JP3934198B2 - Two-stroke internal combustion engine carburetor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is suitable for a two-stroke internal combustion engine that takes in the air-fuel mixture into the crank chamber using pressure fluctuations in the crank chamber caused by the sliding of the piston, pressurizes the air-fuel mixture in the crank chamber, and supplies it to the combustion chamber of the cylinder. It relates to the carburetor.
[0002]
[Prior art]
In the conventional 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 combustion chamber of the cylinder. If scavenging is to be carried out satisfactorily, a blow-through phenomenon occurs in which the air-fuel mixture flowing into the combustion chamber is discharged together with the combustion gas into the atmosphere through the exhaust port. 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 combustion chamber of the cylinder increases, and the irregular combustion process due to incomplete combustion or misfire increases. Eventually, there is a disadvantage that not only the hydrocarbons contained in the exhaust gas increase but also the engine output decreases.
[0004]
Therefore, according to Japanese Patent Laid-Open No. 7-139358, the present applicant connects an air passage to a portion near the scavenging port of the scavenging passage that communicates the scavenging port of the engine and the crank chamber, and air to the scavenging passage is connected to the air passage. A check valve that allows the flow of air is provided, and an air control valve that adjusts the amount of air in the air passage in conjunction with the fuel control valve (throttle valve) is sandwiched between the air purifier and the vaporizer, A two-stroke engine carburetor was proposed in which the air control valve and carburetor were integrated and attached to the engine. That is, as shown in FIG. 4, the air control valve 5 is composed of a single rotary throttle valve, and extends upward from the intake passage to the upper half of the block-shaped control valve body 8 having the intake passage. The same number (three) of valve passages as the scavenging ports 33 are provided across the valve chamber. A connection pipe 6 is coupled to the air outlet of the air control valve 5, that is, the upper end of the valve passage. A rod-shaped air control valve 5 is rotatably inserted into a cylindrical valve chamber orthogonal to the intake passage of the control valve main body 8. The throttle valve lever 10 coupled to the shaft portion 12 of the fuel control valve and the lever 23 coupled to the air control valve 5 are connected by a link mechanism 13, and the fuel control valve and the air control valve 5 are moved by moving the throttle valve lever 10. It is rotated at the same time. The connecting pipe 6 is connected to a connecting pipe 26 adjacent to the scavenging port 33 on the wall of the cylinder 32 by an air passage 25 made of a pipe.
[0005]
In the above-described two-stroke engine, when the crank chamber becomes negative pressure when the piston is raised, 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 supplied from the air passage 25 to the check valve 27. Then, the air is sucked into a portion near the scavenging passage or the scavenging port 33. When the piston descends due to the explosion of the air-fuel mixture, the exhaust port 35 opens near the bottom dead center of the piston, and the combustion gas is discharged. Subsequently, the scavenging port 33 is opened, and the air in the scavenging passage is first ejected into the cylinder 32 by the positive pressure in the crank chamber, and then the air-fuel mixture in the crank chamber is ejected into the cylinder 32. In this case, while the exhaust port 35 is open, the air initially ejected from the scavenging port 33 to the inside of the cylinder 32 flows to the exhaust port 35, and until the air-fuel mixture flows to the exhaust port 35 following the air, the exhaust port 35 closes.
[0006]
However, in the above-described two-stroke engine carburetor, since the fuel control valve and the air control valve 5 are arranged orthogonally, the fuel control valve and the air control valve 5 are connected by the link mechanism 13 so that they are linked. However, it has been found that the link mechanism 13 has the following problems.
[0007]
(a) Since the direction of the rotation axis of each control valve is different, it is difficult to control the rotation in exactly proportion.
[0008]
(b) If looseness occurs in the link mechanism 13 during long-term use, the rotational phases of both control valves change.
[0009]
(c) Both control valves require independent springs, increasing the operating force.
[0010]
(d) Since the link mechanism 13 is disposed outside the vaporizer, it is difficult to make the entire vaporizer compact.
[0011]
(e) Both control valves require independent fuel control valves, increasing manufacturing costs.
[0012]
[Problems to be solved by the invention]
In view of the above-described problems, an object of the present invention is to integrally form a fuel control valve and an air control valve, so that a rotational phase shift does not occur between the two, and the vaporization for a two-stroke internal combustion engine is easy to operate. Is to provide a vessel.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the configuration of the present invention is such that the end of the air passage is connected to a portion of the scavenging passage that communicates the scavenging port of the engine with the crank chamber, and the scavenging passage is connected to the air passage. A carburetor for a two-stroke internal combustion engine comprising a check valve that allows a flow of air, a start end of the air passage connected to an inlet portion of an intake passage, and an air control valve that adjusts an air amount in the air passage A fuel control valve for adjusting the amount of fuel in the intake passage, which is rotatably arranged around an axis crossing the intake passage and the air passage arranged parallel to the carburetor body, and the air control valve; And a needle valve body for adjusting the fuel of the fuel control valve is configured to penetrate the air control valve and be adjustable from the outside .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a fuel control valve that adjusts the amount of fuel in the intake passage and an air passage air amount are adjusted so that the intake passage and the air passage disposed in parallel with the carburetor body can rotate about an axis that crosses the intake passage and the air passage. The air control valve is integrally formed. As a result, an interlocking mechanism such as a link mechanism is abolished, a rotational phase shift between the fuel control valve and the air control valve is eliminated, and a light operation is obtained.
[0015]
【Example】
FIG. 1 is a left side sectional view of a two-stroke engine equipped with a carburetor according to the present invention, and FIG. 2 is an enlarged sectional view of the carburetor. 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. An intake port 37 that opens near the top dead center of the piston 34 is provided in the crankcase 39, and the intake port 37 communicates with the atmosphere via the carburetor B and the air purifier D.
[0016]
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. Specifically, the carburetor B and the air cleaner D are integrally attached to the crankcase 39 of the two-stroke engine via two heat-insulating pipes 21 by two mounting bolts (not shown). As shown in FIG. 2, the carburetor B has a fuel control valve (throttle valve) 15 having a valve hole 15a inserted in a valve chamber or a small-diameter cylindrical portion 50b of the stepped cylindrical portion 50 that crosses the intake passage 9 of the main body 16. The throttle valve lever 10 is coupled to the shaft portion 12 at the upper end of the fuel control 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. The constant pressure fuel chamber 19 is replenished with fuel in a fuel tank (not shown) sequentially by a fuel pump, and is always kept at a constant pressure. While the fuel nozzle 20 protrudes from the constant pressure fuel chamber 19 to the valve hole 15a of the fuel control valve 15, the needle valve body 14 protruding from the shaft portion 12 of the fuel control valve 15 to the valve hole 15a is inserted into the fuel nozzle 20. Thus, the opening of the fuel injection hole is adjusted. When the throttle valve lever 10 is rotated against the force of the return spring 29, the opening of the valve hole 15a of the fuel control valve 15 increases, and at the same time, the lid plate 45 that closes the throttle valve lever 10 and the stepped cylindrical portion 50. , The needle valve body 14 is lifted together with the fuel control valve 15, and the opening of the fuel nozzle hole of the fuel nozzle 20 is increased.
[0017]
Three connecting pipes 26 that form air suction ports are disposed in the wall portion of the cylinder 32, and one end of each connecting pipe 26 communicates with a portion of the scavenging passage 33 a adjacent to the scavenging port 33, and the other end is the air passage 25. , 7, and the air control valve 5 integrated with the fuel control valve 15, and the air cleaner D are communicated to the atmosphere. Each connection pipe 26 is provided with a check valve 27 that allows air to flow from the air passage 25 to the scavenging passage 33a.
[0018]
As shown in FIG. 2, according to the present invention, the air passage 7 is disposed in the main body 16 in parallel with the intake passage 9, and the start end of the air passage 7 is connected to the inlet end of the intake passage 9 by the vertical communication passage 9 a. Communicated. The upper end of the communication passage 9 a is closed by the lid plate 46, and the right end of the air passage 7 is closed by the lid plate 47. The intake passage 9 is disposed adjacent to the constant pressure fuel chamber 19 (FIG. 1), and the air passage 7 is disposed above the intake passage 9. A lateral communication passage 7a is arranged at the end of the air passage 7 so as to intersect, and a plurality of (three in the illustrated example) passage holes 7b (FIG. 1) project upward from the communication passage 7a. Are fitted. Each connecting pipe 6 is connected to an engine connecting pipe 26 by an air passage 25 made of a flexible pipe. The air control valve 5 having the valve hole 5 a is integrally formed with the fuel control valve 15 and is rotatably fitted into the large-diameter cylindrical portion 50 a of the stepped cylindrical portion 50 that crosses the air passage 7 and the intake passage 9.
[0019]
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 passage 9 of the carburetor B, the heat insulating pipe 21, the intake valve 37a, and the intake port 37.
[0020]
As shown in FIG. 3, a mounting bracket for fixing an outer tube of a remote operation cable (not shown) to a mounting plate piece 63a protruding upward from a support plate 63 supported by a plurality of bolts 24 on the upper end wall of the vaporizer body 16 64 is supported, and an inner wire penetrating the mounting bracket 64 is connected to the swivel 10 a supported at the end of the throttle valve lever 10.
[0021]
Next, the operation of the carburetor for a two-stroke internal combustion engine according to the present invention will be described. When the throttle valve lever 10 is rotated clockwise (opening direction) about the shaft portion 12 from the idle position shown in FIG. 3 by the remote operation cable, the air control valve 5 is rotated and the air in the air passage 7 is The amount of air sent from the control valve 5 to the scavenging passage 33a increases.
