JP5549292B2 - Method for manufacturing universal joint yoke - Google Patents

Description

  The present invention relates to a method for manufacturing a universal joint yoke, and more particularly to a method for manufacturing a universal joint yoke that connects shafts that transmit rotation of a steering shaft of a steering device.

  In a steering device that steers the front wheels of a vehicle, the movement of a steering shaft that is rotated by the operation of a steering wheel is transmitted to an input shaft of a steering gear through a universal joint. The movement of the steering wheel is transmitted to the steering gear via a steering shaft and an intermediate shaft that are rotatably provided in the steering column, and the direction of the wheel is steered by the steering gear. Normally, the steering shaft and the input shaft of the steering gear cannot be provided on the same straight line.

  For this reason, conventionally, an intermediate shaft is provided between the steering shaft and the input shaft to the steering gear, the end of the intermediate shaft and the steering shaft, and the end of the intermediate shaft and the end of the input shaft of the steering gear. Are coupled via a universal joint so that power can be transmitted between the steering shaft and the input shaft that do not exist on the same straight line.

  In recent years, there has been an increasing number of column assist type electric power steering devices in which an assist device for applying a steering assist force to a steering shaft is provided between an intermediate shaft and a steering wheel. In such column assist type electric power steering, since the rotational torque applied to the intermediate shaft increases, it is necessary to increase the coupling rigidity of the coupling portion between the intermediate shaft and the universal joint. It is necessary to increase the rigidity.

  In order to manufacture a yoke with high rigidity, it is necessary to use a material with high material strength. However, press forming of a plate material has low formability of a material with high material strength, so cold work with excellent formability. Often formed by forging.

  In a universal joint for a steering device, it is desirable to mold the front end of the arm part into an R convex surface in order to ensure a joint angle as large as possible. In a conventional cold forging yoke, the front end of the arm part is formed into an R convex surface by trimming (punching) by pressing or cutting, but because it is processed in a process different from the cold forging process, There is a problem that the manufacturing cost increases.

  The cold forging method of Patent Document 1 is hermetic forging, in which the R convex surface at the front end of the arm portion is pressed against a mold. Since the cold forging method of Patent Document 1 is hermetic forging, it is necessary to strictly manage the material weight. Further, there is a problem that the manufacturing cost increases because the internal pressure of the molded product increases and the life of the mold is shortened.

  In the cold forging method of Patent Document 2, the R convex surface of the front end of the arm part is formed in a pre-forming process before the extrusion of the arm part. The cold forging method of Patent Document 2 has a problem that the number of steps increases, and the shape of the R convex surface of the front end of the arm portion that is molded in advance collapses at the time of extrusion molding of the arm portion.

Japanese Examined Patent Publication No. 2-59014 JP 58-93532 A

  In the present invention, the molding of the arm portion and the molding of the R convex surface at the front end of the arm portion are simultaneously performed in one step, the load applied to the mold is reduced, the manufacturing cost is reduced, and the mold life is extended. It is an object of the present invention to provide a method for manufacturing a universal joint yoke.

  The above problem is solved by the following means. In other words, the first invention is a pair having a coupling cylinder portion provided with a hole portion for fitting a shaft in the proximal end portion, and a bearing hole for pivotally supporting the cross shaft in the coupling cylinder portion. Is a universal joint yoke forging a yoke integrally formed with a pair of upper and lower molds, the inner circumference being formed on one mold and restraining the outer circumference of the cylindrical yoke material A die having a surface, a punch formed on the other die, and pressing the end face of the yoke material with a predetermined molding load, and formed on either the one die or the other die, the punch An R convex molding punch that is driven independently and presses the front end on the arm part side of the yoke material with a load smaller than the molding load, and forms an R convex surface on the front end on the arm part side, When the forming of the yoke material is completed, the yoke material is A gap is formed between the front end of the mold part side and the tip of the R convex molding punch, and the arm part side is pressed by pressing the front end of the yoke material after the molding with the tip of the R convex molding punch. Forming a R convex surface at the front end of the universal joint yoke.

  According to a second aspect of the present invention, in the method for manufacturing a universal joint yoke according to the first aspect, the R convex surface forming punch is formed on the inner peripheral surface of the die on the one mold and is subjected to forward extrusion molding. A method of manufacturing a universal joint yoke, wherein the yoke material is a knockout punch that presses the front end of the yoke material on the arm portion side and discharges the molded yoke material from one mold.

  According to a third aspect of the present invention, in the method for manufacturing a universal joint yoke according to the first aspect, the R convex molding punch is formed on the outer peripheral surface of the punch on the other mold, and is extruded backward. A yoke manufacturing method for a universal joint, wherein the front end of the yoke material on the arm portion side is pressed by the back pressure of the back pressure generator.

  The universal joint yoke manufacturing method of the present invention is formed on one of the molds or the other mold and driven independently of the punch, and the front end on the arm part side of the yoke material is formed on the molding load. R-shaped convex punch that forms an R-convex surface at the front end on the arm portion side by pressing with a smaller load, and when the yoke material is completely formed, the front end on the arm portion side of the yoke material and the tip of the R-shaped convex punch A gap is formed between them, and the front end on the arm portion side of the yoke material after molding is pressed with the tip of the R convex molding punch to form the R convex surface on the front end on the arm portion side.

  Therefore, it is possible to simultaneously mold the arm part and the R convex surface at the front end of the arm part in one process, thereby reducing the load applied to the mold, reducing the manufacturing cost, and extending the life of the mold. Is possible.

1 is an overall view of a steering device including a universal joint according to an embodiment of the present invention. The welding yoke manufactured by the manufacturing method of Example 1 of this invention is shown, (a) is a front view of a welding yoke, (b) is a right view of (a), (c) is a bottom view of (a). It is. (A) is explanatory drawing which shows the manufacturing method of Example 1 of this invention, Comprising: It is a shaping | molding preparation process which shows the state which mounted | wore the die with the yoke raw material, (b) is the yoke raw material and knockout punch of (a). FIG. (A) is explanatory drawing which shows the preforming process of the post process of FIG. 3, Comprising: The state which completed the preforming is shown, (b) is the side view of the yoke raw material and knockout punch after the preforming of (a) It is. (A) is a preforming step of FIG. 4, the knockout punch is moved upward to form an R convex surface at the front end on the arm side, and the yoke material after the preforming is being discharged from the lower mold. It is explanatory drawing shown, Comprising: (b) is a side view of the yoke raw material and knockout punch of (a). FIG. 5 shows a post-process of FIG. 5, where (a) is a main forming process, and (b) is a relief forming process of the tip of the arm part. It is explanatory drawing which shows the state of each shaping | molding process of the welding yoke manufactured by the manufacturing method of Example 1, Comprising: (a) is a yoke raw material, (b) is the state which completed the preforming process, (c) is this (D) is an explanatory view showing a state in which the relief part forming process at the tip of the arm part is completed. The pinch bolt yoke manufactured by the manufacturing method of Example 2 of this invention is shown, (a) is a front view of a pinch bolt yoke, (b) is a cross-sectional view of (a). (A) is explanatory drawing which shows the manufacturing method of Example 2 of this invention, Comprising: It is a shaping | molding preparation process which shows the state which mounted | wore the die with the yoke raw material, (b) The yoke raw material and knockout punch of (a) FIG. (A) is explanatory drawing which shows the preforming process of the post process of FIG. 9, Comprising: The state which completed the preforming is shown, (b) is the side view of the yoke raw material and knockout punch after the preforming of (a) It is. (A) is a preforming step in FIG. 10, and the knockout punch is moved upward to form an R convex surface at the front end on the arm side, and the yoke material after preforming is being discharged from the lower mold. It is explanatory drawing shown, Comprising: (b) is a side view of the yoke raw material and knockout punch of (a). FIG. 11 shows a post-process of FIG. 11, (a) is a main forming process, and (b) is an ironing process of the outer periphery of the coupling cylinder part. It is explanatory drawing which shows the state of each shaping | molding process of the pinch volt | bolt yoke manufactured by the manufacturing method of Example 2, Comprising: (a) is a yoke raw material, (b) is the state which completed the preforming process, (c) is (D) is an explanatory view showing a state in which the ironing forming process on the outer periphery of the combined cylinder portion is completed. (A) is explanatory drawing which shows the manufacturing method of Example 3 of this invention, Comprising: The state which this shaping | molding was completed is shown, (b) is the yoke raw material after this shaping | molding of (a), and R convex surface shaping | molding punch. It is a side view. 14A is an explanatory view showing a state in which the R convex surface forming punch is moved downward in the main forming step of FIG. 14 and the R convex surface is formed at the front end on the arm side, and FIG. FIG. 6 is a side view of the yoke material and the R convex molding punch.

    Embodiments 1 to 3 of the present invention will be described below with reference to the drawings.

  FIG. 1 is an overall view of a steering apparatus provided with a universal joint according to an embodiment of the present invention. As shown in FIG. 1, the steering apparatus provided with the universal joint of the embodiment of the present invention is a column assist type rack and pinion type power steering apparatus. In order to reduce the operating force of the steering wheel 101, the steering assist force of the motor 102 attached to the intermediate portion of the column 105 is applied to the steering shaft, and the rack of the rack and pinion type steering gear 103 is connected via the intermediate shaft 106. This is a power steering device that reciprocates and steers the steering wheel via the tie rod 104.

  The output shaft 108 protruding from the front end surface of the vehicle body of the assist device (steering assisting portion) 107 for applying assisting torque to the steering shaft is connected to the rear end portion of the intermediate shaft 106 via a universal joint (upper universal joint) 109A. It is linked to. Further, a pinion shaft (hereinafter referred to as a shaft) 103A of the steering gear 103 is coupled to the front end portion of the intermediate shaft 106 via another universal joint (lower universal joint) 109B.

  2A and 2B show a welding yoke manufactured by the manufacturing method according to the first embodiment of the present invention, in which FIG. 2A is a front view of the welding yoke, FIG. 2B is a right side view of FIG. FIG. FIG. 3A is an explanatory view showing the manufacturing method according to the first embodiment of the present invention, and is a forming preparation step showing a state in which the yoke material is mounted on the die, and FIG. It is a side view of a yoke material and a knockout punch.

  FIG. 4A is an explanatory view showing a pre-forming step subsequent to FIG. 3, and shows a state where the pre-forming is completed, and FIG. 4B is a yoke material after the pre-forming shown in FIG. FIG. 6 is a side view of the knockout punch. FIG. 5A shows the preforming step of FIG. 4, in which the knockout punch is moved upward to form an R convex surface at the front end on the arm side, and the preformed yoke material is being discharged from the lower mold. It is explanatory drawing which shows a state, Comprising: FIG.5 (b) is a side view of the yoke raw material and knockout punch of Fig.5 (a).

  FIG. 6 shows a post-process of FIG. 5, (a) is a main forming process, and (b) is a relief forming process of the tip of the arm part. 7A and 7B are explanatory views showing the state of each forming step of the welding yoke manufactured by the manufacturing method of Example 1, wherein FIG. 7A is a yoke material, FIG. 7B is a state where the preliminary forming step is completed, and FIG. ) Is an explanatory view showing a state in which the main forming step is completed, and (d) is an explanatory view showing a state in which the relief portion forming step at the tip of the arm portion is completed.

  As shown in FIG. 2, the welding yoke 2 is formed with a substantially cylindrical coupling tube portion 21, and a shaft (not shown) such as an intermediate shaft 106 is fitted into a circular hole 22 formed in the coupling tube portion 21. Then, the shaft is fixed to the coupling cylinder portion 21 by welding. The welding yoke 2 is formed with a pair of arm portions 23, 23 provided integrally with the coupling cylinder portion 21, and a bearing hole (post-process) for supporting a cross shaft (not shown) in the arm portions 23, 23. Are formed by machining).

  Chamfered portions 24 and 24 for securing a joint angle are formed on both side surfaces of the arm portions 23 and 23. Further, arc-shaped relief portions 25, 25 are formed on the inner side surfaces of the arm portions 23, 23 at the opposite ends. In addition, R chamfers 27 and 27 are formed on the outer peripheral side of the end surface 26 on the arm portion side of the coupling cylinder portion 21. The circular hole portion 22 is formed so as to penetrate from the end surface 28 on the side opposite to the arm portion of the coupling tube portion 21 to the end surface 26 on the arm portion side. The front ends 231 of the arm portions 23 and 23 are formed in an R convex surface in order to secure a joint angle.

  As shown in FIGS. 3 to 6, the mold used in the manufacturing method according to the first embodiment of the present invention includes an upper mold 3 and a lower mold 4. The upper die 3 includes a punch holder 31 that is fixed to an upper bolster (not shown) and moves up and down, and a hollow cylindrical punch 32 attached to the punch holder 31. The lower mold 4 includes a pressure receiving plate 41 fixed to a lower bolster (not shown) and a die 42 fixed to the pressure receiving plate 41.

  An inner peripheral surface 421 for constraining the outer periphery of the welding yoke 2 is formed on the die 42. The punch 32 is formed with an outer peripheral surface 321 that closely fits with the inner peripheral surface 421 of the die 42 and a front end surface 322 that presses the end surface 28 on the side opposite to the arm portion of the coupling cylinder portion 21 of the welding yoke 2. . In the lower mold 4, a rod-shaped mandrel 43 is fixed vertically to the axial center of the inner peripheral surface 421 of the die 42.

  A cylindrical outer peripheral surface 431 and a prismatic outer peripheral surface 432 are formed on the distal end side (the upper end side in FIG. 3) of the mandrel 43. The cylindrical outer peripheral surface 431 restrains the hole 22 of the welding yoke 2. The prismatic outer peripheral surface 432 restrains the opposite inner side surfaces of the arm portions 23, 23 of the welding yoke 2 and the end surface 26 on the arm portion side of the coupling cylinder portion 21.

  In the lower mold 4, a hollow cylindrical knockout punch 44 is interposed between the inner peripheral surface 421 of the die 42 and the prismatic outer peripheral surface 432 of the mandrel 43. The knockout punch 44 is movable in the vertical direction in FIGS. When the knockout punch 44 moves upward, the tip 441 of the knockout punch 44 comes into contact with the front ends (lower ends in FIGS. 3 to 6) 231 of the arm portions 23 and 23 of the welded yoke 2 after molding, and the welding yoke 2 is moved upward. Press to discharge from the lower mold 4. As shown in FIG. 3B, an R concave surface for forming the front ends (see FIG. 2) 231 of the R convex surfaces of the arm portions 23 and 23 is formed at the tip 441 of the knockout punch 44. That is, the knockout punch 44 has the function of an R convex molding punch.

  As shown in FIG. 7A, a hollow cylindrical yoke material 2A is formed in a predetermined volume, and as shown in the molding preparation step of FIG. 3, the yoke is formed on the inner peripheral surface 421 of the die 42 from above the die 42. Wear material 2A. As shown in the preforming step of FIG. 4, the yoke material 2 </ b> A is moved by the front end surface 322 of the punch 32 while the punch 32 is lowered and the outer peripheral surface 321 of the punch 32 is closely fitted to the inner peripheral surface 421 of the die 42. And pressing with a predetermined molding load.

  The yoke material 2A is molded by being constrained by the inner peripheral surface 421 of the die 42, the cylindrical outer peripheral surface 431 of the mandrel 43, and the prismatic outer peripheral surface 432, and a preformed yoke material 2B shown in FIG. . In the preformed yoke material 2B, the connecting cylinder part 21, the hole part 22, the arm part 23, the end face 26 on the arm part side, the chamfered part 24, and the R chamfered part 27 are preformed. Since the welding yoke 2 of Example 1 of the present invention has a simple shape, the preforming step may be omitted.

  When the preforming of the preformed yoke material 2B is completed, a gap is formed between the front ends (lower ends in FIG. 4) 231 of the preformed yoke material 2B and the tip 441 of the knockout punch 44. . Therefore, even if the volume of the yoke material 2A varies, the load applied to the upper mold 3 and the lower mold 4 does not vary, and the load does not become excessive, so that the life of the mold is improved. Since the front ends (lower end in FIG. 4) 231 of the arm portions 23, 23 of the preformed yoke material 2B are free extrusions that do not contact the mold, the front ends of the arm portions 23, 23 when the preforming is completed (see FIG. 4 (lower end of 4) 231 has a distorted shape.

  Next, as shown in FIG. 5, after raising the punch 32, the knockout punch 44 is moved upward so that the front end 231 of the arm portion 23, 23 of the preformed yoke material 2 </ b> B contacts the front end 441 of the knockout punch 44. Then, the preformed yoke material 2 </ b> B is pressed upward and discharged from the lower mold 4. Since an R concave surface is formed at the tip 441 of the knockout punch 44, an R convex surface is formed at the front ends (lower ends in FIG. 5) 231 of the arm portions 23 and 23 by the reaction force of the knockout load. In the first embodiment of the present invention, the molding of the arm portions 23 and 23 and the molding of the R convex surface of the front end 231 of the arm portions 23 and 23 can be simultaneously performed in one step, thereby reducing the number of steps and reducing the manufacturing cost. Can be reduced.

