JP6916771B2 - Exhaust unit - Google Patents

Description

The present disclosure relates to an exhaust unit that allows exhaust to pass through.

Patent Document 1 below proposes an exhaust unit in which a catalyst is arranged in a housing.

Japanese Unexamined Patent Publication No. 2006-207531

Generally, in an exhaust unit, there is a demand for improvement of functionality such as improvement of performance of catalyst and the like and achievement of space saving. One aspect of the present disclosure is that it is desirable to be able to improve the functionality of the exhaust unit in which the catalyst is arranged in the housing.

One aspect of the present disclosure is an exhaust unit, which includes a housing, a wall member, and a catalyst. The housing is configured so that the exhaust gas of the internal combustion engine is introduced from the introduction port and the exhaust gas is discharged from the exhaust port. The wall member is arranged in the housing, and is configured to form a tubular flow path together with a part of the housing in order to circulate the exhaust gas introduced from the introduction port in the housing. The catalyst is placed in the flow path.

In the exhaust unit, the portion of the wall member that surrounds the catalyst together with the housing is referred to as the first portion, and the portion of the housing that surrounds the catalyst together with the wall member is referred to as the second portion. The heat capacity of the first portion is set to be larger than the heat capacity of the second portion.

According to such a configuration, the heat capacity of the first portion, which is relatively unaffected by the outside air, is set to be larger than the heat capacity of the second portion, which is relatively susceptible to the influence of the outside air, so that the catalyst is at a lower temperature than the exhaust gas. It can be made difficult to be cooled by a certain outside air. That is, even if the second portion is cooled by the outside air, a larger amount of heat stored in the first portion can be supplied to the catalyst. Therefore, it is possible to easily maintain the catalyst at an operable temperature. That is, the functionality of the exhaust unit in which the catalyst is arranged in the housing can be improved.

In one aspect of the present disclosure, the first portion of the wall member and the second portion of the housing are formed by processing a plate-like material having the same composition, and the thickness of the first portion is determined. It may be set larger than the thickness of the second portion.

According to such a configuration, when the first part and the second part are materials having the same composition, the thickness of the first part is set to be larger than the thickness of the second part, so that the thickness of the first part is relatively large. The heat capacity can be set to be large.

In one aspect of the present disclosure, the surface area on the catalyst side at the first site may be set larger than the surface area on the catalyst side at the second site.
According to such a configuration, when comparing the amount of heat moving between the first part and the catalyst and the amount of heat moving between the second part and the catalyst, the surface area on the catalyst side in the first part is Since the surface area of the second site is set to be larger than the surface area of the catalyst side, the transfer of heat can be activated on the first site side rather than the second site side. With this configuration, when the catalyst is at a high temperature, the first portion can be efficiently heated and heat dissipation from the second portion can be suppressed. Further, when the catalyst has a low temperature, the amount of heat stored in the first portion can be easily dissipated to the catalyst side.

In one aspect of the present disclosure, the housing may be arranged to cover the first site and the catalyst.
According to such a configuration, the portion covered with the first portion of the catalyst is doubly covered with the first portion and the housing, so that the portion covered with the first portion of the catalyst is used. Heat dissipation can be suppressed.

One aspect of the present disclosure may further include a muffling chamber configured to communicate with the flow path on the downstream side of the flow path with respect to the catalyst. In this case, the first portion may function as a wall surface separating the muffling chamber and the catalyst.

According to such a configuration, since the first part functions as a wall surface separating the muffling chamber and the catalyst, the amount of heat of the exhaust gas flowing through the muffling chamber is stored in the first part, and the amount of heat stored in the first part of the catalyst is stored in the first part. It can be used for heat retention. Therefore, the functionality of the catalyst can be further improved.

It is a block diagram which shows the structure of an exhaust unit. FIG. 2 is a sectional view taken along line II-II of the exhaust unit. FIG. 3 is a sectional view taken along line III-III of the exhaust unit. It is a perspective view in the IV-IV cross section of an exhaust unit.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1-1. Constitution]
The exhaust unit 1 shown in FIG. 1 is, for example, a unit mounted on a vehicle such as a REEV (Range Extender Electric Vehicle) and having a function of purifying and muting sound while passing exhaust gas.

