JP6919478B2 - Exhaust purification device for internal combustion engine - Google Patents

Description

The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device mainly applied to a diesel engine.

A selective reduction type NOx catalyst for reducing and removing NOx (nitrogen oxide) in the exhaust is provided in the exhaust passage of the diesel engine. An injection valve for injecting urea water is provided on the upstream side of the NOx catalyst. _{The NOx catalyst reacts NOx with ammonia NH 3} obtained by hydrolyzing urea water, and reduces NOx in the exhaust gas to nitrogen N _2.

International Publication No. 2010/053033 Japanese Unexamined Patent Publication No. 2008-144644 Japanese Unexamined Patent Publication No. 2006-77576

In order to operate the NOx catalyst with high efficiency, it is desirable to promote the hydrolysis of urea water and maintain the amount of ammonia produced per unit volume of urea water, that is, the ammonia production efficiency at the highest possible level. Then, in order to promote the hydrolysis of the urea water, it is preferable to promote the mixing of the urea water injected into the exhaust passage and the exhaust gas as much as possible.

Therefore, the present invention was conceived in view of such circumstances, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine capable of promoting mixing of injected urea water and exhaust gas.

According to one aspect of the invention
The exhaust passage through which the exhaust gas of the internal combustion engine flows, and
With the catalyst arranged in the exhaust passage,
An injection valve provided on the upstream side of the catalyst and injecting a reducing agent into the exhaust passage.
An upstream partition plate and a downstream partition plate provided apart from each other inside the exhaust passage located on the downstream side of the injection valve and on the upstream side of the catalyst.
The upstream side through hole and the downstream side through hole provided in the upstream side partition plate and the downstream side partition plate, respectively,
An upstream pipe that communicates with the upstream through hole and is provided in the upstream partition plate,
A downstream pipe that communicates with the downstream through hole and is provided in the downstream partition plate.
With
An exhaust gas purification device for an internal combustion engine is provided, wherein the outlet portion of the upstream pipe and the inlet portion of the downstream pipe are arranged in a non-coaxial state with each other.

Preferably, the upstream pipe and the downstream pipe project into the space between the upstream partition and the downstream partition.

Preferably, the outlet portion of the upstream pipe and the inlet portion of the downstream pipe overlap each other in the upstream and downstream directions.

Preferably, the upstream pipe and the downstream pipe are in contact with each other.

Preferably, at least one of the upstream partition plate and the downstream partition plate is inclined with respect to a direction perpendicular to the central axis of the exhaust passage.

According to the present invention, the mixing of the injected urea water and the exhaust gas can be promoted.

It is a longitudinal side view which shows the whole structure of the exhaust gas purification apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal rear view of the exhaust gas purification device, and is the II-II sectional view of FIG. It is a longitudinal front view of the exhaust gas purification device, and is the cross-sectional view of III-III of FIG. It is a longitudinal side view which shows the structure of the inside of the 2nd passage. It is a VV cross-sectional view of FIG. It is a longitudinal side view which shows the internal structure of the 2nd passage in 2nd Embodiment. FIG. 6 is a cross-sectional view taken along the line VII-VII of FIG. It is a longitudinal side view which shows the internal structure of the 2nd passage in 3rd Embodiment. FIG. 8 is a cross-sectional view taken along the line IX-IX of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments.

[First Embodiment]
1 to 3 show the overall structure of the exhaust gas purification device according to the first embodiment of the present invention. 1 is a vertical sectional side view (I-I sectional view of FIG. 2), FIG. 2 is a vertical sectional rear view (II-II sectional view of FIG. 1), and FIG. 3 is a vertical sectional front view (III-III sectional view of FIG. 1). Is. For convenience, each direction of the three orthogonal axes, that is, each direction of front, back, left, right, up and down is defined as shown in the figure. However, it should be noted that each of these directions is merely defined for convenience of explanation regarding the arrangement shown in the figure.

The internal combustion engine (not shown, also referred to as an engine) to which the exhaust purification device is applied is a diesel engine mounted on a vehicle. Vehicles (not shown) are large vehicles such as trucks. However, the type and use of the vehicle and the internal combustion engine are not limited. For example, the vehicle may be a small vehicle such as a passenger car, and the engine may be a gasoline engine.

