JP2008138654A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device having excellent diffusion and mixture of a reducing agent into exhaust gas even when formed in an almost U-turn shape. <P>SOLUTION: The exhaust emission control device comprises an upstream exhaust gas flow path 10 of a straight pipe shape with a particulate filter 2 installed inside, a downstream exhaust gas flow path 20 of a straight pipe shape with a NOx reduction catalyst carrier 4 installed inside, and a mixer section 30 connecting the upstream exhaust gas flow path 10 and the downstream exhaust gas flow path 20 in the almost U-turn shape and having a supply means 34 of the reducing agent, wherein flow changing means 31b, 31c, 32b, 32c are provided in the mixer section 30 for crossing a flow of exhaust gas with a plane F including the upstream exhaust gas flow path 10 and the downstream exhaust gas flow path 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device mounted on an internal combustion engine such as a diesel engine, and relates to an exhaust gas purification device including a diesel particulate filter and a NOx reduction catalyst carrier that reduces nitrogen oxides.

  2. Description of the Related Art As an exhaust gas purifying device used in an internal combustion engine such as a diesel engine, a diesel particulate filter (hereinafter referred to as DPF) is provided in the middle of an exhaust pipe in order to collect particulates (particulate matter) contained in the exhaust gas. ) And those provided with a NOx reduction catalyst carrier in order to reduce the amount of nitrogen oxide (hereinafter referred to as NOx) contained in the exhaust gas.

  In recent years, exhaust gas purification devices equipped with both a DPF and a NOx reduction catalyst carrier have appeared along with the tightening of exhaust gas purification regulations. In Patent Document 1, a DPF is disposed upstream of exhaust gas, An exhaust gas purification device is proposed in which a NOx reduction catalyst carrier is arranged on the downstream side, both communicate with each other through a communication chamber, and the entire exhaust gas purification device is formed in a U shape to make it compact and improve the mountability in a vehicle. Yes. Further, in order to improve the NOx purification efficiency, a configuration in which a urea denitration catalyst is used as a NOx reduction catalyst and urea as a reducing agent is supplied into the exhaust gas, and a urea supply unit is connected to the exhaust gas outlet of the DPF in the communication chamber. A configuration in which a flow guide or a perforated plate is provided in the vicinity and provided with a flow guide or a perforated plate is described in Patent Document 1.

  Further, Patent Document 2 proposes an exhaust gas purification apparatus having a mixer provided with a plurality of dispersion plates that uniformly diffuse the reducing agent into the exhaust gas.

  In the exhaust gas purification device described in Patent Document 2, the exhaust pipe 100 and the mixer 101 are arranged in a straight line as shown in FIG. By doing so, the reducing agent is evenly diffused and mixed in the exhaust gas, and sufficient exhaust gas purification performance is obtained.

However, when the entire exhaust gas purification device is formed in a substantially U-turn shape as in the exhaust gas purification device described in Patent Document 1, as shown in FIG. U-turn part) drifts in the exhaust gas, so even if the two-dimensional exhaust gas meandering as in Patent Document 2 is applied, it is difficult for the reducing agent to be uniformly diffused and mixed in the exhaust gas. There is concern about the decline.
JP 2005-155404 A JP 2006-9608 A

  In view of the above problems, an object of the present invention is to provide an exhaust gas purification device that is excellent in the diffusibility and mixing properties of the reducing agent in the exhaust gas even when the exhaust gas purification device is formed in a substantially U-turn shape. To do.

  According to the first aspect of the present invention, a straight tubular upstream exhaust gas flow path in which the particulate filter is built, a straight tubular downstream exhaust gas flow path in which the NOx reduction catalyst carrier is built, and the upstream exhaust gas. A plane including the upstream exhaust gas flow path and the downstream exhaust gas flow path, including a mixer section that communicates the gas flow path and the downstream exhaust gas flow path in a substantially U-turn shape and has a reducing agent supply means. In contrast, there is provided an exhaust gas purifying device characterized in that a current changing means for crossing the flow of exhaust gas is provided in the mixer section.

