Electronically controlled diesel unit injector

A fuel injector (10) is provided for each cylinder of an internal combustion engine, the injector including an electronically operated control valve (146) disposed between supply passage (42) and a timing chamber (98) to control the admission of fuel into and out of the timing chamber. A primary pumping plunger (62) and a secondary plunger (90) are axially spaced within the central bore of the injection body, and a normally closed injection nozzle (14) is situated at one end of the injector body. A mechanical linkage (27, 28, 30) associated with the camshaft of the engine drives the primary pumping plunger (62) against the bias of a main spring (18). The timing chamber (98) is defined between the plungers (62, 90) and a metering chamber (128) is defined between the secondary plunger (90) and the nozzle (14). An electronic control unit (52) responds to engine operating conditions, and delivers a timing and metering signal to the control valve (146) to close the valve and seal the timing chamber for a controlled period of time. The sealed timing chamber forms a hydraulic link, so that the plungers (62, 90) move in concert during the injection and metering phases of the cycle of operation. When the signal from the ECU is terminated, the control valve opens, and breaks the link so that the primary plunger (62) moves independently of the secondary plunger (90) which is biased in a set position by a spring (96) after termination of the control signal. The timing function can be adjusted by the ECU relative to any preselected position of the crankshaft to optimize engine performance, while the metering function is achieved in a proportionate manner relative to the degree of camshaft rotation. A cam (22), having a linear portion, controls the mechanical linkage, and thus the primary pumping plunger (62), to produce the proportional metering function.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The instant invention relates generally to fuel injection systems, and more 
particularly to electronically operated control valves for regulating the 
quantity of fuel dispensed by each injector within a fuel injection 
system, and for adjusting the timing of the dispensing in dependence upon 
various engine parameters. 
2. Prior Art 
Fuel injectors that are driven mechanically from the crankshaft of an 
internal combustion engine to deliver fuel into the cylinders of an 
internal combustion engine are well known; see, for example, U.S. ,at. No. 
2,997,994, granted Aug. 29, 1961 to Robert F. Falberg. The movement of the 
crankshaft is translated into a force that periodically depresses the pump 
plunger via a cam, cam follower, and rocker arm mechanism. Since the 
rotation of the crankshaft reflects only engine speed, the frequency of 
the fuel injection operation was not adjustable with respect to other 
engine operating conditions. To illustrate, at cranking speeds, at heavy 
loads, and at maximum speeds, the timing and the metering (quantity) 
function for the fuel injector did not take into account actual engine 
operating conditions. 
In order to enable adjustments to be made in the timing of the fuel 
injection phase of the cycle of operation, Falberg proposed that a fluid 
pressure pump 40 introduce fluid into a follower chamber 37 to elevate a 
plunger 35 and thus alter the position of push rod 6 which operates 
plunger member 12 of the fuel injector. By selecting the effective area of 
the plunger, the elevation thereof advances the plunger member relative to 
the desired point in the cycle of engine operation. The fluid pressure 
pump is driven by the internal combustion engine, and a lubricating oil 
pressure pump is frequently utilized as the fluid pressure pump. 
U.S. Pat. No. 3,859,973, granted Jan. 14, 1975 to Alexander Dreisin, 
discloses a hydraulic timing clyinder 15 that is connected to the 
lubricating oil system for hydraulically retarding, or advancing, fuel 
injection for the cranking and the running speeds of an internal 
combustion engine. The hydraulic timing cylinder is positioned between the 
cam 3 which is secured to the engine crankshaft and the hydraulic plunger 
38. The pressure in the lubrication oil pump 160 is related to the speed 
of the engine 1, as shown in FIG. 1. 
U.S. Pat. No. 3,951,117, granted Apr. 20, 1976 to Julius Perr, discloses a 
fuel supply system including hydraulic means for automatically adjusting 
the timing of fuel injection to optimize engine performance. The 
embodiment of the system shown in FIGS. 1-4 comprises an injection pump 17 
including a body 151 having a charge chamber 153 and a timing chamber 154 
formed therein. The charge chamber is connected to receive fuel from a 
first variable pressure fuel supply (such as valve 42, passage 44, and 
line 182), and the timing chamber is connected to receive fuel from a 
second variable pressure fuel supply over line 231, while being influenced 
by pressure modifying devices 222 and 223. The body further includes a 
passage 191 that leads through a distributor 187 which delivers the fuel 
sequentially to each injector 15 within a set of injectors. 
A timing piston 156 is reciprocably mounted in the body of the injection 
pump in Perr between the charge and timing chambers, and a plunger 163 is 
reciprocably mounted in the body for exerting pressure on fuel in the 
timing chamber. The fuel in the timing chamber forms a hydraulic link 
between the plunger and the timing piston, and the length of the link may 
be varied by controlling the quantity of fuel metered into the timing 
chamber. The quantity of fuel is a function of the pressure of the fuel 
supplied thereto, the pressure, in turn, being responsive to certain 
engine operating parameters, such as speed and load. Movement of the 
plunger 163 in an injection stroke results in movement of the hydraulic 
link and the timing piston, thereby forcing fuel into the selected 
combustion chamber. The fuel in the timing chamber is spilled, or vented, 
at the end of each injection stroke into spill port 177 and spill passage 
176. The mechanically driven fuel injector, per se, is shown in FIGS. 
14-17. 
