JP2021127749A - Exhaust emission control device - Google Patents

Abstract

To provide an exhaust emission control device capable of reducing exhaust gas to hit a fuel addition valve.SOLUTION: An exhaust emission control device 1 comprises an exhaust pipe 3 forming an exhaust passage 4 where exhaust gas flows, a fuel addition valve 7 for injecting fuel to the exhaust passage 4, and a cylindrical side wall 10 arranged between the exhaust pipe 3 and the fuel addition valve 7 and forming an injection passage 11 where the fuel to be injected from the fuel addition valve 7 passes, the side wall 10 including a lower wall part 12 connected to the exhaust pipe 3, and an upper wall part 13 arranged on the fuel addition valve 7 side further than the lower wall part 12 and connected to the fuel addition valve 7, the lower wall part 12 having an axial length J1 greater than an axial length J2 of the upper wall part 13, the lower wall part 12 and the upper wall part 13 each having a curved shape in cross section cut in a direction parallel to the axial direction of the side wall 10, so as to be convex to the radial outside of the side wall 10. In a boundary between the lower wall part 12 and the upper wall part 13, an annular concave part 14 is provided extending in the peripheral direction of the side wall 10.SELECTED DRAWING: Figure 2

Description

The present invention relates to an exhaust gas purification device.

As a conventional exhaust gas purification device, for example, the technique described in Patent Document 1 is known. The exhaust purification device described in Patent Document 1 is between an exhaust pipe connected to an internal combustion engine, an injection nozzle that directly injects fuel into the exhaust gas flowing through the exhaust pipe, and the wall surface of the injection nozzle and the exhaust pipe. It is provided with an exhaust gas retention space provided in.

JP-A-2017-25797

However, in the above-mentioned prior art, when fuel is not injected from the injection nozzle (fuel addition valve), a part of the exhaust gas staying inside the exhaust gas retention space may flow toward the injection nozzle. .. In this case, the high-temperature exhaust gas hits the injection nozzle and may cause a deposit.

An object of the present invention is to provide an exhaust purification device capable of reducing the exhaust gas that hits the fuel addition valve.

One aspect of the present invention is an exhaust purification device that purifies exhaust gas discharged from an internal combustion engine, in which fuel is injected toward an exhaust pipe that is connected to the internal combustion engine and forms an exhaust passage through which the exhaust gas flows. A cylindrical side wall that is arranged between the exhaust pipe and the fuel addition valve and forms an injection passage through which fuel injected from the fuel addition valve passes, and the side wall is connected to the exhaust pipe. It has a first wall portion and a second wall portion which is arranged on the fuel addition valve side of the first wall portion and is connected to the fuel addition valve, and the axial length of the first wall portion is the first. It is larger than the axial length of the two wall parts, and the first wall part and the second wall part have a cross section cut in a direction parallel to the axial direction of the side wall so as to be convex outward in the radial direction of the side wall. It has a curved shape, and an annular recess extending in the circumferential direction of the side wall is provided at the boundary between the first wall portion and the second wall portion.

In such an exhaust purification device, when fuel is not injected from the fuel addition valve toward the exhaust passage, a part of the exhaust gas flowing through the exhaust passage enters the injection passage. Here, in the cylindrical side wall forming the injection passage, the axial length of the first wall portion is larger than the axial length of the second wall portion. Further, the first wall portion has a curved shape so as to have a cross section cut in a direction parallel to the axial direction of the side wall and to be convex outward in the radial direction of the side wall. Therefore, the exhaust gas that has entered the injection passage flows along the inner wall surface of the first wall portion and returns to the exhaust passage. However, some exhaust gas reaches the inside of the second wall portion from the inside of the first wall portion. The exhaust gas flows along the inner wall surface of the second wall portion. Here, the second wall portion also has a curved shape that is convex outward in the radial direction of the side wall in a cross section cut in a direction parallel to the axial direction of the side wall. Further, at the boundary between the first wall portion and the second wall portion, an annular recess extending in the circumferential direction of the side wall is provided. Therefore, the diameter of the second wall portion is larger than that in the case where the second wall portion does not have a curved shape that is convex outward in the radial direction of the side wall. Therefore, the exhaust gas that has reached the inside of the second wall portion flows around the inner wall surface of the second wall portion in the circumferential direction of the second wall portion, and then returns to the exhaust passage through the inside of the first wall portion. become. That is, the exhaust gas flows in the second wall portion so as to avoid the radial central portion corresponding to the location of the fuel addition valve. As a result, the exhaust gas that hits the fuel addition valve when the fuel is not injected from the fuel addition valve is reduced.

The maximum diameter of the second wall portion may be the same as the maximum diameter of the first wall portion. In such a configuration, the radial dimension of the second wall portion is suppressed to reduce the size of the side wall, and the second wall portion avoids the radial central portion corresponding to the location where the fuel addition valve is arranged. A space is secured that flows around the inner wall surface of the.

The boundary between the inner wall surface of the first wall portion and the inner wall surface of the second wall portion forms the bottom portion of the recess, and the bottom portion of the recess may have an R shape. In such a configuration, when a part of the exhaust gas flowing along the inner wall surface of the first wall portion reaches the inside of the second wall portion, the exhaust gas flows from the vicinity of the inner wall surface of the first wall portion to the inside of the second wall portion. It will flow smoothly to the vicinity of the wall surface. Therefore, the exhaust gas that hits the fuel addition valve is further reduced.

According to the present invention, the exhaust gas that hits the fuel addition valve can be reduced.

It is a schematic block diagram which shows the exhaust gas purification apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the main part of the exhaust gas purification apparatus shown in FIG. It is sectional drawing which shows the flow of the exhaust gas when the fuel is injected from the fuel addition valve shown in FIG. It is a conceptual diagram which shows how the fuel droplet of the peripheral part of the fuel spray injected from the fuel addition valve shown in FIG. 2 adheres to the inner wall surface of the lower wall part. It is sectional drawing which shows the flow of the exhaust gas when the fuel is not injected from the fuel addition valve shown in FIG. It is sectional drawing which shows the flow of the exhaust gas when the fuel is not injected from the fuel addition valve shown in FIG. It is a figure which shows the cross-sectional view of line VII-VII of FIG. 6 together with the flow of exhaust gas. It is sectional drawing which shows the main part of the exhaust gas purification apparatus as a comparative example together with the flow of exhaust gas.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a schematic configuration diagram showing an exhaust gas purification device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a main part of the exhaust gas purification device shown in FIG. In FIGS. 1 and 2, the exhaust gas purification device 1 of the present embodiment is mounted on a vehicle.

The exhaust purification device 1 purifies the exhaust gas discharged from the diesel engine 2 which is an internal combustion engine. Although not particularly shown, the diesel engine 2 has a plurality of injectors that inject fuel into a plurality of cylinders. The exhaust purification device 1 includes an exhaust pipe 3 connected to the diesel engine 2. The exhaust pipe 3 forms an exhaust passage 4 through which exhaust gas flows.

Further, the exhaust gas purification device 1 includes a DOC5 (diesel oxidation catalyst) and a DPF6 (diesel exhaust fine particle removing filter) which are sequentially arranged in the exhaust passage 4 from the upstream side to the downstream side. DOC5 oxidizes and removes particulate matter (PM) contained in exhaust gas. DPF6 collects PM contained in the exhaust gas.

Further, the exhaust gas purification device 1 includes a fuel addition valve 7 arranged between the diesel engine 2 and the DOC 5 in the exhaust passage 4. The fuel addition valve 7 injects fuel toward the exhaust passage 4 to add fuel. The fuel added by the fuel addition valve 7 is mainly used as a reducing agent when the DPF 6 is regenerated. At the lower end of the fuel addition valve 7, an injection port 7a for injecting fuel in a conical shape toward the exhaust passage 4 is provided.

The fuel addition valve 7 is held by the holding member 8. The injection port 7a is arranged inside the holding member 8 so as not to protrude downward from the lower end of the holding member 8. As a result, the structure is such that the exhaust gas flowing through the exhaust passage 4 does not easily hit the injection port 7a.

The holding member 8 is formed with a water jacket 9 which is a cooling water channel through which cooling water for cooling the fuel addition valve 7 flows. The water jacket 9 is arranged so as to surround the fuel addition valve 7. A flange portion 8a is provided at the lower end portion of the holding member 8.

Further, the exhaust gas purification device 1 includes a cylindrical side wall 10 arranged between the exhaust pipe 3 and the fuel addition valve 7. The side wall 10 has a circular shape with a cross section cut in a direction perpendicular to the axial direction (X direction) of the side wall 10 (see FIG. 7). The axial direction of the side wall 10 corresponds to the arrangement direction of the side wall 10 and the fuel addition valve 7. The side wall 10 forms an injection passage 11 through which the fuel injected from the fuel addition valve 7 passes. The injection passage 11 communicates with the exhaust passage 4. The side wall 10 is provided so as to project from the exhaust pipe 3 toward the fuel addition valve 7. The fuel addition valve 7 is arranged at a position corresponding to the central portion of the side wall 10 in the radial direction (Y direction).

The side wall 10 has a lower wall portion 12 and an upper wall portion 13 arranged on the fuel addition valve 7 side of the lower wall portion 12. The lower wall portion 12 is a first wall portion connected to the exhaust pipe 3. The upper wall portion 13 is a second wall portion connected to the fuel addition valve 7. The upper wall portion 13 is connected to the fuel addition valve 7 via a holding member 8.

The lower wall portion 12 and the upper wall portion 13 are integrated. The lower wall portion 12 and the upper wall portion 13 are integrally formed with the exhaust pipe 3 by casting, for example. The lower wall portion 12 may be joined to the exhaust pipe 3 by welding or the like. The upper wall portion 13 is joined to, for example, the flange portion 8a of the holding member 8 by welding or the like.

The shaft length J1 of the lower wall portion 12 is larger than the shaft length J2 of the upper wall portion 13. The axial length J1 of the lower wall portion 12 is a dimension in the axial direction (X direction) of the lower wall portion 12. The axial length J2 of the upper wall portion 13 is an axial dimension of the upper wall portion 13. The axial length J1 of the lower wall portion 12 is, for example, twice or more larger than the axial length J2 of the upper wall portion 13.

The lower wall portion 12 has a curved shape that is convex outward in the radial direction (Y direction) in a cross section cut in a direction parallel to the axial direction. Therefore, the inner wall surface 12a of the lower wall portion 12 has a curved surface that is concave outward in the radial direction. The position of the convex apex on the lower wall portion 12 is, for example, the central position in the axial direction of the lower wall portion 12.

Like the lower wall portion 12, the upper wall portion 13 has a curved shape having a cross section cut in a direction parallel to the axial direction and convex outward in the radial direction. Therefore, the inner wall surface 13a of the upper wall portion 13 has a curved surface that is concave outward in the radial direction. The position of the convex apex on the upper wall portion 13 is, for example, a position above the central position in the axial direction of the lower wall portion 12 (on the fuel addition valve 7 side).

The maximum diameter K2 of the upper wall portion 13 is equivalent to the maximum diameter K1 of the lower wall portion 12. Here, the maximum diameter K1 of the lower wall portion 12 is the maximum inner diameter of the lower wall portion 12. That is, the maximum diameter K1 of the lower wall portion 12 is the maximum value of the diameter of the inner wall surface 12a of the lower wall portion 12. More specifically, the maximum diameter K1 of the lower wall portion 12 is the diameter of the inner wall surface 12a at the position where the lower wall portion 12 has a convex apex. The maximum diameter K2 of the upper wall portion 13 is the maximum inner diameter of the upper wall portion 13. That is, the maximum diameter K2 of the upper wall portion 13 is the maximum value of the diameter of the inner wall surface 13a of the upper wall portion 13. More specifically, the maximum diameter K2 of the upper wall portion 13 is the diameter of the inner wall surface 13a at the position of the convex apex of the upper wall portion 13.

At the boundary between the lower wall portion 12 and the upper wall portion 13, an annular recess 14 extending in the circumferential direction of the side wall 10 is provided. The recess 14 is open to the outside of the side wall 10 in the radial direction. Therefore, the side wall 10 expands in diameter at the lower wall portion 12 from the lower side (exhaust pipe 3 side) to the upper side (fuel addition valve 7 side), and at the boundary portion between the lower wall portion 12 and the upper wall portion 13. It has a shape that reduces the diameter and expands the diameter again at the upper wall portion 13.

