Exhaust apparatus for internal combustion engine

Abstract

The invention relates to an exhaust device for an internal combustion engine. With regard to an exhaust device for an internal combustion engine (10), a downstream wall portion (33) comprises a peripheral wall portion (34, 35), the peripheral wall portion (34) comprises a side wall portion (341) intersecting a central axis (A), the peripheral wall portion (35) comprises a side wall portion (351) continuous downstream from the side wall portion (341) and overlapping an area in which a catalyst (30a) projects downstream along the central axis (A), and when the downstream wall portion (33) is viewed in a direction perpendicular to a plane comprising the central axis (A) and a central axis (B), the side wall portion (351) is inclined toward the central axis (A) when compared to the side wall portion (341).

Description

Technical Field

[0001] This invention relates to an exhaust device for an internal combustion engine. Background Technology

[0002] An exhaust system for an internal combustion engine is known. This exhaust system includes an exhaust manifold, a catalyst disposed downstream of the exhaust manifold, an exhaust pipe disposed downstream of the catalyst, and a sensor for detecting the state of the exhaust gases disposed in the exhaust pipe. In this exhaust manifold, branch pipe sections connected to the cylinders of the internal combustion engine are collected downstream and connected to a collection pipe section. Furthermore, exhaust strokes are performed in these cylinders at different timings (see, for example, Japanese Unexamined Patent Application Publication No. 2009-257209).

[0003] Due to the direction of exhaust gas flow into the exhaust pipe, the flow rate of exhaust gas flowing through the exhaust pipe may be non-uniform in its cross-section. Furthermore, because exhaust gas is discharged to different branch pipe sections at different timings for each cylinder, the exhaust gas from each cylinder flows into the exhaust pipe via different paths. Therefore, for each cylinder, the non-uniformity of exhaust gas flow rate in the cross-section of the exhaust pipe, as described above, is also different. Consequently, for each cylinder, the flow rate of exhaust gas in contact with the sensor located in the exhaust pipe is also different, and thus, the sensor's detection result may vary for each cylinder.

[0004] Furthermore, for this type of exhaust system used in internal combustion engines, the pressure loss of exhaust gases may increase. This increased pressure loss can lead to an increase in the back pressure of the internal combustion engine, which may affect output performance and fuel efficiency. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide an exhaust device for an internal combustion engine that suppresses the increase in pressure loss of exhaust gas and suppresses changes in sensor detection results.

[0006] The above objectives are achieved by an exhaust system for an internal combustion engine, comprising: an exhaust manifold including branch pipe sections and a manifold section, the branch pipe sections being connected to cylinders of the internal combustion engine, where exhaust strokes are performed at different timings in the cylinders, and the branch pipe sections converging at their downstream ends and connecting to the manifold section; a catalyst disposed downstream of the manifold section in the exhaust manifold; an exhaust pipe disposed downstream of the catalyst; a sensor for detecting the state of exhaust gases and disposed in the exhaust pipe; and a connecting wall section connecting the catalyst and the exhaust pipe and extending along... The flow direction of the exhaust gas extends in different directions relative to the first central axis of the catalyst. The connecting wall portion includes a first peripheral wall portion and a second peripheral wall portion that is continuous downstream from the first peripheral wall portion. The first peripheral wall portion includes a first side wall portion that intersects the first central axis. The second peripheral wall portion includes a second side wall portion that is continuous downstream from the first side wall portion and overlaps with the area in which the catalyst is projected downstream along the first central axis. When the connecting wall portion is viewed in a direction perpendicular to the plane that includes the first central axis and the second central axis of the exhaust pipe connected to the connecting wall portion, the second side wall portion is inclined toward the first central axis when compared with the first side wall portion.

[0007] The inner diameter of the first peripheral wall portion can decrease as the first peripheral wall portion extends downstream.

[0008] The inner diameter of the second peripheral wall portion can be smaller than the inner diameter of the first peripheral wall portion.

[0009] The inclination of the first sidewall portion relative to the first central axis can be 45 degrees or greater and 85 degrees or less.

[0010] The first and second sidewall portions may be inclined to the same side relative to the first central axis.

