EVAPORATIVE EMISSION CONTROL FOR CARBURETTOR
FIELD OF THE INVENTION
[001] The present invention relates to a system of controlling evaporative emissions
from carburettor.
BACKGROUND
[002] It is well known that source of air pollution from vehicles include exhaustive
emissions as well as evaporative emissions. Apart from evaporative emissions from a
fuel tank, evaporative emissions from a carburettor of a vehicle also contribute
substantially to the atmosphere contamination. Fuel loss from the carburettor generally
occurs as a result of evaporation loss of fuel from a carburettor float chamber. Such
evaporative loss becomes significantly noticeable ~hen an engine unit of the vehicle is
hot, for example during hot weather condition or due to extended continuous running of
the engine unit. In order to control evaporative emissions, there exists a need for suitable
means to control loss ofthe evaporated fuel from the carburettor ofthe vehicle.
SUMMARY·
[003) A carburettor of a vehicle is disclosed. In an embodiment, the carburettor
~omprises a carburettor body, a float chamber, a drain pipe for discharging excess fuel in
the float chamber and a breather tube. The carburettor body comprises an air intake
passage and an air channel formed in the carburettor body. The float chamber is
configured at a bottom portion of the carburettor body. The drain pipe comprises a first
end opening and a second end opening. The first end opening of the drain pipe is
disposed in the float chamber at a position higher than a predefined normal fuel level in
the float chamber and the second end opening of the drain pipe is disposed outside of the
float chamber for discharging the excess fuel. The breather tube comprises a first end and
a second end. The first end of the breather tube is connected to the air channel and the
second end of the breather tube is connected to the drain pipe between the first end
opening and the second end opening.
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[004] In an embodiment, the second end of the breather tube is connected to the
drain pipe at a portion of the drain pipe that is outside of the float chamber. In another
embodiment, the breather tube is connected to the portion of the drain pipe outside of the
float chamber using aT-joint. In yet another embodiment, the drain pipe and the breather
tube are configured as a single body using a single mould.
[005] In an embodiment, the carburettor further comprises a piston type throttle
valve disposed in the air intake passage. The piston. type throttle valve is movable across
the air intake passage in a vertical direction substantially perpendicular thereto for
adjusting amount of air in the air intake passage. In an embodiment, the carburettor
furthermore comprises a compression coil spring for biasing the piston type throttle
valve in a direction of closing the air-intake passage.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[006] The invention itself, together with further features and attended advantages,
will become apparent from consideration of the following detailed description, taken in
conjunction with the accompanying drawings. One or more embodiments of the present
invention are now described, by way of example only wherein like reference numerals
represent like elements and in which:
[007] Figure 1 illustrates side view of two wheeled vehicle according to an
embodiment of the present invention;
[008] Figure 2 illustrates vertical sectional view of a carburettor according to an
embodiment of the present invention; and
[009] Figure 3 illustrates view of the carburettor according to an embodiment of the
present invention.
[0010] The drawings referred to in this description are not to be understood as being
drawn to scale except if specifically noted, and such drawings are only exemplary in
nature. The coloured drawings, if provided along with this description are only meant to
make the details of invention clear and have no effect on the scope of the invention.
DETAILED DESCRIPTION
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[0011] While the invention is susceptible to various modifications and alternative
forms, an embodiment thereof has been shown by way of example in the drawings and
will be described here below. It should be understood, however that it is not intended to
limit the invention to the particular forms disclosed, but on the contrary, the invention is
to cover all modifications, equivalents, and alternatives falling within the spirit and the
scope of the invention.
[0012] The terms "comprises", "comprising", or any other variations thereof, are
intended to cover a non-exclusive inclusion, such that a setup, device or method that
comprises a list of components or steps does not include only those components or steps
but may include other components or steps not expressly listed or inherent to such setup
or device or method. In other words, one or more elements in a system or apparatus
proceeded by "comprises ... a" does. not, without more constraints, preclude the existence
of other elements or additional elements in the system or apparatus.
[0013] For the better understanding of this invention, reference would now be made
to the embodiment illustrat~d in the accompanying figures and description here below,
further, in the following figures, the same reference numerals are used to identify the
same components in various views.
