Intake device for internal combustion engine

Abstract

To provide an intake device for an internal combustion engine capable of efficiently supplying air into cylinders of the internal combustion engine using hydrogen as fuel.SOLUTION: An intake device 100 for an internal combustion engine is the intake device for a four-cycle internal combustion engine 1 using hydrogen as fuel. The intake device 100 for the internal combustion engine includes a first intake passage 8x provided in one cylinder of the internal combustion engine 1, and including a first intake port 3cx at the downstream end of which a first intake valve 3ax is provided, a second intake passage 8y provided in the one cylinder, and including a second intake port 3cy at the downstream end of which a second intake valve 3ay is provided, and a main injector 11x provided in the first intake passage 8x for injecting the fuel to the first intake port 3cx. An opening timing for the first intake valve 3ax is later than an opening timing for the second intake valve 3ay.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, the volume of gas to be injected must be larger than that of other gaseous fuels. In a port-injection internal combustion engine that uses hydrogen as fuel, if the volume of fuel occupying the intake port is large, the flow of air in the intake port is likely to be obstructed. As a result, there is a possibility that air cannot be sufficiently supplied to the cylinders of the internal combustion engine.

[0005] An object of the present invention is to provide an intake system for an internal combustion engine that uses hydrogen as fuel and that can efficiently supply air into the cylinders. [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: a first intake passage provided in one cylinder of the internal combustion engine and including a first intake port with a first intake valve provided at its downstream end; a second intake passage provided in the one cylinder and including a second intake port with a second intake valve provided at its downstream end; and a main fuel injection valve provided in the first intake passage and injecting fuel toward the first intake port, wherein the opening timing of the first intake valve is retarded relative to the opening timing of the second intake valve.

[0007] In an intake device for an internal combustion engine according to one aspect of the present invention, a first intake passage in which a main fuel injection valve is provided functions as a passage that mainly supplies fuel into a cylinder. A second intake passage functions as a passage that mainly supplies air into a cylinder. In this way, air is supplied into a cylinder using a second intake passage separate from the first intake passage that supplies fuel into the cylinder, so that the flow of air is not hindered by fuel and air can be efficiently supplied into the cylinder. Therefore, according to the intake device for an internal combustion engine according to one aspect of the present invention, air can be efficiently supplied into a cylinder in an internal combustion engine that uses hydrogen as fuel.

[0008] Here, in a port injection type internal combustion engine that injects hydrogen as fuel toward an intake port, it is also desired to suppress the occurrence of abnormal ignition (backfire) of hydrogen during the intake stroke. In this regard, the opening timing of the first intake valve is retarded from the opening timing of the second intake valve, so that air from the second intake passage is supplied into the cylinder before fuel from the first intake passage. The air supplied into the cylinder first cools the inside of the cylinder before fuel is supplied into the cylinder, so that a sudden increase in temperature of hydrogen as fuel is suppressed. This makes it possible to suppress the occurrence of abnormal ignition of hydrogen during the intake stroke. In this way, according to the intake device for an internal combustion engine according to one aspect of the present invention, in an internal combustion engine that uses hydrogen as fuel, air can be efficiently supplied into the cylinder while suppressing the occurrence of abnormal ignition of hydrogen during the intake stroke.

[0009] In one embodiment, an intake device for an internal combustion engine includes a variable valve provided upstream of a main fuel injection valve in a first intake passage, and a control unit that controls the main fuel injection valve and the variable valve based on an operating state of the internal combustion engine, and the control unit may control the main fuel injection valve and the variable valve so that the variable valve is fully closed during injection from the main fuel injection valve while the first intake valve is open. In this case, since the variable valve is fully closed during injection from the main fuel injection valve, it is possible to prevent fuel injected by the main fuel injection valve from overflowing upstream of the first intake passage.

[0010] In one embodiment, the control unit may control the main fuel injection valve and the variable valve so that, during a period in which the first intake valve is open, the variable valve opens to a larger degree than when it is fully closed after the main fuel injection valve finishes injection. In this case, the variable valve that was fully closed during injection from the main fuel injection valve allows air to flow after the main fuel injection valve finishes injection. Therefore, the fuel injected by the main fuel injection valve can be pushed into the cylinder by the flowing air.

