JP2016166659A - Constant velocity joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant velocity joint capable of suppressing the generation of large stress, in a contacting part between a rolling body and a side surface of a track groove.SOLUTION: A constant velocity joint is equipped with an outside joint member 10 performing thermal processing on side surfaces 16b and 16c of a track groove 16; an inside joint member 20 equipped with a plurality of leg shafts; and a rolling body 32 rolling on the side surfaces of the track groove. A rolling surface of the rolling body and at least one of the side surfaces of the track groove after the heat processing, are formed so as to have convex center portions, and the rolling surface and the side surfaces of the track groove after the heat processing are contacted at center portions a.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a slidable constant velocity joint that allows expansion and contraction in a rotation axis direction.

  Conventionally, there is a tripod type constant velocity joint as a sliding type constant velocity joint. The tripod type constant velocity joint has rolling element units supported by three leg shafts provided on the inner joint member (tripod), and the rolling elements are formed on the inner peripheral surface of the outer joint member (outer ring). The inner joint member can be moved in the rotation axis direction by rolling the side surface of the groove. In such a constant velocity joint, the outer joint member is heat-treated in order to ensure a certain level of hardness of the side surface of the raceway groove on which the rolling elements roll. However, due to this heat treatment, the outer joint member may be distorted into an unintended shape, and problems such as deterioration in performance and durability as a constant velocity joint may occur.

  For this countermeasure, for example, in the constant velocity joint described in Patent Document 1, the raceway groove that is curved in the axial direction of the outer joint member after the heat treatment is formed in a predetermined distorted shape before the heat treatment. Accordingly, it is described that the raceway groove is intentionally distorted by heat treatment to obtain a desired shape. Further, in the constant velocity joint described in Patent Document 2, the raceway groove that is curved in the axial direction of the outer joint member is positively quenched according to predetermined conditions. This describes that the raceway groove is intentionally distorted to obtain a desired shape. Patent Documents 3 and 4 also describe a constant velocity joint in which a rolling element as a needle circulates around the outer periphery of the inner member, and the rolling element rolls on the side surface of the raceway groove of the outer joint member.

JP 2005-180495 A JP-A-3-292418 Japanese Patent Laid-Open No. 3-144118 JP2011-58514A

  By the way, in the constant velocity joints described in Patent Documents 3 and 4, if the vicinity of the end of the rolling element, which is a needle, contacts the side surface of the raceway groove, the stress generated at the contact portion on the side surface of the raceway groove increases. Therefore, the shape of the side surface of the raceway groove is formed into a shape corresponding to the outer peripheral surface of the rolling element. However, since the outer joint member is subjected to heat treatment as described above, even if the shape before the heat treatment is formed into a desired shape, the above problem may occur depending on the shape after the heat treatment. Therefore, by increasing the thickness of the outer joint member, the outer joint member can withstand a large stress. Note that Patent Documents 1 and 2 do not describe any relationship between the shape of the side surface of the raceway groove and the rolling element.

  This invention is made | formed in view of the said situation, and it aims at providing the constant velocity joint which can suppress that big stress arises in the contact part of a rolling element and the side surface of a track groove. .

  In order to solve the above-described problem, the constant velocity joint according to claim 1 is an outer joint member that is formed in a cylindrical shape and has a plurality of raceway grooves formed on an inner peripheral surface, and heat treatment is performed on at least a side surface of the raceway groove. And an inner joint member having a plurality of leg shafts projecting radially outward, a rolling element interposed between the outer peripheral surface of the leg shaft and the side surface of the raceway groove, and rolling on the side surface of the raceway groove, And at least one of the rolling surface of the rolling element and the side surface of the raceway groove after heat treatment is formed in a convex shape at the center in the groove depth direction of the raceway groove, The rolling surface and the side surface of the raceway groove after the heat treatment are in contact with each other at the central portion.

  Thereby, after heat processing of a raceway groove, the rolling surface of a rolling element and the side surface of a raceway groove contact in the center part of the groove depth direction of a raceway groove. For this reason, the rolling surface of the rolling element and the side surface of the raceway groove do not contact at both ends of the rolling element. That is, it is possible to suppress a large stress from being generated at the contact portion between the rolling surface of the rolling element and the side surface of the raceway groove. Therefore, there is no possibility that the durability of the rolling elements and the raceway grooves is lowered. At this time, before the heat treatment, the convex shape may be formed slightly larger than the convex shape after the heat treatment in consideration of distortion caused by the heat treatment. That is, the convex shape may be formed in a direction opposite to the direction of deformation in the heat treatment and slightly larger than the amount deformed by the heat treatment. This convex shape can be easily manufactured by a mold. For this reason, no extra cost is incurred and it is possible to cope with a low cost.

