Information
-
Patent Grant
-
6167869
-
Patent Number
6,167,869
-
Date Filed
Monday, November 3, 199726 years ago
-
Date Issued
Tuesday, January 2, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Marshall, O'Toole, Gerstein, Murray & Borun
-
CPC
-
US Classifications
Field of Search
US
- 123 458
- 123 467
- 123 506
- 123 501
- 123 500
- 137 63015
- 137 628
- 137 63019
- 251 12921
- 251 12908
- 251 12914
-
International Classifications
-
Abstract
A fuel injector includes first and second valves and a solenoid including a solenoid coil and an armature assembly wherein the first and second valves are coupled to the armature assembly. A solenoid drive circuit is coupled to the solenoid coil and delivers a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to operate the first valve without operating the second valve. A second current waveform portion different than the first current waveform portion is applied to the solenoid coil at a second time later than the first time to operate the second valve.
Description
TECHNICAL FIELD
The present invention relates generally to fuel injection apparatus, and more particularly to a fuel injector utilizing a solenoid as a control device.
BACKGROUND ART
Fuel injected engines employ fuel injectors, each of which delivers a metered quantity of fuel to an associated engine cylinder during each engine cycle. Prior fuel injectors were of the mechanically or hydraulically actuated type with either mechanical or hydraulic control of fuel delivery. More recently, electronically controlled fuel injectors have been developed. In the case of an electronic unit injector, fuel is supplied to the injector by a transfer pump. The injector includes a plunger which is movable by a cam-driven rocker arm to compress the fuel delivered by the transfer pump to a high pressure. An electrically operated mechanism either carried outside the injector body or disposed within the injector proper is then actuated to cause the fuel delivery to the associated engine cylinder.
The injector may include a valving mechanism comprising a spill valve and a direct operated check (DOC) valve wherein the former is operated to circulate fuel through the injector for cooling, to control injection pressure and to reduce the back pressure exerted by the injector plunger on the cam following injection. However, the need to separately control two valves leads to the requirement for two separate solenoids to control the valves. Besides adding to the overall cost of the injector, the need for two solenoids undesirably increases component count and undesirably increases the overall size of the injector and/or decreases the space available inside the injector for other components.
SUMMARY OF THE INVENTION
A fuel injector includes a single solenoid which is capable of operating a plurality of moveable elements, such as valves.
More particularly, in accordance with one aspect of the present invention, a fuel injector includes first and second valves, a solenoid including a solenoid coil and an armature assembly wherein the first and second valves are coupled to the armature assembly and a solenoid drive circuit coupled to the solenoid coil. The solenoid drive circuit delivers a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to operate the first valve without operating the second valve. The drive circuit further delivers a second current waveform portion different from the first current waveform portion to the solenoid coil at a second time later than the first time to operate the second valve. Preferably, each of the first and second current waveform portions includes a pull-in current level and a holding current level. Also preferably, the first valve comprises a spill valve, and the second valve may comprise either a two-way valve or a three-way valve which controls fluid pressure delivered to a check.
Still further in accordance with the preferred embodiment, the armature assembly comprises a single armature member coupled to the first and second valves. Also, the armature assembly preferably comprises first and second armature members coupled to the first and second valves, respectively.
Still further in accordance with the preferred embodiment, the first and second valves are biased by first and second springs, respectively, wherein the first and second springs exert first and second biasing forces, respectively.
In accordance with a further aspect of the present invention, a fuel injector includes a solenoid having a single movable armature member and a solenoid coil and a solenoid driver circuit coupled to the solenoid coil. The driver circuit delivers a first current waveform portion to the solenoid coil at a first time to move the armature member to a first position and further delivers a second current waveform portion which may be different than the first current waveform portion to the solenoid coil at a second time later than the first time to move the armature member to a second position different than the first position.
In accordance with yet another aspect of the present invention, a method of controlling a fuel injector having first and second valves and a solenoid including a solenoid coil and an armature assembly wherein the first and second valves are coupled to the armature assembly comprises the steps of delivering a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to close the first valve without closing the second valve and delivering a second current waveform portion which may be different from the first current waveform portion to the solenoid coil at a second time later than the first time to cause the armature assembly to close the second valve.
