JP2003293774A - Two cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly eliminate a trouble of engine stop caused by re-atomizing liquid fuel in a mixture adhered into a crank chamber in a feeding process of the liquid fuel from the crank chamber toward a scavenging passage, perfectly burning it, and feeding fuel into a combustion chamber, even when engine attitude is varied by attitude change of a working machine. <P>SOLUTION: A narrow passage 14 is disposed in an inner peripheral surface 11 at an opening end along a rotating direction of a crank weight 7 in the crank chamber 1, liquid fuel 13 coming into the crank chamber from a suction port 4 and adhering and reserving in it is fed to the scavenging passage 15 through the narrow passage 14 to be atomized like fog, and perfectly burned in the combustion chamber 16. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine, and more particularly to an improvement of a two-cycle engine of a type in which cylinders are horizontally arranged, such as an engine used in a portable working machine such as a chain saw. is there.

[0002]

2. Description of the Related Art Conventionally, a two-cycle engine has been widely used as a power source for various portable working machines because it has an advantage that it can be operated in any posture. There are a piston valve system and a reed valve system, but the reed valve is used in various portable work machines because of the advantage that the carburetor can be arranged at a free position of the machine body.

Among two-cycle engines, particularly those used in chain saws, in which the cylinders are arranged horizontally, for example, Japanese Unexamined Patent Publication No. 9-1517.
39, JP-A-10-169519, JP-A-10-1
As disclosed in Japanese Patent Laid-Open No. 69520/1998 and Japanese Patent Laid-Open No. 10-220309, a crank chamber is connected to one end of a horizontally arranged cylinder, and an intake port having a reed valve is provided obliquely above the crank chamber. From the carburetor attached to this suction port, the air-fuel mixture is sent into the crank chamber by opening and closing the reed valve, and undergoes precompression in the crank chamber,
It is supplied from the scavenging passage to the combustion chamber in the cylinder.

[0004]

The air-fuel mixture introduced into the crank chamber from the suction port is supplied in the direction of the scavenging port leading to the combustion chamber in the cylinder by the pressure in the crank chamber due to the reciprocating movement of the piston. In a horizontally arranged engine, when the air-fuel mixture is supplied from the intake port provided in the crank chamber, the reliquefied part of the air-fuel mixture adheres to a part of the crank chamber and stays there. This may cause a problem that the liquid fuel flows into the combustion chamber in the cylinder due to the change in the attitude of the machine body due to the work, and the engine is stopped due to the supply of the over-concentrated air-fuel mixture.

As described above, the reason why the liquid fuel adheres to and stays in a part of the crank chamber is that even if the fuel is atomized by the carburetor, the air-fuel mixture collides with the surface of the reed valve to cause the air-fuel mixture to mix. A part of it liquefies again and hangs below the surface of the valve and flows into the crank chamber from the suction port,
This is due to the fact that the liquid flows from the upper inclined surface near the suction port in the room to the lower horizontal surface portion and adheres to the horizontal surface portion as a liquid.

[0006] As described above, even if a part of the air-fuel mixture atomized by the vaporizer collides with the reed valve and is liquefied again, the engine is under a high load or at a high speed. Since the temperature of the crank chamber is high at the time of 1), the liquefied fuel is atomized again and is sent to the combustion chamber in the cylinder, so there is no problem of being sent to the combustion chamber as liquid.

Therefore, as described above, when the air-fuel mixture collides with the surface of the reed valve, a part of the air-fuel mixture is liquefied again and the liquid fuel adheres and accumulates in the crank chamber during idle operation. As described above, the fuel consumption amount per unit time is low, the temperature of the crank chamber does not rise, and the rate of occurrence is high when the reed valve does not move actively.

As described above, in the horizontally arranged cylinder type engine, when the idle operation is continued for a long time, the liquid fuel adheres and accumulates in the crank chamber, and the liquid fuel having a high concentration is fueled by the change of the body posture. There is a problem that it flows into the room and causes the engine to stop.

In order to solve the problem in such a horizontally arranged cylinder type engine, in the prior art, the above-mentioned Japanese Patent Laid-Open No. 9-15 has been proposed.
1739, JP-A-10-169519, JP-A-10
No. 169520 and Japanese Patent Laid-Open No. 10-220309, a regulating surface for stopping the flow of the inflowing liquid fuel is provided near the suction port on the circumferential surface of the crank chamber so that the liquid fuel flows into the crank chamber from the suction port. However, a method is known in which the liquid combustion is captured on the regulation surface and is stagnated so that the liquid combustion does not flow in the cylinder direction inward of the regulation surface.

However, in these conventional techniques, as a means for solving the problem, the liquid fuel flowing in from the suction port is captured by the regulation surface near the suction port so as not to flow toward the scavenging passage in the cylinder. As long as the liquid fuel flowing from the intake port is not atomized again and is positively sent to the combustion chamber in the cylinder for combustion, the liquid fuel stays in the crank chamber forever. Therefore, there is a problem that the accumulated liquid fuel is eventually sent to the combustion chamber in the cylinder, and the adverse effect of stopping the engine cannot be reliably eliminated.

