Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to carburetors for internal
combustion engines and more particularly to improvements in a
carburetor of a type provided with a butterfly-shaped throttle valve.
The present invention will be illustrated by way
the accompanying drawings in which:
Fig. 1 is a vertical sectional view showing a basic
structure of a conventional carburetor provided with a butterfly-
shaped throttle valve;
Fig. 2 is a vertical sectional view showing a carburetor
embodying the present invention;
Fig. 3 is a right side view of Fig. 2 as partly sectioned;
Fig. 4 is an elevational view of a nozzle tube;
Fig. 5 is a top view of a main nozzle assembly; and,
Fig. 6 is a vertical sectional view showing another
carburetor embodying the present invention.
Fig. 1 shows a basic structure of a carburetor of a type
provided with a known butterfly-shaped throttle valve used mostly
for internal combustion engines for general purposes. In the drawing
reference numeral 1 indicates a carburetor body, 2 indicates a
venturi portion, 3 indicates a butterfly-shaped throttle valve, 4
indicates a main nozzle, 5 indicates a main jet, 6 indicates a main
air jet, 7 indicates a pilot jet, 8 indicates a pilot air jet, 9
indicates a low speed fuel passage, 10 indicates an idling screw,
11 indicates a float, 12 indicates a cover case for defining a
float chamber, 13 indicates a screw for attaching the cover case 12
to the carburetor body 1 and lA indicates a boss portion hanging
into the float chamber. As this kind of carburetor is arranged as
described above, for example, in case the main jet 5 is to be
removed from the boss portion lA so as to be replaced, first the
cover case 12 will have to be removed from the carburetor body 1.
As a result, when the carburetor is attached to an engine, a very
difficult work will be forced. Further, as the boss portion lA
occupies a comparatively large volume part within the float chamber,
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effective volume of the float chamber will reduce and therefore
the float chamber will have to be comparatively large as a whole.
As the float 11 must also be made to be in such form as will not
contact the boss portion lA, there has been a disadvantage that the
structure is limited. The same problem as in the case of the main
jet S will occur also in the case of replacing the pilot jet 7.
The present invention eliminates the above described
defects in a carburetor of the above mentioned type.
According to the present invention, this is attained by
suspending a main nozzle assembly including a main jet and main
air jet into a float chamber across a venturi portion from the
upper portion of a carburetor body and setting a pilot jet in the
upper portion of the carburetor body.
The present invention also provides a carburetor wherein
such parts as a main nozzle~ main jet and pilot jet are so arranged
as to be able to be easily attached to and removed from a carburetor
body.
The present invention further provides a small carburetor
of a simplified structure.
The present invention again provides a carburetor which
can be manufactured at a low cost.
According to the present invention there is provided a car-
buretor provided with a butterfly-shaped throttle valve, comprising a
carburetor body including therein at least a suction bore having a
horizontally extending venturi portion and through holes extending
vertically across said suction bore and opening in said venturi
portion; a float chamber defined below said body; a main nozzle
assembly capable of being inserted into said through holes from
above said body and including therein a main air jet, at least a
nozzle opening in said suction bore and a main jet capable of being
positioned in said float chamber; and a cover plate secured removably
to the top portion of said body to cover the upper portion of
said main nozzle assembly.
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" ~.
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Referring once more to the accompanying drawings, the
same corresponding reference numerals are attached to the same
parts and portions as in Fig. 1.
First, with reference to Fig. 2, reference numeral 14
indicates a main nozzle assembly including a tubular jet holder
15 air-tightly fitted within a through hole la extending vertically
to a boss portion lA and a nozzle tube 16 inserted air-tightly
through a hole lb made in the upper portion of a carburetor body 1
coaxially with the through hole la and screwed at the lower end to
the upper end of the jet holder 15 within the through hole la. The
air-tightness between the through hole la and jet holder 15 is
secured by an O-ring 17 interposed between a step portion formed
within the through hole la and a flange portion formed in the jet
holder 15. The air-tightness between the hole lb and nozzle tube
16 secured by an O-ring 18 interposed between a step
c ~
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portion formed in the hole lb and a flange portion formed in
the nozzle tube 16. A main jet 19 is screwed to the lower
end of the jet holder 15. The inlet of the main jet 19
communicates with the interior of a float chamber lB through
S a hole lA' made in the side wall of the boss portion lA. A
bleeding pipe 20 is inserted into the nozzle tube 16,
extends in the lower end portion to the upper end portion of
the jet holder 15 and is connected at the upper end to a
main air jet 21 screwed in from the upper open end of the
nozzle tube 16. A vertically extended slot-shaped nozzle
16a (Fig. 4) is formed in the middle portion exposed within
a suction bore lC of the nozzle tube 16 and is directed
toward the downstream side of the suction bore lC, that is,
toward the throttle valve 3. In this case, a plurality of
nozzles 16a may be provided. The head portion of the nozzle
tube 16 is positioned within the large diameter portion of
the hole lb and an annular air chamher lD communicating with
the suction bore lC is formed b~tween the outer peripheral
surface of this head portion and the inner wall surface of
the large diameter portion of the hole lb. A diametrally
extending groove 16b (Fig. 5) is formed on the top surface of
the nozzle tube 16, ~he inlet o~ the main air jet 21
communicates with the a~r chamber lD through the groove 16b.
