JP2002130315A - Manufacturing method for isochronous joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for an inner ring capable of forging with high accuracy and enhancing the lifetime of a die, though the ring is designed so as to have a track groove having a curved cross section at its bottom. SOLUTION: The manufacturing method is the one for manufacturing an inner ring 1 for an isochronous joint wherein a track groove 6 having a curved cross section at its bottom is formed at each of a plurality of points in the direction of the periphery of a spherical external surface along the direction of the axis. A semi-finished material W forged into a shape of an axial groove 6w, which is the track groove 6, is prepared on the surface of the outside diameter of an almost cylindrical shape. Then, the semi-finished material W is forged into a finished shape of the track groove 6 of the inner ring 1 of the isochronous joint having a spherical external surface. Upon the forging, the semi-finished material W is put into a row of divided dies 21, and each divided die 21 is moved to the center side. In this state, the semi-finished material W is compressed by a pair of punches 23, 24 at both ends of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inner race in a constant velocity joint having a curved bottom longitudinal section of a track groove, for example, a barfield type constant velocity joint.

[0002]

2. Description of the Related Art As a constant velocity joint, as shown in FIG. 18, an inner race 1 having a spherical outer surface 1a having a track groove 6 formed along the axial direction, and a spherical groove 2 opposing the track groove 6 on a spherical inner surface 2a. And a torque transmitting ball 3 incorporated between opposed track grooves 6 and 8.
And a retainer 4 that holds the torque transmitting ball 3 and is guided by the spherical outer surface 1a of the inner ring 1 and the spherical inner surface 2a of the outer ring 2. A serration 7 that meshes with the shaft 5 is formed on the inner diameter surface of the inner ring 1. In the BJ-type (bar-field type) constant velocity joint as shown in the figure, the track grooves 6, 8 of the inner ring 1 and the outer ring 2 have a curved bottom vertical cross-sectional shape.

In manufacturing the inner ring 1 of this constant velocity joint,
Generally, the following steps are taken. First, a cylindrical billet is formed into a rough shape of an inner ring by cold forging, the width surface and the outer diameter surface of this inner ring material are turned, and serrations are broached on the inner diameter surface. Thereafter, heat treatment such as carburizing and quenching is performed, the outer diameter 1a is polished, and the track groove 6 is polished, whereby the inner ring 1 is completed. In the constant velocity joint, the shapes and dimensions of the track grooves 6 and 8 are required to have high precision, and as described above,
Are finished by polishing. This polishing step is an expensive step, and the manufacturing cost of the inner ring 1 is high.

For this reason, attempts have been made to finish the track groove 6 of the inner race 1 by forging. In this case, FIG.
In the BJ type shown in (1), the track groove 6 cannot be formed by a method in which the raw material is pushed into a normal die in the axial direction because the vertical sectional shape of the groove bottom is curved. Therefore, a method of forming only one surface in the axial direction of the inner ring material and generating the remaining one surface after inversion, a method of using a plurality of divided dies arranged on the circumference, and the like have been proposed (for example, Japanese Patent Publication No. 61-24092, JP 2000-140
No. 984).

[0005]

However, the above-described method of forming one side at a time requires reversal of the inner ring material, and forging is performed in two steps. There is a seam between the surfaces. The method of using the split die is to reduce the diameter of the row of split dies and compress the columnar material in the axial direction, thereby forming the material on the outer diameter surface forming portion serving as a ridge between the adjacent track grooves 6 of the inner ring 1. Is plastically flowed to form the shape of the inner ring 1, but it is difficult to fill the outer diameter surface forming portion with the material. Therefore, the outer diameter surface 1
The precision of a is difficult to obtain, the machining allowance for turning the outer diameter surface 1a increases, a large load is required for molding, the abrasion of the die is liable to occur, and the life of the die is shortened. In addition, it is difficult to ensure the accuracy of the track groove 6 sufficiently. In particular, by using eight track grooves 6 as compared with a general one having six track grooves 6, the number of the torque transmitting balls 3 is increased to secure a load capacity, and the size is reduced. In the constant velocity joint described above, since the width of the outer diameter surface forming portion between the track grooves 6 is narrow, it is more difficult to fill the outer diameter surface forming portion with the material. Therefore, it becomes more difficult to secure the accuracy of the outer diameter surface 1a and the track groove 6.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a constant velocity joint inner ring in which forging can be performed with high accuracy and the life of a die can be improved even though the inner ring has a track groove with a groove bottom having a curved vertical cross section. It is.

