JP3974957B2 - Two-stroke engine carburetor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a crank chamber compression type 2 in which air-fuel mixture is sucked into the crank chamber by utilizing the pressure fluctuation of the crank chamber accompanying the sliding of the piston, and the air-fuel mixture in the crank chamber is pressurized and supplied to the cylinder or combustion chamber. The present invention relates to a carburetor suitable for a stroke engine.
[0002]
[Prior art]
In the conventional crank chamber compression type two-stroke engine, the air-fuel mixture pressurized in the crank chamber is supplied to the cylinder through the scavenging port to scavenge the combustion gas remaining in the cylinder. If the scavenging of the air is performed satisfactorily, a blow-through phenomenon occurs in which the air-fuel mixture flowing into the cylinder is discharged into the atmosphere through the exhaust port together with the combustion gas. The blow-through phenomenon increases the amount of unburned components (hydrocarbon HC) contained in the exhaust gas, leading to waste of fuel.
[0003]
The blow-off phenomenon can be suppressed by accelerating the closing timing of the exhaust port by the piston, but in this case, the combustion gas remaining in the cylinder increases, increasing the irregular combustion stroke due to incomplete combustion or misfire, and eventually exhausting There is a drawback that not only the hydrocarbons contained in the gas increase, but also the engine output decreases.
[0004]
Therefore, in a two-stroke 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 an adjustment device is provided for adjusting the air flow rate in the air passage in conjunction with the throttle valve operation of the engine. In the above-described two-stroke engine, when the crank chamber becomes negative pressure when the piston rises, the air-fuel mixture generated by the carburetor is sucked into the crank chamber through the intake port, and at the same time, air is scavenged from the air passage through the check valve. Suction is performed in the vicinity of the passage or the scavenging port. When the piston descends due to the explosion of the air-fuel mixture, the exhaust port opens near the bottom dead center of the piston and the combustion gas is discharged. Subsequently, the scavenging port is opened, and the air in the scavenging passage is first ejected to the cylinder by the positive pressure in the crank chamber, and then the air-fuel mixture in the crank chamber is ejected to the cylinder. In this case, while the exhaust port is open, the air initially ejected from the scavenging port to the cylinder flows to the exhaust port, and the exhaust port is closed until the air-fuel mixture flows to the exhaust port following the air.
[0005]
In the adjusting device for the two-stroke engine described above, the first arm is coupled to the shaft of the throttle valve that opens and closes the intake passage of the carburetor, and the second arm coupled to the shaft of the butterfly valve of the adjusting device is coupled to the second arm described above. One arm is connected by a rod, so that the butterfly valve is configured to open and close in conjunction with the throttle valve. However, in the above-described adjusting device, since the throttle valve of the carburetor and the butterfly valve of the adjusting device are linked and connected, the arm of the throttle valve of the carburetor and the arm of the butterfly valve of the adjusting device are directly connected by the rod. In an engine having a plurality of scavenging ports, the same number of adjusting devices and rods as the scavenging ports are required, and the structure becomes complicated. In other words, the provision of a plurality of adjusting devices results in a large overall size because the adjusting mechanism protrudes from the engine, resulting in variations in the opening of the butterfly valve of each adjusting device, making it difficult to synchronize with the throttle valve. Moreover, the opening degree synchronized with long-term use may change, and the scavenging situation of the engine may change. Furthermore, it is necessary to attach an air cleaner to each air passage so that dust or the like does not enter the engine from the air passage. However, in the configuration in which the air passage is independent, it is difficult to mount the air cleaner.
