System and control method

Abstract

This system is provided with: a crankcase and cylinder head of an engine that can be operated using fuel containing hydrogen; an engine intake passage that sucks air into the engine; a crankcase intake passage that is branched from the engine intake passage and introduces air into the crankcase; a dilution air valve disposed in the crankcase intake passage and opening and closing the crankcase intake passage; a compressor disposed upstream of a branching portion branching from the engine intake passage to the crankcase intake passage; a hydrogen sensor that detects the hydrogen concentration inside the crankcase; a communication path that connects the inside of the crankcase and the inside of the cylinder head; and a control device that controls the opening and closing of the dilution air valve on the basis of the hydrogen concentration detected by the hydrogen sensor.

Description

Technical Field

[0001] The present invention relates to a system and a control method.

[0002] This application claims priority from Japanese Patent Application No. 2023-023423 filed in Japan on February 17, 2023, the contents of which are incorporated into this application. Background Art

[0003] In an engine, gas from the combustion chamber sometimes leaks out from between the cylinder and the piston into the crankcase. This leaked gas is called blowby. Some engines can run on fuel containing hydrogen. Compared to other fuels such as natural gas and gasoline, hydrogen has a much wider flammability range and can ignite even when diluted to 10 times the theoretical air-fuel ratio. Therefore, in an engine running on fuel containing hydrogen, the concentration of hydrogen inside the crankcase may be maintained at a level sufficient for ignition. Therefore, in an engine running on fuel containing hydrogen, it is necessary to prevent hydrogen from igniting inside the crankcase.

[0004] For example, Patent Document 1 discloses a four-stroke engine capable of operating on a fuel containing hydrogen. The engine comprises a crankcase with a vent, a ventilation duct connecting the vent to the outside of the crankcase, and a ventilation fan disposed in the ventilation duct. The ventilation fan forcibly exhausts an amount of hydrogen, along with gases other than hydrogen, from the crankcase to the outside, sufficient to reduce the hydrogen concentration inside the crankcase to below the lower limit of the flammable range.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-127704. Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, since a new ventilation fan needs to be installed, there is a high possibility of cost and reliability degradation. Therefore, there is room for improvement in suppressing the degradation of cost and reliability.

[0010] Therefore, an object of the present invention is to provide a system and a control method that can prevent hydrogen gas from igniting inside a crankcase while suppressing deterioration in cost and reliability.

[0011] Solutions for solving problems

[0012] 1. The system of claim 1 , wherein the air in the crankcase is compressed and the air in the crankcase is compressed. The air in the crankcase is compressed and the air in the cylinder is compressed. The air in the crankcase is compressed and the air in the cylinder is compressed.

[0013] Effects of the Invention

[0014] According to the above aspect, it is possible to prevent hydrogen gas from igniting inside the crankcase and to suppress deterioration in cost and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic configuration diagram of the system according to the first embodiment.

[0016] Figure 2 This is a flowchart of an example of a control method of the system according to the first embodiment.

[0017] Figure 3 This is a schematic diagram of the system structure of the second embodiment.

[0018] Figure 4 This is a schematic structural diagram of a system according to the third embodiment.

[0019] Figure 5 This is a flowchart of an example of a control method of the system according to the third embodiment.

[0020] Figure 6 It is a schematic structural diagram of a system according to the fourth embodiment.

[0021] Figure 7 This is a flowchart of an example of a control method of the system according to the fourth embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the embodiments, a hydrogen engine (an example of an engine that can be operated using fuel containing hydrogen) is used as an engine constituting the system.

[0023] <First embodiment>

[0024] <System>

[0025] Figure 1 It is a schematic configuration diagram of the system 1 according to the first embodiment.

[0026] like Figure 1 As shown, the system 1 has a hydrogen engine 2 (hereinafter also referred to as "engine 2"). For example, the engine 2 can be operated using a fuel containing hydrogen, and can also be operated using a fuel that does not contain hydrogen. In addition, the fuel containing hydrogen includes a fuel in which a portion of the fuel is hydrogen and a fuel in which the fuel is entirely hydrogen (i.e., hydrogen itself). In addition, the use of the engine 2 is not particularly limited, and it can be used to drive a vehicle, etc., or to generate electricity. For example, the use of the engine 2 can be changed according to the design specifications.

[0027] The engine 2 includes a cylinder block 10 including cylinders 11 and a crankcase 12 , a cylinder head 13 located above the cylinder block 10 , and pistons 15 that reciprocate inside the cylinders 11 and drive a crankshaft (not shown) via connecting rods 14 .

[0028] The engine 2 has a combustion chamber 20 defined by the inner circumferential surface of the cylinder 11, the upper surface of the piston 15, and the lower surface of the cylinder head 13. An intake port 21 and an exhaust port 22 are formed in the cylinder head 13, each opening into the combustion chamber 20. An intake valve 23 and an exhaust valve 24 are provided in the cylinder head 13. The intake valve 23 opens and closes the portion of the intake port 21 that opens into the combustion chamber 20, while the exhaust valve 24 opens and closes the portion of the exhaust port 22 that opens into the combustion chamber 20. The cylinder head 13 may also be provided with an ignition device 25 for igniting the fuel in the combustion chamber 20.

[0029] The engine 2 may also be provided with a hydrogen injection device 26 for injecting hydrogen as fuel into the combustion chamber 20. In the example shown, the hydrogen injection device 26 is provided in the engine intake passage 30, but the present invention is not limited thereto. For example, the hydrogen injection device 26 may also be provided in the cylinder head 13. Alternatively, the hydrogen injection device 26 may be provided in the cylinder head 13, while a diesel or gasoline injection device may be provided in the cylinder head 13. For example, the location of the hydrogen injection device 26 and its combination with other injection devices may be modified according to design specifications.

[0030] The system 1 includes an engine intake passage 30 that draws air into the engine 2 and an engine exhaust passage 31 that exhausts exhaust gas from the engine 2. The engine intake passage 30 is connected to the air intake port 21. The engine exhaust passage 31 is connected to the exhaust port 22.

