Internal combustion engine

Abstract

To solve a problem that if foreign matters flow back within a communication passage and reach a fuel injection valve, this might cause damage of the fuel injection valve and biting.SOLUTION: An internal combustion engine includes: an engine body 10 having a combustion chamber R where an air-fuel mixture of intake air and gas fuel is burned; and a fuel injection valve 20 for injecting the gas fuel to the combustion chamber R. The engine body 10 includes: an accommodation hole 30 for accommodating the fuel injection valve 20; and a communication passage 35 for connecting the accommodation hole 30 and the combustion chamber R. When an opening on the accommodation hole 30 side in the communication passage 35 is defined as a first opening 35A and an opening on the combustion chamber R side in the communication passage 35 is defined as a second opening 35B, an opening area of the second opening 35B is smaller than that of the first opening 35A.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] The internal combustion engine of Patent Document 1 includes a combustion chamber and a fuel injection valve. The combustion chamber is a space for burning a mixture of intake air and fuel. The fuel injection valve directly injects fuel into the combustion chamber. The internal combustion engine of Patent Document 1 also includes a communication passage through which the fuel injected from the fuel injection valve flows. The communication passage opens toward the combustion chamber. Therefore, the fuel injected from the fuel injection valve reaches the combustion chamber through the communication passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-105655 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an internal combustion engine such as that described in Patent Document 1, foreign matter may enter the combustion chamber from the outside, or deposits that have accumulated on the inner surface of the combustion chamber may peel off and become foreign matter. If such foreign matter flows back through the communication passage and reaches the fuel injection valve, it may cause the fuel injection valve to be damaged or jammed. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides an internal combustion engine comprising an engine body having a combustion chamber in which a mixture of intake air and gaseous fuel is burned, and a fuel injection valve which injects the gaseous fuel into the combustion chamber, wherein the engine body has an accommodating hole which accommodates the fuel injection valve, and a communicating passage which connects the accommodating hole and the combustion chamber, and wherein when an opening of the communicating passage on the accommodating hole side is designated as a first opening, and an opening of the communicating passage on the combustion chamber side is designated as a second opening, the opening area of ​​the second opening is smaller than the opening area of ​​the first opening. Effect of the Invention

[0006] According to the above-described configuration, foreign matter is unlikely to enter the communication passage from the combustion chamber side, so that damage or jamming of the fuel injection valve due to foreign matter is unlikely to occur. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine. [Diagram 2] FIG. 2 is an end view of the fuel injection valve. [Diagram 3] FIG. 3 is an enlarged end view of the cylinder head in the vicinity of the communication passage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, components may be shown enlarged to facilitate understanding. The dimensional ratios of the components may differ from those in the actual drawings or from those in other drawings.

[0009] <General configuration of internal combustion engine> As shown in Fig. 1, the internal combustion engine E includes an engine body 10. The engine body 10 is composed of a cylinder block 11 and a cylinder head 12. The cylinder block 11 has a cylinder 11A. The cylinder 11A is a cylindrical space. The cylinder 11A opens at an end face of the cylinder block 11. Although Fig. 1 shows only one set of the cylinder 11A and its related components, the internal combustion engine E has a plurality of cylinders 11A and their related components.

[0010] The cylinder head 12 is connected to an end face of the cylinder block 11. The cylinder head 12 has a recess 12A, an intake port 12B, and an exhaust port 12C. The recess 12A is recessed in the end face on the cylinder block 11 side. The recess 12A is a roughly hemispherical space. The opening diameter of the recess 12A is the same as the inside diameter of the cylinder 11A. The recess 12A faces the cylinder 11A. The recess 12A and the cylinder 11A form a continuous combustion chamber R. The combustion chamber R is a space in which a mixture of intake air and gaseous fuel is burned.

[0011] The intake port 12B is a passage for intake air to be supplied to the combustion chamber R. A first end of the intake port 12B is connected to the recess 12A. A second end of the intake port 12B is connected to an intake pipe (not shown). The exhaust port 12C is a passage for exhaust air discharged from the combustion chamber R. A first end of the exhaust port 12C is connected to the recess 12A. A second end of the exhaust port 12C is connected to an exhaust pipe (not shown).

[0012] The internal combustion engine E includes a piston 13, an intake valve 14, an exhaust valve 15, and a spark plug 16. The piston 13 is located in a cylinder 11A. The piston 13 reciprocates within the cylinder 11A as the air-fuel mixture is burned in the combustion chamber R. Although not shown, the piston 13 is connected to a crankshaft via a connecting rod. The connecting rod and the crankshaft convert the reciprocating motion of the piston 13 into a rotational motion. In the following description, the direction of motion of the piston 13 when the air-fuel mixture in the combustion chamber R is compressed is referred to as the top dead center direction UP, and the opposite direction is referred to as the bottom dead center direction DW.

