JP2007016851A - Tripod type constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce abrasion of contact parts of leg shafts or needle rollers. <P>SOLUTION: This tripod type constant velocity universal joint comprises an outer joint member 1 provided with axial three track grooves 2 formed on its inner peripheral portion, and having axial roller guide faces 3 respectively at both sides of each of track grooves 2, a tripod member 4 having three leg shafts 5 radially projecting, and rollers 7 mounted on each of the leg shafts 5 of the tripod member 4, rotatably supported through the plurality of needle rollers 6, and inserted into the track grooves 2, and the rollers 7 are movable in the axial direction of the outer joint member 1 along the roller guide faces 3. Uncounted micro recessed voids 8 are formed on surfaces of the needle rollers 6 at random, a surface roughness parameter Ryni of the surface provided with the voids 8 is within a range of 0.4μm≤Ryni≤1.0μm, and a Sk value is -1.6 or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sliding tripod type constant velocity universal joint. In general, a constant velocity universal joint is a type of universal joint that connects two shafts on the drive side and the driven side and can transmit rotational force at a constant speed even if there is an angle between the two shafts. In the formula type, relative axial displacement between the two axes is made possible by plunging the joint, and the tripod type has a tripod member having three leg shafts projecting in the radial direction on one axis. A hollow cylindrical outer joint member having three track grooves extending in the axial direction is coupled to the other shaft, and the leg shaft of the tripod member is accommodated in the track groove of the outer joint member to transmit torque. It is intended to do.

  It is known to use a sliding tripod type constant velocity universal joint to transmit rotational force from an automobile engine to wheels at a constant speed (see, for example, FIG. 10 of Patent Document 1). This sliding tripod type constant velocity universal joint connects two shafts on the drive side and the driven side, transmits rotational torque at a constant speed even if the two shafts have an operating angle, and has a relative axial displacement. It has an acceptable structure.

  An example of this sliding tripod type constant velocity universal joint will be described with reference to FIG. 1 of the present invention. Three cylindrical track grooves 2 are formed in the axial direction of the inner peripheral surface of the outer joint member 1, and the outer An annular roller 7 that is rotatably fitted via a plurality of needle rollers 6 on the cylindrical outer peripheral surface of three leg shafts 5 protruding in the radial direction of a tripod member 4 inserted into the joint member 1. Is inserted into the track groove 2.

  The pair of roller guide surfaces 3 facing each other in the circumferential direction of each track groove 2 are concave curved surfaces parallel to the axial direction, and the outer peripheral surface of each roller 7 of the three leg shafts 5 is a convex that matches the roller guide surface 3. It is a curved surface. Each roller 7 is movable along the track groove 2 while engaging with the roller guide surface 3 of the corresponding track groove 2 and rotating around the leg shaft 5. One of the two shafts is connected to the outer joint member 1, and the other driven shaft is connected to the tripod member 4.

  As described above, the leg shaft 5 of the tripod member 4 and the roller guide surface 3 of the outer joint member 1 are engaged with each other in the biaxial rotation direction via the roller 7, so that the rotational torque is constant from the drive side to the driven side. Communicated in Further, as each roller 7 rolls on the roller guide surface 3 while rotating with respect to the leg shaft 5, relative axial displacement and angular displacement between the outer joint member 1 and the tripod member 4 are absorbed. Is done.

  As shown in FIG. 1B, the roller 7 and the roller guide surface 3 are obliquely crossed with each other as shown in FIG. 1C when the rotational force is transmitted with the joint at the operating angle θ. It becomes. In this case, the roller 7 tries to roll and move in the direction indicated by the arrow t in FIG. 1B, whereas the track groove 2 is a part of a cylindrical surface parallel to the axis of the outer joint member 1. The roller 7 moves while being restrained by the track groove 2. As a result, a slip occurs between the roller guide surface 3 and the roller 7 to generate a slide resistance, and this slip generates an induced thrust in the axial direction. Such slide resistance and induced thrust cause vibration and noise of the vehicle body, affect the NVH performance of the automobile, and reduce the degree of freedom in designing the undercarriage of the vehicle.

