Internal combustion engine system, reciprocating unit, and vehicle

Abstract

An internal combustion engine system according to the present invention comprises: an internal combustion engine including a combustion chamber, an engine piston demarcating the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a reciprocating pump including a fuel gas flow path connecting the combustion chamber to a fuel gas supply source, a compression chamber, and a pump piston demarcating the compression chamber, the reciprocating pump pressurizing fuel gas in the fuel gas flow path; a pump crankshaft supported by the engine crankcase and connected to the engine crankshaft; and a pump connecting rod connecting the pump piston to the pump crankshaft.

Description

Internal combustion engine system, reciprocating unit and vehicle

[0001] The present disclosure relates to internal combustion engine systems, reciprocating units and vehicles.

[0002] In the internal combustion engine system disclosed in Patent Document 1, a fuel tank is connected to the internal combustion engine via a fuel gas pipe, and the fuel gas in the fuel gas pipe is pressurized by a pressure pump.

[0003] Japanese Patent Application Laid-Open No. 2023-181626

[0004] The configuration of Patent Document 1 results in a large system overall. In particular, when an internal combustion engine system is mounted on a vehicle, it is desirable to reduce the overall system size.

[0005] Therefore, one aspect of the present disclosure aims to make an internal combustion engine system more compact.

[0006] An internal combustion engine system according to one aspect of the present disclosure comprises an internal combustion engine including a combustion chamber, an engine piston defining the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a fuel gas flow path connecting the combustion chamber to a fuel gas supply source; a compression chamber, a reciprocating pump including a pump piston defining the compression chamber and pressurizing fuel gas in the fuel gas flow path; a pump crankshaft supported by the engine crankcase and connected to the engine crankshaft; and a pump connecting rod connecting the pump piston to the pump crankshaft.

[0007] A reciprocating unit according to another aspect of the present disclosure comprises an internal combustion engine including a combustion chamber, an engine piston defining the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a reciprocating pump including a compression chamber and a pump piston defining the compression chamber, which pressurizes fuel gas in a fuel gas flow path connecting the combustion chamber to a fuel gas supply source; and a pump reciprocating structure supported by the engine crankcase, which converts rotation of the engine crankshaft into reciprocating motion and transmits it to the pump piston.

[0008] A vehicle according to one aspect of the present disclosure includes the internal combustion engine system or the reciprocating unit.

[0009] According to one aspect of the present disclosure, an internal combustion engine system can be made compact.

[0010] FIG. 1 is a schematic diagram of a vehicle equipped with an internal combustion engine system according to a first embodiment. FIG. 2 is a block diagram of a controller and other components of the internal combustion engine system of FIG. 1. FIG. 3 is a perspective view of a reciprocating unit composed of the internal combustion engine and reciprocating pump of FIG. 1. FIG. 4 is a longitudinal sectional view of the reciprocating unit of FIG. 3. FIG. 5 is a sectional view taken along line V-V of FIG. 4. FIG. 6 is a sectional view taken along line VI-VI of FIG. 4. FIG. 7 is a sectional view of a modified example of FIG. 6. FIG. 8 is a view equivalent to FIG. 4 of a reciprocating unit of an internal combustion engine system according to a second embodiment. FIG. 9 is a sectional view taken along line IX-IX of FIG. 8. FIG. 10 is a view equivalent to FIG. 4 of a reciprocating unit of an internal combustion engine system according to a third embodiment. FIG. 11 is a perspective view of a reciprocating unit of an internal combustion engine system according to a fourth embodiment. FIG. 12 is a sectional view of the reciprocating unit of FIG. 11 as viewed from the direction of the rotational axis. FIG. 13 is a perspective view of a reciprocating unit of an internal combustion engine system according to a fifth embodiment.

[0011] Hereinafter, an embodiment will be described with reference to the drawings.

[0012] First Embodiment FIG. 1 is a schematic diagram of a vehicle V equipped with an internal combustion engine system 1 according to a first embodiment. As shown in FIG. 1, the internal combustion engine system 1 is installed in the vehicle V. The vehicle V may be a manned vehicle or an unmanned vehicle. The vehicle V is, for example, a car equipped with drive wheels W. In the vehicle V, driving force generated by an internal combustion engine E of the internal combustion engine system 1 is transmitted to the drive wheels W via a transmission TM. The vehicle V may be, for example, a two-wheeled vehicle, a three-wheeled vehicle, a four-wheeled vehicle, a railway vehicle, or the like. The drive wheels W are an example of a propulsion force generator that generates propulsion force using the driving force generated by the internal combustion engine E of the internal combustion engine system 1. The vehicle V may also be a ship, an aircraft, or the like. In this case, a propeller or a fan may be used as the propulsion force generator.

[0013] The internal combustion engine system 1 includes a fuel gas supply source 2. The fuel gas supply source 2 includes a liquid fuel tank 3 and a vaporizer 4. The liquid fuel tank 3 stores liquid fuel. The liquid fuel is, for example, liquid hydrogen. The liquid fuel tank 3 has a heat-insulating structure that blocks heat transfer from the outside in order to maintain the interior at an extremely low temperature. The outlet of the liquid fuel tank 3 is connected to the inlet of the vaporizer 4 via a liquid fuel flow path 5. A shut-off valve 6 is provided in the liquid fuel flow path 5. The vaporizer 4 is a heat exchanger that vaporizes the liquid fuel. The fuel gas produced by vaporizing the liquid fuel in the vaporizer 4 is, for example, hydrogen gas.

[0014] The liquid fuel stored in the liquid fuel tank 3 may be other types of liquefied fuel, such as hydrocarbon-based fuel. That is, the fuel gas supplied by the fuel gas supply source 2 may be other types of fuel gas, such as hydrocarbon-based fuel. The fuel gas supply source 2 may be a fuel gas tank that stores fuel gas.

[0015] An outlet of the carburetor 4 is connected to a fuel injector 23 of the internal combustion engine E via a fuel gas passage 7. That is, the fuel gas passage 7 guides the fuel gas from the carburetor 4 toward the internal combustion engine E. A reciprocating pump 9 is disposed in the fuel gas passage 7 to pressurize the fuel gas in the fuel gas passage 7 toward the internal combustion engine E. The reciprocating pump 9 is driven by the driving force of the internal combustion engine E.

[0016] The reciprocating pump 9 includes a compression chamber 72 and a pump piston 56 that defines the compression chamber 72. As the pump piston 56 reciprocates due to the driving force of the internal combustion engine E, fuel gas introduced into the compression chamber 72 through a compression chamber inlet 71 is pressurized, and the pressurized fuel gas is discharged from a compression chamber outlet 73. In the reciprocating pump 9, the pump piston 56 reciprocates due to the reciprocating power of a reciprocating structure 58. In this embodiment, the reciprocating structure 58 converts the rotational force generated by the internal combustion engine E into reciprocating power and transmits it to the pump piston 56 of the reciprocating pump 9. The detailed structure of the reciprocating pump 9 will be described later.

[0017] A sub-pump 8 is disposed in the fuel gas flow path 7 between the fuel gas supply source 2 and the reciprocating pump 9. This increases the pressure of the fuel gas supplied to the reciprocating pump 9. In this embodiment, the sub-pump 8 is a rotary pump. The rotary pump may be, for example, a Roots pump.

[0018] The sub-pump 8 is, for example, a pump driven by the energy of the internal combustion engine E. The sub-pump 8 may be an exhaust pressure-driven pump that is driven by utilizing the pressure energy of the exhaust gas of the internal combustion engine E, or may be a mechanically driven pump that is driven by the driving force of the internal combustion engine E. The sub-pump 8 may also be driven by an electric motor. Note that the sub-pump 8 may be omitted.

