JPH0610659A - Exhaust system for internal combustion engine with catalyst - Google Patents

Abstract

PURPOSE:To provide effective purifying effect by storing the catalyst within a muffler body without upsizing the exhaust system or deteriorating the engine performance. CONSTITUTION:Two outer shells 16, 16 are joined to form a hollow space, the inside of a muffler 6 is divided into three expansion chambers A, B, C by buffle plates 13, 14, and a part of an exhaust pipe 5 where one end of the exhaust pipe is connected to the exhaust port of the engine is inserted into the muffler body 7 so that the other end may reach the expansion chamber A. The main catalyst 18 is supported by the buffle plates 14, 15 so as to connect the expansion chamber A to the expansion chamber B, and a communicating pipe 19 is supported by the buffle plate 14 so as to connect the expansion chamber B to the expansion chamber C to allow the exhaust gas to flow from the engine into the expansion chambers in the order of A B C, and in that process, the exhaust gas is fully purified. The exhaust gas discharged into the expansion chamber C flows through a tail pipe 17 supported by the buffle plate 15 and released into the atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system for an internal combustion engine used in a motorcycle or the like, and more particularly to an improvement of an exhaust system for purifying exhaust gas by providing a catalyst therein.

[0002]

2. Description of the Related Art Conventionally, a catalyst has been installed in an exhaust system in order to achieve exhaust gas purification of a vehicle. On the other hand, as an exhaust device used in conventional motorcycles and the like,
The rear part of the exhaust pipe was introduced into the muffler having a plurality of expansion chambers communicating with each other, and the rear part of the exhaust pipe, specifically the part introduced into the muffler, was expanded rearward to improve engine performance. There was a type of exhaust system.

[0003]

Although exhaust systems of the type described above do not have a catalyst, it is eager to have an internal catalyst to achieve exhaust purification. But,
Providing a catalyst inside the muffler in which the expanded exhaust pipe is introduced has problems such as the muffler, that is, the size of the exhaust system becoming large and the engine performance decreasing due to its arrangement, so it is put to practical use. Was not here. Therefore, in view of the problems of the conventional exhaust system described above, the present invention increases the size of the exhaust system or stores a catalyst inside the muffler without deteriorating the engine performance to obtain an effective purification effect. It is an object of the present invention to provide an exhaust system for an internal combustion engine with a catalyst.

[0004]

In order to achieve the above-mentioned object, an exhaust system for an internal combustion engine with a catalyst according to the present invention has an exhaust pipe rear portion introduced into a muffler, which is expanded in a divergent manner at the same time inside the muffler. In an exhaust device in which at least one partition wall is provided and the inside of the muffler is divided into a plurality of expansion chambers that communicate with each other, a catalyst is provided inside the muffler, and the catalyst is arranged in parallel with the small diameter portion of the exhaust pipe. It is characterized by.

[0005]

In the exhaust system for a catalyst-equipped internal combustion engine of the present invention constructed as described above, the exhaust gas from the engine flows into the muffler through the exhaust pipe and is purified by the catalyst provided in the muffler. Are released into the atmosphere. Since the catalyst described above is provided inside the muffler at the small diameter portion of the exhaust pipe, it is warmed by the action of the relatively high temperature exhaust gas passing through the small diameter portion of the exhaust pipe to enhance the catalytic effect. In addition, as described above, the size of the muffler, that is, the size of the exhaust device is not increased by providing the catalyst along with the small diameter portion of the exhaust pipe.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust system for an internal combustion engine with a catalyst device of the present invention (hereinafter, simply referred to as an exhaust system) will be described below with reference to the accompanying drawings.
An embodiment will be described. 1 is a schematic side view of a motorcycle equipped with an exhaust device of the present invention, FIG. 2 is a schematic top sectional view of the exhaust device, FIG. 3 is a sectional view taken along aa line in FIG. 2, and FIG. 2 is a sectional view taken along the line bb, FIG. 3B is a sectional view taken along the line cc in FIG. 2, and FIG. In the figure, reference numeral 1 denotes a scooter type motorcycle (hereinafter, simply referred to as a motorcycle), in which a two-cycle unit swing type engine 3 is connected to a frame 2 so as to be vertically swingable, and a rear wheel supported by the engine 3. 4 is driven by the engine 3. In addition, the motorcycle 1 is provided with an exhaust device that muffles and purifies exhaust gas from the engine 3, which is composed of an exhaust pipe 5 and a muffler 6.

