U.S. patent application number 12/957094 was filed with the patent office on 2012-05-31 for hydraulic fan circuit having energy recovery.
Invention is credited to Jeffrey L. Kuehn, Bryan E. Nelson, Jeremy T. Peterson.
Application Number | 20120134848 12/957094 |
Document ID | / |
Family ID | 46126804 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120134848 |
Kind Code |
A1 |
Nelson; Bryan E. ; et
al. |
May 31, 2012 |
HYDRAULIC FAN CIRCUIT HAVING ENERGY RECOVERY
Abstract
A hydraulic fan circuit is disclosed. The hydraulic fan circuit
may have a primary pump, a high-pressure passage fluidly connected
to the primary pump, and a low-pressure passage fluidly connected
to the primary pump. The hydraulic fan circuit may also have at
least one accumulator in selective fluid communication with at
least one of the high- and low-pressure passages, a motor, and a
fan connected to the motor. The hydraulic fan circuit may further
have a fan isolation valve fluidly connected to the high- and
low-pressure passages. The fan isolation valve may be movable
between a flow-passing position at which the motor is fluidly
connected to the primary pump via the high- and low-pressure
passages, and a flow-blocking position at which the motor is
substantially isolated from the primary pump.
Inventors: |
Nelson; Bryan E.; (Lacon,
IL) ; Peterson; Jeremy T.; (Washington, IL) ;
Kuehn; Jeffrey L.; (Metamora, IL) |
Family ID: |
46126804 |
Appl. No.: |
12/957094 |
Filed: |
November 30, 2010 |
Current U.S.
Class: |
417/53 ; 417/286;
417/364 |
Current CPC
Class: |
F15B 2211/20561
20130101; F15B 2211/6336 20130101; F15B 2211/27 20130101; F15B
2211/20523 20130101; F15B 2211/625 20130101; F15B 2211/665
20130101; F15B 21/14 20130101; F15B 2211/31529 20130101; F15B
2211/6652 20130101; F01P 7/044 20130101; F15B 2211/633 20130101;
F15B 2211/20569 20130101; F15B 2211/305 20130101; F15B 2211/7058
20130101; E02F 9/226 20130101; F15B 2211/88 20130101 |
Class at
Publication: |
417/53 ; 417/364;
417/286 |
International
Class: |
F04B 49/06 20060101
F04B049/06; F04B 49/00 20060101 F04B049/00; F04B 35/00 20060101
F04B035/00 |
Claims
1. A hydraulic fan circuit, comprising: a primary pump; a
high-pressure passage fluidly connected to the primary pump; a
low-pressure passage fluidly connected to the primary pump; at
least one accumulator in selective fluid communication with at
least one of the high- and low-pressure passages; a motor; a fan
connected to the motor; and a fan isolation valve fluidly connected
to the high- and low-pressure passages, the fan isolation valve
being movable between a flow-passing position at which the motor is
fluidly connected to the primary pump via the high- and
low-pressure passages, and a flow-blocking position at which the
motor is substantially isolated from the primary pump.
2. The hydraulic fan circuit of claim 1, wherein the at least one
accumulator includes: a high-pressure accumulator associated with
the high-pressure passage; and a low-pressure accumulator
associated with the low-pressure passage.
3. The hydraulic fan circuit of claim 2, further including a
discharge valve in fluid communication with the high- and
low-pressure accumulators, the discharge valve being configured to:
selectively pass fluid from the primary pump to the high-pressure
accumulator and from the high-pressure accumulator to the primary
pump; and selectively pass fluid from the motor to the low-pressure
accumulator and from the low-pressure accumulator to the primary
pump.
4. The hydraulic fan circuit of claim 1, further including a
discharge valve in fluid communication with the at least one
accumulator and configured to selectively pass fluid from the
primary pump to the at least one accumulator and from the at least
one accumulator to the primary pump.
5. The hydraulic fan circuit of claim 4, wherein the at least one
accumulator is further configured to receive fluid from another
hydraulic circuit.
6. The hydraulic fan circuit of claim 1, wherein: the primary pump
is a variable displacement pump; the motor is a fixed displacement
motor; and the fan isolation valve is a two-position valve and
moved to the flow-blocking position during discharge of the at
least one accumulator.
7. The hydraulic fan circuit of claim 1, wherein: the primary pump
is a variable displacement pump; the motor is a variable
displacement motor; and the fan isolation valve is movable to any
position between the flow-passing and flow-blocking positions to
adjust an amount of fluid allowed to pass from the at least one
accumulator to the motor.
8. The hydraulic fan circuit of claim 7, further including: a motor
resolver in fluid communication with the high- and low-pressure
passages; and a motor displacement control valve in fluid
communication with the motor resolver and the motor, wherein the
motor resolver and the motor displacement control valve are
substantially isolated from the at least one accumulator and the
primary pump when the fan isolation valve is in the flow-blocking
position.
9. The hydraulic fan circuit of claim 1, further including a makeup
valve in fluid communication with the motor via the fan isolation
valve when the fan isolation valve is in the flow-blocking
position.
10. The hydraulic fan circuit of claim 1, wherein the motor is
allowed to free-spin when the fan isolation valve is in the
flow-blocking position.
11. The hydraulic fan circuit of claim 10, further including a
flywheel connected to the fan to increase a free-spin duration of
the fan.
