Marine engine

Abstract

The present invention aims to suppress the effects of the mixing of alternative fuels into sealing oil. The present invention discloses a marine engine (1) that combusts ammonia fuel in a cylinder (16), which includes a fuel injection valve (3) that injects ammonia fuel into the cylinder (16), and a housing (5) that circulates sealing oil that seals a gap (3b) between a cylindrical body (31) of the fuel injection valve (3) and a valve shaft (32) that is inserted into the cylindrical body (31) and reciprocates along a central axis (Cf), between the housing (5) and the fuel injection valve (3).

Description

Technical Field

[0001] This disclosure relates to a marine engine. Background Technology

[0002] For example, Patent Document 1 discloses a dual-fuel injection device for an internal combustion engine cylinder. This dual-fuel injection device includes a first nozzle valve for introducing a first fuel and a second nozzle valve for introducing a second fuel. Here, the first fuel is, for example, diesel fuel. The second fuel is an alternative fuel such as methanol, ethanol, or LPG.

[0003] Furthermore, to prevent the second fuel from leaking into the surrounding area via the needle guide of the second nozzle valve, the second nozzle valve is configured to receive a supply of sealing lubricating oil. Therefore, the second nozzle valve has a needle lubrication chamber for receiving sealing lubricating oil.

[0004] Generally, the pressure of the sealing lubricating oil is set higher than the fuel pressure. In contrast, the dual-fuel injection device described in Patent Document 1 is configured such that the pressure of the sealing lubricating oil is lower than the fuel pressure through a clever design of the size of the needle lubrication chamber.

[0005] Existing technical documents

[0006] Patent Document 1: Japanese Patent Publication No. 2019-70387 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, if the structure disclosed in Patent Document 1 is adopted, the second fuel may mix into the sealing oil due to the pressure difference between the sealing lubricating oil (hereinafter referred to as sealing oil) and the second fuel. In this case, the second fuel may diffuse into various parts of the sealing oil supply system, such as the sealing oil supply pipe.

[0009] On the other hand, the inventors of this application are researching a scheme to use alternative fuels other than diesel fuel as fuel for marine engines, as described in the second fuel disclosed in Patent Document 1 above. Generally speaking, depending on the composition of the alternative fuel, it may have adverse effects on the equipment and human body associated with the supply system.

[0010] Therefore, if the alternative fuel diffuses into the various parts of the sealing oil supply system as described above, the diffused alternative fuel may reach the equipment associated with the supply system or leak from unexpected locations, which may cause adverse conditions to the equipment and people.

[0011] Therefore, it was considered to follow the previous method of making the sealing oil pressure higher than the alternative fuel pressure. However, generally speaking, because the pressure difference between the two is very small, it is possible for the alternative fuel to mix into the sealing oil, although the amount mixed in is trace. In addition, fundamentally, if the sealing oil supply system fails, a drop in oil pressure could lead to a large amount of alternative fuel mixing in, which is also a concern. Therefore, even if we follow the previous method, it is still not ideal.

[0012] This disclosure was made to solve the above-mentioned technical problems, and its purpose is to suppress the effects caused by alternative fuels mixing into the sealing oil.

[0013] Methods for solving problems

[0014] A first aspect of this disclosure relates to a marine engine that burns a volatile alternative fuel in a cylinder. The marine engine includes a fuel injection valve and a housing. The fuel injection valve has a cylindrical body and a valve shaft extending along a predetermined central axis. The valve shaft is inserted into the cylindrical body and reciprocates along the central axis. The fuel injection valve injects the alternative fuel into the cylinder. The housing allows sealing oil to flow between the housing and the fuel injection valve, sealing the gap between the cylindrical body and the valve shaft.

[0015] According to the first aspect, even if alternative fuel is mixed into the sealing oil, and the volatile components of the alternative fuel leak out, the leaked volatile components can be contained within the casing. Thus, the alternative fuel mixed into the sealing oil and leaked out can be isolated from the equipment and personnel. Therefore, the impact caused by the mixing of alternative fuel can be suppressed.

[0016] Alternatively, according to a second aspect of this disclosure, the marine engine may include an engine body and a support member, the engine body having the cylinder and causing a piston to reciprocate within the cylinder, the support member being fixed to the engine body, the support member being arranged with a gap relative to the ship's floor, and the housing being supported on the engine body via the support member.

[0017] According to the second aspect, the hull is supported on the engine body by support members. This allows it to be transported as a unit with the engine body. Furthermore, the hull, supported on the engine body by the support members, is arranged with a gap relative to the ship's floor. This arrangement allows the hull to vibrate as a unit with the engine body.

[0018] Assuming the housing is placed on the floor, the engine block, acting as the vibration source, vibrates relatively significantly, while the floor and housing do not vibrate as much. In this case, a component or mechanism is needed to absorb the vibration difference between the engine block and the floor on the pipe connecting the housing and the engine block. However, such a component or mechanism may cause alternative fuel to leak from the connection between the component or mechanism and the aforementioned pipe.

[0019] In contrast, by vibrating the housing integrally with the engine body as in the second aspect, the components or mechanisms described above are unnecessary. Therefore, the risk of leakage from the aforementioned connection points can be reduced. Furthermore, by supporting the housing on the engine body, the sealing oil supply system can be constructed within the marine engine. Therefore, even if a substitute fuel leak occurs, the spread of the leaked substitute fuel can be minimized.

[0020] Alternatively, according to a third aspect of this disclosure, the engine body may include a base and a frame, the base constituting the crankcase of the marine engine, the frame being arranged above the base, and the housing being arranged on the side of the frame via the support member.

[0021] According to the third aspect, the housing is arranged on the side of the frame, i.e., above the crankcase. This arrangement allows the fuel injection valve to be close to the housing in the vertical direction. Consequently, the entire sealing oil supply system can be compactly configured. This compactness of the entire sealing oil supply system contributes to the miniaturization of the tank used to store the sealing oil and helps to suppress leakage of alternative fuels from pipelines.

[0022] Alternatively, according to a fourth aspect of this disclosure, the marine engine may include a sealing oil tank for storing the sealing oil, and the housing may house the sealing oil tank.

[0023] According to the fourth aspect, by housing the sealing oil tank within a casing, when alternative fuel is mixed into the sealing oil, both the volatile components of the alternative fuel leaking from components associated with the sealing oil tank and the volatile components of the alternative fuel leaking from connections between components (e.g., fluid joints) can be contained within the casing. This helps to suppress the effects caused by the alternative fuel mixing into the sealing oil.

[0024] Alternatively, according to the fifth aspect of this disclosure, the marine engine may include: a sealing oil conduit, an oil filter, a first pump, and a sealing oil cooler; the sealing oil conduit allows the sealing oil to flow between the sealing oil tank and the fuel injection valve; the oil filter is arranged on the sealing oil conduit to filter the sealing oil flowing in the sealing oil conduit toward the fuel injection valve; the first pump is arranged on the sealing oil conduit to pressurize the sealing oil flowing in the sealing oil conduit toward the fuel injection valve; the sealing oil cooler is arranged on the sealing oil conduit to cool the sealing oil flowing in the sealing oil conduit; and the housing houses one or more of the sealing oil tank, the oil filter, the sealing oil cooler, and the first pump, including the sealing oil tank.

[0025] According to the fifth aspect, by housing various components associated with the flow of sealing oil, represented by the first pump, within a housing, when alternative fuel mixes into the sealing oil, both the volatile components of the alternative fuel leaking from these components and the volatile components of the alternative fuel leaking from the connections between components (e.g., fluid joints) can be contained within the housing. This helps to suppress the effects caused by the alternative fuel mixing into the sealing oil.

[0026] Alternatively, according to a sixth aspect of this disclosure, the marine engine may include a second pump disposed downstream of the first pump on the sealing oil pipeline, which further pressurizes the sealing oil that has been pressurized by the first pump, and the sealing oil cooler is disposed on the sealing oil pipeline, downstream of the first pump and upstream of the second pump.

[0027] According to the sixth aspect, by using a sealing oil cooler to cool the sealing oil, the viscosity of the sealing oil can be ensured. Here, in order to supply the sufficiently cooled sealing oil to the fuel injection valve, it is considered to arrange the sealing oil cooler on the sealing oil pipeline as close as possible to the fuel injection valve. However, if the sealing oil cooler is arranged downstream of the second pump, it may cause abnormalities in the sealing oil cooler due to the sealing oil being pressurized by the second pump being supplied to the sealing oil cooler.

[0028] In contrast, by arranging the sealing oil cooler as described in the sixth aspect, both the viscosity of the sealing oil and the suppression of abnormalities in the sealing oil cooler can be taken into account.

[0029] Alternatively, according to the seventh aspect of this disclosure, the marine engine may include a sealing oil replenishment system connected to the sealing oil tank within the housing, which replenishes the sealing oil to the sealing oil tank.

[0030] According to the seventh aspect, even if volatile components of the alternative fuel leak from fluid joints, the connection between the sealing oil replenishment system and the sealing oil tank, etc., the volatile components can be contained within the casing. This helps to suppress the effects caused by the alternative fuel mixing into the sealing oil.

[0031] Alternatively, according to the eighth aspect of this disclosure, the sealing oil replenishment system may have a storage tank and a sealing oil replenishment pipe, the storage tank storing the sealing oil, and the sealing oil replenishment pipe allowing the sealing oil to flow from the storage tank to the sealing oil tank, wherein at least one of the sealing oil replenishment system and the sealing oil tank is configured to restrict the backflow of the sealing oil from the sealing oil tank to the sealing oil replenishment pipe.

[0032] According to the eighth aspect, even if alternative fuels are mixed into the sealing oil, the backflow of the sealing oil containing alternative fuels into the storage tank can be limited. As a result, the diffusion of sealing oil containing alternative fuels can be prevented, which helps to suppress the effects caused by the mixing of alternative fuels.

[0033] Alternatively, according to the ninth aspect of this disclosure, the marine engine may include a sealing oil pipe, a venting mechanism, and a venting passage, wherein the sealing oil pipe allows the sealing oil to flow between the sealing oil tank and the fuel injection valve, the venting mechanism vents the housing, and the venting passage is connected to at least one of the sealing oil tank and the sealing oil pipe, and the venting passage discharges the alternative fuel that has evaporated in at least one of the sealing oil tank and the sealing oil pipe.

