MANUFACTURING METHOD FOR CONSTANT VELOCITY UNIVERSAL JOINT OUTER JOINT MEMBER 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 of medium carbon steel, the cup member being manufactured by preparing a cup member having cylindrical and bottom portions being integrally formed, and a fitting hole formed in a thick portion of the bottom portion, the shaft member being manufactured by preparing a shaft member having a fitting outer surface formed at an end portion of the shaft member to be joined to the bottom portion of the cup member, and fitting the fitting hole of the cup member to the fitting outer surface of the shaft member. The method also includes welding the cup and shaft members from an inner side of the cup member to a fitted portion between the cup and shaft members.

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 of medium carbon steel, the cup member being manufactured by preparing a cup member having a cylindrical portion and a bottom portion being integrally formed, and a fitting hole formed in a thick portion of the bottom portion in a machining step, the shaft member being manufactured by preparing a shaft member having a fitting outer surface formed at an end portion of the shaft member to be joined to the bottom portion of the cup member, which is formed in a machining step; fitting the fitting hole of the cup member to the fitting outer surface of the shaft member; and welding the cup member and the shaft member by radiating a beam from an inner side of the cup member to a fitted portion between the cup member and the shaft member, wherein the fitting hole of the cup member and the fitting outer surface of the shaft member are formed of a joining portion having a gap and a press-fitting portion having an interference, and an axial dimension of the joining portion is set to be larger than an axial dimension of the press-fitting portion, the joining portion serving as a press-fitting guide.

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

3. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the press-fitting portion has a diameter dimension larger than a diameter dimension of the joining portion, and the press-fitting portion is arranged on an outer side in the thick portion of the bottom portion of the cup member.

4. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the joining portion has the gap having a diameter of 0.5 mm or less.

5. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein, before the welding, at least one of the cup member and the shaft member is subjected to finishing processing after heat treatment.

6. 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.

7. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the welding is performed under a state in which an inner portion of the cup section is at an atmospheric pressure or less.

8. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the cup section and the shaft section are welded to each other in a state of being cooled.

9. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein at least one of pre-heating before the welding and post-heating after the welding is performed to heat the joining portion of the cup section and the shaft section to from 200 C. to 650 C.

10. An outer joint member of a constant velocity universal joint, comprising: 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, the outer joint member being constructed by forming the cup section and the shaft section through use of separate members, and by welding a cup member forming the cup section and a shaft member forming the shaft section, the cup member and the shaft member being formed of medium carbon steel, the cup member having a cylindrical portion and a bottom portion being integrally formed, and a fitting hole formed in a thick portion of the bottom portion, the shaft member having a fitting outer surface formed at an end portion of the shaft member to be joined to the bottom portion of the cup member, the cup member and the shaft member being welded to each other under a state in which the fitting outer surface is fitted to the fitting hole, the outer joint member comprising a welded portion between the cup member and the shaft member, which is formed of a bead formed by a beam radiated from an inner side of the cup member, wherein the fitting hole of the cup member and the fitting outer surface of the shaft member are formed of a joining portion and a press-fitting portion, and an axial dimension of the joining portion is set to be larger than an axial dimension of the press-fitting portion, the joining portion serving as a press-fitting guide.

11. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 10, wherein the joining portion of the cup member has an inner diameter set to an equal dimension for each joint size.

12. The outer joint member of a constant velocity universal joint according to claim 10, wherein the press-fitting portion has a diameter dimension larger than a diameter dimension of the joining portion, and the press-fitting portion is arranged on an outer side in the thick portion of the bottom portion of the cup member.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] 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.

[0034] FIG. 2a is an enlarged partial vertical sectional view for illustrating the outer joint member of FIG. 1.

[0035] FIG. 2b is an enlarged side view for illustrating the outer joint member of FIG. 1.

[0036] FIG. 2c is an enlarged view for illustrating a portion A of FIG. 2a.

[0037] FIG. 3 is a diagram for illustrating an overview of manufacturing steps for the outer joint member of FIG. 1.

[0038] FIG. 4 is a vertical sectional view for illustrating a cup member before welding.

[0039] FIG. 5 is a front view for illustrating a shaft member before welding.

[0040] FIG. 6 is a partial vertical sectional view for illustrating a state in which the cup member and the shaft member are fitted to each other before welding.

[0041] FIG. 7a is a partial vertical sectional view for illustrating details of a fitting hole of the cup member and a fitting outer surface of the shaft member and a centering operation during press-fitting, and for illustrating a state at the start of press-fitting.

[0042] FIG. 7b is a partial vertical sectional view for illustrating details of the fitting hole of the cup member and the fitting outer surface of the shaft member and the centering operation during press-fitting, and for illustrating a state at the end of press-fitting.

[0043] FIG. 8 is a view for illustrating an overview of a welding method in a manufacturing method according to a first embodiment of the present invention.

[0044] FIG. 9 is a front view for illustrating a shaft member assigned with a different product number.

[0045] FIG. 10 is a partial vertical sectional view for illustrating an outer joint member that is manufactured using the shaft member illustrated in FIG. 9.

[0046] FIG. 11 is a diagram for illustrating an example of standardization of a product type of the cup member.

[0047] FIG. 12 is a diagram for illustrating an overview of a modified example of the manufacturing steps for the outer joint member according to the first embodiment.

[0048] FIG. 13 is a diagram for illustrating manufacturing steps in a manufacturing method according to a second embodiment of the present invention.

[0049] FIG. 14 is a diagram for illustrating manufacturing steps in a manufacturing method according to a third embodiment of the present invention.

[0050] FIG. 15 is a partial vertical sectional view for illustrating a constant velocity universal joint using an outer joint member according to the second embodiment of the present invention.

[0051] FIG. 16 is a vertical sectional view for illustrating the outer joint member of FIG. 15.

[0052] FIG. 17 is a vertical sectional view for illustrating an outer joint member according to a related art.

[0053] FIG. 18 is a vertical sectional view for illustrating the outer joint member according to the related art.

[0054] FIG. 19 is a vertical sectional view for illustrating an outer joint member according to a related art.

EMBODIMENTS OF THE INVENTION

[0055] Now, description is made of embodiments of the present invention with reference to the drawings.

[0056] FIG. 3 to FIG. 11 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 and FIG. 2 are illustrations of an outer joint member according to the first embodiment of the present invention. First, the outer joint member according to the first embodiment is described with reference to FIG. 1 and FIG. 2, and FIG. 6 and FIG. 7 as needed. Subsequently, the method of manufacturing an outer joint member according to the first embodiment is described with reference to FIG. 3 to FIG. 11.

[0057] 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.

[0058] The plunging type constant velocity universal joint 10 illustrated in FIG. 1 is a so-called tripod type constant velocity universal joint (TJ), and comprises an outer joint member 11 comprising a cup section 12 and a long shaft section (long stem section) 13 that extends from a bottom portion of the cup section 12 in the axial direction, an inner joint member 16 housed along an inner periphery of the cup section 12 of the outer joint member 11, and a roller 19 serving as a torque transmitting element that is arranged between the outer joint member 11 and the inner joint member 16. The inner joint member 16 comprises a tripod member 17 comprising three equiangular leg shafts 18 on which the roller 19 is externally fitted.

[0059] 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.

[0060] 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.

[0061] 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 tripod member 17 of the plunging type constant velocity universal joint 10. Thus, the intermediate shaft 2 and the tripod member 17 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.

[0062] 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.

[0063] 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 a side view. FIG. 2c is an enlarged view for illustrating a portion A of FIG. 2a. The outer joint member 11 comprises the bottomed cylindrical cup section 12 that is opened at one end and has plurality of track grooves 30 and an inner peripheral surface 31, on which the roller 19 (see FIG. 1) is caused to roll, formed at trisecting positions 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 (inboard side) to an opening side of 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.

