JP7548872B2 - Exhaust Gas Purification Equipment - Google Patents

Description

The present disclosure relates to an exhaust gas purification device.

Selective catalytic reduction (SCR) catalysts may be used in exhaust gas purification devices that purify exhaust gas from diesel engines. SCR is a method of reducing NOx in exhaust gas using a reducing agent and an SCR catalyst (hereinafter also referred to as a reduction catalyst) to reform it into harmless nitrogen. The reduction catalyst is generally installed downstream of another catalyst or a filter.

In SCR, to make the reduction catalyst function efficiently and improve the purification rate of exhaust gas, it is necessary to mix the reducing agent and disperse it homogeneously in the exhaust gas, and to bring the exhaust gas containing the reducing agent into contact with the reduction catalyst evenly. Therefore, Patent Document 1 proposes an exhaust gas purification device that arranges two shielding parts aligned in the flow direction of the exhaust gas upstream of the reduction catalyst, and diffuses the reducing agent by generating multiple swirling flows using these shielding parts.

JP 2018-115586 A

However, in the exhaust gas purification device of Patent Document 1, the upstream shielding part and the downstream shielding part are joined, and when these shielding parts are welded, minute gaps may occur between these shielding parts due to thermal deformation or the like. This may cause the exhaust gas flow to stagnate around the joints of these shielding parts, which may result in impeded evaporation and dispersion of the reducing agent, or the formation of precipitation of the reducing agent components (in other words, deposits).

One aspect of the present disclosure is to promote the evaporation and dispersion of the reducing agent while suppressing deposits.

One aspect of the present disclosure is an exhaust gas purification device for an internal combustion engine, comprising a first casing, a second casing, an injection port, an exhaust gas pipe, and a swirl flow generating member. The first casing is configured to house an exhaust gas purification member. The second casing is provided downstream of the first casing in the exhaust gas flow direction, and is configured to house a reduction catalyst that reduces the exhaust gas in the presence of a reducing agent. The injection port is used to supply the reducing agent to the exhaust gas upstream of the second casing in the exhaust gas flow direction. The exhaust gas pipe communicates between the exhaust port of the first casing and the inlet port of the second casing. The swirl flow generating member is installed in the exhaust gas pipe.

The swirling flow generating member also has a first shielding portion and a second shielding portion. The first shielding portion is configured to shield a portion of the exhaust gas flow. The second shielding portion is disposed downstream of the first shielding portion.

The second shielding portion has an annular portion, a top portion, a sidewall portion, and an opening portion. The annular portion is adjacent to the inner peripheral surface of the exhaust gas pipe and extends around the inner peripheral surface. The top portion is provided inside the annular portion and on the upstream side of the annular portion. The sidewall portion extends from the inner peripheral edge of the annular portion to the outer peripheral edge of the top portion and extends over a portion of the outer periphery of the top portion. The opening portion is provided between the top portion and the annular portion, faces the sidewall portion, and communicates between the upstream side and downstream side of the second shielding portion.

The first shielding portion has a central portion, a peripheral portion, at least one through hole, and a cover portion. The central portion is provided at a position away from the inner peripheral surface of the exhaust gas pipe and faces the top portion. The peripheral portion extends from the central portion to the inner peripheral surface of the exhaust gas pipe and extends over a portion of the outer periphery of the central portion. At least one through hole is provided in the peripheral portion. The cover portion is disposed away from the peripheral portion in the circumferential direction of the exhaust gas pipe. The injection port is located in front of the side wall portion, and at least a portion of the injection area of the reducing agent located in front of the injection port is located downstream of the cover portion. The top portion and the side wall portion are disposed away from the first shielding portion.

According to the above configuration, the top and side wall of the second shielding part are positioned away from the first shielding part. Therefore, there is no need to weld the first shielding part and the top and side wall of the second shielding part, and it is possible to prevent minute gaps from occurring between these parts due to the effects of thermal deformation or manufacturing variations, etc., and therefore it is possible to prevent the flow of exhaust gas from stagnation. In addition, since a gap is formed between the top and side wall of the second shielding part and the first shielding part, it is possible to improve the flow rate of the exhaust gas, and thereby it is possible to prevent the flow of exhaust gas from stagnation between the first and second shielding parts. As a result, it is possible to promote the evaporation and dispersion of the reducing agent supplied through the injection port, and it is possible to suppress deposits.

In one aspect of the present disclosure, the center of the apex may be located farther from the injection port than the central axis of the exhaust gas pipe.
According to the above configuration, the side wall of the second shielding part can be located away from the injection port, which prevents the reducing agent supplied through the injection port from colliding with the side wall and bouncing back, thereby facilitating the evaporation and dispersion of the reducing agent.

In one aspect of the present disclosure, at least one of the top portion and the central portion may be formed with a recess recessed toward the downstream side.
According to the above-mentioned configuration, the surface area of the central portion and/or the top portion is increased, and the reducing agent has more opportunities to collide with the central portion and/or the top portion, thereby accelerating the evaporation of the reducing agent and improving the dispersion of the reducing agent.

