Engine System

Abstract

To provide an engine system which can easily and efficiently discharge blowby gas from a crankcase.SOLUTION: An engine system in which blowby gas having a specific gravity with respect to air of smaller than 1 can be produced comprises a cylinder block 5. The cylinder block 5 includes a cylinder 51 and a crankcase 52 which are aligned in a vertical direction D2, the crankcase 52 being located below the cylinder 51. A ventilation port 502 leading to a ventilation passage 503 which connects an internal space Sp1 of the crankcase 52 and an external space of the cylinder block 5 is opened in an internal peripheral face 501 of the cylinder block 5. The ventilation port 502 is positioned on an upper side relative to a center C1 in the vertical direction D2 in the crankcase 52.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to an engine system in which blow-by gas having a specific gravity of less than 1 based on air may be generated. [Background technology]

[0002] As a related art, there is known an engine system (internal combustion engine) that takes measures against blow-by gas leaking from the combustion chamber into the crank chamber (crankcase) (see, for example, Patent Document 1). In the engine system according to the related art, an intake port is provided on the inner surface of the crank chamber to take in blow-by gas from the crank chamber. The intake port is connected to a blow-by gas passage by an intake passage, and the engine system is configured to return the blow-by gas to the combustion chamber through the blow-by gas passage via the intake system. Here, the intake port (blow-by gas intake portion) is positioned below the crank journal, thereby avoiding interference between the blow-by gas intake portion and the crank journal of the crankshaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-127894 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in an engine system that uses a gaseous fuel such as hydrogen whose specific gravity is less than 1, the blow-by gas that leaks into the crankcase tends to accumulate above the crankcase. Therefore, if the intake port is located below the crank journal as in the related art, the blow-by gas may not be efficiently discharged from the crankcase.

[0005] An object of the present disclosure is to provide an engine system that can easily and efficiently discharge blow-by gas from the crankcase. [Means for solving the problem]

[0006] An engine system according to one embodiment of the present disclosure is an engine system in which blow-by gas having a specific gravity of less than 1 with respect to air may be generated, and the engine system includes a cylinder block. The cylinder block includes cylinders and a crank chamber that are aligned in the vertical direction, and the crank chamber is located below the cylinders. A ventilation port that connects to a ventilation passage that connects an internal space of the crank chamber and an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block. The ventilation port is located above the vertical center of the crank chamber. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide an engine system that can easily and efficiently discharge blow-by gas from the crank chamber. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a system diagram showing a schematic configuration of an engine system according to the first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram showing a schematic configuration of a ship equipped with the engine system according to the first embodiment. [Diagram 3] FIG. 3 is a schematic perspective view of an engine body of the engine system according to the first embodiment. [Figure 4] FIG. 4 is a schematic left side view of the engine body of the engine system according to the first embodiment. [Diagram 5] FIG. 5 is a schematic plan view of the engine body of the engine system according to the first embodiment. [Figure 6] FIG. 6 is a schematic front view of the engine body of the engine system according to the first embodiment. [Figure 7]FIG. 7 is a schematic diagram of a main part of the engine body of the engine system according to the first embodiment, with a part cut away. [Figure 8] FIG. 8 is a schematic explanatory diagram showing the flow of blow-by gas in the engine system according to the first embodiment. [Figure 9] FIG. 9 is a schematic diagram showing a configuration of a ventilation passage of the engine system according to the first embodiment. [Figure 10] FIG. 10 is a schematic left side view of the engine body of the engine system according to the first embodiment. [Figure 11] FIG. 11 is a schematic diagram illustrating the positional relationship between the cylinders, the crank chamber, and the cam chamber in the cylinder block of the engine system according to the first embodiment. [Figure 12] FIG. 12 is a schematic diagram showing a positional relationship between the cylinders, the crank chamber, the cam chamber, and the intake manifold in the cylinder block of the engine system according to the first embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a modified example of the positional relationship between the ventilation opening and the gas inlet of the engine system according to the first embodiment and the air flow forming unit. [Figure 14] FIG. 14 is an enlarged schematic cross-sectional view of the periphery of a piston of the engine system according to the first embodiment. [Figure 15] FIG. 15 is an enlarged schematic cross-sectional view of the periphery of a piston of the engine system according to the first embodiment. [Figure 16] FIG. 16 is an enlarged schematic cross-sectional view of the periphery of a cylinder of another example of the engine system according to the first embodiment. [Figure 17] FIG. 17 is a schematic view of a main part of the engine body of the engine system according to the first embodiment, with a part cut away. [Figure 18] FIG. 18 is a schematic perspective view showing an internal configuration of the cylinder head of the engine system according to the first embodiment. [Figure 19] FIG. 19 is a schematic plan view showing the internal configuration of the cylinder head of the engine system according to the first embodiment. [Figure 20]FIG. 20 is a schematic cross-sectional view showing a configuration around an intake port of the engine system according to the first embodiment. [Figure 21] FIG. 21 is a schematic cross-sectional view showing a configuration around an intake port of the engine system according to the first embodiment. [Figure 22] FIG. 22 is a timing chart showing an example of a control operation of the engine system according to the first embodiment. [Diagram 23] FIG. 23 is a flowchart showing an example of a control operation of the engine system according to the first embodiment. [Figure 24] FIG. 24 is a flowchart showing an example of a control operation of the engine system according to the first embodiment. [Diagram 25] FIG. 25 is a schematic diagram illustrating the positional relationship between the cylinders, the crank chamber, and the cam chamber in an engine system according to a modified example of the first embodiment. [Figure 26] FIG. 26 is a schematic view of a main part of an engine body of an engine system according to the second embodiment, with a part cut away. [Figure 27] FIG. 27 is a schematic explanatory diagram showing the flow of blow-by gas in the engine system according to the second embodiment. [Figure 28] FIG. 28 is a schematic left side view of an engine body of an engine system according to the third embodiment. [Figure 29] FIG. 29 is a schematic cross-sectional view showing a configuration around an intake port of an engine system according to the fourth embodiment. [Diagram 30] FIG. 30 is a schematic cross-sectional view showing a configuration around an intake port of an engine system according to a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. The following embodiment is an example of the present disclosure, and is not intended to limit the technical scope of the present disclosure. All drawings referred to in this disclosure are schematic drawings, and the ratios of sizes and thicknesses of each component in the drawings do not necessarily reflect the actual dimensional ratios.

[0010] (Embodiment 1) [1] Overall structure First, the overall configuration of an engine system 1 according to this embodiment will be described with reference to Figures 1 to 6. In Figure 1, the configuration of each part of the engine system 1 is shown typically, and electrical connections are indicated by dashed arrows (pointing in the direction of electrical signal flow).

[0011] As shown in Fig. 1, an engine system 1 according to this embodiment includes an engine body 2 which is a main component of the engine system 1. The "engine" referred to here is a heat engine that burns fuel to generate mechanical energy (power), and includes an internal combustion engine which is a prime mover that converts thermal energy into mechanical energy by burning fuel inside the engine and using combustion gas as a working gas. In other words, the engine body 2 generates power (mechanical energy) by using the fuel supplied thereto.

[0012] The engine body 2 according to this embodiment is a reciprocating engine that converts the reciprocating motion of a piston 21 (see FIG. 1) into rotational motion and outputs rotational force as motive power. In particular, in this embodiment, a hydrogen fueled internal combustion engine that uses at least hydrogen as fuel, that is, a hydrogen fueled reciprocating engine, will be described as an example of the engine body 2.

[0013] In this embodiment, as an example, an engine system 1 used in a boat 10 will be described as shown in FIG. 1. The engine system 1 is mounted on a hull 100 of the boat 10. That is, the boat 10 according to this embodiment includes the engine system 1 and the hull 100. The engine system 1 is used as a drive source for generating a propulsive force for propelling the hull 100. In this embodiment, the engine system 1 can also be used as a drive source for driving a generator 101 (see FIG. 1) that generates electric energy (electric power) used in the hull 100. That is, the engine system 1 is used as a drive source for generating a propulsive force for the hull 100 or for driving the generator 101. The electric energy generated by the generator 101 may be stored in a power storage device.

[0014] The boat 10 is a mobile body that navigates (sails) on water such as the sea, a lake, or a river. In this embodiment, as an example, the boat 10 is a "pleasure boat", which is a small boat mainly used for sports or recreation on the sea. As shown in FIG. 2, a hull 100 of the boat 10 has a propeller 103 and a propeller shaft 104. The propeller 103 is connected to an engine body 2 of the engine system 1 by the propeller shaft 104. The boat 10 receives power generated by the engine body 2 to rotate the propeller 103 about the propeller shaft 104, thereby generating a propulsive force for moving the hull 100 forward or backward.

[0015] The engine body 2 is mounted, for example, via a base on the inner bottom plate of the engine room of the hull 100. Here, as shown in Fig. 2, the engine body 2 is disposed in a posture inclined by an inclination angle θ1 to one side in the traveling direction of the hull 100 with respect to the horizontal plane when the hull 100 is anchored on the water. Specifically, the engine body 2 is disposed in a "front-up" posture in which the rotation axis Ax1 (see Fig. 3) of the crankshaft 22 (see Fig. 1) is aligned with the traveling direction of the hull 100 and inclined so as to become higher toward the forward traveling side of the traveling direction of the hull 100 (the side moving forward when moving forward).

[0016] In the present embodiment, the vessel 10 is configured to operate in response to the operation (including remote operation) of a person (pilot), and is particularly a manned type on which a person who is a pilot can board. For this reason, the vessel 10 has an operation panel 102 (see FIG. 1) on the hull 100 that accepts the operation of the pilot, and the engine control unit 20 of the engine system 1 drives the engine body 2 in response to the operation of the operation panel 102. As a result, the vessel 10 can drive the engine body 2 in response to the operation of the pilot, and rotate the propeller 103 to move the vessel 100 forward or backward. The vessel 100 further includes various onboard facilities including a steering mechanism, a display device, a communication device, and a lighting system. In addition, when the engine system 1 is used to drive the generator 101, the engine control unit 20 drives the engine body 2 in response to the control state (generator load) of the generator 101 or the operation (including remote operation) of the person (pilot), etc.

[0017] The engine system 1 according to this embodiment is a so-called dual fuel engine (DF engine) that can be used in both a premixed combustion system in which gaseous fuel is mixed with air and then introduced into the combustion chamber 50, and a diffusion combustion system in which liquid fuel is injected into the combustion chamber 50 and burned. Here, the gaseous fuel is, for example, hydrogen, and the liquid fuel is, for example, a fossil fuel (diesel or gasoline, etc.). More specifically, by using diesel fuel as the liquid fuel, the engine system 1 can be used in both a gas mode in which hydrogen is used as fuel, and a diesel mode in which diesel fuel is used as fuel. Here, in the gas mode, a small amount of liquid fuel (diesel, etc.) may be further used as ignition fuel.

[0018] In this embodiment, for convenience of explanation, as shown in FIG. 3, the direction along the rotation axis Ax1 of the crankshaft 22 is defined as the output axis direction D1. Furthermore, as shown in FIG. 3, the direction perpendicular to the output axis direction D1 and along the vertical direction when the engine body 2 is in a usable state is defined as the up-down direction D2, and the direction perpendicular to both the output axis direction D1 and the up-down direction D2 is defined as the width direction D3. Here, one side of the output axis direction D1 is defined as the "front" and the other side is defined as the "rear", and the side of the crankshaft 22 that is connected to the propeller shaft 104 (the side where the flywheel is arranged) is defined as the rear. Similarly, one side of the width direction D3 is defined as the "left" and the other side is defined as the "right". Furthermore, in the up-down direction D2, the side where the cylinder 51 (see FIG. 1) is located as viewed from the crank chamber 52 (see FIG. 1) described later is defined as the "upper" and the opposite side is defined as the "lower".

[0019] In other words, all directions used in this embodiment are directions defined based on the rotation axis Ax1 of the crankshaft 22. Here, as described above, the engine body 2 is disposed in a "front-up" position inclined by the inclination angle θ1 with respect to the horizontal plane while aligning the rotation axis Ax1 of the crankshaft 22 along the traveling direction of the hull 100. Therefore, the imaginary line extending in the up-down direction D2 is inclined by the inclination angle θ1 (towards the rearward direction) with respect to the vertical direction when the engine body 2 is mounted on the hull 100. However, none of these directions are intended to limit the direction of use of the engine body 2 (direction during use).

[0020] A crankshaft 22 as an engine output shaft protrudes rearward from the rear end of the engine body 2. A propeller shaft 104 is connected to the crankshaft 22 via a reduction gear. When the engine body 2 is driven and the crankshaft 22 rotates about the rotation axis Ax1, a propeller 103 connected to the propeller shaft 104 rotates, generating thrust for the hull 100. When the engine system 1 is used to drive a generator 101, the generator 101 is connected to the crankshaft 22. In this case, when the engine body 2 is driven and the crankshaft 22 rotates about the rotation axis Ax1, the generator 101 is driven to generate electric energy.

[0021] The engine system 1 according to this embodiment is a dual fuel engine as described above. Therefore, the engine system 1 can drive the engine body 2 by selecting either a premixed combustion method (gas mode) in which gaseous fuel (hydrogen) is mixed with air and burned, or a diffusion combustion method (diesel mode) in which liquid fuel (diesel) is diffused and burned. Therefore, the engine body 2 is configured to be able to supply two types of fuel, gaseous fuel (hydrogen in this case) and liquid fuel (diesel in this case) from outside the engine body 2.

[0022] That is, as shown in FIG. 1, the engine system 1 includes a fuel supply device 3 for supplying gas fuel, and a liquid fuel supply device 4 for supplying liquid fuel.

