JP2021107703A - Exhaust emission control device and swirl flow generating member - Google Patents

Abstract

To provide an exhaust emission control device capable of enhancing dispersibility of a reducing agent and suppressing backflow of the reducing agent.SOLUTION: An aspect of the present disclosure is an exhaust emission control device including a reducing agent supply part, a first shield part, and a second shield part. The second shield part has an annular portion that shields a flow outside an opening, and a side wall portion that surrounds a part of the opening. The first shield part has a central portion that overlaps with the opening of the annular portion, a peripheral portion that extends from the central portion to an inner peripheral surface of an exhaust gas pipeline, a plurality of through holes provided in the peripheral portion, and a cover portion disposed apart from the peripheral portion. The peripheral portion is disposed to overlap with the outer region of an open portion of an outer edge of the opening, which is not surrounded by the side wall portion. The reducing agent supply part injects a reducing agent toward the side wall portion. The cover portion overlaps with an injection region of the reducing agent.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an exhaust gas purification device and a swirling flow generating member.

An exhaust gas purification device is installed in the exhaust gas flow path of the internal combustion engine for the purpose of complying with the regulations regarding the exhaust gas component of the internal combustion engine. For the exhaust gas purification device, if it is a diesel engine, for example, an exhaust gas purification member such as a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a catalyst for selective catalyst reduction (SCR) is used in combination.

Among these exhaust gas purification members, the SCR catalyst (hereinafter, also referred to as “reduction catalyst”) is generally installed downstream of another catalyst or filter. SCR is a method of reducing NOx in exhaust gas with a reducing agent and a reducing catalyst to reform it into harmless nitrogen.

In SCR, in order to make the reducing catalyst function efficiently and improve the purification rate of the exhaust gas, the reducing agent is mixed and uniformly dispersed in the exhaust gas, and the exhaust gas containing the reducing agent is evenly distributed. It is necessary to bring it into contact with the reducing catalyst.

As a method of dispersing the reducing agent in the exhaust gas, there is a method of arranging a diffusion plate in the flow path of the exhaust gas. However, if the diffusion plate is arranged in the flow path, there is a disadvantage that the pressure loss becomes high and the flow of the exhaust gas is biased.

Therefore, an exhaust gas purification device has been proposed in which a swirling flow generating member having two shielding portions is arranged in the flow path of the exhaust gas, and the reducing agent is diffused by the swirling flow generated by the swirling flow generating member (see Patent Document 1).

JP-A-2019-127879

In the exhaust gas purification device of the above publication, the inflow rate of the exhaust gas into the injection region of the reducing agent located between the first shielding portion and the second shielding portion is high, so that the spray is biased and the dispersion effect is insufficient. There is a possibility of becoming. As a result, the purification performance may be deteriorated and a precipitate (that is, a deposit) of the reducing agent component may be generated.

Further, in the exhaust gas purification device of the above publication, a part of the reducing agent injected between the first shielding portion and the second shielding portion may flow back to the upstream side from the opening portion of the first shielding portion. Therefore, the backflowing reducing agent may come into contact with the catalyst on the upstream side, which may cause the catalyst to crack or deteriorate in function.

One aspect of the present disclosure is to provide an exhaust gas purification device capable of enhancing the dispersibility of the reducing agent and suppressing the backflow of the reducing agent.

One aspect of the present disclosure is an exhaust gas purification device for an internal combustion engine. The exhaust gas purification device includes an exhaust gas purification unit, a reduction unit, a reducing agent supply unit, an exhaust gas pipeline, and a swirling flow generating member. The exhaust gas purification unit is configured to reform or collect environmental pollutants in the exhaust gas. The reducing unit is provided on the downstream side of the exhaust gas purification unit in the flow direction of the exhaust gas, and is configured to reduce the exhaust gas in the presence of a reducing agent. The reducing agent supply unit is configured to supply the reducing agent to the exhaust gas on the upstream side of the reducing unit in the flow direction of the exhaust gas. The exhaust gas pipeline communicates between the exhaust port of the exhaust gas purification unit and the introduction port of the reduction unit. The swirling flow generating member is installed in the exhaust gas pipeline.

The swirling flow generating member includes a first shielding portion configured to shield a part of the flow in the central axis direction of the exhaust gas pipeline, a second shielding portion arranged on the downstream side of the first shielding portion, and a second shielding portion. Has. The second shielding portion has an opening provided at the radial center of the exhaust gas pipeline, and an annular portion configured to shield the flow in the central axial direction on the radial outer side of the opening, and the annular portion to the second. 1 It has a side wall portion that extends to a shielding portion and surrounds a part of the opening of the annular portion in the circumferential direction.

The first shielding portion overlaps with the opening of the annular portion when viewed from the central axis direction, and extends from the central portion to the inner peripheral surface of the exhaust gas pipeline and the central portion separated from the inner peripheral surface of the exhaust gas pipeline. It has a peripheral edge portion, a plurality of through holes provided in the peripheral edge portion, and a cover portion arranged apart from the peripheral edge portion in the circumferential direction of the exhaust gas pipeline. The peripheral edge portion is arranged so as to at least overlap the outer edge of the opening of the annular portion in the radial direction of the open portion not surrounded by the side wall portion when viewed from the central axis direction. The reducing agent supply unit is configured to inject the reducing agent toward the side wall portion. The cover portion overlaps with at least a part of the reducing agent injection region by the reducing agent supply portion when viewed from the central axis direction.

