JPS5838609B2 - Combustion chamber of split combustion internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the shape of a combustion chamber in a split combustion internal combustion engine in which combustion is performed in multiple stages using a reciprocating piston.

For example, the split combustion internal combustion engine is
As seen in the publication, the combustion chamber formed in the cylinder or cylinder head is divided into multiple stages by a piston at a predetermined period before and after top dead center, and ignition occurs in the first stage combustion chamber. When the first-stage combustion chamber communicates with the second-stage combustion chamber due to the lowering of the piston during the expansion stroke, the flame from the first-stage combustion chamber causes the mixture in the second-stage combustion chamber to ignite the torch. It is an internal combustion engine designed to

In such a split-combustion internal combustion engine, by appropriately selecting the combustion weight ratio of each chamber and the combustion chamber division period, etc., and bringing the combustion form closer to constant-pressure combustion, the maximum pressure and temperature of the initial combustion can be improved. It is possible to suppress the generation of nitrogen oxides (NOx), which is a harmful component of exhaust gas, and
In the later stages of combustion, combustion is performed using a torch ignition method, which increases the combustion speed, making it possible to use a lean mixture with a large air-fuel ratio, reducing carbon monoxide (CO) and hydrocarbon (HC) emissions. This has the advantage of reducing fuel consumption, reducing fuel consumption, and maintaining output.

However, in this type of split-combustion internal combustion engine, especially in the type that does not have an exhaust valve in the recess (first combustion chamber) into which the auxiliary piston part protruding from the top of the piston fits, during the exhaust stroke, the first combustion Burned gas is not scavenged and tends to accumulate in the recesses of the chamber as internal residual gas, which impedes ignitability in the first combustion chamber, making combustion unstable and causing engine misfire.

The present invention has been made to solve such problems, and its purpose is to reduce the amount of burned gas remaining inside.
The present invention aims to provide a combustion chamber for a split combustion internal combustion engine that is improved so as to improve ignition performance.

For this purpose, the present invention provides the above-mentioned split combustion internal combustion engine with the following features: the top surface of the auxiliary piston portion forming the first combustion chamber equipped with the ignition plug, and the inner surface of the cylinder head recess facing thereto. By making the opposing surfaces of both cylinders spherical so that their respective recesses face each other, the depth of the recess (first combustion chamber) provided in the cylinder head is made shallow and the amount of residual burnt gas is reduced. In addition, during the compression stroke, the air-fuel mixture is compressed intensively toward the center of the first combustion chamber.

In addition, in a split combustion type internal combustion engine, the inner surface of the first combustion chamber is
An example in which a concave portion with a spherical portion is formed is known from, for example, Japanese Unexamined Patent Publication No. 15908/1982.
This recess is formed by a spherical part at the top of the cylinder head and a cylindrical part continuous thereto,
Further, a sub piston having a recess on the top surface is known, for example, from U.S. Pat. No. 2,688,320, but since the recess is formed by making the top surface slope, Even if the concave portion of the cylinder head and the concave portion of the cylinder head are made to face each other, these opposing surfaces cannot be made into a spherical shape.

Furthermore, a cylinder head in which the spark plug is located in the center of the inner surface of the recess is known, for example, from Japanese Patent Application Laid-open No. 130912/1983.

By the way, in contrast to the prior art, the present invention has the opposing surfaces of both the top of the sub-piston and the inner surface of the cylinder head recess formed into a concave shape so that the respective recesses face each other, and a spherical central part with a large facing interval. It is distinctive in that a spark plug is placed in the middle.

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

In the figure, 1 is a cylinder, 2 is a cylinder head connected to the top of the cylinder, and a piston 3 is slidably inserted into the cylinder 1.

A sub-piston part 3a is provided at the top of the piston 3 and has a protruding shape eccentrically to one side, and the combustion chamber space in the cylinder head 2 is formed in a recess into which the sub-piston part 3a is fitted.
It is divided into a first combustion chamber) 4 and a second combustion chamber 5 separated from the first combustion chamber 4 by fitting the auxiliary piston portion 3a therein.

The first combustion chamber 4 is provided with a spark plug 6 facing toward the upper center, and the second combustion chamber 5 is provided with an intake valve 7 and an exhaust valve 8.
are arranged side by side, and the intake valve 7 is connected to a carburetor 10 via an intake pipe 9, so that a mixture (lean mixture) is sucked into the cylinder 1 from the carburetor 10. Further, an exhaust pipe 11 is connected to the exhaust valve 8.

