JP2015193044A - Block forging method of trunnion for universal joint and trunnion for universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a block forging method of a trunnion for universal joint which is satisfied in product quality even if a shaft part is enlarged in diameter, improved in rigidity, reduced in weight, and compact in size, and the trunnion for the universal joint.SOLUTION: In a block forging method of a trunnion for a universal joint in which a plurality of shaft parts 10 are radially formed at a boss part 8, a forging metal mold is constituted of: openable and closable dies 16, 17 in which cavities 20 substantially corresponding to the trunnion are formed; a pair of upper and lower punches 18, 19 which are relatively and movably arranged on center axes of the dies 16, 17, and press a billet 15b; and sufficing punches 30 which are arranged on center axes of shaft-part molding metal mold parts 16a, 17a of the cavities 20, and can advance and retreat with respect to a radial direction. The billet 15b is inputted into dies 16, 17, the sufficing punches 30 advance into the cavities 20 of the clamped dies 16, 17, the billet 15b is pressed by the upper and lower punches 18, 19, the shaft parts 10, 60 are formed, and recesses 25 are formed in the shaft parts.

Description

  The present invention relates to a closed forging method for a universal joint trunnion and a universal joint trunnion.

  Universal joints are used for propeller shafts and drive shafts. One of these universal joints is, for example, a type of joint called a sliding two-pod joint. The two-pod joint mainly includes an outer joint member, a trunnion having two shaft portions, and a spherical roller attached to the shaft portion of the trunnion via a rolling element.

  Specifically, as shown in FIG. 1, the sliding joint 2 pod joint 1 has a cylindrical cup portion 3 and a shaft portion 4 formed at the bottom of the outer joint member 2. Two track grooves 5 are formed on the inner periphery of the cup portion 3 at halves (180 ° intervals) in the circumferential direction, and a roller guide surface 6 having an arcuate cross section is formed on the opposite side surface of the track groove 5. ing. A concave portion 9 on a circular arc in which the boss portion 8 of the trunnion 7 is fitted is formed at the center of the inner periphery of the cup portion 3.

  The trunnion 7 has two shaft portions 10 formed radially from the boss portion 8 at intervals of 180 °. A spherical roller 12 is rotatably mounted on the shaft portion 10 via needle rollers 11 as rolling elements. The spherical roller 12 is rotatably guided by the roller guide surface 6 of the track groove 5 of the outer joint member 2. With such a structure, relative axial displacement and angular displacement between the outer joint member 2 and the trunnion 7 are absorbed, and rotational torque is transmitted. An example of such a two-pod joint is described in Patent Document 1.

JP 61-171923 A

  In recent years, demands for improving the fuel efficiency of automobiles have become stronger, and further weight reduction and compactness of universal joints are strongly desired. Patent Document 1 does not pay attention to such a requirement.

  The present invention has been proposed in view of the above-mentioned problems, and the object of the present invention is to satisfy the quality as a product even when the diameter of the trunnion shaft is increased, to improve the strength of the trunnion, and to be lightweight. The object is to provide a closed forging method for a trunnion for a universal joint and a trunnion for a universal joint.

The present inventors diligently studied and verified to achieve the above object, and found the following findings.
(1) In order to improve the trunnion strength and achieve compactness, as a product design, it is conceivable to increase the outer diameter of the shaft portion and increase the secondary moment of section.
(2) Therefore, a closed forging test of a trunnion in which the outer diameter of the shaft portion was increased was performed. FIG. 11 shows a trunnion molded product 7 ′ after forging. The outer diameter D of the shaft portion 10 is increased, and the outer diameter D is made larger than the axial length L of the shaft portion 10. As shown in FIG. 12A, the billet 15 is put into the dies 16 and 17. When the billet 15 is pressed by the upper and lower punches 18 and 19 after the mold is closed, the material flows into the cavity 20 as shown in FIG. As a result of the closed forging test, when the outer diameter D of the shaft portion 10 was increased, sink marks 14 were generated in the inner diameter portion 13 of the boss portion 8 as shown in FIGS. 11 and 12B. This is considered to be due to an increase in material flow toward the tip of the shaft 10. From this test result, it was found that the quality of the product could not be satisfied, and therefore the diameter of the shaft portion 10 was more restricted than the forged surface.
(3) As a result of various studies on the above problems, a new closed forging concept of suppressing the material flow rate was conceived and the present invention was achieved.

  As technical means for achieving the above-mentioned object, the present invention is a closed forging method for a universal joint trunnion in which a plurality of shaft portions are radially formed on a boss portion, and the forging die is substantially equivalent to the trunnion. An openable and closable die having a cavity to be formed, a pair of upper and lower punches that are relatively movable on the center axis of the die and press the billet, and the center axis of the cavity mold part It is composed of a sufficiency punch that is arranged on the top and is capable of advancing and retreating in the radial direction. The billet is introduced into the die, and the sufficiency punch is advanced into the cavity of the die that is closed and placed in the cavity. When the billet is pressed by the upper and lower punches in the state, a concave portion is formed in the shaft portion and the inside thereof.

  Further, the present invention as a universal joint trunnion is a universal joint trunnion having a plurality of radially formed shaft portions, wherein the outer diameter of the shaft portion of the trunnion is set larger than the axial length, and the shaft A concave portion formed to suppress the material flow rate during forging is provided on the central axis of the portion.

