Outer joint member of constant velocity universal joint

Abstract

Provided is a method of manufacturing an outer joint member of a constant velocity universal joint, which is constructed by forming a cup section having track grooves, and a shaft section, and by welding a cup member and a shaft member, the method including: forming the cup member and the shaft member of medium carbon steel; preparing a cup member having a cylindrical portion and a bottom portion integrally formed by forging, and a joining end surface in a machining step; preparing a shaft member having a joining end surface formed in a 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; welding the cup member and the shaft member by radiating a beam; and performing, after the welding, an ultrasonic flaw detection-inspection step.

Claims

1. 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 integrally formed by forging, and a joining end surface formed on an outer surface of the bottom portion by machining, the shaft member having a joining end surface to be joined to the joining end surface of the cup member, the joining end surface of the shaft member being formed by machining, wherein the shaft member has a bearing mounting surface at an outer periphery thereof and has a particular specification depending on a type of a vehicle in which the shaft member is to be assembled, the joining end surface of the cup member and the joining end surface of the shaft member being welded in abutment against each other, the outer joint member comprising a welded portion between the cup member and the shaft member, which comprises a bead formed by a beam radiated from an outer side of the cup member in a radial direction of the cup member, the outer joint member comprising a welding depth checking chamfer formed on a radially inner side of any one of the joining end surface of the cup member and the joining end surface of the shaft member.

2. The outer joint member of a constant velocity universal joint according to claim 1, wherein the joining end surface of the shaft member has an outer diameter set to an equal dimension that is fixed for each joint size, and the joining end surface of the cup member has an outer diameter set to an equal dimension that is fixed for each joint size.

3. The outer joint member of a constant velocity universal joint according to claim 1, wherein the welding depth checking chamfer is formed into the same shape for each joint size.

4. The outer joint member of a constant velocity universal joint according to claim 1, wherein the any one of the joining end surface of the cup member and the joining end surface of the shaft member comprises, in addition to the welding depth checking chamfer, an excessive welding depth checking chamfer formed on a radially inner side with respect to the welding depth checking chamfer.

5. The outer joint member of a constant velocity universal joint according to claim 4, wherein the excessive welding depth checking chamfer is formed into the same shape for each joint size.

6. The outer joint member of a constant velocity universal joint according to claim 1, wherein the outer joint member has a protruding surface protruding to a radially inner side with respect to an inner diameter of the any one of the joining end surface of the cup member and the joining end surface of the shaft member, the protruding surface being formed on a radially inner side of another one of the joining end surface of the cup member and the joining end surface of the shaft member without the welding depth checking chamfer.

7. The outer joint member of a constant velocity universal joint according to claim 4, wherein the shaft member comprises the welding depth checking chamfer and the excessive welding depth checking chamfer.

8. The outer joint member of a constant velocity universal joint according to claim 4, wherein the cup member comprises the welding depth checking chamfer and the excessive welding depth checking chamfer.

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 welded portion of FIG. 2a.

(4) FIG. 2c is an enlarged view for illustrating a shape before welding in FIG. 2b.

(5) FIG. 3 is a diagram for illustrating an overview of manufacturing steps for the outer joint member of FIG. 1.

(6) FIG. 4a is a vertical sectional view for illustrating a cup member before welding and after ironing.

(7) FIG. 4b is a vertical sectional view for illustrating the cup member before welding and after turning.

(8) FIG. 5a is a front view for illustrating a shaft member before welding, that is, a billet obtained by cutting a bar material.

(9) FIG. 5b is a partial vertical sectional view for illustrating the shaft member before welding and after forging.

(10) FIG. 5c is a partial vertical sectional view for illustrating the shaft member before welding and after turning and spline processing.

(11) FIG. 6 is a view for illustrating an overview of a welding step.

(12) FIG. 7 is a view for illustrating an overview of the welding step.

(13) FIG. 8 is a front view for illustrating an overview of an ultrasonic flaw detection-inspection apparatus.

(14) FIG. 9 is a plan view for illustrating the overview of the ultrasonic flaw detection-inspection apparatus.

(15) FIG. 10 is a front view for illustrating the overview of the ultrasonic flaw detection-inspection apparatus.

(16) FIG. 11 is a plan view for illustrating the overview of the ultrasonic flaw detection-inspection apparatus.

(17) FIG. 12a is a partial enlarged view as viewed from the arrow F-F of FIG. 10, for illustrating a case of a non-defective welded product.

(18) FIG. 12b is a partial enlarged view as viewed from the arrow F-F of FIG. 10, for illustrating a defective welded product.

(19) FIG. 13 is a view for illustrating findings in the course of development.

(20) FIG. 14 is a front view for illustrating a shaft member assigned with a different product number.

(21) FIG. 15 is a partial vertical sectional view for illustrating an outer joint member that is manufactured using the shaft member illustrated in FIG. 14.

(22) FIG. 16 is a diagram for illustrating an example of standardization of a product type of the cup member.

(23) FIG. 17 is a vertical sectional view for illustrating a modification of the outer joint member according to the first embodiment, specifically, illustrating the entirety of a cup member before welding.

(24) FIG. 18 is an enlarged view for illustrating a state of ultrasonic flaw-detection inspection after welding of the cup member of FIG. 17.

(25) FIG. 19a is a partial vertical sectional view for illustrating another modification of the outer joint member according to the first embodiment.

(26) FIG. 19b is an enlarged view for illustrating a welded portion of FIG. 19a.

(27) FIG. 19c is an enlarged view for illustrating a shape before welding in FIG. 19b.

(28) FIG. 20 is a vertical sectional view for illustrating the entirety of a cup member of FIG. 19c.

(29) FIG. 21 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.

(30) FIG. 22 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.

(31) FIG. 23 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.

(32) FIG. 24a is a partial vertical sectional view for illustrating the outer joint member of the FIG. 23.

(33) FIG. 24b is an enlarged view for illustrating a welded portion of FIG. 24a.

(34) FIG. 24c is an enlarged view for illustrating a shape before welding in FIG. 24b.

