JP2002038958A - Two stroke internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stratified scavenging two stroke internal combustion engine for supplying new mixed air to a combustion chamber after only air is supplied to the combustion chamber in scavenging stroke to drive off combustion gas to an exhaust port. SOLUTION: The combustion chamber 3 and a crankcase 10 are sectioned by fitting a piston 6 into a cylinder main body 4. A mixed air passage of a carburetor is connected with the crankcase 10 via a mixed air passage 15 opened at a top dead center of the piston 6. An upper end of a scavenging passage 12 for connecting the crankcase 10 provided on a peripheral wall of the cylinder main body 4 and the combustion chamber 3 is connected with a scavenging port 17 opened before a bottom dead center of the piston 6. An air passage 18 of the carburetor is connected with the scavenging passage 12 via an air control valve 21 interlocking and rotating with a crank shaft 14. At the end of the combustion stroke, combustion gas of the combustion chamber 3 is discharged to the exhaust port 8 by air of the air passage 18 and mixed air of the crankcase 10 is supplied to the combustion chamber 3 via the scavenging passage 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stratified scavenging two-stroke internal combustion engine in which combustion gas is scavenged only by air.

[0002]

2. Description of the Related Art In a conventional stratified scavenging two-stroke internal combustion engine, an exhaust port is opened at the end of a combustion stroke, a new air-fuel mixture is supplied from the scavenging port, and combustion gas is expelled by the new air-fuel mixture to the exhaust port. Therefore, not only the combustion gas but also a part of the new air-fuel mixture escapes from the exhaust port to the outside, which causes deterioration of exhaust gas components, and makes it difficult to comply with future exhaust gas regulations.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to supply only air to a combustion chamber in a scavenging process to drive out combustion gas to an exhaust port, and then supply a new air-fuel mixture to the combustion chamber. And a stratified scavenging two-stroke internal combustion engine.

[0004]

In order to solve the above-mentioned problems, according to the structure of the present invention, a piston is fitted into a cylinder body to partition a combustion chamber and a crank chamber, and a mixture passage of a carburetor is formed by a piston. Connect to the mixture passage that opens to the crank chamber at the top dead center, connect the upper end of the scavenging passage that connects the crank chamber and the combustion chamber provided on the peripheral wall of the cylinder body to the scavenging port that opens before the bottom dead center of the piston, The air passage of the carburetor is connected to the scavenging passage via an air control valve that rotates in conjunction with the crankshaft, and at the end of the combustion stroke, the combustion gas in the combustion chamber is discharged to the exhaust port by the air from the scavenging passage. The mixture in the chamber is supplied to the combustion chamber through the scavenging passage.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in performing stratified scavenging in accordance with the exhaust gas regulation of a two-stroke internal combustion engine, air is sent from an air pipe of a carburetor to a scavenging passage. As a result, the combustion gas in the combustion chamber is discharged to the exhaust port. Next, the air-fuel mixture that has been sent from the air-fuel mixture pipe of the vaporizer to the crank chamber is sent to the combustion chamber via the scavenging passage. In order to store air used for scavenging at the beginning of scavenging, an air control valve that rotates in synchronization with the crankshaft is provided between the scavenging passage and an air pipe or air passage from the carburetor.

[0006]

As shown in FIG. 2, a piston 6 is fitted into a cylinder body 4, and a combustion chamber 3 is defined above the piston 6, and a crank chamber 10 is defined below the piston 6. An upper end of a connecting rod 9 is connected to the piston 6 by a pin 7, and a lower end of the connecting rod 9 is connected to a crankshaft 14 by a pin 13.
Is connected to an arm 14a (see FIG. 16 for details) integral with the counterweight 30 coupled to the arm. An exhaust port 8 which opens near the bottom dead center of the piston 6 is formed in a peripheral wall of the cylinder body 4, and a mixture pipe or a mixture passage 15 having a mixture throttle valve 16 as a carburetor is opened below the exhaust port 8. Is done. In addition, one or a plurality of scavenging ports 17 are opened substantially facing the exhaust port 8. A vertical scavenging passage 12 is provided on the outer wall of the cylinder body 4.
The lower end 12 a of the scavenging passage 12 is connected near the bottom of the crank chamber 10. The air passage 5 is connected to the upper end of the scavenging passage 12. The air passage 5 and the mixture passage 15 are integrally formed as a carburetor as disclosed in Japanese Patent Application No. 8-106187, for example.

As shown in FIG. 1, according to the present invention, air previously stored in the scavenging passage 12 is supplied to the scavenging port 17 in the scavenging stroke.
To the combustion chamber 3 via an air line or air passage 18 with a carburetor air throttle valve 19 and a scavenging passage 12
An air control valve 21 is provided between the air passages 5 connecting the first and second air passages. An endless belt 32 having no slippage is stretched over a pulley 31 connected to the crankshaft 14 and a pulley 34 connected to the shaft portion 22a of the valve body 22 of the air control valve 21. The air control valve 21 is fitted with a valve body 22 having a small diameter at both ends in a cylindrical valve chamber of a valve housing 20 and is rotatably supported by a pair of bearings 25. An axial groove passage 24 is provided on the peripheral surface of the valve body 22, and both ends of the groove passage 24 communicate with an annular chamber 23 between the valve chamber and both ends of the valve body 22. An air passage 18 that can communicate with the groove passage 24 is opened at the center of the valve housing 20, and a mixture passage 15 that communicates with the chamber 23 is opened at both ends of the valve housing 20.

