EXHAUST TREATMENT DEVICE

Abstract

An exhaust treatment device includes an injection unit that injects urea water into the exhaust pipe, a first plate that is provided upstream of the injection unit in the exhaust pipe, an arc-shaped second plate that is provided along the axial direction in the exhaust pipe and faces the injection unit, and a third plate that is provided downstream of the second plate in the exhaust pipe, wherein the first plate includes a first inflow hole formed at a position away from a central portion thereof, and a guide portion configured to direct the exhaust gas introduced from the first inflow hole toward the injection portion, and the third plate includes an outflow hole formed in a central portion thereof.

Claims

1. An exhaust treatment device comprising: an exhaust pipe through which exhaust gas flows; an injection unit that injects urea water into the exhaust pipe; a first plate that is provided upstream of the injection unit in the exhaust pipe in a manner to be orthogonal to an axial direction of the exhaust pipe; an arc-shaped second plate that is provided along the axial direction in the exhaust pipe and faces the injection unit; and a third plate that is provided downstream of the second plate in the exhaust pipe in a manner to be orthogonal to the axial direction, wherein the first plate includes a first inflow hole formed at a position away from a central portion thereof, and a guide portion configured to direct the exhaust gas introduced from the first inflow hole toward the injection portion, and the third plate includes an outflow hole formed in a central portion thereof.

2. The exhaust treatment device according to claim 1, wherein the first plate is a disk, and when the first plate and the second plate are viewed from the third plate, the first inflow hole is located at a position different from that of the second plate in the circumferential direction of the first plate.

3. The exhaust treatment device according to claim 1, wherein the injection unit is located at an upper end portion of the exhaust pipe in a vertical direction, and the first inflow hole is located at the same position as the outflow hole in the vertical direction.

4. The exhaust treatment device according to claim 3, wherein the first inflow hole is a rectangular hole, and the guide portion is provided obliquely upward in the vertical direction from a lower edge of the first inflow hole.

5. The exhaust treatment device according to claim 3, wherein the first plate is a disk, and a center of the first inflow hole is located farther from a center of the first plate than the outflow hole in a radial direction of the first plate.

6. The exhaust treatment device according to claim 1, wherein the first plate is a disk having a first radius, the second plate has a semicylindrical shape having a second radius smaller than the first radius, and one end portion of the second plate in an axial direction is in contact with the first plate.

7. The exhaust treatment device according to claim 6, wherein the first plate includes a plurality of second inflow holes provided at predetermined intervals along the second plate closer to the center of the first plate with respect to the second plate.

8. The exhaust treatment device according to claim 7, wherein the second inflow hole is located at a position different from that of the first inflow hole in the circumferential direction of the first plate.

9. The exhaust treatment device according to claim 6, wherein the first plate includes a third inflow hole provided along the second plate, at a position closer to an edge of the first plate than the second plate.

10. The exhaust treatment device according to claim 1, wherein the first plate includes a second inflow hole formed at a position adjacent to an inner circumferential surface of the second plate and spaced apart from the first inflow hole by a predetermined angle in a circumferential direction.

11. The exhaust treatment device according to claim 10, wherein the first plate further includes a guide portion configured to direct the exhaust gas introduced from the second inflow hole toward the inner circumferential surface of the second plate.

12. The exhaust treatment device according to claim 11, wherein the second inflow hole is a rectangular hole, and the guide portion is provided obliquely downward in the vertical direction from an upper edge of the second inflow hole.

13. The exhaust treatment device according to claim 1, wherein the first plate includes a fourth inflow hole that is formed at a position where the second plate is not provided in the circumferential direction and into which the exhaust gas flows, and the fourth inflow hole is formed at a position adjacent to the injection unit in the circumferential direction.

14. The exhaust treatment device according to claim 13, wherein the second plate includes a bent portion that is formed at an end portion in the circumferential direction and is connected to the exhaust pipe, and the fourth inflow hole is located between the injection unit and the bent portion in the circumferential direction.

15. The exhaust treatment device according to claim 1, wherein one end portion of the second plate in the axial direction is in contact with the first plate, and the other end portion of the second plate in the axial direction is in contact with the third plate.

16. An exhaust treatment device comprising: an exhaust pipe through which exhaust gas flows; an injection unit that injects urea water into the exhaust pipe; a first plate that is provided upstream of the injection unit in the exhaust pipe in a manner to be orthogonal to an axial direction of the exhaust pipe; an arc-shaped second plate that is provided along the axial direction in the exhaust pipe and faces the injection unit; and a third plate that is provided downstream of the second plate in the exhaust pipe in a manner to be orthogonal to the axial direction, wherein the first plate includes an inflow hole into which the exhaust gas flows, and the third plate includes i) a protruding portion protruding toward the first plate and ii) an outflow hole formed at a distal end of the protruding portion.

17. The exhaust treatment device according to claim 16, wherein the third plate further includes a flat plate portion in a manner to be orthogonal to the axial direction, and an outer diameter of the protruding portion increases from the tip of the protruding portion toward a connection point with the flat plate portion.

18. The exhaust treatment device according to claim 17, wherein an outer peripheral surface of the protruding portion is curved from the tip of the protruding portion toward the connection point.

19. The exhaust treatment device according to claim 16, wherein the protruding portion is cylindrical in shape.

20. The exhaust treatment device according to claim 16, wherein the third plate is a circular flat plate, and the protruding portion protrudes from a central portion of the third plate toward the first plate.

21. The exhaust treatment device according to claim 16, further comprising: a catalyst that is provided downstream of the third plate in the exhaust pipe and causes ammonia generated from the urea water to react with the exhaust gas, wherein a distance between the third plate and the catalyst is smaller than a distance between the third plate and the first plate.

22. The exhaust treatment device according to claim 16, wherein an angle formed by a) a first line passing through one circumferential end of the second plate and a center of the second plate and b) a second line passing through the other circumferential end of the second plate and the center of the second plate is 180or more and 270or less.

23. The exhaust treatment device according to claim 16, wherein one end portion of the second plate in an axial direction is in contact with the first plate, and the other end portion of the second plate in an axial direction is in contact with the third plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 schematically shows a configuration of an exhaust treatment device 1 according to an embodiment.

[0008] FIG. 2 schematically shows a peripheral configuration of an injection unit 16 in an exhaust passage 12.

[0009] FIG. 3 schematically shows an internal configuration of FIG. 2.

[0010] FIG. 4 schematically shows a configuration of an exhaust pipe 13 of FIG. 2 viewed from the rear.

[0011] FIG. 5 schematically shows the configuration of the exhaust pipe 13 of FIG. 2 as viewed from the front.

[0012] FIG. 6 is a schematic view for explaining a flow of exhaust gas in an injection space.

[0013] FIG. 7 schematically shows the peripheral configuration of the injection unit 16 of an exhaust pipe 13 according to a second embodiment.

[0014] FIG. 8 schematically shows an internal configuration of FIG. 7.

[0015] FIG. 9 schematically shows a configuration of the exhaust pipe 13 of FIG. 7 as viewed from the front.

[0016] FIG. 10 schematically shows the configuration of the exhaust pipe 13 of FIG. 7 as viewed from the rear.

[0017] FIG. 11 is a schematic view for explaining flows of exhaust gas and urea water in an injection period.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the present disclosure will be described through exemplary embodiments of the present disclosure, but the following exemplary embodiments do not limit the disclosure according to the claims, and not all of the combinations of features described in the exemplary embodiments are necessarily essential to the solution means of the disclosure.

First Embodiment

Configuration of Exhaust Treatment Device

[0019] FIG. 1 schematically shows a configuration of an exhaust treatment device 1 according to an embodiment. As shown in FIG. 1, the exhaust treatment device 1 includes an engine 10, an exhaust passage 12, a Diesel Particulate Filter (DPF) 14, an injection unit 16, and a Selective Catalytic Reduction (SCR) device 18. As an example, the exhaust treatment device 1 is mounted on a vehicle such as a truck, and purifies exhaust gas from the engine 10.

[0020] The engine 10 is an internal combustion engine that generates power by combusting and expanding a mixture of fuel and intake air. The engine 10 is a diesel engine, for example.

[0021] The exhaust passage 12 includes an exhaust pipe 13 connected to the engine 10, and discharges the exhaust gas from the engine 10. The exhaust passage 12 through which the exhaust gas flows is provided with the DPF 14, the injection unit 16, and the SCR device 18.

[0022] The DPF 14 is a filter that collects particulate matter (PM) contained in the exhaust gas. The DPF 14 is constituted by a honeycomb body made of metal or ceramics, for example, and collects PM by pores or surfaces of the partition walls.

[0023] The injection unit 16 is provided between the DPF 14 and the SCR device 18, and injects urea water into the exhaust pipe 13. The injection unit 16 is provided upstream of the SCR device 18. The urea water injected by the injection unit 16 is evaporated and decomposed by the heat of the exhaust gas flowing through the exhaust pipe 13, and ammonia is generated. The ammonia is used to cause a reduction reaction of NOx in the exhaust gas. As will be described later in detail, the exhaust pipe 13 is provided with a configuration that promotes evaporation and decomposition of urea water.

[0024] The SCR device 18 is a device that converts NOx in the exhaust gas into harmless nitrogen through a reduction reaction. The SCR device 18 includes a reduction catalyst 19 that promotes a reduction reaction of NOx with ammonia. Ammonia generated from urea water is adsorbed on the reduction catalyst 19. The reduction catalyst 19 reduces NOx into nitrogen and water using the adsorbed ammonia, thereby reducing emissions of NOx.

Peripheral Configuration of Injection Unit

[0025] A peripheral configuration of the injection unit 16 in the exhaust pipe 13 will be described with reference to FIG. 2 to FIG. 6.

[0026] FIG. 2 schematically shows the peripheral configuration of the injection unit 16 in the exhaust passage 12. FIG. 3 schematically shows an internal configuration of FIG. 2. FIG. 4 schematically shows a configuration of the exhaust pipe 13 of FIG. 2 as viewed from the rear. FIG. 5 schematically shows the configuration of the exhaust pipe 13 of FIG. 2 as viewed from the front. FIG. 6 is a schematic view for explaining a flow of exhaust gas in an injection space. It should be noted that, in FIG. 2, for convenience of description, the exhaust pipe 13 surrounding a first plate 30, a second plate 40, and a third plate 50 is indicated by a broken line. Arrows shown in FIG. 3 and FIG. 6 indicate the flow of the exhaust gas. Further, as shown in FIGS. 2 and 3, a term front refers to an upstream side in the flow direction of the exhaust gas, and a term rear refers to a downstream side in the flow direction of the exhaust gas.

[0027] In the present embodiment, a plurality of plates are provided in the exhaust pipe 13 to which the injection unit 16 is attached to promote evaporation and decomposition of the urea water injected by the injection unit 16. Specifically, as shown in FIG. 2, the first plate 30, the second plate 40, and the third plate 50 are provided inside the exhaust pipe 13.

[0028] As shown in FIG. 3, the first plate 30 is located upstream of the injection unit 16 in the exhaust pipe 13. The first plate 30 is disposed orthogonal to an axial direction (front-rear direction) of the exhaust pipe 13. The first plate 30 is a disk having a predetermined radius (here, a first radius). The first radius is the same as an inner diameter of the exhaust pipe 13. Therefore, an edge of the first plate 30 is in contact with an inner wall surface of the exhaust pipe 13. The first plate 30 is provided with a plurality of inflow holes (a first inflow hole 32, a second inflow hole 34, and a third inflow hole 35) through which the exhaust gas passes.