12. A hydraulic fan circuit, comprising: a primary pump; a motor; a
fan connected to the motor; a closed circuit fluidly connecting the
primary pump to the motor; a high-pressure accumulator in selective
fluid communication with the closed circuit; a low-pressure
accumulator in fluid communication with the closed circuit; an
accumulator discharge valve in fluid communication with the high-
and low-pressure accumulators; a fan isolation valve fluidly
connected to the closed circuit and to the motor; and a controller
in communication with the accumulator discharge valve and the fan
isolation valve, the controller being configured to: regulate the
accumulator discharge valve to: selectively pass fluid from the
primary pump to the high-pressure accumulator and from the
high-pressure accumulator to the primary pump; and selectively pass
fluid from the motor to the low-pressure accumulator and from the
low-pressure accumulator to the primary pump; and regulate the fan
isolation valve to substantially isolate the motor from the primary
pump during discharge of the high-pressure accumulator.
13. The hydraulic fan circuit of claim 12, wherein the
high-pressure accumulator is further configured to receive fluid
from another hydraulic circuit.
14. A method of recovering energy from a hydraulic fan circuit,
comprising: pressurizing fluid with a pump; directing the
pressurized fluid to drive a fan motor; accumulating excess
pressurized fluid; selectively discharging accumulated fluid to
drive the pump; and substantially isolating the fan motor from the
pump during the discharging.
15. The method of claim 14, wherein accumulating excess pressurized
fluid includes accumulating excess pressurized fluid from the
pump.
16. The method of claim 15, wherein accumulating excess pressurized
fluid also includes accumulating fluid from another circuit.
17. The method of claim 14, further including allowing the fan
motor to free spin during substantial isolation from the pump.
18. The method of claim 14, further including providing makeup
fluid to the fan motor during free spinning.
19. The method of claim 14, further including adjusting pump
displacement to absorb a desired torque during accumulator
discharging.
20. The method of claim 14, wherein accumulating includes
accumulating high-pressure fluid from the pump for discharge to the
pump, and accumulating low-pressure fluid from the fan motor for
discharge to the pump.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to a hydraulic fan
circuit, and more particularly, to a hydraulic fan circuit having
energy recovery.
BACKGROUND
[0002] Engine-driven machines such as, for example, dozers,
loaders, excavators, motor graders, and other types of heavy
equipment typically include a cooling system that cools the
associated engine and other machine components below a threshold
that provides for longevity of the machines. The cooling system
consists of one or more air-to-air and/or liquid-to-air heat
exchangers that chill coolant circulated throughout the engine and
combustion air directed into the engine. Heat from the coolant or
combustion air is passed to air from a fan that is speed controlled
based on a temperature of the engine and based on a temperature of
an associated hydraulic system.
[0003] The cooling system fan is generally hydraulically powered.
That is, a pump driven by the engine draws in low-pressure fluid
and discharges the fluid at elevated pressures to a motor that is
connected to the fan. When a temperature of the engine is higher
than desired, the pump and motor work together to increase the
speed of the fan. When the temperature of the engine is low, the
pump and motor work together to decrease the speed of the fan and,
in some situations, even stop the fan altogether. Under some
conditions, fan rotation can even by reversed such that airflow
through the heat exchanger is also reversed to help dislodge any
debris that has collected in the heat exchanger.
[0004] Although effective at cooling the engine, it has been found
that the hydraulic circuit driving the cooling fan described above
and/or other hydraulic circuits of the same machine may have excess
capacity at times that is not utilized or even wasted. With
increasing focus on the environment, particularly on machine fuel
consumption, it has become increasingly important to fully utilize
all resources.
[0005] One attempt to improve hydraulic circuit efficiency is
described in U.S. Pat. No. 7,444,809 that issued to Smith et al. on
Nov. 4, 2008 ("the '809 patent"). Specifically, the '809 patent
describes a hystat system having an engine-driven pump coupled to a
motor in a closed circuit configuration. During periods of excess
pump capacity, pressurized fluid from the pump is stored in an
accumulator for later use. The store of pressurized fluid can then
be used to drive the pump and/or motor, thereby reducing a load on
the engine. Pressurized fluid from other hydraulic circuits of the
same machine, for example from tool actuator circuits, can also be
stored in the accumulator and selectively used to drive the pump
and motor and thereby further reduce fuel consumption of the
engine.
[0006] Although the system of the '809 patent may have improved
efficiency, it may also have limited applicability. That is, the
system provides no isolation of the motor during energy recovery
operations. In some applications, such as cooling fan drives, a fan
motor driven with accumulated fluid could be caused to operate at
undesired speeds as the pressure within the accumulator varies. In
addition, driving the fan motor when cooling is unnecessary can
waste energy and possibly over-cool the engine.
[0007] The disclosed hydraulic fan circuit is directed to
overcoming one or more of the problems set forth above and/or other
problems of the prior art.
SUMMARY
[0008] In one aspect, the present disclosure is directed to a
hydraulic fan circuit. The hydraulic fan circuit may include a
primary pump, a high-pressure passage fluidly connected to the
primary pump, and a low-pressure passage fluidly connected to the
primary pump. The hydraulic fan circuit may also include at least
one accumulator in selective fluid communication with at least one
of the high- and low-pressure passages, a motor, and a fan
connected to the motor. The hydraulic fan circuit may further
include a fan isolation valve fluidly connected to the high- and
low-pressure passages. The fan isolation valve may be movable
between a flow-passing position at which the motor is fluidly
connected to the primary pump via the high- and low-pressure
passages, and a flow-blocking position at which the motor is
substantially isolated from the primary pump.
