JP2009052628A - Using method of molded bellows and vacuum valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molded bellows reduced in its length by a thinner thickness, a higher crest, a narrower pitch and the smaller number of the crests than a conventional pressure type molded bellows. <P>SOLUTION: The using method of the molded bellows having the plurality of crests is provided with a step for inward expanding an outward protruded shape of a side wall part constituting a part between a trough part and a crest part of the crest into a protruded shape by applying a fluid pressure to the outer side of the molded bellows, and a step for compressing or expanding the molded bellows in such the displacement that the side wall parts expanded in the inward protruded shape are not abutted on each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for using a molded bellows and a vacuum valve having the molded bellows.

  Molded bellows are metallic expansion and contraction pipes made by forming a cylinder (pipe) from a metal material, placing the metal pipe in a mold, and introducing a high-pressure fluid inside the metal pipe. As a gas or liquid hermetic sealing member provided with stretchability, airtightness, and spring property, it is used in various applications such as expansion joints for piping, mechanical seals, vacuum valves, and the like.

  In addition, vacuum valves for vacuum circuit breakers that use molded bellows shut off the vacuum rather than the insulating gas in the gas insulated switchgear (hereinafter referred to as “GIS”) in which the insulating gas is sealed. Because of its high performance, it may be used. In that case, since the pressure of the insulating gas is high (for example, 0.3 MPa or more), the molded bellows used for the vacuum valve for a vacuum circuit breaker needs to have a structural feature that can withstand the high pressure.

Hereinafter, as an example of a molded bellows used for a vacuum valve, an internal pressure type molded bellows which is a molded bellows when a high-pressure fluid is passed inside will be described with reference to FIG.
In the vacuum valve shown in FIG. 1, a vacuum vessel is constituted by the insulating cylinder 1, the fixed side flange 2, and the movable side flange 3, and an airtight structure for moving the movable electrode 6 and maintaining a vacuum is secured by the internal pressure molded bellows 10. One end of the insulating cylinder 1 is sealed with a fixed flange 2 and a movable flange 3 is sealed with the other end. The internal pressure type molded bellows 10 is sealed in the movable lead rod 7 and sealed in the movable side flange 3 at the distal end portion in a state of entering the insulating cylinder 1. The fixed electrode 5 is fixed to the tip of the fixed lead rod 4, and the fixed lead rod 4 penetrates the fixed side flange 2 and is sealed. The movable lead rod 7 having the movable electrode 6 fixed to the tip penetrates the internal pressure type molded bellows 10 and moves the movable electrode 6 in parallel as indicated by an arrow 18 in order to contact and dissociate the fixed electrode 5 and the movable electrode 6. Let

  Such an internal pressure-type molded bellows is employed for a normal vacuum valve of atmospheric specification (0.1 MPa). However, the pressure inside the internal pressure mold bellows 11 increases the pressure of an insulating gas such as SF6 gas sealed in the GIS to improve the insulation performance of the GIS, and the internal pressure mold. When the pressure difference between the inside and outside of the molded bellows is large so that the pressure on the outside 12 of the bellows becomes a vacuum, non-uniform deformation occurs in the radial direction, and the valley portion 14 is reversed to form a peak portion 13. It is known to cause a buckling phenomenon of deformation. Therefore, the internal pressure type molded bellows has an extremely short life in the case where the pressure inside the molded bellows becomes high.

