U.S. patent application number 09/731462 was filed with the patent office on 2002-06-13 for pump system with high pressure restriction.
This patent application is currently assigned to Diesel Technology Company. Invention is credited to Spoolstra, Gregg R., Straub, Robert D..
Application Number | 20020071768 09/731462 |
Document ID | / |
Family ID | 24939604 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020071768 |
Kind Code |
A1 |
Spoolstra, Gregg R. ; et
al. |
June 13, 2002 |
Pump system with high pressure restriction
Abstract
A pumping system for a fuel injection system includes a body
defining a high pressure pumping chamber, a plunger, a high
pressure outlet, a high pressure fluid line connecting the pumping
chamber to the outlet, a control valve along the fluid line, and a
valve and restriction arrangement along the fluid line. The valve
and restriction arrangement includes a restriction and a valve
body. The valve body is movable between an open position in which
fuel flow from the pumping chamber is generally unrestricted by the
restriction and a closed position in which fuel flow from the
pumping chamber is significantly restricted by the restriction to
store energy in the pumping chamber. Advantageously, the high
pressure restriction concept may be utilized in a pumping system
for various types of rate shaping, including boot injection and
square injection, in addition to pilot operation and post injection
operations, and others.
Inventors: |
Spoolstra, Gregg R.; (Byron
Center, MI) ; Straub, Robert D.; (Lowell,
MI) |
Correspondence
Address: |
Jeremy J. Curcuri
Brooks & Kushman P.C.
1000 Town Center
Twenty-Second Floor
Southfield
MI
48075
US
|
Assignee: |
Diesel Technology Company
4300 44th Street, S.E.
Kentwood
MI
888653
|
Family ID: |
24939604 |
Appl. No.: |
09/731462 |
Filed: |
December 7, 2000 |
Current U.S.
Class: |
417/53 ;
417/307 |
Current CPC
Class: |
F02M 45/06 20130101;
F02M 59/366 20130101; F02M 63/0007 20130101; F02M 55/02 20130101;
F02M 45/12 20130101; F02M 57/023 20130101; F02M 59/34 20130101 |
Class at
Publication: |
417/53 ;
417/307 |
International
Class: |
F04B 049/00 |
Claims
What is claimed is:
1. A pump system for a fuel injection system, the pump system
comprising: a body defining a high pressure pumping chamber; a
plunger disposed in the pumping chamber for pressurizing fuel; a
high pressure outlet; a high pressure fluid line connecting the
pumping chamber to the outlet; a control valve along the fluid
line, the control valve including a first valve body movable
between a closed position in which pressurized fuel is routed from
the pumping chamber to the outlet and an open position in which
pressure relief is provided to the fluid line; and a valve and
restriction arrangement along the fluid line, including a
restriction and a second valve body, the second valve body being
movable between an open position in which fuel flow from the
pumping chamber is generally unrestricted by the restriction and a
closed position in which fuel flow from the pumping chamber is
significantly restricted by the restriction to store energy in the
pumping chamber.
2. The system of claim 1 wherein the body is a unit pump body, and
the high pressure outlet is configured for flow communication with
a fuel injector.
3. The system of claim 1 wherein the body is a unit injector body
and defines a needle chamber, the pump further comprising: an
injector nozzle assembly in flow communication with the high
pressure outlet, the assembly including a needle received in the
needle chamber, the needle chamber receiving pressurized fuel from
the pump outlet.
4. The system of claim 1 wherein the second valve body configured
as a pressure-balanced valve.
5. The system of claim 4 wherein the second valve body open
position provides a flow cross-sectional area, not including any
effective flow cross-sectional area of the restriction, of about
two to three millimeters squared.
6. The system of claim 1 wherein the second valve body is
configured as a pressure-balanced valve utilizing a through passage
as the restriction.
7. The system of claim 1 wherein the valve and restriction
arrangement is located between the pumping chamber and the control
valve.
8. The system of claim 1 wherein the valve and restriction
arrangement is located between the control valve and the
outlet.
