Gas engine

Abstract

To suppress damage of a seal member caused by heat with a gas supply passage provided within a cylinder cover.SOLUTION: An engine 1 is a gas engine capable of burning hydrogen gas. The engine 1 includes: a cylinder liner 14; a cylinder cover 15; a gas injection valve 5 for injecting hydrogen gas; gas supply passages 32, 33 for supplying hydrogen gas to the gas injection valve 5; a block body 7 that is fixed to an upper surface 15a of the cylinder cover 15, through which the gas injection valve 5 is inserted and that is constituted separately from the cylinder cover 15; and seal members 62, 63 for sealing between the gas supply passages 32, 33 and the gas injection valve 5. The gas supply passages 32, 33 comprise: the first gas supply passage 32 partitioned within the cylinder cover 15; and the second gas supply passage 33 partitioned within the block body 7 and connecting the first gas supply passage 32 to the gas injection valve 5. The seal members 62, 63 are provided in a connection part S1 between the second gas supply passage 33 and the gas injection valve 5.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to gas engines. [Background technology]

[0002] Patent Document 1 discloses an engine (a large, low-speed, turbocharged, two-stroke diesel engine) configured to supply gas fuel (gaseous fuel) into a combustion chamber as an example of a so-called gas engine. Specifically, this engine includes a gas fuel valve inserted into a cylinder cover (top cover of the cylinder), and a gas supply passage (supply conduit) formed in the cylinder cover for supplying gas fuel to the gas fuel valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-86867 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to suppress leakage of gas fuel from a gas engine, the inventors of the present application considered forming each flow path for circulating the gas fuel integrally by arranging each flow path within a cylinder cover, thereby reducing the number of connection points between the flow paths.

[0005] A specific example of this is to insert a gas fuel valve into a cylinder cover and provide a gas supply passage within the cylinder cover, as disclosed in the aforementioned Patent Document 1. However, when such a configuration is adopted, there remains a concern that gas leakage may occur from the connection between the gas supply passage and the gas fuel valve.

[0006] In order to eliminate such concerns, it is necessary to provide a sealing member such as an O-ring inside the cylinder cover to seal the gap between the gas supply passage and the gas fuel valve.

[0007] However, when a seal member is provided inside the cylinder cover, the seal member may be damaged by heat generated by the combustion of the gas fuel, which is inconvenient in terms of extending the life of the gas engine.

[0008] The technology disclosed here has been developed in consideration of these points, and its purpose is to suppress heat damage to sealing members in a gas engine while providing a gas supply passage within a cylinder cover. [Means for solving the problem]

[0009] A first aspect of the present disclosure relates to a gas engine capable of burning gas fuel in a cylinder. The gas engine includes a cylinder liner for reciprocating a piston, a cylinder cover fixed to an upper end of the cylinder liner and serving as a lid for the cylinder, a gas injection valve provided with an injection port for injecting the gas fuel into the cylinder, a gas supply passage for supplying the gas fuel to the gas injection valve, a block body fixed to an upper surface of the cylinder cover, through which the gas injection valve is inserted and configured separately from the cylinder cover, and a seal member for sealing between the gas supply passage and the gas injection valve, the gas supply passage having a first gas supply passage defined inside the cylinder cover and a second gas supply passage defined inside the block body and connecting the first gas supply passage to the gas injection valve, and the seal member is provided at a connection between the second gas supply passage and the gas injection valve.

[0010] According to the first aspect, the gas injection valve is not directly connected to the first gas supply passage defined within the cylinder cover, but is indirectly connected to the first gas supply passage via a block body that is separate from the cylinder cover.

[0011] Such a connection makes it possible to provide a seal member at the connection between the block body and the gas injection valve (the connection between the second gas supply passage and the gas injection valve) without providing a seal member inside the cylinder cover.

[0012] Here, because the block body is disposed on the top surface of the cylinder cover, the seal member can be located farther away from the combustion chamber than in a configuration in which a seal member is provided inside the cylinder cover, and therefore, by positioning the seal member farther away from the combustion chamber, it is possible to suppress damage to the seal member caused by heat.

[0013] Thus, according to the first aspect, it is possible to suppress damage to the seal member due to heat while providing a gas supply path inside the cylinder cover.

[0014] According to a second aspect of the present disclosure, the gas engine further includes a gas inlet passage that opens into an outer peripheral surface of the gas injection valve and connects the second gas supply passage to the injection port, and an insertion hole that is provided in the block body and through which the gas injection valve is inserted, and in an axial direction of the gas injection valve, the injection port side in the axial direction is defined as a tip end side, and the opposite side of the injection port in the axial direction is defined as a base end side, the outer peripheral surface of the gas injection valve has a first outer peripheral surface extending along the axial direction, a second outer peripheral surface that is arranged closer to the base end side than the first outer peripheral surface, has a larger diameter than the first outer peripheral surface, and extends along the axial direction, and a third outer peripheral surface constituted by a step or a slope that connects the first outer peripheral surface and the second outer peripheral surface, and an inner peripheral surface of the insertion hole is defined as a third outer peripheral surface inscribed in the first outer peripheral surface. a first inner circumferential surface, a second inner circumferential surface that is arranged closer to the base end than the first inner circumferential surface, has a diameter larger than the first inner circumferential surface, and is inscribed in the second outer circumferential surface; and a third inner circumferential surface that is constituted by a step or a slope that connects the first inner circumferential surface and the second inner circumferential surface, wherein, in a state in which the gas injection valve is fastened to the block body, the third outer circumferential surface and the third inner circumferential surface face each other with a gap in the axial direction or in a radial direction perpendicular to the axial direction, the gap defines a first space through which the gas fuel flows in a circumferential direction around a central axis of the gas injection valve, the gas introduction passage opens to communicate with the first space, and the seal member is attached to at least the first outer circumferential surface so as to suppress gas leakage through the first space.

[0015] Consider a hypothetical configuration in which the third outer peripheral surface and the third inner peripheral surface are not provided, the first outer peripheral surface and the second outer peripheral surface are made the same diameter, and the first inner peripheral surface and the second inner peripheral surface are made the same diameter. If such a configuration is adopted, when the gas injection valve is inserted into the block body, the seal member attached to the first outer peripheral surface of the gas injection valve will rub against both the second inner peripheral surface and the first inner peripheral surface. In this case, there is a concern that the seal member may be damaged due to wear.

[0016] In contrast, according to the second aspect, the second inner circumferential surface has a larger diameter than the first inner circumferential surface. Therefore, when the gas injection valve is inserted into the block body, contact between the seal member attached to the first outer circumferential surface of the gas injection valve and the second inner circumferential surface can be suppressed. This makes it possible to suppress damage to the seal member due to the contact. In addition, by making the second outer circumferential surface larger in diameter than the first outer circumferential surface in conjunction with the increase in the diameter of the second inner circumferential surface, it is possible to maintain contact between the inner circumferential surface of the insertion hole and the outer circumferential surface of the gas injection valve. This contributes to suppressing leakage of gas fuel.

[0017] In addition, by partitioning the first space using the third outer peripheral surface and the third inner peripheral surface, a gas reservoir for circumferentially distributing gas fuel can be formed without creating new grooves or the like on the outer peripheral surface of the gas injection valve. Normally, a recess process is required to create such a groove, but by eliminating this process, special tools for recess process are also not required. This improves the workability of the block body.

[0018] In other words, the third outer peripheral surface and the third inner peripheral surface according to the second aspect can simultaneously suppress leakage of gas fuel, suppress damage to the sealing member, allow gas fuel to flow in the circumferential direction, and improve the workability of the block body.

[0019] According to a third aspect of the present disclosure, the gas engine includes a second space that is partitioned between the first outer peripheral surface and the first inner peripheral surface, is located on the tip side of the first space, and receives the gas fuel leaked from the first space, and a third space that is partitioned between the second outer peripheral surface and the second inner peripheral surface, is located on the base side of the first space, and receives the gas fuel leaked from the first space, and the seal member includes a first seal portion that is located on the tip side of the second space and is attached to the first outer peripheral surface so as to be sandwiched between the first outer peripheral surface and the first inner peripheral surface, in this order from the tip side to the base side. a second seal member attached to the first outer peripheral surface so as to be located on the base end side with respect to the second space and sandwiched between the first outer peripheral surface and the first inner peripheral surface; a third seal member attached to the second outer peripheral surface so as to be located on the tip end side with respect to the third space and sandwiched between the second outer peripheral surface and the second inner peripheral surface; and a fourth seal member attached to the second outer peripheral surface so as to be located on the base end side with respect to the third space and sandwiched between the second outer peripheral surface and the second inner peripheral surface, and an upstream end of the gas introduction passage may be disposed between the second seal member and the third seal member in the axial direction.

