CN111263849B

CN111263849B - Exhaust gas purification device for internal combustion engine

Info

Publication number: CN111263849B
Application number: CN201880064351.5A
Authority: CN
Inventors: 伊藤朝幸
Original assignee: Isuzu Motors Ltd
Current assignee: Isuzu Motors Ltd
Priority date: 2017-10-02
Filing date: 2018-09-27
Publication date: 2021-12-31
Anticipated expiration: 2038-09-27
Also published as: WO2019069792A1; JP2019065782A; JP6981156B2; CN111263849A

Abstract

An exhaust gas purification device for an internal combustion engine includes: an exhaust passage through which exhaust gas of the internal combustion engine flows; a catalyst disposed in the exhaust passage; an injection valve (14) that is provided upstream of the catalyst and injects the reducing agent into the exhaust passage; and a return passage (30) which is provided inside the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, and which is configured to return the flow of the exhaust gas from the forward flow direction to the reverse flow direction and then to the forward flow direction.

Description

Exhaust gas purification device for internal combustion engine

Technical Field

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

Background

A selective reduction type NOx catalyst that reduces and removes NOx (nitrogen oxides) in exhaust gas is provided in an exhaust passage of a diesel engine. An injection valve for injecting urea water is provided upstream of the NOx catalyst. Ammonia NH obtained by hydrolyzing urea water by NOx catalyst₃Reacts with NOx to reduce NOx in the exhaust gas to nitrogen N₂。

[ Prior art documents ]

[ patent document ]

Patent document 1: international publication No. 2010/053033

Patent document 2: japanese laid-open patent application No. 2008-144644

Patent document 3: japanese unexamined patent publication No. 2006-77576

Disclosure of Invention

[ problems to be solved by the invention ]

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

The present disclosure is therefore made in view of the above circumstances, and an object thereof is to provide an exhaust gas purification apparatus for an internal combustion engine capable of promoting mixing of injected urea water and exhaust gas.

[ means for solving the problems ]

According to an aspect of the present disclosure, there is provided an exhaust purification apparatus of an internal combustion engine, characterized by comprising:

an exhaust passage through which exhaust gas of the internal combustion engine flows,

a catalyst disposed in the exhaust passage,

an injection valve that is provided on an upstream side of the catalyst and injects a reducing agent into the exhaust passage, and

and a return passage provided in the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, the return passage being configured to return the flow of the exhaust gas from the forward flow direction to the reverse flow direction and then to return the exhaust gas to the forward flow direction.

Preferably the reentrant passageway is defined by a closure member and a cover member,

the closing member closes a peripheral edge portion in the exhaust passage and has a communication pipe protruding toward an upstream side,

the cover member covers the inlet portion of the communication pipe from the upstream side with a gap.

Preferably, the cover member has a portion of which the front end side is tapered toward the front end on the upstream side.

Preferably, the front tapering shape is a conical shape.

Preferably, the inlet portion of the communication pipe has a plurality of segments divided in the circumferential direction thereof, and the plurality of segments are bent alternately radially inward and outward.

Preferably, the exhaust passage includes an inner exhaust passage and an outer exhaust passage, the inner exhaust passage is located radially inward, and the outer exhaust passage is located adjacent to the radially outward side of the inner exhaust passage and surrounds the inner exhaust passage, so that the exhaust gas discharged from the inner exhaust passage flows in the opposite direction.

Preferably, the exhaust gas recirculation system further includes a heat storage member that stores heat of the exhaust gas, the heat storage member being provided at a position downstream of the injection valve and upstream of the return passage.

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

Effects of the invention

According to the present disclosure, an exhaust gas purification apparatus for an internal combustion engine capable of promoting mixing of injected urea water and exhaust gas can be provided.

Drawings

Fig. 1 is a vertical side view showing the entire structure of an exhaust gas purification device according to embodiment 1 of the present invention.

Fig. 2 is a longitudinal rear view of the exhaust gas purifying device, and is a sectional view II-II of fig. 1.

Fig. 3 is a longitudinal front view of the exhaust gas purifying device, and is a sectional view III-III of fig. 1.

Fig. 4 is a vertical sectional side view showing the internal structure of the 2 nd duct.

Fig. 5 is a vertical cross-sectional side view showing the internal structure of the 2 nd duct of embodiment 2.

Fig. 6 is a vertical cross-sectional side view showing the entire structure of the exhaust gas purifying device according to embodiment 2.

