JP2008073735A - Method for manufacturing outer member for constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the dimensional precision of an inner tooth when providing an outer member for constant velocity universal joint having a hollow part in which inner teeth are formed. <P>SOLUTION: A hollow small-diameter part 20 is passed through the inside of an inserting hole 34 of a floating die 32 constituting a drawing die apparatus 30. Then, in the interval between the outer peripheral wall of the hollow small-diameter part 20 and the inner peripheral wall of the inserting hole 34, the clearance CL which is the minimum at the opening hole side of the hollow small-diameter part 20 and becomes larger as nearer the boundary of the hollow small-diameter part 20 and a cup part 28 is formed. In this state, a floating die 32 descends and a teeth-forming part 36 in an inner teeth-forming punch 38 is inserted into the hollow small-diameter part 20. Thereafter, an induction hardening is applied to the hollow small-diameter part 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an outer member for a constant velocity joint including a hollow portion in which internal teeth are formed.

  In an automobile travel engine, for example, a constant velocity joint is interposed between a transmission and a shaft member in order to transmit the rotational driving force of the engine to a tire via the shaft member. That is, the constant velocity joint includes an outer member having a shaft portion connected to the transmission, and an inner member fitted to the tip portion of the shaft member, and a part of the inner member constitutes the outer member. The transmission and the shaft member are connected by slidably engaging with a groove provided on the inner peripheral wall of the bottomed bowl-shaped or cylindrical cup portion.

  Here, the shaft part of the outer member and the transmission are connected by meshing the tooth parts. That is, while a tooth part is normally provided in the outer peripheral wall of the front-end | tip part of a shaft part, the hollow shaft in which the internal tooth for receiving this tooth part was formed in the mission. The transmission and the outer member are connected by engaging the tooth portion with the internal tooth of the hollow shaft.

  In recent years, a constant velocity joint has been proposed in which the tip of the shaft portion of the outer member is a hollow portion, and internal teeth are formed on the inner peripheral wall of the hollow portion (see, for example, Patent Document 1). In this case, as described in Patent Document 1, after the hollow portion is provided at one end and the cup portion is provided at the other end portion, the track groove is provided at the inner peripheral wall of the cup portion and at the same time the hollow portion is provided. Internal teeth are formed on the inner peripheral wall.

Japanese Patent Laid-Open No. 3-60840

  The internal teeth as described above are required to have high durability in order to wipe out the concern that defects may occur during use. As a measure for meeting this requirement, it is conceived that heat treatment such as induction hardening is performed to improve the strength and hardness of the tooth portion.

  However, when induction hardening is performed, there is a tendency that the overpin diameter (OPD) of the inner teeth becomes larger as it becomes the opening side of the hollow portion. In other words, when heat treatment that causes thermal strain is performed, the inner teeth are in a so-called divergent state, which causes a problem that it is not easy to ensure dimensional accuracy.

  The present invention has been made to solve the above-described problems, and provides a method for manufacturing an outer member for a constant velocity joint capable of providing an inner tooth having high strength and high hardness and having dimensional accuracy secured. The purpose is to provide.

In order to achieve the above object, the present invention provides a method for manufacturing an outer member for a constant velocity joint including a hollow portion in which internal teeth are formed.
A first forging process for producing an outer member for a constant velocity joint having a hollow portion;
A second forging process step of inserting a tooth portion forming punch into the hollow portion surrounded by a die and providing inner teeth on the inner peripheral wall of the hollow portion;
A heat treatment step of performing heat treatment on at least the inner teeth;
Have
In the second forging process, the distance between the die and the hollow portion is reduced to the side facing the tooth portion forming punch while being maximized at a position farthest from the tooth portion forming punch. An internal tooth is provided. Here, the first forging process includes an all-forging process for producing an outer member for a constant velocity joint. On the other hand, the second forging process refers to a forging process in which inner teeth are provided on the inner peripheral wall of the hollow portion.

