Constant velocity universal joint

Abstract

Provided is a constant velocity universal joint in which damage to the edge of the outlet-side end of a female spline provided on an inner joint member is prevented. A constant velocity universal joint (1) is provided with: an outer joint member (2); an inner joint member (3); a torque transmission member (roller unit (4)); and a shaft (8) which is inserted from one side in the axial direction into a shaft hole (30) of the inner joint member (3), and on the outer peripheral surface of which a male spline (81) fitted to a female spline (34) is formed. An annular groove (83) formed in a region of the outer peripheral surface of the shaft (8) closer to the other side in the axial direction than the inner joint member (3); and a retainer ring (10) fitted to the annular groove (83) and engaged with the inner joint member (3) from the other side in the axial direction. A hardened layer (37) having a higher hardness than the inside is provided on the surface of the inner joint member (3). An inclined surface (36) is formed at the end of the inner peripheral surface of the inner joint member (3) on the other side in the axial direction.

Description

Technical Field

[0001] The invention relates to a constant velocity universal coupling. Background Art

[0002] The constant velocity universal joint has an outer coupling member, an inner coupling member, and torque transmission members such as balls and rollers that transmit torque between them. The two coupling members have a structure that can transmit torque at a constant speed even when the working angle is taken. By inserting one end of the shaft into the shaft hole of the inner coupling member and fitting the internal spline provided on the inner coupling member with the external spline provided on the shaft, the two can be combined to transmit torque.

[0003] When the shaft is inserted from one axial side into the shaft hole of the inner coupling member, the front end of the shaft sometimes contacts the entrance of the shaft hole of the inner coupling member. Therefore, a bevel is usually provided at the end on one axial side of the inner circumferential surface of the inner coupling member (hereinafter referred to as the "entrance side end") to prevent damage caused by interference with the front end of the shaft. On the other hand, the end on the other axial side of the inner circumferential surface of the inner coupling member (hereinafter referred to as the "exit side end") will not interfere with the front end of the shaft, so there is no need to provide a bevel. For the above reasons, in conventional constant velocity universal couplings, a bevel is provided at the entrance side end of the inner circumferential surface of the inner coupling member, and on the other hand, no bevel is provided at the exit side end (for example, refer to the following patent documents 1 to 3).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6169793

[0007] Patent Document 2: Japanese Patent Application Publication No. 2011-2053

[0008] Patent Document 3: Japanese Patent No. 6486694 Summary of the invention

[0009] Problems to be solved by the invention

[0010] In many cases, the inner coupling member is heat treated after the inner spline is formed. In this case, a hardened layer formed by the heat treatment is formed on the surface of the inner coupling member, and the inner spline formed on the inner circumferential surface of the inner coupling member is also hardened. Therefore, when the inner coupling member after the heat treatment is transported or stored, when the inner coupling member interferes with other components, the edge of the outlet side end of the inner circumferential surface of the inner coupling member, especially the edge of the outlet side end of the inner spline, may be damaged.

[0011] Therefore, the present invention aims to prevent damage to the edge of the outlet side end portion of the internal spline provided on the inner joint member.

[0012] Solutions to Solve Problems

[0013] In order to solve the above-mentioned problem, the present invention provides a constant velocity universal joint, which comprises: an outer coupling member; an inner coupling member, which is arranged on the inner circumference of the outer coupling member and has an internal spline formed on the inner circumferential surface; a torque transmission member, which transmits torque between the outer coupling member and the inner coupling member; a shaft, which is inserted into the axial hole of the inner coupling member from one axial side and has an external spline formed on the outer circumferential surface that engages with the internal spline; an annular groove, which is formed in the outer circumferential surface of the shaft in an area closer to the other axial side than the inner coupling member; and a retaining ring, which is assembled in the annular groove and engages with the inner coupling member from the other axial side.

[0014] The constant velocity universal coupling is characterized in that:

[0015] A hardened layer having a higher hardness than the inner part is provided on the surface of the inner coupling member.

[0016] A slope is formed on the other axial end portion of the inner peripheral surface of the inner joint member.

