JP2000197922A - Core and device for forming recessed part of hollow shaft, and method for forming recessed part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the core and device for forming the recessed part of a hollow shaft, and the method for forming the recessed part by which the recessed shape of a surface of the hollow shaft can correctly and efficiently be pressed. SOLUTION: This hollow shaft recessed part forming device is provided with a rotation release groove part of approximately circular section which is continuously formed on a recessed part 11 provided on a circumferential surface, and a draft part 13 which is continuous to the rotation release part and formed by cutting a core from the surface in an arc-like section the axis of the core. The rotation release part is formed rotatable without being interfered by a projecting part in a hollow shaft 100 after forming the recessed part, the draft part 13 is formed so that the rotating core 10 is pulled without being interfered with the projecting part formed in the hollow shaft 100, and the recessed part is formed in the hollow shaft 100, then the core 10 and the hollow shaft 100 are relatively rotated to pull out the hollow shaft from the core 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow metal core for forming a concave portion of a hollow hollow shaft for forming a concave portion used for fitting a check ball for positioning and the like in a part of a longitudinal direction of a metal hollow shaft. And a recess forming method.

[0002]

2. Description of the Related Art A hollow shaft having a concave portion is shown in FIG.
As shown in FIG. 1, it is used as a shift fork shaft 210 of a manual transmission device 200 of a vehicle. In the case of this example, the shift fork shaft 210
Moves the transmission gear 203 via the shift fork 202 in response to the driving of the shift lever 201 to set the input / output rotation ratio of the transmission device to the selected one or to reverse it.

[0003] Such a shift fork shaft 21
A concave portion 211 is provided at 0, and the check ball 205 of the lock device is fitted into the concave portion 211 to determine its position.

In general, a solid bar is used as the shift fork shaft, and the recess is provided with a broaching machine,
Alternatively, it is manufactured by a cutting machine using a single-purpose machine such as a hob or a press. However, in the case of machining by cutting, man-hours for processing such as burrs and burrs are required, and in the case of press working, man-hours are required for processing by deformation due to molding and excess material generated during processing.

[0005]

In recent years, there has been a demand for the shift fork shaft to be made of a metal hollow body in response to a demand for a lighter vehicle. However, cutting a pipe material causes a decrease in mechanical strength due to a decrease in wall thickness, resulting in an increase in cost, which is disadvantageous economically.

Therefore, it is conceivable to form the concave portion by press working. However, if the hollow portion is simply formed by a forming punch, the rigidity of the hollow shaft is small. There is a problem that a "drip" occurs at the boundary between the peak and the peak, and the concave cannot be formed with high accuracy. When "who" occurs in this way, the moderation of the position determination by the check ball becomes poor, the shift lever operation feeling becomes dull, and the driver does not give a good impression.

[0007] For this reason, if the deformation is corrected and the surplus processing is performed, the cost increases due to an increase in man-hours.

In order to solve such a problem, a soft metal core is disposed inside a hollow portion of the hollow shaft, and the core is left as it is (JP-A-6-31).
No. 350), a core metal made of a low melting metal is used, and after press molding, the core metal is melted and discharged (JP-A-4-143221).
No.) has been proposed.

[0009] However, in the case of using a soft metal core, the metal member is left in the shaft, which is against the demand for weight reduction. In such a case, heat treatment, molten metal discharging treatment, and the like are troublesome, and cannot be easily realized, resulting in an increase in cost.

[0010] Further, there has also been proposed a method in which a plurality of recessed cores are used in the radial direction as a plurality of cores, and each of the divided portions of the core is drawn out one by one (see Japanese Utility Model Application Laid-Open No. HEI 5-5-2).
No. 936212). However, since the divided cored bar tends to have insufficient strength to press the forming punch with a large pressing force, there is a possibility that the cored core may be damaged, and there is a problem that a plurality of steps are required to remove the cored bar.

Accordingly, the present invention provides a core for forming a concave portion of a hollow shaft, a device for forming a concave portion of a hollow shaft, and a method for forming a concave portion, which can accurately and efficiently manufacture a concave portion on the surface of a hollow shaft by press molding. The purpose is to provide.

[0012]

According to the present invention, a core metal for forming a concave portion of a hollow shaft for solving the above-mentioned problems is provided.
0 is fitted in the hollow portion 103 of the hollow shaft 100 in which the concave portion 102 is press-formed on the outer periphery 101, and the concave portion 1
02 is a cylindrical cored bar 10 having a molding recessed portion 11 provided at a position corresponding to the convex portion 104 to the hollow portion of the hollow shaft formed corresponding to the hollowed portion of the hollow shaft. 11 is a rotary relief groove 1 having a substantially arc-shaped cross section and formed continuously from
2 and an escape portion 13 which is continuous with the rotary escape groove portion and is formed by cutting a part of the cross section of the core metal from the surface along the axis of the core metal, and the rotary escape groove portion 12 has a concave portion 102. The outer wall surface 12a of the hollow shaft 100 is formed so that the outer wall surface 12a can rotate without interfering with the convex portion 104 in the formed hollow shaft 100.
4 is formed so as to be inside the inner wall surface 104a.
The outer wall surface 13a of the escape portion 13 is formed inside the projecting position of the convex portion 102 so that the convex portion 104 can be extracted without interfering with the convex portion 104 formed in the inner portion 00.

[0013] In addition, the hollow shaft 100 has a hollow forming device 1 for solving the above-mentioned problems.
The outer periphery 101 has a stamping surface 41 for forming a concave portion 102, and a lowering position D for embossing the concave portion 102 and a rising position U separating from the outer periphery 101 of the hollow shaft 100.
Forming punch 40 and hollow shaft 10
A shaft insertion hole 51 having a cylindrical wall contacting the outer circumference 101 of the shaft 0 and a punch insertion hole 52 facing the cylindrical wall and into which the forming punch 40 is inserted. A pipe fastener 50 that is divided and driven into two states, an open state R and a closed state C, is inserted into the shaft insertion hole 51 of the pipe fastener 50, and is disposed in the hollow portion 103 of the hollow shaft 100. A cylindrical cored bar 10 in which a molded concave portion 11 is recessed at a position corresponding to a convex portion 104 to the hollow portion 103 of the hollow shaft 100 molded corresponding to the concave portion 102;
The core metal 10 includes a rotary escape groove 12 having a substantially arc-shaped cross section formed continuously with the molding recess 11, and a rotary escape groove 12.
And a relief portion 13 formed by cutting a part of the cross section of the core bar 10 from the surface along the axis of the core bar 10, and the rotary relief groove portion 12 is provided with the hollow shaft after the concave portion 102 is formed. In order to be able to rotate without interfering with the convex portion 104 within the convex portion 104, the outer wall surface is formed so as to be inside the inner wall surface of the convex portion 104. Protrusion 1 formed in 100
Extraction escape part 1 so that it can be extracted without interfering with 04
3, a hollow core 100 for forming the concave portion 102 of the hollow shaft 100 formed so that the outer wall surface 13a is located inside the projecting position of the convex portion 102, and a hollow shaft 100 having the concave portion 102 formed by the forming punch 40. The hollow shaft 10 is relatively rotated with respect to the hollow
And a rotation driving means 60 which is located at a position where the core metal 10 for forming the concave portion can be extracted from 0.

Further, the hollow shaft recess forming apparatus 1 is provided.
The rotation driving means 60 may rotate the hollow core 100 in the hollow shaft 100.

Further, the rotation driving means 60 of the hollow shaft recess forming apparatus 1 can rotate the hollow shaft 100 around the recess forming core 10.

In the present invention, a method of forming a concave portion of a hollow shaft to solve the above-mentioned problem is described in the hollow shaft 100.
The outer periphery 101 has a stamping surface 41 for forming a concave portion 102, and a lowering position D for embossing the concave portion 102 and a rising position U separating from the outer periphery 101 of the hollow shaft 100.
Forming punch 40 and hollow shaft 10
A shaft insertion hole 51 having a cylindrical wall that contacts the outer periphery 101 of the shaft 0, and a punch insertion hole 52 that faces the cylindrical wall and into which the forming punch 40 is inserted, and extends along the axis of the shaft insertion hole 51. The pipe clamp 50 is formed into two parts and driven into two states, an open state R and a closed state C, and is inserted into the shaft insertion hole of the pipe clamp and arranged, and is inserted into the hollow portion 103 of the hollow shaft 100. The hollow shaft 10 fitted and molded corresponding to the concave portion 102
0 is a cylindrical metal core 10 in which a molding concave portion 11 is provided at a position corresponding to the convex portion 104 to the hollow portion 103, and the core metal 10 has a substantially cross-sectional shape formed continuously with the molding concave portion 11. An arc-shaped rotating escape groove portion 12; and a withdrawal escape portion 13 which is continuous with the rotating escape groove portion 12 and formed by cutting a part of a cross section of the core metal 10 from the surface along the axis of the core metal 10, The rotary escape groove 12 is formed in the hollow shaft 1 after the concave portion 102 is formed.
The inner wall surface 12a of the convex portion 104 has an outer wall surface 12a so that the outer wall surface 12a can rotate without interfering with the convex portion 104.
a of the withdrawal escape portion 13 so that the rotated cored bar 10 can be extracted without interfering with the convex portion 104 formed in the hollow shaft 100. Hollow shaft 1 formed so that 13a is located inside from the protruding position of the convex portion 102
00, the hollow shaft 100 having the concave portion 102 formed by the forming punch 40, and the concave portion forming core 10 are relatively rotated to form the hollow shaft 1
In the apparatus for forming a concave portion of the hollow shaft 100 having a rotation driving means for setting the position where the core metal 10 for forming the concave portion can be extracted from 00, the forming punch 40 is in the raised position U, and the pipe clamp 50 is in the open state R. In the initial state, a step of arranging the hollow shaft 100 in the shaft insertion hole 51 of the pipe fitting 50 (SA1, SA2) and a step of inserting the recess-forming core 10 into the hollow shaft 100 (S
A1, SA2) and a step of fixing the hollow shaft 100 with the pipe fastener by closing the pipe fastener (SA)
3) and a step of moving the forming punch 40 to the lowered position to form the concave portion 102 in the hollow shaft 100 (SA4, S4).
A5) and a step of relatively rotating the hollow shaft 100 and the recess-forming core 10 to a position where the recess-forming core 10 can be extracted from the hollow shaft 100 (S5).
A6) and a step of opening the pipe fastener (SA)
7) and a step of removing the hollow shaft 100 from the shaft insertion hole of the pipe fitting (SA8). Note that the order of step SA6 and step SA7 can be set as appropriate.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a core for forming a concave portion of a hollow shaft, an apparatus for forming a concave portion of a hollow shaft, and a method of forming a concave portion according to the present invention will be described. 1 to 9 show an example of a hollow shaft recess forming apparatus 1 according to the present embodiment.

The hollow shaft 100 produced by the hollow shaft recess forming apparatus according to the present embodiment is used as a shift fork shaft in the same manner as in the conventional example. As shown in FIG. 4, the hollow shaft 100 has
The recesses 102 are formed at three places, and the check balls 205 of the lock device are fitted into the recesses 102.
(4)), is to be positioned.

As shown in FIGS. 1 and 5 to 8, the hollow shaft recess forming apparatus according to the present embodiment includes a core 10 inserted into a hollow shaft 100 and the core 10 extending over 90 degrees. A core metal rotating device 60 which is a rotary driving means for reciprocatingly rotating between a press position and a removal position, a pipe clamp 50 for fixing the periphery of the hollow shaft 100, and a pipe clamp 50 Metal fitting driving device 80 for driving the open state R and the closed state C, the forming punch 40 for forming the concave portion 102 on the outer periphery 101 of the hollow shaft 100, and pressing the forming punch to the raised position U and the hollow shaft 100. And a punch driving device (not shown) for driving to a lowering position D where these devices are arranged. Further, in this example, a work supply device (not shown) for supplying the hollow shaft (work) before press working to the pipe fitting 50 is provided. The work can be supplied manually.

The forming punch 40 is provided with an embossed surface 41 having three convex portions forming three concave portions 102 of the hollow shaft 100 on the embossed surface 41. Then, the forming punch is driven to an ascending position U and a descending position D where the hollow shaft 100 is pressed by an electrically or hydraulically driven punch driving device.

As shown in FIGS. 1, 5 and 7, the pipe clamp 50 has a shaft insertion hole 51 having a cylindrical wall which comes into contact with the outer periphery 101 of the hollow shaft 100, and faces the cylindrical wall. It has a punch insertion hole 52 into which the forming punch 40 is inserted, and is formed into two parts, a fixing bracket 53 and a moving bracket 54, along the axis of the shaft insertion hole 51. The fixture 53 is fixed to the base 90, while the movable fixture 54 is slidably attached to the base 90 so that the movable fixture 54 can be driven to the open state R and the closed state C.