All of the above-described fuel injection systems employ hydraulic 
adjustment means to alter the timing of the injection phase of the cycle 
of operation of a set of injectors mechanically driven from the crankshaft 
of an internal combustion engine, and the hydraulic means may be 
responsive to the speed of the engine and/or the load imposed thereon. 
While the prior art systems functioned satisfactorily in most instances, 
several operational deficiences were noted. For example, the hydraulic 
adjustment means functioned effectively over a relatively narrow range of 
speeds, and responded rather slowly to changes in the operating parameters 
of the engine. Also, problems were encountered in sealing the hydraulic 
adjustment means, for a rotor-distributor pump was utilized to deliver 
hydraulic fluid to each of the fuel injectors in the set employed within 
the fuel injection system. In order to provide a hydraulic adjustment 
means responsive to both speed and/or the load factor, as suggested in the 
Perr patent, an intricate, multi-component assembly is required, thus 
leading to high production costs, difficulty in installation and 
maintenance, and reduced reliability in performance. 
The deficiencies of the known fuel injection systems utilizing hydraulic 
adjustment means to control fuel injection prompted the applicants and 
other research personnel in the laboratories of the corporate assignee to 
investigate and develop an electronically operated fuel injector assembly, 
either an assembly employing one injector for each cylinder of the engine, 
or a common rail system. 
SUMMARY OF THE INVENTION 
Thus, with the deficiencies of the known fuel injection systems utilizing 
hydraulic adjustment means to control the timing of fuel injection clearly 
in mind, it is an objet of the instant invention to employ one 
electronically operated control valve for each injector utilized within a 
fuel injection system, whether it be a single injector or a multiplicity 
of injectors. Each control valve, in response to a signal pulse from an 
electronic control unit, controls the timing of the injection phase for 
the injector, and also controls the metering function for the injector, 
i.e., the quantity of fuel stored for dispensing during the injection 
phase. 
Another significant object of the instant invention is to provide a 
versatile fuel injection system wherein the timing phase, and the 
subsequent injection phase, of the cycle of operation can be easily 
altered in dependence upon any of one or more parameters of engine 
operation. Such flexibility in the timing phase is in marked contrast to 
most, if not all, known hydraulic and mechanical adjustment means which 
are assembled with a preset schedule of operation. Thus, the instant 
invention lends itself to adaptive control. 
Furthermore, it is another object of the instant fuel injection system to 
utilize existing electronic control units (ECU), such as the ECU described 
in Ser. No. 945,988, filed Sept. 25, 1978 and incorporated by reference 
herein, which respond rapidly to several engine parameters in addition to 
engine speed and load, and generate appropriate signals for the control 
valve associated with each fuel injector. The signals developed by the ECU 
are delivered to the control valve in synchronism with angle of rotation 
of a rotating member of the engine. 
Another object of the instant fuel injection system is to respond more 
quickly to changes in the engine parameters, the inertial effects 
attributable to the numerous components of the known hydraulic adjustment 
means being eliminated. 
It is a further object of the instant invention to provide a compact fuel 
injection system to supply precise signals directly to an electronically 
operated control valve for each fuel injector in the case of unit 
injectors, common rail injectors, or other types of injection systems. 
With regard to known fuel injection systems with hydraulic adjustment 
means, the present invention obviates the prior art problems of (1) 
sealing hydraulic flow lines, (2) utilizing a pump-distributor for 
sequentially feeding each injector within an injection system, and (3) 
flexing of the fluid lines. Also, the present arrangement provides a 
simple and less costly approach. 
Yet another object of the instant invention is to provide a simple, 
compact, yet reliable, electronically operated control valve that 
regulates both the timing and the metering functions of a fuel injector. 
The metering function is proportional to the period that the control valve 
is retained in its closed condition by an electrical signal from the 
electronic control unit with respect to the degrees of rotation of a 
preselected portion of the surface of a cam element. 
Another object of the present invention is to provide a cam having a 
profile that contributes to the proportional control of the metering 
function over an extended phase of the cycle of operation of the injector. 
These, and several other objects, are realized in a fuel injector utilizing 
a primary pumping plunger and a secondary plunger disposed within its 
central bore. An electronically operated control valve selectivity forms a 
hydraulic link between the plungers so that they move in unison during the 
injection and metering phases of the cycle of operation. At other times, 
the secondary plunger is fixed and the primary plunger moves independently 
thereof. The secondary plunger incorporates a check valve arrangement to 
accomplish the objects of the invention. A novel method of operating the 
fuel injector to form a hydraulic link between the plungers is also 
envisioned as an integral part of the instant invention. 