As shown in the figure, the exhaust gas purification device 1 includes a closed box-shaped casing 2 that compactly accommodates a plurality of members (catalysts and the like) described later in a canning state. The casing 2 of the present embodiment has a rectangular parallelepiped shape. A device inlet pipe 3 for introducing the engine exhaust gas G into the casing 2 and a device outlet pipe 4 for discharging the exhaust gas G from the casing 2 are attached to the rear end wall 2R of the casing 2. ing. However, the installation positions of the device inlet pipe 3 and the device outlet pipe 4 can be arbitrarily set.

In the casing 2, a plurality of metal (stainless steel in this embodiment) pipes and plates are attached by welding or the like to appropriately partition the space, thereby defining an exhaust passage 5 through which the exhaust gas G flows. Has been done. Here, the "exhaust passage" means an arbitrary space through which the exhaust gas G flows, and its shape is arbitrary. It may be tubular or chamber-shaped. The exhaust passage 5 is configured to fold back a plurality of exhaust gases G in the front-rear direction.

Inside the casing 2, a front partition plate 6 and a rear partition plate 7 that partition the inside of the casing 2 back and forth are provided. The front end chamber 8F is defined between the front partition plate 6 and the front end wall 2F of the casing 2. The rear end chamber 8R is defined between the rear partition plate 7 and the rear end wall 2R of the casing 2. An intermediate chamber 8M is defined between the front partition plate 6 and the rear partition plate 7.

Hereinafter, the main flow of the exhaust gas G in the casing 2 will be outlined. This main flow is as shown by arrows in FIGS. 1 to 3.

The exhaust gas that has flowed forward in the device inlet pipe 3 goes straight through the first passage 9 that is arranged in the lower left of the casing 2 and extends in the front-rear direction, and at this time, the first oxidation catalyst 21 and the filter 22 are sequentially moved. pass. After that, the exhaust gas enters the second passage 10 as a mixing passage arranged in the central portion of the casing 2 through the feed passage 19 in the feed pipe 19P arranged in the front end chamber 8F. At this time, the exhaust gas is turned back from the front to the rear. Then, the exhaust gas flows from the front to the rear in the second passage 10, then enters the rear end chamber 8R, branches in two directions as shown in FIG. 2, and is arranged at the lower right in the casing 2. It enters the third passage 11 and the fourth passage 12 arranged in the upper left of the casing 2. At this time, the exhaust gas is turned back from the rearward direction to the forward direction.

The exhaust gas flows in the third and fourth passages 11 and 12 from the rear to the front, and at this time, passes through the NOx catalyst 23 and the second oxidation catalyst 24 in order. After that, the exhaust gas enters the front end chamber 8F and is collected in the fifth passage 13 arranged in the upper right of the casing 2 as shown in FIG. At this time, the exhaust gas is turned back from the front to the rear. After that, the exhaust gas flows from the front to the rear in the fifth passage 13, and goes straight to the device outlet pipe 4 as it is and is discharged.

As described above, the exhaust passage 5 includes the first passage 9, the second passage 10, the third passage 11, the fourth passage 12, the fifth passage 13, the feed passage 19, the front end chamber 8F, and the rear end chamber 8R.

An injection valve 14 for injecting urea water as a reducing agent is provided at the upstream end of the second passage 10. The injection valve 10 is arranged coaxially with the second passage 10 in the rearward direction, and injects urea water in the form of a spray toward the rear in the axial direction of the second passage 10.

The injection valve 14 is arranged on the upstream side of the selective reduction NOx catalyst 23, which is a supply target of urea water. The second passage 10 located on the downstream side of the injection valve 14 and on the upstream side of the NOx catalyst 23 serves as a mixing passage for mixing the urea water injected from the injection valve 10 with the exhaust gas.

Four types of post-treatment members, that is, a first oxidation catalyst 21, a filter 22, a selective reduction NOx catalyst 23, and a second oxidation catalyst 24 are provided in series in the exhaust passage 5 in order from the upstream side.

The first oxidation catalyst 21 oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas, and heats and raises the temperature of the exhaust gas with the heat of reaction at this time.

The filter 22 is a so-called diesel particulate filter (DPF: Diesel Particulate Filter) or a soot filter with a catalyst (CSF: Caterized Soot Filter), and is a continuously regenerating filter carrying a catalyst. The filter 22 is of a wall flow type, collects particulate matter (hereinafter referred to as PM: Particulate Matter) contained in the exhaust gas, and continuously oxidizes the collected PM by a catalytic reaction to burn and remove it.

