EP1308415B1 - Hydraulic lifting device in particular for battery-powered industrial trucks and control method therefor - Google Patents

Hydraulic lifting device in particular for battery-powered industrial trucks and control method therefor Download PDF

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Publication number
EP1308415B1
EP1308415B1 EP20020024330 EP02024330A EP1308415B1 EP 1308415 B1 EP1308415 B1 EP 1308415B1 EP 20020024330 EP20020024330 EP 20020024330 EP 02024330 A EP02024330 A EP 02024330A EP 1308415 B1 EP1308415 B1 EP 1308415B1
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EP
European Patent Office
Prior art keywords
pump
pressure
hydraulic
lifting cylinder
line
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
EP20020024330
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German (de)
French (fr)
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EP1308415A2 (en
EP1308415A3 (en
Inventor
Octavian Mare
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Dambach Lagersysteme & Co KG GmbH
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Dambach Lagersysteme & Co KG GmbH
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Publication of EP1308415A3 publication Critical patent/EP1308415A3/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • 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
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/044—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out"
    • 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
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/14—Energy-recuperation means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20538—Type of pump constant capacity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. 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
    • F15B2211/30—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
    • F15B2211/3057—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 having two valves, one for each port of a double-acting output member
    • 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
    • F15B2211/40507—Flow control characterised by the type of flow control means or valve with constant 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
    • F15B2211/405—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
    • F15B2211/411—Flow control characterised by the positions of the valve element the positions being discrete
    • 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
    • F15B2211/46—Control of flow in the return line, i.e. meter-out 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
    • F15B2211/50—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
    • 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
    • F15B2211/50536—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using unloading valves controlling the supply pressure by diverting fluid 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
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5151—Pressure control characterised by the connections of the pressure 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
    • F15B2211/50—Pressure control
    • F15B2211/52—Pressure control characterised by the type of actuation
    • F15B2211/526—Pressure 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
    • F15B2211/50—Pressure control
    • F15B2211/52—Pressure control characterised by the type of actuation
    • F15B2211/528—Pressure 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
    • F15B2211/55—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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7052—Single-acting output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7114—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators
    • F15B2211/7128—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators the chambers being connected in parallel
    • 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
    • F15B2211/75—Control of speed of the output member

