Method for manufacturing outer joint member for constant-velocity universal joint and outer joint member

Abstract

A method of manufacturing an outer joint member of a constant velocity universal joint includes forming cup and shaft members using medium carbon steel, preparing, as the cup member, a cup member having cylindrical and bottom portions integrally formed, and a joining end surface formed on an outer surface of the bottom portion, preparing, as the shaft member, a shaft member having a joining end surface to be joined to the bottom portion of the cup member, and bringing the joining end surfaces of the cup and shaft members into abutment against each other. The method also includes welding the cup and shaft members from an outer side of the cup member to an abutment portion between the cup and shaft members in a radial direction of the cup member under a state in which a hollow cavity portion is formed inside the abutment portion.

Claims

1. A method of manufacturing an outer joint member of a constant velocity universal joint, which is constructed by forming, through use of separate members, a cup section having track grooves formed at an inner periphery of the cup section and engageable with torque transmitting elements, and a shaft section formed at a bottom portion of the cup section, and by welding a cup member forming the cup section and a shaft member forming the shaft section, the method comprising: forming the cup member and the shaft member using medium carbon steel; preparing, as the cup member, a cup member having a cylindrical portion and a bottom portion integrally formed, and a joining end surface formed on an outer surface of the bottom portion in a machining step; preparing, as the shaft member, a shaft member having a joining end surface to be joined to the bottom portion of the cup member, which is formed in the machining step; bringing the joining end surface of the cup member and the joining end surface of the shaft member into abutment against each other; and welding the cup member and the shaft member by radiating a beam from an outer side of the cup member to an abutment portion between the cup member and the shaft member in a radial direction of the cup member under a state in which a hollow cavity portion is formed inside the abutment portion, one of the joining end surface of the cup member and the joining end surface of the shaft member having, on a radially inner side thereof, an annular groove portion shielded from the hollow cavity portion.

2. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the welding comprises electron beam welding.

3. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the joining end surface of the cup member has an outer diameter set to an equal dimension for each joint size.

4. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the hollow cavity portion has an inner diameter surface formed into a cylindrical shape, and the inner diameter surface and the annular groove portion are formed so as to be concentric.

5. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the annular groove portion is formed in the shaft member.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a view for illustrating the entire structure of a drive shaft to which an outer joint member according to a first embodiment of the present invention is applied.

(2) FIG. 2a is an enlarged partial vertical sectional view for illustrating the outer joint member of FIG. 1.

(3) FIG. 2b is an enlarged view for illustrating a portion A of FIG. 2a.

(4) FIG. 2c is a view for illustrating a state of the portion A of FIG. 2a before welding.

(5) FIG. 3a is a vertical sectional view for illustrating a state of an annular groove portion on a joining end surface of FIG. 2a before welding.

(6) FIG. 3b is a vertical sectional view for illustrating a state of the annular groove portion on the joining end surface of FIG. 2a after welding.

(7) FIG. 4a is a partial vertical sectional view for illustrating findings in the course of development and a state before welding.

(8) FIG. 4b is a partial vertical sectional view for illustrating the findings in the course of development and a state after welding.

(9) FIG. 5 is a view for illustrating a method of manufacturing an outer joint member according to a first embodiment of the present invention and an overview of manufacturing steps for the outer joint member of FIG. 1.

(10) FIG. 6a is a vertical sectional view for illustrating a cup member before welding and after ironing.

(11) FIG. 6b is a vertical sectional view for illustrating the cup member before welding and after turning.

(12) FIG. 7a is a front view of a billet cut from a bar material, for illustrating a shaft member before welding.

(13) FIG. 7b is a partial vertical sectional view of the shaft member after forging, for illustrating the shaft member before welding.

(14) FIG. 7c is a partial vertical sectional view after turning and spline processing, for illustrating the shaft member before welding.

(15) FIG. 8 is a view for illustrating an overview of a welding step.

(16) FIG. 9 is a view for illustrating an overview of the welding step.

(17) FIG. 10 is a front view for illustrating a shaft member assigned with a different product number.

(18) FIG. 11 is a partial vertical sectional view for illustrating an outer joint member that is manufactured using the shaft member illustrated in FIG. 10.

(19) FIG. 12 is a diagram for illustrating an example of standardization of a product type of the cup member.

(20) FIG. 13a is a vertical sectional view for illustrating a state of a modified example of the outer joint member according to the first embodiment before welding.

(21) FIG. 13b is a vertical sectional view for illustrating a state of the modified example of the outer joint member according to the first embodiment after welding.

(22) FIG. 14 is a diagram for illustrating an overview of a method of manufacturing an outer joint member according to a second embodiment of the present invention.

(23) FIG. 15 is a diagram for illustrating an overview of a method of manufacturing an outer joint member according to a third embodiment of the present invention.

(24) FIG. 16 is a partial vertical sectional view for illustrating a constant velocity universal joint using an outer joint member according to a second embodiment of the present invention.

(25) FIG. 17a is a partial vertical sectional view of the outer joint member of FIG. 16.

(26) FIG. 17b is a vertical sectional view for illustrating a state of a portion A of FIG. 17a before welding.

(27) FIG. 18 is a vertical sectional view for illustrating an outer joint member according to a related art.

(28) FIG. 19 is a vertical sectional view for illustrating the outer joint member according to the related art.

(29) FIG. 20 is a vertical sectional view for illustrating an outer joint member according to a related art.

DESCRIPTION OF EMBODIMENTS

(30) Now, description is made of embodiments of the present invention with reference to the drawings.

(31) FIG. 5 to FIG. 12 are illustrations of a method of manufacturing an outer joint member of a constant velocity universal joint according to a first embodiment of the present invention, and FIG. 1 to FIG. 3 are illustrations of an outer joint member according to a first embodiment of the present invention. First, the outer joint member according to the first embodiment is described with reference to FIG. 1 to FIG. 3, and subsequently, the method of manufacturing an outer joint member according to the first embodiment is described with reference to FIG. 5 to FIG. 12.

(32) FIG. 1 is a view for illustrating the entire structure of a drive shaft 1 using an outer joint member 11 according to the first embodiment. The drive shaft 1 mainly comprises a plunging type constant velocity universal joint 10 arranged on a differential side (right side of FIG. 1: hereinafter also referred to as inboard side), a fixed type constant velocity universal joint 20 arranged on a driving wheel side (left side of FIG. 1: hereinafter also referred to as outboard side), and an intermediate shaft 2 configured to couple both the constant velocity universal joints 10 and 20 to allow torque transmission therebetween.

(33) The plunging type constant velocity universal joint 10 illustrated in FIG. 1 is a so-called double-offset type constant velocity universal joint (DOJ). The constant velocity universal joint 10 comprises the outer joint member 11 comprising a cup section 12 and a long shaft section (hereinafter referred to also as long stem section) 13 that extends from a bottom portion of the cup section 12 in an axial direction, an inner joint member 16 housed along an inner periphery of the cup section 12 of the outer joint member 11, balls 41 serving as torque transmitting elements that are arranged between track grooves 30 and 40 of the outer joint member 11 and the inner joint member 16, and a cage 44 having a spherical outer peripheral surface 45 and a spherical inner peripheral surface 46 that are fitted to a cylindrical inner peripheral surface 42 of the outer joint member 11 and a spherical outer peripheral surface 43 of the inner joint member 16, respectively, and being configured to retain the balls 41. A curvature center O.sub.1 of the spherical outer peripheral surface 45 and a curvature center O.sub.2 of the spherical inner peripheral surface 46 of the cage 44 are offset equidistantly from a joint center O toward opposite sides in the axial direction.

(34) An inner ring of a support bearing 6 is fixed to an outer peripheral surface of the long stem section 13, and an outer ring of the support bearing 6 is fixed to a transmission case with a bracket (not shown). The outer joint member 11 is supported by the support bearing 6 in a freely rotatable manner, and when the support bearing 6 as described above is provided, vibration of the outer joint member 11 during driving or the like is prevented as much as possible.

(35) The fixed type constant velocity universal joint 20 illustrated in FIG. 1 is a so-called Rzeppa type constant velocity universal joint, and comprises an outer joint member 21 comprising a bottomed cylindrical cup section 21a and a shaft section 21b that extends from a bottom portion of the cup section 21a in the axial direction, an inner joint member 22 housed along an inner periphery of the cup section 21a of the outer joint member 21, balls 23 serving as torque transmitting elements that are arranged between the cup section 21a of the outer joint member 21 and the inner joint member 22, and a cage 24, which is arranged between an inner peripheral surface of the cup section 21a of the outer joint member 21 and an outer peripheral surface of the inner joint member 22, and is configured to retain the balls 23. As the fixed type constant velocity universal joint 20, an undercut-free type constant velocity universal joint may sometimes be used.

(36) The intermediate shaft 2 comprises splines 3 for torque transmission (including serrations; the same applies hereinafter) at outer diameter portions on both end portions thereof. The spline 3 on the inboard side is spline-fitted to a hole portion of the inner joint member 16 of the plunging type constant velocity universal joint 10. Thus, the intermediate shaft 2 and the inner joint member 16 of the plunging type constant velocity universal joint 10 are coupled to each other to allow torque transmission therebetween. Further, the spline 3 on the outboard side is spline-fitted to a hole portion of the inner joint member 22 of the fixed type constant velocity universal joint 20. Thus, the intermediate shaft 2 and the inner joint member 22 of the fixed type constant velocity universal joint 20 are coupled to each other to allow torque transmission therebetween. Although the solid intermediate shaft 2 is illustrated, a hollow intermediate shaft may be used instead.

(37) Grease is sealed inside both the constant velocity universal joints 10 and 20 as a lubricant. To prevent leakage of the grease to an outside of the joint or entry of a foreign matter from the outside of the joint, bellows boots 4 and 5 are respectively mounted to a portion between the outer joint member 11 of the plunging type constant velocity universal joint 10 and the intermediate shaft 2 and a portion between the outer joint member 21 of the fixed type constant velocity universal joint 20 and the intermediate shaft 2.

(38) The outer joint member according to the first embodiment is described with reference to FIG. 2. FIG. 2 are enlarged views for illustrating the outer joint member 11 according to this embodiment. FIG. 2a is a partial vertical sectional view. FIG. 2b is an enlarged view for illustrating a portion A of FIG. 2a. FIG. 2c is a view for illustrating a shape before welding. The outer joint member 11 comprises the bottomed cylindrical cup section 12 that is opened at one end and has the cylindrical inner peripheral surface 42 and the plurality of track grooves 30, on which the balls 41 (see FIG. 1) are caused to roll, formed equiangularly on the inner peripheral surface, and the long stem section 13 that extends from the bottom portion of the cup section 12 in the axial direction and comprises a spline Sp serving as a torque transmitting coupling portion formed at an outer periphery on an end portion thereof on an opposite side to the cup section 12. In this embodiment, the outer joint member 11 is formed by welding a cup member 12a and a shaft member 13a to each other.

(39) The cup member 12a illustrated in FIG. 2a to FIG. 2c is an integrally-formed product being made of medium carbon steel, such as S53C, containing carbon of from 0.40 wt % to 0.60 wt %, and having a cylindrical portion 12a1 and a bottom portion 12a2. The cylindrical portion 12a1 has the track grooves 30 and the cylindrical inner peripheral surface 42 formed at an inner periphery thereof. A projecting portion 12a3 is formed at the bottom portion 12a2 of the cup member 12a. A boot mounting groove 32 is formed at an outer periphery of the cup member 12a on the opening side thereof, whereas a snap ring groove 33 is formed at an inner periphery of the cup member 12a on the opening side thereof. A bearing mounting surface 14 and a snap ring groove 15 are formed at an outer periphery of the shaft member 13a on the cup member 12a side, whereas the spline Sp is formed at an end portion of the shaft member 13a on an opposite side.

(40) The shaft member 13a is made of medium carbon steel, such as S40C, containing carbon of from 0.30 wt % to 0.55 wt %. A joining end surface 50 formed at the projecting portion 12a3 of the bottom portion 12a2 of the cup member 12a and a joining end surface 51 formed at an end portion of the shaft member 13a on the cup member 12a side are brought into abutment against each other, and are welded to each other by electron beam welding performed from an outer side of the cup member 12a in a radial direction. As illustrated in FIG. 2a and FIG. 2b, a welded portion 49 is formed of a bead, which is formed by a beam radiated from a radially outer side of the cup member 12a.

(41) Features of the outer joint member 11 of this embodiment are illustrated in FIG. 3. FIG. 3 are each an enlarged illustration of an upper portion in a radial direction in the vicinity of the welded portion of FIG. 2. FIG. 3a is a vertical sectional view for illustrating a state before welding, and FIG. 3b is a vertical sectional view for illustrating a state after welding. Before description of the features of the outer joint member 11 of this embodiment, findings verified in the course of development are described. FIG. 4 are each an illustration of the findings in the course of development. FIG. 4a is a vertical sectional view for illustrating a state before welding, and FIG. 4b is a vertical sectional view for illustrating a state after welding.

