Note: Descriptions are shown in the official language in which they were submitted.
CA 02506143 2001-O1-04
HIGH-PRESSURE GASEOUS FUEL INJECTION
Field Of The Invention
The present invention generally relates to fuel injectors, and more
particularly high-pressure gaseous fuel injection systems for internal
combustion
engines. This application is divided from and comprises the disclosure of
Canadian Patent Application 2,330,226, filed January 04, 2001. Consequently
the
expression "the invention", and the like, as used herein is not restricted to
subject
matter specifically claimed in this divided application, but may encompass
additional subject matter described but not claimed.
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 (for
example, 15 psig to 60 psig by mechanically actuated fuel injectors, such as
that
disclosed in Fisher, United States Patent 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
CA 02506143 2001-O1-04
2
stability, high misfire rates and significant cycle-to-cycle variations in
peak
pressure. As a result, these engines are not efficient and also are
environmentally
detrimental, 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 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 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 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.
CA 02506143 2001-O1-04
3
Summary Of The Invention
It is a general aim of the present invention to provide commercially reliable
and practical fuel injection systems for injecting high-pressure gaseous fuel
(e.g.
around 300-700 psi or more) into combustion engines.
In one aspect it provides 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 also can 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 the
industry.
Another aspect provides a fuel injection system 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 this aspect of the invention a fuel injection system for
injecting gaseous fuel into the cylinders of an engine comprises an oil
reservoir of
hydraulic oil, and a supply of hydraulic oil at a higher pressure than the oil
reservoir. A gas/oil separator is adapted to separate gaseous fuel from the
hydraulic oil, and return the separated oil to the oil reservoir. A plurality
of fuel-
injector valve assemblies each include an electrohydraulic valve and a fuel
injector; the electrohydraulic valve actuating the fuel-injector valve with
hydraulic
signals derived from the hydraulic oil supply to inject gaseous fuel from the
gaseous fuel supply into at least one of the cylinders of the engine. The fuel-
injector valve assemblies have at least one collection chamber adapted to
collect
hydraulic oil and leaked gaseous fuel; the at least one collection chamber
returning
the hydraulic oil and leaked gaseous fuel to the gas/oil separator.
As mentioned, according to another aspect the invention is directed towards
a novel fuel injector cartridge, a novel fuel injector that includes a tubular
cartridge housing and the fuel injector cartridge inserted therein, and an
CA 02506143 2001-O1-04
4
electrohydraulic fuel injector assembly incorporating the fuel injector and an
electrohydraulic valve, all for facilitating the injection of high-pressure
gaseous
fuel. The fuel injector is operated by hydraulic oil to successively open and
close
to inject gas into the cylinders of the engine in sequence with the engine
cycles.
The invention includes at least one oil collection chamber for collecting
leakage of hydraulic oil and/or any gas for safe removal. According to a
preferred
embodiment, two interconnected chambers are provided. One chamber collects oil
leakage past the piston and gas leakage past the gas valve. The second chamber
collects any other leakage between the electrohydraulic valve and the fuel
injector.
Gas seal leakage is not anticipated for new fuel injectors and their
cartridges, but it
will be appreciated that over the course of several hundred million operating
cycles, wear of gas seals can occur, and particularly, the gas valve seal
engaging
the moving valve, and as such, gas leakage can occur. The collected oil and/or
gas
is directed through a separate outlet port away from the entire assembly to a
remote gas and oil separator to remove gas from the oil and recycle the oil. A
small clearance may be provided between the piston and the piston chamber or
bore in which it reciprocates to regulate and limit the amount of leakage and
thereby provide a controlled amount of leakage.
Several advantages may result from the availability of leaked oil in the fuel
injector assembly. One advantage is that the leaked oil can be used to
lubricate the
contact surfaces between an upper guide and the valve. This allows for a
precision
hardened steel upper guide without wear concerns that provides accurate
guiding
of the gas valve, prolonging the life of the gas valve seat and sliding
dynamic gas
valve seal. Another advantage is that the collection chambers and associated
passages provide a low pressure buffer between the high-pressure gaseous fuel
and high pressure hydraulic operating fluid, as well as between these high
pressure
locations inside the fuel injector and the external atmosphere. In a preferred
embodiment, two collection chambers are provided, one between the
electrohydraulic valve and the fuel injector cartridge, and one between the
valve
and piston inside of the cartridge.
