Vehicle control system

Abstract

To provide a system for reforming fuel suitable for mounting to a vehicle.SOLUTION: A reciprocal engine 3 selectively executes a six-stroke cycle comprising an intake stroke, a compression stroke, an expansion stroke, a re-compression stroke in which combustion gas is compressed due to lifting of a piston 32, a re-expansion stroke in which the piston is lowered and an exhaust stroke and a four-stroke cycle comprising the intake stroke, the compression stroke, the expansion stroke and the exhaust stroke. During execution of the six-stroke cycle, a decomposer 6 decomposes hydrocarbon fuel supplied from a hydrocarbon fuel supply section 45 into carbon and hydrogen gas by using heat and pressure of the combustion gas in the re-compression stroke. A hydrogen gas supply section 5 supplies the hydrogen gas generated by the decomposer into a cylinder 31 as fuel. A controller 21 causes the reciprocal engine to execute the six-stroke cycle when speed is lower than first speed N1, and causes the reciprocal engine to execute the four-stroke cycle when the speed is the first speed or higher.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The technology disclosed herein relates to a vehicle control system.

Background Art

[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 material gas containing hydrocarbons is supplied to the reactor, the carbon generated by the reaction of the catalyst adheres to the catalyst. The reaction gas containing hydrogen passes through the reactor. A hydrogen purification device downstream of the reactor purifies the hydrogen in the reaction gas and increases the hydrogen concentration.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technical field of vehicles (e.g., four-wheel automobiles), efforts towards carbon neutrality are required. In order to achieve carbon neutrality in a vehicle equipped with an engine using hydrocarbon fuel (including gasoline and / or diesel oil), in addition to improving the thermal efficiency of the engine and / or the exhaust emission performance, a new technology for recovering carbon (C) or CO2 from hydrocarbon fuel is necessary.

[0005] In vehicles equipped with engines that utilize hydrocarbon fuels, if carbon or CO2 is to be recovered, two methods are possible: (1) recovering CO2 after the combustion of the hydrocarbon fuel, or (2) decomposing the hydrocarbon fuel into carbon and hydrogen gas before combustion and recovering the carbon. Considering that the recovered CO2 or carbon will be stored in the vehicle, (2) is more advantageous in terms of the vehicle's fuel efficiency because CO2 is heavier than carbon. Furthermore, with (2), it is also possible to use hydrogen gas as engine fuel. Burning hydrogen gas has the advantage of not producing carbon oxides that result from combustion.

[0006] Therefore, it is conceivable to mount the aforementioned conventional decomposition device onto a vehicle. Conventional decomposition devices are equipped with a heating device for raising the temperature of the catalyst. If a conventional decomposition device is mounted on a vehicle, it is possible to utilize the engine's heat to raise the temperature of the catalyst.

[0007] However, using hydrogen gas as engine fuel requires a high concentration of hydrogen gas. Conventional cracking units require a hydrogen purification unit using the PSA (Pressure Swing Adsorption) method to purify hydrogen from the hydrogen-containing reaction gas in order to obtain a high concentration of hydrogen gas. Installing a hydrogen purification unit in a vehicle has the disadvantage of increasing the vehicle's weight. Conventional cracking units are unsuitable for installation in vehicles.

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

[0009] A membrane reactor, which simultaneously decomposes hydrocarbon fuels and separates hydrogen gas, could be used in a vehicle fuel reforming system. The membrane reactor uses a catalyst to decompose hydrocarbon fuels into carbon and hydrogen gas, while a separation membrane allows only the hydrogen gas to pass through, enabling the production of high-concentration hydrogen gas despite its small size. However, to efficiently produce high-concentration hydrogen gas in a membrane reactor, the pressure of the raw material gas containing hydrocarbon fuel supplied to the reactor must be increased.

[0010] The inventors of this application focused on the fact that in a reciprocating engine, the gas inside the cylinder is compressed by the upward movement of the piston, and have completed the technology disclosed herein.

[0011] Specifically, the reciprocating engine of the system disclosed herein operates on a six-stroke cycle. The six-stroke cycle is a cycle that adds a recompression stroke, in which the combustion gases are compressed by the upward movement of the piston, and a re-expansion stroke, in which the piston descends, between the expansion stroke and the exhaust stroke, compared to the four-stroke cycle which consists of an intake stroke, a compression stroke, an expansion stroke, in which the combustion gases are compressed by the upward movement of the piston. By utilizing the heat and pressure of the combustion gases in the recompression stroke, hydrocarbon fuels can be efficiently decomposed into carbon and hydrogen gas by combining this with the operation of the reciprocating engine, without the need to separately install a dedicated device to generate heat and / or pressure.

[0012] However, when a reciprocating engine mounted on a vehicle is the engine that outputs the driving force for the vehicle's movement, its operating conditions vary greatly from low load to high load and from low rotation speed to high rotation speed. When the rotation speed of a reciprocating engine is low, the time per cycle is relatively long, so hydrocarbon fuels can be efficiently decomposed into carbon and hydrogen gas. However, when the rotation speed of a reciprocating engine is high, the time per cycle is short, making it difficult to secure enough time for the decomposition reaction of hydrocarbon fuels.

[0013] Therefore, the technology disclosed herein switches between a 6-stroke cycle that decomposes hydrocarbon fuels and a 4-stroke cycle that does not decompose hydrocarbon fuels, depending on the operating conditions of the reciprocating engine.

[0014] Specifically, the technology disclosed herein relates to a vehicle control system. This control system is A reciprocating engine mounted on a vehicle, which outputs driving force for the vehicle's movement by the reciprocating motion of a piston in a cylinder, A decomposer that decomposes hydrocarbon fuel into carbon and hydrogen gas and stores the carbon, A hydrocarbon fuel supply unit capable of supplying the hydrocarbon fuel to the cylinder and the decomposer, A hydrogen gas supply unit that supplies the hydrogen gas generated by the decomposer as fuel into the cylinder, The system includes a controller for controlling the aforementioned reciprocating engine, The aforementioned reciprocating engine is A 6-stroke cycle having 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 as the piston rises, an expansion stroke in which the piston descends as the mixture burns, a recompression stroke in which the combustion gas is compressed as the piston rises, a re-expansion stroke in which the piston descends, and an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises, A four-stroke cycle is selectively performed, comprising: 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 hydrocarbon fuel supplied into the cylinder is compressed as the piston rises; an expansion stroke in which the piston descends as the mixture burns; and an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises. The decomposer, when the reciprocating engine is performing the six-stroke cycle, uses the heat and pressure of the combustion gas in the recompression stroke to decompose the hydrocarbon fuel supplied from the hydrocarbon fuel supply unit into carbon and hydrogen gas. The controller causes the reciprocating engine to execute the 6-stroke cycle when the rotational speed of the reciprocating engine is lower than the first rotational speed, and causes the reciprocating engine to execute the 4-stroke cycle when the rotational speed is equal to or greater than the first rotational speed.

[0015] The control system includes a fuel reforming system. The reciprocating engine operates on a six-stroke cycle. The fuel reforming system uses the heat and pressure of the combustion gases during the recompression stroke to break down the hydrocarbon fuel.

[0016] Specifically, the fuel reforming system comprises a cracker, a hydrocarbon fuel supply unit, and a hydrogen gas supply unit.

[0017] The hydrocarbon fuel supply unit supplies hydrocarbon fuel to the cracker. The fuel tank mounted on the vehicle should simply store hydrocarbon fuel. The hydrocarbon fuel supply unit then supplies the hydrocarbon fuel from the fuel tank to the cracker.

[0018] The decompressor uses the heat and pressure of the combustion gases during the recompression stroke to break down hydrocarbon fuels into carbon and hydrogen gas. The decompressor can efficiently break down hydrocarbon fuels. The carbon is stored in the decompressor.