[0031] System 1 includes a crankcase intake passage 32 that branches off from the engine intake passage 30 and introduces air into the crankcase 12. The crankcase intake passage 32 is connected to a portion of the crankcase 12 on the side of the intake port 21. The connection position of the crankcase intake passage 32 is not limited to the position described above and can be changed according to design specifications.

[0032] System 1 includes a turbocharger 40 that increases the density of air inhaled by engine 2. This allows more oxygen to be delivered to combustion chamber 20, resulting in higher combustion energy. Turbocharger 40 includes a turbine 41 that rotates in response to exhaust gas flow; a shaft 42 that transmits the rotational force of turbine 41; and a compressor 43 that uses the rotational force transmitted by shaft 42 to inhale and compress air.

[0033] For example, a turbine 41 and a compressor 43 are connected via a shaft 42 so as to be rotatable as one. The turbine 41 is provided in the engine exhaust passage 31. The compressor 43 is provided in the engine intake passage 30. The compressor 43 is arranged upstream of the branching portion 34 that branches from the engine intake passage 30 to the crankcase intake passage 32. The intake air flowing through the engine intake passage 30 is compressed and sent by the compressor 43, and the intake air is forcibly sent into the combustion chamber 20 of the engine 2.

[0034] In the engine intake passage 30, arranged in order from the upstream side in the intake airflow direction are an air filter 50 for filtering the intake air, a compressor 43, and an aftercooler 51 for reducing the temperature of the intake air through heat exchange with the ambient air. Although not shown, an intake throttle valve for opening and closing the engine intake passage 30 may be provided downstream of the aftercooler 51 and upstream of the branching portion 34 in the engine intake passage 30. The intake throttle valve functions as a throttle valve for variably setting the cross-sectional area of ​​the engine intake passage 30.

[0035] System 1 includes a communication path 35 that connects the interior of crankcase 12 with the interior of cylinder head 13. For example, communication path 35 may be a passage (e.g., an oil return hole) for oil (e.g., lubricating oil) that flows to drive the valve system of cylinder head 13. In the example shown in the figure, communication path 35 extends vertically along the side of cylinder head 13. Communication path 35 is connected to a portion of cylinder head 13 on the exhaust port 22 side and a portion of crankcase 12 on the exhaust port 22 side. The connection position of communication path 35 is not limited to the position described above and can be changed according to design specifications.

[0036] The system 1 includes a dilution air valve 55 for opening and closing the crankcase intake passage 32. The dilution air valve 55 is disposed in the crankcase intake passage 32. The dilution air valve 55 functions as a throttle valve for variably setting the passage cross-sectional area of ​​the crankcase intake passage 32.

[0037] The system 1 includes a pressure reducing valve 56 that reduces the pressure of intake air flowing through the crankcase intake passage 32 to a predetermined level or lower. The pressure reducing valve 56 is disposed downstream of the dilution air valve 55 in the crankcase intake passage 32. The dilution air valve 55 and the pressure reducing valve 56 are disposed in the crankcase intake passage 32 in this order, starting from the upstream side in the direction of intake air flow.

[0038] The system 1 includes a hydrogen sensor 60 for detecting the hydrogen concentration inside the crankcase 12. In the example shown in the figure, the hydrogen sensor 60 is located near the lower portion of the crankcase 12 on the exhaust port 22 side. The location of the hydrogen sensor 60 is not limited to the above-described location and can be changed according to design specifications.

[0039] In the engine 2, the intake stroke, compression stroke, combustion expansion stroke, and exhaust stroke are repeated. During the intake stroke, the combustion chamber 20 is filled with a mixed gas of intake gas and fuel. Part of the mixed gas passes through between the cylinder 11 and the piston 15 and leaks into the crankcase 12 mainly during the compression stroke and the combustion expansion stroke. When using a fuel containing hydrogen, hydrogen invades the interior of the crankcase 12. The hydrogen sensor 60 detects the concentration of the invading hydrogen (the hydrogen concentration inside the crankcase 12). The detection signal of the hydrogen sensor 60 (the detected hydrogen concentration) is sent to the control device 3 (ECU in the figure).

[0040] System 1 includes a control device 3 that controls the opening and closing of dilution air valve 55 based on the hydrogen concentration detected by hydrogen sensor 60. When the hydrogen concentration detected by hydrogen sensor 60 reaches or exceeds a threshold, control device 3 controls the opening of dilution air valve 55 to a predetermined value or higher. Control device 3 may also collectively control the components of system 1.

[0041] System 1 includes a pressure relief valve 61 that releases air from the crankcase 12 before the pressure inside the crankcase 12 reaches a predetermined level or higher. In the example shown in the figure, pressure relief valve 61 is located near the lower portion of the portion of the crankcase 12 connected to the communication path 35. The location of pressure relief valve 61 is not limited to the above-described location and can be modified according to design specifications.

[0042] System 1 includes a cylinder head connecting passage 70 that connects the interior of cylinder head 13 with the upstream portion of compressor 43 in engine intake passage 30. In the example shown in the figure, cylinder head connecting passage 70 connects the center portion of the upper surface of cylinder head 13 with the portion of engine intake passage 30 between air filter 50 and compressor 43. The location of cylinder head connecting passage 70 is not limited to the above-described location and can be modified according to design specifications.

[0043] In this embodiment, the communication path 35 connects the interior of the crankcase 12 with the interior of the cylinder head 13. This allows air compressed by the compressor 43 to be introduced into the crankcase 12, creating an air flow from the crankcase 12 to the cylinder head 13 through the communication path 35. Furthermore, in this embodiment, the cylinder head connecting passage 70 connects the interior of the cylinder head 13 with the upstream portion of the compressor 43 in the engine intake passage 30. This creates an air flow from the cylinder head 13 to the upstream portion of the compressor 43. The arrows in the figure indicate the flow of dilution air.

