Exhaust gas recirculation device and engine

Abstract

[Problem] To provide an exhaust gas recirculation device and an engine capable of reducing the number of components, achieving miniaturization and space saving, and reducing pressure loss when EGR gas is introduced. [Solution] An exhaust gas recirculation device 3 includes: an exhaust pipe 26 for guiding exhaust; a diesel oxidation catalyst 261 for purifying exhaust gas; an exhaust recirculation pipe 27 provided between the diesel oxidation catalyst 261 and an intake system; an exhaust discharge pipe 29 provided between the diesel oxidation catalyst 261 and an exhaust gas discharge port; and a branching part 32 for branching the exhaust gas that has passed through the diesel oxidation catalyst 261 to the exhaust recirculation pipe 27 and the exhaust discharge pipe 29. The branching part 32 includes: a first branching part 321 that is provided between the diesel oxidation catalyst 261 and the exhaust recirculation pipe 27, and guides the exhaust gas upward of the diesel oxidation catalyst 261; and a second branching part 322 that is provided between the diesel oxidation catalyst 261 and the exhaust discharge pipe 29, and guides the exhaust gas downward of the diesel oxidation catalyst 261.

Description

Exhaust gas recirculation system and engine

[0001] The present invention relates to an exhaust gas recirculation system and an engine equipped with an exhaust gas recirculation system.

[0002] Exhaust gas recirculation (EGR) is a commonly known means for reducing nitrogen oxides (NOx) contained in engine exhaust gas. An EGR device recirculates a portion of the exhaust gas flowing through the engine's exhaust system back into the engine's intake system as exhaust gas recirculation gas (i.e., EGR gas), and mixes the EGR gas with fresh intake air (i.e., intake air (also called fresh air)). Compared to a case where an EGR device is not provided, an EGR device can lower the combustion temperature in the cylinder and suppress the generation of NOx.

[0003] Patent Document 1 discloses an exhaust gas purification device for an internal combustion engine, the exhaust gas purification device including an EGR passage that recirculates a portion 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 and that cools the EGR gas by heat exchange with cooling water introduced from an engine cooling circuit, and an EGR cooling circuit that connects a cooling water inlet and outlet formed in the EGR cooler to the engine cooling circuit. In this exhaust gas purification device, at least a portion of the EGR cooling circuit extends along the EGR passage, passing through a connection portion 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 thermally conductive separation wall, and the connection portion is provided with a gasket for sealing the cooling water and the EGR gas.

[0004] 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 this front-to-rear direction is the horizontal direction, an intake distribution passage wall is attached to one horizontal side of the cylinder head, an exhaust merging passage wall is attached to the other horizontal 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 side of the cylinder block, and the exhaust merging passage wall is positioned directly above this EGR cooler.

[0005] Patent Document 3 discloses an exhaust gas purification device for a diesel engine, which includes a DOC arranged in the 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 control means for controlling 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.

[0006] However, the installation of such an exhaust gas recirculation system tends to increase the size of the engine, and the installation of a device to purify the exhaust gas leads to further increase in size and 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 engine.

[0007] Furthermore, for example, in a small two-cylinder engine, intake and exhaust pulsations are larger than in an engine with three or more cylinders. Therefore, a commonly used flow sensor is not suitable as a sensor for controlling the amount of EGR gas (i.e., controlling the opening of the EGR valve). Therefore, a NOx sensor (see FIG. 1) may be used instead. In this case, the EGR gas must be recirculated by branching from a location downstream of the NOx sensor in the engine's exhaust system (i.e., immediately before the exhaust is released to the atmosphere). At this branch point, the introduction pressure of the EGR gas approaches atmospheric pressure (i.e., is low), so it is important to minimize pressure loss during the introduction of the EGR gas.

[0008] If the pulsation of the engine intake air, etc. is small and the EGR valve can be controlled based on a flow sensor that measures the intake air volume, then, taking the example of Figure 1, the EGR gas can be recirculated by branching off from the upstream of the DOC 261 in the exhaust pipe 26. In this case, the introduction pressure of the EGR gas becomes close to (i.e., higher than) the pressure at the upstream of the DOC 261, so there is no need to worry as much about pressure loss when introducing the EGR gas as compared to when the EGR gas is recirculated by branching off from the downstream of the NOx sensor.

[0009] JP 2017-096100 A JP 2007-092595 A JP 2013-142363 A

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide an exhaust gas recirculation device and engine that can reduce the number of parts, make the device smaller and more space-saving, and reduce pressure loss when introducing EGR gas.

[0011] A first 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 recirculation gas, comprising: an exhaust pipe that is provided in the exhaust system and guides the exhaust; a purification unit that is provided downstream of the exhaust pipe and purifies the exhaust gas; an exhaust recirculation pipe that is provided between the purification unit and the intake system; an exhaust discharge pipe that is provided between the purification unit and an exhaust gas outlet; and a branch unit that is provided downstream of the purification unit and branches the exhaust gas that has passed through the purification unit to the exhaust recirculation pipe and the exhaust discharge pipe, wherein the branch unit has: a first branch unit that is provided between the purification unit and the exhaust recirculation pipe and guides the exhaust gas above the purification unit; and a second branch unit that is provided between the purification unit and the exhaust discharge pipe and guides the exhaust gas below the purification unit.

[0012] A second 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 an exhaust system to an intake system as exhaust recirculation gas, wherein the exhaust gas recirculation device comprises: an exhaust pipe that is provided in the exhaust system and guides the exhaust; a purification section that is provided downstream of the exhaust pipe and purifies the exhaust gas; an exhaust recirculation pipe that is provided between the purification section and the intake system; an exhaust discharge pipe that is provided between the purification section and an outlet for the exhaust gas; and a branch section that is provided downstream of the purification section and branches the exhaust gas that has passed through the purification section to the exhaust recirculation pipe and the exhaust discharge pipe, wherein the branch section has: a first branch section that is provided between the purification section and the exhaust recirculation pipe and guides the exhaust gas above the purification section; and a second branch section that is provided between the purification section and the exhaust discharge pipe and guides the exhaust gas below the purification section.

[0013] According to the present invention, it is possible to provide an exhaust gas recirculation system and an engine that can control the flow rate of exhaust gas recirculation gas so that the concentration of NOx contained in the exhaust gas reaches a target value.

[0014] FIG. 1 is a schematic diagram illustrating an engine according to the present embodiment; FIG. 2 is a perspective view illustrating an engine according to the present embodiment; FIG. 3 is a perspective view illustrating a branching portion; FIG. 4 is a plan view illustrating a branching portion; FIG. 5 is a perspective view illustrating an attachment portion on the rear side of the diesel oxidation catalyst; FIG. 6 is a front view illustrating an attachment portion on the rear side of the diesel oxidation catalyst; FIG. 7 is a perspective view illustrating an attachment portion on the front side of the diesel oxidation catalyst; FIG. 8 is a front view illustrating an attachment portion on the front side of the diesel oxidation catalyst; FIG. 9 is a perspective view illustrating a flange portion in attachment of the diesel oxidation catalyst.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are preferred specific examples of the present invention, and therefore various technically preferable limitations are applied, 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. Furthermore, in each drawing, similar components are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0016] 1 and 2 are schematic and perspective views illustrating an engine according to an embodiment of the present invention.

