Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02483413 2004-11-09
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GASEOUS FUEL INJECTOR HAVING HIGH HEAT TOLERANCE
This is a divisional application of Canadian Patent Application Serial
No. 2,330,724 filed on January 10, 200I.
Field Of The Invention
The present invention generally relates to fuel injectors, and more
particularly high pressure gaseous fuel injectors for internal combustion
engines. It should be understood that the expression "the invention" and the
like encompasses the subject matter of both the parent and the divisional
applications.
Background Of The Invention
The natural gas transmission industry and chemical process industries
use a Large number of Large-bore, 2-stroke and 4-stroke natural gas engines
for
compressing natural gas. For example, industries use these engines for such
purposes as maintaining pressure in the extensive network of natural gas
pipelines that supply residential housing and commercial businesses. The
network of natural gas pipelines typically operate at high pressures in the
neighborhood of between 500 psig and 1000 psig.
These large-bore, natural gas engines may be powered by a small
portion of the natural gas passing through the pipelines. However, before
being injected into the engine, the pressure of the gas is significantly and
substantially reduced. Gaseous fuel is typically injected into these cylinders
at Low pressures (far example, 15 psig to 60 psig by mechanically actuated
fuel injectors, such as that disclosed in Fisher, U.S. Patent No. 4,365,756).
The problem with low pressure injection is that the fuel pressure provides
little kinetic energy with which to induce cylinder charge mixing. There is
ample evidence that the fuel and air in these large bore engines are not well
mixed and as such exhibit poor combustion stability, high misfire rates and
significant cycle-to-cycle variations in peak pressure. As a result, these
3 o engines are not efficient and also are environmentally detrimental,
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contributing to approximately 10% of the total NOx production in the United
States from stationary combustion sources. according to estimates.
The concept of using high pressure fuel delivery to enhance fuel
mixing in these engines has been proposed as a means to improve efficiency
S and environmental emissions from these engines. However, retrofitting
existing engines provides a significant hurdle because these engines are
manufactured by different companies and also vary in size. Moreover,
injecting fuel at high pressure as opposed to low pressure requires the fuel
injectors to operate under extremely high operating pressures which in turn
greatly increases stresses and powering requirements for opening and closing
the valves. A key requirement for any proposed high pressure fuel injector is
reliability. These large-bore, natural gas engines typically run continuously
over long time periods, meaning that any suitable fuel injector must be
capable of reliably enduring very long operating cycles of the engine. It is
1 S desirable for example, that the fuel injectors reliably operate over
several
hundred million continuous cycles of the engine (about one to two years
before replacement). As such, a valve must achieve reliability over this long
time period or operating interval. Fuel injectors of the prior art such' as
that
disclosed in Fisher, U.S. Patent No. 4,365,756 are not capable of reliably
sealing and accurately controlling the injection of gas at high pressure:
Only.
recently have economic and environmental pressures on the gas industry
resulted in justification for advances in fuel injection technology. For at
least
the foregoing reasons, commercial large bore 2-stroke and 4-stroke natural gas
engines continue to be fueled at low pressure by conventional low pressure
fuel injectors.
Summary Of The Invention
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It is the general aim of the present invention to provide a commercially
reliable and practical fuel injector for injecting high pressure gaseous fuel
(eg.
around 300-700 psi or more) into combustion engines:
It is an object of the present invention according to one aspect to
provide a fuel injector that can withstand the forces of high pressure gaseous
fuel and has a long service operation but does not leak either gaseous fuel or
hydraulic fluid to the external environment.
It is another object of the present invention according to another aspect
to provide a fuel injector that is universal in that the fuel injector
assembly can
be easily adapted without any or any substantial redesign to fit and operate
as
desired on the various types and sizes of combustion engines in industry.
It is a another abject of the present invention according to another
aspect to provide a highly reliable fuel injector, and specifically one that
is not
I S susceptible to thermal damage from the engine.
It is another object to provide a fuel injector with increased operating
life, whereby gas leakage, eventually expected from o-rings and sliding gas
seals, is captured and safely and properly disposed of, on an ongoing basis;
not requiring engine shut-down to replace the injector valve.