[0023] The fuel supply device 3 has an injection unit 31, a liquefied hydrogen tank 32, a fuel supply passage 33, a vaporizer 34, a pressure regulating valve 35, and a gas admission valve 36. The liquefied hydrogen tank 32 is a fuel tank that stores liquefied gaseous fuel (here, hydrogen), and is connected to the gas admission valve 36 through the fuel supply passage 33. The vaporizer 34 and the pressure regulating valve 35 are inserted into the fuel supply passage 33 in this order from the upstream side: the vaporizer 34, the pressure regulating valve 35. The vaporizer 34 vaporizes the liquefied hydrogen. The pressure regulating valve 35 is a gas valve unit that adjusts the amount of gaseous fuel supplied to the engine body 2. The gas admission valve 36 injects the gaseous fuel supplied through the fuel supply passage 33 from the nozzle-shaped (cylindrical) injection unit 31 into the engine body 2.

[0024] The liquid fuel supply device 4 has a liquid fuel injection unit 41. The liquid fuel supply device 4 is connected to a liquid fuel tank via a liquid fuel supply path. The liquid fuel supply device 4 injects the liquid fuel supplied through the liquid fuel supply path into the engine body 2 from the nozzle-shaped (cylindrical) liquid fuel injection unit 41.

[0025] Here, the injection unit 31 that injects gaseous fuel is disposed at a position facing the inside of an intake port 61 that is connected to the combustion chamber 50, and the liquid fuel injection unit 41 that injects liquid fuel is disposed at a position facing the combustion chamber 50. As a result, the injection unit 31 injects gaseous fuel into the intake port 61 and mixes the gaseous fuel with air before allowing it to flow into the combustion chamber 50. On the other hand, the liquid fuel injection unit 41 injects liquid fuel directly into the combustion chamber 50. In other words, as a fuel supply method, a port injection method is adopted for gaseous fuel, and a direct injection method is adopted for liquid fuel.

[0026] As shown in Figures 3 and 4, the engine body 2 is configured by assembling a cylinder head 6 onto a cylinder block 5. The cylinder block 5 has a cylinder 51 and a crank chamber 52. The cylinder head 6 has an intake port 61 and an exhaust port 62. As shown in Figure 3, a crankshaft 22 is rotatably supported at the bottom of the cylinder block 5 with a rotation axis Ax1 facing an output shaft direction D1.

[0027] As shown in Fig. 5, the cylinder block 5 has a plurality of cylinders 51 (six in this embodiment) arranged in a row (in series) along the rotation axis Ax1 of the crankshaft 22. That is, in this embodiment, the engine body 2 is an in-line multi-cylinder engine (in-line six-cylinder engine) in which the cylinders 51 are arranged in series. The output axis direction D1 along the rotation axis Ax1 of the crankshaft 22 coincides with the arrangement direction of the plurality of cylinders 51. As shown in Fig. 1, a piston 21 is accommodated in each cylinder 51 so as to be slidable in the up-down direction D2, that is, so as to be able to reciprocate. The piston 21 is connected to the crankshaft 22 via a connecting rod 24.

[0028] A plurality of cylinder heads 6 are provided in one-to-one correspondence with a plurality of (six in this embodiment) cylinders 51. The plurality of (six in this embodiment) cylinder heads 6 are fixed above one cylinder block 5 so as to cover the cylinders 51 from above. That is, the plurality of cylinder heads 6 are arranged in a line in the output shaft direction D1. As shown in FIG. 1, within the internal space of each cylinder 51, a space surrounded by the upper surface of the piston 21 and the lower surface of the cylinder head 6 functions as a combustion chamber 50. That is, as the piston 21 reciprocates in the vertical direction D2, the combustion chamber 50 alternately expands and contracts.

[0029] The head covers 71 are arranged on the cylinder head 6 in a line in the output shaft direction D1 so as to correspond one-to-one to the multiple (six in this embodiment) cylinders 51. A valve mechanism including a push rod and a rocker arm for operating the intake valve 72 and the exhaust valve 73 is housed inside each head cover 71. The intake valve 72 opens and closes an opening of the intake port 61 formed in the cylinder head 6 that is connected to the combustion chamber 50. The exhaust valve 73 opens and closes an opening of the exhaust port 62 formed in the cylinder head 6 that is connected to the combustion chamber 50. With this, when the intake valve 72 is open, air (intake air) can be taken in from the intake port 61 into the combustion chamber 50. When the exhaust valve 73 is open, exhaust air from the combustion chamber 50 can be discharged to the exhaust port 62.

[0030] The intake valve 72 and the exhaust valve 73 are driven to open and close by a camshaft 23 (see FIG. 1). As shown in FIGS. 1 and 6, the camshaft 23 is housed in a cam chamber 53 arranged to the left of the cylinder 51 in the cylinder block 5. The cam chamber 53 is formed in the cylinder block 5 integrally with the cylinder 51, the crank chamber 52, etc. The cam chamber 53 extends in the output axial direction D1, and rotatably houses the camshaft 23, which also extends in the output axial direction D1. The camshaft 23 rotates about a rotation axis along the output axial direction D1 in conjunction with the rotation of the crankshaft 22, and drives the intake valve 72 and the exhaust valve 73 to open and close.

[0031] A side cover 74 is attached to a portion above the cylinder block 5 and to the left of the cylinder head 6. That is, a step is formed at the upper portion of the left side surface of the engine body 2, and the side cover 74 is attached so as to cover this step portion. In the space covered by the side cover 74, a liquid fuel supply rail pipe, a main fuel injection pump, a pilot fuel supply rail pipe, and the like are arranged. The liquid fuel supply rail pipe is arranged to extend in the output axial direction D1, and distributes and supplies liquid fuel to the combustion chamber 50 of each cylinder 51 during combustion in the diffusion combustion method. The liquid fuel supplied to the liquid fuel supply rail pipe is distributed to the main fuel injection pump provided corresponding to each cylinder 51, and the liquid fuel supplied from the main fuel injection pump is injected into the combustion chamber 50 from the liquid fuel injection unit 41. The pilot fuel supply rail pipe distributes and supplies pilot fuel to the combustion chamber 50 of each cylinder 51 for the purpose of igniting gaseous fuel during combustion in the premixed combustion method.

[0032] 1 and 6, an intake manifold 54 is disposed to the right of the cylinders 51 in the cylinder block 5 to distribute and supply air (intake air) from outside the engine body 2 to the combustion chambers 50 of the cylinders 51. The intake manifold 54 is formed in the cylinder block 5 integrally with the cylinders 51 and the crank chamber 52. The intake manifold 54 extends in the output axial direction D1 and is connected to a plurality of intake ports 61 formed in the plurality of cylinder heads 6. As a result, air is distributed from the intake manifold 54 to the plurality of intake ports 61. In other words, the intake manifold 54 communicates with the combustion chambers 50 of the cylinders 51 through the intake ports 61.

[0033] As shown in Fig. 6, an exhaust manifold 75 is disposed in the upper right of the cylinder head 6 for collecting exhaust gas generated by combustion in the combustion chambers 50 of each cylinder 51 and discharging it to the outside of the engine body 2. The exhaust manifold 75 extends in the output axial direction D1 and is connected to a plurality of exhaust ports 62 formed in the plurality of cylinder heads 6. As a result, exhaust gas from the plurality of exhaust ports 62 is collected in the exhaust manifold 75. In other words, the exhaust manifold 75 is connected to the combustion chambers 50 of each cylinder 51 through the exhaust ports 62.

[0034] Here, the main components constituting the engine body 2, such as the cylinder block 5, the cylinder head 6, and the piston 21, are made of metal materials, such as aluminum alloys and cast iron. These main components have the desired durability (including rigidity and wear resistance) and relatively good thermal conductivity.

[0035] According to the above configuration, when the engine body 2 is driven in the diffusion combustion system, liquid fuel is injected from the liquid fuel injection section 41 into the combustion chamber 50 at an appropriate timing when the air supplied to each cylinder 51 from the intake manifold 54 is compressed by the sliding of the piston 21. When the liquid fuel is injected into the combustion chamber 50, the piston 21 reciprocates within the cylinder 51 by the propulsive force obtained from the explosion generated in the combustion chamber 50, and the reciprocating motion of the piston 21 is converted into the rotational motion of the crankshaft 22 via the connecting rod 24. As a result, the engine body 2 outputs the rotational force of the crankshaft 22 as power (mechanical energy).

[0036] On the other hand, when the engine body 2 is driven in the premixed combustion system, the gaseous fuel supplied from the liquefied hydrogen tank 32 through the fuel supply passage 33 is injected from the injection unit 31 into the intake port 61. As a result, the air supplied from the intake manifold 54 to the intake port 61 and the gaseous fuel are mixed in the intake port 61. Therefore, a mixture of air and gaseous fuel is introduced from the intake port 61 to each cylinder 51, and at an appropriate timing when the mixture is compressed by the sliding of the piston 21, a small amount of pilot fuel is injected into the combustion chamber 50, thereby igniting the gaseous fuel. The piston 21 reciprocates in the cylinder 51 by the propulsive force obtained from the explosion generated in the combustion chamber 50, and the reciprocating motion of the piston 21 is converted into the rotational motion of the crankshaft 22 via the connecting rod 24. As a result, the engine body 2 outputs the rotational force of the crankshaft 22 as power (mechanical energy).

[0037] Regardless of whether the diffusion combustion method or the premixed combustion method is used, the exhaust gas generated by combustion (explosion) in the combustion chamber 50 is pushed out of the cylinder 51 by the movement of the piston 21, collected in the exhaust manifold 75 through the exhaust port 62, and then discharged outside the engine body 2.

[0038] Moreover, the engine system 1 according to this embodiment is a supercharged engine including a supercharger 8 (see FIG. 1) in addition to the engine body 2. The supercharger 8 is disposed above the front part of the engine body 2, as shown in FIGS.

[0039] As shown in FIG. 1, the turbocharger 8 has an intake side turbine 81 and an exhaust side turbine 82. The intake side turbine 81 is disposed on an intake passage 83 for taking in air into the intake manifold 54. The exhaust side turbine 82 is disposed on an exhaust passage 84 connected to the exhaust manifold 75. The exhaust side turbine 82 is connected to the intake side turbine 81, and when the exhaust side turbine 82 is rotated by the flow of air (exhaust) discharged through the exhaust passage 84, the intake side turbine 81 is rotated. When the intake side turbine 81 rotates, the air (intake air) taken in from the intake passage 83 is compressed and sent to the intake manifold 54 through the intercooler 85. As shown in FIG. 6, the intercooler 85 is disposed along the front end surface of the engine body 2, and cools the air (intake air) compressed by the turbocharger 8. The thick arrows in FIG. 1 represent the flow (airflow) of air (including intake air and exhaust air).

[0040] Incidentally, the engine system 1 according to this embodiment further includes an engine control unit 20, an in-cylinder pressure sensor 76, and an engine speed sensor 77, as shown in FIG. 1, in addition to the engine body 2 (and the turbocharger 8) configured as described above.

[0041] The engine control unit 20 mainly comprises a computer system having one or more processors such as a CPU (Central Processing Unit) and one or more memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and executes various processes (information processing). A program (engine control program) for causing the one or more processors to execute an engine control method is recorded in the one or more memories in the engine control unit 20. The engine control unit 20 outputs control signals (electrical signals) to the pressure regulating valve 35, the gas admission valve 36, the liquid fuel injection unit 41, etc., and controls the pressure regulating valve 35, the gas admission valve 36, the liquid fuel injection unit 41, etc. As a result, the engine control unit 20 can control the engine body 2 so as to adjust the output (mainly the rotation speed) of the engine body 2 to an arbitrary value.

[0042] The in-cylinder pressure sensor 76 is disposed at a position facing the combustion chamber 50 of each cylinder 51, measures the pressure inside the combustion chamber 50, and outputs an electric signal corresponding to the measured value (pressure) to the engine control unit 20. The rotation speed sensor 77 measures the rotation speed (and rotation angle) of the crankshaft 22, and outputs an electric signal corresponding to the measured value (rotation speed) to the engine control unit 20.

[0043] [2] Definition In the present disclosure, the term "blow-by gas" refers to the gas leaked from the cylinder 51 (combustion chamber 50) to the crank chamber 52 through a gap between the inner peripheral surface of the cylinder 51 and the outer peripheral surface of the piston 21, among the combustion gas (exhaust gas) and unburned gas that have become high pressure during the compression stroke or combustion stroke of the engine body 2. In other words, the term "blow-by gas" includes "compression leakage gas" that is formed when the air-fuel mixture in the combustion chamber 50 that has become high pressure during the compression stroke leaks into the crank chamber 52. In other words, when the unburned gas in the combustion chamber 50 exceeds the sealing capacity of the piston ring (compression ring) that ensures airtightness between the cylinder 51 and the piston 21, the unburned gas in the combustion chamber 50 may leak into the crank chamber 52 as blow-by gas.

[0044] In this disclosure, "specific gravity" means the ratio of the density of a substance to the density of a reference substance, and the specific gravity of a gas is expressed as the ratio of the density of the gas to that of air as a reference substance at the same temperature and pressure. Therefore, if the specific gravity of the gas blow-by gas is smaller than "1", the mass of the blow-by gas will be smaller (i.e., lighter) than the same volume of air (as the blow-by gas) at the same temperature and pressure as the blow-by gas. Conversely, if the specific gravity of the gas blow-by gas is larger than "1", the mass of the blow-by gas will be larger (i.e., heavier) than the same volume of air (as the blow-by gas) at the same temperature and pressure as the blow-by gas. As an example, the specific gravity of hydrogen is "0.06952", which is sufficiently smaller than "1", so when the main component of the blow-by gas is hydrogen, the specific gravity of the blow-by gas will be smaller than "1", and the blow-by gas will be lighter than the same volume of air at the same temperature and pressure. Alternatively, the specific gravity of a gas may be expressed as the ratio of its density to that of air as a reference substance under standard conditions (0° C., 1 atmosphere).

