JP2021127757A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

To provide an exhaust emission control device of an internal combustion engine capable of improving purification performance of exhaust gas in a case where an exhaust gas outlet communicating with a plurality of exhaust ports and a catalyst converter arranged near a lower edge of the exhaust gas outlet are connected via a connection pipe part with a curved pipe part.SOLUTION: In a throttle part 18 of a connection pipe part 12, when the throttle part 18 is viewed from a direction of a central axis L of a catalytic converter, a passage cross section of a downstream end 18b has a bottom 20a, and a pair of hypotenuses 20b, 20c extending in a direction intersecting with each other from both sides of the bottom 20a, and formed in a trapezoidal shape where the bottom 20a is arranged closer to an exhaust gas outlet than the hypotenuses 20b, 20c. Also, the passage cross section of an upstream end 18a is formed in a semicircular shape having an arc that bulges outward from the pair of hypotenuses, and a communication part communicating the end parts of the arc to each other, and the arc and the hypotenuses 20b, 20c communicate with each other by curved surfaces 22a, 22b that are convex toward the outside of the throttle part 18.SELECTED DRAWING: Figure 6

Description

The present invention relates to an exhaust gas purification device for an internal combustion engine.

The internal combustion engine mounted on the vehicle is equipped with an exhaust purification device having a catalytic converter for purifying the exhaust gas. Since the catalytic converter is installed below the cylinder head of the internal combustion engine, the upstream exhaust pipe of the catalytic converter has a bend that extends horizontally from the exhaust port of the cylinder head and then bends downward.

Therefore, when the exhaust gas discharged from the exhaust port passes through the bent portion, the exhaust gas becomes a biased flow to the outside of the bent portion, and one-sidedly hits the outside of the catalytic converter to purify the exhaust gas by the catalytic converter. May decrease.

Conventionally, the structure of an exhaust pipeline for a vehicle described in Patent Document 1 is known as one that can suppress a decrease in exhaust gas purification performance.

In the structure of the exhaust gas line for vehicles, an exhaust gas purification catalytic converter is arranged in the exhaust line of the internal combustion engine, and a bent portion of the exhaust line is formed immediately before the catalytic converter. The outer corner portion of the bent portion is provided with a constricted portion as a gas flow diversion portion for directing the exhaust gas flow on the upstream side of the catalytic converter to the inner corner portion of the bent portion.

According to the structure of the exhaust gas line for vehicles, the exhaust gas flow that is closer to the outer corner part side at the bend part of the exhaust line line is attracted to the inner corner part side of the bend part by the constriction part, and is the central part of the catalytic converter. Head to. Therefore, the exhaust gas can be introduced into the entire catalytic converter, and the deterioration of the purification performance of the catalytic converter due to the bending of the exhaust pipeline can be suppressed.

Japanese Unexamined Patent Publication No. 2006-17018

By the way, in the exhaust gas purification device, for example, when the catalyst converter and the GPF (Gasoline Particulate Filter) are arranged vertically and housed inside the catalyst case and the catalyst converter is installed at a position close to the exhaust gas outlet, the catalyst converter and the GPF (Gasoline Particulate Filter) are installed from the exhaust gas outlet. The distance to the upstream end of the catalytic converter becomes shorter.

Therefore, it is not possible to deflect the flow of the exhaust gas to the inner corner portion only by providing the constricted portion of Patent Document 1 in the bent portion. As a result, the exhaust gas may not flow evenly over the entire upstream end of the catalytic converter.

The present invention has been made by paying attention to the above circumstances, and a curved pipe portion comprises an exhaust gas outlet communicating with a plurality of exhaust ports and a catalytic converter arranged near the lower edge of the exhaust gas outlet. It is an object of the present invention to provide an exhaust gas purification device for an internal combustion engine capable of improving the exhaust gas purification performance when connected via a connection pipe portion having the above.

