Internal combustion engine

Abstract

To provide an internal combustion engine which can enhance a compression ratio.SOLUTION: An internal combustion engine 10 comprises: a combustion chamber S which is defined between a cylinder head 12 and a top face 13a of a piston 13; and an injector 17 which is accommodated in an injector accommodation hole 26 provided at the cylinder head 12, and injects fuel into the combustion chamber S. A spray escape recess 27 is provided at an opposing face 12b being a face for defining the combustion chamber S of the cylinder head 12. The injector accommodation hole 26 is opened at an inner face of the spray escape recess 27. The piston 13 has a protrusion 33 which protrudes from the top face 13a and is located in the spray escape recess 27 in a state that the piston 13 is located at an upper dead point.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The internal combustion engine described in Patent Document 1 includes a cylinder head, a piston, and an injector. A combustion chamber is defined between the cylinder head and a top surface of the piston. The injector is accommodated in an accommodating hole provided in the cylinder head. The injector injects fuel into the combustion chamber. A spray escape recess is provided on a surface of the cylinder head that defines the combustion chamber. The accommodating hole opens to the inner surface of the spray escape recess. This prevents the fuel injected by the injector from adhering to the cylinder head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-57808 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the spray escape recess is provided, the volume of the combustion chamber increases by the volume of the spray escape recess, resulting in a decrease in the compression ratio. [Means for solving the problem]

[0005] An internal combustion engine for solving the above problems includes a combustion chamber defined between a cylinder head and a top surface of a piston, and an injector accommodated in an injector accommodating hole provided in the cylinder head for injecting fuel into the combustion chamber, wherein a spray escape recess is provided in a surface of the cylinder head defining the combustion chamber, and the injector accommodating hole opens onto an inner surface of the spray escape recess, and the piston has a protrusion that protrudes from the top surface and is located within the spray escape recess when the piston is positioned at top dead center. Effect of the Invention

[0006] According to the present invention, the compression ratio can be increased. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of an internal combustion engine. [Diagram 2] FIG. 2 is a perspective view of the cylinder head. [Diagram 3] FIG. 3 is a perspective view of the piston. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of an internal combustion engine will now be described with reference to Figures 1 to 3. The internal combustion engine of this embodiment is a hydrogen engine that uses hydrogen as fuel. As shown in FIG. 1, the internal combustion engine 10 includes a cylinder block 11, a cylinder head 12, a piston 13, an intake valve 14, an exhaust valve 15, an ignition plug 16, and an injector 17.

[0009] The cylinder block 11 has a cylinder 11a. The cylinder 11a is a cylindrical space. The cylinder 11a opens at an end face 11b of the cylinder block 11. The piston 13 is located in the cylinder 11a. The piston 13 is substantially cylindrical. The axial direction of the piston 13 coincides with the axial direction of the cylinder 11a. The piston 13 reciprocates in the axial direction of the cylinder 11a. FIG. 1 illustrates the piston 13 located at the top dead center. Although not illustrated, the piston 13 is connected to a crankshaft via a connecting rod. The axis of the crankshaft extends in a direction perpendicular to the paper surface of FIG. 1. The connecting rod and the crankshaft convert the linear motion of the piston 13 into the rotational motion of the crankshaft.

[0010] The cylinder head 12 is connected to the end surface 11b of the cylinder block 11 via a gasket (not shown). The cylinder head 12 has a connection surface 12a that is connected to the end surface 11b of the cylinder block 11, and an opposing surface 12b that faces the top surface 13a of the piston 13. The opposing surface 12b is a surface having a circular outer edge. The opposing surface 12b is recessed with respect to the connection surface 12a. A combustion chamber S is defined between the opposing surface 12b of the cylinder head 12 and the top surface 13a of the piston 13. The opposing surface 12b is a surface that defines the combustion chamber S in the cylinder head 12.

[0011] 1 and 2, the opposing surface 12b of the cylinder head 12 has a first recess 21 and a first annular surface 22. The first recess 21 is located in the center of the opposing surface 12b. The first annular surface 22 surrounds the first recess 21.

[0012] As shown in FIG. 2, the cylinder head 12 has two intake ports 23 and two exhaust ports 24. The two intake ports 23 are aligned in the axial direction of the crankshaft. The two exhaust ports 24 are aligned in the axial direction of the crankshaft. The two intake ports 23 and the two exhaust ports 24 are aligned in a direction perpendicular to both the axial direction of the cylinder 11a and the axial direction of the crankshaft. The two intake ports 23 and the two exhaust ports 24 each open on the inner surface of the first recess 21. The intake valve 14 opens and closes the intake port 23. The exhaust valve 15 opens and closes the exhaust port 24.

[0013] The cylinder head 12 has a plug accommodating hole 25. The plug accommodating hole 25 opens to the inner surface of the first recess 21. The plug accommodating hole 25 is located in the center of the first recess 21. The plug accommodating hole 25 is surrounded by two intake ports 23 and two exhaust ports 24. The ignition plug 16 is accommodated in the plug accommodating hole 25. The tip of the ignition plug 16 is located in the combustion chamber S.

[0014] The cylinder head 12 has an injector accommodating hole 26 and a spray escape recess 27. The spray escape recess 27 is recessed from the opposing surface 12b. In this embodiment, the spray escape recess 27 is located between the two intake ports 23 in the axial direction of the crankshaft. In a direction perpendicular to both the axial direction of the cylinder 11a and the axial direction of the crankshaft, the two intake ports 23 are located between the plug accommodating hole 25 and the spray escape recess 27. When the opposing surface 12b of the cylinder head 12 is viewed from the piston 13 side in a direction parallel to the axial direction of the cylinder 11a, the entire opening of the spray escape recess 27 is visible. The spray escape recess 27 of this embodiment is an inner surface of the spray escape recess 27, and is a mountain-shaped space in which the distance between a pair of inner surfaces facing each other in the axial direction of the crankshaft becomes smaller toward the bottom side of the spray escape recess 27. The injector accommodating hole 26 opens on the inner surface of the spray escape recess 27. The injector 17 is accommodated in an injector accommodation hole 26 .

[0015] Intake air is supplied to the combustion chamber S through the intake port 23. The injector 17 injects fuel into the combustion chamber S. More specifically, the injector 17 injects the fuel downward from the spark plug 16. At this time, the spray escape recess 27 prevents the injected fuel from adhering to the cylinder head 12. The spark plug 16 ignites the mixture of intake air and fuel, causing the mixture to burn in the combustion chamber S. The gas in the combustion chamber S is exhausted from the exhaust port 24.

[0016] As shown in FIG. 1 and FIG. 3, the top surface 13a of the piston 13 has a second recess 31 and a second annular surface 32. The second recess 31 is recessed with respect to the second annular surface 32. The second annular surface 32 surrounds the second recess 31. The second recess 31 faces the first recess 21 of the cylinder head 12. The first recess 21 and the second recess 31 define a main combustion chamber S1. The main combustion chamber S1 is located in the center of the combustion chamber S. The second annular surface 32 faces the first annular surface 22 of the cylinder head 12. A squish area S2 is defined between the first annular surface 22 and the second annular surface 32. The squish area S2 surrounds the main combustion chamber S1.

[0017] The piston 13 has a protrusion 33 protruding from the top surface 13a. The protrusion 33 has a shape corresponding to the spray escape recess 27. In this embodiment, the protrusion 33 has a mountain shape in which the distance between a pair of side surfaces that form a pair in the axial direction of the crankshaft becomes smaller toward the tip of the protrusion 33. The protrusion 33 faces the inner surface of the spray escape recess 27.

[0018] 1, when the piston 13 is at the top dead center, the protrusion 33 is located inside the spray escape recess 27. When the protrusion 33 is located inside the spray escape recess 27, a gap is provided between the protrusion 33 and the inner surface of the spray escape recess 27.

