JP6981156B2 - 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 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. 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,
With a turn-back passage provided inside the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, the flow of exhaust gas is turned back from the forward flow direction to the backflow direction and then turned back in the forward flow direction. ,
An exhaust gas purification device for an internal combustion engine is provided.

Preferably, the turn-back passage is
A closing member having a communication pipe that closes the peripheral portion in the exhaust passage and protrudes toward the upstream side.
A cover member that covers the inlet of the communication pipe with a gap from the upstream side,
It is defined by.

Preferably, the cover member has a tapered portion with the tip end facing upstream.

Preferably, the tapered shape is a conical shape.

Preferably, the inlet portion of the communication pipe has a plurality of divided pieces that are divided in the circumferential direction, and the plurality of divided pieces are alternately bent inward and outward in the radial direction.

Preferably, the exhaust passage is located adjacent to the inner exhaust passage located on the inner side in the radial direction and the outer side in the radial direction of the inner exhaust passage, surrounds the inner exhaust passage, and is discharged from the inner exhaust passage. Including the outer exhaust passage that allows the exhaust gas to flow in the opposite direction,
The folded passage is arranged in the inner exhaust passage.

Preferably, it is further provided with a heat storage member provided at a position on the downstream side of the injection valve and on the upstream side of the turn-back passage to store the heat of the exhaust gas.

Preferably, the heat storage member has a tapered portion whose tip end side is directed to the upstream side, and has a plurality of openings in the portion.

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

It is a vertical sectional side view which shows the whole structure of the exhaust gas purification apparatus which concerns on 1st Embodiment of this invention. It is a vertical sectional rear view of the exhaust gas purification apparatus, and is the II-II sectional view of FIG. It is a vertical sectional front view of the exhaust gas purification apparatus, and is the cross-sectional view III-III of FIG. It is a vertical sectional side view which shows the structure of the inside of the 2nd passage. It is a vertical sectional side view which shows the internal structure of the 2nd passage in 2nd Embodiment. It is a vertical sectional side view which shows the whole structure of the exhaust gas purification apparatus which concerns on 2nd Embodiment. It is a vertical sectional side view which shows the internal structure of the 2nd passage in 3rd Embodiment. It is a vertical sectional front view of a heat storage member, and is VIII-VIII sectional view of FIG. It is a vertical sectional front view of the communication pipe, and is the IX-IX sectional view of FIG. It is sectional drawing of the divided piece.

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. On the rear end wall 2R of the casing 2, a device inlet pipe 3 for introducing the exhaust gas G of the engine into the casing 2 and a device outlet pipe 4 for discharging the exhaust gas G from the casing 2 are attached. 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 pipes and plates (stainless steel in the present embodiment) 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 the shape thereof 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 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 is arranged as it is in the lower left of the casing 2 and goes straight through the first passage 9 extending in the front-rear direction. 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 in 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 forward direction to the backward direction. 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 inside 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 backward to forward.

The exhaust gas flows from the rear to the front in the third and fourth passages 11 and 12, 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 forward direction to the backward direction. 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 position of the upstream end of the second passage 10. The injection valve 10 is arranged coaxially with the second passage 10 in the rear direction, and injects urea water in a spray form 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 reaction heat at this time.

The filter 22 is a so-called diesel particulate filter (DPF: Diesel Particulate Filter) or a catalyzed soot filter (CSF: Caterized Soot Filter), and is a continuously regenerative 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 NOx with ammonia NH 3} obtained by hydrolyzing urea water, and reduces NOx in the exhaust to nitrogen N _2.

The second oxidation catalyst 24, also referred to as an ammonia slip oxidation catalyst, oxidizes and removes excess ammonia discharged (slip) 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 in 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. Further, 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 a portion other than that.

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 the present embodiment, in order to promote such mixing, a folded passage 30 is provided inside the second passage 10. As shown by an arrow in the figure, the turn-back passage 30 is configured to turn back the flow of the exhaust gas G from the forward flow direction to the backflow direction and then turn back in the forward flow direction. In the present embodiment, the forward flow direction refers to the direction of the flow from the front to the rear, and the backflow direction means the direction of the flow from the rear to the front.

Specifically, the folded passage 30 is defined by the closing member 31 and the cover member 32. These are arranged coaxially with the central axis C of the second passage 10.

