Internal combustion engine system, vehicle equipped with internal combustion engine system, and control method for internal combustion engine system

Abstract

To improve the performance of an internal combustion engine that burns fuel gas. [Solution] The internal combustion engine system comprises an internal combustion engine including at least one combustion chamber and at least one intake port that directs air into the combustion chamber, a first flow path through which fuel gas flows, a second flow path through which fuel gas flows at a higher pressure than the first flow path, at least one first fuel injector supplied with fuel gas from the first flow path and arranged to inject fuel gas into the intake port of the internal combustion engine, and at least one second fuel injector supplied with fuel gas from the second flow path and arranged to inject fuel gas into the combustion chamber of the internal combustion engine.

Description

[Technical Field]

[0001] The present disclosure relates to an internal combustion engine system, a vehicle equipped with an internal combustion engine system, and a control method for an internal combustion engine system. Regarding. [Background technology]

[0002] Patent Document 1 discloses a system in which a fuel tank that stores fuel gas in a compressed state is connected to an internal combustion engine via a fuel gas pipe, and the fuel gas in the fuel gas pipe is pressurized by a pressure pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-181626 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above system, when the tank internal pressure is low, it is necessary to drive the pressure pump to increase the fuel gas introduced to the internal combustion engine. Further improvements in the performance of the internal combustion engine to which the fuel gas is supplied are desired in terms of efficiency, etc.

[0005] Therefore, one aspect of the present disclosure aims to improve the performance of an internal combustion engine that burns fuel gas. [Means for solving the problem]

[0006] An internal combustion engine system according to one embodiment of the present disclosure comprises an internal combustion engine including at least one combustion chamber and at least one intake port that guides air into the combustion chamber, a first flow path through which fuel gas flows, a second flow path through which fuel gas flows at a higher pressure than the first flow path, at least one first fuel injector supplied with fuel gas from the first flow path and arranged to inject fuel gas into the intake port of the internal combustion engine, and at least one second fuel injector supplied with fuel gas from the second flow path and arranged to inject fuel gas into the combustion chamber of the internal combustion engine.

[0007] A vehicle according to one aspect of the present disclosure includes the above-described internal combustion engine system.

[0008] A control method for an internal combustion engine system according to one embodiment of the present disclosure is a control method for an internal combustion engine system comprising: an internal combustion engine including at least one combustion chamber and an intake port that guides air to the combustion chamber; a first flow path through which fuel gas flows; a second flow path through which fuel gas flows at a higher pressure than the first flow path; a first fuel injector to which fuel gas is supplied from the first flow path and arranged to inject the fuel gas into the intake port of the internal combustion engine; and a second fuel injector to which fuel gas is supplied from the second flow path and arranged to inject the fuel gas into the combustion chamber of the internal combustion engine, the control method including: acquiring status information indicating the operating state of the internal combustion engine, the future operating state of the internal combustion engine, or the state of the fuel gas in the fuel flow path; and individually controlling the first fuel injector and the second fuel injector based on the status information. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, the performance of an internal combustion engine that burns fuel gas can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with an internal combustion engine system according to an embodiment. [Figure 2]FIG. 2 is a plan view of the internal combustion engine etc. shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a block diagram of the controller etc. in FIG. [Figure 6] FIG. 6 is a graph showing an example of time-series data of the rotation speeds of the internal combustion engine, the first booster pump, and the second booster pump of FIG. [Figure 7] FIG. 7 is a cross-sectional view of a main part of an internal combustion engine according to a modified example. [Figure 8] FIG. 8 is a schematic diagram of a main part of an internal combustion engine system according to a first modified example. [Figure 9] FIG. 9 is a schematic diagram of a main part of an internal combustion engine system according to a second modified example. [Figure 10] FIG. 10 is a schematic diagram of a main part of an internal combustion engine system according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

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

[0012] FIG. 1 is a schematic diagram of a vehicle V equipped with an internal combustion engine system 1 according to an embodiment. As shown in FIG. 1, the internal combustion engine system 1 is mounted on 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 20 of the internal combustion engine system 1 is transmitted to drive wheels 22 via a transmission 21. The vehicle V may be, for example, a two-wheeled vehicle, a three-wheeled vehicle, a four-wheeled vehicle, a railcar, or the like. The drive wheels 22 are an example of a propulsion force generator that generates propulsion force using the driving force generated by the internal combustion engine 20 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 gas flow path 5. A shutoff valve 6 is provided in the liquid fuel gas 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 the combustion chamber 33 of the internal combustion engine 20 via a fuel gas passage 7. That is, the fuel gas passage 7 guides the fuel gas from the carburetor 4 toward the combustion chamber 33 of the internal combustion engine 20. A first pressurizing pump 8 is disposed in the fuel gas passage 7 to pressurize the fuel gas in the fuel gas passage 7 toward the internal combustion engine 20. The first pressurizing pump 8 is an unlinked pump that can perform pressurization unlinked to the output of the internal combustion engine 20. Specifically, the first pressurizing pump 8 is an electric pump driven by a pump motor 9 that is an electric motor. The pump motor 9 operates using electric power from the battery 24 that is a power source.

[0016] A second pressurizing pump 10 is disposed in the fuel gas flow path 7 downstream of the first pressurizing pump 8 to pressurize the fuel gas toward the internal combustion engine 20. The second pressurizing pump 10 pressurizes the fuel gas in the first flow path 7a and discharges it into the second flow path 7b. The second pressurizing pump 10 further pressurizes the fuel gas pressurized by the first pressurizing pump 8. The first pressurizing pump 8 and the second pressurizing pump 10 are arranged in series in the fuel gas flow path 7.

[0017] The second pressurizing pump 10 is a different type of pump from the first pressurizing pump 8. The second pressurizing pump 10 is a linked pump that is driven by energy generated by the internal combustion engine 20 and performs pressurization linked to the output of the internal combustion engine 20. Specifically, the second pressurizing pump 10 is a mechanically driven pump that is driven by the driving force generated by the internal combustion engine 20. Therefore, the output of the second pressurizing pump 10 increases as the output of the internal combustion engine 20 increases, and decreases as the output of the internal combustion engine 20 decreases.

[0018] The portion of the fuel gas flow path 7 upstream of the second pressurizing pump 10 is referred to as the first flow path 7a, and the portion of the fuel gas flow path 7 downstream of the second pressurizing pump 10 is referred to as the second flow path 7b. In this embodiment, the first flow path 7a is the portion of the fuel gas flow path 7 from the fuel gas supply source 2 to a first fuel injector 13, which will be described later. In this embodiment, the second flow path 7b is the portion from the second pressurizing pump 10 to a second fuel injector 14, which will be described later. The pressure of the fuel gas flowing through the second flow path 7b is higher than the pressure of the fuel gas flowing through the first flow path 7a. The first flow path 7a includes an upstream flow path 7aa, which is the portion upstream of the first pressurizing pump 8, and a downstream flow path 7ab, which is the portion downstream of the first pressurizing pump 8.

[0019] An intake passage 15 is connected to an intake port of the internal combustion engine 20. The intake passage 15 guides air purified by an air cleaner 16 to the intake port of the internal combustion engine 20. A throttle valve 17 is arranged in the intake passage 15. The amount of intake air supplied to the internal combustion engine 20 is adjusted by the throttle valve 17. The throttle valve 17 is driven by a throttle motor 18. The throttle valve 17 may be configured to be mechanically linked to manual operation by the driver.

