Fuel supply device

Abstract

To provide a fuel supply device that can appropriately supply fuel even when the flow rate of the fuel to be injected by a fuel injection valve is small in an internal combustion engine that uses hydrogen as fuel.SOLUTION: A fuel supply device 100 is a fuel supply device for a four-stroke internal combustion engine 1 that uses hydrogen as fuel and has a plurality of cylinders 2. The fuel supply device comprises: an intake passage 5 having an intake manifold 50 that branches from the upstream side to the downstream side to correspond to the number of cylinders, a single pipe portion 5a upstream of the intake manifold 50, and intake port portions 5b downstream of the intake manifold 50; and a plurality of first fuel injection valves 7 provided in the respective intake port portions 5b. The maximum injection period of the first fuel injection valve 7 is a value corresponding to the opening period of an intake valve 3a of the internal combustion engine 1. A second fuel injection valve 9 is provided in the intake manifold 50. The minimum injection amount of the second fuel injection valve 9 is smaller than the minimum injection amount of the first fuel injection valve 7.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, there is 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] Japanese Patent Application Laid-Open No. 2011-058435 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, internal combustion engines fueled by hydrogen have been considered. Considering the calorific value per volume of hydrogen, for example, to generate the same amount of heat, the volume of gas to be injected must be larger than that of other gaseous fuels. However, generally, when the maximum flow rate of a fuel injector is increased, the minimum injection quantity corresponding to the minimum injection period of the fuel injector also tends to increase accordingly. Therefore, when the fuel flow rate is small, such as during idling, the minimum injection quantity of the fuel injector may be too large, resulting in inadequate fuel supply.

[0005] An object of the present invention is to provide a fuel supply device that can appropriately supply fuel to an internal combustion engine that uses hydrogen as fuel, even when the flow rate of fuel to be injected by a fuel injection valve is small. [Means for solving the problem]

[0006] A fuel supply device according to one embodiment of the present invention is a fuel supply device for a four-stroke internal combustion engine that uses hydrogen as fuel and has multiple cylinders, and is equipped with an intake passage having a branch section that branches from the upstream side to the downstream side in a manner corresponding to the number of cylinders, a single pipe section upstream of the branch section, and an intake port section downstream of the branch section, and multiple first fuel injection valves provided in each of the intake port sections, wherein the maximum injection period of the first fuel injection valve is a value corresponding to the opening period of the intake valve of the internal combustion engine, and a second fuel injection valve is provided in the single pipe section or the branch section, and the minimum injection amount of the second fuel injection valve is smaller than the minimum injection amount of the first fuel injection valve.

[0007] In the fuel supply device according to one aspect of the present invention, when the flow rate of fuel to be supplied to an internal combustion engine is small, for example, when the engine is idling, by using the second fuel injection valve, it is possible to supply fuel at a flow rate smaller than the minimum injection amount of the first fuel injection valve. Therefore, the fuel supply device according to one aspect of the present invention can appropriately supply fuel to an internal combustion engine that uses hydrogen as fuel, even when the flow rate of fuel to be injected by the fuel injection valve is small.

[0008] In one embodiment, the branch portion may connect the upstream intake passage on the upstream side with two or more downstream intake passages on the downstream side, and may have a guide portion that guides the intake air flowing through the upstream intake passage so as to distribute the intake air to each of the downstream intake passages, and the second fuel injection valve may be provided at the branch portion so as to inject fuel from the upstream intake passage toward the guide portion. In this case, the fuel injected from the second fuel injection valve is more reliably guided by the guide portion and is more likely to be appropriately distributed to the multiple cylinders.

[0009] In one embodiment, the branch portion may include a first branch portion that branches one intake passage into two intake passages, and a pair of second branch portions that further branch each of the two intake passages downstream of the first branch portion into two intake passages, and the second fuel injection valve may be provided in each of the pair of second branch portions. In this case, fuel injected from the second fuel injection valve reaches the cylinders more quickly than when the second fuel injection valve is provided in the first branch portion, thereby improving the responsiveness of the internal combustion engine.

