Power transmission shaft

Abstract

In a propeller shaft (PS) which is a power transmission shaft according to the present invention, a fitting amount (L1) of a first constant velocity joint (1) is set to be relatively larger than a slide amount (L2) of a stub shaft (51) with respect to an outer ring member (11). Therefore, on the basis of the dimensional relationship "L1 < L2", one end surface (241) of a retainer (24) in a second constant velocity joint (2) comes into contact with an outer ring-side round portion (213) of an outer ring member (21) so that the sliding of the second constant velocity joint (2) in the axial direction is restricted before an inner ring member (12) and a sleeve member (15) are completely detached from a first shaft (S1) in the first constant velocity joint (1). As a result, there is no concern of the fitting of the first shaft (S1) and the first constant velocity joint (1) becoming loose, even when the second constant velocity joint (2) slides as much as possible.

Description

Power transmission shaft

[0001] The present invention relates to a power transmission shaft.

[0002] A known conventional power transmission shaft is, for example, that described in Patent Document 1 below.

[0003] This power transmission shaft is a so-called propeller shaft used in automobiles, and one axial end is connected to a first shaft on the drive source side, and the other end is connected to a second shaft on the drive wheel side, each via a first constant velocity joint. The inner ring member of the first constant velocity joint is fitted with a spline portion provided on the first shaft with a predetermined axial width of fitting.

[0004] The power transmission shaft is divided in the axial direction into a first shaft member connected to the first shaft and a second shaft member connected to the second shaft, and the first shaft member and the second shaft member are connected via a second constant velocity joint. The second constant velocity joint is configured to be slidable in the axial direction by a predetermined sliding amount in the axial direction.

[0005] JP 2013-194862 A

[0006] However, in the conventional propeller shaft used as a power transmission shaft, no consideration is given to the relationship between the amount of engagement of the first constant velocity joint and the amount of sliding of the second constant velocity joint. Therefore, if the amount of engagement of the first constant velocity joint is relatively small compared to the amount of sliding of the second constant velocity joint, there is a risk that the first shaft will come off when the second constant velocity joint slides the maximum amount, and there is still room for improvement.

[0007] Therefore, the present invention was devised in consideration of the technical problems with the conventional power transmission shafts, and aims to provide a power transmission shaft that can prevent the first shaft from falling off.

[0008] In one aspect of the present invention, the amount of engagement of the first joint with respect to the first shaft is set to be relatively larger than the amount of sliding of the second member with respect to the first member.

[0009] According to the present invention, it is possible to prevent the first shaft from falling off.

[0010] FIG. 1 is a side view of a propeller shaft according to the present invention. FIG. 2 is an enlarged view of a first constant velocity joint shown in FIG. 1. FIG. 3 is a longitudinal sectional view of a second constant velocity joint according to the first embodiment of the present invention. FIG. 4 is a sectional view showing a state in which the second constant velocity joint shown in FIG. 3 has slid to the first shaft side to the maximum, where (a) is a sectional view cut at a circumferential position where a ball is interposed, and (b) is a sectional view cut at a circumferential position where no ball is interposed. FIG. 5 is a sectional view showing a state in which the second constant velocity joint has slid to the first shaft side to the maximum in a bent state. FIG. 6 is an enlarged sectional view of a main portion of the second constant velocity joint, showing a modified example of the first embodiment of the present invention. FIG. 7 is a sectional view showing a state in which the second constant velocity joint shown in FIG. 7 has slid to the first shaft side to the maximum. FIG. 8 is a longitudinal sectional view of the second constant velocity joint shown in FIG. 1, showing a second embodiment of the present invention. FIG. 9 is a sectional view showing a state in which the second constant velocity joint shown in FIG. 9 has slid to the first shaft side to the maximum. FIG. 10 is a sectional view of the second constant velocity joint shown in FIG. 1, showing a third embodiment of the present invention. FIG. 11 is a sectional view showing the second constant velocity joint shown in FIG. 1, showing a fourth embodiment of the present invention. 12 is a cross-sectional view showing a state in which the second constant velocity joint shown in FIG. 11 has slid to the maximum extent toward the first shaft side. FIG.

[0011] Hereinafter, embodiments of a power transmission shaft according to the present invention will be described in detail with reference to the drawings. In each of the following embodiments, the power transmission shaft will be described as being applied to a propeller shaft for an automobile, as in the conventional case.

[0012] (Configuration of Propeller Shaft) Fig. 1 shows a side view of a propeller shaft to which a power transmission shaft according to the present invention is applied. In the following description of the embodiment, for convenience, the left side of Fig. 1 will be referred to as the "front" and the right side as the "rear." In addition, the direction along the rotation axis Z in Fig. 1 will be referred to as the "axial direction," the direction perpendicular to the rotation axis Z as the "radial direction," and the direction around the rotation axis Z as the "circumferential direction."