(42) As illustrated in FIG. 4a, a cup member 12a manufactured in the course of development comprises a joining end surface 50 and an outer diameter B1 thereof. A shaft member 13a comprises a joining end surface 51 and an outer diameter B2 and an inner diameter E thereof, and further comprises a recessed portion 52 on an radially inner side. The outer diameters B1 and B2 have equal dimensions. When the joining end surfaces 50 and 51 are brought into abutment against each other, a hollow cavity portion H is formed. In this state, electron beam welding is performed in a vacuum (low pressure) atmosphere as described later.

(43) It was found that, in the electron beam welding performed in a vacuum (low pressure) atmosphere at such a level as to establish industrial manufacturing of a constant velocity universal joint being a mass-produced product for automobiles and the like, a recess G is formed on an radially inner side of a weld bead 49 due to an internal pressure caused by air slightly remaining in the hollow cavity portion H as illustrated in FIG. 4b. It is considered that the recess G is formed when the radially inner side of the weld bead 49 is pushed out by the internal pressure in the hollow cavity portion H. When the recess G is formed, there is a risk of causing decrease in strength of welding due to the cutaway effect of the recess G and the reduction in joining area. The generation of air bubbles in the weld bead (welded portion) 49 was able to be suppressed.

(44) This embodiment has solved the above-mentioned problem. The features of the outer joint member of this embodiment are described with reference to FIG. 3. As illustrated in FIG. 3a, the cup member 12a comprises the joining end surface 50 and an outer diameter B1 thereof. The shaft member 13a comprises the joining end surface 51 and an outer diameter B2 and an inner diameter surface 53 (inner diameter E) thereof, and further comprises a recessed portion 52 on the radially inner side. As the features, an annular groove portion 51a is formed on the radially inner side of the joining end surface 51, and an annular shielding portion 51b is further formed on the radially inner side thereof. The annular groove portion 51a is formed at a welding joining interface immediately below the weld bead (welded portion) 49 (see FIG. 3b). When the joining end surfaces 50 and 51 are brought into abutment against each other, a hollow cavity portion H is formed. The annular groove portion 51a is separated and shielded from the hollow cavity portion H by the annular shielding portion 51b. The outer diameters B1 and B2 have equal dimensions.

(45) It was found that, when the cup member 12a and the shaft member 13a, respectively having the above-mentioned configurations, are brought into abutment against each other and subjected to electron beam welding, the inner diameter end portion of the weld bead 49 is sufficiently formed up to the annular groove portion 51a while a recess is not formed on the radially inner side of the weld bead 49 as illustrated in FIG. 3b. The reason for this is considered as follows. The internal pressure of the hollow cavity portion H is shielded by the annular shielding portion 51b, and the air remaining in the annular groove portion 51a has a small volume expansion amount by heating due to the small volume of the air. Thus, the influence of the internal pressure is suppressed. With this, the strength, quality, and reliability of the welded portion can be increased. The annular groove portion 51a has a width of from about 1 mm to about 3 mm and a depth of from about 0.5 mm to about 2 mm.

(46) The outer diameter B1 of the joining end surface 50 of the cup member 12a and the outer diameter B2 of the joining end surface 51 of the shaft member 13a need not be set to equal dimensions. In consideration of, for example, a state of the weld bead, a dimensional difference may be given as appropriate in such a manner that the outer diameter B2 of the joining end surface 51 is set slightly smaller than the outer diameter B1 of the joining end surface 50, or that the outer diameter B2 of the joining end surface 51 is set slightly larger than the outer diameter B1 of the joining end surface 50, conversely. The description the outer diameters of the joining end surface 50 and the joining end surface 51 are set to equal dimensions for each joint size herein refers to a concept encompassing a case where the dimensional difference is given as appropriate between the outer diameter B1 of the joining end surface 50 and the outer diameter B2 of the joining end surface 51.

(47) It is preferred that the inner diameter surface 53 forming the hollow cavity portion H of the shaft member 13a be formed into a cylindrical shape, and that the inner diameter surface 53 and the annular groove portion 51a be formed so as to be concentric. With this, the annular groove portion 51a can be easily subjected to turning, and the annular shielding portion 51b having satisfactory shielding efficiency and the annular groove portion 51a can be formed, which is effective for suppressing the recess of the weld bead.

(48) When the annular groove portion 51a is formed on the shaft member 13a, the annular groove portion 51a can be easily formed during turning of the shaft member 13a.

(49) As illustrated in FIG. 2a, in the outer joint member 11 of this embodiment, the welded portion 49 is formed on the joining end surface 51 located on the cup member 12a side with respect to the bearing mounting surface 14 of the shaft member 13a, and hence the bearing mounting surface 14 and the like can be processed in advance so that post-processing after welding can be omitted. Further, due to the electron beam welding, burrs are not generated at the welded portion. Thus, post-processing for the welded portion can also be omitted, which can reduce manufacturing cost. Still further, total inspection on the welded portion through ultrasonic flaw detection can be performed.

(50) Next, the manufacturing method according to the first embodiment of the present invention is described with reference to FIG. 5 to FIG. 12. An overview of manufacturing steps (processing steps) of the manufacturing method of this embodiment is described. FIG. 5 is an illustration of the overview of the manufacturing steps for the outer joint member. In this embodiment, as illustrated in FIG. 5, the cup member 12a is manufactured through manufacturing steps comprising a bar material cutting step S1c, a forging step S2c, an ironing step S3c, and a turning step S4c. Meanwhile, the shaft member 13a is manufactured through manufacturing steps comprising a bar material cutting step S1s, a turning step S2s, and a turning step S3s. Intermediate components of the cup member 12a and the shaft member 13a thus manufactured are each assigned with a product number for management.

(51) After that, the cup member 12a and the shaft member 13a are subjected to a welding step S6, a heat treatment step S7, and a grinding step S8 so that the outer joint member 11 is completed. A machining step described in Claims refers to the turning step S4c and the turning step S2s among the above-mentioned manufacturing steps, and to a grinding step S5s described later (see FIG. 15).

(52) An overview of each step is described. Each step is described as a typical example, and appropriate modification and addition may be made to each step as needed. First, the manufacturing steps for the cup member 12a are described.

(53) [Bar Material Cutting Step S1c]

(54) A bar material is cut into a predetermined length in accordance with a forging weight, thereby producing a billet.

(55) [Forging Step S2c]

(56) The billet is subjected to forging so as to integrally form the cylindrical portion, the bottom portion, and the projecting portion as a preform of the cup member 12a.

(57) [Ironing Step S3c]

(58) Ironing is performed on the track grooves 30 and the cylindrical inner peripheral surface 42 of the preform, thereby finishing the inner periphery of the cylindrical portion of the cup member 12a.