In accordance with these and other objectives, the present invention
provides a fuel injector cartridge and a fuel injector incorporating the same,
that uses the relatively cool gaseous fuel passing through the valve to
directly
cool the exposed surface of the valve and therefore Iimit the amount of heat
transferred from the engine cylinder to the gas seals. The fuel injector
2S cartridge includes a valve body having an outer sleeve, and upper and lower
guide collars mounted in the sleeve. The stem of an elongate valve extends up
into and through the guide collars for radial retention: The valve is slidable
through the guide collars for linear reciprocating movement between open and
closed positions. The guide collars are separated by a cooling chamber
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(which in the preferred embodiment doubles as a spring chamber) in which a
portion of
the valve stem is exposed. The sleeve has at least one cooling port (that
takes the
preferred form of a plurality of cross-holes) that allows the cool gaseous
fuel to pulsate
into and out of the cooling chamber correspondingly as the valve opens
and.closes.
During opening of the valve, gas pressure drops in the gas passageway,
resulting in a
suction effect sucking the now heated gas (by virtue of direct contact with
the valve,
spring and guides) out of the cooling chamber. During closing of the valve,
the pressure
increases in the gas passageway forcing new more cool .gaseous fuel into the
cooling
chamber.
More specifically, the present invention provides a fuel injector comprising a
tubular cartridge housing for injecting gaseous fuel into an engine, a fuel
injector
cartridge inserted into the cartridge housing, the cartridge having a tubular
cartridge body,
a gas passageway generally between the cartridge body and the cartridge
housing for
communicating gaseous fuel to the engine through an outlet port, an elongate
valve
slidably retained in the cartridge body, the valve being linearly movable
between open
and closed positions to open and close the outlet port, a metal O-ring axially
compressed
between the tubular cartridge housing and the cartridge body, and a spring
mechanism
urging the cartridge body axially against the tubular cartridge housing
compressing the
metal O-ring therebetween and providing a seal between the tubular cartridge
body and
the cartridge housing, wherein the cartridge body includes a sleeve, and upper
and lower
guide collars in the sleeve, the upper and Iower guide collars being spaced
apart and
separated by a cooling chamber, and further comprising at least one cooling
port defined
in the sleeve adapted to communicate gaseous fuel into and out of the cooling
chamber
for cooling an exposed surface of the valve.
The present invention also provides a fuel injector comprising a tubular
cartridge
housing for injecting gaseous fuel into an engine, a fuel injector cartridge
inserted into the
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cartridge housing, the cartridge having a tubular cartridge body, a gas
passageway
generally between the cartridge body and the cartridge housing for
communicating
gaseous fuel to the engine through an outlet port, an elongate valve slidably
retained in
the cartridge body, the valve being linearly movable between open and closed
positions to
open and close the outlet port, a metal O-ring axially compressed between the
tubular
cartridge housing and the cartridge body, a spring mechanism urging the
cartridge body
axially against the tubular cartridge housing compressing the metal O-ring
therebetween
and providing a seal between the tubular cartridge body and the cartridge
housing, and an
electrohydraulic valve assembly for actuating the elongate valve, the spring
mechanism
to compressed between the electrohydraulic servo valve and the cartridge body.
The present invention also provides a fuel injector comprising a tubular
cartridge
housing for injecting gaseous fuel into an engine, a fuel injector cartridge
inserted into the
cartridge housing, the cartridge having a tubular cartridge body, a gas
passageway
generally between the cartridge body and the cartridge housing for
communicating
gaseous fuel to the engine through an outlet port, an elongate valve slidably
retained in
the cartridge. body, the valve being linearly movable between open and closed
positions to
open and close the outlet port, a metal O-ring axially compressed between the
tubular
cartridge housing and the cartridge body, and a spring mechanism urging the
cartridge
body axially against the tubular cartridge housing compressing the metal O-
ring
2o therebetween and providing a seal between,the tubular cartridge body and
the cartridge
housing, wherein the fuel injector cartridge has a length selected from a
plurality of
lengths, further comprising a shim adjusting the length of the cartridge to a
predetermined
length and modifying the force provided by the spring mechanism to provide a
predetermined load on the metal O-ring sufficient to provide a seal between
the tubular
cartridge housing and the fuel injector cartridge to prevent transmission of
gas
therebetween.
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4b
The present invention also provides a fuel. injector comprising a tubular
cartridge
housing for injecting gaseous fuel into an engine, a fuel injector cartridge
inserted into the
cartridge housing, the cartridge having a tubular cartridge body, a gas
passageway
generally between the cartridge body and the cartridge housing for
communicating
gaseous fuel to the engine through an outlet port, an elongate valve slidably
retained in
the cartridge body, the valve being linearly movable between open and closed
positions to
open and close the outlet port, a metal O-ring axially compressed between the
tubular
cartridge housing and the cartridge body, a spring mechanism urging the
cartridge body
axially against the tubular cartridge housing compressing the metal O-ring
therebetween
and providing a seal between the tubular cartridge body and the cartridge
housing, and a
cavity formed into the first end of the fuel injector cartridge having a load
pad arranged
therein, the spring mechanism acting on the load pad.
