Dispersion plate

Abstract

To suppress deposition of a reductant to a dispersion plate.SOLUTION: A dispersion plate disposed in a gas flow passage to disperse a reductant supplied to the flow passage includes at least one irregularity part extending in a circumferential direction of the flow passage at a surface directed upstream of the flow passage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a distribution plate for dispersing a reducing agent delivered to a gas flow path. [Background technology]

[0002] Exhaust gas emitted from internal combustion engines such as diesel engines contains nitrogen oxides (NOx), which are air pollutants. A known exhaust gas purification system for purifying such exhaust gas is one that is configured to install a selective catalytic reduction (SCR) catalyst in the exhaust gas passage and inject urea water, a reducing agent, into the exhaust gas upstream of the catalyst.

[0003] The urea solution injected into the exhaust gas is hydrolyzed by the heat of the exhaust gas, and ammonia (NH 3 ) is supplied to the catalyst together with the exhaust gas. Nitrogen oxides in the exhaust gas react with ammonia in the catalyst and are reduced and purified.

[0004] As a dispersion plate for dispersing urea water introduced into the exhaust path, JP 2014-163232 A (Patent Document 1) discloses a configuration in which a number of blades are provided extending from the outer periphery of a cylinder toward the center, and shielding plates are provided at intervals from the number of blades in the axial direction of the cylinder, and a passage opening formed in the center of the cylinder is covered by the number of shielding plates by being surrounded by the tips of the number of blades. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-163232 A Summary of the Invention [Problem to be solved by the invention]

[0006] The shielding plate described in Patent Document 1 is configured by bending a plate-like member parallel to a plane perpendicular to the axial direction of the cylinder toward the center of the cylinder so as to move toward the downstream side of the cylinder axis. The droplets of the reducing agent attached to the shielding plate move toward the tip side of the shielding plate located at the center of the cylinder. As a result, the droplets (liquid film) cannot immediately leave the shielding plate, and a deposit of urea is generated on the shielding plate. The urea deposit grows as the internal combustion engine continues to operate. Urea accumulates on the shielding plate, especially in the center of the cylinder. The deposit absorbs the urea introduced into the exhaust path, and the deposit changes the exhaust gas flow, reducing the dispersibility of the reducing agent. As a result, the purification rate of nitrogen oxides decreases.

[0007] In the present disclosure, a dispersion plate capable of suppressing accumulation of a reducing agent is proposed. [Means for solving the problem]

[0008] According to the present disclosure, there is proposed a distribution plate for distributing a reducing agent supplied to a gas flow passage, the distribution plate having at least one uneven portion extending in a circumferential direction of the flow passage on a surface facing an upstream side of the flow passage.

[0009] In this specification, the reducing agent and the precursor of the reducing agent are collectively referred to as "reducing agent".

[0010] The reducing agent droplets adhering to the dispersion plate are encouraged to flow in the circumferential direction of the exhaust path along the uneven portion. The reducing agent droplets are less likely to gather in the center of the gas flow path. The generation of reducing agent deposits in the center of the gas flow path is suppressed. Since the accumulation of the reducing agent on the dispersion plate can be suppressed, the dispersibility of the reducing agent can be ensured, and a decrease in the purification rate of nitrogen oxides can be suppressed.

[0011] In the above-described dispersion plate, the uneven portion may extend from one edge to the other edge of the dispersion plate in the circumferential direction of the flow passage.

[0012] In the above-mentioned dispersion plate, the uneven portion may have a curved shape when the dispersion plate is viewed from the upstream side of the flow channel.

[0013] In the above dispersion plate, at least one uneven portion may have a plurality of uneven portions, and the plurality of uneven portions may be arranged on concentric circles when the dispersion plate is viewed from the upstream side of the flow channel.

[0014] The above-mentioned dispersion plate may have a first plate and a second plate arranged at a distance from each other in the circumferential direction of the flow path, and when the dispersion plate is viewed from the upstream side of the flow path, the uneven portion of the first plate and the uneven portion of the second plate may be arranged on concentric circles.