[0029] As shown in FIG. 3, the third plate 50 is located downstream of the second plate 40 in the exhaust pipe 13. The third plate 50 is provided, like the first plate 30, orthogonal to the axial direction of the exhaust pipe 13. The third plate 50 is a disk, and the radius of the third plate 50 is the same as the radius of the first plate 30. Therefore, an edge of the third plate 50 is also in contact with the inner wall surface of the exhaust pipe 13. The third plate 50 is provided with an outflow hole 52 through which the exhaust gas passes. In the present embodiment, the outflow hole 52 is provided in a circular shape with a predetermined radius in the central portion of the third plate 50. However, the shape of the outflow hole 52 may be something other than a circle.

[0030] In the injection space defined between the first plate 30 and the third plate 50 in the exhaust pipe 13, urea water is injected from the injection unit 16 located at an upper end portion of the exhaust pipe 13 in a vertical direction (up-down direction). The injection unit 16 is provided along the vertical direction, but may have a predetermined inclination in the front-rear or left-right directions. The exhaust gas that passed through the plurality of inflow holes of the first plate 30 flows into the injection space, evaporates the urea water, and then flows out from the outflow hole 52 of the third plate 50.

[0031] As shown in FIG. 3, the second plate 40 is located between the first plate 30 and the third plate 50 in the exhaust pipe 13, and is provided along the axial direction (front-rear direction). As shown in FIG. 2, the second plate 40 is provided so that a facing surface 42 faces the injection unit 16. Therefore, the urea water injected by the injection unit 16 adheres to the facing surface 42 of the second plate 40. The second plate 40 is heated by the exhaust gas passing through the injection space. Therefore, the urea water adhering to the facing surface 42 evaporates due to the heat of the second plate 40.

[0032] A cross-sectional shape of the second plate 40 in a plane orthogonal to the axial direction is an arc shape. Specifically, the second plate 40 has a semicylindrical shape as shown in FIG. 4. Therefore, the facing surface 42 of the second plate 40 has a curved shape with a predetermined curvature. More specifically, the facing surface 42 of the second plate 40 is a semicylindrical inner surface with a predetermined curvature. The radius of the second plate 40 (hereinafter also referred to as a second radius) is smaller than the first radius of the first plate 30.

[0033] One end portion of the second plate 40 in the axial direction is in contact with the first plate 30, whereas the other end portion of the second plate 40 in the axial direction is separated apart from the third plate 50. The second plate 40 is separated from the inner wall surface of the exhaust pipe 13 by a predetermined distance. Therefore, a space through which the exhaust gas passes (hereinafter, referred to as a passage space) exists between a back surface 44 of the second plate 40 and the inner wall surface of the exhaust pipe 13. The back surface 44 is a surface opposite to the facing surface 42 of the second plate 40, and is an outer surface of the semicylindrical shape with the predetermined curvature.

[0034] The urea water adhering to the facing surface 42 is heated by the exhaust gas and thereby evaporates and decomposes. Ammonia gas is generated as the urea water undergoes evaporation and decomposition. The generated ammonia gas is carried by the exhaust gas flowing toward the outflow hole 52, passes through the outflow hole 52 together with the exhaust gas, and flows toward the SCR device 18 (FIG. 1).

[0035] In the present embodiment, in order to further promote evaporation and decomposition of the urea water in the injection space, the first plate 30 includes a plurality of inflow holes at different positions, and includes guide portions. Specifically, as shown in FIG. 4, the first plate 30 includes the first inflow holes 32, guide portions 33, the second inflow holes 34, and the third inflow hole 35.

[0036] The first inflow holes 32 are holes for allowing the exhaust gas to flow into the injection space surrounded by the first plate 30 and the third plate 50. The exhaust gas flowing from the first inflow holes 32 diffuses the urea water injected into the injection space.

[0037] As shown in FIG. 5, the first inflow holes 32 are located at the same position as the outflow hole 52 in the vertical direction. On the other hand, as shown in FIG. 4, the first inflow holes 32 are formed at positions away from the central portion of the first plate 30 in the horizontal direction (left-right direction). In other words, the outflow hole 52 is provided at the central portion of the third plate 50, and the first inflow holes 32 are provided at positions away from the central portion of the first plate 30 in the horizontal direction (left-right direction). Specifically, lengths from the center of the first plate 30 to the centers of the first inflow holes 32 are longer than a length from the center of the third plate 50 to the outflow hole 52. In other words, the centers of the first inflow holes 32 are located farther from the center of the first plate 30 than the outflow hole 52 in the radial direction of the first plate 30. Therefore, the exhaust gas flowing into the injection space from the first inflow holes 32 flows toward the outflow hole 52 so as not to advance straight and to swirl.

[0038] Here, the first inflow holes 32 are rectangular holes. Specifically, the first inflow holes 32 are horizontally long holes whose long sides are parallel to the horizontal direction (left-right direction) and whose short sides are parallel to the vertical direction (up-down direction). The two first inflow holes 32 are provided at predetermined intervals in the vertical direction. However, the present disclosure is not limited thereto, and three or more first inflow holes 32 may be provided. The first inflow holes 32 may be circular holes.

[0039] As shown in FIG. 6, the guide portions 33 have a function of directing the exhaust gas flowing from the first inflow holes 32 toward the injection unit 16. Specifically, the exhaust gas flowing in from the first inflow holes 32 is redirected in the circumferential direction of the first plate 30 by the guide portions 33, and flows toward the injection unit 16 while swirling and impinging on the inner wall surface of the exhaust pipe 13. The exhaust gas directed toward the injection unit 16 by the guide portions 33 diffuses the urea water injected from the injection unit 16. The urea water injected from the injection unit 16 is diffused by the flow of the exhaust gas toward the injection unit 16. Specifically, the urea water tends to diffuse along the facing surface 42 of the second plate 40. Thus, the urea water adheres to a wide area of the facing surface 42 of the second plate 40.

[0040] The first inflow holes 32 are located at positions different from that of the second plate 40 in the circumferential direction of the first plate 30 when the first plate 30 and the second plate 40 are viewed from the third plate 50 (see FIG. 4). Specifically, the first inflow holes 32, the injection unit 16, and the second plate 40 are arranged in this order in the circumferential direction of the first plate 30 (see FIG. 2). In this case, after the exhaust gas guided by the guide portions 33 flows toward the injection unit 16 while swirling in the injection space, the exhaust gas tends to flow toward the facing surface 42 of the second plate 40 (see FIG. 6). As a result, the urea water tends to adhere while diffusing toward the facing surface 42 due to the swirling flow of the exhaust gas.

[0041] As shown in FIG. 2, the guide portions 33 are provided obliquely upward in the vertical direction from lower edges of the first inflow holes 32. The guide portion 33 is provided in each of the two first inflow holes 32. The guide portions 33 are rectangular flat plates. Further, the guide portions 33 are inclined by a predetermined angle (for example, 45) with respect to the horizontal direction. The guide portions 33 having the above-described configuration efficiently guides the exhaust gas that has passed through the first inflow holes 32 to the injection unit 16.

[0042] It should be noted that the guide portions 33 are flat plates in the above description, but are not limited thereto. For example, the guide portions 33 may be curved plates. Even in this case, the exhaust gas can be guided to the injection unit 16 by the guide portions 33. In addition, the guide portions 33 have a rectangular shape, but are not limited thereto. For example, when the first inflow holes 32 are circular in shape, the guide portions 33 may also be circular in shape.

[0043] The second inflow holes 34, like the first inflow holes 32, are holes for allowing the exhaust gas to flow into the injection space surrounded by the first plate 30 and the third plate 50. A plurality of second inflow holes 34 are provided along the second plate 40 at predetermined intervals on the first plate 30 closer to the center of the first plate 30 with respect to the second plate 40. The exhaust gas that passed through the second inflow holes 34 flows in the axial direction along the facing surface 42 of the second plate 40. Accordingly, the facing surface 42 is heated by the heat of the exhaust gas, whereby the urea water adhering to the facing surface 42 tends to be evaporated. Further, the evaporated urea water and generated ammonia gas are carried by the exhaust gas flowing in the axial direction along the facing surface 42, and can thereby be caused to flow promptly toward the downstream side.

[0044] As shown in FIG. 4, the second inflow holes 34 are located at positions different from those of the first inflow holes 32 in the circumferential direction of the first plate 30. Specifically, the second inflow holes 34 are provided adjacent to, in the circumferential direction of the first plate 30, a portion at which the one end portion of the second plate 40 is in contact. The second inflow holes 34 are provided in a range of 180in the circumferential direction of the first plate 30 so as to correspond to the semicylindrical second plate 40. Accordingly, the exhaust gas that has passed through the second inflow holes 34 tends to flow in the axial direction along the entire facing surface 42 of the second plate 40, and thus the urea water adhering to a wide range of the facing surface 42 can be efficiently evaporated.

[0045] The plurality of second inflow holes 34 are provided at predetermined intervals at positions corresponding to the facing surface 42. In the present embodiment, the second plate 40 has a semicylindrical shape, and is provided so that the facing surface 42 of the second plate 40 is positioned at an equal distance from the center of the first plate 30. Therefore, the plurality of second inflow holes 34 are located on a circle having a predetermined radius from the center of the first plate 30 so as to correspond to the facing surface 42 of the second plate 40. This allows the exhaust gas that passed through the plurality of second inflow holes 34 to flow with a uniform distribution relative to the facing surface 42 of the second plate 40, thereby making it easier to uniformly evaporate the urea water adhering to the facing surface 42. The second inflow holes 34 are circular holes here. However, the present disclosure is not limited thereto, and the second inflow holes 34 may be rectangular holes or arc-shaped holes corresponding to the facing surface 42.

[0046] The third inflow hole 35 is a hole for allowing the exhaust gas to flow into a passage space surrounded by the second plate 40 and the inner wall surface of the exhaust pipe 13. The third inflow hole 35 is provided in the first plate 30 along the second plate 40, at a position closer to an edge of the first plate 30 than the second plate 40. In other words, the third inflow hole 35 is located, in the radial direction of the first plate 30, closer to the edge of the first plate 30 than the one end portion of the second plate 40. The exhaust gas that passed through the third inflow hole 35 flows in the axial direction along the back surface 44 of the second plate 40 opposite to the facing surface 42 (see FIG. 3). At this time, the back surface 44 of the second plate 40 is heated by the heat of the exhaust gas. This allows the urea water adhering to the facing surface 42 of the second plate 40 to be more easily evaporated due to the heat of the second plate 40 heated by the exhaust gas.

[0047] The third inflow hole 35 is provided adjacent to, in the circumferential direction of the first plate 30, a portion where the one end portion of the second plate 40 is in contact. The third inflow hole 35, like the second inflow holes 34, is provided over a range of 180in the circumferential direction of the first plate 30. Here, the third inflow hole 35 is formed by arcuately notching the edge of the first plate 30. According to the above configuration, since the exhaust gas that passed through the third inflow hole 35 tends to flow in the axial direction along the entire back surface 44 of the second plate 40, the entire back surface 44 is heated by the exhaust gas. As a result, evaporation of the urea water due to the heat of the second plate 40 can be promoted.

[0048] As described above, the other end portion of the second plate 40 is not in contact with the third plate 50. Therefore, the exhaust gas flowing through the passage space flows toward the outflow hole 52 of the third plate 50 after passing through the other end portion of the second plate 40. As a result, since the exhaust gas continues to pass through the passage space without staying in the passage space, the back surface 44 of the second plate 40 tends to be heated appropriately.

[0049] The third plate 50 has a protruding portion 54 formed in its central portion. As shown in FIG. 2, the protruding portion 54 protrudes toward the first plate 30. The protruding portion 54 has a cylindrical shape. The outflow hole 52 is formed at the distal end of the protruding portion 54.

[0050] Normally, since the urea water does not uniformly adhere to the second plate 40, the concentration of ammonia gas generated from the urea water is likely to vary. In contrast, when only a single outflow hole 52 is provided, ammonia gas having different concentrations gathers at the outflow hole 52 due to the swirling flow of the exhaust gas, thereby facilitating uniformity of the ammonia gas concentration. As a result, the ammonia gas having a uniform concentration tends to pass through the outflow hole 52.

Effects of Embodiment

[0051] The exhaust treatment device 1 of the above-described embodiment includes the first plate 30, the second plate 40, and the third plate 50, which form the injection space into which the injection unit 16 injects the urea water in the exhaust pipe 13. The first plate 30 includes the first inflow holes 32 formed at positions away from the center portion, and the guide portions 33 that guide the exhaust gas flowing in from the first inflow holes 32 to the injection unit 16.

[0052] By providing the first inflow holes 32 and the guide portions 33 in the first plate 30, the exhaust gas flowing in from the first inflow holes 32 flows toward the outflow hole 52 of the third plate 50 while swirling in the injection space, thereby facilitating diffusion of the urea water injected from the injection unit 16 into the injection space. As a result, the urea water tends to adhere to a wide area of the second plate 40, thereby promoting the evaporation and decomposition of the urea water.

Second Embodiment

[0053] A peripheral configuration of the injection unit 16 in the exhaust pipe 13 according to a second embodiment will be described with reference to FIG. 7 to FIG. 11.

[0054] FIG. 7 schematically shows the peripheral configuration of the injection unit 16 of the exhaust pipe 13 according to the second embodiment. FIG. 8 schematically shows an internal configuration of FIG. 7. FIG. 9 schematically shows a configuration of the exhaust pipe 13 of FIG. 7 as viewed from the front. FIG. 10 schematically shows the configuration of the exhaust pipe 13 of FIG. 7 as viewed from the rear. FIG. 11 is a schematic view for explaining flows of the exhaust gas and the urea water in an injection period. It should be noted that, in FIG. 7, for convenience of description, the exhaust pipe 13 surrounding a first plate 130, a second plate 140, and a third plate 150 is indicated by a broken line. Solid arrows shown in FIG. 8 and FIG. 11 indicate the flow of the exhaust gas, and dashed arrows shown in FIG. 11 indicate the flow of the urea water. Further, as shown in FIG. 7 and FIG. 8, a term front refers to an upstream side in the flow direction of the exhaust gas, and a term rear refers to a downstream side in the flow direction of the exhaust gas.

[0055] In the second embodiment, a plurality of plates are provided in the exhaust pipe 13 to which the injection unit 16 is attached in order to promote evaporation and decomposition of the urea water injected by the injection unit 16. Specifically, also in the second embodiment, the first plate 130, the second plate 140, and the third plate 150 are provided inside the exhaust pipe 13 as shown in FIG. 7.

[0056] The first plate 130 is located on the upstream of the injection unit 16 in the exhaust pipe 13. The first plate 130 is provided in a manner to be orthogonal to the axial direction (front-rear direction) of the exhaust pipe 13. The first plate 130 is a circular plate having a predetermined radius. An edge of the first plate 130 is in contact with the inner wall surface of the exhaust pipe 13. The first plate 130 is provided with a plurality of inflow holes (first inflow holes 132, second inflow holes 134, a third inflow hole 136, and a fourth inflow hole 138) through which the exhaust gas passes. The detailed configuration of the first plate 130 will be described later.

[0057] The third plate 150 is located downstream of the second plate 140 in the exhaust pipe 13. The third plate 150, like the first plate 130, is provided in a manner to be orthogonal to the axial direction of the exhaust pipe 13. The third plate 150 is a disk, and the radius of the third plate 150 is the same as the radius of the first plate 130. Therefore, the edge of the third plate 150 is also in contact with the inner wall surface of the exhaust pipe 13. The third plate 150 is provided with the outflow hole 156 through which the exhaust gas passes. The detailed configuration of the third plate 150 will be described later.

[0058] Urea water is injected from the injection unit 16 attached to the exhaust pipe 13 into the injection space surrounded by the first plate 130 and the third plate 150 in the exhaust pipe 13. The injection unit 16 is provided at a position obliquely above (upper left in FIG. 10) the outer peripheral wall of the exhaust pipe 13. The injection unit 16 injects urea water obliquely downward. The injection direction of the urea water is inclined by a predetermined angle with respect to the vertical direction. The exhaust gas that passed through the plurality of inflow holes of the first plate 130 flows into the injection space, evaporates the urea water, and then flows out from the outflow hole 156 of the third plate 150.

[0059] The second plate 140 is located between the first plate 130 and the third plate 150 in the exhaust pipe 13, and is provided along the axial direction (front-rear direction). The second plate 140 is provided so that the facing surface 142 faces the injection unit 16. Therefore, the urea water injected by the injection unit 16 adheres to the facing surface 142 of the second plate 140. The second plate 140 is heated by the exhaust gas passing through the injection space. Therefore, the urea water adhering to the facing surface 142 evaporates due to the heat of the second plate 140.

