EP0862697B1 - Process and device for driving the hydraulic system of a machine - Google Patents

Process and device for driving the hydraulic system of a machine Download PDF

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Publication number
EP0862697B1
EP0862697B1 EP96945157A EP96945157A EP0862697B1 EP 0862697 B1 EP0862697 B1 EP 0862697B1 EP 96945157 A EP96945157 A EP 96945157A EP 96945157 A EP96945157 A EP 96945157A EP 0862697 B1 EP0862697 B1 EP 0862697B1
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EP
European Patent Office
Prior art keywords
hydraulic
pressure
hydraulic cylinder
cylinder
piston
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.)
Expired - Lifetime
Application number
EP96945157A
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German (de)
French (fr)
Other versions
EP0862697A1 (en
Inventor
Jörg Dantlgraber
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.)
Bosch Rexroth AG
Original Assignee
Mannesmann Rexroth AG
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Publication of EP0862697A1 publication Critical patent/EP0862697A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, 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
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices 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
    • B66F9/075—Constructional features or details
    • B66F9/20—Means for actuating or controlling masts, platforms, or forks
    • B66F9/22—Hydraulic devices or systems
    • 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
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/028—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force
    • F15B11/036—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force by means of servomotors having a plurality of working chambers
    • 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
    • F15B2211/21—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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-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
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • 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
    • F15B2211/40—Flow control
    • F15B2211/41—Flow control characterised by the positions of the valve element
    • F15B2211/413—Flow control characterised by the positions of the valve element the positions being continuously variable, e.g. as realised by proportional 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
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41509—Flow control characterised by the connections of the flow control means in the circuit being connected to a pressure source and a 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
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/426—Flow control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/40—Flow control
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/625—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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6306—Electronic controllers using input signals representing a pressure
    • F15B2211/6309—Electronic controllers using input signals representing a pressure the pressure being a pressure source supply 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6653—Pressure control
    • 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
    • F15B2211/7055—Linear output members having more than two chambers
    • 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 invention relates to a method for control one multi-stage acting against a load Hydraulic cylinder of an implement according to the preamble of claim 1 and one according to the method working hydraulic system of an implement according to Preamble of claim 3.
  • a method and the hydraulic system are known from DE-A-3 836 371.
  • hydraulic cylinders are next to the hydraulic motor an indispensable device for hydraulic forming Energy in mechanical energy.
  • a hydraulic pump is replaced by a Motor driven and hydraulic fluid from a tank sucked in and through the pressure line of the hydraulic system conveyed to the hydraulic cylinder.
  • Via a directional valve in the Leaves pressure line between the hydraulic pump and hydraulic cylinder the direction of movement of the piston in the hydraulic cylinder Taxes.
  • the hydraulic cylinder loaded with a load represents a resistance for the hydraulic fluid, where the pressure in the hydraulic cylinder rises until the resulting force is sufficient to counter the piston Resistance to move the load.
  • the maximum movable Force is essentially given by the maximum Pump pressure and the effective diameter of the Hydraulic cylinders.
  • the maximum travel speed of the piston of the The hydraulic cylinder is of the maximum flow rate Depending on the hydraulic pump. In the event that quick Adjusting movements of the hydraulic cylinder are required a high pump output can be made available. In order to keep the pump output low, the A hydraulic accumulator is provided by the pressure line Pump is filled when the required volume flow to extend the Hydraulic cylinders smaller than the maximum pump volume flow is. Is in an operating state maximum volume flow for rapid extension of the Hydraulic cylinders required, so the difference to Volume flow of the pump taken from the hydraulic accumulator become. The use of this hydraulic accumulator thus allows a reduction in the maximum pump output.
  • the laid-open specification DE 38 36 371 relates to a hydraulic drive device for one Loop lifter with a tandem piston-cylinder unit, two different sizes for the two servo valves Control cylinder spaces in such a way that a constant force is obtained.
  • the invention is based on the object a method for controlling a hydraulic cylinder and to create a hydraulic system of an implement that one with minimal expenditure on device technology Operation of the implement with minimized energy consumption allow.
  • the hydraulic cylinder three is particularly advantageous Has active surfaces, two of which are active surfaces in Extension direction and an effective area in the entry direction the hydraulic cylinder or, more precisely, the piston of the Hydraulic cylinders act, each effective area electrically or hydraulically operated 3/2-way valve assigned.
  • suitable control of the Directional valves can be used in any of the three effective areas combine so that five pressure levels can be set.
  • a particularly simple and compact structure of the Hydraulic cylinders can be obtained by using a cup-shaped differential piston is executed, wherein the effective area formed on the rear of the piston and through a blind hole in the differential piston trained effective area act in the direction of extension, while the ring surface of the differential piston in Entry direction works.
  • A is advantageously in the pressure line Pressure sensor provided that the input signal for the preferably electrically or hydraulically acting Control unit forms.
  • This shows a circuit diagram of a cylinder drive for a hoist.
  • the hoist shown has a lifting cylinder 1, the piston 2 is loaded with a load F, the is movable by extending or retracting the piston 2.
  • the Piston 2 is designed and has a differential design a blind hole inner bore 4, which is in the piston rear, in the following called piston surface 6 opens.
  • the piston 2 is guided in a cylinder jacket 8, the in the embodiment shown with a center column 10 is formed, which is coaxial through the interior of the cylinder jacket 8 extends and into the Immersed inner bore 4 of the piston 2.
  • this is from the cylinder jacket 8 surrounded cylinder space through the center column 10 as Annular space in which the piston 2 is guided.
