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

Abstract

This internal combustion engine system comprises: an internal combustion engine that includes at least one combustion chamber; a fuel gas flow path that connects the combustion chamber of the internal combustion engine to a fuel gas supply source; a first pressurizing pump that pressurizes fuel gas in the fuel gas flow path; and a second pressurizing pump that is disposed downstream of the first pressurizing pump in the fuel gas flow path and that pressurizes the fuel gas in the fuel gas flow path pressurized by the first pressurizing pump.

Description

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

[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 a fuel supply device.

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

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

[0004] There are cases where fuel is required to be supplied to an internal combustion engine even when the internal pressure of the fuel tank is low. In such cases, a large amount of pressure is required from the booster pump to achieve a fuel gas pressure suitable for combustion in the internal combustion engine. This requires the booster pump to have high pressure performance, which reduces the design freedom of the booster pump.

[0005] Therefore, one aspect of the present disclosure aims to improve the degree of freedom in designing a booster pump in an internal combustion engine system.

[0006] An internal combustion engine system according to one aspect of the present disclosure includes an internal combustion engine including a combustion chamber, a fuel gas flow path connecting the combustion chamber of the internal combustion engine to a fuel gas supply source, a first pressure booster pump that pressurizes fuel gas in the fuel gas flow path, and a second pressure booster pump that is arranged in the fuel gas flow path downstream of the first pressure booster pump and pressurizes the fuel gas in the fuel gas flow path that has been pressurized by the first pressure booster pump.

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

[0008] A control method for a fuel supply device according to one aspect of the present disclosure is a control method for a fuel supply device including a fuel gas flow path connecting a combustion chamber of an internal combustion engine to a fuel gas supply source, a first pressure booster pump that pressurizes the fuel gas in the fuel gas flow path, and a second pressure booster pump that is arranged downstream of the first pressure booster pump in the fuel gas flow path and pressurizes the fuel gas in the fuel gas flow path pressurized by the first pressure booster pump, the control method including: acquiring status information indicating the operating status of the internal combustion engine, the future operating status of the internal combustion engine, or the status of the fuel gas in the fuel gas flow path; and controlling at least one of the first pressure booster pump and the second pressure booster pump based on the status information.

[0009] According to one aspect of the present disclosure, it is possible to improve the degree of freedom in designing a booster pump in an internal combustion engine system.

[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 a main portion of an internal combustion engine according to a modified example. FIG. 8 is a schematic diagram of a main portion of an internal combustion engine system according to another 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. That is, 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 between the first pressurizing pump 8 and 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, a portion of the fuel gas flow path 7 branching off from the first flow path 7a is referred to as a third flow path 7c. In this embodiment, 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 and the third flow path 7c.

[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 third passage 7c of the fuel gas passage 7 bypasses the second pressure pump 10 and connects the first passage 7a to the first fuel injector 13. 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.

[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. The second fuel injector 14 injects the fuel gas directly into the combustion chamber 33 of the internal combustion engine 20. 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 gas pressure on the downstream side of the pressure reducing valve 11 reaches a pressure at which 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 connecting 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 functions as an electric motor that starts the internal combustion engine 20 and also functions as a generator. The generator motor 19 may be an ISG (Integrated Starter Generator) that drives the crankshaft 31 when starting the internal combustion engine 20. 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 electric power generated by the generator 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 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 third flow path 7c 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 a flow path that distributes the fuel gas from the third flow path 7c of the fuel gas flow path 7 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 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] 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 pressure pump 10 can be disposed regardless of the shape and position of the intake cam, which increases the options for the pump stroke length, compression chamber shape, layout, and the like.

[0039] 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.

[0040] 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.

[0041] 2, in this embodiment, one second pressurizing pump 10 is disposed between combustion chambers 33, but multiple second pressurizing pumps 10 may be disposed. When multiple second pressurizing pumps 10 are disposed, they are preferably disposed at intervals in the rotational axis direction X of the crankshaft 31. By disposing multiple second pressurizing pumps 10, it is possible to prevent uneven injection pressures among the second fuel injectors 14.

[0042] 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.

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The controller 25 individually controls the first fuel injector 13 or the second fuel injector 14 based on the above-described state 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] According to the configuration described above, the fuel gas supplied from the fuel gas supply source 2 to the internal combustion engine 20 is pressurized in stages as it passes through the first pressurization pump 8 and the second pressurization pump 10, which are arranged in series with each other, so that the pressurization performance per pressurization pump can be reduced compared to when a single pressurization pump is used. This allows for greater design freedom for the first pressurization pump 8 and the second pressurization pump 10.

[0071] Because the first pressurizing pump 8 and the second pressurizing pump 10 are different types of pumps, the design options for the internal combustion engine system can be increased compared to when the first pressurizing pump 8 and the second pressurizing pump 10 are the same type of pressurizing pump, and combustion gas suitable as fuel for the internal combustion engine 20 can be more easily supplied to the internal combustion engine 20. For example, it is possible to combine a pump suitable for boosting pressure from a low-pressure state with a pump suitable for boosting pressure from a high-pressure state. This makes it easier to supply fuel gas at the desired pressure or flow rate to the internal combustion engine 20.

[0072] The second pressurizing pump 10 realizes pressurization linked to the output of the internal combustion engine 20, and therefore can supply fuel gas according to the output of the internal combustion engine 20. The first pressurizing pump 8 realizes pressurization not linked to the output of the internal combustion engine 20, and therefore, if the second pressurizing pump 10 provides excessive or insufficient pressurization, the excessive or insufficient pressurization can be corrected by the first pressurizing pump 8. By using the second pressurizing pump 10 and the first pressurizing pump 8 in this way, the state of the fuel gas supplied to the internal combustion engine 20 can be adjusted.

[0073] By using the first pressurizing pump 8, which is a non-interlocking pump, to pressurize the fuel gas upstream in the fuel gas flow passage 7, it is possible to reduce the pressurizing capacity required of the first pressurizing pump 8 and improve responsiveness. This makes it possible to adjust the state of the fuel gas supplied to the internal combustion engine 20 with good responsiveness.

[0074] The second pressurizing pump 10 is mechanically linked to a drive part driven by the internal combustion engine 20, thereby reducing power transmission loss and realizing pressurization of the fuel gas according to the output of the internal combustion engine 20. Furthermore, the first pressurizing pump 8 is realized by an electric pump, thereby improving the responsiveness of the fuel gas pressurization adjustment.

[0075] Supporting the second pressurizing pump 10 on the internal combustion engine 20 shortens the power transmission path from the internal combustion engine 20 to the second pressurizing pump 10. In particular, arranging the second pressurizing pump 10 inside the cylinder head cover 27 makes it possible to omit a dedicated cover for covering the second pressurizing pump 10, thereby reducing the number of parts.

[0076] By disposing the first pressurizing pump 8 at a distance from the internal combustion engine 20, a temperature rise due to heat from the internal combustion engine 20 is prevented. It is preferable to dispose a heat insulating material or the like between the first pressurizing pump 8 and the internal combustion engine 20. This can further prevent the temperature rise of the first pressurizing pump 8.

[0077] The internal combustion engine system 1 preferably includes a fuel injector 14 that directly injects fuel into the combustion chamber 33. In particular, the fuel injector 14 that directly injects fuel into the combustion chamber 33 preferably injects fuel during the compression stroke. The direct-injection fuel injector 14 that requires such high-pressure injection can inject fuel against the pressure of the combustion chamber 33 by sequentially pressurizing the fuel using the above-described multiple booster pumps 8, 10.

[0078] 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.

