JP2017155694A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a post-treatment unit accommodated in a casing and equipped with a selective reduction type NOx catalyst post-treatment unit, in which a portion having residing urea water is easily replaced.SOLUTION: An exhaust emission control device 100 for an internal combustion engine 1 comprises an exhaust pipe 2, a post-treatment unit 3, and a casing 4 for accommodating the post-treatment unit. The post-treatment unit 3 includes a selective reduction type NOx catalyst 10c, pipe members 31, 33, 34 and 35 extending from the upstream side of the catalyst and toward the selective reduction type NOx catalyst 10c, and an addition valve 36 for adding the urea water. A portion Uf, which is interposed between the addition valve 36 and the selective reduction type NOx catalyst 10c, is made removable. The casing 4 is equipped with an opening 44, and a cover 5 covering the opening 44.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine including an aftertreatment unit.

  Generally, in a vehicle equipped with an internal combustion engine, an exhaust gas purification device including an aftertreatment unit provided in the middle of an exhaust pipe and having a plurality of catalysts for purifying harmful substances in exhaust gas is known. .

JP 2003-184544 A JP 2008-208727 A

  In the exhaust gas purification apparatus described above, it is conceivable that the post-processing unit is accommodated in a casing in order to keep the temperature of the catalyst at a high temperature.

  On the other hand, when the aftertreatment unit has a selective reduction type NOx catalyst (SCR: Selective Catalytic Reduction), urea water as a reducing agent is added upstream of the NOx catalyst. The added urea water flows inside the pipe member extending toward the NOx catalyst while being mixed with the exhaust gas and evaporated, and is supplied to the NOx catalyst. However, if urea water adheres and stays inside the pipe member in a liquid phase state, there is a possibility that the staying portion may be corroded.

  Therefore, the present invention has been created in view of such circumstances, and the object thereof is to easily replace a portion where urea water stays in an aftertreatment unit that is accommodated in a casing and includes a selective reduction type NOx catalyst. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention includes an exhaust pipe, an aftertreatment unit provided in the middle of the exhaust pipe and having a plurality of catalysts for purifying exhaust gas, and a casing that houses the aftertreatment unit. The post-processing unit includes a selective reduction type NOx catalyst, a pipe member that extends from the upstream side of the selective reduction type NOx catalyst toward the selective reduction type NOx catalyst, and through which exhaust gas passes, and in the pipe member An addition valve for adding urea water to a position upstream of the selective reduction type NOx catalyst in the above, and the pipe member is located from the addition valve to a position between the addition valve and the selective reduction type NOx catalyst. A lid having a portion where the added urea water stays, the portion being removable, an opening through which the portion can pass is provided in the casing, and the opening covers the casing so that the opening can be opened and closed Characterized in that it is provided.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention accommodates an exhaust pipe, an aftertreatment unit provided in the middle of the exhaust pipe and having a plurality of catalysts for purifying exhaust gas, and the aftertreatment unit. A tubular first catalyst casing in which at least one catalyst is disposed, and a tubular in which the selective reduction type NOx catalyst is disposed in parallel with the first catalyst casing. And a connecting pipe that is disposed at a position between the first catalyst casing and the second catalyst casing and connects the downstream end of the first catalyst casing and the upstream end of the second catalyst casing. A connecting pipe having a folded portion extending from the rear to the front along the exhaust flow direction, folded back in a U-shape and extending rearward, and upstream of the folded portion A urea water addition valve arranged so as to add urea water from the rear toward the front toward the folded portion, and the folded portion has a detachable front surface portion, and is attached to the front surface of the casing. Is characterized in that an opening through which the front surface portion can pass is formed at a position facing the front surface portion of the folded portion, and a lid that covers the opening portion so as to be openable and closable is provided.

  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, an excellent effect that the portion where the urea water stays can be easily replaced in the aftertreatment unit housed in the casing and provided with the selective reduction type NOx catalyst. Demonstrate.

It is a schematic structure figure showing an exhaust gas purification device concerning one embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention.

  As shown in FIG. 1, an exhaust gas purification apparatus 100 is an aftertreatment unit having an exhaust pipe 2 through which exhaust gas from an internal combustion engine 1 passes and a plurality of catalysts 10 provided in the middle of the exhaust pipe 2 for purifying exhaust gas. 3 and a casing 4 that houses the post-processing unit 3.

  The internal combustion engine 1 is a multi-cylinder compression ignition internal combustion engine mounted on a vehicle (not shown), that is, a diesel engine. The internal combustion engine 1 is provided with an exhaust manifold 12 that collects exhaust gas discharged from each cylinder 11.

