JP4191843B2 - Manufacturing method of bellows - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a bellows, and more particularly, to a method for manufacturing a bellows that can reduce wrinkles (wrinkles) in a bellows-like wall surface portion and can improve product yield.
[0002]
[Prior art]
Rubber bellows are used for various purposes, and for the purpose of imparting high pressure resistance, bellows with a base fabric in which a base fabric is embedded in rubber have been developed. In addition, for example, in order to improve responsiveness for the purpose of using a vibration absorbing member of a precision measuring device, there is an increasing demand for a so-called thin bellows having a thin rubber thickness.
The structure of the bellows generally includes a pair of opposing ring-shaped facing surface portions and a bellows-like wall surface portion (a bellows-like wall surface portion) provided so as to connect the outer peripheral edge portions of these facing surface portions to each other. A plurality of peaks are formed on the wall surface. When manufacturing a bellows having such a structure as a bellows with a base fabric, first, a preform of the bellows is molded with a mold using rubber before vulcanization.
[0003]
Next, for example, a plain-woven sheet-like base fabric is wound around the preform, and then the plain-woven sheet-like base fabric is heated and pressed in the mold to form the side-shaped bellows of the mold. Vulcanize while deforming into shape. During this vulcanization, the temporarily softened rubber material penetrates into the base fabric, so that the bellows after vulcanization molding has a structure in which the base fabric is embedded.
[0004]
[Problems to be solved by the invention]
However, when the base fabric-containing bellows is molded as described above, because there are peaks and valleys on the outer peripheral edge of the bellows, a portion that extends to the base fabric and a portion that does not extend occur, and two or more stages, In particular, in bellows-shaped bellows having three or more ridges, wrinkles are likely to occur, and the base fabric is deformed on the preform, which causes the preform to be scraped or scratched. There was a problem that the yield of the product was extremely bad.
[0005]
The present invention was created based on such a situation, and its purpose is to reduce the occurrence of wrinkles, rubber scraping, and rubber scratching associated with the mounting of the base fabric, and the product yield and work. An object of the present invention is to provide a bellows manufacturing method capable of improving the efficiency.
[0006]
[Means for Solving the Problems]
In order to solve such a problem, the manufacturing method of the bellows of the present invention is a cylindrical base fabric tubular body woven with warp and weft, and the weft elongation is at least two or more. And a base fabric cylindrical body preparation step for preparing a base fabric cylindrical body having a belt-like body having two or more different elongation rate physical properties, and a pair of ring-shaped opposing surface portions arranged so as to face each other And a mold for blow molding for forming a bellows comprising two or more ridges and one or more bellows-shaped wall portions provided so as to connect the outer peripheral edge portions of the opposing surface portions to each other A cylindrical rubber preform made of unvulcanized rubber is placed inside the base cloth cylindrical body, and these are stored in the blow molding die, and then the cylindrical rubber Blow the inside of the preform so that the base fabric cylinder and rubber preform A blow molding step of forming a bellows shape by pressure bonding to the inner surface of the mold, and the base fabric tubular body in the base fabric tubular body preparation step is disposed so as to be positioned in the vicinity of the top of the peak portion. The second belt-like body and the first belt-like body arranged so as to be positioned in the vicinity of the recess of the valley, and the weft of the first belt-like body has an elongation percentage of the weft yarn of the second belt-like body. The base cloth cylindrical body further includes a third belt-like body disposed so as to be positioned on the ring-shaped facing surface portion, and 3 is configured such that the elongation rate of the weft yarn of the belt-like body 3 is set to be equal to or greater than the elongation rate of the weft yarn of the first belt-like body.
[0007]
The manufacturing method of the bellows of the present invention is a tubular base fabric tubular body woven with warp and weft, and the weft yarn has at least two kinds of elongation ratios, and two or more kinds of different elongations are used. A base cloth cylindrical body preparation step for preparing a base cloth cylindrical body having a belt-like body having a rate of physical properties, a pair of ring-shaped facing surface portions arranged to face each other, and an outer peripheral edge portion of the facing surface portion A step of preparing a blow molding die for molding a bellows comprising two or more peak portions and a bellows-like wall surface portion having one or more valley portions provided so as to be connected to each other; A cylindrical rubber preform made of unvulcanized rubber is placed inside the shaped body, and these are stored in the blow molding die, and then the inside of the cylindrical rubber preform is blown to form a base fabric. Bellows shape by pressing the cylindrical body and rubber preform onto the inner surface of the mold A blow molding step to form, and in the blow molding step, a base cloth cylindrical body is disposed in advance in a mold for blow molding that is opened, and the base cloth cylindrical body is formed. A cylindrical rubber preform is extruded into the inside, and then the mold is clamped to perform a blow molding process.