[0064] As illustrated in FIG. 2a and FIG. 2c, the cup member 12a is an integrally-formed product comprising a cylindrical portion 12a1 having the track grooves 30 and the inner peripheral surface 31 at an inner periphery and a bottom portion 12a2. The shaft member 13a comprises a bearing mounting surface 14 and a snap ring groove 15 formed at an outer periphery of the shaft member 13a on the cup member 12a side and comprises a spline Sp formed at an end portion of the shaft member 13a on an inboard side. As illustrated in FIG. 6 and FIG. 7, a fitting hole 50 of the bottom portion 12a2 of the cup member 12a and a fitting outer surface 51 of the end portion of the shaft member 13a on an outboard side are fitted to each other, and a joining portion 50a of the fitting hole 50 and a joining portion 51a of the fitting outer surface 51 are welded to each other through electron beam welding. As illustrated in FIG. 2a and FIG. 2c, a welded portion 49 is formed of a bead formed by a beam radiated from an inner side of the cup member 12a.

[0065] Details of the features of the outer joint member 11 of this embodiment, that is, the fitting hole 50 of the cup member 12a and the fitting outer surface 51 of the shaft member 13a are described with reference to FIG. 7. As illustrated in FIG. 7a, the fitting hole 50 is formed in a thick portion of the bottom portion 12a2 of the cup member 12a, and the fitting hole 50 comprises the joining portion 50a and a press-fitting portion 50b. The fitting outer surface 51 of the shaft member 13a comprises the joining portion 51a and a press-fitting portion 51b.

[0066] An inner diameter B1 of the joining portion 50a of the cup member 12a is set to be slightly larger than an outer diameter B2 of the joining portion 51a of the shaft member 13a, and a gap having a diameter of 0.5 mm or less is formed between the inner diameter B1 and the outer diameter B2. Meanwhile, an inner diameter C1 of the press-fitting portion 50b of the cup member 12a is set to be slightly smaller than an outer diameter C2 of the press-fitting portion 51b of the shaft member 13a, and an interference is formed between the inner diameter C1 and the outer diameter C2. An axial dimension D of the joining portions 50a and 51a is set to be larger than an axial dimension E of the press-fitting portions 50b and 51b. Diameter dimensions C1 and C2 of the press-fitting portions 50b and 51b are set to be larger than diameter dimensions B1 and B2 of the joining portions 50a and 51a, and the press-fitting portions 50b and 51b are arranged on an outer side (right side of FIG. 7a) in the thick portion of the bottom portion 12a2 of the cup member 12a. In FIG. 2a and FIG. 2c, the melted welded portion 49 is illustrated, but it is understood that the diameter dimensions C1 and C2 of the press-fitting portions 50b and 51b are set to be larger than the diameter dimensions B1 and B2 of the joining portions 50a and 51a.

[0067] The above-mentioned dimension relationship is set, and hence, during press-fitting, first, as illustrated in FIG. 7a, the joining portion 51a of the shaft member 13a is faced to the joining portion 50a of the cup member 12a. Then, through use of the joining portions 50a and 51a as press-fitting guides, the press-fitting portion 50b of the cup member 12a and the press-fitting portion 51b of the shaft member 13a are brought into abutment against each other while the cup member 12a and the shaft member 13a are being centered. Under a state in which the cup member 12a and the shaft member 13a are centered, the press-fitting portions 50b and 51b are press-fitted to each other, and thus a press-fitting step is completed as illustrated in FIG. 7b. The press-fitting is performed as described above, and hence the coaxiality of the cup member 12a and the shaft member 13a is enhanced. Further, as described above, the centering operability in the press-fitting step is enhanced.