According to such a configuration, the flow of exhaust gas in the central axial direction of the exhaust gas pipeline (hereinafter, also referred to as “first direction”) is guided to the outside of the side wall portion of the second shielding portion by the first shielding portion. Will be done. The flow thus guided flows toward the opening of the annular portion while being divided into two flows by the side wall portion. As a result, the flow path of the exhaust gas is extended, and two swirling flows having a swirling axis parallel to the first direction and opposite to each other are generated. Therefore, the reducing agent sprayed toward the side wall portion is efficiently diffused. As a result, the evaporation of the reducing agent is promoted and the dispersibility is improved. Further, a part of the exhaust gas flow passes through the plurality of through holes of the first shielding portion and joins the two swirling flows. As a result, the reducing agent and the exhaust gas are effectively agitated.

Further, in the above configuration, the inflow rate of the exhaust gas into the injection region of the reducing agent is reduced by the cover portion. As a result, the bias of the reducing agent is suppressed, and the dispersibility of the reducing agent is improved. In addition, the cover portion suppresses the backflow of the reducing agent to the upstream side.

In one aspect of the present disclosure, the cover portion may overlap the entire injection region when viewed from the central axis direction. According to such a configuration, the bias and the retained portion of the reducing agent are reduced in the flow of the exhaust gas, and the effect of improving the dispersibility of the reducing agent is promoted.

In one aspect of the present disclosure, the cover portion may have a shape symmetrical with respect to the center line of the injection region when viewed from the central axis direction. According to such a configuration, the flow of the exhaust gas to the injection region of the reducing agent becomes symmetrical, so that the effect of improving the dispersibility of the reducing agent is promoted.

One aspect of the present disclosure may further include at least one auxiliary through hole that penetrates the cover portion in the central axial direction. According to such a configuration, the fluidity of the exhaust gas in the reducing agent injection region is increased, and the generation of deposits around the injection port of the reducing agent supply unit can be suppressed.

In one aspect of the present disclosure, at least one auxiliary through hole may be arranged symmetrically with respect to the center line of the injection region when viewed from the central axis direction. According to such a configuration, the diffusion of the reducing agent in the injection region becomes symmetrical, so that the effect of improving the dispersibility of the reducing agent is promoted.

In one aspect of the present disclosure, the first shielding portion may further have a frame portion extending from the peripheral edge portion along the inner peripheral surface of the exhaust gas pipeline. The cover portion may be arranged in a space sandwiched between the frame portion and the central portion. According to such a configuration, the backflow of the reducing agent in the vicinity of the inner peripheral surface of the exhaust gas pipeline can be suppressed by the frame portion.

In one aspect of the present disclosure, the central axis of the opening of the annular portion may be located farther from the injection region than the central axis of the exhaust gas pipeline. According to such a configuration, the distance from the injection port of the reducing agent supply portion to the side wall portion of the second shielding portion can be increased. As a result, it is possible to suppress scattering of the reducing agent due to collision with the side wall portion and reduce the bias of the reducing agent in the injection region.

Another aspect of the present disclosure is an exhaust gas purification unit configured to reform or collect environmental pollutants in the exhaust gas of an internal combustion engine, and a downstream side of the exhaust gas purification unit in the flow direction of the exhaust gas. A reduction unit provided and configured to reduce the exhaust gas in the presence of the reducing agent, and a reduction configured to supply the reducing agent to the exhaust gas on the upstream side of the reducing unit in the flow direction of the exhaust gas. It is a swirling flow generating member arranged in the exhaust gas pipeline of the exhaust gas purification device including the agent supply unit, the exhaust gas pipeline connecting the exhaust port of the exhaust gas purification unit and the introduction port of the reduction unit. ..

The swirling flow generating member includes a first shielding portion configured to shield a part of the flow in the central axis direction of the exhaust gas pipeline, a second shielding portion arranged on the downstream side of the first shielding portion, and a second shielding portion. Has. The second shielding portion has an opening provided at the radial center of the exhaust gas pipeline, and an annular portion configured to shield the flow in the central axial direction on the radial outer side of the opening, and the annular portion to the second. 1 It has a side wall portion that extends to a shielding portion and surrounds a part of the opening of the annular portion in the circumferential direction.

The first shielding portion overlaps with the opening of the annular portion when viewed from the central axis direction, and extends from the central portion to the inner peripheral surface of the exhaust gas pipeline and the central portion separated from the inner peripheral surface of the exhaust gas pipeline. It has a peripheral edge portion, a plurality of through holes provided in the peripheral edge portion, and a cover portion arranged apart from the peripheral edge portion in the circumferential direction of the exhaust gas pipeline. The peripheral edge portion is arranged so as to at least overlap the outer edge of the opening of the annular portion in the radial direction of the open portion not surrounded by the side wall portion when viewed from the central axis direction. The reducing agent supply unit is configured to inject the reducing agent toward the side wall portion. The cover portion overlaps with at least a part of the reducing agent injection region by the reducing agent supply portion when viewed from the central axis direction.

According to such a configuration, the reducing agent and the exhaust gas are effectively agitated in the exhaust gas purifying device in which the swirling flow generating member is arranged. In addition, the cover portion suppresses the backflow of the reducing agent to the upstream side.