[0013] 1 , for example, a propeller shaft PS according to this embodiment is disposed between a first shaft S1 linked to a drive source (e.g., a transmission), not shown, and a second shaft S2 linked to drive wheels (e.g., a differential), not shown. That is, the propeller shaft PS includes a drive shaft 4 connected to the first shaft S1 via a first constant velocity joint 1, which corresponds to the first joint according to the present invention, so as to be integrally rotatable, and a driven shaft 5 connected to the second shaft S2 via a third constant velocity joint 3, so as to be integrally rotatable. The drive shaft 4 and the driven shaft 5 are connected to each other via a second constant velocity joint 2, which corresponds to the second joint according to the present invention, so as to be integrally rotatable. The propeller shaft PS is rotatably supported by a center bearing 64 suspended from a vehicle body (not shown) via a support device 6 provided near the second constant velocity joint 2.

[0014] (Configuration of First Joint) Figure 2 is an enlarged view of the first constant velocity joint 1 shown in Figure 1, and also shows a longitudinal cross-sectional view taken along the direction of the rotation axis Z. Note that Figure 2 shows the first constant velocity joint 1 in a standard state in which the rotation axis of the first shaft S1 and the rotation axis Z of the propeller shaft PS are parallel to each other.

[0015] 2, the first shaft S1 is made of an iron-based metal material and is formed with a stepped diameter at its tip end, is inserted into the first constant velocity joint 1 from the front side, and is normally prevented from coming off inside the first constant velocity joint 1. The first shaft S1 has a large diameter portion S11 that connects to the drive source (transmission) side (not shown), a medium diameter portion S12 that is connected to the rear end of the large diameter portion S11, and a small diameter portion S13 that is connected to the rear end of the medium diameter portion S12, which are integrally formed.

[0016] The medium diameter portion S12 has a circumferentially continuous annular seal groove S121 formed on its outer peripheral surface, and a well-known first seal ring 81 is attached to this seal groove S121. That is, the first seal ring 81 elastically abuts against the inner peripheral surface of a sleeve member 15 (described later), thereby preventing foreign matter such as dust and water from entering the inside of the first constant velocity joint 1 from the outside.

[0017] The small diameter portion S13 has a male spline portion S131 formed on its outer periphery along the axial direction. A male spline-side annular groove S132 is formed on the outer periphery of the tip of the small diameter portion S13, in an axial position overlapping with the male spline portion S131, and has a circumferentially continuous annular shape. A well-known circlip 17 is usually attached to this male spline-side annular groove S132. In other words, the circlip 17 engages with a female spline-side annular groove 122 (described later), thereby restricting axial movement of the first shaft S1 relative to the first constant velocity joint 1.

[0018] The first constant velocity joint 1 has an outer ring member 11 that is open at its front end and joined at its rear end to a tube 40 (see Figure 1) that forms the general part of the drive shaft 4, an inner ring member 12 that is arranged on the inner peripheral side of the outer ring member 11 and fitted to the first shaft S1 with a predetermined fitting amount L1, a plurality of balls 13 that are rolling elements that are arranged to be able to roll between the inner ring member 12 and the outer ring member 11, and a cage 14 that holds each ball 13.

[0019] The outer ring member 11 is formed in a cup shape with its rear end connected to a cylindrical tube 40 (see FIG. 1 ) and its front end open. Furthermore, a plurality of outer ring side engagement grooves 111, into which the respective balls 13 can engage, are formed along the axial direction on the inner periphery of the outer ring member 11. That is, the balls 13 roll in their respective outer ring side engagement grooves 111, allowing relative movement in the axial direction between the outer ring member 11 and the inner ring member 12, and the balls 13 engage with their respective outer ring side engagement grooves 111, restricting relative movement in the circumferential direction between the outer ring member 11 and the inner ring member 12.

[0020] The inner ring member 12 has a generally cylindrical shape and has, on its inner periphery, a female spline portion 121 that can mate with the male spline portion S131 of the first shaft S1. In this embodiment, the inner ring member 12 is fitted to the first shaft S1 such that the rear end 120 of the inner ring member 12 is flush with the front end (rear end) S10 of the first shaft S1 in the radial direction. Furthermore, on the inner periphery of the inner ring member 12, a female spline-side annular groove 122 that can engage with a well-known circlip 17 fitted to the first shaft S1 is continuously formed along the circumferential direction at a predetermined axial position on the female spline portion 121 that can hold the inner ring member 12 in a position where the rear end 120 of the inner ring member 12 is flush with the front end (rear end) S10 of the first shaft S1. In addition, on the outer peripheral side of the inner ring member 12, a plurality of inner ring side engagement grooves 123 are formed along the axial direction, opposite each outer ring side engagement groove 111 of the outer ring member 11, and are used for rolling and engagement of each ball 13.

[0021] Each ball 13 is rollably housed in a track portion formed by the combination of an outer ring side engagement groove 111 and an inner ring side engagement groove 123. Furthermore, each ball 13 engages with the outer ring side engagement groove 111 and the inner ring side engagement groove 123 in a state in which relative rotation is restricted. This enables torque transmission between the outer ring member 11 and the inner ring member 12 while maintaining uniform velocity.

[0022] The retainer 14 is approximately cylindrical in shape, and has window portions 141 formed along the radial direction at predetermined circumferential positions, the same number as the number of balls 13, and each ball 13 is accommodated and held inside each window portion 141.

[0023] With the above configuration, when rotational torque is input to the first shaft S1, the first constant velocity joint 1 transmits this rotational torque from the inner ring member 12, which rotates integrally with the first shaft S1, to the outer ring member 11 via the balls 13. As a result, the rotational torque input from the first shaft S1 is transmitted to the drive shaft 4 while maintaining a constant velocity.