  According to a second aspect of the present invention, in the first aspect of the invention, the current transformation means includes a pair of curved wall portions and curved opening portions that guide exhaust gas, and the curved wall portions and the curved opening portions are There is provided an exhaust gas purifying device provided so as to be shifted from each other in the vertical direction with respect to the plane.

  According to a third aspect of the present invention, there is provided an exhaust gas purifying apparatus according to the second aspect of the present invention, wherein the curved wall portion and the curved opening are integrally formed in a cylindrical shape.

  According to the invention of claim 4, in the invention of any one of claims 1 to 3, the supply means is provided so as to face the exhaust gas flowing out from the upstream side exhaust gas flow path. An exhaust gas purification device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas purification apparatus of the U-turn shape which is excellent in the diffusibility and mixing property of the reducing agent in exhaust gas can be provided.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a partial plan sectional view showing an exhaust gas purifying apparatus according to a first embodiment of the present invention, FIG. 2 is a perspective view of a mixer section according to the first embodiment of the present invention, and FIG. 1 is a cross-sectional view of the mixer section according to the embodiment, taken along line AA in FIG. 1. FIG. 4 is a cross-sectional view of the mixer section according to the second embodiment of the present invention taken along line AA in FIG. FIG. 6 is a cross-sectional view of the mixer section according to the embodiment, taken along line AA in FIG. 1, and FIG. 6 is a cross-sectional view of the mixer section according to the fourth embodiment of the present invention taken along line AA in FIG.

  1 to 3 show an exhaust gas purifying apparatus according to a first embodiment of the present invention. The exhaust gas purification apparatus 1 includes a straight tubular upstream exhaust gas passage 10 in which a DPF 2 is installed via a holding member 3 such as a wire mesh or an alumina mat, and a NOx reduction catalyst carrier 4 via the holding member 3. Both exhaust gases are connected via the connecting flange 5 so that the straight tubular downstream exhaust gas passage 20, the upstream exhaust gas passage 10, and the downstream exhaust gas passage 20 are connected in a substantially U-turn shape. And a mixer unit 30 connected to the flow path. The connection flanges 5 and 5 are fastened and detachable by, for example, bolts and nuts not shown. An exhaust system device such as an exhaust pipe, an exhaust manifold, a turbocharger, etc. (not shown) is connected to an upstream end (the right end in FIG. 1) of the upstream exhaust gas passage 10 via a connection flange 6. . Further, an exhaust system device such as an exhaust pipe and a silencer (not shown) is connected to the downstream end portion (right end in FIG. 1) of the downstream side exhaust gas passage 20 via a connection flange 7.

  The DPF 2 installed in the upstream side exhaust gas passage 10 is formed in a honeycomb structure using a porous material such as cordierite, and collects particulates contained in the exhaust gas. is there. The collected particulates are burned off by combustion of the exhaust gas itself or by heat of catalytic reaction of the oxidation catalyst carrier 8. Alternatively, a noble metal catalyst or an active oxygen release agent may be supported on the DPF, and the particulates may be removed by oxidation (see, for example, Japanese Patent No. 3593305).

  Further, on the upstream side of the DPF 2 in the upstream side exhaust gas passage 10 (the right side in FIG. 1), for example, an oxidation catalyst carrier 8 that oxidizes NO in the exhaust gas or reduces CO and HC is the holding member 3. Decorated through. The oxidation catalyst carrier 8 is not provided in the upstream exhaust gas flow path 10 but is provided in a cylindrical member (not shown) different from the upstream exhaust gas flow path 10 and is connected to the upstream exhaust gas via the connection flange 6. A structure (separate structure) connected to the flow path 10 may be used.