  That is, in the present invention, at the time of the forging process in which the inner teeth are provided, the clearance between the die and the hollow part is increased from the opening side of the hollow part toward the bottomed bowl-shaped part or the cylindrical part. Is set.

  When forming the internal teeth, the hollow portion is deformed by being pressed from the internal tooth forming punch. The amount of deformation increases as the distance between the hollow portion and the die increases, in other words, toward the bottomed bowl-shaped portion or the cylindrical portion. On the other hand, since the processing strain decreases as the deformation amount increases, in the present invention, the processing strain decreases toward the bottomed bowl-shaped portion or the cylindrical portion. That is, the processing strain becomes maximum on the opening side of the hollow portion. Thus, due to the difference in the degree of processing distortion between the bottomed bowl-shaped part or the cylindrical part side and the opening side, the hollow part after the internal tooth profile is formed, for example, in the diametric direction as it goes to the opening side. It shrinks inward, and as a result, a so-called undercut part is formed.

  As described above, by controlling the size of the processing strain in the hollow portion when forming the internal teeth, the hollow portion after the internal tooth shape is formed has a shape in which the opening side contracts in the width direction. And the outer member for constant velocity joints is taken out from a forge molding apparatus, and the process distortion of a hollow part is removed in this case.

  Thereafter, when heat treatment is performed on the inner teeth to cause thermal strain, the amount of expansion in the width direction on the opening side of the hollow portion becomes larger than that on the bottomed bowl-shaped portion or the cylindrical portion side.

  As described above, the hollow side after molding is contracted on the opening side as compared with the bottomed bowl-shaped part or the cylindrical part. Therefore, when the opening side is greatly expanded as compared with the bottomed bowl-shaped part or the cylindrical part, a hollow part extending substantially linearly is formed. For this reason, since the diverging state which becomes large as the OPD of the internal teeth becomes the opening side of the hollow portion is avoided, the dimensional accuracy of the internal teeth can be ensured.

  Moreover, since heat treatment is performed on the inner teeth, it is possible to obtain inner teeth with improved hardness and strength while ensuring dimensional accuracy.

  Here, after performing the ironing forming process using the mold apparatus that is provided in the hollow part and performs the ironing process on the cup part having a diameter larger than that of the hollow part, It is preferable to perform the second forging process. In this case, the ironing process for the cup portion and the inner tooth formation for the hollow portion are performed in one mold apparatus. For this reason, work efficiency improves.

  In addition, in this case, there is no need to manufacture mold devices dedicated for iron molding and for internal tooth formation, thereby reducing the number of mold devices and ultimately reducing the capital investment.

  Thus, in order to carry out the ironing process and the internal tooth formation with one mold device, for example, the hollow part is displaced by displacing the die by pressing the hollow part toward the tooth part forming punch side. A tooth portion forming punch may be inserted into the inner teeth to form the inner teeth.

  A suitable example of heat treatment is induction hardening.

  According to the present invention, the distance between the outer peripheral wall of the hollow portion where the internal teeth are formed and the die surrounding the hollow portion is reduced on the opening side of the hollow portion facing the internal tooth forming punch, while the internal teeth The internal teeth are formed in the hollow portion in a state that is maximized at a position farthest from the forming punch. When the inner teeth are formed in this way, the hollow portion has a shape contracted in the width direction from the bottomed saddle-shaped portion or the cylindrical portion side toward the opening side. Thereafter, when heat treatment is performed on the inner teeth, the opening side of the hollow part is greatly expanded as compared with the bottomed saddle-like part or the cylindrical part side, so that the hollow part extends substantially linearly. For this reason, it is possible to avoid a so-called divergent state in which the OPD of the internal teeth becomes larger as the hollow portion is opened, and as a result, the dimensional accuracy of the internal teeth is ensured.

  Moreover, since heat treatment is performed on the inner teeth, it is possible to obtain an inner tooth having improved hardness and strength while ensuring dimensional accuracy.

