Note: Descriptions are shown in the official language in which they were submitted.
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ELECTROMAGNETICALLY ~CTUATED FUEL INJECTION PUMP
FOR DIESEL ENGINE APPLICATION
This invention relates in general to an automotive
type fuel injection system. More particularly, it
relates to an electromagnetically actuated fuel injection
pump of the plunger type with a booster plunger supplementing
the force of the main solenoid to permit a decrease in the
level of the force necessary of the main solenoid.
U.S. Patent No. 4,327,695 shows and describes
a unit fuel injector asse~bly for a spark ignition type
engine in which each engine cylinder is provided with a
separate fuel injection pump of the plunger type actuated
by a solenoid surrounding the plunger. In each case, the
output required of the injector is relatively small.
Therefore, the size of the plunger and correspondingly the
size of the solenoid to drive it also is small since the
pressures required for injection are at a relatively low
level as compared to that for a diesel engine application.
For example, fuel injection pressures of approximately 750
psi would be suitabl~ for a spark ignition type fuel
injection system, whereas for diesel engine application, an
injection pressure of 2000 psi is more common. To attain
the higher pressure level with the use of an electro-
magnetically controlled plunger type pump generally requires
a very large solenoid. The increase in size of the solenoid,
however, not only can result in an increased cost, but
also a slower response time for actuation of the plunger.
This invention relates to the inclusion of a
booster plunger in series force arrangement with the main
solenoid actuated plunger to provide the high fuel
pressures necessary in a diesel engine application while
permitting reduction in size and, therefore, force of the
main actuating solenoid to that comparable to one that
would be used in connection with spark ignition type
engines previously described.
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In accordance with the previous invention,
there is provided an electromagnetically actuated fuel
pump comprising a primary reciprocating fuel pumping
plunger connected to the armature of a solenoid surrounding
the plunger, energization of the solenoid driving the
plunger through a pumping stroke, and a booster plunger
in series arrangement with the primary plunger actuated
simultaneous with the energization of the solenoid for
concurrent movement with the primary plunger to supplement
the driving force of the primary plunger.
The invention is described further, by way of
illustration, with reference to the accompanying drawings,
wherein,
Figure 1 is a cross-sectional view of a fuel
injection pump unit embodying the invention; and,
Figure 2 is an enlarged view of a detail of
Figure 1.
Referring to the drawings, the fuel injection
pump shown in Figure l consists essentially of three parts,
namely, a main solenoid assembly lO for driving a pumping
plunger 12, a booster plunger 14, and a solenoid actuated
~uel distributor unit 16. The three above-named units
are arranged in a compact manner within a housing consisting
essentially of upper and lower parts 18 and 20. Secured
within upper housing portion 18 is a main pump casing 22
having a stepped diameter bora 24. The smallest diameter
portion of the bore constitutes a fuel inlet 26 to a
larger bore portion 27 within which is a sleeve 28 located
by a stop nut 30. Reciprocably slideable within sleeve 28
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is the pumping plunger 12 having an ex~ended stem portion
34. The latter is threadably engaged with the large
annular armature 36 of the main solenoid assembly 10. The
latter includes a stationary annular core 40 that is
screwed to pump casing 22 as shown. The core surrounds
pump plunger 12 and is spaced radially therefrom, with
suitable coils 42 being wound around the core as shown.
The armature 36 is biased by a spring 44 away from core 40
to provide the conventional gap 46 between the two.
The'upper housing portion 18 contains the booster
plunger 14 that is reciprocable slideable within a
stationary sleeve 48. $he latter is located against a
shoulder of the housing by a stop nut 50. The stem 34 of
plunger 12 i~s extended as shown to be contiguous to and
abutted by the booster plunger 14 under the influence of
fuel pressure admitted to a chamber 52 on the opposite end
of plung'er 14. The fuel pressure in this case would be
the same supply fuel pressure as that in inlet 26 located
on the opposite side of plunger 12. Also located in fuel
pressure chamber 52 would be a position sensor 54, such as
a proximity sensor, connected by wiring 56 electrically to
a microp~ocessor or similar device, not shown. The sensor
would establish a feedback signal indicative of the
position of the booster plunger 14 for comparison with a
desired position signal determined in accordance with a
predetermined schedule of 'operation of the engine.
The solenoid controlled fuel distributing
assembly 16 contained in lower housing portion 20 consists
- in general of an inlet check valve 60, and a number of
small solenoids 62 each controlling fuel flow past fuel
delivery valves 64 to individual engine cylinder fuel
injectors, not shown. 'The solenoids would be clustered in
' a circular pattern around the axis of the pump and equally
spaced circumferentially from one another.
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More particua~ly, housing 20 has a step diameter
central bore 66 that constitutes a fuel inlet from a
source of fuel under a low pressure, not shown. The
larger diameter portion of the bore also constitutes a
recess 67 for reception of an electrical harness that
provides the electrical connection to the main solenoid
assembly 10 and the cluster of small individual solenoids
62 to be described. The bore 66 also contains the one-way
check valve 60 seatable by a spring 68 against a mating
portion of a sleeve member 70. The latter is located
against a shoulder of the bore by a stop nut 72. A secvnd
sleeve 74 containing an orifice 76 connects fuel to a
passage 78 that opens into a fuel distribution chamber 80.
The latter also is connected to passage 26. Chamber 80 in
turn is connected by a number of spoke-like passages 82 to
an equal number of fuel annulii 84 shown more clearly in
Figure 2.
