JP2018053794A - Exhaust pipe structure - Google Patents

Abstract

An exhaust pipe structure capable of achieving both high heat insulation and reduced radiation noise is provided.
An exhaust pipe structure 1A includes an inner pipe 11 forming an exhaust gas circulation space, an outer pipe 12 provided on the outer periphery of the inner pipe 11, and a fibrous shape interposed between the inner pipe 11 and the outer pipe 12. The heat insulating material 13 is provided. The heat insulating material 13 includes a vibration isolating portion 130 that is disposed in a portion 14 that is relatively easy to vibrate in the inner tube 11 and the outer tube 12 and has a higher density than portions disposed in other portions. The anti-vibration part 130 is a dense part with a relatively small air layer, and vibrations can be reduced because the rigidity is relatively high. Since the base part 132 arrange | positioned in said other location contains many air layers relatively, it is excellent in heat insulation. Therefore, the exhaust pipe structure 1 </ b> A can achieve both high heat insulation and reduction of radiated sound.
[Selection] Figure 1

Description

  The present invention relates to an exhaust pipe structure for exhausting exhaust gas from an internal combustion engine mounted on a vehicle to the outside of the vehicle.

  Exhaust gas generated in an internal combustion engine mounted on a vehicle is generally discharged outside the vehicle through an exhaust device. The exhaust device includes a tubular member that forms a flow path of an exhaust gas such as a catalytic converter, a muffler, and a pipe connecting these. Patent Document 1 discloses a configuration in which ceramic wool and glass wool are stacked and filled between inner and outer double pipes as pipes connecting an internal combustion engine and a catalytic converter.

Japanese Utility Model Publication No. 07-008524

  Patent Document 1 assumes that by providing a laminated material of ceramic wool and glass wool, the heat insulation effect can be increased and the radiated sound can be reduced by the sound absorption effect. Here, a material (hereinafter, referred to as a fiber aggregate) in which fibers such as ceramic wool and glass wool are gathered in a cotton shape is excellent in heat insulation by including an air layer between the fibers, but has low rigidity. For this reason, in the above-described tubular member where vibration is likely to be applied, it is not possible to sufficiently obtain the vibration damping effect by the fiber assembly material, and it is desired to reduce the radiated sound caused by the vibration. For example, if the fiber assembly is compressed to reduce the air layer, the rigidity can be increased and the vibration can be suppressed, but the heat insulating property is lowered.

  Therefore, one of the objects of the present invention is to provide an exhaust pipe structure that can achieve both high heat insulation and reduction of radiated sound.

An exhaust pipe structure according to an aspect of the present invention includes:
An exhaust pipe structure that exhausts exhaust gas from the internal combustion engine of the vehicle to the outside of the vehicle,
An inner pipe that forms a flow space for the exhaust gas;
An outer tube provided on the outer periphery of the inner tube;
A fibrous heat insulating material interposed between the inner tube and the outer tube;
The said heat insulating material is arrange | positioned in the location which is easy to vibrate in the said inner tube and the said outer tube | pipe, and is provided with the vibration isolating part with a larger density than the part arrange | positioned in another location.

  The exhaust pipe structure described above has a portion that easily vibrates in the inner tube and the outer tube, and a fibrous heat insulating material having a relatively large density is disposed in this portion. The high-density portion is a dense portion having a relatively small air layer, so that the rigidity is relatively high, and functions as a vibration-proof portion that suppresses vibration. And the thing which is a fibrous heat insulating material and contains relatively many air layers is arrange | positioned in the other location in an inner tube | pipe and an outer tube | pipe. This low density part is excellent in heat insulation. Therefore, the above-described exhaust pipe structure has a simple structure in which the density of the fibrous heat insulating material interposed between the inner pipe and the outer pipe is locally different, while achieving high heat insulation and reduction of radiated sound. Can be compatible.

It is a schematic sectional drawing which shows the muffler provided with the exhaust pipe structure of Embodiment 1. 6 is a schematic cross-sectional view partially showing a muffler having an exhaust pipe structure according to Embodiment 2. FIG.

  Hereinafter, the exhaust pipe structure of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same names.

