Spline structure and constant velocity universal joint

Abstract

To provide a spline structure and a constant velocity universal joint capable of preventing reduction in shaft strength and shaft service life by a torque load direction.SOLUTION: A spline structure includes a female spline formed on an inner diameter surface of a hole part, and a male spline formed on an outer diameter surface of a shaft part and fitted to the female spline. Either the female spline or the male spline is formed as an axial spline along the axial direction. The other spline is composed of a twist spline part twisted in the axial direction and an axial spline part along the axial direction, and the axial spline part is formed on the axial root side which is the opposite shaft end side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spline structure and a constant velocity universal joint. [Background technology]

[0002] Spline structures are used as mechanisms for transmitting power in automobiles, agricultural machinery, ships, machine tools, etc. The spline structure referred to here comprises a female spline formed on the inner diameter surface of a hole, and a male spline formed on the outer diameter surface of a shaft that fits into the female spline.

[0003] Conventionally, the spline structure (spline structure) of a rotating shaft that transmits torque has been such that the male spline on the rotating shaft side has a twist in the axial direction (the female spline is an axial spline that runs along the axial direction) in order to reduce circumferential backlash (circumferential backlash).

[0004] 6 and 7, conventionally, the female spline 41 is an axial spline that extends in the axial direction, and the male spline 42 is a torsion spline that is twisted with respect to the axial direction. That is, the female spline 41 includes recessed portions 43a that are arranged at a predetermined pitch along the circumferential direction, and protruding portions 43b that are provided between the recessed portions 43a, and the axial spline is one in which the recessed portions 43a and protruding portions 43b extend in the axial direction.

[0005] Furthermore, the male spline 42 is made up of convex portions 44a that fit into the concave portions 43a of the female spline 41, and concave portions 44b that are provided between the convex portions 44a. Therefore, in this torsion spline, the convex portions 44a and the concave portions 44b are twisted in the same direction by the same angle θ.

[0006] However, in such cases, there is a problem in that the strength and lifespan of the splines (male spline and female spline) vary depending on the direction of the rotational torque applied to the male spline (shaft spline).

[0007] Furthermore, as shown in FIG. 6, when the female spline 41 is an axial spline extending in the axial direction and the male spline 42 is a torsion spline, the convex portion 44a of the male spline 42 and the concave portion 43a of the female spline 41 are in so-called point contact at the end portion on the axial root side, which is the opposite end of the shaft. This results in a relatively large stress P1 being applied, which may cause deformation or damage to the female spline 41 side or the male spline side. Here, the axial root side refers to the downstream side in the press-fitting direction of the male spline provided on the shaft portion into the female spline. Therefore, a larger stress is applied to the axial root side than to other parts.

[0008] Incidentally, a vehicle driving force transmission structure has been proposed in the past that aims to reduce backlash between the inner ring and drive shaft and to improve the strength of the inner ring and shaft (Patent Document 1). In this vehicle driving force transmission structure, serrations on the inner diameter surface of the inner ring are formed parallel to the axial direction, and the shaft serrations of the left and right drive shafts are twisted in opposite directions on each drive shaft, and in the same direction as the main load torque when viewed in the torque transmission direction, and the shaft serrations are press-fitted into the serrations on the inner diameter surface of the inner ring.

[0009] Patent Document 1 states that "at the opposite end of the shaft serration, the stress acting on the tooth surfaces of the inner ring serration and shaft serration when torque is applied is canceled out by the stress caused by the press-fitting of both serrations, reducing the maximum stress. As a result, the strength and lifespan of the inner ring and drive shaft are improved." [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Publication number 6-33220 Summary of the Invention [Problem to be solved by the invention]

[0011] The device described in Patent Document 1, when the torque load direction is always constant, achieves the effects described in Patent Document 1. However, when the torque load direction is different (opposite) from the direction in which the effects are achieved, stress concentration occurs, which is a phenomenon in which stress increases locally, and the device cannot be said to be effective.