[0034] According to the ninth aspect, even if alternative fuel enters and evaporates into the sealing oil flowing in at least one of the sealed oil tank and sealed oil pipeline, the volatile components can be discharged using a ventilation passage. This isolates the alternative fuel mixed into the sealing oil from equipment and personnel. Therefore, it is more advantageous to suppress the effects caused by the mixing of alternative fuel.

[0035] Furthermore, according to the ninth aspect, even if the volatile components of the alternative fuel leak out instead of being discharged through the ventilation passage, the leaked volatile components can be discharged using the ventilation mechanism. This isolates the alternative fuel that has mixed into the sealing oil and leaked from the equipment and personnel. Therefore, it is more beneficial to suppress the impact caused by the mixing of alternative fuel.

[0036] Furthermore, crew members typically perform routine inspections and other tasks on the marine engine. The ventilation system reliably isolates crew members working on the marine engine from the ammonia fuel. In other words, even if the engine body supports the casing as described in the second aspect, the ventilation system described in the ninth aspect can still isolate the crew from alternative fuel.

[0037] Alternatively, according to the tenth aspect of this disclosure, the marine engine may include an inlet passage connected to at least one of the sealing oil tank and the sealing oil pipeline, the inlet passage introducing compressed air or scavenging gas into at least one of the sealing oil tank and the sealing oil pipeline.

[0038] According to the tenth aspect, when the volatilized alternative fuel flows into at least one of the sealed oil tank and the sealed oil pipeline, it can be purged using the alternative fuel that has been introduced from the inlet passage or scavenging gas and then fed into the ventilation passage. Therefore, it is more beneficial to suppress the effects caused by the mixing of alternative fuel.

[0039] Alternatively, according to the eleventh aspect of this disclosure, the marine engine may include a flow regulating mechanism arranged on the inlet passage to regulate the flow rate of the compressed air or the scavenging gas in the inlet passage.

[0040] According to the eleventh aspect, by arranging a flow regulating mechanism in the inlet passage, the flow rate of compressed air or scavenging gas can be adjusted. Therefore, it is more beneficial to suppress the effects caused by the mixing of alternative fuels.

[0041] Alternatively, according to the twelfth aspect of this disclosure, the marine engine may include an oil receiving pan, a sealing oil discharge pipe, and a leakage sensor. The oil receiving pan is housed in the housing and receives the sealing oil leaking from the contents of the housing. The sealing oil discharge pipe is connected to the oil receiving pan and allows the sealing oil received by the oil receiving pan to flow through. The leakage sensor detects oil in at least one of the oil receiving pan and the sealing oil discharge pipe.

[0042] According to the twelfth aspect, by utilizing the sealing oil discharge system that discharges leaking from the housing, alternative fuel mixed in with the sealing oil can be discharged together with the sealing oil. This helps to suppress the effects caused by alternative fuel mixing into the sealing oil.

[0043] Alternatively, according to the thirteenth aspect of this disclosure, the alternative fuel may be ammonia fuel.

[0044] The adverse effects of leaks and volatilization of ammonia fuel are concerning. This disclosure helps to mitigate such adverse effects.

[0045] Invention Effects

[0046] As explained above, according to this disclosure, the effects caused by alternative fuels mixing into the sealing oil can be suppressed. Attached Figure Description

[0047] Figure 1 This is a schematic diagram showing a frontal view of a marine engine.

[0048] Figure 2 This is a schematic diagram showing a marine engine viewed from the side.

[0049] Figure 3 It is a schematic cross-sectional view showing the upper structure of a marine engine.

[0050] Figure 4 This is a diagram showing the sealing oil supply system.

[0051] Figure 5 This is a longitudinal sectional view showing the structure of the fuel injection valve.

[0052] Figure 6 This is a block diagram showing the structure of a marine engine controller.

[0053] Explanation of reference numerals in the attached figures:

[0054] 1 – Engine (Marine Engine); 10 – Engine Body; 11 – Engine Base; 12 – Frame; 16 – Cylinder; 3 – Fuel Injection Valve; 31 – Cylindrical Body; 32 – Valve Shaft; 33 – Sealing Chamber; 36 – Piston Shaft; 4 – Sealing Oil Supply System; 5 – Housing; 51 – Sealing Oil Tank; 52 – Oil Filter; 53 – Low-Pressure Pump (First Pump); 54 – Sealing Oil Cooler; 57 – Oil Drawer; 58 – Ventilation Mechanism; 58a – Ventilation Fan; 91 – Support Components; 6 – Sealing Oil Circulation System; 6 1 – Sealing oil delivery pipe (sealing oil pipeline); 62 – Sealing oil return pipe (sealing oil pipeline); 63 – High-pressure pump (second pump); 7 – Sealing oil replenishment system; 71 – Sealing oil replenishment pipe; 72 – Sealing oil supply source (storage tank); 9 – Alternative fuel discharge system; 96 – Ventilation passage; 97 – Inlet passage; 98 – Flow regulation mechanism; 8 – Sealing oil discharge system; 82 – Second discharge pipe (sealing oil discharge pipe); Sw3 – First leak sensor; Cf – Central shaft; F – Ship's floor. Detailed Implementation

[0055] The embodiments of this disclosure will now be described with reference to the accompanying drawings. It should be noted that the following description is merely illustrative. Figure 1 This is a schematic diagram showing a frontal view of the marine engine (hereinafter referred to as "engine")1. Figure 2 This is a schematic diagram showing the engine 1 viewed from the side.

[0056] <Overall Structure>

[0057] Engine 1 is an inline multi-cylinder marine engine. This engine 1 is configured as a direct-flow scavenging two-stroke cycle engine and is installed on large ships such as tankers, container ships, and car carriers.

[0058] Engine 1 is configured to burn alternative fuel within cylinder 16 of engine 1. At this time, engine 1 can either burn the alternative fuel alone or burn a mixture of the alternative fuel and oil fuel (e.g., a mixture of ammonia fuel and diesel fuel).

[0059] In this embodiment, a volatile fuel, such as ammonia, is used as an alternative fuel. It should be noted that the alternative fuel is not limited to ammonia. Other alternative fuels such as hydrogen, liquefied natural gas (LNG), liquefied petroleum gas (LPG), alcohol fuels, and biodiesel fuels can also be used. Here, alcohol fuels include fuels containing all alcohols such as methanol and ethanol. Biodiesel fuels include all substances that can be used as biodiesel fuels, such as fatty acid methyl esters (FAME).

[0060] Engine 1, installed on the ship, serves as the main engine propelling the vessel. The output shaft of engine 1 is connected to the ship's propeller via the propeller shaft. As engine 1 operates, its output is transmitted to the propeller, thereby propelling the ship forward.

[0061] <Main Structure>

[0062] like Figure 1 As shown, the engine 1 includes an engine body 10 having one or more (in this embodiment, multiple) cylinders 16, a sealing oil supply system 4, and a controller 100. Each cylinder 16 forms a combustion chamber 17 for burning ammonia fuel.

[0063] (1) Engine body 10

[0064] Figure 3 This is a schematic cross-sectional view showing the upper structure of engine 1.

[0065] The engine body 10 is located in the engine room of the ship. As described above, the engine body 10 has a plurality of cylinders 16. It should be noted that, unless otherwise specified, the following description is common to all cylinders 16, even when there are multiple cylinders 16.

[0066] like Figure 1 As shown, the engine 1 according to this embodiment is configured as a so-called crosshead internal combustion engine to achieve its long stroke. Accompanying this, in the engine body 10 of the engine 1, each cylinder 16 includes a piston rod 22 and a connecting rod 24. The piston rod 22 supports the piston 21 from below, and the connecting rod 24 is connected to the crankshaft 23. The piston rod 22 and the connecting rod 24 are connected by a crosshead 25.

[0067] Specifically, the engine body 10 includes a lowered engine base 11, a frame 12 mounted on the engine base 11, cylinder water jackets 13 mounted on the frame 12, cylinder liners 14, and a cylinder head 15. Each cylinder 16 is disposed within the cylinder water jacket 13. The engine body 10 also includes a piston 21 and an output shaft (e.g., a crankshaft 23), the piston 21 being disposed within the cylinder 16 and reciprocating within the cylinder 16, the output shaft rotating in conjunction with the reciprocating motion of the piston 21.

[0068] Here, the housing 11 forms the crankcase of the engine 1. The housing 11 houses the crankshaft 23 and the bearing 26, which supports the free rotation of the crankshaft 23. The crankshaft 23 is connected to the lower end of the connecting rod 24 via a crank 27.

[0069] The frame 12 houses a pair of guide plates 28, a connecting rod 24, and a crosshead 25. The pair of guide plates 28 are positioned along the width of the engine 1. Figure 1 The connecting rod 24 is arranged with gaps on the left and right sides of the paper. The connecting rod 24 is arranged between a pair of guide plates 28 with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via a crosshead 25.

[0070] The crosshead 25 is arranged between a pair of guide plates 28 and slides vertically along each guide plate 28. That is, the pair of guide plates 28 guide the crosshead 25 to slide. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The crosshead pin 29 is connected to the piston rod 22 in a manner that moves vertically as a unit, and on the other hand, the crosshead pin 29 is connected to the connecting rod 24 in a manner that allows the connecting rod 24 to swing about its upper end as a fulcrum.

[0071] The cylinder water jacket 13 supports the cylinder liner 14, which serves as the inner cylinder. The piston 21 described above is arranged inside the cylinder liner 14. The piston 21 reciprocates along the inner wall of the cylinder liner 14 in the vertical direction. The upper end of the cylinder liner 14 is open.

[0072] The cylinder head 15 is fixed to the upper end of the cylinder liner 14. The cylinder head 15 and the cylinder liner 14 together form the cylinder 16. The cylinder head 15 becomes the cover of the cylinder 16 by closing the upper end of the cylinder liner 14.

[0073] Additionally, an exhaust valve 18 is provided on the cylinder head 15, which is driven by a valve train (not shown). The exhaust valve 18, together with the cylinder 16 formed by the cylinder liner 14 and the cylinder head 15, and the top surface of the piston 21, forms the combustion chamber 17 (see reference). Figure 1The exhaust valve 18 connects or disconnects the combustion chamber 17 from the exhaust pipe 19. The exhaust pipe 19 has an exhaust port that communicates with the combustion chamber 17, and the exhaust valve 18 is configured to open or close the exhaust port.