  In order to solve the above-mentioned problem, the constant velocity joint according to claim 3 is an outer joint member which is formed in a cylindrical shape and has a plurality of raceway grooves formed on the inner peripheral surface, and at least a side surface of the raceway groove is subjected to heat treatment. An inner joint member having a plurality of leg shafts projecting radially outward, and a rolling element that is interposed between the outer peripheral surface of the leg shaft and the side surface of the raceway groove and rolls on the side surface of the raceway groove. And the side surface of the raceway groove before heat treatment is formed in a convex shape at the center in the groove depth direction of the raceway groove, the rolling surface of the rolling element and the raceway groove after the heat treatment The side surface is formed in a convex shape at the center in the groove depth direction of the track groove, or is formed in parallel with the groove depth direction of the track groove.

  As a result, the raceway groove formed in a convex shape in the central portion of the side surface before the heat treatment of the raceway groove, the rolling surface of the rolling element formed in the convex shape in the central portion after the heat treatment, and the groove depth of the raceway groove. Contact at the center in the vertical direction. Alternatively, both the side surfaces of the raceway grooves formed in parallel to the groove depth direction of the raceway grooves and the rolling surfaces of the rolling elements are in contact with each other. For this reason, the rolling surface of the rolling element and the side surface of the raceway groove do not contact at both ends of the rolling element. That is, it is possible to suppress a large stress from being generated at the contact portion between the rolling surface of the rolling element and the side surface of the raceway groove. Therefore, there is no possibility that the durability of the rolling elements and the raceway grooves is lowered. Before the heat treatment, the convex shape may be formed slightly larger than the convex shape or the plane after the heat treatment in consideration of the strain due to the heat treatment. This convex shape is a shape that can be easily manufactured by a mold. For this reason, no extra cost is incurred and it is possible to cope with a low cost.

It is a perspective view of a constant velocity joint, and is a perspective view of the state where the outside joint member was cut in the axial direction. It is sectional drawing orthogonal to a rotating shaft line in the state whose joint angle of a shaft is 0 deg. It is an enlarged view of the B section of FIG. It is a top view of a rolling element unit. It is a top view of an inner member. FIG. 6 is an enlarged cross-sectional view taken along arrow 6-6 in FIG. 5. It is a top view of a holder | retainer. It is a figure explaining the contact surface pressure when the rolling surface of a rolling element and the side surface of a raceway groove contact | abut on surfaces parallel to the groove depth direction of a raceway groove. When the rolling surface of the rolling element is parallel to the groove depth direction of the raceway groove and the side surface of the raceway groove is concave with respect to the groove depth direction of the raceway groove, the rolling surface and the raceway It is a figure explaining the contact surface pressure with the side surface of a groove | channel. When the rolling surface of the rolling element is a surface parallel to the groove depth direction of the raceway groove and the side surface of the raceway groove has a convex shape with respect to the groove depth direction of the raceway groove, the rolling surface and the raceway It is a figure explaining the contact surface pressure with the side surface of a groove | channel. It is a figure explaining the modification 1. FIG. It is a figure explaining the modification 2. FIG.

(1. Overview)
Hereinafter, an embodiment embodying a tripod type constant velocity joint (hereinafter simply referred to as “constant velocity joint”) which is an example of the constant velocity joint of the present invention will be described with reference to FIGS. Here, the case where the constant velocity joint 1 of this embodiment is used for connection of a power transmission shaft of a vehicle will be described as an example. The case is, for example, a case where the shaft portion connected to the differential gear is used as a connecting portion between the intermediate shaft of the drive shaft.

(2. Configuration of constant velocity joint 1)
As shown in FIGS. 1 and 2, the constant velocity joint 1 includes an outer joint member 10, an inner joint member 20, and a rolling element unit 30. FIG. 1 shows a state in which the rotation axis of the shaft 2 drawn by a two-dot chain line is tilted by a predetermined joint angle θ with respect to the rotation axis of the outer joint member 10. 2 shows an outer joint member cut at a plane orthogonal to the rotational axis of the outer joint member 10 and passing through the axis of the leg shaft 22 of the inner joint member 20 described later when the joint angle θ is 0 deg. 10 shows a part of a cross section as viewed from the opening side of 10. In the following description, the term “rotation axis” refers to the rotation axis of the outer joint member 10 without special notice.

  The outer joint member 10 is formed in a bottomed cylindrical shape, and in FIG. 1, the A side (bottom side) of the outer joint member 10 is connected to a differential gear (not shown). On the inner peripheral surface of the cylindrical portion of the outer joint member 10, three (corresponding to a plurality) track grooves 16 extending in the rotation axis direction of the outer joint member 10 are formed at equal intervals in the circumferential direction (note that it corresponds to a plurality of tracks). In FIG. 1, only two are shown, and the other is omitted). In the present embodiment, the outer shape of the outer joint member 10 is as shown in FIGS. In other words, the outer circumferential thickness of the raceway groove 16 is made substantially uniform.

