Fixed constant velocity universal joint

Abstract

The present invention relates to a fixed constant velocity universal joint in which balls are prevented from moving upward toward the edge of a raceway groove in accordance with the formation of a chamfer for assembling a cage. A cage assembly chamfer (24) formed from a surface (e.g., a conical surface) having a cross-sectional radius of curvature that gradually decreases toward the inner side of the joint is provided at the joint opening-side end portion of the boundary between a track groove (22) and an inner diameter spherical surface portion (21) of an outer joint member (2) of a UJ-type constant velocity universal joint (1).

Description

Technical Field

[0001] The invention relates to a fixed constant velocity universal coupling. Background Art

[0002] As a fixed constant velocity universal joint capable of handling high operating angles (e.g., 50° or greater), there are known fixed constant velocity universal joints (hereinafter referred to as "UJ-type constant velocity universal joints"), in which the ball center trajectory of the raceway groove has both arcuate and straight portions. UJ-type constant velocity universal joints often use joints with six balls (for example, see Patent Document 1 below).

[0003] In order to achieve compactness and lightness in a six-ball UJ constant velocity universal joint, if the pitch diameter of the balls is reduced while maintaining strength and load capacity, it is sometimes impossible to simply assemble the retainer to the outer coupling member even if the shapes of the components are optimized through design.

[0004] That is, when the retainer 105 is assembled to the inner periphery of the outer joint member 102, first, as shown in FIG. Figures 14 to 16 As shown, with the axis L102 of the outer coupling member 102 and the axis L105 of the retainer 105 perpendicular to each other, the retainer 105 is inserted from the open side of the outer coupling member 102. After the retainer 105 is press-fitted into the inner portion of the outer coupling member 102, the retainer 105 is rotated 90 degrees about the Y-axis (an axis perpendicular to both the axis L102 of the outer coupling member 102 and the axis L105 of the retainer 105) to be positioned in a normal position.

[0005] However, when the retainer 105 is inserted from the opening side of the outer joint member 102 as described above, Figure 17 As shown in the enlarged view, the vicinity of the edge portion 151 a (hatched area) provided at the axial end of the pocket 151 of the retainer 105 interferes with the vicinity of the raceway chamfer 125 provided at the boundary between the raceway groove 122 and the inner diameter spherical portion 121 of the outer joint member 102 .

[0006] Therefore, in the following patent document 1, Figure 18 As shown, by providing a retainer assembly chamfer (chamfer portion) 124 having a circumferential width greater than that of the raceway chamfer 125 at the opening side end portion of the boundary between the raceway groove 122 of the outer joint member 102 and the inner diameter spherical portion 121, interference between the retainer 105 and the outer joint member 102 is avoided when the retainer 105 is assembled to the outer joint member 102.

[0007] The retainer assembly chamfer 124 is formed by cold forging (thinning and stretching forging) using a thinning and stretching punch. Figure 19After the pre-forged part 200 having a cup 223 and a rod portion 224 shown by the double dotted line is formed by cold forging (pre-forging), a rolling groove 122 and the like are formed on the inner peripheral surface of the cup portion 223 of the pre-forged part 200 by the thinning and stretching punch 300 and the dies 310 and 320 shown by the solid line in the figure.

[0008] like Figure 20 As shown, the outer circumferential surface of the ironing punch 300 includes a track groove forming portion 301, an inner diameter surface forming portion 302, and a notch forming portion 303. The notch forming portion 303 and the track groove forming portion 301 are formed along the entire length of the track groove forming portion 301. The cross-section (a cross-section perpendicular to the longitudinal direction) of the notch forming portion 303 is uniform along the longitudinal direction and, in the illustrated example, is a cylindrical surface curved along the track groove forming portion 301.

[0009] like Figure 21 As shown, the inner circumferential surface of a pre-forged part 200 subjected to the aforementioned ironing and draw forging (hereinafter referred to as "iron-draw forging part 400") is formed with a rolling groove 122, a cutout portion 140, and an inner diameter surface 160, to which the shapes of the rolling groove forming portion 301, the inner diameter surface forming portion 302, and the notch forming portion 303 of the ironing and draw punch 300 are transferred. The notch portion 140 is formed along the longitudinal direction of the rolling groove 122 over the entire length of the rolling groove 122 and has the shape of a cylindrical surface that curves along the rolling groove 122.