[0010] In one embodiment, the fuel supply device further includes a control unit that controls the first fuel injection valve and the second fuel injection valve, and the control unit may inject fuel from the second fuel injection valve when a predetermined low-flow-rate condition is satisfied, and may learn injection amount variations among the first fuel injection valves when the low-flow-rate condition is not satisfied. In this case, it is possible to appropriately learn injection amount variations among cylinders in an internal combustion engine that includes the first fuel injection valve and the second fuel injection valve. [Effects of the Invention]

[0011] According to the present invention, even when the flow rate of fuel to be injected by the fuel injection valve in an internal combustion engine that uses hydrogen as fuel is small, fuel can be supplied appropriately. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of an internal combustion engine equipped with a fuel supply device according to an embodiment; [Figure 2] FIG. 4 is a diagram for explaining an injection period of a fuel injection valve. [Figure 3] 2 is a flowchart showing an example of fuel injection processing by the ECU of FIG. 1; [Figure 4] 4 is a flowchart showing an example of a process for learning injection amount variation in the ECU of FIG. 1; [Figure 5] FIG. 2 is a schematic diagram of an internal combustion engine equipped with a fuel supply device according to a first modified example. [Figure 6] FIG. 10 is a schematic diagram of an internal combustion engine equipped with a fuel supply device according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments 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 redundant description will be omitted.

[0014] Fig. 1 is a schematic diagram of an internal combustion engine equipped with a fuel supply device of one embodiment. As shown in Fig. 1, the fuel supply device 100 is a device that controls the supply of fuel to the internal combustion engine 1. The fuel supply device 100 is mounted on, for example, a vehicle.

[0015] 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 reciprocating engine.

[0016] The internal combustion engine 1 has a plurality of (for example, four) cylinders 2. In each cylinder 2, a combustion chamber 4 is defined by a cylinder head 3 having an intake valve 3a and an exhaust valve 3b, and a piston (not shown). The internal combustion engine 1 takes in air and hydrogen via the intake valve 3a, combusts the hydrogen in the combustion chamber 4, and discharges the exhaust gas produced by the combustion via the exhaust valve 3b.

[0017] An intake passage 5 and an exhaust passage 6 are connected to the internal combustion engine 1 so as to communicate with the combustion chamber 4. As an example, the intake passage 5 has an intake manifold (branching portion) 50 that branches from the upstream side to the downstream side in a manner corresponding to the number of cylinders, a single pipe portion 5a on the upstream side of the intake manifold 50, and an intake port portion 5b on the downstream side of the intake manifold 50. A throttle valve 5c that adjusts the flow rate of intake air is provided in the single pipe portion 5a. The single pipe portion 5a refers to the intake passage 5 from the intake air introduction portion, which includes an air cleaner (not shown), to the upstream end of an inlet portion 51 of the intake manifold 50.

[0018] In this example, the intake manifold 50 is of a 1-2-4 type, branching from one inlet portion 51 to four intake ports 5b corresponding to the four cylinders 2. That is, the intake manifold 50 has a first branch portion 50a that branches from the inlet portion 51, which is a single intake passage, into two intake passages 52, and a pair of second branch portions 50b that further branch from each of the two intake passages 52 downstream of the first branch portion 50a into two each (a total of four intake passages 53). Each of the intake passages 53 extends a predetermined length, and the cylinder head 3 side corresponds to the intake port 5b.

[0019] The intake manifold 50 has a guide portion 54. As an example, the guide portion 54 is provided at a location where one inlet portion 51 branches into two intake passages 52. The guide portion 54 here connects the inlet portion 51, which is an upstream intake passage on the upstream side, with the intake passages 52, which are two or more downstream intake passages on the downstream side, and guides the intake air flowing through the inlet portion 51 so as to distribute it to each of the intake passages 52.

[0020] The guide portion 54 may be, for example, a protrusion that protrudes in a mountain shape from the boundary portion between the two intake passages 52 toward the internal space of the inlet portion 51. If the intake manifold 50 is cast, the protrusion of the guide portion 54 can be formed by forming a mold with a shape that corresponds to the protrusion at the boundary portion between the two intake passages 52, or if the intake manifold 50 is made of sheet metal, the protrusion can be formed by forming a sheet metal member at the boundary portion between the two intake passages 52 into a shape that corresponds to the protrusion.