  The cross-sectional shape of each raceway groove 16 that is orthogonal to the direction of the rotational axis is as shown in FIG. 2, and generally has a U shape that opens toward the center of the rotational axis of the outer joint member 10. As shown in FIG. 2, the bottom surface 16a of each raceway groove 16 is formed in a substantially planar shape. As shown in FIGS. 2 and 3, side surfaces 16b and 16c (corresponding to one surface of the present invention) orthogonal to the bottom surface 16a are opposed to the central portion a in the groove depth direction of the raceway groove 16. The projections are formed so as to protrude toward the side surfaces 16c and 16b. Here, the central portion a in the groove depth direction of the raceway groove 16 of the side surfaces 16b, 16c orthogonal to the bottom surface 16a is orthogonal to the rotation axis and in a direction orthogonal to the planar bottom surface 16a. The center part of the side surfaces 16b and 16c is shown. In addition, the side surfaces 16b and 16c at this time are side surfaces after heat treatment (described in detail later).

  As shown in FIG. 1, the inner joint member 20 is disposed inside the outer joint member 10. The inner joint member 20 can move with respect to the outer joint member 10 in the direction of the rotation axis and can tilt. Further, the inner joint member 20 is integrally connected to the shaft 2. The inner joint member 20 includes a cylindrical boss portion 21 connected to the shaft 2 and three (corresponding to a plurality) leg shafts 22.

  The three leg shafts 22 protrude from the cylindrical outer peripheral surface of the boss portion 21 outward in the radial direction of the boss portion 21 (only one leg shaft 22 is shown in FIG. 2). These leg shafts 22 are formed at equal intervals (120 deg intervals) in the circumferential direction of the boss portion 21. Each leg shaft 22 includes a spherical convex portion 22a having an outer peripheral surface formed into a spherical convex shape, and a root neck portion 22b formed on the boss portion 21 side of the spherical convex portion 22a. And the front-end | tip part of the spherical convex part 22a of the leg axis | shaft 22 is inserted in each track groove 16 of the outer joint member 10. FIG.

  The three rolling element units 30 shown in FIG. 1 are supported on the outer peripheral surface of each leg shaft 22, inserted into the raceway groove 16 from the opening of each raceway groove 16, and roll on the side surfaces 16 b and 16 c of the raceway groove 16. . As shown in FIG. 4, the rolling element unit 30 has a rectangular ring shape as a whole. Each rolling element unit 30 is rotatable around the axis of each leg shaft 22, is movable in the axial direction of each leg shaft 22, and is supported so as to be tiltable with respect to the axis of each leg shaft 22. Each rolling element unit 30 is engaged with the leg shaft 22 in the rotation direction of the constant velocity joint 1. In this way, each rolling element unit 30 transmits a rotational driving force between each leg shaft 22 and the outer joint member 10.

  As shown in FIGS. 2, 3, and 4, the rolling element unit 30 includes a plurality of rolling elements 32 that roll on the raceway groove 16, and an inner member 31 that is interposed between the rolling elements 32 and the leg shaft 22. Two retainers 33 and 33 and two retaining rings 34 and 34 are provided (see FIGS. 2 and 4). The rolling element 32 is interposed between the inner member 31 disposed on the outer peripheral surface of the leg shaft 22 and the side surfaces 16 b and 16 c of the raceway groove 16, and rolls on the side surfaces 16 b and 16 c of the raceway groove 16. In the present embodiment, the rolling element 32 is an axial rolling element.

  As shown in FIGS. 2 and 5, the outer shape of the inner member 31 is formed in a rectangular parallelepiped shape. The inner member 31 is formed in an annular shape with a through hole 31g penetrating between both end faces 31a and 31b. The material of the inner member 31 is formed by cold forging, for example. The inner member 31 is formed by processing only the necessary portions of the material of the inner member 31.

  Specifically, the inner member 31 has both end surfaces 31a and 31b, side surfaces 31c to 31f, and a through hole 31g. Both end surfaces 31 a and 31 b are a pair of planes facing away from each other in the axial direction of the leg shaft 22 in a state where the inner member 31 is assembled to the leg shaft 22. Moreover, two pairs of planes facing away are formed by the side surfaces 31c to 31f.

  Adjacent side surfaces of the side surfaces 31c to 31f of the inner member 31 are connected to each other with an R of an arbitrary size. As shown in FIGS. 2 and 5, the through hole 31g is provided in the central portion of the both end surfaces 31a and 31b so as to penetrate between the both end surfaces 31a and 31b. The spherical convex portion 22a of the leg shaft 22 is inserted into the through hole 31g. Thereby, the axis of the through hole 31 g of the inner member 31 can be tilted with respect to the axis of the leg shaft 22. At this time, the tapered surfaces 31h and 31i are provided so that the leg shaft 22 or the boss portion 21 does not come into contact with the inner member 31 when each of the leg shafts 22 tilts by a predetermined joint angle θ with respect to the inner member 31. It is done. The tapered surfaces 31h and 31i may be arbitrarily set so that interference between the leg shaft 22 or the boss portion 21 and the inner member 31 can be prevented. In the following, when there is no special description and only the axis of the inner member 31 is used, it means the axis of the through hole 31g of the inner member 31.

