Marine engine

Abstract

Suppresses the effects of mixing alternative fuel into sealing oil. A marine engine (1) that burns ammonia fuel in a cylinder (16) comprises a tubular body (31) extending along a predetermined central axis (Cf), a valve shaft (32) inserted into the tubular body (31) and reciprocating along the central axis (Cf), a fuel injection valve (3) that injects ammonia fuel into the cylinder (16), and a housing (5) that circulates sealing oil between the fuel injection valve (3) and the gap (3b) between the tubular body (31) and the valve shaft (32).

Description

Technology Field

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

[0002] For example, Patent Document 1 discloses a dual fuel injection device for a cylinder of an internal combustion engine. This dual fuel injection device comprises 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] In addition, the second nozzle valve is configured to receive a supply of sealing and lubricating oil to avoid the second fuel leaking to the surroundings via the needle guide of the second nozzle valve. Accordingly, the second nozzle valve has a needle lubrication chamber that receives sealing and lubricating oil.

[0004] Generally, the oil pressure of the sealing and lubricating oil is set higher than the fuel pressure. In contrast, the dual fuel injection device according to Patent Document 1 is configured such that the oil pressure of the sealing and lubricating oil is lower than the fuel pressure by devising the dimensional setting of the needle lubrication chamber. Prior art literature

[0005] Patent Document 1: Japanese Patent Publication No. 2019-70387 The problem to be solved

[0006] However, if a configuration as disclosed in the above patent document 1 is adopted, there is a possibility that the second fuel may be mixed into the sealing oil due to the pressure difference between the sealing and lubricating oil (hereinafter referred to as sealing oil) and the second fuel. In this case, the second fuel may spread to various parts of the sealing oil supply system, such as the sealing oil supply pipe.

[0007] Meanwhile, the inventors of the present invention are considering using alternative fuels other than diesel fuel as fuel for marine engines, such as the second fuel according to Patent Document 1. Generally, depending on the composition of the alternative fuel, there is a possibility that it may have adverse effects on equipment related to the supply system and on the human body.

[0008] Therefore, as described above, if the alternative fuel is diffused into each part of the sealing oil supply system, the diffused alternative fuel may reach the equipment related to the supply system or leak from unintended parts, thereby causing problems for the equipment and the human body.

[0009] Therefore, according to conventional methods, it is considered necessary to set the oil pressure of the sealing oil higher than the fuel pressure of the alternative fuel. However, since the pressure difference between the two is generally small, the mixing of the alternative fuel into the sealing oil, albeit in small amounts, may occur. Furthermore, if a problem arises in the sealing oil supply system, there is a concern that a large amount of alternative fuel may be mixed in due to a drop in oil pressure. Therefore, even if the conventional method is followed, it remains inadequate.

[0010] The present disclosure has been made in consideration of these points, and its purpose is to suppress the effects of mixing alternative fuel into sealing oil. means of solving the problem

[0011] A first aspect of the present disclosure relates to a marine engine that burns a volatile alternative fuel in a cylinder. The marine engine comprises a tubular body extending along a predetermined central axis, a valve shaft inserted into the tubular body and reciprocating along the central axis, a fuel injection valve that injects the alternative fuel into the cylinder, and a housing that circulates a sealing oil between the fuel injection valve and the tubular body and sealing the gap between the tubular body and the valve shaft.

[0012] According to the first embodiment above, even if a volatile component of a substitute fuel leaks out when a substitute fuel is mixed into the sealing oil, the leaked volatile component can be contained within the housing. In this way, the substitute fuel leaked after being mixed into the sealing oil can be isolated from the device and the human body. In this way, the effect of the mixing of the substitute fuel can be suppressed.

[0013] Additionally, according to a second aspect of the present disclosure, the marine engine comprises an engine body having the cylinder and reciprocating a piston within the cylinder, and a support member fixed to the engine body, wherein the support member is spaced apart from the floor of the ship, and the housing may be supported on the engine body via the support member.

[0014] According to the second embodiment above, the housing is supported by a support member on the engine body. This allows it to be transported integrally with the engine body. Additionally, the housing supported by the support member on the engine body is positioned with respect to the floor of the ship. By being positioned in this way, the housing vibrates integrally with the engine body.

[0015] For example, if a housing is placed on the floor, the engine body, acting as the source of vibration, vibrates relatively significantly, whereas the floor and housing do not vibrate as much as the engine body. In this case, it is required to connect a component or mechanism that absorbs the difference in vibration between the engine body and the floor to the piping connecting the housing and the engine body. However, such a component or mechanism may cause leakage of alternative fuel from the connection part with the piping.

[0016] In contrast, as in the second embodiment above, by vibrating the housing and the engine body integrally, the aforementioned components or mechanisms become unnecessary. This allows for the suppression of the risk of leakage from the connection part. Furthermore, by supporting the housing on the engine body, the sealing oil supply system can be completed within the marine engine. Therefore, even if, for instance, a leak of alternative fuel occurs, the range of diffusion of the leaked alternative fuel can be minimized.

[0017] In addition, according to a third aspect of the present disclosure, the engine body comprises a bed plate constituting the crankcase of the marine engine and a frame disposed above the bed plate, and the housing may be disposed on the side of the frame via the support member.

[0018] According to the third embodiment above, the housing is positioned on the side of the frame, that is, above the crankcase. By positioning it in this way, the fuel injection valve and the housing can be brought close together in the vertical direction. This allows the entire sealing oil supply system to be configured compactly. The compactness of the entire sealing oil supply system contributes to the reduction of the tank for storing the sealing oil and the suppression of leakage of alternative fuel from the piping.

[0019] Additionally, according to a fourth aspect of the present disclosure, the marine engine may have a sealing oil tank for storing the sealing oil, and the housing may accommodate the sealing oil tank.

[0020] According to the fourth embodiment above, by housing the sealing oil tank in a housing, when alternative fuel is mixed into the sealing oil, volatile components of the alternative fuel leaked from the member associated with the sealing oil tank and volatile components of the alternative fuel leaked from the connection part between the members (e.g., fluid connection part) can be contained within the housing. This makes it advantageous to suppress the effect of alternative fuel mixing into the sealing oil.

[0021] Additionally, according to a fifth aspect of the present disclosure, the marine engine comprises a sealing oil pipe that circulates the sealing oil between the sealing oil tank and the fuel injection valve, an oil filter disposed on the sealing oil pipe and filtering the sealing oil flowing through the sealing oil pipe toward the fuel injection valve, a first pump disposed on the sealing oil pipe and pressurizing the sealing oil flowing through the sealing oil pipe toward the fuel injection valve, and a sealing oil cooler disposed on the sealing oil pipe and cooling the sealing oil flowing through the sealing oil pipe, and the housing may accommodate one or more of the sealing oil tank, the oil filter, the first pump, and the sealing oil cooler, including the sealing oil tank.

[0022] According to the fifth embodiment above, by housing various components related to the circulation of sealing oil, including the first pump, in a housing, volatile components of the alternative fuel leaked from those components and volatile components of the alternative fuel leaked from the connection part between the components (e.g., fluid connection part) when the alternative fuel is mixed into the sealing oil can be contained within the housing. This makes it advantageous to suppress the effect of the alternative fuel being mixed into the sealing oil.

[0023] Additionally, according to a sixth aspect of the present disclosure, the marine engine is provided with a second pump positioned downstream of the first pump in the sealing oil piping and further pressurizing the sealing oil pressurized by the first pump, and the sealing oil cooler may be positioned downstream of the first pump and upstream of the second pump in the sealing oil piping.

[0024] According to the sixth embodiment above, the viscosity of the sealing oil can be secured by cooling the sealing oil with a sealing oil cooler. Here, in order to supply the sufficiently cooled sealing oil to the fuel injection valve, it is considered that the sealing oil cooler should be placed as close as possible to the fuel injection valve on the sealing oil piping. However, for example, if the sealing oil cooler is placed downstream of the second pump, the sealing oil, which is high-pressure-conditioned by the second pump, is supplied, and there is a possibility that it may cause an abnormality in the sealing oil cooler.

[0025] In contrast, by laying out the sealing oil cooler as in the sixth embodiment above, it is possible to achieve both the viscosity of the sealing oil and the suppression of abnormalities in the sealing oil cooler.

[0026] Additionally, according to the seventh aspect of the present disclosure, the marine engine may be provided with a sealing oil replenishment system connected to the sealing oil tank within the housing and replenishing the sealing oil in the sealing oil tank.

[0027] According to the seventh embodiment above, even if volatile components of the alternative fuel leak from the connection part between the sealing oil replenishment system and the sealing oil tank, such as a fluid connection part, the volatile components can be contained within the housing. This makes it advantageous to suppress the effect of mixing the alternative fuel into the sealing oil.

[0028] Additionally, according to the eighth aspect of the present disclosure, the sealing oil replenishment system comprises a storage tank for storing the sealing oil and a sealing oil replenishment pipe for distributing the sealing oil from the storage tank to the sealing oil tank, and at least one of the sealing oil replenishment system and the sealing oil tank may be configured to regulate the backflow of the sealing oil from the sealing oil tank to the sealing oil replenishment pipe.

[0029] According to the eighth embodiment above, even if alternative fuel is mixed into the sealing oil, the backflow of the sealing oil mixed with alternative fuel into the storage tank is regulated. As a result, the diffusion of the sealing oil mixed with alternative fuel can be prevented, and it is advantageous to suppress the effects of the mixing of alternative fuel.

[0030] Additionally, according to the ninth aspect of the present disclosure, the marine engine may comprise a sealing oil pipe for circulating the sealing oil between the sealing oil tank and the fuel injection valve, a ventilation mechanism for ventilating the housing, and a ventilation passage connected to at least one of the sealing oil tank and the sealing oil pipe, for discharging the substitute fuel volatilized from at least one of the sealing oil tank and the sealing oil pipe.