[0020] A first fuel injector 13 is disposed downstream of the throttle valve 17 in the intake passage 15. The first fuel injector 13 is supplied with fuel gas discharged by the first pressurizing pump 8, bypassing the second pressurizing pump 10. The first fuel injector 13 supplies fuel to an intake port of the internal combustion engine 20 by injecting fuel gas into the intake passage 15. The first passage 7a includes a port injection passage R that guides fuel gas pressurized by the first pressurizing pump 8 for port injection to the first fuel injector 13. The fuel gas passage 7 can be shared by the second passage 7b for direct injection and the port injection passage R for port injection using the passage upstream of the second pressurizing pump 10, thereby simplifying the structure of the system 1.

[0021] A pressure reducing valve 11 is arranged in the second flow path 7b of the fuel gas flow path 7 downstream of the second pressurizing pump 10. The pressure reducing valve 11 maintains the injection pressure of the fuel gas into the combustion chamber 33 within a constant range regardless of the state of the internal combustion engine 20 and the state of the fuel gas supply source 2. A second fuel injector 14 is attached to the internal combustion engine 20. The second flow path 7b of the fuel gas flow path 7 is connected to the second fuel injector 14 of the internal combustion engine 20 downstream of the pressure reducing valve 11. The pressure of the fuel gas supplied to the second fuel injector 14 is higher than the pressure of the fuel gas supplied to the first fuel injector 13. The second fuel injector 14 injects the fuel gas directly into the combustion chamber 33 of the internal combustion engine 20. The second pressurizing pump 10 is a pressure reducing pump for direct injection.

[0022] In this embodiment, fuel injection is performed by the second fuel injector 14 during the compression stroke when the intake port 34 is closed, so a high injection pressure is required to overcome the pressure in the combustion chamber 33. For example, the injection pressure is required to be 10 MPa or higher. The pressure reducing valve 11 opens when the gas pressure on the downstream side falls below a predetermined pressure, and directs the combustion gas on the upstream side of the pressure reducing valve 11 to the downstream side of the pressure reducing valve 11. The pressure reducing valve 11 closes when the pressure of the fuel gas on the downstream side of the pressure reducing valve 11 reaches a pressure at which the fuel gas can be injected into the fuel chamber 33 against the pressure in the combustion chamber 33. In order to prevent a decrease in the gas pressure on the upstream side of the pressure reducing valve 11 due to the opening operation of the pressure reducing valve 11, a second booster pump 10 is provided.

[0023] A surge tank 12 is connected to a portion of the second flow path 7b of the fuel gas flow path 7 upstream of the pressure reducing valve 11. As a result, pressure is accumulated in the surge tank 12 when the pressure in the fuel gas flow path 7 is excessive, and the pressure of the surge tank 12 is supplied to the fuel gas flow path 7 when the pressure in the fuel gas flow path 7 is too low. By providing the surge tank 12 in this manner, pressure fluctuations in the combustion gas upstream of the pressure reducing valve 11 are suppressed. For example, the internal combustion engine system 1 can supply fuel gas to the internal combustion engine 20 at an appropriate pressure without complex control. The fuel gas flow path 7, the first pressure booster pump 8, the second pressure booster pump 10, the first fuel injector 13, and the second fuel injector 14 constitute a fuel supply device 90.

[0024] The surge tank 12 may be connected to a portion of the fuel gas flow path 7 between the first pressurizing pump 8 and the second pressurizing pump 10. If the surge tank 12 is disposed upstream of the second pressurizing pump 10, the surge tank 12 can be separated from the internal combustion engine 20 without lengthening the fuel gas flow path 7, thereby increasing the degree of freedom in layout.

[0025] The internal combustion engine 20 is provided with a generator motor 19 mechanically connected to the crankshaft of the internal combustion engine 20. The generator motor 19 is driven by energy generated by the internal combustion engine 20 to generate electricity. In this embodiment, the generator functions as an electric motor that starts the internal combustion engine 20 in addition to generating electricity. The pump motor 9 and the generator 19 are connected to an inverter 23. The inverter 23 is connected to a battery 24. The battery 24 can store electric power generated by the starter motor 19 using mechanical energy generated by the internal combustion engine 20. The inverter 23 may be divided into an inverter for the pump motor 9 and an inverter for the starter motor 19.

[0026] The internal combustion engine system 1 includes a controller 25. The controller 25 controls the shutoff valve 6, the first fuel injector 13, the second fuel injector 14, the throttle motor 18, the inverter 23, etc. The controller 25 controls the first booster pump 8 via the inverter 23.

[0027] FIG. 2 is a plan view of the internal combustion engine 20 and the like shown in FIG. 1. As shown in FIG. 2, the internal combustion engine 20 may be a single-cylinder engine, but in this embodiment, it is a multi-cylinder engine. The internal combustion engine 20 has a plurality of cylinders 30 arranged in a row. The intake passage 15 has a branch passage 15a corresponding to each cylinder 30. The number of first fuel injectors 13 is the same as the number of cylinders 30, and the number of second fuel injectors 14 is also the same as the number of cylinders 30. The multiple first fuel injectors 13 for port injection are each provided in the branch passage 15a of the intake passage 15. The multiple second fuel injectors 14 for direct injection are attached to the internal combustion engine 20 so as to correspond to each cylinder 30.

[0028] The internal combustion engine 20 has a crankshaft 31 extending in the direction in which the cylinders 30 are arranged. The direction in which the rotational axis X of the crankshaft 31 extends is referred to as the rotational axis direction X. A downstream flow path 7ab of the first flow path 7a of the fuel gas flow path 7 includes a first delivery flow path 28 extending in the rotational axis direction X and connected to multiple first fuel injectors 13. The first delivery flow path 28 may be, for example, a flow path within a delivery pipe extending in the rotational axis direction X. The first delivery flow path 28 is disposed in a region on the side where the intake passage 15 is located with respect to an imaginary plane including the circuit axis X of the crankshaft 31 and the cylinder axis Y. In other words, the first delivery flow path 28 is disposed closer to the intake port 34 than to the exhaust port 35 of the internal combustion engine 20. The first fuel injector 13 may be connected to the first delivery flow path directly or via a branch flow path. The first delivery flow path 28 allows the flow path in the fuel gas flow path 7 that distributes the fuel gas from the first pressure pump 8 to the plurality of first fuel injectors 13 to be arranged compactly.

[0029] The second flow passage 7b of the fuel gas flow passage 7 includes a second delivery flow passage 29 extending in the rotational axis direction X and connected to the multiple second fuel injectors 14. The second delivery flow passage 29 may be, for example, a flow passage within a delivery pipe extending in the rotational axis direction X. The second delivery flow passage 29 is disposed in a region on the side where the intake passage 15 is located with respect to an imaginary plane including the rotational axis X of the crankshaft 31 and the cylinder axis Y. In other words, the second delivery flow passage 29 is disposed closer to the intake port 34 than to the exhaust port 35 of the internal combustion engine 20. The second fuel injectors 14 may be connected to the second delivery flow passage directly or via a branch flow passage. The second delivery flow passage 29 allows for a compact arrangement of a flow passage that distributes fuel gas from the second flow passage 7b of the fuel gas flow passage 7 to the multiple second fuel injectors 14.