[0011] In one embodiment, the intake system of the internal combustion engine includes an auxiliary fuel injection valve provided in the second intake passage and injecting fuel toward the second intake port, and the control unit may control the auxiliary fuel injection valve so that the auxiliary fuel injection valve injects fuel when the main fuel injection valve injects fuel at the maximum main injection amount during a period when the first intake valve and the second intake valve are open based on an operating state of the internal combustion engine. In this case, for example, when the amount of fuel required for high load operation of the internal combustion engine is greater than the maximum main injection amount of the main fuel injection valve, the shortage can be made up for by the fuel injected by the auxiliary fuel injection valve. Effect of the Invention

[0012] According to the present invention, air can be efficiently supplied into the cylinders of 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 diagram of the main part of FIG. 1 according to a first operation example of the intake device of the internal combustion engine. [Diagram 3] 1 according to a second operation example of the intake device of the internal combustion engine. FIG. [Figure 4] 1 according to a third operation example of an intake device for an internal combustion engine. FIG. [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] 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 diagram of the main parts of Fig. 1 relating to a first operation example of an intake device of 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 (not shown) 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. The internal combustion engine 1 takes in air and hydrogen via the intake valve 3a, combusts the hydrogen in the combustion chamber 6, and exhausts exhaust gas generated by the combustion via the exhaust valve 3b.

[0017] An intake port 3c and an exhaust port (not shown) 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.

[0018] In the cylinder head 3, a first intake port 3cx and a second intake port 3cy are formed as the intake ports 3c in each cylinder 2. A first intake valve 3ax is provided at the downstream end of the first intake port 3cx. A second intake valve 3ay is provided at the downstream end of the second intake port 3cy.

[0019] An intake passage 8 is connected to the upstream side of the intake port 3c. The intake passage 8 refers to a portion of the intake manifold that corresponds to one cylinder 2 after branching. The intake passage 8 forms a part of the intake passage 7. The intake passage 7 refers to the entire intake system of the internal combustion engine 1.

[0020] 2, the intake passage 8 here has a first intake passage 8x corresponding to the first intake port 3cx and a second intake passage 8y corresponding to the second intake port 3cy. The first intake passage 8x is connected to the upstream side of the first intake port 3cx. The second intake passage 8y is connected to the upstream side of the second intake port 3cy. That is, the intake device 100 of the internal combustion engine includes a first intake passage 8x provided in one cylinder 2 of the internal combustion engine 1 and including a first intake port 3cx with a first intake valve 3ax provided at its downstream end, and a second intake passage 8y provided in the one cylinder 2 and including a second intake port 3cy with a second intake valve 3ay provided at its downstream end.

[0021] The internal combustion engine 1 includes an injector 11 that injects fuel toward the intake port 3c. The internal combustion engine 1 includes, as the injector 11, a main injector 11x that is attached near the first intake port 3cx so that its tip is exposed inside the first intake passage 8x, and an auxiliary injector 11y that is attached near the second intake port 3cy so that its tip is exposed inside the second intake passage 8y. That is, the intake device 100 of the internal combustion engine includes a main injector 11x that is provided in the first intake passage 8x and that injects fuel toward the first intake port 3cx, and an auxiliary injector 11y that is provided in the second intake passage 8y and that injects fuel toward the second intake port 3cy. Each of the injectors 11 of each cylinder 2 is attached, for example, to a rail (not shown), and hydrogen is supplied from a fuel tank (not shown) through the rail. The injector 11 may be attached to the cylinder head 3 so that it is exposed inside the intake port 3c.

[0022] The first intake passage 8x and the first intake port 3cx are passages for mainly supplying fuel into the cylinder 2. The main injector 11x has a larger capacity (maximum main injection amount) than the auxiliary injector 11y. The main injector 11x has a capacity capable of injecting fuel required, for example, for a low load of the internal combustion engine 1 and a part of the low load side of the medium load of the internal combustion engine 1.

[0023] The second intake passage 8y and the second intake port 3cy are passages for mainly supplying air into the cylinder 2. The auxiliary injector 11y has a capacity capable of injecting fuel that exceeds the capacity of the main injector 11x and is insufficient for fuel required, for example, for the high load of the internal combustion engine 1 and the remaining portion on the high load side of the medium load of the internal combustion engine 1.