It is an aspect of the present invention that the lower collar guide is a self
lubricated high temperature graphite/carbon bushing. A bushing retainer is
provided
below the bushing to prevent any chips which may form from dropping into the
outlet
port.
It is another aspect of the present invention that a metal O-ring is used at
the
between the bottom of the cartridge and the cartridge housing to provide a
seal axially
between the cartridge housing and the cartridge body. The metal O-ring can
withstand
2o the high temperatures nearest to the cylinders of the engine and provide a
highly reliably
seal at the same time. Means in the preferred form of load washers engage the
other.axiaI
end of the valve housing to axially compress the metal O-ring. A force in the
rough
neighborhood of about 10,000 is necessary to maintain a seal for high pressure
fuel
injection over about 300 psi.
Brief Description Of The Drawings
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Figure 1 is a cross-sectional view of a high pressure fuel injector
assembly in accordance with a preferred embodiment of the present invention,
illustrated in a closed position.
Figure 2 is a cross-sectional view of a high pressure fuel injector
5 assembly similar to that in FIG. 1 but in an open position.
Figure 3 is an enlarged cross sectional view of a portion of the high
pressure fuel injector illustrated in FIG. 1.
Figure 4 is an enlarged cross sectional view of another portion of the
high pressure fuel injector illustrated in FIG. 1.
Figure 5 is an enlarged cross-sectional view of the high pressure fuel
injector assembly of FIG. 1 but taken about a different plane to indicate the
provision of the gas/oil outlet.
Figure 6 is a schematic illustration of the high pressure. fuel injector
assembly of FIG. 1 in an engine system environment.
Figure 7 is a perspective and partly schematic illustration of multiple
high pressure fuel injector assemblies in an engine system environment and
mounted to an engine.
Figure 8 is a perspective view of the high pressure fuel injector
assembly of FIG. 1.
Figure 9 is a perspective view of the high pressure fuel injector
assembly of FIG. l, but with a different embodiment of the fuel injector
housing.
While the invention will be described in connection with certain
preferred embodiments, there is no intent to limit it to those embodiments. On
the contrary, the intent is to cover all alfernatives, modifications and
equivalents as included within the spirit and scope of the invention as
defined
by the appended claims.
Detailed Description Of The Preferred Embodiments
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6.
Referring to the cross section of FIG. I, the present invention is
embodied in a high pressure fuel injector assembly 20. The high pressure fuel
injector assembly 20 generally comprises a fuel injector 22 and an
electrohydraulic valve assembly 24. In general, the electrohydraulic valve
assembly 24 hydraulically operates the fuel injector 22 to successively inject
gaseous fuel such as natural gas into the cylinders of an engine 121. A partly
schematic illustration of an engine I2I with multiple fuel injector assemblies
20 is illustrated in FIG. 5. The disclosed fuel injector assembly 20 provides
a
commercially reliable and practical fuel injector for injecting high pressure
I O gaseous fuel (eg. around 300-700 psig, but also including greater and
lesser
pressure) into combustion engines, thereby improving the efficiency of the
engine and reducing the environmental emissions therefrom. Detail below
will first be given to the structure and function of the high pressure fuel
injector assembly 20 as shown in FIG. 1 and then to an exemplary engine
operating environment for the assembly 20.
Although electrohydrauIic valves are not believed to have been
previously applied to the present art, it should be noted that
electrohydraulic
valves and associated mounting assemblies are generally known in other
related fields of art. As such, for purposes of the present invention, the
2 4 electrohydraulic valve assembly 24 is intended to have a broad meaning and
may include an electrohydraulic valve 2b, and a mounting block 28 for
mounting the electrohydraulic valve 26 to the fuel injector cartridge 22. A
mounting flange 30 secures the entire assembly 20 to the engine 121 via
conventional fasteners or bolts as shown in FIG. 7. In the preferred
2 5 embodiment, the electrohydraulic valve 26 includes an electrical driver 23
such as an onloff solenoid and a three-way control valve 25. The three way
control valve 25 has a high pressure inlet 27 connected to a pressurized
hydraulic supply of oil or other-suitable hydraulic fluid and a low pressure
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outlet 29 connected to a lower pressure sump of oil. In response to external
electrical pulses or signals from the electronic engine control, the
electrical
driver 23 switches the control valve 25 between two positions to successively
connect an output 31 alternatively to the high pressure inlet 27 and the low
pressure outlet 29. This provides successive hydraulic signals and also
alternates the direction of hydraulic flow between the, electrohydraulic valve
28 and the fuel injector cartridge 22. As illustrated in FIG. 5, the mounting
flange 30 may provide an external gas inlet port 33 for connecting a fuel
supply to the inlet of the cartridge and an external gas/oil outlet port 35
for
connection to a gas oil separator, the function of which will be described in
further detail below.
