EP4080062A1 - Electrohydraulic actuator and method - Google Patents

Electrohydraulic actuator and method Download PDF

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Publication number
EP4080062A1
EP4080062A1 EP22168727.0A EP22168727A EP4080062A1 EP 4080062 A1 EP4080062 A1 EP 4080062A1 EP 22168727 A EP22168727 A EP 22168727A EP 4080062 A1 EP4080062 A1 EP 4080062A1
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EP
European Patent Office
Prior art keywords
hydraulic
hydraulic unit
chamber
actuator
unit
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.)
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Application number
EP22168727.0A
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German (de)
French (fr)
Inventor
Mika SAHLMAN
Peter Stambro
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NORRHYDRO Oy
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NORRHYDRO Oy
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Publication of EP4080062A1 publication Critical patent/EP4080062A1/en
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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
    • 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
    • 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
    • F15B1/033—Installations or systems with accumulators having accumulator charging devices with electrical control means
    • 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
    • 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
    • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
    • F15B7/005—With rotary or crank input
    • F15B7/006—Rotary pump input
    • 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
    • F15B2211/20507—Type of prime mover
    • F15B2211/20515—Electric 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
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20538—Type of pump constant 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
    • F15B2211/20546—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
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/61—Secondary circuits
    • F15B2211/613—Feeding circuits
    • 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
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7052—Single-acting output members
    • 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
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • 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
    • F15B2211/76—Control of force or torque of the output member
    • F15B2211/761—Control of a negative load, i.e. of a load generating hydraulic energy
    • 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
    • F15B2211/76—Control of force or torque of the output member
    • F15B2211/763—Control of torque of the output member by means of a variable capacity motor, i.e. by a secondary control on the 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/785—Compensation of the difference in flow rate in closed fluid circuits using differential actuators
    • 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

  • the present invention relates to electrohydraulic actuators.
  • Electro-hydraulic actuators are apparatuses, in which at least a fluid pressure actuator, a pump driving the actuator and an electric motor rotating the pump are combined. Electro-hydraulic actuators are used in applications, where it is beneficial not to have an external hydraulic system with external pumps, tubing and the like. Electro-hydraulic actuators are also used in applications, where simplicity of system architecture and safety and reliability are essential, such as in aerospace industry.
  • An object of the present invention is to provide a new type of an electrohydraulic actuator and a new method.
  • the object of the invention is achieved by a method and an electrohydraulic actuator which are characterized by what is stated in the independent claims. Some embodiments of the invention are disclosed in the dependent claims.
  • an electrohydraulic actuator comprises an electric motor, a first hydraulic unit, and a second hydraulic unit.
  • the electric motor, the first hydraulic unit, and the second hydraulic unit are connected together such that they convey energy between them.
  • the first hydraulic unit is arranged to feed hydraulic fluid to a hydraulic actuator and the electric motor is arranged to control the feed of hydraulic fluid to the hydraulic actuator by means of the first hydraulic unit.
  • the second hydraulic unit is connected to a hydraulic accumulator. Furthermore, when one of the first hydraulic unit and the second hydraulic unit displaces hydraulic fluid to its pressure port the other may be arranged to displace hydraulic fluid to a low-pressure port and vice versa.
  • Electrical energy may be transferred to pressure, for example.
  • the energy stored to the hydraulic accumulator may be reused.
  • the energy from the hydraulic accumulator may be used for providing higher momentary power, for example. It is also possible to transfer energy stored to the hydraulic accumulator to electric network. Also, the speed of the hydraulic actuator is controlled in a simple manner. All in all, the solution is simple and reliable.
  • the first hydraulic unit is a fixed displacement hydraulic unit.
  • Such a solution is easy to implement and durable. Because the electric motor rotates the fixed displacement hydraulic unit the control of the hydraulic actuator is versatile.
  • the second hydraulic unit is a variable displacement hydraulic unit.
  • the control of the flows of the hydraulic fluid may be made in various ways and still the electric motor and the variable displacement hydraulic unit may be simply mechanically connected.
  • the variable displacement hydraulic unit may be arranged to displace hydraulic fluid. When both the hydraulic units rotate, they displace hydraulic fluid as described above.
