JP7667064B2 - Engine System - Google Patents

Description

This disclosure relates to an engine system in which blow-by gas having a specific gravity of less than 1 relative to air may be generated.

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

JP 2018-127894 A

However, in engine systems that use gaseous fuels with a specific gravity of less than 1, such as hydrogen, blow-by gas that leaks into the crank chamber tends to accumulate above the crank chamber. Therefore, if the intake port is located below the crank journal, as in the related art described above, there is a possibility that the blow-by gas cannot be efficiently discharged from the crank chamber.

The objective of this disclosure is to provide an engine system that can easily and efficiently exhaust blow-by gas from the crankcase.

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

This disclosure makes it possible to provide an engine system that can easily and efficiently exhaust blow-by gas from the crankcase.

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

Embodiments of the present disclosure will be described below with reference to the attached drawings. The following embodiments are examples of the present disclosure and are not intended to limit the technical scope of the present disclosure. All drawings referred to in this disclosure are schematic drawings, and the ratios of sizes and thicknesses of each component in the drawings do not necessarily reflect the actual dimensional ratios.

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

As shown in FIG. 1, the engine system 1 according to this embodiment includes an engine body 2, which is the main component of the engine system 1. The term "engine" as used here refers to a thermal engine that burns fuel to generate mechanical energy (power), and includes an internal combustion engine, which is a prime mover that burns fuel inside the engine and converts thermal energy into mechanical energy using combustion gas as the working gas. In other words, the engine body 2 generates power (mechanical energy) using the fuel supplied to it.

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

In this embodiment, as an example, an engine system 1 used in a ship 10 will be described as shown in FIG. 1. The 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 driving source for generating a propulsive force for propelling the hull 100. In this embodiment, the engine system 1 can also be used as a driving 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 driving source for generating a propulsive force for 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.

The ship 10 is a mobile body that navigates (sails) on water such as the sea, a lake, or a river. In this embodiment, as an example, the ship 10 is a "pleasure boat", a small vessel used primarily for sports or recreation on 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 receives power generated by the engine body 2 and rotates the propeller 103 around the propeller shaft 104, thereby generating a propulsive force for moving the hull 100 forward or backward.

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

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

The engine system 1 according to this embodiment is a so-called dual fuel engine (DF engine) that can handle 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, for example, hydrogen, and the liquid fuel is, for example, a fossil fuel (diesel or gasoline, etc.). More specifically, by using diesel as the liquid fuel, the engine system 1 can handle both a gas mode in which hydrogen is used as fuel, and a diesel mode in which diesel is used as fuel. Here, in the gas mode, a small amount of liquid fuel (diesel, etc.) may also be used as ignition fuel.

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

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

The crankshaft 22 protrudes rearward from the rear end of the engine body 2 as an engine output shaft. The crankshaft 22 is connected to the propeller shaft 104 via a reduction gear. 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, generating thrust 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.

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

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

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

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

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

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

As shown in FIG. 5, the cylinder block 5 has a plurality of cylinders 51 (six in this embodiment) arranged in a row (in series) along the rotation axis Ax1 of the crankshaft 22. In other words, in this embodiment, the engine body 2 is an in-line multi-cylinder engine (in-line six-cylinder engine) in which the cylinders 51 are arranged in series. The output axis direction D1 along the rotation axis Ax1 of the crankshaft 22 coincides with the arrangement direction of the plurality of cylinders 51. As shown in FIG. 1, each cylinder 51 accommodates a piston 21 that can slide in the vertical direction D2, i.e., can move back and forth. The piston 21 is connected to the crankshaft 22 via a connecting rod 24.

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

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

The intake valve 72 and the exhaust valve 73 are driven to open and close by the camshaft 23 (see FIG. 1). As shown in FIG. 1 and FIG. 6, the camshaft 23 is housed in a cam chamber 53 arranged to the left of the cylinder 51 in the cylinder block 5. The cam chamber 53 is formed in the cylinder block 5 integrally with the cylinder 51 and the crank chamber 52. The cam chamber 53 extends in the output shaft direction D1 and rotatably houses the camshaft 23, which 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 the intake valve 72 and the exhaust valve 73 to open and close.