[0024] The opening timing of the first intake valve 3ax is retarded relative to the opening timing of the second intake valve 3ay. For example, the cam profile of the first intake valve 3ax has only a phase difference on the retard side of the cam operating angle with respect to the cam profile of the second intake valve 3ay. The cam profile of the first intake valve 3ax only needs to have at least a retarded valve opening timing compared to the cam profile of the second intake valve 3ay, and the cam operating angle or cam lift may be different.

[0025] Since the opening timing of the first intake valve 3ax is retarded from the opening timing of the second intake valve 3ay, only the second intake valve 3ay opens first. At this time, for example, if the auxiliary injector 11y is not made to inject fuel, only air is supplied into the cylinder 2 before fuel is supplied. This makes it possible to lower the temperature inside the cylinder 2 by the air before fuel is supplied into the cylinder 2.

[0026] The first intake passage 8x and the second intake passage 8y are independent from each other from the upstream end to the downstream end. The first intake passage 8x and the second intake passage 8y have, for example, the same extension length from the upstream end to the downstream end. The extension length of the first intake passage 8x can be, for example, a length such that the volume from the upstream end of the first intake passage 8x to the downstream end of the first intake port 3cx is larger than the volume of fuel injected by the main injector 11x during the period when the first intake valve 3ax is closed. The cross-sectional area of ​​the first intake passage 8x may be determined, for example, according to the design of the output characteristics of the internal combustion engine 1.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] A variable valve 12 is provided inside the first intake passage 8x to suppress the fuel injected by the main injector 11x from flowing back to the upstream side of the first intake passage 8x. The variable valve 12 is provided, for example, inside the first intake passage 8x, upstream of the main injector 11x, so as to be able to adjust the flow rate of gas that can flow through the first intake passage 8x. That is, the intake device 100 for an internal combustion engine includes a variable valve 12 provided upstream of the main injector 11x in the first intake passage 8x.

[0031] The variable valve 12 is disposed, for example, at the upstream end of the first intake passage 8x. The variable valve 12 may be located along the first intake passage 8x such that the volume from the variable valve 12 to the downstream end of the first intake port 3cx is larger than the volume of fuel injected by the main injector 11x while the first intake valve 3ax is closed.

[0032] As an example, an electronically controlled butterfly valve can be used as the variable valve 12. The variable valve 12 has, for example, a valve body having a shape corresponding to the cross-sectional shape (e.g., circular) of the first intake passage 8x. The rotation axis of the variable valve 12 may be provided so that the cross-sectional shape of the first intake passage 8x and the valve body are concentric. The variable valve 12 adjusts the flow rate of gas that can flow through the first intake passage 8x, for example, by rotating a flat valve body about the rotation axis. The variable valve 12 has a fully open state and a fully closed state.

[0033] The fully open state of variable valve 12 is a state in which the flow rate of gas that can flow through the first intake passage 8x is at its maximum, and is a state in which the flow of air flowing through the first intake passage 8x during the intake stroke is least impeded. The fully open state of variable valve 12 may be, for example, a state in which, assuming that there is no valve body of variable valve 12, the flow line of air flowing through the first intake passage 8x 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. 4).

[0034] The fully closed state of the variable valve 12 is a state in which the flow rate of gas that can flow through the first intake passage 8x is the smallest, and is a state in which the flow of air flowing through the first intake passage 8x is most impeded. "A state in which the flow rate of gas that can flow through the first intake passage 8x is the smallest" may also be a state in which gas does not substantially flow through the first intake passage 8x. The fully closed state of the variable valve 12 may be, for example, a state in which the valve element of the variable valve 12 is approximately perpendicular to the extension direction of the first intake passage 8x when viewed from the axial direction of the rotation shaft of the variable valve 12 (see Figures 2, 3, and 5).

[0035] 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 FIG. 6). "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 intake passage 8 and suppresses the fuel injected by the main injector 11x from flowing back to the upstream side of the first intake passage 8x. 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.

[0036] 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.

[0037] 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.

[0038] 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 Fig. 2 to Fig. 7. Fig. 2 to Fig. 7 are schematic diagrams of the main parts of Fig. 1 relating to first to fifth operation examples of the intake device of an internal combustion engine, respectively. Fig. 7 is a flowchart showing a processing example of the ECU of Fig. 1. The processing of Fig. 7 is executed, for example, while the internal combustion engine 1 is in operation.