As shown in FIG. 1, the exhaust unit 1 includes a housing 10. The housing 10 is made of, for example, stainless steel. The housing 10 is formed by processing an arbitrary plurality of plate-shaped materials by a press or the like to form a plurality of members to be parts of the housing 10, and assembling these members. The housing 10 is configured such that the exhaust gas of the internal combustion engine 100 is introduced from the introduction port 11 and the exhaust gas is discharged from the exhaust port 12.

Further, the exhaust unit 1 may include a first flange portion 11J, an exhaust connection portion 12J, a cooling introduction portion 23IN, a cooling discharge portion 23OUT, and an exhaust take-out portion 25J. The housing 10 may include sensor mounting portions 10B, 10C, 10D and a plurality of second flange portions 10J.

As shown in FIG. 2, the sensor mounting portions 10B, 10C, and 10D are provided so as to communicate the inside and outside of the housing 10 on the upstream side and the downstream side of the catalysts 21 and 22, respectively, in the flow path 16 described later. The upstream side and the downstream side indicate the upstream side and the downstream side with respect to the exhaust flow direction. Further, the communication means that a plurality of spaces are connected.

The sensor mounting portions 10B, 10C, 10D are the parts where the sensors 26, 27, 28 shown in FIG. 2 are mounted on the housing 10, and when the sensors 26, 27, 28 are arranged, the sensor mounting portions 10B, 10C, 10D Is sealed. As the sensors 26, 27, 28, for example, any sensor such as an oxygen sensor, a NOx sensor, and a temperature sensor is arranged.

The second flange portion 10J is a portion for fixing the housing 10. A plurality of second flange portions 10J are provided around the housing 10. In FIG. 1, as an example, four second flange portions 10J are provided. Each of the second flange portions 10J is provided with an insertion hole 10H for inserting a fixing member such as a bolt.

The exhaust unit 1 is a fixing member inserted into the insertion hole 10H in a fixed portion such as an internal combustion engine 100 that functions as a generator of REEV or a female screw portion provided in a pedestal portion on which the internal combustion engine 100 is installed. Is attached to the internal combustion engine 100 or the pedestal portion.

The first flange portion 11J is a portion where an introduction port 11 for introducing exhaust gas is formed and is connected to the exhaust pipe of the internal combustion engine 100. When the first flange portion 11J is connected to the exhaust pipe, the introduction port 11 communicates with the exhaust pipe, and exhaust gas can be introduced from the exhaust pipe to the introduction port 11.

The exhaust connection portion 12J is a portion where an exhaust port 12 through which exhaust gas that has passed through the inside of the housing 10 is discharged is formed, and an exhaust pipe that communicates with the atmosphere, which is the outside air, is connected. The exhaust port 12 may communicate with the outside air via some device other than the exhaust unit 1.

The cooling introduction unit 23IN is a portion to which a pipe conducting a heat exchange medium such as cooling water is connected and the heat exchange medium is introduced through the pipe. The cooling discharge unit 23OUT is a portion to which a pipe conducting the heat exchange medium is connected and the heat exchange medium is discharged through the pipe.

The exhaust outlet 25J is a portion where an exhaust outlet 25 is formed, a pipe for conducting exhaust is connected, and a part of the exhaust is discharged through the pipe. The exhaust outlet 25 is an exhaust outlet different from the exhaust port 12 from which most of the exhaust is discharged, and the exhaust discharged from the exhaust outlet 25 is used for, for example, EGR (Exhaust Gas Recirculation).

Next, the internal structure of the housing 10 will be described with reference to FIG. As shown in FIG. 2, the inside of the housing 10 includes a wall member 17 and a plurality of catalysts 21 and 22. In other words, the housing 10 is arranged so as to cover the wall member 17 and the catalysts 21 and 22. The wall member 17 includes a first portion 17F, which will be described later. A heat exchanger 23, an inlet pipe 24, a plurality of plate members 31, 32, and a valve 33 may be provided inside the housing 10.

The wall member 17 is arranged in the housing 10 so as to form a tubular flow path 16 together with a part of the housing 10 in order to circulate the exhaust gas introduced from the introduction port 11 in the housing 10. It is composed. Further, the wall member 17 is made of a material having the same composition as the housing 10 and is formed by processing a plate-shaped material. The tubular flow path 16 is configured to be curved along the outer circumference inside the housing 10.

Further, inside the housing 10, a plurality of muffling chambers 18A, 18B, 18C are arranged on the downstream side of the catalysts 21 and 22 in the flow path 16. The plurality of sound deadening chambers 18A, 18B, 18C are formed in a space surrounded by the inner surface of the housing 10, the inlet pipe 24, and the wall member 17 by partitioning the inside of the housing 10 by the wall member 17. be. The plurality of muffling chambers 18A, 18B, 18C are divided into a plurality of chambers by being partitioned by a plurality of plate members 31, 32.

That is, the wall member 17 forms a flow path 16 together with the outer wall portion 10A of the housing 10, and also constitutes a part of the muffling chambers 18A, 18B, 18C, and is a region through which the exhaust gas immediately after the introduction from the introduction port 11 passes. And functions as a part of the wall surface that separates the muffling chambers 18A, 18B, and 18C. Further, since the outer wall portion 10A of the housing 10 forms a part of the flow path 16 and the sensor mounting portions 10B, 10C, and 10D are arranged on the outer wall portion 10A, a further pipe is provided inside the outer wall portion 10A of the housing 10. The sensor can be arranged in a simpler configuration as compared with the configuration having the above.

Further, in the configuration in which the pipe is provided inside the outer wall portion 10A of the housing 10, there is a possibility that the sensor mounting portions 10B, 10C, and 10D may be displaced due to the difference in thermal stress between the housing 10 and the pipe. Since the outer wall portion 10A of the housing 10 is a part of the flow path 16, there is no concern about such misalignment.

That is, if the flow path 16 is formed only by members other than the housing 10 such as the wall member 17, and the flow path 16 is configured to be in contact with the outside air via the plurality of members, the catalysts 21 and 22 are effectively kept warm. However, in the present embodiment, the housing 10 constitutes a part of the flow path 16 in order to facilitate the arrangement of the sensors 26, 27, 28 that can be attached to and detached from the outside of the housing 10.

Each of the plurality of catalysts 21 and 22 is formed in a cylindrical shape and is arranged in the flow path 16 to have a function as a general catalyst. That is, the plurality of catalysts 21 and 22 have a function of promoting the action of purifying the exhaust gas within a predetermined operating temperature range. Further, the plurality of catalysts 21 and 22 are sandwiched and held between the wall member 17 and the outer wall portion 10A.

Since the plurality of catalysts 21 and 22 are arranged adjacent to the muffling chambers 18A, 18B and 18C via the wall member 17, the catalyst uses the residual heat of the exhaust gas in the muffling chambers 18A, 18B and 18C to set the operating temperature. It can be kept warm so that it can be maintained.

The heat exchanger 23 is arranged on the downstream side of the catalysts 21 and 22 of the flow path 16 and on the lower side in the vertical direction when the exhaust unit 1 is used in the outer circumference of the housing 10. And functions as a well-known heat exchanger. The heat exchanger 23 exchanges heat between the exhaust flowing through the flow path 16 and the heat exchange medium introduced from the cooling introduction unit 23IN and discharged from the cooling discharge unit 23OUT.

The heat exchanger 23 reduces the volume of the exhaust gas by lowering the temperature of the exhaust gas and lowers the pressure of the exhaust gas, thereby promoting the exhaust gas to pass through the catalysts 21 and 22. Therefore, the exhaust unit 1 can suppress the exhaust from leaking to the outside of the housing 10 in the vicinity of the catalysts 21 and 22 as compared with the configuration in which the heat exchanger 23 is not provided in the housing 10.

The inlet pipe 24 includes a plurality of holes 24H for communicating the inside and outside of the inlet pipe 24, and exhaust gas flowing through the inlet pipe 24 to any of the muffling chambers 18A, 18B, 18C via the plurality of holes 24H. Supply. The inlet pipe 24 forms a tubular flow path 16 together with the outer wall portion 10A of the housing 10.

The plurality of plate members 31, 32 function as partition plates for partitioning the muffling chambers 18A, 18B, 18C into a plurality of chambers. Further, the plate member 32 arranged at a position close to the heat exchanger 23 among the plurality of plate members 31 and 32 includes a valve 33 capable of switching whether or not to communicate with the muffling chambers 18A and 18B.

The muffling chamber 18A functions as an expansion chamber for expanding the exhaust gas. Further, the muffling chamber 18C functions as a resonance chamber that resonates the exhaust gas. The muffling chamber 18B functions as an expansion chamber or a resonance chamber depending on the opening and closing of the valve 33.