  As shown in FIG. 5, the inner member 31 includes a fitted portion 35 having a non-cylindrical outer peripheral surface, and an arc groove 36 into which the retaining ring 34 is fitted. The fitted portion 35 has an inner member arc portion 35a and a flat portion 35b.

  The inner member arc portion 35 a is an arc surface formed around the axis of the through hole 31 g of the inner member 31. In other words, the inner member arc portion 35a is an outer peripheral surface having a predetermined diameter φD1 around the axis of the through hole 31g and a predetermined depth d1 from both end surfaces 31a and 31b (see FIG. 6 and cross-sectional view). ).

  The flat part 35b shown in FIG. 5 is a site | part latched in the circumferential direction with respect to the flat part 37b of the fitting part 37 of the holder | retainer 33 mentioned later among the to-be-fitted parts 35 of the inner member 31. FIG. The flat portion 35b is provided on a different plane from the side surfaces 31c and 31d of the inner member 31. The inner member 31 has a planar rolling surface 38 for rolling the rolling elements 32 on the same surface as the side surfaces 31c and 31d.

  The arc groove 36 is a groove having a predetermined depth that is formed coaxially with the outer peripheral surface 35c from the arc-shaped outer peripheral surface 35c toward the inner side in the radial direction of the outer peripheral surface 35c (see FIGS. 5 and 6). The arc center of the arc groove 36 coincides with the axis of the through hole 31 g of the inner member 31. As shown in FIG. 6, the outer peripheral surface 35c is an outer peripheral surface formed from the both end surfaces 31a and 31b to a predetermined depth d2. The outer peripheral surface 35c is formed to have a predetermined diameter φD2 around the axis of the through hole 31g.

  In the present embodiment, the relationship between the diameter φD2 of the outer peripheral surface 35c provided with the arc groove 36 and the diameter φD1 of the inner member arc portion 35a is φD1> φD2. However, it is not limited to this aspect, and φD1 = φD2 may be used.

  As shown in FIG. 7, the cage 33 is formed in a substantially square shape by a plate-like member made of, for example, an iron-based metal. The retainer 33 is formed in an annular shape having a space on the inner peripheral side. The plate-like member is, for example, SPCC (JIS G 3141) which is a cold rolled steel plate. The cage 33 is formed by press molding a plate-like member. A pair of cages 33 are provided on both end surfaces 31 a and 31 b side of the inner member 31. The square corners of the cage 33 in plan view shown in FIG. The predetermined R may be set arbitrarily. The cage 33 includes a fitting portion 37 and a rolling element holding portion 42.

  The fitting part 37 is a part fitted to the fitted part 35 of the inner member 31. As shown in FIG. 7, the fitting portion 37 is provided on the non-cylindrical inner peripheral surface of the cage 33. The fitting portion 37 has two cage arc portions 37a and two flat portions 37b.

  The cage arc portion 37 a is an arc surface that fits into the four inner member arc portions 35 a of the fitted portion 35 of the inner member 31. The two plane portions 37b are planes that are respectively fitted to the two plane portions 35b of the fitted portion 35 of the inner member 31 and locked in the circumferential direction. That is, when the retainer 33 is about to rotate relative to the inner member 31, the two flat portions 35 b of the inner member 31 relatively lock the two flat portions 37 b of the retainer 33 in the circumferential direction. Thus, the relative rotation is prohibited.

  As shown in FIG. 3, the rolling element holding part 42 includes an axial direction movement restriction part 43 and a radial direction movement restriction part 44. The axial movement restricting portion 43 is formed to extend from the fitting portion 37 toward the radially outer side of the inner member 31. The axial movement restricting portion 43 includes an axial restricting surface 43a on the rolling element 32 side. As shown in FIG. 3, the axial restriction surface 43 a abuts on the end surface of the protrusion 41 (end portion) of the rolling element 32 and restricts the movement of the rolling element 32 in the axial direction.

  The radial direction movement restricting portion 44 is formed by bending a portion on the outer peripheral side with respect to the axial direction movement restricting portion 43 toward the rolling element 32, for example, at a right angle. The radial movement restricting portion 44 includes a radial restricting surface 44 a on the protrusion 41 side of the rolling element 32. As shown in FIG. 3, the radial restriction surface 44 a abuts against the side surface of the protrusion 41 of the rolling element 32 and restricts the movement of the rolling element 32 to the outside of the inner member 31. As described above, the rolling element holding part 42 is provided so as to cover the protrusion 41 of the rolling element 32, that is, to cover the axis of the rolling element 32, in the entire outer periphery of the cage 33.

  As shown in FIGS. 1 and 4, the plurality of rolling elements 32 are provided so as to circulate around the outer periphery of the inner member 31. Specifically, the plurality of rolling elements 32 are supported by the rolling element holding portions 42 of the retainers 33 and 33 provided on the side of both end faces 31 a and 31 b in the axial direction of the inner member 31. Is done. That is, the protrusions 41 and 41 at both ends of the rolling element 32 are supported by the axial restriction surfaces 43a and 43a and the radial restriction surfaces 44a and 44a of the cages 33 and 33 so as to be able to roll.

