JPS636293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a cylindrical body from a plate-shaped metal material.

Generally, when molding metal cylindrical bodies used as various parts, it is widely practiced to round a plate-shaped material to match the outer peripheral surface of a metal core.

By the way, with such molding, depending on the material of the material after molding, due to its spring characteristics, the core bar may expand beyond the outer surface shape. Therefore, during molding, the outer diameter of the core metal must be corrected in advance to be slightly smaller than the final dimension, taking into account the spring characteristics of the material. In other words, when molding a cylindrical body with a predetermined diameter, use a core metal with a diameter equal to the final dimension of the cylindrical body minus the correction value for springback, and when the material expands due to springback after molding, it will not work as expected. The diameter must be the same.

However, the above springback correction value is
This varies depending on the material and hardness of the material, so it must be determined experimentally in advance.Furthermore, even slight changes in material properties will change the amount of change in springback, so frequent corrections are required to maintain high accuracy. In reality, if changes after molding due to spring back are corrected only by the dimensions of the core metal, variations in product accuracy will occur and it will be difficult to obtain a stable product. Further, it is difficult to bring the joints of the cylindrical body into close contact with each other as a whole.

The present invention aims to solve the above-mentioned problems, and aims to eliminate dimensional changes due to spring back after molding, and to provide highly accurate and stable products.

The cylindrical body forming method of the present invention involves forming a cylindrical body material as a primary molded product in which a flat plate-shaped material is rounded and abutted against each other with both end surfaces in an unjoined state, and from this cylindrical body material to be formed. A forming method for forming a cylindrical body using a punch and an ironing die, the punch having an outer diameter at a lower part thereof corresponding to the inner diameter of the cylindrical body, and an axial height of the cylindrical body material to be formed. A cylindrical core metal part having a height dimension larger than the dimensions is provided, and a large diameter pressing surface is formed at the upper end of this core metal part,
The ironing die has an inner diameter such that the distance between its inner circumferential surface and the outer circumferential surface of the core metal part is equal to or less than the wall thickness of the cylindrical material to be formed, and has a predetermined length in the axial direction. A circular forming hole having a pressing part is formed, and the cylindrical material to be formed is mounted on the outer peripheral surface of the core part at the lower part of the punch, and then the punch is lowered and the material is inserted into the upper part of the core part. The cylindrical material to be formed is pushed down in the axial direction by the pushing surface of the cylindrical body, and is press-fitted into the ironing part of the forming hole of the ironing die to be ironed.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a cylindrical body formed by the method of the present invention. This cylindrical body 1 is made by forming a flat plate-shaped material made of metal into a cylindrical shape. It is made by joining.

FIG. 2 shows an example of a device used in the method of the present invention, in which a punch 11 is disposed above so as to move up and down. 12 is provided, and a large-diameter pushing surface 13 is formed at the upper end of this core metal portion 12 . Further, a guide die 14 is disposed at a lower position where the punch 11 moves up and down, and a circular guide hole 15 is formed in the guide die 14. Further, an ironing die 16 is disposed below the guide die 14, and a circular forming hole 17 is formed in the ironing die 16. In this molding hole 17, a squeezing part 19 is continuously provided below a guide part 18 which expands outward from the top of the upper end, and a large-diameter falling part 20 is continuously provided below this squeezing part 19.

The core part 12 of the punch 11 has a cylindrical shape that is the same as the shape of the inner surface of the cylindrical body 1. That is, the outer diameter _D1 of the core part 12 is formed to be the same as the final inner diameter dimension of the cylindrical body 1. and the height dimension H ₁ of the core bar 12 is the axial height dimension H ₂ of the cylindrical body material 1a.
It is formed larger. Further, the inner diameter D ₂ of the guide hole 15 of the guide die 14 is formed so that the distance from the outer circumferential surface of the core metal part 12 of the punch 11 is approximately equal to the wall thickness of the cylindrical material 1a installed in the guide hole 15. Furthermore, the inner diameter D ₃ of the ironing part 19 of the ironing die 16 is set to be smaller than the inner diameter of the guide hole 15 of the guide die 14 by a predetermined ratio, that is, the inner circumferential surface of the ironing part 19 and the core metal part 1
The distance between the outer peripheral surface of the cylindrical body material 1a and the outer peripheral surface of the cylindrical body material 1a is formed to be equal to or less than the wall thickness dimension of the cylindrical body material 1a, and the ironing part 19 is formed to have a predetermined length in the axial direction.

Then, in forming the cylindrical body 1, first, a flat plate-shaped material is rounded, and as shown in FIG. A cylindrical material 1a as a molded product is molded. At this stage, both end surfaces of the cylindrical body material 1a, that is, the joints are not completely in contact with each other. In other words, when a flat plate material is rounded, the outer circumferential surface of the cylindrical material 1a does not undergo much elongation due to plastic deformation, so even if the inner surfaces of both end surfaces are brought into close contact, a gap with a V-shaped cross section is formed. g remains, and both end surfaces are butted together in an unjoined state.

Note that this rounding can be done in the same way as before, so a detailed explanation will be omitted, but in this case,
The core metal part 12 of the punch 11 may be used to form the mold along the outer peripheral surface thereof.