In accordance with a still further aspect of the present invention, a method of controlling a fuel injector having first and second moveable armatures controlled by a solenoid coil comprises the steps of delivering a first current waveform portion to the solenoid coil at a first time to move the first armature without substantially moving the second armature and delivering a second current waveform portion different than the first current waveform portion to the solenoid coil at a second time later than the first time to move the second armature.
The present invention utilizes a single solenoid to control a plurality of movable elements, leading to a desirable decrease in component count as well as other possible advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an elevational view of a fuel injector incorporating the present invention together with a cam shaft and rocker arm and further illustrating a block diagram of a transfer pump and a drive circuit for controlling the fuel injector;
FIG. 2
is a sectional view of the fuel injector of FIG.
FIG. 3
is an enlarged, fragmentary sectional view of the fuel injector of
FIG. 2
illustrating the solenoid, high pressure spill valve and DOC valve in greater detail;
FIG. 4
is a waveform diagram illustrating current waveforms supplied to the solenoid coil of
FIGS. 2 and 3
; and
FIG. 5
is a fragmentary sectional view of an alternative fuel injector incorporating the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to
FIG. 1
, a portion of a fuel system
10
is shown adapted for a direct-injection diesel-cycle reciprocating internal combustion engine. However, it should be understood that the present invention is also applicable to other types of engines, such as rotary engines or modifiedcycle engines, and that the engine may contain one or more engine combustion chambers or cylinders. The engine has at least one cylinder head wherein each cylinder head defines one or more separate injector bores, each of which receives an injector
20
according to the present invention.
The fuel system
10
further includes apparatus
22
for supplying fuel to each injector
20
, apparatus
24
for causing each injector
20
to pressurize fuel and apparatus
26
for electronically controlling each injector
20
.
The fuel supplying apparatus
22
preferably includes a fuel tank
28
, a fuel supply passage
30
arranged in fluid communication between the fuel tank and the injector
20
, a relatively low pressure fuel transfer pump
32
, one or more fuel filters
34
and a fuel drain passage
36
arranged in fluid communication between the injector
20
and the fuel tank
28
. If desired, fuel passages may be disposed in the head of the engine in fluid communication with the fuel injector
20
and one or both of the passages
30
and
36
.
The apparatus
24
may be any mechanically actuated device or hydraulically actuated device. In the embodiment shown a tappet and plunger assembly
50
associated with the injector
20
is mechanically actuated indirectly or directly by a cam lobe
52
of an engine-driven cam shaft
54
. In the embodiment shown, the cam lobe
52
drives a pivoting rocker arm assembly
64
which in turn reciprocates the tappet and plunger assembly
50
. Alternatively, a push rod (not shown) may be positioned between the cam lobe
52
and the rocker arm assembly
64
.
The electronic controlling apparatus
26
preferably includes an electronic control module (ECM)
66
which controls: (1) fuel injection timing; (2) total fuel injection quantity during an injection cycle; (3) fuel injection pressure; (4) the number of separate injection segments during each injection cycle; (5) the time interval(s) between the injection segments; and (6) the fuel quantity delivered during each injection segment of each injection cycle.
Preferably, each injector
20
is a unit injector which includes in a single housing apparatus for both pressurizing fuel to a high level (for example, 207 MPa (30,000 p.s.i.)) and injecting the pressurized fuel into an associated cylinder. Although shown as a unitized injector
20
, the injector could alternatively be of a modular construction wherein the fuel injection apparatus is separate from the fuel pressurization apparatus.
Referring now to
FIGS. 2 and 3
, the injector
20
includes a housing
74
, a nozzle portion
76
, an electrical actuator
78
, a high pressure spill valve
80
, a spill valve spring
81
, a plunger
82
disposed in a plunger cavity
83
, a check
84
, a check spring
86
, a two-way direct operated check (DOC) valve
88
and a DOC spring
90
. In the preferred embodiment, the spill valve spring
81
exerts a first spring force when compressed whereas the DOC spring
90
exerts a second spring force greater than the first spring force when compressed.
The electrical actuator
78
comprises a solenoid
100
having a stator
102
and an armature assembly in the form of a single armature
104
. A bolt
106
and a washer
108
bear against a cylindrical member
110
which in turn bear against the armature
104
. The bolt
106
further extends through a pair of additional washers
112
,
114
into a threaded bore
116
in a valve stem or poppet
118
of the DOC valve
88
. (The washer
114
also surrounds the poppet
118
.)
