JPH11226658A - Diaphragm type formed bellows and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability so as to be also used in such a use as generating not only a deformation in a compressing direction but also a deformation in an extending direction and a pressure difference between inside and outside a bellows. SOLUTION: Working is executed by a working force becoming a specific pressure of <=700 Kgf/cm<2> when a material of 20%-40% in elongation is used and working is executed by the working force becoming the specific pressure of <=100 Kgf/cm<2> when a material of >40% in elongation is used so that the ratio R min/t of the minimum bending radius R min to a plate thickness (t) becomes >=0.8. In such a,manner, a compressed wrinkle by strong working is not generated inside bending in an R shape part in a tip end and stress is not concentrated in the part. Therefore, durability is improved because durability is not reduced even though a bellows is used in a tensile side and also stress is not concentrated as well even though the pressure difference is generated inside and outside the bellows.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm type bellows used for a sealing function and a spring function and a method for manufacturing the same.

[0002]

2. Description of the Related Art A diaphragm-shaped bellows having a sectional shape as shown in FIG. 6 is very advantageous in terms of space because it can have a small contact length and a free length (pitch) as compared with a so-called U-shaped bellows. In addition, there is an advantage that the production is easy and the cost is low as compared with the welding bellows having the same shape. As a manufacturing method thereof, an elastic body such as rubber is put into a material processed into a cylindrical shape and pressurized to inflate the material one by one as disclosed in, for example, Japanese Patent Publication No. 1-52095. There is a method of deforming the mountain with a mold that covers the outside so as to crush the mountain in the axial direction. In addition, a liquid is filled into the material processed into a cylindrical shape, pressure is applied, and the outer periphery is pressed by one or a plurality of annular molds to form a mountain, and the mountain is axially moved with the mold. There is also a hydraulic forming method in which deformation is performed one by one or completely.

A bellows preformed by these methods is subjected to a shaping step using a shaping die in order to further obtain a desired cross-sectional shape.

[0004]

However, as shown in FIGS. 7 (a) and 7 (b), which are enlarged parts of FIG. 6, the conventional diaphragm-type molded bellows has a bent shape at the tip R-shaped portion. Compressed wrinkles are generated inside due to strong processing.
Here, the ratio Rmin / t between the minimum bending radius (Rmin) and the bellows plate thickness (t) of the diaphragm-shaped molded bellows shown in FIGS. 6 and 7 is about 0.4. This wrinkle does not become a starting point of stress concentration if the bellows is used on the compression side, but if there is a pressure difference inside or outside the bellows or if the bellows is used for tension (extension), it will be at the wrinkled part. There is a problem that it cannot be used for such an application because it is easily broken at an early stage due to stress concentration.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its main object not only deformation in the compression direction but also deformation in the expansion direction, and a pressure difference between the inside and outside of the bellows. It is an object of the present invention to provide a diaphragm-shaped molded bellows which can be used for various applications and has improved durability and a method for producing the same.

[0006]

According to the present invention, there is provided a diaphragm-type molded bellows according to the present invention, wherein a ratio Rmin / t between a minimum bending radius and a plate thickness is 0.8 or more. , And the ratio Rmi between the minimum bending radius and the plate thickness
This is a method for producing a diaphragm-shaped molded bellows having an n / t of 0.8 or more, and when a material having an elongation of 20% to 40% is used, it is processed with a processing force of 700 kgf / cm ² or less. However, when a material having an elongation of more than 40% is used, it is attained by providing a method for producing a diaphragm-type molded bellows, characterized in that the material is processed with a processing force of a surface pressure of 100 kgf / cm ² or less. You.

[0007]

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

FIG. 1 is a sectional view of a main part of a diaphragm-shaped molded bellows to which the present invention is applied.
(B) is an enlarged view of the main part. As a material of this bellows, elongation is 20% to 40% (JIS Z224).
1) as small as possible, that is, those that do not crack but cannot be easily bent, for example, SUS631, SUS630,
Stainless steel such as SUS410 or nickel alloy such as Inconel 718 is used. Further, the ratio Rmi between the minimum bending radius and the plate thickness at the tip R-shaped portion of the bellows.
n / t is 0.8 or more. By using a material that is relatively hard to bend so that the tip R-shaped portion is not unnecessarily crushed, that is, by defining the ratio between the minimum bending radius and the plate thickness at the tip R-shaped portion, FIG. As shown in (a) and (b), no wrinkles are generated inside the bend at the tip R-shaped portion, and the bellows can be used in the extension direction.

FIGS. 3A to 3C show a molding procedure of the bellows by a hydraulic molding method. The mold to be used is an upper mold part 1 and a lower mold part 2 which close both ends of a cylindrically processed material M in a liquid-tight manner, and are disposed at equal intervals in the axial direction at an intermediate portion thereof. And a plurality of intermediate portions 3 forming an annular shape to surround. Further, a liquid for supplying an internal pressure is filled in the tubular material M sealed by the upper mold part 1 and the lower mold part 2, and the liquid pressure is supplied from the lower mold part 2 side. Note that the annular intermediate portion 3 of the mold is divided into two parts, and is assembled so as to form an annular shape when the cylindrical material M is set.