Definitions

  • the invention relates to a method for controlling a hydraulic lifting device, in particular for battery-powered trucks, which has a driven by an electric motor pump, by means of the at least one hydraulic lifting cylinder hydraulic oil is supplied from a reservoir via a feed line in the lifting operation, wherein the hydraulic oil in the load lowering operation of the lifting cylinder is fed back into the reservoir via a return flow line while flowing through the pump driving the electric motor acting as a generator.
  • the invention relates to a hydraulic lifting device, in particular for carrying out the method, with a drivable by an electric motor pump, by means of the at least one hydraulic lifting cylinder hydraulic oil can be supplied from a reservoir via a supply line in the lifting operation, the hydraulic oil in Lastsenk ceremoniess of the lifting cylinder via a Return flow under the flow of the working as a generator electric motor driving pump is fed back into the reservoir.
  • Such a hydraulic lifting device is often used in electrically driven industrial trucks or forklifts in which the operability or duration is substantially dependent on the capacity of the battery.
  • it is known to partially re-feed the potential energy in the system when the load is raised via an electric motor also operating as a generator into the battery.
  • a hydraulic lifting device with a corresponding energy recovery is shown, for example, in DE 199 21 629 A1, which has an electric motor which drives a pump which sucks hydraulic oil from a reservoir via a suction valve in the lifting operation and conveys it to the hydraulic lifting cylinder.
  • the hydraulic oil is directed by the hydraulic lifting cylinder through the pump operating in this state as a hydraulic motor, which drives a generator or the electric motor operating as a generator in this state, from which by means of a suitable, known per se electric circuit for energy recovery Battery is charged.
  • the speed of the electric motor for controlling the lifting or lowering speed of the hydraulic lifting cylinder is only used when the lifting cylinder is adjusted sufficiently quickly or recorded by a sensor device stroke speed a predetermined first limit or the lowering speed over a predetermined second limit.
  • the feed line has a branch line, via which hydraulic oil can be branched off from the feed line in the load lifting operation.
  • the branch line opens in the suction-side portion of the supply line downstream of the Nachsaugventils, so that the branched-off amount of hydraulic oil is supplied to the pump again.
  • the invention has for its object to provide a hydraulic lifting device of the type mentioned and a method for their control, in which or an excessive Wear of the pump and its internal leakage are largely avoided.
  • This object is achieved in terms of the method for controlling a hydraulic lifting device in that at the beginning of the load lowering operation located both in the upstream of the pump section of the return line and in the downstream of the pump section of the return line substantially prevailing in the lifting cylinder hydraulic pressure, wherein the pump is operated at an actual speed that is below a speed limit, and that a arranged in the return line downstream of the pump proportional pressure relief valve is only fully opened by a ramp function substantially when the actual speed of the pump above the Speed limit is, the electric motor then works as a generator.
  • the invention is based on the idea of minimizing the internal leakage of the pump by bringing the same hydraulic pressure into effect at both outlets of the pump, whereby the internal leakage is excluded even when the pump is at zero speed and consequently the internal leakage Cavitation wear is avoided.
  • the fine control or regulation of small lowering speeds of the load can be achieved by a corresponding low speed of the pump, which then works like a purely volumetric dosing. Since the pressure difference ⁇ p at the pump and its flow Q are minimal in this state, only a very low energy consumption arises.
  • the energy recovery operation is activated, in which the proportional pressure relief valve, which is arranged downstream of the pump in the return line, is fully open and the electric motor operates as a generator, which is driven by the working as a hydraulic motor pump.
  • the invention provides that the pressure in the return line at the beginning of Lastsenk memories means of a proportional pressure control valve, which is arranged upstream of the pump, via a ramp function on the pressure prevailing in the lifting cylinder hydraulic pressure is brought.
  • the pump is preferably never operated at a predetermined minimum speed during lifting operation.
  • the pump starts in the lifting operation via a pressure-free start. This is inventively achieved in that the pump at the beginning of lifting operation, the hydraulic oil as long as via a branch line returns to the reservoir, as the actual speed of the pump is below the speed limit, and that the branch line is closed by a valve, as soon as the actual speed of the pump is above the speed limit.
  • the speed limit value is preferably the predetermined minimum speed of the pump.
  • a hydraulic lifting device 10 shown schematically in FIG. 1 comprises a reservoir 11 for hydraulic oil, which is connected to two hydraulic lifting cylinders 12 via a feed line L1 consisting of several sections and subsequent connecting lines L4.1 and L4.2.
  • the indications "upstream” and “downstream” used refer to an oil flow from the reservoir 11 to the lifting cylinders 12, i. in the feeding direction for the lifting operation.
  • the supply line L1 is made up of a plurality of line sections.
  • a first section L1.1 leads from the reservoir 11 to a hydraulic pump P which is drivable by means of an electric motor M, in a manner not shown via a motor control unit draws energy from a battery.
  • a leakage line L7 (shown in dashed lines) can lead back into the storage container 11.
  • the first section L1.1 of the supply line L1 which represents the suction-side portion of the pump P, designed as a check valve Nachsaugventil NSV is arranged, which allows an oil flow in the feed direction, ie from the reservoir 11 to the pump P and prevents backflow.
  • a second section L1.2 of the supply line L1 connects, which leads to a first seat valve SV1, which is adjustable between an open position in which a flow in both directions is possible, and a blocking position in which an oil flow in the feeding direction, ie is suppressed to the lifting cylinders 12.
  • the first seat valve SV1 is biased by a spring into the blocking position, which it automatically assumes in the event of a power failure.
  • a first check valve RV1 is arranged, which only supplies an oil flow in the feed direction, i. to the lifting cylinders 12 permits and prevents backflow.
  • a pressure line L DA4 branches off between the pump P and the first seat valve SV1, which leads to a fourth pressure sensor DA4, by means of which the pressure prevailing in the second section L1.2 of the supply line L1 is detected can.
  • the first seat valve SV1 is adjoined by a third section L1.3 of the supply line L1, which branches off at its downstream end into the two connecting lines L4.1 and L4.2, which each lead to one of the hydraulic lifting cylinders 12. From the connecting line L4.2 another pressure line L DA1 branches off, which leads to a first pressure sensor DA1, by means of which the pressure prevailing in the connecting line L4.2 and thus the load pressure can be detected.
  • a return line L2 which also consists of several sections L2.1, L2.2 and L2.3.
  • a first section L2.1 of the return line L2 leads from the third section L1.3 of the supply line L1 to a second seat valve SV2, which is adjustable between an open position in which a flow in both directions is possible and a blocking position Oil flow is blocked in both directions.
  • the second seat valve SV2 is biased by a spring in the blocking position.
  • a second section L2.2 of the return line L2 extends from the second seat valve SV2 to a proportional pressure control valve PDRV. From the second section L2.2 of the return line L2 branches off upstream of the proportional pressure control valve PDRV another pressure line L DA3 , which leads to a third pressure transducer DA3, by means of which in the second section L2.2 of the return line L2 prevailing pressure can be detected. From the proportional pressure control valve PDRV, a bypass line L5 leads to the second section L1.2 of the supply line L1. The bypass line L5 opens into the second section L1.2 of the supply line L1 between the pressure line L DA4 and the first seat valve SV1.
  • a third section L2.3 of the return line L2 leads from the proportional pressure control valve PDRV to the suction-side first section L1.1 of the supply line L1 and flows thereinto between the suction valve NSV and the pump P.
  • the return line L2 into the first section L1.1 of the supply line L1 branches off from the third section L2.3 of the return line L2 another pressure line L DA2 , which leads to a second pressure sensor DA2, by means of which in the vicinity of the input of the pump P prevailing pressure can be detected.