Many aspects of the present invention are directed toward the fuel
injector 22 which is operated by any suitable form of hydraulic signals of a
hydraulic type fluid such as oil. Hydraulic actuation provides sufficient
force
to actuate the valve 46 despite large opposing forces due to the high gaseous
fuel pressures, friction, and mechanical spring forces in the cartridge 34.
The
fuel injector 22 generally includes an outer tubular cartridge housing 32 and
an. fuel injector cartridge 34 mounted therein. In the preferred embodiment,
the cartridge housing 32 includes a hollow and cylindrical body tube 36, a
nosepiece 3 8, and a mounting flange 30, all brazed together, and a nozzle 40
press ft into the nose piece 38. Although the nozzle 40 could be integrally
provided by the nose piece 38, providing a separate nozzle 40 allows for easy
design modifications of the nozzle which can be suited to different sizes or
types of engines. The nozzle 40 regulates and optimizes dispersion and
mixing of the gaseous fuel in the cylinders of the engine and as such improves
environmental emissions and efficiency of the engine. In the preferred
embodiment, one end of the cartridge housing 32 is closed by the
electrohydraulic valve assembly 24 and the other end of the outer housing 32
is closed by the combination of the nose piece 38 and the end portion of the
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fuel injector cartridge 34. The cartridge housing 32 contains a gas
passageway 41 for communicating gaseous fuel from the gas inlet port 33 to
the nozzle 40. In the preferred embodiment, the gas passageway 4I is a large
annular chamber between the housing 32 and the cartridge 34. The volume of
this chamber (gas passageway 41) is maximized to provide a large local
reservoir. This large gas reservoir serves to maintain desirably high gas
injection pressure throughout the injection event.
The fuel injector cartridge 34 generally comprises a generally
cylindrical cartridge body 42 that houses a cylindrical piston 44 and an
elongate valve 46. In the preferred embodiment, the cartridge body 42 is
generally of two piece construction, including a lower valve body 48 and an
upper actuator body 50 screwed together via interfitting threads or otherwise
secured together. The combination of the stationary components, eg. the
cartridge body 42 and the outer cartridge housing 32, provide a stationary
support housing that provides the gas passageway 41 into the engine cylinder
and supports the moving components such as the piston 44 and valve 46.
Although it will be appreciated that in alternative embodiments the support
housing may be provided by fewer or more components. The actuator body
50 defines a cylindrical bore or control chamber 52 in which the piston 44 is
slidably mounted for linear reciprocating movement. The control chamber 52
is connected by a drilled passage 54; connector tube 56, and orifice plug 71
to
the output 3 I of the electrohydraulic valve 26 for receiving hydraulic
operating signals. The end of the drilled passage 54 provides a hydraulic
input for receipt of hydraulic signals:
2 5 The valve body 48 generally includes a steel body sleeve 58 and upper
and lower spaced apart cylindrical collar guides 60, 62. In the preferred
embodiment, the upper guide 60 is a solid machined steel member while the
lower guide 62 is a self lubricating, high temperature, carbon/graphite
bushing
formed from a commercially available material. The lower guide 62 is press
fit into the sleeve 58. One potential problem with use of carbon/graphite
material is fragility and the susceptibility to chipping at the edges. As
such, a
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steel washer or other bushing retainer 63 is seated in a recess in the sleeve
58
below the graphite bushing. The bushing retainer 63 prevents graphite or
carbon chips from dropping down and potentially lodging between the valve
46 and valve seat 68. The valve 46 is slidably mounted through axially
aligned Bores in the guides 60, 62 for linear reciprocating movement between
open and closed positions. The guides 60, 62 thus support and guide the
linear reciprocating movement of the valve 46. As illustrated, the end portion
of the valve body 48 closes one end of the cartridge housing 32. The sleeve
58 defines a frusto-conical valve seat 68 surrounding an outlet orifice 70
that
provides for discharge of gaseous fuel into the cylinders of the engine. To
ensure correct alignment of the valve seat 68 and the bore of the lower guide
62, the inner diameter of the conical seat 68 and the inner diameter of the
bore
in the guide 62 are simultaneously or sequentially precision ground, thereby
assuring accurate alignment. This provides precise alignment of the valve
with its seat, resulting in long seat life, low gas leakage, and therefore
more
precise and accurate control over fuel injection. The lower end portion of the
valve body 48 also includes cross holes 72 formed in the sleeve 58 and below
the lower guide 62 to extend the gas passageway 41 to the outlet orifice 70.
A helical compression spring 66 is mounted in a spring chamber 64
2 0 between the sleeve 5 8 and the valve 46 (surrounding the valve 46). The
spring
66 biases the valve 46 to a closed position as shown in FiG. 1 in which an
enlarged frusto-conical closure member 74 on the vale 46 is seated against
the valve seat 68 along a circular contact. Preferably, the respective slope
or-
angles of the mating conical surfaces between the seat 68 and the closure
2 5 member 74 are offset slightly by a degree or more to ensure tight circular
contact which prevents leakage of gaseous fuel into the cylinders of the
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engine. As shown in FIG. 3, the spring 66 engages a disc shaped spring
retainer 76 which is secured to the valve 4b by keepers 78. The spring
provides a large force sufficient to prevent the high pressures of the gaseous
fuel from causing fuel leakage into the engine's cylinder while the valve is
5 closed. Although the spring 66 could be eliminated if a 4-way actuating
valve
was provided in the electrohydraulic valve in which the piston would be
configured to be hydraulically actuated both ways to both open and closed
positions by high pressure hydraulic signals, the spring 66 performs the
necessary function of a fail-safe, in that the spring 66W echanically
maintains
10 the valve 46 in the closed position in the event of failure of the
electrohydraulic valve or the hydraulic pressure supply.
In the preferred embodiment, the valve 46 is a separate member from
the piston 44, but another embodiment of the present invention may integrally
provide the two or otherwise connect the two together. These and other
possibilities are intended to be covered by all of the claims appended hereto.
The piston 44 includes a reduced diameter nose 80 which contacts the top
surface of the valve. Surrounding the nose 80 is a seafing surface 82 which is
adapted to engage the top surface of the upper valve guide 60 acting as a
mechanical stop to control the stroke or maximum distance of linear
movement of the valve 46, and thereby the fuel injection rate.
To open the valve 46, the piston 44 is actuated in response to high
pressure hydraulic signals or pulses from the electrohydraulic valve 26. High
pressure hydraulic signals result by a connection between the output 31 and
the high pressure inlet 27. High pressure hydraulic signals received in the
control chamber 52 overpower the force of the spring and linearly actuate the
valve 46 to an open position as illustrated in FIG. 2 in which the closure
member 74 is lifted off of the valve seat 68 to allow passage of gas through
the outlet orifice 70 and into the corresponding cylinder of the engine.
As or after the valve 46 opens, the electrohydraulic valve 26 ends the
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high pressure hydraulic signal and switches the connection to the output 31 by
connecting the output to the lower pressure outlet 29. The spring 66
automatically returns the valve 46 to the closed position, causing hydraulic
oil
in the control chamber to flow to the lower pressure outlet 29.
S The preferred embodiment also includes an orifice plug 71 located in
the input passage regulating flow between the electrohydraulic valve 26 and
the control chamber 52. It is an advantage that the orifice plug 71 is more
restrictive one way and less restrictive the other way, such that the valve 46
moves more quickly from the closed position to the open position than the
movement from the open position to the closed position. Because the orifice
plug 71 is less restrictive in the direction associated with valve opening,
reduced fluid pressure is required to achieve acceptable valve opening
velocity. Reduced fluid pressure has the advantage of lower hydraulic power
consumption, reduced fluid heating, and less hydraulic system stress.
Reduced closing velocity reduces the impact and resulting wear between the
valve seat 68 and the closure member each time the valve 46 closes. To
accomplish this flow regulation, each side of the orifice plug 7I has a
different
discharge coeff cient. In particular, the plug 71 includes a restriction
orifice
73 and a conical or otherwise chamfered surface 75 on one side of the
restriction orifice 73 and a substantially flat surface 77 on the other side
of the
restriction orifice 73. The restriction orifice 73 determines the maximum
speed of actuation by limiting hydraulic flow. The chamfered surface 75
directs the pressure of the hydraulic signals like a nozzle and increase the
amount of flow through the orifice 73. The substantially flat surface 77 does
not direct the flow into the orifice 73 arid acts as a barrier thereby
reducing the
amount of flow through the orifice 73. As a result, the valve 64 moves more
quickly towards the open position and more slowly towards the closed
position. The force of the spring 66 is also selected to control the return
rate.
