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

Abstract

This internal combustion engine system comprises: an internal combustion engine including at least one combustion chamber and at least one intake port that guides air to the combustion chamber; a first flow path through which a fuel gas flows; a second flow path through which a fuel gas having a higher pressure than in the first flow path flows; at least one first fuel injector to which the fuel gas is supplied from the first flow path and which is disposed so as to inject the fuel gas into the intake port of the internal combustion engine; and at least one second fuel injector to which the fuel gas is supplied from the second flow path and which is disposed so as to inject the fuel gas into the combustion chamber of the internal combustion engine.

Description

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

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

[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.

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

[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.

[0006] An internal combustion engine system according to one aspect of the present disclosure 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.

[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 aspect 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.

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

[0010] FIG. 1 is a schematic diagram of a vehicle equipped with an internal combustion engine system according to an embodiment. FIG. 2 is a plan view of the internal combustion engine and other components of FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a block diagram of the controller and other components of FIG. 1. FIG. 6 is a graph showing an example of time-series data of the rotation speeds of the internal combustion engine, first pressurizing pump, and second pressurizing pump of FIG. 1. FIG. 7 is a cross-sectional view of essential parts of an internal combustion engine according to a modified example. FIG. 8 is a schematic diagram of essential parts of an internal combustion engine system according to a first modified example. FIG. 9 is a schematic diagram of essential parts of an internal combustion engine system according to a second modified example. FIG. 10 is a schematic diagram of essential parts of an internal combustion engine system according to a third modified example.

[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 flow path 7. That is, the fuel gas flow path 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 flow path 7 to pressurize the fuel gas in the fuel gas flow path 7 toward the internal combustion engine 20. The first pressurizing pump 8 is an unsynchronized pump that can perform pressurization unsynchronized with 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 a 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 pressurizes in conjunction with 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] A portion of the fuel gas flow path 7 upstream of the second pressurizing pump 10 is referred to as a first flow path 7a, and a portion of the fuel gas flow path 7 downstream of the second pressurizing pump 10 is referred to as a second flow path 7b. In this embodiment, the first flow path 7a is a portion of the fuel gas flow path 7 from the fuel gas supply source 2 to a first fuel injector 13 described below. In this embodiment, the second flow path 7b is a portion from the second pressurizing pump 10 to a second fuel injector 14 described below. 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 that is a portion upstream of the first pressurizing pump 8, and a downstream flow path 7ab that is a 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. Fuel gas discharged by the first pressurizing pump 8 is supplied to the first fuel injector 13, 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 on the upstream side of the second pressurizing pump 10, simplifying the structure of the system 1.

[0021] A pressure reducing valve 11 is disposed 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 combustion chamber 33 against the pressure in the combustion chamber 33. The second booster pump 10 is provided 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.

[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 motor 19 are connected to an inverter 23. The inverter 23 is connected to a battery 24. The battery 24 can store the electric power generated by the generator motor 19 using the 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 generator 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 other components 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 plurality of first fuel injectors 13 for port injection are each provided in the branch passage 15a of the intake passage 15. The plurality of 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. The 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 of an imaginary plane including the rotational axis X of the crankshaft 31 and the cylinder axis Y, where the intake flow path 15 is located. 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 flow 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 within 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 while 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, an ignition 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 the 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] The valve train 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 the exhaust valve 53, and therefore 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 along 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 a 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 fuel injector 14 in the circumferential direction of the intake passage 15. In this manner, the injectors 13, 14 are disposed in close proximity to each other. The first delivery passage 28 is disposed on a side closer to the second delivery passage 29 with respect to the intake passage 15. The delivery passages 28, 29 are disposed in close proximity to each other. By arranging the two delivery passages 28, 29 in close proximity to each other in this manner, the length of the passage connecting them can be shortened. The first fuel injector 13 and the first delivery passage 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 13 and the first delivery passage 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 passages 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 passages 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 positions the second pressurizing pump 10 near the second fuel injector 14. The second pressurizing pump 10 may be reciprocated by an intake cam connected to the intake camshaft to reciprocate the intake valve. In this case, the number of parts can be reduced by reciprocating the second pressurizing pump by the intake cam. 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 positioned 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 booster pump is disposed between the combustion chambers, but multiple second booster pumps may be disposed. When multiple second booster pumps are disposed, they are preferably disposed at intervals in the crankshaft direction. By disposing multiple second booster pumps, it becomes easier to prevent uneven injection pressures among the second fuel injectors.

