[0001] This invention relates to a carburetor having a fuel metering system for supplying
a homogeneous mixture of fuel and air across the throttle opening of the carburetor
while precisely controlling fuel and air flow rates.
[0002] For so long as internal combustion engines have been in existence, various carburetors
have been developed to supply a required air-fuel mixture to the engine to promote
proper and efficient combustion. Although myriads of car- buretion schemes and devices
have been developed, a continuing problem has been metering of the air-fuel mixture
in a consistently homogeneous blend such that the air-fuel mixture received by each
cylinder of the internal combustion engine is the same as that supplied to each other
cylinder.
[0003] In addition, not only is it important to control the homogeneity of the fuel-air
mixture, it is also important to control the actual quantity of the fuel injected
into the air stream in relation to the density of the air passing through the carburetor.
Thus, when the air density decreases, it is important to also reduce the fuel flow
rate so that the air-fuel blend supplied to the internal combus-, tion engine is not
fuel rich. This is particularly important in aircraft, where at high altitudes, the
air density is considerably reduced. A commensurate reduction in the flow rate of
the fuel must be made in order to properly lean the mixture to avoid fuel waste or
possible engine flooding.
[0004] In conventional carburetors or fuel injection systems, the velocity of the air passing
through a venturi portion is assumed to correspond directly to the air mass flow.
This assumption remains correct so long as there is no change in air density. If the
ambient air temperature or pressure does change, then the resultant change in density
invalidates this assumption and the carburetor or injection system experiences a change
in air-fuel ratio. If the air density increases, then the air-fuel ratio becomes leaner
and if the air density decreases, then the air-fuel ratio becomes richer. In most
carburetor applications except aircraft the recent low cost of fuel has made mixture
control not cost effective. In aircraft, where density- related mixture changes due
to altitude result in large power reductions, mixture control has always been a necessary
feature.
[0005] The venturi system of measuring air flow and metering fuel is based upon the Bernoulli
principle as expressed by the Bernoulli equation as follows:
Where P=Pressure, V=airflow velocity, I=air density
[0006] As the Bernoulli equation applies to air flow in a venturi, it can be rewritten as
follows:
or
with the subscripts 1 and 2 referring to different axial locations in the flow tube.
If the velocity at location 2 is high (such as occurs at the throat of a venturi)
the pressure is lower than the pressure at a location where the velocity is low. From
the Bernoulli equation, it is seen that the amount of pressure difference is much
greater than the velocity difference because the velocities in the equation are squared.
[0007] The pressure that is sensed in a direction perpendicular to the direction of local
flow in a venturi is the static pressure and is equal to that which would be sensed
by a pressure instrument moving with the air flow. The pressure that is sensed by
a probe inserted in the flow path and oriented with its opening, facing the oncoming
air is defined as the total pressure. The difference between the total pressure and
the static pressure is the dynamic pressure and is related to the flow velocity be
Bernoulli's equation as follows:
t
[0008] In the absence of friction, the total pressure remains constant along the length
of a flow tube or venturi. In an areas where the flow velocity increases due to a
constriction in flow area, the static pressure commensurately low.
[0009] Slide-type carburetors consisting of an air passage and a throttle plate movable
to provide an adjustable throttle opening to alterably constrict the air passageway
have been in existence for some time, as evidenced by U.S. Patents No. 3,709,469 and
3,957,930. Such devices provide for throttling of the air flow in combination with
mechanical control of the fuel quantities added to the carburetor. However, because
fuel is injected into one side of the throttle opening in either of these devices,
they suffer from an inability to supply a homogenous air-fuel mixture across the throttle
opening and do not permit a full range of air-fuel mixture control.
[0010] Other devices are known for metering fuel flow across the throat of a carburettor,
as evidenced by U.S. Patents No. 1,142,763 and 4,205,024. While such devices do permit
fuel distribution effectively across the carburettor, it is difficult with such devices
to adjust the air-fuel mixture as the carburettor air passageway is throttled.
[0011] British Patent Specification No. 131,079 discloses a. carburettor having an air fluid
passageway, and a throttle valve having an adjustable throttle aperture. A fuel supply
tube extends across the throttle aperture, and has a distribution outlet extending
across the throttle opening. The distribution outlet has a number of openings to meter
the flow of fuel into the air passageway. The effective size of the openings can vary
along the distribution outlet. Also, adjustment of the throttle aperture changes the
effective length of the distribution outlet, by exposing more or fewer of the openings.
[0012] In GB-A-536549 an apparatus for creating a fuel-rich premixture is described. Air
and fuel are mixed in a side passageway, off the main air passageway, by means of
a rotatable fuel supply tube. The fuel-rich mixture is heated before being admixed
with the air in the main air passageway.
[0013] According to the invention there is provided a carburettor comprising: an air passageway;
a throttle valve slideably mounted across the air passageway to adjust a throttle
aperture, a fuel supply tube connected to a fuel metering tube which extends across
the throttle aperture and has along its length a fuel flow outlet to distribute and
to meter the flow of fuel into the air passageway, the size of the fuel flow outlet
varying along the metering tube, and the slideable throttle valve changing the effective
length of the fuel flow outlet, characterised in that the size of the fuel flow outlet
increases continually along the metering tube in the direction in which the throttle
valve slides to open the throttle aperture, so that air-fuel ratio is maintained substantially
constant at a certain air ambient pressure independent of throttle valve shifting
and in that means are provided for adjusting the air fuel ratio by adjusting the pressure
difference between the fuel pressure upstream of the fuel flow outlet and the air
pressure at the fuel flow outlet, the pressure difference being adjusted by means
of an air pressure of the air passageway which is adjustable between the total air
pressure and the static (air) pressure of the air passageway in the region of the
fuel metering tube, the means for adjusting the air fuel ratio having means for supplying
fuel to the fuel metering tube at a pressure no greater than the total air pressure
in the air passageway.
[0014] In one embodiment of the invention, the adjustment means alters the flow of fuel
through the distribution outlet by changing the orientation of the fuel metering tube
from a maximum lean position, where fuel flow may be essentially eliminated, to a
full fuel flow position, thereby providing the richest possible air-fuel mixture.
