Ventilation system

Abstract

To ventilate gas in a crank chamber without requiring a fan for ventilation.SOLUTION: A ventilation system includes an internal combustion engine, a water vapor increasing device, and a control device. The internal combustion engine uses hydrogen as fuel. The internal combustion engine includes a cylinder, an intake passage, a crank chamber, and a blow-by gas passage. The blow-by gas passage allows gas in the crank chamber to flow into the intake passage. The water vapor increasing device increases an amount of water vapor generated in the crank chamber. The control device controls the water vapor increasing device. The control device executes hydrogen concentration acquiring processing and increase processing. In the hydrogen concentration acquiring processing, hydrogen concentration in the crank chamber is acquired on the basis of an operation state of the internal combustion engine. In the increase processing, on the condition that the hydrogen concentration is equal to or higher than a predetermined threshold, the amount of the water vapor generated in the crank chamber is increased by the water vapor increasing device compared to the case where the hydrogen concentration is lower than the threshold.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a ventilation system. [Background technology]

[0002] The ventilation system of Patent Document 1 includes an internal combustion engine that uses hydrogen as fuel. The internal combustion engine includes a cylinder, a crankcase, a ventilation passage, a ventilation fan, and an outside air introduction passage. The cylinder is a space for burning a mixture of fuel and intake air. The crankcase is a space connected to the cylinder. The outside air introduction passage is connected to the crankcase. The outside air introduction passage is a passage for introducing outside air from outside the ventilation system to the crankcase. The ventilation passage is connected to the crankcase. The ventilation passage is a passage for discharging gas in the crankcase to outside the ventilation system. The ventilation fan is located midway through the ventilation passage.

[0003] The ventilation system of Patent Document 1 also includes a control device that controls the ventilation fan. The control device drives the ventilation fan on condition that the hydrogen concentration in the crankcase is equal to or higher than a predetermined threshold. As a result, gas in the crankcase is exhausted to the outside through the ventilation passage. Accordingly, outside air is introduced into the crankcase through the outside air introduction passage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-127704 Summary of the Invention [Problem to be solved by the invention]

[0005] In the ventilation system of Patent Document 1, it is essential to install a ventilation fan in the ventilation passage. On the other hand, there is also a demand for a technique for ventilating the gas in the crankcase without necessarily requiring a ventilation fan. [Means for solving the problem]

[0006] A ventilation system for solving the above problem is provided which comprises an internal combustion engine having a cylinder, an intake passage, and a crank chamber, and fueled by hydrogen, a water vapor increaser that increases the amount of water vapor generated in the crank chamber, and a control device that controls the water vapor increaser, wherein the internal combustion engine has a blow-by gas passage that circulates gas in the crank chamber to the intake passage, and the control device executes a hydrogen concentration acquisition process that acquires the hydrogen concentration in the crank chamber based on the operating state of the internal combustion engine, and an increase process that increases the amount of water vapor generated in the crank chamber by the water vapor increaser, provided that the hydrogen concentration is equal to or greater than a predetermined threshold value, compared to when the hydrogen concentration is less than the threshold value.

[0007] According to the above configuration, when the hydrogen concentration in the crank chamber is equal to or higher than the threshold, the amount of water vapor generated in the crank chamber increases, causing the pressure in the crank chamber to rise. Then, the gas in the crank chamber is discharged to the intake passage through the blow-by gas passage. In other words, the gas in the crank chamber can be ventilated without the need for a ventilation fan. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a ventilation system. [Diagram 2] 13 is a flowchart showing a water vapor increase control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Outline of ventilation system configuration> Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 and 2. First, a schematic configuration of a ventilation system 100 applied to a vehicle will be described.

[0010] As shown in Fig. 1, the ventilation system 100 includes an internal combustion engine 10. The internal combustion engine 10 is an internal combustion engine that uses hydrogen as fuel. The internal combustion engine 10 includes a head cover 21, a cylinder head 22, a cylinder block 23, a crankcase 24, and an oil pan 25. The internal combustion engine 10 also includes a plurality of pistons 31, a plurality of connecting rods 32, a crankshaft 33, an intake pipe 41, and an exhaust pipe 42.

[0011] The cylinder block 23 has four cylinders 23A and four upper spaces 23B as spaces inside the cylinder block 23. The cylinders 23A extend from the upper end of the cylinder block 23 to near the center in the vertical direction. The cylinders 23A are spaces for burning a mixture of fuel and intake air. The upper space 23B extends from the lower end of the cylinders 23A to the lower end of the cylinder block 23. The pistons 31 are located inside the cylinders 23A. The pistons 31 are connected to the crankshaft 33 via the connecting rods 32. The pistons 31 reciprocate inside the cylinders 23A as the mixture of fuel and intake air is burned in the cylinders 23A. The reciprocating motion of the pistons 31 rotates the crankshaft 33. Note that FIG. 1 shows only one cylinder 23A as a representative.

