U.S. patent number 3,831,846 [Application Number 05/323,624] was granted by the patent office on 1974-08-27 for fuel injector.
This patent grant is currently assigned to Cummins Engine Company, Inc.. Invention is credited to George L. Muntean, Julius P. Perr.
United States Patent |
3,831,846 |
Perr , et al. |
August 27, 1974 |
FUEL INJECTOR
Abstract
A fuel injector for an internal combustion engine, comprising an
injector body and a plunger reciprocable in said body. An injection
chamber in the body receives fuel from a fuel supply, and the
plunger is moved in an injection stroke to force fuel from the
injection chamber and out of the injector through spray holes in
the injector body. A valve in a flow passage between the chamber
and the spray holes is normally open to permit fuel flow during
injection. The plunger moves the valve toward its closed or seated
position during the injection stroke, and when the valve closely
approaches the seated position, a hydraulic force develops which
forces the valve to its seat and thereby abruptly terminates
injection. Release of fuel pressure after termination of injection
is attained by opening a spill port, the flow passage for the
spilled fuel being restricted in order to obtain a gradual release
of the fuel pressure in the chamber. The resulting gradual release
of fuel pressure in the chamber holds the valve firmly seated and
thus prevents secondary injection.
Inventors: |
Perr; Julius P. (Columbus,
IN), Muntean; George L. (Columbus, IN) |
Assignee: |
Cummins Engine Company, Inc.
(Columbus, IN)
|
Family
ID: |
23259995 |
Appl.
No.: |
05/323,624 |
Filed: |
January 15, 1973 |
Current U.S.
Class: |
239/89; 239/90;
239/95 |
Current CPC
Class: |
F02M
61/04 (20130101); F02M 55/04 (20130101); F02M
57/021 (20130101); F02B 2075/025 (20130101) |
Current International
Class: |
F02M
57/02 (20060101); F02M 57/00 (20060101); F02M
61/04 (20060101); F02M 61/00 (20060101); F02M
55/00 (20060101); F02M 55/04 (20060101); F02B
75/02 (20060101); F02m 047/02 (); F02m
045/10 () |
Field of
Search: |
;239/88-91,5,96,95 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
582,783 |
|
Nov 1946 |
|
GB |
|
548,454 |
|
Oct 1942 |
|
GB |
|
447,324 |
|
Apr 1949 |
|
IT |
|
Primary Examiner: Ward, Jr.; Robert S.
Attorney, Agent or Firm: Hibben, Noyes & Bicknell
Claims
I claim:
1. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having a
plunger bore formed therein, a reciprocable plunger mounted in said
bore, said body further having an injection chamber and spray holes
therein, said spray holes connecting said chamber with said engine
cylinder, a tip valve having a vale portion thereon, said body
having a valve seat mating with said valve portion and located in
the path of fuel flow from said chamber to said spray holes, means
normally holding said tip valve off said valve seat but said tip
valve being moved toward said seat by movement of said plunger to
seat said valve portion on said valve seat, and pressure release
means connected to said chamber and actuated by movement of said
plunger to release pressure in said injection chamber at the same
time or after the time that said valve portion seats on said valve
seat.
2. An injector as in claim 1, wherein said pressure release means
comprises a spill passage leading from said injection chamber, said
passage having a restricted flow area to effect a gradual release
in pressure in said injection chamber.
3. An injector as in claim 1, wherein said path of fuel flow from
said chamber to said spray holes is through a passage between said
valve portion and said seat, the flow area of said passage
decreasing as said tip valve is moved toward said seat by said
movement of said plunger, and wherein a hydraulic force develops on
said tip valve when the flow area of said spray holes becomes
greater than said flow area between said valve portion and said
seat, said hydraulic force tending to move said tip valve toward
said seat and causing an abrupt termination of injection.
4. A fuel injector as in claim 1, wherein said tip valve is movably
mounted in said body separate from said plunger, said plunger
moving into engagement with said tip valve to move said tip valve
toward said seat.
5. A fuel injector as in claim 1, wherein said tip valve is movably
mounted in said body and is connected to said plunger by a lost
motion connection.
6. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising a plunger body having an
injection chamber, plunger means for forcing fuel out of said
chamber and into an engine cylinder, valve means in the flow path
of fuel flowing out of said chamber for terminating injection, and
pressure release means in said body for releasing pressure in said
chamber at the same time or after the time that said valve means
terminates injection.
7. A fuel injector as in claim 6, wherein said pressure release
means gradually releases pressure in said chamber.
8. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having a
fuel flow passage formed therein, means for forcing fuel under
pressure through said passage, said body further having spray holes
formed therein for the flow of fuel through said passage and into
said cylinder, valve means in said passage including a valve seat
formed in said body and a movable valve member, said valve member
blocking the flow of fuel through said passage to said spray holes
when said member engages said valve seat and permitting such flow
when said member is displaced from said seat, means for normally
holding said valve member away from said valve seat, means for
moving said valve member toward said seat during an injection
stroke, the flow area through said spray holes being greater than
the flow area between said member and said seat when said member is
displaced, and said flow area between said member and said seat
becoming less than said flow area through said spray holes when
said member closely approaches said seat, whereby the fuel flow
through said valve means is throttled causing the pressure upstream
of said valve means to become greater than the pressure downstream
of said valve means, said greater pressure tending to move said
member to and holding said member on said seat.
9. A fuel injector as in claim 8, wherein a portion of said passage
is upstream of said valve seat and is formed in said valve
member.
10. A fuel injector as in claim 8, wherein a portion of said
passage is upstream of said valve seat and is formed in said body
to one side of said valve member.
11. A fuel injector as in claim 8, and further including means in
said injector body for releasing pressure in said passage upstream
of said seat essentially at the same time that said member engages
said seat.
12. A fuel injector as in claim 11, wherein said pressure release
means gradually releases said pressure, whereby said pressure is
sufficiently maintained to hold said valve member seated and
prevent secondary injection.
13. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having a
chamber formed therein adapted to be connected to receive fuel from
a fuel supply, said body further having spray holes formed therein
and fuel passage means connecting said chamber with said spray
holes, valve means in said passage for closing said passage to
terminate the flow of fuel from said chamber to said spray holes, a
plunger reciprocably mounted in said body and forcing fuel out of
said chamber through said passage when moved in an injection
stroke, and restricted flow spill passage means leading from said
chamber and being the only outlet for fuel from said chamber when
said valve means is closed at the end of said injection stroke,
whereby the fuel contained in said chamber cushions and stops the
movement of said plunger without mechanical impact of said plunger
on said body.
14. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having an
injection chamber formed thereon, said body further having formed
therein spray holes, a passage connecting said chamber with said
spray holes, valve means in said passage including a seat formed in
said body and a valve member movable between an open position where
it opens said passage and a seated position where it closes said
passage, a plunger mounted in said body and movable in an injection
stroke to force fuel from said chamber through said passage when
said member is in said open position and out of said spray holes,
said plunger moving said valve member from said open position
toward said seated position during said injection stroke, said
valve member being moved to said seated position and terminating
injection before said plunger reaches the end of said injection
stroke, and means for starting release of pressure in said chamber
between the time said valve member reaches said seated position and
the time said plunger reaches the end of said injection stroke.
15. A fuel injector as in claim 14, wherein said pressure release
means comprises a spill passage connected to said chamber, and said
plunger opening said passage at essentially the same time that said
valve member reaches said seated position.
16. A fuel injector as in claim 15, wherein said spill passage
leads to a low pressure drain connection.
17. A fuel injector as in claim 15, wherein said spill passage
leads to a closed chamber.
18. A fuel injector as in claim 17, wherein said closed chamber is
formed in said plunger.
19. A fuel injector as in claim 17, wherein said closed chamber is
formed in said injector body.
20. A fuel injector as in claim 17, wherein said plunger connects
said closed chamber to a drain while said spill passage is
closed.
21. A fuel injector as in claim 15, wherein said spill passage is
formed in said body.
22. A fuel injector as in claim 15, wherein said spill passage is
formed in said plunger.
23. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having a
plunger bore formed therein, a reciprocable plunger mounted in said
bore, said body further having an injection chamber and spray holes
therein and a passage connecting said chamber with said holes, said
spray holes being adapted to connect said chamber with said
cylinder, a tip valve having a valve portion thereon, said body
having a valve seat in said passage adapted to mate with said valve
portion, spring means between said tip valve and said body for
urging said tip valve away from said seat and toward said plunger,
said plunger engaging said tip valve and moving said tip valve
toward said seat until the flow area between said valve portion and
said valve seat becomes less than the flow area of said spray holes
at which time a hydraulic force develops on said tip valve forcing
said tip valve out of engagement with said plunger and onto said
valve seat.
24. A fuel injector as in claim 23, wherein said plunger re-engages
said tip valve after said tip valve has been moved onto said
seat.
25. A fuel injector as in claim 24 and further including means
between said plunger and said tip valve permitting said plunger to
continue moving relative to said tip valve after reengaging said
tip valve.
26. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having
formed therein a plunger bore, an injection chamber, spray holes
and a passage connecting said chamber with said spray holes, a
plunger reciprocably mounted in said bore and forcing fuel from
said injection chamber and through said passage when moved in an
injection stroke, a tip valve movably mounted in said chamber and
having a valve portion extending into said passage, a valve seat
formed in said passage and mating with said valve portion, first
spring means connecting said body with said tip valve and urging
said tip valve away from said seat and toward said plunger, second
spring mean connected to said tip valve and engaged by said plunger
during at least a portion of said injection stroke, whereby said
first spring holds said tip valve away from said seat prior to said
injection stroke, and said plunger acts through said second spring
means to move said tip valve toward said seat during said injection
stroke.