The present invention connects a catalyst case, which is installed below the lower edge of an exhaust gas outlet communicating with a plurality of exhaust ports of a cylinder head and houses a catalyst converter, and the exhaust gas outlet and the catalyst case. It has a connecting pipe portion having an exhaust gas passage for sending the exhaust gas discharged from the exhaust gas outlet to the catalyst case, and the connecting pipe portion is curved downward from the exhaust gas outlet toward the catalyst converter. An exhaust gas purification device for an internal combustion engine having a tube portion, a throttle portion connected to the curved tube portion, and a cone-shaped tube portion whose passage cross-sectional area expands from the throttle portion toward the catalyst converter. When the throttle portion is viewed from the central axis direction of the catalyst converter, the throttle portion has a pair of diagonal sides whose downstream end passage cross sections extend in a direction intersecting each other from both sides of the bottom. A pair of arcs whose bases are formed in a trapezoidal or triangular shape arranged closer to the exhaust gas outlet than the pair of diagonal sides, and whose upstream end passage cross section bulges outward from the pair of diagonal sides. The arc is formed in a semicircular shape having a connecting portion that connects the ends of the pair of arcs to each other, and the arc and the oblique side are connected by a curved surface that is convex to the outside of the throttle portion. do.

As described above, according to the present invention, the exhaust gas outlet communicating with the plurality of exhaust ports and the catalytic converter arranged near the lower edge of the exhaust gas outlet are connected via the connecting pipe portion having the curved pipe portion. When connected, the exhaust gas purification performance can be improved.

FIG. 1 is a schematic plan view of an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a front view of an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. FIG. 3 is a left side view of an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. FIG. 4 is a front view of an upstream connection pipe portion of an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the line VV direction of FIG. FIG. 6 is a cross-sectional view taken along the line in the VI-VI direction of FIG. FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. FIG. 9 is a diagram showing a state of exhaust gas flowing through an exhaust gas purification device of an internal combustion engine according to an embodiment of the present invention.

The exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention is installed below the lower edge of an exhaust gas outlet communicating with a plurality of exhaust ports of a cylinder head, and has a catalyst case for accommodating a catalyst converter and exhaust gas. It has a connecting pipe section that connects the gas outlet and the catalyst case and has an exhaust gas passage for sending the exhaust gas discharged from the exhaust gas outlet to the catalyst case, and the connecting pipe section faces the catalyst converter from the exhaust gas outlet. It is an exhaust gas purification device for an internal combustion engine having a curved tube portion that curves downward, a throttle portion that is connected to the curved tube portion, and a cone-shaped tube portion that expands the passage cross-sectional area from the throttle portion toward the catalyst converter. When the throttle portion is viewed from the central axis direction of the catalytic converter, the throttle portion has a base and a pair of oblique sides extending in a direction in which the passage cross section at the downstream end intersects each other from both sides of the bottom, and the bottom. Is formed in a trapezoidal shape or a triangle shape that is arranged closer to the exhaust gas outlet than the pair of diagonal sides, and the passage cross section at the upstream end thereof is a pair of arcs that bulge outward from the pair of diagonal sides and a pair of arcs. It is formed in a semicircular shape having a connecting portion that connects the ends to each other, and the arc and the oblique side are connected by a curved surface that is convex to the outside of the throttle portion.

As a result, the exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention has a curved tube between an exhaust gas outlet communicating with a plurality of exhaust ports and a catalytic converter arranged near the lower edge of the exhaust gas outlet. When connected via a connecting pipe portion having a portion, the purification performance of exhaust gas can be improved.

Hereinafter, the exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.

1 to 9 are views showing an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. In FIGS. 1 to 9, the up / down / front / rear / left / right directions are based on the exhaust purification device installed in the vehicle, the front / rear direction of the vehicle is the front / rear direction, the left / right direction of the vehicle (vehicle width direction) is the left / right direction, and the vehicle. The vertical direction (the height direction of the vehicle) is the vertical direction.

First, the configuration will be described.
In FIGS. 1 to 3, an engine 1 as an internal combustion engine is installed in an engine room (not shown) of a vehicle. The engine 1 includes a cylinder block 2 and a cylinder head 3 provided above the cylinder block 2.

In FIG. 2, the cylinder block 2 is provided with a plurality of cylinders 2A, 2B, and 2C. The engine 1 of this embodiment is a 3-cylinder engine. The number of cylinders of the engine 1 is not limited to three.

Pistons 4A, 4B, and 4C are housed in the cylinders 2A, 2B, and 2C, respectively, and the pistons 4A, 4B, and 4C reciprocate in the vertical direction (cylinder axial direction) with respect to the cylinders 2A, 2B, and 2C. The pistons 4A, 4B, and 4C are connected to a crankshaft (not shown) via a connecting rod (not shown), and the reciprocating motion of the piston is converted into a rotational motion of the crankshaft via the connecting rod.

