JP2008069760A - Exhaust device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust device of a motorcycle capable of effectively reducing exhaust noise and suppressing heat damage. <P>SOLUTION: A catalytic converter 43 for purifying an exhaust gas G is installed in an exhaust passage EP for guiding the exhaust gas G from an engine E. At least a part of the catalytic converter 43 and a part of the exhaust pipe body 38 forming the downstream part of the exhaust passage arranged continuously with the outlet 43d of the catalytic converter 43 are contained in an exhaust chamber 50. A communication part 52 allowing the exhaust passage EP to communicate with the inside of the chamber 50 is formed at a part of the exhaust passage on the downstream side 38. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in an exhaust device that is mounted on a vehicle such as a motorcycle or a four-wheeled vehicle to purify and discharge exhaust gas from an engine.

  2. Description of the Related Art Conventionally, as an exhaust device that is mounted on a vehicle and purifies exhaust gas from an engine, a catalytic converter that purifies the exhaust gas is provided in an exhaust passage for deriving exhaust gas from a multi-cylinder engine. Each of the plurality of exhaust passage upstream portions communicates with the passages separated from each other, and the outlet end of the catalytic converter communicates with the number of exhaust passage downstream portions equal to or less than the number of the exhaust passage upstream portions (for example, Patent Document 1).

In the case of this exhaust system, each of the plurality of exhaust passage upstream portions communicates with the mutually separated passages in the catalytic converter, so that the plurality of exhaust passage upstream portions are substantially extended into the catalytic converter. become. Therefore, the catalytic converter is disposed near the upstream side of the engine in the exhaust passage so that the catalyst can be immediately activated immediately after the engine cold start to purify the exhaust gas, and the length of the upstream portions of the plurality of exhaust passages is substantially reduced. The engine characteristics can be set as desired. In addition, since only one catalytic converter need be provided for the plurality of upstream portions of the exhaust passage, the number of catalytic converters can be reduced, and the structure can be simplified and the cost can be reduced.
JP 2006-77727 A

  However, in the case of the exhaust device, there is a case where a large noise is generated from the periphery of the catalytic converter, and a high temperature portion around the catalytic converter is exposed to the outside to cause heat damage.

  Accordingly, an object of the present invention is to provide a vehicle exhaust device that can effectively reduce exhaust noise and suppress thermal damage.

  In order to achieve the above object, an exhaust system for a vehicle according to the present invention is provided with a catalytic converter for purifying the exhaust gas in an exhaust passage for leading exhaust gas from an engine, and at least a part of the catalytic converter, A portion of the exhaust pipe forming the downstream portion of the exhaust passage connected to the outlet of the catalytic converter is housed in the exhaust chamber, and a communication portion is formed in the exhaust passage downstream portion to connect the exhaust passage and the chamber. .

  According to this configuration, the exhaust gas from the engine led to the exhaust passage is purified by the catalytic converter and then guided to the downstream portion of the exhaust passage. At this time, the exhaust passage downstream portion is exhausted via the communication portion. Since it communicates with the inside of the chamber, exhaust noise can be effectively reduced by a resonator effect. Further, since at least a part of the catalytic converter and at least a part of the downstream portion of the exhaust passage are accommodated in the exhaust chamber, the high temperature part of the catalytic converter is not exposed to the outside, and thermal damage is suppressed. Furthermore, since exhaust noise can be reduced, the silencer can be made smaller and lighter. As a result, in the case of a motorcycle, the balance of weight distribution between the front and rear is improved, and the degree of freedom in design is increased.

  The engine is, for example, a multi-cylinder engine, and in this case, a plurality of exhaust passage upstream portions for leading exhaust gas from each cylinder communicate with mutually separated passages in the catalytic converter, and the exhaust gas is discharged to the outlet of the catalytic converter. It is preferable that the number of exhaust passage downstream portions equal to or less than the number of upstream passage portions communicate with each other. According to this configuration, since the plurality of exhaust passage upstream portions communicate with the mutually separated passages in the catalytic converter, the plurality of exhaust passage upstream portions are substantially extended to the outlet of the catalytic converter. While the exhaust purification function immediately after a cold start is maintained high by bringing the converter position upstream, the plurality of exhaust passages are lengthened, and the output of the engine, particularly in the middle speed region, is improved.

