Fuel reforming system for vehicle mounted with engine

Abstract

To provide a fuel reforming system suitable for mounting to a vehicle.SOLUTION: A reciprocal engine 3 of a fuel reforming system 1 includes: a third port 37 communicating between a cylinder 31 and a decomposition device 6; and an on-off valve 38 for opening / closing the third port. The reciprocal engine executes a 6-stroke cycle having an intake stroke, a compression stroke, an expansion stroke, a re-compression stroke in which combustion gas is supplied to the decomposition device via the third port, a re-expansion stroke in which a piston lowers and an exhaust stroke. The reciprocal engine includes: an execution cycle of executing supply of combustion gas to the decomposition device and supply of hydrocarbon fuel by using a hydrocarbon fuel supply device during the re-compression stroke at cold time of the third port or during a high speed operation of the reciprocal engine; and a stop cycle of stopping the supply of combustion gas and the supply of hydrocarbon fuel.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The technology disclosed herein relates to a fuel reforming system for an engine-equipped vehicle. [Background technology]

[0002] Patent Document 1 describes an apparatus for directly decomposing hydrocarbons into carbon and hydrogen. This conventional decomposition apparatus includes a reactor containing a catalyst. When a raw gas containing hydrocarbons is supplied to the reactor, carbon produced by a catalytic reaction adheres to the catalyst. A reaction gas containing hydrogen passes through the reactor. A hydrogen purification device downstream of the reactor purifies the hydrogen in the reaction gas to increase the hydrogen concentration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-104521 Summary of the Invention [Problem to be solved by the invention]

[0004] In the field of vehicle technology (for example, four-wheeled automobiles), efforts to achieve carbon neutrality are being sought. To achieve carbon neutrality in vehicles equipped with engines that use hydrocarbon fuels (including gasoline and / or diesel), new technologies for recovering carbon (C) or CO2 from hydrocarbon fuels are required, in addition to improving the thermal efficiency of the engine and / or improving exhaust emission performance.

[0005] To capture carbon or CO2 in a vehicle equipped with an engine that uses hydrocarbon fuel, two possible methods are (1) capturing CO2 after the hydrocarbon fuel is combusted, or (2) decomposing the hydrocarbon fuel into carbon and hydrogen gas before combustion and capturing the carbon. Considering that the captured CO2 or carbon will be stored in the vehicle, option (2) is more advantageous in terms of the vehicle's fuel economy because CO2 is heavier than carbon. Option (2) also makes it possible to use hydrogen gas as engine fuel. Combusting hydrogen gas also has the advantage of not generating carbon oxides due to combustion.

[0006] Therefore, it is conceivable to mount the conventional cracking device described above on a vehicle. The conventional cracking device is equipped with a heating device for raising the temperature of the catalyst. When the conventional cracking device is mounted on a vehicle, it is possible to use the heat of the engine to raise the temperature of the catalyst.

[0007] However, if hydrogen gas is to be used as engine fuel, high-concentration hydrogen gas is required. Conventional cracking devices require a hydrogen purification device that uses the PSA (Pressure Swing Adsorption) method to purify hydrogen from hydrogen-containing reaction gas in order to obtain high-concentration hydrogen gas. However, installing a hydrogen purification device on a vehicle has the disadvantage of increasing the vehicle weight. Conventional cracking devices are not suitable for installation on vehicles.

[0008] The technology disclosed herein provides a fuel reforming system suitable for installation in a vehicle. [Means for solving the problem]

[0009] A membrane reactor, which simultaneously decomposes hydrocarbon fuel and separates hydrogen gas, could be used in a vehicle's fuel reforming system. A membrane reactor uses a catalyst to decompose hydrocarbon fuel into carbon and hydrogen gas, while a separation membrane allows only hydrogen gas to pass through. Despite its compact size, it can produce highly concentrated hydrogen gas. However, to efficiently produce highly concentrated hydrogen gas in a membrane reactor, the pressure of the feed gas containing hydrocarbon fuel supplied to the reactor must be increased.

[0010] The inventors of the present invention have focused on the fact that in a reciprocating engine, the gas inside the cylinder is compressed as the piston rises. That is, the fuel reforming system disclosed herein decomposes hydrocarbon fuel by utilizing the heat of the combustion gas generated in the reciprocating engine and the pressure generated when the combustion gas is compressed as the piston rises. The hydrocarbon fuel decomposition process of the fuel reforming system installed in a vehicle is integrated into the operation of the reciprocating engine.

[0011] However, when using the piston stroke of a reciprocating engine to decompose a hydrocarbon fuel, the time for vaporizing the hydrocarbon fuel and / or the time for decomposing the hydrocarbon fuel may not be sufficiently long. As a result, the carbon and hydrogen gas yields of the fuel reforming system may decrease. Hereinafter, the "reaction time" of a hydrocarbon fuel refers to the time allowed for reaction from when the hydrocarbon fuel is injected by the hydrocarbon fuel supply device until the hydrocarbon fuel is vaporized and decomposed into carbon and hydrogen gas by the decomposer. A longer reaction time increases the amount of carbon and hydrogen gas obtained relative to the injected hydrocarbon fuel, resulting in a higher carbon and hydrogen gas yield of the fuel reforming system. The reaction time is primarily determined by the operating conditions of the reciprocating engine. For example, a high reciprocating engine speed shortens the reaction time. A high reciprocating engine speed may reduce the carbon and hydrogen gas yield of the fuel reforming system.

[0012] The cracker that decomposes hydrocarbon fuel is connected to the cylinder via a port. The port functions to supply combustion gas and hydrocarbon fuel to the cracker. Here, if the temperature of the port is low, the hydrocarbon fuel supplied to the cracker is unlikely to vaporize. Even if a certain amount of reaction time is secured, the cracker is unlikely to decompose the hydrocarbon fuel. When the port is cold, the yield of carbon and hydrogen gas in the fuel reforming system may also decrease.

[0013] The techniques disclosed herein increase the carbon and hydrogen gas yield of on-board fuel reforming systems.

[0014] Specifically, the technology disclosed herein relates to a fuel reforming system for an engine-equipped vehicle. a reciprocating engine mounted on a vehicle and having pistons reciprocating within cylinders; a cracker for cracking the hydrocarbon fuel into carbon and hydrogen gas; a hydrocarbon fuel supply device that supplies the hydrocarbon fuel to the cracker, the reciprocating engine has an intake port, an exhaust port, and a third port that connects the cylinder and the cracker and is opened and closed by an on-off valve; The reciprocating engine is an intake stroke in which at least intake air is introduced into the cylinder through the intake port as the piston descends; a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rising of the piston; an expansion stroke in which the piston descends due to combustion of the air-fuel mixture; a recompression stroke in which the on-off valve opens and the piston rises, causing combustion gas to be supplied to the cracker through the third port; a re-expansion stroke in which the piston descends; and a six-stroke cycle having an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises; the hydrocarbon fuel supply device supplies the hydrocarbon fuel to the cracker during the recompression stroke; The reciprocating engine is provided with an execution cycle in which, when the third port is cold or when the reciprocating engine is operating at high speed, the supply of combustion gas to the cracker during the recompression stroke and the supply of hydrocarbon fuel by the hydrocarbon fuel supply device are executed, and a stop cycle in which the supply of combustion gas to the cracker during the recompression stroke and the supply of hydrocarbon fuel by the hydrocarbon fuel supply device are stopped.

[0015] A reciprocating engine operates in a six-stroke cycle, which, in contrast to the usual four-stroke cycle with intake, compression, expansion, and exhaust strokes, adds a recompression stroke, in which the piston rises to compress the burned gases, and a re-expansion stroke, in which the piston descends, between the expansion and exhaust strokes.

[0016] The fuel reforming system includes a cracker and a hydrocarbon fuel supply.

[0017] The hydrocarbon fuel supply device supplies hydrocarbon fuel to the cracker. The hydrocarbon fuel may be stored in a fuel tank mounted on the vehicle. The hydrocarbon fuel supply device supplies the hydrocarbon fuel from the fuel tank to the cracker.

[0018] The cracker is connected to the cylinder through a third port. The on-off valve opens during the recompression stroke. Combustion gas in the cylinder pushed by the piston is supplied to the cracker through the third port.

[0019] The hydrocarbon fuel supply device supplies hydrocarbon fuel to the cracker during the recompression stroke. The cracker cracks the hydrocarbon fuel using the heat of the combustion gas supplied from the cylinder and the pressure of the combustion gas caused by the rising of the piston. The hydrogen gas is used as fuel for the reciprocating engine. The cracker may also store carbon.

[0020] The fuel reforming system has an on cycle and a off cycle when the third port is cold or when the reciprocating engine is operating at high revolutions. In the on cycle, the fuel reforming system supplies combustion gas to the cracker during the recompression stroke and supplies hydrocarbon fuel through the hydrocarbon fuel supply device. In the cracker, the hydrocarbon fuel is decomposed into carbon and hydrogen gas. In the off cycle, the fuel reforming system stops supplying combustion gas to the cracker during the recompression stroke and supplying hydrocarbon fuel through the hydrocarbon fuel supply device. In the off cycle, the cracking of the hydrocarbon fuel supplied to the cracker in the on cycle before the off cycle continues.

[0021] When the third port is cold or the reciprocating engine is operating at high speed, the carbon and hydrogen gas yields of the fuel reforming system tend to decrease. However, because combustion gas and hydrocarbon fuel are not supplied to the cracker in each cycle, the hydrocarbon fuel supplied to the cracker has a longer reaction time. This improves the carbon and hydrogen gas yields of the fuel reforming system relative to the injected hydrocarbon fuel.

