JP2001027154A - Carburetor for general purpose engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure air and liquid tightness at a mating face between a metallic body and a columnar part of a carburetor improved in high temperature restarting performance wherein a constant fuel chamber is provided at a lower part of the metallic body comprising a horizontal intake passage and the columnar part having a fuel reservoir in a fuel passage formed is made of synthetic resin and suspended in the constant fuel chamber. SOLUTION: This carburetor has a flange 12 integrally formed with a columnar part 11 at an upper end thereof and an outer side peripheral part of the flange 12 is put between a body 1 and a fuel vessel 15 while a lower end of the columnar part 11 is contacted to a bottom wall 15b of the fuel vessel 15, and the body 1 is connected with the fuel vessel 15 on an outside of the flange 12 by a screw 18. A mating face 19 can be thereby in close-adhered condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor used for supplying fuel to a general-purpose engine, and more particularly, to a fuel or bleed air passage which is excellent in high-temperature startability, is easily and easily formed, and has no fear of leakage. And a vaporizer for a general-purpose engine.

[0002]

2. Description of the Related Art In recent engines, the air-fuel mixture is diluted to comply with emission regulations, and as a result, the combustion temperature is higher than before. In addition, since the engine that has been widely adopted for noise reduction is surrounded by a soundproof wall, it is difficult to dissipate heat, so that when the engine is stopped, the high temperature state will continue for a long time. Inevitable.

[0003] On the other hand, the body of the carburetor is a die-cast product of metal, generally aluminum, and is connected to the intake manifold. Therefore, the entire body is easily brought to a high temperature state by the high combustion temperature of the engine. In this case, the high temperature state continues for a long time even after the engine is stopped.
For this reason, when the engine is stopped, the fuel in the fuel reservoir in the main fuel passage evaporates.In particular, in a device provided with a means for closing the entrance of the fuel passage when the engine is stopped to prevent dieseling, the fuel passage is provided in the fuel passage. The restart will be started in the absence of any. In addition, when the restart is performed in a high temperature state, even if the fuel is introduced into the fuel reservoir, the fuel evaporates immediately, which makes the high temperature restart difficult.

As a countermeasure, it has been customary to insert a heat insulating gasket between the fuselage and the intake manifold. However, the heat insulating gasket is effective for blocking heat conducted from the engine to the fuselage through the intake manifold to the engine. However, in a soundproof engine, high-temperature radiant heat cannot be prevented from directly acting on the fuselage, and the difficulty of restarting at a high temperature cannot be solved.

As another countermeasure, in a carburetor for a general-purpose engine, a body provided with an intake passage and a passage required for fuel supply and a fuel container forming a constant fuel chamber are made of a material having lower thermal conductivity than metal. It is known that it is made of a certain synthetic resin (see JP-B-49-39710).

Apart from the above-mentioned heat countermeasures, many of the passages for fuel and bleed air provided inside the body made of metal or synthetic resin are bent in the middle. Such a passage is formed by drilling from multiple directions, and their end faces must be individually closed with a closing member such as a ball plug, and the number of processing steps is large, the number of parts is large, There is a problem that the fear of leakage of fuel or bleed air cannot be completely eliminated.

[0007] In addition, metal hulls are fairly complex in shape and are often interspersed with cavities, which short-circuit due to the cavities when the drilled passages are close together. Sometimes. In particular, carburetors for general-purpose engines are small, and a fuel container is attached below the fuselage having a horizontal intake passage, which is often used in this type of carburetor, and a central portion of the fuel container is formed in a columnar portion hanging down from the fuselage. In the structure having the fuel passage, since the passages are extremely close to each other in the columnar portion, there are many chances of short-circuiting due to a cavity, which causes a reduction in product yield. The body made of synthetic resin has no cavities, so there is no danger of short-circuiting even if the passages are formed very close to each other.However, the mechanical strength is inferior, so there is no deformation or breakage when connecting to the intake manifold In addition to the need for reinforcing means, it is difficult to stably mount and hold a metal throttle valve, jet, or the like, which is a functional component.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a carburetor for a general-purpose engine, in particular, it is difficult to perform a high-temperature restart due to the fact that a fuselage made of metal is difficult. The point that the body made of synthetic resin is inferior in mechanical strength to avoid
Further, in addition to the above, it has been made to make the processing of the passage for the fuel and the bleed air troublesome and to avoid the problem of remaining short circuit and leakage.

