Electromagnetic fuel injector

A high flow rate electromagnetic injector valve with a rapid response time is disclosed for utilization in a single point fuel injection system. Centrally bored end caps are fixed at the front and rear ends of a tubular injector body and a coil wound on a bobbin is disposed inside the body chamber between the end caps. The front end cap receives within its bore a valve assembly including a valve housing and a needle valve with attached armature reciprocally movable against a valve seat to obturate a metering orifice in the valve housing. The valve housing contains fuel inlets for the pressurized entry of fuel into the injector and the needle valve is ported to provide fluid communication to the armature to relieve pressure build-up. The rear end cap mounts within its bore a core member acting as a stator which extends through a central bobbin bore to form a controllable air gap adjacent the armature: the core member further contains internally an adjustment screw and ball member. The ball member and adjustment screw cooperate with a recessed closure spring positioned substantially within the armature to controllably bias the needle valve against the valve seat. Because of its recessed position, the force of the closure spring is applied substantially along the central axis of the injector valve and the ball member prevents torsional windup forces from being generated by the spring. O-ring seals for the bobbin bore are provided in compression between recesses in the bobbin and the slower contracting material of the front end cap and core member to produce extended cold temperature operation.

FIELD OF THE INVENTION 
The invention pertains generally to electromagnetic injector valves and is 
more particularly directed to a fast-acting high-flow rate single point 
injector valve. 
BACKGROUND OF THE INVENTION 
Electromagnetic fuel injection valves are gaining wide acceptance in the 
fuel metering art for both multipoint and single point systems where an 
electronic control system produces a pulse width signal representative of 
the quantity of fuel to be metered to an internal combustion engine. These 
injectors operate to open fuel metering orifices leading to the air 
injestion paths of the engine by means of a solenoid actuated armature 
responding to the electronic signal. Because of recent advances, these 
injectors are becomming very precise in their metering qualities and very 
fast in their operation. With these advantages, the electromagnetic fuel 
injector valve will continue to assist the advances in electronic fuel 
metering which improve economy, reduce emissions, and aid drivability of 
the internal combustion engine. 
The electromagnetic injector valve is, however, relatively expensive to 
manufacture because of a precision metering portion which must be 
carefully coupled to a magnetic motor circuit and, thereafter, to an 
electrical control while being contained in a single injector body. All of 
these sections must cooperate properly for the valve to provide maximum 
performance and should be contained in the minimum space. It is important 
in single point metering applications where the injector is mounted above 
the throttle plate that the injector package not block air flow into the 
air ingestion bore. 
The injector body manufacture has been one contributor to the expense of 
manufacturing an injector valve. Generally, the injector body is 
manufactured from a cylindrical metal blank by a plurality of automatic 
machining operations. The most common configuration is a plurality of 
differently stepped or diametered bores which are machined to close 
tolerances and which form shoulders at the steps with the bores coaxial to 
each other. Such an injector body is illustrated in a U.S. Pat. No. 
3,967,597 issued to Schlagmuller. The close tolerance or the depth of the 
bores in relationship to the others are used to locate other portions of 
the injector, such as the valve closure portion precisely with respect to 
the moving section of the valve which contains the armature and stator. 
Usually, all the bores are coaxial because the fluid flow path is centrally 
located through the valve and the needle valve is biased against a conical 
seat and should have an equal peripheral sealing pressure around the seat. 
The precision of the depth of the multiple step bores, their coaxial 
relationship, and their number generally requires that the injector body 
has to be chucked or remounted more than once during the machining 
operation which adds expense to the manufacturing costs. An injector that 
could be manufactured from parts requiring only a single machining 
operation or by eliminating altogether a part requiring multiple machining 
operations would be desirable. 
The static and dynamic fuel flow characteristics are important to the 
operation of the injector valve and are controlled by a number of 
different parameters. In an electromagnetic valve, to provide a fast 
acting valve with a stable dynamic fuel flow, the opening and closing 
times must be minimized but kept relatively certain and reproducible. One 
factor directly influencing the opening and closing times of the injector 
is the closure force that the valve spring applies to the needle valve. 
