Exhaust gas recirculation device and engine

Abstract

To provide an exhaust gas recirculation device and an engine capable of achieving reduction of the number of components, space saving, and reduction of pressure loss in the introduction of an EGR gas.SOLUTION: An exhaust gas recirculation device 3 includes an exhaust pipe 26, an exhaust gas recirculation pipe 27 provided between a diesel oxidation catalyst 261 for purifying an exhaust gas and an induction system, an exhaust gas exhaust pipe 29 provided between the diesel oxidation catalyst 261 and the exhaust port for exhaust gas, and a branching part 32 for causing the exhaust gas passing through the diesel oxidation catalyst 261 to branch to the exhaust gas recirculation pipe 27 and the exhaust gas exhaust pipe 29. The branching part 32 includes a first branching part 321 provided between the diesel oxidation catalyst 261 and the exhaust gas recirculation pipe 27 for guiding the exhaust gas higher than the diesel oxidation catalyst 261, and a second branching part 322 provided between the diesel oxidation catalyst 261 and the exhaust gas exhaust pipe 29 for guiding the exhaust gas toward a side lower than the diesel oxidation catalyst 261.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a means for reducing nitrogen oxides (NOx) contained in the exhaust gas of an engine, exhaust gas recirculation (EGR) is generally known. An exhaust gas recirculation device recirculates a part of the exhaust flowing through the exhaust system of the engine as exhaust reflux gas (i.e., EGR gas) to the intake system of the engine and mixes the exhaust reflux gas with fresh intake air (i.e., intake air (also referred to as outside air)). Compared with the case where the exhaust gas recirculation device is not provided, the exhaust gas recirculation 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, 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 that is provided in the EGR passage and 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 reflux direction of the EGR gas, and is integrally formed with the EGR passage via a heat-conductive separation wall. A gasket for sealing the cooling water and the EGR gas is provided at the connection portion.

[0004] In Patent Document 2, in 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 this 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 passage wall is attached to the other lateral side of the cylinder head, and an EGR cooler is interposed between the exhaust combined 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 passage wall is positioned directly above this EGR cooler. A multi-cylinder engine is disclosed, which is characterized by this.

[0005] In Patent Document 3, a DOC disposed in the exhaust path of a 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 turbine of a turbocharger 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 performing control to adsorb and oxidize HC in the DOC when the differential pressure between the front and rear of 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. An exhaust gas purification device for a diesel engine is disclosed.

[0006] However, providing such an exhaust gas recirculation device tends to cause the engine to become larger, and further, providing a device for purifying exhaust gas leads to further enlargement and an increase in the number of parts. Therefore, in the exhaust gas recirculation device and the engine, reduction in the number of parts, miniaturization, and space saving are desired.

[0007] Also, for example, in a small two-cylinder engine, since the intake and exhaust pulsations are larger compared to an engine with three or more cylinders, a generally used flow sensor is not suitable as a sensor used for controlling the amount of EGR gas (that is, controlling the opening degree of the EGR valve). Therefore, for example, a NOx sensor (see FIG. 1) may be used. In this case, it is necessary to branch and reflux the EGR gas from the downstream stage of the NOx sensor in the exhaust system of the engine (that is, immediately before opening to the atmosphere). At this branching position, since the introduction pressure of the EGR gas becomes close to (that is, lower than) the atmospheric pressure, it becomes important to reduce the pressure loss in the introduction of the EGR gas as much as possible.

[0008] Incidentally, if the pulsation of the intake air of the engine is small and the EGR valve can be controlled based on the flow sensor that measures the intake air volume, taking FIG. 1 as an example, the EGR gas can be refluxed by branching from the upstream side of the DOC261 in the exhaust pipe 26. Then, since the introduction pressure of the EGR gas becomes close to (i.e., higher than) the pressure on the upstream side of the DOC261, compared with the case where the EGR gas is refluxed by branching from the downstream side of the NOx sensor, it is not necessary to worry about the pressure loss in the introduction of the EGR gas up to that point.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust gas recirculation device and an engine capable of reducing the number of parts, miniaturizing and saving space, and reducing the pressure loss in the introduction of EGR gas.

Means for Solving the Problems

[0011] A first aspect of the present invention is an exhaust gas recirculation device that recirculates a part of the exhaust gas flowing through the exhaust system of an engine as recirculation gas to the intake system of the engine, including an exhaust pipe provided in the exhaust system to guide the exhaust gas, a purification unit provided downstream of the exhaust pipe to purify the exhaust gas, an exhaust recirculation pipe provided between the purification unit and the intake system, an exhaust discharge pipe provided between the purification unit and the exhaust gas discharge port, and a branch unit provided downstream of the purification unit to branch the exhaust gas passing through the purification unit into the exhaust recirculation pipe and the exhaust discharge pipe. The branch unit includes a first branch unit provided between the purification unit and the exhaust recirculation pipe to guide the exhaust gas above the purification unit, and a second branch unit provided between the purification unit and the exhaust discharge pipe to guide the exhaust gas below the purification unit. The exhaust gas recirculation device is characterized by this configuration.

[0012] A second aspect of the present invention is an engine equipped with an exhaust gas recirculation device that recirculates a part of the exhaust flowing through the exhaust system as exhaust recirculation gas to the intake system. The exhaust gas recirculation device includes an exhaust pipe provided in the exhaust system to guide the exhaust gas, a purification unit provided downstream of the exhaust pipe to purify the exhaust gas, an exhaust recirculation pipe provided between the purification unit and the intake system, an exhaust discharge pipe provided between the purification unit and the exhaust gas discharge port, and a branch unit provided downstream of the purification unit to branch the exhaust gas passing through the purification unit into the exhaust recirculation pipe and the exhaust discharge pipe. The branch unit includes a first branch unit provided between the purification unit and the exhaust recirculation pipe to guide the exhaust gas above the purification unit, and a second branch unit provided between the purification unit and the exhaust discharge pipe to guide the exhaust gas below the purification unit. The engine is characterized by this configuration.

Advantages of the Invention

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

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[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 thus various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these aspects unless otherwise specified in the following description. In addition, in each drawing, the same reference numerals are assigned to the same components, and detailed descriptions thereof are appropriately omitted.

[0016] FIG. 1 is a schematic diagram illustrating the engine according to this embodiment. FIG. 2 is a perspective view illustrating the engine according to this embodiment.

[0017] The engine 2 according to this embodiment is an internal combustion engine and is a naturally aspirated small 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 displacement of the engine 2 is about 500 cc. However, the displacement is not limited to about 500 cc. The timing difference between the combustion process of the first cylinder 241, which is one of the two cylinders, and the combustion process of the other second cylinder 242 is, for example, 180 degrees as the angle of the crankshaft. However, the timing difference between the combustion process of the first cylinder 241 and the combustion process of the second cylinder 242 is not limited to this, and may be 360 degrees as the angle of the crankshaft. 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) of the cylinder head. The second cylinder 242 is connected to the second branch pipe 222 via an intake port of the cylinder head. The exhaust manifold 25 is connected to the cylinder head and the exhaust pipe 26. Specifically, the exhaust manifold 25 is connected to the first cylinder 241 and the second cylinder 242 via the exhaust ports of the cylinder head. Note that the exhaust pipe 26 is included in an exhaust gas recirculation device 3 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 the high-pressure fuel supplied from a fuel pump (not shown) to a plurality of paths according to the number of cylinders of the engine 2. That is, 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 in the upper part of the first cylinder 241. The first injector 231 opens and closes a needle valve, for example, by a solenoid based on a signal transmitted from the control device 4, and injects the fuel supplied from the rail 23 from an injection hole (not shown) into the combustion chamber formed in the upper part of the first cylinder 241. As the control device 4, for example, an electronic control unit (ECU) can be mentioned.

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

[0023] As shown by the arrow A1 in FIG. 1, the fresh intake air (that is, the intake air (also referred to as the outside air)) passes through the intake pipe 21, passes through the air cleaner 211 provided in the intake pipe 21, and is guided 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 described later. The intake air guided to the intake manifold 22 is distributed to the first branch pipe 221 and the second branch pipe 222, and is guided to the first cylinder 241 through the first branch pipe 221 and to the second cylinder 242 through the second branch pipe 222.

[0024] The exhaust gas discharged from the first cylinder 241 and the second cylinder 242 passes through the exhaust manifold 25 and is led to the exhaust pipe 26. The exhaust gas led to the exhaust pipe 26 passes through the 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 the SOF (Soluble Organic Fraction), CO (carbon monoxide), and HC (hydrocarbon) in the PM (particulate matter) contained in the exhaust gas. As shown by the arrow A2 in FIG. 1, the exhaust gas that has passed through the diesel oxidation catalyst 261 is discharged to the outside of the engine 2 through the exhaust discharge pipe 29. Note that the diesel oxidation catalyst 261 is included in the exhaust gas recirculation device 3 described later.

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

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

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

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

[0029] Accordingly, the exhaust gas passes from the exhaust manifold 25 disposed on the other side in the left-right direction of the engine 2 through the diesel oxidation catalyst 261 at the rear (above the flywheel 201) of the engine 2 and is guided to one side in the left-right direction of the engine 2. A part of the exhaust gas recirculation gas, which is a part of the exhaust gas guided to one side in the left-right direction of the engine 2, is sent to the intake manifold 22 side disposed on one side in the left-right direction of the engine 2, and the remaining is discharged to the outside through the exhaust discharge pipe 29 from one side in the left-right direction of the engine 2. With such an arrangement of the exhaust manifold 25, the intake manifold 22, and the diesel oxidation catalyst 261, the configuration of the exhaust gas recirculation device 3 can be effectively laid out, and the engine 2 equipped with the exhaust gas recirculation device 3 can be downsized.

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

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

[0032] In the layout of the engine 2 as described above, the first branch portion 321 downstream of the connecting portion 320 is formed to guide the exhaust gas above the diesel oxidation catalyst 261, and the second branch portion 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 extending direction of the diesel oxidation catalyst 261 (for example, the right direction), and the first branch portion 321 has a curved body portion 323 that bends the flowing direction of the exhaust gas from the end portion in the extending direction of the connecting portion 320 toward the exhaust gas reflux pipe 27. As shown in FIG. 3, the first branch portion 321 is bent approximately 90° forward by the curved body portion 323, bent upward from the diesel oxidation catalyst 261, and connected to the exhaust gas reflux pipe 27. The second branch portion 322 is connected to a port 324 (see FIG. 4) provided on the side surface of the connecting portion 320 located closer to the diesel oxidation catalyst 261 than the curved body portion 323.

[0034] Due to the first branch portion 321 of such a branch portion 32, the exhaust gas reflux gas is sent above the diesel oxidation catalyst 261, mixed with the outside air above the intake manifold 22, and the air-fuel mixture can be sent to the intake manifold 22 side. In this way, by being mixed with the outside air while the exhaust gas reflux gas is sent to the intake manifold 22 from above, even when, for example, the pulsation of intake and exhaust is large and it is difficult to uniformly mix the outside air and the exhaust gas reflux gas, a sufficient mixing path can be ensured, and a uniform air-fuel mixture can be sent to the intake manifold 22. In particular, in the case of a four-stroke one-cycle two-cylinder engine, when the respective strokes (strokes) of each cylinder are shifted from each other by 180 degrees in terms of the crank rotation angle, the above configuration is effective in the case of the engine 2 with large intake and exhaust pulsation.

[0035] Further, by providing the curved body portion 323 at the end portion in the extending direction of the connecting portion 320, the exhaust gas that has passed through the diesel oxidation catalyst 261 advances straight in the connecting portion 320, and is smoothly bent forward and upward by the curved body portion 323 provided in the front in the advancing direction and sent to the exhaust gas reflux pipe 27. The exhaust gas sent from the diesel oxidation catalyst 261 to the connecting portion 320 easily advances straight due to the inertial force, and is guided from the first branch portion 321 to the exhaust gas reflux pipe 27 with a small pressure loss. If the first branch portion 321 is configured to be connected to the side surface of the connecting portion 320, it is difficult for the exhaust gas to branch, and a large pressure loss will occur while the exhaust gas is sent to the exhaust gas reflux pipe 27.

[0036] In the configuration of the branch portion 32 of the present embodiment, the pressure loss of the exhaust gas due to the first branch portion 321 is smaller than the pressure loss of the exhaust gas due to the second branch portion 322. Thereby, for example, even in the engine 2 with a low introduction pressure of the exhaust recirculation gas, the exhaust recirculation gas can be effectively sent to the intake manifold 22 side, and the reduction effect of nitrogen oxides (NOx) can be exerted.