[0021] The internal combustion engine 1 is equipped with a plurality of first fuel injection valves 7 provided in each of the intake ports 5b. For example, the base end of each of the four first fuel injection valves 7 is attached to a single rail 8 that spans the four intake ports 5b, and the tip end is fixed so as to be pressed against a mounting hole provided in the intake port 5b. The first fuel injection valve 7 is the main fuel injection valve (injector) in the internal combustion engine 1 that uses hydrogen as fuel. Hydrogen is supplied to the first fuel injection valve 7 from a fuel tank (not shown) via the rail 8, and the first fuel injection valve 7 injects the hydrogen into the intake port 5b.

[0022] The first fuel injection valve 7 has a maximum injection quantity corresponding to the flow rate (maximum flow rate) of fuel required for full-load operation of the internal combustion engine 1. The maximum injection quantity of the first fuel injection valve 7 corresponds to the flow rate of hydrogen during the maximum injection period of the first fuel injection valve 7. In a four-stroke internal combustion engine that uses hydrogen as fuel, taking into account the calorific value per volume of hydrogen, it is necessary to inject a larger volume than other gaseous fuels (such as LPG) in order to generate an equal amount of heat, for example. For this reason, the first fuel injection valve 7 is configured as a so-called high-flow injector by increasing the flow rate, for example by increasing the nozzle hole diameter.

[0023] FIG. 2 is a diagram illustrating the injection period of a fuel injector. The horizontal axis of FIG. 2 represents the crank angle of the internal combustion engine 1, and the vertical axis represents the opening amount of the intake valve 3a or the exhaust valve 3b. As shown in FIG. 2, in a four-stroke internal combustion engine, there may be an overlap period during which both the intake valve 3a and the exhaust valve 3b are open. However, in a port-injection internal combustion engine 1 using hydrogen as fuel, hydrogen is supplied during the period during which the intake valve 3a is open. However, to prevent backfire into the intake passage 5, hydrogen is generally not injected during the overlap period during which both the intake valve 3a and the exhaust valve 3b are open. Therefore, the maximum injection period of the first fuel injector 7 is set to a period within which only the intake valve 3a is open. In other words, in the fuel supply device 100, the maximum injection period of the first fuel injector 7 corresponds to the opening period of the intake valve 3a of the internal combustion engine 1.

[0024] If an overlap period exists, the maximum injection period of the first fuel injector 7 is set to a period that falls within the single valve-open period during which the intake valve 3a is open after the exhaust valve 3b is closed (see FIG. 2). If an overlap period does not exist, the maximum injection period of the first fuel injector 7 is set to a period that falls within the entire period during which the intake valve 3a is open. The "period during which the intake valve 3a is open" refers to a period during which the opening amount of the intake valve 3a is greater than zero. The "period during which the intake valve 3a is open" may also refer to a period during which the opening amount of the intake valve 3a is substantially greater than zero, such that the opening amount is equal to or greater than a predetermined valve-opening determination value.

[0025] Next, the minimum injection quantity corresponding to the minimum injection period of the first fuel injection valve 7 will be explained. Generally, in an injector, if the injection period is too short, for example, the lift amount of the needle inside the injector may be insufficient, which may result in an unstable flow rate per injection. Therefore, the minimum injection period is determined in advance as a hardware constraint of the injector, thereby stabilizing the minimum injection quantity. Here, if the injection hole diameter is increased, for example, to increase the maximum injection quantity, this also affects the injection quantity during the minimum injection period. In other words, the minimum injection quantity of the first fuel injection valve 7 increases compared to the minimum injection quantity of fuel injection valves used for other gaseous fuels (e.g., LPG) due to the increase in the maximum injection quantity of the first fuel injection valve 7.

[0026] If the minimum injection quantity of the first fuel injection valve 7 tends to be large in this way, when the flow rate of fuel to be supplied to the internal combustion engine 1 is small, for example, when the engine is idling, the flow rate of fuel to be supplied to the internal combustion engine 1 may be smaller than the minimum injection quantity of the first fuel injection valve 7. Therefore, the fuel supply device 100 is provided with a second fuel injection valve 9 having a minimum injection quantity smaller than the minimum injection quantity of the first fuel injection valve 7.