[0030] The second pressurizing pump 10, which is interposed in the second flow path 7b of the fuel gas flow path 7, is disposed in the internal combustion engine 20. The second pressurizing pump 10 is disposed away from the second fuel injector 14 in the rotational axis direction X. The discharge port of the second pressurizing pump 10 is connected to a second delivery flow path 29. The second delivery flow path 29 allows a flow path that distributes fuel gas from the second pressurizing pump 10 to the multiple second fuel injectors 14 to be disposed compactly. Note that although the system 1 of this embodiment includes one second pressurizing pump 10 per internal combustion engine 20, one internal combustion engine 20 may also include multiple second pressurizing pumps 10 lined up in the rotational axis direction X.

[0031] Figure 3 is a cross-sectional view taken along line III-III in Figure 2. As shown in Figure 3, the internal combustion engine 20 includes a cylinder head 32, a spark plug 37, an intake valve 43, an exhaust valve 53, a valve train 40, and the like. The cylinder head 32 has a combustion chamber 33, an intake port 34 that introduces intake air into the combustion chamber 33, and an exhaust port 35 that introduces exhaust gas from the combustion chamber 33 to an exhaust pipe. The cylinder 30 includes the combustion chamber 33. The combustion chamber 33 is defined by a piston disposed in the cylinder 30. The multiple combustion chambers 33 are aligned in the direction of the rotational axis X.

[0032] The intake port 34 is connected to an intake pipe 36 that defines a portion of the intake flow path 15. The exhaust port 35 is connected to an exhaust pipe. The cylinder head 32 has a central port 38 that opens into the combustion chamber 33 on the cylinder axis Y, which is the central axis of the cylinder 30. An ignition plug 37 that ignites fuel gas in the combustion chamber 33 is disposed in the central port 38. The intake valve 43 opens and closes a communication hole that connects the intake port 34 to the combustion chamber 33. The exhaust valve 53 opens and closes a communication hole that connects the combustion chamber 33 to the exhaust port 35.

[0033] The valve train 40 drives an intake valve 43 and an exhaust valve 53. For example, the valve train 40 includes an intake valve drive structure including an intake camshaft 41, an intake cam 42, an upper spring seat 44, a lower spring seat 45, and a valve spring 46. The intake camshaft 41 is disposed between the cylinder head 32 and a cylinder head cover 27 that covers the cylinder head 32. The intake camshaft 41 extends in the direction of the rotational axis X (see FIG. 2).

[0034] The intake camshaft 41 is mechanically connected to the crankshaft 31 and rotates in conjunction with the crankshaft 31. The intake cam 42 is provided on the intake camshaft 41 and rotates together with the intake camshaft 41. The upper spring seat 44 is fixed to one end of the intake valve 43 that faces the intake cam 42. The lower spring seat 45 is fixed to the cylinder head 32. The valve spring 46 is disposed between the upper spring seat 44 and the lower spring seat 45 and biases the intake valve 43 toward the intake cam 42.

[0035] Valve gear 40 includes an exhaust valve drive structure including an exhaust camshaft 51, an exhaust cam 52, an upper spring seat 54, a lower spring seat 55, and a valve spring 56. This exhaust valve drive structure has the same configuration as the intake valve drive structure described above except that the object to be driven is exhaust valve 53, so a detailed description thereof will be omitted.

[0036] The cylinder head 32 has a side port 39 that opens into the combustion chamber 33 at a position farther away from the cylinder axis Y on the intake side than the intake port 34. The side port 39 is provided with a second fuel injector 14 that is exposed toward the combustion chamber 33. When the discharge axis Z of the second fuel injector 14 is resolved into a component in the direction in which the cylinder axis Y extends and a component in a direction perpendicular to the cylinder axis Y, the discharge axis Z is mainly composed of a component in the direction perpendicular to the cylinder axis Y. A second delivery flow path 29 is connected to the second fuel injector 14. The second fuel injector 14 injects fuel gas directly into the combustion chamber 33 mainly from the direction perpendicular to the cylinder axis Y.

[0037] The first fuel injector 13 is attached to the intake passage 15 and injects fuel gas toward the intake passage 15. That is, the first fuel injector 13 injects fuel gas into the intake port 34. The first fuel injector 13 is connected to the first delivery passage 28. The first fuel injector 13 may be attached to a throttle body having a throttle valve 17 to inject combustion gas into the intake passage 15. That is, the first fuel injector 13 does not inject fuel gas directly into the combustion chamber 33, but may inject fuel gas upstream of the combustion chamber 33.

[0038] In this embodiment, the second fuel injector 14 is connected to the cylinder head 32. The first fuel injector 13 is disposed on a side of the intake passage 15 that is closer to the second injector 14 in the circumferential direction of the intake passage 15. In this manner, the injectors 13, 14 are disposed close to each other. The first delivery pipe 28 is disposed on a side closer to the second delivery pipe 29 with respect to the intake passage 15. The delivery pipes 28, 29 are disposed close to each other. By arranging the two delivery pipes 28, 29 close to each other in this manner, the length of the flow path connecting them can be shortened. The first fuel injector 14 and the first delivery pipe 28 are disposed on a side closer to the crankshaft 31 with respect to the intake passage 15. In other words, the first fuel injector 14 and the first delivery pipe 28 are disposed on a side farther from the cylinder head cover 27 with respect to the intake passage 15. By arranging each of the delivery pipes 28, 29 closer to the intake port 34 than to the exhaust port 35 of the internal combustion engine 20, the temperature rise of the delivery pipes 28, 29 can be reduced.

[0039] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. As shown in FIG. 4, the second pressurizing pump 10 is built into the internal combustion engine 20. The second pressurizing pump 10 is disposed adjacent to the intake valve 43 or the exhaust valve 53 (see FIG. 3) and is driven by power from the camshaft of the valve train 40. In this embodiment, the second pressurizing pump 10 is disposed adjacent to the intake valve 43 (see FIG. 3) and is driven by power from the intake camshaft 41. This allows the second pressurizing pump 10 to be disposed near the second fuel injector 14. The second pressurizing pump 10 may be reciprocated by an intake cam connected to the intake camshaft and reciprocating the intake valve. In this case, the second pressurizing pump is reciprocated by the intake cam, thereby reducing the number of parts. The second pressurizing pump 10 may be reciprocated by a pump cam connected to the intake cam separately from the intake cam. In this case, the second pressurizing pump can be disposed regardless of the shape and position of the intake cam, thereby increasing the options for the pump stroke length, compression chamber shape, layout, and the like.

[0040] The second pressurizing pump 10 is fixed to the cylinder head 32. The second pressurizing pump 10 is disposed on the intake side of the cylinder axis Y. The second pressurizing pump 10 is disposed closer to the intake port 34 than to the exhaust port 35. The first fuel injector 13 is also disposed on the intake side of the cylinder axis Y, and closer to the intake port 34 than to the exhaust port 35. This allows the second flow path 7b of the fuel gas flow path 7 to be shortened. The second fuel injector 14 can also be disposed on the intake side of the cylinder axis Y. This allows the fuel gas flow path 7 to be shortened overall.

[0041] Specifically, the second pressurizing pump 10 is a reciprocating pump. The second pressurizing pump 10 includes a cylinder 61, a piston 62, a compression chamber 63, a pump spring 64, an inlet check valve 66, and an outlet check valve 68. The cylinder 61 is fixed to the cylinder head 32. The piston 62 is slidably housed in the cylinder 61. The compression chamber 63 is defined between the cylinder 61 and the piston 62. The pump spring 64 biases the piston 62 toward a pump drive cam 69.

[0042] As shown in Fig. 2, in this embodiment, one second pressurizing pump is disposed between the combustion chambers, but multiple second pressurizing pumps may be disposed. When multiple second pressurizing pumps are disposed, they are preferably disposed at intervals in the crankshaft direction. By disposing multiple second pressurizing pumps, it becomes easier to prevent uneven injection pressures for each second injector.

[0043] The pump drive cam 69 is disposed inside the internal combustion engine 20, in other words, inside a case that forms the outer shell of the internal combustion engine 20. For example, the pump drive cam 69 is disposed in a valve space between the cylinder head 32 and the cylinder head cover 27. The pump drive cam 69 is provided on the intake camshaft 41, which is a rotating body that moves in conjunction with the crankshaft 31, and rotates together with the intake camshaft 41. The piston 62 is reciprocated by the pressure applied to the piston 62 by the rotating pump drive cam 69 and the biasing force of the pump spring 64. In other words, the pump drive cam 69 provided on the intake camshaft 41 is an example of a pump drive structure 70.

[0044] An inlet check valve 66 is provided at the inlet 65 of the cylinder 61. The inlet check valve 66 allows flow from the first flow path 7a of the fuel gas flow path 7 to the compression chamber 63 and prevents flow in the reverse direction. An outlet check valve 68 is provided at the outlet 67 of the cylinder 61. The outlet check valve 68 allows flow from the compression chamber 63 to the second flow path 7b of the fuel gas flow path 7 and prevents flow in the reverse direction. At least a portion of the fuel gas flow path 7 may be a passage formed in the internal combustion engine 20 (for example, the cylinder head 32 or the crankcase).

[0045] Conceptually speaking, the internal combustion engine 20 includes a crankshaft 31 (see FIG. 2 ), a camshaft 41 that moves in conjunction with the crankshaft 31, an intake port 34 connected to a combustion chamber 33, an intake valve 43 that opens and closes a communication hole between the intake port 34 and the combustion chamber 33, a valve drive cam 42 that rotates together with the camshaft 41 to drive the intake valve 43, and a pump drive cam 69 that rotates together with the camshaft 41 to drive a piston 62 of the second pressurizing pump 10. This allows the mechanically driven pump 69 to be driven using the structure of the internal combustion engine 20, thereby reducing the number of parts and achieving a compact structure for driving the second pressurizing pump 10. Furthermore, since the second pressurizing pump 10 is driven by power indirectly provided by the crankshaft 31, pressurization can be achieved in conjunction with the rotation of the crankshaft 31. Note that fuel gas may be directly supplied from the second pressurizing pump 10 to the second fuel injector 14.

[0046] The sealed space S in which the second pressurizing pump 10 is disposed is connected to the first flow path 7a via a return flow path 76. The sealed space S in which the second pressurizing pump 10 is disposed is a space covered by the cylinder head cover 27. A check valve 77 is disposed in the return flow path 76, which allows a flow from the sealed space S toward the first flow path 7a and prevents a flow in the reverse direction. The return flow path 76 guides fuel gas leaked from a gap between the cylinder 61 and the piston 62 during operation of the second pressurizing pump 10 to the first flow path 7a. This allows the leaked fuel gas to be used as fuel for the internal combustion engine 20, thereby achieving effective use of the fuel gas. Note that if it is difficult to inject the gas in the sealed space S from the injector 14, the return flow path 76 does not need to be provided. A check valve 77 may be disposed in the return flow path 76, which allows a flow from the sealed space S toward the intake passage 15 and prevents a flow in the reverse direction.

[0047] FIG. 5 is a block diagram of the controller etc. of FIG. 1. As shown in FIG. 5, the controller 25 includes a processing circuit 26. The controller 25 includes, for example, a processor 71, a system memory 72, and a storage memory 73. The processor 71 may include, for example, a CPU. The system memory 72 may include, for example, a RAM. The storage memory 73 may include a ROM. The storage memory 73 may include a hard disk, a flash memory, or a combination thereof. The storage memory 73 stores a program P. A configuration in which the processor 71 executes the program P read into the system memory 72 is an example of the processing circuit 26.

[0048] The input interface of the controller 25 is electrically connected to, for example, an accelerator sensor 81, a gear position sensor 82, a brake pressure sensor 83, a rotation speed sensor 84, a vehicle speed sensor 85, a fuel level sensor 86, a first pressure sensor 87, a second pressure sensor 88, etc. The accelerator sensor 81 detects the amount of accelerator operation by the driver of the vehicle V, i.e., the amount of acceleration required. The gear position sensor 82 detects the current gear position of the transmission 21. The brake pressure sensor 83 detects the amount of brake operation by the driver of the vehicle V by detecting the brake pressure of a hydraulic brake device.

[0049] The rotation speed sensor 84 detects the rotation speed of the crankshaft 31 of the internal combustion engine 20. The vehicle speed sensor 85 detects the traveling speed of the vehicle V. The remaining fuel sensor 86 detects the amount of fuel remaining in the liquid fuel tank 3. The first pressure sensor 87 detects the pressure in the first flow path 7a of the fuel gas flow path 7. That is, it detects the pressure between the first pressure pump 8 and the second pressure pump 10 in the fuel gas flow path 7. The second pressure sensor 88 detects the pressure in the second flow path 7b of the fuel gas flow path 7 between the second pressure pump 10 and the pressure reducing valve 11.

[0050] The output interface of controller 25 is electrically connected to first fuel injector 13, second fuel injector 14, spark plug 37, throttle motor 18, inverter 23, etc. Controller 25 is configured to control at least one of first fuel injector 13, second fuel injector 14, spark plug 37, throttle motor 18, and inverter 23 based on detection signals from each of sensors 81 to 87. Controller 25 controls pump motor 9 by controlling inverter 23.

[0051] Fig. 6 is a graph showing an example of time-series data of the rotation speeds of the internal combustion engine 20, first pressurizing pump 8, and second pressurizing pump 10 of Fig. 1. The vertical axis of the graph in Fig. 6 represents the rotation speed per minute of the crankshaft 31 of the internal combustion engine 20, the number of cycles per minute of the first pressurizing pump 8, and the number of cycles per minute of the second pressurizing pump 10. In a rotary pump, one rotation of the pump shaft constitutes one cycle, and in a reciprocating pump, one cycle corresponds to one reciprocating movement of the piston.

[0052] The second pressurizing pump 10 is linked to the rotation of the crankshaft 31 of the internal combustion engine 20, and therefore the rotation speed of the second pressurizing pump 10 increases as the rotation speed of the internal combustion engine 20 increases and decreases as the rotation speed of the internal combustion engine 20 decreases. The controller 25 operates the first pressurizing pump 8 in a pressurization pattern different from that of the second pressurizing pump 10. For example, the controller 25 controls the pump motor 9 so that the rotation speed of the first pressurizing pump 8 is constant. This allows the first pressurizing pump 8 to operate at an efficient rotation speed, and the energy efficiency of the first pressurizing pump 8 can be maintained at a good level.

