WO2014188838A1

WO2014188838A1 - Method for producing outside joint member for use in constant-velocity universal joint, and intermediate forged product to be made into outside joint member

Info

Publication number: WO2014188838A1
Application number: PCT/JP2014/061420
Authority: WO
Inventors: 義忠郁山; 訓弘芝田; 英樹布川
Original assignee: Ntn株式会社
Priority date: 2013-05-22
Filing date: 2014-04-23
Publication date: 2014-11-27
Also published as: JP2014226691A

Abstract

A method for producing an outside joint member (1) which has a cylindrical cup section (2) having a floor and open on one end, and which has a plurality of tracking grooves (5) provided on the inner-diameter surface (4) of the cup section (2) which extend in the axial direction, the outside joint member (1) being produced by executing steps including the following: a pre-forging step for molding a rod-shaped material into an intermediate forged product (21) which has a cylindrical cup section (22) having a floor and having tracking grooves roughly formed on the inner-diameter surface thereof; and an ironing step for molding the intermediate forged product (21) into a final forged product (11) having finished tracking grooves (5). Furthermore, the pre-forging step involves, in advance of proceeding with the ironing treatment during the ironing step thereafter, forming the intermediate forged product (21) in a manner such that a surface (24) having an increasing diameter in the direction in which the plastic deformation margin of the cup section (22) gradually increases is positioned on the outer-diameter surface (23) of the cup section (22).

Description

Manufacturing method of outer joint member for constant velocity universal joint and intermediate forged product processed into outer joint member

The present invention is used in, for example, power transmission systems of automobiles, aircraft, ships, various industrial machines, etc., and is an outer joint for a constant velocity universal joint that transmits rotational power at a constant speed between two axes of a driving side and a driven side. The present invention relates to a member manufacturing method and an intermediate forged product processed into an outer joint member.

As is well known, constant velocity universal joints are roughly classified into fixed constant velocity universal joints that allow only angular displacement and sliding constant velocity universal joints that allow angular displacement and axial displacement. Regardless of whether the constant velocity universal joint is a fixed type or a sliding type, the constant velocity universal joint has a bottomed cylindrical cup portion that is open at one end, and a plurality of track grooves are provided on the inner diameter surface of the cup portion. An outer joint member and joint inner parts such as an inner joint member and a torque transmission member housed in the inner periphery of the cup portion of the outer joint member are provided as main constituent members. Of these joint components, the outer joint member is manufactured by making full use of machining such as cutting and turning and / or plastic working such as forging. However, it is possible to improve production efficiency and yield. In many cases, plastic working is often used.

As an example, Patent Document 1 below is an outer joint member of a tripod type constant velocity universal joint which is a kind of sliding type constant velocity universal joint, and a plurality of track grooves extending in the axial direction are provided on an inner diameter surface. In addition, there is described a method for manufacturing a product having a bottomed cylindrical cup part and a shaft part extending in the axial direction from the bottom part of the cup part through various forging processes. Specifically, a pre-forging step of forming the rod-shaped material into an intermediate forged product having a cup-shaped portion having a track groove roughly formed on the inner diameter surface by sequentially performing upsetting and extrusion processing on the rod-shaped material, and The intermediate forged product has an inner diameter by plastically deforming the cup-shaped portion of the intermediate forged product so as to follow the molding surface of the punch (ironing die) and the die (ironing die) disposed on the inner periphery and outer periphery thereof, respectively. And an ironing process for forming a final forged product having a finished track groove on the surface.

Note that pre-forging (upsetting, extrusion, etc.) for forming a rod-shaped material into an intermediate forged product is often performed in a temperature range (warm, sub-hot or hot) that is higher than warm. The main reason is that at each stage of the pre-forging process, it is necessary to relatively large plastically deform the rod-shaped workpiece, so that it is difficult to ensure the amount of plastic deformation required in the cold. Can be mentioned. On the other hand, ironing is often performed cold. In ironing, it is generally sufficient that the cylindrical part of the cup-shaped part can be extended and deformed in the axial direction. Compared to upsetting and extrusion, it is required even if the temperature of the workpiece (intermediate forging product) or the mold is low. This is because it is advantageous to secure a sufficient amount of plastic deformation and to obtain a highly accurate final forged product and, in turn, an outer joint member.

JP 2002-213476 A

In the above manufacturing method, as shown in FIG. 8, the ironing process for the intermediate forged product 100 is performed so that the thickness reduction rate δ [%] of the cylindrical portion 102 constituting the cup-shaped portion 101 is relatively large ( When executed (for example, δ ≧ 15%), as shown in the diagram on the right side of the figure, a crack 120 is formed at the proximal end portion of the cylindrical portion 112 constituting the cup-shaped portion 111 in the final forged product 110 in particular. The bottom 113 of the cup-shaped part 111 is greatly deformed (the generatrix angle θ of the outer bottom surface of the cup-shaped part 113 with respect to the axis perpendicular to the axis is significantly larger than that of the cup-shaped part 103 before ironing). The occurrence probability of such a situation becomes high. If the crack 120 is formed in the cylindrical portion 112, the final forged product 110 must be disposed of, so that the yield decreases, and when the bottom 113 of the cup-shaped portion 111 is greatly deformed, the bottom 113 is greatly finished. Processing needs to be performed and processing costs increase. Note that the thickness reduction rate δ is δ = {(t1−t2) / t1} × 100, where t1 is the thickness of a predetermined portion before ironing and t2 is the thickness of the same portion after ironing. It is a percentage calculated from the relational expression. The same applies to the case of “thickness reduction rate” in the following description.