As shown in FIGS. 5 and 7, the bracket driving device 80 comprises a link mechanism 83 having a hydraulic actuator 82 having a rod 81 which moves forward and backward and one end of which is pivotally supported on a base 90. The link mechanism 83 drives the movable fitting 54 to the above-described two states via the two rods 84 and 85. The driving mechanism of the bracket driving device 80 may use an electric motor as a driving source or employ another mechanism.

Then, the cored bar 10 is mounted on a cored bar rotating device 60 fixed on the base 90, is inserted into the shaft insertion hole 51 of the pipe clamp 50 and is disposed at the pressing position ( 0 °) and the withdrawal position (90 °).

The metal core 10 is a substantially columnar member made of die steel such as SKD11 and high-speed steel such as SKH6. As shown in FIG. The hollow shaft 100 hollow portion 103
Forming recesses 11 at positions corresponding to the convex portions 104
Is recessed.

The shape of the concave portion 11 can be appropriately changed depending on the shape of the concave portion 102 to be formed in the hollow shaft 100. However, in the case of a shift fork shaft, the concave portion to be formed and the general portion, and the concave portion and the mountain In order not to cause “drip” at the boundary between the portions, it is necessary to form the end portions 15 of the forming concave portion 11 as sharp.

The core metal 10 is formed with a rotary escape groove 12 having a substantially arc-shaped cross section and formed continuously with the molding recess 11. The rotation relief groove 12 is formed such that its outer wall surface is inside the inner wall surface of the protrusion 104 so that it can rotate without interfering with the protrusion 104 in the hollow shaft 100 after the formation of the recess 102. .

That is, the radius r of the rotation relief portion (FIG. 3)
(See (2)) is smaller than the distance d (see FIG. 2) from the axis on which the inner peripheral surface 104 of the convex portion 104 protruding from the hollow portion 102 of the hollow shaft 100 is located.

The shape of the rotation escape portion 104 is arbitrary as long as the above conditions are satisfied. However, if the rotation escape portion 104 is too deep, the cross-sectional area of the core metal is reduced at this portion, and the core metal is damaged by twisting when the core metal is rotated. Might be.

The core metal 10 is connected to the rotary escape groove 12 and is formed with the core metal 10 formed along the axis of the metal core 10 such that a part of the cross section is cut off from the surface in an arc shape.
3 are formed. In the present example, the relief portion 13 has an outer wall surface 13a corresponding to an arc-shaped chord having a cross-sectional shape provided in the same direction as the driving direction of the forming punch 40, that is, perpendicular to the forming direction of the forming recess. ing.

As shown in FIGS. 2 and 3, the escape portion 13 is provided so that the rotated cored bar 10 can be extracted without interfering with the convex portion 104 formed in the hollow shaft 100. The bow shape of the cross-sectional shape of the cut portion 13 is formed to be larger than the convex portion 104.

That is, as shown in FIGS. 2 and 3, in this embodiment, the cross-sectional shape of the escape portion 13 of the cored bar 10 has a dimension A sandwiching the outer wall portion 13a, and a minimum portion 11a of the formation recess.
A> B, where B is the dimension sandwiching. Therefore, the outer wall surface 13a of the escape portion 13 is reliably located inside the inner wall surface 104a of the convex portion 104 of the hollow shaft. Thereby, the core metal 10 can be reliably extracted from the hollow shaft in which the concave portion 102 is formed.

In this embodiment, the escape portion 13 is formed by the core 10
Is formed over the entire length of the convex portion 104, which interferes with the convex portion 104 when the hollow shaft 100 is removed.
May be provided only on one side sandwiching it.

In this embodiment, in the cross-sectional shape of the relief portion 13, the outer wall surface 13a is formed in the same direction as the driving direction of the forming punch 40, that is, perpendicular to the forming direction of the forming recess. This can be appropriately inclined as shown by a virtual line in FIG. Outer wall 13
When a is inclined, the lower end portion of the outer wall surface 13a is formed on the bottom side surface of the hollow portion 102 of the hollow shaft 100, that is, formed in order to prevent the core metal 10 from being damaged and prevent the core metal 10 from biting into the inside of the hollow shaft 100. It is necessary not to reach the part which receives punch driving force directly. When changing the inclination of the outer wall surface 13a, the core metal rotating device 60
It is necessary to set the rotation angle according to the inclination change.