[0079] The technology of the present disclosure is not limited to the above-described embodiment. For example, the internal combustion engine system 1 may be mounted on something other than the vehicle V. The internal combustion engine system 1 may be installed inside a building or on a power generation device. The internal combustion engine system 1 employs two-stage pressurization using the first pressurization pump 8 and the second pressurization pump 10, but three or more pressurization pumps may be arranged in series to compress the fuel gas through three or more stages of pressurization. The second pressurization pump 10 is a linked pump driven by the mechanical energy of the internal combustion engine 20, but it may also be a fluid-driven pump driven by the exhaust energy of the internal combustion engine 20.

[0080] The first pressurizing pump 8 is an electric pump that is not linked to the output of the internal combustion engine 20, but it may be a pump that is driven by a drive source separate from the internal combustion engine 20. The first pressurizing pump 8 is not linked to the internal combustion engine 20 by storing the energy generated by the internal combustion engine 20 in an energy storage device (for example, a storage battery, a flywheel, or a pressure storage device), but the linkage may be eliminated by using a clutch or the like. The second pressurizing pump 10 may be a rotary pump instead of a reciprocating pump.

[0081] The power source is not limited to the battery 24 that stores the electricity generated by a generator that generates electricity using the power of the internal combustion engine 20, but may also be a generator that generates electricity using the power of the internal combustion engine 20, or a battery that stores electricity supplied from an external source.

[0082] The camshaft on which the pump drive cam 69 is provided may be the crankshaft 31 arranged in the crankcase of the internal combustion engine 20, a balancer shaft in the crankcase, or a shaft (e.g., an input shaft) of the transmission 21 in the crankcase. The valve train 40 may be a type housed in the crankcase rather than an overhead cam type. In that case, the pump drive cam 69 is arranged inside the crankcase, and thereby inside the internal combustion engine 20. The pump drive structure 70 may be a connecting rod that converts the rotational motion of the crankshaft 31 into the reciprocating motion of the piston of the second pressurizing pump 10. The first pressurizing pump 8 and the pump motor 9 may be arranged away from the internal combustion engine 20 to reduce the influence of heat from the internal combustion engine.

[0083] Three or more pressure pumps may be provided. The first fuel injector 13 and the third flow path 7c may be omitted. Even in this case, the fuel injector 14 that directly injects fuel gas into the combustion chamber 33 can be supplied with fuel gas at the pressure required for fuel injection by multiple pressure pumps arranged in series. When one of the first pressure pump 8 and the second pressure pump 10 is powered by the internal combustion engine 20 and the other of the first pressure pump 8 and the second pressure pump 10 is powered by a drive source different from the internal combustion engine 20, it is preferable to position the other pressure pump farther from the internal combustion engine 20 than the first pressure pump. This reduces the effect of heat generated by the internal combustion engine 20 on the other pressure pump. By positioning one pressure pump close to the internal combustion engine 20, the power transmission path connecting the first pressure pump to the internal combustion engine 20 can be shortened.

[0084] Of the first pressurizing pump 8 and the second pressurizing pump 10, the pressurizing pump that receives power from the internal combustion engine 20 is preferably supported by the internal combustion engine 20. For example, the pressurizing pump may be supported by a crankcase or a cylinder head cover that forms the outer shell of the internal combustion engine 20. In particular, it is preferable that the pressurizing pump be disposed inside the case or cover as in this embodiment.

[0085] In this embodiment, the reciprocating motion of the booster pump 10 is achieved by the cam 42 of the intake camshaft 41, but the piston 62 may also be reciprocated by a connecting rod connected to the crankshaft 31. This increases the compression ratio of the second booster pump 10, making it easier to achieve the required injection pressure.

[0086] In order to suppress a rise in the temperature of the fuel gas due to the use of multiple pumps 8 and 10, it is preferable to provide a cooler that reduces the temperature of the pressurized fuel gas downstream of at least one of the first pressurizing pump 8 and the second pressurizing pump 10 in the fuel gas flow path 7. Furthermore, the upstream pump 8 may be a reciprocating pump, and the downstream pump 10 may be a rotary pump.

[0087] 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 the rotation of a rotor. The first pressurizing pump 8 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.