[0013] The intake valve 14 is attached to the cylinder head 12. The intake valve 14 opens and closes a first end of the intake port 12B. The intake valve 14 operates in synchronization with the reciprocating motion of the piston 13. The exhaust valve 15 is attached to the cylinder head 12. The exhaust valve 15 opens and closes a first end of the exhaust port 12C. The exhaust valve 15 operates in synchronization with the reciprocating motion of the piston 13.

[0014] The spark plug 16 is attached to the cylinder head 12. The spark plug 16 is located between the intake port 12B and the exhaust port 12C. The tip of the spark plug 16 is located within the recess 12A. The spark plug 16 ignites the air-fuel mixture in the combustion chamber R by spark discharge. The spark plug 16 ignites the air-fuel mixture in synchronization with the reciprocating movement of the piston 13.

[0015] The internal combustion engine E includes a fuel injector 20. The fuel injector 20 is attached to the cylinder head 12. The fuel injector 20 injects gaseous fuel directly into the combustion chamber R without passing through the intake port 12B. An example of the gaseous fuel is hydrogen.

[0016] As shown in FIG. 2, the fuel injection valve 20 has a cylindrical body 21 and a needle valve 22. The cylindrical body 21 is generally cylindrical. The central axis C1 of the cylindrical body 21 is the central axis of the fuel injection valve 20. The cylindrical body 21 has an injection port 21A at an end in the direction along the central axis C1. The injection port 21A is an opening for injecting gas fuel in the cylindrical body 21 to the outside of the fuel injection valve 20. The injection port 21A is circular. The center of the opening of the injection port 21A is located on the central axis C1.

[0017] The needle valve 22 has a valve body 22A and a diamond-like carbon film 22B. The valve body 22A is substantially rod-shaped. The valve body 22A is located inside the cylindrical body 21. The valve body 22A can reciprocate on the central axis C1 by an electromagnetic solenoid (not shown). The valve body 22A opens and closes the injection port 21A of the cylindrical body 21 on the inside side of the cylindrical body 21 by reciprocating. The diamond-like carbon film 22B covers the tip surface of the valve body 22A among the surfaces of the valve body 22A. The diamond-like carbon film 22B is an amorphous film mainly composed of one or more selected from hydrocarbons and carbon. The diamond-like carbon film 22B is sometimes called a hard carbon film. In FIG. 2, the diamond-like carbon film 22B is illustrated by a thick line.

[0018] <Structure around the fuel injection valve> As shown in FIG. 3, the cylinder head 12 has an accommodating hole 30 that accommodates the fuel injection valve 20. The accommodating hole 30 is located on the bottom dead center direction DW side with respect to the intake port 12B. The accommodating hole 30 is a substantially cylindrical space. The accommodating hole 30 has a bottom surface 30A. The bottom surface 30A is an inner surface of the accommodating hole 30 on the combustion chamber R side. The central axis of the accommodating hole 30 is inclined so as to be located closer to the bottom dead center direction DW as it approaches the combustion chamber R.

[0019] The fuel injection valve 20 is located in the accommodation hole 30. The injection port 21A of the cylindrical body 21 faces the bottom surface 30A of the accommodation hole 30. The central axis C1 of the cylindrical body 21 coincides with the central axis of the accommodation hole 30. In other words, the central axis C1 is inclined so as to be located toward the bottom dead center direction DW as it approaches the injection direction of the gas fuel of the fuel injection valve 20. The tip of the cylindrical body 21 on the injection port 21A side is slightly separated from the bottom surface 30A of the accommodation hole 30. In other words, a gap S is generated between the fuel injection valve 20 and the bottom surface 30A of the accommodation hole 30.

[0020] The cylinder head 12 has a communication passage 35 that connects the accommodation hole 30 and the combustion chamber R. The communication passage 35 is a space in a truncated cone shape. In the following, the opening of the communication passage 35 on the accommodation hole 30 side is referred to as a first opening 35A. Also, the opening of the communication passage 35 on the combustion chamber R side is referred to as a second opening 35B.

[0021] The central axis of the communication passage 35 coincides with the central axis C1 of the fuel injection valve 20. Therefore, the entire communication passage 35 from the first opening 35A to the second opening 35B is located on the central axis C1. More specifically, the opening center of the first opening 35A, the opening center of the second opening 35B, and the opening center of the injection port 21A of the fuel injection valve 20 are all located on the central axis C1.