Combustion chambers 3A, 3B, and 3C are formed between the tops of the pistons 4A, 4B, and 4C, the inner walls of the cylinders 2A, 2B, and 2C, and the bottom of the cylinder head 3 (see FIG. 1).

As shown in FIG. 1, the cylinder head 3 is formed with a plurality of intake ports and a plurality of exhaust ports 5A, 5B, and 5C (not shown).

The intake ports communicate with the cylinders 2A, 2B, and 2C, respectively, and introduce the intake air into the cylinders 2A, 2B, and 2C.

One end of the exhaust ports 5A, 5B and 5C communicates with the combustion chambers 3A, 3B and 3C of the cylinders 2A, 2B and 2C. The other ends of the exhaust ports 5A, 5B, and 5C are assembled to form the collecting portion 6, and the collecting portion 6 has an exhaust gas outlet 6A that opens to the wall surface 3a of the cylinder head 3 (see FIG. 5). ..

Exhaust gas burned in the combustion chambers 3A, 3B and 3C is discharged to the exhaust ports 5A, 5B and 5C, and the exhaust gas discharged to the exhaust ports 5A, 5B and 5C is exhausted after being collected in the collecting unit 6. It is discharged to the outside of the cylinder head 3 from the gas outlet 6A.

As shown in FIGS. 1 to 3, the engine 1 is provided with an exhaust gas purification device 10. The exhaust gas purification device 10 includes a catalyst case 11, an upstream side connecting pipe portion 12, and a downstream side connecting pipe portion 13.

The catalyst case 11 houses the catalyst converter 14 and the GPF 15. The catalytic converter 14 and the GPF 15 are separated from each other in the direction in which the exhaust gas flows, and are installed side by side in the direction in which the exhaust gas flows.

The catalyst converter 14 and the GPF 15 are held on the inner peripheral surface of the catalyst case 11 via a supporter (not shown).

Specifically, as shown in FIG. 5, the catalytic converter 14 is installed below the lower edge 6b of the exhaust gas outlet 6A, and as shown in FIGS. 2 and 3, the GPF 15 is the catalytic converter 14. It is installed below.

The catalytic converter 14 oxidizes and reduces HC (hydrocarbon), CO (carbon monoxide), NOx (nitrogen oxide) and the like contained in the exhaust gas to purify the exhaust gas.

GPF15 is formed in a honeycomb shape and collects particulate matter which is a particulate matter.

As shown in FIG. 5, the upstream side connecting pipe portion 12 connects the exhaust gas outlet 6A and the upstream end of the catalyst case 11. An exhaust gas passage 16 is formed inside the upstream side connecting pipe portion 12, and the upstream side connecting pipe portion 12 sends the exhaust gas discharged from the exhaust gas outlet 6A to the catalyst case 11 through the exhaust gas passage 16. ..

As shown in FIGS. 2 and 3, the downstream connecting pipe portion 13 is connected to the downstream end of the catalyst case 11, and an exhaust pipe (not shown) is connected to the downstream end of the downstream connecting pipe portion 13.

As shown in FIGS. 4 and 5, the upstream connecting pipe portion 12 has a curved pipe portion 17, a throttle portion 18, and a cone-shaped pipe portion 19. The curved pipe portion 17 is curved downward from the exhaust gas outlet 6A toward the catalytic converter 14. The upstream side connecting pipe portion 12 of this embodiment constitutes the connecting pipe portion of the present invention.

A flange portion 17A is provided on the curved pipe portion 17. The flange portion 17A is in contact with the wall surface 3a around the exhaust gas outlet 6A, and is fastened to the cylinder head 3 by a bolt (not shown). An exhaust gas inlet 17a is formed at the upstream end of the curved pipe portion 17, and the exhaust gas discharged from the exhaust gas outlet 6A is inside the upstream side connecting pipe portion 12 through the exhaust gas inlet 17a (exhaust gas passage 16). Inflow to.

