JPWO2018078955A1 - Exhaust pipe - Google Patents

Abstract

A portion of the exhaust pipe (10, 10A to 10C) on the outer pipe (70) closer to the muffler (56) than the catalyst (58) is the purified exhaust gas discharged from the catalyst (58) into the muffler (56). It is comprised as an outlet part (84, 90, 96) to flow. One of the lengths (Lpa to Lpc) along the vertical direction (Lpa to Lpc) and the lengths (Lha to Lhc) along the left and right direction at the outlet (84, 90, 96) is the diameter of the catalyst (58) ( Shorter than D), the other length being longer than the diameter (D) of the catalyst (58).

Description

  The present invention relates to an exhaust pipe that contains a catalyst that purifies exhaust gas discharged from a vehicle engine and discharges it to a muffler.

  Conventionally, a catalyst is arranged in an exhaust pipe connecting a vehicle engine and a muffler, the exhaust gas discharged from the engine is purified by the catalyst, and the purified exhaust gas is discharged outside through the muffler. Has been done. Japanese Patent Laid-Open No. 2002-309931 discloses that a bottomed cylindrical partition wall is disposed between an outer wall of an exhaust pipe and a catalyst holding container for holding a catalyst, and exhaust gas discharged from the catalyst is discharged from the catalyst holding container and the partition wall. It is disclosed that the catalyst can be heated up to the activation temperature in a short time via the catalyst holding container so that the purification performance of the catalyst can be sufficiently exerted by flowing the gas flow path formed by Yes.

  However, in the technique disclosed in Japanese Patent Application Laid-Open No. 2002-309931, the exhaust gas outlet surface of the catalyst and the bottom wall portion of the partition wall face each other, and the gas flow path is formed along the outer peripheral surface of the catalyst holding container. Therefore, the exhaust gas discharged from the catalyst is totally reflected by the bottom wall portion of the partition wall and flows through the gas flow path along the outer peripheral surface of the catalyst holding container. This makes it difficult for the exhaust gas to escape well through the muffler, leading to a decrease in output. In addition, by providing a partition wall in the exhaust pipe, parts such as a partition and a stay that supports the partition wall on the outer wall are required, increasing the number of parts of the exhaust pipe and manufacturing man-hours for assembling these parts to the exhaust pipe Will increase.

  Accordingly, an object of the present invention is to provide an exhaust pipe that can raise the temperature of a catalyst without reducing the output and can suppress an increase in the number of parts and the number of manufacturing steps.

  An exhaust pipe according to the present invention is an exhaust pipe that extends from an engine of a vehicle and is connected to a muffler and contains a catalyst that purifies exhaust gas exhausted from the engine and exhausts the exhaust gas to the muffler. .

  1st characteristic; The said exhaust pipe is an outer pipe | tube which accommodates the said inner pipe | tube while the inner pipe | tube which accommodates the said catalyst, one end part is connected to the said engine, and the other end part is connected to the said muffler. With. In this case, a portion of the outer pipe or the inner pipe that is closer to the muffler than the catalyst is configured as an outlet that allows the exhaust gas after purification discharged from the catalyst to flow through the muffler. Of the length along the vertical direction of the vehicle at the outlet and the length along the horizontal direction of the vehicle at the outlet, one length is shorter than the diameter of the catalyst, and the other Is longer than the diameter of the catalyst.

  2nd characteristic; The shape of the said exit part is an ellipse shape or an ellipse shape.

  Third feature: The outer tube has a shape that extends downward from the one end and bends and extends in a substantially horizontal direction from the bent portion toward the other end. In this case, the length of the outlet portion along the vertical direction is shorter than the diameter of the catalyst. Of the lengths along the vertical direction, the lower length from the center line of the catalyst is shorter than the upper length from the center line.

  4th characteristic; The said exit part is a through-hole of the cylinder member arrange | positioned in the location of the said muffler side rather than the said catalyst in the said outer tube | pipe or the said inner tube | pipe.

  5th characteristic; The said exit part is an opening part formed by the wall provided in the location of the said muffler side rather than the said catalyst in the said outer pipe | tube or the said inner pipe | tube. In addition, one of the length along the vertical direction and the length along the horizontal direction at the outlet portion is shorter than the diameter of the catalyst.

  6th characteristic; The said exit part is an opening part formed by making the location by the side of the said muffler rather than the said catalyst in the said outer tube | pipe or the said inner tube | pipe.

  7th characteristic; The said exhaust pipe is further provided with the stay which supports the center part along the longitudinal direction of the said inner pipe to the said outer pipe. In this case, the stay is provided so as to incline toward the muffler along the longitudinal direction from the inner peripheral surface of the outer tube toward the outer peripheral surface of the inner tube.