(35) FIG. 25a is a partial vertical sectional view for illustrating an outer joint member according to a third embodiment of the present invention.

(36) FIG. 25b is an enlarged view for illustrating a welded portion of FIG. 25a.

(37) FIG. 25c is an enlarged view for illustrating a shape before welding in FIG. 25b.

(38) FIG. 26a is an enlarged view for illustrating a state of ultrasonic flaw-detection inspection on a welded portion (non-defective welded product) illustrated in FIG. 25b, specifically, illustrating a state of inspection as to whether or not the welding depth is insufficient.

(39) FIG. 26b is an enlarged view for illustrating a state of ultrasonic flaw-detection inspection on the welded portion (non-defective welded product) illustrated in FIG. 25b, specifically, illustrating a state of inspection as to whether or not the welding depth is excessive.

(40) FIG. 27a is an enlarged view for illustrating states of ultrasonic flaw-detection inspection in cases of a defective welded product and an excessively welded product, specifically, illustrating a state of inspection on the defective welded product having an insufficient welding depth.

(41) FIG. 27b is an enlarged view for illustrating states of ultrasonic flaw-detection inspection in the cases of the defective welded product and the excessively welded product, specifically, illustrating a state of inspection on the excessively welded product.

(42) FIG. 28 is a view for illustrating a welding depth checking chamfer and an excessive welding depth checking chamfer.

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

(44) FIG. 30 is a vertical sectional view for illustrating the outer joint member according to the related art.

(45) FIG. 31 is a vertical sectional view for illustrating an outer joint member according to a related art.

EMBODIMENTS OF THE INVENTION

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

(47) FIG. 3 to FIG. 16 are views for illustrating 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 views for illustrating 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 subsequently, the method of manufacturing an outer joint member according to the first embodiment is described with reference to FIG. 3 to FIG. 16.

(48) 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.

(49) 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.

(50) 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.

(51) 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. Note that, as the fixed type constant velocity universal joint 20, an undercut-free type constant velocity universal joint may sometimes be used.

(52) The intermediate shaft 2 comprises splines 3 for torque transmission (including serrations; the same applies hereinafter) at outer peripheries 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.

(53) 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.

(54) 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 circle 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.

(55) 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.

(56) 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. Although detailed description is made later, outer diameters B of the joining end surface 50 and the joining end surface 51 (see FIG. 4b and FIG. 5c) are set to equal dimensions for each joint size. However, the outer diameter B of the joining end surface 50 of the cup member 12a and the outer diameter B 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 B of the joining end surface 51 is set slightly smaller than the outer diameter B of the joining end surface 50. The description the outer diameters B 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 B of the joining end surface 50 and the outer diameter B of the joining end surface 51.

(57) 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. Note that, features of this embodiment reside in an ultrasonic flaw detection-inspection method and a shape of the welded portion, which are capable of enhancing accuracy and operability in inspection on the welded portion in order to practically achieve the novel manufacturing concept for the outer joint member of the constant velocity universal joint being a mass-produced product. Details thereof are described later.

(58) As illustrated in FIG. 2c, a welding depth checking chamfer 51a is formed on a radially inner side of the joining end surface 51 of the shaft member 13a. An inner diameter D of the joining end surface 50 of the cup member 12a and an inner diameter E of the joining end surface 51 of the shaft member 13a (inner diameter of the welding depth checking chamfer 51a) are set to equal dimensions. In such a state, the cup member 12a and the shaft member 13a are welded to each other. In this embodiment, the welding depth checking chamfer 51a is formed into the same shape for each joint size.

(59) Next, the manufacturing method according to the first embodiment of the present invention is described with reference to FIG. 3 to FIG. 16. Before description of details of the features of the manufacturing method of this embodiment, that is, an ultrasonic flaw detection-inspection step for the welded portion, an overview of manufacturing steps (processing steps) is described. FIG. 3 is an illustration of the overview of the manufacturing steps for the outer joint member. In this embodiment, as illustrated in FIG. 3, 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. On the other hand, the shaft member 13a is manufactured through manufacturing steps comprising a bar material cutting step S1s, a turning step S2s, and a spline processing 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.

(60) After that, the cup member 12a and the shaft member 13a are subjected to a welding step S6, an ultrasonic flaw detection-inspection step S6K, 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. 22).

(61) 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.

(62) [Bar Material Cutting Step S1c]

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

(64) [Forging Step S2c]

(65) 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.

(66) [Ironing Step S3c]

(67) 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.

(68) [Turning Step S4c]

(69) In the preform after ironing, the outer peripheral surface, the boot mounting groove 32, the snap ring groove 33, the joining end surface 50, and the like 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.

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

(71) [Bar Material Cutting Step S1s]

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

(73) [Turning Step S2s]

(74) The outer peripheral surface of the billet (bearing mounting surface 14, snap ring groove 15, minor diameter of the spline, end surface, and the like) and the joining end surface 51, the welding depth checking chamfer 51a, and the like of the billet at the end portion on the cup member 12a side are formed by turning.

(75) [Spline Processing Step S3s]

(76) The spline is formed by rolling in the shaft member after turning. Note that, the method of processing the spline is not limited to the rolling, but 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.

(77) 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.

(78) [Welding Step S6]

(79) 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 and welded to each other.

(80) [Ultrasonic Flaw Detection-Inspection Step S6k]

(81) The welded portion 49 between the cup member 12a and the shaft member 13a is inspected by the ultrasonic flaw-detection method.

(82) [Heat Treatment Step S7]

(83) 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.

(84) [Grinding Step S8]

(85) 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.

(86) 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.

(87) Next, main constituent features of the manufacturing method of this embodiment are described in detail. FIG. 4a is a vertical sectional view for illustrating a state after ironing of the cup member 12a. FIG. 4b 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. 4a.

(88) 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 joining end surface 50 having the outer diameter B and the inner diameter D are formed by turning as illustrated in FIG. 4b.

(89) FIG. 5 are illustrations of states of the shaft member 13a in the respective processing steps. FIG. 5a is a front view for illustrating a billet 13a obtained by cutting a bar material. FIG. 5b is a partial vertical sectional view for illustrating a preform 13a obtained by forging the billet 13a into a rough shape by upset forging. FIG. 5c is a partial vertical sectional view for illustrating the shaft member 13a after turning and spline processing.

