JP2018150926A - Exhaust system for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system for an engine that can improve uniformity per gas to a catalyst in an exhaust emission control device even when adopting an exhaust manifold for guiding an exhaust gas from a cylinder side on one end side toward an exhaust emission control system on a lower side.SOLUTION: In an exhaust system for an engine, a collecting pipe of an exhaust manifold is provided with a circular arc-shaped recess, thereby making a flow of an exhaust gas from a cylinder on one end side uniform and then introducing it into the exhaust emission control device.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an exhaust system for an engine.

  Conventionally, a catalyst for purifying exhaust gas has been disposed upstream of an exhaust path of an automobile engine such as a diesel engine or a gasoline engine.

  For example, in an in-line multi-cylinder engine, an exhaust manifold having a plurality of independent exhaust pipes connected to each exhaust port and a collection portion thereof for collecting exhaust gases from a plurality of cylinders and introducing them into a catalyst Is connected between the exhaust port and the catalyst (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 1-339418

  By the way, as described in Patent Document 1, when adopting a layout in which exhaust flows from the cylinder side at one end toward the catalytic converter below, exhaust streamlines from the cylinder at one end and exhaust from other cylinders There is a possibility that the streamlines are significantly different and the gas contact with the catalyst becomes non-uniform.

  Therefore, the present invention improves the uniformity per gas with respect to the exhaust purification device even when the exhaust manifold that guides the exhaust gas from the cylinder side at one end toward the exhaust purification device below is adopted. Let it be an issue.

  In order to solve the above problems, in the present invention, an arcuate recess or the like is provided in the exhaust manifold to increase the uniformity per gas.

An exhaust system for an engine disclosed herein includes an exhaust manifold connected to an exhaust port of an in-line multi-cylinder engine having an engine body having a plurality of cylinders,
An exhaust purification device connected downstream of the exhaust manifold in the exhaust gas flow direction,
The exhaust manifold is
A plurality of independent exhaust pipes connected to each exhaust port of the engine body;
A collecting pipe that is disposed on one end side in the cylinder row direction of the engine body and extends downward from a distal end portion of the independent exhaust pipe on one end side in the cylinder row direction among the plurality of independent exhaust pipes;
A guide pipe extending in the cylinder row direction for guiding exhaust gas flowing out from each of the remaining independent exhaust pipes of the plurality of independent exhaust pipes toward the independent exhaust pipe on the one end side and guiding it to the collecting pipe;
An L-shaped bent portion formed in a lower portion of the collecting pipe and bent in an L-shape in the lateral direction so that the exhaust gas is directed toward the upstream end face of the exhaust purification device;
Exhaust gas that is formed on the lower surface side of the L-shaped bent portion of the collecting pipe and flows down the collecting pipe along the wall surface continuing downward from the distal end side of the independent exhaust pipe on the one end side of the collecting pipe, An outlet of the L-shaped bent portion that opens toward the exhaust purification device for facilitating swirling of the exhaust gas so as to flow into the exhaust purification device while turning around the axis of the exhaust purification device And an arcuate concave portion having a larger radius than the other.

  According to this, the exhaust gas emitted from the exhaust port on one end side in the cylinder row direction of the engine body flows into the collecting pipe as it is through the independent exhaust pipe on one end side. This collecting pipe extends downward from the tip of the independent exhaust pipe. Accordingly, the exhaust gas flows downward in the collecting pipe mainly along the wall surface continuing from the leading end side of the independent exhaust pipe in the collecting pipe due to inertia when the independent exhaust pipe flows toward the leading end. To reach the L-shaped bend. An arcuate recess having a larger radius than the exit of the L-shaped bent portion is formed on the lower surface side of the L-shaped bent portion. Therefore, the exhaust gas flowing downward along the wall surface continuing from the front end side of the independent exhaust pipe of the collecting pipe flows and rises along the bottom wall surface where the arc-shaped recess is depressed due to inertia, and the axial center of the exhaust gas purification apparatus It flows into the exhaust purification device while turning around. Therefore, it becomes easy for exhaust gas to hit evenly over the entire upstream end face of the exhaust gas purification device.

  On the other hand, the exhaust gas coming out of the remaining independent exhaust pipes excluding the independent exhaust pipe on the one end side flows in the cylinder row direction through the guide pipe and flows into the collecting pipe. Therefore, unlike the exhaust gas exiting from the independent exhaust pipe on one end side, the exhaust gas tends to flow downward in the collecting pipe along the wall surface on the one end side in the cylinder row direction in the collecting pipe. The exhaust gas flowing in such a manner is combined with exhaust gas that flows downward along the wall surface continuing from the front end side of the independent exhaust pipe on the one end side in the collecting pipe and rises as a swirling flow in the arc-shaped recess. Thus, it can be avoided that the exhaust gas concentrates on the lower side of the L-shaped bent portion, and consequently the exhaust gas concentrates on the lower side of the upstream end face of the exhaust purification device.

  As described above, according to the exhaust system described above, the swirling flow of the exhaust gas is induced by the arc-shaped concave portion although the collecting pipe extends downward from the independent exhaust pipe on one end side in the cylinder row direction. As a result, the exhaust gas can easily strike the entire end face on the upstream side of the exhaust purification device, and the exhaust purification device can efficiently purify the exhaust gas.