[0017] The engine 2 according to this embodiment is an internal combustion engine and is a small, naturally aspirated engine. The engine 2 shown in FIG. 1 is an in-line, two-cylinder engine. However, the number of cylinders is not particularly limited and may be three or more. The engine 2 has a displacement of approximately 500 cc. However, the displacement is not limited to approximately 500 cc. The timing difference between the combustion stroke of the first cylinder 241, which is one of the two cylinders, and the combustion stroke of the second cylinder 242, which is the other, is, for example, 180 degrees in crankshaft angle. However, the timing difference between the combustion stroke of the first cylinder 241 and the combustion stroke of the second cylinder 242 is not limited to this and may be 360 ​​degrees in crankshaft angle. Note that the engine 2 according to this embodiment does not include a turbocharger for supercharging.

[0018] As shown in FIG. 1 , the engine 2 includes an intake manifold 22, a cylinder block 24, and an exhaust manifold 25. The intake manifold 22 is connected to the intake pipe 21 and a cylinder head (not shown), and has a first branch pipe 221 and a second branch pipe 222. The cylinder block 24 has a first cylinder 241 and a second cylinder 242. The first cylinder 241 is connected to the first branch pipe 221 via an intake port (not shown) in the cylinder head. The second cylinder 242 is connected to the second branch pipe 222 via an intake port in the cylinder head. The exhaust manifold 25 is connected to the cylinder head and an exhaust pipe 26. Specifically, the exhaust manifold 25 is connected to the first cylinder 241 and the second cylinder 242 via an exhaust port in the cylinder head. The exhaust pipe 26 is included in an exhaust gas recirculation system 3, which will be described later.

[0019] The engine 2 also includes a rail 23, a first injector 231, and a second injector 232. The rail 23 is formed in a cylindrical shape and distributes high-pressure fuel supplied from a fuel pump (not shown) to multiple paths according to the number of cylinders of the engine 2. In other words, the rail 23 supplies the high-pressure fuel supplied from the fuel pump to the first injector 231 and the second injector 232.

[0020] The first injector 231 is attached to the rail 23 and is provided so as to protrude toward the combustion chamber formed above the first cylinder 241. The first injector 231 opens and closes a needle valve, for example, by a solenoid, based on a signal sent from the control device 4, and injects fuel supplied from the rail 23 through an injection hole (not shown) into the combustion chamber formed above the first cylinder 241. An example of the control device 4 is an electronic control unit (ECU).

[0021] The second injector 232 is attached to the rail 23 and is provided so as to protrude toward the combustion chamber formed above the second cylinder 242. The second injector 232 opens and closes a needle valve, for example, by a solenoid, based on a signal sent from the control device 4, and injects fuel supplied from the rail 23 through an injection hole into the combustion chamber formed above the second cylinder 242.

[0022] The fuel pressure inside the rail 23 is measured by a pressure sensor 55 attached to the rail 23. The pressure sensor 55 measures the fuel pressure inside the rail 23 and outputs a signal related to the fuel pressure to the control device 4.

[0023] As indicated by arrow A1 in FIG. 1 , fresh intake air (i.e., intake air (also referred to as outside air)) passes through the intake pipe 21, passes through an air cleaner 211 provided in the intake pipe 21, and is led to the intake manifold 22 side. The intake pipe 21 is a component included in the engine 2, and is also a component included in the exhaust gas recirculation device 3, which will be described later. The intake air led to the intake manifold 22 is distributed to a first branch pipe 221 and a second branch pipe 222, and is led to the first cylinder 241 through the first branch pipe 221 and to the second cylinder 242 through the second branch pipe 222.

[0024] Exhaust gas emitted from the first cylinder 241 and the second cylinder 242 passes through an exhaust manifold 25 and is guided to an exhaust pipe 26. The exhaust gas guided to the exhaust pipe 26 passes through a diesel oxidation catalyst (DOC) 261, which is a purification unit provided in the exhaust pipe 26. At this time, the diesel oxidation catalyst 261 oxidizes SOF (Soluble Organic Fraction), CO (Carbon Monoxide), and HC (Hydrocarbon) in PM (Particulate Matter) contained in the exhaust gas. As indicated by arrow A2 in FIG. 1 , the exhaust gas that has passed through the diesel oxidation catalyst 261 passes through the exhaust discharge pipe 29 and is discharged to the outside of the engine 2. The diesel oxidation catalyst 261 is included in an exhaust gas recirculation device 3, which will be described later.

