JP6500967B2 - Engine exhaust system - Google Patents

Description

  The present invention relates to an exhaust system of 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 provided with 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 to a catalyst. Is connected between the exhaust port and the catalyst (see, for example, Patent Document 1).

Japanese Utility Model Application Publication No. 1-39418

  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 flow lines from the cylinder at one end and exhausts from the other cylinders There is a possibility that the streamlines may be significantly different, resulting in uneven gas contact to the catalyst.

Therefore, even when the present invention adopts an exhaust manifold for guiding the exhaust gas from the cylinder side on one end side of the engine in the cylinder row direction toward the exhaust purification device below, particularly, a catalyst as the exhaust purification device the even when its center axis is arranged parallel to the cylinder row direction, it is an object to improve the uniformity of gas per to said exhaust gas purification apparatus.

  In order to solve the above problems, in the present invention, the exhaust manifold is provided with an arc-shaped recess or the like for enhancing the uniformity of the gas per contact.

The exhaust system of the engine disclosed herein comprises an exhaust manifold connected to an exhaust port of an in-line multi-cylinder engine having an engine body provided with a plurality of cylinders;
And a catalyst as an exhaust gas purification device , which is connected to the downstream side of the exhaust gas flow direction of the exhaust manifold and disposed so that the central axis is parallel to the cylinder row direction .
The exhaust manifold is
A plurality of independent exhaust pipes connected to respective exhaust ports of the engine body;
A collective pipe disposed at one end side of the engine body in the cylinder row direction and extending downward from the tip of the independent exhaust pipe at one end side of the plurality of independent exhaust pipes in the cylinder row direction;
A guide pipe extending in a cylinder row direction for guiding exhaust gas flowing out from the remaining independent exhaust pipes of the plurality of independent exhaust pipes toward the one end side independent exhaust pipe and guiding the exhaust gas to the collecting pipe;
An L-shaped bent portion which is formed in a lower portion of the collecting pipe and which is bent in an L shape in a lateral direction so that exhaust gas is directed to the upstream end face of the exhaust gas purification device;
Exhaust gas flowing downward through the collecting pipe along a wall surface which is formed on the lower surface side of the L-shaped bent portion of the collecting pipe and continues downward from the tip end side of the independent exhaust pipe on the one end side of the collecting pipe is An outlet of the L-shaped bent portion opened toward the exhaust gas purification device for promoting swirling of the exhaust gas so as to flow into the exhaust gas purification device while swirling around the axis of the exhaust gas purification device It is characterized by including an arc-shaped recess having a larger radius than that of the first embodiment.

  According to this, the exhaust gas emitted from the exhaust port at one end side in the cylinder row direction of the engine body flows directly into the collecting pipe through the independent exhaust pipe at the one end side. The collecting pipe extends downward from the tip of the independent exhaust pipe. Therefore, the exhaust gas flows mainly down the collecting pipe along the wall surface continuing from the tip side of the independent exhaust pipe in the collecting pipe due to inertia when flowing toward the tip of the independent exhaust pipe. Reaches the L-shaped bend. On the lower surface side of the L-shaped bent portion, an arc-shaped recessed portion having a radius larger than the outlet of the L-shaped bent portion is formed. Therefore, the exhaust gas flowing downward along the wall surface continuing from the tip side of the independent exhaust pipe of the collecting pipe flows upward along the recessed bottom wall surface of the arc-shaped recess due to inertia, and the shaft center of the exhaust gas purification device It swirls around and flows into the exhaust purification system. Therefore, the exhaust gas can be easily hit evenly over the entire upstream end surface of the exhaust gas purification device.

  On the other hand, the exhaust gas coming out of the remaining independent exhaust pipes except for the independent exhaust pipe on the one end side flows in the cylinder row direction by flowing through the guide pipe and flows into the collecting pipe. Therefore, unlike the exhaust gas emitted from the independent exhaust pipe at one end, the exhaust gas easily flows down the collecting pipe along the wall surface at one end in the cylinder row direction in the collecting pipe. The exhaust gas flowing in such a manner also flows downward along the wall surface along the wall surface continuing from the tip side of the independent exhaust pipe on the one end side in the collecting pipe, and is combined with the exhaust gas rising in a circular flow in the arc-shaped recess. Thus, the concentration of the exhaust gas on the lower side of the L-shaped bent portion and the concentration of the exhaust gas on the lower side of the upstream end surface of the exhaust gas purification device can be avoided.