  The load (knockout load) necessary for discharging the preformed yoke material 2B from the lower mold 4 is a force that resists the lateral force generated in the preformed yoke material 2B within the inner peripheral surface 421 of the die 42. It is. It is empirically known that the force against the lateral force is about 10% of the molding load in which the yoke material 2A is pressed by the punch 32. In the experiment of the present inventor, a predetermined R convex surface could be formed on the front ends 231 of the arm portions 23 and 23 with a knockout load of 18 tons with respect to a forming load of 150 tons.

  In the embodiment of the present invention, as shown in FIG. 4B, the radius R of the R concave surface of the tip 441 of the knockout punch 44 (the radius of the R convex surface of the front end 231 of the arm portion 23) is set to It is set to be larger than ½ of the width W. Therefore, since the molding load of the R convex surface of the front end 231 of the arm portion 23 can be small, the life of the knockout punch 44 is improved.

  Next, as shown in the main forming step in FIG. 6, the preformed yoke material 2 </ b> B described above is mounted on the inner peripheral surface 421 of the die 42 from above the die 42. Thereafter, the punch 32 is lowered, and the preformed yoke material 2B is pressed by the front end surface 322 of the punch 32, thereby forming the main formed yoke material 2C shown in FIG. In the main forming yoke material 2C, the connecting cylinder portion 21, the hole portion 22, the arm portion 23, the end surface 26 on the arm portion side, the chamfered portion 24, and the R chamfer 27 are finally formed.

  When the molding of the main molding yoke material 2C is completed, a gap is formed between the front ends (lower ends of FIG. 6A) 231 of the main molding yoke material 2C and the tip 441 of the knockout punch 44. Has been. Therefore, even if the volume of the yoke material 2A varies, the load applied to the upper mold 3 and the lower mold 4 does not vary, and the life of the mold is improved.

  Next, although not shown, after raising the punch 32, the knockout punch 44 is moved upward, and the tip 441 of the knockout punch 44 is brought into contact with the front ends 231 of the arm portions 23, 23 of the forming yoke material 2C. Then, the main forming yoke material 2 </ b> C is pressed upward and discharged from the lower mold 4. Since an R concave surface is formed at the tip 441 of the knockout punch 44, an R convex surface is formed at the front ends 231 of the arm portions 23 and 23 by the reaction force of the knockout load.

  Next, as shown in the step of forming the relief portion at the tip of the arm portion in FIG. 6B, the above-described formed yoke material 2C is mounted on the inner peripheral surface 421 of the die 42 from above the die 42. Thereafter, the punch 32 is lowered, the main forming yoke material 2C is pressed by the front end surface 322 of the punch 32, and the relief portion forming yoke material 2D at the tip of the arm portion shown in FIG. 7 (d) is formed.

  Arc-shaped relief portions 25, 25 are formed on the inner side surfaces of the arm portions 23, 23 at the front ends thereof in the escape portion molding yoke material 2 </ b> D at the tip of the arm portion. As shown in FIG. 6B, arc-shaped convex surfaces 433 and 433 are formed on the prismatic outer peripheral surface 432 of the mandrel 43. The arc-shaped convex surfaces 433 and 433 constrain the opposing inner side surfaces of the arm portions 23 and 23 to form arc-shaped relief portions 25 and 25.

  When the forming of the escape portion molding yoke material 2D at the tip of the arm portion is completed, the front ends (lower ends of FIG. 6B) 231 of the escape portion forming yoke material 2D at the tip of the arm portion and the tip of the knockout punch 44 are formed. A gap is formed between 441 and 441. Therefore, even if the volume of the yoke material 2A varies, the load applied to the upper mold 3 and the lower mold 4 does not vary, and the life of the mold is improved.

  Next, although not shown, after raising the punch 32, the knockout punch 44 is moved upward, and the tip of the knockout punch 44 is moved to the front end 231 of the arm portions 23, 23 of the relief portion molding yoke material 2D at the tip of the arm portion. 441 is brought into contact. Since an R concave surface is formed at the tip 441 of the knockout punch 44, an R convex surface is formed at the front ends 231 of the arm portions 23 and 23 by the reaction force of the knockout load. The forging process of the welding yoke 2 is completed when the relief portion forming yoke material 2D at the tip of the arm portion is pressed upward by the knockout punch 44 and discharged from the lower mold 4.

  In the manufacturing method of Example 1 of the present invention, the R convex surface of the front ends 231 of the arm portions 23 and 23 is formed by the knockout punch 44 in all the forming steps (preliminary forming step, main forming step, relief portion forming step). However, the R convex surface of the front ends 231 of the arm portions 23 and 23 may be formed by only a part of the forming steps.

  The manufacturing method according to the first embodiment of the present invention is forward extrusion molding, and the end surface 26 on the arm portion side of the coupling cylinder portion 21 is molded in the lower mold 4 of the integral structure. The end face 26 on the side has no mold mating face, and no burr is generated on the end face 26 on the arm part side. In the manufacturing method according to the first embodiment of the present invention, the hollow cylindrical yoke material 2A is used, but a solid yoke material may be used. In that case, after forming the arm portions 23, 23, the hole portion 22 may be formed by machining or punching.

  8A and 8B show a pinch bolt yoke manufactured by the manufacturing method according to the second embodiment of the present invention. FIG. 8A is a front view of the pinch bolt yoke, and FIG. 8B is a transverse sectional view of FIG. FIG. 9 (a) is an explanatory view showing the manufacturing method of Example 2 of the present invention, and is a forming preparation step showing a state in which a yoke material is mounted on a die, and FIG. 9 (b) is a view of FIG. 9 (a). It is a side view of a yoke material and a knockout punch.

  FIG. 10 (a) is an explanatory view showing a preliminary molding step subsequent to FIG. 9, showing a state where the preliminary molding is completed, and FIG. 10 (b) is a yoke material after the preliminary molding in FIG. 10 (a). FIG. 6 is a side view of the knockout punch. FIG. 11A shows the preforming step of FIG. 10, in which the knockout punch is moved upward to form an R convex surface at the front end on the arm side, and the preformed yoke material is being discharged from the lower mold. It is explanatory drawing which shows a state, Comprising: FIG.11 (b) is a side view of the yoke raw material and knockout punch of Fig.11 (a).