[0053] The controller 25 may control the pump motor 9 that drives the first pressurizing pump 8 based on status information that indicates the operating status of the internal combustion engine 20. This makes it easier to bring the fuel gas supplied to the internal combustion engine 20 closer to a pressure suitable for the operation of the internal combustion engine 20. For example, the controller 25 may control the pump motor 9 to decrease the rotation speed of the first pressurizing pump 8 as the rotation speed of the internal combustion engine 20 detected by the rotation speed sensor 84 increases.

[0054] The controller 25 may control the pump motor 9 that drives the first pressurizing pump 8 based on state information that indicates a predicted future operating state of the internal combustion engine 20. That is, the controller 25 may control the pump motor 9 by predicting that an increase in the fuel gas pressure will be required in the future. The first pressurizing pump 8 is driven by an electric motor, which can improve responsiveness compared to the second pressurizing pump 10 that is driven by the internal combustion engine 20. For example, the controller 25 may control the pump motor 9 based on the operation state of the driver. For example, the controller 25 may control the pump motor 9 to increase the rotation speed of the first pressurizing pump 8 as the amount of acceleration request detected by the accelerator sensor 81 increases.

[0055] The controller 25 may control the pump motor 9 to increase the rotation speed of the first pressurizing pump 8 as the gear position of the transmission 21 detected by the gear position sensor 82 becomes lower. The controller 25 may control the pump motor 9 to decrease the rotation speed of the first pressurizing pump 8 as the brake operation amount detected by the brake pressure sensor 83 increases. In addition, the controller 25 may control the pump motor 9 to increase the rotation speed of the first pressurizing pump 8 as the inclination of the road surface detected by the vehicle attitude sensor increases. In this way, by increasing the pressure of the fuel gas by the first pressurizing pump 8 before the pressure of the fuel gas by the second pressurizing pump 10, it is possible to easily prevent a delay in response to a change in the amount of fuel injection supplied to the internal combustion engine 20.

[0056] The controller 25 may control the pump motor 9 that drives the first pressurizing pump 8 based on status information that indicates the operating status of the vehicle V in which the internal combustion engine system 1 is installed. For example, the controller 25 may control the pump motor 9 to reduce the rotation speed of the first pressurizing pump 8 as the traveling speed of the vehicle V detected by the vehicle speed sensor 85 increases. The controller 25 may also control the pump motor 9 to reduce the rotation speed of the first pressurizing pump 8 when the amount of fuel remaining in the liquid fuel tank 3 detected by the remaining fuel sensor 86 becomes less than a lower limit value.

[0057] The controller 25 may control the pump motor 9 that drives the first pressure pump 8 based on status information indicating the status of the fuel gas in the fuel gas flow path 7. For example, the controller 25 may control the pump motor 9 in response to a detection signal from a pressure sensor that detects the internal pressure of the surge tank 12. The controller 25 may increase the output of the pump motor 9 until the internal pressure of the surge tank 12 reaches a predetermined pressure, and then keep the output of the pump motor 9 constant when the internal pressure of the surge tank 12 exceeds a threshold value. The controller 25 may reduce the output of the pump motor 9 when the internal pressure of the surge tank 12 exceeds a threshold value compared to when the internal pressure of the surge tank 12 does not exceed the threshold value.

[0058] The controller 25 may increase the output of the pump motor 9 when the pressure in the surge tank 12 is lower than a predetermined value under conditions that predict a request for an increase in the output of the internal combustion engine 20. The conditions that predict a request for an increase in the output of the internal combustion engine 20 may be a condition that the traveling speed is lower than a threshold value, a condition that the reduction ratio of the transmission 21 is greater than a predetermined value, a condition that the accelerator operation amount by the driver is smaller than a predetermined value, or a condition that the driver is accelerating. Conversely, the controller 25 may decrease the output of the pump motor 9 under conditions that predict a request for a decrease in the output of the internal combustion engine 20.

[0059] In addition, if the second pressurizing pump 10 is a controllable pump, the controller 25 may control the second pressurizing pump 10 instead of or in addition to the various controls of the first pressurizing pump 8 described above.

[0060] The controller 25 may control the first fuel injector 13 and the second fuel injector 14 according to a fuel injection mode. The fuel injection mode includes at least two of a direct injection mode, a port injection mode, and a mixed mode. In the direct injection mode, the controller 25 injects fuel gas from the second fuel injector 14 while stopping the first fuel injector 13. In the port injection mode, the controller 25 injects fuel gas from the first fuel injector 13 while stopping the second fuel injector 14. In the mixed mode, the controller 25 injects fuel gas from both the first fuel injector 13 and the second fuel injector 14. In the mixed injection mode, the injection amount per unit time of the first fuel injector 13 is preferably smaller than the injection amount per unit time of the second fuel injector 14. This prevents abnormal combustion caused by port injection and stabilizes combustion.

[0061] For example, if the amount of fuel gas required to be supplied to the combustion chamber 33 is F, the amount of fuel gas F1 required to be injected by the first fuel injector 13 may be F1=F×α (0≦α≦1), and the amount of fuel gas F2 required to be injected by the second fuel injector 14 may be F2=F×(1−α). Here, the ratio α may be a value selected from continuous values ​​greater than or equal to 0 and less than or equal to 1, or may be a value selected from three discrete values, α=0, 0.5, and 1, or may be a value selected from any two of the three discrete values, α=0, 0.5, and 1. The ratio α may be read from a map indicating the correspondence between a parameter indicating the operating state of the vehicle V and the ratio α.

[0062] The controller 25 acquires status information. The status information indicates the operating status of the internal combustion engine 20, the future operating status of the internal combustion engine 20, the state of the fuel gas in the fuel gas flow path 7, the operating status of the vehicle V, or the state of the remaining fuel in the fuel gas supply source 2. For example, the controller 25 receives the rotation speed of the internal combustion engine 20 from the rotation speed sensor 84 as the operating status of the internal combustion engine 20. The controller 25 receives the driver's acceleration request from the accelerator sensor 81 as the future operating status of the internal combustion engine 20. The controller 25 receives a detection signal from at least one of the first pressure sensor 87 and the second pressure sensor 88 as the status of the fuel gas flow path of the fuel gas flow path 7.

[0063] The controller 25 receives a detection signal from at least one of the gear position sensor 82, the brake pressure sensor 83, and the vehicle speed sensor 85 as the operating state of the vehicle V. The controller 25 receives a detection signal from at least one of the first pressure sensor 87 and the second pressure sensor 88 as the state of the fuel gas in the fuel gas flow path 7. The controller 25 receives a detection signal from the remaining fuel sensor 86 as the state of the remaining fuel in the fuel gas supply source 2.

[0064] The controller 25 individually controls the first fuel injector 13 or the second fuel injector 14 based on the above-described status information. For example, the controller 25 individually controls the first fuel injector 13 or the second fuel injector 14 based on the above-described status information. For example, the controller 25 may implement a port injection mode when it determines that an abnormality has occurred in the internal combustion engine 20. The controller 25 may also determine that an abnormality has occurred in the internal combustion engine 20 when it determines that a rate of change in the rotation speed detected by the rotation speed sensor 84 relative to the acceleration request amount detected by the accelerator sensor 81 is not within a predetermined normal range.

