Method and apparatus for manufacturing tripod with shaft

Abstract

To provide a method for manufacturing a tripod with a shaft capable of surely forming a desired shape by plastic flow without requiring excessive working load in cold closed forging by pushing in a punch from one direction.SOLUTION: In a step of forming a tripod with a shaft from a columnar material by upset forging in which pressing is performed from one direction, a closed mold including a first cavity corresponding to a shaft portion and second cavities corresponding to a plurality of leg portions is configured to be movable forward and backward in a pressing direction, the material is set in the first cavity so that the dividing surface of the closing mold and the center of the material in the pressing direction are at different positions, and the closing mold is moved following the movement of the plurality of leg portions with the progress of the upset forging so that the plane including the third axis, which is the central axis of the plurality of leg portions being formed, and the dividing surface of the closing mold overlap each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for manufacturing a tripod with an axis. [Background technology]

[0002] For example, in tripods constituting a constant velocity joint (CVJ) used in a power transmission mechanism of an automobile or the like, it is common to provide holes 102a for fitting a drive shaft (not shown) in the bases (central parts) 102 of three radially extending trunnion shaft parts 104, as in the tripod 101 illustrated in (a) of Fig. 7. However, instead of providing holes for fitting the drive shaft in this way, a so-called "shafted tripod" in which a shaft part 3 (that fits with the drive shaft) is integrally provided, as in the tripod 1 illustrated in (b) of Fig. 7, has been proposed in Patent Document 1 (JP 2006-183725 A).

[0003] Patent Document 1 also discloses a method for integrally forming a long shaft portion 3 having spline grooves 3b and three leg portions (trunnion shaft portions) 4 extending at right angles and at equal intervals from the shaft portion 3. In this method, a cylindrical blank placed inside a die is pressed from one direction in the axial direction with a punch (closed forging), and the material that makes up the blank (hereinafter sometimes referred to as "filler") flows into one shaft portion forming hole (vertical cavity) and three leg portion forming holes (horizontal cavities) provided in the die.

[0004] However, because cold forging simultaneously forms the shaft and three trunnion shafts requires excessive forging force, the above method must be hot forged. Furthermore, the die and punch wear out rapidly, making this uneconomical process, and burrs are unavoidable. Furthermore, because the material (thickness) that makes up the blank must flow evenly and sufficiently into the shaft and three legs solely through the punch forcing force and stroke, the shape is limited to those that allow for such material flow.

[0005] To address the above issues, Patent Document 2 (Japanese Patent No. 6613945) combines a compression process and a split forming process before a closed forging process (crushing process) with the aim of reducing the load of the extrusion process and forming a shaft-mounted tripod by cold forging. However, because cold forging involves work hardening, each subsequent process step makes the forming process more difficult. In particular, the crushing process (the process of orthogonally forming the diagonal legs formed by split forming with respect to the shaft) also generates springback, making the process extremely difficult. Furthermore, there is a concern that cracks may occur at the bases of the three legs (at the boundary with the shaft) due to work hardening and stress concentration. Additionally, the increased number of processes results in increased costs (costs for manufacturing and maintaining the dies) due to the increased number of dies. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-183725 [Patent Document 2] Patent No. 6613945 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, in the technical field, there is a demand for a method for manufacturing a tripod with a shaft, which is a cold closed forging method using a punch pressed from one direction as disclosed in Patent Document 1, for example, and which can reliably form a desired shape by plastic flow without requiring an excessive processing load. [Means for solving the problem]

[0008] Therefore, as a result of extensive research, the inventors have found that in a manufacturing method for an axle-mounted tripod in which an axle-mounted tripod having a columnar axle and a plurality of legs extending radially from the axle is formed from a cylindrical raw material by upset forging, the above-mentioned problem can be solved by setting the raw material inside the closed mold so that the dividing surface of the closed mold in the pressing direction and the center of the raw material are in different positions, and moving the closed mold in the axial direction of the raw material in accordance with the movement of the plurality of legs being formed.

[0009] Specifically, the manufacturing method of the shafted tripod according to the present invention (hereinafter, sometimes referred to as "the method of the present invention") is a manufacturing method of the shafted tripod in which a shafted tripod having a columnar shaft portion and a plurality of legs extending radially from the shaft portion is formed from a cylindrical raw material by upset forging. The method of the present invention is carried out in a forming device having a closed die, a first punch, a second punch, and a first drive device.

[0010] The closed mold includes a first cavity, which is a columnar space corresponding to the shaft portion, and a plurality of second cavities, which are columnar spaces corresponding to the plurality of leg portions. The closed mold is divided by a dividing surface, which is a plane including a second axis, which is the central axis of the second cavities, and is configured to be able to move forward and backward in the direction of the first axis, which is the central axis of the first cavity. The first punch is fixed to close one end of the first cavity. The second punch is inserted from the other end of the first cavity and is configured to be able to slide inside the first cavity. The first drive device drives the second punch in the direction of the first axis, which is the central axis of the first cavity.

[0011] The method of the present invention comprises the first and second steps listed below. The first step is to insert a raw material into the first cavity, abut one end of the raw material against the first punch, and arrange the raw material and the closed mold so that the center of the raw material in the direction of the first axis and the parting surface of the closed mold are in different positions. The second step is a step of performing an upsetting process in which the other end of the blank is pressed by a second punch driven by the first driving device, causing the material constituting the blank to flow into the second cavity and form multiple legs.

[0012] Furthermore, in the method of the present invention, in the second step, the closed mold moves in accordance with the movement of the multiple legs in the direction of the first axis so that the leg surface, which is a plane including the third axis, which is the central axis of the multiple legs being formed, overlaps with the dividing surface.

