JPS6146306Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a carburetor for a two-stroke engine equipped with a reed valve in the intake pipe.

Conventionally, the outlet side passage of a carburetor in a two-stroke engine equipped with a reed valve has been formed in a circular shape throughout since the passage in the throttle valve part is formed in a circular shape to promote fuel atomization. . However, since the connection part of the reed valve is formed in a rectangular or approximately elliptical shape for structural reasons, when connecting the two, usually one end is connected to the open end of carburetor A, as shown in Figure 1. This is done through a joint C which has a matching circular shape and the other end is shaped into a rectangular or approximately elliptical shape that matches the connecting portion of the reed valve B.

However, in this case, the length of the joint is required to be as short as possible due to space constraints, so the cross-sectional shape of the passage in the joint generally changes rapidly, increasing the flow resistance at the joint, and reducing the air-fuel mixture. This interfered with the suction into the engine and caused a decrease in engine output.

In addition, in recent years, as shown in Utility Model Publication No. 50-15052, a guide piece that is inserted into the open end of the reed valve and corresponds to the valve seat is provided protruding from the tip of the joint, and the inner surface of the guide piece is gradually moved from a circular shape toward the tip. A rectangular joint has also been proposed, but in this type of joint, the cross-sectional shape of the passage is changed by a guide piece in the narrow space between the opening end of the reed valve and the valve seat, so the cross-sectional shape of the passage is changed. Changes will be rapid,
Furthermore, the presence of the guide piece reduces the cross-sectional area of the passage and increases the flow resistance of the air-fuel mixture.

This idea was made in view of the above points, and the shape of the passage from the throttle valve position in the middle of the outlet side passage of the carburetor to the reed valve connection opening end is adjusted so that the tip matches the inner shape of the inlet side opening end of the reed valve. The cross-sectional shape of the passageway is gradually expanded outward to minimize changes in the cross-sectional shape of the passage, thereby smoothing the flow of the air-fuel mixture from the carburetor to the reed valve, and reducing the distance between the carburetor and the reed valve. The purpose of the present invention is to provide a carburetor for a two-stroke engine that can be made shorter and more compact than conventional carburetors.

Hereinafter, an embodiment of this invention will be described based on FIGS. 2 and 3.

Reference numeral 1 denotes a carburetor main body, which has an inlet side passage 3 and an outlet side passage 4 sandwiching a throttle valve (not shown) mounting portion at a substantially central portion 2 of the carburetor body. This outlet side passage 4 is composed of a passage part 4' that is integral with the main body 1 and a carburetor holder 5. The passage part 4' that is integral with the body 1 is circular at the throttle valve mounting part, but While gradually expanding outward toward the tip, it is deformed to correspond to the shape of the opening end of the reed valve B, and is formed into a substantially elliptical shape. A passage 6 is formed in the carburetor holder so that the opening end shape of the passage portion 4' of the main body 1 and the opening end shape of the reed valve B match each other. 1 and reed valve B are connected. Further, an annular projection 7 is provided on the inner periphery of the holder 5 on the passage entrance side, and an annular groove 8 that can be engaged with the projection 7 is provided.
is formed on the outer periphery of the opening end of the passage portion of the main body 1, and the holder 5 is coupled to the main body 1 by engagement of both 7 and 8.

Furthermore, a flange 9 is provided at the opening end of the holder 5 on the passage outlet side, and a flange 9 is provided at the opening end of the reed valve B.
It is butt-joined to B' and connected to the engine with a stopper (not shown).

In this way, a passage whose cross-sectional shape changes from circular to approximately oval in the throttle valve portion of the carburetor A is formed, and is connected to the reed valve B.

As explained above, in this carburetor, the shape of the passage from the throttle valve position in the middle of the outlet side passage to the reed valve connection opening end is gradually expanded outward from the circular part of the throttle valve part toward the tip. Because it matches the inner shape of the reed valve's inlet opening end, the structure is simpler and the passage cross-sectional area is simpler than conventional reed valves that change the cross-sectional shape of the passage by inserting a guide piece into the opening end. It is more compact than conventional models because it allows the air-fuel mixture to flow smoothly without abruptly changing the flow rate or reducing the cross section of the passage, and it also allows the distance between the carburetor and reed valve to be easily shortened. This allows the air cleaner to be enlarged to compensate for the reduced space, resulting in better response.
The change in cross-sectional shape of the passage from the throttle valve of the carburetor to the open end of the reed valve is more gradual than in conventional models, so the air-fuel mixture flows more smoothly, resulting in improved engine output. It is an excellent technical idea that plays a great role.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a conventional general carburetor connected to a reed valve, FIG. 2 is a schematic sectional view showing an embodiment of the carburetor of the present invention,
FIG. 3 is a sectional view taken along the line X--X in FIG. 2. 1...Carburetor body, 2...Central passage,
3... Entrance side passage, 4... Exit side passage, 4'...
Passage portion of main body 1, 5... carburetor holder,
6... Passage of carburetor holder 5, 7... Annular projection, 8... Annular groove, 9... Flange, A...
Carburetor, B...Reed valve, B'...Flange of reed valve A, C...Fitting.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The shape of the passage from the throttle valve position in the middle of the outlet side passage of the carburetor to the reed valve connection opening end is gradually expanded outward from the circular shape of the throttle valve part toward the tip; A carburetor for a two-stroke engine, characterized in that it matches the inner surface shape of the inlet side opening end of a reed valve, which is other than circular. (2) The carburetor according to claim 1, wherein the outlet side passage of the carburetor is constituted by a passage of the carburetor main body and a passage of a carburetor holder connected to the passage.