JPH09137722A - Vibration insulation pipe and joint structure of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sufficient sealing performance in connecting to the other pipe, and to easily' release the connection after the connection. SOLUTION: A vibration insulation pipe 1 is constituted of a bellows 11, an outer pipe 17 and a case 21. The outer pipe 17 is provided with an annular first protrusion 18 whose opening end is extended outward in the radial direction, bent and formed into a curled shape. A connecting pipe 2 is provided with an annular second protrusion 128. A clamp is put in a state where the first protrusion 18 and the second protrusion 128 are brought into contact with each other through the end 12a of the bellows 11, so as to surround them, and a bolt of the clamp is fastened. The clamp presses the first protrusion 18 to the second protrusion 128 side and presses the second protrusion 128 to the first protrusion 18 side, and therefore, both protrusions 18, 128 are connected to each other with excellent sealing performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration isolation pipe connected to an exhaust pipe to absorb vibration of the exhaust pipe.

[0002]

2. Description of the Related Art Exhaust pipes of an exhaust system of a vehicle are subjected to vibrations due to engine rolling, pitching, etc. or vibrations on bad roads. There was a risk of being adversely affected.

In order to solve such a problem, it has been known that a vibration isolation pipe is provided in the middle of an exhaust pipe to isolate the vibration. A typical one of the vibration isolation pipes is called a flexible pipe or a flexible pipe, which has an effect of absorbing vibrations caused by bending and vibrations in the axial direction.

As the joint structure of the vibration isolation pipe and the exhaust pipe, the vibration isolation pipe is inserted into the exhaust pipe, and the insertion portion is tightened with a clamp (U bolt) to bring the contact surfaces of the two into close contact with each other. The structure that made it known was known.

[0005]

However, in such a joint structure, it is necessary to increase the tightening degree of the clamp to the extent that the vibration isolation pipe and the exhaust pipe are deformed in order to improve the sealing property. On the other hand, if the tightening degree is increased as described above, a clearance may be generated between the vibration isolation pipe and the exhaust pipe. Further, since the vibration isolation pipe and the exhaust pipe are deformed, they may not be easily removed after they are assembled, which is a problem in terms of service such as maintenance.

The present invention has been made in view of the above problems, and has a sufficient sealing property when connecting to another pipe,
An object of the present invention is to provide a vibration isolation pipe that can be easily released from the connection after the connection, and a joint structure using the same.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is an end portion of a vibration isolation pipe which is connected to an exhaust pipe and absorbs vibration of the exhaust pipe. Is provided with a first protrusion that protrudes annularly outward in the radial direction.

For this vibration isolating pipe, another pipe having a similar construction, that is, a projection having an annular projecting outward in the radial direction at the end is prepared, and the projection of this pipe and the first projection of the vibration isolating pipe are provided. The pipes are connected to each other by facing each other and fastening them by a clamp so that the two projections come close to each other.

According to this vibration isolating pipe, since both projections are fastened so as to come close to each other, the effect of having a sufficient sealing property can be obtained. Further, if the clamp is loosened, the two can be easily separated from each other, and the effect of easily releasing the connection can be obtained. In addition, it is preferable that the first projection has a substantially arcuate cross-sectional shape at a portion corresponding to the sealing surface, and for example, it is preferable that the first projection is curled. This is because when the clamp is loosened and then the connection is released after connecting with another pipe by the clamp, the original shape is easily restored. In this case, when the connection is released and the connection is made again by the clamp, a sufficient sealing property equivalent to that at the beginning can be obtained.

A second aspect of the present invention is the vibration isolating pipe according to the first aspect, which is a flexible bellows,
A pipe provided so as to surround the periphery of the bellows, supporting the bellows, and having a pipe having the first protrusion at an end thereof.

In this vibration isolation pipe, for example, both ends of the bellows are joined to the pipe by spot welding or the like to support the bellows on the pipe. This pipe is preferably stretchable in the axial direction. With this vibration isolation pipe, even if vibration is transmitted to the exhaust pipe due to engine rolling, pitching, or traveling on a bad road, the vibration can be effectively removed due to the presence of the bellows. When the vibration of the exhaust pipe is cut off in this way, the vibration inside the vehicle is reduced.