Therefore, an attempt was made to execute ironing on the intermediate forged product so that the thickness reduction rate δ of the tube portion does not exceed 15%. However, the smaller the thickness reduction rate δ associated with the ironing process, the shorter the amount of expansion and deformation of the cylinder part associated with the ironing process (the smaller the plastic deformation amount), so the required track groove length cannot be ensured. However, the work hardening associated with the ironing process cannot be sufficiently obtained, and the required mechanical strength cannot be ensured.

It was considered that such a problem can be solved as much as possible by forming an intermediate forging product in which the depth dimension of the cup-shaped part (the axial dimension of the cylinder part) is long in the pre-forging process, for example. . However, if it does in this way, since it will be necessary to increase the deformation amount of the workpiece | work in each step of a pre-forging process, the burden to the forge metal mold | die used at each step of a pre-forging process will become large, and metal mold | die lifetime will be short. Become. In particular, when pre-forging is performed in the temperature range above the warm as described above, the life of the forging die is likely to be shortened. As a specific example, the number of times that the hot forging die can be used is set to be a fraction of 1 to several tenths that of the cold forging die. Therefore, in the above method, an increase in mold cost and a decrease in production efficiency cannot be avoided, and the cost merit by adopting forging cannot be fully enjoyed.

In view of the above circumstances, an object of the present invention is to make it possible to manufacture an outer joint member having a desired shape and strength at low cost, thereby contributing to cost reduction of a constant velocity universal joint.

As a result of repeated studies by the inventors, the above-described various problems are caused by the fact that the thickness of the cylindrical portion 102 constituting the cup-shaped portion 101 of the intermediate forged product 100 is the total axial length as shown in FIG. (The outer diameter surface of the cylindrical portion 102 is formed on a straight surface parallel to the axis), and the allowance for press fitting the cylindrical portion 102 to the ironing die (plastic deformation allowance of the cylindrical portion 102) is Since the ironing process is almost constant from the start to the completion, that is, the thickness reduction rate of the cup-shaped part 101 (cylinder part 102) by the ironing process is substantially the same in the entire axial direction of the cup-shaped part 101. When the rate is increased, it is considered that stress concentration is likely to occur at the proximal end portion of the cylindrical portion 102, which is likely to occur mainly. Accordingly, it has been found that the above-described various problems can be prevented as much as possible by performing ironing so that the press-fitting allowance of the cup-shaped part to the die (plastic deformation allowance of the cup-shaped part) gradually increases. The present invention has been completed.

That is, in order to solve the above problems, the present invention has a bottomed cylindrical cup portion that is open at one end, and a plurality of track grooves extending in the axial direction are provided on the inner diameter surface of the cup portion. A method for producing an outer joint member for a constant velocity universal joint, wherein a rod-shaped material is formed into an intermediate forged product having a bottomed cylindrical cup-shaped portion in which a track groove is roughly formed on an inner diameter surface; and With respect to the cup-shaped part of the intermediate forged product in which the punch is inserted in the inner periphery, the die arranged on the outer diameter side is relatively moved in the press-fitted state from the bottom side of the cup-shaped part toward the opening side, and the cup-shaped part is moved. And an ironing step of forming the intermediate forging product into a final forging product having a track groove having a finished shape on the inner diameter surface by plastic deformation, and in the pre-forging step, the relative movement proceeds in the subsequent ironing step. With the cup-shaped part Wherein the diameter expansion surface in a direction to gradually increase the plastic deformation margin to molding the intermediate forged product provided outside diameter surface of the cup-shaped portion.

The cross-sectional shape of the molding surface provided on the inner diameter surface of the die used in the ironing process generally corresponds generally to the cross-sectional shape of the outer periphery of the cup portion constituting the outer joint member. For this reason, it is not preferable to change the shape of the molding surface of the die because it may increase the possibility of significant post-processing and may affect the function and performance of the outer joint member. Therefore, in the present invention, the above-described problems have been solved by contriving the shape of the intermediate forged product formed in the pre-forging process. Specifically, the intermediate forged product formed in the pre-forging process is moved relative to the outer diameter surface of the cup-shaped part in the press-fitted state of the die and the cup-shaped part of the intermediate forged product in the ironing process after the pre-forging process. As the ironing process progresses, a diameter-enlarged surface in a direction that gradually increases the plastic deformation allowance of the cup-shaped portion is provided.