[0022] The term "cold time of the third port" means that the temperature state of the third port or the cracker is a temperature state in which the hydrocarbon fuel does not easily vaporize. The term "cold time of the third port" may also be the term "cold time of the reciprocating engine." The term "cold time of the reciprocating engine" may be set based on the coolant temperature of the reciprocating engine. Furthermore, even if the reciprocating engine is warm, a case in which the temperature of the third port is low as a result of no combustion gas being supplied to the third port is also included in the term "cold time of the third port" as used herein. The term "cold time of the third port" may also be set based on the temperature of the third port.

[0023] Furthermore, the high rotation speed of the reciprocating engine means that the operating state of the reciprocating engine is an operating state of the reciprocating engine at or above a predetermined rotation speed. The predetermined rotation speed may be set based on the reaction time of the hydrocarbon fuel. The predetermined rotation speed may be set as a rotation speed at which the reaction time of the hydrocarbon fuel cannot be ensured to be sufficiently long.

[0024] the on-off valve is a poppet valve that opens and closes a connection between the third port and the cylinder, The fuel reforming system for the engine-equipped vehicle further includes a valve stop mechanism that stops the opening operation of the on-off valve, The valve stop mechanism may stop the opening of the on-off valve in the stop cycle.

[0025] The valve stop mechanism can switch between opening the poppet valve and stopping the opening of the poppet valve. The fuel reforming system does not require any additional device other than the on-off valve to achieve the stop cycle.

[0026] the on-off valve is a shutter valve that opens and closes the third port at a position in the third port closer to the cylinder than the hydrocarbon fuel supply device, The on-off valve may close the third port in the stop cycle.

[0027] A shutter valve that opens and closes the third port provides a shut-down cycle for the reciprocating engine.

[0028] the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker, the on-off valve is capable of changing an effective opening area of ​​the third port, The on-off valve may be configured to reduce the effective opening area of ​​the third port when the reciprocating engine is in a first operating state of low load and low rotation speed, compared to when the reciprocating engine is in a second operating state of higher load and higher rotation speed than the first operating state, when the on-off valve is open.

[0029] When the on-off valve relatively reduces the effective opening area of ​​the third port, the flow velocity of the combustion gas flowing from the cylinder toward the cracker during the recompression stroke increases. The increased flow velocity of the combustion gas in the third port promotes vaporization of the hydrocarbon fuel injected between the on-off valve and the cracker in the third port. The hydrocarbon fuel is transported to the cracker by the combustion gas. Because the vaporization of the hydrocarbon fuel is promoted, the hydrocarbon fuel is quickly decomposed into carbon and hydrogen gas in the cracker.

[0030] When a reciprocating engine is in the first operating state with low load and low revolutions, the amount of gas introduced into the cylinder is relatively small, and the duration of each stroke is longer than when the engine is in the high revolution state. Therefore, the flow velocity of the combustion gas introduced from the cylinder to the third port is relatively low. When the on-off valve opens, it relatively increases the flow velocity of the combustion gas in the third port, promoting the vaporization of the hydrocarbon fuel. The on-off valve promotes the vaporization of the hydrocarbon fuel when the reciprocating engine is in an operating state unfavorable for the vaporization of the hydrocarbon fuel. The on-off valve contributes to improving the carbon and hydrogen gas yields of the fuel reforming system.

[0031] the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker, the on-off valve is capable of changing an effective opening area of ​​the third port, When the on-off valve is open, if the temperature of the third port is low, the effective opening area of ​​the third port may be smaller than when the temperature of the third port is high.

[0032] As described above, a low temperature of the third port is unfavorable for vaporizing the hydrocarbon fuel injected into the third port. When the third port is at a low temperature, the on-off valve relatively increases the flow velocity of the combustion gas at the third port when it is open. The increased flow velocity of the combustion gas promotes vaporization of the hydrocarbon fuel even when the third port is at a low temperature. When the third port is at a low temperature, the on-off valve increases the carbon and hydrogen gas yields of the fuel reforming system. [Effects of the Invention]

[0033] The fuel reforming system for an engine-mounted vehicle is suitable for installation in a vehicle and can increase the yield of carbon and hydrogen gas. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 shows a fuel reforming system installed in a vehicle. [Figure 2] FIG. 2 shows a cracker for cracking hydrocarbon fuels. [Figure 3] FIG. 3 shows the vehicle control system. [Figure 4] Figure 4 shows each step of the six-stroke cycle. [Figure 5] FIG. 5 shows the injection timing of hydrocarbon fuel. [Figure 6] FIG. 6 shows the relationship between the fuel injection pressure and the engine speed and the engine load. [Figure 7] FIG. 7 shows a control map for a reciprocating engine. [Figure 8] FIG. 8 shows the lift curves of the intake valve, the exhaust valve, and the on-off valve. [Figure 9] FIG. 9 shows a table for determining the frequency of execution of the fuel reforming cycle. [Figure 10] FIG. 10 shows the valve lifts of the intake valve, exhaust valve, and on-off valve when the execution frequency of the fuel reforming cycle is different. [Figure 11] FIG. 11 is a flowchart of engine control. [Figure 12] FIG. 12 shows the relationship between the lift amount and the engine load and revolutions, and the relationship between the lift amount and the temperature of the third port. [Figure 13] FIG. 13 shows a third port according to a modified example. [Figure 14] FIG. 14 is a part of a flowchart of engine control according to a modified example. [Figure 15]FIG. 15 shows the injection timing of hydrocarbon fuel according to a modified example. [Figure 16] FIG. 16 shows the valve lifts of the intake valve, exhaust valve, and on-off valve when the execution frequency of the fuel reforming cycle is different according to a modified example. [Figure 17] FIG. 17 shows the injection timing of hydrocarbon fuel according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, an embodiment of a fuel reforming system for an engine-equipped vehicle will be described with reference to the drawings. The system described here is an example.

[0036] (Configuration of fuel reforming system) FIG. 1 shows a fuel reforming system 1 mounted on a vehicle. A hydrocarbon fuel is stored in a fuel tank mounted on the vehicle. The hydrocarbon fuel is, for example, gasoline. The hydrocarbon fuel is not limited to gasoline. The fuel reforming system 1 decomposes the hydrocarbon fuel into carbon and hydrogen gas. The carbon is stored in a decomposer 6, which will be described later. The hydrogen gas is used as fuel for a reciprocating engine 3. The fuel reforming system 1 achieves carbon neutrality for vehicles that are equipped with hydrocarbon fuel.

[0037] The fuel reforming system 1 includes a reciprocating engine 3. The reciprocating engine 3 has a cylinder 31 and a piston 32 that reciprocates within the cylinder 31. The reciprocating engine 3 has a plurality of cylinders 31. The plurality of cylinders 31 are aligned, for example, in the direction in which the crankshaft of the reciprocating engine 3 extends. The piston 32 of each cylinder 31 is connected to the crankshaft via a connecting rod. The connecting rod converts the reciprocating motion of the piston 32 into rotation of the crankshaft. The crankshaft is connected to the drive wheels via a transmission. The reciprocating engine 3 outputs driving force for running the vehicle. The reciprocating engine 3 may also be used as a driving source for driving a generator.

[0038] The reciprocating engine 3 has an intake port 33. The intake port 33 is connected to the cylinder 31. Each cylinder 31 has one or more intake ports 33. Each cylinder 31 may have, for example, two intake ports 33. The intake port 33 is connected to an intake pipe. As will be described later, intake air is introduced into the cylinder 31 through the intake port 33. The intake air includes at least fresh air. The intake air may also include EGR (Exhaust Gas Recirculation) gas.

[0039] The reciprocating engine 3 has an intake valve 34. The intake valve 34 is a poppet valve that opens and closes the intake port 33. When the intake valve 34 opens, intake air is introduced into the cylinder 31. An intake valve train 41 shown in FIG. 3 opens and closes the intake valve 34. The intake valve train 41 has, for example, an intake camshaft mechanically connected to the intake valve 34. The intake valve train 41 can continuously change the valve timing of the intake valve 34 (so-called S-VT (Sequential-Valve Timing)). The intake valve train 41 can also continuously change the valve lift of the intake valve 34 (so-called CVVL (Continuously Variable Valve Lift)). A known hydraulic or electric mechanism can be used for the intake valve train 41. The intake valve train 41 changes the valve timing and / or valve lift depending on the operating state of the reciprocating engine 3.

[0040] The reciprocating engine 3 has exhaust ports 35. The exhaust ports 35 are connected to the cylinders 31. Each cylinder 31 has one or more exhaust ports 35. Each cylinder 31 may have, for example, one exhaust port 35. The exhaust ports 35 are connected to an exhaust pipe. As will be described later, exhaust gas is discharged from inside the cylinders 31 through the exhaust ports 35.

[0041] The reciprocating engine 3 has an exhaust valve 36. The exhaust valve 36 is a poppet valve that opens and closes the exhaust port 35. When the exhaust valve 36 opens, exhaust gas is discharged to the outside of the cylinder 31. An exhaust valve train 42 shown in FIG. 3 opens and closes the exhaust valve 36. The exhaust valve train 42 has, for example, an exhaust camshaft mechanically connected to the exhaust valve 36. The exhaust valve train 42 can continuously change the valve timing of the exhaust valve 36 (so-called S-VT). The exhaust valve train 42 can also continuously change the valve lift of the exhaust valve 36 (so-called CVVL). A known hydraulic or electric mechanism can be used for the exhaust valve train 42. The exhaust valve train 42 changes the valve timing and / or valve lift depending on the operating state of the reciprocating engine 3.

[0042] The reciprocating engine 3 has a third port 37. The third port 37 is in communication with the cylinders 31. Each cylinder 31 has at least one third port 37. Each cylinder 31 may have, for example, one third port 37.

[0043] A typical reciprocating engine has two intake ports and two exhaust ports per cylinder. One of the two exhaust ports may be converted into a third port 37. The reciprocating engine 3 in FIG. 1 has two intake ports 33, one exhaust port 35, and one third port 37 per cylinder 31. Note that for ease of understanding, the exhaust port 35 and the third port 37 are depicted in offset positions in FIG. 1.