Next, as shown in FIG. 2, the cylindrical material 1a is
is inserted into the guide hole 15 of the guide die 14, and the punch 11 is lowered to fit the core metal part 12 into the cylindrical body material 1a, so that the cylindrical body material 1a is tightly attached to the outer peripheral surface of the core metal part 12. let

Subsequently, the punch 11 is further lowered, and its pushing surface 13 pushes down the cylindrical material 1a in the axial direction, thereby press-fitting the cylindrical material 1a into the forming hole 17 of the ironing die 16. As a result, the cylindrical body material 1a passes in the axial direction from the guide part 18 of the forming hole 17 through the ironing part 19 having a small inner diameter, and here, the cylindrical body material 1a passes through the ironing part 19 having a narrower interval than the wall thickness dimension of the cylindrical body material 1a and the core metal. It is squeezed (squeezed) between the part 12 and dropped to the falling part 20.

By this ironing (drawing), the cylindrical body material 1a is plastically flowed from both sides as shown by the arrow in Fig. 3a, so as to fill the V-shaped gap g at the seam 2 of both end faces, and the inner peripheral side Finally, as shown in FIG. 3B, the entire surface is brought into close contact with no gaps from the inner peripheral surface side to the outer peripheral surface side and throughout the entire axial direction.

In addition, during the above-mentioned forming, the cylindrical body material 1a passes through the ironing part 19 of a predetermined length while being supported by the core metal part 12 on the inside, so that plastic flow in the circumferential direction and axial direction of the cylindrical body material 1a is caused. The elongation is sufficiently supported by the core metal part 12 having a large height dimension _H1 ,
Uniformly formed over the entire axial length.

In this way, the iron-formed cylindrical body 1 is produced by plastic deformation of the cylindrical body material 1a, so that spring back hardly occurs and it is obtained in a stable state with little variation and high precision.

In addition, the ironing rate of the cylindrical body material 1a by the ironing die 16, that is, the ratio of the decrease in the wall thickness after passing through the ironing die 16 to the thickness before passing through the ironing die 16, is larger with respect to the wall thickness dimension of the cylindrical body material 1a. Although the finished product will have a good finish, it may be, for example, about 5 to 10%, and depending on the material, it may be less than this.

In addition, during implementation, the ironing process for the cylindrical body material 1a is not limited to one time, but may be performed multiple times through the ironing die 16 in which the inner diameter D ₃ of the ironing part 19 of the forming hole 17 is successively reduced. In this case, one stroke of the punch 11 passes through one stage of ironing die 16 two or more times, or one stroke of the punch 11 passes through two or more stages of ironing. What is necessary is to pass it through the die 16.

According to the present invention, the cylindrical material to be formed, which has been rounded from a flat material and abutted against each other with both end surfaces unjoined, is attached to the outer circumferential surface of the core metal part of the punch, and as the punch descends, the cylindrical material is pressed. The cylindrical material to be formed is pushed down in the axial direction by the moving surface and press-fitted into the ironing part in the forming hole of the ironing die, thereby forming the cylindrical material to be formed from the outer surface into the ironing part with a narrower interval than the wall thickness dimension. Since the cylindrical material is ironed between the core metal part and the core metal part, the inner circumferential surface of the cylindrical material is supported by the core metal part with a large height dimension over the entire axial length, and by passing through the ironing part of a predetermined length, the cylindrical material is formed into a cylindrical shape. The elongation of the body material due to plastic flow in the circumferential direction and axial direction is sufficiently supported by this core metal portion. Therefore, the cylindrical material is uniformly plastically deformed, and after forming, the spring back force in the direction of opening the abutting portions on both ends can be almost eliminated, and a cylinder with an inner diameter corresponding to the planned diameter of the core metal part can be formed. The body can be manufactured with high precision and efficiency. Also,
The distance between the abutting portions on both end faces of the product can also be formed to a relatively arbitrary dimension, and even when the abutting portions are brought into close contact with each other if necessary, the abutting portions can be formed easily and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a cylindrical body formed by the method of the present invention, FIG. 2 is a longitudinal sectional view showing an example of the apparatus used in the method of the present invention, and FIGS.
b is an explanatory diagram of the ladder forming process. 1... Cylindrical body, 1a... Cylindrical body material, 11...
Punch, 12... Core metal part, 13... Pushing surface, 16
...Stretching die, 17...Forming hole, 19...Stretching part, D ₁ ...Outer diameter of the core metal part, D ₃ ...Inner diameter of the ironing part of the forming hole, H ₁ ...Height of the core metal part Dimensions, _H2 ...
...Axial height dimension of cylindrical body material.

Claims (1)

[Scope of Claims] 1 A cylindrical material as a primary molded product is formed by rounding a flat material and abutted against each other with both end surfaces in an unjoined state, and a punch and ironing die are formed from this cylindrical material to be formed. The punch has a lower part having an outer diameter corresponding to the inner diameter of the cylindrical body and a height larger than the axial height dimension of the cylindrical body material to be formed. The ironing die is provided with a cylindrical core portion having a dimension of A circular forming hole is formed, the inner diameter of which is smaller than the wall thickness of the cylindrical material to be formed, and the cylindrical part having a predetermined length in the axial direction. , Attach the cylindrical material to be formed to the outer circumferential surface of the core metal portion at the bottom of the punch, then lower the punch and axially push the cylindrical material to be formed by the pushing surface at the top of the core metal portion. A method for forming a cylindrical body, characterized by pressing down and press-fitting into the ironing part of the forming hole of the ironing die, and ironing forming.