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

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

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

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

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

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

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

The engine system 1 according to this embodiment is a supercharged engine that includes a supercharger 8 (see FIG. 1) in addition to the engine body 2. The supercharger 8 is disposed above the front part of the engine body 2, as shown in FIGS. 3 and 4.

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

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

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

The cylinder pressure sensor 76 is disposed 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.

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

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

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

In this disclosure, "parallel" refers to two straight lines on a plane that do not intersect no matter how far they are extended, in other words, the angle between them is exactly 0 degrees (or 180 degrees), and also refers to a relationship in which the angle between the two is within an error range of a few degrees (e.g., less than 10 degrees) from 0 degrees. Similarly, in this disclosure, "orthogonal" refers to a relationship in which the angle between the two is exactly 90 degrees, and also refers to a relationship in which the angle between the two is within an error range of a few degrees (e.g., less than 10 degrees) from 90 degrees.

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

In this embodiment, as described above, in addition to the cylinder 51 and the crank chamber 52, the cam chamber 53 and the intake manifold 54 are formed in the cylinder block 5. The cylinder 51, the crank chamber 52, the cam chamber 53 and the intake manifold 54 are each formed of a partition (chamber) separated from each other inside the cylinder block 5, and each has an internal space. Therefore, the inner circumferential surfaces of the cylinder 51, the crank chamber 52, the cam chamber 53 and the intake manifold 54 are all included in the inner circumferential surface 501 of the cylinder block 5. Specifically, the crank chamber 52 is disposed at the bottom of the cylinder block 5, and the cylinder 51, the cam chamber 53 and the intake manifold 54 are disposed above the crank chamber 52. Of the cylinder 51, the cam chamber 53 and the intake manifold 54, the cylinder 51 is disposed in the center of 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 cylinders 51 and crank chambers 52 aligned in the vertical direction D2, with the crank chambers 52 located below the cylinders 51.

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

The cylinder 51 is formed in a cylindrical shape extending in the vertical direction D2, and houses the piston 21 inside so that it can reciprocate along the vertical direction D2. Both end faces of the cylinder 51 in the vertical direction D2 are open. The piston 21 is a cylindrical member with an outer diameter corresponding to the inner diameter of the cylinder 51, and the internal space of the cylinder 51 is divided into two in the vertical direction D2 by the piston 21. Of the internal space of the cylinder 51, the space above the piston 21, 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, of the internal space of the cylinder 51, the space below the piston 21 is continuous with the internal space Sp1 of the crank chamber 52.

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

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

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

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

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

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

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

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

7, the center C1 of the crank chamber 52 in the vertical direction D2 is set at a position that bisects the dimension (height dimension) L1 of the crank chamber 52 in the vertical direction D2. In other words, the center C1 is set at a position that is equidistant from both the upper and lower ends of the crank chamber 52. The ventilation opening 502 is arranged so that it is located on the upper side in the vertical direction D2, that is, on the cylinder 51 side, as viewed from the center C1. The ventilation opening 502 opens in a circular shape (a perfect circle) in a plan view that is large enough to allow blow-by gas to pass through. However, the ventilation opening 502 is not limited to a circular shape, and may open in an elliptical, rectangular, or polygonal shape, for example.

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

As a result, blow-by gas with a specific gravity less than 1 is more likely to be guided toward the ventilation port 502, which is located above the bottom end of the cylinder 51, after leaking from the bottom end of the cylinder 51 into the crank chamber 52. As a result, blow-by gas can be more efficiently discharged from the crank chamber 52, improving the discharge performance of the blow-by gas.

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

As a result, blow-by gas with a specific gravity less than 1 is more likely to be discharged from the ventilation port 502 as it flows upward after leaking from the lower end of the cylinder 51 into the crank chamber 52. As a result, blow-by gas can be more efficiently discharged from the crank chamber 52, improving the discharge performance of the blow-by gas.