[0015] In this embodiment, in order to alter the flow of fuel through the fuel distribution
outlet, the fuel metering tube preferably is rotatable about its longitudinal axis
to change the circumferential location of the distribution outlet. The outlet is positionable
between a maximum lean condition facing upstream in the direction of air passage,
and a maximum rich condition 90 degrees therefrom in which the distribution outlet
faces across the path of air flow.
[0016] In another embodiment of the invention, the fuel supply comprises a fixed metering
tube having its distribution outlet extending along one side and oriented perpendicular
to air flow through the throat of the carburetor. In order to control the fuel flow,
a pressure detecting tube is located in communication with the air passageway to sense
a portion of the dynamic pressure of the air as it passes through the carburetor.
This detected pressure is then used to maintain the pressure of the fuel at the detected
pressure as the fuel is introduced into the fixed metering tube.
[0017] In this second embodiment of the invention, the detecting tube has an inlet in one
side and is very similar to the fuel metering tube of the first embodiment of the
invention. The detecting tube is rotatable to change the circumferential location
of the inlet and therefore change the amount of dynamic air pressure that is sensed.
Therefore, because of the rotatable nature of the detecting tube, the tube can be
made to sense any pressure between the total pressure and the static pressure of the
air flow.
[0018] In order to control the fuel flow in this embodiment of the invention, the invention
includes a balancing regulator which is regulated by the sensed pressure. The balancing
regulator has an inlet on one side for the fuel, and includes a control responsive
to the sensed pressure and operable to permit the flow of fuel through the fuel inlet
at such a rate so as to maintain equality between fuel pressure and the sensed pressure.
[0019] In another embodiment of the invention, the fuel metering tube is also fixed with
the distribution outlet extending perpendicular to the air flow. A pressure transmitting
tube having one end extending into the air flow is oriented to detect the total pressure
of the air. A second pressure transmitting tube has one end extending into the air
at the throttle passageway in order to detect the static pressure of the air passing
therethrough. The tubes are joined at their other ends and a third pressure transmitting
tube leads from this junction to a balancing regulator to control pressure of the
fuel. The second pressure transmitting tube has a valve operable to permit a portion
of the total pressure in the first pressure transmitting tube to bleed into the second
pressure transmitting tube, leaving a resultant differential pressure in the third
pressure transmitting tube. The resultant differential pressure is used to control
the pressure of the fuel as it is introduced into the.fuel outlet.
[0020] In this embodiment of the invention, a balancing regulator is again used to control
the fuel flow. The balancing regulator senses the differential pressure and has an
inlet for the fuel. The regulator includes a fuel control responsive to the sensed
differential pressure and operable to permit flow of fuel through the fuel inlet at
such a rate so as to maintain equality of pressure between the fuel and the sensed
differential pressure.
[0021] In both latter embodiments of the invention, the fuel is delivered to the inlet of
the balancing regulator from some external source such as a fuel pump or elevated
fuel reservoir. The balancing regulator therefore is used to reduce the pressure of
the fuel to the required pressure before fuel is permitted to enter the fuel metering
tube.
[0022] In one form, the distribution outlet in the fuel metering tube comprises a plurality
of apertures spaced axially along one side of the metering tube. In another form,
the distribution outlet comprises an axial slot along one side of the metering tube.
In all cases, the metering tube preferably is positioned in registration with the
throttle valve and extends through a complimentary lateral aperture in the throttle
valve. The throttle valve is slidable upon the metering tube to adjust the throttle
opening and change the effective length of the fuel distribution outlet. Therefore,
no matter how large the throttle opening, a uniform distribution of fuel is maintained
across the throttle opening.
[0023] The throttle valve is adjustable between limits to provide a maximum throttle opening
and a minimum throttle opening. In order to precisely control the fuel-air mixture
at the minimum throttle opening, the axial location of the fuel metering tube can
be adjusted. Thus, a greater or lesser portion of the distribution outlet can be presented
across the throttle opening at its minimum setting.
Brief description of the drawings
[0024] The above features of the invention, and others, are described in greater detail
in the following description of a number of preferred embodiments, where reference
is made to the accompanying drawings, in which:
Figure 1 is an exploded illustration of the invention, with some parts omitted and
other parts in cross-section to permit illustration of the primary components of the
invention.
Figure 2 is a cross-sectional illustration of the assembled invention, illustrating
the throttle valve closed to a minimal throttle opening.
Figure 3 is an illustration similar to Figure 2, but with the throttle valve translated
sufficiently to provide a partial throttle opening.
Figure 4 is a view similar to Figure 2 but with the throttle valve being withdrawn
sufficiently to provide a full throttle opening.
Fig. 5 is an enlarged cross-sectional illustration taken along lines 5-5 of Figure
4.
Figure 6 is an enlarged cross-sectional illustration taken along lines 6-6 of Figure
2.
Figure 7 is an enlarged cross-sectional illustration taken along lines 7-7 of Figure
4.
Figure 8 is an enlarged, partially truncated view of one embodiment of the fuel metering
tube according to the invention.
Figure 9 is an elongated cross-sectional illustration taken along lines 9-9 of Figure
8.
Figure 10 is a truncated top plan view of an alternative embodiment of the fuel metering
tube according to the invention.
Figures 11 through 13 illustrate rotation of the fuel metering tube respectively between
a lean mixture setting, and a rich mixture setting.
Figures 14 illustrates, in cross section, a modified embodiment of the invention.
Figure 15 illustrates a modification of the embodiment of Figure 14, showing another
form of the fuel metering system.
Figure 15a through 15c illustrate a partial cross-section taken along lines 15a-15a
of Figure 15, with Figures 15b and 15c showing rotation of the pressure detecting
tube.
Figure 16 illustrates a further modification of the embodiment of Figure 14, showing
yet another form of the fuel metering system.
Figure 17 illustrates a further modification of the embodiment of Figure 14, showing
a final form of the fuel metering system.
Description of the preferred embodiments
[0025] A fluid mixing device according to the invention, in the form of a carburetor, is
shown in assembly fashion in Figure 1. Primary components of the carburetor include
a top plate 10, a bottom plate 12, a throttle valve 14. Although the top plate 10
and bottom plate 12 are delineated as such, it should be obvious that the designations
"top" and "bottom" are for the purposes of explanation only, and the respective roles
of the plates 10 and 12 can be reversed as necessary. In addition, the top plate 10
has been shown in cross-section for the purposes of description, and would include
a second half complementary to that shown in Figure 1.