[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, an intake 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 pump drive cam 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, because 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 the 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 utilization of the fuel gas. Note that the return flow path 76 does not need to be provided if it is difficult to inject the gas in the sealed space S from the injector 14. The return flow path 76 may also be provided with a check valve 77 that allows a flow from the sealed space S toward the intake flow path 15 and prevents a flow in the reverse direction.

[0047] 5 is a block diagram of the controller and the like in 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 amount 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 the controller 25 is electrically connected to the first fuel injector 13, the second fuel injector 14, the spark plug 37, the throttle motor 18, the inverter 23, etc. The controller 25 is configured to control at least one of the first fuel injector 13, the second fuel injector 14, the spark plug 37, the throttle motor 18, and the inverter 23 based on detection signals from the sensors 81 to 87. The controller 25 controls the inverter 23 to control the pump motor 9.

[0051] Figure 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 Figure 1. The vertical axis of the graph in Figure 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 is considered one cycle, and in a reciprocating pump, one cycle is considered 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 status information indicating 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, thereby enabling it to have higher responsiveness than 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 status 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 in accordance with an increase in the amount of acceleration request detected by the accelerator sensor 81.

[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 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 falls below 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 make 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 described above for the first pressurizing pump 8.

[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 fuel gas flow path status 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 fuel level 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 exists in the internal combustion engine 20. The controller 25 may also determine that an abnormality exists 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 value. This makes it possible to extend the cruising range 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. 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. 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 will not be described again. As shown in FIG. 7 , in the internal combustion engine 120 according to this modified example, the locations of the second fuel injectors 14 and the spark plugs 37 are reversed. The second fuel injectors 14 that ignite fuel gas in the combustion chambers 33 are disposed in the central ports 38 of the cylinder head 32. The spark plugs 37 that are exposed toward the combustion chambers 33 are disposed in the side ports 39 of the cylinder head 32. The second fuel injectors 14 inject fuel gas along the cylinder axis Y, which facilitates uniform distribution of the fuel gas in the combustion chambers 33. Other components are similar to those in the previously described embodiment and will not be described again.

[0073] FIG. 8 is a schematic diagram of a main portion of an internal combustion engine system 101 of a first modified example. Note that components common to the above-described embodiment are denoted by 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, the first passage 107a in which the first pressurizing pump 8 is disposed in the 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 the upstream portion of the first passage 107a of the fuel gas passage 107 relative to 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 essential parts of an internal combustion engine system 201 of a second 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. 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. The other components are similar to those of the above-described embodiment, and therefore a 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 designated by the same reference numerals and will not be described again. 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, and pressurizes the fuel gas flowing through the second fuel gas flow path 7B and discharges the compressed fuel gas toward the second fuel injector 14. The other configurations are the same as those in 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] Although the generator motor 19 is an integrated starter generator (ISG) that drives the crankshaft 31 when starting the internal combustion engine 20, the present invention 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 to provide a cooler 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 31, the present invention is not limited thereto. 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 having 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 disposed in each of the multiple ports. First fuel injector 13 may be disposed 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 fuel 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 location 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 the second pressurizing pump 10 is configured to be driven by power generated by the internal combustion engine 20, it is preferably disposed in a position close to the second fuel injector 14. In other words, it is preferable that the second pressurizing pump 10 be driven by power from a rotor that is driven by a rotor disposed inside the cylinder head cover 27. For example, it is preferable that the second pressurizing pump 10 be driven by rotation of the intake cam 42 or the intake camshaft 41, but the second pressurizing pump may also be driven by rotation of the exhaust cam 52 or the 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 location 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 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.

[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. 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.

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

[0086] (Aspect 1) An internal combustion engine system comprising: an internal combustion engine including at least one combustion chamber and at least one 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 at a higher pressure than the first flow path; at least one 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 at least one second fuel injector that receives fuel gas from the second flow path and is arranged 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. Furthermore, 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 two fuel injectors like this, 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) The internal combustion engine system according to aspect 1, further comprising a pressure pump that pressurizes the fuel gas in the first flow path and discharges the compressed fuel gas into the second flow path.

[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 according to Aspect 1 or 2, further comprising a pressure pump interposed in the first flow path, wherein the first flow path includes at least one of a flow path that guides the fuel gas before being pressurized by the first pressure pump to the first fuel injector and a flow path that guides the fuel gas after being 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) The internal combustion engine system according to any one of aspects 1 to 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 system according to any one of Aspects 2 to 4, wherein the internal combustion engine further includes a cylinder including the combustion chamber and at least one exhaust port through which exhaust gas is guided from the combustion chamber, and the first fuel injector and the second booster pump are disposed closer to the intake port than to the exhaust port relative to an 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 system according to any one of Aspects 2 to 5, wherein 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 guided from the combustion chamber, and the second fuel injector and the second booster pump are disposed closer to the intake port than to the exhaust port relative to an 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 internal combustion engine system according to any one of Aspects 2 to 6, wherein the pressure pump is a reciprocating pump including a piston and a cylinder in which the piston is housed, and 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 internal combustion engine system according to any one of Aspects 2 to 7, wherein the at least one combustion chamber includes a plurality of combustion chambers aligned in one direction, the at least one second fuel injector includes a plurality of second fuel injectors aligned in the one direction, the second fuel flow path includes a delivery flow path extending in the one direction and connected to the plurality of fuel injectors, and 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 equipped with 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 at 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, the control method for an internal combustion engine system including: acquiring status information that indicates 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) In the control method for an internal combustion engine system described in Aspect 10, individually controlling the first fuel injector and the second fuel injector includes selecting one injection mode from a plurality of injection modes, and the plurality of injection modes include at least two of: 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; and a mix injection mode in which fuel gas is injected from both the first fuel injector and the second fuel injector.

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

[0107] (Aspect 12) The 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.

[0109] 1, 101, 201, 302 Internal combustion engine system 2 Fuel gas supply source 5 Liquid fuel flow path 7 Fuel gas flow path 8 First pressure booster pump 10 Second pressure booster 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 Cylinder 31 Crankshaft 33 Combustion chamber 34 Intake port 35 Exhaust port 40 Valve gear 41 Intake camshaft 62 Piston 69 Pump drive cam 70 Pump drive structure 90 Fuel supply device V Vehicle

Claims

1. An internal combustion engine system comprising: an internal combustion engine including at least one combustion chamber and at least one 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 at a higher pressure than the first flow path; at least one 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 at least one second fuel injector that receives fuel gas from the second flow path and is arranged 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 according to claim 1, further comprising a pressure pump disposed in the first flow path, wherein the first flow path includes at least one of a flow path that guides fuel gas before it is pressurized by the pressure pump to the first fuel injector, and a flow path that guides fuel gas after it has been pressurized by the pressure 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 said first fuel injector and said second fuel injector.

5. The internal combustion engine system according to claim 2, wherein the internal combustion engine further includes a cylinder including the combustion chamber and at least one exhaust port through which exhaust gas is guided from the combustion chamber, and 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 system according to claim 2, wherein the internal combustion engine further includes a cylinder including the combustion chamber and at least one exhaust port through which exhaust gas is guided from the combustion chamber, and 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 internal combustion engine system according to claim 2, wherein the pressure pump is a reciprocating pump including a piston and a cylinder in which the piston is housed, and 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 path.

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

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

10. A control method for an internal combustion engine system comprising 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 with a higher pressure than the first flow path flows, 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 fuel gas into the combustion chamber of the internal combustion engine, the control method for an internal combustion engine system comprising: acquiring status information that indicates 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. The control method for an internal combustion engine system according to claim 10, wherein individually controlling the first fuel injector and the second fuel injector includes selecting one injection mode from a plurality of injection modes, the plurality of injection modes including at least two of: 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; and a mix injection mode in which fuel gas is injected from both the first fuel injector and the second fuel injector.

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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