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

By using the space for housing the camshaft 23, blow-by gas can be efficiently discharged from the crank chamber 52 without creating a new space for forming the ventilation port 502. Furthermore, because the cam chamber 53 is located above the crank chamber 52, blow-by gas with a specific gravity of less than 1 tends to collect in the cam chamber 53 in which the ventilation port 502 is formed after leaking into the crank chamber 52, improving the discharge performance of the blow-by gas.

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

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

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

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

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

The gas-liquid separation section 504 is not limited to the protruding wall as described above, but may have the 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 disposed in the ventilation passage 503, or may be a combination of a protruding wall and a filter.

As described above, the engine body 2 according to this embodiment is an in-line multi-cylinder engine (in-line six-cylinder engine) in which multiple cylinders 51 (six in this embodiment) are arranged in series. In this type of engine, blow-by gas can be generated for each of the multiple cylinders 51, but in this embodiment, only one ventilation port 502 for exhausting blow-by gas is provided for the multiple cylinders 51. In other words, the ventilation port 502 is shared by the multiple cylinders 51. That is, in this embodiment, as described above, the crank chamber 52 consists of one section (chamber) connected to the output shaft direction D1. Therefore, no matter which of the multiple cylinders 51 generates blow-by gas, the blow-by gas will eventually leak into the same crank chamber 52. In this sense, it is sufficient to have one ventilation port 502 for exhausting blow-by gas for the multiple cylinders 51.

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

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

In addition, 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 port 505 that connects the internal space Sp1 of the crank chamber 52 to 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 diagram of the cylinder block 5 that shows the positional relationship between the cylinder 51, the crank chamber 52, and the cam chamber 53.

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

11, the ventilation port 502 and the gas inlet 505 are arranged at different positions in the output shaft direction D1 along the rotation axis Ax1 of the crankshaft 22 arranged in the crank chamber 52. In other words, 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 side cylinder 51B at the other end side of the output shaft direction D1, that is, at the rear end of the cylinder block 5. In other words, the ventilation port 502 is arranged at one end (the front end in this embodiment) of the output shaft direction D1, while the gas inlet 505 is arranged at the other end (the rear end in this embodiment) of the output shaft direction D1.

With this configuration, the gas (air) introduced from the gas inlet 505 flows toward the ventilation port 502, forming an airflow along the output shaft direction D1, so that the airflow can act over a wide range in the output shaft direction D1. This can further improve the exhaust performance of blow-by gas by the airflow.

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

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

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

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

In this way, by providing the airflow forming section 506, an airflow can be forcibly formed in the internal space Sp1 of the crank chamber 52, making it difficult for blow-by gas to stagnate within the crank chamber 52. In other words, the airflow forming section 506 promotes the discharge of blow-by gas from the ventilation port 502, thereby further improving the discharge performance of the blow-by gas. Moreover, in this embodiment, since the turbocharger 8 is used as the airflow forming section 506, there is no need to install a new device for forming an airflow.

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

In the modified example shown in "B" of FIG. 13, the airflow forming unit 506 includes an air tank mounted on the hull 100, and sends air from the air tank to the gas inlet 505. In the modified example shown in "C" of FIG. 13, the airflow forming unit 506 includes an electric fan, and sends air from the electric fan to the gas inlet 505. In both examples of "B" and "C" of FIG. 13, the gas inlet 505 is in a state of positive pressure relative to the internal space Sp1 of the crank chamber 52, and an airflow is generated in the crank chamber 52 in a direction that pushes out gas (blow-by gas) from the ventilation port 502.

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

The configuration of the piston 21 of the engine system 1 according to this embodiment will be described in more detail below with reference to Figures 14 and 15. Figures 14 and 15 are schematic cross-sectional views showing an enlarged view of the piston 21 and its surroundings.

