JP2010276000A - Muffler and motorcycle - Google Patents

Abstract

The exhaust performance of a muffler is improved with a simple structure.
Immediately after a catalyst 187 that purifies exhaust gas from an exhaust pipe 23 that has entered the muffler body 18A, a tubular portion 188 having the same inner diameter as the catalyst 187 is formed over a predetermined dimension to form a Exhaust gas was allowed to flow out, and immediately after the tubular portion 188, a convergent portion 189 having a reduced diameter along the flow of the exhaust gas was formed to allow the exhaust gas from the tubular portion 188 to flow out. Thereby, the exhaust gas from the catalyst 187 can be expanded, and a rapid increase in the back pressure can be suppressed while having a simple exhaust passage structure.
[Selection] Figure 8

Description

  The present invention relates to a muffler and a motorcycle equipped with the muffler.

  In the muffler of a scooter type motorcycle, it is common to make the exhaust pipe U-turn in the muffler body for the purpose of downsizing the muffler body and ensuring the length of the exhaust pipe due to the close distance from the combustion chamber to the muffler body It is. Moreover, in the muffler having such a structure, it is common to arrange the catalyst in the muffler body.

  For example, Patent Document 1 discloses a structure in which an exhaust pipe is U-turned and a catalyst is attached to the most downstream end of the exhaust pipe. However, in this structure, since the exhaust passage from the combustion chamber is long, there is a problem that the exhaust gas purification performance is low because the catalyst is difficult to warm up early. Therefore, it is conceivable to improve the warm-up performance of the catalyst by arranging the catalyst in the middle of the exhaust pipe as in the structure disclosed in Patent Document 2.

JP 2002-195027 A JP 2006-291929 A Japanese Utility Model Publication No. 4-006721

  When the catalyst is arranged in the middle of the exhaust pipe as in the structure described in Patent Document 2, in order to achieve both the output performance of the engine and the silencing effect, the exhaust pipe downstream from the catalyst is reduced in diameter (convergent cone part). Need to be formed). However, when such a reduced diameter portion is formed, there is a problem that the back pressure increases and exhaust gas escapes worse.

  Therefore, as in Patent Document 3, it is conceivable to form a plurality of pores in the convergent cone portion immediately after the catalyst. However, a plurality of baffle pipes are provided in the muffler body of this type of muffler, and the pores may face the baffle pipe and the back pressure rise may not be sufficiently suppressed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a muffler that improves the exhaust performance of the muffler with a simple structure.

The muffler of the present invention is a muffler in which a catalyst for purifying exhaust gas from an exhaust pipe that has entered the muffler body is disposed in the muffler body, and is the same as the catalyst over a predetermined dimension immediately after the catalyst. An exhaust gas from the tubular part is formed immediately after the tubular part to form a convergent part whose diameter is reduced along the flow of the exhaust gas. It is characterized by letting out.
A motorcycle according to the present invention is equipped with the muffler described above.

  According to the present invention, the exhaust performance of the muffler can be improved with a simple structure.

1 is a side view of a scooter type motorcycle according to an embodiment of the present invention. 1 is a plan view of a scooter type motorcycle according to an embodiment of the present invention. It is the front view and back view of a scooter type motorcycle concerning an embodiment of the invention. 1 is a simplified side view of a scooter type motorcycle according to an embodiment of the present invention. It is the arrow line view which looked at the muffler from the arrow A direction shown in FIG. It is a see-through | perspective perspective view which shows the state which removed a part of muffler body from the muffler. It is arrow sectional drawing which looked at the muffler from the arrow B direction shown in FIG. It is arrow sectional drawing which looked at the muffler from the arrow C direction shown in FIG. It is arrow sectional drawing which looked at the muffler from the surface orthogonal to the axis line.

  Hereinafter, modes for carrying out the present invention will be described. 1, 2, and 3 are a side view, a plan view, a front view, and a rear view of a scooter type motorcycle (hereinafter referred to as a vehicle) 1 to which the present invention is applied. First, a schematic configuration of the vehicle 1 will be described with reference to FIGS. 1, 2, and 3. In the drawings used in the following description including these figures, the front of the vehicle is indicated by an arrow Fr, the rear of the vehicle is indicated by an arrow Rr, and the lateral right side of the vehicle is indicated by an arrow R as necessary. The left side of the vehicle is indicated by an arrow L.

