WO2018189153A1

WO2018189153A1 - Self-sustaining power supply for hydrostatic pumps and motors

Info

Publication number: WO2018189153A1
Application number: PCT/EP2018/059116
Authority: WO
Inventors: Suenje Marsch; Harry Rasch; Bernd Hames; Andreas Schumacher
Original assignee: Danfoss Power Solutions Gmbh & Co Ohg
Priority date: 2017-04-13
Filing date: 2018-04-10
Publication date: 2018-10-18
Also published as: DE102017206415A1

Abstract

The invention relates to a variable displacement hydraulic unit (1) comprising a casing (50), a positionable adjustment element (3) for adjusting the displacement volume of a driving mechanism (2), and a control unit (9) for controlling an adjustment unit (7) featuring an actuator (8) to position the adjustment element (3). The hydraulic unit (1) further comprises an integrated self- sustaining (autarkic) electrical power source (10) that is located in or on the casing (50) and that energizes at least the control unit (9) and the actuator (8).

Description

SELF-SUSTAINING POWER SUPPLY FOR HYDROSTATIC PUMPS AND MOTORS

The present invention relates according to the preamble of claim 1 to a variable displacement hydraulic unit comprising a casing, a positionable adjustment element for adjusting the dis- placement volume of the driving mechanism of the hydraulic unit and a control unit for controlling an adjustment unit featuring an actuator to position the adjustment element.

Variable displacement hydraulic units, such as hydrostatic motors or pumps, are known from the state of the art. They generally comprise a servo control system with a servo piston slide-ably disposed in a servo cylinder. The servo piston acts commonly via a piston rod on an adjustment element for adjusting the stroke or displacement of the hydraulic unit. An exemplary adjustment element is a tiitable swash-plate in an axial piston hydraulic unit. The position of the servo piston is controlled by supplying or draining hydraulic fluid to or from an end face of the servo piston under control of a control unit acting on a control valve. The control unit comprises, for example, a microcontroller that controls electric power supplied to actuators of the control valve.

Exemplary hydraulic units of this kind are described in EP 2 693 054 A1 and in DD 21 1 603.

Hydraulic units of the state of the art require extensive wiring when they are mounted in their operating environment, such as agricultural machinery, like harvesters or tractors, or in building equipment, like road construction machines or vehicles, like excavators or graders. In these applications the hydraulic units are used for propelling the machinery or for driving auxiliary equipment, like forklifts or the shovels of excavators. At least for control purpose, the different actuators and sensors of the hydraulic unit must be connected to electronic control units and/or, if they are non-mechanically or non-hydraulically driven, to electrical power sources in order to operate properly. This entails the provision of electrical connectors and wiring that may have to be led over considerable distances in the equipment. Such wiring is susceptible to damage and entry of water and dirt, in particular at the connectors, given the rough and/or harsh environment and handling of the working machine. Also, an external power source or power supply must be provided that energizes the electrical components of a hydraulic unit.

It is an object of the present invention to provide a hydraulic unit of the above mentioned kind that greatly simplifies the installation of such hydraulic units in their operating environment and that obviates the problems present with hydraulic units of the state of the art. The object of the invention is solved by providing a hydraulic unit that further comprises an integrated self-sustaining (autarkic) electrical power supply that is located in or at the casing of the hydraulic unit and that energizes at least the control unit and the actuator. By integrating the electrical power supply and all of the electrical and electronic components necessary to operate the hydraulic unit in one package the need for electrical connectors and additional external wiring is eliminated. This greatly facilitates the installation of the hydraulic unit in its intended operating environment, as only the mechanical and hydraulic connections must be provided. Also, service in the field is facilitated, as only the hydrostatic and mechanical hard- ware have to be connected or disconnected in order to install or dismount the hydrostatic unit. In addition, the invention eliminates space required for the installation of wire harnesses and minimizes the possibility of water ingression through electrical wires and connectors. For an operator of a work machine furnished with a hydraulic unit according to the invention the risk of damage is reduced, because no wires can be damaged by the harsh environment present on, e.g., a building site. In general, downtime and maintenance are reduced. In particular, a tedious and time consuming search for broken wires in such vehicles and machines is eliminated.

In implementing the invention the control unit comprises means capable to receive setting commands from a joystick or another remote controller external to the hydraulic unit in a wireless way or by a single Bus-signal line. These commands are processed in the control unit that generates voltages or currents to control the actuator. In a preferred embodiment of the invention the control unit comprises a microprocessor that controls the entire operation of the hydraulic unit in accordance with the setting commands transmitted to the hydraulic unit by a remote controller, e.g., a joystick in the operator^'s cab.

In a preferred embodiment the electrical power supply is an electrical generator that is drivable directly or indirectly by a rotating element of the driving mechanism. Such a rotating element is, for example, a driving or driven shaft of the hydraulic unit. The generator may be connected directly to this shaft or by means of an intermediate set of gears. Such a connection may be per- manent or temporary by means of a clutch that is activated when electrical power is required, e.g. to charge a rechargeable battery. Also, a section of such a shaft may be configured as the rotor of an electrical generator. In a preferred embodiment of the invention the electrical generator is integrated in a speed sensor provided to measure the rotational speed of a shaft of the hydraulic unit.

In an alternative embodiment of the invention the electrical power supply is an electrical generator which is drivable by a hydraulic flow within the hydraulic unit. Such a hydraulic flow for driving the generator can be provided by a charge pump within the hydraulic unit or may be branched- off of a system pressure line, a working line or a loop-flushing line of the hydraulic unit. In this embodiment the electrical generator may be integrated in a flow meter present in one of the hydraulic fluid lines of the hydraulic unit.

Still another embodiment of the present invention ensues from an electrical power supply that further comprises a rechargeable battery for providing electric current to the control unit or to a microcontroller and/or to the actuator and/or to sensors located within the hydraulic unit. In this configuration it is preferred that the rechargeable battery is chargeable by the generator.

The electrical generator used in implementing the invention may be of an alternating current type (AC) or of a direct current type (DC). If the output of the generator is used to charge a rechargeable battery it is preferred to use a DC-generator or to provide an AC/DC converter if an AC-generator is used. In general the output voltage and/or current of the generator is regulated as required from the components of the hydraulic unit. For this purpose, the necessary hardware is included in the package of the hydraulic unit of the invention. Such hardware is well known in the state of the art, so that further details are not necessary for their definition.

The present invention also includes a control unit that is configured as an on-off switching de- vice that in a first state of operation supplies electrical power from the power supply to one or more actuators of a control valve and in a second state of operation isolates the one or more actuators from the power supply. In a preferred embodiment of such a set-up the switching device is configured to provide several different voltage levels that are selectable by means of a wireless command module. In these configurations of the hydraulic unit of the invention it is of particular advantage that the control unit comprises means capable to receive in a wireless way or by a single Bus-signal line setting commands from a joystick or another remote controller external to the hydraulic unit.

Alternatively, a preferred embodiment of the invention includes a microcontroller or micropro- cessor that is integrated in the hydraulic unit and that is configured to receive external command signals that are transmitted in a wireless manner. These command signals can be provided in an exemplary manner by command modules that emit coded electromagnetic or optical radiation, such as infrared. Preferably, such command modules may be hand-held or alternatively mounted in the cabin of, for example, a tractor, excavator or grader. In such an embodiment the hydraulic unit of the invention is equipped with appropriate sensors or antennas that can receive the command signals and feed them to the control unit. In a preferred embodiment of the invention the control unit comprises an electronic displacement unit (EDC) and the actuator is a solenoid which can be commanded by a microcontroller or a switching unit in order to change the position of the control spool in the control unit. In this configuration the control spool is configured to control at least one hydraulic pressure supplied to or discharged from the adjustment unit in order to move the adjustment element. The adjustment unit, e.g., comprises a servo unit, whose servo piston is capable to position the adjustment element, wherein the servo piston can be pressurized single-sided or double-sided. In order to move the adjustment element, the control spool can act also mechanically, i.e. directly on the adjustment unit and/or the adjustment element.

In a preferred embodiment of the invention the hydraulic unit is of the axial piston type featuring a tiltable swashplate or bent axis as positionable adjustment element, wherein the adjustment element is tiltable from an initial position in only one direction or in two directions. In the latter case the fluid flow in the hydraulic unit may be selected in two opposite directions.