  Preferably, the communication portion is formed of a gap in the flow direction of the exhaust gas, and the inlet of the downstream portion of the exhaust passage is opposed to the outlet of the catalytic converter via the gap. Here, the “gap in the flow direction” refers to a space spaced in the flow direction. According to this configuration, since the communication portion can be easily formed simply by disposing the outlet of the catalytic converter and the inlet of the downstream portion of the exhaust passage at an interval, the structure can be simplified and the cost can be reduced.

  In the present invention, on the downstream side of the catalytic converter, a partition plate provided in the exhaust pipe body forming the exhaust passage and extending along the flow direction of the exhaust gas and dividing the exhaust passage into a plurality of parts is provided, The communicating portion is formed by a gap in the flow direction of the exhaust gas, and the inlet of the downstream portion of the exhaust passage faces the outlet of the partition plate via the gap. According to this configuration, since the length of the partitioned exhaust passage extends to the outlet of the partition plate downstream of the catalytic converter, the engine in the medium speed range is disposed while the catalytic converter is disposed close to the upstream side. The output can be further improved. In addition, since the communication portion can be easily formed simply by arranging the outlet of the partition plate and the inlet of the downstream portion of the exhaust passage opposite to the outlet, the structure can be simplified and the cost can be reduced.

  In this invention, it is good also as a structure by which the open hole which forms the said communication part was provided in the exhaust pipe which forms the said exhaust passage downstream part. According to this configuration, the communication portion can be easily formed simply by providing an open hole in the exhaust pipe. Further, the exhaust noise reduction level can be arbitrarily adjusted by arbitrarily setting the number and diameter of the open holes.

  In the present invention, a partition plate that is provided inside the exhaust pipe forming the exhaust passage and extends along the flow direction of the exhaust gas and that divides the exhaust passage into a plurality is provided on the upstream side of the catalytic converter. The partition plate may have a communication hole that communicates a plurality of partitioned exhaust passages.

  According to this configuration, the plurality of partitioned exhaust passages are communicated on the upstream side of the catalytic converter, so that the output at the time of high rotation is improved.

  In the present invention, preferably, the exhaust chamber is disposed in the vicinity of an oil pan provided in a lower portion of the engine. According to this configuration, since the catalytic converter is located below the engine, it is located sufficiently upstream of the exhaust passage, and the exhaust purification performance immediately after the cold start of the engine is improved. Even if the temperature of the catalytic converter becomes high, since the temperature of the exhaust chamber is prevented from being increased, heat is hardly transmitted to the oil pan, and heat damage (heat transfer) to the lubricating oil in the oil pan can be suppressed.

  According to the vehicle exhaust device of the present invention, the exhaust passage downstream portion downstream of the catalytic converter communicates with the exhaust chamber via the communication portion, so that the exhaust noise is effectively reduced by the resonator (resonator) effect. Can be reduced. In addition, since most or all of the catalytic converter excluding the upstream end portion and a part of the downstream portion of the exhaust passage are housed in the exhaust chamber, the high temperature portion of the catalytic converter is not exposed to the outside, resulting in heat damage. It is suppressed. Furthermore, since exhaust noise can be reduced, the silencer can be made smaller and lighter. This improves the balance of weight distribution, especially in the case of motorcycles, and increases the degree of freedom in design.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing a motorcycle equipped with an exhaust device according to a first embodiment of the present invention. In this motorcycle, a front fork 2 is supported at a front end portion of a main frame 1 constituting a front half portion of a vehicle body frame FR, and a front wheel 4 is supported at a lower end portion of the front fork 2. A handle 9 is attached to the upper bracket 8 that supports the upper end of the front fork 2. A swing arm bracket 10 is formed at the lower rear end of the main frame 1, and a front end portion of the swing arm 11 is supported by the swing arm bracket 10 via a pivot shaft 12 so as to be swingable up and down. A rear wheel 13 is supported at the rear end of the swing arm 11. A seat rail 14 connected to the rear portion of the main frame 1 constitutes the rear half of the vehicle body frame FR. A shock absorber 17 for the rear wheel 13 is attached between the main frame 1 and the swing arm 11. An engine E is supported at the center lower portion of the main frame 1, and the rear wheel 13 is driven from the engine E through a chain 18.

  A rider's seat 19 and a passenger's seat 20 are supported on the seat rail 14. A fuel tank 21 is attached between the handle 9 and the rider seat 19 at the upper part of the main frame 1, that is, at the upper part of the vehicle body. A resin cowling 22 that covers a portion from the front of the handle 9 to the side of the front of the vehicle body is attached to the front of the vehicle body. And covering.