  FIG. 12 shows the post-process of FIG. 11, (a) is the main forming step, and (b) is the ironing step of the outer periphery of the combined cylinder part. FIG. 13 is an explanatory view showing the state of each forming step of the pinch bolt yoke manufactured by the manufacturing method of Example 2, wherein (a) is a yoke material, (b) is a state where the preliminary forming step is completed, (c) is a state in which the main forming step is completed, and (d) is an explanatory view showing a state in which the ironing step on the outer periphery of the combined cylinder portion is completed. In the following description, only structural parts different from the above-described embodiment will be described, and redundant description will be omitted. Further, the same parts will be described with the same numbers.

  The manufacturing method of Example 2 is an example in which a pinch bolt yoke is formed by forward extrusion molding. As shown in FIG. 8, the pinch bolt yoke 5 is formed with a substantially cylindrical connecting tube portion 51 having an arcuate outer peripheral surface 513, and a circular hole portion 52 formed in the connecting tube portion 51 is not shown. A shaft (such as the intermediate shaft 106) is fitted. A pair of left and right flange portions 51A and 51B extending in the tangential direction from the coupling cylinder portion 51 are formed. A slit 51C communicating with the hole 52 is formed between the flanges 51A and 51B.

  A stepped bolt hole 511 for inserting a bolt (not shown) is formed in the flange portion 51A, and a bolt hole 512 for inserting a bolt is also formed in the flange portion 51B. The stepped bolt hole 511 and the bolt hole 512 is formed concentrically. In addition, a female screw is formed in the bolt hole 512. A bolt is screwed into the female screw, the diameter of the hole 52 is reduced, and the shaft fitted in the hole 52 is fixed to the coupling cylinder 51.

  The pinch bolt yoke 5 is formed with a pair of arm portions 53, 53 provided integrally with the coupling cylinder portion 51. The arm portions 53, 53 have bearing holes (rear side) for supporting a cross shaft (not shown). Formed by machining of the process).

  R chamfers 57 and 57 are formed on the outer peripheral side of the end surface 56 on the arm portion side of the coupling cylinder portion 51. The circular hole portion 52 is formed so as to penetrate from the end surface 58 on the side opposite to the arm portion of the coupling tube portion 51 to the end surface 56 on the arm portion side. The front ends 531 of the arm portions 53 and 53 are formed as R convex surfaces in order to secure a joint angle.

  As shown in FIGS. 9 to 12, the mold used in the manufacturing method of the second embodiment of the present invention is composed of an upper mold 6 and a lower mold 7 as in the first embodiment. The upper mold 6 includes a punch holder 61 that is fixed to an upper bolster (not shown) and moves up and down, and a hollow cylindrical punch 62 attached to the punch holder 61. The lower mold 7 includes a pressure receiving plate 71 fixed to a lower bolster (not shown) and a die 72 fixed to the pressure receiving plate 71.

  The die 72 is formed with an inner peripheral surface 721 for restricting the outer periphery of the pinch bolt yoke 5. The punch 62 is formed with an outer peripheral surface 621 that is closely fitted to the inner peripheral surface 721 of the die 72 and a front end surface 622 that presses the end surface 58 on the side opposite to the arm portion of the coupling cylinder portion 51 of the pinch bolt yoke 5. Yes. In the lower mold 7, a rod-shaped mandrel 73 is fixed vertically to the axial center of the inner peripheral surface 721 of the die 72.

  A cylindrical outer peripheral surface 731 and a prismatic outer peripheral surface 732 are formed on the distal end side (the upper end side in FIG. 9) of the mandrel 73. The cylindrical outer peripheral surface 731 restrains the hole 52 of the pinch bolt yoke 5. The prismatic outer peripheral surface 732 restrains the opposite inner side surfaces of the arm portions 53, 53 of the pinch bolt yoke 5 and the end surface 56 on the arm portion side of the coupling cylinder portion 51.

  A hollow cylindrical knockout punch 74 is interposed in the lower mold 7 between the inner peripheral surface 721 of the die 72 and the prismatic outer peripheral surface 732 of the mandrel 73. The knockout punch 74 is movable in the vertical direction in FIG. When the knockout punch 74 moves upward, the tip 741 of the knockout punch 74 comes into contact with the front ends (lower ends in FIG. 9) 531 of the arm portions 53 and 53 of the pinch bolt yoke 5 after molding, and presses the pinch bolt yoke 5 upward. Then, it is discharged from the lower mold 7. As shown in FIG. 9B, an R concave surface for forming the front end 531 of the R convex surface of the arm portions 53, 53 is formed at the tip 741 of the knockout punch 74. That is, the knockout punch 74 has the function of an R convex molding punch.

  As shown in FIG. 13 (a), a hollow rectangular tube-shaped yoke material 5A is formed in a predetermined volume, and as shown in the molding preparation step of FIG. 9, from above the die 72 to the inner peripheral surface 721 of the die 72. The yoke material 5A is attached. As shown in the preforming step of FIG. 10, the yoke material 5 </ b> A is moved by the front end surface 622 of the punch 62 while the punch 62 is lowered and the outer peripheral surface 621 of the punch 62 is closely fitted to the inner peripheral surface 721 of the die 72. Press.

  The yoke material 5A is formed by being constrained by the inner peripheral surface 721 of the die 72, the columnar outer peripheral surface 731 of the mandrel 73, and the prismatic outer peripheral surface 732, and the preformed yoke material 5B shown in FIG. . The preformed yoke material 5B is preformed with a connecting cylinder portion 51, a hole 52, an arm portion 53, an end surface 56 on the arm portion side, and an R chamfer 57. Since the pinch bolt yoke 5 according to the second embodiment of the present invention has a simple shape, the preforming step may be omitted.