  The vehicle 1 is configured by forming a vehicle body skeleton by a plurality of vehicle body frames made of steel or aluminum alloy and mounting various parts on the vehicle body frame. The down tube 2 that is a part of the vehicle body frame has a front end coupled to the steering head pipe 3 and extends from the steering head pipe 3 substantially downward, and then curves and extends substantially rearward. A pair of left and right rear frames 4 that are part of the vehicle body frame are coupled to the rear side of the down tube 2, and each extends obliquely upward and rearward.

  The steering head pipe 3 supports a front fork 5 so that the front fork 5 can rotate. A handle bar 6 is fixed to the upper end of the front fork 5, and a front wheel 7 is rotatably supported on the lower end side. A brake disk 8 that rotates integrally with the front wheel 7 is installed.

  An engine bracket 9 is formed at the rear end of the down tube 2, and the engine bracket 9 supports the swing unit type engine 11 via the stay 10, and the swing unit type engine 11 is vertically moved around the support portion of the stay 10. It can be swung toward. The swing unit type engine 11 includes a cylinder assembly 12, a crankcase 13, and a transmission unit 14 including a transmission. The swing unit type engine 11 supports a rear wheel 15 and a shock absorber 16 between the rear frame 4. It also has a function as a swing arm by mounting.

  More specifically, an engine bracket 9 for supporting the swing unit type engine 11 is formed integrally with the down tube 2 at the rear end of the down tube 2 or is firmly attached to the rear end of the down tube 2. It is fixed and extends to the rear of the vehicle. The engine bracket 9 further fixes a stay 10 and supports the swing unit type engine 11 so that the stay 10 can swing in the vertical direction. A swing pivot portion 13A is integrally formed with the crankcase 13 of the swing unit type engine 11, and the swing pivot portion 13A is pivotally supported by the stay 10. The speed change unit 14 located behind the vehicle in the swing unit type engine 11 supports the rear wheel 15 so as to be rotatable on the inner side surface in the vehicle width direction, and supports the shock absorber 16 on the upper surface. With this configuration, the swing unit type engine 11 has a function as a swing arm.

  When the swing unit type engine 11 is mounted on the vehicle 1, the cylinder assembly 12, the crankcase 13, and the transmission unit 14 are arranged in this order from the vehicle front side. The cylinder assembly 12 includes a single-cylinder air-cooled engine, and is mounted in a state where the cylinder axis is substantially horizontal along the vehicle longitudinal direction. The power from the crankshaft included in the crankcase 13 is transmitted to the driven sprocket included in the transmission unit 14 by a transmission member such as a V-belt stretched substantially horizontally along the vehicle longitudinal direction. With such a configuration, the swing unit type engine 11 has a horizontally long shape in a side view and is mounted on the vehicle 1 in a state in which the longitudinal direction is substantially horizontal along the vehicle front-rear direction, thereby suppressing the vehicle height or lowering the center of gravity. The layout configuration is to be achieved.

  In the swing unit type engine 11, an air cleaner 17 is installed on the upper surface of the transmission unit 14, and the air cleaner 17 supplies clean air to the intake port of the cylinder assembly 12. Since the cylinder assembly 12 is located on the front side of the vehicle in the swing unit type engine 11, the purified air from the air cleaner 17 is supplied to the intake port via the intake passage directed toward the front of the vehicle. Further, an exhaust port is formed on the lower surface of the cylinder assembly 12, and the exhaust pipe 23 (FIG. 4) extends rearward from the exhaust port 23 and is connected to the muffler 18 at the rear of the vehicle.

  Also, a rider seat 19 for a rider to sit on is provided above the swing unit type engine 11, and a step board 20 on which a foot is placed while the rider is seated is placed on the down tube 2 in a step frame (not shown). Supported by The step board 20 is formed integrally with a leg frame cover that constitutes the exterior of the vehicle. An article storage space that is a so-called helmet box that is opened and closed by the rider seat 19 is formed between the swing unit type engine 11 and the rider seat 19.

  As a vehicle exterior, various vehicle body covers are supported and attached to appropriate positions such as a vehicle body frame. The front leg shield 21 is mounted with a winker or the like, covers the front side of the vehicle, and is continuous with the above-described step board 20. The rear frame cover 22 is mounted with a blinker and a brake lamp, and covers the vehicle rear side. An article storage space is formed inside the rear frame cover 22. A rear fender 22A is provided at the rear end of the rear frame cover so as to cover the upper portion of the rear wheel 15.

  Next, FIG. 4 is a side view of the vehicle 1 schematically showing a state where the rear frame cover 22 is removed from the vehicle 1, and FIG. 5 shows the muffler 18 and the exhaust pipe 23 in the direction of arrow A in FIG. It is the arrow view seen from.

  An exhaust port (not shown) is formed on the lower surface of the cylinder assembly 12, and an exhaust pipe 23 is connected to the exhaust port as shown in FIG. The exhaust pipe 23 is curved in the vehicle width direction from the exhaust port, and thereafter extends toward the rear of the vehicle and is slightly inclined rearward and upward, and then coupled to the muffler 18. The muffler body 18A constituting the outer surface of the muffler 18 has a cylindrical shape, and the exhaust pipe 23 enters the muffler body 18A from substantially the center of the end surface on the vehicle front side of the muffler body 18A (see also FIG. 6). Exhaust gas flowing into or out of the muffler body 18A from the exhaust pipe 23 passes through an exhaust passage configured in the muffler body 18A, is purified by a catalyst, and is discharged into an expansion chamber partitioned in the muffler body 18A. . The exhaust gas discharged to the expansion chamber is then discharged to the outside from the exhaust pipe 18B (FIG. 5) desired to the outside from the rear end of the muffler body 18A via the plurality of expansion chambers.

  A muffler support bracket 24 is welded to the muffler body 18A and the exhaust pipe 23, and the muffler is fixed by fixing through holes 24A and B formed in the muffler support bracket 24 to fixed portions formed at appropriate positions of the crankcase 13. 18 is fixed to the swing unit type engine 11. In a state where the muffler 18 is mounted on the vehicle 1, the muffler 18 is in a back up state in the vehicle front-rear direction. Further, a muffler cover bracket 24C is attached to the outer side in the vehicle width direction of the circumferential surface (outer surface) of the muffler body 18A, and a muffler cover 25 that covers the longitudinal direction of the muffler 18 is attached thereto.

  Next, the internal structure of the muffler 18 will be described. 6A and 6B are perspective perspective views showing a state where a part of the muffler body 18A is removed from the muffler 18. FIG. 6A and 6B, some members are not shown for convenience. In the following description, in the exhaust passage in the muffler body 18A, the direction closer to the exhaust pipe 23 side may be referred to as upstream, and the far side may be described as downstream.

  As shown in FIGS. 6A and 6B, a disk-shaped first baffle plate 181 and second baffle plate 182 are disposed in the muffler body 18A, respectively. A first expansion chamber 183, a third expansion chamber 184, and a second expansion chamber 185 are partitioned from the front of the vehicle.

  The exhaust pipe 23 that has entered straight from substantially the center of the end surface of the muffler body 18A on the front side of the vehicle is connected to a divergent cone 186 whose diameter increases toward the rear in the first expansion chamber 183. The divergent cone 186 has a truncated cone shape whose upper end is connected to the exhaust pipe 23 and whose lower end is connected to the catalyst 187 having a diameter larger than that of the exhaust pipe 23 (the remaining part from which the cone head is removed, that is, a truncated cone). Is connected to the cylindrical catalyst 187 in the first expansion chamber 183. The center of the lower end of the divergent cone 186 is offset from the central axis of the exhaust pipe 23 toward the outer peripheral side (the muffler body 18A side), whereby the central axis of the catalyst 187 is also offset from the central axis of the exhaust pipe 23. It will be. Note that the catalyst 187 is a three-way catalyst containing platinum, palladium, rhodium, or the like as a main component.

  The catalyst 187 is connected to the tubular member 188 at its downstream end (end on the vehicle rear side). The tubular member 188 is a hollow cylindrical pipe member that is inserted through the first baffle plate 181 and, more specifically, inserted in a light press-fitted state and interposed between the first expansion chamber 183 and the third expansion chamber 184, and an exhaust passage. Part of The tubular member 188 whose one end on the upstream side is connected to the catalyst is connected to a convergent cone 189 whose diameter is reduced rearward at the other end. With such a configuration, the exhaust gas discharged from the divergent cone 186 is purified via the catalyst 187 and then flows toward the rear of the vehicle through the tubular member 188 and the convergent cone 189.

