JP2012092746A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress lowering of exhaust temperature while having a compact configuration with excellent mountability thereby and achieving diffusion effect of a reducing agent.SOLUTION: An exhaust emission control device 2 including an upstream side exhaust emission control device 20 having a filter 23 in a first casing 21, and a downstream side exhaust emission control device 30 having a selective reduction type catalyst 32 in a second casing 31 includes a communication pipe 29 connected to an exhaust outlet 27 provided on a circumferential wall of the first casing 21 and an exhaust inlet 36 provided on a circumferential wall of the second casing 31, and connecting the first casing 21 and the second casing 31, and an addition nozzle 28 provided on the circumferential wall of the first casing 21 opposed to the exhaust outlet 27 to add the reducing agent. The upstream side exhaust emission control device 20 and the downstream side exhaust emission control device 30 are juxtaposed at intervals while the exhaust outlet 27 and the exhaust inlet 36 are situated adjacently, and one end of the communication pipe 29 is extended in the first casing 21 toward the addition nozzle 28 from the exhaust outlet 27.

Description

  The present invention relates to an exhaust purification device for an engine, and more particularly to an exhaust purification device that removes particulates and nitrogen oxides in exhaust gas.

  Engine exhaust, particularly diesel engine exhaust, contains particulate matter (hereinafter referred to as PM), nitrogen oxides (hereinafter referred to as NOx), and the like, which are air pollutants. Therefore, a technique is known in which a particulate filter (Diesel Particulate Filter, hereinafter referred to as DPF) for collecting PM is installed in the exhaust passage of the engine so that PM is not released into the atmosphere. . In addition, a selective catalytic reduction (hereinafter abbreviated as SCR) for removing NOx is installed in the exhaust passage of the engine, and urea water as a reducing agent is added to the exhaust flowing into the SCR. Thus, a technique is known in which the exhaust gas is purified by reducing NOx in the exhaust gas in the SCR.

  In order to efficiently perform such PM collection and NOx reduction, a combination of DPF and SCR, which is used as an exhaust purification device, is proposed in, for example, Patent Document 1. The exhaust purification device described in Patent Document 1 includes an upstream aftertreatment device in which a pre-stage oxidation catalyst and a filter (DPF) are accommodated, and a downstream side aftertreatment device in which a NOx catalyst (SCR) and a post-stage oxidation catalyst are accommodated. It is configured to be accommodated in parallel in one casing.

  A folding chamber for making U-turn exhaust in the casing is formed at the ends of these upstream and downstream aftertreatment devices, and the direction in which the exhaust gas is transferred after passing through the filter is changed in the folding chamber. A first guide plate and a second guide plate for restricting the flow of exhaust gas directly to the NOx catalyst are disposed. In addition, an injection nozzle that injects the urea aqueous solution is provided on one side of the folding chamber. In the folding chamber of the casing, the first guide plate and the second guide plate reduce the path length of the exhaust from the injection nozzle to the NOx catalyst. It is configured so that the diffusion time of the urea aqueous solution can be sufficiently secured by extending.

JP 2009-103034 A

  However, since the exhaust purification device described in Patent Document 1 is installed in a vehicle with the upstream aftertreatment device and the downstream aftertreatment device housed in one rectangular box-like casing, the entire device is large. And the cost increases. Further, the upstream aftertreatment device and the downstream aftertreatment device are arranged in parallel in the casing, a folding chamber is formed at one end of the casing, and a first guide plate and a second guide plate are further arranged in the folding chamber. Since this is necessary, the apparatus is complicated and expensive to manufacture.

  As shown in FIG. 3, the upstream oxidation catalyst 52 and the DPF 53 are accommodated in the cylindrical casing 51 as the upstream side exhaust purification device 50, and the SCR 62 is accommodated in the cylindrical casing 61 as the downstream side exhaust purification device 60. There is also known an exhaust emission control device in which a casing oxidation catalyst 63 is accommodated, the casings 51 and 61 are arranged in parallel, and a communication pipe 59 having bent portions 59a and 59b at both ends is connected therebetween. In this exhaust purification device, the communication pipe 59 is disposed between the upstream side exhaust purification device 50 and the downstream side exhaust purification device 60, and the injection nozzle 58 for injecting the urea aqueous solution is provided on the upstream side of the communication pipe 59. Yes.