Fig. 7 is a vertical sectional side view showing the internal structure of the 2 nd duct of embodiment 3.

Fig. 8 is a longitudinal sectional front view of the heat storage member, and is a sectional view VIII-VIII of fig. 7.

Fig. 9 is a front longitudinal sectional view of the communication pipe, and is a sectional view from IX to IX of fig. 7.

Fig. 10 is a sectional view of the divided piece.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. Note that the present disclosure is not limited to the following embodiments.

[ embodiment 1 ]

Fig. 1 to 3 show an overall structure of an exhaust gas purification device according to embodiment 1 of the present disclosure. Fig. 1 is a longitudinal sectional side view (sectional view I-I of fig. 2), fig. 2 is a longitudinal sectional rear view (sectional view II-II of fig. 1), and fig. 3 is a longitudinal sectional front view (sectional view III-III of fig. 1). For convenience, the directions of the orthogonal three axes, that is, the directions of the front, rear, left, right, up, and down axes are determined as shown in the drawing. However, it should be noted that the directions are determined only for convenience of explanation of the illustrated arrangement.

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

As shown in the drawing, the exhaust gas purifying apparatus 1 includes a box-shaped sealed casing 2 that houses a plurality of members (catalysts, etc.) described later in a compact and packaged state. The case 2 of the present embodiment has a rectangular parallelepiped shape. Mounted on the rear end wall 2R of the housing 2 are: a device inlet pipe 3 for introducing exhaust gas G of the engine into the casing 2; and a device outlet pipe 4 for discharging the exhaust gas G from the inside of the casing 2. However, the positions of the device inlet pipe 3 and the device outlet pipe 4 may be set arbitrarily.

The exhaust passage 5 through which the exhaust gas G flows is defined by appropriately partitioning a space by attaching a plurality of pipes and plates made of metal (stainless steel in the present embodiment) inside the casing 2 by welding or the like. The "exhaust passage" refers to an arbitrary space through which the exhaust gas G flows, and has an arbitrary shape. Can be tubular or chamber-shaped. The exhaust passage 5 is configured to turn the exhaust gas G back and forth a plurality of times in the front-rear direction.

A front partition plate 6 and a rear partition plate 7 for partitioning the inside of the case 2 into front and rear are provided in the case 2. A front end chamber 8F is defined between the front side partition plate 6 and the front end wall 2F of the housing 2. A rear end chamber 8R is defined between the rear side partition plate 7 and the rear end wall 2R of the housing 2. An intermediate chamber 8M is defined between the front side partition plate 6 and the rear side partition plate 7.

Hereinafter, the main flow of the exhaust gas G in the casing 2 will be described in general. This main flow is indicated by the arrows in fig. 1 to 3.

The exhaust gas flowing forward in the apparatus inlet pipe 3 is directly guided straight in the 1 st duct 9 disposed at the lower left in the casing 2 and extending in the front-rear direction, and passes through the 1 st oxidation catalyst 21 and the filter 22 in this order. The exhaust gas then passes through the transfer passage 19 in the transfer pipe 19P disposed in the front end chamber 8F, and enters the 2 nd passage 10 as a mixing passage disposed in the center portion in the casing 2. 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 2 nd duct 10, enters the rear end chamber 8R, branches in two directions as shown in fig. 2, and enters the 3 rd duct 11 disposed at the lower right in the casing 2 and the 4 th duct 12 disposed at the upper left in 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 3 rd and 4

th passages

11 and 12, and passes through the NOx catalyst 23 and the 2 nd oxidation catalyst 24 in this order. The exhaust gas then enters the front end chamber 8F, and as shown in fig. 3, is collected in the 5 th passage 13 disposed at the upper right in the housing 2. At this time, the exhaust gas is turned back from the forward direction to the backward direction. The exhaust gas then flows from front to back in the 5 th channel 13, directly goes to the device outlet pipe 4 and is discharged.

As described above, the exhaust passage 5 includes the 1 st passage 9, the 2 nd passage 10, the 3 rd passage 11, the 4 th passage 12, the 5 th passage 13, the transfer passage 19, the front end chamber 8F, and the rear end chamber 8R.

At the position of the upstream end of the 2 nd passage 10, an injection valve 14 is provided which injects urea water as a reducing agent. The injection valve 10 is arranged to spray the urea water rearward coaxially with the 2 nd route 10 and rearward in the axial direction of the 2 nd route 10.