  • a bypass line L3 Parallel to the first sections of the return line L2 runs a bypass line L3, which at its one end together with the first section L2.1 of the return line L2 in the third section L1.3 of the feed line L1 and with its other end in the third section L2. 3 of the return line L2 opens.
  • a third seat valve SV3 is arranged, which is adjustable between an open position in which a flow in both directions is possible, and a blocking position in which an oil flow in the return direction, i. from the third section L1.3 of the supply line L1 to the third section L2.3 of the return line L2 is prevented.
  • the third seat valve SV3 is biased by a spring in the blocking position.
  • a second check valve RV2 is arranged, which has a flow in the return direction, i. from the third section L1.3 of the supply line L1 to the third section L2.3 of the return line L2 permits and prevents flow in the opposite direction.
  • the hydraulic oil can from the lifting cylinders 12 via a designated in its entirety as a return flow path in the reservoir 11 flow back.
  • the return line comprises the connection lines L4.1 and L4.2, a part of the third section L1.3 of the supply line L1, the return line L2, the bypass line L3, parts of the first and second sections L1.1 and L1.2 of the supply line L1 including the flow through the pump P and the branch line L6.
  • the hydraulic oil In the lifting operation, i. for lifting the lifting cylinder 12, the hydraulic oil must be conveyed from the reservoir 11 through the supply line L1 into the corresponding chambers of the lifting cylinder 12.
  • the proportional pressure relief valve PDBV in the branch line L6 and the first seat valve SV1 in the supply line L1 are opened while the second seat valve SV2 and the third seat valve SV3 are closed.
  • the electric motor M is brought to a minimum speed with the pump P via an adjustable ramp function.
  • the hydraulic oil sucked by the pump P from the reservoir 11 through the sucking valve NSV and the first portion L1.1 of the supply line L1 and conveyed via the continuing second portion L1.2 occurs in this state, i. usually for a few fractions of a second, due to the fully open proportional pressure relief valve PDBV completely in the branch line L6 and is discharged without pressure into the reservoir 11.
  • the proportional pressure relief valve PDBV and the proportional pressure control valve PDRV are closed, whereby the pressure in the supply line L1 increases. If by means of the pressure transducer DA4 is detected that the pressure in the supply line L1 has reached the load floating pressure, which is detected by the pressure transducer DA1, the speed control of the pump P is released and the oil is supplied through the supply line L1 and the connecting lines L4.1 and L4.2 promoted to the lifting cylinders 12 so that they are raised. The speed thus determined, at which the speed control is released, is stored each time and allowed as minimum speed N min for braking the stroke.
  • the pump P continues to operate at a predetermined minimum speed N v (> N min ), the seat valve SV 2 of the return line L2 open and determines the lifting or lowering movement via the proportional pressure control valve PDRV. If the order is given to the proportional pressure control valve PDRV via the energization, to generate a greater pressure than the floating pressure, the load is raised.
  • the oil supply from the pump P to the lift cylinders 12 via the bypass line L5 and the proportional pressure control valve PDRV is opened and the discharge of the oil from the lift cylinder 12 in the third section L2.3 of the return line L2 and thus to the suction side of the pump P is closed at the proportional pressure control valve PDRV.
  • the load is held in position. Since one passes through the state of positional posture at the transition from lifting to lowering and vice versa, this movement can also be compared to a levitation method. It should be noted that the pressure relief or pressure control valves can not regulate any volume and the maximum lifting or lowering speed of the lifting cylinder 12 is limited solely by the pump speed.
  • the proportional pressure relief valve PDBV and the proportional pressure control valve PDRV are slightly adjusted below the load floating pressure detected by the pressure sensor DA1, ie p (DA4) ⁇ p (DA1) or p (DA3) ⁇ p (DA1).
  • the pressure set on the proportional pressure relief valve PDBV is slightly above the load floating pressure.
  • the electric motor M is kept regulated to zero speed and the seat valve SV2 is opened. Subsequently, the current supply of the proportional pressure control valve PDRV is reduced via an adjustable ramp.
  • the pressure at the proportional pressure relief valve PDBV is reduced to its minimum via an adjustable ramp function and the electric motor M starts operating in generator mode in which it is driven by the pump.
  • the braking or stopping the lowering movement takes place in accordance with the reverse order.
  • a pressure control via the pressure control valve PDRV can be used for the levitation method, a speed control using a fine proportional flow controller for small amounts of oil and high resolution in Differenz penflußclar.
  • the fine proportional flow regulator can open with its one connection between the second seat valve SV2 and the proportional pressure control valve PDRV in the second section L2.2 of the return line L2 and with the other terminal to the lying behind the second check valve RV2 and thus the pump P facing portion of the bypass line L3 be connected.
  • the lifting, lowering or floating of the load can be determined by the difference between the pump delivery Q P and the discharge amount Q of PSR over the fine proportional current regulator.
  • the load When the pump delivery amount Q P is greater than the discharge amount Q PSR of the fine proportional flow controller, the load is raised. When the pump delivery amount Q P is smaller than the discharge amount Q PSR of the fine proportional flow controller, the load is slowly lowered. If the two sets Q P and Q PSR are equal, the load is held in position.
  • the amount of oil can be regulated either via the fine proportional flow controller or vary accordingly over the pump speed.
  • the nozzle D1 In the load-lowering mode, the nozzle D1 allows the pressure build-up in the return line L2 at the start of the normal lowering movement.
  • the seat valve SV2 is energized and opened, so that in the return line L2 and also on the input side of the pump P, a pressure increase takes place.
  • the second pressure sensor DA2 detects the predetermined value of the pressure increase, the seat valve SV3 is opened and the speed control of the pump is released.
  • the further course of the lowering operation corresponds to that of the embodiment according to FIG.
  • the target position is approached in the so-called floating state.
  • the pump P is kept in operation at the minimum speed covering the leakage, wherein in the line section L1.2 downstream of the pump P, a pressure must be present, which is determined by the fourth pressure transducer DA4.
  • the first seat valve SV1 and the second seat valve SV2 remain energized open.
  • the volume flow controller SR1 is opened, so that hydraulic fluid over the first section L2.1 and the second section L2.2 of the return line L2 and the pressure line L DA3 , the connecting line L8 and the branch line L6 can flow back into the reservoir 11.
  • the volume flow controller SR1 is opened until the desired lowering speed is reached.
  • the difference dQ between the hydraulic oil amount delivered by the pump P and the amount of hydraulic oil discharged from the volumetric flow controller SR1 determines the direction of movement of the lift cylinders 12. If the difference dQ is positive (dQ> 0), ie, the pump P delivers more hydraulic oil than via the volumetric flow controller SR1 is discharged, the lifting cylinders 12 are raised. Accordingly, the lifting cylinders 12 are lowered when the difference amount is negative, that is, the pump P promotes less hydraulic oil than is discharged through the volumetric flow controller SR1.
  • the position of the lift cylinders is maintained.
  • the individual amounts of hydraulic oil and correspondingly said difference between the delivered and the discharged hydraulic oil quantity can be influenced by a change in the rotational speed of the pump and / or by the current supply and thus the degree of opening of the volumetric flow regulator SR1.
  • the third seat valve SV3 is closed and the pressure at the proportional pressure relief valve PDBV on the prevailing load pressure, which is detected by means of the first pressure transducer DA1, set. Subsequently, the first seat valve SV1 and the second seat valve SV2 opened and the speed of the pump P increased until the desired lifting speed of the lifting cylinder 12 is reached. From then on, the suspension process can be continued in the above-mentioned manner.

