Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02638116 2008-07-23
Attorney Docket: 1763-2
FUEL INTAKE FOR AN ENGINE
FIELD OF THE INVENTION
[oool] This invention relates to gasoline engines. In particular, this
invention relates to a
fuel intake which increases the efficiency of a two stroke gasoline engine.
BACKGROUND OF THE INVENTION
[0002I In two-stroke gasoline engines, the gasoline fuel is mixed with air in
the
carburetor and delivered to the cylinders. The fuel-air mixture is ignited in
the cylinder
and the energy used to provide the mechanical energy of the engine. Because of
the
inherent inefficiencies in the engine, the engine produces both mechanical
energy and
heat energy.
[ooo31 The carburetor is often connected to the engine via an intake manifold
which
communicates the fuel-air mixture from the carburetor to the engine. Often, a
rubber boot
is used between the engine and intake manifold to isolate the engine heat and
vibration
from the carburetor.
[0004) Atomized fuel contains small droplets of fuel mixed with air. Vaporized
fuel
contains the fuel in a gaseous state and mixed with air, a combination that
usually
provides superior burning properties and is more efficient in a two stroke
engine.
100051 However, delivering atomized fuel to the combustion chamber is
beneficial to the
cooling of the cylinder head as it absorbs heat from its surroundings as it is
vaporized.
Pre-heating of the atomized fuel also generally iinproves the burning
properties of the
engine.
[0006) If the fuel-air mixture enters the cylinder too hot, there is a
tendency for the
mixture to lose homogeneity, an effect that can negatively affect the burning
of the fuel
and therefore lower the efficiency of the engine.
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[00071 There are several techniques known in the prior art to heat the
incoming fuel-air
mixture using secondary sources of heat. For example, U.S. Patent No.
5,778,860 issued
July 14, 1998 to Garcia teaches the heating of a portion of the fuel using the
ainbient heat
of the engine compartment. Garcia teaches heating the liquid fuel before it is
atomized by
the carburetor. This requires adjustments be made to the preheating when the
external
ambient temperature changes, such as operating the engine on hot summer days.
In high
outside temperatures, less preheating of the fuel is required as the incoming
fuel is
already partially warmed before entering the intake manifold. Using this
design in cold
climate conditions reduces its effectiveness because the temperature of the
ambient
engine compartment is cooler. This disadvantage is due to its indirect heating
design,
namely that heat from the engine has to heat the ambient air which in turn
heats the
incoming fuel-air mixture.
[00081 The elongated fuel bypass taught in U.S. Patent No. 5,769,059 issued
June 23,
1998 to Wallace uses a bypass adjacent to the intake manifold to preheat the
fuel mixture.
It uses an elongated fuel air bypass of between three and twelve feet to
vaporize the fuel
air mixture, and heat from the ambient environment of the engine compartment
to heat
the fuel-air mixture passing through the bypass. Because the design relies on
heat from
the ambient environment, it uses a large surface requiring both length and a
large outside
diameter. This is expensive, cumbersome and requires additional compensating
devices
to compensate for its flaws. With the large amount of surface area, the design
is subject
to variations in the ambient temperature. In hot weather, it may overheat the
fuel mixture.
In cold weather, the elongated bypass will transfer a lot of heat through the
large surface,
requiring a heavier wall thickness in the bypass or a heat exchanger to
improving the
heating of the fuel mixture. After air supply, an injection system and a
backfire safety
device are other compensating devices taught for this design to work properly.
Further,
this design is suitable only for a four stroke engine, as its use on a two
stroke engine may
impair the scavenging of exhaust in the combustion chamber because of the
turbulence
introduced in the bypass to increase the mixing of the fuel-air mixture.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In drawings which illustrate by way of example only a preferred
embodiment of
the invention,
[oo10] Figure IA is a side elevation of the intake assembly and support
assembly.
[00111 Figure 1 B is a front elevation of the intake assembly and support
assembly of
Figure 1A.
[0012] Figure 2A is an end elevation of the intake tube.
[0013] Figure 2B is a cross-section of the intake tube taken along the line B-
B in Figure
2A.
[0014] Figure 3 is an end elevation showing the aluminium retaining washer
used in the
preferred embodiment to mount the intake to the intake port of the engine.
[0015] Figure 4 is an elevation of the oil injunction tube.