  • the radially expanded collar section 12 of the piston 2 is guided on the inner surfaces of the cylinder jacket 8 and sealed by seals 14.
  • the piston rod side Part 16 of the piston 2 has one according to the figure cup-shaped cross section and interspersed with its Lateral surfaces an annular passage recess 18, the in the piston rod end face of the Cylinder jacket 8 is formed.
  • sealing devices 14 for sealing the Cylinder chamber end face provided in the Through recess 18 are in turn sealing devices 14 for sealing the Cylinder chamber end face provided.
  • the first cylinder chamber 20 is in the radial direction through the Cylinder jacket 8 and the center column 10 and in Axial direction through the lower inner face of the Cylinder jacket 8 and limited by the piston surface 6.
  • the second cylinder chamber 22 is through the front Section of the inner bore 4 and the end face of the Center column 10 formed.
  • the third cylinder space 24 is on the one hand through the annular surface 26 of the collar section 12 of the piston 2 and on the other hand through the inner surface of the upper (representation according to figure) face of the Cylinder jacket 8 and on the other hand through the outer circumference of the piston rod side, radially stepped down Section 16 of the piston 2 and through the Limited inner circumferential surface of the cylinder jacket 8.
  • the effective areas of the cylinder rooms are thus through the Surface A1 of the piston surface 6, the surface A2 of the Annular surface 26 and the end face A3 of the inner bore 4th educated.
  • Two connections 28 and 30 are formed on the cylinder jacket 8, which open into the cylinder space 20 or 24.
  • the Center column 10 of the cylinder jacket 8 is one axial through hole 32 penetrates the second Cylinder chamber 22 opens.
  • the connections 28, 30 and the connection bore 32 are with Working lines 34, 36, 38 connected via the Hydraulic fluid in the respective cylinder spaces 20, 24 and 22 can be fed.
  • the working lines 34, 36, 38 are closed three 3/2-way valves of essentially the same design 40a, b, c performed by a spring in a Basic position (not shown) are biased. In this Switch position is a working connection A with a Pressure port T of each directional control valve 40a, b, c connected.
  • the pressure connections P of the three-way valves 40a, b, c are via connecting lines to a common pressure line 42 performed with a terminal D one Proportional valve 44 is connected.
  • the end position of the proportional valve 44 is the connection D connected to a pump port P 'while a Tank connection T is blocked.
  • In the other end position of the proportional valve 44 is the port D with a Tank T connected.
  • the proportional valve 44 For the pump connection P 'of the proportional valve 44 is one Pump line 46 guided with a variable displacement pump 48 connected is. One branches off from the pump line 46 Branch line to a hydraulic accumulator 50, for example can be designed as a bladder accumulator.
  • the directional control valves are 40a, b, c as electrically operated solenoid valves trained so that when excited Electromagnet 41, the directional valve 40 from the basic position is brought into the switching position shown, in which the each port B connected to a tank port T. is.
  • the control of the electromagnets 41 of the directional control valves 40a, b, c takes place via a control unit 52, via which the Directional control valves 40a, b, c are selectively controllable.
  • a control unit 52 via which the Directional control valves 40a, b, c are selectively controllable.
  • Input signal for controller 52 is shown in the Embodiment the signal of a pressure sensor 54 used, which detects the pressure in the pressure line 42 and outputs a signal to the control unit 52.
  • Proportional valve 44 connects P'-D hydraulic fluid from the pump 48 or from the hydraulic accumulator 50 via the Proportional valve 44 and the directional control valves 40 in the Initiate cylinder spaces 20, 22 and 24, so that - at suitable system pressure - due to the A1 and A3 forces act against the load F against the Ring surface 26 (A2) acting force can be shifted upwards is.
  • Appropriate control of the directional control valves 40 allows five pressure levels to be set.
  • the total effective area counteracting the load F is determined by the area difference A1 + A3 - A2 certainly.
  • the other switching variants can be found in Table 1, the terms "ON” and “OFF” denoting the state in which the respective electromagnet is energized (ON) (see figure) or switched off (OFF).
  • Valve 40a Valve 40b
  • Valve 40c Effective area OUT ON OUT ON OUT ON 1 x x x A3
  • Directional control valves 40a, b, c can be five effective areas preselect 1 to 5 times the smallest area, i.e. the end face A3 of the inner bore 4.
  • the directional control valves 40a, b, c are activated in such a way that there is a pressure - as in the following is executed - sets in the pressure line 42, the is approximately equal to the system pressure in the hydraulic accumulator 50.
  • To a setpoint table is saved in the control unit, according to which the pressure in the pressure line 42 when extending of the piston 2 about the control pressure difference on Proportional valve 44 less than the pressure in Hydraulic accumulator 50 and about when the piston 2 is retracted the control pressure difference at the proportional valve 44 is larger than the system pressure in the hydraulic accumulator 50.
  • the Switch position 5 selected in which the maximum effective Area A1 + A3 is preset by the Solenoids of the directional control valves 40a and 40b are excited and thus the third cylinder space 24 is not included Hydraulic fluid is supplied. Furthermore, it will Proportional valve 44 brought into a position in which the connections D and P 'are connected to each other, so that hydraulic fluid from the pump 48 or from the Hydraulic accumulator 50 inserted into the cylinder spaces 20 and 22 so that the pressure in these rooms increases until the load F is raised. Immediately after Raising the load F becomes the pressure in the pressure line 42 detected by the pressure sensor 54 and as an input signal forwarded to the control unit 52.
  • the control device 52 also allows compensation of short-term fluctuations in the entry and extension movement, according to the preset Target value table by switching the directional valves 40a, b, c to possible pressure fluctuations in the pressure line 42 and thus reacts in the cylinder rooms 20, 22 and 24 can be, without significant hydraulic fluid must be replenished by the pump 48.
  • a corresponding switching of the valves 40a, b, c in the line 42 sets a pressure which is higher than the pressure in the hydraulic accumulator 50 by the control pressure difference in the valve 44 (P D - P p ,) Throttling in valve 44, piston 2 is lowered in a defined manner, hydraulic medium flowing from D to P ′ into accumulator 50.
  • the switch position DT the valve 44 is necessary to relieve the cylinder spaces 20, 22 and 24.
  • control device designed as an electrically acting device
  • control unit can of course also be hydraulic are designed to act, whereby the directional control valves 40 can be designed hydraulically controllable.
  • the control device designed as an electrically acting device
  • the control unit can of course also be hydraulic are designed to act, whereby the directional control valves 40 can be designed hydraulically controllable.
  • the Lift cylinder 1 or the valves shown conceivable, without leaving the basic principle of the invention.