  With the above configuration, even if the diameter of the trunnion shaft portion is increased, there is no sink in the inner diameter portion of the boss portion, and a closed forging method for a universal joint trunnion that satisfies the product quality can be realized. In addition, the thickness of the trunnion shaft is increased by reducing the thickness of the forging due to the recess provided on the central shaft of the shaft, ensuring strength and reducing the size and weight of the trunnion for universal joints. Can be realized.

  The ratio B / A of the cross-sectional area B of the recess to the cross-sectional area A of the shaft is preferably 0.35 to 0.80. Thereby, the sink of the internal diameter part of a boss | hub part can be suppressed. Further, the ratio B / A is more preferably 0.45 to 0.75. Thereby, in addition to being able to suppress the sink of the inner diameter portion of the boss portion, it is possible to suppress an increase in processing load necessary for side extrusion, which is advantageous for the tool life.

  In the closed forging method described above, the sufficiency punch is positioned in the radial direction while the shaft portion and the recess are formed. Thereby, the positioning means for the sufficiency punch can receive a molding load and can have a mold structure without relative movement between the sufficiency punch and the positioning means, so that sliding wear and galling can be prevented.

  It is preferable to provide a stepped portion in the vicinity of the radially outer end of the inner surface of the shaft molding die. Thereby, it can be set as the marking which determines the satisfaction degree of an axial part. Further, since the molding surface by the step portion is molded with high accuracy, it can be used for positioning in grinding finishing of the cylindrical outer peripheral surface of the shaft portion.

  It is preferable that the shape of the recess in the cross section is circular. This simplifies the shape of the sufficiency punch and facilitates production. Also, the material flows smoothly during forging. However, the shape of the cross section of the recess is not limited to a circle, and may be an ellipse, a circle including a partial straight line, and an ellipse.

  Said billet can form the side surface corresponding to an axial part in a flat surface by preforming. Thereby, the sagging of the front end surface of the axial part after shaping | molding can be suppressed.

  Specific examples of the universal joint include a two-pod joint having a trunnion having two shaft portions and a tripod constant velocity universal joint having a trunnion having three shaft portions.

  According to the present invention, it is possible to realize a closed forging method for a universal joint trunnion that does not cause sink marks in the inner diameter portion of the boss portion even when the diameter of the trunnion shaft portion is increased, and satisfies the quality as a product. In addition, the strength can be ensured, and a lightweight and compact trunnion for a universal joint can be realized.

  When the filling punch is configured to be positioned in the radial direction while the shaft portion and the recess are formed, it is possible to obtain a mold structure that prevents sliding wear and galling with a simple mechanism.

The trunnion and universal joint which concern on 1st Embodiment about the trunnion for universal joints of this invention are shown, (a) is a cross-sectional view, (b) is a partial longitudinal cross-sectional view. It is an enlarged view of Fig.1 (a). It is a figure explaining 1st Embodiment about the closed forging method of this invention, and shows the billet before forging the trunnion of FIG. 1, (a) is a perspective view which shows the state which cut | disconnected the bar material, b) is a perspective view showing a state in which the billet of FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining 1st Embodiment about the closed forging method of this invention, (a) is a perspective view which shows the state after the forge of the trunnion of FIG. 1, (b) is the cross-sectional area and recessed part of an axial part. FIG. The closed forging process is shown, (a) is a longitudinal sectional view showing a state in which a billet is charged, and (b) is a longitudinal sectional view showing a completed state. It is a schematic diagram including the advance / retreat mechanism of the sufficiency punch. It is a longitudinal cross-sectional view which shows the state which the sufficiency punch of FIG. 6 retracted. It is a longitudinal cross-sectional view which shows the 1st modification of the drive mechanism of a sufficiency punch. It is a longitudinal cross-sectional view which shows the 2nd modification of the drive mechanism of a sufficiency punch. It is a perspective view which shows the modification of the recessed part of an axial part. It is a perspective view which shows the knowledge of the process leading to this invention. The knowledge of the process leading to the present invention is shown, (a) is a longitudinal sectional view showing a state in which a billet is charged, and (b) is a longitudinal sectional view showing a completed state. The trunnion and tripod type constant velocity universal joint concerning the 2nd Embodiment about the trunnion for universal joints of this invention are shown, (a) is a cross-sectional view, (b) is a partial longitudinal cross-sectional view. It is a fragmentary longitudinal cross-section which shows the state which the tripod type constant velocity universal joint of FIG. 13 took the operating angle. It is an enlarged view of Fig.13 (a). The billet in 2nd Embodiment about the closed forging method of this invention is shown, (a) is a perspective view which shows the state which cut | disconnected the bar material, (b) is the state which preformed the billet of (a). It is a perspective view shown. It is a figure explaining 2nd Embodiment about the closed forging method of this invention, and is a perspective view which shows the state after forging of a trunnion.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show a first embodiment of a trunnion for a universal joint according to the present invention, and FIGS. 3 to 7 show a first embodiment of a closed forging method for a trunnion for a universal joint according to the present invention.

  First, the universal joint trunnion according to the first embodiment will be described with reference to FIG. 1A and 1B show a trunnion and a universal joint according to a first embodiment, wherein FIG. 1A is a transverse sectional view and FIG. 1B is a partial longitudinal sectional view. The universal joint 1 is called a sliding two-pod joint. The two-pod joint 1 mainly includes an outer joint member 2, a trunnion 7 as an inner joint member, a needle roller 11 and a spherical roller 12 as rolling elements.

