Intake device for internal combustion engine

Abstract

To provide an intake device for an internal combustion engine capable of suppressing the back flow of fuel in an intake passage including an intake port in the internal combustion engine using hydrogen as fuel.SOLUTION: An intake device 100 for an internal combustion engine, as the intake device for a four-cycle internal combustion engine 1 using hydrogen as fuel, includes a pipe 8 including an intake port 3c at the downstream end of which an intake valve 3a of the internal combustion engine 1 is provided, an injector 11 provided in the pipe 8 for injecting the fuel to the intake port 3c, a variable valve 12 provided in the pipe 8 at its upstream side further than the injector 11, and an ECU 10 for controlling the variable valve 12 on the basis of the operating condition of the internal combustion engine 1. The ECU 10 controls the variable valve 12 so that its opening becomes smaller than in the fully opened state of the variable valve 12 and larger than in the fully closed state of the variable valve in a period of time from when the intake valve 3a is opened to when it is closed.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] 2. Description of the Related Art Conventionally, there has been known a port injection type internal combustion engine in which a fuel injection valve is provided in an intake port and fuel is injected into the intake port (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-058435 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, internal combustion engines that use hydrogen as fuel have been considered. Considering the calorific value per volume of hydrogen, for example, in order to generate the same amount of heat, it is necessary to make the volume of gas to be injected larger than that of other gaseous fuels. However, in a port-injected internal combustion engine that uses hydrogen as fuel, if the volume of fuel occupying the intake port is large, there is a possibility that fuel will flow back in the intake passage including the intake port, for example, during the overlap period when the intake valve is initially opened, or when the intake valve is closed, fuel that does not fit in the intake port will overflow upstream of the intake port.

[0005] An object of the present invention is to provide an intake device for an internal combustion engine that uses hydrogen as fuel and that is capable of suppressing backflow of fuel in an intake passage including an intake port. [Means for solving the problem]

[0006] One aspect of the present invention is an intake device for a four-stroke internal combustion engine that uses hydrogen as fuel, comprising an intake passage including an intake port at whose downstream end an intake valve of the internal combustion engine is provided, a fuel injection valve provided in the intake passage for injecting fuel toward the intake port, a variable valve provided in the intake passage upstream of the fuel injection valve, and a control unit that controls the variable valve based on the operating state of the internal combustion engine, wherein the control unit controls the variable valve so that the opening angle of the variable valve is smaller than that of a fully open state and larger than that of a fully closed state of the variable valve during the period from when the intake valve opens to when it closes.

[0007] In an intake device for an internal combustion engine according to one aspect of the present invention, a variable valve is controlled so that the opening degree of the intake valve during the period from when the intake valve opens to when it closes is smaller than the fully open state and larger than the fully closed state. As a result, the variable valve suppresses fuel blowback while allowing intake air to flow through the intake passage. Therefore, the intake device for an internal combustion engine according to one aspect of the present invention can suppress backflow of fuel in an intake passage including an intake port in an internal combustion engine that uses hydrogen as fuel.

[0008] Another aspect of the present invention is an intake device for an internal combustion engine that uses hydrogen as fuel, comprising an intake passage including an intake port having an intake valve for the internal combustion engine at its downstream end, a fuel injection valve provided in the intake passage for injecting fuel toward the intake port, a variable valve provided in the intake passage upstream of the fuel injection valve, and a control unit that controls the variable valve based on the operating state of the internal combustion engine, wherein the control unit controls the variable valve so that the variable valve is fully closed while the intake valve is closed.

[0009] In an intake device for an internal combustion engine according to another aspect of the present invention, the variable valve is controlled so that the variable valve is fully closed while the intake valve is closed. As a result, the variable valve prevents fuel remaining in the intake port from overflowing upstream of the intake passage including the intake port while the intake valve is closed. Therefore, the intake device for an internal combustion engine according to another aspect of the present invention can prevent backflow of fuel in the intake passage including the intake port in an internal combustion engine that uses hydrogen as fuel.

[0010] In one embodiment, the control unit may control the variable valve so that the variable valve is in a fully open state during the period from when the intake valve opens to when the fuel injection valve starts injection. In this case, the variable valve can allow a maximum flow of intake air through the intake passage until the fuel injection valve starts injection.

[0011] In one embodiment, when the fuel injection valve starts injection while the intake valve is closed and ends injection after the intake valve is opened, the control unit may control the variable valve so that the variable valve is fully closed during the period from when the intake valve opens to when the fuel injection valve ends injection. In this case, since the variable valve is fully closed during the period from when the intake valve opens to when the fuel injection valve ends injection, it is possible to prevent fuel injected by the fuel injection valve into the intake port from overflowing upstream of the intake passage including the intake port. Effect of the Invention

[0012] According to the present invention, it is possible to suppress backflow of fuel in an intake passage including an intake port in an internal combustion engine that uses hydrogen as fuel. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of an internal combustion engine equipped with an intake device for an internal combustion engine according to an embodiment; [Diagram 2] 2 is a schematic cross-sectional view taken along line XX in FIG. 1 according to a first operation example of an intake device for an internal combustion engine. [Diagram 3] 2 is a schematic cross-sectional view taken along line XX in FIG. 1, showing a second operation example of the intake device of the internal combustion engine. [Figure 4] 2 is a schematic cross-sectional view taken along line XX in FIG. 1, showing a third operation example of an intake device for an internal combustion engine. [Diagram 5] 1 according to a fourth operation example of an intake device for an internal combustion engine. FIG. [Figure 6] 1 according to a fifth operation example of an intake device for an internal combustion engine. FIG. [Figure 7] 1 according to a sixth operation example of an intake device for an internal combustion engine. FIG. [Figure 8] 2 is a flowchart showing an example of processing by an ECU in FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] FIG. 1 is a schematic diagram of an internal combustion engine equipped with an intake device for an internal combustion engine according to an embodiment. As shown in FIG. 1, an intake device 100 for an internal combustion engine according to the embodiment is applied to an internal combustion engine 1. The internal combustion engine 1 is configured as a hydrogen engine that operates using hydrogen gas (hereinafter simply referred to as "hydrogen") as fuel. The internal combustion engine 1 is configured as, for example, a four-stroke port injection type reciprocating engine. The internal combustion engine 1 has a plurality of (for example, four) cylinders 2.

[0016] Fig. 2 is a schematic cross-sectional view taken along line XX in Fig. 1, showing a first operation example of an intake device for an internal combustion engine. As shown in Figs. 1 and 2, the internal combustion engine 1 has a cylinder head 3 including an intake valve 3a and an exhaust valve 3b, and a piston 5 provided in a cylinder 4. In each cylinder 2, a combustion chamber 6 is defined by the cylinder head 3, the cylinder 4, and the piston 5. The internal combustion engine 1 takes in air and hydrogen via the intake valve 3a, burns the hydrogen in the combustion chamber 6, and exhausts exhaust gas produced by the combustion via the exhaust valve 3b.

[0017] An intake port 3c and an exhaust port 3d are formed in the cylinder head 3 so as to communicate with the combustion chamber 6. An intake valve 3a is provided at the downstream end of the intake port 3c. The intake port 3c forms a part of an intake passage 7 of the internal combustion engine 1. That is, the intake device 100 of the internal combustion engine is provided with the intake passage 7 including the intake port 3c at the downstream end of which the intake valve 3a is provided.

[0018] A pipe 8 after branching from the intake manifold is connected to the upstream side of the intake port 3c. Here, one pipe 8 is connected to each intake port 3c. The pipe 8 after branching from the intake manifold forms a part of the intake passage 7 of the internal combustion engine 1.

[0019] In the intake passage 7, for example, an air cleaner 16, a compressor 31 of a turbocharger 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.

[0020] The internal combustion engine 1 includes an EGR unit 24 that recirculates a portion of burned gas generated in the combustion chamber 6 to the intake passage 7 as EGR (exhaust gas recirculation) gas. The EGR unit 24 includes an EGR passage 25 provided to connect the intake passage 7 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.

