JPH09112265A - Flexible tube for exhaust emission of automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy the performance of absorbing expanding and contracting displacement of a flexible tube and to make it compact by setting the total opening area of many openings formed over the whole outer blade to be a specified figure for the whole surface area of the outer blade and combining the outer blade with a specified bellows. SOLUTION: A flexible tube F comprises a bellows 1, an outer blade 2, and a protector 3. The bellows 1 has 15 or less peaks and its thickness is set such that its spring constant is 14kg/10mm in the direction of tension. The outer blade 2 is made by knitting a plurality of batches of band-like wires 2a which are required for a single lap in a slant direction into a cylinder, wherein a batch of band-like wires are made by laterally arranging a plurality of small-diameter metallic wires, and, letting a part surrounded by the side ends of four batches of band-like wires 2a which are knitted in four directions be an opening 4, the total opening area of many openings 4 formed over the whole outer blade 2 is set in the range of 20% to 50% for the whole surface area of the outer blade 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a flexible tube for an automobile exhaust system which is provided in the middle of an exhaust pipe from an engine and absorbs engine vibration and traveling vibration.

[0002]

2. Description of the Related Art Conventionally, as a flexible tube for an automobile exhaust system, those described in Japanese Utility Model Publication No. 63-47613 and Japanese Utility Model Publication No. 3-55778 are known.

In these conventional sources, as shown in FIG. 7, an outer blade 101 provided so as to cover the outer periphery of the bellows 100 is described.

As shown in FIG. 8, each of the outer blades 101 described in the conventional sources has a plurality of thin metal wire rods (stainless steel wire rods) so that adjacent metal wire rods are in contact with each other. One set of wire rod bundles 102 formed into a band by arranging them side by side is formed into a tubular shape by braiding a plurality of sets of band-like wire rod bundles 102 required for one turn in an oblique direction.

Since the outer blade 101 thus formed in the knitted meliath has an appropriate elasticity, it is provided by covering the outer periphery of the bellows 100.
The bellows 100 is protected from foreign matter and its extension is prevented.

And, in this outer blade 101,
When weaving the band-shaped wire bundle 102, as shown in FIG. 8, the portions where the ends of the wire bundles 102 overlap with each other form a slight space to form four wire bundles 102.
A minute opening 103 surrounded by is formed.

[0007]

However, in the conventional outer blade 101, usually, as a result of densely knitting the wire bundle 102, a minute opening portion 103 having an extremely small opening area is formed, and in particular, the opening It wasn't even noticeable.

In a flexible tube for an automobile exhaust system having such an outer blade 101, it is difficult for snowmelt salt from entering the bellows 100 from the outside.
On the other hand, once the snow-melting salt enters the inside, it is not discharged to the outside, and the space between the bellows 100 and the outer blade 101 becomes an environment with a high salt concentration due to the internal accumulation of the snow-melting salt, which causes high temperature salt corrosion. Have.

That is, since the band-shaped wire rod bundle 102 constituting the outer blade 101 is a metal wire rod having a thin wire diameter formed into a band shape, and the band-shaped wire rod bundles are alternately superposed and knitted, When the outer blade 101 expands and contracts to absorb the vibration displacement applied to the exhaust pipe during traveling, a gap is formed between the adjacent metal wire rods or the overlapping portion of the band-shaped wire rod bundle, or the gap is closed, or
The minute opening 10 surrounded by the four wire bundles 102
3 expands and contracts. Therefore, no matter how densely the band-shaped wire bundle is knitted, it is not possible to reliably prevent the snow-melting salt from entering the inside. In addition, the snow-melting water containing salt is used at any time during the formation of the above-mentioned gap or due to the capillary phenomenon.
Infiltrate inside. Then, the invading snow melting salt adheres to the surface of the bellows 100 and the inner surface of the outer blade 101,
After that, salt is deposited by evaporation of water, or the snow-melting salt is dried and becomes a dry salt lump along with the deformation of the bellows 100 or the outer blade 101, and even if it peels off from the surface, the space between the bellows 100 and the outer blade 101 is removed. It remains in space.