The DOC spring
90
is placed in compression between a surface
120
of the armature
104
and a DOC spring preload spacer
122
which abuts the washer
108
. A cylindrical spill valve spacer
126
is disposed between the spacer
122
and a shouldered portion
128
of the spill valve
80
. The DOC spring preload spacer
122
is axially slidable over the cylindrical member
110
, for reasons explained hereinafter.
Prior to the time that injection is to occur, a solenoid coil
130
disposed in the solenoid stator
102
and coupled to a drive circuit
131
is unenergized. Accordingly, the armature
104
is not attracted to the solenoid stator
102
, thereby permitting the spill valve spring
81
to open the spill valve
80
. Fuel circulates from the transfer pump and the fuel supply passage
30
into internal passages (not shown) of the fuel injector
20
which connect with a space
146
below the shouldered portion
128
. The fuel passes through the open spill valve
80
into a space
150
above the spill valve
80
and thence through one or more further passages (not shown) to the plunger cavity
83
. When the plunger
82
is in the full upward position, passages (also not shown) in the plunger
82
conduct the fuel to an annular recess
148
surrounding the plunger
82
, which is in turn coupled in fluid communication with the drain passage
36
. The fuel thus recirculates through the injector
20
during non-injection portions of each engine cycle for the purpose of cooling and to fill the plunger chamber.
Also at this time, the DOC valve poppet
118
is disposed in an open position at which a sealing surface
140
of the valve poppet
118
is spaced from a valve seat
142
defined by a DOC body
144
.
Industrial Applicability
FIG. 4
illustrates a current waveform
170
applied by the drive circuit
131
to the solenoid coil
130
during a portion of an injection sequence to accomplish fuel injection. The current waveform includes a first current waveform portion
172
extending between times t=t
0
, and t=t
5
and a second current waveform portion
174
occurring subsequent to the time t=t
5
. Between time t=t
0
and time t=t
2
, a first pull-in current is provided to the solenoid coil
130
to move the armature
104
a first distance toward the solenoid stator
102
. A first holding current at somewhat reduced levels is thereafter applied between times t=t
2
and t=t
5
. The magnitudes of the first pull-in current and the first holding current are selected so that the magnetic forces developed thereby on the armature
104
exceed the first spring force exerted by the spill valve spring
81
but are less than the second spring force exerted by the DOC valve spring
90
. The motive force developed by the armature
104
is transmitted through the DOC spring
90
, the DOC spring preload spacer
122
and the spill valve spacer
126
to close the spill valve
80
. Movement of the spill valve
80
is damped by fluid flowing through a damping orifice
175
. The force developed by the armature
104
during this interval is insufficient to substantially compress the DOC spring
90
. Further during this interval, the valve poppet
118
moves upwardly with the armature
104
; however, the amount of this travel from the fully opened position of the valve poppet
118
is insufficient to cause the sealing surface
140
to contact the seat
142
, and hence the DOC valve
88
remains open.
Subsequently, fuel is pressurized by downward movement of the plunger
82
in the plunger cavity
83
. The pressurized fuel is conducted through a high pressure fuel passage
152
and a cross passage
154
past the sealing surface
140
and the seat
142
to an upper surface
156
of a DOC piston
158
. The DOC piston
158
in turn bears against a spacer
160
which abuts a top end of the check
84
. The fuel passage
152
further conducts pressurized fluid to a check passage
162
. Accordingly, the fluid pressures across the check
84
are substantially balanced and hence the spring
86
moves the check to the closed position such that a check tip
164
bears against a seat
166
of a tip member
168
.
Thereafter, subsequent to the time t
5
, the second current waveform portion
174
is applied to the solenoid coil
130
. Following a second pull-in current magnitude, a second holding current is supplied to the coil
130
. The second pull-in current and the second holding current in general may be greater in magnitude than the first pull-in current and the first holding current, respectively. In response to application of this current waveform portion, the armature
104
moves the valve poppet
118
against the force of the DOC spring
90
, thereby causing the sealing surface
140
to contact the seat
142
. During such movement, the cylindrical member
110
moves axially upward within the DOC spring preload spacer
122
so that an overtravel characteristic is obtained. Fluid captured in the space above the upper surface
156
of the DOC piston
158
bleeds via a controlled leakage path between a head portion
176
of the valve poppet
118
and a wall
178
of the DOC piston
158
and through a passage (not shown) extending through the side walls of the DOC piston
158
to drain. A low fluid pressure zone is thereby established above the DOC piston
158
thereby causing the check
84
to move upwardly and initiate fuel injection. It should be noted that this controlled leakage path is sufficiently small to maintain a high fluid pressure condition when the DOC valve
88
is open but is large enough to quickly bleed off the high pressure fluid when the DOC valve
88
is closed.