  When the preforming of the preformed yoke material 5B is completed, a gap is formed between the front ends (lower end in FIG. 10) 531 of the preformed yoke material 5B and the tip 741 of the knockout punch 74. . Therefore, even if the volume of the yoke material 5A varies, the load applied to the upper mold 6 and the lower mold 7 does not fluctuate and the load does not become excessive, so that the life of the mold is improved. Since the front ends (lower ends in FIG. 10) 531 of the arm portions 53, 53 of the preformed yoke material 5B are free extrusions that do not come into contact with the mold, the front ends of the arm portions 53, 53 when the preforming is completed (see FIG. 10 (lower end of 10) 531 has a distorted shape.

  Next, as shown in FIG. 11, after raising the punch 62, the knockout punch 74 is moved upward so that the front end 531 of the preformed yoke blank 5B is brought into contact with the front end 531 of the knockout punch 74. Then, the preformed yoke material 5 </ b> B is pressed upward and discharged from the lower mold 7. Since an R concave surface is formed at the tip 741 of the knockout punch 74, an R convex surface is formed at the front ends (lower ends in FIG. 5) 531 of the arm portions 53 and 53 by the reaction force of the knockout load.

  Also in the second embodiment of the present invention, a predetermined R convex surface can be formed on the front ends 531 of the arm portions 53 and 53 with a knockout load of about 10% of the forming load obtained by pressing the yoke material 5A with the punch 62. It was. In the second embodiment of the present invention, the molding of the arm portions 53 and 53 and the molding of the R convex surface of the front end 531 of the arm portions 53 and 53 can be simultaneously performed in one step, thereby reducing the number of steps and reducing the manufacturing cost. Can be reduced.

  Also in the second embodiment of the present invention, as shown in FIG. 10B, the radius R of the R concave surface of the tip 741 of the knockout punch 74 (the radius of the R convex surface of the front end 531 of the arm portion 53) is set to the arm portion 53, It is set to be larger than ½ of the width W of 53. Therefore, since the molding load of the R convex surface of the front end 531 of the arm portion 53 can be small, the life of the knockout punch 74 is improved.

  Next, as shown in the main forming step of FIG. 12A, the above-described preformed yoke material 5 </ b> B is mounted on the inner peripheral surface 721 of the die 72 from above the die 72. Thereafter, the punch 62 is lowered, and the preformed yoke material 5B is pressed by the front end surface 622 of the punch 62, thereby forming the main formed yoke material 5C shown in FIG. In the main forming yoke material 5C, the connecting cylinder portion 51, the hole portion 52, the arm portion 53, the end surface 56 on the arm portion side, and the R chamfer 57 are finally formed.

  When the molding of the main molding yoke material 5C is completed, a gap is formed between the front ends (the lower ends of FIG. 12A) 531 of the main molding yoke material 5C and the tip 741 of the knockout punch 74. Has been. Therefore, even if the volume of the yoke material 5A varies, the load applied to the upper mold 6 and the lower mold 7 does not vary, and the life of the mold is improved.

  Next, although not shown, after raising the punch 62, the knockout punch 74 is moved upward, and the tip 741 of the knockout punch 74 is brought into contact with the front ends 531 of the arm portions 53, 53 of the forming yoke material 5C. Then, the main forming yoke material 5 </ b> C is pressed upward and discharged from the lower mold 7. Since an R concave surface is formed at the tip 741 of the knockout punch 74, an R convex surface is formed at the front ends 231 of the arm portions 53 and 53 by the reaction force of the knockout load.

  Next, as shown in the ironing process of the outer periphery of the connecting cylinder portion in FIG. 12B, the above-described main forming yoke material 5C is inverted 180 degrees (the front end 531 of the arm portion 53 of the main forming yoke material 5C is directed upward). The die 72 is mounted on the inner peripheral surface 721 of the die 72 from above. After that, the punch 62 is lowered, and the end surface 56 on the arm portion side of the combined cylinder portion 51 of the main forming yoke material 5C is pressed by the front end surface 622 of the punch 62, and the outer peripheral forming of the combined cylinder portion shown in FIG. A yoke material 5D is formed.

  An arcuate outer peripheral surface 513 is formed on the outer periphery of the combined cylinder portion 51 in the ironing yoke material 5D on the outer periphery of the combined cylinder portion. The outer peripheral surface 621 of the punch 62 restrains the opposing inner side surfaces of the arm portions 53 and 53. As shown in FIG. 12B, the columnar outer peripheral surface 731 of the mandrel 73 is fitted into the hole 52 of the coupling cylinder portion 51 to restrain the hole 52 and also the inner peripheral surface 623 of the punch 62. And the inner peripheral surface 623 of the punch 62 is guided.

  When the forming of the iron forming yoke material 5D on the outer periphery of the connecting cylinder portion is completed, the end surface (the lower end of FIG. 12B) 58 of the connecting tube portion 51 of the iron forming yoke material 5D on the outer periphery of the connecting tube portion is knocked out. A gap is formed between the tip 741 of the punch 74. Therefore, even if the volume of the yoke material 5A varies, the load applied to the upper mold 6 and the lower mold 7 does not vary, and the life of the mold is improved.

  Next, the knockout punch 74 is moved upward, and the tip 741 of the knockout punch 74 is brought into contact with the end surface 58 on the side opposite to the arm of the coupling cylinder 51 of the ironing yoke material 5D on the outer periphery of the coupling cylinder. If the outer ironing yoke material 5D is pressed upward and discharged from the lower mold 7, the forging process of the pinch bolt yoke 5 is completed. An R concave surface is not formed at the tip 741 of the knockout punch 74 in FIG.

  In the manufacturing method of Example 2 of the present invention, the R convex surface of the front end 531 of the arm portions 53 and 53 is formed by the knockout punch 74 in the pre-forming step and the main forming step, but only one of the forming steps is performed. Thus, the R convex surface of the front end 531 of the arm portions 53 and 53 may be formed.