In accordance with an aspect~of the present invention relating to
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practicality and reliability of the fuel injector 22 and the entire assembly
20, a
small controlled amount of hydraulic oil leakage is allowed past the piston 44
for collection in a collection chamber 83 between the actuator body 50 and the
valve body 48. In the preferred embodiment, the collection chamber 83 is
provided by recesses in the actuator body 50 and mounting block 28. The
piston 44 and its mating bore in actuator body 50 are made with hardened,
wear resistant surfaces. When lubricated by hydraulic oil, these sliding
surfaces exhibit long cyclic life with negligible wear. Conventional sliding
seals are commonly known to not provide the required cyclic life and are
therefore considered to be not satisfactory for sealing between the piston 44
and its bore. It is therefore an advantage to avoid using sliding seals, and
to
simply incorporate the lubricated, hardened, steel surfaces. The lubricating
oil
leakage passing the piston 44 is limited by the small annular clearance
between the piston 44 and its mating bore. There are several other advantages
of this leakage. One significant advantage it that the leaked hydraulic oil
lubricates the sliding movement between metal to metal contact surfaces
between the inner bore of the upper guide 60 and the valve 46. This increases
wear resistance and significantly prolongs the life of the components in the
cartridge 34. Another advantage is that the oil lubricates and prolongs the
life
of a gas seal 84 between the upper guide 60 and the valve 46. The leaked oil
collected in the collection chamber 83 is directed via an outlet in the form
of
an axial outlet passage 86 in the cartridge body 42 that is connected to the
gas/oil outlet port 35 for removal to an external location where gas and oil
separation can occur. It should be noted that the leakage is corZtrolled to be
a
very small flow rate.
The O-ring gasket 85 prevents gas leakage from the gas passageway 41
to the collection chamber 83. The gas seal 84 prevents gaseous fuel leakage
between the valve 46 and the upper guide 60. The gas seal 84 is located at the
far lower end of the upper guide 60 such that oil lubricates all or
substantially
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all,of the contacting surfaces between the upper guide 60 and the valve 46.
When initially installed, the gas seal 84 and the O-ring gasket 85 provide
zero
leakage of gas from the gas passageway 4I (including spring chamber 64) to
the collectibn chamber 83. However, it will be appreciated that over the
lifetime of operation (eg. during several hundred million operating cycles)
wear can occur, which in turn, may and often causes slow gaseous leakage
past the gas seal 84. Indeed, the intense gas pressure exerted by the fi~el
(eg.
typically around 300-700 prig) greatly increases the likelihood of such
leakage occurring. The provision of the collection chamber 83 provides a fail
safe, tolerates such leakage and vastly extends the operating life for the
fuel
injector cartridge 34, because small gas leakage is carried away to an
acceptable disposal means. If it were not for this gas, leakage disposal
means,
the engine would have to be stopped, and the leaking cartridge replaced, at
the
first sign of gas leakage past the seals.
A second collection chamber 87 is also provided at the other axial end
of the passage 86, generally between the actuator body 50 and the mounting
block 28 of the electrohydraulic valve assembly 24. A number of O-ring
gaskets 88-91 are provided in this general vicinity and serve to prevent
leakage. Two connector tube O-rings 88, 89 between the connector tube 56
and the actuator body 50 and the mounting block 28 of the electrohydraulic
valve 26 prevent leakage of oil into the collection chamber 87. However, the
continuous and cyclic pulses of hydraulic oil through the connector tube 56
presents a possibility of oil leakage after a long time period. As such, small
amounts of oil leakage can be allowed or is tolerated as it is collected in
the
second collection chamber 87. An O-ring 90 is also provided between the
mounting flange 30 and the actuator body 50 to prevent leakage of high
pressure gaseous fuel from the gas passageway 41. However, a small amount
of gas leakage is also tolerated at this location, in which gas would be
collected in the second collection chamber 87 for removal. The outer O-ring
CA 02483413 2004-11-09
14
9 T prevents leakage of oil and gas to the external environment. It will be
appreciated that the oil and any combined oil/gas in the second collection
chamber 87 is at relatively low pressure, much lower pressure than either the
high pressure gaseous fuel supply or the hydraulic oil at the high pressure
inlet
27. As a result, little pressure and thus minimal forces are exerted on this
gasket 91 thereby providing a highly reliable seal at this location and
avoiding
leakage to the external environment.