The injection valve 14 is disposed upstream of the NOx selective reduction catalyst 23 that is a target of supply of the urea water. The 2 nd channel 10 located on the downstream side of the injection valve 14 and on the upstream side of the NOx catalyst 23 functions as a mixing channel for mixing the urea water injected from the injection valve 10 with the exhaust gas.

In the

exhaust passage

5, 4 kinds of aftertreatment members, that is, a 1 st oxidation catalyst 21, a filter 22, a selective reduction type NOx catalyst 23, and a 2 nd oxidation catalyst 24 are provided in series in this order from the upstream side.

The 1 st oxidation catalyst 21 oxidizes and purifies unburned components (hydrocarbons HC and carbon monoxide CO) in the exhaust gas, and heats the exhaust gas by the reaction heat at that time.

The Filter 22 is a Filter called a so-called Diesel Particulate Filter (DPF) or a Catalyzed Soot Filter (CSF), and is a continuously regenerating Filter on which a catalyst is supported. The filter 22 is of a wall-flow type, and collects Particulate Matter (hereinafter referred to as PM: Particulate Matter) contained in exhaust gas, and continuously oxidizes the collected PM by a catalytic reaction to burn and remove the PM.

Selective Catalytic Reduction NOx catalyst (SCR) 23 hydrolyzes urea water to obtain ammonia NH₃Reacts with NOx to reduce NOx in the exhaust gas to nitrogen N₂。

The 2 nd 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, two combinations of the NOx catalyst 23 and the 2 nd oxidation catalyst 24 are provided in the 3 rd passage 11 and the 4 th passage 12 in parallel with each other. In addition, as shown in fig. 1, in each combination, the NOx catalyst 23 is formed on the upstream side portion of the downstream side carrier 23B and the entirety of the upstream side carrier 23A, and the 2 nd oxidation catalyst 24 is formed on the downstream side portion of the downstream side carrier 23B by zone coating. However, the supports for the two catalysts may be independent.

The 1 st to 5 th passages 9 to 13 and the conveyance passage 19 are defined by 1 st to 5 th passage pipes 9P to 13P and a conveyance passage pipe 19P. In the present embodiment, the 1 st to 4 th passages 9 to 12 are linear and circular in cross section, and the conveyance passage 19 is linear and oval in cross section. The 5 th duct 13 is formed linearly at the upper right corner of the housing 2, as shown in fig. 2, for example. The tubes corresponding to the channels are also of the same shape. However, the shape of each channel and each tube can be changed as appropriate.

In the exhaust gas flow direction, the 1 st passage pipe 9P extends from the rear end wall 2R to the front end wall 2F, the 2 nd passage pipe 10P extends from the front end wall 2F to the rear side partition plate 7, the 3 rd passage pipe 11P and the 4 th passage pipe 12P extend from the rear side partition plate 7 to the front side partition plate 6, and the 5 th passage pipe 13P extends from the front side partition plate 6 to the rear end wall 2R. Therefore, the front end chamber 8F is partitioned into a 1 st lane 9 portion, a 2 nd lane 10 portion, a transfer lane 19 portion, and the other portions. The rear end chamber 8R is partitioned into a 1 st passage 9, a 5 th passage 13, and the other parts.

Next, the structure of the inside of the 2 nd duct 10 will be described with reference to fig. 4.

As described above, the injection valve 14 for injecting the urea water U rearward is provided at the upstream end of the 2 nd passage 10. A transfer duct 19 is connected to the lower left side of the 2 nd duct 10 located in the front end chamber 8F, and the exhaust gas G is introduced into the 2 nd duct 10 from this transfer duct.

The urea water spray and the exhaust gas G gradually mix as they proceed toward the rear downstream side in the 2 nd passageway 10. In the present embodiment, in order to promote such mixing, the turn-around passage 30 is provided inside the 2 nd passage 10. The reentrant path 30 is configured as shown by arrows: the flow of the exhaust gas G is turned back from the forward flow direction to the reverse flow direction, and then turned back to the forward flow direction. In the present embodiment, the forward direction refers to a direction flowing from the front to the rear, and the backward direction refers to a direction flowing from the rear to the front.

Specifically, the return passage 30 is defined by a closing member 31 and a cover member 32. These members are arranged coaxially with the central axis C of the 2 nd passage 10.

The closing member 31 closes the peripheral edge portion inside the 2 nd passage 10, and has a protrusion on the upstream side (front side) at the central portion thereof. The communication pipe 33 is a member for communicating the upstream side and the downstream side of the closing member 31. In the present embodiment, the communication pipe 33 is formed integrally with the closing member 31, but may be formed separately and fixed by welding or the like. The closing member 31 is a member having a plate-like and annular shape as a whole, and has a curved sectional shape, specifically, a semicircular sectional shape, which is convex toward the downstream side (rear side). Thus, the closing member 31 can smoothly guide the outer corner side of the exhaust gas G that is turned back 1 st.

The cover member 32 covers the communication pipe 33 from the upstream side with a gap. The cover member 32 has a portion in which the leading end side is tapered toward the leading end on the upstream side. The "tapered shape" refers to a shape extending from the base end side to the tip end side and gradually reducing in diameter toward the tip end side. The tapered shape includes various shapes such as a cone, a truncated cone, a hemisphere, and a dome. The pyramidal shape includes various shapes such as a cone, a rectangular pyramid, and a polygonal pyramid. The frustum shape includes various shapes such as a truncated cone, a truncated pyramid, and a truncated pyramid. The tapered shape may be any of these shapes, but in the present embodiment, a conical shape is used in consideration of ease of processing.

The cover member 32 is substantially conical in shape as a whole except for a short straight tubular downstream end portion (rear end portion) 32A. The cover member 32 is formed of a plate material. The maximum outer diameter of the cover member 32 is smaller than the inner diameter of the 2 nd passage tube 10P and larger than the outer diameter of the communication tube 33. In the present 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 radially outer side. Further, a gap is also formed between the front of the communication pipe 33 and the lid member 32. A curved protruding plate 34 protruding into the communication pipe 33 is integrally fixed to the back side of the lid member 32 by welding or the like. The cover member 32 is held coaxially in the 2 nd passage 10 by a plurality of struts, not shown.

In the present embodiment, the turn-back passage 30 is provided at the outlet portion of the 2 nd passage 10. Communication pipe 33 opens into rear end chamber 8R.

As shown in the drawing, when the exhaust gas G is folded for the 1 st time in the folding passage 30, the outer corner side of the exhaust gas G is guided by the closing member 31, and the inner corner side of the exhaust gas G is guided by the downstream end portion 32A of the cover member 32. When the exhaust gas G is turned back for the 2 nd time, the outer corner side of the exhaust gas G is guided by the lid member 32 and the curved convex plate 34, and the inner corner side of the exhaust gas G is guided by the inlet end of the communication pipe 33.

In this way, the exhaust gas G is turned back 2 times when passing through the turn-back passage 30, is turned back 1 time from the outermost peripheral portion in the 2 nd passage 10 toward the inner peripheral side, is further turned back 1 time toward the inner peripheral side, and then travels straight into the rear end chamber 8R.

In the present embodiment, since the turn-back passage 30 is provided inside the 2 nd passage 10, the passage length can be substantially increased within a limited range of the front-rear length of the 2 nd passage 10, and the mixing passage length of the urea water spray and the exhaust gas G can be increased. Therefore, the mixing of the injected urea water and the exhaust gas can be reliably promoted. In addition, this promotes heating of the urea water by the exhaust gas, promotes hydrolysis of the urea water, improves the ammonia generation efficiency, and enables the NOx catalyst to operate efficiently. Thus, the exhaust gas purification performance can be improved.

In addition, when the exhaust gas G is folded for the 1 st time, the outer corner side of the exhaust gas G is guided by the bent closing member 31, so that the folding can be smoothly performed. Similarly, when the exhaust gas G is folded back 2 times, the outer 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, so that the folding back can be performed smoothly. This can minimize the pressure loss when the exhaust gas G passes through the return passage 30.

In addition, since the cover member 32 has a tapered shape (conical shape in the present embodiment), the exhaust gas G going backward can be smoothly guided to the outer peripheral side. Further, since the cover member 32 is always exposed to the high-temperature exhaust gas, it can function as a heat storage body that stores heat of the exhaust gas. When the urea solution (or the mixture of the urea solution and the exhaust gas) comes into contact with the heat-accumulated high-temperature lid member 32, the urea solution can be heated and hydrolysis thereof can be promoted.

In the present embodiment, since the return path 30 is formed by using the space on the back side of the conical cover member 32, the efficiency of space utilization can be improved.