9. A method of controlling a pump system for a fuel injection
system, the pump system having a body defining a high pressure
pumping chamber, a plunger disposed in the pumping chamber for
pressurizing fuel, a high pressure outlet, a high pressure fluid
line connecting the pumping chamber to the outlet, and a control
valve along the fluid line, the control valve including a first
valve body movable between a closed position in which pressurized
fuel is routed from the pumping chamber to the outlet and an open
position in which pressure relief is provided to the fluid line,
the method comprising: controlling a valve and restriction
arrangement along the fluid line, including a restriction and a
second valve body, the second valve body being movable between an
open position in which fuel flow from the pumping chamber is
generally unrestricted by the restriction and a closed position in
which fuel flow from the pumping chamber is significantly
restricted by the restriction to store energy in the pumping
chamber, the valve and restriction arrangement being controlled so
as to control fuel flow from the pumping chamber to the outlet.
10. The method of claim 9 further comprising: closing the control
valve for an injection by moving the first valve body to the closed
position; and restricting fuel flow from the pumping chamber by
moving the second valve body to the closed position to reduce an
injection rate, while the control valve is closed.
11. The method of claim 9 further comprising: closing the control
valve for an injection by moving the first valve body to the closed
position; restricting fuel flow from the pumping chamber by moving
the second valve body to the closed position to reduce an injection
rate, while the control valve is closed; and thereafter, opening
the control valve by moving the first valve body to the open
position.
12. The method of claim 9 further comprising: closing the control
valve for an injection by moving the first valve body to the closed
position; restricting fuel flow from the pumping chamber by moving
the second valve body to the closed position to reduce an injection
rate and store energy in the pumping chamber, while the control
valve is closed; unrestricting fuel flow from the pumping chamber
by moving the second valve body to the open position to increase
the injection rate, while the control valve is closed; and
thereafter, opening the control valve by moving the first valve
body to the open position.
13. The method of claim 9 wherein the valve restriction arrangement
is located between the pumping chamber and the control valve and
wherein the method further comprises: opening the control valve by
moving the first valve body to the open position; restricting fuel
flow from the pumping chamber by moving the second valve body to
the closed position to store energy in the pumping chamber, while
the control valve is open; thereafter, closing the control valve by
moving the first valve body to the closed position; and
unrestricting fuel flow from the pumping chamber by moving the
second valve body to the open position to increase the injection
rate, while the control valve is closed.
14. The method of claim 9 wherein the valve restriction arrangement
is located between the pumping chamber and the control valve and
wherein the method further comprises: closing the control valve by
moving the first valve body to the closed position; unrestricting
fuel flow from the pumping chamber by moving the second valve body
to the open position, while the control valve is closed; and
thereafter, opening the control valve by moving the first valve
body to the open position; and restricting fuel flow from the
pumping chamber by moving the second valve body to the closed
position to reduce pressure release at the plunger, while the
control valve is open.
15. The method of claim 14 further comprising: thereafter, closing
the control valve by moving the first valve body to the closed
position.
16. The method of claim 15 further comprising: thereafter,
unrestricting fuel flow from the pumping chamber by moving the
second valve body to the open position to increase an injection
rate, while the control valve is closed.
Description
TECHNICAL FIELD
[0001] This invention relates to pump systems for fuel injection
systems.
BACKGROUND ART
[0002] Engine exhaust emission regulations are becoming
increasingly restrictive. One way to meet emission standards is to
precisely control the quantity and timing of the fuel injected into
the combustion chamber to match the engine cycle. For certain
engine operating conditions, effective injection rate shaping may
result in reduced levels of particulates and oxides of nitrogen in
the engine exhaust. One form of effective rate shaping injects fuel
slower during the early phase of the combustion process, resulting
in less engine noise.
[0003] Existing rate shaping techniques attempt to control
injection rates by making various modifications to the injector
nozzle assembly. Although these existing rate shaping techniques
have been employed in many applications that have been commercially
successful, there is a need for a rate shaping technique that
allows more precise rate shaping than the existing modified
injector nozzle assemblies.
DISCLOSURE OF INVENTION
[0004] It is, therefore, an object of the present invention to
provide a pump system utilizing a high pressure restriction to
precisely control quantity and timing of fuel injected into the
combustion chamber of an internal combustion engine.