When injection is to be terminated, the current supplied to the solenoid
130
may be reduced to the holding level of the current waveform
172
as illustrated in FIG.
4
. If desired, the current delivered to the solenoid coil
130
may instead be reduced to zero or any other level less than the first holding level. In any case, the magnetic attractive force on the armature
104
is thus reduced, permitting the DOC spring
90
initially to move the valve poppet
118
downwardly to the open position whereby fluid communication is again established between the fuel passage
152
and the space above the upper surface
156
of the DOC piston
158
. The application of high fuel pressure to the top of the DOC piston
158
and the force exerted by the spring
86
cause the check
84
to move downwardly such that the check tip
164
engages the seat
166
, thereby preventing further fuel injection. Subsequently, the current supplied to the solenoid coil
130
may be reduced to zero or any other level less than the first holding level (if it has not already been so reduced). Regardless of whether the applied current level is immediately dropped to the first holding level or to a level less than the first holding level, the spill valve spring
81
opens the spill valve
80
after the DOC spring
90
moves the valve poppet
118
downwardly. Fuel then circulates through the spill valve
80
, the spaces
146
and
150
, the plunger cavity
83
, the passages in the plunger
82
and the annular recess
148
to drain for cooling purposes as described above.
Still further, multiple or split injections per injection cycle can be accomplished by supplying suitable waveform portions to the solenoid coil
130
. For example, the first and second waveform portions
172
,
174
may be supplied to the coil
130
to accomplish a pilot or first injection. Immediately thereafter, the current may be reduced to the first holding current level and then increased again to the second pull-in and second holding levels to accomplish a second or main injection. Alternatively, the pilot and main injections may be accomplished by initially applying the waveform portions
172
and
174
to the solenoid coil
130
and then repeating application of the portions
172
and
174
to the coil
130
. The durations of the pilot and main injections (and hence, the quantity of fuel delivered during each injection) are determined by the durations of the second holding levels in the waveform portions
174
. Of course, the waveform shapes shown in
FIG. 4
may be otherwise varied as necessary or desirable to obtain a suitable injection response or other characteristic.
As should be evident from the foregoing, the drive circuit
131
is capable of moving the armature
104
to first and second positions as a result of the application of first and second waveform portions, respectively, to the solenoid coil
130
. Movement to the first position closes the spill valve
80
whereas movement to the second position closes the DOC valve
88
. Because only a single solenoid is needed to operate the two valves
80
,
88
, as opposed to two solenoids to accomplish this function, size and weight can be reduced.
While the present invention can be utilized in connection with a solenoid having a single armature, it should be noted that a solenoid having more than one armature may alternatively be used. For example,
FIG. 5
illustrates a portion of a fuel injector
200
having a first valve
202
, a second, three-way valve
204
and a solenoid
206
for controlling the first and second valves
202
,
204
. The solenoid
206
includes a stator
208
having a recess
210
within which is disposed a solenoid coil
212
. The solenoid
206
further includes an armature assembly comprising first and second annular armatures
214
,
216
, respectively, which are disposed on either side of an annular central spacer member fabricated of nonmagnetic (i.e., high reluctance) material
218
. The central spacer member
218
is secured to a cylindrical outboard flux conduction member
220
which is molded into a coil bobbin
221
retained within the stator
208
. The first and second armatures
214
,
216
surround a central tube
222
, as do the first and second valves
202
,
204
and the central spacer member
218
.
As in the previous embodiment, the solenoid coil
212
receives the current waveform portions
172
,
174
of
FIG. 4
from a drive circuit
224
.