Further, since the return path 30 is provided at the outlet portion of the 2 nd path 10 and the lid member 32 is spaced apart from the injection valve 14 to the maximum extent, the urea water can be evaporated just before the lid member 32 and then reach the lid member 32 as much as possible. This can suppress the droplets of the urea aqueous solution from adhering to the lid member 32 as much as possible, thereby lowering the temperature of the lid member 32 and losing the heat storage effect.

The exhaust gas purification apparatus 1 of the present embodiment forms an exhaust gas duct 5 that is folded back a plurality of times in the closed box-shaped casing 2, and a plurality of aftertreatment members (catalysts and the like) are disposed in the exhaust gas duct 5, and therefore functions also as a muffler (muffler). Thus, a muffler does not need to be additionally provided, and the manufacturing cost can be reduced.

Further, the turn-back passage 30 of the present embodiment is formed only inside the exhaust passage 5, and is not formed by turning back the exhaust passage 5 itself. Therefore, the turn of the second channel 10 into the 3 rd and 4

th channels

11 and 12 through the rear end chamber 8R is not related to the turn channel 30 of the present embodiment.

The present embodiment may have the following modifications. For example, a plurality of the return passages 30 may be provided as necessary. The sealing member 31 includes the communication pipe 33 and has a curved cross-sectional shape as a whole, but may have an angular cross-sectional shape. The curved raised plate 34 may also be omitted. However, the presence of the curved convex plate 34 is preferable because the exhaust gas can be prevented from entering the back side of the conical tip of the cover member 32, and the exhaust gas can be smoothly returned in a shorter time. The communication pipe 33 may be provided not only in one but in plural in the center.

[ 2 nd embodiment ]

Next, embodiment 2 of the present disclosure is explained. Note that the same portions as those in embodiment 1 are denoted by the same reference numerals in the drawings and description thereof is omitted, and differences from embodiment 1 will be mainly described below.

As shown in fig. 5, the present embodiment is different from embodiment 1 mainly in the configuration near the 2 nd channel 10. That is, the 2 nd duct 10 includes an inner 2 nd duct 41 located radially inward and an outer 2 nd duct 42 located radially outward with respect to the center axis C thereof. The outer 2 nd passage 42 is positioned adjacent to the radially outer side of the inner 2 nd passage 41, and surrounds the inner 2 nd passage 41, so that the exhaust gas discharged from the outlet portion of the inner 2 nd passage 41 flows in the direction opposite to the flow direction in the inner 2 nd passage 41. The return path 30 is disposed in the inner 2 nd path 41.

The inner 2 nd passage 41 and the outer 2 nd passage 42 are arranged coaxially with the central axis C. The inner 2 nd passage 41 and the outer 2 nd passage 42 are defined by an inner 2 nd passage tube 41P and an outer 2 nd passage tube 42P, respectively. Thus, the inner and outer 2

nd channel pipes

41P and 42P are coaxial double pipes. The downstream end (rear end) of the outside 2 nd channel pipe 42P is closed by a curved convex plate 43 similar to the curved convex plate 34 described above. The curved protruding plate 43 is arranged in front-rear symmetry with the curved protruding plate 34.

The turn-back passage 30 is disposed in the vicinity of the outlet portion of the inner 2 nd passage 41, and is disposed slightly upstream of the embodiment 1.

According to this configuration, the exhaust gas G introduced from the conveyance path 19 into the inner 2 nd path 41 flows rearward in the inner 2 nd path 41, passes through the turning path 30, and is discharged from the inner 2 nd path 41. Thereafter, the bent convex plate 43 is folded back, enters the outer 2 nd duct 42, flows forward in the outer 2 nd duct 42, and is discharged to the tip chamber 8F. When the exhaust gas G is returned from the inner 2 nd path 41 to the outer 2 nd path 42, the outer corner side of the exhaust gas G is guided by the curved convex plate 43, and therefore the return can be performed smoothly.

In the present embodiment, since the outer 2 nd path 42 is provided in a double-pipe shape on the outer side in the radial direction of the inner 2 nd path 41, the path length can be further substantially increased within a limited range of the front-rear length of the 2 nd path 10, and the mixing path length of the urea water and the exhaust gas G can be further increased. This can further promote mixing of the urea water with the exhaust gas.