[Embodiment 1]
(overall structure)
With reference to FIG. 1, the exhaust pipe structure 1A of Embodiment 1 is demonstrated.
The exhaust pipe structure 1A of the first embodiment is a tubular member that discharges exhaust gas from an internal combustion engine mounted on a vehicle such as an automobile to the outside of the vehicle and forms a flow path of the exhaust gas. The exhaust pipe structure 1 </ b> A includes an inner pipe 11 that forms an exhaust gas circulation space, an outer pipe 12 provided on the outer periphery of the inner pipe 11, and a fibrous heat insulating material 13 that is interposed between the inner pipe 11 and the outer pipe 12. With. In the exhaust pipe structure 1A, the density of the heat insulating material 13 is partially different, and the heat insulating material 13 is located in the portion 14 where the inner tube 11 and the outer tube 12 are relatively likely to vibrate, rather than the portion disposed in other places. The vibration isolator 130 having a high density is provided. The vibration isolator 130 is a dense part with a relatively small air layer. The exhaust pipe structure 1 </ b> A aims to reduce radiated sound due to vibration by the vibration isolator 130 and to secure high heat insulating performance by the base portion 132 having a relatively low density in the heat insulating material 13.

  Hereinafter, the case where the exhaust pipe structure 1A is applied to the muffler 10 generally provided on the downstream side (side away from the internal combustion engine) in the exhaust gas flow path will be described as an example (the same applies to the second embodiment described later). . FIG. 1 is a longitudinal sectional view of the muffler 10 cut along a plane parallel to the axial direction (left and right direction in FIG. 1).

(Muffler)
First, the outline of the muffler 10 will be described.
The muffler 10 of this example includes an inlet pipe 15 that introduces exhaust gas from the internal combustion engine side, an outlet pipe 16 that discharges exhaust gas, and one end side that is overlapped in the radial direction of the muffler 10 in both pipes 15 and 16. An inner shell 11A (an example of the inner tube 11), end plates 18 and 19 that close the openings of the inner shell 11A, and a plurality of separators 17 that partition the inner shell 11A into a plurality of spaces. With. The pipes 15 and 16 pass through the plates 18 and 19 and the separator 17, and are supported while being spaced apart at predetermined positions in the inner shell 11 </ b> A. With this configuration, the muffler 10 is silenced by an expansion effect or a resonance effect. Further, the muffler 10 includes an outer shell 12A (an example of the outer tube 12) that covers the outer periphery of the inner shell 11A, and a heat insulating material 13 interposed between the shells 11A and 12A. That is, the muffler 10 has a three-layer structure having double shells 11A and 12A and a heat insulating material 13. A known configuration can be used as the basic configuration of the muffler 10. For example, the number of separators 17 is two in FIG. 1, but may be three or more. In particular, in the exhaust pipe structure 1A of the first embodiment, the heat insulating material 13 is a sparsely mixed material as described above, and the arrangement locations of the high-density portion and the low-density portion according to the ease of vibration in the shells 11A and 12A. By setting, radiated sound is reduced.

<Inner shell, outer shell>
At least one of the inner shell 11 </ b> A and the outer shell 12 </ b> A includes a convex portion 120 that protrudes toward the other. For this reason, the interval d ₁₂₀ between the portions where the convex portions 120 are formed between the shells 11A and 12A is smaller (narrower) than the interval d between the other portions. The convex part 120 that forms such a narrow portion is a fibrous heat insulating material interposed between the shells 11A and 12A, and partially compresses the heat insulating material having a uniform density and thickness. Thus, it has a function of forming a high-density portion (anti-vibration portion 130).

  The inner shell 11A in this example is a cylindrical body having a smooth curved surface. The outer shell 12A of this example is a cylindrical body provided with a convex portion 120 that protrudes toward the inner shell 11A. Further, the convex portion 120 in this example is formed by bending at a predetermined position in the plate material constituting the outer shell 12A. Therefore, the thickness of the outer shell 12A is substantially uniform over the entire outer shell 12A.

  The convex part 120 is provided in the location 14 which is relatively easy to vibrate in the inner shell 11A and the outer shell 12A. Here, on the inner peripheral surface of the inner shell 11A, a plurality of separators 17 are attached by spot welding or the like so as to be separated from each other in the axial direction of the inner shell 11A (left and right in FIG. 1). 19 is attached. The location where the inner shell 11A is fixed to the separator 17 and the plates 18 and 19 can be said to be a location with increased rigidity compared to other locations. A portion other than the fixed portion, that is, a central portion between the end plate 18 or 19 and the separator 17 and a central portion between the adjacent separators 17 and 17 have relatively low rigidity. Therefore, it can be said that these portions are portions 14 that tend to be antinodes of amplitude and relatively vibrate. Therefore, the convex portion 120 is provided at such a location 14.