  In one embodiment, the flow of the exhaust gas flowing into the collecting pipe from the guide pipe is directed to the central portion of the upstream end face of the exhaust purification device on the wall surface on one end side in the cylinder row direction of the collecting pipe. The bulge part to the outside is changed.

  According to this, the exhaust gas flowing into the collecting pipe from the guide pipe can be prevented from concentrating on the lower part of the upstream end face of the exhaust gas purification apparatus, so that the exhaust gas can easily hit the entire upstream end face.

  In one embodiment, the guide pipe is curved toward one end side in the cylinder row direction, in a protruding direction from the engine body of the independent exhaust pipe on the one end side, and connected to the tip of the independent exhaust pipe on the one end side. Department.

  According to this, when the exhaust gas flows from the guide pipe into the collecting pipe, the flow direction of the exhaust gas changes so as to approach the protruding direction of the independent exhaust pipe on one end side from the cylinder row direction by the curved portion. As a result, the exhaust gas flowing into the collecting pipe from the guide pipe is similar to the exhaust gas flowing into the collecting pipe from the independent exhaust pipe on one end side along the wall surface continuing to the tip of the independent exhaust pipe on one end side. It becomes easy to flow down. Therefore, it becomes easy to induce the swirling flow of the exhaust gas by the arc-shaped concave portion, and the exhaust gas easily hits the entire upstream end face of the exhaust purification device.

  In one embodiment, oxygen concentration detection means is provided below the bulging portion in the collecting pipe.

  Below the bulging portion of the collecting pipe is where the exhaust gas flowing downward along the wall surface on one end side in the cylinder row direction of the collecting pipe and the exhaust gas swirling and rising by the arc-shaped recess are combined. High nature. Therefore, the detection of the oxygen concentration below the bulging portion increases the reliability of the oxygen concentration obtained by the detection.

In one embodiment, further comprising a downstream side exhaust purification device provided downstream of the exhaust purification device in the exhaust gas flow direction,
The exhaust purification device and the downstream exhaust purification device have mutually intersecting central axes, and when viewed in the axial direction of the downstream exhaust purification device, the downstream portion of the exhaust purification device is the downstream exhaust purification device. It arrange | positions so that it may become the relationship which overlaps with a part of end surface of an upstream.

  According to this, since the distance from the exhaust manifold to the downstream side catalyst device can be shortened, it is advantageous for making the exhaust device compact, and the exhaust gas is allowed to flow into the downstream side exhaust purification device in a state where the temperature does not decrease so much. This is advantageous in ensuring the exhaust gas purification performance.

  With respect to “crossing each other's central axes”, it is preferable that both central axes are substantially orthogonal (the angle formed by both central axes is not less than 80 degrees and not more than 100 degrees).

  As described above, according to the present invention, the swirling flow of the exhaust gas is induced by the arc-shaped concave portion even though the collecting pipe extends downward from the independent exhaust pipe on one end side in the cylinder row direction. As a result, the exhaust gas can easily strike the entire end face on the upstream side of the exhaust purification device, and the exhaust purification device can efficiently purify the exhaust gas.

FIG. 1 is a side view of a state in which an exhaust device according to Embodiment 1 is attached to an engine body, as viewed from the right. FIG. 2 is a plan view of the exhaust device of FIG. FIG. 3 is a perspective view of the exhaust device of FIG. 1 as viewed from the upper right rear. FIG. 4 is a rear view of the exhaust device of FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 8 is a view corresponding to FIG. 6 schematically showing the state of the exhaust gas flow from the second cylinder. FIG. 9 is a view corresponding to FIG. 6 illustrating the exhaust device according to the second embodiment. FIG. 10 is a view corresponding to FIG. 6 with respect to an exhaust device that is not provided with an arcuate concave portion and a bulging portion. FIG. 11 is a graph showing an improvement index of the exhaust gas flow from each cylinder in Examples 1 and 2 and Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

(Embodiment 1)
<Engine>
The engine to which the exhaust device 1 according to Embodiment 1 is applied is an in-line four-cylinder gasoline engine (in-line multi-cylinder engine) mounted on an automobile. This engine is placed horizontally in front of the FF vehicle.

  The present invention can be applied not only to a four-cylinder gasoline engine but also to other multi-cylinder engines and diesel engines. Further, the present invention is not limited to FF vehicles, and can be applied to vehicles adopting various layouts including motorcycles such as RR vehicles and 4WD vehicles.

  As shown in FIG. 1, the engine includes an engine body E having a cylinder block E1 and a cylinder head E2. Although not shown in detail, the engine includes a first cylinder to a fourth cylinder configured by a cylinder block E1 and a cylinder head E2. The first to fourth cylinders are arranged in series in this order from the front of the page to the back side in a direction perpendicular to the page of FIG. A cylinder chamber (not shown) of the cylinder block E1, a piston (not shown) in the cylinder bore, and a cylinder head E2 form a combustion chamber for each cylinder.

  The cylinder head E2 has four exhaust ports (not shown) connected to the four combustion chambers. Exhaust gas generated in the combustion chamber is discharged out of the vehicle through an exhaust path including the exhaust port.