CA 02506143 2001-O1-04
The novel fuel injector cartridge of the present invention may be replaced
periodically, typically more frequently than other components of the system.
The
structure of the preferred embodiment provides a cost effective means for
periodically replacing the fuel injector cartridge.
Other features and advantages of the invention will become more apparent
from the following detailed description when taken in conjunction with the
accompanying drawings, in which:
Brief Description Of The Drawings
FIG. 1 is a cross-sectional view of a high-pressure fuel injector assembly,
illustrated in a closed position.
FIG. 2 is a cross-sectional view of a high-pressure fuel injector assembly
similar
to that in FIG. l, but in an open position.
FIG. 3 is an enlarged cross sectional view of a portion of the high-pressure
fuel
injector illustrated in FIG. 1.
FIG. 4 is an enlarged cross sectional view of another portion of the high-
pressure
fuel injector illustrated in FIG. 1.
FIG. 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.
FIG. 6 is a schematic illustration of the high-pressure fuel injector assembly
of
FIG. l, in an engine system environment.
FIG. 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.
FIG. 8 is a perspective view of the high-pressure fuel injector assembly of
FIG. 1.
FIG. 9 is a perspective view of the high-pressure fuel injector assembly of
FIG. 1,
but with a different embodiment of the fuel injector housing.
CA 02506143 2001-O1-04
6
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 alternatives, modifications and equivalents as
included
within the spirit and scope of the invention as defined by the appended
claims.
S
Detailed Descrietion
Referring to the cross section of FIG. 1, 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
121 with multiple fuel injector assemblies 20 is illustrated in FIG. 7. The
disclosed
fuel injector assembly 20 provides a commercially reliable and practical fuel
injector for injecting high-pressure 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 electrohydraulic 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 electrohydraulic valve
assembly 24 is intended to have a broad meaning and may include an
electrohydraulic valve 26, and a mounting block 28 for mounting the
electrohydraulic valve 26 to the fuel injector 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 embodiment, the electrohydraulic valve 2b includes
an
CA 02506143 2001-O1-04
7
electrical driver 23 such as an on/off 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 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
26
and the fuel injector 22. As illustrated in FIG. S, 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
I 5 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 nose piece 38, and a mounting flange
30,
all brazed together, and a nozzle 40 press fit 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 fuel
CA 02506143 2001-O1-04
8
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 41 is a large annular chamber between
the housing 32 and the cartridge 34. The volume of this 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 31 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.
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 steel washer or other
bushing
. retainer 63 is seated in a recess in the sleeve 58 below the graphite
bushing. T'he
CA 02506143 2001-O1-04
9
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
between the sleeve 58 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 valve 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 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 engine. As shown in FIG. 3, the spring
66
engages a disc shaped spring retainer 76 which is secured to the valve 46 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 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
CA 02506143 2001-O1-04
closed positions by high pressure hydraulic signals, the spring 66 performs
the
necessary function of a fail-safe, in that the spring 66 mechanically
maintains 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.
10 Surrounding the nose 80 is a seating 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 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.
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
CA 02506143 2001-O1-04
11
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 71
has a
different discharge coefficient. 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 and 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 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
CA 02506143 2001-O1-04
12
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 controlled 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 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 41 (including spring chamber 64) to the collection
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 fuel (eg. typically around 300-700 psig)
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.
CA 02506143 2001-O1-04
13
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 91 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
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.
l and 4, the upper guide 60 is compressed axially between the actuator body SO
and a shoulder/recess 93 formed in the valve body sleeve 58. A stop plate 100
and
CA 02506143 2001-O1-04
14
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 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 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
CA 02506143 2001-O1-04
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
5 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 the valve and spring, undesirably raising the
operating
temperature of the spring and seals.
10 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.
15 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 Belleville 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
CA 02506143 2001-O1-04
16
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
S clamping force, compensating for the effects of manufacturing tolerances in
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 to 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 a 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 121. 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
CA 02506143 2001-O1-04
17
be electrically or pneumatically powered, The preferred embodiment illustrated
in
FIG. 7 is an 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 gas/oil
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.
While this invention has been described with an emphasis upon preferred
embodiments, it will be obvious to those of ordinary skill in the art 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.
