U.S. patent application number 11/521889 was filed with the patent office on 2007-03-29 for digital pump with multiple outlets.
This patent application is currently assigned to Sturman Industries, Inc.. Invention is credited to Jeffrey T. Gardner.
Application Number | 20070071609 11/521889 |
Document ID | / |
Family ID | 37894211 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070071609 |
Kind Code |
A1 |
Gardner; Jeffrey T. |
March 29, 2007 |
Digital pump with multiple outlets
Abstract
A pump system for coupling a positive displacement pump capable
of supplying flow sequentially to a number of different volumes at
different pressures. In some embodiments the pump output is coupled
to multiple volumes that may be at the same or different pressures.
The output of the pump is cycled between each such volume by on-off
valves to maintain the required pressure in each volume, with the
output of the pump being returned to its input when necessary to
vent excess flow capacity. A controller may be used to control the
on-off valves responsive to pressure sensors for each volume. In
other embodiments the output of the pump is through on-off valves
coupled to actuators as well as to a by-pass valve, and the valves
are operated at high speed and with a duty cycle to provide
controlled actuator velocities. Various embodiments are
disclosed.
Inventors: |
Gardner; Jeffrey T.;
(Woodland Park, CO) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Assignee: |
Sturman Industries, Inc.
|
Family ID: |
37894211 |
Appl. No.: |
11/521889 |
Filed: |
September 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60720642 |
Sep 26, 2005 |
|
|
|
Current U.S.
Class: |
417/38 |
Current CPC
Class: |
F15B 2211/427 20130101;
F15B 2211/71 20130101; F15B 2211/511 20130101; F15B 2211/455
20130101; F15B 11/16 20130101; F15B 2211/781 20130101; F04B 49/00
20130101; F15B 2211/41509 20130101; F15B 2211/411 20130101; F04B
23/00 20130101; F15B 2211/50536 20130101; F15B 2211/527
20130101 |
Class at
Publication: |
417/038 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Claims
1. A pump system comprising: a positive displacement pump having an
input and an output; a plurality of on-off valves each having an
input coupled to the output of the positive displacement pump; the
outputs of the plurality of on-off valves each being coupled to a
respective control volume to be pressurized; a bypass on-off valve
also having an input coupled to the output of the positive
displacement pump and having an output coupled to the input to the
positive displacement pump; the plurality of on-off valves being
sequenced so that the positive displacement pump is connected to
different control volumes at different times to provide the
necessary flow at a required pressure for each control volume; the
by-pass on-off valve routing any excess pump flow back to the input
to the positive displacement pump.
2. The pump system of claim 1 wherein one and only one of the
plurality of on-off valves or the bypass valve is on at any one
time.
3. The pump system of claim 2 wherein the turn off of one on-off
valve and the turn on of the next on-off valve are phased so that
one on-off valve is partially off as the next on-off valve is
partially on.
4. The pump system of claim 2 wherein the turn off of one on-off
valve and the turn on of the next on-off valve are phased to
maintain flow from the positive displacement pump without a
substantial pressure spike in the output of the positive
displacement pump.
5. The pump system of claim 1 wherein each control volume includes
a pressure sensor and wherein the plurality of on-off valves and
the bypass on-off valve are controlled by a controller, the
controller sequentially checking an output of each pressure sensor
and controlling the plurality of on-off valves and the bypass
on-off valve to provide the necessary flow at the required pressure
for each control volume.
6. The pump system of claim 5 wherein the controller is responsive
to at least one additional input.
7. The pump system of claim 5 wherein the pressure sensors are
pressure switches.
8. The pump system of claim 5 wherein the pressure sensors are
selected from the group consisting of linear and nonlinear pressure
sensors.
9. The pump system of claim 8 wherein the pressure sensors are
biased so as to only sense around the required pressures.
10. The pump system of clam 5 wherein the plurality of on-off
valves provide the necessary flow at the required pressure for each
control volume, each with a predetermined hysteresis around the
required pressure.
11. The pump system of claim 10 wherein the hysteresis is imposed
by the controller.