[0065] The controller 25 may implement the port injection mode when it determines that the remaining amount of fuel in the fuel gas supply source 2 has fallen below a threshold. This makes it possible to extend the cruising distance while reducing the output of the internal combustion engine 20. The controller 25 may switch to the mix injection mode when the rotation speed detected by the rotation speed sensor 84 exceeds a predetermined value in the port injection mode.

[0066] The controller 25 may implement the mix injection mode when it determines that the acceleration request amount detected by the accelerator sensor 81 has increased. The controller 25 may implement the port injection mode when it determines that the brake pressure detected by the brake pressure sensor 83 has exceeded a threshold value. The controller 25 may cause the first fuel injector 13 to discharge fuel gas in the port injection mode or the mix injection mode when it determines that the pressure detected by the first pressure sensor 87 has exceeded a threshold value. The controller 25 may implement the mix injection mode until it determines that the pressure detected by the second pressure sensor 88 has reached a predetermined value, such as when starting the internal combustion engine 20.

[0067] When controller 25 determines that a predetermined low power demand state exists, controller 25 may set the opening time of second fuel injector 14 to be shorter than the opening time of first fuel injector 13 in the mix injection mode. The predetermined low power demand state may be, for example, a state in which internal combustion engine 20 is determined to be idling or decelerating based on the detection signal of rotation speed sensor 84, a state in which the acceleration demand detected by accelerator sensor 81 is less than a predetermined value, or a state in which the gear position detected by gear position sensor 82 is less than a predetermined reduction ratio and the vehicle speed detected by vehicle speed sensor 85 exceeds a predetermined value.

[0068] When it is determined that the power mode has been selected, the controller 25 may set the opening time of the second fuel injector 14 to be shorter than the opening time of the first fuel injector 13 in the mix injection mode, compared to when it is determined that the eco mode has been selected. When it is determined that the mix injection mode is in a predetermined operating range in which the degree of diffusion of fuel gas in the combustion chamber 33 has decreased and abnormal combustion is likely to occur, the controller 25 may switch to the port injection mode.

[0069] The controller 25 may implement a port injection mode in a low load region where the required torque is smaller than a first threshold, a direct injection mode in a medium load region where the required torque is equal to or greater than the first threshold and less than a second threshold that is greater than the first threshold, and a mix injection mode in a high load region where the required torque is equal to or greater than the second threshold.

[0070] In the port injection mode, the controller 25 may adjust the rotation speed of the first pressurizing pump 8 in accordance with the required torque. When the controller 25 determines that the rotation speed detected by the rotation speed sensor 84 exceeds a predetermined value in the port injection mode or the mix injection mode, the controller 25 may increase the rotation speed of the first pressurizing pump 8.

[0071] According to the configuration described above, by injecting high-pressure fuel gas from the second fuel injector 14 into the combustion chamber 33, abnormal combustion of the fuel gas can be prevented and the output of the internal combustion engine 20 can be increased. Furthermore, by injecting fuel into the intake port 34 by the first fuel injector 13, the fuel gas can be used for combustion in the internal combustion engine 20 even when the fuel gas pressure is low. By providing these two fuel injectors 13, 14, the effective pressure range of the fuel gas used for combustion can be expanded, and the performance of the internal combustion engine 20 can be improved.

[0072] FIG. 7 is a cross-sectional view of a main portion of an internal combustion engine 120 according to a modified example. Components common to those in the previously described embodiment are assigned the same reference numerals, and a description thereof will be omitted. As shown in FIG. 7, in the internal combustion engine 120 according to this modified example, the positions of the second fuel injector 14 and the spark plug 37 are reversed. The second fuel injector 14, which ignites fuel gas in the combustion chamber 33, is disposed in a central port 38 of the cylinder head 32. The spark plug 37, exposed toward the combustion chamber 33, is disposed in a side port 39 of the cylinder head 32. The second fuel injector 14 injects fuel gas along the cylinder axis Y, which facilitates uniform distribution of the fuel gas in the combustion chamber 33. Other components are similar to those in the previously described embodiment, and therefore a description thereof will be omitted.

[0073] FIG. 8 is a schematic diagram of a main part of an internal combustion engine system 101 of a first modified example. Note that components common to the above-described embodiment are assigned the same reference numerals and will not be described again. As shown in FIG. 8 , in the internal combustion engine system 101 of the first modified example, a first passage 107a in which a first pressurizing pump 8 is disposed in a fuel gas passage 107 includes a port injection passage R2 that guides fuel gas before being pressurized by the first pressurizing pump 8 to the first fuel injector 13. That is, the port injection passage R2 branches off from a portion of the first passage 107a of the fuel gas passage 107 upstream of the first pressurizing pump 8 toward the first fuel injector 13. This allows the fuel gas supplied to the second fuel injector 14 to be kept at a high pressure while the fuel gas supplied to the first fuel injector 13 is kept at a sufficiently low pressure. This port injection passage R2 may be added to the configuration of FIG. 1 described above. Note that the other components are similar to those of the above-described embodiment and will not be described again.

[0074] FIG. 9 is a schematic diagram of a main part of an internal combustion engine system 201 of a second modified example. Note that components common to the above-described embodiment are assigned the same reference numerals and description thereof will be omitted. As shown in FIG. 9, the internal combustion engine system 201 of the second modified example is provided with only a pressure pump 10 as a pump for pressurizing fuel gas flowing from the fuel gas supply source 2 to the second fuel injector 14. The port injection flow path R3, which guides fuel gas from the fuel gas supply source 2 to the first fuel injector 13, bypasses the pressure pump 10 and is connected to a portion of the fuel gas flow path 7 upstream of the pressure pump 10. This allows the internal combustion engine system 201 to have a simple configuration. Note that other components are similar to those of the above-described embodiment and description thereof will be omitted.

[0075] FIG. 10 is a schematic diagram of essential parts of an internal combustion engine system 301 according to a third modified example. Components common to the above-described embodiment are denoted by the same reference numerals, and a description thereof will be omitted. As shown in FIG. 10, the internal combustion engine system 301 according to the third modified example includes a first fuel gas supply source 2A and a second fuel gas supply source 2B. Fuel gas from the first fuel gas supply source 2A is supplied to the first fuel injector 13 via a first fuel gas flow path 7A. Fuel gas from the second fuel gas supply source 2B is supplied to the second fuel injector 14 via a second fuel gas flow path 7B. The first fuel gas flow path 7A and the second fuel gas flow path 7B are arranged in parallel. A first pressure pump 308 is arranged in the first fuel gas flow path 7A to pressurize the fuel gas flowing through the first fuel gas flow path 7A and discharge the pressurized fuel gas toward the first fuel injector 13. A second pressure pump 310 is disposed in the second fuel gas flow path 7B, which pressurizes the fuel gas flowing through the second fuel gas flow path 7B and discharges it toward the second fuel injector 14. Note that other configurations are similar to those of the above-described embodiment, and therefore description thereof will be omitted.

[0076] The technology of the present disclosure is not limited to the above-described embodiment. The first pressurizing pump 8 may be a linked pump that pressurizes in conjunction with the output of the internal combustion engine 20. Specifically, the first pressurizing pump 8 may be a pump that is driven to rotate by energy generated by the internal combustion engine 20. The first pressurizing pump 8 may be a Roots pump, or an existing pump other than a Roots pump, such as an axial or centrifugal pump that compresses gas by rotating rotors. The first pressurizing pump may be a reciprocating pump. For example, the first pressurizing pump 8 and the second pressurizing pump 10 may be the same type of pump.

[0077] The generator motor 19 is an ISG (Integrated Starter Generator) that drives the crankshaft 31 when starting the internal combustion engine 20, but is not limited to this. A generator having only a power generating function may be used instead of the generator motor 19. The pump motor 9 may be a three-phase AC motor or a DC motor. In order to suppress a rise in the temperature of the fuel gas due to the use of multiple pumps 8, 10, it is preferable that a cooler be provided in the fuel gas flow path 7 downstream of at least one of the first pressurizing pump 8 and the second pressurizing pump 10 to lower the temperature of the pressurized fuel gas.

[0078] Although internal combustion engine 20 is preferably a multi-cylinder engine having multiple cylinders arranged along crankshaft 35, this is not limiting. For example, internal combustion engine 20 may be a single-cylinder engine having a single cylinder. Internal combustion engine 20 may also be an engine with a structure in which multiple cylinders are arranged circumferentially around the crankshaft, such as a V-type, L-type, or opposed-type engine. When multiple intake ports are provided for one combustion chamber, first fuel injector 13 may be provided in one of the ports, or may be provided in each of the multiple ports. First fuel injector 13 may be provided upstream of throttle valve 17, rather than downstream of throttle valve 17.

[0079] A supercharger for pressurizing the intake air may be provided between the air cleaner 16 and the throttle valve 17 in the intake passage 15. When a supercharger is provided, the first pressure pump 8 is required to provide a pressure that allows the first fuel injector 13 to inject against the supercharged intake pressure. The supercharger may be a supercharger or a turbo.

[0080] The first fuel injector 13 may be disposed on a side closer to the cylinder head cover 27 with respect to the intake passage 15. The first fuel injector 13 may be disposed so that its fuel injection axis faces the combustion chamber 33. The internal combustion engine system 1 may be mounted or installed on a site other than the vehicle V. For example, the internal combustion engine system 1 may be installed in a power generation facility that generates energy for power generation, or may be used as a drive source that generates fluid energy using the power of the crankshaft 31.

[0081] When second pressurizing pump 10 is configured to be driven by power generated by internal combustion engine 20, it is preferable that second pressurizing pump 10 be disposed in the vicinity of second fuel injector 14. In other words, second pressurizing pump 10 is preferably driven by power of a rotor that is driven by a rotor disposed within cylinder head cover 27. For example, second pressurizing pump 10 is preferably driven by rotation of intake cam 42 or intake camshaft 41, but the second pressurizing pump may also be driven by rotation of exhaust cam 52 or exhaust camshaft 51.

[0082] The second pressurizing pump 10 is not limited to a reciprocating reciprocating pump, and may have a structure in which fuel is pressurized by a rotary vane that is driven to rotate. Even in this case, power is transmitted to the second pressurizing pump 10 from a rotor disposed inside the cylinder head cover 27, thereby shortening the flow path connecting the second fuel injector 14 and the second pressurizing pump 10. The second pressurizing pump 10 may be disposed at a position away from the second fuel injector 14. For example, the second pressurizing pump 10 may receive power from the crankshaft 31 and be supported by the crankcase. The second pressurizing pump 10 may be driven by an electric motor and disposed at a distance from the internal combustion engine 20.

[0083] As described above, the above-described 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 embodiments and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above-described 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 one embodiment may be separated from other configurations in that embodiment and extracted as desired. 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.

[0084] 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. A processor is considered a processing circuit or circuit because it includes 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.

[0085] [Aspect] The above-described embodiments are examples of the following aspects.

[0086] (Aspect 1) an internal combustion engine including at least one combustion chamber and at least one intake port for directing air into the combustion chamber; a first flow path through which fuel gas flows; a second flow path through which fuel gas having a higher pressure than that of the first flow path flows; at least one first fuel injector that is supplied with fuel gas from the first flow passage and is arranged to inject fuel gas into the intake port of the internal combustion engine; and at least one second fuel injector supplied with fuel gas from the second flow passage and positioned to inject fuel gas into the combustion chamber of the internal combustion engine.

[0087] According to this configuration, by injecting high-pressure fuel gas from the second fuel injector into the combustion chamber, abnormal combustion of the fuel gas can be prevented and the output of the internal combustion engine can be increased. Also, by injecting fuel into the intake port by the first fuel injector, fuel gas can be used for combustion in the internal combustion engine even when the fuel gas pressure is low. By using these two fuel injectors, the effective pressure range of the fuel gas used for combustion can be expanded, thereby improving the performance of the internal combustion engine.

[0088] (Aspect 2) 2. The internal combustion engine system according to claim 1, further comprising: a booster pump that compresses the fuel gas in the first passage and discharges the compressed fuel gas into the second passage.

[0089] With this configuration, fuel gas can be supplied to the internal combustion engine from both the upstream and downstream sides of the booster pump. Also, the second flow path leading to the second fuel injector for direct injection and the first flow path leading to the first fuel injector for port injection can share the flow path upstream of the booster pump, simplifying the system structure.

[0090] (Aspect 3) The internal combustion engine system further includes a booster pump interposed in the first flow path, 3. The internal combustion engine system according to claim 1, wherein the first flow path includes at least one of a flow path that guides the fuel gas before it is pressurized by the first pressure pump to the first fuel injector and a flow path that guides the fuel gas after it is pressurized by the pressure pump to the first fuel injector.

[0091] According to this configuration, the effective range of the injection pressure of the first fuel injector can be expanded. The pressure pump of the second aspect may be the second pressure pump, and the pressure pump of the third aspect may be the first pressure pump.

[0092] (Aspect 4) 4. The internal combustion engine system of any of aspects 1-3, further comprising a processing circuit configured to independently control the first fuel injector and the second fuel injector.

[0093] According to this configuration, by performing either or both of direct injection and port injection depending on the situation, fuel supply to the internal combustion engine can be suitably performed depending on the situation.

[0094] (Aspect 5) the internal combustion engine further includes a cylinder including the combustion chamber and at least one exhaust port through which exhaust gas is directed from the combustion chamber; Aspects 5. The internal combustion engine system according to any one of aspects 2 to 4, wherein the first fuel injector and the second booster pump are disposed closer to the intake port than to the exhaust port relative to the axis of the cylinder.

[0095] According to this configuration, the first fuel injector and the second pressure pump can be disposed close to each other, and the first flow path can be shortened.

[0096] (Aspect 6) the internal combustion engine further includes a piston defining the combustion chamber, a cylinder in which the piston is disposed, and at least one exhaust port through which exhaust gas is directed from the combustion chamber; Aspects 6. The internal combustion engine system according to any one of aspects 2 to 5, wherein the second fuel injector and the second booster pump are disposed closer to the intake port than to the exhaust port relative to the axis of the cylinder.

[0097] According to this configuration, the second fuel injector and the second pressure pump can be disposed close to each other, and the second flow path can be shortened.

[0098] (Aspect 7) the pressure pump is a reciprocating pump including a piston and a cylinder in which the piston is housed, Aspect 7. The internal combustion engine system according to any one of aspects 2 to 6, further comprising: a return passage that guides combustion gas leaking from a gap between the cylinder and the piston during operation of the reciprocating pump to the first flow passage.

[0099] According to this configuration, the leaked fuel gas can be used as fuel for the internal combustion engine, thereby enabling the fuel gas to be used effectively.

[0100] (Aspect 8) the at least one combustion chamber includes a plurality of combustion chambers arranged in one direction; the at least one second fuel injector includes a plurality of second fuel injectors arranged in the same direction; the second fuel flow path includes a delivery flow path extending in the one direction and connected to the plurality of fuel injectors, Aspect 8. The internal combustion engine system according to any one of aspects 2 to 7, wherein a discharge port of the second pressure pump is connected to the delivery flow path.

[0101] According to this configuration, the flow passages that distribute the fuel gas from the second pressure pump to the plurality of fuel injectors can be arranged in a compact manner.

[0102] (Aspect 9) A vehicle comprising the internal combustion engine system according to any one of aspects 1 to 8.

[0103] (Aspect 10) A control method for an internal combustion engine system including an internal combustion engine including at least one combustion chamber and an intake port that introduces air into the combustion chamber, a first flow path through which fuel gas flows, a second flow path through which fuel gas flows that has a higher pressure than the first flow path, a first fuel injector that receives fuel gas from the first flow path and is arranged to inject the fuel gas into the intake port of the internal combustion engine, and a second fuel injector that receives fuel gas from the second flow path and is arranged to inject the fuel gas into the combustion chamber of the internal combustion engine, acquiring status information indicating an operating state of the internal combustion engine, a future operating state of the internal combustion engine, or a state of fuel gas in the first flow path or the second flow path; and individually controlling the first fuel injector and the second fuel injector based on the status information.

[0104] This method allows for a fuel supply that is suited to various conditions.

[0105] (Aspect 11) Independently controlling the first fuel injector and the second fuel injector includes selecting an injection mode from a plurality of injection modes; The plurality of injection modes include: a direct injection mode in which fuel gas is injected from the second fuel injector while the first fuel injector is stopped; a port injection mode in which fuel gas is injected from the first fuel injector while the second fuel injector is stopped; a mix injection mode in which fuel gas is injected from both the first fuel injector and the second fuel injector; 11. The method of controlling an internal combustion engine system according to claim 10, comprising at least two modes of:

[0106] This method allows the fuel injection method to be switched to suit the situation.

[0107] (Aspect 12) A control method for an internal combustion engine system according to aspect 11, wherein selecting one injection mode from the plurality of injection modes includes selecting the port injection mode when it is determined that an abnormality exists in the internal combustion engine.

[0108] According to this method, even if the first fuel injector cannot supply fuel gas to the combustion chamber at an appropriate pressure, the internal combustion engine can continue to operate by supplying fuel gas to the intake port from the second fuel injector. [Explanation of symbols]

[0109] 1,101,201,302 Internal combustion engine systems 2. Fuel gas supply source 5 Liquid fuel flow path 7 Fuel gas flow path 8. First pressure pump 10 Second pressure pump 12 Surge Tank 13 First fuel injector 14 Second fuel injector 20,120 Internal combustion engine 24 Battery 25 Controller 26 Processing circuit 30 cylinders 31 Crankshaft 33 Combustion chamber 34 Intake port 35 exhaust port 40 Valve train 41 Intake camshaft 62 Piston 69 Pump drive cam 70 Pump drive structure 90 Fuel supply system V Vehicle

Claims

1. an internal combustion engine including at least one combustion chamber and at least one intake port for directing air into said combustion chamber; a first flow path through which fuel gas flows; a second flow path through which fuel gas having a higher pressure than that of the first flow path flows; at least one first fuel injector supplied with fuel gas from the first flow passage and arranged to inject fuel gas into the intake port of the internal combustion engine; at least one second fuel injector supplied with fuel gas from the second flow passage and positioned to inject fuel gas into the combustion chamber of the internal combustion engine.

2. The internal combustion engine system according to claim 1 , further comprising a booster pump that compresses the fuel gas in the first passage and discharges it into the second passage.

3. The internal combustion engine system further includes a booster pump interposed in the first flow path, 2. The internal combustion engine system according to claim 1, wherein the first flow path includes at least one of a flow path that guides the fuel gas before being pressurized by the pressurizing pump to the first fuel injector, and a flow path that guides the fuel gas after being pressurized by the pressurizing pump to the first fuel injector.

4. The internal combustion engine system of claim 1 , further comprising a processing circuit configured to independently control each of the first and second fuel injectors.

5. the internal combustion engine further includes a cylinder including the combustion chamber and at least one exhaust port through which exhaust gas is directed from the combustion chamber; 3. The internal combustion engine system according to claim 2, wherein the first fuel injector and the booster pump are disposed closer to the intake port than to the exhaust port relative to the axis of the cylinder.

6. the internal combustion engine further includes a cylinder including the combustion chamber and at least one exhaust port through which exhaust gas is directed from the combustion chamber; 3. The internal combustion engine system according to claim 2, wherein the second fuel injector and the booster pump are disposed closer to the intake port than to the exhaust port relative to the axis of the cylinder.

7. the pressure pump is a reciprocating pump including a piston and a cylinder in which the piston is housed, 3. The internal combustion engine system according to claim 2, further comprising a return passage that guides combustion gas leaking from a gap between the cylinder and the piston during operation of the reciprocating pump to the first flow passage.

8. the at least one combustion chamber includes a plurality of combustion chambers arranged in one direction; the at least one second fuel injector includes a plurality of second fuel injectors arranged in the same direction; the second flow passage includes a delivery flow passage extending in the one direction and connected to the plurality of second fuel injectors, The internal combustion engine system according to claim 2 , wherein a discharge port of the pressure pump is connected to the delivery flow path.

9. A vehicle comprising an internal combustion engine system according to any one of claims 1 to 8.

10. A control method for an internal combustion engine system including an internal combustion engine including a combustion chamber and an intake port that introduces air into the combustion chamber, a first flow path through which fuel gas flows, a second flow path through which fuel gas flows that has a higher pressure than the first flow path, a first fuel injector that receives the fuel gas from the first flow path and is arranged to inject the fuel gas into the intake port of the internal combustion engine, and a second fuel injector that receives the fuel gas from the second flow path and is arranged to inject the fuel gas into the combustion chamber of the internal combustion engine, acquiring status information indicating an operating state of the internal combustion engine, a future operating state of the internal combustion engine, or a state of fuel gas in the first flow path or the second flow path; and individually controlling the first fuel injector and the second fuel injector based on the status information.

11. Independently controlling the first fuel injector and the second fuel injector includes selecting an injection mode from a plurality of injection modes; The plurality of injection modes include: a direct injection mode in which fuel gas is injected from the second fuel injector while the first fuel injector is stopped; a port injection mode in which fuel gas is injected from the first fuel injector while the second fuel injector is stopped; a mix injection mode in which fuel gas is injected from both the first fuel injector and the second fuel injector; 11. The method of claim 10, further comprising at least two of the following modes:

12. 12. The control method for an internal combustion engine system according to claim 11, wherein selecting one injection mode from the plurality of injection modes includes selecting the port injection mode when it is determined that an abnormality exists in the internal combustion engine.

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