[0017] In this way, by forming a slope at the end (outlet side end) on the other axial side of the inner circumferential surface of the inner coupling member, even if a hardened layer is formed on the surface of the inner coupling member to harden the internal spline, damage to the edge of the outlet side end of the internal spline can be prevented.

[0018] The angle of the inclined surface with respect to the surface perpendicular to the axial direction is preferably set to 30 to 60 degrees.

[0019] When the inclined surface is too small, the damage prevention effect of the edge of the internal spline cannot be fully obtained. On the other hand, when the inclined surface is too large, the effective mating length of the internal spline and the external spline becomes shorter, the surface pressure of the spline mating part increases and the strength decreases. In addition, when the inclined surface is too large, the area of ​​the contact part (seat surface) where the retaining ring contacts the end face of the inner coupling member cannot be fully ensured, and the retaining ring is easily deformed due to the engagement with the shaft. Based on the above insights, it is preferred to set the ratio d / e of the diameter d of the outer diameter end of the inclined surface to the minor diameter e of the internal spline of the inner coupling member to 1.04 to 1.08.

[0020] The outer diameter end of the inclined surface can be arranged on the inner diameter side or the outer diameter side of the large diameter portion of the internal spline.

[0021] Sometimes, in order to impart compressive residual stress to the surface of the inner coupling member and improve fatigue strength, shot blasting or other blasting processes are performed. In particular, the inner coupling member of a tripod-type constant velocity universal joint has a boss portion and three foot shafts protruding from the boss portion to the outer diameter side, so stress is easily concentrated at the root of the foot shaft, and blasting processes are often performed. In blasting processes, multiple inner coupling members are placed in a tumbler, and the tumbler is rotated while the processing is performed. In the case of blasting the inner coupling member in this way, the edge of the end of the inner spline is easily damaged due to interference between the members in the tumbler, so the present invention is particularly preferably applied.

[0022] Effects of the Invention

[0023] As described above, according to the present invention, even when the internal spline provided in the inner joint member is hardened by heat treatment, it is possible to prevent the edge of the outlet side end portion of the internal spline from being damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an axial cross-sectional view of a constant velocity universal joint according to an embodiment of the present invention.

[0025] Figure 2 yes Figure 1 Cross-sectional view of line XX.

[0026] Figure 3 yes Figure 1 Cross-sectional view of line YY.

[0027] Figure 4 It is shown Figure 1 An axial cross-sectional view of the constant velocity universal coupling at the working angle.

[0028] Figure 5 yes Figure 1 An enlarged view of part A.

[0029] Figure 6 Observed from the axial direction Figure 5 The front view is obtained by using the tripod component.

[0030] Figure 7 This is an enlarged cross-sectional view of another example of a constant velocity universal joint.

[0031] Figure 8 Observed from the axial direction Figure 7 The front view is obtained by using the tripod component.

[0032] Fig. 9 It is a graph showing the relationship between the displacement of the shaft relative to the tripod member and the pull-out force.

[0033] Description of Reference Numerals

[0034] 1 Constant velocity universal coupling (triplet type constant velocity universal coupling)

[0035] 2 Outer coupling member

[0036] 3 Tripod member (inner coupling member)

[0037] 4 Roller unit (torque transmission member)

[0038] 5 Roller groove

[0039] 6 Roller guide surface

[0040] 8 Axis

[0041] 10 Retaining ring

[0042] 11 Outer ring

[0043] 12 Inner circle

[0044] 13 Roller needle

[0045] 14 Snap ring

[0046] 30 Shaft hole

[0047] 31 Boss

[0048] 32 foot shaft

[0049] 34 Internal spline

[0050] 35 Entrance side slope

[0051] 36 Exit side slope

[0052] 37 Hardened layer

[0053] 81 External spline

[0054] 82 Shoulder

[0055] 83 Annular groove

[0056] 84 flange portion. DETAILED DESCRIPTION

[0057] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0058] exist Figure 1 as well as Figure 21 shows a constant velocity universal coupling 1 of one embodiment of the present embodiment. The constant velocity universal coupling 1 is a double-row roller type tripod type constant velocity universal coupling. It should be noted that in the following description, the axial direction and the circumferential direction respectively mean the axial direction and the circumferential direction of the constant velocity universal coupling 1 when the working angle is set to 0°.