[0010] Then, the inner peripheral surface of the thinned stretch forging 400 is subjected to turning, so that Figure 18 As shown, an inner diameter spherical portion 121, a raceway chamfer 125, and a cup inlet chamfer 126 are formed ( Figure 18 The darker areas are those subjected to turning. This turning removes the entire inner diameter surface 160 of the ironed stretch forging 400, and also removes a portion of the cutout 140. The remaining portion of the cutout 140 becomes the retainer assembly chamfer 124. Specifically, the retainer assembly chamfer 124 is a portion of the cylindrical surface formed along the longitudinal direction of the raceway groove 122.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent No. 6389034 Summary of the Invention

[0014] Problems to be solved by the invention

[0015] like Figure 22As shown, the center of curvature O1 of the inner spherical portion 121 of the outer joint member 102 is offset toward the inner side of the joint (to the left in the figure) relative to the center of curvature O2 of the curved portion 122a of the raceway groove 122. Furthermore, a straight portion 122b parallel to the axis is provided at the end of the raceway groove 122 on the coupling opening side. In this case, the depth of the raceway groove 122 should increase toward the coupling opening. However, the provision of the retainer assembly chamfer 124 reduces the depth of the raceway groove 122 by a corresponding amount. (In the illustrated example, the depth of the raceway groove 122 in the axial region L2 where the retainer assembly chamfer 124 is provided is uniform.) In the illustrated example, the retainer assembly chamfer 124 is cylindrically shaped along the raceway groove 122. Therefore, the axial length L2 of the retainer assembly chamfer 124 is increased, and the axial region where the raceway groove 122 is shallower increases. As a result, the depth of the rolling groove 122 near the axial center, which is frequently used, becomes shallower, and there is a possibility that the balls may move up to the edge of the rolling groove 122 .

[0016] Therefore, an object of the present invention is to prevent the balls from moving upward toward the edge of the raceway grooves due to the formation of the retainer assembly chamfers in a UJ type constant velocity universal joint with six balls.

[0017] Means for solving problems

[0018] In order to solve the above-mentioned problems, the present invention provides a fixed constant velocity universal joint, which is an undercut-free fixed constant velocity universal joint.

[0019] The fixed constant velocity universal joint comprises: an outer coupling member having six rolling grooves formed at equal intervals in the circumferential direction on its inner circumferential surface and an inner diameter spherical portion provided between adjacent rolling grooves; an inner coupling member having six rolling grooves formed at equal intervals in the circumferential direction on its outer circumferential surface and an outer diameter spherical portion provided between adjacent rolling grooves; six balls arranged between the rolling grooves of the outer coupling member and the rolling grooves of the inner coupling member; and a retainer having a spherical outer circumferential surface fitted with the inner diameter spherical portion of the outer coupling member and a spherical inner circumferential surface fitted with the outer diameter spherical portion of the inner coupling member, wherein the retainer holds the six balls.

[0020] The raceway groove of the outer joint member and the raceway groove of the inner joint member each have an arc portion and a straight portion provided on one axial side of the arc portion.

[0021] in,

[0022] The ratio PCD(BALL) / Db of the pitch circle diameter PCD(BALL) of the six balls to the diameter Db of each ball is set in the range of 3.30 to 3.35.

[0023] A retainer assembly chamfer formed by a surface whose cross-sectional curvature radius gradually decreases toward the other axial side is provided at one axial end portion of the boundary between the raceway groove and the inner spherical portion of the outer joint member.

[0024] In a UJ type constant velocity universal joint with six balls, when the ratio of the pitch circle diameter PCD(BALL) of the balls to the diameter Db of each ball, PCD(BALL) / Db, is 3.30 to 3.35, there is a problem of interference between the retainer and the outer coupling member when the retainer is assembled to the outer coupling member. Therefore, it is necessary to provide a retainer assembly chamfer on the outer coupling member. In this case, in the present invention, the retainer assembly chamfer is set as a surface (e.g., a conical surface) whose curvature radius of the cross section gradually decreases as it approaches the other axial side. The axial length L1 of such a conical retainer assembly chamfer (see Figure 4 ) can be longer than the axial length L2 of the cylindrical retainer assembly chamfer (refer to Figure 22 ) is short, thus reducing the axial area where the track groove depth is shallow due to the chamfering for retainer assembly. This ensures the depth of the track groove, particularly near the axial center where it is frequently used, and prevents balls from moving upward toward the edges of the track groove.