  As shown in FIGS. 2 and 3, the rolling element 32 includes a cylindrical portion 39 and a protruding portion 41 that is formed coaxially with the central axis of the cylindrical portion 39. As described above, the rolling element 32 is an axial rolling element (needle). The protrusion 41 protrudes from both ends of the cylindrical portion 39. The cylindrical portion 39 is formed in a cylindrical shape, that is, the rolling surface 32 a of the rolling element 32, which is the outer peripheral surface, is formed in parallel to the groove depth direction of the raceway groove 16, and the cylindrical diameter of the cylindrical portion 39 is the protrusion 41. It is formed to be larger than the cylinder diameter.

  A part of the plurality of rolling elements 32 (in the present embodiment, a total of 6 to 7) is disposed between the side surfaces 16b and 16c of the raceway groove 16 and the side surfaces 31c and 31d of the inner member 31, respectively. It arrange | positions so that rolling is possible along the side surfaces 16b, 16c, 31c, and 31d. By being arranged in this way, the rotational driving force is transmitted via the rolling elements 32 between the side surfaces 31 c and 31 d of the inner member 31 and the side surfaces 16 b and 16 c of the raceway groove 16.

  The retaining rings 34, 34 are C-shaped retaining rings having a cylindrical inner peripheral surface, and are fitted into the arc grooves 36, 36 (see FIG. 4). This prevents the retainers 33, 33 from coming off in the axial direction.

(3. Relationship between rolling element 32 and raceway groove 16)
Here, the relationship between the rolling elements 32 and the raceway grooves 16 will be described. In the assembled state shown in FIG. 2, the ideal state of the contact surface pressure characteristics between the rolling surface 32a of the rolling element 32 and the side surfaces 16b and 16c of the raceway groove 16 is as shown in the graph shown on the left side of FIG. . The graph of FIG. 8 shows the contact surface pressure on the horizontal axis and the distance (position) in the axial direction of the rolling element 32 on the vertical axis. The contact surface pressure characteristic in this ideal state is such that the rolling surface 32a and the side surface 16b (16c) of the raceway groove 16 are flat surfaces (parallel to the groove depth direction of the raceway groove 16) as shown on the right side of FIG. ) It is the characteristic in the state which is contacting each other. However, in reality, it is difficult to establish such a state.

  The contact surface pressure characteristic which is not preferable as opposed to the ideal state is a characteristic indicated by a solid line in the left graph of FIG. 9. In addition, the dashed-two dotted line in a graph describes the characteristic of the graph of FIG. 8 as reference so that it may be easily compared with the solid line of the graph of FIG. The characteristic of the graph of FIG. 9 is that the rolling contact surface 32a of the rolling element 32 has a concave state (concave shape) as shown on the right side of FIG. It is a contact surface pressure characteristic when the rolling surface 32a of the moving body 32 abuts. In this case, the contact surface pressure peaks at both ends b and c in the axial direction of the rolling surface 32a, and the central portion a of the rolling surface 32a (the central portion of the rolling surface 32a in the groove depth direction of the raceway groove 16). Then, it will drop significantly. In this state, durability of both the rolling element 32 and the side surface 16b (16c) of the raceway groove 16 is lowered.

  As described above, the side surfaces 16b and 16c in the concave state (concave shape) that cause a decrease in durability are heat treatment necessary for manufacturing the outer joint member 10 with respect to the side surfaces 16b and 16c that are in a planar state before the heat treatment. As a result, the side surfaces 16b and 16c may be distorted. Therefore, in the present embodiment, the side surface 16b, 16c of the raceway groove 16 and the rolling surface 32a of the rolling element 32 have a groove depth of the raceway groove 16 so that at least the undesirable contact pressure characteristics shown in FIG. It is made to contact in the center part a of a direction.

  For this reason, as described above, in the present embodiment, the central portion a of the side surfaces 16b, 16c (corresponding to one surface) of the raceway groove 16 after the heat treatment in the groove depth direction of the raceway groove 16 is formed in a convex shape. Form. Further, the rolling surface 32 a (the other surface) of the rolling element 32 is formed in parallel to the groove depth direction of the raceway groove 16. Thereby, the rolling surface 32a of the rolling element 32 and the side surfaces 16b and 16c of the raceway groove 16 after the heat treatment are surely brought into contact with each other at the central portion a in the groove depth direction of the raceway groove 16. In the above, induction hardening can be illustrated as an example of heat treatment. In the following description, the central portion a of one and the other surface of the raceway groove 16 in the groove depth direction will be referred to as only “central portion a”, and the side surface parallel to the groove depth direction will be referred to as “parallel”. In some cases, it will be described simply as “.