[0012] The crankcase 24 is connected to the lower end of the cylinder block 23. The crankcase 24 has a so-called ladder frame structure. Therefore, the crankcase 24 has four lower spaces 24A as an internal space of the crankcase 24. The lower spaces 24A extend from the upper end to the lower end of the crankcase 24. The lower spaces 24A are connected to the lower end of the upper space 23B. The cylinder block 23 and the crankcase 24 support the crankshaft 33 while sandwiching it between them.

[0013] The oil pan 25 is connected to the lower end of the crankcase 24. The oil pan 25 is generally shaped like a rectangular box having a bottom. Therefore, the oil pan 25 has an oil space 25A as an internal space of the oil pan 25. The oil space 25A is a space for storing oil. The oil stored in the oil space 25A is supplied to each part of the internal combustion engine 10 by a pump (not shown). In this embodiment, the upper space 23B of the cylinder block 23, the lower space 24A of the crankcase 24, and the oil space 25A of the oil pan 25 form the crank chamber 10Z of the internal combustion engine 10.

[0014] The cylinder head 22 is connected to the upper end of the cylinder block 23. The cylinder head 22 has four intake ports 22A, four exhaust ports 22B, and four combustion recesses 22C as an internal space of the cylinder head 22. The combustion recesses 22C are recessed upward from the lower surface of the cylinder head 22. The combustion recesses 22C are connected to the upper end of the cylinder 23A. The combustion recesses 22C, the cylinder 23A, and the piston 31 define a combustion chamber 10C.

[0015] A first end of the intake port 22A is connected to the combustion recess 22C. A second end of the intake port 22A opens to a side surface of the cylinder head 22. An intake pipe 41 is connected to the second end of the intake port 22A. The intake pipe 41 introduces intake air from outside the internal combustion engine 10 into the intake port 22A. The intake port 22A introduces the intake air that has flowed through the intake pipe 41 into the cylinder 23A. In this embodiment, the intake port 22A and the intake pipe 41 form an intake passage 10A of the internal combustion engine 10.

[0016] A first end of the exhaust port 22B is connected to the combustion recess 22C. A second end of the exhaust port 22B opens to a side surface of the cylinder head 22. An exhaust pipe 42 is connected to the second end of the exhaust port 22B. The exhaust port 22B discharges exhaust from the cylinder 23A to the exhaust pipe 42. The exhaust pipe 42 discharges the exhaust that has flowed through the exhaust port 22B to the outside of the internal combustion engine 10. In this embodiment, the exhaust port 22B and the exhaust pipe 42 form an exhaust passage 10B of the internal combustion engine 10.

[0017] The head cover 21 is connected to an upper end of the cylinder head 22. The head cover 21 covers the cylinder head 22. The head cover 21 defines an accommodation space 21A together with the cylinder head 22. The accommodation space 21A accommodates a valve mechanism and the like (not shown).

[0018] The internal combustion engine 10 includes a plurality of intake valves 34 , a plurality of exhaust valves 35 , a plurality of fuel injectors 36 , and a plurality of ignition devices 37 . The intake valve 34 is located at the connection between the intake port 22A and the combustion recess 22C. The intake valve 34 opens and closes the downstream end of the intake port 22A by a driving force from a valve mechanism (not shown). The exhaust valve 35 is located at the connection between the exhaust port 22B and the combustion recess 22C. The exhaust valve 35 opens and closes the upstream end of the exhaust port 22B by a driving force from a valve mechanism (not shown).

[0019] The tip of the fuel injection valve 36 is located midway through the intake port 22A. The fuel injection valve 36 is supplied with hydrogen stored in a fuel tank (not shown). The fuel injection valve 36 injects hydrogen as fuel into the intake port 22A. As a result, hydrogen is supplied to the cylinder 23A via the intake port 22A and the combustion recess 22C. The tip of the ignition device 37 is located in the combustion recess 22C. The ignition device 37 ignites the mixture of fuel and intake air by spark discharge.

[0020] The internal combustion engine 10 includes a throttle valve 38, an air cleaner 46, a turbocharger 47, and an intercooler 48. The turbocharger 47 includes a compressor wheel 47A, a connecting shaft 47B, and a turbine wheel 47C. The compressor wheel 47A is located in the middle of the intake pipe 41. A first end of the connecting shaft 47B is connected to the compressor wheel 47A. A second end of the connecting shaft 47B is connected to the turbine wheel 47C. The turbine wheel 47C is located in the middle of the exhaust pipe 42. When the turbine wheel 47C rotates due to the flow of exhaust gas from the exhaust pipe 42, the compressor wheel 47A rotates together with the turbine wheel 47C via the connecting shaft 47B. As a result, the intake air compressed by the compressor wheel 47A is supplied to the downstream side of the intake pipe 41 as viewed from the compressor wheel 47A.

[0021] The air cleaner 46 is located in a portion of the intake pipe 41 that is upstream as viewed from the compressor wheel 47A. The air cleaner 46 collects foreign matter contained in the intake air flowing through the intake pipe 41. The intercooler 48 is located in a portion of the intake pipe 41 that is downstream as viewed from the compressor wheel 47A. The intercooler 48 cools the intake air compressed by the compressor wheel 47A. The throttle valve 38 is located in a portion of the intake pipe 41 that is downstream as viewed from the intercooler 48. The throttle valve 38 adjusts the amount of intake air flowing through the intake pipe 41.