The amount of spring pressure is linearly related to the amount the spring 
is compressed, or F=Kx where x is the compression distance. The higher the 
closure force, the slower the opening time of the valve will be, and, 
conversely, the faster the valve will close. 
Another interrelated factor is the distance through which the magnetic 
force acts upon the armature, and thus, the amount of travel the needle 
valve takes from the valve seat, or, as it is commonly called, the lift of 
the valve. The longer the lift or the greater the air gap, the slower the 
valve will open. At the other extreme, there is a minimum air gap that 
should be maintained to allow the collapse of the magnetic field when the 
injector is deenergized. If the minimum gap is not maintained during 
operation, the armature will tend to stick to the stator, and thus, affect 
the closing time of the valve. 
In many prior art valves the lift is designed to be greater than that which 
would restrict static fuel flow. Therefore, the size of the metering 
orifice is designed to be the only controlling factor of flow rate when 
the valve is open. This is not an optimal design because the lift is 
greater than necessary thereby affecting the opening time of the valve, 
and a valuable control parameter for regulating the static flow rate has 
not been utilized. 
In the Schlagmuller reference, the lift of the prior art valve is 
controlled by a spacer collar abutting a precisely machined spacer washer 
of a fixed thickness and the spring pressure force is adjusted upon 
assembly of the valve by axial movement of the core member which is then 
pinned to fix the pressure. In this valve the lift is structurally set and 
subsequently the spring pressure adjusted and fixed during assembly to a 
set value. The lift is such that static fuel flow is controlled only by 
the size of the metering orifice. These valves which have a static fuel 
flow out of tolerance must be disassembled and their metering orifices 
rebored. 
It would be highly desirably, since the two factors of lift and closure 
force are very much related to static fuel metering and the speed of valve 
operation, if they could be independently adjusted so as to complement 
each other. Further, it would be advantageous to adjust these 
characteristics of the electromagnetic injector valve after assembly to 
precisely tailor each valve characteristic. 
Another problem that has affected the speed of operation and reproducible 
opening and closing times of the electromagnetic injector valve has been 
the eccentric loads from the closure spring whereby the needle valve has a 
component or plurality of force components applied to it not acting 
coaxially to the spray axis. This causes wear on the bearing surfaces 
which hold the needle coaxial with the spray axis and frictional spots 
where the valve hesitates as it moves within the valve housing. The long 
moment arm through which the closure spring acts is primarily responsible 
for the eccentric loads. The closure force is usually applied to the 
armature at the point on the needle valve farthest from the valve seat 
which acts as a fulcrum. Any axial offset force is magnified by the moment 
arm and must be absorbed and balanced by the needle valve bearing 
surfaces. 
Torsional or windup pressures on the closure spring will also produce a 
change in the force provided against the needle valve. If possible, while 
adjusting the spring pressure, winding the spring or providing a torsional 
component to the closure force should be avoided and only substantially 
coaxial compression should be applied to the closure spring. 
Another problem that has occured in single point electromagnetic injector 
valves with fuel inlets located substantially at the valve end is that 
fuel will be drawn up the guide bore of the armature and into the air gap 
between the core member and the armature when movement between them 
occurs. As the guide bore and armature form a relatively small clearance 
so as to maintain the needle coaxial, fuel that finds its way into the air 
gap will build up pressure due to the pumping action of the armature 
against the core. This phenomenon of increasing hydraulic pressure at the 
interface of the movement will cause a slowing in the opening time of the 
valve. In this type of single point injector it would be highly desirably 
to provide a means to relieve this pressure so as not to create any 
detrimental affects on the dynamic operation of the valve. 
As the electromagnetic fuel injector is accepted in wide-spread use, there 
will have to be an extension of the environmental temperature range over 
which it is operational. One present limitation of prior art valves has 
been their cold temperature operation because of the sealing properties of 
the O-rings contained therein. Generally, the O-rings are elastomeric 
rings of rubber or material which remains substantially flexible at normal 
ambient temperatures or increased temperatures. They seal relatively well 
between the dissimilar materials of the injector body and the bobbin which 
expand and contract at different volumetric rates. However, at colder 
temperatures, especially in the ranges beyond -20.degree. F., they start 
to become inflexible and fairly brittle. At this point the dissimilar 
contraction rates between the bobbin and injector body will cause a 
separation between the O-ring and its interface and consequent leakage of 
pressurized fuel. It would be advantageous to provide an injector with an 
extended cold temperature range whereby the O-ring sealing structure could 
be extended in operation to approximately -40.degree. F. 