(59) [Turning Step S4c]

(60) In the preform after ironing, the outer peripheral surface, the boot mounting groove 32, the snap ring groove 33, and the like, and the joining end surface 50 are formed by turning. In this embodiment, after the turning step S4c, the cup member 12a in the form of an intermediate component is assigned with a product number for management.

(61) Next, the manufacturing steps for the shaft member 13a are described.

(62) [Bar Material Cutting Step S1s]

(63) A bar material is cut into a predetermined length in accordance with the entire length of the shaft section, thereby producing a billet. After that, the billet is forged into a rough shape by upset forging depending on the shape of the shaft member 13a.

(64) [Turning Step S2s]

(65) The outer peripheral surface of the billet or the forged preform (bearing mounting surface 14, snap ring groove 15, minor diameter of the spline, end surface, and the like) and the joining end surface 51 and the annular groove portion 51a at the end portion on the cup member 12a side are formed by turning.

(66) [Spline Processing Step S3s]

(67) The spline is formed by rolling in the shaft member after turning. Note that, the method of forming the spline is not limited to the rolling, and press working or the like may be adopted instead as appropriate. In this embodiment, after the spline processing, the shaft member 13a in the form of an intermediate component is assigned with a product number for management.

(68) Next, the manufacturing steps in the process of completing the outer joint member 11 from the cup member 12a and the shaft member 13a are described.

(69) [Welding Step S6]

(70) The joining end surface 50 of the cup member 12a and the joining end surface 51 of the shaft member 13a are brought into abutment against each other and welded. After the welding, the welded portion 49 between the cup member 12a and the shaft member 13a is inspected by the ultrasonic flaw-detection method.

(71) [Heat Treatment Step S7]

(72) Induction quenching and tempering are performed as heat treatment on at least the track grooves 30 and the cylindrical inner peripheral surface 42 of the cup section 12 after welding and a necessary range of the outer periphery of the shaft section 13 after welding. Heat treatment is not performed on the welded portion. A hardened layer having a hardness of approximately from 58 HRC to 62 HRC is formed on each of the track grooves 30 and the cylindrical inner peripheral surface 42 of the cup section 12. Further, a hardened layer having a hardness of approximately from 50 HRC to 62 HRC is formed in a predetermined range of the outer periphery of the shaft section 13.

(73) [Grinding Step S8]

(74) After the heat treatment, the bearing mounting surface 14 of the shaft section 13 and the like are finished by grinding. Thus, the outer joint member 11 is completed.

(75) In the manufacturing steps of this embodiment, the heat treatment step is provided after the welding step, and hence the manufacturing steps are suited to a cup member and a shaft member having such shapes and specifications that the hardness of the heat-treated portion may be affected by temperature rise at the periphery due to heat generated during the welding.

(76) Next, main constituent features of the manufacturing method of this embodiment are described in detail. FIG. 6a is a vertical sectional view for illustrating a state after ironing of the cup member 12a. FIG. 6b is a vertical sectional view for illustrating a state after turning. In a preform 12a for the cup member 12a, a cylindrical portion 12a1, a bottom portion 12a2, and a projecting portion 12a3 are integrally formed in the forging step S2c. After that, the track grooves 30 and the cylindrical inner peripheral surface 42 are formed by ironing in the ironing step S3c so that the inner periphery of the cylindrical portion 12a1 is finished as illustrated in FIG. 6a.

(77) After that, in the turning step S4c, the outer peripheral surface, the boot mounting groove 32, the snap ring groove 33, and the like of the cup member 12a as well as the joining end surface 50 of the projecting portion 12a3 of the bottom portion 12a2 and the outer diameter B1 portion are formed by turning as illustrated in FIG. 6b. The joining end surface 50 of the cup member 12a is formed by annular turning, and a center portion in a radial direction retains a forged surface. Thus, the time for the turning can be reduced.

(78) FIG. 7 are illustrations of states of the shaft member 13a in the respective processing steps. FIG. 7a is a front view for illustrating a billet 13a obtained by cutting a bar material. FIG. 7b is a partial vertical sectional view for illustrating a preform 13a obtained by forging the billet 13a into a rough shape by the forging (upset forging). FIG. 7c is a partial vertical sectional view for illustrating the shaft member 13a after turning and spline processing.

(79) When the billet 13a illustrated in FIG. 7a is produced in the bar material cutting step S1s, and the billet 13a is subjected to upset forging as illustrated in FIG. 7b, the preform 13a is produced by increasing the shaft diameter of the billet 13a in a predetermined range and forming a recessed portion 52 at a joining-side end portion (end portion on the cup member 12a side) while forming a step portion 54 in which the joining end surface 51 is formed, a second step portion 55 in which the bearing mounting surface 14 is formed, and a first step portion 56 by upset forging.

(80) After that, in the turning step S2s, the outer diameter portion of the shaft member 13a, the bearing mounting surface 14, the snap ring groove 15, an inner diameter surface 53 (inner diameter E) of the recessed portion 52, the joining end surface 51, the outer diameter B2 portion thereof, and the annular groove portion 51a are formed by turning as illustrated in FIG. 7c. In the spline processing step S3s, the spline Sp is processed at the end portion on the opposite side to the recessed portion 52 by rolling or press forming.

(81) The outer diameter B1 of the joining end surface 50 of the cup member 12a illustrated in FIG. 6b is set to an equal dimension for one joint size. Further, in the shaft member 13a illustrated in FIG. 7c, which is used as a long stem shaft, the outer diameter B2 of the joining end surface 51 is set to an equal dimension for each joint size irrespective of the shaft diameter and the outer peripheral shape. Still further, the joining end surface 51 of the shaft member 13a is located at the position on the cup member 12a side with respect to the bearing mounting surface 14. Through the setting of dimensions as described above, the outer joint member 11 compatible with various vehicle types can be manufactured in such a manner that, while the cup member 12a is prepared for common use, only the shaft member 13a is manufactured to have a variety of shaft diameters, lengths, and outer peripheral shapes depending on vehicle types, and both the members 12a and 13a are welded to each other. Details of the preparation of the cup member 12a for common use are described later.

(82) Next, a method of welding the cup member 12a and the shaft member 13a is described with reference to FIG. 8 and FIG. 9. FIG. 8 and FIG. 9 are views for illustrating an overview of a welding apparatus. FIG. 8 is an illustration of a state before welding. FIG. 9 is an illustration of a state during welding. As illustrated in FIG. 8, a welding apparatus 100 mainly comprises an electron gun 101, a rotation device 102, a chuck 103, a center hole guide 104, a tailstock 105, workpiece supports 106, a center hole guide 107, a case 108, and a vacuum pump 109.