  As described above, according to the exhaust system, the swirling flow of the exhaust gas is induced by the arc-shaped concave portion although the collective pipe extends downward from the independent exhaust pipe at one end side in the cylinder row direction. As a result, the exhaust gas easily strikes uniformly over the entire end face on the upstream side of the exhaust gas purification apparatus, and the exhaust gas purification apparatus efficiently purifies the exhaust gas.

  In one embodiment, a flow of exhaust gas flowing from the guide pipe into the collecting pipe is directed to a central portion of an end face on the upstream side of the exhaust purification device on a wall surface on one end side in the cylinder row direction in the collecting pipe It has an outward bulging part that changes to.

  According to this, since it is avoided that the exhaust gas flowing into the collecting pipe from the guide pipe is concentrated at the lower part of the end face on the upstream side of the exhaust gas purification device, the exhaust gas is easily hit evenly over the entire end face on the upstream side.

  In one embodiment, the guide pipe is curved on one end side of the cylinder row direction in a direction in which the independent exhaust pipe on the one end side protrudes from the engine body and is continuous with a tip of the independent exhaust pipe on the one end side It has a department.

  According to this, when the exhaust gas flows from the guide pipe into the collecting pipe, the curved portion changes the flow direction of the exhaust gas from the cylinder row direction so as to approach the projecting direction of the independent exhaust pipe on one end side. Thus, the exhaust gas flowing into the collecting pipe from the guide pipe is collected along the wall surface continuing to the tip of the independent exhaust pipe on the one end side, like the exhaust gas flowing into the collecting pipe from the independent exhaust pipe on one end side. It becomes easy to flow downward. Therefore, it becomes easy to induce the swirling flow of the exhaust gas by the arc-shaped concave portion, and the exhaust gas easily contacts the entire upstream end surface of the exhaust gas purification device uniformly.

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

  Below the bulging portion in the collecting pipe, the exhaust gas flowing downward along the wall surface at one end side in the cylinder row direction of the collecting pipe and the exhaust gas that swirls and rises by the arc-shaped concave part are combined. Sex is high. 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, the exhaust gas purification apparatus further comprises a downstream exhaust gas purification apparatus provided downstream of the exhaust gas purification apparatus in the exhaust gas flow direction,
When the exhaust gas purification device and the downstream side exhaust gas purification device cross each other's central axes and viewed in the axial direction of the downstream side exhaust gas purification device, the downstream portion of the exhaust gas purification device is the downstream side exhaust gas purification device. It is arrange | positioned so that it may become a relationship which overlaps with a part of end surface by the side of an upstream.

  According to this, the distance from the exhaust manifold to the downstream side catalyst device can be shortened, which is advantageous for making the exhaust device compact, and allows the exhaust gas to flow into the downstream side exhaust purification device in a state where the temperature is not significantly lowered. It is advantageous to secure the exhaust gas purification performance.

  With regard to “intersecting central axes of each other”, it is preferable that both central axes be substantially orthogonal (an angle between the central axes be 80 degrees or more and 100 degrees or less).

  As described above, according to the present invention, although the collecting pipe extends downward from the independent exhaust pipe at one end side in the cylinder row direction, the swirling flow of the exhaust gas is induced by the arc-shaped concave portion As a result, the exhaust gas easily strikes uniformly over the entire end face on the upstream side of the exhaust gas purification apparatus, and the exhaust gas purification apparatus efficiently purifies the exhaust gas.

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

  Hereinafter, embodiments of the present invention will be described in detail based on 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 applications or its uses.

(Embodiment 1)
<Engine>
The engine to which the exhaust system 1 according to the first embodiment is applied is an in-line four-cylinder gasoline engine (in-line multi-cylinder engine) mounted in a car. 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 applicable not only to FF vehicles, but also to vehicles adopting various layouts including motorcycles, such as RR vehicles and 4WD vehicles.