  Specifically, as shown in FIG. 1, the sliding joint 2 pod joint 1 has a cylindrical cup portion 3 and a shaft portion 4 formed at the bottom of the outer joint member 2. Two track grooves 5 are formed on the inner periphery of the cup portion 3 at bisected positions (at intervals of 180 °) in the circumferential direction, and a roller guide surface 6 having an arcuate cross section is formed on the opposite side surface of the track groove 5. ing. A concave portion 9 having a circular arc cross section is formed at the center of the inner periphery of the cup portion 3.

  The trunnion 7 has two shaft portions 10 formed to protrude radially from the boss portion 8 at intervals of 180 °. Each shaft portion 10 includes a cylindrical outer peripheral surface 10a and an annular retaining ring groove 21 formed near the shaft end. A spherical roller 12 is rotatably mounted around a cylindrical outer peripheral surface 10 a of the shaft portion 10 via a plurality of needle rollers 11. The cylindrical outer peripheral surface 10 a of the shaft portion 10 forms the inner raceway surface of the needle roller 11. The inner peripheral surface 12 a of the spherical roller 12 is cylindrical and forms the outer raceway surface of the needle roller 11.

  A retaining ring 23 is attached to a retaining ring groove 21 formed near the shaft end of the shaft portion 10 via an outer washer 22. In the needle roller 11, the axial movement of the shaft portion 10 is restricted by the base step portion of the shaft portion 10 and the outer washer 22. The outer washer 22 includes a disk portion 22 a extending in the radial direction of the shaft portion 10 and a cylindrical portion 22 b extending in the axial direction of the shaft portion 10. The cylindrical portion 22 b of the outer washer 22 has a smaller outer diameter than the inner peripheral surface 12 a of the spherical roller 12, and the outer end 22 c of the cylindrical portion 22 b viewed in the radial direction of the trunnion 7 is the inner peripheral surface of the spherical roller 12. The diameter is larger than 12a. Therefore, the spherical roller 12 can move in the axial direction of the shaft portion 10 and is prevented from falling off by the end portion 22c.

  The spherical roller 12 rotatably mounted on the shaft portion 10 of the trunnion 7 is guided rotatably on the roller guide surface 6 of the track groove 5 of the outer joint member 2. Further, the boss portion 8 of the trunnion 7 is formed in a spherical shape, and this boss portion 8 is fitted in the concave portion 9 of the outer joint member 2 and is slidable in the axial direction of the concave portion 9. Therefore, it is guided so as not to be displaced in a plane orthogonal to each other. With such a structure, relative axial displacement and angular displacement between the outer joint member 2 and the trunnion 7 are absorbed, and rotation is transmitted.

  A female spline 24 is formed on the inner peripheral surface of the boss portion 8 of the trunnion 7, and although not shown, a male spline of an intermediate shaft is fitted into the female spline 24 and connected so as to be able to transmit torque. .

  The two-pod joint 1 according to the present embodiment has the dimensional relationships shown in FIG. 2 in order to reduce weight and size. The ratio d / PCD of the shaft diameter (spline large diameter) d of the intermediate shaft and the PCD of the roller guide surface is set large as 0.65 to 0.75, and the outer diameter Dj of the shaft portion 10 of the trunnion 7 and the shaft diameter are set. The ratio Dj / d with respect to d is set as large as 0.87 to 0.93. Further, the ratio Ln / Dj between the needle roller length Ln and the outer diameter Dj of the shaft portion 10 is as small as 0.40 to 0.47, that is, the outer diameter Dj of the shaft portion 10 is the axial length of the shaft portion 10. It is set significantly larger than this.

  Each shaft portion 10 has a large diameter as described above, but includes a recess 25 formed on the central axis of each shaft portion 10 to suppress the material flow rate during forging. The ratio B / A of the cross-sectional area B (see FIG. 4 (b)) of the recess 25 to the cross-sectional area A (see FIG. 4 (b)) of the shaft 10 is preferably 0.35 to 0.80. The ratio B / A is more preferably 0.45 to 0.75. As a result, even if the diameter of the trunnion shaft is increased, the material flow rate during forging can be sufficiently suppressed, so that there is no occurrence of sink marks, and good product quality can be ensured. In addition, an increase in processing load required for side extrusion can be suppressed, which is advantageous for tool life. This point will be described in more detail in an embodiment of a closed forging method described later.

  Next, a first embodiment of a closed forging method for a universal joint trunnion according to the present invention will be described with reference to FIGS. First, the material before forging is shown in FIG. 3A is a perspective view showing a billet obtained by cutting a bar material, and FIG. 3B is a perspective view showing a state in which the billet of FIG. 3A is preformed.

  A bar material consists of case hardening steel, such as chromium steel (SCr420) and chromium molybdenum steel (SCM420). As shown in FIG. 3A, the bar material is cut at a predetermined length based on the forging weight to produce a cylindrical billet 15a. Prior to the closed forging step (main forming step) of the billet 15a, a preforming material 15b having the shape shown in FIG. The preform 15b has a side surface corresponding to the shaft portion 10 as a flat surface 26, and is recessed at both ends so that the bulging portions 18a and 19a of the upper and lower punches 18 and 19 [see FIG. 27a and 27b (see FIG. 5A) are formed. The preforming material 15b is formed into the above-mentioned shape, and the effect thereof will be described later. Here, the billet refers to both the billet 15a and the preformed material 15b.

