JP2782882B2 - Manufacturing method of hollow member - Google Patents

Description

The present invention relates to a method for manufacturing a hollow member by cold forging, and more particularly to a method for manufacturing a hollow member by forming and punching a solid material using a die and a punch. The present invention relates to a method for manufacturing a hollow member for forming a (hollow member).

[Prior Art] As a conventional method for manufacturing a hollow member, for example, there is a method as shown in FIGS. Fig. 4 (a)-
The manufacturing method shown in (e) is what is called a blow-out method. This method is based on a block-shaped solid material 1
(FIG. 4 (a)) is moved to the die 3 placed on the base 2.
And is brought into contact with a counter ring 4 provided below the die hole 3a. Thereafter, the center of the material 1 is punched at once by a punch 5 (FIG. 4 (b)), thereby processing the material 1 into a cylindrical body 6 having an outer diameter D and an inner diameter d (FIG. 4 (c)). .

Next, this cylindrical body 6 is fitted into an outer surface forming hole 7a of a die 7 having a diameter corresponding to the outer diameter of the final hollow member, and a punch 8 having a diameter corresponding to the inner diameter of the final hollow member is inserted into the cylindrical body 6. And is punched by the punch 8 and the tapered portion 7b of the outer surface forming hole 7a (FIG. 4 (d)). Thus, the intended hollow member 9 is obtained.

The manufacturing method shown in FIGS. 5A to 5G is called a backward piercing method. In this method, first, a material 11 (FIG. 5 (a)) is fitted into a die hole 13a of a die 13 on a base 12 and brought into contact with a counter 14 of the die hole 13a. Thereafter, the material 11 is extruded backward by the punch 15 (FIG. 5 (b)). Thus, the raw material 11 is processed into a bottomed cylindrical body 16 having an outer diameter D and an inner diameter d (FIG. 5 (c)). Next, this bottomed cylindrical body 16 is placed in a die 17 for piercing.
Then, the bottom wall 16a is drilled by the punch 18 to obtain the cylindrical body 19 (FIG. 5 (e)). Finally, this cylindrical body 19 is fitted into an outer surface forming hole 20a of a die 20 having a diameter corresponding to the outer diameter of the final hollow member, and a punch 21 having a diameter corresponding to the inner diameter of the final hollow member is attached to the cylindrical body 19. And is punched by the punch 21 and the tapered portion 20b of the outer surface forming hole 20a (FIG. 5 (f)). Thus, the desired hollow member 22 is obtained.

[Problem to be Solved by the Invention] However, such a conventional method for manufacturing a hollow member has the following problems.

In the blow-off method shown in FIG. 4, since the entire central portion of the raw material 1 is punched out into scrap, the yield of the raw material is very poor. In addition, since the punching process is performed, the life of the punch 5 is short. Furthermore, since the outer diameter and the inner diameter of the cylindrical body 6 and the final hollow member 9 are limited, there is no flexibility in the cross-sectional reduction rate (d ² / D ² ) of the cylindrical body 6 and there is a limit. For example, the cross-section reduction rate in the blow-out method is about 20% to 30%.

Further, in the backward piercing method shown in FIG. 5, the outer diameter and the inner diameter of the bottomed tubular body 16 and the final hollow member 22 formed by the backward extrusion process of FIG. 5B are limited. Therefore, if the tip of the punch 15 is crushed due to repeated use, an error occurs immediately in the outer diameter and the inner diameter of the bottomed cylindrical body 16, and as a result, the number of times the punch 15 can be used is limited, and the punch 15 Life is short. Further, similarly to the blow-off method shown in FIG. 4, there is a limit to the sectional reduction rate (d ² / D ² ) of the bottomed cylindrical body 16. Further, in this method, the remaining portion 19a of the bottom wall 16a remains at the lower portion of the tubular body 19 by the piercing shown in FIG. 5 (d). The inner wall of the member 22 has a flaw 22 caused by the remaining portion 19a of the bottom wall 16a.
There is a problem that a occurs.

Means for Solving the Problems The present invention has been made in view of such a conventional problem, and has a cylindrical body having a bottom, and the cylindrical body is expanded above an upper portion of a die hole of a die. The bottom wall is brought into contact with the tapered guide portion to be opened from the bottom wall side, and the bottom wall is pressed downward by a punch loosely inserted into the cylindrical body, and the outer diameter of the cylindrical body is pressed by the action of the tapered guide portion. After the inner diameter of the cylindrical body is brought into close contact with the punch outer surface by press-fitting into the outer surface forming hole at the lower part of the die hole, the lower part of the cylindrical body is brought into contact with a counter ring disposed in the lower part of the outer surface forming hole. Then, the punch is pushed further downward to punch out the bottom wall of the tubular body, and a method of manufacturing a hollow member is provided.