  In the present invention, in order to obtain the convex shape of the side surfaces 16b and 16c of the raceway groove 16 described above, the shape of the raceway groove 16 of the outer joint member 10 before the heat treatment is set to a predetermined shape. That is, before the heat treatment, the side surfaces 16b and 16c are formed in a predetermined shape in consideration of distortion generated by the heat treatment. As described above, according to the experiment conducted by the inventor, in the outer joint member 10 of the present embodiment, the side surfaces 16b and 16c, which were in a flat state before the heat treatment, are in a concave state (the center portion is rolled) after the heat treatment. It is known that the moving body 32 is separated from the rolling surface 32a. Therefore, the predetermined shape of the side surfaces 16b and 16c before the heat treatment is compared with the convex shape Af at the central portion a of the side surfaces 16b and 16c of the raceway groove 16 required after the heat treatment, as shown by the broken lines in FIGS. Thus, the protruding shape Be is more protruded. The amount of protrusion at this time is determined by actually heat-treating the outer joint member 10 and evaluating it.

  In the above description, the convex shape Be can be easily handled by changing the punch shape when the raceway groove 16 of the outer joint member 10 is manufactured. For this reason, it is possible to cope with a low cost and, as in the prior art, a detailed depth of quenching with respect to the raceway groove surface is applied in order to intentionally apply an external force to the outer joint member before heat treatment, or to control the raceway groove distortion. There is no need to control under different conditions, and it can be handled at low cost.

(4. Measurement result of surface pressure)
The side surfaces 16b and 16c after the outer joint member 10 having the convex shape Be described above is heat-treated, that is, the rolling surfaces 32a of the rolling elements 32 parallel to the side surfaces 16b and 16c having the convex shape Af; The result of measuring the contact surface pressure is shown by a solid line in the left graph of FIG. The two-dot chain line in the graph describes the characteristics of the graphs of FIGS. 8 and 9 as a reference so that it can be easily compared with the solid line of the graph of FIG. According to the contact surface pressure characteristics shown in the graph of FIG. 10, no extreme surface pressure is generated at both ends b and c of the rolling element 32 as shown in the graph of FIG. 9. Thereby, durability of each side surface 16b, 16c of the rolling element 32 and the raceway groove | channel 16 does not fall, and becomes favorable. In this way, in the same process as the normal process for manufacturing the outer joint member 10, only the shape of the punch that forms the side surfaces 16b and 16c of the raceway groove 16 is changed, and the side surfaces 16b and 16c can be reliably rotated. The contact surface pressure with the rolling surface 32a of the moving body 32 could be made favorable.

(5. Effect by embodiment)
According to the above-described embodiment, the constant velocity joint 1 is formed in a cylindrical shape, and three (plural) raceway grooves 16 are formed on the inner peripheral surface, and at least the side surfaces 16b and 16c of the raceway groove 16 are subjected to heat treatment. The outer joint member 10, the inner joint member 20 having three (a plurality) leg shafts 22 projecting radially outward, and the outer peripheral surface of the leg shaft 22 and the side surfaces 16 b and 16 c of the raceway groove 16. A rolling element 32 that interposes and rolls on the side surfaces 16b and 16c of the raceway groove 16. Then, the side surfaces 16b and 16c (corresponding to at least one) of the raceway groove 16 after the heat treatment are formed in a convex shape at the central portion a in the groove depth direction of the raceway groove 16, and the rolling surface 32a of the rolling element 32 is It is formed parallel to the groove depth direction of the raceway groove 16, and the rolling surface 32a of the rolling element 32 and the side surfaces 16b, 16c of the raceway groove 16 after heat treatment are in contact with each other at the central portion a.

  Thereby, after the heat treatment of the outer joint member 10 (track groove 16), the rolling surface 32a of the rolling element 32 and the side surfaces 16b, 16c of the track groove 16 are in the central portion a of the track groove 16 in the groove depth direction. Contact. For this reason, the rolling surface 32 a of the rolling element 32 and the side surfaces 16 b and 16 c of the raceway groove 16 do not contact at both ends of the rolling element 32. That is, it is possible to suppress a large stress from being generated at the contact portion between the rolling surface 32 a of the rolling element 32 and the side surfaces 16 b and 16 c of the raceway groove 16. Therefore, there is no possibility that the surface pressure of the rolling surface 32a of the rolling element 32 and the side surfaces 16b and 16c of the raceway groove 16 increases due to the contact between both, and the durability of the rolling body 32 and the raceway groove 16 is not lowered. At this time, before the heat treatment, in consideration of distortion due to the heat treatment, the convex shape Be may be formed so as to protrude slightly larger than the convex shape Af after the heat treatment. That is, the convex shape may be formed in a direction opposite to the direction of deformation in the heat treatment and slightly larger than the amount deformed by the heat treatment. This convex shape Be can be easily manufactured by a mold (punch). For this reason, no extra cost is incurred and it is possible to cope with a low cost.

  Moreover, according to the said embodiment, the side surfaces 16b and 16c of the track groove 16 before heat processing are formed in convex shape Be. Thereby, a convex shape or a parallel shape can be reliably formed on the side surfaces 16b and 16c after the heat treatment.