[0045] In this disclosure, "backfire" refers to unintentional ignition in the combustion chamber 50 or the intake port 61, for example, during the intake stroke, and the flame is present inside the combustion chamber 50 or the intake port 61, for example. Therefore, if a backfire occurs during the intake stroke (when the intake valve 72 is open), the intake port 61 may be exposed to the flame.

[0046] In this disclosure, "parallel" refers to a case where two straight lines on a plane do not intersect no matter how far they are extended, that is, the angle between the two is exactly 0 degrees (or 180 degrees), as well as a case where the angle between the two is within an error range of a few degrees (e.g., less than 10 degrees) from 0 degrees. Similarly, in this disclosure, "orthogonal" refers to a case where the angle between the two is exactly 90 degrees, as well as a case where the angle between the two is within an error range of a few degrees (e.g., less than 10 degrees) from 90 degrees.

[0047] [3] Cylinder block structure Next, the configuration of the cylinder block 5 (and its surrounding structure) of the engine body 2 will be described in more detail with reference to Figures 7 to 16. Figure 7 is a schematic diagram of the engine body 2 viewed from the rear side (the side from which the crankshaft 22 protrudes), which is one side in the output axial direction D1, with part of the cylinder block 5 cut away and the main cross-sectional parts hatched. In Figure 7, illustration of the side cover 74 and the like is omitted as appropriate.

[0048] In this embodiment, as described above, in addition to the cylinder 51 and the crank chamber 52, the cam chamber 53 and the intake manifold 54 are formed in the cylinder block 5. The cylinder 51, the crank chamber 52, the cam chamber 53 and the intake manifold 54 are each formed of a section (chamber) separated from one another inside the cylinder block 5, and each has an internal space. Therefore, the inner circumferential surfaces of the cylinder 51, the crank chamber 52, the cam chamber 53 and the intake manifold 54 are all included in the inner circumferential surface 501 of the cylinder block 5. Specifically, the crank chamber 52 is disposed in the lower part of the cylinder block 5, and the cylinder 51, the cam chamber 53 and the intake manifold 54 are disposed above the crank chamber 52. Of the cylinder 51, the cam chamber 53 and the intake manifold 54, the cylinder 51 is disposed in the center in the width direction D3, the cam chamber 53 is disposed to the left of the cylinder 51, and the intake manifold 54 is disposed to the right of the cylinder 51. Thus, the cylinder block 5 includes the cylinders 51 and the crank chamber 52 aligned in the vertical direction D2, and the crank chamber 52 is located below the cylinders 51.

[0049] Here, in FIG. 7, the cylinders 51, the crank chamber 52, the cam chamber 53, and the intake manifold 54 are shown one by one, but in reality, a plurality of the cylinders 51 (six in this embodiment) are arranged in the output shaft direction D1 (the direction perpendicular to the paper surface of FIG. 7). On the other hand, the crank chamber 52 is partitioned in the output shaft direction D1 by a partition wall 521 located between adjacent cylinders 51, but is connected to the output shaft direction D1 by a communication hole 522 formed in the lower part of the partition wall 521. In other words, the crank chamber 52 is made up of one section (chamber) that is connected to the output shaft direction D1. In addition, an opening 531 is formed in the lower surface of the cam chamber 53, and the internal space of the cam chamber 53 is connected to the internal space Sp1 of the crank chamber 52 through the opening 531. The intake manifold 54 is made up of one section (chamber) that extends in the output shaft direction D1.

[0050] The cylinder 51 is formed in a cylindrical shape extending in the vertical direction D2, and accommodates the piston 21 therein so as to be capable of reciprocating along the vertical direction D2. Both end faces of the cylinder 51 in the vertical direction D2 are open. The piston 21 is a cylindrical member having an outer diameter corresponding to the inner diameter of the cylinder 51, and the internal space of the cylinder 51 is divided into two in the vertical direction D2 by the piston 21. Of the internal space of the cylinder 51, the space above the piston 21, i.e., the space surrounded by the upper surface of the piston 21 and the lower surface of the cylinder head 6, becomes the combustion chamber 50. On the other hand, of the internal space of the cylinder 51, the space below the piston 21 is continuous with the internal space Sp1 of the crank chamber 52.

[0051] In this embodiment, the piston 21 is made of a hollow member with an open lower surface (surface facing the crank chamber 52). That is, the piston 21 has a cylindrical portion 211 and a partition wall 212. The cylindrical portion 211 is a cylindrical portion with both end surfaces in the up-down direction D2 open, and the partition wall 212 is a portion that covers the upper surface of the cylindrical portion 211. Here, the cylindrical portion 211 and the partition wall 212 are integrally formed, and the piston 21 is formed as a bottomed cylinder as a whole. Therefore, strictly speaking, among the internal space of the cylinder 51, the combustion chamber 50 and a space that is continuous with the internal space Sp1 of the crank chamber 52 are separated by the partition wall 212. In other words, the space above the partition wall 212 becomes the combustion chamber 50, and the space below the partition wall 212, including the internal space of the cylindrical portion 211, is continuous with the internal space Sp1 of the crank chamber 52. The connecting rod 24 is supported by the piston 21 with its upper end inserted into the piston 21 .

[0052] In this embodiment, the cylinder 51 is configured with a cylinder liner 511 that guides the piston 21. The cylinder liner 511 is a cylindrical part, and the piston 21 slides against its inner circumferential surface to regulate the moving direction (vertical direction D2) of the piston 21. The cylinder liner 511 is supported by a liner support wall 55 of the cylinder block 5. The liner support wall 55 is a cylindrical part having an inner diameter one size larger than that of the cylinder liner 511, and the cylinder liner 511 is fixed to the cylinder block 5 by being fitted into the liner support wall 55. Here, the dimension of the cylinder liner 511 in the vertical direction D2 is larger than the dimension of the liner support wall 55 in the vertical direction D2, and the lower end of the cylinder liner 511 protrudes downward (toward the crankshaft 22) from the lower surface of the liner support wall 55. In short, in this embodiment, the cylinder block 5 has the liner support wall 55 that supports the cylinder liner 511 that constitutes the cylinder 51. The lower end of the cylinder liner 511 protrudes downward from the lower end of the liner support wall 55 .

[0053] As described above, the crank chamber 52 is located below the cylinder 51. The crankshaft 22 is accommodated in the internal space Sp1 of the crank chamber 52 so as to be rotatable about the rotation axis Ax1. The crankshaft 22 is rotatably supported by a partition wall 521, and rotates in conjunction with the reciprocating motion of the piston 21 connected via a connecting rod 24. Here, the crank chamber 52 is isolated from the combustion chamber 50 above the piston 21 in the internal space of the cylinder 51 by the piston 21. However, for example, during a compression stroke or the like in which the inside of the combustion chamber 50 becomes high pressure, blow-by gas such as unburned gas may leak from the combustion chamber 50 to the crank chamber 52 through the gap between the cylinder 51 and the piston 21 as described above.

[0054] Meanwhile, as a related art, an engine system that takes measures against blow-by gas leaking from the combustion chamber 50 to the crank chamber 52 is known. In the engine system according to the related art, an intake port that takes in blow-by gas from the crank chamber 52 is provided on the inner surface of the crank chamber 52. The intake port is connected to a blow-by gas passage by an intake passage, and the engine system is configured to return the blow-by gas to the combustion chamber 50 through the air intake system in the blow-by gas passage. Here, the intake port (blow-by gas intake portion) is positioned below the crank journal, thereby avoiding interference between the blow-by gas intake portion and the crank journal of the crankshaft 22.

[0055] However, for example, in an engine system 1 that uses a gaseous fuel such as hydrogen whose specific gravity is less than 1, the blow-by gas that leaks into the crank chamber 52 is likely to accumulate above the crank chamber 52. Therefore, if the intake port is located below the crank journal as in the related art, the blow-by gas may not be efficiently discharged from the crank chamber 52.

[0056] Therefore, in this embodiment, by adopting the configuration described below, it is possible to provide an engine system 1 that can easily and efficiently discharge blow-by gas from the crank chamber 52.

[0057] That is, the engine system 1 according to this embodiment is an engine system 1 in which blow-by gas with a specific gravity based on air of less than 1 may be generated. In such an engine system 1, a ventilation port 502 is opened in an inner peripheral surface 501 of the cylinder block 5. The ventilation port 502 is an opening (hole) leading to a ventilation passage 503 that connects the internal space Sp1 of the crank chamber 52 and the external space of the cylinder block 5. The ventilation port 502 is disposed above the center C1 of the crank chamber 52 in the up-down direction D2.

[0058] In short, for example, by using a gaseous fuel such as hydrogen whose specific gravity is less than 1, blow-by gas whose specific gravity is less than 1 (based on air) may be generated in the engine system 1, the above-mentioned configuration makes it easier to efficiently discharge the blow-by gas. In this type of engine system 1, the blow-by gas leaking into the crank chamber 52 is likely to accumulate above the crank chamber 52. In the engine system 1 according to the present embodiment, the ventilation port 502 is disposed above the center C1 of the crank chamber 52, so that the blow-by gas that accumulates above the crank chamber 52 can be efficiently discharged from the ventilation port 502. That is, the ventilation port 502 that serves as an outlet for the blow-by gas is formed in the upper part of the crank chamber 52 where the blow-by gas accumulates, so that the blow-by gas is efficiently discharged from the internal space Sp1 of the crank chamber 52 via the ventilation port 502 (and the ventilation passage 503). Therefore, it is possible to provide an engine system 1 that makes it easier to efficiently discharge the blow-by gas from the crank chamber 52.

[0059] Specifically, as shown in Fig. 7, the center C1 of the crank chamber 52 in the vertical direction D2 is set at a position that bisects the dimension (height dimension) L1 of the crank chamber 52 in the vertical direction D2. That is, the center C1 is set at a position that is equidistant from both the upper end and the lower end of the crank chamber 52. The ventilation port 502 is disposed so as to be located on the upper side in the vertical direction D2, that is, on the cylinder 51 side, as viewed from the center C1. The ventilation port 502 opens, for example, in a circular shape (a perfect circle) large enough to pass the blow-by gas in a plan view. However, the ventilation port 502 is not limited to a circular shape, and may open, for example, in an elliptical, rectangular or polygonal shape.

[0060] More specifically, the ventilation port 502 is disposed above the lower end of the cylinder 51. That is, the ventilation port 502 is disposed above the center C1 of the crank chamber 52 in the vertical direction D2 and above the lower end of the cylinder 51. The lower end of the cylinder 51 here is the lowest part of the cylinder 51, which faces the crank chamber 52. In this embodiment, as described above, the cylinder liner 511 constituting the cylinder 51 protrudes downward from the lower end of the liner support wall 55, so that the lower end (lower surface) of the cylinder liner 511 is the lower end of the cylinder 51. The lower end of the cylinder 51 (the lower end of the cylinder liner 511) is located above the center C1 of the crank chamber 52 in the vertical direction D2, as shown in FIG. 7, and the ventilation port 502 is disposed further above the lower end of the cylinder 51.

[0061] As a result, blow-by gas with a specific gravity less than 1 leaks from the lower end of cylinder 51 into crank chamber 52 and is then more likely to be guided toward ventilation port 502 located above the lower end of cylinder 51. As a result, blow-by gas can be more efficiently discharged from crank chamber 52, improving the discharge performance of blow-by gas.

[0062] Also, the ventilation port 502 opens downward. Here, in the vertical direction D2, the crank chamber 52 side as viewed from the cylinder 51 is "downward," and the ventilation port 502 opens toward the crank chamber 52 side as viewed from the cylinder 51. Since the ventilation port 502 opens on the inner circumferential surface 501 of the cylinder block 5, the ventilation port 502 is formed on a portion of the inner circumferential surface 501 facing downward, that is, a portion that becomes the top surface, thereby realizing the ventilation port 502 that opens downward. The ventilation port 502 only needs to open downward, and includes not only a configuration that opens strictly directly downward, but also a configuration that opens diagonally downward. In other words, the normal line of the opening surface of the ventilation port 502 may be parallel to the vertical direction D2, or may be inclined with respect to the vertical direction D2.

[0063] As a result, blow-by gas with a specific gravity less than 1 leaks from the lower end of cylinder 51 into crank chamber 52 and then flows upward, and is more likely to be discharged from ventilation port 502. As a result, blow-by gas can be more efficiently discharged from crank chamber 52, and the discharge performance of blow-by gas can be improved.

[0064] In this embodiment, as described above, the cylinder block 5 is connected to the crank chamber 52 and further includes the cam chamber 53 that houses the camshaft 23. Here, the ventilation port 502 is formed in the cam chamber 53. In short, the ventilation port 502 is arranged in the cam chamber 53 of the cylinder block 5 including the cylinder 51, the crank chamber 52, the cam chamber 53, etc., as shown in FIG. 7. Here, as an example, the ventilation port 502 is formed at a position above the camshaft 23 in the cam chamber 53, that is, in the upper wall portion 532 of the cam chamber 53. Here, the ventilation port 502 penetrates the upper wall portion 532 in the up-down direction D2. Since the internal space of the cam chamber 53 is connected to the internal space Sp1 of the crank chamber 52 through the opening 531, the blow-by gas leaking into the crank chamber 52 is introduced into the cam chamber 53 through the opening 531.

[0065] As a result, by utilizing the space for accommodating the camshaft 23, blow-by gas can be efficiently discharged from the crank chamber 52 without creating a new space for forming the ventilation port 502. Moreover, since the cam chamber 53 is located above the crank chamber 52, the blow-by gas with a specific gravity less than 1 is likely to collect in the cam chamber 53 in which the ventilation port 502 is formed after leaking into the crank chamber 52, and the discharge performance of the blow-by gas can be improved.

[0066] In the present embodiment, as an example, the ventilation passage 503 is a cylindrical pipe (tube) extending straight from the ventilation port 502 along the up-down direction D2 as shown in FIG. 7. The ventilation passage 503 is connected to the ventilation port 502 and functions as a passage for blow-by gas discharged from the ventilation port 502. The end of the ventilation passage 503 (the end opposite to the ventilation port 502) is disposed at an appropriate position in the external space of the cylinder block 5. As an example, the end of the ventilation passage 503 may be located inside the side cover 74 or outside the side cover 74. Furthermore, the end of the ventilation passage 503 may be located outside the hull 100 on which the engine body 2 is mounted, or may be connected to a ventilation device provided in the engine room of the hull 100.

[0067] However, the ventilation passage 503 is not limited to this configuration, and may be a shape other than a cylinder, such as a square tube, or may be a tube or a hose. Furthermore, the ventilation passage 503 may be configured to function as a passage for blow-by gas between the internal space Sp1 of the crank chamber 52 and the external space of the cylinder block 5, and is not necessarily required to be a cylindrical member. In other words, it is sufficient that the ventilation port 502 finally communicates with the external space of the cylinder block 5 through the ventilation passage 503, and for example, the internal space of the side cover 74 may function as the ventilation passage 503.

[0068] According to the above-described configuration, as shown in FIG. 8, the blow-by gas is efficiently discharged from the internal space Sp1 of the crank chamber 52 via the ventilation port 502 (and the ventilation passage 503). In FIG. 8, the flow of the blow-by gas is indicated by a thick arrow. That is, the blow-by gas is generated when unburned gas leaks from the combustion chamber 50 to the crank chamber 52 through the gap between the cylinder 51 and the piston 21. In this embodiment, the specific gravity of the blow-by gas is also less than 1 by using a gaseous fuel (hydrogen) having a specific gravity less than 1, so that the blow-by gas leaked into the crank chamber 52 moves upward in the crank chamber 52. Since the cam chamber 53 connected to the internal space Sp1 of the crank chamber 52 through the opening 531 is provided above the crank chamber 52, the blow-by gas moving upward flows into the cam chamber 53 through the opening 531. As a result, the blow-by gas is discharged from the ventilation port 502 of the cam chamber 53 and discharged to the external space of the cylinder block 5 through the ventilation passage 503.

[0069] In this embodiment, as shown in FIG. 9, the ventilation passage 503 has a gas-liquid separation section 504 that separates gas and liquid. As an example, the gas-liquid separation section 504 is composed of a protruding wall provided inside the ventilation passage 503. The protruding wall as the gas-liquid separation section 504 protrudes from the inner circumferential surface of the ventilation passage 503 toward the central axis of the ventilation passage 503. In this embodiment, a plurality of protruding walls as the gas-liquid separation section 504 are provided so that the protruding wall protruding from one (left) side in the width direction D3 of the inner circumferential surface of the ventilation passage 503 and the protruding wall protruding from the other (right) side in the width direction D3 are arranged alternately in the up-down direction D2. The protruding wall protruding from one (left) side in the width direction D3 and the protruding wall protruding from the other (right) side in the width direction D3 overlap each other at their tips in the up-down direction D2.

[0070] By providing such a gas-liquid separation section 504, the inside of the ventilation passage 503 has a labyrinth structure, and the blow-by gas introduced into the ventilation passage 503 from the ventilation port 502 flows in the ventilation passage 503 while meandering between the protruding wall serving as the gas-liquid separation section 504. When the blow-by gas contacts the protruding wall serving as the gas-liquid separation section 504, liquid such as oil or moisture discharged together with the blow-by gas adheres to the protruding wall serving as the gas-liquid separation section 504. As a result, the liquid (oil, moisture, etc.) discharged together with the blow-by gas is captured by the gas-liquid separation section 504 and separated from the gas contained in the blow-by gas. As a result, the blow-by gas is exhausted from the ventilation passage 503 with at least a part of the liquid components such as oil removed, which leads to suppression of oil consumption and the like accompanying the exhaust of the blow-by gas.

[0071] The gas-liquid separation section 504 is not limited to the protruding wall as described above, but may have a function of separating liquid from the blow-by gas discharged from the ventilation port 502. The gas-liquid separation section 504 may be, for example, a filter or the like disposed in the ventilation passage 503, or may be a combination of a protruding wall and a filter.

[0072] Incidentally, the engine body 2 according to this embodiment is an in-line multi-cylinder engine (in-line six-cylinder engine) in which a plurality of cylinders 51 (six in this embodiment) are arranged in line, as described above. In this type of engine, blow-by gas may be generated for each of the cylinders 51, but in this embodiment, only one ventilation port 502 for discharging blow-by gas is provided for the cylinders 51. In other words, the ventilation port 502 is shared by the cylinders 51. That is, in this embodiment, as described above, the crank chamber 52 is made up of one section (chamber) connected to the output shaft direction D1. Therefore, even if blow-by gas is generated in any of the cylinders 51, the blow-by gas will end up leaking into the same crank chamber 52. In this sense, it is sufficient to provide one ventilation port 502 for discharging blow-by gas for the cylinders 51.

[0073] Specifically, as shown in FIG. 10, a plurality of cylinders 51 are provided so as to be aligned in the output shaft direction D1, and the plurality of cylinders 51 include a one-end side cylinder 51A and an other-end side cylinder 51B located on both sides in the output shaft direction D1. Here, the ventilation port 502 is provided at a position corresponding to the one-end side cylinder 51A. In short, among the six cylinders 51 aligned in the output shaft direction D1, the cylinder 51 at one end (front end in this embodiment) of the output shaft direction D1 is defined as the "one-end side cylinder 51A", and the cylinder 51 at the other end (rear end in this embodiment) of the output shaft direction D1 is defined as the "other-end side cylinder 51B". In this case, the ventilation port 502 is formed in the cam chamber 53 at a position corresponding to the one-end side cylinder 51A, that is, at the front end. The ventilation passage 503 is provided so as to extend upward from the ventilation port 502.

[0074] In this way, it is sufficient that there is one ventilation port 502 for the multiple cylinders 51, and as a result, the structure for discharging the blow-by gas can be simplified. In particular, in this embodiment, the engine body 2 is arranged in a "front-up" position (see FIG. 2), so that the blow-by gas leaking into the crank chamber 52 tends to be collected at the front end side, which is relatively located upward. Therefore, in a configuration in which the ventilation port 502 is arranged at the front end of the cylinder block 5 (the cam chamber 53 therein), it becomes possible to more efficiently discharge the blow-by gas from the exhaust pipe 105 (see FIG. 2) provided in the hull 100.

[0075] In this embodiment, in order to more smoothly exhaust the blow-by gas from the ventilation port 502, a gas inlet port 505 that connects the internal space Sp1 of the crank chamber 52 to the external space of the cylinder block 5 is opened in the inner peripheral surface 501 of the cylinder block 5 as shown in Fig. 11. Fig. 11 is a schematic diagram of the cylinder block 5, which shows the positional relationship between the cylinder 51, the crank chamber 52, and the cam chamber 53.

[0076] By providing such a gas inlet 505 separately from the ventilation port 502, it is possible to take in fresh air into the internal space Sp1 of the crank chamber 52 when the blow-by gas is exhausted from the ventilation port 502. As a result, it is possible to more smoothly ventilate the internal space Sp1 of the crank chamber 52 (exhaust the blow-by gas). The gas inlet 505 opens, for example, in a circular shape (perfect circle) large enough to pass air in a plan view. However, the gas inlet 505 is not limited to a circular shape, and may open, for example, in an elliptical, rectangular or polygonal shape.

[0077] As shown in FIG. 11, the ventilation port 502 and the gas inlet 505 are arranged at different positions in the output axial direction D1 along the rotation axis Ax1 of the crankshaft 22 arranged in the crank chamber 52. That is, the ventilation port 502 and the gas inlet 505 are offset from each other in the output axial direction D1. In the example of FIG. 11, the gas inlet 505 is arranged at a position corresponding to the other end side cylinder 51B at the other end side of the output axial direction D1, that is, at the rear end of the cylinder block 5. In other words, the ventilation port 502 is arranged at one end side (front end in this embodiment) of the output axial direction D1, whereas the gas inlet 505 is arranged at the other end side (rear end in this embodiment) of the output axial direction D1.

[0078] According to this configuration, the gas (air) introduced from the gas inlet 505 flows toward the ventilation port 502 to form an airflow along the output shaft direction D1, so that the airflow can be made to act over a wide range in the output shaft direction D1. Therefore, the performance of discharging the blow-by gas by the airflow can be further improved.

[0079] Particularly, in this embodiment, the ventilation port 502 is disposed at a position (front end) corresponding to the one end cylinder 51A, whereas the gas inlet port 505 is disposed at a position (rear end) corresponding to the other end cylinder 51B. In this manner, the ventilation port 502 and the gas inlet port 505 are disposed at both ends of the cylinder block 5 in the output axial direction D1, so that the airflow can be made to act over substantially the entire area in the output axial direction D1 in the crank chamber 52. Therefore, the performance of discharging the blow-by gas by the airflow can be further improved.

[0080] In addition, in this embodiment, the ventilation port 502 and the gas inlet 505 are disposed on opposite sides across the rotation axis Ax1 of the crankshaft 22 disposed in the crank chamber 52 in a plan view. That is, in a plan view, the ventilation port 502 is disposed on one side (the left side in this embodiment) of the width direction D3 as viewed from the rotation axis Ax1, whereas the gas inlet 505 is disposed on the other side (the right side in this embodiment) of the width direction D3 as viewed from the rotation axis Ax1. As an example, the gas inlet 505 is formed in the right side wall of the crank chamber 52 so as to penetrate the right side wall of the crank chamber 52. In this way, the ventilation port 502 and the gas inlet 505 are disposed on opposite sides across the rotation axis Ax1, so that the airflow can act over a wide range of the width direction D3 in the crank chamber 52. Therefore, the exhaust performance of the blow-by gas by the airflow can be further improved.

[0081] Furthermore, in this embodiment, the gas inlet 505 is disposed below the center C1 (see FIG. 7) in the vertical direction D2 of the crank chamber 52. As a result, the airflow of the gas (air) introduced from the gas inlet 505 flows toward the ventilation port 502 diagonally upward, forming an airflow along the vertical direction D2, so that the airflow can act over the entire crank chamber 52. Therefore, the performance of discharging the blow-by gas by the airflow can be further improved.

[0082] Here, the engine system 1 according to this embodiment further includes an airflow forming unit 506, as shown in FIG. 12. The airflow forming unit 506 forms an airflow from the gas inlet 505 toward the ventilation port 502. FIG. 12 is a schematic diagram of the cylinder block 5, which shows the positional relationship between the cylinder 51, the crank chamber 52, the cam chamber 53, and the intake manifold 54. In this embodiment, as an example, a supercharger 8 is used for the airflow forming unit 506. Specifically, the airflow forming unit 506 includes a bypass pipe that connects between the intake manifold 54 and the gas inlet 505. The bypass pipe as the airflow forming unit 506 forms a passage for air from, for example, the end (the rear end in this embodiment) on the downstream side of the airflow in the intake manifold 54 to the gas inlet 505. As a result, the air (intake air) compressed by the turbocharger 8 is sent to the intake manifold 54 through the intercooler 85, and is further sent to the gas inlet 505 through a bypass pipe serving as an airflow forming section 506. As a result, the gas inlet 505 is placed under positive pressure with respect to the internal space Sp1 of the crank chamber 52 by the compressed air, and an airflow is generated in the crank chamber 52 in a direction that pushes out the gas (blow-by gas) from the ventilation port 502.

[0083] In this way, by providing the airflow forming part 506, an airflow can be forcibly formed in the internal space Sp1 of the crank chamber 52, and the blow-by gas is less likely to stagnate in the crank chamber 52. In other words, the airflow forming part 506 promotes the discharge of the blow-by gas from the ventilation port 502, and the discharge performance of the blow-by gas can be further improved. Moreover, in this embodiment, since the turbocharger 8 is used as the airflow forming part 506, there is no need to newly install a device for forming an airflow.

[0084] Fig. 13 shows a modified example of the positional relationship between the ventilation port 502 and the gas inlet port 505, and the airflow forming portion 506. In the modified example shown in "A" of Fig. 13, the ventilation port 502 is disposed in the center of the cylinder block 5 in the output axial direction D1, and the gas inlet ports 505 are disposed at both ends of the cylinder block 5 in the output axial direction D1. In this example, gas (air) introduced from the gas inlet ports 505 formed in two locations flows toward the single ventilation port 502, forming an airflow along the output axial direction D1.

[0085] In a modified example shown in "B" of Fig. 13, the air flow forming section 506 includes an air tank mounted on the hull 100, and sends air from the air tank to the gas inlet 505. In a modified example shown in "C" of Fig. 13, the air flow forming section 506 includes an electric fan, and sends air from the electric fan to the gas inlet 505. In either example of "B" or "C" of Fig. 13, the gas inlet 505 is in a state of positive pressure with respect to the internal space Sp1 of the crank chamber 52, and an air flow is generated in the crank chamber 52 in a direction that pushes out gas (blow-by gas) from the ventilation port 502.

[0086] On the other hand, in the modified example shown in "D" of FIG. 13, the airflow forming part 506 includes an electric fan, and the electric fan draws in the blow-by gas from the ventilation port 502. In this example, the downstream side (the ventilation passage 503 side) of the ventilation port 502 is in a state of negative pressure with respect to the internal space Sp1 of the crank chamber 52, and an airflow is generated in the crank chamber 52 in a direction in which the gas (blow-by gas) is drawn from the gas inlet port 505 to the ventilation port 502. In this way, the airflow forming part 506 may form an airflow by generating either a positive pressure or a negative pressure, or may be configured to generate both a positive pressure and a negative pressure. In the modified examples shown in "C" or "D" of FIG. 13, for example, a pump may be used instead of the electric fan.

[0087] The configuration of the piston 21 of the engine system 1 according to this embodiment will be described in more detail below with reference to Figures 14 and 15. Figures 14 and 15 are schematic cross-sectional views in which the piston 21 and its periphery are enlarged.

[0088] As shown in FIG. 14, a stirring portion 213 that reciprocates along the vertical direction D2 with the movement of the piston 21 is disposed in the piston inner space 210 formed inside the piston 21 that reciprocates along the vertical direction D2 in the cylinder 51. In this embodiment, a wing-like protrusion that protrudes from the inner circumferential surface of the cylindrical portion 211 of the piston 21 toward the central axis of the piston 21 constitutes the stirring portion 213. The piston inner space 210 is a cylindrical space surrounded by the cylindrical portion 211 of the piston 21, and is a space separated from the combustion chamber 50 by a separation wall 212 of the piston 21. The connecting rod 24 is supported by the piston 21 with its upper end inserted into the piston inner space 210. The stirring portion 213 is formed on the entire circumference of the cylindrical portion 211 in the circumferential direction, and a plurality of stirring portions (two in this example) are provided at intervals in the vertical direction D2.

[0089] In short, the piston internal space 210 connected to the internal space Sp1 of the crank chamber 52 is provided with the stirring portion 213 that reciprocates with the movement of the piston 21. By providing such a stirring portion 213, when the piston 21 reciprocates, the stirring portion 213 reciprocates in the piston internal space 210, and the gas in the piston internal space 210 is stirred. Therefore, even if blow-by gas such as unburned gas leaks from the combustion chamber 50 to the piston internal space 210 through the gap between the cylinder 51 and the piston 21, the blow-by gas in the piston internal space 210 is actively caused to flow and is easily moved to the crank chamber 52. Therefore, it becomes easier to suppress the retention of the blow-by gas in the piston internal space 210, and further improvement in the discharge performance of the blow-by gas can be expected.

[0090] Furthermore, the stirring portion 213 may be any configuration that is provided in the piston internal space 210 and reciprocates with the movement of the piston 21, and is not limited to a protrusion protruding from the cylindrical portion 211 of the piston 21, but may be, for example, a protrusion protruding from the upper end portion of the connecting rod 24. In other words, as long as the protrusion is provided on the connecting rod 24 above the lower end of the piston 21, it can stir the gas in the piston internal space 210 with the reciprocating movement of the piston 21, similar to the above-mentioned stirring portion 213. The stirring portion 213 may be provided on both the piston 21 and the connecting rod 24.

[0091] 15, it is preferable that the partition wall 212, which separates the internal space of the cylinder 51 in the vertical direction D2 of the piston 21 that reciprocates in the cylinder 51 along the vertical direction D2, has a hollow portion 214 therein. Specifically, a plate 215 is fixed to the lower surface (the surface opposite to the combustion chamber 50) of the partition wall 212 by an appropriate method such as welding, so that the partition wall 212 has a double structure. As a result, the hollow portion 214 is formed as a heat insulating layer on the upper side (combustion chamber 50 side) of the plate 215.

[0092] In short, the combustion chamber 50 and the space continuing to the internal space Sp1 of the crank chamber 52 in the internal space of the cylinder 51 are separated by the partition wall 212, so that the upper surface of the partition wall 212 is exposed to the combustion chamber 50. Therefore, in a configuration in which the cavity 214 is not provided as in FIG. 14, the heat of the upper surface of the partition wall 212 is easily transferred to the rear surface (lower surface) side of the partition wall 212, and there is a possibility that, for example, the blow-by gas mainly composed of hydrogen or the like is heated. In contrast, according to the configuration in FIG. 15 in which the cavity 214 is formed as a heat insulating layer, the heat is less likely to be transferred to the lower surface side of the plate 215 in the cavity 214. Therefore, it is possible to suppress the heating of the blow-by gas mainly composed of hydrogen or the like by the heat of the combustion chamber 50.

[0093] As a configuration for actively moving the blow-by gas in the piston space 210, a stirring nozzle 216 may be provided in addition to or instead of the stirring portion 213, as shown in FIG. 16. The stirring nozzle 216 is provided in each cylinder 51 at a position where its tip faces the inner space of the cylinder 51 from the lower surface of the cylinder 51. The stirring nozzle 216 intermittently or continuously injects gas (e.g., air) or liquid (e.g., oil) toward the inside of the cylinder 51. As a result, the gas in the piston space 210 is stirred by the gas or liquid injected into the cylinder 51. Therefore, even if the blow-by gas such as unburned gas leaks from the combustion chamber 50 to the piston space 210 through the gap between the cylinder 51 and the piston 21, the blow-by gas in the piston space 210 is actively moved and easily moved to the crank chamber 52. Therefore, it becomes easier to prevent the blow-by gas from accumulating in the piston internal space 210, and further improvement in the exhaust performance of the blow-by gas can be expected.

[0094] Incidentally, the above-mentioned configuration related to the piston 21 can be adopted separately from the configuration (ventilation port 502) for exhausting blow-by gas. That is, the engine system 1 according to one embodiment includes a cylinder block 5 including a cylinder 51 and a crank chamber 52, and a stirring part 213 that reciprocates with the movement of the piston 21 is disposed in a piston inner space 210 formed inside the piston 21 that reciprocates in the cylinder 51. Also, the engine system 1 according to another embodiment includes a cylinder block 5 including a cylinder 51 and a crank chamber 52, and a partition wall 212 that separates the internal space of the cylinder 51 (in the direction in which the piston 21 reciprocates) of the piston 21 that reciprocates in the cylinder 51 has a hollow part 214 therein.

[0095] [4] Cylinder head structure Next, the configuration of the cylinder head 6 (and its surrounding structure) of the engine body 2 will be described in more detail with reference to Figures 17 to 21. Figure 17 is a schematic diagram of the engine body 2 viewed from the rear side (the side from which the crankshaft 22 protrudes), which is one side in the output shaft direction D1, with the cylinder block 5 and cylinder head 6 partially cut away and the main cross-sectional parts hatched. In Figure 17, illustration of the side cover 74 and the like is omitted as appropriate.

[0096] In this embodiment, as described above, the cylinder head 6 is formed with the intake port 61 and the exhaust port 62. The intake port 61 and the exhaust port 62 are each formed of compartments (chambers) separated from each other inside the cylinder head 6, and each has an internal space. Although a plurality of cylinder heads 6 (six in this embodiment) are provided, the plurality of cylinder heads 6 adopt a common configuration. Therefore, the following description will focus on one cylinder head 6 unless otherwise specified.

[0097] In the present embodiment, as an example, as shown in Figs. 18 and 19, two intake ports 61 and two exhaust ports 62 are provided in the cylinder head 6. That is, two intake ports 61 and two exhaust ports 62 are formed in one cylinder head 6. However, the two intake ports 61 basically adopt a common configuration, and the two exhaust ports 62 basically adopt a common configuration. Therefore, unless otherwise specified, the following description focuses on one intake port 61 or one exhaust port 62. Fig. 18 is a schematic perspective view showing the outline of the cylinder head 6 and the cylinder 51 with imaginary lines (two-dot chain lines) and highlighting the intake port 61 and the exhaust port 62. Fig. 19 is a schematic plan view showing a refrigerant passage 63 described later with imaginary lines (two-dot chain lines) and highlighting the intake port 61 and the exhaust port 62.

[0098] 17 and 18, the cylinder head 6 is disposed above the cylinder 51. As a result, the space within the interior space of the cylinder 51 that is surrounded by the upper surface of the piston 21 and the lower surface of the cylinder head 6 functions as a combustion chamber 50. Both the intake port 61 and the exhaust port 62 formed in the cylinder head 6 have openings that communicate with the combustion chamber 50.

[0099] The intake port 61 is a passage for gas (intake air) connecting the intake manifold 54 formed in the cylinder block 5 and the combustion chamber 50. An intake valve 72 is provided at the opening of the intake port 61 on the combustion chamber 50 side, i.e., the opening on the downstream side of the airflow. Therefore, air distributed from the intake manifold 54 is supplied to the combustion chamber 50 through the intake port 61 with the intake valve 72 open.

[0100] Furthermore, in this embodiment, a port injection method is adopted as the fuel supply method for the gaseous fuel, and therefore the fuel supply device 3 supplies the gaseous fuel (hydrogen in this embodiment) to the internal space of the intake port 61. That is, the injection unit 31 of the fuel supply device 3 that injects the gaseous fuel is disposed at a position facing the inside of the intake port 61, and injects the gaseous fuel into the intake port 61. The timing at which the fuel supply device 3 injects the gaseous fuel will be explained in detail in the section "[5] Control operation of engine system".

[0101] On the other hand, the exhaust port 62 is a passage for gas (exhaust) that connects the exhaust manifold 75 and the combustion chamber 50. An exhaust valve 73 is provided at an opening of the exhaust port 62 on the combustion chamber 50 side, i.e., an opening on the upstream side of the airflow. Therefore, the gas discharged from the combustion chamber 50 is discharged (collected) into the exhaust manifold 75 via the exhaust port 62 with the exhaust valve 73 open.

[0102] As shown in Figs. 17 and 19, the cylinder head 6 is formed with a refrigerant passage 63 in addition to the intake port 61 and the exhaust port 62. The refrigerant passage 63 is a passage through which the refrigerant passes. The "refrigerant" here means a heat medium used to transfer heat in a cooling cycle, and is, for example, a liquid such as water (cooling water) or oil, or a gas such as a cooling gas. In other words, by the refrigerant, which is a fluid, flowing through the refrigerant passage 63, it is possible to take heat from the surroundings of the refrigerant passage 63 and to cool the surroundings of the refrigerant passage 63. In this embodiment, as an example, the refrigerant passage 63 is a water jacket for passing cooling water as a refrigerant.

[0103] As shown in Fig. 19, the refrigerant passage 63 is formed in a ring shape surrounding the openings of the intake port 61 and the exhaust port 62 on the combustion chamber 50 side in a plan view. Specifically, as shown in Fig. 17, the refrigerant passage 63 is disposed at a position adjacent to the opening of the intake port 61 on the combustion chamber 50 side. A refrigerant (cooling water) cooled outside the cylinder head 6 is supplied to the refrigerant passage 63 so as to circulate. As a result, the refrigerant flowing through the refrigerant passage 63 mainly cools the periphery of the openings of the intake port 61 and the exhaust port 62 on the combustion chamber 50 side.

[0104] Meanwhile, a dual-injection engine system equipped with an in-cylinder injector and an intake passage injector is known as a related art. In the engine system according to the related art, the occurrence of backfire during the execution of the fuel evaporative gas purge process is suppressed by adjusting (correcting) the fuel injection amount. Specifically, during the execution of the fuel evaporative gas purge process when the contribution ratio of the in-cylinder injector and the intake passage injector is within a predetermined range, the fuel injection amount correction corresponding to the amount of purged fuel introduced is performed by changing only the fuel injection amount from the intake passage injector.

[0105] However, for example, in the engine system 1 using gaseous fuel such as hydrogen, the fuel (gaseous fuel) may be more likely to ignite. Therefore, in the unlikely event that a backfire occurs, it is desirable to take further measures against backfire in anticipation of the fuel (gaseous fuel) supplied into the intake port 61 igniting and causing a chain reaction of backfires.

[0106] Therefore, in this embodiment, by adopting the configuration described below, it is possible to provide an engine system 1 that allows for further measures against backfire.

[0107] That is, the engine system 1 according to this embodiment includes an intake port 61 that supplies air to the combustion chamber 50, and a fuel supply device 3 that supplies gaseous fuel to an internal space Sp2 (see FIG. 20) of the intake port 61. The fuel supply device 3 has an injection unit 31 that injects gaseous fuel. As shown in FIG. 20, a cooling unit 612 is disposed at least at an intersection of an inner circumferential surface 611 of the intake port 61 with a central axis Ax2 of an injection region R1 of the gaseous fuel from the injection unit 31. In other words, the intersection of the inner circumferential surface 611 of the intake port 61 with the central axis Ax2 of the injection region R1 of the gaseous fuel from the injection unit 31 is included in the cooling unit 612.

[0108] In the present disclosure, the term "cooling portion" refers to a portion of the inner circumferential surface 611 of the intake port 61 that becomes relatively cold as a result of being cooled. In other words, the temperature of the inner circumferential surface 611 facing the internal space Sp2 of the intake port 61 is not uniform, and temperature differences may occur depending on the portion, and the portion that becomes relatively colder than other portions constitutes the cooling portion 612. As an example, the portion of the inner circumferential surface 611 of the intake port 61 that is below a reference temperature (for example, the average value or median value of the temperature of the inner circumferential surface 611) constitutes the cooling portion 612.

[0109] In short, for example, in the engine system 1 employing a port injection method in which gaseous fuel such as hydrogen is injected into the internal space Sp2 of the intake port 61, the above configuration can provide further countermeasures against backfire. In this type of engine system 1, for example, in a situation in which the intake port 61 is exposed to flames due to backfire, if the gaseous fuel (hydrogen, etc.) injected into the intake port 61 is ignited, backfires may occur in a chain reaction. In the engine system 1 according to this embodiment, the central axis Ax2 of the injection region R1 of the gaseous fuel is directed toward the cooling section 612, so that the heat of the gaseous fuel is well removed, and ignition of the gaseous fuel due to heating of the gaseous fuel can be suppressed even immediately after the occurrence of a backfire. In this way, by improving the cooling performance of the gaseous fuel in the intake port 61, it is possible to provide an engine system 1 that can suppress chain reactions of backfires and provide further countermeasures against backfire.

[0110] More specifically, as shown in Fig. 20, the intake port 61 has a curved portion 600 whose cross-sectional shape is convex in one direction. In the present embodiment, as an example, the curved portion 600 is provided in the middle of the intake port 61, and by curving the cross-sectional shape so as to be convex upward, the intake port 61 has an inverted U-shaped cross-sectional shape as a whole. Therefore, the flow (air current) of air (intake air) in the internal space Sp2 of the intake port 61 takes a path that draws an arc that is convex in one direction (here, upward) along the curved portion 600. In Fig. 20, the flow of intake air is indicated by a thick arrow.

[0111] In this embodiment, the cooling section 612 is disposed on the surface of the inner circumferential surface 611 of the air supply port 61 that faces the other direction (here, downward) of the curved section 600, that is, on the inner circumferential side surface 602 of the curved section 600. That is, the inner circumferential surface 611 includes the outer circumferential side surface 601 that is the surface on one direction (here, upward) of the curved section 600, and the inner circumferential side surface 602 that is the surface on the other direction (here, downward) of the curved section 600, and the cooling section 612 is disposed on the inner circumferential side surface 602.

[0112] The nozzle-shaped (cylindrical) injection part 31 is disposed with its tip protruding from the outer circumferential side surface 601 into the intake port 61, and the gaseous fuel is injected from the injection part 31 toward the cooling part 612. That is, the tip of the injection part 31 is directed toward at least the cooling part 612 provided on the inner circumferential side surface 602. Here, the central axis Ax2 of the injection region R1 is the central axis of the injection region R1 that spreads in a substantially conical shape with the tip of the injection part 31 as an apex, and substantially coincides with the central axis of the nozzle-shaped (cylindrical) injection part 31.

[0113] 20, an air flow from the right to the left occurs in the air supply port 61, so the cooling unit 612 is disposed on the downstream side of the tip of the injection unit 31 of the fuel supply device 3.

[0114] In this way, by arranging the cooling part 612 downstream of the injection part 31, the gaseous fuel injected from the injection part 31 is likely to reach the cooling part 612 even if it is carried downstream by the air flow. Therefore, it is possible for the cooling part 612 to fully exert the cooling effect of the gaseous fuel.

[0115] Incidentally, specific embodiments of the cooling portion 612 include, for example, a first embodiment, a second embodiment, and a third embodiment, which will be described below. The first embodiment is a refrigerant cooling method using a refrigerant passage 63, the second embodiment is a latent heat of vaporization method using an adherent refrigerant, and the third embodiment is an air-cooling method. That is, the cooling portion 612 of the inner circumferential surface 611 of the air supply port 61 can be realized by the first embodiment, the second embodiment, or the third embodiment, or a combination of these.

[0116] First, in the first embodiment (refrigerant cooling method), as shown in Fig. 20, a portion near the refrigerant passage 63 becomes the cooling section 612. Specifically, the refrigerant passage 63 and the internal space Sp2 of the intake port 61 are physically separated by a partition 64, and the surface of the partition 64 opposite to the refrigerant passage 63 (the inner peripheral surface 611 of the intake port 61) forms the cooling section 612. That is, the engine system 1 includes a cylinder head 6 in which the intake port 61 is formed, and the cylinder head 6 has a refrigerant passage 63 through which the refrigerant passes. Here, the cooling section 612 is disposed in the partition 64 that physically separates at least the refrigerant passage 63 and the intake port 61.

[0117] According to this configuration, the cooling portion 612 can be efficiently cooled by the coolant flowing through the coolant passage 63 provided in the cylinder head 6. Furthermore, since the temperature of the cooling portion 612 can be adjusted by the flow rate of the coolant, etc., it is possible to more reliably cool the gaseous fuel. Therefore, ignition of the gaseous fuel due to heating of the gaseous fuel can be further suppressed.

[0118] Further, as shown in FIG. 20, the partition wall portion 64 includes a thin portion 641 and a thick portion 642. The thin portion 641 has a thickness Th1 between the refrigerant passage 63 and the air supply port 61 that is smaller than the reference thickness. The thick portion 642 has a thickness Th2 between the refrigerant passage 63 and the air supply port 61 that is larger than the reference thickness. The cooling portion 612 is provided only in the thin portion 641 out of the thin portion 641 and the thick portion 642. The "reference thickness" here is a reference thickness of the partition wall portion 64, and is, for example, an average value or a median value of the thickness of the partition wall portion 64. That is, the thickness of the partition wall portion 64 is not uniform, but varies depending on the portion. The cooling portion 612 is provided in the thin portion 641, which is relatively thin, of the partition wall portion 64, and is not provided in the thick portion 642.

[0119] According to this configuration, it is possible to more efficiently cool the cooling portion 612 with the coolant flowing through the coolant passage 63. That is, the cooling portion 612 is disposed in the thin-walled portion 641 of the inner circumferential surface 611 of the partition portion 64, which is relatively close to the coolant passage 63 and where heat is easily transferred to the coolant flowing through the coolant passage 63, so that it is possible to more reliably cool the gaseous fuel. Therefore, it is possible to further suppress ignition of the gaseous fuel due to heating of the gaseous fuel.

[0120] In the second embodiment (evaporation latent heat method), as shown in FIG. 21, the engine system 1 further includes a refrigerant supply unit 65 that causes an adhering refrigerant 651 to adhere to a part of the inner circumferential surface 611 of the intake port 61. The cooling unit 612 is disposed at least at a portion where the adhering refrigerant 651 adheres. The "adhering refrigerant" here means a heat medium mainly used for latent heat of vaporization, and is, for example, a liquid such as water (cooling water) or oil. That is, when the adhering refrigerant 651 adheres to a part of the inner circumferential surface 611 of the intake port 61, the adhering refrigerant 651 removes heat from the inner circumferential surface 611 when it evaporates, thereby cooling the inner circumferential surface 611. Therefore, the cooling unit 612 is cooled by making the part of the inner circumferential surface 611 of the intake port 61 where the adhering refrigerant 651 adheres to be the cooling unit 612. The manner in which the adhering refrigerant 651 is "adhered" includes, for example, spraying, discharging, condensing, or applying the adhering refrigerant 651.

[0121] Specifically, in the example shown in "A" of Fig. 21, a nozzle-shaped (cylindrical) refrigerant supply part 65 that sprays adhering refrigerant 651 is used. This refrigerant supply part 65 is arranged such that its tip part protrudes from the outer peripheral side surface 601 into the air supply port 61, and gas fuel is sprayed from the spray part 31 toward the cooling part 612. In other words, the tip part of the refrigerant supply part 65 is directed toward at least the cooling part 612 provided on the inner peripheral side surface 602. As a result, the adhering refrigerant 651 sprayed from the refrigerant supply part 65 adheres to the cooling part 612 on the inner peripheral surface 611 (inner peripheral side surface 602) of the air supply port 61, and cools the cooling part 612.

[0122] In the example shown in "B" of FIG. 21, a refrigerant supply unit 65 is used to cool the air introduced into the air intake port 61. The refrigerant supply unit 65 is made of a coil-shaped cooler and is disposed near the opening of the air intake port 61 on the air intake manifold 54 side. When the refrigerant is supplied to the refrigerant supply unit 65, the air passing through the refrigerant supply unit 65 is cooled, and when the amount of water vapor in the air exceeds the amount of saturated water vapor, water is generated as the adhering refrigerant 651 due to condensation. The adhering refrigerant 651 is carried by the air flow and adheres to at least the cooling unit 612 provided on the inner circumferential side surface 602. As a result, the adhering refrigerant 651 adheres to the cooling unit 612 on the inner circumferential surface 611 (inner circumferential side surface 602) of the air intake port 61, and cools the cooling unit 612. The refrigerant supplied to the refrigerant supply unit 65 is preferably maintained at a low temperature by, for example, heat exchange with the liquefied hydrogen tank 32.

[0123] 21, in addition to the coolant supply unit 65, the coolant cooling method of the first embodiment is also used by the coolant passage 63, but it is not essential to combine the second embodiment (latent heat of vaporization method) with the first embodiment. In other words, when the second embodiment (latent heat of vaporization method) is adopted, the coolant passage 63 may be omitted, and even in this case, the cooling unit 612 can be realized by the adhering coolant 651.

[0124] In the third embodiment (air-cooling method), the flow of air (air current) in the internal space Sp2 of the intake port 61 is used to form the cooling section 612 on a part of the inner circumferential surface 611 of the intake port 61. That is, for example, by increasing the flow rate of the air using a fan or the like and blowing the air against a part of the inner circumferential surface 611 of the intake port 61, the part of the inner circumferential surface 611 of the intake port 61 that the air hits is cooled by the air current to form the cooling section 612. With this configuration, it is possible to form the cooling section 612 by cooling a part of the inner circumferential surface 611 of the intake port 61 without using a separate refrigerant.

[0125] Additionally, in the engine system 1 according to this embodiment, it is even more effective to employ the following configuration as a countermeasure against backfire.

[0126] As a first configuration, a nozzle cooling structure is provided that cools the injection part 31 of the fuel supply device 3, and the gaseous fuel itself injected from the injection part 31 is cooled. As an example, the nozzle cooling structure can be realized by a coolant passage arranged around the injection part 31. As a result, the injection part 31 is cooled by the coolant, and heat input from the cylinder head 6 to the injection part 31 is suppressed, so that it is possible to suppress a rise in temperature of the gaseous fuel. The coolant passage may extend from the cylinder head 6 in the width direction D3, or may extend upward from the cylinder head 6, for example.

[0127] As a second configuration, a heat insulating material is provided to cover the injection part 31 of the fuel supply device 3, and heat input to the gaseous fuel injected from the injection part 31 is suppressed. This suppresses heat input from the cylinder head 6 to the injection part 31, making it possible to suppress a temperature rise of the gaseous fuel.

[0128] [5] Engine system control operation Next, the control operation of the engine system 1 according to this embodiment will be described with reference to Fig. 22, Fig. 23, and Fig. 24. In this embodiment, as described above, the engine system 1 is controlled by the engine control unit 20, and therefore the control operation of the engine system 1 described below includes processing executed by the engine control unit 20.

[0129] In this embodiment, the engine control unit 20 controls the fuel supply device 3 at a timing as shown in Fig. 22 to execute the injection of gaseous fuel into the intake port 61. In Fig. 22, the horizontal axis represents the crank angle, and indicates the opening degree G1 of the exhaust valve 73 and the opening degree G2 of the intake valve 72 (denoted as "valve opening degree"), the flow velocity of the intake air in the intake port 61 (denoted as "flow velocity"), and the temperature (denoted as "temperature") of the inner circumferential surface 611 (wall surface) near the combustion chamber 50 in the intake port 61. Here, the crank angle changes continuously with the passage of time as the piston 21 reciprocates between the bottom dead center (BDC) and the top dead center (TDC). Therefore, the horizontal axis representing the crank angle corresponds to the time axis.

[0130] In Fig. 22, it is assumed that the piston 21 is at bottom dead center at time t0, at top dead center at time t2, at bottom dead center at time t7, and that a backfire occurs at time t1. Here, time t1 is between time t0 and time t2, and is the timing immediately after the intake valve 72 starts to open. In this case, when the exhaust valve 73 closes (opening degree G1 is 0) at time t3 after time t2, the injection permission period T2 during which the gaseous fuel can be injected starts only after the cooling period T1 has elapsed. Here, when the injection of the gaseous fuel is a divided injection (intermittent injection), the injection permission period T2 is performed from the start of the first injection to the end of the last injection.

[0131] That is, in this embodiment, the fuel supply device 3 starts supplying gas fuel to the internal space Sp2 of the intake port 61 when the cooling period T1 has elapsed after satisfying the supply start condition including the exhaust valve 73 being closed. Here, the cooling period T1 is a period for cooling the cooling portion 612, and is a period during which the injection of gas fuel is prohibited. Specifically, the supply start condition includes the exhaust valve 73 being closed (the opening degree G1 is 0) and the intake valve 72 being opened (the opening degree G2 is greater than 0). In the example of FIG. 22, at time t3, the exhaust valve 73 is closed and the intake valve 72 is open (at the previous time t1), so that the supply start condition is satisfied. Therefore, when the cooling period T1 from time t3 to time t5 has elapsed and the injection permission period T2 has begun, the fuel supply device 3 is able to start injecting (supplying) gas fuel.

[0132] According to this configuration, the cooling period T1 is set before the supply (injection) of the gaseous fuel is started, so that the supply of the gaseous fuel to the internal space Sp2 of the intake port 61 can be started after the cooling portion 612 is reliably cooled. Therefore, even if a backfire occurs, the gaseous fuel is cooled by the cooling portion 612, and it is easy to suppress a chain reaction of backfires.

[0133] The end point of the cooling period T1 is set to be after the point at which the opening degree G2 of the intake valve 72 is maximum. In other words, the end point of the cooling period T1, that is, time t5, is set on the retarded side of the crank angle from time t4 when the opening degree G2 of the intake valve 72 is maximum (the peak of the opening degree G2).

[0134] According to this configuration, the supply of gaseous fuel is started after the timing when the flow velocity of the intake air in the intake port 61 is maximized, and the gaseous fuel can be cooled more efficiently. That is, the flow velocity of the intake air in the intake port 61 is maximized when the opening degree G2 of the intake valve 72 is maximized. By starting the supply of gaseous fuel after this timing (time t4 in FIG. 22), the cooling performance of the gaseous fuel is improved. This makes it easier to suppress the chain reaction of backfires.

[0135] Moreover, the engine system 1 according to this embodiment includes a turbocharger 8 that feeds air into the intake port 61. This makes it easier to feed the gaseous fuel into the combustion chamber 50 even if the timing of starting the supply of the gaseous fuel is delayed by providing the cooling period T1. In other words, the turbocharger 8 accelerates the flow rate of the air, so that the gaseous fuel injected into the intake port 61 flows more easily into the combustion chamber 50.

[0136] Here, as shown in Fig. 22, the injection permission period T2 is set in consideration of the grace period T3 inserted immediately before the intake valve 72 closes. The grace period T3 is a period during which injection of gaseous fuel is prohibited, similar to the cooling period T1. That is, during the grace period T3, injection of gaseous fuel is prohibited from time t6 when the injection permission period T2 ends to time t7 when the intake valve 72 closes (opening degree G2 is 0). In other words, the end point of the cooling period T1 is set to a point (time t5 in Fig. 22) that precedes time t7 when the intake valve 72 closes by the total time of the grace period T3 and the injection permission period T2.

[0137] This configuration suppresses the gaseous fuel from remaining in the intake port 61 due to the intake valve 72 being closed at time t6 when the injection permitted period T2 ends. In other words, even if gaseous fuel remains in the intake port 61 at time t6 when the injection permitted period T2 ends, the remaining gaseous fuel can be discharged into the combustion chamber 50 during the grace period T3.

[0138] Furthermore, it is preferable that the length of the grace period T3 is set based on the distance between (the tip of) the injection part 31 and the opening of the intake port 61 on the combustion chamber 50 side. The distance here refers to the distance on the air flow path in the intake port 61. Specifically, the longer the distance between (the tip of) the injection part 31 and the opening of the intake port 61 on the combustion chamber 50 side, the longer the grace period T3 is set. As a result, the grace period T3 is set taking into consideration the time required for the gaseous fuel injected from the injection part 31 to be discharged into the combustion chamber 50, so that the gaseous fuel is less likely to remain in the intake port 61.

[0139] Incidentally, the configuration related to the control of the fuel supply device 3 described above may be adopted separately from the configuration for exhausting blow-by gas (the ventilation port 502) and the cooling unit 612, etc. That is, the engine system 1 according to one embodiment includes an intake port 61 that supplies air to the combustion chamber 50, and a fuel supply device 3 that supplies gaseous fuel to the internal space Sp2 of the intake port 61. After the supply start condition including the exhaust valve 73 being closed is satisfied and a cooling period T1 has elapsed, the fuel supply device 3 starts supplying gaseous fuel to the internal space Sp2 of the intake port 61.

[0140] FIG. 23 is a flowchart showing an example of the operation (processing) of the engine control unit 20 related to the injection of gas fuel when the engine system 1 is used to drive the generator 101 or to propel the hull 100.

[0141] That is, the engine control unit 20 first determines whether or not the engine system 1 is to be used to drive the generator 101 (S1). If the engine system 1 is to be used to drive the generator 101 (S1: Yes), the engine control unit 20 determines that the engine system 1 is in the power generation mode, and shifts the process to step S2. On the other hand, if the engine system 1 is to be used to propel the hull 100 (S1: No), the engine control unit 20 determines that the engine system 1 is not in the power generation mode, and shifts the process to step S6.

[0142] In step S2, the engine control unit 20 acquires the load of the generator 101 and the rotation speed (actual rotation speed) of the engine body 2. Then, the engine control unit 20 determines the injection timing of the gaseous fuel, that is, the timing to start injection of the gaseous fuel, in reference to a "load-rotation speed map" showing the correlation between the load of the generator 101 and the engine rotation speed (S3). Then, the engine control unit 20 calculates the injection amount of the gaseous fuel (S4), and controls the fuel supply device 3 to inject the gaseous fuel when the injection timing of the gaseous fuel arrives (S5).

[0143] In step S6, the engine control unit 20 acquires the operation amount of the operation panel 102 (throttle lever) and the rotation speed (actual rotation speed) of the engine body 2. Here, the engine control unit 20 sets the target rotation speed of the engine body 2 (S7), and calculates the difference between the target rotation speed and the actual rotation speed (S8). Furthermore, the engine control unit 20 calculates the injection amount of gaseous fuel that is insufficient with respect to the injection amount of gaseous fuel in the immediately preceding cycle (deficient injection amount). Then, the engine control unit 20 determines the injection time of the gaseous fuel in reference to an "injection amount-injection time map" showing the correlation between the injection amount of the gaseous fuel and the injection time of the gaseous fuel (S10). Furthermore, the engine control unit 20 determines the injection timing of the gaseous fuel, that is, the timing to start the injection of the gaseous fuel in reference to an "injection amount-cooling period map" showing the correlation between the injection amount of the gaseous fuel and the cooling period T1 (S11). Then, the engine control unit 20 controls the fuel supply device 3 so as to inject the gaseous fuel when the injection timing of the gaseous fuel arrives (S12).

[0144] The engine control unit 20 repeatedly executes the processes of steps S1 to S12. However, the flowchart shown in Fig. 23 is merely an example, and processes may be added or omitted as appropriate, and the order of processes may be changed as appropriate.

[0145] FIG. 24 is a flowchart showing an example of the operation (processing) of the engine control unit 20 in which, when the engine system 1 is used to drive the generator 101, a cooling period T1 is provided only when a backfire occurs.

[0146] That is, the engine control unit 20 first acquires the load of the generator 101, the rotation speed (actual rotation speed) of the engine body 2, and the pressure in the combustion chamber 50 (in-cylinder pressure) (S21). Here, the in-cylinder pressure is acquired from the in-cylinder pressure sensor 76, and is information on the occurrence or non-occurrence of a backfire. Then, the engine control unit 20 judges whether or not a backfire has occurred based on, for example, the in-cylinder pressure (S22). If the occurrence of a backfire is detected from the waveform of the in-cylinder pressure, etc. (S22: Yes), the engine control unit 20 shifts the process to step S23. On the other hand, if the occurrence of a backfire is not detected from the waveform of the in-cylinder pressure, etc. (S22: No), the engine control unit 20 shifts the process to step S24.

[0147] In step S23, the engine control unit 20 determines the injection timing of the gas fuel, i.e., the timing to start the injection of the gas fuel, in reference to a "first load-rotation speed map" that indicates the correlation between the load and the engine speed of the generator 101. The "first load-rotation speed map" is a map prepared for when a backfire occurs, and is a map for setting the injection timing of the gas fuel in consideration of the cooling period T1.

[0148] In step S24, the engine control unit 20 determines the injection timing of the gas fuel, i.e., the timing to start the injection of the gas fuel, in reference to a "second load-rotation speed map" that indicates the correlation between the load and engine speed of the generator 101. The "second load-rotation speed map" is a map prepared for a steady state in which no backfire occurs, and is a map for setting the injection timing of the gas fuel without considering the cooling period T1.

[0149] Then, the engine control unit 20 calculates the injection amount of gaseous fuel (S25), and controls the fuel supply device 3 to inject the gaseous fuel when the injection timing of the gaseous fuel arrives (S26).

[0150] The engine control unit 20 repeatedly executes the processes of steps S21 to S26. However, the flowchart shown in Fig. 24 is merely an example, and processes may be added or omitted as appropriate, and the order of processes may be changed as appropriate.

[0151] [6] Variations Below, we will list some modified examples of the embodiment 1. The modified examples explained below can be applied in appropriate combinations.

[0152] The engine system 1 in the present disclosure includes a computer system as an engine control unit 20. The computer system mainly includes one or more processors and one or more memories as hardware. The processor executes a program recorded in the memory of the computer system to realize the function of the engine control unit 20 in the present disclosure. The program may be pre-recorded in the memory of the computer system, may be provided through an electric communication line, or may be recorded and provided in a non-transitory recording medium such as a memory card, an optical disk, or a hard disk drive that can be read by the computer system. In addition, some or all of the functional units included in the engine control unit 20 may be configured with electronic circuits.

[0153] Furthermore, it is not essential for the engine system 1 that at least some of the functions of the engine system 1 are concentrated in one housing, and the components of the engine system 1 may be distributed across multiple housings. Conversely, the functions distributed across multiple devices (for example, the engine body 2 and the generator 101) in the first embodiment may be concentrated in one housing.

[0154] Furthermore, at least a part of the engine system 1 is not limited to being mounted on the hull 100, but may be provided separately from the hull 100. As an example, if the engine control unit 20 is embodied by a server device provided separately from the hull 100, the engine system 1 can be controlled by the engine control unit 20 through communication between the server device and the hull 100 (a communication device thereof). At least a part of the functions of the engine control unit 20 may be realized by the cloud (cloud computing) or the like.

[0155] Furthermore, the ship 10 is not limited to a pleasure boat, but may be a merchant ship including a cargo ship and a cargo-passenger ship, a work ship including a tugboat and a salvage ship, a special ship including a weather observation ship and a training ship, a fishing boat, a naval vessel, etc. Furthermore, the ship 10 is not limited to a manned type with a pilot on board, but may be an unmanned type ship that can be remotely operated by a person (pilot) or can be operated autonomously. Furthermore, the ship 10 may be equipped with one or more power sources such as a motor (electric motor) in addition to the engine body 2 in the hull 100. The engine system 1 may be used for things other than the ship 10.

[0156] Furthermore, the engine system 1 is not limited to an in-line multi-cylinder engine in which a plurality of cylinders 51 are arranged in line, but may be, for example, a V-type engine or a horizontally opposed engine in which a plurality of cylinders 51 are arranged in a V shape with the rotation axis Ax1 of the crankshaft 22 as the apex. In the case of a V-type engine, for example, as shown in FIG. 25, a cam chamber 53 connected to an internal space Sp1 of the crank chamber 52 is arranged within a bank angle between the cylinders 51 on both sides. Even with this configuration, for example, by forming a ventilation port 502 in the cam chamber 53, it is possible to efficiently discharge blow-by gas from the crank chamber 52.

[0157] Furthermore, the engine system 1 may be a single-cylinder engine having only one cylinder 51. The engine system 1 is not limited to a dual-fuel engine, and may be, for example, an engine that uses only gaseous fuel (e.g., hydrogen) as fuel (e.g., a hydrogen-only combustion engine). The engine system 1 is not limited to a turbocharged engine, and may be a natural air-supply engine that does not have a turbocharger 8.

[0158] In addition, the method of supplying the gaseous fuel is not limited to the port injection method in which fuel is injected into the intake port 61, but may be a direct injection method in which fuel is directly injected into the combustion chamber 50. In this case, the injection unit 31 that injects the gaseous fuel is disposed at a position facing the combustion chamber 50.

[0159] In addition, the ventilation port 502 does not necessarily have to be open all the time, and may be configured to be openable and closable by, for example, a valve device, etc. In this case, while the ventilation port 502 is open, the blow-by gas is discharged from the ventilation port 502, and while the ventilation port 502 is closed, the blow-by gas is not discharged from the ventilation port 502.

[0160] (Embodiment 2) As shown in Fig. 26 and Fig. 27, the engine system 1A according to this embodiment differs from the engine system 1 according to the first embodiment in the position of the ventilation port 502. Hereinafter, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted as appropriate. In Fig. 27, the flow of blow-by gas is indicated by thick arrows.

[0161] That is, in this embodiment, as shown in FIG. 26, the cylinder block 5 has a liner support wall 55 that supports a cylinder liner 511 that constitutes a cylinder 51. The lower end of the cylinder liner 511 protrudes downward from the lower end of the liner support wall 55. Here, the ventilation port 502 is disposed at the lower end of the liner support wall 55. Specifically, the ventilation port 502 is formed in a part of the circumferential direction of the lower surface of the cylindrical liner support wall 55 that surrounds the cylinder liner 511. In the example of FIG. 26, the ventilation port 502 is formed at a position on the lower surface of the liner support wall 55 that is to the left of the cylinder liner 511. Here, in this embodiment, as shown by an imaginary line (two-dot chain line) in FIG. 26, the opening 531 of the cam chamber 53 is provided with a cam chamber wall 533 that separates the internal space of the cam chamber 53 from the internal space Sp1 of the crank chamber 52. The cam chamber wall 533 may completely separate the internal space of the cam chamber 53 from the internal space Sp1 of the crank chamber 52, or may partially separate the internal space of the cam chamber 53 from the internal space Sp1 of the crank chamber 52.