A third aspect of the present invention is the vibration isolating pipe according to the second aspect, wherein the pipe is provided independently of the case surrounding the bellows and one end of the bellows. An outer pipe that supports and has the first protrusion is provided.

According to this vibration isolation pipe, one end of the bellows is supported by the outer pipe provided independently of the case. Therefore, when the outer pipe moves in the axial direction independently of the case, one end of the bellows also becomes the same. The entire bellows absorbs this axial vibration. Therefore, the bellows can more easily block the vibration in the axial direction.

The invention according to claim 4 is the vibration isolating pipe according to claim 3, characterized in that a first cushioning material is interposed between the outer pipe and the bellows. According to this vibration isolation pipe, when the outer pipe moves in the direction of compressing the bellows, the first cushioning material receives the movement of the outer pipe, so that the outer pipe does not directly collide with the bellows. Therefore, an excessive load is not applied to the bellows, and the durability of the bellows is improved.

The invention according to claim 5 is the vibration isolation pipe according to claim 3 or 4, wherein the outer pipe is
The side supporting the bellows is surrounded by the case, and a second cushioning member is interposed between the outer pipe and the case.

According to this vibration isolation pipe, when the outer pipe moves in the direction of pulling the bellows, the second cushioning material receives the movement of the outer pipe, so that the pulling force does not act directly on the bellows. Therefore, an excessive load is not applied to the bellows, and the durability of the bellows is improved.

According to a sixth aspect of the present invention, there is provided a vibration isolating pipe joint structure, wherein the vibration isolating pipe according to any one of the first to fifth aspects is projected radially outward in an annular shape at an end. And a connecting pipe arranged so as to face the first projection of the vibration isolation pipe, and a first pressing surface for pressing the first projection toward the second projection. And a clamp having a second pressing surface that presses the second protrusion toward the first protrusion.

According to this joint structure, since the first and second protrusions are fastened so as to approach each other, a sufficient sealing property is provided. Also, if the clamp is loosened, they are easily separated from each other and are disconnected. According to a seventh aspect of the present invention, in the joint structure of the vibration isolating pipe according to the sixth aspect, the bellows has an extension portion in which an end portion on the side of the first protrusion extends outward from the pipe. And the extended portion is in close contact with the first protrusion.

According to this joint structure, since the extending portion of the bellows acts as a gasket, even when the surface accuracy of the first projection or the second projection is not so high or the circumferential dimension varies, for example. Therefore, a sufficient sealing property can be obtained. The invention according to claim 8 is the joint structure of the vibration isolating pipe according to claim 6 or 7,
A joint pipe inserted into the vibration isolation pipe and the connection pipe is provided, and the joint pipe has a third protrusion that protrudes radially outward at a substantially central portion, and the third protrusion is the first protrusion. It is characterized in that it is arranged between the protrusion and the second protrusion.

In this joint structure, one joint pipe is inserted into the vibration isolation pipe and the connection pipe, and the third protrusion is arranged between the first protrusion and the second protrusion. By being pressed to the protrusion side, the third
The second protrusion is pressed by the protrusion, and the second protrusion is pressed by the third protrusion by being pressed toward the first protrusion.

According to this joint structure, sufficient sealability can be obtained, the connection can be easily released after the connection, and the joint portion has sufficient strength due to the presence of the joint pipe.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the embodiment of the present invention
It is needless to say that the present invention is not limited to the following embodiments, and can take various forms within the technical scope of the present invention. [First Embodiment] The first embodiment relates to a vibration isolating pipe. The vibration isolation pipe will be described below with reference to FIGS. 1 and 2. FIG. 1 is a broken sectional view of a vibration isolation pipe of this embodiment, and FIG. 2 is a sectional view taken along the line AA of FIG.

The vibration isolation pipe 1 comprises a bellows 11, an outer pipe 17, and a case 21. The bellows 11 is a pipe including fixed portions 12 and 13 provided at both ends and a flexible portion 14 formed between the fixed portions 12 and 13. The fixed portions 12 and 13 have a straight side surface shape, and the flexible portion 14 has a plurality of mountain portions 14.
It has a side surface shape in which a and the valley portion 14b are repeated. Further, the end 12a (extending portion of the present invention) of the one fixing portion 12 is extended outward from the outer pipe 17 and is expanded into a trumpet shape, and is brought into close contact with a first protrusion 18 provided on the outer pipe 17 described later. It is formed so that it can.