[0007]

The manufacturing method of the present invention comprises:
In a method of manufacturing a constant velocity joint inner ring in which a track groove having a groove bottom longitudinal cross-sectional shape is formed along the axial direction at a plurality of locations in the circumferential direction of the spherical outer surface, the outer diameter surface of the substantially cylindrical shape is A process of preparing an intermediate material forged into a shape having the same number of axial grooves as the number of track grooves, and forging the intermediate material into a shape having a finished shape of the track grooves and a spherical outer surface of the inner race of the constant velocity joint. Forging process. According to this method, since an intermediate material having an axial groove corresponding to the track groove is forged, plastic flow to an outer diameter surface forming portion between adjacent track grooves can be reduced. Therefore, the outer diameter surface and the track groove can be accurately forged. Since the accuracy of the outer diameter surface is improved, when turning or grinding is performed later, the cutting allowance can be reduced, the processing time can be reduced, and the yield can be improved. By appropriate contrivance, turning of the outer diameter surface or the like can be omitted. Further, since the track grooves are accurately forged, the step of polishing the track grooves can be omitted, and the manufacturing cost is improved. Since a small amount of plastic flow is required, the wear of the die is small, and a long life of the die can be obtained. The intermediate material has an axial groove,
Since it is substantially cylindrical, it can be easily forged from a columnar material or the like. For this reason, forging can be performed with high productivity with a simple forging facility as compared with a case where an intermediate material having a shape close to the completed shape of the inner ring is used, for example. In the subsequent forging process, even if a cylindrical intermediate material having an axial groove is used, there is less difference in forging equipment and productivity as compared with the case of using an intermediate material having a shape close to the completed inner ring.

The above forging process can be performed, for example, by the following method. That is, a die row is used in which a plurality of divided dies each having a track groove forming die surface and an outer diameter surface forming die surface at an inner end are inwardly arranged on a circumference so as to be able to advance and retreat in a radial direction in a die holder. The intermediate material is inserted into the dice row so that the axial grooves on the outer periphery correspond to the dice, and the dice in the dice row are moved toward the center. In this state, by compressing the intermediate material from both ends with a pair of punches, the inner surface of the track groove is formed in the intermediate material, and the outer diameter surface forming portion between the adjacent track grooves of the inner ring is formed on the outer diameter side. Form to extrude. By using the split dies as described above, the inner race having the track groove having the curved bottom vertical cross section can be forged easily and efficiently and accurately.

The split die may have at its inner end a pair of material guide surfaces extending linearly from the track groove forming die surface and the outer diameter surface forming die surface to both sides in the axial direction. In this way, by using the split die having the material guide surface portion extending linearly, the substantially cylindrical intermediate material is compressed while being guided by the material guide surface portion in the process of being compressed in the axial direction. Therefore, the plastic flow of the material is performed evenly and smoothly without bias, and forging can be performed with higher accuracy.

The operation of moving each divided dice in the dice row toward the center can be performed, for example, by using a dice base surrounding the outer periphery of the dice row. By moving the die base in the axial direction, the outer end of each split die is pushed by an inclined guide surface provided on the inner periphery of the die base, and the split die is moved. In this case, each of the divided dies has a pair of inclined side surfaces which are inclined with respect to the radial direction of the dice row and form a V-shape with each other on both side portions of the outer end, and these inclined side surfaces are formed in the axial direction. The die base has a plurality of recesses into which the outer ends of the divided dies fit, and the inner surface of the recess has the guide surface along the inclined side surfaces on both sides of the divided dies. May be used. In this case, when the die base is moved in the axial direction, each split die is pressed by a pair of guide surfaces in a concave portion of the die base at a pair of inclined side surfaces that form a V-shape with each other at the outer ends. Therefore, the split dies move toward the center while the width direction position is regulated by the pair of guide surfaces of the die base. Therefore, the pitch error of the split dies is suppressed, and a track groove with a small pitch error can be forged.

In the intermediate material, the axial groove may extend from one end to an intermediate position in the axial direction, or may extend over both ends. If the axial groove extends to an intermediate position, forging of the intermediate material is much easier. Even in the axial groove up to such an intermediate position, the filling property at the time of plastic flow at the time of subsequent forging can be sufficiently ensured.