[0021] The EGR passage 25 is a passage for recirculating burnt gas (EGR gas) from the exhaust passage 9 to the intake passage 7. The EGR valve 26 is a valve for adjusting the amount of EGR gas recirculated from the exhaust passage 9 to the intake passage 7. 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.

[0022] The internal combustion engine 1 includes a plurality of injectors (fuel injection valves) 11 that inject fuel toward the intake port 3c. The injectors 11 here are attached near the intake port 3c of the pipe 8 so that their tips are exposed inside the pipe 8 after branching from the intake manifold. That is, the intake device 100 of the internal combustion engine includes the injectors 11 that are provided in the intake passage 7 and inject fuel toward the intake port 3c. The injectors 11 may be attached to the cylinder head 3 so that they are exposed inside the intake port 3c. Each of the multiple injectors 11 is attached to, for example, a rail (not shown), and hydrogen is supplied from a fuel tank (not shown) via the rail.

[0023] A variable valve 12 is provided inside the pipe 8 after the branching of the intake manifold to suppress the fuel injected by the injector 11 from flowing back to the upstream side of the pipe 8. The variable valve 12 is provided, for example, inside the pipe 8, upstream of the injector 11, so as to be able to adjust the flow rate of gas that can flow through the pipe 8. That is, the intake device 100 of the internal combustion engine includes a variable valve 12 provided upstream of the injector 11 in the intake passage 7. The variable valve 12 is provided, for example, in each of the two pipes 8 in one cylinder 2.

[0024] As an example, an electronically controlled butterfly valve can be used as the variable valve 12. A pair of the variable valves 12 may be arranged side by side, sandwiching the center of a predetermined cross section of the tube 8. The rotation axis of the variable valve 12 may be arranged along a predetermined cross section that intersects with the extension direction of the tube 8. The pair of variable valves 12 adjust the flow rate of gas that can flow through the tube 8, for example, by rotating flat valve bodies around the rotation axis in opposite directions. The variable valve 12 has a fully open state and a fully closed state.

[0025] The fully open state of variable valve 12 is the state in which the flow rate of gas that can flow through pipe 8 is at its maximum, and is the state in which the flow of air flowing through pipe 8 during the intake stroke is least impeded. The fully open state of variable valve 12 may be, for example, the state in which, assuming that the valve body of variable valve 12 does not exist, the flow line of air flowing through pipe 8 during the intake stroke, the valve body of variable valve 12 is parallel to the flow line when viewed in the axial direction of the rotation shaft of variable valve 12 (see FIG. 6).

[0026] The fully closed state of variable valve 12 is a state in which the flow rate of gas that can flow through pipe 8 is the smallest, and is a state in which the flow of air flowing through pipe 8 is most impeded. "A state in which the flow rate of gas that can flow through pipe 8 is the smallest" may be a state in which air is allowed to flow through pipe 8 at a flow rate equivalent to idling of internal combustion engine 1, or a state in which gas does not substantially flow through pipe 8. The fully closed state of variable valve 12 may be, for example, a state in which the valve element of variable valve 12 is approximately perpendicular to the extension direction of pipe 8 when viewed from the axial direction of the rotation shaft of variable valve 12 (see FIGS. 2 to 4).

[0027] The variable valve 12 is configured to be adjustable within a range of an opening degree equal to or greater than the fully closed state and equal to or less than the fully open state. The opening degree of the variable valve 12 can be adjusted to an opening degree smaller than the fully open state and larger than the fully closed state (see Figs. 5 and 7). "An opening degree smaller than the fully open state and larger than the fully closed state" means an opening degree that allows air at a flow rate according to the current operating state of the internal combustion engine 1 to flow through the pipe 8 and suppresses the fuel injected by the injector 11 from flowing back to the upstream side of the pipe 8. The opening degree of the variable valve 12 may be continuously adjustable within a range of an opening degree smaller than the fully open state and larger than the fully closed state, or may be adjustable in multiple finite steps.

[0028] An intake device 100 for an internal combustion engine includes an ECU (Electronic Control Unit) 10. The ECU 10 is an electronic control unit that controls the internal combustion engine 1. The ECU 10 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 10 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 10 may be composed of multiple electronic units.