  As shown in FIG. 1, the engine comprises an engine body E having a cylinder block E1 and a cylinder head E2. Although not shown in detail, the engine includes first to fourth cylinders each including a cylinder block E1 and a cylinder head E2. The first to fourth cylinders are disposed in series in order from the front to the back of the paper surface in the direction perpendicular to the paper surface of FIG. 1. A combustion chamber is formed for each cylinder by the cylinder bore (not shown) of the cylinder block E1, the piston (not shown) in the cylinder bore, and the cylinder head E2.

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

<Exhaust route>
As shown in FIG. 1 and FIG. 2, the exhaust device 1 according to the present embodiment is connected to the above-mentioned exhaust port, and a downstream exhaust system (not shown) having a tail pipe is further connected downstream thereof. It is done. As described above, the exhaust path of the engine is configured by the above-described exhaust port, the exhaust device 1, and the downstream exhaust system.

<Exhaust device>
In the exhaust system 1 according to the present embodiment, as shown in FIGS. 1 to 4, a connecting portion N is provided at an exhaust manifold M connected to four exhaust ports of an engine body E and a downstream end outlet M7 of the exhaust manifold M. An exhaust gas purification device Q, an exhaust gas discharge pipe 5 and an EGR gas extraction pipe 6 connected via the same are provided.

  Each component will be described in detail below. The configuration of the exhaust manifold M will be described later.

<Direction>
In the description of the present specification, "vertical direction" and "longitudinal direction" refer to the cylinder head E2 side on the upper side, the cylinder block E1 side on the lower side, the engine body with reference to the engine body E, as shown in FIG. The E side is the front side, and the exhaust manifold M side is the rear side. Further, as shown in FIG. 1 and FIG. 2, “left and right direction” is the arrangement direction of cylinders with reference to the engine main body E, in other words, perpendicular to the sheet of FIG. The direction which makes the left side shall be said. Furthermore, “upstream” and “downstream” may be referred to as “exhaust gas flow direction upstream” or “exhaust gas flow direction downstream” based on the flow direction of exhaust gas discharged from the combustion chamber through the exhaust port. is there.

<Connection section>
The connection portion N is a tubular member for introducing the exhaust gas from the exhaust manifold M into the catalyst device Q.

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

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 three-way catalyst 2 is not described in detail, for example, a catalyst obtained by coating a catalyst component formed by supporting a noble metal such as Pt, Pd, Rh or the like on a support material made of a metal oxide on a honeycomb support Etc. The three-way catalyst 2 is not particularly limited, and any known catalyst can be used.

  The three-way catalyst 2 is a cylindrical catalyst having a central axis L2 as shown in FIGS. 4 and 5. The shape of the three-way catalyst 2 is not particularly limited, but is preferably cylindrical from the viewpoint of easy arrangement in the exhaust path and obtaining 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 circular shape, an elliptical shape, a rectangular shape, or a polygonal shape can be adopted. From the viewpoint of obtaining the exhaust gas flow and suppressing the manufacturing cost, it is preferably a perfect circle or an ellipse.

  As shown in FIG. 4, the three-way catalyst 2 is disposed such that the central axis L2 is parallel to the left-right direction (the 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 face 2A and a downstream end face 2B. For convenience, the upstream end face 2A of the catalyst body and the downstream end face 2B of the catalyst body may be referred to as the upstream end face 2A of the three-way catalyst 2 and the downstream end face 2B of the three-way catalyst 2. Both end faces 2A and 2B are circular with the same diameter.

  The three-way catalyst 2 includes, as a catalyst main body, a front stage 21 disposed upstream and a rear stage 22 disposed downstream. The front stage 21 is a three-way catalyst excellent in low-temperature activity, which purifies low-temperature exhaust gas at low load operation of the engine body E. Further, the rear part 22 is a three-way catalyst excellent in high temperature activity for purifying high temperature exhaust gas at high load operation and the like. In the present embodiment, the three-way catalyst 2 has a two-stage configuration including the front stage 21 and the rear stage 22. However, the present invention is not limited to this, and a single catalyst configuration may be used. Furthermore, it may be a multistage configuration divided into three or more.