The outer pipe 17 is a pipe formed so as to surround one fixing portion 12 of the bellows 11. The outer pipe 17 supports the fixing portion 12 of the bellows 11 by spot welding. Further, the outer pipe 17 has an annular first protrusion 18 formed in a curl shape by folding back the open end while extending outward in the radial direction. Further, the outer pipe 17 has a flange portion 19 on the side opposite to the open end, that is, the end portion on the side facing the flexible portion 14 of the bellows 11. This flange part 19
A ring-shaped first wire mesh 20 (first cushioning material of the present invention) is arranged between the flexible portion 14 and the flexible portion 14.

The case 21 has a small diameter portion 22 and a tapered portion 2.
3, the large diameter portion 24 and the four claw portions 25, and surrounds the other fixed portion 13, the flexible portion 14, and the flange portion 19 of the outer pipe 17 of the bellows 11.
Specifically, the small diameter part 22 supports the fixing part 13 of the bellows 11 by spot welding, and the large diameter part 24 supports the bellows 11.
The flexible portion 14 is surrounded, and the four claw portions 25 surround the flange portion 19. As shown in FIG. 2, the four claw portions 25 are provided at four positions on the open end side (left side in FIG. 1) of the large diameter portion 24, and the flange portion 19 of the outer pipe 17 is provided.
A ring-shaped second wire mesh 26 (the second cushioning material of the present invention) is disposed between and. These claws 25 are
In the state before bending (see the chain double-dashed line in FIG. 1), the first wire mesh 20 is connected to the flexible portion 14 and the flange portion 1.
9 and the second wire mesh 26 is arranged outside the flange portion 19 (on the left side in FIG. 1) and then bent to the position shown by the solid line in FIG. 1 to form the first and second wire meshes. 20 and 26 are pressed and fixed.

The bellows 11 is made of a metal having a thickness of 0.3 mm, and the outer pipe 17 and the case 21 are made of a metal having a thickness of 1.2 mm. Here, some modified examples of the first embodiment will be illustrated. 8 and 9 are explanatory views of a modification of the vibration isolation pipe. For example, as shown in FIG. 8, a first wire mesh 20 and a second wire mesh 26 are integrally formed to form an integrated wire mesh 9, and the integrated wire mesh 9 engages with the flange portion 19 of the outer pipe 17. A mating engagement groove 9a may be provided. At this time, the integrated wire mesh 9 may have a ring shape or a plurality of fan-shaped ones. Also, as shown in FIG. 9, the end portion 12 of the bellows 11 is
The a may not be extended from the open end of the outer pipe 17 to the outside. [Second Embodiment] The second embodiment relates to a joint structure for connecting the vibration isolation pipe 1 of the first embodiment to another pipe. The joint structure will be described below with reference to FIGS. 3 and 4. FIG. 3 is a sectional view of the joint structure, and FIG. 4 is an explanatory view of the clamp.

When connecting the vibration isolating pipe 1, the connecting pipe 2 and the clamp 3 are prepared as other pipes. The connection pipe 2 is, as shown in FIG.
It has an annular second protrusion 28 formed in a curl shape by folding back while opening the open end outward in the radial direction. On the other hand, the clamp 3 is, as shown in FIGS. 4 (a) and 4 (b),
A substantially semicircular upper part 3a and a lower part 3b are integrally formed by a bolt insertion part 4 and formed into an annular shape. A bolt (not shown) is inserted into the insertion hole 4a provided in the bolt insertion portion 4. The upper part 3a and the lower part 3b approach each other as the bolt is tightened, and move away from each other as the bolt is loosened. As shown in FIG. 4D, the clamp 3 is provided with a circumferential groove 5 that opens to the inner peripheral side of the clamp 3. The circumferential groove 5 has first and second groove forming surfaces 5a and 5b formed in a taper shape from the open inner peripheral side toward the outer peripheral side. Further, the distance between the first and second groove forming surfaces 5a and 5b becomes narrower from the inner peripheral side toward the outer peripheral side.