27. A fuel injector as in claim 26, wherein said first spring means
moves said tip valve and said second spring means and holds said
second spring means engaged with said plunger prior to the start of
said injection stroke.
28. A fuel injector as in claim 27, and further including means on
said body for limiting the extent of movement of said tip valve due
to the force of said first spring means.
29. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having
formed therein a plunger bore, an injection chamber, spray holes
and a passage connecting said chamber with said spray holes, a
plunger reciprocably mounted in said bore and forcing fuel from
said injection chamber and through said passage when moved in an
injection stroke, a tip valve movably mounted in said chamber and
having a valve portion extending into said passage, a valve seat
formed in said passage and mating with said valve portion, a lost
motion connection between said plunger and said tip valve, spring
means connected to said tip valve and urging said tip valve toward
said seat and away from said plunger, and spill means connected to
said chamber for relieving pressure in said chamber at the same
time as or after said valve portion engages said seat and
terminates injection.
30. A fuel injector as in claim 29, wherein said lost motion
connection comprises hook portions on said plunger and on said tip
valve.
31. A fuel injector as in claim 30, wherein said hook portions
comprise two semi-cylindrical sleeves which encircle and engage
adjacent portions of said plunger and said tip valve.
32. A fuel injector for injecting fuel into a cylinder of an
internal combustion engine, comprising an injector body having a
plunger bore formed therein, a reciprocable plunger mounted in said
bore, said body further having an injection chamber and spray holes
therein, said spray holes being adapted to connect said chamber
with said cylinder, a tip valve movably mounted in said body and
having a valve portion at one end thereof, said body having a valve
seat adapted to mate with said valve portion and located in the
path of fuel flow from said chamber to said spray holes, said
plunger being adapted to be moved in an injection stroke to exert
pressure on fuel in said injection chamber and the other end of
said tip valve being exposed to said pressure of the fuel in said
injection chamber, said tip valve being moved toward said seat by
said movement of said plunger to seat said valve portion on said
valve seat, and said pressure of the fuel in said injection chamber
on said other end forcing said tip valve toward said seat and
holding said tip valve on said seat after seating.
33. A fuel injector as in claim 32, and further including means
connected to said injection chamber for gradually releasing said
pressure after said seating.
34. A fuel injector as in claim 33, wherein said pressure release
means comprises a spill port connected to said injection
chamber.
35. A fuel injector as in claim 32, wherein said tip valve is
mounted in said body separating from said plunger, and said
pressure in said injection chamber both moves said tip valve onto
and holds said tip valve on said seat.
Description
One type of fuel injector for an internal combustion engine is
referred to as a unit injector and includes, as a unitary
structure, a fuel pump and a fuel injection nozzle. The injector is
mounted with the nozzle projecting into an engine cylinder, and in
the operation of such an injector, the pump, consisting of a cam
actuated plunger, forces a quantity of fuel from the nozzle under
high pressure, thereby atomizing the fuel, into an engine cylinder
at the proper time in the engine cycle.
To attain greater efficiency in burning fuel in the cylinders of
either a four cycle or a two cycle engine and to reduce the amount
of pollutants emitted by such engines, it is important that the
fuel be injected at an optimum rate and that the injection of fuel
into the cylinders be terminated as abruptly as possible. The
reason for this will become apparent from the following discussion
of a four cycle engine, although the general principles also apply
to two cycle engines. In a four cycle combustion ignition engine,
fresh air is drawn into an engine cylinder during the intake stroke
of the piston, at which time the piston is moving away from
top-dead-center (TDC). During the compression stroke, the air
intake passage is closed and the movement of the piston toward TDC
compresses, and thus heats the air in the cylinder. Injection of
fuel may start at, for example, approximately 35.degree. before TDC
and the fuel ignites at approximately 20.degree. before TDC. There
then follows a period of controlled burning during which the fuel
is burned as it is injected. There is mixing of fuel and the air
because the fuel is being injected under high pressure, this
pressure preferably being adjusted to cause the atomized fuel to be
forced outwardly, close to, but not in contact with, the outer
periphery of the cylinder. The fuel flow rate is preferably at a
value chosen to achieve good combustion.
During the latter part of the injection period, the pressure on the
fuel being injected starts to drop and in conventional injectors
the pressure drops gradually until injection ceases. When the
injection pressure drops below a certain value, combustion is
inefficient because the fuel is not forced sufficiently far out in
the cylinder to become thoroughly mixed with the air. Further, many
injectors permit "secondary injection", which is leakage of fuel
from the injector after injection should have been stopped. Such
secondary injection is due to fuel trapped unde high pressure near
the bottom of the injector valve, such pressure forcing the valve
back open after the valve has been closed by the cam. Consequently,
there is an amount of unburned and partially burned fuel remaining
in the cylinder at the start of the exhaust stroke, which is due
both to the above mentioned secondary injection and to inefficient
combustion, and it is this fuel which accounts for a large part of
the visible smoke and toxic unburned hydrocarbons emitted by the
engine. It will therefore be apparent that the amount of harmful
emissions would be reduced if the fuel injection were abruptly
terminated at the point when combustion becomes inefficient.
J.P. Perr U.S. Pat. No. 3,351,288 discloses a prior art unit
injector wherein the lower end of a plunger seats in order to end
injection, and wherein, during operation, the pressure on the fuel
being forced from the injector gradually drops near the end of an
injection period. It might be possible to obtain a more abrupt end
of injection with such an injector by designing the cam which
drives the injector with a steeper ramp and thus forcing the
plunger's lower end hard against the nozzle. Such a construction
would, however, quickly result in failure of the parts because the
stress on the cam and follower surfaces, during injection, would be
excessive and because the momentum of the entire plunger and
actuating linkage against the nozzle would eventually damage the
latter. In addition, hydraulic pressure within the injection after
the plunger seats tends to lift the plunger off its seat, and thus
there is a tendency for secondary injection to occur.
The prior art also includes a unit injector wherein an injector
needle part is carried by a plunger and is moved by a spring to a
seated position to terminate injection. The needle part seats on a
thin-walled part of the injector body and the use of a spring to
seat the needle part thus protects the injector from the strain of
high mechanical impact. The plunger is seated in a heavily
supported part of the injector body to support the strain of
mechanical impact, but such seating limits the amount of overrun
permitted of the plunger, Limited overrun is disadvantageous as
will be apparent hereinafter.
It is therefore an object of the present invention to provide an
injector wherein the injection of fuel may be abruptly terminated
without damage to the injector or other engine parts, and wherein
secondary injection cannot occur. In accordance with the present
invention there is provided a fuel injector for an internal
combustion engine, comprising an injector body having a plunger
bore and a fuel receiving chamber formed therein, said body further
including spray holes formed in one end thereof and a passage
connecting said chamber with said spray holes, a plunger
reciprocably mounted in said bore and adapted to exert pressure on
fuel in said chamber when moved toward said one end, a valve member
movably mounted in said passage and movable to a seated position
where it closes said spray holes, said valve member normally being
in a retracted position where said spray holes are open, said valve
member moving to said seated position in response to movement of
said plunger toward said one end, and pressure release means for
relieving pressure in said chamber at the time that said valve
member moves to said seated position.
The valve member is separate from the plunger and is moved toward
its seated position by the movement of the plunger until the valve
member is close to its seat, at which time a pressure drop develops
adjacent the seat causing the valve member quickly to move to its
seated position. In a preferred form of the invention, the pressure
drop pulls the valve member away from the plunger and into its
seated position. Thus, an abrupt end of injection is obtained
without a high mechanical force being exerted on the valve member
or the other injector parts. Further, the hydraulic force is in a
direction to hold the valve member in its seated position, thus
preventing secondary injection.
In addition to the foregoing advantages, an injector in accordance
with the invention is advantageous in that up to the point of
termination of injection, the rate of injection is very high, thus
producing good combustion. The pressure on the fuel in the
injection chamber at the end of injection is gradually relieved
thereby holding the valve member seated and protecting the injector
parts from the strain of high mechanical impact. Further, at the
beginning of the injection stroke there is a relatively large
volume of fuel in the chamber and consequently a relatively slow
build-up in pressure resulting in a good injection rate.
This invention may be better understood from the following detailed
description taken in conjunction with the accompanying figures of
the drawings, wherein:
FIG. 1 is a fragmentary view partially in section of an engine
including an injector embodying the invention;
FIG. 2 is an enlarged longitudinal sectional view of one form of
the injector;
FIGS. 3 to 5 are fragmentary views of a portion of the injector
shown in FIG. 2 but showing different operating positions of the
injector parts;
FIG. 6 is a fragmentary sectional view of another portion of the
injector shown in FIG. 2;
FIG. 7 is a sectional view taken on the line 7--7 of FIG. 2;
FIGS. 8 and 9 are curves illustrating the operation of the
injector;
FIGS. 10 to 12 are views showing an alternate form of injector;
FIG. 13 is a view showing another alternate form of injector;
FIGS. 14 and 15 are views showing still another alternate form of
injector;
FIG. 16 is a view showing still another alternate form of
injector;
FIGS. 17 to 20 are views showing still another alternate form of
injector;
FIGS. 21 and 22 are views showing still another alternate form of
injector;
FIG. 23 is a view showing still another alternate form of injector;
and
FIG. 24 is a view showing still another alternate form of
injector.
