Engine system

Abstract

To provide an engine system that facilitates efficient discharge of blow-by gas from a crank chamber.SOLUTION: In an engine system, blow-by gas can be generated. The engine system includes a cylinder block 5. In the cylinder block 5, a crank chamber 52 is located below a cylinder 51. A ventilation port 502 connected to a ventilation passage 503 that connects an inner space Sp1 of the crank chamber 52 and an outer space of the cylinder block 5 to each other is opened on an inner peripheral surface 501 of the cylinder block 5. The cylinder block 5 includes a liner support wall 55 that supports a cylinder liner 511 constituting the cylinder 51, and a lower end of the cylinder liner 511 projects downwardly from a lower end of the liner support wall 55. The ventilation port 502 is disposed on the upper side of a lower end of the cylinder 51.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 less than 1 based on air can be generated.

Background Art

[0002] As a related art, an engine system (internal combustion engine) that takes measures against blow-by gas leaking from a combustion chamber to a crank chamber (crankcase) is known (see, for example, Patent Document 1). In the engine system according to the related art, an intake port for taking in blow-by gas from the crank chamber is provided on the inner surface of the crank chamber. The intake port is connected to a blow-by gas passage through an intake passage, and the engine system is configured to reflux blow-by gas to the combustion chamber through an intake system in the blow-by gas passage. Here, the intake port (blow-by gas intake portion) is arranged at a position below the crank journal so as to avoid interference between the blow-by gas intake portion and the crank journal of the crankshaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for example, in an engine system using a gaseous fuel having a specific gravity less than 1 such as hydrogen, blow-by gas leaking into the crank chamber tends to stay above the crank chamber. Therefore, if the intake port is arranged at a position below the crank journal as in the above related art, there is a possibility that blow-by gas cannot be efficiently discharged from the crank chamber.

[0005] An object of the present disclosure is to provide an engine system that can efficiently discharge blow-by gas from a crankcase.

Means for Solving the Problems

[0006] An engine system according to an aspect of the present disclosure is an engine system in which blow-by gas can occur, and includes a cylinder block. The crankcase is located below the cylinder in the cylinder block. A ventilation port that leads to a ventilation passage connecting the internal space of the crankcase and the external space of the cylinder block is opened on the inner peripheral surface of the cylinder block. The cylinder block has a liner support wall that supports a cylinder liner constituting the cylinder, and a lower end of the cylinder liner protrudes downward from a lower end of the liner support wall. The ventilation port is disposed above an upper end of the cylinder.

Advantages of the Invention

[0007] According to the present disclosure, an engine system that can efficiently discharge blow-by gas from a crankcase can be provided.

Brief Description of the Drawings

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The following embodiments are an example of embodying the present disclosure and are not intended to limit the technical scope of the present disclosure. The drawings referred to in the present disclosure are all schematic diagrams, and the ratios of the sizes and thicknesses of the respective components in the drawings do not necessarily reflect the actual dimensional ratios.

[0010] (Embodiment 1) [1] Overall configuration First, the overall configuration of the engine system 1 according to the present embodiment will be described with reference to FIGS. 1 to 6. In FIG. 1, the configurations of the respective parts of the engine system 1 are schematically shown, and the electrical connection relationships are indicated by dashed-dotted arrows (in the direction of the flow of electrical signals).

[0011] As shown in FIG. 1, the engine system 1 according to the present embodiment includes an engine body 2 that is the main configuration of the engine system 1. The "engine" as used herein is a heat engine that burns fuel to generate mechanical energy (power), and includes an internal combustion engine in which the combustion of fuel occurs inside the engine and the combustion gas is used as the working gas to convert thermal energy into mechanical energy. That is, the engine body 2 generates power (mechanical energy) using the supplied fuel.

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

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

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

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

[0016] In addition, in the present embodiment, the ship 10 is configured to operate in response to the operation (including remote operation) of a person (operator), and in particular, it is of a manned type in which a person who is an operator can board. Therefore, the ship 10 has an operation panel 102 (see FIG. 1) for receiving the operation of the operator on the hull 100, and the engine control unit 20 of the engine system 1 drives the engine body 2 in response to the operation on the operation panel 102. As a result, the ship 10 can drive the engine body 2 in response to the operation of the operator and rotate the propeller 103 to move the hull 100 forward or backward. Further, the hull 100 further includes various in-ship facilities including a steering mechanism, a display device, a communication device, and lighting equipment. 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 a person (operator).

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

[0018] In addition, in the present 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. Further, as shown in FIG. 3, the direction orthogonal to the output axis direction D1 and along the vertical direction in a state where the engine body 2 can be used is defined as the vertical direction D2, and the direction orthogonal to both the output axis direction D1 and the vertical direction D2 is defined as the width direction D3. Here, one side of the output axis direction D1 is defined as "front" and the other side is defined as "rear", and the side of the crankshaft 22 where it is connected to the propeller shaft 104 (the side where the flywheel is disposed) is defined as the rear. Similarly, one side of the width direction D3 is defined as "left" and the other side is defined as "right". Further, among the vertical 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 "upper", and the opposite side is defined as "lower".

[0019] In other words, each direction used in the present embodiment is a direction defined with reference to the rotation axis Ax1 of the crankshaft 22. Here, as described above, the engine body 2 is disposed in a "front-upward" posture in which the rotation axis Ax1 of the crankshaft 22 is inclined with respect to the horizontal plane by the inclination angle θ1 while being along the traveling direction of the hull 100. Therefore, the virtual straight line extending in the vertical direction D2 is inclined by the inclination angle θ1 (toward the reverse side) with respect to the vertical direction in a state where the engine body 2 is mounted on the hull 100. However, none of these directions is intended to limit the usage direction (direction during use) of the engine body 2.

[0020] From the rear end of the engine body 2, a crankshaft 22 serving as an engine output shaft projects rearward. A propeller shaft 104 is connected to the crankshaft 22 via a speed reducer. When the engine body 2 is driven and the crankshaft 22 rotates about the rotation axis Ax1, the propeller 103 connected to the propeller shaft 104 rotates to generate a propulsive force for the hull 100. When the engine system 1 is used to drive the 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 electrical energy.

[0021] The engine system 1 according to this embodiment is a dual-fuel engine as described above. Therefore, the engine system 1 can select 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 (light oil) is diffused and burned, to drive the engine body 2. Therefore, the engine body 2 is configured to be able to supply two types of fuel, gaseous fuel (here hydrogen) and liquid fuel (here light oil), from the outside of the engine body 2.

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

[0023] The fuel supply device 3 includes 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 the order of the vaporizer 34 and the pressure regulating valve 35 from the upstream side. The vaporizer 34 vaporizes liquefied hydrogen. The pressure regulating valve 35 is a gas valve unit that adjusts the supply amount of gaseous fuel to the engine body 2. The gas admission valve 36 injects the gaseous fuel supplied through the fuel supply passage 33 into the engine body 2 from the nozzle-shaped (cylindrical) injection unit 31.

[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 through a liquid fuel supply passage. The liquid fuel supply device 4 injects the liquid fuel supplied through the liquid fuel supply passage 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 the air supply port 61 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. Thereby, the injection unit 31 injects gaseous fuel into the air supply port 61, mixes the gaseous fuel with air, and then allows it to flow into the combustion chamber 50. On the other hand, the liquid fuel injection unit 41 directly injects liquid fuel into the combustion chamber 50. That is, as a fuel supply method, the port injection method is adopted for gaseous fuel, and the direct injection method is adopted for liquid fuel.

[0026] As shown in FIGS. 3 and 4, the engine body 2 is configured by assembling a cylinder head 6 on top of a cylinder block 5. The cylinder block 5 has cylinders 51 (cylinders) and a crank chamber 52. The cylinder head 6 has an intake port 61 and an exhaust port 62. As shown in FIG. 3, a crankshaft 22 is rotatably supported at the lower part of the cylinder block 5 with its rotation axis Ax1 directed in the output axis direction D1.

[0027] As shown in FIG. 5, in the cylinder block 5, a plurality (six in this embodiment) of cylinders 51 are 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 a plurality of 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, that is, reciprocally movable, in the vertical direction D2. The piston 21 is connected to the crankshaft 22 via a connecting rod 24.

[0028] A plurality (six in this embodiment) of cylinder heads 6 are provided so as to correspond one-to-one to the plurality of cylinders 51. The plurality (six in this embodiment) of cylinder heads 6 are fixed above a single cylinder block 5 so as to cover the cylinders 51 from above. That is, the plurality of cylinder heads 6 are arranged in a row in the output axis direction D1. As shown in FIG. 1, in the internal space of each cylinder 51, the 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 repeats expansion and contraction.

[0029] A plurality of head covers 71 are arranged in a row in the output shaft direction D1 on the cylinder head 6 so as to correspond one-to-one to a plurality (six in this embodiment) of cylinders 51. Inside each head cover 71, a valve operating mechanism including a push rod, a rocker arm, etc. for operating the intake valve 72 and the exhaust valve 73 is accommodated. The intake valve 72 opens and closes an opening leading to the combustion chamber 50 among the intake ports 61 formed in the cylinder head 6. The exhaust valve 73 opens and closes an opening leading to the combustion chamber 50 among the exhaust ports 62 formed in the cylinder head 6. Thereby, in a state where the intake valve 72 is open, air (intake air) from the intake port 61 can be taken into the combustion chamber 50. In a state where the exhaust valve 73 is open, the exhaust from the combustion chamber 50 can be discharged to the exhaust port 62.