(90) The billet 13a illustrated in FIG. 5a is produced in the bar material cutting step S1s. The preform 13a is produced by increasing, if necessary, 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) by upset forging as illustrated in FIG. 5b.

(91) 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 portion 53 (inner diameter E) of the recessed portion 52, the joining end surface 51 the welding depth checking chamfer 51a, and the joining end surface 50 having the outer diameter B of the joining-side end portion are formed by turning as illustrated in FIG. 5c. 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.

(92) The outer diameter B of the joining end surface 50 located at the projecting portion 12a3 of the bottom portion 12a2 of the cup member 12a illustrated in FIG. 4b is set to an equal dimension for one joint size. Further, in the shaft member 13a illustrated in FIG. 5c, which is used as a long stem shaft, the outer diameter B of the joining end surface 51 located at the end portion on the cup member 12a side is set to an equal dimension to the outer diameter B of the joining end surface 50 of the cup member 12a 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. The outer diameter B and the welding depth checking chamfer 51a of the joining end surface 51 are set to equal dimensions for each joint size. 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 and the welding depth checking chamfer 51a are described later.

(93) Next, a method of welding the cup member 12a and the shaft member 13a is described with reference to FIG. 6 and FIG. 7. FIG. 6 and FIG. 7 are views for illustrating an overview of a welding apparatus. FIG. 6 is an illustration of a state before welding. FIG. 7 is an illustration of a state during welding. As illustrated in FIG. 6, 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.

(94) 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 center hole guide 107 has centered the cup member 12a. The center hole guide 104 is integrally mounted to the tailstock 105 arranged at the other 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 direction of FIG. 6 and FIG. 7).

(95) 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.

(96) 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. 6, 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. 6, 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 an inner diameter portion 50b of the cup member 12a and the recessed portion 52 and the inner diameter portion 53 of the shaft member 13a are reduced as well.

(97) 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. 7 to eliminate the gap between the joining end surfaces 50 and 51 of the cup member 12a and the shaft member 13a. Thus, the cup member 12a is centered by the center hole guide 107 and fixed by the chuck 103, whereas the shaft member 13a is supported by the center hole guide 104. After that, the workpiece supports 106 are moved away from the workpieces. At this time, the distance between the workpiece supports 106 and the workpieces may be infinitesimal, and hence illustration of this distance is omitted from FIG. 7. As a matter of course, the welding apparatus 100 may have such a structure that the workpiece supports 106 are retreated downward greatly.

(98) 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.

(99) Although illustration is omitted, the sealed space 111 is then opened to the air. Then, the center hole guide 104 and the tailstock 105 are retreated to the right side and the chuck 103 is opened under a state in which the workpiece supports 106 are raised to support the workpieces. 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.

(100) 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 a projecting height from the welded surface (0.5 mm or less), which imposed no adverse effect on a product function, 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.

(101) Following the above description of the overview of the manufacturing steps (processing steps) of this embodiment, the features of this embodiment, that is, the ultrasonic flaw detection-inspection step for the welded portion is described with reference to FIG. 8 to FIG. 13. FIG. 8 is a front view for illustrating an overview of an ultrasonic flaw detection-inspection apparatus as viewed from the arrow I-I of FIG. 9. FIG. 9 is a plan view for illustrating the ultrasonic flaw detection-inspection apparatus. In each of the states illustrated in FIG. 8 and FIG. 9, the outer joint member after welding is placed in the ultrasonic flaw detection-inspection apparatus. FIG. 10 is a front view for illustrating a state during inspection as viewed from the arrow H-H of FIG. 11. FIG. 11 is a plan view for illustrating the state during inspection.

(102) As illustrated in FIG. 8 and FIG. 9, an ultrasonic flaw detection-inspection apparatus 120 mainly comprises a water bath 122 mounted at the center of a base 121, a workpiece support 123, a workpiece holding member 124, a rotary drive device 125 configured to rotate an intermediate product 11 of the outer joint member 11 (hereinafter also referred to as workpiece 11), a pressing device 135 configured to press an axial end of the workpiece 11, and a drive positioning device 136 (see FIG. 9) for a probe.

(103) As illustrated in FIG. 8, the workpiece support 123 comprises rollers 126 and 127 configured to allow the workpiece 11 to be placed thereon in a freely rotatable manner. As illustrated in FIG. 9, the rollers 126 and 127 are arranged in pairs so that the shaft section 13 of the workpiece 11 can be stably supported. The rollers 126 are located at a portion close to the welded portion, and the rollers 127 are located at a center portion of the shaft section 13. The rollers 126 and 127 are capable of adjusting the placement position of the workpiece 11 as appropriate in the axial direction (lateral direction of FIG. 9) and the radial direction (vertical direction of FIG. 9) in consideration of a joint size, dimensions, and weight balance of the workpiece 11.

(104) Further, the workpiece holding member 124 is mounted to the workpiece support 123 at a position displaced from an axial line of the workpiece 11 in a horizontal direction (see FIG. 9). The workpiece holding member 124 comprises a lever 128, and a workpiece holding roller 129 is arranged at an end portion of the lever 128. The lever 128 is pivotable in the plane, and is vertically movable.

(105) The workpiece support 123 is mounted to a support 134 through intermediation of a linear-motion bearing 130 comprising rails 131 and linear guides 132, and is movable in the axial direction (lateral direction of FIG. 8 and FIG. 9). The support 134 is mounted to the base 121. A rod 133 is coupled to an end portion (left end portion of FIG. 8 and FIG. 9) of the workpiece support 123 so that the workpiece support 123 is driven to be positioned by an actuator (not shown) on an outside of the water bath 122.

(106) The rotary drive device 125 comprises a rotary shaft 143 having a rotary disc 144 mounted thereto, and this rotary shaft 143 is driven to rotate by a motor (not shown) on the outside of the water bath 122.

