JP2001254623A - Stratified scavenging two-stroke engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stratified scavenging two-stroke engine which will not sacrifice the maximum output of the engine, makes exhaust emission clean, and is excellent in transient responsiveness such as fuel consumption saving and sudden acceleration. SOLUTION: In an air leading type stratified scavenging two-stroke engine, only air is introduced into a scavenging passage 7 of the engine, air-fuel mixture is introduced into a crank chamber 18 of the engine, in scavenging the engine, air in the scavenging passage 7 is led to discharge exhaust gas of a combustion chamber 4, and then the air-fuel mixture is supplied to the combustion chamber 4. An air control valve 35 for controlling the area of the air passage 36 interlocking with throttle valve 48 of a carburetor is provided between the scavenging passage 7 of the engine and the air passage 46 of the carburetor.

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 engine, and more particularly, to a mixture passage and an air passage of a carburetor in a low speed region of the engine, and a mixture passage and an air passage of a carburetor in a high speed region of the engine. The present invention relates to an air-driven stratified scavenging two-stroke engine configured to shut off a passage from a passage.

[0002]

2. Description of the Related Art Generally, in an air-driven stratified scavenging two-stroke engine, the flow of air supplied to the engine from a scavenging passage during rapid acceleration of the engine is combusted through a scavenging passage after being introduced into a crank chamber of the engine. The mixture introduced into the chamber is introduced into the combustion chamber later than the flow of air from the scavenging passage for the following reasons. That is, (a) since only air has a smaller density (lighter) than the air-fuel mixture, the flow of air during rapid acceleration is faster. (B) Since the air-fuel mixture has a long distance from the crank chamber and the scavenging passage to the combustion chamber, when the engine is rapidly accelerated, a large amount of air enters the combustion chamber and the air-fuel mixture becomes lean, resulting in acceleration of the engine. Becomes significantly worse.

[0003] If the air passage is narrowed in order to improve the rapid acceleration of the engine, the acceleration is improved, but the maximum output is reduced.
If the air-fuel mixture passage is widened, the acceleration performance and the maximum output can be satisfied, but the exhaust gas deteriorates as in the conventional two-stroke engine.

[0004] In the stratified scavenging two-stroke engine disclosed in Japanese Patent Application Laid-Open No. 10-121974, the air-fuel mixture valve and the air control valve are provided separately, so that the air control valve throttles the air passage during acceleration of the engine. As a result, the acceleration performance is improved, but the maximum output is reduced.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a clean exhaust gas without sacrificing the maximum output of an engine, excellent fuel economy, and excellent transient response during rapid acceleration.
A stratified scavenging two-stroke engine is provided.

[0006]

In order to solve the above-mentioned problems, according to the present invention, only air is introduced into a scavenging passage of an engine, and a mixture of air and fuel is introduced into a crank chamber of the engine.
In the scavenging passage of the engine, in the scavenging passage of the engine and the air passage of the carburetor in the air-driven stratified scavenging two-stroke engine in which the air in the scavenging passage leads and discharges exhaust gas from the combustion chamber, and then the mixture is supplied to the combustion chamber. And an air control valve for controlling the area of the air passage in conjunction with the throttle valve of the carburetor.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an air control valve is provided between a scavenging passage of an engine and an air valve of a carburetor in conjunction with a throttle valve of the carburetor. The air control valve narrows the air passage to less than half below the middle speed range of the engine, and opens the air passage at the higher speed range of the engine. The air control valve normally opens together with the throttle valve. However, when the engine is rapidly accelerated, the air control valve is opened after the throttle valve.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an engine A according to the present invention has a carburetor C connected to a right side wall provided with an intake port 17 and a scavenging passage 7 via a heat insulator B, and an inlet end of the carburetor C. An air cleaner (not shown) is connected to the wall. In the engine A, a piston 9 is inserted into a cylinder body 10 to define a combustion chamber 4 closed by a cylinder head 3 above the piston 9 and a crank chamber 18 below the piston 9. The upper end of a connecting rod 12 is connected to the piston 9 by a pin 8, and the lower end of the connecting rod 12 is connected to a crank arm integral with the crankshaft and the counterweight 16 by a pin 19. In the illustrated embodiment, three scavenging passages 7 are provided on the right side wall and the front and rear side walls of the cylinder body 10, and the exhaust port 5 is provided on the left side wall of the cylinder body 10. The scavenging port 7a and the exhaust port 5 of the scavenging passage 7 communicate with the combustion chamber 4 at the bottom dead center of the illustrated piston 9.

