Engine device

Abstract

To compactly arrange a two stage supercharger.SOLUTION: The engine device includes a supercharger. The supercharger is constituted by a two stage supercharger 30 including a high-pressure supercharger 51 and a low-pressure supercharger 52. A high pressure fresh air inlet 66 of the high pressure supercharger 51 and a low pressure fresh air supply port 64 of the low pressure supercharger 52 are connected via a low pressure fresh air passage pipe 65, and the low pressure fresh air passage pipe 65 has a curved part.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Conventionally, engine devices are equipped with a turbocharger that compresses fresh air using exhaust energy to increase the air density inside the cylinders of the engine in order to improve engine output and fuel economy (see Patent Document 1). In diesel engines, supplying a large amount of high-density air into the cylinders not only increases engine output and engine torque by burning a large amount of fuel, but also promotes mixing of fuel and air, thereby suppressing premixed combustion and reducing NOx emissions.

[0003] Furthermore, since a single-stage turbocharger using one turbocharger has limitations in meeting the requirements of a high-output engine, an engine equipped with a two-stage turbocharger in which two turbochargers are connected in series at the high-pressure stage and the low-pressure stage has been proposed (see Patent Document 2). [Prior art documents] [Patent documents]

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

[0005] Incidentally, the space available for installing an engine varies depending on the work vehicle (construction machinery, agricultural machinery, etc.) on which it is to be installed, but in recent years, due to demands for lighter and more compact vehicles, the installation space is often limited (narrow). For this reason, it is necessary to layout the engine components in a compact manner.

[0006] The present invention has as its technical object to provide an engine device that has been improved by examining the current situation as described above. [Means for solving the problem]

[0007] An engine system according to one aspect is an engine system including a turbocharger, the turbocharger being a two-stage turbocharger consisting of a high-pressure stage turbocharger and a low-pressure stage turbocharger, wherein a high-pressure stage fresh air inlet of the high-pressure stage turbocharger and a low-pressure stage fresh air supply port of the low-pressure stage turbocharger are connected via a low-pressure fresh air passage pipe, and the low-pressure fresh air passage pipe has a curved portion. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic front view of an embodiment of an engine system; [Figure 2] FIG. [Figure 3] FIG. 2 is a schematic left side view of the embodiment. [Figure 4] FIG. 2 is a schematic right side view of the embodiment. [Figure 5] FIG. 2 is a schematic plan view of the same embodiment. [Figure 6] FIG. 2 is an enlarged schematic left side view showing the periphery of a two-stage turbocharger. [Figure 7] FIG. 2 is an enlarged schematic front view showing the two-stage turbocharger and its surroundings. [Figure 8] FIG. 2 is an enlarged schematic rear view showing the two-stage turbocharger and its surroundings. [Figure 9] FIG. 2 is a schematic plan view showing an enlarged view of the periphery of a low-pressure stage turbocharger with a part of the cylinder head cover cut away. [Figure 10] FIG. 2 is a schematic perspective view for explaining the mounting structure of the low-pressure stage turbocharger. [Figure 11] 3 is an enlarged schematic front view showing the periphery of a support base that supports the exhaust gas purification device. FIG. [Figure 12] FIG. 2 is a schematic left side view showing an enlarged view of the support base and its surroundings. [Figure 13] FIG. 2 is a schematic right side view showing an enlarged view of the support base and its surroundings. [Figure 14] FIG. 2 is an enlarged schematic plan view showing the periphery of the support base. [Figure 15] FIG. 2 is a schematic exploded perspective view for explaining the mounting structure of the support base and the exhaust gas purification device. [Figure 16] 15 is a schematic left side view showing the support base and the exhaust gas purification device taken along the AA line in FIG. 14. [Figure 17] FIG. 2 is an enlarged schematic front view showing the periphery of the cylinder head. [Figure 18] FIG. 2 is an enlarged schematic plan view showing the periphery of the front part of the cylinder head. [Figure 19] FIG. 2 is a schematic left side view showing an enlarged view of the front portion and its periphery of the cylinder head. [Figure 20] FIG. 2 is a schematic perspective view showing a front portion of the cylinder head and an EGR cooler with a portion cut away. [Figure 21] FIG. 2 is a schematic cross-sectional plan view showing the configuration of an exhaust flow path and an intake flow path in the cylinder head. [Figure 22] FIG. 2 is a schematic front view showing the arrangement of wire harnesses around the front portion of the cylinder head. [Figure 23] FIG. 2 is a schematic plan view showing the arrangement of wire harnesses around the front portion of the cylinder head. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. First, the overall structure of an engine 1 as an example of an engine device will be described with reference to Figs. 1 to 5. In this embodiment, the engine 1 is a diesel engine. In the following description, both sides parallel to the crankshaft 5 (both sides sandwiching the crankshaft 5) will be referred to as the left and right, the side where the flywheel housing 7 is installed will be referred to as the front side, and the side where the cooling fan 9 is installed will be referred to as the rear side, and for convenience, these will be used as the basis for the positional relationship between the four sides and the top and bottom of the engine 1.

[0010] As shown in Figures 1 to 5, an intake manifold 3 is disposed on one side of an engine 1 parallel to a crankshaft 5, and an exhaust manifold 4 is disposed on the other side. In this embodiment, the intake manifold 3 is molded integrally with the right side of the cylinder head 2. The exhaust manifold 4 is disposed on the left side of the cylinder head 2. The cylinder head 2 is mounted on a cylinder block 6 that houses the crankshaft 5 and pistons (not shown).

[0011] The front and rear ends of the crankshaft 5 protrude from both the front and rear side surfaces of the cylinder block 6. A flywheel housing 7 is fixed to one side of the engine 1 that intersects with the crankshaft 5 (in this embodiment, the front side of the cylinder block 6). A flywheel 8 is disposed within the flywheel housing 7. The flywheel 8 is fixed to the front end of the crankshaft 5 and is configured to rotate integrally with the crankshaft 5. Power from the engine 1 is extracted via the flywheel 8 to a working unit of a work machine (for example, a hydraulic excavator or a forklift). A cooling fan 9 is provided on the other side of the 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 belt 10.

[0012] An oil pan 11 is disposed 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 sucked by a lubricating oil pump (not shown) located on the right side of the cylinder block 6, at the connecting portion between the cylinder block 6 and the flywheel housing 7, and is supplied to each lubricated part of the 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 lubricated part is then returned to the oil pan 11. The lubricating oil pump is configured to be driven by the rotation of the crankshaft 5.

[0013] As shown in Figure 4, a fuel supply pump 15 for supplying fuel is attached to the right side of the engine 1 at the connection portion between the cylinder block 6 and the flywheel housing 7. The fuel supply pump 15 is located below the EGR device 24. A common rail 16 is also located between the intake manifold 3 of the cylinder head 2 and the fuel supply pump 15. The common rail 16 is fixed to a position near the front of the upper right side of the cylinder block 6. Injectors (not shown) for each of the four cylinders, each having an electromagnetically controlled fuel injection valve, are provided on the top surface of the cylinder head 2, which is covered with a cylinder head cover 18.

[0014] 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 the 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 engine 1.

[0015] 2 and 5, a blow-by gas reduction device 19 that takes in blow-by gas that leaks from the combustion chamber of the engine 1 to the upper side of the cylinder head 2 is provided on the upper surface of a cylinder head cover 18 that covers the intake valves and exhaust valves (not shown) provided on the upper surface of the cylinder head 2. A blow-by gas outlet of the blow-by gas reduction device 19 is connected to the intake part of the two-stage turbocharger 30 via a return hose 68. The blow-by gas from which lubricating oil components have been removed in the blow-by gas reduction device 19 is returned to the intake manifold 3 via the two-stage turbocharger 30, etc.

[0016] As shown in Figure 3, an engine starter 20 is attached to the flywheel housing 7 on the left side of the engine 1. The engine starter 20 is disposed below the exhaust manifold 4. The engine starter 20 is attached to the left side of the rear side of the flywheel housing 7, below the joint between the cylinder block 6 and the flywheel housing 7.

[0017] As shown in Figure 2, a cooling water pump 21 for lubricating the cooling water is disposed at a position near the left of the rear side of the cylinder block 6. Furthermore, an alternator 12 serving as a generator that generates electricity using power from the engine 1 is provided to the left of the cooling water pump 21. Rotational power is transmitted from the front end of the crankshaft 5 via a belt 10 to the cooling fan 9, alternator 12, and cooling water pump 21. Cooling water in a radiator (not shown) mounted on the work vehicle is supplied to the cooling water pump 21 by being driven by the cooling water pump 21. Cooling water is then supplied into the cylinder head 2 and the cylinder block 6, cooling the engine 1.

[0018] As shown in Fig. 3, the cooling water pump 21 is disposed at a height lower than the exhaust manifold 4, and a cooling water inlet pipe 22 that communicates with the cooling water outlet of the radiator is fixed to the left side surface of the cylinder block 6 at approximately the same height as the cooling water pump 21. On the other hand, as shown in Figs. 2 and 5, the cooling water outlet pipe 23 that communicates with the cooling water inlet of the radiator is fixed to a position near the right rear of the top surface of the cylinder head 2. The cylinder head 2 has a cooling water drainage section 35 in its right rear corner, and the cooling water outlet pipe 23 is installed on the top surface of the cooling water drainage section 35.

[0019] 4 and 5, the EGR device 24 is disposed on the right side of the cylinder head 2. The EGR device 24 has a collector 25 as a relay pipe that mixes recirculated exhaust gas (EGR gas from the exhaust manifold 4) of the engine 1 with fresh air (external air from the air cleaner) and supplies the mixture to the intake manifold 3, an intake throttle member 26 that connects the collector 25 to the air cleaner, a recirculated exhaust gas pipe 28 that forms part of a reflux pipe that connects to the exhaust manifold 4 via an EGR cooler 27, and an EGR valve member 29 that connects the collector 25 to the recirculated exhaust gas pipe 28.

[0020] In this embodiment, the collector 25 of the EGR device 24 is connected to the right side surface of the intake manifold 3, which is molded integrally with the cylinder head 2 and forms the right side surface of the cylinder head 2. That is, the outlet opening of the collector 25 is connected to the inlet opening of the intake manifold 3, which is provided on the right side surface of the cylinder head 2. Also, the EGR gas inlet of the recirculation exhaust gas piping 28 is connected to the EGR gas outlet of the EGR gas passage provided in the cylinder head 2, at a position near the front of the right side surface of the cylinder head 2. By attaching the collector 25 to the intake manifold 3 and attaching the recirculation exhaust gas piping 28 to the cylinder head 2, the EGR device 24 is fixed to the cylinder head 2.

