JPH0351888B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field] The present invention relates to a transverse two-stroke internal combustion engine.

[Background Art] Generally, in a two-stroke internal combustion engine, the intake, scavenging, and exhaust periods overlap with each other, resulting in poor gas exchange. Gas exchange is particularly poor at low load and low rotation speeds where the flow velocity is slow, and the fresh air supplied around the spark plug is diluted by residual exhaust gas, resulting in poor ignition performance and unstable combustion conditions in each cycle. Therefore, it is difficult to obtain a smooth rotation state.

[Object of the Invention] An object of the present invention is to stratify fresh air and residual exhaust gas in a combustion chamber during a scavenging stroke, thereby stabilizing the combustion state.

[Structure of the Invention] In order to achieve the above object, the present invention provides a horizontal two-stroke internal combustion engine in which a cylinder is arranged horizontally and a scavenging port and an exhaust port are formed on the inner surface of the cylinder forming a combustion chamber. The opening is set vertically above the scavenging opening.

[Detailed Description of the Invention] FIG. 1 is a partially cutaway front view of a two-cylinder, two-stroke internal combustion engine for an outboard motor to which the present invention is applied, and FIG. 2 is a view taken along the - line in FIG. FIG.

This two-stroke internal combustion engine 10 is of a horizontally installed type, and each cylinder liner 12 is fitted in the upper and lower sides of a cylinder block 11 in the horizontal direction to form each horizontally arranged cylinder 13 on the upper and lower sides, respectively. A cylinder head 14 and a crankcase 15 are integrated into the cylinder block 11. A crankshaft 16 is rotatably supported by the cylinder block 11 and the crankcase 15, a large end of a connecting rod 18 is connected to a crank pin 17 of the crankshaft 16, and a piston pin 19 is connected to a small end of the connecting rod 18. A piston 20 is connected to the piston 20 via.

Each crank chamber 21 formed by the crank case 15 and the cylinder block 11 is connected to each carburetor 23 via each intake pipe 22 having a built-in reed valve. The carburetor 23 is capable of generating a mixture of fuel and air.

Further, a combustion chamber 24 can be formed in each cylinder 13, and a cylinder head 14 facing each combustion chamber 24 is formed.
An ignition plug 25 is disposed at.

The cylinder block 11 has an exhaust passage 26 connected to each combustion chamber 24, and each cylinder liner 12 has an exhaust port 27 formed therein.

Further, the cylinder block 11 is connected to each crank chamber 21.
and left and right scavenging passages 28 that communicate with each combustion chamber 24.
A, 28B, and scavenging ports 29A, 29B opening into the combustion chamber 24 are formed in each cylinder liner 12. 30A is an inlet opening into the crank chamber 21 of the scavenging passage 28A.

Here, the exhaust port 27 is set at the top of the cylinder 13, and the left and right scavenging ports 29A, 29B are set at the bottom of the cylinder 13. That is, exhaust port 2
7 is set at a position above both scavenging ports 29A, 29B in the vertical direction.

Note that the scavenging passages 28A and 28B are connected to the scavenging port 29.
A, 29B and the inlet 30A are set in a substantially horizontal state, and the lowest surface position 31 in the vertical direction is set to the cylinder 13 forming the combustion chamber 24.
It is set at a height position slightly above the lowest surface position 32 in the vertical direction of the inner surface of.

Further, the spark plug 25 is arranged in a position closer to the lower part of the combustion chamber 24 in the cylinder head 14, and scavenging ports 29A, 2 are provided on the top surface of the piston 20.
The flow of fresh air flowing into the combustion chamber 24 from 9B is not directed to the exhaust port 27, but the ignition plug 25
Deflector section 33 that allows the deflector to be directed toward
is formed.

Next, the operation of the above embodiment will be explained.

During the scavenging stroke of the engine 10, the crank chamber 21
When fresh air precompressed in the combustion chamber 24 flows into the combustion chamber 24, the fresh air flowing in from the scavenging ports 29A and 29B has a lower temperature than the residual exhaust gas in the combustion chamber 24, and the exhaust port 27 is a scavenging port. Since the position is set above 29A and 29B, fresh air and residual exhaust gas are stratified inside the combustion chamber 24, the residual exhaust gas is smoothly discharged from the exhaust port 27, and ignitability is created around the ignition plug 25. It becomes possible to form a good layer of fresh air.

