Exhaust gas recirculation device and engine

Abstract

To provide an exhaust gas recirculation device and an engine enabling reduction in the number of components, 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; an EGR cooling part 12 provided in the EGR passage 11 and cooling recirculation gas flowing in the EGR passage 11; and a DOC 20 provided in the EGR passage 11 and oxidizing carbide included recirculation gas flowing in the EGR passage 11. The DOC 20 includes: a body having an inlet part and an outlet part of the recirculation gas and accommodating a catalyst; a first flange part provided at the inlet part of the body; and a second flange part provided at the outlet part of the body. Each of the first flange part and the second flange part includes three fasting parts disposed at positions of apexes of a triangle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exhaust gas recirculation device that recirculates a portion of exhaust gas flowing through an exhaust system to an intake system as recirculated gas, and to an engine. [Background technology]

[0002] Patent Document 1 discloses an exhaust gas purification device for an internal combustion engine, the exhaust gas purification device including an EGR passage for returning a part of exhaust gas from an exhaust passage of the internal combustion engine to an intake passage as EGR gas, an EGR cooler provided in the EGR passage for cooling the EGR gas by heat exchange with cooling water introduced from an engine cooling circuit, and an EGR cooling circuit for connecting an inlet and an 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 a connection part between the EGR passage and the EGR cooler downstream of the EGR cooler in the recirculation direction of the EGR gas, and is formed integrally with the EGR passage via a heat-conductive separation wall, and a gasket for sealing the cooling water and the EGR gas is provided at the connection part.

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

[0004] Patent Document 3 discloses an exhaust gas purification device for a diesel engine that includes a DOC arranged in an exhaust path of the diesel engine, a DPF arranged in the exhaust path downstream of the DOC, a urea injection nozzle arranged in the exhaust path downstream of the DPF, a turbocharger turbine arranged in the exhaust path downstream of the urea injection nozzle, an SCR arranged in the exhaust path downstream of the turbine, and a control means that controls the DOC to adsorb and oxidize HC when the differential pressure before and after the DPF is within a predetermined differential pressure range and the inlet temperature of the DPF is equal to or lower than a predetermined temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-096100 A [Patent Document 2] JP 2007-092595 A [Patent Document 3] JP 2013-142363 A Summary of the Invention [Problem to be solved by the invention]

[0006] The exhaust gas recirculation system is a system that can lower the combustion temperature in the cylinder and suppress the generation of nitrogen oxides (NOx) by mixing a part of the exhaust gas with the fresh intake air as recirculated gas, compared to a system that does not have an exhaust gas recirculation system. The installation of such an exhaust gas recirculation system tends to lead to an increase in the size of the engine, and the installation of a system for purifying the exhaust gas leads to an even larger size and an increase in the number of parts. Therefore, it is desirable to reduce the number of parts, make the engine smaller, and save space in the exhaust gas recirculation system and the engine.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide an exhaust gas recirculation device and an engine that can reduce the number of parts, and can be made smaller and more 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 exhaust gas flowing through an exhaust system of an engine to an intake system of the engine as recirculated gas, the exhaust gas recirculation device comprising: a recirculation path provided between the exhaust system and the intake system; a recirculation gas cooling section provided in the recirculation path that cools the recirculated gas flowing through the recirculation path; and a purification section provided in the recirculation path that purifies the recirculated gas flowing through the recirculation path, the purification section having an inlet portion and an outlet portion for the recirculated gas, the purification section having a main body that accommodates a catalyst, a first flange portion provided in the inlet portion of the main body, and a second flange portion provided in the outlet portion of the main body, each of the first flange portion and the second flange portion having three fastening portions located at the vertices of a triangle.

[0009] Another aspect of the present invention is an engine equipped with an exhaust gas recirculation device that recirculates a portion of exhaust gas flowing through an exhaust system to an intake system as recirculated gas, the exhaust gas recirculation device comprising: a recirculation path provided between the exhaust system and the intake system; a recirculation gas cooling section provided in the recirculation path that cools the recirculation gas flowing through the recirculation path; and a purification section provided in the recirculation path that oxidizes carbides contained in the recirculation gas flowing through the recirculation path, the purification section having an inlet portion and an outlet portion for the recirculation gas, the engine having a main body that accommodates a catalyst, a first flange portion provided in the inlet portion of the main body, and a second flange portion provided in the outlet portion of the main body, each of the first flange portion and the second flange portion having three fastening portions positioned at the vertices of a triangle. Effect of the Invention

