Tripod type constant velocity universal joint

Abstract

To prevent deterioration in vibration characteristic of a double roller type and tripod type constant velocity universal joint and deterioration in durability of a roller unit.SOLUTION: A snap ring 14 includes a cut surface A formed by shearing. The cut surface A includes: a sheared surface A2 provided in a region on a side of a front surface 14d; and a fracture surface A3 provided in a region on a side of a rear surface 14e. The front surface 14d of the snap ring 14 faces a plurality of needle rollers 13.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a tripod-type constant velocity universal joint. [Background technology]

[0002] In driveshafts used in automotive power transmission systems, a sliding-type constant velocity universal joint is often connected to the inboard side (the center side in the vehicle width direction) of the intermediate shaft, and a fixed-type constant velocity universal joint is connected to the outboard side (the outside side in the vehicle width direction).The sliding-type constant velocity universal joint here allows both angular displacement and relative axial movement between the two shafts, while the fixed-type constant velocity universal joint allows angular displacement between the two shafts but does not allow relative axial movement between the two shafts.

[0003] A tripod-type constant velocity universal joint is well known as a sliding-type constant velocity universal joint. This tripod-type constant velocity universal joint is available in single roller and double roller types. The single roller type has rollers inserted into track grooves of an outer joint member, which are rotatably attached to the trunnions of the tripod members via multiple needle rollers. The double roller type has rollers inserted into track grooves of an outer joint member and inner rings fitted onto the trunnions of the tripod members to rotatably support the rollers. The double roller type allows the rollers to oscillate relative to the trunnions, which has the advantage of reducing induced thrust (axial force induced by friction between parts inside the joint) and sliding resistance compared to the single roller type.

[0004] An example of a double-roller tripod constant velocity universal joint is disclosed in Patent Document 1 listed below. In such a double-roller tripod constant velocity universal joint, the rollers are rotatably arranged on the outer periphery of an inner ring via needle rollers. The needle rollers and inner ring are prevented from coming off by a pair of snap rings attached to the inner circumferential surface of the rollers. That is, a pair of mounting grooves are formed on the inner circumferential surface of the rollers, spaced apart in the leg axis direction at a distance corresponding to the length of the needle rollers, and a snap ring is fitted into each of these mounting grooves.

[0005] The snap ring has an open end with a slit in one circumferential position, and is fitted into a mounting groove on the inner peripheral surface of the roller by elastically reducing its diameter. In Patent Document 2 listed below, the circumferential ends of the snap ring are chamfered to prevent interference when the snap ring is fitted to the inner peripheral surface of the roller. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-320563 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-10086 Summary of the Invention [Problem to be solved by the invention]

[0007] Snap rings are often formed by shearing (press molding). Generally, shearing is performed by punching a metal plate 100 using a die 201 and a punch 202, as shown in FIGS. 10 to 13. Specifically, the punch 202 is lowered to bite into the metal plate 100, thereby forming a sag 101 in the metal plate 100 (see FIG. 10). Thereafter, the punch 202 is further lowered, thereby forming a shear surface 102 in the metal plate 100 and generating cracks 103a (see FIG. 11). The punch 202 is further lowered, thereby connecting the cracks 103a to form a fracture surface 103 (see FIG. 12), and the metal plate 100 is divided into a product part 100A and a scrap part 100B (see FIG. 13).

[0008] On the cut surface of the product part 100A thus formed, sagging 101, shear surface 102, and fracture surface 103 are formed in this order from one side in the thickness direction (upper side in the figure) to the other side in the thickness direction (lower side in the figure), as shown in Fig. 4. On the end of fracture surface 103 on the lower side in the figure, burrs (also called burrs) 104 protruding downward in the figure are formed.