[0013] On the other hand, the manufacturing apparatus for an axle-mounted tripod according to the present invention (hereinafter, may be referred to as "the apparatus of the present invention") is an apparatus for carrying out the above-mentioned method of the present invention. Specifically, the apparatus of the present invention is an apparatus for manufacturing an axle-mounted tripod that forms an axle-mounted tripod, which has a columnar axle portion and a plurality of legs extending radially from the axle portion, from a cylindrical material by upset forging. The apparatus of the present invention comprises a closed die, a first punch, a second punch, and a first drive device.

[0014] The closed mold includes a first cavity, which is a columnar space corresponding to the shaft portion, and a plurality of second cavities, which are columnar spaces corresponding to the plurality of leg portions. The closed mold is divided by a dividing surface, which is a plane including a second axis, which is the central axis of the second cavities, and is configured to be able to move forward and backward in the direction of the first axis, which is the central axis of the first cavity. The first punch is fixed to close one end of the first cavity. The second punch is inserted from the other end of the first cavity and is configured to be able to slide inside the first cavity. The first drive device drives the second punch in the direction of the first axis, which is the central axis of the first cavity.

[0015] The apparatus of the present invention is configured to perform the first and second steps listed below. The first step is to insert a raw material into the first cavity, abut one end of the raw material against the first punch, and arrange the raw material and the closed mold so that the center of the raw material in the direction of the first axis and the parting surface of the closed mold are in different positions. The second step is a step of performing an upsetting process in which the other end of the blank is pressed by a second punch driven by the first driving device, causing the material constituting the blank to flow into the second cavity and form multiple legs.

[0016] Furthermore, in the second step, the device of the present invention is configured so that the closed mold moves in accordance with the movement of the multiple legs in the direction of the first axis so that the leg surface, which is a plane including the third axis, which is the central axis of the multiple legs being formed, overlaps with the dividing surface. [Effects of the Invention]

[0017] As described above, in the method of the present invention using the apparatus of the present invention, the closed die moves so that the second cavities follow the movement of the legs in the direction of the first axis as they are being formed by the upsetting process performed in the second step. Therefore, as will be described in detail later, in the method of the present invention using the apparatus of the present invention, the flow of material constituting the blank flowing into the second cavities is simpler and smoother, even though the second step is performed by pressing only the second punch from one side. As a result, according to the method of the present invention using the apparatus of the present invention, the desired shape can be reliably formed by plastic flow without requiring an excessive processing load, despite being cold closed forging in which the punch is pressed from one direction.

[0018] Other objects, other features and attendant advantages of the present invention will be readily apparent from the following description of the embodiments of the present invention which will be given with reference to the drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic perspective view illustrating the configuration of a tripod with shafts formed by a manufacturing method (first method) of a tripod with shafts according to a first embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating the configuration of a molding apparatus used to carry out a first method. [Figure 3]This is a schematic diagram showing how the legs formed by pressing and compressing a columnar material from the top to the bottom move toward the bottom as the material is compressed, without being constrained by the cavity. [Figure 4] 1 is a flowchart illustrating the flow of each step included in a first method. [Figure 5] 1A to 1C are schematic diagrams illustrating the process of forming a tripod with an axis from a columnar material by carrying out the first method. [Figure 6] 10A to 10C are schematic diagrams illustrating the process of forming a tripod with an axis from a columnar material by carrying out the first method according to Modification 1-1. [Figure 7] FIG. 10 is a schematic perspective view illustrating the configuration of a tripod in which a hole for fitting a drive shaft is provided at the base of a trunnion shaft portion, and a tripod with a shaft integrally provided with a shaft portion that fits onto the drive shaft. DETAILED DESCRIPTION OF THE INVENTION

[0020] First Embodiment Hereinafter, a method for manufacturing a tripod with shaft according to a first embodiment of the present invention (hereinafter, may be referred to as a "first method") will be described with reference to the drawings.

[0021] <composition> The first method is a manufacturing method of an axle-mounted tripod in which an axle-mounted tripod having a columnar axle portion and a plurality of legs extending radially from the axle portion is formed from a cylindrical material by upset forging.

[0022] The configuration of the shafted tripod formed by the first method is not particularly limited as long as it has a columnar shaft and a plurality of legs extending radially from the shaft. A specific example of such a shafted tripod is the shafted tripod TP shown in Fig. 1. The shafted tripod TP shown in Fig. 1 has a columnar shaft AP, three legs LP extending radially from the shaft AP, and a base BP where the shaft AP and the three legs LP gather.

[0023] The first method is performed in a molding apparatus including a closed mold, a first punch, a second punch, and a first drive unit. The closed mold includes a first cavity, which is a columnar space corresponding to the shaft portion, and a plurality of second cavities, which are columnar spaces corresponding to the plurality of legs. The first punch is fixed to close one end of the first cavity. The second punch is inserted from the other end of the first cavity and is configured to be slidable inside the first cavity. The first drive unit drives the second punch in the direction of the first axis, which is the central axis of the first cavity. Furthermore, the closed mold is divided by a dividing plane, which is a plane including the second axes, which are the central axes of the plurality of second cavities, and is configured to be freely movable forward and backward in the direction of the first axis.