[0008]
The manufacturing method of the bellows of the present invention is a tubular base fabric tubular body woven with warp and weft, and the weft yarn has at least two kinds of elongation ratios, and two or more kinds of different elongations are used. A base cloth cylindrical body preparation step for preparing a base cloth cylindrical body having a belt-like body having a rate of physical properties, a pair of ring-shaped facing surface portions arranged to face each other, and an outer peripheral edge portion of the facing surface portion A step of preparing a blow molding die for molding a bellows comprising two or more peak portions and a bellows-like wall surface portion having one or more valley portions provided so as to be connected to each other; A cylindrical rubber preform made of unvulcanized rubber is placed inside the shaped body, and these are stored in the blow molding die, and then the inside of the cylindrical rubber preform is blown to form a base fabric. Bellows shape by pressing the cylindrical body and rubber preform onto the inner surface of the mold A blow molding step to form, and the base fabric tubular body in the base fabric tubular body preparation step has an elongation rate of a weft arranged so as to be positioned at the top of the peak portion, Is set so as to be larger than the elongation rate of the weft located in the hollow portion, and the base fabric tubular body has a density of the weft arranged so as to be located at the top of the peak portion. It is comprised so that it may become larger than the density of the weft located in the hollow part of a trough part.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
Bellows formed by the manufacturing method of the present invention
1 is a perspective view showing an embodiment of the bellows of the present invention, FIG. 2 is a plan view of the bellows shown in FIG. 1, and FIG. 3 is a half-sectional view of the bellows shown in FIG. FIG. 1 to 3, the bellows 1 of the present invention is configured so that a pair of opposed ring-shaped rubber facing surface portions 2A and 2B facing each other and the outer peripheral edge portions of the facing surface portions 2A and 2B are connected to each other. And a rubber bellows-like wall surface portion 3 provided.
[0017]
Each of the facing surface portions 2A and 2B has a ring-shaped flat plate shape, and has an opening 4 as a preferred embodiment at the center portion, and a bead portion 5 is formed inside the inner peripheral edge portion (FIG. 3). Furthermore, in this embodiment, a yarn beat 5 a is formed on the innermost surface of the bead portion 5. In principle, even if there is no opening 4, for example, it can be combined with other parts (metal parts), but the opening 4 is necessary in consideration of workability, assembly, structure, and the like. If the opening 4 is present, a form corresponding to it is necessary in order to ensure particularly a sealing property after assembling or to ensure a concentricity between the bellows and other parts. The structure of the bead portion 5 in the present embodiment is a structure in which such consideration has been made, and since the base fabric 10 described later has entered the tip of the bead portion 5 facing inward, when pressed, The cloth due to tension is difficult to come off. This point, sealability, concentricity, etc. are satisfactory. Further, the yarn beat 5a is formed in order to further increase the sealing performance, that is, to increase the partial surface pressure of the bead portion.
[0018]
In the present embodiment, the bellows-like wall surface portion 3 includes a plurality of peak portions 3a (three peak portions in the illustrated example) and valley portions 3b (two valley portions in the illustrated example) positioned between the peak portions 3a. have. And in this bellows 1, the continuous base fabric 10 is embedded in the opposing surface portions 2A and 2B and the bellows-like wall surface portion 3 (FIG. 3).
[0019]
A suitable base fabric 10 used in the present invention is composed of a cylindrical base fabric tubular body woven with warp and weft yarns before being attached to the bellows 1, and has at least two kinds of weft elongation rates. The above is used, and it is configured with a belt-like body having two or more different elongation rate physical properties.
[0020]
FIG. 4 (a) shows a preferred schematic perspective view of the base cloth cylindrical body 10 ′ before being attached to the bellows 1, and FIG. 4 (b) shows the base cloth cylindrical body 10 after being attached. A schematic perspective view of a state in which 'has a predetermined weft elongation at a predetermined location (deformed together with a rubber preform by blow molding) and has changed into a shape similar to the bellows shape of the bellows 1 is shown.