  The three-way catalyst 2 further includes a mat 23 covering the entire outer periphery of the front stage 21 and the rear stage 22 as a catalyst main body, and a cylindrical case 24 covering the entire outer periphery of the mat 23.

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

  The case 24 is for holding the catalyst main body (the front part 21 and the rear part 22) and the mat 23, and is made of metal such as iron or stainless steel. In addition, as the mat 23 and the case 24, you may use a well-known thing.

<GPF>
As shown in FIG. 5, GPF 3 is disposed downstream of the three-way catalyst 2, and particulate matter (hereinafter referred to as “PM”) in the exhaust gas that has passed through the three-way catalyst 2 is trapped. A filter main body (purifying device main body) 33 is provided. The detailed description of the filter body 33 is omitted, but for example, the honeycomb carrier etc. is sealed to add a filter function, and even if it has a catalyst coat to promote the combustion of trapped PM. Good. The PM in the exhaust gas is collected in the partition wall of the filter body 33, and when the PM is deposited, for example, after the main injection of injecting the fuel to the combustion chamber of the engine to obtain the output, the filter body Post injection for injecting fuel into the combustion chamber to raise the temperature of 33 is performed to incinerate and remove PM deposited on the filter body 33. The filter body 33 is not particularly limited, and any known one can be used.

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

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

  As shown in FIG. 5, the filter body 33 of the GPF 3 has an upstream end face 3A and a downstream end face 3B. For convenience, the upstream end face 2A of the filter body 33 and the downstream end face 2B of the filter body 33 may be referred to as the upstream end face 2A of the GPF 3 and the downstream end face 2B 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 body 33, a mat 34 covering the entire outer periphery of the filter body 33, and a cylindrical case 35 covering 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 an exhaust path.

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

  As shown in FIG. 5, the downstream portion of the three-way catalyst 2 is inserted into the L-shaped exhaust pipe 4 from the upstream opening 4A. On the other hand, the GPF 3 has its upstream end 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 disposed in the bend 4C so that the dihedral angle α is approximately 90 degrees. 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, the mutual angles are preferably 60 degrees or more and 120 degrees or less, more preferably 70 degrees or more and 110 degrees or less, particularly preferably 80 degrees or more and 100 degrees or less.

  In addition, the three-way catalyst 2 and the GPF 3 are disposed such that the downstream portion of the three-way catalyst 2 overlaps with a part of the end face on the upstream side of the GPF 3 when viewed in the axial direction of the GPF 3. That is, the overlapping portion 31 is formed on the three-way catalyst 2 and the GPF 3.

  FIG. 5 is a view showing a V-V cross section in FIG. 1, but is a view from the upper side of a cross section including the central axis L2 of the three-way catalyst 2 and parallel to the central axis L3 of GPF3. The cross section described in FIG. 5 is hereinafter referred to as “V-V cross section” (cross section). As shown in FIG. 5, the side length H31 of the three-way catalyst 2 forming the overlapping portion 31 on the V-V cross section is an exhaust gas in the GPF 3 while the three-way catalyst 2 and the GPF 3 are arranged compactly. 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 side length H31 of the three-way catalyst 2 is a GPF 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 V-V cross section of FIG. Preferably, the width W3 is 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 distance between the downstream end of the exhaust manifold M and the GPF 3 is shortened by forming the overlapping portion 31 of the three-way catalyst 2 and GPF 3. Can be Further, while forming the overlapping portion 31, by suppressing the range thereof to be less than the above range, the downsizing of the exhaust device 1 can be realized, and the utilization efficiency of the GPF 3 particularly the portion shaded by the overlapping portion 31 is improved. It can be done.

<The downstream end of the GPF>
As shown in FIG. 5, an exhaust gas discharge pipe 5 which is an outlet of the exhaust gas having passed through the GPF 3 and an EGR which circulates a part of the exhaust gas as an EGR gas to the intake side at an end 7 on the downstream side of the GPF 3 A gas outlet pipe 6 is attached.

<Exhaust gas discharge pipe>
The exhaust gas discharge pipe 5 is for guiding the exhaust gas having passed through the GPF 3 to the downstream side exhaust system, and for accumulating and removing the water generated along with the purification of the exhaust gas by the three-way catalyst 2 and the GPF 3.

