DE102009008514B4 - Hydrostatic drive system of a mobile work machine - Google Patents

Hydrostatic drive system of a mobile work machine Download PDF

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Publication number
DE102009008514B4
DE102009008514B4 DE102009008514.9A DE102009008514A DE102009008514B4 DE 102009008514 B4 DE102009008514 B4 DE 102009008514B4 DE 102009008514 A DE102009008514 A DE 102009008514A DE 102009008514 B4 DE102009008514 B4 DE 102009008514B4
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Prior art keywords
pump
pressure
valve
control
control pressure
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DE102009008514.9A
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DE102009008514A1 (en
Inventor
Markus Schwab
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STILL GmbH
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STILL GmbH
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B66HOISTING; LIFTING; HAULING
    • B66FHOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075Constructional features or details
    • B66F9/20Means for actuating or controlling masts, platforms, or forks
    • B66F9/22Hydraulic devices or systems
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/162Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for giving priority to particular servomotors or users
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/505Pressure control characterised by the type of pressure control means
    • F15B2211/50554Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure downstream of the pressure control means, e.g. pressure reducing valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/60Circuit components or control therefor
    • F15B2211/635Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements
    • F15B2211/6355Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements having valve means
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058Rotary output members

Abstract

Hydrostatic drive system of a mobile working machine, in particular of a truck, with a pump (1) and at least one of the pump (1) can be supplied consumers of a working hydraulics (2) by means of an electro-hydraulically actuated control valve (11), in particular a directional control valve operable is, wherein for actuating the control valve (11) at least one electrically actuable pilot valve is provided, which communicates with a control pressure supply line (25), wherein for generating the in the control pressure supply line (25) pending control pressure with a delivery line (4) of the pump (1) is provided in connection pressure reducing valve (26), characterized in that the pump (1) in addition to the supply of another consumer, in particular a hydraulic steering (3) is provided, wherein in the delivery line (4) of the pump ( 1) for the preferred supply of the further consumer (3) a priority v is arranged (5) and the control pressure supply line (25), in which the pressure reducing valve (26) is arranged, upstream of the priority valve (5) to the delivery line (4) of the pump (1) is connected.

Description

  • The invention relates to a hydrostatic drive system of a mobile work machine, in particular an industrial truck, with a pump and at least one power supplied by the pump load a working hydraulics, which can be actuated by means of an electro-hydraulically actuated control valve, in particular a directional control valve, wherein for actuating the control valve at least an electrically operable pilot valve is provided which is in communication with a control pressure supply line, wherein a pressure reducing valve communicating with a delivery line of the pump is provided for generating the control pressure applied in the control pressure supply line.
  • In electro-hydraulically actuated and pilot operated control valves to achieve high actuation forces for the control valve, a control pressure supply with a constant control pressure level is required, from which by means of appropriate pilot valves, a control pressure is generated for actuating the control valves.
  • From the DE 102 24 731 A1 is a hydrostatic drive system designed as a truck working machine, in which an additional designed as a constant pump pump is provided in the form of a feed pump for generating the constant control pressure for the electro-hydraulically operated control valves of the working hydraulics. In the from the DE 102 24 731 A1 known drive system thus two pumps are required, resulting in a high construction cost of the drive system. To protect the feed pressure level of the feed pump or the feed pressure supply line is usually associated with a pressure relief valve. The throttling of funded by the feed pump and unnecessary control pressure and thus the unused control pressure flow, especially at unconfirmed control valves on the pressure relief valve leads to high hydraulic losses, which lead to high energy consumption of the drive system and a high heat load of the pressure medium.
  • From the DE 37 08 570 C2 and the DE 39 05 654 C2 generic hydrostatic drive systems are known in which there is provided for generating the pending in the control pressure supply line control pressure with a delivery line of the pump pressure reducing valve.
  • The DE 197 48 782 A1 discloses a drive system for a battery powered truck with a pump driven by an electric motor which is provided to supply a lift cylinder, a tilt cylinder and a hydraulic steering. For the preferred supply of the hydraulic steering, a priority valve is provided, which is arranged in the delivery line of the pump in the first place after the pump.
  • The present invention has for its object to provide a hydrostatic drive system of the type mentioned is available, which is improved in terms of energy consumption and heat load of the pressure medium and has a low construction cost.
  • This object is achieved in that the pump continues to supply another consumer, in particular a hydraulic steering, provided, wherein in the delivery line of the pump for preferential supply of the other consumer, a priority valve is arranged and the control pressure supply line upstream of the priority valve to the delivery line Pump is connected. As a result, the pending before the priority valve system pressure of the pump of the working hydraulics can be used in an energy-saving manner to generate the control pressure. According to the invention thus the constant control pressure for pilot control and actuation of the control valves of the working hydraulics is generated directly from the pump of the working hydraulics from the pending in the delivery line of the pump system pressure and provided. The use according to the invention of the system generated by the pump of the working hydraulics and thus existing system pressure to provide the constant control pressure for precontrol of the control valves by eliminating a separate pump, such as a feed pump to produce the control pressure a low construction cost and reduced energy consumption can be achieved. By using a pressure reducing valve also eliminates a previously required pressure relief valve to secure the control pressure levels, so that no throttling of the unused control pressure flow to the container occurs, whereby the heat input can be reduced in the pressure medium of the drive system.
  • Particular advantages arise when, according to an advantageous embodiment of the invention in the control pressure supply line upstream of the pressure reducing valve in the direction of the pressure reducing valve opening check valve, in particular check valve, is arranged. When switching off the pump, especially in a work machine with an electrical, such as battery-electric, drive the pump can be clamped with the check valve in the control pressure supply line pending control pressure in a simple manner.
  • The priority valve is expediently acted upon by means of a spring in the direction of a conveying line connecting the pump to the steering position. The pending before the priority valve system pressure is co-determined by the spring bias of the spring of the priority valve, which can be provided from the system pressure in a simple way, the control pressure for pilot control of the control valves of the working hydraulics.
  • The drive system according to the invention can be designed as a so-called open-center system in which the pump is designed as a fixed displacement pump and the control valve is associated with a circulation pressure, the highest load pressure of the load of the working hydraulics and a spring in the direction of a blocking position and the delivery pressure of the Pump is applied in the direction of a flow position. In such a drive system, the system pressure, in particular for non-actuated consumers, also determined by the spring bias of the spring of the rotary pressure balance, which with the connected to the delivery line of the pump control pressure supply line and arranged in this pressure reducing valve in a simple manner required for actuating the control valves control pressure can be generated.
  • In order to generate the control pressure required for actuation of the control valves in all operating conditions from the system pressure supplied by the pump, the spring bias of the priority valve and / or the spring preload of the recirculation pressure balance according to a preferred embodiment of the invention are set such that at each operating point a minimum control pressure level can be generated in the control pressure supply line. This ensures in a simple manner that in the control pressure supply line required for the actuation of the control valves and certain of the setting of the pressure reducing valve pilot pressure is present in all operating conditions.
  • The drive system according to the invention can also be designed as a so-called closed-center system, in which the pump is designed as a load-sensing variable-displacement pump, which is controlled by the highest load pressure of the working hydraulics and / or the other consumer. Such a variable delivers when not driven consumers of the working hydraulics and / or non-actuated steering a standby pressure as a control variable of the variable, from the means connected to the delivery line of the pump control pressure supply line and arranged in this pressure reducing valve in a simple way, the control pressure for actuating the Control valves can be generated.
  • If according to an advantageous embodiment of the invention in such a drive system, the standby pressure and thus the controlled variable of the pump and / or the spring bias of the priority valve are set such that at each operating point a minimum control pressure level in the control pressure supply line can be generated, the required control pressure for Actuation of the control valves are easily generated in all operating conditions from the system pressure generated by the pump.
  • Further advantages and details of the invention will be explained in more detail with reference to the embodiments illustrated in the schematic figures. Show here
    • 1 a first embodiment of a drive system according to the invention and
    • 2 A second embodiment of a drive system according to the invention.
  • In the 1 is an inventive, designed as an open-center system drive system of a designed example, designed as a truck work machine in a schematic circuit diagram.
  • The drive system comprises a pump designed as a fixed displacement pump 1 , which is operated in the open circuit and to supply a working hydraulics 2 and another consumer, by a hydraulic steering 3 is formed, is provided. The pump 1 sucks out of a container and delivers to a delivery line 4 in the preferred supply of the steering 3 a priority valve 5 is arranged. From the priority valve 5 leads a conveyor branch line 6 to the steering 3 and a conveyor branch line 7 to a control valve block 8th the working hydraulics 2 ,
  • The priority valve 5 is by means of a spring 9 and in a load pressure branch line 10 the steering 3 Pending load pressure of the steering 3 in the direction of a conveyor line 4 with the conveyor branch line 6 for the preferred supply of the steering 3 connecting position 5a acted upon. By means of in the delivery branch line 6 Pending delivery pressure is the priority valve 5 in the direction of a position 5b can be acted upon, in which the delivery line 4 with both branch lines 6 and 7 for the simultaneous supply of the steering 3 and the working hydraulics 2 connected is.
  • The control valve block 8th the working hydraulics 2 includes to control each consumer's working hydraulics 2 designed as a way valve Control valve. In the 1 are schematically illustrated control valves 11 for actuating a linear actuator 12 , A tilt drive, not shown, and possibly an additional drive, not shown, for example, a side slide, the working hydraulics 2 intended.
  • In the control valve block 8th the working hydraulics 2 is according to the 1 a circulation pressure balance 15 arranged in one of the conveyor branch line 7 arranged to container guided branch line. The circulation pressure balance 15 is that of a load pressure branch line 16 pending, highest load pressure of the consumers of the working hydraulics 2 and a spring 17 in the direction of a blocking position and in the delivery branch line 7 applied delivery pressure in the direction of a flow position. To protect the load pressure branch line 16 the working hydraulics 2 a pressure relief valve 18 be assigned.
  • In the 2 is an inventive, designed as a closed-center system drive system of an example designed as a truck work machine shown in a schematic circuit diagram. The same components are provided here with the same reference numerals.
  • To supply the working hydraulics 2 and that of the hydraulic steering 3 formed further consumer provided pump 1 is designed as a load-sensing variable-displacement pump. For controlling the flow rate of the pump 1 is a demand flow regulator 19 provided by the highest load pressure of the steering 3 or the highest load pressure of the working hydraulics 2 is controlled. The load pressure branch line 10 the steering 3 as well as the load pressure branch line 16 the working hydraulics 2 can in this case to the inputs of a shuttle valve device 20 be connected, the output side with the demand flow control device 19 the pump 1 communicates.
  • The control valves 11 for controlling the consumers of the working hydraulics 2 according to the 1 and 2 are each electro-hydraulically actuated. For this purpose, not shown in detail electrically controlled pilot valves, for example by means of a proportional solenoid operated pressure reducing valves, provided by means of which the control valves 11 actuating control pressures can be generated. The pilot valves are on the input side with a control pressure supply line 25 in connection.