The closing member 31 closes the peripheral edge portion in the second passage 10 and has a communication pipe 33 projecting toward the upstream side (front side) in the central portion thereof. The communication pipe 33 is for communicating the upstream side and the downstream side of the closing member 31. In the present embodiment, the communication pipe 33 is integrally formed with the closing member 31, but it may be formed separately and fixed by welding or the like. The closing member 31 is a plate-shaped and ring-shaped member as a whole, and has a curved cross-sectional shape that is convex toward the downstream side (rear side), specifically, a semi-circular cross-sectional shape. As a result, the closing member 31 can smoothly guide the out-corner side of the exhaust gas G to be turned back for the first time.

The cover member 32 covers the communication pipe 33 with a gap from the upstream side. The cover member 32 has a tapered portion whose tip end side is directed toward the upstream side. Here, the "tapered shape" refers to a shape that extends from the proximal end side toward the distal end side and gradually reduces in diameter toward the distal end side. The tapered shape includes each shape such as a cone, a weight base, a hemisphere, and a dome shape. The cone shape includes each shape such as a cone, a quadrangular pyramid, and a polygonal weight. The frustum shape includes each shape such as a truncated cone, a quadrangular pyramid, and a polygonal frustum. As for the tapered shape, any shape can be adopted from each of these shapes, but in this embodiment, a conical shape is adopted in consideration of ease of processing and the like.

The cover member 32 has a conical shape almost entirely except for the short straight tubular downstream end (rear end) 32A. The cover member 32 is made of a plate material. The maximum outer diameter of the cover member 32 is smaller than the inner diameter of the second passage pipe 10P and larger than the outer diameter of the communication pipe 33. In this embodiment, the maximum outer diameter of the cover member 32 is defined by the downstream end portion 32A. The downstream end portion 32A covers the outer peripheral portion of the communication pipe 33 with a gap from the outside in the radial direction. A gap is also formed in front of the communication pipe 33 with the cover member 32. A curved convex plate 34 whose central portion protrudes toward the inside of the communication pipe 33 is integrally fixed to the back side of the cover member 32 by welding or the like. The cover member 32 is coaxially held in the second passage 10 by a plurality of columns (not shown).

In the present embodiment, the folded passage 30 is provided at the exit portion of the second passage 10. The communication pipe 33 is open in the rear end chamber 8R.

As shown in the figure, when the exhaust gas G makes the first turn in the turn-back passage 30, the out-corner side of the exhaust gas G is guided by the closing member 31, and the in-corner side of the exhaust gas G is the downstream end of the cover member 32. Guided by section 32A. When the exhaust gas G makes the second turn, the out-corner side of the exhaust gas G is guided by the cover member 32 and the curved convex plate 34, and the in-corner side of the exhaust gas G is guided by the inlet end of the communication pipe 33. To.

In this way, the exhaust gas G is folded back twice when passing through the folded passage 30, one folded back toward the inner peripheral side from the outermost peripheral portion in the second passage 10, and then another one toward the inner peripheral side. It is turned back and then goes straight into the rear end chamber 8R.

In the present embodiment, since the folded passage 30 is provided inside the second passage 10, the substantial passage length is expanded within the limited front-rear length range of the second passage 10, and urea spray and exhaust gas are used. The mixed passage length of G can be increased. Therefore, it is possible to surely promote the mixing of the injected urea water and the exhaust gas. 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 purification performance can be improved.

Further, when the exhaust gas G makes the first turn, the out corner side of the exhaust gas G is guided by the curved closing member 31, so that the turn can be made smoothly. Similarly, when the exhaust gas G makes the second turn, the out-corner side of the exhaust gas G is guided by the back side (rear side) of the conical cover member 32 and the curved convex plate 34. , Can be folded back smoothly. Therefore, the pressure loss when the exhaust gas G passes through the turn-back passage 30 can be minimized.

In addition, since the cover member 32 has a tapered shape (conical shape in this embodiment), the exhaust gas G toward the rear can be smoothly guided to the outer peripheral side. Since the cover member 32 is constantly exposed to the high-temperature exhaust gas, it also functions as a heat storage body for storing the heat of the exhaust gas. When urea water (or a mixture of urea water and exhaust gas) hits the high-temperature cover member 32 that has stored heat, the urea water can be heated to promote its hydrolysis.

In the present embodiment, the space on the back side of the conical cover member 32 is used to form the folded passage 30, so that the space utilization efficiency can be improved.

