U.S. patent application number 09/986238 was filed with the patent office on 2002-03-07 for gaseous fuel injector having high heat tolerance.
This patent application is currently assigned to Woodward Governor Company. Invention is credited to Popp, Roger C..
Application Number | 20020027170 09/986238 |
Document ID | / |
Family ID | 23910833 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020027170 |
Kind Code |
A1 |
Popp, Roger C. |
March 7, 2002 |
Gaseous fuel injector having high heat tolerance
Abstract
A high pressure gaseous fuel injector for injecting natural gas
or other gaseous fuels at high pressures (eg. 300 to 700 psig more
or less) into combustion engines for improved efficiency, better
performance and reduced environmental emissions. The fuel injector
is powered by hydraulic signals from an electrohydraulic valve. The
fuel injector includes an outer cartridge housing and a universal
valve cartridge mounted therein. The cartridge comprises an
activator body and a valve body secured together, and the valve
body has a gas valve slidable therein. The stroke of the valve is
adjustable by controlling the size of shims in the valve body
assembly, thereby providing a universal valve cartridge that can be
easily adapted to differing fueling requirements for models and
sizes of engines. The valve body includes a spring chamber between
upper and lower valve guides. The valve body also includes
cross-holes to allow cool gaseous fuel to successively pulsate into
and out of the spring chamber and thereby cool the exposed portion
of the valve between guides, preventing heating of the dynamic gas
seal located in the upper guide. An unsealed small clearance
between the actuating piston and its bore in the actuator body
allows controlled leakage of oil. The leakage of oil lubricates
metal to metal contact between the upper guide and the valve and
lubricates the dynamic gas seal. Gaseous fuel leakage into the
leaked oil is tolerated and any combined oil/gaseous fuel is
removed to an external location for separation. Spring washers are
used to urge the valve assembly insert against a metal O-ring
supported by the outer cartridge body.
Inventors: |
Popp, Roger C.; (Cheyenne,
WY) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
6815 WEAVER ROAD
ROCKFORD
IL
61114-8018
US
|
Assignee: |
Woodward Governor Company
5001 North Second Street P.O. Box 7001
Rockford
IL
61125
|
Family ID: |
23910833 |
Appl. No.: |
09/986238 |
Filed: |
October 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09986238 |
Oct 22, 2001 |
|
|
|
09481150 |
Jan 12, 2000 |
|
|
|
Current U.S.
Class: |
239/132.5 |
Current CPC
Class: |
F02M 47/046 20130101;
F02M 21/0251 20130101; Y02T 10/32 20130101; F02M 61/08 20130101;
Y02T 10/30 20130101; F02M 21/0269 20130101 |
Class at
Publication: |
239/132.5 |
International
Class: |
B05B 015/00 |
Claims
What is claimed is:
1. 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.
2. The fuel injector valve cartridge of claim 1 wherein the spring
mechanism comprises at least one spring washer.
3. The fuel injector valve cartridge of claim 1 wherein the
cartridge body includes a sleeve, and upper and lower guide collars
in the sleeve, the upper and lower 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 the
exposed surface of the valve.
4. The fuel injector valve cartridge of claim 1 wherein the gaseous
fuel has a pressure of at least about 300 psi and the spring
mechanism applies an axial force of at least about 10,000
pounds.
5. The fuel injector of claim 1 further comprising an
electrohydraulic valve assembly for actuating the elongate valve,
the spring mechanism compressed between the electrohydraulic servo
valve and the cartridge body.
6. The fuel injector valve of claim 5 further comprising a flow
passage extending through the spring mechanism, the flow passage
carrying actuating fluid from the electrohydraulic servo-valve
actuating the elongate valve
7. The fuel injector valve of claim 6 wherein the spring mechanism
comprises at least one belleville washer.
8. The fuel injector valve cartridge of claim 1 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.
9. The fuel injector valve of claim 1 wherein the metal o-ring
provides an axial seal between the fuel injector cartridge and the
tubular cartridge housing.
10. The fuel injector valve of claim 1 wherein the fuel injector
cartridge is slidably disposed inside the tubular cartridge
housing, the spring mechanism retaining the fuel injector cartridge
inside the tubular cartridge housing.
11. The fuel injector valve of claim 1 wherein the fuel injector
cartridge includes first and second ends, wherein the spring
mechanism acts on the first end and wherein the second end acts on
the metal o-ring.
12. The fuel injector valve of claim 11 further comprising 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.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application is a continuation of copending U.S.
patent application Ser. No. 09/481,150, filed Jan. 12, 2000,
allowed, but still pending.
FIELD OF THE INVENTION
[0002] The present invention generally relates to fuel injectors,
and more particularly high pressure gaseous fuel injectors for
internal combustion engines.
BACKGROUND OF THE INVENTION
[0003] 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.
[0004] 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, U.S. Pat. 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 engines are not efficient and also are
environmentally detrimental, contributing to approximately 10% of
the total NO.sub.x production in the United States from stationary
combustion sources according to estimates.
[0005] 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.
Pat. 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.
BRIEF SUMMARY OF THE INVENTION
[0006] 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.
[0007] 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.
[0008] 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.
[0009] It is a another object of the present invention according to
another aspect to provide a highly reliable fuel injector, and
specifically one that is not susceptible to thermal damage from the
engine.
[0010] 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.
[0011] 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 limit the amount of heat transferred from
the engine cylinder to the gas seals. The fuel injector 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 (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.
[0012] 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.
[0013] 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 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 axial 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.
[0014] Other objectives and advantages of the invention will become
more apparent from the following detailed description when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings incorporated in and forming a part
of the specification illustrate several aspects of the present
invention, and together with the description serve to explain the
principles of the invention. In the drawings:
[0016] FIG. 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.
[0017] FIG. 2 is a cross-sectional view of a high pressure fuel
injector assembly similar to that in FIG. 1 but in an open
position.
[0018] FIG. 3 is an enlarged cross sectional view of a portion of
the high pressure fuel injector illustrated in FIG. 1.
[0019] FIG. 4 is an enlarged cross sectional view of another
portion of the high pressure fuel injector illustrated in FIG.
1.
[0020] 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.
[0021] FIG. 6 is a schematic illustration of the high pressure fuel
injector assembly of FIG. 1 in an engine system environment.
[0022] 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.
[0023] FIG. 8 is a perspective view of the high pressure fuel
injector assembly of FIG. 1.
[0024] 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.
[0025] 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.
DETAILED DESCRIPTION OF THE INVENTION
[0026] 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.
[0027] 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 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 embodiment, the electrohydraulic valve 26 includes an
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 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.
[0028] 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 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 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
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.
[0029] 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.
[0030] 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. 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 bottom 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 valve guide 62 to extend the gas passageway 41
to the outlet orifice 70.
[0031] 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 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.
[0032] 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 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.
[0033] 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.
[0034] 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 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.
[0035] 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 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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. 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 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.
[0040] 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 the valve and spring,
undesirably raising the operating temperature of the spring and
seals.
[0041] 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.
[0042] 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
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 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.
[0043] 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.
[0044] 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 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 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.
[0045] All of the references cited herein, including patents,
patent applications, and publications, are hereby incorporated in
their entireties by reference.
[0046] The foregoing description of various embodiments of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise embodiments disclosed. Numerous
modifications or variations are possible in light of the above
teachings. The embodiments discussed were chosen and described to
provide the best illustration of the principles of the invention
and its practical application to thereby enable one of ordinary
skill in the art to utilize the invention in various embodiments
and with various modifications as are suited to the particular use
contemplated. All such modifications and variations are within the
scope of the invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are
fairly, legally, and equitably entitled.
* * * * *