[0026] The top plate 10 includes an air inlet 16. The bottom plate 12 includes an air-fuel
outlet 18 located in concentric registration with the air inlet 16. The inlet 16 and
outlet 18 are preferably of equal diameter.
[0027] When the carburetor is assembled, the throttle valve 14 is sandwiched between the
top plate 10 and the bottom plate 12 for sliding movement between the two plates.
The plates 10 and 12 are suitably fixed together as by means of a plurality of screws
20 passing through apertures 22 in the bottom plate 12 and engaging corresponding
threaded apertures 24 in the top plate 10.
[0028] Although, as indicated above, the throttle valve 14 is situated between the plates
10 and 12 for sliding movement, the throttle valve 14 is dimensioned for a close fit
in the aperture formed between the plates 10 and 12 when assembled. The throttle valve
14 may be formed of a material susceptible to forming a seal, such as Teflon, while
the plates 10 and 12 may be formed of aluminum, steel or other relatively stiff material.
Other materials may be used as desired.
[0029] As best shown in Figure 1, the throttle valve 14 includes a throttle aperture 26.
The cross sectional dimension of the aperture 26 is the same as the diameters of the
inlet 16 and outlet 18 so that if the inlet 16, opening 26 and outlet 18 are aligned,
an uninhibited throttle opening or bore is formed through the carburetor. At this
position, as described in greater detail below, air flow is maximum and, as is well
known, the carburetor is at its full throttle position.
[0030] As best shown in Figures 2 through 4, the position of the throttle valve 14 between
the sandwiched plates 10 and 12 is determined by means of a control rod 28. The rod
28 is secured within a bore 30 formed in the throttle valve 14 and passes through
an aligned aperture 32 formed in the sidewall of the top plate 10. A pin or set screw
34, passing through a hole 36 in the rod 28 and lodged within a hole 38 formed in
the throttle valve 14, secures the control rod 28 within the throttle valve 14.
[0031] For fuel metering, the carburetor includes a fuel metering tube 40 which passes longitudinally
through the entire throttle valve 14 and extends through apertures 42 and 44 at opposite
ends of the top plate 10. The throttle valve 14 includes a close-fitting longitudinal
aperture 46 through which the fuel metering tube 40 passes and upon which the throttle
valve 14 is mounted for sliding between the extreme location shown in Figures 2 through
4. The longer bore of the longitudinal aperture 46 may include sealing rings or the
like (not illustrated) to assure a fluid-tight seal between the fuel metering tube
40 and the aperture 46.
[0032] The aperture 44 is threaded, as illustrated. A fuel connection nipple 48 is engaged
on the threads of the aperture 44 and is shaped for connection to an external fuel
source (not illustrated) in a well known manner not further described herein. The
fuel connection nipple 48 may include a sealing ring or some similar device to provide
a fluid tight seal between the nipple 48 and the fuel metering tube 40.
[0033] The fuel metering tube 40 is rotatable about its longitudinal axis to control the
fuel-air ratio. Rotation is controlled by means of an arm 50 attached to the end of
the fuel metering tube 40 opposite to that of the connection nipple 48. The arm 50
sealingly closes the tube 40 at its point of connection, and is controlled for rotation
by suitable means (not illustrated), such as a control cable which may be clamped
to the arm 50through a bore 52 by a bolt 54.
[0034] Immediately adjacent the arm 50, a collar 56 is permanently secured to the fuel metering
tube 40. A keeper screw 58, threadedly secured within the top plate 10, engages a
circumferential channel 60 formed in the collar 56. Thus, the keeper screw 58 maintains
precise axial alignment of the fuel metering tube 40. By suitable adjustment of the
keeper screw 58, the axial position of the fuel metering tube 40 may be altered for
purposes described in greater detail below.
[0035] As best shown in Figures 1 and 4, the fuel metering tube 40 includes a distribution
outlet 62 extending across the entire width of the throttle aperture 26 when the throttle
valve 14 is in the full throttle position. Thus, with the axial alignment of the fuel
metering tube 40 being fixed by the keeper screw 58, no matter what position of the
throttle valve 14 between the top and bottom plates 10 and 12, the fuel is dispensed
across the entire width of the effective throttle opening.
[0036] As shown in enlarged fashion in Figures 8 and 9, in this first embodiment, the distribution
outlet 62 is composed of a plurality of holes 64 spaced axially along one side of
the fuel metering tube 40. As shown in Figure 8, the holes 64 have been gathered in
three groups 66, 68 and 70 in order to overcome the reduction of the fuel flow rate
over the length of the distribution outlet 62.
[0037] Figure 10 illustrates an alternative embodiment of the distribution outlet, designated
as 62'. In this embodiment, the holes 64 are eliminated and instead the distribution
outlet 62' comprises an axial slot opening along one side of the metering tube 40.
In the same manner as grouping of the holes 64 in the distribution outlet 62, the
slot of the distribution outlet 62' is formed in an increasing taper fashion, as illustrated,
in order to maintain constant fuel outlet flow through the distribution outlet 62'.
[0038] As is well known, depending on the position of the throttle valve 14 and therefore
the cross sectional dimension of the throttle opening through the carburetor, air
flow through the carburetor is controlled. With the throttle valve 14 in the position
illustrated in Figures 4, 5 and 7, maximum air flow is permitted and therefore the
carburetor is at full throttle. With the throttle valve 14 at the position indicated
in Figures 2 and 6, the carburetor is at its throttle closed position. The location
shown in Figure 3 is a mid-throttle position. As shown in Figure 2, the maximum closure
of the throttle valve 14 is determined by a set screw 72. With the set screw 72 adjusted
to the position shown in Figure 2, a minimum air passageway 74 is formed. As shown
in the drawings, the dimension of minimum air passageway 74 can be increased or decreased
as desired by adjustment of the set screw 72. In fact, if desired, the minimum air
passageway 74 can be omitted completely, although such a situation is not normally
acceptable.