[0005] In carrying out the above object, a pump system for a fuel
injection system is provided. The pump system comprises a body
defining a high pressure pumping chamber, a plunger disposed in the
pumping chamber for pressurizing fuel, a high pressure outlet, and
a high pressure fluid line connecting the pumping chamber to the
outlet. The system further comprises a control valve along the
fluid line, and a valve and restriction arrangement along the fluid
line. The control valve includes a first valve body movable between
a closed position and an open position. In the closed position,
pressurized fuel is routed from the pumping chamber to the outlet.
In the open position, pressure relief is provided to the fluid
line. The valve and restriction arrangement includes a restriction
and a second valve body. The second valve body is movable between
an open position and a closed position. In the open position, fuel
flow from the pumping chamber is generally unrestricted by the
restriction. In the closed position, fuel flow from the pumping
chamber is significantly restricted by the restriction to store
energy in the pumping chamber.
[0006] The pump system of the present invention advantageously
utilizes a high pressure restriction to affect control over the
quantity and timing of the fuel injected into the combustion
chamber. In one embodiment, the body is a unit pump body, and the
high pressure outlet is configured for flow communication with a
fuel injector. In another embodiment, the body is a unit injector
body and defines a needle chamber. An injector nozzle assembly is
in flow communication with the high pressure outlet. The injector
nozzle assembly includes a needle received in the needle chamber.
The needle chamber receives pressurized fuel from the pump outlet.
That is, embodiments of the present invention are suitable for use
in both unit pumps and unit injectors.
[0007] In some embodiments, the second valve body is configured as
a pressure-balance valve. In a particular application, the second
valve body open position provides a flow cross-sectional area, not
including any effective flow cross-sectional area of the
restriction, of about two to three millimeters squared. In some
embodiments, the second valve body is configured as a
pressure-balanced spool valve, and utilizes a through passage as
the restriction.
[0008] Depending on the particular type of control over fuel
injection quantity and timing that is desired, the valve and
restriction arrangement may be located between the pumping chamber
and the control valve, or alternatively, the valve and restriction
arrangement may be located between the control valve and the
outlet. For example, a valve and restriction arrangement of the
present invention between the pumping chamber and the control valve
allows effective control for pilot injection, boot injection,
square injection, and post injection. On the other hand, a valve
and restriction arrangement located between the control valve and
the outlet allows effective control over pilot operations and boot
injection.
[0009] Further, in carrying out the present invention, a method of
controlling a pump system for a fuel injection system is provided.
The pump system has a body defining a high pressure pumping
chamber, a plunger disposed in the pumping chamber for pressurizing
fuel, a high pressure outlet, and a high pressure fluid line
connecting the pumping chamber to the outlet. A control valve along
the fluid line includes a first valve body movable between a closed
position and an open position. In the closed position, pressurized
fuel is routed from the pumping chamber to the outlet. In the open
position, pressure relief is provided to the fluid line. The method
comprises controlling a valve and restriction arrangement along the
fluid line. The valve and restriction arrangement includes a
restriction and a second valve body. The second valve body is
movable between an open position and a closed position. In the open
position, fuel flow from the pumping chamber is generally
unrestricted by the restriction. In the closed position, fuel flow
from the pumping chamber is significantly restricted by the
restriction to store energy in the pumping chamber. The valve and
restriction arrangement is controlled so as to control fuel flow
from the pumping chamber to the outlet.
[0010] Advantageously, the method may be utilized to affect various
types of control over the quantity and timing of the fuel injected
into the combustion chamber. In an embodiment of the invention that
reduces the rate of injection, the method further comprises closing
the control valve for an injection by moving the first valve body
to the closed position, and restricting fuel flow from the pumping
chamber by moving the second valve body to the closed position to
reduce an injection rate, while the control valve is closed. For a
pilot injection, the method further comprises closing the control
valve, restricting fuel flow from the pumping chamber while the
control valve is closed, and thereafter, opening the control valve
by moving the first valve body to the open position, ending the
reduced rate pilot injection.
