Exhaust emission control device

Abstract

To provide an exhaust emission control device in which a deflector plate is arranged upstream of a position where urea water is sprayed within an exhaust passage, allowing the position and orientation of the deflector plate to be easily set three-dimensionally and enabling easy fixation within the passage.SOLUTION: An exhaust emission control device comprises: a body part forming an exhaust passage and having an upstream bent part and a downstream bent part that are bent in substantially opposite directions; a reducing-agent addition device provided on the downstream bent part; and an SCR catalyst disposed downstream of the body part. The reducing-agent addition device is mounted on an outer surface of a seat provided on the downstream bent part so that a reducing agent is sprayed within the body part through an opening in the seat, and the exhaust emission control device further comprises a deflector mounted on an inner surface of the seat. The deflector is composed of a base fixed to the seat, a support arm extending from the base, and a deflector plate formed at a tip of the support arm, the deflector plate being arranged between the upstream bent part and the reducing-agent addition device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification device to be installed in an exhaust pipe of an internal combustion engine. [Background technology]

[0002] Exhaust gas emitted from internal combustion engines such as diesel engines contains nitrogen oxides (NOx), an air pollutant. Exhaust gas purification devices equipped with a selective catalytic reduction (SCR) catalyst are well-known as devices for purifying such exhaust gas. To enhance the purification performance of the SCR catalyst, this type of exhaust purification device often includes a reducing agent addition device upstream of the SCR catalyst that sprays and mixes urea water as a reducing agent into the exhaust gas flowing through the exhaust passage. The urea water sprayed into the exhaust gas is hydrolyzed by the heat of the exhaust gas, and the ammonia (NH3) produced by the hydrolysis is supplied to the SCR catalyst along with the exhaust gas. The nitrogen oxides in the exhaust gas react with the ammonia in the SCR catalyst and are reduced and purified.

[0003] In some cases, this type of reducing agent mixing device curves the exhaust flow path into a substantially S-shape, includes a reducing agent addition device at the downstream curved portion, and sprays urea water in a direction substantially coaxial with the downstream side of the downstream curved portion. However, in such a configuration, the flow velocity of the exhaust gas in the exhaust flow path tends to be uneven, and therefore the distribution of urea water in the exhaust gas after it merges with the exhaust gas also tends to be uneven.

[0004] As a result, the distribution of the urea water flowing into the SCR catalyst is likely to become uneven, raising concerns that the purification performance of the SCR catalyst may not be fully demonstrated.To address this issue, a reducing agent mixing device has been proposed that promotes uniformity in the flow rate of the exhaust gas and the distribution of the urea water by placing a deflector plate in the exhaust flow path upstream of where the urea water is sprayed, which forcibly changes the flow of the exhaust gas (Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6424869 [Patent Document 2] U.S. Patent No. 10,967,334 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the configurations described in Patent Documents 1 and 2, the deflector plate, which is a separate component from the exhaust pipe, must be fixed and supported at a specific position on the inner surface of the exhaust passage, which has a closed cross-section and a curved surface, while maintaining a specific posture. This raises concerns that the fixing work, such as welding, would be extremely complex and difficult. In particular, bridging the inner surface of the exhaust passage to both opposing sides of the closed cross-section, as in Patent Document 1, is extremely difficult, and measures must be taken to address the thermal expansion difference between the inner surface and the deflector plate. Furthermore, due to the constraints of such support surfaces, it is difficult to freely set the relative angle of the deflector plate to the exhaust gas flow in three dimensions.

[0007] In view of the above-mentioned problems, an object of the present invention is to provide an exhaust gas purification device that, when arranging a deflector in an exhaust flow path upstream of where urea water is sprayed, can easily set the position and orientation of the deflector in three dimensions and can easily be fixed in the flow path. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides an exhaust purification device that includes a main body that forms an exhaust flow path and has an upstream bent portion and a downstream bent portion that bend in approximately opposite directions, a reducing agent addition device provided at the downstream bent portion, and an SCR catalyst that is arranged downstream of the main body, wherein the reducing agent addition device is attached to the outer surface of a seat provided at the downstream bent portion so that reducing agent is sprayed into the main body through an opening in the seat, and the device further includes a deflection device attached to the inner surface of the seat, the deflection device comprising a base fixed to the seat, a support arm extending from the base, and a deflection plate formed at the tip of the support arm, and the deflection plate is arranged between the upstream bent portion and the reducing agent addition device. [Effects of the Invention]