[0009] In another aspect, the present disclosure is directed to
another hydraulic fan circuit. This hydraulic fan circuit may
include a primary pump, a motor, a fan connected to the motor, and
a closed circuit fluidly connecting the primary pump to the motor.
The hydraulic fan circuit may also include a high-pressure
accumulator in selective fluid communication with the closed
circuit, a low-pressure accumulator in fluid communication with the
closed circuit, an accumulator discharge valve in fluid
communication with the high- and low-pressure accumulators, and a
fan isolation valve fluidly connected to the closed circuit and to
the motor. The hydraulic fan circuit may further include a
controller in communication with the accumulator discharge valve
and the fan isolation valve. The controller may be configured to
regulate the accumulator discharge valve to selectively pass fluid
from the primary pump to the high-pressure accumulator and from the
high-pressure accumulator to the primary pump, and to selectively
pass fluid from the motor to the low-pressure accumulator and from
the low-pressure accumulator to the primary pump. The controller
may be further configured to regulate the fan isolation valve to
substantially isolate the motor from the primary pump during
discharge of the high-pressure accumulator.
[0010] In yet another aspect, the present disclosure is directed to
a method of recovering energy from a hydraulic fan circuit. The
method may include pressurizing fluid with a pump, directing the
pressurized fluid to drive a fan motor, and accumulating excess
pressurized fluid. The method may further include selectively
discharging accumulated fluid to drive the pump, and substantially
isolating the fan motor from the pump during the discharging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a pictorial illustration of an exemplary disclosed
excavation machine;
[0012] FIG. 2 is a schematic illustration of an exemplary disclosed
hydraulic fan circuit that may be utilized in conjunction with the
excavation machine of FIG. 1; and
[0013] FIG. 3 is a schematic illustration of another exemplary
disclosed hydraulic fan circuit that may be used in conjunction
with the excavation machine of FIG. 1.
DETAILED DESCRIPTION
[0014] FIG. 1 illustrates an exemplary machine 200 performing a
particular function at a worksite 210. Machine 200 may embody a
stationary or mobile machine, with the particular function being
associated with an industry such as mining, construction, farming,
transportation, power generation, oil and gas, or any other
industry known in the art. For example, machine 200 may be an earth
moving machine such as the excavator depicted in FIG. 1, in which
the particular function includes the removal of earthen material
from worksite 210 that alters the geography of worksite 210 to a
desired form. Machine 200 may alternatively embody a different
earth moving machine such as a motor grader or a wheel loader, or a
non-earth moving machine such as a passenger vehicle, a stationary
generator set, or a pumping mechanism. Machine 200 may embody any
suitable operation-performing machine.
[0015] Machine 200 may be equipped with multiple systems that
facilitate the operation of machine 200 at worksite 210, for
example a tool system 220, a drive system 230, and an engine system
240 that provides power to tool system 220 and drive system 230.
During the performance of most tasks, power from engine system 240
may be disproportionately split between tool system 220 and drive
system 230. That is, machine 200 may generally be either traveling
between excavation sites and primarily supplying power to drive
system 230, or parked at an excavation site and actively moving
material by primarily supplying power to tool system 220. Machine
200 generally will not be traveling at high speeds and actively
moving large loads of material with tool system 220 at the same
time. Accordingly, engine system 240 may be sized to provide enough
power to satisfy a maximum demand of either tool system 220 or of
drive system 230, but not both at the same time. Although
sufficient for most situations, there may be times when the total
power demand from machine systems (e.g., from tool system 220
and/or drive system 230) exceeds a power supply capacity of engine
system 240. Engine system 240 may be configured to recover stored
energy during these times to temporarily increase its supply
capacity. This additional supply capacity may also or alternatively
be used to reduce a fuel consumption of engine system 240 by
allowing for selective reductions in the power production of engine
system 240, if desired.
[0016] As illustrated in FIG. 2, engine system 240 may include a
heat engine 12, for example an internal combustion engine, equipped
with a hydraulic fan circuit 10. Hydraulic fan circuit 10 may
include a collection of components that are powered by engine 12 to
cool engine 12. Specifically, hydraulic fan circuit 10 may include
a primary pump 14 connected directly to a mechanical output 16 of
engine 12, a motor 18 fluidly connected to primary pump 14 by a
closed-loop circuit 22, and a fan 20 connected to motor 18. Engine
12 may drive primary pump 14 via mechanical output 16 to draw in
low-pressure fluid and discharge the fluid at an elevated pressure.
Motor 18 may receive and convert the pressurized fluid to
mechanical power that drives fan 20 to generate a flow of air. The
flow of air may be used to cool engine 12 directly and/or
indirectly by way of a heat exchanger (not shown).
[0017] Primary pump 14 may be an over-center, variable-displacement
or variable-delivery pump driven by engine 12 to pressurize fluid.