Further, in this embodiment, the sectional shape of the escape portion 13 is arcuate, but this can be changed as appropriate.

As shown in FIGS. 6 and 8, the core rotating device 60 includes a rotating shaft 61 supported by a casing 64 and having the core 10 attached thereto, a pinion 62 attached to the rotating shaft 61, and The rack 6 that meshes with the pinion 62
3

In this example, the rack 63 is reciprocated by a driving device (not shown) to move the pinion 62
The core 10 is rotated back and forth by 0 °, and the core 10 is pressed to the pressing position (0 °: FIG. 2).
(1), (2))) and withdrawal position (90 °: FIG. 2)
(3) state)). Incidentally, the core metal rotating device 60 may be realized by another mechanism.

[Operation of the present apparatus] The hollow shaft recess forming apparatus 1 of this embodiment operates as follows. First, the forming punch 40 is in the raised position U, and the moving fitting 54 of the pipe clamp 50 is in the open state R in an initial state. In this state, the cored bar 10 is in the normal position (0 °) (SA
1).

In this initial state, the hollow shaft 100 is arranged in the shaft insertion hole 51 of the pipe fitting 50 by the work supply device. At the same time hollow shaft 10
0 is inserted into the recess 10 (SA2: FIG. 2).
(1)).

Then, the fitting driving device 80 is driven to move the moving fitting 54, and the pipe tightening fitting 50 is closed.
Then, the hollow shaft 100 is fixed with the pipe fastener 50 (SA3).

The hollow shaft 100 is used for the pipe fitting 50.
The molding punch 40 is driven by a molding punch driving device to move to the lowering position D while the hollow shaft 10 is fixed.
0, a concave portion 102 is formed (SA4: FIG. 2 (2), FIG. 5, FIG. 6).

Thus, a recess 102 is formed between the forming punch 40 and the cored bar. At this time, the hollow shaft 1
00 is fastened by a pipe fastener 50 and the cored bar is formed with a molded concave portion. Therefore, the concave portion 102 to be molded and the general portion, and the boundary portion 105 between the concave portion 12 and the crest portion 105 are formed.
In this case, it is possible to form a sharp tip without generating "drain".

When the pressing is completed, the forming punch 40 is driven by the forming punch driving device to move to the raised position U (SA5).

Next, the mandrel rotating device 60 is driven to rotate the mandrel by 90 ° and rotate from the press position to the removal position. At this time, since the convex portion 104 formed in the hollow portion of the hollow shaft 100 passes through the rotation escape groove portion 12 of the metal core 10, the metal core 10 is rotated to the removal position without contacting the convex portion 104. (SA6: FIG. 2 (3), FIG. 7, FIG. 8)).

Then, the metal fitting driving device 80 is driven to move the moving metal fitting 54, and the pipe tightening metal fitting 50 is opened.
Release the tightening of the hollow shaft 100 (SA
7). Note that the order of the rotation of the cored bar and the driving of the pipe clamp to the open state can be interchanged. In this case, the hollow shaft 100 needs to be fixed so as not to rotate by the work supply means or other means.

In this state, the hollow shaft 100 is pulled out horizontally from the pipe clamp 50 by the work supply means, and at the same time, the hollow shaft 100 is pulled out from the metal core 10 (SA8).

Thereafter, the mandrel rotating device 50 is rotated in the reverse direction to rotate the mandrel 10 by 90 ° to return to the press position (SA).
9) A series of operations ends.

In the present invention, these procedures can be sequentially performed by an operator to produce a hollow shaft having a concave portion, and a workpiece supply device, a forming punch driving device,
By providing control means for sequentially operating the core metal rotating device 60 and the metal fitting driving device 80, a hollow shaft having a concave portion can be automatically created.

Therefore, according to the hollow shaft concave portion forming apparatus according to the present embodiment, the sharp boundary between the concave portion and the general portion can be obtained without heat treatment or complicated core metal removing step without leaving the core metal. It is possible to easily produce a hollow shaft having an accurate shape provided with.