  Therefore, an external pressure-type molded bellows is used as a molded bellows that is resistant to buckling even with a high differential pressure. FIG. 2 is a diagram showing an external pressure molded bellows employed in a vacuum valve installed in the GIS. The vacuum valve 30 shown in FIG. 2 includes a vacuum vessel composed of the insulating cylinder 1, the fixed flange 2, and the movable flange 3, and the external pressure molded bellows 20 ensures an airtight structure for moving the movable electrode 6 and holding the vacuum. . One end of the insulating cylinder 1 is sealed with a fixed flange 2 and a movable flange 3 is sealed with the other end. The external pressure molded bellows 20 is disposed outside the vacuum container, and its base end is sealed to the movable flange 3 and the other end is sealed by penetrating a movable lead rod 7 having a movable electrode 6 fixed to the tip. Has been. That is, the movable electrode 6 that is the tip of the external pressure molded bellows 20 is fixed to the movable lead rod 7 in a state where the external pressure molded bellows 20 is externally attached to the insulating cylinder 1. The movable lead bar 7 is connected to a current collector 25 connected to a high-voltage circuit via a flexible conductor 26 and a conductor 27, and the movable lead bar 7 is driven by an operating device (not shown) via a link 28. Is done. The fixed electrode 5 is fixed to the tip of the fixed lead rod 4, and the fixed lead rod 4 penetrates the fixed side flange 2 and is sealed. By driving with the operating device, the movable lead rod 7 moves as indicated by an arrow 18, and by moving the movable electrode 6 in parallel, the fixed electrode 5 and the movable electrode 6 come into contact / dissociation.

  Since the vacuum valve 30 is installed in a GIS in which an insulating gas such as SF6 gas is sealed, the pressure inside the external pressure molding bellows 21 becomes a vacuum, and the pressure outside the external pressure molding bellows 22 The pressure of the insulating gas becomes a high pressure of 0.3 MPa or more. When performing the dissociation operation in which the movable lead bar 7 moves to the right of the arrow 18, the external pressure molded bellows inner side 21 is in a vacuum, so that the deformation as described above is unlikely to occur. Therefore, when a molded bellows for a vacuum valve is installed in a GIS filled with a high-pressure insulating gas, an external pressure-type molded bellows is used (for example, Patent Document 1).

Hereinafter, the shape of the molded bellows will be described with reference to FIG.
FIG. 3A is a diagram showing an axial cross-sectional shape of an external pressure molded bellows, and FIG. 3B is a diagram showing compression and expansion of the external pressure molded bellows in a state where a side wall inversion phenomenon occurs due to external pressure. is there. The molded bellows 40 shown in FIG. 3 (a) is molded along the mold, and has a peak portion M1a, a valley portion V1a, and a side wall portion S1a. The pitch Q between the peak portions M1a and the peak height W is determined. Further, in the molded bellows 40, a residual stress generated in the pipe at the time of molding becomes a driving force, and a spring back which is a deformation that recovers elastically occurs, and the side wall portion S1a of the molded bellows 40 is convex outward as indicated by a width b. Is inflated.

  A molded bellows C1 shown in FIG. 3B shows the molded bellows 40 in a state where no external pressure is applied. C2 has a molded bellows shape in which the convex portion of the side wall is inverted from the outside to the inside and compressed by applying an external pressure excessively. As shown in FIG. 3 (b), when the external pressure molded bellows is placed in a high-pressure gas, when a pressure difference is generated between the inside and outside of the molded bellows, the peak is compressed and the valley is expanded. When the pressure is increased and the pressure is further increased, the side wall of the external pressure-type molded bellows that is convex outwards is deformed inwardly (hereinafter referred to as “side wall inversion phenomenon”). For this reason, like the molding bellows C2, the approaching part between the side walls moves from the outside to the inside, and the side walls on the inside approach each other.

  In order to avoid such a side wall inversion phenomenon, a normal external pressure molded bellows usually has a high pressure resistance by increasing the plate thickness, decreasing the height of the peaks, increasing the pitch, and increasing the number of peaks. In other words, the normal external pressure molded bellows determines, as the first design condition, the shape of the mountain such as the plate thickness, the height of the mountain, the pitch, etc. in order to avoid the side wall inversion phenomenon caused by the high differential pressure, As a second design condition, the molded bellows is designed in the order of determining the number of peaks from the required design displacement. Therefore, compared with the non-external pressure type molded bellows that is designed ignoring the first design condition, the normal external pressure type molded bellows has a small plateau and a small displacement amount due to a thick plate thickness. Therefore, the number of peaks increases, and the bellows length becomes longer with respect to the design displacement. That is, the normal external pressure molded bellows tends to have a longer bellows length as the differential pressure increases with respect to the design displacement.

