Air intake system for internal combustion engine

Abstract

To provide an air intake system for an internal combustion engine that can inhibit condensed water which is generated in an intake port of a cylinder head or a branch pipe of an intake manifold from flowing into a combustion chamber.SOLUTION: An air intake system 100 for an internal combustion engine is an air intake system for an engine 1 that burns fuel containing a hydrogen gas. The air intake system for an internal combustion engine includes: an oxygen enrichment part 10 supplied with air or a burnt gas from the engine 1; and a nitrogen passage 13 for communicating between a crankcase internal space 7 of the engine 1 and a nitrogen outlet 10c of the oxygen enrichment part 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an intake system for an internal combustion engine. [Background technology]

[0002] Conventionally, there has been known a four-stroke engine that can be operated with fuel containing hydrogen gas and is equipped with a ventilation fan that forcibly exhausts hydrogen gas from the inside to the outside of the crankcase so that the hydrogen gas contained in the blow-by gas does not ignite inside the crankcase (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-127704 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional technology, outside air or burnt gas is introduced into the crankcase to suppress ignition of hydrogen gas inside the crankcase. However, in order to more reliably suppress ignition of hydrogen gas, it is desirable to further reduce the oxygen concentration inside the crankcase.

[0005] The present invention aims to provide an intake device for an internal combustion engine that burns fuel containing hydrogen gas, which can more reliably suppress the ignition of hydrogen gas inside the crankcase. [Means for solving the problem]

[0006] An intake device for an internal combustion engine according to one embodiment of the present invention is an intake device for an internal combustion engine that burns a fuel containing hydrogen gas, and includes a nitrogen separation section to which air or burnt gas of the internal combustion engine is supplied, and a nitrogen passage that connects the internal space of the crankcase of the internal combustion engine with the nitrogen output section of the nitrogen separation section.

[0007] In an intake device for an internal combustion engine according to one aspect of the present invention, a nitrogen separation unit separates oxygen and nitrogen from supplied air or burned gas. The separated nitrogen flows into the crankcase internal space through a nitrogen passage. Meanwhile, the separated oxygen is prevented from flowing into the crankcase internal space. Therefore, the oxygen concentration in the crankcase internal space can be reduced compared to, for example, a case in which air or burned gas is introduced into the crankcase internal space. Therefore, according to the intake device for an internal combustion engine according to one aspect of the present invention, it is possible to more reliably prevent ignition of hydrogen gas inside the crankcase in an internal combustion engine that burns a fuel containing hydrogen gas.

[0008] In one embodiment, an intake device for an internal combustion engine includes an intake passage that guides intake air to a combustion chamber of the internal combustion engine, and an intake branch passage that branches off at a predetermined position in the intake passage, and the nitrogen separator is connected to the intake branch passage and may receive intake air from the intake passage. With this configuration, the oxygen concentration inside the crankcase can be further reduced by the nitrogen separated by the nitrogen separator using the intake air from the intake passage.

[0009] In one embodiment, an intake device of an internal combustion engine includes an intake passage that introduces intake air to a combustion chamber of the internal combustion engine, an exhaust passage that introduces burnt gas from the combustion chamber, an EGR passage that recirculates the burnt gas from the exhaust passage to the intake passage, and an EGR branch passage that branches off at a predetermined position in the EGR passage, and the nitrogen separation unit is connected to the EGR branch passage and may be supplied with the burnt gas from the EGR passage. With this configuration, the oxygen concentration inside the crankcase can be further reduced by nitrogen separated by the nitrogen separation unit using the burnt gas from the EGR passage.

[0010] In one embodiment, an intake device of an internal combustion engine includes a supercharger provided upstream of a predetermined position in an intake passage, a throttle valve provided downstream of a predetermined position in the intake passage, an EGR valve provided downstream of a predetermined position in an EGR passage, and a controller that controls the supercharger, the throttle valve, and the EGR valve based on an operating state of the internal combustion engine, and the controller may control the supercharger, the throttle valve, and the EGR valve so as to increase the amount of burned gas supplied from the EGR passage to the nitrogen separation section compared to the amount of intake air supplied from the intake passage to the nitrogen separation section when the operating state of the internal combustion engine satisfies either a predetermined low load condition or a predetermined high load condition. In this configuration, a state in which the operating state of the internal combustion engine satisfies either a predetermined low load condition or a predetermined high load condition can be corresponding to a state in which it is difficult to increase the supply of intake air from the intake passage to the nitrogen separation section using the supercharger. In this state, by increasing the amount of burnt gas supplied from the EGR passage to the nitrogen separation section compared to the amount of intake air supplied from the intake passage to the nitrogen separation section, nitrogen separation in the nitrogen separation section can be stabilized. Effect of the Invention