For example, primary pump 14 may embody a rotary or piston-driven
pump having a crankshaft (not shown) connected to engine 12 via
mechanical output 16 such that an output rotation of engine 12
results in a corresponding pumping motion of primary pump 14. The
pumping motion of primary pump 14 may function to draw in
low-pressure fluid expelled from motor 18 via a low-pressure
passage 24, and discharge the fluid at an elevated pressure to
motor 18 via a high-pressure passage 26. Low- and high-pressure
passages 24, 26 together may form closed circuit 22. Primary pump
14 may be dedicated to supplying pressurized fluid to only motor 18
via high-pressure passage 26 or, alternatively, may also supply
pressurized fluid to other hydraulic circuits associated with
machine 200 (e.g., to hydraulic circuits associated with tool
system 220, drive system 230, etc.), if desired. Similarly, primary
pump 14 may be dedicated to drawing low-pressure fluid from only
motor 18 via low-pressure passage 24 or, alternatively, may also
draw in low-pressure fluid from other hydraulic circuits of machine
200, if desired. It should be noted that, in some situations,
primary pump 14 and motor 18 may be operated in reverse direction
and, in these situations, the pressures within low- and
high-pressure passages 24, 26 may be reversed.
[0018] Motor 18 may include a fixed displacement, rotary- or
piston-type hydraulic motor movable by an imbalance of pressure
acting on a driven element (not shown), for example an impeller or
a piston. Fluid pressurized by primary pump 14 may be directed into
motor 18 via high-pressure passage 26 and returned from motor 18
via low-pressure passage 24. The direction of pressurized fluid to
one side of the driven element and the draining of fluid from an
opposing side of the driven element may create a pressure
differential across the driven element (not shown) that causes the
driven element to move or rotate. The direction and rate of fluid
flow through motor 18 may determine the rotational direction and
speed of motor 18 and fan 20, while the pressure imbalance of motor
18 may determine the torque output.
[0019] Fan 20 may be disposed proximate a liquid-to-air or
air-to-air heat exchanger (not shown) and configured to produce a
flow of air directed through channels of the exchanger for heat
transfer with coolant or combustion air therein. Fan 20 may include
a plurality of blades connected to motor 18 and be driven by motor
18 at a speed corresponding to a desired flow rate of air and/or a
desired engine coolant temperature. In one embodiment, a flywheel
28 may be connected to one of fan 20 and motor 18 to rotate
therewith. Flywheel 28 may embody a fixed inertia flywheel, a
variable inertia flywheel, or another type of flywheel known in the
art having one or more rotating masses that move in accordance with
a rotation of motor 18 and fan 20. The inertia of flywheel 28 may
be selected to increase a free-spinning time of fan 20 after
primary pump 14 has stopped driving motor 18. Under most
conditions, a typical closed circuit fan may stop spinning after
about 3 seconds or less, when no longer driven by a pump. Flywheel
28, however, may have an inertia great enough to cause fan 20 to
spin for at least 4 seconds after primary pump 14 has stopped
driving motor 18. In another embodiment, flywheel 28 may be
incorporated into fan 20 (i.e., fan 20 may be oversized to include
the inertia of flywheel 28 that causes it to spin for the at least
4 seconds).
[0020] Low- and high-pressure passages 24, 26 may be interconnected
via multiple different crossover passages. In the exemplary
embodiment, two different crossover passages interconnect low- and
high-pressure passages 24, 26, including a makeup/relief passage 30
and a pressure-limiting passage 32. Makeup/relief passage 30 may
provide makeup fluid to low- and/or high-pressure passages 24, 26
to help ensure that hydraulic fan circuit 10 remains full of fluid,
and also provide a leak path for high-pressure fluid within low-
and/or high-pressure passages 24, 26 such that damage to the
components of hydraulic fan circuit 10 may be avoided.
Pressure-limiting passage 32 may provide for pilot pressure control
associated with a displacement of primary pump 14.
[0021] One or more makeup valves 34, for example check valves, may
be located within makeup/relief passage 30 to selectively connect
the output from a charge pump 36 with low- and/or high-pressure
passages 24, 26 based on pressures of fluid in the different
passages. That is, when a pressure within low- and/or high-pressure
passage 24, 26 falls below a pressure of fluid discharged by charge
pump 36, makeup valve(s) 34 may open and allow fluid to pass from
charge pump 36 into the respective passage(s). Charge pump 36 may
be driven by engine 12 to rotate with primary pump 14 and draw in
fluid from a low-pressure sump 38 via a tank passage 40, and
discharge the fluid into makeup/relief passage 30 via a valve
passage 42.
[0022] One or more relief valves 44 may also be located within
makeup/relief passage 30. Relief valves 44 may be spring-biased and
movable in response to a pressure of low- and/or high-pressure
passages 24, 26 to selectively connect the respective passages with
a low-pressure passage 46, thereby relieving excessive fluid
pressures within low- and high-pressure passages 24, 26. An
additional spring-biased pressure relief valve 48 may be located
within low-pressure passage 46 and selectively moved by a pressure
within low-pressure passage 46 between flow-passing and
flow-blocking (shown in FIG. 2) positions such that a desired
pressure within low-pressure passage 46 may be maintained.
[0023] A resolver 50 may be disposed within pressure-limiting
passage 32 and associated with a pilot pressure limiter 52.
