JP2014190177A - Exhaust cleaning device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust cleaning device for an internal combustion engine that includes a mixer interposed in an exhaust pipe upstream from an exhaust cleaning catalyst and has a spiral exhaust flow passage and an addition valve adding a reductant to an exhaust gas upstream from the mixer or an exhaust gas flowing in an exhaust gas passage in the mixer, and that accelerates mixing of the exhaust gas and reducer while reducing pressure loss when the exhaust gas flows in the mixer.SOLUTION: In an exhaust cleaning device for an internal combustion engine, a mixer includes a cylindrical casing which is arranged coaxially with an exhaust pipe and a plate material which is a spiral plate material defining a spiral exhaust flow passage in the casing and has an angle of rotation larger than 360 degrees, and the plate material has a plurality of through holes formed in a region radially outside a place located on an upstream side and a region radially inside a place located on a downstream side, the two places being at different positions in an axial direction of the casing and at the same position in a peripheral direction.

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 including a mixer that promotes mixing of a reducing agent added to exhaust gas and exhaust gas.

  2. Description of the Related Art As an exhaust gas purification device for an internal combustion engine, an exhaust gas purification device that includes an exhaust gas purification catalyst disposed in an exhaust passage and an addition device that adds a reducing agent to exhaust gas flowing into the exhaust gas purification catalyst is known. As this type of exhaust gas purification apparatus for an internal combustion engine, an apparatus having a mixer has been proposed in order to achieve uniform mixing of the reducing agent and the exhaust gas. The mixer includes a cylindrical casing disposed coaxially with the exhaust pipe, a spiral flow path formed in the casing, and an addition valve that is attached to the peripheral wall of the casing and injects the reducing agent into the flow path. Are known (see, for example, Patent Document 1).

US Patent Application Publication No. 2012/0216513

  By the way, according to the above-described conventional mixer, the reducing agent tends to be biased toward the peripheral edge in the casing (in the vicinity of the inner peripheral surface) due to the inertial force acting outward in the radial direction of the casing. Therefore, there is a possibility that the exhaust gas and the reducing agent are not mixed uniformly. On the other hand, a method of achieving homogeneous mixing of the exhaust gas and the additive by increasing the swirl angle of the exhaust gas in the mixer (increasing the length of the spiral flow path) can be considered. However, when the swirl angle of the exhaust gas increases, the pressure loss when the exhaust gas flows through the mixer increases, and therefore the back pressure acting on the internal combustion engine may increase.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine and an exhaust pipe upstream of the exhaust purification catalyst. In an exhaust emission control device for an internal combustion engine, comprising: a mixer having a gas-like exhaust flow path; and an addition valve for adding a reducing agent to exhaust gas upstream of the mixer or exhaust gas flowing through the exhaust flow path in the mixer. Is to promote the mixing of the exhaust gas and the reducing agent while reducing the pressure loss when flowing through the mixer.

  In order to solve the above-described problems, the present invention provides an exhaust purification catalyst disposed in an exhaust pipe of an internal combustion engine and an exhaust pipe upstream of the exhaust purification catalyst. In an exhaust gas purification apparatus for an internal combustion engine, comprising: a mixer having an exhaust valve that flows through an exhaust pipe upstream from the mixer; or an addition valve that adds a reducing agent to exhaust gas that flows through an exhaust passage in the mixer; The mixer has means for generating an exhaust flow from the radially outer side to the radially inner side of the mixer in addition to the means for generating the spirally swirling exhaust flow.

Specifically, the present invention relates to an exhaust purification catalyst disposed in an exhaust pipe of an internal combustion engine,
A mixer interposed in an exhaust pipe upstream of the exhaust purification catalyst and having a spiral exhaust flow path;
An addition valve for adding a reducing agent to the exhaust flowing through the exhaust pipe upstream from the mixer, or to the exhaust flowing through the exhaust passage in the mixer;
In an exhaust gas purification apparatus for an internal combustion engine comprising:
The mixer includes a cylindrical casing, and a spiral plate member for defining a spiral exhaust passage in the casing, and a plate member having a rotation angle greater than 360 degrees,
The plate member has through holes provided at two locations where the positions in the axial direction in the casing are different and the positions in the circumferential direction overlap,
The through-hole provided in the location located upstream of the two locations is arranged on the radially outer side as compared to the through-hole provided in the location located on the downstream side.