[0029] An engine speed sensor 21 and an intake air amount sensor 22 are connected to the ECU 10 as sensors for acquiring the operating state of the internal combustion engine 1. The engine speed sensor 21 is a known detector that detects the engine speed of the internal combustion engine 1. The engine speed sensor 21 outputs a detection signal of the detected engine speed to the ECU 10. The intake air amount sensor 22 is a known detector that is provided in the intake passage 7 of the internal combustion engine 1 and detects a detection value related to the intake air amount of the internal combustion engine 1. The intake air amount sensor 22 outputs a detection signal of the intake air amount of the internal combustion engine 1 to the ECU 10.

[0030] A processing example of the ECU 10 and an operation example of the intake device 100 of an internal combustion engine will be described with reference to Figs. 2 to 8. Figs. 2 to 8 are schematic cross-sectional views taken along line XX in Fig. 1, showing first to sixth operation examples of the intake device of an internal combustion engine, respectively. Fig. 8 is a flowchart showing a processing example of the ECU in Fig. 1. The processing in Fig. 8 is executed, for example, while the internal combustion engine 1 is in operation.

[0031] 8, the ECU 10 acquires the operating state of the internal combustion engine 1 in S10. The ECU 10 acquires the engine speed based on the detection result of the engine speed sensor 21. The ECU 10 acquires the intake air amount of the internal combustion engine 1 based on the detection result of the intake air amount sensor 22. The ECU 10 controls the injector 11 based on the operating state of the internal combustion engine 1. The ECU 10 calculates the fuel injection amount and the fuel injection period by the injector 11 based on, for example, the engine speed and the intake air amount by a known method.

[0032] The ECU 10 controls the variable valve 12 based on the operating state of the internal combustion engine 1 (S11 to S19). When S11 is YES, the processes of S12 to S17 correspond to the case where the fuel injection period by the injector 11 exists outside the opening period of the intake valve 3a, and when S11 is NO, the processes of S18 and S19 correspond to the case where the fuel injection period by the injector 11 exists within the opening period of the intake valve 3a.

[0033] Specifically, in S11, the ECU 10 judges whether the intake valve 3a is closed or not. The term "the intake valve is closed" may refer to a state in which the opening amount of the intake valve 3a is equal to or less than a predetermined valve-closing judgment value. The term "the intake valve is closed" may refer to a state in which the opening amount of the intake valve 3a is zero. The opening amount of the intake valve 3a may refer to the lift amount of the intake valve 3a from a state in which the intake valve 3a is seated on a valve seat. For example, when the opening amount of the intake valve 3a is equal to or less than a predetermined valve-opening judgment value, the ECU 10 judges that the intake valve 3a is closed. When the opening amount of the intake valve 3a is greater than the predetermined valve-opening judgment value, the ECU 10 judges that the intake valve 3a is not closed (open).

[0034] If it is determined that the intake valve 3a is closed (S11: YES), the ECU 10 controls the variable valve 12 to be fully closed in S12. As a result, the variable valve 12 is fully closed when the intake valve 3a is closed, as shown in Fig. 2 for example. By fully closing the variable valve 12, even if residual hydrogen F1 remains in the intake port 3c, for example, the residual hydrogen F1 is prevented from overflowing upstream of the intake passage 7 including the intake port 3c.

[0035] If it is determined that the intake valve 3a is not closed (is open) (S11: NO), the ECU 10 proceeds to processing in S18, which will be described later.

[0036] In S13, the ECU 10 determines whether or not fuel injection has started. The ECU 10 may determine whether or not fuel injection has started based on the presence or absence of a valve-opening signal to the injector 11, for example.

[0037] When it is determined that fuel injection has not started while the intake valve 3a is closed (S13: NO), the ECU 10 returns to the process of S11. If the intake valve 3a remains closed, the ECU 10 waits by repeating the processes of S11 to S13 until fuel injection starts. If fuel injection has not started while the intake valve 3a is closed and the intake valve 3a opens, the ECU 10 proceeds to the process of S18, which will be described later.

