EP2557239A1 - Combined closed loop hydraulic circuit and hydraulic energy storage system - Google Patents

Combined closed loop hydraulic circuit and hydraulic energy storage system Download PDF

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Publication number
EP2557239A1
EP2557239A1 EP12179392A EP12179392A EP2557239A1 EP 2557239 A1 EP2557239 A1 EP 2557239A1 EP 12179392 A EP12179392 A EP 12179392A EP 12179392 A EP12179392 A EP 12179392A EP 2557239 A1 EP2557239 A1 EP 2557239A1
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EP
European Patent Office
Prior art keywords
hydraulic
circuit
control system
fluid
machine
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12179392A
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German (de)
English (en)
French (fr)
Inventor
Andrew John Smith
Robert Nicholas Harper
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Caterpillar Inc
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Caterpillar Inc
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Filing date
Publication date
Application filed by Caterpillar Inc filed Critical Caterpillar Inc
Publication of EP2557239A1 publication Critical patent/EP2557239A1/en
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/14—Energy-recuperation means
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2289—Closed circuit
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F3/00—Dredgers; Soil-shifting machines
    • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
    • E02F3/28—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets
    • E02F3/36—Component parts
    • E02F3/42—Drives for dippers, buckets, dipper-arms or bucket-arms
    • E02F3/43—Control of dipper or bucket position; Control of sequence of drive operations
    • E02F3/431—Control of dipper or bucket position; Control of sequence of drive operations for bucket-arms, front-end loaders, dumpers or the like
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F3/00—Dredgers; Soil-shifting machines
    • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
    • E02F3/28—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets
    • E02F3/36—Component parts
    • E02F3/42—Drives for dippers, buckets, dipper-arms or bucket-arms
    • E02F3/43—Control of dipper or bucket position; Control of sequence of drive operations
    • E02F3/435—Control of dipper or bucket position; Control of sequence of drive operations for dipper-arms, backhoes or the like
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2217—Hydraulic or pneumatic drives with energy recovery arrangements, e.g. using accumulators, flywheels
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2296—Systems with a variable displacement pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
    • F15B1/02—Installations or systems with accumulators
    • F15B1/027—Installations or systems with accumulators having accumulator charging devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/1409—Characterised by the construction of the motor unit of the straight-cylinder type with two or more independently movable working pistons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
    • F15B1/02—Installations or systems with accumulators
    • F15B1/024—Installations or systems with accumulators used as a supplementary power source, e.g. to store energy in idle periods to balance pump load
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/163—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20561—Type of pump reversible
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20569—Type of pump capable of working as pump and motor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
    • F15B2211/212—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/27—Directional control by means of the pressure source
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7114—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators
    • F15B2211/7121—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators the chambers being connected in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/88—Control measures for saving energy

Definitions

  • This disclosure is directed towards a hydraulic control system comprising a combined closed loop hydraulic circuit for controlling two or more hydraulic actuators and a hydraulic energy storage system comprising one or more accumulators.
  • Work machines including backhoe loaders, excavators, loaders and the like, commonly comprise a hydraulic control system for controlling one or more work tools, such as buckets, booms, backhoes, grapples and the like.
  • the hydraulic control system may comprise an open loop hydraulic circuit for controlling one or more actuators connected to each work tool.
  • the open loop hydraulic circuit may utilise one or more pumps to direct hydraulic fluid to the actuators via one or more valves and conduits.
  • the valve arrangements in such circuits may be complex and, if two or more actuators perform the same function on a work tool, ensuring that consistently similar loads are applied by each of the actuators may require complex control software and circuitry.
  • the hydraulic control system may, therefore, comprise a closed loop hydraulic circuit rather than an open loop hydraulic circuit to overcome these issues.
  • a closed loop hydraulic system for controlling a work tool is disclosed in the document US-B-6,520,731 .
  • the hydraulic control system disclosed is used to control the swing of a backhoe on a backhoe loader.
  • a closed loop circuit comprises a variable displacement pump which directs hydraulic fluid to a pair of swing cylinders via conduits.
  • the swing cylinders are attached to a boom on the backhoe via a frame and control the side to side movement, or swing, of the backhoe.
  • a swashplate inside the variable displacement pump is adjusted to direct hydraulic fluid in either direction around the closed loop circuit, thereby allowing hydraulic fluid to be directed into either of the swing cylinders.
  • the closed loop circuit is arranged such that, when the piston of one of the swing cylinders extends, the piston of the other swing cylinder retracts.
  • the closed loop circuit also comprises a fixed displacement charge pump to supply supplemental hydraulic fluid in the case of any leakages existing in the closed loop circuit.
  • US-B-6,520,731 does not disclose a means by which the closed loop hydraulic circuit may be integrated with further hydraulic circuits for controlling other actuators connected to work tools. Furthermore, the use of a fixed displacement charge pump may add complexity and cost to the hydraulic control system. In addition, US-B-6,520,731 does not disclose a means of supplying power to the variable displacement pump.
  • pumps in hydraulic control systems are supplied with power from the work machine's main power unit, such as an internal combustion engine, a micro turbine, an electrical engine or the like.
  • main power unit such as an internal combustion engine, a micro turbine, an electrical engine or the like.
  • Power units with a capacity for high power outputs are commonly utilised since the hydraulic control system and work machine drivetrain may have high power requirements.
  • power units with high power output capacities may require relatively high amounts of fuel, may be relatively heavy and may emit relatively excessive amounts of waste products. It has, therefore, become commonplace to incorporate hydraulic energy storage systems in work machines comprising power units with a relatively low power output capacity and to release the stored energy when extra power is required.
  • US-B-6,520,731 does not disclose the use of a hydraulic energy storage system with the closed loop hydraulic circuit.
  • a hydraulic control system comprising a power unit and a closed loop hydraulic circuit, said closed loop hydraulic circuit comprising:- a hydraulic machine operably connected to the power unit; first and second accumulators for storing hydraulic fluid; first and second hydraulic actuators; a first valve for selectively directing hydraulic fluid between the hydraulic machine and either the first accumulator or the first hydraulic actuator; and a second valve for selectively directing hydraulic fluid between the hydraulic machine and either the second accumulator or the second hydraulic actuator; wherein the first hydraulic actuator is fluidly connected to the second hydraulic actuator by one or more conduits.
  • the disclosure further provides a method of controlling a hydraulic control system comprising a power unit and a closed loop hydraulic circuit, said closed loop hydraulic circuit comprising:- a hydraulic machine operably connected to the power unit; first and second accumulators for storing hydraulic fluid; first and second hydraulic actuators; first and second valves; wherein the valves are operable to effect either; a charging mode in which hydraulic fluid is directed from the second accumulator to the first accumulator; or a discharging mode in which hydraulic fluid is directed from the first accumulator to the second accumulator such that the hydraulic machine outputs power; or a steering mode in which hydraulic fluid is directed from the first to the second hydraulic actuator or vice-versa.
  • the present disclosure is generally directed towards a hydraulic control system for a work machine which combines a closed loop hydraulic circuit with a hydraulic energy recovery system.
  • a closed loop hydraulic circuit may be used to store hydraulic fluid for later release when extra power is required by other parts of the hydraulic control system.
  • the closed loop hydraulic circuit may also be used to control two or more hydraulic actuators.
  • the hydraulic control system may further comprise a secondary hydraulic circuit for controlling further hydraulic actuators.
  • the present disclosure is directed towards a work machine of any type, examples of which include backhoe loaders, excavators, forest machines, harvesters, track loaders, front shovels, bulldozers and wheel loaders.
  • work machines typically comprise a power unit which directs power, via a transmission, to a hydraulic circuit and/or a driveline.
  • the hydraulic circuit may control the position of a work tool, which typically comprises one or more booms, arms or sticks, to which at least one work implement is attached.
  • the work implement may be of any type, examples of which include buckets, blades, augurs, cold planers, felling heads, forks, grapples, hammers, shears, thumbs and material handling arms.
  • the driveline may transfer power from the transmission to the wheels and/or tracks such that the work machine may move.
  • Figure 1 illustrates an embodiment of a hydraulic control system 10 for controlling a work machine comprising a power unit 11, a transmission 12, a driveline 13, a closed loop hydraulic circuit 14 and a secondary hydraulic circuit 15.
  • the power unit 11 may be of any type, examples of which include internal combustion engines, micro turbines and electric motors.
  • the transmission 12 may be of any type, for example manual, automatic or semi-automatic.
  • a clutch or torque converter (not shown) may be positioned in between the power unit 11 and the transmission 12 to enable the transmission 12 to be engaged and disengaged from the power unit 11.
  • a clutch or torque converter may be positioned in between the transmission 12 and the driveline 13 to enable the driveline 13 to be engaged and disengaged from the transmission 12.
  • the closed loop hydraulic circuit 14 comprises a hydraulic machine 16, a first valve 17, a second valve 18, a first accumulator 19, a second accumulator 20, a first hydraulic actuator 21, a second hydraulic actuator 22 and a number of interconnecting conduits 23, 24, 25, 26, 27, 28, 29, the arrangement of which is described below.
  • the hydraulic machine 16 may be reversible, such that it may behave as a hydraulic fluid pump or as a motor driven by the movement of hydraulic fluid.
  • the hydraulic machine 16 may be a variable displacement pump, such as an axial piston pump, a radial piston pump or a bent axis pump.
  • the hydraulic machine 16 may comprise a driveshaft (not shown) attached to an adjustable device (not shown), such as a swash plate, which controls the flow rate of hydraulic fluid through the hydraulic machine 16.
  • the hydraulic machine 16 is operably connected to the power unit 11.
  • An operable connection enables the transfer of power between components.
  • the power output from the power unit 11 can, therefore, be transferred to the hydraulic machine 16. This may be achieved by directly connecting an output shaft from the power unit 11 to the driveshaft of the hydraulic machine 16.
  • the driveshaft of the hydraulic machine 16 may run through the transmission 12, but not supply power to the transmission 12, and/or be engaged by splines to the output shaft of the power unit 11.
  • the output shaft of the power unit 11 and the driveshaft of the hydraulic machine 16 may be comprised of a single shaft.
  • the driveshaft of the hydraulic machine 16 may be operably connected to an output shaft of the transmission 12.
  • the driveshaft of the hydraulic machine 16 and the output shaft of the transmission 12 may, for example, be operably connected to one another using engaged splines on the shafts or via a clutch or torque converter.
  • the hydraulic machine 16 is fluidly connected to the first valve 17 by the conduit 23 and to the second valve 18 by the conduit 24. These fluid connections enable hydraulic fluid to flow in either direction between components.
  • the first valve 17 is fluidly connected to the first accumulator 19 by the conduit 25 and the first hydraulic actuator 21 by the conduit 27.
  • the second valve 18 is fluidly connected to the second accumulator 20 by the conduit 26 and the second hydraulic actuator 22 by the conduit 28.
  • the first valve 17 and the second valve 18 may be valves of any suitable type, examples of which include selector valves, spool valves, cartridge valves or poppet valves.
  • the first valve 17 and the second valve 18 may be operated in any suitable manner, for example manually, by using pilot hydraulics, or by using electronic controls.
  • the first valve 17 is operable to enable hydraulic fluid to be directed to or from any of the first accumulator 19, the hydraulic machine 16 and the first hydraulic actuator 21.
  • the second valve 18 is operable to enable hydraulic fluid to be directed to or from any of the second accumulator 20, the hydraulic machine 16 and the second hydraulic actuator 22.
  • the pressure of the hydraulic fluid in one or both of the first accumulator 19 and second accumulator 20 may be relatively high and may be higher than the ambient pressure of the hydraulic control system 10.
  • the hydraulic fluid may be stored in the first accumulator 19 at a pressure higher than, lower than or approximately equal to the pressure of the hydraulic fluid stored in the second accumulator 20.
  • the accumulators 19, 20 may be directly connected to, or integrated with, the first and second valves 17, 18 such that the conduits 25, 26 are not required.
  • the first and second hydraulic actuators 21, 22 may be of any type of hydraulic actuator, such as tie-rod, welded, single-acting, double-acting, telescoping, ram or rodless.
  • the first hydraulic actuator 21 and the second hydraulic actuator 22 are double-acting hydraulic actuators.
  • Each of the first and second hydraulic actuators 21, 22 comprises a actuator body 30, 31, a piston 32, 33, a first hydraulic chamber 34, 35 and a second hydraulic chamber 36, 37.
  • the second chambers 36, 37 may be fluidly connected to each other by means of the conduit 29.
  • the second hydraulic chamber 36 of the first hydraulic actuator 21 may be fluidly connected by a conduit (not shown) to the first hydraulic chamber 35 of the second hydraulic actuator 22, and the second hydraulic chamber 37 of the second hydraulic actuator 22 may be fluidly connected by a conduit (not shown) to the first hydraulic chamber 34 of the first hydraulic actuator 21.
  • the pistons 32, 33 may each comprise a piston rod 38, 39 and a piston head 40, 41.
  • the first hydraulic chambers 34, 35 and the second hydraulic chambers 36, 37 may be positioned inside the cylinder bodies 30, 31 on either side of the piston heads 40, 41. Hydraulic fluid may not be transferred between the first hydraulic chambers 34, 35 and the second hydraulic chambers 36, 37 due to the piston heads 40, 41 forming a seal with the inner side of the cylinder bodies 30, 31.
  • the first hydraulic actuator 21 may comprise two cylinder bodies and two pistons, wherein a first hydraulic chamber in each of the two cylinder bodies is fluidly connected to the first valve 17 by the conduit 27 and a second hydraulic chamber in each of the cylinder bodies is fluidly connected to the second hydraulic chamber 37 of the second hydraulic actuator 22 by the conduit 29.
  • the piston rods 38, 39 are illustrated in Figure 1 as extending through the cylinder bodies 30, 31 from the second hydraulic chambers 36, 37. However, the piston rods 38, 39 may extend through the cylinder bodies 30, 31 in the opposite direction from the first hydraulic chambers 34, 35.
  • the pistons 32, 33 may be of the double rod type, wherein the piston rods 38, 39 extend through both the first hydraulic chambers 34, 35 and the second hydraulic chambers 36, 37.
  • the first and second hydraulic actuators 21, 22 may be single-acting hydraulic actuators wherein a spring is positioned inside the second hydraulic chamber 36, 37.
  • the piston rods 38, 39 of the first and second hydraulic actuators 21, 22 may be attached to at least one part of a work tool, such as a boom, such that the position of the work tool may be manipulated.
  • the pistons 32, 33 may also operate a work implement, such as a set of shears or felling heads, attached to the work tool.
  • the first and second hydraulic actuators 21, 22 and any conduits or components in between may be arranged such that when one of the pistons 32, 33 extends the other piston 32, 33 retracts.
  • the secondary hydraulic circuit 15 may comprise a hydraulic pump 42, a valve block 43, a main work tool hydraulic circuit 44 and conduits 45, 46.
  • the hydraulic pump 42 may comprise an input shaft (not shown) operably connected to the drive shaft of the hydraulic machine 16, such that the hydraulic pump 42 is operably connected to, and may receive power from, the power unit 11.
  • the operable connection may comprise engaged splines on the drive shaft of the hydraulic machine 16 and the input shaft of the hydraulic pump 42.
  • the input shaft of the hydraulic pump 42, the drive shaft of the hydraulic machine 16 and the output shaft of the power unit 11 may be comprised of a single shaft.
  • the hydraulic pump 42 may be a variable displacement pump.
  • the hydraulic pump 42 may comprise an adjustable device, such as swash plates, connected to the input shaft which controls the flow rate of hydraulic fluid through the hydraulic pump 42.
  • the hydraulic pump 42 is illustrated on the opposite side of the hydraulic machine 36 to the transmission 12. However, the hydraulic pump 42 may alternatively be placed between the transmission 12 and the hydraulic machine 16.
  • the hydraulic pump 42 may be arranged so as to direct hydraulic fluid from a hydraulic reservoir (not shown) to the valve block 43 via the conduit 45.
  • the flow rate and pressure of the hydraulic fluid in the secondary hydraulic circuit 15 may be controlled by manipulating the position of the adjustable device in the hydraulic pump 42.
  • the valve block 43 may direct hydraulic fluid around the main work tool hydraulic circuit 44 via the conduit 46.
  • the main work tool hydraulic circuit 44 may comprise hydraulic actuators attached to one or more work tools and/or work implements.
  • the main work tool hydraulic circuit 44 may, therefore, control the position of one or more work tools and/or work implements.
  • the main work tool hydraulic circuit 44 may also operate the work implement.
  • the hydraulic actuators of the work tool hydraulic circuit 44 and the first hydraulic actuator 21 and second hydraulic actuator 22 of the closed loop hydraulic circuit 14 may be attached to the same, or different, parts of the work tool and/or work implement.
  • the hydraulic fluid in the closed loop hydraulic circuit 14 remains in the closed loop hydraulic circuit 14 when displaced by the hydraulic machine 16, the first hydraulic actuator 21 or the second hydraulic actuator 22.
  • closed loop circuits comprising components such as valves, pumps and actuators will also typically comprise means by which the hydraulic fluid may leak.
  • a hydraulic charge circuit may be incorporated in the hydraulic control system 10 to supply supplemental hydraulic fluid to the closed loop hydraulic circuit 14 to compensate for any hydraulic fluid leakages or losses. Thereby an approximately constant volume of hydraulic fluid in the closed loop hydraulic circuit 14 may be maintained, and the volume maintained may be held within a predetermined range.
  • the hydraulic charge circuit may draw hydraulic fluid from a hydraulic reservoir or the secondary hydraulic circuit 15 and may supply supplemental hydraulic fluid to any component, including the conduits 24, 27, 29, 28, of the closed loop hydraulic circuit 14.
  • FIG. 2 illustrates an embodiment of a hydraulic control system 47 which includes a hydraulic charge circuit 48.
  • the hydraulic charge circuit 48 comprises a pressure reducing valve 49, check valves 50, 51 and conduits 52, 53.
  • the conduit 52 is illustrated as connected to the conduit 45. However, the conduit 52 may be connected to any part of the secondary hydraulic circuit 15.
  • the pressure reducing valve 49 directs hydraulic fluid from the conduit 52 to the check valves 50, 51 via the conduit 53.
  • the check valves 50, 51 may be fluidly connected to, and therefore direct hydraulic fluid into, the conduits 23, 24.
  • the pressure reducing valve 49 reduces the pressure of the hydraulic fluid supplied to the conduit 53 from the secondary hydraulic circuit 15.
  • the magnitude of the change in hydraulic fluid pressure implemented by the pressure reducing valve 49 may be fixed or adjustable and may be related to the pressure in the closed loop hydraulic circuit 14.
  • the pressure reducing valve 49 may be operated manually, by using pilot hydraulics, or by using electronic controls.
  • the check valves 50, 51 may have a cracking pressure, being the pressure at which the check valves 50, 51 open, suitable such that hydraulic fluid only enters the closed loop hydraulic circuit 14 from the conduit 53 once the hydraulic fluid in the closed loop hydraulic circuit 14 falls below a predetermined pressure.
  • the cracking pressure may be the pressure of the hydraulic fluid in the conduit 53 and therefore the check valves 50, 51 may release hydraulic fluid into the closed loop hydraulic circuit 14 when the pressure in the closed loop hydraulic circuit 14 falls below the pressure in the conduit 53.
  • the hydraulic control system 54 comprises a hydraulic charge circuit 55, wherein a hydraulic charge pump 56 is utilised to supply hydraulic fluid to the closed loop hydraulic circuit 14.
  • the hydraulic charge pump 56 directs hydraulic fluid from a hydraulic reservoir 57 via a conduit 58 to check valves 59, 60 and a pressure reducing valve 61 via a conduit 62.
  • the check valves 59, 60 may be fluidly connected to the conduits 23, 24 or any other component of the closed loop hydraulic circuit 14 and the pressure reducing valve 61 may direct hydraulic fluid to a hydraulic reservoir 63 via a conduit 64.
  • the hydraulic reservoirs 57, 63 may be the same hydraulic reservoir and may be the same as the hydraulic reservoir which supplies hydraulic fluid to the hydraulic pump 42.
  • the hydraulic charge pump 56 may be a fixed displacement hydraulic pump and may comprise internal or external gears.
  • the hydraulic charge pump 56 may be operably connected to the drive shaft of the hydraulic machine 16, an output shaft from the power unit 11, the output shaft of the transmission 12 or the input shaft of the hydraulic pump 42.
  • the hydraulic charge pump 56 is, therefore, operably connected to, and driven by, the power unit 11.
  • the hydraulic pump 42 may be operably connected to the transmission 12 via the hydraulic machine 16 and/or via the hydraulic charge pump 56.
  • the pressure reducing valve 61 may be fixed or adjustable and may control the pressure of the hydraulic fluid in the conduit 62.
  • the pressure maintained in the conduit 62 may be related to the pressure in the closed loop hydraulic circuit 14.
  • the pressure reducing valve 61 may be operated manually, by using pilot hydraulics, or by using electronic controls.
  • the check valves 59, 60 may have a cracking pressure suitable such that hydraulic fluid only enters the closed loop hydraulic circuit 14 once the pressure of the hydraulic fluid in the closed loop hydraulic circuit 14 falls below a predetermined pressure. Any type of directional control valve may be used in place of the check valves 59, 60.
  • the pressure reducing valve 61 ensures that the pressure of the hydraulic fluid in the conduit 62 is maintained at a constant level regardless of the output of the hydraulic charge pump 56. Hydraulic fluid may, therefore, be released into the closed loop hydraulic circuit 15 by the check valves 59, 60 if the pressure of the hydraulic fluid in the closed loop hydraulic circuit 15 falls below the pressure of the hydraulic fluid in the conduit 62. Since leaks in the closed loop hydraulic circuit 14 will cause a reduction in hydraulic fluid pressure, the volume of hydraulic fluid in the closed loop hydraulic circuit 14 will be maintained at a relatively constant level.
  • the power unit 11 may supply power to the transmission 12, the hydraulic machine 16, the hydraulic pump 42 and/or to the driveline 13.
  • the closed loop hydraulic circuit 14 and the secondary hydraulic circuit 15 may be operational simultaneously, operational individually or not operational.
  • the input shaft of the hydraulic machine 16 and the drive shaft of the hydraulic pump 42 may rotate when they receive power via the operable connection to the power unit 11.
  • the adjustable devices in the hydraulic machine 16 and/or the hydraulic pump 42 may be orientated such that hydraulic fluid is not displaced in the closed loop hydraulic circuit 14 and/or the secondary hydraulic circuit 15 when the input shaft of the hydraulic pump 42 and the drive shaft of the hydraulic machine 16 are rotating.
  • one of the adjustable devices is a swashplate
  • the angle between the normal to the shaft and the face of the swashplate may be set to an angle of zero degrees to prevent hydraulic fluid from being displaced.
  • one or more clutches or torque converters may be positioned in between the drive shaft of the hydraulic machine 16 and the output shaft of the transmission 12 or the power unit 11 to enable the hydraulic machine 16 to be engaged and disengaged from the transmission 12 or the power unit 11.
  • a clutch or torque converter (not shown) may be disposed in between the drive shaft of the hydraulic machine 16 and the input shaft of the hydraulic pump 42 to enable the engagement and disengagement of the hydraulic pump 42 from the hydraulic machine 16.
  • the clutches or torque converters may be engaged to provide power to either/both of the hydraulic machine 16 or/and the hydraulic pump 42.
  • the hydraulic pump 42 may be a fixed or variable displacement pump.
  • the hydraulic pump 42 may be operated by engaging the appropriate clutches or torque converters. If variable, the hydraulic pump 42 may be operated by engaging the appropriate clutches or torque converters and by adjusting the orientation of the adjustable devices.
  • the hydraulic machine 16 may be operated by engaging a clutch or torque converter and by adjusting the orientation of the adjustable device in the hydraulic machine 16.
  • hydraulic fluid is directed around the closed loop hydraulic circuit 14.
  • the adjustable device in the hydraulic machine 16 is orientated such that the hydraulic machine 16 behaves as a pump by utilising the power supplied by the power unit 11.
  • the valves 17, 18 are actuated and hydraulic fluid is directed from the second accumulator 20 to the first accumulator 19.
  • the hydraulic fluid is stored at a higher pressure in the first accumulator than in the second accumulator.
  • the adjustable device in the hydraulic device 16 may be orientated such that the hydraulic machine 16 behaves as a motor.
  • the valves 17, 18 are actuated and the first accumulator 19 releases hydraulic fluid, which is directed through the hydraulic machine 16 and into the second accumulator 20.
  • the hydraulic machine 16 thereby supplements the power from the power unit 11 and may supply power to the transmission 12 and/or the hydraulic pump 42 via the operable connections.
  • the hydraulic fluid is transferred from the first accumulator 19 to the second accumulator 20 as a result of the hydraulic fluid being stored at a higher pressure in the first accumulator 19 than in the second accumulator 20.
  • the first and second accumulator may be interchanged. Therefore, the hydraulic fluid may be directed from the second accumulator 20 to the first accumulator 19 in the discharging mode and from the first accumulator 19 to the second accumulator 20 in the charging mode.
  • the adjustable device of the hydraulic machine 16 is orientated such that the hydraulic machine 16 behaves as a pump by utilising the power supplied by the power unit 11.
  • the hydraulic fluid is pumped into the first hydraulic chamber 34 of the first hydraulic actuator 21 from the first hydraulic chamber 35 of the second hydraulic actuator 22 via the first valve 17, the second valve 18 and the conduits 23, 24, 27, 28.
  • the pressure of the hydraulic fluid in the first hydraulic chamber 34 therefore rises and the piston 32 moves, extending the piston rod 38 further out of the cylinder body 30.
  • Hydraulic fluid in the first or second hydraulic chamber 34, 36 of the first hydraulic actuator 21 is transferred to the first or second hydraulic chamber 35, 37 of the second hydraulic actuator 22.
  • the piston 33 therefore moves and the piston rod 39 retracts further inside the cylinder body 31.
  • the hydraulic fluid may be pumped into the first hydraulic chamber 35 of the second hydraulic actuator 22 from the first hydraulic chamber 34 of the first hydraulic actuator 21.
  • the piston 33 may therefore extend and the piston 32 may therefore retract.
  • the steering, charging and discharging modes may be effected at any time either manually or automatically by utilising control circuitry.
  • the steering mode may be engaged when the work tool or work implement attached to the pistons 32, 33 is operated.
  • the charging mode may be effected when the power required from the power unit 11 by the secondary hydraulic circuit 15 and the driveline 13 is low or the power output of the power unit 11 is below a predefined value.
  • the predefined value may be the maximum power output, or power output capacity, of the power unit 11.
  • the power output of the power unit 11 may be increased to supply sufficient power to the hydraulic machine 16 to allow the charging mode to be effected.
  • the discharging mode may be effected when the power required from the power unit 11 by the secondary hydraulic circuit 15 and the driveline 13 is high or the power output of the power unit 11 is above a predefined value.
  • the predefined value may be the maximum power output, or power output capacity, of the power unit 11.
  • power may be supplied to the secondary hydraulic circuit 15 via the hydraulic pump 42 and/or to the driveline 13 via the transmission 12 or the power unit 11.
  • the power supplied may be independent of, or supplemental to, the power supplied by the power unit 11 to the closed loop hydraulic circuit 14, the secondary hydraulic circuit 15, the transmission 12 and the driveline 13.
  • FIG 4 illustrates one type of work machine 65, in the form of a backhoe loader, which may utilise the hydraulic control system 10, 47, 54.
  • the work tools 66, 67 of the backhoe loader are a loader 66 and a backhoe 67, each comprising a series of booms 68, 69, 70, 71.
  • Work implements 72, 73, illustrated in Figure 4 as buckets, are attached to the booms 68, 71.
  • the hydraulic control system 10, 47, 54 as previously described herein, may be used to control the position and orientation of the backhoe loader itself, the backhoe 67 and the loader 71.
  • the pistons 32, 33 may be attached to the backhoe 67 and control the side to side movement, or swing, of the backhoe 67.
  • the actuators of the secondary hydraulic circuit 15 may be attached to, and thereby control the position of, the booms 68, 69, 70, 71 and buckets 70, 71 of the backhoe 67 and the loader 66.
  • the disclosed hydraulic control system 10, 47, 54 in which the closed loop hydraulic circuit 14 combines a closed loop circuit and a hydraulic energy storage system, may be incorporated into a wide variety of work machines.
  • the hydraulic control system 10, 47, 54 may comprise a power unit 11 with a power output capacity which is less than that required by the driveline 13 and/or the secondary hydraulic circuit 15.
  • the discharging mode may be engaged when extra power is required by the driveline 13 and/or the secondary hydraulic circuit 15.
  • the hydraulic control system 10, 47, 54 allows for relatively smooth, simple and consistent control of the first and second hydraulic actuators 21, 22 due to the closed loop closed loop hydraulic circuit 14.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Operation Control Of Excavators (AREA)
  • Wind Motors (AREA)
EP12179392A 2011-08-11 2012-08-06 Combined closed loop hydraulic circuit and hydraulic energy storage system Withdrawn EP2557239A1 (en)

Applications Claiming Priority (1)

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GB1113884.9A GB2493706B (en) 2011-08-11 2011-08-11 Combined closed loop hydraulic circuit and hydraulic energy storage system

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CN (1) CN102927069A (zh)
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Cited By (4)

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Publication number Priority date Publication date Assignee Title
WO2015034726A1 (en) * 2013-09-03 2015-03-12 Caterpillar Inc. Hybrid apparatus and method for hydraulic systems
CN106122126A (zh) * 2016-08-18 2016-11-16 武汉船用机械有限责任公司 一种液压***的控制方法和装置
EP3083369A4 (en) * 2013-12-19 2017-10-04 Volvo Construction Equipment AB A hydraulic load sensing system
US10180135B2 (en) 2014-09-30 2019-01-15 Artemis Intelligent Power Limited Industrial system with synthetically commutated variable displacement fluid working machine

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CN105201931A (zh) * 2014-06-18 2015-12-30 博世力士乐（常州）有限公司 液压***
WO2016042424A1 (en) * 2014-09-19 2016-03-24 Siti - B&T Group S.P.A. Hydraulic system for presses, particularly for presses for manufacturing ceramic products
CN107120320B (zh) * 2017-04-19 2018-09-14 北京科技大学 一种多容器式循环蓄能器及其储释能方法
CN113090610B (zh) * 2021-03-12 2022-08-12 上海卫星工程研究所 一种贴片式压电螺杆泵液压直线作动器及其驱动方法

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DE2106292A1 (de) * 1971-02-10 1972-09-07 Salzgitter Maschinen AG, 3327 Salz gitter Bad Schwenkeinnchtung fur die Schaufel einer Lademaschine
DE9218087U1 (de) * 1991-11-08 1993-10-21 Mannesmann AG, 40213 Düsseldorf Antriebsvorrichtung
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WO2015034726A1 (en) * 2013-09-03 2015-03-12 Caterpillar Inc. Hybrid apparatus and method for hydraulic systems
EP3083369A4 (en) * 2013-12-19 2017-10-04 Volvo Construction Equipment AB A hydraulic load sensing system
US10180135B2 (en) 2014-09-30 2019-01-15 Artemis Intelligent Power Limited Industrial system with synthetically commutated variable displacement fluid working machine
CN106122126A (zh) * 2016-08-18 2016-11-16 武汉船用机械有限责任公司 一种液压***的控制方法和装置

Also Published As

Publication number Publication date
GB2493706B (en) 2013-11-06
GB2493706A (en) 2013-02-20
CN102927069A (zh) 2013-02-13
RU2605514C2 (ru) 2016-12-20
RU2012134393A (ru) 2014-02-20
GB201113884D0 (en) 2011-09-28

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