In the above embodiment, the hollow shaft after molding is taken out after the core is rotated. However, this is done by fixing the core and rotating and taking out the hollow shaft. Is also good. In this case, the hollow shaft recess forming apparatus is provided with a work rotating means for rotating the hollow shaft with respect to the metal core before taking out the hollow shaft as a rotation driving means. Let it.

In this example, after the fastener is opened (SB6), the hollow shaft is rotated to the removal position by the work rotating means (SB7), and the hollow shaft is taken out (SB8). The steps SB1 to SB5 until the pipe fastener is opened (SB6) are the same as those described in the first embodiment.
This is the same as the operating procedures SA1 to SA5 of the hollow shaft recess forming apparatus according to the embodiment.

In the above embodiment, the shift fork shaft has been described as an example of the hollow shaft. However, any hollow shaft that has a recess formed therein and is positioned by a lock device for fitting a check ball or the like into the recess is used. It can also be applied to rocker arm shafts for exhaust, frame pipes for headrests, and others.

[0052]

As described above, according to the core metal for forming the concave portion of the hollow shaft, the concave shaft forming device and the concave portion forming method according to the present invention, the core metal can be left,
It is possible to easily and efficiently manufacture a hollow shaft having a precise shape having a sharp boundary between a concave portion and a general portion without performing a heat treatment or a complicated core removing process.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a hollow shaft recess forming apparatus according to the present invention, wherein (1) is a front view and (2) is a side view.

FIG. 2 is a schematic view showing the operation of the hollow shaft recess forming apparatus according to the present invention.

FIG. 3 is a view showing a core metal for forming a concave portion of the hollow shaft according to the embodiment of the present invention, (1) is a front view, and (2).
FIG. 2 is a sectional view taken along line ii-ii in (1).

FIG. 4 is a view showing a shift fork shaft manufactured by the hollow shaft recess forming apparatus according to the embodiment of the present invention, wherein (1) is a front view, and (2) is ii-ii in (1). Fig. 3 is a sectional view taken along a line, (3) is a view taken along a line iii in (1), and (4) is an enlarged view of an iv part in (1).

FIG. 5 is a front view showing a hollow shaft recess forming apparatus according to the present invention.

FIG. 6 is a side view of the hollow shaft recess forming apparatus shown in FIG. 6;

FIG. 7 is a front view showing the hollow shaft recess forming apparatus shown in FIG. 6;

FIG. 8 is a side view of the hollow shaft recess forming apparatus shown in FIG. 6;

FIG. 9 is a flowchart showing an operation state of the hollow shaft recess forming apparatus shown in FIG. 6;

FIG. 10 is a flowchart showing an operation state of another example of the hollow shaft recess forming apparatus according to the present invention.

FIG. 11 is a cross-sectional view showing a core metal for forming a concave portion of a hollow shaft according to the present invention, a hollow shaft concave portion forming device, and a vehicle transmission device using a shift fork shaft which is a hollow shaft manufactured by the concave portion forming method. FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 recess forming device 10 core metal 11 forming recess 12 rotating escape groove 12 a outer wall surface 13 punching escape portion 13 a outer wall surface 40 forming punch 41 stamping surface 50 pipe tightening fitting 51 shaft insertion hole 52 punch insertion hole 60 rotation drive means (core Gold rotating device) 100 hollow shaft 101 outer periphery 102 concave portion 103 hollow portion 104 convex portion 104a inner wall portion

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takeshi Ken Koya 2-3-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo Shinjuku Monolith Building 21F Inside Ohashi Technica Co., Ltd.

Claims (5)

