Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Descr.iption
Modular Unit Fluid Pump~ _tor
Technical Field
Thls invention relates generally to fluid
pumping and injecting apparatus and more particularly
to unit fuel pump-injectors for delivering fuel
directly to the combustion chambers of a
compression-ignition engine~
Background Art
In prior art unit fuel pump-injectors, such as
disclosed in U.S~ 3,006,556 issued to Shade et al on
October 31, 1961, it has been conventional to provide a
single elongated sleeve-type nut which substantially
encloses a stacked plurality of both injector and pump
components. The nut is threadably mated and tightened
to a housing in order to retain the substantially
enclosed components against separation and thereby join
the respective abutting high pressure sealing end
surfaces of these internal components.
A number of problems are encountered with this
typical unit fuel pump-injector configurationO First,
a relatively large number of internal components, such
as a spray tip, spring cage~ spring retainer, and fuel
pump cylinder, are stacked and clamped between the
single nut and the housing. Thus, the chances of
successfully assembling the pump-injector and
tightening the nut, without undesirably binding the
reciprocable plunger in the pump cylinder, are very
sensitive to the quality of surface finish and
parallelism of each of the numerous abutting high
pressure sealing end surfaces of the components.
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Even if the required quality of surface finish
and parallelism is achieved during manufacture of khe
components, the problem of the plunger binding in the
pump cylinder can arise in attempting to reassemble a
used and worn pump-injector that had been disassembled
for cleaning or rebuilding. In such cases, the nut
must be loosened or removed and the internal components
must be shifted around several times or even relapped
at their end surfaces before the nut can be properly
tightened.
Second, the amount of high pressure fuel
leakage between the internal components is also very
sensitive to the quality of surface finish and
parallelism of the numerous abutting sealing end
surfaces of those parts. Excessive fuel leakage erodes
and thereby irreparably damages the sealing end
surfaces and also helps cause undesirably large
tolerances on injector fuel flow rate and injector
valve opening pressure.
Third, the entire pump-injector must be
disassembled for servicing or rebuilding even though it
is usually only the spray tip of the injector assembly
that requires replacement or cleaning since only the
spray tip is directly exposed to the severe environment
of the engine combustion chamber. The combustion
byproducts build up carbon and corrosive elements in
the seat area between the spray tip and nut, in
addition to the spray tip orifices, making it difficult
to disassemble and clean the spray tip and nut.
Conversely, the injector assembly of the pump-injector
must be disassembled even though it may be only the
pump assembly that requires servicing~
Fourth, evaluation and quality control of
perEormance parameters such as fuel injector flow rate,
fuel internal leakage rate, and injector valve opening
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pressure o~ the pump-injector is time consuming since
the entire pump-injector must be careEully assembled,
bench tested, and then completely disassembled ~n order
to substitute injector spring shims or other internal
components which will bring the parameters within
acceptable tolerances.
In U.S. 2,560,799 issued to Johnson on July
17, 1951 there is disclosed a capsule which contains an
injection valve and nozzle assembly to permit the
assembly to be bench tested and observed in observation
without connecting it to an engine. ~owever, these
teachings have never been adapted or applied to an
injector assembly of a unit fuel purnp-injector.
The present invention is directed to
overcominy one or more of the problems as set forth
above.
Disclosure Of The Invention
In one aspect of the present invention a unit
fluid pump-injector is disclosed having a housing; a
pump assembly including a pump cylinder and a
re~iprocable plunger therein for developing an
injection charge oE pressurized fluid; an encapsulated
injector assembly for injecting the charge of fluid out
of the unit fluid pUTllp injector assembly, said
encapsulate~ injector assembly including A valve body
having a valve seat and a spray orifice, a valve
positioned within the valve body, means for resiliently
biasing the valve against the valve seat~ and a formed
case encapsulating the valve body and the resilient
biasing means and retaining them against separation;
first means for removably retaining the pump cylinder
against the housing so that the pump assembly may be
removed from or assembled to the first retaining means
without altering the position or arrangement of the
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encapsulated injector assembly relative to the first
retaining means, said first retaining means including a
sleeve~type retainer removably fastened to said
housing; and second means for removably retaining the
encapsulated injector assembly against the first
retaining means so that the encapsulated injector
assembly may be removed from or assembled solely as a
unit to the first retaininy means without altering the
position or arrangement of the pump assembly relative
to the first retaining means~ said second retaining
means including a cup-shaped retainer removably
fastened to said sleeve-type retainer.
Conventional unit fuel pump-injectors have a
sinyle elongated sleeve-type nut which retains a
stacked plurality of both injector and pump com,ponents
against a housing. Such a configuration is difficult
to assemble and service since all the high pressure
sealing end surfaces of the numerous abutting internal
components must accurately fit together before the nut
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can be properly tightened. Also servicing of only
either the pump or injector assembly requires
disassemhly of the entire pump~injector.
