JP3768590B2 - Two-stroke internal combustion engine carburetor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-stroke internal combustion engine that suppresses a blow-through phenomenon in which an air-fuel mixture jetted from a scavenging port directly flows into an exhaust port, and particularly an air passage connected to a portion of the scavenging passage close to the scavenging port via a check valve. The present invention relates to a carburetor for a two-stroke internal combustion engine in which an air control valve for adjusting the amount of air is provided so that the opening operation characteristics of the throttle valve and the air control valve of the carburetor can be set optimally.
[0002]
[Prior art]
In a conventional crankcase compression type two-stroke internal combustion engine, an air-fuel mixture pressurized in the crankcase is supplied from a scavenging port to a cylinder or a combustion chamber, thereby discharging combustion gas remaining in the cylinder to an exhaust port (scavenging). Therefore, when scavenging the combustion gas is performed well, a so-called blow-out phenomenon occurs in which the air-fuel mixture flowing into the cylinder is discharged together with the combustion gas into the atmosphere from the exhaust port. As a result of the air-fuel mixture blowout phenomenon, a large amount of hydrocarbon (HC), which is an unburned component, is contained in the exhaust gas, and the amount of fuel consumed in vain increases.
[0003]
If the piston closes the exhaust port earlier, the blow-off phenomenon can be suppressed, but the combustion gas remaining in the cylinder increases, causing irregular combustion due to incomplete combustion or misfire, and eventually carbonization contained in the exhaust gas. There is a drawback that the amount of hydrogen (HC) increases and the output of the engine decreases.
[0004]
Therefore, in the two-stroke internal combustion engine disclosed in JP-A-7-139358, JP-A-7-189704, JP-A-7-269356, etc., an air passage is connected to a portion of the scavenging passage close to the scavenging port. A check valve is provided in the air passage, and the air flow rate in the air passage is adjusted in conjunction with the operation of the throttle valve of the carburetor. According to the above-described two-stroke internal combustion engine, when the crank chamber becomes negative pressure when the piston is raised, the air-fuel mixture flows from the carburetor through the intake port into the crank chamber, and at the same time, air in the air passage pushes the check valve open. , Flows into the scavenging passage or scavenging port. When the piston descends due to the explosion of the air-fuel mixture, the exhaust port opens near the bottom dead center and the combustion gas is discharged. When the scavenging port is subsequently opened, first, air in the scavenging passage is supplied to the cylinder by the positive pressure in the crank chamber, and then the air-fuel mixture in the crank chamber is supplied to the cylinder.
[0005]
However, in the above-described two-stroke internal combustion engine, if the amount of air supplied to the cylinder is too large while the exhaust port and the scavenging port are open, the amount of air-fuel mixture supplied to the cylinder decreases and the engine output decreases. Therefore, it is preferable that the ratio of the air amount to the air-fuel mixture can be adjusted.
[0006]
[Problems to be solved by the invention]
In view of the above-described problems, an object of the present invention is to provide a carburetor for a two-stroke internal combustion engine capable of adjusting an opening operation characteristic of an air control valve with respect to an opening of a throttle valve of the carburetor.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the configuration of the present invention is configured so that an air passage is connected to a portion of the scavenging passage that communicates the scavenging port and the crank chamber close to the scavenging port, and the air flow toward the scavenging passage is transmitted to the air passage. Provide a check valve to allow, an air control valve to control the amount of air supplied from the air purifier to the air passage, a carburetor to supply a mixture of air and fuel through the check valve to the crank chamber, In a carburetor of a two-stroke internal combustion engine that opens and closes an air control valve in conjunction with opening and closing of the valve, the throttle valve and the air control valve are connected by a connecting rod so that the mutual distance can be adjusted. To do.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the air purifier, the air control valve, and the carburetor are integrally attached to the engine, and the throttle valve and the air control valve of the carburetor are connected by a single connecting rod. Is sucked into the crank chamber of the engine, and the air that has passed through the air control valve is sucked into each scavenging passage through the air passage.
[0009]
By adjusting the substantial length of the connecting rod that connects the throttle valve of the carburetor that adjusts the amount of air-fuel mixture and the air control valve that adjusts the amount of air supplied to the cylinder in the scavenging stroke, the opening of the throttle valve Adjusting the opening of the air control valve to suppress the blow-out phenomenon of the air-fuel mixture and increase the scavenging efficiency.