  Of the inner shell 11 </ b> A and the outer shell 12 </ b> A, the formation range of the convex portion 120 along the circumferential direction of the inner shell 11 </ b> A and the outer shell 12 </ b> A, the convex portion along the axial direction. The formation range of 120, the number of convex portions 120, and the like can be selected as appropriate. The protrusions 120 may be provided on at least a part in the circumferential direction of the shell and at least a part in the axial direction with respect to each portion 14. For each location 14, for example, an annular convex portion 120 continuous in the circumferential direction of the shell, an arc-shaped convex portion 120 provided in a part of the circumferential direction of the shell, or a plurality of arc-shaped convex portions 120. Are provided apart from each other in the circumferential direction of the shell, or a plurality of linear protrusions 120 extending in the axial direction of the shell are arranged in parallel in the circumferential direction of the shell. Alternatively, for example, when the shell is viewed in the axial direction with respect to each location 14, a plurality of convex portions 120 are provided apart from each other as shown in FIG. 1, and only one convex portion 120 is provided. And so on. In this example, the outer shell 12 </ b> A includes a total of three sets in which two annular projections 120 extending in the entire circumference are arranged in the axial direction.

  The protruding length of the convex portion 120 is such that the density of the non-compressed portion in the heat insulating material 13 (the base portion 132) can be compressed so that a portion disposed in the portion 14 that is relatively easy to vibrate in the heat insulating material 13 can be compressed to a predetermined density. Density) and thickness, and the distance d between the inner shell 11A and the outer shell 12A other than the portion where the convex portion 120 is formed may be selected. As the protrusion length is larger, the heat insulating material 13 can be reliably compressed to reduce the air layer, and the high-density vibration isolator 130 can be provided. When the plurality of convex portions 120 are provided, as shown in FIG. 1, any form in which the protruding lengths of all the convex parts 120 are equal or different can be used.

  In addition, the inner shell 11 </ b> A and the outer shell 12 </ b> A can be an elliptical body, a rectangular tube body, or the like. Further, FIG. 1 shows a case where the inner shell 11A has a single structure. However, when two or more plate materials are stacked, the rigidity of the inner shell can be increased and further reduction of the radiated sound can be expected.

<Insulation material>
The heat insulating material 13 is a fiber aggregate in which fibers are collected in a cotton shape and include an air layer between the fibers. Typically, a sheet material or the like is easily used. In fiber aggregates composed of a single type of fiber, the higher the proportion (filling rate) of fibers per unit volume, the less the air layer, the more dense, and the higher the rigidity, the better the anti-vibration properties It is in. The lower the filling rate, in other words, the higher the proportion of air per unit volume (porosity = 1−filling rate), the more the air layer, the better the heat insulation. Therefore, in the fibrous heat insulating material 13, rigidity and heat insulation performance can be easily adjusted by adjusting a filling rate (or porosity). Moreover, a filling rate can be easily adjusted by adjusting the thickness of a sheet material, for example.

  Since the heat insulating material 13 is disposed in contact with the inner shell 11A through which high-temperature exhaust gas circulates, the fiber constituting the heat insulating material 13 is preferably a material having excellent heat resistance. For example, the constituent material of the fiber includes an inorganic material such as a nonmetal or a metal. Non-metallic inorganic materials such as glass and other ceramics are excellent in heat resistance and have low thermal conductivity, and the amount of heat transfer from the inner shell 11A to the heat insulating material 13 can be easily reduced. Specific examples of the heat insulating material 13 include glass wool, other ceramic wool, and metal wool such as stainless steel. In particular, glass wool has a sufficiently lower thermal conductivity than metal wool and is inexpensive and easy to use. In this example, glass wool is used. As the heat insulating material, a fiber aggregate containing a plurality of types of inorganic fibers having different constituent materials may be used. However, if a fiber aggregate composed of a single type of inorganic fiber is used, the density due to thickness adjustment, etc. It is easy to make partial changes.

  The heat insulating material 13A of this example includes vibration isolating portions 130 having a relatively large density and base portions 132 having a relatively small density, which are alternately arranged in the axial direction of the inner shell 11A and the outer shell 12A. In this example, such a dense heat insulating material 13A is prepared as a heat insulating material having an overall uniform density and uniform thickness, and this heat insulating material is used as an outer shell 12A having an inner shell 11A and a convex portion 120. Build by interposing. In detail, the heat insulating material which has the above-mentioned uniform density and thickness is arrange | positioned between both shell 11A, 12A. Then, the part arrange | positioned in the location 14 which is relatively easy to vibrate among this heat insulating material is compressed by the convex part 120. Portions that are disposed at locations other than the location 14 that is relatively easy to vibrate are not substantially compressed and are maintained as they are. At least a part of the portion 14 that is relatively easy to vibrate in both shells 11 </ b> A and 12 </ b> A is protected by a portion of the prepared heat insulating material that is compressed by the convex portion 120 and has a higher density than the base portion 132. A vibration unit 130 is interposed. A base portion 132 that is not compressed and includes a portion having a density lower than that of the vibration isolator 130 is interposed at a portion other than the portion 14 that easily vibrates.