[0009] When a snap ring is formed by shearing, burrs are formed on the edges of the fractured surfaces of the cut surfaces (inner circumferential surface, outer circumferential surface, and end surfaces facing each other across a slit). When a tripod-type constant velocity universal joint transmits torque, the roller unit (the rollers, inner ring, and needle rollers integrated by the snap ring) rotates relative to the trunnion while the snap ring slides against the end surfaces of the needle rollers. If burrs are formed on the snap ring at this time, they can interfere with the end surfaces of the needle rollers, hindering the rotation of the roller unit, which could worsen the vibration characteristics of the constant velocity universal joint and reduce the durability of the roller unit.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent deterioration of vibration characteristics of a double roller type tripod constant velocity universal joint and a decrease in durability of the roller unit. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a tripod member comprising: an outer joint member having track grooves formed on an inner peripheral surface at three locations in the circumferential direction, the track grooves extending in the axial direction; a tripod member disposed on the inner circumference of the outer joint member and having three trunnions protruding in the radial direction toward the track grooves; and three roller units rotatably supported by the trunnions and accommodated in the track grooves, The roller unit is a tripod-type constant velocity universal joint having a roller, an inner ring fitted onto the trunnion, a plurality of rolling elements arranged between the inner peripheral surface of the roller and the outer peripheral surface of the inner ring, and a snap ring fitted into a mounting groove formed on the inner peripheral surface of the roller and restricting movement of the inner ring and the plurality of rolling elements in the axial direction of the trunnion, the snap ring has a cut surface formed by shearing, the cut surface has a shear surface provided in a region on one side in the thickness direction and a fracture surface provided in a region on the other side in the thickness direction, The snap ring is characterized in that one surface in the thickness direction thereof faces the plurality of rolling elements.

[0012] In this way, in the present invention, the surface on one side in the thickness direction of the snap ring (i.e., the sheared surface side) faces the rolling elements, and the surface on the other side in the thickness direction of the snap ring (i.e., the fractured surface side) is arranged on the opposite side from the rolling elements. This means that burrs formed on the ends of the fractured surface side of the cut surface of the snap ring are arranged on the opposite side from the rolling elements (e.g., needle rollers), preventing the burrs from interfering with the rolling elements.

[0013] The snap ring may have, for example, a circumferentially circumferentially slit with an open end, and this slit may be inclined relative to the radial direction of the snap ring. In this case, the punching direction of the snap ring, i.e., the front and back of the snap ring (which side faces the sheared surface) can be determined by the inclination direction of the slit. Therefore, when fitting the snap ring into the roller mounting groove, the front and back of the snap ring can be easily identified by the inclination direction of the slit.

[0014] The above-mentioned tripod-type constant velocity universal joint can be configured such that the inner surface of the inner ring has an arc-shaped convex surface that is convex toward the inner diameter side in a cross section including the axis of the inner ring, the outer surface of the trunnion has a straight shape parallel to the axis of the trunnion in a cross section including the axis of the trunnion, and has a substantially elliptical shape in a cross section perpendicular to the axis of the trunnion, and the outer surface of the trunnion abuts against the inner surface of the inner ring in the torque load direction, and a gap is formed between the outer surface of the trunnion and the inner surface of the inner ring in the joint axis direction. [Effects of the Invention]

[0015] As described above, according to the present invention, interference between the burrs formed on the snap ring and the rolling elements can be avoided, thereby preventing deterioration of vibration characteristics and a decrease in durability of the roller unit. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of a double-roller type tripod constant velocity universal joint taken along the joint axis. [Figure 2] FIG. 2 is a cross-sectional view taken along line KK in FIG. 1. [Figure 3] FIG. 2 is a cross-sectional view taken along line LL in FIG. [Figure 4] 2 is a cross-sectional view showing a state in which the tripod constant velocity universal joint of FIG. 1 has an operating angle. [Figure 5] 3 is a plan view of the roller unit attached to the leg shaft as viewed from the direction A in FIG. 2. FIG. [Figure 6] FIG. 4 is a cross-sectional view of the roller unit taken along the axial direction of the leg shaft. [Figure 7] FIG. [Figure 8] FIG. 2 is a perspective view of a cross section of the snap ring. [Figure 9] 8 is a cross-sectional view of the roller unit taken along line MM in FIG. 7. [Figure 10] 1A to 1C are cross-sectional views showing the procedure of shearing. [Figure 11] 1A to 1C are cross-sectional views showing the procedure of shearing. [Figure 12] 1A to 1C are cross-sectional views showing the procedure of shearing. [Figure 13] 1A to 1C are cross-sectional views showing the procedure of shearing. [Figure 14] FIG. 1 is a cross-sectional view of a cut surface produced by shearing. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tripod type constant velocity universal joint according to an embodiment of the present invention will be described with reference to the drawings.

[0018] 1 to 4 is a double-roller type tripod constant velocity universal joint 1. In the following description, the joint axial direction and joint circumferential direction refer to the axial direction and circumferential direction of the tripod constant velocity universal joint when the operating angle is 0°.

[0019] As shown in Figures 1 and 2, this tripod type 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 cup-shaped with one end open, and has three linear track grooves 5 extending in the joint axial direction formed on its inner peripheral surface at equal intervals in the joint circumferential direction. Each track groove 5 is formed with a roller guide surface 6 that is arranged opposite to each other in the joint circumferential direction of the outer joint member 2 and extends in the joint axial direction. The tripod member 3 and the roller unit 4 are housed inside the outer joint member 2.

[0020] The tripod member 3 integrally comprises a body portion 31 (trunnion body portion) having a center hole 30, and three trunnion journals 32 protruding radially from positions equally dividing the outer circumferential surface of the body portion 31 in the joint circumferential direction. The tripod member 3 is coupled to the shaft 8 so as to be able to transmit torque, by fitting a male spline 81 formed on the shaft 8 serving as an axis into a female spline 34 formed in the center hole 30 of the body portion 31. The tripod member 3 is fixed to the shaft 8 in the joint axial direction by engaging an end face on one side of the tripod member 3 in the joint axial direction with a shoulder portion 82 provided on the shaft 8, and engaging a retaining ring 10 attached to the tip of the shaft 8 with an end face on the other side of the tripod member 3 in the joint axial direction.

[0021] The roller unit 4 includes an outer ring 11, which is an annular roller centered on the axis of the trunnion 32; an inner ring 12, which is an annular roller disposed on the inner periphery of the outer ring 11 and fitted onto the trunnion 32; and a large number of rolling elements 13 interposed between the outer ring 11 and the inner ring 12. In this embodiment, full-complement needle rollers without cages are used as an example of the rolling elements 13. The roller unit 4 is housed in the track grooves 5 of the outer joint member 2. As will be described in detail later, the roller unit 4, which is made up of the outer ring 11, inner ring 12, and needle rollers 13, is configured to not disassemble naturally by a pair of snap rings 14.

[0022] In this embodiment, the outer peripheral surface of the outer ring 11 (see FIG. 2) is a convex curved surface whose generating line is an arc having a center of curvature on the axis of the trunnion 32. The outer peripheral surface of the outer ring 11 is in angular contact with the roller guideway 6.

[0023] The needle rollers 13 are arranged rollably between the cylindrical inner peripheral surface of the outer ring 11 as the outer raceway surface and the cylindrical outer peripheral surface of the inner ring 12 as the inner raceway surface.

[0024] The outer circumferential surface of each trunnion 32 of the tripod member 3 has a straight shape parallel to the axis of the trunnion 32 in a cross section in any direction including the axis of the trunnion 32. As shown in FIG. 3 , the outer circumferential surface of the trunnion 32 has a substantially elliptical shape in a cross section perpendicular to the axis of the trunnion 32. The outer circumferential surface of the trunnion 32 contacts the inner circumferential surface 12a of the inner ring 12 in the torque load direction, i.e., the direction of the major axis a. A gap m is formed between the outer circumferential surface of the trunnion 32 and the inner circumferential surface 12a of the inner ring 12 in the joint axial direction, i.e., the direction of the minor axis b.