[0021]
Each hatch (hatched line) on the drawing shown in FIG. 4 is used for convenience in order to distinguish each band-like body described later.
[0022]
In FIG. 4A, a cylindrical base cloth cylindrical body 10 ′ includes a third belt-like body 10c arranged at the upper and lower ends thereof, and a second belt-like shape sequentially arranged in the vertical direction from these positions. The body 10b and the 1st strip | belt-shaped body 10a are provided. The first belt-like body 10a is arranged so as to be located in the vicinity of the depression of the valley 3b constituting the bellows, and the second belt-like body 10b is located near the top of the peak 3a constituting the bellows. Be placed. Moreover, the 3rd strip | belt-shaped body 10c is arrange | positioned so that it may be located in the said ring-shaped opposing surface parts 2A and 2B which comprise a bellows. Each of these band-like bodies is configured in the form of a plain weave woven with warp and weft. For example, the second belt-like body 10b is formed by plain weaving with warp yarns 110b and weft yarns 110a as shown in a partially enlarged view in a circle picked up in a circular shape on the right side of FIG. 4A. Yes. The first belt-like body 10a is formed by plain weaving with warp yarns 100b and weft yarns 100a, as shown in a partially enlarged view in a circle picked up in the right circular shape in FIG. 4A. Yes. Although not shown, the third belt-like body 10c is formed by plain weaving with warps and wefts in the same manner as the first and second belt-like bodies. And in this invention, the elongation rate of the weft 110a which comprises the 2nd strip | belt-shaped body 10b arrange | positioned so that it may be located in the peak part 3a of a bellows is arrange | positioned so that it may be located in the valley part 3b of a bellows. It is set to be larger than the elongation rate of the weft thread 100a constituting the belt-like body 10a.
[0023]
By performing such setting, the base fabric cylindrical body and the rubber preform are pressed against the inner surface of the bellows-like mold by a blow molding process described later, and the shape of the bellows-like wall surface portion of the bellows is met. It can be easily and reliably deformed into a shape, and workability and yield can be significantly improved.
[0024]
Further, the elongation rate of the weft constituting the third belt-like body 10c arranged so as to be positioned on the ring-shaped opposing surface portions 2A and 2B of the bellows is not particularly limited, and may be appropriately selected depending on the specifications of the bellows. . In general, it is preferable to set it so as to be equal to or greater than the elongation rate of the weft yarn of the first belt-like body.
[0025]
In addition, the density of the weft yarn (number per inch width) in each belt-like body may be set as appropriate in consideration of the elongation rate of the base fabric tubular body 10 '. As a preferred embodiment, in consideration of the strength of the belt-like body, the density of the weft arranged so as to be located at the top of the peak is set to be larger than the density of the weft located in the depression of the valley. It is good to do.
[0026]
The elongation and density (number per inch width) of the warp yarns in each strip are usually set to the same value, but can be changed individually for each strip.
[0027]
The elongation rate of the weft yarn and warp yarn constituting the base fabric tubular body 10 'changes the degree of heat setting (heat set) after stretching in the longitudinal direction when forming the yarn, and changes the twisting method. Various things can be obtained. It is also possible to change the elongation rate by adjusting the tension when weaving the base fabric tubular body 10 '.
[0028]
Note that the base fabric tubular body 10 ′ shown in FIG. 4 (a) is a so-called seamless substantially complete tubular body, but as shown in FIG. A base cloth tubular body 10 ′ having a joint surface 17 obtained by rolling an object and joining both ends thereof with, for example, an adhesive may be used. Of course, it goes without saying that both are preferred embodiments of the present invention.
[0029]
As shown in FIG. 4B, the base fabric 10 deformed by extending the yarn by blow molding (actually, deformed together with the rubber preform by blow molding in the mold as described later) has a bellows shape. It is pressure-bonded to the vicinity of the inner surface of the mold, and has a form corresponding to the cross-sectional shape (shape having a peak and a valley) of the wall surface of the bellows.
[0030]
The bellows-like wall surface portion 3 shown in FIG. 3 has a thickness in the range of, for example, about 0.15 to 1.8 mm, and the length of the bellows-like wall surface portion 3 (in FIG. 3, the facing surface portion 2A and the facing surface portion 2B). ), The number of ridges 3a (the number of steps), the shape, dimensions, and the like are not particularly limited, and can be appropriately set in consideration of the purpose of use of the bellows 1, required characteristics, and the like. For example, the cross-sectional shape of the peak portion 3a can be a semicircular shape, a triangular shape, or the like, and the shape and dimensions of the plurality of peak portions 3a may be the same, or consist of two or more types. May be.
[0031]
Such a bellows 1 includes a pair of ring-shaped facing surface portions 2A and 2B and a bellows-like wall surface portion 3 that face each other as described above, and has excellent responsiveness, and the facing surface portions 2A and 2B and the bellows-like wall surface portion. Excellent pressure resistance is imparted by the base fabric 10 embedded in 3.
[0032]
In addition, in order to maintain the form of the bellows 1 simply, you may make it attach a round and a reinforcement ring etc. to the trough part 3b along the circumferential direction.
[0033]
The rubber used in the bellows 1 of the present invention as described above may be a conventionally known synthetic rubber or natural rubber, and is not particularly limited. Synthetic rubbers usable in the present invention include, for example, acrylonitrile-butadiene rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, propylene-butadiene rubber, acrylonitrile-isoprene rubber, chloroprene rubber, butyl rubber, ethylene-propylene rubber, acrylic Examples thereof include rubber, fluorine rubber, ether-thioether rubber, polysulfide rubber, urethane rubber, and silicon rubber. If necessary, additives such as a vulcanizing agent and a vulcanization accelerator, which will be described later, are added to such a rubber material and then kneaded by a kneader, and the resulting rubber mixture is formed into a cylindrical rubber preform. Pre-mold. Thereafter, the bellows 1 can be produced by the production method of the present invention described later using this cylindrical rubber preform.
The vulcanizing agent to be used can be appropriately selected according to the rubber used from sulfur, zinc oxide, magnesium oxide, aromatic nitro compound, organic peroxide and the like.
[0034]
Further, as vulcanization accelerators, thiazole compounds such as 2-mercaptobenzothiazole (MBT), sulfenamide compounds such as N-cyclohexyl-2-benzothiazole sulfenamide (CZ), 2-mercaptothiazoline and the like Thiazoline compounds, thiuram compounds such as tetramethylthiuram monosulfide (TT), tetraethylthiuram disulfide (TET), dithiocarbamate compounds such as dimethyldithiocarbamic acid, aldehyde amine compounds such as hexamethylenetetramine, guanidines such as diphenylguanidine Compounds, thiazole compounds such as N, N-diethylcarbamoyl-2-benzothiazyl sulfide, and the like can be used.
[0035]
Furthermore, you may contain anti-aging agents, organic fatty acids, such as stearic acid, and fillers, such as carbon black, as needed. Such an additive is preferably contained in an amount of 1 to 150 parts by weight per 100 parts by weight of rubber.
[0036]
As the base fabric 10 used in the bellows 1 of the present invention, a fabric made into plain weave using yarns such as polyamide (6 nylon, 66 nylon, etc.), aramid, polyester, cotton and the like is used. In the present invention, at least two or more kinds of wefts are used, and a base fabric tubular body having a belt-like body having two or more different elongation properties is prepared.
[0037]
Method for producing bellows of the present invention
Next, the manufacturing method of the bellows of this invention is demonstrated with reference to FIGS. In addition, since the base fabric cylindrical body preparation process has already been described above, the description thereof is omitted here.
[0039]
(Blow molding mold preparation process)
[0040]
5 to 7 are schematic half-sectional views showing the state of blow molding including the blow molding die 30 used in the present invention over time. As shown in FIGS. 5 to 7, the blow molding die 30 includes a pair of ring-shaped facing surface portions 20 </ b> A and 20 </ b> B disposed so as to face each other in the cavity, and the outside of the facing surface portions 20 </ b> A and 20 </ b> B. A bellows-shaped wall portion 33 having two or more peak portions 30a (three in the illustrated example) and one or more valley portions 30b (two in the illustrated example) provided so as to connect the peripheral portions to each other; I have. The bellows-like wall surface portion 33 of the mold has substantially the same shape as the bellows-like wall surface portion 3 of the bellows which is a molded product.
[0041]
Such a blow molding die 30 usually has a two-part mold structure, and the blow molding die 30 further includes a mold opening / closing moving device, an air blowing device, etc. (not shown). It is attached.