[0039] 7, in S10, the ECU 10 acquires the operating state and the total fuel injection amount of the internal combustion engine 1. The ECU 10 acquires the engine speed based on the detection result of the engine speed sensor 21. The ECU 10 acquires the intake amount of the internal combustion engine 1 based on the detection result of the intake amount sensor 22. The ECU 10 controls the injectors 11 (the main injector 11x and the auxiliary injector 11y) based on the operating state of the internal combustion engine 1.

[0040] The ECU 10 calculates the fuel injection amount by the injector 11 (the total fuel injection amount by both the main injector 11x and the auxiliary injector 11y) by a known method based on, for example, the engine speed and the intake amount. When the total fuel injection amount is equal to or less than the capacity of the main injector 11x, the ECU 10 calculates the total fuel injection amount as the fuel injection amount of the main injector 11x. In this case, the fuel injection amount of the auxiliary injector 11y is 0. When the total fuel injection amount is greater than the capacity of the main injector 11x, the ECU 10 calculates the capacity of the main injector 11x as the fuel injection amount of the main injector 11x, and calculates the shortage of fuel that exceeds the capacity of the main injector 11x as the fuel injection amount of the auxiliary injector 11y. In addition, the ECU 10 calculates the fuel injection period of the main injector 11x and the auxiliary injector 11y according to the opening timing of the first intake valve 3ax and the second intake valve 3ay.

[0041] The ECU 10 controls the main injector 11x and the variable valve 12 based on the operating state of the internal combustion engine 1 (S11 to S20). Note that, when S11 is YES, the processes of S12 to S14 correspond to the case where the fuel injection period by the main injector 11x exists outside the opening period of the first intake valve 3ax, and when S11 is NO, the processes of S15 and S16 correspond to the case where the fuel injection period by the main injector 11x exists within the opening period of the first intake valve 3ax.

[0042] Incidentally, during the period from the immediate closing timing of the second intake valve 3ay to the opening timing of the second intake valve 3ay, and from the opening timing of the second intake valve 3ay to the opening timing of the first intake valve 3ax, the ECU 10 supplies only air from the second intake passage 8y into the cylinder 2 in advance, and therefore does not cause the auxiliary injector 11y provided in the second intake passage 8y to inject fuel.

[0043] Specifically, in S11, the ECU 10 judges whether the first intake valve 3ax is closed or not. The term "the first intake valve is closed" may refer to a state in which the opening amount of the first intake valve 3ax is equal to or less than a predetermined valve-closing judgment value. The term "the first intake valve is closed" may refer to a state in which the opening amount of the first intake valve 3ax is zero. The opening amount of the first intake valve 3ax may refer to a lift amount of the first intake valve 3ax from a state in which the first intake valve 3ax is seated on a valve seat. For example, when the opening amount of the first intake valve 3ax is equal to or less than a predetermined valve-opening judgment value, the ECU 10 judges that the first intake valve 3ax is closed. When the opening amount of the first intake valve 3ax is greater than the predetermined valve-opening judgment value, the ECU 10 judges that the first intake valve 3ax is not closed (open).

[0044] When it is determined that the first intake valve 3ax is closed (S11: YES), the ECU 10 controls the variable valve 12 to be in a fully closed state in S12. As a result, the variable valve 12 is in a fully closed state when the first intake valve 3ax is closed, for example, as shown in Fig. 2. By bringing the variable valve 12 into a fully closed state, even if residual hydrogen F1 remains in the first intake port 3cx, for example, the residual hydrogen F1 is prevented from overflowing upstream of the first intake passage 8x including the first intake port 3cx.

[0045] When it is determined that the first intake valve 3ax is not closed (open) (S11: NO), the ECU 10 proceeds to processing in S15, as described below.

[0046] In S13, the ECU 10 determines whether or not the main fuel injection valve is injecting. The ECU 10 may determine whether or not the main injector 11x is injecting, for example, based on the presence or absence of a valve-opening signal to the main injector 11x.

[0047] When it is determined that the main injector 11x is not injecting while the first intake valve 3ax is closed (S13: NO), the ECU 10 returns to the process of S11. If the first intake valve 3ax remains closed, the ECU 10 waits by repeating the processes of S11 to S13 until the main injector 11x is injecting. If the main injector 11x is not injecting while the first intake valve 3ax is closed and the first intake valve 3ax is opened, the ECU 10 proceeds to the process of S15 described later.