  A convergent cone 189, which is a convergent part that affects the output characteristics and the silencing characteristics of the engine, is reduced in diameter so as to form a gentle taper to the second baffle plate 182 that defines the second expansion chamber 185. It extends to the vicinity of the baffle plate 182. The convergent cone 189 has a rear end formed in a substantially straight tubular shape and is supported by the second baffle plate 182. In the second expansion chamber 185, a U-shaped exhaust pipe 190 curved in a U shape as shown in FIG. 6B is disposed, and the upstream end of the U-shaped exhaust pipe 190 is a converter. Connected to the rear end of the gent cone 189. The U-shaped exhaust pipe 190 is curved so as to change the flow of exhaust in the second expansion chamber 185 by 180 degrees, and the other end is connected to the exhaust pipe 191 extending linearly. The exhaust pipe 191 connects one end on the upstream side to the U-shaped exhaust pipe 190, extends through the second baffle plate 182 and the first baffle plate 181 to the first expansion chamber 183, and has the other end on the downstream side thereof. Exhaust gas is released in the vicinity of the catalyst 187. With such a configuration, the exhaust gas flowing toward the rear of the vehicle is redirected by the U-shaped exhaust pipe 190, flows toward the front, and is discharged in the first expansion chamber 183. .

  The exhaust gas discharged into the first expansion chamber 183 then flows into the second expansion chamber 185. As shown in FIG. 6B, the first expansion chamber 183 and the second expansion chamber 185 communicate with each other through a baffle pipe 192 disposed in parallel with the axis of the exhaust pipe 23 or the like. As a result, the exhaust gas discharged from the exhaust pipe 191 to the first expansion chamber 183 flows into the second expansion chamber 185 located at the rear of the vehicle.

  Then, as shown in FIG. 6B, the second expansion chamber 185 and the third expansion chamber 184 communicate with each other through a baffle pipe 193. As a result, the exhaust gas discharged into the second expansion chamber 185 flows into the third expansion chamber 184. As shown in FIG. 6 (A), the third expansion chamber 184 has a discharge pipe 18B communicating with the outside at one end, and the exhaust gas flowing into the third expansion chamber 184 passes through the discharge pipe 18B. It will be discharged to the outside. That is, in the muffler 18, the third expansion chamber 184 is an expansion chamber into which exhaust gas is finally introduced.

  Next, an exhaust pipe 191 from the rear end side of the exhaust pipe 23 that constitutes an exhaust passage in the muffler body 18A until exhaust gas from the exhaust pipe 23 that has entered the muffler body 18A is released to the first expansion chamber 183. The shape and connection state of each member up to will be described in detail. 7 is a cross-sectional view taken along the line BB as viewed from the arrow B shown in FIG. 5, and FIG. 8 is a cross-sectional view taken along the line C-C as viewed from the arrow C shown in FIG. FIG. 9 is a cross-sectional view of the muffler 18 as seen from the axial direction.

  As shown in FIG. 7, the exhaust pipe 23 enters straight from substantially the center in the vertical direction of the muffler body 18A. FIG. 9A is a view taken along the line DD in FIG. 7, but as shown in this figure, the muffler 18 enters the muffler body 18A from the center in the vehicle width direction. Thereafter, the exhaust pipe 23 extends into the first expansion chamber 183 and is connected to the divergent cone 186 as described above.

  8 is a cross-sectional view taken along the line CC of FIG. 5. More specifically, FIG. 8 is a muffler in a virtual plane including the central axis of the exhaust pipe 23, the central axis of the catalyst 187, and the central axis of the exhaust pipe 191. It is sectional drawing which cut | disconnected 18 (refer also FIG.9 (B)). In the muffler 18, the positional relationship is such that the central axis (L1) of the exhaust pipe 23, the central axis (L2) of the catalyst 187, and the central axis (L3) of the exhaust pipe 191 are included in the same virtual plane. However, such a configuration is not necessarily required.