[0044] The system 1 includes a filter 71 disposed in the cylinder head connection passage 70. The filter 71 filters the exhaust gas. For example, the filter 71 removes (captures) components contained in the exhaust gas from the interior of the cylinder head 13. The components contained in the exhaust gas include particulate matter (PM), hydrocarbons (HC), nitrogen oxides (NO X ), carbon monoxide (CO), carbon dioxide (CO2), sulfur oxides (SO X ) etc. For example, components contained in the exhaust gas also include oil mist and the like.

[0045] <An example of a system control method>

[0046] Figure 2 1 is a flowchart of an example of a control method of the system 1 according to the first embodiment. The control method of the system 1 corresponds to an ignition prevention program executed by the control device 3 .

[0047] The control method of this embodiment includes: a hydrogen concentration acquisition step (step S1) for acquiring the hydrogen concentration inside the crankcase 12; a hydrogen concentration determination step (step S2) for determining whether the hydrogen concentration is above a threshold value; a valve opening step (step S3) for opening the dilution air valve 55 when the hydrogen concentration is determined to be above the threshold value; and a valve closing step (step S4) for closing the dilution air valve 55 when the hydrogen concentration is determined to be below the threshold value.

[0048] Combined with reference Figure 2 First, the hydrogen concentration in the crankcase 12 is obtained (step S1). For example, in step S1, the control device 3 obtains the detection signal (detected hydrogen concentration) of the hydrogen sensor 60. After step S1, the process proceeds to step S2.

[0049] In step S2, the control device 3 determines whether the hydrogen concentration is greater than a threshold value. The threshold value is set to the lower limit of the flammable range of hydrogen gas. Alternatively, the threshold value may be set to a value lower than the lower limit of hydrogen gas by a predetermined amount.

[0050] For example, the flammable range of hydrogen in air is approximately 4 vol% to 75 vol%. Therefore, if the crankcase 12 is filled with hydrogen and air, the lower limit of the flammable range is 4 vol%. In this case, the threshold is set to 4 vol%. Alternatively, the threshold may be set to a value lower than 4 vol% (e.g., 3 vol%) with some margin.

[0051] If it is determined that the hydrogen concentration is equal to or greater than the threshold value ("YES" in step S2), the process proceeds to step S3. If it is determined that the hydrogen concentration is equal to or greater than the threshold value, there is a possibility that hydrogen gas may ignite inside the crankcase 12.

[0052] On the other hand, when it is determined that the hydrogen concentration is not equal to or higher than the threshold value (that is, when it is determined that the hydrogen concentration is lower than the threshold value) (No in step S2 ), the process proceeds to step S4 .

[0053] In step S3, the dilution air valve 55 is opened. For example, in step S3, the control device 3 performs control to open the dilution air valve 55 to a predetermined value or more. After step S3, the process proceeds to step S5.

[0054] In step S4, the dilution air valve 55 is closed. For example, in step S4, the control device 3 performs control to completely close the dilution air valve 55. After step S4, the process proceeds to step S5.

[0055] In step S5, the control device 3 determines whether the operation of the engine 2 has ended. If the operation of the engine 2 is determined to have ended ("Yes" in step S5), the process proceeds to step S6. On the other hand, if the operation of the engine 2 is determined not to have ended ("No" in step S5), the process returns to step S1 and repeats steps S1 to S5 until the operation of the engine 2 has ended.

[0056] In step S6, the dilution air valve 55 is closed. For example, in step S6, the control device 3 performs control to completely close the dilution air valve 55.

[0057] Thus, the flow of the control method of system 1 ends.

[0058] Effects

[0059] As described above, the system 1 of this embodiment includes an engine 2 that can be operated using a fuel containing hydrogen. The system 1 includes: a crankcase 12 and a cylinder head 13 of the engine 2; an engine intake passage 30 that draws air into the engine 2; a crankcase intake passage 32 that branches off from the engine intake passage 30 and introduces air into the crankcase 12; a dilution air valve 55 disposed in the crankcase intake passage 32 to open and close the crankcase intake passage 32; a pressure reducing valve 56 disposed downstream of the dilution air valve 55 in the crankcase intake passage 32; a compressor 43 disposed upstream of the branching portion 34 that branches from the engine intake passage 30 to the crankcase intake passage 32; a hydrogen sensor 60 that detects the hydrogen concentration inside the crankcase 12; a communication path 35 that connects the interior of the crankcase 12 with the interior of the cylinder head 13; and a control device 3 that controls the opening and closing of the dilution air valve 55 based on the hydrogen concentration detected by the hydrogen sensor 60.

[0060] This configuration allows the opening and closing of the dilution air valve 55 to be controlled based on the hydrogen concentration detected by the hydrogen sensor 60 while simultaneously introducing air compressed by the compressor 43 into the crankcase 12. This allows the hydrogen concentration inside the crankcase 12 to be adjusted. Furthermore, since air compressed by the compressor 43 is used, an intake fan or the like is unnecessary, allowing the system to be constructed with minimal additional components within the existing engine 2. Consequently, the likelihood of cost and reliability degradation is minimized. Consequently, ignition of hydrogen gas inside the crankcase 12 can be prevented, and degradation of cost and reliability can be minimized.

[0061] Furthermore, the ventilation of the blowby gas becomes intermittent by operating the dilution air valve 55 based on the hydrogen concentration sensing inside the crankcase 12. Therefore, it is sufficient to use the minimum amount of dilution air required.

[0062] Furthermore, by reducing the pressure of the intake air flowing in the crankcase intake passage 32 to a predetermined level or lower using the pressure reducing valve 56 disposed downstream of the dilution air valve 55 in the crankcase intake passage 32, it is possible to prevent the pressure inside the crankcase 12 from becoming excessively high. Consequently, it is possible to prevent the oil seal provided in the crankcase 12 from falling off, for example.

[0063] Furthermore, the communication path 35 that connects the interior of the crankcase 12 and the interior of the cylinder head 13 can form an air flow from the crankcase 12 to the cylinder head 13. Therefore, the dilution efficiency of the blowby gas can be improved.

