Internal combustion engine

Abstract

This internal combustion engine (1) is a four-cycle port-injection-type internal combustion engine using hydrogen as fuel and comprises: a mixing passage (10) provided along an intake port (33); and an injector (8) provided so as to inject hydrogen toward the inside of the mixing passage (10). The mixing passage (10) includes: an guide-in part (12) which guides air from the intake port (33) to the inside of the mixing passage (10); and a guide-out part (13) which guides hydrogen and air out of the inside of the mixing passage (10) to the intake port (33).

Description

internal combustion engine

[0001] The present invention relates to an internal combustion engine.

[0002] Conventionally, fuel injection devices equipped with a hydrogen gas injector that injects hydrogen gas are known (see, for example, Patent Document 1). The fuel injection device described in Patent Document 1 includes a jet pipe through which hydrogen gas injected from the hydrogen gas injector flows. The jet pipe's nozzle is opened at a position close to the intake valve head within the intake port of an internal combustion engine. The hydrogen gas is injected from the jet pipe's nozzle to a position close to the intake valve head within the intake port, and mixes with air downstream from the injection position within the intake port.

[0003] Japanese Patent Application Laid-Open No. 2022-44553

[0004] The use of a configuration such as the above-mentioned conventional jet pipe prevents the intake port from becoming filled with hydrogen gas, improving the efficiency of filling the cylinder with intake air. It also prevents hydrogen gas from remaining in the intake port during operation of the internal combustion engine, preventing backfires (abnormal combustion).

[0005] However, with a configuration such as the jet pipe of the above-described prior art, when hydrogen gas is injected from the hydrogen gas injector, the jet pipe may become filled with hydrogen gas. If it is difficult to ensure a sufficient mixing distance between hydrogen gas and air, the hydrogen gas may become locally rich in the cylinder, which may lead to NOx generation or poor fuel economy. Furthermore, when the internal combustion engine is stopped, it is desirable to reduce the amount of unburned hydrogen gas (gaseous fuel) remaining inside the internal combustion engine. In this regard, with a configuration such as the jet pipe of the above-described prior art, it may be difficult to eliminate the state in which hydrogen gas remains inside the jet pipe.

[0006] The present invention aims to provide a four-stroke, port-injection internal combustion engine that uses gas fuel, which promotes mixing of gas fuel and air while improving the efficiency of filling air into the cylinder and suppressing the occurrence of abnormal combustion such as backfire, and which makes it easier to prevent injected unburned gas fuel from remaining inside the internal combustion engine.

[0007] One aspect of the present invention is a four-stroke port injection internal combustion engine that uses gas fuel as fuel, and includes a mixing passage provided along an intake port, and a fuel injection valve provided to inject gas fuel toward the inside of the mixing passage, and the mixing passage has an inlet section that introduces air from the intake port into the inside of the mixing passage, and an outlet section that discharges the gas fuel and air from the inside of the mixing passage to the intake port.

[0008] In an internal combustion engine according to one aspect of the present invention, a fuel injection valve injects gas fuel into a mixing passage provided along an intake port. Such a mixing passage prevents gas fuel filling the intake port from interfering with air flow and from remaining in the intake port, thereby contributing to improving the efficiency of air filling into the cylinder and suppressing the occurrence of abnormal combustion such as backfire. In an internal combustion engine according to one aspect of the present invention, air from the intake port is introduced into the mixing passage through an introduction portion. As a result, the injected gas fuel and the introduced air are mixed inside the mixing passage. The gas fuel and air mixed inside the mixing passage are introduced to the intake port through an introduction portion and are taken into the cylinder. Therefore, mixing of the gas fuel and air is promoted compared to, for example, when no introduction portion is provided or no mixing passage is provided at all. Furthermore, when injection of gas fuel by the fuel injection valve stops, the gas fuel remaining inside the mixing passage is pushed out to the introduction portion by the air introduced from the introduction portion. Therefore, in a four-stroke, port-injection internal combustion engine that uses gaseous fuel as fuel, the internal combustion engine according to one aspect of the present invention promotes mixing of the gaseous fuel and air while improving the efficiency of filling air into the cylinders and suppressing the occurrence of abnormal combustion such as backfire, and also makes it easier to prevent injected unburned gaseous fuel from remaining inside the internal combustion engine.