Description

Die Erfindung betrifft ein Verfahren zur Ansteuerung eines gegen eine Last wirkenden mehrstufigen Hydrozylinder eines Arbeitsgerätes gemäß dem Oberbegriff des Patentanspruchs 1 und eine nach dem Verfahren arbeitende Hydroanlage eines Arbeitsgerätes gemäß dem Oberbegriff des Patentanspruchs 3. Ein solches Verfahren und die Hydroanlage sind aus DE-A-3 836 371 bekannt.The invention relates to a method for control one multi-stage acting against a load Hydraulic cylinder of an implement according to the preamble of claim 1 and one according to the method working hydraulic system of an implement according to Preamble of claim 3. Such a method and the hydraulic system are known from DE-A-3 836 371.

Hydrozylinder sind in modernen Hydroanlagen neben dem Hydromotor ein unentbehrliches Gerät für die Umformung hydraulischer Energie in mechanische Energie. Üblicherweise wird bei einer Hydroanlage eine Hydropumpe durch einen Motor angetrieben und Hydraulikfluid aus einem Tank angesaugt und durch die Druckleitung der Hydroanlage hin zum Hydrozylinder gefördert. Über ein Wegeventil in der Druckleitung zwischen Hydropumpe und Hydrozylinder läßt sich die Bewegungsrichtung des Kolbens im Hydrozylinder steuern. Der mit einer Last beaufschlagte Hydrozylinder stellt für das Hydraulikfluid einen Widerstand dar, wobei der Druck im Hydrozylinder solange ansteigt, bis die resultierende Kraft ausreicht, um den Kolben entgegen dem Widerstand der Last zu bewegen. Die maximal bewegbare Kraft ist im wesentlichen vorgegeben durch den maximalen Pumpendruck und den wirksamen Durchmesser des Hydrozylinders.In modern hydraulic systems, hydraulic cylinders are next to the hydraulic motor an indispensable device for hydraulic forming Energy in mechanical energy. Usually In a hydraulic system, a hydraulic pump is replaced by a Motor driven and hydraulic fluid from a tank sucked in and through the pressure line of the hydraulic system conveyed to the hydraulic cylinder. Via a directional valve in the Leaves pressure line between the hydraulic pump and hydraulic cylinder the direction of movement of the piston in the hydraulic cylinder Taxes. The hydraulic cylinder loaded with a load represents a resistance for the hydraulic fluid, where the pressure in the hydraulic cylinder rises until the resulting force is sufficient to counter the piston Resistance to move the load. The maximum movable Force is essentially given by the maximum Pump pressure and the effective diameter of the Hydraulic cylinders.

Die maximale Verfahrgeschwindigkeit des Kolbens des Hydrozylinders ist vom maximalen Förderstrom der Hydropumpe abhängig. Für den Fall, daß schnelle Stellbewegungen des Hydrozylinders erforderlich sind, muß eine hohe Pumpenleistung zur Verfügung gestellt werden. Um die Pumpenleistung gering zu halten, ist in der Druckleitung ein Hydrospeicher vorgesehen, der von der Pumpe gefüllt wird, wenn während eines Arbeitszyklus der erforderliche Volumenstrom zum Ausfahren des Hydrozylinders kleiner als der maximale Pumpenvolumenstrom ist. Wird in einem Betriebszustand der maximale Volumenstrom zum schnellen Ausfahren des Hydrozylinders benötigt, so kann die Differenz zum Volumenstrom der Pumpe aus dem Hydrospeicher entnommen werden. Der Einsatz dieser Hydrospeicher erlaubt somit eine Verringerung der maximalen Pumpenleistung. Beim Einfahren des Hydrozylinders wird das dabei verdrängte Hydraulikfluid wieder zurück in den Tank geführt, wobei es aufgrund der Drosselung des rückströmenden Hydraulikfluids zu Erwärmungen kommt. Die in dem rückströmenden Hydraulikfluid gespeicherte Energie geht praktisch ungenutzt verloren. Da man bei modernen Hydraulikanlagen stets bemüht ist, den Energieaufwand weitestgehend zu minimieren, wurden Lösungen vorgeschlagen, bei denen die Hydraulikpumpe derart ausgelegt ist, daß sie beim Einfahren des Hydrozylinders als Motor wirkt, der durch das rückströmende Hydraulikfluid angetrieben wird. Über diesen Hydromotor kann beispielsweise ein Generator angetrieben werden, so daß ein Teil der im rückströmenden Hydraulikfluid gespeicherten Energie in mechanische oder elektrische Energie umgewandelt wird. Des weiteren wird einer unerwünschten Erwärmung des Hydraulikfluids vorgebeugt, da dieses nicht gedrosselt werden muß.The maximum travel speed of the piston of the The hydraulic cylinder is of the maximum flow rate Depending on the hydraulic pump. In the event that quick Adjusting movements of the hydraulic cylinder are required a high pump output can be made available. In order to keep the pump output low, the A hydraulic accumulator is provided by the pressure line Pump is filled when the required volume flow to extend the Hydraulic cylinders smaller than the maximum pump volume flow is. Is in an operating state maximum volume flow for rapid extension of the Hydraulic cylinders required, so the difference to Volume flow of the pump taken from the hydraulic accumulator become. The use of this hydraulic accumulator thus allows a reduction in the maximum pump output. When entering that of the hydraulic cylinder is displaced Hydraulic fluid fed back into the tank, whereby it due to the throttling of the backflow Hydraulic fluid comes to warming. The one in the backflow Hydraulic fluid stored energy is practical lost unused. Because with modern hydraulic systems always endeavors to save energy Solutions were to minimize as much as possible proposed in which the hydraulic pump such is designed so that when you retract the hydraulic cylinder acts as a motor by the backflow Hydraulic fluid is driven. About this hydraulic motor For example, a generator can be driven that part of the stored in the backflow hydraulic fluid Energy in mechanical or electrical Energy is converted. Furthermore, one becomes undesirable Prevention of heating of the hydraulic fluid because this does not have to be throttled.

Aufgrund der besonderen Ausgestaltung der Hydraulikpumpe erfordert diese Lösung jedoch einen erheblichen vorrichtungstechnischen Aufwand und somit erhöhte Investitionskosten. Due to the special design of the hydraulic pump However, this solution requires a considerable device technology Effort and thus increased Investment costs.

Die Offenlegungsschrift DE 38 36 371 bezieht sich auf eine hydraulische Antriebsvorrichtung für einen Schlingenheber mit einer Tandem-Kolben-Zylinder-Einheit, bei der zwei Servoventile zwei unterschiedliche große Zylinderräume in einer solchen Weise steuern, daß eine konstante Kraft erhalten wird. The laid-open specification DE 38 36 371 relates to a hydraulic drive device for one Loop lifter with a tandem piston-cylinder unit, two different sizes for the two servo valves Control cylinder spaces in such a way that a constant force is obtained.

Demgegenüber liegt der Erfindung die Aufgabe zugrunde, ein Verfahren zur Ansteuerung eines Hydrozylinders und eine Hydroanlage eines Arbeitsgerätes zu schaffen, die bei minimalem vorrichtungstechnischem Aufwand einen Betrieb des Arbeitsgerätes mit minimiertem Energiebedarf erlauben.In contrast, the invention is based on the object a method for controlling a hydraulic cylinder and to create a hydraulic system of an implement that one with minimal expenditure on device technology Operation of the implement with minimized energy consumption allow.