[0042]
(Blow molding process)
[0043]
As shown in FIG. 5, the blow molding die 30 is in an opened state. Normally, in this state, the cylindrical base cloth cylindrical body 10 ′ (more specifically, FIG. 4A) is formed. Installed in the cavity. At this time, the second belt-like body 10b having a weft with a high elongation rate is located in the vicinity of the top of the bellows-like ridge (reference symbol 3a for a product bellows, reference symbol 30a for a mold), It is necessary to arrange so that the first belt-like body 10a to be provided is positioned in the vicinity of the hollow portion of the bellows-like valley (reference numeral 3b in the case of a product bellows and reference numeral 30b in the case of a mold). In order to ensure proper arrangement, it is desirable that the first strip and the second strip are distinguished from each other by color coding.
[0044]
Next, a tubular rubber preform 13 of unvulcanized rubber is inserted and arranged inside the base fabric tubular body 10 ′, and the state shown in FIG. 5 is reached. The cylindrical rubber preform 13 is inserted preferably by connecting an extrusion molding machine to the blow molding die 30 so that the so-called parison-shaped rubber preform 13 can be continuously inserted. It is not limited.
[0045]
After the base cloth cylindrical body 10 ′ and the rubber preform 13 are thus arranged in a predetermined manner, the blow molding die 30 is clamped to reach the state shown in FIG. Thereafter, as shown in FIG. 7, the inside of the cylindrical rubber preform 13 is blown (arrow (A)), and the base fabric cylindrical body 10 and the rubber preform 13 are integrally bonded to the inner surface of the mold. Thus, a bellows shape is formed as illustrated. In the base fabric cylindrical body 10, a part of the flexible rubber passes and is embedded in the rubber preform 13 (the state shown in FIGS. 3 and 7). In the example shown in the figure, the blow (arrow (A) in FIG. 7) is performed from two places above and below the mold.
[0046]
When forming such a bellows shape, since the second belt-like body having a high elongation weft is arranged at the bellows-shaped peak portion, the deformation of the base fabric accompanying the blow molding is extremely easy. It is possible to reliably and reliably improve the molding yield and stabilize the quality. Productivity is also greatly improved. The rubber preform 13 after blow molding is usually heat vulcanized to form a bellows as a final product.
[0047]
In this embodiment, a three-stage bellows (for example, used for vibration isolation) that requires pressure resistance has been described as an example. However, the present invention is not limited to this and includes several stages to several tens of stages. Of course, it can also be applied to the manufacture of bellows. As an example of the bellows consisting of several tens of steps, there is a long protective bellows used to cover the elastic member.
[0048]
【The invention's effect】
As described above in detail, according to the bellows manufacturing method of the present invention, it is a tubular base fabric tubular body woven with warp and weft, and the elongation of the weft is at least two or more. A base fabric tubular body preparation step for preparing a base fabric tubular body having a belt-like body having two or more different elongation rate physical properties, and a pair of ring-shaped facing surface portions arranged to face each other. A blow molding die for molding a bellows comprising two or more peak portions and one or more bellows-shaped wall portions provided so as to connect the outer peripheral edge portions of the opposing surface portions to each other. A step of preparing, and a cylindrical rubber preform of unvulcanized rubber is disposed inside the base cloth cylindrical body, and these are stored in the blow molding die, and then the cylindrical rubber preform Blow the inside of the foam and place the base fabric cylinder and rubber preform in the mold. And a blow molding process for forming a bellows shape by pressure bonding to the bellows, so that it can be easily deformed along the shape of the bellows wall surface of the bellows, Occurrence of wrinkles, rubber scraping, and rubber scratching due to mounting is small, and the product yield and work efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a bellows of the present invention.
FIG. 2 is a plan view of the bellows shown in FIG.
FIG. 3 is a half-sectional view taken along the line AA in FIG. 2;
4 (a) is a preferred schematic perspective view of a base cloth cylindrical body before blow molding, and FIG. 4 (b) is a diagram showing a predetermined elongation at a predetermined position of the base cloth cylindrical body after blow molding. It is a schematic perspective view which shows the state which changed to the form similar to the bellows shape of bellows.
FIG. 5 is a schematic half-sectional view showing the state of blow molding including a blow mold used in the present invention over time.
FIG. 6 is a schematic half-sectional view showing, over time, the state of blow molding including a blow molding die used in the present invention.
FIG. 7 is a schematic half-sectional view showing the state of blow molding including the blow molding die used in the present invention over time.