[0015] In the dispersion plate, the uneven portion may be a groove. Effect of the Invention

[0016] The dispersion plate according to the present disclosure can suppress accumulation of the reducing agent. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing a schematic configuration of an exhaust purification device; [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a dispersion plate. [Diagram 3] FIG. 4 is a cross-sectional view of the dispersion plate, showing the dimensional relationship of the grooves. [Figure 4] FIG. [Diagram 5] 5 is a cross-sectional view of the dispersion plate taken along line VV shown in FIG. 4. [Figure 6] FIG. 11 is a diagram showing a second example of the configuration of the groove portion. [Figure 7] FIG. 11 is a diagram showing a third example of the configuration of the groove portion. [Figure 8] FIG. 11 is a diagram showing a fourth example of the configuration of the groove portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiments will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. In the drawings, configurations may be omitted or simplified for convenience of explanation. It is also intended from the beginning that any configurations may be extracted from the embodiments and arbitrarily combined.

[0019] Fig. 1 is a diagram showing a schematic configuration of an exhaust purification device 1. The exhaust purification device 1 shown in Fig. 1 is for purifying exhaust gas discharged from an internal combustion engine of an automobile. The exhaust purification device 1 includes an exhaust path forming member 2, an injection device 4, a catalyst 7, and a dispersion device 10.

[0020] The exhaust path forming member 2 defines an exhaust path that is a flow path of exhaust gas discharged from an internal combustion engine. The exhaust path forming member 2 has a cylindrical shape. The exhaust path forming member 2 includes a first portion 2A, a second portion 2B, and a third portion 2C. The first portion 2A, the second portion 2B, and the third portion 2C are arranged in this order from the upstream side to the downstream side of the flow of exhaust gas flowing in the exhaust path, and all of them are cylindrical. Hereinafter, the upstream side of the exhaust gas flow will be simply referred to as the upstream side, and the downstream side of the exhaust gas flow will be simply referred to as the downstream side.

[0021] The first portion 2A is located upstream of the injector 4. The second portion 2B is bent and extended from the first portion 2A. The third portion 2C is configured coaxially with the second portion 2B and has an inner diameter larger than the first portion 2A and the second portion 2B. The axis C shown in FIG. 1 is the axis of the exhaust gas flow path, more specifically, the axis of the second portion 2B.

[0022] The injector 4 injects an aqueous urea solution (urea water) as a precursor of a reducing agent into the exhaust path forming member 2 (more specifically, the second portion 2B). Specifically, the injector 4 injects the urea water upstream of the dispersion device 10. The urea water injected into the exhaust gas is hydrolyzed and pyrolyzed by the heat of the exhaust gas to generate ammonia, and the ammonia thus generated functions as a reducing agent.

[0023] The injection device 4 includes a flow path member 5 that defines an introduction path for the urea water. The flow path member 5 has a cylindrical shape. The flow path member 5 is configured, for example, coaxially with the second portion 2B. The flow path member 5 may be provided such that the inner diameter of the flow path gradually increases toward the exhaust flow path. The flow path member 5 is provided so as to penetrate the first portion 2A.

[0024] The dispersion device 10 is disposed in the second portion 2B. The dispersion device 10 is disposed downstream of the injector 4 and upstream of the catalyst 7 in the exhaust path. The dispersion device 10 disperses the reducing agent supplied to its upstream side in the exhaust path toward the downstream side. The dispersion device 10 has a dispersion plate 20 and a swirl generator 40. The dispersion device 10 will be described in detail later.

[0025] The catalyst 7 is accommodated in the third portion 2C. The catalyst 7 is an SCR type catalyst that reduces NOx. The above-mentioned reduction action of ammonia occurs in the catalyst 7, whereby NOx contained in the exhaust gas is reduced to produce nitrogen and water.

[0026] Fig. 2 is a diagram showing a schematic configuration of the dispersion plate 20. The direction in which the axis C shown in Fig. 1 extends (hereinafter simply referred to as the axis C direction) is perpendicular to the paper surface in Fig. 2. Fig. 2 shows the dispersion device 10 as seen from the upstream side along the axis C direction. The dispersion device 10 has the dispersion plate 20 and a swirl generator 40.