[0011] According to the present invention, in an internal combustion engine that burns fuel containing hydrogen gas, it is possible to more reliably suppress ignition of hydrogen gas inside the crankcase. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of an engine equipped with an intake device for an internal combustion engine according to an embodiment; [Diagram 2] 2 is a cross-sectional view showing the intake device of the internal combustion engine of FIG. 1 taken along line XX. [Diagram 3] 2 is a flowchart showing an example of a process of an ECU in FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0014] FIG. 1 is a schematic diagram of an engine equipped with an intake device for an internal combustion engine according to an embodiment. FIG. 2 is a cross-sectional view taken along line XX showing the intake device for an internal combustion engine in FIG. 1. As shown in FIG. 1, an intake device 100 for an internal combustion engine according to an embodiment is applied to an engine (internal combustion engine) 1. The engine 1 is, for example, an in-line four-cylinder four-stroke reciprocating engine that burns fuel containing hydrogen gas. The engine 1 is equipped with an engine body 3 having four cylinders 2.

[0015] 1 and 2, the engine body 3 includes a cylinder head 3a, a cylinder block 3b arranged below the cylinder head 3a, a cylinder liner (not shown) press-fitted into the cylinder block 3b, and a piston 3c arranged in the cylinder liner so as to be capable of ascending and descending reciprocatingly. A space surrounded by the cylinder head 3a, the cylinder liner, and the piston 3c defines a combustion chamber 4. An intake port 6 is formed in the cylinder head 3a, through which intake air flows from an intake passage 8 to the combustion chamber 4. The engine 1 includes, as an example, an injector 5 that directly injects fuel into the combustion chamber 4 of each cylinder 2.

[0016] The engine 1 includes an intake passage 8 that guides intake air to the combustion chamber 4 of the engine 1, and an exhaust passage 9 that guides burned gas from the combustion chamber 4 of the engine 1. The intake passage 8 and the exhaust passage 9 are connected to a cylinder head 3a of the engine body 3.

[0017] In the intake passage 8, for example, an air cleaner 16, a compressor 31 of a turbocharger (supercharger) 30, an intercooler 17, and a throttle valve 18 are arranged from upstream to downstream. In the exhaust passage 9, for example, a turbine 32 of the turbocharger 30 is arranged from upstream to downstream.

[0018] The engine 1 includes an EGR unit 24 that recirculates a portion of burned gas generated in the combustion chamber 4 to the intake passage 8 as EGR (exhaust gas recirculation) gas. The EGR unit 24 includes an EGR passage 25 provided to connect the intake passage 8 and the exhaust passage 9, an EGR valve 26 disposed in the EGR passage 25, an EGR cooler 27 disposed in the EGR passage 25 upstream of the EGR valve 26, a bypass passage 28 connected to the EGR passage 25 to bypass the EGR cooler 27, and a switching valve 29 disposed at a connection portion of the EGR passage 25 with the bypass passage 28.

[0019] The EGR passage 25 is a passage for recirculating burnt gas (EGR gas) from the exhaust passage 9 to the intake passage 8. The EGR valve 26 is a valve for adjusting the amount of EGR gas recirculated from the exhaust passage 9 to the intake passage 8. The EGR cooler 27 cools the EGR gas flowing through the EGR passage 25. The switching valve 29 switches the flow path of the EGR gas to either the EGR cooler 27 or a bypass passage 28.

[0020] In this engine 1, intake air from the intake passage 8 flows into the combustion chamber 4 via the intake port 6. When hydrogen fuel is compressed together with the intake air in the combustion chamber 4, blow-by gas containing hydrogen may leak into the crankcase internal space 7 through a gap between the piston 3c and the cylinder liner. If hydrogen and air are present in the crankcase internal space 7, for example, if the hydrogen concentration exceeds 4%, there is a risk of ignition of the hydrogen gas. Therefore, in order to suppress ignition of the hydrogen gas in the crankcase internal space 7, the intake device 100 of the internal combustion engine is provided with an oxygen enrichment section (nitrogen separation section) 10.