FIG. 1A is a schematic partial transmission perspective view of the exhaust gas purification device of the embodiment, and FIG. 1B is a schematic central sectional view of the exhaust gas purification device of FIG. 1A. FIG. 2 is a schematic perspective view of a swirling flow generating member in the exhaust gas purifying device of FIG. 1A. 3A is a schematic plan view of the swirling flow generating member of FIG. 2, and FIG. 3B is a schematic perspective view of a second shielding portion of the swirling flow generating member of FIG. FIG. 4A is a schematic plan view of a swirling flow generating member of the exhaust gas purification device according to an embodiment different from FIG. 3A, and FIG. 4B is a schematic plan view of the exhaust gas purification device according to an embodiment different from FIGS. 3A and 4A. FIG. 4C is a schematic plan view showing a part of the swirling flow generating member, and FIG. 4C is a schematic showing a part of the swirling flow generating member of the exhaust gas purifying device according to an embodiment different from FIGS. 3A, 4A and 4B. It is a typical plan view. FIG. 5A is a schematic partial transmission perspective view of an exhaust gas purifying device according to an embodiment different from that of FIG. 1A, and FIG. 5B is a schematic central sectional view of the exhaust gas purifying device of FIG. 5A. 6A is a schematic perspective view of the swirling flow generating member in the exhaust gas purifying device of FIG. 5A, and FIG. 6B is a schematic plan view of the swirling flow generating member of FIG. 5A. FIG. 7A is a schematic plan view of a swirling flow generating member of the exhaust gas purification device according to an embodiment different from FIG. 3A, and FIG. 7B is a schematic plan view of the exhaust gas purification device according to an embodiment different from FIGS. 3A and 7A. It is a schematic plan view of the swirling flow generating member. 8A is a schematic plan view of a swirling flow generating member of an exhaust gas purifying device according to an embodiment different from FIGS. 3A, 7A and 7B, and FIG. 8B is a plan view of FIGS. 3A, 7A, 7B and 7B. It is a schematic plan view of the swirling flow generating member of the exhaust gas purification device in the embodiment different from 8A.

Hereinafter, embodiments to which the present disclosure has been applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
The exhaust gas purification device (hereinafter, also simply referred to as “purification device”) 1 shown in FIGS. 1A and 1B is provided in the exhaust gas flow path of the internal combustion engine to reduce environmental pollutants in the exhaust gas. The purification device 1 includes an exhaust gas purification unit 2, a reduction unit 3, a reducing agent supply unit 4, an exhaust gas pipeline 5, and a swirling flow generating member 6.

The internal combustion engine provided with the purification device 1 is not particularly limited, but the purification device 1 can be particularly preferably used as an exhaust gas purification device for a diesel engine. Examples of the diesel engine include those used for driving or power generation in transportation equipment such as automobiles, railways, ships, construction machinery, power generation facilities, and the like.

<Exhaust gas purification unit>
The exhaust gas purification unit 2 reforms or collects environmental pollutants in the exhaust gas. Here, the "environmental pollutant" means carbon monoxide (CO), nitrogen oxide (NOx), particulate matter (PM), sulfur oxide (SOx), hydrocarbons (HC) and the like.

As shown in FIG. 1B, the exhaust gas purification unit 2 has a purification member 2A for purifying the exhaust gas and a tubular casing 2B containing the purification member 2A. The exhaust gas flows along the central axis direction of the casing 2B while contacting the purification member 2A inside the casing 2B.

Examples of the purification member 2A include a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a NOx adsorbent, and the like. DOC is a catalyst that oxidizes soluble organic components (SOF), CO and HC in PM contained in exhaust gas. The DPF is a filter that collects PM contained in the exhaust gas. The NOx adsorbent is a substance that adsorbs and removes NOx.

As the purification member 2A, a tubular body having a honeycomb structure is generally used. When the exhaust gas passes through the inside of the honeycomb structure, the environmental pollutants in the exhaust gas are modified by the catalyst metal contained in the purification member 2A or captured by the purification member 2A.

In FIGS. 1A and 1B, the exhaust gas purification unit 2 is arranged so that the flow direction of the exhaust gas inside is in the vertical direction, that is, the central axis of the tubular casing 2B is in the vertical direction. Further, the exhaust gas discharge port 2C of the exhaust gas purification unit 2 is formed so that the exhaust gas is discharged in the vertical direction. However, the flow direction of the exhaust gas in the exhaust gas purification unit 2 is not limited to the vertical direction, and may be a horizontal direction or a direction inclined with respect to the horizontal direction.

<Reduction section>
The reducing unit 3 reduces the exhaust gas in the presence of a reducing agent. Specifically, the reducing unit 3 reduces NOx in the exhaust gas with ammonia and a reduction catalyst, and reforms it into harmless nitrogen. Ammonia, which is a reducing agent, is generally produced by injecting urea water into an exhaust gas and hydrolyzing urea in the urea water.

The reduction unit 3 has a reduction catalyst 3A and a tubular casing 3B containing the reduction catalyst 3A. The reduction catalyst 3A is composed of a base material such as ceramic and a metal catalyst supported on the base material. The exhaust gas flows along the central axis direction of the casing 3B while contacting the reduction catalyst 3A inside the casing 3B.

The reduction unit 3 is connected to the downstream side of the exhaust gas purification unit 2 in the flow direction of the exhaust gas via an exhaust gas pipeline 5. The reduction unit 3 is arranged so that the flow direction of the exhaust gas inside is the same as that of the exhaust gas purification unit 2. That is, the central axis of the casing 3B of the reduction unit 3 is arranged in a direction that coincides with the central axis of the casing 2B of the exhaust gas purification unit 2.

<Reducing agent supply unit>
The reducing agent supply unit 4 supplies the reducing agent to the exhaust gas on the upstream side of the reducing unit 3 in the flow direction of the exhaust gas. The reducing agent supply unit 4 is configured to inject the reducing agent into the exhaust gas pipeline 5.

Specifically, the reducing agent supply unit 4 has an injector that injects the reducing agent toward the side wall portion 8B of the second shielding portion 8 described later. This injector injects urea water, which is a reducing agent, from the peripheral surface of the exhaust gas pipeline 5 toward the central axis of the exhaust gas pipeline 5.

As the injector of the reducing agent supply unit 4, a known injector can be used. In FIGS. 1A and 1B, only the connecting pipe to the exhaust gas pipeline 5 is shown as the reducing agent supply unit 4, and the injector and other members are not shown.

<Exhaust gas pipeline>
The exhaust gas pipeline 5 is a pipe body that communicates the exhaust port 2C of the exhaust gas purification unit 2 and the introduction port 3C of the reduction unit 3. That is, the exhaust gas discharged from the exhaust gas purification unit 2 is introduced into the reduction unit 3 through the exhaust gas pipeline 5. A swirling flow generating member 6 is arranged inside the exhaust gas pipeline 5. Further, a reducing agent supply unit 4 is connected to the peripheral surface of the exhaust gas pipeline 5.

The direction of the central axis of the exhaust gas pipeline 5 coincides with the direction of the central axis of the casing 2B of the exhaust gas purification unit 2 and the casing 3B of the reduction unit 3. That is, the exhaust gas pipeline 5 forms a straight exhaust gas flow path without bending between the exhaust gas purification unit 2 and the reduction unit 3.

In the present embodiment, the exhaust gas pipeline 5 is a straight pipe, and the exhaust port 2C of the exhaust gas purification unit 2 and the introduction port 3C of the reduction unit 3 have the same diameter. However, the exhaust port 2C of the exhaust gas purification unit 2 and the introduction port 3C of the reduction unit 3 do not necessarily have the same diameter.

<Swirl flow generating member>
The swirling flow generating member 6 is installed in the exhaust gas pipeline 5, and generates a plurality of swirling flows in the exhaust gas. As shown in FIG. 2, the swirl flow generating member 6 has a first shielding portion 7 and a second shielding portion 8.

(1st shield)
The first shielding portion 7 has a plate shape that shields a part of the flow in the first direction D1 toward the downstream side along the central axis direction of the exhaust gas pipeline 5 with respect to the exhaust gas flowing in the exhaust gas pipeline 5. It is a member of.

The first shielding portion 7 has a central portion 7A, a peripheral portion 7B, a plurality of through holes 7C, a frame portion 7F, and a cover portion 7G. The first shielding portion 7 shields a part of the flow of the exhaust gas in the first direction D1 by the central portion 7A, the peripheral portion 7B, the frame portion 7F, and the cover portion 7G.

The central portion 7A is a plate-shaped portion arranged in a direction in which the thickness direction coincides with the first direction D1. The central portion 7A is arranged at a position overlapping the opening 8C of the annular portion 8A, which will be described later, when viewed from the first direction D1.

Specifically, the central portion 7A covers the portion of the opening 8C of the annular portion 8A that does not overlap with the side wall portion 8B (that is, the portion that can be seen from the upstream side) from the upstream side. The central portion 7A is connected to the side wall portion 8B, but is arranged apart from the inner peripheral surface of the exhaust gas pipeline 5.

The peripheral edge portion 7B is a portion extending in the radial direction from the outer edge of the central portion 7A to the inner peripheral surface of the exhaust gas pipeline 5. The peripheral edge portion 7B is arranged so as to at least overlap the outer edge of the opening 8C of the annular portion 8A in the radial direction of the open portion 8D not surrounded by the side wall portion 8B when viewed from the first direction D1.

In the present embodiment, the peripheral edge portion 7B is partially overlapped with the side wall portion 8B when viewed from the first direction D1. The surface on the upstream side of the peripheral edge portion 7B is arranged at a position shifted to the downstream side from the surface on the upstream side of the central portion 7A. That is, the central portion 7A projects upstream with respect to the peripheral portion 7B.

The first end portion 7D and the second end portion 7E in the circumferential direction of the exhaust gas pipeline 5 of the peripheral portion 7B extend parallel to the radial direction of the exhaust gas pipeline 5 from the central portion 7A toward the frame portion 7F, respectively. is doing. Further, the contact portion 7J of the peripheral edge portion 7B with the inner peripheral surface of the exhaust gas pipeline 5 is located downstream from the upstream side surface of the peripheral edge portion 7B along the first direction D1 (that is, to the second shielding portion 8). Stretching (towards).

The length L of the peripheral portion 7B in the circumferential direction of the contact portion 7J (that is, the length of the outer edge of the peripheral portion 7B, more strictly, the length from the first end portion 7D to the second end portion 7E) is the exhaust gas. It is preferably 1/2 or less of the inner peripheral length of the pipeline 5. If the length L of the contact portion is more than 1/2 of the inner peripheral length of the exhaust gas pipeline 5, the opening region in the first shielding portion 7 may become small and the pressure loss may increase. Since the length L of the contact portion is 1/2 or less of the inner peripheral length of the exhaust gas pipeline 5, the region of the side wall portion 8B where the exhaust gas flowing from the upstream collides becomes wider, so that the stirring performance It is possible to reduce the pressure loss while ensuring the above.

The plurality of through holes 7C are provided in the peripheral edge portion 7B. The plurality of through holes 7C penetrate the peripheral edge portion 7B along the first direction D1. The plurality of through holes 7C are arranged radially outside the opening 8C when viewed from the first direction D1.

In the present embodiment, the plurality of through holes 7C are arranged at equal intervals on two arcs having different distances from the center of the exhaust gas pipeline 5. The plurality of through holes 7C can be formed by punching, for example. Further, the shape of the plurality of through holes 7C is not limited to a circular shape.

The frame portion 7F extends from the peripheral edge portion 7B along the inner peripheral surface of the exhaust gas pipeline 5. The frame portion 7F constitutes a ring that abuts on the inner peripheral surface of the exhaust gas pipeline 5 together with the abutting portion 7J of the peripheral edge portion 7B. The frame portion 7F connects the first end portion 7D and the second end portion 7E of the peripheral edge portion 7B in the circumferential direction of the exhaust gas pipeline 5.