[0022]
When the crank chamber 39a and the scavenging passage 33a are in a negative pressure state as the piston 34 rises during engine operation, the check valve 27 is opened, and the atmosphere is air purifier D, air control valve 5, air passages 7, 25. Then, the air is sucked into the scavenging port 33 through the check valve 27 and the scavenging passage 33a. Since air is sucked into the scavenging port 33 over almost the entire period during which the piston 34 ascends, the efficiency of filling the air into the scavenging port 33 is improved, and when scavenging the combustion gas, the scavenging port 33 moves to the cylinder. The momentum of the air flowing into 32 becomes stronger, and the scavenging performance of the combustion gas is improved. On the other hand, when the piston 34 reaches the top dead center, the air-fuel mixture is filled from the carburetor B into the crank chamber 39a through the intake valve 37a and the intake port 37.
[0023]
When the piston 34 rises to the vicinity of the top dead center, the air-fuel mixture in the cylinder 32 is compressed. When the air-fuel mixture is ignited by the ignition plug 31, an explosion occurs in the cylinder 32 and the piston 34 moves down. 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. 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.
[0024]
The scavenging port 33 starts to open following the exhaust port 35, and the air pressurized in the scavenging passage 33 a flows into the cylinder 32 through the scavenging port 33 and pushes the combustion gas remaining in the cylinder 32 to the exhaust port 35. Performs scavenging action. Before and after the scavenging port 33 is opened, the air pressurized in the scavenging passage 33 a flows into the cylinder 32, and then the air-fuel mixture in the crank chamber 39 a passes through the scavenging passage 33 a and the scavenging port 33 to the cylinder 32. Inflow.
[0025]
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 flown into the cylinder 32 first flows into the exhaust port 35 together with the combustion gas, and when the air-fuel mixture flows into the cylinder 32 after the air, the exhaust port 35 is closed. The blow-out phenomenon that the air-fuel mixture flows out into the atmosphere through the exhaust port 35 does not occur.
[0026]
Next, when the piston 34 moves up from the bottom dead center to the vicinity of the top dead center, the crank chamber 39a is in a negative pressure state as described above, and the air-fuel mixture generated in the carburetor B is transferred to the crank chamber. Inhaled to 39a. Since the negative pressure state of the crank chamber 39a is also transmitted to the connecting pipe 26 through the scavenging passage 33a, the air-fuel mixture that has flowed into the scavenging passage 33a in the previous stroke is sucked back into the crank chamber 39a, and at the same time, air is supplied from the air control valve 5 to the air. Is sucked into the scavenging passage 33a through the air passages 7 and 25 and the check valve 27. Therefore, 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 is filled with only air.
[0027]
【The invention's effect】
In the present invention, as described above, the end of the 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 the air flow to the scavenging passage is connected to the air passage. In a carburetor for a two-stroke internal combustion engine, provided with a check valve for allowing, connecting the start end of the air passage to an inlet portion of an intake passage, and having an air control valve for adjusting the amount of air in the air passage, A fuel control valve and an air control valve for adjusting the fuel amount of the intake passage disposed so as to be rotatable about an axis crossing the intake passage and the air passage arranged in parallel are integrally configured. Therefore, the whole carburetor becomes small, the fuel control valve and the air control valve are operated against a single spring, the operation is not unreasonable, the operation force is light, and the rotation control in proportion to both is accurate. can get.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a two-stroke internal combustion engine equipped with a carburetor according to the present invention.
FIG. 2 is an enlarged side sectional view showing the vaporizer.
FIG. 3 is a plan view of the vaporizer.
FIG. 4 is a plan sectional view of a two-stroke internal combustion engine equipped with a carburetor according to the prior application.
[Explanation of symbols]
A: Engine B: Vaporizer D: Air purifier 5: Air control valve 5a: Valve hole 6: Connection pipe 7: Air passage 7a: Communication passage 9: Intake passage 10: Throttle valve lever 12: Shaft portion 14: Needle valve Body 15: Fuel control valve 15a: Valve hole 16: Vaporizer body 17: Atmospheric chamber 18: Membrane 19: Constant pressure fuel chamber 20: Fuel nozzle 21: Thermal insulation pipe 25: Air passage 26: Connection pipe 27: Check valve 29: Return spring 32: Cylinder 32a: Combustion chamber 33: Scavenging port 33a: Scavenging passage 34: Piston 35: Exhaust port 37: Inlet port 37a: Intake valve 38: Crankshaft 39a: Crank chamber 42: Connecting rod 50: Stepped cylinder 50a: Large diameter cylindrical part 50b: Small diameter cylindrical part

Claims (2)

An end of the 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 the flow of air to the scavenging passage is provided in the air passage, A carburetor for a two-stroke internal combustion engine having an air control valve that connects a start end of an air passage to an inlet portion of an intake passage and adjusts an air amount in the air passage.
A fuel control valve for adjusting the amount of fuel in the intake passage disposed so as to be rotatable about an axis crossing the intake passage and the air passage disposed in parallel with the carburetor body, and the air control valve. One-piece ,
The two-stroke internal combustion engine carburetor characterized in that a needle valve body for adjusting fuel of the fuel control valve penetrates the air control valve and is adjustable from the outside .   2. The carburetor for a two-stroke internal combustion engine according to claim 1, wherein the fuel control valve has a smaller diameter than the air control valve and is disposed coaxially with the air control valve in a portion close to the constant pressure fuel chamber.

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