Further, since the return passage 30 is provided at the outlet portion of the second passage 10 and the cover member 32 is separated from the injection valve 14 as much as possible, the urea water is evaporated as much as possible in front of the cover member 32 before reaching the cover member 32. be able to. Therefore, it is possible to suppress as much as possible that droplets of urea water adhere to the cover member 32, the temperature of the cover member 32 drops, and the heat storage effect is lost.

In the exhaust purification device 1 of the present embodiment, a plurality of folding exhaust passages 5 are formed in the sealed box-shaped casing 2, and a plurality of post-treatment members (catalysts and the like) are arranged in the exhaust passages 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.

The folded passage 30 of the present embodiment is formed only inside the exhaust passage 5, not by folding the exhaust passage 5 itself. Therefore, the folding back when entering the third and fourth passages 11 and 12 from the second passage 10 via the rear end chamber 8R is irrelevant to the folding passage 30 of the present embodiment.

The following modifications of this embodiment are also possible. For example, it is possible to provide a plurality of folded passages 30 as needed. The closing member 31 has a curved cross-sectional shape as a whole, including the communication pipe 33, but may have an angular cross-sectional shape. The curved convex plate 34 may be omitted. However, the presence of the curved convex plate 34 is preferable because it prevents the exhaust gas from infiltrating to the back side of the tip of the cone of the cover member 32 and can smoothly return the exhaust gas at an earlier timing. Not only one communication pipe 33 but a plurality of communication pipes 33 may be provided in the central portion.

[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 FIG. 5, the configuration of the vicinity of the second passage 10 of the present embodiment is mainly different from that of the first embodiment. That is, the second passage 10 includes an inner second passage 41 located on the inner side in the radial direction and an outer second passage 42 located on the outer side in the radial direction with the central axis C as a reference. The outer second passage 42 is located adjacent to the outer side in the radial direction of the inner second passage 41, surrounds the inner second passage 41, and exhaust gas discharged from the outlet portion of the inner second passage 41 is discharged to the inner second passage 41. 2 Flow in the direction opposite to the flow direction in the passage 41. The folded passage 30 is arranged in the inner second passage 41.

The inner second passage 41 and the outer second passage 42 are arranged coaxially with the central axis C. The inner second passage 41 and the outer second passage 42 are defined by the inner second passage pipe 41P and the outer second passage pipe 42P, respectively. Therefore, these inner and outer second passage pipes 41P and 42P are coaxial double pipes. The downstream end (rear end) of the outer second passage pipe 42P is closed by a curved convex plate 43 similar to the curved convex plate 34 described above. The curved convex plate 43 is arranged symmetrically with the curved convex plate 34.

The folded passage 30 is arranged near the exit portion of the inner second passage 41, and is arranged slightly upstream from the first embodiment.

According to this configuration, the exhaust gas G introduced from the feed passage 19 to the inner second passage 41 flows rearward in the inner second passage 41, passes through the turn-back passage 30, and is transmitted from the inner second passage 41. It is discharged. After that, it hits the curved convex plate 43, is folded back, enters the outer second passage 42, flows forward in the outer second passage 42, and is discharged to the front end chamber 8F. When the exhaust gas G is folded back from the inner second passage 41 to the outer second passage 42, the out corner side of the exhaust gas G is guided by the curved convex plate 43, so that the folding can be smoothly performed.

In the present embodiment, since the outer second passage 42 is provided in a double tubular shape on the radial outer side of the inner second passage 41, the substantial passage length is further increased within the limited front-rear length range of the second passage 10. It can be expanded and the length of the mixed passage of urea water and the exhaust gas G can be further expanded. Therefore, it is possible to further promote the mixing of urea water and exhaust gas.

Further, since the exhaust gas flowing through the outer second passage 42 can keep or heat the exhaust gas and the urea water in the inner second passage 41, the hydrolysis of the urea water can be further promoted.

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

Incidentally, in the present embodiment, the direction of the exhaust gas G discharged from the second passage 10 is opposite to that of the first embodiment, and the exhaust gas G is discharged into the front end chamber 8F. Therefore, the configuration inside the casing 2 is slightly changed as shown in FIG.

That is, the arrangement of the NOx catalyst 23 and the second oxidation catalyst 24 in the third and fourth passages 11 and 12 is reversed. The fifth passage 13 is omitted, and the positions of the front partition plate 6 and the rear partition plate 7 where the fifth passage 13 was located are closed.

The exhaust gas G discharged from the outer second passage 42 into the front end chamber 8F branches in two directions and enters the third passage 11 and the fourth passage 12. At this time, the exhaust gas is turned back from the forward direction to the backward direction. The exhaust gas flows from the front to the rear in the third and fourth passages 11 and 12, 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 rear end chamber 8R, is collected in the device outlet pipe 4 in the rear end chamber 8R, and is discharged.