[0037] Next, the attachment of the diesel oxidation catalyst 261 will be described. FIG. 5 is a perspective view illustrating an attachment portion on the downstream side of the diesel oxidation catalyst. FIG. 6 is a front view illustrating an attachment portion on the downstream side of the diesel oxidation catalyst. FIG. 6 shows a front view as seen from the exhaust gas outlet side of the diesel oxidation catalyst 261. FIG. 7 is a perspective view illustrating an attachment portion on the upstream side of the diesel oxidation catalyst. FIG. 8 is a front view illustrating an attachment portion on the upstream side of the diesel oxidation catalyst. FIG. 8 shows a front view as seen from the inlet side of the second flange portion 62 of the diesel oxidation catalyst 261. FIG. 9 is a perspective view illustrating a flange portion in the attachment of the diesel oxidation catalyst.

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

[0039] A second flange portion 62 is connected to a second end portion 2612 of the diesel oxidation catalyst 261 via an extension pipe 63. Note that 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 second flange portion 62 is connected to the other end of the extension pipe 63. The first flange portion 61 and the second flange portion 62 are preferably identical in shape to each other. Thereby, the first flange portion 61 and the second flange portion 62 can be made into common parts, and the number of parts can be reduced.

[0040] Further, the first flange portion 61 is attached to the first end portion 2611 of the body portion 2610. Thereby, the attachment plane of the first flange portion 61 is provided substantially parallel to the first end portion 2611 of the body portion 2610. On the other hand, the second flange portion 62 is attached to an end portion of the extension pipe 63 bent from the extending direction of the body portion 2610. Thereby, the attachment plane of the second flange portion 62 is provided non-parallel to the second end portion 2612 of the body portion 2610.

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

[0042] A flange portion 72 that mates with the second flange portion 62 is provided at an end portion of an exhaust manifold 25 that extends rearward and is provided on the other side (for example, the left side) in the left-right direction of the engine 2. Thereby, it is not necessary to bend the extending end side of the exhaust manifold 25 rearward of the engine 2, and the shape is simplified.

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

[0044] Also, as shown in FIG. 8, in the second flange portion 62, when looking at the second end portion 2612 (exhaust gas inlet side) of the diesel oxidation catalyst 261 from the front, the extension pipe 63 is arranged so as not to overlap any of the three fastening portions 65a, 65b, and 65c. Thereby, when fastening by the first flange portion 61 and the second flange portion 62, it becomes possible to access the fastening portions 65a, 65b, and 65c from the fronts of the first flange portion 61 and the second flange portion 62, respectively.

[0045] The arrangement of each of the three fastening portions 65a, 65b, and 65c 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 65a, 65b, and 65c is not limited to these.

[0046] By arranging the three fastening portions 65a, 65b, and 65c at the positions of the vertices of the triangle, it is possible to perform reliable fastening with the front and rear members while saving space. That is, in the case of two-point fixing or less, the reliability of fastening is likely to be insufficient. On the other hand, in the case of four-point fixing or more, the interval between adjacent fastening portions becomes narrow, interference with peripheral members is likely to occur during fastening, and the degree of freedom of layout cannot be sufficiently ensured. Therefore, in the case of three-point fixing, reliable fastening can be achieved, interference with peripheral members during fastening can be easily avoided, and space saving can be achieved.

[0047] In the present embodiment, as shown in FIG. 6, two fastening portions 65a and 65b are arranged vertically on the left side when the first flange portion 61 is viewed from the front, and the remaining one fastening portion 65c is arranged on the right side when viewed from the front so as to be between the two left-side fastening portions 65a and 65b in the vertical direction. Thereby, when the first flange portion 61 is viewed from the front, the exhaust reflux pipe 27 extends obliquely upward so as to pass between the fastening portion 65a and the fastening portion 65c, and the exhaust discharge pipe 29 extends obliquely downward so as to pass between the fastening portion 65b and the fastening portion 65c.

[0048] Also, as shown in FIG. 8, two fastening portions 65a and 65b are arranged vertically on the left side when the second flange portion 62 is viewed from the front, and the remaining one fastening portion 65c is arranged on the right side when viewed from the front so as to be between the two left-side fastening portions 65a and 65b in the vertical direction. Thereby, when the second flange portion 62 is viewed from the front, the extension pipe 63 and the intake manifold 22 are arranged to extend so as to pass between the fastening portion 65a and the fastening portion 65b.

[0049] By making the first flange portion 61 and the second flange portion 62 have the same shape and arranging the three fastening portions 65a, 65b, and 65c in this way, it is possible to reduce the number of parts by commonizing the parts, improve the attachment workability by the first flange portion 61 and the second flange portion 62, and optimize the layout of the peripheral piping.