[0068] The diameter of the gap between the inner diameter B1 of the joining portion 50a of the cup member 12a and the outer diameter B2 of the joining portion 51a of the shaft member 13a is set to 0.5 mm or less, and hence the press-fitting is not performed in the joining portions 50a and 51a. Thus, the effect of the press-fitting guides can be obtained, and a satisfactory welded portion can be obtained without any defects such as the surface recess of the welded portion and burn-through. The gap is illustrated in an exaggerated manner for easy understanding.

[0069] Further, the diameter dimensions C1 and C2 of the press-fitting portions 50b and 51b are set to be larger than the diameter dimensions B1 and B2 of the joining portions 50a and 51a, and the press-fitting portions 50b and 51b are arranged on an outer side (right side of FIG. 7a) in the thick portion of the bottom portion 12a2 of the cup member 13a. Therefore, as illustrated in FIG. 7a, the press-fitting can be performed through the shaft member 13a from the bottom portion 12a2 of the cup member 13a, which enhances productivity.

[0070] Although detailed description is made later, the inner diameter B1 of the joining portion 50a of the cup member 12a is set to an equal dimension for each joint size. The welded portion 49 is formed at the end portion of the shaft member 13a, and hence post-processing of the bearing mounting surface 14 and the like can be omitted. Further, due to the electron beam welding, burrs are not generated in the welded portion, and hence post-processing of the welded portion can also be omitted, which can reduce manufacturing cost. Further, total inspection on the welded portion through ultrasonic flaw detection can be securely performed.

[0071] Next, the manufacturing method according to the first embodiment of the present invention is described with reference to FIG. 3 to FIG. 11. FIG. 3 is a diagram for illustrating an overview of manufacturing steps for the outer joint member. As illustrated in FIG. 3, the cup member 12a is processed into a finished component through main manufacturing steps comprising a bar material cutting step S1c, a forging step S2c, an ironing step S3c, a turning step S4c, and a heat treatment step S5c. Meanwhile, the shaft member 13a is processed into a finished component through main manufacturing steps comprising a bar material cutting step S1s, a turning step S2s, a spline processing step S3s, a heat treatment step S4s, and a grinding step S5s. The cup member 12a and the shaft member 13a as the finished components are each assigned with a product number for management. After that, the cup member 12a and the shaft member 13a are subjected to a welding step S6, to thereby complete the outer joint member 11. The machining step in Claims of the present invention corresponds to the turning step S4c, the turning step S2s, and the grinding step S5s of the above-mentioned manufacturing steps.

[0072] 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.

[0073] [Bar Material Cutting Step S1c]

[0074] A bar material is cut into a predetermined length in accordance with a forging weight, thereby producing a billet.

[0075] [Forging Step S2c]

[0076] The billet is subjected to forging to integrally form the cylindrical portion 12a1 and the bottom portion 12a2 of the cup member 12a, thereby forming a preform.

[0077] [Ironing Step S3c]

[0078] Ironing is performed on the track grooves 30 and the cylindrical inner peripheral surface 31 of the preform, thereby finishing the inner periphery of the cylindrical portion 12a1 of the cup member 12a.

[0079] [Turning Step S4c]

[0080] In the preform after ironing, the outer peripheral surface, a boot mounting groove 32, and the like, and the fitting hole 50 are formed by turning in the thick portion of the bottom portion 12a2.

[0081] [Heat Treatment Step S5c]

[0082] After turning, quenching and tempering are performed as heat treatment on at least the track grooves 30 of the cup section 12a. With this, the cup member 12a is processed into a finished component and assigned with a product number for management.

[0083] Next, the manufacturing steps for the shaft member 13a are described.

[Bar Material Cutting Step S1s]

[0084] 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.

[0085] [Turning Step S2s]

[0086] 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 fitting outer surface 51 on the outboard side end portion are formed by turning.

[0087] [Spline Processing Step S3s]

[0088] 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.

[0089] [Heat Treatment Step S4s]

[0090] Induction quenching and tempering are performed as heat treatment on a necessary range of the outer periphery of the shaft member. Heat treatment is not performed on the fitting outer surface at a shaft end.