In this case, in particular, if the above-mentioned expanded surface is provided on the bottom side of the cup-shaped part, the allowance for press-fitting the cup-shaped part to the die in the initial stage of ironing, that is, the amount of plastic deformation of the cup-shaped part (the amount of ironing) ) Can be reduced. As a result, it is possible to cause a large stress concentration in the vicinity of the base end portion of the cylindrical portion of the cup-shaped portion due to the ironing process, so that cracks are formed in the cup-shaped portion, and the bottom portion can be greatly deformed. As a result, the manufacturing cost of the outer joint member can be reduced through improvement in yield and simplification of finishing. Then, if the above-mentioned problems associated with ironing can be prevented as much as possible, the thickness reduction rate of the cylindrical portion is increased as a whole, that is, the desired track groove length and work hardening (mechanical strength) are increased. It is possible to iron the intermediate forged product so that it can be secured. In addition, if the intermediate forged product can be ironed in such a manner, the intermediate forged product formed in the pre-forging step only needs to have a short cup depth. Accordingly, it is possible to reduce the load on the forging die used in the pre-forging step, and it is possible to reduce the manufacturing cost of the outer joint member through extending the life of the pre-forging die.

As a specific means for effectively enjoying the above-described effects, the intermediate forged product formed in the pre-forging step is arranged such that the minimum diameter portion of the expanded surface is disposed at the outer diameter end of the outer bottom surface of the cup-shaped portion. It can be considered. More specifically, for example, among the cup-shaped portions of the intermediate forged product, the thickness of the portion including the outer diameter end (the smallest diameter portion of the expanded surface) before ironing is Xa, and the thickness after ironing When the thickness of the portion is Xb, the thickness reduction rate δ associated with the ironing of the portion is satisfied so as to satisfy the relational expression of Xb ≧ 0.9Xa (strictly, Xa> Xb ≧ 0.9Xa). Is 10% or less).

In addition, the intermediate forging product shall be provided with the above-mentioned diameter-expanded surface so that the thickness at the base end portion of the cylindrical portion constituting the cup-shaped portion is reduced by 15% or more and 35% or less after the ironing process. Can do. In this case, it is preferable that the intermediate forged product is provided with the above-described diameter-expanded surface so that the thickness of the central portion in the axial direction of the cylindrical portion is significantly reduced after the ironing process. More specifically, it is preferable that the above-described diameter-expanded surface is provided so that the thickness of the central portion in the axial direction of the cylindrical portion is reduced by 15% or more and 60% or less after the ironing process. This effectively prevents a situation in which cracks are formed in the cylindrical portion of the cup-shaped portion or the bottom of the cup-shaped portion is greatly deformed as ironing is performed on the intermediate forged product. A final forged product having a desired track groove length (cup depth) and mechanical strength can be obtained.

In the above configuration, the intermediate forged product may be one in which the maximum diameter portion of the above-mentioned expanded surface is disposed at the axially central portion of the outer diameter surface of the cup-shaped portion (tubular portion).

In the above configuration, it is desirable that the ironing process is performed cold. This is because the molding accuracy of the final forged product can be increased, and this is advantageous in making it possible to manufacture a highly accurate outer joint member at low cost. Moreover, according to the manufacturing method which concerns on this invention, as above-mentioned, the intermediate forging goods which should be shape | molded by a pre-forging process should just have a comparatively short depth dimension of the cup-shaped part. Accordingly, it is possible to perform the pre-forging process cold.

The present invention can be preferably applied when obtaining a final forged product in which the depth of the cup-shaped portion after the ironing step is 30 to 150 mm.

The present invention provides an outer joint member in which each track groove is composed only of a straight portion, for example, a sliding type represented by a tripod type constant velocity universal joint (TJ), a double offset type constant velocity universal joint (DOJ), and the like. It can be applied when manufacturing the outer joint member of the quick universal joint. The present invention also provides an outer joint member in which each track groove is composed of a linear portion and an arc-shaped portion, such as an undercut-free type constant velocity universal joint (UJ) or a barfield type constant velocity universal joint (BJ). It can also be applied when manufacturing an outer joint member of a fixed type constant velocity universal joint represented by.

The present invention can be preferably applied also when manufacturing an outer joint member integrally having a shaft portion extending in the axial direction from the bottom portion of the cup portion.

Moreover, the solution of the above problem can be realized by configuring the intermediate forged product according to the present invention to be processed into the outer joint member as follows. That is, the intermediate forged product of the outer joint member according to the present invention has a bottomed cylindrical cup portion with one end opened, and a constant velocity in which a plurality of track grooves extending in the axial direction are provided on the inner diameter surface of the cup portion. It is processed into an outer joint member for a universal joint, and has a bottomed cylindrical cup-shaped part in which a plurality of track grooves extending in the axial direction are formed on the inner diameter surface, and a punch is inserted into the inner periphery. The cup-shaped part and the die arranged on the outer diameter side thereof are moved relative to each other in the press-fitted state from the bottom side of the cup-shaped part toward the opening side, and the cup-shaped part is plastically deformed, thereby finishing the track groove. The outer diameter surface of the cup-shaped portion is provided with a diameter-expanded surface in a direction that gradually increases the plastic deformation allowance of the cup-shaped portion accompanying the relative movement. Features.

In this intermediate forged product, the above-mentioned diameter-expanded surface can be constituted by, for example, continuously arranging a plurality of surfaces having different inclination angles with respect to the axis in the axial direction.

As described above, according to the present invention, an outer joint member having a desired shape and strength can be manufactured at low cost. Thereby, it can contribute to the cost reduction of a constant velocity universal joint.

