U.S. patent application number 11/603715 was filed with the patent office on 2007-04-19 for fuel system with variable discharge pump.
Invention is credited to Dennis H. Gibson, Mark F. Sommars.
Application Number | 20070086899 11/603715 |
Document ID | / |
Family ID | 32325893 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070086899 |
Kind Code |
A1 |
Sommars; Mark F. ; et
al. |
April 19, 2007 |
Fuel system with variable discharge pump
Abstract
The present invention relates generally to variable discharge
pumps, and specifically pumps used in fuel injection systems.
Typically, such pumps include a dedicated spill control valve for
each pumping plunger, that also doubles as an avenue for refilling
the pumping chambers. This double duty results in compromise in the
design of the spill control valve to operate effectively in both
spill and fill modes. The present invention addresses these issues
by utilizing a shuttle valve member to allow the spill function and
the fill function to be addressed in separate passageways while
also allowing a pair of plungers to share a common spill control
valve. The present invention find particular application in pumps
used to supply high pressure fluid to common rails for fuel
injection systems.
Inventors: |
Sommars; Mark F.; (Sparland,
IL) ; Gibson; Dennis H.; (Chillicothe, IL) |
Correspondence
Address: |
CATERPILLAR c/o LIELL & MCNEIL ATTORNEYS PC
P.O. BOX 2417
511 SOUTH MADISON STREET
BLOOMINGTON
IN
47402-2417
US
|
Family ID: |
32325893 |
Appl. No.: |
11/603715 |
Filed: |
November 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10314879 |
Dec 9, 2002 |
7179060 |
|
|
11603715 |
Nov 22, 2006 |
|
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Current U.S.
Class: |
417/307 ;
417/446 |
Current CPC
Class: |
F02M 59/46 20130101;
F02M 63/0225 20130101; F04B 49/24 20130101; F02M 59/366 20130101;
F02M 59/466 20130101; F02M 59/08 20130101 |
Class at
Publication: |
417/307 ;
417/446 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Claims
1-20. (canceled)
21. A fuel system for an engine comprising: a high pressure pump
having an inlet and an outlet; a fuel rail fluidly connected to the
outlet of the high pressure pump; a plurality of fuel injectors
fluidly connected to the fuel rail via respective branch passages;
an electronic control module in control communication with the high
pressure pump via an electrical actuator; the high pressure pump
including a first plunger within a first pumping chamber and a
second plunger within a second pumping chamber, the first pumping
chamber and the second pumping chamber sharing a common spill
valve, the spill valve being moveable in response to the electrical
actuator; and a shuttle valve being movable between a first
position in which the first pumping chamber is in fluid
communication with the spill valve and a second position in which
the second pumping chamber is in fluid communication with the spill
valve, the shuttle valve being configured to be moved to the first
position when the first plunger is in a pumping stroke and to be
moved to the second position when the second plunger is in a
pumping stroke.
22. The fuel system of claim 21 including a fuel transfer pump with
an outlet fluidly connected to the inlet of the high pressure
pump.
23. The fuel system of claim 22 including a fuel tank fluidly
connected to an inlet of the fuel transfer pump; and a fuel
injector return line fluidly connecting low pressure outlets of the
plurality of fuel injectors to the tank.
24. The fuel system of claim 23 wherein the spill valve includes a
latching valve member; wherein the first and second plungers
reciprocate within the first and second pumping chambers,
respectively; and wherein the latching valve member is moved toward
a closed position by the electrical actuator, but is held in the
closed position by fluid pressure in one of the first and second
pumping chambers when one of the first and second plungers is in
the pumping stroke.
25. The fuel system of claim 24 wherein the high pressure pump
includes first and second intake valves associated with the first
and second pumping chambers, respectively.
26. The fuel system of claim 25 wherein each of the first and
second plungers are reciprocated via rotation of respective three
lobed cams.
27. The fuel system of claim 26 wherein the plurality of fuel
injectors includes three fuel injectors for each pumping
plunger.
28. A method of operating a fuel system, comprising the steps of:
supplying high pressure fuel to a common rail by reciprocating a
first plunger within a first pumping chamber and a second plunger
within a second pumping chamber; controlling the high pressure fuel
displaced from the first and second pumping chambers to the common
rail with a shared spill valve; closing the spill valve by
energizing an electrical actuator coupled to the spill valve; and
moving a shuttle valve to a first position when the first plunger
is in a pumping stroke and moving the shuttle valve to a second
position when the second plunger is in a pumping stroke; and
supplying fuel to a plurality of fuel injectors from the common
rail via individual branch passages.