[0011] The first and second sidewall portions and the second central axis may be tilted to the same side relative to the first central axis, and the tilt of the second central axis relative to the first central axis may be greater than 0 degrees, and may be equal to or less than the tilt of the first sidewall portion relative to the first central axis.

[0012] The inclination of the second central axis relative to the first central axis can be the same as the inclination of the second sidewall portion relative to the first central axis.

[0013] When the connecting wall portion is viewed in a direction perpendicular to the plane, the first sidewall portion may be curved.

[0014] The second sidewall portion can be parallel to the first central axis.

[0015] The connecting wall portion can be part of the outer shell containing the catalyst.

[0016] The catalyst can be a first catalyst, the second catalyst can be located on the downstream side of the exhaust pipe, and the sensor can be positioned closer to the second catalyst than to the first catalyst.

[0017] The sensor can be the first sensor, and the second sensor for detecting the state of the exhaust gas can be located downstream of the second catalyst.

[0018] The sensor may include at least one of the following: air-fuel ratio sensor, oxygen sensor, temperature sensor, carbon dioxide sensor, NOx sensor, PM sensor, flow sensor, and pressure sensor.

[0019] Effects of the present invention

[0020] According to the present invention, an exhaust device for an internal combustion engine can be provided that suppresses the increase in pressure loss of exhaust gas and suppresses changes in sensor detection results. Attached Figure Description

[0021] Figure 1 This is a schematic configuration view of the engine system according to this embodiment;

[0022] Figure 2A This is an enlarged view of the vicinity of the downstream wall portion of the catalytic converter housing, and Figure 2B This is an interpretive view of the exhaust flow in the downstream wall portion of the catalytic converter housing;

[0023] Figure 3 This is a general configuration view of the engine system based on the comparative example;

[0024] Figure 4A This is an enlarged view of the vicinity of the downstream wall portion of the catalytic converter housing in the comparative example, and Figure 4B This is an explanatory view of the exhaust gas flowing in the downstream wall portion of the catalytic converter housing in the comparative example;

[0025] Figure 5A and Figure 5B These are explanatory views of the exhaust flow to the air-fuel ratio sensor in this embodiment and the comparative example, respectively.

[0026] Figure 6A This is a view illustrating the sensing area corresponding to the installation position of the air-fuel ratio sensor in the cross-section, and Figure 6B This is a graph showing the non-uniformity ratio of the flow rate of each exhaust gas from cylinders #1 to #4 through the sensing area relative to the average value in this embodiment and the comparative example; and

[0027] Figure 7A This is an enlarged view of the vicinity of the downstream wall portion of the catalytic converter housing in the first variant, and Figure 7B This is an enlarged view of the vicinity of the downstream wall portion of the catalytic converter housing in the second variant. Detailed Implementation

[0028] [Configuration in this embodiment]

[0029] Figure 1 This is a schematic configuration view of engine system 1 according to this embodiment. Engine system 1 includes engine 10 and exhaust system 2. Engine 10 is an example of an internal combustion engine and is a compression ignition type diesel engine that uses light oil as fuel. However, the engine is not limited to this and can also be a spark ignition type gasoline engine that uses gasoline as fuel. Engine 10 is a four-stroke engine in which a combustion cycle is formed by an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Engine 10 has four cylinders #1 to #4. Engine 10 is not limited to having four cylinders, as long as it has multiple cylinders. In cylinders #1 to #4, the exhaust stroke is performed in cylinders #1, #3, #4, and #2 in the following order, that is, the exhaust stroke is performed at different timings. Each of cylinders #1 to #4 is provided with an in-cylinder injection valve for injecting fuel into the cylinder, but the invention is not limited thereto. For example, in addition to or replacing the in-cylinder injection valve, a port injection valve for injecting fuel into the intake port can be provided in each of the intake ports of cylinders #1 to #4. The intake manifold is connected to engine 10 via an intake manifold.