[0044] One of the two intake ports may be converted into the third port 37. However, two intake ports 33 have the advantage of being able to introduce a large amount of fresh air into the cylinder 31. If an exhaust port or an intake port is converted into the third port 37, a general reciprocating engine can be used as the reciprocating engine 3 of the fuel reforming system 1. The reciprocating engine 3 may have two intake ports 33, two exhaust ports 35, and one third port 37 per cylinder 31.

[0045] The reciprocating engine 3 has an on-off valve 38. The on-off valve 38 is a poppet valve that opens and closes a third port 37. The on-off valve 38 is located at the connection between the third port 37 and the cylinder 31. A third valve train 43 shown in FIG. 3 opens and closes the on-off valve 38. The third valve train 43 has, for example, a third camshaft mechanically connected to the on-off valve 38. The third valve train 43 may open the on-off valve 38 twice per cycle (see FIG. 8). The third valve train 43 can also stop the on-off valve 38 from opening or closing. A known hydraulic or electric mechanism can be used as a valve stop mechanism that stops the on-off valve 38 from opening or closing. The valve stop mechanism may be incorporated, for example, into a rocker arm interposed between the third camshaft and the on-off valve 38. The valve stop mechanism may also be incorporated into a lash adjuster that supports the rocker arm. The on-off valve 38 may be mechanically connected to an intake camshaft or an exhaust camshaft.

[0046] The third valve train 43 can also continuously change (continuously changeable valve lift) the on-off valve 38. The valve lift of the on-off valve 38 changes depending on the load and rotation speed of the reciprocating engine 3, as will be described later.

[0047] An intake port injector 44 is attached to the reciprocating engine 3. An injection hole of the intake port injector 44 faces the inside of the intake port 33. The intake port injector 44 injects hydrocarbon fuel into the intake port 33. A hydrocarbon fuel supply unit 45 is connected to the intake port injector 44. The hydrocarbon fuel supply unit 45 has a fuel tank that stores hydrocarbon fuel and a fuel pump that pressure-feeds the hydrocarbon fuel. The hydrocarbon fuel supply unit 45 supplies hydrocarbon fuel to the intake port injector 44.

[0048] A third port injector 46 is attached to the reciprocating engine 3. An injection hole of the third port injector 46 faces the third port 37. More specifically, in the example of FIG. 1 , the third port injector 46 is located in the third port 37 between the cracker 6 and the on-off valve 38. The third port injector 46 injects hydrocarbon fuel into the third port 37. The third port injector 46 is an example of a hydrocarbon fuel supply device. A hydrocarbon fuel supply unit 45 is also connected to the third port injector 46. The hydrocarbon fuel supply unit 45 selectively supplies hydrocarbon fuel to the intake port injector 44 and the third port injector 46.

[0049] A hydrogen injector 47 is attached to the reciprocating engine 3. The injection holes of the hydrogen injector 47 face the inside of the cylinder 31. The hydrogen injector 47 injects hydrogen gas into the cylinder 31.

[0050] It is also possible to attach an injector that injects hydrocarbon fuel to the reciprocating engine 3 so as to face the inside of the cylinder 31, and attach a hydrogen injector that injects hydrogen gas to the reciprocating engine 3 so as to face the inside of the intake port 33.

[0051] The hydrogen gas supply unit 5 is connected to the hydrogen injector 47. The hydrogen gas supply unit 5 supplies hydrogen gas to the hydrogen injector 47. As described above, the hydrogen gas is hydrogen gas decomposed from a hydrocarbon fuel.

[0052] The cracker 6 is connected to the third port 37. The cracker 6 cracks the hydrocarbon fuel into carbon and hydrogen gas. The cracker 6 is attached to each cylinder 31. The cracker 6 may be common to multiple cylinders 31.

[0053] Figure 2 shows the structure of the cracker 6. The cracker 6 uses a catalyst to decompose the hydrocarbon fuel into carbon and hydrogen gas, and separates the hydrogen gas using a separation membrane 63. The cracker 6 is a so-called membrane reactor. The decomposition of a hydrocarbon fuel, for example, isooctane, is represented by the following chemical reaction formula:

[0054] iC8H 18 (g) = 8C(s) + 9H2 The recovery of solid carbon prevents the weight of the vehicle from increasing. The fuel reforming system 1 is suitable for use as an in-vehicle system.

[0055] The cracker 6 has a catalyst support 61. A catalyst that can be used to crack hydrocarbon fuel is, for example, a Ni-Al-Fe alloy. Various catalysts can be used as long as they can be used to crack hydrocarbon fuel.

[0056] The support 61 can be, for example, an aluminum oxide plate. The catalyst is applied to the surface of the plate. The support 61 is supported on the inner surface of a case 62 of the cracker 6. The case 62 is, for example, cylindrical. The shape of the support 61 is not limited to a specific shape. Carbon produced by the cracking of the hydrocarbon fuel adheres to the surface of the support 61. The cracker 6 also stores the carbon.

[0057] The decomposer 6 has a separation membrane 63. The separation membrane 63 is located more inward of the support 61 in the case 62. The separation membrane 63 has, for example, a cylindrical shape. The separation membrane 63 has a function of allowing only hydrogen gas to permeate. The separation membrane 63 is, for example, a Pd alloy membrane. However, the separation membrane 63 is not limited to a Pd alloy membrane.

[0058] The third port 37 is connected to a first end of the case 62. The second end of the case 62 is closed. Combustion gas from the cylinder 31 and hydrocarbon fuel injected by the third port injector 46 flow into the space between the catalyst support 61 and the separation membrane 63, as shown by the black arrows in FIG. 2. The catalyst decomposes the hydrocarbon fuel into carbon and hydrogen gas. The decomposed hydrogen gas permeates the separation membrane 63, as shown by the white arrows in FIG. 2.

[0059] The cracker 6 has a catalyst section 64 including the above-mentioned catalyst support 61 and separation membrane 63. The catalyst section 64 is located on the third port 37 side of the case 62, and a space 65 is formed in the case 62 on the opposite side of the third port 37 from the catalyst section 64. As will be described later, gas remaining inside the cracker 6 at the start of the recompression stroke is pushed into the space 65 as the combustion gas and hydrocarbon fuel flow into the cracker 6. As a result, the hydrocarbon fuel spreads throughout the catalyst section 64, accelerating the cracking of the hydrocarbon fuel.

[0060] A hydrogen gas passage 50 is connected to one end of the tube made of separation membrane 63. The hydrogen gas passage 50 is connected to a hydrogen gas supply unit 5 (see FIG. 1). The hydrogen gas passage 50 guides hydrogen gas from the cracker 6 to the hydrogen gas supply unit 5. The hydrogen gas is sent to the hydrogen injector 47 via the hydrogen gas supply unit 5. The hydrogen gas supply unit 5 has, for example, a hydrogen gas tank and a hydrogen gas pump.

[0061] (Control system configuration) 3 is a block diagram of the control system 2 of the vehicle equipped with the fuel reforming system 1. The control system 2 has a controller 21. The controller 21 is composed of hardware such as a processor, memory, and interface, and software such as a database and control program.

[0062] The crank angle sensor 22 is electrically connected to the controller 21. The crank angle sensor 22 is attached to the reciprocating engine 3. The crank angle sensor 22 outputs a measurement signal corresponding to the rotation angle of the crankshaft to the controller 21. The controller 21 can grasp the rotation speed of the reciprocating engine 3 based on the measurement signal of the crank angle sensor 22.

[0063] The accelerator position sensor 23 is electrically connected to the controller 21. The accelerator position sensor 23 is attached to the accelerator pedal. The accelerator position sensor 23 outputs a signal corresponding to the depression amount of the accelerator pedal to the controller 21. The controller 21 can grasp the required load of the reciprocating engine 3 based on the measurement signal of the accelerator position sensor 23.

[0064] The temperature sensor 24 is electrically connected to the controller 21. The temperature sensor 24 outputs a measurement signal corresponding to the temperature of the third port 37 to the controller 21. The controller 21 can grasp the temperature of the third port 37 based on the measurement signal of the temperature sensor 24. The temperature sensor 24 may be a water temperature sensor. The water temperature sensor outputs a measurement signal corresponding to the temperature of the cooling water of the reciprocating engine 3 to the controller 21.

[0065] The intake valve train 41, exhaust valve train 42, and third valve train 43 are each electrically connected to the controller 21. The controller 21 outputs control signals to the intake valve train 41, exhaust valve train 42, and third valve train 43, respectively, depending on the operating state of the reciprocating engine 3. The intake valve train 41 changes the valve timing and / or valve lift of the intake valve 34 based on the control signal from the controller 21. The exhaust valve train 42 changes the valve timing and / or valve lift of the exhaust valve 36 based on the control signal from the controller 21. The third valve train 43 switches the on-off valve 38 between open and closed states based on the control signal from the controller 21. The third valve train 43 also changes the valve lift of the on-off valve 38 based on the control signal from the controller 21.

[0066] The intake port injector 44, the third port injector 46, and the hydrogen injector 47 are each electrically connected to the controller 21. The controller 21 outputs a control signal to each of the intake port injector 44, the third port injector 46, and the hydrogen injector 47. The intake port injector 44 injects a predetermined amount of hydrocarbon fuel into the intake port 33 at a predetermined timing based on the control signal from the controller 21. The third port injector 46 injects a predetermined amount of hydrocarbon fuel into the third port 37 at a predetermined timing based on the control signal from the controller 21. The hydrogen injector 47 injects a predetermined amount of hydrogen gas into the cylinder 31 at a predetermined timing based on the control signal from the controller 21.

[0067] The control system 2 has an ignition plug 26. The ignition plug 26 is attached to the reciprocating engine 3 and faces the inside of a cylinder 31. The ignition plug 26 is electrically connected to the controller 21. The controller 21 outputs a control signal to the ignition plug 26. The ignition plug 26 ignites the air-fuel mixture in the cylinder 31 at a predetermined timing based on the control signal from the controller 21.