[0060] The facing surface 142 of the second plate 140 has a curved shape with a predetermined curvature. The radius of the second plate 140 is smaller than the radius of the third plate 150. A cross-sectional shape of the second plate 140 in a plane orthogonal to the axial direction is an arc shape. Specifically, the cross-sectional shape of the second plate 140 is formed such that an angle formed by a first line (a line L1 shown in FIG. 9) passing through one end in the circumferential direction of the second plate 140 and the center of the second plate 140 and a second line (a line L2 shown in FIG. 9) passing through the other end in the circumferential direction of the second plate 140 and the center of the second plate 140 is 180or more and 270or less. Here, the angle formed by the line L1 and the line L2 is 270. Accordingly, since the facing surface 142 is formed over a wide range, the urea water adheres to the wide range of the second plate 140.

[0061] The urea water adhering to the facing surface 142 is heated by the exhaust gas and thereby evaporates and decomposes. Ammonia gas is generated by evaporation and decomposition of the urea water. The generated ammonia gas is carried by the exhaust gas flowing toward the outflow hole 156, passes through the outflow hole 156 together with the exhaust gas, and flows toward the SCR device 18 (FIG. 1).

[0062] When at least one of both end portions of the second plate 140 in the axial direction is not in contact with the first plate 130 and the third plate 150, the urea water may fall from the facing surface 142 of the second plate 140 and adhere to the inner wall surface of the exhaust pipe 13. The urea water adhering to the inner wall surface of the exhaust pipe 13 is difficult to evaporate because the outer wall surface of the exhaust pipe 13 is exposed to the low-temperature outside.

[0063] In contrast, in the present embodiment, as shown in FIG. 8, one end portion of the second plate 140 in the axial direction is in contact with the first plate 130, and the other end portion of the second plate 140 in the axial direction is in contact with the third plate 150. This allows the facing surface 142 of the second plate 140 to accumulate the urea water injected from the injection unit 16, thereby suppressing the urea water from falling from the facing surface 142 and adhering to the inner wall surface of the exhaust pipe 13. The urea water accumulated on the facing surface 142 evaporates over time.

[0064] The second plate 140 includes a bent portion 146. The bent portion 146 is formed at a circumferential end portion of the second plate 140. The bent portion 146 is bent in the radial direction from one end portion in the circumferential direction of the second plate 140. The bent portion 146 is connected to the exhaust pipe 13. Specifically, an end surface of the bent portion 146 is connected to the inner wall surface of the exhaust pipe 13. For example, the end surface of the bent portion 146 is fixed to the inner wall surface of the exhaust pipe 13 by welding.

Detailed Configuration of First Plate

[0065] Also in the second embodiment, the first plate 130 includes a plurality of inflow holes at different positions and guide portions in order to further promote evaporation and decomposition of the urea water in the injection space. Specifically, as shown in FIG. 9, the first plate 130 includes the first inflow holes 132, first guide portions 133, the second inflow holes 134, second guide portions 135, the third inflow hole 136, and the fourth inflow hole 138.

[0066] The first inflow holes 132 are holes for allowing the exhaust gas to flow into the injection space surrounded by the first plate 130 and the third plate 150. The exhaust gas introduced from the first inflow holes 132 diffuses the urea water that was injected into the injection space. The first inflow holes 132, like the first inflow holes 32 described above, are provided at positions away from the center of the first plate 130.

[0067] The first inflow holes 132 are rectangular holes here. Specifically, the first inflow holes 132 are obliquely disposed so that the long sides and the short sides intersect the horizontal direction (left-right direction) and the vertical direction (up-down direction). The two first inflow holes 132 are provided at predetermined intervals in the vertical direction. The first inflow holes 132 are formed at positions adjacent to the facing surface 142 of the second plate 140.

[0068] The first guide portions 133 have a function of directing the exhaust gas flowing in from the first inflow holes 132 to the injection unit 16 located obliquely upward. Specifically, the exhaust gas flowing in from the first inflow holes 132 is guided by the first guide portions 133 toward the injection unit 16 while changing its direction toward the circumferential direction of the first plate 130 and swirling (see FIG. 11). The exhaust gas directed toward the injection unit 16 by the first guide portions 133 diffuses the urea water injected from the injection unit 16. The urea water injected from the injection unit 16 is diffused by the flow of the exhaust gas toward the injection unit 16. Specifically, the urea water tends to diffuse along the facing surface 142 of the second plate 140. Therefore, the urea water adheres to a wide area of the facing surface 142 of the second plate 140.

[0069] The first guide portions 133 are provided obliquely upward in the vertical direction from the lower edge of the first inflow holes 132. The first guide portion 133 is provided in each of the two first inflow holes 132. The first guide portions 133 are rectangular flat plates. Further, as shown in FIG. 8, the first guide portions 133 are inclined by a predetermined angle (for example, 45) with respect to the first plate 130. The exhaust gas that passed through the first inflow holes 132 is efficiently guided to the injection unit 16 by the first guide portions 133 having the above-described configuration.

[0070] The second inflow holes 134 are holes for allowing the exhaust gas to flow into the injection space surrounded by the first plate 130 and the third plate 150. The exhaust gas introduced from the second inflow holes 134 diffuses the urea water injected into the injection space. The second inflow holes 134, like the first inflow holes 32 described above, are provided at positions away from the center of the first plate 130. The second inflow holes 134 are formed at positions away from the first inflow holes 132 by a predetermined angle (for example, 180) in the circumferential direction and adjacent to the facing surface 142 of the second plate 140.