[0021] The oxygen enrichment section 10 at least separates oxygen and nitrogen by supplying air or burned gas of the engine 1, and outputs oxygen-enriched gas and nitrogen-enriched gas. The oxygen enrichment section 10 has a known configuration in which an oxygen enrichment membrane is housed in a container having, for example, a raw gas inlet 10a to which air or burned gas of the engine 1 is supplied by pressure, an oxygen outlet 10b from which the oxygen-enriched gas flows out, and a nitrogen outlet 10c from which the nitrogen-enriched gas flows out. The oxygen enrichment section 10 may separate water vapor and nitrogen, or may output the oxygen-enriched gas including water vapor.

[0022] The oxygen enrichment section 10 is supplied with intake air, for example, from an intake passage 8. As a specific example, an intake device 100 for an internal combustion engine includes an intake branch passage 11 that branches off at a predetermined position 8a in the intake passage 8. A raw material gas inlet 10a of the oxygen enrichment section 10 is connected to the intake branch passage 11. The intake branch passage 11 is diagrammatically indicated by an arrow in FIG. 1, but piping such as a pipe or a hose may be used.

[0023] The throttle valve 18 is provided downstream of a predetermined position 8a in the intake passage 8. By reducing the opening degree of the throttle valve 18, the intake air can be supplied to the intake branch passage 11. Furthermore, the compressor 31 of the turbocharger 30 is provided upstream of the predetermined position 8a in the intake passage 8. By operating the compressor 31 so as to increase the supercharging pressure of the turbocharger 30, the intake air can be supplied to the intake branch passage 11 by utilizing the supercharging pressure.

[0024] The oxygen enrichment section 10 may be supplied with burnt gas from an EGR passage 25. For example, an intake device 100 of an internal combustion engine includes an EGR branch passage 14 that branches off at a predetermined position 25a in the EGR passage 25. A raw material gas inlet 10a of the oxygen enrichment section 10 is connected to the EGR branch passage 14. The EGR branch passage 14 is diagrammatically indicated by an arrow in FIG. 1, but piping such as a pipe or a hose may be used.

[0025] The EGR valve 26 is provided downstream of a predetermined position 25a in the EGR passage 25. By reducing the opening degree of the EGR valve 26, it is possible to use exhaust pressure to supply burnt gas to the EGR branch passage 14. A variable valve 15 may be provided in the EGR branch passage 14. The variable valve 15 adjusts the supply amount of burnt gas flowing through the EGR branch passage 14.

[0026] The raw material gas inlet 10a is provided separately for the intake branch passage 11 and the EGR branch passage 14. The raw material gas inlet 10a may be common to the intake branch passage 11 and the EGR branch passage 14.

[0027] The oxygen outlet 10b of the oxygen enrichment unit 10 is connected to the intake passage 8 downstream of the throttle valve 18 via, for example, an oxygen passage 12. The oxygen enrichment unit 10 can supply oxygen-enriched gas to the intake passage 8 downstream of the throttle valve 18.

[0028] The nitrogen outlet (nitrogen output section) 10c of the oxygen enrichment section 10 is connected to the cylinder block 3b of the engine 1 via, for example, a nitrogen passage 13. That is, the nitrogen passage 13 connects the crankcase internal space 7 of the engine 1 to the nitrogen outlet 10c of the oxygen enrichment section 10. The oxygen enrichment section 10 can supply nitrogen-enriched gas to the crankcase internal space 7 of the engine 1. Note that a breather passage 3d may be provided in the cylinder block 3b. The breather passage 3d may connect the crankcase internal space 7 of the engine 1 to the outside of the cylinder block 3b.

[0029] When nitrogen-rich gas is supplied to the crankcase internal space 7, gas having a higher nitrogen concentration than air is supplied, and therefore the oxygen concentration can be reduced (nitrogen dilution) compared to when hydrogen and air are present in the crankcase internal space 7. For example, by supplying nitrogen-rich gas to the crankcase internal space 7 so that the oxygen concentration is 5.3% or less, it is outside the flammable range of hydrogen gas, and therefore it is possible to suppress ignition of hydrogen gas in the crankcase internal space 7.