The exhaust pipe 5 extends rearward of the vehicle body from an exhaust hole (not shown) of the engine 3, and the downstream end of the tubular pipe 5a is upstream of the tubular pipe 5b having a diameter slightly larger than that of the pipe 5a. The pipe 5b is fitted and connected to the end, and the downstream end of the pipe 5b is fitted and connected to the upstream end of a tubular pipe 5c which is slightly larger in diameter than the pipe 5b and slightly tapered toward the downstream direction. Further, a pipe formed by tapering the downstream end of the pipe 5c toward the downstream direction.
It is configured by fitting to 5d. The exhaust pipe 5 configured as described above is inserted into the muffler 6 from the portion corresponding to the upstream end of the pipe 5c to the rear, and a plurality of shielding plates 14 and 15 to be described later.
It is also held by the support plate 22. The exhaust pipe 5 described above
The portion corresponding to 5b is covered with a tubular protective member 7 to form a double pipe structure, and the half-split tubular members 8 and 8 fixed to the pipe 5b.
A connecting member 9 fixed to the muffler 6 is fitted between the exhaust pipe 5 and the protective member 7 to firmly fix the connecting portion between the exhaust pipe 5 and the muffler 6. Further, catalyst metals 10a 'and 10b' such as platinum are provided on the inner walls of the portions of the exhaust pipe 5 which correspond to the pipes 5b and 5d, respectively.
(Hereinafter referred to as the first auxiliary catalyst 10a and the second auxiliary catalyst 10b, respectively), and a hole 11 is formed on the upstream side of the pipe 5d for guiding a part of the exhaust gas to the main catalyst 18 described later. Has been done. A part of a portion of the exhaust pipe 5 which is in contact with the pipe 5c is punched, and the outer periphery thereof is surrounded by a sound absorbing material 12 such as glass wool, and the sound absorbing material 12 is a tubular pipe 13 which is the exhaust pipe 5.
It is fixed to.

The above-mentioned muffler 6 is of a multi-stage expansion type in which the inside thereof is partitioned by the first shielding plate 14 and the second shielding plate 15, and two outer shells 16, 16 having a substantially symmetrical shape are formed in the middle. It is constructed by joining. The first shielding plate 14 divides the inside of the muffler 6 into a first expansion chamber A and a third expansion chamber C, and penetrates the first expansion chamber A from the pipe 5c and the third expansion chamber C forming the exhaust pipe 5 and the outside air. The main catalyst 18 that connects the tail pipe 17, which is open to the outside, and the first expansion chamber A and the second expansion chamber B communicate with each other. Further, the second shielding plate 15 divides the third expansion chamber C and the second expansion chamber B, and a pipe 5c that constitutes the exhaust pipe 5, and a communication pipe 19 that connects the second expansion chamber B and the third expansion chamber C. , Supporting the main catalyst 18. The main catalyst 18 is formed by stacking the flat strips and the corrugated strips made of thin stainless steel plates in a layered manner so that they come into contact with each other, and a large number of meshes through which exhaust gas can pass in the axial direction. It is a so-called honeycomb-type catalyst constituted by supporting a catalyst metal such as platinum or rhodium on a honeycomb-shaped laminated body having a vent hole and filling the same in a cylindrical metal case with both ends open, As described above, when the exhaust gas passes through the inside, components such as HC and CO of the exhaust gas cause an oxidation reaction with the above-mentioned catalyst metal and are purified. Since this honeycomb type catalyst is conventionally known, the description with reference to the drawings is omitted.

Inside the portions corresponding to the first expansion chamber A of the outer shells 16 and 16, the sound absorbing material 2 formed of glass wool, respectively.
0, 20 are stretched, and the sound absorbing material 20 is firmly fixed to the inside of the outer shell 16 by punched steel plates 21, 21 and a support plate 22. As shown in FIG. 4 (c), the support plate 22 is provided with a plurality of vent holes 22a, and supports the sound absorbing material 20 while also supporting the pipe 5d and the tail pipe 17 which constitute the exhaust pipe 5. . Also, the second expansion chamber B and the third expansion chamber B of the outer shell 16
Inside the part corresponding to the expansion chamber C, 2 glass wool each
3,24 are stretched and these glass wool 23,24
Are fixed inside the outer shell 16 with steel plates 25 and 26, respectively.
It serves as a so-called heat insulating material that prevents the heat of the exhaust gas that has become high temperature in the main catalyst 18 from being transferred to the outer shell 16.