[0030] The exhaust system 2 includes an exhaust manifold 20, a catalytic converter 30, exhaust pipes 40 and 70, a catalytic converter 50, and air-fuel ratio sensors 60 and 80. The exhaust manifold 20 is connected to the engine 10, and exhaust gases emitted from each of cylinders #1 to #4 pass through the exhaust manifold 20. Specifically, the exhaust manifold 20 includes branch pipe sections 21 to 24 respectively connected to cylinders #1 to #4; and a manifold section 25 where the branch pipe sections 21 to 24 are collected and connected at their downstream sides. The catalytic converter 30 is connected to the downstream end of the manifold section 25 of the exhaust manifold 20. The exhaust pipe 40 is connected to the downstream end of the catalytic converter 30. The catalytic converter 50 is connected to the downstream end of the exhaust pipe 40.

[0031] An air-fuel ratio sensor 60 is disposed in the exhaust pipe 40 and detects the air-fuel ratio of the exhaust gas that has passed through the catalytic converter 30. The air-fuel ratio sensor 60 is positioned closer to the catalytic converter 50 than to the catalytic converter 30. The air-fuel ratio sensor 60 is an example of a sensor and a first sensor. The exhaust pipe 70 is connected to the downstream end of the catalytic converter 50. An air-fuel ratio sensor 80 is disposed in the exhaust pipe 70 on the downstream side of the catalytic converter 50 and detects the air-fuel ratio of the exhaust gas that has passed through the catalytic converter 50. Sensor 80 is an example of a second sensor. Exhaust gases emitted from each of cylinders #1 to #4 at different timings flow downstream from the manifold section 25 through branch pipe sections 21 to 24 of the exhaust manifold 20.

[0032] Catalytic converter 30 houses catalyst 30a, which carries a closed-loop NOx reduction catalyst, within a cylindrical housing 30C. Catalytic converter 30 will be described in detail later. Catalytic converter 50 houses catalyst 50a, which carries an oxidation catalyst, within a cylindrical housing 50C. Both catalysts 30a and 50a are formed in a honeycomb shape along the direction of exhaust gas flow. Catalysts 30a and 50a are examples of the first and second catalysts, respectively.

[0033] Engine system 1 is equipped with an electronic control unit (ECU) 100. ECU 100 is an electronic control unit that includes a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and spare RAM. ECU 100 is electrically connected to air-fuel ratio sensors 60 and 80, and the measurements from these sensors are input. ECU 100 controls engine 10 based on the detection results from air-fuel ratio sensors 60 and 80.

[0034] The housing 30C of the catalytic converter 30 has a midstream wall portion 31, an upstream wall portion 32, and a downstream wall portion 33. The midstream wall portion 31 is continuous downstream from the upstream wall portion 32. The downstream wall portion 33 is continuous downstream from the midstream wall portion 31. The midstream wall portion 31 has a constant inner diameter in the downstream direction and holds the catalyst 30a. The inner diameter of the upstream wall portion 32 increases in the downstream direction. An exhaust manifold 20 is connected to the upstream end of the upstream wall portion 32. The inner diameter of the downstream wall portion 33 decreases in the downstream direction. An exhaust pipe 40 is connected to the downstream end of the downstream wall portion 33. The downstream wall portion 33 is an example of a connecting wall portion that connects the catalyst 30a and the exhaust pipe 40. Figure 1The central axis A of catalyst 30a is illustrated. Central axis A is a line segment passing through the center of a cross-section perpendicular to the flow path direction of catalyst 30a disposed in the midstream wall portion 31, and corresponds to the central axis along the flow direction of the exhaust gas. Catalyst 30a is formed in a honeycomb shape as described above, and specifically, catalyst 30a forms flow paths extending from its upstream end surface to its downstream end surface. These flow paths extend along central axis A. The downstream wall portion 33 will be described in detail later. Furthermore, Figure 1 The central axis B of the exhaust duct 40 is shown at the upstream end of the exhaust duct 40, which is connected to the downstream wall portion 33. Central axis B is a line segment passing through the center of a section perpendicular to the flow path at the upstream end of the exhaust duct 40. Central axes A and B are not parallel to each other.

[0035] Figure 2A This is an enlarged view of the vicinity of the downstream wall portion 33 of the housing 30C of the catalytic converter 30. Figure 2A The diagram illustrates the vicinity of the downstream wall portion 33 as viewed in a direction perpendicular to the plane including central axes A and B. The downstream wall portion 33 extends in a direction different from the direction in which central axis A extends. The downstream wall portion 33 includes peripheral wall portions 34 and 35. Peripheral wall portion 35 continues downstream from peripheral wall portion 34. The inner diameter of peripheral wall portion 34 decreases as it approaches the downstream side. The inner diameter of peripheral wall portion 35 is substantially constant. In other words, peripheral wall portion 34 has a funnel shape extending in a direction different from the direction in which central axis A extends, and peripheral wall portion 35 has a cylindrical shape also extending in a direction different from the direction in which central axis A extends. Peripheral wall portions 34 and 35 are examples of the first and second peripheral wall portions, respectively.

[0036] Peripheral wall portion 34 includes sidewall portion 341. Peripheral wall portion 35 includes a continuous sidewall portion 351 extending downstream from sidewall portion 341. Central axis A intersects sidewall portion 341. Sidewall portion 351 is away from central axis A but overlaps with projection area P of catalyst 30a projected downstream along central axis A. Sidewall portion 341 also overlaps with projection area P. Both sidewall portions 341 and 351 are curved, resulting in concave inner surfaces. Compared to sidewall portion 341, sidewall portion 351 is configured to be inclined toward central axis A. That is, compared to sidewall portion 341, sidewall portion 351 is approximately parallel to central axis A. Sidewall portions 341 and 351 are inclined to the same side relative to central axis A. Specifically, sidewall portion 341 is inclined at an angle α relative to central axis A. Sidewall portion 351 is inclined at an angle β relative to central axis A. Here, angle α is greater than angle β, and sidewall portion 341 is more inclined relative to the central axis A than sidewall portion 351. The central axis B is inclined relative to the central axis A to the same side as sidewall portions 341 and 351, and is inclined relative to the central axis A at angle γ. In this embodiment, angle γ is less than angle α and is substantially the same as angle β. Sidewall portions 341 and 351 are examples of the first sidewall portion and the second sidewall portion, respectively.

[0037] Figure 2B This is an explanatory view of the exhaust gas flow in the downstream wall portion 33 of the housing 30C of the catalytic converter 30. As indicated by the arrows in the figure, the exhaust gas flows in each flow path extending along the central axis A of the catalyst 30a. Therefore, immediately after passing through the catalyst 30a, the exhaust gas flows in the direction of the central axis A. A portion of the exhaust gas that has passed through the catalyst 30a collides with the side wall portion 341 and swirls along the inner surface of the side wall portion 341. The swirling exhaust gas also promotes the swirling of the exhaust gas that has passed through the catalyst 30a and does not collide with the side wall portion 341. Therefore, the exhaust gas flows downstream even in the exhaust duct 40 while swirling.

[0038] As described above, the sidewall portion 341 is more inclined relative to the central axis A than the sidewall portion 351. Furthermore, the sidewall portion 341 extends from a predetermined position on the outer periphery of the middle wall portion 31 to a position intersecting the central axis A. Here, generally, the flow velocity of the fluid flowing in the circular pipe increases with increasing proximity to the central axis of the circular pipe. Therefore, the flow velocity of the exhaust gas passing through the catalyst 30a also increases with increasing proximity to the central axis A. This allows a large portion of the exhaust gas that has passed through the catalyst 30a to collide with the sidewall portion 341. This promotes the swirling of the exhaust gas. As will be described in detail later, this swirling of the exhaust gas suppresses changes in the detection result of the air-fuel ratio sensor 60.

[0039] Furthermore, the inner diameter of the peripheral wall portion 34 decreases towards the downstream side. Therefore, a swirling flow with a small radius forms downstream of the peripheral wall portion 34. This promotes the swirling of the exhaust gas. Additionally, the inner diameter of the peripheral wall portion 35 is smaller than the inner diameter of the peripheral wall portion 34. This also allows for maintaining a small radius of the formed swirling flow and maintaining the swirling velocity of the exhaust gas. Figure 2A and Figure 2B In the example, the inner diameter of the peripheral wall portion 35 is substantially constant. However, its inner diameter is not limited to being constant, and the inner diameter of the peripheral wall portion 35 can decrease as it gets closer to the downstream side.