[0031] According to the ninth embodiment above, even if alternative fuel is introduced into and volatilizes in the sealing oil flowing through at least one of the sealing oil tank and the sealing oil piping, the volatilized components can be discharged through a ventilation passage. This allows the alternative fuel mixed in the sealing oil to be isolated from the equipment and the human body. This makes it more advantageous to suppress the effects of the mixing of alternative fuel.

[0032] Furthermore, according to the ninth embodiment above, even if volatile components of the alternative fuel leak without being discharged through the ventilation passage, the leaked volatile components can be discharged by the ventilation device. This allows the alternative fuel leaked and mixed into the sealing oil to be isolated from the equipment and the human body. This makes it more advantageous to suppress the effects of the mixing of the alternative fuel.

[0033] In addition, generally, crew members perform routine tasks such as inspections on a marine engine. By providing a ventilation mechanism, crew members working on a marine engine are reliably isolated from ammonia fuel. That is, even if the housing is supported by the engine body as in the configuration according to the second embodiment, the crew members can be isolated from alternative fuel by providing a ventilation mechanism according to the ninth embodiment.

[0034] Additionally, according to the tenth aspect of the present disclosure, the marine engine may be connected to at least one of the sealing oil tank and the sealing oil pipe and may have an introduction passage for introducing compressed air or scavenging gas to at least one of the sealing oil tank and the sealing oil pipe.

[0035] According to the above tenth embodiment, when volatilized alternative fuel is introduced into at least one of the sealing oil tank and the sealing oil piping, the introduced alternative fuel can be pushed out by compressed air or scavenging gas introduced from the introduction passage and sent to the ventilation passage. This makes it more advantageous to suppress the effects of mixing alternative fuel.

[0036] Additionally, according to the first aspect of the present disclosure, the marine engine may be provided with a flow control means disposed in the introduction passage and controlling the flow rate of the compressed air or the intake gas in the introduction passage.

[0037] According to the eleventh embodiment above, by placing a flow rate adjustment means in the introduction passage, it becomes possible to adjust the flow rate of compressed air or intake gas. This makes it more advantageous to suppress the effects of mixing alternative fuels.

[0038] Additionally, according to the 12th aspect of the present disclosure, the marine engine may comprise an oil pan that is housed in the housing and receives the sealing oil leaked from the housing, a sealing oil discharge pipe connected to the oil pan and circulating the sealing oil received in the oil pan, and a leak sensor that detects the oil content of at least one of the oil pan and the sealing oil discharge pipe.

[0039] According to the above 12th embodiment, by utilizing a discharge system for sealing oil leaked from the housing, the alternative fuel mixed in the sealing oil can be discharged together with the sealing oil. This makes it advantageous to suppress the effect of the alternative fuel being mixed into the sealing oil.

[0040] In addition, according to the 13th aspect of the present disclosure, the alternative fuel may be ammonia fuel.

[0041] Ammonia fuels are a concern due to adverse effects caused by leakage and volatilization. The present disclosure contributes to the suppression of such adverse effects. Effects of the invention

[0042] As explained above, according to the present disclosure, the effect of mixing alternative fuel into the sealing oil can be suppressed. Brief explanation of the drawing

[0043] Figure 1 is a schematic diagram illustrating a marine engine viewed from the front. FIG. 2 is a schematic diagram illustrating a marine engine viewed from the side. FIG. 3 is a cross-sectional view schematically illustrating the superstructure of a marine engine. Figure 4 is a diagram illustrating a sealing oil supply system. FIG. 5 is a cross-sectional view illustrating the configuration of a fuel injection valve. Figure 6 is a block diagram illustrating the configuration of a controller for a marine engine. Specific details for implementing the invention

[0044] Hereinafter, embodiments of the present disclosure will be described based on the drawings. The following description is for illustrative purposes only. FIG. 1 is a schematic diagram illustrating a marine engine (1) (hereinafter also simply referred to as "engine") viewed from the front, and FIG. 2 is a schematic diagram illustrating the engine (1) viewed from the side.

[0045] <Overall Composition>

[0046] The engine (1) is a multi-cylinder inline marine engine. This engine (1) is composed of a uniflow scavenging type 2-stroke 1-cycle engine and is installed in large vessels such as oil tankers, container ships, and car carriers.

[0047] The engine (1) is configured to burn an alternative fuel within the cylinder (16) of the engine (1). At this time, the engine (1) may perform the combustion of the alternative fuel alone, or may perform the combustion of a mixture of the alternative fuel and oil fuel (e.g., a mixture of ammonia fuel and diesel fuel).

[0048] In this embodiment, a volatile fuel, such as ammonia fuel, is used as the alternative fuel. However, the alternative fuel is not limited to ammonia fuel. Other alternative fuels such as hydrogen gas, liquefied natural gas (LNG), liquefied petroleum gas (LPG), alcohol fuel, and biodiesel fuel may be used. Here, alcohol fuel refers to fuels including alcohols in general, such as methanol and ethanol. Biodiesel fuel includes substances that can be used as biodiesel fuel, such as fatty acid methyl esters (FAME).

[0049] The engine (1) mounted on the ship is used as the main engine to propel the ship. The output shaft of the engine (1) is connected to the ship's propeller via a propeller shaft. As the engine (1) is operated, its output is transmitted to the propeller, thereby propulsing the ship.

[0050] <Main Components>

[0051] As illustrated in FIG. 1, the engine (1) comprises an engine body (10) having one or more (in this embodiment, more than one) cylinders (16), a sealing oil supply system (4), and a controller (100). Each cylinder (16) forms a combustion chamber (17) for burning ammonia fuel.

[0052] (1) The main body of the organ (10)

[0053] FIG. 3 is a cross-sectional view schematically illustrating the upper structure of the engine (1).

[0054] The engine body (10) is installed in the engine room of the ship. The engine body (10) has a plurality of cylinders (16) as described above. And, except for special descriptions, the following description is common to each cylinder (16) even if there are a plurality of cylinders (16).

[0055] As shown in FIG. 1, the engine (1) according to the present embodiment is configured as a so-called crosshead type internal combustion engine to realize its long stroke. Accordingly, the engine body (10) of the engine (1) is equipped with a piston rod (22) that supports a piston (21) from below and a connecting rod (24) connected to a crankshaft (23) for each cylinder (16). The piston rod (22) and the connecting rod (24) are connected by a crosshead (25).

[0056] Specifically, the engine body (10) comprises a bed plate (11) located at the bottom, a frame (12) disposed on the bed plate (11), a cylinder jacket (13) disposed on the frame (12), a cylinder liner (14), and a cylinder cover (15). Each cylinder (16) is disposed within the cylinder jacket (13). The engine body (10) also comprises a piston (21) disposed within the cylinder (16) and reciprocating within the cylinder (16), and an output shaft (e.g., a crankshaft (23)) that rotates in conjunction with the reciprocating motion of the piston (21).

[0057] Here, the bed plate (11) forms the crankcase of the engine (1). The bed plate (11) accommodates a crankshaft (23) and a bearing (26) that rotatably supports the crankshaft (23). The lower end of a connecting rod (24) is connected to the crankshaft (23) via a crank (27).

[0058] The frame (12) accommodates a pair of guide plates (28), a connecting rod (24), and a crosshead (25). A pair of guide plates (28) are spaced apart in the width direction of the engine (1) (left-right direction of the drawing in FIG. 1). A connecting rod (24) is positioned between the pair of guide plates (28) with its lower end connected to a crankshaft (23). The upper end of the connecting rod (24) is connected to the lower end of a piston rod (22) via a crosshead (25).

[0059] The crosshead (25) is positioned between a pair of guide plates (28) and slides up and down along each guide plate (28). That is, the pair of guide plates (28) guide the sliding of the crosshead (25). 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) to move up and down integrally, while it is connected to the connecting rod (24) to rotate the connecting rod (24) using the upper end of the connecting rod (24) as a pivot point.

[0060] The cylinder jacket (13) supports the cylinder liner (14) as an inner tube. The aforementioned piston (21) is disposed inside the cylinder liner (14). The cylinder liner (14) causes the piston (21) to reciprocate in an up-and-down direction along the inner wall of the cylinder liner (14). The upper end of the cylinder liner (14) is open.

[0061] The cylinder cover (15) is fixed to the upper end of the cylinder liner (14). The cylinder cover (15) forms the cylinder (16) together with the cylinder liner (14). The cylinder cover (15) becomes a cover for the cylinder (16) by closing the upper end of the cylinder liner (14).

[0062] Additionally, an exhaust valve (18) operated by a valve train not shown is disposed on the cylinder cover (15). The exhaust valve (18) forms a combustion chamber (17) together with the upper surface of the cylinder (16), which consists of the cylinder liner (14) and the cylinder cover (15), and the piston (21) (see FIG. 1). The exhaust valve (18) opens and closes the combustion chamber (17) and the exhaust pipe (19). The exhaust pipe (19) has an exhaust port leading to the combustion chamber (17), and the exhaust valve (18) is configured to open and close the exhaust port.

[0063] Additionally, the cylinder cover (15) partitions the ceiling surface of the combustion chamber (17). One or more fuel injection valves (3) are disposed on this ceiling surface. In this embodiment, two fuel injection valves (3) are disposed in each cylinder (16) (see FIG. 1). Each fuel injection valve (3) injects ammonia fuel as an alternative fuel into the cylinder (16).

[0064] As illustrated in FIG. 3, each fuel injection valve (3) has a tubular body (31), a valve shaft (32), and a sealing chamber (33). Additionally, each fuel injection valve (3) has an injection port (3a) disposed within a combustion chamber (17).

[0065] The tubular body (31) has a tubular shape that extends along a predetermined central axis (Cf). An ammonia fuel supply line (not shown) and a sealing oil supply line (a sealing oil supply system described later) (4) are connected to the tubular body (31).