SUMMARY OF THE INVENTION 
A high flow rate electromagnetic injector valve with a rapid response time 
is provided by the invention. The injector valve of the present invention 
is inexpensive to manufacture and has a linear dynamic flow down to small 
injection pulse widths. These advantages have been provided by solving or 
ameliorating many of the problems herein mentioned with respect to the 
prior art electromagnetic injector valves. 
The injector valve comprises a facile manufacturing configuration wherein a 
tubular injector body is provided with a centrally bored end cap fixed to 
each end. A bobbin wound with a coil and having a central bobbin bore is 
contained within an injector body chamber between the two end caps. The 
injector valve includes means for connecting the coil to a source of an 
injection signal. 
The front end cap receives within its central bore a valve assembly 
including a needle valve and valve housing. The needle valve is reciprocal 
in a valve housing bore to open and obturate a metering orifice in the 
valve housing. The valve housing bore is supplied with fuel under pressure 
which is to be metered with respect to the open and closed durations of 
the needle valve. 
The front end cap bore has a single step forming a shoulder and the valve 
housing is inserted in the central bore of the front end cap to where it 
abuts the shoulder. The valve needle extends past the step and into the 
rear portion of the front end cap bore which forms an armature guide bore. 
An armature for the injector is coupled to the needle valve with an 
interference fit and is guided in the armature guide bore to reciprocate 
therein and move the needle valve therewith. A closure spring applies a 
force against the needle valve to hold the valve closed. The rear end cap 
receives within its bore a core member extending into the bobbin bore to 
form an air gap between the armature and the core member. 
When an injection signal is applied to the coil, a magnetic field is formed 
through the magnetic circuit of the core member, end caps, injector body, 
and armature. The field will attract the armature across the air gap and 
when it overcomes the force of the closure spring will open the valve by 
movement of the needle valve. A collapse of the magnetic field upon 
turning off the injection signal will cause the valve to close as the 
spring seats the needle valve. 
According to this aspect of the invention, there is no precision machining 
operation that must be accomplished on the injector body and only single 
machining operations are necessary for either end cap. This eliminates the 
multiple remounting of parts on a machine tool during manufacture and 
substantially reduces the cost of the overall injector structure. 
The thin-walled tubular body further provides an adequate magnetic path for 
the magnetic motor circuit while increasing the inside chamber area of the 
body available for the coil, thereby retaining a slim silhouette while 
increasing the force available from the electromagnet. A larger 
electromagnet produces a greater magnetic force for a faster acting valve 
and the slim silhouette is advantageous for mounting in an air ingestion 
bore of a single point fuel injection system. 
With the front end cap mounting the valve assembly, exact concentricity 
between the armature and the stationary electromagnetic elements, 
including the coil and core member, does not have to be strictly 
maintained. The armature and needle combination is guided with respect to 
the front end cap and is separated from the stationary elements by the air 
gap. This reduces the number of parts which have to be very closely 
toleranced as to length and diameter. 
With respect to another aspect of the invention, the armature of the 
injector valve contains within a central bore the closure spring which 
fits into a recess in the needle at the point of juncture with the 
armature and extends outwardly from the armature bore into the air gap of 
the injector valve. An internal bore of the core member is provided with 
an adjusting screw having an end pin which forces a ball member against 
the spring adjustably to provide a compressive force. The adjusting screw 
is aligned substantially with the needle valve to adjust the closure 
spring force and transfers its motion through the ball member to the 
spring. Adjustment of the closure force is accomplished by turning the 
adjusting screw to the desired position. 