  However, the exhaust purification apparatus shown in FIG. 3 is advantageous in that the urea aqueous solution injected from the injection nozzle 58 is diffused into the exhaust gas because the entire length of the communication pipe 59 is long. Since the temperature of the exhaust gas flowing through the pipe 59 is lowered, the NOx purification rate in the SCR 63 of the downstream side exhaust purification device 60 may be lowered.

The present invention has been devised in view of such problems, and provides an exhaust emission control device that has a compact structure and is easy to mount and can suppress a reduction in exhaust temperature while obtaining a diffusion effect of a reducing agent. The purpose is to do.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) An exhaust emission control device disclosed herein includes an upstream side exhaust purification device provided with a filter (DPF) for collecting particulate matter (PM) contained in exhaust of a diesel engine in a cylindrical first casing. A downstream side exhaust purification device including a selective reduction catalyst (SCR) for reducing and purifying nitrogen oxide (NOx) contained in the exhaust gas in a cylindrical second casing separate from the first casing; The exhaust gas purification apparatus includes: an exhaust outlet provided at a peripheral wall at one end of the first casing; an exhaust outlet through which exhaust gas flowing through the first casing flows out; a peripheral wall at one end of the second casing; An exhaust inlet through which exhaust gas flowing through the two casings flows, a communication pipe connected to the exhaust outlet and the exhaust inlet to communicate the first casing and the second casing, and the exhaust Provided on the peripheral wall of the first casing facing the outlet, and a reducing agent addition nozzle for adding a reducing agent to exhaust gas flowing into the communicating pipe.

  Further, the upstream side exhaust purification device and the downstream side exhaust purification device are arranged in such a manner that the exhaust outlet and the exhaust inlet are adjacent to each other, and the exhaust flow that circulates in the first casing is spaced apart from the second casing. The exhaust pipe flowing in the casing is arranged in parallel so as to flow in the opposite direction, and one end of the communication pipe on the exhaust outlet side extends into the first casing from the exhaust outlet toward the reducing agent addition nozzle. It is characterized by being installed.

  (2) The communication pipe is a straight pipe, and the opening at the one end of the communication pipe, the exhaust outlet, and the exhaust inlet are arranged in this order from the tip of the reducing agent addition nozzle toward the exhaust downstream side. It is preferable to be provided in a straight line.

  (3) Alternatively, it is preferable that the communication pipe is a curved pipe, and the exhaust inlet is provided eccentrically from a central axis of the second casing.

  According to the disclosed exhaust purification device, the upstream side exhaust purification device and the downstream side exhaust purification device are separated from the exhaust flow that circulates in the first casing with the exhaust outlet and the exhaust inlet being adjacent to each other with a space therebetween. Since the exhaust gas flowing in the two casings is arranged in parallel so as to flow in the opposite direction, the configuration of the entire device is simplified, the overall size is reduced, and the mountability to vehicles, ships, and the like is improved.

In addition, since the communication pipe is connected to the exhaust outlet and the exhaust inlet provided adjacent to each other, the length of the portion exposed to the outside of the communication pipe can be shortened, and communication by heat radiation on the surface of the communication pipe is possible. A decrease in the temperature of the exhaust gas flowing through the pipe can be suppressed, and a decrease in the purification rate of NOx in the exhaust gas in the downstream side exhaust purification device can be suppressed.
In addition, a reducing agent addition nozzle is provided on the peripheral wall of the first casing, and one end on the exhaust outlet side of the communication pipe extends from the exhaust outlet toward the reducing agent addition nozzle in the first casing, so that the upstream side Even if the exhaust gas purification device and the downstream side exhaust gas purification device are arranged adjacent to each other in parallel, the length of the communication pipe can be ensured, and the diffusion effect of the reducing agent into the exhaust gas can be ensured.