[0011] In a boot injection, the method further comprises closing
the control valve for injection by moving the first valve body to
the closed position, and restricting fuel flow from the pumping
chamber by moving the second valve body to the closed position to
reduce an injection rate and store energy in the pumping chamber,
while the control valve is closed. Further, for a boot injection,
the method further comprises unrestricting fuel flow from the
pumping chamber by moving the second valve body to the open
position to increase the injection rate, while the control valve is
closed, and thereafter, opening the control valve by moving the
first valve body to the open position, ending the boot
injection.
[0012] For square injection, the valve and restriction arrangement
is located between the pumping chamber and the control valve, and
the method further comprises opening the control valve by moving
the first valve body to the open position, restricting fuel flow
from the pumping chamber by moving the second valve body to the
closed position to store energy in the pumping chamber, while the
control valve is open. The method further comprises, thereafter,
closing the control valve by moving the first valve body to the
closed position, and unrestricting fuel flow from the pumping
chamber by moving the second valve body to the open position to
increase the injection rate, while the control valve is closed.
[0013] For reducing plunger noise, the valve and restriction
arrangement is located between the pumping chamber and the control
valve and the method further comprises closing the control valve by
moving the first valve to the closed position, and unrestricting
fuel flow from the pumping chamber by moving the second valve body
to the open position, while the control valve is closed. The method
further comprises, thereafter, opening the control valve by moving
the first valve body to the open position, and restricting fuel
flow from the pumping chamber by moving the second valve body to
the closed position to reduce pressure release at the plunger,
while the control valve is open.
[0014] For post injection, in addition to reducing the rate of
pressure release at the plunger, the method further comprises,
closing the control valve by moving the first valve body to the
closed position. Further, thereafter, fuel flow may be unrestricted
from the pumping chamber by moving the second valve body to the
open position to increase an injection rate for post injection,
while the control valve is closed.
[0015] The advantages associated with embodiments of the present
invention are numerous. For example, pumping systems such as unit
pumps or unit injectors made in accordance with the present
invention utilize a high pressure restriction to allow more precise
control over the quantity and timing of injection into the
combustion chamber. Embodiments of the present invention allow
sophisticated control over the quantity and timing of injection and
may be utilized to perform, for example, pilot operation, rate
shaping including boot injection or square injection, and post
injection, in addition to reducing the rate of pressure release at
the plunger after an injection, to reduce noise.
[0016] Further, it is appreciated that the valve and restriction
arrangement may be located between the control valve and the
plunger chamber or alternatively between the control valve and the
outlet depending on the particular control techniques to be
performed. Boot injection may be utilized to reduce oxides of
nitrogen, while square injection may be utilized during high
exhaust gas recirculation rates to reduce particulates. Further,
embodiments of the present invention may be utilized to perform
multiple injections into the combustion chamber during a single
cycle.
[0017] The above object and other objects, features, and advantages
of the present invention will be readily appreciated by one of
ordinary skill in the art from the following detailed description
of the best mode for carrying out the invention when taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a schematic diagram of a first embodiment of the
present invention;
[0019] FIG. 2 is a schematic diagram of a second embodiment of the
present invention;
[0020] FIG. 3 is a side elevation, in section, of a unit pump of
the present invention;
[0021] FIG. 4 is a side elevation, in section, of a unit injector
of the present invention;
[0022] FIGS. 5-8 are enlarged views of the control valve and the
valve and restriction arrangement in an exemplary embodiment of the
present invention, showing the valve bodies in various operational
positions;
[0023] FIG. 9 is a graph depicting valve areas during a boot
injection;
[0024] FIG. 10 is a graph depicting pressure versus cam degrees
during a boot injection;
[0025] FIG. 11 is a graph depicting fuel delivery versus cam
degrees during a boot injection;
[0026] FIG. 12 is a graph depicting pressure versus cam degrees
during a boot injection;
[0027] FIG. 13 is a graph depicting fuel delivery versus cam
degrees during a boot injection;
[0028] FIG. 14 is a graph depicting valve areas during a square