  As shown in FIG. 8, the divergent cone 186 has a frustoconical shape that increases in diameter toward the rear, and the center of the exhaust pipe 23 toward the vehicle inner downward direction (the direction of arrow D in FIG. 9A). The center of the circumferential surface is gradually separated from the axis. Then, the divergent cone 186 is connected to the catalyst 187 at the downstream rear end thereof so that the upstream front end of the catalyst 187 is externally fitted, and then the catalyst 187 is moved to a position close to the first baffle plate 181. Extend. The catalyst 187 extending to the immediate vicinity of the first baffle plate 181 has an inner peripheral end surface of a tubular member 188 disposed so that a downstream rear end thereof straddles the first expansion chamber 183 and the third expansion chamber 184. It is fitted and connected in the form of being fitted outside. The tubular member 188 is inserted into the insertion hole 181A of the first baffle plate 181, but the peripheral surface thereof is in close contact with each other so as to maintain an airtight state between the expansion chambers. The first baffle plate 181 is fitted and inserted into contact with the inner periphery of the insertion hole 181A. Thus, the catalyst 187 is supported with its front end connected to the exhaust pipe 23 and its rear end connected to the tubular member 188, and its peripheral surface is exposed in the first expansion chamber 183. It will be. In such a configuration, the heat of the high-temperature exhaust gas released to the first expansion chamber 183 is directly transmitted to the outer surface of the catalyst 187, so that the warm-up of the catalyst 187 can be accelerated. Further, although the catalyst 187 becomes high temperature, the catalyst 187 is fitted in a form covered with the tubular member 188, and the tubular member 188 is inserted into the insertion hole 181A of the first baffle plate 181. Without direct contact, heat transfer from the catalyst 187 to the muffler body 18A is suppressed.

  FIG. 9B is an EE arrow view in FIG. 7, and more specifically a cross-sectional view of the muffler 18 cut slightly behind the first baffle plate 181. The catalyst 187 is connected to a divergent cone 186 that gradually separates the center of its peripheral surface from the center axis of the exhaust pipe 23 toward the vehicle inner lower side. Therefore, the center axis (L2) of the catalyst 187 is shown in FIG. As shown in B), the position is offset from the central axis (L1) of the exhaust pipe 23 to the outer peripheral side (in the direction of arrow D in FIG. 9A). Therefore, in a state where the muffler 18 is mounted on the vehicle 1, the center axis L2 (axial center) of the catalyst 187 is on the vehicle inner side and lower side between the vertical plane and the horizontal plane of the vehicle 1, that is, the center axis L1. On the other hand, it is located inside and below the vehicle.

  Next, immediately after the catalyst 187, the tubular member 188 forms an exhaust passage having the same or substantially the same inner diameter as the catalyst 187 over a predetermined dimension in the third expansion chamber 184, and a downstream rear end portion thereof Connect to Convergent Cone 189 at (immediately after). The convergent cone 189 has a U-shaped end that is desired to the third expansion chamber 184 through the second baffle plate 182 while gradually or gradually reducing its diameter along the flow of exhaust gas in the third expansion chamber 184. Connected to the mold exhaust pipe 190. In the present embodiment, the distance from the catalyst 187 to the U-shaped exhaust pipe 190, that is, the length of the exhaust passage formed by the tubular member 188 and the convergent cone 189 is about the length occupied by the tubular member 188. About 1/3. In the muffler 18, such a tubular member 188 forms an exhaust passage having substantially the same inner diameter as the catalyst 187 over a predetermined dimension with respect to the exhaust gas exhausted from the catalyst 187, so that the downstream convergent cone 189 is formed. The increase in back pressure due to the is now mitigated. Further, in the present embodiment, the tubular member 188 and the convergent cone 189 are separated, but they may be integrally formed.

  Next, the U-shaped exhaust pipe 190 is curved in a U shape and is coupled to the exhaust pipe 191 at the downstream end thereof. The exhaust pipe 191 extends to the first expansion chamber 183 and discharges exhaust gas from its downstream end. Here, in the muffler 18, as shown in FIG. The central axis (L1) of the exhaust pipe 23, the central axis (L2) of the catalyst 187, and the central axis (L3) of the exhaust pipe 191 are in a positional relationship such that the catalyst 187 Since the central axis (L2) of the exhaust pipe 23 is offset from the central axis (L1) of the exhaust pipe 23 to the outer peripheral side, the central axis (L3) of the exhaust pipe 191 and the central axis (L2) of the catalyst 187 and the exhaust pipe 23 Is located on the opposite side of the center axis (L1).

  Then, after exhaust gas is discharged from the exhaust pipe 191 to the first expansion chamber 183, the exhaust gas flows into the second expansion chamber 185 and the third expansion chamber 184 as described above, and finally from the exhaust pipe 18B. It will be released to the outside. FIG. 9C is a cross-sectional view taken along line FF in FIG. 7, and more specifically, a cross-sectional view in which the muffler 18 is cut slightly behind the second baffle plate 182. As shown in this figure, the baffle pipes 192 and 193 that communicate with the respective expansion chambers are arranged in the muffler body 18A so as not to interfere with the catalyst 187, the exhaust pipe 191 and the like. Further, the exhaust pipe 18B is arranged so that the exhaust side end portion is desired from the center in the vehicle width direction of the muffler 18, and exhaust gas is exhausted from here.