This configuration, having the spring contained within the armature and set 
against a recess in the needle valve, moves the point of closure force 
application forward of the armature and reduces the moment arm through 
which it acts. Less eccentric or oblique forces are applied on the needle 
valve thereby allowing more coaxial closure force. Further, the ball 
member prevents a windup of tortional force to be applied to the spring so 
that the compression force is linear with the distance of compression. 
With respect to still another aspect of the invention, the core member is 
independently adjustable within the bobbin bore to provide an adjustable 
lift for the valve armature separately from the closure force adjustment. 
The end of the core member is provided with a washer-shaped nonmagnetic 
shim member which is configured so as not to affect the opening time of 
the valve and to provide a fixed air gap while the injector is energized 
to aid the closing time. 
The adjustable core member and adjustable closure force are adapted to 
tailor the static and dynamic fuel flow of the valve after assembly. The 
preferred method for accomplishing the adjustment is to measure the static 
flow of the injector valve and trim the flow to the desired rate with 
movement of the core member. The static adjustment is made in an area 
where flow rate is dependent not only on the size of the metering orifice 
but also on the lift. This lift adjustment will also change the dynamic 
characteristics of the valve because of the change in air gap. The amount 
of change will be substantially indeterminable before assembly of an 
individual valve. The dynamic flow rate of the injector can subsequently 
be corrected and calibrated by adjusting the closure force with the 
adjusting screw relative to the changed air gap to assure a desired 
dynamic characteristic. 
With respect to another aspect of the invention and particularly for single 
point applications, the fuel inlets of the injector valve are provided 
proximately to the metering orifice upstream the needle valve and valve 
seat interface. The fuel inlets communicate fuel under pressure to the 
valve housing bore. The needle valve is, in the preferred embodiment, 
hollow with an inner passage which communicates with the recess in the 
valve end and the armature bore. The inner passage of the needle valve 
further communicates through inlet apertures with the valve housing bore 
to provide pressure relief to the air gap between the armature and core 
member to prevent hydraulic pressures from building and detrimentally 
affecting the opening time of the valve. 
With respect to still another aspect of the invention, the valve is sealed 
by a pair of elastomeric O-rings contained under compression within 
recesses of the bobbin and surrounding dissimilar material of the front 
end cap and core member. The material of the front end cap and core member 
contracts more slowly than does the material of the bobbin and, therefore, 
as the temperature decreases a tighter squeeze will be applied to the 
sealing rings. The tighter squeeze will extend the cold temperature range 
of the injector into the -40.degree. F. range. The increasing pressure 
compensates for the decreasing elastomeric response of the O-rings and 
their decreased sealing properties at the colder temperatures. 
These and other features, advantages and aspects of the invention will be 
more fully understood and better explained if a reading of the detailed 
description is undertaken in conjunction with the appended drawings 
wherein:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference now to FIG. 1, there is shown a single point injection 
system for metering fuel to an internal combustion engine. The system 
comprises an electromagnetic injector valve 10 which is electrically 
connected by a set of conductors 14, 16, of a connector 12 to a control 
unit 18. A number of engine operating parameters are input to the control 
unit 18 including the speed or RPM at which the engine is turning, the 
absolute pressure of the intake manifold (MAP), the temperature of the air 
ingested, and the engine coolant temperature by means of conventional 
sensors. 
The injector 10 fits within an injector fuel jacket 22 centrally located in 
a single air induction bore 34 of a throttle body 25 communicating with an 
intake manifold 42 of the internal combustion engine. For throttle bodies 
with multiple air induction bores, an injector per bore can be utilized. 
Air flow for engine ingestion is regulated by a throttle plate 30 which is 
rotatably mounted below the injector jacket 22. Upon the sensing of the 
operating conditions of the engine, the control unit will provide pulse 
width electronic injection signals to the connector 12 representative of 
fuel quantity desired for injection whereby the injector 10 will open and 
close relative to the leading and trailing edges of the signal to meter 
fuel from the injector jacket 22. The fuel is metered in a wide spray 
angle pattern for optimum mixture with the incoming air and delivery into 
the intake manifold. 
Fuel under pressure is delivered to the injector jacket 22 by a fuel inlet 
20 and is circulated through the interior of the injector jacket and 
thereafter to an exit passage 24 where a pressure regulator 40 maintains 
the systemic pressure constant. Spent fuel is returned to a reservoir, 
such as a fuel tank, where it can be then pumped under pressure to the 
jacket 22 once more. The injector is sealed in the jacket by suitable 
resilient means, such as an O-ring 28 at the bottom end of the jacket, and 
an O-ring 26 resting against a shoulder at the top end of the jacket. The 
injector 10 is held in position by a spring clip 36 fixed by a screw 38. 
Such a single point fuel injection system as shown is particularly 
adaptable to run a 2.2 liter engine having four cylinders. By injecting 
twice every revolution or 180.degree. an air/fuel charge per each cylinder 
firing is delivered. The injection is preferably made at some set angle 
relative to an engine event, such as just prior to top dead center (TDC) 
of the number 1 cylinder on the intake stroke, and thereafter cyclicly 
related to that point. The injection timing of firing just before the 
opening of a particular intake valve allows much of the fuel and air 
charge to be transported to the particular cylinder injected. This reduces 
condensation and helps eliminate cylinder-to-cylinder distribution errors. 
To inject a system as that described above, an injector with a high single 
point fuel rate of 400-600 cm.sup.3 /min. and with a dynamic 
characteristic linear into the one millisec range is needed. The invention 
provides such an electromagnetic injector valve 10 with an advantageous 
construction. 
With reference now to FIGS. 2 and 3, the high flow injector valve 10 is 
shown in cross-section to advantage and comprises a tubular injector body 
100 which may be constructed from seamed or unseamed tubing which has been 
cut to length. The injector body 100 is cold-formed at each end to form a 
shoulder 101 with a radially offset rim portion 102 at the front end and a 
shoulder 103 with another radially offset rim portion 104 at the rear end. 
As the tubular body 100 is part of the magnetic circuit of the injector, 
the material used is preferably standard low carbon steel mechanical 
tubing. This material provides excellent mechanical strength and exhibits 
high permeability. The body 100, as well as all other outside surfaces of 
the injector valve 10, can be treated by conventional methods for 
corrosion resistance and environmental hazards. 
A front end cap 106 has a centrally bored cylindrical body that is flanged 
to abut against the shoulder 101 and is fixed in position by crimping or 
swaging the rim 102 against a bevel 108 machined on the flange. Similarly, 
a rear end cap 110 comprising a centrally bored cylindrical body is 
flanged and abuts the shoulder 103 and is affixed thereat by deforming rim 
104 to mate with a bevel 112 machined in the flange of the cap. 
Within the chamber defined by the inner wall of the injector body 100 and 
the inwardly facing surfaces of the front end cap 106 and rear end cap 
110, is a generally elongated molded bobbin 114 wound with a plurality of 
turns of magnet wire forming a coil 116. The coil 116 is electrically 
connected to a set of terminal pins 120 (only one shown) which rearwardly 
exit through an oval-shaped aperture 122 in the rear end cap 110 and are 
protected by a connector 118 integrally molded as part of the bobbin 114. 
The bobbin 114 has a centrally located longitudinal bobbin bore 124 which 
is substantially coaxial with a threaded rear end cap bore 126. A 
rod-shaped core member 128 of a soft magnetic material is screwed into the 
threads of the end cap bore 126 and extends substantially the length of 
the bobbin bore. The core member 128 is slotted at its threaded end 130 to 
provide for adjustment of its extension in the bobbin bore 124. The 
adjustment of the core member determines the air gap distance and the lift 
of the valve. An adjustment screw 132 is threaded into an internal bore of 
the core member 128 to provide adjustment of the valve closure force by 
means of a pin 140 moving against a spherical ball member 136. The 
internal bore of the core member 128 is sealed by an O-ring 138 slipped 
over the pin 140 and sealing against the inner surface of the bore. 
