JP2008064158A - Tripod type constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form uniform quench-hardened layers of a tripod with desired depth for a short time without generating an abnormal layer (internal oxidation layer). <P>SOLUTION: The quench-hardened layers H are formed in leg shaft outer peripheral surface layer parts and their root parts of the tripod 4 by induction hardening. In a type of a joint in which limited portions of leg shaft outer peripheral surface layer parts contact mating components, the quench-hardened layers H can be provided only in the contact portions and their peripheries. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tripod type constant velocity universal joint in which a hardened layer is formed by induction hardening on a leg shaft of the tripod.

  The tripod type constant velocity universal joint includes a hollow cylindrical housing as an outer joint member, a tripod as an inner joint member, and a roller as a torque transmission member as main components.

  The housing is composed of an integrally formed mouse portion and stem portion. The mouse portion has a cup shape opened at one end, and a track groove extending in the axial direction is formed at a position of the inner circumference in the circumferential direction. The mouse part has a non-cylindrical shape in which a large-diameter part and a small-diameter part appear alternately when viewed in cross section. That is, the mouth portion is formed with a large diameter portion and a small diameter portion, so that the three track grooves extending in the axial direction are formed on the inner peripheral surface thereof. Roller guide surfaces are formed on the side walls facing each other in the circumferential direction of each track groove. The stem portion is coupled to the first rotating shaft.

  The tripod includes a boss and a leg shaft. The boss is formed with a spline or serration hole that is coupled to the second rotating shaft so as to transmit torque. The leg shaft protrudes in the radial direction from the circumferentially divided position of the boss. Each leg shaft of the tripod supports the roller rotatably. The roller includes a double roller type having an inner roller and an outer roller and only a single roller type.

  As single roller type sliding type constant velocity universal joints, there are those described in Patent Document 1 (Japanese Patent Laid-Open No. Sho 62-233522) and those described in Patent Document 2 (Japanese Patent Laid-Open No. 2004-2575769). Are known. As a double roller type sliding type constant velocity universal joint, one described in Patent Document 3 (Japanese Patent Laid-Open No. 2000-320563) is known.

The tripods used in these sliding type constant velocity universal joints are heat-treated on the tripod surface layer for the purpose of preventing wear and fatigue damage of the outer peripheral contact portion of the leg shaft and ensuring torsional strength. This heat treatment method is generally a carburizing heat treatment method.
JP-A-62-233522 JP 2004-25769 A JP 2000-320563 A

  The reason for adopting the carburizing heat treatment method is to increase the toughness by first increasing the wear resistance and rolling fatigue life by hardening the surface layer and further lowering the internal hardness from the surface layer. It is because it can do. Secondly, when forging is formed in the initial manufacturing process like tripod, the tripod is made of low carbon steel (carburizing steel) with good workability in consideration of forgeability because the deformation from the material is relatively large. This is because it is preferable to use it. The carbon content of the carburizing steel is preferably in the range of 0.15 to 0.40 wt%.

However, on the other hand, carburizing heat treatment also has the following disadvantages.
1) The time required for carburizing treatment (including diffusion) is long.
2) There is a certain restriction on the depth of the hardened layer.
3) An abnormal layer (grain boundary oxide layer) may occur on the outermost surface.
4) There is a considerable variation in the depth of the hardened layer in each carburizing lot and within the same lot.

  1) and 2) are reflected in the manufacturing cycle time and hence the cost. Carburizing heat treatment takes longer time than induction hardening. In addition, when a relatively deep stress is applied to the inside, there is a limit to the fact that the cycle time is greatly increased even if the carburized layer depth is set to be large correspondingly.

  In addition, when an abnormal layer occurs as in 3), it may cause a reduction in the torsional strength of the tripod.

  4), depending on the carburizing furnace atmosphere (temperature, gas concentration, product position, etc.), there may be some variation in the carburized layer depth not only in each lot but also in the same lot.

  In view of such circumstances, the present invention intends to provide a constant velocity universal joint in which a hardened layer is provided at the outer peripheral surface portion of the leg shaft of the tripod and its root portion by induction hardening instead of the carburizing heat treatment method.