The carburetor C has a stepped valve chamber 61 which is orthogonal to the air passage 46 and the mixture passage 50 passing through the carburetor body 47.
A column-shaped stepped throttle valve 48 is rotatably and vertically inserted. The stepped throttle valve 48 is provided with an air valve having a throttle hole 45 communicable with the air passage 46 and a mixture valve having a throttle hole 55 communicable with the mixture passage 50.
The throttle nozzle 55 has a fuel nozzle 5 supported on the bottom wall of the valve chamber 61.
2, the needle 49 supported by the throttle valve 48 is fitted into the fuel nozzle 52, and the opening of the fuel injection hole of the fuel nozzle 52 is adjusted. The lower end of the fuel nozzle 52 is connected to a constant pressure fuel chamber 57 via a check valve (not shown) and a fuel jet. Intermediate wall 53 connected to the lower end surface of vaporizer body 47
A cover 58 is combined with the membrane 54 with a constant pressure fuel chamber 57 above the membrane 54 and an atmosphere chamber 56 below the membrane 54.

The valve shaft 42 of the throttle valve 48 penetrates a cover plate 43 closing the stepped valve chamber 61 connected to the upper end of the vaporizer main body 47, and the throttle valve lever 41 is connected to the upper end of the valve shaft 42.
In order to configure the cam mechanism, a cam surface formed on the lower surface of the throttle valve lever 41 is pressed against a follower projecting upward from the cover plate 43 by the force of a return spring 44. The return spring 44 is disposed between the cover plate 43 and the throttle valve 48 so as to surround the valve shaft 42. The upper end of the return spring 44 is locked by the cover plate 43, and the lower end of the return spring 44 is locked by the throttle valve 48. The throttle valve 48 is rotationally urged to the illustrated idle position by the force of the return spring 44.

Although not shown, a film-type fuel pump driven by the pulsating pressure of the crank chamber 18 of the engine is disposed in the carburetor body 47, and the fuel in the fuel tank (not shown) is kept at a constant pressure by the fuel pump. The fuel is supplied to the fuel chamber 57. In the constant pressure fuel chamber 57, an almost constant fuel amount is always stored under a constant pressure by an inflow valve which is opened and closed according to the vertical displacement of the membrane 54.

According to the present invention, the heat insulator B is interposed between the cylinder body 10 and the outlet end wall of the carburetor C, and the air passage 46 is connected to the scavenging passage 7 of the engine, that is, the reed valve (return valve) 1.
An air control valve 35 connected to the valve shaft 32 is disposed in an air passage 36 connected to the port 14 a having the pressure control valve 4. Valve shaft 3
A lever 31 is connected to the upper end of the second member 2, and a return spring 34 is interposed between the lever 31 and the upper wall of the heat insulator B. The lever 31 and the throttle valve lever 41 are connected by a link 33. An on-off valve 37 is connected to a lower end of the valve shaft 32. In the heat insulator B, a mixture passage 40 connecting the mixture passage 50 of the carburetor C to the mixture port 17 of the engine and a reed valve (return valve).
39 are provided. The on-off valve 37 is configured to open and close a passage 38 that connects a portion of the air passage 36 downstream of the air control valve 35 with the air-fuel mixture passage 40.