Resolver 50 may be configured to connect fluid from the one of low-
and high-pressure passages 24, 26 having the greater pressure with
pilot pressure limiter 52. In most instances, resolver 50 connects
the pressure from high-pressure passage 26 with pilot pressure
limiter 52 (shown in FIG. 2). However, when primary pump 14 and
motor 18 are operating in the reverse flow direction or during an
overrunning condition of motor 18, it may be possible for the
pressure within low-pressure passage 24 to exceed the pressure
within high-pressure passage 26. Under these conditions, resolver
50 may move to connect the pressure from low-pressure passage 24
with pilot pressure limiter 52. When the pressure of fluid passing
through resolver 50 exceeds a threshold limit, pilot pressure
limiter 52 may move from a flow-blocking position toward a
flow-passing position. It is contemplated that the threshold limit
of pilot pressure limiter 52 may be tunable, if desired, to adjust
a responsiveness or performance of hydraulic fan circuit 10.
[0024] Pilot pressure limiter 52 may be in fluid communication with
a pilot passage 54 that extends between charge pump 36 and a
displacement actuator 56 of primary pump 14. Specifically, pilot
pressure limiter 52 may be connected to pilot passage 54 via a
passage 58. When pilot pressure limiter 52 moves toward the
flow-passing position described above, pilot fluid from within
pilot passage 54 may be allowed to drain to low-pressure sump 38.
The draining of pilot fluid from pilot passage 54 may reduce a
pressure of fluid within pilot passage 54.
[0025] The pilot fluid in passage 54 may be selectively
communicated with displacement actuator 56 to affect a displacement
change of primary pump 14. Displacement actuator 56 may embody a
double-acting, spring-biased cylinder connected to move a
swashplate, a spill valve, or another displacement-adjusting
mechanism of primary pump 14. When pilot fluid of a sufficient
pressure is introduced into one end of displacement actuator 56,
displacement actuator 56 may move the displacement-adjusting
mechanism of primary pump 14 by an amount corresponding to the
pressure of the fluid. Pilot pressure limiter 52 may limit the
pressure within pilot passage 54 based on a pressure of fluid
within low- and high-pressure passages 24, 26 and, accordingly,
also limit the displacement of primary pump 14.
[0026] In some situations, it may be desirable to inhibit the
pressure limiting provided by pilot pressure limiter 52, for
example when an extreme displacement position of primary pump 14 is
desired. For this reason, a pressure override valve 59 may be
disposed within passage 58, between pilot pressure limiter 52 and
pilot passage 54. Pressure override valve 59 may be a
spring-biased, solenoid-actuated control valve that is movable
based on a command from a controller 62. Pressure override valve 59
may be movable between a flow-passing position (shown in FIG. 2) at
which pilot passage 54 is in fluid communication with pilot
pressure limiter 52 via passage 58, and a flow-blocking position at
which fluid communication via passage 58 is inhibited. Pressure
override valve 59 may be spring-biased toward the flow-passing
position.
[0027] A directional control valve 60 may be associated with
displacement actuator 56 to control what end of displacement
actuator 56 receives the pressurized pilot fluid and, accordingly,
in which direction (i.e., which of a displacement-increasing and a
displacement-decreasing direction) the displacement-adjusting
mechanism of primary pump 14 is moved by displacement actuator 56.
Directional control valve 60 may be a spring-biased,
solenoid-actuated control valve that is movable based on a command
from controller 62. Directional control valve 60 may move between a
first position at which a first end of displacement actuator 56
receives pressurized pilot fluid, and a second position at which a
second opposing end of displacement actuator 56 receives
pressurized pilot fluid. When the first end of displacement
actuator 56 is receiving pressurized pilot fluid (i.e., when
directional control valve 60 is in the first position), the second
end of displacement actuator 56 may be simultaneously connected to
low-pressure sump 38 via directional control valve 60. Similarly,
when the second end of displacement actuator 56 is receiving
pressurized pilot fluid (i.e., when directional control valve 60 is
in the second position), the first end of displacement actuator 56
may be simultaneously connected to low-pressure sump 38 via
directional control valve 60. One or more restrictive orifices 64
may be associated with pilot passage 54 to reduce pressure
fluctuations in the pilot fluid entering and exiting the ends of
displacement actuator 56 and, thereby, stabilize fluctuations in a
speed of pump displacement changes.
[0028] A pressure control valve 66 may also be associated with
pilot passage 54 and displacement actuator 56 and configured to
control movement of displacement actuator 56 by varying a pressure
of pilot passage 54. Pressure control valve 66 may be movable from
a first position (shown in FIG. 2) at which full charge pressure is
passed through directional control valve 60, toward a second
position at which some of the charge pressure is vented to
low-pressure sump 38 before reaching directional control valve 60
and displacement actuator 56. Pressure control valve 66 may be
movable from the first position against a spring bias toward the
second position based on a command from controller 62. It is
contemplated that pressure control valve 66 may be directly
controlled via a solenoid (shown in FIG. 2) or, alternatively,
pilot operated via a separate solenoid valve (not shown), as
desired. By selectively moving pressure control valve 66 to any
position between the first and second positions, a pressure of the
pilot fluid in communication with displacement actuator 56 and,
hence, a displacement of primary pump 14, may be controlled.
[0029] At least one accumulator may be associated with closed
circuit 22. In the embodiment of FIG. 2, two accumulators are
illustrated, including a low-pressure accumulator 68 and a
high-pressure accumulator 70. A low-pressure discharge passage 72
and a high-pressure discharge passage 74 may extend from low- and
high-pressure accumulators 68, 70, respectively, to a discharge
control valve 76. A pressure relief valve 78 may be associated with
low-pressure discharge passage 72, if desired, to selectively
relieve fluid from low-pressure accumulator 68 to low-pressure sump
38 and thereby maintain a desired pressure within low-pressure
accumulator 68. Discharge control valve 76 may be fluidly connected
to low- and high-pressure passages 24, 26 by way of passages 80 and
82 respectively.
[0030] Discharge control valve 76 may be a double-acting,
spring-biased, solenoid-controlled valve that is movable between
three distinct positions based on a command from controller 62. In
the first position (shown in FIG. 2), fluid flow through discharge
control valve 76 may be inhibited. In the second position, fluid
may be allowed to pass between low-pressure accumulator 68 and
low-pressure passage 24 and between high-pressure accumulator 70
and high-pressure passage 26. In the third position, fluid may be
allowed to pass between low-pressure accumulator 68 and
high-pressure passage 26 and between high-pressure accumulator 70
and low-pressure passage 24. Discharge control valve 76 may be
spring-biased to the first position.
[0031] Low- and high-pressure accumulators 68, 70 may be in fluid
communication with pilot passage 54. Specifically, a fill passage
81 may fluidly connect each of low- and high-pressure discharge
passages 72, 74 to pilot passage 54. A check valve 83 may be
disposed within fill passage 81 between pilot passage 54 and each
of low- and high-pressure accumulators 68, 70 to help ensure a
unidirectional flow of fluid from charge pump 36 into low- and
high-pressure accumulators 68, 70.
[0032] High-pressure accumulator 70 may also be in fluid
communication with another hydraulic circuit 100 that forms a
portion of, for example, tool system 220, drive system 230, or
another system of machine 200. In particular, an auxiliary supply
passage 102 may fluidly connect hydraulic circuit 100 to
high-pressure accumulator 70 to fill high-pressure accumulator 70
with waste or excess fluid having an elevated pressure. A check
valve 104 and a restrictive orifice 106 may be disposed within
auxiliary supply passage 102 to help provide for a unidirectional
flow of fluid with damped oscillations from hydraulic circuit 100
into high-pressure accumulator 70. A sensor 108, for example a
pressure sensor, temperature sensor, viscosity sensor, etc., may be
associated with auxiliary supply passage 102 to provide a signal to
controller 62 indicative of a fluid parameter of auxiliary supply
passage 102 and/or high-pressure accumulator 70. Hydraulic circuit
100 may include a tool actuation circuit, a transmission circuit, a
brake circuit, a steering circuit, or any other machine circuit
known in the art.
[0033] During accumulator discharge, as will be described in
greater detail below, it may be beneficial to substantially isolate
motor 18 from low- and high-pressure passages 24, 26 (i.e., to
substantially block direct fluid flow to motor 18 via low- and
high-pressure passages 24, 26). For this reason, a fan isolation
valve 84 may be fluidly connected to low- and high-pressure
passages 24, 26, between motor 18 and low- and high-pressure
accumulators 68, 70. Fan isolation valve 84 may be a spring-biased,
solenoid-controlled valve that is movable between two distinct
positions based on a command from controller 62. In the first
position (shown in FIG. 2), fluid may be allowed to flow through
fan isolation valve 84 to motor 18 via low- and high-pressure
passages 24, 26. In the second position, fluid flow through fan
isolation valve 84 may be inhibited. Fan isolation valve 84 may be
spring-biased to the first position.
[0034] When motor 18 is isolated by fan isolation valve 84 (i.e.,
when fan isolation valve 84 is in the second position), fluid may
still circulate through motor 18, and fan 20 may still be spinning.
To help control fluid temperatures during this time, hydraulic fan
circuit 10 may include a motor flushing valve 86 and a pair of
check valves 88 in fluid communication with a motor makeup valve
90. Motor flushing valve 86 may be in fluid communication with
isolated portions of low- and high-pressure passages 24, 26, and
configured to move between three positions based on the pressures
of fluid within these passages. In the first position (shown in
FIG. 2), fluid flow from low- and high-pressure passages 24, 26 to
low-pressure sump 38 may be inhibited. When a pressure difference
occurs between low- and high-pressure passages 24, 26, motor
flushing valve 86 may move to the second or third positions to
remove a small volume of high-temperature fluid to be replaced with
low-temperature oil. Check valves 88 may be located within a
branching passage 92, between motor makeup valve 90 and low- and
high-pressure passages 24, 26. Based on an imbalance of pressure
between branching passage 92 and low- or high-pressure passages 24,
26, check valves 88 may open to allow additional fluid into the
isolated portion of hydraulic fan circuit 10.
[0035] Motor makeup valve 90 may be disposed between
pressure-limiting passage 32 and branching passage 92, and movable
based on a pressure of fluid within pressure-limiting passage 32 to
selective allow fluid into branching passage 92. In particular,
fluid in a low-pressure makeup passage 94 connected to
pressure-limiting passage 32 at a low-pressure side of resolver 50
may push on one end of motor makeup valve 90, while fluid in a
high-pressure makeup passage 96 connected to pressure-limiting
passage 32 at a high-pressure side of resolver 50 may push on an
opposing end of motor makeup valve 90. The one of low- and
high-pressure makeup passages 94, 96 having the higher pressure at
a given point in time may urge motor makeup valve 90 to a position
at which fluid from the lower pressure passage flows into branching
passage 92. Motor makeup valve 90 may be spring biased toward a
position at which fluid from both the low- and high-pressure makeup
passages 94, 96 passes through to branching passage 92.