[0074] Additionally, the cylinder head 15 defines the top surface of the combustion chamber 17. One or more fuel injection valves 3 are disposed on this top surface. In this embodiment, two fuel injection valves 3 are disposed on each cylinder 16 (see reference). Figure 1 Each fuel injection valve 3 injects ammonia fuel as a substitute fuel into cylinder 16.

[0075] like Figure 3 As shown, each fuel injection valve 3 has a cylindrical body 31, a valve shaft 32, and a sealing chamber 33. In addition, each fuel injection valve 3 is provided with an injection port 3a arranged in the combustion chamber 17.

[0076] The cylindrical body 31 has a cylindrical shape extending along a predetermined central axis Cf. The cylindrical body 31 is connected to an ammonia fuel supply line (not shown) and a sealing oil supply line (the sealing oil supply system 4 described later).

[0077] A valve shaft 32 is inserted into a cylindrical body 31. The valve shaft 32 has a needle-like shape extending along the aforementioned central axis Cf. The valve shaft 32 reciprocates along the central axis Cf. This reciprocating movement is a relative movement of the valve shaft 32 relative to the cylindrical body 31. Ammonia fuel is supplied to the space formed between the valve shaft 32 and the cylindrical body 31 (see reference). Figure 5 In the fuel chamber 35).

[0078] The sealing chamber 33 is arranged in the gap 3b between the cylindrical body 31 and the valve shaft 32 (see below). Figure 5 The gap 3b is located at the point where the outer circumferential surface of the valve shaft 32 slides relative to the inner wall surface of the cylindrical body 31 during the reciprocating movement of the valve shaft 32. Sealing oil is supplied to the sealing chamber 33.

[0079] It should be noted that, in this embodiment, fuel oil capable of combustion within the cylinder 16 is supplied to the sealing chamber 33. Furthermore, the fuel injection valve 3 is configured to seal the gap 3b using the fuel oil supplied to the sealing chamber 33.

[0080] In other words, the fuel injection valve 3 and the engine 1 including the fuel injection valve 3 in this embodiment use fuel oil as sealing oil instead of conventional oils known as lubricants for oil seals.

[0081] Fuel oil used as sealing oil includes diesel fuel. Here, the term "diesel fuel" includes any fossil fuel derived from which it can be used in low-speed diesel engines. Diesel fuel used as fuel oil can be heavy oil A, heavy oil B, or heavy oil C.

[0082] As an example, in this embodiment, MGO (Marine Gas Oil) is used as the diesel fuel. MGO is a low-sulfur light distillate oil, which is a marine fuel oil with a low environmental impact.

[0083] It should be noted that the fuel oil used as sealing oil is not limited to diesel fuel. Sealing fuel oil can also be an alternative fuel derived from non-fossil fuels. Specifically, alternative fuels derived from non-fossil fuels can be alcohol fuels or biodiesel fuels. Here, alcohol fuels include fuels containing all alcohols such as methanol and ethanol. Biodiesel fuels include all substances that can be used as biodiesel fuels, such as fatty acid methyl esters (FAME). The sealing fuel oil can be any type of oil, such as biodiesel fuel, that leaves no residue in the fuel injection valve 3.

[0084] Injection port 3a is open on cylindrical body 31. Injection port 3a opens and closes with the reciprocating movement of valve shaft 32. Each fuel injection valve 3 injects ammonia fuel supplied to cylindrical body 31 from the open injection port 3a.

[0085] Furthermore, the valve shaft 32 of each fuel injection valve 3 operates based on the balance between the fuel pressure (ammonia fuel pressure) within the fuel injection valve 3 and the force exerted by the force-applying component 34. The force-applying component 34 applies force to the valve shaft 32 to give it a tendency to close the injection port 3a, as detailed later. The pressure of the ammonia fuel within the fuel injection valve 3 is controlled by supplying working oil to operate the piston shaft 36. The supply of working oil is controlled by operating a solenoid valve (second switching valve 644) arranged in a sealing oil supply system 4 that also serves as a working oil supply line. This solenoid valve is electrically connected to the controller 100, and operates upon receiving a control signal from the controller 100. In other words, the opening and closing of each fuel injection valve 3, and the injection of ammonia fuel from the injection port 3a of each fuel injection valve 3, are controlled by the controller 100.

[0086] Alternatively, one or more fuel injection valves may be provided on the cylinder head 15 to inject "pilot oil" that ignites the ammonia fuel. The opening and closing of the one or more fuel injection valves are controlled by the controller 100 in the same manner as the fuel injection valve 3 described above.

[0087] Each fuel injection valve 3 supplies ammonia fuel to the combustion chamber 17, causing the ammonia fuel to burn within the combustion chamber 17. Through this combustion, the piston 21 reciprocates in the vertical direction. At this time, when the exhaust valve 18 operates, opening the combustion chamber 17, the exhaust gas generated by combustion is forced into the exhaust pipe 19, and the gas is introduced into the combustion chamber 17 through the scavenging port not shown in the diagram.

[0088] Furthermore, when the piston 21 reciprocates due to combustion, the piston rod 22 reciprocates together with the piston 21 in the vertical direction. Consequently, the crosshead 25, connected to the piston rod 22, also reciprocates in the vertical direction. This crosshead 25 is configured to allow the connecting rod 24 to oscillate, causing the connecting rod 24 to oscillate around the connection point where it connects to the crosshead 25. Simultaneously, the crank 27, connected to the lower end of the connecting rod 24, performs cranking motion, and the crankshaft 23 rotates accordingly. Thus, the crankshaft 23 converts the reciprocating motion of the piston 21 into rotational motion, causing the ship's propeller and propeller shaft to rotate together. This propels the ship forward.

[0089] Here, in order for ammonia fuel to be injected from each fuel injection valve 3, the valve shaft 32 needs to be moved along the central axis Cf of the cylindrical body 31 as described above. At this time, the valve shaft 32 slides along the inner wall of the cylindrical body 31. To ensure smooth sliding or to seal the gap between the valve shaft 32 and the cylindrical body 31, sealing oil is appropriately supplied to the sealing chamber 33 of each fuel injection valve 3. The engine 1 utilizes the sealing oil supply system 4 to supply sealing oil to each fuel injection valve 3.

[0090] The following is a detailed description of the structure of the sealing oil supply system 4 and the fuel injection valves 3 connected to the sealing oil supply system 4.

[0091] (2) Sealing oil supply system 4

[0092] Figure 4 This is a diagram showing the sealing oil supply system 4.

[0093] like Figure 4 As shown, the sealing oil supply system 4 includes a housing 5, a sealing oil circulation system 6, a sealing oil replenishment system 7, and a sealing oil discharge system 8 as its main components.

[0094] (Shell 5)

[0095] The housing 5 allows sealing oil to flow between the housing 5 and the fuel injection valve 3. More specifically, the housing 5 allows the sealing oil to circulate between the housing 5 and the fuel injection valve 3. More specifically, the housing 5 supplies sealing oil to the fuel injection valve 3 and receives sealing oil discharged as drain fluid from the fuel injection valve 3. Hereinafter, the sealing oil discharged as drain fluid will be referred to as "drain oil".

[0096] Additionally, the housing 5 is fluidly connected to the fuel injection valve 3 via a sealing oil circulation system 6. This fluid connection via the sealing oil circulation system 6 allows sealing oil to circulate between the housing 5 and the fuel injection valve 3.

[0097] The housing 5 in this embodiment is an outer shell for storing various items. The housing 5, as the outer shell, is configured as a separate unit from the engine body 10 described above. The housing 5 is supported on the engine body 10.

[0098] In detail, the engine 1 according to this embodiment includes a support member 91 for supporting the housing 5. The housing 5 is supported on the engine body 10 via the support member 91.

[0099] Specifically, the support member 91 involved in this embodiment is fixed to the engine body 10 and arranged on the side of the frame 12. The support member 91 is configured as a so-called mounting bracket, forming a mounting surface 91a for mounting the housing 5. This mounting surface 91a extends in a horizontal direction perpendicular to the height direction of the engine body 10, i.e., the direction of movement of the piston 21.

[0100] Therefore, by placing the housing 5 on the aforementioned mounting surface 91a, the housing 5 is arranged on the side of the frame 12 via the support member 91.

[0101] Furthermore, the support member 91 is arranged with a gap relative to the ship's floor F. The support member 91 is fixed integrally with the engine body 10. As a result, the housing 5 vibrates integrally with the engine body 10. In addition, the supply system related to the sealing oil, such as the sealing oil supply system 4, does not need to be built outside the engine 1, but is completed inside the engine 1.

[0102] Furthermore, the contents contained in the housing 5 in an airtight state include components that pose a risk of leakage of the alternative fuel should it mix with the sealing oil. Here, components that pose a risk of leakage of the alternative fuel include components fluidly connected to each other via a fluid joint and the fluid joint itself.

[0103] In detail, the housing 5 houses one or more components, including the sealing oil tank 51, the oil filter 52, the low-pressure pump 53, the sealing oil cooler 54, the sealing oil supply valve 55, and the sealing oil discharge valve 56. These components, like the housing 5, constitute the engine 1 according to this embodiment.

[0104] More specifically, the housing 5 in this embodiment houses the sealing oil tank 51, oil filter 52, low-pressure pump 53, sealing oil cooler 54, sealing oil supply valve 55, and sealing oil discharge valve 56.

[0105] Sealed oil tank 51 stores sealing oil. For example... Figure 4 As implied, the sealed oil tank 51 of this embodiment is box-shaped with a top surface 51a and a bottom surface 51b. As described above, the sealed oil tank 51 is housed in the casing 5.

[0106] A level sensor Sw1 for detecting the level of sealing oil is installed on the sealed oil tank 51. The level sensor Sw1 is electrically connected to the controller 100 and outputs a detection signal of the oil level to the controller 100. The level sensor Sw1 is housed in the housing 5.

[0107] An alternative fuel sensor Sw2 is installed on the sealed oil tank 51 to detect the amount or concentration of ammonia fuel inside. The alternative fuel sensor Sw2 is electrically connected to the controller 100 and outputs a detection signal indicating the amount or concentration of ammonia fuel to the controller 100. The alternative fuel sensor Sw2 is housed in the housing 5. It should be noted that the alternative fuel sensor Sw2 is not strictly necessary.