In the present embodiment, the inner second passage 41 and the outer second passage 42 correspond to the inner exhaust passage and the outer exhaust passage as defined in the claims, respectively.

Regarding the modification, the downstream end (rear end) of the outer second passage pipe 42P may be closed by a simple flat plate.

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

As shown in FIG. 7, the configuration in the vicinity of the second passage 10 is also different from that of the first embodiment in the present embodiment. The overall configuration is the same as that shown in FIG.

The front and rear lengths of the second passage 10 and the second passage pipe 10P are shorter than those of the first embodiment, and the positions of their rear ends are located in front of the rear partition plate 7. Instead, the communication pipe 33 extends rearward to the position of the rear bulkhead plate 7.

The closing member 31 is integrally formed with the second passage pipe 10P by bending the rear end portion of the second passage pipe 10P inward in the radial direction in a semicircular cross section. The straight tubular downstream end 32A of the cover member 32 is connected to the second passage pipe 10P via a plurality of columns 51. In this embodiment, the curved convex plate 34 is omitted.

The communication pipe 33 is formed separately from the closing member 31, and is fixed to the central opening 31A of the closing member 31 by welding or the like. The inlet portion 33B of the communication pipe 33 projects upstream (front side) with respect to the central opening portion 31A. At a position downstream (rear side) from the central opening 31A, a tapered diameter expansion portion 33A is formed in the communication pipe 33 so that the exhaust gas G can be smoothly discharged.

In the present embodiment, a heat storage body different from the cover member 32, that is, a heat storage member 52 is additionally provided. The heat storage member 52 is provided at a position on the downstream side of the injection valve 14 and on the upstream side of the return passage 30. In particular, the heat storage member 52 is provided in the second passage 10 at a position upstream of the cover member 32, and is provided at a position closer to the injection valve 14 than the cover member 32.

Like the cover member 32, the heat storage member 52 has a tapered portion whose tip end side is directed toward the upstream side. Here, as the tapered shape, a truncated cone shape is adopted in consideration of ease of processing and the like.

The heat storage member 52 is provided over the entire cross section of the second passage 10, has a truncated cone-shaped tapered portion 55 which is a substantially entire portion thereof, and has a plurality of openings 53 in the tapered portion 55.

More specifically, the heat storage member 52 is formed of a plate material, and the tapered portion 55 has a truncated cone shape coaxial with the central axis C. The base end portion 54 forming the bottom of the truncated cone has a ring shape perpendicular to the central axis C, and is fixed to the inner peripheral surface of the second passage pipe 10P by welding or the like. As shown in FIG. 8, a plurality of substantially triangular or trapezoidal openings 53 that are long in the front-rear direction are formed in the tapered portion 55 that tapers toward the upstream side from the base end portion 54. To. As a result, fins 56 are formed between the openings 53. In the present embodiment, the fins 56 are along the circumferential direction of the tapered portion 55.

A tip plate 58 perpendicular to the central axis C is fixedly attached to the tip portion 57 of the heat storage member 52 forming the top of the truncated cone. The tip plate 58 has a role of closing the tip portion 57, a role of receiving the flow of exhaust gas at the front surface and storing heat, and a role of applying urea water injected from the injection valve 14 to promote heating of the urea water. ..

On the other hand, the inlet portion 33B of the communication pipe 33 has a plurality of divided pieces 33C divided in the circumferential direction thereof. As also shown in FIGS. 9 and 10, these plurality of divided pieces 33C are alternately bent inward and outward in the radial direction toward the circumferential direction.

More specifically, a plurality of slits are provided at equal intervals in the circumferential direction from the front end of the inlet portion 33B of the communication pipe 33 to the rear by a predetermined distance, and the inlet portion 33B is inside in the radial direction with the position of the slit as a boundary. And alternately bent outwards. As a result, a plurality of divided pieces 33C having different orientations are formed alternately.

According to this configuration, the exhaust gas G introduced from the feed passage 19 into the inner second passage 41 flows rearward in the inner second passage 41, then hits the heat storage member 52 and passes through the plurality of openings 53. Then, it enters the inside of the heat storage member 52. Then, while being guided by the cover member 32, it reaches the folded passage 30, passes through the folded passage 30, and then is discharged to the rear end chamber 8R through the communication pipe 33.