  The density and thickness of the heat insulating material to be prepared are substantially equal to the density and thickness of the base portion 132. Therefore, the density and thickness of the heat insulating material to be prepared according to the distance d between the inner shell 11A and the outer shell 12A other than the portion where the convex portion 120 is formed so that the base portion 132 has a predetermined heat insulating performance. It is good to adjust. An example of the thickness is about 3 mm. By preparing such a heat insulating material, high heat insulating properties can be secured mainly by the base portion 132. On the other hand, the vibration suppression effect is more easily obtained as the density of the vibration isolation unit 130 is larger than that of the base unit 132. In order to obtain a desired vibration suppressing effect, the protrusion height of the protrusion 120 may be adjusted according to the density and thickness of the heat insulating material to be prepared.

  In the heat insulating material 13A, the boundary between the vibration isolating portion 130 and the base portion 132 may not be clear. However, the density of the compressed portion by the convex portion 120 and the non-compressed portion sufficiently separated from the convex portion 120 in the heat insulating material 13A is low. Have a difference.

(effect)
In the exhaust pipe structure 1A of the first embodiment, the fibrous heat insulating material 13 interposed between the inner shell 11A (inner pipe 11) and the outer shell 12A (outer pipe 12) does not have a uniform density. Is different. An anti-vibration part 130 having a relatively high density with a reduced air layer is provided at a relatively easily vibrated portion 14 in both shells 11A and 12A, and a sufficient air layer is provided at a portion other than the easily vibrated portion 14. (Including a relatively large amount) and a base portion 132 having a relatively small density. In the portion 14 that is likely to vibrate, the vibration of the shells 11A and 12A, particularly the vibration of the inner shell 11A, is reduced by the vibration isolator 130 having relatively high rigidity and excellent vibration damping properties, and radiation caused by the vibration. Sound can be reduced. In places other than the place 14 where the vibration is likely to occur, high heat insulation can be secured by the base portion 132 having excellent heat insulation. Therefore, the exhaust pipe structure 1A according to the first embodiment can achieve both high heat insulation and reduction of radiated sound at a high level.

In addition, the exhaust pipe structure 1A of this example also has the following effects.
(1) Since the heat insulating material used in the heat insulating material 13A includes a large amount of an air layer, the amount of the heat insulating material 13A used can be reduced compared with the case of using a high-density heat insulating material with a small air layer, and light weight. Can be achieved. Cost reduction can also be expected from the reduction in the amount used.
(2) It can be easily manufactured by sandwiching a heat insulating material having a uniform density and thickness between the inner shell 11A and the outer shell 12A, and is excellent in productivity.
(3) As a heat insulating material used for the heat insulating material 13A, a density difference can be easily provided by adjusting the thickness by using a single kind of inorganic fiber (here, glass wool).
(4) Since glass wool is used, cost reduction can be expected.

[Embodiment 2]
With reference to FIG. 2, the exhaust pipe structure 1B of Embodiment 2 is demonstrated.
FIG. 2 is a longitudinal sectional view of the muffler 10 cut along a plane parallel to the axial direction (left and right direction in FIG. 2), and shows only the vicinity of the upper half of the inner shell 11B and the outer shell 12B.

  The exhaust pipe structure 1B of the second embodiment is different from the first embodiment in the specification of the heat insulating material 13. Hereinafter, this difference will be described in detail, and detailed description of other configurations and effects will be omitted.

  In the exhaust pipe structure 1B of the second embodiment, both the inner shell 11B and the outer shell 12B are cylindrical bodies that do not have the convex portion 120 and have a smooth curved surface. Therefore, the distance d between the shells 11B and 12B is uniform over the entire length of the shells 11B and 12B. As such a heat insulating material interposed between the shells 11B and 12B, for example, a dense heat insulating material 13B is provided by using an uneven heat insulating material having a uniform density and partially different thickness. The exhaust pipe structure 1B can be constructed. In this case as well, if a fiber assembly composed of a single type of fiber (for example, glass wool) is used as the heat insulating material, the density can be easily changed by adjusting the thickness.