In one aspect of the present disclosure, in a cross section of the second shielding portion that includes the central axis of the exhaust gas pipe, a line that extends linearly from the inner peripheral edge of the annular portion to the outer peripheral edge of the apex may be the reference inclination line. A portion of the side wall portion that is located in the injection area of the reducing agent may be the injection area. At least a portion of the injection area may be located closer to the central axis than the reference inclination line in the cross section.

The above configuration allows the injection area on the side wall of the second shielding part to be spaced away from the injection port. This prevents the reducing agent supplied through the injection port from colliding with the injection area and bouncing back, thereby facilitating the evaporation and dispersion of the reducing agent.

In one aspect of the present disclosure, the second shielding portion may further include at least one obstruction portion that obstructs the flow of exhaust gas passing through the opening.
According to the above-mentioned configuration, the flow velocity of the exhaust gas passing through the opening can be suitably reduced, which makes it possible to suppress an excessive increase in the flow velocity of the exhaust gas and an uneven distribution of the reducing agent, thereby facilitating the vaporization and dispersion of the reducing agent.

In one aspect of the present disclosure, the swirling flow generating member in the exhaust gas purification device described above may be configured alone. Even in such a case, by using the swirling flow generating member in the exhaust gas purification device, it is possible to promote the vaporization and dispersion of the reducing agent and suppress deposits.

1 is a partially transparent perspective view of an exhaust gas purification device according to a first embodiment; 1 is a cross-sectional view taken along a central axis of an exhaust gas purification device according to a first embodiment. FIG. 2 is a perspective view of a swirl flow generating member according to the first embodiment. FIG. 2 is a front view of the first shielding portion of the first embodiment. FIG. 4 is a front view of the second shielding portion of the first embodiment. FIG. 5 is a cross-sectional view taken along the central axis of an exhaust gas purification device according to a second embodiment. FIG. 5 is a cross-sectional view taken along the central axis of an exhaust gas purification device according to a second embodiment. FIG. 11 is a cross-sectional view taken along the central axis of an exhaust gas purification device according to a third embodiment. FIG. 11 is a perspective view of a swirl flow generating member according to a third embodiment. FIG. 11 is a cross-sectional view taken along the central axis of an exhaust gas purification device according to a fourth embodiment. FIG. 13 is a perspective view of a swirl flow generating member according to a fourth embodiment. FIG. 13 is a front view of the second shielding portion of the fourth embodiment. FIG. 11 is a cross-sectional view taken along the central axis of an exhaust gas purification device according to a fifth embodiment. FIG. 13 is a front view of a second shielding portion of the fifth embodiment. FIG. 13 is a front view of a second shielding portion of the fifth embodiment. FIG. 13 is a cross-sectional view taken along the central axis of an exhaust gas purification device according to a sixth embodiment. FIG. 13 is a perspective view of a swirl flow generating member according to a sixth embodiment. FIG. 23 is a front view of the second shielding portion of the sixth embodiment.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.
[First embodiment]
[1. Overall structure]
1 and 2, an exhaust gas purification device 1 (hereinafter, simply referred to as a purification device) is provided in an exhaust gas flow path of an internal combustion engine and reduces environmental pollutants in the exhaust gas. The purification device 1 includes an exhaust gas purification section 2, a reduction section 3, an injection port 4, an exhaust gas pipe 5, and a swirl flow generating member 6.

The internal combustion engine in which the purification device 1 is installed is not particularly limited, but the purification device 1 can be particularly suitably used as an exhaust gas purification device for diesel engines. Examples of diesel engines include those used for driving or generating electricity in transportation equipment such as automobiles, railways, ships, and construction machines, and power generation facilities.

[2. Exhaust gas purification section]
The exhaust gas purification unit 2 reforms or captures environmental pollutants in the exhaust gas (see FIG. 2). Here, "environmental pollutants" refers to carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), sulfur oxides (SOx), hydrocarbons (HC), and the like.

The exhaust gas purification unit 2 has a purification member 2A for purifying the exhaust gas and a cylindrical first casing 2B that houses the purification member 2A. The exhaust gas flows along the central axis 2D of the first casing 2B while contacting the purification member 2A inside the first casing 2B.

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

The purification member 2A is generally a cylindrical body having a honeycomb structure. As the exhaust gas passes through the inside of the honeycomb structure, the environmental pollutants in the exhaust gas are reformed by the catalytic metal contained in the purification member 2A or are captured by the purification member 2A.

In the first embodiment, as an example, the exhaust gas purification unit 2 is arranged so that the flow direction of the exhaust gas inside is vertical, that is, the central axis 2D of the cylindrical first casing 2B is oriented vertically. In addition, the exhaust gas outlet 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 horizontal or inclined relative to the horizontal direction.

[3. Reduction section]
The reduction unit 3 reduces the exhaust gas in the presence of a reducing agent (see FIG. 2). Specifically, the reduction unit 3 reduces NOx in the exhaust gas using ammonia and a reduction catalyst, and reforms it into harmless nitrogen. The ammonia, which is the reducing agent, is generally produced by injecting urea water into the exhaust gas and hydrolyzing the urea in the urea water.