Diese Aufgabe wird hinsichtlich des Verfahrens durch die Merkmale des Patentanspruchs 1 und hinsichtlich der Hydroanlage durch die Merkmale des Patentanspruchs 3 gelöst.This task is carried out with regard to the procedure by the Features of claim 1 and in terms of Hydraulic system by the features of claim 3 solved.

Durch die Maßnahme, einen Hydrozylinder mit einer Vielzahl von Wirkflächen zu versehen und diese Wirkflächen des Hydrozylinders in Abhängigkeit von einem erfassten Arbeitsdruck in der Druckleitung anzusteuern, läßt sich der Druck in der Druckleitung zum Hydraulikzylinder so einstellen, daß er etwa demjenigen des Hydrospeichers entspricht, so daß zumindest ein Teil des rückströmenden Hydraulikfluids beim Einfahren des Hydrozylinders zum Laden des Hydrospeichers verwendet werden kann. Durch diese erfindungsgemäße Maßnahme läßt sich der Energiebedarf der Hydroanlage gegenüber herkömmlichen Lösungen verringern, wobei lediglich ein minimaler vorrichtungstechnischer Aufwand erforderlich ist, da die Ansteuerung der Wegeventile über vergleichsweise kostengünstige hydraulische oder elektrische Steuergeräte erfolgen kann.By taking a hydraulic cylinder with a To provide a variety of active surfaces and these Active areas of the hydraulic cylinder depending on one to control the recorded working pressure in the pressure line, can the pressure in the pressure line to Adjust the hydraulic cylinder so that it is about one corresponds to the hydraulic accumulator, so that at least a part of the backflow hydraulic fluid when retracting the Hydraulic cylinders used to charge the hydraulic accumulator can be. By this measure according to the invention the energy requirements of the hydraulic system reduce conventional solutions, with only one minimal technical outlay required is because the control of the directional valves via comparatively inexpensive hydraulic or electrical control units can be done.

Eine optimale Energieersparnis erreicht man, wenn der Arbeitsdruck in der Druckleitung gemäß den Vorgaben des Unteranspruchs 2 gewählt wird.Optimal energy savings can be achieved if the working pressure in the pressure line in accordance with the requirements of the subclaim 2 is selected.

Besonders vorteilhaft ist es, wenn der Hydrozylinder drei Wirkflächen hat, von denen zwei Wirkflächen in Ausfahrrichtung und eine Wirkfläche in Einfahrrichtung des Hydrozylinders oder, genauer gesagt, des Kolbens des Hydrozylinders wirken, wobei jeder Wirkfläche ein elektrisch oder hydraulisch betätigbares 3/2-Wegeventil zugeordnet ist. Durch geeignete Ansteuerung der Wegeventile lassen sich die drei Wirkflächen beliebig kombinieren, so daß fünf Druckstufen einstellbar sind.It when the hydraulic cylinder three is particularly advantageous Has active surfaces, two of which are active surfaces in Extension direction and an effective area in the entry direction the hydraulic cylinder or, more precisely, the piston of the Hydraulic cylinders act, each effective area electrically or hydraulically operated 3/2-way valve assigned. By suitable control of the Directional valves can be used in any of the three effective areas combine so that five pressure levels can be set.

Dabei ist es besonders vorteilhaft, wenn die Wirkflächenverhältnisse gemäß den Vorgaben des Unteranspruchs 5 gewählt werden, so daß sich fünf gleichmäßig beabstandete Druckstufen einstellen lassen.It is particularly advantageous if the effective area ratios chosen according to the requirements of sub-claim 5 so that five are evenly spaced Have the pressure levels set.

Einen besonders einfachen und kompakten Aufbau des Hydrozylinders erhält man, wenn dieser mit einem tassenförmigen Differentialkolben ausgeführt ist, wobei die an der Kolbenrückseite ausgebildete Wirkfläche und die durch eine Sacklochbohrung des Differentialkolbens ausgebildete Wirkfläche in Ausfahrrichtung wirken, während die Ringfläche des Differentialkolbens in Einfahrrichtung wirkt.A particularly simple and compact structure of the Hydraulic cylinders can be obtained by using a cup-shaped differential piston is executed, wherein the effective area formed on the rear of the piston and through a blind hole in the differential piston trained effective area act in the direction of extension, while the ring surface of the differential piston in Entry direction works.

Vorteilhafterweise wird in der Druckleitung ein Drucksensor vorgesehen, der das Eingangssignal für das vorzugsweise elektrisch oder hydraulisch wirkende Steuergerät bildet.A is advantageously in the pressure line Pressure sensor provided that the input signal for the preferably electrically or hydraulically acting Control unit forms.

Weitere vorteilhafte Ausgestaltungen der Erfindung sind Gegenstand der sonstigen Unteransprüche.Further advantageous embodiments of the invention are Subject of the other subclaims.

Im folgenden wird ein bevorzugtes Ausführungsbeispiel der Erfindung anhand der Figur näher erläutert. Diese zeigt eine Schaltschema eines Zylinderantriebs für ein Hubwerk.In the following, a preferred embodiment of the Invention explained with reference to the figure. This shows a circuit diagram of a cylinder drive for a hoist.

Dabei kann es sich beispielsweise um das Hubwerk eines Gabelstaplers oder eines ähnlichen Arbeitsgerätes handeln. Das dargestellte Hubwerk hat einen Hubzylinder 1, dessen Kolben 2 mit einer Last F beaufschlagt ist, die durch Aus- oder Einfahren des Kolbens 2 bewegbar ist. Der Kolben 2 ist in Differentialbauweise ausgebildet und hat eine Sackloch-Innenbohrung 4, die in der Kolbenrückseite, im folgenden Kolbenfläche 6 genannt mündet.This can be, for example, a hoist Forklift or similar equipment act. The hoist shown has a lifting cylinder 1, the piston 2 is loaded with a load F, the is movable by extending or retracting the piston 2. The Piston 2 is designed and has a differential design a blind hole inner bore 4, which is in the piston rear, in the following called piston surface 6 opens.