On the other hand, since the bellows 100 is made of stainless steel, it has durability against high temperature environment and corrosion resistance against salt under independent conditions.
In an environment with exhaust heat + high salt concentration, where both conditions are applied together, high-temperature salt corrosion will result. That is, when the bellows 100 is subjected to the high temperature heat effect due to the exhaust heat for a long period of time, the chromium of the stainless material is combined with the carbon and the chromium content of the stainless material is reduced, so that sodium chloride or the like enters the clearance reduced in chromium. Corrosion by mechanism. In other words, the chromium content of the stainless steel material is reduced, and the stainless steel material is closer to the iron material and is more likely to be corroded.

Therefore, in the conventional flexible tube using the densely woven outer bellows 101, the plate thickness of the bellows 100 must be set sufficiently thick in consideration of the decrease in plate thickness due to high temperature salt corrosion. Of course, in order to exhibit the expansion / contraction displacement absorbing performance that is the required performance of the bellows 100, the spring constant is kept low by increasing the number of peaks.

Incidentally, FIG. 7 shows an example of a conventional flexible tube using an outer bellows 101 which is tightly woven.

This flexible tube has a bellows 1.
00 is constructed by using a two-layer product in which two stainless steel plates having a thickness of 0.3 mm are stacked, and setting the number of ridges by bending to 28 ridges.
A spring constant in the pulling direction that achieves a displacement of 0 mm is achieved. As a result, although the bellows 100 can exhibit the expansion / contraction displacement absorption performance required by the bellows 100, the total length L2 of the flexible tube is approximately 270 mm,
There is a problem that it becomes large.

The problems to be solved by the present invention are listed below.

Problem 1 is a flexible tube for an automobile exhaust system having an outer blade constituted by weaving a bellows for absorbing expansion and contraction displacement and a thin metal wire,
The purpose of the present invention is to provide a flexible tube that is significantly compact while satisfying the required performance of expansion and contraction displacement absorption by a bellows.

Problem 2 is to provide a flexible tube having a total length of half or less as compared with the conventional flexible tube.

[0017]

[Means for Solving the Problems]

(Solution 1) Solution 1 for the above-mentioned problem 1 (claim 1)
Is an automobile exhaust equipped with a bellows that absorbs expansion and contraction displacement of exhaust pipes connected to both ends, and an outer blade provided so as to cover the outer periphery of the bellows to protect the bellows and prevent extension of the bellows. In a flexible tube for a system, one set of band-shaped wire bundles in which a plurality of thin metal wires are bundled side by side is set, and a plurality of sets of band-shaped wire bundles required for one round are diagonally knitted to form a tubular shape. In addition, the portion surrounded by the side ends of the band-shaped wire bundle woven in four directions is defined as an opening, and the total opening area of a large number of openings formed over the entire outer blade is 20 with respect to the total surface area of the outer blade. The outer blade set in the range of 50% to 50%, and the pulling direction in which the number of peaks is 15 or less and the displacement is 10 mm when the load is 14 kgf or less. A bellows which is set in the thickness with a spring constant, by being configured by a combination of features.

The operation will be described.

When the vehicle travels on a snowy road where the snow-melting salt is sprayed, the snow-melting salt permeates into the inside through the openings formed in the outer blade in large numbers. However, the invading snow melting salt adheres to the surface of the bellows and the inner surface of the outer blade, and then the snow melting salt containing moisture is dried by exhaust heat etc. and becomes a small lump with the deformation of the bellows and the outer blade from the surface. When peeled off, this dried salt lump is discharged to the outside from the opening of the outer blade, and the salt lump does not remain and accumulate in the space between the bellows and the outer blade.

Therefore, the bellows are not exposed to an environment having a high salt concentration, and the high salt corrosion corrosion of the bellows is reduced by keeping the salt concentration low.

As a result, in setting the plate thickness of the bellows, by using the outer blade having the opening,
Since the reduction in plate thickness due to high temperature salt corrosion is small, the plate thickness of the bellows can be set thinner than before. With this thin plate setting, the spring constant of the bellows becomes lower, and even if the number of peaks is made smaller than that of the conventional bellows, the spring constant of a size that allows the expansion displacement absorption performance, which is the required performance of the bellows, to be maintained. be able to.

Therefore, an outer blade having an opening and a bellows having a plate thickness having a spring constant in the tension direction in which the number of peaks is 15 or less and a displacement of 10 mm is obtained when the load is 14 kgf or less are provided. By combining them, the flexible tube can be significantly downsized while satisfying the required performance of expansion and contraction displacement absorption by the bellows.