[0038] If it is determined that fuel injection has started while the intake valve 3a is closed (S13: YES), the ECU 10 maintains the fully closed state of the variable valve 12 and determines in S14 whether the intake valve 3a is open or not.

[0039] When it is determined that the intake valve 3a is not open (the intake valve 3a is kept closed) (S14: NO), the ECU 10 returns to the process of S14. The ECU 10 repeats the process of S14 until the intake valve 3a opens, and waits while controlling the variable valve 12 to keep the variable valve 12 in a fully closed state. In other words, the ECU 10 controls the variable valve 12 so that the variable valve 12 is in a fully closed state while the intake valve 3a is closed.

[0040] In the internal combustion engine 1 using hydrogen as fuel, the volume of hydrogen in a gaseous state required to generate the same amount of heat tends to be larger than that required for other fuels. Therefore, for example, in an operating state in which the engine speed is low to medium and the intake amount is medium to full load, fuel injection from the injector 11 may be started while the intake valve 3a is closed. In this case, as shown in FIG. 3, when fuel injection from the injector 11 is started while the intake valve 3a is closed, the variable valve 12 is fully closed. By maintaining the fully closed state of the variable valve 12, even if the proportion of hydrogen F2 injected from the injector 11 in the intake port 3c increases while the intake valve 3a is closed, the hydrogen F2 is prevented from overflowing upstream of the pipe 8 including the intake port 3c.

[0041] When it is determined that the intake valve 3a is opened (S14: YES), the ECU 10 controls the variable valve to be in a fully closed state in S15. In S16, the ECU 10 determines whether or not the fuel injection has ended. For example, the ECU 10 may determine whether or not the fuel injection has ended based on the presence or absence of a valve opening signal to the injector 11.

[0042] When it is determined that fuel injection has not ended (S16: NO), the ECU 10 returns to the process of S15. The ECU 10 repeats the process of S15 until fuel injection is ended, and maintains the variable valve 12 in the fully closed state in a state in which the intake valve 3a is open but fuel injection continues. In other words, when the injector 11 starts injection while the intake valve 3a is closed and ends injection after the intake valve 3a opens, the ECU 10 controls the variable valve 12 so that the variable valve 12 is in the fully closed state during the period from when the intake valve 3a opens to when the injector 11 ends injection.

[0043] As a result, when the intake valve 3a begins to open, the variable valve 12 is fully closed, as shown in Fig. 4 for example. By maintaining the fully closed state of the variable valve 12, even if, for example, the exhaust valve 3b is open and overlap exists, and blowback occurs through the open intake valve 3a, the hydrogen F3 that starts to be injected from the injector 11 while the intake valve 3a is closed is prevented from overflowing upstream of the intake passage 7 including the intake port 3c.

[0044] When it is determined that the fuel injection has ended (S16: YES), the ECU 10 controls the variable valve 12 in S17 so that the opening degree is smaller than that of the fully open state and larger than that of the fully closed state. As a result, for example, as shown in FIG. 5, when the intake valve 3a is open, the variable valve 12 is opened to an opening degree smaller than that of the fully open state and larger than that of the fully closed state. This allows air to flow through the pipe 8 at a flow rate according to the current operating state of the internal combustion engine 1, and suppresses the backflow of the fuel injected by the injector 11 to the upstream side of the pipe 8 up to S16. Therefore, even if, for example, the exhaust valve 3b is open and overlap exists, and the blowback F4 occurs through the open intake valve 3a, the hydrogen is suppressed from overflowing to the upstream side of the intake passage 7 including the intake port 3c. The ECU 10 may then end the process of FIG. 8, and repeat the process of FIG. 8 again, for example, after the intake valve 3a that is currently open is closed. In other words, the ECU 10 controls the variable valve 12 so that the opening degree of the variable valve 12 during the period from when the intake valve 3a opens to when it closes is smaller than the opening degree of the variable valve 12 in the fully open state and larger than the opening degree of the variable valve 12 in the fully closed state.

[0045] On the other hand, if it is determined after the processing of S10 that the intake valve 3a is not closed (the intake valve 3a is open) (S11: NO), the ECU 10 determines in S18 whether or not fuel injection has started.