When the intermediate material has an axial groove extending over the entire length, the intermediate material is formed such that a large-diameter portion and a small-diameter portion having different outer diameters are interposed via an axially intermediate tapered portion. It may be a continuous shape. The track groove of the inner race of the constant velocity joint generally has a different center between the outer diameter surface and the arc, and therefore has a different depth at one end and the other end. When using an intermediate material having a large diameter portion and a small diameter portion as described above,
According to such a difference in the track groove depth, the difference in plastic flow between the deep portion and the shallow portion can be reduced, and forging can be performed with a smaller load and better filling properties. Therefore, it leads to improvement in accuracy.

In the constant velocity joint inner ring manufactured by the method of the present invention, the track grooves may be provided at eight circumferential positions. The track grooves provided at eight locations use balls having a smaller diameter than before, and the number of grooves is increased in order to increase the number of balls and reduce the size. Is narrow, and it is difficult to obtain fillability due to plastic flow during forging. However, by using the intermediate material having the axial grooves as described above, even for such an inner race having eight track grooves, forging can be performed with good filling properties and accuracy can be ensured.

[0014]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows each process of the method for manufacturing the inner race of the constant velocity joint. As shown in FIG. 2D, the constant velocity joint inner ring 1 manufactured by this manufacturing method has a spherical outer surface 1.
The track groove 6 is formed at a plurality of positions in the circumferential direction of a in the axial direction, and the track groove 6 has a curved bottom 6a in a vertical cross-sectional shape. This manufacturing method
First, an intermediate material W shown in FIG. 6B is forged from a columnar material W0 shown in FIG. Intermediate material W is the outer diameter surface of the substantially cylindrical, is of a shape having an axial groove 6 _W number equal to the of the track grooves 6. The intermediate material W thus prepared is forged into a finished shape of the track groove 6 and a shape having a spherical outer surface 1a as shown in FIG. The forged material WA obtained in this forging process is an unpenetrated one in which the inner diameter hole 1b has a bottom 1c at the middle in the axial direction. The bottom 1c of the forged material WA is punched out by a pressing process or removed by turning, a serration 7 is formed in the inner diameter hole 1b, and the width surface and the spherical outer surface 1a are finished by machining such as turning or grinding. Further, by machining the details such as the opening edge of the inner diameter hole 1b and performing heat treatment, the finished constant velocity joint inner ring 1 shown in FIG. The inner surface of the track groove 6 of the completed inner ring 1 is a finished surface forged in the above-described forging process. The forging of the columnar material W0 and the forging of the intermediate material W are both performed cold.

FIGS. 13 to 17 show specific examples of the shape of the completed inner race 1 of the constant velocity joint. This inner ring 1 is shown in FIG.
8 constitutes a constant velocity joint. As shown in FIG. 13, the center O ₀ of the spherical outer surface 1a of the inner ring 1 is the joint angle center of the constant velocity joint. Center of curvature O of an arc curve formed by the vertical cross-sectional shape of groove bottom 6a of track groove 6
₁ is offset with respect to the center O ₀ of the spherical outer surface 1a. Serrations 7 are formed on the inner surface of the inner diameter hole 1b. As shown in FIG. 14, eight track grooves 6 are equally arranged in the circumferential direction. The outer diameter surface forming portion 1d serving as a ridge between the adjacent track grooves 6, 6 is narrower than the groove width of the track groove 6, and is, for example, less than half the groove width of the track groove 6. The number of track grooves 6 is
The number is not limited to eight, and may be any number, for example, six as shown in FIG.

FIG. 15 shows an example of the cross-sectional shape of the track groove 6. In the example shown in the figure, the track groove 6 has an arc-shaped or elliptical arc-shaped cross section. As shown in FIG. 16, the cross-sectional shape of the track groove 6 may be a gothic arch shape composed of a pair of opposed arcuate curves 6c, 6c. In the case of a gothic arch shape, the torque transmitting ball 3 comes into point contact with two contact points P on both sides of the inner surface of the track groove 6. Therefore, variation in the contact angle θ is reduced. Even when the cross-sectional shape of the track groove 6 is an elliptical arc, two-point contact occurs and the contact angle θ
Is small.

FIGS. 12A to 12C show a first example of the intermediate material W in FIG. 1B, and FIGS. 12D to 12F.
Shows a second example of the intermediate material. The intermediate material W of the first example is
Extending axial grooves 6 _W is the entire length, and is a different large-diameter portion Wa of the outer diameter and the small diameter portion Wb, and has a subsequent via a tapered portion Wc which narrowed gradually in the axially intermediate shape. The axial groove _6W has a constant depth over the entire length. Central concave portions a and b are formed on both end surfaces of the intermediate material W. The intermediate material W is forged into such a shape from the columnar material W0 in FIG. Intermediate material W of the second example
W has the same diameter over the entire length, and each axial groove 6 _W extends from one end to an intermediate position in the axial direction.
Although any of these first and second intermediate materials W and WW may be used, a case where the intermediate material W of the first example is used will be described below.

FIG. 2 shows a step of molding into an intermediate material. The right half of the figure shows a state before molding and the left half shows a state of completion of molding. The intermediate material forging device 10 includes a die 11,
It has upper and lower punches 12 and 13 for pressing the cylindrical material W0 put in the die 11 in the axial direction, and the lower punch 13 also serves as an ejector. The die 11 is installed on a lower base 14, and the upper punch 12 is fixedly installed on an upper base 15 driven up and down. Dice 11
It is the inner surface of the mold surface, which becomes the outer contour of the finished shape of the intermediate material W, and has a protrusion 11a for forming the axial grooves 6 _W to a plurality of positions in the circumferential direction. The upper punch 12 has a projection 12 for forming a central recess a of the intermediate material W.
a at the tip. Further, the upper punch 12, ridges 12b corresponding to the ridge portion between the axial grooves 6 _W of the intermediate material W is formed in a plurality of positions of the outer periphery, thereby the outer peripheral shape of the lower end surface, the intermediate material W It has a shape that matches the upper end surface of. The tip of the lower punch 13 is a molding surface for molding the central concave portion b of the intermediate material W. During forging, the bottom forming member 16 of the molding space of the die 11 has a height corresponding to the depth of the central concave portion b. Protruding from.

At the time of forging, the columnar material W shown in FIG.
0 is inserted into the die 11 and is put on the lower punch 13 as shown in the right half of FIG. In this state, the upper punch 12 enters the die 11,
By compressing the columnar material W0 in the axial direction, the intermediate material W is forged as shown in the left half of FIG.

FIG. 3 shows a forging device 20 for finish forging the intermediate material W, and FIG. 4 is an enlarged view of a main part thereof. FIG. 5 shows the relationship between the dice and the die base, and FIG. 6 shows the shape of the tip of the dice. As shown in FIG. 4, the forging apparatus 20 compresses a die row 22 in which a plurality of divided dies 21 are arranged on a circumference and an intermediate material W inserted inside the die row 22 in both axial directions from both ends. A pair of upper and lower punches 23, 24, a die base 25 for simultaneously moving the divided dies 21 of the die row 22 to the center side, and a backup ring 26 for guiding the die base 25 so as to be movable in the axial direction.

As shown in FIG. 6, the split die 21 has a track groove forming die surface 21a and an outer diameter forming die surface 21b at an inner end. Also, the track groove forming mold surface 2
1a and a pair of material guide surfaces 21c, 2 extending linearly from the outer diameter surface forming die surface 21b to both sides in the axial direction.
1d at the inner end. Track groove forming die surface 21a
Is a molding surface that matches the track groove 6 of the inner race 1 and is formed as a ridge having a cross-sectional shape such as an arc shape corresponding to the cross-sectional shape of the track groove 6. The protrusions serving as the track groove forming die surface 21a are curved in an arc shape so as to follow the groove bottom vertical cross-sectional shape of the track groove 6. The outer diameter surface forming die surface 21b is a spherical forming surface for forming the outer diameter surface 1a of the inner ring 1, and is provided on both sides in the width direction of the track groove forming die surface 21a. A pair of material guide surfaces 21c and 21d
Are curved surface portions 21ca, 21da each formed of an outer surface of a ridge following the track groove forming die surface 21a, and flat surface portions 21cb, 21db provided on both sides of the curved surface portions 21ca, 21da and continuing from the outer diameter surface forming die surface 21b. And

As shown in FIG. 5, the split die 21 has a tapered planar shape whose inner end is narrowed. The outer end of each of the split dies 21 has a pair of inclined side surfaces 2 that are inclined with respect to the radial direction of the die row 22 to form a V-shape with each other on both sides.
1e and 21e. These inclined side surfaces 21e are also inclined surfaces with respect to the axial direction so as to be located on the outer diameter side toward the lower side. A pair of inclined side surfaces 21e, 21
e, the outer end face 21f between the inclined side faces 21e, 21
e is a surface inclined with respect to the axial direction so as to be located on the outer diameter side toward the lower side with a chamfered portion.

The die base 25 has a plurality of recesses 27 into which the outer ends of the split dies are fitted. The die guides are formed on the inner surface of the recesses 27 along the inclined side surfaces 21e on both sides of the split dies 21. The surface 25a is formed. The die guide surface 25a is a surface that pushes the divided dies 21 to the center side by the axial movement of the die base 25, has a slope whose lower side is the outer diameter side, and
The dice base 25 is inclined along the radial direction of the die base 25 along the inclined side surfaces 21e on both sides. That is, the line segment that forms the horizontal cross section of the die guide surface 25 a also has an inclination with respect to the radial direction of the die base 25. The two die guide surfaces 25a of the recess 27,
The bottom surface 25b between 25a is the outer end surface 21 of the split die 21.
It is formed so as not to contact with f.

As shown in FIG. 4, each of the split dies 21
It is installed on the die holder 28 so as to be able to advance and retreat in the radial direction of the die row 22, and is urged to the outer diameter side by a spring member 29. Specifically, the divided die 21 has a guided member 30 fixed to the lower surface thereof with bolts 53, and the guided member 30 is fixed to the guide groove 3 provided in the die holder 28.
1 is fitted to be able to move forward and backward. By this fitting, the split die 21 is guided to be able to move forward and backward. The guide grooves 31 are radially provided for the number of the divided dies 21. The die holder 28 is fixedly installed on the lower mold base 32, and the spring member 29 is disposed in a concave portion provided in the lower mold base 32, and urges the guided member 30 to the outer diameter side. Lower mold stand 3
2, the backup ring 26 is fixedly installed. The backup ring 26 is a member to which the die base 25 is fitted to be able to move up and down when the die base 25 descends.
5 supports the reaction force of the force that pushes the split die 21 toward the center as it descends.

The die base 25 is fixedly installed on the lower surface of an upper mold base 33 which is driven up and down with respect to the lower mold base 32. Inside the die base 25 in the upper mold stand 33,
An upper plate 52 is provided. Upper punch 23
Protrudes from the lower surface at the center of the upper mold base 33, specifically, from the upper plate 52, is vertically movable with respect to the upper mold base 33, and is urged to a rising end position by a return spring 34. The upper punch 23 has its upper end position restricted with respect to the upper mold table 33, and can be moved up and down together with the upper mold table 33.
The lower end surface of the upper punch 23 has an inner hole 1 in the intermediate material W.
A projection 23 for forming b (FIG. 1C) is provided. The lower punch 24 can protrude and sink into the central space of the die row 22 from a hole provided in the center of the die holder 28. On the upper end surface of the lower punch 24, a projection 24a for forming the lower inner diameter hole 1b of the intermediate material W is provided.

As shown in FIG. 3, the upper mold stand 33 is installed so as to be able to move up and down with respect to a fixed frame (not shown), and is driven up and down by a lifting drive source (not shown) such as a hydraulic cylinder. . The upper punch 23 is driven downward by a punch drive source 41 such as a hydraulic cylinder installed in the upper mold stand 33. The upper mold base 33 includes an upper mold base main body 33a that is driven to move up and down, and an upper mold stand separate member 33b that is installed on the lower surface of the upper mold base 33 via a guide member 36 so as to be able to move up and down. The upper mold base 33 is capable of raising and lowering the upper mold base separate member 33b with respect to the upper mold base main body 33a in accordance with the pressing force by a built-in hydraulic damper means 35. This ascending escape operation is delayed by the action of the damper means 35.

The lower mold base 32 is provided with a lower frame 3 having a fixed position.
7 is supported by a mold stand guide 38 on the outer periphery so as to be able to move up and down, and a hydraulically-driven damper means 39, 40 enables a descending and retracting operation in accordance with the pressing force. This descending escape operation is a delayed operation due to the action of the damper means 39, 40. The lower punch 24 is driven up and down by a punch drive source 42 such as a hydraulic cylinder installed in the lower frame 37.

Next, a method of forging an intermediate material W using the forging device 20 will be described with reference to FIGS. First, as shown in FIG. 7, the intermediate material W is inserted into a dice row 22 including a plurality of dice 21. At this time, the lower punch 24 is set in a state where the protrusion 24a at the tip is projected above the die holder 28, and the central recess b (FIGS. 1 and 12) on the lower surface of the intermediate material W is fitted to the center position. Position. The intermediate material W is inserted so that the axial groove 6 _{W on the} outer periphery corresponds to each of the divided dies 21. In this state, the upper mold stand 33 is lowered as shown in FIG. Due to this lowering, each of the divided dies 21 that have spread as shown in FIG. 5C is pushed by the inclined die guide surface 25a of the die base 25, and simultaneously moves to the center side as shown in FIG. 5E. At this time, the pair of dice 21 is pressed by a pair of dice guide surfaces 25 a in the concave portion 27 of the die base 25 because a pair of inclined side surfaces 21 e, 21 e forming a V-shape on both sides of the rear end of the dice 21 are pressed. Errors are eliminated. In this way, the split die 21 moves to the center side, and as shown in FIG. 8, the upper plate 52 presses the upper surface of the die row 22 and the upper punch 23 presses the upper end surface of the intermediate material W, thereby closing the mold. Complete.

Next, as shown in FIG. 9, the upper punch 23 descends and the lower punch 2 moves relative to the die row 22.
Then, the intermediate material W is compressed from both ends. As a result, the intermediate material W is plastically deformed in a space surrounded by the divided dies 21 and the upper and lower punches 23 and 24. This plastic deformation plastically flows into the space generated between the track groove forming die surfaces 21a (FIG. 6) formed by the ridges of each of the split dies 21 by the compression in the axial direction. That is,
Outer diameter surface forming portion 1d between adjacent track grooves 6 of inner ring 1
The material is extruded to the outer diameter side so as to be a portion corresponding to (FIG. 14). As shown in FIG. 10, the upper and lower punches 23, 24
Moves to a predetermined height position, and when the compression in the axial direction is completed, forging is completed, and the intermediate material W becomes a forged material WA. That is, it is formed into a finished shape of the track groove 6 and a shape having a spherical outer surface 1a as shown in FIG. Thereafter, knockout is performed as shown in FIG. That is, the upper punch 23 rises, and the upper mold base 33
At the same time, the die base 25 is raised and retracted, and in a state where the divided dies 21 are returned to the outer diameter side by the restoring force of the spring member 29, the lower punch 24 is raised and the forged material WA is divided into the divided dies 2
Push up out of the space inside 1. The upper surface level of the split die 21 moves up and down with respect to the predetermined level L by the action of the damper means 35, 39, 40 (FIG. 3) in each process, but this vertical movement is not necessarily required.
In this way, from the input of the intermediate material W to the forged material W
The process up to the discharge of A is completed.

[0030] According to this inner ring manufacturing method, thus the cylindrical material W0 in Figure 1, pre-forged to an intermediate material W having an axial groove 6 _W corresponding to the track grooves 6, the axial grooves 6
_{Since the} intermediate material W having _W is forged into the finished shape of the track groove 6 and the shape having the spherical outer surface 1a, the plastic flow to the outer diameter surface forming portion 1d (FIG. 14) between the adjacent track grooves 6, 6 is small. I can do it. Therefore, the outer diameter surface 1a and the track groove 6 can be accurately forged. In particular, as in this embodiment, when the inner race 1 has eight track grooves 6 larger than usual, the improvement of the precision by the improvement of the filling property at the time of plastic flow is more effective.

Further, since the accuracy at the time of completion of forging of the outer diameter surface 1a is improved, when turning or grinding is performed later, the cutting allowance can be reduced, the processing time can be reduced, and the yield can be improved. By appropriate contrivance, turning of the outer diameter surface 1a can be omitted. For example, by forming a shallow concave portion in the intermediate material W in a portion corresponding to the boundary between the adjacent split dies 21 and 21, a streaky bulge along the gap between the split dies 21 and 21 occurs. It can be prevented from protruding from the outer diameter surface. For this reason, if the accuracy at the time of completion of forging of the outer diameter surface 1a is high, machining of the outer diameter surface can be omitted.
Further, since the track groove 6 is forged with high accuracy, the polishing step of the track groove 6 can be omitted, and the manufacturing cost is improved.
Since less plastic flow is required, wear of the split dies 21 is also small, and the life of the dies becomes long. Although the intermediate material W has an axial groove 6 _W , since it is substantially cylindrical,
It can be easily forged from the columnar material W0. Therefore, forging can be performed with high productivity with a simple forging facility as compared with, for example, a case where an intermediate material having a shape close to the completed shape of the inner ring is used in the preliminary forging stage. Forging process to complete shape later be used a cylindrical intermediate material W having an axial groove 6 _W, as compared with the case of using the intermediate material close to the inner ring of the finished shape, the difference between the forging equipment and productivity Less is. Therefore, the intermediate material W having a cylindrical shape and having the axial groove 6 _W can be obtained by:
Overall, it is efficient.

Further, since the split die 21 is used for forging the intermediate material W, it is possible to forge the inner ring 1 having the track groove 6 having a curved bottom vertical sectional shape without difficulty, efficiently and accurately. it can. As shown in FIG. 6, the split die 21 has a pair of material guide surface portions 21c and 21d at the inner end, which extend linearly from the track groove forming die surface 21a and the outer diameter surface forming die surface 21b to both sides in the axial direction. In the process of compressing the substantially cylindrical intermediate material W in the axial direction, the intermediate material W is compressed while being guided by the material guide surfaces 21c and 21d. Therefore, the plastic flow of the material is performed evenly and smoothly without bias, and forging can be performed with higher accuracy.

As shown in FIGS. 12A to 12C, the intermediate material W is divided into a large-diameter portion Wa and a small-diameter portion Wb having different outer diameters.
In the case of a shape having the following, forging can be performed according to the difference in groove depth at both ends of the track groove 6 of the inner ring 1. That is, as shown in FIG. 13, since the groove bottom longitudinal sectional curvature center O ₁ of the shape of the track grooves 6 of the constant velocity joint inner ring 1 is offset with the center O ₀ of the outer surface 1a, one end and the other The depth of the track groove 6 differs from the side. In the example of FIG. 13, the right side becomes deeper. On the other hand, using the intermediate material W having an outer diameter difference as described above, forging the large diameter portion Wa to correspond to the shallower groove depth and the small diameter portion Wb to correspond to the deeper groove depth. Accordingly, in accordance with such a difference in track groove depth, a difference in plastic flow between a deep portion and a shallow portion can be reduced, and forging can be further performed with a smaller load and better filling. Therefore, it leads to improvement in accuracy.

[0034]

According to the method of manufacturing the inner race of the constant velocity joint of the present invention, there is provided a process of preparing an intermediate material forged into a shape having the same number of the axial grooves as the number of the track grooves on a substantially cylindrical outer diameter surface. And, for this intermediate material, a method including a forging process of forging a finished shape of the track groove of the constant velocity joint inner ring and a shape having a spherical outer surface,
Good filling during plastic flow, forging can be performed with high accuracy, and die life is also improved. In addition, the forging into the finished shape of the track groove eliminates the need for a polishing step, thereby improving productivity.
Cost reduction can be realized. In particular, in the case where the inner ring has eight track grooves, which are larger than usual, the improvement of the accuracy by the improvement of the filling property at the time of plastic flow is more effective. When a split die is used in the forging process, forging can be performed without difficulty, efficiently, and with high accuracy, even though the inner ring has a track groove having a groove bottom vertical cross-section. In the case where a material having a material guide surface portion extending linearly from the track groove forming die surface and the outer diameter surface forming die surface is used as the split die, in the process of compressing the substantially cylindrical intermediate material in the axial direction, The material is compressed while being guided by the material guide surface portion, so that forging can be performed with higher accuracy. When each of the divided dies has a pair of inclined sides forming a V shape on both sides of the outer end, and the die base has a guide surface along the inclined side, the pitch of the divided dies is regulated. In addition, the pitch error of the track groove is suppressed. When the intermediate material has a large-diameter portion and a small-diameter portion, the plastic flow can be made uniform according to the difference in the depth at both ends of the track groove, and forging with even higher precision can be performed.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing a method for manufacturing a constant velocity joint inner ring according to an embodiment of the present invention.

FIG. 2 is a sectional view of a step of forging the cylindrical material into an intermediate material.

FIG. 3 is a sectional view of a forging device for forging an intermediate material.

FIG. 4 is a partially enlarged sectional view of the forging device.

5A is a bottom view of a die base in the forging apparatus, FIG. 5B is a cross-sectional view of an unreduced state showing a relationship between the die base and the split dies, and FIG. 5C is a row of the split dies. FIG. 3D is a sectional view of a reduced diameter state showing a relationship between the die base and the divided dies, and FIG. 4E is a plan view of a reduced diameter state of a row of the divided dies.

FIG. 6 is a partially enlarged perspective view of the split die.

FIG. 7 is an explanatory view of an operation of the forging device in a material charging process.

FIG. 8 is an explanatory diagram of the operation of the forging apparatus in a mold clamping completed state.

FIG. 9 is an operation explanatory view showing a state in which the closing stroke of the forging device is half.

FIG. 10 is an operation explanatory view showing a completed state of the forging device.

FIG. 11 is an operation explanatory view showing a state at the time of knockout of the forging device.