(Solution Means 2) Solution Means 2 for Problem 2
(Claim 2) is the flexible tube for an automobile exhaust system according to claim 1, wherein the bellows is 0.2 mm.
It is characterized in that a two-layer product obtained by stacking two thick stainless steel plate materials is used as a material, and the number of peaks is set to 9 by bending.

The operation of the conventional bellows is as follows.
A two-layer product obtained by stacking two 0.3 mm-thick stainless steel plates was used as the material, and the total number L2 was about 270 mm when the number of ridges was set to 28 by bending.
A two-layer product made by stacking two 0.2 mm-thick stainless steel sheets as a material, and the number of ridges set to 9 by bending molding has a total length L1 of about 105 mm, and the total length of the bellows is less than half (about 2 / 5). It should be noted that the interval between the peaks of both flexible tubes and the diameter of the cylindrical portions at both ends are the same.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

 Embodiment 1 First, the configuration will be described.

FIG. 1 is a half sectional view showing a flexible tube for an automobile exhaust system according to a first embodiment corresponding to the inventions of claims 1 and 2, and FIG. 2 is a flexible tube for an automobile exhaust system according to the first embodiment. 3 is a partially enlarged view showing the outer blade of FIG. 3, FIG. 3 is a side view showing the bellows of the automobile exhaust system flexible tube of the first embodiment, and FIG. 4 is an enlarged sectional view of part A in FIG.

In FIG. 1, F is a flexible tube, 1 is a bellows, 2 is an outer blade, and 3 is a protector.

Exhaust pipes (not shown) are connected to both ends of the bellows 1, and the bellows 1 are provided for the purpose of absorbing the expansion and contraction displacement when the exhaust pipes are expanded and contracted due to engine vibration, traveling vibration, or the like.

As shown in FIGS. 3 and 4, the bellows 1 according to the first embodiment is made of a multi-layered product obtained by stacking two layers of austenitic stainless steel plates having a thickness of 0.2 mm.
This is bent and formed to set the ridge portion 1a and the cylindrical portions 1b on both sides by nine ridges. The outer diameters of the five central ridges 1a are constant, but the two ridges 1a on each of the two sides are set such that the outer diameter is gradually increased from the cylindrical portion 1b.

The outer blade 2 is the bellows 1
It is provided so as to cover the outer periphery of the bellows 1 with the original purpose of protecting the same and preventing the extension thereof.

As shown in FIG. 2, the outer blade 2 is prepared by preparing a plurality of stainless wire rods having a small wire diameter and arranging them side by side so that adjacent stainless steel wire rods are in contact with each other to form a band. In addition, a plurality of sets of band-shaped wire bundles 2a required for one round are knitted in an oblique direction to form a tubular shape, and band-shaped wire bundles 2a are knitted in four directions
The portion surrounded by the side edges of the outer blade 2 is defined as the opening 4, and the total opening area of the large number of openings 4 formed over the entire outer blade 2 is in the range of 20% to 30% with respect to the total surface area of the outer blade 2. Is set.

In the outer blade 2 of the first embodiment, the number of sets of the band-shaped wire rod bundle 2a per one turn is 48 (the number of sets of the conventional outer blade per turn is 48, which is unchanged), The wire diameter of the stainless wire material forming the band-shaped wire material bundle 2a is 0.4 mm (the wire diameter of the conventional outer blade is 0.4 mm, which is unchanged), and the number of stainless wire material forming the band-shaped wire material bundle 2a is 10 pieces. By setting the number of openings 4 to be less than the number (14) set by a conventional outer blade that is densely woven with almost no openings 4, the area of each opening 4 is a hole having a diameter of 2 mm to 4 mm. Is set so that the total opening area obtained by adding the opening areas of the respective openings 4 is in the range of 20% to 30% with respect to the total surface area of the outer blade 2.

The protector 3 is for protecting both ends of the bellows 1 and for fixing the outer blade 2,
The bellows 1 and the outer blade 2 are provided at both ends by spot welding (spot welds 5).

Next, the operation will be described.

[Aperture Setting Operation for Outer Blade 2]
The band-shaped wire bundle 2a of the outer blade 2 is not changed by changing the number of groups (48 sets) of the band-shaped wire bundle 2a per revolution.
The weaving interval does not change.

The outer diameter of the stainless wire that constitutes the band-shaped wire bundle 2a (0.4 mm) is not changed, the number of stainless wire is 10 and the outer blade is tightly knitted with almost no openings. By making the number smaller than the set number (14), the width of the band-shaped wire rod bundle 2a becomes narrower as the number becomes smaller.

