JP2022107917A - Pipe connection structure - Google Patents

Abstract

To improve workability effectively during attachment/detachment in a structure of connecting pipes to each other.SOLUTION: In a pipe connection structure, an end of a first pipe 21 and an end of a second pipe 50 are connected by a fixing member 55. The pipe connection structure includes an engagement mechanism 70 having: a through hole 72 provided at the end of the first pipe 21; and a claw part 74 which is provided at the end of the second pipe 50 and may be inserted into the through hole 72. In the engagement mechanism 70, the claw part 74 engages with the through hole 72 to cause the second pipe 50 to engage with the first pipe 21.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present disclosure relates to a pipe connection structure, and more particularly to a technique suitable for connecting exhaust pipes through which exhaust gas from an internal combustion engine flows.

Exhaust post-treatment devices include those equipped with a filter that collects particulate matter (PM) in the exhaust, nitrogen oxides (NOx) in the exhaust, and ammonia produced from urea water. It is known to have a selective catalytic reduction (hereinafter referred to as SCR) for reduction purification as a reducing agent.

As examples of this type of exhaust aftertreatment device, for example, Patent Documents 1 and 2 disclose that a filter is arranged on the upstream side of the exhaust gas and an SCR is arranged on the downstream side of the exhaust gas. A structure is disclosed that includes a mixer chamber that allows

JP 2015-068341 A JP 2013-104395 A

Incombustible ash, etc., which cannot be burned and removed by forced regeneration, accumulates on the filter, so it is necessary to remove the filter from the unit and periodically clean it. During filter maintenance, the mixer chamber must be removed from the unit, but in the case of a flange fastening structure in which the unit and the mixer chamber are fixed to each other with a plurality of bolts and nuts, there is a problem that it takes time to attach and detach. be.

In order to improve the workability during attachment and detachment, it is conceivable to employ a structure in which the unit and the mixer chamber are connected by a V-clamp or the like, as in the structure described in Patent Document 1 above. However, the mixer chamber is heavy and loosening the V-clamp may cause the mixer chamber to fall out of the unit.

The technique of the present disclosure has been made in view of the above circumstances, and aims to effectively improve the workability at the time of attachment and detachment in a tube connection structure.

The technique of the present disclosure is a pipe connection structure in which an end portion of a first pipe and an end portion of a second pipe are connected by a fixing member, and a through hole provided in the end portion of the first pipe. and a pawl portion provided at the end portion of the second pipe and capable of being inserted into the through hole, and by engaging the pawl portion with the through hole, the second pipe is moved to the above It is characterized by comprising a locking mechanism for locking to the first pipe.

Further, the through hole is provided in a first plate member projecting from the upper outer periphery of the end of the first pipe toward the second pipe, and the claw portion is provided in the end of the second pipe. It extends in the direction toward the tube axis from the upper inner circumference of the tube, and is preferably inserted into the through hole from above.

Further, the through-hole is formed in an elongated hole shape extending in the axial direction of the first pipe, and at least the portion of the first plate member provided with the through-hole extends toward the second pipe. It is preferable to incline outward in the radial direction of the first tube as it goes.

Further, the through hole is formed in an elongated hole shape extending in the axial direction of the first pipe, and the claw portion is the second plate member provided on the upper inner circumference of the second pipe. It is formed by bending the end portion on the first pipe side radially inward, and the portion of the upper surface of the first plate member that is closer to the second pipe side than the end portion of the through hole on the first pipe side is. It is preferable that the portion is provided with a restricting protrusion that contacts the lower surface of the second plate member and restricts movement of the second plate member in a direction away from the first pipe.

Further, the fixing member is a V-clamp that brings a first flange portion provided at the end portion of the first pipe and a second flange portion provided at the end portion of the second pipe into close contact with each other. is preferred.

The first pipe is a casing that houses a filter that collects particulate matter contained in the exhaust gas of the internal combustion engine, and the second pipe stirs and mixes the urea water injected from the injector with the exhaust gas. A mixer chamber is preferred.

According to the technique of the present disclosure, it is possible to effectively improve the workability at the time of attachment and detachment in the tube connection structure.

1 is a schematic overall configuration diagram showing an exhaust system of an engine according to an embodiment; FIG. 1 is a schematic perspective view showing an exhaust post-treatment device according to this embodiment; FIG. It is a typical perspective view which shows the locking mechanism which concerns on 1st embodiment. It is a typical sectional view showing a locking mechanism concerning a first embodiment. It is a typical perspective view which shows the locking mechanism which concerns on 2nd embodiment. It is a typical sectional view showing a lock mechanism concerning a second embodiment. It is a typical perspective view which shows the locking mechanism which concerns on 3rd embodiment. It is a typical sectional view showing a locking mechanism concerning a third embodiment.

A pipe connection structure according to this embodiment will be described below with reference to the accompanying drawings. The same parts are given the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[overall structure]
FIG. 1 is a schematic overall configuration diagram showing an exhaust system of an engine 10 according to this embodiment.

As shown in FIG. 1, an engine 10 includes an engine body 11 including a cylinder head, a cylinder block in which a plurality of cylinders are formed, and the like. The cylinder head of the engine main body 11 is provided with an exhaust manifold 12 that collects exhaust gas discharged from each cylinder. An upstream exhaust pipe 13, an exhaust aftertreatment device 20, a downstream exhaust pipe 15, a muffler (not shown), and the like are connected to the exhaust manifold 12 in this order from the exhaust upstream side.

The exhaust aftertreatment device 20 includes, in order from the exhaust upstream side, a pre-stage casing 21 (an example of the first pipe of the present disclosure), a mixer chamber 50 (an example of the second pipe of the present disclosure), a urea water injection device 30, It includes a connection exhaust pipe 60 (an example of the first pipe of the present disclosure) and a rear casing 41 .

The front-stage casing 21 has a substantially cylindrical shape, and an oxidation catalyst 22 and a filter 23 are housed therein in this order from the exhaust upstream side.

The oxidation catalyst 22 is formed, for example, by carrying catalyst components and the like on the surface of a ceramic carrier such as a cordierite honeycomb structure. The oxidation catalyst 22 oxidizes the unburned fuel (hydrocarbon: HC) supplied by the post-injection of the engine 10 or the exhaust pipe injection of an exhaust pipe injector (not shown) to raise the temperature of the exhaust gas.

The filter 23 is formed, for example, by arranging a large number of cells partitioned by porous partition walls along the flow direction of the exhaust gas and alternately plugging the upstream side and the downstream side of these cells. . The filter 23 collects PM in the exhaust gas on the pores and surfaces of the partition walls, and when the amount of accumulated PM reaches a predetermined amount, the filter is forcedly regenerated by burning and removing it.

The mixer chamber 50 has its upstream end connected to the downstream end of the pre-stage casing 21 . An upstream end of a connection exhaust pipe 60 is connected to the downstream end of the mixer chamber 50 , and an upstream end of the post-stage casing 41 is connected to the downstream end of the connection exhaust pipe 60 . A urea water injector 35 of the urea water injection device 30 is provided at a predetermined portion of the mixer chamber 50, and is configured to agitate and mix the urea water injected from the urea water injector 35 with the exhaust gas.

The urea water injection device 30 includes a urea water tank 31 that stores urea water, a strainer 32 that is immersed in the urea water in the urea water tank 31 to remove foreign matter, a supply pipe 33 connected to the strainer 32, a supply A urea water pump 34 that is provided in the pipe 33 and pumps up the urea water from the urea water tank 31 and a urea water injector 35 that injects the urea water supplied from the supply pipe 33 are provided.

The urea water injected from the urea water injector 35 is hydrolyzed by exhaust heat and water vapor in the exhaust gas to produce ammonia (NH3), which is supplied to the downstream SCR 48 as a reducing agent.

The post-stage casing 41 has a substantially cylindrical shape and accommodates therein an SCR 48 and an ammonia slip catalyst 49 in this order from the exhaust upstream side.

The SCR 48 is formed, for example, by supporting zeolite or the like on a porous ceramic carrier. The SCR 48 adsorbs ammonia supplied as a reducing agent from the urea water injector 35, and selectively reduces and purifies NOx from the passing exhaust gas with the adsorbed ammonia. The ammonia slip catalyst 49 is formed, for example, by supporting an oxidation catalyst component or the like on the surface of a ceramic carrier such as a honeycomb structure, and has a function of oxidizing ammonia slipped downstream from the SCR 48 .

[Exhaust aftertreatment device]
FIG. 2 is a schematic perspective view showing the exhaust post-treatment device 20 according to this embodiment.

As shown in FIG. 2, the front casing 21 and the rear casing 41 are formed in a substantially cylindrical shape. The front casing 21 and the rear casing 41 are arranged in parallel so that their axes are substantially parallel to each other, and are connected via a mixer chamber 50 and a connecting exhaust pipe 60 .

The mixer chamber 50 includes a first chamber portion 51 having a substantially arcuate side surface disposed at the downstream end of the front casing 21 and a second chamber portion 51 having a substantially arcuate side surface extending from the side surface of the first chamber portion 51 toward the rear casing 41 side. and a chamber portion 52 . The diameter of the first chamber portion 51 is formed larger than the diameter of the second chamber portion 52, and the boundary between the two is curved in a substantially arc shape. A downstream end of the front casing 21 is connected to the first chamber portion 51 .

In the drawing, the mixer chamber 50 is connected to the rear casing 41 via a connection exhaust pipe 60, and the front casing 21, the mixer chamber 50, the connection exhaust pipe 60, and the rear casing 41 form a substantially S-shape. However, the mixer chamber 50 may be directly connected to the rear casing 41 so that the front casing 21, the mixer chamber 50, and the rear casing 41 are substantially U-shaped. In this case, the first chamber portion 51 and the second chamber portion 52 may be formed to have approximately the same diameter.

The connection exhaust pipe 60 has, in order from the upstream side, a first connection pipe portion 61 that extends substantially linearly, and a second connection pipe portion 62 that bends in a substantially L shape. The first connection pipe portion 61 is arranged such that its axis is substantially parallel to the axes of the front casing 21 and the rear casing 41 , and its upstream end is connected to the second chamber portion 52 . The second connecting pipe portion 62 is an elbow pipe and connects the downstream end of the first connecting pipe portion 61 and the upstream end of the rear casing 41 .

The front casing 21 and the first chamber portion 51 are connected via a V-clamp 55 (an example of the fixing member of the present disclosure), and the second chamber portion 52 and the first connecting pipe portion 61 are connected via a V-clamp 56 (an example of the fixing member of the present disclosure). These V clamps 55 and 56 have an annular shape with an inner peripheral groove having a substantially V-shaped cross section. Specifically, when the V-clamp 55 is tightened in the circumferential direction, the front casing 21 and the flange portions (not shown) provided on the first chamber portion 51 are brought into close contact with each other. and the first chamber portion 51 are connected to each other. Similarly, when the V-clamp 56 is tightened in the circumferential direction, flange portions (not shown) provided on the second chamber portion 52 and the first connection pipe portion 61 are brought into close contact with each other. The chamber portion 52 and the first connecting pipe portion 61 are configured to be connected to each other.

Here, in order to remove the filter 23 from the front casing 21 during maintenance of the filter 23 or the like, it is necessary to remove the mixer chamber 50 from the front casing 21 and the first connecting pipe portion 61 . At this time, if the V clamps 55 and 56 are loosened, the heavy mixer chamber 50 may fall off from the front casing 21 and the first connecting pipe portion 61 . In this embodiment, locking mechanisms 70 and 80 are provided to prevent the mixer chamber 50 from falling off.

Specifically, the first locking mechanism 70 is provided above the front casing 21 and the first chamber portion 51 , and locks the first chamber portion 51 to the front casing 21 to close the mixer chamber 50 . function to prevent the falling off of the The second locking mechanism 80 is provided above the second chamber portion 52 and the first connecting pipe portion 61, and locks the second chamber portion 52 to the first connecting pipe portion 61 to close the mixer chamber. It functions to prevent 50 from falling out. The detailed structure of these locking mechanisms 70 and 80 will be described below. Since the first locking mechanism 70 and the second locking mechanism 80 are both configured in substantially the same manner, the first locking mechanism 70 will be described below, and the second locking mechanism 80 will be described in detail. Description is omitted.

[First embodiment]
FIG. 3 is a schematic perspective view showing the locking mechanism 70 (80) according to the first embodiment, and FIG. 4 is a schematic cross-sectional view showing the locking mechanism 70 (80) according to the first embodiment. It is a diagram.

As shown in FIG. 3 , the locking mechanism 70 includes a first plate member 71 having a through hole 72 and a second plate member 73 having a claw portion 74 . The through hole 72 is formed in an elongated hole shape extending along the longitudinal direction of the first plate member 71 . The second plate member 73 includes a long plate-like plate main body portion 73A, which is bent downward in a substantially L shape from one end in the longitudinal direction of the plate main body portion 73A to a predetermined height from the lower surface of the plate main body portion 73A. and a bent portion 73B protruding at H1. The claw portion 74 is formed to protrude downward from the lower end of the bent portion 73B. The length of the claw portion 74 is preferably longer than the plate thickness of the first plate member 71, the width of the claw portion 74 is preferably shorter than the opening width of the through hole 72 in the lateral direction, and the bent portion It is formed shorter than the width of 73B. When the claw portion 74 is inserted into the through hole 72 from above, the side surface of the claw portion 74 engages with the opening edge of the through hole 72 , thereby locking the second plate member 73 to the first plate member 71 . is configured as At this time, a portion 73C of the lower end surface of the bent portion 73B other than the claw portion 74 is brought into contact with the upper surface of the first plate member 71. As shown in FIG.

As shown in FIG. 4, a substantially annular first flange portion 21A extending in the circumferential direction protrudes from the outer peripheral surface of the upstream casing 21 on the downstream side. Further, the end portion of the mixer chamber 50 facing the front casing 21 is provided with a substantially annular second flange portion 51A formed by bending the end portion radially outward. When connecting the front casing 21 and the mixer chamber 50, the first flange portion 21A and the second flange portion 51A are in contact with each other, and the V clamp 55 (see FIG. 4B) is fitted. By tightening in the circumferential direction, the first flange portion 21A and the second flange portion 51A are brought into close contact with each other.

One longitudinal end 71A of the first plate member 71 is fixed to the upper outer peripheral surface of the front casing 21 , and the longitudinal direction of the through hole 72 is provided so as to substantially match the axial direction of the front casing 21 . . Specifically, the first plate member 71 has one longitudinal end 71A fixed to the outer peripheral surface closer to the end than the first flange portion 21A of the front casing 21, and the other longitudinal end 71B of the mixer chamber. It is attached so as to protrude inside 50 . Here, the method of fixing the first plate member 71 and the front casing 21 is not particularly limited, and they may be fixed by welding or bolts and nuts. Moreover, the first plate member 71 does not need to be separate from the front casing 21 and may be formed integrally with the front casing 21 .

The second plate member 73 is fixed to the upper inner peripheral surface of the mixer chamber 50 facing the upper surface of the first plate member 71 . It is provided so as to extend downward toward the center. That is, the mixer chamber 50 can be easily locked to the front casing 21 simply by inserting the claw portions 74 into the through holes 72 from above and engaging them with each other. Here, the method of fixing the second plate member 73 and the mixer chamber 50 is not particularly limited, and they may be fixed by welding or bolts and nuts. Also, the second plate member 73 need not be separate from the mixer chamber 50 and may be formed integrally with the mixer chamber 50 .

In this embodiment, the claw portion 74 is offset by a predetermined amount toward the inside of the mixer chamber 50 from the second flange portion 51A. This offset amount is set to be substantially equal to or longer than the separation distance D between the one end 71A side end of the through hole 72 and the first flange portion 21A. That is, as shown in FIG. 4A, the claw portion 74 is inserted into the through hole 72, and as shown in FIG. The second flange portion 51A comes into contact with the first flange portion 21A when it is moved to the end portion on the one end 71A side of 72 . At this time, while the claw portion 74 is guided by the through-hole 72, the second plate member 73 (specifically, the portion 73C (see FIG. 3) other than the claw portion 74 of the lower end surface of the bent portion 73B) is pushed downward. Since the upper surface of the one-plate member 71 is slid, the operator can easily move the mixer chamber 50 to the correct mounting position of the V-clamp 55 .

According to the first embodiment detailed above, the first plate member 71 having the through hole 72 is provided on the upper outer peripheral surface of the front casing 21 , and the second plate member 73 having the claw portion 74 is provided at the upper portion of the mixer chamber 50 . Provided on the inner peripheral surface, the mixer chamber 50 can be easily locked to the front-stage casing 21 simply by inserting the claw portion 74 into the through hole 72 from above and engaging it. As a result, when the bolt of the V clamp 55 is loosened to remove the mixer chamber 50 from the front casing 21 or when the mixer chamber 50 is assembled to the front casing 21, the engagement between the claw portion 74 and the through hole 72 allows the Since the mixer chamber 50 is securely held by the front casing 21, it is possible to effectively prevent the mixer chamber 50 from coming off, and it is possible to reliably improve workability during attachment and detachment.

When the claw portion 74 is inserted into the through-hole 72 and the mixer chamber 50 is pushed toward the front casing 21 , the second plate member 73 slides along the longitudinal direction of the through-hole 72 on the upper surface of the first plate member 71 . By doing so, the second flange portion 51A is configured to come into contact with the first flange portion 21A. As a result, the operator can accurately and easily move the mixer chamber 50 to the position where the V-clamp 55 is attached, and the workability of attaching the V-clamp 55 can be reliably improved.

[Second embodiment]
FIG. 5 is a schematic perspective view showing the locking mechanism 70 (80) according to the second embodiment, and FIG. 6 is a schematic cross-sectional view showing the locking mechanism 70 (80) according to the second embodiment. It is a diagram.

As shown in FIGS. 5 and 6, the locking mechanism 70 (80) of the second embodiment is arranged between one end 71A and the other end 71B of the first plate member 71 with respect to each of these ends 71A and 71B. The inclined portion 71C is inclined at a predetermined angle.

Specifically, the inclined portion 71C of the front casing 21 extends from the one end 71A toward the other end 71B such that the other end 71B on the mixer chamber 50 side is located obliquely above the one end 71A on the front casing 21 side. It is formed so as to incline radially outward. The through-hole 72 extends in the longitudinal direction of the inclined portion 71C, and is formed so as to descend from the other end 71B side toward the one end 71A side, in other words, to be inclined radially inward of the front casing 21. . In this embodiment, the height H2 from the upper surface of one end 71A of the first plate member 71 to the upper surface of the other end 71B is the height from the lower end of the bent portion 73B of the second plate member 73 to the lower surface of the plate body portion 73A. It is formed to be lower (shorter) than H1 (H2<H1).

That is, when the claw portion 74 is inserted into the other end 71B side of the through hole 72 as shown in FIG. The upper surface of the inclined portion 71C is configured to slide down toward the front casing 21 side. As a result, the mixer chamber 50 can be stably held in the assembly position of the V-clamp 55 (see FIG. 6(B)) in which the second flange portion 51A and the first flange portion 21A abut against each other due to its own weight. It is possible to effectively improve workability during assembly. In addition, while the mixer chamber 50 is stabilized in the mounting posture of the V-clamp 55, the engagement between the claw portion 74 and the through hole 72 is effectively held, thereby more reliably preventing the mixer chamber 50 from coming off. is also possible.

[Third Embodiment]
FIG. 7 is a schematic perspective view showing the locking mechanism 70 (80) according to the third embodiment, and FIG. 8 is a schematic cross-sectional view showing the locking mechanism 70 (80) according to the third embodiment. It is a diagram.

As shown in FIGS. 7 and 8, the locking mechanism 70 (80) of the third embodiment has a plurality of restricting projections 78 on the upper surface of the first plate member 71. As shown in FIGS.

Specifically, the plurality of restricting projections 78 are formed to have a substantially triangular cross-sectional shape in which a ridgeline L where the upper ends of the side surfaces 78A and 78B intersect extends in a direction orthogonal to the longitudinal direction of the first plate member 71. As shown in FIG. Each of the restricting projections 78 is provided on the upper surface of the first plate member 71 closer to the other end 71B than the end of the through hole 72 on the one end 71A side. In the present embodiment, each pair of restricting projections 78 that face each other across the through hole 72 form a set, and a plurality of sets are arranged in the longitudinal direction of the through hole 72 at predetermined intervals. That is, when the claw portion 74 is inserted into the through hole 72 and the second plate member 73 is moved to a position where the claw portion 74 abuts the end portion of the through hole 72 on the one end 71A side, the lower surface of the second plate member 73 is It is supported by the tip of each regulation protrusion 78 .

The restricting protrusion 78 is formed such that a side surface 78B on the other end 71B side is more gently inclined than a side surface 78A on the one end 71A side with respect to the upper surface of the first plate member 71 . In this embodiment, the restricting protrusion 78 has a side surface 78A on the one end 71A side that stands substantially perpendicular to the upper surface of the first plate member 71, and prevents the second plate member 73 from sliding toward the front casing 21 side. It is configured to restrict sliding movement in the opposite direction while permitting. In this embodiment, the protrusion height H3 of the restricting protrusion 78 from the first plate member 71 is lower than the height H1 from the lower end of the bent portion 73B of the second plate member 73 to the lower surface of the plate main body portion 73A. ) (H3<H1).

That is, when the claw portion 74 is inserted into the through hole 72 to move the second plate member 73 integrally with the mixer chamber 50 toward the front casing 21 side and the second flange portion 51A is brought into contact with the first flange portion 21A, The rear surface of the bent portion 73B faces the side surface 78A of the restricting projection 78, thereby effectively restricting the backward movement of the second plate member 73. As shown in FIG. As a result, the mixer chamber 50 can be stably held in the assembling posture of the V clamp 55 in which the second flange portion 51A and the first flange portion 21A are in contact with each other, effectively improving workability during assembly. becomes possible. In addition, while the mixer chamber 50 is stabilized in the posture when the V-clamp 55 is assembled, the engagement between the claw portion 74 and the through hole 72 is maintained, thereby more reliably preventing the mixer chamber 50 from coming off. It becomes possible.

[others]
It should be noted that the present disclosure is not limited to the above-described embodiments, and can be modified and implemented as appropriate without departing from the gist of the present disclosure.

For example, although the V clamps 55 and 56 are used to connect the exhaust pipes, the present disclosure can be widely applied to a connection structure using fixing members other than the V clamps. In addition, although the above-described embodiment has been described with an exhaust pipe connection structure as an example, it can be widely applied to other pipe connection structures for circulating fluids other than exhaust, such as an intake pipe connection structure.

10 engine (internal combustion engine)
20 Exhaust post-treatment device 21 Pre-stage casing (first pipe)
21A first flange portion 22 oxidation catalyst 23 filter 30 aqueous urea injection device 35 aqueous urea injector 41 post-stage casing 48 SCR
50 mixer chamber (second tube)
51 first chamber portion 51A second flange portion 52 second chamber portion 55, 56 V clamp (fixing member)
57 second flange portion 60 connection exhaust pipe (first pipe)
61 First connection exhaust pipe 70, 80 Locking mechanism 71 First plate member 71C Inclined portion 72 Through hole 73 Second plate member 74 Claw portion 78 Control projection

Claims (6)

In the pipe connection structure in which the end of the first pipe and the end of the second pipe are connected by connecting them with a fixing member,
a through-hole provided at the end of the first tube; and a claw portion provided at the end of the second tube and capable of being inserted into the through-hole, wherein the claw extends through the through-hole. A pipe connection structure comprising: a locking mechanism that locks the second pipe to the first pipe by engaging with a hole. The through hole is provided in a first plate member projecting from the upper outer periphery of the end of the first tube toward the second tube,
2. The pipe connection structure according to claim 1, wherein the claw portion extends from the upper inner circumference of the end portion of the second pipe in a direction toward the pipe axis, and is inserted into the through hole from above. The through hole is formed in an elongated hole shape extending in the axial direction of the first tube,
3. The pipe connection structure according to claim 2, wherein at least a portion of the first plate member provided with the through hole is inclined radially outward of the first pipe toward the second pipe. The through hole is formed in an elongated hole shape extending in the axial direction of the first tube,
The claw portion is formed by bending an end portion on the first pipe side of a second plate member provided on the upper inner circumference of the second pipe radially inward,
A portion of the upper surface of the first plate member that is closer to the second tube than the end of the through hole on the first tube side is in contact with the lower surface of the second plate member, The tube connection structure according to claim 2, further comprising a restricting protrusion that restricts movement in a direction away from the first tube. The fixing member is a V-clamp that brings a first flange portion provided at the end portion of the first pipe and a second flange portion provided at the end portion of the second pipe into close contact with each other. 5. The pipe connection structure according to any one of 1 to 4. The first pipe is a casing that houses a filter that collects particulate matter contained in the exhaust gas of the internal combustion engine, and the second pipe is a mixer chamber that agitates and mixes the urea water injected from the injector with the exhaust gas. The pipe connection structure according to any one of claims 1 to 5.

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