations and embodiments, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0053] In the above embodiment, the drive force transmission path 14 is illustrated as having one first fitting portion 15A and one second fitting portion 15B. However, the number of first fitting portions 15A and the number of second fitting portions 15B are not limited to one and can be changed appropriately as needed. In this case, the number of first fitting portions 15A and the number of second fitting portions 15B may be the same, or the number of first fitting portions 15A may be different from the number of second fitting portions 15B. Furthermore, the structure of the third fitting portion 15C may be changed to that of the first fitting portion 15A, or the structure of the fourth fitting portion 15D may be changed to that of the second fitting portion 15B, as needed.

[0054] In the embodiment described above, the drive force transmission path 14 is provided with four fitting portions 15A, 15B, 15C, and 15D, but other fitting portions may be added as necessary.

Claims

1. The device comprises an input shaft (11) to which a rotational driving force (F) from a drive source (2) is input, a first joint (20) connected to the input shaft, an output shaft (12) to which the rotational driving force is output, a second joint (30) connected to the output shaft, and an intermediate shaft (13) connecting the first joint and the second joint. The drive force transmission path (14) between the input shaft and the output shaft is provided with a plurality of fitting portions, each comprising a spline shaft portion (16) having a plurality of spline teeth (16a) and a spline groove portion (17) having a plurality of fitting grooves (17a) that engage with the plurality of spline teeth. The drive force transmission device (1) includes a first fitting portion (15A) and a second fitting portion (15B) in which the plurality of spline teeth are twisted with respect to the rotational axes (L1, L2), wherein the twisting direction of the plurality of spline teeth is different in the first fitting portion and the second fitting portion.

2. The drive force transmission device according to claim 1, wherein the same number of first fitting portions and second fitting portions are provided.

3. The drive force transmission device according to claim 1 or 2, wherein the first fitting portion is provided at the connection portion between the output shaft and the output side member (4), and the second fitting portion is provided at the connection portion between the second joint and the intermediate shaft.

4. The drive force transmission device according to claim 1 or 2, wherein the plurality of fitting portions include a third fitting portion (15C) provided at the connection portion between the input shaft and the input side member (3), and a fourth fitting portion (15D) provided at the connection portion between the first joint and the intermediate shaft, and in the third fitting portion and the fourth fitting portion, the plurality of spline teeth extend linearly along the rotational axes (L2, L3).

5. The drive force transmission device according to claim 1 or 2, wherein the first joint is a tripod-type constant velocity joint and the second joint is a ball-type constant velocity joint.

6. The drive force transmission device according to claim 1, wherein the plurality of spline teeth extend in a torsional direction that is downward to the right or upward to the right when the direction in which the axis of rotation extends is the left-right direction, and when the torsional direction is downward to the right in the first fitting portion, the torsional direction is upward to the right in the second fitting portion, and when the torsional direction is upward to the right in the first fitting portion, the torsional direction is downward to the right in the second fitting portion.