[0019] A cooler 10 is disposed in the fuel gas flow path 7 downstream of the reciprocating pump 9. The cooler 10 is a heat exchanger that cools the fuel gas that has been pressurized and heated by the reciprocating pump 9. The cooler 10 cools the fuel gas and reduces its volume, thereby improving the efficiency with which the fuel gas is charged into the combustion chamber 62 of the internal combustion engine E. The cooler 10 may be disposed in another location downstream of the reciprocating pump 9.

[0020] A first return flow path 12 that bypasses the reciprocating pump 9 is connected to the fuel gas flow path 7. The first return flow path 12 connects a portion of the fuel gas flow path 7 downstream of the reciprocating pump 9 to a portion upstream of the reciprocating pump 9. A relief valve 13 is arranged in the first return flow path 12. When the pressure in the portion of the fuel gas flow path 7 downstream of the reciprocating pump 9 exceeds a predetermined value, the relief valve 13 opens. The first return flow path 12 may be omitted.

[0021] A pressure reducing valve 11 is disposed in the fuel gas flow path 7 downstream of the cooler 10. By disposing the pressure reducing valve 11, the injection pressure of the fuel gas into the combustion chamber is maintained within a constant range regardless of the state of the internal combustion engine E or the state of the fuel gas supply source 2. The fuel gas flow path 7 is connected to a fuel injector 23 of the internal combustion engine E downstream of the pressure reducing valve 11. The fuel injector 23 injects fuel gas into a combustion chamber 62 or an intake port of the internal combustion engine E. In this embodiment, the fuel injector 23 directly injects fuel gas into the combustion chamber 62 of the internal combustion engine E. In this embodiment, fuel injection is performed during the compression stroke when the intake port is closed, so a high injection pressure is required to overcome the pressure in the combustion chamber 62. For example, the injection pressure is required to be 10 MPa or higher.

[0022] When the pressure of the fuel gas downstream of the pressure reducing valve 11 falls below a predetermined pressure, the pressure reducing valve 11 opens and the fuel gas upstream of the pressure reducing valve 11 is guided downstream. When the pressure of the fuel gas downstream of the pressure reducing valve 11 reaches a pressure at which the fuel gas can be directly injected into the combustion chamber 62 against the pressure in the combustion chamber 62, the pressure reducing valve 11 closes. In order to prevent such a drop in the pressure of the fuel gas upstream of the pressure reducing valve 11 due to the opening operation of the pressure reducing valve 11, a reciprocating pump 9 is provided.

[0023] A surge tank 16 is connected to a portion of the fuel gas flow path 7 between the cooler 10 and the pressure reducing valve 11. By connecting the surge tank 16, pressure fluctuations of the combustion gas upstream of the pressure reducing valve 11 are suppressed. A discharge flow path 17 is connected to a portion of the fuel gas flow path 7 between the pressure reducing valve 11 and the internal combustion engine E. A relief valve 18 is disposed in the discharge flow path 17. When the pressure in the discharge flow path 17 exceeds a predetermined value due to an abnormality or an event such as a stop of the internal combustion engine E, the relief valve 18 opens to reduce the pressure in the discharge flow path 17.

[0024] An intake passage 19 that introduces outside air into a combustion chamber is connected to an intake port of the internal combustion engine E. A throttle valve 20 is disposed in the intake passage 19. The throttle valve 20 is an electronically controlled throttle valve, but may also be a manual throttle valve that is mechanically linked to manual operation by the driver. In a combustion chamber 62 of the internal combustion engine E, fuel gas supplied from a fuel injector 23 is burned together with oxygen in air that is supplied from the intake passage 19 via the throttle valve 20. An exhaust passage 21 that discharges exhaust gas from the combustion chamber 62 is connected to an exhaust port of the internal combustion engine E. A starter motor SM that starts the internal combustion engine E is connected to the internal combustion engine E.

[0025] FIG. 2 is a block diagram of the controller 25 and other components of the internal combustion engine system 1 of FIG. 1 . As shown in FIG. 2 , the internal combustion engine system 1 includes the controller 25. The controller 25 controls the shutoff valve 6, the throttle valve motor 22, the fuel injectors 23, the spark plugs 24, the starter motor SM, the shutoff valve 6, and the like. The controller 25 includes a processing circuit 26. The controller 25 includes, for example, a processor 27, a system memory 28, and a storage memory 29. The processor 27 may include, for example, a CPU. The system memory 28 may include, for example, a volatile memory. The storage memory 29 may include a hard disk, a non-volatile memory, or a combination thereof. The storage memory 29 stores a program P. A configuration in which the processor 27 executes the program P read into the system memory 28 is an example of the processing circuit 26.

[0026] The controller 25 receives detection data from an operation command detection sensor 36 that detects the driver's driving operation, a vehicle state detection sensor 37 that detects the state of the vehicle V, a supply state detection sensor 38 that detects the fuel supply state, and a combustion state detection sensor 39 that detects the state of the internal combustion engine E. The operation command detection sensor 36 detects information related to the driver's driving operation, such as the driver's accelerator operation amount, brake operation amount, and starting operation. The vehicle state detection sensor 37 detects information related to the state of the vehicle while it is moving, such as the vehicle speed, wheel rotation speed, gear ratio, and vehicle attitude of the vehicle V. The supply state detection sensor 38 detects information related to the fuel supply state, such as the pressure, flow rate, and temperature of the fuel present in the fuel gas supply source 2 or the fuel gas flow path 7. The combustion state detection sensor 39 detects information related to the combustion state of the internal combustion engine E, such as the rotation speed of the crankshaft 35, exhaust pressure, and components contained in the exhaust gas.

[0027] The controller 25 controls the various actuators 22, 23, 24, SM, and 6 based on detection information from the various sensors 36 to 39. The controller 25 controls the valves and the sub-pump 8 provided in the fuel supply system based on information on the fuel supply state detected by the supply state detection sensor 38. For example, when the controller 25 predicts a future fuel supply shortage based on the combustion state of the internal combustion engine E, a driver's operation command, and the like, it may control the valves and the sub-pump 8 provided in the fuel supply system to increase the fuel supply amount. When the controller 25 predicts a future fuel supply excess based on the combustion state of the internal combustion engine E, a driver's operation command, and the like, it may control the valves and the sub-pump 8 provided in the fuel supply system to decrease the fuel supply. The controller 25 also controls the combustion state of the internal combustion engine E based on the combustion state of the internal combustion engine E, the state of the vehicle V, and the driver's operation command. As described above, the controller 25 may control the fuel injector 23, the throttle valve motor 22, and the spark plug 24 to maintain an appropriate combustion state of the internal combustion engine E.

[0028] FIG. 3 is a perspective view of a reciprocating unit 30 composed of the internal combustion engine E and the reciprocating pump 9 of FIG. 1. As shown in FIG. 3, the reciprocating unit 30 includes the internal combustion engine E and the reciprocating pump 9. The reciprocating unit 30 integrates the internal combustion engine E and the reciprocating pump 9. In this embodiment, the reciprocating unit 30 includes a one-piece common cylinder block 32. The common cylinder block 32 includes four engine cylinders 42 and one pump cylinder 52. The engine cylinder 42 has a part of the combustion chamber 62 and a reciprocating chamber in which the engine piston 46 reciprocates. The pump cylinder 52 has a part of the compression chamber 72 and a reciprocating chamber in which the pump piston 56 reciprocates.