  The state after closed forging of the trunnion is shown in FIG. As shown in the figure, the trunnion molded product 7 ′ after forging is formed with a shaft portion 10 protruding radially from the boss portion 8 at an interval of 180 °, and the shaft portion 10 has a material flow rate during forging on its central axis. A recess 25 is formed to suppress the above. Concave portions 27 a ′ and 27 b ′ (see FIG. 5B) are formed at both ends of the boss portion 8.

  The closed forging process for obtaining the trunnion molded product 7 ′ will be described with reference to FIGS. FIG. 5A shows a state where the upper and lower dies 16 and 17 are closed after the preforming material 15b is introduced, and the sufficiency punch 30 is arranged at a predetermined molding position. The movement of each mold until reaching this state will be described. In a state where the upper and lower dies 16 and 17 that can be opened and closed are separated, the preforming material 15b is introduced. At this time, the upper and lower punches 18 and 19 are in a standby state in a retracted position, and the recessed portion 27b at the lower end portion of the charged preforming material 15b is fitted into the bulging portion 19a of the lower punch 19 so that the posture is maintained. Set. Thereafter, the upper and lower dies 16, 17 approach each other, and the cam 31 shown in FIG. After the upper and lower dies 16 and 17 are in contact with each other and the mold is closed, the advancement of the sufficiency punch 30 is finished, and the die is placed at a predetermined molding position in the radial direction. This state is shown in FIG. Here, the forging die refers to the upper and lower dies 16 and 17, the upper and lower punches 18 and 19, and the sufficiency punch 30.

  From the state of FIG. 5A, the upper and lower punches 18 and 19 approach, the bulging portion 18a of the upper punch 18 fits into the recess 27a at the upper end portion of the preform 15b, and the lower end surface 18b of the upper punch 18 and the lower portion The upper end surface 19b of the punch 19 presses the upper and lower end surfaces of the preforming material 15b. When the upper and lower punches 18 and 19 are pushed in, as shown in FIG. 5 (b), the preforming material 15b is plastically deformed and formed on the inner surfaces of the shaft forming mold parts 16a and 17a of the upper and lower dies 16 and 17. The material is caused to flow into the cavity 20. At the time of molding, the sufficiency punch 30 is disposed at a predetermined molding position, so that the material flow rate can be suppressed by the cross-sectional area of the sufficiency punch 30 even if the shaft portion 10 of the trunnion 7 has a large diameter. A concave portion 25 is formed on the central axis of the shaft portion 10 during this molding. For this reason, sink marks of the inner diameter portion 13 of the boss portion 8 are suppressed.

  As shown in FIG. 4A, the shaft portion 10 of the trunnion molded product 7 ′ has an outer diameter D that is set to be significantly larger than the axial length L. Based on 4 (b), an advantageous configuration for suppressing the sink marks will be added. The ratio B / A of the cross-sectional area B of the recess 25 formed corresponding to the cross-sectional area of the sufficiency punch 30 with respect to the cross-sectional area A of the shaft portion 10 is preferably 0.35 to 0.80. As a result, even if the outer diameter D of the shaft portion 10 is increased, the cross-sectional area through which the material flows during forging becomes the cross-sectional area A of the shaft portion 10 minus the cross-sectional area B of the recess 25, thereby suppressing the material flow rate. Since this is possible, the sink of the inner diameter portion 13 of the boss portion 8 can be suppressed. In FIG. 4B, the cross-sectional area A of the shaft portion 10 is a hatched portion, and the cross-sectional area B of the recess 25 is a cross-hatched portion. Furthermore, the ratio B / A is more preferably 0.45 to 0.75. Thereby, in addition to the above effect that sink can be suppressed, an increase in processing load necessary for side extrusion can be suppressed, which is advantageous for tool life.

  In the preform 15b shown in FIG. 3B, the side surface corresponding to the shaft portion 10 is the flat surface 26 as described above. This effect will be described. In the closed forging, the portion that becomes the tip surface 10b (see FIG. 5B) of the shaft portion 10 is less liable to flow than the portion in contact with the shaft portion molding die portions 16a, 17a and the sufficiency punch 30. . However, by using the preforming material 15b having the above-described shape, even if the relief portion 20a is provided in the cavity 20 of the shaft portion molding die portions 16a and 17a, as shown in FIG. The droop of 10b can be reduced. In this way, if the sagging of the tip surface 10b of the shaft portion 10 can be reduced, the two-pod joint 1 using the trunnion 7 can be made compact and lightweight. In the preform 15b, the side surface corresponding to the shaft portion is exemplified as the flat surface 26. However, the present invention is not limited to this, and a gentle cylindrical surface or an elliptic cylindrical surface having a large curvature radius may be used.