The recess 14 is defined by an upper end portion of the lower wall portion 12 and a lower end portion of the upper wall portion 13. The bottom portion 14a of the recess 14 has an R shape. The bottom portion 14a of the recess 14 is a boundary portion between the inner wall surface 12a of the lower wall portion 12 and the inner wall surface 13a of the upper wall portion 13.

In the recess 14, the angle θ formed by the upper end of the lower wall 12 and the lower end of the upper wall 13 is an acute angle. The angle θ is, for example, an angle such that the exhaust gas flowing upward along the inner wall surface 12a of the lower wall portion 12 can easily reach the vicinity of the inner wall surface 13a of the upper wall portion 13.

In the exhaust gas purification device 1 as described above, as shown in FIG. 3, when fuel is injected from the injection port 7a of the fuel addition valve 7, the upper region of the injection passage 11 is formed by the flow accompanying the injection of the fuel. Since the pressure drops, an exhaust gas flow (see A in FIG. 3) is generated upward in the injection passage 11. Then, the fuel spray F injected from the fuel addition valve 7 is rewound by the flow of the exhaust gas, and the fuel droplet P in the peripheral portion of the fuel spray F is directed upward.

At this time, the lower wall portion 12 of the side wall 10 has a curved shape that is convex outward in the radial direction of the side wall 10. Therefore, as shown in FIG. 4, the exhaust gas flows upward along the inner wall surface 12a of the lower wall portion 12. Then, due to such an exhaust gas flow, an inertial force is generated in the fuel droplet P in the peripheral portion of the fuel spray F. Therefore, the fuel droplet P in the peripheral portion of the fuel spray F tends to adhere to the inner wall surface 12a of the lower wall portion 12 due to the inertial force, so that it is difficult to reach the injection port 7a of the fuel addition valve 7.

On the other hand, as shown in FIG. 5, when fuel is not injected from the injection port 7a of the fuel addition valve 7, a part of the exhaust gas flowing through the exhaust passage 4 enters the injection passage 11. The exhaust gas that has entered the injection passage 11 flows upward along the inner wall surface 12a of the lower wall portion 12 on the downstream side of the exhaust pipe 3, and then flows onto the inner wall surface 12a of the lower wall portion 12 on the upstream side of the exhaust pipe 3. It flows downward along the line and returns to the exhaust passage 4. Therefore, the exhaust gas does not easily reach the injection port 7a of the fuel addition valve 7.

However, as shown in FIG. 6, a part of the exhaust gas flowing upward along the inner wall surface 12a of the lower wall portion 12 reaches the inside of the upper wall portion 13. At this time, the upper wall portion 13 has a curved shape that is convex outward in the radial direction of the side wall 10. Therefore, the exhaust gas that has reached the inside of the upper wall portion 13 flows in the circumferential direction along the inner wall surface 13a of the upper wall portion 13, as shown in FIGS. 6 and 7. That is, the exhaust gas flows so as to avoid the radial central portion in the upper wall portion 13 corresponding to the location where the fuel addition valve 7 is arranged. Note that FIG. 7 shows only the flow of exhaust gas along the inner wall surface 13a of the upper wall portion 13, and the flow of exhaust gas from the inside of the lower wall portion 12 to the inside of the upper wall portion 13 is omitted.

Then, the exhaust gas circulates around the inner wall surface 13a of the upper wall portion 13 an arbitrary number of times in the circumferential direction, and then flows downward along the inner wall surface 12a of the lower wall portion 12 to the exhaust passage 4. return. Therefore, even if a part of the exhaust gas reaches the inside of the upper wall portion 13, the exhaust gas does not easily reach the injection port 7a of the fuel addition valve 7.

FIG. 8 is a cross-sectional view showing a main part of an exhaust gas purification device as a comparative example. In FIG. 8, the exhaust purification device 50 of this comparative example includes a cylindrical side wall 51 arranged between the exhaust pipe 3 and the fuel addition valve 7. The side wall 51 forms an injection passage 52 through which the fuel injected from the fuel addition valve 7 passes. The side wall 51 has a linear cross section cut in a direction parallel to the axial direction (X direction) of the side wall 51.