[0068] The control system 2 also has an electric motor 27. The electric motor 27 is an assist motor that compensates for insufficient output of the reciprocating engine 3. The electric motor 27 is operated by receiving power supplied from a battery via an inverter 28. The electric motor 27 and the reciprocating engine 3 may be connected in series or in parallel. The combination of the reciprocating engine 3 and the electric motor 27 can output the driving force required to run the vehicle. The inverter 28 is electrically connected to the controller 21. The controller 21 outputs a control signal to the inverter 28. The inverter 28 operates the electric motor 27 based on the control signal from the controller 21.

[0069] The hydrocarbon fuel supply unit 45 and the hydrogen gas supply unit 5 described above are each electrically connected to the controller 21. The controller 21 outputs a control signal to the hydrocarbon fuel supply unit 45 or the hydrogen gas supply unit 5.

[0070] (6-stroke cycle) The reciprocating engine 3 performs a six-stroke cycle in order for the cracker 6 to crack the hydrocarbon fuel. Figure 4 shows the steps involved in the six-stroke cycle.

[0071] S1 is the intake stroke. During the intake stroke S1, the reciprocating engine 3 introduces intake air into the cylinder 31 as the piston 32 descends. During the intake stroke S1, the intake valve 34 opens. The intake air is introduced into the cylinder 31 through the intake port 33. The intake air contains at least fresh air. The intake air may also contain EGR gas. This EGR gas is so-called external EGR gas that has been recirculated to the intake pipe through the EGR passage. During the intake stroke S1, the exhaust valve 36 may open. When the exhaust valve 36 opens, exhaust gas is introduced into the cylinder 31 through the exhaust port 35. The exhaust gas introduced into the cylinder 31 is so-called internal EGR gas. Note that the opening / closing valve 38 of the third port 37 is closed.

[0072] 4, the hydrogen injector 47 injects hydrogen gas into the cylinder 31 during the intake stroke S1. The hydrogen injector 47 may inject hydrogen gas during the compression stroke S2 ​​following the intake stroke S1. The hydrogen injector 47 may inject hydrogen gas during the period from the intake stroke S1 to the compression stroke S2.

[0073] If there is a shortage of hydrogen gas, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the intake stroke S1 to make up for the shortage. If there is no hydrogen gas, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the intake stroke S1, instead of the hydrogen injector 47. If there is a shortage of hydrogen gas to be supplied into the cylinder 31, the intake port injector 44 injects hydrocarbon fuel, thereby ensuring the required amount of fuel for the reciprocating engine 3. The reciprocating engine 3 can be operated using hydrocarbon fuel or both hydrocarbon fuel and hydrogen gas.

[0074] S2 is the compression stroke. In the compression stroke S2, the reciprocating engine 3 compresses the air-fuel mixture in the cylinder 31 by the upward movement of the piston 32. The intake valve 34, the exhaust valve 36, and the on-off valve 38 are all closed.

[0075] The spark plug 26 ignites the air-fuel mixture in the cylinder 31 near the top dead center of the compression stroke. The air-fuel mixture begins to burn. S3 is the expansion stroke. During the expansion stroke S3, the piston 32 descends due to the combustion of the air-fuel mixture. The intake valve 34, exhaust valve 36, and on-off valve 38 are all closed.

[0076] S4 is a recompression stroke. In the recompression stroke S4, the reciprocating engine 3 compresses the combustion gas in the cylinder 31 by raising the piston 32. In the recompression stroke S4, the on-off valve 38 opens. The compressed combustion gas is introduced into the cracker 6 through the third port 37. Also, in the recompression stroke S4, the third port injector 46 injects hydrocarbon fuel into the third port 37. The hydrocarbon fuel is introduced into the cracker 6 together with the combustion gas. In the cracker 6, the hydrocarbon fuel is decomposed into carbon and hydrogen gas by the heat of the combustion gas and the catalyst. The carbon is stored in the cracker 6. The hydrogen gas permeates the separation membrane 63 of the cracker 6 due to the pressure of the combustion gas and is sent to the hydrogen gas supply unit 5.

[0077] Because the high pressure of the combustion gas in the recompression stroke S4 is applied to the cracker 6, the hydrogen gas produced in the cracker 6 quickly permeates the separation membrane 63. Because the hydrogen gas on the right side of the chemical reaction equation described above is discharged from the cracker 6, the cracking reaction of the hydrocarbon fuel in the cracker 6 is accelerated. The cracker 6, which utilizes the pressure of the recompression stroke S4 of the reciprocating engine 3, can produce the amount of hydrogen gas required to operate the reciprocating engine 3 even though it is small.

[0078] S5 is a re-expansion stroke. In the re-expansion stroke S5, the piston 32 descends. The on-off valve 38 opens in the re-expansion stroke S5. When the on-off valve 38 opens, the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder 31 from the third port 37. Opening the on-off valve 38 in the re-expansion stroke S5 is advantageous in reducing pumping loss in the reciprocating engine 3.

[0079] S6 is the exhaust stroke. During the exhaust stroke S6, the reciprocating engine 3 discharges the combustion gas in the cylinder 31 through the exhaust port 35 as the piston 32 rises. During the exhaust stroke S6, the exhaust valve 36 opens. The combustion gas in the cylinder 31 is discharged to the exhaust port 35. During the exhaust stroke S6, the intake valve 34 and the on-off valve 38 are closed.

[0080] After the exhaust stroke S6, the reciprocating engine 3 returns to the intake stroke S1.

[0081] Instead of or together with opening the on-off valve 38 in the re-expansion stroke S5, the on-off valve 38 may be opened in the intake stroke S1. If the on-off valve 38 is opened in the intake stroke S1, the combustion gas from which carbon and hydrogen gas have been removed is introduced into the cylinder 31 through the third port 37. This combustion gas becomes EGR gas.

[0082] If the on-off valve 38 does not open in the re-expansion stroke S5, the hydrocarbon fuel introduced into the cracker 6 in the re-compression stroke S4 will remain in the cracker 6 for a long time, which has the advantage of promoting the cracking reaction of the hydrocarbon fuel.

[0083] In this way, the fuel reforming system 1 including the reciprocating engine 3 that runs a six-stroke cycle stores the carbon produced by the decomposition of hydrocarbon fuel in the cracker 6. Furthermore, because the reciprocating engine 3 burns the hydrogen gas produced by the decomposition of hydrocarbon fuel, no carbon oxides are produced due to combustion. The fuel reforming system 1 can achieve carbon neutrality.

[0084] Furthermore, since this fuel reforming system 1 utilizes the heat and pressure generated by the reciprocating engine 3, there is no need for a separate dedicated device to generate the heat and / or pressure required to decompose the hydrocarbon fuel. The fuel reforming system 1 is useful as an on-board system.

[0085] If the amount of carbon stored in the decomposer 6 increases, the carbon is recovered from the decomposer 6.

[0086] (Structure that promotes vaporization of hydrocarbon fuel) The fuel reforming system 1 decomposes hydrocarbon fuel by utilizing the piston stroke of the reciprocating engine 3. Because the fuel reforming system 1 is combined with the operation of the reciprocating engine 3, it is difficult to ensure that the reaction time of the hydrocarbon fuel is always sufficiently long, regardless of the operating state of the reciprocating engine 3. If a long reaction time cannot be ensured, the yield of carbon and hydrogen gas in the fuel reforming system 1 may decrease.

[0087] The fuel reforming system 1 is configured to promote vaporization of the hydrocarbon fuel, so that the yield of carbon and hydrogen gas in the fuel reforming system 1 is not reduced even if the hydrocarbon fuel is not allowed to react for a sufficiently long time.

[0088] FIG. 2 shows the arrangement of the third port injector 46. The third port injector 46 injects hydrocarbon fuel toward the on-off valve 38, i.e., toward the right of the page in FIG. 2 . More specifically, the axis X of the third port injector 46 is inclined at a predetermined angle θ with respect to the central axis of the third port 37. The third port injector 46 injects hydrocarbon fuel so as to face the combustion gas flowing through the third port 37 from the cylinder 31 toward the cracker 6 during the recompression stroke. Injecting hydrocarbon fuel against the flow of combustion gas generates a strong gas flow within the third port 37. The strong gas flow quickly vaporizes the hydrocarbon fuel. The hydrocarbon fuel is also carried to the cracker 6 by the combustion gas. Because the vaporization of the hydrocarbon fuel is promoted, the cracker 6 can quickly decompose the vaporized hydrocarbon fuel into carbon and hydrogen gas. As a result, the yields of carbon and hydrogen gas of the fuel reforming system 1 are increased.

[0089] Fig. 5 shows the fuel injection timing of the third port injector 46. The dashed line in chart 501 in Fig. 5 illustrates the inflow velocity of combustion gas into the third port 37 during the recompression stroke. Reference numeral 461 in chart 501 in Fig. 5 indicates the fuel injection of the third port injector 46, and the vertical axis of chart 501 represents the fuel injection rate. Furthermore, the solid line in chart 502 in Fig. 5 illustrates the valve lift of the on-off valve 38 during the recompression stroke and the re-expansion stroke.

[0090] The third port injector 46 injects hydrocarbon fuel into the third port 37 immediately after the on-off valve 38 opens during the recompression stroke. This is because the velocity of the combustion gas flowing into the third port 37 increases due to the pressure difference between the cylinder 31 and the third port 37 immediately after the on-off valve 38 opens. At this timing, the hydrocarbon fuel is injected in a direction opposite to the flow of the combustion gas, generating a vigorous gas flow within the third port 37. This further promotes the vaporization of the hydrocarbon fuel.