The reduction section 3 has a reduction catalyst 3A and a cylindrical second casing 3B that houses 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 direction of the central axis 3D of the second casing 3B while contacting the reduction catalyst 3A inside the second casing 3B.

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

[4. Injection nozzle]
The injection port 4 is a tubular portion that protrudes outward from the side wall of the exhaust gas pipe 5 located upstream of the reduction unit 3 and communicates with the inside of the exhaust gas pipe 5, and is configured to be provided with a reducing agent supply unit (not shown) (see FIG. 2 ). The reducing agent supply unit provided in the injection port 4 injects a reducing agent into the exhaust gas pipe 5 through the injection port 4.

Specifically, the reducing agent supply unit has an injector that injects the reducing agent toward an injection area 8E of a side wall 8D in the second shielding unit 8, which will be described later. This injector injects the reducing agent, urea water, from the inner peripheral surface of the exhaust gas pipe 5 toward the central axis 5A of the exhaust gas pipe 5.

[5. Exhaust gas pipe]
The exhaust gas pipe 5 is a pipe that connects the exhaust port 2C of the exhaust gas purification unit 2 and the inlet 3C of the reduction unit 3 (see FIG. 2). In other words, the exhaust gas discharged from the exhaust gas purification unit 2 is introduced into the reduction unit 3 through the exhaust gas pipe 5. A swirl flow generating member 6 is disposed inside the exhaust gas pipe 5. In addition, a reducing agent supply unit is connected to the inner peripheral surface of the exhaust gas pipe 5 via an injection port 4.

The cross section of the exhaust gas pipe 5 perpendicular to the exhaust gas flow direction is, for example, circular, and the central axis 5A of the exhaust gas pipe 5 passing through the center of the cross section coincides with the central axes 2D, 3D of the first and second casings 2B, 3B. In other words, the exhaust gas pipe 5 forms a straight exhaust gas flow path without bends between the exhaust gas purification section 2 and the reduction section 3.

In the following description, the two orthogonal axes in a cross section perpendicular to the exhaust gas flow direction of the exhaust gas pipe 5, which are perpendicular to the central axis 5A, are referred to as the vertical axis 5B and the horizontal axis 5C (see Figures 4 and 5). The vertical axis 5B passes through approximately the center of the above-mentioned injection port 4, and the center line of the injection area A of the reducing agent by the reducing agent supply unit coincides with the vertical axis 5B.

In the first embodiment, the exhaust gas pipeline 5 is a straight pipe, and the exhaust outlet 2C of the exhaust gas purification unit 2 and the inlet 3C of the reduction unit 3 have the same diameter. However, the diameter of the exhaust outlet 2C of the exhaust gas purification unit 2 and the diameter of the inlet 3C of the reduction unit 3 may be different. In this case, the shape of the exhaust gas pipeline 5 is determined according to the respective diameters of the exhaust outlet 2C and the inlet 3C.

[6. Swirling flow generating member]
The swirl flow generating member 6 is installed in the exhaust gas pipeline 5 and generates a plurality of swirl flows in the exhaust gas (see FIG. 3 ). The swirl flow generating member 6 has a first shielding portion 7 and a second shielding portion 8. The first and second shielding portions 7, 8 are disposed apart from each other and are fixed to the exhaust gas pipeline 5 by, for example, welding or press fitting.

<First shielding part>
The first shielding portion 7 is a plate-shaped member that shields part of the flow of exhaust gas toward the downstream side along the central axis 5A of the exhaust gas pipeline 5 in the exhaust gas pipeline 5 (see FIGS. 3 and 4).

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 portion of the flow in the direction of the central axis 5A of the exhaust gas pipeline 5 by means of the central portion 7A, the peripheral portion 7B, the frame portion 7F, and the cover portion 7G.

The central portion 7A is a plate-like portion arranged such that its thickness direction coincides with the central axis 5A. The central portion 7A is separated from the inner peripheral surface of the exhaust gas pipe 5 and is formed as a convex portion protruding upstream, and the top of the central portion 7A protruding upstream has a flat shape. The central portion 7A is circular when viewed along the central axis 5A, and is arranged at a position overlapping with the top 8B of the second shielding portion 8 described later (see FIG. 5). As an example, the center 7L of the central portion 7A is located on or near the vertical axis 5B. The central portion 7A is also eccentrically arranged so that the center 7L is located farther from the nozzle 4 than the central axis 5A.

The peripheral portion 7B extends radially from the outer periphery of the central portion 7A to the inner periphery of the exhaust gas pipe 5. When viewed in the direction of the central axis 5A, the peripheral portion 7B is arranged so as to overlap the opening 8H of the second shielding portion 8 described below, the portion of the annular portion 8A located outside the opening 8H, and the side wall portion 8D.