  FIG. 4A is a perspective view of the trunnion molded product 7 ′ after the closed forging shown in FIG. After the closed forging, the inner wall 8a of the boss 8 of the trunnion molded product 7 'is punched out. Thereafter, the trunnion molded product 7 ′ is formed by turning a predetermined portion of the outer periphery (the end surface and inner peripheral surface of the boss portion 8, the retaining ring groove 21 and the like), and the female spline 24 [FIG. 1 (a), (b), 2) is subjected to a heat treatment. By carburizing, quenching and tempering, the surface hardness is cured to about HRC 58 to 62. After the heat treatment, the cylindrical outer peripheral surface 10a of the shaft portion 10 is finished by grinding to obtain a finished product. As described above, there is a difference in the details of the shaft portion 10 between the trunnion molded product 7 ′ after the closed forging and the finished product 7, but the same reference numeral 10 is attached to the shaft portion of the molded product 7 ′ and the finished product 7. The description will be simplified. Further, there is a grinding allowance (0.1 to 0.2 mm) between the outer diameter D of the shaft portion 10 of the trunnion molded product 7 ′ of FIG. 4A and the outer diameter Dj of the shaft portion 10 shown in FIG. However, the dimensional relationship between D and Dj is regarded as equivalent.

  Step portions 16b and 17b are provided in the vicinity of the outer ends in the radial direction of the inner surfaces of the shaft molding dies 16a and 17a, as shown in FIG. As shown in FIG. 5B, depending on whether or not the shape of the stepped portions 16b and 17b is formed on the tip surface 10b of the shaft portion 10 of the trunnion molded product 7 ′ after the closed forging is finished, It can be set as the marking which determines the satisfaction degree of the part 10. FIG. In addition, since the molding surfaces formed by the stepped portions 16b and 17b formed on the tip surface 10b of the shaft portion 10 are molded with high precision, the cylindrical outer peripheral surface 10a of the shaft portion 10 is positioned during grinding finishing. Can be used. The step portions 16b and 17b are not limited to those provided over the entire circumference in the circumferential direction, and may be provided in a necessary range in a part in the circumferential direction.

  As shown in FIG. 5 (a), the front end surface 30a of the sufficiency punch 30 is formed with a smooth curved surface to smoothly flow the lubricant during forging, and the front end surface 30a and the front end outer diameter surface 30b are appropriately formed. Smooth connection with R shape. Thereby, even if the material flow rate is suppressed by the sufficiency punch 30 during forging, the material flows smoothly. Further, the tip outer diameter surface 30b is formed with a predetermined axial width, and a relief portion 30c is provided on the opposite end side of the tip outer diameter surface 30b. Thereby, the frictional force is reduced, and the molding load at the time of forging and the separation load of the sufficiency punch 30 described later can be reduced. Also, relief portions can be provided on the inner surfaces of the shaft portion molding die portions 16a and 17a facing the relief portion 30c. Thereby, the frictional force can be further reduced.

  As shown in FIGS. 5 (a) and 5 (b), while the trunnion molded product 7 'is molded, the sufficiency punch 30 is positioned at a predetermined molding position in the radial direction. Here, the advance / retreat mechanism of the sufficiency punch 30 will be described with reference to FIGS. FIG. 6 is a longitudinal cross-sectional view showing a state where the sufficiency punch 30 has advanced and is positioned at a predetermined molding position in the radial direction, and the molding has been completed. FIG. 7 is a longitudinal sectional view showing a state in which the sufficiency punch 30 is retracted from the shaft portion 10 after the completion of molding.

  Specifically, the advance / retreat mechanism 32 of the sufficiency punch 30 mainly includes a housing 33, a spring member 34, a cam 31, and a cam receiving member 35. A large number of disc springs 34 a are stacked in the housing 33 to constitute a spring member 34, and a sufficiency punch 30 is inserted into the inner peripheral hole of the disc spring 34 a. A cam receiving member 35 is fitted and fixed to the end of the sufficiency punch 30 on the cam side. The cam surface 35a of the cam receiving member 35 and the cam surface 31a of the cam 31 are in contact with each other, and the cam 31 is movable in the vertical direction in the figure. FIG. 6 shows a state in which the cam 31 is lowered to advance the sufficiency punch 30 against the biasing force of the disc spring 34a and is positioned at a predetermined molding position in the radial direction. Thus, the cam 31 functions as a forward drive means and a positioning means for the sufficiency punch 30.

  As described above, while the trunnion molded product 7 ′ is formed, the sufficiency punch 30 is positioned at a predetermined forming position in the radial direction (see FIGS. 5A, 5B, and 6). . Thus, in the molding process, there is no relative movement between the sufficient punch 30 (cam receiving member 35) and the cam 31, and the tapered cam surfaces 35a and 31a of the sufficient punch 30 (cam receiving member 35) and the cam 31 are provided. Since only the molding load is received and does not slide, the cam surfaces 35a and 31a are not galled.

  After the molding is completed, the upper die 16 and the upper punch 18 retreat upward, and the cam 31 moves upward. When the cam 31 moves upward, as shown in FIG. 7, the sufficiency punch 30 is retracted by the urging force of the spring member 34, and is separated from the trunnion molded product 7 '(shaft portion 10). As described above, the relief portion 30c is provided on the opposite end side of the distal end outer diameter surface 30b of the sufficiency punch 30 (see FIGS. 5A and 5B), so that the separation load can be reduced. By the above operation, the trunnion molded product 7 ′ can be knocked out from the lower die 17. Thereafter, the lower punch 19 knocks out the trunnion molded product 7 ′ from the lower die 17, and the closed forging process is completed.