[0030] The opening and closing drive of the intake valve 72 and the exhaust valve 73 is performed by a camshaft 23 (see FIG. 1). As shown in FIGS. 1 and 6, the camshaft 23 is accommodated in a cam chamber 53 arranged on the left side of the cylinder 51 in the cylinder block 5. The cam chamber 53 is formed integrally with the cylinder 51, the crank chamber 52, etc. in the cylinder block 5. The cam chamber 53 extends in the output shaft direction D1 and rotatably accommodates the camshaft 23 that also extends in the output shaft direction D1. The camshaft 23 rotates about a rotation axis along the output shaft direction D1 in conjunction with the rotation of the crankshaft 22, and drives each of the intake valve 72 and the exhaust valve 73 to open and close.

[0031] Above the cylinder block 5 and hitting the left side of the cylinder head 6, a side cover 74 is attached. That is, a step is formed at the upper part 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, etc. are arranged. The liquid fuel supply rail pipe is arranged so as to extend in the output shaft direction D1 and distributes and supplies liquid fuel to the combustion chambers 50 of the respective cylinders 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 pumps provided corresponding to the respective cylinders 51, and the liquid fuel supplied from the main fuel injection pumps is injected into the combustion chambers 50 from the liquid fuel injection portions 41. The pilot fuel supply rail pipe distributes and supplies pilot fuel to the combustion chambers 50 of the respective cylinders 51 for the purpose of igniting gaseous fuel during combustion in the premixed combustion method.

[0032] Also, as shown in FIGS. 1 and 6, on the right side of the cylinder 51 in the cylinder block 5, an intake manifold 54 for distributing and supplying air (intake air) from the outside of the engine body 2 to the combustion chambers 50 of the respective cylinders 51 is arranged. The intake manifold 54 is formed integrally with the cylinder 51, the crankcase 52, etc. in the cylinder block 5. The intake manifold 54 extends in the output shaft direction D1 and is connected to a plurality of intake ports 61 formed in the plurality of cylinder heads 6. Thereby, air is distributed from the intake manifold 54 to the plurality of intake ports 61. That is, the intake manifold 54 communicates with the combustion chambers 50 of the respective cylinders 51 through the intake ports 61.

[0033] As shown in FIG. 6, an exhaust manifold 75 for collecting the exhaust gas generated by the combustion in the combustion chamber 50 of each cylinder 51 and discharging it to the outside of the engine body 2 is disposed above the upper right of the cylinder head 6. The exhaust manifold 75 extends in the output shaft direction D1 and is connected to a plurality of exhaust ports 62 formed in the plurality of cylinder heads 6. Thereby, the exhaust gas from the plurality of exhaust ports 62 is aggregated in the exhaust manifold 75. That is, the exhaust manifold 75 communicates with the combustion chamber 50 of each cylinder 51 through the exhaust port 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 a metal material such as an aluminum alloy and cast iron. These main components have a desired durability (including rigidity and wear resistance, etc.) and relatively excellent thermal conductivity.

[0035] According to the above configuration, when the engine body 2 is driven in the diffusion combustion mode, the air supplied from the intake manifold 54 to each cylinder 51 is compressed by the slide of the piston 21 at an appropriate timing, and the liquid fuel is injected into the combustion chamber 50 from the liquid fuel injection unit 41. When the liquid fuel is injected into the combustion chamber 50, the piston 21 reciprocates in the cylinder 51 by the propulsive force obtained from the explosion occurring 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. Thereby, 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 mode, the gaseous fuel supplied from the liquefied hydrogen tank 32 through the fuel supply passage 33 is injected into the intake port 61 from the injection unit 31. 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, the air-fuel mixture is introduced into each cylinder 51 from the intake port 61, and at an appropriate timing when the air-fuel mixture is compressed by the slide 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 occurring 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. Thereby, the engine body 2 outputs the rotational force of the crankshaft 22 as power (mechanical energy).

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

[0038] In addition, the engine system 1 according to the present embodiment is a supercharged engine including a supercharger 8 (see FIG. 1) in addition to the engine body 2. As shown in FIGS. 3 and 4, the supercharger 8 is disposed above the front portion of the engine body 2.

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

[0040] Incidentally, in addition to the engine body 2 (and the supercharger 8) having the above-described configuration, the engine system 1 according to the present embodiment further includes an engine control unit 20, a cylinder pressure sensor 76, a rotational speed sensor 77, etc., as shown in FIG. 1.

[0041] The engine control unit 20 mainly includes 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 one or more processors to execute an engine control method is recorded in 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. Thereby, the engine control unit 20 can control the engine body 2 so as to adjust the output (mainly the rotational speed) of the engine body 2 to an arbitrary value.

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

[0043] [2] Definition The "blow-by gas" referred to in the present disclosure means the gas that has leaked from the cylinder 51 (combustion chamber 50) to the crankcase 52 through the 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 process or combustion process of the engine body 2. In other words, the "blow-by gas" includes the "compression leakage gas" formed by the air-fuel mixture in the combustion chamber 50 that has become high pressure during the compression process leaking into the crankcase 52. That is, when the sealing ability of the piston ring (compression ring) for ensuring airtightness between the cylinder 51 and the piston 21 is exceeded by unburned gas or the like in the combustion chamber 50, the unburned gas or the like in the combustion chamber 50 may leak into the crankcase 52 as blow-by gas.

[0044] As used in the present disclosure, "specific gravity" means the ratio of the density of a substance to the density of a reference substance. For gases, the specific gravity is represented by the ratio of the density of the gas to the density of air as the reference substance at the same temperature and pressure. Therefore, if the specific gravity of the blow-by gas (which is a gas) is less than "1", the mass of the blow-by gas is smaller (i.e., lighter) compared to air of the same volume as the blow-by gas at the same temperature and pressure. Conversely, if the specific gravity of the blow-by gas (which is a gas) is greater than "1", the mass of the blow-by gas is larger (i.e., heavier) compared to air of the same volume as the blow-by gas at the same temperature and pressure. As an example, since the specific gravity of hydrogen is "0.06952", which is sufficiently less than "1", when the main component of the blow-by gas is hydrogen, the specific gravity of the blow-by gas is less than "1", and the blow-by gas is lighter than air of the same volume at the same temperature and pressure. Alternatively, the specific gravity of a gas may be represented by the ratio of the density of the gas to the density of air as the reference substance under standard conditions (0°C, 1 atm).

[0045] As used in the present disclosure, "backfire" means, for example, unintended ignition in the combustion chamber 50 or the intake port 61 or the like during the intake stroke, and the flame existing inside the combustion chamber 50 or the intake port 61 or the like. Therefore, when backfire occurs during the intake stroke (with the intake valve 72 open), the intake port 61 may be exposed to the flame.

[0046] As used in the present disclosure, "parallel" means that for two straight lines on a plane, in addition to the case where they do not intersect no matter how far they are extended, i.e., the angle between them is exactly 0 degrees (or 180 degrees), the angle between them is within an error range of several degrees (e.g., less than 10 degrees) with respect to 0 degrees. Similarly, as used in the present disclosure, "orthogonal" means that in addition to the case where the angle between them intersects exactly at 90 degrees, the angle between them is within an error range of several degrees (e.g., less than 10 degrees) with respect to 90 degrees.

[0047] [3] Configuration of the Cylinder Block Next, the configuration of the cylinder block 5 (and its peripheral structure) of the engine body 2 will be described in more detail with reference to FIGS. 7 to 16. FIG. 7 is a schematic view of the cylinder block 5 with a main cross-sectional portion hatched while breaking a part of the cylinder block 5 as seen from the rear side (the side where the crankshaft 22 protrudes), which is one side in the output shaft direction D1. In FIG. 7, illustration of the side cover 74 and the like is appropriately omitted.

[0048] In the present embodiment, in the cylinder block 5, in addition to the cylinder 51 and the crank chamber 52 as described above, a cam chamber 53 and an intake manifold 54 are formed. The cylinder 51, the crank chamber 52, the cam chamber 53, and the intake manifold 54 are all composed of compartments (chambers) separated from each other inside the cylinder block 5 and each has an internal space. Therefore, the inner peripheral surfaces of these cylinder 51, crank chamber 52, cam chamber 53, and intake manifold 54 are all included in the inner peripheral surface 501 of the cylinder block 5. Specifically, the crank chamber 52 is disposed at the lower part of the cylinder block 5, and above the crank chamber 52, the cylinder 51, the cam chamber 53, and the intake manifold 54 are disposed. Among the cylinder 51, the cam chamber 53, and the intake manifold 54, the cylinder 51 is disposed at 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 cylinder 51 and the crank chamber 52 arranged in the vertical direction D2, and the crank chamber 52 is located below the cylinder 51.

[0049] Here, in FIG. 7, the cylinder 51, the crank chamber 52, the cam chamber 53, and the intake manifold 54 are each shown. However, in reality, a plurality (six in this embodiment) of cylinders 51 are arranged side by side in the output shaft direction D1 (the direction orthogonal to the plane of FIG. 7). On the other hand, regarding the crank chamber 52, although it is somewhat partitioned in the output shaft direction D1 by the partition wall 521 located between adjacent cylinders 51, it is integrally continuous through the communication hole 522 formed in the lower part of the partition wall 521. That is, the crank chamber 52 consists of one compartment (chamber) connected in the output shaft direction D1. Further, an opening 531 is formed on the lower surface of the cam chamber 53, and the internal space of the cam chamber 53 is continuous with the internal space Sp1 of the crank chamber 52 through the opening 531. The intake manifold 54 consists of one compartment (chamber) extending in the output shaft direction D1.