[0010]
【Example】
FIG. 1 is a left side sectional view of a two-stroke internal combustion engine equipped with a carburetor according to an embodiment of the present invention. The engine body A has a cylinder 32 coupled to an upper portion of a crankcase 39, and a piston 34 is fitted to the cylinder 32 so as to be movable up and down. The piston 34 is connected to the arm 38 a of the crankshaft 38 supported by the crankcase 39 by a connecting rod 42, and the combustion chamber 32 a is partitioned between the upper end portion of the cylinder 32 and the piston 34. An ignition plug 31 is attached to the head of the cylinder 32, and an exhaust port 35 and a scavenging port 33 that open at the bottom dead center of the piston 34 are formed on the wall of the cylinder 32. The exhaust port 35 communicates with the atmosphere via an exhaust muffler 44, and the scavenging port 33 communicates with a crank chamber 39a via a scavenging passage 33a described later.
[0011]
The carburetor B is attached to the intake port 37 of the crankcase 39 via a heat insulating pipe 21 provided with a check valve (reed valve) 37a as an intake valve. In detail, the carburetor B, the air control valve C, and the air purifier D are integrally attached to the crankcase 39 of the two-stroke internal combustion engine through the heat insulating pipe 21 by two mounting bolts not shown. It is done. In the carburetor B, a throttle valve 15 having a throttle hole is fitted in a cylindrical portion that crosses the intake passage of the main body 16 so as to be able to rotate and move up and down, and a throttle valve lever 10 is coupled to a shaft portion 12 at the upper end of the throttle valve 15. The A constant pressure fuel chamber 19 and an atmospheric chamber 17 are partitioned by a membrane 18 at the lower portion of the main body 16. A fuel in a fuel tank (not shown) is sequentially supplied to the constant pressure fuel chamber 19 by a fuel pump, and is always maintained at a constant pressure. A fuel nozzle 20 projects from the constant pressure fuel chamber 19 into the throttle hole of the throttle valve 15. A rod valve 14 protruding from the shaft portion 12 of the throttle valve 15 to the throttle hole is fitted into the fuel nozzle 20 so as to increase or decrease the opening of the fuel injection hole. When the throttle valve lever 10 is rotated against the force of the return spring, the opening degree of the throttle valve 15 is increased, and at the same time, a throttle mechanism is formed by a cam mechanism formed between the throttle valve lever 10 and the upper end wall of the main body 16. The rod valve 14 rises together with 15 and the opening of the fuel nozzle hole of the fuel nozzle 20 increases.
[0012]
According to the present invention, the check valve (reed valve) 27 that allows the flow of air from the outside to the portion of the scavenging passage 33 a close to the scavenging port 33 is provided on the wall portion of the cylinder 32. Therefore, one end of the connection pipe 26 provided with the check valve 27 is communicated with a portion close to the scavenging port 33 of the scavenging passage 33a, and the other end is connected to the air passage 25, the air control valve C, the intake passage 9, and the air purifier. D is communicated to the atmosphere via D.
[0013]
The air control valve C has valve passages 7 as many as the scavenging ports 33 extending upward from the intake passage 9 and crossing the valve chamber 8a (FIG. 3) in the upper half of the block-shaped main body 8 having the intake passage 9. It is done. The upper end of the valve passage 7 is connected to the connecting pipe 6. As shown in FIG. 3, the rod-shaped valve body 5 is rotatably inserted into a cylindrical valve chamber 8 a that is orthogonal to the intake passage 9 of the main body 8, that is, parallel to the crankshaft 38. The valve body 5 includes a valve passage hole 5a that can communicate with the valve passage 7 that crosses the valve chamber 8a. When the valve body 5 is rotated, the area of the valve passage 7 changes. The lower end of each valve passage 7 communicates with a passage 53 that intersects the intake passage 9. The end of the passage 53 is closed by a lid 52. The air outlet of the air control valve C, that is, the connecting pipe 6 is connected to a connecting pipe 26 attached to the wall portion of the cylinder 32 by an air passage 25 (FIG. 2) made of a pipe.
[0014]
The main body 8 of the air control valve C is provided with a through hole 54 through which the mounting bolt described above is inserted at a symmetrical position across the intake passage 9. The air control valve C is composed of a single rotary throttle valve. A retaining ring 51 is locked to one end of the valve body 5 fitted into the valve chamber 8a, and a lever 23 is connected to the other end of the valve body 5. Combined. A return spring 22 wound around the outer end portion of the valve body 5 is engaged with the main body 8 at one end and the lever 23 at the other end.
[0015]
As shown in FIG. 1, the air purifier D is formed by connecting box-shaped cases 2 and 4 each having a two-part body with a filter 3 interposed therebetween, and is sucked from an intake port 2 a of the case 2. The air flows to the crank chamber 39a through the filter 3, the case 4, the intake passages 9 of the air control valve C and the carburetor B, the heat insulating pipe 21, the check valve 37a as the intake valve, and the intake port 37.