In an alternative embodiment the hydraulic unit is of the radial piston type or the orbiter type, wherein the adjustment unit is capable to change the eccentricity of the adjustment element with respect to a drive shaft axis of the driving mechanism. The invention also includes a hydraulic unit in which the adjustment unit is of a purely electromechanical design. In this case the control valve and the servo unit are replaced by an electrical actuator that directly or indirectly exerts a force on the adjustment element of the driving unit. The actuator can be realized in the form of an electro-magnet with a push-rod connected, for example, to a tiltable swash-plate or by an electro motor with a rack and pinion coupling to the swash-plate. It is understood, that this modification of the hydraulic unit applies also to variable displacement radial piston hydraulic motors or pumps, and are covered by the knowledge of a person with skills in the relevant art, hence covered also by the inventive idea.

The present invention also includes a hydraulic unit that further comprises one or more sensors that monitor the operation of the hydraulic unit and whose signals are routed to the control unit in order to control its operation. Exemplary sensors are capable to detect the angle or eccentricity of the adjustment element or the rotational speed of the driving mechanism. Other sensors monitor the flow rate within a hydraulic line or the pressure within a hydraulic line. Still other sensors may be provided to determine the temperature of the hydraulic fluid or a physical com- ponent of the hydraulic unit. Preferably, sensors that determine the charge and/or generating level of the electrical power supply are provided in implementing the invention. It is clear that any combination of the mentioned sensors can be selected in implementing the invention. In operation of the hydraulic unit of the invention the signal or the signals of the one or more sensors are transmittable to the control unit, e.g., a microcontroller, and/or to a joystick or to a remote controller external to the hydraulic unit in a wireless way or via a Bus-signal line. Exemplary embodiments of a hydraulic unit according to the invention are depicted in the drawings.

Figure 1 shows a first embodiment of a hydraulic unit according to the invention in a schematic representation

Figure 2 depicts schematically a second embodiment of a hydraulic unit according to the invention

Figure 1 shows an exemplary embodiment of a hydraulic unit 1 according to the invention in a schematic presentation. The hydraulic unit 1 comprise a casing 50 in which a driving mechanism 2 is located, for example a variable adjustable driving mechanism 2 of a variable displacement pump, as shown in Figure 1 . The displacement volume of the driving mechanism 2 - comprising in case of an axial piston pump a rotatable driveable cylinder block in which work pistons can reciprocate - is determined in this case by the angle position of an adjustment element 3 limiting the stroke of the pistons. This adjustment element 3 may be positioned, for example, by a lever or rod. The adjustment element 3 may be configured as a swash plate, a bent axis or as any other suitable mechanism for setting the operational parameters of driving mechanisms of hydraulic units. The position of the adjustment element 3 is controlled by means of an adjustment unit 7 that is under control of a control unit 9.

Driving mechanism 2 according to Figure 1 is fluidiy connected to two pressure lines, e.g. a high pressure line 1 1 for delivering hydraulic fluid under high pressure, e.g. to a hydraulic motor, and a low pressure line 12 that supplies fluid to be pressurized by the driving mechanism 2 of the hydraulic pump 1 . Both pressure lines 1 1 and 12 can be connected to a closed hydraulic fluid circuit between a hydraulic motor, not shown in Figure 1 , and the pump^'s driving mechanism 2, which, in this exemplary embodiment, is part of a hydraulic pump 1 having an input drive shaft 29. In this embodiment, shown in Figure 1 , the driving mechanism 2 is driven through a driving shaft 29 connected to an internal combustion engine 100 such as a diesel engine. For this purpose a coupling mechanism 101 can be provided that can be incorporated fully or in part in cas- As shown in Figure 1 in an exemplary and non-limiting manner, a fraction of the high pressure fluid is branched off from high pressure line 1 1 and routed through an electrical generator 13 to low pressure line 12. The voltage output of generator 13, assumed here to be of an alternating current (AC) type, is led by electrical wiring, represented here as electrical lines 15 and 16 to an AC/DC converter. This AC/DC converter is configured to provide DC currents at one or several voltage levels as required by control unit 9, a rechargeable battery 14 and/or an adjustment unit 7. For this purpose AC/DC converter 28 may be configured to be under control of control unit 9. In the configuration, shown in Figure 1 , generator 13 serves mainly to charge battery 14 and to keep its voltage at an essentially constant level as needed to keep hydraulic unit 1 functional. This set-up corresponds to a preferred embodiment of the integrated self-sustaining (autarkic) power supply 10 of the invention.