  However, devices such as a vacuum valve using an external pressure molded bellows having a long bellows length cause a disadvantage that the manufacturing cost is increased due to an increase in the size of the external pressure molded bellows, and a GIS that houses a vacuum valve or the like. The occupied volume of the vacuum valve in the apparatus is increased, leading to an increase in size of the apparatus, increasing the overall dimensions of the apparatus, and increasing the manufacturing cost of the apparatus.

JP-A-60-205926

  In view of the above-described problems, the present invention allows a side wall reversal phenomenon that occurs in a molded bellows in a high differential pressure state, and makes maximum use of the elastic deformation of the molded bellows, It is an object of the present invention to provide a molded bellows that shortens the molded bellows by a thin plate thickness, a high peak, a narrow pitch, a small number of peaks, and the like.

  In order to solve the above-mentioned problem, the method of using a molded bellows having a plurality of peaks according to the present invention is to mold a shape in which the side wall portions between the valleys of the peaks and the peaks are bulged outwardly. And a step of applying fluid pressure to the outside of the bellows to inflate in a convex shape, and a step of compressing or expanding the molded bellows with a displacement in which the side walls inflated in a convex shape do not contact each other. And

  The step of compressing or expanding may include the step of compressing or expanding so that the side wall portions bulging inwardly in a convex shape do not contact each other by setting the amount of compression displacement of the molded bellows to be equal to or less than the amount of expansion displacement.

  In order to solve the above-mentioned problem, a vacuum valve according to the present invention is a molded bellows having a plurality of peaks, which forms a valley between peaks and a peak, and fluid pressure outside the peaks. A molded bellows having a side wall portion that has a shape bulging inward by loading, a vacuum container in which the molded bellows is arranged outside, and airtightly joined to the inside of the molded bellows to penetrate into the vacuum container, A movable lead rod that moves the movable electrode by moving or moving the movable electrode by compressing or expanding the molded bellows with a movable electrode at the tip and a side wall that bulges inwardly so as not to contact each other. And a fixed electrode that is disposed in a direction opposite to the electrode and that is connected to or disconnected from the movable electrode by movement of the movable lead rod.

  In addition, the compression or expansion of the molded bellows may be performed by compressing or expanding the side walls of the molded bellows that protrude inward so as not to contact each other by setting the compression displacement amount of the molded bellows to be equal to or less than the expansion displacement amount.

  As described above, the present invention allows the side wall reversal phenomenon that occurs in the molded bellows in a high differential pressure state, and makes maximum use of the elastic deformation displacement of the molded bellows, compared with the conventional pressure-type molded bellows. It is possible to provide an external pressure type molded bellows that shortens the molded bellows with a thin plate thickness, a high peak, a narrow pitch, a small number of peaks, and the like.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 4 is a view showing a side wall inversion molded bellows according to the present invention.
C1 shows a molded bellows in a state where no external pressure is applied, and is formed along the mold to have a peak portion M1b, a valley portion V1b, a side wall portion S1b, and a pitch Q between the peak portions M1b; The height W of the mountain is determined. Further, in the molded bellows, the residual stress generated in the pipe at the time of molding becomes a driving force, and a spring back that is a deformation that recovers elastically occurs, and the side wall portion S1b of the molded bellows bulges outward as shown by the width b. Yes. C2 is a bellows shape in which the side wall portion S1b is reversed and compressed by applying an external pressure, and E2 is a form of an external pressure molded bellows when it is expanded from C2.

C3 is a form of an external pressure molded bellows when further compressed from C2. In the state indicated by C3, the inverted side wall portions S1c are in close contact with each other. If a force for compressing the external pressure molded bellows is further applied in this state, the bellows is not compressed and stress is applied to the valley portion V1c. The life of the external pressure molded bellows will be shortened.
Therefore, the method for using the molded bellows according to the present invention repeats compression and expansion between the compressed state of the external pressure molded bellows before the side wall contact shown in C2 and the expanded state of the external pressure molded bellows shown in E2.