[0048] When it is determined that the main injector 11x is injecting while the first intake valve 3ax is closed (S13: YES), the ECU 10 maintains the fully closed state of the variable valve 12 and determines in S14 whether the first intake valve 3ax and the second intake valve 3ay are open. Here, since the opening timing of the first intake valve 3ax is retarded from the opening timing of the second intake valve 3ay, if the first intake valve 3ax is open, the second intake valve 3ay is already open. Therefore, the ECU 10 may determine that the first intake valve 3ax and the second intake valve 3ay are open when it is determined that the first intake valve 3ax is open by a determination method similar to that of S11.

[0049] When it is determined that the first intake valve 3ax and the second intake valve 3ay are not open (the first intake valve 3ax is kept closed) (S14: NO), the ECU 10 returns to the process of S14. The ECU 10 repeats the process of S14 until the first intake valve 3ax and the second intake valve 3ay are opened, 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 first intake valve 3ax is closed.

[0050] In the internal combustion engine 1 using hydrogen as fuel, the volume in a gaseous state for generating the same amount of heat tends to be larger than that of other fuels. Therefore, for example, in an operating state where the engine speed is low to medium and the intake amount is medium to full load, fuel injection may be started from the main injector 11x while the first intake valve 3ax is closed. In this case, as shown in FIG. 3, the variable valve 12 is fully closed when the main injector 11x is injecting while the first intake valve 3ax is closed. By maintaining the fully closed state of the variable valve 12, even if the proportion of hydrogen F2 injected from the main injector 11x in the first intake port 3cx increases while the first intake valve 3ax is closed, the hydrogen F2 is prevented from overflowing upstream of the first intake passage 8x including the first intake port 3cx.

[0051] When it is determined that the first intake valve 3ax and the second intake valve 3ay are open (S14: YES), the ECU 10 proceeds to the process of S17, which will be described later.

[0052] On the other hand, if it is determined that the first intake valve 3ax is not closed (open) after the processing of S10 (S11: NO), the ECU 10 determines in S15 whether or not the main injector 11x is injecting.

[0053] For example, if it is determined that the main injector 11x is not injecting (fuel injection has not started) while the first intake valve 3ax is open after there is no fuel injection from the main injector 11x while the first intake valve 3ax is closed (S15: NO), the ECU 10 controls the variable valve 12 to be in a fully open state in S16. As a result, as shown in FIG. 4, for example, in a state in which fuel injection from the main injector 11x has not started while the first intake valve 3ax is open, the variable valve 12 is in a fully open state. 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 S15. The ECU 10 waits by repeating the processes of S15 to S16 until fuel injection from the main injector 11x starts while the first intake valve 3ax is open. In other words, the ECU 10 controls the variable valve 12 so that the variable valve 12 is in a fully open state during the period from when the first intake valve 3ax opens to when the main injector 11x starts injection.

[0054] For example, if it is determined that the main injector 11x is injecting after the first intake valve 3ax opens after there was no fuel injection from the main injector 11x while the first intake valve 3ax was closed (S15: YES), the ECU 10 proceeds to processing of S17.

[0055] In S17, when the main injector 11x is injecting, the ECU 10 judges whether or not the total fuel injection amount is greater than the capacity (maximum main injection amount) of the main injector 11x. When it is judged that the total fuel injection amount is greater than the capacity of the main injector 11x (S17: YES), the ECU 10 injects fuel from the auxiliary fuel injection valve in S18. For example, as shown in FIG. 5, the ECU 10 injects fuel to the auxiliary injector 11y to make up for the shortage of fuel that exceeds the capacity of the main injector 11x. That is, the ECU 10 controls the auxiliary injector 11y so that the auxiliary injector 11y injects fuel when the main injector 11x injects fuel at the maximum main injection amount during the period when the first intake valve 3ax and the second intake valve 3ay are open, based on the operating state of the internal combustion engine 1. Then, the ECU 10 proceeds to the process of S19.

[0056] When it is determined that the total fuel injection amount is equal to or less than the capacity of the main injector 11x (S17: NO), the ECU 10 proceeds to the process of S19. This case corresponds to the state in FIG. 5 where fuel is not injected from the auxiliary injector 11y.

[0057] In S19, the ECU 10 determines whether or not the fuel injection of the main fuel injection valve has ended. The ECU 10 may determine whether or not the fuel injection of the main injector 11x has ended, for example, based on the presence or absence of a valve-opening signal to the main injector 11x.

