JPS6310293B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a combustion chamber of an internal combustion engine.

Conventional technology Previously, harmful components HC, CO and
The use of a lean mixture is known as an effective method for simultaneously reducing NOx. However, when a lean mixture is used, the flame propagation speed is slow, resulting in unstable combustion, which has the disadvantage of causing torque fluctuations.

On the other hand, a method of recirculating exhaust gas from an engine exhaust system to an intake system is known as an effective method for reducing the harmful component NOx in exhaust gas. However, when exhaust gas is recirculated, especially when a large amount of exhaust gas is recirculated, the recirculated exhaust gas and the fuel-air mixture are not sufficiently mixed in the engine cylinders, resulting in unstable combustion and torque fluctuations. It has the disadvantage that it occurs.

In addition, in order to speed up the combustion speed, stabilize combustion, and increase output, the volume of the combustion chamber formed between the top surface of the piston and the cylinder head when the piston is at top dead center has been reduced, in other words, the compression ratio has been increased. A method is known in which the ignition flame is immediately propagated throughout the combustion chamber. However, simply reducing the size of the combustion chamber does not sufficiently increase the combustion rate, and in particular, a sufficient combustion rate cannot be obtained with a lean mixture or a mixture containing a large amount of recirculated exhaust gas. Furthermore, when the compression ratio is set to such a high value, there is a problem in that detonation occurs.

Purpose of the Invention The present invention accelerates the combustion rate of a lean mixture or a mixture containing a large amount of recirculated exhaust gas, thereby achieving stable combustion, preventing the occurrence of detonation, and eliminating harmful components in the exhaust gas. An object of the present invention is to provide an internal combustion engine that can reduce the

Structure of the Invention The structure of the present invention is that in an internal combustion engine equipped with a piston having a flat top surface and a cylinder head having a flat inner wall surface, a cylindrical recess is formed on one side of the flat inner wall surface of the cylinder head. forming on the flat inner wall surface of the cylinder head an inclined groove having a substantially rectangular cross section that extends along the periphery of the flat inner wall surface of the cylinder head and is connected tangentially to the peripheral wall surface of the cylindrical recess;
The bottom surface of the inclined groove is connected to the bottom surface of the cylindrical recess, and the exhaust valve is disposed on the bottom surface of the cylindrical recess, and the intake valve is disposed on the flat inner wall surface of the cylinder head.

Embodiment Referring to FIG. 1, 1 is a cylinder block;
2 is a piston that reciprocates within the cylinder block 1, 3 is a cylinder head fixed onto the cylinder block 1 via a gasket 4, 5 is an intake port, 6 is an intake valve, 7 is an exhaust port, and 8 is an exhaust valve. shows. The intake port 5 has an air-fuel ratio of 18 to 20, for example.
or a vaporizer for forming a mixture near the stoichiometric mixture ratio. When using the latter carburetor, the internal combustion engine is equipped with a device for recirculating exhaust gas from the engine exhaust system to the intake system, and fuel air having an air-fuel ratio near the stoichiometric mixture ratio is introduced into the cylinder. Preferably, a large amount of exhaust gas, 10% or more of the mixture, is recirculated. As shown in FIG. 1, the piston 2 has a flat piston top surface 2a. On the other hand, the cylinder head 3 also has a flat inner wall surface 3a, and a cylindrical recess 22 is formed on one side of the flat inner wall surface 3a. Furthermore, an inclined groove 24 is formed on the flat inner wall surface 3a of the cylinder head, and extends approximately one quarter of the way around the flat inner wall surface 3a. The cylinder head inner wall surface 3a excluding these cylindrical recesses 22 and inclined grooves 24 forms a flat portion 21 as shown by hatching in FIG. Therefore, a flat portion 21, a cylindrical recess 22, and an inclined groove 24 extending from the flat portion 21 along the circumferential direction H and connected within the cylindrical recess 22 are formed on the cylinder head inner wall surface 3a. . As shown in FIGS. 1 and 2, the cylindrical recess 22 has a cylindrical peripheral wall surface and a flat bottom surface 23, on which the exhaust valve 8 is disposed. In addition, the intake valve 6 has a flat portion 2
1. The inclined groove 24 has a substantially rectangular cross section as shown in FIG.
The bottom surface of the cylindrical recess 22 smoothly connects to the flat portion 21 at a position R shown by a broken line in FIG. Further, the inclined groove 24 has a substantially uniform slope over its entire length, and extends from the vicinity of the intake valve 6 to the vicinity of the exhaust valve 8 with a uniform slope. Further, the inclined groove 24 has a width approximately equal to the radius of the cylindrical recess 22 and is tangentially connected to the peripheral wall surface of the cylindrical recess 22 . A screw hole 25 is formed on the peripheral wall surface of the cylindrical recess 22 forming the combustion chamber 9, and the ignition plug 14 is screwed into the screw hole 25 so that the discharge gap does not protrude into the combustion chamber 9. Ru. When the piston 2 reaches the top dead center, a squish area I shown by hatching in FIG. 2 is formed between the flat top surface 2a of the piston 2 and the flat portion 21 of the inner wall surface 3a of the cylinder head.

The combustible air-fuel mixture introduced between the cylinder head inner wall 3a and the piston top surface 2a via the intake valve 6 during the intake stroke is gradually compressed as the piston 2 rises during the compression stroke. When the piston 2 reaches near the top dead center, the combustible air-fuel mixture is forced out from the squish area I through the inclined groove 24 into the combustion chamber 9. This combustible air-fuel mixture flows along the cylindrical circumferential wall surface forming the cylindrical recess 22, thus generating a swirling flow within the combustion chamber 9 as shown by the arrow J in FIG. This swirling combustible mixture is then ignited by the spark plug 14.

Instead of connecting the groove 24 to the bottom surface 23 of the cylindrical recess 22, the inclined groove 24 may open into the recess 22 at an intermediate height of the cylindrical recess 22. However, in this case, the depth of the inclined groove 24 is generally shallower than in the embodiment shown in FIG. 1, and the slope is gentle, so that no strong swirling flow occurs. Therefore, according to the present invention, the groove is deep and has a steep slope, and since the sloped groove 24 is formed over a long distance, an extremely strong swirling flow can be generated. In addition, as described above, the inclined groove 24
is opened at an intermediate height position of the cylindrical recess 22, the residual exhaust gas remaining near the exhaust valve 8 does not mix sufficiently with the combustible air-fuel mixture flowing through the inclined groove 24. Stable combustion cannot be obtained. However, according to the present invention, since the inclined groove 24 is connected to the bottom surface 23 of the cylindrical recess 22, it can sufficiently mix with the residual exhaust gas remaining in the combustion chamber 9, thus achieving stable combustion. .
Furthermore, by connecting the inclined groove 24 to the bottom surface 23 of the cylindrical recess 22, the low-temperature squish flow directly impinges on the valve surface of the exhaust valve 8 where hot spots are likely to occur, thereby cooling the exhaust valve 8 and detonating it. can be prevented from occurring. Furthermore, by retracting the electrode of the spark plug 14 into the screw hole 25, it is possible to avoid direct collision of the strong swirling flow with the electrode, thereby preventing misfires.

In this way, the combustible mixture in the combustion chamber 9 is given turbulence and a strong swirling flow by the strong squishing flow, and is completely mixed with the residual gas remaining in the combustion chamber 9, thus greatly increasing the combustion rate. . Furthermore, by arranging the electrode of the ignition plug 14 near the exhaust valve 8, the flame of the combustible mixture ignited by the ignition plug 14 immediately reaches the combustible mixture around the valve surface of the exhaust valve 8, thus causing detonation. can be prevented from occurring.

4 and 5 show another embodiment. In this embodiment, an auxiliary combustion chamber 16 is provided which is connected only to the inside of the combustion chamber 9 via a communication passage 15.
5, the discharge gap of the spark plug 17 is arranged. In this embodiment, the combustible mixture in the combustion chamber 9 is sent into the auxiliary combustion chamber 16 through the communication passage 15 during the compression stroke, and then this combustible mixture is ignited by the ignition plug 17, and a flame is emitted from the communication passage 15. It is ejected into the combustion chamber 9. The communication path 15 is arranged so that the flame is ejected along the swirling flow j.

Effects of the Invention As described above, according to the present invention, it is possible to generate turbulence in the combustible air-fuel mixture and a strong swirling flow using a strong squishing flow. Therefore, even if the combustible mixture is a lean mixture or a mixture containing a large amount of recirculated exhaust gas, the combustion speed can be increased, thereby achieving stable combustion and reducing harmful substances in the exhaust gas. components can be reduced. At the same time, it is also possible to prevent detonation from occurring.

[Brief explanation of the drawing]

1 is a side sectional view of an internal combustion engine according to the present invention taken along the line - in FIG. 2; FIG. 2 is a bottom view of the cylinder head taken along the line - in FIG. 1;
Figure 3 is a sectional view taken along the - line in Figure 2;
FIG. 4 is a side sectional view of another embodiment, and FIG. 5 is a side sectional view of another embodiment.
FIG. 3 is a sectional view of the cylinder head taken along the - line in the figure. 2... Piston, 9... Cylinder head, 6...
...Intake valve, 8...Exhaust valve, 9...Combustion chamber, 22...
...Cylindrical recess, 24...Slanted groove.

Claims (1)

[Claims] 1. In an internal combustion engine equipped with a piston having a flat top surface and a cylinder head having a flat inner wall surface, a cylindrical recess is formed on one side of the flat inner wall surface of the cylinder head, and a cylindrical recess is formed along the periphery of the flat inner wall surface of the cylinder head. An inclined groove having a substantially rectangular cross section is formed on the flat inner wall surface of the cylinder head, and extends along the cylinder head and is tangentially connected to the peripheral wall surface of the cylindrical recess. A combustion chamber of an internal combustion engine in which an exhaust valve is arranged on the bottom surface and an intake valve is arranged on the flat inner wall surface of the cylinder head.