[0024] A sleeve insertion portion 124 is formed in a stepped, enlarged diameter shape at the open end on the first end side of the inner ring member 12. The sleeve member 15, which constitutes a part of the first constant velocity joint 1, is inserted into this sleeve insertion portion 124. The sleeve member 15 is substantially cylindrical, and is press-fitted into the sleeve insertion portion 124 so as to be rotatable integrally with the inner ring member 12. The inner ring member 12 and the sleeve member 15 may be integrally formed as the inner ring member 12.

[0025] Here, in the first constant velocity joint 1, the inner ring member 12 and the sleeve member 15 are fitted to the first axis S1 so that the rear end 120 of the inner ring member 12 is roughly flush with the front end (rear end) S10 of the first axis S1 in the radial direction, i.e., so that the axial position of the rear end 120 of the inner ring member 12 roughly coincides with the axial position of the front end (rear end) S10 of the first axis S1. In other words, the axial range of the inner ring member 12 and the sleeve member 15 that radially overlap the first axis S1 is equal to the fitting amount L1 of the inner ring member 12 and the sleeve member 15 with respect to the first axis S1.

[0026] A waterproof boot 16 that protects the first constant velocity joint 1 from water and dust is mounted between the outer ring member 11 and the inner ring member 12 so as to straddle the outer ring member 11 and the inner ring member 12. The waterproof boot 16 has a folded-back middle portion that is axially expandable and contractible, and its front end is tightly fastened to the outer peripheral surface of the sleeve member 15 via a well-known boot band 161, while its rear end is crimped to the outer peripheral surface of the outer ring member 11 via a mounting bracket 162.

[0027] 3 is a main view showing a first embodiment of the present invention, and shows a cross-sectional view taken along the direction of the rotation axis Z and passing through the center of the ball 23 at a circumferential position of the cage 24 where the ball 23 is interposed, in the second constant velocity joint 2 in an unbent state where the rotation axis of the drive shaft 4 and the rotation axis of the driven shaft 5 are parallel (coincident). Fig. 4 is a view showing a state in which the second constant velocity joint 2 has slid toward the first axis S1, in which (a) shows a cross-sectional view taken along the direction of the rotation axis Z and passing through the center of the ball 23 at a circumferential position of the cage 24 where the ball 23 is interposed, and (b) shows a cross-sectional view taken along the rotation axis Z at a circumferential position of the cage 24 where the ball 23 is not interposed. FIG. 5 also shows a state in which sliding occurs in the second constant velocity joint 2, which is in a bent state in which the rotation axis of the drive shaft 4 and the rotation axis of the driven shaft 5 intersect (do not coincide).

[0028] For example, as shown in Figure 3, the second constant velocity joint 2 has an inner ring member 22 connected to a stub shaft 51 as a shaft member corresponding to the second member of the present invention, which is provided at the tip of the driven shaft 5, an outer ring member 21 arranged on the outer peripheral side of the inner ring member 22, a plurality of balls 23 as rolling elements arranged to be able to roll between the inner ring member 22 and the outer ring member 21, and a cage 24 that holds each ball 23.

[0029] The outer ring member 21 is formed with a stepped diameter increasing from the front end side to the rear end side, and is formed as a bottomed cylinder with the front end side closed by an end wall 210 and the rear end side open. That is, the outer ring member 21 has a connection base 211 provided at the front end and joined to the tube 40 of the drive shaft 4, and a joint component 212 which is stepped in diameter from the connection base 211 and accommodates joint elements (inner ring member 22, balls 23, and cage 24) in an accommodation space partitioned from the connection base 211 by the end wall 210, and these are integrally formed.

[0030] In this embodiment, the outer ring member 21 is provided at an inner corner between the end wall 210 and the joint component 212 with an outer ring-side rounded portion 213 having a corner radius that is arcuate in longitudinal cross section such that the inner diameter of the joint component 212 gradually decreases toward the end wall 210. The outer ring-side rounded portion 213 is provided to extend to a radial position facing the cage 24 in the axial direction, and is configured to be able to abut against the cage 24 when the second constant velocity joint 2 slides to its maximum extent in the axial direction, in a direction in which the end wall 210 of the outer ring member 21 and the tip end surface 510 of the stub shaft 51 approach each other, as shown in FIG. 4 . In this case, it is desirable that the outer ring-side rounded portion 213 be formed with a relatively large curvature. In other words, it is desirable that the axial width (thickness) of the outer ring-side rounded portion 213 be larger at the portion that abuts against the cage 24 when the second constant velocity joint 2 slides to its maximum extent.

[0031] Furthermore, a plurality of outer ring side engagement grooves 214, into which the balls 23 engage, are formed linearly along the axial direction on the inner peripheral side of the joint component 212. As a result, the balls 23 roll in their respective outer ring side engagement grooves 214, allowing relative movement in the axial direction between the outer ring member 21 and the inner ring member 22, and the balls 13 engage with their respective outer ring side engagement grooves 214, restricting relative movement in the circumferential direction between the outer ring member 21 and the inner ring member 22.