It is a front view of the outside joint member manufactured using the manufacturing method concerning the embodiment of the present invention. FIG. 1B is a schematic cross-sectional view taken along line X1-X1 shown in FIG. 1A. It is a schematic sectional drawing of the rod-shaped raw material thrown into a pre forge process. It is a schematic sectional drawing of the intermediate product obtained at each forge step of a pre-forging process. It is a schematic sectional drawing of the intermediate product obtained at each forge step of a pre-forging process. It is a schematic sectional drawing of the intermediate product obtained at each forge step of a pre-forging process. It is a schematic front view of an intermediate forging product. FIG. 3B is a schematic cross-sectional view taken along line X2-X2 shown in FIG. 3A. It is a principal part enlarged view of FIG. 3B. It is a figure for comparing the shape of the intermediate forging product employ | adopted with the manufacturing method which concerns on this invention, and the intermediate forging product of the conventional method. It is a fragmentary sectional view showing an ironing process typically. It is a principal part expanded sectional view of the intermediate forging product which concerns on other embodiment. It is a figure which shows the problem of the conventional method typically.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, for convenience, an example of an outer joint member manufactured using the manufacturing method according to the present invention will be described first, and then an embodiment of the method of manufacturing the outer joint member according to the present invention will be described.

FIG. 1A shows a schematic front view of an outer joint member 1 for a constant velocity universal joint (hereinafter simply referred to as “outer joint member 1”), and FIG. 1B shows a schematic sectional view of the outer joint member 1 (X1-X1 in FIG. 1A). X1 line schematic sectional drawing) is shown. This outer joint member 1 is an outer joint member for a tripod type constant velocity universal joint that is a kind of sliding type constant velocity universal joint that allows both angular displacement and axial displacement, and includes a cylindrical portion 2a and a bottom portion 2b. Are integrally provided with a bottomed cylindrical cup portion 2 and a shaft portion 3 extending axially outward from a bottom portion 2b of the cup portion 2. The tripod type constant velocity universal joint is completed by incorporating a tripod member as an inner joint member, a roller as a torque transmission member, or the like on the inner periphery of the cup portion 2 of the outer joint member 1.

Three track grooves 5 extending in the axial direction are formed at equal intervals on the inner diameter surface 4 of the cup portion 2 (cylinder portion 2a). Each track groove 5 has a pair of roller guide surfaces 6 and 6 that face each other in the circumferential direction, and is formed in a straight line including the roller guide surfaces 6 and 6 and extending parallel to the axis. As shown to FIG. 1A, the cup part 2 of this embodiment is made into the cross-sectional corollary shape comprised by arranging three large diameter parts and small diameter parts alternately in the circumferential direction, and the internal diameter of each large diameter part A track groove 5 is formed on the surface. In the region between the

track grooves

5 and 5 on the inner peripheral edge of the opening of the cup portion 2, an inlet chamfer for allowing angular displacement of the joint (in order to avoid a shaft extending from a tripod member not shown from interfering with the cup portion 2). 7 is provided. Moreover, the circumferential direction groove | channel 8 by which the one end part of the boot which seals the inside of a coupling is fitted is provided in the outer diameter surface of the cup part 2. As shown in FIG.

Hereinafter, an embodiment of the manufacturing method according to the present invention, which is an example of the manufacturing method of the outer joint member 1 described above, will be described in detail with reference to the drawings. Roughly speaking, the outer joint member 1 described above includes a pre-forging step of forming the rod-shaped material M shown in FIG. 2A into the intermediate forged product 21 shown in FIGS. 3A and 3B, and the intermediate forged product 21 in two points in FIG. Manufactured through an ironing process for forming the final forged product 11 indicated by a chain line, a finishing process for finishing each part of the final forged product 11 into a finished product shape, and a heat treatment process for heat-treating the final forged product 11 finished in the finished product shape. Is done.

In the pre-forging process, a bar-shaped material M shown in FIG. 2A is formed into an intermediate forged product 21 having a cup-shaped portion 22 shown in FIGS. 3A and 3B by going through a plurality of forging steps (here, four steps). .

Specifically, first, in the first forging step, the rod-shaped material M shown in FIG. 2A is subjected to an upsetting process, whereby the rod-shaped material M is converted into a first intermediate product M1 (one outer peripheral edge of which is rounded). (See FIG. 2B). Next, in the second forging step, the first intermediate product M1 is subjected to a forward extrusion process, so that the first intermediate product M1 is formed on one end side with a shaft-like portion 13 (part finally finished to the shaft portion 3). ) Having a second intermediate product M2 (see FIG. 2C). Next, in the third forging step, by performing upsetting on the second intermediate product M2, the second intermediate product M2 and the third intermediate product integrally including the upsetting portion N and the shaft-like portion 13 are provided. Molded to M3 (see FIG. 2D). Then, in the fourth forging step, the third intermediate product M3 is integrated with the cup-shaped portion 22 and the shaft-shaped portion 13 by subjecting the upset portion N of the third intermediate product M3 to rearward extrusion. Is formed into an intermediate forged product 21 (see FIGS. 3A and 3B).