[0025] The inner peripheral surface 12a of the inner ring 12 forms a convex arc shape in any cross section including the axis of the inner ring 12. Because of this, and because the cross section of the trunnion 32 is generally elliptical as described above and a predetermined gap m is provided between the trunnion 32 and the inner ring 12, the inner ring 12 is able to swing relative to the trunnion 32. As described above, the inner ring 12 and the outer ring 11 are assembled in a manner that allows relative rotation via the needle rollers 13, so the outer ring 11 can swing integrally with the inner ring 12 relative to the trunnion 32. In other words, the axes of the outer ring 11 and the inner ring 12 can tilt relative to the axis of the trunnion 32 within a plane including the axis of the trunnion 32 (see Figure 4).

[0026] As shown in Figure 4, when the tripod type constant velocity universal joint 1 rotates through an operating angle, the axis of the tripod member 3 is inclined relative to the axis of the outer joint member 2, but because the roller unit 4 is swingable, it is possible to prevent the outer ring 11 and the roller guideway 6 from intersecting at an angle. As a result, the outer ring 11 rolls horizontally relative to the roller guideway 6, which makes it possible to reduce induced thrust and sliding resistance, thereby enabling the tripod type constant velocity universal joint 1 to achieve low vibration.

[0027] As already mentioned, the cross section (transverse section) of the trunnion 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, so that the outer peripheral surface of the trunnion 32 on the torque load side and the inner peripheral surface 12a of the inner ring 12 come into point contact (including contact over a small area close to point contact) at contact point X, as shown in Figure 3. This reduces the force that tends to tilt the roller unit 4, improving the stability of the posture of the outer ring 11.

[0028] 5 is a plan view of the roller unit 4 attached to the trunnion 32 as viewed from the direction A in FIG. 2, and FIG. 6 is a cross-sectional view of the roller unit 4 along the axial direction of the trunnion 32. As shown in FIG.

[0029] As shown in FIG. 6 , in the roller unit 4, a pair of mounting grooves 11a are provided on the inner peripheral surface of the outer ring 11, spaced apart in the axial direction of the trunnion 32. A pair of snap rings 14 are fitted into the respective mounting grooves 11a, and are attached to the inner peripheral surface 11b of the outer ring 11, spaced apart in the axial direction of the trunnion 32. The snap rings 14 face the end faces of the needle rollers 13 and the inner ring 12 on both sides in the axial direction of the trunnion 32. The pair of snap rings 14 restrict relative movement of the needle rollers 13 and the inner ring 12 with respect to the outer ring 11 in the axial direction of the trunnion 32. Therefore, the pair of snap rings 14 restrict spontaneous disassembly of the roller unit 4.

[0030] As shown in Figure 7, snap ring 14 has a slit C (a gap in the circumferential direction) at one location in the circumferential direction, and is formed in the shape of an end-open ring divided by slit C. Snap ring 14 has a shape in which a strip plate with a rectangular cross section is wound around an axis extending in the thickness direction of the snap ring 14. Slit C extends in a direction inclined relative to the radial direction of snap ring 14.

[0031] The slits C of the snap ring 14 are formed by shearing, typically by punching a metal material (e.g., steel plate) with a die and a punch (see FIGS. 10 to 13). The edges of the flat snap ring 14, specifically, both circumferential end portions 14c of the snap ring 14 (end faces facing each other in the circumferential direction across the slits C), are provided with cut surfaces A by shearing. Depending on the processing method, cut surfaces A may also be provided on the inner circumferential surface 14a and the outer circumferential surface 14b of the snap ring 14. As shown in FIG. 8, these cut surfaces A are formed in this order from the surface on one side in the thickness direction (hereinafter referred to as the "front surface 14d") to the surface on the other side in the thickness direction (hereinafter referred to as the "rear surface 14e"). The sagging A1 is a curved surface with a generally arc-shaped cross section that smoothly connects the front surface 14d and the shear surface A2 of the snap ring 14. The sheared surface A2 is a flat surface approximately parallel to the shear direction (thickness direction), is shiny, and has fine lines in the shear direction. The fractured surface A3 is a rough surface with more irregularities than the sheared surface A2. The burrs A4 are protrusions protruding from the back surface 14e of the snap ring 14.

[0032] As shown in Figure 6, the outer diameter end of the snap ring 14 fits into the mounting groove 11a of the outer ring 11, and the inner diameter end of the snap ring 14 abuts against the end face of the inner ring 12 from the axial direction of the trunnion 32. Then, the radially intermediate portion of the snap ring 14 (the region excluding the outer diameter end and the inner diameter end) abuts against the end face of the needle roller 13 from the axial direction of the trunnion 32. When the constant velocity universal joint 1 rotates, the radially intermediate portion of the snap ring 14 slides against the end face of the needle roller 13, causing the roller unit 4 to rotate around the trunnion 32. In this case, if the back surface 14e of the snap ring 14 (the surface from which the burrs A4 protrude) faces the end surface of the needle rollers 13, there is a risk that the burrs A4 provided on the circumferential end portion 14c of the snap ring 14 will interfere with the needle rollers 13 when the needle rollers 13 (only some of the needle rollers 13 are shown by dotted lines in Figure 7) slide across the slits C of the snap ring 14.

[0033] 9, in this embodiment, front surface 14d of snap ring 14 (the surface from which burrs A4 do not protrude) faces the end surface of needle roller 13, and back surface 14e from which burrs A4 protrude is disposed on the opposite side from needle roller 13. As a result, when needle roller 13 and snap ring 14 slide against each other during rotation of constant velocity universal joint 1, burrs A4 of snap ring 14 do not interfere with needle roller 13, preventing deterioration of the vibration characteristics of the tripod constant velocity universal joint and a decrease in the durability of the roller unit.

[0034] Here, we will explain how to assemble the roller unit 4. The roller unit 4 is assembled by placing the inner ring 12 on the inner periphery of the outer ring 11, arranging a large number of needle rollers 13 between them in a full complement state, and then fitting a snap ring 14 into the mounting groove 11a of the outer ring 11.

[0035] In this embodiment, the front and back of the snap ring 14 are checked before the snap ring 14 is attached to the mounting groove 11a on the inner peripheral surface of the outer ring 11. Because the shear surface A2 and the fracture surface A3 have different surface properties, it is also possible to check the front and back of the snap ring 14 by visually checking the cut surface A. However, because the area of ​​the cut surface A is small, such visual checking is not easy, takes time, and is prone to errors.

[0036] Therefore, in this embodiment, the front and back sides of the snap ring 14 are identified based on the inclination direction of the slits C of the snap ring 14. That is, the inclination direction of the slits C differs when the snap ring 14 is viewed from the front surface 14d side (the sheared surface A2 side) and when viewed from the back surface 14e side (the fractured surface A3 side). Specifically, when the snap ring 14 is viewed from the back surface 14e side, the slits C are inclined toward one circumferential side relative to the radial direction (see FIG. 7). When the snap ring 14 is viewed from the front surface 14d side, the slits C are inclined toward the other circumferential side relative to the radial direction (the opposite side to FIG. 7). Therefore, as shown in FIGS. 5 and 7, when the snap ring 14 is viewed from the axial direction, if the slits C are inclined toward one circumferential side relative to the radial direction, it can be confirmed that the front side is the back surface 14e (the surface toward the fractured surface A3) and the back side is the front surface 14d (the surface toward the sheared surface A2). In this way, the front and back sides of the snap ring 14 can be easily identified based on the inclination direction of the slits C. The inclination direction of the slit C may be checked visually by an operator or automatically by an assembly device.

[0037] After checking the front and back of the snap ring 14 in this way, the snap ring 14 is attached to the attachment groove 11a of the outer ring 11 in a predetermined orientation (see FIG. 9). In this embodiment, as shown in FIG. 5, the snap ring 14 is attached to the attachment groove 11a of the outer ring 11 with the slit C oriented so that it is inclined to one side in the circumferential direction when viewed from the outside in the axial direction of the roller unit 4. This allows the snap ring 14 to be assembled to the outer ring 11 with the front surface 14d of the snap ring 14 facing the needle rollers 13 and the back surface 14e of the snap ring 14 positioned opposite the needle rollers 13, as shown in FIG.

[0038] In this embodiment, the pair of snap rings 14 have the same configuration (are punched out using the same die). Therefore, when the assembled roller unit 4 is viewed from either axial side, the slits C of the snap rings 14 are inclined toward one circumferential side relative to the radial direction (see FIG. 5).

[0039] The present invention is not limited to the above embodiment. For example, in the above embodiment, the snap rings 14 are disposed on both axial sides of the needle rollers 13, but one of the snap rings 14 can be omitted by providing a flange on either axial end of the outer ring.

[0040] The above-described embodiments of the present invention can also be applied to double-roller tripod constant velocity universal joints having other configurations. For example, the outer peripheral surface of the trunnion 32 can be formed as a convex curved surface (e.g., a spherical surface), and the inner peripheral surface 12a of the inner ring 12 can be formed as a cylindrical surface. Alternatively, the outer peripheral surface of the trunnion 32 can be formed as a convex curved surface (e.g., a convex arc-shaped cross section), and the inner peripheral surface 12a of the inner ring 12 can be formed as a concave spherical surface that fits with the outer peripheral surface of the trunnion.

[0041] The application of the tripod constant velocity universal joint 1 described above is not limited to the drive shaft of an automobile, but can be widely used in power transmission paths of automobiles, industrial equipment, and the like. [Explanation of symbols]

[0042] 1 Tripod-type constant velocity universal joint 2 Outer joint member 3 Tripod member 4 Roller unit 5 Track groove 6 Roller guideway 8 shafts 11 Outer Ring (Roller) 11a Mounting groove 12 Inner Ring 13 Needle rollers (rolling elements) 14 Snap ring 14c Circumferential end (end face) 14d surface 14e back side 31 Torso 32 Leg axis A Cut surface A1 Sauce A2 shear plane A3 fracture surface A4 Kaeri C slit

Claims

1. an outer joint member having track grooves formed on an inner peripheral surface at three locations in the circumferential direction, the track grooves extending in the axial direction; a tripod member disposed on the inner peripheral surface of the outer joint member and having three trunnions protruding in the radial direction toward the track grooves; and three roller units rotatably supported by the trunnions and accommodated in the track grooves, The roller unit is a tripod-type constant velocity universal joint having a roller, an inner ring fitted onto the trunnion, a plurality of rolling elements arranged between the inner peripheral surface of the roller and the outer peripheral surface of the inner ring, and a snap ring fitted into a mounting groove formed on the inner peripheral surface of the roller and restricting movement of the inner ring and the plurality of rolling elements in the axial direction of the trunnion, the snap ring has a cut surface formed by shearing, the cut surface has a shear surface provided in a region on one side in the thickness direction and a fracture surface provided in a region on the other side in the thickness direction, A tripod-type constant velocity universal joint in which a surface on one side in the thickness direction of the snap ring faces the plurality of rolling elements.

2. The snap ring has an open end and a slit at one location in the circumferential direction, 2. A tripod type constant velocity universal joint according to claim 1, wherein said slits are inclined relative to the radial direction of said snap ring.

3. an inner peripheral surface of the inner ring having an arc-shaped convex surface that is convex toward the inner diameter side in a cross section including the axis of the inner ring; the outer peripheral surface of the trunnion has a straight shape parallel to the axis in a cross section including the axis of the trunnion, and has a substantially elliptical shape in a cross section perpendicular to the axis of the trunnion; 3. A tripod-type constant velocity universal joint according to claim 1, wherein the outer peripheral surface of the trunnion abuts against the inner peripheral surface of the inner ring in the torque load direction, and a gap is formed between the outer peripheral surface of the trunnion and the inner peripheral surface of the inner ring in the joint axial direction.

4. 4. A tripod type constant velocity universal joint according to claim 1, wherein the rolling elements are needle rollers.

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