[0014] The terms "front I forward", "rear I rearward I backward", "up I upper I top",
"down I lower I lowerward", used herein represents the directions as seen by a vehicle
driver sitting astride and these directions are referred by arrows Fr, Rr, U, Lr in the
drawing figures. Further, "left I leftward", "right I rightward" used herein represents the
directions as seen by a vehicle driver sitting astride.
[0015] Figure 1 illustrates side view of a two wheeled vehicle (1 00) according to an
embodiment of the present invention. The two wheeled vehicle (100) comprises, interalia,
a front fork (121), a head pipe (122), a front fender (172), a front wheel (123), a
headlight (128), a steering handlebar (124), a fuel tank (125), an engine unit (126), an
evaporated fuel collecting device (113); a rear suspension (129), a swing arm (173), a
dress guard (111), a rear wheel (127), a rear fender (116), a tail light (117), and a seat
(130). It may be noted that the two wheeled vehicle (100) is shown to have include above
stated parts, however, those ordinarily skilled in the art would appreciate that the two
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IPD DELHI B2-09~2015 17 11
wheeled vehicle (1 00) includes other parts which may not be relevant for explaining
embodiments of the present invention and hence are not shown and described.
[0016] As depicted in Figure 1, the body frame of the two wheeled vehicle (1 00)
comprises a main frame (1 02), the head pipe (122), a pair of seat rail members
comprising a left seat rail member: (103) and a right seat rail member (not visible in
Figures), a pair of sub-frame members comprising a left sub-frame member (109) and a
right sub-frame member (not visible in Figures), a down frame member (1 05) and one or
more brackets. The main frame (1 02) comprises a front portion (102a) that extends
obliquely in the rearward and downward direction from the head pipe (122) and a rear
portion (102b) changing the direction and thereafter extending further downward. The
pair of seat rails comprising the left seat rail member ( 1 03) and the right seat rail member
(not visible in drawings) extends from a rear end of the front portion (1 02a) of the main
frame (102). The down frame member (105) obliquely extends in the downward
direction from the lower portion of the head pipe (122). The left sub-frame member
( 1 09) and the right sub-frame member connect the rear portion ( 1 02b) of the main frame
(102) and the respective seat-rail, for example, the left seat-rail (103) or the right seatrail,
through a bracket.
· [0017] As illustrated in Figure 1, the front fork (121) is rotatably attached to the head
pipe (122) enabling free steering. The front fork (121) supports the front wheel (123) at
lower end thereof and the steering handlebar (124) at upper end thereof. A front fender.
(172) is provided above to the rear of the front wheel (123) for shielding the operator
frommud ..
[0018] The fuel tank (125) for storing the fuel is supported by the rear portion (102b)
of the main frame (102) of the two wheeled vehicle (100) at a position upper than the
engine unit (126). A piping for sending the evaporated fuel in the fuel tank (125) to the
evaporated fuel collecting device (113), extends obliquely rearwardly from a position
near the fuel cap (not shown in Figures) and extends further downwardly and then
extends from a tunnel plate (not shown in Figures) ofthe fuel tank (125) to the outside of
the fuel tank (125).
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[0019] As illustrated in Figure 1, an air cleaner assembly (not visible in Figures) is
disposed on the rear side ofthe engine unit (126) and on the lower side ofthe seat (130)
and the left seat rail member (103) and the right seat rail member. The air intake pipe
(not shown in Figures) from an air cleaner assembly (115) is connected to a rear portion
of the cylinder head ofthe engine unit (126) via a carburettor (112) such that air and fuel
supplied from the fuel tank (125) are mixed by the carburettor (112) and supplied to the
engine unit (126).
[00201 The left seat rail member (1 03) and the right seat rail member primarily
intended to support the seat (130) for a rider and/or pillion, are disposed above the rear
wheel (127). The dress guard (111) is connected to the left seat rail member (103), and
the dress guard (111) is intended to cover the left side of the rear wheel ( 127). The rear
wheel (127) is covered from above by the rear fender (116) which is mounted onto the
rear end portions of the left seat rail member ( 1 03) and the right seat rail member. The
rear wheel suspension section includes the swing arm (173) supporting the rear wheel
(127) and at least one rear suspension (129) attached between the swing arm (173) and
the left seat rail member (1 03) or the right seat rail member. The tail light ( 11 7) is
mounted on the rear fender (116).
[0021] Figure 2 illustrates a vertical cross section of a carburettor and Figure 3
illustrates a view of the carburettor according to an embodiment of the present invention.