The cover portion 7G is a plate-shaped portion arranged apart from the peripheral edge portion 7B in the circumferential direction of the exhaust gas pipeline 5. The cover portion 7G is arranged at a position closer to the reducing agent supply portion 4 than the central portion 7A between the first end portion 7D and the second end portion 7E of the peripheral portion 7B in the circumferential direction of the exhaust gas pipeline 5. ing.

The cover portion 7G is arranged so as to connect the central portion 7A and the frame portion 7F in the radial direction in the space sandwiched between the frame portion 7F and the central portion 7A. The first end portion 7K and the second end portion 7L of the cover portion 7G in the circumferential direction of the exhaust gas pipeline 5 extend in the radial direction of the exhaust gas pipeline 5 from the central portion 7A toward the frame portion 7F, respectively. There is.

The cover portion 7G divides the space sandwiched between the central portion 7A and the frame portion 7F (that is, the opening region of the first shielding portion 7) into the first opening portion 7H and the second opening portion 7I. The first opening 7H and the second opening 7I are defined by a central portion 7A, a frame portion 7F, a peripheral portion 7B, and a cover portion 7G, respectively.

The first opening 7H is a portion sandwiched between the first end 7D of the peripheral edge 7B and the first end 7K of the cover 7G in the circumferential direction of the exhaust gas pipeline 5. The second opening 7I is a portion sandwiched between the second end portion 7E of the peripheral edge portion 7B and the second end portion 7L of the cover portion 7G in the circumferential direction of the exhaust gas pipeline 5. The first opening 7H and the second opening 7I are arranged side by side in the circumferential direction of the exhaust gas pipeline 5 with the cover portion 7G interposed therebetween.

As shown in FIG. 3A, the cover portion 7G is arranged so as to overlap the entire injection region A of the reducing agent by the reducing agent supply unit 4 when viewed from the first direction D1. The cover portion 7G has a shape symmetrical with respect to the center line of the injection region A when viewed from the first direction D1. The first end portion 7K and the second end portion 7L of the cover portion 7G are located outside the injection region A in the circumferential direction of the exhaust gas pipeline 5, respectively.

In the present embodiment, the injection direction of the reducing agent by the reducing agent supply unit 4 (that is, the center line of the injection region A) is orthogonal to the central axis of the exhaust gas pipeline 5. However, the injection direction of the reducing agent may or may not intersect the central axis of the exhaust gas pipeline 5 at an angle other than 90 °, or may not intersect the central axis of the exhaust gas pipeline 5.

When viewed from the first direction D1, the total area of the area in the exhaust gas pipeline 5 where the first shielding portion 7 is not arranged (that is, the first opening 7H and the second opening 7I) is a plurality of through holes. It is larger than the total area of 7C.

Further, the length of the first opening 7H in the circumferential direction (that is, the distance between the first end 7K of the cover portion 7G and the first end 7D of the peripheral portion 7B) and the circumferential length of the second opening 7I. The length (that is, the distance between the second end portion 7L of the cover portion 7G and the second end portion 7E of the peripheral portion 7B) is equal.

The length (that is, the size of the width) of the exhaust gas pipeline 5 of the cover portion 7G in the circumferential direction is not particularly limited, but for example, the length of the first opening 7H in the circumferential direction and the second opening 7I first opening. It is preferable that the length of the portion 7H is equal to or less than the circumferential length.

(2nd shield)
As shown in FIG. 3B, the second shielding portion 8 is a plate-shaped member having an annular portion 8A and a side wall portion 8B.

The annular portion 8A has an opening 8C provided at the radial center of the exhaust gas pipeline 5. The annular portion 8A is a portion that shields the flow in the first direction D1 on the radial outer side of the opening 8C. The outer diameter of the annular portion 8A coincides with the inner diameter of the exhaust gas pipeline 5. Further, the contact portion 8H of the annular portion 8A with the inner peripheral surface of the exhaust gas pipeline 5 extends from the upstream side surface of the annular portion 8A to the downstream side along the first direction D1.

The side wall portion 8B is a portion extending from the annular portion 8A to the central portion 7A of the first shielding portion 7 in the first direction D1. The side wall portion 8B surrounds a part of the annular portion 8A in the circumferential direction of the opening 8C. That is, the side wall portion 8B projects upstream (that is, toward the first shielding portion 7) from a part of the peripheral edge of the opening 8C.

The side wall portion 8B is arranged at a position overlapping the first opening 7H and the second opening 7I of the first shielding portion 7 in the first direction D1. The open portion 8D of the opening 8C of the annular portion 8A (that is, the portion not surrounded by the side wall portion 8B) is arranged on the side opposite to the reducing agent supply portion 4 with the central axis of the exhaust gas pipeline 5 interposed therebetween. ..

When viewed from the first direction D1, the central position of the open portion 8D in the circumferential direction faces the region where the reducing agent is injected in the side wall portion 8B (that is, on the opposite side of the central axis of the exhaust gas pipeline 5). ) Is good.

The first end portion 8E and the second end portion 8F in the circumferential direction of the side wall portion 8B do not overlap with the first opening 7H and the second opening 7I of the first shielding portion 7 in the first direction D1, respectively. That is, the open portion 8D as a whole overlaps the peripheral edge portion 7B of the first shielding portion 7 in the first direction D1. Further, the open portion 8D is provided with a step portion 8I protruding from the inner edge of the annular portion 8A (that is, the peripheral edge of the opening 8C) toward the upstream side.

The side wall portion 8B has a connecting portion 8G. The connecting portion 8G is an annular portion provided at the upstream end of the side wall portion 8B. The connecting portion 8G is connected to the downstream surface of the central portion 7A of the first shielding portion 7.

[1-2. Action]
Hereinafter, the mechanism for generating the swirling flow in the purification device 1 will be described.
In the purification device 1, the exhaust gas discharged from the exhaust gas purification unit 2 enters the exhaust gas pipeline 5 as it is without changing the direction of the flow.

In the exhaust gas pipeline 5, the flow of the exhaust gas is first partially shielded by the central portion 7A of the first shielding portion 7. That is, the flow path of the exhaust gas is narrowed down to the first opening 7H, the second opening 7I, and the plurality of through holes 7C.

Exhaust gas that has passed through the first opening 7H or the second opening 7I along the first direction D1 collides with the annular portion 8A of the second shielding portion 8. As a result, two swirling flows are formed so as to bypass the side wall portion 8B and head toward the opening 8C. Further, the flow of the exhaust gas that has passed through the plurality of through holes 7C collides with the two swirling flows.

As a result, the reducing agent that collides with the side wall portion 8B and is atomized is caught in the flow of the exhaust gas and diffuses and disperses. As a result, the reducing agent and the exhaust gas that have passed through the exhaust gas pipeline 5 come into uniform contact with the reduction catalyst 3A.

[1-3. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(1a) The flow of the exhaust gas in the first direction D1 is guided to the outside of the side wall portion 8B of the second shielding portion 8 by the first shielding portion 7. The flow thus guided flows toward the opening 8C of the annular portion 8A while being divided into two flows by the side wall portion 8B. As a result, the flow path of the exhaust gas is extended, and two swirling flows in opposite directions having a swirling shaft parallel to the first direction D1 are generated.

Therefore, the reducing agent sprayed toward the side wall portion 8B is efficiently diffused. As a result, the evaporation of the reducing agent is promoted and the dispersibility is improved. Further, a part of the exhaust gas flow passes through the plurality of through holes 7C of the first shielding portion 7 and joins the two swirling flows. As a result, the reducing agent and the exhaust gas are effectively agitated.

(1b) The inflow rate of the exhaust gas into the reducing agent injection region A is reduced by the central portion 7A, the frame portion 7F, and the cover portion 7G, particularly the cover portion 7G. As a result, the bias of the reducing agent is suppressed, and the dispersibility of the reducing agent is improved. In addition, the cover portion 7G suppresses the backflow of the reducing agent to the upstream side.

(1c) Since the cover unit 7G reduces the variation in the pressure distribution in the first direction D1 in the first shielding unit 7, the variation in the flow velocity in the exhaust gas purification unit 2 is suppressed. As a result, the temperature bias of the exhaust gas flowing into the exhaust gas pipeline 5 is suppressed, so that the evaporation and dispersion of the reducing agent are promoted.

(1d) Since the cover portion 7G overlaps the entire injection region A of the reducing agent when viewed from the first direction D1, the bias and retention portion of the reducing agent in the flow of the exhaust gas is reduced, and the dispersibility of the reducing agent is reduced. The improvement effect is promoted.

(1e) Since the cover portion 7G has a shape symmetrical with respect to the center line of the injection region A when viewed from the first direction D1, the flow of the exhaust gas to the injection region A of the reducing agent becomes symmetrical. The effect of improving the dispersibility of the reducing agent is promoted.

(1f) Since the first shielding portion 7 has the frame portion 7F, the backflow of the reducing agent in the vicinity of the inner peripheral surface of the exhaust gas pipeline 5 can be suppressed by the frame portion 7F.

[2. Second Embodiment]
[2-1. Constitution]
The exhaust gas purification device of the second embodiment has the same configuration as the exhaust gas purification device of the first embodiment except for the structure of the swirling flow generating member.

The exhaust gas purification device of the second embodiment includes the swirling flow generating member 16 shown in FIG. 4A. The swirling flow generating member 16 has a first shielding portion 17 and a second shielding portion 8. The second shielding portion 8 is the same as that of the first embodiment.

The first shielding portion 17 has a central portion 7A, a peripheral portion 7B, a plurality of through holes 7C, a frame portion 7F, a cover portion 7G, a first auxiliary through hole 7M, and a second auxiliary through hole 7N. .. The central portion 7A, the peripheral portion 7B, the plurality of through holes 7C, the frame portion 7F, and the cover portion 7G are the same as those in the first embodiment.

The first auxiliary through hole 7M and the second auxiliary through hole 7N each penetrate the cover portion 7G in the first direction D1. The first auxiliary through hole 7M and the second auxiliary through hole 7N are arranged symmetrically with respect to the center line of the injection region A when viewed from the first direction D1.

The first auxiliary through hole 7M and the second auxiliary through hole 7N do not have to overlap with the injection area A (see FIG. 4A), and the first auxiliary through hole 7M and the second auxiliary through hole 7N overlap with the injection area A. It may have a region (see FIGS. 4B, 4C).

The first auxiliary through hole 7M and the second auxiliary through hole 7N are located closer to the reducing agent supply portion 4 and the frame portion 7F than the central portion 7A of the first shielding portion 17, respectively, in the radial direction of the exhaust gas pipeline 5. Have been placed.

The shapes of the first auxiliary through hole 7M and the second auxiliary through hole 7N are not limited to the circular shape shown in FIG. 4A, and may be a quadrangle shown in FIG. 4B. Further, the shape of the first auxiliary through hole 7M and the second auxiliary through hole 7N may be a polygon other than a quadrangle.