[0050] The cylinder 51 is formed in a cylindrical shape extending in the vertical direction D2, and a piston 21 is accommodated therein so as to be reciprocally movable along the vertical direction D2. Both end faces of the cylinder 51 in the vertical direction D2 are open. The piston 21 is a columnar 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. And, among the internal space of the cylinder 51, the space above the piston 21, that is, 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, among 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 a hollow member with an open bottom surface (the 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 part with both end faces in the vertical direction D2 open, and the partition wall 212 is a part 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 in a bottomed cylindrical shape as a whole. Therefore, strictly speaking, among the internal spaces of the cylinder 51, the combustion chamber 50 and the space 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 is continuous with the internal space Sp1 of the crank chamber 52, including the internal space of the cylindrical portion 211. The connecting rod 24 is supported by the piston 21 with its upper end inserted into the piston 21.

[0052] Also, in this embodiment, the cylinder 51 is constituted by a cylinder liner 511 that guides the piston 21. The cylinder liner 511 is a cylindrical part, and by sliding the piston 21 on its inner peripheral surface, the moving direction (vertical direction D2) of the piston 21 is restricted. 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 slightly 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 portion of the cylinder liner 511 protrudes downward (toward the crankshaft 22 side) from the lower surface of the liner support wall 55. In short, in this embodiment, the cylinder block 5 has a liner support wall 55 that supports the cylinder liner 511 constituting the cylinder 51. The lower end of the cylinder liner 511 protrudes downward from the lower end of the liner support wall 55.

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

[0054] By the way, as a related art, an engine system that takes measures against blow-by gas leaking from the combustion chamber 50 into the crank chamber 52 is known. In the engine system according to the related art, an intake port for taking in blow-by gas is provided on the inner surface portion 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 reflux the blow-by gas into the combustion chamber 50 through an air supply system in the blow-by gas passage. Here, the intake port (blow-by gas intake portion) is arranged at a position below the crank journal so as to avoid 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 using a gaseous fuel having a specific gravity less than 1 such as hydrogen, the blow-by gas leaking into the crank chamber 52 tends to stay above the crank chamber 52. Therefore, if the intake port is arranged at a position below the crank journal as in the above related art, there is a possibility that the blow-by gas cannot be efficiently discharged from the crank chamber 52.

[0056] Therefore, in the present embodiment, by adopting the configuration described below, it is possible to provide an engine system 1 in which blow-by gas can be efficiently discharged from the crank chamber 52.

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

[0058] In short, for example, by using a gaseous fuel such as hydrogen having a specific gravity less than 1, in the engine system 1 in which blow-by gas having a specific gravity (based on air) less than 1 can be generated, by adopting the above configuration, it becomes easier to efficiently discharge the blow-by gas. In this type of engine system 1, the blow-by gas leaking into the crankcase 52 tends to stay above the crankcase 52. In the engine system 1 according to the present embodiment, since the ventilation port 502 is disposed above the center C1 in the crankcase 52, it is possible to efficiently discharge the blow-by gas staying above the crankcase 52 from the ventilation port 502. That is, since the ventilation port 502 serving as an outlet for the blow-by gas is formed in the upper part of the crankcase 52 where the blow-by gas stays, the blow-by gas is efficiently discharged from the internal space Sp1 of the crankcase 52 via the ventilation port 502 (and the ventilation passage 503). Therefore, it is possible to provide an engine system 1 in which it is easy to efficiently discharge the blow-by gas from the crankcase 52.

[0059] Specifically, as shown in FIG. 7, the center C1 in the vertical direction D2 in the crank chamber 52 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 equidistant from both the upper end and the lower end of the crank chamber 52. As viewed from this center C1, the ventilation port 502 is arranged so as to be located on the upper side in the vertical direction D2, that is, on the cylinder 51 side. The ventilation port 502 is, for example, circular (a perfect circle) in plan view and has a size sufficient to allow blow-by gas to pass through. However, the ventilation port 502 is not limited to a circular shape and may be, for example, elliptical, square, or polygonal.

[0060] More specifically, the ventilation port 502 is arranged above the lower end of the cylinder 51. That is, in the vertical direction D2, the ventilation port 502 is located above the center C1 of the crank chamber 52 and above the lower end of the cylinder 51. The lower end of the cylinder 51 here refers to the lowest part of the cylinder 51 that faces the crank chamber 52. In the present 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 the lower end (lower surface) of the cylinder liner 511 becomes 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 in the vertical direction D2 in the crank chamber 52 as shown in FIG. 7, and the ventilation port 502 is arranged further above the lower end of the cylinder 51.

[0061] As a result, the blow-by gas having a specific gravity less than 1 is likely to be guided to the side of the ventilation port 502 located above the lower end of the cylinder 51 after leaking from the lower end of the cylinder 51 into the crank chamber 52. As a result, it becomes easier to more efficiently discharge the blow-by gas from the crank chamber 52, and the discharge performance of the blow-by gas can be improved.

[0062] Further, the ventilation port 502 opens downward. Here, in the vertical direction D2, where the side of the crank chamber 52 is "downward" when viewed from the cylinder 51, the ventilation port 502 opens toward the crank chamber 52 side when viewed from the cylinder 51. Since the ventilation port 502 opens in the inner peripheral surface 501 of the cylinder block 5, by forming the ventilation port 502 at a portion of the inner peripheral surface 501 facing downward, that is, at a portion that becomes the top surface, the ventilation port 502 that opens downward is realized. The ventilation port 502 only needs to open downward, and includes not only a configuration that opens strictly downward but also a configuration that opens obliquely downward. That is, 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, the blow-by gas having a specific gravity less than 1 is likely to be discharged from the ventilation port 502 when flowing upward after leaking from the lower end of the cylinder 51 into the crank chamber 52. As a result, it becomes easier to more efficiently discharge the blow-by gas from the crank chamber 52, and the discharge performance of the blow-by gas can be improved.

[0064] Also, in the present embodiment, as described above, the cylinder block 5 is connected to the crank chamber 52 and further includes a 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 disposed in the cam chamber 53 among 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 vertical direction D2. Since the internal space of the cam chamber 53 is continuous with 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] By doing so, by utilizing the space for accommodating the camshaft 23, it is possible to efficiently discharge blow-by gas from the crankcase 52 without newly creating a space for forming the ventilation port 502. Moreover, since the cam chamber 53 is located above the crankcase 52, blow-by gas having a specific gravity less than 1 is likely to gather in the cam chamber 53 where the ventilation port 502 is formed after leaking out from the crankcase 52, and it is possible to improve the discharge performance of the blow-by gas.

[0066] Also, in this embodiment, as an example, as shown in FIG. 7, the ventilation passage 503 is a cylindrical pipe that extends straight along the vertical direction D2 from the ventilation port 502. The ventilation passage 503 is coupled to the ventilation port 502 and functions as a passage for blow-by gas discharged from the ventilation port 502. The tip 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 tip of the ventilation passage 503 may be located inside the side cover 74 or may be located outside the side cover 74. Further, the tip 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. For example, it may have a shape other than a cylindrical shape such as a rectangular tube shape, or may be a tube or a hose. Further, the ventilation passage 503 may be any configuration that can serve as a passage for blow-by gas between the internal space Sp1 of the crankcase 52 and the external space of the cylinder block 5, and it is not even essential that it is a tubular member. That is, it is sufficient that the ventilation port 502 finally communicates with the external space of the cylinder block 5 through the ventilation passage 503. For example, the internal space of the side cover 74 may function as the ventilation passage 503.

[0068] According to the configuration described above, as shown in FIG. 8, blow-by gas is efficiently discharged from the internal space Sp1 of the crankcase 52 via the ventilation port 502 (and the ventilation passage 503). In FIG. 8, the flow of blow-by gas is indicated by thick arrows. That is, unburned gas and the like leaks from the combustion chamber 50 into the crankcase 52 through the gap between the cylinder 51 and the piston 21, generating blow-by gas. In this embodiment, by using a gaseous fuel (hydrogen) with a specific gravity less than 1, the specific gravity of the blow-by gas also becomes less than 1. Therefore, the blow-by gas that leaks into the crankcase 52 moves upward in the crankcase 52. Since a cam chamber 53 connected to the internal space Sp1 of the crankcase 52 at the opening 531 is provided above the crankcase 52, the blow-by gas that moves 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] Also, in this embodiment, as shown in FIG. 9, the ventilation passage 503 has a gas-liquid separation portion 504 that separates gas and liquid. The gas-liquid separation portion 504 is, for example, composed of a protruding wall provided inside the ventilation passage 503. The protruding wall as the gas-liquid separation portion 504 protrudes from the inner peripheral 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 portion 504 are provided such that the protruding wall protruding from one side (left side) in the width direction D3 of the inner peripheral surface of the ventilation passage 503 and the protruding wall protruding from the other side (right side) in the width direction D3 are arranged alternately in the vertical direction D2. The tip ends of the protruding wall protruding from one side (left side) in the width direction D3 and the protruding wall protruding from the other side (right side) in the width direction D3 overlap each other in the vertical 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 from the ventilation port 502 into the ventilation passage 503 flows through the ventilation passage 503 while meandering so as to pass between the protruding walls serving as the gas-liquid separation section 504. When the blow-by gas comes into contact with the protruding wall serving as the gas-liquid separation section 504, liquids such as oil or moisture discharged together with the blow-by gas adhere to the protruding wall serving as the gas-liquid separation section 504. As a result, the liquid (such as oil or moisture) 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. Consequently, the blow-by gas is exhausted from the ventilation passage 503 in a state where at least a part of the liquid component such as oil is removed, leading to suppression of oil consumption and the like associated with the exhaust of the blow-by gas.