Next, the operation of the exhaust device constructed as described above will be described. Exhaust gas discharged from the exhaust hole of the engine 3 is guided into the muffler 6 through the exhaust pipe 5. Then, when passing through the pipe 5b constituting the exhaust pipe 5, an oxidation reaction is caused with the first auxiliary catalyst 10a provided therein, and the first purification is performed. Since the first auxiliary catalyst 10a is located relatively upstream in the exhaust path, the exhaust gas passing therethrough has a high temperature and an efficient purification action is performed, and the reaction heat at this time causes the exhaust temperature to rise to a high temperature. It is guided to the downstream direction while being kept at. At this time, the heat generated in the tube 5b is the same as the above-mentioned tube 5b.
It is kept warm and insulated by the protective material 7 covering the. The exhaust gas that has been first purified by the pipe 5b flows in the pipe 5c connected to the exhaust gas. At this time, the noise of the exhaust gas is absorbed by the sound absorbing material 12 surrounding the punched portion of the pipe 5c.
After that, the exhaust gas is further purified by the second auxiliary catalyst 10b provided therein when passing through the inside of the pipe 5d, and the heat of reaction thereof keeps the exhaust temperature at a high temperature and the first expansion chamber A from the end of the pipe 5d. Open to the public. At this time, the exhaust gas is further absorbed by the expansion action and the action of the sound absorbing material 20 stretched inside the first expansion chamber A, and the noise is efficiently reduced.
The flow direction of exhaust gas is reversed in the first expansion chamber A and flows into the main catalyst 18.

By the way, most of the exhaust gas passing through the inside of the pipe 5d is released from the end portion to the first expansion chamber A as described above, but a part of the exhaust gas is discharged upstream of the pipe 5d. It flows out from the hole 11 provided. The exhaust gas flowing out from the hole 11 flows into the main catalyst 18 while being kept at a high temperature.
The exhaust gas flowing out from this hole 11 has a shorter distance to the main catalyst than the exhaust gas discharged from the end of the pipe 5d, so that the main catalyst 18
The temperature at the time of flowing into can be kept high,
The purification efficiency of the main catalyst 18 is improved. Further, as is clear from the drawing, since the main catalyst 18 is arranged in parallel with the small-diameter portion of the exhaust pipe 5, that is, the pipe 5c, through which the exhaust gas kept at a high temperature by the action of the first auxiliary catalyst 10a passes, The temperature of the pipe 5c heated by the gas is also warmed and the purification efficiency is improved. The exhaust gas, which is opened from the end of the pipe 5d to the first expansion chamber A and whose noise is sufficiently reduced by the action of the sound absorbing material 20 and the like, is the exhaust gas flowing out from the arrangement position and the hole 11 as described above. After being sufficiently purified by the action of the main catalyst 18 having improved purification efficiency, it flows into the second expansion chamber B. The flow of the exhaust gas is further reversed in the second expansion chamber B so that the communication pipe
It flows into the third expansion chamber C via 19, and then passes through the tail pipe 17 to be opened to the atmosphere. Exhaust gas noise is more efficiently reduced in the process of passing through the plurality of expansion chambers.

FIG. 5, FIG. 6 and FIG. 7 are schematic views showing a second embodiment, a third embodiment and a fourth embodiment of the exhaust system of the present invention, respectively, and their detailed construction (for example, construction of the outer shell). Etc.) are the same as those of the exhaust device 6 of the first embodiment, so detailed description thereof is omitted, and only the main parts are shown in the drawings.