(83) The cup member 12a and the shaft member 13a being workpieces are placed on the workpiece supports 106 arranged inside the welding apparatus 100. The chuck 103 and the center hole guide 107 arranged at one end of the welding apparatus 100 are coupled to the rotation device 102. The chuck 103 grips the cup member 12a to rotate the cup member 12a under a state in which the cup member 12a is centered by the center hole guide 107. The center hole guide 104 is integrally mounted to the tailstock 105 arranged at another end of the welding apparatus 100. Both the center hole guide 104 and the tailstock 105 are configured to reciprocate in the axial direction (lateral directions of FIG. 8 and FIG. 9).

(84) A center hole of the shaft member 13a is set on the center hole guide 104 so that the shaft member 13a is centered. The vacuum pump 109 is connected to the case 108 of the welding apparatus 100. A sealed space herein refers to a space 111 defined by the case 108. In this embodiment, the cup member 12a and the shaft member 13a are entirely received in the sealed space 111. The electron gun 101 is arranged at a position corresponding to the joining end surfaces 50 and 51 of the cup member 12a and the shaft member 13a. The electron gun 101 is configured to approach the workpieces up to a predetermined position.

(85) Next, the operation of the welding apparatus 100 constructed as described above and the welding method are described. The cup member 12a and the shaft member 13a being workpieces are stocked at a place different from the place of the welding apparatus 100. The respective workpieces are taken out by, for example, a robot, are conveyed into the case 108 of the welding apparatus 100 opened to the air as illustrated in FIG. 8, and are set at predetermined positions on the workpiece supports 106. At this time, the center hole guide 104 and the tailstock 105 are retreated to the right side of FIG. 8, and hence a gap is formed between the joining end surfaces 50 and 51 of the cup member 12a and the shaft member 13a. After that, a door (not shown) of the case 108 is closed, and the vacuum pump 109 is activated to reduce the pressure in the sealed space 111 defined in the case 108. Thus, the pressures in the recessed portion 52 and the inner diameter surface 53 of the shaft member 13a are reduced as well.

(86) When the pressure in the sealed space 111 is reduced to a predetermined pressure, the center hole guide 104 and the tailstock 105 are advanced to the left side as illustrated in FIG. 9 to eliminate the gap between the joining end surfaces 50 and 51 of the cup member 12a and the shaft member 13a. Along with this, the hollow cavity portion H having a reduced pressure is formed among the joining end surface 50 of the cup member 12a, the inner diameter surface 53 of the shaft member 13a, and the recessed portion 52. Further, the annular groove portion 51a having a reduced pressure is formed so as to be shielded from the hollow cavity portion H by the annular shielding portion 51b (see FIG. 3a). The cup member 12a is fixed with the chuck 103 while being centered with the center hole guide 107, and the shaft member 13a is supported by the center hole guide 104. After that, the workpiece supports 106 are separated from the workpiece. An interval between the workpiece supports 106 and the workpiece in this case may be small. Thus, the above-mentioned interval is omitted in FIG. 9. As a matter of course, the workpiece supports 106 may also be significantly retreated downward.

(87) Although illustration is omitted, the electron gun 101 is then caused to approach the workpieces up to a predetermined position, and the workpieces are rotated to start pre-heating. As a pre-heating condition, unlike the welding condition, the temperature is set lower than the welding temperature by, for example, radiating an electron beam under a state in which the electron gun 101 is caused to approach the workpieces so as to increase the spot diameter. Through the pre-heating, the cooling rate after welding is reduced, thereby being capable of preventing a quenching crack. When a predetermined pre-heating time has elapsed, the electron gun 101 is retreated to a predetermined position, and radiates the electron beam from the outer side of the workpieces in the radial direction to start welding. When the welding is finished, the electron gun 101 is retreated, and the rotation of the workpieces is stopped.

(88) Although illustration is omitted, the sealed space 111 is then opened to the air. Then, under a state in which the workpiece supports 106 are raised to support the workpieces, the center hole guide 104 and the tailstock 105 are retreated to the right side, and the chuck 103 is opened. After that, for example, the robot grips the workpieces, takes the workpieces out of the welding apparatus 100, and places the workpieces into alignment on a cooling stocker. In this embodiment, the cup member 12a and the shaft member 13a are entirely received in the sealed space 111, and hence the configuration of the sealed space 111 defined in the case 108 can be simplified.

(89) Specifically, the cup member 12a having a carbon content of from 0.4% to 0.6% and the shaft member 13a having a carbon content of from 0.3% to 0.55% were used and welded to each other in the above-mentioned welding apparatus 100 under the condition that the pressure in the sealed space 111 defined in the case 108 was set to 6.7 Pa or less. In order to prevent the cup member 12a and the shaft member 13a from being cooled rapidly after the welding to suppress increase in hardness of the welded portion, the joining end surfaces 50 and 51 of the cup member 12a and the shaft member 13a were soaked by pre-heating to have a temperature of from 300 C. to 650 C., and then electron beam welding was performed. As a result, a welded portion having no recess on a radially inner side of the weld bead was obtained. Further, through the soaking by pre-heating, the hardness of the welded portion after completion of the welding was able to be kept within a range of from 200 Hv to 500 Hv, thereby being capable of attaining high welding strength and stable welding state and quality. Still further, the cup member 12a and the shaft member 13a were welded to each other under the condition that the pressure in the sealed space 111 of the welding apparatus 100 was set to an atmospheric pressure or less, thereby being capable of suppressing the change in pressure in the hollow cavity portion during the welding. As a result, the blowing of a molten material and the entry of the molten material toward the radially inner side were able to be prevented. The setting of a pressure of 6.7 Pa or less of the sealed space 111 in the case 108 is the vacuum (low pressure) condition at such a level as to establish industrial manufacturing of a constant velocity universal joint being a mass-produced product for automobiles and the like.

(90) As illustrated in FIG. 3a, in the outer joint member 11 of this embodiment, the shaft member 13a comprises the annular groove portion 51a at the welding joining interface immediately below the weld bead 49 on the radially inner side of the joining end surface 51, and further comprises the annular shielding portion 51b on the radially inner side thereof. The annular groove portion 51a is separated and shielded from the hollow cavity portion H by the annular shielding portion 51b.

(91) It was found that, when the cup member 12a and the shaft member 13a, respectively having the above-mentioned configurations, are brought into abutment against each other and subjected to electron beam welding, the inner diameter end portion of the weld bead 49 is sufficiently formed up to the annular groove portion 51a while a recessed is not formed on the radially inner side of the weld bead 49 as illustrated in FIG. 3b. The reason for this is considered as follows. The internal pressure of the hollow cavity portion H is shielded by the annular shielding portion 51b, and the air remaining in the annular groove portion 51a has a small volume expansion amount by heating due to the small volume of the air. Thus, the influence of the internal pressure is suppressed. With this, the strength, quality, and reliability of the welded portion can be increased.