[0012] Therefore, the present invention provides a spline structure that can prevent a decrease in shaft strength and shaft life due to torque load direction. [Means for solving the problem]

[0013] The first spline structure of the present invention is a spline structure including a female spline formed on the inner diameter surface of a hole and a male spline formed on the outer diameter surface of a shaft portion and mating with the female spline, wherein one of the female spline and the male spline is an axial spline extending along the axial direction, and the other spline is composed of a torsional spline portion twisted in the axial direction and an axial spline portion extending along the axial direction, and the axial spline portion is formed on the axial root side, which is the opposite end of the shaft. Here, the axial root side refers to the downstream side in the press-fitting direction of the male spline provided on the shaft portion into the female spline. Therefore, greater stress is applied to the axial root side than to other portions. In other words, the axial root side is the side to which greater stress is applied.

[0014] In the first spline structure of the present invention, the axial splines are fitted together at the axial base side, so that the convex portions of the male splines and the concave portions of the female splines, and the concave portions of the male splines and the convex portions of the female splines, are in line contact at the axial base side, thereby dispersing the applied stress.

[0015] It is preferable that the length of the axial spline portion be 1 / 3 to 1 / 4 of the length of the torsion spline portion. By setting the length of the axial spline portion in this manner, the effect of dispersing the applied stress can be fully exerted on the axial root side, and further, the effect of regulating backlash in the circumferential direction can be fully exerted on the other side of the axial root side.

[0016] It is preferable that the twisted spline portion be twisted at an angle of 10 minutes to 20 minutes with respect to the axial direction, which has the effect of restricting backlash in the circumferential direction and allows the press-fitting operation to be carried out stably.

[0017] The second spline structure of the present invention is a spline structure comprising a female spline formed on the inner diameter surface of a hole portion and a male spline formed on the outer diameter surface of a shaft portion and mating with the female spline, wherein both the female spline and the male spline are torsional splines twisted in the axial direction, and the torsional angles of the female spline and the male spline are the same at the axial root side, which is the opposite shaft end, and the torsional angles of the female spline and the male spline are different in other locations.

[0018] In the second spline structure of the present invention, the twist angles of the female spline and the male spline are the same at the axial base side, so that at the axial base side, the convex portion of the male spline comes into line contact with the concave portion of the female spline, and the concave portion of the male spline comes into line contact with the convex portion of the female spline, thereby dispersing the applied stress.

[0019] It is preferable that the length dimension of the range with the same twist angle be 1 / 3 to 1 / 4 of the length dimension of the range with different twist angles. By setting it in this way, the effect of dispersing the applied stress can be fully exerted on the axial root side, and moreover, the circumferential backlash can be fully suppressed on the other side of the axial root side.

[0020] The difference in the twist angle range is preferably 10 minutes to 20 minutes, which has the effect of restricting backlash in the circumferential direction and allows the press-fitting operation to be carried out stably.

[0021] The constant velocity universal joint of the present invention is provided with the spline structure. The constant velocity universal joint may be a fixed type constant velocity universal joint. [Effects of the Invention]

[0022] The present invention can effectively prevent a decrease in shaft strength and shaft life due to the direction of the load of rotational torque. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is an enlarged simplified view of a main part of a spline structure according to the present invention; [Figure 2] 2 is a simplified development view of a male spline of the spline structure shown in FIG. 1. [Figure 3] FIG. 2 is a cross-sectional view of the spline structure shown in FIG. [Figure 4] FIG. 10 is an enlarged simplified view of a main part of another embodiment. [Figure 5] FIG. 1 is a longitudinal cross-sectional view of a drive shaft in which a spline structure is used. [Figure 6] FIG. 1 is an enlarged simplified view of a main part of a conventional spline structure. [Figure 7] FIG. 7 is a simplified development view of a male spline of the spline structure shown in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of the present invention will be described below with reference to Fig. 1 to Fig. 5. Fig. 1 is an enlarged simplified view of a main portion of a spline structure, Fig. 2 is a simplified developed view of a male spline of the spline structure, Fig. 3 is a cross-sectional view of the spline structure, and Fig. 5 is a longitudinal sectional view of a drive shaft using the spline structure.