injection;
[0029] FIG. 15 is a graph depicting pressure versus cam degrees
during a square injection;
[0030] FIG. 16 is a graph depicting fuel delivery versus cam
degrees during a square injection;
[0031] FIG. 17 is a graph depicting valve area versus cam degrees
during a post injection;
[0032] FIG. 18 is a graph depicting pressure versus cam degrees
during a post injection;
[0033] FIG. 19 is a graph depicting fuel delivery versus cam
degrees during a post injection; and
[0034] FIG. 20 is a preferred value arrangement for use in pumps
and injectors of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] A pump system for a fuel injection system is generally
indicated at 10, in FIG. 1. An engine driven cam 12 drives a
plunger 14. The pumping chamber of plunger 14 is connected to an
injector via a high pressure fluid line. In embodiments of the
present invention, the pump system may be a unit pump connected via
a high pressure fluid line to an injector, or alternatively, may be
a unit injector. Further, it is appreciated that embodiments of the
present invention are broadly illustrated in FIGS. 1 and 2, and
that the exemplary implementations in FIGS. 3 and 4 are included
for illustration purposes. That is, there are many different ways
to implement embodiments of the present invention in accordance
with the schematic illustrations in FIGS. 1 and 2. With continuing
reference to FIG. 1, a valve and restriction arrangement is
generally indicated at 15, and includes high pressure restriction
16 and valve 18. As shown, the valve body is movable between a
closed position that causes fuel flow through the high pressure
fluid line to be significantly restricted by restriction 16 to
store energy in the pumping chamber at plunger 14. In the open
position, restriction 16 generally does not restrict fluid flow
through the high pressure line, as fluid flow may pass through
valve 18. It is appreciated that significantly restricted by
restriction 16 means that there is a noticeable pressure difference
between the pumping chamber and the other side of the restriction
(the unit pump outlet or the unit injector needle chamber). That
is, significantly restricted means restricted sufficiently to
reduce the rate of injection for a boot injection, or reduced rate
pilot injection, etc. Further, generally unrestricted (when valve
18 is open) means that flow through restriction 16 is minimal and
injection events may occur normally.
[0036] With continuing reference to FIG. 1, the control valve 20 is
closed to route pressurized fuel from the pumping chamber to the
pumping system outlet, which in turn, connects to injector 22. When
control valve 20 is open, fuel flow from the pumping chamber
bypasses the pump system outlet to low pressure reservoir 24. It is
appreciated that the control valve is preferably positioned between
the valve and restriction arrangement 15 and the pump system
outlet. Alternatively, a control valve 26 may be located between
the valve and restriction arrangement and pumping chamber. It is
appreciated that the alternative arrangement may be utilized for
boot injection, while the preferred arrangement may be utilized for
boot injection and square injection. Further, it is appreciated
that embodiments of the present invention are not limited to any
particular injection control strategies, however, embodiments of
the present invention are particularly useful for reduced rate
pilot injection, rate shaping including boot injection, square
injection, and post injection, in addition to reducing plunger
noise after injection.
[0037] Another embodiment of the present invention is illustrated
in FIG. 2. An engine driven cam 32 drives plunger 34 to pressurize
fuel in a pumping chamber. The valve and restriction arrangement 36
utilizes a high pressure restriction as part of the valve. This is
different than FIG. 1, in which the high pressure restriction may
be separate from the valve. The control valve is indicated at 38,
with the injector indicated at 40. Pumping system 30 of FIG. 2 may
alternatively utilize control valve 44 in a similar fashion as the
embodiment of FIG. 1. Further, low pressure fuel reservoir 42
receives fuel that bypasses injector 40 through control valve 38
when control valve 38 is open.
[0038] In FIG. 3, a unit pump in an exemplary implementation of the
invention is generally indicated at 50. Pump 50 includes a pump
body 52 defining high pressure pumping chamber 54. A plunger 56 is
disposed in the pumping chamber for pressurizing fuel. A high
pressure outlet 58 connects to an injector 110 through a high
pressure line, optionally including a check valve. A high pressure
outlet is connected to the pumping chamber by the high pressure
fluid line. In the unit pump embodiment, the high pressure fluid
line includes passage 60 and passage 62. Passage 64 is a high
pressure restriction, while passage 66 is a bypass for the
restriction. Control valve 70 selectively routes pressurized fuel
from the pumping chamber 54 to the outlet 58 or when open, provides
pressure relief to the pumping chamber through relief passage 88.