<Exhaust path>
As shown in FIGS. 1 and 2, the exhaust device 1 according to the present embodiment is connected to the exhaust port, and a downstream exhaust system (not shown) having a tail pipe is connected to the downstream side thereof. Has been. Thus, the exhaust path of the engine is constituted by the above-described exhaust port, the exhaust device 1, and the downstream exhaust system.

<Exhaust device>
As shown in FIGS. 1 to 4, the exhaust device 1 according to this embodiment includes an exhaust manifold M connected to four exhaust ports of the engine body E, and a connection portion N at a downstream end outlet M <b> 7 of the exhaust manifold M. An exhaust purification device Q, an exhaust gas discharge pipe 5 and an EGR gas take-out pipe 6 connected to each other are provided.

  Hereinafter, each configuration will be described in detail. The configuration of the exhaust manifold M will be described later.

<Direction>
In the description of the present specification, “vertical direction” and “front-rear direction” refer to the engine body E as a reference, the cylinder head E2 side is the upper side, the cylinder block E1 side is the lower side, and the engine body, as shown in FIG. A direction in which the E side is the front side and the exhaust manifold M side is the rear side is assumed. Further, as shown in FIGS. 1 and 2, the “left-right direction” refers to the cylinder arrangement direction with respect to the engine body E, in other words, perpendicular to the paper surface of FIG. Is the direction to the left. Further, “upstream” and “downstream” are referred to as “upstream side in the exhaust gas flow direction” and “downstream side in the exhaust gas flow direction” based on the flow direction of the exhaust gas discharged from the combustion chamber through the exhaust port. is there.

<Connection part>
The connection portion N is a tubular member that introduces exhaust gas from the exhaust manifold M into the catalyst device Q.

<Exhaust gas purification device>
As shown in FIGS. 2 to 5, the exhaust purification device Q includes a three-way catalyst 2 as an upstream side exhaust purification device connected to the outlet of the connection portion N, and a downstream side exhaust purification device disposed on the downstream side thereof. GPF (gasoline particulate filter) 3, and an L-shaped exhaust pipe 4 connecting the three-way catalyst 2 and GPF 3.

<Three-way catalyst>
The three-way catalyst 2 is a catalyst for purifying hydrocarbon HC, carbon monoxide CO, and nitrogen oxide NOx in the exhaust gas. Although the detailed description is omitted, the three-way catalyst 2 is a catalyst formed by coating a honeycomb carrier with a catalyst component formed by supporting a noble metal such as Pt, Pd, Rh on a support material made of a metal oxide. Etc. The three-way catalyst 2 is not particularly limited, and any known catalyst can be used.

  As shown in FIGS. 4 and 5, the three-way catalyst 2 is a cylindrical catalyst having a central axis L2. The shape of the three-way catalyst 2 is not particularly limited, but is preferably a cylindrical shape from the viewpoint of being easily disposed in the exhaust path and obtaining a uniform exhaust gas flow. The shape of the cross section perpendicular to the central axis L2 of the three-way catalyst 2 is not particularly limited, and any shape such as a perfect circle shape, an ellipse shape, a rectangular shape, or a polygonal shape can be adopted. From the viewpoint of obtaining an exhaust gas flow and suppressing the manufacturing cost, it is preferably a perfect circle or ellipse.

  As shown in FIG. 4, the three-way catalyst 2 is arranged so that the central axis L2 is parallel to the left-right direction (cylinder row direction).

  As shown in FIG. 5, the catalyst body for purifying the exhaust gas of the three-way catalyst 2 has an upstream end surface 2A and a downstream end surface 2B. For convenience, the end face 2A on the upstream side of the catalyst body and the end face 2B on the downstream side of the catalyst body may be referred to as the end face 2A on the upstream side of the three-way catalyst 2 and the end face 2B on the downstream side of the three-way catalyst 2. Both end faces 2A and 2B are circular with the same diameter.

  The three-way catalyst 2 includes a front stage portion 21 arranged on the upstream side and a rear stage portion 22 arranged on the downstream side as a catalyst body. The front stage 21 is a three-way catalyst excellent in low-temperature activity that purifies low-temperature exhaust gas during low-load operation of the engine body E. Further, the rear stage 22 is a three-way catalyst excellent in high-temperature activity that purifies high-temperature exhaust gas during high-load operation or the like. In the present embodiment, the three-way catalyst 2 has a two-stage configuration including the front stage portion 21 and the rear stage portion 22, but is not limited to this, and may have a single catalyst configuration, Further, it may be a multistage configuration divided into three or more.

  Further, the three-way catalyst 2 includes a mat 23 that covers the entire outer periphery of the front stage portion 21 and the rear stage portion 22 as a catalyst body, and a cylindrical case 24 that covers the entire outer periphery of the mat 23.

  The mat 23 is for stably holding the front-stage part 21 and the rear-stage part 22 as the catalyst body even in an environment exposed to high-temperature exhaust gas. For example, the mat 23 has high heat resistance and heat retention such as ceramic. It is formed with the material which has.

  The case 24 is for holding the catalyst main body (the front stage portion 21 and the rear stage portion 22) and the mat 23, and is made of a metal such as iron or stainless steel, for example. As the mat 23 and the case 24, known ones may be used.