The peripheral portion 7B extends over a portion of the outer periphery of the central portion 7A. In addition, the first end 7D and the second end 7E of the peripheral portion 7B in the circumferential direction of the exhaust gas pipeline 5 each extend in the radial direction of the exhaust gas pipeline 5 from the central portion 7A toward the frame portion 7F. In addition, the abutment portion 7J of the peripheral portion 7B with the inner peripheral surface of the exhaust gas pipeline 5 extends downstream (i.e., toward the second shielding portion 8) from the upstream surface of the peripheral portion 7B along the central axis 5A.

The multiple through holes 7C are provided in the peripheral portion 7B and penetrate the peripheral portion 7B. The multiple through holes 7C are circular and can be formed, for example, by punching. Of course, the shape of the multiple through holes 7C is not limited to a circular shape. Also, a single through hole may be provided in the peripheral portion 7B.

The frame portion 7F extends from the peripheral portion 7B along the inner peripheral surface of the exhaust gas pipeline 5. Together with the abutment portion 7J of the peripheral portion 7B, the frame portion 7F forms a ring that abuts against the inner peripheral surface of the exhaust gas pipeline 5. The frame portion 7F extends in the circumferential direction of the exhaust gas pipeline 5 and is connected to the first end 7D and the second end 7E of the peripheral portion 7B.

The cover portion 7G is a plate-shaped portion disposed away from the peripheral portion 7B in the circumferential direction of the exhaust gas pipe 5. The cover portion 7G is located between the first end 7D and the second end 7E of the peripheral portion 7B in the circumferential direction of the exhaust gas pipe 5, and is disposed closer to the nozzle 4 than the central portion 7A. The vertical axis 5B is located at the circumferential center of the cover portion 7G.

The cover portion 7G extends radially from the central portion 7A to the frame portion 7F, and divides the space between the central portion 7A and the frame portion 7F (i.e., the opening area of the first shielding portion 7) into a first opening 7H and a second opening 7I. The first opening 7H and the second opening 7I are each defined by the central portion 7A, the frame portion 7F, the peripheral portion 7B, and the cover portion 7G.

The first opening 7H is a portion sandwiched between the first end 7D of the peripheral portion 7B and the cover portion 7G in the circumferential direction of the exhaust gas pipeline 5. The second opening 7I is a portion sandwiched between the second end 7E of the peripheral portion 7B and 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, sandwiching the cover portion 7G therebetween.

As shown in FIG. 4, when viewed in the direction of the central axis 5A, the cover portion 7G is wider than the injection area A and is arranged so as to overlap the entire injection area A of the reducing agent injected by the reducing agent supply unit. When viewed in the direction of the central axis 5A, the cover portion 7G has a shape that is approximately symmetrical with respect to the center line of the injection area A (in other words, the vertical axis 5B).

In the first embodiment, the direction in which the reducing agent is injected by the reducing agent supply unit (i.e., the center line of the injection area A) is perpendicular to the central axis 5A of the exhaust gas pipe 5. However, the direction in which the reducing agent is injected may intersect with the central axis 5A at an angle other than 90°, or may not intersect with the central axis 5A.

<Second Shielding Part>
The second shielding portion 8 is provided downstream of the first shielding portion 7 and is a plate-like member having an annular portion 8A, a top portion 8B, a side wall portion 8D, and an opening 8H (see FIGS. 3 and 5).

The annular portion 8A is adjacent to the inner peripheral surface of the exhaust gas pipeline 5 and extends around the inner peripheral surface, blocking the flow of exhaust gas in the direction of the central axis 5A. The outer diameter of the annular portion 8A is the same as the inner diameter of the exhaust gas pipeline 5. In addition, the abutment portion 8I of the annular portion 8A with the inner peripheral surface of the exhaust gas pipeline 5 extends downstream along the central axis 5A from the outer peripheral edge of the annular portion 8A.

The apex 8B is a circular, flat portion that is perpendicular to the central axis 5A. When viewed in the direction of the central axis 5A, the apex 8B is located inside the annular portion 8A and is located upstream of the annular portion 8A. As an example, the center 8C of the apex 8B is located on or near the vertical axis 5B. The apex 8B is also eccentrically disposed so that the center 8C is located farther from the nozzle 4 than the central axis 5A.

The apex 8B is located inside the recess formed by the central portion 7A on the downstream outer surface of the first shielding portion 7, and faces the central portion 7A of the first shielding portion 7 along the central axis 5A. The apex 8B is disposed with a gap between it and the central portion 7A.

The side wall portion 8D is a portion that extends along the central axis 5A from a portion of the inner peripheral edge of the annular portion 8A to the outer peripheral edge of the apex portion 8B. The side wall portion 8D extends over a portion of the outer periphery of the apex portion 8B. That is, when viewed in the direction of the central axis 5A, the side wall portion 8D is located outside the apex portion 8B and extends from the first end portion 8F to the second end portion 8G along the outer periphery of the apex portion 8B. Also, when viewed in the direction of the central axis 5A, the side wall portion 8D overlaps with the first opening portion 7H and the second opening portion 7I of the first shielding portion 7, and the first end portion 8F and the second end portion 8G of the side wall portion 8D do not overlap with the first opening portion 7H and the second opening portion 7I of the first shielding portion 7. Also, the side wall portion 8D is disposed at a distance from the central portion 7A of the first shielding portion 7.