[0030] The intake device 100 of the internal combustion engine includes an ECU [Electronic Control Unit] (controller) 20. The ECU 20 is an electronic control unit that controls a turbocharger 30, a throttle valve 18, and an EGR valve 26 based on the operating state of the engine 1. The ECU 20 includes a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a communication circuit, and the like. For example, the ECU 20 loads a program stored in the ROM into the RAM and executes the program loaded into the RAM by the CPU, thereby achieving various functions. The ECU 20 may be composed of a plurality of electronic units. An engine revolution sensor 21 and an intake amount sensor 22 are connected to the ECU 20.

[0031] The engine speed sensor 21 is a known detector that detects the engine speed of the engine 1. The engine speed sensor 21 outputs a detection signal of the detected engine speed to the ECU 20.

[0032] The intake air amount sensor 22 is provided in the intake passage 8 of the engine 1, and is a known detector that detects a detection value related to the intake air amount of the engine 1. The intake air amount sensor 22 outputs a detection signal of the intake air amount of the engine 1 to the ECU 20.

[0033] Next, a description will be given of an example of the functions and operations of the ECU 20. Figure 3 is a flowchart showing an example of processing by the ECU in Figure 1. The processing in Figure 3 is executed while the engine 1 is in operation.

[0034] 3, in S11, the ECU 20 acquires the operating state of the engine 1. For example, the ECU 20 acquires the engine speed based on the detection result of the engine speed sensor 21. The ECU 20 acquires the intake air amount of the engine 1 based on the detection result of the intake air amount sensor 22. The ECU 20 acquires the operating state of the engine 1 based on the engine speed and the intake air amount of the engine 1. The ECU 20 may acquire, as the operating state of the engine 1, coordinates corresponding to the current engine speed and the current engine load in a full-range performance diagram of the engine 1, with the engine speed on the horizontal axis and the engine load (here, the intake air amount) on the vertical axis.

[0035] In S12, the ECU 20 judges whether the operating state of the engine 1 satisfies a predetermined low load condition. The low load condition is an operating state condition in which the engine load is too low to allow the turbocharger 30 to operate sufficiently, making it difficult to increase the supply of intake air from the intake passage 8 to the oxygen enrichment section 10 using the turbocharger 30. For example, the ECU 20 judges that the operating state of the engine 1 satisfies the low load condition when the engine load is lower than a predetermined low load threshold. The low load threshold may be a map value determined according to the engine speed. If it is judged that the operating state of the engine 1 satisfies the low load condition (S12: YES), the ECU 20 proceeds to processing of S14. If it is judged that the operating state of the engine 1 does not satisfy the low load condition (S12: NO), the ECU 20 proceeds to processing of S13.

[0036] In S13, the ECU 20 judges whether the operating state of the engine 1 satisfies a predetermined high load condition. The high load condition is an operating state condition in which the performance of the turbocharger 30 is almost completely used up due to a large engine load, and it becomes difficult to increase the supply of intake air from the intake passage 8 to the oxygen enrichment section 10 using the turbocharger 30. For example, the ECU 20 judges that the operating state of the engine 1 satisfies the high load condition when the engine load is larger than a predetermined high load threshold. The high load threshold may be a map value determined according to the engine speed. If it is judged that the operating state of the engine 1 satisfies the high load condition (S13: YES), the ECU 20 proceeds to processing of S14. If it is judged that the operating state of the engine 1 does not satisfy the high load condition (S13: NO), the ECU 20 proceeds to processing of S15.

[0037] In S14, the ECU 20 controls the turbocharger 30, the throttle valve 18, the EGR valve 26, and the variable valve 15 so as to increase the amount of burnt gas supplied from the EGR passage 25 to the oxygen enrichment section 10 compared to the amount of intake air supplied from the intake passage 8 to the oxygen enrichment section 10. The ECU 20 increases the amount of burnt gas supplied compared to the amount of intake air supplied by, for example, reducing the boost pressure of the turbocharger 30, increasing the opening of the throttle valve 18, decreasing the opening of the EGR valve 26, and increasing the opening of the variable valve 15. Thereafter, the ECU 20 ends the process of FIG. 3.

[0038] On the other hand, in S15, the ECU 20 controls the turbocharger 30, the throttle valve 18, the EGR valve 26, and the variable valve 15 so that the amount of intake air supplied from the intake passage 8 to the oxygen enrichment section 10 is equal to or greater than the amount of burnt gas supplied from the EGR passage 25 to the oxygen enrichment section 10. The ECU 20 controls the intake air supply to be equal to or greater than the amount of burnt gas supplied, for example, by increasing the boost pressure of the turbocharger 30, decreasing the opening of the throttle valve 18, increasing the opening of the EGR valve 26, and decreasing the opening of the variable valve 15. Then, the ECU 20 ends the process of FIG. 3.

