Carburetor for two-stroke internal combustion engine

Abstract

A carburetor for a two-stroke internal combustion engine whereby airtightness is maintained and intake of uncombusted fuel into an air path is prevented. The carburetor includes a circular cylindrical valve hole and a rotary valve fitted into the valve hole such that it can rotate and is disposed perpendicularly across a fuel intake path and an air intake path which are formed substantially parallel with respect to each other, and a fuel supply-side bore which controls the flow rate along the fuel intake path and the air supply-side bore which controls the air capacity along the air path pass through part of the cylindrical portion perpendicularly to the axial direction of the rotary valve, and annular recesses formed in part of a circumferential wall of an outer circumference of the rotary valve so as not to correspond to at least the fuel supply-side bore and the air supply-side bore.

Claims

1. A carburetor for a two-stroke internal combustion engine comprising a circular cylindrical valve hole formed substantially in the middle of a carburetor unit and a rotary valve which is fitted into the valve hole such that a circular cylindrical portion thereof can rotate, wherein the rotary valve is disposed so as to perpendicularly cross a fuel intake path and an air intake path which are formed substantially parallel with respect to each other in the carburetor, and a fuel supply-side bore which controls the flow rate along the fuel intake path and the air supply-side bore which controls the air capacity along the air path pass through part of the cylindrical portion substantially perpendicularly to the axial direction of the rotary valve, wherein an annular recess is formed in part of a circumferential wall of an outer circumference of the cylindrical portion of the rotary valve so as not to correspond to the fuel supply-side bore and the air supply-side bore.

2. The carburetor for a two-stroke internal combustion engine as claimed in claim 1, wherein the annular recess is provided between the fuel supply-side bore and the air supply-side bore formed in the rotary valve.

3. The carburetor for a two-stroke internal combustion engine as claimed in claim 1, wherein the annular recess is provided to at least part of a top end or a base end of the rotary valve.

4. A carburetor for a two-stroke internal combustion engine comprising a circular cylindrical valve hole formed substantially in the middle of a carburetor unit and a rotary valve which is fitted into the valve hole such that a circular cylindrical portion thereof can rotate, wherein the rotary valve is disposed so as to perpendicularly cross a fuel intake path and an air intake path which are formed substantially parallel with respect to each other in the carburetor, and a fuel supply-side bore which controls the flow rate along the fuel intake path and the air supply-side bore which controls the air capacity along the air path pass through part of the cylindrical portion substantially perpendicularly to the axial direction of the rotary valve, wherein an annular recess is formed in part of a circumferential wall of an inner circumference of the valve hole so as not to correspond to the fuel supply-side bore and the air supply-side bore.

5. The carburetor for a two-stroke internal combustion engine as claimed in claim 4, wherein the annular recess is provided between the fuel supply-side bore and the air supply-side bore formed in the circumferential wall of the inner circumference of the valve hole.

6. The carburetor for a two-stroke internal combustion engine as claimed in claim 4, wherein the annular recess is provided to at least part of a top end or a base end of the circumferential wall of the inner circumference of the valve hole.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an oblique view of a rotary valve according to the present invention.

(2) FIG. 2-1 is a frontal view of a rotary valve according to the present invention.

(3) FIG. 2-2 is a partial cross-sectional frontal view of a rotary valve according to the present invention.

(4) FIG. 3 is another embodiment of a rotary valve according to the present invention.

(5) FIG. 4 is an embodiment wherein an annular recess is provided to a valve-hole side of the rotary valve.

(6) FIG. 5 is a total cross-sectional view of a carburetor for a typical stratified scavenging two-stroke internal combustion engine.

(7) FIG. 6 is an oblique view of a conventional rotary valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) A detailed description of a preferable mode for carrying out the present invention is given below.

(9) FIG. 5 is a partial cross-sectional view of a carburetor for a typical two-stroke internal combustion engine. A carburetor unit 1 is such that a rotary valve 5 is rotatably fitted into a valve hole 4 substantially in the center, and an air path 2 and a fuel intake path 3 are disposed vertically parallel to one another and perpendicular the axis of the rotary valve 5.

(10) When the rotary valve 5 rotates around a throttle shaft 9 (FIG. 6), the aperture area of an air supply-side bore 6 and a fuel supply-side bore 7 is changed, which adjusts the amount of air and fuel flowing through the air path 2 and the fuel intake path 3, the state of the two-stroke internal combustion engine thereby being adjusted to match the driving mode.

(11) As shown in FIG. 1, the rotary valve 5 according to the present invention is a circular cylindrical valve inserted rotatably into the valve hole 4 and having the same diameter as it, provided with the throttle shaft 9 axially attached to a top end of the cylindrical portion 11. In the cylindrical portion 11, the air supply-side bore 6 which communicates with the air path 2 and the fuel supply-side bore 7 which communicates with the fuel intake path 3 are disposed vertically parallel to one another in a tunnel-like formation vertically with respect to the axial direction of the throttle shaft 9.