Therefore, the portion surrounded by the side ends of the band-shaped wire bundle 2a knitted in four directions can be formed by a simple method which does not change the conventional outer blade manufacturing method only by reducing the number of stainless wire rods. As shown in FIG. 2, the opening 4 will be formed.

[Operation of Excluding Snow Melting Salt by Opening] When running on a snowy road where the snow melting salt is sprayed, the snow melting salt enters into the inside through the openings 4 formed in the outer blade 2 in a large number.

The snow-melting salt that has infiltrated adheres to the surface of the bellows 1 and the inner surface of the outer blade 2, and thereafter,
The snow-melting salt containing water is dried by exhaust heat or the like and adheres as a lump of crystalline salt.

However, when the bellows 1 and the outer blade 2 expand and contract and become small lumps of salt that peel off from the surface of the bellows 1 and the inner surface of the outer blade 2, the dried salt lumps form openings in the outer blade 2. 4, the salt lumps are not discharged and accumulated in the space between the bellows 1 and the outer blade 2.

Therefore, since the bellows 1 is not exposed to the environment of high salt concentration and the salt concentration is kept low,
Hot salt corrosion of the bellows 1 is reduced.

By the way, the results of the high temperature salt corrosion test conducted by the present inventor are shown in FIG.

The object of this test is an outer blade with a dense weaving method with almost no openings, which is the same as the conventional bellows made of a multi-layered product of two layers of 0.3 mm thick austenitic stainless steel plates. The flexible tube of the first embodiment in which the conventional flexible tube in which the above are combined with the outer blade in which the opening 4 is formed is combined.

The test method was as follows: immersion in a saturated sodium chloride aqueous solution → high temperature heating (550 ° C. or higher) → cooling as one cycle, artificially creating conditions for high temperature salt corrosion (intergranular corrosion environment), and repeating this. Conduct the measurement of the reduction rate of the thickness of the bellows.

As a result of this high temperature salt corrosion test, as shown in FIG. 5, in the case of the flexible tube using the outer braid according to the knitting method of Embodiment 1, as compared with the flexible tube using the outer braid according to the conventional knitting method, It was confirmed that the reduction rate of the plate thickness of the bellows was significantly reduced.

This means that when the outer blade according to the knitting method of the first embodiment is used, it is proved to be superior in high temperature salt damage corrosion resistance.

[Compact flexible tube]
In setting the plate thickness of the bellows 1, as described above, when the outer blade 2 having the opening 4 is adopted, it is superior in high temperature salt damage corrosion resistance, and the decrease in plate thickness due to high temperature salt damage corrosion is small, The plate thickness of the bellows 1 can be set thinner than before. With this thin plate setting, the spring constant of the bellows 1 becomes lower, and even if the number of peaks is smaller than that of the conventional bellows, the spring constant of a size that allows the expansion displacement absorption performance, which is the required performance of the bellows, is maintained. can do.

This means that by adopting a bellows having a smaller number of ridges than the conventional bellows, it is possible to make the flexible tube compact while satisfying the required performance of expansion and contraction displacement absorption by the bellows.

By the way, FIG. 6 shows the result of the spring constant test of the bellows in the tensile direction conducted by the present inventor.

The target products of this test are bellows made of a two-layer product of an austenitic stainless steel plate material having a thickness of 0.3 mm and having 28, 21, and 27 peaks and a thickness of 0.2 mm. A bellows made of a two-layer austenitic stainless steel plate with 9 or 12 or 15 threads.
I used the one from the mountain. In the test method, one end side of each bellows was fixed, a load in the tensile direction was applied from the other end side, and the elongation displacement of the bellows and the applied load were measured.

As a result of this bellows spring constant test, in the case of a bellows made of a two-layer product having a thickness of 0.3 mm, 28
Spring constant level required only for mountains (load is 14 kgf
In the case of 21 and 27 peaks, the spring constant is higher than the required spring constant level, though the spring constant is less than 10 mm in the following.

On the other hand, in the case of a bellows made of a two-layer product having a thickness of 0.2 mm, all 9, 12, and 15 peaks are below the required spring constant level.

Therefore, the outer blade 2 having the opening 4 and the bellows 1 which is made of a two-layer product obtained by stacking two 0.2 mm-thick stainless steel plate materials, and is set to have 9 peaks by bending molding are used. By combining them, the flexible tube F was significantly made compact while satisfying the required performance of absorbing expansion and contraction displacement by the bellows 1. Specifically, the conventional bellows shown in FIG. 7 in which a two-layer product obtained by stacking two stainless steel plates having a thickness of 0.3 mm is set to 28 peaks by bending molding has a total length L2 of about 2
In contrast to 70 mm, the bellows 1 of the present application shown in FIG. 1 in which a two-layer product obtained by stacking two stainless steel plates having a thickness of 0.2 mm is used as a material and the number of peaks is set to 9 by bending.
Has a total length L1 of about 105 mm, and the total length of the bellows 1 has been shortened to less than half (about 2/5) as compared with the conventional one.
It should be noted that the interval between the peaks of both flexible tubes and the diameter of the cylindrical portions at both ends are the same.

Next, the effects will be described.

(1) A plurality of sets of band-shaped wire bundles 2a required for one turn are knitted in an oblique direction to form a tubular shape, and 4
The portion surrounded by the side ends of the band-shaped wire bundle 2a knitted in the direction is defined as an opening 4, and the total opening area of the openings 4 formed in large numbers over the entire outer blade 2 is the total surface area of the outer blade 2. 20% to 30
%, And an outer blade 2 set to have a range of%, and a multilayer product obtained by stacking two layers of 0.2 mm thick austenitic stainless steel plate material, and using this as a bellows 1 having 9 peaks by bending molding. Since the flexible tube F is configured by combining the above, the flexible tube F that satisfies the required performance of absorbing the expansion and contraction displacement by the bellows 1 and has a significantly smaller overall length than the conventional flexible tube is provided. You can

(2) The number of sets per band of the band-shaped wire bundle 2a and the wire diameter of the stainless wire that composes the band-shaped wire bundle 2a are not changed, and the number of stainless wire rods is made dense with almost no openings. Since the outer blade 2 is configured by making the number smaller than the number set by the outer blade to be knitted, the outer blade 2 is opened by a simple method of reducing the number of stainless steel wire rods forming the band-shaped wire rod bundle 2a. The part 4 can be set.

(3) Since the opening 4 is formed in the outer blade 2, the freedom of movement of the band-shaped wire bundle 2a is increased and the spring constant of the outer blade 2 is reduced as compared with the conventional densely knitted outer blade. can do.

As a result, the vibration absorbing performance can be improved in the blade displacement range of the flexible tube F in which the outer blade 2 having the opening 4 is used (the region where the load and displacement amount are larger than the bellows displacement region). It is preferable in terms of durability and sound vibration.

(4) Since both the bellows 1 and the outer blade 2 are smaller than the conventional flexible tube, the amount of the stainless two-layer plate material as the material of the bellows 1 and the stainless wire material as the material of the outer blade 2 is reduced. Therefore, the cost of the flexible tube F can be reduced.

(Other Embodiments) In the first embodiment, a multilayer product obtained by stacking two layers of austenitic stainless steel plates having a thickness of 0.2 mm is used as a raw material, and this is bent to form a bellows having 9 peaks. Although the example of 1 was shown, the number of mountains is 1
The present invention includes any bellows having a thickness of 5 or less and a spring constant in the tensile direction that allows a displacement of 10 mm with a load of 14 kgf or less. For example,
Using the 2-layer product with a thickness of 0.2 mm shown in FIG.
The present invention also includes mountains and 15 mountains.

In the first embodiment, the number of sets per band of the band-shaped wire rod bundle 2a and the wire diameter of the stainless wire rod are not changed,
The example in which the openings 4 are formed by making the number of stainless wire rods smaller than the number of stainless wire rods set by the outer blade that is densely knitted with almost no openings is shown. Do not change the number of groups per round and the number of metal wire rods, and make the wire diameter of the metal wire rod smaller than the wire diameter of the metal wire rod set by the outer blade that is tightly knitted with almost no openings. Therefore, the opening may be formed. Further, among the number of sets per band of the band-shaped wire bundle, the number of metal wires, and the wire diameter of the metal wire rod, the number of sets per band of the band-shaped wire bundle is reduced to form the opening. Alternatively, two of the number of sets, the number of lines, and the wire diameter may be selected and changed, or all three may be changed to form the opening.