[0006]
[Problems to be solved by the invention]
In view of the above problems, the problem of the present invention is to prevent the blowout phenomenon in which the air-fuel mixture flows from the scavenging port of the engine to the exhaust port, and only the external air prepared in advance in the scavenging stroke of the engine passes through the scavenging port to the cylinder. It is to provide a carburetor for a two-stroke engine that is supplied to the engine.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention connects an air passage to a portion of the scavenging passage that communicates between the scavenging port of the engine and the crank chamber in the vicinity of the scavenging port, and the flow of air to the scavenging passage is connected to the air passage. A check valve is provided, and an air control valve that adjusts the air flow rate of the air passage in conjunction with the throttle valve is sandwiched between the air purifier and the vaporizer, and the air purifier, the air control valve, and the vaporizer are In the two-stroke engine carburetor integrated and attached to the engine, the engine is provided with a plurality of the scavenging ports, the air control valve is constituted by a rotary throttle valve, and the scavenging port is connected to the valve body of the rotary throttle valve. The same number of valve holes are provided, the same number of outlets corresponding to the valve holes are provided in the air control valve, and the outlets are connected to the scavenging ports by independent air passages, respectively .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a rotary throttle valve is provided as an air control valve that adjusts the amount of air in the air passage in conjunction with the throttle valve between the vaporizer and the air cleaner, and the air cleaner, the air control valve, and the vaporizer are provided. The valve body of the rotary throttle valve is provided with the same number of valve holes as the scavenging ports, and each valve hole is connected to each scavenging port via an independent air passage.
[0009]
Since the air purifier, the air control valve, and the carburetor are integrally attached to the engine, the throttle valve and the air control valve of the carburetor need only be connected by a single rod. Is sucked into the crank chamber of the engine, and the air that has passed through the air control valve is supplied to a portion adjacent to each scavenging port of the air passage through the check valve.
[0010]
【Example】
FIG. 1 is a side sectional view of a two-stroke engine equipped with a carburetor according to the present invention, and FIG. 2 is a plan sectional view of the engine. In the two-stroke engine A, a cylinder 32 is coupled to an upper portion of a crankcase 39, and a piston 34 fitted to the cylinder 32 so as to be movable up and down is connected to a crank arm 38a of a crankshaft 38 supported by the crankcase 39 by a connecting rod 42. Has been. An ignition plug 31 that protrudes into the combustion chamber 32 a is attached to the upper end wall of the cylinder 32. An exhaust port 35 and a scavenging port 33 that open near the bottom dead center of the piston 34 are provided on the peripheral wall of the cylinder 32. The exhaust port 35 communicates with the atmosphere through an exhaust muffler 44, and the scavenging port 33 cranks through a scavenging passage 33a. It communicates with the chamber 39a . Air suction port 37 is vaporizer B, communicates to the atmosphere through an air purifier D.
[0011]
The carburetor B is attached to the intake port 37 of the crankcase 39 through a heat insulating pipe 21 having an intake valve (reed valve) 37a. 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 into a cylindrical portion that crosses the intake passage of the main body 16, and the throttle valve lever 10 is coupled to the shaft portion 12 at the upper end of the throttle valve 15. 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 spring, the opening degree of the throttle valve 15 increases, and at the same time, the throttle valve 15 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 the opening of the fuel nozzle hole of the fuel nozzle.
[0012]
According to the present invention, the air suction path 26 is formed in the wall portion of the cylinder 32, one end of the air suction path 26 communicates with a portion of the scavenging passage 33 a close to the scavenging port 33, and the other end is the air passage 25, air The air is communicated with the atmosphere via the control valve C, the intake passage 9 and the air purifier D. A check valve 27 that allows air to flow from the air passage 25 to the scavenging port 33 is provided in the air suction passage 26.
[0013]
The air control valve C extends upward from the intake passage 9 and crosses the valve chamber 8a (FIG. 3) in the upper half of the block-like control valve body 8 having the intake passage 9, and the same number of valve passages 7 as the scavenging ports 33. Equipped with. The air outlet of the air control valve C, that is, the upper end of the valve passage 7 is connected to the connecting pipe 6. As shown in FIG. 3, a rod-shaped valve body 5 is rotatably inserted into a cylindrical valve chamber 8 a orthogonal to the intake passage 9 of the control valve body 8. 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 the air suction path 26 in the wall portion of the cylinder 32 by an air passage 25 made of a pipe.
[0014]
The control valve main body 8 of the air control valve C is provided with a bolt insertion hole 54 at a symmetrical position with the intake passage 9 in between. The air control valve C is constituted by a single rotary throttle valve, and a retaining ring 51 is retained at one end of the valve body 5 fitted in the valve chamber 8a, and a lever 23 is coupled to the other end of the valve body 5. Then, one end of the return spring 22 wound around the outer end portion of the valve body 5 is locked to the control valve body 8 and the other end is locked to the lever 23. As shown in FIG. 2, the throttle valve lever 10 of the vaporizer B and the lever 23 of the air control valve C are connected by a rod 13 at the shortest distance. When the throttle valve lever 10 is operated in the opening direction, the air control valve C is also opened, and the amount of air to the scavenging passage 33a is increased.
