U.S. patent application number 09/370850 was filed with the patent office on 2001-08-30 for gaseous fuel injector having low restriction seat for valve needle.
Invention is credited to FOCHTMAN, JAMES PAUL.
Application Number | 20010017327 09/370850 |
Document ID | / |
Family ID | 23461453 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017327 |
Kind Code |
A1 |
FOCHTMAN, JAMES PAUL |
August 30, 2001 |
GASEOUS FUEL INJECTOR HAVING LOW RESTRICTION SEAT FOR VALVE
NEEDLE
Abstract
An electromagnetically operable fuel injector for a gaseous fuel
injection system of an internal combustion engine, the injector
having a generally longitudinal axis, which comprises, a
ferromagnetic core, a magnetic coil at least partially surrounding
the ferromagnetic core and an armature magnetically coupled to the
magnetic coil and being movably responsive to the magnetic coil.
The armature actuates a valve closing element which interacts with
a fixed valve seat of a fuel valve and is movable away from the
fixed valve seat when the magnetic coil is excited. The fixed valve
seat defines a central fuel opening and a generally annular groove
adjacent the central fuel opening, the armature having a generally
elongated shape and a generally central opening for axial reception
and passage of gaseous fuel from a fuel inlet connector positioned
adjacent thereto. The fuel inlet connector and the armature are
adapted to permit a first flow path of gaseous fuel between the
armature and the magnetic coil as part of a path leading to said
fuel valve. A method of directing gaseous fuel through an
electromagnetically operable fuel injector for a fuel system of an
? combustion engine is also disclosed.
Inventors: |
FOCHTMAN, JAMES PAUL;
(WILLIAMSBURG, VA) |
Correspondence
Address: |
SCOTT J. ANCHELL
MORGAN, LEWIS & BOCKIUS, LLP
1800 M STREET, NW
WASHINGTON
DC
20036-5869
US
|
Family ID: |
23461453 |
Appl. No.: |
09/370850 |
Filed: |
August 10, 1999 |
Current U.S.
Class: |
239/585.4 ;
239/5; 239/533.12; 239/533.2; 239/585.1; 251/129.15;
251/129.21 |
Current CPC
Class: |
Y02T 10/32 20130101;
F02M 51/0671 20130101; F02M 61/18 20130101; Y02T 10/30 20130101;
F02M 51/0682 20130101; F02M 21/0254 20130101; F02M 21/0266
20130101 |
Class at
Publication: |
239/585.4 ;
239/585.1; 239/533.12; 239/5; 239/533.2; 251/129.21;
251/129.15 |
International
Class: |
B05B 001/30 |
Claims
1. An electromagnetically operable fuel injector for a gaseous fuel
injection system of an internal combustion engine, said injector
having a generally longitudinal axis, which comprises: a) a
ferromagnetic core; b) a magnetic coil at least partially
surrounding the ferromagnetic core; and c) an armature magnetically
coupled to said magnetic coil and being movably responsive to said
magnetic coil, said armature actuating a valve closing element
which interacts with a fixed valve seat of a fuel valve and being
movable away from said fixed valve seat when said magnetic coil is
excited, said fixed valve seat defining a central fuel opening and
a generally annular groove adjacent said central fuel opening, said
armature having a generally elongated shape and a generally central
opening for axial reception and passage of gaseous fuel from a fuel
inlet connector positioned adjacent thereto, said fuel inlet
connector and said armature being adapted to permit a first flow
path of gaseous fuel between said armature and said magnetic coil
as part of a path leading to said fuel valve.
2. The electromagnetically operable fuel injector according to
claim 1, further comprising at least one first fuel flow aperture
extending through a wall portion of said armature to define a
second flow path of gaseous fuel as part of a path leading to said
fuel valve.
3. The electromagnetically operable fuel injector according to
claim 2, wherein said armature defines at least one second aperture
in a wall portion thereof to define a third flow path of gaseous
fuel as part of a path leading to said fuel valve.
4. The electromagnetically operable fuel injector according to
claim 3, wherein said at least one second aperture is oriented at a
generally acute angle with respect to the longitudinal axis.
5. The electromagnetically operable fuel injector according to
claim 4, wherein said fuel inlet connector and said armature are
spaced to define a working gap therebetween and are adapted to
permit said first flow path of gaseous fuel within said working
gap.
6. The electromagnetically operable fuel injector according to
claim 5, further comprising a valve body positioned downstream of
said armature and having at least one aperture in a wall portion
thereof for reception of fuel from at least two of said flow paths
of gaseous fuel from said armature and said fuel inlet
connector.
7. The electromagnetically operable fuel injector according to
claim 6, further comprising a valve body shell at least partially
surrounding said armature and said valve body, said valve body
shell defining a radial space with said armature for passage of
said first flow path of gaseous fuel between said armature and said
valve body shell.
8. The electromagnetically operable fuel injector according to
claim 7, wherein said fuel inlet connector is positioned above said
armature and is spaced from said armature by a working gap, said
fuel inlet connector defining a through passage for directing fuel
toward said armature and said fixed valve seat.
9. The electromagnetically operable fuel injector according to
claim 8, wherein said fuel inlet connector comprises an upper end
portion adapted for reception of gaseous fuel from a fuel source,
and a lower end portion for discharging gaseous fuel, said lower
end portion having a lower surface which faces an upper surface of
said armature, said lower surface of said fuel inlet connector
having a plurality of radially extending raised pads defined
thereon, said pads having recessed portions therebetween to permit
fuel to flow therethrough and across said working gap defined
between said fuel inlet connector and said armature.