Further, since the exhaust gas and the urea water in the inner 2 nd passage 41 can be kept warm or heated by the exhaust gas flowing through the outer 2 nd passage 42, the hydrolysis of the urea water can be further promoted.

Other operations and effects are the same as those of embodiment 1.

In the present embodiment, the direction of the exhaust gas G discharged from the 2 nd passage 10 is opposite to that of the 1 st embodiment, and the exhaust gas G is discharged into the front end chamber 8F. Therefore, the structure inside the housing 2 is slightly changed as shown in fig. 6.

That is, the NOx catalyst 23 and the 2 nd oxidation catalyst 24 in the 3 rd and 4

th passages

11 and 12 are arranged in opposite directions. The 5 th passage 13 is omitted, and the positions of the front partition plate 6 and the rear partition plate 7 where the 5 th passage 13 is located are closed.

The exhaust gas G discharged from the outer 2 nd passage 42 into the front end chamber 8F branches into two directions, and enters the 3 rd passage 11 and the 4 th passage 12. 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 3 rd and 4

th passages

11, 12, and passes through the NOx catalyst 23 and the 2 nd oxidation catalyst 24 in this order. Then, the exhaust gas enters the rear end chamber 8R, is collected in the apparatus outlet pipe 4 in the rear end chamber 8R, and is discharged.

In the present embodiment, the inner 2 nd and outer 2

nd passages

41, 42 correspond to the inner and outer exhaust passages described in the claims, respectively.

In a modification, the downstream end (rear end) of the outer 2 nd passage tube 42P may be sealed only by a flat plate.

[ embodiment 3 ]

Next, embodiment 3 of the present invention will be explained.

As shown in fig. 7, the present embodiment also differs from embodiment 1 in the structure of the vicinity of the 2 nd channel 10. The overall configuration is the same as that shown in fig. 1.

The 2 nd tunnel 10 and the 2 nd tunnel pipe 10P are shorter in the front-rear direction than in the embodiment 1, and the rear end portions thereof are positioned forward of the rear side partition plate 7. Instead, the communication pipe 33 extends rearward to the position of the rear partition plate 7.

The closing member 31 is formed integrally with the 2 nd passage pipe 10P by bending the rear end portion of the 2 nd passage pipe 10P radially inward in a semicircular shape in section. The straight-tube-shaped downstream end portion 32A of the cover member 32 is coupled to the 2 nd channel tube 10P via a plurality of struts 51. The curved convex plate 34 is omitted in the present embodiment.

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

In the present embodiment, a heat storage member 52, which is a heat storage body independent from the lid member 32, 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 upstream of the lid member 32 in the 2 nd channel 10 and is provided closer to the injection valve 14 than the lid member 32.

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

The heat storage member 52 is provided over the entire cross section of the 2 nd channel 10, has a truncated cone-shaped tapered portion 55 as 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 54 forming the bottom of the truncated cone is annular and perpendicular to the central axis C, and is fixed to the inner peripheral surface of the 2 nd channel tube 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 over the entire circumference in the tapered portion 55 that is tapered from the base end 54 toward the upstream side. Thereby, the fins 56 are formed between the openings 53. In the present embodiment, the fin 56 is along the circumferential direction of the tapered portion 55.

A front end plate 58 perpendicular to the central axis C is fixed to a front end portion 57 of the heat storage member 52 forming the top of the truncated cone. The front end plate 58 has a function of blocking the front end portion 57, a function of receiving the flow of the exhaust gas on the front surface and storing heat, and a function of contacting the urea water injected from the injection valve 14 and promoting 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 shown in fig. 9 and 10, the plurality of divided pieces 33C are bent alternately radially inward and outward as they advance in 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 a predetermined distance rearward, and the inlet portion 33B is bent alternately radially inward and outward at the positions of the slits. Thereby, the plurality of divided pieces 33C having different orientations are alternately formed.

According to this configuration, the exhaust gas G introduced from the conveyance path 19 into the inner 2 nd path 41 flows rearward in the inner 2 nd path 41, contacts the heat storage member 52, passes through the plurality of openings 53, and enters the inside of the heat storage member 52. Then, the gas is guided by the cover member 32 to reach the folded path 30, passes through the communication pipe 33, and is discharged to the rear end chamber 8R.

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 stores heat. The urea water in the exhaust gas contacts the heat storage member 52, thereby heating the urea water and promoting hydrolysis thereof. Since the urea water also similarly contacts the cover member 32 thereafter, heating and hydrolysis of the urea water are thereby further promoted.