In the present invention, the inner wall surface 2b of the cylinder head 2 forming the first combustion chamber 4 and the top surface 3b of the auxiliary piston portion 3a facing thereto are formed into a concave spherical shape so that the respective recesses face each other. The first combustion chamber 4 is configured to have an upper and lower spherical shape.

In such a configuration, the recess in the first combustion chamber 4 formed in the cylinder head 2 is replaced by a conventional recess (see FIG. In addition, by making the inner surface of the recess on the cylinder head side concave and spherical, the recess around the recess where burnt gas tends to stagnate can be reduced. The depth can also be made shallower, and as a result, while securing a predetermined volume of the first combustion chamber, the recess depth of the cylinder head recess can be configured to be shallower overall.

Therefore, during the exhaust stroke, the piston 3 is in the lowered position as shown in FIG. 2, and the first combustion chamber 4 is a single chamber communicating with the second combustion chamber 5. The burnt gas in the first combustion chamber 4 passes through the second combustion chamber 5 and is discharged from the exhaust valve 8, but in this case, as described above, the depth of the recess on the cylinder head 2 side forming the first combustion chamber 4 Since the recess is spherical and the depth of the recess at the periphery is shallow, the internal amount of burnt gas remaining in the recess of the first combustion chamber is greatly reduced, and the scavenging effect is improved. Improved.

Also, during the compression stroke, the air-fuel mixture taken in by the intake valve 7 is compressed by the rise of the piston 3, but in this case,
The top surface 3b of the sub-piston part and the inner surface of the cylinder head recess,
Since the opposing surfaces of the two are formed in a concave spherical shape so that their respective recesses face each other, the opposing distance between the two is large at the center of the opposing surfaces, and becomes smaller toward the periphery. Therefore, at the end of the compression stroke, 3
When the intake air-fuel mixture flows into the first combustion chamber 4 from the second combustion chamber 5 side and is compressed, the intake air-fuel mixture in the periphery of the first combustion chamber 4 where the opposing distance is small is compressed first, and Due to the squish effect, the air-fuel mixture in the first combustion chamber flows from the periphery to the center, which improves the replacement of residual gas in the center with fresh air (intake air-fuel mixture). By reducing the amount of residual gas, the mixture concentration in the center of the first combustion chamber 4 facing the spark plug 6 is increased,
Ignitability is improved.

Thus, according to the present invention, in a split combustion internal combustion engine,
Since it is possible to improve scavenging of burned gas and improve ignitability, it is possible to provide a split-combustion internal combustion engine that improves combustion and is free from the risk of engine misfire even when using a lean mixture.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, and FIGS. 2 and 3 are action explanatory views. 1...Cylinder, 2...Cylinder head, 2b...Inner wall surface of cylinder head, 3...
... Piston, 3a ... Sub-piston part, 3
b...Top surface of sub-piston part, 4...First combustion chamber, 5...Second combustion chamber, 6...
Spark plug, 7... Intake valve, 8... Exhaust valve, 9... Intake pipe, 10... Carburetor, 11... Exhaust pipe.

Claims (1)

[Claims] 1. The combustion chamber formed in the cylinder or cylinder head is controlled by a sub-piston part protruding from the top of the piston and a recess provided in the cylinder head opposite to this part for a predetermined period before and after top dead center. The combustion chamber is divided into multiple stages, with an ignition plug in the first stage combustion chamber, an intake valve and an exhaust valve in the second stage combustion chamber, and after ignition in the first stage combustion chamber, the piston is activated during the expansion stroke. Split combustion type in which when the first stage combustion chamber communicates with the second stage combustion chamber due to descent, the flame from the first stage combustion chamber ignites the air-fuel mixture in the second stage combustion chamber. In the internal combustion engine, the top surface of the auxiliary piston part forming the first stage combustion chamber and the opposing surface of the inner surface of the cylinder head recess facing thereto,
The first groove is formed into a concave spherical shape so that the concave portions face each other.
A combustion chamber for a split-combustion internal combustion engine, characterized in that the combustion chambers of the stages are formed into upper and lower spherical shapes, and the spark plug is disposed in the center with a large facing interval.