The lower housing portion 20 contains a number of
secondary stepped diameter bores 86 corresponding in
number to the number of engine cylinders and the number of
fuel injectors required for the engine. More
particularly, the lower portion. of each bore contains a
fuel delivery valve 64 of the retraction type having ~
conical surface 90 adapted to seat against a mating
surface 92 on a sleeve type valve body 94. Within the
valve body adjacent delivery valve 64 is a slideable
sleeve 96 having a spherically formed end portion 98
cooperating with a ball valve member 100. The ball valve
when seated as shown blocks the passage of fuel from the
annulus 84 through sleeve 96 to the delivery valve 64.
Sleeve 96 is biased against ball valve 100 by light spring
102.
- Ball valve 100 is maintained in its closed
position by the plunger-like armature 104 of a small
solenoid 62 threadably mounted into housing portion 20.
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The plunger, in this case, is biased by a spring 108
against ball valve 100 to maintain it seated as shown. A
large nut 110 locates the sleeve-type valve body 94 in
position.
In overall operation, fuel is scheduled to be
delivered to only one engine cylinder at a time so as to
coincide with the firing order of the engine. As a
result, only one of the small solenoids 62 will be
energized at any one particular time, and in a particular
sequence, to retract the plunger-armature 104. This will
permit spring 102 to move sleeve 96 and ball valve 100
upwardly to permit entry of fuel from the annulus 84 to
the delivery valve 64. More particularly, as stated
previously, the fluid under pressure for actuating the
booster plunger 14 will be the same or at the same supply
f~el pressure level as that in the fuel distribution
chamber 80 and inlet line 26. When the main solenoid 10
is energized, therefore, retraction of the armature 36
downwardly will causè a downward move~ent of plunger 12
through a pumping stroke to pressurize the fuel in passage
26 and distribution chamber 80 that previously has been
filled by a flow of supply fuel past the check valve 60.
At the same time, the supply of fuel under pressure to
chamber 52 will cause the booster plunger 14 to follow the
motion of the primary plunger 12, adding its force to that
of the primary solenoid 10, and thus reducing the
magnitude.of force required by the primary solenoid 10 to
provide the desired pressure level. At substantially the
same time, the microprocessor unit, not shown, will
activate one of the smaller solenoids 62 to retract the
plunger-armature 104 and permit the ball valve 100 to move
upwardly to an open position. This will allow the fuel
under pressure in the distribution chamber 80 to flow
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through the passages 82 to the annulus 84 and past the
open ball valve 100 to the delivery valve 64. As soon as
the force of the spring 114 of the delivery valve is
overcome, the delivery valve will move downwardly out of
the valve body 94 until the intersecting supply passages
116 permit a free flow of fuel into the injector passage
118.
The duration and magnitude of fuel injected
during each operation will vary as a function of the
current impulses to each small solenoid 62 and to the main
solenoid 10. This will be determined by the
microprocessor unit, not shown, in accordance with a
predetermined schedule of flow for the particular engine
operating conditions at that time. The stroke of the main
plunger 12 and the booster plunger 14 will be sensed by
the proximity sensor 54, and if the volume of fuel
injected as determined by the stroke varies from the
predetermined. schedule, the feedback signal provided by
senso~ 54 will cause the microprocessor to change the
duration or magnitude of voltage to the solenoids to
thereby vary the fuel flow to conform it to the desired
schedule.
Therefore, when fuel injection is terminated by
termination of voltage to the solenoids 62, the residual
pressure in the injector line 118 will drop. When it is
below the level of the force of spring 114l the delivery
valve 62 will begin to move upwardly into the bore of the
valve body 94. The first effect will be to cut off fuel
communication between injector passage 118 and the fuel
annulus 84. The second effect will be, upon continued
upward movement, for the delivery valve 64 to retract a
portion of its body into the bore of the valve body 94,
thereby decreasing the mass in the injector passage 118
and thereby decreasing the pressure, to prevent
after-dribbling and other known secondary injection
effects. Once the delivery valve has retracted,
deenergization of the particular solenoid 62 activated at
that time will cause or permit the spring 108 to move the
plunger-armature 104 and ball valve 100 to its lower
position seated against the valve body 94 and thereby
block off communication of fuel between the annulus 8~ and
the injector line 118. Injection is now terminated.
Simultaneously, the main solenoid return spring 44 will
cause the armature 36 to move upwardly as seen in Figure 1
to return the primary plunger 12 as well as the booster
plunger 14 to their intake positions shown. This latter
movement will also cause an unseating of the intake check
valve 60 and permit a fresh supply of fuel to flow into
the passages and distribution chamber 80 for injection on
the next stroke of the plunger 12.
Figure 1 indicates a construction in which only
two ~njector lines are indicated. However, it will be
clear that any number of smaller solenoid controlled
injector lines can be provided, as desired, merely by
circumferentially spacing the same in a circular cluster
around the prima`ry fuel supply passage 26.
From the foregoing, it will be seen that the
invention provides an electromagnetically operated fuel
injection pump that is particularly suitable for diesel
application and yet is operal~le with small solenoid
assemblies instead of the conventional large ones normally
employed to provide the high fuel pressure necessary to
operate a diesel type injector. It will be seen that this
is made possible by the use of a booster plunger that is
actuated by supply fuel pressure and therefore compliments
the force of the main actuating pump solenoid so that a
smaller main solenoid may be used.
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While the invention has been shown and described
in this preferred embodiment, it will be clear to those
skilled in the arts to which it pertains, that many
changes and modifications may be made thereto without
departing from the scope of the invention.