  As a sliding tripod type constant velocity universal joint for reducing the sliding resistance and the induced thrust, for example, a double roller type tripod type constant velocity universal joint is known (see, for example, FIG. 11 of Patent Document 1). This double roller type tripod type constant velocity universal joint is constituted by a roller cassette comprising a roller that is rotatably fitted to a leg shaft of a tripod member. The roller cassette has an inner roller and an outer roller, and needle rollers are interposed between the two rollers. The inner roller is swingably fitted to the leg shaft, and the outer roller is an outer joint member. Is moved in the axial direction of the outer joint member while rolling on the roller guide surface of the track groove.

In this double roller type tripod type constant velocity universal joint, the roller cassette is swingable and swingable (the roller cassette is tiltable and axially displaceable with respect to the leg shaft), so the outer joint member and the tripod member are When transmitting the rotational force with the operating angle taken, it is possible to avoid the outer roller and the roller guide surface from being obliquely crossed so that the outer roller maintains a posture parallel to the axis of the outer joint member. Are guided by the roller guide surface of the outer joint member, and roll on the roller guide surface in the same posture. Therefore, slip resistance during operation angle operation is reduced, and generation of slide resistance and induced thrust is suppressed.
JP 2000-320563 A (FIGS. 10 and 11)

  Incidentally, in the joint of the type shown in FIG. 10 of Patent Document 1, when a rotational force is transmitted between the outer joint member and the tripod member, rolling and sliding between the leg shaft and the needle roller and between the needle roller and the roller are performed. Occur simultaneously. For this reason, wear is likely to occur at the contact portions of the leg shafts, needle rollers, and rollers, and if this wear proceeds excessively, it may cause vibrations and noise in the vehicle body. Also, in the double roller type joint shown in FIG. 11 of Patent Document 1, rolling and sliding occur simultaneously between the leg shaft and the inner roller, the inner roller and the needle roller, and between the needle roller and the outer roller. For this reason, wear is likely to occur at the contact portion of the leg shaft, the inner roller, the needle roller and the outer roller, and if this wear progresses excessively, it causes vibrations and noise of the vehicle body as well.

  Accordingly, the present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide a tripod type constant velocity universal joint that can reduce wear at a portion where a leg shaft or a needle roller contacts. There is to do.

  As a technical means for achieving the above-mentioned object, the present invention provides an outer joint in which three track grooves in the axial direction are formed on the inner peripheral portion, and axial roller guide surfaces are provided on both sides of each track groove. A member, a tripod member having three leg shafts projecting in the radial direction, and attached to each leg shaft of the tripod member, and rotatably supported through a plurality of needle rollers in the track groove. In a tripod type constant velocity universal joint provided with an inserted roller and movable in the axial direction of the outer joint member along the roller guide surface, a hollow having a micro concave shape is formed on the surface of the needle roller or the leg shaft. The surface roughness parameter Ryni of the surface provided with the depressions is in a range of 0.4 μm ≦ Ryni ≦ 1.0 μm, and the Sk value is −1.6 or less. To do.

  Here, the parameter Ryni is the average value of the maximum height for each reference length, that is, the reference length is extracted from the roughness curve in the direction of the average line, and the distance between the peak line and the valley bottom line of the extracted portion is the roughness curve. It is a value measured in the direction of the vertical magnification (ISO 4287: 1997). By providing an infinite number of minute concave recesses on the surface of the needle roller or the leg shaft, the oil film forming ability is improved and the life is prolonged. In particular, by setting the surface roughness parameter Ryni of the surface provided with the indentation within the range of 0.4 μm ≦ Ryni ≦ 1.0 μm, it is possible to prevent the oil film from being cut and to obtain a longer life than the conventional product. it can. When the surface roughness parameter Ryni is smaller than 0.4 μm or larger than 1.0 μm, or when the Sk value is larger than −1.6, the effect of increasing the lifetime is hardly obtained.

  The parameter Sk indicates the degree of skewness (skewness) of the roughness curve (ISO 4287: 1997), and is a statistic that is a measure of the asymmetry of the uneven distribution. The Sk value is close to 0 in a symmetric distribution such as a Gaussian distribution. That is, when the concave and convex portions are deleted, negative values are obtained, and in the opposite case, positive values are obtained. The Sk value can be controlled by selecting the rotational speed of the barrel sander, the processing time, the amount of workpiece input, the type and size of the chip, and the like. By setting the Sk value to -1.6 or less in both the width direction and the circumferential direction, the hollow with a minute concave shape becomes an oil reservoir, and even when compressed, there is little oil leakage in the sliding direction and the right-angle direction, so that an oil film is formed. Excellent, oil film formation is good, and has the effect of minimizing surface damage.