Further, the first shielding portion 17 may be provided with one auxiliary through hole 7O as shown in FIG. 4C. The auxiliary through hole 7O is arranged so as to cross the injection region A in the circumferential direction of the exhaust gas pipeline 5 when viewed from the first direction D1, and has a shape symmetrical with respect to the center line of the injection region A.

By arranging at least one auxiliary through hole symmetrically with respect to the center line of the injection region A when viewed from the first direction D1, the diffusion of the reducing agent in the injection region A becomes symmetrical, so that reduction is achieved. The effect of improving the dispersibility of the agent is promoted. However, at least one auxiliary through hole does not necessarily have to be arranged symmetrically with respect to the center line of the injection region A when viewed from the first direction D1.

[2-2. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(2a) At least one auxiliary through hole enhances the fluidity of the exhaust gas in the reducing agent injection region A, and can suppress the generation of a deposit around the injection port of the reducing agent supply unit 4.

[3. Third Embodiment]
[3-1. Constitution]
The exhaust gas purification device 21 shown in FIGS. 5A and 5B includes an exhaust gas purification unit 2, a reduction unit 3, a reducing agent supply unit 4, an exhaust gas pipeline 5, and a swirling flow generating member 26.

The exhaust gas purification unit 2, the reduction unit 3, the reducing agent supply unit 4, and the exhaust gas pipeline 5 of the exhaust gas purification device 21 are the same as those of the exhaust gas purification device 1 of the first embodiment. The swirling flow generating member 26 has a first shielding portion 27 and a second shielding portion 28.

As shown in FIGS. 6A and 6B, the first shielding portion 27 is a portion in which the convex portion of the central portion 7A (that is, the side wall portion 8B of the second shielding portion 28 is inserted) in the first shielding portion 7 of the first embodiment. ) Is shifted in the direction away from the reducing agent supply unit 4.

In the second shielding portion 8 of the first embodiment, the second shielding portion 28 is formed by shifting the opening 8C and the side wall portion 8B of the annular portion 8A in a direction away from the reducing agent supply portion 4. Specifically, the central axis P2 of the opening 8C of the annular portion 8A is located farther from the injection region A than the central axis P1 of the exhaust gas pipeline 5.

That is, the central axis P1 of the exhaust gas line 5 and the central axis P2 of the opening 8C are arranged in the order of the central axis P1 of the exhaust gas line 5 and the central axis P2 of the opening 8C in the order closer to the reducing agent supply unit 4. ing.

[3-2. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(3a) Since the central axis P2 of the opening 8C of the annular portion 8A is located farther from the injection region A than the central axis P1 of the exhaust gas pipeline 5, the second shielding portion 28 from the injection port of the reducing agent supply portion 4 The distance to the side wall portion 8B of the As a result, it is possible to suppress scattering of the reducing agent due to collision with the side wall portion 8B and reduce the bias of the reducing agent in the injection region A.

[4. Other embodiments]
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(4a) In the exhaust gas purification device of the above embodiment, the cover portion does not necessarily have to have a shape symmetrical with respect to the center line of the injection region when viewed from the central axis direction of the exhaust gas pipeline. Further, the first end portion and the second end portion of the cover portion do not necessarily have to extend in parallel with the radial direction of the exhaust gas pipeline.

(4b) In the exhaust gas purification device of the above embodiment, the first shielding portion does not necessarily have to have a frame portion. For example, as shown in FIGS. 7A and 7B and 8A and 8B, the cover portion 7G may be a tongue piece-shaped portion protruding radially from the central portion 7A.

In FIGS. 7A and 7B and 8A and 8B, the first opening 7H and the second opening 7I are the central portion 7A, the peripheral portion 7B, the cover portion 7G, and the inner peripheral surface of the exhaust gas pipeline 5, respectively. Is defined by.

(4c) In the exhaust gas purification device of the above embodiment, the cover portion does not necessarily have to overlap the entire injection region when viewed from the central axis direction of the exhaust gas pipeline. That is, the cover portion may overlap only a part of the injection region.

(4d) In the exhaust gas purification device of the above embodiment, the swirling flow generating member may be formed by assembling a component formed as a second shielding portion to a component formed as a first shielding portion. Further, the swirling flow generating member may be composed of one integrally molded member.

(4e) In the exhaust gas purification device of the above embodiment, the inner diameter of the exhaust gas purification portion and / or the reduction portion and the inner diameter of the exhaust gas pipeline do not have to be the same. For example, the inner diameter of the exhaust gas purification unit may be smaller than the inner diameter of the exhaust gas pipeline. In this case, the exhaust gas pipeline has a tapered portion whose diameter is reduced from the downstream to the upstream.

Further, a connecting pipe may be further arranged between the exhaust gas purification unit and the exhaust gas pipeline. This connecting pipe may be curved. By using the connecting pipe curved in this way, the degree of freedom in arranging the exhaust gas purification unit is increased.

(4f) The configuration of the exhaust gas purification device of the second embodiment and the configuration of the exhaust gas purification device of the third embodiment can be combined. That is, an auxiliary through hole may be provided in the cover portion 7G of the first shielding portion 27 of the third embodiment.

(4g) The functions of one component in the above embodiment may be dispersed as a plurality of components, or the functions of the plurality of components may be integrated into one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

1,21 ... Exhaust gas purification device, 2 ... Exhaust gas purification unit, 2A ... Purification member,
2B ... Casing, 2C ... Discharge port, 3 ... Reduction part, 3A ... Reduction catalyst, 3B ... Casing,
3C ... Introduction port, 4 ... Reducing agent supply unit, 5 ... Exhaust gas pipeline,
6,16,26 ... Swirling flow generating member, 7,17,27 ... First shielding part, 7A ... Central part,
7B ... peripheral part, 7C ... through hole, 7D, 7E ... end part, 7F ... frame part, 7G ... cover part,
7H, 7I ... opening, 7J ... contact, 7K, 7L ... end,
7M, 7N, 7O ... Auxiliary through hole, 8, 28 ... Second shielding part, 8A ... Circular part,
8B ... side wall, 8C ... opening, 8D ... open, 8E, 8F ... end, 8G ... connection,
8H ... contact part, 8I ... step part.

