Exhaust system component

Abstract

To provide a technique for suppressing an effect of extension / contraction by thermal expansion of an inner pipe in an exhaust system component with a double pipe structure.SOLUTION: An exhaust system component with a double pipe structure includes an inner pipe and an outer pipe. Exhaust gas passes through inside of the inner pipe. The outer pipe is disposed to surround an outer periphery of the inner pipe. At least one end part of the inner pipe in the axial direction along a center axis of the inner pipe is fixed to the outer pipe by welding. The inner pipe has slits penetrating through a wall of the inner pipe and extending from a first end to a second end in a circumferential direction about the center axis. The first end and the second end are disposed so that the slits have overlapping portions that overlap in the axial direction leaving a gap.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to exhaust system components.

Background Art

[0002] In the exhaust system of an internal combustion engine, an exhaust pipe having a double pipe structure with an inner pipe and an outer pipe may be used. In such an exhaust pipe with a double pipe structure, since high-temperature exhaust gas flows inside the inner pipe, a thermal expansion difference occurs between the inner pipe and the outer pipe.

[0003] In order to suppress the influence of this thermal expansion difference, an exhaust pipe is known in which one end of the inner pipe is fixed to the outer pipe by welding, and the other end of the inner pipe is provided slidably by a wire mesh. However, since the wire mesh is expensive, there is a problem that the material cost becomes high in the exhaust pipe configured to be swingable by the above-described wire mesh.

[0004] Here, Patent Document 1 discloses that in order to suppress the influence of expansion and contraction due to thermal expansion of the inner pipe, one end of the inner pipe is fixed to the outer pipe by welding, and the other end of the inner pipe compression-fitted into the outer pipe is provided slidably by an axially extending slit provided at the end.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the exhaust pipe of the above-cited Patent Document 1, although the end of the inner pipe is slidable by the slit, since the end is in contact with the outer pipe by compression fitting, there is a concern that abnormal noise may occur as the inner pipe expands and contracts in the axial direction. That is, in the exhaust pipe of Patent Document 1, there is a problem that the effect on the expansion and contraction of the inner pipe in the axial direction is insufficient. For this reason, in the exhaust system component having a double pipe structure, a new method capable of suppressing the influence of expansion and contraction due to the thermal expansion of the inner pipe is desired.

[0007] One aspect of the present disclosure aims to provide a technique for suppressing the influence of expansion and contraction due to the thermal expansion of an inner pipe in an exhaust system component having a double pipe structure.

Means for Solving the Problems

[0008] One aspect of the present disclosure is an exhaust system component having a double pipe structure, including an inner pipe and an outer pipe. The inner pipe allows exhaust gas to pass through the inside. The outer pipe is arranged so as to surround the outer circumference of the inner pipe. One end of the inner pipe in the axial direction along the central axis of the inner pipe is fixed to the outer pipe by welding. The inner pipe has a slit that penetrates the wall of the inner pipe and extends from a first end to a second end in the circumferential direction centered on the central axis. The first end and the second end are arranged so that the slit has an overlapping portion where the slit overlaps with a space in the axial direction.

[0009] In such a configuration, the axial elongation of the inner pipe due to thermal expansion can be absorbed by the narrowing of the width of the slit. For this reason, in the exhaust system component having a double pipe structure, the influence of expansion and contraction due to the thermal expansion of the inner pipe can be suppressed.

[0010] In one aspect of the present disclosure, both ends of the inner pipe in the axial direction may be fixed to the outer pipe by welding. According to such a configuration, compared with a configuration in which one end of the inner pipe is not fixed, abnormal noise generated by the contact between the end of the inner pipe and the outer pipe due to vibration, and abnormal noise generated by a stick-slip phenomenon that occurs when the end of the inner pipe moves in the axial direction can be suppressed.

[0011] In one aspect of the present disclosure, the slit may extend spirally. According to such a configuration, since the stretching direction in which the slit extends is inclined with respect to the virtual plane orthogonal to the central axis of the inner tube, it is easier to absorb the axial elongation due to the thermal expansion of the inner tube as compared with the case where the stretching direction of the slit is not inclined with respect to the virtual plane.