The valve 33 includes an opening / closing portion 33A. The opening / closing portion 33A is configured to open when the exhaust pressure increases and close when the exhaust pressure decreases, for example. With this configuration, the opening / closing unit 33A has a configuration in which the exhaust gas passes through only the muffling chambers 18A among the plurality of muffling chambers 18A, 18B and 18C, and the muffling chambers 18A and 18B among the plurality of muffling chambers 18A, 18B and 18C. It is possible to switch between the configuration to be passed and the configuration to be passed. That is, the exhaust unit 1 is configured so that the sizes of the expansion chamber and the resonance chamber can be changed by the valve 33. With this configuration, the frequency of the exhaust sound to be muted can be changed.

Here, as shown in FIGS. 3 and 4, attention is paid to the periphery of the catalyst 21 located on the upper side in the vertical direction among the plurality of catalysts 21 and 22 in the exhaust unit 1. Of the plurality of catalysts 21 and 22, the catalyst 22 located on the lower side in the vertical direction has the same configuration as the catalyst 21, and thus the description thereof will be omitted. Further, FIG. 4 is a perspective view of a state in which the portions of the housing 10 and the wall member 17 are virtually cut out on a flat surface through which the upper and lower surfaces of the cylindrical catalyst 21 pass.

As shown in FIGS. 2, 3 and 4, the portion surrounding the catalysts 21 and 22 together with the housing 10 in the wall member 17 is designated as the first portion 17F, and the catalyst 21 and the catalyst 21 in the housing 10 together with the wall member 17 The portion surrounding 22 is referred to as the second portion 10F. The first portion 17F and the second portion 10F are portions located between the upper surfaces and the lower surfaces of the cylindrical catalyst 21 through which the upper surface and the lower surface pass. In other words, the first site 17F and the second site 10F are sites that come into contact with the catalyst 21 to hold the catalyst 21.

The outer periphery of the first portion 17F is covered with a housing 10. Further, the portion other than the end portion of the first portion 17F is arranged so as to form a space between the first portion 17F and the housing 10 without directly touching the housing 10. In such a configuration, the portion of the catalysts 21 and 22 covered with the first portion 17F is doubly covered by at least the first portion 17F and the housing 10. On the other hand, the portion of the catalysts 21 and 22 covered with the second portion 10F is singlely covered by the housing 10 only. That is, the first portion 17F is configured to be less affected by the outside air than the second portion 10F.

In this configuration, the heat capacity of the first portion 17F is set to be larger than the heat capacity of the second portion 10F. Here, since the first portion 17F and the second portion 10F are made of materials having the same composition, the larger the volume, the larger the heat capacity.

More specifically, as shown in FIGS. 3 and 4, the thickness t1 of the first portion 17F is set to be larger than the thickness t2 of the second portion 10F. Further, the surface area of the surface on the catalyst 21 side in the first portion 17F is set to be larger than the surface area of the surface on the catalyst 21 side in the second portion 10F.

The surface area of the surface on the catalyst 21 side in each of the sites 17F and 10F is represented by the product of the vertical length of the catalyst 21 and the surrounding peripheral length, and the length of the catalyst 21 in the vertical direction is the same in both cases. On the other hand, regarding the peripheral length, as shown in FIG. 3, the first portion 17F surrounds θ1 which is an angle of 180 deg or more out of the 360 deg of the entire circumference of the catalyst 21, and the second portion 10F surrounds the entire circumference of the catalyst 21. It is set to surround θ2, which is an angle of less than 180 deg out of 360 deg. Therefore, the surface area of the surface on the catalyst 21 side in the first portion 17F is larger than the surface area of the surface on the catalyst 21 side in the second portion 10F.

With such a configuration, the volume of the first portion 17F is larger than the volume of the second portion 10F, so that the heat capacity is also large.
[1-2. effect]
According to the embodiment described in detail above, the following effects are obtained.

(1a) One aspect of the present disclosure is an exhaust unit 1, which includes a housing 10, a wall member 17, and catalysts 21 and 22. The housing 10 is configured such that the exhaust gas of the internal combustion engine 100 is introduced from the introduction port 11 and the exhaust gas is discharged from the exhaust port 12. The wall member 17 is arranged in the housing 10 so as to form a tubular flow path 16 together with a part of the housing 10 in order to circulate the exhaust gas introduced from the introduction port 11 in the housing 10. It is composed. The catalysts 21 and 22 are arranged in the flow path 16.