[0108] In detail, the alternative fuel sensor Sw2 consists of an ammonia sensor that detects the ammonia concentration in the gas within the sealed fuel tank 51. For example... Figure 4 As shown, the alternative fuel sensor Sw2 is positioned above the upper limit L1 of the allowable oil level in the sealed oil tank 51. This arrangement allows for more reliable detection of ammonia fuel evaporating from the sealing oil within the sealed oil tank 51. As an example, the alternative fuel sensor Sw2 according to this embodiment is positioned on the top surface 51a of the sealed oil tank 51.

[0109] A sealing oil delivery pipe 61, constituting the sealing oil circulation system 6, is connected to the sealing oil tank 51. The sealing oil delivery pipe 61 is a conduit that allows sealing oil to flow from the sealing oil tank 51 to the fuel injection valve 3, and particularly to the sealing chamber 33. The sealing oil delivery pipe 61 enables the flow of sealing oil between the sealing oil tank 51 and the fuel injection valve 3, and in this respect, the sealing oil delivery pipe 61 is shown as an example of a "sealing oil conduit" in this embodiment.

[0110] In detail, the sealing oil supply pipe 61 fluidly connects the sealing oil tank 51 to the sealing chamber 33 of the fuel injection valve 3. The sealing oil supply pipe 61 supplies fuel oil, which serves as sealing oil, to the sealing chamber 33. More specifically, as... Figure 4 As implied, the sealing oil delivery pipe 61 is connected to or near the bottom surface 51b of the sealing oil tank 51. The portion near the upstream end of the sealing oil delivery pipe 61 (one end on the side of the sealing oil tank 51) is housed within the casing 5.

[0111] An oil filter 52 is arranged on the sealing oil delivery pipe 61. The oil filter 52 filters the sealing oil flowing in the sealing oil delivery pipe 61 toward the fuel injection valve 3. As described above, the oil filter 52 is housed in the housing 5.

[0112] Specifically, the oil filter 52 is arranged on the sealing oil delivery pipe 61, downstream of the sealing oil tank 51 and upstream of the low-pressure pump 53. The oil filter 52 filters the sealing oil that sprays out from the sealing oil tank 51 and flows into the sealing oil delivery pipe 61.

[0113] A low-pressure pump 53 is arranged on the sealing oil delivery pipe 61. The low-pressure pump 53 pressurizes the sealing oil flowing in the sealing oil delivery pipe 61 toward the fuel injection valve 3. As described above, the low-pressure pump 53 is housed in the housing 5. The low-pressure pump 53 is an example of the "first pump" in this embodiment.

[0114] Specifically, the low-pressure pump 53 is arranged on the sealing oil delivery pipe 61, downstream of the oil filter 52 and upstream of the sealing oil cooler 54. The low-pressure pump 53 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signals, the low-pressure pump 53 pressurizes the sealing oil that has been filtered by the oil filter 52.

[0115] It should be noted that only one low-pressure pump 53 is shown in the illustration, but multiple oil pumps can also be connected in parallel on the sealing oil delivery pipe 61, and these multiple oil pumps can constitute the low-pressure pump 53. In this case, either some of the multiple oil pumps can be operated while the remaining oil pumps are allocated as standby, or multiple oil pumps can be operated simultaneously.

[0116] A sealing oil cooler 54 is arranged on the sealing oil delivery pipe 61. The sealing oil cooler 54 cools the sealing oil flowing in the sealing oil delivery pipe 61. As described above, the sealing oil cooler 54 is housed in the housing 5.

[0117] Specifically, the sealing oil cooler 54 is arranged on the sealing oil delivery pipe 61, downstream of the oil filter 52 and the low-pressure pump 53 and upstream of the high-pressure pump 63. The sealing oil cooler 54 is, for example, a heat exchanger that uses a heat exchange medium supplied from inside or outside the engine compartment. The heat exchange medium is, for example, water. The sealing oil cooler 54 cools the sealing oil pressurized by the low-pressure pump 53 via the heat exchange medium flowing within it.

[0118] A sealing oil replenishment pipe 71, constituting the sealing oil replenishment system 7, is connected to the sealing oil tank 51. The sealing oil replenishment pipe 71 is a conduit that allows sealing oil (in this embodiment, fuel oil) to flow from the sealing oil supply source 72 constituting the sealing oil replenishment system 7 to the sealing oil tank 51. The sealing oil replenishment pipe 71 fluidly connects the sealing oil supply source 72 to the sealing oil tank 51.

[0119] A sealing oil supply valve 55 is arranged on the sealing oil replenishment pipe 71. The sealing oil supply valve 55 opens and closes the sealing oil replenishment pipe 71. By opening and closing the sealing oil supply valve 55, the supply of sealing oil from the sealing oil supply source 72 to the sealing oil tank 51 can be started or stopped. As described above, the sealing oil supply valve 55 is housed in the housing 5.

[0120] Specifically, the sealing oil supply valve 55 is arranged on the sealing oil replenishment pipe 71, downstream of the sealing oil supply source 72 and upstream of the sealing oil tank 51. The sealing oil supply valve 55 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signal, the sealing oil supply valve 55 closes or opens according to the signal. When the sealing oil supply valve 55 is closed, the supply of sealing oil from the sealing oil supply source 72 to the sealing oil tank 51 is blocked; when the sealing oil supply valve 55 is open, the supply of sealing oil from the sealing oil supply source 72 to the sealing oil tank 51 is resumed.

[0121] A first discharge pipe 81 constituting the sealing oil discharge system 8 is connected to the sealing oil tank 51. The first discharge pipe 81 is a pipe that discharges sealing oil (in this embodiment, fuel oil) from the sealing oil tank 51.

[0122] A sealing oil drain valve 56 is arranged on the first drain pipe 81. The sealing oil drain valve 56 opens and closes the first drain pipe 81. By opening or closing the sealing oil drain valve 56, the discharge of sealing oil from the sealing oil tank 51 can be started or stopped. As described above, the sealing oil drain valve 56 is housed in the housing 5.

[0123] In detail, the sealing oil discharge valve 56 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signal, the sealing oil discharge valve 56 closes or opens according to the signal. When the sealing oil discharge valve 56 is closed, it blocks the discharge of sealing oil from the sealing oil tank 51; when the sealing oil discharge valve 56 is open, it discharges sealing oil from the sealing oil tank 51.

[0124] In addition, the engine 1 also includes an oil tray 57 housed in the housing 5. The oil tray 57, like other components such as the sealed oil reservoir 51, is housed in the housing 5. The oil tray 57 collects sealing oil that leaks from the contents of the housing 5.

[0125] Here, the contents of housing 5 refer to, as described above, one or more components including sealing oil tank 51, oil filter 52, low-pressure pump 53, sealing oil cooler 54, sealing oil supply valve 55, and sealing oil discharge valve 56.

[0126] The oil receiving tray 57 receives sealing oil leaking from the housing 5, or from the connection (e.g., fluid joint) between the housing and the sealing oil delivery pipe 61, the sealing oil replenishment pipe 71, or the first discharge pipe 81.

[0127] A second discharge pipe 82 constituting the sealing oil discharge system 8 is connected to the oil receiving pan 57. The second discharge pipe 82 is a conduit through which the sealing oil (fuel oil in this embodiment) received by the oil receiving pan 57 flows. The second discharge pipe 82 is an example of the "sealing oil discharge pipe" in this embodiment.

[0128] Furthermore, a first leak sensor Sw3 is connected to at least one of the oil receiving pan 57 and the second discharge pipe 82. The first leak sensor Sw3 detects oil in at least one of the oil receiving pan 57 and the second discharge pipe 82.

[0129] Specifically, as an example, the first leakage sensor Sw3 involved in this embodiment is arranged on the second discharge pipe 82. The first leakage sensor Sw3 detects the sealing oil flowing in the second discharge pipe 82. The first leakage sensor Sw3 is electrically connected to the controller 100 and outputs an oil detection signal to the controller 100. When the first leakage sensor Sw3 is arranged on the second discharge pipe 82, it can be a so-called float switch. In this case, a storage tank for sealing oil is formed on the second discharge pipe 82, and the float switch is placed in this storage tank.

[0130] It should be noted that when the first leak sensor Sw3 is arranged on the oil receiving pan 57, the first leak sensor Sw3 can be, for example, a strip sensor (sensor ribbon).

[0131] As described above, there is a risk of leakage of sealing oil from the housing 5 or from the connection points (the connection points between the housing 5 and the sealing oil supply pipe 61, the sealing oil replenishment pipe 71, or the first discharge pipe 81). In the event that ammonia fuel is mixed into the sealing oil, various adverse conditions can be anticipated due to the volatilization of the ammonia fuel.

[0132] To address such adverse conditions, the housing 5 according to this embodiment has a ventilation mechanism 58 for ventilating the interior of the housing 5. The ventilation mechanism 58 includes a ventilation fan 58a. The ventilation fan 58a is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100.

[0133] As an example, when the sealing oil circulates between the housing 5 and the fuel injection valve 3, the venting mechanism 58 performs venting within the housing 5 in parallel with this circulation. By doing so, even if ammonia fuel is mixed into the sealing oil, the ammonia fuel volatilized from the sealing oil can remain within the housing 5. Furthermore, by operating the ventilation fan 58a, the ammonia fuel volatilized from the sealing oil can be rapidly discharged.

[0134] It should be noted that it is not necessary for the ventilation fan 58a to operate using an electrical signal from the controller 100. The ventilation fan 58a can also be configured to operate by receiving an electrical signal output from a control board independent of the controller 100. In this case, the ventilation fan 58a can operate independently without being linked to the operating state of the engine 1.

[0135] Air drawn from the housing 5 by the operation of the ventilation fan 58a flows into the ventilation path 58b. This ventilation path 58b is connected to an oil mist recovery box 58c, which separates oil from the air. An additional exhaust passage 58d, communicating with the external space such as the atmosphere, is connected to the oil mist recovery box 58c (see reference). Figure 4 ).

[0136] Therefore, the air delivered from the housing 5 by the operation of the ventilation fan 58a is recovered by the oil mist recovery box 58c through the ventilation passage 58b and discharged from the exhaust passage 58d in a state where the oil has been removed.

[0137] (Sealing oil circulation system 6)

[0138] The sealing oil circulation system 6 fluidly connects the housing 5 to the fuel injection valve 3, allowing sealing oil to circulate between the housing 5 and the fuel injection valve 3. In other words, the housing 5 circulates sealing oil between the housing 5 and the fuel injection valve 3 via the fluid connection utilizing the sealing oil circulation system 6.