This pre-forging process is performed in any temperature range between cold, warm, sub-hot, and hot as long as each workpiece (rod-like material M and intermediate products M1 to M3) can be formed into a predetermined shape. Also good. In this connection, cold forging is a technique for forging a workpiece that is approximately 200 ° C. or less, and warm forging is forging a workpiece heated to approximately 600 to 700 ° C. It is a technique to apply. Sub-hot forging is a technique for forging a workpiece heated to about 750 to 1000 ° C., and hot forging is about a workpiece heated to about 1000 to 1200 ° C. This is a technique for forging. From the viewpoint of stably obtaining the high-precision intermediate forged product 21 while extending the life of the mold used in the pre-forging process, it is preferable to perform the pre-forging process cold.

Hereinafter, the detailed structure of the intermediate forged product 21 will be described. As shown in FIGS. 3A and 3B, the cup-shaped portion 22 of the intermediate forged product 21 has a bottomed cylindrical shape integrally including a cylindrical portion 22a and a bottom portion 22b, and has an inner diameter surface (an inner diameter surface of the cylindrical portion 22a). A track groove 15 having a roller guide surface 16 is roughly formed in the circumferentially divided position. The cup-shaped portion 22 of the intermediate forged product 21 has a track groove having a finished shape on the inner diameter surface by plastic deformation of the cylindrical portion 22a following the forming surface of the die 51 and the punch 52 in the ironing process described later (FIG. The cup-shaped portion 12 (see the two-dot chain line in FIG. 6) having the same cross-sectional shape as the cup portion 2 of the outer joint member 1 shown in FIG. Therefore, each part in the circumferential direction of the cylindrical part 22a is thicker than the cylindrical part 2a of the cup part 2, and the depth dimension of the cup-shaped part 22 (axial dimension of the cylindrical part 22a) is the same as that of the cup part 2. It is shorter than the depth dimension (the axial dimension of the cylinder portion 2a).

The inner diameter surface of the cup-shaped part 22 is formed in a straight surface whose entire axial direction is parallel to the axis. On the other hand, the outer diameter surface 23 of the cup-shaped part 22 is formed in a straight surface whose opening side region is parallel to the axis, whereas the bottom side region is formed from the bottom side toward the opening side, and the cylindrical part The outer diameter of 22a is formed on the enlarged surface in the direction of gradually increasing the outer diameter. With this configuration, the thickness of the bottom side region of the cylindrical portion 22a gradually increases from the bottom side toward the opening side. In the present embodiment, the above-described enlarged diameter surface 24 is configured by continuously arranging a plurality of surfaces having different inclination angles with respect to the axis in the axial direction. Here, as shown in an enlarged view in FIG. 4, the first enlarged surface 25 which is located on the relatively opening side and has a tapered surface shape with a relatively small inclination angle with respect to the axis, and the bottom side relatively. The diameter-expanded surface 24 is constituted by the second diameter-expanded surface 26 that is located at a position where the taper surface has a relatively large inclination angle with respect to the axis.

The diameter-expanded surface 24 has a minimum diameter portion (bottom side end portion of the second diameter-expanded surface 26), and the outer-diameter end portion A (strictly speaking, the R portion is not provided) of the outer bottom surface 22b2 of the cup-shaped portion 22. The outer diameter end portion of the cup-shaped portion 22 is arranged at the outer diameter end portion of the cup-shaped portion 22 (hereinafter also referred to as “point A”). It is provided on the outer diameter surface 23 of the cup-shaped portion 22 so as to be disposed at a substantially central portion C in the axial direction of 23 (hereinafter referred to as “C point”). Further, the second enlarged surface 26 has an opening-side end B (a connecting portion between the first enlarged surface 25 and the second enlarged surface 26, hereinafter referred to as “point B”). The outer diameter surface 23 is provided on the outer diameter surface 23 of the cup-shaped portion 22 so as to be disposed at the proximal end portion of the cylindrical portion 22a.

In this embodiment, the diameter dimension d1 [unit: mm] at the point A in the cup-shaped portion 22 is 0 mm with respect to the molding surface 51a (see FIG. 6) of the die 51 that the point A uses in the ironing process described later. It is set to a value that is press-fitted with a plastic deformation allowance of 2 mm or less. That is, of the molding surface 51a of the die 51, when the diameter dimension of the portion into which the point A is press-fitted is D1 [mm], the relational expression of D1 <d1 ≦ D1 + 2 [mm] is satisfied. A diameter dimension d1 is set. If the above relational expression is defined as a relational expression not including a specific dimension value, the thickness of the portion including the point A in the cup-shaped portion 22 before the ironing processing is Xa, and the ironing processing of the portion is performed. When the subsequent thickness is Xb, Xb ≧ 0.9Xa (strictly, Xa> Xb ≧ 0.9Xa) can be satisfied. In other words, the value of the thickness of the portion including the point A of the cup-shaped portion 22 in the intermediate forged product 21 is defined so as to decrease by 10% or less with ironing.