  In this embodiment, the engine E is a four-cylinder four-cycle parallel multi-cylinder engine, and includes an engine body 23 having a crankcase 24, a cylinder 27, a cylinder head 28, a cylinder head cover 29, and an oil pan 80, a transmission 31, and the like. It has. The exhaust device A has four individual (independent) exhaust pipes 32 connected to the cylinder head 28 for leading the exhaust gas G (FIGS. 2 and 4) downward from the front of the engine E; A collecting pipe 34 that collects the rear ends of the two exhaust pipes 32, a single collecting exhaust pipe 38 that communicates with the downstream end of the collecting pipe 34, a most downstream silencer 33, and a downstream of the collecting exhaust pipe 38. A connecting pipe 39 for connecting the end portion and the silencer 33 is provided. The exhaust pipe 32, the collect pipe 34, the collect exhaust pipe 38 and the connection pipe 39, which are exhaust pipe bodies, and the silencer 33 form a series of exhaust passages EP. The collective exhaust pipe 38 incorporates a catalytic converter 43 described later.

  FIG. 2 is a side view of the main part of the exhaust passage constituting the exhaust device A according to the present invention. As shown in the drawing, a part of the collecting pipe (exhaust pipe body) 34 and a part of the collecting exhaust pipe (exhaust pipe body) 38 of the exhaust apparatus A are covered with an exhaust chamber 50. As shown in FIG. 3, the two right and left exhaust pipes 32 communicate with each other through a communication pipe 39 in the middle to effectively use the exhaust inertia. Two oxygen sensors (O2 sensors) or two air-fuel ratio sensors 51 are installed near the inlet of the collecting pipe 34. The sensor 51 checks the concentration of oxygen in the exhaust gas or the presence or absence of oxygen, thereby controlling the air-fuel ratio of the air-fuel mixture supplied to the engine E.

  The collecting pipe 34 gathers four exhaust pipes 32 into two, and as shown in FIG. The cross-sectional shape of the collecting pipe 34 is an oval having a horizontal dimension larger than the vertical dimension, and a single catalytic converter 43 is accommodated in the downstream portion. As shown in FIG. 4, the exhaust chamber 50 has a downstream portion of the collecting pipe 34 inserted therein, whereby a part of the catalytic converter 43, in this example, most of the upstream end portion is excluded from the exhaust chamber 50. It is stored inside. The exhaust chamber 50 also stores a portion (upstream portion) of the downstream portion of the exhaust passage formed by the collective exhaust pipe 38. The exhaust chamber 50 has a so-called “middle structure” that is divided into two parts in the vertical direction, and has a shape in which a space is provided between the outer peripheral surfaces of the collecting pipe 34 and the collecting exhaust pipe 38 and the inner surface of the exhaust chamber 50.

  As shown in FIG. 5, the catalytic converter 43 has a large number of parallel elongated passages through which exhaust gas passes, and an annular flat plate 43a made of a chromium alloy (for example, 20Cr-5Al) or ceramic and an annular wave. This is a honeycomb structure having an oval cross section in which the plates 43b are alternately stacked concentrically. The cross-sectional shape is almost the same as the collecting pipe 34. The cross sectional shapes of the collecting pipe 34 and the catalytic converter 43 may be elliptical or circular. A catalyst such as platinum and rhodium is fired and supported on the flat plate and the corrugated plate. The catalytic converter 43 is arranged such that the axial direction of the cylindrical honeycomb structure, that is, the direction of the eyes (openings) is matched with the flow direction of the exhaust gas in FIG.

  Inside the collecting pipe 34 forming the exhaust passage upstream portion, which is the exhaust passage upstream of the catalytic converter 43, extends along the flow direction of the exhaust gas G, and a plurality of upstream portions of the collecting pipe 34 are arranged on the left and right (this example) Then, two partition plates 55 are provided. Thus, the exhaust passages separated from each other by the partition plate 55 communicate with two different regions S1 and S2 on the front surface which are the inlets of the catalytic converter 43 shown in FIG. A portion of the flat plate 43a and the corrugated plate 43b of the catalytic converter 43 corresponding to the downstream side of the partition plate 55 serves as a partition wall 43c extending along the flow direction of the exhaust gas G, and exhausts from the two regions S1 and S2. Gas G is allowed to pass through without being mixed. That is, the passages 40A and 40B separated from each other are formed in the catalytic converter 43 of FIG. Thus, the exhaust gas G in the two exhaust passages EP is purified by the single catalytic converter 43. The partition plate 55 is formed with a communication hole 56 (FIG. 2) for communicating a plurality of partitioned exhaust passages in order to improve output in a high speed range.