As the NOx reduction catalyst carrier 4 incorporated in the downstream side exhaust gas passage 20, for example, a selective reduction type catalyst carrier (commonly called SCR catalyst carrier) is used, and this catalyst is represented by the following chemical reaction formula: First, urea water as a reducing agent injected into the exhaust gas is hydrolyzed by the heat of the exhaust gas to generate ammonia, and then NOx is reduced by ammonia to purify the exhaust gas.
(NH ₂ ) 2 · CO + H ₂ O → CO ₂ + 2NH ₃
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O

  Then, on the downstream side (the right side in FIG. 1) of the NOx reduction catalyst 4 in the downstream side exhaust gas flow path 20, for example, an oxidation catalyst carrier 9 that oxidizes excess ammonia to render it harmless holds the holding member 3. It is decorated through. The oxidation catalyst carrier 9 is not provided in the downstream exhaust gas passage 20 but is provided in a cylindrical member (not shown) different from the downstream exhaust gas passage 20, and the downstream exhaust gas is connected via the connection flange 7. A structure connected to the flow path 20 may be used.

  The mixer portion 30 is connected to the exhaust gas inflow portion 31 connected to the upstream side exhaust gas passage 10 via one connection flange 5 and to the downstream side exhaust gas passage 20 via the other connection flange 5. The exhaust gas outflow portion 32 and a communication chamber 33 that allows the exhaust gas inflow portion 31 and the exhaust gas outflow portion 32 to communicate with each other.

  As shown in FIGS. 2 and 3, the exhaust gas inflow portion 31 is a bottomed cylindrical body, and includes a wall portion 31 a corresponding to the bottom portion and a curved wall portion 31 b corresponding to the cylinder portion. The curved wall 31b has a curved opening 31c corresponding to approximately ¼ circumference, that is, the curved wall 31b and the curved opening 31c, which are current transformation means, are integrally formed in a cylindrical shape. ing.

  The wall 31a is a surface perpendicular to the direction B of the exhaust gas flowing out from the upstream side exhaust gas flow path 10, and a reducing agent supply portion (hole) 31d is formed on this surface. A supply nozzle 34 serving as a reducing agent supply means is attached to the supply portion 31d so as to face B.

  The manufacturing method of the exhaust gas inflow portion 31 is, for example, bending a metal plate that is previously cut out of an opening corresponding to the curved opening portion 31c into a cylindrical shape, and then welding the peripheral edges of the metal plate together to form the curved wall portion 31b. And a cylindrical body integrally formed with the curved opening 31c. Next, the cylindrical body is manufactured by welding a wall 31a made of a metallic disk. Alternatively, the metal plate may be formed by integrally forming the wall portion 31a and the curved wall portion 31b by pressing or spinning, and then cutting the curved opening portion 31c. By integrally molding, the number of parts can be reduced, and the manufacturing cost can be reduced.

  Exhaust gas outflow portion 32 has substantially the same configuration as the exhaust gas inflow portion 31 except that it does not have a supply portion and a supply nozzle, and includes a wall portion 32a and a curved wall portion 32b. A curved opening portion 32c corresponding to approximately ¼ circumference is formed on the wall surface of the wall portion 32b. That is, the curved wall portion 32b and the curved opening portion 32c serving as a current changing means are integrally formed in a cylindrical shape.

  As shown in FIG. 1, the relationship between the total length L1 and diameter D1 of the exhaust gas inflow portion 31 and the total length L2 and diameter D2 of the exhaust gas outflow portion 32 is set to L1 <L2, D1 = D2. However, it may be arbitrarily set according to the exhaust gas purification performance, the vehicle mountability, the productivity of the mixer section, and the like. L1> L2, D1 = D2 may be set. For example, when L1 = L2, D1 = D2, the curved wall portion 31b and the curved wall portion 32b can be made a common component (strictly speaking, The curved openings 31c and the curved openings 32c have the same shape), and the productivity of the mixer section can be improved.

  The exhaust gas inflow portion 31 and the exhaust gas outflow portion 32 are arranged substantially in parallel, and the cylindrical communication chamber 33 whose end is formed in a substantially semicircular shape is connected to the exhaust gas inflow portion 31 and the exhaust gas outflow portion 32. The mixer part 30 is comprised by interposing and fixing between.