[0071] The gas-liquid separation section 504 is not limited to the protruding wall as described above, and it suffices if it has 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 a combination of a protruding wall and a filter.

[0072] Incidentally, as described above, the engine body 2 according to the present 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 series. In this type of engine, blow-by gas can occur in each of the plurality of cylinders 51. In this embodiment, only one ventilation port 502 for discharging blow-by gas is provided for the plurality of cylinders 51. In other words, the ventilation port 502 is shared among the plurality of cylinders 51. That is, in this embodiment, as described above, the crankcase 52 consists of a single compartment (chamber) connected in the output shaft direction D1. Therefore, even if blow-by gas occurs in any of the plurality of cylinders 51, ultimately, the blow-by gas leaks into the same crankcase 52. Seen in this way, it suffices to have one ventilation port 502 for discharging blow-by gas at one location for the plurality of cylinders 51.

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

[0074] In this way, the ventilation port 502 only needs to be at one location with respect to the plurality of cylinders 51. As a result, the structure for discharging blow-by gas can be simplified. In particular, in this embodiment, since the engine body 2 is arranged in a "front-upward" posture (see FIG. 2), the blow-by gas leaking into the crank chamber 52 is likely to be concentrated on the front end portion side which is relatively upward. Therefore, in the configuration where the ventilation port 502 is arranged at the front end portion of the cylinder block 5 (in the cam chamber 53), it is possible to more efficiently discharge the blow-by gas from the exhaust pipe 105 (see FIG. 2) provided in the hull 100.

[0075] Further, in this embodiment, in order to more smoothly exhaust the blow-by gas from the ventilation port 502, as shown in FIG. 11, a gas inlet 505 that connects the internal space Sp1 of the crank chamber 52 and the external space of the cylinder block 5 is opened on the inner peripheral surface 501 of the cylinder block 5. FIG. 11 is a schematic view of the cylinder block 5 schematically showing the positional relationship among 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 crankcase 52 when exhausting blow-by gas from the ventilation port 502. As a result, ventilation (exhaust of blow-by gas) of the internal space Sp1 of the crankcase 52 can be performed more smoothly. The gas inlet 505 opens in a circular shape (a perfect circle) that is large enough to allow air to pass through, for example, in a plan view. However, the gas inlet 505 is not limited to a circular shape and may open, for example, in an elliptical shape, a rectangular shape, or a polygonal shape.

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

[0078] According to this configuration, the gas (air) introduced from the gas inlet 505 flows toward the ventilation port 502, thereby forming an air flow along the output shaft direction D1. Therefore, the air flow can act over a wide range in the output shaft direction D1. Accordingly, it is possible to further improve the discharge performance of blow-by gas by the air flow.

[0079] In particular, in the present embodiment, the ventilation port 502 is disposed at a position (front end portion) corresponding to the one - end - side cylinder 51A, while the gas inlet 505 is disposed at a position (rear end portion) corresponding to the other - end - side cylinder 51B. In this way, by arranging the ventilation port 502 and the gas inlet 505 at both ends of the cylinder block 5 in the output - shaft direction D1, the air flow can act over substantially the entire area of the crank chamber 52 in the output - shaft direction D1. Therefore, it is possible to further improve the discharge performance of the blow - by gas by the air flow.

[0080] Also, in the present embodiment, the ventilation port 502 and the gas inlet 505 are arranged 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 located on one side (the left - hand side in the present embodiment) of the width direction D3 as viewed from the rotation axis Ax1, while the gas inlet 505 is located on the other side (the right - hand side in the present embodiment) of the width direction D3 as viewed from the rotation axis Ax1. The gas inlet 505 is formed in the right - hand side wall of the crank chamber 52 so as to penetrate the right - hand side wall of the crank chamber 52, for example. In this way, by arranging the ventilation port 502 and the gas inlet 505 on opposite sides across the rotation axis Ax1, the air flow can act over a wide range of the width direction D3 in the crank chamber 52. Therefore, it is possible to further improve the discharge performance of the blow - by gas by the air flow.

[0081] Furthermore, in the present embodiment, the gas inlet 505 is disposed below the center C1 (see FIG. 7) in the vertical direction D2 in the crank chamber 52. As a result, the air flow caused by the gas (air) introduced from the gas inlet 505 flows obliquely upward toward the ventilation port 502, thereby forming an air flow along the vertical direction D2, so that the air flow can act over the entire crank chamber 52. Therefore, it is possible to further improve the discharge performance of the blow - by gas by the air flow.

[0082] Here, as shown in FIG. 12, the engine system 1 according to the present embodiment further includes an airflow forming unit 506. The airflow forming unit 506 forms an airflow from the gas inlet 505 toward the ventilation port 502. FIG. 12 is a schematic view of the cylinder block 5 schematically showing the positional relationship among the cylinder 51, the crank chamber 52, the cam chamber 53, and the intake manifold 54. In the present embodiment, as an example, the supercharger 8 is used for the airflow forming unit 506. Specifically, the airflow forming unit 506 includes a bypass pipe connecting between the intake manifold 54 and the gas inlet 505. The bypass pipe as the airflow forming unit 506 forms, for example, a passage for air from the downstream end (the rear end in the present embodiment) of the airflow in the intake manifold 54 to the gas inlet 505. Thereby, the air (intake air) compressed by the supercharger 8 is sent to the intake manifold 54 through the intercooler 85, and further sent to the gas inlet 505 through the bypass pipe as the airflow forming unit 506. As a result, the gas inlet 505 is in a positive pressure state with respect to the internal space Sp1 of the crank chamber 52 by the compressed air, and an airflow in the direction of pushing out the gas (blow-by gas) from the ventilation port 502 is generated in the crank chamber 52.

[0083] In this way, by providing the airflow forming unit 506, an airflow can be forcibly formed in the internal space Sp1 of the crank chamber 52, and it becomes difficult for blow-by gas to stagnate in the crank chamber 52. That is, the airflow forming unit 506 promotes the discharge of blow-by gas from the ventilation port 502, and further improvement in the discharge performance of blow-by gas can be achieved. Moreover, in the present embodiment, since the supercharger 8 is used for the airflow forming unit 506, there is no need to newly install a device for forming an airflow.

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

[0085] In the modified example shown in "B" of FIG. 13, the airflow forming portion 506 includes an air tank mounted on the hull 100, and air is sent from the air tank to the gas inlet 505. In the modified example shown in "C" of FIG. 13, the airflow forming portion 506 includes an electric fan, and air is sent from the electric fan to the gas inlet 505. In either example of "B" and "C" of FIG. 13, the gas inlet 505 is in a positive pressure state with respect to the internal space Sp1 of the crankcase 52, and an airflow in a direction to push out the gas (blow-by gas) from the ventilation port 502 is generated in the crankcase 52.

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

[0087] Hereinafter, the configuration of the piston 21 of the engine system 1 according to the present embodiment will be described in more detail with reference to FIGS. 14 and 15. FIGS. 14 and 15 are schematic cross-sectional views with an enlarged periphery of the piston 21.

[0088] Inside the piston inner space 210 formed inside the piston 21 that reciprocates along the vertical direction D2 within the cylinder 51, as shown in FIG. 14, a stirring part 213 that reciprocates along the vertical direction D2 as the piston 21 moves is arranged. In the present embodiment, a blade-like protrusion that protrudes from the inner peripheral surface of the cylindrical part 211 of the piston 21 toward the central axis of the piston 21 constitutes the stirring part 213. The piston inner space 210 is a columnar space surrounded by the cylindrical part 211 of the piston 21 and is a space separated from the combustion chamber 50 by the partition 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 part 213 is formed over the entire circumference in the circumferential direction of the cylindrical part 211 and a plurality (here, two) of them are provided at intervals in the vertical direction D2.

[0089] In short, in the piston inner space 210 that is continuous with the internal space Sp1 of the crank chamber 52, a stirring part 213 that reciprocates as the piston 21 moves is provided. By providing such a stirring part 213, when the piston 21 reciprocates, the stirring part 213 reciprocates in the piston inner space 210, and the gas in the piston inner space 210 is stirred. Therefore, even if blow-by gas such as unburned gas leaks from the combustion chamber 50 into the piston inner space 210 through the gap between the cylinder 51 and the piston 21, the blow-by gas in the piston inner space 210 is actively made to flow and is more likely to move to the crank chamber 52. Thus, it becomes easier to suppress the blow-by gas from staying in the piston inner space 210, and a further improvement in the discharge performance of the blow-by gas can be expected.

[0090] In addition, the stirring unit 213 may be provided in the piston internal space 210 and configured to reciprocate as the piston 21 moves. It is not limited to the protrusion protruding from the cylindrical portion 211 of the piston 21. For example, it may be a protrusion protruding from the upper end portion of the connecting rod 24. That is, as long as it is a protrusion provided on the upper side of the lower end of the piston 21 in the connecting rod 24, similar to the above-described stirring unit 213, the gas in the piston internal space 210 can be stirred as the piston 21 reciprocates. The stirring unit 213 may be provided on both the piston 21 and the connecting rod 24.

[0091] Also, as shown in FIG. 15, among the pistons 21 that reciprocate in the cylinder 51 along the vertical direction D2, the partition wall 212 that separates the internal space of the cylinder 51 in the vertical direction D2 preferably has a cavity 214 inside. Specifically, a plate 215 is fixed to the lower surface of the partition wall 212 (the surface opposite to the combustion chamber 50) by an appropriate method such as welding, so that the partition wall 212 has a double structure. Thereby, a cavity 214 as a heat insulation layer is formed above the plate 215 (on the combustion chamber 50 side).