In the present invention, a hardened layer is provided by induction quenching on the outer peripheral surface portion of the leg shaft of the tripod and / or its root portion. According to this induction hardening,
1) A hardened layer can be formed in a short time.
2) Even a large hardened layer depth can be formed in a short time.
3) There is no possibility that an abnormal layer (grain boundary oxide layer) is generated on the outermost surface of the leg shaft.
4) The hardened layer depth can be easily made uniform by fixing the induction hardening conditions.

  In the tripod type constant velocity universal joint of the present invention, the hardened layer depth can be set larger than that of the carburizing heat treatment because the hardened layer is provided on the outer peripheral surface of the leg shaft and / or the base of the leg shaft by induction hardening. , The degree of design freedom increases. In addition, there is no fear of the occurrence of an abnormal layer (grain boundary oxide layer) that tends to occur during carburizing heat treatment in induction hardening. Furthermore, by subjecting the serration portion of the boss portion of the tripod to induction hardening as required, it is possible to improve wear resistance and secure strength of the serration portion.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show the first embodiment, FIGS. 3 and 4 show the second embodiment, and FIG. 5 shows the third embodiment.

  As shown in FIGS. 1A and 1B, the tripod type constant velocity universal joint includes a housing 1, a tripod 4, and a roller 7. That is, three cylindrical concave grooves or track grooves 2 are formed in the axial direction of the inner peripheral surface of the housing 1. A tripod 4 is inserted into the housing 1. A 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 4 via a plurality of needle rollers 6. Inserted into. 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 tripod type constant velocity universal joint, the drive shaft (first rotation shaft) is connected to the housing 1, and the driven shaft (second rotation shaft) is connected to the tripod 4.

  When the leg shaft 5 of the tripod 4 and the roller guide surface 3 of the housing 1 are engaged in the biaxial rotation direction via the roller 7, the rotational torque is transmitted from the drive side to the driven side at a constant speed. 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 housing 1 and the tripod 4 are absorbed.

  In the tripod type constant velocity universal joint of the present invention, a hardened layer is formed at a predetermined depth on the leg shaft 5 of the tripod 4 by induction hardening. FIG. 2A is a cross-sectional view of the tripod 4 (a surface perpendicular to the joint axis and including the leg axis center line), and the hatched portion is a hardened layer H formed by induction hardening. The outer peripheral portion of the leg shaft 5 is a portion where the needle roller 6 as a counterpart part rolls, and a hardened layer H is provided on the entire periphery of the leg shaft 5 as shown in FIGS. Further, since the base portion of the leg shaft 5 is a portion where tensile stress is concentrated when torque is applied to the joint, a hardened layer H having an appropriate depth is also formed here as shown in FIG. To do. The hardened layer H at the root portion may be limited to the tensile stress concentration portion at the time of torque load and its periphery as shown in FIG. The tensile stress concentration portions are on both sides in the circumferential direction of the joint among the root portions of the leg shaft 5.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 3 (A) and 3 (B) and FIGS. 4 (A) to (C '). This second embodiment relates to a tripod type constant velocity universal joint of double roller type (PTJ). 3A shows a cross section of the joint, and FIG. 3B shows a cross section perpendicular to the leg axis.

  In this double roller type tripod type constant velocity universal joint, as shown in FIGS. 3A and 3B, a roller cassette C is fitted to a leg shaft 22 of the tripod 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.

  The housing 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 20 has three leg shafts 22 protruding 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 housing 10. The outer peripheral surface of the outer roller 34 is a convex curved surface that matches the roller guide surface 14.

  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 (B), the needle rollers 36 are assembled 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 circumferential surface of the leg shaft 22 has a straight shape parallel to the axis of the leg shaft 22 as shown in FIG. 3A when viewed in a longitudinal section, and the long axis as shown in FIG. It has an elliptical shape orthogonal to the joint axis. The cross-sectional shape of the leg shaft 22 is substantially elliptical by reducing the thickness seen in the axial direction of the tripod 20. In other words, the cross-sectional shape of the leg shaft 22 is such that the surfaces facing each other in the axial direction of the tripod 20 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 22 in the axial direction, it is also swingable 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, swinging 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.

  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 with the operating angle 20 at an angle, the outer roller 34 and the roller guide surface 14 can be prevented from being obliquely crossed, and the outer roller 34 is parallel to the axis of the housing 10. It is guided by the roller guide surface 14 of the housing 10 so as to maintain the posture, and rolls 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.