Fig.5 (a) is a figure which shows the form of the side wall inversion shaping | molding bellows which concerns on this invention, (b) is a figure which shows the form of the normal shaping | molding bellows in which the side wall part protruded convexly outside.
The peak of the bellows is the portion where the metal pipe is most extended, so the plate thickness is thin and supple (the elastic deformation range is large). Since it is not a stretched portion, the plate is thick and has a high rigidity. In addition, when the bellows in which the side wall of the normal molded bellows 55 shown in FIG. 5 (b) is bulged outward is compressed, the stress concentration portion is the valley portion V1d, and the valley portion V1d is compressed as described above. Stress concentration that causes fatigue failure is likely to occur due to the high rigidity in the direction. However, a normal molded bellows is used with a large amount of displacement on the compression side. %, And at the time of extension 56, it is used at a ratio of about 40%.

  As shown in FIG. 5 (a), the molded bellows 51 according to the present invention is higher than the normal external pressure molded bellows 55 and / or has a thin plate thickness, so that the molded bellows is used. When a predetermined pressure is applied, the side wall is reversed by the pressure difference between the outside and inside of the molded bellows. Further, the molded bellows 51 according to the present invention is higher in the peak and / or thinner than the normal external pressure-type molded bellows 55, so that the maximum allowable bending deformation amount for both the peak M1e and the valley V1e. As shown in the molded bellows 52 when stretched, it is possible to increase the amount of displacement per mountain. Therefore, the number of peaks can be reduced with respect to the design displacement amount of the molded bellows, compared to the normal high-pressure molded bellows 55.

On the other hand, since the side wall portion of the side wall inversion molded bellows 53 during compression according to the present invention swells inward, the side wall easily comes into contact with the compression direction. However, since the deformation amount due to the spring back is less than 20% with respect to the free length pitch, as will be described later, the inner wall does not come into contact even when the compression side displacement amount of the normal molded bellows is 60%. However, the side wall inversion molded bellows 51 according to the present invention has a large permissible displacement amount per mountain, but the displacement amount on the compression side needs to be a displacement amount that is less than the maximum permissible bending deformation amount and avoids side wall contact. .
In order to avoid contact with the inner wall, the intermediate value of the design displacement is not set to the natural length of the bellows. By shifting to the expansion side, the compression side displacement is small and the expansion side displacement is large.

  Table 1 below shows JIS B 2352-2005 Annex 2 (Reference) Strength Evaluation Criteria for Bellows Type Expansion Pipe Joints (Section 3.4: Strength Calculation for Bellows Without Reinforcement Ring (ASME / ANSI B 31.3 APPENDIX) X is a physical property value of a molded bellows calculated based on the following.

  The right column of Table 1 is a physical property value of the molded bellows considered to have undergone side wall inversion according to the present invention, and the left column is a physical property value related to a normal molded bellows. In this calculation, in the physical properties of the molded bellows shown in the right column of Table 1, the height W of the bellows mountain is made higher than that of a normal molded bellows (7.75 mm to 10.0 mm), and the surface area of the bellows is increased. Made relatively large. Accordingly, the axial bending stress due to pressure (the sum of axial film stress S3 due to pressure and axial bending stress S4 due to pressure) is 695 N / mm2 which is the value of S3 + S4 of the bellows in the left column, and the bellows of the bellows in the right column. The S3 + S4 value is increased to 1243 N / mm2, and the S3 + S4 exceeds the allowable stress 1200 N / mm2 obtained by the product of Shb and Cm in Table 1. Therefore, the molded bellows shown in the right column of Table 1 has a side wall inversion phenomenon. It is thought that it has occurred.

  Also, the molded bellows in the right column of Table 1 has no significant difference in St (stress range due to the total movement of the pressure and bellows) compared to the molded bellows in the left column of Table 1 (the left column is 1388 (N / For the mm2), the right column is 1465 (N / mm2)), and the molded bellows shown in the right column and the left column of Table 1 are considered to have no significant difference in the bellows life.