  Further, when the communication pipe is a straight pipe and the opening at one end of the communication pipe, the exhaust outlet, and the exhaust inlet are provided in this order from the front end of the reducing agent addition nozzle to the exhaust downstream side, The reducing agent can be reliably added and diffused into the exhaust gas in the communication pipe. Further, the length of the communication pipe can be minimized, and the configuration can be further simplified.

  Further, when the communication pipe is a curved pipe, the first casing and the second casing can be arranged adjacent to each other, and the entire apparatus can be made more compact. Further, when the exhaust inlet is provided eccentric from the central axis of the second casing, the exhaust can be caused to flow into the second casing while turning, and the reducing agent can be further diffused.

FIG. 1 is a schematic diagram showing a configuration of an exhaust emission control device according to a first embodiment, in which FIG. 1A is an axial sectional view, FIG. 1B is a side view thereof [direction A in FIG. Arrow view]. It is a whole lineblock diagram explaining the exhaust-air-purification device concerning a first embodiment. FIG. 3A is a schematic diagram showing a configuration of an exhaust emission control device according to a second embodiment, FIG. 3A is a plan view thereof, and FIG. 3B is a side view thereof [viewed in the direction B of FIG. Figure]. FIG. 4A is a schematic diagram illustrating a configuration of an exhaust emission control device for explaining a conventional problem. FIG. 4A is an axial cross-sectional view thereof, and FIG. 4B is a side view thereof [direction C in FIG. Arrow view].

[1. First embodiment]
[1-1. overall structure]
Hereinafter, embodiments will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment.

An exhaust emission control device according to this embodiment will be described with reference to FIGS. 1 (a), 1 (b), and 2. FIG. The present exhaust purification apparatus can be applied not only to a vehicle but also to a vehicle equipped with an engine, for example, a ship, etc., but here, an example applied to a vehicle such as a general passenger car, a truck, or a bus will be described. .
As shown in FIG. 2, the engine 1 is here configured as a diesel engine of an in-line 6-cylinder engine. Each cylinder of the engine 1 is provided with a fuel injection valve 11. Each fuel injection valve 11 is supplied with pressurized fuel from a common rail 12 and injects fuel into the cylinder of the corresponding cylinder when the valve is opened. The number of cylinders is not limited to this.

  An intake manifold 13 is mounted on the intake side of the engine 1, and an air passage 15 connected to the upstream end of the intake manifold 13 is provided with an air cleaner 15, a compressor 16 a of a turbocharger 16 and an intercooler 17 from the upstream side. Yes. An exhaust manifold 18 is mounted on the exhaust side of the engine 1, and a turbine 16 b of a turbocharger 16 connected coaxially with the compressor 16 a is connected to the downstream end of the exhaust manifold 18. An exhaust passage 19 is connected to the turbine 16b. An exhaust purification device 2 is provided in the middle of the exhaust passage 19.

The exhaust purification device 2 includes an upstream exhaust purification device 20 provided on the exhaust upstream side, and a downstream exhaust purification device 30 provided on the exhaust downstream side of the upstream exhaust purification device 20, and upstream exhaust purification. The device 20 and the downstream side exhaust purification device 30 are connected by a communication pipe 29.
The upstream side exhaust purification device 20 includes a cylindrical oxidation casing (first casing) 21, a pre-stage oxidation catalyst 22 disposed on the upstream side, and a particulate filter (Diesel Particulate Filter, hereinafter) disposed on the downstream side. , Abbreviated as DPF) 23. Hereinafter, the upstream side exhaust purification device 20 is referred to as a DPF device 20, and the cylindrical casing 21 is referred to as a DPF casing 21.

  The downstream side exhaust purification apparatus 30 includes a selective catalytic reduction (hereinafter abbreviated as SCR) 32 disposed upstream in a cylindrical casing (second casing) 31, and a downstream side. And a post-stage oxidation catalyst 33 arranged in the internal structure. Hereinafter, the downstream side exhaust purification device 30 is referred to as an SCR device 30, and the cylindrical casing 31 is referred to as an SCR casing 31.

