JP2013002334A - Exhaust gas after-treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas after-treatment device whose size reduction is achieved while uniformly dispersing a reducing agent into exhaust gas.SOLUTION: An upstream side of an SCR catalyst 4 in an exhaust gas pipe 2 is provided with a dispersion member 21 for dispersing urea water injected from an injection nozzle 5 in the exhaust gas pipe 2, and a mixer 31 for mixing the dispersed urea water into the exhaust gas are. The dispersion member 21, as a flat plate-shaped member arranged in a position facing the injection nozzle 5, is provided extending parallel to the flow direction of the exhaust gas. Meanwhile, the mixer 31, as a substantially disk-shaped member through which exhaust gas and urea water can flow, is provided perpendicular to the flow direction of the exhaust gas. The dispersion member 21 and the mixer 31 are adjacently provided, and urea water impinging on and dispersed by the dispersion member 21 is immediately supplied to the mixer 31.

Description

  The present invention relates to an exhaust gas aftertreatment device, and more particularly to a configuration for purifying exhaust gas of a diesel engine using a reducing agent.

An example of an exhaust gas aftertreatment device that purifies exhaust gas of a diesel engine is a urea selective reduction system (urea SCR system) that purifies nitrogen oxide (NOx) in exhaust gas using urea water as a reducing agent. For example, as described in Patent Document 1, the urea SCR system includes a reduction catalyst provided in an exhaust pipe, and a reducing agent injection device that injects urea water into the exhaust pipe upstream of the reduction catalyst. . The reduction catalyst reacts ammonia (NH ₃ ) generated from urea water injected into the exhaust pipe with NOx contained in the exhaust gas, and reduces it to harmless nitrogen (N ₂ ) and water (H ₂ O). In order to perform this reduction efficiently, it is necessary to supply urea water with a uniform distribution to the reduction catalyst.

  The urea SCR system described in Patent Document 1 includes a mixer unit for mixing exhaust gas and urea water to make the distribution state of urea water uniform. The mixer unit is a plate-like member provided between the reducing agent injection device and the reduction catalyst, and includes a plurality of passages through which exhaust gas and urea water flow, and fin portions formed on the outlet side of each passage And have. The reducing agent injection device is configured to inject urea water toward the mixer plate, and the urea water atomized by colliding with the mixer plate is dispersed in the exhaust pipe. The dispersed urea water passes through each passage of the mixer plate together with the exhaust gas, and then is mixed with the exhaust gas by the turbulent flow generated by each fin portion and then supplied to the reduction catalyst.

JP 2009-24654 A

  However, in order to uniformly disperse the urea water with the mixer plate described in Patent Document 1, it is necessary to cause the urea water injected from the reducing agent injection device to collide with the entire surface of the mixer unit. In addition, since the reducing agent injection device normally injects urea water in a conical shape, in order to make urea water collide with the entire surface of the mixer unit, the reducing agent injection device and the reducing agent injection device are sufficiently widened. It is necessary to keep a distance from the mixer unit. That is, the urea SCR system described in Patent Document 1 has a problem that the exhaust pipe on the upstream side of the mixer unit cannot be shortened and it is difficult to downsize the entire apparatus.

  The present invention has been made to solve such problems, and provides an exhaust gas after-treatment device that achieves downsizing while uniformly dispersing the reducing agent in the exhaust gas. Objective.

  An exhaust gas aftertreatment device according to the present invention includes an exhaust pipe through which exhaust gas discharged from an internal combustion engine flows, a reducing agent supply device that injects a reducing agent into the exhaust pipe, and a downstream side of the reducing agent supply device. In an exhaust gas aftertreatment device that is disposed and includes a reduction catalyst that purifies exhaust gas by reacting exhaust gas with a reducing agent, the exhaust gas is disposed in a portion facing the reducing agent supply means inside the exhaust pipe. A plate-like dispersion member and a mixing means that is disposed between the dispersion member and the reduction catalyst and that mixes the exhaust gas and the reducing agent are provided, and the dispersion member and the mixing means are arranged adjacent to each other. It is characterized by.

  Since the plate-like dispersion member is provided at a portion facing the reducing agent supply device, the reducing agent injected from the reducing agent supply device directly collides with the dispersion member. The reducing agent that collides with the dispersion member and atomized is dispersed in the exhaust pipe, mixed with the exhaust gas by the mixing means, and then supplied to the reduction catalyst. Since the reducing agent is configured to be dispersed by the dispersion member, the distance between the reducing agent supply device and the mixing unit is used to widen the injection range of the reducing agent, as in the case of injecting the reducing agent toward the mixing unit. There is no need to take large. Further, since the dispersing member and the mixing means are disposed adjacent to each other, it is not necessary to lengthen the exhaust pipe in order to provide the dispersing member. Here, the term “adjacent” means that not only the dispersion member and the mixing means are integrally formed, but also separate parts that are substantially separated within a range where the exhaust gas flow does not change between the dispersion member and the mixing means. Including, for example, those separated by a distance of 10% or less with respect to the diameter of the exhaust pipe. As described above, the exhaust gas aftertreatment device can be miniaturized while the reducing agent is uniformly dispersed in the exhaust gas.

The reducing agent supply device may inject the reducing agent in a direction perpendicular to a direction in which the exhaust gas flows through the exhaust pipe. Until the injected reducing agent collides with the dispersion member, it is less affected by the flow of the exhaust gas, so that the reducing agent can be reliably collided with the dispersion member and efficiently dispersed. Here, the term “vertical” does not have to be strictly vertical as long as it is less susceptible to changes in the flow of exhaust gas. As the angle deviates from the vertical, the vertical component of the penetrating force of the injected reducing agent tends to be weak, so that the vertical component is less likely to be affected by the flow of exhaust gas. It may be in the range of degrees.
Further, the dispersion member may extend parallel to the direction in which the exhaust gas flows through the exhaust pipe. It is possible to supply the reducing agent to the mixing means without increasing the pressure loss. Here, the term “parallel” does not need to be strictly parallel, and includes an angle at which pressure loss is negligible.
Note that the dispersion member may be a single member.

  The dispersion member may have a width capable of contacting the inner peripheral surface of the exhaust pipe. The dispersion member divides the inside of the exhaust pipe into a reducing agent supply device side and an opposite side of the reducing agent supply device. Since the reducing agent is not supplied to the opposite side of the reducing agent supply device, the reducing agent attached to the inner peripheral surface of the exhaust pipe does not remain. On the other hand, the reducing agent dispersed on the reducing agent supply device side immediately flows into the adjacent mixing means and is supplied to the reduction catalyst. That is, since the amount of the reducing agent remaining in the exhaust pipe is reduced, the utilization efficiency of the reducing agent can be improved.

  According to the present invention, the exhaust gas aftertreatment device can be miniaturized while the reducing agent is uniformly dispersed in the exhaust gas.

It is the schematic which shows the structure of the exhaust-gas aftertreatment apparatus which concerns on Embodiment 1 of this invention. 1 is a cross-sectional side view schematically showing a configuration of an exhaust gas aftertreatment device according to Embodiment 1. FIG. FIG. 2 is a perspective view schematically showing a dispersion member and mixing means in the exhaust gas aftertreatment device according to Embodiment 1, wherein (a) is a perspective view seen from the downstream side in the exhaust gas flow direction, and (b) is an upstream side. It is the perspective view seen from the side. FIG. 4 is a cross-sectional view taken along IV-IV in FIG. 2. It is a cross-sectional side view which shows roughly the structure of the exhaust-gas aftertreatment apparatus which concerns on Embodiment 2 of this invention. FIG. 6 is a cross-sectional view showing a modification of the exhaust gas aftertreatment device according to Embodiment 1. FIG. 6 is a cross-sectional view showing a modification of the exhaust gas aftertreatment device according to Embodiment 1.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 schematically shows the configuration of an exhaust system of a diesel engine provided with the exhaust gas aftertreatment device according to the first embodiment. An exhaust pipe 2 is connected to the diesel engine 1 which is an internal combustion engine, and the exhaust gas discharged from the diesel engine 1 into the exhaust pipe 2 is in the direction indicated by the arrow A with the diesel engine 1 side as the upstream side. Circulate. An oxidation catalyst 3 that oxidizes carbon monoxide (CO), hydrocarbon (HC), and the like contained in the exhaust gas is provided in the middle of the exhaust pipe 2. An SCR catalyst 4 that is a reduction catalyst for purifying nitrogen oxide (NOx) contained in the exhaust gas is provided on the downstream side of the oxidation catalyst 3.

The SCR catalyst 4 is a catalyst that purifies NOx by reacting ammonia (NH ₃ ) generated from urea water, which is a reducing agent added to the exhaust gas, and the exhaust gas. The oxidation catalyst 3 and the SCR catalyst 4 Are provided with an injection nozzle 5 as a reducing agent supply device for injecting urea water into the exhaust pipe 2. A urea water tank 6 that stores urea water therein and a urea water addition system 7 that supplies urea water in the urea water tank 6 to the injection nozzle 5 are connected to the injection nozzle 5 via a connection pipe 8. ing. The urea water addition system 7 is electrically connected to an ECU 9 that controls the operation of the diesel engine 1 and the exhaust gas aftertreatment device.

  Further, a NOx sensor 11 and a NOx sensor 12 for detecting the amount of NOx contained in the exhaust gas are provided on the upstream side and the downstream side of the SCR catalyst 4, and these NOx sensors are electrically connected to the ECU 9. ing. The ECU 9 determines the injection amount and the injection timing of the urea water from the injection nozzle 5 based on the NOx amount detected by the NOx sensors 11 and 12, and outputs a signal based on the injection amount to the urea water addition system 7 to thereby inject the injection nozzle. 5 controls the injection of urea water.

  A filter 13 that collects particulate matter (PM) contained in the exhaust gas is provided on the downstream side of the SCR catalyst 4. In addition, on the downstream side of the filter 13, for example, when the amount of ammonia is excessive with respect to the amount of NOx contained in the exhaust gas, the ammonia that has passed through the SCR catalyst 4 without being reacted is removed. A slip catalyst 14 is provided. A muffler (not shown) is connected to the downstream side of the slip catalyst 14, and the exhaust gas that has passed through the slip catalyst 14 is released into the atmosphere after the exhaust noise is reduced inside the muffler.

In the exhaust system of the diesel engine 1 configured as described above, urea water injected from the injection nozzle 5 is atomized and dispersed in the exhaust pipe 2 on the upstream side of the SCR catalyst 4 inside the exhaust pipe 2. There are provided a dispersion member 21 for mixing and a mixer 31 which is a mixing means for mixing the urea water dispersed by the dispersion member 21 into the exhaust gas.
Below, the structure of the dispersion member 21 and the mixer 31 is demonstrated in detail using FIGS. For convenience of the following description, the vertical direction in the exhaust gas aftertreatment device is defined by the arrows shown in FIG.

  As shown in FIG. 2, the dispersion member 21 is a flat plate-like member disposed at a portion facing the injection nozzle 5, and is provided so as to extend in parallel to the exhaust gas flow direction indicated by the arrow A. ing. The length of the dispersion member 21 in the flow direction is long enough for all the urea water injected from the injection nozzle 5 to collide with the dispersion member 21. On the other hand, the mixer 31 is a substantially disk-shaped member disposed adjacent to the downstream end of the dispersion member 21, and is provided so as to be perpendicular to the flow direction of the exhaust gas. In the part where the mixer 31 is located, the exhaust pipe 2 is divided into an upstream pipe 2a and a downstream pipe 2b, and the outer peripheral portion of the mixer 31 is held between them. The injection nozzle 5 injects urea water F indicated by a one-dot chain line in a direction substantially perpendicular to the flow direction of the exhaust gas, that is, in a direction substantially perpendicular to the dispersion member 21. F is caused to directly collide with the dispersion member 21.

  As shown in FIG. 3A, a plurality of fin portions 32 are formed in a portion of the mixer 31 located inside the exhaust pipe 2 by bending a trapezoidal cut that is partially connected. . Further, the mixer 31 has a plurality of openings 33 formed by bending the fin portions 32, and exhaust gas flowing from the upstream side of the mixer 31 passes through these openings 33 and is downstream. It is designed to flow to the side. Further, in the mixer 31 according to the first embodiment, the rectangular pipe member 35 (see FIG. 3b) is disposed on the upstream side corresponding to each opening 33, and the exhaust gas that has passed through the dispersion member 21 flows. The opening 33 is passed through the rectangular pipe member 35 as it is. In addition, the fin part 32 is formed so that the row | line | column by which the front-end | tip part was bend | folded upwards, and the row | line | column bent by the downward direction are located in a line alternately. That is, in this embodiment, the mixer is a device that mixes the fluid that passes by changing the flow of the exhaust gas upward and downward. Further, as shown in FIG. 3B, a pair of support portions 34 projecting to the upstream side are joined to the upstream surface 31 a of the mixer 31, and both sides of the dispersion member 21 are joined by these support portions 34. The part is supported.

  As shown in FIG. 4, the dispersion member 21 is disposed so as to pass through the central portion in the exhaust pipe 2, and has a width W that is substantially the same as the inner diameter of the exhaust pipe 2. Accordingly, the portion where the dispersion member 21 is disposed in the exhaust pipe 2 is in a state of being divided into a region R1 on the upper side of the dispersion member 21, that is, the region R2 on the injection nozzle 5 side, and a region R2 on the lower side. The urea water F injected from the injection nozzle 5 is dispersed in the region R1 without flowing into the region R2. Further, a part of the exhaust gas that has passed through the oxidation catalyst 3 (see FIG. 1) flows through the region R1, and the remaining part flows through the region R2. The NOx sensor 11 provided on the upstream side of the SCR catalyst 4 (see FIG. 1) is provided so as to be positioned below the dispersion member 21 and is separated from the injection nozzle 5 by the dispersion member 21. It has become. As shown in FIG. 3, the upper side and the lower side divided by the dispersing member 21 correspond to the upper side and the lower side where the exhaust gas flows through the fin portion 32 of the mixer 31.

  Here, as described above, the dispersion member 21 is disposed at a portion facing the injection nozzle 5, and the urea water F injected from the injection nozzle 5 directly collides with the dispersion member 21. The urea water is dispersed in the exhaust gas flowing through the region R1. Further, since the dispersion member 21 is disposed adjacent to the mixer 31, the urea water dispersed in the exhaust gas by colliding with the dispersion member 21 is immediately supplied to the mixer 31 by the flow of the exhaust gas. It has come to be. On the other hand, when the urea water is to be dispersed in the exhaust gas without using the dispersion member 21, for example, the urea water is generally injected obliquely toward the mixer 31. In this case, in order to make the distribution of the urea water in the exhaust gas uniform, it is necessary to cause the urea water to collide with the entire surface of the mixer 31, so that the injection range of the urea water extends over the entire surface of the mixer 31. In addition, it is necessary to provide a distance between the spray nozzle 5 and the mixer 31.

  That is, the exhaust gas aftertreatment device according to the present invention disperses urea water using the dispersion member 21 disposed at a portion facing the injection nozzle 5, and disposes the dispersion member 21 and the mixer 31 adjacent to each other. Thus, the distance between the injection nozzle 5 and the mixer 31 is shortened. Accordingly, the distance between the oxidation catalyst 3 (see FIG. 1) and the SCR catalyst 4 is also shortened, so that the exhaust gas aftertreatment device can be miniaturized to improve the mountability on the vehicle. Further, since the apparatus is downsized, the temperature drop until the exhaust gas reaches the SCR catalyst 4 is suppressed, so that the NOx purification by the SCR catalyst 4 can be performed efficiently.

Next, the operation of the exhaust gas aftertreatment device according to Embodiment 1 of the present invention will be described.
As shown in FIG. 1, when the operation of the diesel engine 1 is started, the exhaust gas discharged into the exhaust pipe 2 flows in the direction indicated by the arrow A, passes through the oxidation catalyst 3, and becomes exhaust gas. The contained carbon monoxide (CO), hydrocarbon (HC), and the like are oxidized by the oxidation catalyst 3 and at the same time, a part of nitrogen monoxide (NO) is oxidized to nitrogen dioxide (NO ₂ ). Further, when the operation of the diesel engine 1 is started, the ECU 9 outputs a signal to the urea water addition system 7 and starts injection of urea water by the injection nozzle 5.

  As shown in FIG. 2, part of the exhaust gas that has passed through the oxidation catalyst 3 flows through the region R1 partitioned by the dispersion member 21 on the injection nozzle 5 side (see arrow A1), and the remaining part is on the lower side. Is distributed (see arrow A2). The urea water F injected from the injection nozzle 5 is added to the exhaust gas flowing through the region R1. Since the dispersion member 21 is provided at a portion facing the injection nozzle 5, the urea water F injected from the injection nozzle 5 directly collides with the dispersion member 21, and the urea water atomized by colliding with the dispersion member 21 is formed. Dispersed in the exhaust gas flowing through the region R1. Further, since the dispersing member 21 and the mixer 31 are disposed adjacent to each other, the urea water dispersed in the region R1 is immediately supplied to the mixer 31 by the flow of the exhaust gas. The urea water dispersed in the exhaust gas is hydrolyzed by the heat of the exhaust gas in the process of flowing downstream, thereby generating ammonia. In particular, since the dispersion member 21 is disposed so as to pass through the central portion in the exhaust pipe 2, it is efficiently heated by the heat of the exhaust gas, and further promotes hydrolysis of urea water.

On the other hand, the exhaust gas flowing through the region R2 side is supplied to the mixer 31 as it is. The exhaust gas and urea water flowing from the region R1 side and the exhaust gas flowing from the region R2 side are mixed by turbulent flow generated when they pass through the plurality of fin portions 32 of the mixer 31, As a result, the urea water is uniformly mixed with the exhaust gas flowing through the exhaust pipe 2. With such exhaust gas and ammonia was passed through the mixer 31 is supplied to the SCR catalyst 4, the SCR catalyst 4 is reacted with ammonia and the exhaust gas, and NOx to harmless nitrogen contained in exhaust gas (N ₂₎ Reduce to water (H ₂ O). Since the dispersion member 21 is a flat plate member and is provided so as to be parallel to the exhaust gas flow direction, NOx purification can be performed without increasing the exhaust gas pressure loss. Can do.

  Here, since the injection nozzle 5 injects urea water in a direction perpendicular to the direction in which the exhaust gas flows (in this embodiment, perpendicular to the dispersion member 21), urea water is injected into the exhaust gas. When water is dispersed, it is not easily affected by the flow rate of the exhaust gas. That is, as described above, when urea water is injected obliquely and the urea water is dispersed by the mixer 31 without using the dispersion member 21, the range in which the injected urea water collides with the mixer 31 has a high exhaust gas flow rate. Since it becomes narrow as it becomes, the range where urea water is disperse | distributed with it is also narrowed. On the other hand, when the urea water is injected perpendicularly to the direction in which the exhaust gas circulates, the injected urea water collides with the dispersion member 21 even when the flow rate of the exhaust gas increases, so that the urea water is reliably dispersed. It is possible. In other words, even if the flow rate of the exhaust gas changes, the dispersion characteristics hardly change.

  The dispersion member 21 has a width W (see FIG. 4) that is substantially the same as the inner diameter of the exhaust pipe 2, and divides the interior of the exhaust pipe 2 into a region R1 and a region R2. That is, since the urea water injected from the injection nozzle 5 is not supplied to the region R2 side, the amount of urea water adhering to the inner peripheral surface of the exhaust pipe 2 is reduced. Here, the exhaust pipe 2 is heated by the exhaust gas flowing through the inside thereof. However, since the outer peripheral surface of the exhaust pipe 2 is cooled by the outside air, for example, the exhaust immediately after the diesel engine 1 (see FIG. 1) is started. The temperature of the pipe 2 is lower than the temperature of the exhaust gas. If urea water adheres to the inner peripheral surface of the exhaust pipe 2 in such a state, hydrolysis does not occur, the water of the urea water evaporates and urea remains, and the remaining urea accumulates on the inner peripheral surface of the exhaust pipe. Sometimes. That is, since the accumulated urea does not reach the SCR catalyst 4, the amount of ammonia that is originally required is not supplied to the SCR catalyst 4, and it is necessary to increase the amount of urea water added.

  However, in the exhaust gas aftertreatment device according to the present invention, the inside of the exhaust pipe 2 is partitioned into the region R1 and the region R2 by the dispersing member 21, and the amount of urea water adhering to the inner peripheral surface of the exhaust pipe 2 is reduced. Thus, most of the injected urea water can be supplied to the SCR catalyst. The dispersion member 21 is arranged so as to pass through the central portion of the exhaust pipe 2, that is, a portion that becomes high in temperature, so that it is quickly heated without being affected by the temperature of the exhaust pipe 2. . In addition, the dispersion member 21 is shorter than the exhaust pipe 2 in the flow direction of the exhaust gas and has a small heat capacity, and thus is easily heated by the exhaust gas. Therefore, the generation of ammonia from the urea water adhering to the dispersion member 21 is not hindered due to the low temperature of the exhaust pipe 2.

  Further, the NOx sensor 11 provided on the upstream side of the SCR catalyst 4 usually contains fine ceramics such as zirconia as a material. Further, since the NOx sensor 11 is exposed to the exhaust gas that circulates inside the exhaust pipe 2, the NOx sensor 11 operates at a high temperature such as 600 ° C. to 1000 ° C. When urea water adheres to the NOx sensor 11 operating at such a high temperature, a sudden temperature change occurs, so-called thermal shock is applied, and breakage such as cracking may occur.

In order to prevent such damage, the NOx sensor 11 is generally provided at a predetermined distance on the upstream side of the injection nozzle 5 so that the urea water F does not adhere. However, since the upstream NOx sensor 11 in the present invention is separated from the injection nozzle 5 by the dispersion member 21, the upstream NOx sensor 11 is not damaged due to adhesion of the urea water F, and is disposed in the vicinity of the injection nozzle 5. It is possible to do. Therefore, the distance between the oxidation catalyst 3 (see FIG. 1) and the SCR catalyst 4 can be further shortened to reduce the size of the apparatus.
Further, the upper side and the lower side divided by the dispersion member 21 correspond to the upper side and the lower side where the exhaust gas flows through the fin portion 32 of the mixer 31, so that they are arranged so as to pass through the central portion in the exhaust pipe 2. The urea water or the hydrolyzed ammonia that has collided with the dispersed member 21 is dispersed from the mixer 31 to the upper side and the lower side to be dispersed throughout.

  Returning to FIG. 1, the exhaust gas that has passed through the SCR catalyst 4 passes through the filter 13, and particulate matter contained in the exhaust gas is removed at that time. If the exhaust gas that has passed through the filter 13 contains excess ammonia, the excess ammonia is removed by the slip catalyst 14. The exhaust gas that has passed through the slip catalyst 14 is reduced in noise inside a muffler (not shown) and released into the atmosphere. The NOx sensors 11 and 12 detect the NOx concentration on the upstream side and the downstream side of the SCR catalyst 4 as needed, and the ECU 9 uses the injection nozzle 5 based on the NOx concentration detected by these NOx sensors. The injection amount of the urea water F is controlled.

  As described above, since the plate-like dispersion member 21 is provided at the portion facing the injection nozzle 5, the urea water injected from the injection nozzle 5 directly collides with the dispersion member 21. The reducing agent that collides with the dispersing member 21 and atomized is dispersed in the exhaust pipe 2, mixed with the exhaust gas by the mixer 31, and then supplied to the SCR catalyst 4. Since the urea water is dispersed by the dispersing member 21, the distance between the injection nozzle 5 and the mixer 31 in order to widen the injection range of the urea water as in the case of injecting the urea water toward the mixer 31. There is no need to take large. Further, since the dispersion member 21 and the mixer 31 are disposed adjacent to each other, it is not necessary to lengthen the exhaust pipe in order to provide the dispersion member 21. Therefore, it is possible to reduce the size of the exhaust gas aftertreatment device while uniformly dispersing urea water in the exhaust gas.

Further, since the injection nozzle 5 injects urea water in a direction perpendicular to the direction in which the exhaust gas flows, the influence of the flow of exhaust gas until the injected urea water collides with the dispersion member 21. It becomes difficult to receive. Therefore, the urea water can be reliably collided with the dispersion member 21 and efficiently dispersed in the exhaust gas.
Further, since the dispersion member 21 is provided so as to extend in parallel to the direction in which the exhaust gas flows through the inside of the exhaust pipe 2, it is possible to supply urea water to the mixer 31 without increasing the pressure loss. Become.

Embodiment 2. FIG.
Next, an exhaust gas aftertreatment device according to Embodiment 2 of the present invention will be described.
In the exhaust gas aftertreatment device according to the second embodiment, the exhaust gas aftertreatment device according to the first embodiment includes the single dispersion member 21, whereas the first dispersion member and the plurality of the dispersion members are described below. And a second dispersion member. In each embodiment described below, the same reference numerals as those in FIGS. 1 to 4 are the same or similar components, and thus detailed description thereof is omitted.

  As shown in FIG. 5, five dispersion members 41 a to 41 e each having a flat plate shape are arranged in a state of being arranged in the vertical direction at a portion facing the injection nozzle 5 in the exhaust pipe 2. Yes. Moreover, the mixer 31 is provided so that the downstream edge part of these dispersion members 41a-41e may be adjoined. Among the dispersion members 41a to 41e, the first dispersion member 41a located on the lowermost side is a flat plate-like member similar to the dispersion member 21 in the first embodiment. On the other hand, the four second dispersion members 41b to 41e provided on the upper side of the first dispersion member 41a are flat members in which a plurality of through holes 42 are formed, and are ejected from the ejection nozzle 5. The urea water F can be sequentially passed from the upper side to the lower side.