Referring to Figures 2 and 3, a carburettor (200) includes a carburettor body (201)
provided with an air intake passage (203) wherein intake air circulates. The carburettor
(200) further includes a float chamber (202) as a fuel chamber body provided at the
bottom portion of the carburettor body (201). A piston type throttle valve (204) is
disposed in the air intake passage (203) and is movable across the air intake passage
(203) in a vertical direction substantially perpendicular thereto. A compression coil
spring (205) biases the piston type throttle valve (204) in a direction of closing the air
intake passage (203).
[0022] The piston type throttle valve (204) is provided for adjusting the amount of
air flowing in the air intake passage (203) and is achieved by controlling the movement
of the piston type throttle valve (204) across the air intake passage (203). The movement
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of the piston type throttle valve (204) across the air intake passage (203) is governed by
the actuation of throttle twist grip (not shown in Figures) which is operatively connected
through a cable (not shown in Figures) to the piston type throttle valve (204). The piston
type throttle valve (204) is moved (raised or lowered) across the air intake passage (203)
according to the actuation of throttle twist grip. A choke valve (206) for altering the ratio
of fuel and air quantity entering into the engine unit ( 126) is fixed upstream of the piston
type throttle valve (204) in the air intake passage (203). The choke valve (206) IS
operable by the operator, and is generally used in cold starting conditions.
[0023] The carburettor body (20 1) is formed with a first projecting portion (207)
extending into the float chamber (202). A needle jet (208) and a slow jet (209) are
housed in the first projecting portion (207) and the second projecting portion (214)
respectively, wherein the needle jet (208) and the slow jet (209) are placed as dipped in
the fuel in the float chamber (202). The needle jet (208) is held in the tubular first
projecting portion (207) by a jet holder (210) threadedly engaged with the first projecting
portion (207).
[0024] A needle (212) is mounted at its upper end portion to a bottom wall of the
piston type throttle valve (204) and is inserted in the needle jet (208) such that there is a
gap between the needle jet (208) and the needle (212). The gap between the needle jet
(208) and the needle (212) is modified according to the movement of the piston type
throttle valve (204) thereby changing the amount of fuel supplied to the venturi portion
·formed between the piston type throttle valve (204) and wall of the air intake passage
(203). As illustrated in Figure 3, an air channel (213) (formed in the carburettor body
(201)) is provided for maintaining the atmospheric pressure above the fuel level in the
float chamber (202).
[0025] The carburettor body (201) further includes a second projecting portion (214)
extending into the float chamber (202) near the peripheral edge of the float chamber
(202) and formed at a position spaced from the first projecting portion (207). The fuel
retained in the float chamber (202) forms a liquid surface of certain level defined by a
float (215) that opens and closes a control valve (216). The float (215) is provided in the
float chamber (202) and is pivotably supported by a float pin (218) provided on the
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carburettor body (20 1 ). The float (215) swings according to the varying fuel level in the
float chamber (202).
[0026] In case the excess fuel is supplied into the float chamber (202) beyond the
normal fuel value such an excess rise in fuei level is prevented by providing a drain pipe
(220) having one end opening (e.g., first end opening) (not shown in Figures) positioned
higher than the riormal fuel level (e.g., a predefined normal fuel level in the float
chamber (202)) and the other end opening (e.g., second end opening 220b)
communicating with the outside of the float chamber (202) to discharge excess fuel. The
drain pipe (220) is positioned within the float chamber (202) at an appropriate level to
prevent fuel from filling the float chamber (202) above a predetermined level. For
instance, the drain pipe (220) is positioned between the first projecting portion (207) and
the second projecting portion (214) in the float chamber (202) so as to vertically extend
through a bottom wall of the float chamber (202).
[0027] With reference to Figure 3, a breather tube (223) at its one end (e.g., a first
end 223a) is connected to the air channel (213) for maintaining the atmospheric pressure
above the fuel level in the float chamber (202) and its other end (e.g., a second end 223b)
is connected to the drain pipe (220). The breather tube (223) is connected to the drain
pipe (220) outside of the float chamber (202). In a preferred embodiment, the breather
tube (223) is connected to the drain pipe (220) outside of the float chamber (202) using a
. T-joinL In another embodiment, the drain pipe (220) and the breather tube (223) is a
single body. This single body can be manufactured using a single mould.