[0024] FIG. 2 is a schematic cross-sectional view illustrating the configuration of a molding apparatus used to perform the first method. The molding apparatus PM illustrated in FIG. 2 includes a closed-type mold CM, a first punch P1, a second punch P2, and a first drive unit (not shown). The closed-type mold CM includes a first cavity C1, which is a columnar space corresponding to the columnar shaft portion AP of the shaft-equipped tripod TP illustrated in FIG. 1, and multiple (three in FIG. 2) second cavities C2, which are columnar spaces corresponding to the multiple (three in FIG. 1) leg portions LP. However, since FIG. 2 is a cross-sectional view of the molding apparatus PM taken along a plane that includes the central axis (first axis) of the first cavity and passes through only one of the three second cavities C2, the second cavity C2 is not depicted on the right side of the drawing.

[0025] The first punch P1 is fixed to close the lower end of the first cavity C1. The second punch P2 is inserted from the upper end of the first cavity C1 and is configured to be slidable within the first cavity C1. A first drive unit (not shown) drives the second punch P2 in the direction of the first axis (the vertical direction in FIG. 2). That is, in the forming device PM, cold closed forging is performed by pushing the punch P2 from one direction (see the black arrow). Note that the first drive unit used to perform such cold closed forging can be, for example, a hydraulic press or other equipment or facility known to those skilled in the art. When a press is used as the first drive unit, the second punch P2 can be driven by pressing it with a ram.

[0026] Furthermore, the closed type CM is divided by a dividing plane SP, which is a plane including the central axes (second axes) of the multiple (three) second cavities C2, and is configured to be able to move freely in the direction of the first axis by a gas spring GS. However, the configuration for allowing the closed type CM to move freely in the direction of the first axis is not limited to the gas spring GS.

[0027] By the way, when a columnar material is pressed and compressed from one end to the other in the axial direction, the legs that begin to extend radially (outward in the radial direction) should move toward the other end as the material is compressed if there is no subsequent restraint by the cavity. Figure 3 is a schematic diagram showing how the legs formed by pressing and compressing a columnar material from its upper end to its lower end move toward the lower end as the material is compressed without being restrained by the cavity.

[0028] Figure 3(a) illustrates a state in which the columnar raw material RM begins to be pressed and compressed from one end (upper end) in the axial direction (vertical direction) toward the other end (lower end), as indicated by the solid black arrows. As a result of the pressing and compression of the raw material RM, leg portions LP begin to extend radially from the outer peripheral surface of the raw material RM, as illustrated in Figure 3(b). If the pressing and compression of the raw material RM continues thereafter as indicated by the solid black arrows, the leg portions LP continue to extend further, as illustrated in Figure 3(c), and the leg portions LP move toward the lower end as the raw material RM is compressed (see the thick solid arrows).

[0029] Therefore, in conventional methods in which the position of the cavity for forming the leg (trunnion shaft) is fixed, such as the method described in Patent Document 1, the leg, which would normally move as the material is compressed as described above, must continue to extend while remaining in the fixed position of the cavity. When the position of the cavity for forming the leg is fixed, the flow of the material (meat) that forms the material for filling the cavity to form the leg becomes unnatural and complex. This is thought to be one of the reasons why excessive pushing force is required in conventional methods in which the position of the cavity for forming the leg is fixed.

[0030] On the other hand, in the forming apparatus used to perform the first method, as described above, the closed die is configured to be freely movable in the direction of the central axis (first axis) of the first cavity. Therefore, in the first method, the closed die can move so that the multiple second cavities follow the movement in the direction of the first axis of the multiple leg portions being formed by the upsetting process performed in the second step. As a result, in the first method, the flow of material (wall) that fills the second cavity to form the leg portions is more natural and simple than in conventional methods in which the position of the cavity for forming the leg portions is fixed. Therefore, according to the first method, even though it is cold closed forging using a punch thrust from one direction, it is possible to reliably form the desired shape by plastic flow without requiring excessive processing load.

[0031] The first method includes the first and second steps listed below. Fig. 4 is a flowchart illustrating the flow of each step included in the first method. Fig. 5 is a schematic diagram illustrating the process of forming a tripod with an axis from a columnar material by carrying out the first method.

[0032] The first process executed in step S10 is a process of inserting a blank into the first cavity, bringing one end of the blank into contact with the first punch, and arranging the blank and the closed mold so that the center of the blank in the direction of the first axis and the parting surface of the closed mold are at different positions. That is, in the first process, the center of the blank in the direction of the first axis and the parting surface of the closed mold are set at positions that are offset from each other.

[0033] 5A is a schematic diagram showing an example of the positional relationship between the raw material and the closed mold and the shape of the raw material when the first step is completed. In the example shown in FIG. 5A, the raw material RM is inserted into the first cavity C1, and the lower end of the raw material RM abuts against the first punch P1, which is fixed so as to close one end of the first cavity C1 (the lower end in FIG. 5). As a result, the raw material RM and the closed mold CM are arranged so that the center RMc of the raw material RM in the direction of the first axis (the vertical direction in FIG. 5) and the dividing plane SP, which is the plane separating the split mold CM1 arranged on the first punch P1 side and the split mold CM2 arranged on the second punch P2 side, which constitute the closed mold CM, are located at different positions.

[0034] Specifically, in the example shown in Fig. 5(a), the raw material RM and the closed type CM are arranged so that the dividing surface SP of the closed type CM is located closer to the first punch P1 (lower in Fig. 5) than the center RMc of the raw material RM in the direction of the first axis. That is, in the example shown in Fig. 5(a), the length of the portion of the raw material RM on the second punch P2 side of the dividing surface SP of the closed type CM on the first punch P1 side is longer than the length (dimension in the direction of the first axis) of the portion of the raw material RM on the first punch P1 side of the dividing surface SP of the closed type CM on the

[0035] In Fig. 5, the first cavity C1 has already been inserted with the raw material RM, and therefore the reference symbol "C1" indicating the first cavity is not shown. Furthermore, the second cavities C2 for forming the shaft-equipped tripods having three legs as illustrated in Fig. 1 are not provided at positions facing each other across the first shaft, but in Fig. 5, the second cavities C2 are drawn on both the left and right sides of the drawing in order to clearly illustrate the flow of material that constitutes the raw material RM.

