U.S. patent application number 15/318031 was filed with the patent office on 2017-05-04 for energy recovery system for off-highway vehicles with hydraulic transformer coupled to transmission power take-off.
The applicant listed for this patent is EATON CORPORATION. Invention is credited to Per William DANZL, Chad Anthony LARISH, Michael Berne RANNOW, Meng WANG.
Application Number | 20170121942 15/318031 |
Document ID | / |
Family ID | 54834223 |
Filed Date | 2017-05-04 |
United States Patent
Application |
20170121942 |
Kind Code |
A1 |
DANZL; Per William ; et
al. |
May 4, 2017 |
ENERGY RECOVERY SYSTEM FOR OFF-HIGHWAY VEHICLES WITH HYDRAULIC
TRANSFORMER COUPLED TO TRANSMISSION POWER TAKE-OFF
Abstract
An energy conserving hydraulic system for a mobile work machine
includes a prime mover, a drivetrain, a baseline hydraulic system,
a power-take-off, a transformer, a work implement, and an
accumulator. The drivetrain may include an automated manual
transmission (AMT) that is rotationally coupled to the prime mover
and the power-take-off. The baseline hydraulic system is powered by
the prime mover and includes a first hydraulic circuit. The
transformer is hydraulically coupled to second and third hydraulic
circuits. The work implement is actuated by an actuator that is
adapted to be simultaneously hydraulically coupled to the first and
the second hydraulic circuits. The power-take-off is adapted to
exchange shaft power with the transmission. A clutch selectively
rotationally couples the transmission and the power-take-off. The
accumulator is hydraulically coupled to the second hydraulic
circuit. The second hydraulic circuit is hydraulically coupled to a
first rotating group of the hydraulic transformer, and a third
hydraulic circuit is hydraulically coupled to a second rotating
group of the hydraulic transformer.
Inventors: |
DANZL; Per William; (Edina,
MN) ; RANNOW; Michael Berne; (Eden Prairie, MN)
; WANG; Meng; (Eden Prairie, MN) ; LARISH; Chad
Anthony; (Minnetonka, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EATON CORPORATION |
Cleveland |
OH |
US |
|
|
Family ID: |
54834223 |
Appl. No.: |
15/318031 |
Filed: |
June 10, 2015 |
PCT Filed: |
June 10, 2015 |
PCT NO: |
PCT/US2015/035010 |
371 Date: |
December 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62010446 |
Jun 10, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/2267 20130101;
E02F 9/202 20130101; E02F 9/2253 20130101; B60K 2025/065 20130101;
B60K 25/06 20130101; E02F 9/2217 20130101; B60K 2025/026 20130101;
E02F 9/2029 20130101; B60K 25/00 20130101; B60Y 2200/415
20130101 |
International
Class: |
E02F 9/22 20060101
E02F009/22; B60K 25/06 20060101 B60K025/06; E02F 9/20 20060101
E02F009/20 |
Claims
1. A hydraulic system for a mobile work machine comprising: a prime
mover; a drivetrain including a transmission, the transmission
rotationally coupled to the prime mover; a baseline hydraulic
system powered by the prime mover, the baseline hydraulic system
including a first hydraulic circuit; a second hydraulic circuit
including a hydraulic transformer; and a work implement actuated by
an actuator; wherein the actuator is adapted to be simultaneously
hydraulically coupled to the first hydraulic circuit and the second
hydraulic circuit.
2. The hydraulic system of claim 1, wherein the transmission is an
automated manual transmission (AMT).
3. The hydraulic system of claim 1, further comprising a
power-take-off adapted to exchange shaft power with the
transmission, wherein the hydraulic transformer is rotationally
coupled to the power-take-off.
4. The hydraulic system of claim 3, further comprising a clutch
adapted to selectively rotationally couple the transmission and the
power-take-off.
5. The hydraulic system of claim 1, further comprising an
accumulator hydraulically coupled to the second hydraulic
circuit.
6. The hydraulic system of claim 5, further comprising a third
hydraulic circuit, wherein the second hydraulic circuit is
hydraulically coupled to a first rotating group of the hydraulic
transformer, and wherein the third hydraulic circuit is
hydraulically coupled to a second rotating group of the hydraulic
transformer.
7. The hydraulic system of claim 1, further comprising: a
directional control valve of the first hydraulic circuit adapted to
selectively actuate the actuator, the directional control valve
providing a first valve position feedback; a mode valve of the
second hydraulic circuit adapted to selectively actuate the
actuator, the mode valve providing a second valve position
feedback; and a controller adapted to coordinate actuation of the
actuator using the first valve position feedback and the second
valve position feedback.
8. A method of supplying hydraulic power to an actuator of a work
machine, the method comprising: receiving an operator input signal
from an operator input with an electronic control unit; processing
the operator input signal to determine a desired velocity and/or a
desired force of the actuator; receiving an actuator pressure
signal of an actuator pressure with the electronic control unit;
calculating an actuator flow requirement and/or an actuator
pressure requirement that satisfies the desired velocity and/or the
desired force of the actuator, respectively; allocating a first
portion of the actuator flow requirement to a baseline hydraulic
circuit; allocating a second portion of the actuator flow
requirement to a pump-motor of a hydraulic transformer; and
controlling a first valve position of a first proportional valve
and a second valve position of a second proportional valve and
thereby implementing flow sharing according to the allocating of
the first portion and the second portion of the actuator flow
requirement.
9. The method of claim 8, wherein the calculating of the actuator
flow requirement includes mapping the operator input signal to an
output of a conventional work machine.
10. The method of claim 8, further comprising: receiving an
accumulator pressure signal with the electronic control unit; and
setting a swash plate angle based on the accumulator pressure
signal.
11. The method of claim 8, wherein the first portion of the
actuator flow requirement is zero.
12. The method of claim 8, wherein the second portion of the
actuator flow requirement is zero.
13. The method of claim 8, wherein the controlling of the first
valve position includes measuring a spool position of the first
proportional valve and feeding back the measured spool position in
a feedback loop.
14. A method of recovering energy from an actuator of a work
machine, the method comprising: receiving an operator input signal
from an operator input with an electronic control unit; processing
the operator input signal to determine a desired velocity of the
actuator; receiving an actuator pressure signal of an actuator
pressure with the electronic control unit; calculating an actuator
flow requirement that satisfies the desired velocity of the
actuator; allocating a first portion of the actuator flow
requirement to a baseline hydraulic circuit; allocating a second
portion of the actuator flow requirement to a pump-motor of a
hydraulic transformer; and controlling a first valve position of a
first proportional valve and a second valve position of a second
proportional valve and thereby implementing flow sharing according
to the allocating of the first portion and the second portion of
the actuator flow requirement.
15. The method of claim 14, wherein the first portion of the
actuator flow requirement is zero.
16. The method of claim 14, wherein the second portion of the
actuator flow requirement is zero.
17. The method of claim 14, wherein the controlling of the first
valve position includes measuring a spool position of the first
proportional valve and feeding back the measured spool position in
a feedback loop.
18. A method of supplying hydraulic power to propel a work machine,
the method comprising: receiving an operator input signal from an
operator input with an electronic control unit; processing the
operator input signal to determine a desired velocity of the work
machine; receiving a first pump-motor pressure signal of a first
pump-motor with the electronic control unit; allocating a first
portion of the power requirement to an internal combustion engine;
and allocating a second portion of power requirement to a hydraulic
transformer.
19. The method of claim 18, wherein the first portion of the power
requirement is zero.
20. The method of claim 18, wherein the second portion of the power
requirement is zero.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is being filed on Jun. 10, 2015, as a PCT
International Patent application and claims priority to U.S. Patent
Application Ser. No. 62/010,446 filed on Jun. 10, 2014, the
disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND
[0002] Hybrid hydraulic systems have been developed to improve fuel
economy and reduce emissions for off-highway machines (i.e.,
off-highway vehicles). Such hybrid hydraulic systems typically
include an energy storing device that may store excess energy from
a prime mover and/or store energy from an actuator when the
actuator is in an overrunning situation. The energy storing device
may also supply energy to the actuators and thereby avoid using
energy from the prime mover. The actuators may include hydraulic
cylinders and/or pump/motors used to actuate and/or drive work
implements. The actuators may further include drive pump/motors
used to propel a mobile work machine. The actuators may further
include one or more hydraulic cylinders and/or pump/motors used to
steer the mobile work machine. The energy storing device may
include a hydraulic accumulator.
SUMMARY
[0003] One aspect of the present disclosure relates to a hydraulic
circuit architecture for mobile work machines (e.g., off-highway
vehicles) that provides a hydraulic hybrid system. The hydraulic
hybrid system may improve fuel economy, reduce emissions, and/or
improve productivity of the mobile work machine. The hydraulic
hybrid system may be less expensive than comparable electric hybrid
systems known in the art. The hydraulic hybrid system may be
suitable for use with wheel loaders and/or backhoe loaders.
[0004] Another aspect of the present disclosure relates to
combining a hydraulic transformer, a flow control valve subsystem,
and a high pressure hydraulic accumulator. The hydraulic
transformer enables energy to be supplied and/or recovered at an
extended range of pressures, and the hydraulic accumulator may both
store and release the energy. In certain embodiments, the hydraulic
circuit architecture recovers energy from lift and/or tilt
cylinders as the lift and/or tilt cylinders are moving downward,
aided by gravity. In certain embodiments, braking energy from a
power train of the mobile work machine may be recovered. The energy
may be stored in the hydraulic accumulator and later be used for a
variety of functions that increase productivity, increase fuel
economy, or both. When increasing productivity, the stored energy
may be used to augment the prime mover and thereby serve as a
secondary power source to reduce cycle time by increasing
velocities of various work circuit services. The stored energy may
be used to increase acceleration of the mobile work machine power
train. In embodiments where the hydraulic circuit architecture
increases fuel economy, energy may be both stored and released to
level engine power requirements. By leveling the engine power
requirements, the engine may be run at an optimum configuration, in
terms of fuel efficiency (e.g., at an engine rotational speed and
an engine torque output that are optimized for fuel
efficiency).
[0005] The hydraulic transformer may enable direct engine leveling.
During portions of a duty cycle with low average power
requirements, a first pump-motor of the transformer may operate as
a pump and thereby charge the accumulator. The hydraulic circuit
includes an accumulator isolation valve that is open and may
further include an accumulator bleed valve that is closed during
the charging of the accumulator. During portions of the duty cycle
with high average power, the energy stored in the accumulator can
be directly supplied to a power take-off shaft (i.e., a PTO shaft)
by using the first pump-motor of the transformer as a motor. By
receiving and delivering energy to the PTO shaft, the prime mover
may be operated in an optimum efficiency region of an operating
range of the prime mover. The direct engine leveling may allow
engine downsizing thereby allowing recovery of at least some of the
costs of the hydraulic system. Engine downsizing may further allow
original equipment manufacturers (i.e., OEMs) to comply with
various emissions and/or efficiency regulations (e.g., Tier 4
regulations).
[0006] To achieve practical operating characteristics, accurate
flow sharing may be required. The accurate flow sharing may provide
smooth operation of the mobile work machine and/or meet an
operator's expectations of the mobile work machine. The operator's
expectations may be based on the operator's experience in operating
conventional mobile work machines. To achieve accurate flow
sharing, position feedback may be implemented from directional
control valves and/or mode valves of the hydraulic circuit
architecture. The position feedback may be provided by linear
variable differential transformers (i.e., LVDTs). In certain
embodiments, the LVDTs may be incorporated into and integrated with
the directional control valves and/or the mode valves. In certain
embodiments, the LVDTs may be added to conventional directional
control valves. In certain embodiments, a hybrid system electronic
control unit (i.e., ECU) directly controls the position of the
directional control valves by modulating a control pilot pressure
supplied to the directional control valves.
[0007] The hydraulic system architecture may include the authority
to de-stroke a main pump or a plurality of main pumps if a hybrid
system controller calculates that stored energy within the
accumulator can be supplied to meet some or all of the flow
requirements of the hydraulic system architecture. A form of this
communication may depend on a baseline hydraulic system
architecture of the mobile work machine. Certain conventional
mobile work machines include a pilot pressure to the main pump or
pumps. Certain more recent conventional mobile work machines may
use an analog or digital electrical signal transmitted to
electronically controlled main pumps. This signal may be computed
using a load sense pressure measurement, an excess flow pressure
measurement, and/or a service pressure (e.g., a service pressure of
a tilt cylinder and/or a lift cylinder). The various pressure
measurements may be communicated to the hybrid system ECU via a
controller area network bus (i.e., a CAN bus).
[0008] In certain embodiments, flow control between the
transformer, the tilt service, and the lift service is controlled
by an electronic control unit of a valve subsystem. One such valve
system including suitable position feedback and flow control
capability is the ZTS16 subsystem sold by the Eaton Corporation of
Cleveland, Ohio. The valve subsystem may include a pair of pilot
operated proportional valves with position feedback and flow
control capability. The valve subsystem allows for simultaneous
supply flow to both the tilt and the lift services, or allows for
simultaneous recovery of flow from both the tilt and the lift
services, or allows supply or recovery flow from a single one of
the tilt or lift services. The valve subsystem may function as a
mode valve. The valve subsystem may determine the position of these
valves. In addition, a position of directional control valves of
the tilt and the lift services are determined. An equivalent flow
orifice area may thereby be computed and flow may be divided
between different paths to sum to equal the requested flow from the
operator.
[0009] The requested flow from the operator may be measured by
joystick signals that are either operated by hydraulic pilot
pressure or electrical signals, depending on how the mobile work
machine is configured. A flow request is computed by the hydraulic
system ECU based both on the joystick commands and the system
pressures. An operating map may be used to resolve a flow
requirement from the joystick commands and the system pressures.
The operating map may be a lookup table stored in the hydraulic
system ECU memory. Flow routing may be computed by a control
algorithm that optimizes energy recovery using an objective
function based on flow tracking, torque tracking, and energy
recovery.
[0010] A clutch may be used to disconnect the power take-off output
shaft from the prime mover or a transmission connected to the prime
mover. By disconnecting the clutch, mechanical losses from using
the hydraulic transformer may be eliminated when the energy
recovery system is not in use. The clutch may be commanded by the
hydraulic system electronic control unit. The hydraulic system ECU
may send an electronic or hydraulic signal depending on the
configuration of the mobile work machine. The transmission may be
an automated manual transmission (AMT). Such AMTs are sold by the
Eaton Corporation of Cleveland, Ohio.
[0011] The AMT may enable powertrain control to account for power
drawn and returned by the hydraulic system. The AMT may incorporate
a clutch. The AMT may provide simplified transmission control. The
AMT may further increase fuel economy potential of the mobile work
machine by allowing a second source of power from the hydraulic
transformer to effectively unload the power requirement of the
prime mover. In conventional wheel loaders, a conventional torque
converter does not allow a second source of power to effectively
unload the prime mover. The AMT allows the prime mover to be
unloaded and loaded by the hydraulic transformer in a simple and
controllable manner.
[0012] A normally opened two-position two-way valve may be used to
bleed down the accumulator. The bleed down valve may be controlled
by the hydraulic system ECU. The hydraulic bleed down valve may
provide safe servicing by discharging the accumulator when the
mobile work machine is turned off and/or if certain emergency power
loss situations arise.
[0013] A normally closed two-position two-way valve may be used to
isolate the accumulator. By isolating the accumulator, leakage may
be prevented from the accumulator when energy is being stored
within the accumulator. The accumulator isolation valve may be
opened any time that flow is required to or from the accumulator.
When the accumulator isolation valve is closed, a relief valve may
limit the pressure across the first pump-motor.
[0014] Another aspect of the present disclosure includes
configuring the hydraulic system architecture in a ride control
mode. A ride control mode valve may be added, and functions of a
conventional ride control system may be achieved with the hydraulic
circuit architecture. As the hydraulic circuit architecture already
includes a substantial high pressure accumulator, a separate
accumulator for the ride control mode is not needed. The ride
control mode may be added without the additional expense of the
conventional ride control accumulator, instead sharing the
hydraulic accumulator of the hydraulic system. As the hydraulic
accumulator of the hydraulic system is larger than typical ride
control accumulators, the performance of the ride control system
may be improved over a conventional ride control system.
Furthermore, the first pump-motor may be used to modulate
accumulated pressure. By modulating accumulated pressure, active
damping may be achieved for ride control. Such actively dampened
ride control may significantly improve ride control
performance.
[0015] Still another aspect of the present disclosure relates to
providing a majority of flow to and from the tilt and/or lift
cylinders by the mode valves of the hydraulic system. In
particular, the hydraulic system includes an energy recovery system
including the hydraulic accumulator and the hydraulic transformer.
The directional control valves may be completely closed and thereby
prevent a hydraulic flow path from the rod side of the lift and/or
the tilt hydraulic cylinders to tank. The mode valves of the
hydraulic system of the hybrid system may be used to provide a flow
path in lieu of the flow path through the directional control
valves. In one embodiment, a conventional two-position two-way
valve may be used. In another embodiment, a three-position
three-way valve may be used. The valves may be connected to the rod
side of the tilt and/or the lift cylinders. In certain embodiments,
the conventional two-position two-way valve is connected to the rod
side of the lift cylinder, and the three-way three-position valve
is connected to the rod side of the tilt cylinder. In other
embodiments, similar two-way two-position valves and/or three-way
three-position valves may be used with the tilt and/or lift
cylinders in other combinations. As the two-way valves and/or the
three-way valves may be used to connect the rod side of the tilt
and/or lift cylinders to tank, the same rod-to-tank functionality
provided by the directional control valves may also be provided by
the two-way and/or three-way valves.
[0016] With the three-way three-position valve, a connection may be
made to the pressure supply of the tilt and/or lift services. By
connecting the rod side to the lift and/or tilt supply, and further
connecting the tilt and/or lift supply to the head side of the
hydraulic cylinder, the hydraulic cylinder is converted into a
quick-acting one-way cylinder with an effective piston area equal
to the rod area. This configuration allows the cylinder to be
quickly extended using a minimal amount of flow. This configuration
may further allow less energy to be expended in extending the
hydraulic cylinder and thereby allow for further fuel economy
improvement.
[0017] Yet another aspect of the present disclosure relates to
coordination of hybrid system functionalities of the hydraulic
system by a supervisory control algorithm. In certain embodiments,
the supervisory control algorithm resides in the hydraulic system
ECU. The supervisory control algorithm may be executed by a
supervisory controller and use predictive power management and
optimal control algorithms to adapt the scheduling of the various
hybrid functions to the particular duty cycle currently being
performed by the mobile work machine. The hybrid system ECU
contains duty cycle identification algorithms to determine what
class of duty is being performed. The hybrid system ECU thereby
chooses from a set of control motifs depending on the class of duty
cycle. In certain embodiments, the machine operator can influence
the classification of the duty cycle by selecting a performance
mode. In particular, a "high power" mode enables a set of control
motifs tuned for maximum productivity. An "economy plus" mode will
focus on fuel economy improvements while maintaining the average
productivity of a baseline "economy" mode. By adapting to the duty
cycle in real time, and by enabling the machine operator to choose
the performance mode, the hybrid system may automatically tailor
its control motif to be optimal for any working condition.
[0018] In certain embodiments, a set of measurements may be used by
the supervisory controller to correctly characterize the state of
the hybrid system. Variables including engine speed, accelerator
pedal state, brake pedal state, and forward-neutral-reverse gear
index may be directly readable from the machine communication bus
(e.g., the machine CAN bus, a CAN J1939 bus, etc.).
[0019] A variety of additional aspects will be set forth in the
description that follows. These aspects can relate to individual
features and to combinations of features. It is to be understood
that both the foregoing general description and the following
detailed description are exemplary and explanatory only and are not
restrictive of the broad concepts upon which the embodiments
disclosed herein are based.
DESCRIPTION OF THE DRAWINGS
[0020] Non-limiting and non-exhaustive embodiments are described
with reference to the following figures wherein like reference
numerals refer to like parts throughout the various views, unless
otherwise specified.
[0021] FIG. 1 is a schematic diagram of a hydraulic system having
features that are examples according to the principles of the
present disclosure;
[0022] FIG. 2 is an enlarged portion of the schematic diagram of
FIG. 1;
[0023] FIG. 3 is a perspective view of a wheel loader upon which
the hydraulic system of FIG. 1 may be fully or partially
implemented according to the principles of the present
disclosure;
[0024] FIG. 4 is a side elevation view of the wheel loader of FIG.
3; and
[0025] FIG. 5 is a perspective view of another wheel loader upon
which the hydraulic system of FIG. 1 may be fully or partially
implemented according to the principles of the present
disclosure.
DETAILED DESCRIPTION
[0026] Various embodiments will be described in detail with
reference to the drawings, wherein like reference numerals
represent like parts, like assemblies, and/or like components
throughout the several views. Reference to various embodiments does
not limit the scope of the claims attached hereto. Additionally,
any examples set forth in this specification are not intended to be
limiting and merely set forth some of the many possible embodiments
for the appended claims.
[0027] The present disclosure relates generally to hydraulic
circuit architectures for use in mobile work machines. A hydraulic
circuit architecture, in accordance with the principles of the
present disclosure, can include a propel circuit, a steering
circuit, and/or a work circuit. In typical modern mobile work
machines, priority is given to hydraulically power certain critical
control circuits (e.g., the steering circuit).
[0028] According to the principles of the present disclosure, a
hydraulic system 10 may be included on a mobile work machine 800,
800'. In the depicted embodiment of FIGS. 3 and 4, a first wheel
loader 800 is illustrated according to the principles of the
present disclosure. In the embodiment illustrated at FIG. 5, a
wheel loader 800' is illustrated according to the principles of the
present disclosure. Although the examples provided at FIGS. 3-5 are
to wheel loaders 800, 800', the hydraulic system 10 may be
adaptable to other mobile work machines according to the principles
of the present disclosure.
[0029] As illustrated at FIGS. 1 and 2, the hydraulic system 10
includes a variety of components, sub-systems, and control units.
In certain embodiments, these components, control units, and
sub-systems may be used together as illustrated at FIGS. 1 and 2.
In other embodiments, only certain components, sub-systems, and/or
control units may be used to provide additional embodiments
according to the principles of the present disclosure. Certain
embodiments may remove one or more control unit, component, and/or
sub-system from the hydraulic system illustrated at FIGS. 1 and 2.
Certain embodiments may add one or more additional control units,
components, and/or sub-systems to the hydraulic system illustrated
at FIGS. 1 and 2.
[0030] According to the principles of the present disclosure, the
hydraulic system 10 provides a hydraulic hybrid system to the
mobile work machine 800, 800'. The hydraulic system 10 includes an
accumulator 50 with a port 52 that receives energy when pressurized
hydraulic fluid is forced, under pressure, into the port 52. The
accumulator 50 may also release hydraulic fluid from the port 52
and thereby provide energy to the hydraulic system 10. The mobile
work machine 800, 800' further includes a prime mover 90. As
depicted, the prime mover 90 may be an internal combustion engine
such as a Diesel engine, an Otto-cycle engine, a gas turbine
engine, etc. As depicted, the prime mover 90 may supply
substantially all of the energy provided to the mobile work machine
800, 800'. The accumulator 50 may recover certain energy from
various actuators of the mobile work machine 800, 800' and may
further recover energy from decelerating the mobile work machine
800, 800'. The accumulator 50 may thereby convert inertial energy
into potential energy stored within the accumulator 50. The
hydraulic system 10 may further convert potential energy resulting
from various configurations of the mobile work machine 800, 800'
into potential energy stored within the accumulator 50. Such
potential energy of the mobile work machine 800, 800' may include
loads carried by the mobile work machine 800, 800' that are acted
upon by gravity. The mobile work machine 800, 800' may itself be at
an elevated position (e.g., at the top of a hill). By allowing
gravity to act on the load of the mobile work machine 800, 800' or
act on the mobile work machine 800, 800' itself, potential energy
of the load and/or the mobile work machine 800, 800' may be
converted into potential energy within the accumulator 50.
[0031] The hydraulic system 10 may release the potential energy
stored within the accumulator 50. By releasing the potential energy
stored within the accumulator 50, the hydraulic system 10 may drive
movement of various actuators of the mobile work machine 800, 800',
may drive a drive train of the mobile work machine 800, 800' and
thereby move the mobile work machine 800, 800', may start the prime
mover 90 (e.g., power a hydraulic starting motor), may elevate the
mobile work machine 800, 800' to a higher elevation, may elevate a
load carried by the mobile work machine 800, 800' to a higher
elevation, etc.
[0032] In certain embodiments, the hydraulic system 10 may provide
a ride control system for the mobile work machine 800, 800'. In
particular, various actuators that carry loads of the mobile work
machine 800, 800' may be cushioned as the mobile work machine 800,
800' traverses uneven terrain and/or otherwise experiences dynamic
loads. The hybrid system and the ride control system may both use
the same accumulator 50 to store and release hydraulic energy into
the hydraulic system 10.
[0033] Turning now to FIGS. 3 and 4, the example mobile work
machine 800 is illustrated in detail. In particular, the mobile
work machine 800 is powered by the prime mover 90. The prime mover
90 powers the hydraulic system 10 and thereby propels a drive train
890 of the mobile work machine 800. As illustrated at FIG. 1, the
prime mover 90 is connected to a transmission 100. In the depicted
embodiment, the transmission 100 is an automatic manual
transmission (i.e., an AMT). In other embodiments, the transmission
100 may be one of a number of conventional transmissions. Such
conventional transmissions may include hydrostatic transmissions,
automatic transmissions with torque converters, or conventional
shifted transmissions with a clutch between the prime mover 90 and
an input shaft of the transmission.
[0034] In the depicted embodiment, the transmission 100 includes a
first input/output shaft 102 to a rear drive train 892 and a second
input/output shaft 104 to a front drive train 894. In other
embodiments, the transmission 100 may connect with a drive train of
a mobile work machine via a single input/output shaft.
[0035] An operator may control the direction of the mobile work
machine 800 using a transmission selector 106. In particular, a
forward configuration, a reverse configuration, a neutral
configuration, and/or a parking configuration may be selected by
the transmission selector 106. In certain embodiments, the
transmission selector 106 may further be used to select various
gear ratios of the transmission 100. In certain embodiments, the
transmission selector 106 may be used to deselect one or more of
the input/output shafts 102, 104 and thereby deselect one of the
drive trains 892, 894.
[0036] As depicted at FIG. 1, the prime mover 90 further powers a
baseline hydraulic system 270. As depicted, the baseline hydraulic
system 270 may include an electronic control unit 272 (i.e., ECU).
The baseline hydraulic system 270 may further include memory 274
that is used by the electronic control unit 272. In certain
embodiments, the priority control hydraulic circuit or circuits
(e.g., the steering circuit) are included in the baseline hydraulic
system 270.
[0037] The baseline hydraulic system 270 may power a first
hydraulic actuator 830, 830' of the mobile work machine 800, 800'
and/or a second hydraulic actuator 860, 860' of the mobile work
machine 800, 800'. In certain embodiments, the first actuator 830,
830' and the second hydraulic actuator 860, 860' are excluded from
the priority control hydraulic circuit or circuits and instead are
powered as non-priority circuits in the baseline hydraulic system
270. In the depicted embodiment, the first hydraulic cylinder 830,
830' is a lift cylinder, and the second hydraulic cylinder 860,
860' is a tilt cylinder. In the depicted embodiment, the lift
cylinder 830, 830' includes a pair of hydraulic cylinders joined
together in parallel, and the tilt cylinder 860, 860' is a single
hydraulic cylinder. In other embodiments, the hydraulic cylinders
830, 830', 860, 860' may include multiple hydraulic cylinders
and/or a single hydraulic cylinder. In the depicted embodiment, the
lift cylinder 830, 830' is used to move a bucket 826, 826' between
upper positions and lower positions via moving a boom and thereby
change the elevation of the bucket 826, 826'. In the depicted
embodiment, the tilt cylinder 860, 860' is used to tilt the bucket
826, 826'. When used together by the operator, the lift cylinders
830, 830', the tilt cylinders 860, 860', and the drive train 890
may be used to position the bucket 826, 826' in various digging,
hauling, and dumping configurations. The wheel loader 800, 800' may
thereby be used to move material and/or provide other useful
functions.
[0038] As depicted at FIG. 1, the prime mover 90, the baseline
hydraulic system 270, and/or the transmission 100 may be controlled
by a hybrid system electronic control unit 250. In particular, the
hydraulic system electronic control unit 250 receives sensor inputs
252 and may provide actuator outputs 262. As illustrated, the
sensor inputs 252 and the actuator outputs 262 may connect directly
to a particular sensor and/or a particular actuator controller. The
hybrid system electronic control unit 250 may further receive
inputs and outputs from the prime mover via a signal line 256.
Likewise, the hydraulic system electronic control unit 250 may send
and receive input and output signals from the transmission 100 via
the signal line 254. In addition, the hydraulic system electronic
control unit 250 may send and/or receive input and output signals
from the baseline hydraulic system 270 via a signal line 258. The
hybrid system electronic control unit 250 may store executable
programs, system information, and/or various system state
information in memory 260. As illustrated at FIG. 1, the hybrid
system electronic control unit 250 may communicate via a controller
area network bus 264 (i.e., a CAN bus) of the mobile work machine
800, 800'. In certain embodiments, the hybrid system electronic
control unit 250 may also communicate via a separate controller
area network bus 266. In the example embodiment, the controller
area network bus 266 transfers information to and/or from a flow
control valve subsystem 150. The hydraulic system electronic
control unit 250 may further receive signals and/or send signals to
an accelerator control interface 296 and/or a brake control
interface 298. The baseline hydraulic system electronic control
unit 272 and the hybrid system electronic control unit 250 may work
together to receive various signals including the signals from the
accelerator 296 and the brake 298. The various other signals may
include a load sense pressure signal 280, a non-priority circuit
P_EF pressure signal 282, a tank pressure signal 284, a joystick
lift signal 276 (i.e., a lift signal), a joystick tilt signal 278
(i.e., a tilt signal), and/or other signals. As depicted at FIG. 1,
the hybrid system electronic control unit 250 has supervisory
control over the prime mover 90, the baseline hydraulic system 270,
and/or the transmission 100. In other embodiments, other
architectures may be used.
[0039] As depicted at FIG. 1, the hydraulic system 10 includes a
hydraulic transformer 20. The hydraulic transformer 20 includes a
first rotating group 22 and a second rotating group 32. In the
depicted embodiment, the first rotating group 22 is a first
pump-motor, and the second rotating group 32 is a second
pump-motor. The first and the second rotating groups 22, 32 are
rotationally connected together by a shaft 30. The first rotating
group 22 includes a first port 24, a second port 26, and a variable
swash plate 28. Likewise, the second rotating group 32 includes a
first port 34, a second port 36, and a variable swash plate 38. In
certain embodiments, the variable swash plates 28, 38 may go
over-center. In certain embodiments, one or both variable swash
plates 28 and 38 are equipped with displacement sensors 29 and 39,
respectively, (e.g., LVDTs).
[0040] The first rotating group 22 and the second rotating group 32
are further rotationally connected to a shaft 40. The shaft 40 is
depicted as an input/output shaft and is connected to a
power-take-off (i.e., PTO) 80. The power-take-off 80 includes a
shaft 82 that is connected to a clutch 84. When the clutch 84 is
engaged, the power-take-off 80, and thereby the shaft 40, are
rotationally connected to the transmission 100. When the clutch 84
is disengaged, the power-take-off 80, and thereby the transmission
100, are rotationally disconnected from each other. The hydraulic
transformer 20 is thereby rotationally connected to the
transmission 100 and further to the prime mover 90.
[0041] The power-take-off 80 thereby selectively connects the
hydraulic transformer 20 to the transmission 100. Energy may
thereby be delivered to and from the hydraulic transformer 20 and
the transmission 100. Energy may thereby be transferred from the
hydraulic accumulator 50 and the drive train 890. The accumulator
50 may thereby collect inertial energy and potential energy from
the mobile work machine 800, 800' and store the energy as potential
energy within the accumulator 50. The hydraulic system 10 may
further deliver potential energy from the accumulator 50 to the
drive train 890 and thereby propel the mobile work machine 800,
800'.
[0042] The prime mover 90 may supply energy to the accumulator 50
via the hydraulic transformer 20. In particular, the prime mover 90
may be connected to the transformer 20 via the transmission 100 and
the power-take-off 80. The first rotating group 22 may thereby
transfer hydraulic fluid from a hydraulic tank 500 to the hydraulic
accumulator 50 and pressurize the hydraulic fluid within the
accumulator 50.
[0043] Energy may further be transferred between the transmission
100 and the lift cylinder 830, 830' and/or the tilt cylinder 860,
860'. In particular, the second rotating group 32 may be
hydraulically connected to the lift cylinder 830, 830' and/or the
tilt cylinder 860, 860' via the flow control valve sub-system 150.
The hydraulic transformer 20 may thereby transfer inertial and/or
potential energy to and from the mobile work machine 800, 800' and
the bucket 826, 826' and the boom 824, 824' of the mobile work
machine 800, 800'.
[0044] The hydraulic system 10 may further transfer energy between
the accumulator 50 and the lift cylinder 830, 830' and/or the tilt
cylinder 860, 860'. In particular, energy from the accumulator 50
may be used to lift the boom 824, 824' and the bucket 826, 826',
and potential energy of the boom 824, 824' and the bucket 826, 826'
may be transferred to the hydraulic accumulator 50 (e.g., when
gravity acts on the boom 824, 824' and the bucket 826, 826' and the
lift cylinder 830, 830' is moving in an overrunning direction 847,
as illustrated at FIG. 5).
[0045] As illustrated at FIG. 1, the hydraulic system 10 includes a
first directional control valve (i.e., DCV) 110 and a second
directional control valve 130. As depicted, the directional control
valve 110 may be used to actuate the lift cylinder 830, 830', and
the directional control valve 130 may be used to actuate the tilt
cylinder 860, 860'. The baseline hydraulic system 270 may supply
pressurized hydraulic fluid to the directional control valves 110,
130 via the high pressure side of the non-priority circuit P_EF,
and the directional control valves 110, 130 may correspondingly
transfer the pressurized hydraulic fluid to the hydraulic cylinders
830, 830', 860, 860'. According to the principles of the present
disclosure, the directional control valves 110, 130 may actuate the
actuators 830, 830', 860, 860' with the hydraulic transformer 20
engaged (e.g., the PTO clutch 84 engaged) and may further actuate
the actuators 830, 830', 860, 860' with the hydraulic transformer
20 disengaged (e.g., with the PTO clutch 84 disengaged). The
hydraulic cylinders 830, 830', 860, 860' may be powered by both the
non-priority circuit P_EF of the baseline hydraulic system 270 and
by the hydraulic transformer 20 simultaneously (e.g., when the PTO
clutch 84 is engaged). The non-priority circuit P_EF and the
hydraulic transformer 20 may share in supplying the actuators 830,
830', 860, 860' with pressurized hydraulic fluid. The hybrid system
electronic control unit 250 may coordinate this supply sharing
activity (e.g., match hydraulic pressures, allocate flow,
etc.).
[0046] The first directional control valve 110 includes a first
port 112, a second port 114, a third port 116, and a fourth port
118. A spool within the directional control valve 110 configures
connections and/or disconnections between the ports 112, 114, 116,
118 depending on the position of the spool. In particular, a first
configuration 122 blocks off each of the ports 112, 114, 116, 118.
A second configuration 124 connects the first port 112 and third
port 116 and further connects the second port 114 and the fourth
port 118. A third configuration 126 connects the first port 112 and
the fourth port 118 and further connects the second port 114 and
the third port 116. In certain embodiments, the spool may be varied
in position and thereby connect the various ports together with
additional hydraulic resistance depending on the position of the
spool. The first directional control valve 110 includes a position
sensor 120 connected to the spool. In the depicted embodiment, the
position sensor 120 is a linear variable differential transformer
(i.e., LVDT). The output from the position sensor 120 is
transmitted to the hybrid system electronic control unit 250 and/or
the baseline hydraulic system 270.
[0047] The second directional control valve 130 includes a first
port 132, a second port 134, a third port 136, and a fourth port
138. A spool within the directional control valve 130 configures
connections and/or disconnections between the ports 132, 134, 136,
138 depending on the position of the spool. In particular, a first
configuration 142 blocks off each of the ports 132, 134, 136, 138.
A second configuration 144 connects the first port 132 and third
port 136 and further connects the second port 134 and the fourth
port 138. A third configuration 146 connects the first port 132 and
the fourth port 138 and further connects the second port 134 and
the third port 136. In certain embodiments, the spool may be varied
in position and thereby connect the various ports together with
additional hydraulic resistance depending on the position of the
spool. The second directional control valve 130 includes a position
sensor 140 connected to the spool. In the depicted embodiment, the
position sensor 140 is a linear variable differential transformer
(i.e., LVDT). The output from the position sensor 140 is
transmitted to the hybrid system electronic control unit 250 and/or
the baseline hydraulic system 270.
[0048] As illustrated at FIG. 1, an accumulator bleed valve 64 is
connected to the port 52 of the accumulator 50. The accumulator
bleed valve 64 includes a first port 66 and a second port 68. The
accumulator bleed valve 64 includes a first configuration 70 and a
second configuration 72. In the first configuration 70, the spool
of the accumulator bleed valve 64 connects the first port 66 to the
second port 68. In the second configuration 72, the first port 66
and the second port 68 are blocked off. When the hydraulic system
10 is configured as a hybrid hydraulic system, the accumulator
bleed valve 64 is typically positioned at the second configuration
72. Among other things, the accumulator bleed valve 64 may be used
to discharge the accumulator 50 for various reasons. For example
when servicing the hydraulic system 10, it may be desired to
relieve the hydraulic accumulator 50 of pressure. When the mobile
work machine 800, 800' is shut down, it may be desired to relieve
the hydraulic accumulator 50 of pressure. There further may be
other normal and abnormal situations where it is desired to relive
the hydraulic accumulator 50 of internal pressure, and the
accumulator bleed valve 64 may be configured at the first
configuration 70 thereby draining the hydraulic accumulator 50 to
tank 500.
[0049] The hydraulic system 10 may include an accumulator isolation
valve 54. As depicted, the accumulator isolation valve 54 includes
a first port 56 and a second port 58. The accumulator isolation
valve 54 includes a first configuration 60 and a second
configuration 62. In the first configuration 60, the first port 56
and the second port 58 are blocked off. In the second configuration
62, the first port 56 is connected with the second port 58. By
positioning the accumulator isolation valve 54 at the first
configuration 60, the accumulator 50 is effectively isolated from
other components of the hydraulic system 10. When the hydraulic
system 10 is operated in the hybrid mode, the accumulator isolation
valve 54 is typically operated at the second configuration 62. When
the hydraulic system 10 is operated as a passive ride control
system, the accumulator isolation valve 54 may be configured at the
first configuration 60, thereby isolating the accumulator 50 from
the hydraulic transformer 20. However, a ride control valve 330 may
connect the hydraulic accumulator 50 and the lift cylinder 830,
830'. When the hydraulic system 10 is operated as an active ride
control system, the accumulator isolation valve 54 may be
configured at the second configuration 62, thereby fluidly
connecting the accumulator 50 to the hydraulic transformer 20. The
ride control valve 330 may further connect the hydraulic
accumulator 50 and the lift cylinder 830, 830'.
[0050] The ride control valve 330 may include a first port 332 and
a second port 334. The ride control valve 330 may include a first
configuration 336 and a second configuration 338. When the ride
control valve 330 is at the first configuration 336, the first port
332 and the second port 334 are connected. When the ride control
valve 330 is at the second configuration 338, the first port 332
and the second port 334 are blocked off. When the ride control
valve 330 is at the first configuration 336, the hydraulic system
10 may provide ride control to the work machine 800, 800'. In
particular, the accumulator 50 may dynamically exchange hydraulic
fluid with the lift cylinder 830, 830'. As the mobile work machine
800, 800' experiences dynamic conditions, the hydraulic accumulator
50 may absorb and release energy to the lift cylinder 830, 830'.
The lift cylinder 830, 830' may thereby serve as an energy
absorbing spring-mass-damper system. In certain embodiments, the
accumulator isolation valve 54 may be set to the second
configuration 62 and thereby connect the first rotating group 22 of
the hydraulic transformer 20 to the accumulator 50. The hybrid
system electronic control unit 250 and/or the baseline hydraulic
system electronic control unit 272 may monitor various dynamic
conditions of the mobile work machine 800, 800'. The hybrid system
electronic control unit 250 and/or the baseline hydraulic system
ECU 272 may dynamically adjust the variable swash plate 28 of the
first rotating group 22 and thereby send a response signal to
actively dynamically provide ride control with the first rotating
group 22, the accumulator 50, and the lift cylinder 830, 830'.
[0051] As depicted at FIGS. 1 and 2, the hydraulic system 10
includes the flow control valve sub-system 150. In certain
embodiments and in certain modes, the flow control valve sub-system
150 may operate the lift cylinder 830, 830' and/or the tilt
cylinder 860, 860' independent of the directional control valves
110 and/or 130. In other embodiments and/or in other modes, the
flow control valve sub-system 150 may operate the lift cylinder
830, 830' and/or the tilt cylinder 860, 860' in cooperation with
the first and/or the second directional control valves 110,
130.
[0052] Turning now to FIG. 2, the flow control valve sub-system 150
will be described in detail. As depicted, the flow control valve
sub-system 150 includes a connection to a return line 502 that may
be used to return hydraulic fluid to the tank 500. As depicted, the
flow control valve sub-system 150 may include a connection to a
line 526 that is connected to a source 540 of pilot hydraulic fluid
pressure. As depicted, the flow control valve sub-system 150 may
further include a connection to a line 530 that is connected to the
tilt cylinder 860, 860'. As illustrated, the flow control valve
sub-system 150 may further include a connection to a line 532 that
is connected to the lift cylinder 830, 830'. The flow control valve
system 150 includes a first mode pilot valve 180 that receives a
signal from the hydraulic system electronic control unit 250. The
flow control valve sub-system 150 further includes a second mode
pilot valve 220 that receives a signal from the hybrid system
electronic control unit 250. The signal received by the first mode
pilot valve 180 results in the first mode pilot valve 180
transferring a hydraulic signal to a first mode valve 160. The
first mode valve 160 thereby transfers hydraulic fluid to and from
the lift cylinder 830, 830'. Likewise, the signal received by the
second mode pilot valve 220 results in the second mode pilot valve
220 transferring a hydraulic signal to a second mode valve 200. The
second mode valve 200 thereby transfers hydraulic fluid to and from
the tilt cylinder 860, 860'.
[0053] The connections to and between the first mode valve 160 and
the first mode pilot valve 180 will now be described in detail. In
particular, the first mode valve 160 includes a first port 162, a
second port 164, and a third port 166. The first mode valve 160
includes a first configuration 172, a second configuration 174, and
a third configuration 176. A position sensor 170 is connected to a
spool of the first mode valve 160. When the spool is at the first
configuration 172, the first port 162, the second port 164, and the
third port 166 are blocked off. When the spool of the first mode
valve 160 is at the second configuration 174, the first port 162 is
connected to the third port 166, and the second port 164 is blocked
off. When the spool of the first mode valve 160 is at the third
configuration 176, the second port 164 is connected to the third
port 166, and the first port 162 is blocked off.
[0054] The first mode pilot valve 180 includes a first port 182, a
second port 184, a third port 186 and a fourth port 188. The first
mode pilot valve 180 includes a first configuration 192, a second
configuration 194, and a third configuration 196. The first mode
pilot valve 180 includes an actuator 190. The actuator receives the
electrical signal from the hybrid system electronic control unit
250 and correspondingly actuates a spool of the first mode pilot
valve 180. In particular, the actuator 190 may position the spool
at the first configuration 192 and thereby connect the second port
184 to the third port 186 and the fourth port 188. The first port
182 is blocked off when the first mode pilot valve 180 is at the
first configuration 192. When the first mode pilot valve 180 is at
the second configuration 194, the first port 182 is connected to
the third port 186, and the second port 184 is connected to the
fourth port 188. When the first mode pilot valve 180 is at the
third configuration 196, the first port 182 is connected to the
fourth port 188, and the second port 184 is connected to the third
port 186. The first port 182 is connected to the hydraulic line 526
and is thereby connected to the pilot pressure source 540. The
second port 184 is connected to the line 502 and is thereby
connected to the tank 500. The third port 186 is connected to a
pilot line 152 that is connected to an actuator of the spool of the
first mode valve 160. In particular, when the pilot line 152 is
pressurized, the first mode valve 160 is urged toward the second
configuration 174. The fourth port 188 is connected to a pilot line
154 that in turn is connected to an actuator of the first mode
valve 160. In particular, if the pilot line 154 is pressurized, the
spool of the first mode valve 160 is urged toward the third
configuration 176. The first port 162 of the first mode valve 160
is connected to a line 520. The line 520 is further connected to
the second rotating group 32 of the hydraulic transformer 20. The
second port 164 of the first mode valve 160 is connected to the
hydraulic line 502 and is thereby connected to the tank 500. The
third port 166 is connected to the line 532. The line 532 is
further connected to the lift cylinder 830, 830'. A lift cylinder
service pressure 286 may be monitored by monitoring pressure in the
hydraulic line 532 with a pressure transducer.
[0055] The connections to and between the second mode valve 200 and
the second mode pilot valve 220 will now be described in detail. In
particular, the second mode valve 200 includes a first port 202, a
second port 204, and a third port 206. The first mode valve 200
includes a first configuration 212, a second configuration 214, and
a third configuration 216. A position sensor 210 is connected to a
spool of the second mode valve 200. When the spool is at the first
configuration 212, the first port 202, the second port 204, and the
third port 206 are blocked off. When the spool of the second mode
valve 200 is at the second configuration 214, the first port 202 is
connected to the third port 206, and the second port 204 is blocked
off. When the spool of the second mode valve 200 is at the third
configuration 216, the second port 204 is connected to the third
port 206, and the first port 202 is blocked off.
[0056] The second mode pilot valve 220 includes a first port 222, a
second port 224, a third port 226, and a fourth port 228. The
second mode pilot valve 220 includes a first configuration 232, a
second configuration 234, and a third configuration 236. The second
mode pilot valve 220 includes an actuator 230. The actuator 230
receives the electrical signal from the hybrid system electronic
control unit 250 and correspondingly actuates a spool of the second
mode pilot valve 220. In particular, the actuator 230 may position
the spool at the first configuration 232 and thereby connect the
second port 224 to the third port 226 and the fourth port 228. The
first port 222 is blocked off when the second mode pilot valve 220
is set to the first configuration 232. When the second mode pilot
valve 220 is set to the second configuration 234, the first port
222 is connected to the third port 226, and the second port 224 is
connected to the fourth port 228. When the first mode pilot valve
220 is at the third configuration 236, the first port 222 is
connected to the fourth port 228, and the second port 224 is
connected to the third port 226. The first port 222 is connected to
the hydraulic line 526 and is thereby connected to the pilot
pressure source 540. The second port 224 is connected to the line
502 and is thereby connected to the tank 500. The third port 226 is
connected to a pilot line 156 that is connected to an actuator of
the spool of the second mode valve 200. In particular, when the
pilot line 156 is pressurized, the second mode valve 200 is urged
toward the second configuration 214. The fourth port 228 is
connected to a pilot line 158 that in turn is connected to an
actuator of the second mode valve 200. In particular, if the pilot
line 158 is pressurized, the spool of the second mode valve 200 is
urged toward the third configuration 216. The first port 202 of the
second mode valve 200 is connected to a line 520. The line 520 is
further connected to the second rotating group 32 of the hydraulic
transformer 20. The second port 204 of the second mode valve 200 is
connected to the hydraulic line 502 and is thereby connected to the
tank 500. The third port 206 is connected to the line 530. The line
530 is further connected to the tilt cylinder 860, 860'. A tilt
cylinder service pressure 288 may be monitored by monitoring
pressure in the hydraulic line 530 with a pressure transducer.
[0057] As illustrated at FIG. 1, the lift cylinder 830, 830'
includes a first port 832 (e.g., head-side port), connected to a
first chamber 842 (e.g., head chamber), and a second port 834
(e.g., rod-side port) connected to a second chamber 844 (e.g.,
rod-side chamber). The lift cylinder 830, 830' includes a piston
846 that separates the first chamber 842 from the second chamber
844. A rod 840, 840' is connected to the piston 846 and extends
through the second chamber 844. Likewise, the tilt cylinder 860,
860' includes a first port 862 (e.g., head-side port), connected to
a first chamber 872 (e.g., head chamber), and a second port 864
(e.g., rod-side port) connected to a second chamber 874 (e.g.,
rod-side chamber). The tilt cylinder 860, 860' includes a piston
876 that separates the first chamber 872 from the second chamber
874. A rod 870, 870' is connected to the piston 876 and extends
through the second chamber 874.
[0058] As illustrated at FIG. 1, the flow control valve sub-system
150 may be controlled by the signal line 266 and thereby be
controlled via a dedicated controller area network. In the depicted
embodiment, the flow control valve sub-system 150 is a valve known
by model number ZTS16 and sold by the Eaton Corporation of
Cleveland, Ohio. In other embodiments, other valves may be
used.
[0059] As depicted at FIG. 1, a two-way two-position valve 300 is
connected between the lift cylinder 830, 830' and the tank 500. In
particular, the valve 300 includes a first port 302 and a second
port 304. The valve 300 includes a first configuration 306 and a
second configuration 308. When at the first configuration 306, the
two-way valve 300 blocks off the first and the second ports 302,
304. When at the second configuration 308, the two-way valve 300
connects the first port 302 and the second port 304.
[0060] As illustrated at FIG. 1, a three-way three-position valve
310 is connected between the tilt cylinder 860, 860' and the tank
500 or a high pressure side of the non-priority circuit P_EF. In
particular, the three-way three-position valve 310 includes a first
port 312, a second port 314, and a third port 316. The valve 310
includes a first configuration 318, a second configuration 320, and
a third configuration 322. As illustrated, when the valve 310 is at
the first configuration 318, the first port 312, the second port
314, and the third port 316 are blocked off. In the second
configuration 320, the first port 312 is connected with the second
port 314, and the third port 316 is blocked off. When the valve 310
is at the third configuration 322, the first port 312 is connected
to the third port 316, and the second port 314 is blocked off. The
third port 316 is connected to a line 508 and thereby connected to
the tank 500. The port 314 is connected to a line 528, 528B and
thereby connected to the high pressure side of the non-priority
circuit P_EF.
[0061] Various connections, illustrated at FIG. 1, will now be
described in detail in relation to the various fluid lines to which
the connections are made. The fluid lines may each be thought of as
a node of the hydraulic system 10. Hydraulic fluid line 502 is
connected to the tank 500, the second port 26 of the first rotating
group 22, the second port 36 of the second rotating group 32, a
second port 78 of a relief valve 74, a second port 68 of the
accumulator bleed valve 64, and to various ports within the flow
control valve sub-system 150, as described above. A hydraulic line
504 is also connected to the tank 500. The hydraulic line 504 is
further connected to the second port 134 of the directional control
valve 130 and the second port 114 of the directional control valve
110. A hydraulic line 506 is connected to the tank 500 and further
connected to the second port 304 of the valve 300. The hydraulic
line 508 is connected to the tank 500 and to the third port 316 of
the valve 310.
[0062] The hydraulic line 520 is connected to the port 34 of the
second rotating group 32 and further connected to various ports
within the flow control valve sub-system 150, as mentioned above. A
pressure 292 is measured at the hydraulic line 520. A hydraulic
line 522 is connected to the first port 24 of the first rotating
group 22 and to the first port 76 of the relief valve 74 and
further to the second port 58 of the accumulator isolation valve
54. A hydraulic line 524 may be connected to the first port 56 of
the accumulator isolation valve 54, to the port 52 of the
accumulator 50, to the first port 66 of the accumulator bleed valve
64, and to the second port 334 of the valve 330. A pressure 290 may
be taken at the hydraulic line 524. The hydraulic line 526 may be
connected to the pilot pressure source 540 and to various
connections within the flow control valve sub-system 150, as
mentioned above.
[0063] A hydraulic line 528, 528A may be connected to the high
pressure side of the non-priority circuit P_EF and to a check valve
128 and further to a check valve 148. The check valve 128 is
positioned at the first port 112 of the directional control valve
110. Likewise, the check valve 148 is positioned at the first port
132 of the directional control valve 130. The check valve 128
allows flow from the hydraulic line 528, 528A to flow into the
first port 112 but keeps flow from flowing out of the first port
112 into the hydraulic line 528, 528A. The check valve 148 allows
flow from the hydraulic line 528, 528A to flow into the first port
132 but keeps flow from flowing out of the first port 132 into the
hydraulic line 528, 528A. The hydraulic line 528, 528B connects the
second port 314 of the valve 310 to the high pressure side of the
non-priority circuit P_EF.
[0064] The hydraulic line 530 is connected to the fourth port 138
of the directional control valve 130, to the first port 862 of the
tilt cylinder 860, 860', and to the third port 206 of the second
mode valve 200. The hydraulic line 532 is connected to the fourth
port 118 of the directional control valve 110, the first port 332
of the two-way valve 330, the port 832 of the lift cylinder 830,
830', and the third port 166 of the first mode valve 160. A
hydraulic line 534 is connected to the third port 136 of the
directional control valve 130, the second port 864 of the tilt
cylinder 860, 860', and the first port 312 of the valve 310. A
hydraulic line 536 is connected to the third port 116 of the
directional control valve 110, the second port 834 of the lift
cylinder 830, 830', and the first port 302 of the valve 300.
[0065] Turning now to FIGS. 3 and 4, various features of the
example wheel loader 800 will be described in detail. The wheel
loader 800 includes an operator station 818. The lift cylinder 830
(e.g., a pair of hydraulic cylinders) is attached to a chassis 816
of the wheel loader 800 at a first end. As depicted, the first end
corresponds to the head end of the hydraulic cylinders. A pair of
first attachments 856 is thereby formed between a cylinder housing
of the hydraulic cylinders and the chassis 816. A pair of second
attachments 858 is formed between the rods 840 of the lift cylinder
830 and the boom 824 of the wheel loader 800. The boom 824 may
thereby be actuated by the lift cylinder 830.
[0066] As depicted at FIG. 5, the lift cylinder 830' (e.g., a pair
of hydraulic cylinders) is attached to a chassis 816' of the wheel
loader 800' at a first end. As depicted, the first end corresponds
to the head end of the hydraulic cylinders. A pair of first
attachments 856' is thereby formed between a cylinder housing of
the hydraulic cylinders and the chassis 816'. A pair of second
attachments 858' is formed between the rods 840' of the lift
cylinder 830' and the boom 824' of the wheel loader 800'. The boom
824' may thereby be actuated by the lift cylinder 830'. The wheel
loader 800' includes an operator cabin 818'.
[0067] As depicted at FIGS. 3 and 4, the tilt cylinder 860 is
attached to the chassis 816 of the wheel loader 800 at a first end.
As depicted, the first end corresponds to the head end of the
hydraulic cylinder 860. A first attachment 886 is thereby formed
between a cylinder housing of the hydraulic cylinder 860 and the
chassis 816. A second attachment 888 is formed between the rod 870
of the tilt cylinder 860 and a bucket linkage 828 of the wheel
loader 800. The bucket 826 may be actuated by the bucket linkage
828 in conjunction with the tilt cylinder 860.
[0068] As depicted at FIG. 5, the tilt cylinder 860' is attached to
the chassis 816' of the wheel loader 800' at a first end. As
depicted, the first end corresponds to the head end of the
hydraulic cylinder 860'. A first attachment 886', similar to the
first attachment 886, is thereby formed between the cylinder
housing of the hydraulic cylinder 860' and the chassis 816'. A
second attachment 888' is formed between the rod 870' of the tilt
cylinder 860' and a bucket linkage 828' of the wheel loader 800'.
The bucket 826' may be actuated by the bucket linkage 828' in
conjunction with the tilt cylinder 860'. Extending the hydraulic
cylinder 860' (e.g., by moving the rod 870' in a direction 821)
tilts the bucket 826' in an upward direction 825. The bucket
linkage 828' may be a "Z-bar" bucket linkage, as depicted at FIG.
5, that transforms extension of the hydraulic cylinder 860' into
tilting of the bucket 826' in the upward direction 825. The "Z-bar"
bucket linkage includes a rocking member 827 rotatably mounted on
the boom 824' between a first end 827a and a second end 827b. The
first end 827a includes the second attachment 888'. The second end
827b is rotatably connected to a bucket link 829 at a second end
829b of the bucket link 829. A first end 829a of the bucket link
829 is rotatably connected to the bucket 826'. Extending the
hydraulic cylinder 860' rocks the rocking member 827 in a direction
823.
[0069] The relative movements between the tilt cylinder 860 and the
bucket 826 of the example wheel loader 800 are opposite of the
relative movements between the tilt cylinder 860' and the bucket
826' of the example wheel loader 800'. In particular, extension of
the tilt cylinder 860 tilts the bucket 826 downward (see FIG.
4).
[0070] Various distinguishing features of the hydraulic system 10
will now be described according to the principles of the present
disclosure.
[0071] The accumulator 50 is connected to the pump-motor 22 of the
hydraulic transformer 20. Flow supplied or recovered from the
actuators 830, 830', 860, 860' can be at any pressure. Hydraulic
fluid stored in the accumulator 50 is typically at very high
pressure. The hydraulic transformer 20 provides isolation between
the actuators 830, 830', 860, 860' and the accumulator 50, except
when ride control is enabled. When ride control is enabled by
opening valve 330 to position 336, the directional control valve
110 is closed (i.e., at configuration 122), and the accumulator 50
is connected directly to the head chamber 842 of the lift cylinders
830, 830'.
[0072] The accumulator 50 may be isolated bi-directionally (e.g.,
when the accumulator isolation valve 54, the accumulator bleed
valve 64, and the Ride Control valve 330 are closed).
[0073] The hydraulic system 10 uses drive shaft speed measurement
and swash displacement measurement (e.g., via displacement sensors
29 and 39) to estimate flow coming from the energy recovery system
transformer 20. This, combined with position feedback on the mode
and directional control valves 110, 130, 160, 200, allows precise
matching of flow requests from the operator. The hydraulic system
10 may thereby maintain a machine feel similar to a conventional
machine. By incorporating flow estimates, a precise opening amount
of the mode and directional control valves 110, 130, 160, 200 is
possible and system dynamics may be robustly controlled allowing
productive work to be done by the actuators 830, 830', 860, 860'
while recovering energy and while using recovered energy.
[0074] The transformer 20 may be used in lieu of proportional
metering to achieve flow control. In many cases, motion of the
actuators 830, 830', 860, 860' may be controlled with no throttling
by using the swash control 38 of pump-motor 32. Throttling may be
done when supplying or recovering energy from the lift and tilt
actuators 830, 830', 860, 860' simultaneously and/or when flow
being recovered exceeds the sinking capacity of the transformer
pump-motor 32, in which case excess flow may be throttled to tank
500 using the direction control valves 110, 130 and typical
meter-out control.
[0075] The hybrid system electronic control unit 250 interfaces
with the baseline electronic control unit 272. This provides means
to de-stroke the main pumps of the baseline hydraulic system 270 as
the additional energy source of the hybrid system can be accounted
for in the overall power management of the mobile work machine 800,
800'. Otherwise, during certain times a hybrid system may fight
against a baseline pump control, and other times the two energy
sources may be additive. According to the principles of the present
disclosure, it is better to control the main pumps of the baseline
hydraulic system 270 to account for the additional energy source so
that the overall power trajectory of the mobile work machine 800,
800' can be leveled and not exaggerated. This further allows for
efficient engine operation.
[0076] Conventional wheel loaders with so-called "slush-box" torque
converters may keep the engine saturated at full output regardless
of any energy savings a hybrid system could potentially provide.
According to the principles of the present disclosure, a direct
interface between the transmission 100 and the hybrid system
electronic control unit 250, and optionally replacing the torque
converter with an automated manual transmission, will avoid
unnecessary engine saturation.
[0077] According to the principles of the present disclosure, rod
to tank valves 300 and 310 are used, both to avoid the necessity of
independent metering and to further reduce throttling losses (e.g.,
there may be less loss in a binary valve than a similarly sized
proportional valves). Furthermore, the low-power quick-extend
feature is provided for by enabling the pressurizing of both ports
862 and 864 of the tilt actuators 830, 830'.
[0078] According to the principles of the present disclosure, the
transformer 20 may be set to continuously spin, and thereby have
full flow control authority. This enables engine load leveling and
other functionality that is unavailable with an intermittently
spinning transformer of certain other hybrid systems.
[0079] According to the principles of the present disclosure,
multiple actuators (e.g., multiple linear actuators) may be
hybridized, sharing a common transformer 20.
[0080] According to the principles of the present disclosure,
explicit position feedback on both the mode valves and the
directional control valves 110, 130, 160, 200 is provided. This,
combined with knowing the rotational speed and swash displacement
of the transformer pump-motors 22, 32, results in accurate flow
control and the ability to maintain the same machine feel and
dynamics as a conventional mobile work machine.
[0081] According to the principles of the present disclosure, the
hydraulic system 10 may incorporate a load sense main pump control
architecture. The input/output for the hybrid system ECU 250 may be
set up to provide all necessary interface for a load sense
architecture.
[0082] According to the principles of the present disclosure, the
transformer 20 may be sized smaller than a total flow capacity of
the mobile work machine 800, 800' as a portion of the flow may
bypass the transformer 20. In particular, if a maximum capacity of
the transformer 20 is reached when flow returns from the actuators
830, 830', 860, 860', the excess flow can be routed across the
directional control valves 110, 130, 160, 200. Likewise, if a
maximum capacity of the transformer 20 is reached when flow is
supplied to the actuators 830, 830', 860, 860', the excess flow
required can be supplied by the baseline hydraulic system 270 and
routed across the directional control valves 110, 130. Similarly,
as the transformer 20 may be coupled to the transmission 100, if a
maximum capacity of the transformer 20 is reached when the
transformer 20 acts to decelerate the mobile work machine 800, 800'
(e.g., in combination with flow returns from the actuators 830,
830', 860, 860', the excess flow can be routed across the
directional control valves 110, 130, 160, 200 and/or the PTO clutch
84 can be disengaged. If the PTO clutch 84 is disengaged,
conventional brakes may fully decelerate the mobile work machine
800, 800'. If the PTO clutch 84 is engaged, conventional brakes may
fully or partially decelerate the mobile work machine 800, 800'.
Likewise, if a maximum capacity of the transformer 20 is reached
when the transformer 20 acts to accelerate the mobile work machine
800, 800', flow can be supplied by the baseline hydraulic system
270 and routed across the directional control valves 110, 130 to at
least partially relieve the transformer 20.
[0083] By facilitating the partial use of the transformer 20 and
thereby facilitating the partial use of the accumulator 50, the
hydraulic system 10 permits a smaller capacity and/or more
affordable transformer 20 and/or accumulator 50 to be used while
maintaining control characteristics (e.g., operator feel) of the
mobile work machine 800, 800'. The partial use of the transformer
20 may still cover a substantial portion of a duty cycle of the
mobile work machine 800, 800'. In other words, the transformer 20
and/or the accumulator 50 may be sized based on economic models
rather than for a peak capacity of the mobile work machine 800,
800'. This is especially beneficial in duty cycles that rarely see
peak capacity events.
[0084] The various embodiments described above are provided by way
of illustration only and should not be construed to limit the
claims attached hereto. Those skilled in the art will readily
recognize various modifications and changes that may be made
without following the example embodiments and applications
illustrated and described herein, and without departing from the
true spirit and scope of the disclosure.
* * * * *