When the exhaust gas passes through the heat storage member 52, the flow of the exhaust gas is slightly disturbed, and therefore, 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 gaps 33D between the divided pieces 33C as shown by arrows in fig. 9. Since the flow directly entering the communication pipe 33 in the axial direction collides with the flow entering the communication pipe through the gap 33D from a direction different from the axial direction, turbulence of the flow is generated inside the inlet portion 33B, and mixing of the exhaust gas and the urea water can be promoted.

Other operations and effects are the same as those of embodiment 1.

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

Since the heat storage member 52 is tapered (truncated cone shape in the present embodiment), an increase in exhaust resistance due to the provision of the heat storage member 52 can be suppressed as much as possible. Further, the split piece 33C is formed by cutting and bending only the pipe end of the communication pipe 33, and therefore, is easy to process.

In a modification of the present embodiment, the shape of the opening 53 of the heat storage member 52 may be changed, and may be, for example, a circle or a rectangle. Further, as the communication pipe 33, for example, it is conceivable to provide a plurality of divided pieces 33C independently and fix them by welding or the like. The present embodiment may be combined with embodiment 2, and the 2 nd channel 10 of the present embodiment may have a double-tube structure.

While the embodiments of the present invention have been described in detail, other various embodiments of the present invention are also conceivable.

(1) The turn-back duct according to the present invention can be applied not only to an exhaust gas purifying apparatus having such a closed box-type casing as described above but also to a general exhaust gas purifying apparatus.

(2) The catalyst may or may not be a NOx catalyst of selective reduction type. The reducing agent supplied to the catalyst may be changed depending on the type of the catalyst.

The configurations of the above embodiments may be combined partially or entirely, unless otherwise specifically contradicted. The embodiments of the present invention are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the spirit of the present invention defined by the scope of the claims are included in the present invention. Therefore, the present invention should not be construed as limited thereto, and can be applied to any other technique within the scope of the idea of the present invention.

The present application is based on japanese patent application filed on 10/02/2017 (japanese patent application 2017-.

[ Industrial availability ]

The present disclosure exhibits an effect of promoting mixing of the injected urea water and the exhaust gas, and is useful in that the NOx catalyst provided in the exhaust passage of the diesel engine can be operated efficiently.

[ description of reference numerals ]

1 exhaust gas purification device

5 exhaust passage

10 nd 2 nd channel

14 injection valve

23 NOx catalyst

30 reentrant pathways

31 closure member

32 cover component

33 communicating pipe

33B inlet part

33C partition sheet

41 inner 2 nd channel

42 outer 2 nd channel

52 Heat storage Member

53 opening part

Claims

1. An exhaust gas purification apparatus of an internal combustion engine, characterized by comprising:

a catalyst disposed in the exhaust passage,

a return passage provided in the exhaust passage at a position downstream of the injection valve and upstream of the catalyst, and configured to return the flow of the exhaust gas from a forward flow direction to a reverse flow direction and then to a forward flow direction;

the reentrant passageway is defined by a closure member and a cover member,

the closure member closes a peripheral edge portion inside the exhaust passage and has a communication pipe protruding toward an upstream side,

2. The exhaust gas purifying apparatus of an internal combustion engine according to claim 1,

the cover member has a portion whose front end side is tapered toward the front end on the upstream side.

3. The exhaust gas purifying apparatus of an internal combustion engine according to claim 2,

the leading end taper shape is a conical shape.

4. The exhaust gas purification apparatus of an internal combustion engine according to any one of claims 1 to 3,

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

5. The exhaust gas purification apparatus of an internal combustion engine according to any one of claims 1 to 3,

the exhaust passage comprises an inner exhaust passage and an outer exhaust passage, the inner exhaust passage is positioned at the inner side in the radius direction, the outer exhaust passage is positioned adjacent to the outer side of the inner exhaust passage in the radius direction and surrounds the inner exhaust passage, and the exhaust gas exhausted from the inner exhaust passage flows in the opposite direction;

the return passage is disposed in the inner exhaust passage.

6. The exhaust gas purification apparatus of an internal combustion engine according to any one of claims 1 to 3,

the exhaust gas recirculation system further includes a heat storage member that is provided at a position downstream of the injection valve and upstream of the return passage and stores heat of the exhaust gas.

7. The exhaust gas purifying apparatus of an internal combustion engine according to claim 6,

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