Furthermore, in the above embodiment, when the engine 10 continues to be idling or trolling for a long time, the air-fuel mixture supplied from the carburetor 23 to the crank chamber 21 comes into contact with the low-temperature crankcase 15 and crankshaft 16. and liquefy. This liquefied fuel flows from the crank chamber 21 into each scavenging passage 28A, 28B under the action of gravity. Therefore, engine 1
In the 0th scavenging stroke, the liquefied fuel flowing into the scavenging passages 28A, 28B flows into the combustion chamber 24 from the scavenging ports 29A, 29B together with the atomized fresh air precompressed in the crank chamber 21. Here, in the above embodiment, the scavenging passages 28A, 2
Since the lowest surface position 31 of the cylinder 8B is set above the lowest surface position 32 of the cylinder 13, the liquefied fuel smoothly enters the combustion chamber 24 continuously during the scavenging period, and the inside of the combustion chamber 24 is heated. The distribution of air-fuel mixture concentration will not become uneven due to the presence of intermittent liquefied fuel.

Further, in the above embodiment, a deflector portion 33 is formed on the top surface of the piston 20 to allow the flow of fresh air flowing into the combustion chamber 24 to be directed toward the spark plug 25 during the scavenging stroke of the engine 10. Therefore, this also makes it possible to form a layer of fresh air with good ignitability around the ignition plug 25.

Further, in the above embodiment, as shown in FIG. 2, an exhaust passage 2 is provided around the scavenging passages 28A and 28B.
6 is arranged, the scavenging passage 28A,
heating the liquefied fuel flowing through 28B with exhaust heat;
It is also possible to promote atomization.

That is, according to the embodiment described above, it is possible to equalize the mixture concentration in the combustion chamber 24 even during low-load, low-speed operation, and to form a layer of fresh air with good ignitability around the spark plug 25. It is possible to reliably ignite each cycle and obtain a stable combustion state.

FIG. 3 is a schematic sectional view showing a modification of the present invention. In this modification, the cylinder 41 is arranged horizontally,
On the inner surface of the cylinder 41 forming the combustion chamber 42, left and right scavenging ports 43A, 43B, a lower scavenging port 44, and an exhaust port 45 are formed. Here, the left and right scavenging ports 43A, 43B are connected to the cylinder 41.
The lower exhaust port 44 is set at the bottom of the cylinder 41, and the exhaust port 45 is set at the top of the cylinder 41. That is,
The exhaust port 45 is set at a position above each scavenging port 43A, 43B, and 44 in the vertical direction.

Therefore, even in the case of this modification, when fresh air precompressed in the crank chamber flows into the combustion chamber 42, the fresh air flowing from each scavenging port 43A, 43B, and 44 remains in the combustion chamber 42. The temperature is lower than that of the exhaust gas, and the exhaust port 45 is connected to each scavenging port 43A, 43.
Since the position is set above B, 44, fresh air and residual exhaust gas are stratified in the combustion chamber 42, the residual exhaust gas can be smoothly discharged from the exhaust port 45, and ignitability is created around the ignition plug. It is possible to form a good layer of fresh air.

[Effects of the Invention] As described above, the present invention provides a horizontal two-stroke internal combustion engine in which a cylinder is arranged horizontally and a scavenging port and an exhaust port are formed on the inner surface of the cylinder forming a combustion chamber. It is set at a position vertically above the mouth. Therefore, when fresh air precompressed in the crank chamber flows into the combustion chamber, the fresh air flowing from the scavenging port is lower in temperature than the residual exhaust gas in the combustion chamber, and the exhaust port is located above the scavenging port. Because the spark plug is set at the same position, fresh air and residual exhaust gas are stratified in the combustion chamber, allowing residual exhaust gas to be smoothly discharged from the exhaust port, and a layer of fresh air with good ignitability is formed around the spark plug. This makes it possible to stabilize the combustion state.

[Brief explanation of drawings]

FIG. 1 is a front view showing a cut away main part of an embodiment of a horizontal two-stroke internal combustion engine according to the present invention;
The figure is a sectional view taken along the - line in FIG. 1, and FIG. 3 is a schematic sectional view showing a modification of the present invention. 10... Internal combustion engine, 13, 41... Cylinder,
24, 42... Combustion chamber, 27, 45... Exhaust port,
29A, 29B, 43A, 43B, 44...Scavenging port.

Claims (1)

[Claims] 1 In a horizontal two-stroke internal combustion engine in which the cylinder is arranged horizontally and a scavenging port and an exhaust port are formed on the inner surface of the cylinder forming a combustion chamber, the exhaust port is set vertically above the scavenging port. A horizontally mounted two-stroke internal combustion engine.