12. The pump system of claim 1 wherein the on-off valves are
solenoid operated spool valves
13. A pump system for controlling one or more hydraulic actuators
comprising: a positive displacement pump having a hydraulic fluid
pumping rate; a controller coupled to receive actuator velocity
control signals; a plurality of on-off valves; a bypass on-off
valve having an input coupled to an output of the positive
displacement pump and having an output coupled to an input to the
positive displacement pump; a first half of the plurality of on-off
valves each being configured to couple an output of the positive
displacement pump to a hydraulic actuator input; a second half of
the remaining plurality of on-off valves each being configured to
couple a hydraulic actuator input to a low pressure vent, wherein
each hydraulic actuator has a specific actuator velocity per unit
hydraulic fluid flow rate; the controller being configured to
sequentially and repetitively couple selected ones of the plurality
of on-off valves on and off with a duty cycle selected to provide a
fluid flow rate through the selected on-off valves to cause an
actuator velocity responsive to the actuator velocity control
signals.
14. The pump system of claim 13 wherein one and only one of the
first half of the plurality of on-off valves or the bypass valve is
on at any one time.
15. The pump system of claim 14 wherein the turn off of each of the
first half of the on-off valves and the by-pass valve and the turn
on of the next valve of the first half of the on-off valves and the
by-pass valve are phased so that one on-off valve is partially off
as the next on-off valve is partially on.
16. The pump system of claim 14 wherein the turn off of each of the
first half of the on-off valves and the by-pass valve and the turn
on of the next valve of the first half of the on-off valves and the
by-pass valve are phased to maintain flow from the positive
displacement pump without a substantial pressure spike in the
output of the positive displacement pump.
17. The pump system of claim 13 wherein the on-off valves are
solenoid operated spool valves
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 60/720,642 filed Sep. 26, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of pump
systems.
[0004] 2. Prior Art
[0005] A common method for dividing flow from a single pump is to
provide the required flow for all of the loads at the highest
required pressure and bleed the lower pressure flows from the high
pressure volume through valves to the lower pressure volumes.
Having to supply all of the flow at the highest required pressure,
rather than at the required pressure for each load, is power
inefficient. Also the power lost goes into the fluid being pumped,
and may require special cooling if excessive temperatures are to be
avoided. A more efficient alternative is to provide separate pumps
for each pressure, though this is less attractive from a
manufacturing and maintenance point of view.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a diagram of a pumping system in accordance with
the present invention.
[0007] FIG. 2 is a diagram of one stage of an exemplary multiple
actuator system that may be controlled by the system of FIG. 1.
[0008] FIG. 3 is a block diagram of an exemplary control system for
the pumping system of FIG. 1.
[0009] FIG. 4 is a block diagram of an exemplary control system for
the pumping system for an actuator system using one of more
actuators in accordance with FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The present invention is a fixed displacement pump capable
of supplying flow sequentially to a number of different volumes at
different pressures. Adding a valve or series of valves to the pump
outlet allows the pump to be sequentially connected to a number of
different control volumes, each at a different pressure. When the
pump is not connected to a control volume, it can be connected back
to a sump or to its own inlet. The percentage of time that the pump
spends connected to a particular volume can be utilized to regulate
the pressure in that control volume. Using this methodology, the
fixed displacement pump will on average look like a variable flow
pump to each of the control volumes.
[0011] There are two basic advantages to using this system, namely
hydraulic efficiency and mechanical simplicity. (The word
"hydraulic" as used herein is used in a general sense to mean a
liquid, such as conventional hydraulic fluid, engine oil, fuel
and/or other hydrocarbon and non-hydrocarbon liquids.) At any given
time, the pump is connected to only one control volume. The
pressure rise across the pump is equal to the control volume
pressure and the power required to drive the pump is proportional
to the pump flow rate times the pressure rise. As the valves are
sequenced and the pump is connected to different control volumes,
the pump supplies only the necessary flow at the required pressure
for each control volume. Any excess pump flow not used in any of
the pressurized control volumes is simply routed back to the tank
(and pump input) at a very low pressure. The system can be built
using very simple components, a fixed displacement pump and a
series of "on-off" ("on"=open and "off"=closed) valves. This
potentially replaces a variable displacement pump and a series of
pressure reducing valves. The possible valving combinations to
redirect the pump flow are numerous, and well within the skill of
one skilled in the art.
[0012] Thus the present invention uses a fixed displacement pump to
control pressures in multiple volumes simultaneously using valves
to sequentially connect the pump to each volume, as shown on FIG.
1. In some applications the pressures may be similar or the same.
For instance, the present invention could be used to provide
actuation pressure to multiple actuators to control the position of
the actuators, with actuator return being provided by any of
various means, such as by way of example, a spring, by gravity or
by the provision for hydraulic return also powered by the same
pump. One stage of an exemplary multiple actuator system so
controlled may be seen in FIG. 2.
[0013] The digital pump with multiple outlets of the present
invention may also be advantageously used to pressurize multiple
rails in engine applications. By way of example, in a diesel engine
designed to include a hydraulic engine valve actuation (HVA)
system, the HVA system may operate from one rail and the diesel
injectors may operate from a second rail at a substantially higher
pressure. The present invention may be used to pressurize both
rails in an energy efficient manner.
[0014] The controller for the system of FIG. 1 may be of a rather
conventional configuration such as the basic processor based
controller system of FIG. 3. The inputs to the controller are the
pressures in the various volumes (FIG. 1) and the outputs are the
control signals to valves 1 through n and to the bypass valve. Note
that the valves preferably should be operated so that only one
valve is kept open at any one time, but that two valves are
momentarily at least partially open on switching the pump outlet to
a different destination so that a high pressure spike is not
created and/or the possibility of damage to the pump by its
attempting to pump to a closed system is avoided. The underlap in
valve actuation is preferably chosen so that both a pressure spike
and backflow are minimized or eliminated. Also while the controller
typically cycles sequentially through the various pressure sensor
outputs to determine whether the pressure in the respective volume
is low, it does not necessarily actuate the valves in the same
sequence. By way of example, there may only be one volume that is
using the pressurized fluid at any one time, so that only one such
volume will need fluid replenishment, so that the respective valve
will be opened, and then closed and the bypass valve opened as the
respective target pressure is reached. If no volume needs fluid
replenishment, then the bypass valve will remain open, even though
the pressure sensors are being sequentially monitored. Also note
that tolerances may be set for the pressure in each volume, which
tolerances may be the same or different, volume to volume. By way
of example, one might want to keep the pressure in one volume
rather constant, say within 1%, for repeatability of the devices
serviced by that pressure, while the pressure in another volume
could vary substantially, say 10%, because that volume is only used
to actuate a non-critical actuator. Consequently the percentage
pressure drop in a volume to cause the respective valve to be
opened may be different for different volumes. One might even set
priorities between volumes, and still sequentially interrogate all
volumes. If a volume with a more critical pressure limit was found
to need fluid replenishment, then the output of the pump could be
changed to that volume, even if the prior volume being replenished
had not reached the shut off pressure for that volume. Thus while
pressure sensing is preferably a sequential process, pumping to the
various volumes may well not be a sequential process. Appropriate
control by the controller will allow use of the minimum size pump
possible to meet the overall fluid flow requirements of the
system.
[0015] The pressure sensors used may be linear or non-linear
sensors and may sense from zero pressure or be biased so as to only
sense around the respective target pressure or pressures, as
desired. In some applications, simple pressure switches may be
used, with or without the switches or the controller providing some
hysteresis or dead zone around the target pressure to avoid
unnecessary valve cycling (also perhaps useful when using other
pressure sensors). Also possible are the use of some linear and/or
nonlinear sensors and one or more pressure switches in the same
system, depending on the number of separate volumes to be
pressurized and the specific requirements thereof. If pressure
switches are used, the controller may monitor all switches
simultaneously as a multi-bit parallel input, and in the event of
more than one control volume being below the respective target
pressure, couple flow to each such volume on a predetermined
priority (predetermined order) basis.
