JP4065871B2 - Manufacturing method of hollow shaft - Google Patents

Description

The present invention relates to a method for manufacturing a hollow shaft having a flange by cold forging.

  Recent automobiles are required to reduce the weight of various components in order to improve fuel efficiency. For example, shaft parts such as transfer shafts, which are components of a transmission, are also required to be lightened by making the interior hollow. For example, if the hollow portion is formed on the transfer shaft by machining, the number of processing steps increases, resulting in a cost increase. In other words, it is preferable to form the hollow portion at the same time when the transfer shaft is made into a predetermined shape by cold forging.

By the way, although the transfer shaft has ridges on the outer peripheral surface, Patent Document 1 describes a method of forming a similar shape by cold forging.
This method relates to the molding of a cap pin of a fluorescent lamp. First, a cylindrical workpiece made of copper alloy is loaded into a die, and a punch is press-fitted into the die to form a pilot hole for forming a hollow part. The pilot hole is formed to a depth that reaches the tip of the punch forming position. Next, the workpiece is loaded into another die having the hook forming portion, and the punch is pressed into the pilot hole while the inner and outer diameters of the peripheral wall of the pilot hole are kept constant, thereby forming the punch. Thereafter, the workpiece having the ridges is loaded into another die, a punch is press-fitted into the lower hole of the workpiece, and the lower hole is extended along the axis.
Patent Publication No. 2648902

However, if a hollow shaft such as a transfer shaft is to be formed by this method, the following problems occur.
In other words, the bottom surface of the pilot hole is pressed with a punch, and the ridge is formed by placing the solid part of the workpiece, so that the fluidized material is transferred from the solid part to both the die forming part of the die and the peripheral wall of the pilot hole. Flowing toward the bottom of the hollow portion, a scar mark will be generated near the position where the heel is to be formed.

  In view of such circumstances, an object of the present invention is to provide a method for manufacturing a hollow shaft that does not cause a sink mark on the inner surface of a hollow portion of a workpiece.

The present invention for achieving the above object is a method of manufacturing a hollow shaft having ridges by cold forging, wherein a punch is press-fitted into a work loaded in a first die, and the tip is a heel forming position In a state in which the work is loaded on the first die for forming the hollow hole for forming the hollow portion reaching the vicinity of the second die and the second die having the flange forming portion, and the inner and outer diameters of the peripheral wall of the lower hole are kept constant. A second step of pressing the peripheral wall end surface of the pilot hole to form the ridge, and a work on which the ridge is formed is loaded into a third die, and a punch is press-fitted into the pilot hole to form the pilot hole. A third step of extending along the axis;
It is characterized by comprising.

  According to such a configuration, since the ridge is formed not by the solid part of the work but by the installation of the peripheral wall portion of the pilot hole, the fluidized material flows from the peripheral hole peripheral wall toward the ridge forming portion of the die, Meat sink marks will not occur at the corner of the bottom of the pilot hole.

  In the second step, the pilot hole is preferably formed at a depth such that the tip thereof does not exceed the wrinkle forming scheduled position.

  According to such a configuration, the fluidized material flows in a curved manner from the peripheral wall of the pilot hole toward the die forming part of the die, but when the tip of the pilot hole does not exceed the planned forming position of the die, the fluidized material flows. Will bend gently and will not break into the tip corner of the pilot hole.

In the third step, it is preferable that the punch is press-fitted into the prepared hole while the prepared hole of the workpiece is held coaxially with the punch.
According to such a configuration, the punch is pushed into the solid part of the work in a state where the axis of the punch and the axis of the pilot hole coincide with each other, and the straightness of the hollow part is increased.

  According to the present invention, when the peripheral wall end surface of the pilot hole of the work is pressed in the second step, the fluidized material flows from the peripheral hole peripheral wall toward the die forming portion of the die, so that the tip corner of the pilot hole This eliminates the possibility of flesh marks.

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

  1 to 4 show each forming process of the transfer shaft.

  First, a material wound in a coil shape (for example, structural alloy steel SCM420) is cut into a predetermined size by shearing, loaded into a die 50 shown in FIG. In this step, preliminary forming such as flattening the cut surface of the workpiece and optimizing dimensions is performed. A small-diameter portion 2, a tapered portion 3, and a large-diameter portion 4 are formed on the peripheral surface of the molded workpiece 1, and the end surface of the large-diameter portion 4 is used to guide insertion of a punch in the next process. A recess 5 is formed. Release of the workpiece 1 from the die 50 is performed by an eject pin 52.