[0058] When it is determined that the fuel injection of the main injector 11x has not ended (S19: NO), the ECU 10 returns to the process of S19. The ECU 10 repeats the process of S19 until the fuel injection of the main injector 11x ends, and maintains the variable valve 12 in a fully closed state while the first intake valve 3ax is open and the fuel injection of the main injector 11x continues. In other words, the ECU 10 controls the main injector 11x and the variable valve 12 so that the variable valve 12 is in a fully closed state during the injection of the main injector 11x while the first intake valve 3ax is open.

[0059] As a result, the variable valve 12 is fully closed when the first intake valve 3ax is open, as shown in Fig. 5. 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 first intake valve 3ax, the hydrogen F3 injected from the main injector 11x is prevented from overflowing upstream of the first intake passage 8x including the first intake port 3cx.

[0060] When it is determined that the fuel injection of the main injector 11x has ended (S19: YES), the ECU 10 controls the variable valve 12 in S20 so that the opening degree is larger than that in the fully closed state. That is, the ECU 10 controls the main injector 11x and the variable valve 12 so that the opening degree of the variable valve 12 is larger than that in the fully closed state after the injection of the main injector 11x ends during the period when the first intake valve 3ax is open. As a result, the variable valve 12 is opened to a larger degree than that in the fully closed state when the first intake valve 3ax is open, as shown in FIG. 6 for example. This allows the flow of air through the first intake passage 8x at a flow rate according to the current operating state of the internal combustion engine 1, for example. Therefore, the fuel F4 injected by the main injector 11x is pushed into the cylinder 2 by the air flowing through the first intake passage 8x.

[0061] In addition, in S20, the ECU 10 may control the variable valve 12 so that the opening degree is smaller than the fully open state and larger than the fully closed state. In this case, the backflow of the fuel injected by the main injector 11x to the upstream side of the first intake passage 8x up to S20 is suppressed. For example, even if the exhaust valve 3b is open and overlap exists, and blowback occurs through the open first intake valve 3ax, hydrogen is suppressed from overflowing to the upstream side of the first intake passage 8x including the first intake port 3cx.

[0062] Thereafter, the ECU 10 may end the process of Fig. 7 and, for example, repeat the process of Fig. 7 again after the first intake valve 3ax 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 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 first intake valve 3ax is opened to when it is closed.

[0063] [Action and Effects] In the intake system 100 for an internal combustion engine, the first intake passage 8x in which the main injector 11x is provided functions mainly as a passage for supplying fuel into the cylinder 2. The second intake passage 8y functions mainly as a passage for supplying air into the cylinder 2. In this way, air is supplied into the cylinder 2 using the second intake passage 8y separate from the first intake passage 8x that supplies fuel into the cylinder 2, so that the flow of air is not hindered by the fuel and air can be efficiently supplied into the cylinder 2. Therefore, according to the intake system 100 for an internal combustion engine, air can be efficiently supplied into the cylinder 2 in the internal combustion engine 1 that uses hydrogen as fuel.

[0064] Here, in a port injection type internal combustion engine that injects hydrogen as fuel toward an intake port, it is also desired to suppress the occurrence of abnormal ignition (backfire) of hydrogen during the intake stroke. In this regard, the opening timing of the first intake valve 3ax is retarded from the opening timing of the second intake valve 3ay, so that air from the second intake passage 8y is supplied into the cylinder 2 before fuel from the first intake passage 8x. The air supplied into the cylinder 2 first cools the inside of the cylinder 2 before fuel is supplied into the cylinder 2, so that a sudden increase in temperature of the hydrogen as fuel is suppressed. This makes it possible to suppress the occurrence of abnormal ignition of hydrogen during the intake stroke. In this way, according to the intake device 100 for an internal combustion engine, in an internal combustion engine 1 that uses hydrogen as fuel, it is possible to efficiently supply air into the cylinder 2 while suppressing the occurrence of abnormal ignition of hydrogen during the intake stroke.

[0065] The intake device 100 of the internal combustion engine includes a variable valve 12 provided upstream of the main injector 11x in the first intake passage 8x, and an ECU 10 that controls the main injector 11x and the variable valve 12 based on the operating state of the internal combustion engine 1. The ECU 10 controls the main injector 11x and the variable valve 12 so that the variable valve 12 is fully closed during injection by the main injector 11x during a period in which the first intake valve 3ax is open. As a result, the variable valve 12 is fully closed during injection by the main injector 11x, so that the fuel injected by the main injector 11x can be prevented from overflowing to the upstream side of the first intake passage 8x.