[0032] A circumferentially continuous annular groove 215 is cut out at the open end of the rear end of the joint constituent part 212, and a well-known circlip 26 is fitted into this annular groove 215 so as to face axially the ball 23 that engages with the outer ring side engagement groove 214. This prevents the ball 23 from falling out of the outer ring side engagement groove 214.

[0033] The inner ring member 22 is formed in a substantially cylindrical shape and has, on its inner periphery, a female spline portion 221 that can mate with a male spline portion 511 formed on the outer periphery of the tip end of a stub shaft 51 provided at the front end of the driven shaft 5. Here, the stub shaft 51 is formed at the front end of the driven shaft 5 so that its diameter tapers in a stepped manner toward the tip end, and the male spline portion 511 is formed along the axial direction on the outer periphery of the tip end of a small-diameter portion 513 of the stub shaft 51. The inner ring member 22 is prevented from coming off by a circumferential groove 512 notched in the male spline portion 511 of the stub shaft 51. Here, in this embodiment, the inner ring member 22 is fitted to the stub shaft 51 such that the front end portion 220 of the inner ring member 22 is offset rearward by a predetermined amount from the tip end surface 510, which is the front end surface of the stub shaft 51. On the other hand, on the outer peripheral side of the inner ring member 22, a plurality of inner ring side engagement grooves 222 are formed along the axial direction, opposite each outer ring side engagement groove 214 of the outer ring member 21, and serve to allow each ball 23 to roll and engage.

[0034] Each ball 23 is rollably housed in a track portion formed by the combination of an outer ring side engagement groove 214 and an inner ring side engagement groove 222. Each ball 23 is engaged with the outer ring side engagement groove 214 and the inner ring side engagement groove 222 in a state in which relative rotation is restricted. This enables torque transmission between the outer ring member 21 and the inner ring member 22 while maintaining uniform velocity.

[0035] The cage 24 is substantially cylindrical and has windows 240 formed radially at predetermined circumferential positions, the same number as the balls 23, with each window 240 housing and holding each ball 23. In the present embodiment, one end face 241, which is the front end face of the cage 24, is configured to be substantially flush with the tip end face 510 of the stub shaft 51 in the axial direction. Based on this dimensional relationship, when the second constant velocity joint 2 slides to the maximum in the axial direction in a direction in which the end wall 210 of the outer ring member 21 and the tip end face 510 of the stub shaft 51 approach each other, as shown in FIG. 4 , the outer peripheral edge portion 241 a of the one end face 241 of the cage 24 facing the outer ring-side rounded portion 213 comes into contact with the outer ring-side rounded portion 213 that protrudes rearward beyond the end wall 210, thereby restricting the axial sliding of the second constant velocity joint 2 (see FIG. 4( b)). In other words, in this embodiment, when the second constant velocity joint 2 slides axially to the first axis S1 to its maximum extent, the outer peripheral edge portion 241a of one end face 241 of the retainer 24 primarily comes into contact with the outer ring side curved portion 213.

[0036] In this embodiment, in the standard state shown in Fig. 3, the second constant velocity joint 2 is set so that an axial sliding amount (sliding allowance) L2 of the second constant velocity joint 2, which is the axial distance between one end face 241 of the cage 24 and the outer ring-side rounded portion 213, is relatively large (L1 < L2) compared to a fitting amount L1 of the inner ring member 12 and the sleeve member 15 with respect to the first axis S1 in the first constant velocity joint 1. In other words, based on the dimensional relationship of "L1 < L2", the one end face 241 of the cage 24 in the second constant velocity joint 2 abuts against the outer ring-side rounded portion 213 in the second constant velocity joint 2 before the inner ring member 12 and the sleeve member 15 in the first constant velocity joint 1 fall off the first axis S1, thereby restricting the axial sliding of the second constant velocity joint 2.

[0037] With the above configuration, when rotational torque is input to the outer ring member 21 based on the rotation of the drive shaft 4, the second constant velocity joint 2 transmits this rotational torque from the outer ring member 21, which rotates integrally with the drive shaft 4, to the inner ring member 22 via the balls 23. In this way, the rotational torque input from the drive shaft 4 side is transmitted to the driven shaft 5 side while maintaining a constant velocity.

[0038] A waterproof boot 25 that protects the second constant velocity joint 2 from water and dust is mounted between the outer ring member 21 and the inner ring member 22 so as to straddle the outer ring member 21 and the inner ring member 22. The waterproof boot 25 has a folded-back middle portion and is formed to be expandable and contractible in the axial direction, with a cylindrical first base portion 251 that is relatively thick on the front end side being crimped to the outer circumferential surface of the rear end of the outer ring member 21 via a first boot band 253, while a second base portion 252 that is relatively thick on the rear end side being tightly fastened to a boot mounting surface that is formed on the outer circumferential portion of the base side of the small diameter portion 513 of the stub shaft 51 via a second boot band 254.

[0039] (Operation and Effect of the Present Embodiment) As described above, conventional propeller shafts do not take into consideration the relationship between the amount of fit L1 of the first constant velocity joint 1 and the amount of slide L2 of the second constant velocity joint 2. Therefore, if the amount of fit L1 of the first constant velocity joint 1 is relatively small compared to the amount of slide L2 of the second constant velocity joint 2, there is a risk that the first shaft S1 will come off when the second constant velocity joint 2 slides to the maximum extent toward the first shaft S1, and there is still room for improvement.