29. The method of claim 28 further comprising the steps of
de-energizing the electrical actuator after the spill valve closes
and holding the spill valve closed for a remainder of a pumping
stroke by the high pressure fuel displaced by one of the first
plunger and the second plunger.
30. The method of claim 29 wherein the first and second plungers
are parts of a high pressure pump; and further comprising the step
of supplying low pressure fuel to the high pressure pump via a fuel
transfer pump.
31. The method of claim 28 further comprising the step of supplying
fuel to the first and second pumping chambers via first and second
intake valves, respectively.
32. The method of claim 31 wherein the first and second plungers
are reciprocated by rotating first and second three lobed cams,
respectively.
Description
RELATION TO OTHER PATENT APPLICATION
[0001] This application is a divisional of patent application Ser.
No. 10/314,879, filed Dec. 9, 2002, with the title Variable
Discharge Pump, now U.S. Pat. No. ______.
TECHNICAL FIELD
[0002] The present invention relates generally to variable
discharge pumps, and more particularly to variable discharge pumps
having a pair of pumping plungers for use in a fuel system for an
engine.
BACKGROUND
[0003] In one class of fluid systems, such as common rail fuel
systems for internal combustion engines, a variable discharge pump
is utilized to maintain a pressurized fluid supply for a plurality
of fuel injectors. For instance, European Patent Specification EP
0,516,196 teaches a variable discharge high pressure pump for use
in a common rail fuel injection system. The pump maintains the
common rail at a desired pressure by controllably displacing fluid
from the pump to either the high pressure common rail or toward a
low pressure reservoir with each pumping stroke of each pump
piston. This is accomplished by associating an electronically
controlled spill valve with each pump piston. When the pump piston
is undergoing its pumping stroke, the fluid displaced is initially
pushed into a low pressure reservoir past a spill control valve.
When the spill control valve is energized, it closes the spill
passageway causing fluid in the pumping chamber to quickly rise in
pressure. The fluid in the pumping chamber is then pushed past a
check valve into a high pressure line connected to the common rail.
In this type of system, the pump typically includes several pump
pistons or the system is maintained with several individual unit
pumps. The various pump pistons are preferably out of phase with
one another so that at least one piston is pumping at about the
same time one of the hydraulic devices is consuming fluid from the
common rail. This strategy allows the pressure in the common rail
to be more steadily controlled in a highly dynamic environment.
[0004] As stated, in the pump of the above identified patent, fluid
is initially displaced from each pump chamber through a spill
control valve toward a low pressure reservoir when the individual
pump pistons begin their pumping stroke. When the spill control
valve is energized, this spill passageway is closed allowing fluid
pressure to build and be pushed past a check valve toward the high
pressure common rail. Like many pumps of its type, the spill
control valve is a pressure latching type valve in which the valve
member is held in its closed position via fluid pressure so that
the actuator can be deenergized after the spill control valve has
been closed, which can conserve electrical energy. In other words,
the fluid pressure in the pumping chamber itself holds the spill
control valve closed until that pressure drops toward the end of
the pumping stroke, where a spring or other bias pushes the spill
control valve back to its open position. When the pump piston
undergoes its retracting stroke, fresh fluid is drawn into the
pumping chamber past the spill control valve. Thus, the identified
patent teaches a spill control valve that both fills the pump
cavity with inlet fluid and spills the pump cavity during the time
preceding the closing of the valve and the commencement of pump
discharge toward the high pressure common rail.
[0005] One problem associated with pumps of the type previously
described is that the process of filling the pumping chamber and
that of spilling the pumping chamber before high pressure pumping
begins tend to conflict with one another. Optimizing the spill
control valve details for spilling requires designing the valve and
valve body geometry to, among other things, avoid shutting the
valve due to flow forces before the electrical actuator is
energized.
[0006] This design criteria often conflicts with the need to fill
the pumping chamber through the same fluid circuit. Thus, the pump
previously described suffers from two potential drawbacks in that a
separate spill control valve is needed for each pumping plunger,
and each pump cavity both fills and spills through the spill
control valve, resulting in design compromises to efficiently
achieve both effective spilling and filling.
[0007] The present invention is directed to overcoming one or more
of the problems set forth above.
SUMMARY OF THE INVENTION
[0008] In one aspect, a fuel system for an engine includes a high
pressure pump with an inlet and an outlet, which is fluidly
connected to a fuel rail. A plurality of fuel injectors are fluidly
connected to the fuel rail via respective branch passages. An
electronic control module is in control communication with the high
pressure pump via an electrical actuator. The high pressure pump
includes a first plunger within a first pumping chamber, and a
second plunger within a second pumping chamber. The first pumping
chamber and the second pumping chamber share a common spill valve,
and the spill valve is movable in response to the electrical
actuator. A shuttle valve is movable between a first position in
which the first pumping chamber is in fluid communication with the
spill valve, and a second position in which the second pumping
chamber is in fluid communication with spill valve. The shuttle
valve is configured to be moved to the first position when the
first plunger is in a pumping stroke, and to be moved to the second
position when the second plunger is in a pumping stroke.
[0009] In another aspect, a method of operating a fuel system
includes supplying high pressure fuel to a common rail by
reciprocating a first plunger within a first pumping chamber and a
second plunger within a second pumping chamber. The high pressure
fuel displaced from the first and second pumping chambers is
controlled with a shared spill valve. The spill valve is closed by
energizing an electrical actuator coupled to the spill valve. A
shuttle valve is moved to a first position when the first plunger
is in a pumping stroke, and the shuttle valve is moved to a second
position when the second plunger is in a pumping stroke. Fuel to
the plurality of fuel injectors are supplied from the common rail
via individual branch passages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic illustration of a common rail fuel
system according to one aspect of the present invention;
[0011] FIG. 2 is a front sectioned view of a pump from the fuel
system shown in FIG. 1;
[0012] FIG. 3 is a side sectioned view of the pump of FIG. 2;
[0013] FIG. 4 is an enlarged front sectioned view of the fill and
spill portion of the pump of FIGS. 2 and 3; and
[0014] FIG. 5 is a schematic illustration of a pump according to
another embodiment of the present invention.
DETAILED DESCRIPTION
[0015] Referring to FIG. 1, a fuel system 10 includes a plurality
of fuel injectors 22, which are each connected to a high pressure
fuel rail 20 via an individual branch passage 21. The high pressure
fuel rail 20 is supplied with high pressure fuel from a high
pressure pump 16, which is supplied with relatively low pressure
fluid by a fuel transfer pump 14. Fuel transfer pump 14 draws fuel
from a fuel tank 12, which is also fluidly connected to the fuel
injectors 22 via a leak return passage 23. Fuel system 10 is
controlled in its operation in a conventional manner via an
electronic control module 18 which is connected to an electrical
actuator 28 of pump 16 via a control communication line 29, and
connected to the individual fuel injectors 22 via other
communication lines (not shown). When in operation, control signals
generated by electronic control module 18 determine when and how
much fuel displaced by pump 16 is forced into common rail 20, as
well as when and for what duration (fuel injection quantity) that
fuel injectors 22 operate.
[0016] Referring in addition to FIGS. 2 and 3, high pressure pump
16 includes a high pressure outlet 30 fluidly connected to the high
pressure rail 20, a low pressure outlet 32 connected to fuel tank
12, and an inlet 33 fluidly connected to fuel transfer pump 14.
Pump 16 also includes a first plunger 45 positioned to reciprocate
in a first pumping chamber 46 of a first barrel 44. In addition,
pump 16 includes a second plunger 55 positioned to reciprocate in a
second pumping chamber 56 of a second barrel 54. Although not
necessary, first and second barrels 44, 54 are preferably portions
of a common pump housing 40. A pair of cams 34 and 35 are operable
to cause plungers 45 and 55 to reciprocate out of phase with one
another. In this embodiment, cams 34 and 35 each include three
lobes such that one of the plungers 45 or 55 is undergoing a
pumping stroke at about the time that one of the fuel injectors 22
is injecting fuel. Thus, cams 34 and 35 are preferably driven to
rotate directly by the engine at a rate that preferably
synchronizes pumping activity to fuel injection activity in a
conventional manner.
[0017] When plunger 45 is undergoing its retracting stroke, fresh
low pressure fuel is drawn into pumping chamber 46 past a first
inlet check valve 48 from a low pressure gallery 37 that is fluidly
connected to inlet 33. Likewise, when plunger 55 is undergoing its
retracting stroke, fresh low pressure fuel is drawn into the second
pumping chamber 56 past a second inlet check valve 58 from the
shared low pressure gallery 37. When first plunger 45 is undergoing
its pumping stroke, fluid is displaced from pumping chamber 46
either into low pressure gallery 37 via first spill passage 41 and
spill control valve 38, or into high pressure gallery 39 past first
outlet check valve 47. Likewise, when second plunger 55 is
undergoing its pumping stroke, fuel is displaced from second
pumping chamber 56 either into low pressure gallery 37 via second
spill passage 51 and spill control valve 38, or into high pressure
gallery 39 past second outlet check valve 57.