[0092] In short, in the internal space of the cylinder 51, the combustion chamber 50 and the space continuous with the internal space Sp1 of the crank chamber 52 are separated by the partition wall 212, so the upper surface of the partition wall 212 is exposed to the combustion chamber 50. Therefore, as shown in FIG. 14, in a configuration where the cavity 214 is not provided, the heat on the upper surface of the partition wall 212 easily transfers to the back surface (lower surface) side of the partition wall 212, and for example, blow-by gas mainly composed of hydrogen or the like may be heated. On the other hand, according to the configuration of FIG. 15 in which the cavity 214 as a heat insulation layer is formed, it is difficult for heat to transfer to the lower surface side of the plate 215 in the cavity 214. Therefore, it is possible to suppress the heating of blow-by gas mainly composed of hydrogen or the like by the heat of the combustion chamber 50.

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

[0094] By the way, the configuration regarding the piston 21 described above can be adopted independently, separated from the configuration for exhaust countermeasures of blow-by gas (vent port 502), etc. That is, the engine system 1 according to one aspect includes a cylinder block 5 including a cylinder 51 and a crank chamber 52, and in the piston internal space 210 formed inside the piston 21 that reciprocates in the cylinder 51, a stirring part 213 that reciprocates as the piston 21 moves is arranged. Also, the engine system 1 according to another aspect includes a cylinder block 5 including a cylinder 51 and a crank chamber 52, and the partition wall 212 that separates the internal space of the cylinder 51 in the piston 21 that reciprocates in the cylinder 51 (in the direction in which the piston 21 reciprocates) has a hollow part 214 inside.

[0095] [4] Configuration of the Cylinder Head Next, with reference to FIGS. 17 to 21, the configuration of the cylinder head 6 (and its peripheral structure) of the engine body 2 will be described in more detail. FIG. 17 is a schematic view of the engine body 2 as seen from the rear side (the side where the crankshaft 22 protrudes), which is one side in the output shaft direction D1, with hatching applied to the main cross-sectional part while breaking a part of the cylinder block 5 and the cylinder head 6. In FIG. 17, the illustration of the side cover 74 and the like is appropriately omitted.

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

[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, for one cylinder head 6, two intake ports 61 and two exhaust ports 62 are formed. However, the two intake ports 61 basically adopt a common configuration, and the two exhaust ports 62 basically adopt a common configuration. Therefore, hereinafter, unless otherwise specified, the description will focus on one intake port 61 or one exhaust port 62. FIG. 18 is a schematic perspective view showing the schematic outer shape of the cylinder head 6 and the cylinder 51 with imaginary lines (dashed double lines) and highlighting the intake port 61 and the exhaust port 62. FIG. 19 is a schematic plan view showing the refrigerant passage 63 to be described later with imaginary lines (dashed double lines) and highlighting the intake port 61 and the exhaust port 62.

[0098] As shown in FIGS. 17 and 18, the cylinder head 6 is disposed above the cylinder 51. Thereby, among the internal spaces of the cylinder 51, the 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. Each of the intake port 61 and the exhaust port 62 formed in the cylinder head 6 has an opening leading to the combustion chamber 50.

[0099] The intake port 61 is a passage for a gas (intake air) that connects between the intake manifold 54 formed in the cylinder block 5 and the combustion chamber 50. And, in the intake port 61, an intake valve 72 is provided at the opening on the combustion chamber 50 side, that is, the opening on the downstream side of the air flow. Therefore, the 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 the present embodiment, since the port injection method is adopted as the fuel supply method for the gaseous fuel, the fuel supply device 3 supplies the gaseous fuel (hydrogen in the present embodiment) to the internal space of the intake port 61. That is, the injection part 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 described in detail in the section "[5] Control Operation of the Engine System".

[0101] On the other hand, the exhaust port 62 is a passage for a gas (exhaust gas) that connects between the exhaust manifold 75 and the combustion chamber 50. And, in the exhaust port 62, an exhaust valve 73 is provided at the opening on the combustion chamber 50 side, that is, the opening on the upstream side of the air flow. Therefore, the gas discharged from the combustion chamber 50 is discharged (aggregated) to the exhaust manifold 75 through the exhaust port 62 with the exhaust valve 73 open.

[0102] Also, as shown in FIGS. 17 and 19, in the cylinder head 6, in addition to the intake port 61 and the exhaust port 62, a refrigerant passage 63 is formed. 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 fluid such as a liquid like water (cooling water) or oil, or a gas like a cooling gas. That is, by flowing the refrigerant, which is a fluid, through the refrigerant passage 63, heat can be taken from around the refrigerant passage 63, and it is possible to cool the periphery of the refrigerant passage 63. In this embodiment, as an example, the refrigerant passage 63 is a water jacket for passing cooling water as the refrigerant.

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

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

[0105] However, for example, in the engine system 1 using a gaseous fuel such as hydrogen, it may be easier to ignite the fuel (gaseous fuel). Therefore, in case of a backfire, it is desirable to take further countermeasures against backfire in view of the possibility of igniting the fuel (gaseous fuel) supplied into the air supply port 61 and the backfire being chained.

[0106] Therefore, in the present embodiment, by adopting the configuration described below, it is possible to provide the engine system 1 that enables further countermeasures against backfire.

[0107] That is, the engine system 1 according to the present embodiment includes an air supply 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 (see FIG. 20) of the air supply port 61. The fuel supply device 3 has an injection unit 31 that injects gaseous fuel. Here, as shown in FIG. 20, a cooling unit 612 is disposed at least at the intersection of the inner peripheral surface 611 of the air supply port 61 and the central axis Ax2 of the injection region R1 of the gaseous fuel from the injection unit 31. In other words, the intersection of the inner peripheral surface 611 of the air supply port 61 and 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] The "cooling unit" as referred to in the present disclosure means a portion of the inner peripheral surface 611 of the air supply port 61 that becomes relatively low in temperature by being cooled. That is, the temperature of the inner peripheral surface 611 facing the internal space Sp2 of the air supply port 61 is not uniform, and a temperature difference may occur depending on the portion. The portion that becomes relatively low in temperature compared to other portions constitutes the cooling unit 612. As an example, a portion of the inner peripheral surface 611 of the air supply port 61 that is lower than a reference temperature (for example, the average value or the median value of the temperature of the inner peripheral surface 611, etc.) becomes the cooling unit 612.

[0109] In short, for example, in the engine system 1 adopting a port injection method in which a gaseous fuel such as hydrogen is injected into the internal space Sp2 of the intake port 61, by adopting the above configuration, it becomes possible to take further countermeasures against backfire. In this type of engine system 1, for example, in a situation where the intake port 61 is exposed to a flame due to backfire, if the gaseous fuel (such as hydrogen) injected into the intake port 61 ignites, there is a possibility that the backfire will chain. In the engine system 1 according to the present embodiment, by directing the central axis Ax2 of the injection region R1 of the gaseous fuel toward the cooling portion 612, the heat dissipation of the gaseous fuel is improved, and even immediately after the occurrence of backfire, ignition of the gaseous fuel due to heating of the gaseous fuel can be suppressed. Thus, by improving the cooling performance of the gaseous fuel in the intake port 61, it is possible to suppress the chaining of backfire and provide an engine system 1 capable of taking 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 portion of the intake port 61 and is curved so that the cross-sectional shape is convex upward, whereby the intake port 61 has an inverted U-shaped cross-sectional shape as a whole. Therefore, the flow (airflow) of air (intake air) in the internal space Sp2 of the intake port 61 takes a path that draws an arc 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 the present embodiment, the cooling portion 612 is disposed on the surface on the other direction (here, downward) side of the curved portion 600 of the inner peripheral surface 611 of the intake port 61, that is, on the inner peripheral side surface 602 of the curved portion 600. That is, the inner peripheral surface 611 includes an outer peripheral side surface 601 that is the surface on one direction (here, upward) side of the curved portion 600 and an inner peripheral side surface 602 that is the surface on the other direction (here, downward) side of the curved portion 600, and the cooling portion 612 is disposed on the inner peripheral side surface 602.

[0112] And the nozzle-shaped (cylindrical) injection part 31 is arranged in such a way that its tip protrudes from the outer peripheral side surface 601 into the air supply port 61, and 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 peripheral 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 the apex, and substantially coincides with the central axis of the nozzle-shaped (cylindrical) injection part 31.

[0113] Also, the cooling part 612 is arranged on the downstream side of the air flow from the injection part 31 in the air supply port 61. In the example of FIG. 20, in the air supply port 61, since an air flow from the right to the left occurs, the cooling part 612 is arranged on the left side, which is the downstream side, with respect to the tip of the injection part 31 of the fuel supply device 3.

[0114] In this way, since the cooling part 612 is arranged on the downstream side of the injection part 31, even when the gaseous fuel injected from the injection part 31 is flowed downstream by the air flow, it is easier to reach the cooling part 612. Therefore, it is possible to sufficiently exhibit the cooling effect of the gaseous fuel by the cooling part 612.

[0115] By the way, as specific embodiments of the cooling part 612, for example, there are a first embodiment, a second embodiment, and a third embodiment 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 adhering refrigerant, and the third embodiment is an air cooling method. That is, the cooling part 612 on the inner peripheral 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 thereof.

[0116] First, in the first aspect (refrigerant cooling method), as shown in FIG. 20, the area near the refrigerant passage 63 serves as the cooling part 612. Specifically, the refrigerant passage 63 and the internal space Sp2 of the air supply port 61 are physically separated by the partition part 64, and the surface on the side of the partition part 64 opposite to the refrigerant passage 63 (the inner peripheral surface 611 of the air supply port 61) constitutes the cooling part 612. That is, the engine system 1 includes a cylinder head 6 in which the air supply port 61 is formed, and the cylinder head 6 has a refrigerant passage 63 through which the refrigerant passes. Here, the cooling part 612 is disposed at least in the partition part 64 that physically separates the refrigerant passage 63 and the air supply port 61.