[0022] The opening area of ​​the second opening 35B is smaller than that of the first opening 35A. Specifically, both the second opening 35B and the first opening 35A are circular. The diameter of the second opening 35B is half that of the first opening 35A. Therefore, the opening area of ​​the second opening 35B is a quarter of the opening area of ​​the first opening 35A. The "opening area" is the largest area among the apparent areas of the regions surrounded by the opening edges when the first opening 35A or the second opening 35B is viewed from various directions. In this embodiment, the area when viewed in a direction parallel to the central axis C1 is the opening area of ​​the first opening 35A and the opening area of ​​the second opening 35B.

[0023] In addition, since the communication passage 35 is frustum-shaped, the flow passage cross-sectional area of ​​the communication passage 35 continuously decreases from the first opening 35A to the second opening 35B. In other words, when the communication passage 35 is viewed in cross section along a cross section including its central axis, the inner surface of the communication passage 35 is linear or curved and inclined relative to the central axis of the communication passage 35. In this embodiment, the flow passage cross-sectional area of ​​the communication passage 35 decreases by a constant area from the first opening 35A to the second opening 35B. Note that the "flow passage cross-sectional area" refers to the area inside the communication passage 35 in a cross section perpendicular to the central axis of the communication passage 35.

[0024] <Operation of the embodiment> When the needle valve 22 of the fuel injection valve 20 is opened, the gaseous fuel in the cylinder 21 is injected from the injection port 21A. As described above, the opening center of the first opening 35A, the opening center of the second opening 35B, and the opening center of the injection port 21A in the fuel injection valve 20 are all located on the central axis C1. Therefore, the injected gaseous fuel quickly reaches the combustion chamber R through the communication passage 35 according to the negative pressure in the cylinder 11A generated when the piston 13 moves toward the bottom dead center DW.

[0025] Since the flow path cross-sectional area of ​​the communicating passage 35 becomes continuously smaller toward the second opening 35B, a part of the injected gaseous fuel collides with the inner surface of the communicating passage 35. However, since the gaseous fuel is in a vaporized state, even if the gaseous fuel collides with the inner surface of the communicating passage 35, the possibility that the gaseous fuel will condense on the inner surface of the communicating passage 35 is low.

[0026] <Effects of the embodiment> (1) According to the above embodiment, the opening area of ​​the second opening 35B is smaller than the opening area of ​​the first opening 35A. Therefore, even if a foreign object enters the combustion chamber R, the foreign object is less likely to enter the communication passage 35 compared to a case in which the opening area of ​​the second opening 35B is equal to or larger than the opening area of ​​the first opening 35A. Therefore, it is possible to reduce the possibility that the foreign object that has entered the accommodating hole 30 via the communication passage 35 will cause damage to or jamming of the fuel injection valve 20.

[0027] (2) According to the above embodiment, the flow passage area of ​​the communication passage 35 continuously decreases from the first opening 35A to the second opening 35B. In other words, the inner surface of the communication passage 35 has no clear step and has a gentle shape. This prevents the inner surface of the communication passage 35 from interfering with the flow of the gaseous fuel injected from the injection port 21A of the fuel injection valve 20. Even if a foreign object enters the accommodation hole 30, the foreign object can be easily guided into the combustion chamber R by following the flow of the gaseous fuel.

[0028] (3) According to the above embodiment, the injection port 21A of the fuel injection valve 20 is located on the central axis C1. Furthermore, the entire communication passage 35 from the first opening 35A to the second opening 35B is located on the central axis C1. That is, a linear flow path is secured from the injection port 21A through the communication passage 35 to the combustion chamber R. Therefore, even if the opening area of ​​the second opening 35B is relatively small, the flow of gaseous fuel to the combustion chamber R is prevented from being excessively hindered.

[0029] (4) According to the above embodiment, the opening area of ​​the second opening 35B is half or less, specifically, a quarter, of the opening area of ​​the first opening 35A. By making the opening area of ​​the second opening 35B considerably small in this manner, it is possible to prevent large foreign matter that may damage the fuel injection valve 20 from entering the accommodating hole 30.

[0030] <Example of change> This embodiment can be modified as follows: Furthermore, this embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0031] The configuration of the internal combustion engine E can be modified as appropriate. For example, the internal combustion engine E may include a port injection valve that injects fuel into the intake port 12B in addition to the fuel injection valve 20. The internal combustion engine E may also include a water injection valve that injects cooling water into the intake port 12B.

[0032] As long as the gas fuel can be injected into the cylinder 11A, the position of the fuel injection valve 20 can be adjusted as appropriate. For example, the accommodation hole 30 that accommodates the fuel injection valve 20 may be located on the bottom dead center direction DW side with respect to the exhaust port 12C.