Yet additional objects of the invention, and advantages thereof in relation 
to known fuel injectors and fuel injection systems, will become readily 
apparent to the skilled artisan when the specification is construed in 
harmony with the following drawings in which:

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
Turning now to the drawings, FIG. 1 schematically depicts the major 
components of a fuel injection system employing an electronically operated 
control valve for regulating the timing and metering functions of each 
injector within the system. The system includes a fuel injector 10 that is 
supported by a support block 12 and is controlled to deliver fuel through 
a nozzle 14 directly into the combustion chamber (not shown) of an 
internal combustion engine 16. Although only one injector is shown, it 
should be noted that a set of identical injectors is employed within the 
fuel injection system, one injector being provided for each cylinder in 
the engine. The injector 10 is operated in synchronism with the operation 
of the engine through the reciprocal actuation of a follower 20, the 
follower 20 being biased upwardly by a heavy duty spring 18. 
A cam 22 is secured to the camshaft 24 of the internal combustion engine 
16. Cam 22 rotates at a speed which is a function of engine speed, for the 
camshaft is driven via meshing gears 23, 25 from the crankshaft 26. The 
gear ratio of gears 23, 25 may vary from engine to engine depending on 
various factors, including, inter alia, whether the engine is a two-cycle 
or four-cycle engine. The crankshaft drives the pistons (not shown) within 
the combustion chambers of the engine 16 in the usual manner. A roller 17 
rides along the profile of the cam, and a push rod 28 and rocker arm 30 
translate the movement of the follower into the application of axially 
directed forces upon the follower 20 and the primary piston; the forces 
act in opposition to main spring 18 and vary in magnitude with the speed 
of the engine and the profile of the cam. The cam profile is of particular 
importance to the operation of the injector and will be discussed more 
fully in the discussion of FIGS. 8 and 9. 
A reservoir 32 serves as a source of supply for the fuel to be dispensed by 
each injector 10, and fuel is withdrawn from the reservoir by transfer 
pump 34. Filters 36, 38 remove impurities in the fuel, and distribution 
conduit 40 introduces the fuel, at supply pressure, to each of the 
injectors 10. A branch conduit 42 extends between distribution conduit 40 
and block 12 and makes fuel, at supply pressure, available for circulation 
through injector 10. The fuel that is not dispensed into a combustion 
chamber in the engine is returned to the reservoir 32 via branch return 
conduit 44 and return conduit 46. A fixed orifice 48 is disposed in return 
conduit 46 to control rate of return flow into the reservoir. Directional 
arrows and legends adjacent to the conduits indicate the direction of fuel 
flow. 
The fuel injection system of FIG. 1 responds to several parameters of 
engine performance. In addition to engine speed, which is reflected in the 
rate of rotation of the cam 22 secured upon camshaft 24, several sensors 
50 are operatively associated with engine 16 to determine, inter alia, 
engine speed, temperature, manifold absolute pressure, load on the engine, 
altitude, and air-fuel ratio. The sensors 50 generate electrical signals 
representative of the measured parameters, and deliver the electrical 
signals to the electronic control unit, or ECU 52. The electronic control 
unit then compares the measured parameters with reference values which may 
be stored within a memory in the unit, takes into account the rotational 
speed and angular position of cam 22, and generates a signal to be 
delivered to each injector. The signal, in turn, governs the timing and 
metering functions of each injector. Leads 54, 56 and a connector 58 
interconnect the electronic control unit 52 and the control valve 146 for 
the representative injector shown in FIG. 1. 
FIG. 2 depicts the components of a representative injector 10. The segment 
at the left hand side of FIG. 2 fits atop the segment at the right hand 
side of FIG. 2. 
Referring to the upper end of the injector 10, a fragment of the rocker arm 
30 is visible bearing against the enlarged upper end of follower 20, and 
main spring 18 rests on support block 12 and urges the follower 20 
upwardly. A primary pumping plunger 62 is joined to the lower end of 
follower 20, the follower 20 and primary pumping plunger 62 moving as a 
unitary member. A cylindrical guide 64 insures the axial movement of 
follower 20, while a seal guide 66 provides a seal and insures the axial 
movement of primary pumping plunger 62. It is to be understood that block 
12 and guides 64, 66 may be formed as an integral unit. A slot 68 in the 
follower 20 cooperates with stop 60 to prevent the follower 20 and spring 
18 from becoming disassembled from the remainder of the injector prior to 
association with the cam 30 and to limit the downward travel of follower 
20. 