10. An electromagnetically operable fuel injector for a compressed
natural gas fuel injection system of an internal combustion engine,
said injector having a generally longitudinal axis, which
comprises: a) a ferromagnetic core; b) a magnetic coil at least
partially surrounding said ferromagnetic core; c) an armature
magnetically coupled to said magnetic coil and movably responsive
to said magnetic coil, said armature having a first upper end face
and a lower end portion; d) a valve closing element connected to
said lower end portion of said armature and interactive with a fuel
valve having a fixed valve seat to selectively permit fuel to pass
through said valve seat as said valve closing element is moved to a
valve open position by said armature, said fixed valve seat having
a generally frusto-conically shaped portion surrounded by an
adjacent circular shaped annular groove to reduce the pressure
differential occurring across the valve closing element and said
fixed valve seat upon closing said fuel valve; e) a fuel inlet
connector extending in a generally longitudinal direction above
said armature and defining a path for fuel to enter said inlet
connector and to be directed toward said armature, said fuel inlet
connector having a lowermost end portion having a lowermost surface
spaced above said armature to define a working gap through which
said armature is movable; and f) said armature having a fuel
reception portion for receiving fuel directed from said fuel inlet
connector, said armature further defining a generally axial fuel
passage.
11. The electromagnetically operable fuel injector according to
claim 10, wherein at least a first fuel flow aperture extends
through a wall portion of said armature for directing fuel from
said fuel inlet connector through said generally axial fuel passage
and into said aperture toward said fixed valve seat for entry into
an air intake manifold of the engine, said fuel flow aperture being
oriented generally transverse to said longitudinal axis.
12. The electromagnetically operable fuel injector according to
claim 11, wherein said armature further defines at least a second
fuel flow aperture extending through a lower portion thereof and
oriented at an acute angle with said longitudinal axis, and
positioned for directing fuel therethrough toward said fixed valve
seat.
13. The electromagnetically operable fuel injector according to
claim 12, wherein said lowermost surface of said fuel inlet
connector and said armature are adapted to permit gaseous fuel to
flow across said working gap and between said armature and said
magnetic coil whereby at least three fuel flow paths are
permitted.
14. The electromagnetically operable fuel injector according to
claim 13, wherein said lowermost end portion of said fuel inlet
connector has a generally chamfered configuration along the
lowermost outer surface thereof.
15. The electromagnetically operable fuel injector according to
claim 14, wherein said generally chamfered portion of said fuel
inlet connector has a generally arcuate cross-section.
16. The electromagnetically operable fuel injector according to
claim 15, wherein said valve closing element is a valve needle
adapted for selective engagement and disengagement with said fixed
valve seat.
17. The electromagnetically operable fuel injector according to
claim 16, wherein said valve needle is attached to said armature by
crimped portions of said armature.
18. The electromagnetically operable fuel injector according to
claim 17, wherein a fuel filter is positioned at an upper end
portion of said fuel inlet connector for filtering fuel prior to
reception by said fuel inlet connector.
19. The electromagnetically operable valve according to claim 18,
wherein said fuel inlet connector includes a lower surface portion
having a plurality of radially extending grooves defining a
corresponding plurality of radially extending raised pads so as to
reduce the effective surface area of said lower surface portion of
said fuel inlet connector facing said armature to thereby permit
the gaseous fuel to flow generally transversely in said working
gap, said transverse fuel flow thereby preventing accumulation of
contaminants in said working gap.
20. The electromagnetically operable fuel injector according to
claim 19, wherein said generally radially extending pads have a
generally trapezoidal shape.
21. An electromagnetically operable fuel injector for a gaseous
fuel injection system of an internal combustion engine, said
injector having a generally longitudinal axis, which comprises: a)
a ferromagnetic core; b) a magnetic coil at least partially
surrounding the ferromagnetic core; c) an armature magnetically
coupled to said magnetic coil and being movably responsive to said
magnetic coil, said armature actuating a valve closing needle
having a generally spherically shaped fuel sealing tip portion
which interacts with a fuel valve having a fixed valve seat and
being movable away from said fixed valve seat when said magnetic
coil is excited, said fixed valve seat having a generally annular
sealing surface having a generally frusto-conical cross-sectional
shape for engaged reception of said generally spherically shaped
needle tip portion, said generally annular sealing surface defining
a central opening for passage of gaseous fuel to a fuel intake
manifold, and a generally circular annular groove adjacent said
sealing surface to provide increased volumetric space adjacent said
fixed valve seat for reception of gaseous fuel to thereby reduce
the pressure loss across said needle and said valve seat upon
closure thereof, said armature having a generally elongated shape
and a generally central opening for axial reception and passage of
gaseous fuel from a fuel inlet connector positioned adjacent
thereto; and d) at least one first fuel flow aperture extending
through a wall portion of said armature for reception of gaseous
fuel flowing from said inlet connector and for directing the
gaseous fuel to a valve body at least partially surrounding said
armature, said valve body having a generally elongated central
opening for reception of substantially all of the gaseous fuel from
said armature.