[0066] The valve shaft (32) is inserted into the tubular body (31). The valve shaft (32) has a needle shape that extends along the central axis (Cf). The valve shaft (32) reciprocates along the central axis (Cf). This reciprocating movement is the relative movement of the valve shaft (32) with respect to the tubular body (31). Ammonia fuel is supplied to the space formed between the valve shaft (32) and the tubular body (31) (refer to the fuel chamber (35) in FIG. 5).

[0067] A sealing seal (33) is placed in the gap (3b) between the tubular body (31) and the valve shaft (32) (see FIG. 5 described later). This gap (3b) is placed in the area where the outer surface of the valve shaft (32) slides against the inner wall surface of the tubular body (31) during the reciprocating movement of the valve shaft (32). Sealing oil is supplied to the sealing seal (33).

[0068] And, in this embodiment, fuel oil combustible within the cylinder (16) is supplied to the sealing chamber (33). And, the fuel injection valve (3) is configured to seal the gap (3b) by the fuel oil supplied to the sealing chamber (33).

[0069] In other words, the fuel injection valve (3) according to the present embodiment and the engine (1) equipped with said fuel injection valve (3) are configured to use fuel oil as a sealing oil instead of conventional oil known as a lubricant for oil sealing.

[0070] Fuel oil used in sealing oil includes diesel fuel. Here, the term diesel fuel includes any fuel derived from fossil fuels applicable to low-speed diesel engines. The diesel fuel as fuel oil may be heavy oil A, heavy oil B, or heavy oil C.

[0071] As an example, in this embodiment, Marine Gas Oil (MGO) is used as the diesel fuel. MGO is a low-sulfur diesel fraction and is a fuel oil for ships with a low environmental burden.

[0072] Also, the fuel oil used as sealing oil is not limited to diesel fuel. The fuel oil for sealing may be an alternative fuel derived from non-fossil fuel. Specifically, the alternative fuel derived from non-fossil fuel may be alcohol fuel or biodiesel fuel. Here, alcohol fuel refers to fuel containing alcohols such as methanol and ethanol. Biodiesel fuel includes substances that can be used as biodiesel fuel, such as fatty acid methyl ester (FAME). The fuel oil for sealing oil is suitable if it is a type of oil that does not leave residue inside the fuel injection valve (3), such as biodiesel fuel.

[0073] The nozzle (3a) is opened in the tubular body (31). The nozzle (3a) is opened and closed according to the reciprocating movement of the valve shaft (32). Each fuel injection valve (3) injects ammonia fuel supplied into the tubular body (31) from the open nozzle (3a).

[0074] Additionally, although details will be described later, the valve shaft (32) of each fuel injection valve (3) operates in balance with the fuel pressure (pressure of ammonia fuel) within the fuel injection valve (3) and the pressurizing force of the pressurizing member (34) that pressurizes the valve shaft (32) to close the injection port (3a). The pressure of the ammonia fuel within the fuel injection valve (3) is controlled through the operation of the piston shaft (36) by the supply of hydraulic fluid. The supply of hydraulic fluid is controlled by the operation of an electronic valve (second switching valve (644)) placed in a sealing oil supply system (4) that also serves as the hydraulic fluid supply line. This electronic valve is electrically connected to a controller (100) and operates when a control signal is input from the controller (100). That is, the opening and closing of each fuel injection valve (3), and furthermore, the injection of ammonia fuel from the injection port (3a) of each fuel injection valve (3), are controlled by the controller (100).

[0075] Additionally, one or more oil injection valves for injecting "pilot oil" to ignite ammonia fuel may be provided in the cylinder cover (15). The opening and closing of the one or more oil injection valves can also be controlled by the controller (100), just like the fuel injection valve (3).

[0076] Each fuel injection valve (3) supplies ammonia fuel to the combustion chamber (17) and burns it within the combustion chamber (17). Due to this combustion, the piston (21) moves back and forth in the up and down direction. At this time, when the exhaust valve (18) operates and the combustion chamber (17) is opened, the exhaust gas generated by the combustion is extruded through the exhaust pipe (19), and gas is introduced into the combustion chamber (17) from an unillustrated scavenging port.

[0077] Additionally, when the piston (21) reciprocates due to combustion, the piston rod (22) reciprocates in the up-and-down direction together with the piston (21). As a result, the crosshead (25) connected to the piston rod (22) reciprocates in the up-and-down direction. This crosshead (25) is configured to allow the connecting rod (24) to rotate, and the connecting rod (24) is rotated using the connection point with the crosshead (25) as a pivot point. Then, the crank (27) connected to the lower end of the connecting rod (24) performs a crank motion, and the crank shaft (23) rotates according to this crank motion. In this way, the crank shaft (23) converts the reciprocating motion of the piston (21) into rotational motion and rotates the propeller of the ship together with the propeller shaft. Thus, the ship is propelled.

[0078] Here, in order to inject ammonia fuel from each fuel injection valve (3), it is necessary to move the valve shaft (32) along the central axis (Cf) of the tubular body (31) as described above. At this time, the valve shaft (32) slides along the inner wall of the tubular body (31). In order to facilitate this sliding or to seal the gap between the valve shaft (32) and the tubular body (31), sealing oil is supplied appropriately to the sealing chamber (33) of each fuel injection valve (3). The engine (1) supplies sealing oil to each fuel injection valve (3) by means of a sealing oil supply system (4).

[0079] Hereinafter, the configuration according to the sealing oil supply system (4) and each fuel injection valve (3) connected to the sealing oil supply system (4) will be described in detail.

[0080] (2) Sealing oil supply system (4)

[0081] FIG. 4 is a drawing illustrating a sealing oil supply system (4).

[0082] As shown in FIG. 4, the sealing oil supply system (4) comprises, as main components, a housing (5), a sealing oil circulation system (6), a sealing oil replenishment system (7), and a sealing oil discharge system (8).

[0083] (Housing(5))

[0084] The housing (5) circulates sealing oil between the fuel injection valve (3). In detail, the housing (5) circulates sealing oil between 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 from the fuel injection valve (3). Hereinafter, the sealing oil discharged as drain is also referred to as "drain oil".

[0085] Additionally, the housing (5) is fluidly connected to the fuel injection valve (3) via a sealing oil circulation system (6). The housing (5) circulates sealing oil between itself and the fuel injection valve (3) via the fluid connection through the sealing oil circulation system (6).

[0086] The housing (5) according to the present embodiment is an enclosure that accommodates various types of materials. The housing (5) as an enclosure is configured as a separate unit from the engine body (10). The housing (5) is supported by the engine body (10).

[0087] In detail, the engine (1) according to the present embodiment is provided with a support member (91) for supporting a housing (5). The housing (5) is supported on the engine body (10) via the support member (91).

[0088] Specifically, the support member (91) according to the present embodiment is fixed to the engine body (10) and positioned on the side of the frame (12). The support member (91) is configured as a so-called frame and forms an installation surface (91a) on which the housing (5) is installed. This installation surface (91a) extends in a horizontal direction perpendicular to the height direction of the engine body (10), that is, the direction of movement of the piston (21).

[0089] Accordingly, by installing the housing (5) on the above-mentioned installation surface (91a), the housing (5) is positioned on the side of the frame (12) via the support member (91).

[0090] Additionally, the support member (91) is spaced apart from the floor (F) of the vessel. The support member (91) is fixed integrally to the engine body (10). Thus, the housing (5) vibrates integrally with the engine body (10). Furthermore, a sealing oil supply system, such as a sealing oil supply system (4), is not constructed outside the engine (1) but is completed within the engine (1).

[0091] Additionally, the housing (5) hermetically contained includes a part in which leakage of the mixed alternative fuel is a concern when the alternative fuel is mixed into the sealing oil. Here, the part in which leakage of the alternative fuel is a concern includes a part that is fluidly connected to another through a fluid connection part, and the fluid connection part itself.

[0092] In detail, the housing (5) accommodates one or more components, including the sealing oil tank (51), among 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). These components, like the housing (5), constitute the engine (1) according to the present embodiment.

[0093] More specifically, the housing (5) according to the present embodiment accommodates a sealing oil tank (51), an oil filter (52), a low-pressure pump (53), a sealing oil cooler (54), a sealing oil supply valve (55), and a sealing oil discharge valve (56).

[0094] The sealing oil tank (51) stores sealing oil. As illustrated in FIG. 4, the sealing oil tank (51) according to the present embodiment has a box shape having an upper surface (51a) and a lower surface (51b). As described above, the sealing oil tank (51) is housed in a housing (5).

[0095] A level sensor (Sw1) for detecting the oil level of the sealing oil is installed in the sealing 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).

[0096] The sealing oil tank (51) is equipped with an alternative fuel sensor (Sw2) that detects the amount or concentration of ammonia fuel within the sealing oil tank (51). The alternative fuel sensor (Sw2) is electrically connected to the controller (100) and outputs a detection signal of the amount or concentration of ammonia fuel to the controller (100). The alternative fuel sensor (Sw2) is housed in the housing (5). The alternative fuel sensor (Sw2) is not mandatory.

[0097] In detail, the alternative fuel sensor (Sw2) is composed of an ammonia sensor that detects the concentration of ammonia in the air within the sealing oil tank (51). As shown in FIG. 4, the alternative fuel sensor (Sw2) is positioned above the upper limit (Ll) of the oil height allowed in the sealing oil tank (51). By positioning it in this way, the ammonia fuel volatilized from the sealing oil within the sealing oil tank (51) can be detected more reliably. As an example, the alternative fuel sensor (Sw2) according to the present embodiment is positioned on the upper surface (51a) of the sealing oil tank (51) or near the upper surface (51a).

[0098] A sealing oil supply pipe (61) constituting a sealing oil circulation system (6) is connected to the sealing oil tank (51). The sealing oil supply pipe (61) is composed of a pipe that circulates sealing oil from the sealing oil tank (51) to the fuel injection valve (3), particularly the sealing seal (33). The sealing oil supply pipe (61) exemplifies the "sealing oil pipe" of this embodiment in that it can circulate sealing oil between the sealing oil tank (51) and the fuel injection valve (3).