100161 Figure 5 is a cross section of the carburetor boot.
[0017] Figure 6 is a plan view of the carburetor plate.
100181 Figure 7 is a plan view of the support plate.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Figures 1A and 1B show a preferred embodiment of the intake assembly,
including the intake tube 1, of the invention mounted to a two-stroke engine.
For multi-
cylinder engines, either identical tubes can be used for each cylinder or a
distributor type
arrangement can be employed where a single port at the carburetor is divided
into
separate tubes for each cylinder.
[0020] Generally, the intake tube 1 is a short straight tube connecting the
carburetor
directly to the engine. The thermal conductivity of the material, the length,
diameter and
thickness of the tube, and the thermal coupling of the intake tube I to the
engine are
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selected to optimize the vaporization of the fuel-air mixture passing into the
engine.
Selecting the wall thickness of the tube is the preferred technique for
optimizing the
vaporization of the fuel-air mixture.
[00211 In the description that follows, the preferred embodiment will be
described in the
context of a 500 cubic centimetre (cc.) two cylinder piston ported two stroke
engine with
250 cc. cylinder displacement per cylinder. However, it will be appreciated
that the
intake tube 1 of the invention can be used with other two-stroke engines and
the invention
is not intended to be limited to the particular embodiment shown and described
herein by
way of example.
100221 The intake tube 1 is illustrated in Figures 2A and 2B. In the preferred
embodiment
illustrated, the intake tube 1 of the invention comprises a tube approximately
5.5 inches
long with a 1.4 inch inside diameter. The wall thickness of the tube is
preferably 3/32
inches. The intake tube 1 has a flange 2 flaring outwardly at one end,
preferably formed
integrally with the intake tube, in thermal contact with the cylinder intake
port 6. The
flange 2 facilitates heat transfer between the engine 5 and the intake tube 1.
In the
embodiment shown, the diameter of the flange 2 at the engine is 2.25 inches.
The flange
provides a large surface area between the engine and the intake manifold to
aid in heat
transfer from the engine to the intake tube 1.
[00231 Disposed at an intermediate portion of the intake tube 1, preferably
around the
axial centre, is a copper oil injection tube 20 which extends through the
intake tube 1
generally along a diameter (i.e. generally at the radial centre of the intake
1). The copper
oil injection tube 20 may be installed substantially vertically within the
intake 1(when
mounted) and flush with the outside diameter of the intake at the top 22. At
the bottom of
the intake, the injection tube 20 extends out of the intake by a short
distance, for example
about 0.375 inches. Alternatively, the injection tube 20 may extend only
partially through
the intake tube 1.
100241 Referring to Figure 4, the oil injection tube 20 in the embodiment
shown is
formed from a copper tube with an outside diameter of approximately 0.144
inches and
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an inside diameter of approximately 0.059 inches. It is silver-soldered to the
intake tube 1
at the top 22, closing the upper end of the tube 20, and silver soldered to
the intake at the
bottom 24 to provide a seal between the wall of the intake tube I and the
injection tube
20. At the centerline of the intake tube 1, a small orifice 26 is provided
(for example
drilled) through the wall the injection tube 20, preferably with a diameter of
0.044 inches.
The orifice 26 is directed toward the flanged end of the intake tube 1(that
will be
mounted to the engine 5).
100251 At the bottom of the intake 24, the outside of the injection tube 20
preferably
narrows as at 25 to facilitate coupling with an oil injection hose (not
shown), preferably
to an outside diameter of 0.125 inches to be compatible with a 1/8 inch or 3mm
oil
injection hose (not shown). The oil injection hose is connected to the
engine's oil
injection pump (not shown). Oil can thus be pumped from the engine's oil
injection
puinp, through the oil injection hose to the oil injection tube 20 and out the
orifice 26 into
the intake tube 1. It will be appreciated that providing the connection point
to the oil
injection hose at the bottom of the intake 1 is for convenience only and does
not limit the
positioning or orientation of the oil injection tube 20.
100261 Referring to Figure 3, the intake tube 1 is mounted on the engine using
an
aluininium washer 30, as can be seen in Figure lA. The washer 30 is installed
over the
intake tube 1 and is engaged to the flange 2. Bolts are disposed through holes
31 to secure
the washer 30 to the engine. The dimensions of washer 30 may be selected to
match (or to
be larger than) the flange of the intake 1, which as shown has a diameter of
1.635 inches.