As shown in FIGS. 4, 5 and 8, the upstream end 18a of the throttle portion 18 is connected to the downstream end of the curved pipe portion 17. The upstream end 18a of the throttle portion 18 and the downstream end of the curved pipe portion 17 are at the same height position.

The upstream end of the cone-shaped tube portion 19 is connected to the downstream end 18b of the drawing portion 18, and the passage cross-sectional area of the cone-shaped tube portion 19 is expanded from the drawing portion 18 toward the catalytic converter 14. That is, the downstream end of the cone-shaped tube portion 19 has an opening area having the same size as the opening area of the upstream end of the catalyst case 11. The upstream end of the cone-shaped tube portion 19 and the downstream end 18b of the throttle portion 18 are at the same height position.

Here, "upstream" and "downstream" indicate upstream and downstream with respect to the direction in which the exhaust gas G discharged from the engine 1 flows (see FIG. 3), and the downstream connection pipe portion 13 side with respect to the engine 1 is downstream. The engine 1 side is upstream with respect to the downstream side connecting pipe portion 13.

As shown in FIG. 5, the center of curvature C1 of the curved pipe portion 17 is closer to the exhaust gas outlet 6A than the central axis L of the catalytic converter 14, and is located on the exhaust gas outlet 6A in the direction of the central axis L of the catalytic converter 14. It is located on the lower edge 6b side of the upper edge 6a.

FIG. 5 shows the radius of curvature R of the curved pipe portion 17. The central axis L of the catalyst converter 14 is the same as the central axis of the catalyst case 11 and the central axis of the GPF 15.

As shown in FIGS. 6 and 7, when the throttle portion 18 is viewed from the central axis L direction (upper side) of the catalytic converter 14, the passage cross section of the downstream end 18b of the throttle portion 18 is formed on both sides of the bottom 20a and the bottom 20a. It has a pair of hypotenuses 20b and 20c extending in a direction intersecting each other, and the base 20a is formed in a trapezoidal shape arranged closer to the exhaust gas outlet 6A than the hypotenuses 20b and 20c.

As shown in FIG. 6, when the throttle portion 18 is viewed from the central axis L direction (upper side) of the catalytic converter 14, the passage cross section of the upstream end 18a of the throttle portion 18 expands outward from the pair of hypotenuses 20b and 20c. It is formed in a semicircular shape having a pair of arcs 21a and 21b to be projected and a connecting portion 21c that connects the ends (right end and left end) of the arcs 21a and 21b to each other.

As shown in FIGS. 6 and 8, the diaphragm portion 18 has curved surfaces 22a and 22b that are convex to the outside of the diaphragm portion 18, and the curved surfaces 22a and 22b have arcs 21a and 21b and hypotenuses 20b and 20c, respectively. I'm in touch.

That is, when the throttle portion 18 is viewed from the central axis L direction (upper side) of the catalyst converter 14, the curved surfaces 22a and 22b of the throttle portion 18 are convex outward from the arcs 21a and 21b toward the hypotenuses 20b and 20c. It is formed in a semi-elliptical shape and is connected to the curved tube portion 17.

As shown by arrows in FIGS. 5 and 8, the passage cross-sectional area of the curved pipe portion 17 is formed larger than the opening area of the exhaust gas outlet 6A in the direction in which the exhaust gas G flows. In FIG. 8, the opening area of the exhaust gas inlet 17a and the opening area of the exhaust gas outlet 6A are substantially the same.

Next, the action will be described.
The exhaust gas purification device 10 of this embodiment is installed below the exhaust gas outlet 6A communicating with the exhaust ports 5A, 5B, and 5C of the cylinder head 3, and accommodates the catalyst converter 14 and the GPF 15 and the exhaust gas. It has an upstream connecting pipe portion 12 having an exhaust gas passage 16 that connects the outlet 6A and the catalyst case 11 and sends the exhaust gas discharged from the exhaust gas outlet 6A to the catalyst case 11.

The upstream connection pipe portion 12 includes a curved pipe portion 17 that curves downward from the exhaust gas outlet 6A toward the catalytic converter 14, a throttle portion 18 that is connected to the curved pipe portion 17, and a throttle portion 18 to the catalyst converter 14. It has a cone-shaped tube portion 19 whose cross-sectional area of the passage expands toward the direction.