Der Kolben 2 ist in einem Zylindermantel 8 geführt, der beim gezeigten Ausführungsbeispiel mit einer Mittelsäule 10 ausgebildet ist, die sich koaxial durch den Innenraum des Zylindermantels 8 erstreckt und die in die Innenbohrung 4 des Kolbens 2 eintaucht.The piston 2 is guided in a cylinder jacket 8, the in the embodiment shown with a center column 10 is formed, which is coaxial through the interior of the cylinder jacket 8 extends and into the Immersed inner bore 4 of the piston 2.

Wie aus der Figur hervorgeht, ist der vom Zylindermantel 8 umgebene Zylinderraum durch die Mittelsäule 10 als Ringraum ausgebildet, in dem der Kolben 2 geführt ist.As can be seen from the figure, this is from the cylinder jacket 8 surrounded cylinder space through the center column 10 as Annular space in which the piston 2 is guided.

Der radial erweiterte Bundabschnitt 12 des Kolbens 2 ist an den Innenflächen des Zylindermantels 8 geführt und über Dichtungen 14 abgedichtet. Der kolbenstangenseitige Teil 16 des Kolbens 2 hat gemäß der Figur einen tassenförmigen Querschnitt und durchsetzt mit seinen Mantelflächen eine ringförmige Durchgangsausnehmung 18, die in der kolbenstangenseitigen Stirnfläche des Zylindermantels 8 ausgebildet ist. In der Durchgangsausnehmung 18 sind wiederum Dichtungseinrichtungen 14 zur Abdichtung der Zylinderraumstirnfläche vorgesehen.The radially expanded collar section 12 of the piston 2 is guided on the inner surfaces of the cylinder jacket 8 and sealed by seals 14. The piston rod side Part 16 of the piston 2 has one according to the figure cup-shaped cross section and interspersed with its Lateral surfaces an annular passage recess 18, the in the piston rod end face of the Cylinder jacket 8 is formed. In the Through recess 18 are in turn sealing devices 14 for sealing the Cylinder chamber end face provided.

Durch die oben beschriebene Ausgestaltung des Kolbens 2 werden drei Zylinderräume 20, 22 und 24 gebildet. Der erste Zylinderraum 20 ist in Radialrichtung durch den Zylindermantel 8 und die Mittelsäule 10 und in Axialrichtung durch die untere Innenstirnfläche des Zylindermantels 8 und durch die Kolbenfläche 6 begrenzt. Der zweite Zylinderraum 22 ist durch den stirnseitigen Abschnitt der Innenbohrung 4 und die Stirnfläche der Mittelsäule 10 gebildet. Der dritte Zylinderraum 24 ist einerseits durch die Ringfläche 26 des Bundabschnitts 12 des Kolbens 2 und andererseits durch die Innenfläche der oberen (Darstellung gemäß Figur) Stirnfläche des Zylindermantels 8 und andererseits durch den Außenumfang des kolbenstangenseitigen, radial zurückgestuften Abschnitts 16 des Kolbens 2 und durch die Innenumfangsfläche des Zylindermantels 8 begrenzt. Die wirksamen Flächen der Zylinderräume sind somit durch die Fläche A1 der Kolbenfläche 6, die Fläche A2 der Ringfläche 26 und die Stirnfläche A3 der Innenbohrung 4 gebildet.Due to the design of the piston 2 described above three cylinder spaces 20, 22 and 24 are formed. The first cylinder chamber 20 is in the radial direction through the Cylinder jacket 8 and the center column 10 and in Axial direction through the lower inner face of the Cylinder jacket 8 and limited by the piston surface 6. The second cylinder chamber 22 is through the front Section of the inner bore 4 and the end face of the Center column 10 formed. The third cylinder space 24 is on the one hand through the annular surface 26 of the collar section 12 of the piston 2 and on the other hand through the inner surface of the upper (representation according to figure) face of the Cylinder jacket 8 and on the other hand through the outer circumference of the piston rod side, radially stepped down Section 16 of the piston 2 and through the Limited inner circumferential surface of the cylinder jacket 8. The effective areas of the cylinder rooms are thus through the Surface A1 of the piston surface 6, the surface A2 of the Annular surface 26 and the end face A3 of the inner bore 4th educated.

Am Zylindermantel 8 sind zwei Anschlüsse 28 und 30 ausgebildet, die in den Zylinderraum 20 bzw. 24 münden. Die Mittelsäule 10 des Zylindermantels 8 ist von einer axialen Anschlußbohrung 32 durchsetzt, die im zweiten Zylindrraum 22 mündet.Two connections 28 and 30 are formed on the cylinder jacket 8, which open into the cylinder space 20 or 24. The Center column 10 of the cylinder jacket 8 is one axial through hole 32 penetrates the second Cylinder chamber 22 opens.

Die Anschlüsse 28, 30 und die Anschlußbohrung 32 sind mit Arbeitsleitungen 34, 36, 38 verbunden, über die Hydraulikfluid den jeweiligen Zylinderräumen 20, 24 und 22 zuführbar ist. Die Arbeitsleitungen 34, 36, 38 sind zu drei im wesentlichen gleich aufgebauten 3/2-Wegeventilen 40a,b,c geführt, die über eine Feder in eine Grundstellung (nicht gezeigt) vorgespannt sind. In dieser Schaltstellung ist ein Arbeitsanschluß A mit einem Druckanschluß T jedes Wegeventils 40a,b,c verbunden.The connections 28, 30 and the connection bore 32 are with Working lines 34, 36, 38 connected via the Hydraulic fluid in the respective cylinder spaces 20, 24 and 22 can be fed. The working lines 34, 36, 38 are closed three 3/2-way valves of essentially the same design 40a, b, c performed by a spring in a Basic position (not shown) are biased. In this Switch position is a working connection A with a Pressure port T of each directional control valve 40a, b, c connected.

Die Druckanschlüsse P der drei Wegeventile 40a,b,c sind über Verbindungsleitungen zu einer gemeinsamen Druckleitung 42 geführt, die mit einem Anschluß D eines Proportionalventils 44 verbunden ist. In der gezeigten Endstellung des Proportionalventils 44 ist der Anschluß D mit einem Pumpenanschluß P' verbunden, während ein Tankanschluß T abgesperrt ist. In der anderen Endstellung des Proportionalventils 44 ist der Anschluß D mit einem Tank T verbunden. The pressure connections P of the three-way valves 40a, b, c are via connecting lines to a common pressure line 42 performed with a terminal D one Proportional valve 44 is connected. In the shown The end position of the proportional valve 44 is the connection D connected to a pump port P 'while a Tank connection T is blocked. In the other end position of the proportional valve 44 is the port D with a Tank T connected.