<GPF>
As shown in FIG. 5, the GPF 3 is disposed downstream of the three-way catalyst 2 and traps particulate matter (hereinafter referred to as “PM”) in the exhaust gas that has passed through the three-way catalyst 2. A filter main body (purification device main body) 33 is provided. Although the detailed description of the filter body 33 is omitted, for example, a honeycomb carrier or the like is sealed and a filter function is added, and the filter body 33 may have a catalyst coat to promote combustion of trapped PM. Good. The PM in the exhaust gas is collected in the partition wall of the filter main body 33. When the PM is deposited, for example, after the main injection in which fuel is injected into the combustion chamber of the engine to obtain output, the filter main body in the expansion stroke of the engine Post injection for injecting fuel for increasing the temperature of 33 into the combustion chamber is performed, and PM deposited on the filter main body 33 is incinerated and removed. The filter body 33 is not particularly limited, and any known filter body can be used.

  As shown in FIGS. 1, 2, and 5, the filter body 33 has a cylindrical shape having a central axis L <b> 3. The shape of the filter main body 33 is not particularly limited, but is preferably cylindrical from the viewpoint of easy disposition in the exhaust path and obtaining a uniform exhaust gas flow. The shape of the cross section perpendicular to the central axis L3 of the filter body 33 is not particularly limited, and any shape such as a perfect circle shape, an ellipse shape, a rectangular shape, or a polygonal shape can be adopted. From the viewpoint of obtaining a gas flow and reducing the manufacturing cost, it is preferably a perfect circle or ellipse.

  As shown in FIG. 2, the GPF 3 is arranged such that the central axis L3 is in a direction substantially perpendicular to the front-rear direction, that is, the left-right direction (cylinder row direction).

  As shown in FIG. 5, the filter body 33 of the GPF 3 has an upstream end surface 3A and a downstream end surface 3B. For convenience, the end face 2A on the upstream side of the filter body 33 and the end face 2B on the downstream side of the filter body 33 may be referred to as the end face 2A on the upstream side of the GPF 3 and the end face 2B on the downstream side of the GPF 3. Both end surfaces 3A and 3B are circular with the same diameter.

  Similar to the three-way catalyst 2, the GPF 3 includes a filter main body 33, a mat 34 that covers the entire outer periphery of the filter main body 33, and a cylindrical case 35 that covers the entire outer periphery of the mat 34. The mat 34 and the case 35 are used for the same purpose as the mat 23 and the case 24 of the three-way catalyst 2 described above, and those having the same configuration can be used.

<L-shaped exhaust pipe>
The L-shaped exhaust pipe 4 is a tubular member bent in an L-shape for connecting the three-way catalyst 2 and the GPF 3 and forms a part of the exhaust path.

  As shown in FIG. 5, the L-shaped exhaust pipe 4 includes an upstream opening 4A, a downstream opening 4B, and a bent portion 4C between the openings 4A and 4B.

  As shown in FIG. 5, the three-way catalyst 2 has a downstream portion inserted into the L-shaped exhaust pipe 4 from the upstream opening 4A. On the other hand, the upstream end of the GPF 3 is inserted into the L-shaped exhaust pipe 4 from the downstream opening 4B.

  The end face 2B on the downstream side of the three-way catalyst 2 and the end face 3A on the upstream side of the GPF 3 are arranged so that the dihedral angle α is about 90 degrees in the bent portion 4C. The dihedral angle α is not limited to this angle, but from the viewpoint of sufficiently securing the exhaust gas flow from the three-way catalyst 2 to the GPF 3, it is preferably 60 degrees or more and 120 degrees or less, more preferably It is 70 degrees or more and 110 degrees or less, Most preferably, they are 80 degrees or more and 100 degrees or less.

  In addition, the three-way catalyst 2 and the GPF 3 are disposed so that the downstream portion of the three-way catalyst 2 overlaps a part of the upstream end surface of the GPF 3 when viewed in the axial direction of the GPF 3. That is, an overlapping portion 31 is formed between the three-way catalyst 2 and the GPF 3.

  FIG. 5 is a view showing a VV cross section in FIG. 1, and is a view of a cross section including the central axis L2 of the three-way catalyst 2 and parallel to the central axis L3 of the GPF 3 as viewed from above. The cross section described in FIG. 5 is hereinafter referred to as “VV cross section” (cross section). As shown in FIG. 5, the length H31 of the side surface of the three-way catalyst 2 forming the overlapping portion 31 on the VV cross section is the exhaust gas in the GPF 3 while arranging the three-way catalyst 2 and the GPF 3 in a compact manner. From the viewpoint of making the flow uniform, the total length H2 of the three-way catalyst 2 is preferably 10% or more and less than 50%.

  Further, the length H31 of the side surface of the three-way catalyst 2 is determined from the viewpoint of making the exhaust gas flow in the GPF 3 uniform while arranging the three-way catalyst 2 and the GPF 3 compactly in the VV cross section of FIG. The width W3 is preferably 10% or more and less than 50%.

  As described above, when the three-way catalyst 2 and the GPF 3 are arranged in the lateral direction, the overlapping portion 31 of the three-way catalyst 2 and the GPF 3 is formed, thereby reducing the distance from the downstream end of the exhaust manifold M to the GPF 3. Can be In addition, while forming the overlapping portion 31, by suppressing the range to less than the above range, the exhaust device 1 can be made compact, and the use efficiency of the GPF 3, particularly the portion that becomes a shadow of the overlapping portion 31, can be improved. Can be made.