Therefore, the exhaust gas G discharged from the engine 1 is introduced into the catalyst case 11 from the exhaust gas outlet 6A through the upstream side connecting pipe portion 12, the exhaust gas G is purified by the catalyst converter 14 and the GPF 15, and then the downstream side connecting pipe. It can be exhausted to the atmosphere from section 13 through an exhaust pipe (see FIG. 3).

By the way, when the catalyst converter 14 and the GPF 15 are housed inside the catalyst case 11 side by side in the vertical direction and the catalyst converter 14 is installed at a position close to the lower edge 6b of the exhaust gas outlet 6A, the catalyst converter 14 or the GPF 15 is arranged in the length direction. Since it can be expanded to, the exhaust purification capacity can be enhanced.

However, when the catalytic converter 14 is installed at a position close to the lower edge 6b of the exhaust gas outlet 6A, the distance between the exhaust gas outlet 6A and the upstream connection pipe portion 12 becomes short. Therefore, when the exhaust gas discharged from the exhaust gas outlet 6A passes through the upstream connection pipe portion 12, the exhaust gas becomes a biased flow to the outside of the curved pipe portion 17 and hits the outside of the catalytic converter 14. Therefore, the exhaust gas purification ability is not exhibited, and the exhaust gas purification performance of the catalytic converter 14 may deteriorate.

According to the exhaust gas purification device 10 of the present embodiment, when the throttle portion 18 is viewed from the direction of the central axis L of the catalytic converter 14, the throttle portion 18 has a passage cross section of the downstream end 18b having a base 20a and a bottom 20a. It has a pair of hypotenuses 20b and 20c extending from both sides in a direction intersecting each other, and the base 20a is formed in a trapezoidal shape arranged closer to the exhaust gas outlet 6A than the hypotenuses 20b and 20c.

Further, when the throttle portion 18 is viewed from the direction of the central axis L of the catalyst converter 14, the throttle portion 18 has arcs 21a and 21b in which the passage cross section of the upstream end 18a bulges outward from the pair of hypotenuses 20b and 20b. It is formed in a semicircular shape having a connecting portion 21c that connects the ends of the arcs 21a and 21b to each other, and the arcs 21a and 21b and the hypotenuse 20b are formed by the curved surfaces 22a and 22b that are convex to the outside of the throttle portion 18. , 20c are in contact.

As a result, the exhaust gas G1 (see FIG. 6) discharged from the exhaust gas outlet 6A to the upstream connecting pipe portion 12 and flowing outside the curved pipe portion 17 is rearward and in different directions (left-right direction) by the curved surfaces 22a and 22b. ) Can be reversed.

Therefore, at the upstream end of the catalyst converter 14, the exhaust gas flowing through the upstream connection pipe portion 12 corresponds to the inside of the catalyst converter 14 (the exhaust gas outlet 6A side with respect to the central axis L of the catalyst converter 14). It can be inflowed over a wide area.

FIG. 9 shows the exhaust gas G1 flowing into the portion corresponding to the inside of the catalyst converter 14 and the portion corresponding to the outside of the catalyst converter 14 (the side opposite to the exhaust gas outlet 6A with respect to the central axis L of the catalyst converter 14). The inflowing exhaust gas G2 is shown.

As shown in FIG. 9, according to the exhaust purification device 10 of the present embodiment, the exhaust gases G1 and G2 flowing into the upstream end of the catalytic converter 14 evenly flow into the entire upstream end of the catalytic converter 14. You can see that there is.

Therefore, the exhaust gas can flow evenly in the diameter direction of the catalytic converter 14.

As described above, the exhaust gas purification device 10 of the present embodiment has an exhaust gas outlet 6A communicating with a plurality of exhaust ports 5A, 5B, and 5C, and a catalyst converter 14 arranged in the vicinity of the lower edge 6b of the exhaust gas outlet 6A. When connected via the upstream connecting pipe portion 12 having the curved pipe portion 17, the exhaust gas purification performance can be improved. The passage cross section of the downstream end 18b of the throttle portion 18 may be triangular instead of trapezoidal.

Further, according to the exhaust gas purification device 10 of the present embodiment, the center of curvature C1 of the curved pipe portion 17 is closer to the exhaust gas outlet 6A than the central axis L of the catalytic converter 14, and is located on the central axis L of the catalytic converter 14. It is located on the lower edge 6b side of the upper edge 6a of the exhaust gas outlet 6A in the direction.