[0020] According to the third aspect, the second seal member and the third seal member are disposed on both sides of the first space in the axial direction, and the first seal member and the fourth seal member are disposed on further both sides thereof. With this layout, a double seal structure for the first space using four seal members can be realized.

[0021] Furthermore, by partitioning a second space between the first and second sealing members and partitioning a third space between the third and fourth sealing members, in addition to a double seal structure for the first space, a seal structure for sealing each of the second space and the third space can be simultaneously realized.

[0022] Furthermore, according to a fourth aspect of the present disclosure, the first and second sealing members may be mounted in recesses provided in the first outer peripheral surface, the third and fourth sealing members may be mounted in recesses provided in the second outer peripheral surface, the second space may be defined by a groove provided in the first inner peripheral surface and the first outer peripheral surface facing the groove, and the third space may be defined by a groove provided in the second inner peripheral surface and the second outer peripheral surface facing the groove.

[0023] Consider a configuration in which the third outer peripheral surface and the third inner peripheral surface are not provided, the first outer peripheral surface and the second outer peripheral surface are made to have the same diameter, and the first inner peripheral surface and the second inner peripheral surface are made to have the same diameter. If such a configuration is adopted, the seal member attached to the first outer peripheral surface of the gas injection valve will rub against both the second inner peripheral surface and the first inner peripheral surface when the gas injection valve is inserted into the block body. In this case, when the seal member rubs against the second inner peripheral surface, the particular concern is the rub between the seal member and the groove provided in the second inner peripheral surface.

[0024] In contrast, according to the fourth aspect, when the gas injection valve is inserted into the block body, the seal member attached to the first outer peripheral surface of the gas injection valve and the second inner peripheral surface, and further the groove provided on the second inner peripheral surface, can be prevented from contacting each other, which is advantageous in preventing damage to the seal member due to the contact.

[0025] According to a fifth aspect of the present disclosure, the gas fuel may be hydrogen gas, and an upstream end of the gas introduction passage may open perpendicularly to the first outer circumferential surface.

[0026] According to the fifth aspect, the opening area can be reduced as much as possible, for example, compared to when the upstream end is opened at an angle. Reducing this opening area is effective in narrowing the gap between the second seal member and the third seal member in the axial direction. Narrowing this gap contributes to reducing the volume of the first space. Reducing the volume of the first space reduces the amount of hydrogen gas that can accumulate in the space, which is advantageous in further improving safety. In this way, the gas injection valve according to the fifth aspect has a structure suitable for use when hydrogen gas is used as the gas fuel.

[0027] According to a sixth aspect of the present disclosure, an upstream end of the gas introduction passage may open into a boundary between the first outer circumferential surface and the third outer circumferential surface.

[0028] According to the sixth aspect, by opening the upstream end portion at the boundary portion, the distance between the second seal member and the third seal member in the axial direction can be narrowed, compared to a configuration in which the upstream end portion opens at the tip portion of the first outer peripheral surface, for example. This makes it possible to reduce the volume of the first space and the amount of hydrogen gas that can accumulate in the space. This is further advantageous in terms of further improving safety.

[0029] According to a seventh aspect of the present disclosure, the gas fuel is hydrogen gas, the block body is made of solid steel, the block body has a lower surface attached to an upper surface of the cylinder cover and an insertion hole through which the gas injection valve is inserted, the second gas supply passage has an upstream end opening to the lower surface and a downstream end opening to an inner circumferential surface of the insertion hole, the upstream end being disposed outer than the downstream end in a radial direction perpendicular to an axial direction of the gas injection valve, and the second gas supply passage further has a first portion extending upward from the upstream end, and a second portion continuing from the first portion and extending obliquely inward in the radial direction as it extends upward in a height direction to reach the downstream end.

[0030] When using solid steel material, it is usually considered to process the second gas supply passage by combining a through hole extending in the axial direction and a through hole extending in the radial direction. However, when such through holes are provided in two directions, so-called waste holes are generated, and it is required to block the waste holes with a seal plug or the like. However, using a seal plug is inconvenient because it invites hydrogen gas leakage and hydrogen embrittlement due to hydrogen gas accumulated in the blocked part by the seal plug.

[0031] In contrast, the second gas supply path according to the seventh aspect has a second portion that extends obliquely, which makes it possible to configure the second gas supply path without using a waste hole and therefore a seal plug, which contributes to suppressing hydrogen gas leakage and hydrogen embrittlement.

[0032] According to an eighth aspect of the present disclosure, a dimension of the second portion in a flow direction of the gas fuel may be longer than a dimension of the first portion in the flow direction.

[0033] According to the eighth aspect, by making the dimension of the second portion relatively longer than that of the first portion, the second gas supply passage can be extended obliquely longer. By extending the second gas supply passage obliquely longer, it is possible to smoothly guide hydrogen gas to the downstream end of the second gas supply passage and, ultimately, to the gas injector without retaining hydrogen gas in the middle of the second gas supply passage. Effect of the Invention

[0034] As described above, according to the present disclosure, in a gas engine, damage to a sealing member caused by heat can be suppressed while a gas supply passage is provided inside a cylinder cover. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a side view illustrating an example of the overall configuration of a gas engine. [Diagram 2]FIG. 2 is a schematic diagram illustrating the configuration of a gas engine. [Diagram 3] FIG. 3 is a cross-sectional view that illustrates a schematic example of an upper structure of a gas engine. [Figure 4] FIG. 4 is a perspective view illustrating an example of the peripheral configuration of the cylinder cover. [Diagram 5] FIG. 5 is a plan view illustrating the peripheral configuration of the cylinder cover. [Figure 6] FIG. 6 is a front view illustrating the peripheral configuration of the cylinder cover. [Figure 7] FIG. 7 is a cross-sectional view taken along line AA in FIG. [Figure 8] FIG. 8 is a vertical cross-sectional view illustrating the configuration of a gas injection valve. [Figure 9] FIG. 9 is an enlarged view of the enclosed area XI in FIG. [Figure 10] FIG. 10 is a perspective view illustrating the configuration of the block body. [Figure 11] FIG. 11 is a vertical cross-sectional view illustrating the configuration of the block body. [Figure 12] FIG. 12 is a cross-sectional view taken along line BB of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The following description is an example. Fig. 1 is a side view illustrating an example of the overall configuration of a gas engine (hereinafter, also simply referred to as "engine") 1, Fig. 2 is a schematic diagram illustrating the configuration of the engine 1, and Fig. 3 is a cross-sectional view illustrating a schematic example of an upper structure of the engine 1.

[0037] <Overall composition> The engine 1 is a gas engine capable of burning gas fuel in its cylinder 16. In particular, in this embodiment, the gas fuel is hydrogen gas. The gas fuel is not limited to hydrogen gas. Other gas fuels, such as methane gas, may be used. The engine 1 may be one that burns only the gas fuel, or one that burns the gas fuel in combination with other oil fuel (for example, a mixture of hydrogen gas and heavy oil).

[0038] The engine 1 is configured as a uniflow scavenging two-stroke one-cycle engine, and is installed on large ships such as tankers, container ships, and car carriers. The engine 1 is used as the main engine for propelling the ship on which it is installed. The output shaft of the engine 1 is connected to a propeller (not shown) of the ship via a propeller shaft (not shown). When the engine 1 is operating, its output is transmitted to the propeller, propelling the ship.

[0039] <Main engine components> 1 to 3, the engine 1 includes an engine body 10 having the above-mentioned cylinders 16, and a gas supply system 3. Each cylinder 16 defines a combustion chamber 17 for combusting gas fuel.

[0040] 1, a plurality of cylinders 16 (six in this embodiment) are provided so as to be aligned in a predetermined direction. Hereinafter, the alignment direction of the cylinders 16 is referred to as the front-rear direction or first direction, and the direction perpendicular to the front-rear direction and a piston axis Op (the central axis of the piston 21 inserted in each cylinder 16) illustrated in FIG. 3 is referred to as the left-right direction or second direction.