[0022] The internal combustion engine 10 includes a blow-by gas processing device 50. The blow-by gas processing device 50 includes a main separator 51, a suction passage 52, a connection passage 53, an ejector 54, and a bypass passage 55.

[0023] The main separator 51 is located within the accommodation space 21A of the head cover 21. The main separator 51 collects oil contained in the gas flowing through the main separator 51. A first end of the suction passage 52 is connected to the main separator 51. A second end of the suction passage 52 is connected to the upper space 23B of the cylinder block 23. Therefore, the main separator 51 can introduce gas from the crank chamber 10Z via the suction passage 52.

[0024] A first end of the bypass passage 55 is connected to a portion of the intake pipe 41 that is downstream as viewed from the compressor wheel 47A and upstream as viewed from the intercooler 48. A second end of the bypass passage 55 is connected to a portion of the intake pipe 41 that is downstream as viewed from the air cleaner 46 and upstream as viewed from the compressor wheel 47A. A portion of the bypass passage 55 is located in the accommodation space 21A of the head cover 21. The ejector 54 is located in a portion of the bypass passage 55 that is within the accommodation space 21A of the head cover 21. A first end of the connection passage 53 is connected to the ejector 54. A second end of the connection passage 53 is connected to the main separator 51. Therefore, the ejector 54 can introduce the gas of the main separator 51 through the connection passage 53 by the negative pressure generated in the ejector 54.

[0025] The blow-by gas treatment device 50 includes a PCV passage 57 and a PCV valve 58. A first end of the PCV passage 57 is connected to the main separator 51. A second end of the PCV passage 57 is connected to a downstream portion of the intake pipe 41 as viewed from the throttle valve 38. The PCV valve 58 is located in the middle of the PCV passage 57. The PCV valve 58 opens and closes the flow path of the PCV passage 57. In this embodiment, when the rotation speed of the compressor wheel 47A is relatively low, that is, when the internal combustion engine 10 is in a naturally aspirated state, the PCV valve 58 is in an open state. On the other hand, when the rotation speed of the compressor wheel 47A is relatively high, that is, when the internal combustion engine 10 is in a supercharged state, the PCV valve 58 is in a closed state.

[0026] In this embodiment, the main separator 51, the suction passage 52, the connection passage 53, the ejector 54, the bypass passage 55, and the PCV passage 57 function as a blow-by gas passage that distributes gas in the crank chamber 10Z to the intake passage 10A.

[0027] The blow-by gas processing device 50 includes an auxiliary separator 61, a first introduction passage 62, and a second introduction passage 63. The auxiliary separator 61 is located in the accommodation space 21A of the head cover 21. The auxiliary separator 61 collects oil contained in the gas flowing through the auxiliary separator 61. A first end of the first introduction passage 62 is connected to the auxiliary separator 61. A second end of the first introduction passage 62 is connected to a portion of the intake pipe 41 that is downstream as viewed from the air cleaner 46 and upstream as viewed from the compressor wheel 47A. A first end of the second introduction passage 63 is connected to the auxiliary separator 61. A second end of the second introduction passage 63 is connected to the upper space 23B of the cylinder block 23. Therefore, the auxiliary separator 61, the first introduction passage 62, and the second introduction passage 63 can introduce the intake air of the intake pipe 41 into the crank chamber 10Z.

[0028] In the blow-by gas processing device 50, gas flows as follows. First, when the internal combustion engine 10 is in a naturally aspirated state, the pressure in the downstream portion of the intake pipe 41 as viewed from the throttle valve 38 becomes lower than the pressure in the main separator 51. As a result, the gas in the crank chamber 10Z is introduced into the downstream portion of the intake pipe 41 as viewed from the throttle valve 38 via the suction passage 52, the main separator 51, and the PCV passage 57. Note that a part of the intake air in the portion of the intake pipe 41 that is downstream as viewed from the air cleaner 46 and upstream as viewed from the compressor wheel 47A is introduced into the crank chamber 10Z via the first introduction passage 62, the auxiliary separator 61, and the second introduction passage 63.

[0029] On the other hand, when the internal combustion engine 10 is in a supercharged state, the pressure in the downstream portion of the intake pipe 41 as viewed from the compressor wheel 47A becomes considerably higher than the pressure in the upstream portion of the intake pipe 41 as viewed from the compressor wheel 47A. Then, a part of the intake air in the downstream portion of the intake pipe 41 as viewed from the compressor wheel 47A flows through the bypass passage 55 to the upstream portion of the intake pipe 41 as viewed from the compressor wheel 47A. Then, the pressure in the connection portion of the ejector 54 with the connection passage 53 becomes lower than the pressure of the main separator 51. Therefore, the gas in the crank chamber 10Z is introduced into the ejector 54 through the suction passage 52, the main separator 51, and the connection passage 53. The gas introduced into the ejector 54 is introduced, together with the intake air flowing through the bypass passage 55, into the upstream portion of the intake pipe 41 as viewed from the compressor wheel 47A, via the bypass passage 55. A part of the intake air in the downstream portion of the intake pipe 41 as viewed from the air cleaner 46 and upstream portion as viewed from the compressor wheel 47A is introduced into the crank chamber 10Z via the first introduction passage 62, the auxiliary separator 61, and the second introduction passage 63.

