JPH10288096A - 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 operation stop of an engine when the engine is inclined by the idling operation thereof by providing a ring member having a diameter smaller than that of a heat insulating pipe in the downstream of a throttle valve in an intake passage of a film type carburetor. SOLUTION: When a throttle valve 47 is turned to the accelerating direction, open degree of the 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 nozzle 56, and the predetermined quantity of the fuel is sucked. In a film type carburetor having such a structure, a ring member 26 having a diameter smaller than that of the heat insulating pipe 63 and made of a metal having a large heat conductivity is arranged in an outlet of an intake passage 16 so as to prevent the generation of stay of the fuel inside of the heat insulating pipe 63 or the intake pipe due to the idling operation of an engine. With this structure, flow of the air-fuel mixture is speeded up at the time of idling operation of the engine, and the generation of malfunction that the rich air-fuel mixture is flowed out at a stroke with vibration of the engine and a change of posture of the engine so as to stop the engine operation is eliminated.

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, an air-cooled two-stroke engine equipped with a film-type vaporizer is generally employed, but in recent years, a four-stroke engine has also been used for exhaust gas control. During operation of the engine, the ambient temperature becomes extremely high.To suppress evaporation of fuel inside the carburetor, a synthetic resin made of synthetic resin, which has better heat insulation properties than metal, is installed between the carburetor and the intake port of the engine. Is connected to the heat insulation pipe (insulator).

[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, a porous member is provided on a heat insulating pipe side or a vaporizer side of a connecting portion between the heat insulating pipe and the vaporizer. Is provided. However, especially when the above-described membrane carburetor is mounted on a four-stroke engine, fuel may stagnate upstream of the porous member of the intake passage due to a change in attitude during idle operation of the engine, and the engine may stop. There is.

As shown in FIG. 3, in the conventional rotary throttle valve type carburetor, the opening degree of the throttle valve 47 during idling operation of the engine is small, the flow of the air-fuel mixture is small, and the intake path 16 or 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 No. 6, the fuel may become liquid and adhere.
In the four-stroke engine, the air-fuel mixture is directly supplied from the intake passage to the combustion chamber, so that the change in the concentration of the air-fuel mixture in the intake passage has a large effect on combustion in the combustion chamber, and the engine is easily stopped.

[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]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the structure of the present invention comprises a heat insulating member for connecting the carburetor to the intake port of the engine at a portion of the intake passage of the carburetor downstream of the throttle valve. A ring member having an inner diameter smaller than that of the pipe is provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a metal ring member having an inner diameter smaller than that of an adiabatic pipe (intake pipe) is fitted to a portion of an intake passage of a carburetor downstream of the throttle valve (engine side). As a result, the dead space at the outlet of the intake passage at the closed portion opposite to the open portion of the throttle valve is narrowed, and stagnation of the air-fuel mixture is suppressed during idle operation of the engine. In other words, the inner diameter of the outlet portion of the intake passage is made narrower than that of the conventional one by the ring member to provide a step in the intake passage, thereby increasing the flow of intake air and suppressing fuel from adhering to the wall surface.

Also, the flow of the intake air is disturbed by the step between the outlet of the intake passage of the carburetor and the ring member, and it is difficult for fuel to accumulate even at the opening of the throttle valve at the outlet of the intake passage.

[0010]

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 valve shaft 47a projecting upward from the throttle valve 47
And a cam mechanism 51 is constituted by the cam surface 51a of the throttle valve lever 57 and the follower 52 of the cover plate 53. When the throttle valve 47 is rotated in the acceleration direction by the throttle valve lever 57 against the force of the spring 54, the throttle hole 47b
Of the throttle valve 4 communicates with the intake passage 16 and the throttle valve 4
The needle valve 55 projecting from the nozzle 7 into the throttle hole 47b and inserted into the fuel nozzle 56 rises from the injection hole 56a of the fuel nozzle 56, and the opening of the injection hole 56a increases. The stationary fuel nozzle 56 is fitted and supported in a hole 58 at the bottom of the main body 15 and communicates with the constant pressure fuel chamber 25 of the fuel metering mechanism A via a jet 59 and a 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 12 is defined below the membrane 10. In the four-stroke engine, the fuel pump 11 introduces the pulsating negative pressure of the intake passage 63a through the passage 61 in the four-stroke engine, and introduces the pulsating pressure in the crank chamber in the two-stroke engine to transfer the fuel in the fuel tank 37 into the passage 38 and the inlet. 13, sucks into the pump chamber 9 through the check valve 12 and the passage 12a, and discharges into the passage 7a through the passage 12a and 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 can contact the membrane 29,
When the atmospheric pressure acting on the lower surface of the membrane 29 becomes greater than the force of the spring 24, the lever 28 rotates clockwise to open the inflow valve 2, and 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 check valve 66,
The air is supplied to the intake passage 16 through 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 adiabatic pipe 63 or the intake pipe during the idling operation of the engine, the distance between the intake port of the engine and the carburetor is reduced. A ring member 26 made of a metal having high thermal conductivity, such as aluminum, having a smaller inside diameter than the heat insulating pipe 63 having an intake path 63a connected to the air inlet is provided at the outlet of the intake path 16 of the carburetor. For this reason, a large-diameter cylindrical portion 26a is formed at the outlet end of the intake path 16 of the main body 15, and the large-diameter cylindrical portion 26a
The ring member 26 is fitted to the heat insulating tube 63 and is sandwiched between the heat insulating tube 63 via the gasket 62. 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.
The inner diameter of the heat insulating pipe 63 is the same as the inner diameter of the intake path 16 of the carburetor, and the ring member 26 is provided with an intake path smaller than the inner diameter of the intake path 16 of the carburetor. In other words, a part of the ring member 26 is disposed so as to protrude into the intake path 16.

Next, the operation of the membrane 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 sixth nozzle, flows from the throttle hole 47b to the open portion 16a of the outlet of the intake passage 16, and further flows to the engine via the ring member 26 and the heat insulating pipe 63.

During the idling 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. In the present invention, since the ring member 26 that narrows the passage area is provided at the outlet of the intake passage 16, the closed portion 16b of the outlet of the intake passage 16 that becomes a dead space also becomes narrow, and the flow of the air-fuel mixture becomes faster accordingly, and the fuel Pool is suppressed. Accordingly, 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 as the engine vibrates or changes its attitude, and a rich mixture is supplied to the engine. This eliminates such a problem that the engine stops.

As described above, the present invention relates to the intake passage 1 of the carburetor.
6, the ring member 26 having an inner diameter smaller than the heat insulating pipe 63 for connecting the carburetor to the intake port of the engine is provided at a portion downstream of the throttle valve 47, so that the outlet of the intake passage 16 of the carburetor and the heat insulating pipe 63, the dead space of the closed portion 16b of the throttle valve 47 at the outlet of the intake passage 16 is narrowed,
During idling of the engine, fuel is less likely to accumulate in the closed portion 16b of the throttle valve 47 at the outlet of the intake passage 16.

More specifically, since the inner diameter of the outlet of the intake passage 16 of the carburetor is narrowed by the ring member 26 as compared with the conventional one, the flow of intake air becomes faster, and the fuel flows into the intake passage 16.
Difficult to adhere to wall surfaces. Also, even if fuel adheres to the wall,
Since the inner diameter of the ring member 26 is smaller than the heat insulating pipe 63,
The fuel is blown off at a step 26b from the intake passage 16, and does not flow in a liquid state on the wall surface of the intake passage 16. what if,
Even if the inner diameter of the heat insulating pipe 63 is reduced, fuel does not accumulate at the outlet of the intake passage 16 during idling operation of the engine, but the output is reduced by operation of the engine when the throttle valve 47 is fully opened.

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 effect can be obtained with a butterfly valve type vaporizer and a piston valve type vaporizer.

[0020]

As described above, according to the present invention, since a step is provided by the ring member at the outlet of the intake passage of the carburetor, the closed portion of the throttle valve at the outlet of the intake passage of the carburetor during idling operation of the engine. Fuel is less likely to accumulate in the dead space.

Since the inner diameter of the outlet of the intake passage of the carburetor is made smaller than that of the conventional one by the ring member, the flow of the intake air becomes faster and the fuel is less likely to adhere to the wall surface. Even if the fuel adheres to the wall surface, the inner diameter of the outlet of the intake passage of the carburetor is smaller than that of the heat-insulating pipe, so that the fuel is blown off at the step of the intake passage, and does not flow in a liquid form on the wall of the intake passage. .

In the present invention, since the inside diameter of a part of the intake passage of the carburetor, not the entire length, but a part thereof, that is, the part near the fuel nozzle at the outlet of the intake passage is made small, the air-fuel mixture when the throttle valve is fully opened is set. The flow of the engine is not significantly affected, and the output of the engine is not reduced. In other words, at a portion near the fuel nozzle at the outlet of the intake passage of the carburetor, the fuel sucked from the fuel nozzle is not yet completely vaporized, so that the intake fluid is more concentrated than when the fuel is completely vaporized. The resistance (suction resistance) is small, and the output of the engine is unlikely to decrease. Since the ring member is made of a metal having higher thermal conductivity than the conventional porous material, the ring member is cooled by the heat of vaporization of the fuel during operation of the engine when the throttle valve is fully opened, and the vaporizer body is also cooled. . Therefore, the overheated state of the carburetor body is avoided, and the fuel inside the carburetor is heated by the heat of the engine to become a fuel vapor, and the flow of the fuel becomes poor or the mixture becomes too thin. Institutions do not malfunction.

[Brief description of the drawings]

FIG. 1 is a side 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 Signs] A: Fuel metering mechanism 2: Inflow valve 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 15a: End 15: Vaporizer body 15
b: End 16: Intake path 16a: Open part 16b: Closed part 24: Spring 25: Constant pressure fuel chamber 26: Ring member 26a: Large diameter cylindrical part 26b: Step 27: Shaft 2
8: lever 29: membrane 30: atmosphere chamber 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: lid plate 54: spring 55: needle valve 56: fuel nozzle 56a: injection hole 57: cylindrical portion 58: hole 59: jet 60: bolt 61: passage 61a : End 62: Gasket 63:
Insulated pipe 66: check valve

Claims (2)

[Claims] 1. A membrane characterized in that a ring member having an inner diameter smaller than an adiabatic pipe for connecting a carburetor to an intake port of an engine is provided at a downstream side of a throttle valve in an intake path of a carburetor. Type vaporizer. 2. The film type vaporizer according to claim 1, wherein said ring member is made of a metal having high thermal conductivity.