Further, a flat cut portion 16c (Fig. 5) is provided in the
flange portion of the nozzle tube 16. Onl~ when this cut
portion 16c meets a corresponding flat cllt portion lb'
(Fig. 5) formed on the inner wall of the hole lb, the main
nozzle assembly 14 will be abl~ to occupy a correct position
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~in which the nozzle 16a is directed toward the throttle
valve 3) shown in Fig. 2. The nozzle 16a is directed toward
the throttle valve 3, that is, toward the intake manifold
side in order to make the outflow of the fuel easy and to
prevent the fuel from jetting out to make a too rich
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mixture in the case of spitting back. However, it is nccdlco-
.,,
to say that the direction of the nozzle 16a can be properly
changed depending on the kind of the engine. The main nozzle
assembly 14 is pressed down on the top surface by a cover
plate 23 secured to the carburetor body 1 through a gasket 22
so that the air-tightness between the jet holder 15 and through
hole la and between the nozzle tube 16 and hole lb may be
secured.
A bottomed cylindrical jet block 24 fitted air-tightly
within a hole lc is provided in the upper portion of the
carburetor body 1 adjacent to the air chamber lD. A hole
24a communicating with a passage ld the flow volume of the
fuel passing through which can be adjusted by an idling screw
10 and another hole 24b are made in the peripheral wall of
the jet block 24. Holes 24c communicating with the suction
bore lC are made in the bottom wall of the jet block 24.
The upper opening of this jet block 24 is closed by the cover
plate 23 through the gasket 22. Particularly with reference
to Fig. 3, a fuel passage le opened at one end in the
float chamber lB and connected at the other end to the hole
24b of the jet block 24 is provided within the carburetor
body 1. In the course of this fuel passage le, there are
provided a pilot jet 25 screwed from above into the carburetor
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body 1 and a pilot air jet 26 also screwed from above into the
carburetor body 1. The pilot air jet 26 communicates with
a chamber lE closed by the cover plate 23 through the gasket
22 and communicating with the air chamber lD. ~eference
numeral 27 indicates a bolt screwed to the lower end of
the boss portion lA to liquid-tightly attach the cover case 12
to the carburetor body 1.
As evident from the above description, the main nozzle
assembly 14 forms a main fuel system and the fuel passage
le, pilot jet 25, pilot air jet 26 and jet block 24 form
a low speed fuel system.
Another carburetor embodying the present invention is
shown Fig. 6. In this embodiment, the main nozzle assembly 14
is further simplified. That is to say, the nozzle tube and
jet holder are formed integrally with each other and the
main air jet 21 and main jet 19 are screwed respectively in
the upper portion and lower portion. Further, the main nozzle
assembly 14 is attached to the carburetor body 1 by screwing
as illustrated and no boss portion lA is present It is
needless to say that, in this case, the bleeding pipe may be
inserted into the main nozzle assembly 14 in the same manner
as ir. the embodiment shown in Fig. 2. Further, in this embodi-
ment, the pilot jet 25 is below th~ pilot air jet 26 and these
are arranged concentrically with each other.
As the carburetor according to the present invention is
formed as described above, when the component parts of the
main nozzle assembly 14 must be replaced, the object of
replacing them will be able to be attained simply by only
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removing the cover plate ~3. In the same manner, also in the
case of attachin~ the main nozzle assembly 14 to the carburetor
body l, the necessary work will be able to be completed by
only inserting the main nozzle assembly 14 pre-assembled in
advance into the holes la and lb and securing the cover plate
23 to the carburetor body l. Thus, the above mentioned work
can be made very simple while the carburetor body is attached
to the engine. This advantage ~ill be developed also in the
case of replacing the pilot jet 25 and pilot air jet 26.
As the boss portion lA projecting into the float chamber lB can
be made to be of a shape smaller and simpler than of the
conventional one, the reduction of the effective volume of the
float chamber lB will be able to be reduced and the freedom of
the selection of the structure and attaching position of the
float ll will become larger. As a result, the size of the
entire float chamber will be able to be made smaller and it
will be possible to make the size of the entire carburetor
smaller. Further, if the cover case 12 is to be attached to the
lower end of the boss port1on lA with the bolt 27 from outside
as in the embodiment shown in Fig. 2, the cover case will be
able to be made by pressing a plate without being cast such
as being diecast and therefore the cost of the manufacture
of the entire carburetor will be able to be reduced.
A proper amount of a mixture obtained from a fuel sucked
2~ in through the main jet l9 and air sucked in through the
main air jet will be jetted out through the nozzle 16a
depending on the opened degree of the throttle valve 3.
However, the operation of the carburetor according to
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the present invention is the same as of the conventional
carburetor this kind and therefore shall not be explained in
detail.
By the way, it is needless to say that, in Fig. 2, the
main nozzle assembly 16 can be secured to the carburetor
body 1 by being screwed into the through holes la and/or lb
in the same manner as in the embodiment in Fig. 6. In such
case, it will be preferable to use at least a gasket instead
of the O-ring 18.
