JP2016001042A - Sliding constant-velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the deformation of an outer joint member due to a heat treatment for forming a hardened layer while ensuring the torsional fatigue strength of the outer joint member.SOLUTION: A tripod constant-velocity universal joint comprises: an outer joint member 10 including a roller guide surface extending axially and formed in each of a plurality of circumferential portions on an inner circumferential surface; and a tripod member for transmitting torque while permitting an angular displacement between the tripod member and the outer joint member 10 via a roller inserted into the roller guide surface of the outer joint member 10 so that the roller can roll, the roller and the tripod member being accommodated in the outer joint member 10 axially displaceably while guiding the roller along the roller guide surface of the outer joint member 10, the tripod constant-velocity universal joint being configured so that a hardened layer 17 is formed in a concave portion 15 of an outer circumferential surface of the outer joint member 10 corresponding to a partial axial region B out of all axial regions A in which the roller contacts the roller guide surface at a time of the axial displacement.

Description

  The present invention is used in power transmission systems of automobiles, airplanes, ships, and various industrial machines, and is incorporated into a drive shaft, a propeller shaft, etc. used in, for example, a 4WD vehicle, an FR vehicle, etc. The present invention relates to a sliding type constant velocity universal joint that allows axial displacement and angular displacement between them.

  There are two types of constant velocity universal joints incorporated in drive shafts, propeller shafts, and the like that transmit rotational force from an automobile engine to wheels at a constant speed: fixed constant velocity universal joints and sliding constant velocity universal joints. Both of these constant velocity universal joints have a structure in which two shafts on the driving side and the driven side are connected so that rotational torque can be transmitted at a constant speed even if the two shafts have an operating angle.

  A drive shaft that transmits power from an automobile engine to a driving wheel needs to cope with an angular displacement and an axial displacement caused by a change in a relative positional relationship between the engine and the wheel. A sliding constant velocity universal joint that allows axial displacement and angular displacement on the side), and fixed that allows large angular displacement (operation angle 45 degrees) but not axial displacement on the drive wheel side (outboard side). Each type of constant velocity universal joint is equipped, and both constant velocity universal joints are connected by a shaft.

  One of the sliding type constant velocity universal joints assembled to the drive shaft is a roller type tripod type constant velocity universal joint (TJ) using a roller as a torque transmission member. Another sliding constant velocity universal joint includes a ball type double offset constant velocity universal joint (DOJ) using a ball as a torque transmission member.

  For example, a tripod type constant velocity universal joint includes an outer joint member in which three track grooves extending in the axial direction are formed on the inner peripheral surface and roller guide surfaces facing each other are formed on the inner wall of each track groove; A tripod member having three leg shafts protruding radially and having a tip inserted into the track groove of the outer joint member, and a tripod member rotatably supported by the leg shaft of the tripod member and being transferred to the track groove of the outer joint member. The main part is composed of a roller that is movably inserted and guided along the roller guide surface. On the outer peripheral surface of the outer joint member, a recess is formed in the axial direction at a portion corresponding to the space between the track grooves in order to reduce the weight.

  This tripod type constant velocity universal joint has a structure in which an inner part composed of a roller and a tripod member is accommodated in the outer joint member so as to be axially displaceable while the roller is guided along the roller guide surface of the track groove of the outer joint member. It comprises. In recent years, in the automobile industry, there has been a demand for smaller and lighter constant velocity universal joints, and in order to meet this demand, the outer joint members have been made thinner. If an attempt is made to reduce the thickness of the outer joint member, the torsional fatigue strength of the outer joint member will decrease.

  In particular, the tensile stress generated by the load applied from the roller is concentrated on the back side of the roller guide surface of the track groove of the outer joint member, that is, the portion corresponding to the roller guide surface in the concave portion of the outer peripheral surface of the outer joint member. For this reason, an initial crack is generated at a portion corresponding to the roller guide surface of the concave portion of the outer joint member and becomes a breakage starting point, and it is necessary to ensure the strength of the portion. The present applicant has previously proposed a tripod type constant velocity universal joint in which a hardened layer is formed in that portion in order to ensure the torsional fatigue strength of the portion corresponding to the roller guide surface of the concave portion of the outer joint member (for example, , See Patent Document 1).

JP 2007-270902 A

  By the way, in the conventional tripod type constant velocity universal joint disclosed in Patent Document 1 described above, a hardened layer is formed on the roller guide surfaces located on both sides of the track groove of the outer joint member, and the back side of the roller guide surface, That is, a hardened layer is formed at a portion corresponding to the roller guide surface at the concave portion of the outer peripheral surface of the outer joint member. The hardened layer is formed over the entire axial region where the roller contacts the roller guide surface when the roller is displaced in the axial direction by heat treatment such as induction hardening. In this way, by forming a hardened layer in the portion corresponding to the roller guide surface of the concave portion of the outer joint member, the torsion of the portion where the initial crack is generated due to the concentration of the tensile stress due to the repeated load from the roller and becomes the starting point of breakage Fatigue strength is ensured.

  However, the longer the axial region in which the hardened layer is formed in the concave portion of the outer peripheral surface of the outer joint member corresponding to the roller guide surface, the greater the deformation of the outer joint member due to heat treatment such as induction hardening. Increases nature. When such deformation of the outer joint member occurs, the accuracy of the joint inner shape including the roller guide surface is lowered.

  Accordingly, the present invention has been proposed in view of the above-described improvements, and the object thereof is to deform the outer joint member by heat treatment for forming a hardened layer while ensuring the torsional fatigue strength of the outer joint member. It is an object of the present invention to provide a sliding type constant velocity universal joint that can suppress the above to a minimum.

  As technical means for achieving the above-mentioned object, the present invention provides an outer joint member in which track grooves extending in the axial direction are formed at a plurality of locations in the circumferential direction of the inner peripheral surface, and a track groove of the outer joint member. An inner joint member that transmits torque while allowing angular displacement with the outer joint member via a rolling element that is freely inserted, and the rolling element guides along the track groove of the outer joint member. A sliding type constant velocity universal joint in which the rolling element and the inner joint member are accommodated in the outer joint member so as to be axially displaceable, and the rolling element comes into contact with the track groove when displaced in the axial direction. A hardened layer is formed on the outer peripheral surface portion of the outer joint member corresponding to a part of the axial region.

  In the present invention, since the hardened layer is formed on the outer peripheral surface portion of the outer joint member corresponding to the region where the rolling element is in contact with the track groove when axially displaced, the initial crack is caused by concentration of tensile stress due to repeated load from the rolling element. The torsional fatigue strength can be ensured at the site that is the origin of breakage. Moreover, the hardened layer is formed by forming the hardened layer on the outer peripheral surface portion of the outer joint member corresponding to a part of the axial direction region in the whole axial direction region where the rolling element contacts the track groove when displaced in the axial direction. Therefore, the deformation of the outer joint member due to the heat treatment can be suppressed to the minimum, and the accuracy of the joint internal shape including the track groove can be ensured.

  The hardened layer in the present invention can be formed by quenching. This hardened layer can also be formed by shot blasting or shot peening. In this way, the cured layer can be easily formed by simple means. Furthermore, it is desirable that the hardened layer is formed by quenching, and then shot blasting or shot peening is performed on the hardened layer forming portion. If it does in this way, the compressive residence stress in the outer peripheral surface site | part of the outer joint member in which the hardened layer was formed can be optimized.

  In the outer joint member of the present invention, three track grooves extending in the axial direction are formed on the inner peripheral surface, and roller guide surfaces facing each other are formed on the inner side wall of each track groove. A tripod member having three leg shafts inserted into the track groove, and the rolling element is rotatably supported by the leg shaft and is inserted into the track groove of the outer joint member to be guided along the roller guide surface. A structure that is a roller is desirable. That is, the present invention is applicable to a roller type tripod type constant velocity universal joint having the above-described structure. In this case, the hardened layer in the present invention is formed on the outer peripheral surface portion of the outer joint member corresponding to a part of the axial region of the entire axial region where the roller contacts the roller guide surface when the roller is displaced in the axial direction. become.

  According to the present invention, the hardened layer is formed on the outer peripheral surface portion of the outer joint member corresponding to the region where the rolling element is in contact with the track groove when displaced in the axial direction, thereby concentrating the tensile stress due to the repeated load from the rolling element. It is possible to ensure the torsional fatigue strength at the site where the initial crack is generated and becomes the starting point of breakage. Moreover, the hardened layer is formed by forming the hardened layer on the outer peripheral surface portion of the outer joint member corresponding to a part of the axial direction region in the whole axial direction region where the rolling element contacts the track groove when displaced in the axial direction. Therefore, the deformation of the outer joint member due to the heat treatment can be suppressed to the minimum, and the accuracy of the joint internal shape including the track groove can be ensured.

  Thus, while ensuring the torsional fatigue strength of the outer joint member, the deformation of the outer joint member due to the heat treatment for forming the hardened layer can be suppressed to the minimum, and the accuracy of the inner shape of the joint including the track groove can be improved. Since this can be ensured, the degree of freedom in design is improved in reducing the size and weight of the joint.

1 is a cross-sectional view showing an overall configuration of a tripod type constant velocity universal joint in an embodiment of a sliding type constant velocity universal joint according to the present invention. It is a longitudinal cross-sectional view which shows the whole structure of the tripod type | mold constant velocity universal joint of FIG. It is a longitudinal cross-sectional view which shows the outer joint member of FIG. It is a front view which shows the outer joint member of FIG.

  Embodiments of the sliding type constant velocity universal joint according to the present invention will be described in detail below. In the following embodiment, a single roller type tripod type constant velocity universal joint is illustrated. In addition to the single roller type, the present invention can also be applied to a double roller type tripod type constant velocity universal joint capable of reducing vibration during operation. In addition to the tripod type constant velocity universal joint, the present invention can be applied to other sliding type constant velocity universal joints such as a ball type double offset type constant velocity universal joint.

  1 and 2 show the overall configuration of a single roller type tripod type constant velocity universal joint. The tripod type constant velocity universal joint of the embodiment shown in the same figure is composed of an outer joint member 10, a tripod member 20 which is an inner joint member, and a roller 30 which is a rolling element.

  The outer joint member 10 has a cup shape having an opening 11 at one end, and a shaft 13 is integrally formed at the center of the bottom. Three linear track grooves 12 extending in the axial direction are formed on the inner peripheral surface of the outer joint member 10 at equal intervals in the circumferential direction. Each track groove 12 has a pair of roller guide surfaces 14 opposed to each other on both inner walls thereof. The roller guide surface 14 has an arc-shaped cross section and extends linearly in the axial direction of the outer joint member 10. On the outer peripheral surface of the outer joint member 10, a recess 15 is formed in the axial direction at a portion corresponding to the space between the track grooves 12 for weight reduction. Inside the outer joint member 10, an internal part composed of a tripod member 20 and a roller 30 is accommodated so as to be axially displaceable.

  The tripod member 20 has three leg shafts 22 integrally formed radially at equal intervals in the circumferential direction (120 ° intervals) on the outer peripheral surface of a cylindrical boss 21. The front end of the leg shaft 22 extends in the radial direction to the vicinity of the bottom of the track groove 12, and the outer peripheral surface thereof is generally a cylindrical surface. The shaft end of the shaft 40 is connected to the shaft hole of the boss 21 by spline fitting, and is prevented from coming off from the tripod member 20 by an annular snap ring 41.

  A roller 30 is rotatably disposed via a needle roller 31 between the roller guide surface 14 of the track groove 12 of the outer joint member 10 and the outer peripheral surface of the leg shaft 22. The outer peripheral surface of the roller 30 has an arc shape in vertical section, and may contact with the roller guide surface 14 at two locations by angular contact or contact at one location by circular contact. On the other hand, the inner peripheral surface of the roller 30 is formed in a cylindrical shape. A plurality of needle rollers 31 are arranged between the roller 30 and the leg shaft 22 in a so-called single row full roller state without a cage. The outer circumferential surface of the leg shaft 22 constitutes the inner rolling surface of the needle roller 31, and the inner circumferential surface of the roller 30 constitutes the outer rolling surface of the needle roller 31.

  These needle rollers 31 are in contact with the inner washer 32 fitted to the base portion of the leg shaft 22 on the radially inner side, and are in contact with the outer washer 33 fitted on the tip portion of the leg shaft 22 on the radially outer side. Yes. The outer washer 33 is prevented from coming off by fitting a retaining ring 34 such as a round circlip into an annular groove 23 formed at the tip of the leg shaft 22.

  In this constant velocity universal joint, the leg shaft 22 of the tripod member 20 and the roller guide surface 14 of the outer joint member 10 are engaged with each other in the biaxial rotational direction via the roller 30 to rotate from the driving side to the driven side. Torque is transmitted at a constant speed. Further, the roller 30 rolls on the roller guide surface 14 while rotating with respect to the leg shaft 22, thereby allowing relative axial displacement and angular displacement between the outer joint member 10 and the tripod member 20. The

  In the outer joint member 10 of the constant velocity universal joint having the above configuration, the hardened layer 16 is formed by quenching (for example, induction quenching) on the roller guide surface 14 of the track groove 12 on which high surface pressure is applied when rotational torque is transmitted. Is formed. As shown in FIG. 3, the hardened layer 16 is formed over the entire axial region A where the roller 30 contacts the roller guide surface 14 of the track groove 12 when the roller 30 is displaced in the axial direction. Thus, by forming the hardened layer 16 on the roller guide surface 14, it is possible to prevent the roller guide surface 14 from being worn by the rolling of the roller 30 in advance. The roller 30 that rolls on the roller guide surface 14 is also hardened by quenching (for example, quench quenching). The surface hardness of the hardened layer 16 and the roller 30 is set to HRC57 to 64 to prevent wear.

  On the other hand, the outer joint member 10 is thinned in order to reduce the size and weight of the joint. Due to a decrease in torsional fatigue strength of the outer joint member 10 due to this thinning, the roller guide surface 14 is formed on the back side of the roller guide surface 14 of the track groove 12 of the outer joint member 10, that is, on the concave portion 15 on the outer peripheral surface of the outer joint member 10. The tensile stress generated by the load applied from the roller 30 is concentrated on the corresponding portion. For this reason, an initial crack is generated at a portion corresponding to the roller guide surface 14 of the concave portion 15 of the outer joint member 10 to cause a breakage, and it is necessary to ensure the strength of the portion.

  Therefore, in the constant velocity universal joint of this embodiment, in order to ensure the torsional fatigue strength of the portion corresponding to the roller guide surface 14 of the recess 15 of the outer joint member 10, the roller guide is provided by the recess 15 on the outer peripheral surface of the outer joint member 10. A hardened layer 17 is formed at a portion corresponding to the surface 14 by quenching (for example, induction quenching). As shown in FIG. 4, the hardened layer 17 has an outer side corresponding to a part of the axial region B in the entire axial region A in which the roller 30 contacts the roller guide surface 14 of the track groove 12 when the roller 30 is displaced in the axial direction. It is formed on the outer peripheral surface portion of the joint member 10. The surface hardness of the hardened layer 17 is HRC 57 to 64, and the effective hardening depth is sufficient if the lower limit is 0.05 mm and the upper limit is about 0.13 mm. If it is hardened too deeply, it will be connected to the inner hardened layer 16 and burnout will occur, reducing durability and strength.

  The partial axial direction B of the total axial direction area A is an area (joint) used for normal axial displacement in general vehicle travel with reference to the joint center C which is the center of axial displacement. A region defined by the longitudinal dimension L centered on the center C) is effective. The reason why it is necessary to ensure torsional fatigue strength against repeated load from the roller 30 is a region that is always used for axial displacement in general vehicle traveling, that is, the repeated load from the roller 30 is always applied. It is an area.

  The partial axial direction region B is arbitrarily set depending on the size of joints and usage conditions, but the front-rear axial dimension L = 15 mm with the joint center C as the center is the maximum value. The axial region on the back side of the outer joint member and the axial region on the inlet side outside the partial axial region B are regions that are used less frequently, for example, at the time of full bumps or full rebounds of the vehicle. It is not necessary to form the hardened layer 17 in the entire axial direction area A including the directional area.

  As described above, by forming the hardened layer 17 on the outer peripheral surface portion of the outer joint member 10 corresponding to the region where the roller 30 contacts the roller guide surface 14 when displaced in the axial direction, the tensile stress due to the repeated load from the roller 30 is obtained. It is possible to secure the torsional fatigue strength at the site where the initial crack is generated due to the concentration of and becomes the starting point of breakage.

  Moreover, the above-described hardened layer 17 is formed on the outer peripheral surface portion of the outer joint member 10 corresponding to a part of the axial region B in the entire axial region A where the roller 30 contacts the roller guide surface 14 when the roller 30 is displaced in the axial direction. Therefore, by shortening the axial region B in which the hardened layer 17 is formed, deformation of the outer joint member 10 due to heat treatment for forming the hardened layer can be suppressed to a minimum, and the roller guide surface The accuracy of the joint internal shape including 14 can be ensured.

  The hardened layer 17 described above can be formed by shot blasting or shot peening other than by hardening (for example, induction hardening). Thus, by adopting quenching, shot blasting or shot peening, the hardened layer 17 can be easily formed by simple means.

  The hardened layer 17 may be formed by quenching (for example, induction hardening), and then shot blasting or shot peening may be performed on the hardened layer forming portion. Thus, by performing shot blasting or shot peening after quenching, it is possible to optimize the compressive residual stress at the outer peripheral surface portion of the outer joint member 10 on which the hardened layer 17 is formed. In the case of induction hardening, this hardening layer 17 is effective because induction hardening is not performed simultaneously with the hardening of the inner hardening layer 16 so that the manufacturing process is not increased. On the other hand, when shot blasting or shot peening is performed, although the manufacturing process increases, the compressive residual stress at the outer peripheral surface portion of the outer joint member 10 can be optimized as described above, so the durability of the outer joint member 10 is improved. It is effective for improvement.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the gist of the present invention. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

DESCRIPTION OF SYMBOLS 10 Outer joint member 12 Track groove 14 Roller guide surface 17 Hardened layer 20 Inner joint member (tripod member)
22 Leg shaft 30 Rolling element (roller, ball)
A Full axial direction area B Partial axial direction area

Claims (4)

An outer joint member in which track grooves extending in the axial direction are formed at a plurality of locations in the circumferential direction of the inner peripheral surface; and the outer joint member via a rolling element inserted into the track groove of the outer joint member so as to roll freely. An inner joint member that transmits torque while allowing angular displacement therebetween, and the rolling element and the inner joint member are pivoted to the outer joint member while the rolling element is guided along the track groove of the outer joint member. A sliding type constant velocity universal joint accommodated in a directionally displaceable manner,
A sliding type characterized in that a hardened layer is formed on the outer peripheral surface portion of the outer joint member corresponding to a part of the axial direction region in the entire axial direction region in which the rolling element contacts the track groove when displaced in the axial direction. Constant velocity universal joint.   The sliding constant velocity universal joint according to claim 1, wherein the hardened layer is formed by quenching.   The sliding constant velocity universal joint according to claim 1 or 2, wherein the hardened layer is formed by shot blasting or shot peening.   In the outer joint member, three track grooves extending in the axial direction are formed on the inner peripheral surface, and roller guide surfaces facing each other are formed on the inner side wall of each track groove. A tripod member having three leg shafts inserted into the track groove, wherein the rolling element is rotatably supported by the leg shaft and is inserted into the track groove of the outer joint member to form the roller guide surface. The sliding type constant velocity universal joint according to any one of claims 1 to 3, wherein the roller is a roller guided along the axis.

Images