  The exhaust pipe 2 is a pipe that is connected to the exhaust manifold 12 and discharges exhaust gas from the exhaust manifold 12 in the downstream direction (direction indicated by arrow G) and releases it to the atmosphere.

  More specifically, the exhaust pipe 2 includes an upstream exhaust pipe 21 positioned upstream of the post-processing unit 3 and a downstream exhaust pipe 22 positioned downstream of the post-processing unit 3. The upstream exhaust pipe 21 has a flange 21a at its downstream end, and the downstream exhaust pipe 22 has a flange 22a at its upstream end.

  Next, the post-processing unit 3 will be described. The front-rear and left-right directions of the post-processing unit 3 are shown in FIG. In addition, the front-rear and left-right directions of the illustrated post-processing unit 3 are irrelevant to the front-rear, left-right directions of the vehicle, and are merely determined for convenience of explanation. In the present embodiment, the internal combustion engine 1 is placed vertically on the vehicle, and the left direction of the post-processing unit 3 coincides with the front direction of the vehicle.

  The aftertreatment unit 3 includes an exhaust gas inlet pipe 31, an exhaust gas outlet pipe 32, a first catalyst casing 33 in which at least one catalyst 10 is provided, a second catalyst casing 34 in which an NOx catalyst 10c is provided, A connecting pipe 35 connecting the catalyst casing 33 and the second catalyst casing 34 and an addition valve 36 for adding urea water are provided. Further, the post-processing unit 3 has a substantially symmetrical structure.

  The exhaust gas inlet pipe 31 is disposed at the front end and the left side of the post-processing unit 3, extends from the front to the rear, and the front end is connected to the downstream end of the upstream exhaust pipe 21. Further, the exhaust gas outlet pipe 32 is disposed at the front end and the right side of the post-processing unit 3, extends from the front to the rear, and the front end is connected to the upstream end of the downstream exhaust pipe 22.

  More specifically, a flange 31a is provided at the upstream end of the exhaust gas inlet pipe 31, and the flange 21a of the upstream exhaust pipe 21 is connected to the flange 31a. Similarly, a flange 32a is provided at the downstream end of the exhaust gas outlet pipe 32, and the flange 22a of the downstream exhaust pipe 22 is connected to the flange 32a. The flanges connected to each other are detachably fixed by fastening means such as bolts (not shown).

  The first catalyst casing 33 is formed in a tubular shape, extends rearward from the exhaust gas inlet pipe 31, and has a first side hole 33b on the right side surface of the downstream end portion 33a located at the rear end portion. Further, the first catalyst casing 33 is formed with a first enlarged-diameter portion 33c having a diameter larger than that of the exhaust gas inlet pipe 31 located on the upstream side and the connecting pipe 35 located on the downstream side.

  The first catalyst casing 33 has an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 10a and a particulate filter (hereinafter, referred to as “Diesel Oxidation Catalyst”) from the upstream side through a first heat insulating buffer member (mat) 37 at the position of the first enlarged diameter portion 33c. (Referred to as “DPF”) 10b.

The oxidation catalyst 10a oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas. The oxidation catalyst 10a has a function of heating and raising the temperature of exhaust gas with heat generated during oxidation of HC and CO. The oxidation catalyst 10a oxidizes NO in the exhaust gas to NO _2, also has a function of increasing the NO ₂ concentration in the exhaust gas.

  The DPF 10b collects and removes particulate matter (PM) contained in the exhaust gas. In the present embodiment, a so-called wall flow type DPF 10b is used in which openings at both ends of a honeycomb-shaped heat-resistant substrate are alternately closed in a checkered pattern. However, any type of filter that physically captures PM can be used, such as a mesh-shaped foam shape.

  The DPF 10b is a so-called continuous regeneration type DPF with a catalyst in which a noble metal (catalyst) such as Pt is supported on the inner wall thereof. In this case, during normal operation of the engine, HC in the exhaust gas supplied to the DPF 10b is oxidized and burned by the catalytic action, and at this time, PM accumulated in the DPF 10b is simultaneously burned and removed. In addition, since DPF10b has a catalyst, DPF10b shall also be included in the catalyst 10 said to this invention here.

  The second catalyst casing 34 is formed in a tubular shape, extends rearward from the exhaust gas outlet pipe 32, and has a second side hole 34b on the left side of the upstream end 34a located at the rear end. Further, the second catalyst casing 34 is formed with a second diameter-expanded portion 34c having a diameter larger than that of the exhaust gas inlet pipe 31 located on the upstream side and the exhaust gas outlet pipe 32 located on the downstream side.

  In the second catalyst casing 34, the NOx catalyst 10c and the ammonia oxidation catalyst 10d are installed from the upstream side through the second heat insulating buffer member (mat) 38 at the position of the second enlarged diameter portion 34c.

The NOx catalyst 10c is a catalyst for purifying nitrogen oxides NOx in the exhaust gas. The NOx catalyst 10c is composed of a selective reduction type NOx catalyst (SCR: Selective Catalytic Reduction), and can continuously reduce NOx by ammonia (NH ₃ ) generated by hydrolysis from urea water.

The ammonia oxidation catalyst 10d is a catalyst that oxidizes excess ammonia (NH ₃ ) that has not been consumed in the reduction of NOx by the NOx catalyst 10c to generate N ₂ .

  In the present embodiment, the first catalyst casing 33 and the second catalyst casing 34 are arranged on the left and right in parallel with each other. Further, the first side hole 33b and the second side hole 34d are disposed at positions facing each other.

  The connecting pipe 35 is disposed at a position between the first catalyst casing 33 and the second catalyst casing 34 in the left-right direction, and connects the downstream end X1 of the first catalyst casing 33 and the upstream end Y1 of the second catalyst casing 34. To do. Further, the connecting pipe 35 has a folded portion U that extends from the rear to the front along the exhaust flow direction, is folded back into a U shape, and extends rearward.

  More specifically, the connecting pipe 35 extends from the first side hole 33b toward the second side hole 34b (the right side in the figure) and bends forward, and the second side hole 34b extends to the first side hole 33b. A second portion 35b extending toward the side (the left side in the figure) and bent forward. Specifically, the first portion 35a corresponds to a portion from the first side hole 33b to X2 in the drawing, and the second portion 35b corresponds to a portion from the second side hole 34b to Y2 in the drawing. .

  The connecting pipe 35 has a third portion 35c that extends forward from the downstream end X2 of the first portion 35a, is folded back at the folded portion U and extends rearward, and is connected to the upstream end Y2 of the second portion 35b. . That is, the connection pipe 35 is formed in such a manner that it is folded in a U-shape, so that the pipe length of the connection pipe 35 becomes longer than linearly connecting the first side hole 33b and the second side hole 34d.

  The casing 4 is made of a box-type casing using a heat-resistant material such as stainless steel, and covers the entire post-processing unit 3 in a substantially airtight manner. A heat insulating material 41 such as glass wool is laid on almost the entire inner peripheral surface of the casing 4 in order to keep the post-processing unit 3 warm.

  In the front surface 42 of the casing 4, an inlet hole 42 a through which the exhaust gas inlet pipe 31 of the post-processing unit 3 is inserted and an outlet hole 42 b through which the exhaust gas outlet pipe 32 is inserted are formed at the left and right positions.

  On the other hand, a mounting portion 43a for attaching the addition valve 36 is formed on the rear surface 43 of the casing 4 at a portion located behind the bent portion L of the first portion 35a. The attachment portion 43a is formed to be recessed forward, and an outer insertion hole 43b extending in the front-rear direction is formed at the front end thereof. Further, an inner insertion hole 35d is formed on the rear end surface of the bent portion L coaxially with the outer insertion hole 43b. The addition valve 36 is inserted from the outside (rear) of the casing 4 into both the outer insertion hole 43b and the inner insertion hole 35d, and is fixed to the casing 4 by a boss portion 43c provided in the attachment portion 43a.

  The addition valve 36 is arranged to add urea water from the rear to the front from the upstream side of the folded portion U toward the folded portion U. Here, the upstream side of the folded portion U means the inside of the bent portion L of the first portion 35a.

  As will be described in detail later, the added urea water tends to stay in a liquid phase state on the inner surface of the front surface portion Uf of the folded portion U. Since the portion where the urea water stays may corrode due to the urea water, in this embodiment, the front surface portion Uf is made detachable so that it can be replaced.

  Specifically, the front surface portion Uf is divided from the connecting pipe 35 along a dividing surface S that extends in the vertical and horizontal directions. For convenience, the portion of the connecting pipe 35 excluding the front surface portion Uf is referred to as a connecting pipe main body B. The front surface portion Uf has an elliptical or oval shape when viewed from the front. The position of the dividing surface S is arbitrary, but the front surface portion Uf is set so as to include a portion where the urea water stays in a liquid phase state, and thus a portion that may corrode due to the urea water. In the present embodiment, the folded portion U bends about 90 ° as it goes from the upstream side to the downstream side, and the dividing surface S is set at a position on the pipe center C of the folded portion U.

  A flange 39a and a flange 39b are respectively provided at the rear end portion of the front surface portion Uf and the front end portion of the remaining connecting pipe main body B, and the flanges 39a and 39b are detachably fixed by fastening means such as bolts 39c. The In a state where the flanges 39a and 39b are fixed, the front surface portion Uf and the connecting pipe main body B are hermetically connected.

  On the other hand, when the fixing by the flanges 39a and 39b is released, the front surface portion Uf can be detached from the connecting pipe main body B.

  In the center of the front surface 42 of the casing 4, an opening 44 through which the front end portion Uf can pass is provided at a position facing the front surface portion Uf of the folded portion U.

  The area of the opening 44 is arbitrary, but it is preferable that the opening 44 be sized so that the replacement work of the front face Uf can be easily performed. The shape of the opening 44 is arbitrary, and for example, a circular shape or a square shape can be considered. However, a rectangular shape that is long in the left-right direction may be used in accordance with the shape of the front surface portion Uf.

  The front surface 42 of the casing 4 is provided with a lid 5 that covers the opening 44 so as to be opened and closed from the front. The lid 5 is detachably fixed to the front surface 42 of the casing 4 by fastening means such as a plurality of bolts 45 around the opening 44. In order to keep the post-processing unit 3 warm, a heat insulating material 41 such as glass wool is also laid on the inner surface of the lid 5.

  In addition, all the tubular members located in the upstream of the NOx catalyst 10c are included in the tube member of the post-processing unit 3 in the present invention. That is, the second catalyst casing 34, the connecting pipe 35, the first catalyst casing 33, and the exhaust gas inlet pipe 31 located on the upstream side of the NOx catalyst 10c are included in the pipe member of the present invention. The tube member in this embodiment is the connecting tube 35 among them.

  Next, based on FIG. 1, the effect of the exhaust gas purification apparatus 100 which concerns on this embodiment is demonstrated.

  The exhaust gas of the internal combustion engine 1 passes from the exhaust manifold 12 through the upstream exhaust pipe 21 and flows into the first catalyst casing 33 through the exhaust gas inlet pipe 31.

  The exhaust gas flowing into the first catalyst casing 33 passes through the oxidation catalyst 10a, whereby unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas are oxidized and purified.

  Next, the exhaust gas that has passed through the oxidation catalyst 10a flows into the DPF 10b, and particulate matter (PM) contained in the exhaust gas is collected and removed by the DPF 10b.

  The exhaust gas that has passed through the DPF 10b flows from the first side hole 33b located at the rear end of the first catalyst casing 33 to the first portion 35a of the connecting pipe 35, and moves forward 90 ° along the bent shape of the first portion 35a. The direction is changed to flow to the third portion 35c.

  The exhaust gas that has flowed to the third portion 35c turns 180 ° backward at the turn-up portion U, flows to the rear second portion 35b, turns 90 ° along the bent shape of the second portion, and then turns to the second side. It flows into the second catalyst casing 34 through the hole 34b.

  Here, the addition valve 36 disposed in the bent portion L of the first portion 35a adds urea water from the rear to the front toward the folded portion U of the third portion 35c. The exhaust gas mixed with urea water turns 180 ° backward at the folded portion U, flows to the rear second portion 35b, turns 90 ° along the bent shape of the second portion 35b, and moves to the second side. It flows into the second catalyst casing 34 through the hole 34b. In this process, the urea water added from the addition valve 36 is hydrolyzed to produce ammonia while being mixed with the exhaust gas and evaporating.

  Next, in the second catalyst casing 34, the exhaust gas containing at least one of urea water and ammonia passes through the NOx catalyst 10c. At this time, the NOx catalyst 10c reduces NOx with ammonia generated by hydrolysis of urea water.

  Excess ammonia that has not been consumed in the reduction of NOx by the NOx catalyst 10c is oxidized in contact with the ammonia oxidation catalyst 10d, and the release to the atmosphere is suppressed.

  The exhaust gas that has passed through the ammonia oxidation catalyst 10d is discharged to the downstream exhaust pipe 22 through the exhaust gas outlet pipe 32 and is released from the downstream exhaust pipe 22 to the atmosphere.

  Among the above actions, the oxidation catalyst 10a, the DPF 10b, the NOx catalyst 10c, and the ammonia oxidation catalyst 10d exhibit the exhaust gas purification action effectively when the catalyst temperature (catalyst bed temperature) is in the active temperature range. Therefore, it is effective to keep the temperature of each catalyst 10 as high as possible.

  In the present embodiment, the post-processing unit 3 is accommodated in the casing 4 in which the heat insulating material 41 is laid on the inner peripheral surface, thereby suppressing the post-processing unit 3 from being cooled by outside air or traveling wind, The temperature of the catalyst 10 can be kept high.

  In the post-processing unit 3 of the present embodiment, the connecting pipe 35 is formed by being folded into a U shape. For this reason, rather than forming the connecting pipe 35 linearly, the pipe length of the connecting pipe 35 can be made longer, and the post-processing unit 3 can be made compact.

  Further, the urea water added from the addition valve 36 passes through the long and folded connecting pipe 35, so that the urea water is sufficiently stirred and mixed with the exhaust gas and evaporated. Hydrolysis of is promoted. As a result, ammonia is efficiently generated, which is advantageous for improving the NOx purification rate in the NOx catalyst 10c.

  On the other hand, when the exhaust gas containing urea water passes through the folded portion U, the urea water tends to adhere and stay on the inner surface of the front surface portion Uf in a liquid phase state. In particular, in the folded portion U, the urea water tends to adhere and stay on the inner surface due to a centrifugal force when the urea water changes its direction by 180 °. As a result, the front surface portion Uf may corrode from the inner surface due to the retained urea water.

  In order to respond to the recent tightening of NOx regulations, it is necessary to increase the size of the NOx catalyst and increase the amount of urea water added, so that the staying part may corrode more significantly.

  Therefore, in the exhaust gas purification apparatus 100 according to the present embodiment, the front surface portion Uf that may corrode due to retention of urea water is made detachable from the connecting pipe 35. Further, the front surface 42 of the casing 4 is provided with an opening 44 through which the removed front surface portion Uf can pass and a cover 5 that covers the opening 44 so as to be opened and closed.

  This makes it possible to easily replace the corroded front surface portion Uf while the post-processing unit 3 is housed in the casing 4.

  In this replacement operation, first, the bolt 45 on the front surface 42 of the casing 4 is loosened, the lid 5 is removed, a hand or a tool is inserted through the opening 44 of the casing 4, and the bolt 39c on the front surface portion Uf is loosened. Then, the fixing by the flanges 39a and 39b is released, and the front surface portion Uf is removed from the connecting pipe 35. And the front part Uf for replacement | exchange is attached in the procedure reverse to a removal procedure. Thus, in this embodiment, even if the post-processing unit 3 is still accommodated in the casing 4, the replacement work can be easily performed.

  Moreover, in this embodiment, since the opening part 44 of the casing 4 exists in the position which opposes the front part Uf, it becomes possible to perform replacement | exchange work more easily.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust pipe 3 Aftertreatment unit 4 Casing 5 Cover 10c Selective reduction type NOx catalyst 31 Exhaust gas inlet pipe 32 Exhaust gas outlet pipe 33 First catalyst casing 34 Second catalyst casing 35 Connecting pipe 36 Addition valve 44 Opening portion 100 Exhaust gas purification apparatus

Claims (2)

An exhaust pipe,
An aftertreatment unit provided in the middle of the exhaust pipe and having a plurality of catalysts for purifying exhaust gas;
A casing for accommodating the post-processing unit,
The post-processing unit is
A selective reduction type NOx catalyst;
A pipe member that extends from the upstream side of the selective reduction NOx catalyst toward the selective reduction NOx catalyst and through which exhaust gas passes;
An addition valve for adding urea water to a position upstream of the selective reduction type NOx catalyst in the pipe member,
The pipe member has a portion where urea water added from the addition valve stays at a position between the addition valve and the selective reduction type NOx catalyst,
An exhaust gas purifying apparatus for an internal combustion engine, wherein the part is detachable, an opening through which the part can pass is provided in the casing, and a lid is provided on the casing so as to open and close the opening. An exhaust pipe,
An aftertreatment unit provided in the middle of the exhaust pipe and having a plurality of catalysts for purifying exhaust gas;
A casing for accommodating the post-processing unit,
The post-processing unit is
A tubular first catalyst casing containing at least one catalyst;
A tubular second catalyst casing disposed in parallel with the first catalyst casing and having a selective reduction type NOx catalyst therein;
A connecting pipe disposed at a position between the first catalyst casing and the second catalyst casing and connecting a downstream end of the first catalyst casing and an upstream end of the second catalyst casing; A connecting pipe having a folded portion that extends from the rear to the front along the U, and is folded back into a U shape and extends rearward.
A urea water addition valve arranged to add urea water from the rear to the front from the upstream side of the folded portion toward the folded portion, and
The folded portion has a detachable front surface portion,
The front surface of the casing is provided with an opening through which the front surface portion can pass at a position facing the front surface portion of the folded portion, and a lid that covers the opening portion so as to be openable and closable. An exhaust gas purification device for an internal combustion engine.

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