A "modular" unit fluid pump-injector is
S claimed having two sets of joints for separately
sealably clamping the internal components thereby
facilitating easier assembling and servicing of the
pump-injector. With fewer internal parts clamped
between each joint the pump-injector is less prone to
high pressure fluid leakage and having the plunger bind
in the pump cylinder. Also, either the pump or
injector assembly can be serviced without disturbing
the other one relative to the first retaining means.
Brief Description Of The Drawings
Fig. 1 is a diagrammatic cross sectional view
of an embodiment of the present invention as
incorporated in a cylinder head of an internal
combustion engine.
Fig. 2 is a diagrammatic enlarged partial view
of Fig. 1 in the area of the injector assembly.
Best Mode For Carryi~ Out The Invention
Referriny to Figs. 1 and 2 wherein similar
reference numbers designate the same parts in the two
views, the preferred embodiment oE a unit fluid
pump-injector 10 is shown after it has been assembled
and then seated against an internal frusto-conical seat
or surface 12 located within a stepped bore 14 of a
cylinder head 16.
The upper portion of the p~mp-injector is
conventional and comprises a housing 18 and a pump
assembly 20. As is well known in the art, a two-prong
clamp 22 and a bolt 24 fast2n the housing 18 to the
cylinder head 16.
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The lower portion of t~le purnp-injector 10 is
unconventional and comprises a first ~eans 26 for
removably retaining a portion of the purnp assernbly 20
against the housing 18, an injector assembly 28, and a
second means 30 for removably retaini.ng the injector
assembly 28 against the first retaining means 26 90
that the injector assembly 28 may be removed from or
assembled to the first retaining rneans 26 without
requiring removal of the first retaining means 26 or
even alterin~ the position or arrangement of the pump
assembly 20 relative to the first retaining means 26.
Conversely, the pump assembly 20 may be removed from or
assembled to the first retaining means 26 without
re~uiring removal of the second retaining means 30 or
even altering the position or arrangement of the
injector assembly 28 relative to the first retaining
means 26.
The pump assembly 20 includes a pump cylinder
or barrel 32 and a plunger 34. The pump cylinder 32
has upper and lower fluid ports 36,38 which communicate
with an internal pumpiny charnber 40. The pump cylinder
32 also includes a reduced-diameter external end
portion 42 which is piloted into the housing 18 and is
sealably seated against the housing 18 at a housing
sho~llder 44.
The plunyer 34, haviny an internal transverse
channel 46 communicatiny with an internal longitudinal
channel 48 and a helical fluid-meteriny groove 50, is
slidably positioned within the pumping chamber 40 and
is rotatably clasped by a bifurcated follower 52 which
is reciprocable within the housing 18. A plunyer
return spriny 54 cooperates with a pivotal rocker 56~ a
push rod 58l and an engine~driven rotatable camshaft 60
in effecting reciprocation of the follower 52 and the
plunger 34.
The plunyer 34 is also rotatable within the
pumping chamber 40 and has e~ternal splines 62 which
slidably engage a rot~table pinion year 64 and a
slidable rack 66 positioned in the housin~ 18.
The first retaining means 26 includes a first
elon~ated sleeve-type nut or retainer 68, and a pump
cylinder retainer 70. The first nut 68 has stepped
large, intermediate~ and small diameter bores 72,74,76,
whereby the intermediate and small diameter bores 74,76
define a shoulder 78. The pump cylinder 32 is
positioned in the large diameter bore 72 and the pump
cylinder retainer 70 is positioned within the
intermediate diameter bore 74 and is sealably seated
between the pump cylinder 32 and the shoulder 78. The
inner upper portion of the first nut 68 has a first
internally-threaded portion 80 which is threadably
Mated to the housing 18 and the first nut 68 may be
tightened by a wrench which engages a hexagonal-shaped
exterior surface 82 on the first nut 68~ An annular
seal 84 is positioned adjacent the first threaded
portion 80 and the housing 18. Once the first nut 68
is tightened, the pump cylinder 32 is sealably and
removably retained between the housing shoulder 44 and
the pump cylinder retainer 70.
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68 and the pump cylinder 32 is an annular f.uid
reservoir 86 which communicates with upper and lower
fluid ports 36,38. The first nut 68 also includes
fluid supply and return ports 88,90 which communicate
with the fluid reservoir 86 and also with an annular
space 9~ in the cylinder head bore 14 which
communicates with a fluid supply manifold (not shown)~
A plurality of annular fluid seals 94 are externally
positioned on the first nut 68 above and below the
fluid supply ports 88,90.