The electrical connections depicted in Figure 1 are purely schematic. Thus, electrical lines 15, 16 and 19 as well as signal line 18 could consist of several separate wires or connectors, carry- ing different currents or voltages or they could, in particular with signal line 18, be in the form of bus lines or the like for transmitting signals. Also, their placement and the connections provided by these electrical lines are purely exemplary and could be changed in many ways without leaving the scope of the invention. Electrical connections lead from the rechargeable battery 14 to control unit 9 and to adjustment unit 7, the latter connections being only exemplary and not critical for the implementation of the invention. Control unit 9 is powered directly or indirectly by the generator 13 and/or by the rechargeable battery 14 of the integrated self-sustaining (autarkic) power supply 10, as shown in Figure 1 . Control unit 9 may be configured as a microcontroller in a preferred embodiment of the invention. In another, also preferred embodiment control unit 9 is in the form of a signal receiving and current switching device that directly supplies power derived from power supply 10 and of a predetermined level to actuators present in adjustment unit 7. Such a switching device is activated by means of external signal supplied from an external command module in a wireless manner or by a Bus-line or by mechanical means. Such a signal, e.g., can be received by an antenna 30 and guided for instance by a signal line 31 to control unit 9.

Control unit 9 is connected to adjustment unit 7 by means of at least one power line 19 and at least one signal line 18. Power line 19 supplies one or more actuators present in the adjustment unit 7 with current as required to set the stroke or displacement of the driving mechanism 2. The actuators, not shown in Figure 1 , move the adjustment element 3, for example a swash plate, to a desired position as determined by control unit 9. Signal line 18 represents one or more electrical connections that lead from sensors, not shown in Figure 1 , to control unit 9. Such sensors monitor and measure certain parameters required for the proper operation of hydraulic unit 1 . These parameters may include pressure levels of the hydraulic fluid at various positions in the hydraulic unit 1 or flow rates or rotational speeds of the drive shaft 29, e.g., or the position of adjustment element 3. Other power and signal lines, not shown in Figure 1 may lead to other components of hydraulic unit 1 , such as sensors or actuators forming part of hydraulic unit 1 and situated in or on casing 50 of hydraulic unit 1 .

In an alternate embodiment of the invention, not shown in the figures, the generator 13 is of a direct current (DC) type, which obviates the need for a current or voltage converter. In general, generator 13 can be powered in many different ways in implementing the invention. Thus, the hydraulic fluid under pressure driving the generator 13 could be provided by the output of the pump in hydraulic unit 1 in a system pressure line, as shown in Figure 1 or by a charge pump or branched off from a loop flushing line of hydraulic unit 1 . Alternatively, as shown in an exemplary manner in Figure 2, the generator 13 could be driven by purely mechanical means, as will be explained in more detail below.

In the following description the same reference numerals will be used where appropriate to denote similar parts or features in order to facilitate an understanding of the invention. It is understood, that the embodiments shown in Figure 1 and Figure 2 can be combined with each other without leaving the scope of the inventive idea. Also modifications to the embodiments of Figure 1 and Figure 2 which are within the range of a person with skills in the relevant art are covered by the invention.

In Figure 2 a particularly preferred embodiment of a hydraulic unit 1 of the invention is depicted in a schematic manner. Shown is a simplified version of a conventional type of a hydraulic motor that is widely used in the state of the art. In this embodiment adjustment unit 7 comprises a control valve 24 and a servo unit 4 with a servo cylinder 5 and a servo piston 6 slide-ably mounted therein. The driving mechanism 2 depicted in Figure 2 is assumed to be a variable displacement hydrostatic motor that is powered by hydraulic fluid under pressure provided by a high pressure line 1 1 connected to a hydraulic pump, not shown in Figure 2.