(107) As illustrated in FIG. 8, a mounting base 137 is arranged on an upper side of the ultrasonic flaw detection-inspection apparatus 120. A base plate 145 for the pressing device 135 configured to press the axial end of the workpiece 11 is mounted to the mounting base 137 through intermediation of a linear-motion bearing 138 comprising a rail 139 and a linear guide 140 so that the pressing device 135 is movable in the axial direction (lateral direction of FIG. 8 and FIG. 9). A rod 142 of a pneumatic cylinder 141 is coupled to an end portion of the base plate 145 for the pressing device 135 so that the pressing device 135 is driven. A free bearing 146 is mounted to a portion to be held in abutment against the axial end of the shaft section 13 of the workpiece 11 so that the axial end can be pressed in a freely rotatable manner.

(108) As illustrated in FIG. 9, the drive positioning device 136 for a probe is arranged at a position displaced from an axial line of the workpiece 11 in the horizontal direction. This drive positioning device 136 comprises actuators for the X-axis direction (lateral direction of FIG. 9) and the Y-axis direction (vertical direction of FIG. 9) so that a probe 147 is driven to be positioned in the X-axis and Y-axis directions. An actuator 148 for the X-axis direction and an actuator 149 for the Y-axis direction are each an electric ball-screw type (electric cylinder), which is capable of performing positioning with high accuracy. Reference symbol 150 represents a rail for a linear-motion bearing. The drive positioning device 136 is arranged on the outside of the water bath 122, and the probe 147 and a holder 151 therefor are arranged in the water bath 122.

(109) Next, the operation of the ultrasonic flaw detection-inspection apparatus 120 and the ultrasonic flaw detection-inspection step S6k are described. As illustrated in FIG. 8 and FIG. 9, the workpiece 11 after welding is placed on the workpiece support 123 by a loading device (not shown). At this time, in order that the workpiece 11 is loaded, the workpiece support 123 is located at an appropriate interval from the rotary drive device 125 in the axial direction of the workpiece 11, and the workpiece holding member 124 raises and pivots the lever 128 thereof so as to be substantially parallel to the axial line of the workpiece 11. Further, the pressing device 135 and the drive positioning device 136 for a probe wait at retreated positions.

(110) After that, the lever 128 of the workpiece holding member 124 is pivoted so as to be substantially perpendicular to the axial line of the workpiece 11, and then lowered to hold the workpiece 11 from above (see FIG. 10). Then, water is supplied to the water bath 122. In the ultrasonic flaw detection-inspection apparatus 120 according to this embodiment, flaw detection is performed under water, and hence ultrasonic waves are satisfactorily propagated. Thus, inspection can be performed with high accuracy.

(111) Next, as illustrated in FIG. 10 and FIG. 11, the pneumatic cylinder 141 is driven to cause the pressing device 135 to be advanced and pressed against the axial end of the workpiece 11, thereby pressing the opening rim of the cup section 12 of the workpiece 11 against the rotary disc 144 of the rotary drive device 125. In conjunction with the advance of the pressing device 135, the workpiece support 123 is also moved toward the rotary drive device 125. Thus, the workpiece 11 is positioned in the radial direction and the axial direction. In this state, the motor (not shown) of the rotary drive device 125 is rotated, thereby rotating the workpiece 11.

(112) As illustrated in FIG. 11, the drive positioning device 136 is moved in the X-axis direction, and then moved in the Y-axis direction, thereby positioning the probe 147 at a flaw detection position (in FIG. 10, the probe 147 in this state is indicated by the broken line). Then, the flaw-detection inspection is performed. After the flaw-detection inspection, the water is drained, and the workpiece 11 is unloaded from the ultrasonic flaw detection-inspection apparatus 120 by the loading device (not shown). As described above, the inspection is sequentially repeated on the workpieces 11.

(113) In the ultrasonic flaw detection-inspection apparatus 120 according to this embodiment, in order to reduce the cycle time of the inspection, time-consuming supply and drainage of water are performed simultaneously with the operations of the devices and the members, or at other timings in accordance therewith. Further, some of the operations of the devices and the members may be performed simultaneously with each other or in different orders as appropriate.

(114) Details of the ultrasonic flaw-detection inspection are described with reference to FIG. 12a, FIG. 12b, and FIG. 13. All of FIG. 12a, FIG. 12b, and FIG. 13 are views as viewed from the arrow F-F of FIG. 10. FIG. 12a is an illustration of a non-defective welded product, and FIG. 12b is an illustration of a defective welded product. FIG. 13 is an illustration of findings in the course of development.

(115) The probe 147 is positioned at the flaw detection position away from the welded portion 49 by a predetermined distance. The flaw detection position is preset for each joint size. A target welding depth is denoted by the reference symbol Wa, and a minimum acceptable welding depth is denoted by the reference symbol Wmin. Workpieces having a depth equal to or larger than the minimum acceptable welding depth Wmin are determined as non-defective welded products, and workpieces having a depth smaller than the minimum acceptable welding depth Wmin are determined as defective welded products. When a transmission pulse G is transmitted at an incident angle 1 from the probe 147, the transmission pulse G is refracted by the surface of the shaft section 13, and advances at a refraction angle 2. The ultrasonic flaw-detection inspection of this embodiment is performed under the condition that the incident angle 1 is approximately 20, and the refraction angle 2 is approximately 45. During the flaw-detection inspection, the workpiece 11 is kept rotated by the rotary drive device 125 (see FIG. 10).

(116) The probe 147 positioned at the flaw detection position away from the welded portion 49 by the predetermined distance collects data of the entire periphery of the workpiece 11. Specifically, in consideration of tolerance for displacement of the welding position, at the above-mentioned flaw detection position, first, data of a single rotation (360) of the workpiece 11 is collected. Then, the probe 147 is sequentially shifted in the axial direction at a minute pitch (for example, 0.5 mm) to collect data of a plurality of rotations (for example, five rotations). Based on those pieces of data, non-defective/defective determination is made. A threshold of a reflected echo to be used in the non-defective/defective determination is determined based on a welding pattern corresponding to the minimum acceptable welding depth Wmin.