[0040] Furthermore, the sidewall portion 351 is not inclined as much as the sidewall portion 341 relative to the central axis A, but overlaps with the projection region P. Therefore, it is possible to ensure that exhaust gas flowing through the catalyst 30a does not collide with the sidewall portion 341. For example, if all the exhaust gas that has passed through the catalyst 30a collides with the sidewall portion 341 and swirls, the pressure loss of the exhaust gas may increase. In this embodiment, by providing a sidewall portion 351 that is not significantly inclined relative to the central axis A at the location overlapping with the projection region P, it is possible to ensure that exhaust gas does not collide with the sidewall portion 341. This makes it possible to suppress the increase in the pressure loss of the exhaust gas. The entire sidewall portion 351 can overlap with the projection region P. When only a portion of the sidewall portion 351 overlaps with the projection region P, the ratio of the sidewall portion 341 to the projection region P is large, and in this case, the pressure loss of the exhaust gas may increase.

[0041] If the angle α between the sidewall portion 341 and the central axis A is too small, the exhaust gas may not be swirled. Furthermore, if the angle α is too large, the pressure loss of the exhaust gas may increase. Here, it is assumed that the incident angle of the exhaust gas colliding with the sidewall portion 341 parallel to the central axis A is equal to the reflection angle of the exhaust gas reflected by the sidewall portion 341. The velocity component of the exhaust gas reflected by the sidewall portion 341 is determined by the velocity component along the axis shown in the diagram. Figure 2A The downstream component of the line segment of the schematic sidewall portion 341 and the normal component of the line segment of the schematic sidewall portion 341 are used to represent this. When the angle α is 45 degrees or greater, the magnitude of the normal component is equal to or greater than the magnitude of the downstream component. Here, the magnitude of the normal component corresponds to the magnitude of the swirling velocity of the exhaust gas flowing along the curved inner surface of the sidewall portion 341. As described above, the angle α can be 45 degrees or greater to ensure the swirling velocity. However, when the angle α is greater than 85 degrees, in the flow rate of the exhaust gas colliding with the sidewall portion 341 along the central axis A, the downstream component is greater than the downstream component. Figure 2AThe upward flow of exhaust gas along the line segment of sidewall portion 341, as illustrated in the diagram, increases. This may increase the pressure loss of the exhaust gas. Therefore, the angle α can be 85 degrees or smaller.

[0042] Angle β is a value greater than 0 degrees. That is, sidewall portions 341 and 351 are inclined to the same side relative to the central axis A. For example, when angle β is 0 degrees and sidewall portion 351 is inclined to the opposite side of sidewall portion 341 relative to the central axis A, the exhaust gas may be highly separated near the boundary between sidewall portions 341 and 351, thereby potentially increasing the pressure loss of the exhaust gas.

[0043] As described above, the sidewall portions 341 and 351, which promote the swirling of exhaust gas and suppress the increase in pressure loss of exhaust gas, are part of the housing 30C that houses the catalyst 30a. Therefore, these components are integrated, unlike a case where a pipe with sidewall portions having the same function as sidewall portions 341 and 351 is separately provided from the housing 30C. Furthermore, because the sidewall portions 341 and 351 are formed within a part of the housing 30C, exhaust gas swirling can be achieved near the catalyst 30a. This allows for the formation of a swirling flow of exhaust gas before the flow rate may significantly decrease due to pressure loss, etc., after the exhaust gas has passed downstream through the catalyst 30a. Therefore, a strong swirling flow can be formed.

[0044] Central axes A and B extend in different directions. For example, when central axes A and B extend parallel in the same direction, the downstream wall portion 33 extends in a direction different from central axis A, as described above. Therefore, exhaust gas flowing in the downstream wall portion 33 in a direction different from central axis A collides with the inner wall of the exhaust duct 40 extending along central axis B, which is parallel to central axis A. This may increase the pressure loss of the exhaust gas. Because central axis B is inclined relative to central axis A to the same side as sidewall portions 341 and 351, as in this embodiment, the reduction in the swirling velocity of the exhaust gas flowing into the exhaust duct 40 is suppressed. Therefore, the angle γ can be greater than 0 degrees.