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l'he ~ump cylinder retainer 70 includes a
centrally-located fluid delivery opening 96, whlch
communicates with the pumping chamber 40 and the
injector assembly 28, and a means 98 ~or returning
5 fluid leakage from the small diameter bore 76 of the
first nut 68 to the annular fluid reservoir 86.
Preferably, the fluid leakage return means 98 is a
passage angularly drilled in the pump cylinder retainer
70,
The injector assembly 28 is located partially
in the small diameter bore 76 of the first nut 68 and
includes a valve body 100, an inwardly~opening needle
valve 102 positioned within the valve body 100, a means
104 for resiliently biasing the valve 102, and a formed
case 106 sealably encircling or encapsulating the valve
body 100 and the resilient biasing means 104 and
retaining them against separation.
The valve body 100 includes a spray tip 108
having a valve seat 110 and at least one outlet or
spray orifice 112, a spacer block or spring cage 114
sealably abutting the spray tip 108, and a spring
retainer 116 abutting the spacer block 114 and also
sealably abutting the pump cylinder retainer 70.
Internal portions o the spray tip 108, spacer block
114, and sp~ing retainer 116 define at least one fluid
charge delivery passaye 118 which communicates between
the fluid delivery opening 96 of the pump cylinder
retainer 70 and the outlet 112 of the spray tip 108.
The middle portion of the spray tip 108 defines a
cardioidal or heart-shaped fluid pressure chamber 121
in the passage 118.
The spray tip 108 and spacer block 114 define
a centrally-disposed longitudinal stepped bore 120
which houses the slidable valve 102 and resilient
biasing means 104. Preferably, the resilient biasing
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means 104 includes a helical compression spring 122 and
optionally one or more annular spring-preload shims
1240 The valve 102 includes a conical ~;ip portion 126,
a cylindrical needle portion 12.8, an annular convex
surface portion 130 positioned in the cardioid chamber
121, a relatively larger diameter guide portion 132, a
spring seat portion 134, and a stop portion 1360 The
valve 102 is movable between a first position at which
the tip portion 126 is seated on valve seat 110,
thereby blocking fluid communication hetween the fluid
charge delivery passage 118 and the outlet 112, and a
second position at which the tip portion 126 is
upwardly spaced from the valve seat 110 thereby opening
fluid communication.
The spring retainer 116 has a centrally
disposed cavity 138, facing the fluid delivery opening
96 of the pump cylinder reta.iner 70, and houses a
reverse-flow check valve 140. The check valve 140 in
response to differential fluid pressure and gravity is
movable between a first position at which the check
valve 140 is spaced from the opening 96 and a second
pos.ition at which the check valve 140 seats against the
pump cylinder retainer 70 and blocks the opening 96.
The case 106 of the injector assembly 28 is
preferably formed of a ductile metal having good heat
conducting properties and is pressed or coined to the
shape illustrated around the spray tip 108, spacer
block 114, and spring retainer 116. The case 106 is
substantially tubular and has a frusto-conical end
portion 142 which mates with a frusto-conical end
portion 144 of the spray tip 108~ The case 106 and
spacer block 114 define a fluid bleed-off passage 146
which communicates with the valve body bore 120 and the
fluid leakage return means 98 of the pump cylinder
retainer 70.
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The second retaining means 30 includes a
second cup-shaped nut or retainer 148 haviny a
substantially tubular portion 150 with a longitudinally
splined exterior surface 152 and a frusto-conical end
portion 154 which is positioned in close proximity to
the interiorly disposed cardioidal chamber 121 of the
spray tip 108 and which seats against the internal
frusto-conical seat 12 of the cylinder head 16. The
first nut 68 has a second externally-threaded portion
156 which threadably mates with the tubular portion 150
of the second nut 148. An annular fluid seal 158 is
provided adjacent the second threaded portion 156 and
the second nut 148. Once the second nut 148 is
tightened, the injector assembly 28 is sealably and
removably retained between the pump cylinder retainer
70 and the frusto-conical end portion 154 of the second
nut 148. The sandwiched Erusto-conical end portions
144l142,154 of the spray tip 108, case 106, and second
nut 148, respectively, have the same included angles
S,C,N and are selected from the range of about 40 to
80, and, more preferably are about 50.
This frusto-conical configuration of the end
portions 144,142,154 in assembled cooperation with the
tightened clamp 22 ensures adequate sealing between the
seat 12 and these mating end portions relative to the
combustion chamber. This configuration also induces a
preselected compressive-stress state in the close
proximity region of the spray tip 108 defining the
cardioidal chamber 121, to prevent tensile~stress
induced cracking and improve the fluid-pressure loading
capability and fatigue life of that spray tip region,
and yet prevent a loss of optimal guiding, sliding, and
fluid leakage clearance between the bore 120 and the
slidable valve guide portion 132 when the second nut
14~ is tightened. Moreover, the angles S,C, and N are
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selected to prevent unacceptable stress in the inner
~urface of the second nut 148 when it is tightened.