[0019] The hydrogen gas supply unit supplies hydrogen gas, generated in the decomposer, as fuel into the cylinders of the reciprocating engine. The reciprocating engine operates by burning the hydrogen gas. No carbon oxides are produced as a result of combustion. The vehicle uses the power of the reciprocating engine as the driving force for propulsion. The reciprocating engine, which operates on a 6-stroke cycle, can output power while simultaneously supplying heat and pressure to the decompositioner for hydrocarbon fuel.

[0020] This fuel reforming system can achieve carbon neutrality. In addition, since this fuel reforming system utilizes the heat and pressure generated by the reciprocating engine, no separate device is required to generate the heat and / or pressure necessary for the decomposition of hydrocarbon fuel. The fuel reforming system is useful as an in-vehicle system.

[0021] On the other hand, the fuel reforming system is combined with a reciprocating engine that generates driving force for the vehicle to run. The operating state of the reciprocating engine varies greatly from low rotation speed to high rotation speed and from low load to high load. When the rotation speed of the reciprocating engine is high, since the time per cycle is short, it becomes difficult to secure the time for the decomposition reaction of hydrocarbon fuel.

[0022] Therefore, when the rotation speed of the reciprocating engine is lower than the first rotation speed, the controller of the control system causes the reciprocating engine to execute a six-stroke cycle. The hydrocarbon fuel is efficiently decomposed into carbon and hydrogen gas.

[0023] When the rotation speed of the reciprocating engine is equal to or higher than the first rotation speed, the controller causes the reciprocating engine to execute a four-stroke cycle. The hydrocarbon combustion supply unit supplies hydrocarbon fuel to the reciprocating engine. The reciprocating engine operates by burning the hydrocarbon fuel. During the execution of the four-stroke cycle, although the decomposition of hydrocarbon fuel does not occur, the reciprocating engine can output the driving force required for the vehicle to run.

[0024] The controller may be configured to cause the reciprocating engine to execute the four-stroke cycle when the operating state of the reciprocating engine is in a specific region where the rotation speed of the reciprocating engine is equal to or higher than the first rotation speed and the required load of the reciprocating engine is equal to or higher than the first load, and to cause the reciprocating engine to execute the six-stroke cycle when the operating state of the reciprocating engine is outside the specific region.

[0025] When the load required by a reciprocating engine increases, the amount of air supplied to the cylinder increases, which in turn increases the amount of combustion gas introduced into the decomposer. In a specific operating range where the load required by the reciprocating engine is high and the engine speed is high, the amount of combustion gas introduced into the decomposer increases, and because the reaction time for the decomposition of hydrocarbon fuels is short, it becomes difficult to ensure sufficient time for the decomposition reaction. Conversely, when the load required by the reciprocating engine is low, the amount of combustion gas introduced into the decomposer is small, so the decomposer can decompose hydrocarbon fuels even at high engine speeds.

[0026] Therefore, the controller causes the reciprocating engine to execute a 4-stroke cycle when its operating state is within a specific range, and to execute a 6-stroke cycle when it is outside of that range. This ensures both efficient decomposition of hydrocarbon fuels and the securing of the driving force necessary for the vehicle to run.

[0027] The device is controlled by the aforementioned controller and is equipped with an electric motor to compensate for the insufficient output of the reciprocating engine. The controller may operate the electric motor when the reciprocating engine is executing the 6-stroke cycle and the required load of the reciprocating engine is the second load or higher.

[0028] During a 6-stroke cycle, there are two more strokes per cycle than during a 4-stroke cycle. The output of a reciprocating engine during a 6-stroke cycle is 2 / 3 of the output during a 4-stroke cycle. When the load required by the reciprocating engine increases, it becomes difficult for the engine to meet the load requirements while running a 6-stroke cycle.

[0029] Therefore, the controller operates the electric motor when the reciprocating engine is running a 6-stroke cycle and the required load of the reciprocating engine is the second load or higher. The second load may be the load in the high-load region when the engine's operating range is divided into three equal regions: low load, medium load, and high load.

[0030] An electric motor is an assist motor that compensates for the lack of output in a reciprocating engine. The combination of a reciprocating engine and an electric motor can produce the driving force required for the vehicle to move.

[0031] The reciprocating engine has a third port communicating with the cylinder and an on / off valve for opening and closing the third port. The disassembler is connected to the third port, The hydrocarbon fuel supply unit has a first injector that injects the hydrocarbon fuel into the third port, The controller opens the on / off valve during the recompression stroke, thereby supplying the combustion gas and the hydrocarbon fuel to the decompressor through the third port. The controller may also stop the opening and closing of the on-off valve when the reciprocating engine is performing the four-stroke cycle.

[0032] In the fuel reforming system, a cracker is connected to a third port, and a first injector injects hydrocarbon fuel into the third port. When the valve opens during the recompression stroke, the combustion gas compressed by the rising piston and the hydrocarbon fuel injected by the first injector are supplied to the cracker through the third port. The cracker uses the heat and pressure of the combustion gas to efficiently decompose the hydrocarbon fuel into carbon and hydrogen gas.

[0033] A typical reciprocating engine has multiple intake ports and multiple exhaust ports. In a reciprocating engine for a fuel reforming system, at least one of the multiple intake ports and multiple exhaust ports needs to be repurposed as a third port. A typical reciprocating engine can be adapted for a fuel reforming system.

[0034] Furthermore, the valve does not open or close the third port while the reciprocating engine is running a four-stroke cycle. The reciprocating engine can run a normal four-stroke cycle, just like a typical reciprocating engine.

[0035] The controller performs a fuel cut when the vehicle is in motion and the accelerator pedal is open to zero, thereby stopping the supply of hydrogen gas and hydrocarbon fuel to the reciprocating engine. The controller opens the on / off valve during the stroke in which the piston is rising while the fuel cut is being executed. The decomposer may utilize the heat and pressure of the gas in the cylinder, which is compressed by the upward movement of the piston, to decompose the hydrocarbon fuel injected from the first injector into carbon and hydrogen gas.

[0036] Even when fuel cut is in effect and no combustion gases are being generated, the temperature and pressure of the gas introduced into the cylinder increase as it is compressed by the rising piston. The decomposer utilizes the heat and pressure of the gas in the cylinder to decompose the hydrocarbon fuel injected from the first injector into the third port into carbon and hydrogen gas. The hydrogen gas supply unit stores hydrogen gas, allowing it to be supplied into the cylinder after the fuel cut is restored.

[0037] The hydrogen gas supply unit has a second injector that injects the hydrogen gas into the cylinder, The hydrocarbon fuel supply unit may also have a third injector that injects the hydrocarbon fuel into the intake port.

[0038] The second injector injects hydrogen gas into the cylinder, allowing the reciprocating engine to operate using hydrogen gas as fuel.

[0039] By having the third injector inject hydrocarbon fuel into the intake port, the reciprocating engine can operate using hydrocarbon fuel as well as hydrogen gas.

[0040] The controller may, when the reciprocating engine is executing the four-stroke cycle and abnormal combustion of the reciprocating engine is detected, inject hydrogen gas into the second injector in addition to the hydrocarbon fuel from the third injector.

[0041] The combustion rate of hydrogen gas is significantly faster compared to the combustion of hydrocarbon fuels. The combustion of hydrogen gas is advantageous in suppressing abnormal combustion (e.g., knocking).