  The manufacturing method according to the second embodiment of the present invention is also forward extrusion molding, and the end surface 56 on the arm portion side of the coupling cylinder portion 51 is molded in the lower die 7 of an integral structure. There is no mold mating surface on the side end surface 56, and no burr occurs on the end surface 56 on the arm side. In the manufacturing method of Embodiment 2 of the present invention, the hollow rectangular tube-shaped yoke material 5A is used, but a solid rectangular tube-shaped yoke material may be used. In that case, after forming the arm portions 53, 53, the hole portion 52 may be formed by machining or punching.

  FIG. 14 (a) is an explanatory view showing the manufacturing method of Example 3 of the present invention, showing a state where the main forming is completed, and FIG. 14 (b) is a yoke material after the main forming of FIG. 14 (a). It is a side view of an R convex molding punch. FIG. 15A is an explanatory view showing a state in which the R convex surface forming punch is moved downward in the main forming step of FIG. 14 and the R convex surface is formed at the front end on the arm side, and FIG. FIG. 16 is a side view of the yoke material and R convex molding punch shown in FIG. In the following description, only structural parts different from the above-described embodiment will be described, and redundant description will be omitted. Further, the same parts will be described with the same numbers.

  The manufacturing method of Example 3 is an example in which the welding yoke 2 of Example 1 is formed by backward extrusion molding, and only the main forming step will be described. As shown in FIGS. 14 to 15, the mold used in the manufacturing method of the third embodiment of the present invention is composed of the upper mold 3 and the lower mold 4 as in the first embodiment. A punch holder 31 that is fixed to an upper bolster (not shown) and moves up and down is fixed to the upper die 3. A solid rod-like punch 33 is fixed to the punch holder 31 vertically on the axis of the inner peripheral surface 311 of the punch holder 31. The lower mold 4 includes a pressure receiving plate 41 fixed to a lower bolster (not shown) and a die 42 fixed to the pressure receiving plate 41.

  An inner peripheral surface 421 for constraining the outer periphery of the welding yoke 2 is formed on the die 42. The punch 33 is formed with a cylindrical outer peripheral surface 331 and a prismatic outer peripheral surface 332. The cylindrical outer peripheral surface 331 restrains the hole 22 (see FIG. 2) of the welding yoke 2. The prismatic outer peripheral surface 332 restrains the opposite inner side surfaces of the arm portions 23, 23 of the welding yoke 2 and the end surface 26 (see FIG. 2) on the arm portion side of the coupling cylinder portion 21.

  In the punch holder 31, a hollow cylindrical R convex molding punch 34 is interposed between the inner peripheral surface 311 of the punch holder 31 and the prismatic outer peripheral surface 332 of the punch 33. The R convex molding punch 34 is movable in the vertical direction in FIGS. The R convex molding punch 34 is driven independently of the punch 33 by a back pressure generator such as a hydraulic cylinder or a gas cushion.

  The R convex molding punch 34 includes an outer peripheral surface 341 that is closely fitted to the inner peripheral surface 421 of the die 42, and front ends (upper ends in FIGS. 14 to 15) 231 (FIG. 2) of the welding yoke 2. A tip 342 is formed to press (see). When the R convex molding punch 34 moves downward, the tip 342 of the R convex molding punch 34 is placed on the front ends (upper ends in FIGS. 14 to 15) 231 (see FIG. 2) of the arm portions 23, 23 of the welded yoke 2 after molding. It abuts and presses the welding yoke 2 downward. As shown in FIG. 14B, an R concave surface for molding the front ends (see FIG. 2) 231 of the R convex surfaces of the arm portions 23, 23 is formed at the tip 342 of the R convex molding punch 34.

  A hollow cylindrical knockout pin 45 is inserted between the inner peripheral surface 421 of the die 42 in the lower mold 4. The knockout pin 45 is movable in the vertical direction in FIGS. When the knockout pin 45 moves upward, the tip 451 of the knockout pin 45 comes into contact with the end surface 28 on the side opposite to the arm portion of the joined cylindrical portion 21 of the welded yoke 2 after molding, and presses the welding yoke 2 upward, Discharge from the mold 4.

  14A, the preformed yoke material 2B (see FIG. 7B) is mounted on the inner peripheral surface 421 of the die 42 from above the die 42. Thereafter, the punch 33 is lowered, and the preformed yoke material 2 </ b> B is pressed with a predetermined molding load by the prismatic outer peripheral surface 332 of the punch 33. The preformed yoke material 2B is formed by being constrained by the inner peripheral surface 421 of the die 42, the prismatic outer peripheral surface 332 of the punch 33, and the cylindrical outer peripheral surface 331, and is formed into a main yoke material 2C shown in FIG. Is formed. In the main forming yoke material 2C, the connecting cylinder portion 21, the hole portion 22, the arm portion 23, the end surface 26 on the arm portion side, the chamfered portion 24, and the R chamfer 27 are finally formed.

  When the molding of the main molding yoke material 2C is completed, between the front ends (upper ends of FIG. 14 (a)) 231 of the main molding yoke material 2C and the tip 342 of the R convex molding punch 34, A gap is formed. Therefore, even if the volume of the yoke material 2A varies, the load applied to the upper die 3 and the lower die 4 does not fluctuate and the load does not become excessive, so that the life of the die is improved. Since the front ends (upper ends in FIG. 14) 231 of the arm portions 23 and 23 of the main forming yoke material 2C are free extrusions that do not contact the mold, the front ends of the arm portions 23 and 23 when the main forming is completed (see FIG. 14) 231 has a distorted shape.

  Next, as shown in FIG. 15, the R convex molding punch 34 is moved downward by the back pressure generator, and the tip 342 of the R convex molding punch 34 is attached to the front ends 231 of the arm portions 23 and 23 of the main molding yoke material 2C. The tip 342 of the R convex punch 34 is pressed against the front ends 231 of the arm portions 23 and 23 by the back pressure of the back pressure generator.

  The movement stroke of the R convex molding punch 34 is set to be equal to or less than the entire stroke of the back pressure generator, and is determined by the shape of the R convex surface of the front ends 231 of the arm portions 23 and 23. In Example 3 of the present invention, the required minimum distance of the moving stroke of the R convex molding punch 34 was 5.3 mm. Since the R concave surface is formed at the tip 342 of the R convex molding punch 34, a predetermined R convex surface is formed at the front ends 231 of the arm portions 23, 23. In Embodiment 3 of the present invention, the molding of the arm portions 23 and 23 and the molding of the R convex surface of the front end 231 of the arm portions 23 and 23 can be simultaneously performed in one step, so the number of steps is reduced and the manufacturing cost is reduced. Can be reduced.

  The back pressure of the back pressure generator is set to be smaller than the molding load for pressing the preformed yoke material 2B with the punch 33. When the tip 342 of the R convex molding punch 34 is pressed against the front ends 231 of the arm portions 23 and 23 by the back pressure of the back pressure generator, the forming yoke material 2C is in a sealed state, but the back pressure of the back pressure generator is Since it is smaller than the molding load, the internal pressure of the main molding yoke material 2C does not become excessive, and the life of the mold is improved.

  In the embodiment of the present invention, as shown in FIG. 14 (b), the radius R of the R concave surface of the tip 342 of the R convex molding punch 34 (the radius of the R convex surface of the front end 231 of the arm portion 23) is set to the arm portion 23, 23 is set to be larger than ½ of the width W of 23. Accordingly, since the molding load on the R convex surface of the front end 231 of the arm portion 23 can be small, the life of the R convex molding punch 34 is improved.

  Next, although not shown, after raising the punch 33 and the R convex molding punch 34, the knockout pin 45 is moved upward to reach the end surface 28 on the side opposite to the arm portion of the coupling cylinder portion 21 of the molding yoke material 2C. If the tip 451 of the knockout pin 45 is brought into contact, the main forming yoke material 2C is pressed upward and discharged from the lower mold 4, the main forming step of the welding yoke 2 is completed.

DESCRIPTION OF SYMBOLS 101 Steering wheel 102 Motor 103 Steering gear 103A Pinion shaft 104 Tie rod 105 Column 106 Intermediate shaft 107 Assist device (steering assist part)
108 Output shaft 109A, 109B Universal joint 2 Welding yoke 2A Yoke material 2B Preliminarily formed yoke material 2C Main formed yoke material 2D Relief portion forming yoke material 21 at the tip of the arm portion 21 Coupling tube portion 22 Hole portion 23 Arm portion 231 Front end 24 Chamfered portion 25 Escape part 26 End face on arm side 27 R chamfer 28 End face on opposite arm part 3 Upper die 31 Punch holder 311 Inner peripheral face 32 Punch 321 Outer peripheral face 322 Front end face 33 Punch 331 Cylindrical outer peripheral face 332 Rectangular outer peripheral face Surface 34 R Convex molding punch 341 Outer peripheral surface 342 Tip 4 Lower die 41 Pressure receiving plate 42 Die 421 Inner peripheral surface 43 Mandrel 431 Cylindrical outer peripheral surface 432 Square columnar outer peripheral surface 433 Arc-shaped convex surface 44 Knockout punch 441 Tip 45 Knockout Pin 451 Tip 5 Pinch Bol Yoke 5A Yoke material 5B Preliminarily formed yoke material 5C Main formed yoke material 5D Ironing yoke material 51 on the outer periphery of the combined cylinder portion 51 Combined cylinder portion 511 Stepped bolt hole 512 Bolt hole 513 Arc-shaped outer peripheral surface 51A, 51B Flange portion 51C Slit 52 Hole Part 53 Arm part 531 Front end 56 Arm part side end face 57 R chamfer 58 Counter arm side end face 6 Upper die 61 Punch holder 62 Punch 621 Outer surface 622 Front end surface 623 Inner surface 7 Lower die 71 Pressure receiving plate 72 Dies 721 inner peripheral surface 73 mandrel 731 cylindrical outer peripheral surface 732 prismatic outer peripheral surface 74 knockout punch 741 tip

Claims (3)

A coupling tube portion having a hole for fitting the shaft to the proximal end portion;
A method of manufacturing a universal joint yoke forging a yoke, in which a pair of arm portions having a bearing hole for pivotally supporting a cross shaft is integrally formed in the coupling cylinder portion with a pair of upper and lower molds,
A die formed on one mold and having an inner peripheral surface that restrains the outer periphery of the cylindrical yoke material;
A punch formed on the other mold and pressing the end face of the yoke material with a predetermined molding load;
It is formed on either one of the one mold or the other mold and is driven independently of the punch to press the front end on the arm part side of the yoke material with a load smaller than the molding load. An R convex surface forming punch for forming an R convex surface at the front end on the arm side,
When forming the yoke material, a gap is formed between the front end of the yoke material on the arm portion side and the tip of the R convex molding punch,
A method for manufacturing a universal joint yoke, wherein the front end of the yoke material after molding is pressed with the tip of the R convex molding punch to form the R convex surface at the front end of the arm part. In the manufacturing method of the yoke of the universal joint described in Claim 1,
The R convex molding punch is
A knockout punch that is formed on the inner peripheral surface of the die on the one mold and presses the front end on the arm portion side of the yoke material that is formed by forward extrusion, and discharges the molded yoke material from the one mold. A method of manufacturing a universal joint yoke. In the manufacturing method of the yoke of the universal joint described in Claim 1,
The R convex molding punch is
A universal joint yoke, wherein the other die is formed on the outer peripheral surface of the punch, and the front end on the arm portion side of the yoke material formed by rear extrusion is pressed by a back pressure of a back pressure generator. Production method.

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