The washer 30 should preferably be less than 3/16 inch thick to prevent
excessive heat
retention by the aluminium washer 30. The dimensions of the washer 30 should
allow
some slight movement between the washer 30 and intake tube I to allow for
differing
rates and extents of thermal contraction and expansion between the pai-ts. The
washer 30
may be connected using two intake port studs 32 that are integrated with the
engine 5. It
will be appreciated that the means for attaching the intake tube 1, and
waslier 30 may
depend on the arrangement and model of the engine. Each aluminium washer 30 is
preferably mounted using a washer 33, a bowed spring washer 34 and a locking
nut 35,
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such as that sold under the name Nylocko, as shown in Figure IA. The locking
nuts 35
should preferably be tightened so that the spring washers are about 2/3 flat.
The spring
washer 34 is used to maintain pressure between the intake tube I and the
engine 5 at
different temperatures during engine operation. The joint between the intake
tube I and
the engine 5 should be able to slide to prevent galling of the surface or
eventual cracking.
100271 The end of the intake tube I opposite the flange 2 has a radiused
undercut 28
which reduces the outside diameter of the intake tube I to a diameter of about
1.5 inches.
A carburetor boot 40, such as the Mikuni VM 34 rubber carburetor boot as
shown in
Figure 5, is placed over the end of the intake tube I opposite the flange 2.
The undercut
28 engages with the collar of a carburetor boot 40 to removably lock the
carburetor boot
40 to the intake tube 1. The carburetor boot 40 is bolted, using bolt holes
42, to a
carburetor plate 50, shown in Figure 6, through bolt holes 52. The same bolts
are used to
bolt a second carburetor boot 60, which may be substantially the same as
carburetor boot
40 but in a reverse orientation, to the first carburetor boot 40 through the
carburetor plate
50. The second carburetor boot 60 is in turn attached to the engine carburetor
65. This
assembly aliows the intake tube I to be mounted to the carburetor while
allowing the fuel
mixture to pass from the carburetor through open centres 44, 54 in the pair of
carburetor
boots and the carburetor plate 50, respectively, into the intake tube 1. A
fuel resistant
silicone may be used to seal the carburetor boots 40. The inside diaineter of
intake tube 1,
and the openings through carburetor boots 40 and carburetor plate 50, are
preferably as
large as the engine intake port and the passage through the carburetor so that
the intake
assembly of the invention does not substantially restrict the flow of fuel
mixture to the
engine and starve the engine of fuel. In the preferred embodiment, the inside
diameter of
the intake tube 1 is slightly larger than inside diameter of the carburetor
port.
100281 Figures IA and 1 B show the assembly connecting the carburetor 65 to
the engine
5. Supporting plates 70 and supporting bracket 80 support the intake tube I on
the engine
base 90. The precise shape and arrangement of the supporting plates and
brackets 70, 80
will depend on the design and shape of the engine as will be apparent to a
person skilled
in the art.
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[0029] With reference to the above description, the following section
describes how the
inventor believes the invention works. However, this is only one theory which
might
explain the operation of the invention, and no representation is made that the
operation is
actually as described.
[00301 The general operation of the intake assembly 1 relies upon engine heat
transferred
by conductivity from the engine 5 to the intake tube 1 through the contact
surface area
between the engine 5 and the flange 2. The high thermal conductivity of the
copper intake
tube 1 allows the heat to transfer to the intake tube 1, exposing the fuel
mixture with
sufficient heat to homogenize the fuel droplets without substantially heating
the fuel
mixture temperature.. The length, diameter and thickness and other dimensions
of the
intake tube 1 are designed to vaporize substantially all of the fuel-air
mixture before it
enters the engine but not substantially heat the mixture. In the preferred
embodiment, the
primary factor is the wall thickness of the intake tube 1.
[00311 Preferably, in normal engine operation, the intake tube 1 will be
substantially at
the ambient temperature of the engine compartment and the fuel will be
homogenized.