The engine partially shown in FIG. 1 includes a cylinder head 51
and a block 52. A cylinder liner 53 is mounted in the block in a
conventional manner and forms a cylinder 55. A piston 56 is mounted
for reciprocating movement within the cylinder 55, and the upper
end of a connecting rod 57 is pivotally connected to the piston 56
by a wrist pin 58. Piston rings 59 are mounted on the piston 56 and
form a seal between the piston 56 and the liner 53. The crown 61 of
the piston 56 has an annular cavity 62 formed in its upper
surface.
The head 51 of the engine includes coolant passages 63 therein, and
intake and exhaust valve mechanisms (not shown) connect the upper
end of the cylinder 55 with intake and exhaust manifolds (not
shown) of the engine. A fuel injector 64 embodying the invention is
mounted in the head 51 with its lower end 66 extending through an
opening 67 formed in the head 51, the end 66 opening into the
interior of the cylinder 55 at the center thereof. The injector 64
is mounted in an opening 68 formed in the head 51 and is held in
place by a yoke-shaped clamp 69. The clamp 69 has two fingers 71
which press down against the upper surface of a flange 72 of the
injector 54, and a screw 73 holds the fingers 71 firmly against the
injector flange 72. The screw 73 extends through a hole 74 in the
clamp 69 and is threaded into the head 51.
The injector 64 is operated by a connecting linkage mechanism 75
including an injector cam 76 which is fastened to and rotates with
an engine driven cam shaft 77. A cam follower mechanism 78 includes
a roller 79 which rides on the outer surface of the rotating cam
76. The cam follower mechanism 78 further includes a tappet 81 for
the roller 79, the tappet 81 being reciprocably mounted in an
opening 82 of the block 52.
Connected to the cam follower mechanism 78 is a push rod 87 which
extends upwardly to a rocket arm 88 pivotably mounted on the head
51 by a rocket shaft 89. A pivotable arrangement including an
adjusting screw 91 connects the upper end of the push rod 87 with
one end of the rocker arm 88. The other end of the rocker arm 88
pivotably engages the upper rounded end of a link rod 93 which
extends downwardly to operate the injector 64.
As will be explained in greater detail hereinafter, the injector 64
includes a fuel intake or supply passage and fuel drain or return
passages therein. Fuel is supplied to and returned from the
injector 64 by fuel passages or rails formed in the head 51. The
fuel supply rail is shown schematically in FIG. 1 and is indicated
by the reference numeral 96 and receives fuel from, in the present
illustration, a variable pressure fuel supply 97. The fuel return
rail is also indicated schematically and is indicated by the
reference numeral 98 and carries fuel from the injector 64 to a
sump, which may be the main fuel tank. The arrangement of the fuel
supply and return rails and the construction of the fuel supply 97
do not form part of the present invention.
With reference to FIGS. 2 to 7, the injector 64 includes a body
including an adaptor 101, a barrel 102 which abuts the lower end of
the adapter 101, and a cup or nozzle 105 which abuts the lower end
of the barrel 102. The nozzle 105 forms the lower end 66 of the
injector, referred to in connection with FIG. 1. The foregoing
parts 101, 102 and 105 are held in assembled relation by a retainer
103 which fits around the barrel 102 and has its upper end
internally threaded as at 104 to the lower end of the adapter 101.
The lower end of the retainer 103 includes a ledge 106 which
engages and presses upwardly against a shoulder 107 formed on the
outer periphery of the nozzle 105. Thus, when the retainer 103 is
threaded tightly on the adapter 101, the ledge 106 presses upwardly
against the nozzle 105, and thereby holds the parts tightly
assembled. Vertically extending pins (not shown) may be provided to
angularly align the adapter 101 and the barrel 102.
At the upper end of the adapter 101 is secured an adapter extension
111 having the flange 72 formed thereon, which is engaged by the
clamp 69. The interior of the extension 111 is internally threaded
and a stop screw 112 is threaded into the extension 111. A lock nut
110 is preferably provided on the stop screw 112 to lock the stop
screw 112 in an adjusted position. The opening 67 in the head 51
includes a seat 116 which abuts the lower end of the injector 64 to
form a seal. Thus, the U-shaped yoke clamp 69 presses downwardly
against the flange 72 and holds the injector pressed tightly
against the seat 116, thereby clamping the injector 64 firmly in
place in the head 51.
The fuel supply rail 96 communicates with an annular groove 120 in
the outer periphery of the retainer 101, and the fuel return rail
98 communicates with a second annular groove 121 formed in the
retainer 101. O-ring seals 122 are positioned in grooves formed in
the retainer 101 above, below and between the grooves 120 and 121,
to seal the grooves.
A plunger bore 126 is formed centrally in the adapter 101 and in
the barrel 102, and a plunger 127 is mounted for reciprocating
movement in the plunger bore 126. A flange 128 formed on the upper
end of the plunger 127 extends over the upper surface of a stop
washer 129. A retraction spring 131 is positioned between the stop
washer 129 and a ledge 132 formed on the inner periphery of the
adapter 101, the compression spring 131 urging the stop washer 129
upwardly toward the screw 112. The outer periphery of the stop
washer 129 extends into a vertical spaced formed between the upper
end of the adapter 101 and the stop screw 112. During installation
of the injector in the engine, a technician tightens the screw 91
to properly tension the cam actuated mechanism 75, and if the screw
91 is excessively tightened, the washer 129 engages the retainer
101 and thus prevents damage to the injector tip. The washer 129
and the retainer 101 do not however normally meet.
The plunger 127 is formed in two parts, an upper hollow coupling
part and a lower part which is secured to the coupling part. The
link 93 extends through the coupling part and pivotally engages the
upper end of the lower part. During turning movement of the cam 76,
the link 93 moves downwardly and overcomes the force of the spring
131 in order to move the plunger 127 downwardly. This action ejects
fuel from the injector and into the engine cylinder 55 as will be
explained subsequently. The spring 131 returns the plunger 127 to
its upward position upon continued turning movement of the cam
76.
Below the lower end of the plunger 127 and within the nozzle 105 is
mounted an elongated tip valve 141 (FIGS. 2 to 5 and 7). In the
present instance, the tip valve 141 is generally cylindrical and
the nozzle 105 has a cylindrical bore 142 formed therein, the tip
valve 141 being mounted for reciprocating movement within the bore
142. The lower end of the bore 142 is slanted inwardly to form a
conical valve seat 143, and the lower end of the tip valve 141 has
a complementary shaped valve portion 144 which, when seated on the
seat 143, seals the lower end of the bore 142. The lower end of the
nozzle 105 has spray holes 146 and a sac hole 147 formed therein,
through which the fuel passes as it is injected into the interior
of the cylinder 55.
The bore 142 has an enlarged diameter upper portion 136 (FIG. 5)
which receives a spring 156 to be described. The lower end of the
bore 142 is stepped radially inwardly as at 137 to the conical
valve seat 143. The tip valve 141 has a close sliding fit in the
intermediate portion of the bore 142, and it is also stepped
radially inwardly as at 138 to a smaller diameter portion 145 which
is equal in diameter to the upper end of the valve portion 144. As
shown in FIGS. 2 and 3, when the tip valve 141 moves downwardly to
seat the portion 144 on the valve seat 143, the steps 137 and 138
are axially spaced a short distance apart.
The upper end of the tip valve 141 has an internally threaded hole
indicated at 148 (see FIG. 2), and a screw 149, preferably of the
Lock Tite type, is screwed into the threaded hole 148. An impact
button 151 is positioned around the head 153 of the screw 147, the
button 151 having an inwardly extending flange 152 which fits
underneath the head 153 of the screw 149. The button 151 extends
upwardly around the outside of the head 153 and normally engages
the lower end surface of the plunger 127, as shown in FIGS. 3 to 5.
The lower end of the plunger 127 may be hollowed as indicated at
155 to provide clearance for the head 153. The button 151 is forced
upwardly toward the plunger 127 by the outer compression spring 156
which has its upper end in engagement with the underside of the
button 151 and its lower end seated on a shim 157 which is
supported on a ledge in the nozzle 105. Further, the tip valve 141
is urged downwardly relative to the button 151 by an inner
compression spring 158 which extends between the underside of the
button 151 and the upper surface of the tip valve 141. The two
springs 156 and 158 are of course arranged concentrically around
the screw 149 and within the bore 142.
As previously mentioned, fuel flows to the injector 64 through the
passage 96 formed in the head 51, the fuel being received from the
variable pressure fuel supply 97. The adapter 101 has a fluid
passage 165 formed therein which opens from the groove 120. A
filter screen 166 covers the opening of the supply passage 165, and
a balance orifice 167 is formed in a plug located in the opening of
the supply passage 165. The passage 165 connects with a passage 168
(FIGS. 2 and 6) formed in the barrel 102, and a check valve 169 is
located in the passage 168. The foregoing passages and check valve
are generally similar to those shown in the previously mentioned
Perr U.S. No. 3,351, 288. The lower end of the passage 168
communicates with an annular groove 171 (FIGS. 2 and 6) formed in
the upper surface of the nozzle 105. Angularly displaced from the
passage 168 is a passage 172 (FIGS. 2 to 5) in the barrel 102,
which extends upwardly from the groove 171. A feed or metering
orifice 173 connects the passage 172 with the plunger bore 126 and
a scavenging port or orifice 174 is located above or upstream from
the orifice 173 and also connects the passage 172 with the plunger
bore 126.