  In addition, according to the above embodiment, the constant velocity joint 1 is formed in a cylindrical shape, a plurality of raceway grooves 16 are formed on the inner circumferential surface, and the side surfaces 16b and 16c of the raceway groove 16 are subjected to heat treatment. Interposed between the member 10, the inner joint member 20 having three (plural) leg shafts 22 projecting radially outward, and the outer peripheral surface of the leg shaft 22 and the side surfaces 16 b and 16 c of the raceway groove 16, Rolling elements 32 that roll on the side surfaces 16b and 16c of the raceway groove 16. The side surfaces 16b and 16c of the raceway groove 16 before the heat treatment are formed such that the central portion a in the groove depth direction of the raceway groove 16 has a convex shape, and the rolling surface of the rolling element 32 and the side surface of the raceway groove 16 after the heat treatment are formed. The central portions a in the groove depth direction of the raceway grooves 16 are convex or formed parallel to the depth direction of the raceway grooves 16.

  Thereby, the raceway groove 16 in which the central portion of the side surfaces 16b and 16c is formed in a convex shape before the heat treatment of the raceway groove 16, the rolling surface of the rolling element 32 in which the central portion a is formed in a convex shape after the heat treatment. 32a contacts with the central portion a of the raceway groove 16 in the groove depth direction. Alternatively, the side surfaces 16b and 16c of the raceway groove 16 formed in parallel with the groove depth direction of the raceway groove 16 and the rolling surface 32a of the rolling element 32 are in contact with each other. For this reason, the rolling surface 32 a of the rolling element 32 and the side surfaces 16 b and 16 c of the raceway groove 16 do not contact at both ends of the rolling surface 32 a of the rolling element 32. That is, it is possible to suppress a large stress from being generated at the contact portion between the rolling surface 32 a of the rolling element 32 and the side surfaces 16 b and 16 c of the raceway groove 16. Therefore, there is no possibility that the durability of the rolling elements 32 and the side surfaces 16b and 16c of the raceway groove 16 is lowered. Before the heat treatment, in consideration of distortion due to the heat treatment, the convex shape may be formed slightly larger than the convex shape or plane after the heat treatment. This convex shape is a shape that can be easily manufactured by a mold. For this reason, no extra cost is incurred and it is possible to cope with a low cost.

  Moreover, according to the said embodiment, the side surfaces 16b and 16c of the track groove 16 after heat processing are formed in convex shape, and the rolling surface 32a of the rolling element 32 is formed in parallel. Thereby, the rolling surface 32a of the rolling element 32 and the side surfaces 16b, 16c of the raceway groove 16 of the raceway groove 16 are in contact with each other at the center portion of the raceway groove 16 in the groove depth direction. For this reason, the rolling surface 32a of the rolling element 32 and the side surfaces 16b and 16c of the raceway groove 16 do not contact at both ends of the rolling element 32, and the same effect as described above can be obtained.

  Moreover, according to the said embodiment, the rolling element 32 is a needle, and the outer peripheral surface of a needle contacts the side surfaces 16b and 16c of the track groove 16, and rolls. Thus, the present invention can be applied to a rolling element circulation type constant velocity joint having a plurality of rolling elements 32.

  In addition, it is not restricted to the aspect of the said embodiment, the side surfaces 16b and 16c of the track groove 16 are made into one surface, the center part a of the side surfaces 16b and 16c is made into convex shape, and the other surface is the rolling surface 32a of the rolling element 32. The center part of the rolling surface 32a may be formed in a convex shape. Further, the side surfaces 16b and 16c may be parallel side surfaces, and the central portion a of the rolling surface 32a (one surface) of the rolling element 32 may be formed in a convex shape. Furthermore, the side surfaces 16b and 16c and the rolling surface 32a of the rolling element 32 may be formed on parallel side surfaces. Also by these, the same effect as the above-mentioned embodiment is acquired.

  In the above embodiment, the rolling surfaces 32a of the rolling elements 32 and the side surfaces 16b and 16c of the raceway groove 16 after the heat treatment are in contact with the side surfaces 16b and 16c of the raceway groove 16 so that they contact each other at the center of the center portion a. The surface shape was formed into a convex shape Af. That is, the description has been made on the assumption that the distortion of the side surfaces 16b and 16c of the raceway groove 16 after the heat treatment protrudes so that the center of the central portion a becomes the apex. However, actually, the way of distortion varies depending on the outer peripheral shape and the like of the outer joint member 10. Therefore, after the heat treatment of the outer joint member 10, the groove bottom (bottom surface 16 a) side of the raceway groove 16 is distorted such that the amount of heat shrinkage with respect to the state before the heat treatment is larger than the opening side of the raceway groove 16. In this case, as a first modification, the convex shapes of the side surfaces 16b and 16c of the raceway groove 16 before the heat treatment may be formed closer to the opening side in the central portion a (see FIG. 11). In addition, after the heat treatment of the outer joint member 10, when the opening side of the raceway groove 16 has a larger amount of heat shrinkage than the groove bottom (bottom surface 16a) side of the raceway groove 16 with respect to the state before the heat treatment, the modified example 2, the convex shape of the side surfaces 16b and 16c of the raceway groove 16 before the heat treatment may be formed closer to the groove bottom (bottom surface 16a) side in the central portion a (see FIG. 12). As a result, the same effect as in the above embodiment can be obtained. In FIG. 11 and FIG. 12, a convex shape Be (broken line) before heat treatment is described for reference.