(117) Next, advantages to be obtained by the shape of the welded portion of this embodiment are described. As described above, the welding depth checking chamfer 51a is formed on the radially inner side of the joining end surface 51 of the shaft member 13a (see FIG. 12b). The inner diameter D of the joining end surface 50 of the cup member 12a and the inner diameter E of the joining end surface 51 of the shaft member 13a are set to equal dimensions. In such a state, the cup member 12a and the shaft member 13a are welded to each other. The welding depth checking chamfer 51a is formed into the same shape for each joint size.

(118) Details of the advantages to be obtained by the shape of the above-mentioned welded portion are described by way of an example of cases of the non-defective welded product and the defective welded product. In the case of the non-defective welded product, when the transmission pulse G from the probe 147 is input as illustrated in FIG. 12a, a reflected echo of the transmission pulse G scattered by a boundary surface of a back bead 49a at the depth equal to or larger than the minimum acceptable welding depth Wmin is generated. A part of the reflected echo is transmitted as a reflected echo R1 in the direction of the transmission pulse G, and is received by the probe 147. In this embodiment, the inventors of the present invention have focused on the fact that the part of the reflected echo which is generated by the transmission pulse G scattered by the boundary surface of the back bead 49a is transmitted as the reflected echo R1 in the direction of the transmission pulse G, and the reflected echo R1 is relatively weak. In the case of the non-defective welded product, the intensity of the reflected echo R1 is equal to or less than the threshold of the non-defective/defective determination. Thus, determination that the welded product is non-defective is made.

(119) Meanwhile, in the case of the defective welded product, as illustrated in FIG. 12b, a distal end of the bead 49a does not reach the minimum acceptable welding depth Wmin, and hence the welding depth checking chamfer 51a remains. In this state, when the transmission pulse G from the probe 147 is input, the transmission pulse G is reflected by the welding depth checking chamfer 51a. The welding depth checking chamfer 51a is formed in a direction perpendicular to the transmission pulse G, and hence a reflected echo R2 that is not affected by scattering of the transmission pulse G and remains strong is received by the probe 147. As a result, the intensity of the reflected echo R2 is more than the threshold of the reflected echo for the non-defective/defective determination, and hence determination that the welded product is defective is made.

(120) As for the shape of the welded portion of this embodiment, the inventors of the present invention have focused on the fact that, as described above, in the case of the non-defective welded product, the part of the reflected echo which is generated by the transmission pulse G scattered by the back bead 49a is received by the probe 147, and in the case of the defective welded product, the reflected echo is received by the probe 147 without being affected by the scattering of the transmission pulse G due to the welding depth checking chamfer 51a. Thus, the features of the present invention resides in that the determination as to whether the welded product is non-defective or defective is made through discrimination between the intensities of the reflected echoes.

(121) The findings in the course of the development to arrive at the shape of the welded portion of this embodiment are illustrated in FIG. 13. FIG. 13 is an illustration of a defective welded product that does not comprise the welding depth checking chamfer on the radially inner side of the joining end surface 51 of the shaft member 13a and has a welding depth smaller than the minimum acceptable welding depth Wmin. When the transmission pulse G from the probe 147 is input, a reflected echo which is generated by the transmission pulse G scattered by the joining end surface 51 and a normal chamfered portion is generated. A part of the reflected echo is transmitted as a reflected echo R3 in the direction of the transmission pulse G, and is received by the probe 147. Thus, also in the case of the defective welded product, the reflected echo is scattered. For this reason, the intensity of the above-mentioned reflected echo R3 is equal to or less than the threshold of the above-mentioned non-defective/defective determination. As a result, it was proved that the determination as to whether the welded product was non-defective or defective was difficult. Based on those findings, the inventors of the present invention arrived at the shape of the welded portion of this embodiment.

(122) Dimensions of the welding depth checking chamfer 51a are set to such dimensions that the welding depth checking chamfer 51a is eliminated by a width of the back bead 49a in the axial direction at the minimum acceptable welding depth Wmin as illustrated in FIG. 12a. Thus, the intensities of the reflected echoes can be discriminated from each other, and hence the determination as to whether the welded product is non-defective or defective can be made with high accuracy.

(123) As described above, the ultrasonic flaw detection-inspection apparatus 120 according to this embodiment mainly comprises the water bath 122 mounted at the center of the base 121. In the water bath 122, the workpiece support 123, the workpiece holding member 124, the rotary disc 144 of the rotary drive device 125 configured to rotate the workpiece 11, the free bearing 146 of the pressing device 135 configured to press the axial end of the workpiece 11, and the probe 147 mounted to the drive positioning device 136 are arranged. With this configuration, the operation of loading the workpiece 11, the supply and drainage of water, the flaw-detection inspection, and the operation of unloading the workpiece 11 can be performed in conjunction with each other, and the ultrasonic flaw-detection inspection can be automated. Thus, accuracy, operability, and efficiency in the inspection can be enhanced, which is suited to the inspection on the welded portion of the outer joint member of the constant velocity universal joint being a mass-produced product.

(124) Further, the outer diameter B of the joining end surface 50 of the cup member 12a of this embodiment is set to an equal dimension for each joint size. Also with this configuration, in the ultrasonic flaw-detection inspection, setup operations with respect to the outer joint members 11 having the different product numbers are simplified. Thus, the efficiency in the inspection can be further enhanced.

(125) Still further, flaw detection is performed under water, and hence ultrasonic waves are satisfactorily propagated. Thus, inspection can be performed with much higher accuracy. In addition, through employment of the shape of the welded portion, in which the welding depth checking chamfer 51a is formed on the radially inner side of the joining end surface 51, the intensities of the reflected echoes can be discriminated from each other. Thus, the determination as to whether the welded product is non-defective or defective can be made with high accuracy.

(126) 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. 5. A shaft member 13b illustrated in FIG. 14 and FIG. 15 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. 4b) of the bottom portion 12a2 (projecting portion 12a3) of the cup member 12a. The outer diameter B and the inner diameter E of the joining end surface 51 are set to the equal dimensions to the outer diameter B and the inner diameter E of the joining end surface 51 of the shaft member 13a of the long stem type illustrated in FIG. 5. Also in this case, the welding depth checking chamfer 51a is formed on the radially inner side of the joining end surface 51 of the shaft member 13b. In such a state, the cup member 12a and the shaft member 13b are welded to each other.