[0025] The drive shaft shown in Fig. 5 is made up of a fixed constant velocity universal joint 51 and a sliding constant velocity universal joint 52 connected by a power transmission shaft (intermediate shaft) 50. In this example, a Birrfield type constant velocity universal joint is used as the fixed constant velocity universal joint 51, and a tripod type constant velocity universal joint is used as the sliding constant velocity universal joint 52.

[0026] The fixed type constant velocity universal joint 51 includes an outer joint member 55 having a plurality of axially extending track grooves 53 formed on an inner diameter surface 54, an inner joint member 58 having a plurality of axially extending track grooves 56 formed on an outer diameter surface 57 at equal intervals in the circumferential direction, a plurality of balls 59 interposed between the track grooves 53 of the outer joint member 55 and the track grooves 56 of the inner joint member 58 to transmit torque, and a cage 60 interposed between the inner diameter surface 54 of the outer joint member 55 and the outer diameter surface 57 of the inner joint member 58 to hold the balls 59. The outer joint member 55 also includes a cup portion 55a having the track grooves 53 formed therein, and a stem portion 55b projecting from a bottom wall of the cup portion 55a.

[0027] The sliding type constant velocity universal joint 52 includes an outer joint member 62 having three axially extending track grooves 61 formed on its inner periphery and roller guideways facing each other on the inner walls of each track groove 61; a tripod member 64 having three radially protruding trunnions 63; an inner roller 65 fitted onto the trunnions 63; and an outer roller 66 inserted into the track grooves 61 and fitted onto the inner roller 65. In other words, the sliding type constant velocity universal joint 52 is a double-roller type in which the outer roller 66 is rotatable relative to the trunnions 63 and movable along the roller guideways. The tripod member 64 also includes a boss 67 and the trunnions 63. The trunnions 63 protrude radially from three equally spaced positions in the circumferential direction of the boss 67. Needle rollers 71 are interposed between the inner roller 65 and the outer roller 66. The outer joint member 62 is made up of a cup portion 62a in which the track grooves 61 are formed, and a stem portion 62b projecting from the bottom wall of the cup portion 62a.

[0028] In this case, the inner joint member 58 of the fixed type constant velocity universal joint 51 and the intermediate shaft 50 are connected to each other via the spline structure M of the present invention so as to be able to transmit torque, and the tripod member 64 of the sliding type constant velocity universal joint 52 and the intermediate shaft 50 are connected to each other via the spline structure M of the present invention so as to be able to transmit torque.

[0029] As shown in Figure 3, the spline structure M includes a female spline 2 formed on the inner diameter surface 1a of the hole portion 1, and a male spline 4 formed on the outer diameter surface 3a of the shaft portion 3 and fitted with the female spline 2.

[0030] For this reason, on the fixed type constant velocity universal joint 51 side, a female spline 2 is formed on the inner diameter surface 1a of the hole portion 1 formed in the inner joint member 58, and a female spline 2 is formed on the outer diameter surface 3a of the shaft portion 3 at the end of the fixed type constant velocity universal joint 51 of the intermediate shaft 50. On the sliding type constant velocity universal joint 52 side, a female spline 2 is formed on the inner diameter surface 1a of the hole portion 1 formed in the boss 67 of the tripod member 64, and a female spline 2 is formed on the outer diameter surface 3a of the shaft portion 3 at the end of the sliding type constant velocity universal joint 52 of the intermediate shaft 50.

[0031] As shown in Fig. 3, the female spline 2 of the spline structure M comprises recesses 2a arranged at a predetermined pitch along the circumferential direction and protrusions 2b arranged between the recesses 2a, while the male spline 4 comprises protrusions 4a arranged at a predetermined pitch along the circumferential direction and recesses 4b arranged between the protrusions 4a. Therefore, the protrusions 4a of the male spline 4 fit into the recesses 2a of the female spline 2, and the protrusions 2b of the female spline 2 fit into the recesses 4b of the male spline 4. The cross-sectional shape of the protrusions 2b of the female spline 2 is trapezoidal. The protrusions 4b of the male spline 4 comprise an upper side 4b1 and a pair of inclined side faces 4b2, 4b2, and the inclined side faces 4b2, 4b2 are inclined faces that approach each other from the outer peripheral surface of the shaft portion toward the upper side 2b1.