[0039] Also as shown in Figure 2, only a very small portion of the distribution outlet 62
extends into the minimum air passageway 74. If desired, a greater portion of the distribution
outlet can extend into the minimum air passageway 74 by adjustment of the keeper screw
58. Assuming that, in the position shown in Figure 2, a single hole 64 (Figure 8)
of the distribution outlet 62 extends into the minimum air passageway 74, by suitable
adjustment of the keeper screw 58 a greater portion of the distribution outlet 62
can appear in the minimum air passageway 74, allowing one or more additional holes
64 to inject fuel into the minimum air passageway. Thus, by adjustment of the set
screw 72 and the keeper screw 58, the dimensions of the minimum air passageway 74
are dictated, and also the fuel metering capacity at this minimum setting is determined.
[0040] In many carburetors, such as an aircraft carburetor of the nature of the invention,
fuel pressure entering the carburetor fuel metering section is essentially equal to
ambient pressure. Therefore, fuel is aspirated from the distribution outlet 62 of
the fuel metering tube 40 by pressure differences created within the effective air
passageway. In many situations, and in particular in an aircraft, the carburetor must
have the capability of reducing the fuel flow as increases in aircraft altitude reduce
the density of the air entering the air inlet 16 of the carburetor. Changes in the
air-fuel mixture are effected by rotation of the fuel metering tube 40, as best shown
diagrammatically in Figures 11 through 13. With the fuel metering tube 40 in the position
shown in Figure 11, the distribution outlet is aimed upstream directly toward the
air inlet 16, and the carburetor is in the "idle cutoff" position. When the fuel pressure
in the metering tube is regulated in such a way so as to be maintained approximately
equal to the total pressure of the air, the dynamic air pressure within the air inlet
16 completely inhibits the flow of fuel, causing the engine to stop.
[0041] In the position shown in Figure 13, the distribution outlet 62 is turned at 90 degrees
to the airflow. This is the position for providing the richest possible air-fuel mixture
such as is normally required at low altitudes. In this position, the fuel flow from
the distribution outlet is being aspirated into the air passageway by the difference
in pressure between the fuel inside the fuel metering tube 40 and the static air pressure
outside of the distribution outlet 62 which is reduced below ambient pressure in accordance
with the Bernoulli equation.
[0042] To adjust the carburetor to a leaner air-fuel mixture as would be required at higher
altitudes, the fuel metering tube 40 is rotated to a mid-way orientation such as that
shown in Figure 12. In this position, the air pressure outside of the fuel distribution
outlet 62 is increased by a dynamic component of the velocity of the air entering
the air inlet 16. This reduces the differential between the static and dynamic pressures
which aspirates the fuel from the distribution outlet 62, and therefore reduces the
fuel flow rate from that of the orientation shown in Figure 13. Consequently, a leaner
fuel mixture is attained without fuel flow cutoff as shown in Figure 11.
[0043] Therefore, the invention achieves an even fuel distribution with precise air-fuel
mixing to enable the carburetor to control an engine no matter what ambient conditions
may be encountered. Not only does the throttle valve 14 control the air flow through
the carburetor, but also the throttle valve 14, when sliding along the fuel metering
tube 40 across the distribution outlet 62, maintains the air-fuel mixture constant
no matter what -the throttle position, contrary to conventional carburetors. In addition,
by rotation of the fuel metering tube 40, the richness of the air-fuel mixture can
be precisely controlled to account for changes in ambient air density.
[0044] Figure 14 illustrates an alternative embodiment of the invention having modification
of the throttle valve and fuel system leading to the fuel inlet tube 40. Other components
of the invention remain the same and therefore bear the same reference numerals. Since
these elements were described above, further description is omitted.
[0045] As illustrated, the throttle valve 14' in Figure 14 is truncated, omitting a portion
of the throttle valve 14 which is unnecessary. As shown, the throttle valve 14' includes
a throttle aperture 26' having a diameter equal to that of the air-fuel mixture outlet
18 so that, in a full throttle open position (such as that illustrated in Figure 4),
there is no obstruction to flow by the throttle valve 14'.
[0046] In this embodiment, the invention includes a balancing regulator 90 operable to control
fuel pressure in the fuel inlet tube 40 to ambient pressure. The balancing regulator
90 has an inlet 92 for fuel under pressure. The inlet 92 leads to a nipple 94 which
may be connected to a source of fuel (not illustrated).
[0047] The inlet 92 is terminated by a fluid control ball valve 96 or by a conventional
needle valve and seat assembly (not illustrated). The valve 96 has an internal orifice
98 which may be closed by a pair of balls 100. An arm 102, pivotally connected in
its mid-section at 104 to the balancing regulator 90, has one end which bears against
the larger of the balls 100. The other end of the arm 102 bears against a biasing
compression spring 106 which in turn bears against a screw 108 threaded into the body
of the top plate 10. Depending on the compression strength of the spring 106, the
spring normally pivots the arm about the pivot 104, urging the balls 100 into the
orifice 98 to preclude fuel flow through the inlet 92 into the interior of the balancing
regulator 90 and from there into the fuel inlet tube 40. Fine adjustment of the compression
strength of the spring 106 with the screw 108 to achieve this end is well-known.
[0048] The balancing regulator 90 also includes a movable diaphragm 110 having a central
contact 112 in alignment with one end of the arm 102. The balancing regulator 90 also
includes an opening 114 to the ambient surroundings.
[0049] The metering system of the balancing regulator 90 operates in a well-known manner.
Since the opening 114 is to the ambient pressure which is usually equal to the airflow
total pressure, the ambient pressure normally urges the contact 112 against the arm
102, permitting fuel to enter the regulator 90 through the inlet 92. Not only does
the entering fuel flow through the fuel inlet tube 40 and exit through the distribution
outlet 62, the fuel also bears against the opposite side of the diaphragm 110 from
that open to the ambient pressure experienced through the opening 114. If the fuel
pressure is higher than the ambient pressure, the increased pressure of the fuel tends
to urge the contact 112 away from the arm 102, permitting the spring 106 to pivot
the arm about the pivot 104, urging the balls 100 into the closed position. Therefore,
the diaphragm 110 always positions itself as necessary to equalize the fuel pressure
on the fuel side of the diaphragm with the ambient air pressure on the air side of
the diaphragm. Thus, the fuel pressure in the inlet tube 40 is always maintained at
approximately the same pressure as the ambient air pressure surrounding the carburetor.
