JPH041167B2 - - Google Patents

Description

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

[Background Art] Conventionally, outboard motors and the like have employed horizontal two-stroke internal combustion engines in which cylinders are arranged horizontally. In such a two-stroke internal combustion engine, if low-load, low-speed operation such as idling or trolling is continued, the air-fuel mixture comes into contact with the low-temperature crankshaft or the inside of the crankshaft chamber and tends to liquefy.

By the way, in the above conventional two-stroke internal combustion engine, the crank chamber and the combustion chamber formed in the cylinder are communicated through a scavenging passage, and the lowest surface position in the vertical direction of at least one exhaust passage is connected to the combustion chamber. It is set at a position below the lowest surface position in the vertical direction of the inner surface of the cylinder forming the cylinder.

Therefore, in the above-mentioned conventional two-stroke internal combustion engine, the fuel liquefied in the crank chamber accumulates in the middle part of the scavenging passage set at the lower position, and the liquefied fuel also accumulates in the scavenging passage. During this period, a phenomenon occurs in which droplets intermittently enter the combustion chamber. As a result, the distribution of the mixture concentration within the combustion chamber becomes non-uniform, and the mixture concentration for each combustion cycle also varies, making the combustion state unstable in the low-load, low-speed operation range.

[Object of the Invention] An object of the present invention is to smoothly supply fuel to the combustion chamber during the scavenging period and stabilize 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 crank chamber and a combustion chamber formed in the cylinder are communicated through a scavenging passage. In an engine, the lower surface of the passage between the inlet opening into the crank chamber of the scavenging passage and the scavenging air opening opening into the combustion chamber is made substantially flat, and the lowest surface position in the vertical direction of the scavenging passage forms the combustion chamber. The height position is set to be equal to or higher than the lowest surface position in the vertical direction of the inner surface of the cylinder.

[Operation of the Invention] According to the present invention, the liquefied fuel generated on the crank chamber side does not stay in the middle part of the scavenging passage, and the liquefied fuel is continuously and smoothly supplied to the combustion chamber during the scavenging period, thereby improving the combustion state. It becomes possible to stabilize the

[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 ventilation 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 scavenging passages 28A and 28B are the scavenging ports 2
The lower surface of the passage between 9A, 29B and the inlet 30A is set to be a substantially horizontal plane, and the lowermost surface position 31 in the vertical direction is the lowermost surface in the vertical direction of the inner surface of the cylinder 13 forming the combustion chamber 24. It is set at a height slightly above position 32.

Note that the exhaust port 27 is set at the top of the cylinder 13, and the left and right exhaust ports 29A and 29B are located at the top of the cylinder 13.
It is set at the bottom of 3. That is, the exhaust port 27 is set at a position above the scavenging ports 29A and 29B in the vertical direction.

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.

When the engine 10 remains 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 liquefies. This liquefied fuel flows from the crank chamber 21 into each scavenging passage 28A, 28B under the action of gravity. Therefore, in the scavenging stroke of the engine 10, the liquefied fuel flowing into the scavenging passages 28A, 28B together with the atomized fresh air precompressed in the crank chamber 21 flows from the exhaust ports 29A, 29B into the combustion chamber 2.
4. Here, in the above embodiment,
Exhaust ports 29A, 29B of scavenging passages 28A, 28B
Since the lower surface of the passage between the and the inlet 30A is flat, and the lowermost surface position 31 of the scavenging passages 28A, 28B is set above the lowermost surface position 32 of the cylinder 13, the liquefied fuel is The liquefied fuel continuously and smoothly enters the combustion chamber 24 during the scavenging period, and the distribution of the mixture concentration within the combustion chamber 24 will not be made uneven by the presence of the liquefied fuel that intermittently enters. Further, the mixture concentration for each combustion cycle does not vary from one another.

Further, in the above embodiment, when fresh air precompressed in the crank chamber 21 flows into the combustion chamber 24 during the scavenging stroke of the engine 10, the exhaust port 29
Since the fresh air flowing in from A and 29B is at a lower temperature than the residual exhaust gas in the combustion chamber 24, and the exhaust port 27 is set above the exhaust ports 29A and 29B, the fresh air and residual exhaust gas are This makes it possible to stratify the residual exhaust gas inside the combustion chamber 24, to smoothly discharge the residual exhaust gas from the exhaust port 27, and to form a layer of fresh air with good ignitability around the spark plug 25.

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 above embodiment, even during low-load, low-speed operation, it is possible to make the distribution of the mixture concentration in the combustion chamber 24 uniform, and to form a layer of fresh air with good ignitability around the ignition plug 25. In addition, the mixture concentration for each combustion cycle does not vary from one another, and 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,
A crank chamber (not shown) and a combustion chamber 42 formed in the cylinder 41 are communicated through left and right scavenging passages 43 and an upper scavenging passage 44. Here, the lowest surface position 45 in the vertical direction of the left and right scavenging passages 43 is as follows:
Similar to the embodiment described above, the height position is set slightly above the lowest surface position 46 in the vertical direction of the inner surface of the cylinder 41. Note that 47 is an exhaust passage.

Therefore, even in the case of this modification, the liquefied fuel produced on the crank chamber side does not stay in the middle part of the exhaust passage 43, and the liquefied fuel is continuously and smoothly supplied to the combustion chamber 42 during the scavenging period. , it becomes possible to stabilize the combustion state.

In addition, in the above embodiment, the lowest surface position of the scavenging passage is
Although the case where the scavenging passage is set above the lowest position on the inner surface of the cylinder has been described, in the present invention, the lowermost surface position of the scavenging passage may be set at a height equal to or higher than the lowest position on the inner surface of the cylinder. Good.

[Effects of the Invention] As described above, the present invention provides a horizontal two-stroke internal combustion engine in which the cylinder is arranged horizontally and the crank chamber and the combustion chamber formed in the cylinder are communicated through a scavenging passage. The lower surface of the passage between the inlet opening into the crank chamber of the scavenging passage and the scavenging opening opening into the combustion chamber is made substantially flat (not limited to a horizontal plane, but also an inclined plane), and the lower surface of the passage in the vertical direction of the scavenging passage is The lowest surface position is set at a height equal to or higher than the lowest surface position in the vertical direction of the inner surface of the cylinder forming the combustion chamber. Therefore, the liquefied fuel produced on the crank chamber side does not stay in the middle part of the scavenging passage, and the liquefied fuel can be continuously and smoothly supplied to the combustion chamber during the scavenging period, thereby stabilizing the combustion state. Become.

[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,
21... Crank chamber, 24, 42... Combustion chamber, 2
8A, 28B, 43...Scavenging passage, 29A, 29
B...Scavenging port, 30A...Inflow port, 31, 45...
...Bottom surface position, 32, 46...Bottom surface position.

Claims (1)

[Claims] 1. In a horizontal two-stroke internal combustion engine in which the cylinder is arranged horizontally and the crank chamber and the combustion chamber formed in the cylinder are communicated through a scavenging passage,
The lower surface of the passage between the inlet opening into the crank chamber of the scavenging passage and the scavenging opening opening into the combustion chamber is made substantially flat, and the lowest surface position in the vertical direction of the scavenging passage is set to the inner surface of the cylinder forming the combustion chamber. 1. A horizontal two-stroke internal combustion engine, characterized in that the engine is set at a height equal to or higher than the lowest position in the vertical direction of the engine.