<Downstream end of GPF>
As shown in FIG. 5, at the downstream end 7 of the GPF 3, there is an exhaust gas discharge pipe 5 that is an outlet of the exhaust gas that has passed through the GPF 3, and EGR that recirculates a part of the exhaust gas to the intake side as EGR gas. A gas outlet pipe 6 is attached.

<Exhaust gas exhaust pipe>
The exhaust gas discharge pipe 5 is for guiding the exhaust gas that has passed through the GPF 3 to the downstream exhaust system, and for collecting and removing moisture generated by the purification of the exhaust gas by the three-way catalyst 2 and the GPF 3.

  A line indicated by a symbol PRL31 shown in FIG. 5 (a cross-sectional view taken along the line VV in FIG. 1) is a projection line on the VV cross section of the central axis L3 of the GPF3. A line indicated by a symbol L5 indicates the central axis of the exhaust gas discharge pipe 5. The point indicated by reference sign P5 is a point on the central axis L5 of the exhaust gas discharge pipe 5 and indicates the center of the inlet of the exhaust gas discharge pipe 5.

  As shown in FIG. 5, the center position P5 of the exhaust gas discharge pipe 5 is biased to the right side of the projection line PRL31 on the VV cross section of the GPF central axis L3 of the GPF 3, that is, to the three-way catalyst 2 side. . According to this structure, the flow which goes to the exhaust-gas exhaust pipe 5 arises about the exhaust gas which flowed into GPF3. If it does so, the amount of exhaust gas which flows into the part which becomes the shadow of the duplication part 31 will increase with the flow which goes to the exhaust-gas exhaust pipe 5. FIG. Thus, the utilization efficiency of GPF 3 can be improved.

  As shown in FIG. 5, the amount of deviation of the exhaust gas discharge pipe 5 is sufficient from the viewpoint of improving the utilization efficiency of the GPF 3 by sufficiently securing the amount of exhaust gas flowing into the shadowed portion of the overlapping portion 31. Preferably, on the VV cross section, the right side surface 5A on the three-way catalyst 2 side of the exhaust gas discharge pipe 5 is positioned on the right side of the GPF side surface 3C on the three-way catalyst 2 side of the GPF 3, that is, on the three-way catalyst 2 side. It can be set to the extent to do. At this time, from the viewpoint of suppressing an increase in ventilation resistance in the vicinity of the exhaust gas exhaust pipe 5, the left side surface 5B of the exhaust gas exhaust pipe 5 is more than the GPF side surface 3C on the three-way catalyst 2 side of the GPF 3 on the VV cross section. It is preferable to set the amount of deviation of the exhaust gas discharge pipe 5 to such an extent that it is located on the left side.

<EGR gas outlet pipe>
The engine body E has an EGR that recirculates part of the exhaust gas to the engine intake system for the purpose of preventing knocking and reducing the amount of nitrogen oxides NOx. An EGR gas extraction pipe 6 for exhaust gas is connected to the section.

  As shown in FIG. 5, the EGR gas extraction pipe 6 is disposed on the opposite side of the exhaust gas discharge pipe 5 with respect to the projection line PRL31 on the VV cross section and spaced apart from the exhaust gas discharge pipe 5. ing. According to this configuration, a sufficient amount of exhaust gas for EGR can be secured, and the flow of exhaust gas in the GPF 3 can be dispersed and uniformized on the exhaust gas discharge pipe 5 side and the EGR gas extraction pipe 6 side. Can do. Therefore, the utilization efficiency / function / performance of the GPF 3 can be further improved.

<Exhaust manifold>
Exhaust gas discharged from the four combustion chambers of the engine through the exhaust port is sent from the exhaust manifold M to the catalyst device Q through the connection portion N.

  As shown in FIG. 2, the exhaust manifold M has four independent ports connected to the exhaust ports of the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder (all not shown) of the engine body E. Exhaust pipes, that is, the first independent exhaust pipe M1 (independent exhaust pipe on one end side in the cylinder row direction), the second independent exhaust pipe M2 (remaining independent exhaust pipe), and the third independent exhaust pipe M3 (remaining independent exhaust pipe) ) And a fourth independent exhaust pipe M4 (remaining independent exhaust pipe).

  As shown in FIGS. 1, 3, and 4, the exhaust manifold M is disposed on one end side in the cylinder row direction of the engine body, and extends downward from the distal end portion of the independent exhaust pipe M <b> 1 on one end side in the cylinder row direction. A collecting pipe M5 is provided.

  The exhaust manifold M guides exhaust gas flowing out from the remaining independent exhaust pipes M2 to M4 out of the plurality of independent exhaust pipes toward the independent exhaust pipe M1 on one end side and guides it to the collecting pipe M5. A guide tube M6 extending in the direction is provided. The guide pipe M6 is connected to the distal end side of the second independent exhaust pipe M2, the third independent exhaust pipe M3, and the fourth independent exhaust pipe M4, and is connected to the connection position between the first independent exhaust pipe M1 and the collecting pipe M5. Has been.