[0009] In one embodiment, the mixing passage is a pipe member provided inside the intake port so as to extend from the upstream side to the downstream side of the intake port, an inlet portion is provided in the pipe member upstream of the intake port, and an outlet portion is provided in the pipe member downstream of the intake port, and the fuel injection valve is provided to inject gas fuel toward the inlet portion. In this case, the mixing passage can be formed by the pipe member provided inside the intake port.

[0010] In one embodiment, the mixing passage is a partial passage partitioned by a partition member provided inside the intake port so as to extend from the upstream side to the downstream side of the intake port, an inlet portion is provided in the partial passage upstream of the intake port, and an outlet portion is provided in the partial passage downstream of the intake port, and the fuel injection valve is provided to inject gas fuel toward the inlet portion. In this case, the mixing passage can be configured by the partial passage partitioned by the partition member provided inside the intake port.

[0011] In one embodiment, the outlet portion may be located on the opposite side of the intake valve stem from the spark plug of the cylinder. In this case, the flow of gas fuel and air delivered to the intake port via the outlet portion is obstructed by the intake valve stem, thereby preventing the gas fuel from approaching the spark plug.

[0012] According to the present invention, in a four-cycle port injection type internal combustion engine that uses gas fuel, the efficiency of filling air into the cylinder is improved and the occurrence of abnormal combustion such as backfire is suppressed, while the mixing of gas fuel and air is promoted and it becomes easier to prevent injected unburned gas fuel from remaining inside the internal combustion engine.

[0013] FIG. 1 is a schematic configuration diagram of an internal combustion engine of an embodiment; FIG. 2 is a schematic perspective view showing a mixing passage of a first example; FIG. 3 is a schematic plan view showing an inlet portion of the mixing passage of the first example; FIG. 4 is a schematic perspective view showing an outlet portion of the mixing passage of the first example; FIG. 5 is a diagram for explaining promotion of mixing of gas fuel and air; FIG. 6 is a diagram for explaining that gas fuel is less likely to remain inside the mixing passage; FIG. 7 is a schematic plan view showing the outlet portion of the mixing passage of the first example; FIG. 8 is a schematic perspective view showing a modified example of the outlet portion of the mixing passage of the first example; FIG. 9 is a schematic perspective view showing a mixing passage of a second example; FIG. 10 is a schematic perspective view showing the outlet portion of the mixing passage of the second example; FIG. 11 is a schematic cross-sectional view showing an example of in-cylinder flow in an internal combustion engine of a comparative example;

[0014] 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.

[0015] The internal combustion engine 1 according to the embodiment is configured as a four-stroke port-injection reciprocating engine that uses gas fuel, such as hydrogen gas (hereinafter simply referred to as "hydrogen").

[0016] Figure 1 is a schematic diagram of an internal combustion engine according to one embodiment. As shown in Figure 1, the internal combustion engine 1 has a plurality of (e.g., four) cylinders 2 and a cylinder head 3 having an intake valve 31 and an exhaust valve 32. In each cylinder 2, a combustion chamber 5 is defined by an inner wall surface 2a of the cylinder 2, the cylinder head 3, and a piston 4 (see Figure 2). The cylinder head 3 is formed with an intake port 33 and an exhaust port 34 that communicate with the combustion chamber 5. An intake valve 31 is provided at the downstream end of the intake port 33.

[0017] An intake passage 6 and an exhaust passage 7 are connected to the cylinder head 3. The intake passage 6 has, for example, an intake manifold 6a attached to the cylinder head 3 so as to communicate with the intake port 33 of the cylinder head 3. The intake passage 6 refers to the passage for intake air from the intake portion including an air cleaner (not shown) to the downstream end after branching of the intake manifold 6a. The intake passage 6 may be provided with a throttle valve 6b for adjusting the flow rate of intake air.

[0018] Here, the internal combustion engine 1 is configured as a two-valve crossflow engine, for example. In each cylinder 2, one intake valve 31 and one exhaust valve 32 are provided in the cylinder head 3, and an intake port 33 and an exhaust port 34 extend in opposite directions. The intake valve 31 and the exhaust valve 32 are arranged side by side, for example, on the opposite side of the cylinder head 3 from the intake manifold 6a. The internal combustion engine 1 takes in air and hydrogen via the intake valve 31, combusts the hydrogen in the combustion chamber 5, and discharges the exhaust gas produced by the combustion into the exhaust passage 7 via the exhaust valve 32.

[0019] FIG. 2 is a schematic perspective view showing a mixing passage of the first example. In FIG. 2, the downstream end of the intake manifold 6a is shown with its outer shape, but the outer shapes of the cylinder 2, intake port 33, and exhaust port 34 are not shown for convenience of illustration. In reality, the cylinder, intake port, and exhaust port are spaces formed inside the cylinder head or cylinder block. The shapes of the cylinder 2, intake port 33, and exhaust port 34 shown in FIG. 2 represent the shapes of the boundary surfaces that define the spaces inside, such as a 3D-CAD surface model. In the following description, when referring to the cylinder 2, intake port 33, and exhaust port 34, it is intended to refer to the actual cylinder, intake port, and exhaust port (the same applies to FIGS. 3, 4, and 7 to 10).

[0020] 2, the intake port 33 connects the downstream end of the intake manifold 6a to the combustion chamber 5. A connection portion 6c between the downstream end of the intake manifold 6a and the intake port 33 corresponds to the side surface of the cylinder head 3. An injector (fuel injection valve) 8 is attached above the connection portion 6c on the side surface of the cylinder head 3. The injector 8 is inserted into and fixed in a through-hole formed in the cylinder head 3 so that the tip of the injector 8 faces the intake port 33.

[0021] 1, the injector 8 is connected to an ECU (Electronic Control Unit) 50. The ECU 50 is an electronic control unit that controls the internal combustion engine 1. An engine rotation sensor and an intake air amount sensor (not shown) are connected to the ECU 50 as sensors that acquire the operating state of the internal combustion engine 1. The ECU 50 calculates the amount of fuel injected by the injector 8 using a known method based on the engine rotation speed and the intake air amount, and transmits a control signal to the injector 8 to inject hydrogen.

[0022] As shown in FIG. 2 , the intake valve 31 and the exhaust valve 32 are supported reciprocally relative to the cylinder head 3. The intake valve 31 has a valve stem 31a and an umbrella portion 31b (see FIG. 4 ) provided at the lower end of the valve stem 31a. The valve stem 31a passes through a through-hole 33a provided in the cylinder head 3 and is slidably supported via a cylindrical valve guide (not shown) inserted coaxially into the through-hole 33a. The intake valve 31 opens and closes the intake port 33 when the umbrella portion 31b moves away from or contacts a valve seat (not shown) attached to the opening of the intake port 33 that opens to the combustion chamber 5. The intake valve 31 here is positioned so that the valve stem 31a extends substantially parallel to the axial direction of the cylinder 2 and the lower surface of the umbrella portion 31b is substantially parallel to the top surface of the piston 4. The exhaust valve 32 has a similar configuration to the intake valve 31, except for, for example, the size of the umbrella portion.

[0023] The upstream side of the intake port 33 has an inlet at the downstream end of the intake manifold 6a and extends along the underside of the cylinder head 3 in a direction substantially perpendicular to the axial direction of the cylinder 2. The downstream side of the intake port 33 forms a bent portion 33b that bends and extends toward the opening of the intake port 33 that opens to the combustion chamber 5. Above the bent portion 33b in the intake port 33, there is a through hole 33a through which the valve stem 31a of the intake valve 31 passes. Above the bent portion 33b in the intake port 33, the portion surrounding the through hole 33a is thickened so as to surround the valve guide, and a bulge 33c is formed that bulges toward the internal space of the intake port 33.

[0024] The internal combustion engine 1 includes a mixing passage 10 provided along the intake port 33. The mixing passage 10 is an intake passage that promotes mixing of hydrogen and air while preventing the entire intake port 33 from being filled with hydrogen (gaseous fuel). As a first example, the mixing passage 10 can be a tubular member 11 provided inside the intake port 33 and extending from the upstream side to the downstream side of the intake port 33. The tubular member 11 extends, for example, from the upstream side to the downstream side of the intake port 33, from the injector 8 toward the opening of the intake port 33 that opens into the combustion chamber 5, at an angle with respect to the extension direction of the intake port 33. The tubular member 11 has an upstream end 11a that is positioned toward the downstream end of the intake manifold 6a and the injector 8, and a downstream end 11b that is positioned toward the opening of the intake port 33 that opens into the combustion chamber 5.

[0025] The tubular member 11 has a straight portion 11c that extends linearly from the upstream end 11a for a predetermined length coaxially with the injector 8. The straight portion 11c may be, for example, a portion that extends linearly from the upstream end 11a coaxially with the injector 8 and reaches the lower inner wall surface of the intake port 33. The straight portion 11c of the tubular member 11 makes it difficult for the hydrogen injected from the injector 8 to hit the inner wall surface of the tubular member 11, making it easier for the hydrogen injected from the injector 8 to mix with the air. The cross-sectional area of ​​the tubular member 11 may be determined, for example, depending on the design of the output characteristics of the internal combustion engine 1, the amount of hydrogen injected, etc.

[0026] Figure 3 is a schematic plan view showing the introduction portion of the mixing passage of Example 1. In Figure 3, the boundary surface that defines the internal space of the intake port 33 is cut away so that the interior of the intake port 33 can be seen, but although the metal portion of the cylinder head 3 would actually be hatched, for convenience it is shown as a thin-walled pipe (the same applies to Figures 4 and 7 to 10).

[0027] 3, the upstream end 11a of the pipe member 11 is fixed to the inner wall surface of the intake port 33. The upstream end 11a is fixed to the inner wall surface of the intake port 33, for example, by abutting against the periphery of a through-hole in the cylinder head 3 into which the injector 8 is inserted. The upstream end 11a is disposed coaxially with the injector 8.

[0028] An inlet section 12 is provided in the pipe member 11 upstream of the intake port 33. The inlet section 12 is an opening that introduces air from the intake port 33 into the inside of the pipe member 11. The inlet section 12 is formed, for example, by cutting out a part of the outer circumferential surface of the pipe member 11 (for example, half the circumference of the outer circumferential surface) at the upstream end 11a. The inlet section 12 opens, for example, toward the upstream side in the air flow direction at the intake port 33. Inside the pipe member 11, the tip of the injector 8 faces just inside the inlet section 12. In other words, the injector 8 is configured to inject hydrogen toward the inlet section 12.

[0029] 4 is a schematic perspective view showing the outlet portion of the mixing passage of the first example. As shown in FIGS. 2 and 4 , the downstream end 11b of the tubular member 11 is curved to follow the bent portion 33b of the intake port 33. For example, the downstream end 11b of the tubular member 11 is curved from the portion where the straight portion 11c extending from the upstream end 11a reaches the lower inner wall surface of the intake port 33 to follow the lower inner wall surface of the intake port 33. The downstream end 11b of the tubular member 11 is curved downward along the bent portion 33b of the intake port 33 so that the axial direction of the tubular member 11 approaches the axial direction of the cylinder 2. The downstream end 11b of the tubular member 11 may be fixed to the inner wall surface of the intake port 33 by being sandwiched between the lower inner wall surface of the intake port 33 and the bulge portion 33c above the bent portion 33b.

[0030] The pipe member 11 is provided with a discharge section 13 downstream of the intake port 33. The discharge section 13 is an opening that discharges gas fuel and air from inside the pipe member 11 to the intake port 33. The inlet section 12 and the discharge section 13 are arranged, for example, from upstream to downstream along the air flow direction in the intake port 33, in this order. The discharge section 13 is, for example, an opening at the lower end of the pipe member 11 that has been cut in a plane to have a circular cross section. In the example of FIG. 4 , the discharge section 13 opens toward the umbrella section 31b along the axial direction of the cylinder 2.

[0031] 5A and 5B are diagrams for explaining the promotion of mixing of gas fuel and air. In Figures 5A and 5B, an outer cylinder 41 corresponds to an intake port, an inner cylinder 42 corresponds to a conventional jet pipe, and an inner cylinder 44 corresponds to a mixing passage. Figures 5A and 5B show, in grayscale, a simulation of the mixing of air (white in the figure) and gas fuel inside the outer cylinder 41 after injecting gas fuel (black in the figure) into the inner cylinders 42 and 44.

[0032] 5A shows a comparative example in which the inner cylinder 42 is not provided with an introduction portion. In this case, when gas fuel is injected into the inner cylinder 42, the interior of the inner cylinder 42 is substantially entirely dark black. This means that the interior of the inner cylinder 42 is filled with gas fuel. In this configuration, the gas fuel and air begin to mix behind the downstream end of the inner cylinder 42, and it can be seen that it is difficult to sufficiently mix the gas fuel and air at a distance up to the downstream end of the outer cylinder 41, for example.