[0029] The portions of the common cylinder block 32 corresponding to the four engine cylinders 42 function as an engine cylinder block 41. The portion of the common cylinder block 32 corresponding to one pump cylinder 52 functions as a pump cylinder block 51. In other words, the engine cylinder block 41 and the pump cylinder block 51 are continuous with each other.

[0030] By integrating the engine cylinder block 41 and the pump cylinder block 51 into a single unit, the internal combustion engine E and the reciprocating pump 9 can be made compact and the number of parts can be reduced. When manufacturing the reciprocating unit 30, the engine cylinders 42 and the pump cylinders 52 can be formed through a series of processes, which reduces the number of work steps. While the internal combustion engine E has four cylinders, it may have three or fewer or five or more. While the reciprocating pump 9 has one cylinder, it may have two or more. For example, the number of engine cylinders 42 is selected appropriately depending on the required output. The number of pump cylinders 52 is selected appropriately depending on the required compression ratio. For example, by making the number of pump cylinders 52 fewer than the number of engine cylinders 42, it is possible to achieve both a compact reciprocating unit 30 and sufficient fuel compression.

[0031] The reciprocating unit 30 includes a crankcase 31 to which a common cylinder block 32 is fixed. That is, the common cylinder block 32 is fixed to the crankcase 31 with fasteners such as bolts, thereby being integrated with the engine crankcase 31. The engine crankcase 31 has a portion that houses an engine crankshaft and a portion that houses a pump crankshaft. That is, the portion that houses the engine crankshaft and the portion that houses the pump crankshaft are continuous with each other. Since the internal combustion engine E and the reciprocating pump 9 share the engine crankcase 31, the configuration of the internal combustion engine system 1 is simplified. In this embodiment, the engine crankcase 31 is divided into an upper case and a lower case. In this case, the upper case of the engine crankcase 31 may be one piece that is integrally molded with the common cylinder block 32. The engine crankcase 31 may be divided in a direction other than vertically.

[0032] The reciprocating unit 30 includes a common cylinder head 33 fixed to a common cylinder block 32. The common cylinder head 33 is one piece. The portions of the common cylinder head 33 corresponding to the four engine cylinders 42 function as an engine cylinder head 45. The portion of the common cylinder head 33 corresponding to one pump cylinder 52 functions as a pump cylinder head 55. In other words, the engine cylinder head 45 and the pump cylinder head 55 are continuous with each other.

[0033] The engine cylinder head 45 has a portion of a combustion chamber 62, an intake port 61 communicating with the combustion chamber 62, and an exhaust port 63 communicating with the combustion chamber 62. An intake passage 19 is connected to the intake port 61 of the internal combustion engine E. The internal combustion engine E has an intake valve that opens and closes the intake port 61 and an exhaust valve that opens and closes the exhaust port 63, and the intake valve and exhaust valve are driven by a valve mechanism that is linked to the crankshaft 35 (described below). The pump cylinder head 55 has a compression chamber 72, a compression chamber inlet 71 that communicates with the compression chamber 72, and a compression chamber outlet 73 that communicates with the compression chamber 72. An upstream portion 7a of the fuel gas passage 7, located upstream of the reciprocating pump 9, is connected to the compression chamber inlet 71 of the reciprocating pump 9, and a downstream portion 7b of the fuel gas passage 7, located downstream of the reciprocating pump 9, is connected to the compression chamber outlet 73 of the reciprocating pump 9.

[0034] FIG. 4 is a longitudinal cross-sectional view of the reciprocating unit 30 of FIG. 3 . As shown in FIG. 4 , the crankcase 31 has a mating surface 31 a. In this embodiment, the mating surface 31 a is a flat surface perpendicular to the reciprocating direction of the pistons. Instead of being flat, the mating surface 31 a may be a surface including a step. The common cylinder block 32 is superimposed on the mating surface 31 a of the crankcase 31. In other words, the engine cylinder block 41 and the pump cylinder block 51 are integrally joined to the crankcase 31 with fastening members such as bolts while abutting against the mating surface 31 a of the crankcase 31. Arranging the mating surfaces of the cylinder blocks 41, 51 on a common virtual plane makes it easy to share the mating surface 31 a. For example, during the manufacturing of the reciprocating unit 30, the mating surfaces of the cylinder blocks 41, 51 and the mating surfaces 31 a of the crankcase 31 corresponding to the cylinder blocks 41, 51 can be formed through a series of processes, which reduces the number of work steps.

[0035] The multiple engine cylinders 42 are arranged adjacent to one another in a row in the direction of the rotational axis Y of the crankshaft 35. An engine piston 46 is housed in each engine cylinder 42. The engine piston 46 is slidable along an engine cylinder axis X1, which is the axis of the engine cylinder 42. A combustion chamber 62 is defined by the engine piston 46 and the engine cylinder head 45.

[0036] In this embodiment, the pump cylinder 52 is disposed adjacent to one of the multiple engine cylinders 42. Specifically, the pump cylinder 52 is located outside the end-located engine cylinder 42 in the rotational axis direction Y of the crankshaft 35. This configuration reduces the heat that the pump cylinder 52 receives from the engine cylinder block 41 compared to when engine cylinders 42 are disposed on both sides of the pump cylinder 52. A pump piston 56 is slidably housed in the pump cylinder 52. The pump piston 56 is slidable along a pump cylinder axis X2, which is the axis of the pump cylinder 52. The compression chamber 72 is defined by the pump piston 56 and the pump cylinder head 55.

[0037] In this embodiment, the bore diameter of the pump cylinder 52 is the same as the bore diameter of the engine cylinder 42. Also, in this embodiment, the stroke length of the pump cylinder 52 is the same as the stroke length of the engine cylinder 42. This allows each cylinder 42, 52 to be formed in a single process, which makes it easy to reduce the number of steps. By making the bore diameter of the pump cylinder 52 the same as the bore diameter of the engine cylinder 42, it is easy to use a common engine piston 42 and a common pump piston 52. By making the stroke length of the pump cylinder 52 the same as the stroke length of the engine cylinder 42, it is easy to use a common engine crankshaft 35A and a common pump crankshaft 35B.

[0038] By making the shape of the pump cylinder 52 similar to that of the engine cylinder 42 in this way, it is easy to enlarge the compression chamber 72, making it easier to increase the compression ratio compared to a rotary pump. Furthermore, the bore diameter and stroke length of the pump cylinder 52 can be appropriately selected depending on the required compression ratio. For example, one of the bore diameter and stroke length of the pump cylinder 52 may be the same as that of the engine cylinder 42, while the other may be different. Furthermore, both the bore diameter and stroke length of the pump cylinder 52 may be different from those of the engine cylinder 42. For example, because the required strength of the pump cylinder 52 is different from that of the engine cylinder 42, where explosion occurs during the combustion stroke, the bore diameter of the pump cylinder 52 may be larger than that of the engine cylinder 42. This allows for a further increase in the compression ratio of the reciprocating pump 9. Furthermore, if there is a strong demand for a more compact reciprocating unit 30, at least one of the bore diameter and stroke length of the pump cylinder 52 may be smaller than that of the engine cylinder 42.

