Information
-
Patent Grant
-
6748738
-
Patent Number
6,748,738
-
Date Filed
Friday, May 17, 200222 years ago
-
Date Issued
Tuesday, June 15, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Finnegan, Henderson, Farabow, Garrett & Dunner
- Burrows; J. W.
- Hanley; Steve M.
-
CPC
-
US Classifications
Field of Search
US
- 060 464
- 060 484
- 060 414
- 091 444
- 091 446
- 091 454
- 091 455
- 091 456
- 091 457
- 091 508
- 091 523
-
International Classifications
-
Abstract
A hydraulic regeneration system for a work machine is provided. The hydraulic regeneration system includes a first hydraulic actuator having a first chamber and a second chamber, a second hydraulic actuator having a third chamber and a fourth chamber, and a source of pressurized fluid. A first directional control valve is disposed between the source of pressurized fluid and the first chamber of the first hydraulic actuator and the third chamber of the second hydraulic actuator. A second directional control valve is disposed between the source of pressurized fluid and the second chamber of the first hydraulic actuator and the fourth chamber of the second hydraulic actuator. An accumulator may also be used to store pressurized fluid and selectively supply pressurized fluid to increase the efficiency of the work machine.
Description
TECHNICAL FIELD
The present invention is directed to hydraulic regeneration. More particularly, the present invention is directed to a system and method for accumulating and using regenerated hydraulic energy.
BACKGROUND
Work machines are commonly used to move heavy loads, such as earth, construction material, and/or debris. These work machines, which may be, for example, wheel loaders, excavators, bulldozers, backhoes, and track loaders, typically include at least two types of power systems, a propulsion system and a work implement system. The propulsion system may be used, for example, to move the work machine around or between work sites and the work implement system may be used, for example, to move a work implement through a work cycle at a job site.
The efficiency of a work machine may be measured by comparing the amount of energy input into the work machine with the amount of work performed by the work machine. Typically, a work machine will include an engine that powers both the propulsion system and the work implement system. Thus, the energy input to the work machine may be measured as a function of the amount of fuel supplied to the engine. The work output of the work machine may be measured as a function of the work performed by the propulsion system and the work implement system. A work machine with a high efficiency will perform a greater amount of work on a given quantity of fuel.
A work implement system for a work machine may include a hydraulic system that is powered by pressurized fluid. In this type of system, a source of pressurized fluid converts energy generated by the combustion of fuel in the engine into pressurized fluid. This pressurized fluid may then be directed to a hydraulic actuator, which may be, for example, a hydraulic cylinder or a fluid motor, to move the work implement. Because the pressurized fluid represents energy, the efficiency of the work machine is reduced when pressurized fluid is released to a tank. The reduction in efficiency results from the release of energy as heat to the tank as the pressure of the fluid drops. In other words, the release of pressurized fluid to the tank results in energy being used to add heat to the fluid in the tank instead of being used to move the work implement.
An exemplary hydraulic system for a work machine that recovers or recycles fluid from a lifting cylinder is described in International Publication No. WO 00/00748 to Laars Bruun. As described therein however, an additional pump operated by the drive unit of the work machine is required to communicate fluid between an accumulator and the head end of the lifting cylinder. Depending upon the desired direction of movement of the lift cylinder, and the pressure difference between accumulator and cylinder, the drive unit supplies energy to, or receives energy from, the hydraulic circuit. Thus, an additional energy input is required to recycle the captured energy and the efficiency gains are, therefore, minimized.
Energy may also be wasted by the propulsion system of a work machine. For example, a significant amount of energy generated by the engine may be converted to kinetic energy of the work machine through a transmission on the work machine. This kinetic energy is typically dissipated as heat through the brakes when the ground speed of the work machine is reduced.
Thus, the efficiency of a work machine may be improved by limiting the amount of energy that is inefficiently used or wasted during the ordinary operation of the work machine. In addition, the efficiency of the work machine may be improved by capturing energy in a device such as an accumulator that would otherwise be wasted. The captured energy may then be used in a future operation of the work machine, thereby reducing the fuel demands of the engine.
The hydraulic regeneration system of the present invention solves one or more of the problems set forth above.
SUMMARY OF THE INVENTION
One aspect of the present invention is directed to a hydraulic system that includes a first hydraulic actuator having a first chamber and a second chamber, a second hydraulic actuator having a third chamber and a fourth chamber, and a source of pressurized fluid. A first directional control valve is disposed between the source of pressurized fluid and the first chamber of the first hydraulic actuator and the third chamber of the second hydraulic actuator. A second directional control valve is disposed between the source of pressurized fluid and the second chamber of the first hydraulic actuator and the fourth chamber of the second hydraulic actuator.
In another aspect, the present invention is directed to a hydraulic system that includes an accumulator, a source of pressurized fluid, a first directional control valve, and a second directional control valve. A first fluid line connects the source of pressurized fluid with the first directional control valve and a second fluid line connects the source of pressurized fluid with the second directional control valve. A third directional control valve is configured to control the rate and direction of fluid flow between the accumulator and the first and second fluid lines.
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 invention, as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description, serve to explain the principles of the invention. In the drawings:
FIG. 1
is a schematic and diagrammatic illustration of an exemplary embodiment of a hydraulic system according to the present invention;
FIGS. 2
a
-
2
e
are schematic and diagrammatic illustrations of exemplary hydraulic circuits that may be created with the hydraulic system of
FIG. 1
;
FIG. 3
is a schematic and diagrammatic illustration of another exemplary embodiment of a hydraulic system according to the present invention; and
FIG. 4
is a schematic and diagrammatic illustration of another exemplary embodiment of a hydraulic system according to the present invention.
DETAILED DESCRIPTION
Reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
As diagrammatically illustrated in
FIG. 1
, a hydraulic system
10
for a work machine
11
is provided. Work machine
11
may be any type of machine commonly used to move loads, such as, for example, earth, construction material, or debris. Work machine
10
may be, for example, a wheel loader, a track loader, a backhoe, an excavator, or a bulldozer. Work machine
11
includes a work implement
13
. Work implement
13
may include a ground engaging tool, such as, for example, a bucket or blade, and a linkage assembly upon which the ground engaging tool is mounted.
A first hydraulic actuator
16
and a second hydraulic actuator
18
are operatively connected with work implement
13
. First and second hydraulic actuators
16
and
18
may be, for example, hydraulic cylinders or fluid motors. In the exemplary embodiment illustrated in
FIG. 1
, first and second hydraulic actuators
16
and
18
are hydraulic cylinders.
First and second hydraulic actuators
16
and
18
may be connected to the ground engaging tool of the work implement or the linkage assembly of the work implement. In one exemplary embodiment, first and second hydraulic actuators
16
and
18
are connected to the linkage assembly of the work implement and are configured to provide lifting power for the work implement. As one skilled in the art will recognize, first and second hydraulic actuators may perform alternative functions on work machine
11
.
As shown in
FIG. 1
, first hydraulic actuator
16
includes a housing
32
that slidably receives a piston
30
and a rod
28
. Piston
30
defines a first chamber
20
and a second chamber
22
within housing
32
of first hydraulic actuator
16
. First chamber
20
may also be referred to as the rod end of first hydraulic actuator
16
, and second chamber
22
may also be referred to as the head end of first hydraulic cylinder
16
.
Similarly, second hydraulic actuator
18
includes a housing
38
that slidably receives a piston
36
and a rod
34
. Piston
36
defines a third chamber
24
and a fourth chamber
26
within housing
38
of second hydraulic actuator
18
. Third chamber
24
may also be referred to as the rod end of second hydraulic actuator
18
, and fourth chamber
26
may also be referred to as the head end of second hydraulic cylinder
18
.
As also shown in
FIG. 1
, hydraulic system
10
includes a source of pressurized fluid
12
, which may be, for example, a fixed capacity or variable capacity pump. Source of pressurized fluid
12
draws fluid from a tank
14
and works the fluid to a predetermined pressure. A check valve
85
may be disposed between tank
14
and source of pressurized fluid
12
to prevent an undesirable flow of fluid from source of pressurized fluid
12
to tank
14
.
Source of pressurized fluid
12
directs the pressurized fluid through a fluid line
40
to a first directional control valve
44
. A check valve
42
may be positioned in fluid line
40
to prevent an undesirable flow of fluid from first directional control valve
44
to source of pressurized fluid
12
. First directional control valve
44
is connected to first chamber
20
of first hydraulic actuator
16
through a fluid line
76
. First directional control valve
44
is also connected to third chamber
24
of second hydraulic actuator
18
through a fluid line
78
.
First directional control valve
44
includes a first metering valve
48
, a second metering valve
50
, a third metering valve
52
, and a fourth metering valve
54
. Each of the first
48
, second
50
, third
52
, and fourth
54
metering valves are independently adjustable to meter a flow of fluid therethrough. For example, first metering valve
48
may be opened to allow a variable flow rate of fluid to flow from fluid line
40
to fluid lines
76
and
78
and into first chamber
20
and third chamber
24
, respectively. Alternatively, first directional control valve
44
may be comprised of any type of valve readily apparent to one skilled in the art, such as, for example, a spool valve.
As also illustrated in
FIG. 1
, first directional control valve
44
is connected to a second directional control valve
46
through fluid lines
83
and
84
. Second directional control valve
46
also includes a first metering valve
56
, a second metering valve
58
, a third metering valve
60
, and a fourth metering valve
62
. Each of the first
56
, second
58
, third
60
, and fourth
62
metering valves are independently controllable to meter a flow of fluid therethrough.
Second directional control valve
46
is connected to second chamber
22
of first hydraulic actuator
16
through a fluid line
80
and to fourth chamber
26
of second hydraulic actuator
18
through a fluid line
82
. Second directional control valve
46
is also connected to the inlet of source of pressurized fluid
12
and tank
14
through a fluid line
86
. Alternatively, second directional control valve
46
may be comprised of any type of valve readily apparent to one skilled in the art, such as, for example, a spool valve.
As illustrated in
FIG. 1
, work machine
11
may include a third hydraulic actuator
98
. Third hydraulic actuator
98
may be connected to work implement
13
or may be connected to a second work implement (not shown) on work machine
11
. Third hydraulic actuator
98
may control a secondary function, such as tilt, for work implement
13
.
Third hydraulic actuator
98
includes a housing
108
that slidably receives a piston
104
and a rod
106
. Piston
104
defines a fifth chamber
100
and a sixth chamber
102
within housing
108
. Fifth chamber
100
may also be referred to as the rod end of third hydraulic actuator
98
, and sixth chamber
102
may also be referred to as the head end of third hydraulic cylinder
98
.
As further shown in
FIG. 1
, a third directional control valve
66
controls the rate and direction of fluid flow to and from third hydraulic actuator
98
. Third directional control valve
66
includes a first metering valve
68
, a second metering valve
70
, a third metering valve
72
, and a fourth metering valve
74
. Each of the first
68
, second
70
, third
72
, and fourth
74
metering valves are independently controllable to meter a flow of fluid therethrough.
Third directional control valve
66
is connected to fifth chamber
100
through fluid line
110
and to sixth chamber
102
through fluid line
112
. Third directional control valve
66
is also connected to source of pressurized fluid
40
through fluid line
118
, which connects to fluid line
40
. In addition, third directional control valve
66
is connected to tank
14
and the inlet of source of pressurized fluid
12
through fluid line
114
, which connects to fluid line
86
. Alternatively, third directional control valve
66
may be comprised of any type of valve readily apparent to one skilled in the art, such as, for example, a spool valve.
A check valve
116
may be disposed in fluid line
114
. Check valve
116
may prevent fluid released from second directional control valve
46
from flowing to third directional control valve
66
. In an alternative embodiment, fluid line
114
may be connected directly to tank
14
.
As further illustrated in
FIG. 1
, hydraulic system
10
includes an accumulator
64
. A fourth directional control valve
88
is provided to control the rate and direction of fluid flow to accumulator
64
. Fourth directional control valve
88
includes a first metering valve
90
, a second metering valve
92
, a third metering valve
94
, and a fourth metering valve
96
. Each of the first
90
, second
92
, third
94
, and fourth
96
metering valves are independently controllable to meter a flow of fluid therethrough. Alternatively, fourth directional control valve
88
may be comprised of any type of valve readily apparent to one skilled in the art, such as, for example, a spool valve.
As also shown in
FIG. 1
, fourth directional control valve
88
is disposed between accumulator
64
, fluid line
40
, fluid line
86
, and tank
14
. A fluid line
41
connects fourth directional control valve
88
with fluid line
40
. A fluid line
43
connects fourth directional control valve
88
with fluid line
86
. A fluid line
45
connects fourth directional control valve
88
with tank
14
.
The exemplary embodiment of hydraulic system
10
described above is operable to control the motion of work implement
13
as well as to capture energy in the form of pressurized fluid released from one or more of first, second, and third hydraulic actuators
16
,
18
, and
98
. The pressurized fluid may be stored in accumulator
64
and used by work machine
11
to perform a future operation.
First and second directional control valves
44
and
46
control the direction and rate of fluid flow into first and second hydraulic actuators
16
and
18
and, thus, the rate and direction of movement of work implement
13
. For example, to move work implement
13
in the direction indicated by arrow
29
, which, for the purposes of the present disclosure, will be considered as lifting work implement
13
, second
50
and fourth
54
metering valves of first directional control valve
44
and second
58
and fourth
62
metering valves of second directional control valve
46
are opened. This configuration allows pressurized fluid to flow from source of pressurized fluid
12
through fluid lines
84
,
80
, and
82
to reach second chamber
22
of first hydraulic actuator
14
and fourth chamber
26
of second hydraulic actuator. The force of the pressurized fluid moves pistons
30
and
36
in the direction of arrow
29
. As pistons
30
and
36
move, fluid is forced out of first chamber
20
and third chamber
24
. This fluid flows through fluid lines
76
,
83
and
86
to return to tank
14
or to the inlet of source of pressurized fluid
12
.
To move work implement
13
in the direction indicated by arrow
31
, which, for the purposes of the present disclosure, will be considered as lowering of work implement
13
, fluid may be released from second chamber
22
and fourth chamber
26
and fluid may be added to first chamber
20
and third chamber
24
. The metering valves of first, second, and fourth directional control valves
44
,
46
, and
88
may be metered open in several different combinations to achieve the desired direction of fluid flow to lower work implement
13
. Several of the possible valve combinations are described in greater detail below.
In one combination configured to lower work implement
13
, second metering valve
50
of first directional control valve
44
; second
58
, third
60
, and fourth
62
metering valves of second directional control valve
46
; and third metering valve
94
of fourth directional control valve
88
may be partially or completely opened. The fluid connections created by this valve combination are schematically illustrated in
FIG. 2
a.
As shown in
FIG. 2
a
, opening valves in this combination allows fluid to flow from second chamber
22
and fourth chamber
26
through fluid lines
80
and
82
, respectively. The fluid exiting from second chamber and fourth chamber
26
may flow through metering valves
58
,
60
, and
62
and into fluid line
86
. Third metering valve
94
of fourth directional control valve
88
may be opened to meter the fluid flowing in fluid line
86
to tank
14
. Alternatively, third metering valve
94
of fourth directional control valve
88
may be closed to direct the fluid flowing in fluid line
86
to the inlet of source of pressurized fluid
12
. Directing pressurized fluid to the inlet of source of pressurized fluid
12
may reduce the torque required to operate the source of pressurized fluid
12
and thereby increase the efficiency of work machine
11
.
As described previously, fluid will be added to first chamber
20
and third chamber
24
as the volume of these chambers increases with movement of pistons
30
and
36
. Because the weight of work implement
13
may be sufficient to force the fluid out of second and fourth chambers
22
and
26
, the fluid supplied to the first chamber
20
and third chamber
24
may not need to be pressurized. Accordingly, metering valve
50
of first directional control valve
44
may be opened to meter fluid exiting second and fourth chambers
22
and
26
into first and third chambers
20
and
24
. By returning some of the fluid released from second and fourth chambers
22
and
26
to first and third chambers
20
and
24
, the amount of pressurized fluid required from source of pressurized fluid
12
may be reduced. In this manner, the overall efficiency of work machine
11
may be increased as less energy is required to lower work implement
13
.
Another valve configuration arranged to lower work implement
13
is schematically illustrated in
FIG. 2
b
. As shown therein, fluid flowing through fluid line
86
may be metered into accumulator
64
through fourth metering valve
96
of fourth directional control valve
88
. Fourth metering valve
96
of fourth directional control valve
88
may be metered open depending on the pressure of the fluid in fluid line
86
.
Under certain circumstances, the weight of work implement
13
acting through pistons
30
and
36
may pressurize the fluid in second and fourth chambers
22
and
26
to a level suitable for storing the fluid in accumulator
64
. If this pressurized fluid were directed to tank
14
, instead of accumulator
64
, the energy of the pressurized fluid would be dissipated as heat. By storing the pressurized fluid in accumulator
64
, at least a portion of the potential energy of an elevated work implement
13
may be captured and, as explained in greater detail below, may be used to assist work machine
11
in performing future tasks.
As shown in
FIG. 1
, hydraulic system
10
may include a series of pressure sensors
87
. Pressure sensors
87
may be disposed, for example, in fluid lines
40
and
86
, as well as adjacent accumulator
64
. Pressure sensors
87
may be any device capable of sensing the pressure of a fluid in a fluid line. Fourth metering valve
96
of fourth directional control valve
88
may be metered open when the sensed pressure indicates that the pressure of the fluid in fluid line
86
is above a predetermined pressure. Alternatively, fourth metering valve
96
of fourth directional control valve
88
may be metered open when work machine
11
encounters a set of operating conditions that are known to result in the pressurization of the fluid in fluid line
86
above the predetermined limit. The pressure of the fluid entering accumulator
64
may be adjusted by opening or closing third metering valve
94
to increase or decrease the amount of fluid flowing to tank
14
.
Another combination of valves configured to lower work implement
13
is illustrated in
FIG. 2
c
. To achieve this combination, first metering valve
48
of first directional control valve
44
; second
58
, third
60
and fourth
62
metering valves of second directional control valve
46
; and third metering valve
94
of fourth directional control valve
88
may be opened (referring to FIG.
1
).
In this valve combination, source of pressurized fluid
12
is connected to first and third chambers
20
and
24
. The force of the pressurized fluid acts on pistons
30
and
36
to move pistons
30
and
36
in the direction of arrow
31
. The flow rate of fluid into first and third chambers
20
and
24
and the rate of movement of pistons
30
and
36
and work implement
13
may be controlled by adjusting first metering valve
48
of first directional control valve
44
.
The movement of pistons
30
and
36
forces fluid from second and fourth chambers
22
and
26
. The fluid released from second and fourth chambers
22
and
26
is directed through metering valves
58
,
60
and
62
into fluid line
86
. This released flow of fluid may then flow to the inlet of source of pressurized fluid
12
or may flow through metering valve
94
to tank
14
. In addition, if the pressure of the fluid in fluid line
86
is above the predetermined limit, fourth metering valve
96
may be metered open to direct at least a portion of the pressurized fluid into accumulator
64
.
The particular combination of valves opened to lower work implement
13
may depend upon the particular operating conditions and/or the desires of the operator. For example, the valve combination illustrated in
FIG. 2
a
may be used if a rapid lowering of work implement
13
is desired. The valve combination illustrated in
FIG. 2
b
may be used under normal operating conditions to improve the efficiency of work machine
11
by storing pressurized fluid in accumulator
64
. The valve combination illustrated in
FIG. 2
c
may be used to “power down” work implement
13
, i.e. provide an additional force to lower work implement
13
when the weight of work implement
13
is not sufficient to lower work implement
13
.
The pressurized fluid stored in accumulator
64
may be used to supplement or replace the pressurized fluid typically provided by source of pressurized fluid
12
to perform a function on work machine
11
. With reference to
FIG. 1
, the pressurized fluid in accumulator
64
may be metered through fluid line
41
and into fluid line
40
by opening first metering valve
90
of fourth directional control valve
88
. The pressurized fluid released from accumulator
64
may then be directed through first and second directional control valves
44
and
46
in the manner described previously to move or assist in the moving of work implement
13
. By utilizing the fluid stored in accumulator
64
, the amount of pressurized fluid required from source of pressurized fluid
12
is reduced. Thus, less external energy is required to move work implement
13
and the overall efficiency of work machine
11
may be increased.
Another possible use of the pressurized fluid stored in accumulator
64
is to assist in moving third hydraulic actuator
98
. Referring to
FIG. 1
, third hydraulic actuator
98
may be moved by introducing pressurized fluid into one of fifth chamber
100
or sixth chamber
102
and allowing fluid to flow out of the other chamber. The pressurized fluid will act to move piston
104
within housing
108
.
The pressurized fluid used to move third hydraulic actuator
98
may come from accumulator
64
. By metering open first metering valve
90
of fourth directional control valve
88
, fluid may flow from accumulator
64
to third directional control valve
66
. One of first and fourth metering valves
68
and
74
may then be opened to allow the pressurized fluid from the accumulator
64
to flow to one of fifth chamber
100
or sixth chamber
102
. In addition, one of second and third metering valves
70
and
72
may be metered open to allow fluid to flow from one of fifth and sixth chambers
100
and
102
to fluid line
86
. It should be noted that the flow of pressurized fluid from accumulator
64
to third hydraulic actuator
98
may be supplemented or replaced by a flow of pressurized fluid generated by source of pressurized fluid
12
.
In addition, pressurized fluid released by either of first or second hydraulic actuators
16
and
18
may be directed through first and second directional control valves
44
and
46
to third hydraulic actuator
98
. For example, when pressurized fluid is released from second chamber
22
of first hydraulic actuator
16
, fourth metering valve
54
of first directional control valve
44
may be opened. This will direct the released fluid into fluid line
118
and towards third hydraulic actuator
98
.
By using the pressurized fluid stored in accumulator
64
or the pressurized fluid released from first and second hydraulic actuators
16
and
18
to move third hydraulic actuator
98
, the amount of pressurized fluid required from source of pressurized may be further reduced. In this manner, the efficiency of work machine
11
may be further improved.
As mentioned above, when piston
104
of third hydraulic actuator
98
is moving, fluid will be released from either fifth chamber
100
or sixth chamber
102
, depending upon the direction of movement of piston
104
. In certain operating conditions, the fluid released from either fifth chamber
100
or sixth chamber
102
may be pressurized above the pre-determined level. In these situations, fourth metering valve
96
of third directional control valve
88
may be opened to direct the pressurized fluid into accumulator
64
. In this manner, additional energy in the form of pressurized fluid released from third hydraulic actuator
98
may be captured in accumulator
64
.
Another potential use of the pressurized fluid stored in accumulator
64
is to assist the propulsion of work machine
11
. As schematically illustrated in
FIG. 2
d
, pressurized fluid released from accumulator
64
may be directed to the inlet of source of pressurized fluid
12
. This may be accomplished by opening fourth metering valve
96
of fourth directional control valve
88
to allow fluid to flow into fluid line
86
. A check valve
117
may be disposed in fluid line
86
between fourth directional control valve
88
and second directional control valve
46
to prevent fluid from flowing from accumulator
64
to second directional control valve
46
. Fluid exiting source of pressurized fluid
12
will therefore be directed to tank
14
through second metering valve
92
of fourth directional control valve
88
.
As shown in
FIG. 1
, source of pressurized fluid
12
is connected to an engine
63
through a crankshaft
65
. Typically, source of pressurized fluid
12
includes a drive gear (not shown) that engages a corresponding gear (not shown) secured to crankshaft
65
. The operation of engine
63
exerts a torque on crankshaft
65
that drives source of pressurized fluid
12
. In operation, source of pressurized fluid
12
draws in fluid at an ambient or low-charge pressure and works the fluid to increase the pressure of the fluid.
If, however, pressurized fluid is introduced to the inlet of source of pressurized fluid
12
, the energy in the pressurized fluid may assist the torque generated by engine
63
. For example, introducing pressurized fluid to the inlet of a fixed capacity pump may effectively reverse the operation of the pump and cause the pump to operate as a fluid motor. The pump will therefore exert a torque on crankshaft
65
that assists the operation of engine
63
. Thus, when work machine
11
is accelerating, pressurized fluid may be directed to the inlet of source of pressurized fluid
12
to assist engine
63
in propelling the work vehicle. In this manner, the amount of fuel required to accelerate work machine
11
to a given speed may be reduced.
Thus, by directing pressurized fluid from accumulator
64
to the inlet of source of pressurized fluid
12
, the operation of engine
63
may be assisted. This additional energy may be used, for example, to assist engine
63
when accelerating work machine
11
. This additional energy may also be used, for example, to maintain the speed of work machine
11
.
In addition, accumulator
64
may be used to capture the kinetic energy of work machine
11
when the operator instructs that the ground speed of work machine be reduced. The ground speed of work machine
11
may be reduced by decreasing the amount of energy applied to propelling the vehicle and/or by exerting a force that opposes the motion of work machine
11
. The amount of energy applied to propel work machine
11
may be decreased, for example, by decreasing the amount of fuel combusted by the engine. A force opposing the movement of work machine may be exerted, for example, by applying a brake.
In addition, as schematically illustrated in
FIG. 2
e
, a force opposing the movement of work machine
11
may be exerted by engaging source of pressurized fluid
12
and directing the generated pressurized fluid to accumulator
64
. The torque required by source of pressurized fluid
12
to pressurize the fluid will oppose the rotation of engine crankshaft
65
and, therefore, will oppose the operation of the transmission of work machine
11
.
Thus, when an operator requests that the ground speed of work vehicle
11
be reduced, first metering valve
90
of fourth directional control valve
88
may be opened to connect source of pressurized fluid with accumulator
64
. In this manner, at least a portion of the kinetic energy of the moving work machine
11
may be converted to energy in the form of pressurized fluid in accumulator
64
. It should be noted that the brakes of work machine
11
may be applied in combination with, or instead of, pressurizing additional fluid to reduce the ground speed of work machine
11
.
Accumulator
64
may also be used to capture energy when work machine
11
encounters a “bucket pinning” situation. A bucket pinning situation may be encountered when work machine
11
engages an obstacle, such as, for example, a work pile that exerts a significant force on the work machine and holds the work machine in a stationary position. In this situation, the torque exerted by engine
63
through the transmission may cause the traction devices, which may be wheels or tracks, of the work machine to slip or spin on the ground while the work machine remains stationary. In other words, the energy used by work machine
11
attempting to move the work machine is wasted as the work machine is held stationary by the obstacle.
This energy may be captured as pressurized fluid or used to provide a boost to the hydraulic actuators moving the work implement. For example, with reference to the exemplary embodiment of
FIG. 1
, when the torque generated by engine
63
is great enough to cause the traction devices of work machine
11
to slip, source of pressurized fluid
12
may be engaged to reduce the torque exerted on the traction devices. As discussed above, engaging source of pressurized fluid
12
to generate additional pressurized fluid will require additional torque from engine
63
and will thereby reduce the torque exerted on the traction devices. Thus, the excess torque that causes the traction devices to slip or spin may be used to generate additional pressurized fluid. This additional pressurized fluid may be directed into accumulator
64
or may be directed to one or more of first, second, and third hydraulic actuators
16
,
18
,
98
to assist in the movement of work implement
13
.
One skilled in the art will also recognize that in certain work machines, source of pressurized fluid
12
is often separated from the traction devices through a device, such as a torque converter. In this configuration, the spinning of the traction device may not result in an excess torque on crankshaft
65
of engine
63
. As illustrated in
FIG. 3
, to capture this excess energy, a second source of pressurized fluid
120
may be connected to traction device
130
. Second source of pressurized fluid
120
may be directly connected to traction device
130
or a clutch
122
may be disposed between second source of pressurized fluid
120
and traction device
130
. A gear reduction
123
that may have clutch and brake mechanisms may be operatively engaged with traction device
130
.
As also shown in
FIG. 3
, a fluid line
128
connects second source of pressurized fluid
120
with fluid line
86
. Second source of pressurized fluid
120
may draw fluid from tank
14
or receive fluid released from one or more of the first, second, or third hydraulic actuators
16
,
18
, or
98
. In addition, as described previously, accumulator
64
may release pressurized fluid to the inlet of second source of pressurized fluid
120
to thereby drive the second source of pressurized fluid as a fluid motor.
Second source of pressurized fluid
120
may direct pressurized fluid into fluid line
126
. A check valve
124
may be disposed in fluid line
126
to prevent fluid from returning to second source of pressurized fluid
120
. Fluid line
126
may be connected to fluid line
41
. Thus, pressurized fluid provided by second source of pressurized fluid
120
may be directed by fourth directional control valve
88
into accumulator
64
or may flow through fluid line
40
to be used in moving first, second, or third hydraulic actuators
16
,
18
,
98
.
When work machine
11
is operating under normal circumstances, however, engagement of second source of pressurized fluid
120
with traction device
130
may cause a resistance to movement of traction device
130
. To prevent this resistance, clutch
122
may be disengaged to disconnect second source of pressurized fluid
120
from traction device
130
. Alternatively, a fifth metering valve may be disposed in fourth directional control valve
88
. Fifth metering valve
97
may be opened to allow second source of pressurized fluid to circulate fluid flow and thereby reduce the resistance exerted against traction device
130
.
Excess energy created by a work machine having a hydrostatic drive system in a bucket-pinning situation may also be captured with the above-described hydraulic system. As illustrated in
FIG. 4
, a work machine may include a hydrostatic drive
132
. Hydrostatic drive
132
includes a fluid motor
138
that is connected to second source of pressurized fluid
120
by fluid lines
134
and
136
. Fluid motor
138
is connected to traction device
130
through gear reduction
123
, which may include a brake
121
.
As will be recognized by one skilled in the art, second source of pressurized fluid
120
is operable to generate a flow of pressurized fluid through one of fluid lines
134
and
136
. The generated flow of pressurized fluid acts on fluid motor
138
to generate an output torque that may be transmitted to traction device
130
to move work machine
11
. Brake
121
is operable to assist active braking and park braking of work machine
11
.
As also shown in
FIG. 4
, a resolver valve
146
may be disposed between fluid lines
134
and
136
. Resolver valve
146
may be connected to fourth directional control valve
88
and fluid line
41
through a fluid line
150
. A valve
154
may be disposed in fluid line
150
to control the rate of fluid flow therethrough. Valve
154
may be an independent metering valve or any other device readily apparent to one skilled in the art as capable of selectively regulating a flow of fluid.
Resolver valve
146
is configured to connect fluid line
150
with the one of fluid lines
134
and
136
that contains the higher pressure fluid. If, for example, second source of pressurized fluid
120
is driving fluid motor with a flow of pressurized fluid in fluid line
134
, the returning fluid flow in fluid line
136
will be at a lower pressure. Accordingly, resolver valve
146
will open to connect fluid line
134
with fluid line
150
. As shown, resolver valve
146
may contain a check ball with opposing seats. Resolver valve
146
may also be any other device readily apparent to one skilled in the art.
In a bucket-pinning situation, where the work machine is stationary and fluid motor
138
exerts an excessive torque on traction device
130
, valve
154
may be opened to reduce the torque on traction device
130
. If, for example, fluid line
134
contains the pressurized fluid flow, valve
154
may be opened to direct some of the pressurized fluid into fluid line
150
instead of into fluid motor
138
. Fourth directional control valve
88
may direct the flow of pressurized fluid from fluid line
150
into accumulator
64
or into the first and second directional control valves through fluid line
40
. Thus, the energy that would have been otherwise wasted as excessive torque, may be saved for future use in accumulator
64
or used to provide a boost to the work implement.
As one skilled in the art will recognize, any fluid that is removed from hydrostatic drive
132
through fluid line
150
will need to be replaced. As shown, in the exemplary embodiment of
FIG. 4
, make-up fluid may be provided to hydrostatic drive
132
through a charge shuttle
140
. It is recognized that makeup fluid may be provided to hydrostatic drive through any other suitable device.
Charge shuttle
140
is disposed between fluid lines
134
and
136
and is configured to provide a fluid connection with the low pressure side of hydrostatic drive
132
. Charge shuttle
140
may include a pair of connected check valves
141
that are configured to engage opposing seats. The pressure of the fluid in fluid lines
134
and
136
controls the movement of connected check valves
141
to establish a fluid connection with the fluid line containing the lower pressure fluid. For example, if second source of pressurized fluid
120
is driving fluid motor
138
with pressurized fluid in fluid line
134
and is receiving low pressure fluid from fluid line
136
, the pressure difference between fluid lines
134
and
136
will move connected check valves
141
such that a fluid connection is established with fluid line
136
, which represents the low pressure side of hydrostatic drive.
Make-up fluid may be provided to charge shuttle
140
in any manner readily apparent to one skilled in the art. For example, an auxiliary pump
142
may be connected to charge shuttle
140
and configured to draw fluid from tank
14
and provide a flow of make-up fluid to charge shuttle
140
. A pressure relief valve
144
may be disposed between auxiliary pump
142
and charge shuttle
140
. Pressure relief valve
144
is configured to open and allow pressurized fluid to flow to tank
14
if the pressure of the fluid between auxiliary pump
142
and charge shuttle
140
exceeds a pre-determined pressure limit.
Make-up fluid may also be provided to hydrostatic drive
132
from fluid line
86
. As shown in
FIG. 4
, charge shuttle
140
may be connected to fluid line
86
through a fluid line
148
and a valve
152
. Valve
152
may be configured to selectively control the rate at which fluid flows through fluid line
148
. Valve
152
may be an independent metering valve or any other device readily apparent to one skilled in the art as capable of selectively regulating a flow of fluid. When valve
152
is opened, fluid may flow from fluid line
86
to charge shuttle
140
and into hydrostatic drive
132
. Thus, the fluid in fluid line
86
, which may be fluid returning from one of the first, second, or third hydraulic actuators, may be used to replace fluid extracted from hydrostatic drive
132
, instead of generating additional pressurized fluid with auxiliary pump
142
. This pressurized fluid may also be used to pressurize the inlet of source of pressurized fluid
120
and assist engine
63
in providing torque to propel work machine
11
and/or move work implement
13
.
Industrial Applicability
As will be apparent from the foregoing description, the present invention provides a hydraulic regeneration system for a work machine. The hydraulic regeneration system captures energy that would otherwise be wasted in the normal operation of the work machine and stores this energy in the form of pressurized fluid in an accumulator. The pressurized fluid stored in the accumulator may be used to perform a future operation of the work machine, such as for example, assisting in the movement of a work implement or assisting in the movement of the work machine.
Thus, with the present invention, the energy requirements of the engine may be reduced and a smaller engine may be used. In addition, the present invention may lower the amount of heat generated during normal operation. The reduction in generated heat may extend the operating life of component parts, thereby reducing the amount of required service.
By capturing and reusing energy, the present invention may increase the productivity of the work machine while decreasing the fuel demands of the work machine. Thus, the present invention may improve the overall efficiency of the work machine. In addition, the reduced fuel consumption may result in a reduced level of noise and emissions produced by the work machine.
It will be apparent to those skilled in the art that various modifications and variations can be made in the hydraulic regeneration system of the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and their equivalents.
Claims
- 1. A hydraulic system, comprising:a first hydraulic actuator having a first chamber and a second chamber; a second hydraulic actuator having a third chamber and a fourth chamber, the second hydraulic actuator being capable of operating independently from the first hydraulic actuator; a source of pressurized fluid; a first directional control valve disposed between (i) the source of pressurized fluid and (ii) the first chamber of the first hydraulic actuator and the third chamber of the second hydraulic actuator; and a second directional control valve disposed between (i) the source of pressurized fluid and (ii) the second chamber of the first hydraulic actuator and the fourth chamber of the second hydraulic actuator.
- 2. The hydraulic system of claim 1, wherein each of the first and second directional control valves includes a set of four independent metering valves.
- 3. The hydraulic system of claim 1, further including:a third hydraulic actuator having a fifth chamber and a sixth chamber; and a third directional control valve connected to at least one of the first and second directional control valves and operable to direct pressurized fluid released from at least one of the first, second, third, and fourth chambers into at least one of the fifth and sixth chambers.
- 4. The hydraulic system of claim 3, wherein each of the first, second, and third hydraulic actuators is a hydraulic cylinder.
- 5. The hydraulic system of claim 1, further including:an accumulator in fluid communication with the first hydraulic actuator and the second hydraulic actuator; and a fourth directional control valve operable to selectively direct a flow of pressurized fluid from at least one of the first, second, third, and fourth chambers into the accumulator.
- 6. The hydraulic system of claim 5, wherein the accumulator is connected to the first and second directional control valves to provide pressurized fluid to at least one of the first, second, third, and fourth chambers.
- 7. The hydraulic system of claim 5, wherein the fourth directional control valve is configured to direct pressurized fluid from the accumulator to the source of pressurized fluid.
- 8. The hydraulic system of claim 5, wherein the fourth directional control valve is configured to direct pressurized fluid from the source of pressurized fluid to the accumulator.
- 9. A method of moving a work implement actuated by a first hydraulic actuator having a first chamber and a second chamber and a second hydraulic actuator having a third chamber and a fourth chamber, comprising:directing a flow of fluid through a first directional control valve to the first chamber of the first hydraulic actuator and the third chamber of the second hydraulic actuator to move the work implement in a first direction; directing a flow of fluid through a second directional control valve to the second chamber of the first hydraulic actuator and the fourth chamber of the second hydraulic actuator to move the work implement in a second direction; and directing fluid released from at least one of the first, second, third, and fourth chambers through a third directional control valve into at least one of a fifth and a sixth chamber of a third hydraulic actuator.
- 10. The method of claim 9, further including directing the fluid released from at least one of the first, second, third, and fourth chambers through a fourth directional control valve into an accumulator.
- 11. The method of claim 10, further including directing pressurized fluid stored in the accumulator through one of the first and second directional control valves to at least one of the first, second, third, and fourth chambers.
- 12. The method of claim 10, further including directing pressurized fluid stored in the accumulator to a source of pressurized fluid.
- 13. The method of claim 10, further including directing a flow of pressurized fluid from a source of pressurized fluid through the fourth directional control valve to the accumulator.
- 14. A hydraulic system, comprising:an accumulator; a source of pressurized fluid; a first directional control valve; a second directional control valve; a first fluid line connecting the source of pressurized fluid with the first directional control valve; a second fluid line connecting the source of pressurized fluid with the second directional control valve; and a third directional control valve configured to control the rate and direction of fluid flow between the accumulator and the first and second fluid lines.
- 15. The hydraulic system of claim 14, wherein each of the first, second, and third directional control valves include a set of four independent metering valves.
- 16. The hydraulic system of claim 15, further including a second source of pressurized fluid in fluid connection with the first and second fluid lines.
- 17. The hydraulic system of claim 16, wherein the third directional control valve includes a fifth independent metering valve.
- 18. The hydraulic system of claim 14, further including:a first hydraulic actuator having a first chamber and a second chamber; a second hydraulic actuator having a third chamber and a fourth chamber; and a third hydraulic actuator having a fifth chamber and a sixth chamber, wherein the first directional control valve is disposed between the source of pressurized fluid and the first chamber of the first hydraulic actuator and the third chamber of the second hydraulic actuator, the second directional control valve is disposed between the source of pressurized fluid and the second chamber of the first hydraulic actuator and the fourth chamber of the second hydraulic actuator, and the third directional control valve is disposed between the source of pressurized fluid and the fifth and sixth chambers of the third hydraulic actuator.
- 19. A method of using pressurized fluid stored in a hydraulic circuit having a source of pressurized fluid and an accumulator, comprising:connecting the source of pressurized fluid to a first directional control valve with a first fluid line; connecting the source of pressurized fluid to a second directional control valve with a second fluid line; and directing a flow of pressurized fluid from the accumulator through a third directional control valve to one of the first and second fluid lines.
- 20. The method of claim 19, further including:operating the first directional control valve to control a flow of pressurized fluid to a first chamber of a first hydraulic actuator and a third chamber of a second hydraulic actuator; and operating the second directional control valve to control a flow of pressurized fluid to a second chamber of the first hydraulic actuator and a fourth chamber of the second hydraulic actuator.
- 21. A work machine, comprising:a work implement; a first hydraulic actuator having a first chamber and a second chamber and operatively connected to the work implement; a second hydraulic actuator having a third chamber and a fourth chamber and operatively connected to the work implement, the second hydraulic actuator being capable of operating independently from the first hydraulic actuator; a source of pressurized fluid; a first directional control valve disposed between (i) the source of pressurized fluid and (ii) the first chamber of the first hydraulic actuator and the third chamber of the second hydraulic actuator; and a second directional control valve disposed between (i) the source of pressurized fluid and (ii) the second chamber of the first hydraulic actuator and the fourth chamber of the second hydraulic actuator.
- 22. The work machine of claim 21, wherein each of the first and second directional control valves includes a set of four independent metering valves.
- 23. The work machine of claim 21, further including:a third hydraulic actuator having a fifth chamber and a sixth chamber; and a third directional control valve connected to at least one of the first and second directional control valves and operable to direct pressurized fluid released from at least one of the first, second, third, and fourth chambers into at least one of the fifth and sixth chambers.
- 24. The work machine of claim 23, wherein each of the first, second, and third hydraulic actuators is a hydraulic cylinder.
- 25. The work machine of claim 21, further including:an accumulator in fluid communication with the first hydraulic actuator and the second hydraulic actuator; and a fourth directional control valve operable to selectively direct a flow of pressurized fluid from at least one of the first, second, third, and fourth chambers into the accumulator.
- 26. The work machine of claim 25, wherein the accumulator is connected to the first and second directional control valves to provide pressurized fluid to at least one of the first, second, third, and fourth chambers.
- 27. The work machine of claim 25, wherein the fourth directional control valve is configured to direct pressurized fluid from the accumulator to the source of pressurized fluid.
- 28. The work machine of claim 25, wherein the fourth directional control valve is configured to direct pressurized fluid from the source of pressurized fluid to the accumulator.
- 29. A work machine, comprising:a work implement; an accumulator; a source of pressurized fluid; a first directional control valve disposed between the source of pressurized fluid and the work implement; a second directional control valve disposed between the source of pressurized fluid and the work implement; a first fluid line connecting the source of pressurized fluid with the first directional control valve; a second fluid line connecting the source of pressurized fluid with the second directional control valve; and a third directional control valve configured to control the rate and direction of fluid flow between the accumulator and the first and second fluid lines.
- 30. The work machine of claim 29, further including a traction device and a second source of pressurized fluid operatively engaged with the traction device and in fluid connection with the third directional control valve.
- 31. The work machine of claim 30, further including a clutch operable to selectively engage the second source of pressurized fluid with the traction device.
- 32. The work machine of claim 29, wherein each of the first, second, and third directional control valves include a set of four independent metering valves.
- 33. The work machine of claim 32, wherein the third directional control valve includes a fifth independent metering valve.
- 34. The work machine of claim 29 further including a hydrostatic drive having a second source of pressurized fluid, a fluid motor, and a valve configured to provide pressurized fluid from the hydrostatic drive to the third directional control valve.
- 35. The work machine of claim 34, wherein a metering valve is disposed between said valve and the third directional control valve.
- 36. The work machine of claim 34, further including a charge shuttle configured to provide a fluid communication with a low pressure side of the hydrostatic drive.
- 37. The work machine of claim 36, further including an auxiliary pump configured to provide a flow of pressurized fluid to the charge shuttle.
- 38. The work machine of claim 36, wherein the charge shuttle is connected to the second fluid line.
- 39. The work machine of claim 38, wherein a metering valve is disposed between the charge shuttle and the second fluid line.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5819536 |
Mentink |
Oct 1998 |
A |
6467264 |
Stephenson et al. |
Oct 2002 |
B1 |
6502393 |
Stephenson et al. |
Jan 2003 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
WO 0000748 |
Jan 2000 |
WO |