  As described above, in the present embodiment, in the muffler 18, the tubular member 188 forms an exhaust passage having substantially the same inner diameter as the catalyst 187 over a predetermined dimension immediately after the catalyst 187, and the downstream end of the downstream end In the part (immediately after), it is connected to the convergent cone 189. The convergent cone 189 is gradually or gradually reduced in diameter along the flow of exhaust gas to form an exhaust passage, and exhaust gas flows out downstream. Thus, by not forming the convergent cone part (reduced diameter part) immediately after the catalyst 187, the exhaust resistance (flow path resistance) immediately downstream of the catalyst 187 can be reduced without forming pores or the like in the reduced diameter part. Can be reduced. Therefore, formation of pores and the like is unnecessary, and a rapid increase in back pressure can be suppressed while having a simple exhaust passage structure.

  Further, the catalyst 187 is coupled by connecting the rear end of the catalyst 187 so as to be covered (externally fitted) by the tubular member 188, and the tubular member 188 is inserted into the insertion hole 181A of the first baffle plate 181. . With such a configuration, the temperature of the catalyst 187 becomes high, but since the catalyst 187 does not directly contact the first baffle plate 181, heat transfer from the catalyst 187 to the muffler body 18 </ b> A is suppressed.

  In addition, the tubular member 188 is partially exposed to the high-temperature first expansion chamber 183 at the site where the catalyst 187 is bonded, but most of the tubular member 188 is the third expansion chamber which is the last expansion chamber in the muffler 18. It is arranged in the chamber 184. In the third expansion chamber 184, which is the last expansion chamber, the temperature of the exhaust gas is relatively low, so that the temperature increase of the tubular member 188 itself due to the first expansion chamber 183 or the catalyst 187 can be suppressed. The heat transfer to the muffler body 18A via the first baffle plate 181 can be further suppressed.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, in the present embodiment, the muffler according to the present invention is applied to a scooter type motorcycle, but may be applied to other motorcycles.

  1 Scooter type motorcycle (vehicle), 2 down tube, 3 steering head pipe, 4 rear frame, 5 front fork, 6 handlebar, 7 front wheel, 8 brake disc, 9 engine bracket, 10 stay, 11 swing unit type engine, 12 Cylinder Assembly, 13 Crankcase, 13A Swing Pivot, 14 Transmission Unit, 15 Rear Wheel, 16 Shock Absorber, 17 Air Cleaner, 18 Muffler, 18A Muffler Body, 18B Discharge Pipe, 19 Rider Seat, 20 Step Board, 21 Front Leg Shield, 22 Rear frame cover, 22A Rear fender, 23 Exhaust pipe, 24 Muffler support bracket, 24A, 24B Through hole, 25 Muffler cover, 181 1st Baffle plate, 181A through hole, 182 second baffle plate, 183 first expansion chamber, 184 third expansion chamber, 185 second expansion chamber, 186 diver jet cone, 187 catalyst, 188 tubular member, 189 convergent cone, 190 U-shape Type exhaust pipe, 191 exhaust pipe, 192 baffle pipe, 193 baffle pipe.

Claims (5)

A muffler in which a catalyst for purifying exhaust gas from an exhaust pipe that has entered the muffler body is disposed in the muffler body,
Immediately after the catalyst, a tubular portion having the same inner diameter as that of the catalyst is formed over a predetermined dimension to allow exhaust gas to flow out from the catalyst, and immediately after the tubular portion, the diameter is reduced along the flow of the exhaust gas. A muffler characterized in that an exhaust gas from the tubular part is caused to flow out by forming a convergent part.   The catalyst has a front end connected to the exhaust pipe and a rear end fitted on the inner peripheral end surface of the tubular portion, and the tubular portion defines an expansion chamber in the muffler body. The muffler according to claim 1, wherein the muffler is fitted into a plate.   The expansion chamber defined by the baffle plate into which the tubular portion is inserted and from which the tubular portion extends is an expansion chamber into which exhaust gas flows into the end of the plurality of expansion chambers. Item 3. The muffler according to Item 2.   The catalyst which is curved in a U shape from the downstream end portion of the convergent cone portion, and then forms an exhaust passage extending linearly, and the exhaust gas from the exhaust passage is partitioned by the baffle plate The muffler according to claim 2, wherein the muffler is extended to an expansion chamber in which is disposed.   A motorcycle equipped with the muffler according to any one of claims 1 to 4.

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