[0139] Specifically, the sealing oil circulation system 6 involved in this embodiment, in addition to the sealing oil delivery pipe 61 described above, also includes a high-pressure pump 63, a first pressure sensor Sw4, a control valve unit 64, and a sealing oil return pipe 62.

[0140] A high-pressure pump 63 is arranged downstream of the low-pressure pump 53 on the sealing oil delivery pipe 61, which serves as a sealing oil pipeline. The high-pressure pump 63 further pressurizes the sealing oil that has been pressurized by the low-pressure pump 53. The high-pressure pump 63 is an example of a "second pump" in this embodiment.

[0141] Specifically, the high-pressure pump 63 is arranged on the sealing oil delivery pipe 61, downstream of the low-pressure pump 53 and the sealing oil cooler 54 and upstream of the control valve unit 64. The high-pressure pump 63 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signals, the high-pressure pump 63 pressurizes the sealing oil that has been pressurized by the low-pressure pump 53 and cooled by the sealing oil cooler 54.

[0142] In other words, the sealing oil cooler 54 in this embodiment is arranged downstream of the low-pressure pump 53 and upstream of the high-pressure pump 63 on the sealing oil delivery pipe 61.

[0143] It should be noted that only one high-pressure pump 63 is shown in the illustration, but multiple oil pumps can also be connected in parallel on the sealing oil delivery pipe 61, and these multiple oil pumps can constitute the high-pressure pump 63. In this case, either some of the multiple oil pumps can be operated while the remaining oil pumps are allocated as standby, or the multiple oil pumps can be configured to operate simultaneously.

[0144] In addition, such as Figure 2 As shown, the high-pressure pump 63 is configured as a separate unit relative to the housing 5, but it can also be fixed to the engine body 10 via the support member 91 in the same way as the housing 5.

[0145] In addition, such as Figure 2 As shown, the high-pressure pump 63 is housed in an outer casing 93, which is separate from the aforementioned housing 5. This outer casing 93 is connected to the housing 5 via a pipe 94. Ammonia volatilized inside the outer casing 93 is sent to the housing 5 via the pipe 94 and then ventilated by the ventilation mechanism 58.

[0146] It should be noted that the housing 93 for the high-pressure pump 63, like the housing 5 and the housing 95 for the control valve unit 64 described later, houses an oil drip tray (not shown). This oil drip tray collects sealing oil leaking from the high-pressure pump 63. The oil drip tray for the high-pressure pump 63 is connected to the confluence pipe 84 between the second discharge pipe 82 and the third discharge pipe 83. Oil leaks can be detected by using, for example, a float sensor to detect the oil flowing in this connection pipe.

[0147] The first pressure sensor Sw4 is located on the sealing oil delivery pipe 61, downstream of the high-pressure pump 63. The first pressure sensor Sw4 detects the pressure of the sealing oil after it has been pressurized by the high-pressure pump 63.

[0148] In detail, the first pressure sensor Sw4 is arranged on the sealing oil delivery pipe 61, downstream of the high-pressure pump 63 and upstream of the control valve unit 64. The first pressure sensor Sw4 is electrically connected to the controller 100 and outputs a detection signal of the sealing oil pressure to the controller 100. The first pressure sensor Sw4 is, for example, a pressure transmitter (so-called "PT") that integrates a pressure sensor and an amplifier.

[0149] The control valve unit 64 is arranged on the sealing oil supply pipe 61, which serves as a sealing oil pipeline, downstream of the first pressure sensor Sw4 and upstream of the fuel injection valve 3. The control valve unit 64 controls the supply of sealing oil to the fuel injection valve 3.

[0150] In detail, the control valve unit 64, starting from the upstream side in the direction of seal oil flow, includes a first pressure reducing valve 641, a first switching valve 642, and a second pressure sensor Sw5. These elements are all arranged on the seal oil delivery pipe 61.

[0151] The first pressure reducing valve 641 regulates the pressure of the sealing oil after it has been pressurized by the high-pressure pump 63. Specifically, the sealing oil pressurized by the high-pressure pump 63 flows into the primary side (upstream side) of the first pressure reducing valve 641, and the sealing oil regulated by the first pressure reducing valve 641 flows out from the secondary side (downstream side) of the first pressure reducing valve 641.

[0152] The first switching valve 642 opens and closes the sealing oil delivery pipe 61. When the first switching valve 642 opens the sealing oil delivery pipe 61, the sealing oil, after being pressurized by the first pressure reducing valve 641, reaches the fuel injection valve 3 through the first switching valve 642. When the first switching valve 642 closes the sealing oil delivery pipe 61, the sealing oil after being pressurized by the first pressure reducing valve 641 is blocked by the first switching valve 642.

[0153] In detail, the first switching valve 642 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signal, the first switching valve 642 closes or opens according to the signal. The first switching valve 642 is, for example, a solenoid valve.

[0154] The second pressure sensor Sw5 is located on the sealing oil delivery pipe 61, downstream of the first switching valve 642. The second pressure sensor Sw5 detects the pressure of the sealing oil immediately after passing through the first switching valve 642.

[0155] Specifically, the second pressure sensor Sw5 is located on the sealing oil delivery pipe 61, downstream of the first switching valve 642 and upstream of the fuel injection valve 3. The second pressure sensor Sw5 is electrically connected to the controller 100 and outputs a detection signal of the sealing oil pressure to the controller 100. The second pressure sensor Sw5 may be, for example, a pressure transmitter (so-called "PT") integrating a pressure sensor and amplifier.

[0156] In addition, in this embodiment, the fuel oil that functions as a sealing oil is also used as a working oil.

[0157] Therefore, the sealing oil delivery pipe 61 involved in this embodiment and Figure 4The working oil supply pipe 65 shown is connected. The working oil supply pipe 65 connects the sealing oil delivery pipe 61 to the fuel injection valve 3. More specifically, as... Figure 4 As shown, the working oil supply pipe 65 connects the first pressure sensor Sw4 and the first pressure reducing valve 641 on the sealing oil delivery pipe 61 to the working oil chamber 38 in the fuel injection valve 3.

[0158] As an element associated with the supply of working oil, the control valve unit 64 according to this embodiment also includes, in sequence from the upstream side in the flow direction of the sealing oil (working oil), a second switching valve 644, a second pressure reducing valve 645, a third pressure sensor Sw7, and a working oil pump 646. These elements are all arranged on the working oil supply pipe 65.

[0159] The second switching valve 644 opens and closes the working oil supply pipe 65. When the second switching valve 644 opens the working oil supply pipe 65, the sealing oil pressurized by the high-pressure pump 63 reaches the second pressure reducing valve 645 through the second switching valve 644. When the second switching valve 644 closes the working oil supply pipe 65, the sealing oil pressurized by the high-pressure pump 63 is blocked by the second switching valve 644.

[0160] In detail, the second switching valve 644 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signal, the second switching valve 644 closes or opens according to the signal. The second switching valve 644 is, for example, a solenoid valve.

[0161] The second pressure reducing valve 645 regulates the pressure of the sealing oil that has passed through the second switching valve 644. Specifically, the sealing oil that has passed through the second switching valve 644 flows into the primary side (upstream side) of the second pressure reducing valve 645, and the sealing oil that has been pressure-regulated by the second pressure reducing valve 645 flows out from the secondary side (downstream side) of the second pressure reducing valve 645.

[0162] The third pressure sensor Sw7 is located on the working oil supply pipe 65, downstream of the second pressure reducing valve 645. The third pressure sensor Sw7 detects the pressure of the sealing oil after it has been regulated by the second pressure reducing valve 645.

[0163] Specifically, the third pressure sensor Sw7 is located on the working oil supply pipe 65, downstream of the second pressure reducing valve 645 and upstream of the working oil pump 646. The third pressure sensor Sw7 is electrically connected to the controller 100 and outputs a detection signal of the sealing oil pressure to the controller 100. The third pressure sensor Sw7 is, for example, a pressure transmitter (so-called "PT") that integrates a pressure sensor and an amplifier.

[0164] The working oil pump 646 is located on the working oil supply pipe 65, downstream of the third pressure sensor Sw7. The working oil pump 646 pumps the sealing oil, whose pressure has been regulated by the second pressure reducing valve 645 and detected by the third pressure sensor Sw7, to the fuel injection valve 3.

[0165] In detail, the working oil pump 646 is arranged on the working oil supply pipe 65, downstream of the second pressure reducing valve 645 and the third pressure sensor Sw7 and upstream of the fuel injection valve 3. The working oil pump 646 is electrically connected to the controller 100 and operates by receiving electrical signals from the controller 100. Upon receiving the electrical signals, the working oil pump 646 pressurizes the sealing oil, which has been regulated by the second pressure reducing valve 645, as working oil to the fuel injection valve 3.

[0166] Furthermore, the control valve unit 64 is housed within a housing 95 for the control valve unit 64. For example, as... Figure 2 As shown, the outer casing 95 is separate from the casing 5 and the casing 93 used for the high-pressure pump 63.

[0167] It should be noted that it is not necessary for the housing 95 for the control valve unit 64 to be separate from both the housing 5 and the housing 93 for the high-pressure pump 63. The housing 95 may also be integrated with at least one of the housing 5 and the housing 93 for the high-pressure pump 63. Alternatively, the housing 95 may be composed of multiple housings that respectively house different components.

[0168] And, as Figure 4 As shown, the control valve unit 64 also includes a second oil receiving tray 643 housed in a housing 95 for the control valve unit 64. The second oil receiving tray 643 receives sealing oil leaking from the components of the control valve unit 64. The components of the control valve unit 64 include a first pressure reducing valve 641, a first switching valve 642, a second pressure sensor Sw5, a second switching valve 644, a second pressure reducing valve 645, a third pressure sensor Sw7, and a working oil pump 646.

[0169] A third discharge pipe 83, constituting the sealing oil discharge system 8, is connected to the second oil receiving pan 643. The third discharge pipe 83 is a conduit through which the sealing oil (fuel oil in this embodiment) received by the second oil receiving pan 643 flows.

[0170] Furthermore, a second leak sensor Sw6 is connected to at least one of the second oil receiving pan 643 and the third discharge pipe 83. The second leak sensor Sw6 detects oil in at least one of the second oil receiving pan 643 and the third discharge pipe 83.