[0039] The engine crankcase 31 houses a crankshaft 35, an engine connecting rod 47, and a pump connecting rod 57. The crankshaft 35 includes a supported portion and a biased portion that is radially offset from the supported portion. The crankshaft 35 is formed in a so-called crank shape. The engine connecting rod 47 and the pump connecting rod 57 are rotatably connected to the biased portion. Pistons 46, 56 are link-connected to the end of each connecting rod 47, 57 opposite the portion link-connected to the crankshaft 35. As the crankshaft 35 rotates, the pistons 46, 56 reciprocate radially of the crankshaft 35.

[0040] In this embodiment, the crankshaft 35 has a portion that functions as the engine crankshaft 35A and a portion that functions as the pump crankshaft 35B. The crankshaft 35 is a one-piece shaft in which the engine crankshaft 35A and the pump crankshaft 35B are continuous with each other. Because the crankshaft 35 is integrally formed, the reciprocating unit 30 can shorten the power transmission path from the engine crankshaft 35A to the pump crankshaft 35B. The reciprocating unit 30 can be made more compact and the number of parts can be reduced. The support structure for the engine crankshaft 35A also serves as part or all of the support structure for the pump crankshaft 35B, simplifying the support structure. The supported portion of the engine crankshaft 35A is formed coaxially with the supported portion of the pump crankshaft 35B. In other words, the crankcase 31 has a structure for supporting the engine crankshaft 35A and a structure for supporting the pump crankshaft 35B, and the structure for supporting the engine crankshaft 35A also serves as the structure for supporting the pump crankshaft 35B, thereby simplifying the support structure.

[0041] An engine connecting rod 47 connects a crank pin 35Aa of the engine crankshaft 35A to the engine piston 46. One end of the crankshaft 35 transmits power to drive wheels. In this embodiment, the driving force of the crankshaft 35 is transmitted to the drive wheels via a transmission TM. In this embodiment, one end of the crankshaft 35 is mechanically connected to an input shaft of the transmission TM. The crankshaft 35 is driven by a starter motor SM to which it is mechanically connected, thereby providing the crankshaft 35 with the rotational force required to start the internal combustion engine E.

[0042] The pump connecting rod 57 connects the crank pin 35Ba of the pump crankshaft 35B to the pump piston 56. The pump crankshaft 35B and the pump connecting rod 57 are an example of a reciprocating motion structure 60 that converts the rotation of the pump crankshaft 35B into reciprocating motion and transmits it to the pump piston 56.

[0043] As described above, in this embodiment, the pump crankshaft 35B and the pump connecting rod 57 that constitute the reciprocating structure 60 are supported by the engine crankcase 31. This simplifies the structure compared to when a separate structure is formed to support the reciprocating structure 60, allowing for a more compact overall structure. Furthermore, in this embodiment, the pump crankshaft 35B and the engine crankshaft 35A are integrated, thereby simplifying the power transmission path from the engine crankshaft 35A to the pump crankshaft 35B, allowing for a more compact system 1. Furthermore, by forming the reciprocating unit 30 in which the internal combustion engine E and the reciprocating pump 9 are integrated, a common mounting structure can be used, facilitating installation and removal operations compared to when the internal combustion engine E and the reciprocating pump 9 are mounted at separate, distant locations.

[0044] In this embodiment, the reciprocating mechanism 60 is housed in the engine crankcase 31, eliminating the need to cover the reciprocating mechanism 60 with a separate cover, thereby reducing the size of the internal combustion engine system 1. For example, by disposing the pump crankshaft 35B inside the engine crankcase 31, the reciprocating mechanism 60 can be located closer to the internal combustion engine E than if the pump crankshaft 35B were disposed outside the engine crankcase 31. Furthermore, because the pump piston 56 of the reciprocating pump 9 is driven by the pump crankshaft 35B via the pump connecting rod 57, the pump crankshaft 35B can be supported by a bearing, allowing the reciprocating pump 9 to be driven with minimal mechanical loss. Furthermore, because the pump crankshaft 35B is connected to the reciprocating pump 9 by the pump connecting rod 57, the power transmission structure from the pump crankshaft 35B to the reciprocating pump 9 is simplified. Furthermore, a reciprocating mechanism using a connecting rod makes it easier to increase the compression ratio than a reciprocating mechanism using a cam.

[0045] In this embodiment, a partition plate 83 is disposed in the internal space S of the engine crankcase 31. The partition plate 83 divides the internal space S of the engine crankcase 31 into a first space S1 in which the engine connecting rods 47 are disposed and a space S2 in which the reciprocating mechanism 60 is disposed. In this embodiment, the partition plate 83 functions as a bearing to support the crankshaft 35. The crankshaft 35 extends from the first space S1 to the second space S2 through a through-hole 83a in the partition plate 83. A seal member 84 is interposed between the through-hole 83a in the partition plate 83 and the crankshaft 35. The partition plate 83 prevents blow-by gas leaking from the combustion chamber 62 past the engine piston 46 into the first space S1 from mixing with gas leaking from the compression chamber 72 past the pump piston 56 into the second space S2. Note that the partition plate 83 may be omitted.

[0046] FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. As shown in FIGS. 3 to 5, the pump cylinder block 51 overlaps the engine cylinder block 41 when viewed from the rotational axis direction Y, which is the direction in which the rotational axis Y of the crankshaft 35 extends. When viewed from the rotational axis direction Y, the outer edge of the pump cylinder block 51 coincides with the outer edge of the engine cylinder block 41. When viewed from the rotational axis direction Y, the reciprocating pump 9 and the reciprocating mechanism 60 are located inside the outer edge of the internal combustion engine E. This allows the internal combustion engine E and the reciprocating pump 9 to be made compact as a whole when viewed from the rotational axis direction Y. In this embodiment, when viewed from the rotational axis direction Y, the engine cylinder axis X1 and the pump cylinder axis X2 overlap. That is, the engine cylinder 42 and the pump cylinder 52 are aligned in a row along the rotational axis direction Y. This allows the stroke length of the pump cylinder 52 to be increased while preventing the reciprocating unit 30 from becoming larger.

[0047] The pump cylinder block 51 may partially overlap the engine cylinder block 41 when viewed from the rotational axis direction Y. That is, the pump cylinder block 51 may be offset around the rotational axis Y with respect to the engine cylinder block 41. By having at least a portion of the reciprocating pump 9 and the reciprocating structure 60 overlap with the internal combustion engine E, the engine can be made more compact than if they were not overlapped.

[0048] 5 , the pump cylinder head 55 has a compression chamber 72, a compression chamber inlet 71 communicating with the compression chamber 72, and a compression chamber outlet 73 communicating with the compression chamber 72. An upstream portion 7a of the fuel gas flow path 7 located upstream of the reciprocating pump 9 is connected to the compression chamber inlet 71. A downstream portion 7b of the fuel gas flow path 7 located downstream of the reciprocating pump 9 is connected to the compression chamber outlet 73.

[0049] An inlet check valve 74 is provided at the compression chamber inlet 71 of the reciprocating pump 9. The inlet check valve 74 allows a flow from the upstream portion 7 a of the fuel gas flow path 7 toward the compression chamber inlet 71 of the reciprocating pump 9, and prevents a backflow from the compression chamber inlet 71 of the reciprocating pump 9 toward the upstream portion 7 a of the fuel gas flow path 7.

[0050] An outlet check valve 75 is provided at the compression chamber outlet 73 of the reciprocating pump 9. The outlet check valve 75 allows a flow from the downstream portion 7 b of the fuel gas flow path 7 toward the compression chamber outlet 73 of the reciprocating pump 9, and prevents a backflow from the downstream portion 7 b of the fuel gas flow path 7 toward the compression chamber outlet 73 of the reciprocating pump 9. Note that instead of the inlet check valve 74 and the outlet check valve 75, intake valves and exhaust valves that are linked to the rotation of the crankshaft 35, as in the internal combustion engine E, may be used.