[0091] [Grinding Step S5s]

[0092] After the heat treatment, the bearing mounting surface 14 of the shaft section 13a and the like are finished by grinding. Thus, the shaft member 13a is completed and assigned with a product number for management.

[0093] [Welding Step S6]

[0094] The cup member 12a and the shaft member 13a as the finished components are fitted and welded to each other. With this, the outer joint member 11 is completed.

[0095] Next, main constituent features of the manufacturing method of this embodiment are described. FIG. 4 is a vertical sectional view for illustrating a state before welding of the cup member 12a as the finished component. The cup member 12a comprises the cylindrical portion 12a1 having the track grooves 30 and the inner peripheral surface 31 at an inner periphery and the bottom portion 12a2 that extends radially inward from the end portion on the inboard side thereof, and comprises the fitting hole 50 in the thick portion of the bottom portion 12a2. The cup member 12a is formed of medium carbon steel such as S53C, containing carbon of from 0.40 wt % to 0.60 wt %. The fitting hole 50 is subjected to cutting work in the turning step S4c described above. Although illustration is omitted, a hardened layer having a hardness of approximately from 58 HRC to 62 HRC is formed on each of the track grooves 30 and other predetermined portions.

[0096] FIG. 5 is an illustration of a state before welding of the shaft member 13a as the finished component. The shaft member 13a comprises the fitting outer surface 51 to be fitted to the fitting hole 50 of the cup member 12a at the end portion on the outboard side (left side of FIG. 5), the bearing mounting surface 14 and the snap ring groove 15 on the inboard side (right side of FIG. 5) of the fitting outer surface 51, and the spline Sp at the end portion on the inboard side. The shaft member 13a is formed of medium carbon steel, such as S40C, containing carbon of from 0.30 wt % to 0.55 wt %. Although illustration is omitted, a hardened layer having a hardness of approximately from 50 HRC to 62 HRC is formed on a predetermined range of the outer periphery by induction quenching as heat treatment. Heat treatment is not performed on the fitting outer surface 51. After the heat treatment step S4s, the bearing mounting surface 14 is finished by grinding or the like.

[0097] As described above, the inner diameter B1 of the joining portion 50a of the cup member 12a illustrated in FIG. 4 is set to an equal dimension for one joint size. In the shaft member 13a illustrated in FIG. 5, which is used as a long stem shaft, the outer diameter B2 of the joining portion 51a at the end portion on the outboard side to be fitted to the joining portion 50a is set to a dimension having the predetermined gap (see FIG. 7a) from the inner diameter B1 of the joining portion 50a irrespective of the shaft diameter and the outer peripheral shape. 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.

[0098] The cup member 12a and the shaft member 13a as the finished products manufactured as described above are subjected to press-fitting as illustrated in FIG. 6. As illustrated in FIG. 7b, the press-fitting portion 50b of the cup member 12a and the press-fitting portion 51b of the shaft member 13a are subjected to press-fitting, and hence both the members 12a and 13a are temporarily fixed in a state of being centered coaxially.

[0099] The details of the dimensional relationship of the fitting hole 50, the joining portion 50a, and the press-fitting portion 50b of the cup member 12a and the fitting outer surface 51, the joining portion 51a, and the press-fitting portion 51b of the shaft member 13a, the states of the cup member 12a and the shaft member 13a during press-fitting, and the action and effect are as described above with reference to FIG. 7a and FIG. 7b.

[0100] Next, the welding step S6 in the manufacturing method according to the first embodiment of the present invention is described with reference to FIG. 8. FIG. 8 is a view for illustrating an overview of the welding step S6. The cup member 12a and the shaft member 13a that are temporarily fixed through press-fitting are set on a welding apparatus (not shown). As illustrated in FIG. 8, a seal member 53 arranged at a cover member 52 is brought into abutment against an opening end portion of the cup member 12a to form a sealed space 54 in the cup member 12a. An electron gun 55 is arranged on the cover member 52, and a vacuum pump 56 configured to evacuate the sealed space 54 is connected to the cover member 52 through intermediation of a pipeline 57. Cooling jackets 58 are arranged on an outer side of the outer peripheral surface of the cup member 12a and on an outer side of the outer peripheral surface of the shaft member 13a, respectively.