Valve and restriction arrangement 72 selectively directs fuel
through restriction 64 or, when open, allows fuel to effectively
bypass high pressure restriction 64 through passage 66. Fuel
annulus 80 allows fuel to be drawn into the pumping chamber 54
through passage 88 when both valves are open. O-rings 82 and 84
seal off inlet 80. Passage 86 allows any leakage past plunger 56 to
return to the low pressure fuel source (not shown) connected to
inlet 80.
[0039] Plunger 56 has a tail end 92 received in plunger seat 90. A
plunger spring 96 biases the plunger to the retracted position. The
plunger may be driven to the extended position by an engine driven
cam (not shown). A cam follower assembly 94 receives the plunger
seat and has a cam roller 98 that is driven by a cam to urge the
plunger to the extended position, compressing fuel in the pumping
chamber. As the plunger is continuously driven from the retracted
to the extended position, the valves 70 and 72 are controlled to
selectively supply fuel at various pressures to outlet 58, and to
injector 110. The extended position of the plunger is shown in
phantom at 100.
[0040] With continuing reference to FIG. 3, control valve 70
includes a valve body 112 secured to an armature 114. Solenoid 116
is energized to close the valve by pulling armature 114 towards
solenoid 116. As shown, the valve is open. When closed, seating
surface 120 is urged into closing contact with valve seat 122. A
spring 118 biases the control valve toward the open position. Valve
72 operates in a similar fashion, and includes valve body 140
secured to armature 142. A solenoid 144 is energized to pull
armature 142 towards solenoid 144 and close the valve. The valve 72
is shown in the open position. When closed, valve seating surface
148 is pulled into closing contact with seating surface 150. Spring
146 biases control valve 72 toward the open position. When valve 72
is closed, pressurized fuel from pumping chamber 54 is
significantly restricted by restriction 64 to create a pressure
differential between pumping chamber 54 and outlet 62. When valve
72 is opened, flow from pumping chamber 54 is generally
unrestricted, and fuel may flow through passage 66. Similarly, when
valve 70 is closed, pressurized fuel may be routed from chamber 54
to outlet 62, with the pressure at outlet 62 possibly being reduced
while valve 72 is closed. When valve 70 is open, the fuel flow from
the pumping chamber may pass valve seating surface 120 and return
through passage 88 to the low pressure inlet 80.
[0041] It is appreciated that embodiments shown in FIG. 3 operates
similar to the schematic shown in FIG. 1, but may alternatively be
arranged to operate more similar to the schematic of FIG. 2.
Alternatively, valve 72 of the valve and restriction arrangement
may be replaced with a normally closed solenoid poppet type valve
or other suitable valve as appreciated by one of ordinary skill in
the art. Some flexibility is comprised by utilizing a poppet valve,
but such a solution may provide a cost-effective solution for rate
shape and higher initial injection rate implementations.
Specifically, the poppet valve would not be able to reclose for
post injection.
[0042] In FIG. 4, a unit injector exemplary implementation is
generally indicated at 170. Unit injector 170 includes an injector
body 172 that defines a pumping chamber 174. A plunger 176 is
driven by a cam that drives against plunger holder and spring seat
178. Spring 180 biases the plunger to the retracted position.
[0043] An inlet 182 supplies low pressure fuel to the unit
injector. O-rings 184 and 186 effectively seal fuel inlet when the
unit injector is received in the engine block. Passage 188 connects
inlet 182 to the control valve and valve and restriction
arrangement. The valve and restriction arrangement is generally
indicated at 196 while the control valve is generally indicated at
194. The valves operate similar to the valves in the unit pump
shown in FIG. 3. The output of the pumping system is passage 192,
which passes pressurized fuel to the injector nozzle assembly 200.
Lower or needle chamber 202 receives pressurized fuel at a pressure
controlled by controlling valves 194 and 196 as plunger 176 is
reciprocated. Sufficient pressure in chamber 202 causes needle
seating surface 210 of needle 204 to lift off of needle seat 212,
allowing fuel to flow through passage 214 and out the end of the
injector through holes 216.