  In the above-described configuration, it is desirable that the surface roughness parameter Rymax of the surface provided with the depression is in the range of 0.4 to 1.0. Here, the parameter Rymax is the maximum value of the maximum height for each reference length (ISO 4287: 1997). Further, when the surface roughness of the surface provided with the above-mentioned depression is represented by the parameter Rqni, the value Rqni (L) of the ratio between the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C). / Rqni (C) is preferably 1.0 or less. Here, the parameter Rqni is the square root of the value obtained by integrating the square of the height deviation from the roughness center line to the roughness curve in the measurement length interval and averaging the interval, which is also known as the root mean square roughness. It is also called. Rqni is obtained by numerical calculation from the cross-sectional curve and roughness curve recorded in an enlarged manner, and is measured by moving the stylus of the roughness meter in the width direction and the circumferential direction.

  According to the present invention, the roller having the above-described configuration is an outer roller rotatably supported via a plurality of needle rollers on an inner roller that is externally fitted to the leg shaft of the tripod member. Further, the present invention can be applied to a double roller type tripod type constant velocity universal joint in which an assembly body is constituted by outer rollers.

  According to the present invention, the surface of the needle roller or the leg shaft of the tripod type constant velocity universal joint is provided with an infinite number of minute concave depressions, so that the contact portion with the needle roller or the leg shaft is provided. The oil is stably held in the recess, and the oil film can be prevented from being cut. As a result, an effect of reducing wear at the contact portion of the needle roller or the leg shaft can be obtained, and phenomena such as vehicle body vibration and noise caused by increased wear can be suppressed.

  The first embodiment of the present invention will be described in detail below with reference to FIGS. 1 (A) to 1 (C) and FIGS. 2 (A) and 2 (B). The tripod type constant velocity universal joint of the embodiment shown in FIGS. 1A to 1C and FIGS. 2A and 2B is structurally similar to the conventional one.

  As shown in FIGS. 1A to 1C, three cylindrical track grooves 2 are formed in the axial direction of the inner peripheral surface of the outer joint member 1. A tripod member 4 is inserted into the outer joint member 1. An annular roller 7 is rotatably fitted on the cylindrical outer peripheral surface of the three leg shafts 5 projecting in the radial direction of the tripod member 4 via a plurality of needle rollers 6. Is inserted into the track groove 2. The pair of roller guide surfaces 3 facing each other in the circumferential direction of each track groove 2 is a concave curved surface parallel to the axial direction, and the outer peripheral surface of each roller 7 is a convex curved surface adapted to the roller guide surface 3. Each roller 7 is movable along the track groove 2 while engaging with the roller guide surface 3 of the corresponding track groove 2 and rotating around the leg shaft 5. In this constant velocity universal joint, the drive shaft is connected to the outer joint member 1, and the driven shaft is connected to the tripod member 4.

  As described above, the leg shaft 5 of the tripod member 4 and the roller guide surface 3 of the outer joint member 1 are engaged with each other in the biaxial rotation direction via the roller 7, so that the rotational torque is constant from the drive side to the driven side. Communicated in Further, as each roller 7 rolls on the roller guide surface 3 while rotating with respect to the leg shaft 5, relative axial displacement and angular displacement between the outer joint member 1 and the tripod member 4 are absorbed. Is done.

  The tripod type constant velocity universal joint of this embodiment is different from the conventional one in that, as shown in FIGS. 2A and 2B, the surface of the needle roller 6 or the leg shaft 5, at least the needle roller 6 or the leg shaft 5 is used. Innumerable indentations 8 having a small concave shape are randomly provided on the outer peripheral surface. The minute concave recess 8 may be provided on either the needle roller 6 or the leg shaft 5 or on both the needle roller 6 and the leg shaft 5.

  The surface roughness parameter Ryni of the surface provided with the recess 8 is preferably in the range of 0.4 μm ≦ Ryni ≦ 1.0 μm. The Sk value is −1.6 or less, preferably in the range of −4.9 to −1.6. Further, the surface roughness parameter Rymax of the surface provided with the recess 8 is preferably within the range of 0.4 to 1.0. Further, when the surface roughness of the surface provided with the recess 8 is expressed by the parameter Rqni, the value Rqni (L) / L of the ratio between the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C). Rqni (C) is preferably set to 1.0 or less. As the surface processing for obtaining such a fine rough surface, a desired finished surface can be obtained by special barrel polishing, but a shot or the like may be used.