[0040] In contrast, the propeller shaft PS according to this embodiment can solve the problems of the conventional propeller shafts by achieving the following effects.

[0041] The propeller shaft PS is a power transmission shaft provided between a first shaft S1 provided on the drive source side of the vehicle and a second shaft S2 provided on the drive wheel side, and has a first joint (first constant velocity joint 1) that is fitted to the first shaft S1 in the axial direction with a predetermined fitting amount L1, a tube 40 having one end joined to the first joint (first constant velocity joint 1), a first member (outer ring member 21) connected to the other end of the tube 40, a second member (stub shaft 51) that links with the second shaft S2, and coupling elements (inner ring member 22, balls 23, and cage 24) that connect the second member (stub shaft 51) rotatably relative to the first member (outer ring member 21) and slidably in the axial direction with a predetermined sliding amount L2 that is relatively smaller than the fitting amount L1.

[0042] As described above, in this embodiment, the amount of fit L1 of the first constant velocity joint 1 is set to be relatively larger than the amount of sliding L2 of the stub shaft 51, which is the second member, relative to the outer ring member 11, which is the first member. Therefore, based on the dimensional relationship of "L1 < L2," the one end surface 241 of the cage 24 in the second constant velocity joint 2 abuts against the outer ring member 21 (outer ring-side rounded portion 213) before the inner ring member 12 and the sleeve member 15 in the first constant velocity joint 1 completely drop off from the first axis S1, thereby restricting axial sliding of the second constant velocity joint 2. As a result, even if the first constant velocity joint 1 slides to the maximum in a direction that reduces the amount of fit L1 of the first constant velocity joint 1 relative to the outer ring member 11, that is, in a direction that brings the end wall 210 of the outer ring member 21 and the tip end surface 510 of the stub shaft 51 closer to each other, there is no risk of the first constant velocity joint 1 coming out of engagement with the first axis S1. This prevents the first shaft S1 from falling off when the second constant velocity joint 2 slides to its maximum axial extent, even if the inner ring member 12 is not fixed axially relative to the first shaft S1, for example, if the circlip 17 is forgotten to be attached to the first shaft S1.

[0043] Furthermore, in this embodiment, the first member is an outer ring member 21, the second member is a shaft member (stub shaft 51), the coupling element includes an inner ring member 22 disposed on the inner peripheral side of the outer ring member 21 and fixed to the outer peripheral side of the shaft member (stub shaft 51), rolling elements (balls 23) that roll within rolling grooves (outer ring side engagement grooves 214 and inner ring side engagement grooves 222) provided on the inner peripheral surface of the outer ring member 21 and the outer peripheral surface of the inner ring member 22, respectively, and a cage 24 that holds the rolling elements (balls 23), and the first member (outer ring member 21) and the coupling element (inner ring member 22, balls 23, and cage 24) form a second joint (second constant velocity joint 2) that connects the tube 40 and the second member (stub shaft 51).

[0044] As described above, in this embodiment, the second constant velocity joint 2 is configured as a ball-type sliding joint using balls 23 as rolling elements. This makes it possible to reduce radial backlash compared to when the second constant velocity joint 2 is configured as a so-called tripod-type sliding joint using rollers as rolling elements. This makes it possible to suppress the generation of vibrations and noise due to the backlash.

[0045] In this embodiment, the sliding of the second joint (second constant velocity joint 2 ) is restricted by the contact between the outer ring member 21 and the cage 24 .

[0046] As described above, in this embodiment, the axial sliding of the second constant velocity joint 2 is restricted by the abutment between the outer ring member 21 and the cage 24. Typically, a rounded corner portion is formed at the inner corner of the outer ring member 21 during manufacturing of the outer ring member 21. Therefore, when restricting the axial sliding of the second constant velocity joint 2, the cage 24 abuts against the rounded corner portion, which is relatively thicker than the end face of the outer ring member 21. This ensures the rigidity of the outer ring member 21 when restricting the sliding of the second constant velocity joint 2, thereby improving the durability of the propeller shaft PS.

[0047] In addition, in this embodiment, the outer ring member 21 has an outer ring side rounded portion 213 at the inner end of the rolling groove (outer ring side engagement groove 214 and inner ring side engagement groove 222), and the sliding of the second joint (second constant velocity joint 2) is regulated by the abutment between the retainer 24 and the outer ring side rounded portion 213.

[0048] As described above, in this embodiment, the abutment between the cage 24 and the outer ring side rounded portion 213 restricts the axial sliding of the second constant velocity joint 2. This reduces stress concentration that occurs at the inner end (inner corner) of the outer ring member 21. Furthermore, abutting the cage 24 against the outer ring side rounded portion 213 reduces the sliding amount L2 of the second constant velocity joint 2, more effectively preventing the first shaft S1 from falling off. Furthermore, the formation of the outer ring side rounded portion 213 contributes to improving the productivity of the outer ring member 21.