  According to the first feature of the present invention, one of the length along the vertical direction of the vehicle at the outlet and the length along the horizontal direction of the vehicle at the outlet is greater than the diameter of the catalyst. The other length is set longer than the catalyst diameter. As described above, since the short diameter of the outlet portion is shorter than the diameter of the catalyst, a part of the exhaust gas discharged from the catalyst collides with the formation portion of the short diameter portion of the outlet portion in the outer tube or the inner tube, and the catalyst side Returned to

  In this case, if the outlet portion is provided in the outer pipe, a part of the exhaust gas that has collided is returned to the gap between the outer pipe and the inner pipe. As a result, the returned part of the exhaust gas raises the temperature of the catalyst (the outer peripheral portion thereof) via the inner pipe, so that the purification performance of the catalyst can be improved. On the other hand, if the outlet portion is provided in the inner pipe, a part of the exhaust gas that has collided is returned to the outer peripheral side of the catalyst and raises the temperature of the outer peripheral portion of the catalyst. It becomes possible to improve.

  As described above, according to the first feature, the output is reduced because it is a simple configuration in which a part of the exhaust gas is returned to the catalyst side at the formation portion of the short diameter portion of the outlet portion in the outer tube or the inner tube. Thus, the temperature of the catalyst can be increased without increasing the number of exhaust pipe parts and the number of manufacturing steps.

  According to the second feature of the present invention, since the outlet portion has an elliptical shape or an oval shape, the return flow rate of the exhaust gas can be made uniform.

  By the way, the flow rate of the exhaust gas in the exhaust pipe is faster in the lower part than in the upper part in the exhaust pipe. Therefore, according to the third feature of the present invention, by making the length along the vertical direction at the outlet portion shorter than the diameter of the catalyst, the vertical direction of the outlet portion becomes the short diameter portion, and along this vertical direction. Among these lengths, the lower length from the center line of the catalyst is set shorter than the upper length from the center line. This makes it difficult for the exhaust gas in the lower portion having a high flow rate to escape from the outlet portion, so that the temperature of the upper and lower portions of the catalyst can be raised evenly.

  According to the fourth feature of the present invention, the cylindrical member is the outer tube or the inner tube by using the through hole of the cylindrical member disposed in the outer tube or the inner tube at a location closer to the muffler than the catalyst. The outlet portion can be configured with a simple mounting structure that fits into the housing. As a result, the number of exhaust pipe parts and the number of manufacturing steps can be efficiently reduced.

  According to the fifth feature of the present invention, an opening formed by a wall provided at a location closer to the muffler than the catalyst in the outer tube or the inner tube is an outlet portion, and the length along the vertical direction in the outlet portion is Of the lengths along the horizontal direction, one length is set shorter than the diameter of the catalyst. Thereby, when a part of the exhaust gas collides with the wall, the part of the exhaust gas is returned to the catalyst side, so that the temperature of the catalyst can be efficiently raised by the returned part of the exhaust gas.

  According to the sixth aspect of the present invention, since the opening formed by flattening the portion on the muffler side of the catalyst in the outer tube or the inner tube is the outlet portion, a part of the exhaust gas collides with the flat portion. The exhaust gas can be returned to the catalyst side to raise the temperature of the catalyst efficiently.

  According to the seventh feature of the present invention, the central portion along the longitudinal direction of the inner tube is supported by the outer tube by the stay, and the stay extends from the inner circumferential surface of the outer tube toward the outer circumferential surface of the inner tube. It is provided so as to be inclined toward the muffler along the longitudinal direction of the tube. As a result, a part of the exhaust gas returned from the outlet part hits the upstream stay, reaches the downstream outlet part along the outer peripheral surface of the stay and the inner tube, and is discharged from the outlet part to the muffler. Is done. As a result, it is possible to prevent part of the exhaust gas from returning to the upstream side more than necessary, and to improve exhaust gas exhaust from the exhaust pipe.

1 is a right side view of a main part of a motorcycle incorporating an exhaust pipe according to an embodiment. It is a partially broken side view of the exhaust pipe of the first embodiment. FIG. 3 is a partial cross-sectional view of the exhaust pipe of FIG. 2. FIG. 4A is a side view of the cylindrical member, and FIG. 4B is a front view of the cylindrical member. 5A and 5B are perspective views showing the flow of exhaust gas discharged from the catalyst. It is a partially broken side view of the exhaust pipe of 2nd Example. FIG. 7A is a front view illustrating an upper barrier and a lower barrier formed in the outer tube, and FIG. 7B is a perspective view illustrating a flow of exhaust gas discharged from the catalyst. It is a partial cross section figure of the exhaust pipe of 3rd Example.

  The exhaust pipe according to the present invention will be described in detail below with reference to the accompanying drawings with preferred embodiments.