The selective reduction NOx catalyst (SCR: Selective Catalytic Reduction) 23 _{reacts ammonia NH 3} obtained by hydrolyzing urea water with NOx, and reduces NOx in the exhaust to nitrogen N _2.

The second oxidation catalyst 24 is also referred to as an ammonia slip oxidation catalyst, and oxidizes and removes excess ammonia discharged (slipped) from the NOx catalyst 23.

In the present embodiment, a total of two combinations of the NOx catalyst 23 and the second oxidation catalyst 24 are provided in parallel with each other in the third passage 11 and the fourth passage 12. Further, as shown in FIG. 1, in each combination, the NOx catalyst 23 is formed on the entire upstream carrier 23A and the upstream portion of the downstream carrier 23B, and the second oxidation catalyst 24 is on the downstream side of the downstream carrier 23B. It is formed by a zone coat on the part. However, the carriers of both catalysts may be separate.

The first to fifth passages 9 to 13 and the feed passage 19 are defined by the first to fifth passage pipes 9P to 13P and the feed passage pipe 19P. In the present embodiment, the first to fourth passages 9 to 12 are straight and have a circular cross section, and the feed passage 19 is straight and has an oval cross section. Further, as shown in FIG. 2, for example, the fifth passage 13 is formed linearly at the upper right corner portion of the casing 2. Each pipe corresponding to each passage has the same shape. However, the shape of each passage and each pipe can be changed as appropriate.

Along the exhaust flow direction, the first passage pipe 9P extends from the rear end wall 2R to the front end wall 2F, the second passage pipe 10P extends from the front end wall 2F to the rear partition plate 7, and the third passage pipe 11P and the fourth passage pipe 4P. The passage pipe 12P extends from the rear partition plate 7 to the front partition plate 6, and the fifth passage pipe 13P extends from the front partition plate 6 to the rear end wall 2R. Therefore, the inside of the front end chamber 8F is divided into a portion of the first passage 9, a portion of the second passage 10, a portion of the feed passage 19, and a portion other than that. The inside of the rear end chamber 8R is divided into a portion of the first passage 9, a portion of the fifth passage 13, and other portions.

Next, with reference to FIG. 4, the internal configuration of the second passage 10, which is the main feature of the present embodiment, will be described.

As described above, an injection valve 14 for injecting urea water U toward the rear is provided at the upstream end of the second passage 10. A feed passage 19 is connected to the lower left side surface portion of the second passage 10 located in the front end chamber 8F, and the exhaust gas G is introduced into the second passage 10 from here.

The urea spray and the exhaust gas G are gradually mixed as they proceed to the rear downstream side in the second passage 10. In this embodiment, the following configuration is adopted to promote such mixing.

Inside the second passage 10, an upstream side partition plate 31A and a downstream side partition plate 31B provided apart from each other in the upstream and downstream directions, an upstream side pipe 32A provided in the upstream side partition plate 31A, and a downstream side A downstream pipe 32B provided on the partition plate 31B is arranged. The upstream side partition plate 31A and the downstream side partition plate 31B are provided with the upstream side through hole 33A and the downstream side through hole 33B, respectively, and the upstream side pipe 32A and the downstream side pipe 32B are provided with the upstream side through hole 33A and the downstream side through hole, respectively. It is connected to 33B in communication. In particular, the outlet portion 34 of the upstream side pipe 32A and the inlet portion 35 of the downstream side pipe 31B are arranged in a non-coaxial state with each other. In the figure, the central axis of the outlet portion 34 of the upstream side pipe 32A is indicated by C1, and the central axis of the inlet portion 35 of the downstream side pipe 31B is indicated by C2.

The upstream side partition plate 31A and the downstream side partition plate 31B partition the inside of the second passage 10 to the front and back, that is, to the upstream and downstream sides, respectively. The upstream side partition plate 31A and the downstream side partition plate 31B are formed of a plate material and fixed to the inner peripheral surface of the second passage pipe 10P by welding or the like. In the case of the present embodiment, the upstream partition plate 31A and the downstream partition plate 31B are inclined in the same direction at the inclination angles α1 and α2 with respect to the direction perpendicular to the central axis C of the second passage 10.