[0041] (1) Engine body 10 As described above, the engine body 10 has a plurality of cylinders 16. The engine body 10 is a two-stroke engine and is installed in the engine room of the ship. The following description is common to all six cylinders 16 unless otherwise specified.

[0042] As shown in Fig. 2, the engine body 10 according to this embodiment is configured as a so-called crosshead type internal combustion engine in order to realize a long stroke. That is, in this engine body 10, a piston rod 22 that supports a piston 21 from below and a connecting rod 24 that is connected to a crankshaft 23 are connected by a crosshead 25.

[0043] Specifically, the engine body 10 includes a bed plate 11 located below, a frame 12 provided on the bed plate 11, a cylinder jacket 13 provided on the frame 12, a cylinder liner 14, and a cylinder cover 15. Each cylinder 16 is provided within the cylinder jacket 13. The engine body 10 also includes a piston 21 that is disposed within the cylinder 16 and reciprocates within the cylinder 16, and an output shaft (e.g., a crankshaft 23) that rotates in conjunction with the reciprocating motion.

[0044] Here, the base plate 11 constitutes the crankcase of the engine 1, and houses the 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.

[0045] The crosshead 25 is disposed between a pair of guide plates 28, and slides up and down along each of the guide plates 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 so as to move up and down integrally therewith, and is connected to the connecting rod 24 so as to rotate the connecting rod 24 about the upper end of the connecting rod 24 as a fulcrum.

[0046] The cylinder jacket 13 supports a cylinder liner 14 which is configured as an inner cylinder and which reciprocates a piston 21. More specifically, the above-mentioned piston 21 is disposed inside the cylinder liner 14. The cylinder liner 14 reciprocates the piston 21 in the up and down direction along the inner wall of the cylinder liner 14. The upper end of the cylinder liner 14 is open.

[0047] Furthermore, the cylinder cover 15 is fixed to the upper end of the cylinder liner 14. The cylinder cover 15, together with the cylinder liner 14, constitutes a cylinder 16. The cylinder cover 15 closes the upper end of the cylinder liner 14, thereby serving as a lid for the cylinder 16.

[0048] In addition, the cylinder cover 15 is provided with an exhaust valve 18 that is operated by a valve train (not shown). The exhaust valve 18, together with a cylinder 16 formed by the cylinder liner 14 and the cylinder cover 15, and the top surface of a piston 21, defines a combustion chamber 17. The exhaust valve 18 opens and closes between the combustion chamber 17 and an exhaust pipe 19. The exhaust pipe 19 has an exhaust port that communicates with the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

[0049] 2 and 3, the cylinder cover 15 is provided with one or more gas injection valves 5 for supplying hydrogen gas to the combustion chamber 17. The gas injection valve 5 is provided with an injection port 5a for injecting hydrogen gas into the cylinder 16.

[0050] In this embodiment, two gas injectors 5 are provided for each cylinder 16, and each is provided in such a position that it faces the interior of the combustion chamber 17. Each gas injector 5 has an injection port 5a at its tip, and is configured to inject hydrogen gas from the injection port 5a. Hereinafter, one of the two gas injectors 5 may be referred to as a "first gas injector 5A" and the other as a "second gas injector 5B."

[0051] 3, one or more block bodies 7 configured separately from the cylinder cover 15 are fixed to the upper surface of the cylinder cover 15. As shown in FIGS. 4 to 6 described later, the block bodies 7 according to this embodiment are provided in the same number as the gas injection valves 5 (i.e., two in this embodiment), and the corresponding gas injection valves 5 are inserted into each of them. Hereinafter, of the two block bodies 7, one into which the first gas injection valve 5A is inserted may be referred to as the "first block body 7A," and the other into which the second gas injection valve 5B is inserted may be referred to as the "second block body 7B."

[0052] 3, each gas injection valve 5 is connected to a gas supply system 3. Hydrogen gas is supplied from the gas supply system 3 to each gas injection valve 5 through first and second gas supply passages 32 and 33 described below. When each gas injection valve 30 is opened while hydrogen gas is being supplied, hydrogen gas is supplied into the combustion chamber 17.

[0053] Each gas injection valve 5 supplies hydrogen gas to the combustion chamber 17, causing combustion in the combustion chamber 17. The combustion causes a piston 21 to reciprocate up and down. When the exhaust valve 18 operates to open the combustion chamber 17, exhaust gas generated by the combustion is pushed out into the exhaust pipe 19, and gas is introduced into the combustion chamber 17 from a scavenging port (not shown).

[0054] When the piston 21 reciprocates due to combustion, the piston rod 22 reciprocates up and down together with the piston 21. This causes the crosshead 25 connected to the piston rod 22 to reciprocate up and down. This crosshead 25 allows the connecting rod 24 to rotate, and rotates the connecting rod 24 around the connection point with the crosshead 25 as a fulcrum. Then, the crank 27 connected to the lower end of the connecting rod 24 performs crank motion, and the crankshaft 23 rotates in response to this crank motion. In this way, the crankshaft 23 converts the reciprocating motion of the piston 21 into rotational motion, and rotates the propeller of the ship together with the propeller shaft. This propels the ship.

[0055] (2) Gas supply system 3 3, the gas supply system 3 includes a gas supply module 31, gas supply paths 32 and 33, a gas gate valve (GGV) 34, and a gas pipe 39. In addition, the engine 1 according to this embodiment further includes seal members 62 and 63 as members related to the supply of hydrogen gas.

[0056] Of these, the gas supply module 31 has a hydrogen tank 31a and a gas valve train (GVT) 31b.

[0057] The hydrogen tank 31a stores hydrogen gas. The hydrogen gas stored in the hydrogen tank 31a is adjusted to an appropriate temperature by a temperature adjustment mechanism (not shown) when a pump (not shown) is operated, and then supplied to the GVT 31b.

[0058] The GVT 31b has various pipes (not shown) and solenoid valves (not shown) that open and close each pipe. Each solenoid valve of the GVT 31b is electrically connected to the controller 100 and operates according to a control signal input from the controller 100. The GVT 31b is connected to the gas supply paths 32 and 33 via a gas pipe 39. The supply of hydrogen gas to the gas supply paths 32 and 33 and thus to each gas injection valve 5 is controlled by the GVT 31b opening and closing each solenoid valve.

[0059] The gas supply passages 32, 33 are connected to the gas injection valve 5 and supply hydrogen gas to the gas injection valve 5. The above-mentioned sealing members 62, 63 seal between the gas supply passages 32, 33 and the gas injection valve 5.

[0060] More specifically, the gas supply passages 32, 33 are respectively a first gas supply passage 32 defined inside the cylinder cover 15 and a second gas supply passage 33 defined inside the block body 7 and connecting the first gas supply passage 32 to the gas injection valve 5.

[0061] The first gas supply path 32 connects the downstream end of the gas pipe 39 and the upstream end of the second gas supply path 33. A gas gate valve 34 that opens and closes the first gas supply path 32 is disposed in the middle of the first gas supply path 32. The gas gate valve 34 is configured to block the flow of hydrogen gas in the first gas supply path 32 by operating in response to the hydraulic pressure of the hydraulic oil.

[0062] The second gas supply path 33 connects the downstream end of the first gas supply path 32 to a first internal flow path 57 serving as a gas introduction path. As described later, the second gas supply path 33 is composed of a flow path connected to the first gas injection valve 5A and a flow path connected to the second gas injection valve 5B. To be connected to these flow paths, the first gas supply path 32 branches into two flow paths (see reference numerals 32a and 32b in FIG. 5) midway.

[0063] <Cylinder cover peripheral configuration> In the engine 1 of this embodiment, the sealing members 62, 63 are provided not between the cylinder cover 15 and the gas injection valve 5, as shown in FIG. 3, but at the connection portion between the second gas supply passage 33 and the gas injection valve 5 (in other words, the connection portion between the block body 7 and the gas injection valve 5).

[0064] Hereinafter, a detailed description will be given of the cylinder cover 15, the gas injection valves 5, and the block body 7 according to this embodiment. Note that the following description is common to each of the multiple cylinders 16 and each of the first and second gas injection valves 5A, 5B unless otherwise specified.

[0065] (1) Specific configuration of cylinder cover 15 FIG. 4 is a perspective view illustrating the peripheral configuration of the cylinder cover 15, FIG. 5 is a plan view illustrating the peripheral configuration of the cylinder cover 15, and FIG. 6 is a front view illustrating the peripheral configuration of the cylinder cover 15.