The return rail 98 leads from the groove 121 of the injector 64, as
previously explained, and two return or drain passages 176 and 177
(FIG. 2) are formed in the adapter 101 and in the barrel 102. The
two passages 176 and 177 are angularly displaced, and the upper
ends of both passages 176 and 177 open into the groove 121, while
the lower ends of both passages open into the plunger bore 126. The
lower end of the passage 176 is referred to herein as a spill port
and is indicated by the reference numeral 178. The lower end of the
passage 177 is referred to herein as the drain port and is
indicated by the reference numeral 179. The scavenging port 174 and
the drain port 179 are substantially transversely aligned, and the
plunger 127 has an annular recess or groove 181 formed therein,
which is located to connect the ports 174 and 179 when the plunger
127 is in its extended or downwardly displaced position, shown in
FIGS. 2 and 3. The orifice 173 is located below the ports 174 and
179 and is positioned such that it is uncovered by the lower end of
the plunger 127 only when the plunger is in its retracted or
upwardly displaced position, shown in FIG. 4. The spill port 178 is
formed below the port 179 and is located relative to a second
annular groove 182 in the plunger 127 such that the groove 182
opens the spill port 178 to a limited extent only when the plunger
127 is in its maximum extended position, shown in FIG. 3. As best
shown in FIGS. 2 and 4, a hole 183 extends axially through the
screw 149 and from the upper end of the tip valve 141 downwardly to
the valve portion 144. A radially extending hole 184 (FIGS. 2 and
7) is formed in the tip valve 141 below the step 138 and above the
valve portion 144, from the exterior surface of the tip valve 141
to the center hole 183. The upper end of the hole 183, at the top
of the screw 149, opens into the cavity or recess 155 formed in the
lower end of the plunger 127. An axial hole 186 (FIG. 3) is formed
in the lower end of the plunger 127 and extends from the cavity 155
to the level of the groove 182, and a radial hole 185 connects the
hole 186 with the groove 182. Consequently, as shown in FIG. 3,
when the plunger 127 is in its maximum downwardly extended
position, the holes and passages 183 to 186 place the portion of
the bore 142 around the lower end of the tip valve 141, in
communication with the spill port 178.
A number of the passages in the barrel 102 are formed by drilling
holes from the outside of the barrel, and in a number of instances,
the outer ends of the holes are sealed by plugs 190 (FIG. 3).
The injector further includes fuel passage means connecting the
upper and lower portions of the bore 142. In the form of the
injector shown in FIGS. 1 to 7, this passage means is formed in the
tip valve 141. With particular reference to FIGS. 5 and 7, a
plurality of longitudinally extending slots or grooves 189 are
formed in the outer surface of the tip valve 141, the grooves 189
extending from its upper end downwardly to the step 138. The total
cross-sectional area of the grooves 189 must be greater than the
total area of the spray holes 146 to prevent a hydraulic lock from
occurring during injection of fuel.
Considering the operation of the injector disclosed in FIGS. 1 to
7, when the cam shaft 77 (FIG. 1) is at an angular position such
that the follower roller 79 engages a reduced radius section 191 of
the cam 76, the plunger 127 is in its maximum upwardly displaced,
or retracted, position which is shown in FIG. 4. As previously
mentioned, the spring 131 moves the plunger 127 to this position,
and the spring 156 moves the tip valve 141 upwardly and holds the
button 151 against the plunger 127. FIG. 8 shows a curve 192
representing the plunger 127 travel as a function of the angle of
the crankshaft driven by the piston 56. The plunger 127 is in its
maximum retracted position (FIG. 4) during the portion 193 of the
curve 192, this retracted position occurring from approximately the
end of the air suction stroke until approximately 50.degree. before
the end of the compression stroke of the piston 56. During the time
that the plunger 127 is in the retracted position, fuel flows from
the supply 97, through the passages 165, 168 and 172, through the
metering orifice 173 and into an injection or metering chamber 194
(FIG. 4). The chamber 194 is formed by the space below the plunger
127 within the bore 142 of the nozzle 105 and, when the plunger 127
is retracted, within the lower end of the plunger bore 126. The tip
valve 141, the springs 156 and 158, the bolt 149 and the button 153
are located in the injection chamber 194. While the plunger 127 is
retracted, the land portion of the plunger 127 between the grooves
181 and 182 closes the scavenging port 174 and thus prevents flow
of fuel between the ports 174 and 179. The portion of the plunger
127 below the lower groove 182 closes the spill port 178. The
quantity of fuel flowing into the injection chamber 194 is
dependent upon the pressure of the fuel from the supply 97, the
size or flow area of the metering orifice 173, and the length of
time the plunger 127 is retracted and the metering orifice is open.
Since the amount of fuel injected into the cylinder 55 in each
cycle is dependent upon the quantity of fuel metered into the
injection chamber 194, the amount of fuel injected into the
cylinder 55 in each engine cycle may thus be varied by a change in
the fuel pressure.
Continued turning movement of the cam shaft 77 in the
counter-clockwise direction as seen in FIG. 1 causes a ramp 196 of
the cam 76 to engage the roller 79 and displace it upwardly and the
plunger 127 downwardly toward the fuel in the injection chamber.
The chamber 194 is always only partially filled with fuel when the
plunger starts downwardly on its injection stroke, and injection
starts when the lower end of the plunger meets the fuel and causes
pressure to build up in the fuel in the metering chamber 194. The
plunger 127 meets the fuel at approximately the point 193a on the
curve 192. Shortly after the lower edge of the plunger 127 closes
the orifice 173, the lower edge of the groove 181 of the plunger
127 opens the two ports 174 and 179 (FIG. 5), permitting scavenging
fuel to flow through the passage 172, through the ports 174 and 179
and the groove 181, to the drain passage 177.
The rate at which the pressure builds up in the injection chamber
is gradual because of the large volume, as compared with
conventional injectors, of fuel trapped in the injection chamber
194, and this gradual pressure build-up is highly advantageous
because it produces a gradual increase in the rate of fuel
injection. This gradual rate increase is illustrated by the curve
of FIG. 9, and produces good fuel burning characteristics. The
movement of the plunger 127 from the position shown in FIG. 5
toward the position shown in FIG. 2 creates extremely high fuel
pressure in the injection chamber 194. The fuel in the chamber 194
flows downwardly through the slots 189 formed in the tip valve 141,
to the space below the step 138, to the sac hole 147, and out of
the spray holes 146. As previously mentioned, the total area of the
slots 189 must be much greater than the total area of the spray
holes 146 to prevent the formation of a hydraulic lock. This fuel
is sprayed into the cylinder 55 in highly atomized form, from the
holes 146 which are regularly spaced around the circumference of
the nozzle 155, resulting in uniform distribution of the atomized
fuel in the cylinder 55. Fuel injection starts at approximately the
point indicated by the reference numeral 193a (FIG. 8) which point
is dependent upon the quantity of fuel metered into the chamber
194. With reference to FIG. 9 which represents fuel flow rate as a
function of time, it will be noted that the fuel flow rate
increases as the plunger 127 is forced downwardly and reaches its
maximum rate at the point indicated by the numeral 203.
As the plunger 127 moves downwardly and displaces fuel from the
chamber 194, the tip valve 141 is also moved downwardly by the
force of the plunger 127 on the impact button 151, the inner spring
158 holding the valve 141 extended downwardly from the button 151.
When the plunger almost reaches the position shown in FIG. 2, the
size of the flow area between the tip valve portion 144 and the
seat 143, becomes less than the flow area of the spray holes 146.
At this point, the pressure in the sac hole 147 quickly drops due
to the throttling of the fuel flow between the portion 144 and the
seat 143, and this same throttling causes a rapid increase in the
fuel pressure above or upstream of the portion 144. This rapid
change in fuel pressures creates a downwardly directed hydraulic
force on the tip valve 141, which overcomes the force of the spring
156 and moves the valve 141 downwardly increasingly faster than the
plunger 127. As shown in FIG. 2, the hydraulic force moves the
impact button 151 and the tip valve downwardly out of engagement
with the plunger 127 and moves the tip valve 141 into engagement
with the seat 143. With reference to FIG. 8, the line 193b
represents the travel of the tip valve 141 and it will be noted
that the tip valve moves abruptly to the position of the seat 143
indicated by the numeral 193c in FIG. 8. Thus, the tip valve 141
abruptly terminates injection while the plunger 127 is still moving
downwardly, and, because of the small size of the tip valve,
injection is terminated with very little mechanical impact on the
thin walled portion of the cup 105 in which the sac hole 147 is
located. The spill port 178 is just starting to open when the tip
valve 141 seats, and the restricted opening plus the continued
downward movement of the plunger 127 results in the maintenance of
a hydraulic force on the upper end of the tip valve, which holds
the tip valve seated and therefore prevents secondary injection.
The hydraulic pressure on the upper end of the tip valve acts over
a much larger area and is much higher than the cylinder pressure
acting on the lower end of the tip valve, and therefore the tip
valve is held firmly seated. Such operation is the opposite of
prior art injectors wherein the pressure on the fuel trapped in the
injector when the plunger seats, is in the direction to lift the
plunger off its seat. Such prior art injectors, consequently,
permit secondary injection of fuel, which is not true of the
present injector. The valve formed by the portion 144 and the seat
143 is very close to the sac hole 147 and the size of the sac hole
is very small. Consequently, there is essentially no fuel which can
dribble into the cylinder. The lower end of the plunger then again
engages the impact button 151 and the lower edge of the groove 182
increasingly opens the spill port 178 (FIG. 3). Flow out of the
chamber 194 continues to be restricted, however, because of the
realtively small size of the flow passages, such as the passage
186, and because, as shown in FIG. 3, the spill port 178 is
gradually and only partially opened. Therefore, the pressure in the
chamber 194 is only gradually released by the opening of the spill
port 178, and this continued hydraulic force plus the force of the
spring 158 holds the tip valve seated and prevents secondary
injection. The plunger 127 and the impact button 151 move
downwardly during a period of overtravel, indicated in FIG. 8 by
the portion 193d of the curve 192, which is between the line 193c
and a line 193e. During this overtravel, fuel is squeezed from the
chamber 194 through the passages 184, 189, 186 and 182 to drain,
which is advantageous because it removes from the lower end of the
injection chamber 194 any air bubbles and extremely small size
carbon particles that may collect there. The carbon particles enter
the injector through the spray holes 146 when the tip valve 141 is
up. The fact that the impact button 151 is pressed tightly against
the lower end of the plunger prevents fuel from flowing out of the
top of the chamber 194 to the passage 186. Consequently, fuel
enters the chamber 194 at its upper end and fuel is drained from
the chamber 194 at its lower end, providing fuel flow in a loop
through the chamber 194 and clearing it of any air bubbles and the
small size carbon particles. The plunger remains in its lower
extended position during the remainder of the power stroke and
during the exhaust stroke of the piston 56, as scavenging fuel
flows from the port 174 through the groove 181, and out of the port
179 to drain.
With reference to FIG. 9, it will be apparent that the fuel flow
rate drops extremely abruptly to zero on the portion of the curve
indicated by the reference numeral 211, and this is accomplished
without excessive load on the tip valve 141 and on the nozzle 105
of the injector. Since the injection of the fuel is abruptly
terminated at approximately the point 212, fuel is not leaked into
the cylinder during the portion of the engine cycle when it could
cause a large amount of smoke and unburned hydrocarbons, and the
effective duration of injection can be reduced. Thus, the amount of
visible smoke and other pollutants from the engine is drastically
reduced.
As a comparison to more conventional injectors, it should be
apparent that, if the tip valve 141 were rigidly attached to the
plunger 127, it would have to be forced downwardly very hard
against the nozzle 105 in order to close off injection abruptly and
such high impact forces on the injector parts would quickly damage
it. The dashed line 193f in FIG. 8 illustrates the valve movement
in an injector where the valve is rigid with the plunger, as shown
in Perr U.S. Pat. No. 3,351,288, for example, and it should be
noted that such a valve moves relatively slowly to a seated
position. The dashed line 210 in FIG. 9 illustrates the gradual
drop in flow rate, which is customary in a conventional injector.
The portion of the fuel injected after the point 212 is poorly
burned.
The injector thus obtains an abrupt termination of injection at a
point in the injection cycle when the rate of injection is very
high, which is a highly advantageous feature. This feature is also
illustrated by FIG. 8 wherein the slopes of lines 193b, 193a and
193f where they cross the line 193c indicate the degree of
abruptness of the termination of injection. The line 193b
illustrates the operation of the injector forms of FIGS. 1 through
16, and has a very steep slope, and the line 193b occurs when the
plunger 127 is moving rapidly. Since it is not necessary for the
plunger to seat in order to terminate injection or to stop its
movement, the plunger is permitted almost unlimited overrun,
represented by line 193d. Movement of the plunger and the actuating
mechanism is stopped by the retraction spring 131 and by
compression and gradual release of the fuel in the injection
chamber. The slope of the line 193a where it crosses the line 193c
represents the abruptness of termination of injection of the
injector forms illustrated in FIGS. 17 to 24, and it will be noted
that this slope is also very steep. For comparison, the line 193f
represents the operation of a prior art injector of the character
shown in the Perr U.S. Pat. No. 3,351,288, and the slope of this
line is quite low.
Applicant's injector also differs from prior art injectors in the
function of the spill port 178. In applicant's injector, opening of
the spill port 178 does not terminate injection. Termination of
injection is accomplished by seating of the tip valve 141, and
opening of the spill port serves to release pressure in the
injection chamber in order to protect the parts. In prior art
injectors including spill ports, opening of the spill port serves
to terminate injection.
The plunger 127 and the tip valve 141 are held in the downward
position shown in FIG. 3 during the power and exhaust strokes,
thereby preventing any cylinder gases from entering the injector
through the spray holes. During the suction stroke, the roller 79
moves down a second ramp 196a of the cam 76, permitting the spring
131 to return the plunger 127 upwardly to the position shown in
FIG. 4, and the outer spring 156 moves the tip valve 141 upwardly
also to start a new cycle.
In an injector of form shown in FIGS. 1 to 7, the pressure in the
injection chamber rises to approximately 15,000 psi, while the
pressure of the fuel received from the fuel supply is on the order
of 200 psi. The total plunger stroke may be approximately 0.2 inch,
and the volume of fuel in the injection chamber at the start of
injection is approximately 10 times greater than the volume of fuel
in the injector shown in the above mentioned Perr patent.
The form of the injector illustrated in FIGS. 10 through 12 is
generally similar in construction and operation to the form shown
in FIGS. 1 through 7. This injector comprises a barrel 225, a cup
or nozzle 226, and a retainer 227 that holds the cup 226 and barrel
225 in assembled relation with an adapter (not shown). A fuel
supply passage 228 is formed in the barrel 225 and leads from a
source of fuel under variable pressure to an annular groove 229
formed in the upper surface of the cup 226. A vertically extending
supply passage 231 is also formed in the barrel 225 at a location
which is angularly displaced from the supply passage 228, and leads
upwardly from the groove 229 to a metering orifice 232 and to a
scavenging port 233. The orifice 232 and the port 233 open into a
plunger bore 235 in which a plunger 238 is reciprocably mounted.
The plunger 238 includes a first or upper reduced diameter portion
239 (FIGS. 11 and 12) which is located to connect the port 233 with
a drainport 237 when the plunger 238 is in its downwardly displaced
position, shown in FIGS. 11 and 12. The plunger also includes a
second or lower reduced diameter portion 241 which interconnects a
spill port 242 wih a drain port 236 only when the plunger 238 is in
its downwardly displaced position which is shown in FIG. 12, the
ports 236 and 242 being formed in the barrel 225 at angularly
displaced positions. The ports 236 and 237 are connected to two
drain passages 240 which are similar to the passages 176 and 177
shown in FIG. 2. The spill port 242 forms part of spill passage 243
formed in the barrel 225 between the bore 235 and an injection
chamber 246, the lower end 244 of the passage 243 opening into the
injection chamber 246. A spill restriction is provided in the
passage 243, the restriction consisting of a plug 247 which is
fixed in place in the passage 243 and which has a small orifice 248
formed therein.
The injection chamber 246 is generally similar in configuration to
the chamber 194 of the injector form shown in FIGS. 1 through 7,
and therefore will not be described in detail. A tip valve 251 is
movably mounted in the chamber 246 and includes a lower conically
shaped valve portion 252 which, when seated on a conical valve seat
253 of the cup 226, closes a sac hole 260 and spray holes 254
formed in the cup 226. Again, the tip valve 251 includes fuel
passages 250 formed on the outer surface thereof, the passages 250
in the present instance being formed by flat sides on an otherwise
round intermediate portion 256 of the tip valve. Above the
intermediate portion 256 of the tip valve is formed a shank 257
having a threaded upper end 258. A washer 259 is positioned around
the upper end of the shank 257, and a nut 261 is threaded onto the
end 258 over the washer 259. Inner and outer springs 262 and 263
are mounted around the tip valve 251, these two springs being
mounted similarly to and performing the same function as the
springs 157 and 158 shown in FIGS. 2 to 5. Thus, the outer spring
263 urges the washer 259, the nut 261 and the tip valve 251
upwardly relative to the cup 226, while the inner spring 262 urges
the tip valve 251 downwardly relative to the washer 259. Also,
positioned around the upper end of the tip valve and around the nut
261 is an annular impact button 264, the lower surface of the
button 264 seating on the upper side of the washer 259. As shown in
FIG. 10, the outer diameter of a step 265 of the button 264 is
large enough to catch under the lower corner of the barrel 225 when
the plunger 238 moves upwardly, thereby preventing the tip valve
251 from moving the entire distance upwardly with the plunger 238.
Slots 266 (FIG. 10) are formed in the step 265 to permit fuel flow
therethrough.
Considering the operation of the injector shown in FIGS. 10 to 12,
assume that the plunger 238, which is driven by a cam as in the
first described injector form, is in its uppermost position shown
in FIG. 10. The spring 263 holds the washer 259 and the impact
button 264 upwardly against the lower end of the barrel 225, and
the tip valve 251 is in its uppermost position. It will be noted
that the lower edge of the plunger 238 is above the metering
orifice 232, and consequently, fuel is metered into the injection
chamber 246 formed below the plunger. As previously mentioned, the
amount of fuel metered into the injection chamber 246 varies with
the pressure of the fuel supply connected to the passage 228. The
plunger 238 is forced downwardly by the cam actuating mechanism and
the plunger closes the orifice 232 to end the metering portion of
the injector cycle. When the plunger meets the fuel trapped in the
chamber 246, the fuel is forced downwardly through the flow area
formed by the flats 256 of the tip valve 251, to the sac hole 250,
and out of the spray holes 254.