The upstream partition plate 31A is inclined so that the upper side where the upstream through hole 33A and the upstream pipe 32A are provided is located rearward with respect to the lower side. The downstream partition plate 31B is inclined so that the lower side on which the downstream through hole 33B and the downstream pipe 32B are provided is located forward with respect to the upper side. In this embodiment, α1 = α2, and the upstream partition plate 31A and the downstream partition plate 31B are parallel to each other. However, α1 and α2 do not have to be equal, and the upstream partition plate 31A and the downstream partition plate 31B do not have to be parallel. Further, at least one of the upstream partition plate 31A and the downstream partition plate 31B may not be inclined.

The upstream side through hole 33A and the downstream side through hole 33B are formed by penetrating the upstream side partition plate 31A and the downstream side partition plate 31B in the plate thickness direction. The upstream side through hole 33A and the downstream side through hole 33B are parallel to the central axis C of the second passage 10, that is, the inclination angle α1 with respect to the direction perpendicular to the plate surface of the upstream side partition plate 31A and the downstream side partition plate 31B. , It is tilted by an angle equal to α2. As shown in FIG. 5, the upstream side through hole 33A and the downstream side through hole 33B are offset with respect to the central axis C of the second passage 10 by equal distances L1 and L2 in the vertical direction. However, the upstream side through hole 33A and the downstream side through hole 33B do not have to be aligned vertically in this way, and can be aligned in any direction, for example, may be aligned horizontally. Further, the offset distances L1 and L2 do not necessarily have to be equal, and may be different from each other.

In the present embodiment, the upstream pipe 32A and the downstream pipe 32B are both formed of a pipe having a circular cross section and a straight tubular cross section, and are arranged so as to project in the space 36 between the upstream partition plate 31A and the downstream partition plate 31B. ing. The upstream side pipe 32A and the downstream side pipe 32B are coaxially connected to the upstream side through hole 33A and the downstream side through hole 33B. Therefore, the upstream pipe 32A and the downstream pipe 32B are also arranged parallel to the central axis C of the second passage 10 and offset by the same distances L1 and L2 in the vertical direction with respect to the central axis C of the second passage 10. Be placed. However, similarly to the above, the upstream pipe 32A and the downstream pipe 32B can be aligned in any direction, and the offset distance can be set arbitrarily.

The inner and outer diameters of the upstream pipe 32A and the downstream pipe 32B are constant. Their inner diameters are made equal to the hole diameters of the upstream side through hole 33A and the downstream side through hole 33B so that a step does not occur at the joint between the pipe and the through hole. The inlet end of the upstream pipe 32A and the outlet end of the downstream pipe 32B are cut diagonally and fixed to the surfaces of the upstream partition plate 31A and the downstream partition plate 31B in the space 36 by welding or the like. Therefore, the upstream pipe 32A and the downstream pipe 32B extend only into the space 36 so as to face each other from the upstream partition plate 31A and the downstream partition plate 31B. The upstream side pipe 32A extends from the upstream side partition plate 31A toward the rear downstream side, and the downstream side pipe 32B extends from the downstream side partition plate 31B toward the front upstream side. However, as a modification, at least one part of the upstream pipe 32A and the downstream pipe 32B may extend out of the space 36.

In the case of the present embodiment, the outlet portion 34 of the upstream side pipe 32A and the inlet portion 35 of the downstream side pipe 32B overlap each other in the front-rear direction, that is, the upstream / downstream direction. The overlap length is indicated by L. However, such overlap does not have to be provided.

As described above, in the present embodiment, the straight tubular upstream pipe 32A and the downstream pipe 32B extend from the upstream partition plate 31A and the downstream partition plate 31B so as to face each other in a state of being parallel and non-coaxial with each other. ..

The flow of the exhaust gas G in the second passage 10 is as follows. As shown by an arrow in FIG. 4, the exhaust gas G introduced from the feed passage 19 into the second passage 10 enters the upstream pipe 32A through the upstream through hole 33A. At this time, since the upstream partition plate 31A is inclined so that the upstream through hole 33A is located rearward, the exhaust gas G flows along the front surface of the upstream partition plate 31A and smoothly reaches the upstream through hole 33A. Can guide you to.

