JP2005098450A - Outside joint member of constant velocity universal joint and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the torsional strength of a thin outside joint member, a cup-like or cylindrical mouth member of which is formed from a plate material or a pipe material by cold working such as press working in a constant velocity universal joint. <P>SOLUTION: This constant velocity universal joint has a hardened layer formed by heat treatment on the outer peripheral surface of a track groove part of the outside joint member formed from the plate material or pipe material by cold working. Shot peening is applied to the surface of the hardened layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  This invention is a cold working such as pressing a cup-shaped or cylindrical mouse member from a plate material or a tube material out of a tripod type or double offset type sliding constant velocity universal joint or a barfield type constant velocity universal joint. The present invention relates to a constant velocity universal joint having a thin outer joint member formed by the above method.

  In a constant velocity universal joint, as a conventional manufacturing technique for an outer joint member having a cup-shaped mouth portion in which an inner diameter portion and a track groove portion with which a rolling element engages are alternately arranged in the circumferential direction, an integral material is used. As a method of molding by warm forging or hot forging, or by molding a cup-shaped or cylindrical mouse member by cold working such as pressing from a plate or tube material, and joining it with a stem member produced as a separate body There is a method of forming an outer joint member.

In recent years, in the automobile industry, the constant velocity universal joint is required to be small and light, and the outer joint member obtained by the cold forming of the latter meets such needs. Further, in the former forming method by warm or hot forging, the forging die is deteriorated by heat, the forging die is required uniformly for a wide variety of product shapes, forging process and pretreatment. There is a problem that the manufacturing cost cannot be reduced due to the complicated multi-process. On the other hand, in the latter cold forming, the cost can be reduced as a whole from the viewpoints of process reduction, tool life extension and rationalization.
JP-A-8-49727 (paragraph number 0008) JP-A-9-177808 (paragraph number 0006)

  In cold forming such as pressing, cracks are likely to occur in parts that give large deformation to the material, and the amount of deformation that can be applied to the material is small compared to warm or hot forging. As a result, the cup-shaped or cylindrical mouse member obtained by cold forming such as press is thinner in cross section than the cup-shaped mouse part of the outer joint member obtained by warm forging or hot forging. And it becomes a substantially uniform cross-sectional shape with a small difference in thickness at each part on the circumference.

  On the other hand, as the mouse portion becomes thinner, the torsional fracture strength decreases. In particular, the thickness of the mouth portion of the outer joint member on the line extending in the load direction from the point of application of the load applied from the rolling element in the track groove part with which the rolling element engages is a major factor that affects its torsional fracture strength. is there. That is, as the track groove portion becomes thinner, the tensile stress generated by the load applied from the rolling element is concentrated near the intersection between the outer peripheral surface of the track groove portion and the load direction line, and breakage occurs at a lower load. Since the load applied to the track groove from the rolling element is generated in proportion to the load torque applied to the constant velocity universal joint, the allowable load torque of the constant velocity universal joint is also reduced when the torsional fracture strength of the outer joint member is low. Therefore, there has been a problem that the outer joint member constituted by a mouse member formed by cold working such as a press can be applied only to a constant velocity universal joint having a low allowable load torque.

  In order to solve this problem, Japanese Patent Application Laid-Open No. 9-177808 discloses a method for improving the torsional fracture strength of the cup-shaped member by making the hardness of the outer peripheral surface of the track groove portion lower than that of the inner peripheral surface. In this method, the torsional fracture strength can be increased when the load acting on the track groove from the rolling element is static. However, when the dynamic repeated load acts, that is, the strength against torsional fatigue failure. It is difficult to obtain the effect. Therefore, when the torsional fatigue strength of the mouse member is particularly important depending on the application situation of the constant velocity universal joint, there is no effective countermeasure method.

  An object of the present invention is to improve the torsional fatigue strength of a thin outer joint member obtained by forming a mouse member from a plate material or a tube material by cold working such as press working of a constant velocity universal joint.

  This invention removes the abnormal surface layer caused by the heat treatment by performing shot peening on the outer peripheral surface of the track groove portion where the shallow hardened layer is provided on the surface in advance by carburizing quenching or induction quenching, A surface layer portion having a high compressive residual stress is provided to improve the torsional fatigue strength of the mouse member.

  The abnormal surface layer generated by heat treatment refers to an incomplete structure due to grain boundary oxidation and hardenability degradation, where oxides form along the surface grain boundaries, and in the outer joint member mouse member as described above. In the portion where the tensile stress is concentrated, initial cracks are likely to occur along the grain boundary. By removing the abnormal surface layer by shot peening, the occurrence of initial cracks can be suppressed and the torsional fatigue strength can be increased.