[0059] The constant velocity universal joint 1 includes an outer joint member 2, a tripod member 3 as an inner joint member, and a roller unit 4 as a torque transmission member. The outer joint member 2 is in the shape of a cup with one axial end (left end in the figure) open and the other axial end (not shown) closed (see FIG. Figure 4 Three linear raceway grooves 5 extending in the axial direction are formed at equal intervals in the circumferential direction on the inner circumferential surface of the outer joint member 2 (see Figure 2 ). Roller guide surfaces 6 are formed in each raceway groove 5 and are arranged opposite to each other in the circumferential direction and extend in the axial direction. The tripod member 3 and the roller unit 4 are accommodated in the outer joint member 2.

[0060] The tripod member 3 integrally comprises: a boss portion 31 having an axial hole 30; and three pins 32 protruding in the radial direction from the outer peripheral surface of the boss portion 31 at positions which divide the circumference of the coupling into three equal parts. Figure 1 The tripod member 3 is inserted into the axial hole 30 of the shaft 8, and the internal spline 34 of the axial hole 30 formed on the boss portion 31 is engaged with the external spline 81 formed on the outer peripheral surface of the shaft 8, so that the tripod member 3 and the shaft 8 can be combined to transmit torque.

[0061] The roller unit 4 includes an annular outer ring 11, an annular inner ring 12 disposed on the inner periphery of the outer ring 11 and externally fitted to the foot shaft 32, and a plurality of needle rollers 13 sandwiched between the outer ring 11 and the inner ring 12. The roller unit 4 is accommodated in the raceway groove 5 of the outer coupling member 2. The roller unit 4 including the outer ring 11, the inner ring 12 and the needle rollers 13 is structured so as not to be naturally disassembled by a pair of snap rings 14.

[0062] The outer peripheral surface of each leg shaft 32 of the tripod member 3 is in a straight shape parallel to the axis of the leg shaft 32 in a cross section in any direction including the axis of the leg shaft 32. Figure 3 As shown in the figure, the outer peripheral surface of the pin shaft 32 is substantially elliptical in a cross section perpendicular to the axis of the pin shaft 32. The outer peripheral surface of the pin shaft 32 contacts the inner peripheral surface of the inner ring 12 in the torque load direction, that is, in the direction of the major axis a. In the axial direction, that is, in the direction of the minor axis b, a gap m is formed between the outer peripheral surface of the pin shaft 32 and the inner peripheral surface 12a of the inner ring 12.

[0063] The inner circumferential surface of the inner ring 12 is in a convex arc shape in any cross section including the axis of the inner ring 12. Due to this fact and the fact that the cross-sectional shape of the foot shaft 32 is substantially elliptical as described above and a predetermined gap m is provided between the foot shaft 32 and the inner ring 12, the inner ring 12 can swing relative to the foot shaft 32. As described above, the inner ring 12 and the outer ring 11 are assembled to rotate freely relative to each other via the needle rollers 13, so the outer ring 11 can swing relative to the foot shaft 32 as a whole with the inner ring 12.

[0064] like Figure 4 As shown, when the constant velocity universal joint 1 rotates at the working angle, although the axis of the tripod member 3 is inclined relative to the axis of the outer joint member 2, the roller unit 4 can swing, so it is possible to avoid the outer ring 11 and the roller guide surface 6 from being oblique. As a result, the outer ring 11 rolls horizontally relative to the roller guide surface 6, so that the induced thrust and sliding resistance can be reduced, and the constant velocity universal joint 1 can achieve low vibration.

[0065] As already described, the cross section (cross section) of the foot shaft 32 is substantially elliptical, and the cross section (longitudinal section) of the inner peripheral surface 12a of the inner ring 12 is an arc-shaped convex cross section. Figure 3 As shown, the outer circumference of the foot shaft 32 on the torque load side is in point contact with the inner circumference 12a of the inner ring 12 at the contact point X (including the case of contact with a narrow area close to point contact). Therefore, the force to tilt the roller unit 4 is reduced, and the stability of the posture of the outer ring 11 is improved.