[0066] As shown in Figures 4 to 6, the cylinder cover 15 is formed of a thick metal block having a flat top surface 15a along the front-rear and left-right directions. The cylinder cover 15 has a plurality of (six in the illustrated example) cover fastening holes 15b and a plurality of (four in the illustrated example) exhaust valve fastening holes 15c. The plurality of cover fastening holes 15b and the exhaust valve fastening holes 15c all open to the top surface 15a.

[0067] Further, a through hole 15d is formed in the center of the cylinder cover 15, which is coaxial with the central axis Op of the piston 21. This through hole 15d has a circular cross section and penetrates the cylinder cover 15 in the thickness direction.

[0068] Here, fasteners (e.g., bolts) for fastening the cylinder cover 15 to the cylinder liner 14 are inserted into the cover fastening holes 15b. The cover fastening holes 15b are arranged at equal intervals along the circumferential direction about the central axis Op. Each cover fastening hole 15b penetrates the cylinder cover 15 in the thickness direction (up-down direction).

[0069] Meanwhile, fasteners (e.g., bolts) for fastening the exhaust valves 18 to the cylinder cover 15 are inserted into the exhaust valve fastening holes 15c. The exhaust valve fastening holes 15c are arranged at equal intervals along the circumferential direction. Each exhaust valve fastening hole 15c is arranged on the inner side (radially inner side) of each cover fastening hole 15b and on the outer side (radially outer side) of the through hole 15d in a radial direction perpendicular to the central axis Op.

[0070] Moreover, the cylinder cover 15 has an asymmetric shape in the left-right direction. Specifically, the cylinder cover 15 has a semicircular portion 151 protruding to one side (right side) in the left-right direction, and a flange portion 152 protruding to the other side (left side) in the left-right direction. The semicircular portion 151 has a right side surface that is curved in a semicircular shape. The central axis (center of the arc) of the semicircle on the right side surface approximately coincides with the piston axis Op.

[0071] On the other hand, the flange portion 152 protrudes outward from the plurality of cover fastening holes 15b in the radial direction. The plurality of cover fastening holes 15b and the plurality of exhaust valve fastening holes 15c open into the semicircular portion 151.

[0072] The gas gate valve 34 is adapted to be inserted into the upper surface of the flange portion 152. The first gas supply path 32, which is opened and closed by the gas gate valve 34, is defined inside the flange portion 152 and the semicircular portion 151, as shown by the dashed lines in Fig. 5. The first gas supply path 32 branches into two flow paths 32a and 32b starting from the insertion point of the gas gate valve 34 in the flange portion 152, and each of the flow paths extends toward the semicircular portion 151.

[0073] In addition, the upper surface 15a of the cylinder cover 15 is provided with a first mounting surface 153A on which a first block body 7A supporting the first gas injection valve 5A is placed, and a second mounting surface 153B on which a second block body 7B supporting the second gas injection valve 5B is placed.

[0074] As shown in Fig. 6, the first and second mounting surfaces 153A, 153B each extend in a radial direction so as to incline downward as they move away from the piston axis Op. As shown in the figure, the first mounting surface 153A and the second mounting surface 153B are formed to be substantially symmetrical with respect to the piston axis Op.

[0075] 5, a downstream end of one (flow path 32a) of the flow paths constituting the first gas supply path 32 is opened in the bottom surface (inclined surface) of the first mounting surface 153A. In this bottom surface, an insertion hole 154 for inserting the tip of the first gas injection valve 5A is also opened, as shown in Fig. 6. This insertion hole 154 is a hole with a bottom and a circular cross section that extends along the central axis (valve axis Ov described later) of the first gas injection valve 5A.

[0076] Similarly, the downstream end of the other one of the flow paths (flow path 32b) constituting the first gas supply path 32 is open to the bottom surface (inclined surface) of the second mounting surface 153B. An insertion hole 154 for inserting the tip of the second gas injection valve 5B is also open to this bottom surface. The insertion hole 154 is a hole that extends along the valve axis Ov and has a bottom and a circular cross section.

[0077] As shown by the broken line Lx in Fig. 5, the arrangement direction of the first gas injection valve 5A and the second gas injection valve 5B is inclined with respect to the front-rear direction in a plan view. This inclination angle is set to, for example, 1.0° or more and 6.0° or less, more specifically, 2.0° or more and 5.0° or less, and more specifically, 3.0° or more and 4.0° or less. By inclining in this manner, it is possible to ensure the thickness of the cooling passage arranged in the cylinder cover 15 while suppressing interference between the first and second gas injection valves 5A and 5B and other valve members. Note that the "other valve members" referred to here include valve members that can be attached to the cylinder cover 15, such as a fuel oil injection valve (FOV) and a gas injection valve for premixing.

[0078] As described above, the first block body 7A is placed on the first mounting surface 153A and the first gas injection valve 5A is supported by the first block body 7A. On the other hand, the second block body 7B is placed on the second mounting surface 153B and the second gas injection valve 5B is supported by the second block body 7B.

[0079] 4 to 6, that is, the second block body 7B and the second gas injection valve 5B will be described in detail below. The following description is substantially the same as the description of the first block body 7A and the first gas injection valve 5A.

[0080] (2) Specific configurations of block body 7 and gas injection valve 5 Fig. 7 is a cross-sectional view taken along line AA in Fig. 5, and Fig. 8 is a vertical cross-sectional view illustrating the configuration of the gas injection valve 5. Fig. 9 is an enlarged view of the enclosed area XI in Fig. 7, and Fig. 12 is a cross-sectional view taken along line BB in Fig. 7. Fig. 10 is a perspective view illustrating the configuration of the block body 7, and Fig. 11 is a vertical cross-sectional view illustrating the configuration of the block body 7.

[0081] 7 and 8, the gas injection valve 5 includes a cylindrical body 50 and a valve stem 54 housed in the cylindrical body 50. The gas injection valve 5 is configured to inject hydrogen gas from an injection port 5a provided at the tip of the valve stem 54 by opening the valve stem 54 against a spring force.

[0082] In the following description, instead of various definitions based on the piston axis Op, the direction along the central axis (hereinafter also referred to as the "valve axis") Ov of the valve shaft 54 ​​illustrated in Figures 6 to 8 will be referred to as the "valve axial direction" or simply as the "axial direction." The direction extending radially from the valve axis Ov will be referred to as the "radial direction," and the clockwise and counterclockwise directions around the valve axis Ov will be referred to as the "circumferential direction."

[0083] The radial direction is perpendicular to the valve axis direction. In addition, in the radial direction, one side closer to the valve axis Ov may be referred to as the "inner side," and the other side farther away from the valve axis Ov may be referred to as the "outer side."

[0084] In addition, the tip side of the gas injection valve 5 in the valve axial direction (the side of the injection port 5a in the same direction, and the lower side of the paper in Figures 7 and 8) may simply be referred to as the "tip side", and the base side of the gas injection valve 5 in the valve axial direction (the side opposite the injection port 5a in the same direction, and the upper side of the paper in Figures 7 and 8) may simply be referred to as the "base side".

[0085] Specifically, the gas injection valve 5 according to this embodiment includes, in addition to the cylindrical body 50 and the valve shaft 54 ​​described above, a biasing member 55, an oil chamber 56, and a first internal flow passage 57.

[0086] Of these, the cylindrical body 50 has, in order from the base end side in the valve axial direction, a first body portion 51 for accommodating a biasing member 55, a second body portion 52 for accommodating a valve shaft 54, and a third body portion 53 in which an injection port 5a is provided.

[0087] As shown in Fig. 7, the first body portion 51 is formed into a cylindrical shape with a bottom surface at its base end and an open end at its tip end, and houses a biasing member 55 made of a compression coil spring or the like. As shown in Fig. 7, the biasing member 55 presses the base end of the valve shaft 54, biasing it toward the tip end in the valve axial direction.

[0088] 6, the base end of the first body portion 51 forms a flange portion 51a that is partially enlarged in diameter. As shown in the figure, a first fastener 81 such as a bolt is inserted into this flange portion 51a. The insertion direction of the first fastener 81 is set to be parallel to the valve axial direction.

[0089] 7 and 8, the third body portion 53 is formed in a generally cylindrical shape with its base end side open. The generally cylindrical hollow portion forms a second internal flow path 53a extending along the valve axial direction. The second internal flow path 53a is opened and closed by the tip of the valve stem 54. The aforementioned injection port 5a is connected to the downstream end (tip) of the second internal flow path 53a.