[0027] The second fuel injector 9 is a fuel injector for supplying fuel at a flow rate smaller than the minimum injection amount of the first fuel injector 7 to the internal combustion engine 1 that uses hydrogen as fuel. The minimum injection amount of the second fuel injector 9 is smaller than the minimum injection amount of the first fuel injector 7. The minimum injection amount of the second fuel injector 9 may correspond to, for example, a flow rate equal to or lower than the minimum fuel flow rate that is the combustion limit on the low load side of the internal combustion engine 1, so as to cover the low flow rate side of the fuel to be supplied to the internal combustion engine 1. The minimum fuel flow rate can be determined, for example, by bench testing of the internal combustion engine 1. The maximum injection amount of the second fuel injector 9 may be equal to or higher than the minimum injection amount of the first fuel injector 7.

[0028] In the example of FIG. 1 , the second fuel injection valve 9 is provided in the intake manifold 50. More specifically, the second fuel injection valve 9 is provided in the inlet portion 51 of the intake manifold 50 so as to inject fuel from the inlet portion 51 toward the guide portion 54. Unlike the first fuel injection valve 7, the second fuel injection valve 9 is supplied with hydrogen from a fuel tank (not shown) without passing through a rail 8. By providing the second fuel injection valve 9 in the intake manifold 50 in this way, it is possible to suppress restrictions on the degree of freedom in layout due to the installation of a rail, etc., compared to a configuration in which, for example, a number of additional injectors corresponding to the number of cylinders are provided in the intake port portion 5b.

[0029] The fuel supply device 100 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. The ECU 10 realizes various functions by, for example, loading a program stored in the ROM into the RAM and executing the program loaded into the RAM by the CPU. The ECU 10 may be composed of multiple electronic units.

[0030] The ECU 10 controls the first fuel injector 7 and the second fuel injector 9. Examples of functions and processing of the ECU 10 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a flowchart showing an example of fuel injection processing by the ECU of Fig. 1. The processing of Fig. 3 is executed while the internal combustion engine 1 is operating.

[0031] 3, in S01, the ECU 10 calculates the fuel injection flow rate. The ECU 10 calculates the fuel injection flow rate based on, for example, a detection signal from an engine rotation sensor (not shown) that detects the engine speed of the internal combustion engine 1 and a detection signal from an intake air amount sensor (not shown) that detects a detection value related to the intake amount of the internal combustion engine 1. The engine rotation sensor may be a known component (e.g., a crank angle sensor, etc.). The intake air amount sensor may be a known component (e.g., an intake negative pressure sensor, an air flow sensor, etc.).

[0032] In S02, the ECU 10 determines whether a predetermined low flow rate condition is satisfied. The low flow rate condition is a condition for switching whether or not to inject fuel from the second fuel injection valve 9. The ECU 10 may determine whether or not the low flow rate condition is satisfied depending on, for example, whether or not the calculated fuel injection flow rate is smaller than the minimum injection amount of the first fuel injection valve 7.

[0033] If it is determined that the low flow rate condition is satisfied (S02: YES), the ECU 10 injects fuel at the calculated fuel injection flow rate using the second fuel injection valve 9 in S03. That is, when the predetermined low flow rate condition is satisfied, the ECU 10 injects fuel using the second fuel injection valve 9 without using the first fuel injection valve 7. The ECU 10 then ends the processing of FIG. 3.

[0034] On the other hand, if it is determined that the low flow rate condition is not satisfied (S02: NO), the ECU 10 injects fuel at the calculated fuel injection flow rate using the first fuel injection valve 7 in S04. In this case, the ECU 10 may inject fuel using both the first fuel injection valve 7 and the second fuel injection valve 9. The ECU 10 then ends the processing of FIG. 3.

[0035] The ECU 10 may learn the injection amount variation among the multiple first fuel injection valves 7. The injection amount variation refers to the variation in the amount of fuel injected for each cylinder 2, and is caused by, for example, manufacturing tolerances of the first fuel injection valves 7. Here, the fuel supply device 100 is provided with a second fuel injection valve 9 in addition to the multiple first fuel injection valves 7. During fuel injection by the second fuel injection valve 9, the fuel injected by the second fuel injection valve 9 may affect the injection amount variation among the first fuel injection valves 7. Therefore, the ECU 10 may learn the injection amount variation among the multiple first fuel injection valves 7 when the second fuel injection valve 9 is not injecting fuel. The learning of the injection amount variation itself can be performed using a known learning method, for example, based on fluctuations in the engine speed for each cylinder 2.