(127) 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 B of the joining end surface 51 of the shaft member 13a or 13b is set to an equal dimension.

(128) The outer diameter B of the joining end surface 50 of the cup member 12a and the joining end surface 51 of the shaft member 13a or 13b 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 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.

(129) 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.

(130) As a summary of the above description, FIG. 16 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. 16, 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 B of the joining end surface of each of those cup members has an equal dimension.

(131) A first modification of the outer joint member according to the first embodiment is described with reference to FIG. 17 and FIG. 18. FIG. 17 is a vertical sectional view for illustrating the entirety of a cup member before welding, and FIG. 18 is an illustration of a state of the ultrasonic flaw-detection inspection as viewed from the arrow F-F of FIG. 10. An inner diameter dimension of a joining end surface of the cup member of this modification is different from that in the first embodiment, and other features are the same as those in the first embodiment. Thus, parts that have the same function are denoted by the same reference symbols (except for the subscripts), and only main points are described.

(132) As illustrated in FIG. 17 and FIG. 18, an inner diameter D.sub.1 of a joining end surface 50.sub.1 of a cup member 12a.sub.1 is set smaller than the inner diameter E of the joining end surface 51 of the shaft member 13a. On the joining end surface 50.sub.1 of the cup member 12a.sub.1, a protruding surface 50a.sub.1 protruding to the radially inner side with respect to the inner diameter E of the joining end surface 51 of the shaft member 13a is formed. In such a state, the cup member 12a.sub.1 and the shaft member 13a are welded to each other. Although illustration is omitted, as in the first embodiment, the welding depth checking chamfer 51a is formed on the radially inner side of the joining end surface 51 of the shaft member 13a.

(133) FIG. 18 is an illustration of a case of a non-defective welded product. When the transmission pulse G from the probe 147 is input as illustrated in FIG. 18, the transmission pulse G enters a cup section 12.sub.1 through the back bead 49a at the depth equal to or larger than the minimum acceptable welding depth Wmin, and travels straight as it is. Alternatively, the transmission pulse G is transmitted to the cup section 12.sub.1 side by being reflected due to the inner diameter D.sub.1 of the cup section 12.sub.1. In those cases, the probe 147 does not receive a reflected echo. This is because, as described above, on the joining end surface 50.sub.1 of the cup member 12a.sub.1, the protruding surface 50a.sub.1 protruding to the radially inner side with respect to the inner diameter E of the joining end surface 51 of the shaft member 13a is formed. Thus, even when the transmission pulse G enters the back bead 49a, the boundary surface of the back bead 49a, which is perpendicular to the transmission pulse G, does not exist. For this reason, a reflected echo having such an intensity as to cause a detection error of the probe 147 is not generated. The intensity of the reflected echo is equal to or less than the threshold of the non-defective/defective determination, and hence determination that the welded product is non-defective is made.

(134) Although illustration is omitted, in the case of the defective welded product, as in the case of the first embodiment, the transmission pulse G is reflected by the welding depth checking chamfer 51a. Thus, the intensity of the reflected echo R2 that is not scattered is more than the threshold of the non-defective/defective determination. As a result, determination that the welded product is defective is made.

(135) As described above, the welding depth checking chamfer 51a and the protruding surface 50a.sub.1 are formed on the joining end surface 51 and on the radially inner side of the joining end surface 50, respectively. Thus, the discrimination between the non-defective welded product and the defective welded product can be positively made based on presence/absence of the reflected echo. As a result, the operability and the efficiency in the inspection as to whether the welded product is non-defective or defective can be further enhanced.

(136) A second modification of the outer joint member according to the first embodiment is described with reference to FIG. 19 and FIG. 20. FIG. 19a is a partial vertical sectional view for illustrating an outer joint member of this modification, FIG. 19b is an enlarged view for illustrating a circle A of FIG. 19a, and FIG. 19c is a view for illustrating a state before welding in FIG. 19b. FIG. 20 is a vertical sectional view for illustrating the entirety of a cup member before welding. A form of a protruding surface formed on a joining end surface of the cup member of this modification is different from that in the first modification described above, and other features are the same as those in the first modification. Thus, parts that have the same function are denoted by the same reference symbols (except for the subscripts), and only main points are described.

(137) As illustrated in FIG. 19c and FIG. 20, a joining end surface 50.sub.2 formed on a projecting portion 12a3.sub.2 of a bottom portion 12a2.sub.2 of a cup member 12a.sub.2 is formed by annular turning. In this case, a diameter D.sub.2 of the joining end surface 50.sub.2 on the radially inner side corresponds to the inner diameter D.sub.1 of the joining end surface 50.sub.1 of the cup member 12a.sub.1 of the first modification. Thus, as illustrated in FIG. 19c, a portion on the radially inner side with respect to the inner diameter E of the shaft member 13a corresponds to a protruding surface 50a.sub.2. The cup member 12a.sub.2 of this modification can be formed by turning an end surface of the projecting portion 12a3 of the preform 12a for the above-mentioned cup member after ironing, which is illustrated in FIG. 4a, at only a portion corresponding to the joining end surface 50.sub.2 on the radially outer side of the projecting portion 12a3.sub.2 as illustrated in FIG. 20. Thus, the time for the turning can be reduced. Note that, the present invention is not limited thereto, and a projecting surface portion 50b.sub.2 on the radially inner side with respect to the joining end surface on the radially inner side of FIG. 20 may be subjected to turning. In this modification, as in the first modification, the reflected echo to the probe is not generated in the case of the non-defective welded product.

(138) Other features and advantages, 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 ultrasonic flaw detection-inspection 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 the first and second modifications to omit redundant description.

(139) FIG. 21 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. 3 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 ultrasonic flaw detection-inspection 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.

(140) As illustrated in FIG. 4b, 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.

(141) 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.

(142) In this embodiment, in FIG. 16 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. 16 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.