[0030] The ventilation system 100 includes a plurality of water injection valves 71 and an oil heater 72. The tip of the water injection valve 71 is located in the middle of the intake port 22A. The water injection valve 71 receives water from a water tank (not shown). The water injection valve 71 injects water into the intake port 22A. When the injected water evaporates, the intake port 22A is cooled, and the intake air introduced from the intake port 22A to the cylinder 23A is cooled. Note that a part of the water injected from the water injection valve 71 into the intake port 22A is supplied as moisture to the crank chamber 10Z through the cylinder 23A. Therefore, the water injection valve 71 also functions as a water supply device that supplies moisture to the crank chamber 10Z. In addition, the water injection valve 71 functions as a water vapor increase device that increases the amount of water vapor generated in the crank chamber 10Z. In this embodiment, the ventilation system 100 includes four water injection valves 71 corresponding to the four cylinders 23A.

[0031] The oil heater 72 is located in the oil space 25A of the oil pan 25. Specifically, the oil heater 72 is fixed to the bottom surface of the oil pan 25 in the oil space 25A. The oil heater 72 is capable of heating the oil stored in the oil space 25A. That is, the oil heater 72 heats the oil stored in the crank chamber 10Z. The oil heater 72 functions as a water vapor increaser that increases the amount of water vapor generated in the crank chamber 10Z.

[0032] As shown in FIG. 1, the ventilation system 100 includes an accelerator operation amount sensor 81, a vehicle speed sensor 82, a crank angle sensor 83, a water temperature sensor 84, and an oil temperature sensor 85. The accelerator operation amount sensor 81 detects an accelerator operation amount ACC, which is an operation amount of an accelerator pedal (not shown) operated by a driver of the vehicle. The vehicle speed sensor 82 detects a vehicle speed SP, which is a vehicle speed. The crank angle sensor 83 detects a crank angle SC, which is an angular position of the crankshaft 33. The water temperature sensor 84 detects a water temperature TW, which is a temperature of the cooling water discharged from the internal combustion engine 10. Specifically, the water temperature sensor 84 detects the temperature of the cooling water flowing through the downstream end of the water jacket for cooling the cylinder 23A as the water temperature TW. The oil temperature sensor 85 detects an oil temperature TA, which is a temperature of the oil stored in the oil space 25A.

[0033] The ventilation system 100 includes a control device 90. The control device 90 obtains a signal indicating an accelerator operation amount ACC from an accelerator operation amount sensor 81. The control device 90 obtains a signal indicating a vehicle speed SP from a vehicle speed sensor 82. The control device 90 obtains a signal indicating a crank angle SC from a crank angle sensor 83. The control device 90 obtains a signal indicating a water temperature TW from a water temperature sensor 84. The control device 90 obtains a signal indicating an oil temperature TA from an oil temperature sensor 85. The control device 90 calculates an engine rotation speed NE, which is the rotation speed of the crankshaft 33, based on the crank angle SC.

[0034] The control device 90 calculates the hydrogen concentration CA, which is the concentration of hydrogen contained in the gas in the crank chamber 10Z, based on the injection amount from the fuel injection valve 36, the engine rotation speed NE, etc. For example, the control device 90 calculates the increase in the hydrogen concentration CA per unit time based on the injection amount from the fuel injection valve 36, the engine rotation speed NE, etc. The control device 90 also calculates the decrease in the hydrogen concentration CA per unit time based on the operating state of the internal combustion engine 10, such as the engine rotation speed NE. The control device 90 then calculates the final hydrogen concentration CA by adding the difference between the increase in the hydrogen concentration CA and the decrease in the hydrogen concentration CA to the previously calculated hydrogen concentration CA. The above process is an example of a hydrogen concentration acquisition process that acquires the hydrogen concentration CA based on the operating state of the internal combustion engine 10.

[0035] The control device 90 calculates the moisture concentration CB, which is the concentration of moisture contained in the oil stored in the crank chamber 10Z, based on the injection amount from the fuel injection valve 36, the engine rotation speed NE, the injection amount from the water injection valve 71, the oil temperature TA, and the like. For example, the control device 90 calculates the increase in the moisture concentration CB per unit time. At this time, the control device 90 calculates the increase in the moisture concentration CB as a larger value as the injection amount from the fuel injection valve 36 increases, as the engine rotation speed NE increases, and as the injection amount from the water injection valve 71 increases. The control device 90 also calculates the decrease in the moisture concentration CB per unit time. At this time, the control device 90 calculates the decrease in the moisture concentration CB as a larger value as the oil temperature TA increases. Then, the control device 90 calculates the final moisture concentration CB by adding the difference between the increase in the moisture concentration CB and the decrease in the moisture concentration CB to the moisture concentration CB calculated previously. The above process is an example of a moisture concentration acquisition process for acquiring the moisture concentration CB based on the operating state of the internal combustion engine 10.