[0036] Fig. 4 is a flowchart showing an example of the injection amount variation learning process of the ECU of Fig. 1. As shown in Fig. 4, in S11, the ECU 10 calculates the fuel injection flow rate in the same manner as in S01 of Fig. 3.

[0037] In S12, the ECU 10 determines whether a predetermined low flow rate condition is satisfied, in the same manner as in S02 of FIG.

[0038] If it is determined that the low flow rate condition is satisfied (S12: YES), the ECU 10 does not learn the injection amount variation among the plurality of first fuel injection valves 7, and ends the processing of FIG. 3. On the other hand, if it is determined that the low flow rate condition is not satisfied (S12: NO), the ECU 10 proceeds to S13 to learn the injection amount variation among the plurality of first fuel injection valves 7. The ECU 10 then ends the processing of FIG. 3.

[0039] [Action and effect] In the fuel supply device 100 as described above, when the flow rate of fuel to be supplied to the internal combustion engine 1 is small, for example, when the engine is idling, by using the second fuel injection valve 9, it is possible to supply fuel at a flow rate smaller than the minimum injection amount of the first fuel injection valve 7. Therefore, the fuel supply device 100 can appropriately supply fuel to the internal combustion engine 1 that uses hydrogen as fuel, even when the flow rate of fuel to be injected by the fuel injection valve is small.

[0040] In the fuel supply device 100, the intake manifold 50 communicates an inlet portion 51, which is an upstream intake passage, with two or more downstream intake passages 52, which are downstream intake passages, and has a guide portion 54 that guides the intake air flowing through the inlet portion 51 so as to distribute the intake air to each of the intake passages 52. The second fuel injection valve 9 is provided in the intake manifold 50 so as to inject fuel from the inlet portion 51 toward the guide portion 54. This allows the fuel injected from the second fuel injection valve 9 to be more reliably guided by the guide portion 54, making it easier to appropriately distribute the fuel to the multiple cylinders 2.

[0041] By providing the second fuel injection valves 9 in the intake manifold 50, it is possible to suppress restrictions on the degree of freedom in layout due to the installation of rails, etc., compared to a configuration in which, for example, the same number of additional injectors as the number of cylinders are provided in the intake port portion 5b, and it is possible to increase the degree of freedom in installation. Furthermore, by reducing the number of second fuel injection valves 9, it is possible to reduce costs.

[0042] The fuel supply device 100 further includes an ECU 10 that controls the first fuel injection valves 7 and the second fuel injection valves 9. The ECU 10 injects fuel from the second fuel injection valves 9 when a predetermined low flow rate condition is met. When the low flow rate condition is not met, the ECU 10 learns the injection amount variation among the multiple first fuel injection valves 7. This makes it possible to appropriately learn the variation between cylinders in the internal combustion engine 1 that is equipped with the first fuel injection valves 7 and the second fuel injection valves 9.

[0043] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0044] In the above embodiment, the second fuel injection valve 9 is provided in the intake manifold 50 and located downstream of the throttle valve 5c. However, this is not limiting. For example, as shown in the fuel supply system 100A in FIG. 5, the second fuel injection valve 9 may be provided upstream of the throttle valve 5c in the single pipe section 5a. Furthermore, while the 1-2-4 type intake manifold 50 having a tubular intake passage is illustrated as an example of a branch section, this is not limiting. For example, a 1-4 type intake manifold may be used, or the branch section may include a volume corresponding to a surge tank while taking backfire into consideration. The internal combustion engine may have multiple cylinders other than four, and the intake manifold may correspond to a number of cylinders other than four. In short, the second fuel injection valve may be provided in the single pipe section or the branch section.

[0045] In the above embodiment, the second fuel injection valve 9 is provided in the inlet portion 51 of the intake manifold 50 so as to inject fuel from the inlet portion 51 toward the guide portion 54, but the present invention is not limited to this. For example, as shown in a fuel supply device 100B in FIG. 6, the second fuel injection valve 9 may be provided in each of a pair of second branch portions 50b. In this case, the fuel injected from the second fuel injection valve 9 reaches the cylinder 2 more quickly than when the second fuel injection valve 9 is provided in the first branch portion 50a, thereby improving the responsiveness of the internal combustion engine 1. Note that, although the second branch portion 50b does not have a guide portion in the example in FIG. 6, it may have a guide portion.