[0009] According to the present invention, the position and orientation of the deflector plate disposed in the exhaust flow passage upstream of the point where the urea water is sprayed can be easily set three-dimensionally, and the deflector plate can be easily fixed in the flow passage. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a side view of an exhaust gas purification device according to a first embodiment of the present invention. [Figure 2] 1 is a front view of a deflection device of an exhaust purification device according to a first embodiment of the present invention. [Figure 3] 2 is a schematic diagram showing the relationship between the deflection device of the present invention and the exhaust gas flow. FIG. [Figure 4] FIG. 6 is a rear view of a deflection device of an exhaust purification device according to a second embodiment of the present invention. [Figure 5] 10A and 10B are a rear view and a side view of a deflection device of an exhaust purification device according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a rear view of the deflection device of the exhaust purification device according to the fourth embodiment of the present invention. [Figure 7] FIG. 10 is a rear view of the deflection device of the exhaust purification device according to the fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A preferred embodiment of the present invention will be described below with reference to Figures 1 to 3. In this embodiment, taking into consideration the mounting position of the exhaust purification device on a vehicle, the left side of Figure 1 is the vehicle travel direction and the exhaust upstream side, and the upper side of Figures 1 to 3 is the upper side of the vehicle. Exhaust gas flows downward from left to right in Figure 1.

[0012] (First embodiment) FIG. 1 is a side view showing an exhaust gas purification device 1 according to a first embodiment of the present invention. The exhaust gas purification device 1 comprises an upstream main body 2, a tapered portion 18 connected to its downstream end 7, an outer casing 3 connected to the rear end of the tapered portion 18 and housing an SCR catalyst 17, and a reducing agent addition device 9 attached to the outer surface of a seating surface 8 of the main body 2. The main body 2 is also provided with a deflection device 11 (described later) on its inner surface. The upstream end 6 of the main body 2 is connected to an upstream exhaust pipe (not shown), and the rear end of the outer casing 3 is connected to a downstream exhaust pipe (not shown). For ease of explanation, the main body 2, tapered portion 18, and outer casing 3 are shown in cross section. The main body 2 includes an upstream bent portion 4 and a downstream bent portion 5 that bends in a direction substantially opposite to the upstream bent portion 4, forming a substantially S-shaped exhaust flow path overall. The exhaust flow path of the main body 2 extends from the upstream end 6 in FIG. 1 from the upper left to the lower right to the upstream bent portion 4, where it bends slightly downward before reaching the downstream bent portion 5. The downstream bent portion 5 is bent largely to the right in FIG. 1 at an angle close to a right angle, and the exhaust flow path extends from the downstream bent portion 5 to a downstream end portion 7 further to the right.

[0013] A seat 8 is provided on the main body 2 just before the outer wall surface of the downstream bent portion 5 bends, downstream of the upstream bent portion 4. The seat 8 of the main body 2 is a flat surface with a fixed area, and an opening 16 is drilled in its center. In this embodiment, the seat 8 is substantially circular, but any flat shape is acceptable. A reducing agent addition device 9 is attached to the outer surface of the seat 8 by a screw thread, and its tip faces the opening 16. A reducing agent spray 10 is added and diffused from the opening 16 into the main body 2. The seat 8 is configured so that the spray 10 is directed toward the center of the upstream end face of the downstream SCR catalyst 17. Because the outer wall surface of the downstream bent portion 5 bends at an angle close to a right angle, the seat 8 is a surface that is substantially perpendicular to the direction A shown in FIG. 1 .

[0014] A base 14 of the deflection device 11 is fixed to the inner surface of the seat surface 8 by welding. FIG. 2(a) is a view from direction A in FIG. 1, showing the base 14 as viewed perpendicularly. The base 14 of the deflection device 11 is ring-shaped and has a base opening 15 in the center. The center of the base opening 15 and opening 16 are set coaxially. For reference in understanding the shape of the deflection device 11, FIG. 2(b) is a rear view of FIG. 2(a), and FIG. 2(c) is a side view of FIG. 2(b). Note that the tip shape of the reducing agent addition device 9, which would normally be visible within opening 16, has been omitted from the illustration for simplification.

[0015] A support arm 13 formed integrally with the base 14 extends in the direction of the upstream bent portion 4. A deflector plate 12 that forcibly changes the flow of exhaust gas is formed integrally with the other end of the support arm 13. The deflector plate 12 is bent from the support arm 13 toward the front side of the paper in FIG. 2 and extends from the wall side of the exhaust flow path of the main body 2 toward the center. In this embodiment, the deflector plate 12 is a flat surface with a certain area, but it may also be a curved surface, or the deflector plate 12 may be connected to the support arm 13 as a separate body.

[0016] By adjusting the shape and extension direction of the support arm 13 using this deflection device 11, it is possible to freely set the relative angle and position of the base 14 and the deflection plate 12. In other words, it is possible to arbitrarily set the shape, position, and angle of the deflection plate 12 to correct the flow of exhaust gas in the exhaust flow path inside the main body 2. In addition, since it is easy to join the flat surfaces of the base 14 and the seat surface 8, it is also easy to attach the deflection device 11 to the main body 2.

[0017] FIG. 3 is a schematic diagram showing an example of forced deflection of exhaust gas by such a deflection device 11. In FIG. The exhaust gas that passes through the upstream bend 4 in the upstream direction (top of the figure) becomes a biased flow in the cross section of the flow path, but by arranging a deflector plate 12 at an optimal position and angle, the exhaust flow from upstream is divided into exhaust branch flows α and β, and by causing α and β to collide downstream of the reducing agent addition device 9, it is possible to control the flow to be uniformly distributed in the cross section of the exhaust flow path downstream of the deflector device 11, and also to promote the diffusion of the spray 10 and the thermal decomposition reaction.

[0018] (Second embodiment) 4 is a rear view showing a deflection device 21 according to a second embodiment of the present invention. The deflection device 21 is the deflection device 11 of the first embodiment, with openings 23 formed in the deflection plate 12. The deflection plate 22 having the openings 23 allows a portion of the exhaust gas to pass through the openings 23, improving the degree of freedom in controlling the flow of the exhaust gas.

[0019] (Third embodiment) 5 is a rear view and a side view showing a deflection device 31 according to a third embodiment of the present invention. While the support arm 13 and the base 14 of the deflection device 11 of the first embodiment are integrally molded, in this embodiment the support arm 32 and the base part 33 are separated and fixed to each other by overlapping at a connecting part 34. Such a separated structure makes it easy to form the support arm 13 three-dimensionally.

[0020] (Fourth embodiment) 6 is a rear view showing a deflection device 41 according to a fourth embodiment of the present invention. The deflection plate 12 of the deflection device 11 of the first embodiment has a reduced area to form a deflection plate 42. Tuning the area of ​​the deflection plate 42 improves the degree of freedom in controlling the flow of exhaust gas.

[0021] (Fifth embodiment) 7 is a rear view showing a deflection device 51 according to a fifth embodiment of the present invention. The ring-shaped pedestal 14 of the deflection device 11 of the first embodiment has been reduced in area to form a pedestal 52. As such, the pedestal does not necessarily have to be ring-shaped, and the shape can be set appropriately depending on manufacturing requirements and mounting requirements.

[0022] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and even if there are modifications in the scope that deviate from the spirit of the present invention, they are still included in the present invention. [Explanation of symbols]

[0023] 1 Exhaust gas purification device 2 Main body 3 Outer cylinder 4. Upstream bend 5 Downstream bend 6 Upstream end 7 Downstream end 8 Seat 9. Reducing agent addition device 10 spray 11, 21, 31, 41, 51 deflection device 12, 22, 42 deflection plate 13, 32 Support arm 14, 52 pedestal 15 Pedestal opening 16 Seat opening 17 SCR catalyst 18 Tapered section 23 Open hole 33 Base 34 Connection α, β Exhaust branch

Claims

[Claim 1] An exhaust gas purification device including: a main body portion that forms an exhaust flow path and has an upstream bent portion and a downstream bent portion that bend in approximately opposite directions; a reducing agent addition device provided at the downstream bent portion; and an SCR catalyst that is arranged downstream of the main body portion, the reducing agent addition device is attached to an outer surface of a seat provided in the downstream bent portion, and the reducing agent is sprayed into the main body through an opening in the seat; a deflection device attached to an inner surface of the seating surface; the deflection device comprises a base fixed to the seat surface, a support arm extending from the base, and a deflection plate formed at the tip of the support arm, The deflector is disposed between the upstream bent portion and the reducing agent addition device.

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