  Hereinafter, preferred embodiments of the method for manufacturing an outer member for a constant velocity joint according to the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, an outer member of a tripod type constant velocity joint will be described as an example of an outer member for a constant velocity joint.

  The outer member for a constant velocity joint according to the present embodiment includes a first forging process for obtaining a fourth molded product 12 shown in FIG. 1E from a billet 10 made of carbon steel shown in FIG. 1A, The quaternary molded article 12 includes a second forging process for providing the inner member 14 (see FIG. 1F) as an outer member 16 and a heat treatment process for subjecting the outer member 16 to induction hardening.

  First, the first forging process is performed. That is, the fourth molded product 12 is formed by subjecting the billet 10 to forging molding a plurality of times.

  The billet 10 is first subjected to spheroidizing annealing. As a result, the billet 10 is softened, and the subsequent multiple forging processes are facilitated.

  Next, a chemical conversion coating for lubrication is formed on the billet 10. That is, for example, so-called bonderite treatment is performed, and as a result, a lubricating chemical conversion film made of zinc phosphate or the like is formed on the surface of the billet 10. The billet 10 on which this lubricating chemical film is formed exhibits good lubricity. The bonderite treatment is performed by immersing the billet 10 in a solvent in which zinc phosphate or the like is dissolved for a predetermined time.

  Next, an initial forging process is performed. Specifically, forward extrusion is performed in which the billet 10 on which the lubricating chemical film is formed is pressed from one end surface side. By this forward extrusion, as shown in FIG. 1B, the large-diameter portion 18, the hollow small-diameter portion 20 having a smaller diameter and a bottomed hole shape than the large-diameter portion 18, the large-diameter portion 18 and the hollow small-diameter portion 20 A primary molded product 22 having a reduced diameter portion 21 that is interposed between and reduced in a tapered shape is obtained.

  Next, preliminary upset molding is performed on the primary molded product 22. That is, the primary molded product 22 is loaded into the cavity of the pre-upsetting mold apparatus. At that time, the hollow small-diameter portion 20 is inserted into a shaft holding portion provided in the preliminary upsetting mold apparatus.

  In this forming process, the large-diameter portion 18 is pressed by a punch from the upper end surface side while the distal end portion of the hollow small-diameter portion 20 inserted into the shaft portion holding portion is supported. By this pressing, the large-diameter portion 18 is crushed and expanded in diameter, and as a result, the secondary molded product 24 shown in FIG. 1C is obtained. Note that this preliminary upsetting may be omitted.

  Subsequently, upsetting is performed to further compress and expand the large-diameter portion 18 of the secondary molded product 24 to form a tertiary molded product 26 shown in FIG. 1D. That is, using the upsetting mold apparatus, the large-diameter portion 18 of the secondary molded product 24 loaded in the cavity is pressed from the upper end surface side with a punch. As a result, the large-diameter portion 18 of the secondary molded product 24 is compressed and deformed in the axial direction, and a tertiary molded product 26 shown in FIG. 1D is obtained.

  After upsetting, the low temperature annealing for removing stress from the tertiary molded product 26, the shot blasting process for removing oxide scales, etc. generated during this low temperature annealing, the surface of the tertiary molded product 26 Bonderite treatment is carried out to form a lubricating chemical conversion film made of zinc phosphate or the like. By performing these various processes, the third molded product 26 can be easily plastically deformed.

  Next, the third molded product 26 is loaded into the cavity of the forging die device, and the central portion of the solid large-diameter portion 18 is pressed with a punch constituting the forging die device. Along with this pressing, a meat flow in a direction opposite to the pressing direction occurs in a portion of the large diameter portion 18 that is not pressed by the punch. As a result, as shown in FIG. 1E, a hollow cylindrical cup portion 28 is formed, and the fourth molded product 12 is obtained. At this point, the first forging process is completed.

  Thus, at the same time as the cup portion 28 is formed, the convex shape provided on the punch is transferred to the inner peripheral wall of the cup portion 28, and a track groove is formed in the inner peripheral wall.

  Thereafter, in the second forging process, ironing, which is final sizing, and formation of the inner teeth 14 on the inner peripheral wall of the hollow small diameter portion 20 are performed.

  Here, the principal part longitudinal cross-sectional explanatory drawing of the ironing die apparatus is shown in FIG. This ironing mold apparatus 30 is disposed in a floating die 32 that is elastically biased upward in FIG. 2 by a resilient member such as a coil spring (not shown), and in the insertion hole 34 of the floating die 32. An internal tooth forming punch 38 provided with a tooth portion forming portion 36, a ironing punch 40 disposed on the side facing the cup portion 28, and a support die 42 surrounding the cup portion 28. Among these, the floating die 32 is slidably disposed in the insertion hole 46 of the die main body 44 surrounding the floating die 32.

  In the present embodiment, the internal tooth forming punch 38 is positioned and fixed, while the ironing punch 40 is movable up and down.

  In the ironing mold apparatus 30 configured as described above, ironing and internal tooth formation are performed as follows.

  Prior to loading of the fourth molded product 12, a liquid lubricant is applied to the surface of the fourth molded product 12. The liquid lubricant may be applied to the internal tooth forming punch 38, the ironing punch 40, the floating die 32, and the support die 42. Of course, the liquid lubricant may be applied to both the fourth molded product 12 and at least one of the internal tooth forming punch 38, the ironing punch 40, the floating die 32, and the support die 42. As the liquid lubricant, a known liquid lubricant that has been conventionally used may be used.

  When the liquid lubricant is applied in this way, the fourth molded product 12, the internal tooth forming punch 38, the ironing punch 40, the floating die 32, and the support die 42 are seized during the ironing and internal tooth formation described later. Can be avoided.

  In the fourth molded product 12, the hollow small diameter portion 20 is inserted into the insertion hole 34 of the floating die 32, and finally the bottom surface of the cup portion 28 is seated on the upper end surface of the floating die 32, and the cup portion 28 is supported by the support die. By being inserted into the cavity 48 of 42, it is supported by the ironing mold apparatus 30. At this time, as shown in FIG. 3 in an enlarged manner, a clearance is provided between the outer peripheral wall of the hollow small diameter portion 20 and the inner peripheral wall of the insertion hole 34 of the floating die 32 surrounding the hollow small diameter portion 20. CL occurs.

  Here, in the present embodiment, the clearance CL, in other words, the distance between the outer peripheral wall of the hollow small diameter portion 20 and the inner peripheral wall of the insertion hole 34 of the floating die 32 is not constant, and the hollow small diameter portion 20 is not constant. It changes according to the part of. Specifically, the separation distance is set to be smaller on the side facing the internal teeth forming punch 38 (opening side of the hollow small diameter portion 20) and larger toward the cup portion 28. The separation distance is maximized in the portion of the hollow small diameter portion 20 that is the most spaced from the internal tooth forming punch 38, that is, in the vicinity of the boundary with the cup portion 28.

  In this state, the driving unit of the ironing mold apparatus 30 is energized, and the ironing punch 40 is lowered toward the cup unit 28. The ironing punch 40 is inserted into the cup portion 28 and presses the cup portion 28 from the inner peripheral wall side (see FIG. 2). With this pressing, the meat of the cup portion 28 flows in the direction opposite to the pressing direction. That is, the cup part 28 extends, and finally, the thickness of the cup part 28 and the width and depth of the track groove have predetermined dimensions.

  The descending of the ironing punch 40 is continued even after the meat flow is finished. Along with this, a large pressing force starts to act on the floating die 32 on which the bottom surface of the cup portion 28 is seated. When this pressing force exceeds the elastic urging force on the floating die 32, the floating die 32 is displaced downward as shown in FIG. As a result, the hollow small diameter portion 20 is lowered to the position of the internal tooth forming punch 38, and the internal tooth forming punch 38 is inserted into the hollow small diameter portion 20.

  As described above, the tooth portion forming portion 36 is provided at the distal end portion of the internal tooth forming punch 38. The shape of the tooth portion forming portion 36 is transferred to the inner peripheral wall of the hollow small diameter portion 20, and the inner teeth 14 are formed on the inner peripheral wall.

  At this time, the force acting on the hollow small-diameter portion 20 is schematically shown in FIG. The internal tooth forming punch 38 presses the inner peripheral wall of the hollow small diameter portion 20 substantially evenly. For this reason, the force which acts on the inner peripheral wall from the internal tooth forming punch 38 is substantially equal.

  On the other hand, the separation distance between the floating die 32 and the hollow small-diameter portion 20 is set so as to increase from the opening side of the hollow small-diameter portion 20 toward the cup portion 28 as described above. Therefore, the force acting on the outer peripheral wall of the hollow small-diameter portion 20 from the floating die 32 becomes smaller from the opening side of the hollow small-diameter portion 20 toward the cup portion 28 as shown in FIG. This is because when the separation distance is large, the reaction force against the pressing force of the internal tooth forming punch 38 is small.

  The deformation amount of the hollow small-diameter portion 20 increases as it goes toward the cup portion 28 where the clearance CL is large. On the other hand, the processing strain decreases toward the cup portion 28, contrary to the deformation amount. Thus, due to the fact that the degree of processing strain changes from the cup part 28 side to the opening side, the dimension in the diameter direction of the hollow small diameter part 20 after providing the internal teeth 14 is larger than that of the cup part 28 side. The opening side becomes smaller. In other words, the hollow small-diameter portion 20 has a shape that shrinks inward in the diametrical direction toward the opening side, and thus a so-called undercut portion is formed.

  When the formation of the inner teeth 14 on the inner peripheral wall of the hollow small diameter portion 20 is completed, the pressing force to the cup portion 28 is reduced as the ironing punch 40 rises. When the elastic biasing force to the floating die 32 becomes larger than the pressing force to the cup portion 28 of the ironing punch 40, the floating die 32 is displaced upward and follows this, as shown in FIG. The hollow small-diameter portion 20 rises and is separated from the internal tooth forming punch 38. Along with this, the processing strain of the hollow small-diameter portion 20 is removed.

  In this way, the outer member 16 provided with the inner teeth 14 is subjected to induction hardening in the heat treatment step. Induction hardening may be performed on the entire outer member 16 or only on the hollow small-diameter portion 20.

  During the induction hardening, the hollow small diameter portion 20 is deformed so as to expand further outward in the diameter direction. In addition, the amount of expansion on the opening side of the hollow small diameter portion 20 is larger than that on the cup portion 28 side.

  Here, as described above, the hollow small-diameter portion 20 has a shape that contracts inward in the diametrical direction toward the opening side, and is induction-hardened in this state. And since the opening side shrunk | reduced rather than the cup part 28 side with formation of the internal tooth 14 becomes large at the time of induction hardening, the opening side in the hollow small diameter part 20 and the cup part 28 side are the final. The dimensions are almost the same. Eventually, the hollow small diameter portion 20 extends substantially linearly. As a result, a so-called divergent state in which the OPD of the inner teeth 14 becomes larger toward the opening side of the hollow portion can be avoided, so that it is easy to ensure the dimensional accuracy of the inner teeth 14.

  The OPD of the internal teeth 14 may be set to be slightly smaller than the vicinity of the boundary between the hollow small-diameter portion 20 and the cup portion 28 on the opening side of the hollow small-diameter portion 20. In this case, when the difference in OPD is about 0.1 mm, the separation distance between the outer peripheral wall near the boundary between the hollow small-diameter portion 20 and the cup portion 28 and the inner peripheral wall of the floating insertion hole 34 is, for example, about 0.1 mm. What is necessary is just to set to 5 mm.