A second embodiment of the exhaust system of the present invention will be described below with reference to FIG. FIG. 5 (a) is a schematic cross-sectional view showing a second embodiment of the exhaust system of the present invention, which is cut at substantially the same position as the AA cross-sectional view of the first embodiment (that is, FIG. 3) and shows only a main part thereof. And Fig. 5 (b) is a2-a2 in Fig. 5 (a).
A sectional view, FIG. 5C is a sectional view taken along line b2-b2 in FIG. This exhaust system is composed of an exhaust pipe 34 and a muffler 30, one end of which is connected to an exhaust hole of an engine (not shown).

The muffler 30 is of a multi-stage expansion type in which the inside thereof is divided into three expansion chambers by a first shielding plate 31 and a second shielding plate 32. The first shield plate 31 divides the inside of the muffler 30 into a closed chamber X and a second expansion chamber B2.
As shown in (b), it holds a tail pipe 33 and an exhaust pipe 34 which penetrate the closed chamber X from the second expansion chamber B2 and are open to the atmosphere. In addition, the second shielding plate 32 makes the second inside the muffler 30 second.
It is divided into the expansion chamber B2 and the first expansion chamber A2, as shown in FIG. 5 (c).
As shown in FIG. 2, the main catalyst 35 which communicates the first expansion chamber A2 and the second expansion chamber B2 and the exhaust pipe 34 are held. The exhaust pipe 34 is inserted into the muffler 30 so that the downstream end thereof penetrates the first expansion chamber A2 and the second expansion chamber B2 inside the muffler 30 to reach the closed chamber X. The portion inserted into 30 is expanded in diameter in the downstream direction, and the subcatalyst 36 is formed by carrying the catalyst metal 36 'on the inner surface of the portion before being inserted into the muffler 30.
A hole 37 for guiding the exhaust gas to the main catalyst 35 is formed in a portion corresponding to the expansion chamber A2.

Explaining the operation of the exhaust system of the second embodiment of the present invention constructed as described above, the high temperature exhaust gas discharged from the exhaust hole of the engine (not shown) is exhaust pipe 34.
It flows into the inside and is purified when passing through the auxiliary catalyst 36 provided therein, and the exhaust gas flows in the downstream direction while the exhaust temperature is kept high due to the reaction heat at this time. After that, the exhaust gas passes through the inside of the exhaust pipe 34 and is opened to the closed chamber X in the muffler 30, and the pressure wave thereof returns to the exhaust pipe 34 again as a positive pressure. At this time, most of the exhaust gas is the auxiliary catalyst 36.
Immediately after being purified by (1), it is discharged from the hole 37 to the first expansion chamber A2 and guided to the main catalyst 35. The exhaust gas mentioned above is the auxiliary catalyst 36.
Since the temperature is maintained by the heat of reaction at 1, the purification efficiency of the main catalyst 35 can be improved, and after being sufficiently purified there, it is released from the tail pipe 33 to the atmosphere through the second expansion chamber B2. Although not shown in the drawing, this muffler 30
Needless to say, a sound absorbing material such as glass wool, a heat insulating material, and a heat insulating material are provided at appropriate places.

Next, a third embodiment of the exhaust system of the present invention will be described with reference to FIG. FIG. 6 (a) is a schematic cross-sectional view of the third embodiment of the exhaust system of the present invention, taken along the line AA of the first embodiment (that is, FIG. 3) and showing only the main portion thereof. 6 (b) is a sectional view taken along the line a3-a3 in FIG. 6 (a), and FIG. 6 (c) is a sectional view taken along the line b3-b3 in FIG. 6 (a).
(d) is a c3-c3 sectional view in FIG. 6 (a). The exhaust system includes an exhaust pipe 45 and a muffler 40, one end of which is connected to an exhaust hole of an engine (not shown).

The muffler 40 is of a multi-stage expansion type in which the inside thereof is divided into three expansion chambers by a first shielding plate 41 and a second shielding plate 42. The first shielding plate 41 divides the muffler 40 into a first expansion chamber A3 and a third expansion chamber C3. As shown in FIG. 6 (b), the third expansion chamber C3 to the first expansion chamber A3 are divided.
The tail pipe 43 and the first through the
A main catalyst 44 connecting the expansion chamber A3 and the second expansion chamber B3,
Holds the exhaust pipe 45. The second shielding plate 42 divides the muffler 40 into a third expansion chamber C3 and a second expansion chamber B3. As shown in FIG. 6 (c), the second expansion chamber B3 and the third expansion chamber C3 are separated from each other. It holds a main catalyst 44 which is in communication, and a communication pipe 46 and an exhaust pipe 45 which are in communication between the second expansion chamber B3 and the third expansion chamber C3. The exhaust pipe 45 is inserted into the muffler 40 such that the downstream end of the exhaust pipe 45 penetrates the second expansion chamber B3 and the third expansion chamber C3 inside the muffler 40 to reach the first expansion chamber A3. The diameter of the cut portion is increased in the downstream direction. The portion of the exhaust pipe 45 corresponding to the first expansion chamber A3 inside the muffler 40 has a multi-tube structure as shown in FIGS. 6 (a) and 6 (d), in which a catalyst such as platinum or rhodium is added. The metal 47 'is carried to form the auxiliary catalyst 47.

Explaining the operation of the exhaust system of the third embodiment of the present invention constructed as above, the high temperature exhaust gas discharged from the exhaust hole of the engine (not shown) is exhaust pipe 45.
It flows into the inside of the muffler 40 and is opened to the first expansion chamber A3 of the muffler 40 through the exhaust pipe 45. At this time, the exhaust gas is purified by the auxiliary catalyst 47 formed in the downstream portion of the exhaust pipe 45, and is kept at a high temperature by the reaction heat at that time. The exhaust gas purified by the auxiliary catalyst 47 reverses its flow direction in the first expansion chamber A3, flows into the main catalyst 44, passes through this, and flows into the second expansion chamber B3. At this time, the exhaust gas is kept at a high temperature by the action of the reaction heat of the auxiliary catalyst 47, and the main catalyst 44 is further warmed by the heat of the small diameter portion of the exhaust pipe 45 through which the high temperature exhaust gas arranged in parallel passes. Therefore, the purification efficiency of the main catalyst 44 is improved and sufficient purification is achieved. The exhaust gas purified by the main catalyst 44 further reverses its flow direction in the second expansion chamber B3, passes through the communication pipe 46, flows into the third expansion chamber C3, and then passes through the tail pipe 43. Then it is opened to the atmosphere. The noise of the exhaust gas is sufficiently reduced while passing through the plurality of expansion chambers, and the components such as HC and CO are sufficiently purified by the action of the auxiliary catalyst 47 and the main catalyst 44. Although not shown, it goes without saying that the muffler 40 is provided with a sound absorbing material such as glass wool, a heat insulating material, and a heat insulating material at appropriate places. When the rear portion of the exhaust pipe 45 has a multi-tube structure as in the third embodiment, and the catalyst metal 47 'such as platinum is supported on the rear pipe to form the auxiliary catalyst 47, the area of contact of the exhaust gas with the auxiliary catalyst 47 is reduced. Since the temperature of the exhaust gas can be increased and the temperature of the exhaust gas can be kept sufficiently high, there is an effect that it is not necessary to provide a sub catalyst on the upstream side of the exhaust pipe.

Next, a fourth embodiment of the exhaust system of the present invention will be described with reference to FIG. FIG. 7 (a) is a schematic cross-sectional view showing a fourth embodiment of the exhaust system of the present invention, taken along the line AA of the first embodiment (that is, FIG. 3) at substantially the same position and showing only the main part thereof. And Fig. 7 (b) is a4-a4 in Fig. 7 (a).
7C is a sectional view taken along the line b4-b4 in FIG. 7A. The exhaust system is composed of an exhaust pipe 55 and a muffler 50, one end of which is connected to an exhaust hole of an engine (not shown).