  Next, the preformed workpiece 1 is loaded into a die 60 shown in FIG. 2, and a punch 61 is press-fitted into the die 60 to form a pilot hole 11 for forming a hollow part. The pilot hole 11 is formed at a depth that reaches the position where the tip thereof is in the vicinity of the wrinkle forming scheduled position and does not exceed the wrinkle forming planned position. In addition to the pilot hole 11, a small diameter portion 12, a tapered portion 13, and a large diameter portion 14 are formed on the workpiece 10 formed in this process. Further, a tapered portion 15 is formed on the peripheral surface of the large diameter portion 14. The workpiece 10 is released from the die 60 by an eject pin 62.

  By the way, in order to prevent the workpiece 10 from adhering to the punch 61 and being pulled away from the die 60 when the punch holder 63 is separated from the die 60 after completion of molding, the punch holder 63 is provided with the following mechanism. .

  That is, the movable plate 67 is slidably disposed in the hole 63 a of the punch holder 63, and the rod 64 is fixed to the movable plate 67. The movable plate 67 moves in the hole 63a of the punch holder 63 in conjunction with a driving mechanism (not shown). A plate member 65 is fixed to the tip of the rod 64 with a bolt 64 a, and a sleeve 66 is fixed to the plate member 65. The plate member 65 is slidably supported by the punch 61 through the sleeve 61 through the punch 61, and is normally in contact with the lower surface of the punch holder 63 as shown in FIG. When the punch holder 63 starts to rise after the molding of the workpiece 10 is finished, the sleeve 66 is pushed down by a drive mechanism (not shown), and the workpiece 10 is pulled away from the punch 61.

  The workpiece 10 formed with the pilot hole 11 is subjected to a saddle forming process by a forging device shown in FIG. First, the configuration of this forging device will be described.

  The die 70 is provided with an eject pin 71 for releasing the workpiece 20. On the surface of the die 70, a hook forming portion 72 is formed (see FIG. 5A). The punch holder 73 is fixed with a mandrel 74 and a ring member 75 arranged concentrically with the punch 74. The pressing sleeve 76 is configured such that the upper flange portion 76 a slides on the peripheral surface of the hole 77 while being guided through the mandrel 74. A plurality of rods 78 are disposed around the mandrel 74, and the lower ends of these rods 78 face the open ends of the holes 77. The pressing sleeve 76 is urged by a spring 79 attached to the rod 78 and normally presses the flange portion 76 a against the stepped portion 77 a of the hole 77. Now, when the punch holder 73 is lowered, the tip of the mandrel 74 is inserted into the pilot hole 11 of the work 10, and the lower end of the pressing sleeve 76 comes into contact with the peripheral wall end surface 11a of the pilot hole 11 of the work 10 and presses. The sleeve 76 is pushed up against the biasing force of the spring 79. When the tip of the mandrel 74 contacts the bottom surface 11 b of the pilot hole 11, the flange portion 75 a of the pressing sleeve 76 contacts the lower end of the rod 78 at the same time. That is, in a state where the mandrel 74 is completely inserted into the prepared hole 11, the pressing sleeve 76 presses the prepared hole peripheral wall 11 c of the workpiece 10, and the forming of the collar is started. When the punch holder 73 is lifted after the forming of the workpiece 20, the pressing sleeve 76 pulls the workpiece 20 away from the mandrel 74 by the urging force of the spring 79.

  Next, a forming method using this forging apparatus will be described with reference to FIG.

  The workpiece 10 formed by the forging device of FIG. 2 is loaded into a die 70 as shown in FIG. In the workpiece 10, insertion of the die 70 into the forming hole 70 a is restricted by the tapered portion 15. When the punch holder 73 is lowered, the ring member 75 is fitted into the prepared hole peripheral wall 11 b of the workpiece 10, and the mandrel 74 is inserted into the prepared hole 11. That is, the pressing sleeve 76 presses the work hole 10 peripheral wall 11c while keeping the inner and outer diameters of the work hole 10 peripheral hole wall 11c constant, and the flange 21 is formed by placing the work hole peripheral wall 11c. .

  FIG. 9 shows the workpiece 20 formed by the above-described cocoon forming process.

  Here, the “saddle forming scheduled position” refers to the position of the end face 21 a on the side of the pilot hole opening of the saddle 21 with respect to the axial direction of the workpiece 20. In other words, in the present embodiment, “the lower hole 22 is formed at a depth such that the tip thereof does not exceed the wrinkle forming scheduled position” means that the lower hole bottom surface 22 a and the lower hole of the flange 21 with respect to the peripheral wall end surface 22 a If the distances to the end surface 21a on the opening side are L1 and L2, respectively, the relationship of L1 <L2 is established. In addition, the small diameter part 23, the taper part 24, and the large diameter part 25 are formed in the workpiece | work 20 shape | molded by the scissors forming process.