[0049] Furthermore, by configuring the retainer 24 to abut against the outer ring-side rounded portion 213, when the second constant velocity joint 2 is in a bent state as shown in Fig. 5, for example, the side of the outer peripheral edge 241a of the retainer 24 farther from the end wall 210 follows the curved surface of the outer ring-side rounded portion 213 and acts in a direction to reduce the amount of bending of the second constant velocity joint 2 when sliding of the second constant velocity joint 2 is restricted. As a result, compared to when the second constant velocity joint 2 is in a state in which it is bent significantly as shown in Fig. 5, in the second constant velocity joint 2 with a reduced amount of bending, it is possible to increase the contact area of ​​the retainer 24 with the outer ring-side rounded portion 213 (outer ring member 21), as shown in Fig. 4(b), for example, and damage to the outer ring member 21 when the retainer 24 abuts against the outer ring-side rounded portion 213 can be suppressed.

[0050] 6 shows a modified example of the first embodiment of the propeller shaft as a power transmission shaft according to the present invention, in which the specific shape of the cage 24 according to the first embodiment is changed. Note that the basic configuration other than this change is the same as that of the first embodiment, and therefore the same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0051] FIG. 6 is a diagram showing a modified example of the propeller shaft PS (retainer 24) according to the first embodiment, and shows an enlarged cross-sectional view of a main portion of the second constant velocity joint 2.

[0052] 6 , for example, in this modification, a retainer-side rounded portion 243 is provided on an outer peripheral edge 241 a of one end face 241 of the retainer 24 that faces the end wall 210 (outer ring-side rounded portion 213) of the outer ring member 21, where the one end face 241 and the outer peripheral surface 242 of the retainer 24 are connected by a smooth convex arc surface (convex rounded surface). Note that it is desirable for the retainer-side rounded portion 243 to be formed with a relatively large curvature that is smaller than that of the outer ring-side rounded portion 213. In other words, by setting the retainer-side rounded portion 243 to have a relatively large curvature, it is possible to reduce the surface pressure of the retainer-side rounded portion 243 against the outer ring-side rounded portion 213 of the outer ring member 21 when the retainer-side rounded portion 243 abuts against the outer ring-side rounded portion 213.

[0053] (Operation and Effect of This Modification) As described above, in this modification, the cage 24 has the cage-side rounded portion 243 that abuts against the outer ring-side rounded portion 213. Therefore, when sliding of the second constant velocity joint 2 is restricted, the cage-side rounded portion 243 formed by a smooth convex arc surface (convex rounded surface) abuts against the outer ring-side rounded portion 213, making it possible to prevent damage to the outer ring-side rounded portion 213. This prevents a decrease in functionality of the second constant velocity joint 2 and further improves the durability of the propeller shaft PS.

[0054] 7 and 8 show a second embodiment of a propeller shaft as a power transmission shaft according to the present invention, in which the means for restricting sliding of the second constant velocity joint 2 according to the first embodiment is changed. Note that the basic configuration other than this change is the same as that of the first embodiment, and therefore the same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0055] Fig. 7 is a diagram showing a second embodiment of the present invention, and is a cross-sectional view of the second constant velocity joint 2 shown in Fig. 1 taken along the direction of the rotation axis Z. Fig. 7 shows the standard state of the second constant velocity joint 2, in which the rotation axis of the drive shaft 4 and the rotation axis of the driven shaft 5 are parallel (aligned), and no sliding occurs in the second constant velocity joint 2 toward the first axis S1. Fig. 8 is a cross-sectional view showing the second constant velocity joint 2 shown in Fig. 7 in a state where it has slid to the maximum extent toward the first axis S1.

[0056] 7, in this embodiment, the front end 220 of the inner ring member 22 is formed to protrude further toward the end wall 210 of the outer ring member 21 than one end face 241 of the cage 24 and the tip end surface 510 of the stub shaft 51. In this embodiment, the front end 220 of the inner ring member 22 is formed to face the end wall 210 of the outer ring member 21 in the axial direction when the propeller shaft PS is in a horizontal state.

[0057] 7 , the axial sliding amount (permissible sliding amount) L2 of the second constant velocity joint 2, which is the axial distance between the front end 220 of the inner ring member 22 and the end wall 210, is set to be relatively large (L1<L2) compared to the fitting amount L1 of the inner ring member 12 and the sleeve member 15 with respect to the first axis S1 in the first constant velocity joint 1. In other words, based on the dimensional relationship of "L1<L2," the front end 220 of the inner ring member 22 of the second constant velocity joint 2 comes into axial contact with the end wall 210 of the outer ring member 21 before the inner ring member 12 and the sleeve member 15 in the first constant velocity joint 1 fall off the first axis S1, thereby restricting the axial sliding of the second constant velocity joint 2.

[0058] (Operation and Effect of the Present Embodiment) As described above, in the present embodiment, the second joint (second constant velocity joint 2) is configured so that the sliding is restricted by the abutment between the outer ring member 21 and the inner ring member 22. That is, in the present embodiment, the inner ring member 22, which has higher rigidity than the cage 24, is brought into abutment with the outer ring member 21, thereby restricting the axial sliding of the second constant velocity joint 2 toward the first axis S1 (see FIG. 8 ). This improves the durability of the second constant velocity joint 2 compared to the first embodiment, in which the cage 24 is brought into abutment with the outer ring member 21 to restrict the sliding of the second constant velocity joint 2 toward the first axis S1.