[Operation] According to this means, the punch is loosely inserted after the bottomed cylindrical body is brought into contact with the upwardly expanding tapered guide portion formed corresponding to the outer diameter from the bottom wall side. . Then, the bottom wall of the tubular body is pressed by the punch, and the tubular body is pressed into the outer surface forming hole below the die hole while being squeezed by the action of the tapered guide portion. The outer peripheral surface of the press-fitted cylindrical body is
The inner surface of the punch is pressed down to the outer diameter of the final hollow member by the restraint of the outer surface forming hole, and is pressed down to the inner diameter of the final hollow member by the close contact of the pressing outer peripheral surface. The punch descends in parallel with the ironing, and the cylindrical body pressed by the punch reaches the counter ring provided below the outer surface forming hole, and the bottom wall thereof contacts the counter ring. Furthermore, the punch is displaced downward while pressing the bottom wall,
The bottom wall of the tubular body is punched. Thereby, a hollow member having a required outer diameter and inner diameter is formed.

[Examples] Hereinafter, the present invention will be described based on examples.

1 to 3 show an embodiment of the present invention.

First, the structure will be described.
First Step of Forming a Bottomed Cylindrical Body 32 by Backward Extrusion of a Solid Block-shaped Material 31 (FIGS. 1 (a) to 1 (a))
(C)) and a second step of forming a hollow member 33 having an outer diameter D and an inner diameter d by punching the bottom wall 32a while squeezing the bottomed cylindrical body 32 formed in the first step (first step). Figure (d)-
(G)).

As shown in FIG. 2, the cold forging machine that achieves the backward extrusion of the raw material 31 in the first step includes a die 35 mounted on a base 34 and having a die hole 35a, and a die 35 in the die hole 35a. A punch 36 that is displaced and presses the material 31 in the die hole 35a, a pressing body 37 that fits into the punch 36 and supports the upper end of the material 31, and a punch 36 that is disposed below the die hole 35a.
And a solid counter 38 for back-pressing the material 31 pressed by the pressure from below. Diameter larger than the outer diameter D of the inner diameter D ₁ of the die hole 35a of the die 35 is the last of the hollow member 33 (D _1> D)
The outer diameter d ₁ of the punch 36 is set to be larger in diameter (d _1> d) than the internal diameter d of the hollow member 33.

Further, as shown in FIG. 3, the cold forging die for performing the ironing and the punching of the bottomed cylindrical body 32 in the second step is placed on the base 39 and the die hole 40 is formed.
a die 40 having a, a punch 41 for displacing the inside of the die hole 40a downward to push the cylindrical body 32 into the die hole 40a, and a counter ring 42 provided below the die hole 40a. . The counter ring 42 allows the punch 41 to punch the bottom wall 32a by pressing down the cylindrical body 32 from below, and a punching hole having the same diameter as the punch 41 is formed on the center shaft thereof.
42a. Furthermore, the die hole 40a includes an upwardly expanding tapered guide portion 40b that forms an upper portion of the die hole 40a, and an outer surface forming hole portion 40c that communicates with the tapered guide portion 40b and that forms a lower portion of the die hole 40a. Taper guide 40b
It may form a tilt angle of for example 10 to 15 degrees, and the diameter of the upper rim is formed to be substantially equal to the outer diameter D ₁ of the cylindrical body 32. As a result, the cylindrical body 32 fitted in the large-diameter hole portion 40b 'communicating with the upper portion of the tapered guide portion 40b is
With this, it is possible to press-fit into the outer surface forming hole 40c. The inner diameter of the outer surface forming hole 40c is the final hollow member 3
The outer diameter D of the hollow member 33 is set to be equal to the outer diameter D of the cylindrical member 32. On the other hand, the outer diameter of the punch 41 is set equal to the inner diameter d of the hollow member 33.

Next, the operation of the method for manufacturing a hollow member having such a configuration will be described.

According to the first step, the block-shaped material 31 fitted in the die hole 35a of the die 35 is pressed from above by the punch 36 (FIGS. 1 (a) and 1 (b)). The material 31 pressed by the punch 36 is press-fitted below the die hole 35a,
It is held down by the counter 38 below the die hole 35a.
When the punch 36 further presses and lowers the material 31 while the counter 38 is in the reverse holding state, the outer portion of the material 31 is pushed upward in a state where the outer portion of the material 31 is in close contact with the inner wall of the die hole 35a and the outer wall of the punch 36. The upper end of the pushed-up material 31 is prevented from moving upward by the pressing body 37. This allows the deformed material
31 is tightly filled between the die hole 35a and the punch 36, and the bottom wall 3
A cylindrical body 32 having an outer diameter D ₁ and an inner diameter d ₁ having 2a is formed (FIG. 1 (c)). Thus, the outer diameter D and the inner diameter d of the hollow member 33 are
Since the bottomed cylindrical body 32 having a larger outer diameter D ₁ and inner diameter d ₁ is formed to allow a certain selection of the cross-sectional reduction rate (d ₂ ² / D ₂ ² ) of the cylindrical body 32 (for example, 30% -40%), the life of the punch 36 is prolonged.