[0088] The generator motor 19 is an integrated starter generator (ISG) that rotates and drives the crankshaft 31 when starting the internal combustion engine 20, but is not limited to this. A generator that only has a power generation 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.

[0089] 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.

[0090] If the second pressurizing pump 10 is 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 disposed within the cylinder head cover 27. For example, the second pressurizing pump 10 is preferably driven by rotation of the intake cam 42 or the intake camshaft 41. However, the second pressurizing pump 10 may also be driven by rotation of the exhaust cam 52 or the exhaust camshaft 51. The second pressurizing pump 10 is not limited to a reciprocating pump and may be configured to pressurize fuel using a rotary vane that is driven to rotate. Even in this case, power is transmitted from a rotor disposed within the cylinder head cover 27 to the second pressurizing pump 10, thereby shortening the flow path connecting the second fuel injector 14 and the second pressurizing pump 10. Note that the second pressurizing pump 10 may be disposed in a position away from the second fuel injector 14. For example, the second booster pump 10 may receive power from the crankshaft 31 and be supported on the crankcase of the internal combustion engine 20. The second booster pump 10 may be driven by an electric motor and disposed remotely from the internal combustion engine 20.

[0091] FIG. 8 is a schematic diagram of an internal combustion engine system 101 according to another modified example. Components common to those in the previously described embodiment are denoted by the same reference numerals, and a description thereof will be omitted. As shown in FIG. 8 , in the internal combustion engine system 101 according to the modified example, a first flow path 107a in which the first pressurizing pump 8 is disposed in the fuel gas flow path 107 includes a branch flow path R2 that guides fuel gas before being pressurized by the first pressurizing pump 8 to the first fuel injector 13. That is, the branch flow path R2 branches from a portion of the first flow path 107a of the fuel gas flow path 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 branch flow path R2 may be added to the configuration shown in FIG. 1 . The other components are similar to those in the previously described embodiment, and therefore a description thereof will be omitted.

[0092] 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 in the embodiments can be separated and arbitrarily extracted from other configurations in the 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.

[0093] 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.

[0094] [Aspects] The above-described embodiments are specific examples of the following aspects.

[0095] (Aspect 1) An internal combustion engine system comprising: an internal combustion engine including a combustion chamber; a fuel gas flow path connecting the combustion chamber of the internal combustion engine to a fuel gas supply source; a first pressure booster pump that pressurizes fuel gas in the fuel gas flow path; and a second pressure booster pump that is disposed in the fuel gas flow path downstream of the first pressure booster pump and pressurizes the fuel gas in the fuel gas flow path that has been pressurized by the first pressure booster pump.

[0096] With this configuration, the fuel gas supplied from the fuel gas supply source to the internal combustion engine is pressurized in stages as it passes through the first and second pressurization pumps in sequence, so the pressurization performance per pump can be reduced compared to when a single pressurization pump is used, thereby improving the design flexibility of the pressurization pump.

[0097] (Aspect 2) The internal combustion engine system according to aspect 1, wherein the first pressure booster pump and the second pressure booster pump are realized by different pumps.

[0098] According to this configuration, different pumps can be combined to compress fuel gas, which increases options compared to when a single compression pump is used for compression, and combustion gas in a state suitable for use as fuel for an internal combustion engine can be supplied to the internal combustion engine. For example, a first compression pump suitable for boosting pressure from a low-pressure state and a second compression pump suitable for boosting pressure from a high-pressure state can be used. This makes it easier to supply fuel gas at the desired pressure and flow rate to the internal combustion engine. Furthermore, the operation of the two compression pumps or the supply flow path can be switched depending on the state of the internal combustion engine. This makes it possible to supply fuel gas to the internal combustion engine that is suitable for the state of the internal combustion engine.

[0099] (Aspect 3) An internal combustion engine system according to Aspect 1 or 2, wherein one of the first pressurizing pump or the second pressurizing pump is a linked pump that is driven by energy generated by the internal combustion engine and performs pressurization in conjunction with the output of the internal combustion engine, and the other of the first pressurizing pump or the second pressurizing pump is a non-linked pump that is capable of performing pressurization not in conjunction with the output of the internal combustion engine.