[0027] The dispersion plate 20 has an inner tubular member 21 and a plate portion 22. The inner tubular member 21 has a hollow tubular shape extending along the exhaust path. The inner tubular member 21 extends along the axial direction C. The axial direction of the inner tubular member 21 is the axial direction C. The center of the inner tubular member 21 is located at the center of the exhaust path in the second portion 2B. The inner tubular member 21 may have a cylindrical shape as shown in FIG. 2, or may have another shape such as a rectangular tube shape.

[0028] The plate portion 22 is bent from the upstream end of the inner tubular member 21 towards the center of the inner tubular member 21. The root portion 23 of the plate portion 22 is located at the upstream end of the inner tubular member 21. The tip portion 24 of the plate portion 22 is located at the center of the exhaust path. The plate portion 22 is provided radially from the center of the exhaust path. The plate portion 22 may have a roughly flat plate-like shape from the root portion 23 to the tip portion 24. The plate portion 22 may be bent one or more times so that the tip portion 24 is located downstream of the root portion 23.

[0029] The multiple plate portions 22 are arranged side by side in the circumferential direction of the inner tubular member 21. The plate portions 22 include a first plate 22A, a second plate 22B, and a third plate 22C. The first plate 22A, the second plate 22B, and the third plate 22C are arranged at intervals in the circumferential direction of the exhaust path. When viewed from the upstream side of the exhaust path, the first plate 22A, the second plate 22B, and the third plate 22C are arranged side by side in this order in the clockwise direction. The first plate 22A, the second plate 22B, and the third plate 22C are arranged at positions shifted from each other by about 120° along the circumferential direction of the exhaust path.

[0030] When viewed from the upstream side of the exhaust path, the tip portion 24 of the first plate 22A, the tip portion 24 of the second plate 22B, and the tip portion 24 of the third plate 22C overlap each other at the center of the inner tubular member 21 (the center of the exhaust path). The tip portion 24 of the first plate 22A, the tip portion 24 of the second plate 22B, and the tip portion 24 of the third plate 22C are arranged in this order from the upstream side to the downstream side of the exhaust path. The tip portion 24 of the first plate 22A is located upstream of the tip portion 24 of the second plate 22B. The tip portion 24 of the second plate 22B is located upstream of the tip portion 24 of the third plate 22C.

[0031] The main surface of the plate portion 22 facing the upstream side of the flow passage has a flat surface 25 and a groove portion 30 recessed relative to the flat surface 25. The groove portion 30 in the embodiment shown in FIG. 2 extends in the circumferential direction of the exhaust path. The groove portion 30 extends from one edge to the other edge of the plate portion 22 in the circumferential direction of the exhaust path. When viewed from the upstream side of the exhaust path, the groove portion 30 has a curved shape. Typically, the groove portion 30 has an arc shape.

[0032] A plurality of (more specifically, six) grooves 30 are formed in the first plate 22A. When viewed from the upstream side, the six grooves formed in the first plate 22A are arranged on concentric circles. The six grooves formed in the first plate 22A are formed at equal intervals in the radial direction of the exhaust path. The same number (six) of grooves 30 as in the first plate 22A are formed in the second plate 22B and the third plate 22C. When viewed from the upstream side, the grooves 30 formed in the first plate 22A, the grooves 30 formed in the second plate 22B, and the grooves 30 formed in the third plate 22C are each arranged on concentric circles.

[0033] In the case where the plate portion 22 is bent, forming arc-shaped grooves 30 in a flat plate and then bending the flat plate to form the plate portion 22 may cause a misalignment between the circumferential flow direction of the exhaust gas described below and the extension direction of the grooves 30. In order to fully obtain the effect of moving the droplets 50 by the gas flow described below, it is desirable that the grooves 30 are arranged on a concentric circle when the bent plate portion 22 is viewed from the upstream side.

[0034] The swirl generator 40 has an outer tubular member 41 and a blade portion 42. The outer tubular member 41 has a hollow tubular shape extending along the exhaust path. The outer tubular member 41 extends along the axis C direction. The axial direction of the outer tubular member 41 is the axis C direction. The center of the outer tubular member 41 is located at the center of the exhaust path in the second portion 2B. The outer tubular member 41 may have a cylindrical shape as shown in FIG. 2, or may have another shape such as a rectangular tube shape.