The bobbin bore 124 is hydraulically sealed at the internal face of the 
rear end cap 110 by an O-ring 139 and sealed at the front end cap 106 by 
an O-ring 141. These sealing means are under compression, at normal 
ambient temperatures (65.degree. F.), between two materials with differing 
thermal expansion and contraction rates. O-ring 139 is compressed in an 
annular space formed by the outside cylindrical surface of the core member 
128 and the inside cylindrical surface of a recessed area 127 of the 
bobbin 114. O-ring 141 is compressed in a similar annular area formed by 
the outside cylindrical surface of a rearward extension of the body of the 
front end cap 106 and the inside cylindrical surface of a recessed area 
143 in the bobbin 114. 
The end cap 106 and core member 128 materials are similar low carbon steels 
while the bobbin 114 is molded from a glass fiber reinforced nylon. The 
inside cylindrical surfaces of the bobbin and the outside cylindrical 
surfaces of the end cap and core member all contract radially during a 
decrease in temperature. The bobbin, however, contracts more rapidly 
because of its differing material and increases the compression at lower 
temperatures. The increasing pressure applied by the more rapidly 
contracting bobbin will extend the cold temperature range of operation of 
the valve by compensating for the lack of flexibility in the O-ring seals 
below -20.degree. F. 
Located in the central bore 107 of the front end cap 106 is a single step 
dividing the bore into an armature guide bore 142 and a mounting bore 144. 
A valve housing 146 is received in the mounting bore 144 until it abuts 
the internal shoulder 145 formed at the step between the bores. The valve 
housing 146 is held in place by bending the front rim of the mounting bore 
144 over a chamfer in the valve housing 146. The valve housing 146 has a 
longitudinal valve housing bore 148 which communicates on one end with the 
armature guide bore 142 and at the other end is terminated with a conical 
valve seat 150 which curves into a smooth transitional area 152 to finally 
become a cylindrical metering orifice 154. 
The valve housing bore 148 is in fluid communication with fuel in the 
jacket 22 by means of a plurality of fuel inlets 149 spaced around the 
valve housing 146. The inlets 149 are proximate to the metering orifice 
154 for minimum pressure drop during low pressure operation and are 
protected from contamination by the surrounding mesh of a molded filter 
element 154 slip-fitted onto the valve housing. 
Reciprocal in the valve housing bore 148 is a valve needle 156 which is 
press-fitted at its distal end into a generally annular-shaped armature 
158. The needle valve, as is further illustrated in cross-section in FIG. 
3, has a medial section which is triangular in cross-section and at each 
angular apex forms a curved bearing surface which slides against the valve 
housing bore 148 to center the needle valve within the bore. 
The needle valve extends into a valve tip 160 having a sealing surface 162 
which mates with the conical valve seat 150 to close the valve. From the 
valve tip the needle valve forms a pintle which ends in a deflection cap 
164 which shapes the fuel spray into the hollow-cone or wide angle spray 
pattern as described hereinabove. The deflection cap is recessed in the 
injector housing 146 for protection. 
The needle valve 156 is substantially hollow with an inner passage 155 
drilled from the valve tip to its valve end connection at the armature 
158. The valve end has a spring recess 147 supporting a closure spring 147 
within the centered bore in the armature 158. The passage 155 communicates 
with the valve housing bore 148 by means of a port 153 cut into each face 
of the medial section of the valve needle. The passage 155 and centered 
armature bore thus provides pressure relief to an air gap located between 
the armature and core member to prevent hydraulic forces from increasing 
there and affecting the opening time of the valve. 
The closure spring is compressed by the ball member 136 against the valve 
needle recess 147 to produce a closure force on the valve needle which can 
be adjusted by turning adjustment screw 132. Tortional winding forces are 
not generated during adjustment as the pin 140 will turn on the ball 
member 136 and cause only axial movement of member. Any tendency on the 
part of the closure spring to wind up will cause slippage against the 
surface of the ball member and dissipation of the tortional force 
component. 
The closure spring, by being contained in the armature 158 and recessed in 
the valve end, applies the closure force forward of the air gap and 
reduces the moment arm through which eccentric force components act. 
