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Variable venturi carburetor

Imported: 24 Feb '17 | Published: 06 Jan '04

Jun Takano, Hitoshi Terakado, Giovanni Vimercati

USPTO - Utility Patents

Abstract

A variable venturi carburetor for a combustion engine has an uprighted cup-shaped piston head which forms an integral part of a venturi within a fuel-and-air mixing passage carried by a carburetor body, and a needle that projects rigidly downward from the head into a fuel feed passage. The position of the piston head controls air flow by adjusting the air flow cross-section of the variable venturi, and the needle simultaneously controls fuel flow into the fuel-and-air mixing passage at the venturi via obstruction of the fuel feed passage. The piston head and needle move in unison by a flexible diaphragm engaged to and disposed above the head. An atmospheric chamber is defined below the diaphragm and a vacuum chamber is defined generally above the diaphragm. A vacuum passage extends through the bottom of the head communicating between the fuel-and-air mixing passage at the venturi and the vacuum chamber. As vacuum at the venturi increases, the volume of the vacuum chamber decreases and the flexing diaphragm moves the head partially out of the fuel-and-air mixing passage until a balance of forces between the vacuum draw and the resilient compression of a spring disposed within the vacuum chamber and which biases the head into the passage is reached. During cold engine starts, cold idling, and cold acceleration, a cold engine priming device sensing the temperature of the engine and delivers additional fuel into the fuel-and-air mixing passage from a fuel chamber when the engine is below a pre-set value.

Description

DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims, and accompanying drawings in which:

FIG. 1 is a part diagrammatic and a side sectional view of a variable venturi carburetor having a cold-start fuel priming device of the present invention;

FIG. 2 is a fragmentary cross-sectional view of the variable venturi carburetor illustrating a cross section of a needle and fuel feed tube when in an open position taken along line

2

2 of FIG. 1;

FIG. 3 is a partial diagrammatic and a fragmentary sectional view of a second embodiment of the variable venturi carburetor illustrating a cold-start fuel priming device;

FIG. 4 is a part diagrammatic and a side sectional view of a third embodiment of the variable venturi carburetor; and

FIG. 5 is an enlarged section view of a fuel-and-air mixture isolation valve of the variable venturi carburetor of FIG.

4.

Claims

1. A variable venturi carburetor of a combustion engine having a body defining a fuel-and-air mixing passage communicating through the body between an inlet and an outlet, a fuel chamber carried by the body, and a throttle valve disposed within the fuel-and-air mixing passage, the variable venturi carburetor comprising:

2. The variable venturi carburetor set forth in claim 1 wherein the isolation valve is electromagnetic which opens when the engine is started.

3. The variable venturi carburetor set forth in claim 2 comprising the isolation valve having a thermo-switch, whereby the switch controls the electric power to the isolation valve thereby closing the isolation valve when an upper preset engine temperature is reached.

4. The variable venturi carburetor set forth in claim 1 wherein the isolation valve is a biased closed check valve that opens upon a preset vacuum at the outlet.

5. The variable venturi carburetor set forth in claim 1 wherein the fuel nozzle of the sub-atmospheric fuel idle passage is diametrically opposed to the bore.

6. A variable venturi carburetor for a combustion engine comprising:

7. The variable venturi carburetor set forth in claim 6 wherein the isolation valve is electromagnetic which opens when the engine is started.

8. The variable venturi carburetor set forth in claim 7 comprising the isolation valve having a thermo-switch, whereby the switch controls the electric power to the isolation valve thereby closing the isolation valve when an upper preset engine temperature is reached.

9. The variable venturi carburetor set forth in claim 6 wherein the isolation valve is a biased closed check valve that opens upon a preset vacuum at the outlet.

10. The variable venturi carburetor set forth in claim 6 comprising: