Compressed natural gas injector with gaseous damping for armature needle assembly during opening

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, 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 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 through a working gap between the fuel inlet connector and the armature and between the armature and the magnetic coil as part of a path leading to the fuel valve. The combined flow area across the working gap between the armature and the magnetic coil and valve body shell exceeds the area available for fuel flow through the armature. A method of directing gaseous fuel through the fuel injector is also disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present application relates to a Gaseous Damping System and method of 
controlling gaseous fuel flows for a compressed natural gas injector 
during opening of the injector. 
2. Description of the Related Art 
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 fuel injectors, hereinafter referred to as "CNG 
injectors", or simply "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 and sequences of 
operation are required to optimize the combustion of the fuel. 
The CNG (Compressed Natural Gas) injector is required to open and close 
very quickly to promote efficient fuel consumption. In order to accomplish 
this objective effectively the magnetic circuit utilized to open the valve 
needle must produce a magnetic field--or flux--relatively quickly across 
the working gap between the fuel inlet connector and the armature. The CNG 
injector has a magnetic circuit consisting of an inlet connector, 
armature, valve body shell, housing and a coil. When energized, the coil 
produces a magnetic field which is conducted through the magnetic circuit. 
The flux is conducted through the components and creates an attractive 
force at the working gap, which force causes upward movement of the 
armature, with consequent upward movement of the valve needle to open the 
injector valve. 
The CNG injector is required to open and close very quickly. This quick 
opening creates a relatively severe impact between the armature and the 
inlet connector. In the CNG injector, the factors which effect impact 
velocity between the armature and inlet connector are more severe then in 
a gasoline injector. Compared to a gasoline injector, the CNG injector has 
two to three times the lift, less spring preload and similar force 
required to open the injector. The difference is then exaggerated by the 
lower viscosity (CNG) fluid then gasoline. 
A CNG injector requires a much higher flow rate and area to obtain the same 
amount of energy flow through the injector in a given pulse. This is 
caused by the lower density of the gaseous CNG when compared to standard 
gasoline. This requires that the lift for a CNG injector be much greater 
than it is for a gasoline injector. 
The increased lift creates two problems. First, the increased lift 
substantially reduces the magnetic force available to open the injector. 
Second, the velocities created because of the longer flight times can be 
higher, creating higher impact momentum. The reduction in magnetic force 
also creates another problem. This reduction in force requires the use of 
a lighter spring preload than in a standard gasoline injector. 
A standard gasoline injector usually utilizes about 4 Newton's of spring 
preload and a very small gasoline force on the needle armature assembly 
while the injector is closed. In a CNG injector, the force of the gas 
pressure is about 3 Newton's and the force of the spring is about 2 
Newton's. When the CNG injector is energized, the needle armature will 
begin to move when the magnetic force reaches a level which can overcome 
the spring and the gas force. The gasoline injector will operate in the 
same way. However, in a CNG injector, the gas force is removed as soon as 
the needle/seat seal is broken and the pressure equalizes at the tip of 
the needle. At this point the magnetic force is substantially higher then 
it needs to be to lift the armature needle assembly against the force of 
the spring. This excess magnetic force, combined with a relatively light 
spring preload, high lift and low viscosity fluid all contribute to high 
impact velocities between the armature and the inlet connector. We have 
invented a Compressed Natural Gas Injector which provides gaseous damping 
for the armature/needle assembly during opening of the gaseous fuel valve. 
SUMMARY OF THE INVENTION 
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, 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 armature 
has 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 through a working gap 
between the fuel inlet connector and said armature and between the 
armature and the magnetic coil as part of a path leading to the fuel 
valve. At least one first fuel flow aperture extends through a wall 
portion of the armature to define a second flow path of gaseous fuel as 
part of a path leading to the fuel valve, the at least one fuel flow 
aperture being dimensioned to provide predetermined fuel flows past said 
armature and through said armature. Preferably the 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 the fuel valve. The at 
least one second aperture is dimensioned and oriented with respect to the 
longitudinal axis to provide predetermined volumetric flow rates around 
the armature and through the armature such that the combined flow area 
across the working gap and through the working gap between the armature 
and the magnetic coil exceeds the area available for fuel flow through the 
armature. Preferably the at least one second aperture is oriented at a 
generally acute angle with respect to the longitudinal axis. 