  • the electric motor, the first hydraulic unit, and the second hydraulic unit are mechanically connected to each other.
  • Such a solution is durable.
  • variable displacement hydraulic unit is non-overcenter. Such a solution is cost effective.
  • the hydraulic actuator may be a single-acting cylinder, a double acting cylinder, or a rotating cylinder.
  • the hydraulic actuator is a single-acting cylinder and when one of the first hydraulic unit and the second hydraulic unit displaces hydraulic fluid to its pressure port the other may be arranged to displace hydraulic fluid to a tank via the low-pressure port and vice versa.
  • FIG. 1 shows an electrohydraulic actuator 1.
  • the electrohydraulic actuator 1 comprises a first hydraulic unit 2.
  • the first hydraulic unit 2 may be a rotating hydraulic unit such as a hydraulic pump/motor.
  • the first hydraulic unit 2 is a fixed displacement hydraulic unit.
  • the first hydraulic unit 2 is connected to a hydraulic actuator 3.
  • the hydraulic actuator 3 in Figure 1 is a single-acting cylinder. Feeding hydraulic fluid by the first hydraulic unit 2 to a chamber 4 of the hydraulic actuator 3 raises the piston 5 of the hydraulic actuator 3.
  • the electric motor 6 rotates the first hydraulic unit 2.
  • means for controlling the electric motor are not shown in Figure 1 .
  • characteristics to an electrohydraulic actuator electric motor 6 is arranged to control the feed of hydraulic fluid to the hydraulic actuator 3 by means of the first hydraulic unit 2.
  • the electrohydraulic actuator 1 also comprises a second hydraulic unit 7.
  • the second hydraulic unit 7 may be a rotating hydraulic unit such as a hydraulic pump/motor. In the embodiment shown in Figure 1 the second hydraulic unit 7 is a variable displacement hydraulic unit.
  • the second hydraulic unit 7 is connected to a hydraulic accumulator 8.
  • the electric motor 6, the first hydraulic unit 2, and the second hydraulic unit 7 are connected together such that they convey energy between them.
  • the electric motor 6, the first hydraulic unit 2, and the second hydraulic unit 7 may be mechanically or electrically connected to each other.
  • the second hydraulic unit 7 displaces hydraulic fluid via its low-pressure port 7b to a tank 9 and vice versa.
  • first hydraulic unit 2 displaces hydraulic fluid to its pressure port
  • second hydraulic unit 7 displaces hydraulic fluid via its low-pressure port 7b to the tank 9.
  • energy stored as pressure to the hydraulic accumulator 8 may be used for boosting the feed of hydraulic fluid to the hydraulic actuator 3.
  • hydraulic fluid may be fed from the hydraulic accumulator 8 to rotate the second hydraulic unit 7. Because the hydraulic units 2 and 7 are connected such that they convey energy between them the energy in the hydraulic accumulator 8 enhances feeding the fluid to the hydraulic actuator 3.
  • the piston 5 When the piston 5 is allowed to lower due to gravity, for example, the piston 5 pushes hydraulic fluid to the first hydraulic unit 2 rotating it.
  • the first hydraulic unit 2 displaces hydraulic fluid via its low-pressure port 2b to the tank 9.
  • the rotation of the first hydraulic unit 2 causes the second hydraulic unit 7 to displace hydraulic fluid to its pressure port 7a and therethrough to the hydraulic accumulator 8.
  • Energy is thus stored to the hydraulic accumulator 8.
  • electric energy from an electric network may be stored to the hydraulic accumulator 8 such that the electric motor 6 is rotated, naturally providing that not all the energy supplied to the electric motor 6 is used for other purposes such as raising the piston 5.
  • Figures 2 , 3, and 4 show electrohydraulic actuators 1 having double acting cylinders 3.
  • hydraulic fluid is fed either to a first chamber 4a or to a second chamber 4b.
  • Feeding hydraulic fluid to the first chamber 4a moves the piston 5 upwards in the Figures.
  • Feeding hydraulic fluid to the second chamber 4b moves the piston 5 downwards in the Figures.