[0059] 9 and 10 show a third embodiment of a propeller shaft as a power transmission shaft according to the present invention, in which the means for restricting sliding of the second constant velocity joint 2 according to the first embodiment is changed. Note that the basic configuration other than this change is the same as that of the first embodiment, and therefore the same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0060] Fig. 9 is a diagram showing a third embodiment of the present invention, and is a cross-sectional view of the second constant velocity joint 2 taken along the direction of the rotation axis Z. Fig. 9 shows the standard state of the second constant velocity joint 2, in which the rotation axis of the drive shaft 4 and the rotation axis of the driven shaft 5 are parallel (aligned), and no sliding occurs in the second constant velocity joint 2 toward the first axis S1. Fig. 10 is a cross-sectional view showing the second constant velocity joint 2 shown in Fig. 9 in a state where it has slid to the maximum extent toward the first axis S1.

[0061] 9 , in this embodiment, the tip end surface 510 of the stub shaft 51 is formed to protrude further toward the end wall 210 of the outer ring member 21 than one end surface 241 of the cage 24. Note that in this embodiment, when the propeller shaft PS is in a horizontal state, the tip end surface 510 of the stub shaft 51 faces the end wall 210 of the outer ring member 21 in the axial direction.

[0062] 9 , the axial sliding amount (permissible sliding amount) L2 of the second constant velocity joint 2, which is the axial distance between the tip end surface 510 of the stub shaft 51 and the end wall 210, is set to be relatively large (L1<L2) compared to the fitting amount L1 of the inner ring member 12 and the sleeve member 15 with respect to the first axis S1 in the first constant velocity joint 1. In other words, based on the dimensional relationship of "L1<L2," the tip end surface 510 of the stub shaft 51 in the second constant velocity joint 2 comes into axial contact with the end wall 210 of the outer ring member 21 in the second constant velocity joint 2 before the inner ring member 12 and the sleeve member 15 in the first constant velocity joint 1 fall off the first axis S1, thereby restricting the axial sliding of the second constant velocity joint 2.

[0063] (Operation and Effect of the Present Embodiment) As described above, in the present embodiment, the sliding is restricted by the abutment between the outer ring member 21 and the second member (stub shaft 51). That is, in the present embodiment, the axial sliding of the second constant velocity joint 2 toward the first axis S1 side is restricted by abutting the stub shaft 51, which has greater rigidity than the inner ring member 22, against the outer ring member 21 (see FIG. 10 ). This further improves the durability of the second constant velocity joint 2 compared to the second embodiment, in which the inner ring member 22 abuts against the outer ring member 21 to restrict sliding of the second constant velocity joint 2 toward the first axis S1 side.

[0064] 11 and 12 show a fourth embodiment of a propeller shaft as a power transmission shaft according to the present invention, in which the means for restricting sliding of the second constant velocity joint 2 according to the first embodiment is changed. Note that the basic configuration other than the changes is the same as that of the first embodiment, and therefore the same components as those of the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0065] Fig. 11 is a diagram showing a fourth embodiment of the present invention, showing a cross-sectional view of the second constant velocity joint 2 and the support device 6 taken along the direction of the rotation axis Z. Fig. 11 shows the standard state of the second constant velocity joint 2, in which the rotation axis of the drive shaft 4 and the rotation axis of the driven shaft 5 are parallel (aligned), and no sliding occurs in the second constant velocity joint 2 toward the first axis S1. Fig. 12 is a cross-sectional view showing the second constant velocity joint 2 shown in Fig. 11 slid to the maximum extent toward the first axis S1.

[0066] For example, as shown in FIG. 11 , in this embodiment, the sliding of the second constant velocity joint 2 toward the first axis S1 is restricted by abutting a first cover member 671 (described later) of the support device 6 against the waterproof boot 25 of the second constant velocity joint 2.

[0067] Here, the support device 6 comprises a bracket 61 attached to a vehicle body not shown, a rubber elastic member 62 provided inside the bracket 61, a cylindrical inner ring member 63 provided on the inner periphery of the elastic member 62, and a center bearing 64 held inside the inner ring member 63.

[0068] The axial movement of the outer ring member 641 of the center bearing 64 is restricted by being sandwiched between an inner ring step 634 formed between the small diameter portion 631 and the medium diameter portion 632 of the inner ring member 63, and a retaining ring member 65 fixed to the inner peripheral side of the large diameter portion 633 of the inner ring member 63. The axial movement of the inner ring member 642 of the center bearing 64 fitted onto the outer periphery of the medium diameter portion 514 of the stub shaft 51 is restricted by being sandwiched between a cylindrical retaining member 66 fixed by press fitting to the front end side of the medium diameter portion 514 of the stub shaft 51, and a stub shaft step 516 between the medium diameter portion 514 and large diameter portion 515 of the stub shaft 51.