[0064] Furthermore, since hydrogen is lighter than air, it can flow smoothly from the interior of the crankcase 12 to the cylinder head 13 located above the engine 2. Therefore, ignition of hydrogen inside the crankcase 12 can be more reliably prevented.

[0065] In the present embodiment, when the hydrogen concentration detected by the hydrogen sensor 60 reaches or exceeds a threshold value, the control device 3 performs control to open the dilution air valve 55 to a predetermined value or more.

[0066] With this configuration, while air compressed by the compressor 43 is introduced into the crankcase 12, the dilution air valve 55 can be opened to a predetermined level or higher when the hydrogen concentration detected by the hydrogen sensor 60 is above a threshold value. This allows the hydrogen concentration inside the crankcase 12 to be outside the flammable range. Consequently, ignition of hydrogen gas inside the crankcase 12 can be more reliably prevented.

[0067] In this embodiment, the system 1 includes a cylinder head connecting passage 70 that allows the interior of the cylinder head 13 to communicate with the upstream of the compressor 43 in the engine intake passage 31 , and a filter 71 disposed in the cylinder head connecting passage 70 .

[0068] According to this configuration, the exhaust gas from the cylinder head connecting passage 70 can be purified by the filter 71. Therefore, the compressor 43 can be prevented from being contaminated by components (for example, oil mist) contained in the exhaust gas.

[0069] In the present embodiment, the system 1 includes a relief valve 61 for releasing the air in the crankcase 12 before the pressure in the crankcase 12 reaches a predetermined level or higher.

[0070] According to this configuration, the pressure inside the crankcase 12 can be prevented from being excessively high by the relief valve 61. Therefore, it is possible to prevent the oil seal provided in the crankcase 12 from falling off.

[0071] In this embodiment, the control method includes: a hydrogen concentration acquisition step (step S1) for acquiring the hydrogen concentration inside the crankcase 12; a hydrogen concentration determination step (step S2) for determining whether the hydrogen concentration is above a threshold value; a valve opening step (step S3) for opening the dilution air valve 55 when the hydrogen concentration is determined to be above the threshold value; and a valve closing step (step S4) for closing the dilution air valve 55 when the hydrogen concentration is determined to be below the threshold value.

[0072] According to this method, it is possible to prevent the ignition of hydrogen gas inside the crankcase 12 and to suppress deterioration in cost and reliability.

[0073] Furthermore, by including the valve opening step and the valve closing step, ventilation of the blowby gas becomes intermittent, so that the minimum necessary amount of dilution air is sufficient.

[0074] Furthermore, the valve opening step can make the hydrogen concentration inside the crankcase 12 outside the flammable range. Therefore, it is possible to more reliably prevent the ignition of hydrogen gas inside the crankcase 12.

[0075] <Second embodiment>

[0076] The first embodiment describes an example in which the dilution air valve 55 and the pressure reducing valve 56 are provided in the crankcase intake passage 32 in order from the upstream side in the intake air flow direction. The second embodiment differs from the first embodiment in that a crankcase connecting passage 282 is provided, for example, which branches off from the portion between the dilution air valve 55 and the pressure reducing valve 56 in the crankcase intake passage 32 and communicates with the interior of the crankcase 12. In the following description, components identical to those of the first embodiment are denoted by the same reference numerals, and their description is omitted.

[0077] Figure 3 This is a schematic configuration diagram of a system 201 according to the second embodiment.

[0078] like Figure 3 As shown, the system 201 has: an intake throttle 280, which is arranged downstream of the compressor 43 and upstream of the branch portion in the engine intake passage 30; a first check valve 281, which is arranged downstream of the pressure reducing valve 56 in the crankcase intake passage 32, and only allows air flow from the pressure reducing valve 56 to the interior of the crankcase 12; a crankcase connecting passage 282, which branches from the portion between the dilution air valve 55 and the pressure reducing valve 56 in the crankcase intake passage 32 and communicates with the interior of the crankcase 12; and a second check valve 283, which is arranged in the crankcase connecting passage 282, and only allows air flow from the interior of the crankcase 12 to the crankcase intake passage 32.

[0079] Intake throttle valve 280 is provided in engine intake passage 30 downstream of aftercooler 51 and upstream of branch portion 34. Intake throttle valve 280 is a valve that opens and closes engine intake passage 30. Intake throttle valve 280 functions as a throttle valve that variably sets the cross-sectional area of ​​engine intake passage 30.

[0080] The first check valve 281 restricts air flow from the interior of the crankcase 12 to the pressure reducing valve 56 in the crankcase intake passage 32, while allowing air flow from the pressure reducing valve 56 to the interior of the crankcase 12. For example, the first check valve 281 may be spring-loaded (maintained in a closed position by the spring) or may be spring-free. For example, the configuration of the first check valve 281 may vary depending on design specifications.

[0081] In the example shown in the figure, the crankcase connecting passage 282 is connected to the portion of the crankcase intake passage 32 between the dilution air valve 55 and the pressure reducing valve 56, and to the vicinity of the lower portion of the portion of the crankcase 12 on the intake port 21 side (the portion connected to the crankcase intake passage 32). The connection position of the crankcase connecting passage 282 is not limited to the above-described position and can be changed according to design specifications.

[0082] The second check valve 283 restricts airflow from the crankcase connecting passage 282 to the interior of the crankcase 12, while allowing airflow from the interior of the crankcase 12 to the crankcase intake passage 32. For example, the second check valve 283 may be spring-loaded (maintained in a closed position by the spring) or may be spring-free. For example, the configuration of the second check valve 283 may vary depending on design specifications.

[0083] <Airflow during supercharging>

[0084] For example, during supercharging, the positive pressure of the intake air can be used to dilute the mixed gas inside the crankcase 12. In the example shown in the figure, as indicated by the arrows for the airflow during supercharging, air compressed by the compressor 43 can be introduced into the crankcase 12 via the crankcase intake passage 32 and the like, and an air flow from the crankcase 12 to the cylinder head 13 is formed through the communication path 35. Furthermore, an air flow from the cylinder head 13 to the upstream of the compressor 43 can be formed through the cylinder head connecting passage 70.