  In addition, the compressive residual stress depends on the processing conditions (shot material, hardness, diameter, projection speed, projection time, etc.) in shot peening, but the compressive residual stress is different from the tensile residual stress described above. Since it acts in the direction to cancel the stress and suppresses the growth of fatigue cracks, the torsional fatigue strength of the mouse member can be increased by providing a surface layer portion on which compressive residual stress acts.

  ADVANTAGE OF THE INVENTION According to this invention, the torsional fatigue strength of an outer joint member can be improved, and the constant velocity universal joint with the outstanding performance can be provided at low cost.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, with reference to FIGS. 12 to 14, the integration of an outer joint member composed of a mouth portion and a stem portion will be described taking a double offset type constant velocity universal joint as an example.

  As shown in FIG. 12, the outer joint member includes a mouth portion 1 and a stem portion 5. The mouse portion 1 is formed into a cup shape by pressing a pipe material made of a thin steel plate or a cylindrical material with a bottom. As shown in FIGS. 13 (a) and 14 (a), a plurality of track grooves 2 are formed at equidistant positions in the circumferential direction of the mouse part 1, and as a result, the open end of the mouse part 1 has a flower crown shape. ing. FIG. 13A and FIG. 14A illustrate the case where the number of track grooves 2 is six, but there may be cases other than six, for example, eight. As shown by an imaginary line in FIG. 12B, a constant velocity universal joint is configured by incorporating a torque transmission member 3 including a ball, a cage, an inner ring, and the like inside the mouse portion 1. A through hole 4 is formed in the center of the end wall 1a of the mouse portion 1 by press punching. The through hole 4 is a polygon as shown in FIG. 13A, or a serration hole or a spline hole as shown in FIG. 14A, and is subjected to surface effect treatment such as carburizing treatment or induction hardening.

  On the other hand, the stem portion 5 to be joined to the mouse portion 1 has a serration or spline 6 formed at one end, a large diameter portion 8 formed at the other end, and a tip surface of the large diameter portion 8. A protrusion 7 having a smaller diameter than the large diameter portion 8 is formed. The protrusion 7 remains a raw material, and the surface is not cured. Further, the outer diameter dimension of the protruding portion 7 is set to be slightly larger than the inscribed circle diameter of the through hole 4 of the mouse portion 1. A circumferential groove is formed in a step portion between the large diameter portion 8 and the protruding portion 7, and a seal member 9 is attached to the circumferential groove.

  As shown in FIG. 12A, the mouse part 1 and the stem part 5 are joined by pressing the protruding part 7 of the stem part 5 into the through hole 4 of the mouse part 1 and protruding inside the mouse part 1. The tip of the portion 7 is struck in the axial direction by the caulking tool 10 and caulked as shown in FIG. 12B, so that the mouse portion 1 and the stem portion 5 are integrated.

  The embodiment shown in FIG. 1 will be described. FIG. 1A shows a longitudinal section of a tripod type constant velocity universal joint, and FIG. 1B shows a transverse section thereof. The tripod type constant velocity universal joint includes a tripod member 14 connected to a drive shaft or a driven shaft, and an outer joint member 16 connected to the driven shaft or the drive shaft. In this embodiment, the outer joint member 16 is configured by joining a cup-like mouse member 11 formed by continuous pressing from a plate material and a stem member 12 manufactured separately from the cup-like mouse member 11.

  As shown in FIG. 1B, the mouse member 11 formed by press working has a substantially uniform cross-sectional shape as shown in FIG. In press working, a material having a low carbon content is easier to process, and therefore, low carbon steel for carburizing and quenching is used. The mouse member 11 is joined to the stem member 12 after providing a hardened layer on the entire surface including the inner and outer peripheral surfaces of the track groove portion 15 by carburizing and quenching after molding. The shot peening process may be performed on the outer peripheral surface of the track groove portion 15 before or after joining to the stem member 12 as long as it is after carburizing and quenching.

Due to the rotational torque T ₁ acting on the inner joint member 14 in the direction of the arrow in FIGS. 1B and 2A, a load is applied from the rolling element 13 to the track groove portion 15, and Z ₁ of the outer peripheral surface of the track groove portion 15 is increased. Tensile stress concentrates on the part. Therefore, although an initial crack is generated in the Z ₁ portion and becomes a starting point of breakage, in a sliding type constant velocity universal joint such as a tripod type constant velocity universal joint, the relative angle of the inner joint member 14 with respect to the outer joint member 16 is Since it is used for an application that rotates while its axial position fluctuates, the contact position between the rolling element 13 and the track groove 15 and the Z ₁ portion where the tensile stress concentrates also move in the axial direction. Therefore, the shot peening is performed in the range L ₁ a on the outer peripheral contour in the cross section (FIG. 2A) and the axial range L ₁ b in which the track groove portion 15 and the rolling element 13 can contact (FIG. 2B). ), And the range is six in the tripod type. Some of them are indicated by hatched portions in FIG. Moreover, if these ranges are included, the range to which the shot peening process is performed may be a wider range or the entire outer peripheral surface. A range L ₁ a on the outer peripheral contour in the cross section (FIG. 2A) is approximately the same as the width of the track groove portion 15.

  Next, the embodiment shown in FIG. 3 will be described. FIG. 3 (a) shows a longitudinal section of a double offset constant velocity universal joint, and FIG. 3 (b) shows a transverse section thereof. The double offset type constant velocity universal joint includes an inner joint member 24 connected to the drive shaft or the driven shaft, and an outer joint member 26 connected to the driven shaft or the drive shaft. In this embodiment, the outer joint member 26 is configured by joining a cup-shaped mouth member 21 formed by continuous pressing from a plate material and a stem member 22 manufactured separately from the cup-like mouth member 21.

  As shown in FIG. 3B, the mouse member 21 formed by press working has a substantially uniform cross-sectional shape as shown in FIG. In press working, a material having a low carbon content is easier to process, and therefore, low carbon steel for carburizing and quenching is used. The mouse member 21 is joined to the stem member 22 after providing a hardened layer on the entire surface including the inner and outer peripheral surfaces of the track groove portion 25 by carburizing and quenching after molding. The shot peening process may be performed on the outer peripheral surface of the track groove portion 25 before or after joining the stem member 22 as long as it is after carburizing and quenching.

A load is applied from the rolling element 23 to the track groove portion 25 by the rotational torque T ₂ acting on the inner joint member 24 in the direction of the arrow in FIGS. 3B and 4A, and Z _{2 on} the outer circumferential surface of the track groove portion 25. Tensile stress concentrates on the part. Therefore, although an initial crack is generated in the Z ₂ portion and becomes a starting point of damage, in a sliding type constant velocity universal joint such as a double offset type, the relative angle and axial position of the inner joint member 24 with respect to the outer joint member 26 Therefore, the contact position between the rolling element 23 and the track groove portion 25 and the Z ₂ portion where the tensile stress is concentrated also move in the axial direction. Therefore, the shot peening is performed in the range L ₂ a on the outer peripheral contour in the cross section (FIG. 4A) and the axial range L ₂ b in which the track groove portion 25 and the rolling element 23 can contact (FIG. 4B). ), And the range is 12 in the double offset type. Several of them are indicated by hatched portions in FIG. Moreover, if these ranges are included, the range to which the shot peening process is performed may be a wider range or the entire outer peripheral surface. A range L ₂ a on the outer peripheral contour in the cross section (FIG. 4A) is about 2/3 of the diameter of the rolling element 23.

  The processing conditions in the shot peening process are set so as to generate a compressive residual stress of −1000 MPa or more in a depth range of 10 to 50 μm when the surface hardness of the carburized and quenched mouse members 11 and 21 is around HRC60. Generally, if the shot diameter is reduced, a high compressive residual stress is likely to be generated in a shallow range from the surface, and a compressive residual stress is likely to be generated from the surface layer to a deep range as the shot diameter is increased. In addition, when the surface abnormal layer is hard to be removed by carburizing and quenching, it is effective to perform pre-processing under processing conditions for the purpose of removing the surface abnormal layer in advance.

  In the tripod type constant velocity universal joint as shown in FIGS. 1 and 2, the difference in strength against torsional fatigue failure of the cup-shaped or cylindrical mouse member 11 with or without shot peening is shown in FIG. 5 and FIG. The result confirmed using this sample is shown in FIG. The outer joint member 46 of the sample is fixed, a load torque is repeatedly applied to the inner joint member 44 in a certain rotational direction, and the cylindrical mouse member 41 is repeatedly fatigued from the outer peripheral surface of the track groove 45 as a starting point. The number of times is recorded. 5 and FIG. 6 with respect to the embodiment shown in FIG. 1, the mouse member 41 and the stem member 42 are structured by welding the boundary portion 49 of the outer peripheral surface, The difference is that it is obtained by machining from the material rather than by cold working such as pressing, but the track groove portion of the cup-shaped or cylindrical mouse member having an axial cross-sectional shape with a substantially uniform wall thickness is different. It is possible to confirm the difference in torsional fatigue strength depending on the presence or absence of shot peening on the outer peripheral surface.