[0099] In detail, the sealing oil supply pipe (61) fluidically connects the sealing oil tank (51) and the sealing chamber (33) of the fuel injection valve (3). The sealing oil supply pipe (61) supplies fuel oil as sealing oil to the sealing chamber (33). More specifically, as illustrated in FIG. 4, the sealing oil supply pipe (61) is connected to the bottom surface (51b) of the sealing oil tank (51) or near the bottom surface (51b). The portion of the sealing oil supply pipe (61) near its upstream end (one end on the side of the sealing oil tank (51)) is received in the housing (5).

[0100] An oil filter (52) is placed on a sealing oil supply pipe (61). The oil filter (52) filters the sealing oil flowing through the sealing oil supply pipe (61) toward the fuel injection valve (3). As described above, the oil filter (52) is housed in a housing (5).

[0101] In detail, the oil filter (52) is positioned in the sealing oil supply 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 discharged from the sealing oil tank (51) and introduced into the sealing oil supply pipe (61).

[0102] A low-pressure pump (53) is positioned on a sealing oil supply pipe (61). The low-pressure pump (53) pressurizes the sealing oil flowing through the sealing oil supply pipe (61) toward the fuel injection valve (3). As described above, the low-pressure pump (53) is housed in a housing (5). The low-pressure pump (53) is an example of the "first pump" of this embodiment.

[0103] In detail, the low-pressure pump (53) is positioned downstream of the oil filter (52) and upstream of the sealing oil cooler (54) in the sealing oil supply pipe (61). The low-pressure pump (53) is electrically connected to the controller (100) and operates by receiving an electrical signal from the controller (100). Upon receiving the electrical signal, the low-pressure pump (53) pressurizes the sealing oil filtered by the oil filter (52).

[0104] In addition, although only one low-pressure pump (53) is shown in the drawing example, multiple oil pumps may be connected in parallel to the sealing oil supply pipe (61) and the low-pressure pump (53) may be formed by these multiple oil pumps. In this case, some of the multiple oil pumps may be operated while the remaining oil pumps are assigned to backup, or multiple oil pumps may be operated simultaneously.

[0105] A sealing oil cooler (54) is placed on a sealing oil supply pipe (61). The sealing oil cooler (54) cools the sealing oil flowing through the sealing oil supply pipe (61). As described above, the sealing oil cooler (54) is housed in a housing (5).

[0106] In detail, the sealing oil cooler (54) is positioned downstream of the oil filter (52) and the low-pressure pump (53) and upstream of the high-pressure pump (63) in the sealing oil supply pipe (61). The sealing oil cooler (54) is configured by a heat exchanger using a heat exchange medium supplied, for example, from inside or outside the engine room. The heat exchange medium is, for example, water. The sealing oil cooler (54) cools the sealing oil pressurized by the low-pressure pump (53) through the heat exchange medium flowing through the sealing oil cooler (54).

[0107] A sealing oil replenishment pipe (71) constituting a sealing oil replenishment system (7) is connected to the sealing oil tank (51). The sealing oil replenishment pipe (71) is composed of a pipe that circulates sealing oil (fuel oil in this embodiment) from a 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) and the sealing oil tank (51).

[0108] A sealing oil supply valve (55) is positioned on a 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 source (72) to the sealing oil tank (51) can be started or the supply can be cut off. As described above, the sealing oil supply valve (55) is housed in a housing (5).

[0109] In detail, the sealing oil supply valve (55) is positioned in the sealing oil replenishment pipe (71) downstream of the sealing oil 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 an electrical signal from the controller (100). Upon receiving the electrical signal, the sealing oil supply valve (55) closes or opens. When the sealing oil supply valve (55) closes, the supply of sealing oil from the sealing oil source (72) to the sealing oil tank (51) is cut off, and when the sealing oil supply valve (55) opens, the supply of sealing oil from the sealing oil source (72) to the sealing oil tank (51) is executed.

[0110] A first discharge pipe (81) constituting a sealing oil discharge system (8) is connected to the sealing oil tank (51). The first discharge pipe (81) is composed of a pipe that discharges sealing oil (fuel oil in this embodiment) from the sealing oil tank (51).

[0111] A sealing oil discharge valve (56) is positioned on a first discharge pipe (81). The sealing oil discharge valve (56) opens and closes the first discharge pipe (81). By opening and closing the sealing oil discharge valve (56), the discharge of sealing oil from the sealing oil tank (51) can be initiated or the discharge can be blocked. As described above, the sealing oil discharge valve (56) is housed in a housing (5).

[0112] In detail, the sealing oil discharge valve (56) is electrically connected to the controller (100) and operates by receiving an electrical signal from the controller (100). Upon receiving the electrical signal, the sealing oil discharge valve (56) is closed or opened. When the valve of the sealing oil discharge valve (56) is closed, the discharge of sealing oil from the sealing oil tank (51) is blocked, and when the valve of the sealing oil discharge valve (56) is opened, the discharge of sealing oil from the sealing oil tank (51) is performed.

[0113] In addition, the engine (1) further comprises an oil pan (57) that is housed in the housing (5). The oil pan (57) is housed in the housing (5) just like other parts, including the sealing oil tank (51). The oil pan (57) receives the sealing oil that has leaked from the housing (5).

[0114] Here, the contents of the housing (5) refer to one or more parts including the sealing oil tank (51), among 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), as described above.

[0115] The oil pan (57) receives sealing oil leaked from the housing (5) or sealing oil leaked from the connection portion (e.g., fluid connection portion) between the housing and the sealing oil supply pipe (61), sealing oil replenishment pipe (71) or the first discharge pipe (81).

[0116] A second discharge pipe (82) constituting a sealing oil discharge system (8) is connected to the oil pan (57). The second discharge pipe (82) is composed of a pipe that circulates sealing oil (fuel oil in this embodiment) received from the oil pan (57). The second discharge pipe (82) is an example of a "sealing oil discharge pipe" of this embodiment.

[0117] And, a first leak sensor (Sw3) is connected to at least one of the oil pan (57) and the second discharge pipe (82). The first leak sensor (Sw3) detects oil in at least one of the oil pan (57) and the second discharge pipe (82).

[0118] In detail, the first leak sensor (Sw3) according to the present embodiment is placed on the second discharge pipe (82) as an example. This first leak sensor (Sw3) detects sealing oil flowing through the second discharge pipe (82). The first leak sensor (Sw3) is electrically connected to the controller (100) and outputs an oil detection signal to the controller (100). When the first leak sensor (Sw3) is placed on the second discharge pipe (82), a so-called float switch can be used as the first leak sensor (Sw3). In this case, a reservoir for sealing oil is formed on the second discharge pipe (82), and a float switch is laid out in the reservoir.

[0119] And, when the first leak sensor (Sw3) is placed in the oil pan (57), for example, a ribbon-shaped sensor (sensor ribbon) can be used for the first leak sensor (Sw3).

[0120] As described above, there is a concern regarding leakage of sealing oil from the contents of the housing (5), or leakage of sealing oil from the connection part (the connection part between the contents of the housing (5) and the sealing oil supply pipe (61), sealing oil replenishment pipe (71), or the first discharge pipe (81). If ammonia fuel is mixed into the sealing oil, various problems caused by the volatilization of the ammonia fuel are expected.

[0121] To address this problem, the housing (5) according to the present embodiment has a ventilation mechanism (58) for ventilating the inside of the housing (5). The ventilation mechanism (58) includes a ventilation fan (58a). The ventilation fan (58a) is electrically connected to a controller (100) and operates by receiving an electrical signal from the controller (100).

[0122] For example, the ventilation mechanism (58) performs ventilation within the housing (5) in parallel with the circulation of sealing oil between the housing (5) and the fuel injection valve (3). By doing so, even if ammonia fuel is mixed into the sealing oil, the ammonia fuel volatilized from the sealing oil can be stored within the housing (5). Furthermore, by operating the ventilation fan (58a), the ammonia fuel volatilized from the sealing oil can be quickly discharged.

[0123] Furthermore, it is not mandatory to operate the ventilation fan (58a) by an electrical signal from the controller (100). The ventilation fan (58a) may 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).

[0124] Air discharged from within the housing (5) by the operation of the ventilation fan (58a) flows into the ventilation passage (58b). This ventilation passage (58b) is connected to a mist box (58c). A separate exhaust passage (58d) communicating with an external space, such as the atmosphere, is connected to the mist box (58c) (see FIG. 4).

[0125] Accordingly, the air discharged from the housing (5) by the operation of the ventilation fan (58a) passes through the ventilation passage (58b), is recovered by the mist box (58c), has oil removed from the air, and is then discharged through the exhaust passage (58d).

[0126] (Sealing oil circulation system (6))

[0127] The sealing oil circulation system (6) fluidly connects the housing (5) and the fuel injection valve (3) to circulate sealing oil between the housing (5) and the fuel injection valve (3). In other words, the housing (5) is configured to circulate sealing oil between itself and the fuel injection valve (3) via a fluid connection through the sealing oil circulation system (6).

[0128] Specifically, the sealing oil circulation system (6) according to the present embodiment has, in addition to the sealing oil supply pipe (61) described above, a high-pressure pump (63), a first pressure sensor (Sw4), a control valve unit (64), and a sealing oil return pipe (62).

[0129] A high-pressure pump (63) is positioned downstream of a low-pressure pump (53) in a sealing oil supply pipe (61) that serves as a sealing oil pipe. 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" of this embodiment.

[0130] In detail, the high-pressure pump (63) is positioned downstream of the low-pressure pump (53) and the sealing oil cooler (54) and upstream of the control valve unit (64) in the sealing oil supply pipe (61). The high-pressure pump (63) is electrically connected to the controller (100) and operates by receiving an electrical signal from the controller (100). Upon receiving the electrical signal, the high-pressure pump (63) pressurizes the sealing oil that has been pressurized by the low-pressure pump (53) and then cooled by the sealing oil cooler (54).