The side wall 8D also has an injection area 8E located in front of the injection port 4. The injection area 8E is located in the injection area A of the reducing agent by the reducing agent supply unit. The entire side wall 8D spreads out like the side of a cone. The injection area 8E as a whole extends linearly from the inner periphery of the annular portion 8A to the outer periphery of the apex 8B in a cross section along the central axis 5A, forming a reference inclined line (described later) that inclines toward the central axis 5A as it moves upstream (see FIG. 2).

The opening 8H is formed between the top 8B and the annular portion 8A, and is a portion that communicates the upstream side and downstream side of the second shielding portion 8. When viewed in the direction of the central axis 5A, the opening 8H is located outside the top 8B, extends circumferentially from the first end 8F to the second end 8G of the side wall portion 8D, and faces the side wall portion 8D across the central axis 5A. When viewed in the direction of the central axis 5A, the opening 8H overlaps with the peripheral portion 7B of the first shielding portion 7. When viewed in the direction of the central axis 5A, the circumferential center position of the opening 8H is located on the vertical axis 5B, and faces the injection port 4 across the central axis 5A.

[7. Action]
The mechanism by which the swirling flow is generated in the purification device 1 will be described below.
In the purification device 1, the exhaust gas discharged from the exhaust gas purification section 2 enters the exhaust gas pipe 5 as it is without changing its flow direction.

In the exhaust gas pipe 5, the flow of the exhaust gas is first partially blocked by the center portion 7A of the first blocking portion 7. In other words, the flow path of the exhaust gas is narrowed down to the first opening 7H, the second opening 7I, and the multiple through holes 7C.

The exhaust gas that passes through the first opening 7H or the second opening 7I along the central axis 5A collides with the annular portion 8A of the second shielding portion 8. This creates two swirling flows that bypass the side wall portion 8D and head toward the opening 8H. In addition, the flow of exhaust gas that passes through the multiple through holes 7C collides with these two swirling flows.

As a result, the reducing agent that collides with the injection area 8E of the side wall 8D and is atomized is caught up in the flow of exhaust gas and diffuses and disperses. As a result, the reducing agent and exhaust gas that pass through the exhaust gas pipe 5 come into homogeneous contact with the reduction catalyst 3A.

[8. Effects]
(1) According to the first embodiment, the top 8B and the side wall 8D of the second shielding part 8 are disposed away from the first shielding part 7. Therefore, there is no need to weld the first shielding part 7 and the top 8B and the side wall 8D of the second shielding part 8, and it is possible to suppress the generation of a small gap between these parts due to the influence of thermal deformation or manufacturing variations, and therefore it is possible to suppress the stagnation of the flow of the exhaust gas. In addition, since a gap is formed between the top 8B and the side wall 8D of the second shielding part 8 and the first shielding part 7, it is possible to improve the flow rate of the exhaust gas, and thus it is possible to suppress the stagnation of the flow of the exhaust gas between the first and second shielding parts 7 and 8. As a result, it is possible to promote the vaporization and dispersion of the reducing agent supplied through the injection port 4, and to suppress deposits.

(2) In addition, the center 8C of the top 8B of the second shielding portion 8 is offset from the central axis 5A of the exhaust gas pipe 5 to the opposite side of the injection port 4. This allows the injection area 8E of the side wall portion 8D of the second shielding portion 8 to be spaced away from the injection port 4. As a result, the reducing agent supplied through the injection port 4 can be prevented from colliding with the injection area 8E and bouncing back, and the vaporization and dispersion of the reducing agent can be promoted.

[Second embodiment]
[1. Overall structure]
The purification device 1 of the second embodiment has a similar configuration to that of the first embodiment (see Figs. 6 and 7). However, in the first embodiment, the injection area 8E in the side wall 8D of the second shielding part 8 forms a reference inclined line 8J in a cross section along the central axis 5A. On the other hand, the injection area 8E of the second embodiment is recessed toward the central axis 5A, and at least a part of the injection area 8E is curved so as to protrude toward the central axis 5A side beyond the reference inclined line 8J in the cross section. The purification device 1 of the second embodiment differs from the first embodiment in this respect.

Specifically, for example, the entire portion of the injection area 8E that intersects with the vertical axis 5B may be located closer to the central axis 5A than the reference inclination line 8J in the cross section (see FIG. 6). Also, for example, a portion of that portion may be located closer to the central axis 5A than the reference inclination line 8J in the cross section (see FIG. 7). Also, as shown in FIGS. 6 and 7, the depth of the recess in the injection area 8E may be determined appropriately.