[0036] Controller 62 may embody a single or multiple
microprocessors, field programmable gate arrays (FPGAs), digital
signal processors (DSPs), etc. that include a means for controlling
an operation of hydraulic fan circuit 10 in response to signals
received from sensor 108, one or more engine sensors 110, a pump
displacement sensors 112, and a motor speed sensor 113. Numerous
commercially available microprocessors can be configured to perform
the functions of controller 62. It should be appreciated that
controller 62 could readily embody a microprocessor separate from
that controlling other machine-related functions, or that
controller 62 could be integral with a machine microprocessor and
be capable of controlling numerous machine functions and modes of
operation. If separate from the general machine microprocessor,
controller 62 may communicate with the general machine
microprocessor via datalinks or other methods. Various other known
circuits may be associated with controller 62, including power
supply circuitry, signal-conditioning circuitry, actuator driver
circuitry (i.e., circuitry powering solenoids, motors, or piezo
actuators), and communication circuitry.
[0037] Controller 62 may be in communication with valves 59, 60,
66, 76, and 84 to control operations of hydraulic fan circuit 10
during at least two distinct modes of operation based on input from
sensors 108, 110, 112, and 113. The modes of operation may include
a normal mode during which primary pump 14 drives motor 18 to cool
engine 12, and an energy recovery mode during which motor 18 drives
primary pump 14 to recover energy directed back to engine 12. These
modes of operation will be described in more detail in the
following section to further illustrate the disclosed concepts
[0038] FIG. 3 illustrates another embodiment of hydraulic fan
circuit 10. In this embodiment, the fixed displacement motor 18
described above may be replaced with a variable displacement motor
114 having a displacement actuator 116 that controls a displacement
of motor 114, a displacement control valve 118 that controls
movement of displacement actuator 116, and a resolver 120 that
controls fluid communication between low- and high-pressure
passages 24, 26 and displacement control valve 118. Resolver 120
may be movable to allow fluid from the one of low- and
high-pressure passages 24, 26 having the higher pressure at a given
point in time to communicate with displacement control valve 118.
Displacement control valve 118 may be movable based on a command
from controller 62 between a first position at which all fluid from
resolver 120 passes to displacement actuator 116, and a second
position at which some or all of the fluid from resolver 120 is
blocked before it reaches displacement actuator 116. Movement of
displacement control valve 118 between the first and second
positions may affect a pressure of the fluid acting on displacement
actuator 116 and, subsequently, movement of displacement actuator
116. Displacement actuator 116 may be a single-acting,
spring-biased cylinder configured to adjust a displacement of motor
114 when exposed to fluid of a particular pressure. Motor 114, by
having an adjustable displacement, may provide additional
functionality during accumulator discharge not otherwise available
with a fixed-displacement motor, as will be described in more
detail below. It is contemplated that motor 114 may be an
over-center motor, if desired.
INDUSTRIAL APPLICABILITY
[0039] The disclosed hydraulic fan circuit may be applicable to any
heat engine where cooling and energy recovery is desired. The
disclosed hydraulic fan circuit may provide for energy recovery
from any machine circuit through the selective use of accumulator
storage and discharge. Operation of hydraulic fan circuit 10 will
now be described.
[0040] During the normal mode of operation, engine 12 may drive
primary pump 14 to rotate and pressurize fluid. The pressurized
fluid may be discharged from primary pump 14 into high-pressure
passage 26 and directed into motor 18. As the pressurized fluid
passes through motor 18, hydraulic power in the fluid may be
converted to mechanical power used to rotate fan 20 and flywheel
28. As fan 20 rotates, a flow of air may be generated that
facilitates cooling of engine 12. Fluid exiting motor 18, having
been reduced in pressure, may be directed back to primary pump 14
via low-pressure passage 24 to repeat the cycle.
[0041] The fluid discharge direction and displacement of pump 14
during the normal mode of operation may be regulated based on
signals from sensors 108, 110, 112, and/or 113, for example based
on an engine speed signal, an engine temperature signal, a motor
speed signal, a pump displacement signal, an accumulator pressure
signal, and/or another similar signal. Controller 62 may receive
these signals and reference a corresponding engine speed, engine
temperature, pump displacement angle, motor speed, accumulator
pressure, or other similar parameter with one or more lookup maps
stored in memory to determine a desired discharge direction and
displacement setting of primary pump 14 and a corresponding
rotation direction and speed of fan 20. Controller 62 may then
generate appropriate commands to be sent to directional control
valve 60 and pressure control valve 66 to affect corresponding
adjustments to the displacement of primary pump 14.