[0085] <Airflow during non-supercharged operation>

[0086] For example, during non-supercharging, the mixed gas inside the crankcase 12 can be diluted even when the intake air is at a negative pressure. During non-supercharging, the intake throttle 280 is equivalent to a state in which the air flow is in operation. When the intake throttle 280 operates and the pressure becomes negative, the air flow is opposite to that during supercharging. In the example of the figure, as indicated by the arrows of the air flow during non-supercharging, an air flow from the upstream of the compressor 43 to the cylinder head 13 can be formed through the cylinder head connecting passage 70. In addition, an air flow from the cylinder head 13 to the crankcase 12 can be formed through the connecting path 35. Furthermore, an air flow from the crankcase 12 to the downstream of the intake throttle 280 can be formed through the crankcase connecting passage 282 and the like.

[0087] Effects

[0088] In this embodiment, the system 201 has: an intake throttle 280, which is arranged downstream of the compressor 43 and upstream of the branch portion in the engine intake passage 30; a first check valve 281, which is arranged downstream of the pressure reducing valve 56 in the crankcase intake passage 32, and only allows air flow from the pressure reducing valve 56 to the interior of the crankcase 12; a crankcase connecting passage 282, which branches from the portion between the dilution air valve 55 and the pressure reducing valve 56 in the crankcase intake passage 32 and communicates with the interior of the crankcase 12; and a second check valve 283, which is arranged in the crankcase connecting passage 282, and only allows air flow from the interior of the crankcase 12 to the crankcase intake passage 32.

[0089] According to this configuration, during supercharging, air compressed by the compressor 43 can be introduced into the crankcase 12 via the crankcase intake passage 32 and the like, forming an air flow from the crankcase 12 to the cylinder head 13 via the communication path 35. On the other hand, during non-supercharging, air can be flowed from the crankcase 12 to the downstream side of the intake throttle valve 280 via the crankcase connecting passage 282 and the like. Thus, the mixed gas inside the crankcase 12 can be diluted by the positive or negative pressure of the intake air.

[0090] <Third embodiment>

[0091] In the first embodiment, an example of providing a filter 71 in the cylinder head connecting passage 70 was given and described. The third embodiment differs from the first embodiment in that it includes a cylinder head exhaust passage 390 that branches off from the cylinder head connecting passage 70 and exhausts air from the interior of the cylinder head 13. In the following description, components identical to those in the first and second embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0092] Figure 4 This is a schematic configuration diagram of a system 301 according to the third embodiment.

[0093] like Figure 4 As shown, the system 301 has: a cylinder head exhaust passage 390, which branches off from the cylinder head connecting passage 70 and discharges the air inside the cylinder head 13; and a switching valve 392, which is arranged at the branch portion 391 that branches off from the cylinder head connecting passage 70 to the cylinder head exhaust passage 390, and switches the first path V1 of the cylinder head exhaust passage 390 open to the atmosphere and the second path V2 of the cylinder head connecting passage 70 to the upstream of the compressor 43.

[0094] When the hydrogen concentration detected by the hydrogen sensor 60 reaches or exceeds the threshold, the control device 3 controls the switching valve 392 to switch to the second path V2. When the hydrogen concentration detected by the hydrogen sensor 60 does not reach or exceed the threshold (i.e., when the hydrogen concentration is less than the threshold), the control device 3 controls the switching valve 392 to switch to the first path V1.

[0095] <An example of a system control method>

[0096] Figure 5 3 is a flowchart of an example of a control method of the system 301 of the third embodiment. The control method of the system 301 corresponds to the ignition prevention program executed by the control device 3 .

[0097] The control method of this embodiment includes: a second path switching step (step S303), in which the switching valve 392 is switched to the second path V2 when the hydrogen concentration is determined to be above the threshold; and a first path switching step (step S304), in which the switching valve 392 is switched to the first path V1 when the hydrogen concentration is determined to be less than the threshold.

[0098] Combined with reference Figure 5 First, the hydrogen concentration in the crankcase 12 is obtained (step S301). For example, in step S301, the control device 3 obtains the detection signal (detected hydrogen concentration) of the hydrogen sensor 60. After step S301, the process proceeds to step S302.

[0099] In step S302, the control device 3 determines whether the hydrogen concentration is greater than a threshold value. The threshold value is set to the lower limit of the flammable range of hydrogen gas (e.g., 4 vol%). Alternatively, the threshold value may be set to a value lower than the lower limit of hydrogen gas by a predetermined amount (e.g., 3 vol%).

[0100] If the hydrogen concentration is determined to be above the threshold ("Yes" in step S302), the process proceeds to step S303. On the other hand, if the hydrogen concentration is determined to be below the threshold (i.e., below the threshold) ("No" in step S303), the process proceeds to step S304.

[0101] In step S303, the cylinder head connecting passage 70 is switched to a passage upstream of the compressor 43 (second passage V2). For example, in step S303, the control device 3 controls the switching valve 392 to switch to the second passage V2. This causes the interior of the cylinder head 13 to connect to the engine intake passage 30 upstream of the compressor 43. After step S303, the process proceeds to step S305.

[0102] In step S305, the dilution air valve 55 is opened. For example, in step S305, the control device 3 performs control to open the dilution air valve 55 to a predetermined value or more. After step S305, the process proceeds to step S307.

[0103] On the other hand, in step S304, the cylinder head exhaust passage 390 is opened to the atmosphere (first path V1). For example, in step S304, the control device 3 controls the switching valve 392 to switch to the first path V1. After step S304, the process proceeds to step S306.

[0104] In step S306, the dilution air valve 55 is closed. For example, in step S306, the control device 3 performs control to fully close the dilution air valve 55. After step S306, the process proceeds to step S307.

[0105] In step S307, the control device 3 determines whether the operation of the engine 2 has ended. If it is determined that the operation of the engine 2 has ended ("Yes" in step S307), the process proceeds to step S308. On the other hand, if it is determined that the operation of the engine 2 has not ended ("No" in step S307), the process returns to step S301 and repeats steps S301 to S307 until the operation of the engine 2 has ended.