[0050] Figure 15 illustrates a modified version of the invention in which fuel flow is controlled
totally by air pressure and the fuel inlet tube 40 is fixed with the inlet 62 oriented
so as to sense static pressure, in this embodiment perpendicular to the direction
of air flow through the carburetor.
[0051] As seen in Figure 15, the opening 114 of the balancing regulator 90 is not opened
to ambient pressure. Rather, a conduit 116 leads from the opening 114 to a pressure
detecting tube 118 extending across the air inlet 16. The tube 118 must be immediately
adjacent the fuel distribution outlet 62, and is shown directly above the tube 40
in Figure 15. The detecting tube 118 includes an aperture 120 therein, thus permitting
the tube 118 to sense the air pressure in the air inlet 16. The tube 118 is axially
rotatable as shown in Figure 15 and in Figures 15a-15c in order to permit altering
the circumferential location of the aperture and therefore vary the percentage of
the dynamic pressure that is sensed.
[0052] Since the distribution outlet 62 of the fuel inlet tube 40 is fixed at an orientation
perpendicular to the air flow through the carburetor, the distribution outlet 62 experiences
only the static component of the total air pressure in the carburetor at its particular
location. So long as the fuel introduced into the inlet tube 40 is at a pressure greater
than the static pressure existing at the distribution outlet 62, fuel will flow from
the distribution outlet and be mixed with the incoming ambient air.
[0053] The pressure balancing function of the balancing regulator 90 causes the pressure
in the metering tube 40 to be equal to the pressure sensed by the pressure detecting
tube 118. With the orientation of the aperture 120 shown in Figure 15 and Figure 15a
(open to the air flow), the aperture 120 detects the total pressure of the air at
this location. The balancing regulator adjusts the fuel pressure in the metering tube
40 to equal the total pressure sensed by the aperture 120. Since the pressure at the
fuel outlet 62 is equal to the static pressure, fuel flow occurs through the fuel
outlet 62.
[0054] If, on the otherhand, the aperture 120 is oriented as shown in Figure 15b, the aperture
120 senses a lower pressure that is equal to the static pressure plus a lesser dynamic
component that depends on the upstream orientation of the aperture 120. This lower
pressure is transmitted through the conduit 116 to the diaphragm 110. The diaphragm
110 positions itself such that the 6all valve 96 admits fuel to the fuel side of the
diaphragm 110 at such a rate so as to make the fuel pressure in the metering tube
40 equal to the air pressure sensed by the aperture 120 in the pressure detecting
tube 118.
[0055] When the pressure sensing aperture is oriented as shown in Figure 15c, the resulting
pressure in the fuel metering tube 40 is equal to the static pressure existing at
the outlet 62. With the orientation shown in Figure 15c, no fuel would flow.
[0056] Figure 16 illustrates a modification of the system for injecting fuel into the carburetor.
A portion of the air inlet 16 of the top plate 10 is shown superimposed above the
cross-sectional illustration of the carburetor as depicted and described in Figure
14. In this embodiment, a first pressure transmitting tube 122 leads from the air
inlet 16 and joins a second pressure transmitting 124 leading from the mixture outlet
18. A third pressure transmitting tube 126 leads from the juncture of the tubes 122
and 124 to the opening 114 of the balancing regulator 90. As shown, the end 128 of
the tube 122 in the air inlet 16 faces upstream and therefore senses the total air
pressure in the air inlet 16. The tube 124 is introduced at the side of the mixture
outlet 18, and therefore detects the static pressure at that location. An adjustable
needle valve 130 is located in the tube 124 and may be adjusted to close the tube
124 completely, or permit any opening required.
[0057] Because the end 128 of the tube 122 is opened to the total pressure, and because
the tube 124 is opened to the lower static pressure, if the needle valve 130 is opened
slightly, a portion of the total pressure in the tube 122 is bled through the needle
valve 130 into the tube 124. This leaves a resultant differential pressure in the
tube 126, which is directed through the opening 114 to the interior of the balancing
regulator 90. Thus, by judicious adjustment of the needle valve 130, the differential
pressure experienced by the balancing regulator 90 may be adjusted as desired. Since
the distribution outlet 62 of the fuel inlet tube 40 is oriented perpendicular to
the flow direction, and therefore experiences only the static pressure of the flow,
the balancing regulator 90 is operated as described above and fuel is driven through
the outlet 62 by the difference between the differential pressure within the tube
126 and the static pressure at the distribution outlet 62. So long as the differential
pressure is greater than the static pressure, fuel will flow.
[0058] Figure 17 illustrates another embodiment of the invention having modification of
the throttle valve and fuel system leading to the fuel inlet tube 40. Components which
have been described above bear the same reference numerals and perform the same functions.
Further description, therefore, is omitted.
[0059] In this embodiment, the invention includes a fuel metering float regulator 140 operable
to maintain fuel pressure in the fuel inlet tube 40 at ambient pressure. The float
regulator 140 includes the fluid control ball valve 96 and associated component described
above. The arm 102 of the prior embodiments of Figures 14 through 16 is replaced with
an arm 142 which is pivotally connected in its mid-section at 144. One end of the
arm 142 bears against the larger of the balls 100. The other end of the arm 142 is
connected to a float 146 maintained within a fuel reservoir 148 of the float regulator
140. The float 146 is situated such that during normal operation, the level of the
fuel 150 within the fuel reservoir 148 is sufficient to allow fuel to enter the fuel
inlet tube 40. If the pressure of the fuel 150 within the reservoir 148 is greater
than the air pressure experienced at the distribution outlet 62 of the inlet tube
40, fuel will flow from the distribution outlet. Conversely, if the air pressure is
the same as or higher than the fuel pressure, no fuel will flow from the distribution
outlet 62.
[0060] As shown diagrammatically, the fuel reservoir 148 includes an aperture 152 open to
the ambient surroundings. Therefore, the fuel 150 within the reservoir 148 is maintained
at ambient pressure.