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

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

The stirring portion 213 may be provided in the piston inner space 210 and may be configured to reciprocate with the movement of the piston 21, and is not limited to a protrusion protruding from the cylindrical portion 211 of the piston 21. For example, the stirring portion 213 may be a protrusion protruding from the upper end of the connecting rod 24. In other words, as long as the protrusion is provided on the connecting rod 24 above the lower end of the piston 21, it can stir the gas in the piston inner space 210 with the reciprocating movement of the piston 21, similar to the stirring portion 213 described above. The stirring portion 213 may be provided on both the piston 21 and the connecting rod 24.

As shown in FIG. 15, the isolation wall 212 that separates the internal space of the cylinder 51 in the vertical direction D2 of the piston 21 that reciprocates in the vertical direction D2 within the cylinder 51 preferably has a cavity 214 therein. Specifically, a plate 215 is fixed to the lower surface of the isolation wall 212 (the surface opposite the combustion chamber 50) by an appropriate method such as welding, thereby giving the isolation wall 212 a double structure. As a result, a cavity 214 is formed as an insulating layer on the upper side (combustion chamber 50 side) of the plate 215.

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

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

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

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

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

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

As shown in Figures 17 and 18, the cylinder head 6 is disposed above the cylinder 51. As a result, the space within the internal space of the cylinder 51 that is surrounded by the upper surface of the piston 21 and the lower surface of the cylinder head 6 functions as the combustion chamber 50. Both the intake port 61 and the exhaust port 62 formed in the cylinder head 6 have openings that connect to the combustion chamber 50.

The intake port 61 is a passage for gas (intake air) that connects the intake manifold 54 formed in the cylinder block 5 and the combustion chamber 50. An intake valve 72 is provided at the opening of the intake port 61 on the combustion chamber 50 side, i.e., the opening downstream of the airflow. 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.

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

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

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

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

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

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

Therefore, in this embodiment, by adopting the configuration described below, it is possible to provide an engine system 1 that provides further countermeasures against backfire.

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

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

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

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 this embodiment, as an example, the curved portion 600 is provided in the middle of the intake port 61, and by curving the cross-sectional shape so that it is convex upward, the intake port 61 has an inverted U-shaped cross-sectional shape as a whole. Therefore, the flow (air current) of air (intake air) in the internal space Sp2 of the intake port 61 follows a path that describes an arc that is convex in one direction (here, upward) along the curved portion 600. In FIG. 20, the flow of intake air is indicated by a thick arrow.

In this embodiment, the cooling section 612 is disposed on the inner circumferential surface 611 of the air supply port 61 on the other side (here, downward) of the curved section 600, i.e., on the inner circumferential side surface 602 of the curved section 600. In other words, the inner circumferential surface 611 includes the outer circumferential side surface 601, which is the surface on one side (here, upward) of the curved section 600, and the inner circumferential side surface 602, which is the surface on the other side (here, downward) of the curved section 600, and the cooling section 612 is disposed on the inner circumferential side surface 602.

The nozzle-shaped (cylindrical) injection part 31 is arranged with its tip protruding from the outer peripheral side surface 601 into the air supply port 61, and gas fuel is injected from the injection part 31 toward the cooling part 612. In other words, 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 out in an approximately conical shape with the tip of the injection part 31 as its apex, and approximately coincides with the central axis of the nozzle-shaped (cylindrical) injection part 31.

The cooling section 612 is also arranged downstream of the airflow in the air intake port 61 relative to the injection section 31. In the example of FIG. 20, an airflow from right to left occurs in the air intake port 61, so the cooling section 612 is arranged downstream to the left of the tip of the injection section 31 of the fuel supply device 3.

In this way, by arranging the cooling section 612 downstream of the injection section 31, the gaseous fuel injected from the injection section 31 is more likely to reach the cooling section 612 even if it is carried downstream by the air current. Therefore, it is possible for the cooling section 612 to fully exert its cooling effect on the gaseous fuel.

Specific examples of the cooling section 612 include the first, second, and third modes described below. The first mode is a refrigerant cooling method using a refrigerant passage 63, the second mode is a latent heat of vaporization method using an attached refrigerant, and the third mode is an air-cooling method. In other words, the cooling section 612 of the inner surface 611 of the air supply port 61 can be realized by the first, second, or third mode, or a combination of these.

