JP2001355450A - Stratified scavenging two-stroke internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a mixture suitable for combustion by pushing out combustion gas in a combustion chamber by a lean mixture at the end of a combustion stroke, and then feeding the combustion chamber with an over-rich mixture. SOLUTION: A lean mixture passage extending from a main carburetor 20 is connected to a first mixture port 17 opened to a crank chamber 10 near the top dead center of a piston 6. The outer peripheral wall of a cylinder body 4 is provided with a scavenge air passage 12 connecting the crank chamber 10 to a scavenge port 12a, and mixture passages 52, 52a. The upper ends of the mixture passages 52, 52a are connected to an over-rich mixture passage 55 extending from an auxiliary carburetor 60, and to a second mixture port 57 opened to the combustion chamber 3 at the bottom dead center of the piston 6, and the lower ends are connected to an inlet 52b of the crank chamber 10. At the end of a combustion stroke, combustion gas in the combustion chamber 3 is pushed out to an exhaust port 8 by a lean mixture form the scavenge air passage 12 to produce an appropriate mixture out of the over-rich mixture from the mixture passages 52, 52a and the lean mixture from the scavenge air 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 by a lean mixture.

[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 pushed out to the exhaust port by the new air-fuel mixture. I have. Therefore, a blow-by phenomenon occurs in which not only the combustion gas but also a part of the new air-fuel mixture is exhausted to the exhaust port, 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-mentioned problems, it is an object of the present invention to push a combustion gas in a combustion chamber to an exhaust port with a lean mixture at the end of a combustion stroke, and then send an rich mixture to the combustion chamber. It is another object of the present invention to provide a stratified scavenging two-stroke internal combustion engine which generates a mixture suitable for combustion.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a first mixture port which opens a lean mixture passage extending from a main carburetor to a crank chamber near a top dead center of a piston. And a scavenging passage connecting the crank chamber and a scavenging port opening to the combustion chamber near the bottom dead center of the piston on the outer peripheral wall of the cylinder body; The upper end of the mixture passage is connected to the rich mixture passage extending from the sub-carburetor and to the second mixture port opening to the combustion chamber at the bottom dead center of the piston, and the lower ends of the first and second mixture passages are connected. Are connected to each other, the upper end of the second mixture passage is connected to an inlet cut off from the crankcase at the bottom dead center of the piston, and at the end of the combustion stroke, the combustion gas in the combustion chamber is supplied by the lean mixture from the scavenging passage. To the exhaust port, the rich mixture from the mixture passage and the scavenging And generates the proper mixture by a lean mixture from the road into the combustion chamber.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a lean air-fuel mixture sucked into a crank chamber through a first air-fuel mixture port from a lean air-fuel mixture passage is sent to a combustion chamber through a scavenging air passage and a scavenging air port at the end of a combustion stroke. Then, the combustion gas in the combustion chamber is pushed out to the exhaust port by the lean air-fuel mixture, and then the rich air-fuel mixture sucked into the air-fuel mixture passage from the rich air-fuel mixture passage is burned through the second air-fuel mixture at the end of the combustion process. The mixture is sent to the chamber, and a mixture appropriate for combustion is generated in the combustion chamber from the rich mixture and the lean mixture. The lean mixture passage extends from a main carburetor having a mixture throttle valve. The rich mixture passage extends from a sub-vaporizer having a mixture throttle valve.

[0006] An exhaust port is provided above the first mixture port of the cylinder body, and one or more scavenging ports are provided opposite the exhaust port. The mixture passage is provided on the outer wall of the cylinder body, and the upper end of the mixture passage is connected to the second mixture port.
The lower end of the mixture passage bypasses the bottom of the crankcase and connects to the inlet of the crankcase.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a piston 6 is fitted in 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. The upper end of the connecting rod 9 is connected to the piston 6 by a pin 7, and the lower end of the connecting rod 9 is connected to an arm 14 a integral with the crankshaft 14 by a pin 13. The peripheral wall of the cylinder body 4 is provided with an exhaust port 8 and a second air-fuel mixture port 57 that open near the bottom dead center of the piston 6, and further below the exhaust port 8,
A first mixture port 17 is provided for connecting a lean mixture passage 15 extending from a main carburetor 20 having a mixture throttle valve 16 to the crank chamber 10. In addition, one or a plurality of scavenging ports 12a are provided on the peripheral wall of the cylinder body 4 at a position in the circumferential direction substantially facing the exhaust port 8. The scavenging port 12 a is arranged at a position that is opened near the bottom dead center of the piston 6, and always communicates with the crank chamber 10 through a scavenging passage 12 provided in the outer wall of the cylinder body 4 in a vertical direction.

