JPS6137790Y2 - - Google Patents

Description

[Detailed explanation of the invention] In two-stroke internal combustion engines, it is common practice to use pulsation in the exhaust system to improve scavenging efficiency and charging efficiency, and this has great effects, but exhaust pulsation There are often engine speed ranges where the intake and exhaust systems are not synchronized and the output decreases.

This tendency is particularly strong in the two-stroke internal combustion engine shown in FIG. 1 in which the reed valve 02 is provided in the intake valve 01 and the auxiliary scavenging hole 04 is directly provided between the reed valve 02 and the crank chamber 03. Note that 05 is the main scavenging hole.

One of the causes of this low output engine rotation range is that the exhaust gas pressure reaches the reed valve 02 through the auxiliary scavenging hole 04 between the reed valve 02 and the crank chamber 03, as shown by the arrow in FIG. This is due to the fact that the reed valve 02 follows a propagation path such that the reed valve 02 acts as a valve closing force.

The present invention relates to an improvement of a two-stroke internal combustion engine that eliminates such inconveniences, and its purpose is to:
The object of the present invention is to provide a two-stroke internal combustion engine with a simple structure, which has high charging efficiency and can improve combustion efficiency regardless of changes in engine speed.

An embodiment of the present invention illustrated in FIGS. 2 and 3 will be described below.

1 is a two-stroke gasoline engine, and a piston 3 is fitted into a cylinder 2 of the engine 1 so as to be able to move up and down, and the piston 3 and a crank 4 are connected by a connecting rod 5.

Further, an intake passage 7 communicating with the crank chamber 6 is provided with a carburetor and a reed valve 8 (not shown).

Furthermore, an exhaust hole 9 is formed approximately in the center of the cylinder 2 on the opposite side of the intake passage 7, sandwiching the piston 3, and is located approximately in the center of the cylinder 2 on both sides of the plane connecting the intake passage 7 and the exhaust hole 9. A main scavenging hole 10 is formed which communicates the crank chamber 6 with the crank chamber 6.

Furthermore, in the portion of the cylinder 2 adjacent to the intake passage 7, the substantially central portion thereof and the crank chamber 6
is communicated with the auxiliary scavenging hole 11, and the auxiliary scavenging hole 1
1 is separated from the intake passage 7 by a partition wall 12 that faces the reed valve 8.

Thus, an intake hole 13 communicating with the crank chamber 6 from the intake passage 7, and intake holes 14 located on both sides of the auxiliary intake hole 11 and the partition wall 12 and communicating with the cylinder 2 are formed.

Since the embodiment shown in FIGS. 2 and 3 is configured as described above, the air-fuel mixture is sucked into the crank chamber 6 from the intake passage 7 through the intake hole 14 during the upward stroke of the piston 3. be done.

Also, at the end of the upward stroke of the piston 3, the cylinder 2
The air-fuel mixture inside is ignited and causes an explosion, causing piston 3
Even when the air enters the scavenging stroke, where the intake air begins to descend, the reed valve 8 remains open due to the inertial force of the intake air, and the air-fuel mixture continues to be sucked in.
When the spring force becomes equal to the spring force, the reed valve 8 is closed and intake of the air-fuel mixture is stopped.

At the beginning of this scavenging stroke, if the engine 1 rotates at an engine speed that is not synchronized with the exhaust system, even if blowback occurs to the auxiliary scavenging hole 11 through the cylinder 2 due to the backflow of exhaust gas pressure from the exhaust hole 9, The pressure of the exhaust gas due to the blowback remains within the crank 4 and does not reach the reed valve 8, so the reed valve 8 is not prevented from opening due to the intake inertia, and the intake inertia is effectively used to avoid a drop in output. be able to.

Further, since the auxiliary scavenging hole 11 is opened obliquely upward toward the inside of the cylinder 2, the auxiliary scavenging hole 11
Directivity is given to the auxiliary scavenging air flow injected into the cylinder 2 from the main scavenging hole 10, and the auxiliary scavenging air, together with the main scavenging air flowing through the main scavenging hole 10, contributes to improved gas exchange and improves combustion efficiency.

In the embodiment shown in FIGS. 2 and 3, the auxiliary scavenging hole 11 is located in the cylinder chamber 1 of the cylinder 2.
5 is separated by a cylinder partition wall 16,
If there is no problem such as poor contact of the piston 3, the cylinder partition wall 16 may be removed as shown in FIG.

Furthermore, in the embodiments shown in FIGS. 2 to 4,
The auxiliary scavenging hole 11 is connected to the intake passage 7 and the intake hole 1
It was completely sealed against 3rd and 14th, but the 5th
As shown in the figure, the auxiliary scavenging hole 17 may be partitioned by a partition wall 18 facing the reed valve 8 and communicated with the intake hole 14. Even in such an embodiment, the exhaust gas pressure can be increased by blowback. The partition wall 18 can prevent the air from propagating to the valve 8, and the intake inertia can also be effectively utilized to prevent the output from decreasing.

The present invention has a main scavenging hole and an auxiliary scavenging hole communicating from the crank chamber into the cylinder, and the auxiliary scavenging hole is connected to the intake passage in which the crank chamber and a check valve such as a reed valve connected to the crank chamber are interposed in the middle of the passage. In a two-stroke internal combustion engine in which a scavenging hole is open, a partition wall facing the check valve is provided from one side close to the check valve at the opening of the auxiliary scavenging hole to the intake passage. Even if the engine rotates at a speed that is not synchronized with the engine rotation speed and exhaust gas blows back into the auxiliary scavenging hole due to a backflow of exhaust gas, the partition wall prevents the exhaust gas pressure from propagating to the reed valve due to the blowback. A decrease in engine output can be prevented by effectively utilizing the intake inertia in the valve.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional side view of a conventional two-stroke internal combustion engine, Fig. 2 is a longitudinal sectional side view illustrating an embodiment of the two-stroke internal combustion engine according to the present invention, Fig. 3 is a transverse plan view thereof, and Fig. 4. 5 is a cross-sectional plan view of another embodiment of the present invention, and FIG. 5 is a cross-sectional bottom view of still another embodiment of the present invention, viewed from the bottom to the top. 1... Two-stroke gasoline engine, 2... Cylinder, 3... Piston, 4... Crank, 5...
...Connecting rod, 6...Crank chamber, 7
...Intake passage, 8...Reed valve, 9...Exhaust hole,
10...Main scavenging hole, 11...Auxiliary scavenging hole, 12...
... partition wall, 13, 14 ... intake hole, 15 ... cylinder chamber, 16 ... cylinder partition wall, 17 ... auxiliary scavenging hole, 18 ... partition wall.

Claims (1)

[Scope of utility model registration request] It has a main scavenging air hole and an auxiliary scavenging air hole that communicate from the crank chamber to the cylinder chamber, and the auxiliary scavenging hole opens in the intake passage where the crank chamber and a check valve such as a reed valve connected thereto are interposed in the middle of the passage. A two-stroke internal combustion engine having a two-stroke internal combustion engine, characterized in that a partition wall is provided that faces the check valve from one side of the opening of the auxiliary scavenging hole to the intake passage that is close to the check valve. Internal combustion engine.