[0066] During the period when the first intake valve 3ax is open, the ECU 10 controls the main injector 11x and the variable valve 12 so that the variable valve 12 opens to a larger degree than when it is fully closed after the main injector 11x finishes injection. As a result, the variable valve 12, which was fully closed during the injection of the main injector 11x, allows air to flow after the main injector 11x finishes injection. Therefore, the fuel injected by the main injector 11x can be pushed into the cylinder 2 by the flowing air.

[0067] The intake device 100 of the internal combustion engine includes an auxiliary injector 11y that is provided in the second intake passage 8y and injects fuel toward the second intake port 3cy. The ECU 10 controls the auxiliary injector 11y so that the auxiliary injector 11y injects fuel when the main injector 11x injects fuel at the maximum main injection amount during a period when the first intake valve 3ax and the second intake valve 3ay are open, based on the operating state of the internal combustion engine 1. As a result, when the amount of fuel required for high-load operation of the internal combustion engine 1 is greater than the maximum main injection amount of the main injector 11x, for example, the fuel injected by the auxiliary injector 11y can make up for the shortage.

[0068] [Variations] Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0069] In the above embodiment, the intake device 100 of the internal combustion engine includes the variable valve 12, but the variable valve 12 may be omitted. In short, it is sufficient that the opening timing of the first intake valve 3ax is retarded from the opening timing of the second intake valve 3ay. In this case, the ECU 10 prevents the auxiliary injector 11y provided in the second intake passage 8y from injecting fuel during the period from the immediate closing timing of the second intake valve 3ay to the opening timing of the second intake valve 3ay and from the opening timing of the second intake valve 3ay to the opening timing of the first intake valve 3ax, thereby enabling only air to be supplied in advance from the second intake passage 8y into the cylinder 2.

[0070] In the above embodiment, the internal combustion engine 1 was provided with not only the main injector 11x but also the auxiliary injector 11y. However, for example, if the maximum main injection amount of the main injector 11x is greater than the required fuel injection amount of the internal combustion engine 1, the auxiliary injector 11y may be omitted. [Explanation of symbols]

[0071] 1...internal combustion engine, 2...cylinder, 3ax...first intake valve, 3ay...second intake valve, 3cx...first intake port, 3cy...second intake port, 8x...first intake passage, 8y...second intake passage, 10...ECU (control unit), 12...variable valve, 100...intake system of internal combustion engine.

Claims

1. An intake system for a four-stroke internal combustion engine that uses hydrogen as fuel, comprising: a first intake passage provided in one cylinder of the internal combustion engine and including a first intake port having a first intake valve provided at a downstream end thereof; a second intake passage provided in the one cylinder and including a second intake port having a second intake valve provided at a downstream end thereof; a main fuel injection valve provided in the first intake passage and configured to inject the fuel toward the first intake port, An intake system for an internal combustion engine, wherein an opening timing of the first intake valve is retarded relative to an opening timing of the second intake valve.

2. a variable valve provided in the first intake passage upstream of the main fuel injection valve; a control unit that controls the main fuel injection valve and the variable valve based on an operating state of the internal combustion engine, 2. The intake device of an internal combustion engine according to claim 1, wherein the control unit controls the main fuel injection valve and the variable valve so that the variable valve is fully closed during injection from the main fuel injection valve during a period in which the first intake valve is open.

3. 3. The intake device of an internal combustion engine according to claim 2, wherein the control unit controls the main fuel injection valve and the variable valve so that, during a period in which the first intake valve is open, the opening degree of the variable valve is greater than that of a fully closed state after injection from the main fuel injection valve ends.

4. an auxiliary fuel injection valve provided in the second intake passage and configured to inject the fuel toward the second intake port; 4. The intake device of an internal combustion engine according to claim 2 or 3, wherein the control unit controls the auxiliary fuel injection valve so that the auxiliary fuel injection valve injects the fuel when the main fuel injection valve injects the fuel at a maximum main injection amount during a period in which the first intake valve and the second intake valve are open, based on an operating state of the internal combustion engine.

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