[0131] That is, the sealing oil cooler (54) according to the present embodiment is positioned downstream of the low-pressure pump (53) and upstream of the high-pressure pump (63) on the sealing oil supply pipe (61).

[0132] In addition, although only one high-pressure pump (63) is shown in the example drawing, multiple oil pumps may be connected in parallel to the sealing oil supply pipe (61) and the high-pressure pump (63) may be formed by these multiple oil pumps. In this case, some of the multiple oil pumps may be operated while the remaining oil pumps are assigned to backup, or the multiple oil pumps may be configured to operate simultaneously.

[0133] In addition, as shown in FIG. 2, the high-pressure pump (63) is configured as a separate unit with respect to the housing (5), and like the housing (5), it may be fixed to the engine body (10) by interposing a support member (91).

[0134] Additionally, as shown in FIG. 2, the high-pressure pump (63) is housed in an enclosure (93) separate from the housing (5). This enclosure (93) is connected to the housing (5) via a duct (94). Ammonia volatilized within the enclosure (93) is sent to the housing (5) via the duct (94) and then ventilated by a ventilation mechanism (58).

[0135] And, in the enclosure (93) for the high-pressure pump (63), an oil pan (not shown) is accommodated, just like the housing (5) and the enclosure (95) for the control valve unit (64) described later. This oil pan accommodates sealing oil leaked from the high-pressure pump (63). The oil pan for the high-pressure pump (63) is connected to a confluence pipe (84) between the second discharge pipe (82) and the third discharge pipe (83). Oil leakage can be detected by detecting the oil flowing through the confluence pipe, for example, by a float sensor.

[0136] The first pressure sensor (Sw4) is positioned downstream of the high-pressure pump (63) in the sealing oil supply pipe (61). The first pressure sensor (Sw4) detects the pressure of the sealing oil immediately after the pressure is increased by the high-pressure pump (63).

[0137] In detail, the first pressure sensor (Sw4) is positioned in the sealing oil supply 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 configured, for example, by a pressure transmitter (so-called "PT") in which the pressure sensor and the amplifier are integrated.

[0138] The control valve unit (64) is positioned downstream of the first pressure sensor (Sw4) and upstream of the fuel injection valve (3) in the sealing oil supply pipe (61) which serves as the sealing oil pipe. The control valve unit (64) controls the supply of sealing oil to the fuel injection valve (3).

[0139] In detail, the control valve unit (64) has a first pressure reducing valve (641), a first switching valve (642), and a second pressure sensor (Sw5) in order from the upstream side in the direction of flow of the sealing oil. All of these elements are placed on the sealing oil supply pipe (61).

[0140] The first pressure reducing valve (641) pressure-regulates the sealing oil that has been pressurized by the high-pressure pump (63). Specifically, the sealing oil that has been 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 pressure-regulated by the first pressure reducing valve (641) flows out from the secondary side (downstream side) of the first pressure reducing valve (641).

[0141] The first switching valve (642) opens and closes the sealing oil supply pipe (61). When the sealing oil supply pipe (61) is opened by the first switching valve (642), the sealing oil, whose pressure is regulated by the first pressure reducing valve (641), passes through the first switching valve (642) and reaches the fuel injection valve (3). When the sealing oil supply pipe (61) is closed by the first switching valve (642), the sealing oil, whose pressure is regulated by the first pressure reducing valve (641), is blocked by the first switching valve (642).

[0142] In detail, the first switching valve (642) is electrically connected to the controller (100) and operates by receiving an electrical signal from the controller (100). Upon receiving the electrical signal, the first switching valve (642) closes or opens. The first switching valve (642) is configured, for example, by a solenoid-type electronic valve.

[0143] A second pressure sensor (Sw5) is positioned downstream of the first switching valve (642) in the sealing oil supply pipe (61). The second pressure sensor (Sw5) detects the pressure of the sealing oil immediately after it passes through the first switching valve (642).

[0144] In detail, the second pressure sensor (Sw5) is positioned in the sealing oil supply 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) is configured, for example, by a pressure transmitter (so-called "PT") in which the pressure sensor and the amplifier are integrated.

[0145] In addition, in this embodiment, the fuel oil functioning as a sealing oil also serves as an operating oil.

[0146] Accordingly, the operating oil supply pipe (65) shown in FIG. 4 is connected to the sealing oil supply pipe (61) according to the present embodiment. The operating oil supply pipe (65) connects the sealing oil supply pipe (61) and the fuel injection valve (3). Specifically, as shown in FIG. 4, the operating oil supply pipe (65) connects the first pressure sensor (Sw4) and the first pressure reducing valve (641) of the sealing oil supply pipe (61) with the operating oil (38) at the fuel injection valve (3).

[0147] As elements related to the supply of hydraulic fluid, the control valve unit (64) according to the present embodiment additionally has a second switching valve (644), a second pressure reducing valve (645), a third pressure sensor (Sw7), and a hydraulic fluid pump (646) in order from the upstream side in the flow direction of the sealing oil (hydraulic fluid). All of these elements are disposed on the hydraulic fluid supply pipe (65).

[0148] The second switching valve (644) opens and closes the hydraulic fluid supply pipe (65). When the hydraulic fluid supply pipe (65) is opened by the second switching valve (644), the sealing oil, which is pressurized by the high-pressure pump (63), passes through the second switching valve (644) and reaches the second pressure reducing valve (645). When the hydraulic fluid supply pipe (65) is closed by the second switching valve (644), the sealing oil, which is pressurized by the high-pressure pump (63), is blocked by the second switching valve (644).

[0149] In detail, the second switching valve (644) is electrically connected to the controller (100) and operates by receiving an electrical signal from the controller (100). Upon receiving the electrical signal, the second switching valve (644) is closed or opened. The second switching valve (644) is configured, for example, by a solenoid-type electronic valve.

[0150] The second pressure reducing valve (645) pressure-regulates 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 pressure-regulated by the second pressure reducing valve (645) flows out from the secondary side (downstream side) of the second pressure reducing valve (645).

[0151] A third pressure sensor (Sw7) is positioned downstream of the second pressure reducing valve (645) in the hydraulic fluid supply pipe (65). The third pressure sensor (Sw7) detects the pressure of the sealing oil immediately after it is pressure-regulated by the second pressure reducing valve (645).

[0152] In detail, the third pressure sensor (Sw7) is positioned in the hydraulic fluid supply pipe (65) downstream of the second pressure reducing valve (645) and upstream of the hydraulic fluid 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 configured, for example, by a pressure transmitter (so-called "PT") in which the pressure sensor and the amplifier are integrated.

[0153] The hydraulic fluid pump (646) is positioned downstream of the third pressure sensor (Sw7) in the hydraulic fluid supply pipe (65). The hydraulic fluid pump (646) pumps the sealing oil, whose pressure is detected by the third pressure sensor (Sw7) after being pressure-regulated by the second pressure reducing valve (645), to the fuel injection valve (3).

[0154] In detail, the hydraulic fluid pump (646) is positioned in the hydraulic fluid 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 hydraulic fluid pump (646) is electrically connected to the controller (100) and operates by receiving an electrical signal from the controller (100). Upon receiving the electrical signal, the hydraulic fluid pump (646) pumps the sealing oil, which is pressure-regulated by the second pressure reducing valve (645), to the fuel injection valve (3) as hydraulic fluid.

[0155] In addition, the control valve unit (64) is housed in an enclosure (95) for the control valve unit (64). As an example, this enclosure (95) is separate from both the housing (5) and the enclosure (93) for the high-pressure pump (63), as shown in FIG. 2.

[0156] Furthermore, it is not necessary to have the enclosure (95) for the control valve unit (64) separate from both the housing (5) and the enclosure (93) for the high-pressure pump (63). The enclosure (95) may be integrated with at least one of the housing (5) and the enclosure (93) for the high-pressure pump (63). Alternatively, the enclosure (95) may be composed of a plurality of housings each accommodating different members.

[0157] And, as shown in FIG. 4, the control valve unit (64) additionally comprises a second oil pan (643) housed in an enclosure (95) for said control valve unit (64). The second oil pan (643) receives sealing oil leaked 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 an operating oil pump (646).

[0158] A third discharge pipe (83) constituting a sealing oil discharge system (8) is connected to the second oil pan (643). The third discharge pipe (83) is composed of a pipe that circulates the sealing oil (fuel oil in this embodiment) received from the second oil pan (643).

[0159] And, a second leak sensor (Sw6) is connected to at least one of the second oil pan (643) and the third discharge pipe (83). The second leak sensor (Sw6) detects oil in at least one of the second oil pan (643) and the third discharge pipe (83).

[0160] In detail, the second leak sensor (Sw6) according to the present embodiment is placed on the third discharge pipe (83) as an example. This second leak sensor (Sw6) detects sealing oil flowing through the third discharge pipe (83). The second leak sensor (Sw6) is electrically connected to the controller (100) and outputs an oil detection signal to the controller (100). When the second leak sensor (Sw6) is placed on the third discharge pipe (83), a so-called float switch may be used for the second leak sensor (Sw6). In this case, a reservoir for sealing oil is formed on the third discharge pipe (83), and a float switch is laid out in the reservoir.

[0161] And, when the second leak sensor (Sw6) is placed in the second oil pan (643), for example, a ribbon-shaped sensor (sensor ribbon) can be used for the second leak sensor (Sw6).

[0162] Also, returning to FIG. 2, the control valve unit (64) is configured as a separate unit for the housing (5) and the high-pressure pump (63). The control valve unit (64) according to the present embodiment is supported on the engine body (10) via a second support member (92).

[0163] The second support member (92) is formed by a so-called frame and is fixed to the cylinder 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), at a position above the housing (5) and the high-pressure pump (63).