(92) Next, to summarize the manufacturing concept, standardization of a product type of the cup member is additionally described while exemplifying a shaft member having a product number different from that of the above-mentioned shaft member 13a of the long stem type illustrated in FIG. 7. A shaft member 13b illustrated in FIG. 10 and FIG. 11 is used as a general stem type on the inboard side. The shaft member 13b has the joining end surface 51 to be brought into abutment against the joining end surface 50 (see FIG. 6b) of the bottom portion 12a2 (projecting portion 12a3) of the cup member 12a. The outer diameter B2 of the joining end surface 51 is set to the equal dimension to the outer diameter B2 of the joining end surface 51 of the shaft member 13a of the long stem type illustrated in FIG. 7.

(93) The shaft member 13b is used as the general stem type on the inboard side. Accordingly, the shaft member 13b comprises a shaft section with a small length, and a sliding bearing surface 18 formed on an axial center portion thereof, and a plurality of oil grooves 19 are formed in the sliding bearing surface 18. The spline Sp and a snap ring groove 48 are formed in an end portion of the shaft member 13b on the side opposite to the cup member 12a side. As described above, even when there are differences in types, such as the general length stem type and the long stem type, and shaft diameters and outer peripheral shapes vary in each vehicle type, the diameter B2 is set to an equal dimension for each joint size.

(94) The outer diameter B1 of the joining end surface 50 of the cup member 12a and the outer diameter B2 of the joining end surface 51 of the shaft member 13a or 13b are set to an equal dimension for each joint size. Thus, the cup member prepared for common use for each joint size, and the shaft member having a variety of specifications of the shaft section for each vehicle type can be prepared in a state before heat treatment. Further, the intermediate component of each of the cup member 12a and the shaft member 13a or 13b can be assigned with a product number for management. Even when standardizing product types of the cup member 12a, various types of the outer joint members 11 satisfying requirements can be produced quickly through combination of the cup member 12a and the shaft member 13a or 13b having a variety of specifications of the shaft section for each vehicle type. Therefore, standardization of a product type of the cup member 12a can reduce cost and alleviate a burden of production management.

(95) The standardization of the product type of the cup member is described above by taking the differences in types, such as the general length stem type and the long stem type, as an example for easy understanding, but the present invention is not limited thereto. The same applies to standardization of the product type of the cup member for shaft members having a variety of specifications of the shaft section for each vehicle type among the general length stem types, and for shaft members having a variety of specifications of the shaft section for each vehicle type among the long stem types.

(96) As a summary of the above description, FIG. 12 is a diagram for illustrating an example of standardization of a product type of the cup member according to this embodiment. As illustrated in FIG. 12, the cup member is prepared for common use for one joint size, and is assigned with, for example, a product number C001 for management. In contrast, the shaft member has a variety of specifications of the shaft section for each vehicle type, and is assigned with, for example, a product number S001, S002, or S(n) for management. For example, when the cup member assigned with the product number C001 and the shaft member assigned with the product number S001 are combined and welded to each other, the outer joint member assigned with a product number A001 can be produced. Thus, owing to standardization of a product type of the cup member, it is possible to reduce cost and to alleviate a burden of production management. In the standardization of a product type, the cup member is not limited to one type for one joint size, that is, not limited to one type assigned with a single product number. For example, the cup member comprises cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size based on different specifications of a maximum operating angle, and are each prepared so that the outer diameter B1 of the joining end surface of each of those cup members has an equal dimension.

(97) FIG. 13 are each an illustration of a modified example of the outer joint member according to the first embodiment. FIG. 13 are each an enlarged illustration of an upper portion in a radial direction in the vicinity of the welded portion. FIG. 13a is a vertical sectional view for illustrating a state before welding, and FIG. 13b is a vertical sectional view for illustrating a state after welding. This modified example is different from the first embodiment in that the annular groove portion and the annular shielding portion are arranged on the joining end surface side of the cup member. The other configurations of this modified example are the same as those of the first embodiment. Thus, parts that have the same functions as those of the first embodiment are denoted by the same reference symbols (except for the subscripts), and only different points are described.

(98) As illustrated in FIG. 13a, the outer joint member 11 of this modified example comprises an annular groove portion 50a.sub.1 formed on an radially inner side of a joining end surface 50.sub.1 of a cup member 12a.sub.1 and an annular shielding portion 50b.sub.1 formed on an radially inner side thereof. An inner diameter surface 50c.sub.1 of the annular shielding portion 50b.sub.1 has an inner diameter E.sub.1. An annular groove portion 51a.sub.1 is formed at a welding joining interface immediately below a weld bead 49.sub.1 (see FIG. 13b). When the joining end surfaces 50.sub.1 and 51.sub.1 are brought into abutment against each other, a hollow cavity portion H.sub.1 is formed. The annular groove portion 50a.sub.1 is separated and shielded from the hollow cavity portion H.sub.1 by the annular shielding portion 50b.sub.1. The outer diameters B1 and B2 have equal dimensions.

(99) It was found that, when the cup member 12a.sub.1 and the shaft member 13a.sub.1, respectively having the above-mentioned configurations, are brought into abutment against each other and subjected to electron beam welding, the inner diameter end portion of the weld bead 49.sub.1 is sufficiently formed up to the annular groove portion 51a.sub.1 while a recess is not formed on the radially inner side of the weld bead 49.sub.1 as illustrated in FIG. 13b. The reason for this is considered as follows. As in the first embodiment, the internal pressure of the hollow cavity portion H.sub.1 is shielded by the annular shielding portion 50b.sub.1, and the air remaining in the annular groove portion 51a has a small volume expansion amount by heating due to the small volume of the air. Thus, the influence of the internal pressure is suppressed. With this, the strength, quality, and reliability of the welded portion can be increased. The annular groove portion 51a.sub.1 has a width of from about 1 mm to about 3 mm and a depth of from about 0.5 mm to about 2 mm. Other features and actions, that is, the overview of the respective steps, the states of the cup member and the shaft member in the main processing steps, the preparation of the cup member for common use, the welding method, the standardization of the product type, the configuration of the outer joint member, and the like as described above in the first embodiment on the manufacturing method are the same as those of the first embodiment. Therefore, all the details of the first embodiment are applied in this embodiment to omit redundant description.

(100) FIG. 14 is an illustration of a manufacturing method according to a second embodiment of the present invention. In the manufacturing steps of this embodiment, the heat treatment step for the cup member, which is involved in the heat treatment step S7 in FIG. 5 as described above in the first embodiment, is provided before the welding step S6 in the sequence and named heat treatment step S5c, to thereby prepare the cup member as a finished product. Details of other aspects of the second embodiment than this aspect, that is, details of the overview of the respective steps, the states of the cup member and the shaft member in the main processing steps, the preparation of the cup member for common use, the welding method, the standardization of the product type, the configuration of the outer joint member, and the like as described above in the first embodiment on the manufacturing method are the same as those of the first embodiment. Therefore, all the details of the first embodiment are applied in this embodiment, and only the difference is described.

(101) As illustrated in FIG. 6b, the cup member 12a has a shape extending from the joining end surface 50 to the large-diameter cylindrical portion 12a1 via the bottom portion 12a2, and the portions to be subjected to heat treatment that involves quenching and tempering are the track grooves 30 and the cylindrical inner peripheral surface 42 located at the inner periphery of the cylindrical portion 12a1. Therefore, the cup member 12a generally has no risk of thermal effect on the heat-treated portion during the welding. For this reason, the cup member 12a is subjected to heat treatment before the welding to be prepared as a finished component. The manufacturing steps of this embodiment are suitable in practical use.

(102) In the manufacturing steps of this embodiment, the cup member 12a is subjected to heat treatment for preparing the cup member 12a as a finished product, and is therefore assigned with a product number indicating a finished product for management. Thus, the standardization of the product type of the cup member 12a remarkably reduces the cost and alleviates the burden of production management. Further, the cup member 12a can be manufactured solely until the cup member 12a is completed as a finished product through the forging, turning, and heat treatment. Thus, the productivity is enhanced by virtue of reduction of setups and the like as well.

(103) In this embodiment, in FIG. 12 for illustrating the example of standardization of the product type of the cup member as described above in the first embodiment, only the product number of the cup member in FIG. 12 is changed to the product number indicating a finished product, whereas the product numbers of the shaft member and the outer joint member are the same as those of the first embodiment. Therefore, description thereof is omitted herein.

(104) FIG. 15 is an illustration of a manufacturing method according to a third embodiment of the present invention. In the manufacturing steps of this embodiment, the heat treatment steps for the cup section and the shaft section, which are involved in the heat treatment step S7 in FIG. 5 as described above in the first embodiment, and the grinding step S8 for the shaft section in FIG. 5 are provided before the welding step S6 in the sequence and named heat treatment step S5c for cup member, heat treatment step S4s for shaft member, and grinding step S5s. Thus, both the cup member and the shaft member are prepared as finished products. Details of other aspects of the third embodiment than this aspect, that is, details of the overview of the respective steps, the states of the cup member and the shaft member in the main processing steps, the preparation of the cup member for common use, the welding method, the standardization of the product type, the configuration of the outer joint member, and the like as described above in the first embodiment on the manufacturing method are the same as those of the first embodiment. Therefore, all the details of the first embodiment are applied in this embodiment, and only the difference is described.

(105) After the spline processing step S3s, a hardened layer having a hardness of approximately from 50 HRC to 62 HRC is formed in a predetermined range of the outer peripheral surface of the shaft member by induction quenching in the heat treatment step S4s. Heat treatment is not performed on a predetermined portion in the axial direction, which includes the joining end surface 51 or 51.sub.1. The heat treatment for the cup member, the assignment of the product number, and the like are the same as those of the second embodiment on the manufacturing method, and redundant description is therefore omitted herein.

(106) After the heat treatment step S4s, the shaft member is transferred to the grinding step S5s so that the bearing mounting surface 14 and the like are finished. Thus, the shaft member is obtained as a finished product. Then, the shaft member is assigned with a product number indicating a finished product for management. The manufacturing steps of this embodiment are suitable in a case of a cup member and a shaft member having shapes and specifications with no risk of thermal effect on the heat-treated portion during the welding.

(107) In the manufacturing steps of this embodiment, both the cup member and the shaft member can be assigned with product numbers indicating finished products for management. Thus, the standardization of the product type of the cup member further remarkably reduces the cost and alleviates the burden of production management. Further, the cup member and the shaft member can be manufactured independently of each other until the cup member and the shaft member are completed as finished products through the forging, turning, heat treatment, grinding after heat treatment, and the like. Thus, the productivity is further enhanced by virtue of reduction of setups and the like as well.

(108) In this embodiment, in FIG. 12 for illustrating the example of standardization of the product type of the cup member as described above in the first embodiment, the product numbers of the cup member and the shaft member in FIG. 12 are changed to the product numbers indicating finished products. The product number of the outer joint member is the same as that of the first embodiment. Therefore, description thereof is omitted herein. Note that, the cup member and the shaft member to be prepared as finished components are not limited to the cup member and the shaft member subjected to finishing such as the above-mentioned grinding after heat treatment or cutting after quenching, and encompass a cup member and a shaft member in a state in which the heat treatment is completed while the finishing is uncompleted.

(109) As described in the standardization of the product type, the cup member is not limited to one type for one joint size, that is, not limited to one type assigned with a single product number. Specifically, as described above, the cup member encompasses, for example, cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size based on different specifications of a maximum operating angle, and are also prepared so that the outer diameter B1 of the above-mentioned joining end surfaces of the cup members are set to equal dimensions. In addition, the cup member encompasses, for example, cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size in order to achieve management of the cup members in a plurality of forms including intermediate components before heat treatment and finished components in consideration of the joint function, the circumstances at the manufacturing site, the productivity, and the like, and are also prepared so that the outer diameters B1 of the above-mentioned joining end surfaces of the cup members are set to equal dimensions.

(110) Next, an outer joint member according to a second embodiment of the present invention is described with reference to FIG. 16 and FIG. 17. In this embodiment, parts that have the same function as those of the outer joint member according to the first embodiment are denoted by the same reference symbols (excluding subscripts), and only main points are described.

(111) A plunging type constant velocity universal joint 10.sub.2 illustrated in FIG. 16 is a tripod type constant velocity universal joint (TJ), and comprises an outer joint member 11.sub.2 comprising a cup section 12.sub.2 and the long stem section 13 that extends from a bottom portion of the cup section 12.sub.2 in the axial direction, an inner joint member 16.sub.2 housed along an inner periphery of the cup section 12.sub.2 of the outer joint member 11.sub.2, and rollers 19 serving as torque transmitting elements that are arranged between the outer joint member 11.sub.2 and the inner joint member 16.sub.2. The inner joint member 16.sub.2 comprises a tripod member 17 comprising three equiangular leg shafts 18 on which the rollers 19 are externally fitted.