[0044] As mentioned previously, there are many implementations for
the control valve and the valve and restriction arrangement and the
implementation illustrated in FIGS. 3 and 4 is provided to help
facilitate an understanding of the present invention. Specifically,
FIGS. 5-8 illustrate the various relative positions of the two
valves during various operations of the pump system in the unit
pump or the unit injector. Further, the preferred arrangement for
the valves is shown in FIG. 20, where a spool valve forms the valve
and restriction arrangement.
[0045] In FIG. 5, an exemplary implementation of the high pressure
restriction concept for pump systems is generally indicated at 220.
Passage 222 receives pressurized fuel from the pumping chamber,
while passage 224 directs fuel to the pump system outlet, which may
be the outlet of a unit pump or the needle chamber of a unit
injector. The control valve is generally indicated at 226, while
the valve and restriction arrangement is generally indicated at
228. First valve body 230 is secured to armature 232, and may be
closed by actuating solenoid 234. Spring 236 abuts spring seat 238
and urges valve body 230 to the open position, as shown. Valve and
restriction arrangement 228 includes second valve body 260, which
is shown in the open position. A high pressure restriction 252
allows a pressure differential to develop between the two valves.
Path 250 allows fuel to bypass the restriction when valve body 260
is in the open position, as shown.
[0046] In FIGS. 6-8, like reference numerals are used to indicate
like parts from FIG. 5. Specifically, FIG. 6 illustrates the
control valve in the closed position at 270, and the valve for
controlling the restriction in the closed position at 272. That is,
in FIG. 6, pressure builds at the outlet, pressure builds at the
pumping chamber, and restriction 252 allows the pressure
differential to develop between the two valves.
[0047] In FIG. 7, the control valve is closed at 274, while valve
276 is open to allow fuel flow from pumping chamber to bypass the
restriction. In FIG. 8, the control valve is open at 278, while the
valve 280 is closed, allowing pressure to build in the pumping
chamber while relieving pressure at the outlet.
[0048] In FIG. 20, a preferred valve arrangement is illustrated.
Because many components shown in FIG. 20 are similar to the
components shown in FIGS. 5-8, like reference numerals have been
used. Specifically, the valve and restriction arrangement of FIG.
20 is a true spool type valve 500, shown with the solenoid
energized, pulling spool valve 500 to the right side of FIG. 20 and
restricting fuel flow with restriction passage 502. When the
solenoid is de-energized, spool valve body 500 moves to the left so
that fuel flow past spool valve 500 is unrestricted. It is
appreciated that the restriction may be a small diameter passage,
as illustrated, or in the alternative, the restriction may be
determined by the class of fit and/or the overlap of spool valve
500 and the surrounding pump body. That is, the restriction could
be affected at area 504.
[0049] The remaining figures, with the exception of FIG. 20,
illustrate the operation of the high pressure restriction concept
in a pump system of the present invention for various injection
control strategies. FIGS. 9-13 illustrate utilizing the high
pressure restriction concept of the present invention for
performing a boot injection. It is appreciated that parameters such
as cam velocity, plunger diameter, and plunger cavity volume may be
optimized for boot injection, square injection, post injection, or
any other type of injection desired to be performed in accordance
with the high pressure restriction concept, and that the various
values for the parameters may present trade offs between the
different types of injections. In the following description, the
term control valve means the valve that controls the bypass to the
low pressure reservoir (valve 20 in FIG. 1, valve 38 in FIG. 2).
Further, the term restriction valve means the valve that controls
fuel flow through the high pressure restriction (valve 18 in FIG.
1, valve 36 in FIG. 2). Even further, the remaining figures
illustrate various injection control strategies when the control
valve is located between the restriction valve and the outlet. In
the alternative, some strategies (such as boot injection or other
reduced rate injections) may be performed with the control valve
between the restriction valve and the pumping chamber. Even
further, valve area means the cross-sectional area allowed for
fluid flow through a valve.
[0050] In FIG. 9, valve area versus cam degrees is indicated at
300. Plot 302 indicates effective valve area for the restriction
valve, while plot 304 indicates effective valve area for the
control valve. Plot 306 indicates cam velocity. It is appreciated
that FIG. 9 and the remaining figures illustrate operation of the
embodiment shown in FIG. 1 (when the restriction valve area is
shown as effectively 0, fuel flows through the restriction 16
preferably having an area that is optimized for the particular
injection strategies being implemented). In FIG. 9, the restriction
valve is closed to throttle fuel flow through the restriction,
causing energy to be stored in the plunger cavity. Then, the
control valve is closed for boot injection to begin. Opening the
restriction valve releases the stored energy causing high pressure
injection.