FIGS. 12A to 12C are a plan view, a sectional view, and a bottom view of an intermediate material of the first example, respectively, and FIGS.
FIG. 3 is a plan view, a cross-sectional view, and a bottom view of the intermediate material of the second example.

FIG. 13 is a sectional view of the completed inner race of the constant velocity joint.

FIG. 14 is a front view of the inner ring of the equivalent speed joint.

FIG. 15 is an enlarged cross-sectional view of a track groove of the inner race of the equivalent speed joint.

FIG. 16 is an enlarged sectional view showing a modified example of the track groove of the inner race of the equivalent speed joint.

FIG. 17 is a front view of a modification of the inner ring of the equivalent speed joint.

FIG. 18 is a sectional view of a constant velocity joint.

[Explanation of symbols]

1 ... constant velocity joint inner race 1a ... outer surface 1d ... outer surface forming portion 6 ... track grooves 6 _W ... axial grooves 10 ... intermediate material forging device 20 ... forging device 21 ... split die 21a ... track grooves mold surface 21b ... Outer diameter surface forming die surface 21c, 21d ... Material guide surface portion 21e ... Slope side surface 22 ... Dice row 23 ... Upper punch 24 ... Lower punch 25 ... Dice base 25a ... Dice guide surface 26 ... Backup ring W ... Intermediate material WA: Forged material W0: Columnar material Wa: Large diameter portion Wb: Small diameter portion

Continued on the front page (72) Inventor Yoshihiro Sagisaka 1578 Higashikaizuka, Iwata-shi, Shizuoka Prefecture Inside (72) Inventor Nobuo Suzuki 1578 Higashikaizuka, Iwata-shi, Shizuoka Prefecture Inside F-term (reference) 4E087 AA08 AA09 CA14 CA33 CC03 DA04 EC13 EC42 EE02 HA25

Claims (7)

[Claims] 1. A method of manufacturing a constant velocity joint inner ring in which a track groove having a curved bottom longitudinal section at a plurality of positions in a circumferential direction of a spherical outer surface is formed along an axial direction. Surface, a process of preparing an intermediate material forged into a shape having the same number of axial grooves as the number of the track grooves, and applying the intermediate material to the finished shape and the spherical outer surface of the track grooves of the inner race of the constant velocity joint. And a forging process of forging into a shape having a constant velocity joint inner ring. 2. The forging step comprises: forming a plurality of split dies having a track groove forming die surface and an outer diameter surface forming die surface at an inner end inwardly on a die holder so as to be able to advance and retreat in a radial direction; Using a row of dies arranged in a row, the intermediate material is inserted inside the row of dies such that the axial groove on the outer periphery corresponds to each of the split dies, and each of the split dies in the dice row is moved to the center side, so that By pressing the intermediate material from both ends with a punch, the inner surface of the track groove is formed in the intermediate material, and the outer diameter surface forming portion between the adjacent track grooves of the inner ring is formed so as to be extruded to the outer diameter side. Item 2. A method for manufacturing a constant velocity joint inner ring according to item 1. 3. The split die having at its inner end a pair of material guide surfaces extending linearly from the track groove forming die surface and the outer diameter surface forming die surface to both sides in the axial direction. The method for manufacturing the inner race of the constant velocity joint described in the above. 4. Each of the dice in the dice row is moved outside the dice by an inclined guide surface provided on the inner circumference of the dice base by axially moving a dice base surrounding the outer circumference of the dice row. By pressing the ends, these split dies are simultaneously moved to the center side, and each of the split dies is provided on both sides of the outer end with a pair of slopes which are inclined with respect to the radial direction of the die row and form a V-shape with each other. Side surfaces, these inclined side surfaces are also inclined surfaces with respect to the axial direction, and the die base has a plurality of concave portions into which the outer ends of the respective divided dies are fitted. The method according to claim 2 or 3, wherein the guide surface is formed along the inclined side surfaces on both sides. 5. The method according to claim 1, wherein the intermediate material has the axial groove extending from one end to an intermediate position in the axial direction. 6. The intermediate material has a shape in which the axial groove extends over the entire length, and a large-diameter portion and a small-diameter portion having different outer diameters continue through an axially intermediate tapered portion. A method for manufacturing a constant velocity joint inner ring according to any one of claims 1 to 5. 7. The method of manufacturing a constant velocity joint inner ring according to claim 1, wherein the constant velocity joint inner ring has the track grooves provided at eight positions in a circumferential direction.