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Description

Die Erfindung betrifft ein Verfahren zur Steuerung einer hydraulischen Hubvorrichtung insbesondere für batteriegetriebene Flurförderzeuge, die eine von einem Elektromotor antreibbare Pumpe aufweist, mittels der im Lasthebebetrieb zumindest einem hydraulischen Hubzylinder Hydrauliköl aus einem Vorratsbehälter über eine Zuführleitung zugeführt wird, wobei das Hydrauliköl im Lastsenkbetrieb von dem Hubzylinder über eine Rückströmleitung unter Durchströmen der den als Generator arbeitenden Elektromotor antreibenden Pumpe in den Vorratsbehälter zurückgeführt wird. Darüber hinaus betrifft die Erfindung eine hydraulische Hubvorrichtung insbesondere zur Durchführung des Verfahrens, mit einer von einem Elektromotor antreibbaren Pumpe, mittels der im Lasthebebetrieb zumindest einem hydraulischen Hubzylinder Hydrauliköl aus einem Vorratsbehälter über eine Zuführleitung zuführbar ist, wobei das Hydrauliköl im Lastsenkbetriebs von dem Hubzylinder über eine Rückströmleitung unter Durchströmen der den als Generator arbeitenden Elektromotor antreibenden Pumpe in den Vorratsbehälter zurückführbar ist.The invention relates to a method for controlling a hydraulic lifting device, in particular for battery-powered trucks, which has a driven by an electric motor pump, by means of the at least one hydraulic lifting cylinder hydraulic oil is supplied from a reservoir via a feed line in the lifting operation, wherein the hydraulic oil in the load lowering operation of the lifting cylinder is fed back into the reservoir via a return flow line while flowing through the pump driving the electric motor acting as a generator. In addition, the invention relates to a hydraulic lifting device, in particular for carrying out the method, with a drivable by an electric motor pump, by means of the at least one hydraulic lifting cylinder hydraulic oil can be supplied from a reservoir via a supply line in the lifting operation, the hydraulic oil in Lastsenkbetriebs of the lifting cylinder via a Return flow under the flow of the working as a generator electric motor driving pump is fed back into the reservoir.