  In the exhaust gas purification apparatus for an internal combustion engine thus configured, the exhaust gas discharged from the internal combustion engine flows into the mixer through an exhaust pipe upstream from the mixer. The exhaust gas flowing into the mixer flows through a spiral exhaust flow path (hereinafter referred to as “spiral flow path”) defined by the spiral plate member and the inner wall surface of the casing. That is, the exhaust gas flowing into the mixer flows while swirling spirally.

  Here, when the exhaust gas flowing through the spiral flow path contains a reducing agent, the reducing agent in the exhaust gas is caused by the inertial force (centrifugal force) acting from the radially inner side to the radially outer side of the casing. There is a possibility that it is biased to the vicinity of the inner wall surface of the casing. On the other hand, it is conceivable to increase the length of the spiral flow path (rotation angle of the spiral flow path), but a contradiction occurs in that the pressure loss increases when exhaust flows through the mixer.

  On the other hand, the exhaust gas purification apparatus for an internal combustion engine of the present invention has a rotation angle (in other words, a rotation angle of a spiral flow path) of a spiral plate material (hereinafter referred to as “spiral plate”) built in a casing of a mixer. ) Larger than 360 degrees, and through-holes are provided in each of the two locations where the axial position of the casing is different and the circumferential positions overlap in the spiral plate. Furthermore, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, a through hole provided in a location located on the upstream side (hereinafter referred to as “first location”) of the two locations of the plate member is located on the downstream side. Compared with the through-hole provided in (hereinafter referred to as “second location”), it is arranged on the radially outer side.

  Here, in the spiral plate, the two locations where the axial positions of the casing are different and the circumferential positions overlap are the two locations facing each other through the spiral flow path in the axial direction of the casing. For example, when the rotation angle of the spiral plate is 480 degrees, the range of 0 to 120 degrees as the rotation angle of the spiral plate is the first place, and the range of 360 to 480 degrees is Second place. In addition, when the rotation angle of the spiral plate is 540 degrees, a range of 0 to 180 degrees as the rotation angle of the spiral plate becomes the first place, and a range of 360 to 540 degrees Second place.

  When the through hole is provided in each of the first place and the second place, and the through hole in the first place is arranged on the radially outer side from the through hole in the second place, the through hole in the first place (hereinafter, At least a part of the exhaust gas passing through the “first through hole” passes through the second through hole (hereinafter referred to as “second through hole”). As a result, the pressure loss when the exhaust flows through the mixer is reduced. In addition, in the spiral flow path defined by the first location and the second location, an exhaust flow from the radially outer side of the casing toward the radially inner side is generated, so that the reducing agent contained in the exhaust is placed on the peripheral edge in the casing. Biasing is suppressed.

  Therefore, according to the exhaust gas purification apparatus for an internal combustion engine of the present invention, it is possible to promote the mixing of the exhaust gas and the reducing agent while reducing the pressure loss when the exhaust gas flows through the mixer.

Note that in the spiral flow path defined by the first location and the second location of the spiral plate, focusing on generating the exhaust flow from the radially outer side of the casing to the radially inner side more reliably, the radial direction of the casing The position of the first through hole and the position of the second through hole in are preferably different. In other words, it is preferable that the portion located radially inward in the first through hole is located radially outward from the portion located radially outer in the second through hole. When the first through hole and the second through hole are arranged in this manner, the flow of exhaust gas from the radially outer side of the casing toward the radially inner side is further increased in the spiral flow path defined by the first place and the second place. Therefore, the bias of the reducing agent can be more reliably suppressed.

  In the exhaust gas purification apparatus for an internal combustion engine of the present invention, the number of the first through holes and the second through holes may be one, or two or more. Here, when at least one of the first through-hole or the second through-hole is provided, the through-hole is formed so as to extend in the circumferential direction of the plate material (first place or second place) (that is, It may be formed in an arc shape.

  In the exhaust gas purification apparatus for an internal combustion engine of the present invention, the addition valve may be attached to the casing so as to inject the reducing agent into the spiral flow path defined by the first location and the second location. According to such a configuration, the reducing agent injected from the addition valve is dispersed into the exhaust gas flowing spirally and the exhaust gas flowing from the radially outer side to the radially inner side of the casing. Dispersibility is improved and exhaust gas and reducing agent are mixed more homogeneously. In addition, when the addition valve is attached to the casing of the mixer, the on-board performance of the exhaust emission control device can be improved.

  According to the present invention, an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine, a mixer having a spiral exhaust passage interposed in an exhaust pipe upstream of the exhaust purification catalyst, and a mixer In an exhaust gas purification apparatus for an internal combustion engine comprising an addition valve for adding a reducing agent to exhaust gas flowing upstream or exhaust gas flowing in a mixer, while reducing pressure loss when the exhaust gas flows through the mixer, Mixing of exhaust and reducing agent can be promoted.

It is a figure which shows schematic structure of the exhaust system of the internal combustion engine to which this invention is applied. It is a perspective view which shows the structure of a mixer. It is a figure which shows the relationship between the rotation angle of a spiral board, the pressure loss at the time of exhaust_gas | exhaustion flowing through a mixer, and the homogeneity degree of the reducing agent density | concentration in exhaust_gas | exhaustion. It is a figure which shows arrangement | positioning of a 1st through-hole and a 2nd through-hole. It is a 1st figure which shows the flow of the exhaust_gas | exhaustion in a mixer. It is a 2nd figure which shows the flow of the exhaust_gas | exhaustion in a mixer.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

FIG. 1 is a diagram showing a schematic configuration of an exhaust system of an internal combustion engine to which the present invention is applied. In FIG. 1, an exhaust pipe 2 is connected to the internal combustion engine 1. A cylindrical catalyst casing 3 is disposed in the middle of the exhaust pipe 2. The catalyst casing 3 accommodates a selective reduction type (SCR: Selective Catalytic Reduction). The exhaust purification catalyst housed in the catalyst casing 3 may be an occlusion reduction type catalyst, or a selective reduction type catalyst or a particulate filter carrying an occlusion reduction type catalyst. In short, the exhaust purification catalyst may be any catalyst that can purify exhaust in the presence of a reducing agent.

A mixer 4 is provided in the exhaust pipe 2 upstream of the catalyst casing 3. As shown in FIG. 2, the mixer 4 has a cylindrical casing 40 having an outer diameter and an inner diameter substantially equal to those of the exhaust pipe 2 and arranged coaxially with the exhaust pipe 2. The casing 40 includes a plate material (spiral plate) 41 formed in a spiral shape. The length of the spiral plate 41 is set to such a length that the rotation angle of the spiral plate 41 is larger than 360 degrees. In the example shown in FIG. 1, the length of the spiral plate 41 is set to a length at which the rotation angle of the spiral plate 41 is 480 degrees. In that case, a spiral flow path (spiral flow path) 42 defined by the spiral plate 41 and the inner wall surface of the casing 40 is formed inside the casing 40, and the rotation angle of the spiral flow path 42 is 480 degrees. become.

  Here, the casing 40 may be configured as a member separate from the exhaust pipe 2 or may be configured integrally with the exhaust pipe 2 (that is, a part of the exhaust pipe 2 also serves as the casing 40. You may). When a part of the exhaust pipe 2 also serves as the casing 40, the spiral plate 41 may be disposed in the exhaust pipe 2. Further, the outer diameter and inner diameter of the casing 40 may be made larger than the outer diameter and inner diameter of the exhaust pipe 2 within a range that can be mounted on the vehicle.

  One end of a cylindrical injection pipe 43 is connected to the outer peripheral surface of the casing 40. At that time, it is desirable that the opening end of the injection pipe 43 is disposed in the upstream as much as possible in a range where the rotation angle of the spiral flow path 42 is larger than 360 degrees. On the other hand, the addition valve 5 is attached to the other end of the injection pipe 43. The addition valve 5 is a valve mechanism that injects the reducing agent from the inside of the injection pipe 43 toward the spiral flow path 42. The reducing agent injected from the addition valve 5 is, for example, ammonia or an ammonia precursor. As the reducing agent that is a precursor of ammonia, an aqueous solution of urea or ammonium carbamate can be used. The addition valve 5 communicates with the tank 51 via the pump 50. The tank 51 is a tank that stores a reducing agent. The pump 50 is a pump that sucks the reducing agent stored in the tank 51 and discharges it toward the addition valve 5.

  In the mixer 4 configured as described above, when the exhaust gas flows into the mixer 4 from the exhaust pipe 2 upstream of the mixer 4, the exhaust gas flows while spirally turning along the spiral flow path 42. At this time, when the reducing agent is injected from the addition valve 5, the reducing agent flows into the spiral flow path 42 through the injection pipe 43. The reducing agent that has flowed into the spiral flow path 42 from the injection pipe 43 is mixed with the exhaust gas while spirally turning along the spiral flow path 42. Here, when the mixer 4 is disposed, the path from the position where the reducing agent is added to the exhaust gas to the catalyst casing 3 becomes longer than when the mixer 4 is not disposed. Even when the length of the exhaust pipe 2 between them is short, mixing of the exhaust gas and the reducing agent can be promoted.

  By the way, in the mixer 4 described above, there is a possibility that the reducing agent is biased to a radially outer range (near the inner wall surface of the casing 40) due to an inertial force (centrifugal force) acting from the radially inner side to the radially outer side of the casing 40. is there. On the other hand, a method of increasing the length of the spiral flow path 42 (rotation angle of the spiral flow path 42) can be considered, but there is a possibility that pressure loss when exhaust flows through the mixer 4 may increase. FIG. 3 is a diagram showing the relationship between the rotation angle of the spiral plate 41, the pressure loss when the exhaust gas passes through the mixer 4, and the degree of homogeneity of the reducing agent concentration in the exhaust gas. As shown in FIG. 2, the greater the rotation angle of the spiral plate 41, the higher the degree of homogeneity, but the contradiction that the pressure loss also increases. If the pressure loss when the exhaust gas passes through the mixer 4 increases, exhaust efficiency and back pressure may increase, and the output of the internal combustion engine 1 may decrease.

  Therefore, the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment increases the rotation angle of the spiral plate 41 (rotation angle of the spiral flow path) included in the casing 40 to be greater than 360 degrees, The through holes 411a and 412a are provided in two places where the positions in the axial direction are different and the positions in the circumferential direction overlap. At that time, in the exhaust flow direction, through holes (hereinafter referred to as “first through holes”) 411a provided in a location (first location) 411 located upstream of the two locations are the two locations. It is assumed that it is arranged on the outer side in the radial direction as compared with a through hole (hereinafter referred to as “second through hole”) 412 a provided in a location (second location) 412 located on the downstream side of 4.

  Here, since the rotation angle of the spiral plate 41 of this embodiment is 540 degrees, the first location 411 is a region included in the range from 0 degrees to 180 degrees in the rotation angle. On the other hand, the second location 412 is a region included in a range from 360 degrees to 540 degrees in the rotation angle. Therefore, as shown in FIGS. 2 and 4, the first through hole 411 a is formed in a radially outer portion of the spiral plate 41 in the range from 0 degree to 360 degrees (first place 411). On the other hand, the 2nd through-hole 412a is formed in the site | part of the radial inside of the range (2nd location 412) from 360 degree | times of the spiral board 41 to 540 degree | times.

  It is desirable that the radial position of the first through hole 411a and the radial position of the second through hole 412a do not overlap each other. That is, the radially innermost portion of the first through hole 411a is disposed on the radially outer side as compared with the radially outermost portion of the second through hole 412a. For example, as shown in FIGS. 2 and 4, when a plurality of first through holes 411a and a plurality of second through holes 412a are provided, the first through hole located at the innermost side in the radial direction among the plurality of first through holes 411a. The hole 411a is arranged on the radially outer side compared to the second through hole 412a located on the outermost side in the radial direction among the plurality of second through holes 412a.