[0032] In this case, as shown in FIG. 1, the spline structure M has the female spline 2 as an axial spline 5 extending along the axial direction, and the male spline 4 as an axial spline portion 5 twisted in the axial direction. The axial spline portion 7 is formed on the axial root side, which is the opposite end of the shaft. Here, the axial root side is the downstream side in the press-fitting direction when the male spline 4 is press-fitted into the female spline 2, and is the opposite end of the shaft of the male spline 4. For this reason, greater stress is applied to the axial root side than to other portions. In other words, the axial root side is the side to which greater stress is applied.

[0033] As shown in FIG. 1, the length dimension L1 of the range H1 of the axial spline portion 7 is set to be (1 / 3) to (1 / 4) of the length dimension L2 of the range H2 of the torsion spline portion 6, and as shown in FIG. 2, the torsion spline portion 6 is twisted at an angle θ (10 minutes to 20 minutes) relative to the axial direction.

[0034] By providing the axial spline portion 7 on the axial root side of the male spline 4, the axial root side is fitted to the axial spline portion 5, and the convex portion 4a of the axial spline portion 7 of the male spline 4 and the concave portion 2a of the female spline (axial spline 5) come into line contact with each other, and the concave portion 4b of the axial spline portion 7 of the male spline 4 and the convex portion 2b of the female spline (axial spline portion) come into line contact with each other. This distributes the applied stress. If the axial root side does not have an axial spline portion as shown in FIG. 6, stress P1 is applied only to the contact portion (the edge portion on the axial root side) during torque transmission. In contrast, if the axial spline portion 7 is provided on the axial root side, as shown in FIG. 1, line contact occurs, and stress is distributed within a range H1 on the axial root side. In other words, a large amount of stress P2 is applied. In this case, P1 > P2.

[0035] Therefore, the spline structure according to the present invention can effectively prevent a decrease in shaft strength and shaft life due to the load direction of rotational torque. Furthermore, even if the direction of applied stress is opposite to the direction of stress shown in Figure 1, the range H1 on the axial root side is the axial spline portion 7, so the stress is dispersed.

[0036] It is preferable that the length L1 of the axial spline portion 7 is 1 / 3 to 1 / 4 of the length L2 of the torsional spline portion 6. By setting it in this manner, the effect of dispersing the applied stress can be sufficiently exhibited on the axial root side, and further, the circumferential backlash can be sufficiently suppressed on the parts other than the axial root side.

[0037] It is preferable that the twisted spline portion 6 is twisted at an angle of 10 minutes to 20 minutes with respect to the axial direction. By setting it in this way, it is possible to have the effect of restricting backlash in the circumferential direction and to carry out the press-fitting operation stably.

[0038] 4, both the female spline 11 and the male spline 12 are twisted splines that are twisted in the axial direction. In this case, the female spline 11 has a first female spline portion 13a on the root side and a second female spline portion 13b in the other portion, and the male spline 12 has a first male spline portion 14a on the root side and a second male spline portion 14b in the other portion.

[0039] The twist angle θ1 of the first female spline portion 13a on the root side and the twist angle θ2 of the first male spline portion 14a on the root side are made the same, and the twist angle θ3 of the second female spline portion 13b and the twist angle θ4 of the second male spline portion 14b are made different. In this case, θ3 > θ4 in the illustrated example, but the reverse may also be true.

[0040] In this case, the length dimension L3 of the range H3 where the twist angle is the same is (1 / 3) to (1 / 4) of the length dimension L4 of the range where the twist angle is different, and the angle difference of the range H4 where the twist angle is different is 10 minutes to 20 minutes.

[0041] 4, by making the twist angles of the first female spline portion 13a and the first male spline portion 14a the same at the axial root side, the convex portion on the first male spline portion 14a side and the concave portion on the first female spline portion 13a side, and the concave portion on the first male spline portion 14a side and the convex portion of the first female spline portion 13a are in line contact at the axial root side. This distributes the applied stress, has the effect of restricting backlash in the circumferential direction, and allows for stable press-fitting.

