Diaphragm-type carburetor

Gas and liquid contact apparatus – Fluid distribution – Pumping

Reexamination Certificate

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Details

C261S035000, C261S069200, C261SDIG006, C261SDIG008

Reexamination Certificate

active

06202988

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diaphragm-type carburetor, and in particular, to an improvement in a diaphragm-type carburetor including a constant-pressure fuel chamber having an outlet bore communicating with a lower end of a fuel nozzle through a fuel jet and a check valve, a fuel pump incorporated in a fuel passage which communicates between an inlet bore in the constant-pressure fuel chamber and a fuel tank for providing fuel for the constant-pressure fuel chamber in response to a pulsation pressure in a pulsation pressure generating source, and a fuel introduction control valve for controlling the introduction of the fuel into the constant-pressure fuel chamber by opening or closing the inlet bore in the constant-pressure fuel chamber. The fuel introduction control valve is provided with a cylindrical valve seat member mounted on an upper wall of the constant-pressure fuel chamber and having the inlet bore in its upper end, and a valve member lifted and lowered within the valve seat member to open and close the inlet bore.
2. Description of the Related Art
A diaphragm-type carburetor is already known, as disclosed, for example, in Japanese Patent Application Laid-Open No. 1-151758.
In such a carburetor, fuel delivered to a constant-pressure fuel chamber by operation of a fuel pump is often subjected to pressure pulsation received from the fuel pump, heat or vibration received from an engine or the like to produce fuel vapor. The fuel vapor introduced into the constant-pressure fuel chamber is ejected from a fuel nozzle along with the fuel, because the constant-pressure fuel chamber has no air vent (to enable the operating attitude of the engine in all directions). In the prior art, however, the fuel vapor may stagnate in the constant-pressure chamber depending on the operational attitude of the engine. When the operational attitude of the engine is changed, a large amount of stagnating fuel vapor may be ejected at one time from the fuel nozzle to extremely reduce the fuel-air ratio of the fuel-air mixture, thereby causing misoperation of the engine.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a diaphragm-type carburetor of the above-described type, wherein when the fuel vapor is introduced into the constant-pressure fuel chamber, the fuel vapor immediately moves towards the fuel nozzle without stagnating in the constant-pressure fuel chamber, whereby the extreme reduction in fuel-air ratio of the fuel-air mixture caused by the fuel vapor can be avoided.
To achieve the above object, according to the present invention, there is provided a diaphragm-type carburetor comprising a constant-pressure fuel chamber having an outlet bore communicating with a lower end of a fuel nozzle through a fuel jet and a check valve. A fuel pump is incorporated in a fuel passage for permitting communication between an inlet in the constant-pressure chamber and a fuel tank for providing fuel to the constant-pressure fuel chamber in response to a pulsation pressure in a pulsation pressure generating source. A fuel introduction control valve controls the introduction of the fuel into the constant-pressure fuel chamber by opening and closing an inlet bore in the constant-pressure fuel chamber. The fuel introduction control valve is provided with a cylindrical valve seat member mounted on an upper wall of the constant-pressure fuel chamber and has the inlet bore at an upper end thereof. A valve member is raised and lowered within the valve seat member for opening and closing the inlet bore, wherein a fuel well is defined between the outlet bore in the constant-pressure fuel chamber and the check valve, and the lower end of the valve seat member is in communication with the fuel well through a bypass passage extending above the constant-pressure fuel chamber.
With the above feature, when the valve member of the fuel introduction control valve opens the inlet bore of the valve seat member, the fuel delivered from the fuel pump is introduced into the constant-pressure fuel chamber through the valve seat member. In this case, if fuel vapor is contained in the fuel, the fuel vapor rises up in the bypass passage connected to the lower end of the valve seat member to enter the fuel well, as soon as it passes through the valve seat member. Thus, the fuel vapor can be ejected promptly from the fuel nozzle along with the other fuel. Therefore, the amount of the fuel vapor ejected from the fuel nozzle is very small and hardly varies the fuel-air ratio of the fuel-air mixture, and hence, the normal operation of the engine can be ensured.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 3765657 (1973-10-01), Du Bois
patent: 3825237 (1974-07-01), Aoyama et al.
patent: 4003968 (1977-01-01), Rickert
patent: 4271093 (1981-06-01), Kobayashi
patent: 5441673 (1995-08-01), Gerhardy
patent: 5599484 (1997-02-01), Tobinai
patent: 5676887 (1997-10-01), Soeda et al.
patent: 5681508 (1997-10-01), Gerhardy
patent: 1-151758 (1989-06-01), None

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