22. An electromagnetically operable fuel injector for an internal
combustion engine, said injector defining a generally longitudinal
axis, which comprises: a) an outer housing; b) a fuel inlet
connector positioned in the upper end portion of said outer
housing, said fuel inlet connector having an uppermost end portion
for reception of fuel therein and a lowermost end portion for
discharge of fuel therefrom: c) an armature positioned below said
fuel inlet connector and defining a generally axial elongated
central opening to receive fuel flow from said fuel inlet
connector, said armature having an uppermost end portion positioned
below said lowermost end portion of said fuel inlet connector to
define a working gap, and a lowermost end portion having a valve
closing element positioned thereon for interaction with a fuel
valve to selectively permit fuel to flow through said valve
aperture when said armature is selectively moved upwardly toward
said fuel inlet connector, said fuel valve defining a fixed valve
which surrounds a central fuel opening for passage of gaseous fuel,
said fixed valve seat further being surrounded by a generally
circular annular groove adjacent thereto for reception of gaseous
fuel passing therethrough so as to reduce the gaseous pressure loss
across said valve during closure thereof; d) said fuel inlet
connector having a lowermost end portion having a lowermost surface
which faces said uppermost end portion of said armature, said
lowermost end portion of said fuel inlet connector having a
plurality of radially extending grooves separated by a
corresponding plurality of radially extending raised pads to reduce
the effective contact surface area between said inlet connector and
said armature and to permit fuel to flow from said fuel inlet
connector across said working gap; e) a magnetic coil system for
moving said armature and said valve closing element away from said
fixed valve seat and toward said fuel inlet connector when said
magnetic coil system is energized so as to permit fuel to flow
through said fixed valve seat; f) a resilient device to bias said
armature and said valve closing element to move toward said fixed
valve seat when said magnetic coil system is deenergized; g) at
least one first aperture extending through a wall portion of said
armature for receiving fuel flow from said fuel inlet connector and
directing said fuel flow from said generally elongated central
opening of said armature toward said fixed valve seat, said at
least one aperture being generally transverse to the longitudinal
axis; and h) at least one second aperture extending through a wall
portion of said armature for receiving fuel flow from said fuel
inlet connector and directing said fuel flow toward said fixed
valve seat, said second aperture being oriented at a generally
acute angle relative to the longitudinal axis for directing fuel
from said generally central opening outwardly of said armature and
downwardly toward said fixed valve seat.
23. The electromagnetically operable fuel injector according to
claim 22, wherein said valve closing element is a generally
elongated valve needle having a spherically shaped end portion and
configured and adapted to engage a frusto-conically shaped fixed
valve seat to close said valve, and movable therefrom to open said
valve to permit fuel to pass therethrough toward the intake
manifold of the internal combination engine.
24. The electromagnetically operable fuel injector according to
claim 23, wherein said valve needle is connected to the lower end
portion of said armature by crimped portions.
25. The electromagnetically operable fuel injector according to
claim 24, wherein said resilient device is a coil spring in
engagement at one end with said fuel inlet connector and at the
other end with said armature to bias said armature downwardly
toward said valve seat.
26. The electromagnetically operable fuel injector according to
claim 25, wherein said armature includes at least two of said first
apertures extending through wall portions thereof and generally
transverse to the longitudinal axis for receiving fuel from said
generally axial elongated central opening.
27. The electromagnetically operable fuel injector according to
claim 26, wherein said armature defines a plurality of said first
apertures for receiving fuel from said generally axial elongated
central opening.
28. The electromagnetically operable fuel injector according to
claim 27, wherein said armature defines at least a plurality of
said second apertures, each said second apertures extending at a
generally acute angle to the longitudinal axis to receive fuel from
said generally central opening.
29. A method of directing gaseous fuel through an
electromagnetically operable fuel injector for a fuel system of an
internal combustion engine, said injector having a generally
longitudinal axis, and including a fuel inlet end portion and a
fuel outlet end portion, a fuel inlet connector positioned at said
fuel inlet end portion and having a fuel inlet end portion and a
fuel outlet end portion, an armature positioned adjacent said fuel
outlet end portion of said fuel inlet connector, said armature
being spaced from said fuel inlet connector to define a working gap
to permit movement of said armature toward and away from said fuel
inlet connector to selectively open and close a fuel valve by
providing upward and downward movement of a valve closing element
to selectively permit gaseous fuel to pass therethrough to an air
intake manifold, comprising: a) directing the gaseous fuel to pass
axially through said fuel inlet connector; b) directing the gaseous
fuel to pass from said fuel inlet connector to said generally
elongated central opening of said armature in an axial direction
toward said fuel valve; and c) providing an annular groove adjacent
said fixed valve seat for reception of fuel so as to reduce
pressure losses across said fuel valve during closure thereof.
30. A method of directing gaseous fuel through air
electromagnetically operable fuel injector for a fuel system of an
internal combustion engine, said injector having a generally
longitudinal axis, and including a fuel inlet end portion and a
fuel outlet end portion, a fuel inlet connector positioned at said
fuel inlet end portion and having a fuel inlet end portion and a
fuel outlet end portion, an armature positioned adjacent said fuel
outlet end portion of said fuel inlet connector and having a
generally central elongated opening for reception of fuel from said
fuel inlet connector, said armature being spaced from said fuel
inlet connector to define a working gap to permit movement of said
armature toward and away from said fuel inlet connector to
selectively open and close a fuel valve having a valve seat and a
fuel passage aperture by providing upward and downward movement of
a valve needle with respect to a needle/seat interface to permit
gaseous fuel to pass through said aperture toward an intake
manifold, comprising: a) directing the gaseous fuel to pass axially
through said fuel inlet connector; b) directing the gaseous fuel to
pass from said fuel inlet connector to said generally elongated
central opening of said armature in an axial direction toward said
fuel valve; c) directing at least a portion of the fuel flow from
said fuel inlet connector to said armature to flow generally
transversely across said working gap; d) diverting at least a
portion of the flow of gaseous fuel passing through said armature
to flow in a direction away from said axial direction; and e)
permitting fuel to enter a volumetric space adjacent said
needle/seat interface to thereby reduce pressure losses thereacross
during closure of said fuel valve.
31. The method according to claim 30, wherein said step of
permitting fuel to enter a volumetric space adjacent said
needle/seat interface is accomplished by providing an annular
groove in said valve seat adjacent said passage aperture.
Description
BACKGROUND OF THE INVENTION
[0001] 1. FIELD OF THE INVENTION
[0002] The present application relates to a compressed natural gas
injector which incorporates an improved low restriction valve
needle seat to control the fuel flow in the needle valve seat
area.
[0003] 2. DESCRIPTION OF THE RELATED ART
[0004] Compressed natural gas (hereinafter sometimes referred to as
"CNG") is becoming a common automotive fuel for commercial fleet
vehicles and residential customers. In vehicles, the CNG is
delivered to the engine in precise amounts through gas injectors,
hereinafter referred to as "CNG injectors". The CNG injector is
required to deliver a precise amount of fuel per injection pulse
and maintain this accuracy over the life of the injector. In order
to maintain this level of performance for a CNG injector, certain
strategies are required to help reduce the effects of contaminants
in the fuel and to control the flow of fuel through the
injector.
[0005] Compressed natural gas is delivered throughout the country
in a pipeline system and is mainly used for commercial and
residential heating. While the heating systems can tolerate varying
levels of quality and contaminants in the CNG, the tolerance levels
in automotive gas injectors is significantly lower. Accordingly,
utilizing CNG in engines presents problems unique to CNG as well as
to the contaminant levels.
[0006] These contaminants, which have been acceptable for many
years in CNG used for heating affect the performance of the
injectors to varying levels and will need to be considered in
future CNG injector designs. Some of the contaminants found in CNG
are small solid particles, water, and compressor oil. Each of these
contaminants needs to be addressed in the injector design for the
performance to be maintained over the life of the injector.
[0007] The contaminants can enter the pipeline from several
sources. Repair, maintenance and new construction to the pipeline
system can introduce many foreign particles into the fuel. Water,
dust, humidity and dirt can be introduced in small quantities with
ease during any of these operations. Oxides of many of the metal
types found in the pipeline can also be introduced into the system.
In addition, faulty compressors can introduce vaporized compressor
oils which blow by the seals of the compressor and enter into the
gas. Even refueling can force contaminants on either of the
refueling fittings into the storage cylinder. Many of these
contaminants are likely to reach vital fuel system components and
alter the performance characteristics over the life of the
vehicle.
[0008] In general, fuel injectors require extremely tight
tolerances on many of the internal components to accurately meter
the fuel. For CNG injectors to operate on CNG while remaining
contaminant tolerant, the guide and impact surfaces for the
armature needle assembly require certain specifically unique
characteristics.
[0009] The CNG injector is required to accurately inject metered
pulses of fuel over the life of the injector. It is also necessary
to be able to calibrate the injector to a specific calibration.
Before it is possible to calibrate a CNG injector, the design must
have solved many of the specific problems inherent in using CNG,
including higher fuel pressures and needle lift when compared to a
standard gasoline injector, choked sonic flow, and pressure losses
through the injector. For proper calibration of the injector, the
two most important parameters which require control are pressure
upstream of the choked flow, and orifice size.
[0010] In addition, to problems of contaminants in gaseous fuels,
other problems relating to flow conditions and pressure losses must
also be addressed. For example, whereas in a standard gasoline
injector orifice size is a parameter that is controlled to
extremely tight tolerances, pressure loss is a CNG, or other
gaseous fuel, specific problem which must be considered in the
overall design when using gaseous fuels in such injectors.
Nevertheless, pressure loss is a natural phenomenon which occurs as
fluid flows through any system. As the velocity of the fluid is
increased and the fluid is forced through tortuous paths the losses
can become quite substantial over the length of the path. These
losses contribute directly to the loss of overall mass flow
available from the injector. Without proper control of the high
pressure loss areas in the injector, static flows would be nearly
impossible to correlate.
[0011] The CNG injector generally has sonic flow exiting the
injector. This occurs with CNG any time there is a 55% pressure
differential across any given point in the system. While sonic
choked flow is achieved, the downstream pressure is no longer
included in the mass flow function. The only variables which
contribute to the theoretical mass flow in a choked flow system are
gas constants, upstream pressure, upstream temperature, and flow
area. The gas constants for any given fuel passing through the
injector from the fuel rail will be constant from injector to
injector, and at present the area for the orifice is controlled
very closely for gasoline applications. This leaves pressure and
temperature as potential variables. The fuel temperature will not
vary significantly from injector to injector due to the short time
available for heat transfer. However, the pressure above the
orifice is affected by all of the losses throughout the injector
and may vary between injectors.
[0012] As the fuel flows from the fuel rail through the injector,
each item comprising the flow path contributes to the total loss in
pressure. Some of these losses are small and some are quite
substantial. In the present CNG injector art, the main fuel path
consists of the filter, upper inlet connector, adjusting tube,
armature, valve body, lower guide, lower guide/seat masked area,
needle/seat interface and lastly, the orifice.
[0013] The filter, upper inlet connector, adjusting tube, lower
guide and valve body account for a very small portion of the
overall pressure loss in the injector. The armature has a small
intentional loss to allow for faster breakaway and dampening during
opening impact of the valve needle. This leaves only the lower
guide/seat interface and the needle/seat interface as the main
controllable limiting factors for controlling pressure losses.
[0014] Theoretically, the needle/seat interface can be controlled
through seat angle, spherical needle radius and lift. An increase
in lift would reduce the magnetic force of the solenoid coil and
lengthen the opening time and linearity of the injector. As the
spherical radius of the needle increases, it thereby increases the
exposed area for a given lift with the result that the net force of
the gas pressure increases. This also lengthens the opening time of
the injector. Presently such injectors utilize a needle/seat angle
of approximately 90.degree.. If the seat angle is increased from
the present 90.degree. angle, the flow area exposed for a given
lift also increases as long as the needle spherical radius is
changed to accommodate the reduced sealing diameter. This concept,
although appearing relatively simple, has several serious
drawbacks.
[0015] When the seat angle is increased, two problems occur. The
first problem is that the increased seat angle is more difficult to
grind on existing seat grinding equipment. A good compromise
between grinding capabilities and design can be reached to reduce
the effect of this problem. The second problem is that the flow
past the lower needle guide/seat interface becomes pinched and the
flow loss from this interface becomes significant. The present
invention provides significant flow control while avoiding the loss
of fuel flow through a novel valve structure which incorporates a
novel valve needle seat.
