JPS5949317A - 2-cycle internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the efficiency of engine through enlargement of the opening areas of exhaust and scavenging ports, by providing an exhaust port which is opened to one side of the wide side walls of a cylinder having an oblong cross sectional form and forming scavenging ports which are opened to the other side and narrow side walls. CONSTITUTION:An exhaust port 16 is opened to one wide side wall of a cylinder hole 5 having an oblong cross sectional form and a suction port 19 is opened to the other wide side wall. Further, 3 pairs of scavenging ports 21, 24, and 27 are opened to both narrow side wall 5c of the cylinder hole 5, at their respective one ends and are open to the crank chamber a crank case 4 at the other ends. In case the cylinder hole 5 has the same area as that of a conventional circular hole, the peripheral length can be increased, the opening areas of an exhaust port opening part 17, a suction port opening part 20, and scavenging port outlet opening parts 22, 25 and 28 can be set to increased values, thus flow resistance is reduced, resulting in improvement of efficiency.

Description

[Detailed description of the invention] A two-stroke internal combustion engine consisting of a cylinder with a circular cross section.
In order to increase the output per cylinder, it is possible to increase the inner diameter of the cylinder, but the cross-sectional area of the intake boat, scavenging boat, and exhaust port does not increase in proportion to the increase in stroke volume. The efficiency of scavenging and exhaust air tends to decrease.

In order to solve this problem, the cylinder cross section is shaped into an oval shape in which both ends of opposing semicircles are connected with a straight line at a predetermined interval, or an oval shape with a large ratio of the major axis to the minor axis. In a two-stroke internal combustion engine in which an exhaust port is provided on one side of the wide side wall of the cylinder and a scavenging boat is provided on the other side and both sides of the narrow side wall, the exhaust port and the scavenging boat are disposed of in relation to the stroke volume. It is possible to increase the area ratio and improve exhaust efficiency and scavenging efficiency.

Since the length is short, the scavenging air jetted into the cylinder from the scavenging boat flows directly to the exhaust port, which tends to cause fresh air to blow through.

The present invention relates to an improvement of a two-stroke internal combustion engine that eliminates such inconveniences, and its purpose is to provide a two-stroke internal combustion engine that has high efficiency in intake, scavenging, and exhaust air, and reduces blow-through of fresh air. It is in.

An embodiment of the present invention illustrated in the drawings will be described below.

1 is the engine body of a two-stroke internal combustion engine. When the engine body 1 has a cylinder head 3 superimposed on the upper part of the cylinder block 2, a crankcase 4 is superposed on the lower part of the same cylinder block 2, and these three parts are superimposed on each other. 2.3.4 are connected together with a connecting bolt or the like.

The cylinder block 2 also includes a cylinder with an oval cross section (an oval shape with a long axis and a short specific force of 1), in which both ends of opposing semicircles are connected with parallel straight lines at a predetermined interval. Hole 5 is drilled.

Furthermore, a piston 6 having the same transverse shape as the assimilation 5 is slidably fitted into the cylinder hole 5 , and the small diameter portions 9 of two connecting rods 8 are attached to the piston pins 7 of these pistons 6 . are connected to each other, and the large diameter portion 10 of these connecting rods 8 is connected to the crankcase 4.
The crankshaft 11 is connected to a crank bin 12 of a crankshaft 11 which is rotatably mounted on the crankshaft 11 .

Furthermore, a combustion chamber 13 having an oval cross section is formed in the cylinder head 3, and two spark plugs 14 are fitted into the combustion chamber 13.

Further, an exhaust port column 15 is disposed in the center of one wide planar side wall 5a of the oval-shaped cylinder hole 5, and exhaust ports 1 formed in the cylinder block 2 are disposed on both sides of the column C1.
One end of the cylinder hole 6 has a symmetrical opening 17, and an intake port pillar 18 is disposed in the center of the other flat wide side wall 5b of the oval-shaped cylinder hole 5, and an intake port pillar 18 is formed on both sides of the cylinder block 2. When one end of the intake port 19 is symmetrically opened 20 g n , one end of the scavenging boat 30 communicating with the intake port 19 is slid into the opening 31 above the intake port opening 20 .

The other end of the intake boat 19 is the reed valve 33'? i: Connected to an intake pipe 34 equipped with a carburetor, not shown.

Roughly speaking, on both sides of the narrow cylindrical side wall 5c of the cylinder hole 5, one end of three pairs of scavenging ports 2, 24, 27 formed in the cylinder block 2 is opened 22.5, 4, respectively, and a scavenging boat is provided. The other ends 21, 24, 27 are opened 23, 26, 29 into the crank chamber 32 of the crank case 4.

Therefore, the angles θ1, θ2.3, and θ4 formed between the inner wall of the outflow opening 22.5.28.31 of the scavenging boat 21.24.27.30 and the horizontal plane are in the relationship θ θ, <θ2<θ3<θ4. The same outflow opening error 22.5.28 is established so that
X3] is formed.

Since the illustrated embodiment is constructed as described above, its operating cycle is similar to that of a conventional two-stroke internal combustion engine.

That is, in the scavenging stroke in which the piston 6 descends, the new air-fuel mixture that has already been drawn into the crank chamber 32 from the intake port 19 in the previous compression stroke is transferred to the scavenging boat 21, 24, 27, 30'.
The air-fuel mixture in the combustion chamber 13 is compressed during the next compression stroke in which the piston 6 moves up, and the new air-fuel mixture flows through the reed valve 33 and the intake boat 19 into the crank chamber. 32 , and the compressed air-fuel mixture in the combustion chamber 13 is ignited by a spark from the spark plug 14 and exploded and combusted. Furthermore, during the scavenging stroke in which the piston 6 descends, the exhaust port 16, the scavenging boats 2I, 24, 27, and 30 are opened, and the burned gas is removed from the exhaust port 16 by the new air-fuel mixture flowing into the combustion chamber 13 from the crank chamber 32. Forced to be ejected.

Further, in the above embodiment, the cylinder hole 5 is oval-shaped, so when the cross-sectional area is the same as that of a conventional circular cylinder hole, the circumference of the oval-shaped cylinder hole 5 is longer than the circumference of the circular cylinder hole. < 11, resulting in exhaust port opening 1
7. Intake boat opening addition, scavenging port outflow opening 22.
The area of each opening can be set to be 2.5% to 28.31%, and the flow resistance of intake air, scavenging air, and exhaust air can be reduced and the efficiency of these can be improved.

Further, the inner wall of the outflow opening 22 of the scavenging boat 21 adjacent to the exhaust port 16 is connected to the opening 20 of the exhaust port 16.
However, since the directions of the exhaust gas flowing through the exhaust port 16 and the scavenging air flowing through the scavenging boat 21 are opposite, the direction from the scavenging boat 21 to the exhaust port 1 is reversed.
No new air-fuel mixture will blow through to 6.

Furthermore, since the inner wall of the outflow opening 31 of the scavenging boat 30 facing the exhaust port 16 is highly inclined at θ4, the new air-fuel mixture flowing into the cylinder hole 5 from the scavenging boat 30 is directed upward. As soon as the blow-by of the fresh air-fuel mixture from the scavenging boat 30 to the exhaust port 16 is prevented as much as possible, the top of the piston 6 is cooled by the upward fresh air-fuel mixture.

Moreover, the angles θ1, θ2, θ3, and θ4 formed by the inner wall of the outflow opening 22.5.28.31 of the scavenging air bow) 21.24.27.30 and the horizontal plane are in the relationship of θ, <θ2<θ3<θ4 2], 24.
27. The scavenging air flowing into the cylinder hole 5 from 30 generates a swirl toward the cylinder head 3 without mutual interference, and the combustion exhaust gas in the cylinder hole 5 is discharged without remaining, and the scavenging air in the cylinder hole 5 is The volume increases and filling efficiency improves.

As described above, in the present invention, in a two-stroke internal combustion engine in which a piston is reciprocatably fitted into a cylinder having an oval cross-section, a piston is provided on one side of the wide side wall of the cylinder, on one side of the wide side wall of the cylinder, on the other side, and on both sides of the narrow side wall. Since the scavenging boats are each opened, the opening area 2 of the exhaust port and the scavenging boat can be increased, thereby improving the efficiency of exhaust and scavenging.

In addition, in the present invention, the inner wall of the opening of the scavenging boat is formed so that the angle of inclination of the boat adjacent to the exhaust port increases upward by 2, thereby allowing fresh air to blow through from the scavenging boat to the exhaust port as much as possible. If this can be prevented, it is also possible to generate a swirl in the scavenging air flow from the scavenging boat into the cylinder, thereby improving the filling efficiency.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional side view illustrating an embodiment of a two-stroke internal combustion engine related to the misfire 1111, Fig. 2 is a vertical cross-section taken along the line ■-■ in Fig. 1, and Fig. 3 is its side view. FIG. 8, which is a cross-sectional view of the main part, is a developed view of the inner peripheral surface of the cylinder hole in the above embodiment. DESCRIPTION OF SYMBOLS 1... Two-cycle internal combustion engine body, 2... Cylinder block, 3... Cylinder head, 4... Crank case, 5... Cylinder hole, 6... Piston, 7...
・Piston pin, 8...Connecting rod, 9・
...Small diameter Wr, 1.0...Large diameter part, 1.1...Crankshaft, 12...Crank pin, 13...Combustion chamber, 14...Spark plug, 15...Exhaust Port pillar, ]
6...Exhaust port, 17...Exhaust boat opening, 1
8... Intake boat pillar, 19... Intake boat, 2o.
...Intake boat opening, 21...Scavenging boat, 22.
...Scavenging boat outflow opening 123...Scavenging boat inflow opening, 24...Scavenging boat, z5...Scavenging boat outflow opening, 26...Scavenging boat inflow opening, 27.
...Scavenging boat, 28...Scavenging boat outflow opening, 2
9...Scavenging boat inflow opening, 30...Scavenging boat, 31...Scavenging air outflow opening, 32...Crank chamber, 33...Reed valve, 34...Intake pipe.

Claims (1)

[Claims] In a two-stroke internal combustion engine in which a piston is reciprocatably fitted into a cylinder having an oval cross-section, an exhaust hoard is provided on one side of a wide side wall of the cylinder, and a scavenging boat is provided on the other side and both sides of the narrow side wall. 2. A two-stroke internal combustion engine, wherein the scavenging boat has an opening, and an inner wall of the opening of the scavenging boat is formed with a larger inclination angle sequentially upward from the boat adjacent to the exhaust port.