[0042] When a reciprocating engine is operating on a four-stroke cycle, in other words, when combustion using hydrocarbon fuel is occurring, and abnormal combustion is detected in the reciprocating engine, the controller injects hydrogen gas into the second injector. The hydrogen gas injected into the cylinder acts as a combustion accelerator. This can suppress abnormal combustion when combustion using hydrocarbon fuel is occurring. [Effects of the Invention]

[0043] The aforementioned vehicle control system enables the installation of a fuel reforming system in the vehicle. [Brief explanation of the drawing]

[0044] [Figure 1] Figure 1 shows the fuel reforming system installed in the vehicle. [Figure 2] Figure 2 shows a decomposer for breaking down hydrocarbon fuels. [Figure 3]Figure 3 shows the hydrogen gas supply unit that supplies hydrogen gas into the cylinder. [Figure 4] Figure 4 shows the vehicle's control system. [Figure 5] Figure 5 shows each stroke of the 6-stroke cycle. [Figure 6] Figure 6 shows the modes of the hydrogen gas supply unit. [Figure 7] Figure 7 is a flowchart of the mode switching control for the hydrogen gas supply unit. [Figure 8] Figure 8 shows a modified example of the hydrogen gas supply unit. [Figure 9] Figure 9 is a flowchart of the mode switching control of the hydrogen gas supply unit according to a modified example. [Figure 10] Figure 10 shows the control map for a reciprocating engine. [Figure 11] Figure 11 shows the lift curves of the intake valve, exhaust valve, and on / off valve. [Figure 12] Figure 12 shows another control map for a reciprocating engine. [Figure 13] Figure 13 is a flowchart of the switching control between a 6-stroke cycle and a 4-stroke cycle. [Figure 14] Figure 14 is a flowchart of the fuel injection switching control. [Modes for carrying out the invention]

[0045] The following describes embodiments of the vehicle's fuel reforming system and vehicle control system with reference to the drawings. The systems described here are illustrative examples.

[0046] (Configuration of the fuel reforming system) Figure 1 shows a fuel reforming system 1 installed in a vehicle. A hydrocarbon fuel is stored in the fuel tank installed in the vehicle. Hydrocarbon fuel is, for example, gasoline. 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 the reciprocating engine 3. The fuel reforming system 1 achieves carbon neutrality for vehicles equipped with hydrocarbon fuel.

[0047] 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 arranged, 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 the vehicle to move.

[0048] The reciprocating engine 3 has intake ports 33. The intake ports 33 communicate with the cylinders 31. Each cylinder 31 has one or more intake ports 33. Each cylinder 31 may have, for example, two intake ports 33. The intake ports 33 are connected to the intake manifold. As will be described later, intake air is introduced into the cylinders 31 through the intake ports 33. The intake air contains at least fresh air. The intake air may contain EGR (Exhaust Gas Recirculation) gas.

[0049] 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 is open, intake air is introduced into the cylinder 31. The intake valve train 41 shown in Figure 4 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), see Figure 11). The intake valve train 41 can employ a known hydraulic or electric mechanism. The intake valve train 41 changes the valve timing and / or valve lift according to the operating state of the reciprocating engine 3.

[0050] The reciprocating engine 3 has an exhaust port 35. The exhaust port 35 is in communication with the cylinder 31. Each cylinder 31 has one or more exhaust ports 35. Each cylinder 31 may have, for example, one exhaust port 35. The exhaust port 35 is connected to an exhaust pipe. As will be described later, exhaust gas is discharged from inside the cylinder 31 through the exhaust port 35.

[0051] 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 is open, exhaust gas is discharged outside the cylinder 31. The exhaust valve train 42 shown in Figure 4 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, see Figure 11). The exhaust valve train 42 can employ a known hydraulic or electric mechanism. The exhaust valve train 42 changes the valve timing and / or valve lift according to the operating state of the reciprocating engine 3.

[0052] The reciprocating engine 3 has a third port 37. The third port 37 communicates with the cylinder 31. Each cylinder 31 has at least one third port 37. Each cylinder 31 may have, for example, one third port 37.

[0053] A typical reciprocating engine has two intake ports and two exhaust ports per cylinder. One of the two exhaust ports may be repurposed as a third port 37. The reciprocating engine 3 in Figure 1 has two intake ports 33, one exhaust port 35, and one third port 37 per cylinder 31. Note that in Figure 1, the exhaust port 35 and the third port 37 are depicted with their positions offset for ease of understanding.

[0054] Furthermore, one of the two intake ports may be repurposed as a third port 37. However, the two intake ports 33 have the advantage of being able to introduce a large amount of fresh air into the cylinder 31. When an exhaust port or intake port is repurposed as a third port 37, a general reciprocating engine can be used as the reciprocating engine 3 of the fuel reforming system 1. Furthermore, the reciprocating engine 3 may have two intake ports 33, two exhaust ports 35, and one third port 37 per cylinder 31.

[0055] 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. A third valve train 43, shown in Figure 4, 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 opens the on-off valve 38 twice per cycle (see Figure 11). The third valve train 43 can also stop the opening and closing of the on-off valve 38. A known hydraulic or electric valve stop mechanism can be used to stop the opening and closing of the on-off valve 38. The valve stop mechanism may be incorporated into a rocker arm interposed between the third camshaft and the on-off valve 38, for example. 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.

[0056] An intake port injector 44 is attached to the reciprocating engine 3. The injection port of the intake port injector 44 faces into the intake port 33. The intake port injector 44 injects hydrocarbon fuel into the intake port 33. The intake port injector 44 is an example of a third injector. A hydrocarbon fuel supply unit 45 is connected to the intake port injector 44. The hydrocarbon fuel supply unit 45 has a fuel tank for storing hydrocarbon fuel and a fuel pump for pressurizing and pumping the hydrocarbon fuel. The hydrocarbon fuel supply unit 45 supplies hydrocarbon fuel to the intake port injector 44.

[0057] A third port injector 46 is attached to the reciprocating engine 3. The injection port of the third port injector 46 faces into the third port 37. The third port injector 46 injects hydrocarbon fuel into the third port 37. The third port injector 46 is an example of a first injector. 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.

[0058] A hydrogen injector 47 is attached to the reciprocating engine 3. The injection port of the hydrogen injector 47 faces into the cylinder 31. The hydrogen injector 47 injects hydrogen gas into the cylinder 31. The hydrogen injector 47 is an example of a second injector.

[0059] Furthermore, it is also possible to install a hydrocarbon fuel injector facing the cylinder 31 into the reciprocating engine 3, and a hydrogen gas injector facing the intake port 33 into the reciprocating engine 3.

[0060] 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 mentioned above, the hydrogen gas is hydrogen gas decomposed from hydrocarbon fuel. The configuration of the hydrogen gas supply unit 5 will be described later.

[0061] The decomposer 6 is connected to the third port 37. The decomposer 6 decomposes the hydrocarbon fuel into carbon and hydrogen gas. The decomposer 6 is installed for each cylinder 31. The decomposer 6 may be common to multiple cylinders 31.

[0062] Figure 2 shows the structure of the decomposer 6. The decomposer 6 uses a catalyst to decompose hydrocarbon fuels into carbon and hydrogen gas, and separates the hydrogen gas using a separation membrane 63. The decomposer 6 is a so-called membrane reactor. The decomposition of hydrocarbon fuels, such as isooctane, is represented by the following chemical equation.

[0063] iC8H 18 (g) = 8C(s) + 9H2 Recovering solid carbon helps to minimize the increase in vehicle weight. Fuel reforming system 1 is suitable as an on-board system.

[0064] The decomposer 6 has a reaction vessel 61. The reaction vessel 61 is, for example, a cylindrical body. The reaction vessel 61 is made of, for example, porous ceramic. The porous ceramic is, for example, zirconia. The reaction vessel 61 has the function of housing the catalyst support 62, which will be described later, and the function of allowing the generated hydrogen gas to pass through. The reaction vessel 61 can employ various structures as long as it has the two functions described above.

[0065] The decomposer 6 has a catalyst support 62. A catalyst that can be used for decomposing hydrocarbon fuels is, for example, a Ni-Al-Fe alloy. Various catalysts can be used, as long as they are suitable for decomposing hydrocarbon fuels.

[0066] The support 62 can be, for example, balls of aluminum oxide. The catalyst is coated on the surface of the balls. A large number of support 62 are packed inside the reaction vessel 61. Using balls as the support 62 increases the surface area of ​​the catalyst and improves the decomposition efficiency of the decomposer 6. The shape of the support 62 is not limited to a specific shape.

[0067] The carbon generated by the decomposition of hydrocarbon fuels adheres to the surface of the support 62. The decomposer 6 also stores carbon. The use of balls increases the amount of carbon stored in the decomposer 6, and even with the increased amount of stored carbon, the decomposition capacity of the decomposer 6 can be maintained. In addition, the use of balls facilitates the separation of hydrogen gas decomposed from hydrocarbon fuels. As will be described later, efficient separation of hydrogen gas also suppresses the decrease in the decomposition capacity of the decomposer 6.

[0068] The decomposer 6 has a separation membrane 63. The separation membrane 63 is attached to the inner surface of the reaction vessel 61. The reaction vessel 61 is a holder that holds the separation membrane 63. The separation membrane 63 has the function of permeating only hydrogen gas. The separation membrane 63 is, for example, a Pd alloy membrane. However, the separation membrane 63 is not limited to a Pd alloy membrane. The hydrogen gas that has permeated the separation membrane 63 passes through the reaction vessel 61 to the outside of the reaction vessel 61 (see the white arrow in Figure 2).

[0069] The decomposer 6 has a case 64. The reaction vessel 61 is housed inside the case 64. A space is formed between the outer surface of the reaction vessel 61 and the inner surface of the case 64. The case 64 has the function of collecting hydrogen gas and guiding it to the hydrogen gas passage 50, which will be described later.

[0070] A third port 37 is connected to the end of case 64. More specifically, the third port 37 is connected to the inside of a cylindrical reaction vessel 61. The combustion gas and hydrocarbon fuel are introduced into the reaction vessel 61 through the third port 37. Inside the reaction vessel 61, the hydrocarbon fuel is decomposed into carbon and hydrogen gas.

[0071] A hydrogen gas passage 50 is connected to the side of case 64. Hydrogen gas generated inside the reaction vessel 61 passes through the separation membrane 63 and the reaction vessel 61 to the outside of the reaction vessel 61. The hydrogen gas is sent to the hydrogen gas supply unit 5 through the hydrogen gas passage 50. As shown in Figure 3, the hydrogen gas passage 50 is connected to the hydrogen injector 47 via the hydrogen gas supply unit 5.

[0072] Figure 3 shows the structure of the hydrogen gas supply unit 5. As described above, the hydrogen gas supply unit 5 supplies hydrogen gas to the hydrogen injector 47. The hydrogen gas supply unit 5 can be common to multiple cylinders 31. Alternatively, a hydrogen gas supply unit 5 may be provided for each cylinder 31.

[0073] The hydrogen gas supply unit 5 has a first tank 51. The first tank 51 is connected to the hydrogen gas passage 50. The first tank 51 stores hydrogen gas from the decomposer 6.

[0074] The hydrogen gas supply unit 5 has a bypass passage 53. The bypass passage 53 bypasses the first tank 51. A first switching valve 54 is provided upstream of the first tank 51, and a second switching valve 55 is provided downstream of the first tank 51. The first switching valve 54 and the second switching valve 55 receive control signals from a controller 21 (described later) and switch the hydrogen gas flow path between the side of the first tank 51 and the side of the bypass passage 53. The switching of the first switching valve 54 and the second switching valve 55 will be described later.

[0075] The hydrogen gas supply unit 5 has a pump 56. The pump 56 is connected to the hydrogen gas passage 50 downstream of the second switching valve 55. The pump 56 increases the pressure of the hydrogen gas.

[0076] The hydrogen gas supply unit 5 has a second tank 52. The second tank 52 is connected to the hydrogen gas passage 50 downstream of the pump 56. The second tank 52 is located in the hydrogen gas passage 50 between the pump 56 and the hydrogen injector 47. The second tank 52 stores high-pressure hydrogen gas.

[0077] The pressure in the first tank 51 is lower than the pressure in the second tank 52. The low pressure of the first tank 51 lowers the pressure on the secondary side of the separation membrane 63 (i.e., the pressure outside the reaction vessel 61) to the pressure on the primary side (i.e., the pressure inside the reaction vessel 61). The low pressure of the first tank 51 increases the pressure difference between the primary and secondary sides of the separation membrane 63. A large pressure difference promotes the permeation of hydrogen gas through the separation membrane 63. Since the hydrogen gas generated inside the reaction vessel 61 permeates rapidly to the outside of the reaction vessel 61, the decomposition reaction of the hydrocarbon fuel inside the reaction vessel 61 is promoted. The first tank 51 is an example of a pressure reduction section that lowers the pressure in the hydrogen gas passage 50 to the pressure inside the reaction vessel 61. The combination of this pressure reduction section and the heat and pressure of the combustion gas in the recompression stroke described later significantly promotes the decomposition reaction in the decompressor 6. Accelerating the decomposition reaction of hydrocarbon fuels makes it possible to secure the amount of hydrogen gas necessary for operating the reciprocating engine 3, even if the decomposer 6 is small.

[0078] Furthermore, as will be described later, when the hydrogen gas flow path is switched to the bypass passage 53, the pressure on the secondary side of the separation membrane 63 decreases due to the operation of the pump 56. The pump 56 is also an example of a pressure reduction unit that lowers the pressure in the hydrogen gas passage 50 to below the pressure inside the reaction vessel 61.

[0079] The high-pressure second tank 52 can stably supply high-pressure hydrogen gas to the hydrogen injector 47. The hydrogen injector 47 can inject hydrogen gas into the cylinder 31 at a timing near top dead center of compression when the pressure inside the cylinder 31 is high. The pump 56 makes it possible to supply high-pressure hydrogen gas to the hydrogen injector 47 while maintaining a low pressure in the first tank 51.

[0080] (Control system configuration) Figure 4 is a block diagram of the control system 2 of a vehicle equipped with the fuel reforming system 1. The control system 2 has a controller 21. The controller 21 consists of hardware such as a processor, memory, and interface, and software such as a database and control programs.

[0081] The rotational speed sensor 22 is electrically connected to the controller 21. The rotational speed sensor 22 is attached to the reciprocating engine 3. The rotational speed sensor 22 outputs a measurement signal corresponding to the rotational speed of the crankshaft to the controller 21. Based on the measurement signal from the rotational speed sensor 22, the controller 21 can determine the rotational speed of the reciprocating engine 3.

[0082] 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 to the controller 21 that corresponds to the amount the accelerator pedal is pressed. Based on the measurement signal from the accelerator position sensor 23, the controller 21 can determine the required load of the reciprocating engine 3.

[0083] The knock sensor 24 is electrically connected to the controller 21. The knock sensor 24 is attached to the reciprocating engine 3. When knocking occurs in the reciprocating engine 3, the knock sensor 24 outputs a knock detection signal to the controller 21. Based on the knock detection signal, the controller 21 can determine that knocking has occurred.

[0084] The tank pressure sensor 25 is electrically connected to the controller 21. The tank pressure sensor 25 is attached to the second tank 52 of the hydrogen gas supply unit 5. The tank pressure sensor 25 outputs a signal to the controller 21 that corresponds to the amount of hydrogen gas in the second tank 52. Based on the signal from the tank pressure sensor 25, the controller 21 can determine the amount of hydrogen gas that can be supplied to the cylinder 31.

[0085] The intake valve train 41, exhaust valve train 42, and third valve train 43 described above 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, according to 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 / closed and stopped based on the control signal from the controller 21.

[0086] 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 control signals to each of the intake port injector 44, the third port injector 46, and the hydrogen injector 47. Based on the control signal from the controller 21, 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.

[0087] The control system 2 has a spark plug 26. The spark plug 26 is mounted on the reciprocating engine 3, facing into the cylinder 31. The spark plug 26 is electrically connected to the controller 21. The controller 21 outputs a control signal to the spark plug 26. Based on the control signal from the controller 21, the spark plug 26 ignites the fuel-air mixture in the cylinder 31 at a predetermined timing.

[0088] The control system 2 also has an electric motor 27. The electric motor 27 is an assist motor that compensates for the insufficient output of the reciprocating engine 3. The electric motor 27 operates on power supplied from the battery through the 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 for the vehicle to move. 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.