SUMMARY OF THE INVENTION
[0016] An electromagnetically operable fuel injector for a gaseous
fuel injection system of an internal combustion engine is
disclosed, the injector having a generally longitudinal axis, which
comprises, a ferromagnetic core, a magnetic coil at least partially
surrounding the ferromagnetic core, an armature magnetically
coupled to the magnetic coil and being movably responsive to the
magnetic coil, the armature actuating a valve closing element which
interacts with a fixed valve seat of a fuel valve and being movable
away from the fixed valve seat when the magnetic coil is excited.
The fixed valve seat of the fuel valve defines a central fuel
opening and a generally annular groove adjacent the central fuel
opening, the armature having a generally elongated shape and a
generally central opening for axial reception and passage of
gaseous fuel from a fuel inlet connector positioned adjacent
thereto. The fuel inlet connector and the armature are adapted to
permit a first flow path of gaseous fuel between the armature and
the magnetic coil as part of a path leading to the fuel valve.
[0017] In a preferred embodiment an electromagnetically operable
fuel injector for a compressed natural gas fuel injection system of
an internal combustion engine is disclosed, the injector having a
generally longitudinal axis, which comprises, a ferromagnetic core,
a magnetic coil at least partially surrounding the ferromagnetic
core, an armature magnetically coupled to the magnetic coil and
movably responsive to the magnetic coil, the armature having a
first upper end face and a lower end portion. A valve closing
element is connected to the lower end portion of the armature and
is interactive with a fuel valve having a fixed valve seat to
selectively permit fuel to pass through the valve seat as the valve
closing element is moved to a valve open position by the armature.
The fixed valve seat has a generally frusto-conically shaped
portion surrounded by an adjacent circular shaped annular groove to
reduce the pressure differential occurring across the valve closing
element and the fixed valve seat upon closing the fuel valve. A
fuel inlet connector extends in a generally longitudinal direction
above the armature and defines a path for fuel to enter the inlet
connector and to be directed toward the armature, the fuel inlet
connector having a lowermost end portion having a lowermost surface
spaced above the armature to define a working gap through which the
armature is movable. The armature has a fuel reception portion for
receiving fuel directed from the fuel inlet connector, and further
defines a generally axial fuel passage.
[0018] A method of directing gaseous fuel through an
electromagnetically operable fuel injector for a fuel system of an
internal combustion engine is also disclosed, the injector having a
generally longitudinal axis, and including a fuel inlet end portion
and a fuel outlet end portion. A fuel inlet connector is positioned
at the fuel inlet end portion and has a fuel inlet end portion and
a fuel outlet end portion. An armature is positioned adjacent the
fuel outlet end portion of the fuel inlet connector, the armature
being spaced from the fuel inlet connector to define a working gap
to permit movement of the armature toward and away from the fuel
inlet connector to selectively open and close a fuel valve by
providing upward and downward movement of a valve closing element
to selectively permit gaseous fuel to pass therethrough to an air
intake manifold. The method comprises directing the gaseous fuel to
pass axially through the fuel inlet connector, directing the
gaseous fuel to pass from the fuel inlet connector to the generally
elongated central opening of the armature in an axial direction
toward the fuel valve, and providing an annular groove adjacent the
fixed valve seat for reception of fuel so as to reduce pressure
losses across the fuel valve during closure thereof. In particular,
the fuel is permitted to enter in volumetric space adjacent the
fuel valve to reduce the pressure losses thereacross during closure
of the fuel valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Preferred embodiments of the invention are described
hereinbelow with reference to the drawings wherein:
[0020] FIG. 1 is an elevational view, partially in cross-section,
of a preferred embodiment of a compressed natural gas injector
incorporating a valve needle seat constructed according to the
invention;
[0021] FIG. 2 is an enlarged elevational cross-sectional view of
the lower portion of the injector of FIG. 1, showing an enlarged
view of the valve needle seat shown in FIG. 1;
[0022] FIG. 3 is a partial elevational cross-sectional view of the
lower end portion of the fuel inlet connector of the injector shown
in FIGS. 1 and 2;
[0023] FIG. 4 is a plan view of the bottom surface of the preferred
fuel inlet connector shown in FIGS. 1 and 2;
[0024] FIG. 5 is an elevational cross-sectional view of a preferred
embodiment of the armature shown in FIGS. 1 and 2 and illustrating
the improved fuel flow paths resulting therefrom;
[0025] FIG. 6 is an elevational cross-sectional view of the upper
portion of a preferred embodiment of the valve body shown in FIGS.
1 and 2;
[0026] FIG. 7 is an enlarged cross-sectional view of a valve needle
seat of the type presently used in such injectors, the valve needle
being shown in a "valve open" position; and
[0027] FIG. 8 is an enlarged cross-sectional view of an improved
valve needle seat constructed according to the present invention
and as shown in the injector in FIGS. 1 and 2, the valve needle
being shown in a "valve open" position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Referring initially to FIG. 1 there is shown a CNG injector
which is constructed according to the present invention. Injectors
of the type contemplated herein are described in commonly assigned
U.S. Pat. No. 5,494,224, the disclosure of which is incorporated by
reference herein. Injectors of this type are also disclosed in
commonly assigned copending applications; U.S. application Ser. No.
09/320,178, filed May 26, 1999, entitled Contaminant Tolerant
Compressed Natural Gas Injector and Method of Directing Gaseous
Fuel Therethrough, and U.S. application Ser. No. 09/320,176, filed
May 26, 1999, entitled Compressed Natural Gas Injector Having
Improved Low Noise Valve Needle, the disclosures of which are
incorporated herein by reference. Other commonly assigned,
copending applications include U.S. application Ser. No.
09/320,177, filed May 26, 1999, entitled Compressed Natural Gas
Injector with Gaseous Damping for Armature Needle Assembly During
Opening, U.S. application Ser. No. 09/320,175, filed May 26, 1999,
entitled Gaseous Injector with Columnated Jet Orifice Flow
Directing Device and U.S. application Ser. No. 09/320,179, filed
May 26, 1999, entitled Compressed Natural Gas Injector Having
Magnetic Pole Face Flux Director, the disclosures of which are also
incorporated herein by reference.
[0029] The injector 10 includes housing 12 containing armature 14
to which valve needle 16 is attached by crimping in a known manner.
Fuel inlet connector 18 includes central fuel flow opening 13 and
CNG filter 20 at the upper end portion of opening 19 as shown. The
fuel inlet connector 18 also includes adjusting tube 22 connected
thereto at 24 by a known crimping procedure. Housing 12 includes
inner non-magnetic shell 26 which surrounds the inlet connector 18
and armature 14 having central fuel flow opening 11 as shown.
Armature 14 and fuel inlet connector 18 define with housing 12, an
enclosure for solenoid coil 28 which is selectively energized to
move armature 14 and needle 16 upwardly to open the valve aperture
41, and selectively deenergized to permit armature 14 and needle 16
to return to the "closed valve" position as shown, under the force
of coil spring 30. Fuel flow into the injector begins at filter 20
and passes through fuel inlet connector 18, to armature 14, and
ultimately to valve aperture 41 of valve seat 40 into the intake
manifold of the engine (not shown).
[0030] Referring further to FIG. 1 in conjunction with FIG. 2,
valve body shell 32, which is made of a ferromagnetic material and
which forms part of a magnetic circuit, surrounds valve body 34 and
has at the upper end, upper guide 36 as shown. Space 36a between
upper guide 36 and armature 14 is about .010 to about .015 mm on
the diameter, and permits guiding movement of armature 14. Lower
O-rings 38 provide sealing between the injector 10 and the engine
intake manifold (not shown) and upper 0-rings 39 provide sealing
between the injector 10 and the fuel rail (also not shown). Valve
body 34 defines central fuel flow opening 35.
[0031] In FIG. 2, valve body shell 32 is attached to valve body 34,
preferably by weld 32a, and at the upper end by weld 26a, to
non-magnetic shell 26. Non-magnetic shell 26 is in turn welded to
fuel inlet connector at 26b. Thus, fuel flowing from fuel inlet
connector 18 across working gap 15 must flow through the clearance
space 14a between armature 14 and valve body shell 23 which is also
provided to permit upward and downward movement of armature 14. The
space 14a is approximately 0.10 to 0.30 mm on the diameter.
[0032] Referring again to FIGS. 1 and 2, valve seat 40 contains a
valve orifice 41 and a funnel shaped needle rest 42 having a
frusto-conical cross-sectional shape. The valve seat 40 is
maintained in position by back-up washer 44 and sealed against fuel
leakage with valve body 34 by O-ring 46. Overmold 48 of suitable
plastic material such as nylon supports terminal 50 which extends
into coil 28 and is connected via connection 51 to provide
selective energization of the coil to open the valve by raising the
armature 14 and valve needle 16 against the force of spring 30.
Armature upward and downward movement is permitted by interface
space 15 (or working gap) between the inlet connector 18 and the
armature 14. The working gap is generally extremely small i.e. in
the order of about 0.3 mm (millimeters). Solenoid coil 28 is
surrounded by dielectric plastic material 53 as shown in the
FIGS.
[0033] In injectors of this type, the interface space 15 (or
working gap 15) between the inlet connector and the armature is
extremely small, i.e. in the order of about 0.3 mm (millimeters),
and functions relatively satisfactorily with conventional fuels
which are relatively free of contaminants such as water, solids,
oil, or the like, particularly after passing through a suitable
fuel filter. Accordingly, when the two surfaces surrounding space
15 are in such intimate contact that the atmosphere between them is
actually displaced in relatively significant amounts, atmospheric
pressures acting on the two members actually force the two surfaces
together. Any liquid contaminant present at the armature/inlet
connector interface would allow for the atmosphere to be displaced,
thereby adversely affecting the full and free operation of the
armature/needle combination.
[0034] When known injectors, which functioned at relatively
acceptable levels with relatively clean conventional fuels, were
utilized with CNG, impurities such as oil or water at the inlet
connector/armature interface produced a force of about 16.5 Newtons
holding the armature to the inlet connector. In comparison, the
force provided by spring 30 is in the order of about 3 Newtons,
thus fully explaining the erratic closing of the armature/valve
needle when the fuel utilized with known injectors is CNG. In
particular, the 16.5 Newton force holding the inlet connector and
armature together is due to the fact that the fuel operating
pressure within the injector is about 8 bar (i.e. 8 atmospheres)
and this force of about 16.5 Newtons acts across the lower surface
area of the inlet connector 18, which is about 21 square
millimeters (i.e. mm.sup.2). Thus a relatively minor slick of oil
or other impurity within space 15 of a known injector will cause
the inlet connector and the armature to become temporarily attached
to each other, particularly due to the 8 bar pressure acting on the
remaining surfaces of the inlet connector and armature. As noted,
the tendency for the armature to become attached to the inlet
connector results in erratic valve closing.
[0035] The present injector eliminates the aforementioned erratic
valve closing and improve the operation of the injector with
gaseous fuels. In FIG. 3, the lower end portion of inlet connector
18 is configured as shown by the arcuately chamfered end 52. This
configuration provides a beneficial effect in that it directs and
orients the magnetic field across the working gap 15 in a manner
which optimizes the useful magnetic force created for moving the
armature through the working gap. This feature is disclosed in
commonly assigned application entitled Compressed Natural Gas Fuel
Injector Having Magnetic Pole Face Flux Director, the disclosure of
which is incorporated herein by reference. Additional related
features are also disclosed in the aforementioned commonly assigned
copending application entitled Compressed Natural Gas Injector
Having Gaseous Dampening For Armature Needle Assembly During
Opening.
[0036] In addition, as shown in FIG. 4, radial slots in the form
recessed surfaces 18a are provided in the lowermost surface of
inlet connector 18 to reduce the effective contact surface area
between the armature and the inlet connector by about one-third of
the total cross-sectional area which was utilized in prior art
conventional injectors. This configuration provides six coined pads
18b of about 0.005 mm in height, thus creating six corresponding
rectangular shaped radial slots 18a to provide fuel flow paths. By
reducing, the effective surface area of the lowermost face of the
inlet connector 18 as shown, the tendency to develop an attractive
force between the inlet connector 18 and the armature 14 is
significantly reduced to about one-third of its original valve, and
the ability to tolerate fuel contaminants at the interface without
producing an attractive force therebetween is also significantly
increased. As noted, preferably, the rectangular radial slots 18a
are of a shallow depth, i.e. about 0.05 mm, (i.e., millimeters) in
order to provide the benefit of reducing the inlet
connector/armature interface surface area while still providing a
relatively unobtrusive location for collection of solid
contaminants which are ultimately removed by the flow of gaseous
CNG.
[0037] As noted, the provision of recessed surfaces 14a in the
lowermost surface of inlet connector 18 creates raised pads 18b on
the surface, which pads improve the tolerance of the injector to
fuel contaminants in several ways. The recessed surfaces 18a may be
made by any suitable process, but are preferably coined. The first
effect is to reduce the contact area of the inlet connector at the
armature interface, thereby significantly reducing any attractive
force generated therebetween by liquid contaminants such as oil or
water. Furthermore, as noted, the radial pads 18b provide hidden
areas between the pads where contaminants can collect without
affecting the operative working gap 15 until being drawn away by
the fuel flow. The working gap for gasoline is about 0.08 mm to
about 0.14 mm and about 0.3 mm for compressed natural gas. In
addition, as noted, the provision of the six rectangular recessed
portions in the form of slots 18a and six raised pads 18b, each
having a generally trapezoidal shape, on the inlet connector,
provide a unique fuel flow path past transversely through the
working gap 15 as shown at 56 in FIG. 5 and allow for the control
of the fuel flow around and through the armature by controlling the
pressure losses.
[0038] Also, by controlling the sizes of the recessed surfaces 18a
and raised pads 18b, and the various apertures 58, 60, 66 in the
armature and the valve body as will be described--as well as the
numbers and combinations of such openings--the fuel flow can be
controlled over at least three flow paths and pressure losses can
also be controlled. For example, a small pressure differential
across the armature while fully open, assists spring 30 during
breakaway upon closing the provides dampening on opening impact.
The additional fuel flow path also reduces the possibility of
contaminants collecting above upper guide 36 as shown in FIG. 2. In
summary, numerous combinations of apertures and sizes thereof--as
well as slots and pads on the fuel inlet connector--can be made to
direct the gaseous fuel flow in any desired manner which is best
for optimum fuel burning and engine application.
[0039] Referring now to FIGS. 5 and 6 in conjunction with FIGS.
1-3, there is illustrated still another significant improvement
which renders the present fuel injector assembly more fully capable
of operation with CNG. In injectors which were used with relatively
contaminant free liquid fuels the fuel would pass through the
filter down through the inlet connector into the armature and out
an opening positioned relatively close to the lowest portion of the
armature which was located substantially immediately above the
valve aperture. In the present structure there is provided a
relatively diagonally oriented aperture 58 in the armature as shown
in FIG. 5, which directs the CNG flow therethrough and downwardly
toward valve aperture 41 for entry into the intake manifold of the
internal combustion engine.
[0040] As shown in FIG. 5, aperture 58 forms a generally acute
angle with longitudinal axis A--A of the fuel injector 10. In
addition, the armature of the present invention provides at least
one side opening 60 which is generally transverse to the
longitudinal axis A--A, to permit fuel flowing downwardly through
the center of the armature to be directed sidewardly out of the
armature and thereafter downwardly toward the valve aperture 41
shown in FIG. 1. In the embodiment shown in FIG. 1, aperture 60 is
generally horizontal, but may be oriented at an acute angle to the
longitudinal axis if desired. Aperture 58 is not shown in the
cross-sectional view of armature 14 in FIG. 1. The fuel flowing
through aperture 60 is indicated by the flow lines 62 and the fuel
flowing through aperture 58 is indicated schematically by flow
lines 64. Optionally several additional horizontal apertures 60 may
be provided in the armature at different radial locations
thereabout, or alternatively as shown, one aperture 60 may be
provided, depending upon the fuel flow pattern sought in each
particular instance. It can be seen that the fuel flow from the
fuel inlet connector 18 is divided into three paths, a first path
expanding across working gap 15, a second path through aperture(s)
60, and a third path through aperture(s) 58. The first path extends
between the armature 14 and the magnetic coil 28 and is ultimately
joined by the second flow path passing through aperture(s) 60.
[0041] It can also be readily appreciated that the diameters of
each aperture 58, 60 can be varied to direct the fuel flow in any
predetermined desired direction. For example, by reducing the size
of apertures 58, 60 fuel will be encouraged to flow with increased
volume cross the working gap 15. Alternatively, increasing the
diameter of apertures 58, 60 will attract greater volume of fuel
through those apertures and thereby reduce the fuel flow across the
working gap. It has also been found that the diameters of the
apertures 58, 60 and the numbers and locations of such apertures
affect the dampening characteristics of the valve needle 16, both
upon opening and upon closing. Accordingly, the diameter of fuel
flow apertures 58, 60 and the numbers, locations, and orientations
of such apertures will depend upon the desired volumetric flow
characteristics and desired flow patterns in each instance;
however, diameters within the range of 1-2 mm have been found to be
preferable.