[0171] Specifically, as an example, the second leakage sensor Sw6 involved in this embodiment is arranged on the third discharge pipe 83. The second leakage sensor Sw6 detects the sealing oil flowing in the third discharge pipe 83. The second leakage sensor Sw6 is electrically connected to the controller 100 and outputs an oil detection signal to the controller 100. When the second leakage sensor Sw6 is arranged on the third discharge pipe 83, it can be a so-called float switch. In this case, a storage tank for sealing oil is formed on the third discharge pipe 83, and the float switch is placed in the storage tank.

[0172] It should be noted that when the second leak sensor Sw6 is arranged on the second oil receiving pan 643, the second leak sensor Sw6 can be, for example, a strip sensor (sensor strip).

[0173] Additionally, returning Figure 2 The control valve unit 64 is configured as a separate unit relative to the housing 5 and the high-pressure pump 63. In this embodiment, the control valve unit 64 is supported on the engine body 10 via a second support member 92.

[0174] The second support member 92 is formed by a so-called mounting frame and is fixed to the cylinder water jacket 13 or cylinder liner 14. The second support member 92 supports the control valve unit 64 in the height direction of the engine 1 above the housing 5 and the high pressure pump 63.

[0175] The sealing oil return pipe 62 is a conduit that allows sealing oil to flow from the fuel injection valve 3 and various parts of the sealing oil supply system 4 to the sealing oil tank 51. The sealing oil return pipe 62 includes a first return pipe 621, a second return pipe 622, a third return pipe 623, a fourth return pipe 624, a fifth return pipe 625, a first on / off valve 626, and a second on / off valve 627. The sealing oil return pipe 62 enables the flow of sealing oil between the sealing oil tank 51 and the fuel injection valve 3; in this respect, the sealing oil return pipe 62, together with the aforementioned sealing oil delivery pipe 61, is shown as an example of a "sealing oil conduit" in this embodiment.

[0176] The first return pipe 621 is a pipe that returns the exhaust oil discharged from the fuel injection valve 3 to the sealed oil tank 51. The first return pipe 621 fluidly connects each fuel injection valve 3 to the sealed oil tank 51. The portion near the downstream end of the first return pipe 621 (the end on the side of the sealed oil tank 51) is housed in the housing 5.

[0177] The second return pipe 622 is a conduit that returns the leaking sealing oil (hereinafter also referred to as "leaking oil") from the high-pressure pump 63 (described later) to the sealing oil tank 51. The second return pipe 622 fluidly connects the high-pressure pump 63 to the sealing oil tank 51. The portion near the downstream end of the second return pipe 622 (the end on the sealing oil tank 51 side) is housed in the housing 5.

[0178] The third return pipe 623 controls the discharge pressure of the high-pressure pump 63. The third return pipe 623 fluidly connects the outlet of the high-pressure pump 63 to the sealed oil tank 51. The portion near the downstream end of the third return pipe 623 (on the side of the sealed oil tank 51) is housed within the casing 5. Furthermore, as... Figure 4 As shown, a first on / off valve 626 is arranged midway through the third return pipe 623. The first on / off valve 626 operates by receiving an electrical signal from the controller 100, thereby changing its opening degree. The controller 100 regulates the discharge pressure of the high-pressure pump 63 to the desired pressure by controlling the opening degree of the first on / off valve 626. It should be noted that a pressure regulating valve can also be arranged to replace the first on / off valve 626 electrically connected to the controller 100.

[0179] The fourth return pipe 624 is constructed from a conduit that returns leaked oil from the first switching valve 642 and the second switching valve 644 back to the sealed oil tank 51. The fourth return pipe 624 fluidly connects the first switching valve 642 and the second switching valve 644 to the third return pipe 623 at an intermediate point. In other words, the fourth return pipe 624 connects to the sealed oil tank 51 after merging with the third return pipe 623.

[0180] The fifth return pipe 625 controls the discharge pressure of the low-pressure pump 53. The fifth return pipe 625 fluidly connects the outlet of the low-pressure pump 53 to the sealed oil tank 51. The entire fifth return pipe 625, from its upstream end to its downstream end, is housed within the casing 5. Furthermore, as... Figure 4 As shown, a second on / off valve 627 is arranged midway through the fifth return pipe 625. The second on / off valve 627 operates by receiving an electrical signal from the controller 100, thereby changing its opening degree. The controller 100 regulates the discharge pressure of the low-pressure pump 53 to the desired pressure by controlling the opening degree of the second on / off valve 627. It should be noted that a pressure regulating valve can also be used instead of the second on / off valve 627 electrically connected to the controller 100.

[0181] Here, the connection point between the sealing oil return pipe 62 and the sealing oil tank 51 is located above the connection point between the sealing oil delivery pipe 61 and the sealing oil tank 51.

[0182] Specifically, the connection point between the sealing oil return pipe 62 and the sealing oil tank 51 is positioned above the upper limit L1 of the allowable oil level in the sealing oil tank 51. More specifically, the sealing oil return pipe 62 is connected to or near the top surface 51a of the sealing oil tank 51.

[0183] (Sealing oil replenishment system 7)

[0184] The sealing oil replenishment system 7 is connected to the housing 5. Specifically, the sealing oil replenishment system 7 is connected to the sealing oil tank 51 within the housing 5. This sealing oil replenishment system 7 replenishes sealing oil to the sealing oil tank 51 within the housing 5.

[0185] Specifically, the sealing oil replenishment system 7 of this embodiment, in addition to the sealing oil replenishment pipe 71 described above, also includes the sealing oil supply source 72, oil cooler 73, and filter 74 described above.

[0186] The sealing oil supply source 72 is a tank for storing fuel oil such as MGO used as sealing oil. The sealing oil supply source 72 is fluidly connected to the sealing oil tank 51 inside the housing 5 via the sealing oil replenishment pipe 71. The sealing oil supply source 72 is an example of a "storage tank" in this embodiment.

[0187] An oil cooler 73 is arranged on the sealing oil supply pipe 71. The oil cooler 73 cools the sealing oil flowing in the sealing oil supply pipe 71. The oil cooler 73 is, for example, a heat exchanger that uses a heat exchange medium supplied from inside or outside the engine compartment. The heat exchange medium is, for example, water.

[0188] A filter 74 is arranged on the sealing oil supply pipe 71 to filter the sealing oil flowing in the sealing oil supply pipe 71.

[0189] Furthermore, at least one of the sealing oil replenishment system 7 and the sealing oil tank 51 is configured to restrict the backflow of sealing oil from the sealing oil tank 51 to the sealing oil replenishment pipe 71.

[0190] For example, in this embodiment, such as Figure 4 As shown, the connection point between the sealing oil replenishment pipe 71 and the sealing oil tank 51 is located above the connection point between the sealing oil delivery pipe 61 and the sealing oil tank 51.

[0191] Specifically, the connection point between the sealing oil replenishment pipe 71 and the sealing oil tank 51 is positioned above the upper limit L1 of the allowable oil level in the sealing oil tank 51. More specifically, the sealing oil replenishment pipe 71 is connected to or near the top surface 51a of the sealing oil tank 51.

[0192] In this way, by cleverly designing the connection position between the sealing oil replenishment pipe 71 and the sealing oil tank 51, the backflow of sealing oil from the sealing oil tank 51 to the sealing oil replenishment pipe 71 is suppressed. Alternatively, based on or replacing these structures, components such as check valves that can suppress backflow of sealing oil can be arranged on the sealing oil replenishment pipe 71, or the sealing oil supply source 72 can be positioned higher than the sealing oil replenishment pipe 71.

[0193] (Sealing oil drainage system 8)

[0194] The sealing oil discharge system 8 discharges the remaining sealing oil, such as leaked oil, from various parts of the sealing oil supply system 4.

[0195] Specifically, the sealing oil discharge system 8 involved in this embodiment, in addition to having the first discharge pipe 81, the second discharge pipe 82, the first leakage sensor Sw3, the third discharge pipe 83 and the second leakage sensor Sw6 as described above, also has a merging pipe 84.

[0196] A first discharge pipe 81, a second discharge pipe 82, and a third discharge pipe 83 are connected to the confluence pipe 84. The confluence pipe 84 discharges the sealing oil flowing into the first discharge pipe 81, the second discharge pipe 82, and the third discharge pipe 83 to the engine compartment. Even if ammonia fuel is mixed in the sealing oil, the ammonia fuel will be discharged to the engine compartment along with the sealing oil.

[0197] (3) Fuel injection valve 3

[0198] Figure 5 This is a longitudinal sectional view showing the structure of the fuel injection valve 3.

[0199] like Figure 5 As shown, the fuel injection valve 3 includes, in addition to the aforementioned cylindrical body 31, valve shaft 32, and sealing chamber 33, a fuel chamber 35, piston shaft 36, pressure delivery chamber 37, and working oil chamber 38.

[0200] Hereinafter, the direction extending along the central axis Cf of the cylindrical body 31 will be referred to as the central axis direction. Furthermore, one end of the cylindrical body 31 in the central axis direction (the lower side in the figure) will be designated as the top end, and the other end in the central axis direction will be designated as the base end. For example, the injection port 3a of the fuel injection valve 3 is as follows... Figure 5 As shown, an opening is made at the top of the cylindrical body 31.

[0201] A working oil chamber 38 is formed inside the cylindrical body 31. The working oil chamber 38 is fluidly connected to a working oil supply pipe 65. Fuel oil, which serves as the working oil, is pressurized from the working oil supply pipe 65 into the working oil chamber 38. In addition, any remaining working oil in the working oil chamber 38 is discharged from the working oil chamber 38 as effluent.

[0202] A pressure chamber 37 is formed inside the cylindrical body 31. The pressure chamber 37 is arranged at the top end of the working oil chamber 38 in the central axis direction. Ammonia fuel, as an alternative fuel, is supplied from the outside into the pressure chamber 37 via a check valve 39. The pressure chamber 37 is also fluidly connected to the fuel chamber 35 via a first path L1 formed within the cylindrical body 31.

[0203] A through hole 3c is formed inside the cylindrical body 31. The through hole 3c extends along the central axis in such a way that the working oil chamber 38 communicates with the pressure chamber 37. A piston shaft 36 is inserted into this through hole 3c.

