accumulator

Abstract

To provide an accumulator using an S-shaped bellows, which can reduce its weight while suppressing deterioration in durability.SOLUTION: An accumulator according to the present invention comprises an exterior body comprising a bottom, a shell, and a port, and a flexible S-shaped bellows provided inside the exterior body. When the bellows maximally expands in the accumulator, the bellows expands relative to a free state in which no load other than gravity is applied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates, for example, to an accumulator. [Background technology]

[0002] Conventionally, bellows have been used in accumulators as fluid separation membranes or fluid sealing membranes that are airtight and flexible (see, for example, Patent Document 1). Bellows are tubular members with bellows-shaped sides that are flexible and flexible. Bellows with bellows portions that are U-shaped or S-shaped are known. Bellows are also provided in an internal space formed by an exterior body that includes a bottom, a shell, and a port. In accumulators, S-shaped bellows are typically used in a manner that expands and contracts as they deform from a state in which no load other than weight is applied to a state in which they are compressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 187165 Summary of the Invention [Problem to be solved by the invention]

[0004] When weight reduction of accumulators is required, bellows must also be reduced in weight. In this case, for example, if an attempt is made to reduce the weight of material by reducing the number of peaks in the bellows section of an S-shaped bellows, the distance between the peaks (pitch) increases, which increases the amplitude per peak and may reduce the durability of the bellows.

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide an accumulator using an S-shaped bellows that can be made lighter while suppressing a decrease in durability. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the accumulator of the present invention is an accumulator comprising an exterior body consisting of a bottom, a shell, and a port, and an expandable and contractible S-shaped bellows provided inside the exterior body, wherein when the bellows is maximally expanded in the accumulator, the bellows is expanded relative to a free state in which no load other than gravity is applied.

[0007] In the accumulator according to the present invention, the elongation rate on the extension side of the bellows is set to be equal to or less than an allowable elongation rate calculated based on Weibull analysis.

[0008] Moreover, in the accumulator according to the present invention, the allowable elongation is 9.3%.

[0009] Furthermore, in the accumulator according to the present invention, in the above invention, the bellows is a cylindrical bellows that extends in an accordion-like shape, and is formed by repeating an outer circumferential folded portion provided on the outer circumferential side, an inner circumferential folded portion provided on the inner circumferential side, and a plurality of curved portions provided between the outer circumferential side and the inner circumferential folded portion, the curved portions having an opposite curved pattern to adjacent curved portions.

[0010] In addition, the accumulator according to the present invention is characterized in that, in the above invention, the bellows is formed using stainless steel. [Effects of the Invention]

[0011] According to the present invention, in an accumulator using an S-shaped bellows, it is possible to reduce the weight while suppressing a decrease in durability. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a cross-sectional view showing the configuration of an accumulator according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the bellows in region R shown in FIG. [Figure 3] FIG. 3 is a diagram for explaining expansion and contraction of a bellows applied to an accumulator. [Figure 4] FIG. 4 is a diagram for explaining the number of times the bellows can be extended or contracted before breaking. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. Note that the drawings are schematic, and the relationship between the thickness and width of each part, the thickness ratio of each part, etc. may differ from the actual ones, and the drawings may also include parts with different dimensional relationships and ratios.

[0014] (Embodiment) Fig. 1 is a cross-sectional view showing the configuration of an accumulator according to one embodiment of the present invention. The accumulator 1 shown in Fig. 1 includes a bottom 11, a shell 12, a port 13, a bellows 14 housed in an internal space formed by the bottom 11, the shell 12, and the port 13, a cap main body 15, a cap elastic portion 16, and a guide bellows 17. The bottom 11, the shell 12, and the port 13 form the exterior body of the accumulator 1. Here, the bottom 11 and the port 13 are formed, for example, using a cold-worked material, and the shell 12 is formed, for example, using a hot-worked material.

[0015] In the accumulator 1, the space formed by the bottom 11, shell 12, and port 13 is divided by the bellows 14. Specifically, different spaces are formed inside and outside the bellows 14. The internal space of the bellows 14 communicates with the outside via the hole 11a in the bottom 11. The external space of the bellows 14 communicates with the outside via the hole 13a in the port 13. FIG. 1 shows an example in which the central axes of the holes 11a and 13a coincide with the central axis N of the accumulator 1. The bottom 11, the shell 12 and the port 13 are fixed together by welding at their respective connecting portions.

[0016] In the accumulator 1, a liquid (hydraulic oil) or a gas (e.g., nitrogen gas) is sealed in the space formed by the exterior body and the bellows 14 (the bellows external space) and in the internal space of the bellows 14. For example, a liquid is introduced into the bellows external space, and a gas is sealed in the internal space.