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

With this configuration, the cooling section 612 can be efficiently cooled by the refrigerant flowing through the refrigerant passage 63 provided in the cylinder head 6. Furthermore, since the temperature of the cooling section 612 can be adjusted by 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.

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

With this configuration, the cooling section 612 can be cooled more efficiently by the refrigerant flowing through the refrigerant passage 63. That is, the cooling section 612 is disposed on the thin-walled section 641 of the inner circumferential surface 611 of the partition section 64, which is relatively close to the refrigerant passage 63 and where heat is easily transferred to the refrigerant flowing through the refrigerant passage 63, so that the gaseous fuel can be cooled more reliably. This further suppresses ignition of the gaseous fuel due to heating of the gaseous fuel.

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

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

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

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

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

In addition, in the engine system 1 according to this embodiment, it is even more useful to adopt the following configuration as a backfire prevention measure.

In the first configuration, a nozzle cooling structure is provided that cools the injection part 31 of the fuel supply device 3, and the gaseous fuel itself injected from the injection part 31 is cooled. As an example, the nozzle cooling structure can be realized by a coolant passage arranged around the injection part 31. This allows the injection part 31 to be cooled by the coolant, 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 coolant passage may extend, for example, from the cylinder head 6 in the width direction D3, or may extend upward from the cylinder head 6.

The second configuration is to provide a heat insulating material that covers the injection part 31 of the fuel supply device 3, suppressing heat input to the gas fuel injected from the injection part 31. This suppresses heat input from the cylinder head 6 to the injection part 31, making it possible to suppress the temperature rise of the gas fuel.

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

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

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

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

With this configuration, the cooling period T1 is set before the supply (injection) of gaseous fuel is started, so that the supply of gaseous fuel to the internal space Sp2 of the intake port 61 can be started after the cooling section 612 has been completely cooled. Therefore, even if a backfire occurs, the cooling section 612 cools the gaseous fuel, making it easier to prevent a chain reaction of backfires.

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

With this configuration, the supply of gaseous fuel begins after the timing when the flow rate of the intake air in the intake port 61 is at its maximum, making it possible to cool the gaseous fuel more efficiently. In other words, the flow rate of the intake air in the intake port 61 is at its maximum when the opening degree G2 of the intake valve 72 is at its maximum. By starting the supply of gaseous fuel after this timing (time t4 in FIG. 22), the cooling performance of the gaseous fuel is improved. This makes it even easier to suppress the chain reaction of backfires.

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

As shown in FIG. 22, the injection permission period T2 is set in consideration of the grace period T3 inserted immediately before the intake valve 72 closes. The grace period T3 is a period during which injection of gaseous fuel is prohibited, similar to the cooling period T1. That is, during the grace period T3, injection of gaseous fuel is prohibited from time t6, when the injection permission period T2 ends, to time t7, when the intake valve 72 closes (opening degree G2 is 0). In other words, the end of the cooling period T1 is set to a time (time t5 in FIG. 22) that is the sum of the grace period T3 and the injection permission period T2, prior to time t7, when the intake valve 72 closes.

This configuration prevents gaseous fuel from remaining in the intake port 61 when the intake valve 72 is closed at time t6 when the injection permission period T2 ends. In other words, even if gaseous fuel remains in the intake port 61 at time t6 when the injection permission period T2 ends, the remaining gaseous fuel can be discharged into the combustion chamber 50 during the grace period T3.

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

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

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

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

In step S2, the engine control unit 20 acquires the load of the generator 101 and the rotation speed (actual rotation speed) of the engine body 2. The engine control unit 20 then determines the injection timing of the gaseous fuel, i.e., the timing to start injecting the gaseous fuel, in reference to a "load-rotation speed map" that shows the correlation between the load of the generator 101 and the engine rotation speed (S3). The engine control unit 20 then 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).