[0106] In step S308, the cylinder head exhaust passage 390 is opened to the atmosphere (first path V1). After step S308, the process proceeds to step S309.

[0107] In step S309, the dilution air valve 55 is closed. For example, in step S309, the control device 3 performs control to completely close the dilution air valve 55.

[0108] Thus, the process of the control method of system 301 ends.

[0109] Effects

[0110] In this embodiment, the system 301 has: a cylinder head exhaust passage 390, which branches off from the cylinder head connecting passage 70 to discharge the air inside the cylinder head 13; and a switching valve 392, which is arranged at the branch portion 391 that branches off from the cylinder head connecting passage 70 to the cylinder head exhaust passage 390, and switches between a first path V1 in which the cylinder head exhaust passage 390 is open to the atmosphere and a second path V2 in which the cylinder head connecting passage 70 leads to the upstream of the compressor 43.

[0111] With this configuration, the switching valve 392 can be used to select whether the diluted air exhausted from the cylinder head 13 is released to the atmosphere (switching to the first path V1) or returned upstream of the compressor 43 (switching to the second path V2). Therefore, when switching to the second path V2, exhaust gas from the cylinder head exhaust passage 390 is not discharged externally. Consequently, the adverse effects of exhaust emissions can be minimized.

[0112] On the other hand, when switching to the first path V1, exhaust gas from the cylinder head 13 does not flow upstream of the compressor 43. This prevents contamination of the compressor 43 by components contained in the exhaust gas (e.g., oil mist). For example, if the cylinder head connecting passage 70 is provided with a filter 71, this, combined with the purification provided by the filter 71, can further improve the durability and reliability of the compressor 43.

[0113] In the present embodiment, when the hydrogen concentration detected by the hydrogen sensor 60 reaches or exceeds a threshold value, the controller 3 performs control to switch the switching valve 392 to the second path V2 .

[0114] With this configuration, when the hydrogen concentration detected by the hydrogen sensor 60 reaches or exceeds a threshold, air from the cylinder head connecting passage 70 (second path V2) is compressed by the compressor 43, and this compressed air can be introduced into the crankcase 12. Therefore, when the hydrogen concentration detected by the hydrogen sensor 60 reaches or exceeds the threshold, exhaust gas from the cylinder head exhaust passage 390 is not discharged to the outside. Consequently, the adverse effects of exhaust emissions can be minimized.

[0115] In this embodiment, the control method includes: a second path switching step (step S303), in which the switching valve 392 is switched to the second path V2 when the hydrogen concentration is judged to be above the threshold; and a first path switching step (step S304), in which the switching valve 392 is switched to the first path V1 when the hydrogen concentration is judged to be less than the threshold.

[0116] According to this method, the exhaust gas from the cylinder head exhaust passage 390 is not discharged to the outside due to the second path switching step, thereby minimizing the adverse effects of exhaust gas emissions.

[0117] On the other hand, the first path switching step prevents the exhaust gas from the cylinder head 13 from flowing upstream of the compressor 43. Therefore, the compressor 43 can be prevented from being contaminated by components (eg, oil mist) contained in the exhaust gas.

[0118] <Fourth embodiment>

[0119] The first embodiment describes an example in which the hydrogen sensor 60 is installed in the crankcase 12. The fourth embodiment differs from the first embodiment in that the hydrogen sensor 60 is located downstream of the filter 71 in the cylinder head connecting passage 70. In the following description, components identical to those in the first embodiment are designated by the same reference numerals, and their descriptions are omitted.

[0120] Figure 6 This is a schematic configuration diagram of a system 401 according to the fourth embodiment.

[0121] like Figure 6 As shown, system 401 includes a hydrogen sensor 60 that detects the hydrogen concentration inside crankcase 12 in cylinder head connecting passage 70. In the example shown, hydrogen sensor 60 is located in cylinder head connecting passage 70 near the location where filter 71 is located (near downstream of filter 71) relative to the portion connected upstream of compressor 43. The location of hydrogen sensor 60 is not limited to the above-described location and can be changed according to design specifications.

[0122] <An example of a system control method>

[0123] Figure 7 4 is a flowchart of an example of a control method of the system 401 of the fourth embodiment. The control method of the system 401 corresponds to the ignition prevention program executed by the control device 3.

[0124] The control method of this embodiment is the same as that of the first embodiment, except for the valve opening step (step S403) of opening the dilution air valve 55 when the hydrogen concentration is determined to be greater than the threshold value. Steps S401, S402, S404, S405, and S406 of this embodiment are the same as steps S1, S2, S4, S5, and S6 of the first embodiment, and therefore detailed descriptions thereof are omitted.

[0125] Combined with reference Figure 7 If the hydrogen concentration is determined to be above the threshold ("Yes" in step S402), the process proceeds to step S403. On the other hand, if the hydrogen concentration is determined to be below the threshold (i.e., below the threshold) ("No" in step S402), the process proceeds to step S404.

[0126] In step S403, the dilution air valve 55 is opened for a predetermined time (e.g., 0 seconds). For example, in step S403, the control device 3 controls the dilution air valve 55 to be opened for a predetermined time or longer for a few seconds. After step S403, the process proceeds to step S405.

[0127] After step S405 , the same control as that of the first embodiment is performed.

[0128] Thus, the process of the control method of system 401 ends.

[0129] Effects

[0130] In the present embodiment, the hydrogen sensor 60 is arranged downstream of the filter 71 in the cylinder head connecting passage 70 .

[0131] This configuration prevents the hydrogen sensor 60 from being contaminated by components contained in the exhaust gas (eg, oil mist), thereby further improving the durability and reliability of the hydrogen sensor 60 compared to when the hydrogen sensor 60 is installed in the crankcase 12 .