To connect the vibration isolation pipe 1 and the connection pipe 2, as shown in FIG. 3, the first protrusion 18 of the vibration isolation pipe 1 and the second protrusion 28 of the connection pipe 2 are connected to the end of the bellows 11. The clamp 3 is covered so as to surround the first and second protrusions 18 and 28 in a state of being in contact with each other via the portion 12a, and then a bolt (not shown) inserted into the bolt insertion hole 4a of the clamp 3 is tightened. When you tighten this bolt,
The groove forming surface 5a presses the first protrusion 18 toward the second protrusion 28. The second groove forming surface 5b presses the second protrusion 28 toward the first protrusion 18 side.

As a result, the first protrusion 18 and the second protrusion 28, which were in light contact with each other before tightening the bolt, are
When 8 are pressed in the direction of coming into contact with each other, they come into strong contact with each other, and the adhesion, that is, the sealing property is improved. Further, the end portion 12a of the bellows 11 is provided between the first protrusion 18 and the second protrusion 28.
Intervenes, which acts as a gasket,
For example, even when the surface accuracy of the first projection 18 and the second projection 28 is not very high, or when there are variations in the circumferential dimension, sufficient sealing performance can be obtained.

In such a connected state, for example, as shown in FIG.
When a force is applied to move the connecting pipe 2 to the right, the outer pipe 17 also moves to the right, and the flange portion 19 moves to the mountain portion 1 of the flexible portion 14 of the bellows 11.
Attempts to compress 4a and valley 14b. However, since the first wire mesh 20 is interposed between the flange portion 19 and the flexible portion 14, the first wire mesh 20 absorbs the force of moving the outer pipe 17 to the right, and the force is directly applied. It does not join the flexible portion 14. Further, for example, when a force that moves the connecting pipe 2 to the left in FIG. 3 is applied, the outer pipe 17 also moves to the left and the flexible portion 14 of the bellows 11 moves.
Attempts to pull the peaks 14a and the valleys 14b. However, since the second wire mesh 26 is interposed between the flange portion 19 and the claw portion 25 of the case 21, this second wire mesh 26
The wire mesh 26 absorbs the force of the outer pipe 17 moving to the left, and the force is not directly applied to the flexible portion 14. In this way, even if a compressive load or a tensile load is applied to the outer pipe 17, the load is not directly applied to the bellows 11, so that the durability of the bellows 11 is improved.

Subsequently, when the bolts of the clamp 3 are loosened from the tightened state as described above, the upper portion 3a and the lower portion 3b of the clamp 3 are separated from each other. At this time, since the vibration isolation pipe 1 and the connection pipe 2 are merely in contact with each other by the first and second projections 18 and 28, they are easily separated from each other. That is, the effect that the connection can be easily released after the connection is obtained.

Further, of the first and second protrusions 18 and 28, the portions pressed by the first and second groove forming surfaces 5a and 5b forming the circumferential groove 5 of the clamp 3 and the bellows 11.
Since the portions that are in contact with each other via the end portions 12a of each are curled, they are easily restored and return to the original state. Therefore, even after the connection between the vibration isolation pipe 1 and the connection pipe 2 is released, their respective shapes hardly change. Therefore, even if the assembly is carried out again, the same sealability as in the case of the first assembly can be obtained.

Here, some modified examples of the second embodiment will be illustrated. FIG. 5 is a partial explanatory view showing a modified example of the joint structure. FIG. 5A shows a combination of the vibration isolation pipe 1 and the connection pipe 2 having the second protrusion 128 that bulges radially outward in the vicinity of the end of the pipe. Since the second protrusion 128 is formed in a substantially arcuate cross section, it has elastic force and restoring force like the second protrusion 28. FIG. 5B shows a combination of the vibration isolation pipe 1 and the connection pipe 2 having the second protrusion 228 whose pipe end portion is linearly extended outward in the radial direction. Since the bent portion 228a of the second protrusion 228 is formed with a predetermined radius of curvature, the second protrusion 228 has elastic force and restoring force like the second protrusion 28. FIG. 5C is a vibration isolating pipe having a first protrusion 318 having a shape in which the opening end of the outer pipe 17 is linearly extended outward in the radial direction and is bent back at a bent portion 318a with a predetermined radius of curvature. 1 and the connection pipe 2 including the second protrusion 328 having the same shape as the first protrusion 318. Since the first and second protrusions 318 and 328 are folded back at the bent portions 318a and 328a with a predetermined radius of curvature, they have elastic force and restoring force like the second protrusion 28. With these modified examples, the same effect as that of the second embodiment can be obtained.