[0016] Finally, it should be noted that the desired pressures, and
perhaps the pressure tolerances or other parameters such as which
of the n volumes are active at any time (need their pressure
maintained) may also be provided as other inputs to the controller,
as shown in FIG. 3. As one example, a parameter responsive to fluid
temperature may be used to vary the pressures maintained to
compensate for changes in fluid viscosity with temperature. As
another example, another input may be time or a time related
parameter, such as crankshaft angle in an engine system, so that
fluid pressures may be maintained before the fluid under pressure
is needed from the respective volume, but may be delayed at other
times to maintain other pressures in the system.
[0017] The control of a pump system like that of FIG. 2 may be
somewhat different, as shown in FIG. 4. Such a system typically may
include multiple hydraulic actuators of the general type shown in
FIG. 2, each controlled by an on-off Supply valve and an on-off
Vent valve as shown. Such an actuation system may be used when the
actuator return force is provided by some other source, such as by
way of example, by gravity, a spring or compressed air. Note that
in addition to the by-pass on-off valve, one half of the other
plurality of on-off valves are operated (on) one at a time and
phased so that two are partially on during the transition between
valves to limit or eliminate a pressure spike in the system. The
remaining on-off valves are coupled to a low pressure vent, and
each is preferably off before the respective actuator is coupled to
the pump output.
[0018] In other cases, a hydraulic return may also be provided for
some or all actuators in the system merely by duplicating the
control valve valving system for the actuator, but operative to
actuate the actuator in the opposite direction, the four control
valves being operated in pairs to vent one side of the actuator
piston and to pressurize the other side of the actuator piston to
cause actuator motion when desired. Venting of one side may precede
or be phased with the pressurization of the other side of the
actuator, but may not follow the pressurization of the other side
since one and only one on-off valve connected to the positive
displacement pump is on at any one time.
[0019] In the control system of FIG. 4, assume for simplicity, all
actuators are the same size, so all have the same linear velocity
for the same fluid flow rate (this is for convenience in the
explanation and not a limitation of the invention). Also assume
that the control inputs call for the operation of actuators 1 and
2, each at a rate of 3 feet per second, with all other actuators
remaining stationary. Also assume that the positive displacement
pump has a pumping rate equivalent to 10 feet per second for one
such actuator. To get the desired 3 feet per second velocity from
the first and second actuators and to hold all other actuators
stationary, the controller would hold all vent valves V vent closed
(off), and would cycle actuator valve Avalve#1 on and off, then
cycle actuator valve Avalve#2 on and off, then cycle the Bypass
valve on and off, then repeat this sequence. The desired average
velocities for actuators 1 and 2 are obtained by operating these
three valves with a relative on-time of 1, 1 and 4/3.
Alternatively, one might us a sequence of Avalve#1 on and off,
Bypass valve on and off, Avalve#2 on and off, Bypass valve on and
off, then repeat the sequence. Now the relative on times would be
1, 2/3, 1 and 2/3. Note that this type of control may be used for
control of a single actuator or multiple actuators in excess of two
as described. In the event, the Control inputs called for a
combined actuator motion exceeding the pumping rate of the fixed
displacement pump, priorities may be set so that higher priority
actuators receive most or all their flow rate needs at the expense
of lower priority actuators.
[0020] Using valves that are very fast, such as solenoid actuated
spool valves having a single solenoid, spring return or double
solenoid valves, the motion obtained is usually quite smooth and
the pressure fluctuations quite limited by the compressibility of
the fluid used and the elasticity of the hydraulic system, thus
simulating a constant velocity. On-off (Two way) valves generally
in accordance with U.S. Pat. No. 5,640,987 may be used, the
disclosure of which is hereby incorporated by reference, though the
latching feature need not be used, and/or one solenoid may be
replaced by a return spring.
[0021] If further smoothing is desired, normally some accumulator
effect may be added, such as by providing more elasticity to the
plumbing of the system.
[0022] Thus while certain preferred embodiments of the present
invention have been disclosed and described herein for purposes of
illustration and not for purposes of limitation, it will be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and scope of the invention.
* * * * *