[0036] The control device 90 calculates the vehicle required output, which is a required value of the output necessary for the vehicle to travel, based on the accelerator operation amount ACC and the vehicle speed SP. The control device 90 controls the internal combustion engine 10 based on the vehicle required output. Specifically, the control device 90 executes various controls such as adjustment of the fuel injection amount by the fuel injection valve 36, adjustment of the ignition timing of the ignition device 37, adjustment of the opening degree of the throttle valve 38, and opening and closing of the PCV valve 58. The control device 90 also executes various controls such as adjustment of the water injection amount by the water injection valve 71, and adjustment of the heating temperature by the oil heater 72.

[0037] The control device 90 may be configured as a circuit including one or more processors that execute various processes according to a computer program (software). The control device 90 may also be configured as a circuit including one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any medium that can be accessed by a general-purpose or dedicated computer.

[0038] <Water vapor increase control> Next, there will be described the water vapor increase control executed by the control device 90. In this embodiment, the control device 90 repeatedly executes the water vapor increase control on condition that the internal combustion engine 10 is in operation.

[0039] As shown in FIG. 2, when the control device 90 starts the water vapor increase control, it executes the process of step S11. In step S11, the control device 90 judges whether the hydrogen concentration CA is equal to or greater than a predetermined threshold value A. Here, the threshold value A is determined, for example, as follows. First, an upper limit value of the hydrogen concentration CA that is allowable in the internal combustion engine 10 in terms of design is obtained through experiments or the like. Then, a value that is a certain value lower than the obtained upper limit value of the hydrogen concentration CA is determined as the threshold value A. An example of the threshold value A is about several percent. In step S11, if the control device 90 judges that the hydrogen concentration CA is less than the threshold value A (S11: NO), the control device 90 ends the current water vapor increase control. On the other hand, in step S11, if the control device 90 judges that the hydrogen concentration CA is equal to or greater than the threshold value A (S11: YES), the control device 90 advances the process to step S21.

[0040] In step S21, the control device 90 judges whether the water concentration CB is equal to or greater than a predetermined specified value B. Here, the specified value B is determined, for example, as follows. First, a lower limit value of the water concentration CB that is the minimum required for evaporating the water contained in the oil in the crank chamber 10Z and generating water vapor in the crank chamber 10Z is obtained through experiments or the like. Then, a value that is higher than the obtained lower limit value of the water concentration CB by a predetermined value is determined as the specified value B. An example of the specified value B is about several percent to several tens of percent. In step S21, when the control device 90 judges that the water concentration CB is equal to or greater than the specified value B (S21: YES), the control device 90 advances the process to step S61. That is, when the hydrogen concentration CA is equal to or greater than the threshold value A and the water concentration CB is equal to or greater than the specified value B, the control device 90 executes the processes of steps S61 to S63.

[0041] In step S61, the control device 90 calculates a required water vapor amount X, which is the amount of water vapor that needs to be generated in the crank chamber 10Z, based on the hydrogen concentration CA. Specifically, the control device 90 calculates the required water vapor amount X to be a larger value as the hydrogen concentration CA increases. The control device 90 then advances the process to step S62.

[0042] In step S62, the control device 90 calculates a target oil temperature Y, which is a target value for the temperature of the oil stored in the crank chamber 10Z, based on the required water vapor amount X. Specifically, the control device 90 calculates the target oil temperature Y to be a higher value as the required water vapor amount X is larger. Thereafter, the control device 90 advances the process to step S63.

[0043] In step S63, the control device 90 performs an increase process in which the oil heater 72 heats the oil stored in the crank chamber 10Z. In the increase process in step S63, the control device 90 operates the oil heater 72 by outputting a control signal to the oil heater 72. Then, the control device 90 controls the oil heater 72 so that the oil temperature TA becomes the target oil temperature Y. Note that as the oil temperature TA rises, the moisture contained in the oil is more likely to evaporate. Therefore, when the process in step S63 is performed, the amount of water vapor generated in the crank chamber 10Z by the oil heater 72 increases. In this way, the control device 90 heats the oil stored in the crank chamber 10Z by the oil heater 72 without increasing the amount of moisture supplied to the crank chamber 10Z by the water injection valve 71. After that, the control device 90 ends the current water vapor increase control.

[0044] On the other hand, in the above-mentioned step S21, when the control device 90 determines that the water concentration CB is less than the specified value B (S21: NO), the control device 90 advances the process to step S31.

[0045] In step S31, the control device 90 judges whether the crank chamber 10Z is warm. For example, when the oil temperature TA is equal to or higher than a predetermined temperature C, the control device 90 judges that the crank chamber 10Z is warm. On the other hand, when the oil temperature TA is lower than the predetermined temperature C, the control device 90 judges that the crank chamber 10Z is not warm. Here, the predetermined temperature C is determined, for example, as follows. First, a lower limit value of the oil temperature TA that is the minimum required to evaporate the moisture contained in the oil stored in the crank chamber 10Z is obtained by experiment or the like. Then, a value that is higher than the lower limit value of the obtained oil temperature TA by a certain value is determined as the predetermined temperature C. An example of the predetermined temperature C is several tens of degrees Celsius. In step S31, when the control device 90 judges that the crank chamber 10Z is warm (S31: YES), the control device 90 advances the process to step S71.

