JPS5851373Y2 - 2-stroke internal combustion engine - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a two-stroke internal combustion engine.

As a two-stroke internal combustion engine that can significantly reduce fuel consumption and harmful components in exhaust gas and achieve quiet operation, the cross-sectional area of the scavenging passage that connects the engine crank chamber and combustion chamber has been changed to the side closer to the crank chamber. The present inventor has already proposed an active thermal atmosphere combustion two-stroke internal combustion engine in which fresh air is allowed to flow into the combustion chamber at a low speed by throttling the engine.

In this two-stroke internal combustion engine, fresh air is allowed to flow into the combustion chamber at a low speed to create an active thermal atmosphere within the combustion chamber, and then this atmospheric state is maintained continuously during the compression stroke, and at the end of the compression stroke, fresh air is introduced into the combustion chamber. is caused to ignite and burn.

The object of the present invention is to provide an improved structure for this type of two-stroke internal combustion engine.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, 1 is a crankcase, 2 is a cylinder block fixed on a crankcase 1, 3 is a cylinder head fixed on a cylinder block 2, and 4 has a substantially flat top surface. and a piston that can reciprocate within a cylinder liner 5 fitted in the cylinder block 2; 6 a combustion chamber formed between the cylinder head 3 and the piston 4;
7 is a spark plug arranged on the top surface of the combustion chamber 6; 8 is a crank chamber formed in the crankcase 1; 9 is a balance weight; 10 is a connecting rod; 11 is an intake hole formed in the cylinder liner 5; 12 is an intake passage, 13 is a carburetor, 14 is a carburetor throttle valve, 15 is a cylindrical recess formed in the center of the cylinder head 3, 16 is an exhaust hole formed in the cylinder liner 5, and 17 is an exhaust The tubes 18 each indicate an exhaust passage.

The effective compression ratio of the two-stroke internal combustion engine shown in Figure 1 is 6.
．． It is 5.

In the two-stroke internal combustion engine according to the present invention, one end of the first scavenging passage 19 opens into the cylindrical recess 15, as shown in FIG. An on-off valve 20 whose opening and closing are controlled by is provided.

Note that instead of the on-off valve 20, an automatic on-off valve such as a check valve that automatically opens when the pressure in the first scavenging passage 19 becomes higher than the pressure in the combustion chamber 6 can be provided.

In the embodiment shown in FIG. 1, the cylindrical recess 15 is arranged at the center of the inner wall surface of the cylinder head 3, but the cylindrical recess 15 is formed around the inner wall surface of the cylinder head 3.
An on-off valve 20 can also be provided inside.

On the other hand, the other end of the first scavenging passage 19 is connected to the bottom of the crank chamber 8 via a second scavenging passage 21 which is a conduit having a smaller cross-sectional area and a longer length than the first scavenging passage 19 .

FIG. 2 shows the opening timing of the on-off valve 20.

In FIG. 2, EO indicates the opening timing of the exhaust hole 16, and E
C indicates the closing timing of the exhaust hole 16, and arrow A indicates the closing timing of the on-off valve 20.
indicates the valve opening period.

During engine operation, fresh air introduced into the crank chamber 8 from the intake hole 11 is compressed as the piston 4 descends, and then forced into the second scavenging passage 21 from the bottom of the crank chamber 8.

As shown in FIG. 1, since the cross-sectional area of the second scavenging passage 21 is extremely small, fresh air flows at a high speed within the second scavenging passage 21, and as a result, flow energy is given to the fresh air, so that the fuel is Vaporization will be promoted.

After the vaporization of the fuel is sufficiently promoted in this way, the fresh air in the second scavenging passage 21 is sent into the first scavenging passage 19.

At this time, the fresh air sent out from the second scavenging passage 21 is
Since the fresh air collides with the inner wall surface of the scavenging passage 19 and the cross-sectional area of the first scavenging passage 19 is much larger than the cross-sectional area of the second scavenging passage 21, the fresh air also sent out from the second scavenging passage 21 is rapidly decelerated. .

Next, the fresh air flows at a low speed in the first scavenging passage 19, and flows into the combustion chamber 6 at a low speed when the on-off valve 20 is opened.

When fresh air flows into the combustion chamber 6, even if the pressure inside the crank chamber 8 is considerably higher than the pressure inside the combustion chamber 6, the second scavenging passage 21 performs a throttling action because of its small cross-sectional area. Due to this effect, fresh air cannot be injected into the combustion chamber 6 quickly, so that the inflow velocity of the fresh air is low throughout the inflow period.

When the fresh air flows into the combustion chamber 6, it is guided by the cylindrical inner wall surface of the recess 15 and sent toward the approximate center of the combustion chamber 6, and this fresh air then flows into the combustion chamber 6 at a low velocity. do.

As a result, the fresh air appears to be surrounded by the residual burnt gas, and there is almost no flow of the residual burnt gas, and thus the residual burnt gas is maintained at a high temperature.

Particularly at the beginning of compression during partial load operation, a large amount of residual burnt gas is present in the combustion chamber 6.

Since the residual burnt gas in the combustion chamber 6 is large in quantity and at high temperature, the fresh air sent into the combustion chamber 6 is heated and radicals are generated in the gas phase where the fresh air and the residual burnt gas come into contact. As a result, an active thermal atmosphere (an atmosphere in which radicals are generated is referred to as an active thermal atmosphere) is formed in the combustion chamber 6.

During the compression stroke, the gas flow in the combustion chamber 6 is very small, so there is little turbulence and thermal energy loss to the combustion chamber wall, so the gas in the combustion chamber 6 becomes increasingly hot as compression progresses, and as a result, the fresh air Generates more radicals.

When radicals are being generated in this way, combustion called a pre-flame reaction has already started, and when the gas temperature in the combustion chamber 6 rises at the end of the compression stroke, a hot flame is generated and the spark plug 7 is not activated. Self-ignites.

Then, controlled gentle combustion is performed using the residual burnt gas, and when the piston 4 descends to open the exhaust hole 16, the burnt gas in the combustion chamber 6 is discharged into the exhaust passage 18.

In the embodiment shown in FIG. 1, ignition is performed by the ignition plug 7 only when the engine is started and for a while after the engine is started.
After that, the fresh air in the combustion chamber 6 self-ignites without depending on the ignition plug 7.

As described above, according to the present invention, an active atmosphere combustion two-stroke internal combustion engine with a new structure is provided, and this two-stroke internal combustion engine can greatly improve the fuel consumption rate and also minimize harmful components in exhaust gas. can be reduced to

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a two-stroke internal combustion engine according to the present invention, and FIG. 2 is a diagram showing the opening timing of the on-off valve. 11...Intake hole, 15...Recess, 16
...exhaust hole, 19...first exhaust passage,
20...Opening/closing valve, 21...Second scavenging passage.

Claims (1)

[Scope of utility model registration request] In a two-stroke internal combustion engine in which an air-fuel mixture compressed in a crank chamber is supplied into a combustion chamber, a first scavenging passage is formed in the cylinder head, and one end of the first scavenging passage is placed above the inner wall surface of the cylinder head. The first scavenging passage is opened into the combustion chamber, and an on-off valve is provided at one end of the first scavenging passage, and the on-off valve is opened over a crank angle range that is approximately equal to the crank angle range in which the exhaust hole opens. A two-stroke internal combustion engine connected to a crank chamber through a second scavenging passage, which is longer than the first scavenging passage and has a smaller cross-sectional area, at the other end of the passage.