  A line indicated by reference numeral PRL31 shown in FIG. 5 (cross-sectional view taken along the line V-V in FIG. 1) is a projection line onto the V-V cross section of the central axis L3 of GPF3. Further, a line indicated by reference sign L5 indicates the central axis of the exhaust gas discharge pipe 5. A point indicated by a symbol 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 of the projection line PRL31 onto the V-V cross section of the GPF central axis L3 of GPF3, that is, to the three-way catalyst 2 side. . According to this configuration, the exhaust gas flowing into the GPF 3 has a flow toward the exhaust gas discharge pipe 5. As a result, the amount of exhaust gas flowing into the shadowed portion of the overlapping portion 31 increases following the flow toward the exhaust gas discharge pipe 5. Thus, the utilization efficiency of GPF 3 can be improved.

  In addition, as shown in FIG. 5, the bias amount of the exhaust gas discharge pipe 5 sufficiently secures the amount of exhaust gas flowing into the portion behind the overlapping portion 31 to improve the utilization efficiency of the GPF 3. Preferably, on the V-V cross section, the right side surface 5A of the exhaust gas discharge pipe 5 on the three-way catalyst 2 side is located on the right side of the GPF side surface 3C on the three-way catalyst 2 side of GPF 3, ie, on the three-way catalyst 2 side. It can be set to the extent that At this time, from the viewpoint of suppressing an increase in ventilation resistance in the vicinity of the exhaust gas discharge pipe 5, the left side surface 5B of the exhaust gas discharge pipe 5 is closer than the GPF side surface 3C on the three-way catalyst 2 side of GPF 3 on the V-V 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>
As the configuration of the engine body E, EGR is employed to recirculate part of the exhaust gas to the intake system of the engine for the purpose of preventing occurrence of knocking and reducing the amount of nitrogen oxides NOx, and the end of the GPF3 downstream side An EGR gas extraction pipe 6 of exhaust gas is connected to the part.

  As shown in FIG. 5, the EGR gas outlet pipe 6 is disposed on the V-V cross section on the opposite side of the exhaust gas outlet pipe 5 with respect to the projection line PRL 31 so as to be separated from the exhaust gas outlet pipe 5. ing. According to this configuration, a sufficient amount of exhaust gas can be secured for EGR, and the flow of exhaust gas in the GPF 3 is dispersed to the exhaust gas discharge pipe 5 side and the EGR gas extraction pipe 6 side to be uniform. Can. Therefore, the utilization efficiency, function, and performance of GPF 3 can be further improved.

<Exhaust manifold>
Exhaust gas exhausted from the four combustion chambers of the engine through the exhaust port is fed from the exhaust manifold M to the catalyst device Q through the connection 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 (none of which are shown) of the engine body E. Exhaust pipe, ie, first independent exhaust pipe M1 (independent exhaust pipe at one end side in the cylinder row direction), second independent exhaust pipe M2 (remaining independent exhaust pipe), third independent exhaust pipe M3 (remaining independent exhaust pipe And a fourth independent exhaust pipe M4 (remaining independent exhaust pipe).

  As shown in FIG. 1, FIG. 3 and FIG. 4, the exhaust manifold M is disposed at one end side of the engine body in the cylinder row direction, and extends downward from the tip of the independent exhaust pipe M1 at one end side of the cylinder row direction. The collecting pipe M5 is provided.

  The exhaust manifold M guides the exhaust gas flowing out of the remaining independent exhaust pipes M2 to M4 of the plurality of independent exhaust pipes toward the independent exhaust pipe M1 on one end side and guides the exhaust gas to the collecting pipe M5. It has a guide pipe M6 extending in the direction. 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. It is done.

  At the lower part of the collecting pipe M5, an L-shaped bent portion M50 is formed which is bent in an L shape in the lateral direction (left direction) so that the exhaust gas is directed to the upstream end face 2A 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 connection portion N. The downstream end outlet M7 is circular, and the opening surface of the outlet M7 is parallel to the upstream end surface 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 arc-shaped concave portion M51 having a radius larger than the downstream end outlet M7 of the collecting pipe M5. Is provided.