[0045] Furthermore, angle γ can be angle α or smaller. For example, when angle γ is greater than angle α, the inclination of the central axis B relative to the central axis A, that is, the inclination of the exhaust pipe 40 relative to the central axis A, is greater than the inclination of the sidewall portion 341 relative to the central axis A. In this case, the exhaust pipe 40 is more inclined relative to the central axis A than the sidewall portion 351. Therefore, the exhaust gas flowing in the downstream wall portion 33 may collide with the inner wall of the exhaust pipe 40, and the pressure loss of the exhaust gas may increase. Therefore, angle γ can be angle α or smaller.

[0046] As described above, in order to suppress pressure loss of the exhaust gas, angle γ can be greater than 0 degrees and equal to or less than angle α. However, angle γ can be substantially the same as angle β. This allows for sufficient reduction of pressure loss when the exhaust gas flows from the peripheral wall portion 35 into the exhaust pipe 40.

[0047] [Comparison of example structures]

[0048] Figure 3 This is a schematic configuration view of an engine system 1x based on a comparative example. Engine system 1x includes an exhaust system 2x. Exhaust system 2x includes a catalytic converter 30x. Figure 4A This is an enlarged view of the vicinity of the downstream wall portion 33x of the housing 30Cx of the catalytic converter 30x in the comparative example. Figure 4B This is an interpretive view of the exhaust gas flowing in the downstream wall portion 33x of the housing 30Cx of the catalytic converter 30x in the comparative example. Figure 3 , Figure 4A and Figure 4B Corresponding to respectively Figure 1 , Figure 2A and Figure 2B In the comparative examples, those components that are identical to those in this embodiment are labeled with the same reference numerals, and repeated descriptions will be omitted.

[0049] As in Figure 4A As illustrated, the peripheral wall portion 34x and the side wall portion 341x of the downstream wall portion 33x do not intersect the central axis A. Therefore, as in Figure 4B Schematic diagram: Exhaust gas that has passed through catalyst 30a flows along sidewall portion 341x in exhaust pipe 40. As described above, in the comparative example, unlike in this embodiment, the exhaust gas is less likely to swirl.

[0050] [Differences in exhaust flow to air-fuel ratio sensor 60 between this embodiment and the comparative example]

[0051] Next, a description of the differences in exhaust flow between this embodiment and the comparative example will be given. Figure 5A and Figure 5B These are explanatory views of the exhaust flow of the air-fuel ratio sensor 60 in this embodiment and the comparative example, respectively. Figure 5A and Figure 5BThe section S, orthogonal to the extension direction of the exhaust pipe 40, is shown by shading at the installation location of the air-fuel ratio sensor 60. In this embodiment, the exhaust gas from each of cylinders #1 to #4 passes through section S while swirling in the exhaust pipe 40. In the comparative example, the exhaust gas from cylinders #1 to #4 flows substantially linearly in the exhaust pipe 40 and passes through section S. Here, in both this embodiment and the comparative example, the exhaust gas emitted from cylinders #1 to #4 flows through branch pipe sections 21 to 24 respectively and flows into the exhaust pipe 40. In this embodiment, as described above, the exhaust gas that has passed through each of branch pipe sections 21 to 24 swirls in the downstream wall section 33 in the same manner and flows in the exhaust pipe section 40 while swirling. Therefore, in this embodiment, the flow distribution of the exhaust gas from each of cylinders #1 to #4 in section S is substantially uniform.

[0052] In the comparative example, the exhaust gases that have passed through each of the branch pipe sections 21 to 24 flow non-uniformly in the manifold section 25 and the catalytic converter 30x, while maintaining this non-uniformity, flow in the exhaust pipe 40. For example, a large amount of exhaust gas from cylinder #1 flows from branch pipe section 21 through manifold section 25 and the catalytic converter 30x along one side surface, and also flows along one side surface in the exhaust pipe 40. On the other hand, the exhaust gas from cylinder #4 flows from branch pipe section 24 through manifold section 25 and the catalytic converter 30x along another side surface, and also flows along another side surface in the exhaust pipe 40. In this way, in the comparative example, the flow distribution of the exhaust gases from each of cylinders #1 to #4 in section S is non-uniform, and the flow distribution is also different for each of cylinders #1 to #4.

[0053] Figure 6A This is a view showing the sensing area R corresponding to the installation position of the air-fuel ratio sensor 60 in section S. Figure 6B This is a graph showing the non-uniformity ratio of the flow rate of each exhaust gas from cylinders #1 to #4 passing through sensing area R relative to the average value in this embodiment and the comparative example. The average value in this embodiment is the average flow rate of the exhaust gas from cylinders #1 to #4 passing through sensing area R in this embodiment. The average value in the comparative example is the average flow rate of the exhaust gas from cylinders #1 to #4 passing through sensing area R in the comparative example. (As in...) Figure 6BAs illustrated, the difference in the non-uniformity ratio of the exhaust gas flow rate from cylinders #1 to #4 in sensing region R is large in the comparative example, but small in this embodiment. This is because, as described above, the flow rate distribution in section S is non-uniform in the comparative example, while it is substantially uniform in section S in this embodiment. Therefore, compared to the comparative example, in this embodiment, the change in the air-fuel ratio of the exhaust gas from each of cylinders #1 to #4 detected by the air-fuel ratio sensor 60 is suppressed.

[0054] In this embodiment, as in Figure 1 Schematic diagram: The air-fuel ratio sensor 60 is positioned closer to the catalytic converter 50 than to the catalytic converter 30. That is, this ensures a suitable distance from the downstream wall portion 33 to the air-fuel ratio sensor 60. Therefore, the exhaust gases are sufficiently swirled until they reach the air-fuel ratio sensor 60 from the downstream wall portion 33, thus adequately mixing the exhaust gases from each of cylinders #1 to #4. This suppresses any changes in the air-fuel ratio of the exhaust gases from each of cylinders #1 to #4 detected by the air-fuel ratio sensor 60.

[0055] Furthermore, because the flow distribution is uniform at the location of the air-fuel ratio sensor 60, the flow distribution is also uniform at the location of the air-fuel ratio sensor 80, which is further downstream of the air-fuel ratio sensor 60. This also suppresses changes in the air-fuel ratio of the exhaust gas from each of cylinders #1 to #4 detected by the air-fuel ratio sensor 80.

[0056] [Variation]

[0057] Next, variant examples will be described. In the variant examples, the same components as those in the embodiments described above are labeled with the same reference numerals, and repeated descriptions will be omitted. Figure 7A This is an enlarged view of the vicinity of the downstream wall portion 33A of the housing 30CA of the catalytic converter 30A in the first variant. Figure 7A Corresponding to Figure 2AIn the catalytic converter 30A, the sidewall portion 341A is bent so that it bulges outward when viewed in the vicinity of the downstream wall portion 33A in a direction perpendicular to the plane including the central axes A and B. Specifically, when viewed in a direction perpendicular to the plane including the central axes A and B, the tangent at any point on the ridge of the sidewall portion 341A is inclined relative to the central axis A, and the inclination of any tangent can gradually increase from the upstream side to the downstream side in the sidewall portion 341A. As a result, it is possible to suppress the increase in pressure loss of the exhaust gas while promoting the swirling of the exhaust gas colliding with the sidewall portion 341A. The maximum angle of inclination of the tangent at any point on the ridge of the sidewall portion 341A relative to the central axis A can be 90 degrees or less. Furthermore, in the first variant, the sidewall portion 351 is also configured to be inclined relative to the sidewall portion 341A toward the central axis A.

[0058] Figure 7B This is an enlarged view of the vicinity of the downstream wall portion 33B of the housing 30CB of the second variant catalytic converter 30B. Figure 7B Corresponding to Figure 2A In the catalytic converter 30B, when the periphery of the downstream wall portion 33B is viewed in a direction perpendicular to the plane including the central axes A and B, the side wall portion 351B is parallel to the central axis A. To suppress exhaust gas pressure loss, as in this embodiment described above, the side wall portion 351 can be inclined relative to the central axis A to the same side as the side wall portion 341. However, since at least the side wall portion 351B is parallel to the central axis A, exhaust gas pressure loss is suppressed.