[0066] The overall structure of the constant velocity universal joint 1 is as described above. Hereinafter, the connection portion between the tripod member 3 and the shaft 8, which is a characteristic structure of the constant velocity universal joint 1 of the present invention, will be described in detail.

[0067] At the inlet side end portion ( Figure 1 The left end of the shaft 8 is provided with an inlet side inclined surface 35. Thus, when the shaft 8 is moved from one side in the axial direction ( Figure 1 When the shaft 8 is inserted into the axial hole 30 of the tripod member 3 (on the left side), the front end of the shaft 8 can be prevented from interfering with the inlet side end of the inner circumferential surface of the tripod member 3 and being damaged. The shaft 8 is inserted until the conical shoulder 82 provided on the outer circumferential surface of the shaft 8 abuts against the inlet side inclined surface 35 of the tripod member 3. In this state, by providing the outer circumferential surface of the shaft 8 on the axially other side ( Figure 1 The retaining ring 10 is assembled in the annular groove 83 in the area (on the right side of the body), and the retaining ring 10 is engaged with the end face of the tripod member 3, so that the tripod member 3 is fixed in the axial direction relative to the shaft 8.

[0068] In this embodiment, if Figure 5As shown, at the outlet side end portion ( Figure 5 The right end of the tripod member 3 is provided with an outlet side inclined surface 36. In this way, the edge of the outlet side end portion of the internal spline 34 of the tripod member 3 is removed, thereby preventing the edge of the outlet side end portion of the internal spline 34 from being damaged.

[0069] The angle α of the outlet side inclined surface 36 relative to the surface orthogonal to the axial direction is preferably set to 30 to 60 degrees, and is set to 45 degrees in the example shown in the figure. In addition, if the outlet side inclined surface 36 is too small, the damage prevention effect cannot be fully obtained, so the size of the outlet side inclined surface 36 is preferably set to a predetermined size or larger. For example, the ratio d / e of the diameter d of the outer diameter end of the outlet side inclined surface 36 and the minor diameter e of the internal spline 34 of the tripod member 3 is preferably set to 1.04 or more.

[0070] For example, in Figure 7 When the outlet side inclined surface 36 is enlarged as shown, the diameter d of the outer diameter end of the outlet side inclined surface 36 becomes larger, so the area S of the contact portion P1 where the end face of the tripod member 3 contacts the retaining ring 10 becomes smaller. In addition, in the present embodiment, the flange portion 84 provided on the shaft end side of the annular groove 83 in the shaft 8 is smaller in diameter than the tooth root (minimum diameter portion) of the external spline 81 in order to avoid interference with the internal spline 34 of the tripod member 3. Therefore, when the shaft 8 is pulled out from the tripod member 3 ( Figure 7 When the retaining ring 10 moves to the left side, the contact portion P1 where the retaining ring 10 contacts the tripod member 3 and the contact portion P2 where the retaining ring 10 contacts the shaft 8 are separated to a greater extent in the radial direction, so the torque load applied to the retaining ring 10 increases, and the retaining ring 10 is easily deformed.

[0071] exist Figure 7 In the state where the shaft 8 is assembled to the tripod member 3, when a force in the direction of pulling out the shaft 8 from the tripod member 3 is applied, as shown in FIG. Fig. 9 As shown in FIG. 1 , the axial displacement of the shaft 8 relative to the tripod member 3 increases approximately in proportion to the extraction force until the extraction force of the shaft 8 reaches a predetermined value. When the extraction force reaches a predetermined value, the retaining ring 10 bends, so that the extraction force does not increase (or decreases slightly) and the shaft 8 is displaced relative to the tripod member 3. At this time, a portion parallel to the horizontal axis or tilted to the lower right is generated in the extraction force graph (see FIG. 1 ). Fig. 9 When the extraction force is further increased, the curved retaining ring 10 is caught between the shaft 8 and the tripod member 3 and functions as a disengagement prevention member, so that the displacement of the shaft 8 and the extraction force increase again in approximate proportion. As a result, the maximum value of the extraction force of the shaft 8 is equal to that in the case where no inclined surface is provided (refer to Fig. 9 The maximum pull-out force under the solid line is roughly the same.

