Exhaust gas recirculation system and engine

Abstract

To provide an exhaust gas recirculation device and an engine enabling reduction in the size and space saving.SOLUTION: An exhaust gas recirculation device 10 includes: an EGR passage 11 provided between an exhaust system and an intake system; and an EGR cooling part 12 provided in the EGR passage 11 and cooling recirculation gas flowing in the EGR passage 11. The EGR cooling part 12 includes: a body 121 having openings serving as an inlet part 121a and an outlet part 121b of the recirculation gas; piping 122 having a one end part 122a connected to the body 121 and the other end part 122b extending from the one end part 122a to the outer side of the body 121 and causing cooling water to flow; and flange parts 123 each connected to the opening of the body 121. An intermediate part 122c located between the one end part 122a and the other end part 122b of the piping 122 is fixed to an outer edge 123a of the flange part 123.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exhaust gas recirculation device and an engine that recirculate a part of the exhaust gas flowing through the exhaust system as recirculation gas to the intake system.

Background Art

[0002] Patent Document 1 discloses an exhaust gas purification device for an internal combustion engine, which includes an EGR passage that recirculates a part of the exhaust from the exhaust passage of the internal combustion engine to the intake passage as EGR gas, an EGR cooler provided in the EGR passage that cools the EGR gas by exchanging heat with the cooling water introduced from the engine cooling circuit, and an EGR cooling circuit that connects the inlet and outlet of the cooling water formed in the EGR cooler to the engine cooling circuit. In this exhaust gas purification device, at least a part of the EGR cooling circuit extends along the EGR passage through the connection portion between the EGR passage and the EGR cooler on the downstream side of the EGR cooler in the recirculation direction of the EGR gas, and is integrally formed with the EGR passage through a heat-conductive separation wall. A gasket for sealing the cooling water and the EGR gas is provided at the connection portion.

[0003] Patent Document 2 discloses a multi-cylinder engine in which the installation direction of the crankshaft is the front-rear direction, the width direction of the cylinder head orthogonal to the front-rear direction is the lateral direction, an intake distribution passage wall is attached to one lateral side of the cylinder head, an exhaust combined flow passage wall is attached to the other lateral side of the cylinder head, an EGR cooler is interposed between the exhaust combined flow passage and the intake distribution passage, the EGR cooler is installed in the front-rear direction on the lateral side of the cylinder block, and the exhaust combined flow passage wall is positioned directly above the EGR cooler.

[0004] Patent Document 3 discloses an exhaust gas purification device for a diesel engine, comprising: a DOC disposed in the exhaust path of the diesel engine; a DPF disposed in the exhaust path downstream of the DOC; a urea injection nozzle disposed in the exhaust path downstream of the DPF; a turbocharger turbine disposed in the exhaust path downstream of the urea injection nozzle; an SCR disposed in the exhaust path downstream of the turbine; and control means for controlling the adsorption and oxidation of HC in the DOC when the differential pressure across the DPF is within a predetermined differential pressure range and the inlet temperature of the DPF is below a predetermined temperature. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-096100 [Patent Document 2] Japanese Patent Publication No. 2007-092595 [Patent Document 3] Japanese Patent Publication No. 2013-142363 [Overview of the project] [Problems that the invention aims to solve]

[0006] An exhaust gas recirculation system is a device that reduces the combustion temperature in the cylinder compared to a system without exhaust gas recirculation by mixing a portion of the exhaust gas with the new intake air as recirculated gas, thereby suppressing the generation of nitrogen oxides (NOx). However, installing such an exhaust gas recirculation system tends to lead to larger engines, so miniaturization and space-saving of exhaust gas recirculation systems are desirable.

[0007] This invention has been made in view of the above circumstances, and aims to provide an exhaust gas recirculation device and engine that can be miniaturized and space-saving. [Means for solving the problem]

[0008] One aspect of the present invention is an exhaust gas recirculation device that recirculates a portion of the exhaust gas flowing through the exhaust system of an engine as recirculated gas to the intake system of the engine, comprising: a recirculation path provided between the exhaust system and the intake system; and a recirculation gas cooling section provided in the recirculation path for cooling the recirculated gas flowing through the recirculation path, wherein the recirculation gas cooling section comprises a main body having openings that serve as an inlet and outlet for the recirculated gas, one end connected to the main body, and another end extending outward from the one end to the main body, and a pipe for passing cooling water, and a flange portion connected to the openings of the main body, and the intermediate portion of the pipe located between the one end and the other end is fixed to the outer edge of the flange portion.

[0009] Another aspect of the present invention is an engine equipped with an exhaust gas recirculation device that recirculates a portion of the exhaust gas flowing through the exhaust system as recirculated gas to the intake system, wherein the exhaust gas recirculation device comprises a recirculation path provided between the exhaust system and the intake system, and a recirculation gas cooling unit provided in the recirculation path for cooling the recirculated gas flowing through the recirculation path, wherein the recirculation gas cooling unit comprises a main body having openings that serve as an inlet and outlet for the recirculated gas, one end connected to the main body, and another end extending outward from the one end to the main body, and a pipe for passing cooling water, and a flange portion connected to the openings of the main body, and the intermediate portion of the pipe located between the one end and the other end is fixed to the outer edge of the flange portion. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an exhaust gas recirculation device and an engine that can be miniaturized and space-saving. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view illustrating an engine equipped with an exhaust gas recirculation device according to this embodiment. [Figure 2]It is a partially enlarged perspective view illustrating an engine equipped with an exhaust gas recirculation device according to the present embodiment. [Figure 3] It is a perspective view illustrating an EGR cooler. [Figure 4] It is a plan view illustrating an EGR cooler. [Figure 5] It is a side view illustrating an EGR cooler. [Figure 6] It is a perspective view illustrating a DOC. [Figure 7] It is a perspective view illustrating a DOC. [Figure 8] It is a front view of the DOC as seen from the flange portion side. [Figure 9] It is a perspective view illustrating the arrangement state of the DOC. [Figure 10] It is a front view illustrating the arrangement state of the DOC.

Mode for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The embodiments described below are preferred specific examples of the present invention, and thus are technically preferably subject to various limitations. However, the scope of the present invention is not limited to these aspects unless there is a description to specifically limit the present invention in the following description. Also, in each drawing, the same reference numerals are given to the same components, and detailed descriptions are appropriately omitted.

[0013] (Engine) FIG. 1 is a perspective view illustrating an engine equipped with an exhaust gas recirculation device according to the present embodiment. FIG. 2 is a partially enlarged perspective view illustrating an engine equipped with an exhaust gas recirculation device according to the present embodiment. For convenience of explanation, a part of the piping is omitted in FIG. 2. The engine 1 shown in FIGS. 1 and 2 is an internal combustion engine, for example, a diesel engine. The engine 1 is mounted on, for example, industrial machines such as vehicles, construction machines, and agricultural machines.

[0014] The engine 1 includes a cylinder head 2, an intake manifold 3, an exhaust manifold 4, and an exhaust gas recirculation device 10.

[0015] The cylinder head 2 of the engine 1 is, for example, a cylinder head of a multi-cylinder engine having a plurality of cylinders. The intake manifold 3 is an example of intake distribution means for distributing intake air to each cylinder of the engine 1. The exhaust manifold 4 is an example of exhaust collection means for collecting exhaust gas from each cylinder of the engine 1. The exhaust gas recirculation device 10 is provided between the exhaust manifold 4 which is an exhaust system and the intake manifold 3 which is an intake system, and a part of the exhaust gas flowing through the exhaust system is refluxed as reflux gas to the intake system of the engine 1.

[0016] (Exhaust Gas Recirculation Device) The exhaust gas recirculation device 10 has an EGR passage 11, an EGR cooler 12, and an EGR (Exhaust Gas Recirculation) valve 13. The EGR passage 11 is an example of the "reflux passage" of the present invention. Also, the EGR cooler 12 is an example of the "reflux gas cooler" of the present invention. The exhaust gas recirculation device 10 may include a DOC (Diesel Oxidation Catalyst). The DOC 20 is an example of an oxidation catalyst and is also an example of a purification unit. When the DOC 20 is provided, the DOC 20 is provided between the exhaust manifold 4 and the EGR passage 11.

[0017] The EGR passage 11 is connected to the exhaust manifold 4 and is a path for refluxing the reflux gas to the intake system. When the DOC 20 is provided, the EGR passage 11 is connected to the exhaust manifold 4 via the DOC 20. In the engine 1 according to the present embodiment, the EGR passage 11 has a first branch portion 1101 and is branched by the first branch portion 1101 into a first EGR passage 111 and a second EGR passage 112. A second branch portion 1102 is provided in the first EGR passage 111, one of the branches is connected to the EGR cooler 12, and the other branch is connected to the outlet side. The EGR cooler 12 is not provided in the second EGR passage 112.

[0018] The EGR cooling unit 12 is a heat exchanger provided in the EGR path 11 (in this embodiment, the first EGR path 111) to cool the recirculated gas. The EGR cooling unit 12 uses the coolant of the engine 1 to cool the recirculated gas. The cooled recirculated gas is mixed with fresh intake air taken in from the intake manifold 3 and returned to the combustion chamber. Since the second EGR path 112 does not have an EGR cooling unit 12, the recirculated gas flowing through the second EGR path 112 is sent to the intake manifold 3 without being cooled.

[0019] The EGR valve 13 is an example of an adjustment means for adjusting the amount of recirculated gas supplied. In the engine 1 according to this embodiment, there is a first EGR valve 131 provided in the first EGR path 111 and a second EGR valve 132 provided in the second EGR path 112. The operation control (valve control) of the first EGR valve 131 and the second EGR valve 132 controls whether the recirculated gas via the first EGR path 111 is sent to the intake manifold 3 or whether the recirculated gas via the second EGR path 112 is sent to the intake manifold 3. For example, if the exhaust gas temperature is below a predetermined value, the recirculated gas is returned without cooling, so valve control is performed to make the second EGR path 112, which does not have an EGR cooling unit 12, the main path. If the exhaust gas temperature is above a predetermined value, the recirculated gas is cooled, so valve control is performed to make the first EGR path 111, which has an EGR cooling unit 12, the main path.

[0020] (EGR cooling section) Figure 3 is a perspective view illustrating the EGR cooling section. Figure 4 is a plan view illustrating the EGR cooling section. Figure 5 is a side view illustrating the EGR cooling section. The EGR cooling unit 12 of the exhaust gas recirculation device 10 according to this embodiment includes a main body 121 having openings that serve as an inlet 121a and an outlet 121b for the recirculated gas, a pipe 122 for passing cooling water, and a flange portion 123 connected to the openings of the main body 121. The main body 121 is provided in a box or cylindrical shape, and has a plurality of tubes (not shown) inside for passing the recirculated gas. The plurality of tubes extend from the inlet 121a to the outlet 121b.

[0021] The piping 122 has one end 122a connected to the main body 121 and the other end 122b extending outward from the one end 122a to the main body 121. The piping 122 has a first piping 1221 and a second piping 1222. For the sake of explanation, when referring to the first piping 1221 and the second piping 1222 collectively without distinction, we will refer to them as piping 122. The first piping 1221 is, for example, a piping that supplies cooling water to the main body 121, and the second piping 1222 is, for example, a piping that discharges cooling water from the main body 121. The cooling water supplied to the main body 121 from the first piping 1221 cools the recirculating gas flowing through multiple tubes inside the main body 121. The cooling water that has exchanged heat with the recirculating gas inside the main body 121 is then discharged outside the main body 121 from the second piping 1222.

[0022] Flange portions 123 are connected to the inlet portion 121a and the outlet portion 121b, which are openings of the main body 121. The flange portion 123 connected to the inlet portion 121a is the first flange portion 1231, and the flange portion 123 connected to the outlet portion 121b is the second flange portion 1232. For the sake of explanation, when referring to the first flange portion 1231 and the second flange portion 1232 collectively without distinction, they will be referred to as flange portion 123. The flange portion 123 is the part that connects the main body 121 to the first EGR path 111.

[0023] The first flange portion 1231 is connected to the pipe of the first EGR path 111 branched at the second branch portion 1102, and the second flange portion 1232 is connected to the pipe connected to the first EGR valve 131. The main body 121, the piping 122, and the flange portion 123 are each made of, for example, stainless steel. The components are connected, for example, by brazing.

[0024] One end 122a of the pipe 122 is connected to the side surface of the main body 121. The pipe 122 has an intermediate section 122c located between the one end 122a and the other end 122b. The one end 122a of the pipe 122 has a separation section A extending away from the main body 121, and a bend B provided between the separation section A and the intermediate section 122c. In this embodiment, the one end 122a of the pipe 122 is connected to the side surface of the main body 121, is separated from the side surface of the main body 121 by the separation section A, and is bent at approximately 90 degrees at the bend B. As a result, the pipe 122 has an approximately L-shape from the one end 122a to the intermediate section 122c and the other end 122b. A tube for carrying cooling water is fitted to the other end 122b of the pipe 122.

[0025] In such a pipe 122, the intermediate portion 122c is fixed to the outer edge 123a of the flange portion 123. The flange portion 123 has a fastening hole 123h, which is a fastening portion connected to the first EGR path 111. The intermediate portion 122c of the pipe 122 is fixed to the outer edge 123a opposite to the opening of the fastening hole 123h. That is, the flange portion 123 has an extension portion 123b that extends away from the opening of the main body 121 (outside the position of the fastening hole 123h). The intermediate portion 122c of the pipe 122 is connected to the outer edge 123a of the extension portion 123b of the flange portion 123, for example, by brazing.

[0026] Here, by separating the pipe 122 from the main body 121, it can be made less susceptible to the effects of the heat of the main body 121. On the other hand, separating the pipe 122 from the main body 121 increases its extension distance, which hinders miniaturization and makes it more prone to bending due to vibrations and other factors. Therefore, as in this embodiment, by separating the pipe 122 and fixing the intermediate portion 122c to the outer edge 123a of the flange portion 123, the pipe 122 with its increased extension distance can be reliably supported by the intermediate portion 122c.

[0027] Furthermore, one end 122a of the pipe 122 is separated from the side of the main body 121 by a separation section A, bent at approximately 90 degrees at a bending section B, and extends outward in the direction of extension of the main body 121. For example, the first pipe 1221 is separated from the side of the main body 121 by a separation section A, bent at approximately 90 degrees at a bending section B, and fixed to the outer edge 123a of the first flange section 1231. On the other hand, the second pipe 1222 is separated from the side of the main body 121 by a separation section A, bent at approximately 90 degrees in the opposite direction from the first pipe 1221 at a bending section B, and fixed to the outer edge 123a of the second flange section 1232. In other words, the first pipe 1221 and the second pipe 1222 extend in opposite directions to each other in the direction of extension of the main body 121, and are each fixed to the outer edge 123a of the flange section 123. This makes it possible to save space in the EGR cooling section 12 while avoiding close proximity between the first pipe 1221 and the second pipe 1222.

[0028] (DOC: Purification Department) Figures 6 and 7 are perspective views illustrating the DOC. Figure 6 shows a perspective view of the DOC20 from above, and Figure 7 shows a perspective view of the DOC from below. The DOC20 comprises a main body 21 that houses a catalyst, and a first flange portion 221 and a second flange portion 222 provided on the main body 21. The main body 21 is provided in a cylindrical shape having an EGR gas inlet portion 21a and an outlet portion 21b. The main body 21 is made of, for example, stainless steel. Inside the cylinder of the main body 21 is a catalyst that oxidizes SOF (soluble organic matter), CO (carbon monoxide), and HC (hydrocarbons) in PM (particulate matter) contained in the exhaust gas.

[0029] A first flange portion 221 is provided at the inlet portion 21a of the main body 21, and a second flange portion 222 is provided at the outlet portion 21b of the main body 21. Each of the first flange portion 221 and the second flange portion 222 is provided with fastening portions 225 that connect the main body 21 to the front and rear members. In this embodiment, each of the first flange portion 221 and the second flange portion 222 has three fastening portions 225. The three fastening portions 225 are arranged at the vertices of a triangle. That is, each of the first flange portion 221 and the second flange portion 222 is fastened and connected to the front and rear members by three-point fastening using the three fastening portions 225. The arrangement of each of the three fastening portions 225 is preferably an isosceles triangle, and more preferably an equilateral triangle. However, the shape of the triangle in the arrangement of the three fastening portions 225 is not limited to these.

[0030] The three fastening points 225 are positioned at the vertices of a triangle, allowing for secure fastening to the front and rear members while saving space. In other words, with two fastening points or fewer, the reliability of the fastening tends to be insufficient. On the other hand, with four or more fastening points, the spacing between adjacent fastening points becomes narrow, making interference with surrounding members more likely during fastening and limiting the freedom of layout. Therefore, with three fastening points, secure fastening is achieved while also making it easier to avoid interference with surrounding members during fastening, thus achieving space savings.

[0031] Furthermore, it is preferable that the first flange portion 221 and the second flange portion 222 are provided in the same shape as each other. By making the first flange portion 221 and the second flange portion 222 the same shape as each other, the number of parts can be reduced.

[0032] Figure 8 is a front view of the DOC as seen from the flange side. Figure 8 shows a front view as seen from the first flange portion 221 side, but the front view as seen from the second flange portion 222 is the same. As an example, the arrangement of the three fastening portions 225 of the first flange portion 221 is at the vertices of an equilateral triangle. The main body 21 is provided with legs 215 for stably placing the DOC 20 on a support member. For example, four legs 215 are provided on the underside of the main body 21. In the extending direction of the main body 21 (viewed from the flange portion side), it is preferable that the legs 215 are positioned to overlap with one of the three fastening portions 225. This allows the fastening portion 225 to be housed within the protruding region of the leg 215 when viewed from the flange portion side, thereby saving space for the DOC 20.

[0033] Figure 9 is a perspective view illustrating the arrangement of the DOCs. Figure 10 is a front view illustrating the arrangement of the DOC. Figure 10 shows a front view as seen from the first flange portion 221 side. As shown in Figure 9, in the exhaust gas recirculation device 10 according to this embodiment, the DOC 20 is positioned to extend laterally above the flywheel 6 at the rear of the engine 1. As a result, the exhaust system of the engine 1 is routed from the exhaust manifold 4, through the rear DOC 20, to the opposite side of the exhaust manifold 4. A support member 30 for the DOC 20 is provided above the flywheel 6, and the legs 215 provided on the main body 21 of the DOC 20 are placed on this support member 30. The legs 215 are provided with, for example, female screw holes, and the support member 30 and the legs 215 are fastened together.

[0034] The exhaust manifold 4 extends to the rear of the engine 1, and its extended end 4a opens inward, to which a flange portion 41 is attached. The first flange portion 221 of the DOC 20 abuts against the flange portion 41 of the exhaust manifold 4 and fastens together. As a result, the DOC 20 is attached to the extended end 4a of the exhaust manifold 4 at approximately a right angle to the direction of extension of the exhaust manifold 4.

[0035] As shown in Figure 10, when viewed from the front of the first flange portion 221, the three fastening portions 225 of the first flange portion 221 are positioned without overlapping with the extended end portion 4a of the exhaust manifold 4. Therefore, when fastening the flange portion 41 of the exhaust manifold 4 to the first flange portion 221 of the DOC20, the fastening work can be performed without interference with the exhaust manifold 4. Furthermore, since the DOC20 is attached almost perpendicular to the extended end portion 4a of the exhaust manifold 4, even if the DOC20 is positioned above the flywheel 6, the routing of the exhaust manifold 4 can be minimized, thereby saving space in the engine 1. Moreover, the three-point fastening of the DOC20 minimizes the protrusion of the first flange portion 221 and the second flange portion 222 toward the rear of the engine.

[0036] The EGR cooling unit 12 is located above the flywheel 6, similar to the DOC 20, and is positioned between the DOC 20 and the intake manifold 3. Furthermore, the EGR cooling unit 12 is provided to extend upward (vertically) from the downstream side of the DOC 20. This exhaust system layout and the placement of the EGR cooling unit 12 make it possible to achieve a compact exhaust system while still incorporating the DOC 20 and EGR cooling unit 12, thereby reducing the size of the engine 1.

[0037] According to this embodiment, it is possible to provide an exhaust gas recirculation device 10 and an engine 1 that can be miniaturized and space-saving.

[0038] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. For example, the purification unit is not limited to DOC20, but may be, for example, urea SCR (Urea-Selective Catalytic Reduction) or LNT (Lean Nox Trap). Furthermore, parts of the configuration of the above embodiments can be omitted or combined in any way that differs from those described above. [Explanation of Symbols]

[0039] 1...Engine, 2...Cylinder head, 3...Intake manifold, 4...Exhaust manifold, 4a...Extended end, 6...Flywheel, 10...Exhaust gas recirculation device, 11...EGR path, 12...EGR cooling section, 13...EGR valve, 20...DOC, 21...Main body, 21a...Inlet, 21b...Outlet, 30...Support member, 41...Flange, 111...First EGR path, 112...Second EGR path, 121...Main body, 121a...Inlet, 121b...Outlet, 122...Piping, 122 a...one end, 122b...other end, 122c...intermediate section, 123...flange section, 123a...outer edge, 123b...extension section, 123h...fastening hole, 131...first EGR valve, 132...second EGR valve, 215...leg section, 221...first flange section, 222...second flange section, 225...fastening section, 1101...first branch section, 1102...second branch section, 1221...first piping, 1222...second piping, 1231...first flange section, 1232...second flange section, A...separated section, B...bend section

Claims

1. An exhaust gas recirculation device that recirculates a portion of the exhaust gas flowing through the engine's exhaust system back into the engine's intake system as recirculated gas, A recirculation path provided between the exhaust system and the intake system, A reflux gas cooling unit is provided in the reflux path and cools the reflux gas flowing through the reflux path, Equipped with, The aforementioned reflux gas cooling section is The main body has openings that serve as the inlet and outlet portions of the refluxed gas, A pipe having one end connected to the main body and the other end extending outward from the one end toward the main body, through which cooling water is passed, The main body has a flange portion connected to the opening, The flange portion has a fastening portion with respect to the return path and an extension portion that extends outward from the position of the fastening portion in a direction away from the opening of the main body, An exhaust gas recirculation device, the intermediate portion located between the one end and the other end of the piping, is fixed to the outer edge of the extension portion in the flange portion.

2. The exhaust gas recirculation device according to claim 1, wherein the intermediate portion of the piping is fixed to the outer edge of the fastening portion opposite to the opening when the opening is viewed from the front.

3. The one end of the piping has a separated portion that extends away from the main body and a bent portion that bends from the separated portion toward the other end, The exhaust gas recirculation device according to claim 1, wherein the intermediate portion is provided between the bent portion and the other end.

4. The aforementioned end of the piping is connected to the side of the main body, The bent portion is provided bent at approximately 90 degrees from one end toward the other end. The exhaust gas recirculation device according to claim 3, wherein the one end is located outward in the extending direction of the main body from the opening of the main body.

5. It has a plurality of flange portions and a plurality of pipes, The plurality of flange portions include a first flange portion provided at the inlet portion and a second flange portion provided at the outlet portion. The plurality of pipes include a first pipe for introducing the cooling water into the main body and a second pipe for discharging the cooling water from the main body. The exhaust gas recirculation device according to claim 1, wherein the intermediate portion of the first pipe is fixed to the outer edge of the first flange portion or the second flange portion, and the intermediate portion of the second pipe is fixed to the outer edge of the second flange portion or the first flange portion.

6. The reflux path further comprises an oxidation catalyst section, The exhaust gas recirculation device according to claim 1, wherein the reflux gas cooling section is provided downstream of the oxidation catalyst section in the reflux path.

7. The exhaust gas recirculation device according to claim 6, wherein the reflux gas cooling section is arranged from the downstream side of the oxidation catalyst section upward.

8. The exhaust gas recirculation device according to claim 1, wherein the recirculation path comprises a first recirculation path provided with the recirculation gas cooling unit and a second recirculation path not provided with the recirculation gas cooling unit.

9. An engine equipped with an exhaust gas recirculation device that recirculates a portion of the exhaust gas flowing through the exhaust system back into the intake system as recirculated gas, The exhaust gas recirculation device is, A recirculation path provided between the exhaust system and the intake system, A reflux gas cooling unit is provided in the reflux path and cools the reflux gas flowing through the reflux path, Equipped with, The aforementioned reflux gas cooling section is The main body has openings that serve as the inlet and outlet portions of the refluxed gas, A pipe having one end connected to the main body and the other end extending outward from the one end toward the main body, through which cooling water is passed, The main body has a flange portion connected to the opening, The flange portion has a fastening portion with respect to the return path and an extension portion that extends outward from the position of the fastening portion in a direction away from the opening of the main body, An engine in which the intermediate portion located between the one end and the other end of the piping is fixed to the outer edge of the extension portion in the flange portion.

10. The engine according to claim 9, wherein the intermediate portion of the piping is fixed to the outer edge of the fastening portion opposite to the opening when the opening is viewed from the front.

11. The one end of the piping has a separated portion that extends away from the main body and a bent portion that bends from the separated portion toward the other end, The engine according to claim 9, wherein the intermediate portion is provided between the bent portion and the other end.

12. The aforementioned end of the piping is connected to the side of the main body, The bent portion is provided bent at approximately 90 degrees from one end toward the other end. The engine according to claim 11, wherein the one end is located outward in the extending direction of the main body from the opening of the main body.

13. It has a plurality of flange portions and a plurality of pipes, The plurality of flange portions include a first flange portion provided at the inlet portion and a second flange portion provided at the outlet portion. The plurality of pipes include a first pipe for introducing the cooling water into the main body and a second pipe for discharging the cooling water from the main body. The engine according to claim 9, wherein the intermediate portion of the first pipe is fixed to the outer edge of the first flange portion or the second flange portion, and the intermediate portion of the second pipe is fixed to the outer edge of the second flange portion or the first flange portion.

14. The reflux path further comprises an oxidation catalyst section, The engine according to claim 9, wherein the reflux gas cooling section is provided downstream of the oxidation catalyst section in the reflux path.

15. The engine according to claim 14, wherein the reflux gas cooling section is arranged from the downstream side of the oxidation catalyst section upward.

16. The engine according to claim 9, wherein the recirculation path comprises a first recirculation path provided with the recirculation gas cooling section and a second recirculation path not provided with the recirculation gas cooling section.

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