[0051] The second space S2 of the crankcase 31 is connected to the upstream portion 7a of the fuel gas flow path 7 by the second return flow path 14. A check valve 15 is disposed in the second return flow path 14. The check valve 15 allows flow from the second space S2 of the crankcase 31 toward the upstream portion 7a of the fuel gas flow path 7 and prevents backflow from the upstream portion 7a of the fuel gas flow path 7 toward the second space S2 of the crankcase 31. This allows gas that has leaked from the compression chamber 72 past the pump piston 56 into the second space S2 to be resupplied to the compression chamber 72 via the second return flow path 14. As described above, the partition plate 83 prevents blow-by gas from entering the second space S2 from the first space S1, thereby allowing fuel gas with reduced exhaust gas contamination to be guided to the upstream portion 7a of the fuel gas flow path 7. Note that the second return flow path 14 may be connected to a location other than the upstream portion 7a of the fuel gas flow path 7. For example, the second return passage 14 may be formed to guide gas within the engine crankcase 31 to the intake passage 19 .

[0052] 6 is a cross-sectional view taken along line VI-VI in FIG. 4. As shown in FIG. 6, the common cylinder block 32 has an engine cooling channel 43 and a pump cooling channel 53. The engine cooling channel 43 surrounds the entire four engine cylinders 42 from the horizontal direction. The pump cooling channel 53 surrounds the pump cylinder 52 from the horizontal direction. A portion of the engine cooling channel 43 and a portion of the pump cooling channel 53 are interposed between the pump cylinder 52 and the adjacent engine cylinder 42. The adjacent distance L2 between the pump cylinder 52 and the adjacent engine cylinder 42 is wider than the adjacent distance L1 between the multiple engine cylinders 42. Note that the adjacent distance L2 may be the same as the adjacent distance L1.

[0053] The engine cooling flow path 43 and the pump cooling flow path 53 constitute a coolant circulation flow path 80. The coolant circulation flow path 80 is a closed-loop flow path through which a coolant such as cooling water flows. A coolant pump 81 and a radiator 82 are arranged in series in the coolant circulation flow path 80. The engine cooling flow path 43 and the pump cooling flow path 53 are connected in parallel to each other in the coolant circulation flow path 80.

[0054] The coolant discharged from the coolant pump 81 is divided into coolant that flows into the engine cooling channel 43 and coolant that flows into the pump cooling channel 53. The coolant that flows out from the engine cooling channel 43 and the coolant that flows out from the pump cooling channel 53 join together and flow through the radiator 82. The coolant that flows out from the radiator 82 flows into the coolant pump 81. That is, the coolant that flows out from the engine cooling channel 43 flows toward the radiator 82 without flowing toward the pump cooling channel 53. This configuration prevents excessive heat from being transferred from the engine cylinder 42 to the pump cylinder 52.

[0055] The coolant flowing into the pump cooling channel 53 may be set to have a different temperature or amount than the coolant flowing into the engine cooling channel 43. The pump cooling channel 53 may be set to have a lower coolant temperature or a larger coolant amount. For example, the portion of the pump cooling channel 53 closer to the engine cylinder 42 may have a larger horizontal cross-sectional area than the remaining portion. This makes it easier to prevent the temperature of the pump cylinder 52 from rising.

[0056] The pump cooling passage 53 may be connected in series with the engine cooling passage 43 and disposed upstream of the engine cooling passage 43. This makes it easier to prevent a rise in temperature around the pump cylinder. The engine cooling passage 43 and the pump cooling passage 53 may be combined. A dedicated radiator for the pump cooling passage 53 may be provided separately from a radiator for the engine cooling passage 43.

[0057] FIG. 7 is a cross-sectional view of a modified example of FIG. 6 . As shown in FIG. 7 , the common cylinder block 32 may have a pump cooling passage 153 that does not surround the pump cylinder 52 in the region between the pump cylinder 52 and the adjacent engine cylinder 42. For example, the pump cooling passage 153 may be disposed only in the region between the pump cylinder 52 and the adjacent engine cylinder 42. The common cylinder block 32 may have a cam chain tunnel 154 in the region between the pump cylinder 52 and the adjacent engine cylinder 42. A cam chain that transmits the driving force of the crankshaft to part of the valve mechanism of the internal combustion engine E, i.e., a valve gear including a cam mechanism that drives the intake valves and exhaust valves of the internal combustion engine E, passes through the cam chain tunnel 154. This suppresses the temperature rise of the pump cylinder 52. Note that the cam chain tunnel 154 may also be applied to the configuration of FIG. 6 .

[0058] Second Embodiment FIG. 8 is a view equivalent to FIG. 4 of a reciprocating unit 130 of an internal combustion engine system according to a second embodiment. FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. Note that components common to the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted. As shown in FIGS. 8 and 7, in the reciprocating unit 130 of the second embodiment, the type of reciprocating mechanism 160 that converts the rotation of the crankshaft 135 into reciprocating motion and transmits the motion to the pump piston 56 is different from that of the first embodiment. The reciprocating mechanism 160 of the second embodiment has a cam structure. Specifically, the reciprocating mechanism 160 includes a rod 185, a cam 186, and a spring 187. The reciprocating mechanism 160 is housed in the crankcase 31.

[0059] The rod 185 extends from the pump piston 56 along the pump cylinder axis X2 in a direction away from the compression chamber 72 and protrudes into the internal space of the crankcase 31. The crankshaft 135 has a portion that functions as the engine crankshaft 35A and a portion that functions as the pump camshaft 135B. The crankshaft 135 is a one-piece shaft in which the engine crankshaft 35A and the pump camshaft 135B are continuous with each other, but the engine crankshaft 35A and the separate pump camshaft 135B may also be a shaft in which they are directly connected to each other. The cam 186 is fixed to the pump camshaft 135B of the crankshaft 135 that extends on the rotational axis Y. The pump camshaft 135B is provided with a cam 186. The cam 186 is eccentric with respect to the rotational axis Y.

[0060] A spring 187 biases the rod 185 in a direction in which the rod 185 moves toward the cam 186. When the crankshaft 135 rotates, the cam 186 presses the end face of the rod 185 in the direction in which the pump cylinder axis X2 extends, causing the rod 185 to reciprocate. The reciprocating movement of the rod 185 causes the pump piston 56 to reciprocate.

[0061] By realizing reciprocating structure 160 using cam 186, it is possible to further reduce the size of reciprocating structure 160 compared to when a reciprocating structure is realized using a connecting rod, making it easier to achieve a more compact overall structure. In the second embodiment, cam 158, pump camshaft 135B, and rod 185, which are reciprocating structure 160, are also supported by crankcase 31. This simplifies the structure compared to when a separate structure is formed to support reciprocating structure 160, and makes the overall structure more compact.

[0062] The cam 186 may be provided on a rotating body (for example, a balancer shaft) that rotates in conjunction with the engine crankshaft 35A. Even in this case, the reciprocating mechanism is supported by the crankcase 31, making it possible to make the overall structure more compact. Furthermore, by accommodating the reciprocating mechanism within the crankcase 31, it is possible to eliminate the need to employ a structure that covers the reciprocating mechanism with a separate cover. Note that the other configurations are the same as those of the first embodiment described above, and therefore description thereof will be omitted.

