EP0882186A1 - Circuit hydraulique a detection de charge d'une machine de travail ou engin hydraulique automoteur - Google Patents

Circuit hydraulique a detection de charge d'une machine de travail ou engin hydraulique automoteur

Info

Publication number
EP0882186A1
EP0882186A1 EP97943839A EP97943839A EP0882186A1 EP 0882186 A1 EP0882186 A1 EP 0882186A1 EP 97943839 A EP97943839 A EP 97943839A EP 97943839 A EP97943839 A EP 97943839A EP 0882186 A1 EP0882186 A1 EP 0882186A1
Authority
EP
European Patent Office
Prior art keywords
load
pressure
sensing
bypass valve
pump
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97943839A
Other languages
German (de)
English (en)
Inventor
Volker BÖSEBECK
Michael Holtmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CNH Industrial Baumaschinen GmbH
Original Assignee
O&K Orenstein and Koppel GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by O&K Orenstein and Koppel GmbH filed Critical O&K Orenstein and Koppel GmbH
Publication of EP0882186A1 publication Critical patent/EP0882186A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/165—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for adjusting the pump output or bypass in response to demand
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2225—Control of flow rate; Load sensing arrangements using pressure-compensating valves
    • 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
    • F15B2211/20553—Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • 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
    • F15B2211/25—Pressure control functions
    • F15B2211/253—Pressure margin control, e.g. pump pressure in relation to load pressure
    • 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/30555—Inlet and outlet of the pressure compensating valve being connected to the directional control valve
    • 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • 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
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3105—Neutral or centre positions
    • F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • 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
    • F15B2211/30—Directional control
    • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/3157—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
    • 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
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50518—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief valves
    • F15B2211/50527—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief valves using cross-pressure relief valves
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/55—Pressure control for limiting a pressure up to a maximum pressure, e.g. by using a pressure relief valve
    • 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
    • F15B2211/605—Load sensing 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6052—Load sensing circuits having valve means between output member and the load sensing circuit using check valves
    • 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
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6054—Load sensing circuits having valve means between output member and the load sensing circuit using shuttle valves
    • 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
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6055—Load sensing circuits having valve means between output member and the load sensing circuit using pressure relief valves
    • 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
    • F15B2211/615—Filtering 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
    • 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
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders

Definitions

  • the invention relates to a device for load pressure-dependent automatic opening and closing of a closed-center load-sensing hydraulic circuit containing control and / or regulating elements for mobile hydraulic construction and work machines.
  • the hydraulic systems used today in small and standard excavators can be divided into open-center and closed-center hydraulic systems.
  • the basic circuit of an open center hydraulic circuit consists of a variable or constant pump in connection with a 6/3 or 8/3 way valve with neutral circulation.
  • the term open center is derived from the free circulation of the pump volume flow in the neutral position of the directional control valves.
  • pressure-controlled load-sensing systems with primary or secondary pressure compensators are often designed as closed-center hydraulic systems, whereby the directional control valves have a closed neutral position without free pump circulation.
  • Closed-center hydraulic circuits have the disadvantage that the return flow volume used for hydraulic oil cooling is not available in stand-by operation of the construction and working machine, since the pressure-controlled variable displacement pump of the closed-center load-sensing system is in stand-by - Operation only covers the leakage losses to maintain the control pressure difference.
  • the object of the invention is therefore to eliminate the disadvantages that exist in closed-center load-sensing systems by optimizing the open-loop and closed-loop control system.
  • This goal is achieved by means of a device for automatic opening and closing of a closed-center load-sensing hydraulic circuit containing control and / or regulating elements for mobile hydraulic construction and work machines with at least one a variable displacement pump which can be controlled via an associated pressure regulator, the signals causing the opening or closing of the hydraulic circuit being derived from the pumps and load-sensing load pressure present in the hydraulic circuit.
  • the subject matter of the invention relates to a device which consists of a self-switching load-sensing bypass valve, which is preferably integrated in the control block and which, depending on the load-sensing load and pump pressure present, opens the connection from the pump channel to the tank channel via a defined throttle .
  • the control pressure difference generated by the variable pump during the load-free phases in stand-by mode drops when the bypass valve is open via the device-specific throttle, which results in a defined volume flow available for cooling the hydraulic medium in the tank channel of the control spool and thus in the return line from Control spool to hydraulic oil cooler.
  • FIG. 2 partial representation of the load-sensing integrated in the control block according to FIG.
  • FIG. 1 includes a control principle in which a pressure-controlled load-sensing variable pump 1, a closed-center load-sensing control block 2 with six load-pressure-compensated sections 3, 4, 5, 6, 7, 8 and secondary scales 9, 10, 11 , 12,13,14 supplied with hydraulic oil.
  • the subject matter of the invention relates to a device which consists of a self-switching load-sensing bypass valve 15 which is integrated in the control block 2 and which is dependent on the load-sensing load pressure p L s present in the line 16 or 17 and on the pump pressure p P in line 18 or 19 the connection from the pump channel (line 19) to the tank channel 20 opens via a defined throttle 21.
  • the control pressure difference ⁇ p_s generated by the pump 1 during the load-free phases in the stand-by mode drops when the bypass valve 15 is open via the device-specific throttle 21, which results in a defined volume flow available in the tank for cooling the hydraulic medium. channel 20 or 22 of the control slide 2 and thus in the return line 23 from the control slide 2 to the hydraulic oil cooler 24.
  • the variable displacement pump 1 is equipped with a pressure regulator 25. Via the load signal line 26, the load pressure signal p LS is communicated to the pressure regulator 25 of the variable pump 1, which then reacts with an output pressure signal p P in the pump line 18 which is higher than the load pressure signal p_s by the control pressure difference ⁇ p_s.
  • FIG. 2 shows a partial area of the load-sensing bypass valve 15 including the throttle point 21.
  • the load-sensing bypass valve 15 contains a switching piston 27, which has a conical seat surface 28.
  • the tank channel 20 can also be seen.
  • a spring 29 is provided in the area of the switching piston 27.
  • the switching piston 27 contains 2 active surfaces, namely A and A 2 .
  • the pump pressure PP acts on the active surface A 2
  • the load-sensing load pressure p LS acts on the active surface Ai in conjunction with the active force of the spring 29.
  • the highest load pressure signal p L s p . m a x corresponding pressure signal effective in the load-sensing signaling channel 16 of the control slide 2.
  • the load pressure signal p_s is communicated to the pressure regulator 25 of the variable displacement pump 1, which then reacts with an output pressure signal p P in the pump line 18 that is higher than the load pressure signal p L s by the control pressure difference ⁇ p L s.
  • the pressure signals p LS and p P are applied to the active surfaces Ai and A 2 of the switching piston 27 of the load-sensing bypass valve 15 via the pressure channels 17 and 19.
  • PLS PLmax (2) gives the following relationship for determining the minimum effective area A 1n .in required for the automatic closing operation on the conical seat 28 of the switching piston 27
  • the load-sensing bypass valve 15 or its switching piston 27 is automatically activated by the pressure signals p S present on the corresponding active surfaces i and A 2 , p P , PT and p F closed.
  • the load-sensing bypass valve 15 is automatically activated by the pressure signals p S present on the corresponding active surfaces i and A 2 , p P , PT and p F closed.
  • the pressure signal ps present in the load reporting line 26 drops to the tank pressure level p ⁇ .
  • the pump pressure p P in the line 18 thereby also drops to the level lying by ⁇ p LS above the input pressure of the load signaling line 26.
  • the bypass valve 15 or the switching piston 27 opens the connection from the pump channel 18 via the throttle 21, which results in a defined volume flow in the return line 23 and thus in the hydraulic oil cooler 24 sets the load-free phases.
  • a max for the effective area A ⁇ is calculated using the equation below from the control pressure difference ⁇ p_s of the effective area A 2 , the flow force F str and the spring equivalent pressure p F.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Operation Control Of Excavators (AREA)