[0016]
As shown in FIG. 4, according to the present invention, the opening degree of the air control valve C can be arbitrarily changed with respect to the opening degree of the throttle valve 15. That is, the operation lever 61 for driving the throttle valve lever 10 of the carburetor B is supported on the upper end wall of the main body 16 by the support shaft 62, and the operation lever 61 and the lever 23 of the air control valve C are interlocked by one connecting rod 13. Link. By adjusting the substantial length of the connecting rod 13, that is, the mutual distance between the operation lever 61 and the lever 23 of the air control valve C, the opening degree of the air control valve C with respect to the opening degree of the throttle valve 15 is adjusted. Therefore, a plurality of adjustment holes 61 a for locking the end portion 13 b of the connecting rod 13 are provided in the arm 61 b of the operation lever 61 at different distances from the rotation center of the operation lever 61. As shown in FIG. 5, the lever 23 of the air control valve C may be provided with a plurality of adjustment holes 23 a for engaging the end portion 13 a of the connecting rod 13 at different distances from the rotation center.
[0017]
An attachment wire 64 for fixing an outer tube of a remote operation cable (not shown) is supported on an attachment plate piece 63 a protruding upward from a support plate 63 supported on the upper end wall of the vaporizer body 16, and an inner wire penetrating the attachment fitting 64. Is connected to a swivel 65 supported at the end of the operation lever 61.
[0018]
Next, the operation of the carburetor for a two-stroke internal combustion engine according to the present invention will be described. When the operation lever 61 is rotated clockwise from the idle position shown in FIG. 4 around the support shaft 62, that is, in the opening direction of the throttle valve lever 10 by the remote operation cable, the pin 10a is pushed by the operation lever 61, and the throttle The valve lever 10 is driven in the opening direction. At the same time, the lever 61 of the air control valve C is rotated by the arm 61 b via the connecting rod 13, the air control valve C is opened, and the amount of air sent to the scavenging port 33 is increased. If the adjustment hole 61a of the operation lever 61 or the adjustment hole 23a of the lever 23 of the air control valve C is selected and the end 13b or the end 13a of the connection rod 13 is locked, the substantial length of the connection rod 13 changes. Then, as shown by lines a to c in FIG. 6, the opening degree of the air control valve C with respect to the opening degree of the throttle valve 15 can be adjusted.
[0019]
During operation of the engine, before the piston 34 reaches top dead center, the air-fuel mixture is charged into the crank chamber 39a from the intake port 37, and air is charged into the scavenging passage 33a and the scavenging port 33 from the connection pipe 26. On the other hand, the compressed air-fuel mixture exists in the cylinder 32 in a state immediately before the piston 34 reaches the top dead center. When the compressed air-fuel mixture in the cylinder 32 is ignited by the spark plug 31, the air-fuel mixture explodes inside the cylinder 32 and the piston 34 descends. When the piston 34 descends, the air-fuel mixture in the crank chamber 39a is pressurized. At the same time, the pressure in the crank chamber 39a is transmitted to the scavenging port 33 through the scavenging passage 33a, and the air in the scavenging port 33 is also pressurized.
[0020]
When the piston 32 further descends, the exhaust port 35 starts to open, and the combustion gas in the cylinder 32 is discharged into the atmosphere through the exhaust port 35 and the exhaust muffler 44. As soon as the exhaust port 35 is opened, the scavenging port 33 starts to open, the pressurized air in the scavenging passage 33a and the scavenging port 33 flows into the cylinder 32, and the scavenging gas that pushes the combustion gas remaining in the cylinder 32 to the exhaust port 35. Perform the action. Next, the air-fuel mixture in the crank chamber 39 a flows into the cylinder 32 through the scavenging passage 33 a and the scavenging port 33. The air flowing into the cylinder 32 from the scavenging port 33 and the air-fuel mixture flowing into the cylinder 32 from the crank chamber 39a through the scavenging passage 33a and the scavenging port 33 are first mixed in a state where they are not mixed and then mixed. Qi flows in.
[0021]
Next, when the piston 34 moves upward from the bottom dead center and reaches the vicinity of the top dead center, the crank chamber 39a is in a negative pressure state, the check valve 37a of the intake port 37 is opened, and is generated by the carburetor B. The air-fuel mixture is sucked from the intake port 37 into the crank chamber 39a. At the same time, the air-fuel mixture that flows into the scavenging port 33 and remains in the previous stroke is sucked back into the crank chamber 39a. Further, the check valve 27 is opened by the negative pressure in the crank chamber 39a, and air is sucked from the air cleaner D into the crank chamber 39a through the air control valve C, the air passage 25, the check valve 27, and the scavenging passage 33a. . Thus, when the piston 34 almost reaches the top dead center, the crank chamber 39a is filled with the air-fuel mixture, and the scavenging passage 33a and the scavenging port 33 are filled with only air.