(112) Similarly to the outer joint member according to the first embodiment, the inner ring of the support bearing 6 is fixed to the outer peripheral surface of the long stem section 13, and the outer ring of the support bearing 6 is fixed to the transmission case with the bracket (not shown). The outer joint member 11.sub.2 is supported by the support bearing 6 in a freely rotatable manner, and thus the vibration of the outer joint member 11.sub.2 during driving or the like is prevented as much as possible.

(113) FIG. 17 are each an illustration of an outer joint member 11.sub.2. FIG. 17a is a partial vertical sectional view of the outer joint member 11.sub.2, and FIG. 17b is a vertical sectional view for illustrating a state of a portion A of FIG. 17a before welding. As illustrated in FIG. 17, the outer joint member 11.sub.2 comprises a bottomed cylindrical cup section 12.sub.2 that is opened at one end and has inner peripheral surfaces 31.sub.2 and the track grooves 30.sub.2, on which the rollers 19 (see FIG. 16) are caused to roll, formed at three equiangular positions on an inner peripheral surface of the cup section 12.sub.2, and the long stem section 13 that extends from a bottom portion of the cup section 12.sub.2 in the axial direction and comprises the spline Sp serving as the torque transmitting coupling portion formed at the outer periphery of the end portion on the opposite side to the cup section 12.sub.2 side. The outer joint member 11.sub.2 is formed by welding the cup member 12a.sub.2 and the shaft member 13a to each other.

(114) As illustrated in FIG. 17a, the cup member 12a.sub.2 is an integrally-formed product having a cylindrical portion 12a1.sub.2 and a bottom portion 12a2.sub.2. The cylindrical portion 12a1.sub.2 has the track grooves 30.sub.2 and the inner peripheral surfaces 31.sub.2 formed at the inner periphery thereof. A projecting portion 12a3.sub.2 is formed at the bottom portion 12a2.sub.2 of the cup member 12a.sub.2. The boot mounting groove 32 is formed at an outer periphery of the cup member 12a.sub.2 on the opening side thereof. The bearing mounting surface 14 and the snap ring groove 15 are formed at the outer periphery of the shaft member 13a on the cup member 12a.sub.2 side, whereas the spline Sp is formed at the end portion on the opposite side to the cup member 12a.sub.2 side. As in the first embodiment, the annular groove portion 51a is formed on the radially inner side of the joining end surface 51 of the shaft member 13a, and the annular shielding portion 51b is further formed on the radially inner side thereof. The annular groove portion 51a is formed at the welding joining interface immediately below the weld bead 49. When joining end surfaces 50.sub.2 and 51 are brought into abutment against each other, the hollow cavity portion H is formed. The annular groove portion 51a is separated and shielded from the hollow cavity portion H by the annular shielding portion 51b.

(115) As illustrated in FIG. 17b, the joining end surface 50.sub.2 of the cup member 12a.sub.2 and the joining end surface 51 of the shaft member 13a are brought into abutment against each other and welded by electron beam welding from a radially outer side. The welded portion 49 is formed of a bead formed by a beam radiated from a radially outer side of the cup member 12a.sub.2. The outer diameter B1 of the joining end surface 50.sub.2 and the outer diameter B2 of the joining end surface 51 have equal dimensions. The outer diameters B1 and B2 are respectively set to an equal dimension for each joint size. The welded portion 49 is formed on the joining end surface 51 on the cup member 12a.sub.2 side from the bearing mounting surface 14 of the shaft member 13a. Therefore, the bearing mounting surface 14 and the like can be processed in advance, and hence post-processing after the welding can be omitted. The above-mentioned welding comprises electron beam welding. Thus, burrs are not generated on the joining portion. Therefore, the post-processing of the welded portion can be omitted to reduce manufacturing cost.

(116) The details of the outer joint member according to this embodiment are the same as the details of the outer joint member according to the first embodiment, and the manufacturing method according to the first to third embodiments as described above. Therefore, all of those details are applied in this embodiment to omit redundant description.

(117) In any of the above-mentioned embodiments and modified examples, as the shape of the welded portion, the annular groove portion separated and shielded from the hollow cavity portion is arranged at the welding joining interface on the radially inner side of the joining end surface of the cup member or the joining end surface of the shaft member. Therefore, the recess on the radially inner side of the weld bead is suppressed, and the problems of the cutaway effect of the welded portion and the reduction in joining area can be avoided to prevent a decrease in strength of welding. As a result, the strength, quality, and reliability of the welded portion can be increased.

(118) In the above-mentioned embodiments and the above-mentioned modified examples, the case to which electron beam welding is applied is described, but laser welding is also similarly applicable.

(119) In the outer joint member according to the embodiments and the modified examples described above, the cases where the present invention is applied to the double-offset type constant velocity universal joint as the plunging type constant velocity universal joint 10, and to the tripod type constant velocity universal joint as the plunging type constant velocity universal joint 10 are described. However, the present invention may be applied to an outer joint member of another plunging type constant velocity universal joint such as a cross-groove type constant velocity universal joint, and to an outer joint member of a fixed type constant velocity universal joint. Further, in the above, the present invention is applied to the outer joint member of the constant velocity universal joint, which is used to construct the drive shaft. However, the present invention may be applied to an outer joint member of a constant velocity universal joint, which is used to construct a propeller shaft.

(120) The present invention is not limited to the above-mentioned embodiments and the above-mentioned modified examples. As a matter of course, various modifications can be made thereto without departing from the gist of the present invention. The scope of the present invention is defined in Claims, and encompasses equivalents described in Claims and all changes within the scope of claims.

DESCRIPTION OF REFERENCE SIGNS

(121) 1 drive shaft 2 intermediate shaft 3 spline 4 boot 5 boot 6 support bearing 10 plunging type constant velocity universal joint 11 outer joint member 12 cup section 12a cup member 12a1 cylindrical portion 12a2 bottom portion 13 long shaft section 13a shaft member 13a billet 13a preform 14 bearing mounting surface 16 inner joint member 17 tripod member 19 torque transmitting element (roller) 20 fixed type constant velocity universal joint 21 outer joint member 22 inner joint member 23 torque transmitting element (ball) 24 cage 30 track groove 31 inner peripheral surface 40 track groove 41 torque transmitting element (ball) 42 cylindrical inner peripheral surface 49 welded portion 50 joining end surface 50a annular groove portion 50b annular shielding portion 51 joining end surface 51a annular groove portion 51b annular shielding portion 52 recessed portion 54 step portion 100 welding apparatus 101 electron gun 108 case 109 vacuum pump 111 sealed space B1 outer diameter B2 outer diameter H hollow cavity portion O joint center O1 curvature center O2 curvature center Sp spline