[0117] According to this configuration, it is possible to efficiently cool the cooling part 612 with the refrigerant flowing through the refrigerant passage 63 provided in the cylinder head 6. Furthermore, since it is also possible to adjust the temperature of the cooling part 612 according to the flow rate of the refrigerant, 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] Furthermore, as shown in FIG. 20, the partition part 64 includes a thin part 641 and a thick part 642. The thickness Th1 between the refrigerant passage 63 and the air supply port 61 in the thin part 641 is smaller than the reference thickness. The thickness Th2 between the refrigerant passage 63 and the air supply port 61 in the thick part 642 is larger than the reference thickness. The cooling part 612 is provided only in the thin part 641 out of the thin part 641 and the thick part 642. The "reference thickness" here is the thickness serving as a reference for the partition part 64, and as an example, it is the average value or the median value of the thickness of the partition part 64, etc. That is, the thickness of the partition part 64 is not uniform and varies depending on the part. And the cooling part 612 is provided in the relatively thin thin part 641 of the partition part 64 and not in the thick part 642.

[0119] According to this configuration, it is possible to more efficiently cool the cooling section 612 with the refrigerant flowing through the refrigerant passage 63. That is, among the inner peripheral surface 611 of the partition section 64, the cooling section 612 is arranged at the thin wall section 641 where the distance to the refrigerant passage 63 is relatively close and heat is easily transferred from the refrigerant flowing through the refrigerant passage 63. Therefore, it is possible to more reliably cool the gaseous fuel. Thus, ignition of the gaseous fuel due to heating of the gaseous fuel can be further suppressed.

[0120] In the second aspect (latent heat of vaporization method), as shown in FIG. 21, the engine system 1 further includes a refrigerant supply section 65 that attaches an attached refrigerant 651 to a part of the inner peripheral surface 611 of the intake port 61. The cooling section 612 is arranged at least at the part where the attached refrigerant 651 adheres. The "attached refrigerant" here mainly means a heat medium used for the latent heat of vaporization and is, for example, a liquid such as water (cooling water) or oil. That is, when the attached refrigerant 651 adheres to a part of the inner peripheral surface 611 of the intake port 61, the heat of the inner peripheral surface 611 is taken away when the attached refrigerant 651 vaporizes, thereby cooling the inner peripheral surface 611. Therefore, by setting the part of the inner peripheral surface 611 of the intake port 61 where the attached refrigerant 651 adheres as the cooling section 612, cooling of the cooling section 612 is realized. As a mode of "attaching" the attached refrigerant 651, for example, there are spraying, discharging, condensation, or coating of the attached refrigerant 651.

[0121] Specifically, in the example shown in "A" of FIG. 21, a nozzle-shaped (cylindrical) refrigerant supply section 65 that injects the attached refrigerant 651 is used. This refrigerant supply section 65 is arranged such that its tip protrudes into the intake port 61 from the outer peripheral side surface 601, and gaseous fuel is injected from the injection section 31 toward the cooling section 612. That is, the tip of the refrigerant supply section 65 is directed at least toward the cooling section 612 provided on the inner peripheral side surface 602. Thereby, the attached refrigerant 651 injected from the refrigerant supply section 65 adheres to the cooling section 612 of the inner peripheral surface 611 (inner peripheral side surface 602) of the intake port 61 and cools the cooling section 612.

[0122] Also, in the example shown as "B" in FIG. 21, a refrigerant supply unit 65 for cooling the air introduced into the air supply port 61 is used. This refrigerant supply unit 65 is composed of a coiled cooler and is disposed near the opening on the air supply manifold 54 side at the air supply port 61. When refrigerant is supplied to the refrigerant supply unit 65, the air passing through the refrigerant supply unit 65 is cooled. When the amount of water vapor in the air exceeds the saturated water vapor amount, 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 part 612 provided on the inner peripheral side surface 602. Thereby, the adhering refrigerant 651 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. The refrigerant supplied to the refrigerant supply unit 65 is preferably maintained at a low temperature, for example, by heat exchange with the liquefied hydrogen tank 32.

[0123] In the example of FIG. 21, in addition to the refrigerant supply unit 65, the refrigerant cooling method of the first aspect is also used in combination by the refrigerant passage 63, but it is not essential to combine the second aspect (latent heat of vaporization method) and the first aspect. That is, when the second aspect (latent heat of vaporization method) is adopted, the refrigerant passage 63 may be omitted. Even in this case, the cooling part 612 can be realized by the adhering refrigerant 651.

[0124] In the third aspect (air cooling method), a cooling part 612 is formed on a part of the inner peripheral surface 611 of the air supply port 61 by using the air flow (air current) in the internal space Sp2 of the air supply port 61. That is, for example, by using a fan or the like to increase the air flow velocity and directing the air to a part of the inner peripheral surface 611 of the air supply port 61, the part of the inner peripheral surface 611 of the air supply port 61 that the air hits is cooled by the air current to form the cooling part 612. According to this configuration, it is possible to configure the cooling part 612 by cooling a part of the inner peripheral surface 611 of the air supply port 61 without using a refrigerant separately.

[0125] In addition, in the engine system 1 according to the present embodiment, it is more useful to adopt the following configuration as a backfire countermeasure.

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

[0127] As a second configuration, a heat insulating material covering the injection part 31 of the fuel supply device 3 is provided to suppress the heat input to the gaseous fuel injected from the injection part 31. Thereby, the heat input from the cylinder head 6 to the injection part 31 is suppressed, so that the temperature rise of the gaseous fuel can be suppressed.

[0128] [5] Control operation of the engine system Next, the control operation of the engine system 1 according to the present embodiment will be described with reference to FIGS. 22, 23, and 24. In the present embodiment, as described above, the control of the engine system 1 is performed by the engine control unit 20. Therefore, the control operation of the engine system 1 described below includes the processes executed by the engine control unit 20.

[0129] In the present embodiment, the engine control unit 20 controls the fuel supply device 3 at the 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 shows 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 of the inner peripheral surface 611 (wall surface) near the combustion chamber 50 in the intake port 61 (denoted as "temperature"). Here, the crank angle continuously changes as the piston 21 reciprocates between the bottom dead center (BDC) and the top dead center (TDC) in accordance with the passage of time. Therefore, the horizontal axis indicating the crank angle corresponds to the time axis.

[0130] In FIG. 22, assume that at time t0, the piston 21 is at the bottom dead center, at time t2, the piston 21 is at the top dead center, at time t7, the piston 21 is at the bottom dead center, and a backfire occurred 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, at time t3 after time t2, when the exhaust valve 73 closes (opening degree G1 becomes 0), then, only after the cooling period T1 elapses, the injection permission period T2 during which gaseous fuel can be injected starts. Here, when the injection of the gaseous fuel is split injection (intermittent injection), from the start of the first injection to the end of the last injection is executed within the injection permission period T2.

[0131] That is, in the present embodiment, after the fuel supply device 3 satisfies the supply start condition including the closing of the exhaust valve 73 and the cooling period T1 elapses, the fuel supply device 3 starts to supply gaseous fuel to the internal space Sp2 of the intake port 61. Here, the cooling period T1 is a period for cooling the cooling unit 612 and is a period during which the injection of gaseous fuel is prohibited. Specifically, the supply start condition includes, in addition to the exhaust valve 73 closing (opening degree G1 becomes 0), the intake valve 72 opening (opening degree G2 is greater than 0). In the example of FIG. 22, at time t3, since the exhaust valve 73 closes and (at the previous time t1) the intake valve 72 is open, the supply start condition is satisfied. Therefore, when the cooling period T1 from time t3 to time t5 elapses and enters the injection permission period T2, the fuel supply device 3 can start injecting (supplying) gaseous fuel.

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

[0133] In addition, the end point of the cooling period T1 is set after the point in time when the opening degree G2 of the intake valve 72 reaches its maximum. That is, the point in time t5, which is the end point of the cooling period T1, is set on the retarded crank angle side when viewed from the point in time t4 when the opening degree G2 of the intake valve 72 reaches its maximum (peak of the opening degree G2).

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

[0135] In addition, the engine system 1 according to the present embodiment includes a supercharger 8 that sends air into the intake port 61. As a result, even if the timing of starting the supply of the gaseous fuel is delayed by providing the cooling period T1, it becomes easier to send the gaseous fuel into the combustion chamber 50. That is, by accelerating the flow velocity of the air by the supercharger 8, the gaseous fuel injected into the intake port 61 easily flows into the combustion chamber 50.

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

[0137] According to this configuration, the residual gas fuel in the air supply port 61 due to the closing of the air supply valve 72 at the time t6 when the injection permission period T2 ends is suppressed. That is, even if gas fuel remains in the air supply port 61 at the time t6 when the injection permission period T2 ends, the remaining gas fuel can be discharged into the combustion chamber 50 during the delay period T3.

[0138] Furthermore, it is preferable that the length of the delay period T3 is set based on the distance between the injection part 31 (the tip thereof) and the opening on the combustion chamber 50 side in the air supply port 61. The distance here is the distance on the air flow path in the air supply port 61. Specifically, the longer the distance between the injection part 31 (the tip thereof) and the opening on the combustion chamber 50 side in the air supply port 61, the longer the delay period T3 is set. Thereby, considering the time required for the gas fuel injected from the injection part 31 to be discharged into the combustion chamber 50, the delay period T3 is set, so that it is less likely for gas fuel to remain in the air supply port 61.