FIG. 8 is a schematic perspective view showing another preferred embodiment of the base fabric tubular body before blow molding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Bellows 2A, 2B ... Opposite surface part 3 ... Bellows-like wall surface part 3a ... Mountain part 3b ... Valley part 4 ... Opening part 5 ... Bead part 10 ... Base cloth 10 '... Base cloth cylindrical body 10a, 10b, 10c ... Band-shaped body 13 ... Bellows rubber preform 30 ... Blow molding dies 20A, 20B ... Opposite surface part (mold)
33 ... Bellows-shaped wall surface (mold)
30a ... Yamabe (mold)
30b ... Tanibe (mold)

Claims (3)

A tubular base fabric tubular body woven with warp and weft, wherein at least two kinds of wefts are used, and two or more kinds of belts having different elongation properties are used. A base fabric tubular body preparation step for preparing a fabric tubular body;
A bellows-like wall surface having a pair of ring-shaped facing surface portions arranged so as to face each other, and two or more peak portions and one or more valley portions provided so as to connect the outer peripheral edge portions of the facing surface portions to each other A step of preparing a blow molding die for molding a bellows comprising a portion;
A cylindrical rubber preform made of unvulcanized rubber is placed inside the base cloth cylindrical body, and these are stored in the blow molding die, and then the inside of the cylindrical rubber preform is blown. Te, have a, a blow molding process to form a bellows shape the base fabric tubular body and rubber preform is pressed against the inner surface of the mold,
The base cloth cylindrical body in the base cloth cylindrical body preparation step is positioned in the vicinity of the second belt-shaped body disposed so as to be positioned in the vicinity of the top portion of the peak portion and the recess portion of the valley portion. The first belt-shaped body is disposed, and the elongation rate of the weft yarn of the second belt-shaped body is set to be larger than the elongation rate of the weft yarn of the first belt-shaped body; The rod-shaped body includes a third belt-like body arranged so as to be positioned on the ring-shaped facing surface portion, and the elongation rate of the weft yarn of the third belt-like body is the stretch of the weft yarn of the first belt-like body. A method for producing a bellows, characterized in that it is set to be equal to or greater than the rate . A tubular base fabric tubular body woven with warp and weft, wherein at least two kinds of wefts are used, and two or more kinds of belts having different elongation properties are used. A base fabric tubular body preparation step for preparing a fabric tubular body;
A bellows-like wall surface having a pair of ring-shaped facing surface portions arranged so as to face each other, and two or more peak portions and one or more valley portions provided so as to connect the outer peripheral edge portions of the facing surface portions to each other A step of preparing a blow molding die for molding a bellows comprising a portion;
A cylindrical rubber preform made of unvulcanized rubber is placed inside the base cloth cylindrical body, and these are stored in the blow molding die, and then the inside of the cylindrical rubber preform is blown. Te, have a, a blow molding step of forming a bellows shape the base fabric tubular body and rubber preform is pressed against the inner surface of the mold,
In the blow molding step, a base cloth cylindrical body is previously placed in a mold for blow molding that has been opened, and a cylindrical rubber preform is extruded into the base cloth cylindrical body. Then, the mold is clamped and a blow molding process is performed . A tubular base fabric tubular body woven with warp and weft, wherein at least two kinds of wefts are used, and two or more kinds of belts having different elongation properties are used. A base fabric tubular body preparation step for preparing a fabric tubular body;
A bellows-like wall surface having a pair of ring-shaped facing surface portions arranged so as to face each other, and two or more peak portions and one or more valley portions provided so as to connect the outer peripheral edge portions of the facing surface portions to each other A step of preparing a blow molding die for molding a bellows comprising a portion;
A cylindrical rubber preform made of unvulcanized rubber is placed inside the base cloth cylindrical body, and these are stored in the blow molding die, and then the inside of the cylindrical rubber preform is blown. Te, have a, a blow molding process to form a bellows shape the base fabric tubular body and rubber preform is pressed against the inner surface of the mold,
In the base fabric tubular body preparation step, the stretch rate of the weft arranged so as to be located at the top of the peak portion is greater than the stretch rate of the weft located in the recessed portion of the valley portion. Further, the density of the wefts arranged so that the base fabric cylindrical body is located at the top of the peak is the density of the wefts located at the depression of the valley It is set so that it may become larger than this , The manufacturing method of the bellows characterized by the above-mentioned .

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