[0035] The outer cylindrical member 41 is disposed on the outer circumferential side of the inner cylindrical member 21. The inner circumferential surface of the outer cylindrical member 41 and the outer circumferential surface of the inner cylindrical member 21 are in contact with each other. The inner cylindrical member 21 is fixed to the outer cylindrical member 41. As a result, the dispersion plate 20 and the swirl generator 40 are formed as an integrated structure.

[0036] The blade portion 42 is disposed in the exhaust path so as to be located downstream of the plate portion 22 of the dispersion plate 20. The blade portion 42 is bent from the outer tubular member 41 toward the center of the outer tubular member 41. The blade portions 42 are arranged side by side in the circumferential direction of the outer tubular member 41. The blade portion 42 includes a first blade 42A, a second blade 42B, a third blade 42C, a fourth blade 42D, a fifth blade 42E, a sixth blade 42F, a seventh blade 42G, and an eighth blade 42H. The first to eighth blades 42A to 42H are arranged side by side in the circumferential direction of the exhaust path. When viewed from the upstream side of the exhaust path, the first to eighth blades 42A to 42H are arranged side by side in this order in the clockwise direction.

[0037] Each of the blades 42 is inclined at a predetermined angle with respect to a virtual line extending in the radial direction of the outer tubular member 41 as a rotation axis. Each of the blades 42 is inclined with respect to the circumferential direction of the outer tubular member 41 and with respect to the axial direction C. When viewed from the upstream side of the exhaust path, the downstream edge of the blade 42 overlaps with the upstream edge of the adjacent blade 42. As shown in FIG. 2, the downstream edge of the first blade 42A overlaps with the upstream edge of the second blade 42B. The downstream edge of the fourth blade 42D overlaps with the upstream edge of the fifth blade 42E. The downstream edge of the sixth blade 42F overlaps with the upstream edge of the seventh blade 42G.

[0038] Because the vanes 42 are inclined as described above, a circumferential flow component is generated in the exhaust gas passing through the swirl generator 40. The exhaust gas swirls in a clockwise direction in FIG. 2. The swirl generator 40 is configured to generate a swirl flow in the exhaust gas flow passing through it. The exhaust gas flows in a spiral shape as it passes through the dispersion plate 20 and the swirl generator 40.

[0039] Fig. 3 is a cross-sectional view of the dispersion plate 20, showing the dimensional relationship of the groove portion 30. Fig. 3 and subsequent Figs. 4 to 8 representatively show one plate portion 22 out of the multiple plate portions 22 that constitute the dispersion plate 20. Fig. 3 shows a cross-section of the plate portion 22 extending in the radial direction of the inner cylindrical member 21. The left-right direction in Fig. 3 corresponds to the radial direction of the inner cylindrical member 21.

[0040] A plurality of grooves 30 are formed in the plate portion 22 and aligned in the radial direction of the inner tubular member 21. The grooves 30 are recessed relative to the flat surface 25. The groove depth GD shown in Fig. 3 indicates the distance from the flat surface 25 to the bottom surface 31 of the groove 30 in the thickness direction of the plate portion 22 (the up-down direction in Fig. 3). The groove width GW indicates the distance between both edges of the groove 30 in the radial direction of the inner tubular member 21. The groove interval GI indicates the distance between the centers of the groove widths GW of two adjacent grooves 30.

[0041] The groove width GW and the groove depth GD may be approximately equal in dimension. For example, the groove width GW may be 1 mm or more and 2 mm or less. The groove depth GD may be 1 mm or more and 2 mm or less. The groove depth GD may be half or less of the thickness of the plate portion 22. The groove interval GI may be a dimension larger than the groove width GW. For example, the groove interval GI may be 3 mm or more and 5 mm or less.

[0042] FIG. 4 is a diagram showing the function of the groove portion 30. FIG. 5 is a cross-sectional view of the dispersion plate 20 along the line VV shown in FIG. 4. Referring also to FIG. 2, the groove portion 30 extends in an arc shape. The upstream edge 27 corresponds to one edge of the plate portion 22 in the circumferential direction of the exhaust path, and the downstream edge 28 corresponds to the other edge of the plate portion 22 in the circumferential direction of the exhaust path. The radial direction of the inner tubular member 21 is the up-down direction in FIG. 4, and is the direction perpendicular to the paper surface in FIG. 5. The line VV extends in the circumferential direction of the exhaust path.