[0101] Specifically, the seal member 53 arranged at the cover member 52 is brought into abutment against the opening end portion of the cup member 12a to form the sealed space 54 in the cup member 12a, and then, the sealed space 54 is evacuated to about 1.3 Pa which is equal to or less than an atmospheric pressure. In this embodiment, the sealed space 54 is limited in the cup member 12a, and the space volume is reduced. Therefore, the cycle time for evacuation is reduced. Along with the evacuation, in order to prevent rapid cooling after the welding to suppress increase in hardness of the welded portion, the periphery including the fitting hole 50 (see FIG. 6) and the fitting outer surface 51 is subjected to pre-heating to have a temperature of from 200 C. to 650 C. with an electron beam 59. The pre-heating is performed by enlarging the beam width of the electron beam 59 and turning the beam at high speed. After the pre-heating, as illustrated in FIG. 8, the beam of the electron beam 59 is narrowed down, to thereby perform welding. In this case, the welding is performed under the condition where the outer periphery of the cylindrical portion 12a1 of the cup member 12a and the outer periphery of the periphery of the bearing mounting surface 14 of the shaft member 13a are being cooled with the cooling jacket 58. Through adjustment of the hardness of the welded portion to from 200 Hv to 500 Hv by the pre-heating, a satisfactory welded portion that satisfies required strength can be obtained, and decrease in hardness of a region subjected to heat treatment can be prevented.

[0102] The above-mentioned welding step S6 is described with an example in which the pre-heating is performed before the welding in order to adjust the hardness of the welded portion. However, the joining portion may be subjected to post-heating to have a temperature of from 200 C. to 650 C. after the welding, to thereby adjust the hardness of the welded portion. Further, the pre-heating and the post-heating may be performed with a heat source such as induction heating in place of the electron beam.

[0103] Next, 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. 5. A shaft member 13a illustrated in FIG. 9 and FIG. 10 is used as a general stem type on the inboard side. The shaft member 13a has the fitting outer surface 51 to be fitted to the fitting hole 50 (see FIG. 4) of the bottom portion 12a2 of the cup member 12a. The outer diameter B2 of the joining portion 51a of the fitting outer surface 51 is set to the equal dimension to the outer diameter B2 of the fitting outer surface 51 of the shaft member 13a of the long stem type illustrated in FIG. 5.

[0104] The shaft member 13a is used as the general stem type on the inboard side. Accordingly, the shaft member 13a 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 13a on the inboard 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 outer diameter B2 of the joining portions 51a of the fitting outer surfaces 51 of the shaft members 13a and 13a are set to an equal dimension.

[0105] The inner diameter B1 of the joining portion 50a of the fitting hole 50 of the cup member 12a is 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 as finished components. Further, the cup member and the shaft member can be assigned with a product number for management. Even with standardization of product types of the cup member, various types of the outer joint members 11 satisfying requirements can be produced quickly through combination of the cup member and the shaft member having a variety of specifications of the shaft section for each vehicle type. Therefore, standardization of a product type of the cup member can reduce cost and alleviate a burden of production management.

[0106] As a summary of the above description, FIG. 11 is a diagram for illustrating an example of standardization of a product type of the cup member. As illustrated in FIG. 11, 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 diameter of the joining portion of each of those cup members has an equal dimension.