[0033] The fuel injection valve 20 may have a plurality of injection ports 21A. Furthermore, the injection ports 21A may be oriented in a direction inclined with respect to the central axis C1. There may be no gap S between the fuel injection valve 20 and the bottom surface 30A of the accommodation hole 30. As long as the injection port 21A of the fuel injection valve 20 and the communication passage 35 are connected, the presence or absence of the gap S does not matter.

[0034] The shape of the communication passage 35 is not limited to a truncated cone. For example, the shape of the communication passage 35 may be an elliptical truncated cone or a polygonal truncated cone. The shape of the communication passage 35 may be a bent shape or a curved shape.

[0035] The flow passage area of ​​the communication passage 35 does not necessarily have to be continuously smaller toward the second opening 35B. For example, the flow passage area of ​​the communication passage 35 may be gradually smaller from the first opening 35A toward the second opening 35B. Even in this case, the opening area of ​​the second opening 35B is smaller than the opening area of ​​the first opening 35A.

[0036] Furthermore, so long as the opening area of ​​the second opening 35B is smaller than the opening area of ​​the first opening 35A, there is no problem with the flow path area in the middle of the communication passage 35. For example, the flow path area in the middle of the communication passage 35 may be larger than the opening area of ​​the second opening 35B and the opening area of ​​the first opening 35A.

[0037] The centers of the first opening 35A and the second opening 35B do not have to be located on the central axis C1. Furthermore, the entire first opening 35A and the entire second opening 35B do not have to be located on the central axis C1.

[0038] The opening area of ​​the second opening 35B may be less than the opening area of ​​the first opening 35A. However, from the viewpoint of preventing large foreign matter that may damage the fuel injection valve 20 from entering the accommodating hole 30, the opening area of ​​the second opening 35B is preferably half or less of the opening area of ​​the first opening 35A.

[0039] The cylinder head 12 may have other communication passages in addition to the communication passage 35 of the above embodiment. In this case, the opening areas of both ends of the other communication passages may be in any size relationship.

[0040] The diamond-like carbon film 22B may be omitted from the needle valve 22. Also, in the needle valve 22, another protective film may be used in place of the diamond-like carbon film 22B.

[0041] <Additional Notes> The technical ideas that can be derived from the above-described embodiments and modifications will be described below. <Appendix 1> an engine body having a combustion chamber in which a mixture of intake air and gaseous fuel is burned; a fuel injection valve that injects the gaseous fuel into the combustion chamber; It is equipped with the engine body has an accommodation hole that accommodates the fuel injection valve, and a communication passage that connects the accommodation hole and the combustion chamber, When an opening of the communication passage on the side of the accommodation hole is defined as a first opening and an opening of the communication passage on the side of the combustion chamber is defined as a second opening, The opening area of ​​the second opening is smaller than the opening area of ​​the first opening. Internal combustion engine.

[0042] <Appendix 2> The flow passage area of ​​the communication passage becomes continuously smaller from the first opening toward the second opening. 2. An internal combustion engine as described in appended claim 1.

[0043] <Appendix 3> the fuel injection valve has an injection port for the gas fuel, The injection port is located on a central axis of the fuel injection valve, and the entire communication passage from the first opening to the second opening is located on the central axis of the fuel injection valve. 3. An internal combustion engine according to claim 1 or 2.

[0044] <Appendix 4> The opening area of ​​the second opening is equal to or less than half the opening area of ​​the first opening. 4. An internal combustion engine according to any one of claims 1 to 3. [Explanation of symbols]

[0045] E…Internal combustion engine 10. Main body of the engine 12...Cylinder head 20...Fuel injector 30…Housing hole 35…Communication path 35A…1st opening 35B…Second opening R…Combustion chamber

Claims

1. an engine body having a combustion chamber in which a mixture of intake air and gaseous fuel is burned; a fuel injection valve that injects the gaseous fuel into the combustion chamber; Equipped with the engine body has an accommodation hole that accommodates the fuel injection valve, and a communication passage that connects the accommodation hole and the combustion chamber, When an opening of the communication passage on the side of the accommodating hole is defined as a first opening and an opening of the communication passage on the side of the combustion chamber is defined as a second opening, The opening area of ​​the second opening is smaller than the opening area of ​​the first opening. Internal combustion engine.

2. The flow passage area of ​​the communication passage becomes continuously smaller from the first opening toward the second opening.

2. The internal combustion engine of claim 1.

3. the fuel injection valve has an injection port for the gas fuel, The injection port is located on a central axis of the fuel injection valve, and the entire communication passage from the first opening to the second opening is located on the central axis of the fuel injection valve.

2. The internal combustion engine of claim 1.

4. The opening area of ​​the second opening is equal to or less than half the opening area of ​​the first opening.

2. The internal combustion engine of claim 1.

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