The muffler 50 includes a first shield plate 51 and a second shield plate 51.
It is a multi-stage expansion type in which the inside is divided into three expansion chambers by a shield plate 52. The first shield plate 51 is a muffler 50.
The inside is divided into a first expansion chamber A4 and a third expansion chamber C4, and as shown in FIG. 7 (b), a tail opening from the third expansion chamber C4 through the first expansion chamber A4 to the atmosphere. It holds a pipe 53 and a main catalyst 54 and an exhaust pipe 55 which communicate the first expansion chamber A4 and the second expansion chamber B4. Also, the second shielding plate
Reference numeral 52 divides the muffler 50 into a third expansion chamber C4 and a second expansion chamber B4, and as shown in FIG. 7 (c), the main catalyst which connects the second expansion chamber B4 and the third expansion chamber C4. 54, a communication pipe 57 for communicating the second expansion chamber B4 and the third expansion chamber C4, and an exhaust pipe
Holding 55. As shown in the sectional views (FIGS. 7 (b) and 7 (c)), the main catalysts 54 are juxtaposed so that their side surfaces come into contact with the side surfaces of the exhaust pipe 55. The exhaust pipe 55 is inserted into the muffler 50 such that the downstream end thereof penetrates the second expansion chamber B4 and the third expansion chamber C4 inside the muffler 50 to reach the first expansion chamber A4. The portion inserted into the muffler 50 is expanded in the downstream direction,
Further, a catalyst metal 56 'is carried on the inner surface corresponding to the portion not in contact with the main catalyst 54 to form the sub catalyst 56.

Explaining the operation of the exhaust system of the fourth embodiment of the present invention configured as described above, the high temperature exhaust gas discharged from the exhaust hole of the engine (not shown) is exhaust pipe 55.
When it flows into the inside of the exhaust pipe 55 and passes through the exhaust pipe 55, it is purified by the auxiliary catalyst 56 provided on the inner wall of the exhaust pipe 55, and its temperature is kept high by the reaction heat at this time. The exhaust gas purified by the auxiliary catalyst 56 reverses its flow direction in the first expansion chamber A4 and flows into the main catalyst 54. At this time, the exhaust gas heated to a high temperature by the reaction heat flows through the main catalyst 54. Since they are arranged in parallel so as to contact the exhaust pipe 55, the temperature is transmitted from the exhaust pipe 55 to heat them, and the exhaust gas itself is also purified by the auxiliary catalyst 56 to the point where it is opened to the first expansion chamber A4. Since the reaction is carried out and the reaction heat at that time is maintained at a high temperature, the purification efficiency of the main catalyst 54 is improved and sufficient purification is performed.

Further, since the auxiliary catalyst 56 is not provided in the portion in contact with the main catalyst 54, the auxiliary catalyst 56 and the main catalyst 54
The reaction heat does not cause the third expansion chamber C4 to have an abnormally high temperature. Further, the exhaust gas purified by the main catalyst 54 flows into the second expansion chamber B4, where the flow direction is reversed, flows through the communication pipe 57 into the third expansion chamber C4, and then passes through the tail pipe 53. Open to the atmosphere. The exhaust gas is sufficiently reduced in noise while passing through the plurality of expansion chambers, and the auxiliary catalyst 56 and the main catalyst 54 work to generate H
The components such as C and CO are also sufficiently purified. Although not shown, it goes without saying that the muffler 50 is provided with a sound absorbing material such as glass wool, a heat insulating material, and a heat insulating material at appropriate places.

In this embodiment, the exhaust system using the honeycomb catalyst as the main catalyst has been described. However, the catalyst used in the exhaust system of the present invention is not limited to this, and HC contained in the exhaust gas, Any catalyst may be used as long as it can purify components such as CO, and for example, a pellet catalyst in which the catalyst metal is granulated and packed in a container as desired. The holes (the holes 11 in the first embodiment and the holes 37 in the second embodiment) for guiding a part of the exhaust gas provided in the exhaust systems of the first and second embodiments in the present embodiment to the main catalyst are The present invention is not limited to the present embodiment, and any configuration can be used as long as it can guide a part or most of the exhaust gas whose temperature is kept at a high temperature by the purifying action of the auxiliary catalyst to the main catalyst at a high temperature. For example, a guide tube 60 may be provided so as to positively guide the exhaust gas to the main catalyst as shown by a phantom line in FIG.

In the exhaust system of this embodiment, the main catalyst is provided on the shield plate in the reversing type muffler in the first, second, third, and fourth embodiments and the narrow diameter portion of the exhaust pipe. Since they are arranged in parallel, the exhaust path can be taken long enough,
This has the effect that the device itself becomes a companion. In the exhaust system of this embodiment, in all of the first, second, third, and fourth embodiments, the auxiliary catalyst is provided on the downstream side of the main catalyst, specifically, in the exhaust pipe inserted in the muffler. Even if the main catalyst is provided on the downstream side of the exhaust path, the temperature of the exhaust gas will not change even if the main catalyst is provided while keeping the temperature of the exhaust gas at a high temperature by the reaction heat of the auxiliary catalyst. This brings about an effect that the purification efficiency is not deteriorated due to the decrease.