[0033] In Figure 5(b), the gas fuel nozzle 43 and the inner cylinder 44 have different diameters, and the gap between them functions as an inlet. In this case, when gas fuel is injected into the inner cylinder 44, the inside of the nozzle 43 is dark black, but the black becomes lighter inside the inner cylinder 44, creating a contrasting shade. This means that air is introduced from the inlet, and mixing of the gas fuel and air is progressing inside the inner cylinder 44 behind the inlet. In this configuration, compared to Figure 5(a), there is more space in the distance to the downstream end of the outer cylinder 41, for example, which promotes mixing of the gas fuel and air.

[0034] 6A and 6B are diagrams for explaining that gas fuel is less likely to remain inside the mixing passage. Figures 6A and 6B show, in grayscale, a simulation of the gas fuel remaining in the inner cylinders 42 and 44 after the gas fuel is injected into the inner cylinders 42 and 44 using a configuration similar to that shown in Figures 5A and 5B.

[0035] 6A shows a comparative example in which no introduction section is provided in the inner cylinder 42. In this case, after the gas fuel is injected into the inner cylinder 42, a black gradation area remains over a wide area inside the inner cylinder 42. With this configuration, it is clear that it is difficult to eliminate the state in which the gas fuel remains inside the inner cylinder 42 after the gas fuel is injected into the inner cylinder 42 (for example, when the internal combustion engine is stopped).

[0036] In Fig. 6(b), after the gas fuel is injected into the inner cylinder 44, almost no black color remains inside the inner cylinder 44. This means that, because air is introduced from the inlet, the gas fuel remaining inside the inner cylinder 44 is pushed out (purged) by the air introduced from the inlet. It can be seen that, compared to Fig. 6(a), this configuration makes it easier to eliminate the injected gas fuel remaining inside the inner cylinder 44 after the gas fuel is injected into the inner cylinder 44 (for example, when the internal combustion engine is stopped).

[0037] FIG. 7 is a schematic plan view showing the outlet portion of the mixing passage of the first example. As shown in FIG. 7, the outlet portion 13 is located, for example, on the opposite side of the valve stem 31a of the intake valve 31 from the spark plug 9 of the cylinder 2. In FIG. 7, the electrode of the spark plug 9 is shown in the lower right corner of the page. The spark plug 9 is attached to the cylinder head 3 so that the electrode faces, for example, near the center of the upper part of the combustion chamber 5 (see FIG. 11). In FIG. 7, when the direction as viewed from the center of the intake valve 31 is represented by an angle where the direction of the dashed line is 0° and the counterclockwise direction in the plan view of FIG. 7 is a positive sign, the center P of the outlet portion 13 is located at a position of approximately 225°. The center of the outlet portion 13 is not limited to the position of approximately 225° and may be located within a range of, for example, 135° to 315°. The center P of the outlet portion 13 may be located at a position further back from the spark plug (at approximately 45°) than an imaginary plane extending perpendicular to an imaginary line connecting the spark plug and the valve stem 31a and including the axis of the valve stem 31a.

[0038] FIG. 11 is a schematic cross-sectional view showing an example of in-cylinder flow in an internal combustion engine of a comparative example. The internal combustion engine 100 of FIG. 11 differs from the internal combustion engine 1 in that it does not include a mixing passage 10. FIG. 11 shows the in-cylinder flow obtained by analyzing, by simulation, the distribution of excess air ratio and the intake air streamlines when the intake valve 131 of the internal combustion engine 100 is open. As shown in FIG. 11 , in the internal combustion engine 100, a vortex is generated near the spark plug 109 in the combustion chamber 105. This vortex is thought to occur when an airflow passing through the gap where the intake valve 131 is open, farther from the spark plug 109 (left side in the figure), collides with the top surface of the piston 104, becomes a counterclockwise airflow in the figure, and collides with an airflow passing through the gap where the intake valve 131 is open, closer to the spark plug 109 (right side in the figure). This vortex can easily draw hydrogen flowing from the intake port 133 into the combustion chamber 105 into the vicinity of the spark plug 109, which may cause abnormal combustion such as backfire.