  A communication portion 52 that connects the exhaust passage EP and the inside of the exhaust chamber 50 is formed in a part of the downstream portion of the exhaust passage that is the collective exhaust pipe 38 shown in FIG. The communication portion 52 is formed by a gap 52A for spacing the exhaust gas in the flow direction, and the outlet 43d of the catalytic converter 43 is connected to the inlet 38a of the downstream portion of the exhaust passage formed of the collective exhaust pipe 38 via the gap 52A. Are facing each other. The gap 52A can be easily formed, unlike an open hole, which will be described later, which requires machining accuracy, so that the structure can be simplified and the cost can be reduced. These dimensional relationships indicate that the distance L from the outlet 43d of the catalytic converter 43 to the inlet 38a is 0.7 to 1.5D, where D is the diameter of the inlet 38a at the downstream portion of the exhaust passage which is the collective exhaust pipe 38. Is preferred. The diameter of the catalytic converter 43 is set larger than the diameter D of the inlet 38a.

  Next, the operation of the exhaust device A according to the first embodiment will be described. First, exhaust gas G is led out from a plurality of exhaust ports of the engine E of FIG. 1, and is exhausted from the plurality of exhaust pipes 32 through the exhaust chamber 50 through the collective exhaust pipe 38 and the connection pipe 39 to the atmosphere from the silencer 33. The As shown in FIG. 2, the exhaust gas G from the plurality of exhaust pipes 32 is guided to the collecting pipe 34. The exhaust gas G passes through the upper end portion of the collecting pipe 34 of FIG. 4 divided by the partition plate 55 and is purified through the catalytic converter 43 housed in the downstream part of the collecting pipe 34. A part of the exhaust gas G purified by the catalytic converter 43 is introduced as it is from the inlet 38a into the collective exhaust pipe 38, and is discharged from the silencer 33 of FIG. 1 into the atmosphere. The other part is diffused and expanded in the exhaust chamber 50 of FIG. 4, and exhaust noise is reduced by the resonator effect. Further, the collecting pipe 34, which is a part of the exhaust passage EP, is partitioned by the partition plate 55, and the exhaust passage EP separated into two in combination with the partition wall 43c of the catalytic converter 43 becomes long. The output in the area is improved.

  Further, since most of the catalytic converter 43 except the upstream end portion is accommodated in the exhaust chamber 50, the outer peripheral wall of the catalytic converter 43 is not exposed to the outside. As a result, heat damage (heat transfer) by the catalytic converter 43 is prevented. Can be reduced. In particular, since a space exists between the outer periphery of the catalytic converter 43 and the inner surface of the exhaust chamber 50, heat is shielded by the air layer in this space, and the temperature rise of the exhaust chamber 50 is suppressed. Further, since the silencer 33 in FIG. 1 can be made smaller and lighter by reducing the exhaust noise, the balance of weight distribution before and after the motorcycle is improved, and the degree of freedom in designing the motorcycle is increased.

  Next, an exhaust device according to a second embodiment of the present invention will be described. As shown in FIG. 6, in the second embodiment, in the exhaust chamber 50, the collecting pipe 34, which is an exhaust pipe body incorporating the catalytic converter 43, extends downstream from the catalytic converter 43 to provide an extending portion 34a. A partition plate 60 that divides the collecting pipe 34 that extends along the flow direction of the exhaust gas G and forms a part of the exhaust passage into a plurality of portions is provided inside the extending portion 34a. The partition plate 60 is located at substantially the same position on the passage cross section as the partition plate 55 with the catalytic converter 43 interposed therebetween. Thus, the exhaust gas G passes through a series of passages partitioned by the partition plate 55, the partition wall 43 c of the catalytic converter 43 and the partition plate 60. The extending part 34a is tapered in a funnel shape. The communicating portion 52 is composed of a gap 52B in the exhaust gas flow direction, and is an exhaust pipe body that forms an exhaust passage downstream portion at the outlet of the extending portion 34a, that is, the outlet of the partition plate 60 via the gap 52B. An inlet 38a of a certain collective exhaust pipe 38 is opposed. As shown in FIG. 7, communication holes 56 and 57 are provided in each of the upstream and downstream partition plates 55 and 60 sandwiching the catalytic converter 43.