Zum Pumpenanschluß P' des Proportionalventils 44 ist eine Pumpenleitung 46 geführt, die mit einer Verstellpumpe 48 verbunden ist. Von der Pumpenleitung 46 zweigt eine Zweigleitung zu einem Hydrospeicher 50 ab, der beispielsweise als Blasenspeicher ausgebildet sein kann.For the pump connection P 'of the proportional valve 44 is one Pump line 46 guided with a variable displacement pump 48 connected is. One branches off from the pump line 46 Branch line to a hydraulic accumulator 50, for example can be designed as a bladder accumulator.

Beim gezeigten Ausführungsbeispiel sind die Wegeventile 40a,b,c als elektrisch betätigbare Magnetventile ausgebildet, so daß bei Erregung des jeweiligen Elektromagnets 41 das Wegeventil 40 aus der Grundstellung in die gezeigte Schaltstellung gebracht wird, in der der jeweilige Anschluß B mit einem Tankanschluß T verbunden ist.In the embodiment shown, the directional control valves are 40a, b, c as electrically operated solenoid valves trained so that when excited Electromagnet 41, the directional valve 40 from the basic position is brought into the switching position shown, in which the each port B connected to a tank port T. is.

Die Ansteuerung der Elektromagneten 41 der Wegeventile 40a,b,c erfolgt über ein Steuergerät 52, über das die Wegeventile 40a,b,c wahlweise ansteuerbar sind. Als Eingangssignal für das Steuergerät 52 wird beim gezeigten Ausführungsbeispiel das Signal eines Drucksensors 54 verwendet, der den Druck in der Druckleitung 42 erfasst und ein Signal an das Steuergerät 52 abgibt.The control of the electromagnets 41 of the directional control valves 40a, b, c takes place via a control unit 52, via which the Directional control valves 40a, b, c are selectively controllable. As Input signal for controller 52 is shown in the Embodiment the signal of a pressure sensor 54 used, which detects the pressure in the pressure line 42 and outputs a signal to the control unit 52.

Gemäß der vorliegenden Verschaltung läßt sich in der gezeigten Ausgangsposition (Elektromagnete 41 nicht erregt, Proportionalventil 44 verbindet P'-D) Hydraulikfluid von der Pumpe 48 oder aus dem Hydrospeicher 50 über das Proportionalventil 44 und die Wegeventile 40 in die Zylinderräume 20, 22 und 24 einleiten, so daß - bei geeignetem Systemdruck - aufgrund des auf die Flächen A1 und A3 wirkenden Kräfte die Last F gegen die auf die Ringfläche 26 (A2) wirkende Kraft nach oben verschiebbar ist.According to the present interconnection, Starting position (electromagnet 41 not excited, Proportional valve 44 connects P'-D) hydraulic fluid from the pump 48 or from the hydraulic accumulator 50 via the Proportional valve 44 and the directional control valves 40 in the Initiate cylinder spaces 20, 22 and 24, so that - at suitable system pressure - due to the A1 and A3 forces act against the load F against the Ring surface 26 (A2) acting force can be shifted upwards is.

Die Flächen der Wirkflächen A1, A2 und A3 sind beim gezeigten Ausführungsbeispiel so gewählt, daß: A1 = 4 x A3 A1 = 2 x A2 und somit A2 = 2 x A3. The areas of the active areas A1, A2 and A3 are chosen in the embodiment shown so that: A1 = 4 x A3 A1 = 2 x A2 and thus A2 = 2 x A3.

Durch entsprechende Ansteuerung der Wegeventile 40 lassen sich fünf Druckstufen einstellen. Bei dem in der Figur dargestellten Schaltzustand wird die der Last F entgegenwirkende Gesamtwirkfläche durch die Flächendifferenz A1 + A3 - A2 bestimmt. Die weiteren Schaltvarianten lassen sich der Tabelle 1 entnehmen, wobei mit dem Begriff "EIN" und "AUS" der Zustand gekennzeichnet ist, bei dem der jeweilige Elektromagnet erregt ist (EIN) (siehe Figur) oder abgeschaltet (AUS) ist. Schaltstellung Ventil 40a Ventil 40b Ventil 40c Wirksame Fläche AUS EIN AUS EIN AUS EIN 1 x x x A3 2 x x x A1-A2=2A3 3 x x x A1-A2+A3=3A3 4 x x x A1=4A3 5 x x x A1+A3=5A3 Appropriate control of the directional control valves 40 allows five pressure levels to be set. In the switching state shown in the figure, the total effective area counteracting the load F is determined by the area difference A1 + A3 - A2 certainly. The other switching variants can be found in Table 1, the terms "ON" and "OFF" denoting the state in which the respective electromagnet is energized (ON) (see figure) or switched off (OFF). Switch position Valve 40a Valve 40b Valve 40c Effective area OUT ON OUT ON OUT ON 1 x x x A3 2nd x x x A1-A2 = 2A3 3rd x x x A1-A2 + A3 = 3A3 4th x x x A1 = 4A3 5 x x x A1 + A3 = 5A3

Das heißt, durch entsprechende Ansteuerung der Wegeventile 40a, b, c lassen sich fünf Wirkflächen vorwählen, die das 1 bis 5-fache der kleinsten Fläche, d.h. der Stirnfläche A3 der Innenbohrung 4 betragen.That is, by appropriately controlling the Directional control valves 40a, b, c can be five effective areas preselect 1 to 5 times the smallest area, i.e. the end face A3 of the inner bore 4.