In such an exhaust gas purification device 50, as shown in FIG. 8A, when fuel is injected from the fuel addition valve 7, the flow of exhaust gas toward the fuel addition valve 7 side in the injection passage 52 ( (See A in FIG. 8A) causes rewinding of the fuel spray F injected from the injection port 7a of the fuel addition valve 7. Therefore, the fuel droplet P in the peripheral portion of the fuel spray F may adhere to the injection port 7a of the fuel addition valve 7 to generate a deposit that causes clogging of the injection port 7a.

On the other hand, as shown in FIG. 8B, when fuel is not injected from the fuel addition valve 7, when a part of the exhaust gas flowing through the exhaust passage 4 enters the injection passage 52, the exhaust gas is injected. It flows upward through the passage 52 toward the fuel addition valve 7. Therefore, the high-temperature exhaust gas hits the injection port 7a of the fuel addition valve 7, and the temperature of the injection port 7a rises, which may cause a deposit.

In response to such a problem, in the present embodiment, when fuel is not injected from the fuel addition valve 7 toward the exhaust passage 4, a part of the exhaust gas flowing through the exhaust passage 4 enters the injection passage 11. Here, in the cylindrical side wall 10 forming the injection passage 11, the axial length J1 of the lower wall portion 12 is larger than the axial length J2 of the upper wall portion 13. Further, the lower wall portion 12 has a curved shape so as to have a cross section cut in a direction parallel to the axial direction of the side wall 10 and to be convex outward in the radial direction of the side wall 10. Therefore, the exhaust gas that has entered the injection passage 11 flows along the inner wall surface 12a of the lower wall portion 12 and returns to the exhaust passage 4. However, some of the exhaust gas reaches the inside of the upper wall portion 13 from the inside of the lower wall portion 12. The exhaust gas flows along the inner wall surface 13a of the upper wall portion 13. Here, the upper wall portion 13 also has a curved shape that is convex outward in the radial direction of the side wall 10 in a cross section cut in a direction parallel to the axial direction of the side wall 10. Further, at the boundary between the lower wall portion 12 and the upper wall portion 13, an annular recess 14 extending in the circumferential direction of the side wall 10 is provided. Therefore, the diameter of the upper wall portion 13 is larger than that in the case where the upper wall portion 13 does not have a curved shape that is convex outward in the radial direction of the side wall 10. Therefore, the exhaust gas that has reached the inside of the upper wall portion 13 flows around the inner wall surface 13a of the upper wall portion 13 in the circumferential direction of the upper wall portion 13, and then passes through the lower wall portion 12 and flows through the exhaust passage. It will return to 4. That is, the exhaust gas flows in the upper wall portion 13 so as to avoid the radial central portion corresponding to the location where the fuel addition valve 7 is arranged. As a result, the exhaust gas that hits the fuel addition valve 7 is reduced when the fuel is not injected from the fuel addition valve 7. As a result, the temperature rise of the fuel addition valve 7 due to the high temperature exhaust gas is prevented. Further, since the exhaust gas circulates along the inner wall surface 13a of the upper wall portion 13 and flows, the exhaust gas is effectively cooled by the water jacket 9.

Further, when fuel is injected from the fuel addition valve 7 toward the exhaust passage 4, the exhaust gas that has entered the injection passage 11 flows along the inner wall surface 12a of the lower wall portion 12. Then, the fuel droplet P in the peripheral portion of the fuel spray F is effectively collected on the inner wall surface 12a of the lower wall portion 12 by the inertial force. As a result, the fuel droplet P that hits the fuel addition valve 7 is reduced.

Since the exhaust gas and the fuel droplet P that hit the fuel addition valve 7 are reduced in this way, it is possible to suppress the generation of a deposit on the fuel addition valve 7 and suppress the clogging of the injection port 7a of the fuel addition valve 7. ..