  The workpiece 20 formed with the flange 21 is subjected to a pilot hole extension process by a forging device shown in FIG. First, the configuration of this forging device will be described.

  The die 80 includes an eject pin 81 for releasing the workpiece 30. The housing 83 of the punch holder 82 is formed with a hole 84 that opens to the die 80 side, and a punch 85 is fixed while maintaining the concentricity with the hole 84. The punch 85 has a slightly smaller diameter than the punch 61 formed with the pilot hole 22 of the workpiece 20. A cylindrical holding member 86 is slidably accommodated in the housing 83 while maintaining the same core as the punch 85, and a bottomed cylindrical guide member 87 is fixed above the holding member 86. A spring 88 is interposed between the guide member 87 and the holding member 86. Further, the sleeve member 89 is inserted into the punch 85 and the lower end thereof is inserted into the holding member 86. The sleeve member 89 is arranged to be movable up and down while sliding the upper end flange 89a on the inner peripheral surface of the holding member 86. A plurality of rods 90 are arranged around the punch 85, and the lower ends of these rods 90 face the opening end of the guide member 87.

  The sleeve member 89 is urged by a spring 91 attached to the rod 90, and the upper end flange 89 a is normally pressed against the bottom wall 87 a of the guide member 87. On the other hand, the holding member 86 is biased by a spring 88 and normally presses the upper end flange 89 a against the step portion 83 a of the housing 83.

  Now, when the punch holder 83 is lowered, the holding member 86 is fitted into the lower hole peripheral wall 22c of the workpiece 20, and the lower end of the sleeve member 89 is brought into contact with the peripheral wall end surface 22a of the lower hole 22 of the workpiece 20. The member 89 is pushed up against the urging force of the spring 91. When the punch holder 73 is further lowered, the tip of the punch 85 starts to be inserted into the prepared hole 11 of the workpiece 20.

  Then, when the holding member 86 is completely fitted into the pilot hole peripheral wall 11 c of the workpiece 20 and the lower end thereof comes into contact with the flange 21 of the workpiece 20, the holding member 86 is pushed up against the urging force of the spring 88. When the punch holder 73 is further lowered, the tip of the punch 85 comes into contact with the bottom surface 11c of the pilot hole 11 of the workpiece 20, and the punch 85 starts to be press-fitted into the solid portion 26 of the worm 20. The extension of the workpiece 20 due to the press-fitting of the punch 85 is absorbed by the contraction of the spring 88. When the punch holder 82 is raised after the workpiece 20 is formed, the sleeve member 89 pulls the workpiece 30 away from the punch 85 by the biasing force of the spring 88.

  Next, a forming method using this forging device will be described with reference to FIG.

  The workpiece 20 on which the flange 21 is formed by the forging device of FIG. 3 is loaded into a die 80 as shown in FIG. Next, the punch holder 82 is lowered to fit the holding member 86 to the prepared hole peripheral wall 21 b of the workpiece 20. That is, the punch 85 is press-fitted into the solid portion 26 of the workpiece 20 while the pilot hole 22 of the workpiece 20 is held coaxially with the punch 85, thereby extending the pilot hole 22 along the axis of the workpiece 20. FIG. 10 shows the workpiece 30 formed by the above steps. The worm 30 is formed with a hollow portion 31 that extends along the axis and opens at one end face. The hollow portion 31 has a small diameter in the vicinity of the flange 32. Further, a small diameter portion 33, a tapered portion 34, and a large diameter portion 35 are formed at the other end portion of the workpiece 20.

  In the above embodiment, as shown in FIG. 5 (B), the pilot hole peripheral wall 22c of the workpiece 20 is pressed by the pressing sleeve 76, and the flange 21 is formed by placing the pilot hole peripheral wall 22c. The material does not flow from the peripheral hole peripheral wall 22 c toward the flange forming part 72 of the die 70, and no fleck marks are generated at the tip corner of the prepared hole 11.

  On the other hand, as shown in FIG. 7, when the punch hole P is pressed by the punch P and the flange 21 is formed by placing the solid portion 26 of the workpiece 20 (the method described in Patent Document 1), the flow Since the converted material flows from the solid part 26 of the workpiece 20 toward both the flange forming part 72 of the die 70 and the peripheral hole peripheral wall 11c, a skin mark C is likely to occur at the corner of the bottom hole bottom surface 22a.