The exhaust gas G flows through the upstream pipe 32A and then is discharged backward along the direction of the outlet portion 34. After that, it turns back toward the front and heads toward the inlet 35 of the downstream pipe 32B. When entering the inlet 35 of the downstream pipe 32B, the exhaust gas G folds backward and then enters the inlet 35 backward along the direction of the inlet 35. In this way, the exhaust gas G is folded back twice before exiting from the outlet portion 34 and entering the inlet portion 35.

After flowing through the downstream pipe 32B, the exhaust gas G is discharged backward from the downstream pipe 32B and the downstream through hole 33B along the direction of the outlet 38. After that, it flows through the second passage 10 and enters the rear end chamber 8R. Since the downstream partition plate 31B is inclined so that the downstream through hole 33B is located forward, the exhaust gas G immediately after being discharged from the downstream through hole 33B is also along the rear surface portion of the downstream partition plate 31B. It is possible to smoothly discharge the air from the through hole 33B on the downstream side.

As described above, in the present embodiment, since the outlet portion 34 of the upstream pipe 32A and the inlet portion 35 of the downstream pipe 31B are arranged in a non-coaxial state with each other, the exhaust gas discharged from the outlet portion 34 of the upstream pipe 32A It is possible to prevent the flow of the gas G from entering the inlet portion 35 of the downstream pipe 31B straight. Then, a bend can be given to the flow of the exhaust gas G between the outlet portion 34 of the upstream side pipe 32A and the inlet portion 35 of the downstream side pipe 31B, and the bending allows the injected urea water and the exhaust gas G to be bent. Mixing can be promoted. Further, this makes it possible to promote the heating of the urea water by the exhaust gas, promote the hydrolysis of the urea water, increase the ammonia production efficiency, and operate the NOx catalyst with high efficiency. And the exhaust gas purification performance can be improved.

Further, in the present embodiment, since the upstream pipe 32A and the downstream pipe 32B are projected into the space 36 between the upstream partition plate 31A and the downstream partition plate 31B, the exhaust gas G is formed in the narrow space 36. The flow can be bent in a relatively complicated manner, and the mixing of urea water and exhaust gas G can be further promoted.

Further, in the present embodiment, since the outlet portion 34 of the upstream pipe 32A and the inlet portion 35 of the downstream pipe 32B overlap each other in the upstream and downstream directions, the above-mentioned double-folding flow can be surely realized, and urea can be reliably realized. The mixing of water and exhaust gas G can be further promoted. Further, the substantial passage length can be expanded within the limited front-rear length range (space 36), and the mixed passage length of the urea water and the exhaust gas G can be substantially expanded. Therefore, effective use of space can be achieved.

Further, in the present embodiment, since the upstream partition plate 31A and the downstream partition plate 31B are inclined as described above, the exhaust gas G is smoothly guided to the upstream through hole 33A, and the exhaust gas G is smoothly guided to the upstream through hole 33B and exhausted from the downstream through hole 33B. The gas G can be discharged smoothly. In addition, the retention of urea water on the surface of the partition plate can be suppressed, and the formation of deposits due to the retention can be suppressed.

In addition, since the upstream partition plate 31A and the downstream partition plate 31B and the upstream pipe 32A and the downstream pipe 32B are constantly exposed to the high temperature exhaust gas, a heat storage body that stores the heat of the exhaust gas. Also works as. Since urea water (or a mixture of urea water and exhaust gas) comes into contact with these heat storage bodies that have stored heat and become hot, the urea water can be heated and its hydrolysis can be promoted.

In particular, in the present embodiment, since the upstream pipe 32A and the downstream pipe 32B are provided, the surface area of the heat storage body and the heat storage body and the urea water are larger than those in the case where only the upstream partition plate 31A and the downstream partition plate 31B are provided. The contact area can be increased and the heating and hydrolysis of urea water can be promoted.

In the exhaust purification device 1 of the present embodiment, an exhaust passage 5 that folds back a plurality of times is formed in the sealed box-shaped casing 2, and a plurality of post-treatment members (catalysts and the like) are arranged in the exhaust passage 5, so that the muffler ( It also functions as a muffler). Therefore, it is not necessary to separately install a muffler, and the manufacturing cost can be reduced.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are designated by the same reference numerals in the drawings, and the description thereof will be omitted. Hereinafter, the differences from the first embodiment will be mainly described.