Initially during an injection sequence, the solenoid coil
212
is unenergized, thereby permitting a first valve spring
226
(which exerts a first spring force) to open the first valve
202
such that a sealing surface
228
is spaced from a valve seat
230
. Also at this time, a second valve spring
232
(which exerts a second spring force greater than the first spring force) moves the second valve
204
upwardly to a position whereby a sealing surface
234
is spaced from a valve seat
236
and such that a further sealing surface
238
is in sealing contact with a further valve seat
240
. Under these conditions, fuel flowing through a passage
242
enters a space
243
and thereafter flows to drain through a further passage (not shown). Subsequently, the lobe on the cam pushes down on a plunger (not shown) of the injector
200
and pressurizes the fuel in the passage
242
, thereby effectively metering the amount of fuel in the injector. The current waveform portion
172
is then delivered to the solenoid coil
212
by the drive circuit
224
. The pull-in and holding current levels of the portion
172
and the first and second valve springs
226
,
232
are selected such that the motive force developed by the first armature
214
exceeds the first spring force but the motive force developed by the second armature
216
is less than the second spring force. Consequently the first armature
214
moves upwardly against a spacer
241
and closes the first valve
202
. At this point, the sealing surface
228
is moved into sealing contact with the seat
230
, thereby shutting off the path to drain for the fluid in the passage
242
. Also during this time, because the second valve spring
232
exerts a greater spring force than the force developed by the second armature
216
, the second valve
204
remains open in the previously described condition. Pressurized fluid is thereby delivered to first and second check end passages
244
,
246
leading to bottom and top ends of a check assembly (not shown). Because the fluid pressures on the ends of the check assembly are substantially balanced, the check remains closed at this time.
The drive circuit
224
thereafter delivers the second current waveform portion
174
to the solenoid coil
212
. This increased current level develops an increased force on the second armature
216
which exceeds the second spring force, causing such armature to move downwardly. This downward movement is transmitted by a spacer
248
to the valve
204
to cause the valve
204
also to move downwardly such that the sealing surface
234
is moved into sealing contact with the valve seat
236
. In addition, the sealing surface
238
moves out of sealing contact with the further valve seat
240
. The effect of this movement is to isolate the second check end passage
246
from the high pressure fluid in the passage
242
and to permit fluid communication between the second check end passage
246
and a drain passage
250
. The pressures across the check assembly then become unbalanced, thereby overcoming the check spring force and driving the check upwardly and permitting fuel to be injected into an associated cylinder.
When injection is to be terminated, the current delivered to the solenoid coil
212
is reduced to the holding level of the first current waveform portion
172
as illustrated in
FIG. 4
to move the second valve
204
upwardly, thereby reconnecting the second check end passage
246
to the passage
242
. The fluid pressures across the check thus become balanced, thereby allowing a check spring and fluid forces to close the check. The current may then be reduced to zero, allowing the first valve spring
226
to open the first valve
202
.
If desired, the solenoid coil may receive more than two current waveform portions to cause either a single armature or multiple armatures to move to any number of positions (not just two), and thereby operate one or more valves or other movable elements. Split or multiple injections can be obtained by application of proper current waveforms, as explained in connection with the previous embodiment.
Numerous modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.
Claims
- 1. A fuel injector, comprising:first and second valves; a solenoid including a solenoid coil and an armature assembly having an aperture extending fully therethrough, wherein the armature assembly is disposed between the first and second valves and wherein a portion of one of the first and second valves passes through the aperture and is coupled to the armature assembly; and a solenoid drive circuit coupled to the solenoid coil and delivering a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to operate the first valve without operating the second valve and delivering a second current waveform portion different than the first current waveform portion to the solenoid coil at a second time later than the first time to operate the second valve.
- 2. The fuel injector of claim 1, wherein each of the first and second current waveform portions includes a pull-in current level and a holding current level.
- 3. The fuel injector of claim 1, wherein the first valve comprises a spill valve.
- 4. The fuel injector of claim 1, further including a check which is movable to an open position and wherein the second valve comprises a two-way valve which controls fluid pressure delivered to the check.
- 5. The fuel injector of claim 1, further including a check which is movable to an open position and wherein the second valve comprises a three-way valve which controls fluid pressure delivered to the check.
- 6. The fuel injector of claim 1, wherein the armature assembly comprises a single armature member coupled to the first and second valves.
- 7. The fuel injector of claim 1, wherein the armature assembly comprises first and second armature members coupled to the first and second valves, respectively.