  As described above, the mold structure can be simplified as the entire mold structure because there is no relative movement between the sufficient punch and the die or cam in the molding process, and the separation load can be reduced. Various modifications shown below can be adopted for the advance / retreat mechanism.

  Next, a first modification of the advance / retreat mechanism of the sufficiency punch 30 will be described with reference to FIG. The advance / retreat mechanism 32 of the present modification mainly includes a hydraulic cylinder 36, a piston 37, and a cam (not shown). A sufficient punch 30 is fitted and fixed to the piston 37, and a cam surface 37a is formed on the piston 37. The operation of moving the sufficiency punch 30 forward and positioning it at a predetermined molding position in the radial direction is the same as the advance / retreat mechanism 32 of the first embodiment, and the cam (not shown) descends and presses the cam surface 37a of the piston 37. Is done. At this time, the hydraulic pressure in the hydraulic cylinder 36 is reduced.

  When the cam moves upward after completion of molding, as shown in FIG. 8, hydraulic pressure is applied to the cylinder 36, and the piston 37 and the sufficiency punch 30 are retracted and separated from the trunnion molded product 7 ′ (shaft portion 10). . Since other operations are the same as those in the first embodiment, the contents of the first embodiment are applied mutatis mutandis and description thereof is omitted.

  A second modification of the advance / retreat mechanism of the sufficiency punch 30 will be described with reference to FIG. The advancing / retreating mechanism 32 of this modification mainly includes a housing 33, a cam receiving member 35, and two types of cams. The sufficient punch 30 is fitted and fixed to the cam receiving member 35, and the cam receiving member 35 is formed with two types of cam surfaces 35a and 35b at both ends in the axial direction. The operation of moving the sufficiency punch 30 forward and positioning it at a predetermined molding position in the radial direction is the same as that of the advance / retreat mechanism 32 of the first embodiment, and the cam (not shown) is lowered and the cam surface 35a of the cam receiving member 35 is lowered. This is done by pressing.

  When the cam (not shown) moves upward after the molding is completed, as shown in FIG. 9, the second cam 38 that causes the sufficiency punch 30 to move backward is raised, and the cam surface 38a of the second cam 38 is raised. Comes into contact with the cam surface 35b of the cam receiving member 35, and the cam receiving member 35 and the sufficiency punch 30 are retracted and separated from the trunnion molded product 7 '(shaft portion 10). Since other operations are the same as those in the first embodiment, the contents of the first embodiment are applied mutatis mutandis and description thereof is omitted.

  Next, a modified example of the two-pot joint trunnion will be described with reference to FIG. FIG. 10 is also a perspective view showing the trunnion molded product 7 ′ after the closed forging. This trunnion molded product 7 ′ differs from the trunnion molded product 7 ′ of the first embodiment in the cross-sectional shape of the recess 25 formed on the central axis of the shaft portion 10. Since the other configuration is the same as that of the trunnion molded product 7 ′ of the first embodiment, portions having the same functions are denoted by the same reference numerals and only the main points will be described.

  The cross-sectional shape of the concave portion 25 formed in the trunnion molded product 7 ′ of this modification is composed of a circular portion 25 a and a straight portion 25 b. The straight portion 25 b is disposed in the torque load direction of the shaft portion 10. As a result, the thickness of the hollow shaft portion 10 in the torque load direction can be increased, the strength of the shaft portion 10 can be improved, and further downsizing and weight reduction can be achieved.

  Also in the case of the cross-sectional shape of the recess 25, the ratio B / A of the cross-sectional area B of the recess 25 to the cross-sectional area A of the shaft portion 10 is set to 0.35 to 0.80, as in the first embodiment. It is preferable. Thereby, the sink of the internal diameter part of a boss | hub part can be suppressed. Further, the ratio B / A is more preferably 0.45 to 0.75. Thereby, in addition to being able to suppress the sink of the inner diameter portion of the boss portion, it is possible to suppress an increase in processing load necessary for side extrusion, which is advantageous for the tool life. Other configurations, functions and effects, billet preforming, and closed forging process are the same as the trunnion molded product and closed forging method of the first embodiment, so all the contents described in the first embodiment apply mutatis mutandis. The description is omitted.

  A second embodiment of the universal joint trunnion of the present invention will be described with reference to FIGS. 13 and 14. The trunnion for universal joints of this embodiment is a trunnion for tripod type constant velocity universal joints having three shaft portions. Fig.15 (a) is a cross-sectional view of a tripod type constant velocity universal joint, and FIG.15 (b) is a longitudinal cross-sectional view. As illustrated, the tripod type constant velocity universal joint 51 mainly includes an outer joint member 52, a trunnion 57 as an inner joint member, a needle roller 61 and a spherical roller 62 as rolling elements.

  The outer joint member 52 has a cylindrical cup portion 53 and a shaft portion 54 formed at the bottom thereof. Three track grooves 55 extending in the axial direction are formed on the inner circumference of the cup portion 53 at the three-way positions in the circumferential direction, and a roller guide surface 56 is formed on the opposite side surface of each track groove 55. The roller guide surface 56 is formed of a part of a cylindrical surface, that is, a partial cylindrical surface.