  • According to the invention is to a control pressure port of the control valve block 8th the working hydraulics 2 Guided control pressure supply line 25 to the support line 4 the working hydraulics 2 and the steering 3 supplying pump 1 upstream of the priority valve 5 connected. In the control pressure supply line 25 is a pressure reducing valve for generating a constant control pressure level 26 formed, hydraulically controlled pressure reducing valve, whose setting the control pressure level at the control pressure port of the control valve block 8th Are defined. To adjust the control pressure level is the pressure reducing valve 26 with a spring 27 Provided. Upstream of the pressure reducing valve 26 is in the control pressure supply line 25 one towards the pressure reducing valve 26 opening check valve 28 arranged, which is designed as a check valve.
  • In a drive system according to the 1 or the 2 put the pump 1 the volume flow to supply the consumers of the working hydraulics 2 and of the steering 3 further consumer made available. The priority valve 5 prioritizes the steering 3 when operating in front of the working hydraulics 2 with simultaneous operation of the steering 3 and the working hydraulics 2 , The spring preload of the spring 9 of the priority valve 5 changes the performance of the priority valve 5 and determines the flow resistance and thus the pressure drop across the priority valve 5 , With uncontrolled steering 3 is the priority valve 5 in the position 5b acted in the volume flow of the pump 1 completely the control valve block 8th and thus the control valves 11 the working hydraulics 2 flows in. At the priority valve 5 occurs in this case, a pressure difference, in direct dependence on the spring preload of the spring 9 stands.
  • For non-actuated control valves 11 the working hydraulics 2 becomes the circulation pressure balance 15 according to the 1 acted upon in the flow position, provided that in the delivery branch line 7 pending system pressure the spring preload of the spring 17 the circulation pressure balance 15 This causes the work hydraulics to flow in the event of unconfirmed consumers 2 and uncontrolled steering 3 the full volume flow of the pump 1 via the priority valve 5 and the circulation pressure balance 15 to the container. The pressure difference at the circulation pressure balance 15 This is in direct dependence on the spring preload of the spring 17 ,
  • From the spring 27 of the pressure reducing valve 26 the minimum control pressure in the control pressure supply line is defined, the pilot control and thus actuation of the control valves 8th is required.
  • The spring preload of the spring 9 of the priority valve 5 and the spring preload of the spring 17 the circulation pressure balance are in the drive system according to the invention according to the 1 adjusted so that when un-actuated consumers, the sum of the pressure difference at the priority valve 5 and the pressure difference at the circulation pressure balance 15 plus the line resistances and flow resistances of other components at least equal to the minimum control pressure provided by the spring 27 is defined, whereby the pilot pressure for actuating the control valves 11 the working hydraulics 2 from the pump 1 in the promotion line 4 generated system pressure can be provided in all operating conditions.
  • In a drive system according to the invention according to the 2 settles at non-actuated consumers of working hydraulics 2 and not operated steering 3 the system pressure in the delivery line 4 from the sum of, for example, a spring at the demand flow control device 19 certain standby pressure of the pump 1 and the pressure difference at the priority valve 5 plus the line resistance and flow resistance of other components together. By appropriate adjustment of the standby pressure of the pump 1 and the spring bias of the spring 9 of the priority valve 5 This can also be achieved in a simple manner that from the system pressure of the pump 1 in the promotion line 4 the one from the spring 27 of the pressure reducing valve 26 certain pilot pressure for actuation of the control valves of the working hydraulics in all operating conditions can be generated and provided.
  • At actuated loads of working hydraulics 2 sets the minimum system pressure of the pump 1 from the sum of the lowest load pressure of the consumers of the working hydraulics 2 of which the circulation pressure balance 15 is acted upon in the blocking position or the demand flow control device 19 the pump 1 is applied, and the pressure difference at the priority valve 5 plus the line resistance and flow resistance of other components together. The minimum system pressure of the pump 1 at the lowest load of the working hydraulics corresponds at least to that of the spring 27 defined minimum control pressure, which by the pump 1 generated system pressure to provide the pilot pressure for actuating the control valves 11 the working hydraulics can be used.
  • By only slightly increasing the system pressure compared to drive systems of the prior art can in the drive system according to the invention with the pressure reducing valve 26 an external pilot pressure supply for the electrohydraulically actuated and pilot operated control valves 11 the working hydraulics 2 with constant control pressure from that of the pump 1 generated system pressure can be achieved.
  • With the pressure reducing valve 26 can here with low construction costs and low energy consumption and a low thermal load of the pressure medium, a control pressure supply with a constant control pressure level for the electro-hydraulically operated control valves 11 the working hydraulics 2 in one as an open-center system according to the 1 or as a closed-center system according to the 2 trained hydrostatic drive system from the pump 1 generated system pressure can be achieved.
  • The invention may in this case in internal combustion engine operated forklift trucks, in which the pump 1 is driven by an internal combustion engine, or electrically, in particular battery-powered industrial trucks, where the pump 1 is driven by an electric motor used.
  • In addition, from the pump 1 other consumers are operated and driven, for example, a brake release device of a parking brake and / or a hydrostatic fan device.