Table 2 shows the displacement of the molded bellows calculated based on the result calculated in Table 1. The lower row of Table 2 shows the displacement of compression / extension of the molded bellows considered to have caused the side wall inversion shown in the right column of Table 1, and the upper row of Table 2 shows the compression / extension of the normal molded bellows shown in the left column of Table 1. Indicates the displacement. As shown in Table 1, the molded bellows in which side wall inversion is considered to occur has a mountain pitch W higher than that of a normal molded bellows (7.75 mm to 10.0 mm). The q becomes smaller (4.35 mm to 4.21 mm), and the number N of necessary peaks for the total axial displacement 40 mm is also reduced (23.0 to 22.0). Therefore, as shown in Table 2, it can be seen that the molded bellows in which side wall inversion is considered to have a shorter length of compression, natural length, and extension than a normal molded bellows.
From the above, as shown in Table 1 and Table 2, from the physical properties of the molded bellows calculated based on JIS, by allowing the side wall inversion phenomenon of the molded bellows, each of the compression bellows compression, natural length, and extension It can be seen that the length can be shortened.

  Furthermore, as described above, in the side wall inverted molded bellows, the maximum allowable bending deformation amount per mountain is larger than that of a normal high pressure type molded bellows due to the change in the shape of the ridges and valleys due to the side wall inversion from the viewpoint of material mechanics. Therefore, the number of peaks with respect to the design displacement amount of the side wall inverted molded bellows is smaller than that of a normal molded bellows. However, since the change in the allowable bending deformation amount based on the change in the shape of the peaks and valleys is not taken into account in the JIS calculation formula, the actual sidewall inversion molding bellows is a molding in which the side wall inversion shown in Table 2 occurs. From the bellows displacement calculation results, it is clear that the compression, natural length, and extension are all small.

  FIG. 6 is a diagram showing an experimental apparatus for verifying the durability of the sidewall inversion molded bellows according to the present invention. In this apparatus, a side wall inversion molded bellows 61a and a side wall inversion molding bellows 61b are connected to each other around a member 63, and each side wall inversion molding bellows 61b is connected to a vacuum vessel 62a and a vacuum vessel 62b simulating a vacuum valve. Has been. The durability test of the sidewall-reversed molded bellows is performed by reciprocating these two sidewall-reversed molded bellows with a fixed displacement in the horizontal direction by a driving device (not shown).

  FIG. 7 is a diagram showing a graph showing experimental results of examining the lifetime of the sidewall-reversed molded bellows according to the present invention. An example of an experiment conducted for examining the bellows life is shown below.

Experimental example 1
External vacuum type molded bellows 61b, vacuum tube 61b, overall length 122mm, metal fitting length 29mm, bellows length Lb = 93mm, pitch q = 4.67mm, number of peaks N = 20, peak height W = 10mm, QW value (q / [2W]) = 0.233 (QW value is an index indicating the shape of the bellows), QDT value (q / [2.2√ (Dmtp)]) = 0.78 Then, after setting it in a high pressure vessel in a state extended 27 mm from the bellows length Lb and filling a 0.7 MPa insulating gas to form a side wall inversion molded bellows, a stroke 40 mm (extension side 27 mm, compression side) 13 mm) continuous stretch test. The side wall inversion molded bellows expansion / contraction result 71b cracks at 50000 times (N = 11 on the graph), and has the same durability as the expansion / contraction number result 72b of a normal high-pressure molded bellows with the same QW value. confirmed.

Experimental example 2
Similarly, after compressing the external pressure type molded bellows 61a from the bellows length Lb 93 mm to 32 mm to 61 mm and filling it with 0.7 MPa insulating gas to form a sidewall-reversed molded bellows, the stroke 40 mm (extension) A continuous expansion and contraction test of 8 mm on the side and 32 mm on the compression side was performed. The expansion / contraction frequency result 71a of the side wall inversion molded bellows cracked at 4500 times (N = 1 on the graph), and it was confirmed that the durability was inferior to the expansion / contraction frequency result 71b of the normal high-pressure molded bellows.

  From the calculation results based on JIS shown in Table 1, the molded bellows in which the side wall inversion occurred has no significant difference in St (stress range due to the total movement of the pressure and bellows) compared to the normal molded bellows. Therefore, it is considered that there is no big difference in the bellows life, but as can be seen from Experimental Example 1, the side wall inversion molded bellows has an extension of 67% (27 mm / 40 mm) and a compression side of 33% with respect to the bellows length Lb (93 mm). When used at (13 mm / 40 mm), the side wall contact on the compression side does not occur, so the bellows life is almost the same as the normal high-pressure molded bellows, and even if the side wall is inverted, the bellows life It was confirmed by experiments that there was no significant difference in

  As can be seen from Experimental Example 2, when the bellows length Lb (93 mm) is used at a compression of 80% (32 mm / 40 mm) and an expansion side of 20% (8 mm / 40 mm), side wall contact on the compression side occurs. It can be seen that the lifetime of the bellows is shorter than that of a normal high-pressure molded bellows. Therefore, it has been confirmed by experiments that the side wall-reversed molded bellows has a shorter lifetime than the normal molded bellows when the side wall contact occurs.