[0018] Referring now in addition to FIG. 4, only one of the pumping
chambers 46 or 56 is fluidly connected to spill control valve 38 at
a time. These fluid connections are controlled by a shuttle valve
member 80 that includes a first hydraulic surface 81 exposed to
fluid pressure in first pumping chamber 46, and a second hydraulic
surface 82, which is oriented in opposition to first hydraulic
surface 81 and exposed to fluid pressure in second pumping chamber
56. Because pumping plungers 44 and 54 are out of phase with one
another, one pumping chamber will be at low pressure (retracting)
when the other pumping chamber is at high pressure (advancing), and
vice versa. This action is exploited to move shuttle valve member
80 back and forth to connect either first spill passage 41 to spill
control valve 38, or fluidly connect second spill passage 51 to
spill control valve 38. Thus, first hydraulic surface 81 and second
hydraulic surface 82 actually define a portion of first spill
passage 41 and second spill passage 51, respectively. This allows
pumping chambers 46 and 56 to share a common spill control valve
38. In other words, when first plunger 44 is undergoing its pumping
stroke while second plunger 54 is undergoing its retracting stroke,
shuttle valve member 80 will be in a position shown in FIG. 4 in
which first pumping chamber 56 is fluidly connected to spill
control valve 38. This is caused by hydraulic fluid pressure acting
on first hydraulic surface 81 from pumping chamber 44 pushing
shuttle valve member 80 to the right to close second spill passage
51. The affect of this is twofold. First, a single spill control
valve 38 can be used to control high pressure discharge from two
separate pumping chambers. And second, second pumping chamber 56 is
refilled past a second inlet check valve 58 rather than past the
spill control valve as in the prior art. These features allow the
spill control valve 38 to be optimized for flow in one direction,
namely in the spill direction without requiring it to also perform
the duty of reverse flow to fill a pumping chamber(s). In addition,
this strategy also allows for the usage of a simple cartridge check
valve 58 for controlling low pressure fill into the second pumping
chamber 56. When second plunger 54 is undergoing its pumping stroke
and first plunger 44 is undergoing its retracting stroke, shuttle
valve member 80 moves to the left to connect second spill passage
51 to spill control valve 38, while low pressure fuel refills first
pumping chamber 46 past first inlet check valve 48.
[0019] Spill control valve 38 has a structure that shares many
features in common with known valves of its type. For instance, it
includes a spill valve member 60 that includes a closing hydraulic
surface 62 that produces a latching affect when valve member 60 is
in contact with valve seat 63. Spill valve member 60 is normally
biased downward toward its open position, as shown in FIG. 4, via a
biasing spring 64. However, spill valve member 60 can be moved
upward to close valve seat 63 by energizing electrical actuator 28.
In the illustrated embodiment, electrical actuator 28 is a solenoid
that includes an armature 36 attached to move with spill valve
member 60. Nevertheless, those skilled in the art will appreciate
that electrical actuator 28 could take a variety of forms,
including but not limited to piezo and/or piezo bender actuators.
In the illustrated embodiment, electrical actuator 28 controls the
output from a pair of pumping chambers.
[0020] Referring now to FIG. 5, a schematic illustration of a high
pressure pump 116 according to another embodiment of the present
invention is similar to the previous embodiment in that it includes
a shuttle valve member 180 that permits the sharing of a single
spill control valve 138 between a pair of pumping plungers 145 and
155. This embodiment differs from the earlier embodiment in that no
inlet check valves are needed, and the two pumping chambers 146 and
156 share a common outlet check valve 148. When first plunger 145
is undergoing its pumping stroke and second plunger 155 is
undergoing its retracting stroke, as shown, the pressure
differentials produced in respective pumping chambers 146 and 156
cause shuttle valve member 180 to move to the right to the position
shown. This is caused by an increase of fluid pressure acting on
first hydraulic surface 181 via a first pressure communication
passage 42 while a lower pressure force is acting on second
hydraulic surface 182 via a second pressure communication passage
152. When shuttle valve member 180 is in the position shown, first
pumping chamber 146 is fluidly connected to outlet gallery 139 via
first outlet passage 143. In addition, first pumping chamber 146 is
also fluidly connected to spill control valve 138 via first spill
passage 144 and common spill passage 141. Finally, first pumping
chamber 146 is fluidly disconnected from low pressure gallery 137
and supply passage 136 due to shuttle valve member 180 closing
first supply passage 147. Thus, when spill control valve 138 is
energized, common spill passage 141 will close and high pressure
fluid will be displaced from first pumping chamber 146 past outlet
check valve 148.
[0021] At the same time that first plunger 145 is undergoing its
pumping stroke, second plunger 155 is undergoing its retracting
stroke, and fresh low pressure fuel is drawn into second pumping
chamber 156 from low pressure gallery 137 via supply passage 136
and second supply passage 157. At the same time shuttle valve
member 180 blocks second spill passage 154 and second outlet
passage 153. Thus, the spool valve nature of shuttle valve member
180 allows for the elimination of inlet check valves and allows for
the sharing of a single outlet check valve as well as the sharing
of a single spill control valve between two separate plungers
reciprocating out of phase with one another.
INDUSTRIAL APPLICABILITY
[0022] The present invention finds potential application in any
fluid system where there is a desire to control discharge from a
pump. The present invention finds particular applicability in
variable discharge pumps used in relation to fuel injection
systems, especially common rail fuel injection systems.
Nevertheless, those skilled in the art will appreciate that the
present invention could be utilized in relation to other hydraulic
systems that may or may not be associated with an internal
combustion engine. For instance, the present invention could also
be utilized in relation to hydraulic systems for internal
combustion that use a hydraulic medium, such as engine lubricating
oil, to actuate various sub-systems, including but not limited to
hydraulically actuated fuel injectors and gas exchange valves, such
as engine brakes. A pump according to the present invention could
also be substituted for a pair of unit pumps in other fuel systems,
including those that do not include a common rail.
[0023] Referring to FIG. 1, when fuel system 10 is in operation,
cams 34 and 35 rotate causing pump plungers 45 and 55 to
reciprocate in respective barrels 44 and 54 out of phase with one
another. When first plunger 45 is undergoing its pumping stroke,
second plunger 55 will be undergoing its retracting stroke. This
action is exploited via shuttle valve member 80 to either connect
first pumping chamber 46 or second pumping chamber 56 to spill
control valve 38. As one of the plungers begins its pumping stroke,
fluid is initially displaced from the pumping chamber through spill
control valve 38 to low pressure gallery 37. When there is a desire
to output high pressure from the pump, electrical actuator 28 is
energized to close spill control valve 38. This causes fluid in the
pumping chamber to be pushed past the respective check valve 47 or
57 into high pressure gallery 39 and then into high pressure rail
20. Those skilled in the art will appreciate that the timing at
which electrical actuator 28 is energized determines what fraction
of the amount of fluid displaced by the plunger action is pushed
into the high pressure gallery and what other fraction is displaced
back to low pressure gallery 37. This operation serves as a means
by which pressure can be maintained and controlled in high pressure
rail 20. While one plunger is pumping, the other plunger is
retracting drawing low pressure fuel into its pumping chamber past
one of the respective inlet check valves 48 or 58. This action
allows for the spill control valve 38 to be optimized for flow in
one direction, namely in a spill direction. Likewise, the spill
action of the pump can be optimized for features known in the art
independent of spill control valve 38.
[0024] Referring now to FIG. 5, pump 116 operates in much a similar
manner as pump 16 described earlier accept that shuttle valve
member 180 is a spool valve member that allows for the elimination
of inlet check valves and allows for the sharing of a single outlet
check valve between the two pumping plungers 145 and 155. Thus,
pump 116 works in a virtually identical manner with a more complex
shuttle valve member but a lower part count regarding check valves
associated with the pump.
[0025] Thus, the present invention utilizes one electrical actuator
valve combination to control the discharge of two plungers. To
facilitate that arrangement, a shuttle valve is located between the
plunger pumping cavities and the spill control valve. The pumping
action of the first plunger combined with the intake action of the
second forces the shuttle valve to a position that blocks fluid
entry into the filling plunger while providing an open path between
the pumping plunger and the spill control valve. The spill control
valve can then be activated at any time between the commencement of
the pumping plunger's motion and the end of its motion. Closing the
valve initiates a rise in plunger cavity pressure, an opening of
the outlet check valve and a start of the delivery of high pressure
fuel to the high pressure fuel rail. The increase in pressure holds
the shuttle valve shut until the plunger slows and stops at the end
of its motion, at which time the solenoid biasing spring opens the
spill control valve in preparation for the next plunger's action.
As the second plunger switches modes from filling to pumping (and
the first plunger switches from pumping to filling), the shuttle
valve moves to the other side of its cavity blocking fluid entry
into the filling plunger, and opening the path between the pumping
plunger and the spill control valve allowing the spill control
valve to control the discharge of the second plunger cavity.
[0026] It should be understood that the above description is
intended for illustrative purposes only, and is not intended to
limit the scope of the present invention in any way. Thus, those
skilled in the art will appreciate that other aspects, objects, and
advantages of the invention can be obtained from a study of the
drawings, the disclosure and the appended claims.
* * * * *