An internally threaded jacket 70 is screwed into engagement with the 
mounting block 12, and the interior of the jacket surrounds the distinct 
segments that comprise the body of the fuel injector 10. Each segment of 
the body is generally cylindrical in shape, is generally executed in 
metal, has a central bore and has passages drilled, or otherwise formed 
therethrough, in alignment with the central bore and the passages of the 
adjacent segment. Thus, in FIG. 2, fuel injector 10 includes an elongated 
sleeve 72, a disc-like segment 74, and a spring cage 76 that communicates 
with nozzle 14. A seal 78 seals the juncture between the block 12 and the 
threaded jacket 70. Supply passages 80, 82 of which there are two pairs of 
each, only one each of which are shown, extend through the various 
segments, and an annular cavity 84 is defined beneath the seal guide 66 
and the upper end of the axial passages. The lowermost ends of passages 
80, 82 extend radially inwardly to terminate in annulus 83. The passages 
80, 82 (a total of four passages arranged around piston 62) also extend 
radially inwardly to terminate in annulus 85, spaced above annulus 83 in 
the sleeve of the injector. 
A cylindrical recess 86 is located in the lower end of the primary pumping 
plunger 62, and stud 88 is located within the recess to form a spring 
retaining member. A secondary plunger 90 is axially movable within the 
central bore of the sleeve 72, and a valve seat insert 92, with a recess 
94 in its upper surface, is situated at the upper end of the secondary 
plunger. A spring 96 extends between stud 88 and the insert 92 and 
constantly maintains a downwardly directed biasing force upon the 
secondary plunger. A variable volume timing chamber 98 is defined between 
the lower end of plunger 62 and the upper end of secondary plunger 90. 
Secondary plunger 90 slides freely within the bore of sleeve 72 and 
primary plunger 62 travels within the bore 97 of support block 12. 
A passage 99 extends axially through the valve seat insert 92 to 
communicate with cross-hole passage 100 which opens into annulus 102 
formed on the surface of secondary plunger 90. A first check valve 104, 
preferably in the form of a poppet valve, is normally biased by spring 106 
against a valve seat 108 formed in passage 100 to control fluid 
communication between chamber 98 and passage 100. The spring 106 is seated 
in a guide cavity 110 in the secondary plunger 90. 
An annulus 112 is formed in the outer surface of secondary plunger 90 at 
approximately the mid-section thereof, annulus 112 communicating with a 
cross-hole passage 114 and an axial passage 116. A second check valve 118 
in the secondary plunger is biased against its valve seat 120 by a spring 
121 disposed in a cavity 122 formed in the plunger 90. Valve 118 thus 
controls communication between passage 116 and inverted L-shaped passages 
124, 126, of which three are two each, which extend axially through the 
lower end of the secondary plunger. The passages open into an annulus 125 
formed in the exterior surface of plunger 90. A variable volume metering 
chamber 128 is defined between the lower end of secondary plunger 90 and 
the disc-like segment 74. 
A disc 130 fits within a recess 132 at the upper end of segment 74, and the 
disc is of sufficient area to seal off one end of metering chamber 128 to 
prevent gases in the cylinders in the engine from blowing back into the 
injector in the event the nozzle 14 fails to seal. The recess 132 opens 
downwardly into a plurality of passages 134, 136, sets of which are 
arranged circumferentially around the central axis of injector 10, passage 
136 communicating with nozzle 14. The upper end of a needle valve 144 is 
secured to a spring retaining member 142, and a spring 138 is disposed 
between element 74 and member 142 to bias valve 144 downwardly against a 
valve seat 145 to prevent fuel from being dispensed from the nozzle 14. 
Only when the pressure in passage 136 significantly exceeds the combined 
forces of the spring biasing pressure and the supply pressure is the 
needle valve unseated to permit a fine atomized spray of fuel to be 
issueed from nozzle 14. 
Branch conduit 42 introduces fuel, at supply pressures of 50-200 psi, into 
support block 12 through conduit 43 and thence into injector 10. An 
electronically operated control valve 146 is disposed between conduit 42 
and conduit 43 to control both the timing and the metering fucntions for 
injector 10 as will be more fully explained hereafter. Branch conduit 43, 
as suggested by the diagonally extending dotted lines, communicates fuel 
at supply pressure with timing chamber 98 when the control valve 146 is 
open. 
The functioning of the several components of the fuel injector of FIG. 2 
will best be appreciated by reviewing the sequence of operation shown in 
FIGS. 3-7. However, in order to better portray the sequence of operational 
events, license has been taken in depicting the various elements of the 
injector 10. For example, the segments housed within jacket 70 are shown 
as a unitary member, the guides 64, 66 and disc 130 have been omitted, the 
follower 20 and the primary pumping piston 62 have been shown as a unitary 
member, etc. 
