U.S. patent application number 11/376366 was filed with the patent office on 2007-09-20 for variable discharge pump.
Invention is credited to Daniel R. Puckett, Scott F. Shafer, Ye Tian, Jianhua Zhang.
Application Number | 20070217925 11/376366 |
Document ID | / |
Family ID | 38518028 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070217925 |
Kind Code |
A1 |
Tian; Ye ; et al. |
September 20, 2007 |
Variable discharge pump
Abstract
A variable discharge pump is provided, the pump comprising a
pumping chamber and a reciprocating plunger disposed within a
plunger bore so as to reciprocate within the pumping chamber. The
pump also has an electrically actuated spill control valve which
opens or closes fluid communication between the pumping chamber and
a low pressure area. The control valve is operated for a first
period of time extending from a first time point occurring after
the plunger passes bottom dead center to a second time point
occurring before the plunger passes top dead center. The control
valve is then operated for a second period of time extending from a
third time point occurring between the second time point and the
passing of the plunger through top dead center to a fourth time
point occurring after the plunger has passed top dead center.
Inventors: |
Tian; Ye; (Bloomington,
IL) ; Shafer; Scott F.; (Morton, IL) ; Zhang;
Jianhua; (Dunlap, IL) ; Puckett; Daniel R.;
(Peoria, IL) |
Correspondence
Address: |
Caterpillar Inc.;Intellectual Property Dept.
AB 6490
100 N.E. Adams Street
PEORIA
IL
61629-6490
US
|
Family ID: |
38518028 |
Appl. No.: |
11/376366 |
Filed: |
March 15, 2006 |
Current U.S.
Class: |
417/279 |
Current CPC
Class: |
F04B 2201/0201 20130101;
F04B 49/24 20130101 |
Class at
Publication: |
417/279 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Claims
1. A pump comprising: a first pumping chamber; a first
reciprocating plunger disposed within a first plunger bore so as to
reciprocate within the first pumping chamber; a first electrically
actuated spill control valve adapted to open or close fluid
communication between the first pumping chamber and a low pressure
area; and a controller adapted to operate the first control valve
for a first period of time extending from a first time point
occurring after the first plunger passes bottom dead center to a
second time point occurring before the first plunger passes top
dead center; and the controller being adapted to operate the first
control valve for a second period of time extending from a third
time point occurring between the second time point and the passing
of the first plunger through top dead center to a fourth time point
occurring after the first plunger has passed top dead center.
2. The pump according to claim 1, wherein the first control valve
is a solenoid valve.
3. The pump according to claim 1, wherein the controller comprises
an electronic control unit.
4. The pump according to claim 3, wherein the electronic control
unit includes a data storage device which stores one or more fluid
pressure parameters, and wherein the control unit is adapted to
vary the operating of the first control valve according to the
stored parameters.
5. The pump according to claim 3, wherein the electronic control
unit includes a receiver adapted to receive data relating to fluid
pressure parameters from an external device, and wherein the
control unit is adapted to vary the operating of the first control
valve according to the received signals.
6. The pump according to claim 1 and including: a second pumping
chamber; and a second reciprocating plunger disposed within a
second plunger bore so as to reciprocate within the second pumping
chamber; wherein the first control valve is adapted to open or
close fluid communication between the second pumping chamber and
the low pressure area; wherein the controller is adapted to operate
the first control valve for a first period of time extending from
the first time point occurring after one of the plungers passes
bottom dead center to the second time point occurring before the
one of the plungers moves through top dead center; and wherein the
controller is adapted to operate the first control valve for a
second period of time extending from the third time point occurring
between the second time point and the movement of the one of the
plungers through top dead center to the fourth time point occurring
after the one of the plungers has moved through top dead
center.
7. The pump according to claim 6, wherein the one of the plungers
is the second plunger.
8. The pump according to claim 6, wherein the first and second
plungers are adapted so as to reciprocate out of phase with one
another.
9. The pump according to claim 6 and including: a spill passage
fluidly connecting the first and second pumping chambers; and a
shuttle valve located in the spill passage and adapted to be
exposed to fluid pressure in the first and second pumping chambers;
the shuttle valve including a shuttle valve member moveable between
a first position in which the first pumping chamber is fluidly
connected to the control valve and a second position in which the
second pumping chamber is fluidly connected to the control
valve.
10. The pump according to claim 9, wherein the shuttle valve is a
ball valve and the shuttle valve member is a ball.
11. The pump according to claim 6, wherein the first control valve
is a solenoid valve.
12. The pump according to claim 6, wherein the controller comprises
an electronic control unit.
13. The pump according to claim 12, wherein the electronic control
unit includes a data storage device which stores one or more fluid
pressure parameters, wherein the control unit may vary the
operation of the control valve according to the stored
parameters.
14. The pump according to claim 13, wherein the electronic control
unit includes a receiver adapted to receive data relating to fluid
pressure parameters from an external device, wherein the control
unit may vary the operation of the control valve according to the
received signals.
15. The pump according to claim 1 and including: a second pumping
chamber; a second reciprocating plunger disposed within a second
plunger bore so as to reciprocate within the second pumping
chamber; and a second electrically actuated spill control valve
adapted to open or close fluid communication between the second
pumping chamber and the low pressure area; wherein the controller
is adapted to operate the second control valve for a first period
of time extending from a first time point occurring after the
second plunger passes bottom dead center a second time point
occurring before the second plunger moves through top dead center;
and wherein the controller is adapted to operate the second control
valve for a second period of time extending from a third time point
occurring between the second time point and the movement of the
second plunger through top dead center to a fourth time point
occurring after the second plunger has moved through top dead
center.
16. The pump according to claim 15, wherein the first and second
plungers are adapted so as to reciprocate out of phase with one
another.
17. The pump according to claim 15, wherein the first control valve
is a solenoid valve.
18. The pump according to claim 15, wherein the second control
valve is a solenoid valve.
19. The pump according to claim 15, wherein the controller
comprises an electronic control unit.
20. The pump according to claim 19, wherein the electronic control
unit includes a data storage device which stores one or more fluid
pressure parameters, wherein the control unit may vary the
operation of the control valve according to the stored
parameters.
21. The pump according to claim 19, wherein the electronic control
unit includes a receiver adapted to receive data relating to fluid
pressure parameters from an external device, wherein the control
unit may vary the operation of the control valve according to the
received signals.
22. The pump according to claim 15, wherein the first and second
control valves are actuatable towards a closed position when
operated.
23. The pump according to claim 15 including first and second
springs adapted to bias the first and second control valves,
respectively, in the open position.
24. An internal combustion engine including a pump according to
claim 1.
25. A method of pressurizing fluid in a pump, the method comprising
the steps of: supplying low pressure fluid to a pumping chamber;
reciprocating a plunger within the pumping chamber so as to force
fluid from the pumping chamber; returning a portion of the fluid
from the pumping chamber through an electrically actuated spill
control valve; operating the electrically actuated spill control
valve to pressurize the fuel in the pumping chamber during a
forward stroke of the plunger; and discharging the pressurized fuel
through a discharge port in communication with the pumping chamber;
wherein the operating step includes operating the control valve for
two separate periods of time, a first period of time extending from
a first time point occurring after the plunger passes bottom dead
center to a second time point occurring before the plunger passes
top dead center, and a second period of time extending from a third
time point occurring between the second time point and the passing
of the plunger through top dead center to a fourth time point
occurring after the plunger has passed top dead center.
26. The method according to claim 25 and including the step of
receiving data relating to fluid pressure parameters from an
external device, and varying one or both of the first and second
periods of time of the operating step according to the received
data.
27. The method according to claim 26, wherein a dwell time period
between the fourth time point of the operating step and the first
time point of a subsequent operating step is varied according to
the received data.
28. The method according to claim 26 further comprising the step of
storing data relating to one or more fluid pressure parameters, and
varying one or both of the first and second periods of time of the
operating step according to the stored data.
29. The method according to claim 28, wherein the fourth time point
is varied according to the stored data and the received data.
Description
TECHNICAL FIELD
[0001] The present invention relates to the field of variable
discharge pumps. Particularly, though not exclusively, the
invention relates to a variable discharge pump suitable for pumping
fuel into the common rail of a common rail fuel injection
system.
BACKGROUND
[0002] The present invention relates to the field of variable
discharge pumps. Particularly, though not exclusively, the
invention relates to a variable discharge pump suitable for pumping
fuel into the common rail of a common rail fuel injection
system.
[0003] Each downward stroke of the plungers feeds fuel from the
fuel feed port into the pumping chamber. When the control valve
member is open, the fuel passes through the valve and back to the
feed port via the return passage when the plungers move upward.
When pressurized fuel is to be fed into the common rail, a control
pulse moves the control valve member into the closed position. At
the same time, the plunger is undertaking an upward stroke. Because
the control valve is closed, pressurization of the fuel takes place
in the pumping chamber. When the fuel pressure reaches a certain
level, the discharge valve opens and the pressurized fuel passes
from the pumping chamber into the common rail. The consequent drop
in fuel pressure in the pumping chamber allows the valve spring to
push the control valve member into its open position, whereupon it
comes into contact with a valve stop.
[0004] In order to maintain fuel pressure in the common rail, the
control valves in the pump are required to very frequently
pressurize fuel in the pumping chambers. For each rotation of the
pump camshaft, each control valve will be required to pressurize
fuel several times depending upon the number of lobes on the cam.
This means that the control valve member is being energized and
de-energized extremely frequently. Every time that the valve member
is de-energized, it impacts the valve seat under the action of the
spring. Over a long period of time, this impact between the valve
member and valve seat may damage the valve member. This may lead to
a shortening of valve life and deterioration of the seal effected
by the valve member when closed. Such seal deterioration may lead
to variation in fuel pressure in the pumping chamber and consequent
variation in overall pump performance.
[0005] It is an aim of the present invention to obviate or mitigate
one or more disadvantages associated with prior art devices and
methods.
SUMMARY OF THE INVENTION
[0006] According to a first aspect of the invention, there is
provided a pump comprising a first pumping chamber and a first
reciprocating plunger disposed within a first plunger bore so as to
reciprocate within the first pumping chamber. The pump includes a
first electrically actuated spill control valve adapted to open or
close fluid communication between the first pumping chamber and a
low pressure area. The pump also includes a controller adapted to
operate the first control valve for a first period of time
extending from a first time point occurring after the first plunger
passes bottom dead center to a second time point occurring before
the first plunger passes top dead center. The controller may also
be adapted to operate the control valve for a second period of time
extending from a third time point occurring between the second time
point and the passing of the first plunger through top dead center
to a fourth time point occurring after the first plunger has passed
top dead center.
[0007] According to a second aspect of the present invention, there
is provided an internal combustion engine including a pump
according to the first aspect of the present invention.
[0008] According to a third aspect of the present invention, there
is provided a method of pressurizing fluid in a pump, the method
comprising the steps of supplying low pressure fluid to a pumping
chamber and reciprocating a plunger within the pumping chamber so
as to force fluid from the pumping chamber. The fluid may be
returned from the pumping chamber through an electrically actuated
spill control valve. The control valve may be operated to
pressurize the fuel in the pumping chamber during a forward stroke
of the plunger. The pressurized fuel may be discharged through a
discharge port in communication with the pumping chamber. The
operating step may include operating the control valve for two
separate periods of time, a first period of time extending from a
first time point occurring after the plunger passes bottom dead
center to a second time point occurring before the plunger passes
top dead center, and a second period of time extending from a third
time point occurring between the second time point and the passing
of the plunger through top dead center to a fourth time point
occurring after the plunger has passed top dead center.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic illustration of a common rail fuel
injection system;
[0010] FIG. 2 is a front sectioned view of a variable discharge
pump suitable for use in the injection system of FIG. 1;
[0011] FIG. 3 is a side sectioned view of the pump of FIG. 2;
[0012] FIG. 4 is a detail view taken from the side view of FIG. 3
showing the control valve of the pump; and
[0013] FIG. 5 is a chart illustrating the operation of a spill
control valve forming part of the pump of FIGS. 2-4.
DETAILED DESCRIPTION
[0014] Referring to FIG. 1, a fuel system, generally designated 10,
is shown. The system 10 includes a number of fuel injectors 22,
each of which is connected to a high pressure fuel rail 20 via a
respective branch passage 21. The fuel rail 20 is supplied with
high pressure fuel from a variable discharge pump 16 which receives
low pressure fuel from a fuel tank 12 via a fuel transfer pump 14.
The fuel tank 12 is also connected to the injectors 22 by way of a
leak return passage 23. The system 10 is controlled via an
electronic controller, or control unit (ECU), 18. The ECU 18 is
connected to an electrical actuator 28 of the pump 16 via a control
communication line 29 and also connected to each injector 22 via
further communication lines (not shown). When in operation, control
signals from the ECU 18 control when and how much fuel from the
pump 16 is fed into the common rail 20, as well as when and for how
long the injectors 22 inject fuel.
[0015] FIGS. 2 and 3 show that the pump 16 includes a high pressure
outlet 30 fluidly connected to the high pressure rail 20 and an
inlet 33 fluidly connected to the fuel transfer pump 14. A supply
passage 43 connects the inlet 33 with first and second pumping
chambers 46,56. The pump 16 also includes a first plunger 45
adapted for reciprocating movement in the first pumping chamber 46
in a first barrel 44. Furthermore, the pump 16 includes a second
plunger 55 adapted for reciprocating movement in the second pumping
chamber 56 in a second barrel 54. The first and second barrels are
preferably formed in a common pump housing 40. A pair of cams 34
and 35 are operable to cause the plungers to reciprocate out of
phase with one another. In the illustrated embodiment, the cams
34,35 each have three lobes such that one of the plungers 45,55 is
undergoing a pumping stroke at about the time that one of the fuel
injectors 22 is injecting fuel. Thus, the cams 34,35 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.
[0016] When the first 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 area, or
gallery, 37 fluidly connected to the inlet 33. Similarly, when the
second 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 gallery 37. When the first
plunger 45 is undergoing its pumping stroke, fuel is displaced from
the pumping chamber 46 either into the low pressure gallery 37 via
a first portion 41 of a spill passage and spill control valve 38,
or into a high pressure gallery 39 past a first outlet check valve
47. Similarly, when the second plunger 55 is undergoing its pumping
stroke, fuel is displaced from the second pumping chamber 56 either
into the low pressure gallery 37 via a second portion 51 of a spill
passage and spill control valve 38, or into the high pressure
gallery 39 past a second outlet check valve 57.
[0017] Referring in particular to FIG. 4, only one of the pumping
chambers 46,56 is fluidly connected to spill control valve 38 at
any one time. These fluid connections are controlled by a shuttle
valve 80 which includes a ball valve member 81. The ball valve
member 81 is exposed to fluid pressure in both the first and second
pumping chambers 46,56. Because the plungers 45,55 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 the
ball valve member 81 back and forth to connect either first spill
passage 41 to the spill control valve 38, or the second spill
passage 51 to the spill control valve 38. Dependent on its
position, the ball valve 81 defines a portion of either the first
or second spill passage 41,51 which allows the pumping chambers
46,56 to share a common control valve 38. When the first plunger 45
is undergoing its pumping stroke, the second pumping chamber 56 is
refilled past the second inlet check valve 58. When the second
plunger 55 is undergoing its pumping stroke, the first pumping
chamber 46 is refilled past the first inlet check valve 48.
[0018] The spill control valve 38 includes a spill valve member 60
that includes a closing hydraulic surface 62. The spill valve
member 60 is normally biased downward towards its open position via
a biasing means, here represented by a biasing spring 64. The valve
member 60 rests upon a valve stop 63 when in its open position. The
spill valve member 60 can be moved upward to close by energizing an
electrical actuator 28. In the illustrated embodiment, the actuator
28 is a solenoid having an armature 36 adapted to move the spill
valve member 60. That said, those skilled in the art will
appreciate that the actuator 28 could take a variety of forms,
including piezo and/or piezo bender actuators.
[0019] FIG. 5 is a chart illustrating the operation and control of
the spill control valve 38 over one complete rotation of the pump
camshaft, i.e. the rotation of the camshaft over 360 degrees. The
ECU 18 monitors the rotational position of the camshaft and also
the angle of specific cams via sensors (not shown). The signals
generated by the sensors allow the ECU to accurately determine when
a specific plunger 45,55 is at its bottom dead center (BDC)
position. Lines A and B in the FIG. 5 chart illustrate the movement
of the first and second plungers, respectively, under the action of
the first and second cams 34,35, over a single rotation of the
camshaft. As the pump 16 has two plungers 45,55 and each of the
cams 34,35 has three lobes, the pump 16 is able to pump fuel six
times for each rotation of the camshaft. The lines C1 and C2
illustrate first and second control signals, respectively, fed to
the spill control valve 38 via the actuator 28 during the operation
of the pump. The first control signal C1 pulls the spill valve
member into a closed position against the biasing force of the
valve spring, while the second control signal C2 acts against the
bias of the spring to decelerate the opening valve and reduce the
impact of the valve member on the valve seat. The chart of FIG. 5
also shows the dwell D between the first and second signals C1,C2
and also the dwell d between the second signal C2 and the first
signal C1 of the subsequent pumping event.
INDUSTRIAL APPLICABILITY
[0020] The present device and method may be used in any fluid
system where there is a desire to control discharge using a pump
having reduced valve wear and damage. In particular, the present
device and method may be used with common rail fuel injection
systems. However, those skilled in the art will appreciate that the
present device and method may also be used in other hydraulic
systems that may or may not be associated with an internal
combustion engine.
[0021] Referring to FIG. 1, when the fuel system 10 is in
operation, the first and second cams 34,35 rotate, causing the
plungers 45,55 to reciprocate in their respective barrels 44,54 out
of phase with one another. When the first plunger 45 is undergoing
its pumping stroke, second plunger 55 will be undergoing its
retracting stroke. This action is exploited via ball valve 80 to
either connect the first pumping chamber 46 or the second pumping
chamber 56 to the spill control valve 38. As one of the plungers
begins its pumping stroke, fuel is initially displaced from the
pumping chamber through spill control valve 38 to the 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. The first control signal C1 lasts for a first period of
time extending from a first time point occurring after one of the
plungers passes bottom dead center (BDC) to a second time point
occurring before the plunger passes top dead center (TDC). During
this first time period, the spill valve member is closed and then
is stopped at the second time point as the increased pressure in
the pumping chamber is sufficient to hold the valve member 60
closed against the bias of the valve spring 64. In the dwell D
between the first and second control signals C1,C2, the advancing
stroke of the plunger continues to compress the fuel in the pumping
chamber until it reaches a sufficient pressure to be pushed past
the respective check valve 47,57 into the high pressure gallery 39
and into the common rail 20.
[0022] As the pressurized fuel is discharged through one of the
check valves 47,57, the pressure in the pumping chamber 46,56
rapidly drops. As a result, the forces on the valve member 60 are
now unbalanced, with the force of the valve spring 64 outweighing
the hydraulic forces on the lifting surface 62 of the valve member
60. The second control signal C2 is generated for a second period
of time extending from a third time point occurring after the
second time point (the end of first control signal C1) but before
the passing of the plunger through TDC, to a fourth time point
occurring after the plunger has passed TDC. In this way, the second
control signal C2 is generated just as the pressurized fuel is
discharged from the pumping chamber. The purpose of the second
control signal C2 is to partially counter the force of the spring
64. In this way, the second control signal C2 decelerates the valve
member as it returns towards the open position, ensuring that the
impact of the valve member 60 on its valve stop 63 is significantly
reduced compared with conventional arrangements in which the valve
returns to the open position unchecked under the force of the
spring 64.
[0023] It will be appreciated that the timing of the control
signals, and the first control signal C1 in particular, determines
what fraction of fuel displaced by the plungers enters the high
pressure gallery 39 and what fraction returns to the low pressure
gallery 37. This operation ensures that the pressure can be
maintained and controlled in the common rail. While one plunger is
advancing (pumping), the other plunger is retracting and drawing
low pressure fuel into its pumping chamber past one of the
respective inlet check valves 48,58.
[0024] By generating a second control signal, the pump of the
present invention ensures that wear and damage on the control valve
member is reduced compared with previous proposals for variable
discharge pumps. This will ensure that maintenance and replacement
of pumps according to the present invention will be less than at
present, with associated cost savings for users of such pumps. In
addition, with less wear and damage on the valve member, the
performance of the pump will be more consistent over its operating
life than is the case at the moment.
[0025] It will be understood by those skilled in the art that the
duration of the second control signal C2, i.e. the position of the
fourth time point, and the dwell d between the end of the second
control signal C2 and the beginning of the subsequent first control
signal C1, can be varied by the ECU. The ECU can be provided with a
receiving means which allows the ECU to receive data relating to
fluid pressurization parameters from an external device, e.g. an
engine speed sensor on an internal combustion engine. In addition,
reference data relating to fluid pressurization parameters can be
stored either by the ECU or by a data storage device connected to
the ECU. This allows the ECU to vary the fourth time point for
particular engine speeds (received data) and desired rail pressures
(stored data). In addition, the ECU can vary the dwell d depending
on data received for the external device.
[0026] Although the preferred embodiment of the pump described
above comprises a pair of pumping chambers with associated plungers
and plunger bores, it will be understood that the present invention
could be provided with only a single pumping chamber with an
associated plunger and plunger bore if desired.
[0027] Additionally, although the preferred embodiment of the
present invention described above includes a single spill control
valve opening and closing fluid communication between the pumping
chambers and the low pressure area, the present invention may be
modified to include a second spill control valve. In such an
arrangement, the present invention includes first and second
control valves opening and closing fluid communication between
their respective first and second pumping chambers and the low
pressure area. The controller is consequently adapted to operate
each of the first and second control valves for first and second
time periods dictated by the reciprocating movements of the
respective first and second plungers, in the manner described
above.
[0028] These and other modifications and improvements may be
incorporated without departing from the scope of the present
invention.
* * * * *