[0063] Third Embodiment FIG. 10 is a diagram equivalent to FIG. 4 of a reciprocating unit 230 of an internal combustion engine system according to a third embodiment. Components common to those of the first embodiment are designated by the same reference numerals and will not be described again. As shown in FIG. 10 , in the reciprocating unit 230 of the third embodiment, the pump cylinder block 251 of the reciprocating pump 209 is a separate piece from the engine cylinder block 241 of the internal combustion engine E and is spaced apart from the engine cylinder block 241. That is, a gap G is provided between the engine cylinder block 241 and the pump cylinder block 251. This reduces heat transfer from the engine cylinder 42 to the pump cylinder 52. The gap G between the engine cylinder block 241 and the pump cylinder block 251 may be an air space with no objects present, or a heat insulating material 287 may be disposed in part or entirely within the gap G.

[0064] The engine cylinder block 241 and the pump cylinder block 251 are integrated with the crankcase 31. A heat insulator 286 is sandwiched between the pump cylinder block 251 and the crankcase 31. The heat insulator 286 may be, for example, glass wool. This reduces the heat transferred from the engine cylinder 42 to the pump cylinder 52 via the crankcase 31. The heat insulator 286 may also be applied to other embodiments. A heat insulator may also be sandwiched between the engine cylinder block and the crankcase. The other configurations are the same as those of the first embodiment, and therefore will not be described again.

[0065] As a modified example, the engine crankcase that houses the engine crankshaft 35A and the pump crankcase that houses the pump crankshaft 35B may be separate pieces. In this case, the pump cylinder block 251 may be a common piece with the engine cylinder block 241 of the internal combustion engine E, or may be a separate piece. Even with this configuration, the reciprocating mechanism 60 is supported directly or indirectly by the crankcase, thereby simplifying the structure and making the overall structure more compact. Furthermore, the cam chain tunnel 154 described above may be disposed in a portion of the engine cylinder block 241 that faces the gap G.

[0066] Fourth Embodiment FIG. 11 is a perspective view of a reciprocating unit 330 of an internal combustion engine system according to a fourth embodiment. FIG. 12 is a cross-sectional view of the reciprocating unit 330 of FIG. 11 as viewed from the rotational axis direction Y. Note that other configurations are similar to those of the first embodiment, and therefore description thereof will be omitted. As shown in FIGS. 11 and 12 , the reciprocating unit 330 of the fourth embodiment includes an internal combustion engine E, which is a V-engine. The internal combustion engine E includes a first engine cylinder block 341A connected to a crankcase 31 and a second engine cylinder block 341B connected to the crankcase 31 at a position circumferentially offset about the rotational axis Y from the first engine cylinder block 341A. The first engine cylinder block 341A and the second engine cylinder block 341B are arranged in a V-shape as viewed from the rotational axis direction Y.

[0067] The reciprocating unit 330 includes a first reciprocating pump 309A and a second reciprocating pump 309B. The first reciprocating pump 309A has a first pump cylinder block 351A connected to the crankcase 31. The second reciprocating pump 309B includes a second pump cylinder block 351B connected to the crankcase 31 at a position circumferentially offset about the rotational axis Y from the first pump cylinder block 351A. The first pump cylinder block 351A and the second pump cylinder block 351B are arranged in a V-shape when viewed from the rotational axis Y.

[0068] The first pump cylinder block 351A is adjacent to the first engine cylinder block 341A along the rotational axis direction Y. The first pump cylinder block 351A may form a one-piece common cylinder block with the first engine cylinder block 341A, or may be a separate piece from the first engine cylinder block 341A.

[0069] The second pump cylinder block 351B is adjacent to the second engine cylinder block 341B along the rotational axis direction Y. The second pump cylinder block 351B may form a one-piece common cylinder block together with the second engine cylinder block 341B, or may be a separate piece from the second engine cylinder block 341B.

[0070] The pump cylinder 52 of the second reciprocating pump 309B is arranged to be offset in the circumferential direction about the rotational axis direction Y with respect to the engine cylinder 42 of the first engine cylinder block 341A. The pump cylinder 52 of the first reciprocating pump 309A is arranged to be offset in the circumferential direction about the rotational axis direction Y with respect to the engine cylinder 42 of the second engine cylinder block 341B. The other configurations are the same as those of the first embodiment described above, and therefore description thereof will be omitted.

[0071] The first reciprocating pump 309A or the second reciprocating pump 309B may be omitted. The first engine cylinder block 341A or the second engine cylinder block 341B may be omitted. The cylinder blocks 341A, 341B may be spaced apart from each other circumferentially at any angle as viewed from the rotational axis direction Y, and may be L-shaped with 90 degrees apart or may be opposed with 180 degrees apart. In this way, the arrangement of the engine cylinder blocks 341A, 341B may employ various existing layouts. Furthermore, the number of engine cylinder blocks 341A, 341B and the number of pump cylinder blocks 341A, 341B may differ from each other. For example, the number of pump cylinders may be fewer than the number of engine cylinders.

[0072] Fifth Embodiment Fig. 13 is a perspective view of a reciprocating unit 430 of an internal combustion engine system according to a fifth embodiment. Components common to those of the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted. As shown in Fig. 13, the reciprocating unit 430 of the fifth embodiment includes an engine cylinder block 441 connected to the crankcase 31, and a pump cylinder block 451 connected to the crankcase 31 at a position offset from the engine cylinder block 441 in the circumferential direction around the rotation axis Y.

[0073] The engine cylinder block 441 and the pump cylinder block 451 are arranged in a V-shape when viewed from the rotational axis direction Y. All of the engine cylinders 42 of the internal combustion engine E are arranged circumferentially offset from the pump cylinders 52 of the pump cylinder block 451 in the rotational axis direction Y. In other words, there is no engine cylinder block adjacent to the pump cylinder block 451 in the rotational axis direction Y. This makes the pump cylinders 52 less susceptible to the heat from the engine cylinders 42, and suppresses a rise in the temperature of the fuel gas caused by the reciprocating pump 409. Note that other configurations are the same as those of the first embodiment described above, and therefore description thereof will be omitted.

[0074] It should be noted that the technology of the present disclosure is not limited to the above-described embodiment. For example, the reciprocating structure 60, 160 may be a structure that is directly or indirectly supported by the crankcase 31 and disposed outside the crankcase 31. In this case, a cover structure that covers the reciprocating structure 60, 160 may be fixed to the crankcase 31. For example, the end of the crankshaft 35 that protrudes outward from the crankcase 31 may be connected to a pump connecting rod 57 that is disposed outside the crankcase 31. In a reciprocating unit, when part or all of the reciprocating pump 9 is formed separately from the internal combustion engine E, it is preferable that the reciprocating pump 9 be a structure that is supported by the internal combustion engine E.

[0075] The engine crankshaft 35A and the pump crankshaft 35B may be separate from each other. For example, the engine crankshaft 35A and the pump crankshaft 35B may be joined together on the same axis to form the crankshaft 35. The pump crankshaft 35B may be directly connected to the engine crankshaft 35A by a shaft coupling structure such as a spline connection or a flange connection. Similarly, the engine crankshaft 35A and the pump camshaft 135B may be separate from each other. For example, the engine crankshaft 35A and the pump camshaft 135B may be joined together on the same axis to form the crankshaft 135. The pump camshaft 135B may be joined to the engine crankshaft 35A by a shaft coupling structure such as a spline connection or a flange connection.

[0076] Even in this case, the above-described effect can be obtained by directly or indirectly supporting the pump crankshaft 35B or the pump camshaft 135B on the crankcase 31. It is preferable that at least a portion of the pump crankshaft 35B or the pump camshaft 135B is directly or indirectly supported on the crankcase 31, and the pump crankshaft 35B or the pump camshaft 135B may be supported on one side or the other by a cantilever. Furthermore, the reciprocating structure 60, 160 may be supported on the crankcase 31 via one or more relay members fixed to the crankcase 31.

[0077] The pump crankshaft 35B or the pump camshaft 135B may be disposed coaxially with the engine crankshaft 35A, or may be disposed non-coaxially, for example, parallel to the engine crankshaft 35A. In this case, the power of the internal combustion engine E may be transmitted from the engine crankshaft 35A to the pump crankshaft 35B or the pump camshaft 135B by a power transmission mechanism such as gears or a chain. A required compression ratio and a compact reciprocating unit may be achieved by making the rotation speed of the pump crankshaft 35B or the pump camshaft 135B different from that of the engine crankshaft 35A using a speed-up or speed-down mechanism including gears.

[0078] From the viewpoint of reducing the size of the unit, it is preferable that the power transmission mechanism that transmits power from the engine crankshaft 35A to the pump crankshaft 35B or the pump camshaft 135B be housed within the crankcase 31. The reciprocating directions of the engine piston 46 and the pump piston 56 may be different from each other, and the pump piston 56 may have an outer shape that is suitable for the space in the vehicle V. For example, the reciprocating direction of the pump piston 56 may be parallel to the engine crankshaft 35, and the pump cylinder 52 may be disposed on the intake port side of the engine cylinder block 41.

[0079] Rotational power from the engine crankshaft 35A may be transmitted to the reciprocating structure 60, 160 via an internal combustion engine rotor that rotates in conjunction with the rotation of the crankshaft 35. For example, the internal combustion engine rotor may be a gear or shaft housed in the crankcase 31. Specifically, the internal combustion engine rotor may be a balancer gear for vibration reduction, a balancer shaft, or a rotor for a valve mechanism housed in the crankcase. Additionally, the internal combustion engine rotor may be a starter gear used to start the internal combustion engine, a gear that transmits power to a generator, a gear that transmits power to a circulation pump that delivers coolant or lubricating oil, or an idle gear that transmits power to these gears. If a transmission or clutch is housed in the crankcase, the internal combustion engine rotor may be a gear of the transmission or clutch that rotates in conjunction with the crankshaft of the internal combustion engine.

[0080] Alternatively, at least a portion of the fuel gas flow path 7 may include a passage formed in the crankcase 31. The vehicle V may be provided with a traveling wind passage that directs traveling wind toward the reciprocating pump rather than the internal combustion engine E. In the fuel gas flow path 7, another pressurizing pump may be disposed downstream of the reciprocating pump 9. In the fuel gas flow path 7, multiple pumps may be provided upstream or downstream of the reciprocating pump 9. The sub-pump 8 may be an existing pump other than a Roots pump, such as an axial or centrifugal pump that compresses gas by rotating a rotor. The sub-pump 8 may also be a reciprocating pump. The internal combustion engine system 1 may be mounted or installed in a location other than a vehicle. For example, it may be installed in a power generation facility that generates energy for power generation, or it may be used as a driving source that generates fluid energy using the power of the crankshaft. The reciprocating pump 9 may be a membrane-shaped piston, a so-called diaphragm-type piston pump, instead of a cylindrical piston. The reciprocating structure 60, 160 may include a reduction gear or the like.

[0081] As described above, the above embodiments have been described as examples of the technology disclosed in this application. However, the technology of the present disclosure is not limited to these and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above embodiments can be combined to create new embodiments. For example, some configurations or methods in one embodiment may be applied to other embodiments, and some configurations in an embodiment can be separated and arbitrarily extracted from other configurations in that embodiment. Furthermore, the components described in the accompanying drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem, and are used to illustrate the technology.

[0082] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. Processors are considered processing circuits or circuits because they include transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0083] [Aspects] The above-described embodiments are specific examples of the following aspects.

[0084] (Aspect 1) An internal combustion engine system comprising: an internal combustion engine including a combustion chamber, an engine piston defining the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a fuel gas flow path connecting the combustion chamber to a fuel gas supply source; a reciprocating pump including a compression chamber and a pump piston defining the compression chamber, and pressurizing fuel gas in the fuel gas flow path; a pump crankshaft supported by the engine crankcase and connected to the engine crankshaft; and a pump connecting rod connecting the pump piston to the pump crankshaft.

[0085] This configuration simplifies the power transmission path from the engine crankshaft to the reciprocating pump, making the system more compact. Furthermore, by pressurizing the fuel gas with a pump piston, it is easier to increase the compression ratio compared to pumps that compress gas with rotors, which contributes to a more compact system while also increasing the compression ratio.

[0086] (Aspect 2) The internal combustion engine system according to aspect 1, wherein the pump crankshaft and the pump connecting rod are housed in the engine crankcase.

[0087] According to this configuration, the pump connecting rod is housed in the engine crankcase, so the engine crankshaft and the pump connecting rod can be brought closer together, making the system more compact.

[0088] (Aspect 3) The internal combustion engine system according to Aspect 1 or 2, wherein the internal combustion engine further includes an engine cylinder block having an engine cylinder that houses the engine piston, the reciprocating pump further includes a pump cylinder block having a pump cylinder that houses the pump piston, and the pump cylinder block is integrated into the engine cylinder block or the engine crankcase.

[0089] According to this configuration, the reciprocating pump is integrated into the crankcase, and the internal combustion engine is used as a structure for mounting the reciprocating pump, thereby improving the mountability of the reciprocating pump.

[0090] (Aspect 4) The internal combustion engine system according to any one of Aspects 1 to 3, wherein the internal combustion engine further includes an engine cylinder block having an engine cylinder that houses the engine piston, the reciprocating pump further includes a pump cylinder block having a pump cylinder that houses the pump piston, and at least a portion of the pump cylinder block overlaps with the engine cylinder block when viewed from the direction of the rotational axis of the engine crankshaft.

[0091] According to this configuration, the engine cylinder block and the pump cylinder block overlap, so the internal combustion engine and the reciprocating pump as a whole can be made more compact than if they were arranged offset from each other.

[0092] (Aspect 5) The internal combustion engine system according to aspect 3 or 4, wherein the crankcase has a mating surface, and the pump cylinder block is placed on the mating surface of the engine crankcase.

[0093] This configuration allows the internal combustion engine and reciprocating pump to be made compact overall, while simplifying the manufacture of the crankcase and other components.

[0094] (Aspect 6) The internal combustion engine system according to any one of Aspects 3 to 5, wherein the engine cylinder block and the pump cylinder block are continuous with each other and form a one-piece common cylinder block.

[0095] According to this configuration, by integrating the entire engine cylinder block and the entire pump cylinder block into one unit, the entire internal combustion engine and reciprocating pump can be made compact and the number of parts can be reduced.

[0096] (Aspect 7) The internal combustion engine system according to aspect 6, wherein the pump cylinder is disposed adjacent to the engine cylinder, and the common cylinder block has a cooling passage between the pump cylinder and the engine cylinder.

[0097] This configuration reduces the heat transferred from the engine cylinder to the pump cylinder.

[0098] (Aspect 8) The internal combustion engine system according to any one of Aspects 3 to 7, wherein at least a portion of the pump cylinder is disposed offset relative to the engine cylinder in the circumferential direction around the engine crankshaft.

[0099] According to this configuration, at least a portion of the pump cylinder is positioned offset relative to the engine cylinder, so that the pump cylinder is less susceptible to the heat from the engine cylinder, and the temperature rise of the fuel gas due to the pump can be suppressed.

[0100] (Aspect 9) The internal combustion engine system according to any one of Aspects 3 to 8, wherein the pump cylinder block is integrated with the engine crankcase, and the engine cylinder block and the pump cylinder block are spaced apart from each other.

[0101] This configuration reduces the heat transferred from the engine cylinder to the pump cylinder.

[0102] (Aspect 10) The internal combustion engine system according to any one of Aspects 3 to 9, further comprising a heat insulating material sandwiched between the pump cylinder block and one of the engine cylinder block and the engine crankcase.

[0103] This configuration reduces the heat transferred from the engine cylinder to the pump cylinder.

[0104] (Aspect 11) The internal combustion engine system according to any one of Aspects 1 to 10, further comprising a cooler disposed downstream of the reciprocating pump in the fuel gas flow path.

[0105] According to this configuration, the fuel gas pressurized and heated by the reciprocating pump is cooled and reduced in volume, thereby improving the filling efficiency of the fuel gas supplied to the combustion chamber of the internal combustion engine.

[0106] (Aspect 12) The internal combustion engine system according to any one of Aspects 1 to 11, further comprising a sub-pump interposed in the fuel gas flow path between the reciprocating pump and the fuel gas supply source, for pressurizing the fuel gas in the fuel gas flow path.

[0107] According to this configuration, the pressure of the fuel gas can be increased suitably.

[0108] (Aspect 13) A reciprocating unit comprising: an internal combustion engine including a combustion chamber, an engine piston defining the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a reciprocating pump including a compression chamber and a pump piston defining the compression chamber, the reciprocating pump pressurizing fuel gas in a fuel gas flow path connecting the combustion chamber to a fuel gas supply source; and a pump reciprocating structure supported by the engine crankcase, converting rotation of the engine crankshaft into reciprocating motion and transmitting the reciprocating motion to the pump piston.

[0109] This configuration simplifies the power transmission structure from the engine crankshaft to the reciprocating pump, making the unit more compact. Furthermore, by pressurizing the fuel gas with the pump piston, it is easier to increase the compression ratio compared to pumps that compress gas with rotors, which contributes to a more compact system while increasing the compression ratio.

[0110] (Aspect 14) The reciprocating unit according to aspect 13, wherein the pump reciprocating structure is housed in the engine crankcase.

[0111] According to this configuration, the pump reciprocating structure is housed in the engine crankcase, so the engine crankshaft and the pump reciprocating structure can be placed close to each other, making the system more compact.

[0112] (Aspect 15) A vehicle including the internal combustion engine system according to any one of Aspects 1 to 12 or the reciprocating unit according to Aspect 13 or 14.

[0113] According to this configuration, by installing an internal combustion engine system or a reciprocating unit that can be made compact, it is possible to improve the mountability in vehicles with limited mounting space.

[0114] REFERENCE SIGNS LIST 1 Internal combustion engine system 2 Fuel gas supply source 7 Fuel gas flow path 8 Sub-pump 9, 209, 309A, 309B, 409 Reciprocating pump 10 Cooler 30, 130, 230, 430, 530 Reciprocating unit 31 Engine crankcase 31a Mating surface 32 Common cylinder block 35, 135 Crankshaft 35A Engine crankshaft 35B Pump crankshaft 41, 241, 341A, 341B, 441 Engine cylinder block 42 Engine cylinder 43 Engine cooling flow path 46 Engine piston 47 Engine connecting rod 51, 251, 351A, 351B, 451 Pump cylinder block 52 Pump cylinder 53 Pump cooling flow path 56 Pump piston 57 Pump connecting rod 60, 160 Reciprocating structure 62 Combustion chamber 72 Compression chamber 286 Heat insulating material E Internal combustion engine Y Rotation axis direction V Vehicle

Claims

1. An internal combustion engine system comprising: an internal combustion engine including a combustion chamber, an engine piston defining the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a fuel gas flow path connecting the combustion chamber to a fuel gas supply source; a reciprocating pump including a compression chamber and a pump piston defining the compression chamber, and pressurizing fuel gas in the fuel gas flow path; a pump crankshaft supported by the engine crankcase and connected to the engine crankshaft; and a pump connecting rod connecting the pump piston to the pump crankshaft.

2. The internal combustion engine system according to claim 1, wherein the pump crankshaft and the pump connecting rod are housed in the engine crankcase.

3. An internal combustion engine system according to claim 1 or 2, wherein the internal combustion engine further includes an engine cylinder block having an engine cylinder that houses the engine piston, and the reciprocating pump further includes a pump cylinder block having a pump cylinder that houses the pump piston, and the pump cylinder block is integrated into the engine cylinder block or the engine crankcase.

4. An internal combustion engine system according to claim 1 or 2, wherein the internal combustion engine further includes an engine cylinder block having an engine cylinder that houses the engine piston, and the reciprocating pump further includes a pump cylinder block having a pump cylinder that houses the pump piston, and at least a portion of the pump cylinder block overlaps with the engine cylinder block when viewed from the direction of the rotational axis of the engine crankshaft.

5. The internal combustion engine system according to claim 3 or 4, wherein the engine crankcase has a mating surface, and the pump cylinder block is superimposed on the mating surface of the engine crankcase.

6. The internal combustion engine system according to any one of claims 3 to 5, wherein the engine cylinder block and the pump cylinder block are continuous with each other and constitute a one-piece common cylinder block.

7. The internal combustion engine system according to claim 6, wherein the pump cylinder is disposed adjacent to the engine cylinder, and the common cylinder block has a cooling passage between the pump cylinder and the engine cylinder.

8. An internal combustion engine system according to any one of claims 3 to 7, wherein at least a portion of the pump cylinder is offset relative to the engine cylinder in the circumferential direction around the engine crankshaft.

9. An internal combustion engine system according to any one of claims 3 to 8, wherein the pump cylinder block is integrated into the engine crankcase, and the engine cylinder block and the pump cylinder block are spaced apart from each other.

10. An internal combustion engine system according to any one of claims 3 to 9, further comprising a thermal insulator sandwiched between the pump cylinder block and one of the engine cylinder block or the engine crankcase.

11. The internal combustion engine system according to any one of claims 1 to 10, further comprising a cooler disposed downstream of the reciprocating pump in the fuel gas flow path.

12. An internal combustion engine system according to any one of claims 1 to 11, further comprising a sub-pump interposed in the fuel gas flow path between the reciprocating pump and the fuel gas supply source, for pressurizing the fuel gas in the fuel gas flow path.

13. A reciprocating unit comprising: an internal combustion engine including a combustion chamber, an engine piston defining the combustion chamber, an engine crankshaft, an engine connecting rod connecting the engine piston to the engine crankshaft, and an engine crankcase accommodating the engine crankshaft and the engine connecting rod; a reciprocating pump including a compression chamber and a pump piston defining the compression chamber, and pressurizing fuel gas in a fuel gas flow path connecting the combustion chamber to a fuel gas supply source; and a pump reciprocating structure supported by the engine crankcase, converting rotation of the engine crankshaft into reciprocating motion and transmitting the reciprocating motion to the pump piston.

14. A reciprocating unit as set forth in claim 13, wherein said pump reciprocating structure is housed in said engine crankcase.

15. A vehicle equipped with an internal combustion engine system according to any one of claims 1 to 12 or a reciprocating unit according to claim 13 or 14.

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