[0100] With this configuration, the interlocking pump achieves pressurization linked to the output of the internal combustion engine, allowing fuel gas to be supplied in accordance with the output of the internal combustion engine. The non-interlocking pump achieves pressurization not linked to the output of the internal combustion engine, allowing the interlocking pump to correct any excess or shortage of pressurization that occurs. In this way, using the interlocking pump and the non-interlocking pump makes it possible to regulate the state of the fuel gas supplied to the internal combustion engine.

[0101] (Aspect 4) The internal combustion engine system according to aspect 3, wherein the first pressurizing pump is the non-linked pump, and the second pressurizing pump is the linked pump.

[0102] With this configuration, by using the uninterlocked pump to pressurize the upstream side of the fuel gas flow path, the pressurization capacity required of the uninterlocked pump can be reduced, improving responsiveness, and thereby enabling the state of the fuel gas supplied to the internal combustion engine to be adjusted with good responsiveness.

[0103] (Aspect 5) The internal combustion engine system according to Aspect 4, wherein the interlocking pump is a mechanically driven pump driven by energy generated by the internal combustion engine, and the non-interlocking pump is an electric pump driven by electric power from a power source.

[0104] With this configuration, the interlocking pump is mechanically interlocked with a drive part driven by the internal combustion engine, thereby minimizing power transmission loss and realizing fuel gas pressurization according to the output of the internal combustion engine. Also, since the non-interlocking pump is realized by an electric motor, the responsiveness of fuel gas pressurization adjustment can be improved.

[0105] (Aspect 6) The internal combustion engine system according to aspect 5, wherein the power supply is capable of storing electric power generated by energy generated by the internal combustion engine.

[0106] This configuration makes it possible to reduce the amount of electric power supplied from outside the internal combustion engine system to drive the electric pump.

[0107] (Aspect 7) The internal combustion engine system of any of Aspects 3 to 6, further comprising a processing circuit configured to control the uncoupled pump, wherein the processing circuit operates the uncoupled pump with a different pressurization pattern than the coupled pump.

[0108] According to this configuration, the processing circuit controls the non-interlocked pump, thereby making it possible to supply fuel gas while preventing a situation in which the interlocked pump generates an excess or shortage.

[0109] (Aspect 8) The internal combustion engine system according to any one of Aspects 3 to 7, further comprising a pump drive structure connected to a rotating body that rotates in conjunction with the internal combustion engine, the linked pump being a reciprocating pump including a piston, and the pump drive structure including a pump drive cam connected to the rotating body and driving the piston.

[0110] According to this configuration, the link pump can be driven by utilizing the structure of the internal combustion engine, and the number of parts can be reduced.

[0111] (Aspect 9) The internal combustion engine system according to any one of Aspects 3 to 8, wherein the internal combustion engine further includes a crankshaft, and the link pump is driven by power provided directly or indirectly from the crankshaft.

[0112] This configuration makes it possible to realize pressure application linked to the rotation of the crankshaft.

[0113] (Aspect 10) The internal combustion engine system according to any one of Aspects 1 to 9, further comprising a surge tank connected to a portion of the fuel gas flow path downstream of the first booster pump.

[0114] With this configuration, when the pressure in the fuel gas flow path is excessive, pressure is accumulated in the surge tank, and when the pressure in the fuel gas flow path is too low, the pressure in the surge tank is supplied to the fuel gas flow path, so that fuel gas can be supplied to the internal combustion engine at an appropriate pressure without complex control.

[0115] (Aspect 11) A vehicle equipped with the internal combustion engine system according to any one of aspects 1 to 10.

[0116] According to this configuration, it is possible to increase the output of the internal combustion engine to which fuel gas is supplied while suppressing a decrease in the degree of freedom in the layout of the internal combustion engine system in the vehicle.