  • one of the ports of the first hydraulic unit 2 is not directly connected to the tank 9 but to a hydraulic line 11 connected to the second chamber 4b of the hydraulic actuator 3. All in all, the embodiment shown in Figure 2 is simple and reliable. However, when the volumes on the opposite sides of the piston 5 are different, energy cannot be recovered efficiently when the pressure raises above a pressure limit.
  • the solutions shown in Figures 3 and 4 obviate the shortcoming mentioned in connection with the embodiment shown in Figure 2 .
  • the embodiment shown in Figure 3 comprises a third hydraulic unit 10, which is connected to the first hydraulic unit 2, and the second hydraulic unit 7 such that they convey energy between them.
  • the third hydraulic unit 10 may be a rotating hydraulic unit such as a hydraulic pump/motor.
  • the third hydraulic unit 10 is a fixed displacement hydraulic unit.
  • one of the ports of the second hydraulic unit 7 is directly connected to the hydraulic accumulator 8 and the other port of the second hydraulic unit 7 is directly connected to the tank 9.
  • one of the ports of the second hydraulic unit 7 is not directly connected to the tank 9 but to a hydraulic line 11 connected to the second chamber 4b of the hydraulic actuator 3.
  • the embodiment shown in Figure 4 does not need so many rotating hydraulic units as the embodiment shown in Figure 3 .
  • valves needed are not mainly shown in the Figures.
  • the hydraulic actuator 3 is a double acting cylinder having the first chamber 4a on the first side of the piston 5 and the second chamber 4b on the second side of the piston 5.
  • One of the ports of the first hydraulic unit 2 is directly connected to the first chamber 4a and the other port of the first hydraulic unit 2 is directly connected to the second chamber 4b.
  • One of the ports of the second hydraulic unit 7 is directly connected to the hydraulic accumulator 8 and the other port is directly connected to the second chamber 4b.
  • the other port of the second hydraulic unit 7 may be directly connected either to the second chamber 4b or to the first chamber 4a, especially when the volumes of the first chamber 4a and the second chamber 4b are equal.
  • the volume of the second chamber 4b is smaller than the volume of the first chamber 4a. That means that the effective surface area of the piston 5 on the side of the second chamber 4b is smaller than the effective surface area of the piston 5 on the side of the first chamber 4a. If the volume of the second chamber 4b is smaller than the volume of the first chamber 4a it is preferable that the other port of the second hydraulic unit 7 is directly connected to the second chamber 4b to enhance efficient energy recovery and overall operation of the electrohydraulic actuator 1.
  • both the first hydraulic unit 2 and the second hydraulic unit 7 are fixed displacement hydraulic units.
  • the electric motor 6, the first hydraulic unit 2, and the second hydraulic unit 7 are electrically connected to each other.
  • variable displacement hydraulic unit may be non-overcenter.
  • the hydraulic actuator 3 is a double acting cylinder, or a rotating cylinder the second hydraulic unit 7 may be over-center.

Abstract

In the presented solution an electrohydraulic actuator (1) comprises an electric motor (6), a first hydraulic unit (2), and a second hydraulic unit (7). The electric motor (6), the first hydraulic unit (2), and the second hydraulic unit (7) are connected together such that they convey energy between them. The first hydraulic unit (2) is arranged to feed hydraulic fluid to a hydraulic actuator (3) and the electric motor (6) is arranged to control the feed of hydraulic fluid to the hydraulic actuator (3) by means of the first hydraulic unit (2). The second hydraulic unit (7) is connected to a hydraulic accumulator (8). Furthermore, when one of the first hydraulic unit (2) and the second hydraulic unit (7) displaces hydraulic fluid to its pressure port (2a, 7a) the other may be arranged to displace hydraulic fluid to a low-pressure port (2b, 7b) and vice versa.

Description

    FIELD OF THE INVENTION
  • The present invention relates to electrohydraulic actuators.
    • BACKGROUND
  • Electro-hydraulic actuators (EHA) are apparatuses, in which at least a fluid pressure actuator, a pump driving the actuator and an electric motor rotating the pump are combined. Electro-hydraulic actuators are used in applications, where it is beneficial not to have an external hydraulic system with external pumps, tubing and the like. Electro-hydraulic actuators are also used in applications, where simplicity of system architecture and safety and reliability are essential, such as in aerospace industry.