[0164] The sealing oil return pipe (62) is a pipe that distributes sealing oil from each part of the fuel injection valve (3) and the sealing oil supply system (4) to the sealing oil tank (51). The sealing oil return pipe (62) has 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 shut-off valve (626), and a second shut-off valve (627). The sealing oil return pipe (62) exemplifies the "sealing oil piping" of this embodiment together with the sealing oil supply pipe (61) in that it can distribute sealing oil between the sealing oil tank (51) and the fuel injection valve (3).

[0165] The first return pipe (621) is composed of a pipe that returns the drain oil discharged from the fuel injection valve (3) to the sealing oil tank (51) from the fuel injection valve (3). The first return pipe (621) fluidically connects each fuel injection valve (3) and the sealing oil tank (51). A portion near the downstream end of the first return pipe (621) (one end on the sealing oil tank (51) side) is accommodated in the housing (5).

[0166] The second return pipe (622) is composed of a pipe that returns the sealing oil (hereinafter also referred to as "leakage oil") leaked from the high-pressure pump (63), which will be described later, back from the high-pressure pump (63) to the sealing oil tank (51). The second return pipe (622) fluidically connects the high-pressure pump (63) and the sealing oil tank (51). A portion near the downstream end of the second return pipe (622) (one end on the side of the sealing oil tank (51)) is accommodated in the housing (5).

[0167] The third return pipe (623) controls the discharge pressure of the high-pressure pump (63). The third return pipe (623) fluidically connects the outlet of the high-pressure pump (63) with the sealing oil tank (51). A portion near the downstream end of the third return pipe (623) (one end on the side of the sealing oil tank (51)) is accommodated in the housing (5). Then, as illustrated in FIG. 4, a first shut-off valve (626) is positioned in the middle of the third return pipe (623). The first shut-off valve (626) changes its opening degree by receiving an electrical signal from the controller (100) and operating. The controller (100) adjusts the discharge pressure of the high-pressure pump (63) to a desired pressure by controlling the opening degree of the first shut-off valve (626). Also, instead of the first opening / closing valve (626) electrically connected to the controller (100), a pressure regulating valve may be placed.

[0168] The fourth return pipe (624) is composed of a pipe that returns the leaked oil from the first switching valve (642) and the second switching valve (644) to the sealing oil tank (51). The fourth return pipe (624) fluidically connects the first switching valve (642) and the second switching valve (644) with the intermediate portion of the third return pipe (623). That is, the fourth return pipe (624) is connected to the sealing oil tank (51) after joining with the third return pipe (623).

[0169] The fifth return pipe (625) controls the discharge pressure of the low-pressure pump (53). The fifth return pipe (625) fluidically connects the outlet of the low-pressure pump (53) with the sealing oil tank (51). The entire fifth return pipe (625), from its upstream end to its downstream end, is housed in the housing (5). And, as illustrated in FIG. 4, a second shut-off valve (627) is positioned in the middle of the fifth return pipe (625). The second shut-off valve (627) changes its opening degree by receiving an electrical signal from the controller (100) and operating. The controller (100) adjusts the discharge pressure of the low-pressure pump (53) to a desired pressure by controlling the opening degree of the second shut-off valve (627). And, instead of the second shut-off valve (627) electrically connected to the controller (100), a pressure regulating valve may be positioned.

[0170] Here, the connection position between the sealing oil return pipe (62) and the sealing oil tank (51) is located above the connection position between the sealing oil supply pipe (61) and the sealing oil tank (51).

[0171] In detail, the connection location between the sealing oil return pipe (62) and the sealing oil tank (51) is positioned above the upper limit (Ll) of the oil height allowed in the sealing oil tank (51). More specifically, the sealing oil return pipe (62) is connected to the upper surface (51a) of the sealing oil tank (51) or near the upper surface (51a).

[0172] (Sealing oil replenishment system (7))

[0173] 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 in the sealing oil tank (51) within the housing (5).

[0174] Specifically, the sealing oil replenishment system (7) according to the present embodiment has, in addition to the sealing oil replenishment pipe (71) described above, the sealing oil supply source (72), oil cooler (73), and filter (74) described above.

[0175] The sealing oil source (72) is an oil tank that stores fuel oil used as sealing oil, such as MGO. The sealing oil 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 source (72) is an example of the "storage tank" of the present embodiment.

[0176] An oil cooler (73) is placed on a sealing oil replenishment pipe (71). The oil cooler (73) cools the sealing oil flowing through the sealing oil replenishment pipe (71). The oil cooler (73) is composed of a heat exchanger using a heat exchange medium supplied, for example, from inside or outside the engine room. The heat exchange medium is, for example, water.

[0177] A filter (74) is placed on a sealing oil replenishment tube (71) and filters the sealing oil flowing through the sealing oil replenishment tube (71).

[0178] And, at least one of the sealing oil replenishment system (7) and the sealing oil tank (51) is configured to regulate the backflow of sealing oil from the sealing oil tank (51) to the sealing oil replenishment pipe (71).

[0179] For example, in this embodiment, as illustrated in FIG. 4, the connection position between the sealing oil replenishment pipe (71) and the sealing oil tank (51) is located above the connection position between the sealing oil supply pipe (61) and the sealing oil tank (51).

[0180] In detail, the connection position between the sealing oil replenishment pipe (71) and the sealing oil tank (51) is positioned above the upper limit (Ll) of the oil height allowed in the sealing oil tank (51). More specifically, the sealing oil replenishment pipe (71) is connected to the upper surface (51a) of the sealing oil tank (51) or near the upper surface (51a).

[0181] In this way, by devising a connection position between the sealing oil replenishment pipe (71) and the sealing oil tank (51), backflow of sealing oil from the sealing oil tank (51) to the sealing oil replenishment pipe (71) is suppressed. In addition to these configurations, or instead of these configurations, a member capable of suppressing backflow of sealing oil, such as a check valve, may be placed on the sealing oil replenishment pipe (71), or a sealing oil supply source (72) may be placed at a position higher than the sealing oil replenishment pipe (71).

[0182] (Sealing oil drainage system (8))

[0183] The sealing oil discharge system (8) discharges excess sealing oil, such as leaked oil, from each part of the sealing oil supply system (4).

[0184] Specifically, the sealing oil discharge system (8) according to the present embodiment has a confluence pipe (84) in addition to the aforementioned first discharge pipe (81), second discharge pipe (82), first leakage sensor (Sw3), third discharge pipe (83) and second leakage sensor (Sw6).

[0185] The first discharge pipe (81), the second discharge pipe (82), and the third discharge pipe (83) are each connected to the confluence pipe (84). The confluence pipe (84) discharges the sealing oil that has flowed into each of the first discharge pipe (81), the second discharge pipe (82), and the third discharge pipe (83) out of the engine room. For example, even if ammonia fuel is mixed into the sealing oil, the ammonia fuel is discharged out of the engine room together with the sealing oil.

[0186] (3) Fuel injection valve (3)

[0187] FIG. 5 is a cross-sectional view illustrating the configuration of a fuel injection valve (3).

[0188] As shown in FIG. 5, the fuel injection valve (3) is equipped with a fuel chamber (35), a piston shaft (36), a pressure chamber (37), and an operating chamber (38), in addition to the aforementioned tubular body (31), valve shaft (32), and sealing chamber (33).

[0189] Hereinafter, the direction extending along the central axis (Cf) of the tubular body (31) is referred to as the central axis direction. Also, one end of the central axis direction of the tubular body (31) (the lower end in the drawing) is designated as the tip, and the other end of the central axis direction of the tubular body (31) is designated as the base. For example, the injection port (3a) of the fuel injection valve (3) is opened at the tip of the tubular body (31), as shown in FIG. 5.

[0190] The working fluid chamber (38) is formed inside the tubular body (31). The working fluid chamber (38) is fluidically connected to the working fluid supply pipe (65). Fuel oil as working fluid is pumped into the working fluid chamber (38) from the working fluid supply pipe (65). Additionally, excess working fluid in the working fluid chamber (38) is discharged from the working fluid chamber (38) as drain oil.

[0191] The pressure chamber (37) is formed inside the tubular body (31). The pressure chamber (37) is positioned at the front end of the operating chamber (38) in the direction of the central axis. Ammonia fuel as an alternative fuel is supplied to the pressure chamber (37) from the outside 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 tubular body (31).

[0192] A through hole (3c) is formed inside the tubular body (31). The through hole (3c) extends along the central axis direction to connect the operating chamber (38) and the pressure chamber (37). A piston shaft (36) is inserted into this through hole (3c).

[0193] The piston shaft (36) conveys ammonia fuel by reciprocating in a predetermined direction. The fuel injection valve (3) according to the present embodiment is configured to reciprocate the piston shaft (36) by the hydraulic pressure of the fuel oil supplied to the piston shaft (36). In other words, the fuel oil functions as an operating fluid that reciprocates the piston shaft (36).

[0194] In detail, the piston shaft (36) according to the present embodiment is disposed inside the tubular body (31) and reciprocates along the central axis (Cf) of the tubular body (31) as illustrated in FIG. 5. Furthermore, reciprocating the piston shaft (36) along the central axis (Cf), that is, aligning the central axis of the piston shaft (36) with the central axis (Cf) of the tubular body (31), is not mandatory. For example, the direction of movement of the piston shaft (36) may intersect with the central axis (Cf) of the tubular body (31). In this case, the fuel injection valve (3) may be provided with a separate tubular body that accommodates the piston shaft (36) and is inclined with respect to the tubular body (31), separate from the tubular body (31) in which the valve shaft (32) is accommodated.

[0195] More specifically, the piston shaft (36) extends from the operating chamber (38) to the fuel chamber (35) via a through hole (3c) so as to block communication between the operating chamber (38) and the pressure chamber (37). The ceiling surface of the pressure chamber (37) is formed by the lower surface (upper surface on the tip side) of the piston shaft (36).