Die Ansteuerung der Wegeventile 40a, b, c erfolgt derart, daß sich ein Druck - wie im folgenden noch näher ausgeführt wird - in der Druckleitung 42 einstellt, der etwa gleich dem Systemdruck im Hydrospeicher 50 ist. Dazu wird im Steuergerät eine Sollwerttafel abgespeichert, gemäß der der Druck in der Druckleitung 42 beim Ausfahren des Kolbens 2 etwa um die Regeldruckdifferenz am Proportionalventil 44 geringer als der Druck im Hydrospeicher 50 und beim Einfahren des Kolbens 2 etwa um die Regeldruckdifferenz am Proportionalventil 44 größer als der Systemdruck im Hydrospeicher 50 ist. Durch diese Maßnahme ist gewährleistet, daß bei der Verdrängung von Hydraulikfluid aus den Zylinderräumen des Hubzylinders 1 dieses zurück in den Hydrospeicher 50 führbar ist und nicht "ungenutzt" in den Tank entspannt werden muß. Auf diese Weise läßt sich der Energieverbrauch der Anlage gegenüber herkömmlichen Lösungen ganz erheblich minimieren, wobei lediglich ein minimaler vorrichtungstechnische Aufwand erforderlich ist. The directional control valves 40a, b, c are activated in such a way that there is a pressure - as in the following is executed - sets in the pressure line 42, the is approximately equal to the system pressure in the hydraulic accumulator 50. To a setpoint table is saved in the control unit, according to which the pressure in the pressure line 42 when extending of the piston 2 about the control pressure difference on Proportional valve 44 less than the pressure in Hydraulic accumulator 50 and about when the piston 2 is retracted the control pressure difference at the proportional valve 44 is larger than the system pressure in the hydraulic accumulator 50. Through this Measure ensures that the displacement of Hydraulic fluid from the cylinder chambers of the lifting cylinder 1 this can be guided back into the hydraulic accumulator 50 and does not have to be "unused" into the tank. On in this way the energy consumption of the plant can be compared significantly reduce conventional solutions, with only a minimal expenditure on device technology is required.

Zum besseren Verständnis soll im folgenden kurz die Arbeitsweise der erfindungsgemäßen Vorrichtung erläutert werden.For a better understanding, the method of operation is briefly described below of the device according to the invention explained become.

Beim Anheben einer unbekannten Last F wird zunächst die Schaltstellung 5 vorgewählt, in der die maximale wirksame Fläche A1 + A3 voreingestellt ist, indem die Elektromagnete der Wegeventile 40a und 40b erregt werden und somit der dritte Zylinderraum 24 nicht mit Hydraulikfluid versorgt wird. Des weiteren wird das Proportionalventil 44 in eine Stellung gebracht, in der die Anschlüsse D und P' miteinander verbunden sind, so daß Hydraulikfluid von der Pumpe 48 oder aus dem Hydrospeicher 50 in die Zylinderräume 20 und 22 eingeführt wird, so daß der Druck in diesen Räumen ansteigt, bis die Last F angehoben wird. Unmittelbar nach dem Anheben der Last F wird der Druck in der Druckleitung 42 durch den Drucksensor 54 erfasst und als Eingangssignal an das Steuergerät 52 weitergeleitet. In diesem erfolgt ein Vergleich des Ist-Drucks in der Druckleitung 42 mit einem vorgegebenen Soll-Wert, der in Abhängigkeit vom voreingestellten Systemdruck (Speicherdruck) vorgegeben ist. In Abhängigkeit von dem Vergleichsergebnis werden dann die Wegeventile 40a,b,c derart angesteuert, daß sich in der Druckleitung 42 durch geeignete Wahl der Wirkflächen (A1 bis A3) ein Druckniveau einstellt, das etwa um die Regeldruckdifferenz niedriger ist, als der Systemdruck im Druckspeicher 50 (Anheben). Zum Absenken der Last F wird der Sollwert derart abgeändert, daß der sich einstellende Druck in der Druckleitung 42 um die Regeldruckdifferenz größer ist, als der Druck im Hydrospeicher 50.When lifting an unknown load F, the Switch position 5 selected in which the maximum effective Area A1 + A3 is preset by the Solenoids of the directional control valves 40a and 40b are excited and thus the third cylinder space 24 is not included Hydraulic fluid is supplied. Furthermore, it will Proportional valve 44 brought into a position in which the connections D and P 'are connected to each other, so that hydraulic fluid from the pump 48 or from the Hydraulic accumulator 50 inserted into the cylinder spaces 20 and 22 so that the pressure in these rooms increases until the load F is raised. Immediately after Raising the load F becomes the pressure in the pressure line 42 detected by the pressure sensor 54 and as an input signal forwarded to the control unit 52. This is done a comparison of the actual pressure in the pressure line 42 with a predetermined target value, which depends on preset system pressure (storage pressure) is. Depending on the comparison result then the directional control valves 40a, b, c are controlled in such a way that in the pressure line 42 by suitable choice of Effective areas (A1 to A3) sets a pressure level that is about the control pressure difference lower than that System pressure in the accumulator 50 (lifting). To lower the load F the setpoint is changed so that the resulting pressure in the pressure line 42 by the control pressure difference is greater than the pressure in the hydraulic accumulator 50.

Das erfindungsgemäße Steuergerät 52 erlaubt auch das Ausgleichen von kurzzeitigen Schwankungen in der Einfahr- und Ausfahrbewegung, wobei gemäß der voreingestellten Soll-Werttafel durch Umschalten der Wegeventile 40a, b, c auf eventuelle Druckschwankungen in der Druckleitung 42 und somit in den Zylinderräumen 20, 22 und 24 reagiert werden kann, ohne daß Hydraulikfluid in erheblichem Maße von der Pumpe 48 nachgefördert werden muß.The control device 52 according to the invention also allows compensation of short-term fluctuations in the entry and extension movement, according to the preset Target value table by switching the directional valves 40a, b, c to possible pressure fluctuations in the pressure line 42 and thus reacts in the cylinder rooms 20, 22 and 24 can be, without significant hydraulic fluid must be replenished by the pump 48.

Zum endgültigen Absenken des Kolbens 2 wird durch entsprechende Schaltung der Ventile 40a,b,c in der Leitung 42 ein Druck eingestellt, der um die Regeldruckdifferenz im Ventil 44 (PD - Pp,) höher ist als der Druck im Hydrospeicher 50. Durch Drosselung im Ventil 44 wird der Kolben 2 definiert abgesenkt, wobei Hydraulikmedium von D nach P' in den Speicher 50 fließt. Die Schaltstellung DT des Ventils 44 ist zur Entlastung der Zylinderräume 20, 22 und 24 nötig.For the final lowering of the piston 2, a corresponding switching of the valves 40a, b, c in the line 42 sets a pressure which is higher than the pressure in the hydraulic accumulator 50 by the control pressure difference in the valve 44 (P D - P p ,) Throttling in valve 44, piston 2 is lowered in a defined manner, hydraulic medium flowing from D to P ′ into accumulator 50. The switch position DT the valve 44 is necessary to relieve the cylinder spaces 20, 22 and 24.

Beim gezeigten Ausführungsbeispiel ist das Steuergerät als elektrisch wirkende Einrichtung ausgebildet, selbstverständlich kann das Steuergerät auch hydraulisch wirkend ausgeführt werden, wobei auch die Wegeventile 40 hydraulisch ansteuerbar ausgestaltet werden können. Des weiteren sind auch andere Ausgestaltungen des Hubzylinders 1 oder der gezeigten Ventile vorstellbar, ohne das erfindungsgemäße Grundprinzip zu verlassen.In the embodiment shown, the control device designed as an electrically acting device, the control unit can of course also be hydraulic are designed to act, whereby the directional control valves 40 can be designed hydraulically controllable. Of other configurations of the Lift cylinder 1 or the valves shown conceivable, without leaving the basic principle of the invention.

Claims (8)

  1. A method for controlling a multi-stage hydraulic cylinder (1) of a utility vehicle, which acts against a load, includes at least two effective areas (A1, A2, A3) which may optionally be connected, and is supplied with hydraulic fluid through a hydraulic pump (48), a hydraulic accumulator (50) and a control valve (44), characterised by the steps:
    detecting the operating pressure in a pressure line (42) leading to the hydraulic cylinder (1);
    controlling the effective areas (A1-A3) of the hydraulic cylinder (1) in dependence on the detected operating pressure such that the resulting operating pressure corresponds to a nominal value permitting to return the hydraulic fluid from the hydraulic cylinder (1) to the hydraulic accumulator (50).
  2. The method according to claim 1, wherein the hydraulic installation is a lifting gear of a utility vehicle, preferably of a forklift, characterised in that the nominal pressure upon advancing the hydraulic cylinder (1) approximately corresponds to the accumulator pressure minus the control pressure difference at the control valve (44), and upon retraction corresponds to approximately the accumulator pressure plus the control pressure difference at the control valve (44).
  3. A hydraulic installation of a utility vehicle, in particular for implementing a method according to one of claims 1 or 2, including a hydraulic cylinder (1) which may be supplied with hydraulic fluid for advancing, holding or retracting a piston (2) through a control valve (44) from a hydraulic accumulator (50) and/or a hydromotor (48), wherein the hydraulic cylinder (1) includes several effective areas (A1-A3) which may be optionally controlled in order to actuate the hydraulic cylinder (1),
    characterised in that to each effective area (A1-A3) there is associated a respective valve (40a,b,c), and that a control apparatus (52) is provided through which the valves (40a,b,c) may be controlled depending on the operating pressure in the pressure line (42) leading to the hydraulic cylinder (1), so that the resulting work pressure corresponds to a nominal value allowing to return the hydraulic fluid from the hydraulic cylinder (1) to the hydraulic accumulator (50).
  4. The hydraulic installation according to claim 3, characterised in that the hydraulic cylinder (1) includes three effective areas (A1-A3) of which a first and third effective areas (A1, A3) act in the advancing direction, and a second effective area (A2) acts in the direction of retraction, wherein to each cylinder cavity (20, 22, 24) constituting an effective area (A1-A3) a 3/2-distributing valve (40a,b,c) is associated through which the respective cylinder cavity (20, 22, 24) may optionally be connected to the pressure line (42) or to a tank (T).
  5. The hydraulic installation according to claim 4, characterised in that the area ratios of first, second and third effective areas (A1-A3) are selected as follows: A1 = 4 A3 A1 = 2 A2.
  6. The hydraulic installation according to one of claims 3 to 5, characterised in that the piston (4) of the hydraulic cylinder (1) is designed as a cup-shaped differential piston (2) and that the first effective area (A1) is formed by the piston rear side (6), the third effective area (A3) is formed by an inner front surface of a blind bore (4) of the differential piston (2), and the second effective area (A2) is formed by the annular surface (26) of the stage-shaped extension of the differential piston (2).
  7. The hydraulic installation according to one of claims 3 to 6, characterised in that a pressure sensor (54), the signal of which is used as an input signal for the control apparatus (52), is provided in the pressure line (42).
  8. The hydraulic installation according to one of claims 3 to 7, characterised in that the control apparatus (52) is formed to operate hydraulically or electrically.
EP96945157A 1995-11-24 1996-10-11 Process and device for driving the hydraulic system of a machine Expired - Lifetime EP0862697B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19543876 1995-11-24
DE19543876A DE19543876A1 (en) 1995-11-24 1995-11-24 Method and device for controlling a hydraulic system of an implement
PCT/DE1996/001934 WO1997020146A1 (en) 1995-11-24 1996-10-11 Process and device for driving the hydraulic system of a machine

Publications (2)

Publication Number Publication Date
EP0862697A1 EP0862697A1 (en) 1998-09-09
EP0862697B1 true EP0862697B1 (en) 2000-08-09

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP96945157A Expired - Lifetime EP0862697B1 (en) 1995-11-24 1996-10-11 Process and device for driving the hydraulic system of a machine

Country Status (4)

Country Link
US (1) US6145307A (en)
EP (1) EP0862697B1 (en)
DE (2) DE19543876A1 (en)
WO (1) WO1997020146A1 (en)

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DE102011108256A1 (en) * 2011-07-22 2013-01-24 Rheinisch-Westfälische Technische Hochschule Aachen Hydraulic drive apparatus for e.g. excavator, has control unit to control piston chambers of cylinder-piston units via control of switching valves based on measurement result of pressure sensors
CN108351045A (en) * 2015-09-10 2018-07-31 费斯托股份有限两合公司 Fluid system and process valve

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DE102010061840A1 (en) 2010-06-14 2011-12-15 Sms Siemag Ag Piston-cylinder unit as a switchable step cylinder
WO2011157462A1 (en) 2010-06-14 2011-12-22 Sms Siemag Ag Piston-cylinder unit in the form of a switchable stepped cylinder
DE102010061840B4 (en) 2010-06-14 2020-01-16 Sms Group Gmbh Piston-cylinder unit as a switchable step cylinder
DE102011108256A1 (en) * 2011-07-22 2013-01-24 Rheinisch-Westfälische Technische Hochschule Aachen Hydraulic drive apparatus for e.g. excavator, has control unit to control piston chambers of cylinder-piston units via control of switching valves based on measurement result of pressure sensors
CN108351045A (en) * 2015-09-10 2018-07-31 费斯托股份有限两合公司 Fluid system and process valve

Also Published As

Publication number Publication date
EP0862697A1 (en) 1998-09-09
DE59605729D1 (en) 2000-09-14
WO1997020146A1 (en) 1997-06-05
DE19543876A1 (en) 1997-05-28
US6145307A (en) 2000-11-14

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