(143) FIG. 22 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. 3 as described above in the first embodiment, and the grinding step S8 for the shaft section in FIG. 3 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 ultrasonic flaw detection-inspection 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.

(144) 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. 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.

(145) 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.

(146) 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.

(147) In this embodiment, in FIG. 16 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. 16 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 quenched-steel cutting work, but encompass a cup member and a shaft member in a state in which the heat treatment is completed while the finishing is uncompleted.

(148) 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 diameters B 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 B of the above-mentioned joining end surfaces of the cup members are set to equal dimensions.

(149) Next, an outer joint member according to a second embodiment of the present invention is described with reference to FIG. 23 and FIG. 24. 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, and only main points are described.

(150) A plunging type constant velocity universal joint 10.sub.3 illustrated in FIG. 23 is a tripod type constant velocity universal joint (TJ), and comprises an outer joint member 11.sub.3 comprising a cup section 12.sub.3 and the long stem section 13 that extends from a bottom portion of the cup section 12.sub.3 in the axial direction, an inner joint member 16.sub.3 housed along an inner periphery of the cup section 12.sub.3 of the outer joint member 11.sub.3, and rollers 19 serving as torque transmitting elements that are arranged between the outer joint member 11.sub.3 and the inner joint member 16.sub.3. The inner joint member 16.sub.3 comprises a tripod member 17 comprising three equiangular leg shafts 18 on which the rollers 19 are externally fitted.

(151) 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.3 is supported by the support bearing 6 in a freely rotatable manner, and thus the vibration of the outer joint member 11.sub.3 during driving or the like is prevented as much as possible.

(152) FIG. 24 are partial vertical sectional views for illustrating the outer joint member 11.sub.3. As illustrated in FIG. 24, the outer joint member 11.sub.3 comprises a bottomed cylindrical cup section 12.sub.3 that is opened at one end and has inner peripheral surfaces 31.sub.3 and the track grooves 30.sub.3, on which the rollers 19 (see FIG. 23) are caused to roll, formed at three equiangular positions on an inner peripheral surface of the cup section 12.sub.3, and the long stem section 13 that extends from a bottom portion of the cup section 12.sub.3 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.3 side. The outer joint member 11.sub.3 is formed by welding the cup member 12a.sub.3 and the shaft member 13a to each other.

(153) As illustrated in FIG. 24, the cup member 12a.sub.3 is an integrally-formed product having a cylindrical portion 12a1.sub.3 and a bottom portion 12a2.sub.3. The cylindrical portion 12a1.sub.3 has the track grooves 30.sub.3 and the inner peripheral surfaces 31.sub.3 formed at the inner periphery thereof. A projecting portion 12a3.sub.3 is formed at the bottom portion 12a2.sub.3 of the cup member 12a.sub.3. The boot mounting groove 32 is formed at an outer periphery of the cup member 12a.sub.3 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.3 side, whereas the spline Sp is formed at the end portion on the opposite side to the cup member 12a.sub.3 side.

(154) A joining end surface 50.sub.3 formed at the projecting portion 12a3.sub.3 of the bottom portion 12a2.sub.3 of the cup member 12a.sub.3 and the joining end surface 51 formed at the end portion of the shaft member 13a on the cup member 12a.sub.3 side are brought into abutment against each other, and are welded to each other by electron beam welding performed from the radially outer side. The welded portion 49 is formed of a bead, which is formed by a beam radiated from the radially outer side of the cup member 12a.sub.3. Similarly to the outer joint member of the first embodiment, the outer diameters B of the joining end surface 50.sub.3 and the joining end surface 51 are set to equal dimensions for each joint size. The welded portion 49 is formed on the joining end surface 51 located on the cup member 12a.sub.3 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 the manufacturing cost.

(155) The details of the outer joint member and the method of manufacturing the outer joint member according to this embodiment are the same as the details of the outer joint member according to the first embodiment, the modifications thereof, 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.

(156) Next, an outer joint member according to a third embodiment and a manufacturing method according to a fourth embodiment of the present invention are described with reference to FIG. 25 to FIG. 28. Features of the outer joint member and the method of manufacturing the outer joint member of those embodiments reside in that, in addition to the welding depth checking chamfer formed on the joining end surface, an excessive welding depth checking chamfer is formed on the radially inner side with respect to the welding depth checking chamfer. In those embodiments, determination as to whether or not the welding depth is kept within a satisfactory range of being not insufficient or not excessive can be made. Thus, it is possible to achieve the outer joint member and the method of manufacturing the outer joint member, which are capable of preventing excess of the welding depth, further reducing welding cost, and achieving satisfactory operability in the inspection.

(157) The details of the outer joint member according to the third embodiment are described with reference to FIG. 25. FIG. 25a is a partial vertical sectional view for illustrating the outer joint member, FIG. 25b is an enlarged view for illustrating a circle A of FIG. 25a, and FIG. 25c is an enlarged view for illustrating a shape before welding in FIG. 25b. A cup section 12.sub.2 and the cup member 12a.sub.2 of an outer joint member 114 according to this embodiment are the same as the cup section 12.sub.2 and the cup member 12a.sub.2 of the second modification of the first embodiment, respectively. Thus, parts of the cup section 12.sub.2 and the cup member 12a2 according to this embodiment, which have the same function as those in the second modification of the first embodiment, are denoted by the same reference symbols to omit redundant description.

(158) A shaft member 13a.sub.1 is described with reference to FIG. 25c. On a joining end surface 51.sub.1 of the shaft member 13a.sub.1, the welding depth checking chamfer 51a is formed similarly to the shaft members 13a and 13b of the embodiments and the modifications described above. Further, in the shaft member 13a.sub.1 according to this embodiment, in addition to the welding depth checking chamfer 51a, an excessive welding depth checking chamfer 51b is formed on the radially inner side with respect to the joining end surface 51.sub.1. The excessive welding depth checking chamfer 51b is formed to determine whether or not the welding depth is excessive.

(159) FIG. 25b is an illustration of a non-defective welded product welded to an extent that the welding depth checking chamfer 51a does not remain and having a welding depth equal to or larger than the minimum acceptable welding depth Wmin, whereas the excessive welding depth checking chamfer 51b remains.