  In the case of the second embodiment, the exhaust gas G purified by the catalytic converter 43 passes through the extending portion 34a along the partition plate 60 of FIG. The exhaust gas G throttled by the extending portion 34a passes through the gap 52B at a high flow rate and is introduced into the collective exhaust pipe 38 from the inlet 38a. At this time, exhaust noise is reduced by a resonator (resonator) effect through the gap 52B. As described above, the exhaust passage EP in which the collecting pipe 34 is divided into a plurality of partitions by the partition plate 60 becomes substantially longer, so that the output of the engine E in the medium speed range can be further improved. In addition, since the plurality of partitioned exhaust passages EP are communicated by the open holes 56 and 57 on the upstream and downstream sides of the catalytic converter 43, the output at the time of high rotation is improved. This effect will be described later.

  Furthermore, the exhaust apparatus concerning 3rd Embodiment of this invention is demonstrated. As shown in FIG. 8, the tapered extending portion 34 a of the collecting pipe 34 and the collecting exhaust pipe 38 are connected without a gap in the exhaust chamber 50, and an open hole 52 </ b> C is provided as the communicating section 52 in the collecting exhaust pipe 38. ing. For example, six open holes 52C are formed in the circumferential direction of the collecting pipe 34 at regular intervals. Partition plates 55 and 63 extending in the flow direction of the exhaust gas G and partitioning the collecting pipe 34 into a plurality are provided on the upstream side and the downstream side of the catalytic converter 43. In the case of the third embodiment, the exhaust gas G is purified by the catalytic converter 43 and then guided to the extending portion 34a and the collective exhaust pipe 38 which are downstream of the exhaust passage. At this time, the exhaust gas G passes through the open hole 52C. Exhaust noise can be reduced more effectively by the effect of the resonator. Further, the exhaust noise reduction level can be adjusted by arbitrarily setting the number and diameter of the open holes 52C formed in the exhaust pipe.

  In the third embodiment, as shown in FIG. 9, communication holes 56 and 57 are formed on the upstream side and the downstream side, respectively, across the catalytic converter 43. FIG. 10 shows the output characteristics of the engine with and without the communication holes 56 and 57 of the partition plates 55 and 63. In the figure, a solid line indicates a case where there is no communication hole, a long broken line indicates a case where the diameter of the communication holes 56 and 57 is d, and a short broken line indicates a case where the diameter is 2d. The height P (FIG. 9) of the partition plates 55 and 63 is 2.5d. As is apparent from the experimental data of the output characteristics, when the communication holes 56 and 57 are provided, the engine output is improved from the middle speed region toward the high speed region to the high speed region as compared with the case where the communication holes 56 and 57 are not provided. It was seen.

  FIG. 11 is a front view showing the arrangement of the exhaust chamber 50 and the oil pan 80 in the exhaust device according to the present invention. As shown in the figure, the exhaust chamber 50 is disposed in the vicinity of an oil pan 80 provided in the lower part of the engine E. Even if the catalytic converter 43 becomes high temperature, the exhaust chamber is prevented from being heated, so that heat is hardly transmitted to the oil pan, and heat damage (heat transfer) to the lubricating oil in the oil pan can be suppressed. In this case, the oil pan 80 has a deep bottom portion 80a and a shallow bottom portion 80b located above the deep bottom portion 80a. A recess 81 is provided below the shallow bottom portion 80b, and the exhaust chamber 50 is disposed in the recess 81. ing. Thereby, the space below the engine E is effectively used.

  Further, since the deep bottom portion 80a is provided, when a predetermined amount of oil M such as lubricating oil is accommodated in the oil pan 80, the storage depth h of the deep bottom portion 80a increases as shown in FIG. As shown in FIG. 3, even if the motorcycle is lowered forward or backward due to acceleration / deceleration of the motorcycle during traveling, the oil level changes from the H1 position to the H2 (acceleration) or H3 (deceleration) position. The suction port 2a of the suction pipe 82 can always be kept immersed in the oil surface, and the lubrication function does not deteriorate. The oil level H2 indicates the oil level during acceleration. An inclined surface 54 is formed outside the exhaust chamber 50 shown in FIG. 11 to avoid contact with the road surface during banking. Further, the exhaust chamber 50 has a monaca structure composed of two upper and lower members each having an oblique dividing surface 71. The split structure facilitates assembly of the collecting pipe 34 and the collecting exhaust pipe 38. Thus, even if the exhaust chamber 50 is brought close to the oil pan 80 provided in the lower part of the engine E, heat damage (heat transfer) from the catalytic converter 43 is suppressed due to the heat shielding effect by the exhaust chamber 50. Further, since the dividing surface 71 extends obliquely upward toward the outer side, the flange forming the dividing surface 71 is positioned upward at the outer side portion, so that the bank angle is not easily restricted.

  In each of the above embodiments, a part of the catalytic converter 43 in FIG. 4 is accommodated in the exhaust chamber 50. However, the entire catalytic converter 43 may be accommodated in the exhaust chamber 50. The entire converter 43 can be effectively shielded from heat. In addition, two exhaust passages are communicated with the upstream end of the catalytic converter 43, and the collective exhaust pipe 38 that forms one exhaust passage downstream portion smaller than this is communicated with the downstream end. Can connect the same number of exhaust passage downstream portions with the upstream end, thereby further increasing the length of the partitioned exhaust passage.

1 is a side view of a motorcycle including an exhaust device according to a first embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part of the exhaust passage of the same exhaust apparatus. It is a top view which shows the principal part of the exhaust passage of the same exhaust apparatus. It is a horizontal sectional view showing the principal part of the exhaust passage of the exhaust device. It is sectional drawing along the VV line of FIG. It is a horizontal sectional view showing the principal part of the exhaust passage in the exhaust device concerning a 2nd embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part of the exhaust passage of the same exhaust apparatus. It is a horizontal sectional view showing the principal part of the exhaust passage in the exhaust device concerning a 3rd embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part of the exhaust passage of the same exhaust apparatus. It is a characteristic view which shows the relationship between an engine speed and an engine output. It is a front view which shows arrangement | positioning of an exhaust apparatus and an oil pan. It is a longitudinal cross-sectional view explaining the change of the oil surface state in the oil pan at the time of acceleration / deceleration of the motorcycle.

Explanation of symbols

32 Exhaust pipe 34 Collecting pipe (exhaust pipe body forming the exhaust passage upstream portion)
34a Inlet 38 at the downstream portion of the exhaust passage Collecting exhaust pipe (exhaust pipe body forming the downstream portion of the exhaust passage)
40A, 40B Separated passage 43 Catalytic converter 50 Exhaust chamber 52 Communication portion 52A, 52B Gap 52C Open hole 56, 57 Communication hole 55, 60, 63, Partition plate 80 Oil pan A Exhaust device E Engine EP Exhaust passage

Claims (7)

A catalytic converter for purifying the exhaust gas is provided in an exhaust passage for deriving exhaust gas from the engine;
At least a part of the catalytic converter and a part of an exhaust pipe body forming a downstream portion of the exhaust passage connected to the outlet of the catalytic converter are housed in an exhaust chamber,
An exhaust system for a vehicle, wherein a communication portion for communicating the exhaust passage and the inside of the chamber is formed at a downstream portion of the exhaust passage.   2. The engine according to claim 1, wherein the engine is a multi-cylinder engine, and a plurality of exhaust passage upstream portions for leading exhaust gas from each cylinder communicate with mutually separated passages in the catalytic converter, and the outlet of the catalytic converter is connected to the outlet of the catalytic converter. An exhaust system for a vehicle in which the number of exhaust passage downstream portions equal to or less than the number of exhaust passage upstream portions communicates.   3. The exhaust system for a vehicle according to claim 1, wherein the communication portion includes a gap in a flow direction of exhaust gas, and an inlet of the downstream portion of the exhaust passage is opposed to an outlet of the catalytic converter via the gap. In Claim 2, a partition plate is provided on the downstream side of the catalytic converter, provided inside the exhaust pipe body forming the exhaust passage, extending along the flow direction of the exhaust gas, and dividing the exhaust passage into a plurality of sections,
The exhaust device for a vehicle, wherein the communication portion is formed of a gap in an exhaust gas flow direction, and an inlet of the downstream portion of the exhaust passage is opposed to an outlet of the partition plate via the gap.   The exhaust system for a vehicle according to any one of claims 1 to 4, wherein an open hole that forms the communication portion is provided in an exhaust pipe body that forms a part of the exhaust passage downstream portion.   6. The exhaust passage according to claim 1, wherein the exhaust passage is provided upstream of the catalytic converter in an exhaust pipe forming an exhaust passage and extends in a flow direction of the exhaust gas, and the exhaust passage is divided into a plurality of sections. An exhaust system for a vehicle in which a partition plate is provided, and a communication hole is formed in the partition plate to communicate a plurality of partitioned exhaust passages.   The exhaust system for a vehicle according to any one of claims 1 to 6, wherein the exhaust chamber is disposed in proximity to an oil pan provided in a lower portion of the engine.

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