[0012] In one aspect of the present disclosure, at least one edge of the first end and the second end of the slit may be formed in a curved shape.

[0013] In such a configuration, the stress that tends to concentrate at the end of the slit is likely to be dispersed over the entire edge of the end without concentrating at a single point. Therefore, it is possible to suppress the concentration of stress on a specific portion at the end of the slit.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0015] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration] The exhaust system component 100 shown in FIG. 1 is, for example, a muffler having a double-tube structure used in an exhaust system that constitutes an exhaust gas flow path of an internal combustion engine mounted on a vehicle. Note that the exhaust system component is not limited to a muffler, and may be, for example, an exhaust pipe having a double-tube structure. The exhaust system component 100 includes an inner tube 1 and an outer tube 2.

[0016] <Inner tube> The inner pipe 1 is a metal pipe through which the exhaust gas passes inside. The inner pipe 1 is, for example, cylindrical and is a straight pipe with a constant diameter. In the present embodiment, the inner pipe 1 is constituted by a substantially rectangular plate-like member 10 shown in FIG. 2. Specifically, the plate-like member 10 is wound to form the cylindrical inner pipe 1 shown in FIG. 1.

[0017] In the present embodiment, the upstream end portion 11 and the downstream end portion 12 in the axial direction along the central axis A of the inner pipe 1 are fixed to the outer pipe 2 described later by welding. The central axis A extends in the extending direction of the inner pipe 1 and passes through the approximate center of the cross section of the inner pipe 1 orthogonal to the central axis A. An upstream member 3 constituting an exhaust gas flow path on the upstream side of the exhaust system component 100 is inserted into the opening on the upstream end portion 11 side of the inner pipe 1, and the outer surface of the upstream member 3 is fixed to the inner surface of the inner pipe 1 by welding. Further, a downstream member 4 constituting an exhaust gas flow path on the downstream side of the exhaust system component 100 is inserted into the opening on the downstream end portion 12 side of the inner pipe 1, and the outer surface of the downstream member 4 is fixed to the inner surface of the inner pipe 1 by welding. The inner pipe 1 has two slits 5 and a plurality of communication holes 6. In addition, in FIGS. 2, 3A, and 3B, the illustration of the plurality of communication holes 6 is omitted.

[0018] As shown in FIGS. 1 and 3A, the slit 5 penetrates the wall of the inner pipe 1 and extends from the first end 51 to the second end 52 in the circumferential direction centered on the central axis A. Specifically, the slit 5 extends in a spiral shape centered on the central axis A and circulates around the central axis A at least one full turn or more. The width in the direction orthogonal to the extending direction of the slit 5 (hereinafter simply referred to as the width) is substantially the same from the first end 51 to the second end 52. Note that the width of the slit 5 can take any width. The edges of the first end 51 and the second end 52 are each formed in a curved shape.

[0019] In the present embodiment, two slits 5 are provided in the inner pipe 1. Specifically, each slit 5 is disposed near the upstream end portion 11 of the inner pipe 1 and near the downstream end portion 12 of the inner pipe 1. Among both ends 51 and 52 of each slit 5, the end located on the upstream end portion 11 side of the inner pipe 1 or the downstream end portion 12 side of the inner pipe 1 is defined as the first end 51, and the end located more inward in the axial direction than the first end 51 is defined as the second end 52.

[0020] In this embodiment, each slit 5 is formed as described below. First, as shown in FIG. 2, a plurality of notches 53 are provided in the plate-like member 10 that forms the inner tube 1. Each notch 53 extends from the edge of one of the two long sides of the plate-like member 10 toward the other long side so as to be inclined with respect to the short side of the plate-like member 10. In this embodiment, four notches 53 are provided. Two adjacent notches 53 extend from the edges of different long sides of the plate-like member 10, respectively, and extend parallel to each other.