Turning now to FIG. 3, which shows a convenient but arbitrarily selected 
starting point for the cycle of operation, control valve 146 is shown in 
its normally opened condition to allow fuel at supply pressure (e.g., 
50-200 psi) in the branch conduit 42 access to supply passage 43 and the 
timing chamber 98. Actually, an equilibrium pressure condition exists 
(supply pressure) as the primary plunger 62 has ceased its upward motion 
and is prepared to start its downward motion due to the action of camshaft 
24 and cam 22 on plunger 62 as will be seen from a description of FIGS. 8 
and 9. The timing chamber 98 and metering chamber 128 previously have been 
filled with fuel as will be seen from a description of FIGS. 6 and 7. With 
the control valve 146 open, fuel is free to flow into and out of timing 
chamber 98. As shown in FIG. 3, check valve 104 is biased against its seat 
by spring 106 and check valve 118 is biased against its seat by spring 
121. 
The primary pumping plunger 62 and the secondary plunger 90 sealingly 
engage the central bores 97, 69, respectively, of the injector, and the 
spring 96 continuously imparts a downward bias upon plunger 90. A precise 
amount of fuel is present in metering chamber 128 due to a pior metering 
operation, to be described in conjunction with the description of FIGS. 6 
and 7, and the trapped fuel acts against spring 96. With the control valve 
146 opened, timing chamber 98 is in its equilibrium condition, so that 
when rocker arm 30 forces follower 20 and primary pumping plunger 62 
downwardly, at the rate suggested by the arrow beneath plunger 62, fuel is 
forced out of timing chamber 98 through passages 43, 42. The secondary 
plunger is unaffected by such movement and remains stationary under the 
bias of spring 96 and trapped fluid in metering chamber 128. The duration 
of the period during which valve 146 is maintained in its opened condition 
relative to a fixed reference is a variable quantity determined by the ECU 
52 in response to actual engine conditions and independent on the travel 
of plunger 62. Thus, the instant at which the valve 146 is closed, and the 
timing chamber 98 isolated from the supply passage 42, can be adjusted 
relative to the fixed reference, e.g., the top dead center (TDC) position 
of the crankshaft 26, over fairly broad limits. 
FIG. 4 shows the various components of the fuel injector 10 at the instant 
that injection starts through nozzle 14 due to the high pressure (several 
thousand psi) created by the trapped fluid in timing chamber 98 and 
metering chamber 128. During the downward travel of plunger 62 from the 
arbitrarily selected starting position of FIG. 3, and a very short period 
of time before the instant of injection shown in FIG. 4, the valve 146 is 
closed as described above. With the valve closed, timing chamber 98 is 
sealed, and the continued downward movement of plunger 62 causes the 
downward movement of secondary plunger 90 to rapidly increase the pressure 
of the fuel trapped in chamber 128. The downward movement of the secondary 
plunger 90 pressurizes the fuel in chamber 128 to a level sufficient to 
unseat needle valve 144 and permits a fine spray of pressurized fuel to be 
discharged through the pin holes in nozzle 14. 
The second check valve 118 remains seated during the injection phase of the 
cycle of operation due to the fact that the high pressure below check 
valve 118 created by the pressure in metering chamber 128, as communicated 
thereto by passages 124, 126, is greater than the supply pressure in 
passages 80, 82 and cross-hole 114. 
FIG. 5 shows the various components of the fuel injector immediately after 
the termination of the injection shown in FIG. 4, FIG. 5 illustrating the 
"dumping" or pressure relieving phase of operation. In this phase the 
control valve 146 is still closed and the primary pumping plunger 62 is 
approaching its limit of downward travel, as suggested by the small arrow 
beneath the plunger. In this phase, the annulus 125 is in fluid 
communication with annulus 83 thereby communicating the high pressure in 
passages 124, 126, 136 with the supply pressure in passages 80, 82. As the 
pressure in passages 124, 126, 136 approaches the supply pressure existing 
in passages 80, 82, the pressure on the needle valve is insufficient to 
hold valve 144 open and the needle valve 144 is again seated against seat 
145. The pressure buildup in passage 136 and metering chamber 128 is 
rapidly relieved, so that the undesirable dribble of fuel through the 
nozzle is prevented. 
At the same time, the pressure of the fuel in timing chamber 98, which has 
been intensified by the downward movement of plunger 62, is relieved to 
permit the primary plunger 62 to complete its downward travel after the 
termination of injection and preclude excess pressure on the parts of the 
injector subject to the pressure in timing chamber 98. More specifically, 
the annulus 102 is in fluid communication with annulus 85 thereby 
communicating passage 100 below valve 104 with the supply pressure in 
passages 80, 82. The pressurized fuel in chamber 98, as compared to supply 
pressure in passage 100, creates a pressure differential across first 
check valve 104 to unseat check valve 104. Fuel flows from timing chamber 
98, through check valve 104, annulus 102, and annulus 85 back into axial 
passages 80, 82. Check valve 104 has been provided to check the flow of 
fuel from passage 80 to timing chamber 98, through annuli 85, 102, just 
prior to the metering phase of operation. If valve 104 did not seat, fuel 
flow from passage 80 to timing chamber 98 would preclude the metering to 
be described below. 