[00321 Further, heat from the intake tube 1, the oil injection tube 20 and the
fuel-air
mixture aids in the vaporization of the oil injected from the oil injection
tube 20. The heat
provided by the walls of the intake tube 1, the oil is at least partially
vaporized and mixed
with the fuel mixture. The main purpose of the oil injected into the fuel-air
mixture is to
lubricate the engine. In the experience of the inventor, less oil is required
to lubricate an
engine when the oil is vaporized.
[00331 As the atomized fuel mixture enters the intake tube 1, heat from the
intake tube I
vaporizes the mixture, especially around the circumference of the intake tube
I interior,
where the fuel mixture is in direct contact with the intake tube 1. As the
fuel mixture
approaches the copper oil injection tube 20, there is sufficient heat
available to fully
vaporize the remaining atomized fuel in the center of the intake tube 1.
Further, the heat
from the oil injection tube 20 itself may aid with vaporizing the fuel mixture
along the
axial centre of the intake tube 1. After passing the oil injunction tube 20,
some heat may
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be transferred from the fuel mixture to the oil to vaporize the oil. It is
desirable that all the
heat that is transferred to the intake tube I be used in the vaporization
process of the fuel
mixture and oil, resulting in a minimal temperature increase of the fuel
mixture.
I00341 In the preferred embodiment, the dimensions of the intake tube 1,
including the
length and thickness of the copper are designed so that the intake tube I
remains at
approximately the same temperature as the fuel-air mixture temperature
entering the
intake from the carburetor during most engine operating conditions.
100351 Preferably, the fuel mixture is vaporized before the oil is introduced
in the intake
tube 1. In the inventor's experience, separate vaporizations of the fuel
mixture and oil
results in a more consistent vaporization over a variety of engine operating
conditions.
[0036] The dimensions of the oil injection tube 20 are important so that the
oil is not over
heated. The thickness of the walls of the oil injection tube 20 and the size
of the orifice 26
affect the rate at which the heat from the intake tube 1 is transferred to the
injected oil.
Since some heat is transferred to the oil, the viscosity of the oil is reduced
and the orifice
26 may be made smaller. The size of the orifice 26 affects the rate at whicli
oil is injected
into the intake 1.
100371 Further, the oil injection tube 20 must have a small outside diaineter
in relation to
the inside diameter of intake tube 1, as mentioned above, so it does not cause
undue
turbulence in the flow of fuel mixture to the engine. Turbulence in the fuel
mixture is
undesirable and for two-stroke engines can interfere with the scavenging
process to expel
burnt fuel from the cylinder. Turbulence may cause inconsistent fuel
atomization and or
inconsistent control of fuel vaporization.
[0038] It will be appreciated that the use of an oil injection tube 20 may not
be required
in some embodiments of the invention. For example, a four stroke may not
require oil
injection and it is possible to pre-mix the oil with the fuel for use in a two
stroke engine.
[0039] In the applicant's experience, the use of the invention in the
preferred embodiment
requires substantially less oil than the typical 50:1 fuel to oil mix and
preferred operation
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uses a reduction in the oil injection ratio of approximately 35:1. The oil
injection pump
volume was also reduced to half from the stock 50:1.
[0040] Depending on the specific engine design, it may be necessary to modify
the
exhaust or ports of the engine to address overheating of the homogenized fuel
mixture in
the exhaust pipe before being drawn back in to the cylinder. Preferrably, the
exhaust `y'
pipe is extended between one cylinder exhaust port and the joint with the
other cylinder
exhausts.
100411 Copper is used in the preferred embodiment because of its high thermal
conductivity. In the preferred embodiment, tellurium copper alloy in
particular is used
because it is easier to machine than copper. A person skilled in the art will
recognize that
other metals and alloys with high thermal conductivity could be used,
including plain
copper.
[00421 Proper alignment of the intake tube 1 with the intake ports and the
carburetor is
important for smooth vibration free operation. As is known to someone skilled
in the art,
it may be necessary to make adjustments, including shimming and bracing, to
the
invention to allow vibration free operation and efficiency. Especially
important to this
invention is the contact between the engine 5 at the intake ports and the
copper flange 2
of the intake tube 1. Proper contact is required for the thermal conductivity
between the
engine and the intake, therefore it is preferred that the intake ports and
flange be
machined flat and have a good flat surface.
[0043] Various embodiments of the present invention having been thus described
in
detail by way of example, it will be apparent to those skilled in the art that
variations and
modifications may be made without departing from the invention.
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