  Also, the flow of exhaust gas flowing from the guide pipe M6 into the collecting pipe M5 is directed to the central portion of the end face 2A on the upstream side 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 outward bulging portion M52 is formed.

  As shown in FIGS. 4 and 6, etc., the collecting pipe M5 is formed by fitting the right collecting pipe M5A and the left collecting pipe M5B, and the arc-shaped recess M51 is formed in the fitting portion. There is. The collecting pipe M5 may be divided into a plurality of parts as described above, or may be integrally formed.

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

  Generally, it is known that fluid such as exhaust gas tends to flow along a curved surface with a large radius of curvature. Therefore, the exhaust gas discharged from the first independent exhaust pipe M1 at one end side in the cylinder row direction is mainly generated by the inertia when flowing toward the tip of the first independent exhaust pipe M1. 1) Flow downward through the collecting pipe M5 along the wall surface continuing from the tip side of the independent exhaust pipe M1.

  Then, the exhaust gas reaches the L-shaped bent portion M50 as shown by the broken line arrow in FIG. 10, and the flow direction changes so as to be directed to the three-way catalyst 2. It becomes easy to hit the lower part of end face 2A.

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

  Therefore, the exhaust gas mainly flows downward through the collecting pipe M5 along the wall surface at one end side in the cylinder row direction of the collecting pipe M5, as shown by a dashed dotted arrow in FIG. Therefore, the exhaust gas changes its flow direction toward the three-way catalyst 2 at the L-shaped bent portion M 50 in the same manner as the exhaust gas flow from the first independent exhaust pipe M 1. It becomes easy to hit the lower part of end face 2A on the upstream side. The exhaust gas exhausted from the third and fourth independent exhaust pipes M3 and M4 also has the same flow as the exhaust gas exhausted from the second independent exhaust pipe M2.

  FIG. 6 shows the flow of exhaust gas when the collecting pipe M5 is provided with the arc-shaped concave portion M51 and the bulging portion M52.

  As indicated by the solid line arrow in FIG. 6, the exhaust gas discharged from the first independent exhaust pipe M1 is collected mainly along the wall surface continuing from the tip side of the first independent exhaust pipe M1 in the collecting pipe M5 due to inertia. It flows downward through M5 to reach the L-shaped bend M50.

  On the lower surface side of the L-shaped bent portion M50, an arc-shaped recessed portion M51 having a radius larger than that of the downstream end outlet (the downstream end outlet of the L-shaped bent portion M50) M7 of the collecting pipe M5 is formed. Therefore, the exhaust gas having reached the L-shaped bent portion M50 flows along the recessed bottom wall surface of the arc-shaped concave portion M51 and rises by inertia as shown by solid arrows in FIG. It flows into the three-way catalyst 2 while turning around the axis. Therefore, the exhaust gas can easily hit the entire upstream end face 2A 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, the exhaust gas flows downward along the wall of the collecting pipe M5 mainly along the wall in the cylinder row direction of the collecting pipe M5 due to inertia, and reaches the wall of the bulging portion M52. Then, the exhaust gas is guided by the wall surface of the bulging portion M52 so that the flow direction is changed to the center of the upstream end surface 2A of the three-way catalyst 2. Therefore, the exhaust gas is likely to uniformly hit the entire upstream end face 2A of the three-way catalyst 2.

<About the curved part of the guide tube>
As shown in FIG. 2 and FIG. 3, the guide pipe M6 is curved at one end side of the cylinder row direction in a protruding direction from the engine body of the first independent exhaust pipe M1 at one end side, and the first independent exhaust pipe It has a curved portion M61 connected to the tip of M1.

  Therefore, when the exhaust gas discharged from the second to fourth independent exhaust pipes M2 to M4 flows from the guide pipe M6 into the collecting pipe M5, the flow direction of the exhaust gas is changed from the cylinder row direction by the curved portion M61. (1) It changes so as to approach the protrusion direction of the independent exhaust pipe M1.

  Thus, the exhaust gas flowing from the guide pipe M6 into the collecting pipe M5 continues to the tip of the first independent exhaust pipe M1 like the exhaust gas flowing from the first independent exhaust pipe M1 at one end into the collecting pipe M5. It becomes easy to flow down the collection pipe M5 along the wall surface. Therefore, the swirling flow of the exhaust gas can be easily induced by the arc-shaped concave portion M51, and the exhaust gas can easily hit the entire upstream end surface 2A of the three-way catalyst 2 uniformly.