In the above-described stratified scavenging two-stroke internal combustion engine,
During one rotation of the crankshaft 14, the exhaust port 8, the scavenging port 1
7, the mixture air port 15 and the air passage 5 are opened and closed as shown in FIGS. The valve body 22 of the air control valve 21 rotates in synchronization with the crankshaft 14 to open and close the air passage 5. FIG.
As shown in FIG. 3, when the piston 6 passes through the bottom dead center, the mixture passage 15, the scavenging port 17 and the air passage 5 are closed, and the exhaust port 8 is also closed as shown in FIG. Qi is compressed. As shown in FIGS. 4 and 5, while the air-fuel mixture in the combustion chamber 3 is continuously compressed, the air-fuel mixture passage 15 is opened, and the air-fuel mixture from the carburetor is sucked into the crank chamber 10. At the same time, the air A in the air passage 18 flows into the scavenging passage 12 via the groove passage 24, the chamber 23, and the air passage 5.

As shown in FIG. 6, the air-fuel mixture in the combustion chamber 3 is ignited by the spark plug 2 before the top dead center of the piston 6, the piston 6 is pushed down by the explosive force, and the air control valve 21
Thereby, the air passage 5 is closed. As shown in FIGS. 7 and 8, as the piston 6 descends, the mixture passage 15 is closed, and the mixture in the crank chamber 10 is compressed. Figures 9 and 1
As shown in FIG.
And the exhaust port 8 is opened, and the air B in the scavenging passage 12 enters the combustion chamber 3 and expels the combustion gas in the combustion chamber 3 to the exhaust port 8. Next, the air-fuel mixture in the crank chamber 10 flows into the combustion chamber 3 through the scavenging passage 12. Hereinafter, the same process as that described with reference to FIGS.

In the embodiment shown in FIGS. 11 to 14, the air control valve for opening and closing the air passage 5 comprises a cam 33 provided on the crankshaft 14 and an on-off valve 35 driven by the cam 33. The air passage 5 connecting the two scavenging ports 17 and the air passage 18 are arranged in parallel and adjacent to each other, and an on-off valve 35 is acted on by a spring 37 by a valve seat provided in a passage communicating the air passages 5 and 18. Energized to the closed position. A cam 33 formed on the crankshaft 14 is engaged with the lower end of the stem of the on-off valve 35, and the piston 6 is located near the top dead center (about −10 ° to 3 °).
(°), the on-off valve 35 is opened by the cam 33 against the spring 37 against the force.

As shown in FIG. 11, during the upward stroke of the piston 6, the mixture passage 15, the scavenging port 17, the exhaust port 8
And the air passage 5 is closed, and the air-fuel mixture in the combustion chamber 3 is compressed. As shown in FIGS. 12 and 13, as the piston 6 approaches the top dead center, the air-fuel mixture in the combustion chamber 3 is continuously compressed, while the air-fuel mixture passage 15 is opened to allow the air-fuel mixture from the carburetor to flow into the crank chamber. Inhaled to 10. At the same time, the on-off valve 35 is opened, and the air in the air passage 18 passes through the air passage 5 and the scavenging passage 1
Flow into 2.

Before the top dead center of the piston 6, the air-fuel mixture in the combustion chamber 3 is ignited by the ignition plug 2, and the piston 6 is pushed down by the explosive force. As shown in FIG. , The on-off valve 35 is closed. As the piston 6 descends, the mixture passage 15 is closed, and the mixture in the crank chamber 10 is compressed. 2 to 10, before the bottom dead center of the piston 6, the scavenging port 17 and the exhaust port 8 are opened, the air in the scavenging passage 12 enters the combustion chamber 3, and the combustion gas in the combustion chamber 3 To the exhaust port 8. Next, the air-fuel mixture in the crank chamber 10 flows into the combustion chamber 3 through the scavenging passage 12.

In the embodiment shown in FIGS. 15 to 18, an air control valve for opening and closing the air passage 5 is provided with a pair of bearings 29 on the cylinder body 4 in a valve housing provided on the wall of the cylinder body 4.
The valve body is integrated with both ends of the crankshaft 14 supported by the valve body. The air passage 18 and the air passage 5 are opened at different axial positions in the valve housing, while the valve body is provided with an axial open groove passage 26 and an annular groove 27 intersecting the groove passage 26. Can be The air control valve is located near the top dead center of the piston (approximately −10 °) as in the above-described embodiments.
３3 °), the air in the air passage 18 is stored in the scavenging passage 12, and at the beginning of the scavenging stroke, the air in the scavenging passage 12 is first sent to the combustion chamber 3 to expel fuel gas to the exhaust port 8, and then the crank chamber 10 Is sent to the combustion chamber 3 through the scavenging passage 12.