(12) An annular recess 8 is formed on an outer wall of the cylindrical portion 11 between the fuel supply-side bore 7 and the air supply-side bore 6.

(13) As shown in FIGS. 2-1 and 2-2, the rotary valve 5 is formed substantially in the middle of the carburetor unit 1 and a needle 10 for adjusting the fuel supply is formed inside the throttle shaft 9 of the rotary valve 5.

(14) As another embodiment shown in FIG. 3, the annular recess 8 is provided in two places, to the top and bottom of the rotary valve 5. If it is formed at least on the top end or the base end of the rotary valve 5, this would be effective for preventing intake of fuel into the air supply-side bore 6 from the gap between the carburetor unit 1 and the rotary valve 5, which would make it possible to achieve appropriate adjustment, taking into account the size and location of the carburetor incorporating the rotary valve according to the present invention.

(15) By providing the annular recess 8 to part of the outer circumference of the rotary valve of the two-stroke internal combustion engine, which is the present embodiment, even if fuel remaining in the fuel intake path is drawn up along the outer wall of the rotary valve from the gap between the rotary valve and the valve hole by the negative pressure in the engine, the presence of the annular recess 8 can prevent the fuel from entering the air path.

(16) Moreover, by constituting the recess so as to be ring-shaped, the fuel can be thoroughly prevented from entering the air path, no matter where in the outer wall of the rotary valve 5 it leaks from.

(17) FIG. 4 is an embodiment in which an annular recess 12, indicated by the dotted line, is provided to part of an inner circumferential wall of the valve hole 4 into which the rotary valve 5 is fitted. In other words, the groove is not provided to the rotary valve 5, but rather to the inner circumferential wall of the valve hole 4.

(18) In the present embodiment, the annual recess 12 is provided to the inner circumferential wall of the valve hole 4 at a position corresponding to the annular recess 8 on rotary valve shown in FIG. 1 or FIG. 3, which provides the same effect as providing the annular recess to the rotary valve.

(19) Note that if the groove is provided to at least the top, bottom, or middle of the valve hole 4, this has the same effect in terms of preventing intake of fuel into the air supply-side bore 6 from between the carburetor unit 1 and the rotary valve 5, and therefore the valve hole 4 of carburetor for a two-stroke internal combustion engine according to the present embodiment is provided with the annular recess 12 to one part of its inner circumference, which means that even if fuel which remains in the fuel intake path is drawn up along the outer wall of the rotary valve from between the rotary valve and the valve hole by the negative pressure in the engine, the present of the annular recess 12 can prevent entry of fuel into the air path.

(20) By forming the recess in an annular shape, entry of fuel into the air path can be prevented thoroughly no matter where on the outer wall of the rotary valve 5 the fuel leaks from.

(21) Thus, as discussed above, the present invention has as an object to prevent inflow of part of the fuel from between the rotary valve 5 and the carburetor 1 in a two-stroke internal combustion engine into an air supply-side bore 6, and can therefore thoroughly prevent intake of fuel without a concomitant increase in the number of members, such as a sealing member, or other parts.

(22) All features, elements, components, functions, and steps described with respect to any embodiment provided herein are intended to be freely combinable and substitutable with those from any other embodiment. If a certain feature, element, component, function, or step is described with respect to only one embodiment, then it should be understood that that feature, element, component, function, or step can be used with every other embodiment described herein unless explicitly stated otherwise. This paragraph therefore serves as antecedent basis and written support for the introduction of claims, at any time, that combine features, elements, components, functions, and steps from different embodiments, or that substitute features, elements, components, functions, and steps from one embodiment with those of another, even if the following description does not explicitly state, in a particular instance, that such combinations or substitutions are possible. Express recitation of every possible combination and substitution is overly burdensome, especially given that the permissibility of each and every such combination and substitution will be readily recognized by those of ordinary skill in the art upon reading this description.

(23) In many instances entities are described herein as being coupled to other entities. It should be understood that the terms coupled and connected (or any of their forms) are used interchangeably herein and, in both cases, are generic to the direct coupling of two entities (without any non-negligible (e.g., parasitic) intervening entities) and the indirect coupling of two entities (with one or more non-negligible intervening entities). Where entities are shown as being directly coupled together, or described as coupled together without description of any intervening entity, it should be understood that those entities can be indirectly coupled together as well unless the context clearly dictates otherwise.

(24) While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that these embodiments are not to be limited to the particular form disclosed, but to the contrary, these embodiments are to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, any features, functions, steps, or elements of the embodiments may be recited in or added to the claims, as well as negative limitations that define the inventive scope of the claims by features, functions, steps, or elements that are not within that scope.

KEY

(25) 1 Carburetor

(26) 2 Air path

(27) 3 fuel intake path

(28) 4 Valve hole

(29) 5 Rotary valve

(30) 6 Air supplyside bore

(31) 7 fuel supplyside bore

(32) 8 Annular recess

(33) 9 Throttle shaft

(34) 10 Needle

(35) 11 Cylindrical part

(36) 12 Annular recess