[0090] In this embodiment, the third body portion 53 is laid out so as to be embedded in the insertion hole 154. This insertion hole 154 is formed with a through hole penetrating the cylinder cover 15, particularly the semicircular portion 151 thereof, and the injection port 5a is exposed to the inside of the combustion chamber 17 through the through hole.

[0091] 7 and 8, the second body portion 52 is formed in a generally cylindrical shape with its tip and base ends open. A valve stem 54 is inserted into the generally cylindrical hollow portion.

[0092] Here, the tip end of the first body part 51 is attached to the opening on the base end side of the second body part 52. By this attachment, the base end of the valve shaft 54 ​​is pressed by the tip of the biasing member 55.

[0093] The base end of the third body portion 53 is inserted into the opening on the tip side of the second body portion 52. This insertion causes the tip of the valve shaft 54 ​​to abut against or be separated from the upstream end (base end) of the second internal flow path 53a.

[0094] Furthermore, in the hollow portion of the second body portion 52 (the hollow portion into which the valve stem 54 is inserted), a portion in the valve axial direction is made larger in diameter than the outer circumferential surface of the valve stem 54. An oil chamber 56 to which hydraulic oil is supplied is defined by the inner circumferential surface of this larger diameter portion and the outer circumferential surface of the valve stem 54. By increasing the hydraulic pressure in the oil chamber 56, the force acting on the larger diameter portion of the valve stem 54 is utilized to move the valve stem 54 upward. By moving the valve stem 54 upward, the second internal flow path 53a can be opened.

[0095] The second body portion 52 is configured such that its tip end portion is embedded in the insertion hole 154 and its base end portion is exposed from the insertion hole 154 and inserted into the block body 7. The above-mentioned first internal flow passage 57 in the gas injection valve 5 opens to the outer circumferential surface of the latter of the tip and base end portions of the second body portion 52.

[0096] More specifically, the first internal flow passage 57 is configured to open to the outer circumferential surface of the gas injection valve 5 (particularly, the outer circumferential surface of the base end side portion of the second body portion 52) and to connect the second gas supply passage 33 to the injection port 5a. Note that the outer circumferential surface here does not refer to an end surface perpendicular to the valve axial direction, but to a side surface extending along the valve axial direction. The outer circumferential surface of the gas injection valve 5 faces radially outward.

[0097] More specifically, the outer peripheral surface of the second body portion 52 has, in order from the tip side in the valve axial direction, a first outer peripheral surface 52a, a third outer peripheral surface 52c, and a second outer peripheral surface 52b. The first outer peripheral surface 52a extends along the valve axial direction. The second outer peripheral surface 52b is disposed on the base end side of the first outer peripheral surface 52a, has a larger diameter than the first outer peripheral surface 52a, and extends along the valve axial direction. The third outer peripheral surface 52c is disposed between the first outer peripheral surface 52a and the second outer peripheral surface 52b in the valve axial direction. The third outer peripheral surface 52c is configured by a step or a slope (a slope in the illustrated example) that connects the first outer peripheral surface 52a and the second outer peripheral surface 52b.

[0098] The first outer surface 52a has a circular cross section and is configured so that its tip portion (section Lt in FIG. 8) is embedded in the insertion hole 154 and its base portion (section Lp in FIG. 8) is exposed from the insertion hole 154 and inserted into the block body 7.

[0099] 8, the tip end portion of the first outer circumferential surface 52a is provided with a first recessed portion 50a and a second recessed portion 50b. The first recessed portion 50a is formed as a groove extending over the entire circumferential direction. The second recessed portion 50b is disposed closer to the base end than the first recessed portion 50a and is formed as a groove extending over the entire circumferential direction.

[0100] The second outer surface 52b has a circular cross-section with a larger diameter (larger dimension in the radial direction) than the first outer surface 52a, and is configured so that its entire length from the tip to the base end is exposed from the insertion hole 154 and is inserted into the block body 7.

[0101] 8, the second outer peripheral surface 52b is provided with a third recessed portion 50c and a fourth recessed portion 50d. The third recessed portion 50c extends in the circumferential direction and is formed as a groove having a larger diameter than the first and second recessed portions 50a and 50b. The fourth recessed portion 50d is disposed closer to the base end side than the third recessed portion 50c, extends in the circumferential direction, and is formed as a groove having the same diameter as the third recessed portion 50c.

[0102] The third outer peripheral surface 52c has a circular cross section that gradually reduces in diameter from the base end side to the tip end side, and is configured so that its entire portion from the tip to the base end is exposed from the insertion hole 154 and positioned inside the block body 7.

[0103] 8, the upstream end of the first internal flow passage 57 opens at the boundary between the first outer peripheral surface 52a and the third outer peripheral surface 52c. In this embodiment, the first internal flow passage 57 opens at the base end (upper end on the paper) of the first outer peripheral surface 52a. The upstream end of the first internal flow passage 57 opens perpendicularly to the first outer peripheral surface 52a. The first internal flow passages 57 are provided at approximately 90 degree intervals along the circumferential direction as shown in FIG. 12.

[0104] Specifically, the first internal flow passage 57 has, in order from the upstream side, an upstream passage 57a and a downstream passage 57b. The upstream passage 57a opens at a base end (upper end on the paper) of the first outer circumferential surface 52a and extends from the base end toward the inside in the radial direction. The upstream passage 57a includes the upstream end of the first internal flow passage 57. The downstream passage 57b extends continuously from the upstream passage 57a and extends obliquely toward the second internal flow passage 53a.

[0105] 8 and other figures, four seal members 61 to 64 are attached to the outer circumferential surface of the gas injection valve 5. Specifically, the four seal members 61 to 64 are configured, in order from the tip end side to the base end side of the gas injection valve 5, by a first seal member 61 and a second seal member 62 attached to the first outer circumferential surface 52a, and a third seal member 63 and a fourth seal member 64 attached to the second outer circumferential surface 52b.

[0106] In detail, a first seal member 61 is attached to the first recessed portion 50a, a second seal member 62 is attached to the second recessed portion 50b, a third seal member 63 is attached to the third recessed portion 50c, and a fourth seal member 64 is attached to the fourth recessed portion 50d. The first seal member 61 to the fourth seal member 64 are all constituted by O-rings extending in the circumferential direction.

[0107] 10 and other drawings, the block body 7 has a rectangular section 70 formed in a substantially rectangular shape. The block body 7 is provided with insertion holes 74 through which the corresponding gas injection valves 5 are inserted. In this embodiment, the rectangular section 70 of the block body 7 is made of a solid steel material (e.g., forged steel material).

[0108] In detail, the rectangular portion 70 in this embodiment has a front surface 70f facing approximately forward, a rear surface 70b facing approximately rearward, a left surface 70l facing approximately left, a right surface 70r facing approximately right, an upper surface 70t facing approximately upward, and a lower surface 70u facing approximately downward.

[0109] The insertion hole 74 provided in the block body 7 is formed as a through hole extending from the upper surface 70t to the lower surface 70u, and is laterally surrounded by the front surface 70f, the rear surface 70b, the left surface 70l, and the right surface 70r.

[0110] Specifically, as shown in each drawing such as FIG. 9, the inner peripheral surface of the insertion hole 74 has a first inner peripheral surface 74a, a third inner peripheral surface 74c, and a second inner peripheral surface 74b in order from the tip side in the valve axial direction. The first inner peripheral surface 74a extends along the valve axial direction and is inscribed in the first outer peripheral surface 52a of the gas injection valve 5. The second inner peripheral surface 74b extends along the valve axial direction like the first inner peripheral surface 74a. The second inner peripheral surface 74b is also disposed on the base end side of the first inner peripheral surface 74a, has a larger diameter than the first inner peripheral surface 74a, and is inscribed in the second outer peripheral surface 52b. The third inner peripheral surface 74c is disposed between the first inner peripheral surface 74a and the second inner peripheral surface 74b in the valve axial direction. The third inner peripheral surface 74c is constituted by a step or a slope (a slope in the drawing) connecting the first inner peripheral surface 74a and the second inner peripheral surface 74b. The inner circumferential surface of the insertion hole 74 faces radially inward.

[0111] 9 and 10, the first inner circumferential surface 74a is provided with a first groove portion 77 extending in the circumferential direction along the first inner circumferential surface 74a. The dimension of the first groove portion 77 in the axial direction is at least narrower than the distance between the first recessed portion 50a and the second recessed portion 50b (in other words, the distance between the first seal member 61 and the second seal member 62).