[0021] Then, the plate-like member 10 is wound so that the two long sides of the plate-like member 10 are connected to form the cylindrical inner tube 1. At this time, one set of two adjacent notches 53 are connected at the end portions on each long side of the plate-like member 10 in each notch 53, and another set of two adjacent notches 53 are connected at the end portions on each long side of the plate-like member 10 in each notch 53. As a result, two slits 5 extending in a spiral shape are formed.

[0022] In this embodiment, the end portions on the side opposite to the long side of the plate-like member 10 in two adjacent notches 53, that is, the first end 51 and the second end 52 of the slit 5, are arranged so as to have an overlapping portion 50 where the slits 5 overlap with a gap in the axial direction.

[0023] Specifically, the overlapping portion 50 is formed by arranging the first end 51 and the second end 52 of the slit 5 to be separated from each other at different positions in the axial direction, and arranging a predetermined section in the circumferential direction of the slit 5 including the first end 51 and a predetermined section in the circumferential direction of the slit 5 including the second end 52 to overlap in the axial direction. Note that the overlapping portion is also formed when the first end and the second end of the slit are arranged to be separated from each other at different positions in the axial direction and at the same position in the circumferential direction. As a result, a slit 5 that spirally extends around the central axis A one or more times is formed in the inner tube 1.

[0024] In this embodiment, the four notches 53 are all inclined in the same direction with respect to the short side of the plate-like member 10. As a result, the extending directions of the two slits 5 formed by two sets of two adjacent notches 53 are inclined in the same direction with respect to a virtual plane orthogonal to the central axis A. Note that the four notches may be inclined in different directions with respect to the short side of the plate-like member, such that one set of two adjacent notches and another set of two adjacent notches are inclined in different directions. As a result, the extending directions of the two slits formed by two sets of two adjacent notches may be inclined in different directions with respect to the above-described virtual plane.

[0025] As shown in FIG. 1, the communication holes 6 are substantially circular through-holes that penetrate the wall of the inner tube 1, and a plurality of them are provided in the inner tube 1. Note that the communication holes can take various shapes other than circular. The communication holes 6 communicate the inside of the inner tube 1 with the outside of the inner tube 1 (i.e., the space 7 formed between the inner tube 1 and an outer tube 2 described later). The exhaust system component 100 exhibits a sound absorption effect due to the space 7. A sound absorbing material 8 such as wool is disposed in the space 7. Note that the sound absorbing material 8 may not be disposed in the space 7. The plurality of communication holes 6 are disposed over the entire inner tube 1 in a region between the two slits 5 in the inner tube 1. Note that the inner tube may not have a plurality of communication holes.

[0026] <Outer tube> The outer tube 2 is a metal pipe disposed so as to surround the outer periphery of the inner tube 1. The outer tube 2 is, for example, cylindrical, and has an inner diameter larger than the outer diameter of the inner tube 1. In this embodiment, the outer tube 2 is formed such that both end portions in the axial direction are reduced in diameter. In other words, the outer tube 2 is a pipe with a diameter-expanded center. The central axis of the outer tube 2 is disposed so as to coincide with the central axis A of the inner tube 1. Note that these central axes do not necessarily coincide. The outer tube 2 has a main body portion 21, an upstream portion 22, a downstream portion 23, a first fixing portion 24, and a second fixing portion 25.

[0027] The main body portion 21, the first fixing portion 24, and the second fixing portion 25 are each a straight tubular portion with a constant cross-sectional area (hereinafter simply referred to as the cross-sectional area) in a cross-section orthogonal to the axial direction. Note that the diameter of the main body portion 21 is larger than the diameters of the first fixing portion 24 and the second fixing portion 25.

[0028] The upstream portion 22 is a frustum-shaped portion whose cross-sectional area gradually expands as it goes from the first fixing portion 24 toward the main body portion 21. The downstream portion 23 is a frustum-shaped portion whose cross-sectional area gradually decreases as it goes from the main body portion 21 toward the second fixing portion 25.