  An L-shaped bent portion M50 that is bent in an L shape in the lateral direction (leftward) is formed at the lower portion of the collecting pipe M5 so that the exhaust gas is directed toward the end face 2A on the upstream side of the three-way catalyst 2. As shown in FIG. 6, the downstream end outlet of the L-shaped bent portion M50, that is, the downstream end outlet M7 of the collecting pipe M5 is connected to the three-way catalyst 2 via the connecting portion N. The downstream end outlet M7 is circular, and the opening surface of the outlet M7 is parallel to the upstream end face 2A of the three-way catalyst 2.

  As shown in FIGS. 6 and 7, on the lower surface side (lower half circumference side) of the L-shaped bent portion M50 of the collecting pipe M5, an arcuate recess M51 whose radius is larger than that of the downstream end outlet M7 of the collecting pipe M5. Is provided.

  Further, the flow of the exhaust gas flowing into the collecting pipe M5 from the guide pipe M6 is changed to the central portion of the upstream end face 2A of the three-way catalyst 2 on the wall surface on one end side in the cylinder row direction in the collecting pipe M5. An outwardly bulging portion M52 is formed.

  As shown in FIG. 4, FIG. 6, etc., the collecting pipe M5 is formed by fitting the right collecting pipe M5A and the left collecting pipe M5B, and the arcuate recess M51 is formed in the fitting part. Yes. The collecting pipe M5 may be divided into a plurality of parts as described above, or may be integrally formed.

<About the functions of the arc-shaped concave portion and the bulging portion>
FIG. 10 shows the flow of exhaust gas when the arcuate recess M51 and the bulge M52 are not formed.

  In general, it is known that a fluid such as exhaust gas tends to flow along a curved surface having a large curvature radius. Therefore, the exhaust gas discharged from the first independent exhaust pipe M1 on the one end side in the cylinder row direction mainly flows through the first independent exhaust pipe M1 toward the front end portion, mainly due to inertia in the collecting pipe M5. The independent exhaust pipe M1 flows downward along the collecting pipe M5 along the wall surface continuing from the front end side.

  Then, the exhaust gas reaches the L-shaped bent portion M50 and changes its flow direction toward the three-way catalyst 2, as indicated by a broken line arrow in FIG. It becomes easy to hit the lower part of the end face 2A.

  Exhaust gas discharged from an independent exhaust pipe other than the first independent exhaust pipe M1, for example, the second independent exhaust pipe M2, flows in the direction of the cylinder row by passing through the guide pipe M6 and flows into the collecting pipe M5.

  Accordingly, the exhaust gas flows downward in the collecting pipe M5 mainly along the wall surface on one end side in the cylinder row direction in the collecting pipe M5, as indicated by a one-dot chain line arrow in FIG. Therefore, the exhaust gas changes in the L-shaped bent portion M50 so that the flow direction is directed to the three-way catalyst 2 in the same manner as the exhaust gas flow from the first independent exhaust pipe M1. It becomes easy to hit the lower portion of the upstream end surface 2A. The exhaust gas discharged from the third and fourth independent exhaust pipes M3 and M4 has the same flow as the exhaust gas discharged from the second independent exhaust pipe M2.

  FIG. 6 shows an exhaust gas flow when the arcuate recess M51 and the bulging portion M52 are provided in the collecting pipe M5.

  As indicated by solid arrows in FIG. 6, the exhaust gas discharged from the first independent exhaust pipe M1 mainly collects along the wall surface continuing from the front end side of the first independent exhaust pipe M1 in the collection pipe M5 due to inertia. It flows down M5 and reaches the L-shaped bend M50.

  An arcuate recess M51 having a larger radius than the downstream end outlet (downstream end outlet of the L-shaped bent portion M50) M7 of the collecting pipe M5 is formed on the lower surface side of the L-shaped bent portion M50. Accordingly, the exhaust gas that has reached the L-shaped bent portion M50 flows and rises along the concave bottom wall surface of the arc-shaped concave portion M51 due to inertia, as indicated by the solid line arrow in FIG. It flows into the three-way catalyst 2 while turning around the axis. Therefore, it becomes easy for the exhaust gas to strike the entire end face 2A on the upstream side of the three-way catalyst 2 evenly.

  As indicated by solid arrows in FIG. 8, the exhaust gas discharged from the second to fourth independent exhaust pipes M2 to M4 flows through the guide pipe M6 in the cylinder row direction and flows into the collecting pipe M5.

  Therefore, due to inertia, the exhaust gas flows downward along the collecting pipe M5 along the wall surface of the collecting pipe M5 in the cylinder row direction, and reaches the wall surface of the bulging portion M52. Then, the exhaust gas is guided by the wall surface of the bulging portion M <b> 52 and the flow direction is changed so as to go to the center of the end surface 2 </ b> A on the upstream side of the three-way catalyst 2. Therefore, the exhaust gas easily hits the entire end face 2A on the upstream side of the three-way catalyst 2 evenly.

<About the curved portion of the guide tube>
As shown in FIGS. 2 and 3, the guide pipe M6 is curved in the direction in which the first independent exhaust pipe M1 on one end side protrudes from the engine body on one end side in the cylinder row direction. A bending portion M61 connected to the distal end portion of M1 is provided.