As described above, in the present invention, the vaporizer main body 47 is used.
Is a pneumatic valve having a throttle hole 45 and a throttle valve 5.
And a mixture valve having the same. The minimum opening area of the air control valve 35 provided on the heat insulator B is about half of the normal opening area, and it is not necessary to fully close the opening area.
The lever 31 of the valve shaft 32 of the air control valve 35 of the heat insulator B and the throttle valve lever 41 are connected by a link 33, and the air control valve 35 controls only air and opens later than the throttle valve 48 by a certain phase difference. . Since the operating angle of the air control valve 35 may be smaller than that of the throttle valve 48, the air control valve 35 is connected so as to hardly operate when the throttle valve 48 is not more than the middle opening degree. The valve 35 is opened.

In the low speed region of the engine, the mixture passage 40 and the air passage 36 are communicated by the passage 38, and in the high speed region of the engine, the passage 38 is closed. When the passage 38 communicates with the engine in a low speed range, a part of the air-fuel mixture is supplied to the air passage 36, and the fuel entering the air passage 36 at the time of rapid acceleration of the engine assists the acceleration. However, in the high-speed region of the engine, that is, in the fully open position of the throttle valve 48, the harmful components of the exhaust gas increase, so that the passage 38 is closed.

During operation of the engine, when the piston 9 rises, the pressure in the crank chamber 18 decreases, and the mixture flows into the mixture passage 4.
The air flows into the crank chamber 18 through the air passage 36, the reed valve 14, and the scavenging passage 7, while flowing into the crank chamber 18 via the reed valve 39 and the mixture port 17.
That is, the scavenging passage 7 is filled with air, and the crank chamber 18 is diluted with air.

Next, when the air-fuel mixture in the combustion chamber 4 is ignited by the ignition plug 2, the pressure in the combustion chamber 4 suddenly increases, and when the piston 9 descends, the pressure in the crank chamber 18 increases. When the piston 9 descends to a predetermined position, the exhaust port 5 opens, the combustion gas in the combustion chamber 4 flows out from the exhaust port 5, and the pressure in the combustion chamber 18 drops rapidly. At the same time, the scavenging port 7a of the scavenging passage 7 which is in contact with the combustion chamber 4 is opened. First, the air of the scavenging passage 7 flows into the combustion chamber 4, and then the air-fuel mixture of the crank chamber 18 flows into the combustion chamber 4 via the scavenging passage 7. .

FIG. 3 shows how the air quantity of the air-fuel mixture valve represented by the throttle hole 55 responsive to the throttle valve 48, and the air amount of the air valve represented by the throttle hole 45 and the air control valve 35 change. . The air control valve 35 opens quickly near the fully open position of the mixture valve represented by the throttle hole 55. Since there is a time difference between the operation of the air control valve 35 from the idle position to the fully open position, when the engine is rapidly accelerated, the engine speed rapidly rises from the idle position, and the air-fuel mixture valve is opened before the air control valve 35 is fully opened. When the engine is fully opened, a rich air-fuel mixture (an air-fuel mixture that is not diluted by the air from the scavenging air passage 7) is supplied to the engine from the air-fuel mixture passage 40, and helps the engine to rotate faster. Pneumatic control valve 3 after engine rotation
Even if 5 opens quickly and the air is supplied to the scavenging passage 7, the acceleration operation does not become a problem because the engine speed is sufficiently high.

In the embodiment shown in FIG. 2, in order to improve the acceleration of the engine, the air damper 7 is used as a delay means for delaying the air control valve 35 from the throttle valve 48 when the engine is rapidly accelerated.
0 is provided on the upper wall of the heat insulator B. Air damper 7
0 is formed with a piston 68 fitted in the cylinder 63, a throttle hole 65 is formed in a wall plate 64 closing the chamber 67, and a force of a spring 66 interposed between the wall plate 64 and the piston 68 causes the piston 68 to move from the piston 68. The protruding rod 68a contacts the lever 31 connected to the valve shaft 32. Link 33 is lever 3
A spring 62 is interposed between the lever 31 and the spring seat 61a, which is supported by the base 1 and is connected to the end of the link 33. In this embodiment, the passage 38 and the on-off valve 37 are not provided.

At the time of rapid acceleration of the engine, the spring 62 is compressed even if the throttle valve lever 41 is suddenly turned to the full open direction, and the lever 31 is rotated.
Is rotated later by the action of the air damper 70. Eventually, the piston 68 is pushed by the lever 31 against the force of the spring 66 and gradually moves to the left. As shown in FIG. 4, after the throttle valve 48 of the carburetor C reaches the fully open position, the air control is started. Valve 35 opens.

[0020]

As described above, according to the present invention, only air is introduced into the scavenging passage of the engine, and a mixture of air and fuel is introduced into the crank chamber of the engine. In a two-stroke air-driven stratified scavenging engine in which exhaust gas is discharged from the combustion chamber and then an air-fuel mixture is supplied to the combustion chamber, a throttle valve of the carburetor is disposed between the scavenging passage of the engine and the air passage of the carburetor. An air control valve for controlling the area of the air passage in conjunction therewith is provided, and there is no air-fuel mixture blow-through, the exhaust gas is clean, and particularly when the engine is rapidly accelerated, the air control valve opens with a delay ( Since the air passage is narrowed), the acceleration is improved. However, in a steady operation, the air control valve is fully opened, so that the maximum output of the engine is not sacrificed and the fuel consumption does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a stratified scavenging two-stroke engine according to the present invention.

FIG. 2 is a plan view of a heat insulator of a stratified scavenging two-stroke engine according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between the opening of a throttle valve and the opening of an air valve and an air control valve of the engine.

FIG. 4 is a diagram showing a relationship between the opening of a throttle valve and the openings of an air valve and an air control valve of the engine.

[Explanation of symbols]

A: Internal combustion engine B: Heat insulator C: Vaporizer 3: Cylinder head 4: Combustion chamber 5: Exhaust port 7: Scavenging passage 7
a: Scavenging port 9: Piston 10: Cylinder body 12: Connecting rod 14: Reed valve 14a: Port 1
5: crankshaft 16: balance weight 17: mixture port
18: Crank chamber 31: Lever 32: Valve shaft 33:
Link 34: Coil spring 35: Air control valve 36:
Air passage 37: open / close valve 39: reed valve 40: mixture passage 41: throttle valve lever 42: valve shaft 43: cover plate 44: return spring 45: throttle hole (air valve)
46: air passage 47: vaporizer main body 48: stepped throttle valve 49: needle 50: mixture passage 52: fuel nozzle 54: membrane 55: throttle hole (mixture valve) 56: atmosphere chamber 57: constant pressure fuel chamber 61: Stepped valve room 70: Air damper

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02M 17/04 F02M 17/04 Z

Claims (4)

[Claims] An air-only fuel is introduced into a scavenging passage of an engine, a mixture of air and fuel is introduced into a crank chamber of the engine, and the air in the scavenging passage leads to exhaust gas of a combustion chamber during scavenging of the engine. Then, in the air-driven stratified scavenging two-stroke engine in which the air-fuel mixture is supplied to the combustion chamber, the air passage is interposed between the scavenging passage of the engine and the air passage of the carburetor in conjunction with the air-fuel mixture valve of the carburetor. A stratified scavenging two-stroke engine, comprising an air control valve for controlling an area. 2. The air control valve according to claim 1, wherein said air control valve narrows an air passage to a half of a normal area below a middle speed range of said engine, and opens said air passage to a normal area above a middle speed of said engine. Stratified scavenging two-stroke engine. 3. The stratified scavenging two-stroke engine according to claim 1, further comprising delay means for gradually opening the air control valve after the air-fuel mixture valve is fully opened during rapid acceleration of the engine. 4. An on-off valve for opening and closing a passage connecting an air-fuel mixture passage and an air passage on a valve shaft of the air control valve, wherein the on-off valve is opened in a low speed range of the engine, and the on-off valve is opened in a high speed range of the engine. 2. The stratified scavenging two-stroke engine of claim 1, wherein the engine is closed.