[0069] A generally U-shaped first cover member 671, which opens rearward (toward the second axis S2) by being folded back so as to overlap the inner and outer peripheries of the front end of the inner ring member 63, is disposed on the outer periphery of the front end of the retaining member 66. Meanwhile, a generally U-shaped second cover member 672, which opens forward (toward the first axis S1) by being folded back so as to overlap the inner and outer peripheries of the tip of the pressing ring member 65, is disposed on the outer periphery of the rear end of the large diameter portion 515 of the stub shaft 51. By disposing the first cover member 671 and the second cover member 672 in this manner, a so-called labyrinth structure is formed between the first cover member 671 and the inner ring member 63, and between the second cover member 672 and the pressing ring member 65, which prevents foreign matter from entering the center bearing 64 from the outside.

[0070] In this embodiment, when the stub shaft 51 of the second constant velocity joint 2 slides forward (towards the first axis S1), as shown in FIG. 12 , the first cover member 671 comes into contact with the first bent portion 255, which is formed with a relatively large thickness near the first base portion 251 of the waterproof boot 25, as the stub shaft 51 moves axially forward (towards the first axis S1), thereby restricting the sliding of the stub shaft 51.

[0071] 11 , the axial sliding amount (permissible sliding amount) L2 of the second constant velocity joint 2, which is the axial distance between the front end 671a of the first cover member 671 and the first bent portion 255 of the waterproof boot 25, is set to be relatively large (L1<L2) compared to the fitting amount L1 of the inner ring member 12 and the sleeve member 15 with respect to the first axis S1 of the first constant velocity joint 1. In other words, based on the dimensional relationship of "L1<L2," the front end 671a of the first cover member 671 in the second constant velocity joint 2 comes into axial contact with the first bent portion 255 of the waterproof boot 25 in the first constant velocity joint 1 before the inner ring member 12 and the sleeve member 15 in the first constant velocity joint 1 fall off the first axis S1, thereby restricting the axial sliding of the second constant velocity joint 2.

[0072] (Action and effect of this embodiment) As described above, in this embodiment, the second member (stub shaft 51) is elastically supported on the vehicle body (not shown) via the support device 6, the second joint (second constant velocity joint 2) is provided with a predetermined axial gap L2 relative to the support device 6 (front end 671 a of the first cover member 671), and sliding of the second joint (second constant velocity joint 2) is restricted by the abutment between the second joint (second constant velocity joint 2) and the support device 6 (front end 671 a of the first cover member 671), and the axial gap L2 is set to be smaller than the fitting amount L1.

[0073] As described above, in this embodiment, the amount of fit L1 of the first constant velocity joint 1 is set to be relatively larger than the axial gap L2 between the first bent portion 255 of the waterproof boot 25 of the second constant velocity joint 2 and the front end 671 a of the first cover member 671 of the support device 6. Therefore, even if the stub shaft 51 of the second constant velocity joint 2 slides to its maximum in a direction that reduces the amount of fit L1 of the first constant velocity joint 1 relative to the outer ring member 21, that is, until the first bent portion 255 of the waterproof boot 25 of the second constant velocity joint 2 comes into contact with the front end 671 a of the first cover member 671 of the support device 6, there is no risk of the first constant velocity joint 1 becoming disengaged. This makes it possible to prevent the first shaft S1 from falling off.

[0074] The present invention is not limited to the configurations and aspects exemplified in the above-described embodiments, and can be freely modified depending on the specifications and costs of the target object as long as the configuration can achieve the above-described effects of the present invention.

Claims

1. A power transmission shaft provided between a first shaft provided on the drive source side of a vehicle and a second shaft provided on the drive wheel side, comprising: a first joint that is fitted to the first shaft in the axial direction with a specified amount of fitting; a tube having one end joined to the first joint; a first member connected to the other end of the tube; a second member that links to the second shaft; and a coupling element that connects the second member rotatably relative to the first member and slidably in the axial direction with a specified sliding amount that is relatively smaller than the amount of fitting.

2. A power transmission shaft as described in claim 1, wherein the first member is an outer ring member, the second member is a shaft member, the coupling element comprises an inner ring member disposed on the inner peripheral side of the outer ring member and fixed to the outer peripheral side of the shaft member, rolling elements which roll within rolling grooves provided on the inner peripheral surface of the outer ring member and the outer peripheral surface of the inner ring member, respectively, and a retainer which holds the rolling elements, and wherein the first member and the coupling element form a second joint which connects the tube and the second member.

3. A power transmission shaft as claimed in claim 2, characterized in that the sliding of the second joint is restricted by the contact between the outer ring member and the retainer.

4. A power transmission shaft as claimed in claim 3, characterized in that the outer ring member has an outer ring side rounded portion at the inner end of the rolling groove, and the second joint regulates the sliding by the abutment between the retainer and the outer ring side rounded portion.

5. A power transmission shaft as set forth in claim 4, characterized in that the retainer has a retainer side rounded portion that abuts against the outer ring side rounded portion.

6. A power transmission shaft as claimed in claim 2, characterized in that the sliding of the second joint is restricted by the abutment of the outer ring member and the inner ring member.

7. A power transmission shaft as claimed in claim 2, characterized in that the second joint restricts the sliding by the contact between the outer ring member and the second member.

8. A power transmission shaft as claimed in claim 2, wherein the second member is elastically supported on the vehicle body via a center bearing, the second joint is provided with a predetermined axial gap relative to the center bearing, sliding of the second joint is restricted by contact between the second joint and the center bearing, and the axial gap is set smaller than the amount of engagement.

Images