  By the way, in the molding process of the flange 21, the fluidized material flows curvedly from the pilot hole peripheral wall 22c toward the flange forming portion 72 of the die 70 (see FIG. 5B). As shown in FIG. 8, when the pilot hole 22 is formed at a depth L1 in which the tip 22b of the pilot hole 22 exceeds the scissor forming position 21a, the fluidized material flow suddenly outwards near the pilot hole tip 22b. Since it bends, it is easy to bend in the front-end corner part of the pilot hole 11, and to produce the damage | damage D. On the other hand, in this embodiment, since the tip 22b of the prepared hole 22 does not exceed the scissor forming position 21a, the flow of the fluidized material is gently curved and is bent at the tip corner of the prepared hole 22. There will be no injuries (see FIG. 5B).

  Furthermore, in the present embodiment, in the step of forming the pilot hole 11, the tapered portion 15 is formed on the peripheral surface of the workpiece 10 at a position slightly closer to the tip than the scissor forming scheduled position. Expands outward to form ridges 21. For this reason, it is easy to secure the volume of the flange 21 and the molding accuracy of the flange 21 is increased.

  By the way, since the transfer shaft 30 is a component that rotates at high speed, if the straightness of the hollow portion 31 is not good, it may cause noise and vibration. Therefore, in the present embodiment, as shown in FIG. 6 (A), the holding member 86 is fitted into the prepared hole peripheral wall 21c of the workpiece 20 so that the prepared hole 22 of the workpiece 20 is held coaxially with the punch 85. The straightness of the hollow portion 31 is improved by press-fitting 85 into the solid portion 26 of the workpiece 20.

  Incidentally, although the transfer shaft 30 is useful for weight reduction as the volume of the hollow portion 31 is increased, in this embodiment, the distal end side of the hollow portion 31 has a small diameter. If an attempt is made to continuously form the hollow portion 31 having the same diameter using the punch 85 having the same diameter as the pilot hole 11 in the pilot hole extending step shown in FIG. Is likely to occur. This is because the material fluidized by the pressing of the punch 85 flows from the solid portion 26 of the workpiece 20 toward both the flange forming portion 72 of the die 70 and the peripheral hole peripheral wall 11c (see FIG. 7). This is because such a phenomenon becomes remarkable when the punch 85 having a diameter is used.

Sectional drawing which shows the forging apparatus used at the preforming process of this invention. Sectional drawing which shows the forging apparatus used at the pilot hole forming process of this invention. Sectional drawing which shows the forging apparatus used at the scissors forming process of this invention. Sectional drawing which shows the forging apparatus used at the pilot hole extension process of this invention. Explanatory drawing of the wrinkle forming process of FIG. Explanatory drawing of the pilot hole extension process of FIG. The figure explaining generation | occurrence | production of the defect in a soot molding process. The figure explaining generation | occurrence | production of the defect in a soot molding process. Sectional drawing of the workpiece | work shape | molded by the scissors forming process of this invention. Sectional drawing of the workpiece | work shape | molded by the pilot hole extension process of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work 10 Work 11 Pilot hole 11a Pilot hole peripheral wall end face 11c Pilot hole peripheral wall 20 Work 21 鍔 22 Pilot hole 30 Work 31 Hollow part 60 Die 61 Punch 70 Die 72 鍔 Molding part 74 Mandrel 75 Ring member 85 Punch 86 Holding member

Claims (3)

A method for producing a hollow shaft having a flange by cold forging,
A first step in which a punch is press-fitted into a workpiece loaded in a first die to form a pilot hole for forming a hollow portion whose tip reaches a vicinity of a punch forming position;
A second step of charging the workpiece into a second die having a ridge forming portion and pressing the peripheral wall end face of the pilot hole while holding the inner and outer diameters of the peripheral wall of the pilot hole constant; ,
A third step of loading the workpiece formed with the ridge into a third die, press-fitting a punch into the prepared hole, and extending the prepared hole along the axis;
A process for producing a hollow shaft, comprising:   2. The method for manufacturing a hollow shaft according to claim 1, wherein, in the second step, the pilot hole is formed at a depth such that a tip of the pilot hole does not exceed a wrinkle forming scheduled position. 3. The method for manufacturing a hollow shaft according to claim 1, wherein in the third step, the punch is press-fitted into the pilot hole in a state where the pilot hole of the workpiece is held coaxially with the punch. .

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