[0028] In another embodiment, the breather tube (223) is such that it vents all the
condensed fuel out of the. breather tube (223) through the drain pipe (220) to the
atmosphere.
[0029] The connection of the air channel (213) with the drain pipe (220) through the
breather tube (223) aids in controlling the evaporative emissions from the float chamber
(202) of the carburettor (200). It will be known to those skilled in the art that in a
conventional arrangement, a float chamber of a carburettor communicates with the
atmosphere through a breather tube and a drain pipe, hence there is formed a circulation
path for the atmospheric air. Hence, in an example of the conventional arrangements, the
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atmospheric air can enter through the breather tube above the fuel level in the float
chamber and can escape through the drain pipe. However, those skilled in the art would
appreciate that in various embodiments of the present invention, the breather tube (223)
and the drain pipe (220) are connected to· each other, so the float chamber (202) is in
communication with the atmosphere through the drain pipe (220) only. Therefore, no
circulation path is readily formed that aids in reducing the evaporative emissions from
the carburettor (200).
. [0030] In the event wherein the breather tube (223) is connected using the T-joint as
shown in Figure 3, there is no path for the air to en~er. As fuel vapours are heavier than
the atmospheric air, it does not allow air to come inside the drain pipe (220) of the
carburettor (200). The vapours formed get accumulated inside the T-Joint pipe routing of
the breather tube (223) preventing the vapours to come out from the drain pipe (220).
However if the amount of vapours becomes more, the vapours start slowly coming out
from the drain pipe (220) of the carburettor (200).
[0031] Various embodiments of the present invention provide a system of
controlling the evaporative emission from the float chamber of the carburettor without
requmng a separate emission control valve. Various embodiments of the present
invention provide systems of controlling the evaporative emission from the float
chamber of the carburettor wherein the arrangement of controlling the evaporative
emission is easy to mount and service.
[0032] Various embodiments provide systems for controlling evaporative emissions
from the float chamber of carburettor without changing existing layout of the vehicle.
Moreover, in systems for controlling evaporative emissions from a carburettor, controls
of evaporative emissions are achieved· through cost effective means.
[0033] While few embodiments of the present invention have been described above,
it is to be understood that the invention is not limited to the above embodiments and
modifications may be appropriately made thereto within the spirit and scope of the
invention.
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[0034] While considerable emphasis has been placed herein on the particular features
of this invention, it will be appreciated that various modifications can be made, and that
many changes can be made in the preferred embodiments without departing from the
principles of the invention. These and other modifications in the nature of the invention
or the preferred embodiments will be apparent to those skilled in the art from the
disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive
matter is to be interpreted merely as illustrative of the invenlion and not as a limitation.

CLAIMS
We claim:
1. A carburettor of a vehicle, the carburettor comprising:
a carburettor body comprising:
an air intake passage, and
an air channel formed in the carburettor body;·
a float chamber configured at a bottom. portion of the carburettor body;
a drain pipe for discharging excess fuel in the float chamber, the drain pipe
comprising a first end opening and a second end opening, the first end opening of the
drain pipe disposed in the float chamber at a position higher. than a predefined normal
fuel level in the float chamber and the second end opening of the drain pipe disposed
outside of the float chamber for discharging the excess fuel; and
a breather tube comprising a first end and a second end, the first end of the
breather tube connected to the air channel and the second end of the breather tube
connected to the drain pipe between the first end opening and the second end opening.
2. The carburettor as claimed in claim 1, wherein the second end of the breather
tube is connected to the drain pipe at a portion of the drain pipe that is outside of the
float chamber.
3. The carburettor as claimed in claims 1 or 2, wherein the breather tube is
connected to the portion of the drain pipe outside of the float chamber using aT-joint.
4. The carburettor as claimed in claims 1 or 2, wherein the drain pipe and the
breather tube are configured as a single body using a single mould.
5. The carburettor as claimed in claims 1 or 2, further comprising a piston type
throttle valve disposed in the air intake passage, the piston type throttle valve movable
across the air intake passage in a vertical direction substantially perpendicular thereto
for adjusting amount of air in the air intake passage.
6. The carburettor as claimed in any of the claims 1 to 5, further comprising a
compression coil spring for biasing the piston type throttle valve in a direction of
closing the air intake passage.