- 8. The fuel injector of claim 1, wherein the first and second valves are biased by first and second springs, respectively, and wherein the first and second springs exert first and second biasing forces, respectively.
- 9. A fuel injector having first and second valves, comprising:a solenoid including a movable armature member having an aperture extending fully therethrough and a solenoid coil, wherein the movable armature member is disposed between the first and second valves so that a portion of one of the first and second valves passes through the aperture; and a solenoid driver circuit coupled to the solenoid coil and delivering a first current waveform portion to the solenoid coil at a first time to move the armature member to a first position and delivering a second current waveform portion different than the first current waveform portion to the solenoid coil at a second time later than the first time to move the armature member to a second position different than the first position.
- 10. The fuel injector of claim 9, wherein each of the first and second current waveform portions includes a pull-in current level and a holding current level.
- 11. The fuel injector of claim 10, further including a check which is movable to an open position and wherein the second valve comprises a two-way valve which controls fluid pressure delivered to the check.
- 12. The fuel injector of claim 11, further including a spill valve and a two-way valve coupled to the armature member.
- 13. The fuel injector of claim 9, further including a spill valve and a three-way valve coupled to the armature member.
- 14. The fuel injector of claim 13, wherein the spill valve and the three-way valve are biased by first and second springs, respectively, and wherein the first and second springs exert first and second biasing forces, respectively.
- 15. A method of controlling a fuel injector having first and second valves and a solenoid including a solenoid coil and an armature assembly having an aperture extending fully therethrouqh, wherein the armature assembly is disposed between the first and second valves and wherein a portion of one of the first and second valves [are] passes through the aperture and is coupled to the armature assembly, the method comprising the steps of:delivering a first current waveform portion to the solenoid coil at a first time to cause the armature assembly to close the first valve without closing the second valve; and delivering a second current waveform portion different than the first current waveform portion to the solenoid coil at a second time later than the first time to cause the armature assembly to close the second valve.
- 16. The method of claim 15, wherein each step of delivering comprises the step of providing a pull-in current and a holding current to the solenoid coil.
- 17. The method of claim 15, wherein the first valve comprises a spill valve.
- 18. The method of claim 15, wherein the fuel injector includes a check which is movable to an open position and wherein the second valve comprises a two-way valve which controls fluid pressure delivered to the check.
- 19. The method of claim 15, wherein the fuel injector includes a check which is movable to an open position and wherein the second valve comprises a three-way valve which controls fluid pressure delivered to the check.
- 20. The method of claim 15, wherein the armature assembly comprises a single armature member coupled to the first and second valves.
- 21. The method of claim 15, wherein the armature assembly comprises first and second armature members coupled to the first and second valves, respectively.
- 22. The method of claim 15, wherein the first and second valves are biased by first and second springs, respectively, and wherein the first and second springs exert first and second biasing forces, respectively.
- 23. A method of controlling a fuel injector having first and second valves and first and second movable armatures controlled by a solenoid coil and disposed between the first and second valves so that a portion of one of the first and second valves passes through an aperture that extends fully through one of the movable armatures, the method comprising the steps of:delivering a first current waveform portion to the solenoid coil at a first time to move the first armature without substantially moving the second armature; and delivering a second current waveform portion different than the first current waveform portion to the solenoid coil at a second time later than the first time to move the second armature.
- 24. The method of claim 23, wherein the step of delivering comprises the step of providing a pull-in current and a holding current to the solenoid coil.
- 25. The method of claim 24, wherein the first armature is coupled to a spill valve.
- 26. The method of claim 25, wherein the fuel injector includes a check which is movable to an open position and wherein the second armature is coupled to a two-way valve which controls fluid pressure delivered to the check.
- 27. The method of claim 26, wherein the spill valve and the two-way valve are biased by first and second springs, respectively, and wherein the first and second springs exert first and second biasing forces, respectively.
- 28. The method of claim 25, wherein the fuel injector includes a check which is movable to an open position and wherein the second armature is coupled to a three-way valve which controls fluid pressure delivered to the check.
- 29. The method of claim 28, wherein the spill valve and the three-way valve are biased by first and second springs, respectively, and wherein the first and second springs exert first and second biasing forces, respectively.
US Referenced Citations (22)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1102329 |
Feb 1968 |
GB |