JPS60187752A - Carburetor - Google Patents

Abstract

PURPOSE:To prevent air-fuel mixture from becoming too lean by the air introduced from a low-speed fuel system when a main fuel system is operated, by providing a check valve just on the downstream side of a branch portion of the low-speed fuel system in a carburetor in which the low-speed fuel system is branched from the main fuel system. CONSTITUTION:Main fuel is supplied from a main jet 16 provided in a float chamber 14 of a carburetor 10 via a passage 20 and a nozzle 18. On the other hand, low-speed fuel is supplied from an idle port 28 and a low-speed port 26 via passages 32, 34, 36 branched from the main fuel system. A check valve 50 is provided at the branch portion 30 just on the downstream side of the low-speed fuel system. Arrangement being as above, the negative pressure at the idle port 28 and the low-speed port 26 is lowered and air tends to enter into the main fuel system from the low-speed fuel system 32 when a throttle valve 24 is opened sufficiently and fuel is supplied from the main nozzle 18. However, intrusion of air into the main fuel system is prevented by the function of the check valve 50, so that air-fuel mixture is prevented from becoming too lean.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carburetor, and particularly to a carburetor equipped with a so-called common type low-speed system in which a main system and a low-speed system are shared.

In a carburetor, a low-speed system structure in which a fuel passage between a main jet and a main nozzle branches off and low-speed fuel flows to a low-speed jet is usually called a common type.

Conventionally, in carburetors equipped with this common low-speed system,
During light load, low speed operation, there is high negative pressure in the conduit on the slow jet side of the carburetor and atmospheric pressure in the conduit on the main jet side.

So, I listened to the throttle valve further and found that 1. When fuel starts to flow from the main system, the negative pressure in the main system conduit gradually increases, the negative pressure in the low speed system decreases, and the opening of the throttle valve increases beyond a certain level. As a result, the negative pressure in the main system conduit becomes extremely high, while the negative pressure in the low speed system decreases extremely, and finally the air from the low speed generator h is not drawn into the low speed system, but flows into the main system, and the jet becomes the main air Breed Chef 1~
"hack bleed"
occurs. When this back bleed occurs in the carburetor, the air-fuel ratio becomes extremely lean, leading to a decrease in engine output and interfering with fuel control.

From the above point of view, this invention provides that the negative pressure in the low-speed system
When the drop exceeds a certain limit, the back
The main objective is to provide a vaporizer that does not cause bleed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a carburetor which has an extremely simple structure and which can extremely effectively avoid the back bleed phenomenon.

In order to understand the above objectives and other effects of this invention,
This will be explained in detail based on the attached drawing.

The carburetor 10 of the present invention is equipped with a common type system, and includes a venturi section 12, a float chamber 14 for storing fuel, a main jet 1G of the float chamber 14, and a main jet 1G of the float chamber 14. a main fuel passage 20 that guides fuel therein to a main nozzle 18 that opens into the venturi portion 12;
A main air bleed pipe 22 is provided for guiding air into a portion of the main fuel passage 20 and controlling the negative pressure acting on the main nozzle 18.

In addition, as a low-speed system, in order to guide fuel from the main jet 1G of the float chamber 14 to a bypass boat 26 and an idle boat 28 provided close to the throttle valve 24 of the carburetor 10, a main fuel A low speed fuel passage 32, 34, 36 branching from the passage 20 is provided.

Connected to the low speed fuel passage 32 is a first low speed air bleed 38 for introducing air into the passage, and a low speed jut 40 is provided in the passage 32.

Additionally, a second low velocity air bleed 42 may be disposed in the passageway 36.

Since the structure described above is common in conventional common type low-speed system carburetors, it is shown in a simplified manner in the drawings.

In the common type low-speed system carburetor having the above-described structure, as mentioned earlier, when the opening degree of the throttle valve 24 exceeds a certain level, the amount of fuel drawn into the low-speed system decreases. This is because the negative pressure from the bypass boat 26 and idle boat 28 decreases, and if this negative pressure decreases significantly, the air from the low speed air bleed 38, 42 will not be drawn into the low speed system and will be drawn into the main system. It is drawn into the main fuel passage system by the nozzle negative pressure. It induces so-called park breed.

In the carburetor 10 of the present invention, a portion of the main fuel passage 20 downstream of the branching portion 30 and upstream of the low-speed jet 40 blocks the flow of fluid from the low-speed jet 40 side to the branching portion 30 side. A check valve 50 is provided.

That is, according to the present invention, in a region where the negative pressure in the low-speed system is high, the check valve 50 is connected to the branch portion 30 of the main fuel passage 20.
As with normal carburetors of this type, without any effect on the inflow of fuel into the lower speed fuel passage 32 side,
Fuel is supplied from the main jet 16 to the low-speed fuel passages 32, 34, 36 through the branch 30 and check valve 50, but the negative pressure to the low-speed system decreases and the main nozzle negative pressure becomes strong. Reach first and second low speed air bleed 38.42
When the air from the passage 32 is about to be drawn into the main nozzle 18 through the low-speed jet 40, the check valve 50 is activated to block the passage so as to prevent the air from flowing back from the passage 32 to the branch part 30. It is a thing. The check valve 50 can be selected from any suitable type, such as a reverse umbrella valve, reed valve, or duck bill.

[Brief explanation of the drawing]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings are schematic diagrams, partially shown in cross section, for explaining the structure of the carburetor of the present invention. In the drawings, the symbols representing main parts are as follows. 10... Carburetor 12... Venturi section 14... Float chamber 16... Main jet 20... Main fuel passage 24... Throttle valve 30... Branch section 32, 34, 36...・Low speed fuel passage

Claims (1)

[Claims] The main fuel passage that supplies fuel from the float chamber to the main jet that opens in the venturi part of the carburetor, and the low-speed fuel injection port that opens in the vicinity of the throttle valve, are connected to the flow 1 to air from the air. A carburetor of a type comprising a low speed fuel passage having a low speed shet in the passage for supplying fuel, and the main fuel passage and the low speed fuel passage being branched from a common passage from the flow 1 to chambers, 1) in a region upstream of the low-speed shet on the low-speed passage side of the branching part between the main fuel passage and the low-speed fuel passage;
A carburetor, characterized in that it is provided with a check valve that prevents the flow of fluid from the low speed path (a) to the branch portion.