[Schematic configuration of motorcycle 12]
FIG. 1 is a right side view of a main part of a motorcycle 12 as a vehicle on which an exhaust pipe 10 according to this embodiment is mounted. The motorcycle 12 is a saddle type vehicle in which a driver sits on a seat 14. In FIG. 1, the motorcycle 12 is illustrated around the exhaust pipe 10, and illustration of other portions is omitted or simplified. In the description of the present embodiment, the front-rear, left-right, and up-down directions will be described according to the direction viewed from the driver seated on the seat 14. Furthermore, in the following description, the vertical direction of the motorcycle 12 refers to the up-down direction, and the horizontal direction refers to the front-rear direction and the left-right direction.

  The motorcycle 12 includes a vehicle body frame 16, a front wheel steering unit 20 that supports a front wheel 18 so as to be steerable at a front portion of the vehicle body frame 16, and a drive source suspended on the vehicle body frame 16 behind the front wheel steering unit 20. An engine 22, a rear wheel suspension portion 26 that supports the rear wheel 24 in a swingable manner with respect to the vehicle body frame 16 behind the engine 22, and a fuel tank attached to the front and rear of the vehicle body frame 16 behind the front wheel steering portion 20. 28 and the sheet 14.

  The vehicle body frame 16 includes a head pipe 30 that supports the front wheel steering unit 20 so as to be steerable. A main frame 32 extends obliquely downward from the head pipe 30 toward the rear. The main frame 32 has a downward bent portion 34 that is bent downward, and supports the engine 22 and the fuel tank 28. A down frame 36 extends obliquely downward from the head pipe 30 toward the rear. On the other hand, the seat 14 is supported by a seat rail 38 extending rearward from the downward bent portion 34 of the main frame 32.

  The front wheel steering unit 20 includes a steering handle 40 and a front fork 42 that extends downward from the steering handle 40, and the front wheel 18 is rotatably supported at the lower end of the front fork 42. The rear wheel suspension portion 26 includes a swing arm 44 extending rearward from the lower portion of the main frame 32, and a rear cushion (not shown) passed between the swing arm 44 and the seat rail 38. The rear wheel 24 is rotatably supported.

  The engine 22 includes a crankcase 46 and a cylinder portion 48 that slightly tilts forward from the upper surface of the crankcase 46 and extends upward. An intake device (not shown) is connected to the intake port formed on the rear wall of the cylinder portion 48, while the exhaust port 10 according to the present embodiment is connected to the exhaust port formed on the front wall of the cylinder portion 48. One end 50 is connected. The front part of the crankcase 46 is attached to a hanger (not shown) provided at the lower part of the down frame 36, and the rear part of the crankcase 46 is attached to the rear hanger 52 provided at the lower part of the main frame 32. The engine 22 is suspended.

[Schematic configuration of exhaust pipe 10]
Next, the exhaust pipe 10 according to the present embodiment will be described.

  The exhaust pipe 10 is mounted on the motorcycle 12, and the one end portion 50 side extends forward from the front wall of the cylinder portion 48. The exhaust pipe 10 is bent downward from a portion extending forward from the one end portion 50, the bent portion extends obliquely downward along the crankcase 46, and further rearward in a substantially horizontal direction below the crankcase 46. It extends to. The other end 54 at the rear of the exhaust pipe 10 is connected to a muffler 56 that extends obliquely upward toward the rear.

  A catalyst 58 (to be described later) is accommodated in the exhaust pipe 10 immediately below the crankcase 46. Therefore, the exhaust pipe 10 is configured as an exhaust device with the catalyst 58. Further, a portion of the exhaust pipe 10 behind the catalyst 58 is supported by the rear hanger 52 by a stay member 60.

  Next, three examples (first to third examples) relating to the internal configuration of the exhaust pipe 10, particularly, the configuration around the catalyst 58 will be described with reference to FIGS. 2 to 8. In the following description, the exhaust pipe 10 is referred to as the exhaust pipes 10A to 10C of the first to third embodiments.

[First embodiment]
A first embodiment will be described with reference to FIGS.

  The exhaust pipe 10A of the first embodiment has an outer pipe 70 that constitutes the external shape of the exhaust pipe 10A. Therefore, the outer tube 70 has one end 50 connected to the cylinder 48 and the other end 54 connected to the muffler 56. In addition, the outer tube 70 has a relatively small diameter portion from the one end portion 50 to the bent portion in front of the crankcase 46, while the horizontal portion in which the catalyst 58 is accommodated has a relatively large diameter tube shape.

  As shown in FIGS. 1 to 3, the location where the catalyst 58 is disposed in the outer tube 70 is a small-diameter portion 72 on the upstream side (one end 50 side) connected to the bent portion and a rear side from the small-diameter portion 72. An expanded portion 74 that expands toward the rear and a large-diameter portion 76 that extends substantially horizontally from the expanded portion 74 toward the rear. A cylindrical inner tube 78 that houses the catalyst 58 and extends in the front-rear direction along the large-diameter portion 76 is disposed inside the large-diameter portion 76 of the outer tube 70.