[0042] Low- and/or high-pressure accumulators 68, 70 may be charged
during the normal mode of operation in a least three different
ways. For example, when primary pump 14 is driven to pressurize
fluid, any excess fluid not consumed by motor 18 may fill
high-pressure accumulator 70 via discharge control valve 76, when
discharge control valve 76 is in the second position. Similarly,
fluid exiting motor 18 may fill low-pressure accumulator 68. Low-
or high-pressure accumulators 68, 70 may only be filled while
discharge control valve 76 is in the second position and pressures
within low- or high-pressure passages 24, 26 are greater than
pressures within low- or high-pressure accumulators 68, 70,
respectively. Otherwise, low- or high-pressure accumulators 68, 70
may discharge fluid into low- or high-pressure passages 24, 26 when
discharge control valve 76 is moved to the second position. The
movement of discharge control valve 76 may be closely regulated
based at least in part on the signal provided by pressure sensor
108, such that low- and high-pressure accumulators 68, 70 may be
charged and discharged at the appropriate times. It should be noted
that only one of low- and high-pressure accumulators 68, 70 may be
filled at a time, while the other of low- and high-pressure
accumulators 68, 70 will be discharging, and vice versa.
[0043] Alternatively or additionally, low- or high-pressure
accumulators 68, 70 may be continuously charged via charge pump 36.
Specifically, at any time during normal operation, when a pressure
of fluid from charge pump 36 is greater than pressures within low-
or high-pressure accumulators 68, 70, fluid may be passed from
charge pump 36, through fill passage 81, and past check valves 83
into the respective low- or high-pressure accumulator 68, 70.
Pressure relief valve 78 may help ensure that low-pressure
accumulator 68 does not over-pressurize during charging by charge
pump 36. Again, it should be noted that only one of low- and
high-pressure accumulators 68, 70 may be fill or discharge at a
time.
[0044] High-pressure accumulator 70 may also be charged by
hydraulic circuit 100. That is, at any time during normal
operations, when a pressure of fluid from hydraulic circuit 100 is
greater than a pressure within high-pressure accumulator 70, fluid
may be passed from circuit 100, through auxiliary supply passage
102, and past check valve 104 into high-pressure accumulator
70.
[0045] When the signal from engine sensor 110 indicates that
sufficient cooling has been obtained (i.e., when the demand for
cooling air flow has been reduced) and fan 20 may be slowed or even
stopped, controller 62 may implement the energy recovery mode of
operation. During the energy recovery mode of operation, controller
62 may command fan isolation valve 84 to isolate motor 18 from
primary pump 14, and then command discharge control valve 76 to
move to one of the second and third positions depending on the
desired flow direction of primary pump 14. At about this same time,
controller 62 may command override valve 59 to move to the
flow-blocking position and also command pressure control valve 66
to begin destroking primary pump 14. When the appropriate valve
commands have been issued, fluid from within one of low- or
high-pressure accumulators 68, 70 may discharge into low- or
high-pressure passages 24, 26, respectively, via passages 72, 74,
discharge control valve 76, and passages 80, 82, thereby driving
primary pump 14 as a motor. By driving primary pump 14, hydraulic
power from the accumulated fluid may be converted to mechanical
power directed into engine 12 via mechanical output 16. This power
assist may help to increase a power supply capacity and/or decrease
a fuel consumption of engine 12 during the energy recovery mode of
operation.
[0046] During discharge of one of low- or high-pressure
accumulators 68, 70, while motor 18 is isolated from primary pump
14, fan 20 may continue to spin. As described above, fan 20, if
equipped with flywheel 28 or oversized to integrate the mass of
flywheel 28, may spin for an extended period of time without motor
18 being driven. In one example, the extended period of time may be
at least 4 seconds. In this manner, a significant amount of engine
cooling may still be possible during discharge of low- or
high-pressure accumulators 68, 70, and the speed of motor 18 may be
substantially unaffected by the changing fluid pressures within the
accumulators. In addition, energy from the accumulated fluid may
not be wasted on unnecessarily driving motor 18.
[0047] It is contemplated that accumulator discharge could
alternatively occur without complete motor isolation, if desired.
Specifically, fan isolation valve 84 could be controlled to move to
any position between the first and second positions described above
such that a desired amount of pressurized fluid from high-pressure
accumulator 70 passes through and drives motor 114 (referring to
the embodiment of FIG. 2), while the remainder of the accumulated
fluid passes through and drives primary pump 14. In order to
provide for a desired motor/fan speed during accumulator discharge,
however, while pressures within high-pressure accumulator 70 are
changing (i.e., decreasing), the displacement of motor 114 may be
selectively adjusted based on the fluid pressure signal from sensor
108 and/or based on the motor speed signal from sensor 113.
[0048] The disclosed hydraulic fan circuit may be relatively
inexpensive and provide multiple levels of energy recovery. In
particular, because the hydraulic fan circuit largely utilizes
existing components to recover otherwise wasted energy, the cost of
the system may remain low. Further, because low- and high-pressure
accumulators 68, 70 can fill with fluid from different sources and
discharge in different ways, an amount of energy recovery may be
increased.
[0049] It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed hydraulic
fan circuit. For example, although the disclosed pumps and motors
are described as being variable and fixed displacement or variable
and variable displacement type devices, respectively, it is
contemplated that the disclosed pumps and motors may alternatively
both be fixed displacement type devices, if desired. Other
embodiments will be apparent to those skilled in the art from
consideration of the specification and practice of the disclosed
hydraulic fan circuit. It is intended that the specification and
examples be considered as exemplary only, with a true scope being
indicated by the following claims and their equivalents.
* * * * *