[0107] FIG. 12 is an illustration of a modified example obtained by partially changing the manufacturing steps illustrated in FIG. 3. In the manufacturing steps of FIG. 12, the grinding step S5s for the shaft member of FIG. 3 is changed to a grinding step S7 after the welding step S6. In the manufacturing steps, the cup member and the shaft member are welded to each other, and then, the bearing mounting surface and the sliding bearing surface of the shaft member are finished by grinding. Therefore, in the heat treatment step S4s in the manufacturing steps for the shaft member of FIG. 12, there is described substantial completion of shaft member. The other features are the same as those of the manufacturing steps illustrated in FIG. 3. Thus, the same processing steps are denoted by the same reference symbols to omit redundant description. In Specification and Claims of the present invention, the cup member and the shaft member as the finished components are not limited to members subjected to finishing (e.g., bearing mounting surface and sliding bearing surface) such as the grinding after the heat treatment or the cutting work after the quenching as described above in the first embodiment, and the cup member and the shaft member encompass members assuming a state after completion of heat treatment but before being subjected to the finishing.

[0108] Next, a manufacturing method according to a second embodiment of the present invention is described with reference to FIG. 13. The manufacturing steps of the first embodiment and the modified example described above are based on the cup member and the shaft member as the finished components. However, the second embodiment is different from the manufacturing steps of the first embodiment and the modified example in that the shaft member is prepared as an intermediate component obtained through the steps up to spline processing although the cup member is prepared as a finished component. 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.

[0109] As illustrated in FIG. 13, in this embodiment, the heat treatment step S4s and the grinding step S5s for the shaft member 13a in FIG. 3 are inserted as a heat treatment step S7 and a grinding step S8 after the welding step S6. In this embodiment, the heat treatment step S7 for the shaft member 13a is performed after the welding step S6. Therefore, there is no problem of reduction in hardness of a region subjected to heat treatment caused by increase in temperature of a peripheral portion due to heat generated during the welding, and the cooling jacket 58 configured to cool the outer periphery of the periphery of the bearing mounting surface 14 of the shaft member 13a in FIG. 8 can be omitted.

[0110] As illustrated in FIG. 4, the cup member 12a has a shape extending from the fitting hole 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 inner peripheral surface 31 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.

[0111] In this embodiment, in FIG. 11 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 shaft member in FIG. 11 is changed to the product number indicating an intermediate product, whereas the product numbers of the cup member and the outer joint member are the same as those of the first embodiment. Therefore, description thereof is omitted herein.

[0112] A manufacturing method according to a third embodiment of the present invention is described with reference to FIG. 14. In this embodiment, the heat treatment step S5c for the cup member of the second embodiment is further inserted as a heat treatment step S7 after the welding step S6. 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.

[0113] As illustrated in FIG. 14, in this embodiment, the heat treatment step S7 for the cup member 12a and the shaft member 13a is performed after the welding step S6. Therefore, there is no problem of reduction in hardness of a region subjected to heat treatment caused by increase in temperature of a peripheral portion due to heat generated during the welding, and the cooling jacket 58 of FIG. 8 can be omitted.

[0114] In this embodiment, in FIG. 11 for illustrating the standardization of the product type of the cup member described above in the first embodiment, both the product numbers of the cup member and the shaft member of FIG. 11 serve as product numbers of intermediate components. The other aspects are the same as those of the first embodiment, and hence description is omitted.

[0115] Next, an outer joint member according to a second embodiment of the present invention is described with reference to FIG. 15 and FIG. 16. 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). Therefore, description thereof is omitted herein.

[0116] A plunging type constant velocity universal joint 10.sub.1 illustrated in FIG. 15 is a double-offset constant velocity universal joint (DOJ). The constant velocity universal joint 10.sub.1 comprises an outer joint member 11.sub.1 comprising a cup section 12.sub.1 and the long stem section 13 that extends from a bottom portion of the cup section 12.sub.1 in an axial direction, an inner joint member 16.sub.1 housed along an inner periphery of the cup section 12.sub.1 of the outer joint member 11.sub.1, balls 41 serving as torque transmitting elements that are arranged between the outer joint member 11.sub.1 and track grooves 30.sub.1 and 40 of the inner joint member 16.sub.1, 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.sub.1 and a spherical outer peripheral surface 43 of the inner joint member 16.sub.1, 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 from a joint center O toward opposite sides in the axial direction.