  Specifically, as shown in FIG. 3, the pair of curved walls 31 b and 32 b are on a virtual plane F including the central axis 10 a of the upstream exhaust gas passage 10 and the central axis 20 a of the downstream exhaust gas passage 20. In contrast, the pair of curved openings 31c and 32c are provided on a virtual plane F including the central axis 10a of the upstream side exhaust gas passage 10 and the central axis 20a of the downstream side exhaust gas passage 20 while being provided so as to be offset from each other in the vertical direction. On the other hand, they are offset from each other in the vertical direction. Then, one end portion 33a of the communication chamber 33 covers approximately 1/4 circumference of the curved wall portion 31b and the curved opening portion 31c, and the other end portion 33b corresponds to approximately 1/4 circumference of the curved wall portion 32b and the curved opening. The mixer section 30 is configured by covering the section 32c.

  As shown by an arrow B in FIG. 1, the exhaust gas flowing in the exhaust gas purification device 1 of the present embodiment first flows in the upstream exhaust gas passage 10 in which the oxidation catalyst carrier 8 and the DPF 2 are housed. NO oxidation and CO and HC in the exhaust gas are reduced, and particulates are removed. Next, as shown by an arrow C, the exhaust gas flows in the mixer unit 30. At this time, the reducing agent supplied from the supply nozzle 34 is diffused and mixed in the exhaust gas. Details of this will be described later. Next, as shown by an arrow D in FIG. 1, the exhaust gas mixed with the reducing agent is in the downstream exhaust gas flow path 20 in which the NOx reduction catalyst (selective reduction type catalyst carrier) 4 and the oxidation catalyst carrier 8 are housed. Into the exhaust gas, NOx in the exhaust gas is reduced and excess ammonia is purified.

  Next, the flow of exhaust gas passing through the mixer section 30 and the diffusion and mixing of the reducing agent will be described. As shown in FIG. 2, when the exhaust gas discharged from the upstream side exhaust gas flow path 10 flows into the exhaust gas inflow portion 31 (arrow B), the supply portion in which urea water as a reducing agent is formed on the wall portion 31a ( Hole) 31d and injected into the exhaust gas inflow portion 31 (arrow E). At this time, since the exhaust gas inflow direction (arrow B) and the urea water injection direction (arrow E) are substantially opposed to each other, they both collide front-to-face, and the exhaust gas and urea water are diffused well. Then, the diffused exhaust gas collides with the wall portion 31a, and the exhaust gas and urea water are further diffused and mixed. Next, the diffused exhaust gas is smoothly guided to the curved opening 31c along the curved wall 31b, and flows into the communication chamber 33 through the curved opening 31c. At this time, since the flow rate of the exhaust gas is increased, the diffusibility is good. Next, the exhaust gas diffused in the communication chamber 33 flows into the exhaust gas outlet 32 through the curved opening 32c (arrow C). As shown in FIGS. 1 and 3, the exhaust gas (arrow C) intersects a virtual plane F including the central axis 10 a of the upstream exhaust gas passage 10 and the central axis 20 a of the downstream exhaust gas passage 20. That is, the exhaust gas (arrow B) that has flowed two-dimensionally along the virtual plane F is forcibly changed to a three-dimensional flow (arrow C) that intersects the virtual plane F. The reductant is sufficiently diffused and mixed in the exhaust gas even with respect to the drift of the exhaust gas that occurs because the direction changes greatly and the entire exhaust gas purification device has a U-turn shape. Then, the exhaust gas flowing into the exhaust gas outflow portion 32 collides with the curved wall portion 32b and diffuses along the curved wall portion 32b. As described above, the exhaust gas repeatedly collides and diffuses, whereby the reducing agent is uniformly mixed in the exhaust gas, and the purification performance of the selective catalytic reduction catalyst carrier can be sufficiently exhibited.

  In this embodiment, the wall and the opening are curved. However, the wall and the opening may be straight, or may be a combined shape of the curve and the straight, but if it is straight, the exhaust resistance increases. Therefore, it should be set appropriately with this in mind.