An addition nozzle (reducing agent addition nozzle) 28 for adding urea water as a reducing agent is provided on the exhaust downstream side of the DPF 23 and upstream of the communication pipe 29, and the addition nozzle 28 is a tank (not shown). The urea water pumped from is injected into the exhaust toward the SCR device 30 and added. The addition amount and timing of addition of the urea water are controlled by the controller 40.
A controller (ECU, Engine (electronic) Control Unit) 40 is a CPU that executes various arithmetic processes related to engine control and exhaust gas purification control, a ROM that stores programs and data necessary for the control, CPU calculation results, and the like. Are temporarily stored, and an input / output port for inputting / outputting signals to / from the outside.

[1-2. Configuration of exhaust purification device]
Next, the DPF device 20 and the SCR device 30 will be described in detail with reference to FIGS. 1 (a) and 1 (b).
The DPF device 20 has a function of collecting particulate matter (hereinafter abbreviated as PM) contained in exhaust gas and a function of continuously oxidizing and removing the collected PM. In addition, PM is a particulate material in which fuel, lubricant components, sulfur compounds, and the like that remain unburned around carbon black smoke (soot) are attached.

The pre-stage oxidation catalyst 22 is an oxidation catalyst having an oxidation performance with respect to components in exhaust gas, and is a catalyst in which a catalyst material is supported on a honeycomb-shaped carrier made of metal, ceramics or the like. Components in the exhaust gas oxidized by the pre-stage oxidation catalyst 22 include NO, hydrocarbons in unburned fuel, and carbon monoxide. For example, when NO is oxidized by the pre-stage oxidation catalyst 22, NO ₂ is generated.

  The DPF 23 is a porous filter (for example, a ceramic filter) that collects PM. The inside of the DPF 23 is divided into a plurality of portions along the flow direction of the exhaust gas by a porous wall body. A large number of pores having a size commensurate with the particulates of PM are formed in the wall. When the exhaust gas passes near or inside the wall body, PM is collected on the wall body and the wall body surface, and the exhaust gas is filtered. Such regeneration control of the DPF 23 is controlled by the controller 40.

  The DPF device 20 is configured such that a front oxidation catalyst 22 and a DPF 23 are built in a cylindrical DPF casing 21 in series in the axial direction thereof. In the DPF casing 21, a DPF inlet space 24 is provided on the exhaust upstream side of the pre-stage oxidation catalyst 22, and a space 25 called a mixing chamber is provided on the exhaust downstream side of the DPF 23. The DPF inlet space 24 is formed with a DPF inlet 26 that is an inlet for exhaust gas to flow into the DPF casing 21 from the exhaust passage 19, and the exhaust gas flowing through the DPF casing 21 flows into the mixing chamber 25. A DPF outlet (exhaust outlet) 27 is formed. In the present embodiment, as shown in FIG. 1B, the DPF inlet 26 and the DPF outlet 27 are the peripheral walls at both ends of the DPF casing 21 and are formed at positions shifted by 180 degrees in the circumferential direction. Yes.

The addition nozzle 28 is provided on the peripheral wall of the DPF casing 21 facing the DPF outlet 27, and the tip thereof is disposed toward the opening 29 a of the communication pipe 29.
One end of the communication pipe 29 connected to the DPF casing 21 of the DPF device 20 is disposed through the DPF outlet 27 formed in the peripheral wall of the DPF casing 21 into the DPF casing 21. The opening 29a is extended toward the addition nozzle 28 so as to be cantilevered by the peripheral wall. That is, the end of the communication pipe 29 on the exhaust upstream side is provided to protrude into the mixing chamber 25 from the DPF outlet 27 formed on the peripheral wall of the DPF casing 21. The communication pipe 29 constitutes a part of the exhaust passage 19 and is the most common cylindrical pipe. In the present embodiment, the communication pipe 29 is a straight pipe. The communication pipe 29 is not limited to a general cylindrical pipe, and may be another cylindrical pipe.