[0132] Modifications

[0133] The above embodiment illustrates an example in which the system further includes a cylinder head connecting passage that connects the interior of the cylinder head to the upstream portion of the compressor in the engine intake passage, and a filter disposed in the cylinder head connecting passage. However, the system is not limited thereto. For example, the system may not include a filter. For example, the placement of the filter can be modified according to design specifications.

[0134] In the above embodiment, the system is described as including a pressure relief valve that releases air from the crankcase before the pressure inside the crankcase reaches a predetermined level. However, the system is not limited to this. For example, the system may not include a pressure relief valve. For example, the placement of the pressure relief valve can be modified according to design specifications.

[0135] While the embodiments of the present invention have been described above, the present invention is not limited thereto, and additions, omissions, substitutions, and other modifications of the structures can be made without departing from the gist of the present invention. The above embodiments can also be appropriately combined.

[0136] (Note 1)

[0137] A system comprising an engine capable of operating on a fuel containing hydrogen, the system comprising:

[0138] The crankcase and cylinder head of the above engine;

[0139] an engine intake passage, which draws air into the engine;

[0140] a crankcase intake passage branching off from the engine intake passage and introducing air into the crankcase;

[0141] a dilution air valve disposed in the crankcase intake passage to open and close the crankcase intake passage;

[0142] a pressure reducing valve disposed downstream of the dilution air valve in the crankcase intake passage;

[0143] a compressor disposed upstream of a branching portion that branches from the engine intake passage to the crankcase intake passage;

[0144] a hydrogen sensor that detects a hydrogen concentration inside the crankcase; and

[0145] a communication path that allows the interior of the crankcase to communicate with the interior of the cylinder head; and

[0146] A control device controls opening and closing of the dilution air valve based on the hydrogen concentration detected by the hydrogen sensor.

[0147] (Note 2)

[0148] The system according to Supplement 1, wherein:

[0149] The control device performs control to open the dilution air valve to a predetermined value or more when the hydrogen concentration detected by the hydrogen sensor reaches or exceeds a threshold value.

[0150] (Note 3)

[0151] The system according to Supplement 1 or 2, further comprising:

[0152] an intake throttle valve disposed in the engine intake passage downstream of the compressor and upstream of the branch portion;

[0153] a first check valve disposed downstream of the pressure reducing valve in the crankcase intake passage and allowing air flow only from the pressure reducing valve to the interior of the crankcase;

[0154] a crankcase connecting passage branching from a portion of the crankcase intake passage between the dilution air valve and the pressure reducing valve and communicating with the interior of the crankcase; and

[0155] The second check valve is disposed in the crankcase connecting passage and only allows air flow from the interior of the crankcase to the crankcase intake passage.

[0156] (Note 4)

[0157] The system according to any one of Supplementary Notes 1 to 3, further comprising:

[0158] a cylinder head connecting passage communicating the interior of the cylinder head with an upstream portion of the compressor in the engine intake passage; and

[0159] a cylinder head exhaust passage branching from the cylinder head connecting passage to discharge air from the interior of the cylinder head; and

[0160] The switching valve is arranged at a branching portion that branches from the cylinder head connecting passage to the cylinder head exhaust passage, and switches between a first path in which the cylinder head exhaust passage is open to the atmosphere and a second path in which the cylinder head connecting passage leads upstream of the compressor.

[0161] (Note 5)

[0162] The system according to Supplement 4, wherein:

[0163] The control device controls the switching valve to switch to the second path when the hydrogen concentration detected by the hydrogen sensor reaches or exceeds a threshold value.

[0164] (Note 6)

[0165] The system according to any one of Supplementary Notes 1 to 5, further comprising:

[0166] a cylinder head connecting passage communicating the interior of the cylinder head with an upstream portion of the compressor in the engine intake passage; and

[0167] The filter is arranged in the cylinder head connecting passage.

[0168] (Note 7)

[0169] The system according to Supplementary Note 6, wherein:

[0170] The hydrogen sensor is arranged downstream of the filter in the cylinder head connecting passage.

[0171] (Note 8)

[0172] The system according to any one of Supplementary Notes 1 to 7, further comprising:

[0173] The pressure relief valve releases air in the crankcase before the pressure in the crankcase reaches a predetermined level or higher.

[0174] (Note 9)

[0175] A method for controlling a system comprising an engine capable of operating on a fuel containing hydrogen,

[0176] The above system has:

[0177] The crankcase and cylinder head of the above engine;

[0178] an engine intake passage, which draws air into the engine;

[0179] a crankcase intake passage branching off from the engine intake passage and introducing air into the crankcase;

[0180] a dilution air valve disposed in the crankcase intake passage to open and close the crankcase intake passage;

[0181] a pressure reducing valve disposed downstream of the dilution air valve in the crankcase intake passage;

[0182] a compressor disposed upstream of a branching portion that branches from the engine intake passage to the crankcase intake passage;

[0183] a hydrogen sensor that detects a hydrogen concentration inside the crankcase; and

[0184] a communication path that allows the interior of the crankcase to communicate with the interior of the cylinder head,

[0185] The above control method includes:

[0186] a step of obtaining the hydrogen concentration inside the crankcase;

[0187] a step of determining whether the hydrogen concentration is above a threshold;

[0188] opening the dilution air valve when it is determined that the hydrogen concentration is equal to or greater than a threshold; and

[0189] The step of closing the dilution air valve when it is determined that the hydrogen concentration is lower than a threshold value.

[0190] (Note 10)

[0191] The control method according to Supplementary Note 9, wherein:

[0192] The above system also has:

[0193] a cylinder head connecting passage communicating the interior of the cylinder head with an upstream portion of the compressor in the engine intake passage;

[0194] a cylinder head exhaust passage branching from the cylinder head connecting passage to discharge air from the interior of the cylinder head; and

[0195] a switching valve disposed at a branching portion that branches from the cylinder head connecting passage to the cylinder head exhaust passage, and switches between a first path in which the cylinder head exhaust passage is open to the atmosphere and a second path in which the cylinder head connecting passage leads to the upstream of the compressor;

[0196] The above control method includes:

[0197] When it is determined that the hydrogen concentration is equal to or greater than a threshold value, switching the switching valve to the second path; and

[0198] The step of switching the switching valve to the first path when it is determined that the hydrogen concentration is lower than a threshold value.