[0046] In the above embodiment, the first fuel injection valve 7 is the main fuel injection valve in the internal combustion engine 1 that uses hydrogen as fuel, but the second fuel injection valve 9 may be used as the main fuel injection valve.

[0047] The constituent elements of various aspects of the present invention will be described below. <Invention 1> A fuel supply device for a four-stroke internal combustion engine that uses hydrogen as fuel and has multiple cylinders, an intake passage including a branch portion branching from an upstream side to a downstream side in a number corresponding to the number of cylinders, a single pipe portion upstream of the branch portion, and an intake port portion downstream of the branch portion; a plurality of first fuel injection valves provided in the intake port portions, a maximum injection period of the first fuel injection valve is a value corresponding to an opening period of an intake valve of the internal combustion engine, a second fuel injection valve is provided in the single pipe portion or the branch portion, A fuel supply device, wherein the minimum injection amount of the second fuel injection valve is smaller than the minimum injection amount of the first fuel injection valve. <Invention 2> the branching section connects the upstream intake passage on the upstream side with two or more downstream intake passages on the downstream side, and has a guide section that guides the intake air flowing through the upstream intake passage so as to distribute the intake air to each of the downstream intake passages, The fuel supply device according to invention 1, wherein the second fuel injection valve is provided at the branching portion so as to inject the fuel from the upstream intake passage toward the guide portion. <Invention 3> the branching portion includes a first branching portion that branches from one intake passage into two intake passages, and a pair of second branching portions that further branch from the two intake passages downstream of the first branching portion into two intake passages each, 3. The fuel supply device according to claim 1, wherein the second fuel injection valve is provided in each of the pair of second branch portions. <Invention 4> a control unit that controls the first fuel injection valve and the second fuel injection valve, The control unit injecting the fuel from the second fuel injection valve when a predetermined low flow rate condition is satisfied; 4. The fuel supply device according to any one of the first to third aspects, wherein, when the low flow rate condition is not satisfied, learning of the injection amount variation among the plurality of first fuel injection valves is performed. [Explanation of symbols]

[0048] 1...internal combustion engine, 2...cylinder, 3a...intake valve, 5, 52, 53...intake passage, 5a...single pipe portion, 5b...intake port portion, 7...first fuel injection valve, 9...second fuel injection valve, 10...ECU (control unit), 50...intake manifold (branch portion), 50a...first branch portion, 50b...second branch portion, 54...guide portion, 100, 100A, 100B...fuel supply device.

Claims

1. A fuel supply system for a four-stroke internal combustion engine that uses hydrogen as fuel and has multiple cylinders, comprising: an intake passage including a branch portion that branches from an upstream side toward a downstream side in a manner corresponding to the number of cylinders, a single pipe portion upstream of the branch portion, and an intake port portion downstream of the branch portion; a plurality of first fuel injection valves provided in the intake port portions, a maximum injection period of the first fuel injection valve is a value corresponding to an opening period of an intake valve of the internal combustion engine, a second fuel injection valve is provided in the single pipe portion or the branch portion, A fuel supply device, wherein a minimum injection amount of the second fuel injection valve is smaller than a minimum injection amount of the first fuel injection valve.

2. the branching portion communicates an upstream intake passage on an upstream side with two or more downstream intake passages on a downstream side, and has a guide portion that guides the intake air flowing through the upstream intake passage so as to distribute the intake air to each of the downstream intake passages, 2. The fuel supply device according to claim 1, wherein the second fuel injection valve is provided at the branching portion so as to inject the fuel from the upstream intake passage toward the guide portion.

3. the branching portion includes a first branching portion that branches from one intake passage into two intake passages, and a pair of second branching portions that further branch from each of the two intake passages downstream of the first branching portion into two intake passages, 3. The fuel supply device according to claim 1, wherein the second fuel injection valve is provided in each of the pair of second branch portions.

4. a control unit that controls the first fuel injection valve and the second fuel injection valve, The control unit is injecting the fuel from the second fuel injection valve when a predetermined low flow condition is satisfied; 3. The fuel supply system according to claim 1, further comprising: a learning step for learning a variation in injection amount among the first fuel injection valves when the low flow rate condition is not satisfied.

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