The SCR 32 in the SCR device 30 is a urea-added nitrogen oxide selective reduction type catalyst in which a catalyst is supported on a honeycomb-structured carrier in which a plurality of minute holes parallel to each other in the axial direction are communicated. It has a function of hydrolyzing urea water supplied from the addition nozzle 28 provided in the tank into ammonia and adsorbing ammonia, and further reducing NOx in the exhaust gas to N ₂ using the adsorbed ammonia as a reducing agent. . The type of catalyst supported on the SCR 32 is arbitrary. For example, it is conceivable to use a catalyst such as zeolite or vanadium. Further, a reducing agent other than urea water may be used.

The post-stage oxidation catalyst 33 is an oxidation catalyst for removing excess ammonia in the reduction reaction at the SCR 32.
The SCR device 30 is configured such that an SCR 32 and a post-stage oxidation catalyst 33 are built in a cylindrical SCR casing 31 in series in the axial direction thereof. In the SCR casing 31, an SCR inlet space 34 is provided on the exhaust upstream side of the SCR 32, and an SCR outlet space 35 is provided on the exhaust downstream side of the post-stage oxidation catalyst 33. The SCR inlet space 34 is formed with an SCR inlet (exhaust inlet) 36 that is an inlet through which the exhaust flows from the communication pipe 29 into the SCR casing 31. The SCR outlet space 35 circulates in the SCR casing 31. An SCR outlet 37, which is an outlet for exhaust gas to flow out, is formed. In the present embodiment, as shown in FIG. 1B, the SCR inlet 36 and the SCR outlet 37 are the peripheral walls at both ends of the SCR casing 31, and are formed at positions shifted by 180 degrees in the circumferential direction. Yes.

  In the exhaust purification device 2 according to the present embodiment, the DPF device 20 and the SCR device 30 configured as described above are spaced apart in a state where the DPF outlet 27 and the SCR inlet 36 are adjacent to each other in the DPF casing 21. The exhaust flow flowing through and the exhaust flow flowing through the SCR casing 31 are arranged in parallel so as to flow in opposite directions. Furthermore, the DPF casing 21 and the SCR casing 31 are casings of the same shape (same size), and are arranged in plane symmetry with the DPF outlet 27 and the SCR inlet 36 facing each other.

In other words, the DPF casing 21 and the SCR casing 31 having the same shape are arranged in parallel so that the DPF inlet space 24 and the SCR outlet space 35 are adjacent to each other, and the mixing chamber 25 and the SCR inlet space 34 are adjacent to each other. The DPF outlet 27 and the SCR inlet 36 are provided to face each other.
The interval between the DPF outlet 27 and the SCR inlet 36 can be set as appropriate depending on the length of the communication pipe 29 for urea water diffusion and the arrangement relationship with surrounding members and devices. The communication pipe 29 connects the DPF casing 21 and the SCR casing 31 by connecting the adjacent DPF outlet 27 and the SCR inlet 36.

[1-3. Action, effect]
Since the exhaust emission control device 2 according to the present embodiment is configured as described above, the exhaust gas is purified as follows.
During operation of the engine 1, the exhaust discharged from the engine 1 is introduced into the DPF device 20 through the upstream portion of the exhaust passage 19, passes through the pre-stage oxidation catalyst 22 and the DPF 23, and is transferred into the mixing chamber 25. It is introduced into the communication pipe 29. At this time, urea water as a reducing agent is added into the exhaust toward the SCR device 30 from the addition nozzle 28 provided on the upstream side of the communication pipe 29.

  The added urea water is hydrolyzed by exhaust heat while being mixed with the exhaust gas in the communication pipe 29 to generate ammonia, flows through the communication pipe 29 and is introduced from the SCR inlet 36 to the SCR inlet space 34. After passing through the SCR 32 and the post-stage oxidation catalyst 33, the SCR outlet 37 passes through the exhaust pipe 39 and is discharged into the atmosphere. At this time, PM in the exhaust gas is collected by the DPF 23, and NOx in the exhaust gas is reduced by the SCR 32, and these actions prevent discharge of harmful components into the atmosphere.

  Therefore, according to the exhaust emission control device 2 according to the present embodiment, the DPF device 20 and the SCR device 30 circulate in the DPF casing 21 with an interval in a state where the DPF outlet 27 and the SCR inlet 36 are adjacent to each other. Since the exhaust flow and the exhaust flow flowing through the SCR casing 31 are arranged in parallel so as to flow in opposite directions, the overall configuration of the exhaust purification device 2 is simplified, the overall size is reduced, and the mounting property to the vehicle is also improved. improves. Furthermore, since the two casings have the same shape and are arranged in plane symmetry, the overall configuration of the exhaust purification device 2 is further simplified.

  Further, since the communication pipe 29 is connected to the DPF outlet 27 and the SCR inlet 36 provided adjacent to each other, the length of the portion exposed to the outside of the communication pipe 29 can be shortened. Therefore, it is possible to suppress the temperature decrease of the exhaust gas flowing through the communication pipe 29 due to the heat radiation on the surface of the communication pipe 29, and it is possible to suppress the decrease in the purification rate of NOx in the exhaust gas in the SCR 32 of the SCR device 30.

  Further, the addition nozzle 28 is provided on the peripheral wall of the DPF casing 21, and one end of the communication pipe 29 on the DPF outlet 27 side extends from the DPF outlet 27 toward the addition nozzle 28 in the DPF casing 21. Even if the casing 21 and the SCR casing 31 are arranged adjacent to each other in parallel, the length of the communication pipe 29 can be secured, and the urea water can be diffused into the exhaust gas in the communication pipe 29.

  Further, in this embodiment, the communication pipe 29 is a straight pipe, and the opening 29a at one end of the communication pipe 29, the DPF outlet 27, and the SCR inlet 36 are arranged in this order from the tip of the addition nozzle 28 toward the exhaust downstream side. Since it is provided in a straight line, the urea water added from the addition nozzle 28 can surely flow into the communication pipe 29 and diffuse into the exhaust gas in the communication pipe 29, and supply ammonia to the SCR 32. can do. Further, the length of the communication pipe 29 can be minimized, and the configuration can be further simplified.

[2. Second embodiment]
[2-1. Configuration of exhaust purification device]
Next, the exhaust emission control device according to the second embodiment will be described with reference to FIGS. 3 (a) and 3 (b). In addition, the same member as 1st embodiment attaches | subjects the same code | symbol as the thing of 1st embodiment, and the overlapping description is abbreviate | omitted.

As shown in FIGS. 3 (a) and 3 (b), the exhaust emission control device 2 according to the present embodiment includes the shape of the communication pipe 29 ', the positions of the SCR inlet 36 and the SCR outlet 37 of the SCR device 30, and Except for the arrangement of the SCR device 30 with respect to the DPF device 20, the configuration is the same as that of the first embodiment.
In the present embodiment, the DPF device 20 and the SCR device 30 are arranged with a gap in a state where the DPF outlet 27 and the SCR inlet 36 are adjacent to each other, and the SCR device 30 is viewed from the side with respect to the DPF device 20. In FIG. Further, as shown in FIG. 3B, the SCR inlet 36 is formed at a position eccentric by a length X in a direction away from the DPF device 20 from the central axis of the SCR casing 31. The SCR outlet 37 is also provided eccentric from the central axis of the SCR casing 31.

  The communication pipe 29 'is a curved pipe having one end connected to the DPF casing 21 penetrating from the DPF outlet 27 formed in the peripheral wall of the DPF casing 21 into the DPF casing 21, The DPF outlet 27 of the DPF device 20 and the SCR inlet 36 of the SCR device 30 are connected.

[2-2. Action, effect]
Since the exhaust gas purification device 2 according to the present embodiment is configured as described above, the exhaust gas that has passed through the DPF device 20 flows into the communication pipe 29 'from the DPF outlet 27, and passes through the communication pipe 29'. And flows into the SCR device 30 from the SCR inlet 36. At this time, since the SCR inlet 36 is provided eccentrically from the central axis of the SCR casing 31, a swirling flow is formed in the SCR inlet space 34.

  Therefore, according to the exhaust purification device 2, the overall configuration of the exhaust purification device 2 can be made compact. Further, the length of the portion exposed to the outside of the communication pipe 29 ′ is slightly longer than that of the first embodiment, and a swirling flow can be generated in the SCR inlet space 34. Can be diffused.

[3. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In any of the above-described embodiments, the DPF inlet 26 and the DPF outlet 27 of the DPF device 20 are provided at positions shifted by 180 degrees in the circumferential direction. However, the positions of the DPF inlet 26 and the DPF outlet 27 are not limited thereto. I can't. For example, the DPF inlet 26 may be provided at a position shifted from the DPF outlet 27 by 90 degrees in the circumferential direction. Further, the DPF inlet 26 may be provided not on the peripheral wall of the DPF casing 21 but on the end wall in the axial direction of the DPF casing 21. Further, the SCR outlet 37 may be provided not on the peripheral wall of the SCR casing 31 but on the end wall in the axial direction of the SCR casing 31.

Further, the DPF casing 21 and the SCR casing 31 are not limited to a cylindrical cylindrical casing, and the DPF casing 21 and the SCR casing 31 may not have the same shape.
In the second embodiment, the SCR inlet 36 may be provided on the central axis of the SCR casing 31 without being eccentric from the central axis of the SCR casing 31. In this case, although the effect due to the swirling flow cannot be obtained, the length exposed to the outside of the communication pipe 29 'can be shortened, so that a decrease in the exhaust temperature can be suppressed.

1 engine (diesel engine)
2 Exhaust purification device 20 DPF device (upstream exhaust purification device)
21 DPF casing (first casing)
22 Pre-stage oxidation catalyst 23 DPF (filter, particulate filter)
26 DPF inlet 27 DPF outlet (exhaust outlet)
28 Addition nozzle (reducing agent addition nozzle)
29 Communication pipe 30 SCR device (downstream exhaust purification device)
31 SCR casing (second casing)
32 SCR (Selective Reduction Catalyst)
33 Rear oxidation catalyst 36 SCR inlet (exhaust inlet)
37 SCR outlet 40 Controller (ECU)

Claims (3)

An upstream side exhaust purification device provided with a filter (DPF) for collecting particulate matter (PM) contained in the exhaust of a diesel engine in a cylindrical first casing, and nitrogen oxide (NOx) contained in the exhaust An exhaust purification device comprising a downstream side exhaust purification device provided with a selective reduction type catalyst (SCR) for reducing and purifying a catalyst in a cylindrical second casing separate from the first casing,
An exhaust outlet provided on a peripheral wall at one end of the first casing, through which exhaust gas flowing through the first casing flows out;
An exhaust inlet provided on a peripheral wall of one end of the second casing, into which exhaust gas flowing through the second casing flows;
A communication pipe connected to the exhaust outlet and the exhaust inlet to communicate the first casing and the second casing;
A reducing agent addition nozzle that is provided on a peripheral wall of the first casing facing the exhaust outlet and adds a reducing agent to the exhaust gas flowing into the communication pipe;
The upstream exhaust purification device and the downstream exhaust purification device are arranged in a state in which the exhaust outlet and the exhaust inlet are adjacent to each other with an interval between them, and the exhaust flow flowing in the first casing and the second casing Are arranged in parallel so that the exhaust flow flowing through the
One end of the communication pipe on the exhaust outlet side extends in the first casing from the exhaust outlet toward the reducing agent addition nozzle. The communication pipe is a straight pipe, and the opening of the one end of the communication pipe, the exhaust outlet, and the exhaust inlet are provided in this order from the tip of the reducing agent addition nozzle to the exhaust downstream side. The exhaust emission control device according to claim 1, wherein: The exhaust emission control device according to claim 1, wherein the communication pipe is a curved pipe, and the exhaust inlet is provided eccentrically from a central axis of the second casing.

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