[0162] The ventilation passage 503 connected to the ventilation opening 502 has a vertical passage 503A extending straight upward from the ventilation opening 502 along the vertical direction D2, and a horizontal passage 503B extending leftward from the upper end of the vertical passage 503A along the width direction D3. The vertical passage 503A may extend upward from the ventilation opening 502 along the vertical direction D2, for example, may extend obliquely upward from the ventilation opening 502, or may extend upward from the ventilation opening 502 while meandering. This ventilation passage 503 is an intra-wall passage formed inside the liner support wall 55. In this way, the ventilation passage 503 includes the vertical passage 503A and the horizontal passage 503B having different extension directions, and has an inflection portion 503C (see FIG. 27) at the connection portion between the vertical passage 503A and the horizontal passage 503B. In other words, the connection portion between the vertical passage 503A and the horizontal passage 503B constitutes the inflection portion 503C.

[0163] According to the above-described configuration, as shown in FIG. 27, the blow-by gas is efficiently discharged from the internal space Sp1 of the crank chamber 52 through the ventilation port 502 (and the ventilation passage 503). That is, the blow-by gas is generated when unburned gas leaks from the combustion chamber 50 to the crank chamber 52 through the gap between the cylinder 51 and the piston 21. In this embodiment, the specific gravity of the blow-by gas is also less than 1 by using a gaseous fuel (hydrogen) having a specific gravity less than 1, so that the blow-by gas leaked into the crank chamber 52 moves upward in the crank chamber 52. Since the lower end of the cylinder liner 511 protrudes downward from the lower end of the liner support wall 55, the blow-by gas leaked from the lower end of the cylinder liner 511 into the crank chamber 52 moves toward the lower surface of the liner support wall 55 recessed upward, as if turning back at the lower end of the cylinder liner 511. As a result, the blow-by gas is discharged from the ventilation port 502 at the lower end (lower surface) of the liner support wall 55 and is discharged to the external space of the cylinder block 5 through the ventilation passage 503.

[0164] Here, the lower end (lower surface) of the liner support wall 55 is not perpendicular but inclined with respect to the central axis of the cylinder 51. That is, as shown in FIG. 27, the lower surface of the liner support wall 55 is inclined to the left so that the end (left end) where the ventilation port 502 is provided is located higher. Therefore, the blow-by gas that stays at the lower end of the liner support wall 55 is collected at the left end side so as to detour around the cylinder liner 511 due to the inclination of the lower surface of the liner support wall 55. Therefore, the blow-by gas is efficiently discharged from the ventilation port 502 provided at the left end of the lower end of the liner support wall 55.

[0165] In this embodiment, the inflection portion 503C of the ventilation passage 503 functions as the gas-liquid separation portion 504. In short, by providing such an inflection portion 503C (gas-liquid separation portion 504), the blow-by gas introduced into the ventilation passage 503 from the ventilation port 502 flows in the ventilation passage 503 so as to collide with the end surface of the vertical passage 503A when passing through the inflection portion 503C as the gas-liquid separation portion 504. Then, when the blow-by gas contacts the inner peripheral surface of the inflection portion 503C as the gas-liquid separation portion 504, the liquid such as oil or moisture discharged together with the blow-by gas adheres to the inner peripheral surface of the inflection portion 503C as the gas-liquid separation portion 504. As a result, the liquid (oil or moisture, etc.) discharged together with the blow-by gas is captured by the gas-liquid separation portion 504 and separated from the gas contained in the blow-by gas.

[0166] Thus, in this embodiment, the ventilation passage 503 has the inflection portion 503C where the flow direction of the gas changes. The gas-liquid separation portion 504 includes the inflection portion 503C. As a result, the blow-by gas is exhausted from the ventilation passage 503 with at least a part of the liquid components such as oil removed, which leads to suppression of oil consumption and the like accompanying the exhaust of the blow-by gas.

[0167] The cam chamber wall 533 is not an essential component and may be omitted as appropriate. The configuration according to the second embodiment (including modified examples) can be adopted in appropriate combination with the various configurations (including modified examples) described in the first embodiment.

[0168] (Embodiment 3) 28, the engine system 1B according to this embodiment is different from the engine system 1 according to the first embodiment in that a plurality of ventilation openings 502 are provided in one-to-one correspondence with a plurality of cylinders 51. Hereinafter, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0169] That is, in this embodiment, a plurality (six) of cylinders 51 are provided aligned in the output shaft direction D1. Here, the ventilation ports 502 are formed in six locations in the output shaft direction D1 in the cam chamber 53 so as to correspond to all of the plurality of cylinders 51. A plurality of ventilation passages 503 are provided so as to extend upward from each of the plurality (six in this embodiment) of ventilation ports 502.

[0170] Here, the tips (upper ends) of the multiple ventilation passages 503 are connected to one common exhaust pipe 507. The common exhaust pipe 507 extends along the output shaft direction D1, and its tip (the rear end in this embodiment) is located in the external space of the engine body 2. As a result, blow-by gas generated in each of the multiple cylinders 51 is collected into the common exhaust pipe 507 through the ventilation ports 502 and the ventilation passages 503, and is discharged into the external space of the engine body 2 through the common exhaust pipe 507.

[0171] In this embodiment, the common exhaust pipe 507 is not parallel to the rotation axis Ax1 of the crankshaft 22 but is inclined. That is, as shown in FIG. 28, the common exhaust pipe 507 is inclined upward toward the rear so that one end (the rear end in this embodiment) of the output shaft direction D1 is positioned higher. Therefore, the blow-by gas collected in the common exhaust pipe 507 is collected at the tip side (rear end side) of the common exhaust pipe 507 due to the inclination of the common exhaust pipe 507. Therefore, the blow-by gas is efficiently discharged from the common exhaust pipe 507.

[0172] The configuration according to the third embodiment can be adopted in appropriate combination with the various configurations (including modified examples) described in the first or second embodiment.

[0173] (Embodiment 4) 29, the engine system 1C according to this embodiment differs from the engine system 1 according to the first embodiment in that a cooling unit 612 is disposed on an outer peripheral side surface 601. Hereinafter, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0174] That is, in this embodiment, the air intake port 61 has a curved portion 600 whose cross-sectional shape is convex in one direction. The cooling portion 612 is disposed on the surface of the inner circumferential surface 611 of the air intake port 61 on one side (here, the upper side) of the curved portion 600, that is, the outer circumferential side surface 601. That is, the inner circumferential surface 611 includes the outer circumferential side surface 601 which is the surface on one side (here, the upper side) of the curved portion 600, and the inner circumferential side surface 602 which is the surface on the other side (here, the lower side) of the curved portion 600, and the cooling portion 612 is disposed on the outer circumferential side surface 601.

[0175] In this way, by arranging the cooling portion 612 on the outer peripheral side surface 601, the gaseous fuel injected from the injection portion 31 can easily reach the cooling portion 612 even when it is carried away by the air flow. In short, since the air flow in the curved portion 600 mainly passes close to the outer peripheral side surface 601, the presence of the cooling portion 612 on the outer peripheral side surface 601 makes it easier for the gaseous fuel to be cooled by the cooling portion 612. Therefore, it is possible for the cooling portion 612 to fully exert its cooling effect on the gaseous fuel.

[0176] In this embodiment, the nozzle length of the injection portion 31 is set to be relatively long, thereby improving the directivity of the gaseous fuel injected from the injection portion 31. In other words, the longer the injection portion 31 is, the more the directivity of the gaseous fuel injected from the injection portion 31 is improved, and the easier it is for the gaseous fuel to reach the cooling portion 612.

[0177] In the present embodiment, as an example, in order to realize the cooling portion 612 arranged on the outer peripheral side surface 601, as shown in FIG. 29, a valve seat portion 66 on which the intake valve 72 is seated is provided at the end of the intake port 61 on the combustion chamber 50 side. The cooling portion 612 is arranged on the valve seat portion 66. Specifically, a refrigerant passage 661 for passing a refrigerant is formed on the surface of the valve seat portion 66 opposite to the internal space Sp2 of the intake port 61. The refrigerant flows through the refrigerant passage 661, whereby the valve seat portion 66 is cooled, and the cooling portion 612 provided on the valve seat portion 66 is cooled. That is, as a specific aspect of the cooling portion 612, the first aspect (refrigerant cooling method) is adopted.

[0178] According to this configuration, the gaseous fuel can be cooled at the valve seat portion 66 of the intake port 61, which is the portion closest to the combustion chamber 50. Therefore, even if a flame (or heated gas) flows into the intake port 61 from the combustion chamber 50 due to a backfire, the fuel can be cooled by the cooling portion 612 provided at the inlet (valve seat portion 66) of the intake port 61, and the chain reaction of backfires can be further suppressed.

[0179] As a modification of the fourth embodiment, a throttle portion 67 may be used as shown in FIG. 30 to realize a cooling portion 612 disposed on the outer peripheral side surface 601. The throttle portion 67 is a portion of the intake port 61 where the cross-sectional area perpendicular to the airflow, i.e., the flow path cross-sectional area, is locally reduced. In other words, the flow path cross-sectional area of ​​the intake port 61 is not uniform, and at least the throttle portion 67 is smaller (narrower) than the upstream side and downstream side of the throttle portion 67. Such a throttle portion 67 is realized by a rib or the like formed on the inner peripheral surface 611 of the intake port 61. In the example of FIG. 30, the throttle portion 67 where the flow path cross-sectional area of ​​the intake port 61 is locally narrowed is configured by a rib protruding rearward (toward the viewer of the paper of FIG. 30) from the inner peripheral surface 611 of the intake port 61.

[0180] By providing such a throttling portion 67, the air whose flow speed is increased when passing through the throttling portion 67 travels in a substantially straight line and collides with the inner circumferential surface 611 (here, the outer circumferential side surface 601) of the intake port 61. As a result, the part of the inner circumferential surface 611 of the intake port 61 that the air hits can be cooled by the air flow to form the cooling portion 612. In short, in the example of FIG. 30, the intake port 61 has the throttling portion 67 in which the cross-sectional area perpendicular to the air flow is partially reduced. The cooling portion 612 includes an intersection point of the inner circumferential surface 611 of the intake port 61 with a virtual line VL1 that extends vertically from the cross section of the throttling portion 67 in the intake port 61 toward the downstream side of the air flow. In this way, the cooling portion 612 realized by using the throttling portion 67 is a type of the third mode (air-cooling method).

[0181] According to this configuration, by simply providing the throttle portion 67, it is possible to realize the cooling portion 612 by air cooling without using a device such as a fan for increasing the air flow speed. Therefore, it is possible to simplify the configuration for realizing the cooling portion 612. In the example of Fig. 30, the refrigerant passage 661 of the valve seat portion 66 can be omitted.

[0182] In this embodiment, the refrigerant passage 63 can be omitted as appropriate. The configuration (including the modified examples) according to the fourth embodiment can be adopted in appropriate combination with the various configurations (including the modified examples) described in the first, second, or third embodiment. [Explanation of symbols]

[0183] 1,1A~1C Engine System 5 Cylinder block 23 Camshaft 51 cylinders 51A One end cylinder 51B Other end cylinder 52 Crankcase 53 Cam chamber 55 Liner support wall 210 Piston space 212 Isolation Wall 213 Mixing section 214 Cavity 501 (Cylinder block) inner surface 502 Ventilation vent 503 Ventilation Passage 503C Inflection part 504 Gas-liquid separation section 511 Cylinder liner 505 Gas inlet 506 Airflow forming section Ax1 Rotation axis C1 center D1 Output shaft direction D2 Vertical direction Sp1 (crankcase) internal space

Claims

1. An engine system in which blow-by gas having a specific gravity of less than 1 based on air may be generated, a cylinder block including cylinders and a crank chamber arranged in a vertical direction, the crank chamber being located below the cylinders; a ventilation port connected to a ventilation passage connecting an internal space of the crank chamber and an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block, The ventilation opening is disposed above a center of the crank chamber in the up-down direction, the cylinder block has a liner support wall that supports a cylinder liner that configures the cylinder, A lower end of the cylinder liner protrudes downward from a lower end of the liner support wall, The ventilation opening is disposed at a lower end of the liner support wall. Engine system.

2. An engine system in which blow-by gas having a specific gravity of less than 1 based on air may be generated, a cylinder block including cylinders and a crank chamber arranged in a vertical direction, the crank chamber being located below the cylinders; a ventilation port connected to a ventilation passage connecting an internal space of the crank chamber and an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block, The ventilation opening is disposed above a center of the crank chamber in the up-down direction, a gas inlet port that connects an internal space of the crank chamber with an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block, An airflow forming unit that forms an airflow from the gas inlet toward the ventilation port, the ventilation port and the gas inlet port are disposed at different positions from each other in an output axial direction along a rotation axis of a crankshaft disposed in the crank chamber, The cylinders are provided in a plurality of rows in the output shaft direction, the plurality of cylinders includes a first end cylinder and an second end cylinder located on opposite sides in the output shaft direction, The ventilation port is disposed at a position corresponding to the one end side cylinder, The gas inlet is disposed at a position corresponding to the other end side cylinder. Engine system.

3. The cylinder block further includes a cam chamber that is connected to the crank chamber and that accommodates a camshaft, The ventilation hole is formed in the cam chamber. The engine system of claim 2 .

4. The ventilation port and the gas inlet port are disposed on opposite sides across a rotation axis of a crankshaft disposed in the crank chamber in a plan view. The engine system of claim 2 .

5. The ventilation opening is disposed above the lower end of the cylinder. The engine system according to any one of claims 1 to 4.

6. The ventilation opening opens downward. The engine system according to any one of claims 1 to 5.

7. The ventilation passage has a gas-liquid separation section that separates gas and liquid. The engine system according to any one of claims 1 to 6.

8. The ventilation passage has an inflection portion where the flow direction of the gas changes, The gas-liquid separation section includes the inflection section, The engine system of claim 7.

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