In the first embodiment, the total opening area of the openings 4 is 20% to the total surface area of the outer blade 2.
Although the one set in the range of 30% is shown, the total opening area of the opening is 20 with respect to the total surface area of the outer blade.
The present invention is included in the present invention as long as it is set in the range of% (lower limit in consideration of salt lump discharge function) to 50% (upper limit in consideration of bellows protection function).

In the first embodiment, the flexible tube having no inner blade inside the bellows 1 is shown, but the flexible tube provided with the inner blade or the inner pipe inside the bellows has the opening of the present application. An outer blade can also be applied.

[0064]

According to the first aspect of the invention, a flexible tube for an automobile exhaust system having a bellows for absorbing expansion and contraction displacement and an outer blade formed by weaving a thin metal wire rod is used. A set of band-shaped wire bundles in which a plurality of metal wire rods each having a wire diameter are bundled side by side are set as one set, and a plurality of sets of band-shaped wire bundles required for one round are knitted in an oblique direction to form a tubular shape and braided in four directions. The portion surrounded by the side ends of the band-shaped wire bundle is formed as an opening, and the total opening area of a large number of openings formed over the entire outer blade is in the range of 20% to 50% with respect to the total surface area of the outer blade. The set outer blade, the number of peaks is 15 or less, and the load is 14 kgf
Since it is composed of a bellows set to a plate thickness that has a spring constant in the tensile direction that can obtain a displacement of 10 mm below, it is a flexible structure that achieves significant compactness while satisfying the required performance of absorbing expansion and contraction displacement by the bellows. The effect is that a tube can be provided.

According to the invention of claim 2, claim 1
In the flexible tube for automobile exhaust system described,
Since the bellows is made of a two-layer product in which two stainless steel plates having a thickness of 0.2 mm are stacked, and the number of peaks is set to 9 by bending, the bellows satisfy the required performance of absorbing expansion and contraction displacement while maintaining the conventional performance. It is possible to provide a flexible tube whose total length is less than half that of the flexible tube.

Further, as a result, the total length of the flexible tube is significantly shortened, so that restrictions on the design of the exhaust system are reduced and the degree of freedom in design is increased.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a flexible tube for an automobile exhaust system according to a first embodiment of the present invention.

FIG. 2 is a partial enlarged view showing an outer blade of the flexible tube of the first embodiment.

FIG. 3 is a side view showing the bellows of the flexible tube of the first embodiment.

FIG. 4 is a sectional view of a portion of FIG. 3A of the bellows according to the first embodiment.

FIG. 5 is a result diagram of a high temperature salt damage corrosion test result of the flexible tube of the first embodiment and a conventional flexible tube using a densely knitted outer blade.

FIG. 6 is a comparison diagram of spring constant characteristics measured by changing the thickness and the number of peaks of the bellows.

FIG. 7 is a half cross-sectional view showing a conventional flexible tube for an automobile exhaust system.

FIG. 8 is a partial enlarged view showing an outer blade of a conventional flexible tube for an automobile exhaust system.

[Explanation of symbols]

 F Flexible tube 1 Bellows 1a Mountain part 1b Cylindrical part 2 Outer blade 2a Band-shaped wire bundle 3 Protector 4 Opening part

Claims (2)

[Claims] 1. A bellows for absorbing expansion and contraction displacement of an exhaust pipe connected to both ends, and an outer blade provided so as to cover the outer periphery of the bellows for protecting the bellows and for preventing extension of the bellows. In a flexible tube for automobile exhaust system, one set of band-shaped wire bundles made by bundling a plurality of thin metal wires side by side is formed by diagonally knitting a plurality of sets of band-shaped wire bundles required for one round. In addition to having a cylindrical shape, the portion surrounded by the side ends of the band-shaped wire bundle woven in four directions is defined as an opening, and the total opening area of a large number of openings formed over the entire outer blade is the total surface area of the outer blade. On the other hand, the outer blade is set in the range of 20% to 50%, the number of peaks is 15 or less, and the load is 14 kgf or less.
A flexible tube for an automobile exhaust system, which is configured by a combination of a bellows set to a plate thickness having a spring constant in a tensile direction capable of obtaining a displacement of 0 mm, and. 2. The flexible tube for an automobile exhaust system according to claim 1, wherein the bellows is made of a two-layer product obtained by stacking two stainless steel plates having a thickness of 0.2 mm, and the bellows is formed by bending to have 9 peaks. A flexible tube for automobile exhaust systems, characterized by being set to.