[Claims] 1. A concave portion is fitted in a hollow portion of a hollow shaft having a concave portion formed on the outer periphery and formed at a position corresponding to a convex portion of the hollow shaft hollow portion molded corresponding to the concave portion. A cylindrical cored bar, wherein the cored bar is formed with a rotating escape groove having a substantially arc-shaped cross section formed continuously with the molding concave portion, and an axial line of the cored bar which is continuous with the rotating relief groove. And a relief portion formed by cutting the core metal from the surface along the outer surface.The outer wall surface of the rotary escape groove portion is formed so as to be rotatable without interfering with the convex portion in the hollow shaft after the concave portion is formed. The withdrawal escape portion is formed so that the rotated cored bar can be extracted without interfering with the convex portion formed in the hollow shaft. Hollow formed inside the overhang position of the protrusion A core metal for forming the concave portion of the shaft. 2. A forming punch provided with an embossing surface on the outer periphery of the hollow shaft, the embossing surface forming a recess, and driven into two states: a lowering position for embossing the recess, and an ascending position separated from the outer periphery of the hollow shaft. A shaft insertion hole having a cylindrical wall in contact with the outer periphery of the hollow shaft; and a punch insertion hole facing the cylindrical wall and into which the forming punch is inserted, and divided into two along the axis of the shaft insertion hole. A pipe fastener formed and driven into two states, an open state and a closed state; and a pipe fitting inserted into a shaft insertion hole of the pipe fastener, fitted in a hollow part of a hollow shaft, and the recessed part. A cylindrical core having a molding recess formed at a position corresponding to the projection to the hollow portion of the hollow shaft which is molded corresponding to the core, and the core is formed continuously with the molding recess. Rotation relief groove with a substantially circular cross section And a withdrawal portion formed by cutting a part of the cross section of the core metal from the surface along the axis of the core metal and continuing to the rotary relief groove portion, wherein the rotary relief groove portion is hollow after the concave portion is formed. The outer wall surface is formed so as to be inside the inner wall surface of the convex portion so that it can rotate without interfering with the convex portion in the shaft, and the relief hole is formed by rotating a cored bar in the hollow shaft. And a recess formed by the forming punch, wherein the hollow wall is formed such that the outer wall surface of the escape portion is located inside the overhanging position of the protrusion so that the protrusion can be extracted without interfering with the protrusion. And a rotation driving means for relatively rotating the hollow shaft thus formed and the core metal for forming a concave portion so as to be able to extract the core metal for forming a concave portion from the hollow shaft. . 3. The hollow shaft recess forming apparatus according to claim 2, wherein the rotation driving means rotates the recess forming core metal in the hollow shaft. 4. The hollow shaft recess forming apparatus according to claim 2, wherein the rotation driving means rotates the hollow shaft around the recess forming core. 5. A forming punch provided with an embossing surface for forming a concave portion on the outer periphery of the hollow shaft, and driven into two states: a lowering position for embossing the concave portion, and an ascending position separated from the outer periphery of the hollow shaft. A shaft insertion hole having a cylindrical wall in contact with the outer periphery of the hollow shaft; and a punch insertion hole facing the cylindrical wall and into which the forming punch is inserted, and divided into two along the axis of the shaft insertion hole. A pipe fastener formed and driven into two states, an open state and a closed state; and a pipe fitting inserted into a shaft insertion hole of the pipe fastener, fitted in a hollow part of a hollow shaft, and the recessed part. A cylindrical core having a molding recess formed at a position corresponding to the projection to the hollow portion of the hollow shaft which is molded corresponding to the core, and the core is formed continuously with the molding recess. Rotation relief groove with a substantially circular cross section And a withdrawal portion formed by cutting a part of the cross section of the core metal from the surface along the axis of the core metal and continuing to the rotary relief groove portion, wherein the rotary relief groove portion is hollow after the concave portion is formed. The outer wall surface is formed so as to be inside the inner wall surface of the convex portion so that it can rotate without interfering with the convex portion in the shaft, and the relief hole is formed by rotating a cored bar in the hollow shaft. And a recess formed by the forming punch, wherein the hollow wall is formed such that the outer wall surface of the escape portion is located inside the overhanging position of the protrusion so that the protrusion can be extracted without interfering with the protrusion. In the hollow shaft recess forming apparatus comprising a hollow shaft and a rotation driving unit that relatively rotates the recess forming core and the recess forming core can be extracted from the hollow shaft. Molding punch A step of disposing a hollow shaft in the shaft insertion hole of the pipe fastener, in a raised position, and in an initial state in which the pipe fastener is in an open state; a step of inserting a recess-forming core into the hollow shaft; A step of fixing the hollow shaft with the pipe fastener with the fastener closed, a step of moving the forming punch to a lowered position and forming a recess in the hollow shaft, a hollow shaft, and the recess forming core metal; Relatively rotating the hollow shaft to a position where the core metal for forming the concave portion can be extracted from the hollow shaft; and a step of opening the pipe tightening bracket; and moving the hollow shaft from within the shaft insertion hole of the pipe tightening bracket. Removing the hollow shaft.