  When the mixer 4 is configured in this way, a part of the exhaust gas flowing into the mixer 4 flows in the spiral flow path 42 while turning in the circumferential direction. Further, as shown in FIG. 5, the remaining exhaust gas passes through the first through hole 411a and is surrounded by the first location 411, the second location 412 and the inner wall surface of the casing 40 (hereinafter referred to as “this”). Part of the spiral flow channel 42 flows into the “specific flow channel 42a”. A part of the exhaust gas flowing into the specific flow path 42a flows in the circumferential direction through the specific flow path 42a, and the remaining exhaust gas flows into the second through hole 412a of the second location 412. Therefore, in the specific flow path 42a, as shown in FIG. 6, a flow in which the exhaust turns in the circumferential direction and a flow in which the exhaust goes from the radially outer side to the radially inner side are generated. When the exhaust flows from the radially outer side to the radially inner side, the reducing agent injected from the addition valve 5 is suppressed from being biased to the vicinity of the peripheral edge of the specific flow path 42a, and the dispersibility of the reducing agent in the exhaust gas (diffusion) Property). Moreover, since a part of the exhaust gas flowing into the mixer 4 can flow through the first through hole 411a and the second through hole 412a, the pressure loss when the exhaust gas passes through the mixer 4 is kept low. You can also.

  Therefore, according to the exhaust gas purification apparatus for an internal combustion engine of the present embodiment, the exhaust gas and the reducing agent can be homogeneously mixed while suppressing the pressure loss when the exhaust gas flows through the mixer 4.

  In this embodiment, the example in which the rotation angle of the spiral plate 41 is set to 540 degrees has been described. However, the present invention is not limited to this, and is less than 540 degrees as long as the exhaust gas and the reducing agent are uniformly mixed. The rotation angle may be set, or may be set to a rotation angle larger than 540 degrees as long as an excessive increase in pressure loss is not caused.

  In the present embodiment, the first through hole 411a and the second through hole 412a are described as being formed in a relatively small-diameter round shape, but the size of the first through hole 411a and the second through hole 412a is described. The shape, number, or number can be appropriately changed according to the specifications of the internal combustion engine 1 or the like. For example, when the number of at least one of the first through-hole 411a or the second through-hole 412a is one, the shape of the through-hole may be formed in an arc shape extending in the circumferential direction. In short, as long as a flow from the radially outer side to the radially inner side occurs in the spiral flow path 42 and the pressure loss when the exhaust gas passes through the mixer 4 does not increase remarkably, the first through hole 411a and the second through hole 411a. The shape, size, or number of the through holes 412a can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust pipe 3 Catalyst casing 4 Mixer 5 Addition valve 40 Casing 41 Spiral plate 42 Spiral flow path 43 Injection pipe 50 Pump 51 Tank 411 1st location 411a 1st through-hole 412 2nd location 412a 2nd through-hole

Claims (3)

An exhaust purification catalyst disposed in an exhaust pipe of an internal combustion engine;
A mixer interposed in an exhaust pipe upstream of the exhaust purification catalyst and having a spiral exhaust flow path;
An addition valve for adding a reducing agent to the exhaust flowing through the exhaust pipe upstream from the mixer, or to the exhaust flowing through the exhaust passage in the mixer;
In an exhaust gas purification apparatus for an internal combustion engine comprising:
The mixer includes a cylindrical casing, and a spiral plate that defines a spiral exhaust passage in the casing and has a rotation angle greater than 360 degrees,
The plate member has through holes provided in each of two places where positions in the axial direction of the casing are different and positions in the circumferential direction overlap.
Of the two locations, a through hole provided at a location located on the upstream side in the exhaust flow direction is arranged on a radially outer side than a through hole provided at a location located on the downstream side. An exhaust purification device for an internal combustion engine.   2. The innermost radial direction portion of the through hole provided at a location located upstream of the exhaust flow direction in the two locations is the largest diameter of the through hole provided at a location located downstream. An exhaust emission control device for an internal combustion engine, wherein the exhaust gas purification device is located on a radially outer side as compared with a portion on a radially outer side.   3. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the addition valve is attached to the casing so as to inject a reducing agent into an exhaust passage defined by the two portions of the plate member. .

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