[0036] Next, the second process executed in step S20 is a process of performing upsetting processing, in which the other end of the blank is pressed by a second punch driven by the first driving device, causing the material constituting the blank to flow into the second cavity and form multiple legs.

[0037] 5(b) is a schematic diagram showing an example of the positional relationship between the raw material RM and the closed mold CM and the shape of the raw material RM at the time when the second step is performed and the material constituting the raw material RM flows into the second cavity C2 and the leg portion LP begins to form. During the period until the leg portion LP begins to form, the split mold CM2 on the second punch P2 side tries to move toward the first punch P1 due to friction with the portion of the raw material RM that is pressed by the second punch P2 and tries to contract toward the first punch P1. Meanwhile, in the split mold CM1 on the first punch P1 side, the raw material RM is fixed by abutting against the first punch P1, so the split mold CM1 on the first punch P1 side tries to resist the movement of the split mold CM2 on the second punch P2 side due to friction with the portion of the raw material RM.

[0038] However, as described above, the material RM and the closed mold CM are arranged so that the dividing surface SP of the closed mold CM is located closer to the first punch P1 than the center RMc of the material RM in the direction of the first axis. Therefore, as shown in FIG. 5A, the contact area RC2 between the divided mold CM2 and the material RM is larger than the contact area RC1 between the divided mold CM1 and the material RM (RC2 > RC1). Therefore, the force that causes the divided mold CM2 to move toward the first punch P1 due to friction with the material RM (solid arrow) is larger than the force that causes the divided mold CM1 to resist this movement due to friction with the material RM (open arrow). As a result, the divided mold CM1 cannot resist the movement of the divided mold CM2 toward the first punch P1, and as shown in FIG. 5B, the entire closed mold CM moves toward the first punch P1. That is, as can be seen by comparing FIGS. 5A and 5B, the dividing surface SP of the closed mold CM, which was located closer to the first punch P1 than the center RMc of the material RM, moves further toward the first punch P1. In FIG. 5, the change in the position of the dividing plane SP is indicated by a thick solid arrow drawn between the dividing planes SP (dash-dotted lines) drawn in (a) and (b) of FIG.

[0039] After that, as illustrated in FIG. 5B, once the leg portion LP is formed, the positional relationship between the leg portion LP and the closed-type CM is fixed by the engagement between the leg portion LP being formed and the second cavity C2. Meanwhile, as described above with reference to FIG. 3, the leg portion LP moves toward the first punch P1 as the pressing and compression of the raw material RM by the second punch P2 progresses. Therefore, as illustrated in FIG. 5C, the closed-type CM moves toward the first punch P1 together with the leg LP while maintaining the position of the leg LP and the position of the second cavity C2 in the first axial direction aligned. Note that in the example illustrated in FIG. 5C, the material constituting the raw material RM has not yet completely filled the second cavity C2 and the formation of the leg portion LP has not yet been completed, but the pressing and compression of the raw material RM by the second punch P2 continues, and the formation of the leg portion LP is eventually completed.

[0040] That is, in the first method, in the second step, the closed mold moves in accordance with the movement of the multiple legs in the direction of the first axis so that the leg surface, which is a plane including the third axis, which is the central axis of the multiple legs being formed, and the dividing surface overlap.

[0041] 5(a), at the time when the first step is completed, the portion of the closed type CM of the raw material RM that is closer to the second punch P2 than the dividing surface SP is longer than the portion of the closed type CM of the raw material RM that is closer to the first punch P1 than the dividing surface SP of the closed type CM. Furthermore, until the leg portion LP is formed in the second step and engages with the second cavity C2, the frictional force acting between the split type CM2 and the raw material RM is greater than the frictional force acting between the split type CM1 and the raw material RM, so the closed type CM moves further toward the first punch P1.

[0042] Therefore, although the overall length of the raw material RM in the direction of the first axis becomes shorter as the second step progresses, the portion of the raw material RM closer to the second punch P2 than the parting surface SP of the closed type CM becomes longer than the portion of the raw material RM closer to the first punch P1 than the parting surface SP of the closed type CM. In the example shown in FIG. 5, at the completion of the second step, a longer columnar portion remains closer to the second punch P2 than the parting surface SP of the closed type CM closer to the first punch P1. Therefore, in the first method, as illustrated in FIG. 5(c), the columnar portion thus formed can be used as the shank portion AP of the shafted tripod. That is, in the example shown in FIG. 5, by performing the second step, multiple legs LP can be formed closer to the first punch P1 than the center of the shank portion AP in the direction of the first axis.

[0043] <effect> As described above, in the first method, the closed die moves so that the second cavities follow the movement of the legs in the first axis direction as they are being formed by the upsetting process performed in the second step. Therefore, in the first method, even though the second step is performed by pressing from one side only with the second punch, the flow of material constituting the blank into the second cavities is simpler and smoother. As a result, according to the first method, even though it is cold closed forging in which the punch is pressed from one direction, it is possible to reliably form the desired shape by plastic flow without requiring an excessive processing load.

[0044] <Variation 1-1> As described above, in the first step included in the first method, a blank is inserted into the first cavity, one end of the blank is brought into contact with the first punch, and the blank and the closed mold are arranged so that the center of the blank and the parting surface are located at different positions in the first axis direction. As a specific example of the arrangement of the blank and the closed mold, the above description of the first method illustrates a case in which, as shown in FIG. 5, the blank and the closed mold are arranged in the first step so that the parting surface is located closer to the first punch than the center of the blank in the first axis direction, and the second step is performed to form multiple legs closer to the first punch than the center of the stem portion in the first axis direction. However, the positional relationship that must be satisfied between the center of the blank and the parting surface in the first axis direction in the first method is not limited to the above.

[0045] The first method according to variant example 1-1 is a method for manufacturing a tripod with an axis, in which in the first step, the raw material and the closed mold are arranged so that the dividing surface of the closed mold is located closer to the second punch than the center of the raw material in the direction of the first axis, and by performing the second step, multiple legs are formed closer to the second punch than the center of the axis in the direction of the first axis.

[0046] 6A and 6B are schematic diagrams illustrating a process of forming a shafted tripod from a columnar raw material by performing a first method according to Modification 1-1. (a) of FIG. 6 is a schematic diagram illustrating an example of the positional relationship between the raw material and the closed mold and the shape of the raw material upon completion of the first step included in the first method according to Modification 1-1. In the example shown in (a) of FIG. 6, similar to (a) of FIG. 5, the raw material RM is inserted into the first cavity C1, and the lower end of the raw material RM abuts against the first punch P1, which is fixed so as to close one end (lower end) of the first cavity C1. As a result, as illustrated in (a) of FIG. 6, the raw material RM and the closed mold CM are arranged so that the parting surface SP of the closed mold CM is located closer to the second punch P2 (upper side in FIG. 6) than the center RMc of the raw material RM in the direction of the first axis. That is, in the example shown in (a) of Figure 6, the length of the portion of the material RM on the first punch P1 side of the dividing surface SP of the closed type CM is greater than the length of the portion of the material RM on the second punch P2 side of the dividing surface SP of the closed type CM.

[0047] 6, the reference symbol "C1" indicating the first cavity is not shown because the raw material RM has already been inserted into the first cavity C1, as in Fig. 5. Furthermore, the second cavities C2 for forming the shaft-equipped tripods having three legs as illustrated in Fig. 1 are not provided at positions facing each other across the first shaft, but in Fig. 6, as in Fig. 5, the second cavities C2 are drawn on both the left and right sides of the drawing in order to clearly illustrate the flow of material that constitutes the raw material RM.

[0048] (b) of FIG. 6 is a schematic diagram showing an example of the positional relationship between the material RM and the closed mold CM and the shape of the material RM when the material constituting the material RM starts to flow into the second cavity C2 and the leg portion LP starts to be formed in the second step. In the period until the leg portion LP starts to be formed in this way, due to the friction between the portion of the material RM that is pressed by the second punch P2 and tries to shrink toward the first punch P1, the split mold CM2 on the second punch P2 side tries to move toward the first punch P1 side. On the other hand, in the split mold CM1 on the first punch P1 side, since the material RM is fixed by contact with the first punch P1, due to the friction between the material RM and the portion, the split mold CM1 on the first punch P1 side tries to resist the movement of the split mold CM2 on the second punch P2 side.

[0049] However, as described above, since the material RM and the closed mold CM are arranged such that the split surface SP of the closed mold CM is located on the second punch P2 side rather than the center RMc of the material RM in the direction of the first axis, as shown in (a) of FIG. 6, the contact area RC2 between the split mold CM2 and the material RM is smaller than the contact area RC1 between the split mold CM1 and the material RM (RC2 < RC1). Therefore, the force (black arrow) that the split mold CM2 tries to move toward the first punch P1 side due to friction with the material RM is smaller than the force (white arrow) that the split mold CM1 tries to resist this movement due to friction with the material RM. As a result, the split mold CM1 suppresses the movement of the split mold CM2 toward the first punch P1 side, and as shown in (b) of FIG. 6, only the material RM is compressed toward the first punch P1 side while the entire closed mold CM maintains the position at the end of the first step shown in (a) of FIG. 6. That is, as can be seen by comparing (a) and (b) of FIG. 6, the position of the split surface SP of the closed mold CM does not change.

[0050] After that, as illustrated in FIG. 6(b), once the leg portion LP is formed, the positional relationship between the leg portion LP and the closed-type CM is fixed by the engagement between the leg portion LP being formed and the second cavity C2. Meanwhile, as described above with reference to FIG. 3, the leg portion LP moves toward the first punch P1 as the pressing and compression of the raw material RM by the second punch P2 progresses. Therefore, as illustrated in FIG. 6(c), the closed-type CM moves toward the first punch P1 together with the leg LP while maintaining the position of the leg LP and the position of the second cavity C2 aligned in the first axis direction. Note that in the example illustrated in FIG. 6(c), similar to FIG. 5(c), the material constituting the raw material RM has not yet completely filled the second cavity C2 and the formation of the leg portion LP has not yet been completed. However, the pressing and compression of the raw material RM by the second punch P2 continues, and the formation of the leg portion LP is eventually completed.

[0051] 6(a), at the time when the first step is completed, the portion of the closed type CM of the raw material RM that is closer to the first punch P1 than the portion of the closed type CM of the raw material RM that is closer to the second punch P2 than the parting surface SP of the closed type CM of the raw material RM. Furthermore, until the leg portion LP is formed in the second step and engages with the second cavity C2, the frictional force acting between the split type CM1 and the raw material RM is greater than the frictional force acting between the split type CM2 and the raw material RM, so the closed type CM does not move toward the first punch P1.

[0052] Therefore, although the overall length of the raw material RM in the direction of the first axis becomes shorter as the second step progresses, the portion of the raw material RM closer to the first punch P1 than the part of the closed CM dividing surface SP becomes longer than the portion of the raw material RM closer to the second punch P2 than the part of the closed CM dividing surface SP. In the example shown in FIG. 6, at the completion of the second step, a longer columnar portion remains closer to the first punch P1 than the part of the closed CM dividing surface SP closer to the second punch P2. Therefore, in the first method according to the modified example 1-1, the columnar portion thus formed can be used as the shank portion AP of the shafted tripod, as illustrated in FIG. 6(c). That is, in the example shown in FIG. 6, by performing the second step, multiple legs LP can be formed closer to the second punch P2 than the center of the shank portion AP in the direction of the first axis.

[0053] Second Embodiment Hereinafter, a method for manufacturing a tripod with shaft according to a second embodiment of the present invention (hereinafter, may be referred to as a "second method") will be described with reference to the drawings.

[0054] As described above, in the forming apparatus used to perform the first method, the closed die is configured to freely advance and retreat in the direction of the central axis (first axis) of the first cavity. Therefore, in the first method, the closed die can move so that the multiple second cavities follow the movement in the direction of the first axis of the multiple leg portions being formed by the upsetting process performed in the second step. As a result, in the first method, the flow of material (wall) that fills the second cavity to form the leg portions is more natural and simple than in conventional methods in which the position of the cavity for forming the leg portions is fixed. Therefore, according to the first method, even though it is cold closed forging using a punch thrust from one direction, it is possible to reliably form the desired shape by plastic flow without requiring excessive processing load.

[0055] In the explanation of the first method described above, an example was given in which, in the second step, during the period before the first point in time at which the legs that begin to form as the material constituting the raw material flows into the second cavity and engage with the second cavity, the closed mold moves due to the frictional force acting between the inner surface of the first cavity and the outer surface of the raw material, and after the first point in time, the closed mold moves due to the legs that engage with the second cavity.

[0056] However, the manner in which the closed die is moved so that the second cavities follow the movement in the first axis direction of the multiple legs being formed by the upsetting process performed in the second step is not limited to the above. For example, instead of moving the closed die only by the frictional force acting between the inner circumferential surface of the first cavity and the outer circumferential surface of the blank and the engagement between the second cavity and the legs as described above, the movement of the closed die may be controlled more precisely using a driving device.

[0057] <composition> Therefore, the second method is the above-mentioned first method, in which the molding device further includes a second drive device that drives the closed mold in the direction of the first axis, and the second drive device drives the closed mold so as to follow the movement in the direction of the first axis of the leg that begins to be formed in the second step as the material that makes up the blank flows into the inside of the second cavity.

[0058] The specific configuration of the second drive device is not particularly limited as long as it is capable of controlling the movement of the closed mold so as to follow the movement of the leg being formed in the second step in the direction of the first axis as described above. Such a second drive device can be appropriately selected from various means known to those skilled in the art, such as a hydraulic actuator. The first drive device and the second drive device can also be realized by a hydraulic press capable of cooperative control. Furthermore, in the second method, a sensor or control device can be used to precisely control the movement of the closed mold using the second drive device.

[0059] <effect> As described above, in the second method, the molding apparatus further includes a second drive device that drives the closed mold in the first axial direction, and the closed mold is driven by the second drive device to follow the movement of the multiple legs being formed in the first axial direction in the second step. Therefore, according to the second method, the closed mold can be moved more reliably and accurately so that the multiple second cavities follow the movement of the multiple legs being formed in the first axial direction, thereby reducing the processing load while reliably forming the desired shape through plastic flow. Furthermore, as long as the effect achieved by the second method is not significantly impaired, it is also possible to adjust the position on the shaft where the multiple legs are formed by moving the second cavities to the desired position using the second drive device.

[0060] Third Embodiment Hereinafter, a manufacturing device for a shafted tripod according to a third embodiment of the present invention (hereinafter, may be referred to as a "first device") will be described with reference to the drawings.

[0061] As mentioned at the beginning of this specification, the present invention not only relates to a method for manufacturing an axle tripod, but also to an apparatus for manufacturing an axle tripod.

[0062] <composition> The first device is a manufacturing device for a shafted tripod that forms a shafted tripod having a columnar shaft portion and a plurality of legs extending radially from the shaft portion from a cylindrical raw material by upset forging. The device of the present invention includes a closed die, a first punch, a second punch, and a first drive device.

[0063] The closed mold includes a first cavity, which is a columnar space corresponding to the shaft portion, and a plurality of second cavities, which are columnar spaces corresponding to the plurality of leg portions. The closed mold is divided by a dividing surface, which is a plane including a second axis, which is the central axis of the second cavities, and is configured to be able to move forward and backward in the direction of the first axis, which is the central axis of the first cavity. The first punch is fixed to close one end of the first cavity. The second punch is inserted from the other end of the first cavity and is configured to be able to slide inside the first cavity. The first drive device drives the second punch in the direction of the first axis, which is the central axis of the first cavity.

[0064] The first device is configured to perform the first and second steps listed below. The first step is to insert a raw material into the first cavity, abut one end of the raw material against the first punch, and arrange the raw material and the closed mold so that the center of the raw material in the direction of the first axis and the parting surface of the closed mold are in different positions. The second step is a step of performing an upsetting process in which the other end of the blank is pressed by a second punch driven by the first driving device, causing the material constituting the blank to flow into the second cavity and form multiple legs.