4A is a cross-sectional view of the tripod 20. In this case as well, as shown in FIGS. 4B and 4C, the leg shaft 22 outer peripheral surface and the leg shaft root portion are formed as in the first embodiment described above. The hardened layer H is provided by induction hardening. In FIG. 4, the contact portion with the counterpart component (inner roller 32) is limited to a part of the leg shaft 22, and therefore intersects with the major axis of the elliptical cross section of the outer periphery of the leg shaft as shown in FIG. The hardened layer H may be provided selectively by induction hardening in and around the contact portion. Further, as shown in FIG. 4 (C '), the hardened layer H at the base portion of the leg shaft may be limited to the tensile stress concentration portion at the time of torque load and its periphery. The tensile stress concentration portions are on both sides in the circumferential direction of the joint in the root portion of the leg shaft 22.

  Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, not only the leg shafts 5 and 22 and the root shaft root portions but also the serration portion S surface layer formed on the inner diameter of the boss B of the tripods 4 and 20 for connection to the second rotating shaft is induction-hardened. Thus, the hardened layer H is provided at a predetermined depth. Thereby, the abrasion of the serration tooth and the improvement of the root strength can be achieved.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

1A and 1B show a first embodiment, where FIG. 1A is a transverse cross-sectional view of a tripod constant velocity universal joint, and FIG. 1B is a longitudinal cross-sectional view with an operating angle θ. (A) is a longitudinal sectional view of the tripod leg shaft, (B) is a transverse sectional view of the leg shaft, and (C) and (C ′) are transverse sectional views of the root portion of the leg shaft. The second embodiment is shown, in which (A) is a cross-sectional view of a tripod constant velocity universal joint, and (B) is a cross-sectional view of a roller cassette including a leg shaft. (A) is a longitudinal sectional view of a tripod leg shaft, (B) and (B ') are transverse sectional views of the leg shaft, and (C) and (C') are transverse sectional views of the root portion of the leg shaft. The longitudinal cross-sectional view of a tripod leg axis | shaft which shows 3rd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Track groove 3 Roller guide surface 4 Tripod 5 Leg shaft 7 Roller 10 Housing 12 Track groove 14 Roller guide surface 20 Tripod 22 Leg shaft 32 Inner roller 33, 35 Washer 34 Outer roller B Boss C Roller cassette H Hardened layer S Serration Part

Claims (5)

A hollow cylindrical housing that is fixed at the end of the first rotating shaft and that is formed at one end side in the axial direction and has a concave groove extending in the axial direction at a circumferentially equally divided position on the inner peripheral surface;
A tripod having a boss fixed to the end of the second rotation shaft and a leg shaft protruding in a radial direction from a circumferentially divided position of the boss;
In a tripod type constant velocity universal joint that is fitted to the outer peripheral surface of the leg shaft and is accommodated in a concave groove of the housing and is capable of rolling in the housing axial direction,
A tripod type constant velocity universal joint characterized in that a hardened layer is provided by induction hardening on a leg shaft outer peripheral surface portion of the tripod and its root portion. Three track grooves in the axial direction are formed in the inner peripheral portion, a housing having an axial roller guide surface on each side of each track groove, a tripod having three leg shafts protruding in the radial direction, A roller assembly mounted on each leg shaft of the tripod, the roller assembly swingably swingable with respect to the leg shaft, and parallel to the axis of the outer joint member along the roller guide surface A constant velocity universal joint including an outer roller guided by the inner roller, and the roller assembly includes an inner roller that is extrapolated to the leg shaft and rotatably supports the outer roller;
A tripod type constant velocity universal joint, wherein a hardened layer is provided by induction hardening on a leg shaft of the tripod and a base portion thereof.   The outer peripheral surface of the leg shaft has a straight shape in the vertical cross section, and in the horizontal cross section, the outer periphery of the leg shaft contacts the inner roller in a direction orthogonal to the joint axis, and the inner peripheral surface of the inner roller in the axial direction of the joint. The tripod type constant velocity universal joint according to claim 2, wherein a gap is formed therebetween.   The tripod type constant velocity universal joint according to any one of claims 1 to 3, wherein a hardened layer is provided by induction hardening limited to both sides of the joint in the circumferential direction of the root portion of the leg shaft.   The tripod type constant velocity universal joint according to any one of claims 1 to 4, wherein a hardened layer is provided by induction hardening in a serration portion formed on an inner diameter of the boss in order to fix the second rotating shaft. .

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