Injection continues as the plunger 238 moves downwardly and the
lower end of the plunger 238 strikes the upper end of the impact
button 264. The spring 263 is compressed and the tip valve 251 is
moved downwardly toward the seat 253. As in the form of the
injector shown in FIGS. 1 to 7, when the portion 252 is
sufficiently close to the seat 253 that the flow area between the
portion 252 and the seat 253 is less than the flow area of the
holes 254, a hydraulic force develops on the tip valve 251, which
abruptly moves the valve 251 downwardly away from the plunger 238
and against the seat 253. This position is shown in FIG. 11 and it
is at this time that injection is terminated.
Essentially at the same time as the termination of injection, the
lower edge of the reduced diameter portion 241 of the plunger opens
the spill port 242. As the plunger 238 continues to move
downwardly, the hydraulic force on the tip valve holds the tip
valve 251 firmly seated and thus prevents secondary emission, and
continued downward movement of the plunger 238 causes the plunger
to re-engage the impact button 264. The reduced diameter portion
connects the ports 236 and 242 and permits a gradual release of the
pressure within the metering chamber 246, the release being gradual
because of the restricted orifice 248. When the plunger 238 is all
the way down, as shown in FIG. 12, fuel flows from the supply
passage 228, upwardly through the passage 231 and out of the
scavenging port 233, across the upper reduced diameter portion 239
and to drain through the port 237. An overtravel gap 267 opens up
between the nut 261 and the washer 259 at this time. The plunger
238 remains in the downward position until, during the suction
stroke, the plunger rises. The tip valve, however, moves upwardly
only to the position shown in FIG. 10, as previously mentioned.
Thus, the form of the injector shown in FIGS. 10 to 12 is generally
similar in construction and operation to the first described form
of the injector, the two principal differences being, first, that
the plunger 238 moves upwardly completely away from the tip valve
251, and secondly by the arrangement of the spill port.
A third form of the injector is shown in FIG. 13, which is similar
in most respects to the form of the injector shown in FIGS. 10
through 12. It includes an injector barrel 271, a cup 272, a
retainer 273 and an aligning ring 274 which may be provided to
bridge the joint between the cup 272 and the barrel 271 in order to
align these two parts. The fuel supply passages in the barrel 271
include a downwardly extending passage 276, an annular groove 277,
an upwardly extending passage 278, a metering orifice 279, and a
scavenging port 281, similar to the corresponding passages included
in the injector of FIGS. 10 to 12. A drain port 282 is formed in
the barrel 271 across the port 281 and a reduced diameter portion
283 of a plunger 284 connects the ports 281 and 282 when the
plunger is downwardly displaced.
An injection chamber 286 is formed in the cup 272 and in the lower
end of the barrel 271, below the plunger 284, and a tip valve 287
extends upwardly into the chamber 286. Two springs 288 and 289 and
an impact button 291 are connected to the tip valve 287, similar to
the corresponding components in the form of FIGS. 10 to 12. The
outer diameter of the impact button 291 is sized to be held by a
shoulder 292 of the barrel 271 and thus limit the upward movement
of the impact button 291. A spill passage 293 connects the upper
end of the injection chamber 286 with the plunger bore, and the
spill port 294 of the passage 293 is located to be opened by the
lower edge of the reduced diameter portion 283 of the plunger 284
at essentially the same time that the tip valve 287 terminates
injection, similar to the other forms of the injector.
Whereas in the forms of the injector described in FIGS. 1 to 12
flow passages or grooves are formed in the sides of the tip valve,
in the injector form shown in FIG. 13 a flow passage 296 is formed
in the cup 272 to one side of the hole for the tip valve 287. The
shank or central portion 297 of the tip valve 287 has a close
sliding fit in a hole 298 formed in the cup 272. During injection
of fuel, fuel flows from the upper end of the injection chamber
286, through holes 303 in the button 291, downwardly through the
passage 296 to a cavity 299 formed in the cup 272 adjacent the
lower end of the tip valve 287. The cavity 299 is just above a
valve seat 305 for the tip valve 287. When the tip valve 287 is
upwardly displaced, the cavity 299 is in flow communication with a
sac hole 301 and spray holes 302. The parts of the injector form of
FIG. 13, which have not been described in detail, are generally
similar to the corresponding parts of the earlier described
forms.
COnsidering the operation of the injector shown in FIG. 13, assume
that the plunger 284 and the tip valve 287 are upwardly displaced
similar to the position of the injector parts shown in FIG. 10.
Downward movement of the plunger 284 forces fuel downwardly through
the holes 303 in the impact button 291, through the passage 296,
the cavity 299 and out of spray holes 302.
Once again, the flow area of the passage 296 must be larger than
the flow area of the spray holes 302 to prevent a hydraulic lock
from occurring. When the plunger 284 moves downwardly, it strikes
the impact button 291 and moves the tip valve 287 downwardly until
the lower end surface 304 of the tip valve closely approaches the
seat 305. As previously explained, the tip valve 287 is then
abruptly moved downwardly by a hydraulic force to terminate
injection. The remainder of the operation is generally similar to
that of the injector form shown in FIGS. 10 to 12.
The form of the injector shown in FIG. 13 illustrates the fact that
it is not necessary for fuel to flow through passages formed in or
closely adjacent the tip valve for a hydraulic force to develop
which seats the tip valve.
The form of the injector illustrated in FIGS. 14 and 15 is
generally similar to that illustrated in FIGS. 10 to 12, the
principal difference being that the pill port, when opened, spills
the high pressure fuel from the injection chamber into a closed
volume or space, rather than to a drain connection. The injector
shown in FIGS. 14 and 15 includes a barrel 310, a cup 311 and a
retainer 312, these components being generally similar to the
corresponding parts illustrated in FIGS. 10 to 12. A plunger 313 is
reciprocably mounted within a plunger bore 314 formed in the barrel
310, and a tip valve 316 is movably mounted within the cup 311
below the lower end of the plunger 313. A fuel supply passage (not
shown) in the barrel 310 is connected to supply fuel to an annular
passage 317 formed in the upper surface of the cup 311, and a
vertically extending passage 318 is formed in the barrel 310 and
extends upwardly from the passage 317. The passage 318 supplies
fuel to a metering orifice 319 and to a scavenging port 321, both
of which extend from the passage 318 to the plunger bore 314. A
drain passage 322 is formed in the barrel 310 and includes a drain
port 323 in the plunger bore 314 which is generally opposite the
scavenging port 321.
The form of the injector shown in FIGS. 14 and 15 furthre includes
an injection chamber 326 formed in the cup 311 and in the lower end
of the barrel 310 below the plunger 313, the tip valve 316
extending into the injection chamber 326. Outer and inner springs
327 and 328 and an impact button 329 are positioned in the chamber
326 around the upper portion of the tip valve 316. Once again, the
outer diameter of the impact button 329 is large enough to catch
under the lower corner of the barrel 310 to limit the extent of
upward movement of the button 329 and the tip valve 316. As in the
injector form shown in FIG. 13, the form shown in FIGS. 14 and 15
further includes a snap ring 331 fastened to the tip valve 316 and
a washer 332 at approximately midway along its length, and a
transversely enlarged head 333 is formed on the upper end of the
tip valve 316. The impact button 329 is slidable on the tip valve
316 and hooks underneath the head 333. The inner spring 328 is
positioned between the impact button 329 and the washer 332 while
the outer spring 327 is positioned between the impact button 329
and a ledge 330 formed on the cup 311. The lower portion 334 of the
tip valve 316 has flat sides 336 formed thereon, through which fuel
flows during injection as previously explained in connection with
an earlier described form. In the lower end of the cup 311 is
formed a sac hole 337 and spray holes 338.
The barrel 310 further has a spill passage 341 formed therein
extending from the upper end of injection chamber 326 to a spill
port 342 opening to the plunger bore 314. The plunger 313 has a
lower reduced diameter portion 343 formed therein which is located
to open the spill port 342 as the plunger 313 approaches its
maximum downwardly displaced position shown in FIG. 15. The drain
port 323 is located so that it is opened by the reduced diameter
portion 343 when the plunger 313 is upwardly displaced as shown in
FIG. 14. Also, when the plunger 313 is downwardly displaced as
shown in FIG. 15, the scavenging port 321 is placed in flow
communication with the drain port 323 by an upper reduced diameter
portion 344 of the plunger 313. It should be noted from FIG. 15
that the reduced diameter portion 343 is not connected with the
drain port 323 or any other fuel outlet passage when the portion
343 opens the spill port 342.
During operation of the form of the injector shown in FIGS. 14 and
15, when the plunger 313 and the tip valve 316 are in their
upwardly displaced positions, shown in FIG. 14, the lower edge of
the plunger 313 is above the metering orifice 319 and fuel flows
from the supply passage 318 into the injection chamber 326. The
land portion of the plunger 313, which is between the two reduced
diameter portions 343 and 344, closes the scavenging port 321 and
therefore no fuel flows out of this port. The lower reduced
diameter portion 343 is in flow communication with the drain
passage 322, and consequently the portion 343 is filled with fuel
at drain, or atmospheric pressure. The spill port 342 is closed by
the lower end portion of the plunger 313.