[0019] <Actions and Effects of the Present Embodiment> The operation and effects of this embodiment will be described. (1) The piston 13 has a protrusion 33 protruding from the top surface 13a. When the piston 13 is located at the top dead center, the protrusion 33 is located inside the spray escape recess 27. This suppresses an increase in the volume of the combustion chamber S due to the spray escape recess 27, making it possible to increase the compression ratio. As a result, it is possible to increase the thermal efficiency.

[0020] (2) The volume of the gap between the inner surface of the spray escape recess 27 and the protrusion 33 changes due to the reciprocating motion of the piston 13. In detail, when the piston 13 moves from the bottom dead center to the top dead center, the volume of the gap between the inner surface of the spray escape recess 27 and the protrusion 33 decreases. Therefore, an airflow that blows out from the gap between the inner surface of the spray escape recess 27 and the protrusion 33 to the main combustion chamber S1, that is, a squish airflow, is generated. This improves the strength of the airflow around the spray escape recess 27, and promotes flame propagation. On the other hand, when the piston 13 moves from the top dead center to the bottom dead center, the volume of the gap between the inner surface of the spray escape recess 27 and the protrusion 33 increases. Therefore, an airflow that draws the flame that has propagated near the spray escape recess 27 into the gap between the inner surface of the spray escape recess 27 and the protrusion 33, that is, a reverse squish airflow, is generated. This promotes flame propagation to the spray escape recess 27, and thus combustion in the spray escape recess 27, and therefore the generation of unburned gas in the spray escape recess 27 can be suppressed.

[0021] (3) Because the spray escape recess 27 is a narrow portion surrounded by a wall surface, the temperature of the gas in the combustion chamber S is easily taken away by the inner surface of the spray escape recess 27. In this case, the combustion speed decreases, and unburned gas is easily generated in the spray escape recess 27. In contrast, in this embodiment, when the piston 13 is located at top dead center, the protrusion 33 is located in the spray escape recess 27. Therefore, the temperature of the gas in the combustion chamber S is not easily taken away by the inner surface of the spray escape recess 27. Therefore, the generation of unburned gas in the spray escape recess 27 can be suppressed.

[0022] (4) As a method for maintaining the compression ratio while providing the spray escape recess 27, it is possible to reduce the volume of the combustion chamber S by moving the piston 13 closer to the cylinder head 12 at top dead center. However, in this case, the flattening of the combustion chamber S increases, and the strength of the airflow is likely to attenuate from the intake stroke to the compression stroke. In this case, the combustion speed decreases, and the thermal efficiency decreases. In contrast, in this embodiment, the piston 13 is provided with the protrusion 33, so that the volume of the combustion chamber S can be reduced without increasing the flattening of the combustion chamber S. Therefore, the decrease in the combustion speed can be suppressed, and the thermal efficiency can be improved.

[0023] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0024] The shapes of the spray escape recess 27 and the projection 33 may be changed as appropriate. The squish area S2 of the combustion chamber S may be omitted. The position of the spray escape recess 27 may be changed. For example, the spray escape recess 27 may be located between the two exhaust ports 24 in the axial direction of the crankshaft.

[0025] The internal combustion engine 10 is not limited to a hydrogen engine. The internal combustion engine 10 may be a gasoline engine or a diesel engine. [Explanation of symbols]

[0026] 10: internal combustion engine, 12: cylinder head, 13: piston, 13a: top surface, 17: injector, 26: injector accommodating hole, 27: spray escape recess, 33: protrusion, S: combustion chamber

Claims

[Claim 1] a combustion chamber defined between a cylinder head and a top surface of a piston; and an injector accommodated in an injector accommodation hole provided in the cylinder head for injecting fuel into the combustion chamber, a spray escape recess is provided on a surface of the cylinder head that defines the combustion chamber, The injector accommodating hole is open to an inner surface of the spray escape recess, The piston has a protrusion that protrudes from the top surface and is located within the spray escape recess when the piston is at top dead center.

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