In step S6, the engine control unit 20 acquires the amount of operation of the operation panel 102 (throttle lever) and the rotation speed (actual rotation speed) of the engine body 2. Here, the engine control unit 20 sets the target rotation speed of the engine body 2 (S7) and calculates the difference between the target rotation speed and the actual rotation speed (S8). Furthermore, the engine control unit 20 calculates the injection amount of gaseous fuel that is insufficient with respect to the injection amount of gaseous fuel in the previous cycle (deficient injection amount). 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 of the gaseous fuel (S10). Furthermore, the engine control unit 20 determines the injection timing of the gaseous fuel, that is, the timing to start injection of 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 gaseous fuel when the injection timing for gaseous fuel arrives (S12).

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

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

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

In step S23, the engine control unit 20 determines the injection timing of the gas fuel, i.e., the timing to start injecting the gas fuel, in reference to the "first load-rotation speed map" which shows the correlation between the load on the generator 101 and the engine speed. The "first load-rotation speed map" is a map prepared for when a backfire occurs, and is a map for setting the injection timing of the gas fuel taking into account the cooling period T1.

In step S24, the engine control unit 20 determines the injection timing of the gas fuel, i.e., the timing to start injecting the gas fuel, in reference to the "second load-rotation speed map" which shows the correlation between the load on the generator 101 and the engine speed. The "second load-rotation speed map" is a map prepared for steady-state operation when no backfire is occurring, and is a map for setting the injection timing of the gas fuel without taking into account the cooling period T1.

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

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

[6] Modifications Below, we will list modifications of the first embodiment. The modifications described below can be applied in appropriate combinations.

The engine system 1 in the present disclosure includes a computer system as the engine control unit 20. The computer system is mainly composed of one or more processors and one or more memories as hardware. The functions of the engine control unit 20 in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, may be provided via a telecommunication line, or may be provided by recording it on a non-transitory recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. In addition, some or all of the functional units included in the engine control unit 20 may be configured with electronic circuits.

In addition, it is not essential for engine system 1 that at least some of the functions of engine system 1 are concentrated in one housing, and the components of engine system 1 may be distributed across multiple housings. Conversely, in embodiment 1, functions that are distributed across multiple devices (e.g., engine body 2 and generator 101) may be concentrated in one housing.

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

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

The engine system 1 is not limited to an in-line multi-cylinder engine in which multiple cylinders 51 are arranged in series, but may be, for example, a V-type engine or a horizontally opposed engine in which multiple 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 hole 502 in the cam chamber 53, it is possible to efficiently exhaust blow-by gas from the crank chamber 52.

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

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

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

(Embodiment 2)
As shown in Figures 26 and 27, the engine system 1A according to this embodiment differs from the engine system 1 according to the first embodiment in the position of the ventilation port 502. Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals and will not be described as appropriate. In Figure 27, the flow of blow-by gas is indicated by thick arrows.

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

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

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

Here, the lower end (lower surface) of the liner support wall 55 is inclined, not perpendicular, to the central axis of the cylinder 51. In other words, as shown in FIG. 27, the lower surface of the liner support wall 55 has a "leftward upward" slope so that the end (left end) where the ventilation port 502 is provided is located higher. Therefore, the blow-by gas that remains at the lower end of the liner support wall 55 is collected at the left end side, bypassing the cylinder liner 511 due to the slope of the lower surface of the liner support wall 55. Therefore, the blow-by gas is efficiently discharged from the ventilation port 502 provided at the left end of the lower end of the liner support wall 55.

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

In this manner, in this embodiment, the ventilation passage 503 has an inflection section 503C where the flow direction of the gas changes. The gas-liquid separation section 504 includes the inflection section 503C. As a result, the blow-by gas is exhausted from the ventilation passage 503 with at least some of the liquid components such as oil removed, which leads to the suppression of oil consumption and the like associated with the exhaust of the blow-by gas.

The cam chamber wall 533 is not an essential component and may be omitted as appropriate. The configuration of embodiment 2 (including modified examples) can be adopted in appropriate combination with the various configurations (including modified examples) described in embodiment 1.

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

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

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

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

The configuration of embodiment 3 can be adopted in appropriate combination with the various configurations (including modified examples) described in embodiment 1 or embodiment 2.

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

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

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

In this embodiment, the nozzle length of the injection section 31 is set to be relatively long, thereby improving the directionality of the gaseous fuel injected from the injection section 31. In other words, the longer the injection section 31 is, the better the directionality of the gaseous fuel injected from the injection section 31 is, and the easier it is for the gaseous fuel to reach the cooling section 612.

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

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

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

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

With this configuration, the cooling section 612 can be realized by simply providing the throttling section 67, without using a device such as a fan to increase the air flow rate. Therefore, it is possible to simplify the configuration for realizing the cooling section 612. In the example of Figure 30, the refrigerant passage 661 of the valve seat section 66 can be omitted.

In addition, in this embodiment, the refrigerant passage 63 can be omitted as appropriate. The configuration of embodiment 4 (including modified examples) can be adopted in appropriate combination with the various configurations (including modified examples) described in embodiment 1, embodiment 2, or embodiment 3.

1, 1A to 1C Engine system 5 Cylinder block 23 Camshaft 51 Cylinder 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 Isolation wall 213 Stirring portion 214 Cavity 501 Inner circumferential surface (of cylinder block) 502 Ventilation port 503 Ventilation passage 503C Inflection portion 504 Gas-liquid separation portion 511 Cylinder liner 505 Gas inlet port 506 Air flow forming portion Ax1 Rotation axis C1 Center D1 Output shaft direction D2 Up-down direction Sp1 Internal space (of crank chamber)

Claims (8)

An engine system in which blow-by gas having a specific gravity of less than 1 based on air may be generated,
a cylinder block including cylinders and a crank chamber arranged in a vertical direction, the crank chamber being located below the cylinders;
a ventilation port connected to a ventilation passage connecting an internal space of the crank chamber and an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block,
The ventilation opening is disposed above a center of the crank chamber in the up-down direction,
the cylinder block has a liner support wall that supports a cylinder liner that configures the cylinder,
A lower end of the cylinder liner protrudes downward from a lower end of the liner support wall,
The ventilation opening is disposed at a lower end of the liner support wall.
Engine system. An engine system in which blow-by gas having a specific gravity of less than 1 based on air may be generated,
a cylinder block including cylinders and a crank chamber arranged in a vertical direction, the crank chamber being located below the cylinders;
a ventilation port connected to a ventilation passage connecting an internal space of the crank chamber and an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block,
The ventilation opening is disposed above a center of the crank chamber in the up-down direction,
a gas inlet port that connects an internal space of the crank chamber with an external space of the cylinder block is opened on an inner peripheral surface of the cylinder block,
An airflow forming unit that forms an airflow from the gas inlet toward the ventilation port,
the ventilation port and the gas inlet port are disposed at different positions from each other in an output axial direction along a rotation axis of a crankshaft disposed in the crank chamber,
The cylinders are provided in a plurality of rows in the output shaft direction,
the plurality of cylinders includes a first end cylinder and an second end cylinder located on opposite sides in the output shaft direction,
The ventilation port is disposed at a position corresponding to the one end side cylinder,
The gas inlet is disposed at a position corresponding to the other end side cylinder.
Engine system. The cylinder block further includes a cam chamber that is connected to the crank chamber and that accommodates a camshaft,
The ventilation hole is formed in the cam chamber.
The engine system of claim 2 . The ventilation port and the gas inlet port are disposed on opposite sides across a rotation axis of a crankshaft disposed in the crank chamber in a plan view.
The engine system of claim 2 . The ventilation opening is disposed above the lower end of the cylinder.
The engine system according to any one of claims 1 to 4 . The ventilation opening opens downward.
The engine system according to any one of claims 1 to 5 . The ventilation passage has a gas-liquid separation section that separates gas and liquid.
The engine system according to any one of claims 1 to 6 . The ventilation passage has an inflection portion where the flow direction of the gas changes,
The gas-liquid separation section includes the inflection section,
The engine system of claim 7 .