[0042] Furthermore, it is preferable that the length L3 of the range H3 where the twist angle is the same be between 1 / 3 and 1 / 4 of the length L4 of the range H4 where the twist angle is different. By setting it in this manner, the effect of dispersing the applied stress can be fully exerted on the axial root side, and further, the effect of regulating backlash in the circumferential direction can be fully exerted on the areas other than the axial root side.

[0043] The angle difference in the range H4 of different twist angles is preferably 10 minutes to 20 minutes, which has the effect of restricting backlash in the circumferential direction and allows the press-fitting operation to be carried out stably.

[0044] In the spline structure M shown in Fig. 1, the female spline 2 is an axial spline, but the male spline 4 may be an axial spline, and the female spline 2 may have an axial spline portion at the axial root side and a torsion spline portion at other locations. Even in this case, the same effects as those of the spline structure M shown in Fig. 1 are achieved. Even in this case, it is preferable that the length of the axial spline portion is (1 / 3) to (1 / 4) of the length of the torsion spline portion, and that the torsion spline portion is twisted at an angle of 10 minutes to 20 minutes with respect to the axial direction.

[0045] Although the present invention has been described above with reference to an embodiment, various modifications are possible without being limited to the above embodiment. In the embodiment, the spline structure may be a square spline (a square spline with parallel side faces) or an involute spline (in which an involute curve is used for the teeth). Furthermore, it may be formed by a tooth profile with a curvature and a small involute curve (involute serration), or may be formed by cutting a large number of small triangular teeth into the shaft and hole (triangular serration). Therefore, in the present invention, the term "spline structure" includes a serration structure. Furthermore, the number of teeth of the spline structure may be set arbitrarily.

[0046] The application of this spline structure is not limited to drive shafts, but can also be used in power transmission components of automobiles, agricultural machinery, ships, machine tools, etc. Furthermore, the constant velocity universal joint in which this spline structure is used may be a sliding type constant velocity universal joint that allows axial displacement and operating angle displacement, or a fixed type constant velocity universal joint that allows only operating angle displacement. Sliding type constant velocity universal joints include double offset types, tripod types, and cross groove types, while fixed type constant velocity universal joints include Rzeppa types and undercut-free types. [Explanation of symbols]

[0047] 1 Hole 1a Inner diameter surface 2 female splines 3 Shaft 3a Outer diameter surface 4 male splines 6 Torsion spline part 7 Axial spline section 11 female spline 12 male splines 13a First female spline part 13b Second female spline part 14a First male spline part 14b Second male spline part

Claims

1. A spline structure including a female spline formed on an inner diameter surface of a hole portion and a male spline formed on an outer diameter surface of a shaft portion and fitted with the female spline, a spline structure in which either the female spline or the male spline is an axial spline extending along the axial direction, and the other spline is composed of a torsional spline portion twisted with respect to the axial direction and an axial spline portion extending along the axial direction, and the axial spline portion is formed on the axial root side, which is the opposite shaft end side.

2. 2. The spline structure according to claim 1, wherein the length of the axial spline portion is 1 / 3 to 1 / 4 of the length of the torsional spline portion.

3. 2. The spline structure according to claim 1, wherein the twisted spline portion is twisted at an angle of 10 minutes to 20 minutes with respect to the axial direction.

4. A spline structure including a female spline formed on an inner diameter surface of a hole portion and a male spline formed on an outer diameter surface of a shaft portion and fitted with the female spline, A spline structure characterized in that both the female spline and the male spline are twisted splines that are twisted in the axial direction, and the twist angles of the female spline and the male spline are the same at the axial root side, which is the anti-axial end side, and the twist angles of the female spline and the male spline are different in other locations.

5. 5. The spline structure according to claim 4, wherein the length dimension of the range in which the twist angle is the same is 1 / 3 to 1 / 4 of the length dimension of the range in which the twist angle is different.

6. 5. The spline structure according to claim 4, wherein the difference in the range of twist angles is from 10 minutes to 20 minutes.

7. A constant velocity universal joint comprising the spline structure according to claim 1.

8. 8. The constant velocity universal joint according to claim 7, which is a fixed type constant velocity universal joint.

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