[0043] The reducing agent injected from the injector 4 (FIG. 1) is atomized by colliding with the plate portion 22 of the dispersion plate 20. The reducing agent passes through the dispersion plate 20, which promotes dispersion of the reducing agent in the exhaust path. The reducing agent is uniformly dispersed in the exhaust gas flowing in the exhaust path. The reducing agent, whose dispersion has been increased by the dispersion plate 20, is supplied to the catalyst 7 (FIG. 1).

[0044] The swirl generator 40 generates a swirling flow in the exhaust gas flow. Since the dispersion plate 20 is disposed immediately upstream of the swirl generator 40, the exhaust gas passing through the dispersion plate 20 has a circumferential flow component. The exhaust gas flows along the grooves 30 formed in the plate portion 22 as a guide, which further promotes the swirling flow. The flow direction FD shown by the two-dot chain line in Figures 4 and 5 indicates the circumferential flow component of the exhaust gas. The upstream edge 27 of the plate portion 22 is the edge of the plate portion 22 on the upstream side of the flow direction FD. The downstream edge 28 of the plate portion 22 is the edge of the plate portion 22 on the downstream side of the flow direction FD.

[0045] The droplets 50 shown in Figs. 4 and 5 are droplets of the reducing agent that collide with the plate portion 22 and enter the groove portion 30. The groove portion 30 extends along the flow direction FD. The droplets 50 move on the plate portion 22 due to the gas flow along the flow direction FD. The droplets 50 move along the groove portion 30. The droplets 50 move within the groove portion 30 along the circumferential direction of the exhaust path. The droplets 50 move from the upstream edge 27 toward the downstream edge 28. When the droplets 50 reach the downstream edge 28, they leave the plate portion 22 and flow toward the catalyst 7 through the swirl generator 40. This prevents the droplets 50 from staying on the plate portion 22.

[0046] The bottom surface 31 of the groove portion 30 shown in Fig. 5 has a flat shape and extends parallel to the flat surface 25, but the shape of the groove portion 30 is not limited to this. Fig. 6 is a diagram showing a second example of the configuration of the groove portion 30. As shown in Fig. 6, the bottom surface 31 of the groove portion 30 may be inclined with respect to the flat surface 25. By inclining the bottom surface 31 so that the groove depth GD (Fig. 3) gradually increases from the upstream edge 27 to the downstream edge 28, the movement of the droplets 50 toward the downstream edge 28 by the gas flow along the flow direction FD is promoted.

[0047] Fig. 7 is a diagram showing a third example of the configuration of the groove portion 30. As shown in Fig. 7, the groove portion 30 may have a chamfered portion 32 at a portion facing the upstream edge 27. The chamfered portion 32 increases the opening area of ​​the groove portion 30 at the upstream edge 27, making it easier for gas to flow into the groove portion 30. By increasing the flow rate of the gas flowing inside the groove portion 30, the movement of the droplets 50 toward the downstream edge 28 by the gas flow along the flow direction FD is promoted.

[0048] Although the groove portion 30 described with reference to Fig. 2 has an arc shape when viewed from the upstream side, the shape of the groove portion 30 is not limited to this. The multiple groove portions 30 do not necessarily have to be arranged on concentric circles. Fig. 8 is a diagram showing a fourth example of the configuration of the groove portion 30.

[0049] 8, the groove portion 30 may be formed so as to be closest to the tip portion 24 of the plate portion 22 at the upstream edge 27, and closest to the root portion 23 of the plate portion 22 at the downstream edge 28. The groove portion 30 may be formed so as to move away from the tip portion 24 of the plate portion 22 as it moves from the upstream edge 27 toward the downstream edge 28. In this way, as the droplets 50 move from the upstream edge 27 toward the downstream edge 28, the droplets 50 move toward the radial outside of the exhaust path, and the droplets 50 move away from the tip portion 24 of the plate portion 22. The droplets 50 are prevented from accumulating at the tip portion 24 of the plate portion 22.

[0050] The grooves 30 may have any other shape as long as they extend in a direction intersecting the radial direction of the exhaust path. When viewing the dispersion plate 20 from the upstream side, the grooves 30 may have other types of curved shapes. The grooves 30 do not necessarily have to have a curved shape, and may extend linearly when viewed from the upstream side. The multiple grooves 30 do not necessarily have to be arranged at equal intervals in the radial direction of the exhaust path.