Eine derartige hydraulische Hubvorrichtung findet häufig bei elektrisch angetriebenen Flurförderzeugen oder Gabelstaplern Verwendung, bei denen die Betriebsfähigkeit bzw. -dauer im wesentlichen von der Kapazität der Batterie abhängig ist. Um die Betriebsdauer der Batterie bis zu ihrem nächsten notwendigen Aufladen zu verlängern, ist es bekannt, die bei angehobener Last im System befindliche potentielle Energie über einen auch als Generator arbeitenden Elektromotor in die Batterie teilweise wieder einzuspeisen. Eine hydraulische Hubvorrichtung mit einer entsprechenden Energierückspeisung ist beispielsweise in der DE 199 21 629 A1 gezeigt, die einen Elektromotor aufweist, der eine Pumpe treibt, die im Lasthebebetrieb Hydrauliköl aus einem Vorratsbehälter über ein Nachsaugventil ansaugt und zu dem hydraulischen Hubzylinder fördert. Im Lastsenkbetrieb wird das Hydrauliköl von dem hydraulischen Hubzylinder durch die in diesem Zustand als Hydromotor arbeitende Pumpe geleitet, die einen Generator oder den in diesem Zustand als Generator arbeitenden Elektromotor antreibt, von dem aus mittels einer geeigneten, an sich bekannten elektrischen Schaltung zur Energierückspeisung die zugehörige Batterie aufgeladen wird. Dabei wird die Drehzahl des Elektromotors zur Regelung der Hub- bzw. Senkgeschwindigkeit des hydraulischen Hubzylinders nur dann verwendet, wenn der Hubzylinder ausreichend schnell verstellt wird bzw. die mittels einer Sensorvorrichtung erfaßte Hubgeschwindigkeit einen vorbestimmten ersten Grenzwert bzw. die Senkgeschwindigkeit einen vorbestimmten zweiten Grenzwert überschreiben. Wenn der Hubzylinder mit einer relativ geringen Geschwindigkeit unterhalb der genannten Grenzwerte verstellt wird, wie es beispielsweise beim Anfahren aus der Ruhestellung infolge der Trägheit und auch bei einer gewählten Schleichgeschwindigkeit der Fall ist, wird die Geschwindigkeit des Hubzylinders nicht über die Drehzahl des Elektromotors und somit der Pumpe, sondern über den Volumen- bzw. Massenstrom des in der Zuführ- bzw. Rückführleitung strömenden Hydrauliköls verändert. Zu diesem Zweck weist die Zuführleitung eine Zweigleitung auf, über die im Lasthebebetrieb Hydrauliköl aus der Zuführleitung abzweigbar ist. Die Zweigleitung mündet in dem saugseitigen Abschnitt der Zuführleitung stromab des Nachsaugventils, so daß die abgezweigte Menge an Hydrauliköl der Pumpe wieder zugeführt wird.Such a hydraulic lifting device is often used in electrically driven industrial trucks or forklifts in which the operability or duration is substantially dependent on the capacity of the battery. In order to extend the operating life of the battery to its next necessary charging, it is known to partially re-feed the potential energy in the system when the load is raised via an electric motor also operating as a generator into the battery. A hydraulic lifting device with a corresponding energy recovery is shown, for example, in DE 199 21 629 A1, which has an electric motor which drives a pump which sucks hydraulic oil from a reservoir via a suction valve in the lifting operation and conveys it to the hydraulic lifting cylinder. In the load-lowering mode, the hydraulic oil is directed by the hydraulic lifting cylinder through the pump operating in this state as a hydraulic motor, which drives a generator or the electric motor operating as a generator in this state, from which by means of a suitable, known per se electric circuit for energy recovery Battery is charged. The speed of the electric motor for controlling the lifting or lowering speed of the hydraulic lifting cylinder is only used when the lifting cylinder is adjusted sufficiently quickly or recorded by a sensor device stroke speed a predetermined first limit or the lowering speed over a predetermined second limit. If the lifting cylinder is displaced at a relatively low speed below the specified limits, as is the case, for example, when starting from the rest position due to inertia and at a selected crawl speed, the speed of the lifting cylinder is not on the speed of the electric motor and thus the pump, but changed over the volume or mass flow of the hydraulic oil flowing in the supply and return line. For this purpose, the feed line has a branch line, via which hydraulic oil can be branched off from the feed line in the load lifting operation. The branch line opens in the suction-side portion of the supply line downstream of the Nachsaugventils, so that the branched-off amount of hydraulic oil is supplied to the pump again.

Um die Positionierzeiten einer hydraulischen Hubvorrichtung eines batteriegetriebenen Flurförderzeuges zu verkürzen bzw. die Reaktionszeiten innerhalb der Positionssuche zu verringern, ist es sinnvoll, die Pumpe beim Richtungswechsel der Lastbewegung laufen zu lassen und nicht wie üblich auszuschalten. Dabei stellt sich jedoch das Problem, daß die Pumpe bei relativ niedrigen Drehzahlen einem erhöhtem Kavitationsverschleiß unterliegt. Wenn die Pumpe eine Pumpe mit konstantem Verdrängungsvolumen, beispielsweise eine Flügelzellenpumpe, eine Spindelpumpe oder eine Innenzahnradpumpe ist, tritt das weitere Problem einer nicht zu vernachlässigenden inneren Leckage auf. Infolge der inneren Leckage ist eine sichere Lasthaltung bzw. eine geringe Senkgeschwindigkeit nicht zu erreichen. Wenn man darüber hinaus noch berücksichtigt, daß die Pumpe zur Vermeidung von übermäßigen Beschädigungen mit einer Mindestdrehzahl betrieben werden muß, führt dies zusammen mit der inneren Leckage zu einem undefinierten Absinken der Last. Die Betriebsbedingungen ändern sich desweiteren in Abhängigkeit von der Temperatur und dem sich im Laufe der Zeit einstellende Verschleiß der Pumpe.In order to shorten the positioning times of a hydraulic lifting device of a battery-powered industrial truck or to reduce the response times within the position search, it makes sense to run the pump when changing direction of the load movement and not turn off as usual. However, there is the problem that the pump is subject to increased cavitation wear at relatively low speeds. If the pump is a constant displacement pump, such as a vane pump, a spindle pump, or an internal gear pump, there is the further problem of not insignificant internal leakage. Due to the internal leakage a safe load holding or a low lowering speed can not be achieved. In addition, taking into account that the pump must be operated at a minimum speed to avoid excessive damage, this, together with the internal leakage leads to an undefined drop in the load. The operating conditions also change depending on the temperature and the over time adjusting wear of the pump.

Der Erfindung liegt die Aufgabe zugrunde, eine hydraulische Hubvorrichtung der genannten Art und ein Verfahren zu deren Steuerung zu schaffen, bei der bzw. dem ein übermäßiger Verschleiß der Pumpe und deren innere Leckage weitestgehend vermieden sind.The invention has for its object to provide a hydraulic lifting device of the type mentioned and a method for their control, in which or an excessive Wear of the pump and its internal leakage are largely avoided.

Diese Aufgabe wird hinsichtlich des Verfahrens zur Steuerung einer hydraulischen Hubvorrichtung dadurch gelöst, daß zu Beginn des Lastsenkbetriebes sowohl im stromauf der Pumpe gelegenen Abschnitt der Rückströmleitung als auch im stromab der Pumpe gelegenen Abschnitt der Rückströmleitung im wesentlichen der im Hubzylinder herrschende hydraulische Druck aufgebaut wird, wobei die Pumpe mit einer IST-Drehzahl betrieben wird, die unterhalb eines Drehzahl-Grenzwertes liegt, und daß ein in der Rückströmleitung stromab der Pumpe angeordnetes proportionales Druckbegrenzungsventil über eine Rampenfunktion erst dann im wesentlichen vollständig geöffnet wird, wenn die IST-Drehzahl der Pumpe oberhalb des Drehzahl-Grenzwertes liegt, wobei der Elektromotor dann als Generator arbeitet.This object is achieved in terms of the method for controlling a hydraulic lifting device in that at the beginning of the load lowering operation located both in the upstream of the pump section of the return line and in the downstream of the pump section of the return line substantially prevailing in the lifting cylinder hydraulic pressure, wherein the pump is operated at an actual speed that is below a speed limit, and that a arranged in the return line downstream of the pump proportional pressure relief valve is only fully opened by a ramp function substantially when the actual speed of the pump above the Speed limit is, the electric motor then works as a generator.

Die Erfindung geht von dem Grundgedanken aus, die innere Leckage der Pumpe zu minimieren, indem an beiden Ausgängen der Pumpe der gleiche hydraulische Druck zur Wirkung gebracht wird, wodurch auch bei Stillstand der Pumpe (Null-Drehzahl) die innere Leckage ausgeschlossen und dementsprechend der innere Kavitationsverschleiß vermieden ist. Die Feinsteuerung bzw. Regelung von kleinen Senkgeschwindigkeiten der Last kann dabei durch eine entsprechende geringe Drehzahl der Pumpe erreicht werden, die dann wie eine rein volumetrische Dosieranlage arbeitet. Da die Druckdifferenz Δp an der Pumpe und deren Durchfluß Q in diesem Zustand minimal sind, entsteht auch nur ein sehr geringer Energieverbrauch. Wenn die IST-Drehzahl der Pumpe beim Lastsenkbetrieb den Drehzahl-Grenzwert übersteigt, wird der Energie-Rückgewinnungsbetrieb aktiviert, bei dem das proportionale Druckbegrenzungsventil, das stromab der Pumpe in der Rückströmleitung angeordnet ist, vollständig geöffnet ist und der Elektromotor als Generator arbeitet, der von der als Hydromotor arbeitende Pumpe angetrieben wird.The invention is based on the idea of minimizing the internal leakage of the pump by bringing the same hydraulic pressure into effect at both outlets of the pump, whereby the internal leakage is excluded even when the pump is at zero speed and consequently the internal leakage Cavitation wear is avoided. The fine control or regulation of small lowering speeds of the load can be achieved by a corresponding low speed of the pump, which then works like a purely volumetric dosing. Since the pressure difference Δp at the pump and its flow Q are minimal in this state, only a very low energy consumption arises. When the actual speed of the pump in the load lowering operation exceeds the speed limit, the energy recovery operation is activated, in which the proportional pressure relief valve, which is arranged downstream of the pump in the return line, is fully open and the electric motor operates as a generator, which is driven by the working as a hydraulic motor pump.