2. Effects
According to the second embodiment, since the injection area 8E of the second shielding portion 8 is recessed toward the central axis 5A, the injection area 8E can be moved away from the injection port 4. Therefore, it is possible to suppress the reducing agent supplied through the injection port 4 from colliding with the injection area 8E and bouncing back, and it is possible to promote the vaporization and dispersion of the reducing agent.

[Third embodiment]
[1. Overall structure]
The purification device 1 of the third embodiment has a similar configuration to that of the first embodiment, but differs from the first embodiment in that the degree of eccentricity of the central portion 7A of the first shielding portion 7 and the top portion 8B and the side wall portion 8D of the second shielding portion 8 is greater than that of the first embodiment (see FIGS. 8 and 9). In other words, the center 7L of the central portion 7A and the center 8C of the top portion 8B are located farther from the injection port 4 than in the first embodiment.

For this reason, the portion of the peripheral portion 7B of the first shielding portion 7 located on the opposite side of the injection port 4 has a narrower radial width than that of the first embodiment, and the portion does not have a plurality of through holes 7C. In addition, the annular portion 8A of the second shielding portion 8 extends in the circumferential direction from near the first end 8F of the side wall portion 8D to near the second end 8G, and the opening 8H is located near the abutment portion 8I.

In addition, the portion of the peripheral portion 7B on the injection port 4 side has a wider radial width than in the first embodiment, and the widths of the first and second openings 7H and 7I formed in that portion are also wider than in the first embodiment.

The cover portion 7G is narrower than the cover portion 7G of the first embodiment, and is positioned so as to overlap a portion of the injection area A of the reducing agent by the reducing agent supply unit when viewed in the direction of the central axis 5A. In other words, when viewed in the direction of the central axis 5A, a portion of the injection area A reaches an area that does not overlap with the cover portion 7G.

2. Effects
According to the third embodiment, compared to the first embodiment, the injection area 8E of the second shielding portion 8 can be further away from the injection port 4. As a result, the reducing agent supplied through the injection port 4 can be further prevented from colliding with the injection area 8E and bouncing back, and the vaporization and dispersion of the reducing agent can be promoted.

[Fourth embodiment]
[1. Overall structure]
The purification device 1 of the fourth embodiment has a similar configuration to that of the first embodiment, but differs from the first embodiment in that recesses 7K and 8K recessed toward the downstream side are provided in the central portion 7A of the first shielding portion 7 and the top portion 8B of the second shielding portion 8, respectively (see FIGS. 10 and 11 ). The recesses 7K and 8K are circular when viewed along the central axis 5A, and are arranged to overlap with each other, with a gap formed between the recesses 7K and 8K.

The depth of the recesses 7K, 8K is greater than the plate thickness of the central portion 7A and the top portion 8B. The recess 7K in the central portion 7A has a depth that at least reaches the inner space of the recess formed by the recess 8K on the outer surface of the upstream side of the top portion 8B. In the fourth embodiment, as an example, the depth of the recesses 7K, 8K is less than the height at which the central portion 7A protrudes upstream. However, this is not limited to this, and the depth of the recesses 7K, 8K may be greater than the height at which the central portion 7A protrudes. In this case, it is preferable that the depth of the recesses 7K, 8K is less than the distance between the top portion 8B and the annular portion 8A in the direction of the central axis 5A.

2. Modifications
A first obstruction portion 8L that obstructs the flow of exhaust gas may be provided at the opening 8H in the second shielding portion 8 of the purification device 1 of the fourth embodiment (see FIG. 12).

The first inhibition portion 8L is located at the circumferential center of the opening 8H, and is a band-shaped portion that extends in a straight line from the inner peripheral edge of the annular portion 8A to the outer peripheral edge of the apex portion 8B. When viewed in the direction of the central axis 5A, the first inhibition portion 8L extends along the vertical axis 5B and faces the injection port 4 across the central axis 5A. The opening 8H is also divided by the first inhibition portion 8L into two openings that are aligned in the circumferential direction.

3. Effects
(1) According to the fourth embodiment, the recesses 7K and 8K are provided in the central portion 7A of the first shielding portion 7 and the top portion 8B of the second shielding portion 8, so that the surface areas of the central portion 7A and the top portion 8B are increased, and the reducing agent has more opportunities to collide with the central portion 7A and the top portion 8B. This promotes the vaporization of the reducing agent and improves the dispersion of the reducing agent. In addition, the recesses 7K and 8K can reduce the flow rate of the exhaust gas flowing down between the central portion 7A and the top portion 8B. This can prevent the flow rate of the exhaust gas from increasing excessively or the reducing agent from being biased, and as a result, the vaporization and dispersion of the reducing agent can be promoted. In addition, since the recesses 7K and 8K protrude downstream, the central portion 7A can be prevented from protruding upstream from the exhaust gas pipe 5 and coming into contact with the purifying member 2A.

(2) Furthermore, according to the modified example, the first obstruction portion 8L in the second shielding portion 8 can suitably reduce the flow velocity of the exhaust gas passing through the opening 8H. This makes it possible to prevent the flow velocity of the exhaust gas flowing down the swirling flow generating member 6 from increasing excessively, and promotes the evaporation and dispersion of the reducing agent.

[Fifth embodiment]
[1. Overall structure]
The purification device 1 of the fifth embodiment has a similar configuration to that of the first embodiment, but differs from that of the first embodiment in the second shielding portion 8 (see FIG. 13 ). The following describes the differences between the purification device 1 of the fifth embodiment and the first embodiment.

[2. Second shielding part]
The second shielding portion has an annular portion 8A, a top portion 8B, a side wall portion 8D, and an opening portion 8H similar to the first embodiment (see FIG. 14).

However, in the fifth embodiment, the apex 8B is substantially semicircular, and when viewed in the direction of the central axis 5A, the diameter portion that forms the diameter at the outer periphery of the apex 8B extends along the horizontal axis 5C. The side wall portion 8D extends from a part of the inner periphery of the annular portion 8A to the diameter portion. The injection area portion 8E in the side wall portion 8D is recessed toward the central axis 5A, and the injection area portion 8E is curved so as to protrude toward the central axis 5A side from the reference inclination line 8J in a cross section along the central axis 5A. Also, in the fifth embodiment, the apex 8B is provided eccentrically so that the center 8C is located farther from the injection port 4 than the central axis 5A. The center 8C of the apex 8B may be, for example, the center of gravity of the apex 8B.

When viewed in the direction of the central axis 5A, the opening 8H is provided along an arc-shaped portion extending in an arc shape at the outer periphery of the top 8B. The opening 8H is provided with a plurality of second and third obstruction portions 8M and 8N that obstruct the flow of exhaust gas.

The second inhibition portion 8M is a band-shaped portion that extends linearly from the inner peripheral edge of the annular portion 8A to the arc portion of the apex 8B. In the fifth embodiment, as an example, four second inhibition portions 8M are provided in the opening 8H, spaced apart and aligned in the circumferential direction. An opening through which exhaust gas passes is formed in the portion between adjacent second inhibition portions 8M in the opening 8H. Similar openings are also formed between the first end 8F of the side wall portion 8D and the first inhibition portion 8L, and between the second end 8G and the first inhibition portion 8L.

In other words, when viewed in the direction of the central axis 5A, the opening 8H is divided into five openings arranged in the circumferential direction by the four second inhibition portions 8M. These openings are arranged linearly symmetrically about the vertical axis 5B, and the central opening intersects with the vertical axis 5B and faces the injection port 4 across the central axis 5A. The central opening is closed by a plate-shaped third inhibition portion 8N. The third inhibition portion 8N has multiple through holes.

The third inhibitor 8N may be provided at other openings in the opening 8H, or at multiple openings or all openings. Also, the third inhibitor 8N may not be provided at any opening in the opening 8H (see FIG. 15). The shape and number of the openings 8H may be determined as appropriate.

3. Effects
(1) According to the fifth embodiment, the flow velocity of the exhaust gas passing through the opening 8H can be suitably reduced by the second inhibition portion 8M or the second and third inhibition portions 8M and 8N in the second shielding portion 8. As a result, it is possible to suppress an excessive increase in the flow velocity of the exhaust gas flowing down the swirl flow generating member 6, and it is possible to promote the vaporization and dispersion of the reducing agent.

(2) The top 8B of the second shielding portion is semicircular, and the center 8C of the top 8B is eccentrically located on the opposite side of the injection port 4 from the central axis 5A. This makes the inclination of the side wall 8D gentler, and the injection area 8E of the side wall 8D can be located farther away from the injection port 4. As a result, the reducing agent supplied through the injection port 4 can be prevented from colliding with the injection area 8E and bouncing off, and the vaporization and dispersion of the reducing agent can be promoted.

Sixth Embodiment
[1. Overall structure]
The purification device 1 of the sixth embodiment has a similar configuration to that of the fifth embodiment, but differs from the fifth embodiment in that the central portion 7A of the first shielding portion 7 and the top portion 8B of the second shielding portion 8 are provided with recesses 7K and 8K recessed toward the downstream side, respectively (see FIGS. 16 to 18). The recesses 7K and 8K are substantially elliptical when viewed along the central axis 5A, extend along the horizontal axis 5C, and are arranged so as to overlap each other. A gap is formed between the recesses 7K and 8K. The depth to which the recesses 7K and 8K are recessed is determined in the same manner as in the fourth embodiment.

2. Effects
According to the sixth embodiment, the central portion 7A of the first shielding portion 7 and the top portion 8B of the second shielding portion 8 are provided with recesses 7K and 8K, and the opening 8H of the second shielding portion 8 is provided with second and third inhibition portions 8M and 8N. Therefore, similar to the fourth embodiment, the recesses 7K and 8K promote the vaporization of the reducing agent, and suppress an excessive increase in the flow rate of the exhaust gas. Furthermore, similar to the fifth embodiment, the second and third inhibition portions 8M and 8N suppress an excessive increase in the flow rate of the exhaust gas and an imbalance of the reducing agent. Therefore, the vaporization and dispersion of the reducing agent can be promoted.