[0015]
As shown in FIG. 1, an air purifier D is formed by connecting box-shaped cases 2 and 4 each having a two-part body with a filter 3 between them, and the air sucked from the intake port 2a of the case 2 is , Flows through the filter 3, the case 4, the intake passage 9 of the air control valve C, the carburetor B, the heat insulating pipe 21, the intake valve 37 a, and the intake port 37 to the crank chamber 39 a.
[0016]
Next, the operation of the carburetor for a two-stroke engine according to the present invention will be described. When the crank chamber 39a and the scavenging passage 33a are brought into a negative pressure state as the piston 34 moves up, the check valve 27 is opened, and air in the atmosphere is sucked into the scavenging port 33 through the air suction passage 26. Since air is sucked into the scavenging port 33 over almost the entire period of the stroke in which the piston 34 rises, the efficiency of filling the air into the scavenging port 33 is improved, and when scavenging the combustion gas, The momentum of the air flowing into the cylinder 32 becomes stronger, and the scavenging performance of the combustion gas is improved.
[0017]
In a state where the piston 34 is raised to a position immediately before the top dead center, when the air-fuel mixture compressed in the cylinder 32 is ignited by the spark plug 31, an explosion occurs in the cylinder 32 and the piston 34 moves to a lowering stroke. On the other hand, when the piston 34 reaches the top dead center, the air-fuel mixture is filled into the crank chamber 39a from the intake port 37, and air is filled into the scavenging passage 33a from the air intake passage 26 .
[0018]
When the piston 34 descends due to the explosion of the air-fuel mixture in the cylinder 32, the air-fuel mixture in the crank chamber 39a is pressurized, and at the same time, the pressure in the crank chamber 39a is transmitted to the scavenging port 33 through the scavenging passage 33a. Air is also pressurized. When the piston 34 further descends and the exhaust port 35 begins to open, the combustion gas in the cylinder 32 is discharged into the atmosphere through the exhaust port 35 and the exhaust muffler 44. When the exhaust port 35 starts to open, the scavenging port 33 starts to open, and the air pressurized in the scavenging passage 33a flows into the cylinder 32 through the scavenging port 33, and the combustion gas remaining in the cylinder 32 is discharged to the exhaust port. The scavenging action of pushing out to 35 is performed.
[0019]
On the other hand, before or after the scavenging port 33 is opened, as the air pressurized to the scavenging port 33 flows into the cylinder 32, the air-fuel mixture in the crank chamber 39a passes through the scavenging passage 33a to the scavenging port 33. Then, it flows into the cylinder 32 through the scavenging passage 33a. As described above, the air and the air-fuel mixture flowing into the cylinder 32 from the scavenging port 33 flow in a separated state without being mixed with each other. That is, when the exhaust port 35 and the scavenging port 33 open back and forth and the combustion gas is scavenged, the air first flows from the scavenging port 33 to the cylinder 32, and then the air-fuel mixture flows from the scavenging port 33 to the cylinder 32. . Therefore, only the air that has flowed into the cylinder 32 first is discharged together with the combustion gas to the exhaust port 35. When the air-fuel mixture flows into the cylinder 32 after the air, the exhaust port 35 is closed. Therefore, the blow-through phenomenon that the air-fuel mixture flows out into the atmosphere through the exhaust port 35 does not occur.
[0020]
Turning now to the stroke of the piston 34 is raised from the bottom dead center, at elevated process until the top dead center, Runode crankcase 39a is a negative pressure state, the air-fuel mixture generated by the carburetor B inlet 37 And is sucked into the crank chamber 39a. At the same time, the negative pressure state of the crank chamber 39a is also transmitted to the air suction passage 26 via the scavenging passage 33a, so that air is sucked into the scavenging passage 33a via the air suction passage 26 . It was but connexion, when the piston 34 reaches to approximately the top dead center, the air-fuel mixture into the crank chamber 39a is filled, in a state where only the air is filled with the scavenging port 33.