    • BRIEF DESCRIPTION
  • An object of the present invention is to provide a new type of an electrohydraulic actuator and a new method. The object of the invention is achieved by a method and an electrohydraulic actuator which are characterized by what is stated in the independent claims. Some embodiments of the invention are disclosed in the dependent claims.
  • In the presented solution an electrohydraulic actuator comprises an electric motor, a first hydraulic unit, and a second hydraulic unit. The electric motor, the first hydraulic unit, and the second hydraulic unit are connected together such that they convey energy between them. The first hydraulic unit is arranged to feed hydraulic fluid to a hydraulic actuator and the electric motor is arranged to control the feed of hydraulic fluid to the hydraulic actuator by means of the first hydraulic unit. The second hydraulic unit is connected to a hydraulic accumulator. Furthermore, when one of the first hydraulic unit and the second hydraulic unit displaces hydraulic fluid to its pressure port the other may be arranged to displace hydraulic fluid to a low-pressure port and vice versa. In the presented solution it is possible to store energy to the hydraulic accumulator from mechanical movement of the hydraulic actuator or from electrical network, for example. Electrical energy may be transferred to pressure, for example. The energy stored to the hydraulic accumulator may be reused. The energy from the hydraulic accumulator may be used for providing higher momentary power, for example. It is also possible to transfer energy stored to the hydraulic accumulator to electric network. Also, the speed of the hydraulic actuator is controlled in a simple manner. All in all, the solution is simple and reliable.
  • According to an embodiment the first hydraulic unit is a fixed displacement hydraulic unit. Such a solution is easy to implement and durable. Because the electric motor rotates the fixed displacement hydraulic unit the control of the hydraulic actuator is versatile.
  • According to an embodiment the second hydraulic unit is a variable displacement hydraulic unit. Thereby the control of the flows of the hydraulic fluid may be made in various ways and still the electric motor and the variable displacement hydraulic unit may be simply mechanically connected. Naturally, when a variable displacement hydraulic unit is used having a zero angle it does not displace hydraulic fluid. However, the variable displacement hydraulic unit may be arranged to displace hydraulic fluid. When both the hydraulic units rotate, they displace hydraulic fluid as described above.
  • According to an embodiment the electric motor, the first hydraulic unit, and the second hydraulic unit are mechanically connected to each other. Such a solution is durable.
  • According to an embodiment the variable displacement hydraulic unit is non-overcenter. Such a solution is cost effective.
  • According to an embodiment the hydraulic actuator may be a single-acting cylinder, a double acting cylinder, or a rotating cylinder.
  • According to an embodiment the hydraulic actuator is a single-acting cylinder and when one of the first hydraulic unit and the second hydraulic unit displaces hydraulic fluid to its pressure port the other may be arranged to displace hydraulic fluid to a tank via the low-pressure port and vice versa. Such a solution is versatile and reliable.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which
    • Figure 1 shows schematically an electrohydraulic actuator having a single-acting cylinder;
    • Figure 2 shows schematically an electrohydraulic actuator having a double acting cylinder according to an embodiment;
    • Figure 3 shows schematically an electrohydraulic actuator having a double acting cylinder according to another embodiment; and
    • Figure 4 shows schematically an electrohydraulic actuator having a double acting cylinder according to yet another embodiment.
    DETAILED DESCRIPTION
  • Figure 1 shows an electrohydraulic actuator 1. The electrohydraulic actuator 1 comprises a first hydraulic unit 2. The first hydraulic unit 2 may be a rotating hydraulic unit such as a hydraulic pump/motor. In the embodiment shown in Figure 1 the first hydraulic unit 2 is a fixed displacement hydraulic unit.
  • The first hydraulic unit 2 is connected to a hydraulic actuator 3. The hydraulic actuator 3 in Figure 1 is a single-acting cylinder. Feeding hydraulic fluid by the first hydraulic unit 2 to a chamber 4 of the hydraulic actuator 3 raises the piston 5 of the hydraulic actuator 3.
  • The electric motor 6 rotates the first hydraulic unit 2. For the sake of clarity means for controlling the electric motor are not shown in Figure 1. As is characteristics to an electrohydraulic actuator electric motor 6 is arranged to control the feed of hydraulic fluid to the hydraulic actuator 3 by means of the first hydraulic unit 2.
  • The electrohydraulic actuator 1 also comprises a second hydraulic unit 7. The second hydraulic unit 7 may be a rotating hydraulic unit such as a hydraulic pump/motor. In the embodiment shown in Figure 1 the second hydraulic unit 7 is a variable displacement hydraulic unit.
  • The second hydraulic unit 7 is connected to a hydraulic accumulator 8. The electric motor 6, the first hydraulic unit 2, and the second hydraulic unit 7 are connected together such that they convey energy between them. The electric motor 6, the first hydraulic unit 2, and the second hydraulic unit 7 may be mechanically or electrically connected to each other.
  • When the first hydraulic unit 2 displaces hydraulic fluid to its pressure port the second hydraulic unit 7 displaces hydraulic fluid via its low-pressure port 7b to a tank 9 and vice versa. For example, when the first hydraulic unit 2 is rotated such that it displaces hydraulic fluid to its pressure port 2a for raising the piston 5, the second hydraulic unit 7 displaces hydraulic fluid via its low-pressure port 7b to the tank 9. Simultaneously, energy stored as pressure to the hydraulic accumulator 8 may be used for boosting the feed of hydraulic fluid to the hydraulic actuator 3. Thus, hydraulic fluid may be fed from the hydraulic accumulator 8 to rotate the second hydraulic unit 7. Because the hydraulic units 2 and 7 are connected such that they convey energy between them the energy in the hydraulic accumulator 8 enhances feeding the fluid to the hydraulic actuator 3.
  • When the piston 5 is allowed to lower due to gravity, for example, the piston 5 pushes hydraulic fluid to the first hydraulic unit 2 rotating it. The first hydraulic unit 2 displaces hydraulic fluid via its low-pressure port 2b to the tank 9. The rotation of the first hydraulic unit 2 causes the second hydraulic unit 7 to displace hydraulic fluid to its pressure port 7a and therethrough to the hydraulic accumulator 8. Energy is thus stored to the hydraulic accumulator 8. Also, electric energy from an electric network may be stored to the hydraulic accumulator 8 such that the electric motor 6 is rotated, naturally providing that not all the energy supplied to the electric motor 6 is used for other purposes such as raising the piston 5.
  • Figures 2, 3, and 4 show electrohydraulic actuators 1 having double acting cylinders 3. Depending on the rotating direction of the first hydraulic unit 2 hydraulic fluid is fed either to a first chamber 4a or to a second chamber 4b. Feeding hydraulic fluid to the first chamber 4a moves the piston 5 upwards in the Figures. Feeding hydraulic fluid to the second chamber 4b moves the piston 5 downwards in the Figures.
  • In the embodiment shown in Figure 2 one of the ports of the first hydraulic unit 2 is not directly connected to the tank 9 but to a hydraulic line 11 connected to the second chamber 4b of the hydraulic actuator 3. All in all, the embodiment shown in Figure 2 is simple and reliable. However, when the volumes on the opposite sides of the piston 5 are different, energy cannot be recovered efficiently when the pressure raises above a pressure limit.
  • The solutions shown in Figures 3 and 4 obviate the shortcoming mentioned in connection with the embodiment shown in Figure 2. The embodiment shown in Figure 3 comprises a third hydraulic unit 10, which is connected to the first hydraulic unit 2, and the second hydraulic unit 7 such that they convey energy between them. The third hydraulic unit 10 may be a rotating hydraulic unit such as a hydraulic pump/motor. In the embodiment shown in Figure 3 the third hydraulic unit 10 is a fixed displacement hydraulic unit.
  • In the embodiments shown in Figures 2 and 3 one of the ports of the second hydraulic unit 7 is directly connected to the hydraulic accumulator 8 and the other port of the second hydraulic unit 7 is directly connected to the tank 9. In the embodiment shown in Figure 4 one of the ports of the second hydraulic unit 7 is not directly connected to the tank 9 but to a hydraulic line 11 connected to the second chamber 4b of the hydraulic actuator 3. The embodiment shown in Figure 4 does not need so many rotating hydraulic units as the embodiment shown in Figure 3. For the sake of clarity valves needed are not mainly shown in the Figures.
  • In the embodiment shown in Figure 4 the hydraulic actuator 3 is a double acting cylinder having the first chamber 4a on the first side of the piston 5 and the second chamber 4b on the second side of the piston 5. One of the ports of the first hydraulic unit 2 is directly connected to the first chamber 4a and the other port of the first hydraulic unit 2 is directly connected to the second chamber 4b. One of the ports of the second hydraulic unit 7 is directly connected to the hydraulic accumulator 8 and the other port is directly connected to the second chamber 4b.
  • The other port of the second hydraulic unit 7 may be directly connected either to the second chamber 4b or to the first chamber 4a, especially when the volumes of the first chamber 4a and the second chamber 4b are equal. However, in the embodiment shown in Figure 4 the volume of the second chamber 4b is smaller than the volume of the first chamber 4a. That means that the effective surface area of the piston 5 on the side of the second chamber 4b is smaller than the effective surface area of the piston 5 on the side of the first chamber 4a. If the volume of the second chamber 4b is smaller than the volume of the first chamber 4a it is preferable that the other port of the second hydraulic unit 7 is directly connected to the second chamber 4b to enhance efficient energy recovery and overall operation of the electrohydraulic actuator 1.
  • According to an embodiment both the first hydraulic unit 2 and the second hydraulic unit 7 are fixed displacement hydraulic units. In such a case the electric motor 6, the first hydraulic unit 2, and the second hydraulic unit 7 are electrically connected to each other.
  • The variable displacement hydraulic unit may be non-overcenter. When the hydraulic actuator 3 is a double acting cylinder, or a rotating cylinder the second hydraulic unit 7 may be over-center.
  • It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims (7)

  1. An electrohydraulic actuator, comprising
    an electric motor (6), a first hydraulic unit (2), and a second hydraulic unit (7) which are connected together such that they convey energy between them,
    the first hydraulic unit (2) being arranged to feed hydraulic fluid to a hydraulic actuator (3) and the electric motor (6) being arranged to control the feed of hydraulic fluid to the hydraulic actuator (3) by means of the first hydraulic unit (2),
    the second hydraulic unit (7) being connected to a hydraulic accumulator (8),
    whereby the arrangement is such that when one of the first hydraulic unit (2) and the second hydraulic unit (7) displaces hydraulic fluid to its pressure port (2a, 7a) the other may be arranged to displace hydraulic fluid to a low-pressure port (2b, 7b) and vice versa, and
    wherein the hydraulic actuator (3) is a single-acting cylinder and when one of the first hydraulic unit (2) and the second hydraulic unit (7) displaces hydraulic fluid to its pressure port (2a, 7a) the other may be arranged to displace hydraulic fluid to a tank (9) via the low-pressure port (2b, 7b) and vice versa, or
    wherein the hydraulic actuator (3) is a double acting cylinder having a first chamber (4a) on a first side of a piston (5) and a second chamber (4b) on a second side of the piston (5), one of the ports of the first hydraulic unit (2) is directly connected to the first chamber (4a) and the other port of the first hydraulic unit (2) is directly connected to the second chamber (4b), one of the ports of the second hydraulic unit (7) is directly connected to the hydraulic accumulator (8) and the other port of the second hydraulic unit (7) is directly connected either to the second chamber (4b) or to the first chamber (4a) or to the tank (9).
  2. An electrohydraulic actuator as claimed in claim 1, wherein the first hydraulic unit (2) is a fixed displacement hydraulic unit.
  3. An electrohydraulic actuator as claimed in claim 1 or 2, wherein the second hydraulic unit (7) is a variable displacement hydraulic unit.
  4. An electrohydraulic actuator as claimed in claim 3, wherein the variable displacement hydraulic unit (7) is non-overcenter.
  5. An electrohydraulic actuator as claimed in any one of the preceding claims, wherein the electric motor (6), the first hydraulic unit (2), and the second hydraulic unit (7) are mechanically connected to each other.
  6. An electrohydraulic actuator as claimed in any one of the preceding claims, wherein the hydraulic actuator (3) is a double acting cylinder having a first chamber (4a) on a first side of a piston (5) and a second chamber (4b) on a second side of the piston (5) and wherein the volume of the second chamber (4b) is smaller than the volume of the first chamber (4a) and said other port of the second hydraulic unit (7) is directly connected to the second chamber (4b).
  7. A method in connection with an electrohydraulic actuator the method comprising
    providing an electrohydraulic actuator (1), comprising an electric motor (6), a first hydraulic unit (2), and a second hydraulic unit (7) which are connected together such that they convey energy between them,
    feeding hydraulic fluid to a hydraulic actuator (3) by the first hydraulic unit (2) and controlling by the electric motor (6) the first hydraulic unit (2) to control the feed of hydraulic fluid to the hydraulic actuator (3),
    connecting the second hydraulic unit (7) to a hydraulic accumulator (8), whereby in the method when one of the first hydraulic unit (2) and the second hydraulic unit (7) displaces hydraulic fluid to its pressure port (2a, 7a) the other displaces hydraulic fluid to a low-pressure port (2b, 7b) and vice versa, and
    wherein the hydraulic actuator (3) is a single-acting cylinder and when one of the first hydraulic unit (2) and the second hydraulic unit (7) displaces hydraulic fluid to its pressure port (2a, 7a) the other displaces hydraulic fluid to a tank (9) via the low-pressure port (2b, 7b) and vice versa, or
    wherein the hydraulic actuator (3) is a double acting cylinder having a first chamber (4a) on a first side of a piston (5) and a second chamber (4b) on a second side of the piston (5), one of the ports of the first hydraulic unit (2) is directly connected to the first chamber (4a) and the other port of the first hydraulic unit (2) is directly connected to the second chamber (4b), one of the ports of the second hydraulic unit (7) is directly connected to the hydraulic accumulator (8) and the other port of the second hydraulic unit (7) is directly connected either to the second chamber (4b) or to the first chamber (4a) or to the tank (9).
EP22168727.0A 2021-04-23 2022-04-19 Electrohydraulic actuator and method Withdrawn EP4080062A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FI20215477 2021-04-23

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EP4080062A1 true EP4080062A1 (en) 2022-10-26

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EP (1) EP4080062A1 (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0641644A1 (en) * 1993-09-02 1995-03-08 Maschinenfabrik Müller-Weingarten AG Method for controlling the drive of a hydraulic press and apparatus for carrying out the method
DE102004061559A1 (en) * 2004-12-21 2006-06-29 Brueninghaus Hydromatik Gmbh Hydraulic drive
CN1987124A (en) * 2006-12-14 2007-06-27 浙江大学 Energy saving hydraulic lifting system of variable hydraulic counterweight
CN101956405A (en) * 2010-07-15 2011-01-26 吉林大学 Gravitational potential energy recovery device during descending of engineering machinery movable arm
EP2640657A2 (en) * 2010-11-18 2013-09-25 National Oilwell Varco Norway AS A heave compensating system
CN107131159A (en) * 2017-06-20 2017-09-05 北京交通大学 Electrohydrostatic actuator under gravitational load

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0641644A1 (en) * 1993-09-02 1995-03-08 Maschinenfabrik Müller-Weingarten AG Method for controlling the drive of a hydraulic press and apparatus for carrying out the method
DE102004061559A1 (en) * 2004-12-21 2006-06-29 Brueninghaus Hydromatik Gmbh Hydraulic drive
CN1987124A (en) * 2006-12-14 2007-06-27 浙江大学 Energy saving hydraulic lifting system of variable hydraulic counterweight
CN101956405A (en) * 2010-07-15 2011-01-26 吉林大学 Gravitational potential energy recovery device during descending of engineering machinery movable arm
EP2640657A2 (en) * 2010-11-18 2013-09-25 National Oilwell Varco Norway AS A heave compensating system
CN107131159A (en) * 2017-06-20 2017-09-05 北京交通大学 Electrohydrostatic actuator under gravitational load

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