According to the present invention, during the rising stroke of the piston 6, that is, the compression stroke of the combustion chamber 3, the lean mixture is supplied from the main carburetor 20 to the crank chamber 10, and the rich mixture is supplied from the auxiliary carburetor 60 to the first mixture. In order to guide the mixture passages 52, 52 a to the second mixture passages 52, 52 a, respectively, the mixture passages 52, 52 a extending vertically in the outer wall portion of the cylinder body 4 and partitioned in the radial direction (inside and outside) or in the circumferential direction by the partition wall 54. Provided. Mixture passage 5
The upper end of 2 is connected to a rich mixture passage 55 extending from a sub-vaporizer 60 having a mixture throttle valve 56 and a second mixture port 57. The lower end of the mixture passage 52 is connected to the lower end of the mixture passage 52a, and the upper end of the mixture passage 52a is
Is connected to the entrance 52b which is almost closed at the bottom dead center. It is preferable that the sub-vaporizer 60 and the main vaporizer 20 are integrally formed as disclosed in, for example, Japanese Patent Application No. 8-106187.

In the above-described stratified scavenging two-stroke internal combustion engine,
When the piston 6 shown in FIG. 1 has passed the bottom dead center, the first and second mixture ports 17 and 57 are closed, and the combustion gas D in the combustion chamber 3 is exhausted by the lean mixture A from the scavenging port 12a. The exhaust gas is pushed out to the port 8, and the exhaust port 8 is closed as shown in FIG. 2, and the air-fuel mixture in the combustion chamber 3 is compressed with the rise of the piston 6.

As shown in FIGS. 3 to 6, with the expansion of the crank chamber 10, the first mixture port 17 is opened, and the lean mixture A passes from the lean mixture passage 15 to the first mixture port 17. After that, it is sucked into the crank chamber 10. The rich mixture is sucked from the rich mixture passage 55 into the mixture passages 52 and 52a. On the other hand, when the air-fuel mixture in the combustion chamber 3 is compressed and ignited by the spark plug 2 near the top dead center of the piston 6, the piston 6 is pushed down by the explosive force.

As shown in FIG. 7, the exhaust port 8 is opened, and the lean air-fuel mixture A in the crank chamber 10 is supplied to the scavenging passage 12 and the scavenging port 12.
After passing through a, the mixture is sent to the combustion chamber 3 as a lean mixture C, and the combustion gas D in the combustion chamber 3 is pushed out to the exhaust port 8 as shown in FIG. Subsequently, the second mixture port 57 is opened to open the mixture passage 5.
The rich mixture B of 2,52a is sent to the combustion chamber 3 through the second mixture port 57. As shown in FIG.
Passes through the bottom dead center, the rich mixture B from the second mixture port 57 and the lean mixture C from the scavenging port 12a become
And the mixture becomes a mixture suitable for combustion. Eventually, Figure 1,
As shown in FIG. 2, the exhaust port 8 is closed, and the air-fuel mixture in the combustion chamber 3 is compressed. Hereinafter, the same process is repeated.

In the embodiment shown in FIGS. 10 and 11, first and second mixture passages 62 and 62 a extend from the second mixture port 57 to the outer peripheral wall of the cylinder body 4 to bypass the bottom wall of the crank chamber 10. And the end of the first mixture passage 62 is connected to a rich mixture passage 55 extending from a sub-carburetor 60 having a mixture throttle valve 56. The second mixture passage 62a is connected to an inlet 62b that closes near the bottom dead center of the piston 6. First and second mixture passages 6
2, 62a are partitioned by a partition 64, and are arranged inside and outside doubly or arranged adjacently in the circumferential direction. Preferably, the main carburetor 20 and the sub carburetor 60 are arranged vertically, and the mixture throttle valve 16 and the mixture throttle valve 56 are linked by a link 45. That is, the lever 42 connected to the valve shaft 41 of the air-fuel mixture throttle valve 16 and the lever 44 connected to the valve shaft 43 of the air-fuel mixture throttle valve 56 are connected by the link 45. Other configurations are the same as those shown in FIGS.

According to this embodiment, the lean mixture in the lean mixture passage 15 is drawn into the crank chamber 10 from the first mixture port 17 during the upward stroke of the piston 6. Mixture passage 55
From the mixture enters the right end of the mixture passage 62,
Return from the upper left side to the mixture passage 62a, and the inlet 62b
Inhaled up to near. During the lowering stroke of the piston 6, the lean mixture in the crank chamber 10 is sent to the combustion chamber 3 through the scavenging passage 12 and the scavenging port 12a as the lean mixture C, and the rich mixture in the mixture passages 62, 62a is discharged to the second mixture. Is sent to the combustion chamber 3 through an air-fuel mixture port 57.

In each of the above-described embodiments, the amount of lean mixture supplied to the combustion chamber 3 with respect to the rotation angle of the mixture throttle valve 16 of the main carburetor 20 is indicated by a line 72 in FIG. The quantity is represented by line 73, and the total quantity is represented by line 71.