When the end portion 12a of the bellows 11 of the vibration isolation pipe 1 is not extended out from the open end of the outer pipe 17 (see FIG. 9),
The first protrusion 18 and the second protrusion 28 are in direct contact with each other. Even in this case, the same operation and effect as those of the second embodiment can be obtained. [Third Embodiment] The third embodiment relates to a joint structure for connecting the vibration isolation pipe 1 of the first embodiment to another pipe. The joint structure will be described below with reference to FIG. FIG. 6 is a partial sectional view of the joint structure.

When connecting the vibration isolation pipe 1, the connection pipe 8 as another pipe and the clamp 3 (see FIG. 3) are prepared, and the joint pipe 6 is facilitated. As shown in FIG. 6, the connection pipe 8 has an annular second protrusion 88 that is formed by curling the opening end while extending outward in the radial direction and is formed in a curl shape. A section 89 is provided. The joint pipe 6 has an annular third protrusion 68 that bulges outward in the radial direction at substantially the center, and a notch 61 is provided at the end on the connection pipe 8 side along the axial direction. The notch 61 is formed in the connection pipe 8 so that when the joint pipe 6 is inserted into the connection pipe 8, the second protrusion 88 and the third protrusion 68 of the joint pipe 6 come into contact with each other at a predetermined position shown in FIG. It is for engaging with the provided convex part 89 and positioning.
The vibration isolation pipe 1 may be provided with a protrusion similar to the protrusion 89, and the joint pipe 6 may be provided with a notch similar to the notch 61.

To connect the vibration isolation pipe 1 and the connection pipe 8, the joint pipe 6 is inserted into both pipes 1, 8 and the first protrusion 18 of the vibration isolation pipe 1 is attached to the bellows 1.
The second projection 8 of the connection pipe 8 is brought into contact with the third projection 68 of the joint pipe 6 through the end 12a of the first pipe 8 and the second projection 8 of the connection pipe 8.
In the state where 8 is also in contact with the third protrusion 68,
Clamp 3 so as to surround the third protrusion 18, 88, 68.
Then, the bolt (not shown) inserted in the bolt insertion hole 4a (see FIG. 4) of the clamp 3 is tightened. When this bolt is tightened, the first groove forming surface 5a presses the first protrusion 18 toward the second protrusion 88 and also radially inwardly. Further, the second groove forming surface 5b presses the second protrusion 88 toward the first protrusion 18 side and also inward in the radial direction.

As a result, before the bolt is tightened, the third protrusion 6
The first projection 18 and the second projection 8 that were in light contact with
8 is pressed in the direction of coming into contact with each other
The effect of strongly contacting the protrusion 68 and improving the adhesiveness, that is, the sealing property is obtained. Further, the first and second protrusions 18 and 88 are also pressed inward in the radial direction by the first and second groove forming surfaces 5a and 5b.
The contact between 8, 88 and the joint pipe 6 becomes more dense. Also, in this joint structure, the joint pipe 6
As a result, the effect of improving the bending strength at the joint portion can be obtained. Further, as in the second embodiment, the end portion 12a of the bellows 11 plays a role of a gasket, and therefore, for example, when the surface accuracy of the first to third protrusions 18, 88, 68 is not very high or the dimension in the circumferential direction is large. Even if there are variations, sufficient sealing performance can be obtained.

The outer pipe 1 is connected in this manner.
Even if a compressive load or a tensile load is applied to 7, the load is not directly applied to the bellows 11 as in the second embodiment, so that the durability of the bellows 11 is improved. When the bolts of the clamp 3 are loosened from the assembled state as described above, the upper portion 3a and the lower portion 3b of the clamp 3 are separated from each other. At this time, since the vibration isolation pipe 1 and the connection pipe 8 are only in contact with the third protrusion 68, they are easily separated from each other. Then, of the first and second protrusions 18, 88, the first and second groove forming surfaces 5 that form the circumferential groove 5 of the clamp 3.
The portion that has been pressed by a and 5b, and the third protrusion 6
The parts that were in contact with 8 are the first and second protrusions 1
It easily returns to its original shape due to the restoring force of 8,88. That is,
The effect that the connection can be easily released after the connection is obtained. Further, even if the re-assembling is performed again, it is possible to obtain the effect that it is possible to obtain the same sealing property as the case of the first assembling.