[0091] The third port injector 46 injects all of the required amount of hydrocarbon fuel at this injection timing. The third port injector 46 is an injector with high injection pressure. The third port injector 46 can be an in-cylinder direct injection injector. The in-cylinder direct injection injector atomizes the injected fuel, which is also advantageous for vaporizing the hydrocarbon fuel. Note that the amount of hydrocarbon fuel injected at the above timing does not have to be all, but may be most of it.

[0092] The injection pressure of the third port injector 46 may be increased in proportion to the flow velocity of the combustion gas at the third port 37. Figure 6 shows a relationship 601 of the injection pressure of the third port injector 46 with respect to the rotation speed and required load of the reciprocating engine 3.

[0093] When the load of the reciprocating engine 3 is high, the flow velocity of the combustion gas at the third port 37 is higher than when the load is low. When the load of the reciprocating engine 3 is high, the injection pressure of the third port injector 46 is increased above the injection pressure when the load is low, thereby increasing the amount of hydrocarbon fuel injected into the third port 37. As the amount of hydrocarbon fuel increases, the amount of hydrogen gas increases. When the load of the reciprocating engine 3 is high, the amount of hydrogen gas required as the fuel amount to operate the reciprocating engine 3 increases, but increasing the injection pressure of the third port injector 46 can accommodate the increased required amount of hydrogen gas.

[0094] Furthermore, when the rotation speed of the reciprocating engine 3 is high, the flow velocity of the combustion gas at the third port 37 is higher than when the rotation speed is low. When the rotation speed of the reciprocating engine 3 is high, the injection pressure of the third port injector 46 can be increased compared to the injection pressure when the rotation speed is low, thereby making the gas flow at the third port 37 caused by the fuel injection of the third port injector 46 more intense. The intense gas flow can further promote the vaporization of the hydrocarbon fuel. When the rotation speed of the reciprocating engine 3 is high, the reaction time is shorter, but increasing the injection pressure of the third port injector 46 is advantageous in improving the yield of carbon and hydrogen gas in the fuel reforming system 1 by promoting the vaporization of the hydrocarbon fuel.

[0095] The maximum injection pressure of the third port injector 46 may be, for example, one digit MPa or higher.

[0096] As shown by the dashed line in chart 501, the inflow velocity of the combustion gas during the recompression stroke increases immediately after the on-off valve 38 opens, and then decreases temporarily. Thereafter, as the upward speed of the piston 32 increases, the inflow velocity of the combustion gas also increases again. Then, when the piston 32 reaches top dead center, the inflow velocity becomes substantially zero.

[0097] The third port injector 46 may inject hydrocarbon fuel into the third port 37 throughout the period during which the combustion gas is flowing into the third port 37 during the recompression stroke. The hydrocarbon fuel injected counter to the flow of the combustion gas is diffused by the combustion gas flowing from the cylinder 31 toward the cracker 6. This promotes vaporization of the hydrocarbon fuel. Note that if the injection period of the third port injector 46 is long, the injection pressure of the third port injector 46 may be lower than the injection pressure of the in-cylinder direct injection injector.

[0098] The fuel reforming system 1 can promote vaporization of the hydrocarbon fuel by the above-described arrangement of the third port injector 46 and the fuel injection timing of the third port injector 46. Promotion of vaporization of the hydrocarbon fuel increases the yield of carbon and hydrogen gas in the fuel reforming system 1 combined with the operation of the reciprocating engine 3.

[0099] The arrangement of the third port injector 46 is not limited to the structure shown in Fig. 2. The third port injector 46 may be attached to the third port 37 so as to inject hydrocarbon fuel in a direction perpendicular to the flow direction of the combustion gas (see, for example, Fig. 15).

[0100] (Switching between 6-stroke and 4-stroke cycles) The reciprocating engine 3 included in the fuel reforming system 1 is also an engine that outputs driving force for running the vehicle. The operating state of the reciprocating engine 3 varies greatly from low load to high load and from low rotation to high rotation. When the rotation speed of the reciprocating engine 3 is low, the time per cycle is relatively long, so the cracker 6 can efficiently decompose the hydrocarbon fuel into carbon and hydrogen gas. However, when the rotation speed of the reciprocating engine 3 is high, the time per cycle is short, so it becomes difficult to ensure the time for the decomposition reaction of the hydrocarbon fuel, in other words, the reaction time.

[0101] Therefore, the vehicle control system 2 switches between a six-stroke cycle that decomposes hydrocarbon fuel and a four-stroke cycle that does not decompose hydrocarbon fuel depending on the operating state related to the rotation speed and required load of the reciprocating engine 3.

[0102] 7 shows a control map 101 of the reciprocating engine 3. The control map 101 corresponds to an operating region of the reciprocating engine 3 defined by the engine speed and required load. The controller 21 operates the reciprocating engine 3 in accordance with the control map 101.

[0103] The control map 101 divides the operating range of the reciprocating engine 3 into a six-stroke cycle region 102 and a four-stroke cycle region 103. The six-stroke cycle region 102 is a region where the rotational speed is lower than a first rotational speed N1. The six-stroke cycle region 102 also includes a region where the rotational speed is equal to or higher than the first rotational speed N1 and where the required load is lower than a load Pe1. The four-stroke cycle region 103 is a region where the rotational speed is equal to or higher than the first rotational speed N1 and where the required load is equal to or higher than a load Pe1. The first rotational speed N1 may be a rotational speed included in the medium rotational speed region when the operating range of the reciprocating engine 3 is divided into three equal regions in the rotational speed direction: a low rotational speed region, a medium rotational speed region, and a high rotational speed region. The load Pe1 may be a load included in the medium load region when the operating range of the reciprocating engine 3 is divided into three equal regions in the load direction: a low load region, a medium load region, and a high load region.

[0104] The controller 21 causes the reciprocating engine 3 to execute a six-stroke cycle in the six-stroke cycle region 102. Specifically, the controller 21 causes the intake valve 34 and the exhaust valve 36 to open at predetermined timings via the intake valve train 41 and the exhaust valve train 42, and also causes the on-off valve 38 to open at predetermined timings via the third valve train 43.

[0105] Figure 8 shows an example of lift curves for the intake valve 34, exhaust valve 36, and on-off valve 38. The horizontal axis of Figure 8 represents crank angle, and the vertical axis represents valve lift. Chart 801 shows an example of lift curves for the intake valve 34, exhaust valve 36, and on-off valve 38 when a six-stroke cycle is being executed.

[0106] In chart 801, the on-off valve 38 opens during the re-compression stroke and also opens during the re-expansion stroke. During the re-compression stroke, the combustion gas in the cylinder 31 is introduced into the third port 37, and during the re-expansion stroke, the combustion gas flows from the third port 37 into the cylinder 31.

[0107] Chart 801 shows a lift curve when the required load is relatively low. In the exhaust stroke following the re-expansion stroke, the exhaust valve 36 opens. Exhaust gas in the cylinder 31 is discharged to the exhaust port 35. Then, in the intake stroke following the exhaust stroke, the exhaust valve 36 opens again. Some of the exhaust gas in the exhaust port 35 is reintroduced into the cylinder 31 as EGR gas. When the load of the reciprocating engine 3 is relatively low, the exhaust valve 36 that opens in the intake stroke has, for example, maximum lift. Also, in the intake stroke, the intake valve 34 opens. In chart 801, the intake valve 34 has maximum lift. A relatively large amount of fresh air is introduced into the cylinder 31, and a relatively small amount of EGR gas is introduced.

[0108] Here, when the reciprocating engine 3 is executing a six-stroke cycle, there are two more strokes per cycle than when it is executing a four-stroke cycle. The output of the reciprocating engine 3 when executing a six-stroke cycle is two-thirds of the output when it is executing a four-stroke cycle. When the required load of the reciprocating engine 3 is high, it is difficult for the reciprocating engine 3 when executing a six-stroke cycle to meet the required load.

[0109] Therefore, in the vehicle control system 2, when the reciprocating engine 3 is running a six-stroke cycle and the required load of the reciprocating engine 3 is equal to or greater than the load Pe2, the electric motor 27 is operated (see FIG. 7). The electric motor 27 functions as an assist motor that compensates for the insufficient output of the reciprocating engine 3. The reciprocating engine 3 and the electric motor 27 work together to output the driving force required to run the vehicle.

[0110] The load Pe2 may be a load included in the high load range when the operating range of the reciprocating engine 3 is divided into three equal parts in the load direction: low load, medium load, and high load.

[0111] When the required load is low, the amount of combustion gas introduced into the cracker 6 decreases. Even if the rotation speed of the reciprocating engine 3 is high and the reaction time is short, the cracker 6 can crack the hydrocarbon fuel if its cracking power is high. Therefore, in the control map 101 of Figure 7, the six-stroke cycle region 102 in which the six-stroke cycle is executed is expanded to the high rotation speed, low load region. Expanding the six-stroke cycle region 102 narrows the region in which hydrocarbon fuel is burned, which is advantageous for carbon neutralization.

[0112] The six-stroke cycle region 102 is divided into a first region, a second region, and a third region. The first region is a region where the rotational speed is lower than the first rotational speed N1. The second region is a region where the required load is lower than Pe1 and the rotational speed is equal to or higher than the first rotational speed but lower than the second rotational speed N2. The third region is a region where the required load is lower than Pe1 and the rotational speed is equal to or higher than the second rotational speed N2. The second rotational speed N2 may be a rotational speed included in the high rotational speed region. The operation of the fuel reforming system 1 in each of the first, second, and third regions will be described later.

[0113] The controller 21 also causes the reciprocating engine 3 to operate in a four-stroke cycle in the four-stroke cycle region 103. Specifically, the controller 21 opens the intake valve 34 and the exhaust valve 36 at predetermined timing via the intake valve train 41 and the exhaust valve train 42, while stopping the opening of the on-off valve 38 via the third valve train 43. Chart 802 in FIG. 8 shows lift curves of the intake valve 34 and the exhaust valve 36 when the four-stroke cycle is being performed. When the four-stroke cycle is being performed, the recompression stroke and the re-expansion stroke are omitted, thereby reducing pumping losses in the reciprocating engine 3. Although the reciprocating engine 3 runs on hydrocarbon fuel, its fuel consumption can be reduced. The reciprocating engine 3 has a mechanism for changing the speed ratio between the crankshaft and the camshaft when switching between the six-stroke cycle and the four-stroke cycle.