[0025] By forming the retainer assembly chamfer into a conical surface as described above, the other axial end portion of the retainer assembly chamfer can be arranged axially toward one side relative to the center O of the coupling.

[0026] When a raceway chamfer is provided in a region of the boundary between the raceway groove and the spherical portion of the outer joint member on the axially other side than the retainer assembly chamfer, the raceway chamfer and the retainer assembly chamfer can be formed as forged surfaces.

[0027] The present invention can be applied to a UJ-type constant velocity universal joint that seeks to be compact and lightweight, and optimizes the dimensions of each component to achieve strength, load capacity, aging resistance, and low transmission torque loss that are equal to or greater than those of existing products. Specifically, the present invention can be applied to a UJ-type fixed constant velocity universal joint in which the center of curvature Oto of the ball center trajectory of the arc portion of the raceway groove of the outer raceway member and the center of curvature Oti of the ball center trajectory of the arc portion of the raceway groove of the inner raceway member are offset axially to opposite sides by equal distances relative to the raceway center O, and when the angle formed by a straight line connecting the center of curvature Oto of the ball center trajectory of the arc portion of the raceway groove of the outer raceway member and the center of the ball is defined as an offset angle η and a plane P passing through the raceway center O and perpendicular to the axis, the offset angle η is 7° to 7.1°.

[0028] In addition, the present invention can be applied to the following UJ type fixed constant velocity universal joint, that is, the curvature center Oco of the spherical outer peripheral surface of the retainer and the curvature center Oci of the spherical inner peripheral surface are offset to opposite sides by equal distances relative to the coupling center O, and when the axial distance between the curvature center Oco of the spherical outer peripheral surface of the retainer and the coupling center O is set to the retainer offset f2, and the axial distance between the curvature center Oto of the ball center trajectory of the arc portion of the rolling groove of the outer coupling member and the coupling center O is set to the total offset F, the ratio f2 / F of the retainer offset f2 to the total offset F is 0.143~0.145.

[0029] Effects of the Invention

[0030] As described above, according to the UJ type constant velocity universal joint with six balls of the present invention, it is possible to prevent the balls from moving upward toward the edge of the raceway groove due to the formation of the retainer assembly chamfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an axial cross-sectional view of a fixed constant velocity universal joint according to one embodiment of the present invention.

[0032] Figure 2 This is a front view of the fixed constant velocity universal joint as viewed from the axial direction.

[0033] Figure 3 This is a cross-sectional view of the contact point between the balls and the raceway grooves of the fixed constant velocity universal joint.

[0034] Figure 4 This is an axial cross-sectional view of the outer coupling member of the fixed constant velocity universal joint.

[0035] Figure 5 This is an enlarged view of the front view of the outer joint member of the fixed constant velocity universal joint as seen from the axial direction of the outer joint member. Figure 14 (An enlarged view of a portion corresponding to section P).

[0036] Figure 6 It is a cross-sectional view showing a state where the precursor of the outer joint member is subjected to extrusion forging.

[0037] Figure 7 Is set at Figure 6 A three-dimensional view of multiple extrusion punches of a metal die.

[0038] Figure 8 It is a three-dimensional diagram of an extrusion punch.

[0039] Figure 9 It is a cross-sectional view showing a state where extrusion forging is completed.

[0040] Figure 10 It is a three-dimensional diagram of an extruded forging.

[0041] Figure 11 This is a cross-sectional view showing the state of die opening after stretch forging.

[0042] Figure 12 It is a cross-sectional view showing the state of demolding an extruded forging.

[0043] Figure 13 It is a three-dimensional view of the outer coupling component.

[0044] Figure 14 This is a front view of a conventional outer joint member in which a retainer is assembled, as seen from the axial direction of the outer joint member.

[0045] Figure 15 yes Figure 14 Cross-sectional view along line A-A.

[0046] Figure 16 yes Figure 14 Cross-sectional view along line BB.

[0047] Figure 17 yes Figure 14 Magnified view of the P section.

[0048] Figure 18 This is a perspective view of a conventional outer coupling member.

[0049] Figure 19 It is a cross-sectional view showing a state where ironing and draw forging are performed on a precursor of an outer joint member.

[0050] Figure 20 yes Figure 19 A three-dimensional view of the ironing and drawing punch of a metal die.

[0051] Figure 21 It is a three-dimensional image of a thinned and stretched forging.

[0052] Figure 22 yes Figure 18 Axial cross-section of the outer coupling member.

[0053] Description of reference numerals:

[0054] 1. Fixed constant velocity universal coupling (UJ type constant velocity universal coupling)

[0055] 2 Outer coupling member

[0056] 2' precursor (pre-forged part)

[0057] 2” Extruded Forgings

[0058] 3 Inner coupling member

[0059] 4 balls

[0060] 5 Cage

[0061] 21 inner diameter spherical part

[0062] 22 raceway groove (outer ring raceway groove)

[0063] 22a Arc part

[0064] 22b Straight section

[0065] 23 Cup Department

[0066] 24 Chamfer for cage assembly

[0067] 25 Raceway chamfer

[0068] 26 cup inlet chamfer

[0069] 31 outer diameter spherical part

[0070] 32 raceway groove (inner ring raceway groove)

[0071] 32a Straight section

[0072] 32b arc part

[0073] 51 Concave Pocket

[0074] 70 Forging Device

[0075] 71 Die

[0076] 72 Punch unit

[0077] 73 Extrusion Punch

[0078] O Coupling Center

[0079] Oti is the center of curvature of the ball center trajectory in the arc portion of the inner ring raceway groove.

[0080] Oto The center of curvature of the ball center trajectory in the arc portion of the outer ring raceway groove

[0081] Oci is the center of curvature of the inner surface of the cage

[0082] Oco is the center of curvature of the outer surface of the cage. DETAILED DESCRIPTION

[0083] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0084] Figure 1 and Figure 2A UJ type constant velocity universal joint 1 is shown as a fixed constant velocity universal joint according to one embodiment of the present invention. The UJ type constant velocity universal joint 1 includes an outer joint member 2, an inner joint member 3, six balls 4, and a retainer 5. A shaft 10 is connected to the inner joint member 3. The shaft 10 extends from the outer joint member 2 to one side in the axial direction ( Figure 1 The UJ type constant velocity universal joint 1 is installed at the outer end of the drive shaft of a motor vehicle, for example, and a sliding type constant velocity universal joint is installed at the end (inner end) on the opposite side of the shaft 10 (intermediate shaft). Below, the side ( Figure 1 The right side of the coupling is called the "coupling open side", and the opposite side ( Figure 1 The left side of the coupling is called the "inside coupling".

[0085] The outer joint member 2 integrally includes a cup portion 23 having six raceway grooves 22 (hereinafter referred to as "outer ring raceway grooves 22") formed on the inner circumferential surface thereof, and a shaft portion (not shown) protruding from the bottom wall of the cup portion 23. An inner diameter spherical portion 21 (see FIG. 1 ) is provided between the raceway grooves 22 in the circumferential direction of the inner circumferential surface of the outer joint member 2. Figure 2 Six raceway grooves 32 (hereinafter referred to as "inner ring raceway grooves 32") are formed on the outer peripheral surface of the inner joint member 3 to form pairs with the raceway grooves 22 of the outer joint member 2 (see Figure 1 ). An outer diameter spherical portion 31 is provided between the raceway grooves 32 in the circumferential direction of the outer peripheral surface of the inner joint member 3 (refer to Figure 2 One ball 4 is positioned between each of the outer ring raceway grooves 22 and inner ring raceway grooves 32. The outer ring raceway grooves 22 and inner ring raceway grooves 32 are formed at equal intervals (60° pitch) along the circumference. Therefore, the six balls 4, serving as torque transmission members, are arranged at equal intervals (60° pitch) along the circumference.

[0086] The inner joint member 3 has an inner hole formed with an inner spline portion 33 (see Figure 1 The end of the shaft 10 is inserted into the inner hole of the inner coupling member 3. The external spline portion 11 formed at the end of the shaft 10 engages with the internal spline portion 33 of the inner coupling member 3, thereby connecting the two in a torque-transmitting manner. A circumferential groove 12 is formed at the end of the shaft 10. A retaining ring 6 mounted in this circumferential groove 12 prevents the shaft 10 from disengaging from the inner coupling member 3 in the axial direction.

[0087] The outer ring raceway groove 22 has an arcuate portion 22a located on the inner side of the coupling and a straight portion 22b located on the coupling opening side. The inner ring raceway groove 32 has a straight portion 32a located on the inner side of the coupling and an arcuate portion 32b located on the coupling opening side. The ball center trajectory of the arcuate portions 22a and 32b of each raceway groove 22 and 32 is arcuate, while the ball center trajectory of the straight portions 22b and 32a of each raceway groove 22 and 32 is straight. It should be noted that the ball center trajectory refers to the trajectory that the center of the ball 4 passes through when the ball moves along the raceway grooves 22 and 32.

[0088] The center of curvature Oto of the ball center trajectory of the arcuate portion 22a of the outer ring raceway groove 22 and the center of curvature Oti of the ball center trajectory of the arcuate portion 32b of the inner ring raceway groove 32 are offset axially in opposite directions by equal distances F and F relative to the coupling center O. In the illustrated example, the center of curvature Oto of the ball center trajectory of the arcuate portion 22a of the outer ring raceway groove 22 is offset toward the coupling opening relative to the coupling center O, while the center of curvature Oti of the ball center trajectory of the arcuate portion 32b of the inner ring raceway groove 32 is offset toward the inner side of the coupling relative to the coupling center O. The straight portion 22b of the outer ring raceway groove 22 extends tangentially from the end of the arcuate portion 22a on the coupling opening side, parallel to the axial direction in the illustrated example. The straight portion 32a of the inner ring raceway groove 32 extends tangentially from the end of the arcuate portion 32b on the coupling inner side, parallel to the axial direction in the illustrated example.

[0089] The retainer 5 is provided with six pockets 51, each housing a ball 4. The spherical outer surface 52 of the retainer 5 engages with the inner spherical portion 21 of the outer joint member 2, while the spherical inner surface 53 of the retainer 5 engages with the outer spherical portion 31 of the inner joint member 3. The diameter of the outer surface 52 of the retainer 5 is approximately equal to the diameter of the inner spherical portion 21 of the outer joint member 2, while the diameter of the inner surface 53 of the retainer 5 is approximately equal to the diameter of the outer spherical portion 31 of the inner joint member 3. The center of curvature Oco of the outer surface 52 of the retainer 5 (i.e., the center of curvature of the inner spherical portion 21 of the outer joint member 2) and the center of curvature Oci of the inner surface 53 of the retainer 5 (i.e., the center of curvature of the outer spherical portion 31 of the inner joint member 3) are offset axially to opposite sides by an equal distance f2 relative to the joint center O. In the example shown in the figure, the center of curvature Oco of the outer peripheral surface 52 of the retainer 5 is offset toward the coupling opening relative to the coupling center O, and the center of curvature Oci of the inner peripheral surface 53 of the retainer 5 is offset toward the coupling inner side relative to the coupling center O.

[0090] Here, the axial distance between the center of curvature Oto of the ball center trajectory of the arcuate portion 22a of the outer ring raceway groove 22 and the center of curvature Oco of the outer peripheral surface 52 of the retainer 5 (= the axial distance between the center of curvature Oti of the ball center trajectory of the arcuate portion 32b of the inner ring raceway groove 32 and the center of curvature Oci of the inner peripheral surface 53 of the retainer 5) is the raceway offset amount f1. Furthermore, the axial distance between the center of curvature Oco of the outer peripheral surface 52 of the retainer 5 and the coupling center O (= the axial distance between the center of curvature Oci of the inner peripheral surface 53 of the retainer 5 and the coupling center O) is the retainer offset amount f2. Moreover, the sum of the raceway offset f1 and the retainer offset f2, that is, the axial distance between the center of curvature Oto of the ball center trajectory of the arc portion 22a of the outer ring raceway groove 22 and the coupling center O (= the axial distance between the center of curvature Oti of the ball center trajectory of the arc portion 32b of the inner ring raceway groove 32 and the coupling center O) is the total offset F.

[0091] Figure 3 This is a cross-sectional view of the contact points between ball 4 and raceway grooves 22 and 32. The cross-sectional shapes of outer raceway groove 22 and inner raceway groove 32 are elliptical and Gothic arch-like. Ball 4 makes angular contact with outer raceway groove 22 at points C1 and C2, and with inner raceway groove 32 at points C3 and C4.

[0092] The above-described UJ constant velocity universal joint 1 is designed to be compact and lightweight, while optimizing the dimensions of each component to achieve strength, load capacity, aging resistance, and low transmission torque loss comparable to or better than existing products. Specifically, the dimensions of each component of the UJ constant velocity universal joint 1 are shown in Table 1 below.

[0093] [Table 1]

[0094]

[0095] The definitions of the items in Table 1 above are as follows.

[0096] Deviation angle η

[0097] exist Figure 1 In the axial cross-section shown, when the working angle is 0°, the angle between the plane P passing through the center O of the coupling and perpendicular to the axis and the straight line connecting the center of the ball 4 and the center of curvature Oti of the ball center trajectory of the arc portion 32b of the inner ring rolling groove 32 (= the angle between the plane P and the straight line connecting the center of the ball 4 and the center of curvature Oto of the ball center trajectory of the arc portion 22a of the outer ring rolling groove 22) is set as the offset angle η.

[0098] Contact angle α

[0099] exist Figure 3In the cross section shown, the angle formed by a straight line passing through the center of the ball 4 and the contact points C1, C2, C3, and C4 between the ball 4 and the raceway grooves 22 and 32 and a plane Q passing through the axis and the center of the ball 4 is referred to as the contact angle α.

[0100] ·Base shaft diameter Ds

[0101] The outer diameter of the minimum diameter portion 13 in the torque load region (the axial region between the external spline portions formed at both axial ends) of the shaft 10 is defined as the reference shaft diameter.

[0102] Ball pitch diameter PCD (BALL)

[0103] The distance between the center of curvature Oto of the ball center trajectory of the arc portion 22a of the outer ring rolling groove 22 and the ball center (= the distance between the center of curvature Oti of the ball center trajectory of the arc portion 32b of the inner ring rolling groove 32 and the ball center) is PCR (refer to Figure 1 ), twice the value of PCR is the pitch circle diameter PCD (BALL) of the ball.

[0104] Cage wall thickness Tc

[0105] In the state where the working angle is 0°, the radial wall thickness of the retainer 5 in the plane P passing through the coupling center O and perpendicular to the axis is defined as the retainer wall thickness Tc (refer to Figure 1 ).

[0106] As described above, when the UJ type constant velocity universal joint 1 is made compact, specifically, when the ratio PCD(BALL) / Db of the pitch circle diameter PCD(BALL) of the ball 4 to the ball diameter Db is set within the range of 3.30 to 3.35, Figures 14 to 16 When the retainer 5 is assembled to the inner periphery of the outer coupling member 2 using the same method, the two will interfere with each other. Therefore, in this embodiment, a retainer assembly chamfer 24 is provided at the coupling opening side end portion of the boundary between the raceway groove 22 and the inner diameter spherical portion 21 of the outer coupling member 2, and this portion is recessed toward the outer diameter side.

[0107] Specifically, if Figure 4 As shown, the boundary between the raceway groove 22 and the inner diameter spherical portion 21 of the outer coupling member 2 is formed with a retainer assembly chamfer 24 provided at the end portion on the coupling opening side and a raceway chamfer 25 provided adjacent to the inner side of the coupling. Figure 5 As shown, when the retainer 5 is assembled to the outer joint member 2 , interference between the edge portion 51 a provided at the axial end portion of the pocket 51 of the retainer 5 and the outer joint member 2 can be avoided.

[0108] The retainer assembly chamfer 24 is a surface whose cross-sectional radius of curvature gradually decreases as it approaches the inner side of the coupling, and in the illustrated example, is a conical surface. The raceway chamfer 25 is a cylindrical surface curved along the raceway groove 22, extending to the end of the raceway groove 22 on the inner side of the coupling. A conical cup inlet chamfer 26 is provided along the entire circumference of the inner circumference of the cup portion 23, on the coupling opening side.

[0109] As described above, by forming the retainer assembly chamfer 24 into a conical surface, Figure 22 Compared with the cylindrical surface-shaped retainer assembly chamfer 124 shown in FIG. 1 , the axial length can be shortened (L1 < L2). Specifically, the coupling inner end of the retainer assembly chamfer 24 is arranged at a position closer to the coupling center O (see FIG. 1 ). Figure 1 ) is positioned closer to the coupling opening. In the illustrated example, it is positioned closer to the coupling opening than the center of curvature of the inner spherical portion 21 (i.e., the center of curvature Oco of the outer peripheral surface 52 of the retainer 5). By shortening the axial length of the retainer assembly chamfer 24, the axial region of the raceway groove 22 shallowed by the retainer assembly chamfer 24 is shortened. Consequently, the depth of the raceway groove 22 is maintained, particularly in the axial region near the coupling center O, which is frequently used. This prevents the balls 4 from ascending toward the edge of the raceway groove 22 in this region.

[0110] In the illustrated example, the ridgeline 28 at the boundary between the retainer assembly chamfer 24 and the track groove 22 is tilted so as to shift radially inward as it approaches the inner side of the coupling. Consequently, the track groove 22 gradually deepens (D1 < D2 < D3) from the coupling opening end of the retainer assembly chamfer 24 toward the inner end of the coupling. This ensures a sufficient depth in the track groove 22 near the inner end of the retainer assembly chamfer 24, preventing the balls 4 from climbing toward the edge of the track groove 22 in this area.

[0111] The conical retainer assembly chamfer 24 can be formed by extrusion. Specifically, the outer joint member 2 is formed by forming a pre-forged part 2' having a cup part 23' and a rod part 27' (see Figure 6 ), an extrusion forging step in which the pre-forged piece 2' is extruded to form the raceway grooves 22 and the retainer assembly chamfers 24, and a turning step in which the inner circumferential surface of the cup portion 23' is turned. The extrusion forging step will be described in detail below.

[0112] Use as Figure 6 The extrusion forging device 70 shown in FIG. 1 is used for the extrusion forging process. The extrusion forging device 70 includes a die 71 and a punch unit 72. The punch unit 72 has a Figure 7 The six extrusion punches 73 are divided according to the raceway grooves. Figure 8As shown, each extrusion punch 73 includes a spherical surface forming portion 73a, a track groove forming portion 73b, a first chamfer forming portion 73c, a second chamfer forming portion 73d, and a third chamfer forming portion 73e. The track groove forming portion 73b, the first chamfer forming portion 73c, and the second chamfer forming portion 73d have shapes corresponding to the track groove 22, the retainer assembly chamfer 24, and the track chamfer 25 of the finished product, respectively. While the spherical surface forming portion 73a and the third chamfer forming portion 73e do not completely match the inner diameter spherical portion 21 and the cup inlet chamfer 26 of the finished product, they have substantially the same shapes.

[0113] In the extrusion forging process, such as Figure 6 As shown, the die 71 is lowered while the pre-forged part 2' is set on the punch unit 72, thereby squeezing the outer peripheral surface of the pre-forged part 2' (see Figure 9 ). Thus, the shape of the extrusion punch 73 is transferred to the inner peripheral surface of the pre-forged part 2', as shown in FIG. Figure 10 As shown, an extruded forging 2" has a spherical portion 21', a raceway groove 22, a chamfer 24 for retainer assembly, a raceway chamfer 25 and a cup inlet chamfer 26' formed on the inner circumferential surface. The raceway groove 22, the chamfer 24 for retainer assembly and the raceway chamfer 25 of the extruded forging 2" have the same shape as the finished part and are not subsequently processed. The spherical portion 21' and the cup inlet chamfer 26' of the extruded forging 2" are not exactly the same as the inner diameter spherical portion 21 and the cup inlet chamfer 26 of the finished part, and traces 29' of the circumferential gaps of multiple extrusion punches 73 are formed.