[Other embodiments]
(1) In the first to sixth embodiments, the apex 8B of the second shielding portion 8 is provided eccentrically so that the center 8C is located farther from the ejection port 4 than the central axis 5A. However, the center 8C of the apex 8B may be located on the central axis 5A or closer to the ejection port 4 than the central axis 5A. Even in the case of such a configuration, the same effect can be obtained.

(2) In the fourth and sixth embodiments, a recess may be provided in either the central portion 7A of the first shielding portion 7 or the top portion 8B of the second shielding portion 8. Even in the case of such a configuration, the surface area of the central portion 7A or the top portion 8B is increased, and the reducing agent has more opportunities to collide with the central portion 7A or the top portion 8B. This promotes the vaporization of the reducing agent and improves the dispersion of the reducing agent. In addition, since the flow rate of the exhaust gas flowing down between the central portion 7A and the top portion 8B can be reduced, the flow rate of the exhaust gas flowing down the swirl flow generating member 6 is prevented from increasing excessively and the reducing agent is prevented from being biased, and as a result, the vaporization and dispersion of the reducing agent can be promoted.
Also, instead of the recesses 7K, 8K, a convex portion protruding toward the upstream side may be provided on both or one of the central portion 7A of the first shielding portion 7 and the top portion 8B of the second shielding portion 8.

(3) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

1...exhaust gas purification device, 2...exhaust gas purification section, 2A...purification member, 2B...first casing, 2D...central axis, 3...reduction section, 3A...reduction catalyst, 3B...second casing, 3D...central axis, 4...injection port, 5...exhaust gas pipe, 5A...central axis, 6...swirl flow generating member, 7...first shielding section, 7A...center, 7B...periphery, 7C...multiple through holes, 7G...cover section, 7K...recess, 8...second shielding section, 8A...annular section, 8B...top, 8C...center, 8D...side wall section, 8E...injection area section, 8H...opening, 8J...reference inclined line, 8K...recess, 8L-8N...first to third obstruction sections.

Claims (5)

An exhaust gas purification device for an internal combustion engine,
A first casing configured to accommodate an exhaust gas purification member;
a second casing provided downstream of the first casing in a flow direction of the exhaust gas and configured to accommodate a reduction catalyst that reduces the exhaust gas in the presence of a reducing agent;
an injection port used for supplying the reducing agent to the exhaust gas upstream of the second casing in a flow direction of the exhaust gas;
an exhaust gas pipe connecting an exhaust port of the first casing and an inlet port of the second casing;
a swirl flow generating member disposed in the exhaust gas pipe,
The injection port is a cylindrical portion provided in the exhaust gas pipe and extending along an axis of the injection port,
The swirl flow generating member is
A first shielding portion configured to shield a portion of the exhaust gas flow;
a second shielding portion disposed on the downstream side of the first shielding portion,
The second shielding portion is
an annular portion adjacent to an inner peripheral surface of the exhaust gas pipe and extending circumferentially along the inner peripheral surface;
a top portion disposed inside the annular portion and on the upstream side of the annular portion;
a sidewall portion extending from an inner peripheral edge of the annular portion to an outer peripheral edge of the apex and over a portion of the outer periphery of the apex;
an opening provided between the top portion and the annular portion, facing the side wall portion, and communicating between the upstream side and the downstream side of the second shielding portion,
The first shielding portion is
a central portion provided at a position away from an inner circumferential surface of the exhaust gas pipe and facing the top portion;
A peripheral portion that spreads from the central portion to an inner peripheral surface of the exhaust gas pipe and extends over a part of an outer periphery of the central portion;
At least one through hole provided in the peripheral portion;
a cover portion disposed away from the peripheral edge portion in the circumferential direction of the exhaust gas pipe,
The side wall portion is located on an extension of an axis of the injection port,
At least a part of the injection area of the reducing agent located in front of the injection port is located on the downstream side of the cover portion,
The top portion and the side wall portion are disposed away from the first shielding portion.
Exhaust gas purification device. The exhaust gas purification device according to claim 1,
The center of the apex is located farther from the injection port than the central axis of the exhaust gas pipe.
Exhaust gas purification device. The exhaust gas purification device according to claim 1 or 2,
At least one of the top portion and the central portion has a recess formed therein that is recessed toward the downstream side.
Exhaust gas purification device. The exhaust gas purification device according to any one of claims 1 to 3,
a reference inclination line is a line that extends linearly from an inner peripheral edge of the annular portion to an outer peripheral edge of the apex portion in a cross section of the second shielding portion that includes a central axis of the exhaust gas pipeline;
a portion of the side wall portion that is located in the injection area of the reducing agent is defined as an injection area portion,
At least a portion of the injection area is located on the central axis side of the reference inclination line in the cross section. The exhaust gas purification device according to any one of claims 1 to 4,
The exhaust gas purification device, wherein the second shielding portion further includes at least one obstruction portion that obstructs a flow of the exhaust gas passing through the opening portion.

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