  The measurement method and conditions of the parameters Ryni, Rymax, Sk, Rqni are exemplified as follows. When the surface properties represented by these parameters are measured for the needle roller 6 or the leg shaft 5 of the tripod type constant velocity universal joint, a measured value at one location can be relied on as a representative value. 6 or two opposite positions in the diameter direction of the leg shaft 5 may be measured.

Parameter calculation standard: JIS B 0601: 1994 (Surfcom JIS 1994)
Cut-off type: Gaussian Measurement length: 5λ
Cut-off wavelength: 0.25mm
Measurement magnification: × 10000
Measurement speed: 0.30 mm / s
Measurement location: needle roller center or leg shaft center Number of measurements: 2
Measuring device: Surface roughness measuring device Surfcom 1400A (Tokyo Seimitsu Co., Ltd.)

  In the tripod type constant velocity universal joint shown in FIG. 1, joints A and B (comparative example) in which the outer peripheral surface of the needle roller 6 or the leg shaft 5 is finished to a smooth surface, and the outer periphery of the needle roller 6 or the leg shaft 5 A life test conducted on joints C to E (comparative example) and F and G (examples) in which infinitely small indentations 8 are formed on the surface will be described (see Table 1). In any of the joints A to G used, the outer diameter of the needle roller 6 is 2 mm, and the outer diameter of the leg shaft 5 is 19 mm. In addition, the outer peripheral surface of the needle roller 6 or the leg shaft 5 in the joints A and B of the comparative example is ground and not hollowed. On the outer peripheral surface of the needle roller 6 or the leg shaft 5 in the joints C to E of the comparative example and the joints F and G of the examples, innumerable minute recesses 8 are randomly formed by barrel polishing special processing. In addition, about Rqni (L / C), the joints C to G are 1.0 or less, and the joints A and B are around 1.0.

  The life test was performed under the conditions of rotational torque: 834 [Nm], operating angle θ: 6 °, and rotational speed: 230 [rpm]. From Table 1, the joints F and G of the examples are the joints A to A of the comparative example. Compared to E, it was confirmed that the amount of wear was reduced.

［寿命判定基準］
○；異常無し、△；摩耗小（継続運転可）、×；摩耗大
［試験条件］
Ｔ＝８３４Ｎｍ、θ＝６°、回転数Ｎ＝２３０ｒｐｍ

[Life criteria]
○: No abnormality, △: Small wear (continuous operation possible), ×: Large wear [Test conditions]
T = 834 Nm, θ = 6 °, rotation speed N = 230 rpm

  Next, a second embodiment of the present invention will be described in detail with reference to FIGS. 3 (A) to 3 (D) and FIGS. 4 (A) and 4 (B). This embodiment is a double roller type tripod type constant velocity universal joint, wherein FIG. 3 (A) shows a transverse section of the joint, and FIG. 3 (B) shows a longitudinal section of the joint in a state where the operating angle θ is taken. 3 (C) shows a cross section perpendicular to the leg axis, and FIG. 3 (D) shows a cross section of the inner roller. In FIG. 3B, the symbol e represents the amount of eccentricity.

  As shown in FIGS. 3A to 3D, the roller cassette C is fitted to the leg shaft 22 of the tripod member 20 so as to swing freely. The roller cassette C is constituted by an assembly body including an inner roller 32, an outer roller 34, and needle rollers 36 interposed between the two rollers.

  Specifically, the outer joint member 10 has three track grooves 12 extending in the axial direction on the inner peripheral surface. Roller guide surfaces 14 are formed on the side walls of each track groove 12 facing each other in the circumferential direction. The tripod member 20 has three leg shafts 22 projecting in the radial direction, and a roller cassette C is attached to each leg shaft 22. The outer roller 34 of the roller cassette C is accommodated in the track groove 12 of the outer joint member 10. The outer peripheral surface of the outer roller 34 is a convex curved surface that matches the roller guide surface 14.

  The outer peripheral surface of the outer roller 34 is a convex curved surface with a circular arc having a center of curvature at a position away from the axis of the leg shaft 22 in the radial direction, and the roller guide surface 14 has a Gothic arch shape. As a result, the outer roller 34 and the roller guide surface 14 form an angular contact (see the one-dot chain line in FIG. 3A). Even if the cross-sectional shape of the roller guide surface 14 is tapered with respect to the spherical outer peripheral surface of the outer roller 34, angular contact between the two is realized.

  By adopting a configuration in which the outer roller 34 and the roller guide surface 14 form an angular contact in this way, the outer roller 34 is less likely to shake, and the posture is stabilized. In the case where the angular contact is not employed, for example, the roller guide surface 14 is configured by a part of a cylindrical surface whose axis is parallel to the axis of the outer joint member 10, and the cross-sectional shape thereof is a generatrix of the outer peripheral surface of the outer roller 34. It can also be a corresponding arc.

  An inner roller 32 is fitted on the outer peripheral surface of the leg shaft 22. The inner roller 32 and the outer roller 34 are unitized via a plurality of needle rollers 36 to constitute a roller cassette C that can rotate relative to each other. That is, the cylindrical outer peripheral surface of the inner roller 32 is used as an inner raceway surface, and the cylindrical inner peripheral surface of the outer roller 34 is used as an outer raceway surface.

  As shown in FIG. 3 (C), the needle roller 36 is incorporated in a so-called full roller state in which as many rollers as possible are inserted and there is no cage. Reference numerals 33 and 35 indicate a pair of washers attached to an annular groove formed on the inner peripheral surface of the outer roller 34 to prevent the needle rollers 36 from falling off. These washers 33 and 35 have a cut at one place in the circumferential direction, and are mounted in an annular groove on the inner peripheral surface of the outer roller 34 in a state of being elastically reduced in diameter.

  The outer peripheral surface of the leg shaft 22 has a straight shape parallel to the axis of the leg shaft 22 when viewed in a longitudinal section [FIG. 3A or FIG. 3B], and is viewed in a transverse section [FIG. 3C]. And the long axis is an elliptical shape perpendicular to the axis of the joint. The cross-sectional shape of the leg shaft 22 is substantially elliptical by reducing the wall thickness seen in the axial direction of the tripod member 20. In other words, the cross-sectional shape of the leg shaft 22 is such that the surfaces of the tripod member 20 facing each other in the axial direction are retracted in the mutual direction, that is, on the smaller diameter side than the virtual cylindrical surface.

  The inner peripheral surface of the inner roller 32 has an arcuate convex cross section as shown in FIG. That is, the generatrix of the inner peripheral surface is a convex arc with a radius r. Since the cross-sectional shape of the leg shaft 22 is substantially elliptical as described above and a predetermined clearance is provided between the leg shaft 22 and the inner roller 32, the inner roller 32 has a leg shaft. In addition to being able to move in the axial direction of 22, it can swing and swing with respect to the leg shaft 22.

  Further, as described above, the inner roller 32 and the outer roller 34 are unitized so as to be rotatable relative to each other via the needle rollers 36. Therefore, the inner roller 32 and the outer roller 34 swing as a unit with respect to the leg shaft 22. It is in a swingable relationship. Here, the swing means that the axes of the inner roller 32 and the outer roller 34 are inclined with respect to the axis of the leg shaft 22 in a plane including the axis of the leg shaft 22 (see FIG. 3B).

  In this double roller type tripod type constant velocity universal joint, the roller cassette C is swingable and swingable (the roller cassette C is tiltable and axially displaceable with respect to the leg shaft 22). When the rotational force is transmitted in a state where the tripod member 20 takes the operating angle, the outer roller 34 and the roller guide surface 14 can be prevented from being obliquely crossed, and the outer roller 34 is connected to the outer joint member 10. Are guided by the roller guide surface 14 of the outer joint member 10 so as to maintain a posture parallel to the axis of the roller, and roll on the roller guide surface 14 in the same posture. Therefore, the slip resistance during the operating angle operation is reduced, and the occurrence of slide resistance and induced thrust is suppressed.

  Further, the cross-sectional shape of the leg shaft 22 is in contact with the inner peripheral surface of the inner roller 32 in a direction orthogonal to the axis of the joint, and a gap is formed between the inner peripheral surface of the inner roller 32 in the axial direction of the joint. Therefore, the leg shaft 22 can be inclined with respect to the outer joint member 10 without changing the posture of the roller cassette C when the joint takes an operating angle. In addition, since the contact ellipse between the outer peripheral surface of the leg shaft 22 and the inner roller 32 approaches the point from the horizontally long, the frictional moment to tilt the roller cassette C is reduced. Accordingly, the posture of the roller cassette C is always stable, and the outer roller 34 is held in parallel with the roller guide surface 14, so that it can roll smoothly.