Industr al Ap~licabilit~
While the operation of the present invention
is believed clearly apparent from the foregoing
description, further amplification will be made in the
following brief summary of such operation.
In operation, a fluid, for example diesel
fuel, is supplied under relatively low pressure to the
annular reservoir 86 from the fuel manifold (not
shown), through the annular space 92 and fluid supply
port 88. In the position shown, the valve 102 is
seated and the reciprocable plunger 34 is at the top of
its stroke thereby uncovering the lower port 38 and
allowing fuel to flow from the annular reservoir 92
into the pumpiny chamber ~0 and fluid charge delivery
passage 118. ~s the plunger 34 descends under the
cooperative influence of the engine-driven rotatable
camshaft 60, pushrod ~8, pivotal rocker 56, and
reciprocable follower 52, the plunger 34 first covers
the lower port 38 and then pumps fuel through the
internal channels 46,48, metering groove 50, out
through upper port 36, and back to the annular fluid
reservoir 86 until the metering groove 50 no longer
communicates with the upper port 36. As the plunger 34
continues descending after the upper port 36 is
blocked, the fuel pressure rises rapidly in both the
pumping chamber 40 and the fluid charge delivery
passage 118 until the high fuel pressure in the
cardioidal chamber 121 acting on the exposed annular
surface portion 130 of the valve 102 is sufficient to
slightly lift the resiliently biased valve 102 of its
seat 110 thereby additionally exposing the conical tip
portion 126 of the valve 102 to high fuel pressure.
The needle valve 102 continues to be lifted inwardly
away from the valve seat until its stop portion 136
abuts the spring retainer 116. When the valve 102 is
unseated frorn the valve seat 110, high pressure fuel is
injected into the com~ustion chamber (not shown)
through the outlets 112. The injection continues under
the influerlce o~ the downwardly moving plunger 34 until
the metering groove 50 communicates with the lower port
38 thereby bypassing the remaining fuel in the pumping
charnber 4U to the annular reservoir 86 and relieving
the high fuel pressure which then allows the spring 122
to seat the valve 102 and terminate fuel injection
until the cycle is repeated.
The modular design of the unit fluid
pump-injector, having one threaded joint which
removably and sealably clamps the pump cylinder 32
between the pump cylinder retainer 70 and the housing
18 and another threaded joint which removably and
sealably clamps the in~ector assembly 28 to the pump
cylinder retainer 70, advantageously is less prone to
high pressure fuel leakage or to having the plunger
hind during assembly since fewer parts are stacked and
clamped together.
The modular design also advantageously allows
merely the second nut 1~8 to be threadably unfastened
frorn the first nut 68 so that the injector assembly 28
can be rernoved, for easier servicing or replacement,
from the small diameter bore 76 of the first nut 68
without requiring removal of the first nut 68 or
altering the position or arrangement of the pump
assembly 20 relative to the first nut 68
Conversely, the housing 18 may be threadably
removed from the first nut 68 so that the pump assembly
20 can be removed from the large diameter bore 72 of
the first nut 68 without requiring removal of the
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second nut 148 or altering the position or arrangement
of the injector assembly 28 relative to the first nut
68.
The configuration of the injector assembly 28
advantageously allows the spray tip 108, spacer block
114, spring retainer 116/ and resilient biasing means
104 to be clamped together in a test fixture for
testing, adjustment, and close control of desired
operating characteristics such as fuel flow rate, valve
lift, and valve opening fuel pressure. Afterwards
these parts are substantially encapsulated and retained
against separation by the tamper proof case 106. The
injector assembly 28 may then be coded for
identification of its operating characteristics and
selectively installed as a new or replacement part in a
new or rebuilt unit fuel pump-injector.
The sandwiched frusto-conical end portions
154,142,144 of the second nut 148, case 106, and spray
tip 108, respectively, which seat at surface 12 in the
bore 14 of the cylinder head 16 provide a tight seal
against carbon formation from the combustion chamber
thus facilitating easier removal and servicing of the
injector assembly 28. Moreover, the sandwiched
frusto-conical end portions in seated cooperation with
the tightened clamp 22 and cylinder head seat 12 create
a preselected compressive stress state in the close
proximity region of the spray tip 108 defining the
cardioidal chamber 121 to prevent cracking and improve
the fluid-pressure loading capability and fatigue life
o~ that spray tip region.
Other aspects, objects and advantages of this
invention can be obtained from a study of the drawings,
the disclosure, and the appended claims.