[0072] As described above, even when a large outlet side slope 36 is provided, the maximum value of the extraction force of the shaft 8 is ensured, so it will not be a fatal defect as a product. However, the axial movement of the shaft 8 and the tripod member 3 corresponding to the bending amount of the retaining ring 10 is allowed, so abnormal noise, vibration, etc. are likely to be generated. Therefore, it is preferred that the retaining ring 10 is not bent, that is, in the graph showing the relationship between the extraction force and the displacement of the shaft 8, a portion Q parallel to the horizontal axis or inclined to the lower right is not generated (see Fig. 9 ) to set the size and shape of the outlet side slope 36.

[0073] In addition, when the outlet side inclined surface 36 is enlarged, the axial dimension of the outlet side inclined surface 36 becomes larger, so the axial length L of the fitting portion where the internal spline 34 and the external spline 81 are fitted together (the axial length of the contact portion between the two splines 34 and 81) becomes shorter, and the surface pressure of the spline fitting portion increases and the strength decreases.

[0074] For the above reasons, the size of the outlet side slope 36 is preferably set to a value below a predetermined value. Specifically, the ratio d / e of the diameter d of the outer diameter end of the outlet side slope 36 to the minor diameter e of the internal spline 34 of the tripod member 3 is preferably set to 1.08 or less. Figure 5 In the example shown, the outer diameter end of the outlet side inclined surface 36 is arranged at a position closer to the inner diameter side than the large diameter portion (tooth root) of the internal spline 34. In this case, the outlet side inclined surface 36 is provided at a plurality of locations separated in the circumferential direction (see Figure 6 hatched area).

[0075] It should be noted that if the area of ​​the contact portion P1 between the retaining ring 10 and the tripod member 3 and the length L of the spline fitting portion can be sufficiently ensured, Figure 7 As shown in FIG. 1 , the outer diameter end of the outlet side inclined surface 36 is arranged at a position closer to the outer diameter side than the large diameter portion of the internal spline 34. In this case, the outlet side inclined surface 36 is as shown in FIG. Figure 8 Specifically, the outlet side inclined surface 36 is provided with a plurality of inner diameter regions 34a provided at the outlet side end of each tooth of the internal spline 34, and an annular outer diameter region 34b which connects the plurality of inner diameter regions 34a in the circumferential direction at a position closer to the outer diameter side than the internal spline 34.

[0076] Next, a method for manufacturing the tripod member 3 will be described.

[0077] The tripod member 3 is formed of steel, for example, chrome steel or chrome-molybdenum steel, and is integrally formed. The tripod member 3 is manufactured through a forging process, a turning process, a broaching process, a heat treatment process, a blasting process, and a grinding process.

[0078] In the forging process, a blank is put into the cavity of the forging die, and the blank is filled with the die through plastic working. Thus, a tripod component blank having a boss portion and a foot shaft is obtained. It should be noted that the reference numerals of the various parts of the tripod component blank used below refer to the reference numerals of the various parts of the tripod component 3 mentioned above.

[0079] In the turning step, the inner circumference of the boss portion 31 and the outer circumference of the pin 32 in the tripod member blank are machined. By turning the inner circumference of the boss portion 31, the small diameter of the internal spline 34 and the inlet side slope 35 and the outlet side slope 36 are formed.

[0080] In the broaching step, the inner peripheral surface of the shaft hole of the tripod member blank after turning is broached to form the internal spline 34 .

[0081] In the heat treatment step, the tripod member blank after the broaching step is subjected to carburizing annealing and tempering, and a hardened layer 37 ( Figure 5 as well as Figure 7 Scattered point area). The hardened layer 37 has a higher hardness and carbon concentration than the interior. The hardened layer 37 is formed on the entire area of ​​the inner circumference of at least the boss portion 31 in the surface of the tripod member blank. In the present embodiment, the hardened layer 37 is formed on the entire surface of the tripod member blank. The depth of the hardened layer 37 is deeper than the radial dimension of the internal spline 34. As a result, the hardened layer 37 is formed on the entire internal spline 34 (the entire area in the radial direction from the root of the tooth to the top of the tooth). The hardness of the surface of the tripod member 3 is the highest, and the hardness decreases as it approaches the interior, and the area with a hardness of 513Hv or more is set as the hardened layer 37. It should be noted that the heat treatment is not limited to carburizing annealing and tempering, and can also be other quenching treatments (such as high-frequency quenching).

