JPS6321692Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine, particularly an internal combustion engine suitable for use as a two-stroke engine.

Various inventions have been made to improve the efficiency of internal combustion engines. Among these, the same applicant has already proposed that the shape of the cylinder hole be oval or have a long axis and a short axis in order to increase the opening area of each port for the purpose of improving the efficiency of intake, exhaust, scavenging, etc. An internal combustion engine with an oval shape with a large ratio was published in Japanese Patent Application Publication No. 1983-
This is proposed in Publication No. 66428.

The present invention is a further improvement of the internal combustion engine described above, and its purpose is to improve combustion by correcting non-uniform flame propagation speed of the ignited air-fuel mixture by making the cylinder hole shape oblong or elliptical. An object of the present invention is to provide an internal combustion engine with improved efficiency and improved scavenging efficiency within a cylinder hole.

In order to achieve the above-mentioned object, the present invention provides a piston in an internal combustion engine in which the cross-sectional shape of the cylinder hole formed in the cylinder block is formed into an elliptical shape or an elliptical shape with a large ratio of the major axis to the minor axis. A protrusion is provided on the upper surface to partition the combustion chamber into two in the short axis direction at the center, and a smooth guide surface is provided from this protrusion toward the outer periphery of the upper surface facing each port provided on the cylinder block, and The present invention is characterized in that a plug is disposed in each of the combustion chambers partitioned by the protrusions.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is a cylinder block, and the cross-sectional shape of the cylinder hole 2 is formed into an oval shape. Further, on the inner surface of the cylinder block 1, an exhaust port 3 is provided on one of the straight portions, and a scavenging port 4 communicating with the intake port is provided on the other straight portion and the curved portion.

On the other hand, on the top of the cylinder block 1, there is a cylinder head 6 provided with two plugs 5 in the longitudinal direction.
is fixed. The cylinder head 6 has an inner surface formed as a combustion chamber 7 in the shape of an oblong dish.

In addition, the cylinder hole 2 of the cylinder block 1 has
A piston 8 is fitted so as to be vertically movable. This piston 8 also has an elliptical planar shape, and a protrusion 9 having a height substantially matching the inner surface shape of the cylinder head 6 is provided in the short axis direction at the center of the upper surface. A smooth guide surface 11 defined by veins 10 is provided from this protrusion 9 toward the outer periphery of the upper surface of the piston 8 corresponding to the positions of the ports 3 and 4 provided in the cylinder block 1.

The internal combustion engine configured as described above has a piston 8
When the plugs 5 ignite the air-fuel mixture compressed near the top dead center, each plug 5 combusts the air-fuel mixture in the combustion chamber 7 partitioned by the protrusion 9. Therefore, compared to the case where only one plug 5 is provided in the center of the cylinder head 6, the flame propagation distance is shorter, combustion is completed in a shorter time, and the flame propagation is performed at a stable speed. Combined with the fact that the cylinder hole 2 is formed into an oval shape, the surface area of the combustion chamber wall is increased and overheating is prevented, so that spontaneous ignition of the air-fuel mixture during the compression process, which is before the plug 5 is activated, can be prevented. In addition, since a smooth guide surface 11 is provided on the upper surface of the piston 8 from the protrusion 9 toward the outer circumference of the upper end corresponding to each port 3 and 4 provided in the cylinder block 1, scavenging air can be directed upward to the cylinder hole 2. Since direct outflow of fresh air can be prevented, combustion gas can be discharged quickly and combustion efficiency can also be improved.

In the above description, the cylinder hole 2 is elliptical in shape, but the same effect can be obtained even if the cylinder hole 2 is elliptical in shape with a large ratio of the major axis to the minor axis.

As mentioned above, the present invention makes it possible to uniformize the flame propagation speed and achieve stable and good combustion even in internal combustion engines with a large displacement per cylinder and a large cylinder bore diameter. This aims to reduce pollutant emissions and improve scavenging efficiency.

In particular, by dividing the combustion chamber into two in the longitudinal direction by a protrusion on the top surface of the piston, and arranging a plug in each, the distance between the plug and each scavenging port can be shortened and made uniform, resulting in a high combustion level. rate can be significantly improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a longitudinal sectional front view of an internal combustion engine, Fig. 2 is a longitudinal sectional side view, and Fig. 3 is a sectional view taken along the line -
FIG. 4 is a perspective view of the piston. 1 is the cylinder block, 2 is the cylinder hole, 3 is the exhaust port, 4 is the scavenging port, 5 is the plug, 6 is the cylinder head, 7 is the combustion chamber, 8 is the piston, 9
10 is a rib, 11 is a guide surface.

Claims (1)

[Scope of utility model registration request] In an internal combustion engine in which the cross-sectional shape of the cylinder hole formed in the cylinder block is formed into an ellipse or an ellipse with a large ratio of the major axis to the minor axis, the combustion chamber is placed on the upper surface of the piston in the direction of the minor axis in the center. A protrusion is provided to partition the combustion chamber into two, and a smooth guide surface is provided from this protrusion toward the outer periphery of the upper surface facing each port provided on the cylinder block, and the combustion chamber partitioned by the protrusion is An internal combustion engine characterized by having a plug installed in each end.