[0065] Furthermore, in the second step, the first device is configured so that the closed mold moves in accordance with the movement of the multiple legs in the direction of the first axis so that the leg surface, which is a plane including the third axis, which is the central axis of the multiple legs being formed, overlaps with the dividing surface.

[0066] The first device corresponds to a molding device used to carry out the first method described above, and its configuration has already been described in detail in the explanation of the first method with reference to Figures 2, 5, and 6, so its explanation will be omitted here.

[0067] As described in the explanation of the first method, the first device may be configured such that in the second step, the closed mold moves due to the frictional force acting between the inner surface of the first cavity and the outer surface of the raw material during the period before the first time point at which the legs, which begin to be formed as the material constituting the raw material flows into the second cavity, engage with the second cavity, and that after the first time point, the closed mold moves due to the frictional force acting between the inner surface of the first cavity and the outer surface of the raw material.

[0068] <effect> As described above, in the first device, the closed die moves so that the second cavities follow the movement of the legs in the direction of the first axis as they are being formed by the upsetting process performed in the second step. Therefore, in the first device, even though the second punch presses from one side in the second step, the flow of material constituting the blank into the second cavities is simpler and smoother. As a result, with the first device, even though it is cold closed forging in which the punch is pressed from one direction, it is possible to reliably form the desired shape by plastic flow without requiring an excessive processing load.

[0069] Furthermore, as described above in the explanation of the first method and the first method according to variant 1-1, by appropriately setting the positional relationship between the position of the center of the material in the direction of the first axis and the dividing surface of the closed mold in the first step, it is possible to extend multiple legs from desired positions on the shaft portion that constitutes the finally obtained shafted tripod.

[0070] Fourth Embodiment Hereinafter, a manufacturing device for a shafted tripod according to a fourth embodiment of the present invention (hereinafter, may be referred to as a "second device") will be described with reference to the drawings.

[0071] As described above, the forming apparatus used to perform the first method (i.e., the first apparatus) is configured so that the closed die can freely move in the direction of the central axis (first axis) of the first cavity. Therefore, in the first apparatus, the closed die can move so that the multiple second cavities follow the movement in the direction of the first axis of the multiple leg portions being formed by the upsetting process performed in the second step. As a result, in the first apparatus, the flow of material (wall) that fills the second cavity to form the leg portions is more natural and simple than in conventional methods in which the position of the cavity for forming the leg portions is fixed. Therefore, with the first apparatus, despite being cold closed forging using a punch thrust from one direction, the desired shape can be reliably formed by plastic flow without requiring excessive processing load.

[0072] As described above, the first device may be configured such that in the second step, during the period before the first time point at which the legs, which begin to be formed as the material constituting the raw material flows into the second cavity, engage with the second cavity, the closed mold moves due to the frictional force acting between the inner surface of the first cavity and the outer surface of the raw material, and after the first time point, the closed mold moves due to the legs engaging with the second cavity.

[0073] However, the manner in which the closed die is moved so that the second cavities follow the movement in the first axis direction of the multiple legs being formed by the upsetting process performed in the second step is not limited to the above. For example, instead of moving the closed die only by the frictional force acting between the inner circumferential surface of the first cavity and the outer circumferential surface of the blank and the engagement between the second cavity and the legs as described above, the movement of the closed die may be controlled more precisely using a driving device.

[0074] <composition> Therefore, the second device is the first device described above, further comprising a second drive device that drives the closed mold in the direction of the first axis, and is configured to drive the closed mold by the second drive device so as to follow the movement in the direction of the first axis of the leg that begins to be formed in the second process as the material that makes up the raw material flows into the inside of the second cavity. This is an apparatus for manufacturing an axis-equipped tripod.

[0075] As described in the description of the second method, the specific configuration of the second drive device is not particularly limited as long as it is capable of controlling the movement of the closed mold to follow the movement of the leg being formed in the second step in the direction of the first axis as described above. Such a second drive device can be appropriately selected from various means known to those skilled in the art, such as a hydraulic actuator. The first drive device and the second drive device can also be realized by a hydraulic press capable of cooperative control. Furthermore, the second device can be equipped with a sensor and a control device for precisely controlling the movement of the closed mold using the second drive device.

[0076] <effect> As described above, the second device further includes a second drive device that drives the closed mold in the first axial direction, and the second drive device drives the closed mold so that it follows the movement of the multiple legs being formed in the first axial direction in the second step. Therefore, the second device more reliably and accurately moves the closed mold so that the multiple second cavities follow the movement of the multiple legs being formed in the first axial direction, thereby reliably forming the desired shape through plastic flow while reducing the processing load. Furthermore, as long as the effect achieved by the second device is not significantly impaired, it is also possible to adjust the position on the shaft where the multiple legs are formed by moving the second cavities to the desired position using the second drive device.

[0077] For the purpose of explaining the present invention, several embodiments and modifications having specific configurations have been described above, sometimes with reference to the accompanying drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments and modifications, and it goes without saying that modifications can be made as appropriate within the scope of the claims and the matters described in the specification.