As a result, the exhaust gas discharged from the exhaust gas outlet 6A to the curved pipe portion 17 can be curved toward the catalytic converter 14 in the vicinity of the exhaust gas outlet 6A. Therefore, the catalytic converter 14 can be installed close to the lower edge 6b of the exhaust gas outlet 6A, and the exhaust purification device 10 can be installed on the upper side of the side surface of the engine 1.

In the exhaust purification device 10 of the present embodiment, even when the catalyst converter 14 is installed close to the lower edge 6b of the exhaust gas outlet 6A, the exhaust gases G1 and G2 are evenly flowed into the entire upstream end of the catalyst converter 14. And the purification performance of exhaust gas can be improved.

Further, according to the exhaust gas purification device 10 of this embodiment, the curved surfaces 22a and 22b are connected to the curved pipe portion 17. That is, the curved surfaces 22a and 22b are continuous with the curved pipe portion 17.

As a result, it is possible to prevent the exhaust gas flowing from the curved pipe portion 17 to the curved surfaces 22a and 22b from being obstructed by the curved surfaces 22a and 22b, and the curved surfaces 22a and 22b cause the exhaust gas to be rearward and in different directions (left and right directions). It can be reversed smoothly.

Further, according to the exhaust gas purification device 10 of the present embodiment, the passage cross-sectional area of the curved pipe portion 17 is formed larger than the opening area of the exhaust gas outlet 6A in the direction in which the exhaust gas flows.

As a result, the pressure loss in the curved pipe portion 17 can be reduced as compared with the case where the passage cross-sectional area of the curved pipe portion 17 is formed smaller than the opening area of the exhaust gas outlet 6A. Therefore, the exhaust gas discharged from the exhaust gas outlet 6A to the curved pipe portion 17 can be smoothly flowed to the throttle portion 18 through the curved pipe portion 17.

Although the embodiments of the present invention have been disclosed, it is clear that some skilled in the art can make changes without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 ... engine (internal combustion engine for vehicles), 3 ... cylinder head, 6A ... exhaust gas outlet, 6b ... lower edge (lower edge of exhaust gas outlet), 10 ... exhaust purification device, 11 ... catalyst case, 12 ... upstream connection pipe (connection pipe), 14 ... catalyst converter, 16 ... exhaust gas passage, 17 ... curved pipe, 19 ... cone Cylinder part, 20a ... bottom, 20b, 20c ... diagonal side, 21a, 21b ... arc, 21c ... connecting part, 22a, 22b ... curved surface, L1 ... central axis of catalytic converter

Claims (3)

A catalyst case that is installed below the lower edge of the exhaust gas outlet that communicates with multiple exhaust ports of the cylinder head and houses the catalyst converter.
It has a connecting pipe portion that connects the exhaust gas outlet and the catalyst case and has an exhaust gas passage for sending the exhaust gas discharged from the exhaust gas outlet to the catalyst case.
A curved pipe portion in which the connecting pipe portion curves downward from the exhaust gas outlet toward the catalytic converter, a throttle portion connected to the curved pipe portion, and a passage cut from the throttle portion toward the catalytic converter. An exhaust gas purification device for an internal combustion engine having a cone-shaped pipe portion whose area is expanded.
When the throttle portion is viewed from the central axis direction of the catalyst converter, the throttle portion has a base and a pair of hypotenuses extending in a direction in which the cross section of the passage at the downstream end intersects each other from both sides of the bottom. The base is formed in a trapezoidal shape or a triangular shape that is arranged closer to the exhaust gas outlet than the pair of hypotenuses, and the cross section of the passage at the upstream end thereof is a pair of arcs that bulge outward from the pair of hypotenuses. , Formed in a semicircular shape with a connecting part that connects the ends of the pair of arcs to each other.
An exhaust gas purification device for an internal combustion engine, characterized in that the arc and the hypotenuse are connected by a curved surface that is convex to the outside of the throttle portion. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the curved surface is continuous with the curved pipe portion. The exhaust gas purification device for an internal combustion engine according to claim 1 or 2, wherein the passage cross-sectional area of the curved pipe portion is larger than the opening area of the exhaust gas outlet in the direction in which the exhaust gas flows.

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