JPH0424132Y2 - - Google Patents

Description

[Detailed explanation of the invention] A. Purpose of the invention (1) Industrial application field This invention is based on the invention that the bleed air passage to be mixed with the fuel drawn into the intake duct of the carburetor, especially the carburetor body, is located near the float chamber. The present invention relates to a type of vaporizer formed by penetrating the vaporizer body.

(2) Prior Art Conventionally, in such a carburetor, the bleed air passage was formed through the wall of the carburetor body.

(3) Problems to be solved by the invention By the way, the carburetor body is generally cast and molded, and as the engine temperature rises, the carburetor body itself tends to heat up. Therefore, the bleed air passage in the wall of the carburetor body The passing bleed air may be heated more than necessary by the carburetor body, and in this case, especially when the fuel is heated by the carburetor body and is at a relatively high temperature, the hot bleed air may be heated to the fuel. If mixed, there was a risk that the evaporation of the fuel would be promoted and the air-fuel mixture would become excessively rich.

An object of the present invention is to provide a carburetor that can solve the above problems by utilizing the upper space of the float chamber.

B. Structure of the invention (1) Means for solving the problem In order to achieve the above object, the present invention is designed so that the passage for bleed air to be mixed with the fuel drawn into the intake passage of the carburetor body is connected to the upper air in the float chamber. The vaporizer is installed across a chamber, and a tube member that extends between both side walls of the upper air chamber and whose interior becomes a part of the passage is sealed in a pair of holes respectively opened in the both side walls. The tube member is fitted through a ring, and a gap is formed between the tube member and the upper wall surface of the upper air chamber.

(2) Effect The above pipe member is prevented from coming into direct contact with the carburetor body in the portion that crosses the upper air chamber and the portion surrounded by the seal ring, and is therefore less susceptible to the effects of heat from the carburetor body. Therefore, even if the carburetor body reaches a relatively high temperature, it is possible to suppress as much as possible the bleed air passing through the passage from being heated by the carburetor body and increasing its temperature. Even when the fuel is in a heated state, there is less risk that the fuel will rapidly evaporate due to the mixing of bleed air.

Furthermore, although the pipe member that becomes a part of the bleed air passage crosses the upper air chamber of the float chamber, a gap is formed between the pipe member and the upper wall surface of the upper air chamber, and the pipe member forms a part of the bleed air passage. Since it is possible to avoid dividing the upper space of the upper air chamber due to the member, when a bumping phenomenon of fuel occurs in the float chamber, it is possible to prevent fuel evaporation gas from spreading throughout the upper space of the upper air chamber. The air can be evenly retained, and a part of the upper space does not become an air pocket, so that rapid outflow of evaporated gas from the air vent to the intake passage is suppressed to the utmost.

(3) Embodiment An embodiment of the present invention will be explained below with reference to the drawings. First, in FIGS. 1 and 2, this carburetor is a composite type carburetor, and the main body 1
An automatic check yoke mechanism 3 including a check yoke opener 2, a throttle opener 4, a doss pot 5, a secondary throttle valve switch 6, an acceleration pump 7, and the like are attached.

Referring also to FIG. 3, the carburetor body 1 includes, in order from the bottom, a throttle body block 8,
It is constructed by stacking a mixture body block 9 and an air horn block 10 and connecting each block 8, 9, and 10 integrally. Moreover, mixture body block 9 and air horn block 10
is made of synthetic resin, and the throttle body block 8 is made of metal, such as aluminum.

A main intake passage 11 and a secondary intake passage 12 are installed in the carburetor body 1 in parallel. A mixture body block 9 forming an intermediate portion of the main intake passage 11 is provided with an outer bench lily 13, and an inner bench lily 14 is provided upstream of the outer bench lily 13. The air horn block 10 also includes the inner bench lily 14.
A throttle valve 15 located upstream of the outer bench lily 13 is eccentrically supported, and a throttle valve 16 located downstream of the outer bench lily 13 is supported eccentrically.

On the other hand, an outer bench lily 1 is attached to the mixture body block 9 that forms the middle part of the secondary intake passage 12.
7 is provided, and an inner bench lily 18 is provided upstream of the outer bench lily 17. Further, a secondary throttle valve 19 located downstream of the outer bench lily 17 is pivotally supported by the throttle body block 8.

In FIG. 4, the float chamber 21 is defined by the combination of the mixture body block 9 and the air horn block 10, and an upper air chamber 22 above the fuel oil level l in the float chamber 21. A passage 23 for bleed air to be mixed with the fuel drawn into the main intake passage 11 is provided across the main intake passage 11. A part of this passage 23 is connected to a cylindrical metal joint member 25 as a pipe member. , and the remaining portion thereof is constituted by a passage hole 24 formed in the air horn block 10.

The wall surface defining the upper air chamber 22 is formed by the mixture body block 9 and the air horn block 10. The air horn block 10 has a passage hole 24 coaxially opened at the closed end and an upper portion of the upper air chamber 22. A bottomed hole 27 that opens in the side wall surface 26 and a through hole 29 that opens at both ends between the other side wall surface 28 and the outer surface facing the side wall surface 26 are on the same axis with the upper air chamber 22 in between. to be drilled.

The joint member 25 has a bottomed hole 27 at its tip.
The joint member 25 is fitted into the through hole 29 and the bottomed hole 27 so as to come into contact with the closed end of the joint member 25 , thereby extending the joint member 25 between the both side wall surfaces 26 and 28 . Moreover, the positions of the passage 24, the bottomed hole 27, and the through hole 29 are determined so that a gap is formed between the upper wall surface 30 of the upper air chamber 22 and the joint member 25, and the upper part of the joint member 25 is The outer diameter of the portion 25a facing the air chamber 22 is made small.

O-rings 31 and 32 as seal rings are interposed between the joint member 25 and the inner circumferential surface of the bottomed hole 27 and the inner circumferential surface of the through hole 29, respectively. is press-fitted into the inner wall surface of the external opening end of the through hole 29 and fixed by welding. That is, a small diameter cylindrical portion 35 is provided on the joint member 25 outward from a portion corresponding to the intermediate portion of the through hole 29 via an outwardly facing step portion 34, and the collar 33 is connected to the air horn block 10. It is formed into a ring shape surrounding the small diameter cylindrical portion 35 using the same synthetic resin. This collar 33 comes into contact with the stepped portion 34 and joins the joint member 2.
5, the joint member 25 is press-fitted and welded to the inner wall surface of the external open end of the through hole 29, and thus the joint member 25 is clamped and fixed between the collar 33 and the closed end of the bottomed hole 27.

Referring again to FIG. 2, the joint member 25
Another joint member 36 is attached to the air horn block 10 at a position adjacent to the air horn block 10 with a structure similar to that described above, and this joint member 36 also connects to both side walls 26, It will be constructed over 28 spaces.

Next, the operation of this embodiment will be explained. The pipe member 25 that becomes a part of the bleed air passage 23
is the part of it that crosses the upper air chamber 22, and O
Direct contact with the carburetor main body 1 (that is, the air horn block 10) is avoided in the portion surrounded by the rings 31 and 32, and the structure is such that it is not easily affected by the heat of the block 10. Even if the temperature is relatively high, the bleed air passing through the passage 23 is heated by the block 10 and the temperature rise can be suppressed as much as possible, so that the fuel is heated by the carburetor main body 1. Even in such a case, there is less risk that the fuel will rapidly evaporate due to the mixing of bleed air, and this is effective in preventing over-enrichment of the air-fuel mixture.

By the way, when the carburetor main body 1 is in a relatively high temperature state immediately after the engine is started, if fresh fuel containing a large amount of volatile components flows into the float chamber 21 when the engine is restarted, the entire inside of the float chamber 21 will be in a bumping state. It is known that this phenomenon (SPEW phenomenon) occurs. At this time, if the upper air chamber 22 is small, the evaporated gas will be ejected from the air vent,
It may flow into the intake passage and cause engine malfunction.
If the volume of the upper air chamber 22 is sufficiently large, the degree of damage will be light. However, even if the volume of the upper air chamber is sufficiently large, for example, if a bleed air passage is bored in a wall that hangs down from the upper wall surface of the upper air chamber, the upper space of the upper air chamber will be reduced due to the hanging wall. The upper air chamber is divided and becomes an air pocket in a part of the upper air chamber, reducing the effective volume of the upper air chamber, which may cause engine malfunction as described above. However, according to the embodiment, since a gap is formed between the joint member 25 and the upper wall surface 30 of the upper air chamber 22, the upper space of the upper air chamber 22 is divided by the member 25. Therefore, even if the fuel bumping phenomenon occurs in the float chamber 21, the fuel evaporative gas can be evenly retained in the entire upper space of the upper air chamber 22, and the Since a part of the upper space does not become an air pocket, the rapid outflow of evaporative gas from the air vent to the intake tract can be suppressed to the utmost, and engine malfunctions caused by the sudden outflow can be avoided.

Furthermore, the shape of the portion of the air horn block 10 made of synthetic resin facing the upper air chamber 22 can be simplified, thereby simplifying the shape of the mold, and eliminating the need for passage drilling, thereby reducing costs.

C. Effects of the invention As described above, according to the invention, the carburetor is a carburetor in which the passage for the bleed air to be mixed with the fuel drawn into the intake path of the carburetor body is provided across the upper air chamber in the float chamber. Then, a tube member that extends between both side walls of the upper air chamber and whose inside becomes a part of the passage is fitted into a pair of holes formed in each side wall surface through a seal ring, and the tube member Since a gap is formed between the pipe member and the upper wall surface of the upper air chamber, the pipe member is in direct contact with the carburetor main body in the portion that crosses the upper air chamber and in the portion surrounded by the seal ring. Contact is avoided, making it less susceptible to the effects of heat from the carburetor body, and therefore, even if the carburetor body becomes relatively hot, the bleed air passing through the passage is heated more than the carburetor body and its temperature rises. Even when the fuel is heated by the carburetor body, there is less risk of the fuel evaporating rapidly due to the mixing of bleed air, which prevents the mixture from becoming over-enriched. Effective in prevention.

Furthermore, although the pipe member that becomes part of the bleed air passage crosses the upper air chamber of the float chamber, a gap is formed between the pipe member and the upper wall surface of the upper air chamber. It is possible to avoid dividing the upper space of the upper air chamber due to the pipe member, and therefore, when a bumping phenomenon of fuel occurs in the float chamber, fuel evaporation gas is distributed throughout the upper space of the upper air chamber. Since the upper space does not become an air pocket, the sudden outflow of evaporative gas from the air vent to the intake duct can be suppressed as much as possible. Engine malfunctions caused by this can be avoided.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view of the carburetor, FIG. 2 is a view taken in the direction of the arrow in FIG. 1, and FIG. 3 is an enlarged sectional view taken along the line - in FIG. Fourth
The figure is an enlarged sectional view taken along the line - in FIG. 2. 21...Float chamber, 22...Upper air chamber, 2
3...Passway, 25...Joint member as a pipe member, 26, 28...Side wall surface, 27, 29...Bottomed hole as hole, through hole, 30...Top wall surface, 3
1, 32... O-ring as a seal ring.

Claims (1)

[Scope of utility model registration request] This is a carburetor in which a bleed air passage 23 to be mixed with the fuel drawn into the intake passage 11 of the carburetor main body 1 is provided across the upper air chamber 22 in the float chamber 21. The passageway 23 extends between both side wall surfaces 26 and 28, and the inside thereof is the passage 23.
The pipe member 25 which becomes a part of the side wall surfaces 26,
The tube member 25 is fitted into a pair of holes 27 and 29 opened in the upper air chamber 28 via seal rings 31 and 32, respectively, and a gap is formed between the tube member 25 and the upper wall surface 30 of the upper air chamber 22. Characteristic vaporizer.