[0061] The metering system of the float regulator 140 operates in a known manner. Since
the aperture 152 is opened to ambient pressure, and assuming fuel pressure in the
inlet 92 is greater than ambient pressure, fuel enters the reservoir 148 from the
inlet 92 and maintains a level permitted by the float 146. The fuel 150, at ambient
pressure, also enters the fuel inlet tube 40, and is present at the distribution outlet
62. With the distribution outlet aimed upstream in the orientation illustrated in
Figure 17, the total pressure is experienced. Since the total pressure equals the
ambient pressure, at the orientation illustrated, fuel flow through the outlet 62
will be prevented. However, if the fuel inlet tube 40 is rotated slightly, the pressure
experienced at the distribution outlet will be less than the total pressure. Thus,
fuel will flow from the distribution outlet 62. The fuel/air mixture is therefore
controlled by the rotational orientation of the fuel inlet tube 40, in the same manner
as described above with regard to prior embodiments.
[0062] In this embodiment of the invention, fuel will enter the reservoir 148 from the inlet
92 so long as the fuel in the inlet 92 is under pressure. Therefore, when an internal
combustion engine incorporating the invention is stopped, operation of the pump (not
illustrated) supplying fuel to the inlet 92 must also be stopped. The fuel 150 contained
within the reservoir 148 will, therefore, at maximum drain to a lower level where
no fuel enters the inlet tube 40.
[0063] The invention provides a novel, precise system for metering fluid flow and mixing
of two fluids. By appropriate orientation of the fuel outlet 62 of the fuel inlet
tube 40 in combination with regulated fuel pressure and appropriate adjustment of
the throttle valve 14, optimum fuel/air ratio can be provided over the full range
of engine power and operating environment.
[0064] Because no obstructions exist downstream of the fuel outlet, the carburetor according
to the invention is non-icing. This feature is quite advantageous particularly in
aircraft which operate at altitudes or temperatures where icing can occur in conventional
carburetors.
[0065] Conventional carburetors which are used in automotive applications require a choke
valve of some nature to provide extra richness for engine starting. No choke valve
is required in the present invention since the required richness for starting can
be obtained by the combination of the fuel inlet tube 40, throttle valve 14, and pressure
and outlet rate of the fuel within the inlet tube 40.
[0066] With the exception of the embodiment of Figure 17, the invention can be used at any
attitude orientation, and also with the exception of the embodiment of Figure 17 can
be used in any condition of horizontal or vertical acceleration. Conventional carburetors
having a float system for fuel metering require a substantially consis- tant orientation
to prevent fuel starvation or flooding in the carburetor.
1. A carburettor comprising: an air passageway (16, 18); a throttle valve (14) slideably
mounted across the air passageway (16, 18) to adjust a throttle aperture (26), a fuel
supply tube connected to a fuel metering tube (40) which extends across the throttle
aperture (26) and has along its length a fuel flow outlet (62) to distribute and to
meter the flow of fuel into the air passageway (16, 18), the size of the fuel flow
outlet (62) varying along the metering tube (40), and the slideable throttle valve
changing the effective length of the fuel flow outlet (62), characterised in that
the size of the fuel flow outlet (62) increases continually along the metering tube
(40) in the direction in which the throttle valve slides to open the throttle aperture,
so that air-fuel ratio is maintained substantially constant at a certain air ambient
pressure independent of throttle valve shifting and in that means (40, 52; 124, 130;
114,120) are provided for adjusting the air fuel ratio by adjusting the pressure difference
between the fuel pressure upstream of the fuel flow outlet and the air pressure at
the fuel flow outlet (62), the pressure difference being adjusted by means of an air
pressure of the air passageway (16, 18) which is adjustable between the total air
pressure and the static (air) pressure of the air passageway in the region of the
fuel metering tube (40), the means for adjusting the air fuel ratio having means for
supplying fuel to the fuel metering tube at a pressure no greater than the total air
pressure in the air passageway.
2. A carburettor according to claim 1, in which the fuel flow outlet comprises a plurality
of apertures (Figure 8) spaced axially along at least one side of the fuel metering
tube.
3. A carburettor according to claim 1, in which said fuel flow outlet comprises at
least one axial slot (Figure 10) extending along one side of the fuel supply tube.
4. A carburettor according to claim 1, 2 or 3, in which the fuel metering tube (40)
extends through a complementary longitudinal aperture (46) in the throttle valve (14),
and the throttle valve (14) is slidable upon the metering tube to adjust the throttle
opening and change the effective length of the fuel flow outlet (62).
5. A carburettor according to claim 1, 2, 3 or 4, including means (58, 60) to adjust
the axial location of the fuel metering tube.
6. A carburettor according to any preceding claim, in which the throttle valve (14)
is adjustable between limits to provide a maximum throttle opening and a minimum throttle
opening, and further including means (72) to set the minimum throttle opening.
7. A carburettor according to any preceding claim, in which the adjusting means comprises
means (50-60) to rotate the fuel supply tube about its longitudinal axis to change
the circumferential location of fuel flow outlet (62).
8. A carburettor according to any one of claims 1 to 6, in which the adjustment means
comprises a pressure detecting tube (118) in the air passageway (16,18), and means
(90, 114-116) to control the fuel pressure using the detected pressure.
9. A carburettor according to claim 8, in which there is an inlet in one side of the
detecting tube, and the detecting tube is rotatable to change the circumferential
location of the inlet and thereby change the pressure which is sensed.
10. A carburettor according to claim 8 or 9, in which the control means comprises
a balancing regulator (90) regulated by the sensed pressure, the balancing regulator
having a fuel inlet controlling fuel pressure responsive to the sensed pressure and
operable to permit flow of fuel through the fuel inlet at such a rate so as to cause
substantial equality of pressure between the fuel and the sensed pressure.
11. A carburettor according to any one of claims 1 to 6, in which the adjustment means
comprises a first pressure transmitting tube (122) having one end oriented so as to
detect high air pressure and a second pressure transmitting tube (124) having one
end positioned so as to detect a lower pressure, the tubes being joined at their other
ends and having a third pressure transmitting tube (126) leading therefrom, the second
pressure transmitting tube having valve means (130) therein operable to permit a portion
of the higher pressure in the first pressure transmitting tube (122) to bleed into
the second pressure transmitting tube (124), leaving a resultant differential pressure
in the third pressure transmitting tube (126), and the adjustment means having means
(90) to control the pressure of the fuel at substantially said differential pressure.