[0196] Then, the piston shaft (36) slides along the through hole (3c) in the direction of the central axis according to the hydraulic pressure of the operating chamber (38). As the piston shaft (36) slides, the volume of the pressure chamber (37) changes. As a result, the ammonia fuel supplied to the pressure chamber (37) from the outside is pressured from the pressure chamber (37) to the first path (L1).

[0197] The fuel chamber (35) is formed inside the tubular body (31). The fuel chamber (35) is positioned in the direction of the central axis, at the leading end of the pressure chamber (37) and at the leading end of the nozzle (3a). Ammonia fuel is pressure-transported into the fuel chamber (35) from the pressure chamber (37) via a first path (L1). The fuel chamber (35) is also connected to the nozzle (3a).

[0198] The valve shaft (32) is positioned inside the tubular body (31) as described above. The valve shaft (32) extends to penetrate the fuel chamber (35) and slides along the inner wall of the tubular body (31) in the direction of the central axis. By sliding the valve shaft (32), communication between the fuel chamber (35) and the nozzle (3a) is blocked or released. The valve shaft (32) is pressurized by a pressurizing member (34) to maintain the blockage of communication between the fuel chamber (35) and the nozzle (3a).

[0199] When the fuel pressure (pressure of ammonia fuel) in the fuel chamber (35) increases, the valve shaft (32) slides in a direction that resists the pressurization by the pressurizing member (34) and connects the fuel chamber (35) and the nozzle (3a). By connecting the fuel chamber (35) and the nozzle (3a), ammonia fuel is supplied from the fuel chamber (35) to the nozzle (3a), and the ammonia fuel is injected from the nozzle (3a).

[0200] In this way, the valve shaft (32) slides along the inner wall of the tubular body (31). Accordingly, in order to seal the gap (3b) between the outer wall of the valve shaft (32) and the inner wall of the tubular body (31), fuel oil as a sealing oil is supplied to the sealing seal (33) placed in the gap (3b), as described above.

[0201] The sealing oil supplied to the sealing seal (33) seals the gap (3b) between the tubular body (31) and the valve shaft (32). By supplying sealing oil to the sealing seal (33), leakage of ammonia fuel through the gap (3b) is suppressed, and the sliding of the valve shaft (32) relative to the tubular body (31) can be lubricated.

[0202] Returning to the description of the sealing chamber (33), the sealing chamber (33) according to the present embodiment is positioned between the pressurizing member (34) and the fuel chamber (35). The sealing chamber (33) is fluidically connected to the sealing oil supply pipe (61). Fuel oil as sealing oil is pumped into the sealing chamber (33) from the sealing oil supply pipe (61). Additionally, excess working oil in the sealing chamber (33) is discharged from the sealing chamber (33) as drain oil.

[0203] (4) Alternative fuel emission system (9)

[0204] In the various pipes constituting the sealing oil supply system (4), there is a concern regarding the mixing of ammonia fuel into the pipes and, furthermore, the volatilization of the mixed ammonia fuel. Regarding the volatilized ammonia fuel, any volatile components leaked into the housing (5) can be discharged to the outside by the ventilation device (58) described above. However, it is appropriate if such volatile components can be discharged in advance.

[0205] Accordingly, the engine (1) according to the present embodiment further comprises an alternative fuel exhaust system (9) illustrated in FIG. 4. As shown in FIG. 4, the alternative fuel exhaust system (9) has a ventilation passage (96), an introduction passage (97), and a flow rate adjustment means (98).

[0206] The ventilation passage (96) is connected to at least one of the sealing oil tank (51) and the sealing oil piping (sealing oil supply pipe (61) and sealing oil return pipe (62)). The ventilation passage (96) discharges volatilized ammonia fuel from at least one of the sealing oil tank (51) and the sealing oil piping (sealing oil supply pipe (61) and sealing oil return pipe (62)).

[0207] In detail, the ventilation passage (96) according to the present embodiment includes a downstream end connected to a mist box (58c) and an upstream end connected to each of the sealing oil tank (51) and the sealing oil return pipe (62) after 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).

[0208] And, the ventilation passage (96) according to the present embodiment discharges the ammonia fuel volatilized from the sealing oil tank (51) and the ammonia fuel volatilized from the sealing oil return pipe (62), in the drawing example, the first return pipe (621), through the mist box (58c).

[0209] The introduction passage (97) is connected to at least one of the sealing oil tank (51) and the sealing oil piping (sealing oil supply pipe (61) and sealing oil return pipe (62)). The introduction passage (97) introduces compressed air or scavenging gas into at least one of the sealing oil tank (51) and the sealing oil piping (sealing oil supply pipe (61) and sealing oil return pipe (62)). Here, the word "scavenging gas" refers to gas that scavenges the inside of the combustion chamber (17).

[0210] In detail, the introduction passage (97) according to the present embodiment is connected to the sealing oil tank (51). This introduction passage (97) introduces compressed air or scavenging gas into the sealing oil tank (51).

[0211] A flow rate adjustment means (98) is placed in the introduction passage (97). The flow rate adjustment means (98) adjusts the flow rate of compressed air or scavenging gas in the introduction passage (97).

[0212] In detail, the flow rate adjustment means (98) according to the present embodiment is configured, for example, by an orifice or a flow rate adjustment valve. More specifically, the flow rate adjustment means (98) is configured by a flow rate adjustment valve in the present embodiment.

[0213] (5) Controller (100)

[0214] FIG. 6 is a block diagram illustrating the configuration of a controller (100) of an engine (1). The controller (100) has a processor, volatile memory, non-volatile memory, and an input / output bus. For example, a level sensor (Sw1), an alternative fuel sensor (Sw2), a first leakage sensor (Sw3), a first pressure sensor (Sw4), a second pressure sensor (Sw5), a second leakage sensor (Sw6), and a third pressure sensor (Sw7) are connected to the controller (100).

[0215] The controller (100) generates a control signal based on the signals input from these sensors and inputs the control signal to the low-pressure pump (53), sealing oil supply valve (55), ventilation mechanism (58), high-pressure pump (63), first switching valve (642), second switching valve (644), hydraulic oil pump (646), first shut-off valve (626), and second shut-off valve (627), etc. Through these control signals, the controller (100) controls the circulation of fuel oil, which functions as both sealing oil and hydraulic oil in the sealing oil supply system (4), and ventilation within the housing (5) by the ventilation mechanism (58).

[0216] (6) Effects, etc.

[0217] As explained above, according to the above embodiment, even if ammonia fuel is mixed into the sealing oil and the ammonia fuel volatilizes and leaks, the leaked volatilized components can be contained within the housing (5) illustrated in FIG. 4. In this way, the ammonia fuel mixed into the sealing oil and leaked can be isolated from the equipment and the human body. In this way, the effect of the mixing of ammonia fuel can be suppressed.

[0218] Additionally, as illustrated in FIGS. 1 and 2, the housing (5) is supported by the engine body (10) by a support member (91). This allows it to be transported integrally with the engine body (10). Furthermore, the housing (5), which is supported by the engine body (10) by the support member (91), is positioned with a gap from the floor (F) of the ship. By positioning it in this way, the housing (5) vibrates integrally with the engine body (10).

[0219] For example, when a housing (5) is placed on a floor (F), the engine body (10) acting as the source of vibration vibrates relatively significantly, whereas the floor (F) and the housing (5) do not vibrate as much as the engine body (10). In this case, it is required to connect a member or mechanism that absorbs the difference in vibration between the engine body (10) and the floor (F) to the piping connecting the housing (5) and the engine body (10). However, such a member or mechanism may cause leakage of ammonia fuel from the connection part with the piping.

[0220] In contrast, by vibrating the housing (5) and the engine body (10) as a whole, the aforementioned components or mechanisms become unnecessary. This allows for the suppression of the risk of leakage from the connection part. Furthermore, as described above, since the sealing oil supply system (4) is completed within the engine (1), even if a leak of ammonia fuel occurs, the range of diffusion of the leaked ammonia fuel can be minimized.

[0221] Additionally, as illustrated in FIGS. 1 and 2, the housing (5) is positioned on the side of the frame (12), that is, above the crankcase. By positioning it in this way, the fuel injection valve (3) and the housing (5) can be brought close together in the vertical direction. This allows the entire sealing oil supply system to be configured compactly. The compactness of the entire sealing oil supply system contributes to the miniaturization of the sealing oil tank (51) for storing sealing oil, and to the suppression of leakage of ammonia fuel from the piping.

[0222] In addition, as illustrated in FIG. 4, by housing various components including a sealing oil tank (51) and a low-pressure pump (53) in the housing (5), when ammonia fuel is mixed into the sealing oil, volatile components of ammonia fuel leaked from the various components related to the sealing oil tank (51), and volatile components of ammonia fuel leaked from the connection part between components (e.g., fluid connection part) can be contained within the housing (5) on both sides. This makes it advantageous to suppress the effect of ammonia fuel mixing into the sealing oil.

[0223] In addition, as illustrated in FIG. 4, the viscosity of the sealing oil can be secured by cooling the sealing oil with a sealing oil cooler (54). Here, in order to supply the sufficiently cooled sealing oil to the fuel injection valve (3), it is considered that the sealing oil cooler (54) should be positioned as close as possible to the fuel injection valve (3) on the sealing oil supply pipe (61) which serves as the sealing oil pipe. However, for example, if the sealing oil cooler (54) is positioned downstream of the high-pressure pump (63), there is a possibility that the sealing oil cooler (54) may be damaged as the sealing oil, which has been pressurized by the high-pressure pump (63), is supplied.

[0224] In contrast, as illustrated in FIG. 4, by laying out a sealing oil cooler (54) between the low-pressure pump (53) and the high-pressure pump (63), the viscosity of the sealing oil and the suppression of abnormalities in the sealing oil cooler (54) can be achieved.