  As described above, the side wall inversion molded bellows according to the present invention allows the side wall reversal phenomenon that occurs in the bellows in a high differential pressure state to compress and expand, and the compression side displacement becomes a displacement that does not cause side wall contact, and a larger displacement is caused on the expansion side. By taking it, the same life as a normal molded bellows can be obtained. And as demonstrated in relation to Table 1 and Table 2, the side wall inversion molding bellows which concerns on this invention can shorten a molding bellows by a high peak, a small peak number, etc. compared with the conventional pressure type molding bellows. It is.

  The side wall inverted molded bellows according to the present invention shown in FIGS. 3 to 5 can be applied as the molded bellows 20 of the vacuum valve 30 shown in FIG. 2, but the application is not limited to the vacuum valve 30. However, the present invention is applicable to any expansion joint for piping, mechanical seal, and the like that require a seal because a differential pressure is generated inside and outside the molded bellows.

It is a figure which shows an internal pressure type shaping | molding bellows. It is a figure which shows the external pressure type | mold shaping | molding bellows employ | adopted as the vacuum valve installed in GIS. It is a figure which shows the shape of a shaping | molding bellows. It is a figure which shows the side wall inversion molding bellows which concerns on this invention. (A) is a figure which shows the form of the side wall inversion shaping | molding bellows which concerns on this invention, (b) is a figure which shows the form of the normal shaping | molding bellows which the side wall part bulged convexly outside. It is a figure which shows the experimental apparatus which verifies durability of the side wall inversion molding bellows which concerns on this invention. It is a figure showing the graph which shows the experimental result which examined the lifetime of the side wall inversion molding bellows which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation cylinder 2 Fixed side flange 3 Movable side flange 4 Fixed lead rod 5 Fixed electrode 6 Movable electrode 7 Movable lead rod 10 Internal pressure type bellows 20 External pressure type bellows 25 Current collector 26 Flexible conductor 27 Conductor 28 Link 30 Vacuum valve 40 Molded bellows 61a, 61b Side wall inversion molded bellows 62a, 62b Vacuum container 63 Member

Claims (4)

A method of using a molded bellows having a plurality of peaks,
The step of inflating the outer side of the molded bellows with the fluid pressure on the outer side of the molded bellows, and the side wall constituting the valley between the peaks and the ridges bulges inward.
Compressing or expanding the molded bellows with a displacement in which the side walls protruding inwardly do not contact each other;
A method of using a molded bellows characterized by comprising:   2. The compression or expansion step includes a step of compressing or expanding the side wall portions bulging in a convex shape so as not to contact each other by setting the compression displacement amount of the molded bellows to be equal to or less than the expansion displacement amount. The method described in 1. A molded bellows having a plurality of peaks, the side wall having a shape that is formed between the valleys of the peaks and the peaks and is bulged inward by applying fluid pressure to the outside of the peaks A molded bellows having
A vacuum container for arranging the molded bellows outside;
Airtightly joined to the inside of the molded bellows, penetrates into the vacuum vessel, has a movable electrode at the tip, and compresses the molded bellows with a displacement in which the side walls that bulge inwardly do not contact each other Or a movable lead bar that moves the movable electrode by stretching;
A fixed electrode that is disposed in a direction opposite to the movable electrode in the vacuum vessel and is connected to or dissociated from the movable electrode by movement of the movable lead rod;
A vacuum valve characterized by comprising:   The compression or expansion of the molded bellows is performed by compressing or expanding the side wall portions bulging inwardly so as not to contact each other by setting the compression displacement amount of the molded bellows to be equal to or less than the expansion displacement amount. The vacuum valve described.

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