[0022]
As described above, in the present invention, the adjustment hole 61a of the operating lever 61 or the adjustment hole 23a of the lever 23 of the air control valve C is selected and the end portion 13b or the end portion 13a of the connecting rod 13 is locked, thereby restricting the aperture. The optimum opening degree of the air control valve C relative to the opening degree of the valve 15 is obtained. Therefore, only the air that has flown into the cylinder 32 first in the scavenging stroke flows out to the exhaust port 35 together with the combustion gas, and Since the air-fuel mixture that flows into the cylinder 32 later stays in the cylinder 32, scavenging efficiency is increased, the amount of unburned components (HC) contained in the exhaust gas is reduced, fuel is not wasted, and the engine output is increased. .
[0023]
In addition, although the above-mentioned Example demonstrated the film | membrane type vaporizer used frequently for a portable working machine, this invention is not limited to this kind of vaporizer.
[0024]
【The invention's effect】
As described above, the present invention provides a check valve that connects an air passage to a portion near the scavenging port of the scavenging passage that communicates the scavenging port and the crank chamber, and allows the air passage to flow toward the scavenging passage. Equipped with an air control valve that controls the amount of air supplied from the air purifier to the air passage, and equipped with a carburetor that supplies a mixture of air and fuel via a check valve to the crank chamber, linked to the opening and closing of the throttle valve In the carburetor of a two-stroke internal combustion engine that opens and closes the air control valve, the throttle valve and the air control valve are connected by a connecting rod so that the mutual distance can be adjusted. The valve opening characteristics can be set to the optimum value, adjustment is easy, and air and air-fuel mixture are stratified in the combustion chamber, and a rich air-fuel mixture is generated around the spark plug. Improvement, fuel efficiency improvement, exhaust gas purification, engine output Stabilization is obtained.
[0025]
The interlocking mechanism of the throttle valve and air control valve of the carburetor can be adapted to engines with different specifications without making levers or parts with different positions of the adjustment holes for locking the connecting rod.
[Brief description of the drawings]
FIG. 1 is a left side sectional view of a two-stroke internal combustion engine equipped with a carburetor according to the present invention.
FIG. 2 is a plan sectional view of the two-stroke internal combustion engine.
3 is a front cross-sectional view of the air control valve of the carburetor according to line 3A-3A in FIG. 2;
FIG. 4 is a plan view showing an interlocking mechanism between a throttle valve and an air control valve of the vaporizer.
FIG. 5 is a left side view of a lever of the air control valve of the vaporizer.
FIG. 6 is a diagram showing opening operation characteristics of a throttle valve and an air control valve of the vaporizer.
[Explanation of symbols]
A: Engine body B: Vaporizer C: Air control valve D: Air purifier 5: Valve body 5a: Valve passage 6: Connection pipe 7: Valve passage 8: Body 9: Intake passage 10: Throttle valve lever 12: Shaft Part 13: Connecting rod 14: Rod valve 15: Throttle valve 16: Vaporizer body 17: Atmospheric chamber 18: Membrane 19: Constant pressure fuel chamber 20: Fuel nozzle 21: Thermal insulation pipe 22: Return spring 23: Lever 23a: Adjustment hole 25 : Air passage 26: Connection pipe 27: Check valve 31: Spark plug 32: Cylinder 32 a: Combustion chamber 33: Scavenging port 33 a: Scavenging passage 34: Piston 35: Exhaust port 37: Inlet port 37 a: Check valve (intake valve) 38: Crankshaft 38a: Arm 39: Crankcase 39a: Crank chamber 42: Connecting rod 44: Exhaust muffler 51: Retaining ring 52: Lid 53: Passage 54: Through hole 61: Operation lever 61a: Adjustment hole 61b: Arm 62: Support shaft 63: Support plate 63a: Vertical plate piece 64: Fixing bracket 65: Swivel

Claims (4)

An air passage is connected to a portion of the scavenging passage that connects the scavenging port and the crank chamber in the vicinity of the scavenging port, and a check valve is provided in the air passage to allow the flow of air toward the scavenging passage. An air control valve that controls the amount of air supplied to the engine is provided, and a carburetor that supplies a mixture of air and fuel to the crank chamber via a check valve is provided. A carburetor for a two-stroke internal combustion engine, characterized in that the throttle valve and the air control valve are connected by a connecting rod so that the mutual distance can be adjusted. The carburetor for a two-stroke internal combustion engine according to claim 1, wherein the opening degree of the air control valve can be arbitrarily changed with respect to the opening degree of the throttle valve. An operating lever for driving the throttle valve lever of the carburetor is provided, and the operating lever is interlocked and connected to the lever of the air control valve by a connecting rod. The carburetor for a two-stroke internal combustion engine according to claim 1, wherein a plurality of adjustment holes are provided for locking the two-stroke internal combustion engine. 2. The carburetor for a two-stroke internal combustion engine according to claim 1, wherein the lever of the air control valve is provided with a plurality of adjustment holes for engaging the end of the connecting rod at different distances from the rotation center.

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