As shown in FIGS. 6 and 7, the configuration of the outlet portion 34 of the upstream pipe 32A is different from that of the first embodiment in this embodiment. That is, in the first embodiment, the entire upstream pipe 32A was a straight tube, and the outlet portion 34 thereof was also a straight tube. On the other hand, in the present embodiment, except for the outlet portion 34 of the upstream pipe 32A, the outlet portion 34 is a straight tubular portion, but the outlet portion 34 is curved and has a curved tubular shape. As a result, the outlet portion 34 of the upstream side pipe 32A and the inlet portion 35 of the downstream side pipe 31B are arranged in a state of being non-parallel and non-coaxial with each other.

In the present embodiment, the outlet portion 34 is curved in a direction avoiding the downstream pipe 31B, and is curved so as to be obliquely rearward and downward to the left. However, the orientation is not limited to this. The outlet portion 34 is curved so as to be outward in the radial direction with respect to the central axis C3 of the inlet portion 37. The angle formed by the central axis C3 of the inlet portion 37 and the central axis C2 of the outlet portion 34, that is, the bending angle α3 is preferably an obtuse angle as in the present embodiment. As a result, the bending becomes loose, and the resistance to the flow of the exhaust gas G can be reduced. The central axis C2 of the outlet portion 34 is defined by the central axis at the position of the outlet end (pipe end) of the outlet portion 34.

The flow of the exhaust gas G in this embodiment is as follows. As shown by arrows in FIGS. 6 and 7, the exhaust gas G discharged diagonally backward to the left and downward from the outlet portion 34 of the upstream pipe 32A swirls along the inner peripheral surface of the second passage pipe 10P while swirling. It folds forward, then folds backward, and enters the inlet 35 of the downstream pipe 32B.

Therefore, in addition to the flow that folds back twice in the front-rear direction, the flow in the turning direction can be added, and the mixing of the urea water and the exhaust gas G can be further promoted. And the heating and hydrolysis of urea water can be further promoted.

The remaining effects are the same as those in the first embodiment. Regarding the modified example of the present embodiment, the inlet portion 35 of the downstream pipe 32B can also be curved to form a bent tubular shape.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.

As shown in FIGS. 8 and 9, in the present embodiment, the direction of inclination of the downstream partition plate 31B, the direction of the upstream pipe 32A, and the installation position and orientation of the downstream pipe 32B are mainly the same as those of the first embodiment. Is different.

That is, the direction of inclination of the downstream partition plate 31B is opposite to that of the first embodiment, and the downstream partition plate is located so that the upper side where the downstream through hole 33B and the downstream pipe 32B are provided is located forward with respect to the lower side. 31B is tilted. However, the magnitude of the inclination angle is α2, which is the same as that of the first embodiment. As a result, the upstream partition plate 31A and the downstream partition plate 31B are arranged so as to be mirror-symmetrical as shown in FIG.

An upstream side through hole 33A and a downstream side through hole 33B are provided above and at the same height position of the upstream side partition plate 31A and the downstream side partition plate 31B, and a straight tubular upstream side pipe 32A and a downstream side pipe 32B are provided there. Is installed. The upstream pipe 32A is arranged so as to be slightly inclined so that the outlet portion 34 faces the rear diagonally lower left, and the downstream pipe 32B is arranged so that the inlet 35 thereof faces the front diagonally lower right so that the pipes do not interfere with each other. It is arranged at a slight inclination. Therefore, the outlet portion 34 of the upstream side pipe 32A and the inlet portion 35 of the downstream side pipe 31B are arranged in a state of being non-parallel and non-coaxial with each other.

The outlet portion 34 of the upstream pipe 32A and the inlet portion 35 of the downstream pipe 32B are in contact with each other at their overlapping portions. It is preferred that the contacts are welded and the contact area is substantially increased.

The directions of the upstream side through hole 33A and the downstream side through hole 33B are slightly changed from the first embodiment so as to be coaxial with the inlet portion 37 of the upstream side pipe 32A and the outlet portion 38 of the downstream side pipe 32B. There is.

The flow of the exhaust gas G in this embodiment is as follows. As shown by arrows in FIGS. 8 and 9, the exhaust gas G discharged diagonally backward to the left and downward from the outlet portion 34 of the upstream pipe 32A swirls along the inner peripheral surface of the second passage pipe 10P while swirling. It folds forward, then folds backward, and enters the inlet 35 of the downstream pipe 32B.

Therefore, as in the second embodiment, in addition to the flow that folds back twice in the front-rear direction, the flow in the turning direction can be added, and the mixing of the urea water and the exhaust gas G can be further promoted. And the heating and hydrolysis of urea water can be further promoted.

Further, in the present embodiment, urea water and exhaust gas G are mixed using a relatively wide space 36 below the upstream pipe 32A and the downstream pipe 32B before exiting from the outlet 34 and entering the inlet 35. It can, and this can also promote mixing.

Further, in the present embodiment, since the upstream pipe 32A and the downstream pipe 32B are in contact with each other, the exposed area of the pipe surface into the space 36 is reduced, heat dissipation from the pipe into the space 36 is suppressed, and the pipe is used. The heat storage effect can be enhanced. In the first and second embodiments as well, a modified example in which the upstream pipe 32A and the downstream pipe 32B are brought into contact with each other is possible.

The remaining effects are the same as those in the first embodiment.

Although the embodiments of the present invention have been described in detail above, various other embodiments of the present invention can be considered.

(1) The present invention can be applied not only to an exhaust gas purification device having a closed box-shaped casing as described above, but also to an ordinary exhaust gas purification device.

(2) The catalyst does not necessarily have to be a NOx catalyst, and may not be a selective reduction type NOx catalyst. The reducing agent supplied to the catalyst can also be changed according to the type of catalyst.

(3) The cross-sectional shape of the upstream pipe and the downstream pipe is arbitrary, and the inner and outer diameters thereof may not be constant or may change.

(4) The number of combinations of the partition plate and the pipe is two in the above embodiment, but may be three or more. In this case, the present invention can be applied to any two combinations adjacent to each other on the upstream and downstream sides.

(5) The upstream pipe and the downstream pipe do not have to extend so as to face each other. For example, the upstream pipe may extend from the upstream partition plate to the rear downstream side, and the downstream pipe may extend from the downstream partition plate to the rear downstream side. Even in this way, if the outlet portion of the upstream pipe and the inlet portion of the downstream pipe are in a non-coaxial state, the flow of exhaust gas from the former to the latter can be bent. Even in this way, the heat storage effect and the urea water heating effect of both pipes can still be guaranteed.

The configurations of each of the above embodiments can be combined partially or wholly, unless otherwise inconsistent. The embodiment of the present invention is not limited to the above-described embodiment, and all modifications, applications, and equivalents included in the idea of the present invention defined by the claims are included in the present invention. Therefore, the present invention should not be construed in a limited manner and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 Exhaust purification device 5 Exhaust passage 10 Second passage 14 Injection valve 23 NOx catalyst 31A Upstream partition plate 31B Downstream partition plate 33A Upstream through hole 33B Downstream through hole 32A Upstream pipe 32B Downstream pipe 34 Outlet 35 Inlet Part 36 space

Claims (5)

The exhaust passage through which the exhaust gas of the internal combustion engine flows, and
With the catalyst arranged in the exhaust passage,
An injection valve provided on the upstream side of the catalyst and injecting a reducing agent into the exhaust passage.
An upstream partition plate and a downstream partition plate provided apart from each other inside the exhaust passage located on the downstream side of the injection valve and on the upstream side of the catalyst.
The upstream side through hole and the downstream side through hole provided in the upstream side partition plate and the downstream side partition plate, respectively,
An upstream pipe that communicates with the upstream through hole and is provided in the upstream partition plate,
A downstream pipe that communicates with the downstream through hole and is provided in the downstream partition plate.
With
An exhaust gas purification device for an internal combustion engine, characterized in that the outlet portion of the upstream pipe and the inlet portion of the downstream pipe are arranged in a non-coaxial state with each other. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the upstream pipe and the downstream pipe project into a space between the upstream partition plate and the downstream partition plate. The exhaust gas purification device for an internal combustion engine according to claim 2, wherein the outlet portion of the upstream pipe and the inlet portion of the downstream pipe overlap each other in the upstream and downstream directions. The exhaust gas purification device for an internal combustion engine according to claim 2 or 3, wherein the upstream pipe and the downstream pipe are in contact with each other. The exhaust gas purification of an internal combustion engine according to any one of claims 1 to 4, wherein at least one of the upstream partition plate and the downstream partition plate is inclined in a direction perpendicular to the central axis of the exhaust passage. Device.

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