[0082] The blasting process is a process for increasing fatigue strength by blasting the surface of the tripod member blank to increase the compressive residual stress on the surface. Blasting is a process in which hard small balls called blasting materials are blown toward an object, such as shot blasting and shot peening. In this embodiment, a plurality of tripod member blanks are put into a rotating drum, and the blasting materials are blown toward the tripod member blanks inside the drum while the drum is rotated. As a result, the entire surface area of ​​the tripod member blank becomes a surface subjected to blasting. By blasting, the compressive residual stress on the surface of the tripod member blank is increased.

[0083] In this embodiment, the inclined surfaces 35 and 36 are provided at both axial ends of the internal spline 34 of the tripod member blank subjected to the blasting, so that the edges at both axial ends of the internal spline 34 can be prevented from being damaged by the blasting.

[0084] In the grinding step, the outer peripheral surface of the leg shaft of the tripod member blank is finished by grinding. The tripod member 3 is completed through the above processing.

[0085] The tripod member 3 produced through the above-mentioned process is stored in the standby space and then transported to the assembly process. In this way, when the tripod member 3 is processed as a single body, the outlet side end of the inner peripheral surface of the tripod member 3 sometimes contacts other tripod members 3, equipment, etc. In particular, as described above, the internal spline 34 is hardened as a whole, so the end of the internal spline 34 is easily damaged. In this embodiment, as described above, by providing the outlet side inclined surface 36 on the inner peripheral surface of the tripod member 3, it is possible to prevent the edge of the outlet side end of the internal spline 34 from being damaged.

[0086] The present invention is not limited to the above-mentioned double-row roller type tripod constant velocity universal coupling, and can be applied to single-row roller type tripod constant velocity universal coupling, double-row offset type and other sliding constant velocity universal couplings, or fixed constant velocity universal couplings. In addition, the constant velocity universal coupling of the present invention is not limited to the drive shaft of a motor vehicle, and can be widely used in the power transmission path of a motor vehicle, industrial equipment, etc.

Claims

1. A constant velocity universal coupling, comprising: Outer coupling member; an inner coupling member, which is arranged on the inner periphery of the outer coupling member and has an inner spline formed on the inner peripheral surface; a torque transmission member that transmits torque between the outer coupling member and the inner coupling member; a shaft, which is inserted into the shaft hole of the inner coupling member from one axial side and has an outer spline formed on its outer peripheral surface to engage with the inner spline; an annular groove formed in a region of the outer peripheral surface of the shaft that is closer to the other axial side than the inner joint member; and a retaining ring, which is mounted in the annular groove and is engaged with the inner coupling member from the other axial side, The constant velocity universal coupling is characterized in that: A hardened layer having a higher hardness than the inner part is provided on the surface of the inner coupling member. A slope is formed on the other axial end portion of the inner peripheral surface of the inner joint member.

2. The constant velocity universal joint according to claim 1, wherein: The angle of the inclined surface relative to the surface perpendicular to the axial direction is 30 to 60 degrees.

3. The constant velocity universal joint according to claim 1, wherein: A ratio d / e of a diameter d of an outer diameter end of the inclined surface to a minor diameter e of the internal spline of the inner joint member is 1.04 to 1.

08.

4. The constant velocity universal joint according to claim 1, wherein: The outer diameter end of the inclined surface is arranged on the inner diameter side of the large diameter portion of the internal spline.

5. The constant velocity universal joint according to claim 1, wherein: The outer diameter end of the inclined surface is arranged on the outer diameter side relative to the large diameter portion of the internal spline.

6. The constant velocity universal joint according to claim 1, wherein: The surface of the inner joint member is subjected to blasting.

7. The constant velocity universal joint according to claim 6, wherein: The inner coupling member has a boss portion and three pins protruding radially outward from the boss portion. A roller as the torque transmission member is rotatably supported on each leg shaft. The rollers are accommodated in three raceway grooves formed on the inner peripheral surface of the outer joint member.

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