[0017] Port 13 extends cylindrically and has introduction portion 131 which is an inlet for introducing liquid into shell 12 , and locking portion 132 which is connected to one end of introduction portion 131 and locks onto the inner wall surface of shell 12 .

[0018] The bellows 14 is cylindrical. The side surface of the bellows 14 is accordion-shaped with repeated concave and convex shapes, and expands and contracts under external load. Furthermore, the guide bellows 17 provided on the outer periphery of the bellows 14 maintains the gap between the shell 12 and the bellows 14, allowing for smooth expansion and contraction. The bellows 14 is made of, for example, stainless steel (SUS304). The guide bellows 17 is made of, for example, polybutylene terephthalate (PBT) or polyamide.

[0019] The shape of the bellows 14 will now be described in detail with reference to FIG. 2. FIG. 2 is an enlarged view of the bellows in region R shown in FIG. 1. The bellows 14 has five curved portions and two straight portions from the outer circumferentially folded portion to the inner circumferentially folded portion. Specifically, the bellows 14 has an outer circumferentially folded portion 141, an inner circumferentially folded portion 142, a first straight portion 143, a first curved portion 144, a second curved portion 145, a third curved portion 146, a fourth curved portion 147, a fifth curved portion 148, and a second straight portion 149. From the outer circumferentially folded portion 141 to the inner circumferentially folded portion 142, the first straight portion 143, the first curved portion 144, the second curved portion 145, the third curved portion 146, the fourth curved portion 147, the fifth curved portion 148, and the second straight portion 149 are located in this order. Each curved portion is curved in such a way that the curved manner of the adjacent curved portion is opposite to each other.

[0020] The bellows 14 has a bellows shape formed by repeating S-shaped protrusions, with the outer circumferential folded portion 141 as a peak and the inner circumferential folded portion 142 as a valley. For example, the outer diameter is 60 mm, the inner diameter is 43 mm, and the distance (pitch) between the peaks (outer circumferential folded portions 141) is set within a range of 1.9 mm to 2.4 mm. Furthermore, the length of the bellows in the expansion / contraction direction when adjacent protrusions are in close contact with each other (closed state) is 30% to 40% (for example, approximately 34%) of the length in the state where no load other than gravity is applied (free state). Conventional bellows have been designed so that the range of expansion / contraction in accumulators is within a range from the free state to the closed state.

[0021] Returning to FIG. 1 , the cap body 15 is plate-shaped and covers the opening of the bellows 14 on the side opposite the bottom 11, with the end of the bellows 14 welded to seal the opening. The cap body 15 is made of a material that can withstand the pressure conditions (low pressure or high pressure) inside the accumulator 1. The cap body 15 is made of, for example, metal, specifically hot-rolled mild steel plate (Steel Plate Hot Commercial: SPHC). It is preferable that the cap body 15 have heat resistance appropriate for the usage conditions.

[0022] The cap elastic part 16 is plate-shaped and is provided on the opposite side of the cap main body 15 from the bellows 14. The cap elastic part 16 is located between the port 13 and the cap main body 15, and seals the liquid (hydraulic oil) between the shell 12 and the bellows 14. The cap elastic part 16 is formed using, for example, acrylonitrile butadiene rubber (NBR) or ethylene propylene rubber (EPDM).

[0023] The cap main body portion 15 and the cap elastic portion 16 are formed by performing a surface treatment on the adhesive surface of the cap main body portion 15 by applying a phosphoric acid treatment, and then adhering the cap elastic portion 16 to the cap main body portion 15 by applying an adhesive to the adhesive surface, for example.

[0024] In the accumulator 1, when the pressure in the line connecting to the accumulator 1 changes by supplying / sucking liquid through the hole 13a of the port 13, the liquid flows in through the hole 13a of the port 13 and pushes up the cap bellows assembly 100. The pressure in the space between the bellows 14 and the shell 12 is always the same as the pressure inside the bellows 14.

[0025] Furthermore, when hydraulic oil flows in through hole 13a due to an increase in hydraulic pressure in the line connected to accumulator 1, bellows 14 contracts when the hydraulic oil causes the pressure in bellows 14 to exceed the pressure sealed in accumulator 1. In contrast, when the hydraulic pressure in the line drops and bellows 14 expands (returns) from its contracted state, hydraulic oil is released to the outside through hole 13a. The pressurized state of accumulator 1 is controlled by the release of liquid from hole 13a.

[0026] FIG. 3 is a diagram for explaining the expansion and contraction of a bellows applied to an accumulator. (a) of FIG. 3 shows the bellows 14 in a state where no load other than gravity is applied (free state). (b) of FIG. 3 shows the bellows 14 in a state where it has been expanded from the free state (expanded state). (c) of FIG. 3 shows the bellows 14 in a state where it has been contracted from the free state (contracted state). (b) and (c) of FIG. 3 show the bellows 14 in the maximum expansion (d) within the range of use. MAX ) or contraction (d MIN3(c) shows the state in which the sheet is compressed. The contracted state shown in FIG. 3(c) corresponds to the above-mentioned tightly contacted state.