As the plunger 313 moves downwardly in an injection stroke, it
closes the feed orifice 319, strikes the fuel in the injection
chamber 326 and forces the fuel downwardly through holes formed in
the impact button 329, through the passages 336 formed in the tip
valve 316, into the sac hole 337 and out of the spray holes 338.
Again, the flow area through the passages 336 must be greater than
the flow area of the spray holes 338. The reduced diameter portion
343 remains filled with fuel at drain pressure during this downward
movement of the plunger 313. The lower end of the plunger 313
strikes the impact button 329 and moves it and the tip valve 316
downwardly until, as previously described, a hydraulic force
develops on the tip valve 316 when the lower end of the tip valve
316 is close to the valve seat formed in the cup 311. The tip valve
316 is moved downwardly by hydraulic force and the impact button
329 moves downwardly away from the lower end of the plunger 313.
The tip valve 316 quickly moves to its seated position to abruptly
terminate injection and, substantially simultaneously, the lower
edge of the reduced portion 343 opens the spill port 342. As the
plunger 313 moves further downwardly, it again strikes the impact
button 329, the spring 327 is compressed and the plunger squeezes
some of the fuel from the injection chamber 326 through the spill
passage 341 and into the reduced diameter portion 343. The fuel in
the portion 343 comes under extremely high pressure of the order of
25,000 psi, and at such pressures the fuel compresses slightly,
thereby absorbing some of the force of the plunger 313 and the cam
actuating mechanism. Such compression of the fuel plus any leakage
of the fuel around the plunger to drain serves to gradually release
the high pressure in the injection chamber 326. This pressure of
course holds the tip valve 316 seated to prevent secondary
injection.
When the plunger 313 subsequently moves upwardly again, it releases
the pressure within the injection chamber 326 to permit the outer
spring 327 to move the impact button 329 and the tip valve 316
upwardly once again to the position shown in FIG. 14. The high
pressure fuel within the reduced diameter portion 343 is then
vented to the drain passage 322 when the plunger 313 reaches the
position shown in FIG. 14 at the start of the next operating
cycle.
The form shown in FIGS. 14 and 15 is advantageous in that there is
no tendency for air bubbles to form in the injection chamber as may
be the case when the injection chamber is vented or spilled to a
low pressure drain connection.
The form of the injector shown in FIG. 16 is generally similar to
the form of the invention shown in FIGS. 10 to 12 but differs in
the arrangement of the spill port and the spill passage. The
injector of FIG. 16 includes a barrel 351, a cup or nozzle 352 and
a retainer 353, similar to the above described forms. A fuel supply
passage 354 formed in the barrel 351 carries fuel to a groove 355
in the cup 352 and to a vertically extending passage 356 in the
barrel 351. A plunger bore 357 is formed in the barrel 351, and a
metering orifice 358 and a scavenging port 359 are formed in the
barrel 351 and connect the passage 356 with the plunger bore 357. A
drain passage 361 formed in the barrel 351 has a drain port 362
generally opposite the scavenging port 359. A plunger 363 is
reciprocably mounted in the bore 357 and includes a reduced
diameter portion 364 which connects the scavenging port 359 with
the drain port 362 when the plunger 363 is downwardly displaced to
the position shown in FIG. 16.
The injector further includes an injection chamber 366 formed in
the cup 352 and in the barrel 351 below the plunger 363. A tip
valve 367, outer and inner springs 368 and 369 and an impact button
371 are mounted around the tip valve 367 within the injection
chamber 366 as previously explained in connection with other forms.
Once again, the outer diameter of the impact button 371 is
sufficiently large that it catches under the lower edge of the
barrel 351 and thus limits the amount of upward movement of the
impact button 371.
A shoulder or ledge 372 is also formed on the cup 352 within the
injection chamber 366 and is sized to be engaged by the impact
button 371 to limit its downward movement. The function is similar
to that of the stop washer 129 (FIG. 2) which is engageable with
the upper end of the adapter 101 to limit the downward movement of
the plunger 127. The construction of the tip valve 367, the flow
passages around it and the spray holes at the lower end of the cup
352 are similar to the corresponding parts of the injector form
shown in FIGS. 14 and 15, and therefore are not described in
detail.
Instead of providing a spill port and passage in the barrel 351 as
in the above described forms of the invention, a spill passage 376
is formed in the plunger 363, which extends from the reduced
diameter portion 364 downwardly and diagonally of the plunger to a
port 377 formed in one side and near the lower end of the plunger
363. The port 377 is located to be opened by being moved downwardly
to the lower edge of the barrel 352, this occurring when the
plunger 363 approaches its lowermost position, shown in FIG. 16.
Once again, the pressure is released gradually when the drain port
377 opens because the size of the drain passage 376 is relatively
small and because the drain port 377 is only slightly and gradually
opened. Passages 370 may be formed through the impact button 371 to
permit flow of fuel therethrough from the lower end of the
injection chamber to the spill passage 376, when the button 371 has
seated on the ledge 372. It will be noted that the flow of fuel
from the scavenging port 359 to the drain port 362 is through the
reduced diameter portion 364 when the plunger 363 is downwardly
displaced, and the fuel spilled through the spill passage 376
simultaneously flows through the reduced diameter portion 364 to
the port 362. The remainder of the construction and operation of
the injector form shown in FIG. 16 is generally similar to the
other described forms of the injector.
In the form of the injector shown in FIGS. 17 through 20, the tip
valve is movably connected to the plunger rather than being mounted
separately from the plunger as in the previously described injector
forms. Consequently, the tip valve of this form follows the line
193a (FIG. 8) rather than the line 193b as in the previously
described forms. This injector form includes an adapter 385, a
barrel 386, a cup 387 and a retainer 388 for holding the parts in
assembled relation, generally similar to the other forms. A fuel
supply passage 389 is formed in the adapter 385, which supplies
fuel to a supply passage 391 (FIG. 18) formed in the barrel 386,
similar to the passages formed in the injector form shown in FIGS.
1 through 7. The lower end of the passage 391 connects with an
annular groove 392 formed in the upper surface of the cup 387, and
this groove 392 carries fuel to another vertically extending supply
passage 393 (FIG. 18) formed in the barrel 386. The passage 393 is
of course angularly displaced from the passage 391. A metering
orifice 394 and a scavenging port 396 connect the passage 393 with
a plunger bore 397 formed in the barrel 386 and in the adapter 385.
With reference to FIGS. 17, 19 and 20, a drain passage 398 is
formed in the barrel 386 and in the adapter 385, and connects the
plunger bore 397 with a drain groove 399 formed in the outer
surface of the adapter 385.
The plunger bore 397 receives a reciprocable plunger 402 having a
reduced diameter portion 403 formed therein which is spaced
upwardly from the lower end of the plunger. At the lower end of the
plunger 402 is attached an upper hook-shaped part 404. The part 404
may be formed integrally with or separately from the plunger. The
part 404 is connected to a similar hook-shaped part 407 on the
upper end of a tip valve 406, the hook parts 404 and 407 being
interconnected to form a lost motion connection. The part 407 may
also be formed integrally with or separately from the tip valve
406. A compression spring 408 is positioned around the two parts
404 and 407, and between the underside of the plunger 402 and the
tip valve 406, and the compression spring 408 normally holds the
tip valve 406 downwardly extended from the lower end of the plunger
402. A washer 409 and a snap ring 411 connect the spring 408 to the
tip valve 406.
The tip valve 406 is slidably mounted in the hole 412 formed in the
cup 387, and a valve portion 413 formed on the lower end of the tip
valve 406 mates with a similarly shaped valve seat 414 formed in
the cup 387 at the lower end of the hole 412. Once again, a sac
hole 416 and spray holes 417 are formed in the lower end of the cup
387. A fuel flow passage is formed through the tip valve 406 by a
longitudinally extending hole 419 formed in the central portion of
the tip valve 406 and a transversely extending hole 421 formed in
the tip valve near its lower end above the valve portion 413. The
passage 419 extends from the transverse hole 421 upwardly through
the hook-shaped portion 407, thus placing the upper portion of an
injection chamber 422 in flow communication with the lower end of
the hole 412.
A spill passage 423 and a spill port 424 are formed in the barrel
386 and connect the injection chamber 422 with the plunger bore 397
at a location where the spill port 424 is opened by the lower edge
of the reduced diameter portion 403 when the plunger 402 approaches
its maximum downwardly displaced position shown in FIG. 20.
Once again, the size of the passage 419 and the hole 421 must be
greater than the size of the spray holes 417 to prevent a hydraulic
lock from forming.
Considering the operation of the injector shown in FIGS. 17 to 20,
assume that the injector plunger 402 and the tip valve 406 are
initially in the upwardly displaced positions illustrated in FIGS.
17 and 18. In this position of the plunger, the scavenging port 396
(FIG. 18) and the port of the drain passage 398 (FIG. 17) are
closed, and the metering orifice 394 is open. Fuel flows through
the passages 389 and 391, groove 392 and passage 393, and out of
the orifice 394 into the injection chamber 422.
During downward movement of the plunger 402, fuel trapped in the
injection chamber 422 flows downwardly through the passage 419
formed in the tip valve 406, out of the hole 421, downwardly to the
sac hole 416 and out of the spray holes 417. The tip valve 406 is
held extended downwardly in the position shown in FIGS. 17 and 18
by the compression spring 408 during this movement.