[0046] In step S71, the control device 90 calculates the required water vapor amount X based on the hydrogen concentration CA. The process of step S71 is the same as the process of step S61. After that, the control device 90 advances the process to step S72.

[0047] In step S72, the control device 90 calculates the water injection amount Z, which is the amount of water to be injected from the water injector 71, based on the required water vapor amount X. Specifically, the control device 90 calculates the water injection amount Z to be a larger value as the required water vapor amount X is larger. Note that, when injection from the water injector 71 is required to cool the intake port 22A, the water injection amount Z is the sum of the injection amount for cooling the intake port 22A and the injection amount for supplying moisture to the crank chamber 10Z. Thereafter, the control device 90 advances the process to step S73.

[0048] In step S73, the control device 90 performs an increase process to increase the amount of water supplied to the crank chamber 10Z by the water injector 71 compared to when the increase process is not performed. In the increase process of step S73, the control device 90 outputs a control signal to the water injector 71 to inject water from the water injector 71. If the oil heater 72 is operating at the time of the process of step S73, the control device 90 stops the operation of the oil heater 72. As described above, even if water is injected from the water injector 71 to cool the intake port 22A before the process of step S73 is performed, the injection amount of water from the water injector 71 increases when the process of step S73 is performed. Then, when the injection amount of water increases, the amount of water supplied to the crank chamber 10Z increases. When the amount of water supplied to the crank chamber 10Z increases, the moisture in the crank chamber 10Z is more likely to evaporate. Therefore, when the process of step S73 is performed, the amount of water vapor generated in the crank chamber 10Z by the water injector 71 increases. Thereafter, the control device 90 ends the current water vapor increase control.

[0049] On the other hand, in the above-mentioned step S31, when the control device 90 determines that the crank chamber 10Z is not warm (S31: NO), the control device 90 advances the process to step S81. In step S81, the control device 90 calculates the required water vapor amount X based on the hydrogen concentration CA. The process of step S81 is the same as the process of step S61. After that, the control device 90 advances the process to step S82.

[0050] In step S82, the control device 90 calculates the water injection amount Z based on the required water vapor amount X. The process of step S82 is the same as the process of step S72. After that, the control device 90 advances the process to step S83.

[0051] In step S83, the control device 90 calculates a target oil temperature Y based on the required water vapor amount X. The process of step S83 is the same as the process of step S62. After that, the control device 90 advances the process to step S84.

[0052] In step S84, the control device 90 performs, as the increase process, a process of heating the oil stored in the crank chamber 10Z by the oil heater 72. Furthermore, as the increase process, the control device 90 performs a process of increasing the amount of water supplied to the crank chamber 10Z by the water injector 71 compared to a case where the increase process is not performed. Specifically, the control device 90 operates the oil heater 72 by outputting a control signal to the oil heater 72. Then, the control device 90 controls the oil heater 72 so that the oil temperature TA becomes the target oil temperature Y. Furthermore, the control device 90 outputs a control signal to the water injector 71 to inject water from the water injector 71. In this way, in step S84, the increase process using the oil heater 72 and the increase process using the water injector 71 are used together. After that, the control device 90 ends the current water vapor increase control.

[0053] <Action of this embodiment> In the internal combustion engine 10, a part of hydrogen supplied to the cylinder 23A flows into the crank chamber 10Z through a gap between the inner peripheral surface of the cylinder 23A and the outer peripheral surface of the piston 31. Then, the hydrogen concentration CA in the crank chamber 10Z gradually increases. As shown in FIG. 2, in the ventilation system 100, the process from step S21 onward is executed on the condition that the hydrogen concentration CA in the crank chamber 10Z is equal to or higher than the threshold value A. For example, in the process from step S81 onward, when water is injected from the water injection valve 71 into the intake port 22A, a part of the water is introduced into the cylinder 23A. Then, a part of the water supplied to the cylinder 23A flows into the crank chamber 10Z through the gap between the inner peripheral surface of the cylinder 23A and the outer peripheral surface of the piston 31. Then, the amount of moisture that can evaporate in the crank chamber 10Z increases. Furthermore, for example, in the processing after step S81, when the oil stored in the crank chamber 10Z is heated by the oil heater 72, the moisture in the crank chamber 10Z is likely to evaporate.

[0054] <Effects of this embodiment> (1) In the ventilation system 100, the amount of water that can evaporate in the crank chamber 10Z increases as the amount of water injected from the water injection valve 71 increases. Therefore, the amount of water vapor generated in the crank chamber 10Z increases compared to when the hydrogen concentration CA in the crank chamber 10Z is less than the threshold value A. In addition, when the oil heater 72 heats the oil, the water in the crank chamber 10Z is more likely to evaporate. Therefore, the amount of water vapor generated in the crank chamber 10Z increases compared to when the hydrogen concentration CA in the crank chamber 10Z is less than the threshold value A. In this way, when the hydrogen concentration CA in the crank chamber 10Z is equal to or greater than the threshold value A, the amount of water vapor generated in the crank chamber 10Z increases, thereby increasing the pressure in the crank chamber 10Z. Then, the gas in the crank chamber 10Z is more likely to be discharged to the intake pipe 41 via the suction passage 52, etc. As a result, in the ventilation system 100, the gas in the crank chamber 10Z can be ventilated without requiring a ventilation fan.

[0055] (2) As shown in FIG. 2, when the determination in step S21 is negative, that is, when the moisture concentration CB is less than the specified value B, the amount of moisture that can evaporate in the crank chamber 10Z is small. Therefore, even if the temperature of the crank chamber 10Z is relatively high due to, for example, the heat of the cylinder 23A of the internal combustion engine 10, water vapor is unlikely to be generated in the crank chamber 10Z. In response to this, in the ventilation system 100, water is injected from the water injector 71 in step S73 or step S84. In this way, the water injector 71 supplies moisture to the crank chamber 10Z, so that the amount of moisture that can evaporate in the crank chamber 10Z increases. This makes it possible to prevent the amount of water vapor generated in the crank chamber 10Z from decreasing due to the small amount of moisture that can evaporate in the crank chamber 10Z.

[0056] (3) Even if moisture is supplied into the crank chamber 10Z, if the temperature of the crank chamber 10Z is relatively low, water vapor is unlikely to be generated in the crank chamber 10Z. In contrast, in the ventilation system 100, if a negative determination is made in step S31, that is, if the temperature of the crank chamber 10Z is relatively low, the oil stored in the crank chamber 10Z is heated by the oil heater 72 in the process of step S84. This makes it easier for moisture in the crank chamber 10Z to evaporate. This makes it possible to prevent the amount of water vapor generated in the crank chamber 10Z from decreasing due to the low temperature of the crank chamber 10Z.

[0057] (4) If the determination in step S21 is affirmative, that is, if the hydrogen concentration CA is equal to or greater than the threshold value A and the water concentration CB is equal to or greater than the specified value B, the amount of water injected from the water injection valve 71 is increased. In this case, the oil in the crank chamber 10Z may be deteriorated due to the excessive increase in the water concentration CB. In contrast, in the ventilation system 100, if the hydrogen concentration CA is equal to or greater than the threshold value A and the water concentration CB is equal to or greater than the specified value B, the amount of water injected from the water injection valve 71 is not increased. Therefore, the water concentration CB is prevented from becoming excessively high due to an increase in the amount of water injected from the water injection valve 71. On the other hand, in the above case, the oil is heated by the oil heater 72. Therefore, the amount of water vapor generated in the crank chamber 10Z is increased by heating the oil, while the water concentration CB is prevented from becoming high by heating the oil.

[0058] (5) In the ventilation system 100, the water injector 71 that injects water into the intake port 22A also functions as a water supply device. Therefore, in the ventilation system 100, cooling of the cylinder 23A and the like and supply of moisture to the crank chamber 10Z can be achieved with a single device.

[0059] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0060] In the above embodiment, the water vapor increase control may be changed. For example, the process of step S21 may be omitted. If a positive determination is made in step S11, any one of a series of processes from step S61 to step S63, a series of processes from step S71 to step S73, and a series of processes from step S81 to step S84 may be executed. Note that, if the process of step S21 is omitted, the moisture concentration acquisition process may also be omitted.

[0061] For example, the process of step S31 may be omitted. If the internal combustion engine 10 is running, the temperature of the crank chamber 10Z increases due to the heat of the cylinder 23A of the internal combustion engine 10. Therefore, the process of step S31 may be omitted. As a specific example, the control device 90 may advance the process to step S71 when a negative determination is made in step S21 regardless of whether the crank chamber 10Z is warm or not. As another specific example, if there is little adverse effect caused by operating the oil heater 72, the control device 90 may advance the process to step S81 when a negative determination is made in step S21 regardless of whether the crank chamber 10Z is warm or not.

[0062] In the above embodiment, the hydrogen concentration acquisition process may be modified. For example, a hydrogen concentration sensor that detects the hydrogen concentration CA may be employed in the ventilation system 100. In this case, the control device 90 may execute the hydrogen concentration acquisition process by acquiring a signal indicative of the hydrogen concentration CA from the hydrogen concentration sensor.

[0063] In the above embodiment, the water concentration acquisition process may be changed. For example, a moisture concentration sensor that detects the moisture concentration CB may be employed in the ventilation system 100. In this case, the control device 90 may execute the moisture concentration acquisition process by acquiring a signal indicating the moisture concentration CB from the moisture concentration sensor.

[0064] In the above embodiment, the configuration of the water vapor increasing device may be changed. For example, as the water supply device, instead of or in addition to the water injector 71 that injects water into the intake port 22A, a water injector that injects water into the cylinder 23A may be used. Also, for example, as the water supply device, instead of or in addition to the water injector 71, a water injector that injects water into the crank chamber 10Z may be used.