[0027] In a conventional accumulator, the bellows 14 is designed to operate between the free state shown in Fig. 3(a) and the contracted state shown in Fig. 3(c). In other words, conventionally, the bellows 14 operates only on the compression side.

[0028] In contrast to this, the present embodiment is designed to operate between an expanded state and a contracted state. That is, the bellows 14 operates between the expanded side and the contracted side via the free state. Therefore, when the bellows 14 is expanded to the maximum in the accumulator 1, the bellows 14 is expanded relative to the free state. At this time, when the bellows 14 is expanded to the maximum (d MAX ) when stretched d 11 is set according to the allowable elongation rate, which is the elongation rate at which a fatigue strength equivalent to that of the bellows when amplitude is applied on the compression side is obtained.

[0029] FIG. 4 is a diagram for explaining the number of times that a bellows can withstand breakage in response to expansion or contraction. It is a diagram in which the elongation percentage at the number of times that a bellows can withstand breakage on the expansion side and the number of times that a bellows can withstand breakage on the contraction side are plotted (◇) for the above-mentioned size (outer diameter: 60 mm, inner diameter: 43 mm). In FIG. 4, zero elongation percentage is taken as the free state, and the elongation on the contraction side is indicated by a minus (-). The free length in the free state was measured using a load testing machine, and the elongation percentage was calculated by comparing the breakage position (upper or lower limit) with the free length. Also, in FIG. 4, the number of times that a bellows can withstand breakage within a range of elongation percentages was determined by Weibull analysis and plotted with circles. The analysis range in the Weibull analysis was 5% elongation percentage, e.g., 0-5%, 5-10%, . . . , 15-20%. The "n" attached to the plot indicates the number of samples within that range. The analysis points (◯) for each range indicate the change point P Ft Calculate this change point P FtThe elongation rate corresponding to this is set as the allowable elongation rate. This allowable elongation rate is set as the maximum elongation rate of the bellows 14. In the example shown in FIG. 4, the allowable elongation rate is 9.3%.

[0030] In this embodiment, the range of extension of the bellows 14 is set to the sum of the extension rate from the free state to the contracted state (closed state) and the extension rate from the free state to the extended state. Therefore, when the bellows 14 is in the maximum extended state, it is in an extended state.

[0031] In this embodiment, the range of expansion and contraction of the bellows 14 in the accumulator 1 is set to use the expansion side as well within the allowable expansion rate. According to this embodiment, the accumulator 1 can have the same number of durability cycles as a bellows that uses only the contraction side, while the size in the free state can be made smaller than a bellows that uses only the contraction side, i.e., the number of peaks (protrusions) can be reduced, thereby making it possible to reduce the weight of the accumulator 1 or the bellows 14 while suppressing a decrease in durability.

[0032] Although the embodiments for carrying out the present invention have been described above, the present invention should not be limited to only the above-described embodiments.

[0033] In this way, the present invention can include various embodiments not described here, and various design changes can be made within the scope that does not deviate from the technical idea specified by the claims.

[0034] As described above, the accumulator according to the present invention is suitable for reducing the weight of an accumulator using an S-shaped bellows while suppressing a decrease in durability. [Explanation of symbols]

[0035] 1 accumulator 11 Bottom 12 shells 13 ports 14 Bellows 15 Cap body 16 Cap elastic part 17 Guide bellows 141 Outer fold 142 Inner circumferential folded part 143 1st straight section 144 First curved section 145 Second curved section 146 Third curve 147 Fourth Curve 148 5th curve 149 2nd straight section

Claims

1. an exterior body consisting of a bottom, a shell, and a port; an expandable S-shaped bellows provided inside the exterior body; An accumulator comprising: When the bellows is maximally extended in the accumulator, the bellows is extended relative to a free state in which no load other than gravity is applied, The bellows has an expansion / contraction range set to a range that is a sum of an elongation rate from a free state to a contracted state and an elongation rate from a free state to an extended state, The elongation rate of the extension side of the bellows is set to an allowable elongation rate of 9.3 or less calculated based on Weibull analysis. An accumulator characterized by:

2. The bellows It is a cylindrical shape that extends in an accordion shape, an outer circumferential folded portion provided on the outer circumferential side; an inner circumferential folded portion provided on the inner circumferential side; a plurality of curved portions provided between the outer circumferential side and the inner circumferential side folded portion, the curved portions having curved patterns opposite to each other of adjacent curved portions; This is repeated.

2. The accumulator according to claim 1 .

3. The bellows is formed using stainless steel.

3. The accumulator according to claim 1 or 2.

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