[0225] In addition, as illustrated in FIG. 4, by connecting the sealing oil replenishment system (7) and the sealing oil tank (51) within the housing (5), even if volatile components of the ammonia fuel leak from the connection part between the sealing oil replenishment system (7) and the sealing oil tank (51), such as a fluid connection part, the volatile components can be contained within the housing (5). This makes it advantageous to suppress the effect of mixing ammonia fuel into the sealing oil.

[0226] In addition, as illustrated in FIG. 4, by configuring the sealing oil to regulate the backflow of sealing oil from the sealing oil tank (51) to the sealing oil replenishment pipe (71), the backflow of the sealing oil mixed with ammonia fuel to the sealing oil supply source (72) is regulated, even if, for example, ammonia fuel is mixed into the sealing oil. As a result, the diffusion of the sealing oil mixed with ammonia fuel can be prevented, and it is advantageous to suppress the effects of the mixing of ammonia fuel.

[0227] In addition, even if ammonia fuel is introduced into the sealing oil flowing through at least one of the sealing oil tank (51) and the sealing oil piping (sealing oil supply pipe (61) and sealing oil return pipe (62)) and volatilizes, the volatilized components can be discharged through the ventilation passage (96) illustrated in FIG. 4. By doing so, the ammonia fuel mixed into the sealing oil can be isolated from the equipment and the human body. This makes it more advantageous to suppress the effects of the mixing of ammonia fuel.

[0228] In addition, for example, even if the volatile components of the ammonia fuel leak out without being discharged through the ventilation passage (96), the leaked volatile components can be discharged by the ventilation device (58) illustrated in FIG. 4. This allows the leaked ammonia fuel mixed into the sealing oil to be isolated from the equipment and the human body. This makes it more advantageous to suppress the effects of the mixing of ammonia fuel.

[0229] In addition, generally, on the engine (1), a crew member performs daily tasks such as inspections. By providing a ventilation device (58), the crew member working on the engine (1) is reliably isolated from the ammonia fuel. That is, by providing a ventilation device (58), the crew member can be isolated from the ammonia fuel even if the housing (5) is supported by the engine body (10).

[0230] Additionally, when volatilized ammonia fuel is introduced into at least one of the sealing oil tank (51) and the sealing oil piping (sealing oil supply pipe (61) and sealing oil return pipe (62)), the ammonia fuel can be pushed out by compressed air or scavenging gas introduced from the introduction passage (97) illustrated in FIG. 4 and sent to the ventilation passage (96). This makes it more advantageous to suppress the effects of mixing ammonia fuel.

[0231] In addition, as illustrated in FIG. 4, by placing a flow rate adjustment means (98) in the introduction passage (97), it becomes possible to adjust the flow rate of compressed air or intake gas. This makes it more advantageous to suppress the effects of mixing alternative fuels.

[0232] In addition, as illustrated in FIG. 4, the ammonia fuel mixed in the sealing oil can be discharged along with the sealing oil by using the sealing oil discharge system (sealing oil discharge system (8)) that leaks from the housing (5). This makes it advantageous to suppress the effect of ammonia fuel mixing into the sealing oil.

[0233] In addition, fuel oil does not generate residue even under high temperatures. Therefore, as in the above embodiment, by sealing the fuel injection valve (3) with fuel oil, various problems caused by residue do not occur even if the sealing oil is mixed with ammonia fuel, for instance. This allows the effect of the sealing oil being mixed with ammonia fuel to be suppressed.

[0234] Furthermore, as in the above embodiment, using diesel fuel as the sealing oil more reliably suppresses the generation of residue. This is advantageous for suppressing the effects of mixing the sealing oil into ammonia fuel. Additionally, using an alternative fuel instead of diesel fuel as the sealing oil can also promote carbon neutrality.

[0235] In addition, in order to supply sufficiently cooled sealing oil to the fuel injection valve (3), it is thought that the sealing oil cooler (54) should be placed as close as possible to the fuel injection valve (3) on the sealing oil supply pipe (61) which serves as the sealing oil pipe. However, for example, if the sealing oil cooler (54) is placed downstream of the high-pressure pump (63), there is a possibility that the sealing oil cooler (54) may be damaged as the sealing oil, which has been high-pressure by the high-pressure pump (63), is supplied.

[0236] In contrast, as illustrated in FIG. 4, by laying out a sealing oil cooler (54) between the low-pressure pump (53) and the high-pressure pump (63), the viscosity of the sealing oil and the suppression of abnormalities in the sealing oil cooler (54) can be achieved.

[0237] In addition, as described above, fuel oil does not generate residue even at high temperatures. Therefore, as in the above embodiment, by using fuel oil as the operating fluid to operate the fuel injection valve (3), various problems caused by residue do not occur even if the operating fluid is mixed with ammonia fuel, for instance. This allows the effects of mixing the operating fluid with ammonia fuel to be suppressed.

[0238] (7) Other embodiments

[0239] In the above embodiment, fuel oil was used for both the sealing oil and the operating oil, but the present disclosure is not limited to such a configuration. Lubricating oil for oil sealing may be used for at least one of the sealing oil and the operating oil. If lubricating oil is used as the sealing oil, either the low-pressure pump (53) or the high-pressure pump (63) may be omitted accordingly. Explanation of the symbols

[0240] 1 : Engine (Marine Engine) 10: Organ body 11: Bed plate 12 : Frame 16 : Cylinder 3: Fuel injection valve 31: Tube-shaped body 32 : Valve shaft 33 : Sealing room 36 : Piston shaft 4: Sealing oil supply system 5 : Housing 51: Sealing oil tank 52: Oil filter 53 : Low-pressure pump (1st pump) 54 : Sealing oil cooler 57 : Oil pan 58: Ventilation equipment 58a : Ventilation fan 91: Support member 6: Sealing oil circulation system 61 : Sealing oil supply pipe (sealing oil piping) 62 : Sealing oil return pipe (sealing oil piping) 63: High-pressure pump (2nd pump) 7: Sealing Oil Replenishment System 71: Sealing oil refill tube 72 : Sealing oil supply (reservoir tank) 9: Alternative Fuel Emission System 96: Ventilation passage 97 : Introduction Passage 98: Flow control means 8: Sealing oil drainage system 82 : 2nd discharge pipe (sealing oil discharge pipe) Sw3: 1st leakage sensor Cf : Central axis F: Ship's floor

Claims

Claim 1 A marine engine for burning a volatile alternative fuel within a cylinder, comprising: a tubular body extending along a predetermined central axis; a valve shaft inserted into the tubular body and reciprocating along the central axis; a fuel injection valve for injecting the alternative fuel into the cylinder; and a housing for circulating a sealing oil between the fuel injection valve and the tubular body and sealing the gap between the tubular body and the valve shaft. Claim 2 A marine engine according to claim 1, comprising: a main body having the cylinder and reciprocating a piston within the cylinder; a support member fixed to the main body; the support member being spaced apart from the floor of the vessel; and a housing being supported on the main body through the support member. Claim 3 In paragraph 2, the engine body comprises a bed plate constituting the crankcase of the marine engine and a frame disposed above the bed plate, and the housing is disposed on the side of the frame via the support member, for a marine engine. Claim 4 In claim 1, a marine engine having a sealing oil tank for storing the sealing oil, and the housing accommodating the sealing oil tank. Claim 5 In claim 4, the marine engine comprises a sealing oil pipe for circulating the sealing oil between the sealing oil tank and the fuel injection valve, an oil filter disposed on the sealing oil pipe and filtering the sealing oil flowing through the sealing oil pipe toward the fuel injection valve, a first pump disposed on the sealing oil pipe and pressurizing the sealing oil flowing through the sealing oil pipe toward the fuel injection valve, and a sealing oil cooler disposed on the sealing oil pipe and cooling the sealing oil flowing through the sealing oil pipe, wherein the housing accommodates one or more of the sealing oil tank, the oil filter, the first pump, and the sealing oil cooler, including the sealing oil tank. Claim 6 A marine engine according to claim 5, comprising a second pump positioned downstream of the first pump in the sealing oil piping and further pressurizing the sealing oil pressurized by the first pump, and the sealing oil cooler positioned downstream of the first pump and upstream of the second pump in the sealing oil piping. Claim 7 A marine engine according to claim 4, comprising a sealing oil replenishment system connected to the sealing oil tank within the housing and replenishing the sealing oil in the sealing oil tank. Claim 8 In claim 7, the sealing oil replenishment system comprises a storage tank for storing the sealing oil and a sealing oil replenishment pipe for distributing the sealing oil from the storage tank to the sealing oil tank, and at least one of the sealing oil replenishment system and the sealing oil tank is configured to regulate the backflow of the sealing oil from the sealing oil tank to the sealing oil replenishment pipe, for a marine engine. Claim 9 A marine engine according to claim 4, comprising: a sealing oil pipe for circulating the sealing oil between the sealing oil tank and the fuel injection valve; a ventilation mechanism for ventilating the inside of the housing; and a ventilation passage connected to at least one of the sealing oil tank and the sealing oil pipe, for discharging the substitute fuel volatilized from at least one of the sealing oil tank and the sealing oil pipe. Claim 10 A marine engine according to claim 9, having an introduction passage connected to at least one of the sealing oil tank and the sealing oil pipe, and for introducing compressed air or scavenging gas into at least one of the sealing oil tank and the sealing oil pipe. Claim 11 A marine engine according to claim 10, comprising a flow control means disposed in the introduction passage and controlling the flow rate of the compressed air or the scavenging gas in the introduction passage. Claim 12 A marine engine according to claim 4, comprising: an oil pan received in the housing and receiving the sealing oil leaked from the received housing; a sealing oil discharge pipe connected to the oil pan and circulating the sealing oil received in the oil pan; and a leak sensor for detecting oil in at least one of the oil pan and the sealing oil discharge pipe. Claim 13 In any one of paragraphs 1 to 12, the alternative fuel is ammonia fuel, for a marine engine.

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