Exhaust system of an internal combustion engine

Abstract

The exhaust system includes: an exhaust manifold having multiple branch pipes and a collector; and a catalytic converter housing connected to the downstream side of the collector in the exhaust manifold. The multiple branch pipes of the exhaust manifold are configured such that the direction of the exhaust flowing into the collector forms an acute angle with respect to the axial direction of the catalytic converter housing. Furthermore, the collector is configured such that its internal space is spherical.

Description

Technical Field

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

[0002] In the exhaust manifold of an internal combustion engine, a structure with an arc-shaped recess in the manifold is known (for example, see Japanese Patent Application Publication No. 2018-150926). Japanese Patent Application Publication No. 2018-071353 discloses a configuration in which a bend is provided in the exhaust passage from the internal combustion engine to the catalyst, the bend causing the flow velocity of the exhaust gas entering the exhaust purification catalyst to become uniform in a direction orthogonal to the catalyst axis. Japanese Patent Application Publication No. 2006-283586 discloses a configuration in which the axis of the branch pipe of the exhaust manifold intersects the axis of the exhaust purification catalyst in an exhaust pipe structure where the exhaust purification catalyst is connected. Furthermore, it discloses a configuration in which a protrusion is provided in the manifold at the intersection of the exhaust pipe structure. Japanese Patent Application Publication No. 2020-002831 discloses a configuration in which an enlargement is provided in the exhaust passage connecting the oxidation catalyst and the DPF, and a guide wall for rotating the exhaust gas is provided in the enlargement. Japanese Patent Application Publication No. 2007-303398 discloses a configuration in which the inlet side of the catalyst shell is formed to be curved while the diameter is expanded. Summary of the Invention

[0003] The purpose of this invention is to provide a technique that is effective in suppressing the blowing out of exhaust gas in an exhaust gas purification catalyst.

[0004] One aspect of the present invention is an exhaust system for an internal combustion engine. In one example, the exhaust system for this internal combustion engine may include: an exhaust manifold having multiple branch pipes respectively connected to multiple cylinders of the internal combustion engine and a collection portion formed by the confluence of the multiple branch pipes; and a catalyst housing connected to the downstream side of the collection portion in the exhaust manifold, wherein the multiple branch pipes are configured such that the direction of the exhaust flowing into the collection portion forms an acute angle with respect to the axial direction of the catalyst housing, and the collection portion is configured such that its internal space is spherical.

[0005] According to the present invention, a technique that is effective in suppressing the blowing out of exhaust gas in an exhaust gas purification catalyst can be provided. Attached Figure Description

[0006] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0007] Figure 1 This is a cross-sectional view schematically illustrating an example of the configuration of the exhaust system in the embodiment.

[0008] Figure 2 This is Figure 1, used to illustrate the flow of exhaust gas in the exhaust system of the embodiment.

[0009] Figure 3 This is the second diagram illustrating the flow of exhaust gas in the exhaust system of the embodiment.

[0010] Figure 4 This is Figure 3, used to illustrate the flow of exhaust gas in the exhaust system of the embodiment. Detailed Implementation

[0011] An exhaust system for an internal combustion engine is known to have an exhaust purification catalyst (catalyst housing) disposed downstream of the exhaust manifold connected to the internal combustion engine. In such an exhaust system, in operating regions where the exhaust flow rate increases (e.g., high-speed operating regions), the phenomenon of unpurified components in the exhaust passing through the exhaust purification catalyst (so-called blow-out) may occur.

[0012] The present invention preferably suppresses the aforementioned blowout. In one example, the exhaust system of the internal combustion engine according to the present invention includes an exhaust manifold and a catalyst housing. The exhaust manifold according to the present invention has multiple branch pipes connected to multiple cylinders of the internal combustion engine and a collection section formed by the confluence of the multiple branch pipes. The catalyst housing according to the present invention is connected to the downstream side of the collection section in the exhaust manifold. Furthermore, the multiple branch pipes according to the present invention are each configured such that the direction of the exhaust flowing into the collection section is at an acute angle relative to the axial direction of the catalyst housing. As a result, the exhaust flowing into the collection section from the multiple branch pipes flows toward the inner wall surface of the collection section and collides with the inner wall surface. Furthermore, the collection section according to the present invention is configured such that the internal space of the collection section is spherical. As a result, the exhaust flowing into the collection section from the multiple branch pipes rotates along the inner wall surface after colliding with the inner wall surface of the collection section. At this time, by changing the exhaust flow rate according to the operating state of the internal combustion engine, even if the collision position of the exhaust on the inner wall surface of the collection section changes, the exhaust can be rotated. Therefore, the exhaust gas flowing into the manifold from multiple branch pipes loses kinetic energy through collision with the inner wall of the manifold and rotation along the inner wall, thus slowing down. The decelerated exhaust gas then flows from the manifold into the catalyst housing. Therefore, during operation of the internal combustion engine in the region where the exhaust gas flow rate is higher, the aforementioned blowout can be suppressed.

[0013] In the exhaust system of the internal combustion engine according to this invention, a protrusion extending radially inward can be provided at the outlet portion of the manifold. This reduces the amount of exhaust gas circulating within the internal space of the manifold that flows from the outlet portion of the manifold into the inlet portion of the catalyst housing. In other words, it increases the amount of exhaust gas continuing to circulate within the internal space of the manifold. Consequently, the flow rate of the exhaust gas discharged from the outlet portion of the manifold can be reduced more reliably.

[0014] Implementation

[0015] Hereinafter, specific embodiments of the present invention will be described based on the accompanying drawings. Unless otherwise specified, the dimensions, materials, shapes, relative arrangements, etc., of the constituent components described in this embodiment are not intended to limit the technical scope of the invention to these.

[0016] Overview of the exhaust system

[0017] Figure 1 This is a cross-sectional view schematically illustrating an example of the configuration of the exhaust system Es1 of the internal combustion engine 1 in this embodiment. The internal combustion engine 1 is mounted in a vehicle for driving or generating electricity. The internal combustion engine 1 of this embodiment has multiple cylinders. The internal combustion engine 1 of this embodiment can be a spark-ignition internal combustion engine or a compression-ignition internal combustion engine.

[0018] An exhaust manifold 2 is connected to the internal combustion engine 1. In this embodiment, the exhaust manifold 2 is configured to include multiple branch pipes 20 through which the combusted gas (exhaust) burned in the multiple cylinders 10 of the internal combustion engine 1 flows. Furthermore, the exhaust manifold 2 in this embodiment is configured to include a collecting section (gas collector) 21 that merges the exhaust gases flowing in the multiple branch pipes 20. Additionally, in Figure 1 Only one of the multiple branch pipes 20 of the exhaust manifold 2 is shown in the diagram, but the exhaust manifold 2 includes multiple branch pipes 20. The detailed configuration of the exhaust manifold 2 in this embodiment will be described later.

[0019] A catalyst housing 3 is connected to the outlet (downstream side) of the collection section 21 of the exhaust manifold 2. The catalyst housing 3 is configured to have a cylindrical portion for housing an exhaust gas purification catalyst 30 and conical portions disposed before and after the cylindrical portion. The exhaust gas purification catalyst 30 purifies the target components contained in the exhaust gas. In one example, the exhaust gas purification catalyst 30 may be configured to purify hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. x Exhaust components such as nitrogen oxides (NOx) are present. Furthermore, the exhaust purification catalyst 30 is not limited to a three-way catalyst; it can also be an oxidation catalyst, NOx, etc. x Storage reducing catalyst (NSR catalyst) or selective reduction catalyst (SCR catalyst).

[0020] In the exhaust system Es1 configured as described above, exhaust gases from multiple cylinders of the internal combustion engine 1 flow into the collection section 21 of the exhaust manifold 2 and merge with each other. At this time, the exhaust gases from the multiple cylinders of the internal combustion engine 1 pass through multiple branch pipes 20 of the exhaust manifold 2. The exhaust gases that merge in the collection section 21 flow into the catalyst housing 3 and are discharged downstream through the exhaust purification catalyst 30 inside the catalyst housing 3. At this time, the components to be purified contained in the exhaust gas are purified by the exhaust purification catalyst 30.

[0021] Composition of the exhaust manifold

[0022] Here, the specific configuration of the exhaust manifold 2 in this embodiment will be described. For example... Figure 1 As shown, in this embodiment, the collection portion 21 of the exhaust manifold 2 is configured to form a spherical internal space. Within the collection portion 21, a generally cylindrical outlet 22 for discharging exhaust gas from the interior of the collection portion 21 is provided at a position axially opposite to the exhaust gas purification catalyst 30 housed in the catalyst housing 3. The axial direction of the exhaust gas purification catalyst 30 is an imaginary straight line extending from the central axis of the exhaust gas purification catalyst 30 towards the collection portion 21. Figure 1 (The single-dotted arrow CL1 in the diagram). In one example, the outlet 22 may be configured to be approximately coaxial with the central axis of the exhaust purification catalyst 30. A protrusion 23 protruding radially inward (towards the center of the outlet 22) is provided on the inner wall surface of the collection section 21 at the portion surrounding the outlet 22. The protrusion 23 may be provided on the entire circumference of the inner wall surface surrounding the outlet 22, or it may be provided on a portion of the inner wall surface surrounding the outlet 22. The location of the protrusion 23 when it is provided on a portion of the inner wall surface surrounding the outlet 22 can be determined based on the direction of exhaust flow within the internal space of the collection section 21, as described later.

[0023] Furthermore, in this embodiment, the multiple branch pipes 20 of the exhaust manifold 2 are configured such that the direction of the exhaust flowing from the branch pipes 20 into the collection section 21 forms an angle with the axial direction CL1 of the exhaust purification catalyst 30 housed in the catalyst housing 3. Figure 1 Angle A1 in the middle is an acute angle. The direction of the exhaust gas as it flows from branch pipe 20 into collection section 21 is... Figure 1 The solid arrow De1 in the figure. An acute angle is an angle less than 90 degrees. In addition, the connection position of the multiple branch pipes 20 in the collection section 21 and the aforementioned angle A1 are not particularly limited as long as they can generate the exhaust flow described later in the internal space of the collection section 21.

[0024] Function and effects of this implementation method

[0025] In the exhaust system Es1 of this embodiment, the exhaust gas flowing from each branch pipe 20 into the collection section 21 collides with the inner wall surface of the collection section 21 before being discharged from the outlet 22. This is because the direction De1 of the exhaust gas flowing from the multiple branch pipes 20 into the collection section 21 forms an acute angle A1 with the axial direction CL1 of the exhaust purification catalyst 30. Furthermore, the collection section 21 in this embodiment is configured to form a spherical internal space, therefore, as Figure 2 As shown, the exhaust gas colliding with the collection section 21 flows in a rotary manner along the inner wall surface of the collection section 21. Figure 2 (Solid arrow Ef1 in the image). At this time, by changing the exhaust flow rate according to the operating state of the internal combustion engine 1, the exhaust can be rotated even if the collision position of the exhaust on the inner wall surface of the collection section 21 changes. As a result, the exhaust flowing into the collection section 21 from each branch pipe 20 consumes kinetic energy through collision with the inner wall surface of the collection section 21 and rotation in the internal space of the collection section 21, thereby decelerating.

[0026] And, as Figure 3 As shown, at least a portion of the exhaust gas rotating within the internal space of the collection section 21 is blocked from flowing into the outlet 22 by the protrusion 23, thus continuing to rotate within the internal space of the collection section 21. Figure 3 (Solid arrow Ef2 in the image). This increases the amount of exhaust gas that continues to circulate within the internal space of the collection section 21. Consequently, the flow rate of exhaust gas discharged from the outlet 22 of the collection section 21 can be reduced more reliably.

[0027] Additionally, the flow of exhaust gas rotating within the internal space of the collection section 21, such as Figure 4 As shown by the solid arrow Ef3, the direction of rotation may change midway. This is because the exhaust flow is pressured by the exhaust gas newly flowing into the internal space of the manifold 21 from the multiple branch pipes 20. Even in this case, at least a portion of the exhaust gas rotating within the internal space of the manifold 21 is blocked from flowing into the outlet 22 by the protrusion 23, thus reliably slowing down the flow rate of the exhaust gas discharged from the outlet 22 of the manifold 21.

[0028] Therefore, according to the exhaust system Es1 of this embodiment, even when the exhaust flow rate from the internal combustion engine 1 increases, such as when the internal combustion engine 1 is running at high speed, the exhaust flow rate flowing into the catalyst housing 3 can be slowed down. This is because the exhaust flow rate can be slowed down in the collection section 21 of the exhaust manifold 2. As a result, the amount of the target purification component (the unpurified component that passes through the exhaust purification catalyst 30) blown out of the exhaust purification catalyst 30 can be reduced.

[0029] Variations

[0030] In the above embodiment, a protrusion 23 is provided at the outlet 22 of the collection section 21, but this protrusion 23 may not be provided. In particular, if it is an internal combustion engine with a relatively small displacement (total cylinder volume) or a relatively low speed limit, the protrusion 23 can be omitted. This is because even without the protrusion 23, the flow rate of the exhaust gas flowing into the exhaust purification catalyst 30 can be sufficiently slowed down.

Claims

1. An exhaust system of an internal combustion engine, characterized by, have: An exhaust manifold having multiple branch pipes respectively connected to multiple cylinders of an internal combustion engine and a collection section formed by the confluence of the multiple branch pipes; and Catalyst housing, which is connected downstream of the collection section in the exhaust manifold. The multiple branch pipes are configured such that the direction of the exhaust gas flowing into the collection section forms an acute angle with respect to the axial direction of the catalyst housing. The assembly section is configured such that its internal space is spherical.

2. The exhaust system of the internal combustion engine according to claim 1, characterized in that, The outlet portion of the collection section is provided with a protrusion that protrudes radially inward.

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