[0114] (Configuration that ensures long reaction time for the fuel reforming system) As described above, the fuel reforming system 1 has a structure that promotes the vaporization of hydrocarbon fuel. However, even if the vaporization of hydrocarbon fuel is promoted, the hydrocarbon fuel injected into the third port 37 may not vaporize quickly depending on the operating state of the reciprocating engine 3 or the operating state of the fuel reforming system 1. For example, this may occur when the reciprocating engine 3 is operating at high speed and the available response time is short.

[0115] Furthermore, for example, when the temperature of the third port 37 is low, the hydrocarbon fuel injected into the third port 37 is also less likely to vaporize. The temperature of the third port 37 is low not only when the reciprocating engine 3 is cold, but also when, as described above, the six-stroke cycle for reforming the hydrocarbon fuel is not being executed and combustion gas does not flow into the third port 37, resulting in a low temperature of the third port 37. A cold state of the third port 37 does not necessarily mean a cold state of the reciprocating engine 3.

[0116] The fuel reforming system 1 does not inject hydrocarbon fuel in every cycle when the reciprocating engine 3 is operating at high speed or when the temperature of the third port 37 is low, as described above, and is provided with a stop cycle in which hydrocarbon fuel is not injected. In the stop cycle, the valve stop mechanism of the third valve gear 43 stops the opening of the on-off valve 38. In the stop cycle, the supply of combustion gas from the cylinder 31 to the third port 37 is also stopped.

[0117] During the stop cycle, the hydrocarbon fuel injected into the third port 37 before the stop cycle continues to vaporize, and the hydrocarbon fuel continues to be decomposed in the cracker 6. Providing a stop cycle is equivalent to extending the reaction time. As a result, when the reciprocating engine 3 is operating at high speed or when the temperature of the third port 37 is cold and low, the hydrocarbon fuel injected into the third port 37 is decomposed into carbon and hydrogen gas, thereby increasing the yield of the fuel reforming system 1.

[0118] FIG. 9 illustrates a table 901 related to a shutdown cycle. The table 901 is stored in the memory of the controller 21. The table 901 defines the frequency of execution cycles according to the first, second, and third regions of the control map 101 and the temperature of the third port 37, i.e., normal temperature, low temperature, and extremely low temperature. Here, the normal temperature refers to a temperature at which the third port 37 and the cracker 6 can vaporize and decompose the hydrocarbon fuel. The low temperature refers to a temperature lower than the normal temperature at which the efficiency of the third port 37 and the cracker 6 at vaporizing and decomposing the hydrocarbon fuel decreases. The extremely low temperature refers to a temperature lower than the low temperature at which the efficiency of the third port 37 and the cracker 6 at vaporizing and decomposing the hydrocarbon fuel further decreases. The temperature of the third port 37 is based on a measurement signal of the temperature sensor 24.

[0119] Specifically, when the operating state of the reciprocating engine 3 is within the first region and the third port 37 is at room temperature, the third port injector 46 injects hydrocarbon fuel in every cycle. In other words, the fuel reforming system 1 does not have a stop cycle. This is because the rotation speed of the reciprocating engine 3 is relatively low and the temperature of the third port 37 is relatively high, allowing the hydrocarbon fuel to vaporize and decompose.

[0120] 10 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46, when no stop cycle is provided. In each of the nth cycle, the (n+1)th cycle, and the (n+2)th cycle, the on-off valve 38 opens and closes, and the third port injector 46 injects hydrocarbon fuel into the third port 37.

[0121] When the operating state of the reciprocating engine 3 is within the first region and the third port 37 is at a low or extremely low temperature, the third port injector 46 injects hydrocarbon fuel once every two cycles. In other words, the fuel reforming system 1 has a stop cycle once every two cycles.

[0122] 10 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46, when a stop cycle is provided once every two cycles. In each of the nth cycle and the (n+2)th cycle, the on-off valve 38 opens and closes, and the third port injector 46 injects hydrocarbon fuel into the third port 37. In the (n+1)th cycle, the on-off valve 38 remains closed, and the third port injector 46 does not inject hydrocarbon fuel into the third port 37.

[0123] When the operating state of the reciprocating engine 3 is within the second region, that is, when the rotation speed is higher than when it is within the first region, the fuel reforming system 1 provides a stop cycle as shown in table 901. Specifically, when the third port 37 is at room temperature or a low temperature, hydrocarbon fuel is injected once every two cycles (see chart 1002 in FIG. 10), and when it is at an extremely low temperature, the third port injector 46 injects hydrocarbon fuel once every three cycles.

[0124] 10 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46, when two stop cycles are provided in every three cycles. In the nth cycle, the on-off valve 38 opens and closes, and the third port injector 46 injects hydrocarbon fuel into the third port 37. In each of the (n+1)th cycle and the (n+2)th cycle, the on-off valve 38 remains closed, and the third port injector 46 does not inject hydrocarbon fuel into the third port 37. If the vaporization and decomposition of the hydrocarbon fuel do not proceed easily, the injection frequency of the hydrocarbon fuel is reduced to further extend the reaction time.

[0125] When the operating state of the reciprocating engine 3 is within the third region, i.e., when the rotation speed is higher than when it is within the second region, the fuel reforming system 1 provides a stop cycle as shown in table 901. Specifically, when the third port 37 is at room temperature, hydrocarbon fuel is injected once every two cycles, and when it is at low or extremely low temperature, the third port injector 46 injects hydrocarbon fuel once every three cycles.

[0126] Therefore, when the operating state of the reciprocating engine 3 is within the first region and the third port 37 is at room temperature, the fuel reforming system 1 does not provide a stop cycle. In contrast, when the temperature of the third port 37 is cold and lower than room temperature, the fuel reforming system 1 provides a stop cycle and an execution cycle. Furthermore, when the reciprocating engine 3 is operating at high speeds, where the rotational speed is higher than the first region, the fuel reforming system 1 provides a stop cycle and an execution cycle.

[0127] (Control flow of reciprocating engine and fuel reforming system) The flowchart in Fig. 11 shows a control procedure for switching between a six-stroke cycle and a four-stroke cycle. In step S131 after starting, the controller 21 reads various signals. In the following step S132, the controller 21 determines whether the operating state of the reciprocating engine 3 is in the six-stroke cycle region 102 based on the read signals and the control map 101. If the determination in step S132 is Yes, that is, if the operating state of the reciprocating engine 3 is in the six-stroke cycle region 102, the controller 21 sets the opening and closing of the on-off valve 38 of the third port 37 in step S133. Furthermore, in step S134, the controller 21 sets the injection of hydrocarbon fuel from the third port injector 46. The reciprocating engine 3 operates in a six-stroke cycle. In step S134, the controller 21 sets the injection pressure of the third port injector 46 based on the rotation speed and the required load of the reciprocating engine 3 in accordance with the relationship 601 in FIG.

[0128] In step S135, the controller 21 sets the frequency of fuel injection into the third port 37 based on the table 901 in FIG.

[0129] In step S136, the controller 21 sets the lift of the on-off valve 38 when it is opened, depending on the load of the reciprocating engine 3 and the temperature of the third port 37. As shown by the hollow arrow in chart 502 in Fig. 5, when the lift of the on-off valve 38 decreases, the effective cross-sectional area through which the combustion gas flows in the third port 37 decreases, and therefore the flow velocity of the combustion gas in the third port 37 increases (see the hollow arrow in chart 501).

[0130] 12 illustrates relationships 1201 and 1202 that the controller 21 uses to set the lift of the on-off valve 38 in step S136. The relationships 1201 and 1202 are stored in the memory of the controller 21. The relationship 1201 indicates the relationship between the load and rotation of the reciprocating engine 3 and the lift of the on-off valve 38, and the relationship 1202 indicates the relationship between the temperature of the third port 37 and the lift of the on-off valve 38.

[0131] When the load and rotation of the reciprocating engine 3 are low, the amount of gas in the cylinder 31 is relatively small, the amount of fuel supplied to the cylinder 31 is also small, and the duration of each stroke is longer than when the rotation is high. When the load and rotation of the reciprocating engine 3 are low, the flow velocity of the combustion gas introduced from the cylinder 31 to the third port 37 is low.

[0132] The controller 21 reduces the lift amount of the on-off valve 38 when the load and rotation speed of the reciprocating engine 3 are low compared to when the load and rotation speed are high. By reducing the lift amount, the flow velocity of the combustion gas flowing through the third port 37 increases, and as a result, vaporization of the hydrocarbon fuel injected from the third port injector 46 is promoted.

[0133] The lift amount of the on-off valve 38 may be increased linearly as the load and rotation speed of the reciprocating engine 3 increase. Note that the lift amount of the on-off valve 38 may be increased in stages as the load on the reciprocating engine 3 increases.

[0134] Furthermore, the lift amount of the on-off valve 38 may be kept constant at a large lift when the load on the reciprocating engine 3 exceeds a predetermined load. The lift amount of the on-off valve 38 may be kept constant at a maximum lift when the load on the reciprocating engine 3 exceeds a predetermined load. When the load on the reciprocating engine 3 increases, the amount of gas in the cylinder 31 increases, and the amount of fuel supplied to the cylinder 31 also increases. As a result, when the load on the reciprocating engine 3 increases, the flow velocity of the combustion gas introduced from the cylinder 31 to the third port 37 increases. Therefore, the lift amount of the on-off valve 38 may be kept constant at a large lift. Increasing the lift amount of the on-off valve 38 reduces the flow resistance of the third port 37, which has the advantage of reducing pumping losses in the reciprocating engine 3.