[0051] Although there is some overlap with the above description, the characteristic configuration of this embodiment and its actions and effects can be enumerated as follows.

[0052] 2 to 8, the surface of the plate portion 22 of the dispersion plate 20 facing the upstream side of the exhaust path has a groove portion 30. The groove portion 30 extends in the circumferential direction of the exhaust path.

[0053] The moisture (droplets 50) adhering to the plate portion 22 of the dispersion plate 20 is encouraged to flow in the circumferential direction of the exhaust path along the groove portion 30. Since the droplets 50 are caused to flow in the circumferential direction of the exhaust path before approaching the center of the exhaust path, the droplets 50 are less likely to gather in the center of the exhaust path. The generation of deposits of the reducing agent at the tip portion 24 of the plate portion 22 at the center of the exhaust path is suppressed. Since the deposition of the reducing agent on the dispersion plate 20 can be suppressed, the dispersibility of the reducing agent can be ensured and the decrease in the purification rate of nitrogen oxides can be suppressed. Compared to the case where the droplets 50 move along the longitudinal direction of the plate portion 22 toward the center of the exhaust path, the movement distance of the droplets 50 is shorter, so the droplets 50 are more likely to leave the plate portion 22 and the droplets 50 can be suppressed from staying on the plate portion 22.

[0054] 2, 4 to 8, the groove portion 30 extends from the upstream edge 27 to the downstream edge 28 of the plate portion 22. Since the groove portion 30 opens to the upstream edge 27, gas can easily flow into the groove portion 30. The droplets 50 move from the upstream edge 27 to the downstream edge 28 by the gas flow along the flow direction FD in the groove portion 30. Since the groove portion 30 opens to the downstream edge 28, when the droplets 50 reach the downstream edge 28, the droplets 50 easily leave the plate portion 22. This makes it possible to prevent the droplets 50 from accumulating on the plate portion 22.

[0055] 2, 4, and 8, the groove portion 30 has a curved shape when viewed from the upstream side of the exhaust path. By forming the groove portion 30 in a curved shape along the flow direction FD of the exhaust gas passing through the dispersion plate 20, it is possible to promote the movement of the droplets 50 due to the gas flow.

[0056] 2, when viewed from the upstream side of the exhaust path, the multiple grooves 30 formed in the plate portion 22 are arranged on concentric circles. By forming multiple grooves 30 in the plate portion 22, the effect of making it difficult for the droplets 50 to gather in the center of the exhaust path can be more significantly obtained. By forming the grooves 30 in an arc shape that follows the swirling flow of the exhaust gas, the movement of the droplets 50 by the gas flow can be promoted.

[0057] 2, the grooves 30 formed in the first plate 22A, the second plate 22B, and the third plate 22C are arranged on concentric circles. Since the dispersion plate 20 has a plurality of plate portions 22, and the grooves 30 are formed in each of the plurality of plate portions 22, the effect of making it difficult for the droplets 50 to gather in the center of the exhaust path can be more significantly obtained. By forming the grooves 30 in an arc shape that follows the swirling flow of the exhaust gas, the movement of the droplets 50 by the gas flow can be promoted.

[0058] In the embodiment, an example has been described in which the surface of the plate portion 22 has the groove portion 30. By having the groove portion 30 on the surface of the plate portion 22, the droplets 50 can be captured in the groove portion 30 and moved along the groove portion 30 by the gas flow, and the droplets 50 are prevented from remaining on the plate portion 22.

[0059] The surface of the plate portion 22 may have ridges extending in the circumferential direction of the exhaust path in addition to the grooves 30 or instead of the grooves 30. The plate portion 22 may have only the grooves 30, only the ridges, or both the grooves 30 and the ridges. The surface of the plate portion 22 may have an uneven portion. The uneven portion may have a groove recessed into the flat surface 25 and / or a ridge protruding from the flat surface 25. The uneven portion may have either the grooves 30 or the ridges, or both. The uneven portion guides the flow of the exhaust gas, thereby promoting the swirling flow of the exhaust gas, and thus improving the function of moving the droplets 50 by the gas flow.

[0060] In the embodiment, an example in which the surface of the plate portion 22 has six grooves 30 has been described, but the number of uneven portions is not limited to this. The plate portion 22 does not necessarily have to have a plurality of uneven portions. If the surface of the plate portion 22 has at least one uneven portion, it is possible to obtain an effect of suppressing the droplets 50 from staying on the plate portion 22. In the case where the plate portion 22 has only one uneven portion, if the uneven portion is arranged at the tip portion 24, the effect of making it difficult for the droplets 50 to gather at the center is reduced, so it is desirable to arrange the uneven portion radially outward from the tip portion 24. For example, only one uneven portion may be formed at the center of the plate portion 22 in the radial direction of the exhaust path.

[0061] In the embodiment, a configuration in which the plate portion 22 of the dispersion plate 20 is provided with uneven portions has been described, but uneven portions may also be provided on the surface facing the upstream side of the blade portion 42 of the swirl generator 40. In this way, accumulation of the reducing agent on the blade portion 42 can be suppressed, so that a decrease in the purification rate of nitrogen oxides can be more reliably suppressed.

[0062] [Note] The above description includes the following additional features.

[0063] (Appendix 1) A dispersion plate disposed in a gas flow path for dispersing a reducing agent supplied to the gas flow path, A dispersion plate, the surface facing the upstream side of the flow path having at least one uneven portion extending in a circumferential direction of the flow path.

[0064] (Appendix 2) 2. The dispersion plate according to claim 1, wherein the uneven portion extends from one edge to the other edge of the dispersion plate in a circumferential direction of the flow path.

[0065] (Appendix 3) 3. The dispersion plate according to claim 1, wherein the uneven portion has a curved shape when the dispersion plate is viewed from the upstream side of the flow path.

[0066] (Appendix 4) The at least one uneven portion has a plurality of the uneven portions, 4. The dispersion plate according to claim 1, wherein the plurality of concave and convex portions are arranged on concentric circles when the dispersion plate is viewed from the upstream side of the flow path.

[0067] (Appendix 5) The flow passage includes a first plate and a second plate spaced apart from each other in a circumferential direction of the flow passage, 5. The dispersion plate according to claim 1, wherein, when the dispersion plate is viewed from the upstream side of the flow path, the uneven portion of the first plate and the uneven portion of the second plate are arranged on concentric circles.

[0068] (Appendix 6) 6. The dispersion plate according to claim 1, wherein the uneven portion is a groove.

[0069] Although the embodiment has been described above, the disclosed embodiment should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0070] 1 exhaust purification device, 2 exhaust path forming member, 4 injection device, 7 catalyst, 10 dispersion device, 20 dispersion plate, 21 inner tubular member, 22 plate portion, 22A first plate, 22B second plate, 22C third plate, 23 root portion, 24 tip portion, 25 flat surface, 27 upstream edge, 28 downstream edge, 30 groove portion, 31 bottom surface, 32 chamfered portion, 40 swirl generator, 41 outer tubular member, 42 blade portion, 50 droplet, C axis, FD flow direction, GD groove depth, GI groove spacing, GW groove width.

Claims

1. A dispersion plate disposed in a gas flow path for dispersing a reducing agent supplied to the gas flow path, A dispersion plate, the surface facing the upstream side of the flow passage having at least one uneven portion extending in a circumferential direction of the flow passage.

2. The dispersion plate according to claim 1 , wherein the uneven portion extends from one edge to the other edge of the dispersion plate in a circumferential direction of the flow passage.

3. The dispersion plate according to claim 1 or 2, wherein the uneven portion has a curved shape when the dispersion plate is viewed from the upstream side of the flow path.

4. The at least one uneven portion has a plurality of the uneven portions, 3. The dispersion plate according to claim 1, wherein the plurality of concave and convex portions are arranged on concentric circles when the dispersion plate is viewed from the upstream side of the flow path.

5. A first plate and a second plate are arranged at an interval in a circumferential direction of the flow path, 3. The dispersion plate according to claim 1, wherein the uneven portion of the first plate and the uneven portion of the second plate are arranged on concentric circles when the dispersion plate is viewed from the upstream side of the flow path.

6. The dispersion plate according to claim 1 or 2, wherein the uneven portion is a groove.

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