Um beim Starten des Senkvorganges einen sanften Bewegungsanlauf zu erreichen, ist in Weiterbildung der Erfindung vorgesehen, daß der Druck in der Rückströmleitung zu Beginn des Lastsenkbetriebes mittels eines proportionalen Druckregelventils, das stromauf der Pumpe angeordnet ist, über eine Rampenfunktion auf den im Hubzylinder herrschenden hydraulischen Druck gebracht wird.In order to achieve a smooth motion start when starting the lowering process, the invention provides that the pressure in the return line at the beginning of Lastsenkbetriebes means of a proportional pressure control valve, which is arranged upstream of the pump, via a ramp function on the pressure prevailing in the lifting cylinder hydraulic pressure is brought.

Um einen übermäßigen Verschleiß der Pumpe zu verhindern, wird diese beim Lasthebebetrieb vorzugsweise nie unter einer vorgegebenen Mindestdrehzahl betrieben. Zusätzlich wird dafür gesorgt, daß die Pumpe im Lasthebebetrieb über einen drucklosen Anlauf startet. Dies wird erfindungsgemäß dadurch erreicht, daß die Pumpe zu Beginn des Lasthebebetriebs das Hydrauliköl solange über eine Zweigleitung drucklos in den Vorratsbehälter zurückleitet, wie die IST-Drehzahl der Pumpe unterhalb des Drehzahl-Grenzwertes liegt, und daß die Zweigleitung mittels eines Ventils geschlossen wird, sobald die IST-Drehzahl der Pumpe oberhalb des Drehzahl-Grenzwertes liegt. Bei dem Drehzahl-Grenzwert handelt es sich vorzugsweise um die vorgegebene Mindestdrehzahl der Pumpe.To prevent excessive wear of the pump, it is preferably never operated at a predetermined minimum speed during lifting operation. In addition, it is ensured that the pump starts in the lifting operation via a pressure-free start. This is inventively achieved in that the pump at the beginning of lifting operation, the hydraulic oil as long as via a branch line returns to the reservoir, as the actual speed of the pump is below the speed limit, and that the branch line is closed by a valve, as soon as the actual speed of the pump is above the speed limit. The speed limit value is preferably the predetermined minimum speed of the pump.

Hinsichtlich der hydraulischen Hubvorrichtung wird die oben genannte Aufgabe durch die Merkmale des Anspruchs 5 oder 6 gelöst.With regard to the hydraulic lifting device, the above-mentioned object is achieved by the features of claim 5 or 6.

Weitere Einzelheiten und Merkmale der Erfindung und insbesondere der hydraulischen Hubvorrichtung sind aus der folgenden Beschreibung eines Ausführungsbeispiels unter Bezugnahme auf die Zeichnung ersichtlich. Es zeigen:

Figur 1
ein schematisches Schaltbild einer erfindungsgemäßen hydraulischen Hubvorrichtung, und
Figur 2
eine Abwandlung des Schaltbildes gemäß Fig. 1.
Further details and features of the invention and in particular of the hydraulic lifting device can be seen from the following description of an embodiment with reference to the drawing. Show it:
FIG. 1
a schematic diagram of a hydraulic lifting device according to the invention, and
FIG. 2
a modification of the circuit diagram of FIG. 1.

Eine in der Figur 1 schematisch dargestellte hydraulische Hubvorrichtung 10 umfaßt einen Vorratsbehälter 11 für Hydrauliköl, der über eine aus mehreren Abschnitten bestehenden Zuführleitung L1 und nachfolgende Verbindungsleitungen L4.1 und L4.2 mit zwei hydraulischen Hubzylindern 12 verbunden ist. Die im folgenden verwendeten Angaben "stromauf" und "stromab" beziehen sich auf eine Ölströmung vom Vorratsbehälter 11 zu den Hubzylindern 12, d.h. in Zuführrichtung für den Lasthebebetrieb.A hydraulic lifting device 10 shown schematically in FIG. 1 comprises a reservoir 11 for hydraulic oil, which is connected to two hydraulic lifting cylinders 12 via a feed line L1 consisting of several sections and subsequent connecting lines L4.1 and L4.2. The indications "upstream" and "downstream" used refer to an oil flow from the reservoir 11 to the lifting cylinders 12, i. in the feeding direction for the lifting operation.