[0117] Similarly to the first embodiment for describing the outer joint member, 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.1 is supported by the support bearing 6 in a freely rotatable manner, and thus the vibration of the outer joint member 11.sub.1 during driving or the like is prevented as much as possible.

[0118] FIG. 16 is a partial vertical sectional view of the outer joint member 11.sub.1. As illustrated in FIG. 16, the outer joint member 11.sub.1 comprises the bottomed cylindrical cup section 12.sub.1 that is opened at one end and has the six or eight track grooves 30.sub.1, on which the balls 41 (see FIG. 15) are arranged, formed on the inner peripheral surface 42, and the long stem section 13 that extends from the bottom portion of the cup section 12.sub.1 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 (inboard side) to the cup section 12.sub.1. In the same manner as in the first embodiment, the outer joint member 11.sub.1 is formed by welding a cup member 12a.sub.1 and a shaft member 13a to each other.

[0119] A fitting hole 50.sub.1 is formed in a thick portion of a bottom portion 12a2.sub.1 of the cup member 12a.sub.1, and the fitting hole 50.sub.1 comprises a joining portion 50a.sub.1 and a press-fitting portion 50b.sub.1. A fitting outer surface 51.sub.1 of the shaft member 13a comprises a joining portion 51a.sub.1 and a press-fitting portion 51b.sub.1. The press-fitting portions 50b.sub.1 and 51b.sub.1 are arranged on an outer side (right side of FIG. 16) in the thick portion of the bottom portion 12a2.sub.1 of the cup member 13a.sub.1.

[0120] 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.

[0121] In the above-mentioned embodiments, the case to which electron beam welding is applied is described, but laser welding is also similarly applicable.

[0122] In the outer joint member according to the embodiments described above, the cases where the present invention is applied to the tripod type constant velocity universal joint as the plunging type constant velocity universal joint 10, and to the double-offset constant velocity universal joint as the plunging type constant velocity universal joint 10.sub.1 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.

[0123] The present invention is not limited to the above-mentioned embodiments. 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

[0124] 1 drive shaft [0125] 2 intermediate shaft [0126] 3 spline [0127] 4 boot [0128] 5 boot [0129] 6 support bearing [0130] 10 plunging type constant velocity universal joint [0131] 11 outer joint member [0132] 12 cup section [0133] 12a cup member [0134] 12a1 cylindrical portion [0135] 12a2 bottom portion [0136] 13 long shaft section [0137] 13a shaft member [0138] 14 bearing mounting surface [0139] 16 inner joint member [0140] 17 tripod member [0141] 19 torque transmitting element (roller) [0142] 20 fixed type constant velocity universal joint [0143] 21 outer joint member [0144] 22 inner joint member [0145] 23 torque transmitting element (ball) [0146] 24 cage [0147] 30 track groove [0148] 31 inner peripheral surface [0149] 40 track groove [0150] 41 torque transmitting element (ball) [0151] 49 welded portion [0152] 50 fitting hole [0153] 50a joining portion [0154] 50b press-fitting portion [0155] 51 fitting outer surface [0156] 51a joining portion [0157] 51b press-fitting portion [0158] 52 cover member [0159] 54 sealed space [0160] 55 electron gun [0161] 56 vacuum pump [0162] 58 cooling jacket [0163] 59 electron beam [0164] B1 diameter dimension (inner diameter) [0165] B2 diameter dimension (outer diameter) [0166] C1 diameter dimension (inner diameter) [0167] C2 diameter dimension (outer diameter) [0168] D axial dimension [0169] E axial dimension [0170] O joint center [0171] O.sub.1 curvature center [0172] O.sub.2 curvature center [0173] Sp spline [0174] gap