[0021] In the EGR device 24, the intake manifold 3 and an intake throttle member 26 for introducing fresh air are connected in communication via a collector 25. The collector 25 is connected in communication with an EGR valve member 29 that is connected to the outlet side of a recirculated exhaust gas pipe 28. The collector 25 is formed in a generally cylindrical shape that is longitudinal in the front-to-rear direction. The intake throttle member 26 is bolted to the intake air intake side (front side in the longitudinal direction) of the collector 25. The intake air discharge side of the collector 25 is bolted to the inlet side of the intake manifold 3. The EGR valve member 29 adjusts the opening of an EGR valve located therein, thereby adjusting the amount of EGR gas supplied to the collector 25.

[0022] Fresh air is supplied to the collector 25, and EGR gas (a portion of the exhaust gas discharged from the exhaust manifold 4) is supplied to the collector 25 from the exhaust manifold 4 via the EGR valve member 29. The fresh air and the EGR gas from the exhaust manifold 4 are mixed in the collector 25, and then the mixed gas in the collector 25 is supplied to the intake manifold 3. In other words, by returning a portion of the exhaust gas discharged from the engine 1 to the exhaust manifold 4 from the intake manifold 3 to the engine 1, the maximum combustion temperature during high load operation is lowered and the amount of NOx (nitrogen oxides) emitted from the engine 1 is reduced.

[0023] 1 and 3 to 5, the EGR cooler 27 is fixed to the front side of the cylinder head 2. Cooling water and EGR gas flowing inside the cylinder head 2 flow in and out of the EGR cooler 27, and the EGR gas is cooled inside the EGR cooler 27. A pair of left and right EGR cooler connectors 33, 34 that connect the EGR cooler 27 protrude from the front side of the cylinder head 2. The EGR cooler 27 is connected to the front sides of the EGR cooler connectors 33, 34. In other words, the EGR cooler 27 is disposed above the flywheel housing 7 and in front of the cylinder head 2, with the rear side of the EGR cooler 27 separated from the front side of the cylinder head 2.

[0024] As shown in Figures 1 to 3 and 5, a two-stage turbocharger 30 is disposed on the left side of the cylinder head 2. The two-stage turbocharger 30 includes a high-pressure stage turbocharger 51 and a low-pressure stage turbocharger 52. The high-pressure stage turbocharger 51 includes a high-pressure stage turbine case 53 incorporating a turbine wheel (not shown) and a high-pressure stage compressor case 54 incorporating a blower wheel (not shown). The low-pressure stage turbocharger 52 includes a low-pressure stage turbine case 55 incorporating a turbine wheel (not shown) and a low-pressure stage compressor case 56 incorporating a blower wheel (not shown).

[0025] In the exhaust path of the two-stage turbocharger 30, the high-pressure stage turbine case 53 is connected to the exhaust manifold 4, the high-pressure stage turbine case 53 is connected to the low-pressure stage turbine case 55 via a high-pressure exhaust gas pipe 59, and the low-pressure stage turbine case 55 is connected to an exhaust connecting pipe 119. The high-pressure exhaust gas pipe 59 is formed of a flexible pipe. In this embodiment, a portion of the high-pressure exhaust gas pipe 59 is formed in a bellows shape.

[0026] A tailpipe (not shown) is connected to the exhaust manifold 119 via an exhaust gas purification device 100. Exhaust gas discharged from each cylinder of the engine 1 into the exhaust manifold 4 passes through the two-stage turbocharger 30, the exhaust gas purification device 100, etc., and is then released to the outside from the tailpipe.

[0027] In the intake path of the two-stage turbocharger 30, the low-pressure stage compressor case 56 is connected to the air cleaner via an intake pipe 62, the high-pressure stage compressor case 54 is connected to the low-pressure stage compressor case 56 via a low-pressure fresh air passage pipe 65, and the intake throttle member 26 of the EGR device 24 is connected to the high-pressure stage compressor case 54 via an intercooler (not shown). Fresh air (outside air) sucked into the air cleaner is cleaned and purified by the air cleaner, and then sent to the intake manifold 3 via the two-stage turbocharger 30, the intercooler, the intake throttle member 26, the collector 25, etc., and is then supplied to each cylinder of the engine 1.

[0028] The exhaust gas purification device 100 is for collecting particulate matter (PM) and the like in exhaust gas. As shown in FIGS. 1 to 5, the exhaust gas purification device 100 has a generally cylindrical shape that extends long in the left-right direction intersecting the crankshaft 5 in a plan view. In this embodiment, the exhaust gas purification device 100 is disposed above the front side surface of the cylinder head 2. The exhaust gas purification device 100 is supported on the front part of the cylinder head 2 via a left support bracket 117, a right support bracket 118, and a support base 121.

[0029] An exhaust gas intake side and an exhaust gas discharge side are provided on both the left and right sides (one longitudinal end side and the other longitudinal end side) of the exhaust gas purification device 100. An exhaust gas inlet pipe 116 on the exhaust gas intake side of the exhaust gas purification device 100 is connected to the exhaust outlet of the low-pressure stage turbine case 55 of the two-stage turbocharger 30 via an exhaust connecting member 120 having an exhaust gas passage that is approximately L-shaped in a side view, and a straight exhaust connecting pipe 119. The exhaust connecting member 120 is fixed to the left side surface of a support base 121. The exhaust gas discharge side of the exhaust gas purification device 100 is connected to the exhaust gas intake side of a tailpipe (not shown).

[0030] The exhaust gas purification device 100 has a structure in which a diesel oxidation catalyst 102 made of, for example, platinum and a honeycomb soot filter 103 are arranged in series and housed inside. In the above-mentioned configuration, nitrogen dioxide (NO2) generated by the oxidation action of the diesel oxidation catalyst 102 is captured in the soot filter 103. Particulate matter contained in the exhaust gas of the engine 1 is trapped in the soot filter 103 and is continuously oxidized and removed by the nitrogen dioxide. Therefore, in addition to removing particulate matter (PM) from the exhaust gas of the engine 1, the content of carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas of the engine 1 is reduced.

[0031] The exhaust gas purification device 100 includes an upstream case 105 having an exhaust gas inlet pipe 116 on its outer circumferential surface, an intermediate case 106 connected to the upstream case 105, and a downstream case 107 connected to the intermediate case 106. The upstream case 105 and the intermediate case 106 are arranged in series and connected to form a gas purification housing 104 made of a heat-resistant metal material. A diesel oxidation catalyst 102 and a soot filter 103 are housed within the gas purification housing 104 via a cylindrical inner case (not shown). The downstream case 107 also includes an inner case (not shown) with a large number of sound-absorbing holes, and a ceramic fiber sound-absorbing material is filled between the inner case and the downstream case, forming a silencer.

[0032] When the exhaust gas passes through the diesel oxidation catalyst 102 and the soot filter 103, if the exhaust gas temperature exceeds the regeneration temperature (for example, approximately 300°C), the nitrogen monoxide in the exhaust gas is oxidized to unstable nitrogen dioxide by the action of the diesel oxidation catalyst 102. Then, the particulate matter accumulated on the soot filter 103 is oxidized and removed by the oxygen released when the nitrogen dioxide returns to nitrogen monoxide, thereby restoring the particulate matter trapping ability of the soot filter 103 and regenerating the soot filter 103.

[0033] Next, the configuration and mounting structure of the two-stage turbocharger 30 will be described with reference to Figures 6 to 10 etc. The two-stage turbocharger 30 compresses fresh air that flows into the intake manifold 3 of the cylinder head 2 by using the fluid energy of exhaust gas discharged from the exhaust manifold 4. The two-stage turbocharger 30 is composed of a high-pressure stage turbocharger 51 connected to the exhaust manifold 4 and a low-pressure stage turbocharger 52 connected to the high-pressure stage turbocharger 51.

[0034] 7 and 8, the high-pressure stage turbocharger 51 is disposed on the left side of the exhaust manifold 4. The low-pressure stage turbocharger 52 is disposed above the exhaust manifold 4. That is, the small-capacity high-pressure stage turbocharger 51 is disposed facing the left side surface of the exhaust manifold 4, while the large-capacity low-pressure stage turbocharger 52 is disposed facing the left side surfaces of the cylinder head 2 and the cylinder head cover 18. Therefore, in the space to the left of the cylinder head 2, not only can the exhaust manifold 4 and the two-stage turbocharger 30 be compactly disposed within a substantially rectangular frame when viewed from the front and from the back, but the top position of the two-stage turbocharger 30 can be positioned lower than the top position of the engine 1. This can contribute to the downsizing of the engine 1.

[0035] 3 and 6, when the engine 1 is viewed from the left side, the low-pressure stage turbocharger 52 is disposed on the left side of the cylinder head 2 and further forward than the high-pressure stage turbocharger 51. Therefore, a larger space can be provided below the low-pressure stage turbocharger 52 and around the front left side of the cylinder block 6 for arranging other application parts. For example, an external auxiliary device such as a hydraulic pump that is operated by the rotational force of the crankshaft 5 can be disposed between the low-pressure stage turbocharger 52 and the starter 20 for starting the engine.

[0036] 6 to 8 , the high-pressure stage turbocharger 51 includes a high-pressure stage turbine case 53, a high-pressure stage compressor case 54 disposed rearward of the high-pressure stage turbine case 53, and a high-pressure stage center housing 72 connecting the two cases 53, 54. The high-pressure stage turbine case 53 includes a high-pressure stage exhaust inlet 57 communicating with the exhaust manifold exhaust outlet 49 of the exhaust manifold 4, and a high-pressure stage exhaust outlet 58 communicating with the upstream end of a high-pressure exhaust gas pipe 59. The high-pressure stage compressor case 54 includes a high-pressure stage fresh air inlet 66 communicating with the downstream end of a low-pressure fresh air passage pipe 65, and a high-pressure stage fresh air supply port 67 connected to an intercooler (not shown). Note that the upstream end of the pipe means the end on the upstream side of the gas flow, and the downstream end means the end on the downstream side of the gas flow.

[0037] On the other hand, the low-pressure stage turbocharger 52 includes a low-pressure stage turbine case 55, a low-pressure stage compressor case 56 arranged rearward of the low-pressure stage turbine case 55, and a low-pressure stage center housing 75 connecting both cases 55, 56. The low-pressure stage turbine case 55 includes a low-pressure stage exhaust inlet 60 communicating with the downstream end of the high-pressure exhaust gas piping 59, and a low-pressure stage exhaust outlet 61 communicating with the upstream end of the exhaust connecting pipe 119. The low-pressure stage compressor case 56 includes a low-pressure stage fresh air inlet 63 communicating with the downstream end of the air intake pipe 62, and a low-pressure stage fresh air supply port 64 communicating with the upstream end of the low-pressure fresh air passage pipe 65.

[0038] The exhaust manifold 4 has an exhaust manifold exhaust outlet 49, through which exhaust gas is discharged, that opens toward the left. The high-pressure stage turbine case 53 has a high-pressure stage exhaust inlet 57 that opens toward the exhaust manifold 4, while a high-pressure stage exhaust outlet 58 that opens toward the front. The low-pressure stage turbine case 55 has a low-pressure stage exhaust inlet 60 that opens downward, while a low-pressure stage exhaust outlet 61 that opens toward the front.

[0039] 6 to 8 , in the two-stage turbocharger 30, the high-pressure stage compressor case 54 has a high-pressure stage fresh air inlet 66 that opens rearward, and a high-pressure stage fresh air supply port 67 that opens downward. Moreover, the low-pressure stage compressor case 56 has a low-pressure stage fresh air inlet 63 that opens rearward, and a low-pressure stage fresh air supply port 64 that protrudes from the left side and then faces rearward. The high-pressure stage fresh air inlet 66 is connected to the downstream end of a U-shaped low-pressure fresh air passage pipe 65, and the low-pressure stage fresh air supply port 64 is connected to the upstream end of the low-pressure fresh air passage pipe 65.

[0040] 6 to 8, the exhaust manifold exhaust outlet 49 of the exhaust manifold 4 and the high-pressure stage exhaust inlet 57 of the high-pressure stage turbine case 53 are bolted together at their flanges. This allows the high-pressure stage turbocharger 51 to be fixed to the robust exhaust manifold 4. Furthermore, the high-pressure stage exhaust outlet 58 of the high-pressure stage turbine case 53 is bolted together at its flange to the downstream end (rear end) of a substantially L-shaped high-pressure exhaust gas pipe 59, while the low-pressure stage exhaust inlet 60 of the low-pressure stage turbine case 55 is bolted together at its flange to the upstream end (upper end) of the high-pressure exhaust gas pipe 59. The substantially L-shaped high-pressure exhaust gas pipe 59 is made of flexible pipe, and in this embodiment, a bellows tube portion 59a is provided at the portion extending in the front-rear direction.

[0041] 9 and 10, the low-pressure stage turbocharger 52 is fixed to the left side surface (exhaust side surface) of the cylinder head 2. In this embodiment, a low-pressure stage turbocharger mounting portion 131 is provided in a front central portion of the left side surface of the cylinder head 2 (see also FIGS. 12, 16, and 19). The low-pressure stage turbocharger mounting portion 131 is provided above the exhaust manifold 4 and in a position facing the low-pressure stage turbine case 55. The low-pressure stage turbocharger 52 is mounted to the low-pressure stage turbocharger mounting portion 131 via a substantially L-shaped mounting bracket 132. The mounting bracket 132 has a turbocharger-side flat surface 132a disposed in the left-right direction, and a head-side flat surface 132b protruding forward from the right end of the turbocharger-side flat surface 132a.

[0042] A turbocharger-side flat surface 132b of the mounting bracket 132 is fixed to the right edge of the front side surface of the low-pressure stage compressor case 56 by a bolt 133. A head-side flat surface 132a of the mounting bracket 132 is fixed to the low-pressure stage turbocharger mounting portion 131 by a pair of front and rear bolts 133. In this way, the low-pressure stage turbocharger 52 is fixed to the robust cylinder head 2.

[0043] In this embodiment, the low-pressure stage turbocharger 52 is fixed to the left side surface (exhaust side surface) of the cylinder head 2, and the high-pressure stage turbocharger 51 is fixed to the exhaust manifold 4, so the high-pressure stage turbocharger 51 and the low-pressure stage turbocharger 52 that constitute the two-stage turbocharger 30 can be firmly fixed by dividing them into the sturdy cylinder head 2 and exhaust manifold 4. In addition, the low-pressure stage turbocharger 52 is connected to a support base 121 fixed to the front part of the cylinder head 2 via an exhaust connecting pipe 119 and an exhaust connecting member 120, so that the low-pressure stage turbocharger 52 can be reliably fixed to the engine 1, and consequently the two-stage turbocharger 30 can be reliably fixed to the engine 1.

[0044] Moreover, since the high-pressure stage exhaust outlet 58 of the high-pressure stage turbocharger 51 and the low-pressure stage exhaust inlet 60 of the low-pressure stage turbocharger 52 are connected via a flexible high-pressure exhaust gas piping 59, the risk of low-cycle fatigue failure of the high-pressure exhaust gas piping 59 due to thermal expansion can be reduced. Furthermore, the stress applied to the two-stage turbocharger 30 due to thermal expansion of the high-pressure exhaust gas piping 59 can be reduced. This reduces the stress applied to the connecting portion between the high-pressure stage turbocharger 51 and the exhaust manifold 4 and the stress applied to the connecting portion between the low-pressure stage turbocharger 52 and the cylinder head 2, and prevents poor connection at these connecting portions and damage to connecting members.

[0045] As shown in Figures 9 and 10, the cylinder head 2 is provided therein with a rib 135 extending from the low-pressure stage turbocharger mounting portion 131 toward the right side surface (intake side surface) of the cylinder head 2. The rib 135 protrudes upward from a cylinder head bottom surface 136. This improves the rigidity of the cylinder head 2 around the low-pressure stage turbocharger mounting portion 131, and prevents deformation of the cylinder head 2 due to the mounting of the low-pressure stage turbocharger 52 to the cylinder head 2. In addition, a valve arm mechanism mounting seat 137 extending in the left-right direction is provided on the cylinder head bottom surface 136 so as to protrude upward, continuing from the right end of the rib 135. This improves the rigidity of the rib 135, and ultimately improves the rigidity of the cylinder head 2 around the low-pressure stage turbocharger mounting portion 131.

[0046] In this embodiment, the engine 1 is an OHV type, and the space surrounded by the cylinder head 2 and the cylinder head cover 18 constitutes a valve arm chamber. As shown in Figure 9, the valve arm chamber accommodates an injector 138 and a valve train. A plurality of valve arm mechanism mounting seats 137 are arranged at equal intervals in the front-to-rear direction, and a valve arm shaft support portion 139 that supports a valve arm shaft (not shown) is arranged on the valve arm mechanism mounting seats 137, and a plurality of valve arms 140 are pivotally supported on the valve arm shaft so that they can swing freely. Each valve arm 189 swings around the valve arm shaft, thereby opening and closing the intake valve and exhaust valve (not shown) of each cylinder.

[0047] 3, 5, and 6, the low-pressure stage turbocharger 52 is disposed near the front side (one side) of the cylinder head 2 when viewed from the left, while a low-pressure stage exhaust outlet 61 of the low-pressure stage turbine case 55 is provided facing the front side of the cylinder head 2. In addition, an exhaust gas inlet pipe 116 constituting an exhaust inlet of the exhaust gas purification device 100 is disposed near the corner where the front side and the right side (exhaust side) of the cylinder head 2 intersect. Therefore, the exhaust connecting pipe 119 and the exhaust connecting member 120, which serve as piping connecting the low-pressure stage exhaust outlet 61 of the low-pressure stage turbocharger 52 and the exhaust gas inlet pipe 116 of the exhaust gas purification device 100, can be made short and simple. As a result, the exhaust gas supplied to the exhaust gas purification device 100 can be maintained at a high temperature, and a decrease in the regeneration capability of the exhaust gas purification device 100 can be prevented.

[0048] In the present invention, as long as the exhaust inlet of the exhaust gas purification device 100 is arranged near the corner where the front side (one side) and the right side (exhaust side) of the cylinder head 2 intersect, the same effects as those of this embodiment can be obtained regardless of the mounting position or orientation of the exhaust gas purification device 100. For example, the exhaust gas purification device 100 may be arranged horizontally in front of the cylinder head 2 above the flywheel housing 7 (see, for example, Japanese Patent Application Laid-Open No. 2011-012598), or may be arranged horizontally in front of the cylinder head 2 (direction along the crankshaft 5) above the cylinder head 2 (see, for example, Japanese Patent Application Laid-Open No. 2016-079870).

[0049] As shown in Figures 3, 5, and 6, a blow-by gas return system 19 that takes in blow-by gas is installed on the cylinder head 2. The blow-by gas return system 19 is mounted and fixed on the upper surface of a cylinder head cover 18 that covers the upper surface of the cylinder head 2. Above the cylinder head 2, a blow-by gas outlet 70 of the blow-by gas return system 19 is disposed near the rear side (the other side) of the cylinder head 2, facing the left side. In addition, a low-pressure stage fresh air inlet 63 of the low-pressure stage compressor case 56 of the low-pressure stage turbocharger 52 opens rearward. An air intake pipe 62 extending in the front-to-rear direction is connected to the low-pressure stage fresh air inlet 63. This allows the air intake pipe 62 to be disposed near the blow-by gas outlet 70, and the return hose 68 connecting the blow-by gas outlet 70 and the air intake pipe 62 to be shortened, preventing the return hose 68 from freezing in low-temperature environments.

[0050] 6, the low-pressure stage compressor case 56 and the high-pressure stage compressor case 54 have a low-pressure stage fresh air inlet 63, a low-pressure stage fresh air supply port 64, and a high-pressure stage fresh air inlet 66 that open in the same direction (rearward). This makes it easy to connect the air intake pipe 62 that communicates with the air cleaner to the low-pressure stage fresh air inlet 63, and also makes it easy to connect the low-pressure fresh air passage pipe 65 to the low-pressure stage fresh air supply port 64 and the high-pressure stage fresh air inlet 66, improving the ease of assembly.

[0051] The low-pressure fresh air passage pipe 65 is composed of a substantially U-shaped metal pipe 65a, one end of which is bolted to the high-pressure stage fresh air inlet 66 by a flange connection, and a resin pipe 65b that connects the other end of the metal pipe 65a to the low-pressure stage fresh air supply port 64 of the low-pressure stage compressor case 56. As a result, the low-pressure fresh air passage pipe 65 is fixed with high rigidity to the high-pressure stage compressor case 54 by the metal pipe 65a, while the resin pipe 65b allows communication between the low-pressure stage compressor case 56 and the metal pipe 65a while mitigating assembly errors between them.

[0052] Furthermore, the low-pressure stage fresh air supply port 64 of the low-pressure stage compressor case 56 extends diagonally upward to the left from the lower left part of the outer peripheral surface of the low-pressure stage compressor case 56 and is further curved toward the rear, which allows the curvature of the bent portion of the low-pressure fresh air passage pipe 65 (metal pipe 65a) to be large. As a result, the generation of turbulence in the low-pressure fresh air passage pipe 65 is suppressed, and the compressed air discharged from the low-pressure stage compressor case 56 is smoothly supplied to the high-pressure stage compressor case 54.

[0053] As shown in Figure 8, the high-pressure stage turbocharger 51 has a fresh air supply port 64 extending downward in a right-side position on the lower outer peripheral surface of the high-pressure stage compressor case 54. The high-pressure stage compressor case 54 is connected to a high-pressure fresh air passage pipe 71 that is in communication with the intercooler, and supplies compressed air to the intercooler via the high-pressure fresh air passage pipe 71. In addition, a cooling water inlet pipe 22 that opens toward the left is provided below the high-pressure stage compressor case 54. A cooling water pipe 150 that leads to a radiator is connected to the cooling water inlet pipe 22. This allows the routing of the high-pressure fresh air passage pipe 71 and the cooling water pipe 150 to be consolidated, which not only simplifies the piping structure on the machine side on which the engine 1 is mounted, but also makes assembly and maintenance easier.

[0054] 2, 4, and 5, the engine 1 has the coolant outlet pipe 23, the air intake pipe 62, and the intake throttle member 26 disposed at its rear (on the cooling fan 9 side). Therefore, when a radiator, air cleaner, and intercooler that use the cooling air from the cooling fan 9 are disposed behind the cooling fan 9 on the machine on which the engine 1 is mounted, not only can the coolant piping connecting to the radiator and the fresh air piping communicating with the air cleaner and intercooler be shortened, but the piping connection work can be performed all at once. This not only facilitates assembly and maintenance work on the machine side, but also allows the various parts connected to the engine 1 to be efficiently disposed on the machine side.

[0055] 6 to 8, in the high-pressure stage turbocharger 51, a high-pressure lubricating oil supply pipe 73 and a high-pressure lubricating oil return pipe 74 are connected to the upper and lower parts of the outer peripheral surface of a high-pressure stage center housing 72, which is the connecting part between the high-pressure stage turbine case 53 and the high-pressure stage compressor case 54. In the low-pressure stage turbocharger 52, a low-pressure lubricating oil supply pipe 76 and a low-pressure lubricating oil return pipe 77 are connected to the upper and lower parts of the outer peripheral surface of a low-pressure stage center housing 75, which is the connecting part between the low-pressure stage turbine case 55 and the low-pressure stage compressor case 56.

[0056] The high-pressure lubricating oil supply pipe 73 has a lower end connected to a connecting member 78a provided in the center of the left side surface of the cylinder block 6, and an upper end connected to an upper part of a high-pressure stage center housing 72 of the high-pressure stage turbocharger 51. A connecting joint 78b is provided at the upper part of the high-pressure stage center housing 72, connecting the upper end of the high-pressure lubricating oil supply pipe 73 to the lower end of a low-pressure lubricating oil supply pipe 76. The upper end of the low-pressure lubricating oil supply pipe 76 is connected to a connecting member 78c provided at the upper part of a low-pressure stage center housing 75 of the low-pressure stage turbocharger 52. As a result, lubricating oil flowing through the oil passages in the cylinder block 6 is supplied to the high-pressure stage center housing 72 of the high-pressure stage turbocharger 51 through the high-pressure lubricating oil supply pipe 73, and is also supplied to the low-pressure stage center housing 75 of the low-pressure stage turbocharger 52 through the high-pressure lubricating oil supply pipe 73 and the low-pressure lubricating oil supply pipe 76.

[0057] The high-pressure lubricating oil supply pipe 73 is led diagonally upward and rearward from a connecting member 78a on the left side surface of the cylinder block 6, passes between the high-pressure stage compressor case 54 and the cylinder block 6, and is led to a position facing the left side surface of the cylinder head 2. Furthermore, the high-pressure lubricating oil supply pipe 73 bypasses the rear end of the exhaust manifold 4, passes through the right side of the high-pressure stage center housing 72, and is led to a connecting joint 78b. The low-pressure lubricating oil supply pipe 76 has a substantially L-shape in side view, and is led from the connecting joint 78b to a connecting member 78c so as to run along the high-pressure stage turbocharger 51 and the high-pressure exhaust gas pipe 59. In this way, by shortening the lubricating oil supply pipes 73, 76 and piping them so as to be surrounded by the two-stage turbocharger 30, which is a highly rigid component, it is possible to efficiently supply lubricating oil to the two-stage turbocharger 30, and also to prevent damage to the lubricating oil supply pipes 73, 76 due to external forces.

[0058] Moreover, one end (lower end) of the high-pressure lubricating oil return pipe 74 is connected to the tip surface of a connecting joint 80 installed above the connecting member 78a in the center of the left side surface of the cylinder block 6. The other end (upper end) of the high-pressure lubricating oil return pipe 74 is connected to the lower part of the outer circumferential surface of the high-pressure stage center housing 72 of the high-pressure stage turbocharger 51. Moreover, one end (lower end) of the low-pressure lubricating oil return pipe 77 is connected to a connection part that protrudes obliquely upward and forward from the middle of the connecting joint 80. On the other hand, the other end (upper end) of the low-pressure lubricating oil return pipe 77 is connected to the lower part of the outer circumferential surface of the low-pressure stage center housing 75 of the low-pressure stage turbocharger 52. Therefore, the lubricating oil flowing through the high-pressure stage turbocharger 51 and the low-pressure stage turbocharger 52 passes through the lubricating oil return pipes 74, 77 from the lower parts of the center housings 72, 75, is joined at the connecting joint 80, and is returned to the oil passage in the cylinder block 6.

[0059] The high-pressure lubricant oil return pipe 74 passes from below the high-pressure stage turbine case 53 below the exhaust manifold exhaust outlet 49 of the exhaust manifold 4 and is led to the connecting joint 80. In addition, the low-pressure working oil return pipe 77 passes between the high-pressure exhaust gas piping 59 and the exhaust manifold 4 and is led to the connecting joint 80. In this way, by shortening the lubricant oil return pipes 74, 77 and piping them so as to be covered by the two-stage turbocharger 30, which is a highly rigid part, it is possible to efficiently supply lubricant oil to the two-stage turbocharger 30 and at the same time prevent damage to the lubricant oil return pipes 74, 77 due to external forces.

[0060] 11 to 16, etc., the mounting structure of the exhaust gas purification device 100 will be described. The exhaust gas purification device 100 is configured by connecting an upstream case 105, an intermediate case 106, and a downstream case 107 in series in that order, and is disposed above the front part of the cylinder head 2 in a horizontally elongated manner.

[0061] The connecting portion between the upstream case 105 and the intermediate case 106 is sandwiched and connected from both sides in the exhaust gas movement direction by a pair of thick plate-shaped clamping flanges 108, 109. That is, a joining flange provided on the downstream opening edge of the upstream case 105 and a joining flange provided on the upstream opening edge of the intermediate case 106 are sandwiched between the clamping flanges 108, 109 to connect the downstream side of the upstream case 105 and the upstream side of the intermediate case 106, thereby forming the gas purification housing 104. At this time, by bolting the clamping flanges 108, 109 together, the upstream case 105 and the intermediate case 106 are detachably connected.

[0062] The connecting portion between intermediate case 106 and downstream case 107 is sandwiched from both sides in the exhaust gas movement direction by a pair of thick plate-shaped clamping flanges 110, 111. That is, a joining flange provided on the downstream opening edge of intermediate case 106 and a joining flange provided on the upstream opening edge of downstream case 107 are sandwiched between clamping flanges 108, 109, thereby detachably connecting the downstream side of intermediate case 106 and the upstream side of downstream case 107.

[0063] An exhaust gas inlet pipe 116 is provided on the outer periphery of the exhaust inlet side of the upstream case 105, and the exhaust intake side of the exhaust gas inlet pipe 116 communicates with the low-pressure stage exhaust outlet 61 (see FIG. 6, etc.) of the two-stage turbocharger 30 via an exhaust connecting member 120 and an exhaust connecting pipe 119, which serve as an exhaust relay path. The exhaust connecting member 120 is configured to be approximately L-shaped in side view, with the exhaust intake side facing rearward to connect to the exhaust connecting pipe 119, and the exhaust discharge side facing upward to connect to the exhaust gas inlet pipe 116 of the exhaust gas purification device 100. As shown in FIGS. 11, 12 and 16, the exhaust connecting member 120 is detachably attached to the front part of the left side surface of a support base 121 by a pair of upper and lower bolts 122, 122.

[0064] 11 and 15, the exhaust gas purification device 100 is attached to the front of the cylinder head 2 via left and right support brackets 117, 118 and a support base 121. The exhaust gas purification device 100 includes a left bracket fastening leg 112 welded to the lower part of the outer circumferential surface of the upstream casing 105, and a right bracket fastening leg 113 formed on the lower part of the clamping flange 110.

[0065] The left and right support brackets 117, 118 are generally L-shaped and include a horizontal portion and upright portions projecting upward from the left and right outer ends of the horizontal portion. The horizontal portion of the left support bracket 117 is fixed to a left-side portion of the upper surface of the flat portion 121a of the support base 121 by a pair of front and rear bolts. The horizontal portion of the right support bracket 118 is fixed to a right-side edge portion of the upper surface of the flat portion 121a of the support base 121 by a pair of front and rear bolts. The left and right bracket fastening legs 112, 113 of the exhaust gas purification device 100 are attached to the left and right support brackets 117, 118 by a pair of front and rear bolts and nuts, respectively.

[0066] The upper surface of the upright portion of the right support bracket 118 is formed with notches 118a into which the heads of the bolts fastening the lower parts of the clamping flanges 110, 111 can be temporarily placed. When assembling the exhaust gas purification device 100 to the engine 1, with the left and right support brackets 117, 118 and the exhaust connecting member 120 attached to the support base 121, the heads of the bolts fastening the lower parts of the clamping flanges 110, 111 are aligned with the notches 118a of the right support bracket 118. This makes it possible to align the exhaust gas purification device 100 with the engine device 1, and also makes it easier to tighten the bolts when assembling the exhaust gas purification device 100 to the engine 1, improving the ease of assembly.

[0067] 11 to 16, the flat surface 121a of the support base 121 has a generally L-shape in which the right side is longer than the left side in plan view. The flat surface 121a is disposed along the front and right side surfaces of the cylinder head 2 in plan view so as to cover the front portion of the cylinder head 2. The exhaust gas purification device 100 is mounted on the flat surface 121a.

[0068] The support base 121 also has a plurality of legs 121b, 121c, 121d, and 121e that protrude downward from the flat portion 121a and are fixed to the cylinder head 2. An upwardly convex arch shape is formed between the legs 121b, 121c, 121d, and 121e. The cylinder head 2 has an exhaust-side mounting portion 123b at the front portion of the left side surface, a first central mounting portion 123c at an upper portion of the center of the front side surface, a second central mounting portion 123d at the right edge portion of the front side surface, and an intake-side mounting portion 123e at the front end portion of the upper surface of the intake manifold 3 that is integrally molded with the right side surface.

[0069] The lower end of the exhaust-side leg 121b is fixed to the exhaust-side mounting part 123b with a pair of front and rear bolts. The lower end of the first central leg 121c is fixed to the first central mounting part 123c with one bolt. The lower part of the second central leg 121d is fixed to the second central mounting part 123d with a pair of upper and lower bolts. The intake-side leg 121e has a pair of front and rear bolt insertion holes drilled in the vertical direction, and is attached to the intake-side mounting part 123e with a pair of front and rear bolts inserted into the bolt insertion holes.

[0070] As shown in Figures 11, 13 to 15, and 21, the intake manifold 3 is integrally molded with the right side surface of the cylinder head 2. The intake-side leg 121e is fixed to an intake-side mounting portion 123e provided on the intake manifold 3, so that the intake-side leg 121e can be placed on the sturdy intake manifold 3 and firmly fixed thereto. Furthermore, the pair of front and rear bolts for fixing the intake-side leg 121e to the intake manifold 3 can be tightened and loosened from above the cylinder head 2. Therefore, for example, the support base 121 can be attached and removed with the EGR device 24 (see Figure 5, etc.) located on the right side of the cylinder head 2 attached to the intake manifold 3, improving the ease of assembly and maintenance of the engine 1.

[0071] 11, 13, and 15, a pair of front and rear reinforcing ribs 124, 124 protrude from the right side and bottom surface of the intake manifold 3 below the intake-side mounting portion 123e. The reinforcing ribs 124, 124 extend in the vertical direction, improving the strength of the intake manifold 3 around the intake-side mounting portion 123e. This prevents deformation of the intake manifold 3 and the cylinder head 2 caused by mounting the support base 121 to the intake manifold 3.

[0072] As shown in FIGS. 11 to 16, the support base 121 has a flat portion 121a and legs 121b, 121c, 121d, and 121e integrally molded, while the legs 121b, 121c, 121d, and 121e are formed in an arched shape. This allows the support base 121 to be lightweight while maintaining its rigidity. Furthermore, by forming the support base 121 as an integrally molded part, the number of parts can be reduced. Furthermore, the arched gaps formed between the legs 121b, 121c, 121d, and 121e prevent heat accumulation around the legs 121b, 121c, 121d, and 121e. This prevents thermal damage to electronic components mounted around the legs, such as the exhaust pressure sensor 151 described below, and insufficient cooling of cooling components, such as the EGR cooler 27.

[0073] The support base 121 also includes an exhaust-side leg 121b fixed to the left side surface of the cylinder head 2, an intake-side leg 121e fixed to the right side surface of the cylinder head 2, and central legs 121c and 121d fixed to the front side surface of the cylinder head 2. Therefore, the support base 121 can be fixed to a total of three surfaces of the cylinder head 2, namely the right side surface, left side surface, and front side surface, thereby improving the support rigidity of the exhaust gas purification device 100.

[0074] 11, 13, and 15, the arch shape between intake-side leg 121e and second central leg 121d, the arch shape between central legs 121c and 121d, and the arch shape between exhaust-side leg 121b and first central leg 121c are different in height and size (width). Furthermore, exhaust-side leg 121b and intake-side leg 121e have different lengths in the up-down direction. By appropriately designing these arch shapes and leg lengths, it becomes possible for the support base 121 to cancel out vibrations on the intake side and exhaust side, thereby reducing vibrations of the exhaust gas purification device 100.

[0075] As shown in FIGS. 11 and 16, the flat surface 121a and the legs 121b, 121c, 121d, and 121e of the support base 121 are spaced apart from the cylinder head cover 18. As a result, a cooling air passage 148 is formed between the support base 121 and the cylinder head cover 18, through which cooling air 149 flows from a cooling fan 9 (see FIG. 3, etc.) disposed at the rear of the engine 1. Therefore, the cooling air 149 from the cooling fan 9 can be guided to the front side of the cylinder head 2 via the cooling air passage 148, thereby appropriately cooling the periphery of the front side of the cylinder head 2. In this embodiment, the EGR cooler 27 and an exhaust pressure sensor 151, which will be described later, are attached to the front side of the cylinder head 2. Therefore, the cooling air 149 guided from the cooling fan 9 to the front side of the cylinder head 2 via the cooling air passage 148 can promote cooling of the EGR cooler 27 and prevent thermal damage to the exhaust pressure sensor 151.

[0076] Next, the configuration of the periphery of the front side of the cylinder head 2 will be described with reference to Figures 17 to 21, etc. As shown in Figure 21, the cylinder head 2 is formed with a plurality of intake passages 36 that introduce fresh air into a plurality of intake ports (not shown) and a plurality of exhaust passages 37 that guide exhaust gas from a plurality of exhaust ports. An intake manifold 3 that brings together the plurality of intake passages 36 is formed integrally with the right side of the cylinder head 2. By configuring the cylinder head 2 and the intake manifold 3 integrally, it is possible to improve the gas sealing performance from the intake manifold 3 to the intake passages 36 and to increase the rigidity of the cylinder head 2.

[0077] An EGR gas outlet 41, which communicates with the upstream EGR gas passage 31 in the cylinder head 2, and an exhaust inlet 42, which communicates with the multiple exhaust flow paths 37, are opened side by side in the front-to-rear direction on the right side of the exhaust manifold 4, which is connected to the left side of the cylinder head 2. An exhaust manifold 43, which communicates with the EGR gas outlet 41 and the exhaust inlet 42, is formed inside the exhaust manifold 4. An exhaust manifold exhaust outlet 49, which communicates with the exhaust manifold 43, is opened at the rear of the left side of the exhaust manifold 4. When exhaust gas from the exhaust flow paths 37 of the cylinder head 2 flows into the exhaust manifold 43 through the exhaust inlet 42, some of the exhaust gas flows as EGR gas from the EGR gas outlet 41 into the upstream EGR gas passage 31 in the cylinder head 2, and the remainder of the exhaust gas flows from the exhaust manifold exhaust outlet 49 into the two-stage turbocharger 30 (see FIG. 7, etc.).

[0078] The cylinder head 2 has an exhaust manifold 4 connected to its left side (exhaust side), which is opposite to the right side (intake side) on which the intake manifold 3 is integrally molded, and an EGR cooler 27 connected to its front side (one of two sides intersecting the exhaust side). Left and right EGR cooler connectors 33, 34 protrude forward from both left and right edges of the front side of the cylinder head 2 (front left and right corners of the cylinder head 2). The EGR cooler 27 is connected to the front sides of the left and right EGR cooler connectors 33, 34. EGR gas passages 31, 32 and cooling water passages 38, 39 are formed within the EGR cooler connectors 33, 34.

[0079] By configuring the EGR gas passages 31, 32 and the cooling water passages 38, 39 in the EGR cooler connecting portions 33, 34, there is no need to provide cooling water piping and EGR gas piping between the EGR cooler 27 and the cylinder head 2. Therefore, not only can sealing be ensured at the connecting portion with the EGR cooler 27 without being affected by expansion and contraction of the piping due to EGR gas or cooling water, but resistance (structural stability) to external fluctuations such as heat and vibration is improved and a compact configuration is possible.

[0080] 17, 20, and 21, an upstream EGR gas passage 31 is provided in the left EGR cooler connecting portion 33, and a downstream EGR gas passage 32 is provided in the right EGR cooler connecting portion 34. The upstream EGR gas passage 31 is generally L-shaped in plan view, with one end and the other end opening on the front side surface and left side surface of the left EGR cooler connecting portion 33, and connects a lower left portion of the back surface of the EGR cooler 27 to an EGR gas outlet 41 provided in a front portion of the right side surface of the exhaust manifold 4. The downstream EGR gas passage 32 is generally L-shaped in plan view, with one end and the other end opening on the front side surface and right side surface of the right EGR cooler connecting portion 34, and connects an upper right portion of the back surface of the EGR cooler 27 to an EGR gas inlet of the recirculation exhaust gas piping 28.

[0081] A downstream cooling water passage 38 is formed in the left EGR cooler connecting portion 33, leading from the front side surface of the left EGR cooler connecting portion 33 to the rear side. The downstream cooling water passage 38 is provided above the upstream EGR gas passage 31, and sends the cooling water discharged from the upper left part of the back surface of the EGR cooler 27 to the cooling water passage in the cylinder head 2. In addition, an upstream cooling water passage 39 is formed in the right EGR cooler connecting portion 34, leading from the front side surface of the right EGR cooler connecting portion 34 to the rear side. The upstream cooling water passage 39 is provided below the downstream EGR gas passage 32, and sends the cooling water flowing through the cooling water passage in the cylinder head 2 to the lower right part of the back surface of the EGR cooler 27.

[0082] As shown in Figures 17 to 20, an exhaust pressure sensor 151 that detects the exhaust gas pressure inside the exhaust manifold 4 is provided on the front side surface of the cylinder head 2. The exhaust pressure sensor 151 is attached to an exhaust pressure sensor attachment portion 152 that protrudes forward from an upper central portion of the front side surface of the cylinder head 2. The exhaust pressure sensor attachment portion 152 is provided between the left and right EGR cooler connecting portions 33, 34. In the engine 1 of this embodiment, the left edge of the exhaust pressure sensor attachment portion 152 is formed contiguous with an upper right edge portion of the left EGR cooler connecting portion 33.

[0083] The exhaust pressure sensor 151 is connected to the exhaust manifold 4 via an exhaust pressure bypass path 153 provided in the cylinder head 2 and an exhaust pressure detection pipe 154 that connects the exhaust pressure bypass path 153 and the exhaust manifold 4. The exhaust pressure bypass path 153 is drilled from the front end portion of the left side surface of the cylinder head 2 toward the right side, passes through the inside of the left EGR cooler connecting portion 33, and is led to the inside of the exhaust pressure sensor mounting portion 152. The exhaust pressure bypass path 153 is also bent toward the front side within the exhaust pressure sensor mounting portion 152 and opens at the front side surface of the exhaust pressure sensor mounting portion 152. A hole filling member 155 that closes the end of the exhaust pressure bypass path 153 is attached to the front side surface of the exhaust pressure sensor mounting portion 152.

[0084] 18, the exhaust pressure sensor mounting portion 152 has a sensor mounting hole 152a drilled downward from its upper surface and connected to the exhaust pressure bypass path 153. When the exhaust pressure sensor 151 is mounted in the sensor mounting hole 152a, the lower end of the exhaust pressure sensor 151 is exposed to the exhaust pressure bypass path 153.

[0085] On the other hand, the exhaust pressure detection pipe 154 is disposed above the exhaust manifold 4, to the left of the front portion of the left side surface of the cylinder head 2. A detection pipe mounting base 156 protrudes upward from a front portion of the top surface of the exhaust manifold 4. A rear joint member 157 is attached to the top surface of the detection pipe mounting base 156. A front joint member 158 is attached to the end of the exhaust pressure bypass path 153, which opens at the front end portion of the left side surface of the cylinder head 2. The front end of the exhaust pressure detection pipe 154 is connected to the exhaust pressure bypass path 153 via the front joint member 158. The rear end of the exhaust pressure detection pipe 154 is connected to the exhaust manifold 4 via the rear joint member 157 to the exhaust collection section 43 (see FIG. 21 ) in the exhaust manifold 4. An exhaust gas temperature sensor 159 is attached to the top surface of the detection pipe mounting base 156, at a position forward of the rear joint member 157. The exhaust gas temperature sensor 159 detects the temperature of the exhaust gas flowing through the exhaust collection portion 43 in the exhaust manifold 4 .

[0086] Heat transferred from the exhaust manifold 4, which becomes hot, to the exhaust pressure detection pipe 154 is diffused in the cylinder head 2 via the front joint member 158. This prevents heat from the exhaust manifold 4 and the exhaust pressure detection pipe 154 from being directly transferred to the exhaust pressure sensor 151, which is sensitive to heat. Therefore, the length of the exhaust pressure detection pipe 154 can be shortened while preventing breakdowns and malfunctions of the exhaust pressure sensor 151 caused by heat from the exhaust manifold 4 and the exhaust pressure detection pipe 154. Furthermore, shortening the length of the exhaust pressure detection pipe 154 improves the reliability of the exhaust pressure detection pipe 154 and makes it easier to arrange the exhaust pressure detection pipe 154, thereby reducing design man-hours and improving the manufacturability and assembly of the engine 1.

[0087] 17 and 20, the downstream cooling water passage 38 is provided in the left EGR cooler connecting portion 33 near the exhaust pressure bypass path 153, so the temperature of the gas in the exhaust pressure bypass path 153 can be efficiently reduced. Therefore, the exhaust pressure bypass path 153 can be shortened while keeping the heat transferred from the gas in the exhaust pressure bypass path 153 to the exhaust pressure sensor 151 within an allowable range, making it easy to form the exhaust pressure bypass path 153 in the cylinder head 2. In addition, the exhaust pressure bypass path 153 passes through the left EGR cooler connecting portion 33 and the exhaust pressure sensor mounting portion 152, which protrude from the front side surface of the cylinder head 2, so the gas in the exhaust pressure bypass path 153 can be efficiently cooled, and breakdowns or malfunctions of the exhaust pressure sensor 151 caused by heat can be prevented. Furthermore, since the exhaust pressure sensor 151 is attached to the exhaust pressure sensor attachment portion 152 that protrudes from the front side of the cylinder head 2 between the pair of EGR cooler connecting portions 33, 34, the exhaust pressure sensor 151 can be cooled efficiently, and breakdowns or malfunctions of the exhaust pressure sensor 151 due to heat can be prevented.

[0088] 19 , the front joint member 158 is attached at a position higher than the upper surface of the detection pipe mounting base 156. The exhaust pressure detection pipe 154 extends diagonally forward and left from the rear joint member 157, then bypasses the exhaust gas temperature sensor 159, curves to the right, and is led diagonally upward. It is then disposed substantially horizontally forward along the left side surface of the cylinder head 2 and connected to the front joint member 158. The end of the exhaust pressure detection pipe 154 on the front joint member 158 side is positioned higher than the end on the rear joint member 157 side. This prevents oil and moisture contained in the exhaust gas from liquefying in the exhaust pressure detection pipe 154 and entering the exhaust pressure bypass path 153, thereby enabling accurate detection of the exhaust gas pressure.

[0089] 17 to 21, by configuring the EGR cooler connecting portions 33, 34 to protrude, it is not necessary to provide piping for EGR gas that connects the exhaust manifold 4, the EGR cooler 27, and the EGR device 24, and the number of connecting points in the EGR gas passage is reduced. Therefore, in the engine 1 that aims to reduce NOx by EGR gas, not only is it possible to reduce EGR gas leakage, but it is also possible to suppress deformation due to stress changes caused by expansion and contraction of the piping. Furthermore, because the EGR gas passages 31, 32 and the cooling water passages 38, 39 are formed within the EGR cooler connecting portions 33, 34, the shapes of the passages 31, 32, 38, 39 formed in the cylinder head 2 are simplified, and the cylinder head 2 can be easily cast without using a complex core.

[0090] Furthermore, because the left EGR cooler connecting portion 33 on the exhaust manifold 4 side and the right EGR cooler connecting portion 34 on the intake manifold 3 side are spaced apart, mutual influence due to thermal deformation of the EGR cooler connecting portions 33, 34 can be suppressed. Therefore, not only can gas leakage, coolant leakage, and damage at the connecting portion between the EGR cooler connecting portions 33, 34 and the EGR cooler 27 be prevented, but also the rigidity balance of the cylinder head 2 can be maintained. Furthermore, because the volume of the front side surface of the cylinder head 2 can be reduced, the weight of the cylinder head 2 can be reduced. Furthermore, because the EGR cooler 27 can be disposed away from the front side surface of the cylinder head 2 and a configuration can be created in which there are spaces in front of and behind the EGR cooler 27, cooling air can flow around the EGR cooler 27, and the cooling efficiency of the EGR cooler 27 can be improved.

[0091] 17, the downstream cooling water passage 38 and the upstream EGR gas passage 31 are arranged one above the other in the left EGR cooler connecting portion 33, and the downstream EGR gas passage 32 and the upstream cooling water passage 39 are arranged one above the other in the right EGR cooler connecting portion 34. The cooling water inlet of the downstream cooling water passage 38 and the EGR gas inlet of the downstream EGR gas passage 32 are arranged 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 passage 32 are arranged at the same height.

[0092] By configuring the EGR gas passages 31, 32 and the cooling water passages 38, 39 to be provided inside the separately protruding EGR cooler connection portions 33, 34, the effects of thermal deformation in both EGR cooler connection portions 33, 34 are mitigated. Furthermore, within the EGR cooler connection portions 33, 34, the EGR gas flowing through the EGR gas passages 31, 32 is cooled by the cooling water flowing through the cooling water passages 38, 39, thereby suppressing thermal deformation in the EGR cooler connection portions 33, 34. Furthermore, in each of the EGR cooler connection portions 33, 34, the EGR gas passages 31, 32 and the cooling water passages 38, 39 are arranged at opposite vertical heights. Therefore, the heat distribution in the EGR cooler connection portions 33, 34 is reversed, thereby reducing the effects of thermal deformation in the vertical direction of the cylinder head 2.

[0093] Next, with reference to Figures 22 and 23, etc., a portion of the harness structure arranged around the front side surface of the cylinder head 2 will be described. In the engine 1 of this embodiment, a harness assembly 171 bundling a plurality of harnesses is arranged in the front-rear direction along the right side surface of the cylinder head cover 18. The harness assembly 171 branches off from a main harness assembly (not shown) extending from an external connection harness connector (not shown) attached to the engine 1.

[0094] The front end of the harness assembly 171 is disposed between the cylinder head cover 18 and the intake-side leg 121e of the support base 121. The harness assembly 171 branches into an EGR valve harness 172, an EGR gas temperature sensor harness 173, and a sensor harness assembly 174 near the right front corner of the cylinder head cover 18. The EGR valve harness 172 passes between the second central leg 121d and the intake-side leg 121e of the support base 121 and is electrically connected to the EGR valve member 29. The EGR gas temperature sensor harness 173 passes between the second central leg 121d and the intake-side leg 121e and is electrically connected to an EGR gas temperature sensor 181 that detects the exhaust gas temperature in the recirculation exhaust gas pipe 28.

[0095] The sensor harness assembly 174 is led leftward from the harness assembly 171 and bent downward in front of the right portion of the front surface of the cylinder head cover 18. The front end of the sensor harness assembly 174 branches into a rotation angle sensor harness assembly 175 and an exhaust pressure sensor harness 176. The exhaust pressure sensor harness 176 is led leftward from the harness assembly 174, passing between the cylinder head cover 18 and the first central leg 121c of the support base 121, and is electrically connected to the exhaust pressure sensor 151.

[0096] The rotation angle sensor harness assembly 175 extends downward from the sensor harness assembly 174 along the front side surface of the cylinder head 2. The rotation angle sensor harness assembly 175 is bent toward the left at a position directly above the flywheel housing 7 and led to a position forward of the lower left corner of the front side surface of the cylinder head 2. The rotation angle sensor harness assembly 175 branches into a crankshaft rotation angle sensor harness 177 and a camshaft rotation angle sensor harness 178. The crankshaft rotation angle sensor harness 177 is electrically connected to a crankshaft rotation angle sensor 182 (see FIG. 1) attached to a position near the upper left corner of the front part of the flywheel housing 7. The camshaft rotation angle sensor harness 178 is electrically connected to a camshaft rotation angle sensor 183 (see FIG. 1) attached to the upper left edge of the flywheel housing 7.

[0097] 17, locking member mounting portions 185, 186 are formed one above the other in the left-right central portion of the front side surface of the cylinder head 2. The upper locking member mounting portion 185 is located near the upper portion of the front side surface of the cylinder head 2, between the right EGR cooler connecting portion 34 and the first central mounting portion 123c. The lower locking member mounting portion 186 is located near the lower portion of the front side surface of the cylinder head 2, between the left and right EGR cooler connecting portions 33, 34, and directly below the upper locking member mounting portion 185.

[0098] 22 and 23, the portion of the rotational angle sensor harness assembly 175 facing the front side surface of the cylinder head 2 is attached to the front side surface of the cylinder head 2 by locking members 187, 188 attached to upper and lower locking member mounting portions 185, 186. The rotational angle sensor harness assembly 175 then passes from the harness assembly 174 between the right EGR cooler connecting portion 34 and the first central leg portion 121c of the support base 121, and between the cylinder head 2 and the EGR cooler 27, to a position facing the lower edge of the front side surface of the cylinder head 2.

[0099] The EGR cooler 27 is attached to a pair of left and right EGR cooler connecting portions 33, 34 that protrude forward from the front side surface of the cylinder head 2. A space is formed between the rear surface of the EGR cooler 27 and the cylinder head 2. By disposing the rotational angle sensor harness assembly 175 in the vertical direction in this space, the rotational angle sensor harness assembly 175 can be protected and the layout design of the rotational angle sensor harness assembly 175 becomes easier.

[0100] Furthermore, a space is formed between the side surface of the cylinder head cover 18 and the support base 121. By utilizing this space to arrange the harness assemblies 171 and 174 and the harnesses 172, 173, and 176, these harnesses and harness assemblies can be protected and the layout design of the harnesses can be facilitated.

[0101] As shown in FIGS. 1 to 10 , the engine 1 includes an exhaust manifold 4 provided on an exhaust side (e.g., the left side), which is one side of the cylinder head 2, and a two-stage turbocharger 30 driven by exhaust gas discharged from the exhaust manifold 4. The two-stage turbocharger 30 is composed of a high-pressure stage turbocharger 51 connected to the exhaust manifold 4 and a low-pressure stage turbocharger 52 connected to the high-pressure stage turbocharger 51. The high-pressure stage turbocharger 51 is disposed to the side of the exhaust manifold 4, and the low-pressure stage turbocharger 52 is disposed above the exhaust manifold 4, so that the exhaust manifold 4 and the two-stage turbocharger 30 can be compactly arranged within a substantially rectangular frame, thereby realizing a compact engine 1. Furthermore, the high-pressure stage exhaust outlet 58 of the high-pressure stage turbocharger 51 and the low-pressure stage exhaust inlet 60 of the low-pressure stage turbocharger 52 are connected via a high-pressure exhaust gas pipe 59, which is an example of a flexible pipe, so that the risk of low-cycle fatigue failure of the high-pressure exhaust gas pipe 59 due to thermal elongation can be reduced.

[0102] In the engine 1, the low-pressure stage turbocharger 52 is fixed to the exhaust side of the cylinder head 2, and the high-pressure stage turbocharger 51 is fixed to the exhaust manifold 4, so the high-pressure stage turbocharger 51 and the low-pressure stage turbocharger 52 constituting the two-stage turbocharger 30 can be allocated and firmly fixed to the robust cylinder head 2 and exhaust manifold 4. Furthermore, the high-pressure stage exhaust outlet 58 of the high-pressure stage turbocharger 51 and the low-pressure stage exhaust inlet 60 of the low-pressure stage turbocharger 52 are connected via a flexible high-pressure exhaust gas piping 59, so that stress applied to the two-stage turbocharger 30 due to thermal expansion of the high-pressure exhaust gas piping 59 can be reduced. This makes it possible to reduce stress applied to the connecting portion between the high-pressure stage turbocharger 51 and the exhaust manifold 4 and stress applied to the connecting portion between the low-pressure stage turbocharger 52 and the cylinder head 2, and to prevent poor connection at these connecting portions and damage to connecting members.

[0103] Furthermore, the cylinder head 2 is provided with a rib 135 inside that extends from the low-pressure stage supercharger mounting portion 131 on the exhaust side toward the intake side (e.g., the right side) opposite the exhaust side, thereby improving the rigidity of the area around the low-pressure stage supercharger mounting portion 131 in the cylinder head 2 and preventing deformation of the cylinder head 2 due to the mounting of the low-pressure stage supercharger 52 to the cylinder head 2.

[0104] The engine 1 also includes an exhaust gas purification device 100 that purifies exhaust gas from the engine 1. An exhaust gas inlet pipe 116 serving as an exhaust inlet of the exhaust gas purification device 100 is disposed near a corner where one of two side surfaces of the cylinder head 2 that intersect with the exhaust side surface intersects with the exhaust side surface, and the low-pressure stage turbocharger 52 is disposed closer to the one side surface when viewed from the exhaust side surface, with a low-pressure stage exhaust outlet 61 of the low-pressure stage turbocharger 52 facing the one side surface. Therefore, the engine 1 can have a short and simple exhaust connecting pipe 119 and exhaust connecting member 120, which are examples of piping that connect the low-pressure stage exhaust outlet 61 of the low-pressure stage turbocharger 52 to the exhaust gas inlet pipe 116 of the exhaust gas purification device 100. This allows the exhaust gas supplied to the exhaust gas purification device 100 to be maintained at a high temperature, preventing a decrease in the regeneration capacity of the exhaust gas purification device 100.

[0105] Furthermore, above the cylinder head 2, a blow-by gas outlet 70 of the blow-by gas reduction device 19 is disposed toward the exhaust side at a position closer to the other side surface opposite to the one side surface of the cylinder head 2, and a low-pressure stage fresh air inlet 63 of the low-pressure stage turbocharger 52 is provided toward the other side surface. Also, the blow-by gas outlet 70 is connected via a return hose 68 to an intake pipe 62 that is connected to the low-pressure stage fresh air inlet 63 of the low-pressure stage turbocharger 52. Therefore, in the engine 1, by disposing both the blow-by gas outlet 70 of the blow-by gas reduction device 19 and the intake pipe 62 that is connected to the low-pressure stage fresh air inlet 63 of the low-pressure stage turbocharger 52 at a position closer to the other side surface of the cylinder head 2, the return hose 68 can be shortened, and measures to prevent the inside of the return hose 68 from freezing are not required.

[0106] As shown in FIGS. 1 to 5 and 11 to 16, the engine 1 includes an exhaust gas purification device 100 mounted above a cylinder head 2 via a support base 121. The support base 121 includes a flat portion 121a on which the exhaust gas purification device 100 is mounted, and multiple legs 121b, 121c, 121d, and 121e that protrude downward from the flat portion 121a and are fixed to the cylinder head 2. The flat portion 121a and the legs 121b, 121c, 121d, and 121e are integrally molded. Furthermore, the spaces between the legs 121b, 121c, 121d, and 121e are formed in an arch shape. Therefore, the integrally molded structure and arch shape ensure the rigidity of the support base 121 while reducing its weight. Furthermore, by forming the support base 121 as an integrally molded part, the number of parts can be reduced. Furthermore, by forming arch-shaped gaps between the multiple legs 121b, 121c, 121d, and 121e, it is possible to prevent heat pools from forming around the legs of the support base 121, thereby preventing heat damage to electronic components such as the exhaust pressure sensor 151, which is an example of a sensor mounted around the legs, and preventing insufficient cooling of cooling components such as the EGR cooler 27.

[0107] The engine 1 is configured such that the exhaust manifold 4 and the intake manifold 3 are allocated and arranged on the exhaust side and the intake side of the opposing cylinder head 2. The support base 121 is arranged above one of the two sides of the cylinder head 2 that intersect with the axial direction of the crankshaft 5, and has legs including an exhaust-side leg 121b fixed to the exhaust side, an intake-side leg 121e fixed to the intake side, and central legs 121c and 121d fixed to the one side. Therefore, the support base 121 can be fixed to a total of three sides of the cylinder head 2: the exhaust side, the intake side, and the one side, improving the support rigidity of the exhaust gas purification device 100. Furthermore, by making the height and size of the arch shapes between the exhaust side leg 121b and the first central leg 121c and between the intake side leg 121e and the second central leg 121d different from each other, or by making the lengths of the exhaust side leg 121b and the intake side leg 121e different from each other, it becomes possible for the support base 121 to cancel out vibrations on the intake side and exhaust side, thereby reducing vibrations of the exhaust gas purification device 100.

[0108] The engine 1 is also configured to include a cooling fan 9 on the other of the two sides of the cylinder head 2. A cooling air passage 148 through which cooling air 149 from the cooling fan 9 flows is formed between the cylinder head cover 18 on the cylinder head 2 and the support base 121. Therefore, the engine 1 can guide the cooling air from the cooling fan 9 to the one side of the cylinder head 2 via the cooling air passage 148, and can appropriately cool the periphery of the one side of the cylinder head 2.

[0109] Furthermore, the engine 1 is configured to include an EGR device 24 that returns a portion of the exhaust gas discharged from the exhaust manifold 4 to the intake manifold 3 as EGR gas, an EGR cooler 27 that cools the EGR gas, and an exhaust pressure sensor 151 that detects the exhaust gas pressure in the exhaust manifold 4. The EGR cooler 27 and the exhaust pressure sensor 151 are attached to the one side surface of the cylinder head 2. Therefore, cooling air 149 that is guided from the cooling fan 9 to the one side surface through a cooling air passage 148 can promote cooling of the EGR cooler 27 and prevent thermal damage to the exhaust pressure sensor 151.

[0110] Furthermore, in the engine 1, the intake manifold 3 is integrally molded on the intake side surface of the cylinder head 2, and the intake-side leg 121e is fixed to the upper surface of the intake manifold 3, so that the intake-side leg 121e can be placed and firmly fixed on the sturdy intake manifold 3. Furthermore, since the bolts for fixing the intake-side leg 121e to the intake manifold 3 can be tightened or loosened from above the cylinder head 2, the installation and removal of the support base 121 can be performed with the EGR device 24, which is arranged laterally on the intake side surface of the cylinder head 2, attached to the intake manifold 3, improving the ease of assembly and maintenance of the engine 1.

[0111] As shown in FIGS. 1 to 5 and 17 to 21 , the engine 1 includes an exhaust manifold 4 provided on the exhaust side of the cylinder head 2, and an exhaust pressure sensor 151 that detects the exhaust gas pressure in the exhaust manifold 4. The exhaust pressure sensor 151 is attached to the cylinder head 2, and the exhaust manifold 4 and the exhaust pressure sensor 151 are connected via an exhaust pressure bypass path 153 provided in the cylinder head 2 and an exhaust pressure detection pipe 154 that connects the exhaust pressure bypass path 153 and the exhaust manifold 4. This allows heat from the exhaust pressure detection pipe 154 to be dispersed by the cylinder head 2. Therefore, the engine 1 can shorten the length of the exhaust pressure detection pipe 154 while preventing failure or malfunction of the exhaust pressure sensor 151 caused by heat from the exhaust manifold 4 and the exhaust pressure detection pipe 154. Furthermore, shortening the length of the exhaust pressure detection pipe 154 improves the reliability of the exhaust pressure detection pipe 154 and simplifies the arrangement of the exhaust pressure detection pipe 154, thereby reducing the number of design steps and improving the manufacturability and assembly of the engine 1. Furthermore, in the engine 1, the cooling water passage 38 is provided in the cylinder head 2 near the exhaust pressure bypass path 153, so the gas temperature in the exhaust pressure bypass path 153 can be efficiently reduced. Therefore, the engine 1 can shorten the exhaust pressure bypass path 153 while keeping the heat transferred from the gas in the exhaust pressure bypass path 153 to the exhaust pressure sensor 151 within an allowable range, making it easy to form the exhaust pressure bypass path 153 in the cylinder head 2.

[0112] The engine 1 is configured to include an EGR device 24 that returns a portion of the exhaust gas discharged from the exhaust manifold 4 to the intake manifold 3 as EGR gas, and an EGR cooler 27 that cools the EGR gas. The cylinder head 2 is equipped with a pair of EGR cooler connectors 33, 34 that protrude from one of two side surfaces of the cylinder head 2 that intersect with the exhaust side surface, and a cooling water passage 38 passes through one of the EGR cooler connectors 33 and connects to the EGR cooler 37, and an exhaust pressure bypass path 153 passes through the EGR cooler connector 33. Therefore, the engine 1 can efficiently cool the gas in the exhaust pressure bypass path 153, and can prevent breakdowns or malfunctions of the exhaust pressure sensor 151 caused by heat.

[0113] Furthermore, the exhaust pressure sensor 151 is attached to an exhaust pressure sensor attachment portion 152 that protrudes from the one side surface of the cylinder head 2 between the pair of EGR cooler connecting portions 33, 34. Therefore, the engine 1 can efficiently cool the exhaust pressure sensor 151, and prevent breakdowns or malfunctions of the exhaust pressure sensor 151 caused by heat.

[0114] The configuration of each part in the present invention is not limited to the illustrated embodiment, and various modifications are possible within the scope of the present invention.

[0115] (Addendum) (Appendix 1) An engine system including an exhaust manifold provided on an exhaust side, which is one side of a cylinder head, and a turbocharger driven by exhaust gas discharged from the exhaust manifold, the turbocharger is a two-stage turbocharger including a high-pressure stage turbocharger connected to the exhaust manifold and a low-pressure stage turbocharger connected to the high-pressure stage turbocharger, an exhaust outlet of the high-pressure stage turbocharger and an exhaust inlet of the low-pressure stage turbocharger are connected to each other; and the high-pressure stage turbocharger is fixed to the exhaust manifold and disposed to the side of the exhaust manifold, and the low-pressure stage turbocharger is fixed to the exhaust side surface of the cylinder head and disposed above the exhaust manifold.

[0116] (Appendix 2) 2. The engine device according to claim 1, wherein the cylinder head includes a rib disposed therein, the rib extending from a mounting portion of the low-pressure stage turbocharger on the exhaust side surface toward an intake side surface opposite the exhaust side surface.

[0117] (Appendix 3) An exhaust gas purification device that purifies exhaust gas from the exhaust manifold, an exhaust inlet of the exhaust gas purification device is disposed near a corner where one of two side surfaces of the cylinder head intersects with the exhaust-side surface, and the exhaust-side surface intersects with the one side surface, The engine device according to Appendix 1, wherein the low-pressure stage turbocharger is disposed closer to the one side surface when viewed from the exhaust side surface side, and an exhaust outlet of the low-pressure stage turbocharger is provided facing the one side surface side.

[0118] (Appendix 4) 4. The engine apparatus according to claim 3, wherein a blow-by gas outlet of a blow-by gas reduction device is disposed above the cylinder head at a position closer to the other side surface opposite to the one side surface of the cylinder head, facing the exhaust side surface, a fresh air inlet of the low-pressure stage turbocharger is provided facing the other side surface, and the blow-by gas outlet is connected via a reduction hose to an air intake pipe connected to the fresh air inlet of the low-pressure stage turbocharger.

[0119] (Appendix 5) 5. The engine device according to claim 1, wherein the low-pressure stage turbocharger has a fresh air inlet provided at a position closer to the cylinder head than a fresh air supply port.

[0120] (Appendix 6) 6. The engine device according to claim 5, wherein the fresh air supply port of the low-pressure stage turbocharger and the fresh air inlet of the high-pressure stage turbocharger are open in the same direction.

[0121] (Appendix 7) 7. The engine device according to any one of claims 1 to 6, wherein an exhaust outlet of the high-pressure stage turbocharger and an exhaust inlet of the low-pressure stage turbocharger are connected via a flexible pipe.

[0122] In the engine device described in Appendix 1, a small-capacity high-pressure stage turbocharger is disposed to the side of the exhaust manifold, and a high-capacity low-pressure stage turbocharger is disposed above the exhaust manifold, so the exhaust manifold and the two-stage turbocharger can be compactly disposed within a substantially rectangular frame, thereby achieving a compact engine device. Furthermore, if the exhaust outlet of the high-pressure stage turbocharger and the exhaust inlet of the low-pressure stage turbocharger are connected via flexible piping, the risk of low-cycle fatigue failure of the piping due to thermal elongation can be reduced. Furthermore, since the low-pressure stage turbocharger is fixed to the exhaust side of the cylinder head and the high-pressure stage turbocharger is fixed to the exhaust manifold, the high-pressure stage turbocharger and the low-pressure stage turbocharger constituting the two-stage turbocharger can be firmly fixed by dividing them into a robust cylinder head and exhaust manifold. Furthermore, if the exhaust outlet of the high-pressure stage turbocharger and the exhaust inlet of the low-pressure stage turbocharger are connected via flexible piping, stress applied to the two-stage turbocharger due to thermal elongation of the piping can be reduced. This reduces the stress applied to the connection between the high-pressure stage turbocharger and the exhaust manifold, and the stress applied to the connection between the low-pressure stage turbocharger and the cylinder head, preventing poor connection at these connection points and damage to the connecting members.

[0123] Furthermore, the engine device of the present invention is an engine device including an exhaust manifold and a turbocharger, wherein the turbocharger is configured as a two-stage turbocharger consisting of a high-pressure stage turbocharger and a low-pressure stage turbocharger, the high-pressure stage turbocharger is attached to the exhaust manifold, the low-pressure stage turbocharger is disposed above the exhaust manifold, and the high-pressure stage turbocharger and the low-pressure stage turbocharger are connected to each other.

[0124] In the engine apparatus of the present invention, the high-pressure stage turbocharger may be disposed in the vicinity of the exhaust manifold.

[0125] In the engine device of the present invention, the low-pressure stage turbocharger may be arranged closer to the exhaust outlet of the high-pressure stage turbocharger than the high-pressure stage turbocharger.

[0126] Moreover, the engine system of the present invention may further include an exhaust gas purification device that purifies exhaust gas from the exhaust manifold, and an exhaust inlet of the exhaust gas purification device may be arranged closer to the exhaust outlet than the low-pressure stage turbocharger.

[0127] The engine device of the present invention allows the exhaust manifold and the two-stage turbocharger to be arranged compactly.

[0128] An engine system according to one aspect is an engine system including a turbocharger, the turbocharger being a two-stage turbocharger including a high-pressure stage turbocharger and a low-pressure stage turbocharger, wherein an exhaust outlet of the high-pressure stage turbocharger and an exhaust inlet of the low-pressure stage turbocharger are connected via a flexible pipe.

[0129] An engine device according to one embodiment is an engine device including a turbocharger, the turbocharger being a two-stage turbocharger consisting of a high-pressure stage turbocharger and a low-pressure stage turbocharger. An exhaust outlet of the high-pressure stage turbocharger and an exhaust inlet of the low-pressure stage turbocharger are connected via a pipe, and the pipe has a substantially L-shaped bent portion. The bent portion is directly connected to the low-pressure stage turbocharger. [Explanation of symbols]

[0130] 1 Engine (engine equipment) 2. Cylinder head 3. Intake manifold 4 exhaust manifold 30 Two-stage turbocharger 51 High-pressure stage turbocharger 52 Low-pressure stage turbocharger 59 High-pressure exhaust gas piping (flexible piping) 131 Low pressure stage turbocharger mounting section 135 Ribs 100 Exhaust gas purification device 116 Exhaust gas inlet pipe (exhaust inlet of exhaust gas purification device) 19 Blow-by gas reduction device 70 Blow-by gas outlet 63 Low pressure stage fresh air inlet (fresh air inlet for low pressure stage turbocharger) 62 Air supply pipe 68 Reduction Hose

Claims

1. An engine device equipped with a supercharger, the turbocharger is a two-stage turbocharger consisting of a high-pressure stage turbocharger and a low-pressure stage turbocharger, a high-pressure stage fresh air inlet of the high-pressure stage turbocharger and a low-pressure stage fresh air supply port of the low-pressure stage turbocharger are connected via a low-pressure fresh air passage pipe, The low-pressure fresh air passage pipe has a curved portion. Engine equipment.

2. The low-pressure fresh air passage pipe includes a substantially U-shaped portion. The engine device according to claim 1 .

3. the low-pressure fresh air passage pipe includes a straight portion extending along the axial direction of the turbine shaft; The engine device according to claim 1 or 2.

4. The low-pressure fresh air passage pipe includes a metal pipe and a resin pipe. The engine device according to any one of claims 1 to 3.

5. the low-pressure stage turbocharger is disposed closer to an exhaust outlet of the high-pressure stage turbocharger than the high-pressure stage turbocharger, The engine device according to any one of claims 1 to 4.

6. The low-pressure stage turbocharger is disposed above the high-pressure stage turbocharger. The engine device according to any one of claims 1 to 5.

7. The low-pressure stage turbocharger is disposed above the exhaust manifold. The engine device according to any one of claims 1 to 6.

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