[0199] Industrial applicability

[0200] According to the above aspect, ignition of hydrogen gas inside the crankcase is prevented, and deterioration of cost and reliability is suppressed.

[0201] Description of Reference Numerals

[0202] 1: system;

[0203] 2: Engine;

[0204] 3: Control device;

[0205] 12: crankcase;

[0206] 13: Cylinder head;

[0207] 30: Engine air intake passage;

[0208] 32: crankcase air intake passage;

[0209] 34: a branching portion for branching from the engine air intake passage to the crankcase air intake passage;

[0210] 35: connected path;

[0211] 43: compressor;

[0212] 55: dilution air valve;

[0213] 56: pressure reducing valve;

[0214] 60: hydrogen sensor;

[0215] 70: cylinder head connecting channel;

[0216] 71: filter;

[0217] 201: system;

[0218] 280: intake throttle;

[0219] 281: first check valve;

[0220] 282: crankcase connecting channel;

[0221] 283: Second check valve;

[0222] 301: system;

[0223] 390: cylinder head exhaust passage;

[0224] 391: a branching portion for branching from the cylinder head connecting passage to the cylinder head exhaust passage;

[0225] 392: switching valve;

[0226] 401: System;

[0227] V1: first path;

[0228] V2: Second path.

Claims

1. A system comprising an engine capable of operating on a fuel containing hydrogen, the system comprising: a crankcase and cylinder head of said engine; an engine intake passage that draws air into the engine; a crankcase intake passage branching off from the engine intake passage and introducing air into the crankcase; a dilution air valve, disposed in the crankcase intake passage, for opening and closing the crankcase intake passage; a pressure reducing valve disposed downstream of the dilution air valve in the crankcase intake passage; a compressor disposed upstream of a branching portion that branches from the engine intake passage to the crankcase intake passage; a hydrogen sensor that detects a hydrogen concentration inside the crankcase; a communication path that communicates the interior of the crankcase with the interior of the cylinder head; and A control device controls opening and closing of the dilution air valve based on the hydrogen concentration detected by the hydrogen sensor.

2. The system according to claim 1, wherein: When the hydrogen concentration detected by the hydrogen sensor reaches or exceeds a threshold value, the control device performs control to open the dilution air valve to a predetermined value or more.

3. The system according to claim 1 or 2, wherein: Also features: an intake throttle valve disposed in the engine intake passage downstream of the compressor and upstream of the branch portion; a first check valve disposed downstream of the pressure reducing valve in the crankcase intake passage and allowing air flow only from the pressure reducing valve to the interior of the crankcase; a crankcase connecting passage branching from a portion of the crankcase intake passage between the dilution air valve and the pressure reducing valve to communicate with the interior of the crankcase; as well as A second check valve is disposed in the crankcase connecting passage and only allows air flow from the interior of the crankcase to the crankcase intake passage.

4. The system according to claim 1 or 2, wherein: Also features: a cylinder head connecting passage communicating the interior of the cylinder head with an upstream portion of the compressor in the engine intake passage; a cylinder head exhaust passage branching off from the cylinder head connecting passage to discharge air from the interior of the cylinder head; as well as The switching valve is arranged at a branching portion that branches from the cylinder head connecting passage to the cylinder head exhaust passage, and switches between a first path in which the cylinder head exhaust passage is open to the atmosphere and a second path in which the cylinder head connecting passage leads upstream of the compressor.

5. The system according to claim 4, wherein: The control device controls the switching valve to switch to the second path when the hydrogen concentration detected by the hydrogen sensor reaches or exceeds a threshold value.

6. The system according to claim 1 or 2, wherein: Also features: a cylinder head connecting passage communicating the interior of the cylinder head with an upstream portion of the compressor in the engine intake passage; and A filter is arranged in the cylinder head connecting passage.

7. The system according to claim 6, wherein: The hydrogen sensor is arranged downstream of the filter in the cylinder head connecting passage.

8. The system according to claim 1 or 2, wherein: Also features: The pressure relief valve releases air inside the crankcase before the pressure inside the crankcase reaches a predetermined level or higher.

9. A method for controlling a system comprising an engine capable of operating on a fuel containing hydrogen, The system has: a crankcase and cylinder head of said engine; an engine intake passage that draws air into the engine; a crankcase intake passage branching off from the engine intake passage and introducing air into the crankcase; a dilution air valve, disposed in the crankcase intake passage, for opening and closing the crankcase intake passage; a pressure reducing valve disposed downstream of the dilution air valve in the crankcase intake passage; a compressor disposed upstream of a branching portion that branches from the engine intake passage to the crankcase intake passage; a hydrogen sensor that detects a hydrogen concentration inside the crankcase; as well as a communication path that allows the interior of the crankcase to communicate with the interior of the cylinder head, The control method includes: a step of obtaining a hydrogen concentration inside the crankcase; a step of determining whether the hydrogen concentration is above a threshold; When it is determined that the hydrogen concentration is equal to or greater than a threshold value, opening the dilution air valve; and The step of closing the dilution air valve when it is determined that the hydrogen concentration is lower than a threshold value.

10. The control method according to claim 9, wherein: The system also has: a cylinder head connecting passage communicating the interior of the cylinder head with an upstream portion of the compressor in the engine intake passage; a cylinder head exhaust passage branching off from the cylinder head connecting passage to discharge air from the interior of the cylinder head; as well as a switching valve disposed at a branching portion that branches from the cylinder head connecting passage to the cylinder head exhaust passage, and switches between a first path in which the cylinder head exhaust passage is open to the atmosphere and a second path in which the cylinder head connecting passage leads upstream of the compressor; The control method includes: When it is determined that the hydrogen concentration is equal to or greater than a threshold value, switching the switching valve to the second path; as well as The step of switching the switching valve to the first path when it is determined that the hydrogen concentration is lower than a threshold value.

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