  As described above, the exhaust gas is likely to uniformly hit the entire upstream end face 2A of the three-way catalyst 2 by the arc-shaped concave part M51, the bulging part M52, and the curved part M61. It is effectively used for purification of exhaust gas, and therefore, purification of exhaust gas can be facilitated.

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

  Below the bulging part M52 of the collecting pipe M5, there is a place where the exhaust gas flowing downward along the wall surface at one end side of the collecting pipe M5 in the cylinder row direction and the exhaust gas which swirls and rises by the circular recess M51 , The exhaust gas homogeneity is high. Therefore, the detection of the oxygen concentration below the bulging portion M52 increases the reliability of the oxygen concentration obtained by the detection.

Second Embodiment
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 the 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, as shown in FIG. 9, only the arc-shaped concave portion M51 is provided in the second embodiment. Since the collecting pipe M5 is not provided with the bulging portion M52, its formation becomes easy.

  In the case where the bulging portion M52 is not provided, the exhaust gas flowing from the guide pipe M6 into the collecting pipe M5 tends to flow downward through the collecting pipe M5 as shown by a dashed dotted arrow in FIG. However, the exhaust gas flowing in such a manner also flows downward along the collecting pipe M5 along the wall surface continuing from the tip side of the first independent exhaust pipe M1 in the collecting pipe M5, and the exhaust gas swirls and rises by the circular concave portion 51 By combining, concentration on the lower side of the L-shaped bent portion M50 and, consequently, concentration on the lower side of the upstream end surface 2A of the three-way catalyst 2 can be avoided.

  In particular, also in the second embodiment, in the case where the curved portion M61 is provided, when the exhaust gas flows from the guide pipe M6 into the collecting pipe M5, the flow direction of the exhaust gas is from the cylinder row direction by the curved portion M61. It changes so as to approach the protrusion direction of the first independent exhaust pipe M1. Therefore, since the amount of exhaust gas that swirls and rises due to the arc-shaped concave portion 51 increases, even when the bulging portion M52 is not provided, the exhaust gas is on the lower side of the L-shaped bent portion M50, and hence the three-way catalyst 2 Concentration on the lower side of the upstream end face 2A is avoided.

(Other embodiments)
In the first and second embodiments, the upstream exhaust purification device is the three-way catalyst 2 and the downstream exhaust purification device is the GPF 3. However, the exhaust purification device is not limited to such a configuration, and various purification devices are employed. be able to. For example, when the exhaust system 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 disposed on the first cylinder side, but the collecting pipe M5 is disposed on the fourth cylinder side, and the end face 2A on the upstream side of the three-way catalyst 2 May be configured to be on the left side.
(Evaluation of gas permeability for three-way catalyst)
A computational fluid dynamics (CFD) model was created and analyzed. Then, 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 from the flow velocity distribution of the exhaust gas at the three-way catalyst start face 2A, uniformity per gas of each cylinder Was evaluated as an indicator of improvement per gas. The results are shown in FIG.

  In Comparative Example 1 and Examples 1 and 2, only the arc-shaped recess M51 shown in FIG. 9 was formed when neither the arc-shaped recess M51 and the bulging portion M52 shown in FIG. 10 were formed respectively. This is a result of the case where both the arc-shaped concave portion M51 and the bulging portion M52 shown in FIG. 6 are formed.

  As shown in FIG. 11, the uniformity per exhaust gas from one or more cylinders is improved and the uniformity per exhaust gas from all the cylinders is improved in Example 1 and Example 2 as compared with Comparative Example 1. It is understood that you are doing.

  Specifically, based on Comparative Example 1, in the first cylinder, the improvement index per gas was improved by about 30% and about 50% in Example 1 and 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 reduced by about 160% and equal in each of Example 1 and Example 2.

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

  In addition, 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 between Example 1 and Example 2 is smaller on the basis of Comparative Example 1, respectively. The uniformity per exhaust gas from the above etc. was improved.