[0025] Furthermore, the engine 2 is equipped with an exhaust gas recirculation device 3. The exhaust gas recirculation device 3 recirculates a portion of the exhaust gas flowing through the exhaust system of the engine 2 to the intake system of the engine 2 as exhaust gas recirculation gas, thereby reducing nitrogen oxides (NOx) contained in the exhaust gas.

[0026] The exhaust gas recirculation system 3 according to this embodiment includes an exhaust pipe 26, a diesel oxidation catalyst 261, an exhaust gas recirculation pipe 27, an exhaust gas discharge pipe 29, and a branching section 32. The downstream side of the diesel oxidation catalyst 261 is branched by the branching section 32 into an exhaust gas recirculation pipe 27 side and an exhaust gas discharge pipe 29 side. The exhaust gas recirculation pipe 27 is a pipe that guides exhaust gas recirculation gas, which is a portion of the exhaust gas branched by the branching section 32, toward the intake manifold 22 side. The exhaust gas discharge pipe 29 is a pipe that guides the remaining portion of the exhaust gas branched by the branching section 32 to an exhaust port. The exhaust gas recirculation pipe 27 is provided with a flow rate adjusting means 28. The flow rate adjusting means 28 is, for example, called an EGR valve. The flow rate adjusting means 28 adjusts the flow rate of the exhaust gas recirculation gas flowing through the exhaust gas recirculation pipe 27 based on a signal transmitted from the control device 4.

[0027] The engine 2 also has a control device 4, a rotation sensor 51, a NOx sensor 53, a temperature sensor 54, a water temperature sensor 56, and an accelerator position sensor (not shown). The engine 2 also has various other sensors, such as a cam angle sensor 52 and a pressure sensor 55. The control device 4 performs calculations based on signals from the various sensors to control fuel injection by the first injector 231 and the second injector 232, and to control the flow rate of the exhaust gas recirculation gas by the flow rate adjustment means 28.

[0028] 2 , the direction along the crankshaft of the engine 2 is defined as the front-rear direction, the direction perpendicular to the crankshaft of the engine 2 is defined as the left-right direction, and the direction perpendicular to the front-rear and left-right directions is defined as the up-down direction, with the intake manifold 22 disposed on one side in the left-right direction of the engine 2 (e.g., the right side), and the exhaust manifold 25 disposed on the other side in the left-right direction of the engine 2 (e.g., the left side). The diesel oxidation catalyst 261 is disposed on the flywheel 201 side of the engine 2 (rearward of the engine 2) and above the flywheel 201.

[0029] As a result, the exhaust gas passes from the exhaust manifold 25 located on the other left-right side of the engine 2 through the diesel oxidation catalyst 261 located behind the engine 2 (above the flywheel 201) and is guided to one left-right side of the engine 2. Exhaust gas, which is a portion of the exhaust gas guided to one left-right side of the engine 2, is sent to the intake manifold 22 located on one left-right side of the engine 2, and the remainder is discharged from one left-right side of the engine 2 to the outside via the exhaust discharge pipe 29. Such an arrangement of the exhaust manifold 25, intake manifold 22, and diesel oxidation catalyst 261 allows for an effective layout of the configuration of the exhaust gas recirculation device 3, and enables the engine 2 equipped with the exhaust gas recirculation device 3 to be made more compact.

[0030] The exhaust gas recirculation device 3 according to this embodiment includes a branch section 32 in addition to the previously described exhaust pipe 26, the diesel oxidation catalyst 261 serving as a purification section, the exhaust gas recirculation pipe 27, and the exhaust discharge pipe 29. The branch section 32 is provided downstream of the diesel oxidation catalyst 261, and is a section that branches the exhaust gas that has passed through the diesel oxidation catalyst 261 into the exhaust gas recirculation pipe 27 and the exhaust discharge pipe 29. That is, the branch section 32 has a first branch section 321 provided between the diesel oxidation catalyst 261 and the exhaust gas recirculation pipe 27, and a second branch section 322 provided between the diesel oxidation catalyst 261 and the exhaust gas discharge pipe 29.

[0031] Fig. 3 is a perspective view illustrating the branching portion. Fig. 4 is a plan view illustrating the branching portion. Fig. 4 shows a plan view of the branching portion as viewed from above. The branching portion 32 has a connecting portion 320 provided between the diesel oxidation catalyst 261 and a first branching portion 321 and a second branching portion 322. In other words, the downstream side of the diesel oxidation catalyst 261 is branched into the first branching portion 321 and the second branching portion 322 via the connecting portion 320, with the first branching portion 321 side connected to the exhaust gas recirculation pipe 27 and the second branching portion 322 side connected to the exhaust gas discharge pipe 29.

[0032] In the layout of the engine 2 as described above, the first branch section 321 at the rear of the connecting section 320 is formed to guide the exhaust gas above the diesel oxidation catalyst 261, and the second branch section 322 is formed to guide the exhaust gas below the diesel oxidation catalyst 261.

[0033] Specifically, the connecting portion 320 is provided to guide the exhaust gas in the extension direction (e.g., rightward) of the diesel oxidation catalyst 261, and the first branch portion 321 has a curved body portion 323 that bends the flow direction of the exhaust gas from the end of the connecting portion 320 in the extension direction toward the exhaust gas recirculation pipe 27. As shown in Fig. 3 , the first branch portion 321 is bent forward by approximately 90° by the curved body portion 323 and bent above the diesel oxidation catalyst 261 to be connected to the exhaust gas recirculation pipe 27. The second branch portion 322 is connected to a port 324 (see Fig. 4 ) provided on a side surface of the connecting portion 320 that is located closer to the diesel oxidation catalyst 261 than the curved body portion 323.

[0034] The first branch portion 321 of the branch portion 32 allows the exhaust recirculation gas to be sent above the diesel oxidation catalyst 261 and mixed with outside air above the intake manifold 22, and the mixture can be sent to the intake manifold 22. In this way, the exhaust recirculation gas is mixed with outside air while being sent from above to the intake manifold 22, so that a sufficient mixing path can be secured, and a uniform mixture can be sent to the intake manifold 22, even if, for example, intake and exhaust pulsation is large and it is difficult to uniformly mix the outside air and the exhaust recirculation gas. The above configuration is particularly effective for an engine 2 with large intake and exhaust pulsation, such as a four-stroke, one-cycle, two-cylinder engine in which the strokes of the cylinders are offset by 180 degrees in crank rotation angle.

[0035] Furthermore, by providing the curved body portion 323 at the end of the connecting portion 320 in the extension direction, the exhaust gas that has passed through the diesel oxidation catalyst 261 travels straight through the connecting portion 320, and is smoothly bent forward and upward by the curved body portion 323 provided in front of the connecting portion 320 in the traveling direction, before being sent to the exhaust gas recirculation pipe 27. The exhaust gas sent from the diesel oxidation catalyst 261 to the connecting portion 320 tends to travel straight due to inertial force, and is led from the first branch portion 321 to the exhaust gas recirculation pipe 27 with little pressure loss. If the first branch portion 321 were connected to the side of the connecting portion 320, the exhaust gas would have difficulty branching, and a large pressure loss would occur while the exhaust gas was being sent to the exhaust gas recirculation pipe 27.

[0036] In the configuration of the branch portion 32 of this embodiment, the pressure loss of the exhaust gas caused by the first branch portion 321 is smaller than the pressure loss of the exhaust gas caused by the second branch portion 322. As a result, even in the engine 2 in which the exhaust gas recirculation gas introduction pressure is low, the exhaust gas recirculation gas can be effectively sent to the intake manifold 22 side, and the effect of reducing nitrogen oxides (NOx) can be achieved.

[0037] Next, the installation of the diesel oxidation catalyst 261 will be described. Fig. 5 is a perspective view illustrating an example of the installation portion on the rear stage of the diesel oxidation catalyst. Fig. 6 is a front view illustrating an example of the installation portion on the rear stage of the diesel oxidation catalyst. Fig. 6 shows a front view of the diesel oxidation catalyst 261 as seen from the exhaust gas outlet side. Fig. 7 is a perspective view illustrating an example of the installation portion on the front stage of the diesel oxidation catalyst. Fig. 8 is a front view illustrating an example of the installation portion on the front stage of the diesel oxidation catalyst. Fig. 8 shows a front view of the second flange portion 62 of the diesel oxidation catalyst 261 as seen from the inlet side. Fig. 9 is a perspective view illustrating an example of the flange portion when installing the diesel oxidation catalyst.

[0038] The diesel oxidation catalyst 261 has a tubular (e.g., substantially cylindrical) body portion 2610 and a first end portion 2611 and a second end portion 2612 that are parallel to each other and are opposite ends of the body portion 2610. A first flange portion 61 for fastening the diesel oxidation catalyst 261 to the branch portion 32 is provided on the first end portion 2611. The first flange portion 61 is fastened to a mating flange portion 71 provided on the connecting portion 320 side.

[0039] The second flange portion 62 is connected to the second end portion 2612 of the diesel oxidation catalyst 261 via an extension pipe 63. The extension pipe 63 may be common to all or part of the exhaust pipe 26. One end of the extension pipe 63 is connected to the second end portion 2612, and the other end of the extension pipe 63 is connected to the second flange portion 62. It is preferable that the first flange portion 61 and the second flange portion 62 have the same shape. This allows the first flange portion 61 and the second flange portion 62 to be common parts, thereby reducing the number of parts.

[0040] The first flange portion 61 is attached to the first end 2611 of the body portion 2610. As a result, the attachment plane of the first flange portion 61 is arranged approximately parallel to the first end 2611 of the body portion 2610. On the other hand, the second flange portion 62 is attached to the end of the extension tube 63 that is bent from the extension direction of the body portion 2610. As a result, the attachment plane of the second flange portion 62 is arranged non-parallel to the second end 2612 of the body portion 2610.

[0041] The extension pipe 63 is formed into a bent tubular shape by, for example, sheet metal processing a metal material. The extension pipe 63 is provided so as to bend at approximately 90° from the extension direction of the body portion 2610 of the diesel oxidation catalyst 261. By connecting the second flange portion 62 to the end of this extension pipe 63, the attachment surface of the second flange portion 62 becomes approximately perpendicular to the second end portion 2612 of the body portion 2610.

[0042] A flange portion 72 that serves as a counterpart to the second flange portion 62 is provided at the end of the exhaust manifold 25 that extends rearward and is provided on the other side in the left-right direction (e.g., the left side) of the engine 2. This eliminates the need to bend the extending end side of the exhaust manifold 25 toward the rear of the engine 2, simplifying the shape.

[0043] 6 and 8 , each of the first flange portion 61 and the second flange portion 62 has three fastening portions 65 a, 65 b, and 65 c that are located at the vertices of a triangle. The fastening portions 65 a, 65 b, and 65 c are, for example, fastening holes. As shown in FIG. 6 , in the first flange portion 61, when the first end portion 2611 (the exhaust gas outlet side) of the diesel oxidation catalyst 261 is viewed from the front, the first branch portion 321 and the second branch portion 322 are positioned so as not to overlap any of the three fastening portions 65 a, 65 b, or 65 c.

[0044] 8 , in the second flange portion 62, the extension pipe 63 is arranged so as not to overlap any of the three fastening portions 65 a, 65 b, and 65 c when viewed from the front of the second end portion 2612 (the exhaust gas inlet side) of the diesel oxidation catalyst 261. This makes it possible to access the fastening portions 65 a, 65 b, and 65 c from the front of each of the first flange portion 61 and the second flange portion 62 when fastening the first flange portion 61 and the second flange portion 62 together.

[0045] The arrangement of the three fastening portions 65a, 65b, and 65c is preferably an isosceles triangle, and more preferably an equilateral triangle, although the triangular shape of the arrangement of the three fastening portions 65a, 65b, and 65c is not limited to this.

[0046] By arranging the three fastening portions 65a, 65b, and 65c at the vertices of a triangle, it is possible to securely fasten the front and rear components while saving space. That is, with two or fewer fastening points, the fastening is likely to be insufficient. On the other hand, with four or more fastening points, the spacing between adjacent fastening portions becomes narrow, which makes it more likely that interference with surrounding components will occur during fastening, and it is not possible to ensure sufficient layout freedom. 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.

[0047] 6, in this embodiment, when viewed from the front of the first flange portion 61, two fastening portions 65a and 65b are lined up vertically on the left side, and the remaining fastening portion 65c is arranged on the right side so as to be located between the two fastening portions 65a and 65b on the left side in the vertical direction. As a result, when viewed from the front of the first flange portion 61, the exhaust recirculation pipe 27 extends obliquely upward so as to pass between the fastening portions 65a and 65c, and the exhaust discharge pipe 29 extends obliquely downward so as to pass between the fastening portions 65b and 65c.

[0048] 8, when viewed from the front of the second flange portion 62, two fastening portions 65a and 65b are lined up vertically on the left side, and the remaining fastening portion 65c is arranged on the right side so as to be located between the two fastening portions 65a and 65b on the left side in the vertical direction. As a result, when viewed from the front of the second flange portion 62, the extension pipe 63 and the intake manifold 22 are arranged to extend between the fastening portions 65a and 65b.

[0049] By making the first flange portion 61 and the second flange portion 62 identical to each other and arranging the three fastening portions 65a, 65b and 65c in this manner, the number of parts can be reduced by standardizing the parts, and the installation workability of the first flange portion 61 and the second flange portion 62 can be improved and the layout of the surrounding piping can be optimized.

[0050] As described above, according to this embodiment, it is possible to provide an exhaust gas recirculation device 3 and an engine 2 that can reduce the number of parts, make the device smaller and more space-saving, and reduce the pressure loss when introducing EGR gas.

[0051] The above describes the embodiments of the present invention. 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. The configurations of the above embodiments can be partially omitted or arbitrarily combined in a different manner from the above.

[0052] 2: Engine, 3: Exhaust gas recirculation device, 4: Control device, 21: Intake pipe, 22: Intake manifold, 23: Rail, 24: Cylinder block, 25: Exhaust manifold, 26: Exhaust pipe, 27: Exhaust gas recirculation pipe, 29: Exhaust gas discharge pipe, 32: Branch portion, 51: Revolution sensor, 52: Cam angle sensor, 53: NOx sensor, 54: Temperature sensor, 55: Pressure sensor, 56: Water temperature sensor, 61: First flange portion, 62: Second flange portion, 63: Extension pipe, 65a: Fastening portion, 65b: Fastening portion, 65c: Fastening portion, 71: Flange portion, 72: Flange portion, 201: Flywheel, 211: Air cleaner, 221: First branch pipe, 222: Second branch pipe 231: First injector, 232: Second injector, 241: First cylinder, 242: Second cylinder, 261: Diesel oxidation catalyst, 320: Connection portion, 321: First branch portion, 322: Second branch portion, 323: Curved body portion, 324: Port, 2610: Body portion, 2611: First end portion, 2612: Second end portion

Claims

1. An exhaust gas recirculation device that recirculates a portion of exhaust gas flowing through an engine's exhaust system to an intake system of the engine as recirculated gas, comprising: an exhaust pipe provided in the exhaust system and directing the exhaust; a purification section provided downstream of the exhaust pipe and purifying the exhaust gas; an exhaust recirculation pipe provided between the purification section and the intake system; an exhaust exhaust pipe provided between the purification section and an exhaust gas outlet; and a branch section provided downstream of the purification section and branching the exhaust gas that has passed through the purification section to the exhaust recirculation pipe and the exhaust exhaust pipe, wherein the branch section has: a first branch section provided between the purification section and the exhaust recirculation pipe and directing the exhaust gas above the purification section; and a second branch section provided between the purification section and the exhaust exhaust pipe and directing the exhaust gas below the purification section.

2. The exhaust gas recirculation device described in claim 1, characterized in that the branch portion has a connecting portion provided between the purification portion and the first and second branch portions, the first branch portion has a curved body portion that bends the flow direction of the exhaust gas from the end of the extension direction of the connecting portion toward the exhaust recirculation pipe, and the second branch portion is connected to a port provided on the side of the connecting portion on the purification portion side of the curved body portion.

3. The exhaust gas recirculation device described in claim 1, characterized in that the branch portion has a connecting portion provided between the purification section and the first and second branch portions, and when looking at the exhaust gas outlet of the purification section from the front, the first branch portion is connected above the center of the connecting portion, and the second branch portion is connected below the center of the connecting portion.

4. An exhaust gas recirculation device as described in claim 1, further comprising a first flange portion provided in the purification section for fastening the purification section and the branch portion, the first flange portion having three fastening portions arranged at the vertices of a triangle, and when viewing the exhaust gas outlet in the purification section from the front, each of the first branch portion and the second branch portion is arranged so as not to overlap any of the three fastening portions.

5. An exhaust gas recirculation device as described in claim 4, further comprising a second flange portion provided in the purification section for fastening the purification section to the exhaust pipe, the second flange portion having the same shape as the first flange portion.

6. The exhaust gas recirculation device described in claim 5, characterized in that the purification section has a cylindrical body portion, a first end portion and a second end portion which are parallel to each other and are opposite ends of the body portion, and an extension tube having one end connected to the second end portion and the other end connected to the second flange portion, wherein a mounting plane of the first flange portion is arranged parallel to the first end portion, and a mounting plane of the second flange portion is arranged non-parallel to the second end portion.

7. An engine equipped with an exhaust gas recirculation device that recirculates a portion of the exhaust gas flowing through an exhaust system to an intake system as exhaust recirculation gas, wherein the exhaust gas recirculation device comprises: an exhaust pipe provided in the exhaust system and directing the exhaust; a purification section provided downstream of the exhaust pipe and purifying the exhaust gas; an exhaust recirculation pipe provided between the purification section and the intake system; an exhaust exhaust pipe provided between the purification section and an exhaust gas outlet; and a branch section provided downstream of the purification section and branching the exhaust gas that has passed through the purification section to the exhaust recirculation pipe and the exhaust exhaust pipe, wherein the branch section has: a first branch section provided between the purification section and the exhaust recirculation pipe and directing the exhaust gas above the purification section; and a second branch section provided between the purification section and the exhaust exhaust pipe and directing the exhaust gas below the purification section.

8. An engine as described in claim 7, characterized in that a direction perpendicular to the crankshaft of the engine is defined as a first direction, an intake manifold in the intake system is disposed on one side of the engine in the first direction, and an exhaust manifold in the exhaust system is disposed on the other side of the engine in the first direction, and the purification unit is disposed on the flywheel side of the engine and above the flywheel.

9. An engine according to claim 7, which is a four-stroke, one-cycle, two-cylinder type, the strokes of each cylinder being offset from each other by 180 degrees in crank rotation angle.

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