[0112] 9 and 10, the second inner circumferential surface 74b is provided with a second groove portion 78 extending circumferentially along the second inner circumferential surface 74b. The dimension of the second groove portion 78 in the axial direction is at least narrower than the distance between the third recessed portion 50c and the fourth recessed portion 50d (in other words, the distance between the third seal member 63 and the fourth seal member 64).

[0113] The lower surface 70u of the block body 7 is adapted to be attached to the upper surface of the cylinder cover 15, particularly to the first or second attachment surface 153A or 153B described above. The second gas supply passage 33 described above opens to the lower surface 70u and the insertion hole 74 of the block body 7.

[0114] That is, the second gas supply passage 33 according to this embodiment has an upstream end 33a that opens into the lower surface 70u of the block body 7, and a downstream end 33b that opens into the inner circumferential surface of the insertion hole 74 (particularly, the boundary between the second inner circumferential surface 74b and the third inner circumferential surface 74c). At least a portion of the second gas supply passage 33 extends obliquely with respect to the valve axial direction from the upstream end 33a side toward the downstream end 33b.

[0115] Particularly in this embodiment, the upstream end 33a is disposed radially outwardly of the downstream end 33b (left-right direction on the paper in FIG. 11). In detail, the upstream end 33a opens to the lower surface 70u radially outwardly of the insertion hole 74 and the downstream end 33b and radially inwardly of the second fastening hole 73, as shown in FIG.

[0116] The downstream end 33b opens to the second or third inner circumferential surface 74b, 74c of the inner circumferential surface of the block body 7. More specifically, the downstream end 33b opens to the boundary between the second inner circumferential surface 74b and the third inner circumferential surface 74c. In this embodiment, the downstream end 33b opens to the tip end portion (the lower end portion on the paper surface) of the second inner circumferential surface 74b. The downstream end 33b opens obliquely with respect to the second inner circumferential surface 74b.

[0117] More specifically, the second gas supply passage 33 has a first portion 75 extending upward in the height direction from the upstream end 33a, and a second portion 76 continuing from the first portion 75 and extending obliquely radially inward as it extends upward to reach the downstream end 33b. Note that the "height direction" here refers to the up-down direction shown in Figures 3 to 6. In this embodiment, "upward" generally corresponds to the direction toward the base end side in the valve axial direction.

[0118] 11, the dimension L2 of the second portion 76 in the flow direction of the hydrogen gas is longer than the dimension L1 of the first portion 75 in the flow direction. Note that the "flow direction of the hydrogen gas" here refers to the direction in which the hydrogen gas flows from the upstream end 33a to the downstream end 33b of the second gas supply path 33. In this embodiment, this flow direction is bent at the boundary between the first portion 75 and the second portion 76.

[0119] As shown in FIGS. 10 to 12, the block body 7 has a pair of first fastening holes 72 on the upper surface 70u of its rectangular portion 70, and second fastening holes 73 arranged at the four corners of the upper surface 70t.

[0120] The first fastening hole 72 is a fastening hole for fastening the gas injection valve 5 to the block body 7, and is adapted to receive the above-mentioned first fastener 81. The first fastening hole 72 does not penetrate the block body 7 in the thickness direction. That is, the inner bottom of the first fastening hole 72 is partitioned inside the block body 7 as shown in Figures 10 and 11.

[0121] The second fastening hole 73 is a fastening hole for fastening the block body 7 to the upper surface 15a of the cylinder cover 15, and is adapted to receive a second fastener 82 such as a bolt. The second fastening hole 73 penetrates the block body 7 in the thickness direction. That is, the inner bottom of the second fastening hole 73 is defined inside the cylinder cover 15, although not shown in the figure.

[0122] 10, the second fastening hole 73 is disposed radially outward of the first fastening hole 72. The first and second fastening holes 73 both extend along the valve axial direction. The gas injection valve 5 is fastened to the block body 7 by the first fastening hole 72 and the first fastener 81, and the block body 7 is fastened to the cylinder cover 15 by the second fastening hole 73 and the second fastener 82.

[0123] 9, in a state in which the gas injector 5 is fastened to the block body 7, the third outer peripheral surface 52c of the gas injector 5 and the third inner peripheral surface 74c of the block body 7 face each other with a gap in the axial or radial direction (axial direction in the illustrated example). As shown in Fig. 9 and Fig. 12, this gap defines a first space S1 through which hydrogen gas flows in the circumferential direction about the central axis Ov of the gas injector 5.

[0124] More specifically, as shown in FIG. 9, the first space S1 is surrounded by the base end (upper end on the paper) of the first outer peripheral surface 52a, the third outer peripheral surface 52c, the tip end (lower end on the paper) of the second inner peripheral surface 74b, and the third inner peripheral surface 74c, forming a ring-shaped space as shown in FIG. 12.

[0125] As described above, the first internal flow passage 57 opens at the base end of the first outer peripheral surface 52a. That is, the first internal flow passage 57 as a gas introduction passage opens so as to communicate with the first space S1 (see FIG. 12). Similarly, the second gas supply passage 33 opens at the tip end of the second inner peripheral surface 74b as described above. That is, the second gas supply passage 33 also opens so as to communicate with the first space S1 (see FIG. 9).

[0126] The first space S1 functions as a connection portion between the second gas supply passage 33 and the gas injection valve 5, that is, a so-called "gas reservoir." The seal members 62, 63 according to this embodiment are provided in the first space S1 serving as the connection portion, and are provided on at least the first outer circumferential surface 52a so as to suppress gas leakage through the first space S1.

[0127] In this embodiment, of the first sealing member 61 to the fourth sealing member 64 described above, the second sealing member 62 and the third sealing member 63 correspond to sealing members for directly sealing the first space S1, and the first sealing member 61 and the fourth sealing member 64 correspond to sealing members for doubly sealing the first space S1.

[0128] As described above, the first seal member 61 and the second seal member 62 are provided on the first outer peripheral surface 52a, and the third seal member 63 and the fourth seal member 64 are provided on the second outer peripheral surface 52b. In order to realize a double seal structure on both the tip and base ends in the axial direction, the upstream end (opening) of the first internal flow path 57 is disposed between the second seal member 62 and the third seal member 63 in the axial direction, as shown in FIG.

[0129] Further, a second space S2 and a third space S3 for allowing hydrogen gas leaked from the first space S1 to flow therein and for discharging the hydrogen gas to the outside are defined between the inner peripheral surface of the insertion hole 74 and the outer peripheral surface of the gas injection valve 5. The first space S1, the second space S2, and the third space S3 are all defined as ring-shaped spaces extending in the circumferential direction.

[0130] The second space S2 is defined between the first groove portion 77 of the first inner circumferential surface 74a and the first outer circumferential surface 52a facing the first groove portion 77. The second space S2 is located closer to the tip side than the first space S1, and allows hydrogen gas leaking from the first space S1 to flow into it. The hydrogen gas that has flowed into the second space S2 is discharged via a flow path defined inside the gas injection valve 5, piping (not shown), and the like.

[0131] The third space S3 is defined between the second groove portion 78 of the second inner circumferential surface 74b and the second outer circumferential surface 52b facing the second groove portion 78. The third space S3 is located closer to the base end than the first space S1, and allows hydrogen gas leaking from the first space S1 to flow into it. The hydrogen gas that has flowed into the third space S3 is discharged via a flow path defined inside the gas injection valve 5, piping (not shown), and the like.

[0132] The first seal member 61 to the fourth seal member 64 described above not only form a double seal structure for the first space S1, but also have the function of sealing the second space S2 and the third space S3.

[0133] Specifically, the first seal member 61 is located on the tip side with respect to the second space S2, and is attached to the first outer peripheral surface 52a so as to be sandwiched between the first outer peripheral surface 52a and the first inner peripheral surface 74a.

[0134] Further, the second seal member 62 is located on the base end side with respect to the second space S2, and is attached to the first outer circumferential surface 52a so as to be sandwiched between the first outer circumferential surface 52a and the first inner circumferential surface 74a.

[0135] The third seal member 63 is located on the tip side with respect to the third space S3, and is attached to the second outer circumferential surface 52b so as to be sandwiched between the second outer circumferential surface 52b and the second inner circumferential surface 74b.