  The relatively thick portion (convex portion) in the prepared heat insulating material is likely to vibrate so as to be disposed at a location 14 where it is relatively easy to vibrate when the heat insulating material is interposed between the shells 11B and 12B. It is provided corresponding to the location 14. The thickness t of the thick part is made larger than the distance d between the shells 11B and 12B (t> d). If the thickness of the relatively thin portion is, for example, substantially the same as the distance d, the two shells 11B and 12B are not substantially compressed, and the air layer can be sufficiently included. And the heat insulating material from which the above-mentioned thickness differs partially between shells 11B and 12B is arranged. Then, the thick part arrange | positioned in the location 14 which is easy to vibrate among this heat insulating material is compressed by being pinched | interposed into both shells 11B and 12B, and the thin part arrange | positioned in places other than the location 14 which is easy to vibrate is mentioned. The portion (recessed portion) is not substantially compressed by both shells 11B and 12B, and the state is maintained as it is. At least a part of the portion 14 that easily vibrates in both shells 11B and 12B includes a vibration isolator 130 that is formed by compressing the thick portion of the prepared heat insulating material, and the portion 14 that easily vibrates. The base part 132 comprised from the said thin part of an uncompressed state interposes in locations other than.

  Alternatively, as another heat insulating material, for example, it is possible to use a heat insulating material having an entirely uniform thickness and partially different in density. The relatively high-density portion in the heat insulating material to be prepared is located in the portion 14 that easily vibrates so that the heat insulating material is interposed between the shells 11B and 12B, and the portion 14 is likely to vibrate relatively. Correspondingly provided. Such a heat insulating material can be easily used by combining sheet pieces having different densities as a single aggregate sheet material. And the vibration isolating part 130 comprised from a part with a higher density than the base part 132 is interposed in at least a part of the part 14 that easily vibrates in the shells 11B and 12B, and the part other than the part 14 that easily vibrates. A base portion 132 composed of a portion having a lower density than the vibration isolator 130 is interposed. In this case as well, when a fiber assembly composed of a single type of fiber (for example, glass wool) is used as the heat insulating material, a partial change in density can be easily performed by combining sheet pieces adjusted in degree of compression. .

  In the heat insulating material 13B, the boundary between the vibration isolator 130 and the base 132 is relatively clear.

  As in the first embodiment, the exhaust pipe structure 1B according to the second embodiment including the heat insulating material 13B suppresses vibration by the vibration isolating section 130 in which the air layer is reduced, and is highly insulated by the base section 132 that sufficiently includes the air layer. To ensure high heat insulation and reduce radiation noise. In particular, since the exhaust pipe structure 1B of the second embodiment uses a heat insulating material having a partially different thickness or a heat insulating material having a partially different density, both the inner shell 11B and the outer shell 12B have a simple outer shape. it can.

The present invention is not limited to these exemplifications, but is defined by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.
(1) The exhaust pipe structure of the present invention is not only the above-described muffler 10 but also a tubular member that forms an exhaust gas flow path, and has a portion that is relatively easy to vibrate, and has a heat insulating property and a radiated sound. It can be used in places where reduction is required.
(2) As the convex portion 120 of the outer shell 12A described in the first embodiment, a rib formed by partially increasing the thickness of the plate material constituting the outer shell 12A can be used. In this case, vibration suppression of the outer shell 12A can also be expected by the reinforcing function of the rib itself.
(3) The outer shell 12A described in the first embodiment does not have the convex portion 120, is a simple cylindrical body, and the inner shell 11A can include a convex portion that protrudes toward the outer shell 12A.
Or both shell 11A, 12A can be provided with a convex part. In this case, it can be set as the form by which the convex part which protrudes from both shell 11A, 12A is opposingly arranged, and the form by which the convex part which protrudes from both shell 11A, 12A is shifted | deviated to the axial direction of a muffler.

DESCRIPTION OF SYMBOLS 1A, 1B Exhaust pipe structure 10 Muffler 11 Inner pipe 11A, 11B Inner shell 12 Outer pipe 12A, 12B Outer shell 120 Convex part 13,13A, 13B Pipe 17 Separator 18, 19 End plate

Claims (1)

An exhaust pipe structure that exhausts exhaust gas from the internal combustion engine of the vehicle to the outside of the vehicle,
An inner pipe that forms a flow space for the exhaust gas;
An outer tube provided on the outer periphery of the inner tube;
A fibrous heat insulating material interposed between the inner tube and the outer tube;
The said heat insulating material is an exhaust pipe structure provided with the vibration isolator which is arrange | positioned in the location which is relatively easy to vibrate in the said inner pipe and the said outer pipe, and has a larger density than the part arrange | positioned in another location.

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