Further, in the present embodiment, the maximum diameter K2 of the upper wall portion 13 is equivalent to the maximum diameter K1 of the lower wall portion 12. Therefore, while suppressing the radial dimension of the upper wall portion 13 to reduce the size of the side wall 10, the inside of the upper wall portion 13 so that the exhaust gas avoids the radial central portion corresponding to the location where the fuel addition valve 7 is arranged. A space is secured that flows around the wall surface 13a.

Further, in the present embodiment, the bottom portion 14a of the recess 14 formed by the boundary portion between the inner wall surface 12a of the lower wall portion 12 and the inner wall surface 13a of the upper wall portion 13 has an R shape. Therefore, when a part of the exhaust gas flowing along the inner wall surface 12a of the lower wall portion 12 reaches the inside of the upper wall portion 13, the exhaust gas flows from the vicinity of the inner wall surface 12a of the lower wall portion 12 to the inner wall surface of the upper wall portion 13. It will flow smoothly to around 13a. Therefore, the exhaust gas that hits the fuel addition valve 7 is further reduced.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the maximum diameter K2 of the upper wall portion 13 is equivalent to the maximum diameter K1 of the lower wall portion 12, but the present embodiment is not particularly limited, and the maximum diameter K2 of the upper wall portion 13 is the lower wall portion 12. The maximum diameter K1 of the upper wall portion 13 may be larger than the maximum diameter K1 of the lower wall portion 12, or the maximum diameter K2 of the upper wall portion 13 may be smaller than the maximum diameter K1 of the lower wall portion 12.

In a structure in which the maximum diameter K2 of the upper wall portion 13 is larger than the maximum diameter K1 of the lower wall portion 12, the exhaust gas should avoid the radial central portion corresponding to the location of the fuel addition valve 7 in the upper wall portion 13. Exhaust gas is less likely to hit the fuel addition valve 7. In a structure in which the maximum diameter K2 of the upper wall portion 13 is smaller than the maximum diameter K1 of the lower wall portion 12, the side wall 10 can be arranged even if the space in the vicinity of the holding member 8 is narrow.

Further, although the exhaust gas purification device 1 of the above embodiment includes a DPF 6, the present invention can also be applied to an exhaust gas purification device provided with, for example, a diesel PM, a NOx simultaneous reduction catalyst (DPNR) or the like as a filter.

Further, the present invention is not particularly limited to a diesel engine, and is also applicable to an exhaust purification device that purifies exhaust gas emitted from a gasoline engine.

1 ... Exhaust purification device, 2 ... Diesel engine (internal combustion engine), 3 ... Exhaust pipe, 4 ... Exhaust passage, 7 ... Fuel addition valve, 10 ... Side wall, 11 ... Injection passage, 12 ... Lower wall part (first wall part) ), 12a ... Inner wall surface, 13 ... Upper wall portion (second wall portion), 13a ... Inner wall surface, 14 ... Recession, 14a ... Bottom, J1, J2 ... Shaft length, K1, K2 ... Maximum diameter.

Claims (3)

In an exhaust purification device that purifies the exhaust gas emitted from an internal combustion engine
An exhaust pipe that is connected to the internal combustion engine and forms an exhaust passage through which the exhaust gas flows.
A fuel addition valve that injects fuel toward the exhaust passage and
It is provided between the exhaust pipe and the fuel addition valve and has a cylindrical side wall that forms an injection passage through which fuel injected from the fuel addition valve passes.
The side wall has a first wall portion connected to the exhaust pipe, a second wall portion arranged on the fuel addition valve side of the first wall portion, and a second wall portion connected to the fuel addition valve. death,
The axial length of the first wall portion is larger than the axial length of the second wall portion.
The first wall portion and the second wall portion have a curved shape such that the cross section is cut in a direction parallel to the axial direction of the side wall and is convex outward in the radial direction of the side wall.
An exhaust gas purification device provided with an annular recess extending in the circumferential direction of the side wall at a boundary between the first wall portion and the second wall portion. The exhaust gas purification device according to claim 1, wherein the maximum diameter of the second wall portion is equivalent to the maximum diameter of the first wall portion. The boundary between the inner wall surface of the first wall portion and the inner wall surface of the second wall portion forms the bottom portion of the recess.
The exhaust gas purification device according to claim 1 or 2, wherein the bottom of the recess has an R shape.

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