Claims (8)

Exhaust gas purification device for internal combustion engine
An exhaust gas purification unit configured to reform or collect environmental pollutants in the exhaust gas,
A reducing unit provided on the downstream side of the exhaust gas purification unit in the flow direction of the exhaust gas and configured to reduce the exhaust gas in the presence of a reducing agent.
A reducing agent supply unit configured to supply the reducing agent to the exhaust gas on the upstream side of the reducing unit in the flow direction of the exhaust gas.
An exhaust gas pipeline that communicates the exhaust port of the exhaust gas purification unit and the introduction port of the reduction unit,
A swirling flow generating member installed in the exhaust gas pipeline and
With
The swirling flow generating member is
A first shielding portion configured to shield a part of the flow in the central axis direction of the exhaust gas pipeline, and a first shielding portion.
A second shielding portion arranged on the downstream side of the first shielding portion, and
Have,
The second shielding portion is
An annular portion having an opening provided in the radial center of the exhaust gas pipeline and configured to shield the flow in the central axial direction on the radial outer side of the opening.
A side wall portion that extends from the annular portion to the first shielding portion and surrounds a part of the annular portion in the circumferential direction of the opening.
Have,
The first shielding portion is
A central portion that overlaps the opening of the annular portion when viewed from the central axis direction and is separated from the inner peripheral surface of the exhaust gas pipeline.
A peripheral portion extending from the central portion to the inner peripheral surface of the exhaust gas pipeline, and a peripheral portion.
A plurality of through holes provided in the peripheral portion and
A cover portion arranged apart from the peripheral portion in the circumferential direction of the exhaust gas pipeline, and a cover portion.
Have,
The peripheral edge portion is arranged so as to at least overlap the outer edge of the opening of the annular portion in the radial direction of the open portion not surrounded by the side wall portion when viewed from the central axis direction.
The reducing agent supply unit is configured to inject the reducing agent toward the side wall portion.
An exhaust gas purifying device in which the cover portion overlaps with at least a part of an injection region of the reducing agent by the reducing agent supply portion when viewed from the central axis direction. The exhaust gas purification device according to claim 1.
The cover portion is an exhaust gas purifying device that overlaps the entire injection region when viewed from the central axis direction. The exhaust gas purification device according to claim 1 or 2.
The cover portion is an exhaust gas purification device having a shape symmetrical with respect to the center line of the injection region when viewed from the central axis direction. The exhaust gas purification device according to any one of claims 1 to 3.
An exhaust gas purification device further comprising at least one auxiliary through hole that penetrates the cover portion in the central axis direction. The exhaust gas purification device according to claim 4.
An exhaust gas purification device in which the at least one auxiliary through hole is arranged symmetrically with respect to the center line of the injection region when viewed from the central axis direction. The exhaust gas purification device according to any one of claims 1 to 5.
The first shielding portion further has a frame portion extending from the peripheral portion along the inner peripheral surface of the exhaust gas pipeline.
The cover portion is an exhaust gas purifying device arranged in a space sandwiched between the frame portion and the central portion. The exhaust gas purification device according to any one of claims 1 to 6.
An exhaust gas purification device in which the central axis of the opening of the annular portion is located at a position farther from the injection region than the central axis of the exhaust gas pipeline. An exhaust gas purification unit configured to reform or collect environmental pollutants in the exhaust gas of an internal combustion engine,
A reducing unit provided on the downstream side of the exhaust gas purification unit in the flow direction of the exhaust gas and configured to reduce the exhaust gas in the presence of a reducing agent.
A reducing agent supply unit configured to supply the reducing agent to the exhaust gas on the upstream side of the reducing unit in the flow direction of the exhaust gas.
An exhaust gas pipeline that communicates the exhaust port of the exhaust gas purification unit and the introduction port of the reduction unit,
A swirling flow generating member arranged in the exhaust gas pipeline of an exhaust gas purifying device comprising the above.
A first shielding portion configured to shield a part of the flow in the central axis direction of the exhaust gas pipeline, and a first shielding portion.
A second shielding portion arranged on the downstream side of the first shielding portion, and
With
The second shielding portion is
An annular portion having an opening provided in the radial center of the exhaust gas pipeline and configured to shield the flow in the central axial direction on the radial outer side of the opening.
A side wall portion that extends from the annular portion to the first shielding portion and surrounds a part of the annular portion in the circumferential direction of the opening.
Have,
The first shielding portion is
A central portion that overlaps the opening of the annular portion when viewed from the central axis direction and is separated from the inner peripheral surface of the exhaust gas pipeline.
A peripheral portion extending from the central portion to the inner peripheral surface of the exhaust gas pipeline, and a peripheral portion.
A plurality of through holes provided in the peripheral portion and
A cover portion arranged apart from the peripheral portion in the circumferential direction of the exhaust gas pipeline, and a cover portion.
Have,
The peripheral edge portion is arranged so as to at least overlap the outer edge of the opening of the annular portion in the radial direction of the open portion not surrounded by the side wall portion when viewed from the central axis direction.
The reducing agent supply unit is configured to inject the reducing agent toward the side wall portion.
The cover portion is a swirling flow generating member that overlaps with at least a part of the reducing agent injection region by the reducing agent supply portion when viewed from the central axis direction.

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