Combustion chamber structure of internal combustion engine

Abstract

To inhibit occurrence of preignition in an internal combustion engine which uses hydrogen as a fuel.SOLUTION: A combustion chamber 12 is formed at a cylinder head 10 of an internal combustion engine which uses hydrogen as a fuel. A wall surface 14 forming the combustion chamber 12 is formed by a surface which does not have a bottomed recessed part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a combustion chamber structure of an internal combustion engine that uses hydrogen as fuel. [Background technology]

[0002] As shown in Fig. 2, in the internal combustion engine described in Patent Document 1, a wall surface 114 that forms a combustion chamber 112 is formed in a cylinder head 100. Also, a tip portion 121 of an in-cylinder injection valve that injects liquid fuel into the cylinder is assembled so as to be exposed to the combustion chamber 112. And, in order to prevent the fuel injected from the tip portion 121 of the in-cylinder injection valve from adhering to the wall surface 114, a spray escape portion 300 is formed around the tip portion 121 exposed to the combustion chamber 112. The spray escape portion 300 is a recessed portion formed in the wall surface 114. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-2201 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, pre-ignition is more likely to occur in an internal combustion engine that uses hydrogen as fuel than in an internal combustion engine that uses gasoline or other fuels. Therefore, it is desirable to suppress the occurrence of pre-ignition. [Means for solving the problem]

[0005] The combustion chamber structure of an internal combustion engine that solves the above problem is a combustion chamber structure formed in a cylinder head of an internal combustion engine that uses hydrogen as fuel, and the wall surface that forms the combustion chamber is composed of a surface that does not have a bottomed recess. Effect of the Invention

[0006] This combustion chamber structure of an internal combustion engine can suppress the occurrence of pre-ignition in an internal combustion engine that uses hydrogen as fuel. [Brief description of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view of a cylinder head of an internal combustion engine according to one embodiment. [Diagram 2] FIG. 1 is a cross-sectional view of a conventional cylinder head of an internal combustion engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, one embodiment of a combustion chamber structure for an internal combustion engine will be described with reference to FIG. <About the structure of the cylinder head and surrounding area of ​​an internal combustion engine> 1 shows the peripheral structure of a cylinder head 10 provided in a direct injection type internal combustion engine. The internal combustion engine of this embodiment is an internal combustion engine that uses hydrogen, which is a gaseous fuel, as fuel.

[0009] A combustion chamber 12 is formed in the lower surface of the cylinder head 10. Further, the cylinder head 10 is formed with an intake port 15 for introducing intake air into the combustion chamber 12 and an exhaust port 16 for discharging exhaust gas from the combustion chamber 12 .

[0010] An intake valve 17 is disposed at an opening of the intake port 15 to the combustion chamber 12 . The intake valve 17 opens during the intake stroke of the internal combustion engine to connect the combustion chamber 12 to the intake port 15 . An exhaust valve 18 is disposed at an opening of the exhaust port 16 to the combustion chamber 12 . The exhaust valve 18 opens during the exhaust stroke of the internal combustion engine to communicate between the combustion chamber 12 and the exhaust port 16 .

[0011] In the cylinder head 10, a plug insertion hole 11 is formed in the center of the top surface of the combustion chamber 12. An ignition plug 19 is attached to the plug insertion hole 11, and the ignition plug 19 ignites a mixture of fuel and air by spark discharge.

[0012] Further, an in-cylinder injection valve that directly injects hydrogen gas into a cylinder of the internal combustion engine is attached to the cylinder head 10. A nozzle hole for injecting fuel is formed in a tip portion 21 of the in-cylinder injection valve.

[0013] An insertion hole 13 that opens into the combustion chamber 12 is formed in the cylinder head 10. Into the insertion hole 13, a tip portion 21 of a direct injection valve is inserted. A through hole 32 is formed between the tip portion 21 of the in-cylinder injection valve and the combustion chamber 12. The inner diameter of the through hole 32 is smaller than the insertion hole 13. The fuel injected from the injection hole of the tip portion 21 is supplied into the combustion chamber 12 via the through hole 32.

[0014] The wall surface 14 forming the upper surface of the combustion chamber 12 does not have a spray escape portion for preventing the fuel injected from the in-cylinder injection valve from adhering to the wall surface 14. In other words, the wall surface 14 is configured as a surface that does not have a bottomed recess.

[0015] <Action and Effects> The operation and effects of this embodiment will be described. In an internal combustion engine that uses hydrogen as fuel, if a spray escape section with a concave shape as described in the conventional literature is formed in the combustion chamber of the cylinder head, unburned high-temperature hydrogen gas remains in the spray escape section even during the exhaust stroke after combustion has ended. This is because in an internal combustion engine that injects gaseous fuel such as hydrogen gas, the injected fuel is guided upward by the upward tumble flow in the cylinder immediately after injection and tends to remain in the concave. In addition, hydrogen is lighter than air, so it tends to remain in the concaves on the wall of the combustion chamber.

[0016] The inventors have discovered that if hydrogen fuel is supplied into the cylinder while residual gas remains in the recesses in this manner, pre-ignition is likely to occur with the high-temperature residual gas acting as an ignition source.

[0017] Therefore, in this embodiment, the wall surface 14 that forms the combustion chamber 12 in the cylinder head 10 is configured with a surface that does not have any recesses. Therefore, since there are no areas in the combustion chamber 12 formed in the cylinder head 10 where hydrogen gas is likely to remain, it is possible to suppress the occurrence of pre-ignition caused by residual hydrogen gas as an ignition source.

[0018] <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.

[0019] The above-described through hole 32 may be omitted, and the tip portion 21 of the direct injection valve may be exposed to the inside of the combustion chamber 12 . Instead of the in-cylinder injection valve, the internal combustion engine may be provided with a port injection valve that injects fuel into the intake port 15. In this case, the insertion hole 13 and the through hole 32 are omitted. [Explanation of symbols]

[0020] 10...Cylinder head 11...Plug insertion hole 12…Combustion chamber 13…Insertion hole 14…Wall 15…Intake port 16…Exhaust port 17…Intake valve 18...Exhaust valve 19…Spark plug 21...Tip 32...Through hole 100…Cylinder head 112…Combustion chamber 114…Wall 121...Tip 300…Spray escape section

Claims

1. A structure of a combustion chamber formed in a cylinder head of an internal combustion engine that uses hydrogen as fuel, The wall surface forming the combustion chamber is configured with a surface that does not have a bottomed recess. Combustion chamber structure of an internal combustion engine.

2. The wall surface forming the combustion chamber does not have a spray escape portion for preventing the fuel injected from the in-cylinder injection valve from adhering to the wall surface. A combustion chamber structure for an internal combustion engine according to claim 1.

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