  The internal teeth 14 subjected to induction hardening are increased in strength and hardness as compared with those before induction hardening. That is, according to the present embodiment, the internal teeth 14 having high strength and high hardness and good dimensional accuracy can be provided.

  Moreover, in the present embodiment, the iron molding apparatus 30 is used to perform the iron molding process on the cup portion 28, and then the fourth molded product 12 is not taken out from the iron molding apparatus 30. The outer member 16 is manufactured by forming the inner teeth 14 in the hollow small-diameter portion 20. For this reason, work efficiency improves. In addition, since the ironing mold apparatus also serves as the internal tooth forming mold apparatus, it is not necessary to prepare mold apparatuses dedicated for iron forming and for internal tooth formation. Therefore, since the number of mold apparatuses is reduced, there is an advantage that the capital investment is reduced.

  In the present embodiment, the outer member of the tripod type constant velocity joint has been described as an example of the outer member 16; however, other types of outer members for constant velocity joints, such as the outer member of a barfield type constant velocity joint, have been described. Needless to say, it may be.

  Moreover, heat processing is not specifically limited to induction hardening, What is necessary is just heat processing which a thermal strain produces.

  Furthermore, it is needless to say that the tooth portion may be formed by raising the inner tooth forming punch 38 toward the outer member 16 and inserting it into the hollow small diameter portion 20.

1A to 1F are flowcharts showing an outline of a process of providing an outer member from a billet. It is principal part longitudinal cross-section explanatory drawing of the ironing die apparatus used at a 2nd forge-forming process. FIG. 3 is an enlarged longitudinal sectional view of a main part of the ironing mold apparatus of FIG. 2. FIG. 3 is an enlarged longitudinal sectional view of a main part showing a state in which a floating die constituting the ironing mold apparatus of FIG. 2 is displaced. It is the principal part longitudinal cross-section schematic diagram which showed typically the force which acts on this hollow small diameter part, when providing a tooth | gear part in a hollow small diameter part. It is a principal part expanded vertical sectional view which shows the state which the hollow small diameter part went up and was spaced apart from the internal tooth formation punch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 ... Internal tooth 16 ... Outer member 20 ... Hollow small diameter part 28 ... Cup part 30 ... Molding apparatus for ironing molding 32 ... Floating die 34 ... Insertion hole 36 ... Tooth part formation part 38 ... Internal tooth formation punch 40 ... Ironing punch 48 ... cavity CL ... clearance

Claims (4)

A method for producing an outer member for a constant velocity joint having a hollow portion in which inner teeth are formed,
A first forging process for producing an outer member for a constant velocity joint having a hollow portion;
A second forging process step of inserting a tooth portion forming punch into the hollow portion surrounded by a die and providing inner teeth on the inner peripheral wall of the hollow portion;
A heat treatment step of performing heat treatment on at least the inner teeth;
Have
In the second forging process, the distance between the die and the hollow portion is reduced to the side facing the tooth portion forming punch while being maximized at a position farthest from the tooth portion forming punch. A method for manufacturing an outer member for a constant velocity joint, wherein an inner tooth is provided.   The manufacturing method according to claim 1, wherein the ironing process is performed using a mold device that is connected to the hollow part and performs ironing processing on a cup part having a diameter larger than that of the hollow part. Then, the manufacturing method of the outer member for constant velocity joints which performs the said 2nd forge forming process process in the said metal mold apparatus.   3. The manufacturing method according to claim 2, wherein the tooth part forming punch is inserted into the hollow part by displacing the die by pressing the hollow part toward the tooth part forming punch side to insert the tooth part forming punch into the hollow part. The manufacturing method of the outer member for constant velocity joints which forms a tooth | gear.   The method for manufacturing an outer member for a constant velocity joint according to claim 1, wherein induction hardening is performed as the heat treatment.

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