The fuel inlet connector and the armature are spaced to define a working 
gap therebetween and are adapted to permit the first flow path of gaseous 
fuel within the working gap. The fuel injector further comprises a valve 
body positioned downstream of the armature and having at least one 
aperture in a wall portion thereof for reception of fuel from at least two 
of the flow paths of gaseous fuel from the armature and the fuel inlet 
connector. 
The fuel injector further comprises a valve body shell at least partially 
surrounding the armature and the valve body, the valve body shell defining 
a radial space with the armature for passage of the first flow path of 
gaseous fuel between the armature and the magnetic coil and valve body 
shell. The fuel inlet connector is positioned above the armature and is 
spaced from the armature by a working gap, the fuel inlet connector 
defining a through passage for directing fuel toward the armature and the 
fixed valve seat. The 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, the lower end portion having a lower 
surface which faces an upper surface of the armature, the lower surface of 
the fuel inlet connector having a plurality of radially extending raised 
pads defined thereon, the pads having recessed portions therebetween to 
permit fuel to flow therethrough and across the working gap defined 
between said fuel inlet connector and said armature. The at least one 
first and second apertures in the armature are from about 1 to about 2.0 
mm in diameter. 
The 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 
the fixed valve seat, the at least one second aperture having a diameter 
from about 1.0 mm to about 2.0 mm. The lowermost surface of the fuel inlet 
connector and the 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. Further, a fuel 
filter is positioned at an upper end portion of the fuel inlet connector 
for filtering fuel prior to reception by the fuel inlet connector. 
The 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 the lower surface portion of the fuel inlet connector facing the 
armature to thereby permit the gaseous fuel to flow generally transversely 
in the working gap, the transverse fuel flow thereby preventing 
accumulation of contaminants in the working gap. The generally radially 
extending pads preferably have a generally trapezoidal shape and are about 
0.05 mm in height. 
A method is disclosed for 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 the fuel inlet end portion 
and having a fuel inlet end portion and a fuel outlet end portion, an 
armature positioned adjacent the fuel outlet end portion of the fuel inlet 
connector and having a generally central elongated opening for reception 
of fuel from the fuel inlet connector. The armature is 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 to permit gaseous fuel to pass therethrough to an 
air intake manifold. The method comprises directing the gaseous fuel to 
pass axially through said 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, 
directing at least a portion of the fuel flow from the fuel inlet 
connector to the armature to flow generally transversely across the 
working gap, and diverting at least a portion of the flow of gaseous fuel 
passing through the armature to flow through at least one aperture in a 
wall portion of the armature, the aperture being dimensioned between about 
1.0 mm and about 2.0 mm and being oriented in a direction away from the 
axial direction. According to the method, the aperture in the wall portion 
of the armature extends generally transverse to the axial direction and 
the combined flow area across the working gap and through the working gap 
and between the radial space between the armature and the valve body shell 
exceeds the area available for fuel flow through the armature. The lower 
end portion of the fuel inlet connector faces an upper end portion of the 
armature and is configured to permit the gaseous fuel to flow from the 
fuel inlet connector to be directed transversely across the working gap. 
The gaseous fuel flowing in the armature is permitted to pass through at 
least one second aperture in a lower wall portion thereof, the at least 
one second aperture extending at an acute angle to the longitudinal axis, 
and being dimensioned between about 1.0 mm and about 2.0 mm in diameter, 
whereby at least three separate fuel flow paths are established. According 
to the method, the fuel inlet connector includes a plurality of adjacent 
raised pads on a lowermost end portion thereof, the raised pads being 
respectively spaced by adjacent recessed portions and being about 0.05 mm 
in height to permit the flow of gaseous fuel through the working gap when 
the armature moves toward the fuel inlet connector to thereby open the 
fuel valve. Predetermined numbers of the first and second apertures are 
provided and the diameters thereof are predetermined to establish a 
predetermined number of fuel flow paths and volumetric flow rates thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring initially to FIG. 1 there is shown a CNG injector 10 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. 
Significant features of the present invention are also disclosed in 
commonly assigned, commonly filed (Attorney Docket No. 98P7677US01) 
copending application entitled "Contaminant Tolerant Compressed Natural 
Gas Injector and Method of Directing Gaseous Fuel Therethrough, the 
disclosure of which is incorporated herein by reference. 