[0046] For example, when it is determined that fuel injection has not started while the intake valve 3a is open after there has been no fuel injection while the intake valve 3a is closed (S18: NO), the ECU 10 controls the variable valve 12 to be in a fully open state in S19. As a result, the variable valve 12 is in a fully open state in a state in which fuel injection has not started while the intake valve 3a is open, as shown in FIG. 6 for example. By setting the variable valve 12 in a fully open state, for example, when there is little risk of hydrogen backflow, it becomes easier to exert the overlap scavenging effect, and the decrease in intake efficiency can be suppressed. After that, the ECU 10 returns to the process of S18. The ECU 10 waits by repeating the processes of S18 to S19 until fuel injection starts while the intake valve 3a is open. That is, the ECU 10 controls the variable valve 12 to be in a fully open state during the period from when the intake valve 3a opens to when the injector 11 starts injection.

[0047] For example, when it is determined that fuel injection has started after the intake valve 3a is opened after there has been no fuel injection while the intake valve 3a is closed (S18: YES), the ECU 10 proceeds to the process of S17. In S17, the ECU 10 controls the variable valve 12 so that the opening degree is smaller than the fully open state and larger than the fully closed state. As a result, for example, as shown in FIG. 7, when the intake valve 3a is open and fuel injection has started, the variable valve 12 is opened to an opening degree smaller than the fully open state and larger than the fully closed state. This allows air to flow through the pipe 8 at a flow rate according to the current operating state of the internal combustion engine 1, and suppresses the backflow of fuel injected by the injector 11 to the upstream side of the pipe 8 up to S16. Therefore, for example, even if the exhaust valve 3b is open and there is an overlap, and blowback F5 occurs through the open intake valve 3a, hydrogen is suppressed from overflowing to the upstream side of the intake passage 7 including the intake port 3c. The ECU 10 may then end the process of Fig. 8 and, for example, repeat the process of Fig. 8 again after the currently open intake valve 3a closes. In other words, the ECU 10 controls the variable valve 12 so that the opening degree of the variable valve 12 is smaller than that of the fully open state of the variable valve 12 and larger than that of the fully closed state of the variable valve 12 during the period from when the intake valve 3a opens to when it closes.

[0048] [Action and Effects] In the intake system 100 for an internal combustion engine as described above, the variable valve 12 is controlled so that the opening degree of the intake valve 3a during the period from when it opens to when it closes is smaller than the fully open state and larger than the fully closed state. In this way, the variable valve 12 suppresses the blow-back of fuel while allowing the flow of intake air in the intake passage 7. Therefore, the intake system 100 for an internal combustion engine can suppress the backflow of fuel in the intake passage 7 including the intake port 3c in the internal combustion engine 1 that uses hydrogen as fuel.

[0049] In the intake device 100 for an internal combustion engine, the variable valve 12 is controlled so that the variable valve 12 is fully closed while the intake valve 3a is closed. In this way, the variable valve 12 prevents fuel remaining in the intake port 3c from overflowing upstream of the intake passage 7 including the intake port 3c while the intake valve 3a is closed. The intake device 100 for an internal combustion engine can prevent backflow of fuel in the intake passage 7 including the intake port 3c in an internal combustion engine 1 that uses hydrogen as fuel.

[0050] In the intake system 100 of an internal combustion engine, the ECU 10 controls the variable valve 12 so that the variable valve 12 is fully open during the period from when the intake valve 3a opens until when the injector 11 starts injection. This allows the variable valve 12 to allow maximum flow of intake air through the intake passage 7 until when the injector 11 starts injection.

[0051] In the intake system 100 of an internal combustion engine, when the injector 11 starts injection while the intake valve 3a is closed and ends injection after the intake valve 3a is opened, the ECU 10 controls the variable valve 12 so that the variable valve 12 is fully closed during the period from when the intake valve 3a opens to when the injector 11 ends injection. This causes the variable valve 12 to be fully closed during the period from when the intake valve 3a opens to when the injector 11 ends injection, thereby preventing the fuel injected by the injector 11 into the intake port 3c from overflowing upstream of the intake passage 7 including the intake port 3c.

[0052] [Variations] Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0053] In the above embodiment, the internal combustion engine 1 is provided with two intake ports 3c and pipes 8 for each cylinder 2, and each of the two pipes 8 is provided with a variable valve 12, but this is not limited to the example. The internal combustion engine 1 may be provided with one intake port 3c and pipe 8 for each cylinder 2, and each pipe 8 may be provided with a variable valve 12.

[0054] The constituent elements of various aspects of the present invention will be described below. <Invention 1> An intake system for a four-stroke internal combustion engine that uses hydrogen as fuel, comprising: an intake passage including an intake port having an intake valve of the internal combustion engine provided at a downstream end thereof; a fuel injection valve provided in the intake passage and configured to inject the fuel toward the intake port; a variable valve provided in the intake passage upstream of the fuel injection valve; a control unit that controls the variable valve based on an operating state of the internal combustion engine, The control unit controls the variable valve so that the opening angle of the variable valve during the period from when the intake valve opens to when it closes is smaller than that of a fully open state of the variable valve and larger than that of a fully closed state of the variable valve. <Invention 2> An intake system for an internal combustion engine that uses hydrogen as fuel, comprising: an intake passage including an intake port having an intake valve of the internal combustion engine provided at a downstream end thereof; a fuel injection valve provided in the intake passage and configured to inject the fuel toward the intake port; a variable valve provided in the intake passage upstream of the fuel injection valve; a control unit that controls the variable valve based on an operating state of the internal combustion engine, The control unit controls the variable valve so that the variable valve is fully closed while the intake valve is closed. <Invention 3> 3. An intake device for an internal combustion engine as described in claim 1 or 2, wherein the control unit controls the variable valve so that the variable valve is fully open during the period from when the intake valve opens to when the fuel injection valve starts injection. <Invention 4> The control unit controls the variable valve so that, when the fuel injection valve starts injection while the intake valve is closed and ends injection after the intake valve opens, the variable valve is fully closed during the period from when the intake valve opens to when the fuel injection valve ends injection. An intake device for an internal combustion engine as described in any one of Inventions 1 to 3. [Explanation of symbols]

[0055] 1...internal combustion engine, 3a...intake valve, 3c...intake port, 7...intake passage, 8...pipe (intake passage), 10...ECU (control unit), 11...injector (fuel injection valve), 12...variable valve, 100...intake device of internal combustion engine.

Claims

1. An intake system for a four-stroke internal combustion engine that uses hydrogen as fuel, comprising: an intake passage including an intake port having an intake valve of the internal combustion engine provided at a downstream end thereof; a fuel injection valve provided in the intake passage and configured to inject the fuel toward the intake port; a variable valve provided in the intake passage upstream of the fuel injection valve; a control unit that controls the variable valve based on an operating state of the internal combustion engine, The control unit controls the variable valve so that the opening angle of the variable valve during the period from when the intake valve opens to when it closes is smaller than that of a fully open state of the variable valve and larger than that of a fully closed state of the variable valve.

2. An intake system for an internal combustion engine that uses hydrogen as fuel, comprising: an intake passage including an intake port having an intake valve of the internal combustion engine provided at a downstream end thereof; a fuel injection valve provided in the intake passage and configured to inject the fuel toward the intake port; a variable valve provided in the intake passage upstream of the fuel injection valve; a control unit that controls the variable valve based on an operating state of the internal combustion engine, The control unit controls the variable valve so that the variable valve is fully closed while the intake valve is closed.

3. 3. The intake device of an internal combustion engine according to claim 1, wherein the control unit controls the variable valve so that the variable valve is in a fully open state during a period from when the intake valve opens to when the fuel injection valve starts injection.

4. 3. The intake device of an internal combustion engine according to claim 1, wherein the control unit controls the variable valve so that, when the fuel injection valve starts injection while the intake valve is closed and ends injection after the intake valve opens, the variable valve is fully closed during the period from when the intake valve opens to when the fuel injection valve ends injection.

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