[0059] In the embodiment described above, air-fuel ratio sensors 60 and 80 detect the air-fuel ratio of the exhaust gas as exhaust gas, but the invention is not limited thereto. For example, in addition to air-fuel ratio sensors 60 and 80, or instead of at least one of them, at least one of the following can be used: an oxygen sensor that detects the oxygen concentration in the exhaust gas, a temperature sensor that detects the temperature of the exhaust gas, a carbon dioxide sensor that detects the carbon dioxide concentration in the exhaust gas, a NOx sensor that detects the nitrogen oxide (NOx) concentration in the exhaust gas, a PM sensor that detects the particulate matter (PM) concentration in the exhaust gas, a flow sensor that detects the flow rate of the exhaust gas, and a pressure sensor that detects the pressure of the exhaust gas. Furthermore, these sensors are not limited to being installed in the sensing area R of the cross section S described above. The engine system 1 can be installed, for example, in an engine vehicle or a hybrid vehicle.

[0060] Furthermore, in the embodiment described above, catalyst 50a is disposed downstream of catalyst 30a, but the present invention is not limited thereto. That is, an exhaust device in which only catalyst 30a is disposed without catalyst 50a can be provided.

[0061] Although some embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments, but can be modified or varied within the scope of the claimed invention.

Claims

1. An exhaust device for an internal combustion engine, the exhaust device comprising: Exhaust manifold, the exhaust manifold comprising: Branch pipe sections, each connected to a cylinder of the internal combustion engine, perform exhaust strokes at different timings in the cylinders of the internal combustion engine. A collection pipe section, wherein the branch pipe sections converge at the downstream side of the branch pipe section and are connected to the collection pipe section; A catalyst, wherein the catalyst is disposed on the downstream side of the manifold portion in the exhaust manifold; An exhaust pipe is disposed downstream of the catalyst; A sensor, which detects the state of exhaust gas, is disposed in the exhaust duct; and A connecting wall portion, which connects the catalyst and the exhaust pipe, extends in different directions relative to the first central axis of the catalyst along the flow direction of the exhaust gas. The connecting wall portion includes: The first peripheral wall portion, and The second peripheral wall portion continues downstream from the first peripheral wall portion. The first peripheral wall portion includes a first side wall portion that intersects the first central axis. The second peripheral wall portion includes a second sidewall portion that is continuous downstream of the first sidewall portion and overlaps with the region of the catalyst projected downstream along the first central axis. When the connecting wall portion is viewed in a direction perpendicular to a plane including the first central axis and the second central axis of the exhaust pipe connected to the upstream end of the connecting wall portion, the second sidewall portion is inclined toward the first central axis when compared with the first sidewall portion. The first peripheral wall portion has a funnel shape extending in a direction different from the first central axis.

2. The exhaust device for an internal combustion engine according to claim 1, wherein, The inner diameter of the first peripheral wall portion decreases as the first peripheral wall portion extends downstream.

3. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The inner diameter of the second peripheral wall portion is smaller than the inner diameter of the first peripheral wall portion.

4. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The inclination of the first sidewall portion relative to the first central axis is 45 degrees or greater and 85 degrees or less.

5. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The first sidewall portion and the second sidewall portion are inclined to the same side relative to the first central axis.

6. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein: The first sidewall portion, the second sidewall portion, and the second central axis are inclined to the same side relative to the first central axis, and The inclination of the second central axis relative to the first central axis is greater than 0 degrees, and is equal to or less than the inclination of the first sidewall portion relative to the first central axis.

7. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The inclination of the second central axis relative to the first central axis is the same as the inclination of the second sidewall portion relative to the first central axis.

8. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, When the connecting wall portion is viewed in a direction perpendicular to the plane, the first sidewall portion is curved.

9. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The second sidewall portion is parallel to the first central axis.

10. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The connecting wall portion is part of the outer shell containing the catalyst.

11. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein: The catalyst is the first catalyst. The second catalyst is located on the downstream side of the exhaust pipe, and The sensor is positioned closer to the second catalyst than to the first catalyst.

12. The exhaust system for an internal combustion engine according to claim 11, wherein... The sensor is the first sensor, and A second sensor for detecting the state of the exhaust gas is located downstream of the second catalyst.

13. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein, The sensor includes at least one of the following: air-fuel ratio sensor, oxygen sensor, temperature sensor, carbon dioxide sensor, NOx sensor, PM sensor, flow sensor, and pressure sensor.

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