[0039] In the intake device 100 of the internal combustion engine as described above, the oxygen enrichment unit 10 separates oxygen and nitrogen from the supplied intake air or burned gas. The separated nitrogen (nitrogen-enriched gas) flows into the crankcase internal space 7 through the nitrogen passage 13. On the other hand, the separated oxygen (oxygen-enriched gas) is prevented from flowing into the crankcase internal space 7. For this reason, the oxygen concentration in the crankcase internal space 7 can be reduced compared to, for example, a case in which intake air or burned gas is introduced into the crankcase internal space 7. Therefore, according to the intake device 100 of the internal combustion engine, it is possible to more reliably prevent ignition of hydrogen gas in the crankcase internal space 7 in the engine 1 that burns fuel containing hydrogen gas.

[0040] The intake system 100 of an internal combustion engine includes an intake passage 8 that guides intake air to the combustion chamber 4 of the engine 1, and an intake branch passage 11 that branches off at a predetermined position 8a in the intake passage 8. The oxygen enrichment section 10 is connected to the intake branch passage 11, and is supplied with intake air from the intake passage 8. With this configuration, the oxygen concentration in the crankcase internal space 7 can be further reduced by nitrogen separated in the oxygen enrichment section 10 using the intake air from the intake passage 8.

[0041] The intake device 100 of the internal combustion engine includes an exhaust passage 9 that guides burnt gas from the combustion chamber 4 of the engine 1, an EGR passage 25 that recirculates the burnt gas from the exhaust passage 9 to the intake passage 8, and an EGR branch passage 14 that branches off at a predetermined position 25a in the EGR passage 25. The oxygen enrichment section 10 is connected to the EGR branch passage 14, and may be supplied with burnt gas from the EGR passage 25. With this configuration, the oxygen concentration in the crankcase internal space 7 can be further reduced by nitrogen separated in the oxygen enrichment section 10 using the burnt gas from the EGR passage 25.

[0042] The intake device 100 of the internal combustion engine includes a turbocharger 30 provided upstream of a predetermined position 8a in an intake passage 8, a throttle valve 18 provided downstream of the predetermined position 8a in the intake passage 8, an EGR valve 26 provided downstream of a predetermined position 25a in an EGR passage 25, and an ECU 20 that controls the turbocharger 30, the throttle valve 18, and the EGR valve 26 based on the operating state of the engine 1. When the operating state of the engine 1 satisfies either a predetermined low load condition or a predetermined high load condition, the ECU 20 controls the turbocharger 30, the throttle valve 18, and the EGR valve 26 so as to increase the amount of burnt gas supplied from the EGR passage 25 to the oxygen enrichment section 10 compared to the amount of intake air supplied from the intake passage 8 to the oxygen enrichment section 10. With this configuration, the operating state of the engine 1 satisfying either a predetermined low load condition or a predetermined high load condition can be made to correspond to a state in which it is difficult to increase the supply of intake air from the intake passage 8 to the oxygen enrichment section 10 using the turbocharger 30. In this state, by increasing the amount of burnt gas supplied from the EGR passage 25 to the oxygen enrichment section 10 compared to the amount of intake air supplied from the intake passage 8 to the oxygen enrichment section 10, it is possible to stabilize the separation of nitrogen in the oxygen enrichment section 10.

[0043] In addition, the intake device 100 of the internal combustion engine can utilize the nitrogen-rich gas more effectively than, for example, a configuration in which the nitrogen-rich gas is returned to the exhaust passage. More specifically, by supplying the nitrogen-rich gas to the crankcase internal space 7, the hydrogen concentration in the crankcase internal space 7 can be reduced, and the nitrogen concentration can be increased above that of air, thereby relatively reducing the oxygen concentration. In addition, in the intake device 100 of the internal combustion engine, the oxygen enrichment unit 10 separates water vapor and nitrogen, and outputs the oxygen-rich gas including the water vapor. As a result, the nitrogen-rich gas, which is dry air, is supplied to the crankcase internal space 7, so that the humidity in the crankcase internal space 7 can be reduced, and moisture can be removed from the engine oil, thereby suppressing deterioration and emulsification of the engine oil. In addition, since the boost pressure or exhaust pressure is used, it is not necessary to add a separate ventilation device to the crankcase. On the other hand, since the oxygen-rich gas is supplied to the combustion chamber 4, the combustion speed is improved due to the increase in the oxygen concentration in the combustion chamber 4, which also leads to a decrease in the unburned hydrogen concentration during lean combustion of hydrogen gas. In addition, a reduction in NOx can be expected due to the reduced nitrogen concentration.

[0044] [Variations] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

[0045] In the above embodiment, the oxygen enrichment section 10 is connected to the intake branch passage 11 and is supplied with intake air from the intake passage 8, but this is not limited to the above. For example, air may be supplied to the oxygen enrichment section 10 from a blow-off valve or the like, or air may be supplied to the oxygen enrichment section 10 from outside air by providing an independent pipe separate from the intake passage 8. That's good.

[0046] In the above embodiment, the oxygen enrichment section 10 is connected to the EGR branch passage 14 and is supplied with burnt gas from the EGR passage 25, but this is not limited to this. For example, a pipe separate from the EGR passage 25 may be provided to supply burnt gas from the exhaust passage 9 to the oxygen enrichment section 10.

[0047] In the above embodiment, the ECU 20 is provided to control the turbocharger 30, the throttle valve 18, and the EGR valve 26 based on the operating state of the engine 1, but the present invention is not limited to this. For example, the amount of intake air supplied from the intake passage 8 to the oxygen enrichment section 10 and the amount of burnt gas supplied from the EGR passage 25 to the oxygen enrichment section 10 may be adjusted using a mechanical configuration such as an actuator that uses intake negative pressure, without using the ECU 20.

[0048] In the above embodiment, the injector 5 is configured to directly inject fuel into the combustion chamber 4 of each cylinder 2, but it may also be configured for port injection.

[0049] In the above embodiment, engine 1, which is a four-stroke reciprocating engine, is used as an example of an internal combustion engine, but other internal combustion engines may be used as long as they burn fuel containing hydrogen gas and it is desired to suppress the ignition of hydrogen gas inside the crankcase. [Explanation of symbols]

[0050] 1...engine (internal combustion engine), 4...combustion chamber, 7...crankcase internal space, 8...intake passage, 8a...predetermined position in intake passage, 25a...predetermined position in EGR passage, 9...exhaust passage, 10...oxygen enrichment section (nitrogen separation section), 20...ECU (controller), 10c...nitrogen outlet (nitrogen output section), 11...intake branch passage, 13...nitrogen passage, 14...EGR branch passage, 30...turbocharger (supercharger), 18...throttle valve, 25...EGR passage, 26...EGR valve, 100...intake device of internal combustion engine.

Claims

1. An intake system for an internal combustion engine that burns fuel containing hydrogen gas, comprising: A nitrogen separation section to which air or burned gas from the internal combustion engine is supplied; an intake system for an internal combustion engine, comprising: a nitrogen passage that connects an internal space of a crankcase of the internal combustion engine with a nitrogen output portion of the nitrogen separator.

2. an intake passage that introduces intake air into a combustion chamber of the internal combustion engine; an intake branch passage that branches at a predetermined position in the intake passage, 2. The intake system for an internal combustion engine according to claim 1, wherein the nitrogen separator is connected to the intake branch passage and receives the intake air from the intake passage.

3. an intake passage that introduces intake air into a combustion chamber of the internal combustion engine; an exhaust passage for guiding the burnt gas from the combustion chamber; an EGR passage for recirculating the burnt gas from the exhaust passage to the intake passage; an EGR branch passage that branches off at a predetermined position in the EGR passage, 3. The intake system for an internal combustion engine according to claim 1, wherein the nitrogen separation section is connected to the EGR branch passage and receives the burnt gas from the EGR passage.

4. a supercharger provided upstream of the predetermined position in the intake passage; and a throttle valve provided downstream of the predetermined position in the intake passage; an EGR valve provided downstream of the predetermined position in the EGR passage; a controller that controls the turbocharger, the throttle valve, and the EGR valve based on an operating state of the internal combustion engine, 4. The intake device of an internal combustion engine according to claim 3, wherein the controller controls the turbocharger, the throttle valve, and the EGR valve so as to increase the amount of the burnt gas supplied from the EGR passage to the nitrogen separation section compared to the amount of the intake air supplied from the intake passage to the nitrogen separation section when an operating state of the internal combustion engine satisfies either a predetermined low load condition or a predetermined high load condition.

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