  As described above, particularly in the third cylinder of the first embodiment, although the uniformity per gas is lowered, the gas per exhaust gas flow from all cylinders to the three-way catalyst front end face 2A is largely homogenized. I found that.

  The present invention is extremely useful because it can improve the uniformity per gas for the exhaust gas purification device in the exhaust system of an engine.

1 Engine exhaust system 2 Three-way catalyst (upstream exhaust gas purification system)
2A End face 2B on the upstream side of the three-way catalyst 2 End face 3 GPF (downstream side exhaust purification device) on the downstream side of the three-way catalyst
3A GPF upstream end face 3B GPF downstream end face 4 L-shaped exhaust pipe 4A upstream side opening 4B downstream side opening 4C bent part 5 exhaust gas discharge pipe 6 EGR gas extraction pipe 31 overlapping part 33 filter body (purification device Body)
E Engine L2 Three-way catalyst central axis L3 GPF central axis L5 Exhaust gas exhaust pipe central axis M Exhaust manifold M1 first independent exhaust pipe (independent exhaust pipe at one end)
M2 2nd independent exhaust pipe (remaining independent exhaust pipe)
M3 3rd independent exhaust pipe (remaining independent exhaust pipe)
M4 4th independent exhaust pipe (remaining independent exhaust pipe)
M5 collecting pipe M6 guiding pipe M7 downstream end outlet M50 L-shaped bent portion M51 arc-shaped recessed portion M52 bulging portion M61 curved portion N connecting portion

Claims (5)

An exhaust manifold connected to an exhaust port of an in-line multi-cylinder engine having an engine body provided with a plurality of cylinders;
An exhaust system of an engine comprising: a catalyst as an exhaust gas purification device connected to a downstream side of an exhaust gas flow direction of the exhaust manifold and disposed so that a central axis is parallel to a cylinder row direction ,
The exhaust manifold is
A plurality of independent exhaust pipes connected to respective exhaust ports of the engine body;
A collective pipe disposed at one end side of the engine body in the cylinder row direction and extending downward from the tip of the independent exhaust pipe at one end side of the plurality of independent exhaust pipes in the cylinder row direction;
A guide pipe extending in a cylinder row direction for guiding exhaust gas flowing out from the remaining independent exhaust pipes of the plurality of independent exhaust pipes toward the one end side independent exhaust pipe and guiding the exhaust gas to the collecting pipe;
An L-shaped bent portion which is formed in a lower portion of the collecting pipe and which is bent in an L shape in a lateral direction so that exhaust gas is directed to the upstream end face of the exhaust gas purification device;
Exhaust gas flowing downward through the collecting pipe along a wall surface which is formed on the lower surface side of the L-shaped bent portion of the collecting pipe and continues downward from the tip end side of the independent exhaust pipe on the one end side of the collecting pipe is An outlet of the L-shaped bent portion opened toward the exhaust gas purification device for promoting swirling of the exhaust gas so as to flow into the exhaust gas purification device while swirling around the axis of the exhaust gas purification device An exhaust system for an engine, comprising: an arc-shaped recess having a larger radius than the arc-shaped recess. In claim 1,
On the wall surface at one end side in the cylinder row direction of the collecting pipe, the flow of exhaust gas flowing from the guide pipe into the collecting pipe is changed to be directed to the central portion of the end face on the upstream side of the exhaust gas purification device An exhaust system for an engine comprising a bulging portion. In claim 1 or claim 2,
The guide pipe includes, on one end side of the cylinder row direction, a curved portion which curves in a direction in which the independent exhaust pipe on the one end side protrudes from the engine body and continues to a tip of the independent exhaust pipe on the one end side. Engine exhaust system characterized by In claim 2 or claim 3 which refers to claim 2
An exhaust system for an engine, wherein an oxygen concentration detecting means is provided below the bulging portion in the collecting pipe. In any one of claims 1 to 4,
It further comprises a downstream exhaust purification device provided downstream of the exhaust purification device in the exhaust gas flow direction,
When the exhaust purification device and the downstream exhaust purification device have their central axes substantially orthogonal to each other and 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 An exhaust system of an engine, wherein the exhaust system of the engine is disposed so as to overlap a part of the end face on the upstream side.

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