In the exhaust unit 1, the portion of the wall member 17 that surrounds the catalyst 21 and 22 together with the housing 10 is the first portion 17F, and the portion of the housing 10 that surrounds the catalyst 21 and 22 together with the wall member 17 is the second portion. It is set to 10F. The heat capacity of the first portion 17F is set to be larger than the heat capacity of the second portion 10F.

According to such a configuration, the heat capacity of the first portion 17F, which is located inside the housing 10 and is relatively unaffected by the outside air, is located on the outer peripheral side of the housing 10 and is relatively affected by the outside air. Since the heat capacity is set to be larger than the heat capacity of the easy second portion 10F, it is possible to make it difficult for the catalysts 21 and 22 to be cooled by the outside air having a temperature lower than that of the exhaust gas. That is, since a larger amount of heat can be stored in the first part 17F, even if the second part 10F is cooled by the outside air, a larger amount of heat stored in the first part 17F can be stored in the catalysts 21 and 22. Can be supplied to.

Therefore, according to such a configuration, the catalysts 21 and 22 can be easily maintained at an operable temperature, and the functionality of the exhaust unit 1 can be improved.
(1b) In one aspect of the present disclosure, the first portion 17F of the wall member 17 and the second portion 10F of the housing 10 are made of materials having the same composition and formed by processing a plate-like material. The thickness t1 of the first portion 17F is set to be larger than the thickness t2 of the second portion 10F.

According to such a configuration, when the first part 17F and the second part 10F are materials having the same composition, the thickness t1 of the first part 17F is set to be larger than the thickness t2 of the second part 10F, so that they are relative to each other. The heat capacity of the first portion 17F can be set to be large.

(1c) In one aspect of the present disclosure, the surface area on the catalyst 21 and 22 side in the first site 17F is set to be larger than the surface area on the catalyst 21 and 22 side in the second site 10F.
According to such a configuration, when comparing the amount of heat moving between the first part 17F and the catalysts 21 and 22, and the amount of heat moving between the second part 10F and the catalysts 21 and 22, the first Since the surface area of the catalyst 21 and 22 on the site 17F is set to be larger than the surface area of the catalyst 21 and 22 on the second site 10F, the heat transfer can be performed on the first site 17F side rather than the second site 10F side. Can be activated. With this configuration, when the catalysts 21 and 22 are at a high temperature, the first portion 17F can be efficiently heated, and heat dissipation from the second portion 10F can be suppressed. Further, when the catalysts 21 and 22 are at a low temperature, the amount of heat stored in the first portion 17F can be easily dissipated to the catalysts 21 and 22.

(1d) In one aspect of the present disclosure, the housing 10 may be arranged so as to cover the first portion 17F and the catalysts 21 and 22.
According to such a configuration, the portion covered with the first portion 17F of the catalysts 21 and 22 is doubly covered with the first portion 17F and the housing 10, so that the second of the catalysts 21 and 22 It is possible to suppress heat dissipation from the site catalysts 21 and 22 covered with one site 17F.

(1e) One aspect of the present disclosure further includes muffling chambers 18A, 18B, 18C configured to communicate with the flow path 16 on the downstream side of the flow path 16 with respect to the catalysts 21 and 22. Further, the first portion 17F functions as a wall surface that separates the muffling chambers 18A, 18B, 18C and the catalysts 21 and 22.

According to such a configuration, the first portion 17F functions as a wall surface separating the muffling chambers 18A, 18B, 18C and the catalysts 21 and 22, so that the amount of heat of the exhaust gas flowing through the muffling chambers 18A, 18B, 18C is the first portion. The amount of heat stored in the 17th floor and stored in the first portion 17F can be used to keep the catalysts 21 and 22 warm. Therefore, the functionality of the catalysts 21 and 22 can be further improved.

[2. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be implemented in various modifications.

(2a) In the above embodiment, the thickness t1 of the first part 17F is set to be larger than the thickness t2 of the second part 10F, and the surface area of the surface on the catalyst 21 side in the first part 17F is the second. It is set to be larger than the surface area of the surface on the catalyst 21 side in the site 10F, but the configuration is not limited to this. For example, the thickness t1 of the first part 17F is set to be larger than the thickness t2 of the second part 10F, and the surface area of the surface on the catalyst 21 side of the first part 17F is the surface of the surface of the second part 10F on the catalyst 21 side. It may be set smaller than the surface area of. However, it is preferable that the volume of the first portion 17F is set to be larger than the volume of the second portion 10F.

(2b) For example, the surface area of the surface on the catalyst 21 side in the first portion 17F is set to be larger than the surface area of the surface on the catalyst 21 side in the second portion 10F, and the thickness t1 of the first portion 17F is the first. It may be set smaller than the thickness t2 of the two sites 10F. However, it is preferable that the volume of the first portion 17F is set to be larger than the volume of the second portion 10F.

(2c) In the above embodiment, the first part 17F (wall member 17) and the second part 10F (housing 10) are made of materials having the same composition, but the structure is not limited to this. For example, the first portion 17F may be composed of a material having a higher specific heat than the second portion 10F. For example, the second portion 10F may be made of stainless steel, while the first portion 17F may be made of ceramic such as alumina.

According to such a configuration, the heat capacity of the first portion 17F can be further increased.
(2d) In the above embodiment, the portion of the wall member 17 and the housing 10 that comes into contact with the catalysts 21 and 22 has been described as a portion that surrounds the catalysts 21 and 22, but the interpretation is not limited to this. For example, in the wall member 17 and the housing 10, in addition to the portion in contact with the catalysts 21 and 22, the portion around the wall member 17 and the housing 10 in which the amount of heat can be transferred to and from the catalysts 21 and 22. The inner part may be a part surrounding the catalysts 21 and 22.

(2e) In the above embodiment, the housing 10 is provided with the heat exchanger 23, but the housing 10 may not be provided with the heat exchanger 23. Further, in the above embodiment, the housing 10 is provided with the muffling chambers 18A, 18B, 18C, but the muffling chambers 18A, 18B, 18C may not be provided. Further, the wall member 17 is configured to be in direct contact with the muffling chambers 18A, 18B, 18C, but it is not necessary to have this configuration. Further, in the above embodiment, the housing 10 is provided with two catalysts 21 and 22, but the number of catalysts may be one or three or more.

(2f) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or one function possessed by one component may be realized by a plurality of components. .. Further, a plurality of functions possessed by the plurality of components may be realized by one component, or one function realized by the plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other above embodiment.

1 ... Exhaust unit, 10 ... Housing, 10A ... Outer wall part, 10B ... Sensor mounting part, 10F ... Second part, 10H ... Insertion hole, 10J ... Second flange part, 11 ... Introduction port, 11J ... First flange part , 12 ... exhaust port, 12J ... exhaust connection, 16 ... flow path, 17 ... wall member, 17F ... first part, 18A, 18B, 18C ... muffling chamber, 21,22 ... catalyst, 23 ... heat exchanger, 23IN ... Cooling introduction unit, 23OUT ... Cooling discharge unit, 24 ... Inlet pipe, 24H ... Hole, 25 ... Exhaust outlet, 25J ... Exhaust outlet, 26, 27, 28 ... Sensor, 31, 32 ... Plate member, 33 ... Valve, 33A ... Opening and closing part, 100 ... Internal combustion engine.

Claims (5)

A housing configured so that the exhaust of the internal combustion engine is introduced from the introduction port and the exhaust is discharged from the discharge port.
A wall member arranged in the housing and configured to form a tubular flow path for circulating the exhaust gas introduced from the introduction port in the housing together with a part of the housing.
With the catalyst arranged in the flow path,
With
The portion of the wall member that surrounds the catalyst together with the housing is the first portion, and the portion of the housing that surrounds the catalyst together with the wall member is the second portion, and the heat capacity in the first portion is determined. An exhaust unit that is set to be larger than the heat capacity of the second part. The exhaust unit according to claim 1.
The first portion of the wall member and the second portion of the housing are formed by processing a plate-like material having the same composition, and the thickness of the first portion is the first portion. An exhaust unit that is set larger than the thickness of two parts. The exhaust unit according to claim 1 or 2.
An exhaust unit in which the surface area of the catalyst side in the first portion is set to be larger than the surface area of the catalyst side in the second portion. The exhaust unit according to any one of claims 1 to 3.
The housing is an exhaust unit arranged so as to cover the first portion and the catalyst. The exhaust unit according to any one of claims 1 to 4.
Further, a sound deadening chamber configured to communicate with the flow path on the downstream side of the flow path from the catalyst is further provided.
The first portion is an exhaust unit configured to function as a wall surface separating the muffling chamber and the catalyst.

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