[0029] The first fixing portion 24 is a portion for fixing the upstream end portion 11 of the inner pipe 1, and the second fixing portion 25 is a portion for fixing the downstream end portion 12 of the inner pipe 1. The inner surface of the first fixing portion 24 and the outer surface of the upstream end portion 11 of the inner pipe 1 are in contact with each other, and the outer surface of the upstream end portion 11 is fixed to the inner surface of the first fixing portion 24 by welding. Also, the inner surface of the second fixing portion 25 and the outer surface of the downstream end portion 12 of the inner pipe 1 are in contact with each other, and the outer surface of the downstream end portion 12 is fixed to the inner surface of the second fixing portion 25 by welding.

[0030] The main body portion 21, the upstream portion 22, and the downstream portion 23 are portions spaced apart from the inner pipe 1. By covering the inner pipe 1 in a state where the main body portion 21, the upstream portion 22, and the downstream portion 23 are spaced apart, the above-described space 7 is formed. In the present embodiment, the above-described slit 5 is disposed axially inward of the portion of the inner pipe 1 covered by the first fixing portion 24 and the second fixing portion 25 of the outer pipe 2. Specifically, the slit 5 is disposed in the portion of the inner pipe 1 covered by the upstream portion 22 and the downstream portion 23 of the outer pipe 2, respectively.

[0031] [2. Effects] According to the embodiment described in detail above, the following effects can be obtained. (2a) When high-temperature exhaust gas passes through the inside of the inner pipe 1, the inner pipe 1 extends in the axial direction and expands and spreads in the circumferential direction. In such a case, in a configuration without the slit 5, the axial length of the inner pipe becomes longer, and the circumferential length of the inner pipe becomes longer, so that the diameter of the inner pipe becomes larger.

[0032] On the one hand, in this embodiment, a slit 5 extending from a first end 51 to a second end 52 in the circumferential direction is provided in the inner tube 1. Thereby, as shown in FIGS. 3A and 3B, the axial elongation due to the thermal expansion of the inner tube 1 can be absorbed by the narrowing of the width of the slit 5. For this reason, the axial elongation of the inner tube 1 due to thermal expansion is suppressed by the slit 5. Therefore, in the exhaust system component 100 having a double-tube structure, the influence of the expansion and contraction due to the thermal expansion of the inner tube 1 can be suppressed. Further, in this embodiment, two slits 5 are provided in the inner tube 1. For this reason, it is easier to further suppress the axial elongation of the inner tube 1 due to thermal expansion than in the configuration in which one slit 5 is provided in the inner tube.

[0033] (2b) When the length of the slit that circulates around the central axis A is shorter than one turn, starting from the portion between the first end and the second end of the slit in the circumferential direction, that is, the portion where no gap is formed in the circumferential direction, the inner tube 1 is likely to be distorted due to the axial thermal elongation of the inner tube 1. On the one hand, in this embodiment, the first end 51 and the second end 52 of the slit 5 are arranged such that the slit 5 has an overlapping portion 50. Thereby, a slit 5 extending around the central axis A for one turn or more is formed in the inner tube 1. That is, the gap formed by the slit 5 is provided over the entire circumference in the circumferential direction. For this reason, compared with the case where the length of the slit is shorter than one turn, it is possible to suppress the inner tube 1 from being distorted.

[0034] (2c) In this embodiment, the slit 5 extends in a spiral shape. Thereby, since the extending direction in which the slit 5 extends is inclined with respect to the virtual plane orthogonal to the central axis A of the inner tube 1, the axial elongation due to the thermal expansion of the inner tube 1 is more easily absorbed than when the extending direction of the slit 5 is not inclined with respect to the virtual plane.

[0035] (2d) In this embodiment, both axial end portions 11 and 12 of the inner tube 1 are fixed to the outer tube 2 by welding. For this reason, compared with the configuration in which one end portion of the inner tube is not fixed to the outer tube, the generation of abnormal noise caused by the contact between the end portion of the inner tube and the outer tube due to vibration, and the generation of abnormal noise caused by the stick-slip phenomenon that occurs when the end portion of the inner tube moves in the axial direction can be suppressed.