The direction of flow of pressurized fuel from both the timing chamber 98 
and the metering chamber 128 is indicated by directional arrows. After 
entering the axial passages, the fuel is returned to reservoir 32 via 
conduits 44, 46 (FIG. 1). 
FIG. 6 shows the various components of the fuel injector after the primary 
pumping plunger 62 has completed its downward travel and has started its 
upward travel under the urging of spring 18 to create the "metering" phase 
of operation. The control valve 146 is retained in its closed condition, 
and annulus 102 is out of communication with annulus 85, thereby sealing 
timing chamber 98. The fuel in timing chamber 98 is approximately at 
supply pressure due to the dumping shown in FIG. 5. First check valve 104, 
which was unseated during the "dumping" phase of the cycle of operation, 
as shown in FIG. 5 is again held against its seat 108 by spring 106 to 
prevent communication between chamber 98 and passage 100. 
As the primary pumping plunger 62 moves upwardly, as suggested by the arrow 
atop the head of follower 20, the pressure in timing chamber 98 drops to a 
pressure level below supply pressure as the volume of chamber 98 increases 
rapidly. The pressure of the fuel beneath secondary plunger 90 in metering 
chamber 128 is greater than the combined forces of the fuel in chamber 98 
and the biasing force of spring 96. The secondary piston 90 thus follows 
the primary pumping piston 62 in its ascent because of the net, upwardly 
directed pressure differential. During this early movement of secondary 
plunger 90, while annuli 125, 83 are in alignment, fuel flows from 
passages 80, 82, through passages 124, 126, to metering chamber 128. 
As the secondary plunger moves upwardly, the lowermost annulus 125 defined 
on the plunger 90 moves out of alignment with annulus 83, thereby sealing 
metering chamber 128 from the annulus 83. The intermediate annulus 112, 
which opens into cross-hole passage 114, stays in alignment with the lower 
portion of annulus 85. Consequently, supply pressure in passages 42, 80, 
82 is impressed on annulus 85, thence into annulus 112, and passage 114, 
to the upper portion of second check valve 118. This pressure differential 
across check valve 118 created by the relatively high supply pressure 
above check valve 118 as compared to the relatively low pressure in 
metering chamber 128, unseats check valve 118. Thus, fuel flows into 
metering chamber 128 through check valve 118, through passages 124, 126, 
as shown by the arrows in FIG. 6. 
The quantity of fuel that flows into metering chamber 128 is proportional 
to the volumetric displacement of plunger 90 created by the pressure 
differential across plunger 90. The plunger 90 can only move in concert 
with plunger 62 while control valve 146 is closed. In summarizing these 
relationships, it will be appreciated that the quantity of fuel introduced 
into the metering chamber 128 is proportionally related to the duration or 
interval, in crankshaft degrees, during which the control valve 146 is 
held closed after the start of the upward travel of secondary plunger 90. 
Obviously, when the valve 146 is held closed by a signal from the ECU 52 
for the entire interval in crankshaft degrees allocated for metering, the 
chamber 128 will be filled with the maximum amount of fuel. When the valve 
146 is held closed by a signal from the ECU for only half of the interval, 
defined in degrees of crankshaft rotation, then the metering chamber will 
be half filled. Other proportional relationships are available in 
accordance with the fraction of the crankshaft rotational interval 
selected to hold valve 146 closed. This proportionallity will become more 
apparent during the discussion of FIGS. 8 and 9. 
FIG. 7 shows the various components of the fuel injector at the termination 
of the metering phase of the cycle of operation. The metering phase is 
terminated by terminating the electrical signal from ECU 52 to the control 
valve 146, which then returns to its normally opened condition. With valve 
146 opened, the fuel at supply pressure in passages 42, 43 and the fuel in 
timing chamber 98 quickly establish an equilibrium condition at 
approximately supply pressure level. The pressure differential across 
plunger 90 is removed and secondary plunger 90 is, in effect, disconnected 
and cannot follow primary pumping plunger 62 as plunger 62 continues its 
upward movement. With valve 146 opened, the combined forces of the fuel in 
timing chamber 98 and spring 96 are greater than the force of the fuel, at 
supply pressure, retained in metering chamber 128. Therefore, plunger 90 
is "locked" or retained in fixed position. The instant at which the signal 
to valve 146 is terminated is determined by engine operating parameters 
sensed by the ECU relative to the number of degrees of angular rotation of 
the camshaft 24 as measured by the crankshaft 26 rotation from the 
above-described fixed reference, as determined by conventional sensors. 
Primary pumping plunger 62 continues upwardly, following the cam surface, 
under the urging of spring 18 independently of secondary plunger 90, as 
suggested by the arrow atop follower 20 in FIG. 7. When primary pumping 
plunger 62 reaches its uppermost position, as shown in FIG. 3, then the 
cycle of operation for the fuel injection can be repeated in the manner 
shown progressively in FIGS. 3-7. 