Here, a modified example of the joint structure of the third embodiment will be illustrated. FIG. 7 is an explanatory view of main parts of a modification of the third embodiment. That is, the joint pipe 6 of the third embodiment
And a vibration isolation pipe 1 of the first embodiment, and a connection pipe provided with a projection 288 (having a predetermined radius of curvature at the bent portion 288a) in which the pipe end portion is linearly extended outward in the radial direction. 8 and the clamp 3 are combined, and this modified example can also obtain substantially the same operational effect as the third embodiment.

When the end portion 12a of the bellows 11 of the vibration isolation pipe 1 is not extended from the open end of the outer pipe 17 (see FIG. 9),
The first protrusion 18 and the third protrusion 68 are in direct contact with each other. Even in this case, the same operation and effect as those of the third embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a broken sectional view of a vibration isolation pipe of a first embodiment.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a joint structure according to a second embodiment.

FIG. 4 is an explanatory diagram of a clamp.

FIG. 5 is an explanatory diagram of a modified example of the second embodiment.

FIG. 6 is a sectional view of a joint structure according to a third embodiment.

FIG. 7 is an explanatory diagram of a modified example of the third embodiment.

FIG. 8 is an explanatory diagram of a modified example of the first embodiment.

FIG. 9 is an explanatory diagram of a modified example of the first embodiment.

[Explanation of symbols]

1 ... Vibration isolation pipe, 2 ... Connection pipe, 3 ... Clamp, 5 ... Circumferential groove, 5a ... First groove forming surface, 5b ... Second
Groove forming surface, 6 ... Joint pipe, 8 ...
Connection pipe, 11 ... Bellows, 12a
... Ends, 14 ... Flexible parts, 17 ...
..Outer pipe, 18 ... First projection,
19 ... Flange portion, 20 ... First wire mesh, 21 ... Case, 25 ... Claw portion,
26 ... second wire mesh, 28 ... second
Protrusions,

Claims (8)

[Claims] 1. A vibration isolating pipe, which is connected to an exhaust pipe and absorbs vibration of the exhaust pipe, comprising a first protrusion protruding in a radial outward direction in an annular shape at an end thereof. Pipes. 2. A flexible bellows, and a pipe which is provided so as to surround the circumference of the bellows, supports the bellows, and has the first protrusion at an end thereof. Vibration isolation pipe. 3. The pipe includes a case surrounding the bellows, and an outer pipe which is provided independently of the case and which supports one end of the bellows and has the first protrusion. The vibration isolation pipe according to claim 2. 4. The vibration isolating pipe according to claim 3, wherein a first cushioning material is interposed between the outer pipe and the bellows. 5. The outer pipe is surrounded by the case on a side supporting the bellows, and a second cushioning material is interposed between the outer pipe and the case. The vibration isolation pipe described. 6. The vibration isolation pipe according to any one of claims 1 to 5, and the second projection that annularly projects outward in a radial direction at an end,
The second protrusion includes a connection pipe arranged to face the first protrusion of the vibration isolation pipe, a first pressing surface for pressing the first protrusion toward the second protrusion and the second protrusion. 1. A joint structure for a vibration isolating pipe, comprising: a clamp having a second pressing surface that presses against one projection side. 7. The bellows has an extending portion whose end on the first protrusion side extends outward from the pipe, and the extending portion is in close contact with the first protrusion. The joint structure of the vibration isolating pipe according to claim 6. 8. A joint pipe inserted into the vibration isolation pipe and the connection pipe, wherein the joint pipe has a third protrusion that projects annularly in a radially outward direction at substantially the center of the joint pipe. The joint structure of the vibration isolating pipe according to claim 6 or 7, wherein a protrusion is disposed between the first protrusion and the second protrusion.