  Moreover, in the said embodiment, the induction hardening which is heat processing was demonstrated as what is given to the outer side joint member 10 whole. However, the heat treatment may be performed only on the side surfaces 16b and 16c of the raceway groove 16 without being limited to this mode. Further, the heat treatment is not limited to induction hardening, and any heat treatment may be used. The same effect can be obtained by these.

  Moreover, in the said embodiment, it was set as the structure which forms the inner member 31 with one member. However, it is not limited to this aspect. The inner member may be a split type member that splits right and left. Also by this, the same effect as the above embodiment can be obtained.

  In the above embodiment, the constant velocity joint 1 is a circulation type constant velocity joint that includes the rolling element unit 30 and in which the plurality of rolling elements 32 of the rolling element unit 30 circulate around the outer periphery of the side surface of the inner member 31. Explained as a thing. However, it is not limited to this aspect. If the outer joint member 10 has a raceway groove on the inner peripheral surface and the rolling element having an outer peripheral surface formed parallel to the groove depth direction of the raceway groove is a slide type constant velocity joint that rolls on the raceway groove The present invention may be applied to any constant velocity joint. The present invention may also be applied to a constant velocity joint of a type in which a rolling element that rolls on the raceway groove is a roller, and an outer peripheral surface of the roller is formed in parallel with the groove depth direction of the raceway groove. Also by these, the same effect as the above-mentioned embodiment is acquired.

DESCRIPTION OF SYMBOLS 1 ... Constant velocity joint, 2 ... Shaft, 10 ... Outer joint member, 16 ... Track groove, 16a ... Groove side (bottom surface), 16b, 16c ... Side, 16b, 16c 1c, 31d ... each side surface, 20 ... inner joint member, 22 ... leg shaft, 31 ... inner member, 32 ... rolling element, 32a ... rolling surface, a ... -Central part, Af ... convex shape, Be ... convex shape.

Claims (7)

A plurality of raceway grooves formed on the inner peripheral surface of the inner circumference surface, and an outer joint member that is heat-treated at least on the side surfaces of the raceway grooves;
An inner joint member comprising a plurality of leg shafts projecting radially outward;
A rolling element interposed between the outer peripheral surface of the leg shaft and the side surface of the raceway groove, and rolling on the side surface of the raceway groove;
With
At least one of the rolling surface of the rolling element and the side surface of the raceway groove after heat treatment is formed in a convex shape at the center in the groove depth direction of the raceway groove,
The constant velocity joint in which the rolling surface of the rolling element and the side surface of the raceway groove after the heat treatment are in contact with each other at the center. The side surface of the raceway groove before the heat treatment is formed in the convex shape,
The constant velocity joint according to claim 1, wherein the side surface of the raceway groove after the heat treatment is formed in parallel with the convex shape or a groove depth direction of the raceway groove. A plurality of raceway grooves formed on the inner peripheral surface of the inner circumference surface, and an outer joint member that is heat-treated at least on the side surfaces of the raceway grooves;
An inner joint member comprising a plurality of leg shafts projecting radially outward;
A rolling element interposed between the outer peripheral surface of the leg shaft and the side surface of the raceway groove, and rolling on the side surface of the raceway groove;
With
The side surface of the raceway groove before heat treatment is formed in a convex shape in the center part of the groove depth direction of the raceway groove,
The rolling surface of the rolling element and the side surface of the raceway groove after the heat treatment are formed in a convex shape at the center in the groove depth direction of the raceway groove, or in the groove depth direction of the raceway groove. Constant velocity joints formed in parallel. The side surface of the raceway groove after the heat treatment is formed in the convex shape,
The constant velocity joint according to any one of claims 1 to 3, wherein the rolling surface of the rolling element is formed in parallel with the convex shape or a groove depth direction of the raceway groove. After the heat treatment of the outer joint member,
When the groove bottom side of the raceway groove has a larger amount of heat shrinkage than the opening side of the raceway groove before the heat treatment, the convex shape of the side surface of the raceway groove before the heat treatment is the central portion. The constant velocity joint according to claim 2, wherein the constant velocity joint is formed closer to the opening side. After the heat treatment of the outer joint member,
If the opening side of the raceway groove has a larger amount of heat shrinkage than the bottom side of the raceway groove before the heat treatment, the convex shape of the side surface of the raceway groove before the heat treatment is the center part. The constant velocity joint according to claim 2, wherein the constant velocity joint is formed closer to the groove bottom side. The rolling element is a needle;
The constant velocity joint according to any one of claims 1 to 6, wherein the side surface of the raceway groove rolls with an outer peripheral surface of the needle in contact therewith.

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