  A part of the urea water F injected to the upper surface of the uppermost second dispersion member 41e is dispersed in the exhaust gas by colliding with the second dispersion member 41e, and the remaining part is in the through hole 42. Pass through. Similarly, part of the urea water that has passed through the through hole 42 of the second dispersion member 41e is dispersed in the exhaust gas by colliding with the second dispersion member 41d, and the remaining part is dispersed in the second dispersion member 41c, It passes through 41b sequentially and finally collides with the first dispersion member 41a. Therefore, the urea water F can be widely dispersed in the exhaust pipe 2 by reducing the amount of the urea water F passing through the through holes 42 of the second dispersion members 41b to 41e by, for example, 20%. It is possible. Other configurations are the same as those in the first embodiment.

  As described above, even if a plurality of dispersion members are used and the first dispersion member having no through holes and the second dispersion member having the through holes are configured, urea water that collides with each dispersion member and is dispersed immediately To the mixer 31. Therefore, as in the first embodiment, the exhaust gas aftertreatment device can be reduced in size.

In the first embodiment, the injection nozzle 5 as the reducing agent supply device is configured to inject urea water in a direction perpendicular to the dispersion member 21, but limits the direction in which urea water is injected. is not. For example, even if the spray nozzle 5 ′ and the spray nozzle 5 ″ shown in FIG. 6 are provided at an angle with respect to the dispersion member 21, the urea water directly collides with the dispersion member 21, so that the same In addition, since the injection nozzles 5 'and 5 "are injected perpendicularly to the flow direction, both of the exhaust gas is discharged until the injected reducing agent collides with the dispersion member. Less affected by flow.
In addition, the dispersion member 21 in the first embodiment is arranged so as to be parallel to the flow direction of the exhaust gas. However, for example, like the dispersion member 51 shown in FIG. It is also possible to add an angle. In this case, the pressure loss increases, but the dispersibility can be adjusted by adjusting the direction of the exhaust gas flowing into the mixer.
Further, the dispersion member is not in direct contact with the exhaust pipe 2 at the end, and may be separated. In this case, the dispersion member may be supported only by the mixer. In this case, the temperature of the dispersion member can be kept high because it is in contact with the outside air and separated from the exhaust pipe 2 having a relatively low temperature. Conversely, the end portion may be directly supported by the exhaust pipe 2 without being supported by the mixer.
In the first embodiment, the dispersion member 21 is disposed so as to pass through the central portion in the exhaust pipe 2, but is not limited to this configuration. What is necessary is just to oppose the injection nozzle 5 and to arrange | position adjacent to the mixer 31. As for the position of the dispersion member 21, for example, the surface on which the urea water collides may be arranged at the center of the mixer.

  DESCRIPTION OF SYMBOLS 1 Diesel engine (internal combustion engine), 2 exhaust pipe, 4 SCR catalyst (reduction catalyst), 5 injection nozzle (reducing agent supply apparatus), 21, 51 dispersion member, 31 mixer (mixing means), 41a 1st dispersion member (dispersion) Member), 41b, 41c, 41d, 41e Second dispersion member (dispersion member).

Claims (4)

An exhaust pipe through which exhaust gas discharged from the internal combustion engine flows;
A reducing agent supply device for injecting a reducing agent into the exhaust pipe;
In the exhaust gas aftertreatment device, which is disposed on the downstream side of the reducing agent supply device and includes a reduction catalyst that purifies the exhaust gas by reacting the exhaust gas with the reducing agent,
In the exhaust pipe,
A plate-like dispersion member disposed at a portion facing the reducing agent supply means;
A mixing means disposed between the dispersion member and the reduction catalyst and mixing the exhaust gas and the reducing agent;
The exhaust gas aftertreatment device, wherein the dispersion member and the mixing means are disposed adjacent to each other.   The exhaust gas aftertreatment device according to claim 1, wherein the reducing agent supply device injects the reducing agent in a direction perpendicular to a direction in which the exhaust gas flows through the exhaust pipe.   The exhaust gas after-treatment device according to claim 1, wherein the dispersion member extends in parallel to a direction in which the exhaust gas flows through the inside of the exhaust pipe.   The exhaust gas aftertreatment device according to any one of claims 1 to 3, wherein the dispersion member is a single member.

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