[0011]

A two-stroke engine according to the present invention solves the above-mentioned problems in the conventional two-stroke engine and allows liquid fuel flowing from the suction port into the crank chamber to flow near the suction port. Reliably solves the problem that the engine will stop even if the attitude of the aircraft is freely changed, instead of being trapped and retained and positively atomized again in the crank chamber and sent to the combustion chamber in the cylinder for combustion. The purpose of the present invention is to provide a two-cycle internal combustion engine that can be operated.

In the two-stroke engine according to the present invention, as a specific means therefor, the cylinders are arranged horizontally,
In a two-cycle engine having a suction opening opened and closed by a reed valve in a part of a crank chamber connected to one end of the cylinder, a crank chamber opening end inner peripheral surface along a rotation direction of a crank weight rotating in the crank chamber A thin pipe passage having a cross-sectional area smaller than the cross-sectional area of the scavenging passage of the cylinder for atomizing the liquid fuel entering the crank chamber and adhering to the crank chamber in the form of mist, and supplying the liquid fuel in the direction of the scavenging passage of the cylinder. It is characterized by

It is preferable that the narrow pipe passage is formed by a hole-shaped passage in which the inner peripheral surface of the crank chamber opening end is linearly cut out in the opening direction of the crank chamber along the rotation direction of the crank weight.

Further, only one narrow passage is provided on the inner peripheral surface of the crank chamber opening end located below the crank chamber in the upright state of the body in which the cylinders are horizontally arranged. In consideration of the case where the machine body is in an inverted state, which is used for work machines with various posture changes, and considering the inflow balance of the left and right scavenging gas in the scavenging stroke, the crank chamber located below the crank chamber is considered. It is preferable to provide the inner peripheral surface of the opening end and the inner peripheral surface of the opening end of the crank chamber located above the crank chamber at two locations.

[0015]

In the two-stroke engine of the present invention, when the air-fuel mixture is supplied into the crank chamber from the intake port provided in the crank chamber, the liquid component of the air-fuel mixture rotates in a semicircular crank weight in the crank chamber. When the flow from the inclined surface of the part to the horizontal plane close to the cylindrical connection part with the cylinder and adhered and accumulated, a thin pipe passage is provided on the inner peripheral surface of the opening end with the cylinder, which connects from the crank chamber to the scavenging passage of the cylinder. By receiving the compressive force generated in the crank chamber due to the reciprocating motion of the piston, the liquid fuel adhering to the crank chamber is pushed into the narrow tube passage.

When liquid fuel is pushed into the capillary passage,
The liquid combustion in the passage receives the compressive force in the crank chamber from one end of the passage, and vigorously passes through the narrow passage and is rapidly sent toward the scavenging passage of the cylinder.At that time, when passing through the narrow passage, Will be atomized by the jet output of. Therefore, the liquid fuel adhering to the wall surface of the crank chamber is atomized into fine particles by passing through the narrow pipe passage, and is sent into the combustion chamber from the scavenging passage to be reliably burned.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment in which the two-cycle engine according to the present invention is used as a power source for a chain saw will be described. FIG.
2 is a cross-sectional view showing a state in which a cylinder 2 is connected, a cylinder 2 is horizontally arranged, and an intake port 4 opened and closed by a reed valve 3 is provided obliquely above a crank chamber 1 connected to the cylinder 2.

Although not shown in the drawings, a carburetor is attached to the suction port 4, a saw blade is provided on the right side of the cylinder 2, and a handle for operation is provided above the carburetor attached to the suction port 4. It is configured to be.

The crank chamber 1 has a rotating chamber portion 5 of a crank weight 7 having the suction port 4 at one end, and a cylindrical cylinder connecting portion 6 at the other end. Has an open end 6a connected to the cylinder 2.
A crank weight 7 is rotatably mounted in the rotating chamber portion 5 of the crank weight 7, and a crank shaft 8 of the crank weight 7 and a piston 9 in the cylinder 2 are connected by a connecting rod 10. There is.

Further, the cylindrical connecting portion 6 in the crank chamber 1
The inner peripheral surface 11 of the opening end is smaller than the inner diameter of the inner peripheral surface 5a of the crankweight rotating part 5, and the piston 9 in the cylinder 2 fits into the inner peripheral surface 11 of the open end.
A gap 12 is provided between the scavenging passage 15 and the piston outer peripheral surface 9a so that the mixture can be supplied from the scavenging passage 15 to the cylinder combustion chamber even if the mixture does not pass through a narrow tube passage 14 described later. This makes it possible to obtain an output equivalent to that of a conventional engine. If the gap 12 is too large, the liquid droplet fuel will not flow into the narrow pipe passage 14, so the cross-sectional area of the gap 12 is small.
It is necessary to set in consideration of conditions such as the distribution of air-fuel mixture.

Further, the liquid fuel 13 that has entered the inner peripheral surface 11 of the cylindrical connecting portion 6 along the rotation direction of the crank weight 7 from the suction port 4 and adheres to the inner wall surface of the crank weight rotating portion 5 is atomized. A thin tube passage 14 is provided to guide the cylinder 2 in the direction of the scavenging passage 15 of the cylinder 2.

The narrow pipe passage 14 is composed of a tubular hole formed by linearly hollowing the inner peripheral surface 11 of the open end of the tubular connecting portion 6 in the direction of the open end 6a of the crank chamber 1 along the rotational direction of the crank weight 7. The cross-sectional area of this passage 14 is
It is configured to be smaller than the cross-sectional area of the scavenging passage 15 of the cylinder 2 coaxially communicating with the passage 14.

On the other hand, the cylinder 2 connected to the crank chamber 1 is provided with a scavenging passage 15 formed by hollowing the inner wall of the cylinder 2 on the same axis as the narrow tube passage 14 of the crank chamber 1, and the tip of this scavenging passage 15 is Combustion chamber 16 of cylinder 2
Is in communication with.

As shown in FIG. 1, when the machine body is in an upright state such that the cylinder 2 is placed horizontally, the liquid combustion which enters the inner wall of the crank chamber 1 through the suction port 4 is exclusively performed by the crank weight rotating part 5 and the cylinder. Since it adheres to and stays in the portion between the cylinder-shaped cylinder connecting part 6 and the cylinder-shaped connecting part 6,
Although it is necessary to provide only one on the lower side of the crankshaft, the narrow pipe passages 14 are provided at two positions on the lower side and the upper side of the crank chamber tubular connection portion 6 in consideration of the inflow balance of the right and left scavenging gases in the scavenging stroke. Is being used.

[0025]

As described above, in the two-cycle engine of the present invention, when liquid fuel enters through the intake port provided in the crank chamber and adheres and accumulates in the crank chamber,
By changing the compression force in the crank chamber or the attitude of the machine so that the chainsaw provided on the left side of the machine shown in FIG. The liquid fuel that has been poured into the narrow pipe passage receives the compressive force from the crank chamber in the narrow pipe passage and vigorously passes through the narrow passage, resulting in atomization into a fine atomization. It is possible to surely combust the fuel by sending it to the combustion chamber from the scavenging passage.

Therefore, according to the engine of the present invention, even if the liquid fuel enters the crank chamber and adheres and stays in the chamber,
Unlike the conventional technique in which the liquid fuel is stored in the crank chamber forever, the liquid fuel that has penetrated into the crank chamber is positively supplied in the cylinder direction through the narrow passage to ensure that the liquid fuel is restored again. Since it can be atomized, even if liquid fuel adheres to the crank chamber by continuing idle operation for a long time,
Since this can be atomized again and burned, no matter how the attitude of the machine is changed and used, the machine can be used stably without fear of engine stop.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a two-cycle engine according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

[Explanation of symbols]

1: Crank chamber, 2: Cylinder, 3: Reed valve, 4: Inhalation port, 5: Crank weight rotating part, 6: tubular connection, 6a: open end, 7: Crank weight, 8: crankshaft, 9: piston, 10: connecting rod, 11: inner peripheral surface of opening end, 12: Gap, 13: Liquid fuel, 14: capillary passage, 15: Scavenging passage, 16: combustion chamber,

Claims (4)

[Claims] 1. A two-cycle engine in which a cylinder is horizontally arranged, and a suction opening opened and closed by a reed valve is provided in a part of a crank chamber connected to one end of the cylinder,
The liquid fuel that has penetrated from the suction port and adhered to the crank chamber is atomized into the inner circumferential surface of the crank chamber opening along the rotational direction of the crank weight rotating in the crank chamber, and is guided in the direction of the scavenging passage of the cylinder. A two-cycle engine, characterized in that it is provided with a capillary passage having a cross-sectional area smaller than a cross-sectional area of the scavenging passage of the cylinder for supplying. 2. The narrow tube passage is a hole-shaped passage formed by linearly hollowing the inner peripheral surface of the crank chamber opening end toward the opening end of the crank chamber along the rotational direction of the crank weight. Cycle engine. 3. The thin tube passage is provided only on the inner peripheral surface of the crank chamber opening end located on the lower side of the crank chamber in the upright state of the machine body in which the cylinders are horizontally arranged.
2 cycle engine. 4. The inner peripheral surface of the crank chamber opening end located below the crank chamber and the crank chamber opening end located above the crank chamber when the narrow pipe passage is in an upright state in which the cylinder is horizontally arranged. The two-cycle engine according to claim 1, wherein the two-cycle engine is provided at two locations on the peripheral surface.