As described above, since the point A is the minimum diameter portion of the expanded surface 24, the plastic deformation allowance of the cup-shaped portion 22 accompanying the ironing process is larger than the point A at the point B, and further the point C. Then, the plastic deformation allowance of the cup-shaped part 22 accompanying ironing becomes larger than B point. Here, the thickness tb (see FIG. 4) of the base end portion including the B point in the cylindrical portion 22a is set to a value that decreases by 15% or more and 30% or less after the ironing process, and the shaft including the C point. The thickness tc (see FIG. 3B) at the center in the direction is set to a value that is larger than the base end portion of the cylindrical portion 22a after ironing and decreases by 15% or more and 60% or less.

The intermediate forged product 21 having the above configuration is transferred to the ironing process. In the ironing process, as shown in FIG. 6, the intermediate forged product 21 (the cup-shaped portion 22 thereof) is formed by subjecting the intermediate forged product 21 to a cold ironing process using a coaxially disposed die 51 and a punch 52. The final forged product 11 having a cup-shaped portion 21 indicated by a two-dot chain line in FIG. Although detailed illustration is omitted, the inner surface of the die 51 is provided with a molding surface (ironing surface) 51 a that extends along the axis and corresponds to the cross-sectional shape of the outer periphery of the cup portion 2. The radial surface is provided with a molding surface corresponding to the cross-sectional shape of the inner periphery of the cup portion 2.

Ironing is performed by relatively moving the die 51 in a press-fit state from the bottom side of the cup-shaped portion 22 toward the opening side with the punch 52 inserted in the inner periphery of the cup-shaped portion 22 of the intermediate forged product 21. Is called. In the present embodiment, since the molding surface 51a of the cup-shaped portion 22 and the die 51 has the above-described shape, the ironing process is performed by pressing the cup-shaped portion 22 into the die 51 (plastic deformation of the cup-shaped portion 22). It progresses in such a way that the amount increases gradually. As the ironing process proceeds, the cup-shaped part 22 (the cylindrical part 22a) gradually expands and deforms in the axial direction while following the molding surface 51a of the die 51 and the molding surface of the punch 52, and the ironing process is performed. Is completed, a final forged product 11 (see a two-dot chain line in FIG. 6) having a cup-shaped portion 12 having a finished track groove on the inner diameter surface is obtained. The cup depth of the final forged product 11 varies depending on the use of the constant velocity universal joint having the outer joint member 1 as a component (vehicle type, etc.), but is generally in the range of 30 mm to 150 mm.

The final forged product 21 obtained in the ironing process is transferred to the finishing process. In the finishing process, it is difficult to form by the forging process described above (for example, the circumferential groove 8 to be provided on the outer diameter surface of the cup portion 2 or the spline to be provided on the outer diameter of the free end of the shaft portion 3). In addition to the process for forming the end forged product 11, a turning process for finishing the open end surface of the cup-shaped portion 12 to a flat surface is appropriately applied to the final forged product 11, and the entire final forged product 11 is finished into a finished product shape. And the outer joint member 1 shown in FIG. 1 is completed by performing heat processing, such as quenching, on the final forged product 11 which has been finished into a finished product shape as a whole.

As described above, the cross-sectional shape of the molding surface 51a provided on the inner diameter surface of the die 51 used in the ironing process corresponds to the cross-sectional shape of the outer periphery of the cup portion 2 constituting the outer joint member 1. For this reason, if the shape of the molding surface 51 a of the die 51 is changed, it is not preferable because it may affect the outer peripheral shape of the cup portion 2 and consequently the function and performance of the outer joint member 1. Therefore, in the present invention, in the pre-forging process, as the relative movement (scoring processing) in the press-fitted state of the die 51 and the cup-shaped part 22 proceeds in the subsequent ironing process, the plastic deformation allowance of the cup-shaped part 22 is increased. The intermediate forged product 21 in which the diameter-expanded surface 24 in the direction of gradually increasing the diameter is provided on the outer-diameter surface 23 of the cup-shaped portion 22 is formed. More specifically, the intermediate forged product 21 is configured such that the minimum diameter portion of the expanded surface 24 is disposed at the outer diameter end A (point A) of the outer bottom surface 22b1 of the cup-shaped portion 22, and the outer diameter associated with the ironing process. It is assumed that the thickness reduction rate of the portion including the end A is press-fitted into the die 51 so as to be 10% or less (in the present embodiment, the outer diameter end A has a plastic deformation allowance of 2 mm or less to the die 51. To be press-fitted).

In this way, it is possible to reduce the press-fitting allowance of the cup-shaped portion 22 to the die 51 in the initial stage of ironing, that is, the amount of plastic deformation (the amount of ironing) of the cup-shaped portion 22. As a result, as the ironing process is performed, stress concentration occurs in the vicinity of the base end portion of the cylindrical portion 22a constituting the cup-shaped portion 22, and cracks are formed in the cup-shaped portion 22. It is possible to prevent the bottom portion 22b of the shape portion 22 from being greatly deformed as much as possible, and the manufacturing cost of the outer joint member 1 can be reduced through improvement in yield and simplification of finishing. Further, in the intermediate forged product 21, if the plastic deformation allowance of the outer diameter end A of the outer bottom surface 22b1 of the cup-shaped portion 22 which is a substantial starting point of the ironing process is 2 mm or less (the portion including the outer diameter end A) If the ironing process is performed so that the thickness reduction rate δ of the die is 10% or less), the burden on the die 51 is effectively reduced, so that the life of the die 51 can be extended.