  One end on the upstream side of the inner pipe 78 enters the expanded portion 74 and is connected to the inner peripheral surface of the expanded portion 74. The other end on the downstream side (the other end portion 54 side) of the inner pipe 78 is open near the end portion on the downstream side of the large diameter portion 76. A stay 80 for supporting the inner tube 78 on the inner peripheral surface of the large-diameter portion 76 is provided at a position slightly downstream of the central portion along the longitudinal direction (front-rear direction) of the inner tube 78. .

  The stay 80 is a substantially annular member that connects the outer peripheral surface of the inner tube 78 and the inner peripheral surface of the large-diameter portion 76 of the outer tube 70, and as shown in FIG. 3, the inner peripheral surface of the large-diameter portion 76. From the inner surface to the outer peripheral surface of the inner tube 78 so as to be inclined rearward. As a result, the gap between the inner pipe 78 and the large-diameter portion 76 is partitioned by the stay 80 into an upstream space and a downstream space.

  A cylindrical catalyst 58 is disposed inside the inner pipe 78 along the longitudinal direction of the inner pipe 78. The upstream surface (exhaust gas inlet surface 79) of the catalyst 58 is located slightly downstream from the upstream end of the inner pipe 78. On the other hand, the downstream surface (exhaust gas outlet surface 81) of the catalyst 58 is positioned slightly upstream from the other downstream end of the inner pipe 78.

  Therefore, the exhaust gas discharged from the engine 22 flows into the inner pipe 78 from the one end 50 of the outer pipe 70 via the bent portion, the small diameter portion 72 and the expanded portion 74 and reaches the inlet surface 79 of the catalyst 58. If the temperature of the catalyst 58 is raised to the activation temperature, the catalyst 58 can purify the exhaust gas flowing in from the inlet surface 79 and discharge the purified exhaust gas from the outlet surface 81 to the downstream side. it can. 2 and 3, the exhaust gas inflow direction to the inlet surface 79 of the catalyst 58 (an arrow from the right side of the drawing toward the inlet surface 79) and the exhaust gas discharge direction from the outlet surface 81 (from the outlet surface 81 to the left side of the drawing). (Arrows heading toward) are respectively illustrated.

  Note that, when the temperature of the catalyst 58 is lower than the activation temperature, such as when the engine 22 is started, the catalyst 58 is likely to be deteriorated due to sulfur poisoning. Therefore, the temperature of the catalyst 58 is raised to the activation temperature. It is desirable to purify the exhaust gas in a heated state. Further, since the exhaust gas discharged from the engine 22 has a relatively high temperature, the temperature of the catalyst 58 is increased by the exhaust gas flowing through the inlet surface 79. Accordingly, the purified exhaust gas discharged from the outlet surface 81 is at a lower temperature than the exhaust gas flowing in via the inlet surface 79.

  A cylindrical member 82 is fitted in the large diameter portion 76 on the downstream side of the catalyst 58 and the inner pipe 78. The cylindrical member 82 is an annular member having a shape that decreases in diameter from the downstream side (the muffler 56 side) toward the upstream side (the inner tube 78 side), and an upstream elliptical opening portion (through-hole shown in FIG. 4B). ) Is configured as an outlet portion 84 for flowing the exhaust gas after purification to the muffler 56.

  Here, the relationship between the size of the outlet portion 84 and the size of the catalyst 58 will be described.

  First, one of the length Lpa along the up-down direction (vertical direction) and the length Lha along the left-right direction (horizontal direction) at the outlet portion 84 is set to be shorter than the diameter D of the catalyst 58. The other length is set longer than the diameter D. 2, 3 and 4B, the vertical length Lpa of the outlet portion 84 is set shorter than the diameter D of the catalyst 58, and the horizontal length Lha is set longer than the diameter D. (Lpa <D and Lha> D).

  Therefore, as shown in FIGS. 2, 3, and 4 </ b> B, the upper end position and the lower end position of the elliptical outlet 84 are center lines 86 extending in the front-rear direction of the catalyst 58 relative to the upper end position and the lower end position of the catalyst 58. Get closer. As a result, a portion along the vertical direction of the outlet portion 84 becomes a short diameter portion of the outlet portion 84. Therefore, as shown in FIG. 4B, when the catalyst 58 is viewed from the muffler 56 side, the upper portion and the lower portion of the cylindrical member 82 that form the short diameter portion of the outlet portion 84 are the upper portion and the lower portion of the catalyst 58, respectively. It is configured to cover (block) the side portion. On the other hand, the left and right sides of the long diameter portion of the outlet portion 84 are outward from the left and right portions of the catalyst 58.

  Of the length Lpa along the vertical direction at the outlet 84, the lower length Lpda from the center line 86 is preferably set shorter than the upper length Lpua from the center line 86 (Lpda). <Lpua).

  In the exhaust pipe 10A configured in this way, out of the purified exhaust gas exhausted from the outlet surface 81 of the catalyst 58, exhaust gas (one exhaust gas) exhausted from the upper part and the lower part of the outlet surface 81. 2, 3, 5 </ b> A, and 5 </ b> B, the upper part and the lower part of the cylindrical member 82 collide with each other and are returned to the inner tube 78 side. The returned exhaust gas flows into the gap between the large diameter portion 76 and the inner pipe 78.

  The exhaust gas flowing into the gap gives heat to the catalyst 58 via the inner pipe 78 and raises the temperature of the upper and lower portions of the catalyst 58 (the outer peripheral portion of the catalyst 58 downstream from the stay 80). When the catalyst 58 is disposed inside the inner pipe 78 as shown in FIGS. 2 and 3, when the exhaust gas is purified, the temperature near the center line 86 of the catalyst 58 is relatively high, and the outer peripheral portion is relatively low. It becomes. If the temperature of the outer peripheral portion rises to the activation temperature due to the temperature rise of the outer peripheral portion of the catalyst 58 caused by the exhaust gas flowing into the gap, the exhaust gas purification performance in the outer peripheral portion can be sufficiently exerted. . Thereafter, the exhaust gas that has flowed into the gap collides with the annular stay 80 and is returned to the downstream side, along with the exhaust gas after purification discharged from the central portion of the outlet surface 81 of the catalyst 58, on both the left and right sides of the outlet portion 84. To the muffler 56.

[Second Embodiment]
A second embodiment will be described with reference to FIGS. 6 to 7B. In the exhaust pipe 10B of the second embodiment, the same components as those in the exhaust pipe 10A of the first embodiment of FIGS. 2 to 5B are denoted by the same reference numerals, detailed description thereof is omitted, and so on. And

  In the exhaust pipe 10B of the second embodiment, an upper barrier 88u and a lower barrier 88d are provided at locations downstream of the catalyst 58 and the inner tube 78 in the large diameter portion 76, and the upper side of the locations is the upper side. The opening portion excluding the barrier 88u and the lower barrier 88d is different from the exhaust pipe 10A of the first embodiment in that it is formed as an outlet 90 for discharging the exhaust gas after purification to the muffler 56. The upper barrier 88u and the lower barrier 88d are formed symmetrically with respect to the center line 86.

  Specifically, as shown in FIG. 7A, the upper barrier 88u includes an arc-shaped portion 92u extending downward from the upper portion of the large-diameter portion 76, and a protruding portion 94u protruding from the arc-shaped portion 92u toward the center line 86. Consists of In this case, the arc-shaped portion 92u extends downward from the upper portion of the large-diameter portion 76 and the projecting portion 94u projects so as to incline toward the upstream side from the tip portion of the arc-shaped portion 92u in a side view of FIG. ing.

  On the other hand, as shown in FIG. 7A, the lower barrier 88d includes an arc-shaped portion 92d extending upward from the lower portion of the large-diameter portion 76, and a protruding portion 94d protruding from the arc-shaped portion 92d toward the center line 86. Consists of In this case, the arc-shaped portion 92d extends upward from the lower portion of the large-diameter portion 76 in the side view of FIG. 6, and the projecting portion 94d is inclined so as to incline toward the upstream side from the tip portion of the arc-shaped portion 92d. It protrudes.

  Accordingly, similarly to the cylindrical member 82 of the first embodiment (see FIGS. 2 to 4A), the upper barrier 88u and the lower barrier 88d are located downstream of the catalyst 58 and the inner pipe 78 in the large diameter portion 76. It is formed to reduce the diameter upstream. In addition, as shown in FIG. 7A, the location where the upper barrier 88u and the lower barrier 88d are provided is viewed as if the outlet 90 is formed in an oval shape when viewed from the muffler 56 side.

  Also in the second embodiment, regarding the relationship between the size of the outlet portion 90 and the size of the catalyst 58, the length between the two protruding portions 94d and 94u in the outlet portion 90 (the length along the vertical direction) Lpb And the length Lhb along the left-right direction, one length is set shorter than the diameter D of the catalyst 58, and the other length is set longer than the diameter D. In FIG. 7A, the vertical length Lpb of the outlet 90 is set to be shorter than the diameter D of the catalyst 58, and the horizontal length Lhb is set to be longer than the diameter D (Lpb <D and Lhb > D).

  Therefore, the upper end position (position of the protruding portion 94 u) and the lower end position (position of the protruding portion 94 d) of the oval outlet portion 90 are closer to the center line 86 than the upper end position and the lower end position of the catalyst 58. As a result, the portion along the vertical direction of the outlet portion 90 becomes the short diameter portion of the outlet portion 90, and the upper barrier 88u and the lower barrier 88d forming the short diameter portion of the outlet portion 90 are the upper portion of the catalyst 58 and It is configured to cover (block) the lower part. On the other hand, the left and right sides of the long diameter portion of the outlet portion 90 are outward from the left and right portions of the catalyst 58.

  Of the length Lpb along the vertical direction at the outlet 90, the lower length Lpdb from the center line 86 is preferably set shorter than the upper length Lpub from the center line 86 (Lpdb <Lpub).

  In the exhaust pipe 10B configured in this way, out of the purified exhaust gas exhausted from the outlet surface 81 of the catalyst 58, exhaust gas (one exhaust gas) exhausted from the upper and lower portions of the outlet surface 81. 6B and 7B, the upper part 88b collides with the upper barrier 88u and the lower barrier 88d, respectively, and is returned to the inner tube 78 side. The returned exhaust gas flows into the gap between the large diameter portion 76 and the inner pipe 78.

  The exhaust gas flowing into the gap gives heat to the catalyst 58 via the inner pipe 78, raises the temperature of the upper and lower portions (outer peripheral portion) of the catalyst 58, and purifies the exhaust gas at the outer peripheral portion of the catalyst 58. Improve performance. Thereafter, the exhaust gas that has flowed into the gap collides with the stay 80 and returns to the downstream side, along with the purified exhaust gas discharged from the central portion of the outlet surface 81 of the catalyst 58, and the mufflers 56 from both the left and right sides of the outlet portion 90. It is discharged toward

[Third embodiment]
A third embodiment will be described with reference to FIG. The exhaust pipe 10C of the third embodiment has an elliptical shape that exhausts exhaust gas to the muffler 56 side by flattening a portion downstream of the catalyst 58 and the inner pipe 78 in the large diameter portion 76 in the vertical direction. It differs from exhaust pipe 10A, 10B by the point which formed the exit part 96 as an opening part. Accordingly, this portion is configured as a reduced diameter portion 98 in which the large diameter portion 76 is reduced in diameter toward the rear.

  Also in the third embodiment, regarding the relationship between the size of the outlet portion 96 and the size of the catalyst 58, one of the length Lpc along the vertical direction of the outlet portion 96 and the length Lhc along the left-right direction is used. The length is set shorter than the diameter D of the catalyst 58, and the other length is set longer than the diameter D. In FIG. 8, the vertical length Lpc of the outlet 96 is set shorter than the diameter D of the catalyst 58, and the horizontal length Lhc is set longer than the diameter D (Lpc <D and Lhc). > D).

  Therefore, the upper end position and the lower end position of the elliptical outlet portion 96 are closer to the center line 86 than the upper end position and the lower end position of the catalyst 58. As a result, the portion along the vertical direction of the outlet portion 96 becomes the short diameter portion of the outlet portion 96, and the reduced diameter portion 98 that forms the short diameter portion of the outlet portion 96 forms the upper portion and the lower portion of the catalyst 58. It is configured to cover (block). On the other hand, the left and right sides of the long diameter portion of the outlet portion 96 are outward from the left and right portions of the catalyst 58.

  Of the length Lpc along the vertical direction in the outlet portion 96, the lower length Lpdc from the center line 86 is preferably set shorter than the upper length Lpuc from the center line 86 (Lpdc). <Lpuc).

  In the exhaust pipe 10 </ b> C configured in this manner, out of the purified exhaust gas exhausted from the outlet surface 81 of the catalyst 58, the exhaust gas exhausted from the upper and lower portions of the outlet surface 81 (one exhaust gas). Part) hits the reduced diameter part 98 and is returned to the inner tube 78 side. The returned exhaust gas flows into the gap between the large diameter portion 76 and the inner pipe 78.

  The exhaust gas flowing into the gap gives heat to the catalyst 58 via the inner pipe 78, raises the temperature of the upper and lower portions (outer peripheral portion) of the catalyst 58, and purifies the exhaust gas at the outer peripheral portion of the catalyst 58. Improve performance. Thereafter, the exhaust gas that has flowed into the gap collides with the stay 80 and returns to the downstream side, together with the purified exhaust gas discharged from the central portion of the outlet surface 81 of the catalyst 58, the muffler 56 from both the left and right sides of the outlet portion 96. It is discharged toward

[Effect of this embodiment]
As described above, according to the exhaust pipe 10 according to the present embodiment (the exhaust pipes 10A to 10C of the first to third examples), the lengths Lpa to the outlet portions 84, 90, and 96 along the vertical direction Among Lpc and the lengths Lha to Lhc in the left-right direction at the outlet portions 84, 90, 96, one length is shorter than the diameter D of the catalyst 58 and the other length is larger than the diameter D of the catalyst 58. Is also set longer. Thus, since the short diameters of the outlet portions 84, 90, 96 are shorter than the diameter D of the catalyst 58, a part of the exhaust gas discharged from the catalyst 58 is not allowed It collides with the formation part of the short diameter part (the cylindrical member 82, the upper barrier 88u, the lower barrier 88d, the reduced diameter part 98) and is returned to the catalyst 58 side. The returned part of the exhaust gas flows into the gap between the outer tube 70 and the inner tube 78 and raises the temperature of the catalyst 58 (the outer peripheral portion thereof) via the inner tube 78, so that the purification performance of the catalyst 58 is improved. It becomes possible to improve.

  As described above, since the configuration is such that a part of the exhaust gas is returned to the catalyst 58 side at the position where the short diameter portions of the outlet portions 84, 90, 96 in the outer pipe 70 are formed, the catalyst 58 is not reduced without reducing the output. It is possible to increase the number of parts and manufacturing man-hours of the exhaust pipe 10 (10A to 10C).

  Further, since the outlet portions 84, 90, and 96 have an elliptical shape or an oval shape, the return flow rate of the exhaust gas to the upstream side when viewed from the muffler 56 side can be made uniform.

  By the way, the flow rate of the exhaust gas in the exhaust pipe 10 (10A to 10C) is faster in the lower part than in the upper part in the exhaust pipe 10 (10A to 10C). Therefore, by making the lengths Lpa to Lpc along the vertical direction of the outlet portions 84, 90, 96 shorter than the diameter D of the catalyst 58, the vertical direction of the outlet portions 84, 90, 96 is made the short diameter portion. Of the lengths Lpa to Lpc along the vertical direction, the lower lengths Lpda to Lpdc from the center line 86 of the catalyst 58 are set shorter than the upper lengths Lpua to Lpuc from the center line 86. . This makes it difficult for the exhaust gas in the lower portion having a high flow rate to escape from the outlet portions 84, 90, 96, so that the upper portion and the lower portion of the catalyst 58 can be heated uniformly.

  In the exhaust pipe 10A according to the first embodiment, the cylindrical member 82 is removed from the outer pipe 70 by using the through hole of the cylindrical member 82 disposed at a position closer to the muffler 56 than the catalyst 58 in the outer pipe 70 as an outlet portion 84. The outlet portion 84 can be configured with a simple mounting structure that fits into the tube 70. As a result, the number of parts and the number of manufacturing steps of the exhaust pipe 10A can be efficiently reduced.

  Further, in the exhaust pipe 10B of the second embodiment, an opening formed by the upper barrier 88u and the lower barrier 88d provided at a location closer to the muffler 56 than the catalyst 58 in the outer pipe 70 is defined as the outlet 90. One of the length Lpb along the vertical direction and the length Lhb along the left-right direction in the portion 90 is set to be shorter than the diameter D of the catalyst 58. As a result, when a part of the exhaust gas collides with the upper barrier 88u and the lower barrier 88d, the part of the exhaust gas is returned to the catalyst 58 side. The temperature can be increased efficiently.

  Furthermore, in the exhaust pipe 10C of the third embodiment, the opening formed by flattening the portion on the muffler 56 side with respect to the catalyst 58 in the outer pipe 70 is the outlet 96, so the diameter of the reduced diameter forming the outlet 96 is reduced. When a part of the exhaust gas collides with the portion 98, the part of the exhaust gas can be returned to the catalyst 58 side to raise the temperature of the catalyst 58 efficiently.

  In the exhaust pipe 10 (10A to 10C), a central portion along the longitudinal direction of the inner pipe 78 is supported by the outer pipe 70 by the stay 80, and the stay 80 extends from the inner peripheral surface of the outer pipe 70 to the inner pipe 78. It is provided so as to be inclined toward the muffler 56 along the longitudinal direction of the inner tube 78 toward the outer peripheral surface. Thereby, a part of the exhaust gas returned from the outlet portions 84, 90, 96 hits the upstream stay 80, and then the downstream outlet portion 84, along the outer peripheral surface of the stay 80 and the inner pipe 78. 90 and 96 and are discharged from the outlet portions 84, 90 and 96 to the muffler 56. As a result, it is possible to prevent a part of the exhaust gas from returning to the upstream side more than necessary, and to improve the escape of the exhaust gas from the exhaust pipe 10 (10A to 10C).

[Description of modification]
In the above description, the case where the outlet portions 84, 90, 96 are formed on the inner side of the outer tube 70 (large diameter portion 76) has been described. It is also possible to form the portions 84, 90, 96. In this case, (1) whether the cylindrical member 82 is fitted downstream of the outlet surface 81 in the inner pipe 78, or (2) whether the upper barrier 88u and the lower barrier 88d are provided downstream of the outlet surface 81 in the inner pipe 78 Alternatively, (3) the reduced diameter portion 98 may be formed by flattening the downstream side of the outlet surface 81 in the inner pipe 78 in the vertical direction. In either case, a part of the exhaust gas discharged from the outlet surface 81 can be returned to the catalyst 58 side, and the temperature of the outer peripheral portion of the catalyst 58 can be raised.

  Further, in the above description, the case where the vertical direction of the outlet portions 84, 90, 96 is the short diameter portion has been described, but the above description has been given even when the horizontal direction of the outlet portions 84, 90, 96 is the short diameter portion. Of course, each effect can be obtained.

  Further, in the above description, the center portion of the inner pipe 78 is supported on the inner peripheral surface of the outer pipe 70 by the annular stay 80. However, even when the stay 80 is not provided, the outer pipe 70 and the inner pipe are supported. It is possible to raise the temperature of the outer peripheral portion of the catalyst 58 by the exhaust gas flowing into the gap with 78.

  As mentioned above, although this invention was demonstrated using suitable embodiment, the technical scope of this invention is not limited to the description range of said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can also be included in the technical scope of the present invention. Further, the reference numerals in parentheses described in the claims are appended to the reference numerals in the attached drawings for easy understanding of the present invention, and the present invention is limited to the elements to which the reference numerals are attached. Is not to be interpreted.

Claims (7)

A catalyst (58) that extends from the engine (22) of the vehicle (12) and is connected to the muffler (56), purifies exhaust gas discharged from the engine (22), and discharges the exhaust gas to the muffler (56). In the exhaust pipe (10, 10A to 10C),
An inner pipe (78) containing the catalyst (58);
One end (50) is connected to the engine (22), the other end (54) is connected to the muffler (56), and an outer pipe (70) that houses the inner pipe (78). ,
With
A portion of the outer pipe (70) or the inner pipe (78) that is closer to the muffler (56) than the catalyst (58) is configured to remove the purified exhaust gas discharged from the catalyst (58) from the muffler ( 56) is configured as an outlet portion (84, 90, 96) flowing through
The length (Lpa to Lpc) along the vertical direction of the vehicle (12) at the exit (84, 90, 96) and the horizontal of the vehicle (12) at the exit (84, 90, 96). Of the lengths (Lha to Lhc) along the direction, one length is shorter than the diameter (D) of the catalyst (58), and the other length is shorter than the diameter (D) of the catalyst (58). Exhaust pipe (10, 10A to 10C) characterized by being long. The exhaust pipe (10, 10A to 10C) according to claim 1,
The exhaust pipe (10, 10A to 10C) is characterized in that the outlet portion (84, 90, 96) has an elliptical shape or an oval shape. In the exhaust pipe (10, 10A to 10C) according to claim 1 or 2,
The outer pipe (70) extends downward from the one end (50) and bends, and has a shape extending in a substantially horizontal direction from the bent portion toward the other end (54).
The length (Lpa to Lpc) along the vertical direction at the outlet (84, 90, 96) is shorter than the diameter (D) of the catalyst (58),
Of the lengths (Lpa to Lpc) along the vertical direction, the lower length (Lpda to Lpdc) from the center line (86) of the catalyst (58) is the upper length from the center line (86). An exhaust pipe (10, 10A to 10C) characterized by being shorter than (Lpua to Lpuc). In the exhaust pipe (10A) according to any one of claims 1 to 3,
The outlet portion (84) is a through-hole of a cylindrical member (82) disposed at a location closer to the muffler (56) than the catalyst (58) in the outer tube (70) or the inner tube (78). An exhaust pipe (10A) characterized by In the exhaust pipe (10B) according to any one of claims 1 to 3,
The outlet portion (90) is formed by walls (88d, 88u) provided at a location closer to the muffler (56) than the catalyst (58) in the outer tube (70) or the inner tube (78). Opening.
Of the length (Lpb) along the vertical direction and the length (Lhb) along the horizontal direction at the outlet (90), one length is larger than the diameter (D) of the catalyst (58). An exhaust pipe (10B) characterized by being short. In the exhaust pipe (10C) according to any one of claims 1 to 3,
The outlet part (96) is an opening formed by flattening the portion on the muffler (56) side of the catalyst (58) in the outer pipe (70) or the inner pipe (78). An exhaust pipe (10C) characterized by that. In the exhaust pipe (10, 10A to 10C) according to any one of claims 1 to 6,
A stay (80) for supporting a central portion along the longitudinal direction of the inner pipe (78) on the outer pipe (70);
The stay (80) is provided so as to be inclined toward the muffler (56) along the longitudinal direction from the inner peripheral surface of the outer tube (70) toward the outer peripheral surface of the inner tube (78). Exhaust pipes (10, 10A to 10C) characterized by being.

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