[0114] Then, by raising the extrusion forging 2" together with the plurality of extrusion punches 73, as shown in FIG. Figure 11 As shown in FIG. 1 , the plurality of extrusion punches 73 are approached to each other in the circumferential direction while being reduced in diameter. Furthermore, if the maximum outer diameter of the extrusion punch 73 is smaller than the inner diameter of the opening of the extrusion forging 2″, then Figure 12 As shown, the extruded forging 2 ″ is separated from the punch unit 72 .

[0115] After that, the spherical portion 21' and the cup inlet chamfer 26' on the inner circumferential surface of the extrusion forging 2" are turned to form the inner diameter spherical portion 21 and the cup inlet chamfer 26, thereby completing the Figure 13 The outer coupling member 2 shown. It should be noted that, Figure 13 The dark areas in the figure represent areas where turning has been performed. The raceway groove 22, retainer assembly chamfer 24, and raceway chamfer 25 on the inner circumferential surface of the outer coupling member 2 manufactured through the above steps are forged surfaces, while the inner diameter spherical portion 21 and cup inlet chamfer 26 are turned surfaces.

Claims

1. A fixed constant velocity universal coupling, which is an undercut-free fixed constant velocity universal coupling. The fixed constant velocity universal joint has: an outer coupling member having six raceway grooves formed on an inner peripheral surface at equal intervals in the circumferential direction and an inner diameter spherical portion provided between adjacent raceway grooves; an inner coupling member having six raceway grooves formed on an outer peripheral surface at equal intervals in the circumferential direction and an outer diameter spherical portion provided between adjacent raceway grooves; six balls disposed between the raceway groove of the outer coupling member and the raceway groove of the inner coupling member; and a retainer having a spherical outer peripheral surface fitted with the inner diameter spherical portion of the outer joint member and a spherical inner peripheral surface fitted with the outer diameter spherical portion of the inner joint member, wherein the retainer holds the six balls; The raceway groove of the outer joint member and the raceway groove of the inner joint member each have an arc portion and a straight portion provided on one axial side of the arc portion. in, The ratio PCD(BALL) / Db of the pitch circle diameter PCD(BALL) of the six balls to the diameter Db of each ball is set in the range of 3.30 to 3.

35. A retainer assembly chamfer formed by a surface whose cross-sectional curvature radius gradually decreases toward the other axial side is provided at one axial end portion of the boundary between the raceway groove and the inner spherical portion of the outer joint member.

2. The fixed constant velocity universal joint according to claim 1, wherein: The retainer assembly chamfer is formed by a conical surface.

3. The fixed constant velocity universal joint according to claim 1, wherein: The other axial end portion of the retainer assembly chamfer is located axially closer to one side than the center O of the coupling.

4. The fixed constant velocity universal joint according to claim 1, wherein: A raceway chamfer is provided in a region of the boundary between the raceway groove and the inner diameter spherical portion of the outer joint member, which is on the axially other side than the retainer assembly chamfer. The raceway chamfer and the cage assembly chamfer are forged surfaces.

5. The fixed constant velocity universal joint according to claim 1, wherein: The center of curvature Oto of the ball center locus of the arc portion of the raceway groove of the outer joint member and the center of curvature Oti of the ball center locus of the arc portion of the raceway groove of the inner joint member are offset axially to opposite sides by equal distances relative to the raceway center O. When the angle formed by the straight line connecting the center of curvature Oto of the ball center trajectory of the arc portion of the rolling groove of the outer joint member and the center of the ball and the plane P passing through the joint center O and perpendicular to the axis is defined as the offset angle η, the offset angle η is 7° to 7.1°.

6. The fixed constant velocity universal joint according to claim 1, wherein: The center of curvature Oco of the spherical outer peripheral surface of the retainer and the center of curvature Oci of the spherical inner peripheral surface are offset to the opposite sides by equal distances relative to the coupling center O. When the axial distance between the center of curvature Oco of the spherical outer surface of the retainer and the center O of the coupling is set as the retainer offset f2, and the axial distance between the center of curvature Oto of the ball center trajectory of the arc portion of the rolling groove of the outer coupling member and the center O of the coupling is set as the total offset F, the ratio f2 / F of the retainer offset f2 to the total offset F is 0.143~0.145.

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