When the exhaust gas passes through the heat storage member 52, the heat of the exhaust gas is transferred to the heat storage member 52, and the heat storage member 52 is stored. When the urea water in the exhaust gas hits the heat storage member 52, the urea water is heated and its hydrolysis is promoted. After that, the urea water also hits the cover member 32, which further promotes the heating and hydrolysis of the urea water.

When the exhaust gas passes through the heat storage member 52, the flow of the exhaust gas is somewhat disturbed, so that the mixing of the exhaust gas and the urea water can be promoted.

On the other hand, when the exhaust gas enters the inlet portion 33B of the communication pipe 33, the exhaust gas also enters from the gap 33D between the divided pieces 33C as shown by an arrow in FIG. Since the flow that enters straight in the axial direction of the communication pipe 33 and the flow that enters through the gap 33D from a different direction collide with each other, the flow is turbulent inside the inlet portion 33B, which causes turbulence of the flow. It can promote the mixing of exhaust gas and urea water.

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

As described above, since the heat storage member 52 is provided in the present embodiment, it is possible to promote the mixing of the urea water and the exhaust gas and the heating of the urea water, and promote the hydrolysis of the urea water. Further, since the plurality of divided pieces 33C are provided at the inlet portion 33B of the communication pipe 33, the mixing of the urea water and the exhaust gas can be promoted, and the hydrolysis of the urea water can be promoted.

Since the heat storage member 52 has a tapered shape (conical cone shape in this embodiment), an increase in exhaust resistance due to the provision of the heat storage member 52 can be suppressed as much as possible. Further, since the divided piece 33C is simply bent by cutting the pipe end portion of the communicating pipe 33, the processing is easy.

Regarding the modification of the present embodiment, for example, the shape of the opening 53 of the heat storage member 52 may be changed, and may be, for example, a circle or a quadrangle. Further, regarding the communication pipe 33, for example, it is conceivable to provide a plurality of divided pieces 33C separately and fix them by welding or the like. The second embodiment and the second embodiment may be combined to form a double pipe structure in the second passage 10 of the present 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 folded passage according to 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.

The configurations of each of the above embodiments can be partially or wholly combined, as long as there is no particular contradiction. 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 scope of 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 30 Folded passage 31 Closing member 32 Cover member 33 Communication pipe 33B Inlet 33C Divided piece 41 Inner second passage 42 Outer second passage 52 Heat storage member 53 Opening Department

Claims (6)

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,
With a turn-back passage provided inside the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, the flow of exhaust gas is turned back from the forward flow direction to the backflow direction and then turned back in the forward flow direction. ,
Equipped with
The turnaround passage
A closing member having a communication pipe that closes the peripheral portion in the exhaust passage and protrudes toward the upstream side.
A cover member that covers the inlet of the communication pipe with a gap from the upstream side,
An exhaust gas purification device for an internal combustion engine, which is characterized by being defined by an internal combustion engine. The exhaust gas purification device for an internal combustion engine according to claim 1 , wherein the cover member has a tapered portion whose tip side is directed to the upstream side. The exhaust gas purification device for an internal combustion engine according to claim 2 , wherein the tapered shape is a conical shape. The inlet portion of the communication pipe has a plurality of divided pieces divided in the circumferential direction, and the plurality of divided pieces are alternately bent inward and outward in the radial direction. Claims 1 to 3. The exhaust gas purification device for an internal combustion engine according to any one of the above. 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,
With a turn-back passage provided inside the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, the flow of exhaust gas is turned back from the forward flow direction to the backflow direction and then turned back in the forward flow direction. ,
Equipped with
The exhaust passage is located adjacent to the inner exhaust passage located inside in the radial direction and the outer side in the radial direction of the inner exhaust passage, surrounds the inner exhaust passage, and exhaust gas discharged from the inner exhaust passage. Including the outer exhaust passage that allows the air to flow in the opposite direction,
The folded passage is arranged in the inner exhaust passage.
An exhaust gas purification device for an internal combustion engine. 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,
With a turn-back passage provided inside the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, the flow of exhaust gas is turned back from the forward flow direction to the backflow direction and then turned back in the forward flow direction. ,
A heat storage member provided at a position on the downstream side of the injection valve and on the upstream side of the turn-back passage to store the heat of the exhaust gas .
Equipped with
The heat storage member has a tapered portion whose tip side is directed to the upstream side, and has a plurality of openings in the portion.
An exhaust gas purification device for an internal combustion engine.

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