[0078] For example, in this specification, the manufacturing of a so-called "axis-mounted tripod" having one axis and three legs has been mainly described, but the articles manufactured by the axis-mounted tripod manufacturing method and manufacturing apparatus of the present invention are not limited to such axis-mounted tripods, and the axis-mounted tripod manufacturing method and manufacturing apparatus of the present invention can be applied to the manufacturing of a wide variety of articles having an axis and multiple legs. [Explanation of symbols]

[0079] RM…Material RMc…the heart of materials TP...Tripod with shaft BP…Base AP…Shaft part LP…legs PM...Forming equipment (machining equipment for tripods with shafts) CM...Occluded type, CM1, CM2…Split type SP: Closed type split surface P1...first punch P2...Second punch C1...first cavity C2: Second cavity GS...Gas spring RC1: Contact area between split CM1 and material RM RC2: Contact area between split CM2 and material RM

Claims

1. A manufacturing method of an axle-mounted tripod, in which an axle-mounted tripod having a columnar axle portion and a plurality of legs extending radially from the axle portion is formed from a cylindrical material by upset forging, a closed mold including a first cavity that is a columnar space corresponding to the shaft portion and a plurality of second cavities that are columnar spaces corresponding to the plurality of leg portions, the closed mold being divided by a dividing surface that is a plane including second axes that are central axes of the second cavities and configured to be freely advanced and retreated in the direction of the first axis that is the central axis of the first cavity; a first punch fixed to close one end of the first cavity; a second punch inserted from the other end of the first cavity and configured to be slidable inside the first cavity; a first drive device that drives the second punch in the direction of the first axis; In a molding apparatus comprising: a first step of inserting the blank into the first cavity, bringing one end of the blank into contact with the first punch, and arranging the blank and the closed die so that the center of the blank in the direction of the first axis and the parting surface are at different positions; a second step of performing an upsetting process in which the second punch driven by the first driving device presses the other end of the blank, causing the material constituting the blank to flow into the second cavity, thereby forming the plurality of legs; Including, In the second step, the closed mold moves in accordance with the movement of the plurality of legs in the direction of the first axis so that a leg surface, which is a plane including a third axis that is a central axis of the plurality of legs being formed, and the dividing surface overlap. Manufacturing method of tripod with shaft.

2. A method for manufacturing a tripod with an axis according to claim 1, In the first step, the blank and the closed die are disposed so that the dividing surface is positioned closer to the second punch than the center of the blank in the direction of the first axis; By performing the second step, a plurality of the legs are formed on the first punch side of the center of the shaft portion in the direction of the first axis. Manufacturing method of tripod with shaft.

3. A method for manufacturing a tripod with an axis according to claim 1, In the first step, the blank and the closed die are disposed so that the dividing surface is positioned closer to the first punch than the center of the blank in the direction of the first axis; By performing the second step, a plurality of the legs are formed on the second punch side of the center of the shaft portion in the direction of the first axis. Manufacturing method of tripod with shaft.

4. A manufacturing method of the shafted tripod according to any one of claims 1 to 3, In the second step, during a period before a first time point at which the leg portion begins to be formed as the material constituting the blank flows into the second cavity and engages with the second cavity, the closed mold is moved by a frictional force acting between the inner peripheral surface of the first cavity and the outer peripheral surface of the blank, and after the first time point, the closed mold is driven and moved by the leg portion engaged with the second cavity. Manufacturing method of tripod with shaft.

5. A manufacturing method of the shafted tripod according to any one of claims 1 to 3, The molding device further includes a second drive device that drives the closed mold in the direction of the first axis, In the second step, the closed mold is driven by the second driving device so as to follow the movement of the leg portion in the direction of the first axis, the leg portion being formed by the material constituting the blank flowing into the second cavity. Manufacturing method of tripod with shaft.

6. A manufacturing device for a shaft-mounted tripod that forms a shaft-mounted tripod having a columnar shaft portion and a plurality of legs extending radially from the shaft portion by upset forging from a cylindrical material, a closed mold including a first cavity that is a columnar space corresponding to the shaft portion and a plurality of second cavities that are columnar spaces corresponding to the plurality of leg portions, the closed mold being divided by a dividing surface that is a plane including second axes that are central axes of the second cavities and configured to be freely advanced and retreated in the direction of the first axis that is the central axis of the first cavity; a first punch fixed to close one end of the first cavity; a second punch inserted from the other end of the first cavity and configured to be slidable inside the first cavity; a first drive device that drives the second punch in the direction of the first axis; Equipped with a first step of inserting the blank into the first cavity, bringing one end of the blank into contact with the first punch, and arranging the blank and the closed die so that the center of the blank in the direction of the first axis and the parting surface are at different positions; a second step of performing an upsetting process in which the second punch driven by the first driving device presses the other end of the blank, causing the material constituting the blank to flow into the second cavity, thereby forming the plurality of legs; The method is configured to perform a manufacturing method of an axis-mounted tripod, including In the second step, the closed mold is configured to move following the movement of the plurality of legs in the direction of the first axis so that a leg surface, which is a plane including a third axis that is a central axis of the plurality of legs being formed, and the dividing surface overlap. Manufacturing equipment for tripods with shafts.

7. 7. The manufacturing apparatus for a tripod with shaft according to claim 6, In the second step, during a period before a first time point at which the leg portion, which begins to be formed as the material constituting the blank flows into the second cavity, is fitted with the second cavity, the closed mold is moved by a frictional force acting between the inner peripheral surface of the first cavity and the outer peripheral surface of the blank, and after the first time point, the closed mold is driven and moved by the leg portion fitted with the second cavity. Manufacturing equipment for tripods with shafts.

8. 7. The manufacturing apparatus for a tripod with shaft according to claim 6, a second drive device that drives the closed mold in the direction of the first axis; In the second step, the closed mold is driven by the second drive device so as to follow the movement of the leg in the direction of the first axis, the leg beginning to be formed by the material constituting the blank flowing into the second cavity. Manufacturing equipment for tripods with shafts.

Images