[0009]

A fuel container forming a constant fuel chamber is mounted below a body having a lateral intake passage, and a columnar portion extending below the body is inserted into the inside of the fuel container. In order to avoid the above-mentioned problems, a carburetor for a general-purpose engine, in which a fuel passage for feeding fuel in a constant fuel chamber to an intake passage extends from a columnar portion to a fuselage, the present invention relates to a fuselage. The main body is made of metal and the columnar part is made of synthetic resin, and the fuel reservoir of the fuel passage is formed in the synthetic resin part.

As described above, a fuel reservoir is formed inside a columnar portion made of a synthetic resin, which is a material having a lower thermal conductivity than metal, and this columnar portion is inserted into a fuel container to lower the fuel. Due to the immersion of the part, the high-temperature heat after the engine is stopped is difficult to be transmitted to the fuel pool, and therefore, the fuel evaporation is introduced at the restart even if the evaporation of the fuel is small or large. Evaporation of fuel is suppressed, and high-temperature restart can be easily and reliably performed.

Further, since the body connected to the intake manifold is made of metal, it has a sufficient mechanical strength, does not deform, and can stably mount a functional part such as a throttle valve.

In the present invention, as described above, first, a flange is integrally provided at the upper end of the columnar portion, the outer peripheral edge of the flange is sandwiched between the body and the fuel container, and the lower end of the columnar portion is provided. Contact the bottom wall of the fuel container,
By connecting the body and the fuel container by screws on the outside of the flange, the lower surface of the body and the columnar portion and the upper surface of the flange were overlapped with each other in a state of being in close contact with each other.

As described above, the outer peripheral portion of the flange and the columnar portion located at the center thereof are indirectly subjected to the tightening force of the screw via the fuel container and are pressed against the body, whereby the screw is used. There is no need to worry about deformation and breakage due to direct compression stress, and the entire lower surface of the fuselage is superimposed with an even load. Don't worry.

Secondly, in the first embodiment, a seal piece is provided so as to surround the outer peripheral portion of the mating surface and each of the fuel passages passing through the mating surface.

The sealing piece can further improve the air-tightness and liquid-tightness of the mating surface itself and the fuel passage.

Further, thirdly, a part of the low-speed fuel passage in the fuel passage of the first fuel supply passage, or fourthly, a fuel supply passage for feeding fuel to the constant fuel chamber in addition to the third fuel passage. A part was formed in the mating surface, and the mating surface, the mating surface penetration of the main fuel passage and the groove passage were each surrounded by a sealing piece.

As described above, a groove is formed by using the mating surface of the body, the columnar portion, and the flange, and the groove is formed as a part of the passage through which the fuel flows, thereby greatly reducing the number of drilling operations from multiple directions. In addition, since the columnar portions where the fuel passages are close to each other are made of synthetic resin and surrounded by a sealing piece, there is no need to worry about short-circuiting and leakage, and reliability should be ensured. Can be.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described. A body 1, which is a die-cast product of metal, generally aluminum, has a lateral intake passage 2 penetrating front and rear. The choke valve 3, the venturi 4, and the throttle valve 5 are arranged in this intake passage 2 in order from the inlet to the outlet.
Is provided. The valve shafts 3a, 5a of the choke valve 3 and the throttle valve 5 are fitted and supported in bearing holes formed in the body 1, and the choke valve levers 6, 6,
The opening and closing of the choke valve 3 and the throttle valve 5 by the throttle valve lever 7 is the same as in a normal carburetor. Further, a lower surface 8 formed of a circular flat surface whose diameter is the passage length of the intake passage 2 is formed on the body 1.

The columnar portion 11 integrally has a disk-shaped flange 12 slightly smaller in diameter than the lower surface 8 at the upper end, and these are molded products of a hard synthetic resin. The columnar portion 11 and the upper surface 13 of the flange 12 are formed in a circular plane.

The fuel container 15 is bowl-shaped and has a mounting flange 16 having an outer diameter equal to that of the lower surface 8 at the upper end.
A step portion 17 having a height substantially equal to the thickness of the flange 12 and slightly larger than the thickness of the flange 12 is formed on the inner peripheral surface of the upper end transitioning from 5 a to the mounting flange 16. It is a molded product.

Then, the lower end of the columnar portion 11 is
5 and the upper surface 1 and the lower surface 1 in a state where the outer peripheral edge of the flange 12 is fitted to the step portion 17 while being in contact with the center of the bottom wall 15b.
3 and the mounting flange 16 is overlapped with the portion of the lower surface 8 exposed to the outside of the flange 12,
Screw 1 from the mounting flange 16 to the fuselage 1
The fuel container 15 is connected to the fuselage 1 by screwing 8.

The lower surface 8 and the upper surface 13 are in close contact with each other to form a mating surface 19, and the mating surface 19 is pushed by the screw 18 so that the peripheral portion of the flange 12 is pushed by the step 17, and at the same time, a columnar portion at the center is formed. 11 is pressed by the bottom wall 15b, so that an almost uniform contact state is achieved over the entire surface. Further, the flange 12 can be indirectly received without directly receiving the tightening force of the screw 18 and can escape inside the stepped portion 17, so that not only there is no fear of deformation and breakage, but also high and low temperatures are repeated. No deformation occurs because there is no strong stress acting part.
No. 9 ensures the overall adhesion.

The interior of the fuel container 15 forms a constant fuel chamber 20, into which a columnar portion 11 is inserted. The fixed fuel chamber 20 is provided with a float 22 supported by a pin 21 in a cantilever manner, and a fuel valve 23 attached to the float 22 is fitted into a valve seat 24 fixed to the flange 12.

Fuel supplied from a fuel tank (not shown) via a fuel pump is formed by opening downwardly to a joint pipe 26a protruding to one side of the body 1, a hole passage 26b of the body 1 and the lower surface 8. The fuel supply passage 26, which is formed by the groove passage 26c and the hole passage 26d of the flange 12, forms a valve seat 24.
And is supplied to the constant fuel chamber 20 according to the opening / closing operation of the fuel valve 23 which moves up and down in accordance with a change in the oil level of the constant fuel chamber 20. As a result, a constant amount of fuel is held in the constant fuel chamber 20 in the same manner as a normal float type carburetor.

An electromagnetically driven fuel cutoff valve 28 is mounted at the center of the bottom wall 15b of the fuel container 15, and its valve body 29 projects into a valve chamber 30 formed at the lower end of the columnar portion 11 to protrude into the fuel passage. The inlet end of the main jet 32 provided at the inlet of the engine 33 is closed when the engine is stopped, and is opened during operation of the engine, and the fuel that has entered the valve chamber 30 from the constant fuel chamber 20 is measured by the main jet 32 and sent to the fuel passage 33. To enter.

The fuel passage 33 extends upward from the main jet 32 and extends through the columnar portion 11 and the body 1 to reach the narrowest portion of the venturi 4.
2 and a low-speed fuel passage 42 that branches off from the main fuel passage 34 and reaches a slow port chamber 45 that opens a slow port 46 to the side of the throttle valve 5.

The main fuel passage 34 has an emulsion pipe 36 inserted into a vertically extending mounting hole 35 provided continuously with the columnar portion 11 and the body 1, and is integrally formed at an upper portion thereof with a portion of the mounting hole 35 of the body 1. And a main nozzle 37 fitted in a pressure contact state with the outlet end of the main jet 32 at the lower end of the emulsion tube 36 and fixing it to the bottom of the mounting hole 35.

A main bleed air passage 40 having an air jet 39 at the inlet end is connected to the mounting hole 35 at the upstream end face of the air intake passage 2 of the body 1 so that the air entering the mounting hole 35 is The fuel is mixed with the fuel contained in the emulsion pipe 33 and sent out from the main nozzle 37 to the intake passage 2. The main bleed air passage 40 includes a hole passage 40 a in the front-rear direction of the body 1, a hole passage 40 b in the vertical direction, and a groove passage 40 c formed in the lower surface 8, and the groove passage 40 c communicates with the mounting hole 35.

The low-speed fuel passage 42 is a lateral passage 42a extending laterally from the bottom of the mounting hole 35, which is the outlet end of the main jet 32, and a hole passage extending upward inside the columnar portion 11 in parallel with the mounting hole 35. 42b, a groove passage 42c formed in the lower surface 8, a hole passage 42d extending upward on the side of the intake passage 2 of the body 1, and a hole passage 42e extending in the front-rear direction of the body 1. The hole passage 42d is fitted with the low-speed jet 43. The hole passage 42e communicates with the slow port chamber 45.

A part of the fuel that has entered the emulsion pipe 36 from the main jet 32 immediately flows into the low-speed fuel passage 42 from the bottom of the mounting hole 35, is measured by the low-speed jet 43, and is sent out from the slow port 46 to the intake passage 2. You. Hole passage 4
On the extension of 2e opposite to the slow port chamber 45, an air jet 48 at the inlet end is provided on the upstream end surface of the intake passage 2 of the body 1.
A low-speed bleed air passage 49 having an opening is provided, and bleed air mixes with the fuel measured by the low-speed jet 43.

According to this embodiment, the main fuel passage 34
The fuel reservoirs 38 and 44 formed by the portion of the emulsion pipe 36, the lateral passage 42a of the low-speed fuel passage 42, and the lower half of the hole passage 42b are columnar portions 1 made of synthetic resin.
1, and the lower half of the columnar portion 11 is immersed in the fuel in the constant fuel chamber 20, so that when the engine is stopped, even if the engine itself and its surroundings are at a high temperature, the columnar portion 11 evaporates. Are kept in small quantities. Also body 1
Therefore, even if a large amount of fuel is evaporated by the heat received by the main nozzle pipe 37 and the emulsion pipe 36, the evaporation of the fuel introduced at the time of restarting is suppressed to a very small amount, and high-temperature restarting can be easily and reliably performed. Can be.

The body 1 connected to the intake manifold
Since it is made of metal, it has a sufficient mechanical strength and can stably mount the choke valve 3, the throttle valve 5, and the main nozzle 37. On the other hand, the columnar portion 11 made of a synthetic resin having poor mechanical strength is sandwiched between the lower surface 8 of the body 1 and the bottom wall 15b of the fuel container 15, and the main nozzle 37 fixed to the body 1 By using the emulsion tube 36 as a reinforcing member, the emulsion tube 36 is maintained in a predetermined shape without deformation. This also allows the main jet 32 inside the columnar portion 11 to be stably attached.

Further, since the mounting hole 35 and the hole passage 42b which are arranged close to each other inside the columnar portion 11 are formed in a synthetic resin molded product in which bubbles corresponding to the cavities are not scattered. There is no need to worry about short-circuiting and impairing each function.

On the other hand, according to this embodiment, the hole passage 26b of the fuel supply passage 26 is formed by drilling from the side surface and the lower surface 8 of the body 1, and the hole passage 26d is formed by, for example, a return pin of a molding die for the columnar portion 11. Each of them can be formed by utilizing. Also. Main fuel passage 34
The mounting hole 35 and the hole passage 42b of the low-speed fuel passage 42 can be formed by providing pins in a mold of the body 1 or a molding die of the columnar portion 11, and by drilling if necessary. Further, the hole passages 40a and 40b of the main bleed air passage 40 are drilled from the front surface and the lower surface 8 of the body 1, and the hole passage 42d of the low-speed fuel passage 42 is drilled from the lower surface 8 by the hole passage 42e.
The low-speed bleed air passage 49 can be formed by drilling from the front surface of the body 1.

Since the groove passages 26c, 40c and 42c can be formed by providing projections on the mold of the body 1, the end face of the lateral passage 42a of the low-speed fuel passage 42 formed by drilling is closed. All the passages 26, 34, 40,
42 and 49 can be reduced in number of processing steps and without fear of leakage.

Since the volume of the groove passage 42c of the low-speed fuel passage 42 is extremely small, even if the fuel in this portion evaporates when the engine is stopped, it is replenished immediately upon restart and does not hinder high-temperature restart.

Further, as described above, the mating surface 19 is brought into substantially uniform contact with the front surface.
5 and the groove passages 26c, 40c, 42c are gas- and liquid-tight, but the present invention is provided with a sealing member 51 to make this more reliable. In the illustrated embodiment, in addition to the above, in order to also improve the airtightness of the open end faces of the choke valve shaft 3a and the throttle valve shaft 5a to the lower surface 8, the seal members 51 are respectively surrounded and surrounded outside. A seal piece formed so as to surround almost the entire mating surface 19 is connected to each other to form an integrated O-ring, and is attached to the lower surface 8 and is attached to the lower surface 8 of the columnar portion 11 made of synthetic resin and the upper surface of the flange 12. 13 was further improved.

That is, the sealing member 51 is
And a substantially oval sealing portion 51b surrounding the groove passage 26c, and a substantially oval sealing portion surrounding the mounting hole 35 and the groove passage 40c. Piece 51c, a substantially elliptical seal piece 51d surrounding the groove passage 42c, and a circular seal piece 51 surrounding the open end faces of the choke valve shaft 3a and the throttle valve shaft 5a, respectively.
e, 51f are connected to each other to form an integral product,
It is fitted directly into a groove that matches the shape of the seal member 51 provided on the lower surface 8. Thus, each seal piece 51
When a ... 51f is integrated, there is an advantage that not only the handling is easy and the mounting to the lower surface 8 can be performed at once, but also that the connecting portion helps to further improve the gas-liquid tightness.

The groove passages 26c, 40c and 42c may be formed on the columnar portion 11 and the upper surface 13 of the flange 12, or may be formed by providing shallow grooves on both the lower surface 8 and the upper surface 13 so as to face each other. The fuel supply passage 26 may directly communicate the hole passages 26b and 26d without providing the groove passage 26c depending on the layout. Further, there is a case where the main bleed air passage 40 is formed obliquely straight in the body 1 and connected to the mounting hole 35 without passing through the groove passage 40c. Further, the lower end of the columnar portion 11 may be in contact with the valve body of the fuel cutoff valve 28 so as to be indirectly in contact with the bottom wall 15b of the fuel container 15.

[0040]

As described above, the body having the intake passage is made of metal, and the columnar portion where the fuel reservoir is formed is made of synthetic resin. The property can be good. In addition, since the flange integrated with the columnar portion and the columnar portion itself are sandwiched between the body and the fuel container and are not directly subjected to the tightening force of the screws connecting them, the columnar portion, which is inferior in strength, and the flange are deformed or damaged. And the entire surface of the mating surface of the body and the columnar portion and the flange is brought into close contact with each other to prevent leakage of fuel and bleed air. Further, the passage for fuel and bleed air can be formed with a small number of processing steps by using the mating surface, and by providing a sealing member on the mating surface, the passage structure is excellent in air / liquid tightness and has no fear of leakage. be able to.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a partial sectional view taken along the line BB of FIG. 1;

FIG. 4 is a partial sectional view taken along the line CC of FIG. 1;

FIG. 5 is a cross-sectional view of FIG.

FIG. 6 is a bottom view of the body in the embodiment of FIG. 1;

[Explanation of symbols]

1 body, 2 intake passage, 8 bottom surface, 11 columnar part,
12 Flange, 13 upper surface, 15 fuel container, 18 screw, 19 mating surface, 20 constant fuel chamber, 26 fuel supply passage, 26c, 40c, 42c groove passage, 28 fuel cutoff valve, 33 fuel passage, 34 main fuel passage, 38 , 44 fuel reservoir, 40 main bleed air passage, 42 low speed fuel passage, 51 seal member,

Claims (5)

[Claims] 1. A fuel container forming a constant fuel chamber is attached below a body having a lateral intake passage, and a columnar portion extending downward from the body is inserted into the fuel container. In a general-purpose engine carburetor in which a fuel passage that sends fuel from the constant fuel chamber to the intake passage is formed from the columnar portion to the body, the body and the columnar portion are separate bodies, and the body is The columnar portion, which is made of metal and in which the fuel reservoir of the fuel passage is present, is made of synthetic resin and has a flange integrally at an upper end, and an outer peripheral portion of the flange is formed between the body and the fuel container. The body and the fuel container are screwed on the outside of the flange while being sandwiched therebetween and the lower end of the columnar portion is in contact with the bottom wall of the fuel container. Carburetor for general-purpose engines, characterized in that, the upper surface of the columnar portion and the flange and the lower surface of the body are superposed on the entire surface close contact with each other. 2. The carburetor for a general-purpose engine according to claim 1, wherein a seal piece is provided around an outer peripheral portion of a mating surface between the body and the columnar portion and the flange, and the mating surface is provided. A seal piece surrounding a fuel passage passing therethrough. 3. The carburetor for a general-purpose engine according to claim 1, wherein a part of the low-speed fuel passage in the fuel passage is formed by a groove passage provided on a mating surface between the body, the columnar portion, and the flange. And a seal piece surrounding the outer peripheral portion of the mating surface, and a seal piece surrounding the mating surface penetrating portion of the main fuel passage and the groove passage, respectively. A carburetor for a general-purpose engine. 4. The carburetor for a general-purpose engine according to claim 1, wherein a part of a fuel supply passage for sending fuel to the constant fuel chamber and a part of a low-speed fuel passage in the fuel passage are connected to the body and the body. Each is formed by a groove passage provided on a mating surface with the columnar portion and the flange, and a sealing piece is provided around an outer peripheral portion of the mating surface,
A carburetor for a general-purpose engine, characterized in that a seal piece is provided so as to surround the joint portion of the main fuel passage and the two groove passages. 5. The carburetor for a general-purpose engine according to claim 2, wherein the plurality of seal pieces forming the respective enclosures are connected to each other to form an integral product.