[0135] The controller 21 also reduces the lift amount of the on-off valve 38 when the temperature of the third port 37 is low compared to when the temperature is high. This is because the hydrocarbon fuel injected into the third port 37 is less likely to vaporize when the temperature of the third port 37 is low. When the temperature of the third port 37 is low, the controller 21 reduces the lift amount of the on-off valve 38, thereby increasing the flow velocity of the combustion gas flowing through the third port 37. As a result, this is advantageous for vaporizing the hydrocarbon fuel injected from the third port injector 46.

[0136] 12, the lift amount of the on-off valve 38 may be increased linearly as the temperature of the third port 37 increases. Note that the lift amount of the on-off valve 38 may be increased stepwise as the temperature of the third port 37 increases.

[0137] Furthermore, the lift amount of the on-off valve 38 may be kept constant at a large lift when the temperature of the third port 37 exceeds a predetermined temperature. The lift amount of the on-off valve 38 may be kept constant at a maximum lift when the temperature of the third port 37 exceeds a predetermined temperature. This is because, as the temperature of the third port 37 increases, the vaporization of the hydrocarbon fuel is promoted by that temperature. By increasing the lift amount of the on-off valve 38, the pumping loss of the reciprocating engine 3 is reduced.

[0138] The controller 21 may store relational expressions corresponding to the relationships 1201 and 1202 in memory instead of the relationships 1201 and 1202.

[0139] The controller 21 controls the opening and closing of the on-off valve 38 and the fuel injection of the third port injector 46 based on the settings in steps S133, S134, S135, and S136.

[0140] In step S137, the controller 21 adjusts the opening of the intake valve 34 and / or the exhaust valve 36 in accordance with the required output. In step S138, the controller 21 determines whether the required load Pe is equal to or greater than the load Pe2. If the determination in step S138 is Yes, the controller 21 operates the electric motor 27 in step S139 to cause the electric motor 27 to assist the reciprocating engine 3. If the determination in step S138 is No, the controller 21 does not operate the electric motor 27.

[0141] Returning to step S132, if the determination in step S132 is No, the controller 21 stops the on-off valve 38 in step S1310. The reciprocating engine 3 executes a four-stroke cycle.

[0142] In step S1311, the controller 21 adjusts the opening of the intake valve 34 and / or the exhaust valve 36 according to the required output.

[0143] (Variation 1) 13 shows a modified example of the third port 37. The reciprocating engine 3 has a butterfly valve 39 located in the third port 37. The butterfly valve 39 is a valve that opens and closes the third port 37 in place of the on-off valve 38. The butterfly valve 39 is located in the third port 37 between the third port injector 46 and the cylinder 31. In other words, the butterfly valve 39 is located upstream of the third port injector 46 with respect to the flow direction of the combustion gas from the cylinder 31 toward the cracker 6.

[0144] When fully closed, the butterfly valve 39 closes the third port 37 (see the two-dot chain line in Figure 13). The butterfly valve 39 is an example of a shutter valve. The butterfly valve 39 is a highly responsive on-off valve that can open and close in response to the operation of the reciprocating engine 3. The butterfly valve 39 also has a continuously adjustable opening. When the opening of the butterfly valve 39 is small, the effective opening area of ​​the third port 37 becomes small, and the velocity of the combustion gas flowing from the cylinder 31 to the cracker 6 increases. When the opening of the butterfly valve 39 is large, the effective opening area of ​​the third port 37 becomes large, and the velocity of the combustion gas flowing from the cylinder 31 to the cracker 6 decreases.

[0145] The controller 21 outputs a control signal to the butterfly valve 39 so that the opening degree of the butterfly valve 39 can be changed, including fully closed. The butterfly valve 39 changes its opening degree in response to the control signal from the controller 21. The butterfly valve 39 is, for example, a solenoid valve.

[0146] Fig. 14 shows a flow relating to the operation control of a reciprocating engine 3 having a butterfly valve 39. Compared to the flow in Fig. 11, the flow in Fig. 14 differs from the flow in Fig. 11 in that steps S1312, S1313, and S1314 are different from steps S133, S136, and S1310 in the flow in Fig. 11.

[0147] In step S1312, because the operating state of the reciprocating engine 3 is in the six-stroke cycle region 102, the controller 21 determines to open and close the butterfly valve 39 in accordance with the progress of the cycle of the reciprocating engine 3. The frequency of opening and closing the butterfly valve 39 is determined in step S135 based on table 901 (see FIG. 9).

[0148] On the other hand, in step S1314, the controller 21 keeps the butterfly valve 39 fully closed because the operating state of the reciprocating engine 3 is in the four-stroke cycle region 103.

[0149] Furthermore, in step S1313, the controller 21 sets the opening degree of the butterfly valve 39 when it is opened, depending on the load of the reciprocating engine 3 or the temperature of the third port 37. For example, the vertical axes of the relationships 1201 and 1202 shown in Fig. 12 may represent the opening degree of the butterfly valve 39 instead of the lift amount of the on-off valve 38. The controller 21 sets the opening degree of the butterfly valve 39 smaller when the load and rotation speed of the reciprocating engine 3 are low than when the load and rotation speed are high. As a result of the increase in the flow velocity of the combustion gas flowing through the third port 37, vaporization of the hydrocarbon fuel injected from the third port injector 46 is promoted.

[0150] The opening degree of the butterfly valve 39 may be increased linearly as the load on the reciprocating engine 3 increases. Note that the opening degree of the butterfly valve 39 may be increased in stages as the load on the reciprocating engine 3 increases.

[0151] Furthermore, the opening of the butterfly valve 39 may be kept constant at a large opening when the load on the reciprocating engine 3 exceeds a predetermined load. When the load on the reciprocating engine 3 increases, the amount of gas in the cylinder 31 increases, and the amount of fuel supplied to the cylinder 31 also increases. As a result, when the load on the reciprocating engine 3 increases, the flow velocity of the combustion gas introduced from the cylinder 31 to the third port 37 increases. Therefore, the opening of the butterfly valve 39 may be kept constant at a large opening. Increasing the opening of the butterfly valve 39 reduces the flow resistance of the third port 37, which has the advantage of reducing pumping losses in the reciprocating engine 3.

[0152] The controller 21 also opens the butterfly valve 39 less when the temperature of the third port 37 is low than when it is high. Even when the temperature of the third port 37 is low, the velocity of the combustion gas increases, which promotes vaporization of the hydrocarbon fuel injected from the third port injector 46.

[0153] The opening of the butterfly valve 39 may be increased linearly as the temperature of the third port 37 increases. Alternatively, the opening of the butterfly valve 39 may be increased stepwise as the temperature of the third port 37 increases. The opening of the butterfly valve 39 may be kept constant at a large opening once the temperature of the third port 37 exceeds a predetermined temperature. The opening of the butterfly valve 39 may be kept constant at a maximum opening once the temperature of the third port 37 exceeds a predetermined temperature.

[0154] (Variation 2) The fuel reforming system 1 described above promotes vaporization of the hydrocarbon fuel by utilizing the flow of combustion gas at the third port 37. Alternatively, the fuel reforming system 1 may promote vaporization of the hydrocarbon fuel by utilizing the heat of the third port 37. The fuel reforming system 1 may also devise a fuel injection timing for the third port injector 46.

[0155] Fig. 15 shows the fuel injection timing of the third port injector 46. Chart 1501 in Fig. 15 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing of the third port injector 46. In chart 1501 in Fig. 15, the fuel injection timing of the third port injector 46 is indicated by reference numeral 461. Chart 1502 in Fig. 15 shows pressure changes in the third port 37 and the cracker 6.

[0156] The third port injector 46 injects hydrocarbon fuel into the third port 37 while the on-off valve 38 is closed. More specifically, as shown in S16-S13 of Fig. 15 , the third port injector 46 injects hydrocarbon fuel into the third port 37 between the cracker 6 and the on-off valve 38 during the exhaust stroke. In other words, with reference to the flow of fuel gas flowing from the cylinder 31 to the cracker 6, the third port injector 46 injects fuel upstream of the cracker 6. The injected hydrocarbon fuel vaporizes while the on-off valve 38 is closed, more specifically, while the reciprocating engine 3 passes through the exhaust stroke, intake stroke, compression stroke, and expansion stroke.

[0157] At the timing when the third port injector 46 injects hydrocarbon fuel, there is substantially no gas flow in the third port 37. This is because the on-off valve 38 is closed. Increasing the injection pressure of the third port injector 46 is advantageous in promoting vaporization of the hydrocarbon fuel when the hydrocarbon fuel is injected into the third port 37, where there is substantially no gas flow.

[0158] The third port injector 46 may inject hydrocarbon fuel while the on-off valve 38 is closed, but the longest time for vaporizing the hydrocarbon fuel can be ensured by injecting fuel at the timing furthest from the timing at which the on-off valve 38 opens. The third port injector 46 may also inject hydrocarbon fuel immediately after the on-off valve 38 closes. The timing immediately after the on-off valve 38 closes corresponds to the exhaust stroke described above.

[0159] As described above, the on-off valve 38 opens during the recompression stroke. As indicated by the black arrow in S14, combustion gas flows from the cylinder 31 toward the cracker 6. The combustion gas carries the hydrocarbon fuel in the third port 37 toward the cracker 6. A catalytic reaction in the cracker 6 decomposes at least a portion of the hydrocarbon fuel into carbon and hydrogen gas. The carbon is stored in the cracker 6, and the hydrogen gas is sent to the hydrogen gas supply unit 5 through the hydrogen gas passage 50. When the piston 32 reaches top dead center during the recompression stroke, the combustion gas containing the hydrocarbon fuel and a portion of the carbon and hydrogen gas pass through the catalyst unit 64 of the cracker 6 and flow into the space 65.