[0139] By the way, regarding the configuration related to the control of the fuel supply device 3 described above, it can be adopted independently, separated from the configuration for exhaust countermeasures of blow-by gas (vent port 502), the cooling part 612, etc. That is, an engine system 1 according to one aspect includes an air supply port 61 that supplies air to the combustion chamber 50, and a fuel supply device 3 that supplies gas fuel to the internal space Sp2 of the air supply port 61. After the fuel supply device 3 satisfies the supply start condition including the closing of the exhaust valve 73 and the cooling period T1 elapses, it starts supplying gas fuel to the internal space Sp2 of the air supply 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 for driving the generator 101 or propelling the hull 100.

[0141] That is, the engine control unit 20 first determines whether to use the engine system 1 to drive the generator 101 (S1). When the engine system 1 is used to drive the generator 101 (S1: Yes), the engine control unit 20 determines that it is in the power generation mode and shifts the process to step S2. On the other hand, when the engine system 1 is used to propel the hull 100 (S1: No), the engine control unit 20 determines that it 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 rotational speed (actual rotational 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 injecting the gaseous fuel, in light of the "load - rotational speed map" showing the correlation between the load of the generator 101 and the engine rotational 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 rotational speed (actual rotational speed) of the engine body 2. Here, the engine control unit 20 sets the target rotational speed of the engine body 2 (S7) and calculates the difference between the target rotational speed and the actual rotational speed (S8). Further, the engine control unit 20 calculates the injection amount of the gaseous fuel (insufficient injection amount) that is insufficient with respect to the injection amount of the gaseous fuel in the previous cycle. Then, the engine control unit 20 determines the injection time of the gaseous fuel in light of the "injection amount - injection time map" showing the correlation between the injection amount of the gaseous fuel and the injection time (S10). Also, the engine control unit 20 determines the injection timing of the gaseous fuel, that is, the timing to start injecting the gaseous fuel, in light of the "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 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 above. However, the flowchart shown in FIG. 23 is merely an example, and processes may be added or omitted as appropriate, or the order of processes may be changed as appropriate.

[0145] FIG. 24 is a flowchart showing an example of the operation (process) 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 backfire occurs.

[0146] That is, the engine control unit 20 first acquires the load of the generator 101, the rotational speed (actual rotational 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 regarding the occurrence of backfire. Then, the engine control unit 20 determines whether or not backfire has occurred, for example, based on the in-cylinder pressure (S22). When the occurrence of backfire is detected from the waveform of the in-cylinder pressure or the like (S22: Yes), the engine control unit 20 shifts the process to step S23. On the other hand, when the occurrence of backfire is not detected from the waveform of the in-cylinder pressure or the like (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 gaseous fuel, that is, the timing at which the injection of the gaseous fuel starts, in light of the "load-rotational speed first map" showing the correlation between the load of the generator 101 and the engine rotational speed. The "load-rotational speed first map" is a map prepared for use when backfire occurs and is a map for setting the injection timing of the gaseous fuel in consideration of the cooling period T1.

[0148] In step S24, the engine control unit 20 determines the injection timing of the gaseous fuel, that is, the timing to start injecting the gaseous fuel, with reference to the "Load - Rotation Speed Map 2" indicating the correlation between the load of the generator 101 and the engine speed. The "Load - Rotation Speed Map 2" is a map prepared for steady - state operation where no backfire occurs, and it is a map for setting the injection timing of the gaseous fuel without considering the cooling period T1.

[0149] Then, the engine control unit 20 calculates the injection amount of the 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 appropriately added or omitted, or the order of processes may be appropriately changed.

[0151] [6] Modification Hereinafter, modifications of Embodiment 1 will be listed. The modifications described below can be applied in appropriate combinations.

[0152] The engine system 1 in the present disclosure includes a computer system as the engine control unit 20. The computer system mainly includes one or more processors as hardware and one or more memories. By the processor executing the program recorded in the memory of the computer system, the functions as the engine control unit 20 in the present disclosure are realized. The program may be pre - recorded in the memory of the computer system, may be provided through a telecommunication line, or may be provided by being recorded on a non - transitory recording medium such as a computer - readable memory card, an optical disk, or a hard disk drive. Also, some or all of the functional units included in the engine control unit 20 may be configured by electronic circuits.

[0153] Moreover, it is not an essential configuration of the engine system 1 that at least some functions of the engine system 1 are integrated in one housing, and the components of the engine system 1 may be provided dispersedly in a plurality of housings. Conversely, in Embodiment 1, functions dispersed in a plurality of devices (for example, the engine main body 2 and the generator 101) may be integrated in one housing.

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

[0155] Also, the ship 10 is not limited to a pleasure boat and may be a merchant ship including a cargo ship and a passenger-cargo 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, and a warship. Furthermore, the ship 10 is not limited to a manned type on which an operator boards and may be an unmanned type of ship that can be remotely operated by a person (operator) or can operate autonomously. Also, the ship 10 may be provided with one or more power sources such as a motor (electric motor) in addition to the engine main body 2 on the hull 100. The engine system 1 may be used other than for the ship 10.

[0156] Further, the engine system 1 is not limited to an in-line multi-cylinder engine in which a plurality of cylinders 51 are arranged in series. For example, it may be 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 the internal space Sp1 of the crank chamber 52 is arranged within the 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] Further, 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). Also, the engine system 1 is not limited to a supercharged engine, and may be a naturally aspirated engine that does not include a supercharger 8.

[0158] Further, the fuel supply method for gaseous fuel is not limited to the port injection method in which fuel is injected into the intake port 61, and 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 gaseous fuel is arranged at a position facing the combustion chamber 50.

[0159] Further, it is not essential for the ventilation port 502 to be always open, and for example, it may be configured to be openable and closable by a valve device or the like. In this case, blow-by gas is discharged from the ventilation port 502 during the period when the ventilation port 502 is open, and blow-by gas is not discharged from the ventilation port 502 during the period when the ventilation port 502 is closed.

[0160] (Embodiment 2) As shown in FIGS. 26 and 27, the engine system 1A according to this embodiment is different from the engine system 1 according to Embodiment 1 in the position of the ventilation port 502. Hereinafter, for the same configurations as those in Embodiment 1, common reference numerals are given and the description thereof is omitted as appropriate. In FIG. 27, the flow of blow-by gas is indicated by thick solid arrows.

[0161] That is, in this embodiment, as shown in FIG. 26, the cylinder block 5 has a 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. 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 on 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 to the left of the cylinder liner 511 on the lower surface of the liner support wall 55. Here, in this embodiment, as shown by the imaginary line (two-dot chain line) in FIG. 26, it is assumed that 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 is provided at the opening 531 of the cam chamber 53. 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 port 502 includes a vertical passage 503A extending straight upward along the vertical direction D2 from the ventilation port 502, and a horizontal passage 503B extending leftward along the width direction D3 from the upper end of the vertical passage 503A. The vertical passage 503A only needs to extend upward along the vertical direction D2 from the ventilation port 502. For example, it may extend obliquely upward from the ventilation port 502, or may extend upward while meandering from the ventilation port 502. This ventilation passage 503 is a passage within the wall formed inside the liner support wall 55. In this way, by including the vertical passage 503A and the horizontal passage 503B with different extension directions, the ventilation passage 503 has a bending portion 503C (see FIG. 27) at the connection portion between the vertical passage 503A and the horizontal passage 503B. That is, the connection portion between the vertical passage 503A and the horizontal passage 503B constitutes the bending portion 503C.

[0163] According to the configuration described above, as shown in FIG. 27, the blow-by gas is efficiently discharged from the internal space Sp1 of the crankcase 52 via the ventilation port 502 (and the ventilation passage 503). That is, unburned gas and the like leak from the combustion chamber 50 into the crankcase 52 through the gap between the cylinder 51 and the piston 21, generating blow-by gas. In this embodiment, by using a gaseous fuel (hydrogen) with a specific gravity less than 1, the specific gravity of the blow-by gas is also less than 1. Therefore, the blow-by gas leaking into the crankcase 52 moves upward. 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 leaking from the lower end of the cylinder liner 511 into the crankcase 52 moves toward the lower surface of the liner support wall 55 that is recessed upward, 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 (bottom surface) of the liner support wall 55 is not perpendicular to the central axis of the cylinder 51 but is inclined. That is, as shown in FIG. 27, the bottom surface of the liner support wall 55 has a "rising left" gradient such that the end (left end) side where the ventilation port 502 is provided is positioned higher. Therefore, the blow-by gas staying at the lower end of the liner support wall 55 is collected toward the left end side by bypassing around the periphery of the cylinder liner 511 due to the gradient of the bottom surface of the liner support wall 55. Thus, 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] Also, in the present embodiment, the bent portion 503C of the ventilation passage 503 functions as a gas-liquid separation portion 504. In short, by providing such a bent portion 503C (gas-liquid separation portion 504), the blow-by gas introduced from the ventilation port 502 into the ventilation passage 503 flows in the ventilation passage 503 so as to collide with the abutting surface of the vertical passage 503A when passing through the bent portion 503C as the gas-liquid separation portion 504. Then, when the blow-by gas comes into contact with the inner peripheral surface of the bent portion 503C as the gas-liquid separation portion 504, liquids such as oil or moisture discharged together with the blow-by gas adhere to the inner peripheral surface of the bent portion 503C as the gas-liquid separation portion 504. Thereby, the liquids (such as oil or moisture) discharged together with the blow-by gas are captured at the gas-liquid separation portion 504 and separated from the gas contained in the blow-by gas.

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

[0167] The cam chamber wall 533 is not an essential configuration and may be omitted as appropriate. The configurations (including modified examples) according to Embodiment 2 can be adopted in appropriate combination with the various configurations (including modified examples) described in Embodiment 1.

[0168] (Embodiment 3) The engine system 1B according to the present embodiment is different from the engine system 1 according to Embodiment 1 in that a plurality of ventilation ports 502 are provided so as to correspond one-to-one to a plurality of cylinders 51, as shown in FIG. 28. Hereinafter, for the same configurations as those in Embodiment 1, the same reference numerals will be given and the description will be omitted as appropriate.

[0169] That is, in the present embodiment, a plurality (six) of cylinders 51 are provided so as to be arranged in the output shaft direction D1. Here, the ventilation ports 502 are formed at six positions in the output shaft direction D1 so as to correspond to all of the plurality of cylinders 51 in the cam chamber 53. A plurality of ventilation passages 503 are provided so as to extend upward from these plurality (six in the present embodiment) of ventilation ports 502, respectively.

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

[0171] In the present 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 has an "upward rearward" gradient so as to be positioned higher toward one end (the rear end in the present embodiment) side in the output shaft direction D1. Therefore, the blow-by gas collected in the common exhaust pipe 507 is collected toward the tip side (rear end side) of the common exhaust pipe 507 due to the gradient of the common exhaust pipe 507. Thus, the blow-by gas is efficiently discharged from the common exhaust pipe 507.

[0172] The configuration according to Embodiment 3 can be adopted in appropriate combination with various configurations (including modified examples) described in Embodiment 1 or Embodiment 2. (Embodiment 4) The engine system 1C according to this embodiment is different from the engine system 1 according to Embodiment 1 in that the cooling unit 612 is arranged on the outer peripheral side surface 601, as shown in FIG. 29. Hereinafter, for the same configurations as those in Embodiment 1, the same reference numerals will be given and the description will be omitted as appropriate.

[0173] That is, in this embodiment, the intake port 61 has a curved portion 600 whose cross-sectional shape is convex in one direction. The cooling unit 612 is arranged on the surface of the inner peripheral surface 611 of the intake port 61 on the one-direction (here, upward) side of the curved portion 600, that is, on the outer peripheral side surface 601. That is, the inner peripheral surface 611 includes the outer peripheral side surface 601 that is the surface on the one-direction (here, upward) side of the curved portion 600 and the inner peripheral side surface 602 that is the surface on the other direction (here, downward) side of the curved portion 600, and the cooling unit 612 is arranged on the outer peripheral side surface 601.

[0174] In this way, since the cooling unit 612 is arranged on the outer peripheral side surface 601, even when the gaseous fuel injected from the injection unit 31 is flowed by the air flow, it is easy to reach the cooling unit 612. In short, since the air flow in the curved portion 600 mainly passes near the outer peripheral side surface 601, the presence of the cooling unit 612 on the outer peripheral side surface 601 makes it easy for the gaseous fuel to be cooled by the cooling unit 612. Therefore, it is possible to sufficiently exhibit the cooling effect of the gaseous fuel by the cooling unit 612.

[0175] Here, in this embodiment, by setting the nozzle length of the injection unit 31 to be relatively long, the directivity of the gaseous fuel injected from the injection unit 31 is enhanced. That is, the longer the injection unit 31 is, the more the directivity of the gaseous fuel injected from the injection unit 31 is improved, and the gaseous fuel is more likely to reach the cooling unit 612.

[0176] Incidentally, in the present embodiment, as an example, in order to realize the cooling unit 612 disposed on the outer peripheral side surface 601, as shown in FIG. 29, the valve seat portion 66 is utilized. That is, at the end portion on the combustion chamber 50 side in the air supply port 61, a valve seat portion 66 on which the air supply valve 72 is seated is provided. The cooling unit 612 is disposed on the valve seat portion 66. Specifically, on the surface of the valve seat portion 66 opposite to the internal space Sp2 of the air supply port 61, a refrigerant passage 661 for passing refrigerant is formed. When refrigerant flows through this refrigerant passage 661, the valve seat portion 66 is cooled, and the cooling unit 612 provided on the valve seat portion 66 is cooled. That is, as a specific aspect of the cooling unit 612, the first aspect (refrigerant cooling method) is adopted.

[0177] According to this configuration, the gaseous fuel can be cooled at the valve seat portion 66 closest to the combustion chamber 50 in the air supply port 61. Therefore, even if a flame (or heated gas) flows from the combustion chamber 50 into the air supply port 61 due to backfire, cooling can be achieved by the cooling unit 612 provided at the inlet (valve seat portion 66) of the air supply port 61, and the chain reaction of backfire can be further suppressed.

[0178] Further, as a modification of Embodiment 4, in order to realize the cooling unit 612 disposed on the outer peripheral side surface 601, as shown in FIG. 30, a throttle portion 67 may be utilized. The throttle portion 67 is a portion where the cross-sectional area perpendicular to the air flow in the air supply port 61, that is, the flow path cross-sectional area, is locally reduced. That is, the flow path cross-sectional area of the air supply port 61 is not uniform, and at least at the throttle portion 67, it is smaller (narrower) than the upstream side and the downstream side of the throttle portion 67. Such a throttle portion 67 is realized by ribs or the like formed on the inner peripheral surface 611 of the air supply port 61. In the example of FIG. 30, a throttle portion 67 in which the flow path cross-sectional area of the air supply port 61 is locally narrowed is configured by ribs protruding rearward (the front side of the paper surface in FIG. 30) from the inner peripheral surface 611 of the air supply port 61.

[0179] By providing such a throttle portion 67, the air whose flow velocity is increased when passing through the throttle portion 67 substantially travels straight and collides with the inner peripheral surface 611 (here, the outer peripheral side surface 601) of the air supply port 61. As a result, the portion of the inner peripheral surface 611 of the air supply port 61 that is hit by the air can be cooled by the air flow to form a cooling portion 612. In short, in the example of FIG. 30, the air supply port 61 has a throttle portion 67 whose cross-sectional area orthogonal to the air flow is partially reduced. The cooling portion 612 includes the intersection of the inner peripheral surface 611 of the air supply port 61 with a virtual line VL1 that extends vertically from the cross-section of the throttle portion 67 in the air supply port 61 toward the downstream side of the air flow. Thus, the cooling portion 612 realized by using the throttle portion 67 is a kind of the third mode (air cooling method).

[0180] According to this configuration, by simply providing the throttle portion 67, the cooling portion 612 by the air cooling method can be realized without using a device such as a fan for increasing the flow velocity of the air. 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.

[0181] Also, in the present embodiment, the refrigerant passage 63 can be appropriately omitted. The configuration according to Embodiment 4 (including modifications) can be adopted in appropriate combination with various configurations (including modifications) described in Embodiment 1, Embodiment 2, or Embodiment 3.

[0182] <Supplementary Note of the Invention> An engine system according to an aspect of the present disclosure is an engine system in which blow-by gas having a specific gravity based on air smaller than 1 can be generated, and includes a cylinder block. The cylinder block includes cylinders and a crankcase arranged in the vertical direction, and the crankcase is located below the cylinders. A ventilation port that leads to a ventilation passage connecting the internal space of the crankcase and the external space of the cylinder block opens on the inner peripheral surface of the cylinder block. The ventilation port is arranged above the center in the vertical direction in the crankcase.

Explanation of Reference Numerals

[0183] 1,1A to 1C engine system 5-cylinder block 23 camshaft 51 cylinders 51A one-end side cylinder 51B other-end side cylinder 52 crank chamber 53 cam chamber 55 liner support wall 210 piston inner space 212 partition wall 213 stirring part 214 cavity part 501 inner peripheral surface (of cylinder block) 502 ventilation port 503 ventilation passage 503C bending part 504 gas-liquid separation part 511 cylinder liner 505 gas inlet 506 air flow formation part Ax1 rotating shaft C1 center D1 output shaft direction D2 up-down direction Sp1 internal space (of crank chamber)

Claims

1. An engine system capable of generating blow-by gas, comprising: a cylinder block having a crank chamber located below a cylinder; a ventilation port communicating with 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 cylinder block has a liner support wall for supporting a cylinder liner constituting the cylinder; a lower end of the cylinder liner protrudes downward from a lower end of the liner support wall; the ventilation port is disposed above a lower end of the cylinder; the engine system.

2. In a plan view, the ventilation port is disposed on a side opposite to an exhaust manifold with respect to a rotation axis of a crankshaft disposed in the crank chamber. The engine system according to claim 1.

3. The cylinder block communicates with the crank chamber and further includes a cam chamber for accommodating a camshaft; the ventilation port is formed in the cam chamber. The engine system according to claim 1 or 2.

4. a gas inlet communicating with 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; in a plan view, the ventilation port and the gas inlet are disposed on opposite sides with respect to a rotation axis of a crankshaft disposed in the crank chamber. The engine system according to any one of claims 1 to 3.

5. The ventilation port opens downward. The engine system according to any one of claims 1 to 4.

6. The ventilation passage has a gas-liquid separation section for separating gas and liquid. The engine system according to any one of claims 1 to 5.

7. The ventilation passage has a bent section where a flow direction of gas changes; the gas-liquid separation section includes the bent section. The engine system according to claim 6.

8. a plurality of cylinders are provided; a plurality of ventilation passages are provided corresponding to the plurality of cylinders; end portions on a side opposite to the ventilation ports in the plurality of ventilation passages are connected to a single common exhaust pipe. The engine system according to any one of claims 1 to 7.

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