Shorter and narrower bearing surfaces on the medial section of the valve 
needle can be used to balance the forces. The use of a shorter triangular 
medial section with less bearing surface in combination with the hollow 
valve needle and armature, significantly reduces the mass of the moving 
part of the injector. The reduction of the mass of the moving section and 
the increase in force produced by the enlargement of a coil will increase 
the opening time of the valve. 
In operation, when current in the form of an injection signal is supplied 
to the terminal pins 120 from the connector 12, and thus, to coil 116, a 
longitudinal magnetic field is set up through the core member 128, the 
rear end cap 110, the injector body 100, and the front end cap 106 to 
attract the soft magnetic material of the armature 158 across the air gap 
to abut a nonmagnetic shim 135 on the face of the core member. The shim 
135 aids the closing time of the valve by maintaining a minimum gap during 
energization. When the magnetic attraction overcomes the force of the 
closure spring, the valve needle will be lifted away from the valve seat 
and fuel will be metered by the valve seat interface and metering orifice 
until the current to the terminal pins 120 is terminated and the closure 
spring force seals the valve once more. 
After assembly, the lift and air gap can be adjusted by turning core member 
128 and the closure force adjusted by turning adjustment screw 132. The 
two adjustments will complement each other to calibrate static and dynamic 
fuel flow and then be set by a sealing component 121. 
The static fuel flow adjustment of the valve will now be more fully 
explained with respect to FIG. 4. The static fuel flow Q of the injector 
valve 10 is graphically illustrated as a function of valve lift L. At 
small valve lifts in region A, the restriction produced by the needle 
valve and valve seat interface dominates and the static fuel flow is 
independent of the metering orifice size. In this region .DELTA.Q/.DELTA.L 
is a relative constant K related to the increasing opening area between 
the interface of the needle valve and valve seat. 
In region C where the lift is increased beyond where the valve needle 
provides a restriction to fuel flow, the metering orifice size is the 
determining factor of the static fuel flow. .DELTA.Q/.DELTA.L in this 
region, as would be expected, is zero. Between regions A and C is a 
smaller region B where the static fuel flow of the injector valve is 
substantially a function of metering orifice size, but is also related to 
valve lift. .DELTA.Q/.DELTA.L in this region is much less than K and is 
approaching the value of zero found in region C. The change in static fuel 
flow for a change of lift is related to the ratio of the changing 
interface area with respect to the metering orifice area. 
By adjusting the lift in this region, a relatively controllable trim can be 
generated to calibrate the static fuel flow of an already assembled 
injector to a specified value. Generally, it has been found that this 
method will provide the optimal results if the range of trimming is 5% of 
the static fuel flow rate for a 0.001" change in lift. The adjustment 
threads on the core member 128 are suitably chosen to provide controllable 
lift changes in this region. 
After the static flow calibration, a dynamic calibration is undertaken to 
match the closure force to the air gap which was varied during static 
calibration and to calibrate the dynamic response. With respect to FIG. 5 
the dynamic fuel flow rate as a function of pulse width is illustrated. 
The line D, which is dotted, indicates an ideal valve which has a static 
flow rate (slope) of 600 cm.sup.3 /min. and whose graphical representation 
goes through the origin. 
The opening and closing times of a real valve are, however, finite and the 
actual dynamic characteristic will form a parallel line to the right of 
the ideal, for example, line E. The less ideal and slower the valve 
operates, the more to the right of line D the real dynamic line will be. 
Critical operation at higher engine speeds requires maximum injection 
quantity while the time available for injection is decreasing. High flow 
rate valves with steep dynamic slopes are necessary to meet these 
requirements, but cause very small pulse widths to be used for the minimum 
injection quantities. The closer the valve can be calibrated to ideal with 
linearity, the more advantageous it will be to the system. 
With the goals in mind, the dynamic calibration is accomplished by picking 
the minimum flow rate of the valve at point G which is some safety factor 
below the minimum quantity injected at idle, or point F. The closure force 
is then adjusted to minimize the offset of line E from the ideal response 
at line D. 
While the preferred embodiments of the invention have been shown, it will 
be obvious to those skilled in the art that modifications and changes may 
be made to the disclosed system without departing from the spirit and 
scope of the invention as defined by the appended claims.