The exhaust system of this embodiment is the same as that of the first embodiment,
In all of the second, third, and fourth embodiments, the auxiliary catalyst is provided on the inner surface of the exhaust pipe. However, since the position where the auxiliary catalyst is provided is located outside the main catalyst, details will be given. Since the main catalyst does not have a sub-catalyst in the small diameter portion arranged in parallel, it has an effect that the reaction heat of the sub-catalyst and the reaction heat of the main catalyst does not cause the temperature to become too high.
Furthermore, the exhaust system of the present embodiment includes the first embodiment, the second embodiment,
In both the third embodiment and the fourth embodiment, since the main catalyst is arranged in parallel in the small diameter portion of the exhaust pipe, there is no resistance in the exhaust pipe, and the engine performance is not reduced.

[0026]

The exhaust system for an internal combustion engine with a catalyst of the present invention is
In an exhaust device in which a rear portion of an exhaust pipe introduced into a muffler is expanded in a divergent manner, and at least one partition wall is provided inside the muffler to divide the muffler into a plurality of expansion chambers communicating with each other, a catalyst is provided in the muffler. Since the catalyst is provided in parallel with the small diameter portion of the exhaust pipe, the muffler is not increased without increasing the size of the muffler, that is, the size of the exhaust system, and without reducing the performance of the engine. It is possible to provide an exhaust device having a catalyst provided inside thereof.

[Brief description of drawings]

FIG. 1 is a schematic side view of a motorcycle equipped with an exhaust device of the present invention.

FIG. 2 is a partially cutaway schematic top view of the exhaust device of the present invention.

3 is a schematic aa cross-sectional view in FIG.

4 (a) is a schematic bb sectional view in FIG. (b) It is a schematic cc sectional view in FIG. (c) It is a schematic dd view in FIG.

FIG. 5 (a) is a schematic sectional view showing a second embodiment of the exhaust system of the present invention. (b) It is a schematic a2-a2 sectional view in FIG. 5 (a). (c) It is a schematic b2-b2 sectional view in FIG. 5 (a).

FIG. 6 (a) is a schematic side view showing a third embodiment of the exhaust system of the present invention. (b) It is a schematic a3-a3 sectional view in FIG. 6 (a). (c) It is a schematic b3-b3 sectional view in FIG. 6 (a). (d) It is a schematic c3-c3 sectional view in FIG. 6 (a).

FIG. 7 (a) is a schematic side view showing a fourth embodiment of the exhaust system of the present invention. (b) It is a schematic a4-a4 sectional view in FIG. 7 (a). (c) It is an outline b4-b4 sectional view in FIG. 7 (a).

[Explanation of symbols]

 1 Motorcycle 2 Frame 3 Engine 4 Rear Wheel 5 Exhaust Pipe 5a Pipe 5b Pipe 5c Pipe 5d Pipe 6 Muffler 7 Protective Material 8 Half-Cylinder Protective Material 9 Connecting Member 10a 1st Sub-catalyst 10b 2nd Sub-catalyst 10a 'Catalyst Metal 10b 'Catalyst metal 11 Hole 12 Sound absorbing material 13 Pipe 14 First shielding plate 15 Second shielding plate 16 Outer shell 17 Tail pipe 18 Main catalyst 19 Communication pipe 20 Sound absorbing material 21 Steel plate 22 Support material 22a Vent hole 23 Glass wool 24 Glass wool 25 Steel plate 26 Steel plate A First expansion chamber B Second expansion chamber C Third expansion chamber

Claims (1)

[Claims] 1. An exhaust system in which a rear portion of an exhaust pipe introduced into a muffler is expanded in diameter toward the end and at least one partition wall is provided inside the muffler, and the muffler is divided into a plurality of expansion chambers communicating with each other. An exhaust device for an internal combustion engine with a catalyst, wherein a catalyst is provided in a muffler, and the catalyst is provided in parallel with a small diameter portion of the exhaust pipe.