[0036] Further, in a configuration where one end of the inner tube is not fixed to the outer tube, for example, in a configuration where a wire mesh is fixed to the outer peripheral surface of one end of the inner tube and the outer tube and the wire mesh slide, it is necessary to provide the outer tube longer than the inner tube in consideration of the axial elongation due to the thermal expansion of the inner tube. On the other hand, in the configuration of the present embodiment, the upstream member 3 can be fixed in the upstream end portion 11 of the inner tube 1, and the downstream member 4 can be fixed in the downstream end portion 12 of the inner tube 1. As a result, it is not necessary to provide the outer tube 2 longer than the inner tube 1, so that an increase in material cost can be suppressed.

[0037] (2e) In a configuration in which corners are formed at the ends of the slit, stress tends to concentrate at the corners. On the other hand, in the present embodiment, since the edges of the first end 51 and the second end 52 are each formed in a curved shape, the stress that tends to concentrate on both ends 51 and 52 is likely to be dispersed over the entire edges of both ends 51 and 52 without concentrating at a single point. For this reason, it is possible to suppress stress from concentrating on a specific portion at both ends 51 and 52 of the slit.

[0038] [3. Other Embodiments] As described above, the embodiments of the present disclosure have been described. Needless to say, the present disclosure can take various forms without being limited to the above embodiments.

[0039] (3a) In the above-described embodiment, two slits 5 were provided in the inner tube 1, and each slit 5 was disposed in the vicinity of the upstream end portion 11 of the inner tube 1 and in the vicinity of the downstream end portion 12 of the inner tube 1. However, the number and positions of the slits provided in the inner tube are not limited thereto. For example, one or three or more slits may be provided in the inner tube. Also, for example, the slit may be provided at any position between the first end portion and the second end portion of the inner tube. Also, for example, when a plurality of slits are provided in the inner tube, the positions of the first end and the second end of each slit may be the same position in the circumferential direction or may be different positions in the circumferential direction. Also, for example, when a plurality of slits are provided in the inner tube, the lengths of the respective slits may be the same length or may be different lengths.

[0040] (3b) In the above-described embodiment, the tubular inner tube 1 having the slit 5 was formed by winding the plate-like member 10 provided with a plurality of notches 53. However, the method of forming the inner tube having the slit is not limited thereto. For example, after the inner tube is formed by winding a plate-like member having no notch, a slit may be provided in the inner tube to form an inner tube having a slit. In this case, it is possible to form a spiral slit that circulates around the central axis A two or more times.

[0041] (3c) In the above-described embodiment, the width of the slit 5 was substantially the same from the first end 51 to the second end 52. However, the shape of the slit is not limited thereto. For example, as shown in FIG. 4, the slit 5a provided in the inner tube 1a may have a main slit portion 54 and a wide portion 55.

[0042] The wide portion 55 is wider than the main slit portion 54. The wide portion 55 is provided at the first end 51a of the slit 5a. Note that the wide portion may be provided only at the second end of the slit, or may be provided at both the first end and the second end of the slit. The edges of the wide portion 55 and the portions of the edges of the main slit portion 54 that are close to the wide portion 55 are formed in a curved shape. In such a configuration, at the first end 51a of the slit 5a, a substantially circular gap that is wide in the axial direction and formed in a curve is formed by the wide portion 55.

[0043] Here, in a configuration where the width of the slit becomes narrower toward the end, stress tends to concentrate on the tip portion of the end. Also, in a configuration where a corner is formed at the end of the slit, stress tends to concentrate on the corner.

[0044] On the other hand, when the slit 5a has the wide portion 55 as described above, the stress that tends to concentrate on the first end 51a of the slit 5a is easily dispersed throughout the wide portion 55. Therefore, it is possible to suppress stress from concentrating on a specific portion at the first end 51a of the slit 5a.

[0045] (3d) In the above embodiment, both end portions 11, 12 of the inner tube 1 were fixed to the outer tube 2, but one end portion of the inner tube may not be fixed to the outer tube. For example, one end portion of the inner tube may be configured to be slidable by a wire mesh disposed between the end portion and the outer tube. Even in such a configuration, when the slit 5 as described above is provided in the inner tube, the axial elongation due to the thermal expansion of the inner tube is suppressed by the slit 5. Therefore, the thickness of the wire mesh can be minimized, and as a result, it is possible to suppress an increase in material cost compared to a configuration that is slidable only by the wire mesh without having the slit 5.

[0046] (3e) In the above-described embodiment, the slit 5 extended spirally, but the shape of the slit is not limited to this. For example, the second end of the slit may bifurcate into a first portion and a second portion, and the first end of the slit may enter between the first portion and the second portion, so that the slit may have an overlapping portion. Also, for example, only the vicinity of the second end of the slit may be bent or curved, and the second end may be arranged at a position axially displaced with respect to the first end of the slit, so that the slit may have an overlapping portion. Even in the two slit shapes described above, since the slit extends around the central axis of the inner tube one or more times, the axial elongation due to the thermal expansion of the inner tube is suppressed. Therefore, in the exhaust system component having a double-tube structure, the influence of the expansion and contraction due to the thermal expansion of the inner tube can be suppressed.

[0047] (3f) In the above-described embodiment, the inner tube 1 and the outer tube 2 were cylindrical, but the shapes of the inner tube and the outer tube can take various shapes.

[0048] (3g) The functions of one component in the above-described embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Also, a part of the configuration of the above-described embodiment may be omitted. Further, at least a part of the configuration of the above-described embodiment may be added to, replaced with, etc. the configuration of other above-described embodiments.

[0049] [4. Technical Ideas Disclosed in this Specification] [Item 1] An exhaust system component having a double-tube structure, an inner tube through which exhaust gas passes inside, an outer tube arranged so as to surround the outer periphery of the inner tube, and comprising the inner tube at least one end in the axial direction along the central axis of the inner tube is fixed to the outer tube by welding, has a slit that penetrates the wall of the inner tube and extends from a first end to a second end in the circumferential direction centered on the central axis, The first end and the second end are arranged such that the slit has an overlapping portion that overlaps with a space in the axial direction, an exhaust system component.

[0050] [Item 2] The exhaust system component according to Item 1, wherein both ends of the inner pipe in the axial direction are fixed to the outer pipe by welding, an exhaust system component.

[0051] [Item 3] The exhaust system component according to Item 1 or Item 2, wherein the slit extends in a spiral shape, an exhaust system component.

[0052] [Item 4] The exhaust system component according to any one of Items 1 to 3, wherein at least one edge of the first end and the second end of the slit is formed in a curved shape, an exhaust system component.

Explanation of Reference Numerals

[0053] 1, 1a... inner pipe, 2... outer pipe, 3... upstream member, 4... downstream member, 5, 5a... slit, 6... communication hole, 7... space, 8... sound absorbing material, 10... plate-like member, 11... upstream end, 12... downstream end, 21... main body portion, 22... upstream portion, 23... downstream portion, 24... first fixing portion, 25... second fixing portion, 50... overlapping portion, 51, 51a... first end, 52... second end, 53... notch, 54... main slit portion, 55... wide portion, 100... exhaust system component, A... central axis.

Claims

1. An exhaust system component having a double-pipe structure, an inner pipe through which exhaust gas passes inside, an outer pipe arranged to surround the outer periphery of the inner pipe, and comprising, the inner pipe, at least one end in the axial direction along the central axis of the inner pipe is fixed to the outer pipe by welding, has a slit that penetrates the wall of the inner pipe and extends from a first end to a second end in the circumferential direction centered on the central axis, the first end and the second end are arranged so that the slit has an overlapping portion where the slit overlaps with a space in the axial direction, an exhaust system component.

2. The exhaust system component according to claim 1, both ends in the axial direction of the inner pipe are fixed to the outer pipe by welding, an exhaust system component.

3. The exhaust system component according to claim 1 or claim 2, the slit extends in a spiral shape, an exhaust system component.

4. The exhaust system component according to claim 1 or claim 2, at least one edge of the first end and the second end of the slit is formed in a curved shape, an exhaust system component.

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