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 inlet connector 18 define with housing 12, an 
enclosure for 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). 
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 0.010 to about 0.015 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 O-rings 
40 provide sealing between the injector 10 and the fuel rail (also not 
shown). Valve body 34 defines central fuel flow opening 35. 
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 32 which is also provided to permit upward and downward movement of 
armature 14. The space 14a is approximately 0.10 to about 0.30 mm on the 
diameter. 
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. Coil 28 is 
surrounded by dielectric plastic material 53 as shown in the FIGS. 
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. Lower O-rings 38 provide sealing between the injector 
10 and the engine intake manifold (not shown) and upper O-rings 40 provide 
sealing between the injector 10 and the fuel rail. 
Referring again to FIGS. 1 and 2, valve seat 40 contains a valve orifice 41 
and a funnel shaped needle rest 42. 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 supports terminal 50 which extends into 
coil 28 and is connected via connection 51 (shown schematically) 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. Coil 
28 is surrounded by dielectric plastic material 53 as shown in the FIGS. 
As shown in FIG. 4, radial slots in the form of 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 0.05 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 value, 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. 
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 the inlet 
connector/armature interface in a manner which causes the gaseous fuel to 
pass 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. 
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 and 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. 
Referring now to FIGS. 5 and 6 in conjunction with FIGS. 1-3, there is 
illustrated still another significant improvement which renders the fuel 
injector assembly more fully capable of operation with CNG. In prior art 
injectors 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 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. 
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 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. 
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 damping 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. 
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 such that when the needle 16 is lifted, the fuel is 
permitted to enter aperture 41 and thereafter directed into the intake 
manifold of the engine, neither of which are 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, 62 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 provision of the unique 
CNG flow pattern which creates a force free environment between the inlet 
connector and the armature. 
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. 
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. 
The operation of the present invention will now be described. The stages 
that a CNG injector goes through while initiating opening begin with 
energizing the coil and building of magnetic flux (force) across the 
working gap. Next, this force builds to a level greater than the combined 
spring and gas forces acting on the armature needle assembly, opening the 
injector. After the armature begins moving toward the inlet connector, the 
gas force is removed, the magnetic force increases rapidly, and the spring 
is compressed to store energy which will close the injector when the coil 
is deenergized. 
The last stage of opening presents a difficult damping problem. The spring 
30 only removes (i.e., stores) energy linearly as the working gap 15 is 
decreased. The magnetic circuit adds energy to the armature assembly 
roughly as the square of the working gap. This fact alone already accounts 
for a difficult problem. When the gas force is also considered to have 
been removed after beginning to open, the armature assembly 14 undergoes a 
significant acceleration. This acceleration creates high velocity and high 
impact forces. To solve this problem the present invention provides 
damping of the components. 
As described hereinabove, according to the invention, multiple paths are 
provided by which fuel flows through the armature and past the working 
gap. The sequence of flow is shown in the stages of opening shown in FIGS. 
7-9. In particular, the present invention intentionally allows more total 
flow past the armature (around and through) while it is in motion than 
while it is fully open. When the armature nears the inlet connector, the 
armature is attempting to restrict already established flow across the 
working gap, thus forcing the fuel to pass through the armature. This 
restriction thus creates the damping. By controlling the available flow 
area below the working gap and through the armature, the amount of damping 
can be adjusted. Such control is achieved by controlling the dimensions 
and numbers of apertures 58, 60, as well as by controlling the dimensions 
and numbers of recessed slots 1 8b and pads 1 8a on inlet connector 18. 
In the present instance, the CNG injector has three flow paths. One path is 
across the working gap and around the armature. The second path is through 
aperture(s) 60 to meet the first path. The third path is through the 
armature and aperture(s) 58. Ultimately all paths are directed to fuel 
valve aperture 41 and to the intake manifold of the engine. While in 
motion, the combined flow area across the working gap and through the gap 
between the armature and the magnetic coil and valve body shellexceeds the 
area available for fuel flow through the armature. As the armature nears 
the inlet connector, the flow area across the working gap is restricted to 
the point that a pressure differential is created. This pressure 
differential, higher pressure inside the armature and lower pressure 
outside, removes energy from the incoming armature and reduces it's impact 
velocity. 
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.