12. A carburettor according to claim 11, in which the control means comprises a balancing
regulator (90) regulated by the differential pressure, the balancing regulator having
a fuel inlet (96) being responsive to said differential pressure and operable to permit
flow of fuel through fuel inlet at such a rate so as to maintain substantial equality
of pressure between the fuel and said differential pressure.
1. Vergaser mit: einem Luftkanal (16,18); einem Drosselventil (14), das über den Luftkanal
(16, 18) schiebbar montiert ist, um eine Drosselöffnung (26) einzustellen, eine Brennstoff-Zuführleitung,
die an eine Brennstoffmeßleitung (40) angeschlossen ist, welche sich über die Drosselöffnung
(26) erstreckt und entlang ihrer Länge einen Brennstoffauslaß (62) hat, um den Brennstoffstrom
in den Luftkanal (16, 18) zu verteilen und abzumessen, wobei die Größe des Brennstoffauslasses
(62) entlang der Meßleitung (40) variiert, und wobei das verschiebbare Drosselventil
die wirksame Länge des Brennstoffauslasses (62) verändert, dadurch gekennzeichnet,
daß die Größe des Brennstoffauslasses (62) kontinuierlich entlang der Meßleitung (40)
in der Richtung zunimmt, in der das Drosselventil zum Öffnen der Drosselöffnung gleitet,
so daß das Brennstoff-Luftverhältnis bei einem bestimmten Umgebungsluftdruck unabhängig
von einer Drosselventilverschiebung im wesentlichen konstant gehalten wird und daß
Mittel (40, 52; 124, 130; 114, 120) vergesehen sind, um das Brennstoff-Luftverhältnis
durch Einstellen der Druckdifferenz zwischen dem Brennstoffdruck stromaufwärts von
dem Brennstoffauslaß und dem Luftdruck am Brennstoffauslaß (62) einzustellen, wobei
die Druckdifferenz durch einen Luftdruck im Luftkanal (16, 18), der zwischen dem Gesamtluftdruck
und dem statischen (Luft)Druck im Luftkanal im Bereich der Brennstoffmeßleitung (40)
einstellbar ist, eingestellt wird, wobei die Mittel zum Einstellen des Brennstoff-Luftverhättnisses
Mittel zum Zuführen von Brennstoff zu der Brennstoffmeßleitung bei einem Druck besitzen,
der nicht größer als der gesamte Luftdruck in dem Luftkanal ist.
2. Vergaser nach Anspruch 1, wobei der Brennstoffauslaß eine Anzahl von Öffnungen
(Figur 8) aufweist, die axial entlang von zumindest einer Seite der Brennstoffmeßleitung
beabstandet sind.
3. Vergaser nach Anspruch 1, wobei der Brennstoffauslaß zumindest einen axialen Schlitz
(Figur 10) aufweist, der sich entlang einer Seite der Brennstoffzuführleitung erstreckt.
4. Vergaser nach Anspruch 1, 2 oder 3, wobei sich die Brennstoffmeßleitung (40) durch
eine komplementäre Längsoffnung (46) in dem Drosselventil (14) erstreckt und das Drosselventil
(14) auf der Meßleitung verschiebbar ist, um die Drosselöffnung einzustellen und die
wirksame Länge des Brennstoffauslasses (62) zu verändern.
5. Vergaser nach Anspruch 1, 2, 3 oder 4, mit Mitteln (58, 60) zum Einstellen der
axialen Anordnung der Brennstoffmeßleitung.
6. Vergaser nach einem der vorhergehenden Ansprüche, bei dem das Drosselventil (14)
zwischen Grenzwerten einstellbar ist, um eine maximale Drosselöffnung und eine minimale
Drosselöffnung zu schaffen, und ferner mit Mitteln (72) zum Einstellen der minimalen
Drosselöffnung.
7. Vergaser nach einem der vorhergehenden Ansprüche, wobei das Einstellmittel Mittel
(50-60) aufweist, um die Brennstoffzuführleitung um ihre Längsachse zu drehen, um
die Umfangsanordnung des Brennstoffauslasses (62) zu verändern.
8. Vergaser nach einem der Ansprüche 1 bis 6, wobei das Einstellmittel eine Druckmeßleitung
(118) in dem Luftkanal (16, 18) aufweist, und wobei Mittel (90, 114-116) vorgesehen
sind, um den Brennstoffdruck unter Verwendung des gemessenen Drucks zu steuern.
9. Vergaser nach Anspruch 8, bei dem an einer Seite der Meßleitung ein Einlaß vorgesehen
ist und wobei die Meßleitung drehbar ist, um den Umfangsort des Einlasses und dadurch
den gemessenen Druck zu verändern.
10. Vergaser nach Anspruch 8 oder 9, wobei das Steuermittel einen Ausgleichsregler
(90) aufweist, der von dem gemessenen Druck geregelt wird, wobei der Ausgleichsregler
einen Brennstoffeinlaß besitzt, der den Brennstoffdruck in Abhängigkeit von dem gemessenen
Druck regelt und der so betreibbar ist, daß er eine Brennstoffströmung durch den Brennstoffeinlaß
mit einer Rate zuläßt, die einen wesentlichen Druckausgleich zwischen dem Brennstoff
und dem gemessenen Druck bewirkt.
11. Vergaser nach einem der Ansprüche 1 bis 6, wobei das Einstellmittel eine erste
Druckübertragungsleitung (122) aufweist, von der ein Ende so ausgerichtet ist, daß
es hohen Luftdruck mißt und wobei eine zweite Druckübertragungsleitung (124) mit einem
Ende so positioniert ist, daß ein tieferer Druck gemessen wird, wobei die beiden Leitungen
mit ihren anderen Enden verbunden sind und davon eine dritte Druckübertragungsleitung
(126) abzweigt, wobei die zweite Druckübertragungsleitung eine Ventileinrichtung (130)
enthält, die so betreibbar ist, daß ein Teil des höheren Drucks in der ersten Druckübertragungsleitung
(122) in die zweite Druckübertragungsleitung (124) abgelassen wird, was zu einem Differenzdruck
in der dritten Druckübertragungsleitung (126) führt, und wobei das Einstellmittel
Mittel (90) zum Steuern des Brennstoffdruckes bei im wesentlichen diesem Differenzdruck
aufweist.
12. Vergaser nach Anspruch 11, bei dem das Steuermittel einen Ausgleichsregler (90)
aufweist, der durch den Differenzdruck geregelt wird, wobei der Ausgleichsregler einen
Brennstoffeinlaß (96) besitzt, der auf den Differenzdruck anspricht und der so betreibbar
ist, daß er eine Brennstoffströmung durch den Brennstoffeinlaß mit einer solchen Rate
zuläßt, daß im wesentlichen Druckgleichgewicht zwischen dem Brennstoff- und dem Differenzdruck
aufrechterhalten wird.
1. Un carburateur comprenant: un passage d'air (16, 18), une soupape d'étranglement
(14) montée coulissante à travers le passage d'air (16, 18) pour régler une ouverture
d'étranglement (26), un tube d'alimentation en carburant connecté à un tube de mesure
de carburant (40) qui s'étend à travers l'ouverture d'étranglement (26) et a dans
sa longueur une sortie de débit de carburant (62) pour distribuer et mesurer le débit
de carburant dans le passage d'air (16, 18), la taille de la sortie de débit de carburant
(62) variant le long du tube de mesure (40), et la soupape d'étranglement coulissante
modifiant la longueur effective de la sortie de débit de carburant (62), caractérisé
en ce que la taille de la sortie de débit de carburant (62) croît de façon continue
le long du tube de mesure (40) dans la direction où la soupape d'étranglement coulisse
pour ouvrir l'ouverture d'étranglement, de façon à ce que le taux air-carburant soit
maintenu essentiellement constant à une certaine pression de l'air ambiant indépendamment
du changement de la soupape d'étanglement et pour cela des moyens (40, 52, 124,130,114,120)
sont fournie pour régler le taux air-carburant en réglant la différence de pression
entre la pression du carburant en amont de la sortie de débit du carburant et la pression
d'air à la sortie de débit du carburant (62), la différence de pression étant réglée
au moyen d'une pression d'air du passage d'air (16, 18) qui est réglable entre la
pression d'air totale et la pression (d'air) statique du passage d'air dans la partie
du tube de mesure du carburant (40), les moyens pour régler le taux air-carburant
possédant les moyens pour fournir du carburant au tube de mesure de carburant à une
pression qui ne soit pas plus élevée que la pression d'air totale dans le passage
d'air.
2. Carburateur selon la revendication 1, caractérisé en ce que la sortie de débit
de carburant comprend une pluralité d'ouvertures (figure 8) espacées axialement) le
long au moins d'un côté du tube de mesure du carburant.
3. Carburateur selon la revendication 1, caractérisé en ce que la sortie de débit
de carburant comprend au moins une fente axiale (figure 10) s'étendant le long d'un
côté du tube d'alimentation en carburant.
4. Carburateur selon la revendication 1, 2 ou 3, caractérisé en ce que le tube de
mesure de carburant (40) s'étend à traverse une ouverture complémentaire longitudinale
(46) dans la soupape d'étranglement (14), et la soupape d'étranglement (14) est coulissable
sur le tube de mesure pour régler l'ouverture d'étranglement et changer la longueur
effective de la sortie de débit de carburant (62).
5. Carburateur selon la revendication 1, 2, 3 ou 4, caractérisé en ce qu'il comprend
des moyens (58, 60) pour régler la position axiale du tube de mesure du carburant.
6. Carburateur selon l'une quelconque des revendications précédentes, caractérisé
en ce que la soupape d'étranglement (14) est réglable dans certaines -limites pour
ménager une ouverture d'étranglement maximum et une ouverture d'étranglement minimum,
et comprend en outre un moyen (72) pour fixer l'ouverture minimum d'étranglement.
7. Carburateur selon l'une quelconque des revendications précédentes, caractérisé
en ce que le moyen de réglage comprend des moyens (50, 60) pour faire tourner le tube
d'alimentation en carburant sur son axe longitudinal pour changer la position périphérique
de la sortie de débit de carburant (62).
8. Carburateur selon l'une quelconque des revendications 1 à 6, caractérisé en ce
que le moyen de réglage comprend un tube détecteur de pression (118) dans le passage
d'air (16,18) et des moyens (90, 114-116) pour régler la pression de carburant en
utilisant la pression détectée.
9. Carburateur selon la revendication 8, caractérisé en ce qu'il y a une entrée sur
un côté du tube détecteur, et le tube détecteur est rotatif pour changer la position
périphérique de l'entrée et ainsi changer la pression qui est captée.
10. Carburateur selon la revendication 8 ou 9, caractérisé en ce que le moyen de contrôle
comprend un régulateur d'équilibre (90) régulé par la pression captée, le régulateur
d'équilibre possédant une entrée de carburant contrôlant la pression de carburant
sensible à la pression captée et actionnable pour permettre le débit de carburant
à travers l'entrée de carburant à un taux tel qu'une égalité de pression essentielle
soit obtenue entre le carburant et la pression captée.
11. Carburateur selon l'une quelconque des revendications 1 à 6, caractérisé en ce
que le moyen de réglage comprend un premier tube transmetteur de pression (122) possédant
une extrémité orientée de façon à détecter une pression d'air élevée et un second
tube transmetteur de pression (124) possédant une extrémité placée de façon à détecter
une pression plus basse, les tubes étant joints à leurs autres extrémités et possédant
un troisième tube transmetteur de pression (126) partant de là, le second tube transmetteur
de pression possédant un moyen de soupape (130) actionnable pour permettre à une partie
de la pression plus élevée dans le premier tube transmetteur de pression (122) de
s'écouler dans le second tube transmetteur de pression (124), laissant apparaître
une pression résultante différentielle dans le troisième tube transmetteur de pression
(126), et le moyen de réglage possédant un moyen (90) pour commander la pression du
carburant essentiellement à la valeur de la pression différentielle.
12. Carburateur selon la revendication 11, caractérisé en ce que le moyen de contrôle
comprend un régulateur d'équilibre (90) régulé par la pression différentielle, le
régulateur d'équilibre possédant une entrée de carburant (96) sensible à ladite pression
différentielle et actionnable pour permettre l'écoulement de carburant à travers l'entrée
de carburant à un taux capable de maintenir une égalité essentielle de pression entre
le carburant et la pression différentielle.