Engine equipment

Abstract

To arrange a two-stage supercharger as compactly as possible when arranging the two-stage supercharger in a Diesel engine.SOLUTION: An engine device 1 comprises an exhaust manifold 4 and a supercharger 30. The supercharger 30 is configured as a two-stage supercharger consisting of a high-pressure supercharger 51 connected to the exhaust manifold 4 and a low-pressure supercharger 52 connected to the high-pressure supercharger 51. An exhaust outlet of the high-pressure supercharger 51 and an exhaust inlet of the low-pressure supercharger 52 are located at different positions in a crankshaft direction. The low-pressure supercharger 52 is located above the high-pressure supercharger 51.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an engine device provided with a supercharger. [Background Art]

[0002] Conventionally, for the purpose of improving engine output and fuel efficiency, a supercharger that compresses fresh air using exhaust energy to increase the air density in the cylinders of an engine has been mounted on engine devices (see Patent Document 1). In a diesel engine, supplying a large amount of high-density air into the cylinders allows a large volume of fuel to be combusted, which not only increases engine output and engine torque, but also suppresses premixed combustion by promoting mixing of fuel and air, thereby reducing NOx emissions.

[0003] Furthermore, since a single-stage supercharger using one supercharger has a limit in meeting the requirements of high-output engines, an engine equipped with a two-stage supercharger in which two superchargers are connected in series as a high-pressure stage and a low-pressure stage has been proposed (see Patent Document 2). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent No. 4517550 [Patent Document 2] Japanese Patent No. 5237785 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Incidentally, the mounting space for diesel engines varies depending on the type of work vehicle (construction machinery, agricultural machinery, etc.), but in recent years, due to the demand for lighter and more compact designs, mounting space is often constrained (very small). For this reason, the components of the diesel engine need to be laid out compactly. In addition to the constraints of mounting space, the cylinder head requires a highly rigid structure because it is used to connect and support components such as the EGR system and turbocharger.

[0006] Furthermore, as in the engine system described in Patent Document 2, when the high-pressure and low-pressure turbochargers in a two-stage turbocharger are positioned vertically at a distance from the exhaust manifold, the moment acting on the exhaust manifold outlet supporting the two-stage turbocharger increases, resulting in a decrease in the support rigidity of the two-stage turbocharger. In addition, since the bypass path provided on the turbine side of the high-pressure stage is external piping, the piping structure in the two-stage turbocharger becomes complex, making assembly to the engine system complicated.

[0007] The present invention aims to provide an engine device that addresses the above-mentioned current situation and incorporates improvements, which is its technical objective. [Means for solving the problem]

[0008] An engine system according to one aspect of the present invention is an engine system comprising an exhaust manifold and a supercharger. The supercharger is a two-stage supercharger consisting of a high-pressure supercharger connected to the exhaust manifold and a low-pressure supercharger connected to the high-pressure supercharger. The low-pressure supercharger is located above the high-pressure supercharger. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view of the engine. [Figure 2] This is a rear view of the engine. [Figure 3] This is a left side view of the engine. [Figure 4] This is a right-side view of the engine. [Figure 5] It is a plan view of an engine. [Figure 6] It is a bottom view of an engine. [Figure 7] It is a perspective view of the engine seen from obliquely forward. [Figure 8] It is a perspective view of the engine seen from obliquely rearward. [Figure 9] It is an enlarged perspective view of a cylinder head seen from the intake manifold side. [Figure 10] It is an exploded perspective view of a cylinder head seen from the exhaust manifold side. [Figure 11] It is an exploded perspective view of a cylinder head seen from the intake manifold side. [Figure 12] It is a plan view of a cylinder head. [Figure 13] It is a front view of a cylinder head. [Figure 14] It is a cross-sectional perspective view of a cylinder head and an EGR device. [Figure 15] It is a cross-sectional perspective view of a cylinder head and an exhaust manifold. [Figure 16] It is a cross-sectional perspective view of the connection portion with an EGR cooler in a cylinder head. [Figure 17] It is a cross-sectional perspective view of an EGR device. [Figure 18] It is a plan view of an EGR device. [Figure 19] It is an exploded perspective view of an EGR device. [Figure 20] It is an exploded view of the connection portion with an EGR cooler in a cylinder head. [Figure 21] It is a cross-sectional view of the connection portion with an EGR cooler in a cylinder head. [Figure 22] It is a left side view of an engine for explaining the arrangement of a two-stage supercharger. [Figure 23] It is an enlarged rear view of an engine. [Figure 24] It is an enlarged front view of an engine. [Figure 25] It is a left side view of a two-stage supercharger. [Figure 26]This is a perspective view of a two-stage supercharger. [Figure 27] This is a right-side view of a two-stage turbocharger. [Figure 28] This is a disassembled perspective view of a cooling water pump. [Figure 29] This is a partial cross-sectional view of the cooling water pump mounting area. [Modes for carrying out the invention]

[0010] The following describes embodiments of the present invention based on the drawings. First, the overall structure of the diesel engine (engine device) 1 will be described with reference to Figures 1 to 8. In the following description, the sides parallel to the crankshaft 5 (the sides on either side of the crankshaft 5) will be referred to as left and right, the side where the flywheel housing 7 is installed will be referred to as the front, and the side where the cooling fan 9 is installed will be referred to as the rear. For convenience, these will be used as the reference points for the positional relationships in the four directions and up and down of the diesel engine 1.

[0011] As shown in Figures 1 to 8, the intake manifold 3 is located on one side of the diesel engine 1 parallel to the crankshaft 5, and the exhaust manifold 4 is located on the other side. In this embodiment, the intake manifold 3 is integrally molded with the cylinder head 2 on the right side of the cylinder head 2, and the exhaust manifold 4 is installed on the left side of the cylinder head 2. The cylinder head 2 is mounted on a cylinder block 6 which houses the crankshaft 5 and pistons (not shown).

[0012] The front and rear ends of the crankshaft 5 protrude from both the front and rear sides of the cylinder block 6. A flywheel housing 7 is fixed to one side of the diesel engine 1 that intersects with the crankshaft 5 (in this embodiment, the front side of the cylinder block 6). A flywheel 8 is positioned inside the flywheel housing 7. The flywheel 8 is pivotally supported on the front end of the crankshaft 5 and is configured to rotate integrally with the crankshaft 5. Power from the diesel engine 1 is extracted to the operating parts of working machinery (e.g., hydraulic excavators and forklifts) via the flywheel 8. A cooling fan 9 is provided on the other side of the diesel engine 1 that intersects with the crankshaft 5 (in this embodiment, the rear side of the cylinder block 6). Rotational force is transmitted from the rear end of the crankshaft 5 to the cooling fan 9 via a V-belt 10.

[0013] An oil pan 11 is located on the underside of the cylinder block 6. Lubricating oil is stored in the oil pan 11. The lubricating oil in the oil pan 11 is drawn in by an oil pump (not shown) located on the right side of the cylinder block 6 at the connection point with the flywheel housing 7, and supplied to each lubrication part of the diesel engine 1 via an oil cooler 13 and an oil filter 14 located on the right side of the cylinder block 6. The lubricating oil supplied to each lubrication part is then returned to the oil pan 11. The oil pump (not shown) is configured to be driven by the rotation of the crankshaft 5.

[0014] A fuel supply pump 15 is mounted at the connection point between the cylinder block 6 and the flywheel housing 7, and the fuel supply pump 15 is positioned below the EGR device 24. A common rail 16 is fixed to the side of the cylinder block 6 below the intake manifold 3 of the cylinder head 2 and is positioned above the fuel supply pump 15. On the upper surface of the cylinder head 2, which is covered by a head cover 18, there are four injectors (not shown) each having an electromagnetically controlled fuel injection valve.

[0015] Each injector is connected to a fuel tank (not shown) mounted on the work vehicle via a fuel supply pump 15 and a cylindrical common rail 16. Fuel from the fuel tank is pumped from the fuel supply pump 15 to the common rail 16, and high-pressure fuel is stored in the common rail 16. By controlling the opening and closing of the fuel injection valve of each injector, the high-pressure fuel in the common rail 16 is injected from each injector into each cylinder of the diesel engine 1.

[0016] On the upper surface of the head cover 18, which covers the intake valve and exhaust valve (not shown) etc. located on the upper surface of the cylinder head 2, leaks from the combustion chamber of the diesel engine 1 to the upper surface of the cylinder head 2. A blow-by gas recirculation device 19 is provided to take in the blow-by gas. The blow-by gas outlet of the blow-by gas recirculation device 19 is connected to the intake section of the two-stage supercharger 30 via a recirculation hose 68. The blow-by gas from which lubricating oil components have been removed in the blow-by gas recirculation device 19 is returned to the intake manifold 3 via the two-stage supercharger 30.

[0017] An engine starter 20 is mounted on the flywheel housing 7, and the engine starter 20 is positioned below the exhaust manifold 4. The engine starter 20 is mounted on the flywheel housing 7 at a position below the connection between the cylinder block 6 and the flywheel housing 7.

[0018] A coolant pump 21 for coolant lubrication is located below the cooling fan 9 on the left rear side of the cylinder block 6. The rotation of the crankshaft 5 drives the coolant pump 21 together with the cooling fan 9 via a V-belt 10 for driving the cooling fan. Coolant from a radiator (not shown) mounted on the work vehicle is supplied to the coolant pump 21 by the drive of the coolant pump 21. Coolant is then supplied to the cylinder head 2 and cylinder block 6, cooling the diesel engine 1.

[0019] The coolant pump 21 is located below the exhaust manifold 4, and a coolant inlet pipe 22, which communicates with the coolant outlet of the radiator, is fixed to the left side of the cylinder block 6 at the same height as the coolant pump 21. On the other hand, a coolant outlet pipe 23, which communicates with the coolant inlet of the radiator, is fixed to the upper rear surface of the cylinder head 2. The cylinder head 2 has a coolant drain section 35 that protrudes from the rear of the intake manifold 3, and the coolant outlet pipe 23 is installed on the upper surface of the coolant drain section 35.

[0020] The inlet side of the intake manifold 3 is connected to an air cleaner (not shown) via the collector (EGR main case) 25 of an EGR device 24 (exhaust gas recirculation device), which will be described later. Fresh air (outside air) drawn into the air cleaner is purified and dust-removed by the air cleaner, then sent to the intake manifold 3 via the collector 25, and then supplied to each cylinder of the diesel engine 1. In this embodiment, the collector 25 of the EGR device 24 is connected to the right side of the intake manifold 3, which is integrally molded with the cylinder head 2 and constitutes the right side of the cylinder head 2. That is, the outlet opening of the collector 25 of the EGR device 24 is connected to the inlet opening of the intake manifold 3, which is provided on the right side of the cylinder head 2. In this embodiment, as will be described later, the collector 25 of the EGR device 24 is connected to the air cleaner via an intercooler (not shown) and a two-stage supercharger 30.

[0021] The EGR device 24 includes a collector 25 which serves as a relay line that mixes recirculated exhaust gas from the diesel engine 1 (EGR gas from the exhaust manifold 4) with fresh air (outside air from the air cleaner) and supplies it to the intake manifold 3, an intake throttle member 26 which connects the collector 25 to the air cleaner, a recirculated exhaust gas pipe 28 which is part of the return line that is connected to the exhaust manifold 4 via an EGR cooler 27, and an EGR valve member 29 which connects the collector 25 to the recirculated exhaust gas pipe 28.

[0022] The EGR device 24 is located to the right of the intake manifold 3 in the cylinder head 2. That is, the EGR device 24 is fixed to the right side of the cylinder head 2 and communicates with the intake manifold 3 inside the cylinder head 2. The collector 25 of the EGR device 24 is connected to the intake manifold 3 on the right side of the cylinder head 2, and the EGR gas inlet of the recirculating exhaust gas pipe 28 is connected and fixed to the front portion of the intake manifold 3 on the right side of the cylinder head 2. In addition, an EGR valve member 29 and an intake throttle member 26 are connected to the front and rear of the collector 25, respectively, and the EGR gas outlet of the recirculating exhaust gas pipe 28 is connected to the rear end of the EGR valve member 29.

[0023] The EGR cooler 27 is fixed to the front side surface of the cylinder head 2, and the cooling water and EGR gas flowing inside the cylinder head 2 flow into and out of the EGR cooler 27, where the EGR gas is cooled. The front side surface of the cylinder head 2 has EGR cooler connecting bases 33 and 34 protruding from its left and right positions, and the EGR cooler 27 is connected to the connecting bases 33 and 34. In other words, the EGR cooler 27 is positioned above the flywheel housing 7 and in front of the cylinder head 2, such that the rear end surface of the EGR cooler 27 and the front side surface of the cylinder head 2 are spaced apart.

[0024] A two-stage supercharger 30 is positioned to the side (left side in this embodiment) of the exhaust manifold 4. The two-stage supercharger 30 comprises a high-pressure supercharger 51 and a low-pressure supercharger 52. The high-pressure supercharger 51 has a high-pressure turbine 53 with a turbine wheel (not shown) and a high-pressure compressor 54 with a blower wheel (not shown), while the low-pressure supercharger 52 has a low-pressure turbine 55 with a turbine wheel (not shown) and a low-pressure compressor 56 with a blower wheel (not shown).

[0025] The exhaust inlet 57 of the high-pressure turbine 53 is connected to the exhaust manifold 4, the exhaust inlet 60 of the low-pressure turbine 55 is connected to the exhaust outlet 58 of the high-pressure turbine 53 via a high-pressure exhaust gas pipe 59, and the exhaust gas intake end of the exhaust gas discharge pipe (not shown) is connected to the exhaust outlet 61 of the low-pressure turbine 55. Meanwhile, the fresh air supply side (fresh air outlet side) of the air cleaner (not shown) is connected to the fresh air intake port (fresh air inlet) 63 of the low-pressure compressor 56 via an air supply pipe 62, the fresh air intake port 66 of the high-pressure compressor 54 is connected to the fresh air supply port (fresh air outlet) 64 of the low-pressure compressor 56 via a low-pressure fresh air passage pipe 65, and the fresh air intake side of the intercooler (not shown) is connected to the fresh air supply port 67 of the high-pressure compressor 54 via a high-pressure fresh air passage pipe 71.

[0026] The high-pressure turbocharger 51 is connected to the exhaust outlet 58 of the exhaust manifold 4 and fixed to the left side of the exhaust manifold 4, while the low-pressure turbocharger 52 is connected to the high-pressure turbocharger 51 via the high-pressure exhaust gas pipe 59 and the low-pressure fresh air passage pipe 65 and fixed above the exhaust manifold 4. In other words, the small-diameter high-pressure turbocharger 51 and the exhaust manifold 4 are arranged side by side below the large-diameter low-pressure turbocharger 52, so that the two-stage turbocharger 30 surrounds the left side and top of the exhaust manifold 4. That is, the exhaust manifold 4 and the two-stage turbocharger 30 are arranged in a rectangular shape when viewed from the rear (front) and are compactly fixed to the left side of the cylinder head 2.

[0027] Next, the configuration of the cylinder head 2 will be described below with reference to Figures 9 to 16. As shown in Figures 9 to 16, the cylinder head 2 has multiple intake passages 36 for introducing fresh air into multiple intake ports (not shown) and multiple exhaust passages 37 for discharging exhaust gas from multiple exhaust ports. An intake manifold 3, which collects the multiple intake passages 36, is integrally formed on the right side of the cylinder head 2. By integrating the cylinder head 2 and the intake manifold 3, the gas sealing performance from the intake manifold 3 to the intake passages 36 can be improved, and the rigidity of the cylinder head 2 can be increased.

[0028] The cylinder head 2 has an exhaust manifold 4 connected to its left side, which is opposite to the right side where the intake manifold 3 is located, and an EGR cooler 27 is connected to the front side (the side facing the flywheel housing 7) adjacent to both the left and right sides. Connecting bases (EGR cooler connecting bases) 33 and 34 that connect to the EGR cooler 27 are formed protruding from the front side of the cylinder head 2, and EGR gas passages (EGR gas relay passages) 31 and 32 and cooling water passages (cooling water relay passages) 38 and 39 are formed within the connecting bases 33 and 34.

[0029] By configuring the EGR gas relay passages 31, 32 and cooling water passages 38, 39 in the connecting bases 33, 34 to which the EGR cooler 27 is connected, it is not necessary to provide cooling water piping and EGR gas piping between the EGR cooler 27 and the cylinder head 2. Therefore, it is possible to ensure sealing performance at the connection point with the EGR cooler 27 without being affected by the expansion and contraction of piping due to EGR gas and cooling water, as well as improving resistance to external fluctuations such as heat and vibration (structural stability), and enabling a compact configuration.

[0030] The cylinder head 2 is equipped with an upstream EGR gas relay passage 31 that communicates from the front left side to the front side, and the EGR gas outlet 41 located at the front end of the exhaust manifold 4 is in communication with the upstream EGR gas relay passage 31. The cylinder head 2 is also equipped with a downstream EGR gas relay passage 32 that communicates from the front right side (in front of the intake manifold 3) to the front side, and the EGR gas inlet of the recirculating exhaust gas pipe 28 is in communication with the downstream EGR gas relay passage 32. The cylinder head 2 is equipped with EGR cooler connecting bases 33 and 34 that protrude forward from both the left and right edges of its front side (front left corner and front right corner of the cylinder head 2). The upstream EGR gas relay passage 31 is provided within the connecting base 33, and the downstream EGR gas relay passage 32 is provided within the connecting base 34.

[0031] The EGR device 24 is connected to an intake manifold 3 that protrudes from the right side of the cylinder head 2. The intake manifold 3 is located towards the rear (cooling fan 9 side) of the right side of the cylinder head 2 and is formed by protruding to the right from the lower right side of the cylinder head 2, with an intake inlet 40 at its front-to-back center. The intake outlet 83 of the collector 25 of the EGR device 24 is connected to the intake inlet 40 of the intake manifold 3 that protrudes from the right side of the cylinder head 2, and the EGR device 24 is fixed to the right side of the cylinder head 2.

[0032] A connecting base 34 is provided projecting forward from the front right side of the cylinder head 2 (towards the flywheel housing 7), and the EGR cooler 27 is connected to it. The EGR gas outlet of the downstream EGR gas relay passage 32 is open on the right side of the connecting base 34. One end of the recirculating exhaust gas pipe 28 of the EGR device 24 is connected to the right side of the connecting base 34, so that the collector 25 of the EGR device 24 communicates with the downstream EGR gas relay passage 32 inside the cylinder head 2 via the recirculating exhaust gas pipe 28 and the EGR valve member 29.

[0033] A coolant drain section (thermostat case) 35 is provided projecting backward from the rear right side of the cylinder head 2 (on the side of the cooling fan 9), with its top surface open and communicating with the coolant outlet pipe (thermostat cover) 23. A thermostat (not shown) is installed inside this section. Because the coolant drain section 35 is offset from the rear right side of the cylinder head 2, the V-belt 10, which is wound around the fan pulley 9a to which the cooling fan 9 is fixed, can be passed through the space below the coolant drain section 35, thereby shortening the front-to-rear length of the diesel engine 1. The coolant drain section 35 also protrudes from the right side of the cylinder head 2, and the intake manifold 3 and the coolant drain section 35 are provided side by side on the right side of the cylinder head 2.

[0034] A connecting base 33, which connects to the EGR cooler 27, is provided projecting forward from the front left side of the cylinder head 2 (towards the flywheel housing 7), and the EGR gas inlet 96 of the upstream EGR gas relay passage 31 opens on the left side of the connecting base 33. In other words, on the left side of the cylinder head 2, the EGR gas inlet 96 of the upstream EGR gas relay passage 31 and the exhaust outlets of the multiple exhaust passages 37 open side by side in the front-to-back direction. On the other hand, on the right side of the exhaust manifold 4, which is the connecting surface with the left side of the cylinder head 2, the EGR gas outlet 41, which communicates with the upstream EGR gas relay passage 31, and the exhaust inlet 42, which communicates with the multiple exhaust passages 37, open side by side in the front-to-back direction. Therefore, since the EGR inlet and exhaust outlet are provided side by side on the same surface of the cylinder head 2, airtightness (gas sealing) can be easily ensured at the connection portion between the cylinder head 2 and the exhaust manifold 4 by sandwiching a single gasket 45.

[0035] The exhaust manifold 4 has an exhaust collector 43 installed inside, which communicates with the EGR gas outlet 41 and the exhaust inlet 42, with its longitudinal direction being the front-to-back direction. An exhaust outlet 44, which communicates with the exhaust collector 43, is opened on the rear left side of the exhaust manifold 4. When exhaust gas from the exhaust passage 37 of the cylinder head 2 flows into the exhaust collector 43 through the exhaust inlet 42, a portion of the exhaust gas becomes EGR gas and flows from the EGR gas outlet 41 into the upstream EGR gas relay passage 31 of the cylinder head 2, and the remaining exhaust gas flows from the exhaust outlet 44 into the two-stage turbocharger 30.

[0036] On the front side of the cylinder head 2, a pair of EGR cooler connecting bases 33 and 34 are provided on the left and right sides, respectively, on the exhaust manifold 4 side and the intake manifold 3 side. The EGR cooler connecting base 33 is provided with an upstream EGR gas relay passage 31 that connects the EGR gas passages of the exhaust manifold 4 and the EGR cooler 27. On the other hand, the EGR cooler connecting base 34 is provided with a downstream EGR gas relay passage 32 that connects the EGR gas passages of the EGR device 24 and the EGR cooler 27. The EGR cooler connecting base 33 is also provided with a downstream cooling water passage 38 through which cooling water is discharged from the EGR cooler 27. On the other hand, the EGR cooler connecting base 34 is provided with an upstream cooling water passage 39 that supplies cooling water to the EGR device 24 and the EGR cooler 27.

[0037] By providing protruding EGR cooler connecting bases 33 and 34, the need for EGR gas piping to connect the exhaust manifold 4, EGR cooler 27, and EGR device 24 is eliminated, reducing the number of connection points in the EGR gas flow path. Therefore, in a diesel engine 1 that aims to reduce NOx emissions using EGR gas, not only can EGR gas leakage be reduced, but deformation due to stress changes caused by expansion and contraction of piping can also be suppressed. Furthermore, since the EGR gas relay passages 31 and 32 and cooling water passages 38 and 39 are configured on the EGR cooler connecting bases 33 and 34, the shapes of each passage 31, 32, 38, and 39 configured within the cylinder head 2 are simplified, allowing the cylinder head 2 to be easily cast without the use of complex cores.

[0038] Because the EGR cooler connecting base 33 on the intake manifold 3 side and the EGR cooler connecting base 34 on the exhaust manifold 4 side are spaced apart, mutual influence due to thermal deformation of the connecting bases 33 and 34 can be suppressed. Therefore, not only can gas leaks and damage be prevented at the connection point between the EGR cooler connecting bases 33 and 34 and the EGR cooler 27, but the rigidity balance of the cylinder head 2 can also be maintained. Furthermore, since the volume on the front side of the cylinder head 2 can be reduced, the weight of the cylinder head 2 can be reduced. In addition, since the EGR cooler 27 can be positioned spaced apart from the front side of the cylinder head 2, and a configuration can be made with space in front of and behind the EGR cooler 27, cooling air can be circulated around the EGR cooler 27, thereby improving the cooling efficiency of the EGR cooler 27.

[0039] The EGR cooler connecting base 33 has a downstream cooling water passage 38 and an upstream EGR gas relay passage 31 arranged vertically, while the EGR cooler connecting base 34 has a downstream EGR gas relay passage 32 and an upstream cooling water passage 39 arranged vertically. The cooling water inlet of the downstream cooling water passage 38 and the EGR gas inlet of the downstream EGR gas relay passage 32 are at the same height, while the cooling water outlet of the upstream cooling water passage 39 and the EGR gas outlet of the downstream EGR gas relay passage 32 are at the same height.

[0040] By integrating the EGR gas relay passages 31 and 32 and the cooling water passages 38 and 39 into the separate, protruding EGR cooler connecting bases 33 and 34, the effects of thermal deformation in both the EGR cooler connecting bases 33 and 34 are mitigated. Furthermore, within the EGR cooler connecting bases 33 and 34, the EGR gas flowing through the EGR gas relay passages 31 and 32 is cooled by the cooling water flowing through the cooling water passages 38 and 39, thereby suppressing the thermal deformation of the EGR cooler connecting bases 33 and 34 themselves. Moreover, in each of the EGR cooler connecting bases 33 and 34, the EGR gas relay passages 31 and 32 and the cooling water passages 38 and 39 are arranged with their respective vertical height positions swapped. As a result, the heat distribution in the EGR cooler connecting bases 33 and 34 is in the opposite vertical direction, reducing the effects of thermal deformation in the vertical direction of the cylinder head 2.

[0041] The cylinder head 2 is equipped with a spacer 46 that connects to the lower edge of the head cover 18 by an outer peripheral wall that is erected upward from the upper edge of the cylinder head 2. The spacer 46 has a plurality of openings 47 on its right side, and fuel pipes 48 that connect the injector (not shown) provided in the cylinder head 2 to the common rail 16 pass through these openings 47. By providing the spacer 46 integrally above the cylinder head 2, the rigidity of the cylinder head 2 is increased, which not only reduces distortion of the cylinder head 2 itself but also allows for highly rigid support of each component connected to the cylinder head 2.

[0042] Next, the configuration of the EGR device 24 will be described below with reference to Figures 9 to 11, 14, 15, and 17 to 19. As shown in Figures 9 to 11, 14, 15, and 17 to 19, the EGR device 24 is equipped with a collector (main body case) 25 that mixes fresh air and EGR gas and supplies it to the intake manifold 3, and the intake manifold 3 and the intake throttle member 26 for introducing fresh air are connected in communication via the collector 25. An EGR valve member 29, which is connected to the outlet side of the recirculating exhaust gas pipe 28, is connected in communication with the collector 25.

[0043] Within the collector 25, the fresh air flow direction and the EGR gas flow direction intersect at an orthogonal or obtuse angle, and the direction in which the mixed gas of EGR gas and fresh air is drawn into the intake manifold 3 is a direction that intersects with both the fresh air flow direction and the EGR gas flow direction. Furthermore, a fresh air inlet 81 to which fresh air is supplied and an EGR gas inlet 82 to which EGR gas is supplied are opened on both the front and rear sides of the collector 25, and an intake outlet 83 that connects to the intake manifold 3 is opened on the left side of the collector 25. The EGR gas inlet 82 and the intake outlet 83 are located at the same height, while the fresh air inlet 81 and the EGR gas inlet 82 are located at different heights.

[0044] Within the collector 25, fresh air introduced from the intake throttle member 26 to the fresh air inlet 81 flows in an L-shape, bending from the front-to-back direction to the up-to-down direction, while EGR gas introduced from the EGR valve member 29 to the EGR gas inlet 82 flows diagonally upward. As a result, the EGR gas flows in in the same direction as the fresh air, making it easier for the EGR gas to mix with the fresh air. Furthermore, the mixed gas of fresh air and EGR gas flows in an L-shape, bending from the up-to-down direction to the left-to-right direction, and flows into the intake manifold 3 from the intake outlet 83. Since the direction of discharge of the mixed gas intersects not only the direction of introduction of fresh air and EGR gas, but also the direction of flow of fresh air and EGR gas within the collector 25, the mixing distribution of EGR gas into the fresh air can be made uniform.

[0045] As described above, within the collector 25, the direction of EGR gas flow relative to the direction of fresh air flow is 90° or more, and the fresh air flow and EGR gas flow intersect, making the mixture distribution of EGR gas relative to the fresh air uniform and suppressing the uneven flow of EGR gas within the intake manifold 3. As a result, the EGR gas concentration of the intake air supplied to each of the multiple intake passages 36 in the cylinder head 2 is made uniform, and variations in the combustion operation of each cylinder in the diesel engine 1 can be suppressed. As a result, the generation of black smoke is suppressed, and the amount of NOx can be reduced while maintaining a good combustion state in the diesel engine 1. In other words, exhaust gas purification (cleaning) by the recirculation of EGR gas can be achieved without causing misfires in specific cylinders.

[0046] The collector 25 is constructed by connecting an upper case (first case) 84 having a fresh air inlet 81 and a lower case (second case) 85 having an EGR gas inlet 82 and an intake outlet 83. By making the collector 25 separable into upper and lower cases 84 and 85, a mixing channel in which the EGR gas flow and fresh air flow intersect at an angle of 90° or more can be easily constructed within the collector 25. Therefore, the collector 25 can be constructed from a highly rigid casting, and by using an aluminum-based casting, its weight can be reduced.

[0047] The upper case 84 is provided with a downstream EGR gas passage (first EGR gas passage) 86a, which is part of the EGR gas passage 86 through which the EGR gas flows, and a mixing chamber 87 for mixing fresh air and EGR gas. The lower case 85 is provided with an upstream EGR gas passage (second EGR gas passage) 86b, which connects the downstream EGR gas passage 86a and the EGR gas inlet 82, and a mixed gas passage 88 that supplies the mixed gas, which is a mixture of fresh air and EGR gas, from the mixing chamber 87 to the intake manifold 3.

[0048] Since the lower case 85 is provided with an EGR gas inlet 82, while the upper case 84 is provided with a fresh air inlet 81 and a mixing chamber 87, the fresh air flowing in from the fresh air inlet 81 and the EGR gas flowing in from the lower case 85 flow in a way that crosses each other in the mixing chamber 87, allowing the fresh air and EGR gas to mix efficiently. Furthermore, since the lower case 85 is provided with an intake outlet 83, the fresh air flowing into the upper case 84 tends to flow towards the lower case 85, thus homogenizing the mixing of the EGR gas flowing towards the upper case 84 with the fresh air. In addition, the EGR gas flow path 86, the mixing chamber 87, and the mixed gas flow path 88 can each be compactly configured within the collector 25, allowing for a smaller collector 25.

[0049] In a plan view, the downstream EGR gas passage 86a is offset and connected to the side opposite to the side (right side) where the intake outlet 83 is located (left side) with respect to the central axis of the mixing chamber 87, and the downstream EGR gas passage 86a and the upstream EGR gas passage 86b are in communication, so that the EGR gas passage 86 is configured in a spiral shape. That is, the EGR gas passage 86 formed by the downstream EGR gas passage 86a and the upstream EGR gas passage 86b is curved in a plan view so as to bulge out on the opposite side (right side) from the intake outlet 83. Furthermore, the bottom of the upstream EGR gas passage 86b is composed of an inclined surface (a rearward upward inclined surface) that extends from the EGR gas inlet 82 toward the upper case 84.

[0050] In the mixing chamber 87, the point of communication with the EGR gas flow path 86 is on the opposite side from the intake outlet 83. Therefore, the EGR gas flowing into the mixing chamber 87 is guided by the flow of fresh air to the intake outlet 83, allowing the EGR gas to be uniformly mixed with the fresh air. Furthermore, the EGR gas flowing from the EGR gas flow path 86 into the mixing chamber 87 flows in the opposite direction to the flow from the mixing chamber 87 to the mixed gas flow path 88. As a result, the fresh air and EGR gas flow in the mixing chamber 87 in a manner that causes them to collide with each other, allowing the EGR gas to mix smoothly with the fresh air.

[0051] Furthermore, because the EGR gas flows along the spiral EGR gas flow path 86, the EGR gas enters the mixing chamber 87 as a swirling flow forming a clockwise vortex. As this turbulent EGR gas flows in the opposite direction to the flow of fresh air, the EGR gas is smoothly mixed with the fresh air flowing inside the mixing chamber 87 at the same time as it enters the chamber. Therefore, the fresh air and EGR gas can be efficiently mixed in the collector 25 while being agitated before being sent to the intake manifold 3 (the EGR gas can be smoothly dispersed in the mixed gas), and variations (unevenness) in the gas mixing state within the collector 25 can be more reliably suppressed. As a result, a less uneven mixed gas can be distributed to each cylinder of the diesel engine 1, and variations in the amount of EGR gas between cylinders can be suppressed, thereby suppressing the generation of black smoke and reducing the amount of NOx while maintaining a good combustion state of the diesel engine 1. Furthermore, by making the EGR gas flow path 86 spiral-shaped, sufficient swirling motion is given to the EGR gas flowing into the mixing chamber 87, allowing the collector 25 to be made shorter in the front-to-back direction.

[0052] The lower flange 84a of the upper case 84 and the upper flange 85a of the lower case 85 are bolted together to form a collector 25 having openings in three directions (front-rear direction and left direction) (fresh air inlet 81, EGR gas inlet 82, and intake outlet 83). The fresh air outlet of the intake throttle member 26 is bolted to the rear flange 84b of the upper case 84, which has an opening for the fresh air inlet 81. The intake throttle member 26 adjusts the amount of fresh air supplied to the collector 25 by adjusting the opening degree of the intake valve (butterfly valve) 26a located inside it.

[0053] The lower case 85 has a front flange 85b with an opening for the EGR gas inlet 82, to which the EGR gas outlet of the EGR valve member 29 is bolted via a rectangular tubular intermediate flange 89. The EGR valve member 29 adjusts the amount of EGR gas supplied to the collector 25 by adjusting the opening of the EGR valve (not shown) located inside it. The reed valve 90, which is inserted into the EGR gas inlet 82, is fixed inside the front flange 85b of the lower case 85. The intermediate flange (spacer) 89, which is bolted to the front flange 85b, covers the front of the reed valve 90, so that the collector 25 has the reed valve 90 built into the EGR gas flow path 86 on the EGR gas inlet 82 side.

[0054] The intermediate flange 89 has an EGR gas outlet 89a opening on its rear surface, which connects to the collector 25, and communicates with the EGR gas inlet 82. The front surface of the intermediate flange 89 has valve connecting seats 89b and 89c protruding from it, which connect to the EGR valve member 29, and the openings of the valve connecting seats 89b and 89c communicate with the EGR gas outlet of the EGR valve member 29. In the intermediate flange 89, EGR gas is combined at the EGR gas inlets of the upper and lower valve connecting seats 89b and 89c and flows from the EGR gas inlet 82 through the reed valve 90 into the EGR gas flow path 86 in the collector 25.

[0055] The EGR valve member 29 has an EGR valve (not shown) installed in an EGR gas passage 29f provided in the valve body 29e, and an actuator 29d for adjusting the opening degree of the EGR valve is provided above the valve body 29e and connected to the front of the collector 25 via a relay flange 89 with the vertical direction as the longitudinal direction. On the rear surface of the lower valve body 29e, the EGR valve member 29 has outlet side flanges 29a and 29b provided above and below, which connect to the valve connecting seats 89b and 89c of the relay flange 89, respectively. On the other hand, the front surface of the EGR valve member 29 is provided with an inlet side flange 29c that has an EGR gas inlet that communicates with the EGR gas outlet of the recirculating exhaust gas pipe 28.

[0056] When EGR gas cooled by the EGR cooler 27 flows into the EGR gas inlet of the inlet flange 29c via the downstream EGR gas relay passage 32 and the recirculated exhaust gas pipe 28 of the EGR cooler connecting base 34, the EGR gas is distributed vertically through the EGR gas passage 29f of the valve body 29e. The EGR gas that has flowed vertically through the EGR gas passage 29f is then flow-through adjustment by the EGR valve and flows into the relay flange 89 from the EGR gas outlets at the upper and lower outlet flanges 29a and 29b.

[0057] The recirculating exhaust gas pipe 28 has a gas pipe section 28a that is bent in an L-shape in plan view, and a flat plate-shaped rib 28b that protrudes from the inner circumference of the outer wall of the gas pipe section 28a. The recirculating exhaust gas pipe 28 has an outlet flange 28c that connects to the inlet flange 29c of the EGR valve member 29 at one end (rear end) of the gas pipe section 28a, while an inlet flange 28d that connects to the right side of the EGR cooler connecting base 34 is provided at the other end (left end) of the gas pipe section 28a. Furthermore, the recirculating exhaust gas pipe 28 has a sensor mounting seat 28e for attaching an EGR gas temperature sensor on the upper surface of the bent portion of the gas pipe section 28a.

[0058] The EGR device 24 allows for a shorter collector length, thus reducing the distance between the EGR valve member 29 and the intake throttle member 26, and consequently, shortening the overall length of the EGR device 24. Furthermore, since the EGR valve member 29 has an actuator 29d positioned above it, the uppermost parts of the EGR valve member 29, collector 25, and intake throttle member 26 can be at the same height. This not only reduces the vertical height of the EGR device 24 but also allows for a narrower horizontal width. Consequently, the compact design of the EGR device 24 allows for easy connection to the right side of the cylinder head 2, which is integrally formed with the intake manifold 3, simply by adjusting the recirculating exhaust gas pipe 28, contributing to the miniaturization of the diesel engine 1.

[0059] The recirculating exhaust gas pipe 28 is configured with flat ribs 28b connected to both ends of the gas pipe section 28a, thereby providing the recirculating exhaust gas pipe 28 with high rigidity and increasing the support strength of the front end of the EGR device 24 relative to the cylinder head 2. Furthermore, since the recirculating exhaust gas pipe 28 is configured with flat ribs 28b along the EGR gas flow path 28f within the gas pipe section 28a, the heat dissipation area in the gas pipe section 28a is increased by the ribs 28b, thereby enhancing the cooling effect of the EGR gas flowing through the EGR gas flow path 28f. As a result, it contributes to the cooling of the mixed gas purified by the EGR device 24, making it easier to maintain the NOx reduction effect of the mixed gas at an appropriate level.

[0060] Next, the configuration of the EGR cooler 27 will be described below with reference to Figures 9 to 11, 13 to 16, and 20 to 21. As shown in Figures 9 to 11, 13 to 16, and 20 to 21, the EGR cooler 27 comprises a heat exchange section 91 in which cooling water passages and EGR gas passages are alternately stacked, and a pair of left and right flange sections 92 and 93 provided at both ends of one side of the heat exchange section 91. Cooling water outlets 94 and 95 are provided on the left and right flange sections 92 and 93, while EGR gas inlets 96 and EGR gas outlets 97 are provided on the left and right flange sections 92 and 93. The left and right flange sections 92 and 93 are connected to the front side of the cylinder head 2, and the EGR cooler 27 is fixed to the cylinder head 2.

[0061] By providing openings for cooling water and EGR gas in each of the left and right flange sections 92 and 93, not only can the flange sections 92 and 93 be constructed from common materials, but the material costs for the flange sections 92 and 93 can also be reduced. Furthermore, since the flange sections 92 and 93 are constructed by drilling through holes 94 to 97 for cooling water and EGR gas, respectively, into a flat plate that connects to the cylinder head 2, the manufacturing of the EGR cooler 27 is simplified. In addition, since the connection between the flange sections 92 and 93 and the heat exchange section 91 can be minimized, the amount of heat transferred from the cylinder head 2 to the heat exchange section 91 can be reduced, thereby improving the cooling effect of the EGR gas in the heat exchange section 91.

[0062] The EGR cooler 27 has flange portions 92 and 93 that protrude from the rear surface of the heat exchange portion 91, thereby creating a space between the heat exchange portion 91 and the cylinder head 2. Consequently, a wide area of ​​the front and rear surfaces of the heat exchange portion 91 is exposed to the outside air, and heat is also dissipated from the heat exchange portion 91, thus increasing the cooling effect of the EGR gas in the EGR cooler 27. Therefore, compared to the case where the front surface of the rear surface of the heat exchange portion 91 is attached, the number of layers in the heat exchange portion 91 can be reduced, and the front-to-rear length of the EGR cooler 27 can be shortened, which also contributes to the miniaturization of the diesel engine 1.

[0063] The left flange portion 92 is provided with a cooling water outlet 94 and an EGR gas inlet 96, while the right flange portion 93 is provided with a cooling water inlet 95 and an EGR gas outlet 97. Furthermore, the cooling water outlet 94 and the EGR gas inlet 96 are positioned vertically on the left flange portion 92, while the EGR gas outlet 97 and the cooling water inlet 95 are positioned vertically on the right flange portion 93. In addition, the cooling water outlet 94 and the EGR gas outlet 97 are positioned at the same height, while the cooling water inlet 95 and the EGR gas inlet 96 are positioned at the same height.

[0064] At this time, the left and right flange portions 92 and 93 of the EGR cooler 27 are connected to the EGR cooler connecting bases 33 and 34, which are formed to protrude from the front side surface of the cylinder head 2, respectively. The upstream EGR gas relay passage 31 and the downstream cooling water relay passage 38 of the left EGR cooler connecting base 33 are in communication with the EGR gas inlet 96 and the cooling water outlet 94 of the left flange portion 92, respectively, and the downstream EGR gas relay passage 32 and the upstream cooling water relay passage 39 of the right EGR cooler connecting base 34 are in communication with the EGR gas outlet 97 and the cooling water inlet 95 of the right flange portion 93, respectively.

[0065] The EGR gas relay passages 31 and 32 and cooling water passages 38 and 39 are configured on the connecting bases 33 and 34 to which the flange portions 92 and 93 of the EGR cooler 27 are connected, and the EGR gas inlet 96 and outlet 97 and the cooling water outlet 94 and inlet 95 are connected to the flange portions 92 and 93. Therefore, there is no need to provide cooling water piping and EGR gas piping between the EGR cooler 27 and the cylinder head 2. Consequently, the sealing performance at the connection point between the EGR cooler 27 and the cylinder head 2 can be ensured without being affected by the expansion and contraction of the piping due to EGR gas and cooling water, and the EGR cooler 27 has improved resistance to external fluctuations such as heat and vibration, and can be compactly installed on the cylinder head 2.

[0066] By providing a cooling water outlet 94 and an EGR gas inlet 96 at the top and bottom of the flange portion 92, while providing an EGR gas outlet 97 and a cooling water inlet 95 at the top and bottom of the flange portion 93, the flange portions 92 and 93, which have the same shape, can be attached to the heat exchange portion 91 by inverting each other vertically. As a result, the number of types of parts constituting the EGR cooler 27 can be reduced, improving the ease of assembly of the EGR cooler 27 and reducing parts costs.

[0067] Furthermore, flange portion 92 is provided with a cooling water outlet 94 and an EGR gas inlet 96 through which high-heat cooling water or EGR gas passes, while flange portion 93 is provided with a cooling water inlet 95 and an EGR gas outlet 97 through which low-heat cooling water or EGR gas passes. As a result, not only is distortion due to thermal deformation suppressed in flange portions 92 and 93, but because flange portions 92 and 93 are constructed as separate parts, the influence of thermal deformation on each other is minimized, thus preventing damage or failure of the EGR cooler 27.

[0068] In a rear view, the EGR cooler 27 has a coolant outlet 94 and a coolant inlet 95 positioned diagonally opposite each other, as well as an EGR gas inlet 96 and an EGR gas outlet 97 positioned diagonally opposite each other. Since the EGR gas and coolant, which have different heat values, are supplied or discharged from diagonal positions, the thermal deformation at the connection between the EGR cooler 27 and the cylinder head 2 is mutually mitigated, thereby suppressing bending and loosening of the connection. Consequently, not only is leakage of EGR gas and coolant between the EGR cooler 27 and the cylinder head 2 prevented, but a decrease in connection strength is also prevented.

[0069] A plate-shaped gasket 98 is sandwiched between the cylinder head 2 and the flange portions 92 and 93, so as to span the left and right flange portions 92 and 93. Ring-shaped sealing members, O-rings 99, are embedded in the coolant inlet and coolant outlet of the cylinder head 2, which communicate with the coolant outlet 94 and coolant inlet 95 of the flange portions 92 and 93, respectively, and the O-rings 99 are covered by the flange portions 92 and 93.

[0070] Since the separate flange portions 92 and 93 are connected to the connecting bases 33 and 34 of the cylinder head 2 via gaskets 98, thermal deformation at the connection points with the cylinder head 2 causes tension to act on the gaskets 98. As a result, the sealing performance (sealing ability) by the gaskets 98 is improved at the connection points of the EGR gas inlet 96 and the EGR gas outlet 97, preventing leakage of EGR gas flowing between the cylinder head 2 and the EGR cooler 27. Furthermore, since the O-rings 99 are embedded in the space formed by the cooling water inlet and outlet of the connecting bases 33 and 34 of the cylinder head 2 and the rear end faces of the flange portions 92 and 93, when cooling water flows, the connecting portions of the connecting bases 33 and 34 and the flange portions 92 and 93 come into contact with the O-rings 99, ensuring the sealing performance (sealing ability) of the connection points at the cooling water inlet and outlet 94 and 95. Therefore, even if the EGR cooler 27, which handles the inflow and outflow of liquid and gas, is connected to the cylinder head 2, sealing performance for both the liquid and gas can be ensured, preventing leakage of both EGR gas and coolant.

[0071] Through holes 100 for bolt fastening are drilled on the outer periphery of the flange portions 92 and 93, at their outer positions. Specifically, the left flange portion 92 has five through holes 100 on the top, bottom, and left side, and the right flange portion 93 has five through holes 100 on the top, bottom, and right side. Therefore, the left flange portion 92 has through holes 100 above the coolant outlet 94, below the EGR gas inlet 96, and to the left of the space between the coolant outlet 94 and the EGR gas inlet 96, ensuring a seal at the coolant outlet 94 and the EGR gas inlet 96 when bolted to the connecting base 33 of the cylinder head 2. Similarly, the right flange portion 93 has through holes 100 below the coolant inlet 95, above the EGR gas outlet 97, and to the right of the space between the coolant inlet 95 and the EGR gas outlet 97, ensuring a seal at the coolant inlet 95 and the EGR gas outlet 97 when bolted to the connecting base 34 of the cylinder head 2.

[0072] The gasket 98 is constructed by bonding together two plates 98a and 98b, each having through holes 101 to 103. EGR gas passes through the through hole (for EGR gas) 101, coolant passes through the through hole (for coolant) 102, and fastening bolts are inserted into the through hole (for bolts) 103. The gasket 98 has a shape in which the inner periphery of the EGR gas through hole 101 is branched so as to curve in the front-rear direction, and is configured so that the opening area of ​​the coolant through hole 102 is larger than the opening area of ​​the coolant inlet and outlet 94 and 95.

[0073] The gasket 98 has the inner edge of the EGR gas through-hole 101 of the front plate 98a curved forward, while the inner edge of the EGR gas through-hole 101 of the rear plate 98b curved backward. By welding the front plate 98a and the rear plate 98b together, the inner edge of the EGR gas through-hole 101 has a Y-shaped cross-section. By making the inner edge of the EGR gas through-hole 101 curved forward and backward, the front and rear surfaces of the inner edge of the EGR gas through-hole 101 are brought into close contact with the end faces of the connecting bases 33, 34 and flange portions 92, 93, respectively, thereby ensuring sufficient airtightness.

[0074] The gasket 98 is configured such that the opening of the cooling water through-hole 102 is wider than the cooling water inlets and outlets 94 and 95, so that the O-ring 99 is inserted into the cooling water through-hole 102. In other words, the communication portion between the cooling water inlets and outlets 94 and 95 of the flange portions 92 and 93 and the cooling water relay passages 38 and 39 in the connecting bases 33 and 34 is sealed by the O-ring 99 fitted into the cooling water through-hole 102 of the gasket 98.

[0075] Furthermore, the connecting bases 33 and 34 of the cylinder head 2 have stepped openings for the coolant inlets and outlets 94 and 95, respectively, making the openings larger than the diameter of the coolant relay passages 38 and 39 within the connecting bases 33 and 34. An O-ring 99 is fitted to the outer circumference of the coolant relay passages 38 and 39 relative to the coolant inlets and outlets 94 and 95 of the connecting bases 33 and 34. That is, the O-ring 99 is inserted into the gasket 98 and fitted to the stepped portion of the coolant inlets and outlets 94 and 95 in the connecting bases 33 and 34, and is held in place by the connecting bases 33 and 34 and the flange portions 92 and 93. Consequently, as the coolant passes inside the O-ring 99, which is made of an elastic material, the O-ring 99 deforms to expand outward, and by closely contacting the connecting bases 33 and 34 and the flange portions 92 and 93, the sealing performance of the coolant is ensured.

[0076] The ring-shaped O-ring 99 has a shape in which its inner circumference bulges forward and backward. When the cooling water passing through the inner circumference of the O-ring 99 presses against it, the front and rear edges of the inner circumference deform so that they protrude forward and backward. As a result, the inner circumference of the O-ring 99 comes into close contact with the connecting bases 33, 34 and the flange portions 92, 93, thereby improving the sealing performance of the cooling water at the connection between the cylinder head 2 and the EGR cooler 27.

[0077] Furthermore, the ring-shaped O-ring 99 has a shape in which the inner circumference is bulging forward and backward, and has a recess on its inner surface. That is, by configuring the inner surface of the O-ring 99 with a Y-shaped cross section that is curved forward and backward, the cooling water passing through the inner circumference of the O-ring 99 presses against it, causing the front and rear edges of the inner circumference to protrude further forward and backward, thereby improving the contact between the inner circumference of the O-ring 99 and the connecting bases 33, 34 and flange portions 92, 93. Consequently, the sealing performance of the cooling water at the connection between the cylinder head 2 and the EGR cooler 27 can be improved.

[0078] Next, the configuration of the two-stage supercharger 30 will be described below with reference to Figures 22 to 27, etc. As shown in Figures 22 to 27, the two-stage supercharger 30 compresses the fresh air flowing into the intake manifold 3 of the cylinder head 2 using the fluid energy of the exhaust gas discharged from the exhaust manifold 4. The two-stage supercharger 30 consists of a high-pressure supercharger 51 connected to the exhaust manifold 4 and a low-pressure supercharger 52 connected to the high-pressure supercharger 51.

[0079] The high-pressure turbocharger 51 is positioned to the left of the exhaust manifold 4, while the low-pressure turbocharger 52 is positioned above the exhaust manifold 4. In other words, the small-capacity high-pressure turbocharger 51 is positioned opposite the exhaust manifold 4, while the large-capacity low-pressure turbocharger 52 is positioned above the exhaust manifold 4, which is installed protruding to the left of the cylinder head 2. Therefore, not only can the exhaust manifold 4 and the two-stage turbocharger 30 be compactly arranged in the space to the left of the cylinder head 2, but the uppermost position of the two-stage turbocharger 30 can be lower than the uppermost position of the diesel engine 1. As a result, this not only contributes to the miniaturization of the diesel engine 1, but also allows the low-pressure turbocharger 52 to be positioned closer to the cylinder head 2, enabling the two-stage turbocharger 30 to be fixed with high rigidity.

[0080] The high-pressure turbocharger 51 comprises a high-pressure turbine 53 that communicates with the exhaust outlet 44 of the exhaust manifold 4, and a high-pressure compressor 54 that supplies compressed air to the intake manifold 3. The high-pressure compressor 54 communicates with the fresh air inlet 81 (see Figure 17, etc.) of the intake throttle member 26 via an intercooler (not shown), thereby supplying compressed air to the intake manifold 3 via the EGR device 24. On the other hand, the low-pressure turbocharger 52 comprises a low-pressure turbine 55 whose exhaust inlet communicates with the exhaust outlet of the high-pressure turbine 53 via an exhaust-side relay pipe, and a low-pressure compressor 56 whose fresh air outlet communicates with the fresh air inlet of the high-pressure compressor 54 via a fresh air-side relay pipe. The low-pressure compressor 56 is positioned above the high-pressure turbine 53, and the high-pressure compressor 54 is positioned on one side of the front and rear of the high-pressure turbine 53, while the low-pressure turbine 55 is positioned on the other side of the front and rear of the low-pressure compressor 56.

[0081] The exhaust manifold 4 has an exhaust outlet 44 that opens to one side (left or right) for discharging exhaust gas. The high-pressure turbine 53 has an exhaust inlet 57 that opens toward the exhaust manifold 4, while its exhaust outlet 58 opens toward the front. The low-pressure turbine 55 has an exhaust inlet 60 that opens toward the bottom, while its exhaust outlet 61 opens toward the front.

[0082] The exhaust outlets 44 of the opposing exhaust manifolds 4 and the exhaust inlet 57 of the high-pressure turbine 53 are bolted together with flanges, and the high-pressure turbocharger 51 is fixed to the left side of the exhaust manifold 4. The exhaust outlet 58 of the high-pressure turbine 53 is bolted together with flanges to one end (rear end) of the L-shaped high-pressure exhaust gas pipe 59 (exhaust-side relay pipe), while the exhaust inlet 60 of the low-pressure turbine 55 is bolted together with flanges to the other end (upper end) of the high-pressure exhaust gas pipe 59, and the low-pressure turbocharger 52 is fixed above the high-pressure turbocharger 51.

[0083] By connecting the high-pressure turbine 53 to the exhaust manifold 4 via a flange connection, the high-pressure turbocharger 51 is supported with high rigidity. Furthermore, by connecting the low-pressure turbine 55 via a flange connection to the upper surface of the high-pressure exhaust gas pipe 59, which is connected to the front of the high-pressure turbocharger 51 via a flange connection, the low-pressure turbocharger 52 can be supported from below by the high-pressure turbocharger 51. In addition, since the low-pressure turbocharger 52 is installed closer to the top of the exhaust manifold 4, the center of gravity of the low-pressure turbocharger 52 is located above the connection point between the exhaust manifold 4 and the high-pressure turbocharger 51. Consequently, the two-stage turbocharger 30 can be supported with high rigidity and in a compact manner around the diesel engine 1.

[0084] The high-pressure compressor 54 has a fresh air intake port 63 (fresh air inlet) opening towards the rear, while a fresh air supply port 64 (fresh air outlet) opening downwards. On the other hand, the low-pressure compressor 56 has a fresh air intake port 66 (fresh air inlet) opening towards the rear, while a fresh air supply port 67 (fresh air outlet) is configured to protrude from the left side and then face towards the rear. One end of a U-shaped low-pressure fresh air passage pipe 65 (fresh air side relay pipe) is fixed to the fresh air intake port 63 (fresh air inlet) of the high-pressure compressor 54, while the other end of the low-pressure fresh air passage pipe 65 is connected to the fresh air supply port 67 (fresh air outlet) of the low-pressure compressor 56.

[0085] The high-pressure compressor 54 and the low-pressure compressor 56 are connected by a U-shaped low-pressure fresh air passage pipe 65 at the rear, and the front part of the low-pressure supercharger 52 can be fixed to the high-pressure supercharger 51, which is supported with high rigidity by the exhaust manifold 4. The low-pressure compressor 56 has its fresh air intake port 66 and fresh air supply port 67 extending in the same direction (rear), and is configured to be easily connected to the air supply pipe 62 and the low-pressure fresh air passage pipe 65, which communicate with an air cleaner (not shown), thereby improving assembly workability.

[0086] The low-pressure fresh air passage pipe 65 consists of a metal pipe 65a, one end of which is bolted to the fresh air intake port 66 of the high-pressure compressor 54 via a flange connection, and a resin pipe 65b that connects the other end of the metal pipe 65a to the fresh air supply port 67 of the low-pressure compressor 56. As a result, the metal pipe 65a of the low-pressure fresh air passage pipe 65 is fixed to the high-pressure compressor 54 with high rigidity, while the resin pipe 65b allows for communication between the low-pressure compressor 56 and the metal pipe 65a while mitigating assembly errors.

[0087] Because the fresh air supply port 67 of the low-pressure compressor 56 is configured to protrude to the left from the left side of the low-pressure compressor 56 and then bend upward and rearward, the curvature of the bent portion of the low-pressure fresh air passage pipe 65 (metal pipe 65a) is increased. As a result, the generation of turbulence within the low-pressure fresh air passage pipe 65 is suppressed, and the compressed air discharged from the low-pressure compressor 56 is smoothly supplied to the high-pressure compressor 54.

[0088] A blow-by gas recirculation device 19, which takes in blow-by gas, is installed on the cylinder head 2. The blow-by gas recirculation device 19 is mounted and fixed on the upper surface of the head cover 18 that covers the upper surface of the cylinder head 2. A blow-by gas outlet 70 located behind the blow-by gas recirculation device 19 is connected to the fresh air intake port 66 (fresh air inlet) of the low-pressure compressor 56 via an air intake pipe 62 and a recirculation hose 68. The air intake pipe 62 is also positioned between the low-pressure fresh air passage pipe 65 (fresh air side relay pipe) and the cylinder head 2.

[0089] Since the intake pipe 62 is connected to the rear of the low-pressure supercharger 52, which is an upper component of the two-stage supercharger 30, and is positioned closer to the cylinder head 2, the distance between the blow-by gas recirculation device 19, which is located above the cylinder head 2, and the intake pipe 62 can be reduced. As a result, the recirculation hose 68 can be shortened, preventing freezing inside the recirculation hose 68 in low-temperature environments. The intake pipe 62 is positioned in the space enclosed by the low-pressure fresh air passage pipe 65 and the cylinder head 2, which prevents damage due to external forces at the connection point with the resin pipe connected to the air cleaner (not shown).

[0090] The high-pressure supercharger 51 has a fresh air supply port 64 protruding downwards from the cylinder head 2 side on the underside of the high-pressure compressor 54. The high-pressure compressor 54 is connected to a high-pressure fresh air passage pipe 71 which communicates with an intercooler (not shown), and supplies compressed air to the intercooler via the high-pressure fresh air passage pipe 71. Below the high-pressure compressor 54, there is a coolant inlet pipe 22 which opens to the left side. By routing the high-pressure fresh air passage pipe 71 together with the coolant piping which communicates with a radiator (not shown) to the rear left side of the cylinder block 6, it can be connected to the coolant inlet pipe 22 and the fresh air supply port 64 of the high-pressure compressor 54, respectively. Therefore, the routing of the coolant piping and the high-pressure fresh air passage pipe 71 can be consolidated, which not only simplifies the piping structure on the main unit side where the diesel engine 1 is installed, but also makes assembly and maintenance work easier.

[0091] Furthermore, the diesel engine 1 has a coolant outlet pipe 23, an intake pipe 62, and an intake throttle member 26 positioned above the cylinder head 2 and on the side of the cooling fan 9. Therefore, when a radiator (not shown), an air cleaner (not shown), and an intercooler (not shown) that utilize the cooling air from the cooling fan 9 are positioned behind the cooling fan 9 on the machine side in which the diesel engine 1 is installed, not only can the coolant piping connected to the radiator and the fresh air piping communicating with the air cleaner and intercooler be shortened, but the piping connection work can also be performed all at once. As a result, assembly and maintenance work on the machine side becomes easier, and the various components connected to the diesel engine 1 can be efficiently arranged on the machine side.

[0092] The exhaust outlet 58 of the high-pressure turbine 53 is provided with a turbine exhaust hole 58a for discharging exhaust gas that rotates the turbine wheel (not shown), a bypass hole 58b connecting the exhaust inlet 57 and the exhaust outlet 58, and a wastegate valve 69 for opening and closing the bypass hole 58b. By arranging the turbine exhaust hole 58a and the bypass hole 58b side by side at the exhaust outlet 58 of the high-pressure turbine 53, the ability to perform compression operation by the high-pressure supercharger 51 can be set according to the rotational speed of the diesel engine 1. Therefore, the two-stage supercharger 30 can efficiently use exhaust energy to stabilize the amount of fresh air supplied to the combustion chamber, increase engine output, and reduce black smoke emissions.

[0093] Furthermore, since the bypass route from the exhaust manifold 4 to the low-pressure turbine 55 is established by opening the bypass hole 58b of the high-pressure turbine 53, only the high-pressure exhaust gas pipe 59 connecting the high-pressure turbine 53 and the low-pressure turbine 55 needs to be piped, eliminating the need for bypass piping connecting the exhaust manifold 4 and the low-pressure turbine 55. Consequently, not only is the piping structure of the two-stage turbocharger 30 simplified, but the space around the two-stage turbocharger 30 can be expanded. For example, a hydraulic pump for a work machine (not shown) can be installed above and below the front of the two-stage turbocharger 30, alongside the engine starter 20.

[0094] The high-pressure supercharger 51 has a high-pressure hydraulic oil supply pipe 73 and a high-pressure hydraulic oil return pipe 74 connected to the top and bottom of the center housing 72, which is the connection point between the high-pressure turbine 53 and the high-pressure compressor 54. Similarly, the low-pressure supercharger 52 has a low-pressure hydraulic oil supply pipe 76 and a low-pressure hydraulic oil return pipe 77 connected to the top and bottom of the center housing 75, which is the connection point between the low-pressure turbine 55 and the low-pressure compressor 56.

[0095] The lower end of the high-pressure hydraulic fluid supply pipe 73 is connected to a connecting member 78 installed on the left side of the cylinder block 6, while the upper end is connected to the upper surface of the center housing 72 of the high-pressure supercharger 51. A connecting joint 79 is installed on the upper surface of the center housing 72 of the high-pressure supercharger 51, connecting the upper end of the high-pressure hydraulic fluid supply pipe 73 to the lower end of the low-pressure hydraulic fluid supply pipe 76. The upper end of the low-pressure hydraulic fluid supply pipe 76 is connected to the upper surface of the center housing 75 of the low-pressure supercharger 52. As a result, the hydraulic fluid flowing through the oil passages in the cylinder block 6 is supplied to the center housing 72 of the high-pressure supercharger 51 through the high-pressure hydraulic fluid supply pipe 73, and also to the center housing 75 of the low-pressure supercharger 52 through the high-pressure hydraulic fluid supply pipe 73 and the low-pressure hydraulic fluid supply pipe 76.

[0096] The high-pressure hydraulic fluid supply pipe 73 passes between the cylinder head 2 and cylinder block 6 and the high-pressure supercharger 51, and is routed around the exhaust outlet 44 of the exhaust manifold 4. The low-pressure hydraulic fluid supply pipe 76 is routed in an L-shape along the top surface of the high-pressure supercharger 51 and the center housing 75 of the low-pressure supercharger 52. By shortening the length of the hydraulic fluid supply pipes 73 and 76 and routing them around the highly rigid two-stage supercharger 30, hydraulic fluid can be efficiently supplied to the two-stage supercharger 30, while simultaneously preventing damage to the hydraulic fluid supply pipes 73 and 76 due to external forces.

[0097] The high-pressure hydraulic fluid return pipe 74 has one end (lower end) connected to the tip (left end) of a connecting joint 80 installed on the left side of the cylinder block 6, while the other end (upper end) is connected to the underside of the center housing 72 of the high-pressure supercharger 51. The low-pressure hydraulic fluid return pipe 77 has one end (lower end) connected to the branched upper end of the connecting joint 80, while the other end (upper end) is connected to the underside of the center housing 75 of the low-pressure supercharger 52. Therefore, the hydraulic fluids flowing through the high-pressure supercharger 51 and the low-pressure supercharger 52 are merged at the connecting joint 80 from the low-pressure hydraulic fluid return pipes 74 and 77 located below the center housings 72 and 75, and returned to the oil passages within the cylinder block 6.

[0098] The high-pressure hydraulic fluid return pipe 74 is routed around the rear of the exhaust outlet 44 of the exhaust manifold 4. The low-pressure hydraulic fluid return pipe 77 passes between the cylinder head 2 and cylinder block 6 and the high-pressure supercharger 51, and is routed around the front of the exhaust outlet 44 of the exhaust manifold 4. In this way, by shortening the length of the hydraulic fluid return pipes 74 and 77 and routing them around the two-stage supercharger 30, which is a highly rigid component, hydraulic fluid can be efficiently supplied to the two-stage supercharger 30, while simultaneously preventing damage to the hydraulic fluid return pipes 74 and 77 due to external forces.

[0099] Next, the configuration of the cooling water pump 21 and the cooling water inlet pipe 22 will be described below with reference to Figures 28 and 29, etc. As shown in Figures 28 and 29, etc., a cooling water pump mounting portion 319 to which the cooling water pump 21 (see Figure 2, etc.) is attached and an inlet pipe mounting seat 320 to which the cooling water inlet pipe 22 (see Figure 3, etc.) is attached are provided protruding from the rear side portion of the left side of the cylinder block 6. The cooling water pump mounting portion 319 and the inlet pipe mounting seat 320 are integrally molded with the cylinder block 6. In addition, the rear side portion of the inlet pipe mounting seat 320 is connected to the cooling water pump mounting portion 319. The cooling water pump mounting portion 319 and the inlet pipe mounting seat 320 protrude away from the crankshaft 5, which improves the rigidity, strength and cooling efficiency of the cylinder block 6.

[0100] A cooling water pump 21 for circulating cooling water is bolted to the rear side surface 312 and the cooling water pump mounting portion 319 of the cylinder block 6. The cooling water pump 21 is broadly composed of a base plate portion 331, a cover plate portion 332, and a pump pulley 333.

[0101] The base plate portion 331 and the cover plate portion 332 are fixed together at their peripheries by inserting and fastening cover bolts 347 from the cover plate portion 332 side into five through bolt holes provided on the periphery of the base plate portion 331 and through holes in the cover plate portion 332 corresponding to those through bolt holes.

[0102] Furthermore, the cooling water pump 21 is bolted to the cylinder block 6 by inserting mounting bolts 348 into nine through holes provided on the periphery of the base plate portion 331 and the cover plate portion 332, so that the plates 331 and 332 are fastened together. When the mounting bolts 348 are tightened, the periphery of the base plate portion 331 and the cover plate portion 332 are tightly fixed to each other, the periphery of the cooling water passage outlet 327 of the cylinder block 6 and the periphery of the pump inlet 334 of the cooling water pump 21 are tightly fixed to each other, and the periphery of the cooling water inlet 328 of the cylinder block 6 and the periphery of the pump discharge port 335 of the cooling water pump 21 are tightly fixed to each other. In the arrangement of bolts 347, 348 along the periphery of the cooling water pump 21, one or two mounting bolts 348 are positioned between adjacent cover bolts 347, 347.

[0103] The base plate portion 331 and the cover plate portion 332 are connected by cover bolts 347, which allows the coolant pump 21 to be distributed as a single component and simplifies the installation process when attaching the coolant pump 21 to the cylinder block 6 using mounting bolts 348.

[0104] The base plate portion 331 includes, for example, the portion of the cooling water pump mounting portion 319, and is connected to a pump inlet 334 that is connected to a cooling water passage outlet 327 which is opened on the left side of the rear surface of the cylinder block 6, and a pump discharge port 335 that is connected to a cooling water inlet 328 which is opened on the left side of the rear surface of the cylinder block 6.

[0105] The base plate portion 331 and the cover plate portion 332 are in close contact at their peripheral edges to form a pump cooling water passage 336 that connects the pump inlet 334 and the pump outlet 335. An annular sealing member is positioned at the contact point between the base plate portion 331 and the cover plate portion 332, surrounding the pump inlet 334, the pump outlet 335, and the pump cooling water passage 336. The cover plate portion 332 rotatably supports the pump shaft 337, to which an impeller is fixed at one end. A pump pulley 333 is fixed to the other end of the pump shaft 337.

[0106] A cooling water passage inlet 329 is opened on the left side of the cylinder block 6. The cooling water passage inlet 329 opens into an inlet pipe mounting seat 320 that protrudes from the left side. Inside the cylinder block 6, a roughly L-shaped internal cooling water passage 338 (cooling water passage) is formed, connecting the cooling water passage inlet 329 opened on the left side and the cooling water passage outlet 327 opened on the rear side.

[0107] The inlet pipe mounting seat 320 has a pair of bolt holes on either side of the coolant passage inlet 329, and the coolant inlet pipe 22 (coolant inlet member) having a coolant inlet 339 is detachably bolted to the inlet pipe mounting seat 320. A pipe leading to the coolant outlet of the radiator is connected to the coolant inlet pipe 22. Coolant from the radiator is taken into the engine 1 through the coolant inlet pipe 22 and introduced into the cylinder block 6 through the coolant inlet 328 via the internal coolant passage 338 and the coolant pump 21.

[0108] In the engine 1 of this embodiment, the coolant inlet pipe 22 having a coolant inlet 339 is detachably attached to the coolant passage inlet 329 connected to the pump suction port 334 of the coolant pump 21. Therefore, the position of the coolant inlet 339 can be changed simply by changing the shape of the coolant inlet pipe 22. This makes it possible to change the position of the coolant inlet 339 of the coolant pump 21 in a simple manner without causing significant design changes or increased manufacturing costs.

[0109] Furthermore, the coolant passage outlet 327, which supplies coolant from the radiator to the coolant pump 21, and the coolant inlet 328, which introduces coolant from the coolant pump 21 into the cylinder block 6, are located on the left and right sides of the cylinder block 6. In addition, the internal coolant passage 336 of the pump, which connects the coolant passage outlet 327 and the coolant inlet 328, is located from the left side to the right side of the cylinder block 6. With this configuration, the coolant passing through the internal coolant passage 336 is cooled by the cooling air from the cooling fan 9 (see Figure 2) as it moves from the coolant passage outlet 327 to the coolant inlet 328. Therefore, the coolant can be cooled in the coolant pump 21 before being introduced into the cylinder block 6 from the coolant inlet 328, thereby improving the cooling efficiency of the engine 1.

[0110] Furthermore, the configuration of each part in the present invention is not limited to the illustrated embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0111] <Notes on the invention> An engine system according to one embodiment includes an exhaust manifold and an intake manifold arranged in a cylinder head, and a supercharger that compresses fresh air into the intake manifold using the fluid energy of the exhaust gas discharged from the exhaust manifold, wherein the supercharger is a two-stage supercharger consisting of a high-pressure supercharger connected to the exhaust manifold and a low-pressure supercharger connected to the high-pressure supercharger, and the low-pressure compressor of the low-pressure supercharger has its fresh air inlet located closer to the cylinder head than the fresh air outlet.

[0112] In the engine device described above, the fresh air outlet may be provided so as to protrude from one side of the low-pressure compressor.

[0113] In the above-described engine system, the low-pressure compressor may have its fresh air inlet and fresh air outlet facing either the front or rear or to the side.

[0114] In the above-described engine system, the fresh air inlet of the high-pressure compressor of the high-pressure supercharger may be oriented to one side, either front or rear.

[0115] In the above-described engine system, the high-pressure supercharger may be positioned on one side of the exhaust manifold, and the low-pressure supercharger may be positioned above the exhaust manifold.

[0116] According to the above configuration, the fresh air inlet of the low-pressure supercharger is located in the space enclosed by the fresh air outlet of the low-pressure supercharger and the cylinder head. This not only contributes to miniaturization of the engine system but also prevents damage caused by external forces at the connection point with the resin pipe connected to the air cleaner (not shown).

[0117] Furthermore, an engine system according to one aspect of the present invention is an engine system comprising an exhaust manifold and an intake manifold arranged in a cylinder head, and a supercharger that compresses fresh air into the intake manifold using the fluid energy of the exhaust gas discharged from the exhaust manifold, wherein the supercharger is a two-stage supercharger consisting of a high-pressure supercharger connected to the exhaust manifold and a low-pressure supercharger connected to the high-pressure supercharger, and the center of the low-pressure supercharger is positioned closer to the cylinder head than the center of the high-pressure supercharger in a plan view.

[0118] Furthermore, an engine system according to one aspect of the present invention is an engine system equipped with a supercharger that compresses fresh air flowing into the intake manifold using the fluid energy of the exhaust gas discharged from the exhaust manifold. The supercharger is a two-stage supercharger consisting of a high-pressure supercharger connected to the exhaust manifold and a low-pressure supercharger connected to the high-pressure supercharger. The exhaust gas pipe connecting the exhaust outlet of the high-pressure supercharger and the exhaust inlet of the low-pressure supercharger is connected to the high-pressure supercharger in one direction in a plan view and to the low-pressure supercharger in the vertical direction.

[0119] An engine system according to one aspect of the present invention is an engine system equipped with a supercharger that compresses fresh air flowing into the intake manifold using the fluid energy of exhaust gas discharged from the exhaust manifold. The supercharger is a two-stage supercharger consisting of a high-pressure supercharger connected to the exhaust manifold and a low-pressure supercharger connected to the high-pressure supercharger. The exhaust outlet of the high-pressure supercharger and the exhaust inlet of the low-pressure supercharger are located at different positions in the crankshaft direction. [Explanation of Symbols]

[0120] 1 Engine 2 Cylinder heads 3. Intake Manifold 4 Exhaust Manifold 5 Crankshaft 6 Cylinder Block 7 Flywheel Housing 8 Flywheel 9 Cooling fan 51 High-pressure supercharger 52 Low-pressure supercharger 53 High-pressure turbine 54 High-pressure compressor 55 Low-pressure turbine 56 Low-pressure compressor 57 Exhaust Inlet 58 Exhaust outlet 58a Turbine exhaust port 58b Bypass hole 59 High-pressure exhaust gas pipe 60 Exhaust Inlet 61 Exhaust outlet 62 Air intake pipe 63 New air intake 64 Fresh air supply port 65 Low-pressure fresh air passage pipe 65a metal tube 65b Resin pipe 66 New air intake 67 Fresh air supply port 68 Reduction Hose 69 Wastegate Valve 70 Blow-by gas outlet 71 High-pressure fresh air passage pipe 72 Center Housing 73. High-pressure hydraulic fluid supply pipe 74. High-pressure hydraulic fluid return pipe 75 Center Housing 76 Low-pressure hydraulic fluid supply pipe 77. Low-pressure hydraulic fluid return pipe 78 Connecting member 79 Connecting joint 80 Connecting joint

Claims

1. An engine system comprising an exhaust manifold and a supercharger, The supercharger is a two-stage supercharger consisting of a high-pressure supercharger connected to the exhaust manifold and a low-pressure supercharger connected to the high-pressure supercharger. The low-pressure supercharger is located above the high-pressure supercharger. The midpoint between the low-pressure turbine and the low-pressure compressor in the crankshaft direction of the low-pressure supercharger and the midpoint between the high-pressure turbine and the high-pressure compressor in the crankshaft direction of the high-pressure supercharger are positioned at a distance of a first displacement in a plan view. The second displacement between the center of the exhaust outlet of the high-pressure supercharger and the center of the exhaust inlet of the low-pressure supercharger in the crankshaft direction is smaller than the first displacement. Engine unit.

2. The exhaust inlet of the low-pressure supercharger is located on the flywheel side in the crankshaft direction compared to the exhaust outlet of the high-pressure supercharger. The engine device according to claim 1.

3. The exhaust gas pipe connecting the exhaust outlet of the high-pressure supercharger and the exhaust inlet of the low-pressure supercharger is connected to the high-pressure supercharger along one direction in a plan view and connected to the low-pressure supercharger along the vertical direction. The engine device according to claim 1 or 2.

4. The center of the low-pressure supercharger is located, in a plan view, closer to the cylinder head than the center of the high-pressure supercharger. The engine device according to any one of claims 1 to 3.

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