(160) Next, the manufacturing method according to the fourth embodiment of the present invention is described with reference to FIG. 26 to FIG. 28. FIG. 26 are enlarged views for illustrating states of ultrasonic flaw-detection inspection on the welded portion (non-defective welded product) illustrated in FIG. 25b. FIG. 26a is an illustration of a state of inspection as to whether or not the welding depth is insufficient, and FIG. 26b is an illustration of a state of the inspection as to whether or not the welding depth is excessive.

(161) As illustrated in FIG. 26a, when the transmission pulse G from the probe 147 is input at a flaw detection position corresponding to the welding depth checking chamfer, the transmission pulse G travels straight as it is to the cup section 12.sub.2 side. Thus, the probe 147 does not receive a reflected echo.

(162) After that, when the probe 147 is shifted in the axial direction, and the transmission pulse G from the probe 147 is input at a flaw detection position corresponding to the excessive welding depth checking chamfer as illustrated in FIG. 26b, the transmission pulse G is reflected by the excessive welding depth checking chamfer 51b. The excessive welding depth checking chamfer 51b is formed in the direction perpendicular to the transmission pulse G, and hence a reflected echo R4 that is not scattered and remains strong is received by the probe 147.

(163) As described above, in the case of the non-defective welded product, when the transmission pulse G from the probe 147 is input at each of the two flaw detection positions corresponding to the welding depth checking chamfer 51a and the excessive welding depth checking chamfer 51b, the reflected echo R4 is solely received. Thus, determination can be made.

(164) Next, states of ultrasonic flaw-detection inspection in the case of the defective welded product (having an insufficient welding depth) and a case of a product having an excessive welding depth are described. FIG. 27a is an illustration of a defective welded product, and FIG. 27b is an illustration of the product having an excessive welding depth. As illustrated in FIG. 27a, in the case of the defective welded product having an insufficient welding depth, as in FIG. 12b for illustrating the manufacturing method according to the first embodiment, the distal end of the bead 49a does not reach the minimum acceptable welding depth Wmin, and hence the welding depth checking chamfer 51a remains. The transmission pulse G from the probe 147 at this flaw detection position is input and reflected by the welding depth checking chamfer 51a. The welding depth checking chamfer 51a is formed in the direction perpendicular to the transmission pulse G, and hence the reflected echo R2 that is not scattered and remains strong is received by the probe 147. Although illustration is omitted, in this embodiment, after that, the probe 147 is shifted in the axial direction, and the probe 147 receives the second strong reflected echo R4 (see FIG. 26b) at the flaw detection position corresponding to the excessive welding depth checking chamfer 51b. When the two strong reflected echoes R2 and R4 are received as described above, determination that the welded product has an insufficient welding depth and hence is defective is made.

(165) As illustrated in FIG. 27b, in the case of the product having an excessive welding depth, welding is performed to an extent that none of the welding depth checking chamfer 51a and the excessive welding depth checking chamfer 51b remains. Thus, at any of the flaw detection position corresponding to the welding depth checking chamfer 51a and the flaw detection position corresponding to the excessive welding depth checking chamfer 51b, the probe 147 does not receive the reflected echo. When no reflected echo is received as described above, determination that the welding depth is excessive is made.

(166) As described above, in this embodiment, through the ultrasonic flaw-detection inspection, determination that the welded product has an insufficient welding depth and hence is defective is made when the probe 147 receives the two reflected echoes, determination that the welded product is non-defective is made when the probe 147 receives the one of the reflected echoes, and determination that the welding depth is excessive is made when the probe 147 receives none of the reflected echoes. Note that, the excessively welded product is not necessarily defective when determination that a beam intensity during welding is high, determination that duration of the welding is long, or other determination may be made. When over quality is suppressed and such welding conditions are changed as appropriate, cost reduction and other advantages can be obtained.

(167) The welding depth checking chamfer 51a and the excessive welding depth checking chamfer 51b are summarized with reference to FIG. 28. The minimum acceptable welding depth Wmin corresponds to a welding depth under the state in which the welding depth checking chamfer 51a is eliminated, and an excessive-welding determination depth Wmax corresponds to a start end of the excessive welding depth checking chamfer 51b. A region J from an outer periphery of the shaft member 131 to the minimum acceptable welding depth Wmin corresponds to the defective welded product, a region K between the minimum acceptable welding depth Wmin and the excessive-welding determination depth Wmax corresponds to the non-defective welded product, and a region L on the radially inner side with respect to the excessive-welding determination depth Wmax corresponds to the excessively welded product.

(168) All the 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 ultrasonic flaw detection-inspection 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 applied to the outer joint member according to the third embodiment and the manufacturing method according to the fourth embodiment to omit redundant description.

(169) In the above-mentioned embodiments and the above-mentioned modifications, the case where the welding depth checking chamfer and the excessive welding depth checking chamfer are formed on the radially inner side with respect to the joining end surface of the shaft member is exemplified. However, conversely, the welding depth checking chamfer and the excessive welding depth checking chamfer may be formed on the radially inner side with respect to the joining end surface of the cup member. In this case, there are no problems as long as the ultrasonic flaw-detection inspection is performed from a surface side of the cup member.

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

(171) In the outer joint member according to the embodiments and the modifications 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.

(172) The present invention is not limited to the above-mentioned embodiments and the above-mentioned modifications. 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.

REFERENCE SIGNS LIST

(173) 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 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 protruding surface 51 joining end surface 51a welding depth checking chamfer 51b excessive welding depth checking chamfer 52 recessed portion 100 welding apparatus 101 electron gun 108 case 109 vacuum pump 111 sealed space 120 ultrasonic flaw detection-inspection apparatus 121 base 122 water bath 123 workpiece support 124 workpiece holding member 125 rotary drive device 135 pressing device 136 drive positioning device for probe 147 probe B outer diameter D inner diameter E inner diameter G transmission pulse R reflected echo O joint center O.sub.1 curvature center O.sub.2 curvature center Sp spline