[0065] The ventilation system 100 may include multiple oil heaters 72. For example, one of the water supply device and the oil heater 72 may be omitted. That is, the ventilation system 100 may be provided with one or more water supply devices or one or more oil heaters 72 as the water vapor increasing device.

[0066] In the above embodiment, the ventilation system 100 may include a ventilation fan for discharging the gas in the crank chamber 10Z to the outside in addition to the water vapor increase device. That is, the present technology can be used in combination with a technology for performing ventilation using a ventilation fan. This configuration may allow the size of the ventilation fan to be reduced.

[0067] <Related technical ideas> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. (Appendix 1) an internal combustion engine that uses hydrogen as fuel and has a cylinder, an intake passage, and a crankcase; a water vapor increase device for increasing the amount of water vapor generated in the crankcase; A ventilation system comprising: a control device for controlling the water vapor increasing device, the internal combustion engine has a blow-by gas passage that allows gas in the crank chamber to flow into the intake passage, The control device includes: a hydrogen concentration acquisition process for acquiring a hydrogen concentration in the crank chamber based on an operating state of the internal combustion engine; an increase process for increasing the amount of water vapor generated in the crank chamber by the water vapor increase device, on condition that the hydrogen concentration is equal to or greater than a predetermined threshold value, compared to when the hydrogen concentration is less than the threshold value; Run Ventilation system.

[0068] (Appendix 2) The water vapor increasing device includes a water supply device for supplying moisture to the crank chamber, The control device increases the amount of water supplied to the crank chamber by the water supply device in the increasing process compared to when the increasing process is not executed. 13. A ventilation system as described in appended claim 1.

[0069] (Appendix 3) The water supply device is a water injection valve that injects water into the cylinder or the intake passage. 2. A ventilation system as described in Appendix 2.

[0070] (Appendix 4) The water vapor increasing device includes an oil heater that heats oil stored in the crank chamber, The control device heats the oil stored in the crank chamber by the oil heater in the increasing process. The ventilation system according to any one of claims 1 to 3.

[0071] (Appendix 5) The water vapor increasing device includes an oil heater that heats oil stored in the crank chamber, The control device is capable of executing a water concentration acquisition process to acquire a water concentration contained in oil stored in the crank chamber based on an operating state of the internal combustion engine, When the hydrogen concentration is equal to or higher than the threshold value and the water concentration is equal to or higher than a predetermined specified value, the control device heats the oil stored in the crank chamber by the oil heater without increasing the amount of water supplied to the crank chamber by the water supply device in the increasing process. 10. The ventilation system of claim 2 or 3. [Explanation of symbols]

[0072] 10. Internal combustion engine 10A…Intake passage 10B…Exhaust passage 10C…Combustion chamber 10Z…Crankcase 22…Cylinder head 23…Cylinder block 23A…Cylinder 24…Crankcase 25…Oil pan 36…Fuel injector 41…Intake pipe 42…Exhaust pipe 47...Turbocharger 50...Blow-by gas treatment device 51…Main separator 52...Suction passage 53...Connecting passage 54…Ejector 55...Bypass passage 57…PCV passage 58…PCV valve 71...Water injection valve 72...Oil heater 90...Control device 100…Ventilation system

Claims

1. an internal combustion engine that uses hydrogen as fuel and has a cylinder, an intake passage, and a crankcase; a water vapor increase device for increasing the amount of water vapor generated in the crankcase; A ventilation system comprising: a control device for controlling the water vapor increasing device, the internal combustion engine has a blow-by gas passage that allows gas in the crank chamber to flow into the intake passage, The control device includes: a hydrogen concentration acquisition process for acquiring a hydrogen concentration in the crank chamber based on an operating state of the internal combustion engine; an increase process for increasing the amount of water vapor generated in the crankcase by the water vapor increase device, on condition that the hydrogen concentration is equal to or greater than a predetermined threshold value, compared to when the hydrogen concentration is less than the threshold value; Run Ventilation system.

2. The water vapor increasing device includes a water supply device for supplying moisture to the crank chamber, The control device increases the amount of water supplied to the crank chamber by the water supply device in the increasing process compared to a case where the increasing process is not executed.

2. The ventilation system of claim 1.

3. The water supply device is a water injection valve that injects water into the cylinder or the intake passage.

3. The ventilation system of claim 2.

4. The water vapor increasing device includes an oil heater that heats oil stored in the crank chamber, The control device heats the oil stored in the crank chamber by the oil heater in the increasing process. A ventilation system according to any one of claims 1 to 3.

5. The water vapor increasing device includes an oil heater that heats oil stored in the crank chamber, The control device is capable of executing a water concentration acquisition process to acquire a water concentration contained in oil stored in the crank chamber based on an operating state of the internal combustion engine, When the hydrogen concentration is equal to or higher than the threshold value and the water concentration is equal to or higher than a predetermined specified value, the control device heats the oil stored in the crank chamber by the oil heater without increasing the amount of water supplied to the crank chamber by the water supply device in the increasing process. A ventilation system according to claim 2 or claim 3.

Images