[0010] According to the present invention, it is possible to provide an exhaust gas recirculation device and an engine that can reduce the number of parts, and can be made smaller and more space-saving. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view illustrating an engine equipped with an exhaust gas recirculation device according to an embodiment of the present invention; [Diagram 2] 1 is a partially enlarged perspective view illustrating an example of an engine equipped with an exhaust gas recirculation device according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a perspective view illustrating an EGR cooling portion. [Figure 4] FIG. 2 is a plan view illustrating an EGR cooling portion. [Diagram 5] FIG. 2 is a side view illustrating an EGR cooling portion. [Figure 6] FIG. 2 is a perspective view illustrating a DOC. [Figure 7] FIG. 2 is a perspective view illustrating a DOC. [Figure 8] FIG. 2 is a front view of the DOC as seen from the flange portion side. [Figure 9] FIG. 2 is a perspective view illustrating an example of an arrangement state of a DOC. [Figure 10] FIG. 2 is a front view illustrating an example of the arrangement of the DOC. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 therefore various technically preferable limitations are applied to them, but the scope of the present invention is not limited to these aspects unless otherwise specified in the following description to the effect that the present invention is limited to them. In addition, in each drawing, similar components are given the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

[0013] (engine) FIG. 1 is a perspective view illustrating an engine equipped with an exhaust gas recirculation device according to this embodiment. 2 is a partially enlarged perspective view illustrating an engine equipped with an exhaust gas recirculation device according to this embodiment, in which some of the piping is omitted for ease of explanation. 1 and 2 is an internal combustion engine, such as a diesel engine, and is mounted on, for example, a vehicle or industrial machinery, such as construction machinery or agricultural machinery.

[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, the cylinder head of a multi-cylinder engine having multiple cylinders. The intake manifold 3 is an example of an intake distribution means that distributes intake air to each cylinder of the engine 1. The exhaust manifold 4 is an example of an exhaust collection means that collects exhaust 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 recirculates a portion of the exhaust gas flowing through the exhaust system to the intake system of the engine 1 as recirculated gas.

[0016] (Exhaust Gas Recirculation System) The exhaust gas recirculation device 10 has an EGR path 11, an EGR cooling section 12, and an EGR (Exhaust Gas Recirculation) valve 13. The EGR path 11 is an example of a "recirculation path" of the present invention. The EGR cooling section 12 is an example of a "recirculation gas cooling section" of the present invention. The exhaust gas recirculation device 10 includes a DOC (Diesel Oxidation Catalyst) 20. The DOC 20 is an example of a "purification section" of the present invention, and is also an example of an oxidation catalyst. The DOC 20 is provided between the exhaust manifold 4 and the EGR path 11.

[0017] The EGR passage 11 is connected to the exhaust manifold 4 and is a passage for recirculating the recirculated 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 this embodiment, the EGR passage 11 has a first branching portion 1101, and is branched into a first EGR passage 111 and a second EGR passage 112 by the first branching portion 1101. The first EGR passage 111 is provided with a second branching portion 1102, one of which is connected to the EGR cooling portion 12, and the other of which is connected to the exhaust port side. The second EGR passage 112 is not provided with the EGR cooling portion 12.

[0018] The EGR cooling unit 12 is a heat exchanger provided in the EGR passage 11 (in this embodiment, the first EGR passage 111) and cools the recirculated gas. The EGR cooling unit 12 cools the recirculated gas by using the cooling water of the engine 1. The cooled recirculated gas is mixed with new intake air taken in from the intake manifold 3 and returned to the combustion chamber. Since the second EGR passage 112 is not provided with the EGR cooling unit 12, the recirculated gas flowing through the second EGR passage 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 supply amount of recirculated gas. The engine 1 according to this embodiment includes a first EGR valve 131 provided in the first EGR passage 111 and a second EGR valve 132 provided in the second EGR passage 112. By controlling the operation (valve control) of each of the first EGR valve 131 and the second EGR valve 132, control is performed as to whether the recirculated gas via the first EGR passage 111 is sent to the intake manifold 3 or the recirculated gas via the second EGR passage 112 is sent to the intake manifold 3. For example, when the temperature of the exhaust gas is below a predetermined value, valve control is performed so that the recirculated gas is returned without being cooled, and when the temperature of the exhaust gas is equal to or higher than a predetermined value, valve control is performed so that the first EGR passage 111 provided with the EGR cooling section 12 is used as the main passage to cool the recirculated gas.

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

[0021] The pipe 122 has one end 122a connected to the main body 121 and the other end 122b extending from the one end 122a toward the outside of the main body 121. The pipe 122 has a first pipe 1221 and a second pipe 1222. For convenience of explanation, the first pipe 1221 and the second pipe 1222 will be referred to as the pipe 122 when they are not distinguished from each other and are collectively referred to as the pipe 122. The first pipe 1221 is, for example, a pipe that feeds cooling water to the main body 121, and the second pipe 1222 is, for example, a pipe that discharges cooling water from the main body 121. The cooling water is fed from the first pipe 1221 to the main body 121 to cool the reflux gas flowing through a plurality of tubes in the main body 121. Then, the cooling water that has exchanged heat with the reflux gas in the main body 121 is discharged from the second pipe 1222 to the outside of the main body 121.

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

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

[0024] One end 122a of the pipe 122 is connected to a side surface of the main body 121. The pipe 122 has an intermediate portion 122c located between the one end 122a and the other end 122b. The one end 122a of the pipe 122 has a separation portion A extending in a direction away from the main body 121, and a bent portion B provided between the separation portion A and the intermediate portion 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 substantially perpendicularly by the separation portion A, and is bent at approximately 90 degrees at the bent portion B. As a result, the pipe 122 has a substantially L-shaped shape from the one end 122a to the intermediate portion 122c and the other end 122b. A tube through which cooling water passes is fitted to the other end 122b of the pipe 122.

[0025] In such a pipe 122, the middle portion 122c is fixed to the outer edge 123a of the flange portion 123. The flange portion 123 has fastening holes 123h that are fastening portions connected to the first EGR path 111. The middle portion 122c of the pipe 122 is fixed to the outer edge 123a on the opposite side to the opening of the fastening holes 123h. That is, the flange portion 123 has an extending portion 123b that extends in a direction away from the opening of the main body 121 (outside the position of the fastening holes 123h). The middle portion 122c of the pipe 122 is connected to the outer edge 123a of the extending portion 123b of the flange portion 123 by, for example, brazing.

[0026] Here, by separating the pipe 122 from the main body 121, it is possible to make the pipe 122 less susceptible to the effects of heat from the main body 121. On the other hand, by separating the pipe 122 from the main body 121, the extension distance becomes longer, which hinders miniaturization and makes the pipe 122 more likely to break due to the effects of vibration, etc. Therefore, by fixing the middle part 122c to the outer edge 123a of the flange part 123 while separating the pipe 122 as in this embodiment, the pipe 122 with a longer extension distance can be reliably supported by the middle part 122c.

[0027] Moreover, one end 122a of the pipe 122 is separated from the side surface of the main body 121 by a separation portion A in a substantially perpendicular direction, is bent at a bend portion B at a substantially 90 degree angle, and extends outward in the extending direction of the main body 121. For example, the first pipe 1221 is separated from the side surface of the main body 121 by the separation portion A, is bent at a substantially 90 degree angle at a bend portion B, and is fixed to the outer edge 123a of the first flange portion 1231. On the other hand, the second pipe 1222 is separated from the side surface of the main body 121 by the separation portion A, is bent at a substantially 90 degree angle at a bend portion B in the opposite direction to the first pipe 1221, and is fixed to the outer edge 123a of the second flange portion 1232. That is, the first pipe 1221 and the second pipe 1222 extend in opposite directions to each other in the extending direction of the main body 121, and are fixed to the outer edge 123a of the flange portion 123, respectively. This makes it possible to reduce the space required for the EGR cooling section 12 while preventing the first pipe 1221 and the second pipe 1222 from coming close to each other.

[0028] (DOC: Purification Department) 6 and 7 are perspective views illustrating the DOC. Fig. 6 shows a perspective view of the DOC 20 as seen from above, and Fig. 7 shows a perspective view of the DOC as seen from below. The DOC 20 has a main body 21 that houses a catalyst, and a first flange portion 221 and a second flange portion 222 that are provided on the main body 21. The main body 21 is provided in a cylindrical shape having an inlet portion 21a and an outlet portion 21b for EGR gas. The main body 21 is formed of, for example, stainless steel. A catalyst that oxidizes SOF (soluble organic fraction), CO (carbon monoxide), and HC (hydrocarbon) in PM (particulate matter) contained in exhaust gas is housed inside the cylinder of the main body 21.

[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 includes a fastening portion 225 that connects the main body 21 to 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 apexes 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 by the three fastening portions 225. The arrangement of the three fastening portions 225 is preferably an isosceles triangle, and more preferably an equilateral triangle. Note that the shape of the triangle in the arrangement of the three fastening portions 225 is not limited to these.

[0030] By arranging the three fastening parts 225 at the vertices of a triangle, it is possible to securely fasten the front and rear components while saving space. In other words, fastening at two points or less is likely to be insufficient. On the other hand, fastening at four points or more narrows the gap between adjacent fastening parts, making it easy for interference with surrounding components to occur during fastening, and making it difficult to ensure sufficient freedom of layout. Therefore, with three-point fastening, it is possible to securely fasten the components while also making it easier to avoid interference with surrounding components during fastening, thereby achieving space savings.

[0031] Moreover, it is preferable that the first flange portion 221 and the second flange portion 222 are provided to have the same shape. By making the first flange portion 221 and the second flange portion 222 to have the same shape, it is possible to reduce the number of parts.

[0032] Fig. 8 is a front view of the DOC as seen from the flange portion side. Fig. 8 shows a front view as seen from the first flange portion 221 side, but a front view as seen from the second flange portion 222 side is the same. As an example, the three fastening parts 225 of the first flange part 221 are arranged 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 lower side of the main body 21. It is preferable that the legs 215 are arranged at a position overlapping one of the three fastening parts 225 in the extending direction of the main body 21 (the direction seen from the flange part side). This allows the fastening parts 225 to be contained within the protruding region of the legs 215 when seen from the flange part side, thereby enabling the DOC 20 to save space.

[0033] FIG. 9 is a perspective view illustrating an arrangement state of the DOC. Fig. 10 is a front view showing an example of the arrangement of the DOC, as viewed from the first flange portion 221 side. 9, in the exhaust gas recirculation device 10 according to this embodiment, the DOC 20 is disposed above the flywheel 6 at the rear of the engine 1, extending laterally. As a result, the exhaust system of the engine 1 is routed from the exhaust manifold 4 to the opposite side of the exhaust manifold 4 via the rear DOC 20. A support member 30 for the DOC 20 is provided above the flywheel 6, and a leg 215 provided on the body 21 of the DOC 20 is placed on this support member 30. For example, a female screw hole is provided in the leg 215, and the support member 30 and the leg 215 are fastened and connected.

[0034] The exhaust manifold 4 extends to the rear of the engine 1, and its extending end portion 4a opens inward, to which a flange portion 41 is attached. The first flange portion 221 of the DOC 20 is butted against the flange portion 41 of the exhaust manifold 4, and they are fastened and connected to each other. As a result, the DOC 20 is attached to the extending end portion 4a of the exhaust manifold 4 at a substantially right angle to the extension direction of the exhaust manifold 4.

[0035] As shown in FIG. 10, when viewed from the front of the first flange portion 221, the three fastening portions 225 of the first flange portion 221 are arranged without overlapping with the extended end portion 4a of the exhaust manifold 4. Therefore, when the flange portion 41 of the exhaust manifold 4 and the first flange portion 221 of the DOC 20 are butt-fitted and fastened to each other, the fastening work can be performed without interfering with the exhaust manifold 4. In addition, since the DOC 20 is attached to the extended end portion 4a of the exhaust manifold 4 at a substantially right angle, even if the DOC 20 is arranged above the flywheel 6, the exhaust manifold 4 can be routed in the shortest distance, thereby saving space in the engine 1. Moreover, the three-point fastening of the DOC 20 can minimize the protrusion of the first flange portion 221 and the second flange portion 222 toward the rear of the engine.

[0036] The EGR cooling section 12 is disposed above the flywheel 6, similarly to the DOC 20, between the DOC 20 and the intake manifold 3. The EGR cooling section 12 is provided so as to extend upward (vertically) from the downstream side of the DOC 20. With such an exhaust system layout and the arrangement of the EGR cooling section 12, it is possible to downsize the engine 1 by layouting the exhaust system compactly while including the DOC 20 and the EGR cooling section 12.

[0037] According to this embodiment, it is possible to provide an exhaust gas recirculation device 10 and an engine 1 that can reduce the number of parts, and can be made smaller and more space-saving.

[0038] The 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 the DOC 20, and may be, for example, a urea-SCR (Urea-Selective Catalytic Reduction) or an LNT (Lean Nox Trap: NOx storage catalyst). In addition, the configurations of the above embodiments may be partially omitted or arbitrarily combined differently from the above. [Explanation of symbols]

[0039] 1...engine, 2...cylinder head, 3...intake manifold, 4...exhaust manifold, 4a...extension 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 section, 21b...outlet section, 30...support member, 41...flange section, 111...first EGR path, 112...second EGR path, 121...main body, 121a...inlet section, 121b...outlet section, 122...piping, 122 a...one end portion, 122b...other end portion, 122c...middle portion, 123...flange portion, 123a...outer edge, 123b...extending portion, 123h...fastening hole, 131...first EGR valve, 132...second EGR valve, 215...leg portion, 221...first flange portion, 222...second flange portion, 225...fastening portion, 1101...first branch portion, 1102...second branch portion, 1221...first piping, 1222...second piping, 1231...first flange portion, 1232...second flange portion, A...separated portion, B...bent portion

Claims

1. An exhaust gas recirculation device that recirculates a part of exhaust gas flowing through an exhaust system of an engine to an intake system of the engine as a recirculated gas, a reflux path provided between the exhaust system and the intake system; a reflux gas cooling unit provided in the reflux path and configured to cool the reflux gas flowing through the reflux path; a purification unit provided in the reflux path and configured to purify the reflux gas flowing through the reflux path; Equipped with The purification section includes: a main body having an inlet and an outlet for the reflux gas and containing a catalyst; A first flange portion provided at the inlet portion of the main body; a second flange portion provided at the outlet portion of the main body, An exhaust gas recirculation device, wherein each of the first flange portion and the second flange portion has three fastening portions arranged at apexes of a triangle.

2. The exhaust gas recirculation device according to claim 1 , wherein the first flange portion and the second flange portion have the same shape as each other.

3. 2. The exhaust gas recirculation system of claim 1, wherein each of the three fastening portions is disposed at a vertex of an isosceles triangle.

4. The exhaust gas recirculation device according to claim 1 , wherein each of the first flange portion and the second flange has a leg portion that is positioned to overlap one of the three fastening portions when viewed in the extension direction of the main body.

5. 2. The exhaust gas recirculation system according to claim 1, wherein the purification section is provided upstream of the recirculation gas cooling section in the recirculation path.

6. 2. The exhaust gas recirculation system according to claim 1, wherein the purification section has an oxidation catalyst that oxidizes carbides contained in the recirculated gas.

7. An engine equipped with an exhaust gas recirculation device that recirculates a portion of exhaust gas flowing through an exhaust system to an intake system as recirculated gas, The exhaust gas recirculation device includes: a reflux path provided between the exhaust system and the intake system; a reflux gas cooling unit provided in the reflux path and configured to cool the reflux gas flowing through the reflux path; a purification unit provided in the reflux path and configured to oxidize carbides contained in the reflux gas flowing through the reflux path; Equipped with The purification section includes: a main body having an inlet and an outlet for the reflux gas and containing a catalyst; A first flange portion provided at the inlet portion of the main body; a second flange portion provided at the outlet portion of the main body, An engine, wherein each of the first flange portion and the second flange portion has three fastening portions arranged at apexes of a triangle.

8. The engine of claim 7 , wherein the first flange portion and the second flange portion are identical to one another.

9. 8. An engine according to claim 7, wherein the locations of each of the three fasteners are at the vertices of an isosceles triangle.

10. The engine according to claim 7 , wherein each of the first flange portion and the second flange has a leg portion that is arranged at a position overlapping one of the three fastening portions when viewed in the extension direction of the main body.

11. The engine according to claim 7 , wherein the purification section is provided upstream of the recirculation gas cooling section in the recirculation path.

12. 8. The engine according to claim 7, wherein the purification section has an oxidation catalyst that oxidizes carbides contained in the recirculated gas.

13. 8. The engine according to claim 7, wherein the purification section is disposed above a flywheel provided at the rear of the engine.

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