[0014]

As described above, according to the present invention, the piston is fitted to the cylinder body to partition the combustion chamber and the crank chamber, and the mixture passage of the carburetor is opened to the crank chamber at the top dead center of the piston. Connect to the mixture passage, connect the upper end of the scavenging passage that connects the crank chamber and the combustion chamber provided on the peripheral wall of the cylinder body to the scavenging port that opens before the bottom dead center of the piston, and connect the air passage of the carburetor to the crankshaft. It is connected to the scavenging passage via an interlockingly rotating air control valve, and at the end of the combustion stroke, the combustion gas in the combustion chamber is expelled to the exhaust port by air from the scavenging passage, and then the air-fuel mixture in the crank chamber passes through the scavenging passage. In the initial stage of the scavenging stroke of the two-stroke engine, the air in the scavenging passage is supplied to the combustion chamber to scavenge the combustion gas, and the mixture in the crank chamber is removed during the scavenging stroke. Through scavenging passage to combustion chamber Since the feed, fully reliable combustion is obtained, the exhaust gas is kept clean.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing a stratified scavenging two-stroke internal combustion engine equipped with an air control valve according to a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a state near a bottom dead center of a piston of the two-stroke internal combustion engine.

FIG. 3 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 4 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 5 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 6 is a side sectional view showing a state of a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 7 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 8 is a side sectional view showing a state near a bottom dead center of a piston of the two-stroke internal combustion engine.

FIG. 9 is a side sectional view showing a state near a bottom dead center of a piston of the two-stroke internal combustion engine.

FIG. 10 is a side sectional view showing a state of a bottom dead center of a piston of the two-stroke internal combustion engine.

FIG. 11 is a side sectional view showing a state near a top dead center of a piston of a stratified scavenging two-stroke internal combustion engine including an air control valve according to a second embodiment of the present invention.

FIG. 12 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 13 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 14 is a side sectional view showing a state of a bottom dead center of a piston of the two-stroke internal combustion engine.

FIG. 15 is a plan sectional view showing a main part of a stratified scavenging two-stroke internal combustion engine including an air control valve according to a third embodiment of the present invention.

FIG. 16 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 17 is a side sectional view showing a state near a top dead center of a piston of the two-stroke internal combustion engine.

FIG. 18 is a side sectional view showing a state of a top dead center of a piston of the two-stroke internal combustion engine.

[Explanation of symbols]

2: spark plug 3: combustion chamber 4: cylinder body 5: air passage 6: piston 8: exhaust port 9: connecting rod 10:
Crank chamber 12: scavenging passage 14: crankshaft 15: mixture passage 16: mixture throttle valve 17: scavenging port 18: air passage 19: air throttle valve 20: valve housing 21: air control valve 22: valve body 24: groove passage Road
26: groove passage 27: annular groove 31: pulley 32: endless belt 33: cam 34: pulley 35: open / close valve
37: Spring

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Masao Suzuki, Inventor 2-3-3 Shiba-koen, Minato-ku, Tokyo Inside Walbro Japan Co., Ltd. (72) Michiyasu Togashi 2-3-3, Shiba-koen, Minato-ku, Tokyo No. 3 F-term in Japan Walbro Co., Ltd. (reference) 3G065 AA02 CA12 HA05 KA01

Claims (3)

[Claims] A combustion chamber and a crank chamber are defined by fitting a piston to a cylinder body, and a mixture passage of a carburetor is connected to a mixture passage opening to the crank chamber at a top dead center of the piston. The upper end of the scavenging passage connecting the crank chamber and the combustion chamber provided on the peripheral wall of the main body is connected to a scavenging port that opens before the bottom dead center of the piston, and the air passage of the carburetor passes through an air control valve that rotates in conjunction with the crankshaft. Connected to the scavenging passage, exhausting combustion gas in a combustion chamber to an exhaust port by air from the scavenging passage at the end of a combustion stroke, and then supplying a mixture in a crank chamber to the combustion chamber through the scavenging passage. A stratified scavenging two-stroke internal combustion engine, characterized in that: 2. The air control valve according to claim 1, wherein a valve body that rotates in conjunction with a crankshaft is fitted in a cylindrical valve chamber of a valve housing.
2. The stratified scavenging two-stroke internal combustion engine according to claim 1, wherein an air passage of a carburetor communicates with the scavenging passage near a top dead center of a piston. 3. The air control valve has an air passage extending from a scavenging port and an air passage extending from a carburetor arranged in parallel and adjacent to each other, and an on-off valve is provided on a valve seat provided in a passage connecting both air passages. 2. The layered scavenging device according to claim 1, wherein the spring is biased to a closed position by a force, and a cam formed on a crankshaft for opening the on-off valve is engaged with an end of a stem of the on-off valve. Two-stroke internal combustion engine.