From the foregoing, it will be appreciated by those skilled in the art
that the first and second collection chambers 83, 87 each provide a fail-safe
for oil leakage or gas leakage at several locations and two separate means for
tolerating leakage of oil and gas at least one location in the fuel injector
assembly and for removal of any leakage of hydraulic fluid and gas from the
fuel injector assembly.
In accordance with another aspect of the present invention relating to
1 S universality of the valve cartridge 22, a shim 92 is used to control the
maximum stroke or distance of reciprocating movement of the valve 46. As
shown in FIGS. 1 and 4, the upper guide 60 is compressed axially between the
actuator body 50 and a shoulder/recess 93 formed in the valve body sleeve 58.
A stop plate 100 and shim 92 are positioned axially between the upper guide
60 and the shoulder/recess to control the amount that the upper guide 60
protrudes from the valve body 48 and the resulting overall axial length of the
valve body 48. Excess threads in the two bodies 48, 50 are provided to
accommodate variations in their engagements due to different sizes of shims.
A thicker shim 92 will increase the protrusion of the upper guide 60 relative
to
the upper face of the valve 46. As a result, the distance between the outer
face
of the piston 44 and the face of the upper guide will be reduced, causing the
stroke of the valve to be reduced. This in turn results in less gaseous fuel
being injected into the cylinders of the engine during each cycle. A thinner
shim 92 will increase the allowable stroke of the valve 46, resulting in more
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1~
gaseous fuel being injected into the cylinders of the engine during each
cycle.
The selection of the shim 92 thickness allows the valve cartridge 22 to be
easily adjusted for larger and smaller types of engines which have different
fueling requirements. Thus the preferred embodiment provides a valve
S cartridge and fuel injector that are universal for a variety of different
engines.
Using the shim 92, conventional opening distances for the valve closure
member 74 of the preferred embodiment can be conveniently adjusted over
the range of opening distance range desired for these types of engines. This
is
an important advantage when considering that the fuel injector 22 is used to
retrofit existing engines which exist in a wide variety of models and sizes.
Also as shown, the shim 92 and a stop plate 100 axially retain. the gas seal
84.
In accordance with another aspect of the present invention relating to
cooling and reliability, openings in the form of cross-holes 94 are drilled
into
the valve body sleeve 58 at radially spaced intervals. The cross-holes 94
allow the cool gaseous fuel entering the gas inlet 33 and flowing through the
gas passageway 41 to cool the exposed surface of the valve 46 inside the
spring chamber 64. During operation, the nozzle 40 and closure member 74
are exposed to extreme temperatures inside the cylinder of the engine, eg. up
to about 2000 degrees Fahrenheit. . In contrast, the conventional material of
gas seal and other conventional material gaskets and spring materials start to
thermally deteriorate at. around 300-400 degrees Fahrenheit. By cooling the
exposed surface of the valve 46, life of the gaskets/seals and spring and
therefore life of the cartridge 34 is prolonged. During operation, the
pressure
in the gas passageway 41 rises and falls as the valve ~46 opens and closes.
This in turn causes relatively cool gas to pulsate into and out of the spring
chamber vastly enhancing the cooling effect achieved. These cross-holes 94
direct this gas flow towards the valve and spring and improve the life span
and
reliability of the cartridge 34 by removing heat that would otherwise travel
up
CA 02483413 2004-11-09
16
the valve and spring, undesirably raising the operating temperature of the
spring and seals.
Still another function of the cross-holes 94 is to provide a means of
restraining the gas valve body 48 while tightening/loosening the threaded
joint
joining the actuator body 50 and the gas valve body 48. This is accomplished
by engaging pins in the cross-holes 94 using a holding fixture designed for
that purpose.
Another novel feature of the preferred embodiment is the provision of a
metal O-ring 95 for sealing the contacting surfaces between the cartridge
housing 32 and the cartridge 34. The metal O-ring provides a highly reliable
seal in a location proximate the engine cylinders where the temperatures are
extreme. It will be appreciated that current materials for other more
conventional types of gaskets would likely fail from thermal damage in this
type of environment. To maintain the metal O-ring 95 in sealing relationship,
a large axial force, eg. of about 10,000 pounds, is applied by a spring in the
form of two BeIlevilIe load or spring washers 96 supported by the body of the
electrohydraulic valve 26 and engaging the other axial end of the cartridge
34.