First, as shown in FIG. 3A, a predetermined internal pressure is supplied into the tubular material M to cause the tubular material M to bulge radially outward. At this time, the portion pressed by the annular intermediate portion 3 does not swell. Then, the upper mold part 1, the plurality of intermediate parts 3 and the lower mold part 2 are gradually approached as they bulge (FIG. 3B). Then, the swollen portion of the tubular material M buckles in the axial direction to form the basic shape of the bellows (preliminary molding).

Next, as shown in FIG. 4, the preformed bellows is wrapped around a cylindrical cored bar 11 and is sandwiched between upper and lower forming dies 12 and 13 having an S-shaped cross section. The bellows are pressed by the pressing members 14 and 15 having the shape of a circle to form the final shape of the bellows.

At this time, when a material having an elongation of 20% to 40% is used, the surface pressure is adjusted so as to be 700 kgf / cm ² or less, and the ratio Rmin / t between the minimum bending radius and the plate thickness is adjusted.
Is 0.8 or more. When a material having an elongation exceeding 40% is used, the surface pressure is 100 kgf / c.
If it is adjusted so as to be equal to or less than m ² , Rmin / t is set to 0.1.
8 or more.

The thus formed diaphragm-shaped molded bellows includes an expansion joint for piping, an accumulator, a seal for a non-leak valve, a pressure detection device (detects expansion and contraction of the bellows due to a difference in pressure between the inside and outside of the bellows), a pressure control device, a temperature control device and the like. Can be used for

FIG. 5 shows the results of a durability test of only expansion and contraction (no pressure difference between the inside and outside of the bellows). From this graph, it can be seen that the durability does not decrease even when used under tension, and the durability is equivalent to that when used only under compression. In addition, by using a material having a small elongation of 20% to 40% as the material of the bellows (SUS631), the durability can be improved by a factor of 10 or more as a whole in conjunction with the change in shape.

On the other hand, the present invention can be used for applications in which a pressure difference occurs between the inside and outside of the bellows. As a result of performing FEM analysis when a pressure of 4 kgf / cm ² was applied to the inside of the bellows according to the present invention, the maximum principal stress was 70 kgf / m before the shape change.
m ² was 31 kgf / mm ² after the change, and the stress was reduced by about 56%.

[0016]

As is apparent from the above description, according to the diaphragm-shaped molded bellows and the method of manufacturing the same according to the present invention, the ratio Rmin / t between the minimum bending radius and the plate thickness is set to 0.8 or more. When a material having an elongation of 20% to 40% is used, the material is processed with a processing force of a surface pressure of 700 kgf / cm ² or less, and when a material having an elongation of more than 40% is used, 100 kgf / cm 2 is used. By processing with a processing force that results in a surface pressure of ² or less, compression wrinkles due to strong processing do not occur inside the bend at the tip R-shaped part, and since stress does not concentrate on that part, use it on the tension side. However, even if a pressure difference occurs between the inside and outside of the bellows, the stress is not similarly concentrated, so that the durability is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part of a diaphragm-type molded bellows to which the present invention is applied.

FIGS. 2A and 2B are enlarged views of a main part of FIG.

FIGS. 3A to 3C are diagrams showing a molding procedure of a bellows by a hydraulic molding method.

FIG. 4 is a view showing a shape forming step after preforming of bellows.

FIG. 5 is a graph showing the results of a durability test by repeated expansion and contraction of a diaphragm-shaped molded bellows to which the present invention is applied.

FIG. 6 is a sectional view of a main part of a conventional diaphragm-type molded bellows.

FIGS. 7A and 7B are enlarged views of a main part of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper mold part 2 Lower mold part 3 Annular middle part 11 Core metal 12 and 13 Vertical molding type

Claims (5)

[Claims] 1. The ratio of the minimum bending radius to the thickness Rmin /
A diaphragm-shaped molded bellows, wherein t is 0.8 or more. 2. The diaphragm-type formed bellows according to claim 1, wherein the bellows is made of a material having an elongation of 20% to 40%. 3. The ratio of the minimum bending radius to the plate thickness Rmin /
A method for producing a diaphragm-shaped molded bellows in which t is 0.8 or more, wherein a material having an elongation of 20% to 40% is used.
If the material is processed with a processing force that results in a surface pressure of 0 kgf / cm ² or less and the elongation exceeds 40%, 100 k
A method for producing a diaphragm-shaped molded bellows, characterized by processing with a processing force that provides a surface pressure of gf / cm ² or less. 4. The diaphragm mold according to claim 3, wherein the manufacturing process includes a preforming step and a shaping step after the preforming, and the processing is performed in the shaping step. Manufacturing method of molded bellows. 5. The method according to claim 4, wherein the preforming step is performed by hydraulic forming.