[0039] In this regard, by preventing hydrogen from the intake port from approaching the vicinity of the spark plug, it is possible to suppress abnormal combustion such as backfire. Therefore, by positioning the outlet portion 13 on the opposite side of the valve stem 31a of the intake valve 31 from the spark plug 9 of the cylinder, as shown in Figure 7, the flow of hydrogen and air discharged to the intake port 33 via the outlet portion 13 is obstructed by the valve stem 31a, making it difficult for hydrogen to approach the spark plug 9. In other words, it is possible to retard (delay) the inflow of hydrogen into the vicinity of the spark plug 9. Retarding the inflow of hydrogen reduces the temperature of the spark plug 9 by the time the hydrogen approaches the spark plug 9, which is presumably effective in preventing abnormal combustion caused by hydrogen approaching the spark plug 9 and igniting.

[0040] [Operation and Effects] In the internal combustion engine 1, hydrogen is injected by the injector 8 toward the inside of the mixing passage 10 provided along the intake port 33. The mixing passage 10 prevents hydrogen filling the intake port 33 from obstructing the flow of air (air block effect) and from remaining in the intake port 33, thereby contributing to improving the efficiency of air filling into the cylinder 2 and suppressing the occurrence of abnormal combustion such as backfire. In the internal combustion engine 1, air from the intake port 33 is introduced into the mixing passage 10 through the introduction portion 12. As a result, the injected hydrogen and the introduced air are mixed inside the mixing passage 10. The hydrogen and air mixed inside the mixing passage 10 are led out to the intake port 33 through the lead-out portion 13 and taken into the cylinder 2. Therefore, mixing of hydrogen and air is promoted compared to, for example, a case in which the introduction portion 12 is not provided or the mixing passage 10 itself is not provided. Furthermore, when the injection of hydrogen by the injector 8 stops, the hydrogen remaining inside the mixing passage 10 is pushed (purged) into the outlet portion 13 by the air introduced from the inlet portion 12. Therefore, when the internal combustion engine 1 is stopped, hydrogen is less likely to remain inside the mixing passage 10. Therefore, in a four-stroke, port-injection internal combustion engine 1 that uses hydrogen as fuel, the internal combustion engine 1 promotes mixing of hydrogen and air while improving the efficiency of filling air into the cylinders 2 and suppressing the occurrence of abnormal combustion such as backfire, and also makes it easier to prevent injected unburned hydrogen from remaining inside the internal combustion engine 1.

[0041] The mixing passage 10 is a pipe member 11 provided inside the intake port 33 so as to extend from the upstream side to the downstream side of the intake port 33. An inlet section 12 is provided in the pipe member 11 upstream of the intake port 33, and an outlet section 13 is provided in the pipe member 11 downstream of the intake port 33. The injector 8 is provided to inject hydrogen toward the inlet section 12. In this way, the pipe member 11 provided inside the intake port 33 can form the mixing passage 10 of the first example.

[0042] The outlet portion 13 is located on the opposite side of the valve stem 31a of the intake valve 31 from the spark plug 9 of the cylinder 2. This makes it possible to prevent hydrogen from approaching the spark plug 9 by utilizing the fact that the flow of hydrogen and air that has been led to the intake port 33 via the outlet portion 13 is obstructed by the valve stem 31a of the intake valve 31.

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

[0044] In the above embodiment, the tubular member 11 is used as an example of the mixing passage 10, but this is not limiting. The mixing passage may be a tubular member 11A in which the orientation of the outlet portion 13 is changed, as shown in FIG. 8 . FIG. 8 is a schematic perspective view showing a modified example of the outlet portion of the mixing passage of the first example. A tubular member 11A is provided downstream of the intake port 33 with an outlet portion 13A oriented in a direction different from that of the outlet portion 13. The outlet portion 13A is inclined with respect to the axial direction of the cylinder 2 and opens toward the umbrella portion 31b. The center of the outlet portion 13A may be positioned at an angle of approximately 270°, instead of the 225° position shown in FIG. 7 . By inclining the outlet portion 13A and opening toward the umbrella portion 31b in this manner, hydrogen can be introduced into the cylinder 2 along the swirl flow within the cylinder 2.

[0045] In the above embodiment, the introduction section 12 is open toward the upstream side of the air flow direction in the intake port 33, but this is not limited to this example. The introduction section may be open toward a side other than the upstream side of the air flow direction in the intake port 33. Alternatively, the introduction section may be a punched section including a large number of through holes that penetrate the pipe member 11 in the radial direction.

[0046] In the above embodiment, the upstream end 11a abuts against the periphery of the through-hole of the cylinder head 3 into which the injector 8 is inserted, but this is not limiting. For example, the outer peripheral surface of the pipe member 11 may be fixed to the inner wall surface of the intake port 33 via a member that functions as a stay, so that the entire end face of the upstream end 11a is separated from the injector 8 or the cylinder head 3.

[0047] As another example of the mixing passage 10, for example, a pipe member may not be used, as in the internal combustion engine 1A shown in Figures 9 and 10. Figure 9 is a schematic perspective view showing a mixing passage of a second example. Figure 10 is a schematic perspective view showing an outlet portion of the mixing passage of the second example. The mixing passage 10 of the second example is a partial passage 15 partitioned by a partition member 14 provided inside the intake port 33 so as to extend from the upstream side to the downstream side of the intake port 33.

[0048] The partition member 14 is, for example, a plate-like member provided inside the intake port 33 so as to divide the internal space of the intake port 33 into two sections along the extension direction of the intake port 33. The partition member 14 extends along the width direction of the intake port 33 on the upstream side of the intake port 33 so as to divide the internal space of the intake port 33 into upper and lower sections. The partition member 14 extends from the upstream side to the downstream side of the intake port 33, toward the opening of the intake port 33 that opens from the injector 8 to the combustion chamber 5. The partition member 14 is continuous with the inner wall surface of the intake port 33 at both ends in the width direction of the intake port 33. The partition member 14 may be formed integrally with the intake port 33 by casting. Alternatively, the partition member 14 may be a plate-like member separate from the intake port 33 and joined to the inner wall surface of the intake port 33.

[0049] The partial passage 15 here is the upper space of the space inside the intake port 33 divided into upper and lower halves. The cross-sectional area of ​​the partial passage 15 may be determined, for example, in accordance with the design of the output characteristics of the internal combustion engine 1, the amount of hydrogen injection, etc. In the examples of Figures 9 and 10, the cross-sectional area of ​​the upstream side of the partial passage 15 is set equal to or smaller than the cross-sectional area of ​​the portion of the intake port 33 excluding the partial passage 15.

[0050] An introduction section 16 is provided in the partial passage 15 upstream of the intake port 33. The introduction section 16 is an opening that introduces air from the intake port 33 into the interior of the partial passage 15. The introduction section 16 is, for example, the upper opening of the intake port 33 that is divided into upper and lower halves at the connection section 6c with the intake manifold 6a. The tip of the injector 8 faces the introduction section 16 inside the partial passage 15. In other words, the injector 8 is configured to inject hydrogen toward the introduction section 16.

[0051] 10 , the downstream end 14a of the partition member 14 is curved at the downstream end 15a of the partial passage 15 so as to fit along the bent portion 33b of the intake port 33. The end face of the downstream end 14a of the partition member 14 is located further back than the valve stem 31a of the intake valve 31 when viewed from the upstream side of the intake port 33. Therefore, the cross-sectional area of ​​the downstream side of the partial passage 15 is smaller than the cross-sectional area of ​​the portion of the intake port 33 excluding the partial passage 15. The downstream end 14a of the partition member 14 is provided with a through-hole 14b through which the valve stem 31a of the intake valve 31 passes. A recess 14c may be provided at the downstream end 14a of the partition member 14 to prevent interference with the head portion 31b of the intake valve 31 when the valve is closed.

[0052] An outlet portion 17 is provided in the partial passage 15 downstream of the intake port 33. The outlet portion 17 is an opening that leads gas fuel and air from inside the partial passage 15 to the intake port 33. The outlet portion 17 is, for example, an opening at the lower end of the downstream end portion 15a of the partial passage 15. In the example of FIG. 10 , the outlet portion 17 is located on the opposite side of the valve stem 31a of the intake valve 31 from the spark plug 9 of the cylinder 2, and opens toward the head portion 31b. In the internal combustion engine 1A, the spark plug 9 is arranged in the same manner as in FIG. 7 .

[0053] In the mixing passage 10 of the second example described above, the mixing passage 10 is a partial passage 15 partitioned by a partition member 14 provided inside the intake port 33 so as to extend from the upstream side to the downstream side of the intake port 33. An inlet portion 16 is provided in the partial passage 15 upstream of the intake port 33. An outlet portion 17 is provided in the partial passage 15 downstream of the intake port 33. The injector 8 is provided to inject hydrogen toward the inlet portion 16. As a result, the mixing passage 10 of the second example can be formed by the partial passage 15 partitioned by the partition member 14 provided inside the intake port 33. Note that this configuration can improve mountability compared to when using the tubular member 11, by eliminating the need to install the tubular member 11.