With reference to FIG. 19, the valve portion 413 of the tip valve
406 engages the valve seat 414 and terminates injection at
substantially the same time that the spill port 424 is opened. When
the valve portion 413 is close to the valve seat 414, a hydraulic
force develops on the tip valve 406 as previously explained and
this force holds the tip valve 406 extended from the plunger and
prevents any possible compression of the spring 408 at this time.
After the valve portion 413 has engaged the seat 414 and terminated
injection, the hydraulic pressure within the injection chamber 422
holds the tip valve 406 seated to prevent secondary injection. The
plunger 402 continues its downward movement after termination of
injection to the maximum downwardly displaced position shown in
FIG. 20, and the spring 408 compresses slightly while the two
hook-shaped parts 404 and 407 move relative to each other to form
an overtravel gap 430 (FIG. 20). The spill port 424 during this
final movement is open and since the sizes of the spill passage 423
and the opening of the spill port are restricted, there is a
gradual release in pressure in the injection chamber 422 as
previously explained.
When the plunger 402 is subsequently retracted, the hook-shaped
part 404 again moves upwardly to engage the other hook-shaped part
407 and lift the tip valve 406 upwardly. The plunger and the tip
valve are then returned to the position illustrated in FIGS. 17 and
18 by the retraction spring for the beginning of a new operating
cycle.
The form of the injector illustrated in FIGS. 21 and 22 is similar
to the form illustrated in FIGS. 17 through 20 in that the tip
valve is attached by a lost motion connection to the lower end of
the plunger. This form differs however in the construction and
attachment of the tip valve with the plunger, and in the
arrangement of the spill port. The injector form of FIGS. 21 and 22
includes a barrel 436, a cup 437, a retainer 438 and a plunger 439.
The plunger 439 is reciprocably mounted in a plunger bore 441
formed in the barrel 436. A fuel supply passage 442 in the barrel
436 supplies fuel to an annular groove 443 in the cup 437, and a
vertically extending passage 444 in the barrel 436 carries fuel to
a metering orifice 446 and to a scavenging port 447. Also formed in
the barrel 436 is a drain passage 448 connected to a drain port 449
and to a spill port 451, the ports 449 and 451 opening into the
plunger bore 441.
An injection chamber 452 is formed in the barrel 436 and in the cup
437 below the plunger 439, and a tip valve 453 is connected by a
lost motion connection to the lower end of the plunger 439, the
lost motion connection comprising an annular groove 454 formed in a
reduced diameter section 455 of the lower end of the plunger 439
and inwardly extending ribs 456 formed on the upper end of the tip
valve 453. The vertical dimension of the groove 454 is greater than
the height of the ribs 456, and therefore the tip valve 453 is able
to move vertically relative to the plunger 439. A compression
spring 457 is positioned around the section 455, between the main
body of the plunger and the tip valve 453, and urges the tip valve
453 downwardly from the plunger.
To fasten the tip valve 453 to the portion 455, a slot may be
formed laterally through the upper end of the tip valve, as by
milling, and the portion 455 of the plunger may be inserted into
the slot from one end thereof. Alternatively, a hole may be formed
in the upper end of the tip valve and the edges of the hole
deformed inwardly to form the ribs 456.
The tip valve 453 includes an upper cylindrical portion 460 and a
conically shaped valve portion 461 which, upon downward movement of
the plunger and the tip valve, engages a complementary valve seat
462 formed in the cup 437. Below the valve seat 462 is formed a sac
hole 463 and spray holes 464.
A spill passage 466 is formed in the lower end portion of the
plunger 439, the lower end of the passage 466 being adjacent the
upper end of the reduced diameter portion 455 and the upper end of
the passage 466 opening into a reduced diameter portion 467 formed
in the plunger 439. The portion 467 is located relative to the
spill port 451 such that the lower edge of the portion 467 slightly
opens the spill port 451 as the plunger 439 approaches its maximum
downwardly displaced position, shown in FIG. 22. The plunger 439
also includes an upper reduced diameter portion 468 which connects
the drain and scavenging ports 449 and 447 when the plunger 339 is
downwardly displaced as shown in FIG. 22. With reference to FIG.
21, it will be noted that the lower edge of the plunger 439 opens
the metering orifice 446 when the plunger 439 is up.
When the plunger 439 is upwardly displaced as shown in FIG. 21,
fuel flows from the metering orifice 446 into the injection chamber
452 and, as in the other forms of the injector, the amount of fuel
flowing into the chamber 462 is a function of the pressure of the
fuel supply. At the end of the fuel metering portion of the
injector cycle, the plunger 439 is moved downwardly and the spring
457 holds the tip valve 453 extending downwardly from the plunger
439. After the plunger 439 has closed the metering orifice 446 and
strikes the fuel in the chamber 452, the fuel is forced downwardly
in the chamber 452 around the outer periphery of the cylindrical
portion 460 of the tip valve 453, to the sac hole 463 and out of
the spray holes 464. Once again, the size of the flow passage
around the periphery of the cylindrical portion 460 must be greater
than the size of spray holes 464. When the valve portion 461 of the
tip valve 453 approaches the seat 462, a hydraulic force develops
as previously explained and this hydraulic force holds the tip
valve 453 extended from the plunger 439 and thus assures that the
tip valve 453 will move rapidly onto the seat 462 in order to
abruptly terminate injection. As the tip valve 453 is seated, the
lower edge of the groove 467 opens the spill port 451. Pressure in
the injection chamber 452 is gradually released as the plunger 439
completes its downward movement. After the plunger 439 has stopped
at the position shown in FIG. 22, the pressure in the injection
chamber 452 continues to be gradually released, the gradual release
being accomplished by the restricted size of the passage 466 and by
the restricted opening of the spill port 451. As in the form of the
injection of the injector shown in FIGS. 17 to 20, an overtravel
gap 465 (FIG. 22) opens up at the connection between the tip valve
453 and the plunger 439. When the plunger 439 subsequently moves
upwardly, it again engages the tip valve 453 and returns it to the
position shown in FIG. 21.
The form of the injector illustrated in FIG. 23 is similar to that
illustrated in FIGS. 21 and 22, the principal difference being that
the fuel is spilled into a closed volume or chamber rather than to
drain. Since most of the structure of the form shown in FIG. 23 is
the same as that of the form of FIGS. 21 and 22, the details of
construction will not be repeated. The form shown in FIG. 23
includes a spill port 470 formed in a barrel 471, the spill port
470 being connected to a chamber 472 formed in the barrel 471. The
chamber 472 is of course similar to the passage 448 shown in FIGS.
21 and 22, but instead of being connected to drain, the upper end
of the chamber 472 is closed by a plug or stop 473. The chamber 472
is filled with fuel during operation, and when the spill port 470
is opened upon downward movement of the plunger 474, fuel is
spilled from the injection chamber into the chamber 472 rather than
to the drain. This portion of the operation of the injector 423 is
of course similar to that shown in FIG. 15 and therefore will not
be described in further detail.
The form of the injector shown in FIG. 24 is also similar to the
form shown in FIGS. 21 and 22 but differs in the manner in which
the tip valve is connected to the lower end of the plunger. The
arrangement shown in FIG. 24 may be advantageously used when the
amount of space within the injector available for the injection
chamber is limited. The form shown in FIG. 24 includes a plunger
481 which is reciprocably mounted in a plunger bore 482 formed in a
barrel 483. A cup 484 is connected to the lower end of the barrel
483 by a retainer 486, and fuel flow passages are formed in the
injector parts similar to the injector form illustrated in FIGS. 21
and 22.
A tip valve 487 is connected to the lower end of the plunger 481 by
two semi-cylindrical sleeves 488 and 489 which, together,
substantially encircle the lower end of the plunger 481 and the
upper end of the tip valve 487. The upper and lower ends of the two
halves 488 and 489 are both turned inwardly and engage annular
grooves 491 and 492 formed in the lower end of the plunger 481 and
in the upper end of the tip valve 487, respectively. The outer
surfaces of the two halves 488 and 489 slidingly engage the inner
wall of the cup 484 and thus are held in assembled relation with
the plunger and the tip valve. A compression spring 493 is
positioned between the plunger 481 and the tip valve 487 in order
to hold the tip valve 487 extended downwardly from the plunger. The
connection of the halves 488 and 489 with the plunger 481 and the
tip valve 487 are lost motion connections and thus permit limited
movement of the tip valve 487 relative to the plunger 381, as
previously explained in connection with the form of the injector
illustrated in FIGS. 21 and 22.
In summary, all of the form of the injector illustrated and
described herein include novel means for abruptly terminating
injection at the optimum time in the injector cycle, and also
include novel means for preventing the occurrence of secondary
injection. The hydraulic force developed on the tip valve, which is
mounted for movement relative to the plunger in each of the
injector forms, assures that the tip valve rapidly moves onto its
valve seat in order to terminate injection. While all of the
injector forms include a spill port, the spill port does not
function to terminate injection but, rather, to relieve pressure
within the injection chamber, while the tip valve performs the
function of terminating injection. Because of this operation, the
injector is able to maintain pressure on the tip valve in order to
prevent secondary injection. Further, the flow of fuel from the
injection chamber through the spill passage is restricted, thus
providing a gradual release in pressure in the injection
chamber.
* * * * *