[0051] In FIG. 10, pressure versus cam degrees is generally
indicated at 310 for a boot injection performed at 900 rpm (engine
speed). Pumping chamber pressure is indicated at plot 314, while
pressure at the needle is indicated at 316. For reference purposes,
pumping chamber plot 312 indicates pumping chamber pressure in a
standard pump (without the high pressure restriction). As shown,
pumping chamber pressure 314 steadily increases, and nozzle needle
pressure dramatically increases just after the restriction valve is
opened.
[0052] In FIG. 11, fuel delivery is generally indicated at 320, and
corresponds to the pressure plots of FIG. 10. Injection rate is
indicated at plot 326, while injection quantity is indicated at
plot 328. For reference purposes, injection rate 322 and injection
quantity 324 for a base implementation (without the restriction)
are also shown.
[0053] In FIG. 12, pump pressure versus cam degrees is generally
indicated at 340 for a boot injection at 600 rpm (engine speed).
Plot 344 is the pumping chamber pressure, while plot 346 is the
needle chamber pressure. For reference purposes, plot 342
illustrates pumping chamber pressure without the high pressure
restriction.
[0054] In FIG. 13, fuel delivery versus cam degrees is generally
indicated at 350, and corresponds to the pressure plots of FIG. 12.
Injection rate is indicated at plot 356 while injection quantity is
indicated at plot 358. For reference purposes, base injection rate
plot 352 and base injection quantity plot 354 (no high pressure
restriction) are also provided.
[0055] FIGS. 14-16 illustrate performance of a square injection. In
FIG. 14, valve area versus cam degrees is generally indicated at
370. The control valve is indicated at 374 while the restriction
valve is indicated at 372. Plunger velocity is indicated at 376. As
shown, the restriction valve is closed to store pressure in the
pumping chamber. The control valve is closed and the restriction
valve is opened at nearly the same time to cause a high initial
rate of injection at just past 390 degrees.
[0056] In FIG. 15, pump pressure versus cam degrees for square
injection at approximately 900 rpm (engine speed) is indicated at
380. Pumping chamber pressure is indicated at 386, while needle
chamber pressure is indicated at 388. Base (without the high
pressure restriction) pumping chamber pressure plot 382 and needle
chamber pressure plot 384 are provided for reference purposes.
[0057] In FIG. 16, square injection at 900 rpm is illustrated at
400. Injection rate plot 406 and injection quantity plot 408
illustrate the utilization of a high pressure restriction concept
for performing the square injection. For reference purposes, base
injection rate plot 402 and base injection quantity plot 404 are
provided (no restriction).
[0058] In FIG. 17, valve are versus cam degrees for a post
injection is generally indicated at 420. Valve area for the
restriction valve is indicated at plot 422, while valve area for
the control valve is indicated at plot 424. As shown, at about 390
degrees, the control valve is closed and the restriction valve is
open for a main injection, while at about 400 degrees, the
restriction valve is closed and the control valve is open to end
the main injection. Then, the control valve is re-closed for a post
injection, and the restriction valve is open to release the
pressure stored in the pumping chamber. Thereafter, the control
valve is then opened to end the post injection.
[0059] In FIG. 18, pressure versus degrees for a post injection at
about 900 rpm (engine speed) is indicated at 440. Pumping chamber
pressure is indicated at plot 446, while needle chamber pressure is
indicated at plot 448. As shown by plot 448, a main injection is
followed by a post injection. Baseline pumping chamber pressure
plot 442 and needle chamber pressure plot 444 are provided for
reference purposes (no restriction).
[0060] In FIG. 19, fuel delivery for post injection at 900 rpm is
generally indicated at 460. Plot 466 illustrates injection rate,
while plot 468 illustrates injection quantity. Portion 470 of plot
466 illustrates injection rate for the post injection. Base
injection rate plot 462 and injection quantity plot 464 (without
the high pressure restriction concept) are provided for reference
purposes).
[0061] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *