JPH10288097A - Film type carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of stay of the fuel inside of a heat insulating pipe or an intake pipe, and prevent the generation of operation stop of an engine when the engine is inclined by providing plural axial grooves, which is formed deeper, as it comes close to an engine, in the inner peripheral wall of a heat insulating pipe for connecting an intake passage of a carburetor to an intake port of the engine. SOLUTION: When a throttle valve 47 is turned to the accelerating direction, open degree of a throttle hole 47b communicated with an intake passage 16 is increased, and open degree of an injection hole 56a is increased with a rise of a needle valve 55 from the injection hole 56a of a fuel injection nozzle 56, and the predetermined quantity of the fuel is sucked. In a film type carburetor having such a structure, plural axial groove 65, which are formed deeper, as they come close to an engine, are formed in the inner peripheral wall of a heat insulating pipe 63 with an equal space in the circumferential direction. With this structure, at the time of idling operation of the engine, the fuel adhered to the inner peripheral wall of the intake passage 16 and having a specific gravity larger than that of the intake air is flowed into the axial groove 65, and the generation of sudden suck of the fuel is prevented so as to prevent the generation of engine stop due to the supply of the rich air-fuel mixture to the engine at a stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses a sudden increase in the amount of fuel supplied to an engine when the attitude of the engine changes due to accumulation of fuel in an adiabatic pipe or an intake pipe during idling operation of an internal combustion engine. In particular, the present invention relates to a film-type vaporizer which is particularly effective for a four-stroke engine.

[0002]

2. Description of the Related Art Engines for portable working machines such as power saws and brush cutters are required to be small, light, high-output, and capable of operating in all postures. For this reason, generally, an air-cooled two-stroke engine equipped with a film-type vaporizer is mounted, but in recent years, a four-stroke engine has also been mounted for measures against exhaust gas. During operation of the engine, the ambient temperature becomes extremely high, so the heat insulation between the carburetor and the engine's intake port (intake port) is better than that of metal to suppress the evaporation of fuel inside the carburetor. The heat insulating pipe (insulator) made of synthetic resin is connected.

[0003] In a conventional membrane carburetor, the fuel is not sufficiently atomized or vaporized at the time of cold start or idle operation of the engine. Therefore, the fuel sucked into the intake passage of the carburetor is insulated in a liquid state. May accumulate inside the tube. If a large amount of fuel accumulated inside the heat insulating pipe is suddenly supplied to the engine due to a change in the posture of the portable work machine, the air-fuel mixture becomes suddenly rich and the engine may stop.

[0004] In a membrane type vaporizer of an engine disclosed in Japanese Patent Application No. 8-357202 filed by the applicant of the present invention, unvaporized fuel is provided on the heat insulating pipe side or the vaporizer side of the connecting portion between the heat insulating pipe and the vaporizer. Is provided. However, even when the above-described membrane carburetor is attached to a four-stroke engine, the fuel that has accumulated on the upstream side of the porous member of the intake passage is suddenly supplied to the engine due to a change in attitude during idle operation of the engine. The engine may stop.

As shown in FIG. 3, in the conventional rotary throttle valve type carburetor, the amount of air-fuel mixture is small because the opening of the throttle valve 47 is small during idling operation of the engine. The flow of the air-fuel mixture in the intake passage 63a of the heat-insulating pipe 63 is fast, and particularly, the air-fuel mixture stagnates at the outlet of the intake passage 16 in the closed portion 16b opposite to the open portion 16a of the throttle valve 47 as shown by a number of points. Tends to occur. Intake path 1
If the air-fuel mixture stays in the closed portion 16b of the throttle valve 47 at the outlet of the fuel cell 6, the fuel may become liquid and adhere to the road wall. In a four-stroke engine, the air-fuel mixture is directly supplied to the combustion chamber via the intake passages 16 and 63a, so that the change in the concentration of the air-fuel mixture in the intake passages 16 and 63a greatly affects the combustion in the combustion chamber. But easy to stop.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to prevent fuel from accumulating in a heat insulating pipe or an intake pipe of a four-stroke engine, and to tilt the engine during idling operation of the engine. An object of the present invention is to provide a film-type carburetor which does not sometimes stop the engine.

[0007]

In order to solve the above-mentioned problems, the configuration of the present invention is such that an intake pipe of a carburetor is provided on an inner peripheral wall of a heat insulating pipe connecting to an intake port of the engine, and is directed toward the engine. A plurality of axial grooves that gradually become deeper are provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an axial groove is provided on an inner peripheral wall of an intake passage so that even if fuel of an air-fuel mixture adheres to the inner peripheral wall of the intake passage, the mixture is caused to flow by the intake air flow and collect in the axial groove. Thus, it is possible to prevent a large amount of fuel from being suddenly supplied to the engine due to a change in the attitude of the engine. By arranging a plurality of axial grooves on the inner peripheral wall of the intake passage at equal intervals in the circumferential direction, fuel that has not been vaporized in any posture of the engine is accumulated in the axial grooves.
The depth of the axial groove is configured to gradually increase as approaching the engine, thereby securing the fuel holding capacity. The fuel flowing into the axial groove is gradually flown toward the engine by the intake air flow, and is supplied to the engine sequentially from the end of the axial groove.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a main body 15 of a film-type carburetor is connected to an intake port (not shown) of an engine via a heat insulating pipe 63 and a gasket 62. The illustrated carburetor is of a known rotary throttle valve type, in which a cylindrical portion 57 orthogonal to the intake passage 16 is formed in the main body 15, and a throttle valve 47 having a throttle hole 47b in the cylindrical portion 57 is rotatable. It is inserted so as to be able to move up and down. A throttle valve lever 51 is coupled to a shaft portion 47a of a throttle valve 47 projecting upward from a lid plate 53 that closes the cylindrical portion 57, and a cam surface 51a of the throttle valve lever 51 and the lid plate 53 are connected.
And a follower 52 constitute a cam mechanism. When the throttle valve 47 is rotated in the acceleration direction by the throttle valve lever 51 against the force of the spring 54, the opening degree at which the throttle hole 47b communicates with the intake passage 16 increases, and the throttle hole 47b moves from the throttle valve 47 to the throttle hole 47b. Needle valve 55 protruding and fitted into fuel nozzle 56
Rises from the injection hole 56a of the fuel nozzle 56,
The opening of “a” increases. The stationary fuel nozzle 56 is attached to the body 15
And is connected to the constant-pressure fuel chamber 25 of the fuel metering mechanism A via the jet 59 and the check valve 66.

A fuel pump 11 and a fuel metering mechanism A are provided below the carburetor body 15. That is, the fuel pump 1
1 couples the intermediate body 49 to the lower end of the main body 15 with the membrane 10 interposed therebetween, and forms the pulsating pressure chamber 8 containing the spring 8a above the membrane 10;
A pump chamber 9 is defined below the membrane 10. The fuel pump 11 introduces the pulsating intake pressure in the intake passage 63a into the pulsating pressure chamber 8 via the passage 61 in the four-stroke engine, and introduces the pulsating pressure in the crank chamber into the pulsating pressure chamber 8 in the two-stroke engine. The fuel in the fuel tank 37 is sucked into the pump chamber 9 via the passage 38, the inlet 13, the check valve 12, and the passage 12a, and
2a, discharge to the passage 7a through the check valve 7.

The fuel metering mechanism A has a membrane 2
The cover 30a is combined with the fuel cell 9 interposed therebetween to partition the constant-pressure fuel chamber 25 and the atmosphere chamber 30. Lever 2 inside constant pressure fuel chamber 25
8 is rotatably supported by a shaft 27. One end of the lever 28 is engaged with the inflow valve 2, and the inflow valve 2 is configured to abut on the valve seat at the end of the passage 7 a under the force of the spring 24. The other end of the lever 28 is in contact with the membrane 29,
When the force of the atmospheric pressure acting on the lower surface of the spring becomes larger than the force of the spring 24, the lever 28 rotates clockwise to open the inflow valve 2, and the fuel is supplied from the passage 7a to the constant pressure fuel chamber 25,
Thus, the constant-pressure fuel chamber 25 holds a predetermined amount of fuel at a predetermined pressure. The fuel in the constant pressure fuel chamber 25 is supplied to the intake passage 16 through the check valve 66, the jet 59, the injection hole 56a, and the throttle hole 47b.

The above-mentioned film-type vaporizer is disclosed in, for example,
No. 20551, the fuel sent to the constant-pressure fuel chamber 25 by the fuel pump 11 in any attitude of the engine (for example, in the state of being rolled over) is injected into the injection hole 56a of the fuel nozzle 56 by the suction negative pressure of the engine. To the intake path 16.

As shown in FIG. 2, according to the present invention, in order to prevent fuel from accumulating in the heat insulating pipe 63 or the inside of the intake pipe during idling operation of the engine, the inner circumferential wall of the heat insulating pipe 63 has a circumferential direction or the like. A plurality (four in the illustrated embodiment) of axial grooves 65 are provided at the intervals, which are progressively deeper as they approach the engine. The intake path 63a of the heat insulating pipe 63 has an inner diameter substantially equal to that of the intake path 16 of the carburetor, and expands in a wrapper shape at the terminal end 64 to be connected to the intake port 4 of the engine 3. In the embodiment shown, a plurality of through bolts 60 fasten the end flange of the carburetor, the gasket 62 and the heat insulating tube 63 to the engine wall.

Next, the operation of the film type vaporizer according to the present invention will be described. During idling operation of the engine, the throttle valve 47 is in the state shown in FIG. 2, and the intake air sucked into the intake passage 16 is:
When passing through the throttle hole 47b of the throttle valve 47, the fuel nozzle 5
The fuel is sucked from the injection hole 56a of the suction passage 6 and flows from the throttle hole 47b to the open portion 16a of the outlet of the intake passage 16, and further the heat insulating pipe 6
Flow through 3 to the engine.

During the idle operation of the engine, the flow of the air-fuel mixture is slow, so that the air-fuel mixture stagnates in the closed portion 16b of the outlet of the intake path 16, which is a so-called dead space, and fuel having a specific gravity greater than that of the intake air tends to accumulate. Fuel adhering to the inner peripheral wall of the intake passage 16 flows toward the engine through the heat insulating pipe 63 as the attitude of the engine changes. At this time, the fuel is supplied to the intake passage 63a of the heat insulating pipe 63.
Flows into the inside of the axial groove 65 which gradually becomes deeper, and is not suddenly sucked into the engine.
Is gradually sucked into the engine from the end 64 of the engine, so that the engine does not stop. Since the four axial grooves 65 are arranged at equal intervals in the circumferential direction, the same applies to the attitude of the engine in all directions.

As described above, during idling operation of the engine, fuel accumulated in the closed portion 16b of the outlet of the intake passage 16 flows out at once with the vibration and attitude change of the engine, and a rich mixture is supplied to the engine. Problems such as a stop of the engine are eliminated.

Although the present invention has been described based on the rotary throttle valve type film vaporizer, the present invention is not limited to this, and the same effects can be obtained with a butterfly valve vaporizer and a piston valve vaporizer.

[0018]

As described above, the present invention provides a plurality of axial grooves which gradually become deeper toward the engine in the inner peripheral wall of the heat insulating pipe connecting the intake path of the carburetor to the intake port of the engine. Even if fuel accumulates on the inner peripheral wall of the intake passage during idling operation of the engine, fuel eventually flows into the axial groove and is retained by capillary action, so even if the attitude of the engine changes, It does not occur that a large amount of fuel accumulated in the axial groove is suddenly supplied to the engine and the engine stops.

Since the heat-insulating pipe is made of synthetic resin, the axial groove can be easily formed in the heat-insulating pipe only by changing a part of the mold, and an increase in manufacturing cost can be suppressed.

In the present invention, since the intake path of the carburetor and the intake path of the heat insulating pipe have the same diameter and are continuous, the flow of the air-fuel mixture when the throttle valve is fully opened is not so affected, and the output of the engine is reduced. I will not do it.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a film type vaporizer according to the present invention.

FIG. 2 is an enlarged plan sectional view showing a main part of the film type vaporizer.

FIG. 3 is an enlarged plan sectional view showing a main part of a conventional film-type vaporizer.

[Explanation of symbols]

A: Fuel metering mechanism 2: Inflow valve 3: Engine 4: Inlet 5: Gasket 7: Check valve 7a: Passage 8: Pulsating pressure chamber 8a: Spring 9: Pump chamber 10: Membrane 11: Fuel pump 12: Check Valve 12a: Passage 13: Inlet
15: vaporizer main body 15a: end 15b: end 16: intake path 16a:
Open part 16b: Closed part 24: Spring 25: Constant pressure fuel chamber 27: Shaft 28: Lever 29: Membrane 30: Atmospheric chamber 30a: Cover 37: Fuel tank 38: Passage 47:
Throttle valve 47a: Shaft portion 47b: Throttle hole 49: Intermediate body 51: Throttle valve lever 51a: Cam surface 52: Follower 53: Cover plate 54: Spring 55: Needle valve 56: Fuel nozzle 56a: Injection hole 57: Cylindrical portion 58 : Hole 59: Diet 60: Bolt 61: Passage 61 a: End 62: Gasket 63:
Insulated pipe 63a: Intake path 64: End 65: Axial groove 66: Check valve

Claims (3)

[Claims] A plurality of axial grooves are provided on an inner peripheral wall of a heat insulating pipe connecting an intake path of a carburetor to an intake port of an engine, the axial grooves gradually becoming deeper toward the engine. Membrane vaporizer. 2. The film-type vaporizer according to claim 1, wherein the axial grooves are four grooves arranged at equal intervals in a circumferential direction of the heat insulating pipe. 3. The film-type vaporizer according to claim 1, wherein the intake path of the heat insulating pipe has an inner diameter substantially equal to that of the intake path of the carburetor, and expands in a wrapper shape at the end to connect to the intake port of the engine. vessel. A film type vaporizer characterized by the above-mentioned.