[0015]

As described above, according to the present invention, the lean mixture passage extending from the main carburetor is connected to the first mixture port which opens to the crank chamber near the top dead center of the piston, and the outer peripheral wall of the cylinder body is provided. A scavenging passage connecting the crank chamber and a scavenging port opening to the combustion chamber near the bottom dead center of the piston, and first and second air-fuel mixture passages, wherein the upper end of the first air-fuel mixture passage is a sub-carburetor. And a second mixture port that opens to the combustion chamber at the bottom dead center of the piston, and lower ends of the first and second mixture paths are connected to each other to form a second mixture. The upper end of the air passage is connected to the inlet cut off from the crank chamber at the bottom dead center of the piston, and at the end of the combustion stroke, the lean gas mixture from the scavenging passage pushes out the combustion gas in the combustion chamber to the exhaust port, and Appropriate depending on the rich mixture from the passage and the lean mixture from the scavenging passage An exhaust gas mixture is generated in the combustion chamber, and at the end of the combustion stroke, the exhaust port, the scavenging port, and the second air-fuel mixture port are opened almost simultaneously with the lowering of the piston, and the lean air-fuel mixture in the crank chamber opens the scavenging port. Since the fuel gas is supplied to the combustion chamber through the combustion chamber and the combustion gas is pushed out to the exhaust port, blow-through of fuel is suppressed, contamination of exhaust gas components is improved, and exhaust gas can be kept clean.

In the combustion chamber, the lean air-fuel mixture and the rich air-fuel mixture are mixed, and the air-fuel mixture suitable for combustion is provided for combustion, thereby improving the performance and fuel efficiency of the engine.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a state near a bottom dead center of a piston of a stratified scavenging two-stroke internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a front sectional view showing a state near a top dead center of a piston of the internal combustion engine.

FIG. 3 is a front sectional view showing a state near a top dead center of a piston of the internal combustion engine.

FIG. 4 is a front sectional view showing a state near a top dead center of a piston of the internal combustion engine.

FIG. 5 is a front sectional view showing a state of a top dead center of a piston of the internal combustion engine.

FIG. 6 is a front sectional view showing a state near a top dead center of a piston of the internal combustion engine.

FIG. 7 is a front sectional view showing a state near a bottom dead center of a piston of the internal combustion engine.

FIG. 8 is a front sectional view showing a state near a bottom dead center of a piston of the internal combustion engine.

FIG. 9 is a front sectional view showing a state of a bottom dead center of a piston of the internal combustion engine.

FIG. 10 is a front sectional view showing a state near a bottom dead center of a piston of a stratified scavenging two-stroke internal combustion engine according to a second embodiment of the present invention.

FIG. 11 is an enlarged front sectional view showing a main part of the internal combustion engine.

FIG. 12 is a diagram showing a relationship between a mixture amount and a rotation angle of a mixture throttle valve of the internal combustion engine.

[Explanation of symbols]

2: spark plug 3: combustion chamber 4: cylinder body 6: piston 8: exhaust port 9: connecting rod 10: crank chamber 1
2: scavenging passage 12a: scavenging port 14: crankshaft 1
5: lean mixture passage 16: mixture throttle valve 17: first
Mixture port 20: Main vaporizer 52: Mixture passage 52
a: air-fuel mixture passage 52b: inlet 54: partition wall 55: rich air-fuel mixture passage 56: air-fuel mixture throttle valve 57: second air-fuel mixture port 60: auxiliary vaporizer 62: air-fuel mixture passage 62a: air-fuel mixture passage 62b: inlet 64: Partition wall

 ──────────────────────────────────────────────────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 (reference) in Japan Walbro Co., Ltd. 3G005 DA04 EA02 FA37 GB15 GB17

Claims (2)

[Claims] 1. A lean air-fuel mixture passage extending from a main carburetor is connected to a first air-fuel mixture port that opens to a crank chamber near a top dead center of a piston, and the crank chamber and the piston are bottom-dead on an outer peripheral wall of a cylinder body. A scavenging passage that connects a scavenging port that opens to the combustion chamber near the point, and first and second mixture passages, and an upper rich mixture passage extending at the upper end of the first mixture passage from the sub-carburetor; The lower end of the piston is connected to the second mixture port which opens to the combustion chamber at the bottom dead center, the lower ends of the first and second mixture paths are connected to each other, and the upper end of the second mixture path is connected to the lower part of the piston. Connected to the inlet cut off from the crank chamber at the dead point, at the end of the combustion stroke, the lean gas mixture from the scavenging passage pushes the combustion gas in the combustion chamber to the exhaust port, and the rich mixture from the mixture passage An appropriate mixture is generated in the combustion chamber with the lean mixture from the scavenging passage. Characterized in that, the stratified scavenging two-stroke internal combustion engine. 2. A first air-fuel mixture passage extending from a second air-fuel mixture port to an opposite side of the crank chamber around an outer bottom portion of the first air-fuel mixture passage on an outer peripheral wall of the cylinder body. The stratified scavenging two-stroke internal combustion engine of claim 1, wherein an end is connected to the rich mixture passage, and an end of a second mixture passage is connected to the inlet of a crankcase.