[0054] In the above embodiment, the outlet portions 13, 17 are located on the opposite side of the valve stem 31a of the intake valve 31 from the spark plug 9 of the cylinder 2, but this arrangement is not essential.

[0055] In the above embodiment, the inlet portion 12 of the pipe member 11 and the inlet portion 16 of the partial passage 15 are provided at their respective upstream ends, but they may be provided at a location other than the upstream end (for example, a location other than the upstream end within their respective upstream ranges). The outlet portion 13 of the pipe member 11 and the outlet portion 17 of the partial passage 15 are provided at their respective downstream ends, but they may be provided at a location other than the downstream end (for example, a location other than the downstream end within their respective downstream ranges).

[0056] In the above embodiment, the inlet section 12 and the outlet section 13 are arranged in this order from upstream to downstream along the air flow direction in the intake port 33, for example. However, this is not limiting. The inlet section and the outlet section may also be arranged in the reverse order from upstream to downstream along the air flow direction in the intake port 33, for example. In this case, the mixing passage may be a loop-shaped passage that passes along the outside of the intake port, so that air is introduced from the inlet section arranged downstream in the air flow direction in the intake port 33 and the air is discharged from the outlet section arranged upstream in the air flow direction in the intake port 33.

[0057] The constituent elements of various aspects of the present invention are described below. [1] A four-stroke port injection internal combustion engine fueled by gaseous fuel, comprising: a mixing passage provided along an intake port; and a fuel injection valve provided to inject the gaseous fuel toward the interior of the mixing passage, wherein the mixing passage has an inlet portion that introduces air from the intake port into the mixing passage, and an outlet portion that discharges the gaseous fuel and the air from the interior of the mixing passage to the intake port. [2] The internal combustion engine according to [1], wherein the mixing passage is a pipe member provided inside the intake port so as to extend from the upstream side to the downstream side of the intake port, the inlet portion is provided in the pipe member upstream of the intake port, and the outlet portion is provided in the pipe member downstream of the intake port, and the fuel injection valve is provided to inject the gaseous fuel toward the inlet portion. [3] The internal combustion engine according to [1], wherein the mixing passage is a partial passage partitioned by a partition member provided inside the intake port so as to extend from the upstream side to the downstream side of the intake port, the partial passage is provided with the inlet portion upstream of the intake port, the partial passage is provided with the outlet portion downstream of the intake port, and the fuel injection valve is provided to inject the gas fuel toward the inlet portion. [4] The internal combustion engine according to any of [1] to [3], wherein the outlet portion is located on the opposite side of the valve stem of the intake valve from the spark plug of the cylinder.

[0058] REFERENCE SIGNS LIST 1, 1A Internal combustion engine 2 Cylinder 8 Injector (fuel injection valve) 9 Spark plug 10 Mixing passage 11, 11A Pipe member 12, 16 Inlet portion 13, 13A, 17 Outlet portion 14 Partition member 15 Partial passage 31 Intake valve 31a Valve stem 33 Intake port

Claims

1. A four-stroke port injection internal combustion engine using gas fuel, comprising a mixing passage provided along an intake port, and a fuel injection valve provided to inject the gas fuel toward the inside of the mixing passage, wherein the mixing passage has an introduction portion for introducing air from the intake port into the inside of the mixing passage, and a derivation portion for deriving the gas fuel and the air from the inside of the mixing passage into the intake port.

2. The internal combustion engine according to claim 1, wherein the mixing passage is a pipe member provided to extend from the upstream side to the downstream side of the intake port inside the intake port, the introduction portion is provided on the upstream side of the intake port in the pipe member, the derivation portion is provided on the downstream side of the intake port in the pipe member, and the fuel injection valve is provided to inject the gas fuel toward the introduction portion.

3. The internal combustion engine according to claim 1, wherein the mixing passage is a partial passage partitioned by a partition member provided to extend from the upstream side to the downstream side of the intake port inside the intake port, the introduction portion is provided on the upstream side of the intake port in the partial passage, the derivation portion is provided on the downstream side of the intake port in the partial passage, and the fuel injection valve is provided to inject the gas fuel toward the introduction portion.

4. The internal combustion engine according to claim 2 or 3, wherein the derivation portion is located on the side opposite to the ignition plug of the cylinder with respect to the valve stem of the intake valve.

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