[0050] As described above, according to the present embodiment, it is possible to provide an exhaust gas recirculation device 3 and an engine 2 that can reduce the number of parts, miniaturize and save space, and reduce the pressure loss in the introduction of EGR gas.

[0051] As described above, the embodiments of the present invention have been described. 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 differently from the above.

Explanation of Reference Numerals

[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 reflux pipe, 29: Exhaust discharge pipe, 32: Branch portion, 51: Rotation 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: Connecting portion, 321: First branch portion, 322: Second branch portion, 323: Crankcase portion, 324: Port, 2610: Body portion, 2611: First end portion, 2612: Second end portion

Claims

1. An exhaust gas recirculation device that recirculates a part of the exhaust gas flowing through the exhaust system of an engine as recirculation gas to the intake system of the engine, comprising: An exhaust pipe provided in the exhaust system for guiding the exhaust; A purification unit provided downstream of the exhaust pipe for purifying the exhaust gas; An exhaust reflux pipe provided between the purification unit and the intake system; An exhaust discharge pipe provided between the purification unit and the exhaust gas discharge port; A branch unit provided downstream of the purification unit for branching the exhaust gas that has passed through the purification unit into the exhaust reflux pipe and the exhaust discharge pipe; Characterized by comprising: The branch unit includes: A first branch unit provided between the purification unit and the exhaust reflux pipe for guiding the exhaust gas above the purification unit; A second branch unit provided between the purification unit and the exhaust discharge pipe for guiding the exhaust gas below the purification unit.

2. The branch unit has a connecting unit provided between the purification unit, the first branch unit, and the second branch unit, The first branch unit has a curved body portion that bends the flow direction of the exhaust gas from an end in the extending direction of the connecting unit toward the exhaust reflux pipe, The exhaust gas recirculation device according to claim 1, wherein the second branch unit is connected to a port provided on a side surface of the connecting unit closer to the purification unit than the curved body portion.

3. The branch unit has a connecting unit provided between the purification unit, the first branch unit, and the second branch unit, When viewed from the front, the first branch unit is connected above the center of the connecting unit, and the second branch unit is connected below the center of the connecting unit, at the exhaust gas outlet of the purification unit. The exhaust gas recirculation device according to claim 1, characterized by this.

4. The purification unit is further provided with a first flange unit for fastening the purification unit and the branch unit, The first flange unit has three fastening portions arranged at the positions of the vertices of a triangle, When viewed from the front at the exhaust gas outlet of the purification unit, each of the first branch unit and the second branch unit is arranged so as not to overlap any of the three fastening portions. The exhaust gas recirculation device according to claim 1, characterized by this.

5. The purification unit is further provided with a second flange unit for fastening the purification unit and the exhaust pipe, The exhaust gas recirculation device according to claim 4, wherein the second flange portion has the same shape as the first flange portion.

6. The purification unit includes a cylindrical body portion, a first end portion and a second end portion that are parallel to each other and are both ends of the body portion, an extension pipe having one end connected to the second end portion and the second flange portion connected to the other end, and has the mounting plane of the first flange portion is provided parallel to the first end portion, The exhaust gas recirculation device according to claim 5, wherein the mounting plane of the second flange portion is provided non-parallel to the second end portion.

7. An engine provided with an exhaust gas recirculation device that recirculates a part of the exhaust gas flowing through the exhaust system as exhaust reflux gas to the intake system, wherein the exhaust gas recirculation device an exhaust pipe provided in the exhaust system for guiding the exhaust gas, a purification unit provided downstream of the exhaust pipe for purifying the exhaust gas, an exhaust reflux pipe provided between the purification unit and the intake system, an exhaust discharge pipe provided between the purification unit and the exhaust gas discharge port, a branch portion provided downstream of the purification unit for branching the exhaust gas that has passed through the purification unit into the exhaust reflux pipe and the exhaust discharge pipe, and includes the branch portion a first branch portion provided between the purification unit and the exhaust reflux pipe for guiding the exhaust gas above the purification unit, a second branch portion provided between the purification unit and the exhaust discharge pipe for guiding the exhaust gas below the purification unit, and characterized by the engine having.

8. Taking the direction perpendicular to the crankshaft of the engine as the first direction, the intake manifold in the intake system is arranged on one side of the engine in the first direction, and the exhaust manifold in the exhaust system is arranged on the other side of the engine in the first direction. The engine according to claim 7, wherein the purification unit is located on the flywheel side of the engine and above the flywheel.

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

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