In particular, as in the present embodiment, the intermediate forged product 21 is formed so that the wall thickness tb at the base end portion of the cylindrical portion 22a constituting the cup-shaped portion 22 is reduced by 15% or more and 35% or less after the ironing process. If the diameter expansion surface 24 is provided such that the wall thickness tc of the central portion in the axial direction of the cylindrical portion 22a is larger than the base end portion and reduced by 15% or more and 60% or less after the ironing step. The desired track groove is effectively prevented while cracking is formed in the cylindrical portion 22a of the cup-shaped portion 22 or the bottom portion 22b of the cup-shaped portion 22 is greatly deformed due to the ironing process. A final forged product 21 having a length (cup depth) and mechanical strength can be obtained.

It should be noted that the thicknesses tb and tc of the base end portion and the axially central portion of the cylindrical portion 22a are reduced by 15% or more after the ironing process (the thickness reduction rate δ of the thicknesses tb and tc is 15% or more). (Ii) The increased diameter surface 24 is provided on the outer diameter surface 23 of the cup-shaped portion 22 because the desired track groove length or the like cannot be obtained if the thickness reduction rate δ of both portions is less than 15%. This is because the possibility increases. Further, if the thickness tb of the base end portion of the cylindrical portion 22a is reduced by about 45% due to the ironing process, the possibility that a crack is formed in the cup-shaped portion 22 (cylindrical portion 22a) is remarkably increased. In consideration of the safety factor, the radial surface 24 is preferably provided on the outer diameter surface 23 of the cup-shaped portion 22 so that the thickness tb of the base end portion of the cylindrical portion 22a is reduced by 35% or less with ironing. . Further, the thickness tc of the central portion in the axial direction of the cylindrical portion 22a is reduced by about 65% with the ironing process (the thickness reduction rate δ at the central portion in the axial direction of the cylindrical portion 22a with the ironing processing is about 65%. ) And the possibility that a crack is formed in the cylindrical portion 22a of the cup-shaped portion 22 is remarkably increased. Therefore, in consideration of the safety factor, the diameter-expanded surface 24 is formed so that the thickness tc of the central portion in the axial direction of the cylindrical portion 22a is reduced by 60% or less (corresponding to the central portion in the axial direction of the cylindrical portion 22a). It is desirable to provide it on the outer diameter surface 23 of the cup-shaped portion 22 so that the thickness reduction rate δ accompanying the ironing process is 60% or less.

In addition, it is possible to prevent as much as possible the situation in which a crack is formed in the cup-shaped portion 22 (12) or the bottom portion 22b of the cup-shaped portion 22 is greatly deformed due to the ironing process. Then, the intermediate forging 21 is subjected to ironing so that the thickness reduction rate of the cylindrical portion 22a is increased as a whole, that is, the desired track groove length and work hardening (mechanical strength) can be ensured. It becomes possible. Thus, if the intermediate forged product 21 can be ironed so as to increase the thickness reduction rate of the cylindrical portion 22a, the intermediate forged product 21 formed in the pre-forging process has a short cup depth. Is enough. Actually, if the manufacturing method according to the present invention is adopted, as shown in FIG. 5, it becomes possible to form an intermediate forged product 21 having a cup depth shorter than that of the conventional one. In this case, it becomes possible to reduce the load on the forging die used in the pre-forging step (in this embodiment, the forging die for backward extrusion used particularly in the fourth forging step). Through extending the service life, the manufacturing cost of the outer joint member 1 can be reduced.

As mentioned above, although the manufacturing method of the outer joint member 1 which concerns on one Embodiment of this invention was demonstrated, this invention is not limitedly applied to said embodiment, Various in the range which does not deviate from the summary. It is possible to make changes.

For example, among the enlarged diameter surfaces 24 to be provided on the outer diameter surface 23 of the cup-shaped portion 22 of the intermediate forged product 21, the second enlarged diameter surface 26 is not tapered as described above, but as shown in FIG. It can also be formed in a circular arc shape. Further, the diameter-expanded surface 24 is not necessarily configured by a plurality of surfaces continuously arranged in the axial direction (in the embodiment described above, the first diameter-expanded surface 25 and the second diameter-expanded surface 26). It can also be constituted by a tapered surface or an arc surface. In short, the diameter-expanded surface 24 is more preferably further in the axial direction of the cylindrical portion 22a so that the thickness tb of the base end portion of the cylindrical portion 22a of the cup-shaped portion 22 is reduced by 15% or more and 35% or less after the ironing process. As long as the thickness tc of the central portion is formed so as to decrease by 15% or more and 60% or less after the ironing process, any form can be adopted without any problem.

In the above, the present invention is applied when the pre-forging process is configured by four forging steps (when the intermediate forged product 21 is obtained through four forging steps), but the intermediate forged product 21 is 3 or less or 5 or more. The present invention can be preferably applied also when the forging step is obtained.

In the above, the present invention is applied when manufacturing the outer joint member 1 for a tripod type constant velocity universal joint (TJ) which is a kind of sliding type constant velocity universal joint. However, the present invention is a double offset type. The invention can also be preferably applied to the production of outer joint members of other sliding constant velocity universal joints such as constant velocity universal joints (DOJ).

Furthermore, the present invention provides not only an outer joint member of a sliding type constant velocity universal joint that allows both angular displacement and axial displacement, but also a fixed type constant velocity universal joint that allows only angular displacement, such as a barfield type. The present invention can also be applied when manufacturing an outer joint member of a speed universal joint (BJ) or an undercut free type constant speed universal joint (UJ). In the outer joint member of the fixed type constant velocity universal joint, each track groove provided on the inner diameter surface of the cup portion includes a linear portion and an arc-shaped portion.

DESCRIPTION OF SYMBOLS 1 Outer joint member 2 Cup part 3 Shaft part 5 Track groove 6 Guide surface 11 Final forged product 12 Cup-shaped part 21 Intermediate forged product 22 Cup-shaped part 23 Outer diameter surface 24 Expanded surface 25 First expanded surface 26 Second expanded surface Diameter 51 Die 51a Molding surface 52 Punch A Outer end of the outer bottom of the cup-shaped part M Bar material tb Thickness of the base end of the cylindrical part tc Thickness of the axially central part of the cylindrical part

Claims

A method of manufacturing an outer joint member for a constant velocity universal joint having a bottomed cylindrical cup portion having one end opened, and having a plurality of track grooves extending in an axial direction on an inner diameter surface of the cup portion,
A pre-forging step of forming a rod-shaped material into an intermediate forged product having a bottomed cylindrical cup-shaped portion having a track groove roughly formed on an inner diameter surface;
With respect to the cup-shaped portion of the intermediate forged product in which a punch is inserted on the inner periphery, a die disposed on the outer diameter side thereof is relatively moved in a press-fit state from the bottom side of the cup-shaped portion toward the opening side, thereby the cup. An intermediate forging product is formed into a final forging product having track grooves of a finished shape by plastically deforming the shape portion,
In the pre-forging step, as the relative movement proceeds in the subsequent ironing step, a diameter-expanding surface in a direction that gradually increases the plastic deformation allowance of the cup-shaped portion is provided on the outer diameter surface of the cup-shaped portion. A method for producing an outer joint member for a constant velocity universal joint, wherein the intermediate forged product is formed.
The outer joint for a constant velocity universal joint according to claim 1, wherein the intermediate forged product is configured such that a minimum diameter portion of the enlarged diameter surface is disposed at an outer diameter end of an outer bottom surface of the cup-shaped portion. Manufacturing method of member.
The intermediate forged product is characterized in that the diameter-expanded surface is provided so that the thickness at the base end portion of the cylindrical portion constituting the cup-shaped portion is reduced by 15% or more and 35% or less after the ironing step. The manufacturing method of the outer joint member for constant velocity universal joints of Claim 1 or 2.
The intermediate forging product is characterized in that the diameter-expanded surface is provided so that the thickness of the central portion in the axial direction of the cylindrical portion is reduced more than the base end portion after the ironing step. 4. A method for producing an outer joint member for a constant velocity universal joint according to claim 3.
The intermediate forging product is characterized in that the diameter-expanded surface is provided so that the thickness of the central portion in the axial direction of the cylindrical portion is reduced by 15% or more and 60% or less after the ironing step. The manufacturing method of the outer joint member for constant velocity universal joints of description.
The intermediate forged product according to any one of claims 1 to 5, wherein a maximum diameter portion of the expanded surface is arranged in an axial central portion of an outer diameter surface of the cup-shaped portion. The manufacturing method of the outer joint member for constant velocity universal joints of description.
The method for manufacturing an outer joint member for a constant velocity universal joint according to any one of claims 1 to 6, wherein the ironing step is performed cold.
The method for manufacturing an outer joint member for a constant velocity universal joint according to any one of claims 1 to 7, wherein the track groove is applied only to a linear portion.
The method for manufacturing an outer joint member for a constant velocity universal joint according to any one of claims 1 to 7, wherein the track groove is applied to a groove formed of a linear portion and an arc-shaped portion.
It is an intermediate forged product that is machined into an outer joint member for a constant velocity universal joint that has a bottomed cylindrical cup portion that is open at one end, and is provided with a plurality of track grooves extending in the axial direction on the inner diameter surface of the cup portion. A cup-shaped portion having a bottomed cylindrical shape in which a plurality of track grooves extending in the axial direction on the inner diameter surface are roughly formed, and arranged on the outer diameter side of the cup-shaped portion in which a punch is inserted in the inner periphery The molded die is molded into a final forged product having a finished track groove by plastically deforming the cup-shaped portion by relatively moving the die from the bottom side of the cup-shaped portion toward the opening side. In
An intermediate forged product characterized in that an outer diameter surface of the cup-shaped portion is provided with a diameter-expanded surface in a direction that gradually increases a plastic deformation allowance of the cup-shaped portion accompanying the relative movement.
11. The intermediate forged product according to claim 10, wherein the diameter-expanded surface is configured by continuously arranging a plurality of surfaces having different inclination angles with respect to the axis in the axial direction.