[0160] In the re-expansion stroke following the re-compression stroke, the on-off valve 38 opens and the piston 32 descends. As the piston 32 descends, the gas in the third port 37 flows from the cracker 6 toward the cylinder 31 (see the open arrow in S15). The combustion gas containing hydrocarbon fuel and a portion of the carbon and hydrogen gas in the space 65 flow with the gas flow toward the catalyst section 64 and remain there.

[0161] When the on-off valve 38 closes during the exhaust stroke after the re-expansion stroke, the on-off valve 38 remains closed during the subsequent exhaust stroke, intake stroke, compression stroke, and expansion stroke (see S16-S13). Because the hydrocarbon fuel remains in the catalyst section 64, a sufficiently long time is ensured for the hydrocarbon fuel to decompose during the period until the on-off valve 38 opens during the re-compression stroke S14.

[0162] The third port injector 46 injects the hydrocarbon fuel during the stroke when the on-off valve 38 is closed, which ensures a long time for the hydrocarbon fuel to vaporize and a long time for the hydrocarbon fuel to remain in the catalyst section 64 of the cracker 6, thereby increasing the yield of carbon and hydrogen gas in the fuel reforming system 1.

[0163] During the exhaust stroke from S16 to S13, as described above, the third port injector 46 injects hydrocarbon fuel to promote vaporization. In the subsequent recompression stroke at S14, the vaporized hydrocarbon fuel is transported to the catalyst section 64 by the combustion gas.

[0164] 16 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46, when a stop cycle is provided and when it is not provided in Modification 2. A chart 1601 in Fig. 16 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46, when a stop cycle is not provided. In each of the nth cycle, the (n+1)th cycle, and the (n+2)th cycle, the on-off valve 38 opens and closes, and the third port injector 46 injects hydrocarbon fuel into the third port 37. As described above, the fuel injection timing 461 occurs while the on-off valve 38 is closed, more specifically, during the exhaust stroke.

[0165] Chart 1602 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46 when the third port injector 46 injects hydrocarbon fuel once every two cycles. In other words, the fuel reforming system 1 has a stop cycle once every two cycles. In each of the nth cycle and the (n+2)th cycle, the on-off valve 38 opens and closes, and the third port injector 46 injects hydrocarbon fuel into the third port 37. In the (n+1)th cycle, the on-off valve 38 remains closed, and the third port injector 46 does not inject hydrocarbon fuel into the third port 37. Because the reaction time is further extended, the yield of the fuel reforming system 1 is improved when the reciprocating engine 3 is operating at high speeds or when the temperature of the third port 37 is low during cold operation.

[0166] Chart 1603 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing 461 of the third port injector 46, when the fuel reforming system 1 has two stop cycles every three cycles. In the nth cycle, the on-off valve 38 opens and closes, and the third port injector 46 injects hydrocarbon fuel into the third port 37. In each of the n+1th and n+2th cycles, the on-off valve 38 remains closed, and the third port injector 46 does not inject hydrocarbon fuel into the third port 37. The injection frequency of hydrocarbon fuel is low to further extend the reaction time. The hydrocarbon fuel injected into the third port 37 is decomposed into carbon and hydrogen gas, thereby increasing the yield of the fuel reforming system 1.

[0167] (Variation 3) Regarding the second modification, the position of the third port injector 46 and the injection timing of the hydrocarbon fuel may be changed. In the modification shown in Fig. 17, the third port injector 46 is located in the space 65 of the cracker 6 and injects the hydrocarbon fuel into the space 65. In other words, the third port injector 46 is located downstream of the catalyst section 64 of the cracker 6 with respect to the flow direction of the combustion gas flowing from the cylinder 31 to the cracker 6.

[0168] 15, chart 1501 in Fig. 17 shows the valve lifts of the intake valve 34, exhaust valve 36, and on-off valve 38, and the fuel injection timing of the third port injector 46. In chart 1501 in Fig. 17, the fuel injection timing of the third port injector 46 is indicated by reference numeral 462. Chart 1502 in Fig. 17 shows pressure changes in the third port 37 and the cracker 6.

[0169] The third port injector 46 injects hydrocarbon fuel into the space 65 while the on-off valve 38 is open and the piston 32 is moving up. More specifically, as shown in S14 in Fig. 17, the third port injector 46 injects hydrocarbon fuel into the space 65 of the cracker 6 during the recompression stroke.

[0170] Here, the third port injector 46 may inject the hydrocarbon fuel into the space 65 in the latter half of the recompression stroke. The latter half of the recompression stroke may be the latter half of the recompression stroke when the recompression stroke is divided into an equal first half and a second half. This is because the pressure in the third port 37 and the cracker 6 is high and the temperature in the third port 37 and the cracker 6 is also high in the latter half of the recompression stroke, which is advantageous for vaporizing the injected hydrocarbon fuel. Furthermore, as will be described later, in order to retain the hydrocarbon fuel in the catalyst section 64 by utilizing the gas flow in the re-expansion stroke, it is advantageous to inject the hydrocarbon fuel into the space 65 in the latter half of the recompression stroke.

[0171] In the re-expansion stroke following the recompression stroke, the injected hydrocarbon fuel travels from the space 65 to the catalyst section 64 of the cracker 6 along with the gas flow from the cracker 6 toward the cylinder 31, and remains there (see S15). Thereafter, while the on-off valve 38 is closed, specifically during the exhaust stroke, intake stroke, compression stroke, and expansion stroke, the hydrocarbon fuel vaporizes and is decomposed into carbon and hydrogen gas by the catalyst (see S16-S13). The carbon adheres to the surface of the catalyst support 61.

[0172] The on-off valve 38 then opens during the recompression stroke (see S14). As indicated by the black arrows, the combustion gas flows from the cylinder 31 toward the cracker 6. Due to the gas flow within the third port 37, the hydrogen gas passes through the separation membrane 63 to the hydrogen gas passage 50, and is then sent to the hydrogen gas supply unit 5 through the hydrogen gas passage 50.

[0173] Then, during the recompression stroke, the third port injector 46 injects hydrocarbon fuel into the space 65 as previously described.

[0174] The third port injector 46 injects the hydrocarbon fuel during the stroke in which the on-off valve 38 is open and the piston 32 is rising, thereby ensuring a long period of time for the hydrocarbon fuel to vaporize and a long period of time for the hydrocarbon fuel to remain in the catalyst section 64 of the cracker 6, thereby increasing the yield of carbon and hydrogen gas in the fuel reforming system 1.

[0175] In the third modification, it is also possible to switch between providing and not providing a stop cycle, similar to FIG.

[0176] It should be noted that the technology disclosed herein is not limited to the above configuration. For example, the reciprocating engine 3 may be a compression ignition engine.

[0177] Furthermore, the cracker 6 of the fuel reforming system 1 is not limited to a membrane reactor. The cracker 6 may have any structure as long as it can crack the hydrocarbon fuel using the heat and pressure of the combustion gas. [Explanation of symbols]

[0178] 1 Fuel reforming system 3 Reciprocating engine 31 cylinders 32 piston 33 Intake port 35 exhaust port 37 Third Port 38 On-off valve 6 Decomposer S1 Intake stroke S2 compression stroke S3 Expansion stroke S4 Recompression process S5 Re-expansion stroke S6 exhaust stroke

Claims

1. a reciprocating engine mounted on a vehicle and having pistons reciprocating within cylinders; a cracker for cracking the hydrocarbon fuel into carbon and hydrogen gas; a hydrocarbon fuel supply device that supplies the hydrocarbon fuel to the cracker, the reciprocating engine has an intake port, an exhaust port, and a third port that connects the cylinder and the cracker and is opened and closed by an on-off valve, The reciprocating engine is an intake stroke in which at least intake air is introduced into the cylinder through the intake port as the piston descends; a compression stroke in which the mixture containing the hydrogen gas supplied into the cylinder is compressed by the rising of the piston; an expansion stroke in which the piston descends due to combustion of the air-fuel mixture; a recompression stroke in which the on-off valve opens and the piston rises, causing combustion gas to be supplied to the cracker through the third port; a re-expansion stroke in which the piston descends; and a six-stroke cycle having an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises; the hydrocarbon fuel supply device supplies the hydrocarbon fuel to the cracker during the recompression stroke; The reciprocating engine is provided with an execution cycle in which, when the third port is cold or when the reciprocating engine is operating at high speed, the supply of combustion gas to the cracker during the recompression stroke and the supply of hydrocarbon fuel by the hydrocarbon fuel supply device are executed, and a stop cycle in which the supply of combustion gas to the cracker during the recompression stroke and the supply of hydrocarbon fuel by the hydrocarbon fuel supply device are stopped.

2. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, the on-off valve is a poppet valve that opens and closes a connection between the third port and the cylinder, The valve stop mechanism further includes a valve stop mechanism that stops the opening operation of the on-off valve. The valve stop mechanism stops the opening of the on-off valve during the stop cycle.

3. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, the on-off valve is a shutter valve that opens and closes the third port at a position in the third port closer to the cylinder than the hydrocarbon fuel supply device, The on-off valve closes the third port in the stop cycle.

4. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker, the on-off valve is capable of changing an effective opening area of ​​the third port, A fuel reforming system for an engine-equipped vehicle, wherein when the on-off valve is open, if the reciprocating engine is in a first operating state of low load and low rotation, the effective opening area of ​​the third port is smaller than when the reciprocating engine is in a second operating state of higher load and higher rotation than the first operating state.

5. 2. The fuel reforming system for an engine-equipped vehicle according to claim 1, the hydrocarbon fuel supply device injects the hydrocarbon fuel into the third port between the on-off valve and the cracker, the on-off valve is capable of changing an effective opening area of ​​the third port, A fuel reforming system for an engine-equipped vehicle, wherein when the on-off valve is open, if the third port is at a low temperature, the effective opening area of ​​the third port is smaller than when the third port is at a high temperature.

Images