  According to this embodiment, since the mixer part is comprised by a pair of curved wall part and a pair of curved opening part, it is excellent in productivity and compactness of a mixer part. Further, the exhaust gas meanders from one curved opening to the other curved opening and flows smoothly along the curved wall, and the exhaust gas meanders excels in diffusibility and mixing of the reducing agent, and exhaust gas Pressure loss can be reduced by the smooth flow of gas.

  FIG. 4 shows an exhaust gas purifying apparatus according to a second embodiment of the present invention, and is a cross-sectional view taken along line AA in FIG. In this embodiment, the opening area of the curved opening portion is made smaller than that of the mixer portion described in the first embodiment.

  The mixer unit 40 includes an exhaust gas inflow portion 41, an exhaust gas outflow portion 42, and a communication chamber 43 that allows the exhaust gas inflow portion 41 and the exhaust gas outflow portion 42 to communicate with each other.

  The exhaust gas inflow portion 41 is a bottomed cylindrical body, and includes a wall portion 41a corresponding to the bottom portion and a curved wall portion 41b corresponding to the cylindrical portion, and the wall surface of the curved wall portion 41b has a quarter circumference. A curved opening 41c smaller than the minute is formed. The exhaust gas outflow portion 42 has the same configuration as the exhaust gas inflow portion 41, and includes a wall portion 42a corresponding to the bottom portion and a curved wall portion 42b corresponding to the cylindrical portion, and is provided on the wall surface of the curved wall portion 42b. Is formed with a curved opening 42c smaller than a quarter circumference. Therefore, the curved wall portion 41 b and the curved wall portion 42 b have an overlap portion 44.

  The overlap portion 44 has a large influence on the diffusibility of the reducing agent and the pressure loss of the exhaust gas. The longer the overlap portion 44, the longer the meandering path of the exhaust gas and the larger the area of the curved wall portion (exhaust gas). The frequency of collision with the curved wall increases, and the diffusibility and mixing properties of the reducing agent are improved. However, on the other hand, the pressure loss of the exhaust gas tends to increase. Therefore, the length of the overlap portion 44 is set in consideration of the diffusibility of the reducing agent and the pressure loss of the exhaust gas.

  FIG. 5 shows an exhaust gas purifying apparatus according to a third embodiment of the present invention, and is a cross-sectional view taken along line AA in FIG. In this embodiment, a guide member is provided in the communication chamber described in the first embodiment.

  Like the mixer unit 30 of the first embodiment, the mixer unit 50 includes an exhaust gas inflow portion 31, an exhaust gas outflow portion 32, and a communication chamber 33. In this embodiment, the curved opening portion 31c and the curved portion are provided. A curved guide member 51 and a convex rectifying member 54 that are connected from the vicinity of the opening 32c to the inner wall of the communication chamber 33 are further provided. Therefore, the diffused exhaust gas flows smoothly while being guided by the guide member 51 from the curved opening 31c to the curved opening 32c, and the pressure loss of the exhaust gas can be reduced. However, the exhaust gas guided by the guide member 51 changes into a spiral flow that flows along the wall surface of the curved wall portion 32b in the exhaust gas outflow portion 32, and this spiral flow flows into the downstream exhaust passage 20 that follows. Therefore, the flow rate of the exhaust gas flowing through the central portion of the NOx reduction catalyst carrier 4 is smaller than the flow rate of the exhaust gas flowing through the centrifugal portion of the NOx reduction catalyst carrier 4, and the exhaust gas purification performance may not be sufficiently exhibited. Therefore, the upstream side of the NOx reduction catalyst carrier 4, for example, as shown in FIG. 1, a donut-shaped rectifying plate 53 is provided in the exhaust gas outflow portion 20 so that the exhaust gas is directed to the center of the NOx reduction catalyst 4. Also good. Alternatively, although not shown, at least a part of the exhaust gas outflow part 32 may be reduced in diameter to replace the rectifying plate 53.

  By providing the guide member 51, a dead space 52 in which exhaust gas does not enter into the mixer portion 50 is formed. However, even if the guide member 51 does not exist, the dead space 52 originally has exhaust gas. Since it is not a site that actively enters, there is little effect on the diffusibility of the reducing agent.

  FIG. 6 shows an exhaust gas purifying apparatus according to a fourth embodiment of the present invention, and is a cross-sectional view taken along line AA in FIG. In this embodiment, the exhaust gas inflow portion and the exhaust gas outflow portion described in the first embodiment are partially cross-sectioned.

  The mixer section 60 includes an exhaust gas inflow section 61 and an exhaust gas outflow section 62 whose outer shapes are partially formed in a square cross section, and other configurations are the same as those of the first embodiment. By setting the partial cross section, the volume of the mixer portion can be increased as compared with the case of the circular cross section of Example 1, and the diffusibility and mixing properties of the reducing agent are improved. The outer shape is not limited to that shown in FIG. 6 and may be other polygons.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Even if there is a change of the range which does not deviate from the meaning of this invention, it is included in this invention. For example, the curved wall and the curved opening may be formed separately. In addition, the pair of curved walls and the pair of curved openings may have different shapes as long as they are curved. In the above embodiment, the curved opening is a curved quadrangle, but it may be a curved ellipse or an ellipse. Further, the reducing agent supply section may be provided at any position of the exhaust gas inflow section as long as the reducing agent is diffused and mixed stably.

FIG. 1 is a partial plan sectional view showing an exhaust gas purifying apparatus according to a first embodiment of the present invention. The perspective view of the mixer part which concerns on 1st Example of this invention. 1 is a cross-sectional view of the mixer section according to the first embodiment of the present invention taken along line AA in FIG. Sectional view taken along line AA in FIG. 1 of the mixer section according to the second embodiment of the present invention. Sectional view along line AA in FIG. 1 of the mixer section according to the third embodiment of the present invention. Sectional view taken along line AA in FIG. 1 of the mixer section according to the fourth embodiment of the present invention. Conceptual diagram showing the flow of exhaust gas in a conventional exhaust gas purification device Conceptual diagram showing the flow of exhaust gas in another conventional exhaust gas purification device

Explanation of symbols

1 Exhaust gas purification device 2 DPF
4 NOx reduction catalyst carrier 8, 9 Oxidation catalyst carrier 10 Upstream exhaust gas passage 20 Downstream exhaust gas passage 30, 40, 50, 60 Mixer portion 31, 41, 61 Exhaust gas inflow portion 32, 42, 62 Exhaust gas Outflow part 31a, 32a, 41a, 42a Wall part 31b, 32b, 41b, 42b Curved wall part (current transformation means)
31c, 32c, 41c, 42c Curved opening (current transformation means)
31d, 41d supply section (supply means)
33, 43 Communication chamber 34 Supply nozzle (supply means)

Claims (4)

  A straight tubular upstream exhaust gas passage in which a particulate filter is internally provided, a straight tubular downstream exhaust gas passage in which a NOx reduction catalyst carrier is internally provided, the upstream exhaust gas passage and the downstream exhaust gas And a mixer section having a reducing agent supply means that communicates the flow path in a substantially U-turn shape, and the flow of the exhaust gas intersects a plane including the upstream exhaust gas flow path and the downstream exhaust gas flow path. An exhaust gas purification apparatus characterized in that a current transformation means is provided in the mixer section.   The current transformation means includes a pair of curved wall portions and curved opening portions for guiding exhaust gas, and the curved wall portions and the curved opening portions are provided so as to be shifted from each other in the vertical direction with respect to the plane. The exhaust gas purification device according to claim 1, wherein   The exhaust gas purifying apparatus according to claim 2, wherein the curved wall portion and the curved opening portion are integrally formed in a cylindrical shape.   The exhaust gas purification apparatus according to any one of claims 1 to 3, wherein the supply means is provided so as to face the exhaust gas flowing out from the upstream side exhaust gas flow path.

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