Abstract

L'invention a pour objet un dispositif pour l'ouverture et la fermeture automatiques, en fonction du poids de charge, d'un circuit hydraulique de détection de la charge à système d'accumulation présentant des éléments de commande et de régulation, pour des machines de travail ou des engins hydrauliques automoteurs, ayant au moins une pompe à cylindrée variable pouvant être commandée via un régulateur de pression associé, dispositif dans lequel les signaux provoquant l'ouverture ou la fermeture du circuit hydraulique sont prélevés à partir de la pression de charge des pompes situées dans le circuit hydraulique et du système de détection de charge.
EP97943839A 1996-09-27 1997-09-06 Circuit hydraulique a detection de charge d'une machine de travail ou engin hydraulique automoteur Withdrawn EP0882186A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19639772 1996-09-27
DE1996139772 DE19639772C1 (de) 1996-09-27 1996-09-27 Load-Sensing-Hydraulikkreis einer mobilhydraulischen Bau- und Arbeitsmaschine
PCT/EP1997/004846 WO1998013604A1 (fr) 1996-09-27 1997-09-06 Circuit hydraulique a detection de charge d'une machine de travail ou engin hydraulique automoteur

Publications (1)

Publication Number Publication Date
EP0882186A1 true EP0882186A1 (fr) 1998-12-09

Family

ID=7807090

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97943839A Withdrawn EP0882186A1 (fr) 1996-09-27 1997-09-06 Circuit hydraulique a detection de charge d'une machine de travail ou engin hydraulique automoteur

Country Status (3)

Country Link
EP (1) EP0882186A1 (fr)
DE (1) DE19639772C1 (fr)
WO (1) WO1998013604A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE602004012846T2 (de) * 2004-06-24 2009-04-09 Walvoil S.P.A. Load-sensing-Hydrauliksystem mit mehreren Sektionen
JP4081487B2 (ja) 2004-12-28 2008-04-23 東芝機械株式会社 油圧制御弁
DE102013221683A1 (de) * 2013-10-25 2015-04-30 Robert Bosch Gmbh Hydraulische Steuervorrichtung, Satz von hydraulischen Steuervorrichtungen, Verfahren zum Steuern einer hydraulischen Steuervorrichtung

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3878864A (en) * 1973-12-07 1975-04-22 Borg Warner Bypass valve
US4938022A (en) * 1987-10-05 1990-07-03 Hitachi Construction Machinery Co., Ltd. Flow control system for hydraulic motors
DE3821348C2 (de) * 1988-06-24 1997-09-11 Linde Ag Hydraulisches System
JP2579202Y2 (ja) * 1992-04-10 1998-08-20 株式会社小松製作所 圧力補償弁を備えた操作弁

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9813604A1 *

Also Published As

Publication number Publication date
DE19639772C1 (de) 1998-04-02
WO1998013604A1 (fr) 1998-04-02

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