[0021]
As described above, according to the present invention, the scavenging effect of after opening the exhaust port 35, the air flowing above the cylinder 32 is pushed out combustion gases Runode, scavenging of the combustion gas is ensured, the engine It can greatly contribute to output improvement. Moreover, the amount of hydrocarbons that are unburned components contained in the exhaust gas is reduced, and fuel is not wasted.
[0022]
FIG. 1 shows a film type vaporizer frequently used in a portable work machine, but the present invention is not limited to this type of vaporizer.
[0023]
【The invention's effect】
In the present invention, as described above, an air passage is connected to a portion of the scavenging passage that communicates between the scavenging port of the engine and the crank chamber in the vicinity of the scavenging port, and the check that allows the air flow to the scavenging passage. A valve is provided, and an air control valve that adjusts the air flow rate of the air passage in conjunction with the throttle valve is sandwiched between the air purifier and the vaporizer, and the air purifier, the air control valve, and the vaporizer are integrated. In the two-stroke engine carburetor attached to the engine, the air control valve is composed of a rotary throttle valve, so that conventional products can be used as they are for the carburetor and the air purifier. By sandwiching the control valve body in between, they are integrally and compactly attached to the engine, and one air purifier serves to clean the air flowing to both the carburetor and the air control valve.
[0024]
The throttle valve of the carburetor and the air control valve can be connected by a single rod at the shortest distance, and even when used for a long time, the tuning of the throttle valve and the air control valve does not change.
[0025]
Since the air control valve and the air intake port of each scavenging port can be connected by an independent passage, the length of each connection passage can be changed as necessary.
[0026]
Since the air control valve is a rotary throttle valve, it is easy to manufacture and the control valve body does not become large.
[0027]
Even if a number of valve holes are provided in the air control valve, no special configuration for tuning or connection is required.
[0028]
Since the valve body of the air control valve is arranged upstream of the intake passage of the control valve body, the fuel blown from the carburetor is not supplied to the scavenging port via the air control valve, and the exhaust port is discharged during the scavenging stroke. There is no increase in the amount of hydrocarbons in the exhaust gas discharged to
[Brief description of the drawings]
FIG. 1 is a side cross-sectional view of a two-stroke engine equipped with a carburetor according to the present invention.
FIG. 2 is a plan sectional view of the engine.
3 is a front cross-sectional view of the air control valve taken along line 2A-2A in FIG.
[Explanation of symbols]
A: Engine body B: Vaporizer C: Air control valve D: Air purifier 2: Case 2a: Inlet 3: Filter 4: Case 5: Valve body 5a: Valve passage 6: Connection pipe 7: Valve passage 8: Body 8a: Valve chamber 9: Intake passage 10: Throttle valve lever 12: Shaft portion 13: Rod 14: Rod valve 15: Throttle valve 16: Vaporizer body 17: Atmosphere chamber 18: Membrane 19: Constant pressure fuel chamber 20: Fuel nozzle 21: Heat insulation pipe 22: Return spring 23: Lever 25: Air passage 26: Air inflow passage 27: Check valve 31: Spark plug 32: Cylinder 32a: Combustion chamber 33: Scavenging port 33a: Scavenging passage 34: Piston 35: Exhaust Port 37: Air intake port 37a: Air intake valve 38: Crank shaft 38a: Arm 39: Crank case 39a: Crank chamber 42: Connecting rod 44: Exhaust muffler 51: Retaining ring 52: Lid 53: Passage 54: Bolt insertion hole

Claims (1)

An air passage is connected to a portion of the scavenging passage that communicates between the scavenging port of the engine and the crank chamber, and a check valve that allows air flow to the scavenging passage is provided in the air passage. For a two-stroke engine, an air control valve that adjusts the air flow rate of the air passage in conjunction with the throttle valve is sandwiched between the carburetor and the air purifier, air control valve, and carburetor are integrated into the engine. In the vaporizer,
A plurality of scavenging ports are provided in the engine;
The air control valve is composed of a rotary throttle valve, the valve body of the rotary throttle valve is provided with the same number of valve passage holes as the scavenging ports, and the air control valve has the same number of outlets corresponding to the valve passage holes, respectively. A two-stroke engine carburetor characterized in that each outlet is connected to each scavenging port by an independent air passage .

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