[0117] (Aspect 12) A control method for a fuel supply device including a fuel gas flow path connecting a combustion chamber of an internal combustion engine to a fuel gas supply source, a first pressurizing pump that pressurizes the fuel gas in the fuel gas flow path, and a second pressurizing pump that is arranged in the fuel gas flow path downstream of the first pressurizing pump and pressurizes the fuel gas in the fuel gas flow path that has been pressurized by the first pressurizing pump, the control method for a fuel supply device including: acquiring status information that indicates an operating status of the internal combustion engine, a future operating status of the internal combustion engine, or a status of the fuel gas in the fuel gas flow path; and controlling at least one of the first pressurizing pump and the second pressurizing pump based on the status information.

[0118] This method makes it easier to bring the fuel gas pressure close to that suitable for operating the internal combustion engine.

[0119] REFERENCE SIGNS LIST 1 Internal combustion engine system 2 Fuel gas supply source 5 Liquid fuel flow path 7 Fuel gas flow path 8 First booster pump 10 Second 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 31 Crankshaft 33 Combustion chamber 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 system comprising: an internal combustion engine including a combustion chamber; a fuel gas flow path connecting the combustion chamber of the internal combustion engine to a fuel gas supply source; a first pressure booster pump that pressurizes fuel gas in the fuel gas flow path; and a second pressure booster pump that is disposed in the fuel gas flow path downstream of the first pressure booster pump and pressurizes the fuel gas in the fuel gas flow path that has been pressurized by the first pressure booster pump.

2. The internal combustion engine system according to claim 1, wherein the first booster pump and the second booster pump are realized by different types of pumps.

3. An internal combustion engine system as described in claim 1, wherein one of the first pressurizing pump or the second pressurizing pump is a linked pump that is driven by energy generated by the internal combustion engine and pressurizes in conjunction with the output of the internal combustion engine, and the other of the first pressurizing pump or the second pressurizing pump is a non-linked pump that is capable of pressurizing in conjunction with the output of the internal combustion engine.

4. The internal combustion engine system according to claim 3, wherein the first booster pump is the non-coupled pump, and the second booster pump is the coupled pump.

5. An internal combustion engine system according to claim 4, wherein the interlocking pump is a mechanically driven pump driven by energy generated by the internal combustion engine, and the non-interlocking pump is an electric pump driven by electric power from a power source.

6. The internal combustion engine system according to claim 5, wherein the power source is capable of storing electric power generated from energy produced by the internal combustion engine.

7. The internal combustion engine system of claim 3, further comprising a processing circuit configured to control the uncoupled pump, the processing circuit operating the uncoupled pump in a different pressurization pattern than the coupled pump.

8. The internal combustion engine system according to claim 3, further comprising a pump drive structure connected to a rotating body that rotates in conjunction with the internal combustion engine, the linked pump being a reciprocating pump including a piston, and the pump drive structure including a pump drive cam connected to the rotating body and driving the piston.

9. The internal combustion engine system according to claim 3, wherein the internal combustion engine further includes a crankshaft, and the linked pump is driven by power provided directly or indirectly from the crankshaft.

10. The internal combustion engine system according to claim 1, further comprising a surge tank connected to a portion of the fuel gas flow path downstream of the first booster pump.

11. A vehicle equipped with an internal combustion engine system according to any one of claims 1 to 10.

12. A control method for a fuel supply device comprising a fuel gas flow path connecting a combustion chamber of an internal combustion engine to a fuel gas supply source, a first pressurizing pump that pressurizes the fuel gas in the fuel gas flow path, and a second pressurizing pump that is arranged downstream of the first pressurizing pump in the fuel gas flow path and pressurizes the fuel gas in the fuel gas flow path that has been pressurized by the first pressurizing pump, the control method for a fuel supply device comprising: acquiring status information that indicates the operating status of the internal combustion engine, the future operating status of the internal combustion engine, or the status of the fuel gas in the fuel gas flow path; and controlling at least one of the first pressurizing pump and the second pressurizing pump based on the status information.

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