[0071] The second inflow holes 134, like the first inflow holes 132, are rectangular holes. Specifically, the second inflow holes 134 are obliquely disposed so that the long sides and the short sides intersect the horizontal direction (left-right direction) and the vertical direction (up-down direction). The two second inflow holes 134 are provided at predetermined intervals in the vertical direction. The size of the second inflow holes 134 is the same as the size of the first inflow holes 132, but is not limited thereto, and the size of the second inflow holes 134 may be different from the size of the first inflow holes 132. The second inflow holes 134 are located below the first inflow holes 132 in the vertical direction.

[0072] The second guide portions 135 have a function of directing the exhaust gas flowing from the second inflow holes 134 toward the facing surface 142 of the second plate 140. Specifically, the exhaust gas flowing in from the second inflow holes 134 is guided by the second guide portions 135 toward the facing surface 142 of the second plate 140 while changing its direction toward the circumferential direction of the first plate 130 and swirling (see FIG. 11). Then, as the exhaust gas flows along the facing surface 142 of the second plate 140, the exhaust gas evaporates the urea water adhering to the facing surface 142. Further, when the exhaust gas flows toward the outflow hole 156, the exhaust gas directs the ammonia gas generated by evaporating urea water toward the outflow hole 156.

[0073] The second guide portions 135 are provided obliquely downward in the vertical direction from the upper edges of the second inflow holes 134. The second guide portions 135 are provided in each of the two second inflow holes 134. The second guide portions 135 are rectangular flat plates. In addition, the second guide portions 135 are inclined by a predetermined angle (for example, 45) with respect to the first plate 130.

[0074] The third inflow hole 136 is a hole for allowing the exhaust gas to flow into a passage space surrounded by the second plate 140 and the inner wall surface of the exhaust pipe 13. The third inflow hole 136 is provided in the first plate 130 along the second plate 140, at a position closer to an edge of the first plate 130 than the second plate 140. In other words, the third inflow hole 136 is located, in the radial direction of the first plate 130, closer to the edge of the first plate 130 than the one end portion of the second plate 140. Here, the third inflow hole 136 is formed arcuately notching the edge of the first plate 130 (see FIG. 7). The third inflow hole 136 is provided over a range of 270in the circumferential direction of the first plate 130.

[0075] The exhaust gas that passed through the third inflow hole 136 flows in the axial direction along the back surface 144 of the second plate 140 opposite to the facing surface 142. At this time, the back surface 144 of the second plate 140 is heated by the heat of the exhaust gas. As a result, the urea water adhering to the facing surface 142 of the second plate 140 tends to evaporate due to the heat of the second plate 140 heated by the exhaust gas, whereby ammonia gas is more easily generated.

[0076] The fourth inflow hole 138 is a hole for allowing the exhaust gas to flow into the injection space surrounded by the first plate 130 and the third plate 150. The fourth inflow hole 138 is different from the first inflow holes 132 and the second inflow holes 134, and has a fan shape here, but is not limited thereto, and may have other shapes. The fourth inflow hole 138 is formed at a position where the second plate 140 is not provided in the circumferential direction. The fourth inflow hole 138 is formed at a position adjacent to the injection unit 16 in the circumferential direction. The fourth inflow hole 138 is adjacent to the inner wall surface of the exhaust pipe 13. Further, the fourth inflow hole 138 is not provided with a guide portion. As a result, since the exhaust gas flowing in from the fourth inflow hole 138 flows along the inner wall surface of the exhaust pipe 13, it is possible to prevent the flow of the exhaust gas guided to the injection unit 16 by the first guide portions 133 from being concentrated toward the inner wall surface of the exhaust pipe 13, thereby facilitating diffusion of the urea water along the facing surface 142 of the second plate 140.

[0077] Unlike the present embodiment, when the fourth inflow hole 138 is not provided, the urea water injected from the injection unit 16 tends to flow toward the bent portion 146 of the second plate 140 by the exhaust gas flowing toward the injection unit 16 by the first guide portions 133. As a result, there is a possibility that the urea water will adhere to the bent portion 146 and will not be properly evaporated.

[0078] In contrast, in the present embodiment, the fourth inflow hole 138 is located in the direction in which the urea water injected from the injection unit 16 flows (specifically, in the direction in which the urea water flows due to the swirling flow of the exhaust gas). More specifically, the fourth inflow hole 138 is located between the injection unit 16 and the bent portion 146 of the second plate 140 in the circumferential direction. Accordingly, the flow of exhaust gas directed toward the third plate 150 from the fourth inflow hole 138 prevents the flow of exhaust gas guided to the injection unit 16 by the first guide portions 133 from concentrating toward the inner wall surface of the exhaust pipe 13, thereby facilitating the diffusion of the urea water along the facing surface 142 of the second plate 140, and thus suppressing adhesion of the urea water to the bent portion 146.

Detailed Configuration of Third Plate

[0079] As shown in FIG. 7 and FIG. 10, the third plate 150 includes a flat plate portion 152, the protruding portion 154, and the outflow hole 156.

[0080] The flat plate portion 152 has a circular flat plate shape. The flat plate portion 152 is orthogonal to the axial direction. The outer peripheral surface of the flat plate portion 152 is joined to the inner wall surface of the exhaust pipe 13, and no gap is formed between the outer peripheral surface of the flat plate portion 152 and the inner wall surface of the exhaust pipe 13.

[0081] As shown in FIG. 8, the protruding portion 154 protrudes toward the first plate 130. The protruding portion 154 is provided at a central portion of the flat plate portion 152. Therefore, the protruding portion 154 protrudes from the central portion of the flat plate portion 152 toward the first plate 130. The protruding portion 154 is integrally formed with the flat plate portion 152. For example, the protruding portion 154 is formed by drawing the central portion of the flat plate portion 152.

[0082] The protruding portion 154 has a cylindrical shape through which exhaust gas can pass. However, the protruding portion 154 does not have a cylindrical shape like the protruding portion 54 (FIG. 2) described above. The radius of the protruding portion 154 varies in the axial direction. Specifically, the protruding portion 154 is formed so that the outer diameter of the protruding portion 154 increases from the tip of the protruding portion 154 toward a connection point 157 (FIG. 10) between the protruding portion 154 and the flat plate portion 152. The outer peripheral surface of the protruding portion 154 is curved from the tip of the protruding portion 154 toward the connection point 157. Specifically, the protruding portion 154 has a dome shape. The protruding portion 154 is located closer to the center in the radial direction with respect to the second plate 140.

[0083] The outflow hole 156 is a hole through which the exhaust gas in the injection space flows out. The outflow hole 156 is a circular hole, for example. The exhaust gas that passed through the outflow hole 156 flows toward the reduction catalyst 19 (FIG. 1) of the SCR device 18. The reduction catalyst 19 is provided downstream of the third plate 150 in the exhaust passage 12. It should be noted that the ammonia gas generated from the urea water in the injection space also flows toward the reduction catalyst 19 through the outflow hole 156. As a result, the ammonia gas and the exhaust gas react in the reduction catalyst 19.

[0084] The outflow hole 156 is located at the center of the third plate 150. Unlike the above-described four inflow holes of the first plate 130, only a single outflow hole 156 is provided. Therefore, the exhaust gas and the ammonia gas in the injection space pass through the single outflow hole 156. Since the exhaust gas flows while swirling in the injection space by the first guide portions 133 and the second guide portions 135 provided in the first plate 130, the ammonia gas generated at the second plate 140 tends to be directed toward the outflow hole 156 by the swirling flow of the exhaust gas.

[0085] Normally, since the urea water does not uniformly adhere to the second plate 140, the concentration of ammonia gas generated from the urea water tends to vary. In contrast, when only the single outflow hole 156 is provided, the ammonia gas having different concentrations gathers in the outflow hole 156 due to the swirling flow of the exhaust gas, thereby facilitating uniformity of the ammonia gas concentration. As a result, the ammonia gas with a uniform concentration tends to pass through the outflow hole 156.

[0086] The outflow hole 156 is formed at the distal end of the protruding portion 154. Therefore, the outflow hole 156 is located closer to the first plate 130 than the flat plate portion 152. In this case, as compared with the case where the outflow hole 156 is formed in the flat plate portion 152, the ammonia gas having different concentrations can be more quicky made uniform.

[0087] The reduction catalyst 19 shown in FIG. 1 is located in the vicinity downstream of the third plate 150. Here, the distance between the third plate 150 and the reduction catalyst 19 is smaller than the distance between the third plate 150 and the first plate 130. At this time, unlike the present embodiment, when an outflow hole is formed in the flat plate portion 152, since the distance between the outflow hole and the reduction catalyst 19 is short, there is a possibility that the exhaust gas and the ammonia gas that passed through the outflow hole are not sufficiently mixed before reaching the reduction catalyst 19.

[0088] In contrast, when the outflow hole 156 is located at the tip end of the protruding portion 154, the distance between the outflow hole 156 and the reduction catalyst 19 can be increased, thereby increasing the space for mixing the exhaust gas and the ammonia gas that have passed through the outflow hole 156. In addition, since the outer diameter of the protruding portion 154 increases along the axial direction, compared with the case where the outer diameter of the protruding portion is uniform, the exhaust gas and the ammonia gas are more easily mixed when flowing along the inner wall surface of the protruding portion 154.

[0089] In the above description, the outflow hole 156 is located at the center of the third plate 150, but is not limited thereto. For example, the outflow hole 156 may be provided at a position away from the center of the third plate 150. Even in this case, since the ammonia gas gathers in the outflow hole 156, the concentration of the ammonia gas tends to be made uniform.

[0090] The outer peripheral surface of the protruding portion 154 is curved in the above description, but is not limited thereto. For example, the outer peripheral surface of the protruding portion 154 may be an inclined surface inclined at a predetermined angle. The outer peripheral surface of the protruding portion 154 may have a stepped shape.

Effects of Second Embodiment

[0091] The exhaust treatment device 1 of the second embodiment includes the first plate 130, the second plate 140, and the third plate 150 that form an injection space into which the injection unit 16 injects urea water in the exhaust pipe 13. The first plate 130 includes the inflow holes (first inflow holes 132 and the like) into which the exhaust gas flows. Further, the third plate 150 includes the protruding portion 154 protruding toward the first plate 130, and the outflow hole 156 formed at the tip end of the protruding portion 154.

[0092] Thus, even if the concentration of ammonia gas generated from urea water on the second plate 140 varies, the ammonia gas gathers in the outflow hole 156 due to the swirling flow of the exhaust gas, thereby facilitating uniformity of the ammonia gas concentration. 87 In addition, also in the second embodiment, the first plate 130 includes the first inflow holes 132 formed at positions away from the center portion, and the first guide portions 133 that direct the exhaust gas flowing in from the first inflow holes 132 toward the injection unit 16. Accordingly, since the exhaust gas flowing in from the first inflow holes 132 flows toward the outflow hole 156 of the third plate 150 while swirling in the injection space, the urea water injected into the injection space from the injection unit 16 tends to be diffused. As a result, the urea water tends to adhere to a wide area of the second plate 140, thereby promoting the evaporation and decomposition of the urea water.

[0093] The present disclosure is explained on the basis of the exemplary embodiments. The technical scope of the present disclosure is not limited to the scope explained in the above embodiments and it is possible to make various changes and modifications within the scope of the disclosure. For example, all or part of the apparatus can be configured with any unit which is functionally or physically dispersed or integrated. Further, new exemplary embodiments generated by arbitrary combinations of them are included in the exemplary embodiments of the present disclosure. Further, effects of the new exemplary embodiments brought by the combinations also have the effects of the original exemplary embodiments.