  Therefore, when the exhaust gas discharged from the second to fourth independent exhaust pipes M2 to M4 flows into the collecting pipe M5 from the guide pipe M6, the curved portion M61 causes the exhaust gas flow direction to change from the cylinder row direction. It will change so that it may approach the protrusion direction of 1 independent exhaust pipe M1.

  As a result, the exhaust gas flowing into the collecting pipe M5 from the guide pipe M6 continues to the tip of the first independent exhaust pipe M1 in the same manner as the exhaust gas flowing into the collecting pipe M5 from the first independent exhaust pipe M1 on one end side. It becomes easy to flow down the collecting pipe M5 along the wall surface. Therefore, it becomes easy to induce a swirling flow of the exhaust gas by the arc-shaped recess M51, and the exhaust gas easily hits the entire end face 2A on the upstream side of the three-way catalyst 2 evenly.

  As described above, the exhaust gas easily hits the entire end face 2A on the upstream side of the three-way catalyst 2 by the arc-shaped concave portion M51, the bulging portion M52, and the curved portion M61. It is effectively used for purification of exhaust gas, and therefore, purification of exhaust gas easily proceeds.

<About the oxygen sensor>
An oxygen sensor base M53 is formed on the wall surface facing the downstream end outlet M7 of the collecting pipe M5 and below the bulging portion M52. The pedestal M53 is provided with an oxygen sensor 93 (oxygen concentration detection means), and the oxygen concentration detection portion of the oxygen sensor 93 projects into the internal space of the L-shaped bent portion M50.

  Below the bulging portion M52 in the collecting pipe M5 is where the exhaust gas flowing downward along the wall surface on one end side in the cylinder row direction of the collecting pipe M5 and the exhaust gas swirling and rising by the arc-shaped recess M51 are combined. High exhaust gas homogeneity. Therefore, the detection of the oxygen concentration below the bulging portion M52 increases the reliability of the oxygen concentration obtained by the detection.

(Embodiment 2)
Hereinafter, Embodiment 2 according to the present invention will be described in detail. In the description of the second embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment, both the arc-shaped concave portion M51 and the bulging portion M52 are provided in the collecting pipe M5. However, in the second embodiment, only the arc-shaped concave portion M51 is provided as shown in FIG. Since the collecting pipe M5 does not include the bulging portion M52, the forming becomes easy.

  When the bulging portion M52 is not provided, the exhaust gas flowing into the collecting pipe M5 from the guide pipe M6 tends to flow downward through the collecting pipe M5 as indicated by a one-dot chain line arrow in FIG. However, the exhaust gas flowing in such a manner also flows into the collecting pipe M5 downward along the wall surface continuing from the front end side of the first independent exhaust pipe M1 in the collecting pipe M5, and the exhaust gas swirling and rising by the arcuate recess 51. By combining, it is possible to avoid concentrating on the lower side of the L-shaped bent portion M50, and thus concentrating on the lower side of the end face 2A on the upstream side of the three-way catalyst 2.

  In particular, also in the second embodiment, in the case where the curved portion M61 is provided, when the exhaust gas flows into the collecting tube M5 from the guide tube M6, the flow direction of the exhaust gas is changed from the cylinder row direction by the curved portion M61. It changes so that it may approach the protrusion direction of the 1st independent exhaust pipe M1. Therefore, since the amount of exhaust gas swirled and raised by the arc-shaped concave portion 51 increases, even when the bulging portion M52 is not provided, the exhaust gas is located on the lower side of the L-shaped bent portion M50, and thus the three-way catalyst 2 Concentration on the lower side of the upstream end face 2A can be avoided.

(Other embodiments)
In the first and second embodiments, the upstream side exhaust purification device is the three-way catalyst 2 and the downstream side exhaust purification device is the GPF 3, but the exhaust purification device is not limited to such a configuration, and various purification devices are adopted. be able to. For example, when the exhaust device 1 is applied to a diesel engine, a diesel particulate filter may be employed instead of the GPF. Further, an oxidation catalyst may be employed as the upstream side exhaust purification device, and a NOx purification catalyst may be employed as the downstream side exhaust purification device, or vice versa.

In the first and second embodiments, the collecting pipe M5 of the exhaust manifold M is arranged on the first cylinder side. However, the collecting pipe M5 is arranged on the fourth cylinder side, and the upstream end face 2A of the three-way catalyst 2 is used. May be configured to be on the left side.
(Evaluation of gas contact performance for three-way catalyst)
A computational fluid dynamics (CFD) model was created and analyzed. Based on the analysis result, the flow velocity, pressure, temperature, etc. of the exhaust gas flowing into the three-way catalyst 2 are estimated, and the uniformity per gas of each cylinder is determined from the flow velocity distribution of the exhaust gas at the three-way catalyst start end surface 2A. Was evaluated as an improvement index per gas. The results are shown in FIG.

  In addition, in Comparative Example 1, Example 1 and Example 2, when neither the arc-shaped concave portion M51 and the bulging portion M52 shown in FIG. 10 are formed, only the arc-shaped concave portion M51 shown in FIG. 9 is formed. This is a result when both the arc-shaped concave portion M51 and the bulging portion M52 shown in FIG. 6 are formed.