The cylindrical body 32 formed in the first step in this manner is transferred to the second step, and the bottom wall 32a is formed on the tapered guide portion 40b of the die 40.
(FIG. 1 (d)). Thereafter, the cylindrical body 32 on the tapered guide portion 40b is pressed downward by the punch 41 loosely inserted into the hollow portion thereof, and is pressed into the outer surface forming hole portion 40c by the guide of the tapered guide portion 40b ( FIG. 1 (e)). When the cylindrical body 32 is pressed down inside the outer surface forming hole 40c by the punch 41, the outer peripheral surface and the inner peripheral surface of the cylindrical body 32 are formed on the inner wall of the outer surface forming hole 40c and the outer wall of the punch 41. The outer diameter and the inner diameter of the tubular body 32 are constrained, and are shaped into the outer diameter D and the inner diameter d of the final hollow member 33. Further, after the cylindrical body 32 is pressed down and comes into contact with the upper surface of the counter ring 42, only the punch 41 is displaced downward. At this time, the punch 41 is
a is punched out and inserted into the punched hole 42a of the counter ring 42 (FIG. 1 (f)). By this punching process,
The bottom wall 32a of the tubular body 32 is punched without leaving any remaining portion, and is discharged from the punched hole 42a as a small amount of scrap. In this way, a hollow member having a good yield without scratches on the inner wall.
33 are formed (FIG. 1 (g)). Further, since the hollow member 33 is formed by squeezing the bottomed cylindrical body 32 formed in the first step, the hollow member 33 having a cross-sectional reduction rate (d ² / D ² ) of 10% to 15% is used. It can be easily manufactured.

[Effects of the Invention] As described above, according to the present invention, a cylindrical body having a bottom is prepared, and the cylindrical body is provided with a bottom wall at a tapered guide portion which expands above an upper portion of a die hole of a die. Side, and press the bottom wall downward with a punch loosely inserted into the cylindrical body and press the outer diameter of the cylindrical body by the action of the tapered guide portion to form an outer surface forming hole below the die hole. After the inner diameter of the cylindrical body is brought into close contact with the outer surface of the punch by press-fitting the lower part of the cylindrical body, the lower part of the cylindrical body is brought into contact with a counter ring arranged in the lower part of the outer surface forming hole, and the punch is further lowered. By pushing, the bottom wall of the cylindrical body was punched out, so that the outer diameter of the punch and the inner diameter of the die hole for performing ironing and punching were set to the inner diameter and outer diameter of the final hollow member. Has a good cross-section reduction rate A hollow member can be obtained. Furthermore, since the bottom wall of the bottomed cylindrical body is punched out without leaving the remainder, the inner wall of the hollow member is not damaged as in the conventional piercing backward method, and the blow-out method is used. Such a large amount of scrap is not generated. As a result, a practically useful effect that a hollow member having a smooth inner wall and a good yield can be formed is exhibited.

[Brief description of the drawings]

1 to 3 are views showing an embodiment of a method for manufacturing a hollow member according to the present invention, wherein FIGS. 1 (a) to 1 (g) are process diagrams shown in cross section, and FIG. 2 is a diagram of FIG. FIG. 3 is a sectional view showing a cold forging die used in the first step, FIG. 3 is a sectional view showing a cold forging die used in the second step of FIG. 1, and FIGS. 4 (a) to (e).
5 (a) to 5 (g) are process drawings showing cross sections of a conventional method of manufacturing a hollow member, which is a blow-out method and a piercing backward method. 31… Material 32… Bottomed cylindrical body 32a… Bottom wall 33… Hollow member 35,40… Dice 35a, 40a… Die hole 36,41… Punch 40b… Taper guide 40c… Outer surface forming hole 42… Counter ring

Claims (1)

(57) [Claims] 1. A cylindrical body having a bottom is prepared, and the cylindrical body is brought into contact with a tapered guide portion expanding above a die hole of a die from a bottom wall side, and is loosely inserted into the cylindrical body. By pressing the bottom wall downward with a punch and pressing the outer diameter of the cylindrical body into the outer surface forming hole part below the die hole while squeezing by the action of the tapered guide part, the inner diameter of the cylindrical body Is brought into close contact with the outer surface of the punch, and then the lower portion of the cylindrical body is brought into contact with a counter ring disposed in the lower portion of the outer surface forming hole, and the punch is further pushed downward, so that the bottom wall of the cylindrical body is formed. A method for manufacturing a hollow member, wherein