Claims (7)

  1. Hydrostatic drive system of a mobile working machine, in particular of a truck, with a pump (1) and at least one of the pump (1) can be supplied consumers of a working hydraulics (2) by means of an electro-hydraulically actuated control valve (11), in particular a directional control valve operable is, wherein for actuating the control valve (11) at least one electrically actuable pilot valve is provided, which communicates with a control pressure supply line (25), wherein for generating the in the control pressure supply line (25) pending control pressure with a delivery line (4) of the pump (1) is provided in connection pressure reducing valve (26), characterized in that the pump (1) in addition to the supply of another consumer, in particular a hydraulic steering (3) is provided, wherein in the delivery line (4) of the pump ( 1) for the preferred supply of the further consumer (3) a priority Valve (5) is arranged and the control pressure supply line (25), in which the pressure reducing valve (26) is arranged, upstream of the priority valve (5) to the delivery line (4) of the pump (1) is connected.
  2. Hydrostatic drive system according to Claim 1 , characterized in that in the control pressure supply line (25) upstream of the pressure reducing valve (26) in the direction of the pressure reducing valve (26) opening check valve (28), in particular check valve, is arranged.
  3. Hydrostatic drive system according to Claim 1 or 2 , characterized in that the priority valve (5) by means of a spring (9) in the direction of the delivery line (4) of the pump (1) with the position which connects consumers (5a).
  4. Hydrostatic drive system according to one of Claims 1 to 3 , characterized in that the pump (1) is designed as a fixed displacement pump and the control valve (11) is associated with a circulation pressure compensator (15) of the highest load pressure of the load of the working hydraulics (2) and a spring (17) in the direction of a blocking position and the delivery pressure of the pump (1) is acted upon in the direction of a flow position.
  5. Hydrostatic drive system according to Claim 4 , characterized in that the spring bias of the priority valve (5) and / or the spring preload of the circulation pressure compensator (15) are set such that at each operating point, a minimum control pressure level in the control pressure supply line (25) can be generated.
  6. Hydrostatic drive system according to one of Claims 1 to 3 , characterized in that the pump (1) is designed as a load-sensing-controlled variable displacement pump, which is controlled by the highest load pressure of the working hydraulics (2) and / or the further consumer (3).
  7. Hydrostatic drive system according to Claim 6 , characterized in that the standby pressure of the pump (1) and / or the spring bias of the priority valve (5) are set such that at each operating point, a minimum control pressure level in the control pressure supply line (25) can be generated.
DE102009008514.9A 2009-02-11 2009-02-11 Hydrostatic drive system of a mobile work machine Active DE102009008514B4 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE102009008514.9A DE102009008514B4 (en) 2009-02-11 2009-02-11 Hydrostatic drive system of a mobile work machine

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102009008514.9A DE102009008514B4 (en) 2009-02-11 2009-02-11 Hydrostatic drive system of a mobile work machine
EP10000411.8A EP2218675A3 (en) 2009-02-11 2010-01-18 Hydrostatic drive system for a mobile work machine

Publications (2)

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DE102009008514A1 DE102009008514A1 (en) 2010-08-12
DE102009008514B4 true DE102009008514B4 (en) 2019-08-14

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DE102009008514.9A Active DE102009008514B4 (en) 2009-02-11 2009-02-11 Hydrostatic drive system of a mobile work machine

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DE (1) DE102009008514B4 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3708570C2 (en) 1987-03-17 1995-11-16 Bosch Gmbh Robert Electro-hydraulic device for actuating a piston-like part which can be displaced in a housing bore
DE3905654C2 (en) 1989-02-24 1998-10-29 Bosch Gmbh Robert Hydraulic control device
DE19748782A1 (en) 1997-11-05 1999-05-06 Clark Material Handling Gmbh Hydraulic lifting arrangement for battery-powered fork-lift truck or similar
DE10224731A1 (en) 2001-06-29 2003-01-16 Linde Ag Method by which a hydraulic operating circuit is protected from overload has a safety valve system incorporated which reacts to a load signal

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5524213A (en) * 1978-08-04 1980-02-21 Diesel Kiki Co Ltd Apparatus for controlling speed of hydraulic actuator for remote control
US4343151A (en) * 1980-05-16 1982-08-10 Caterpillar Tractor Co. Series - parallel selector for steering and implement
DE3321484A1 (en) * 1983-06-14 1984-12-20 Linde Ag Hydraulic system with two hydraulic energy consumers
US5060475A (en) * 1990-05-29 1991-10-29 Caterpillar Inc. Pilot control circuit for load sensing hydraulic systems
DE10047631A1 (en) * 2000-09-26 2002-04-11 Linde Ag Hydraulic system for battery-operated electric load conveying vehicle has hydraulic unit acting as pump and motor coupled to electrical unit acting as motor and generator
DE10151831B4 (en) * 2001-10-20 2011-12-22 Still Gmbh Hydraulic system for a truck

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3708570C2 (en) 1987-03-17 1995-11-16 Bosch Gmbh Robert Electro-hydraulic device for actuating a piston-like part which can be displaced in a housing bore
DE3905654C2 (en) 1989-02-24 1998-10-29 Bosch Gmbh Robert Hydraulic control device
DE19748782A1 (en) 1997-11-05 1999-05-06 Clark Material Handling Gmbh Hydraulic lifting arrangement for battery-powered fork-lift truck or similar
DE10224731A1 (en) 2001-06-29 2003-01-16 Linde Ag Method by which a hydraulic operating circuit is protected from overload has a safety valve system incorporated which reacts to a load signal

Also Published As

Publication number Publication date
EP2218675A2 (en) 2010-08-18
EP2218675A3 (en) 2013-10-16
DE102009008514A1 (en) 2010-08-12

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