[0136] The fourth seal member 64 is located on the base end side with respect to the third space S3, and is attached to the second outer peripheral surface 52b so as to be sandwiched between the second outer peripheral surface 52b and the second inner peripheral surface 74b.

[0137] The first seal member 61 and the second seal member 62 seal the second space S2 in addition to the first space S1. The third seal member 63 and the fourth seal member 64 seal the third space S3 in addition to the first space S1.

[0138] Additionally, a first annular groove 791 and a second annular groove 792 as shown in FIGS. 10 and 11 are provided on the lower surface 70u of the block body 7, particularly on the lower surface 70u around the upstream end 33a of the second gas supply path 33.

[0139] A fifth seal member 65 made of an O-ring or the like is sandwiched between the first annular groove 791 and the upper surface 15a of the cylinder cover 15, particularly the first or second mounting surface 153A, 153B (see Figs. 7 and 9 for the fifth seal member 65). Similarly, a sixth seal member 66 made of an O-ring or the like is sandwiched between the second annular groove 792 and the upper surface 15a of the cylinder cover 15, particularly the first or second mounting surface 153A, 153B (see Figs. 7 and 9 for the sixth seal member 66). The fifth and sixth seal members 65, 66 can seal between the block body 7 and the upper surface 15a of the cylinder cover 15. Specifically, the fifth seal member 65 is fitted in the first annular groove 791 to seal the upstream end 33a opening to the lower surface 70u. Similarly, by fitting the sixth seal member 66 to the second annular groove 792, the upstream end 33a and the insertion hole 77 that opens in the lower surface 70u like the upstream end 33a are sealed. These seal members 65, 66 are disposed on the upper surface of the cylinder cover 15, and therefore are advantageous in suppressing damage caused by heat compared to seal members disposed inside the cylinder cover 15.

[0140] (3) The significance of block number 7 As described above, in this embodiment, the gas injection valve 5 is not directly connected to the first gas supply passage 32 defined within the cylinder cover 15, but is indirectly connected via the block body 7 that is separate from the cylinder cover 15 (see Figures 3, 7, 9, etc.).

[0141] By connecting in this manner, it becomes possible to provide the first seal member 61 to the fourth seal member 64 at the connection portion S1 between the block body 7 and the gas injection valve 5 (the connection portion between the second gas supply passage 33 and the gas injection valve 5) without providing any seal member inside the cylinder cover 15.

[0142] Here, because the block body 7 is disposed on the upper surface of the cylinder cover 15, the first seal member 61 to the fourth seal member 64 can be located farther away from the combustion chamber 17 than in a configuration in which seal members are provided inside the cylinder cover 15. Therefore, by placing the first seal member 61 to the fourth seal member 64 farther away from the combustion chamber 17, damage to the first seal member 61 to the fourth seal member 64 due to heat can be suppressed.

[0143] Thus, according to this embodiment, while providing the first gas supply passage 32 inside the cylinder cover 15, damage to the first seal member 61 to the fourth seal member 64 due to heat can be suppressed.

[0144] Suppose that the third outer peripheral surface 52c and the third inner peripheral surface 74c shown in Fig. 9 and the like are not provided, and the first outer peripheral surface 52a and the second outer peripheral surface 52b have the same diameter, and the first inner peripheral surface 74a and the second inner peripheral surface 74b have the same diameter. If such a configuration is adopted, when the gas injection valve 5 is inserted into the block body 7, the seal members (for example, the first and second seal members 61, 62) attached to the first outer peripheral surface 52a of the gas injection valve 5 will rub against both the second inner peripheral surface 74b and the first inner peripheral surface 74a. In this case, there is a concern that the first and second seal members 61, 62 may be damaged due to wear.

[0145] In contrast, according to this embodiment, as shown in FIG. 11, the second inner circumferential surface 74b has a larger diameter than the first inner circumferential surface 74a. Therefore, when the gas injection valve 5 is inserted into the block body 7, contact between the seal member attached to the first outer circumferential surface 52a of the gas injection valve 5 and the second inner circumferential surface 74b can be suppressed. This makes it possible to suppress damage to the first and second seal members 61, 62 due to the contact. In addition, by making the second outer circumferential surface 52b larger in diameter than the first outer circumferential surface 52a in conjunction with the increase in the diameter of the second inner circumferential surface 74b, it is possible to maintain contact between the inner circumferential surface of the insertion hole 74 and the outer circumferential surface of the gas injection valve 5. This contributes to suppressing leakage of hydrogen gas.

[0146] Furthermore, by partitioning the first space S1 using the third outer peripheral surface 52c and the third inner peripheral surface 74c, a gas reservoir for circumferentially distributing gas fuel can be formed without providing new grooves or the like on the outer peripheral surface of the gas injection valve 5. Normally, a recess process is required to create such a groove, but by making this unnecessary, a special tool for the recess process is also not required. This improves the workability of the engine 1.

[0147] In other words, the third outer peripheral surface 52c and the third inner peripheral surface 74c in this embodiment can simultaneously suppress leakage of hydrogen gas, suppress damage to the first and second seal members 61, 62, allow hydrogen gas to flow in the circumferential direction, and improve the workability of the block body 7.

[0148] 8 and 9, a second seal member 62 and a third seal member 63 are disposed on both sides of the first space S1 in the valve axial direction, and a first seal member 61 and a fourth seal member 64 are disposed on further both sides thereof. With this layout, a double seal structure for the first space S1 by the four seal members 61, 62, 63, and 64 can be realized.

[0149] Furthermore, by partitioning a second space S2 between the first and second sealing members 61, 62 and partitioning a third space S3 between the third and fourth sealing members 63, 64, in addition to the double seal structure for the first space S1, a seal structure for sealing the second space S2 and the third space S3 can be simultaneously realized.

[0150] Let us assume that the third outer peripheral surface 52c and the third inner peripheral surface 74c shown in Fig. 9 and the like are not provided, and the first outer peripheral surface 52a and the second outer peripheral surface 52b have the same diameter, and the first inner peripheral surface 74a and the second inner peripheral surface 74b have the same diameter. If such a configuration is adopted, when the gas injection valve 5 is inserted into the block body 7, the first and second seal members 61, 62 attached to the first outer peripheral surface 52a of the gas injection valve 5 rub against both the second inner peripheral surface 74b and the first inner peripheral surface 74a. In this case, when the first and second seal members 61, 62 rub against the second inner peripheral surface 74b, there is a particular concern about the rub between the first and second seal members 61, 62 and the second groove portion 78 provided in the second inner peripheral surface 74b.

[0151] In contrast, according to this embodiment, when the gas injection valve 5 is inserted into the block body 7, it is possible to suppress contact between the first and second seal members 61, 62 attached to the first outer peripheral surface 52a of the gas injection valve 5 and the second inner peripheral surface 74b, and further the second groove portion 78 provided in the second inner peripheral surface 74b. This is advantageous in suppressing damage to the first and second seal members 61, 62 due to the contact.

[0152] Also, as shown in FIG. 8 and other figures, the upstream end (upstream passage 57a) of the first internal flow passage 57 is opened perpendicularly to the second outer circumferential surface 52b, so that the opening area can be reduced as much as possible, compared to the case where the upstream end is opened at an angle. Reducing the opening area is effective in narrowing the gap between the second seal member 62 and the third seal member 63 in the valve axial direction. Narrowing this gap contributes to reducing the volume of the first space S1. Reducing the volume of the first space S1 reduces the amount of hydrogen gas that can accumulate in the space S1, which is advantageous in further improving safety. In this way, the gas injection valve 5 according to this embodiment has a structure suitable for the case where hydrogen gas is used as the gas fuel.

[0153] 8 and 9, the upstream end (upstream passage 57a) of the first internal flow passage 57 is opened at the boundary between the first outer peripheral surface 52a and the third outer peripheral surface 52c, so that the distance between the second seal member 62 and the third seal member 63 in the valve axial direction can be narrowed compared to a configuration in which the upstream end (upstream passage 57a) is opened at the tip end of the first outer peripheral surface 52a (for example, the boundary between the second body portion 52 and the third body portion 53). This makes it possible to suppress the volume of the first space S1 and to suppress the amount of hydrogen gas that can accumulate in the space S1. This is further advantageous in terms of further improving safety.

[0154] Furthermore, when using solid steel material, it is usually considered to process the second gas supply passage 33 by combining a through hole extending in the valve axial direction and a through hole extending in the radial direction perpendicular thereto. However, when such through holes are provided in two directions, so-called waste holes are generated, and it is required to block the waste holes with a seal plug or the like. However, using a seal plug is inconvenient because it invites hydrogen gas leakage and hydrogen embrittlement due to hydrogen gas accumulated in the blocked portion by the seal plug.

[0155] In contrast, the second gas supply path 33 according to this embodiment has a second portion 76 that extends obliquely, as shown in Fig. 11 etc. This makes it possible to configure the second gas supply path 33 without using a waste hole and therefore a seal plug, which contributes to suppressing hydrogen gas leakage and hydrogen embrittlement.

[0156] 11 and other drawings, the second gas supply path 33 can be extended obliquely longer by making the dimension L2 of the second portion 76 relatively longer than the dimension L1 of the first portion 75. By extending the second gas supply path 33 obliquely longer, it is possible to smoothly guide the hydrogen gas to the downstream end 33b of the second gas supply path 33 and ultimately to the gas injector 5 without the hydrogen gas being retained in a portion of the second gas supply path 33.

[0157] <Other embodiments> In the embodiment described above, the first groove portion 77 is provided in the first inner circumferential surface 74a, and the second groove portion 78 is provided in the second inner circumferential surface 74b, but the present disclosure is not limited to such a configuration. For example, the first groove portion 77 may be provided in the first outer circumferential surface 52a facing the first inner circumferential surface 74a, and the second groove portion 78 may be provided in the second outer circumferential surface 52b facing the second inner circumferential surface 74b. [Explanation of symbols]

[0158] 1 Engine (gas engine) 14 Cylinder liner 15 Cylinder cover 15a Top of cylinder cover 16 cylinders 21 Piston 3 Gas supply system 32 First gas supply path (gas supply path) 33 Second gas supply path (gas supply path) 33a Upstream end 33b Downstream end 34 Gas Gate Valve 5 Gas injection valve 5A First gas injection valve 5B Second gas injection valve 5a injection port 50 Cylindrical body 50a: First recess (recess provided on the first outer circumferential surface) 50b: second recess (recess provided on the first outer circumferential surface) 50c: third recess (recess provided on the second outer peripheral surface) 50d Fourth recessed portion (recessed portion provided on the second outer peripheral surface) 51 First Body Part 52 Second Body Section 52a 1st outer surface 52b Second outer surface 52c 3rd outer surface 53 Third Body Section 57 First internal flow passage (gas introduction passage) 57a Upstream passage (upstream end of gas introduction passage) 61 First seal member (seal member) 62 Second seal member (seal member) 63 Third seal member (seal member) 64 Fourth seal member (seal member) 7 Block Letters 7A First Block 7B 2nd block 70 Rectangular section 70u bottom 72 1st fastening hole 73 2nd fastening hole 74 Insertion hole 74a 1st inner surface 74b 2nd inner circumferential surface 74c 3rd inner surface 75 Part 1 76 Part 2 77 First groove portion (groove provided on the first inner peripheral surface) 78 Second groove portion (groove provided on the second inner peripheral surface) L1 1st part dimension L2 Dimension of second part Op Piston central axis Ov Gas injection valve central axis S1 First space (connection between the second gas supply passage and the gas injection valve, gap) S2 Second Space S3 3rd Space

Claims

1. A gas engine capable of burning gas fuel in a cylinder, A cylinder liner that reciprocates the piston; a cylinder cover fixed to an upper end of the cylinder liner and serving as a lid for the cylinder; a gas injection valve having an injection port for injecting the gas fuel into the cylinder; a gas supply passage for supplying the gas fuel to the gas injection valve; a block body fixed to an upper surface of the cylinder cover, through which the gas injection valve is inserted, and which is constructed separately from the cylinder cover; a seal member that seals between the gas supply passage and the gas injection valve, The gas supply path is A first gas supply passage defined inside the cylinder cover; a second gas supply passage defined inside the block body and connecting the first gas supply passage to the gas injection valve; The sealing member is provided at a connection portion between the second gas supply passage and the gas injection valve. A gas engine characterized by:

2. 2. The gas engine according to claim 1, a gas introduction passage that opens to an outer circumferential surface of the gas injection valve and connects the second gas supply passage to the injection port; an insertion hole provided in the block body and through which the gas injection valve is inserted; In the axial direction of the gas injection valve, the injection port side in the axial direction is defined as a tip end side, and the opposite side of the injection port in the axial direction is defined as a base end side. The outer circumferential surface of the gas injection valve is A first outer circumferential surface extending along the axial direction; a second outer circumferential surface disposed closer to the base end than the first outer circumferential surface, having a larger diameter than the first outer circumferential surface and extending along the axial direction; a third outer circumferential surface formed by a step or a slope connecting the first outer circumferential surface and the second outer circumferential surface, The inner circumferential surface of the insertion hole is A first inner peripheral surface inscribed in the first outer peripheral surface; a second inner circumferential surface that is disposed closer to the base end than the first inner circumferential surface, has a larger diameter than the first inner circumferential surface, and is inscribed in the second outer circumferential surface; a third inner circumferential surface formed by a step or a slope connecting the first inner circumferential surface and the second inner circumferential surface, When the gas injection valve is fastened to the block body, the third outer peripheral surface and the third inner peripheral surface face each other with a gap therebetween in the axial direction or in a radial direction perpendicular to the axial direction, the gap defines a first space through which the gas fuel flows in a circumferential direction around a central axis of the gas injection valve, The gas introduction passage is opened so as to communicate with the first space, The seal member is attached to at least the first outer circumferential surface so as to suppress gas leakage through the first space. A gas engine characterized by:

3. 3. The gas engine according to claim 2, a second space that is partitioned between the first outer circumferential surface and the first inner circumferential surface, is located on the tip side of the first space, and receives the gas fuel leaked from the first space; a third space that is partitioned between the second outer circumferential surface and the second inner circumferential surface, that is located closer to the base end than the first space, and that receives the gas fuel leaked from the first space, The sealing member is, in order from the distal end side to the proximal end side, a first seal member that is located on the tip side with respect to the second space and is attached to the first outer peripheral surface so as to be sandwiched between the first outer peripheral surface and the first inner peripheral surface; a second seal member that is located on the base end side with respect to the second space and is attached to the first outer peripheral surface so as to be sandwiched between the first outer peripheral surface and the first inner peripheral surface; a third seal member that is located on the tip side with respect to the third space and is attached to the second outer peripheral surface so as to be sandwiched between the second outer peripheral surface and the second inner peripheral surface; a fourth seal member that is located on the base end side with respect to the third space and is attached to the second outer peripheral surface so as to be sandwiched between the second outer peripheral surface and the second inner peripheral surface, An upstream end of the gas introduction passage is disposed between the second seal member and the third seal member in the axial direction. A gas engine characterized by:

4. 4. The gas engine according to claim 3, the first and second seal members are mounted in recesses provided in the first outer circumferential surface, the third and fourth seal members are mounted in recesses provided in the second outer circumferential surface, the second space is defined by a groove provided in the first inner circumferential surface and the first outer circumferential surface facing the groove, The third space is defined by a groove provided in the second inner circumferential surface and the second outer circumferential surface facing the groove. A gas engine characterized by:

5. 4. The gas engine according to claim 3, the gas fuel is hydrogen gas; The upstream end of the gas introduction passage is open perpendicular to the first outer circumferential surface. A gas engine characterized by:

6. 6. The gas engine according to claim 5, An upstream end of the gas introduction passage opens to a boundary portion between the first outer circumferential surface and the third outer circumferential surface. A gas engine characterized by:

7. 2. The gas engine according to claim 1, the gas fuel is hydrogen gas; The block body is made of a solid steel material, The block body is A lower surface attached to an upper surface of the cylinder cover; an insertion hole through which the gas injection valve is inserted; The second gas supply path is An upstream end portion that opens to the lower surface; a downstream end portion that opens to an inner circumferential surface of the insertion hole, the upstream end portion is disposed outwardly of the downstream end portion in a radial direction perpendicular to an axial direction of the gas injection valve, The second gas supply path is a first portion extending upward from the upstream end; a second portion that is continuous with the first portion, extends obliquely toward the inside in the radial direction as it extends upward in the height direction, and reaches the downstream end portion. A gas engine characterized by:

8. 8. The gas engine according to claim 7, The dimension of the second portion in the flow direction of the gas fuel is longer than the dimension of the first portion in the flow direction. A gas engine characterized by:

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