[0089] The aforementioned hydrogen gas supply unit 5 is electrically connected to the controller 21. The controller 21 outputs control signals to the first switching valve 54, the second switching valve 55, and the pump 56 of the hydrogen gas supply unit 5.

[0090] (6-stroke cycle) The reciprocating engine 3 performs a six-stroke cycle for the decomposer 6 to decompose the hydrocarbon fuel. Figure 5 shows each stroke included in the six-stroke cycle.

[0091] S1 is the intake stroke. In the intake stroke S1, the reciprocating engine 3 introduces intake air into the cylinder 31 by the downward movement of the piston 32. In the intake stroke S1, the intake valve 34 is open. 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 the so-called external EGR gas that has been recirculated to the intake manifold through the EGR passage. In the intake stroke S1, the exhaust valve 36 may also be open. If the exhaust valve 36 is open, exhaust gas is introduced into the cylinder 31 through the exhaust port 35. The exhaust gas introduced into the cylinder 31 is the so-called internal EGR gas. The on / off valve 38 of the third port 37 is closed.

[0092] In Figure 5, the hydrogen injector 47 injects hydrogen gas into the cylinder 31 during the intake stroke S1. The hydrogen injector 47 may also inject hydrogen gas during the compression stroke S2 ​​following the intake stroke S1. The hydrogen injector 47 may also inject hydrogen gas during the period from the intake stroke S1 to the compression stroke S2.

[0093] Furthermore, if hydrogen gas is insufficient, the intake port injector 44 may inject hydrocarbon fuel into the intake port 33 during the intake stroke S1 to compensate for the deficiency. Also, if hydrogen gas is unavailable, 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. When there is insufficient hydrogen gas supplied into the cylinder 31, the intake port injector 44 injects hydrocarbon fuel to ensure the necessary amount of fuel for the reciprocating engine 3. The reciprocating engine 3 can be operated using hydrocarbon fuel, or using both hydrocarbon fuel and hydrogen gas.

[0094] 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, exhaust valve 36, and on / off valve 38 are all closed.

[0095] The spark plug 26 ignites the fuel-air mixture in the cylinder 31 at a timing near top dead center of compression. The mixture begins to burn. S3 is the expansion stroke. During the expansion stroke S3, the piston 32 descends due to the combustion of the fuel-air mixture. The intake valve 34, exhaust valve 36, and on / off valve 38 are all closed.

[0096] S4 is the recompression stroke. In the recompression stroke S4, the reciprocating engine 3 compresses the combustion gas in the cylinder 31 by the upward movement of the piston 32. In the recompression stroke S4, the on-off valve 38 opens. The compressed combustion gas is introduced into the decomposer 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 decomposer 6 along with the combustion gas. As described above, in the decomposer 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 decomposer 6. The hydrogen gas is sent to the hydrogen gas supply unit 5 by permeating the separation membrane 63 of the decomposer 6 due to the pressure of the combustion gas.

[0097] Because the high pressure of the combustion gases during the recompression stroke is applied to the inside of the decompressor 6, the hydrogen gas generated inside the decompressor 6 quickly permeates through the separation membrane 63. Since the hydrogen gas on the right side of the aforementioned chemical reaction equation is discharged from inside the decompressor 6, the decomposition reaction of the hydrocarbon fuel inside the decompressor 6 is promoted. The decompressor 6, which utilizes the pressure of the recompression stroke S4 of the reciprocating engine 3, can generate the amount of hydrogen gas necessary for the operation of the reciprocating engine 3 even if it is small in size.

[0098] S5 is the re-expansion stroke. During the re-expansion stroke S5, the piston 32 descends. The on-off valve 38 may open during the re-compression stroke S4. When the on-off valve 38 is open, the combustion gas from which carbon and hydrogen gas have been removed is introduced from the decompressor 6 to the cylinder 31. Opening the on-off valve 38 during the re-expansion stroke S5 is advantageous in reducing the pumping losses of the reciprocating engine 3.

[0099] S6 is the exhaust stroke. During the exhaust stroke S6, the reciprocating engine 3 expels the combustion gases 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 gases in the cylinder 31 are discharged to the exhaust port 35. During the exhaust stroke S6, the intake valve 34 and the on / off valve 38 are closed.

[0100] After the exhaust stroke S6, the reciprocating engine 3 returns to the intake stroke S1.

[0101] Alternatively, instead of the valve 38 opening in the re-expansion stroke S5, or in conjunction with the opening of the valve 38, the valve 38 may open in the intake stroke S1. If the valve 38 opens in the intake stroke S1, the combustion gas from which carbon and hydrogen gas have been removed is introduced from the decomposer 6 to the cylinder 31. This combustion gas becomes the EGR gas.

[0102] If the valve 38 does not open during the re-expansion stroke S5, the hydrocarbon fuel introduced into the decompressor 6 during the re-compression stroke S4 will remain in the decompressor 6 for a longer period of time, which has the advantage of accelerating the decomposition reaction of the hydrocarbon fuel.

[0103] Thus, the fuel reforming system 1, which includes a reciprocating engine 3 that operates on a six-stroke cycle, stores the carbon produced by the decomposition of hydrocarbon fuel in a decomposer 6. Furthermore, since the reciprocating engine 3 burns the hydrogen gas produced by the decomposition of hydrocarbon fuel, no carbon oxides are generated due to combustion. The fuel reforming system 1 can achieve carbon neutrality.

[0104] Furthermore, since this fuel reforming system 1 utilizes the heat and pressure generated by the reciprocating engine 3, it does not require a separate dedicated device to generate the heat and / or pressure necessary for the decomposition of hydrocarbon fuels. The fuel reforming system 1 is useful as an on-board system.

[0105] Furthermore, if the carbon storage capacity of the decomposer 6 increases, carbon will be recovered from the decomposer 6. For example, when a vehicle is brought in for maintenance, the carbon-covered carrier 62 is removed from the decomposer 6, and the carbon is removed from the carrier 62 using, for example, a mill. The recovered carbon can be used as industrial carbon. The carrier 62 from which the carbon has been removed can be refilled into the decomposer 6 after being recoated with catalyst as needed.

[0106] (Mode switching for the hydrogen gas supply unit) The hydrogen gas supply unit 5 switches between the first mode, the second mode, and the third mode depending on the state of the reciprocating engine 3. Figure 6 shows each mode of the hydrogen gas supply unit 5.

[0107] The first mode is a mode in which hydrocarbon fuel is decomposed and the generated hydrogen gas is stored in the first tank 51 while the hydrogen gas is supplied to the reciprocating engine 3. In the first mode, the first switching valve 54 and the second switching valve 55 direct the hydrogen gas flow path toward the first tank 51. The hydrogen gas from the decomposer 6 flows into the first tank 51. As mentioned above, the first tank 51 lowers the pressure in the hydrogen gas passage 50 to a level lower than the pressure inside the reaction vessel 61.

[0108] The pump 56 is also driven. The hydrogen gas in the first tank 51 is pressurized and sent to the second tank 52. High-pressure hydrogen gas is stored in the second tank 52. Then, high-pressure hydrogen gas is supplied from the second tank 52 to the hydrogen injector 47, which injects the hydrogen gas into the cylinder 31.

[0109] The first mode may be, for example, the mode when starting the reciprocating engine 3 and / or when the pressure in the second tank 52 is low. The reciprocating engine 3 can be started and / or operated using hydrogen gas that has been previously stored in the first tank 51. As mentioned above, if hydrogen gas is insufficient, hydrocarbon fuel is injected into the intake port 33.

[0110] The second mode is a mode in which hydrocarbon fuel is decomposed and the generated hydrogen gas is immediately supplied to the reciprocating engine 3. In the second mode, the first switching valve 54 and the second switching valve 55 direct the hydrogen gas flow towards the bypass passage 53. The hydrogen gas from the decomposer 6 bypasses the first tank 51 and reaches the pump 56. The pump 56 is driven. When the pump 56 is driven, the pressure on the inlet side decreases. Consequently, the pressure on the secondary side of the separation membrane 63 of the decomposer 6 decreases. In the second mode, the pump 56 corresponds to a pressure reduction section.

[0111] The hydrogen gas is pressurized by the drive of the pump 56 and sent to the second tank 52. High-pressure hydrogen gas is stored in the second tank 52. Then, high-pressure hydrogen gas is supplied from the second tank 52 to the hydrogen injector 47, which injects the hydrogen gas into the cylinder 31.

[0112] The second mode may be, for example, the mode used during normal operation of the reciprocating engine 3. Normal operation means all times except during startup, when the second tank 52 is at low pressure, and during fuel cut-off, as described later. The second mode may also be the basic mode used when executing a 6-stroke cycle. Because the fuel reforming system 1 has high efficiency in decomposing hydrocarbon fuel in the decomposer 6, it can operate the reciprocating engine 3 by supplying the hydrogen gas generated while decomposing the hydrocarbon fuel.

[0113] The third mode is one in which the supply of hydrogen gas to the reciprocating engine 3 is stopped while hydrocarbon fuel is decomposed and the generated hydrogen gas is stored in the first tank 51. The hydrogen injector 47 stops operating and stops injecting hydrogen gas, while the third port injector 46 injects hydrocarbon fuel into the third port 37.

[0114] In the third mode, the first switching valve 54 and the second switching valve 55 direct the hydrogen gas flow path towards the first tank 51. The hydrogen gas from the decomposer 6 is stored in the first tank 51. The pump 56 is stopped. Hydrogen gas is not sent from the first tank 51 to the second tank 52. However, the pump 56 may be driven. In this case, the supply of hydrogen gas from the second tank 52 to the hydrogen injector 47 is stopped.

[0115] The third mode may be, for example, the fuel cut-off mode for the reciprocating engine 3. The controller 21 can determine whether or not fuel cut-off is in effect based on the measurement signal from the accelerator position sensor 23. In the third mode, the amount of hydrogen gas stored in the first tank 51 increases. In the first mode, the hydrogen gas stored in the first tank 51 is supplied to the hydrogen injector 47.

[0116] Switching between the first, second, and third modes may be performed depending on the operating state of the reciprocating engine 3, the pressure of the second tank 52, and whether or not fuel cut is in effect. Figure 7 shows the control procedure for switching modes of the hydrogen gas supply unit 5. In step S71 after startup, the controller 21 reads various signals. In the following step S72, the controller 21 determines whether or not the hydrogen gas supply unit 5 should be set to second mode. As mentioned above, during normal operation of the reciprocating engine 3, the controller 21 determines that the hydrogen gas supply unit 5 should be set to second mode. If the determination in step S72 is Yes, then in the following step S73, the controller 21 uses the first switching valve 54 and the second switching valve 55 to bypass the first tank 51, directing the hydrogen gas flow path to the bypass passage 53. Then, in step S76, the controller 21 drives the pump 56.

[0117] If the decision in step S72 is No, then in step S74, the controller 21 uses the first switching valve 54 and the second switching valve 55 to direct the hydrogen gas flow path towards the first tank 51. Then, in step S75, the controller 21 decides whether or not to put the hydrogen gas supply unit 5 into the third mode. As mentioned above, when the fuel cut of the reciprocating engine 3 occurs, the controller 21 decides that the hydrogen gas supply unit 5 should be put into the third mode. If the decision in step S75 is Yes, then in step S77, the controller 21 stops the pump 56. If the decision in step S75 is No, then in step S76, the controller 21 drives the pump 56. The hydrogen gas supply unit 5 enters the first mode.

[0118] Figure 8 shows a modified example of the hydrogen gas supply unit. The hydrogen gas supply unit 59 has a second pump 57 instead of a second tank 52. The second pump 57 is located in the hydrogen gas passage 50 between the decomposer 6 and the first switching valve 54. In the hydrogen gas supply unit 59 of Figure 8, to distinguish between the two pumps, the pump located between the second switching valve 55 and the hydrogen injector 47 is called the first pump 56. The first pump 56 is a pump that supplies high-pressure hydrogen gas to the hydrogen injector 47.

[0119] When the second pump 57 is activated, the pressure on the inlet side of the second pump 57 decreases. This decrease in inlet pressure reduces the pressure on the secondary side of the separation membrane 63 in the decomposer 6. The second pump 57 is an example of a pressure reduction unit that lowers the pressure in the hydrogen gas passage 50 to a level lower than the pressure inside the reaction vessel 61.

[0120] The hydrogen gas supply unit 59 also switches between first mode, second mode, and third mode. Figure 9 shows the control procedure for mode switching of the hydrogen gas supply unit 59. In step S91 after startup, the controller 21 reads various signals. In the following step S92, the controller 21 determines whether or not to set the hydrogen gas supply unit 59 to second mode. If the determination in step S92 is Yes, then in the following step S93, the controller 21 uses the first switching valve 54 and the second switching valve 55 to direct the hydrogen gas flow path to the bypass passage 53 so that the first tank 51 is bypassed. Then, in step S96, the controller 21 drives the first pump 56 and the second pump 57. Hydrogen gas decomposed from hydrocarbon fuel is supplied to the hydrogen injector 47 through the second pump 57, the bypass passage 53, and the first pump 56.

[0121] If the decision in step S92 is No, the controller 21, in step S94, uses the first switching valve 54 and the second switching valve 55 to direct the hydrogen gas flow path toward the first tank 51. Then, in step S95, the controller 21 determines whether or not to put the hydrogen gas supply unit 59 into the third mode. If the decision in step S95 is Yes, the controller 21, in step S97, stops the first pump 56 and drives the second pump 57. The supply of hydrogen gas to the hydrogen injector 47 is stopped, and the generated hydrogen gas is stored in the first tank 51. If the decision in step S95 is No, the controller 21 drives the first pump 56 and the second pump 57 in step S96. Hydrogen gas decomposed from hydrocarbon fuel is supplied to the first tank 51, and from the first tank 51 through the first pump 56 to the hydrogen injector 47. The hydrogen gas supply unit 59 enters the first mode.

[0122] (Switching between 6-stroke and 4-stroke cycles) The reciprocating engine 3 included in the fuel reforming system 1 is also the engine that outputs the driving force for the vehicle. The operating conditions of the reciprocating engine 3 vary greatly, from low load to high load and from low rotation to high rotation. When the rotational speed of the reciprocating engine 3 is low, the time per cycle is relatively long, so the decomposer 6 can efficiently decompose the hydrocarbon fuel into carbon and hydrogen gas. However, when the rotational speed of the reciprocating engine 3 is high, the time per cycle is short, making it difficult to secure enough time for the decomposition reaction of the hydrocarbon fuel.

[0123] Therefore, the vehicle's control system 2 switches between a 6-stroke cycle that decomposes hydrocarbon fuel and a 4-stroke cycle that does not decompose hydrocarbon fuel, depending on the operating conditions related to the rotational speed and required load of the reciprocating engine 3.

[0124] Figure 10 shows the control map 101 of the reciprocating engine 3. The control map 101 corresponds to the operating range of the reciprocating engine 3, defined by the engine speed and the required load. The controller 21 operates the reciprocating engine 3 according to the control map 101.

[0125] The control map 101 divides the operating range of the reciprocating engine 3 into a first range 102 and a second range 103. The first range 102 is the range where the rotational speed is lower than the first rotational speed N1. The second range 103 is the range where the rotational speed is equal to or greater than the first rotational speed N1. The first rotational speed N1 may be the rotational speed included in the medium rotational speed range when the operating range of the reciprocating engine 3 is divided into three equal parts in the direction of rotational speed: a low rotational speed range, a medium rotational speed range, and a high rotational speed range.

[0126] In the first region 102, the controller 21 causes the reciprocating engine 3 to execute a 6-stroke cycle. Specifically, the controller 21 opens the intake valve 34 and exhaust valve 36 at predetermined timings through the intake valve train 41 and exhaust valve train 42, while opening the on / off valve 38 at predetermined timings through the third valve train 43.

[0127] Figure 11 illustrates the lift curves of the intake valve 34, exhaust valve 36, and on-off valve 38. The horizontal axis of Figure 11 represents the crank angle, and the vertical axis represents the valve lift. Charts 111 to 114 show the lift curves of the intake valve 34, exhaust valve 36, and on-off valve 38 during a 6-stroke cycle. The required load on the reciprocating engine 3 increases in the order of Charts 111, 112, 113, and 114.

[0128] In charts 111, 112, 113, and 114, the lift curve of the on-off valve 38 is the same. The on-off valve 38 opens during the recompression stroke and also during the re-expansion stroke. During the recompression stroke, combustion gases in the cylinder 31 are introduced into the third port 37, and during the re-expansion stroke, combustion gases flow from the decompressor 6 into the cylinder 31. Alternatively, the on-off valve 38 may open during the intake stroke instead of, or in conjunction with, opening during the re-expansion stroke.

[0129] Chart 111 shows the lift curve when the required load is low. When the required load is low, relatively less fresh air is introduced into the cylinder 31 and relatively more EGR gas is released. In the exhaust stroke following the re-expansion stroke, the exhaust valve 36 opens. The 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. A portion of the exhaust gas in the exhaust port 35 is reintroduced into the cylinder 31 as EGR gas. When the load on the reciprocating engine 3 is low, the exhaust valve 36 that opens in the intake stroke is, for example, at its maximum lift. Also, in the intake stroke, the intake valve 34 opens. The intake valve 34 has a relatively small lift. Relatively less fresh air is introduced into the cylinder 31 and relatively more EGR gas is released.

[0130] Chart 112 represents a higher load requirement than Chart 111. A higher load requirement results in a greater lift of the intake valve 34. The intake valve 34 lift in Chart 112 is, for example, the maximum lift. The exhaust valve 36 lift in Chart 112 is the same as in Chart 111. This increases the amount of fresh air introduced into the cylinder 31 and reduces the amount of EGR gas.

[0131] Chart 113 represents a higher load requirement than Chart 112. As the lift of the intake valve 34 increases to its maximum lift, the lift of the exhaust valve 36, which opens during the intake stroke, decreases as the load requirement increases. In Chart 113, the lift of the intake valve 34 remains at its maximum lift. This increases the amount of fresh air introduced into the cylinder 31 and further reduces the amount of EGR gas.

[0132] Chart 114 represents a higher load requirement than Chart 113. As the load requirement increases, the lift of the exhaust valve 36, which opens during the intake stroke, decreases. As a result, in Chart 114, the exhaust valve 36 does not open during the intake stroke. The amount of EGR gas introduced into the cylinder 31 is virtually zero.

[0133] The controller 21 changes the load on the reciprocating engine 3 during a 6-stroke cycle by controlling the opening of the intake valve 34 and the exhaust valve 36.

[0134] Here, when the reciprocating engine 3 is running a 6-stroke cycle, there are two more strokes per cycle than when it is running a 4-stroke cycle. The output of the reciprocating engine 3 during a 6-stroke cycle is 2 / 3 of the output during a 4-stroke cycle. When the load required of the reciprocating engine 3 is high during a 6-stroke cycle, it becomes difficult for the reciprocating engine 3 to meet the required load.

[0135] Therefore, the vehicle control system 2 operates the electric motor 27 when the reciprocating engine 3 is executing a 6-stroke cycle and the required load for the reciprocating engine 3 is greater than or equal to load Pe2 (see Figure 10). The electric motor 27 functions as an assist motor to compensate for the insufficient output of the reciprocating engine 3. Through the cooperation of the reciprocating engine 3 and the electric motor 27, the driving force required for the vehicle to move is output.

[0136] Furthermore, the load Pe2 may be defined as the load included in the high-load region when the operating range of the reciprocating engine 3 is divided into three equal regions in the load direction: low-load, medium-load, and high-load.

[0137] The controller 21 also causes the reciprocating engine 3 to execute a four-stroke cycle in the second region 103. Specifically, the controller 21 opens the intake valve 34 and exhaust valve 36 at predetermined timings via the intake valve train 41 and exhaust valve train 42, while stopping the opening of the on-off valve 38 via the third valve train 43. Chart 115 in Figure 11 shows the lift curves of the intake valve 34 and exhaust valve 36 when the four-stroke cycle is executed. When the four-stroke cycle is executed, the recompression stroke and re-expansion stroke are omitted, thus reducing the pumping loss of the reciprocating engine 3. The reciprocating engine 3 is operated on hydrocarbon fuel, and its fuel consumption can be suppressed. The reciprocating engine 3 also has a mechanism to change the speed ratio between the crankshaft and the camshaft when switching between the six-stroke cycle and the four-stroke cycle.

[0138] Figure 12 shows a modified control map of the reciprocating engine 3. Control map 104 also divides the operating range of the reciprocating engine 3 into a first range 105 and a second range 106. The first range 105 is the range where the rotational speed is lower than the first rotational speed N1, and the range where the rotational speed is N1 or higher and the required load is lower than load Pe1. The second range 106 is the range where the rotational speed is N1 or higher and the required load is Pe1 or higher. Load Pe1 may be the load included in the medium load range when the operating range of the reciprocating engine 3 is divided into three equal ranges in the load direction: low load, medium load, and high load.

[0139] When the required load is low, the amount of combustion gas introduced into the decomposer 6 decreases. Even if the rotational speed of the reciprocating engine 3 is high and the reaction time is short, if the decomposition capacity of the decomposer 6 is high, the decomposer 6 can decompose the hydrocarbon fuel. Therefore, the first region 105 in which the 6-stroke cycle is executed may be expanded to the high-speed, low-load region. Expanding the first region 105 reduces the region in which hydrocarbon fuel is burned, which is advantageous for carbon neutrality.

[0140] The flowchart in Figure 13 shows the control procedure for switching between a 6-stroke cycle and a 4-stroke cycle. In step S131 after starting, the controller 21 reads various signals, and in the following step S132, the controller 21 determines whether the operating state of the reciprocating engine 3 is in the first region 102 or 105 based on the read signals and control map 101 or 104. If the determination in step S132 is Yes, that is, if the operating state of the reciprocating engine 3 is in the first region 102 or 105, the controller 21 opens or closes the on-off valve 38 of the third port 37 in step S133. The reciprocating engine 3 then executes a 6-stroke cycle.

[0141] In step S134, the controller 21 adjusts the opening of the intake valve 34 and / or exhaust valve 36 according to the requested output. In the following step S135, the controller 21 sets the fuel. The fuel setting in step S135 will be described later.

[0142] In step S136, the controller 21 determines whether the requested load Pe is greater than or equal to load Pe2. If the determination in step S136 is Yes, the controller 21 operates the electric motor 27 in step S137, causing the electric motor 27 to assist the reciprocating engine 3. If the determination in step S136 is No, the controller 21 does not operate the electric motor 27.

[0143] Returning to step S132, if the determination in step S132 is No, the controller 21 stops the on-off valve 38 in step S138. The reciprocating engine 3 performs a four-stroke cycle.

[0144] In step S139, the controller 21 adjusts the opening of the intake valve 34 and / or exhaust valve 36 according to the requested output. In the following step S1310, the controller 21 determines whether the knock sensor 24 has detected knocking. If the determination in step S1310 is Yes, the controller 21 injects hydrogen gas into the hydrogen injector 47 in step S1311 to suppress the occurrence of abnormal combustion.

[0145] Generally, when an engine using hydrocarbon fuel is operated at high load and high rotation speed, there is a problem that abnormal combustion (e.g., knocking) is likely to occur. When the operating state of the reciprocating engine 3 is in the second region 103 or 106, the rotation speed of the reciprocating engine 3 is high, and because it burns hydrocarbon fuel, if the required load increases, there is a risk of abnormal combustion occurring.

[0146] Here, comparing the combustion of hydrocarbon fuel with the combustion of hydrogen gas, the combustion of hydrogen gas is characterized by a significantly faster combustion speed. Therefore, when the operating state of the reciprocating engine 3 is in the second region 103 or 106 and knocking is detected, the vehicle control system 2, in addition to the intake port injector 44 injecting hydrocarbon fuel into the intake port 33, injects hydrogen gas into the cylinder 31 with a hydrogen injector 47. The hydrogen gas used is, for example, hydrogen gas stored in the first tank 51. The hydrogen injector 47 may inject hydrogen gas into the cylinder 31 at, for example, during the compression stroke. Hydrogen gas injected into the cylinder 31 at the appropriate timing acts as a combustion accelerator and increases the combustion speed. When combustion using hydrocarbon fuel is performed and the operating state of the reciprocating engine 3 is high load and high rotation, abnormal combustion can be suppressed. Suppression of abnormal combustion by hydrogen gas injection has the advantage that abnormal combustion can be suppressed without reducing the thermal efficiency of the reciprocating engine 3.

[0147] If the decision in step S1310 is No, the controller 21 does not inject hydrogen gas into the hydrogen injector 47.

[0148] Step S1310 may also determine whether the requested load Pe is equal to or greater than load Pe3. Load Pe3 may be the load included in the high-load region 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 regions, as shown in Figure 10 or 12. There are no particular restrictions on the relative height of loads Pe2 and Pe3. Abnormal combustion can be prevented by injecting hydrogen gas into the cylinder 31 in the region where abnormal combustion is likely to occur.

[0149] Figure 14 shows the control procedure for fuel setting in step S135 of the flowchart in Figure 13. First, in step S141, the controller 21 obtains the amount of hydrogen gas that can be supplied to the cylinder 31 based on the signal from the tank pressure sensor 25. Then, in step S142, the controller 21 determines, based on the requested output and the amount of hydrogen gas, whether or not it is possible to inject only hydrogen gas, in other words, whether or not the requested output can be met by the amount of hydrogen gas.

[0150] If the determination in step S142 is Yes, the controller 21 sets the injection to hydrogen gas only in step S143. If the determination in step S142 is No, there is a shortage of hydrogen gas, so the controller 21 sets the injection to both hydrogen gas and hydrocarbon fuel in step S144. The amount of hydrocarbon fuel injected is set to the amount of the hydrogen gas shortage.

[0151] Switching between a 6-stroke cycle and a 4-stroke cycle will help make the reciprocating engine 3 carbon neutral while enabling the operation of vehicles powered by the reciprocating engine 3.

[0152] Furthermore, the technology disclosed herein is not limited to the above-described configuration. For example, the reciprocating engine 3 may be a compression-ignition type engine.

[0153] Furthermore, the decomposer 6 of the fuel reforming system 1 is not limited to a membrane reactor. The decomposer 6 can have any structure as long as it can decompose the hydrocarbon fuel using the heat and pressure of the combustion gas. [Explanation of symbols]

[0154] 2. Control System 21 Controller 27 Electric motor 3 Reciprocating engines 31 cylinders 32 pistons 33 Intake Ports 35 Exhaust Ports 37 Third Port 38. Shut-off valve 44. Intake port injector (third injector) 45. Hydrocarbon Fuel Supply Section 46. ​​Third port injector (first injector) 47. Hydrogen Injector (Second Injector) 5. Hydrogen gas supply unit 59 Hydrogen Gas Supply Department 6 Decomposer S1 Intake Stroke S2 Compression Stroke S3 Expansion Stroke S4 Recompression Stroke S5 Re-expansion process S6 exhaust stroke

Claims

1. A reciprocating engine mounted on a vehicle, which outputs driving force for the vehicle's movement by the reciprocating motion of a piston in a cylinder, A decomposer that decomposes hydrocarbon fuel into carbon and hydrogen gas and stores the carbon, A hydrocarbon fuel supply unit capable of supplying the hydrocarbon fuel to the cylinder and the decomposer, A hydrogen gas supply unit that supplies the hydrogen gas generated by the decomposer as fuel into the cylinder, The system includes a controller for controlling the aforementioned reciprocating engine, The aforementioned reciprocating engine is A six-stroke cycle having 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 as the piston rises, an expansion stroke in which the piston descends as the mixture burns, a recompression stroke in which the combustion gas is compressed as the piston rises, a re-expansion stroke in which the piston descends, and an exhaust stroke in which exhaust gas is discharged through the exhaust port as the piston rises, A four-stroke cycle is selectively performed, comprising: an intake stroke in which at least intake air is introduced into the cylinder through the intake port by the downward movement of the piston; a compression stroke in which the mixture containing the hydrocarbon fuel supplied into the cylinder is compressed by the upward movement of the piston; an expansion stroke in which the piston descends due to the combustion of the mixture; and an exhaust stroke in which exhaust gas is discharged through the exhaust port by the upward movement of the piston. The decomposer, when the reciprocating engine is performing the six-stroke cycle, uses the heat and pressure of the combustion gas in the recompression stroke to decompose the hydrocarbon fuel supplied from the hydrocarbon fuel supply unit into carbon and hydrogen gas. The controller is a vehicle control system that causes the reciprocating engine to execute the six-stroke cycle when the rotational speed of the reciprocating engine is lower than a first rotational speed, and to execute the four-stroke cycle when the rotational speed is equal to or greater than the first rotational speed.

2. In the vehicle control system according to claim 1, The controller is a vehicle control system that causes the reciprocating engine to execute the four-stroke cycle when the operating state of the reciprocating engine is in a specific region where the rotational speed of the reciprocating engine is equal to or greater than the first rotational speed and the required load of the reciprocating engine is equal to or greater than the first load, and causes the reciprocating engine to execute the six-stroke cycle when the operating state of the reciprocating engine is outside the specific region.

3. In the vehicle control system according to claim 1, The device is controlled by the aforementioned controller and includes an electric motor to compensate for the insufficient output of the reciprocating engine. The controller is a vehicle control system that operates the electric motor when the reciprocating engine is executing the six-stroke cycle and the required load of the reciprocating engine is the second load or higher.

4. In the vehicle control system according to claim 1, The reciprocating engine has a third port communicating with the cylinder and an on / off valve for opening and closing the third port. The disassembler is connected to the third port, The hydrocarbon fuel supply unit has a first injector that injects the hydrocarbon fuel into the third port, The controller opens the on / off valve during the recompression stroke, thereby supplying the combustion gas and the hydrocarbon fuel to the decompressor through the third port. The controller is also a vehicle control system that stops the opening and closing of the on-off valve when the reciprocating engine is performing the four-stroke cycle.

5. In the vehicle control system according to claim 4, The controller performs a fuel cut when the vehicle is in motion and the accelerator pedal is open to zero, thereby stopping the supply of hydrogen gas and hydrocarbon fuel to the reciprocating engine. The controller opens the on / off valve during the stroke in which the piston is rising while the fuel cut is being executed. The decomposer is a vehicle control system that uses the heat and pressure of the gas in the cylinder, which is compressed by the upward movement of the piston, to decompose the hydrocarbon fuel injected from the first injector into carbon and hydrogen gas.

6. In the vehicle control system according to any one of claims 1 to 5, The hydrogen gas supply unit has a second injector that injects the hydrogen gas into the cylinder. The vehicle control system comprises a hydrocarbon fuel supply unit having a third injector that injects the hydrocarbon fuel into the intake port.

7. In the vehicle control system according to claim 6, The controller is a vehicle control system that, when the reciprocating engine is performing the four-stroke cycle and abnormal combustion of the reciprocating engine is detected, injects hydrogen gas into the second injector in addition to the hydrocarbon fuel from the third injector.

Images