Specifically, the load washers 96 engage a load pad 97 situated in the second
collection chamber 87. and seated in a formed recess in the actuator body 50.
Shim 98 is interposed between the load pad 97 and the recess in the actuator
body 50. It should be noted that the thickness of the shim 98 is selected to
maintain the desired force on the metal O-ring 95. In particular, recalling
that
the thickness of the shim 92 is variable depending upon the fueling rate
requirements of the intended engine, the thickness of the second shim 98
depends upon the thickness of the first shim 92. The thicker the first shim
92,
the thinner the second shim 98 is to thereby maintain the same force on the
metal O-ring 97. The thickness of second shim 98 is also adjusted to achieve
deflection of the load washers as required to generate the desired metal O-
ring
clamping force, compensating for the effects of manufacturing tolerances in
CA 02483413 2004-11-09
17
the parts. A threaded hole 99 is also drilled 180 degrees apart from the axial
passage 54 to facilitate insertion of screw which can then be used to lift the
cartridge 34 out of the housing 32. Together, threaded hole 99 and passage
86, diametrically opposite each other in the face of actuator body 50,
conveniently accommodate a common spanner wrench adapter to facilitate
tightening/loosening the threaded joint connecting the actuator body 50 and
the valve body 48.
Because of the number of moving components and seals, the fuel
injector cartridge 34 is intended fo have a lifespan of about one to two
years.
As such, the cartridge 34 is easily replaced by removing the electrohydraulic
valve assembly 24, and the various parts between the electrohydraulic valve
and the cartridge and pulling the cartridge 34 from the cartridge housing 32.
The electrohydraulic valve 26, cartridge housing 32 and interposed parts can
be reused with a new replacement fuel injector cartridge 34 and new metal O-
ring 95.
FIGS. 6 and 7 illustrate one such high pressure fuel injection system
120 incorporating the high pressure fuel injector assembly 20. The primary
advantage of this type of system is that the fuel injector 22 injects fuel at
high
pressures greatly increasing air and fuel mixing in the cylinders and thereby
resulting in fewer harmful environmental emissions and increasing engine
efficiency. FIG. 6 illustrates the system 120 in schematic form with a single
fuel injector valve assembly 20 while FIG. 7 illustrates the system 120 on an
engine 121 with multiple valve assemblies 20, one for each cylinder of the
engine I21. The system 120 includes a hydraulic pumping unit 122 for
supplying high pressure hydraulic oil to the electrohydraulic valve 26 and an -
electronic controller 124 for driving the electrical driver 23 via electrical
signals on electrical line 123. The hydraulic pumping unit 122 in this case is
located remote from the engine cylinders and may be electrically or
pneumatically powered. The preferred embodiment illustrated in FIG. 7 is an
CA 02483413 2004-11-09
~g
engine driven pump 126, a low pressure sump or reservoir 128, and a gas/oil
separator 130. The pump 126 is adapted to pump hydraulic oil from the
reservoir 128 to the high pressure inlet 27 of the electrohydraulic valve 26
via
a high pressure hydraulic oil supply line 132. The pressure in this line 132
may be in the rough neighborhood of around 800 psig. A low pressure
hydraulic return line 134 connects the low pressure outlet 29 with the
reservoir 128. This pressure in this line 134 may be in the rough
neighborhood of about 45 psig. A gas/oil return line 136 connects the gas/oil
outlet port 35 to the gas/oil separator 130. The gasloil separator 130 allows
any combined gas and oil to sit for a sufficient time at which the gas
separates
and is exhausted via a gas vent 138 to a non-explosive location. A gaseous
fuel supply 140 of a combustible gas is connected to the gas inlet 33 by a gas
line 142 that may have a pressure in the neighborhood of between about 300-
700 psig, or other suitable lower or higher pressure. Other associated
equipment includes a hydraulic oil filter 144 for keeping the hydraulic oil
clean and a gas leakage indicator 146 for sensing excessive gas leakage which
could indicate hazardous conditions. y
While this invention has been described with an emphasis upon
preferred embodiments, it will be obvious to those of ordinary skill in the
art
2 0 that variations of the preferred embodiments may be used and that it is
intended that the invention may be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all modifications
encompassed within the spirit and the scope of the invention as defined by the
following claims.