[0042] Referring now to FIG. 6, a valve body 34 is also provided
with central fuel flow opening 35 and several diagonally oriented
fuel path apertures 66 which are intended to receive the CNG fuel
flowing from the first and second flow paths from the working gap
15 and aperture(s) 60 along the sides of the armature 14 and to
redirect the fuel downwardly toward the valve aperture 41. When the
needle 16 is lifted, the fuel is permitted to enter aperture 41 and
thereafter directed into the intake manifold of the engine, which
is not shown in the drawings. Fuel flowing along the third flow
path through aperture(s) 58 lead directly toward aperture 41. It
has been found that the unique provisions of the apertures 58 and
60--as well as rectangular radial slots 18a on the inlet connector
lowermost face--create a fuel flow pattern which induces the CNG to
flow in the manner shown by the fuel flow lines at 56 61 and 64 in
FIG. 5 and such fuel flow lines actually create ideal pressure
conditions to avoid causing the armature to be attracted to the
inlet connector. Thus the attractive forces between the armature
and inlet connector are minimized by the several factors mentioned,
namely the elimination of the tendency of the oil and contaminates
to accumulate in the space 15 located between the armature and the
inlet connector, the reduction of the effective inlet
connector/armature interface area by provision of radial pads on
the face of the inlet connector, and the unique CNG flow patter
which creates a force free environment between the inlet connector
and the armature.
[0043] As indicated, alternatively, apertures 60 may be provided in
several locations about the circumference of the armature, and
apertures 58 may be provided in several locations thereabout. Also
their angular orientations may be varied. However, it has been
found that a single aperture on each side, as shown is sufficient
to produce the desired flow path and the force free environment.
Also, as noted, it should be noted that the diameter of each
aperture can be altered in order to provide control of the fuel
pressures and flow patterns in the areas surrounding the inlet
connector, the armature, and the valve body, so as to provide a
predetermined fuel flow pattern throughout the injector as may be
desired. This feature is more fully disclosed in the aforementioned
commonly assigned, copending application entitled Compressed
Natural Gas Injector Having Gaseous Damping For Armature Needle
Assembly During Opening.
[0044] It should also be noted that the presence of the diagonally
oriented fuel flow apertures 66 in valve body 34 eliminates the
problems of prior art injectors wherein debris and contaminants
would accumulate in the area of the upper valve guide 36, causing
abrasive action and intermittent guidance between the upper guide
36 and the armature 14. Thus, the provision of the diagonally
oriented apertures 66 in valve body 34 encourage the flow of CNG
past the area surrounding the upper guide 36 and eliminate any
accumulation tendencies for contaminants in the area of upper guide
36.
[0045] Referring now to FIGS. 7 and 8 there is shown a comparison
between the valve needle seat of the type used in earlier
developments, and the low restriction valve needle seat constructed
according to the present invention.
[0046] In FIG. 7, there is illustrated a tip portion 17 of a valve
needle 16 of the type shown in FIGS. 1 and 2, in combination with a
valve needle seat 82 of the type used in earlier developments.
Lower needle guide 80 is shown in cross-section in combination with
the tip portion 17 of needle 16, and is also shown in FIG. 9. As
can be seen, the valve needle seat 82 has a frusto-conically shaped
needle rest, all sides of which form an angle of approximately
90.degree., and a valve orifice 81 which, together with the needle
rest surfaces 84, 86 form a funnel like arrangement through which
the gaseous fuel must pass. Although needle rest surfaces 85, 86
actually form part of the same frust-conical surface, they are
referred to separately for convenience of the description.
[0047] In contrast to the valve needle seat shown in FIG. 7, the
valve needle seat 40 constructed according to the present invention
is shown in FIG. 8. Referring to FIG. 8, it can be seen that the
valve needle seat 40 includes frusto-conical valve needle seat
surface 88, which is continuous and which forms an angle of
approximately 90.degree. in cross-section. However, valve needle
seat 40 also includes an arcuate circular annular groove 92 having
an arcuate surface 94 as shown, which connects the vertical surface
and the horizontal surface of the groove 92 as shown. The function
and purpose of groove 92 will best be appreciated by referring to
FIG. 9, which illustrates a plan view of lower valve needle guide
80.
[0048] Referring now to FIG. 9, lower valve needle guide 80
includes arcuate apertures 96 which permit the flow of gaseous fuel
therethrough for passage through valve aperture 41. Although
arcuate apertures 96 are relatively large, the lower valve needle
guide nevertheless tends to present a restriction to the passage of
gaseous fuel thereby. Accordingly, in the structure shown in FIG.
7, as the needle 16 moves downwardly toward the valve seat 82 to
pinch the flow at the contact points 43, immediately prior to
actual contact, the pressure differential across the contact points
43 is substantial in that the pressure between the lower valve
guide and the contact points 43 is substantially greater than the
pressure on the opposite side of the contact points 43 just prior
to contact being completed. In fact, the presence of the lower
needle guide 80 tends to increase the pressure in the zone
immediately above the contact points 43. Although "contact points
43" are referred to as "points," they each in fact are points on
the same circle formed by the points of tangency between the
arcuate needle contact surface and the needle rest surface.
However, they are referred to separately for convenience of the
description.
[0049] In contrast thereto, as shown in FIG. 8, the presence of the
annular groove 92 which is provided in the needle valve seat tends
to reduce the differential pressure across the seal points 43 by
providing additional volumetric space between the lower needle
guide 80 and the valve seat 40. Thus, the pressure differential
across the seal points 43 is somewhat reduced thereby reducing the
flow reducing pressure losses otherwise occurring across the point
of contact between the needle 16 and the valve seat 40. Since such
pressure losses tend to reduce the fuel flow passing through the
injector, the provision of the unique valve seat 40 as shown in
FIG. 8 has been found to avoid such reduction in fuel flow which
occurs normally as a result of such pressure losses. This factor
increases the energy flow into the engine with correspondingly
increased efficiency.
[0050] Although the invention has been described in detail with
reference to the illustrated preferred embodiments, variations and
modifications may be provided within the scope and spirit of the
invention as described and as defined by the following claims.
* * * * *