Referring to FIGS. 8 and 9, FIG. 8 illustrates, in graphic form, the 
profile, or lift, of the cam surface of cam 22 (FIG. 1) relative to the 
number of degrees of crankshaft rotation, and FIG. 9 illustrates, in 
graphic form, the vertical motion of primary pumping plunger 62 relative 
to the same number of degrees of crankshaft rotation and the relationship 
thereto of the single ECU pulse which initiates injection and terminates 
metering. Both figures, FIG. 9 particularly, correlate the various phases 
of injector operation described in conjunction with the description of 
FIGS. 3 to 7 with degrees of crankshaft rotation. From FIGS. 8 and 9, a 
very graphic illustration of the proportionallity of the metering phase 
may be seen. Thus, the termination of the ECU pulse to control valve 146 
will be seen to be linearly related to the number of degrees of crankshaft 
rotation after a preselected reference point (for example, top dead 
center). 
Specifically describing FIG. 8, there is illustrated the lift of the cam, 
or cam profile surface plotted against the number of degrees of crankshaft 
rotation, and includes various points (A, B, C, D) along the curve. The 
curve approaches point A, which is the lowest point of the curve, and will 
be seen to correspond to the arbitrarily selected starting position 
described in conjunction with the description of FIG. 3. The curve 
progresses through the injection phase, between points B and C; the 
dumping phase, between points C and D; and the metering phase, between 
points D and E. Point E corresponds to the end of the metering phase and a 
point F corresponds for the next sequence to point A for the previous 
sequence. 
FIG. 9 is a composite, graphic representation of the operation of one 
injector 10 in the set of injectors employed in the instant fuel injection 
system. The upper graph plots the movement, or stroke, of primary pumping 
plunger 62 along the vertical axis against the degrees of rotational 
movement of the crankshaft 26; the rotational movement being measured by 
sensors that provide a signal representative of crankshaft rotation in 
degrees. The trace of the plunger 62 shows that the plunger 
instantaneously peaks, then moves downwardly until it reaches a nadir 
position, and then linearly returns upwardly to the peak position. For a 
two cycle engine, a complete cycle occurs within 360.degree. of rotational 
movement of the crankshaft; for a four cycle engine, a complete cycle 
occurs within 720.degree. of rotational movement of the crankshaft. 
The lower graph in FIG. 9 plots the opening and closing of control valve 
146 by the ECU, and other events, against the degrees of rotational 
movement of the crankshaft 26. The leading edge of the signal to control 
valve 146 causes the valve to change state from its normally opened state 
to its closed state, and the trailing edge of the signal causes the valve 
to change state again and return to its normally opened position. It will 
be noted that a single pulse from the ECU initiates the injection phase 
and terminates the metering phase, while the internal configuration of the 
injector (annuli, check valves, etc.) terminates the injection phase and 
initiates the metering phase. 
The upper and lower graphs of FIG. 9 may be correlated by following the 
progression of steps indicated by reference characters A, B, C, D, E and 
F. It is to be understood that the duration of the period A to D, in 
degrees, is determined by the sum of injection timing variation and 
injection duration. It is believed that the determination of the duration 
of the period A to D is well within the scope of one skilled in the art. 
The plunger 62 assumes its peak upward position under the bias of main 
spring 18 at the start of the cycle of operation (FIG. 3). This is point A 
on the curve and, with the control valve 146 still in its normally opened 
state, as seen at the bottom of FIG. 9, the plunger 62 starts downwardly 
under the force of rocker arm 30 pressing against follower 20. 
During the course of the downward movement of plunger 62, the ECU 52 
delivers a signal to valve 146, and closes the valve as described in 
conjunction with the description of FIG. 4. Point B on the curve 
designates the instant at which injection occurs during the timing 
function due to the closing of the valve 146, while point C indicates when 
the injection ceases due to the communication of annuli 102, 85 as 
described in conjunction with the description of FIG. 5. The ECU can be 
adjusted, either manually or automatically, in accordance with actual 
engine operating parameters, to shift the timing of the leading edge of 
the signal relative to the downward movement of the plunger 62. Point B 
will then shift along the curve to reflect such adjustments. The ability 
to adjust the instant at which valve 146 is closed to start the injection 
function assists in more completely burning the fuel discharged into each 
combustion chamber in the engine 16. Thus, the closure of valve 146 starts 
the injection phase of the cycle of operation as shown in FIG. 4. 
The compression-injection phase of the cycle of operation lasts for the 
brief interval B-C, the length of which is determined by the quantity of 
fuel which has been metered into metering chamber 98. During the period 
B-C the secondary plunger follows the primary plunger downwardly and 
forces the fuel out of metering chamber 128 and through nozzle 14. The 
plungers are coupled through the sealed timing chamber 98 which forms a 
hydraulic link between the two plungers. 