[0204] The piston shaft 36 pressurizes ammonia fuel by reciprocating in a predetermined direction. The fuel injection valve 3 according to this embodiment is configured to use the oil pressure of fuel oil supplied to the piston shaft 36 to cause the piston shaft 36 to reciprocate. In other words, the fuel oil functions as the working oil that causes the piston shaft 36 to reciprocate.

[0205] In detail, the piston shaft 36 involved in this embodiment is arranged inside the cylindrical body 31, such as... Figure 5 As shown, the piston shaft 36 reciprocates along the central axis Cf of the cylindrical body 31. It should be noted that it is not necessary for the piston shaft 36 to reciprocate along the central axis Cf, i.e., for the central axis of the piston shaft 36 to coincide with the central axis Cf of the cylindrical body 31. For example, the direction of movement of the piston shaft 36 may also intersect the central axis Cf of the cylindrical body 31. In this case, the fuel injection valve 3 may also include a separate cylindrical body, in addition to the cylindrical body 31 housing the valve shaft 32, that houses the piston shaft 36 and is inclined relative to the cylindrical body 31.

[0206] More specifically, the piston shaft 36 extends from the working oil chamber 38 to the fuel chamber 35 via the through hole 3c in a manner that blocks the communication between the working oil chamber 38 and the pressure chamber 37. The top surface of the pressure chamber 37 is formed by the lower surface (top surface on the top side) of the piston shaft 36.

[0207] Furthermore, the piston shaft 36 slides along the through hole 3c in the central axis direction according to the oil pressure in the working oil chamber 38. As the piston shaft 36 slides, the volume of the pressure chamber 37 changes. Thus, the ammonia fuel supplied from the outside to the pressure chamber 37 is pressure-fed from the pressure chamber 37 to the first path L1.

[0208] Fuel chamber 35 is formed inside cylindrical body 31. Fuel chamber 35 is arranged in the central axis direction, closer to the top side than pressure chamber 37 and closer to the base side than injection port 3a. Ammonia fuel is pressurized from pressure chamber 37 into fuel chamber 35 via first path L1. Fuel chamber 35 is also in communication with injection port 3a.

[0209] The valve shaft 32 is arranged inside the cylindrical body 31 as described above. The valve shaft 32 extends through the fuel chamber 35 and slides along the inner wall of the cylindrical body 31 in the central axis direction. By sliding the valve shaft 32, the communication between the fuel chamber 35 and the injection port 3a is blocked or released. The valve shaft 32 is forceped by the force-applying member 34 to maintain the blocked state of communication between the fuel chamber 35 and the injection port 3a.

[0210] When the fuel pressure (ammonia fuel pressure) in the fuel chamber 35 increases, the valve shaft 32 slides in the direction that overcomes the force applied by the force-applying component 34, thereby connecting the fuel chamber 35 with the injection port 3a. Through the connection between the fuel chamber 35 and the injection port 3a, ammonia fuel is supplied from the fuel chamber 35 to the injection port 3a, and the ammonia fuel is injected from the injection port 3a.

[0211] In this way, the valve shaft 32 slides along the inner wall of the cylindrical body 31. Therefore, in order to seal the gap 3b between the outer wall of the valve shaft 32 and the inner wall of the cylindrical body 31, fuel oil as sealing oil is supplied to the sealing chamber 33 arranged in the gap 3b as described above.

[0212] The sealing oil supplied to the sealing chamber 33 seals the gap 3b between the cylindrical body 31 and the valve shaft 32. By supplying sealing oil to the sealing chamber 33, leakage of ammonia fuel through the gap 3b can be suppressed, and the sliding of the valve shaft 32 relative to the cylindrical body 31 can be lubricated.

[0213] Returning to the description related to the sealing chamber 33, the sealing chamber 33 in this embodiment is arranged between the force-applying member 34 and the fuel chamber 35. The sealing chamber 33 is fluidly connected to the sealing oil delivery pipe 61. Fuel oil, which serves as sealing oil, is pressurized from the sealing oil delivery pipe 61 into the sealing chamber 33. In addition, any remaining working oil in the sealing chamber 33 is discharged from the sealing chamber 33 as discharge oil.

[0214] (4) Alternative fuel exhaust system 9

[0215] Among the various types of pipes constituting the sealing oil supply system 4, there is a risk of ammonia fuel mixing into these pipes, as well as the volatilization of the mixed ammonia fuel. The volatile components of the volatilized ammonia fuel that leak into the housing 5 can be discharged to the outside through the aforementioned ventilation mechanism 58. However, it is preferable to discharge such volatile components in advance.

[0216] Therefore, the engine 1 according to this embodiment also includes Figure 4 The alternative fuel exhaust system 9 is shown. As shown in the figure, the alternative fuel exhaust system 9 has an air exchange passage 96, an inlet passage 97, and a flow regulation mechanism 98.

[0217] Ventilation passage 96 is connected to at least one of sealing oil tank 51 and sealing oil pipeline (sealing oil delivery pipe 61 and sealing oil return pipe 62). Ventilation passage 96 discharges ammonia fuel volatilized in at least one of sealing oil tank 51 and sealing oil pipeline (sealing oil delivery pipe 61 and sealing oil return pipe 62).

[0218] In detail, the ventilation passage 96 involved in this embodiment includes a downstream end and an upstream end. The downstream end is connected to the oil mist recovery box 58c, and the upstream end is connected to the sealing oil tank 51 and the sealing oil return pipe 62 respectively, based on the branching into two passages. More specifically, the two upstream ends of the ventilation passage 96 are connected to the sealing oil tank 51 and the first return pipe 621.

[0219] Furthermore, the ventilation passage 96 involved in this embodiment discharges the ammonia fuel volatilized in the sealed oil tank 51 and the ammonia fuel volatilized in the sealed oil return pipe 62, which is the first return pipe 621 in the illustration, through the oil mist recovery box 58c.

[0220] The inlet passage 97 is connected to at least one of the sealing oil tank 51 and the sealing oil pipeline (sealing oil delivery pipe 61 and sealing oil return pipe 62). The inlet passage 97 introduces compressed air or scavenging gas into at least one of the sealing oil tank 51 and the sealing oil pipeline (sealing oil delivery pipe 61 and sealing oil return pipe 62). Here, the term "scavenging gas" refers to the gas used to scaveng the combustion chamber 17.

[0221] In detail, the inlet passage 97 involved in this embodiment is connected to the sealed oil tank 51. The inlet passage 97 introduces compressed air or scavenging gas into the sealed oil tank 51.

[0222] A flow regulating mechanism 98 is arranged on the inlet passage 97. The flow regulating mechanism 98 regulates the flow rate of compressed air or scavenging gas in the inlet passage 97.

[0223] In detail, the flow regulating mechanism 98 involved in this embodiment is, for example, constituted by an orifice or a flow regulating valve. More specifically, in this embodiment, the flow regulating mechanism 98 is constituted by a flow regulating valve.

[0224] (5) Controller 100

[0225] Figure 6 This is a block diagram showing the structure of the controller 100 of the engine 1. The controller 100 has a processor, volatile memory, non-volatile memory, and an input / output bus. The controller 100 is connected, for example, to a level sensor Sw1, an alternative fuel sensor Sw2, a first leak sensor Sw3, a first pressure sensor Sw4, a second pressure sensor Sw5, a second leak sensor Sw6, and a third pressure sensor Sw7.

[0226] The controller 100 generates control signals based on signals input from these sensors and inputs these control signals to the low-pressure pump 53, the sealing oil supply valve 55, the ventilation mechanism 58, the high-pressure pump 63, the first switching valve 642, the second switching valve 644, the working oil pump 646, the first on / off valve 626, and the second on / off valve 627, etc. The controller 100 uses these control signals to control the circulation of fuel oil, which functions as both sealing oil and working oil in the sealing oil supply system 4, and the ventilation within the housing 5 performed by the ventilation mechanism 58, etc.

[0227] (6) Effects, etc.

[0228] As explained above, according to the above embodiments, even if ammonia fuel mixes into the sealing oil and leaks due to volatilization, the leaked volatile components can be contained within the oil. Figure 4 The ammonia fuel, mixed in with the sealing oil and leaking out, is contained within the casing 5 shown. This isolates the equipment and personnel from the ammonia fuel. Therefore, the effects of ammonia fuel contamination can be suppressed.

[0229] In addition, such as Figure 1 and Figure 2 As shown, the housing 5 is supported on the engine body 10 by the support member 91. This allows the housing 5 and the engine body 10 to be transported as a single unit. Furthermore, the housing 5, supported on the engine body 10 by the support member 91, is arranged with a gap relative to the ship's floor F. This arrangement allows the housing 5 and the engine body 10 to vibrate as a single unit.

[0230] Assuming the housing 5 is positioned on the floor F, the engine body 10, acting as the vibration source, vibrates relatively significantly, while the floor F and housing 5 do not vibrate as much. In this case, a component or mechanism is needed to absorb the vibration difference between the engine body 10 and the floor F by connecting the pipe connecting the housing 5 and the engine body 10. However, such a component or mechanism may cause ammonia fuel to leak from the connection between the component or mechanism and the aforementioned pipe.

[0231] In contrast, by vibrating the housing 5 integrally with the engine body 10, the components or mechanisms described above are unnecessary. Therefore, the risk of leakage from the aforementioned connection points can be reduced. Furthermore, as described above, the sealing oil supply system 4 is constructed within the engine 1, thus minimizing the spread of leaked ammonia fuel even in the event of ammonia fuel leakage.

[0232] In addition, such as Figure 1 and Figure 2As shown, the housing 5 is arranged to the side of the frame 12, above the crankcase. This arrangement allows the fuel injection valve 3 to be close to the housing 5 in the vertical direction. Thus, the entire sealing oil supply system can be compactly configured. This compactness of the entire sealing oil supply system contributes to the miniaturization of the sealing oil tank 51 used for storing the sealing oil and helps to suppress ammonia fuel leakage from pipelines.

[0233] In addition, through such Figure 4 As shown, various components, such as the sealing oil tank 51 and the low-pressure pump 53, are housed in the housing 5. When ammonia fuel mixes into the sealing oil, the housing 5 can contain both the volatile components of ammonia fuel leaking from the various components associated with the sealing oil tank 51 and the volatile components of ammonia fuel leaking from the connections between components (e.g., fluid joints). This helps to suppress the effects caused by ammonia fuel mixing into the sealing oil.

[0234] In addition, through such Figure 4 As shown, cooling the sealing oil using the sealing oil cooler 54 ensures the viscosity of the sealing oil. Here, in order to supply the sufficiently cooled sealing oil to the fuel injection valve 3, it is considered to arrange the sealing oil cooler 54 on the sealing oil delivery pipe 61, which serves as the sealing oil pipeline, as close as possible to the fuel injection valve 3. However, if the sealing oil cooler 54 is arranged downstream of the high-pressure pump 63, it may cause abnormalities in the sealing oil cooler 54 due to the sealing oil being pressurized by the high-pressure pump 63 being supplied to the sealing oil cooler 54.

[0235] In contrast, through, as Figure 4 As shown, by positioning the sealing oil cooler 54 between the low-pressure pump 53 and the high-pressure pump 63, both the viscosity of the sealing oil and the abnormal suppression of the sealing oil cooler 54 can be taken into account.

[0236] In addition, through such Figure 4 As shown, by connecting the sealing oil replenishment system 7 to the sealing oil tank 51 within the housing 5, even if volatile components of ammonia fuel leak from fluid joints or the connection between the sealing oil replenishment system 7 and the sealing oil tank 51, these volatile components can be contained within the housing 5. This helps to suppress the effects of ammonia fuel mixing into the sealing oil.

[0237] In addition, through such Figure 4 As shown, the configuration restricts the backflow of sealing oil from the sealing oil tank 51 to the sealing oil replenishment pipe 71, thus preventing the backflow of sealing oil containing ammonia fuel to the sealing oil supply source 72 even if ammonia fuel is mixed into the sealing oil. As a result, the diffusion of sealing oil containing ammonia fuel can be prevented, which helps to suppress the effects caused by the mixing of ammonia fuel.

[0238] Furthermore, even if ammonia fuel enters and evaporates into the sealing oil flowing in at least one of the sealing oil tank 51 and the sealing oil pipelines (sealing oil delivery pipe 61 and sealing oil return pipe 62), it can still be utilized. Figure 4 The ventilation passage 96 shown discharges the volatile components. This isolates the ammonia fuel mixed in the sealing oil from the equipment and personnel. Therefore, it is more effective in suppressing the effects of ammonia fuel contamination.

[0239] Furthermore, even if the volatile components of ammonia fuel leak out instead of being discharged through the ventilation passage 96, they can still be utilized. Figure 4 The ventilation mechanism 58 shown discharges leaked volatile components. This isolates leaked ammonia fuel mixed with the sealing oil from equipment and personnel. Therefore, it is more effective in suppressing the effects of ammonia fuel contamination.

[0240] In addition, occupants typically perform routine inspections and other tasks on engine 1. The ventilation mechanism 58 reliably isolates occupants working on engine 1 from ammonia fuel. In other words, the ventilation mechanism 58 ensures that even when the engine body 10 supports the housing 5, occupants can still be isolated from ammonia fuel.

[0241] Furthermore, when the volatilized ammonia fuel flows into at least one of the sealed oil tank 51 and the sealed oil pipeline (sealed oil delivery pipe 61 and sealed oil return pipe 62), it is possible to utilize the... Figure 4 The compressed air or scavenging gas introduced through the inlet passage 97 purges the ammonia fuel and is then fed into the ventilation passage 96. This is therefore more effective in suppressing the effects of ammonia fuel contamination.

[0242] In addition, through such Figure 4 As shown, a flow regulating mechanism 98 is arranged on the inlet passage 97 to regulate the flow rate of compressed air or scavenging gas. Therefore, it is more beneficial to suppress the effects caused by the mixing of alternative fuels.

[0243] In addition, such as Figure 4 As shown, by utilizing the sealing oil discharge system (sealing oil discharge system 8) that discharges the sealing oil leaking from the contents of the housing 5, ammonia fuel mixed in with the sealing oil can be discharged together with the sealing oil. This helps to suppress the effects caused by ammonia fuel mixing into the sealing oil.

[0244] Furthermore, fuel oil does not produce residue even at high temperatures. Therefore, by sealing the fuel injection valve 3 with fuel oil as described above, even if the sealing oil mixes into the ammonia fuel, no adverse conditions caused by residue will occur. Thus, the effects of sealing oil mixing into the ammonia fuel can be suppressed.

[0245] Furthermore, by using diesel fuel as the sealing oil as described in the above embodiments, the generation of residues can be suppressed more reliably. This helps to mitigate the effects of the sealing oil mixing with ammonia fuel. Additionally, using an alternative fuel instead of diesel fuel as the sealing oil also promotes carbon neutrality.

[0246] Furthermore, in order to supply the fully cooled sealing oil to the fuel injection valve 3, it is considered to arrange the sealing oil cooler 54 on the sealing oil delivery pipe 61, which serves as the sealing oil pipeline, as close as possible to the fuel injection valve 3. However, if the sealing oil cooler 54 is arranged downstream of the high-pressure pump 63, it may cause malfunctions in the sealing oil cooler 54 due to the sealing oil being pressurized by the high-pressure pump 63 being supplied to the sealing oil cooler 54.

[0247] In contrast, through, as Figure 4 As shown, by positioning the sealing oil cooler 54 between the low-pressure pump 53 and the high-pressure pump 63, both the viscosity of the sealing oil and the abnormal suppression of the sealing oil cooler 54 can be taken into account.

[0248] Furthermore, as mentioned above, fuel oil does not produce residues even at high temperatures. Therefore, by using fuel oil as the working oil to operate the fuel injection valve 3 as described in the above embodiment, even if the working oil mixes into the ammonia fuel, no adverse conditions caused by residues will occur. Thus, the effects caused by the working oil mixing into the ammonia fuel can be suppressed.

[0249] (7) Other implementation methods

[0250] In the above embodiments, fuel oil is used as both the sealing oil and the working oil, but this disclosure is not limited to this structure. Oil seal lubricating oil may also be used as at least one of the sealing oil and the working oil. When lubricating oil is used as the sealing oil, one of the low-pressure pump 53 and the high-pressure pump 63 may be correspondingly omitted.

Claims

1. A marine engine that causes a volatile alternative fuel to burn in a cylinder, characterized in that: The marine engine includes a fuel injection valve and a housing. The fuel injection valve has a cylindrical body and a valve shaft. The cylindrical body extends along a predetermined central axis, and the valve shaft is inserted into the cylindrical body and reciprocates along the central axis. The fuel injection valve injects the alternative fuel into the cylinder. The housing allows sealing oil, which seals the gap between the cylindrical body and the valve shaft, to flow between the housing and the fuel injection valve.

2. The marine engine according to claim 1, characterized in that: The marine engine includes an engine body and supporting components. The engine body has the cylinder and causes the piston to reciprocate within the cylinder. The support component is fixed to the engine body. The support components are arranged with gaps relative to the ship's floor. The housing is supported on the engine body via the support member.

3. The marine engine according to claim 2, characterized in that: The engine body includes a base and a frame. The engine base forms the crankcase of the marine engine. The frame is arranged above the base. The housing is arranged on the side of the frame via the support member.

4. The marine engine according to claim 1, characterized in that: The marine engine includes a sealed oil tank for storing the sealing oil. The housing contains the sealed oil tank.

5. The marine engine according to claim 4, characterized in that: The marine engine includes a sealing oil pipeline, an oil filter, a first pump, and a sealing oil cooler. The sealing oil conduit allows the sealing oil to flow between the sealing oil tank and the fuel injection valve. The oil filter is arranged on the sealing oil pipeline to filter the sealing oil flowing in the sealing oil pipeline toward the fuel injection valve. The first pump is arranged on the sealing oil pipeline to pressurize the sealing oil flowing in the sealing oil pipeline toward the fuel injection valve. The sealing oil cooler is arranged on the sealing oil pipeline to cool the sealing oil flowing in the pipeline. The housing includes one or more of the following: the sealed oil tank, the oil filter, the sealed oil cooler, and the first pump, including the sealed oil tank.

6. The marine engine according to claim 5, characterized in that: The marine engine includes a second pump. The second pump is arranged downstream of the first pump on the sealing oil pipeline, so as to further pressurize the sealing oil that has been pressurized by the first pump. The sealing oil cooler is arranged on the sealing oil pipeline, downstream of the first pump and upstream of the second pump.

7. The marine engine according to claim 4, characterized in that: The marine engine includes a sealing oil replenishment system. The sealing oil replenishment system is connected to the sealing oil tank inside the housing and replenishes the sealing oil to the sealing oil tank.

8. The marine engine according to claim 7, characterized in that: The sealing oil replenishment system includes a storage tank and a sealing oil replenishment pipe. The storage tank stores the sealing oil. The sealing oil replenishment pipe allows the sealing oil to flow from the storage tank to the sealing oil tank. At least one of the sealing oil replenishment system and the sealing oil tank is configured to restrict the backflow of the sealing oil from the sealing oil tank to the sealing oil replenishment pipe.

9. The marine engine according to claim 4, characterized in that: The marine engine includes a sealed oil pipe, a ventilation mechanism, and a ventilation passage. The sealing oil conduit allows the sealing oil to flow between the sealing oil tank and the fuel injection valve. The ventilation mechanism ventilates the interior of the housing. The ventilation passage is connected to at least one of the sealed oil tank and the sealed oil pipeline, and the ventilation passage discharges the alternative fuel that evaporates in at least one of the sealed oil tank and the sealed oil pipeline.

10. The marine engine according to claim 9, characterized in that: The marine engine includes an inlet passage. The inlet passage is connected to at least one of the sealing oil tank and the sealing oil pipeline, and the inlet passage introduces compressed air or scavenging gas into at least one of the sealing oil tank and the sealing oil pipeline.

11. The marine engine according to claim 10, characterized in that: The marine engine includes a flow regulation mechanism. The flow regulating mechanism is arranged on the inlet passage to regulate the flow rate of the compressed air or the scavenging gas in the inlet passage.

12. The marine engine according to claim 4, characterized in that: The marine engine includes an oil receiving pan, a sealed oil drain pipe, and a leak sensor. The oil receiving tray is housed within the housing and collects the sealing oil leaking from the contents of the housing. The sealing oil discharge pipe is connected to the oil receiving pan, and the sealing oil discharge pipe allows the sealing oil collected by the oil receiving pan to circulate. The leakage sensor detects oil in at least one of the oil receiving pan and the sealing oil discharge pipe.

13. The marine engine according to any one of claims 1 to 12, characterized in that: The alternative fuel is ammonia fuel.

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