  As shown in FIG. 11, in the first and second embodiments, the uniformity per exhaust gas from one or more cylinders is improved and the homogeneity per exhaust gas from all cylinders is improved compared to the first comparative example. You can see that

  Specifically, on the basis of the comparative example 1, the improvement index per gas improved about 30% and about 50% in the first cylinder in the example 1 and the example 2, respectively.

  In the second cylinder, the improvement index per gas was improved by about 50% and about 7.5% in Example 1 and Example 2, respectively.

  In the third cylinder, the improvement index per gas was about 160% lower and equivalent in Examples 1 and 2.

  In the fourth cylinder, the improvement index per gas in Example 1 was almost the same, but in Example 2, it improved about 10%.

  Moreover, when the difference between the maximum value and the minimum value of the improvement index per gas is evaluated, about 50% and about 70% difference are small in Example 1 and Example 2, respectively, based on Comparative Example 1. The homogeneity per exhaust gas from the above etc. was improved.

  In this way, in particular, in the third cylinder of the first embodiment, although the per-gas uniformity is reduced, the per-gas per unit of the three-way catalyst start face 2A of the exhaust gas flow from all the cylinders is greatly homogenized. I found out.

  INDUSTRIAL APPLICABILITY The present invention is extremely useful because it can improve the uniformity per gas with respect to an exhaust purification device in an engine exhaust device.

1 Engine exhaust system 2 Three-way catalyst (upstream exhaust purification system)
2A End face 2B upstream of the three-way catalyst End face 3 downstream of the three-way catalyst 3 GPF (downstream exhaust purification device)
3A Upstream end face 3B of GPF Downstream end face 4 of GPF L-shaped exhaust pipe 4A Upstream side opening 4B Downstream side opening 4C Bending part 5 Exhaust gas discharge pipe 6 EGR gas extraction pipe 31 Overlapping part 33 Filter body (purifier) Body)
E Engine L2 Center axis of three-way catalyst L3 Center axis of GPF L5 Center axis of exhaust gas discharge pipe M Exhaust manifold M1 First independent exhaust pipe (independent exhaust pipe on one end side)
M2 Second independent exhaust pipe (remaining independent exhaust pipe)
M3 Third independent exhaust pipe (remaining independent exhaust pipe)
M4 4th independent exhaust pipe (remaining independent exhaust pipe)
M5 Collecting pipe M6 Guide pipe M7 Downstream end outlet M50 L-shaped bent part M51 Arc-shaped recessed part M52 Swelling part M61 Curved part N Connecting part

Claims (5)

An exhaust manifold connected to an exhaust port of an in-line multi-cylinder engine having an engine body with a plurality of cylinders;
An exhaust system for an engine comprising an exhaust purification device connected to a downstream side of the exhaust manifold in the exhaust gas flow direction,
The exhaust manifold is
A plurality of independent exhaust pipes connected to each exhaust port of the engine body;
A collecting pipe that is disposed on one end side in the cylinder row direction of the engine body and extends downward from a distal end portion of the independent exhaust pipe on one end side in the cylinder row direction among the plurality of independent exhaust pipes;
A guide pipe extending in the cylinder row direction for guiding exhaust gas flowing out from each of the remaining independent exhaust pipes of the plurality of independent exhaust pipes toward the independent exhaust pipe on the one end side and guiding it to the collecting pipe;
An L-shaped bent portion formed in a lower portion of the collecting pipe and bent in an L-shape in the lateral direction so that the exhaust gas is directed toward the upstream end face of the exhaust purification device;
Exhaust gas that is formed on the lower surface side of the L-shaped bent portion of the collecting pipe and flows down the collecting pipe along the wall surface continuing downward from the distal end side of the independent exhaust pipe on the one end side of the collecting pipe, An outlet of the L-shaped bent portion that opens toward the exhaust purification device for facilitating swirling of the exhaust gas so as to flow into the exhaust purification device while turning around the axis of the exhaust purification device An exhaust system for an engine comprising an arc-shaped recess having a larger radius than that of the engine. In claim 1,
An outer wall that changes the flow of exhaust gas flowing from the guide pipe into the collecting pipe toward the central portion of the upstream end face of the exhaust purification device on the wall surface on one end side in the cylinder row direction of the collecting pipe. An exhaust system for an engine, comprising a bulge portion. In claim 1 or claim 2,
The guide pipe includes a curved portion at one end side in the cylinder row direction, curved in a protruding direction from the engine main body of the independent exhaust pipe on the one end side, and connected to a distal end portion of the independent exhaust pipe on the one end side. An exhaust system for an engine. In claim 2 or claim 3 quoting claim 2,
An exhaust system for an engine, wherein oxygen concentration detection means is provided below the bulging portion of the collecting pipe. In any one of Claims 1 thru | or 4,
Further comprising a downstream exhaust purification device provided downstream of the exhaust purification device in the exhaust gas flow direction,
The exhaust purification device and the downstream side exhaust purification device have their central axes substantially orthogonal to each other, and when viewed in the axial direction of the downstream side exhaust purification device, the downstream portion of the exhaust purification device is the downstream side exhaust purification device. An exhaust system for an engine, wherein the exhaust system is disposed so as to overlap a part of an upstream end face of the engine.

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