  The trunnion 57 includes a boss portion 58 and a shaft portion 60, and three shaft portions 60 are formed so as to protrude in the radial direction from the circumferentially divided position of the boss portion 58. Each shaft portion 60 includes a cylindrical outer peripheral surface 60a and an annular retaining ring groove 71 formed near the shaft end. A spherical roller 62 is rotatably mounted around a cylindrical outer peripheral surface 60 a of the shaft portion 60 via a plurality of needle rollers 61. The cylindrical outer peripheral surface 60 a of the shaft portion 60 forms the inner raceway surface of the needle roller 62. The inner peripheral surface 62 a of the spherical roller 62 is cylindrical and forms the outer raceway surface of the needle roller 62.

  A retaining ring 73 is attached to a retaining ring groove 71 formed in the vicinity of the shaft end of the shaft portion 60 via an outer washer 72. In the needle roller 61, the axial movement of the shaft portion 60 is restricted by the root step portion of the shaft portion 60 and the outer washer 72. The outer washer 72 includes a disk portion 72 a extending in the radial direction of the shaft portion 60 and a cylindrical portion 72 b extending in the axial direction of the shaft portion 60. The cylindrical portion 72 b of the outer washer 72 has an outer diameter smaller than the inner peripheral surface 62 a of the spherical roller 62, and the outer end portion 72 c of the cylindrical portion 72 b viewed in the radial direction of the trunnion 57 is the inner peripheral surface of the spherical roller 62. The diameter is larger than 62a. Therefore, the spherical roller 62 can move in the axial direction of the shaft portion 60 and is prevented from falling off by the end portion 72c.

  The spherical roller 62 rotatably mounted on the shaft portion 60 of the trunnion 57 is guided rotatably on the roller guide surface 56 of the track groove 55 of the outer joint member 52. With such a structure, relative axial displacement and angular displacement between the outer joint member 52 and the trunnion 57 are absorbed, and rotation is transmitted at a constant speed.

  FIG. 14 is a longitudinal sectional view showing a state when the tripod type constant velocity universal joint 51 takes the operating angle θ. As illustrated, when the trunnion 57 is tilted, the trunnion 57 is tilted with respect to the roller guide surface 56 of the track groove 55 of the outer joint member 52. Since the spherical roller 62 mounted on the trunnion 57 is restrained in the radial direction by the roller guide surface 56, the spherical roller 62 relatively moves in the axial direction of the needle roller 61 disposed on the shaft portion 60.

  A female spline 74 is formed on the inner peripheral surface of the boss portion 58 of the trunnion 57. Although not shown, the male spline of the intermediate shaft is fitted to the female spline 74 and is connected so as to transmit torque. .

  The tripod type constant velocity universal joint 51 according to the present embodiment also has the dimensional relationships shown in FIG. 15 in order to reduce weight and size. The ratio d / PCD of the shaft diameter (spline large diameter) d of the intermediate shaft and the PCD of the roller guide surface 56 is set large as 0.62 to 0.70, and the outer diameter Dj of the shaft portion 60 of the trunnion 57 and the shaft The ratio Dj / d with the diameter d is set as large as 0.87 to 0.93. Further, the ratio Ln / Dj between the needle roller length Ln and the outer diameter Dj of the shaft portion 60 is as small as 0.40 to 0.47, that is, the outer diameter Dj of the shaft portion 60 is the axial length of the shaft portion 60. It is set significantly larger than this.

  A second embodiment of the closed forging method for a universal joint trunnion according to the present invention will be described with reference to FIGS. 16 and 17. 16 shows a material before forging, FIG. 16 (a) is a perspective view showing a billet obtained by cutting a bar material, and FIG. 16 (b) shows a state where the billet of FIG. 16 (a) is preformed. It is a perspective view. FIG. 17 is a perspective view showing a trunnion molded product after forging.

  An outline of the trunnion molded product shown in FIG. 17 will be described. The trunnion molded product 57 ′ has three shaft portions 60 that project radially from the circumferentially divided position of the boss portion 58. The shaft portion 60 is formed with a recess 75 on the central shaft for suppressing the material flow rate during forging. The inner wall 8a of the boss 58 of the trunnion molded product 57 'is punched out. Thereafter, the trunnion molded product 57 ′ is subjected to a heat treatment after turning a predetermined portion on the outer periphery (end surface, inner peripheral surface, retaining ring groove, etc. of the boss portion 58) and broaching the female spline. By carburizing, quenching and tempering, the surface hardness is cured to about HRC 58 to 62. After the heat treatment, the cylindrical outer peripheral surface 60a of the shaft portion 60 is finished by grinding to obtain a finished product. Similar to the trunnion of the first embodiment, the cylindrical outer peripheral surface 60 a of the shaft portion 60 forms the inner raceway surface of the needle roller 61 as a rolling element, and the spherical roller 62 is rotatable via the needle roller 61. Installed.

  The closed forging method of the present embodiment is different from the first embodiment in that the number of shaft portions 60 of the trunnion molded product 57 ′ is three, and the other configuration is the same as that of the first embodiment. Only the main points will be explained. The columnar billet 15a ′ shown in FIG. 16A is manufactured by cutting a bar material made of case-hardened steel such as chromium steel (SCr420) or chromium molybdenum steel (SCM420) to a predetermined length based on the forging weight. To do. Prior to the closed forging process of the billet 15a ', a preforming material 15b' having a shape shown in FIG. The preformed material 15b ′ is formed with three flat surfaces 26 on the side surfaces corresponding to the three shaft portions 60, and recessed portions 27a and 27b (in which the bulging portions of the upper and lower punches for closed forging are fitted at both ends. (Not shown) is formed. The effects of the flat surface 26 and the recesses 27a and 27b are the same as those in the closed forging method of the first embodiment.