As shown in Figure 2 a hydraulic line 21 connected to a two-way check valve 20 branches off from high pressure line 1 1 and leads to control valve 24. Control valve 24 has an outlet line 27 with a through flow reducing orifice 22 that leads to servo cylinder 5. Fluid flows through the con- trol valve 24, and regulates the pressure level in a front chamber of the servo cylinder 5 by means of an actuator 8, acting on one side of a control piston 25. The actuator 8 is energized by the control unit 9. A spring 26, whose action opposes that of actuator 8, is provided for moving control piston 25 in control valve 24 back to the initial position, when the actuator 8 is de- energized. The operating principles of such hydraulic units are well documented in the state of the art such that further details thereof can be omitted here. In the embodiment of the invention depicted in Figure 2 the generator 13, forming part of the integrated self-sustaining (autarkic) power supply 10, is driven by an extension of shaft 29 of driving mechanism 2. Electrical lines 15 and 16 connect generator 13 with control unit 9. Control unit 9 comprises, for example, a microcontroller and means to convert the output of generator

13 into usable currents or voltages. These means would include an AC/DC converter if electrical generator 13 provides alternating current. Connected to control unit 9 is a rechargeable battery

14 that is kept at a predetermined charge level range by control unit 9 that draws the required currents from generator 13. In this configuration generator 13 and rechargeable battery 14 constitute main elements of integrated self- sustaining power supply 10 of the invention. As shown in Figure 2 in an exemplary manner, an electrical power line 17 connects control unit 9 with an actuator 8 of control valve 24. Activation of actuator 8 through power line 17 shifts control piston 25 of control valve 24 thus regulating the flow of hydraulic fluid to servo unit 4, which changes the position of adjustment element 3. This in turn sets the displacement of driving mechanism 2 and hence the maximum available torque and speed of rotation at driving shaft 29. Power line 17 represents symbolically any electrical connection that supplies power to actuators or other similar components of hydraulic unit 1 . Control unit 9 is also in communication by means of a signal line 18 with a sensor 23. This sensor 23 is configured here as a rotational speed sensor for driving shaft 29. In a conceivable different embodiment of the invention generator 13 is integrated with a rotational speed sensor operably connected to driving shaft 29.

In operation of a hydraulic unit 1 of the invention the electrical power required to activate and operate control unit 9, adjustment unit 7 and sensors 23, is provided in a preferred embodiment by the rechargeable battery 14 provided in or at casing 50, e.g. on the outside of casing 50. The charge level of this battery 14 is maintained by current provided by electrical generator 13 when driving mechanism 2 is in motion, as shown in Figure 2, or when hydraulic fluid drives generator 13, as depicted in Figurel . In this embodiment it is preferable to provide the rechargeable battery 14 with means that enable charging by temporary connection to an external charging device. This entails the provision of appropriate coupling contacts on casing 50. Such contacts are useful for a first charging of rechargeable battery 14 and also for diagnostic purposes during service of hydraulic unit 1 . In a different embodiment, that features no rechargeable battery 14, an initial rotation of driving shaft 29 under action of internal combustion engine 100 would cause driving mechanism 2 to rotate and produce electricity in generator 13 that is coupled either hydraulically or mechanically to the driving mechanism 2. This electricity powers control unit 9 that in turn activates the other components of hydraulic unit 1 . Here it is preferred for the embodiment of Figure 1 that driving mechanism 2 is initially set at maximal displacement when actuator 8 is de-energized, because then a sufficient flow of hydraulic fluid to power generator 13 is produced instantly. As soon as the produced power level is sufficient to operate control unit 9 and adjustment unit 7 of the hydraulic unit 1 can be operated in the same manner as known from the state of the art, without electrical power supply lines to the hydraulic unit 1 .

The casing 50 contains all electrical and mechanical components of hydraulic unit 1 . Thus hydraulic unit 1 requires no external electrical cabling or connections, with the possible exception of an antenna or a sensor for the reception of external wirelessly transmitted command signals or a single Bus line for the input of such signals. In essence, casing 50 is provided solely with connection elements for supply and drainage of hydraulic fluid and with coupling elements for connecting the driving shaft 29 of driving mechanism 2, preferable with a gear box axel or with an internal combustion engine 100 or a drive train or any other propel application.

List of Reference Numerals

1 Hydraulic unit

2 Driving mechanism

3 Adjustment element

4 Servo unit

5 Servo cylinder

6 Servo piston

7 Adjustment unit

8 Actuator

9 Control unit

10 Power supply

1 1 High pressure line

12 Low pressure line

13 Generator

14 Rechargeable battery

15 Electrical line

16 Electrical line

17 Power line

18 Signal line

19 Electrical line

20 Double sided check-valve

21 Hydraulic line

22 Orifice

23 Sensor

24 Control valve

25 Control piston

26 Spring

27 Outlet line

28 AC/DC converter

29 Driving shaft

30 Antenna

31 Signal line

50 Casing

100 Internal combustion engine

101 Coupling mechanism

Claims

1 . Variable displacement hydraulic unit (1 ) comprising a casing (50), an adjustment element (3) capable to be positioned for adjusting the displacement volume of a driving mechanism (2) of the hydraulic unit (1 ), and a control unit (9) for controlling an adjustment unit (7) featuring an actuator (8) to position the adjustment element (3),

characterized in that,

the hydraulic unit (1 ) further comprises an integrated, self-sustained (autarkic) electrical power supply (10) that is located in or at the casing (50) and that energizes at least the control unit (9) and the actuator (8).

2. Hydraulic unit (1 ) according to claim 1 , wherein the control unit (9) comprises means capable to receive setting commands from a joystick or another remote controller external to the hydraulic unit (1 ) in a wireless way or by a Bus-signal line and wherein the control unit (9) is capable to command the actuator (8).

3. Hydraulic unit (1 ) according to claim 1 or 2, wherein the electrical power source (10) is a generator (13) which is drivable directly or indirectly by a rotating element of the driving mechanism (2).

4. Hydraulic unit (1 ) according to claim 1 or 2, wherein the electrical power source (10) is a generator (14) which is drivable by a hydraulic flow within the hydraulic unit (1 ).

5. Hydraulic unit (1 ) according to claim 4, wherein the hydraulic flow for driving the generator (13) can be provided by a charge pump within the hydraulic unit or is branched-off of a system pressure line (1 , 12) or a working line or a loop-flushing line of the hydraulic unit (1 ).

6. Hydraulic unit (1 ) according to one of the previous claims, wherein the electrical power supply (10) further comprises a rechargeable battery (14) for providing electric current to the control unit (9) and/or to the actuator (8) and/or to sensors (23) located within the hydraulic unit (1 ), wherein the rechargeable battery (14) is chargeable by the generator (13).

7. Hydraulic unit (1 ) according to one of the previous claims, wherein the control unit (9) is an electronic displacement unit and the actuator (8) is a solenoid for changing the position of a control piston (25) in the control valve (24).

8. Hydraulic unit (1 ) according to one of the previous claims, wherein, in order to move the adjustment element (3), the control piston (25) is capable to control at least one hydraulic pressure ported to or discharged from the adjustment unit (7).

9. Hydraulic unit (1 ) according to claim 8, wherein the adjustment unit (7) comprises a servo unit (4), whose servo piston (6) is capable to position the adjustment element (3), wherein the servo piston (6) can be pressurized single-sided or double-sided.

10. Hydraulic unit (1 ) according to one of the claims 1 to 7, wherein, in order to move the adjustment element (3), the control piston (24) can act mechanically in the adjustment unit (7).

1 1 . Hydraulic unit (1 ) according to one of the previous claims, wherein the hydraulic unit (1 ) is of the axial piston construction type showing a tiltable swashplate or bent axis as posi- tionable adjustment element (3), wherein the adjustment element (3) is tiltable from an initial position in only one direction or in two directions.

12. Hydraulic unit (1 ) according to one of claims 1 to 10, wherein the hydraulic unit (1 ) is of the radial piston type or the orbiter type, wherein the adjustment unit (7) is capable to change the eccentricity of the adjustment element (3) with respect to an drive shaft axis ( 10) of the driving mechanism (2).

13. Hydraulic unit (1 ) according to one of the previous claims, wherein the hydraulic unit (1 ) further comprises one or more sensors (23) capable to detect at least:

the angle or the eccentricity of the adjustment element (3), and/or the rotational speed of the driving mechanism (2), and/or

the flow rate within a hydraulic fluid line, and/or

the pressure within a hydraulic fluid line, and/or

the temperature of the hydraulic fluid or a physical component of the hydraulic unit (1 ), and/or

the charge and/or generating level of the electrical power supply (10);

wherein the signal or the signals of the one or more sensors (23) are transmittable to the control unit (9), and/or to a joystick or to a remote controller external to the hydraulic unit (1 ) in a wireless way or via a Bus-signal line.