The outer joint member 46 of the sample shown in FIG. 5 is formed by cutting the mouse member 41 from the SCM415 material and then forming a surface hardened layer by carburizing and quenching and tempering. It is a thing. Sample 1 and sample 2 in FIG. 11 are produced by preparing two types having different surface hardness and hardened layer depth before and after HRC60. Further, for each of the samples 1 and 2, the outer peripheral face of the track groove 45 of the mice member 41, the range L ₁ a and the axial extent of the outer peripheral contour of an axial section of a mouse member 11 shown in FIG. 2 described above L ₁ The outer peripheral surface including the same six locations as b was subjected to shot peening processing (white circles and white squares in FIG. 11) and those not so (black circles and black squares in FIG. 11) were prepared. The processing conditions for shot peening were set so as to generate a compressive residual stress of −1000 MPa or more in a depth range of 10 to 50 μm.

  As shown in FIG. 11, although there is a difference in effect due to the difference in surface hardness in sample 1 or sample 2, the number of repetitions until breakage is about 3.9 times in sample 1 and sample 2 by performing shot peening. It is increased by about 6.6 times. Thereby, the improvement effect with respect to the torsional fatigue strength of the mouse member 41 by the shot peening process was confirmed.

  In the embodiment shown in FIGS. 7 and 8, in a tripod type constant velocity universal joint, a steel material having a carbon content of about 0.5% is used as a material for the cup-shaped mouse member 51, and heat treatment is performed by induction hardening. Is the case. In the case of carburizing and quenching tempering according to the embodiment shown in FIG. 1, a hardened layer is formed on the entire surface of the mouse member, whereas in the induction hardening, the surface hardened layer is provided by partially heating and cooling. Is different. In order to obtain compressive residual stress by shot peening, the target surface must be hardened by heat treatment, and the track is required to suppress wear due to contact between the outer joint member 56 and the rolling element 53. In addition to the surface hardened layer 57 on the inner surface of the groove portion 55, it is necessary to provide a relatively shallow surface hardened layer 58 on the outer peripheral surface of the track groove portion 55 on which shot peening is performed. At this time, since the torsional fatigue strength is remarkably reduced if the core is hardened to the core as well as the inner and outer peripheral surfaces of the track groove 55, the core is required to be a non-hardened portion of HRC45 or less. is there. Therefore, the inner peripheral surface and the outer peripheral surface of the track groove portion 55 need to be induction-hardened in two steps. However, the hardened part in the first step may be tempered by the influence of the heating in the second step. Then, after induction hardening the outer peripheral surface of the track groove portion 55 as the first step, the inner peripheral surface requiring higher surface hardness is induction hardened as the second step, so that the surface hardness of the inner peripheral surface is around HRC60, the outer peripheral surface. Surface hardened layers 57 and 58 having a surface hardness of around HRC55 are obtained. If the surface hardness of the outer peripheral surface of the track groove portion 55 is about HRC55, an improvement effect on the torsional fatigue strength of the mouse member 51 by the shot peening process can be easily obtained.

  In addition, the method of performing shot peening by providing hardened layers on the inner and outer peripheral surfaces of the track groove by induction hardening as described above is applied to the mouse member of the double offset type constant velocity universal joint (see FIGS. 3 and 4). You may apply.

  9 and 10, the outer joint member 66 is a cup-like mouth member 61 formed by continuous pressing from a plate material, and a stem member 62 manufactured separately is welded to the boundary portion 69 of the outer peripheral surface. The embodiment in the barfield type constant velocity universal joint comprised by doing is shown.

  The cup-shaped mouse member 61 formed by press working has a substantially uniform wall cross-sectional shape due to processing restrictions as described in the background section. In press working, a material having a low carbon content is easier to process, and therefore, low carbon steel for carburizing and quenching is used. The mouse member 61 is joined to the stem member 62 after providing a hardened layer on the entire surface including the inner and outer peripheral surfaces of the track groove portion 65 by carburizing and quenching after molding. The shot peening process may be performed on the outer peripheral surface of the track groove portion 65 before or after joining to the stem member 62 as long as it is after carburizing and quenching. In addition, the vicinity of the boundary portion 69 of the mouse member 61 may be subjected to a carbon-proof treatment to prevent cracking during welding.

A load is applied from the rolling element 63 to the track groove portion 65 by the rotational torque T ₆ acting on the inner joint member 64 in the direction of the arrow in FIGS. 9B and 10A, and Z _{6 on} the outer circumferential surface of the track groove portion 65. Tensile stress concentrates on the part. For this reason, an initial crack is generated in the Z ₆ portion and becomes a starting point of damage. However, in a Barfield type constant velocity universal joint, it is used for a purpose of rotating while the relative angle of the inner joint member 64 to the outer joint member 66 varies. The contact position between the rolling element 63 and the track groove portion 65 and the Z ₆ portion where the tensile stress is concentrated move along the track of the track groove portion 65. Therefore, the shot peening is performed in the range L ₆ a on the outer peripheral contour in the cross section (FIG. 10A) and the axial range L ₆ b in which the track groove 65 and the rolling element 63 can contact (FIG. 10B). Must be performed on the outer peripheral surface including There are 12 such ranges in the bar field type, and several of them are shown by hatching in FIG. 10 (b). The range L ₆ a is about 2/3 of the diameter of the rolling element 63.

  The processing conditions in the shot peening process are: compressive residual stress of −1000 MPa or more in a depth range of 10 to 50 μm when the surface hardness is around HRC60 in a carburized and hardened cup-shaped mouse member as in this embodiment. Is set to produce. Generally, if the shot diameter is reduced, a high compressive residual stress is likely to be generated in a shallow range from the surface, and a compressive residual stress is likely to be generated from the surface layer to a deep range as the shot diameter is increased. In addition, when the surface abnormal layer is hard to be removed by carburizing and quenching, it is effective to perform pre-processing under processing conditions for the purpose of removing the surface abnormal layer in advance.

  Conversely, the method of performing shot peening by providing a surface hardened layer on the inner peripheral surface of the track groove portion by induction hardening described above in connection with the embodiment of the tripod type constant velocity universal joint shown in FIG. It may be applied to a mouse member of a barfield type constant velocity universal joint.

  The constant velocity universal joint of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention.

(A) is a longitudinal cross-sectional view of a tripod type constant velocity universal joint, (b) is a cross-sectional view. (A) is the same cross-sectional view as FIG.1 (b), (b) is a side view. (A) is a longitudinal cross-sectional view of a double offset type constant velocity universal joint, (b) is a cross-sectional view. (A) is the same cross-sectional view as FIG.3 (b), (b) is a side view. (A) is a longitudinal cross-sectional view of the tripod type constant velocity universal joint for a test, (b) is a cross-sectional view. (A) is the same cross-sectional view as FIG.5 (b), (b) is a side view. (A) is a longitudinal cross-sectional view of a tripod type constant velocity universal joint, (b) is a cross-sectional view. (A) is the same cross-sectional view as FIG.7 (b), (b) is a side view. (A) is a longitudinal cross-sectional view of a barfield type constant velocity universal joint, and (b) is a cross-sectional view. (A) is the same cross-sectional view as FIG.9 (b), (b) is a side view. It is a graph which shows the result of a fatigue fracture test. (A) is a longitudinal cross-sectional view which shows the manufacturing process of the outer joint member of a tripod type constant velocity universal joint, (b) is a longitudinal cross-sectional view of a tripod type constant velocity universal joint. (A) is an end view of the outer joint member in FIG. 12 (a), (b) is an end view of the stem member. (A) is an end view of the outer joint member in FIG. 12 (a), (b) is an end view of the stem member.

Explanation of symbols

11, 21, 41, 51, 61 Mouse member 12, 22, 42, 52, 62 Stem member 13, 23, 43, 53, 63 Rolling element 14, 24, 44, 54, 64 Inner joint member 15, 25, 45 , 55, 65 Track groove 16, 26, 46, 56, 66 Outer joint member 49, 69 Boundary portion 57, 58 Surface hardened layer

Claims (2)

  It is an outer joint member formed by cold working from a plate material or a pipe material, and has a hardened layer by heat treatment on the outer peripheral surface of the track groove portion of the outer joint member, and the surface of the hardened layer is subjected to shot peening processing An outer joint member of a constant velocity universal joint as a feature.   An outer joint member is formed from a plate material or a pipe material by cold working, a hardened layer is formed by heat treatment on the outer peripheral surface of the track groove portion of the outer joint member, and the surface of the hardened layer is subjected to shot peening, etc. A method for manufacturing an outer joint member of a speed universal joint.

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