Point C on the curve designates the cessation of the injection phase of the 
cycle of operation and the period between points C-D represents the 
overtravel and dumping portion of the cycle. At point C, while the control 
valve 146 remains closed, the passages 124 and 126 in the secondary 
plunger 90 are in fluid communication with the annuli 125, 83 to 
communicate metering chamber 128 and passage 138 with the supply pressure 
in passages 80, 82 and vent, or dump, the pressurized fuel trapped in the 
metering chamber 128 and the nozzle 14 back into the low pressure of axial 
passages 80, 82. The venting of the nozzle enables the needle valve to be 
re-seated and prevent dribble of fuel through the nozzle into the 
combustion chamber. 
Due to the alignment of annuli 102, 85, the pressure below check valve 104 
is reduced to supply pressure (below the pressure in timing chamber 98), 
and the upper check valve 104 is unseated so that the pressure in the 
timing chamber 98 is reduced, or dumped, to supply pressure, while the 
primary plunger is decelerating. The relationships that exist at the 
instant of dumping the pressurized fuel from chamber 128, the nozzle 14, 
and chamber 98 are shown in FIG. 5. 
The downward travel of the primary pumping plunger 62 continues for the 
interval C-D, or until the plunger 62 reaches its maximum travel. The 
overtravel of the plunger 62 beyond the termination of injection (point C) 
and end of dumping (point D) provides sufficient time to equalize the 
pressures in the injector at supply pressure and to provide the necessary 
range of timing and injection. When plunger 62 reaches point D, the nadir 
of travel, and then starts to travel upwardly under the urging of main 
spring 18, its return trip to its peak upward position occurs over a major 
portion of the cycle of operation which corresponds to the metering phase 
(FIGS. 6 and 7). 
The curve from point D through points E and F is a linear curve having a 
constant slope. The linear slope is achieved by a unique profile on the 
cam 22, which slope is important to the proportional operation of the 
metering phase of operation. Point E represents the instant that the 
metering function ceases and corresponds to the termination of the signal 
from the ECU. The termination of the signal to control valve 146 causes 
the control valve to return to its normally opened condition, which allows 
the timing chamber 98 to reach an equilibrium condition with the fuel at 
supply pressure in passage 42. Spring 96 locks secondary plunger 90 in 
fixed position in metering chamber 128, and plunger 62 can move 
independently in response to the application of forces by rocker arm 30 
and spring 18. This termination is described in conjunction with the 
description of FIG. 7. 
The metering function can be terminated at any point along the slope D-F; 
if the metering function is terminated shortly after the primary plunger 
starts its return trip, then the interval D-E will be shorter than the 
interval from E-F. The greater the interval D-E, the greater the volume of 
fuel admitted into metering chamber 128. It is to be noted that the 
linearity of the portion of the curve between points D and F permits a 
direct, proportional relationship between the amount of fuel metered and 
the number of degrees of camshaft rotation. The interval, in degrees of 
rotation, between points D and F represents the maximum volume of fuel 
which can be metered, any lesser amount is a direct function 
(proportional) to the number of degrees of rotation the control valve 
remains closed after point D. Thus, if point E occurs one-half the number 
of degrees between D and F, one-half the quantity of fuel is metered. 
It should be noted that the metering function can occur, potentially, over 
more than half the cycle of operation. This "stretching out" of the 
metering function increases the opportunity to accurately fill the 
metering chamber 128 to the desired level. As described above, the slope 
of the curve D-F through the metering function is linearly proportional to 
the degrees of angular rotation of the crankshaft 26. Thus, if the 
metering function is assumed to occur, potentially, over 300.degree. of 
angular rotation for the crankshaft for a two cycle engine, then the 
termination of the signal from ECU 52 to control valve 146 after 
150.degree. of angular rotation, would allow the metering chamber 128 to 
be half-filled. Alternatively, if the termination of the signal from ECU 
52 to control valve 146 occurred after 75.degree. of rotation, metering 
chamber 128 would be a quarter-filled. Obviously, the metering chamber can 
be filled to an infinite variety of fractional levels. 
It will be readily apparent to the skilled artisan that the foregoing 
embodiment of this fuel injection system is susceptible of numerous 
changes without departing from the basic inventive concepts. For example, 
the primary pumping plunger 62 and follower 20 could be formed as a 
unitary plunger, and the check valves 104, 112, which are preferably shown 
as poppet valves, could be disc valves, ball valves, etc. The control 
valve 146, which is shown as a gate valve responsive to electromagnetic 
forces, could assume diverse other forms. The profile of cam 22 can also 
be altered to adjust the duration of the metering function and the rate of 
return of the primary plunger 62. Also, the spring 96 could be joined to 
the central bore of the injector, and need not have one end seated in a 
cavity in the primary pumping plunger; the key consideration is the 
ability of the spring 96 to always exert a downward force on the secondary 
plunger and, when necessary, at the end of the metering operation, lock 
plunger 90 in fixed position. Numerous other modifications and revisions 
are feasible. Consequently, the appended claims should be liberally 
construed, and should not be unduly limited to their literal terms.