  As shown in FIG. 17, a recess 75 for suppressing the material flow rate during forging is formed on the central axis of the three shaft portions 60 of the trunnion molded product 57 ′. The trunnion of the first embodiment Similar to the concave portion 25 of the molded product 7 ′, it is set as follows. The ratio B / A of the cross-sectional area B of the recess 25 to the cross-sectional area A of the shaft part 60 is preferably 0.35 to 0.80. Further, the ratio B / A is more preferably 0.45 to 0.75. Thereby, the suppression of the sink of the internal diameter part of the boss | hub part 58 and the increase in the processing load required for side extrusion can be suppressed, and it becomes advantageous with respect to a tool life.

  In contrast to the two shaft portions 10 of the trunnion molded product 7 ′ of the first embodiment, the number of shaft portions 10 of the trunnion molded product 7 ′ of the present embodiment is different from three, but the material flow rate during forging is suppressed. Since the formability per one large-diameter shaft portion 10 is an essential technical problem, the setting of the cross-sectional area of the recess 75 described above is the same.

  Other configurations, functions and effects, and the specific closed forging process are the same as the closed forging method of the first embodiment. Therefore, the content described in the first embodiment with the number of shaft portions 60 being three is as follows. All are applied mutatis mutandis and description is omitted.

  In the above embodiment, the number of trunnion shaft portions is two and three. However, the present invention is not limited to this, and can be applied to a trunnion having four shaft portions of a cross joint. it can.

  In the above embodiment, as the cross-sectional shape of the recesses 25 and 75, a circular shape and a circular portion and a straight portion are exemplified. However, the shape is not limited to this, and the material flow, the strength of the shaft portion, and the like are taken into consideration. Thus, an elliptical shape, a circular shape including a partial straight line, and an elliptical shape may be used.

  In the above embodiment, the closed forging is performed using the preforms 15b and 15b ′ as the billet. However, the preforms 15b and 15b ′ are not necessarily used. Closed forging may be performed directly from columnar billets 15a and 15a 'cut by length.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the scope of the present invention. The scope of the present invention is not limited to patents. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Universal joint 2,52 Outer joint member 5,55 Track groove 6,56 Roller guide surface 7,57 Trunnion 7 ', 57'Trunnion molded product 8,58 Boss part 10,60 Shaft part 11,61 Needle roller 12, 62 Spherical rollers 15a, 15a 'billets 15b, 15b' preform 16 upper die 16a shaft molding die 16b step 17 lower die 17a shaft molding die 17b step 18 upper punch 19 lower punch 20 cavity 25 , 75 Recess 30 Satisfactory punch 32 Satisfactory punch advance / retreat mechanism 51 Tripod type constant velocity universal joint A Shaft cross-sectional area B Recess cross-sectional area D Shaft outer diameter L Shaft axial length

Claims (10)

In the closed forging method of the trunnion for universal joints in which a plurality of shaft portions are formed radially on the boss portion,
The forging die is an openable and closable die formed with a cavity substantially corresponding to the trunnion, a pair of upper and lower punches that are arranged to be relatively movable on the central axis of the die, and press the billet, and the cavity The filling punch is disposed on the central axis of the shaft molding die portion, and is composed of a sufficiency punch capable of advancing and retreating in the radial direction. The billet is placed in the die, and the sufficiency punch is placed in the cavity of the die which is closed In a state in which the shaft is advanced and disposed in the cavity, the billet is pressed by the upper and lower punches to form the shaft portion and a recess in the interior thereof, and a closed forging method for a universal joint trunnion.   2. The closed forging method for a trunnion for a universal joint according to claim 1, wherein a ratio B / A of a cross-sectional area B of the concave portion to a cross-sectional area A of the shaft portion is set to 0.35 to 0.80.   The closed forging method for a trunnion for a universal joint according to claim 1 or 2, wherein the sufficiency punch is positioned in a radial direction while the shaft portion and the recess are formed.   The closed forging method for a trunnion for a universal joint according to any one of claims 1 to 3, wherein a step portion is provided in the vicinity of the radially outer end of the inner surface of the shaft portion molding die portion.   The closed forging method for a trunnion for a universal joint according to any one of claims 1 to 4, wherein a shape of the recess in a cross section is circular.   6. The closed forging method for a trunnion for a universal joint according to any one of claims 1 to 5, wherein the billet has a flat side surface corresponding to the shaft portion by pre-molding.   In the trunnion for a universal joint in which a plurality of shaft portions are radially formed, the outer diameter of the shaft portion of the trunnion is set larger than the axial length, and the material flow rate during forging is set on the central axis of the shaft portion. A trunnion for a universal joint, comprising a concave portion formed for restraining.   The trunnion for a universal joint according to claim 7, wherein a ratio B / A of a cross-sectional area B of the concave portion to a cross-sectional area A of the shaft portion is 0.35 to 0.80.   The universal joint trunnion according to claim 7 or 8, wherein the universal joint is a two-pod joint.   The universal joint trunnion according to claim 7 or 8, wherein the universal joint is a tripod type constant velocity universal joint.

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