  Also in the double roller type tripod type constant velocity universal joint in the second embodiment, as in the first embodiment, as shown in FIGS. 4A and 4B, at least the needle roller 36 or the leg shaft 22 is provided. An infinite number of minute concave depressions 37 are randomly provided on the outer peripheral surface by barrel polishing or shots. Thereby, the lubricity between the inner roller 32 and the needle roller 36, between the needle roller 36 and the outer roller 34, or between the leg shaft 22 and the inner roller 32 is improved. The wear at the contact portion can be reduced, and the life of the tripod type constant velocity universal joint can be improved.

  The present invention is not limited to the first and second embodiments described above, and various modifications can be made based on the technical idea described in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS The tripod type constant velocity universal joint of 1st embodiment of this invention is shown, (A) is a cross-sectional view of a joint, (B) is a longitudinal cross-sectional view of the state which took the operating angle of the joint of (A) (C) is a typical perspective view which shows the mutual relationship of the roller and roller guide surface in (B). (A) is a front view which shows the tripod member of FIG. 1, (B) is a front view which shows the needle roller of FIG. The tripod type constant velocity universal joint of 2nd embodiment of this invention is shown, (A) is a cross-sectional view of a joint, (B) is a longitudinal cross-sectional view of the state which took the operating angle of the joint of (A) (C) is sectional drawing perpendicular | vertical to the leg axis | shaft of a roller cassette, (D) is sectional drawing of an inner side roller. (A) is a front view which shows the tripod member of FIG. 3, (B) is a front view which shows the needle roller of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer joint member 2 Track groove 3 Roller guide surface 4 Tripod member 5 Leg shaft 6 Needle roller 7 Roller 8 Micro concave recess 10 Outer joint member 12 Track groove 14 Roller guide surface 20 Tripod member 22 Leg shaft 32 Inner roller 34 Outer roller 36 Needle roller 37 Micro concave recess

Claims (5)

  Tripod member having three axial track grooves formed on the inner periphery, outer joint members having axial roller guide surfaces on both sides of each track groove, and three leg shafts projecting in the radial direction And a roller that is attached to each leg shaft of the tripod member and is rotatably supported via a plurality of needle rollers, and the roller is inserted along the roller guide surface. In the tripod type constant velocity universal joint movable in the axial direction of the outer joint member, an infinite number of minute concave recesses are randomly provided on the surface of the needle roller, and the surface roughness parameter Ryni of the surface provided with the recess is set. A tripod type constant velocity universal joint having a range of 0.4 μm ≦ Ryni ≦ 1.0 μm and a Sk value of −1.6 or less.   The roller is an outer roller that is rotatably supported via a plurality of needle rollers on an inner roller that is externally fitted to a leg shaft of the tripod member, and an assembly body is formed by the inner roller, the needle rollers, and the outer roller. The tripod type constant velocity universal joint of Claim 1 which comprises these.   Tripod member having three axial track grooves formed on the inner periphery, outer joint members having axial roller guide surfaces on both sides of each track groove, and three leg shafts projecting in the radial direction And a roller that is attached to each leg shaft of the tripod member and is rotatably supported via a plurality of needle rollers, and the roller is inserted along the roller guide surface. In the tripod type constant velocity universal joint that is movable in the axial direction of the outer joint member, an infinite number of minute concave recesses are randomly provided on the surface of the leg shaft, and the surface roughness parameter Ryni of the surface provided with the recess is 0. A tripod type constant velocity universal joint, characterized in that it is within the range of 4 μm ≦ Ryni ≦ 1.0 μm and the Sk value is −1.6 or less.   The tripod type constant velocity universal joint according to claim 1 or 2, wherein a surface roughness parameter Rymax of the surface provided with the depression is in a range of 0.4 to 1.0.   When the surface roughness of the surface provided with the depression is represented by the parameter Rqni, the ratio value Rqni (L) / Rqni (R) of the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C) The tripod type constant velocity universal joint according to claim 1 or 2, wherein C) is 1.0 or less.

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