Die Zuführleitung L1 ist aus mehreren Leitungsabschnitten aufgebaut. Ein erster Abschnitt L1.1 führt vom Vorratsbehälter 11 zu einer Hydropumpe P, die mittels eines Elektromotors M antreibbar ist, der in nicht dargestellter Weise über eine Motor-Steuereinheit Energie von einer Batterie bezieht. Von der Pumpe P kann eine (gestrichelt dargestellte) Leckageleitung L7 zurück in den Vorratsbehälter 11 führen. In dem ersten Abschnitt L1.1 der Zuführleitung L1, der den saugseitigen Abschnitt der Pumpe P darstellt, ist ein als Rückschlagventil ausgebildetes Nachsaugventil NSV angeordnet, das eine Ölströmung in Zuführrichtung, d.h. aus dem Vorratsbehälter 11 zu der Pumpe P zuläßt und eine Rückströmung verhindert.The supply line L1 is made up of a plurality of line sections. A first section L1.1 leads from the reservoir 11 to a hydraulic pump P which is drivable by means of an electric motor M, in a manner not shown via a motor control unit draws energy from a battery. From the pump P, a leakage line L7 (shown in dashed lines) can lead back into the storage container 11. In the first section L1.1 of the supply line L1, which represents the suction-side portion of the pump P, designed as a check valve Nachsaugventil NSV is arranged, which allows an oil flow in the feed direction, ie from the reservoir 11 to the pump P and prevents backflow.

Stromab der Pumpe P schließt sich ein zweiter Abschnitt L1.2 der Zuführleitung L1 an, der zu einem ersten Sitzventil SV1 führt, das zwischen einer Offenstellung, in der eine Strömung in beide Richtungen möglich ist, und einer Sperrstellung verstellbar ist, in der eine Ölströmung in Zuführrichtung, d.h. zu den Hubzylindern 12 unterbunden ist. Das erste Sitzventil SV1 ist mittels einer Feder in die Sperrstellung vorgespannt, die es bei einem eventuellen Stromausfall selbsttätig einnimmt.Downstream of the pump P, a second section L1.2 of the supply line L1 connects, which leads to a first seat valve SV1, which is adjustable between an open position in which a flow in both directions is possible, and a blocking position in which an oil flow in the feeding direction, ie is suppressed to the lifting cylinders 12. The first seat valve SV1 is biased by a spring into the blocking position, which it automatically assumes in the event of a power failure.

Unmittelbar hinter dem ersten Sitzventil SV1 ist ein erstes Rückschlagventil RV1 angeordnet, das nur eine Ölströmung in Zuführrichtung, d.h. zu den Hubzylindern 12 zuläßt und eine Rückströmung verhindert.Immediately behind the first seat valve SV1, a first check valve RV1 is arranged, which only supplies an oil flow in the feed direction, i. to the lifting cylinders 12 permits and prevents backflow.

Von dem zweiten Abschnitt L1.2 der Zuführleitung L1 zweigt zwischen der Pumpe P und dem ersten Sitzventil SV1 eine Druckleitung LDA4 ab, die zu einem vierten Druckaufnehmer DA4 führt, mittels dessen der im zweiten Abschnitt L1.2 der Zuführleitung L1 herrschende Druck erfaßt werden kann.From the second section L1.2 of the supply line L1, a pressure line L DA4 branches off between the pump P and the first seat valve SV1, which leads to a fourth pressure sensor DA4, by means of which the pressure prevailing in the second section L1.2 of the supply line L1 is detected can.

Von dem zweiten Abschnitt L1.2 der Zuführleitung L1 zweigt zwischen der Pumpe P und der Druckleitung LDA4 eine Zweigleitung L6 ab, in der ein proportionales Druckbegrenzungsventil PDBV angeordnet ist und die in dem Vorratsbehälter 11 mündet.From the second section L1.2 of the supply line L1 branches off between the pump P and the pressure line L DA4 from a branch line L6, in which a proportional pressure relief valve PDBV is arranged and which opens into the reservoir 11.

An das erste Sitzventil SV1 schließt sich ein dritter Abschnitt L1.3 der Zuführleitung L1 an, der sich an seinem stromab gelegenen Ende in die zwei Verbindungsleitungen L4.1 und L4.2 verzweigt, die jeweils zu einem der hydraulischen Hubzylinder 12 führen. Von der Verbindungsleitung L4.2 zweigt eine weitere Druckleitung LDA1 ab, die zu einem ersten Druckaufnehmer DA1 führt, mittels dessen der in der Verbindungsleitung L4.2 herrschende Druck und somit der Lastdruck erfaßt werden kann.The first seat valve SV1 is adjoined by a third section L1.3 of the supply line L1, which branches off at its downstream end into the two connecting lines L4.1 and L4.2, which each lead to one of the hydraulic lifting cylinders 12. From the connecting line L4.2 another pressure line L DA1 branches off, which leads to a first pressure sensor DA1, by means of which the pressure prevailing in the connecting line L4.2 and thus the load pressure can be detected.

Im dritten Abschnitt L1.3 der Zuführleitung L1 zweigt eine Rückführleitung L2 ab, die ebenfalls aus mehreren Abschnitte L2.1, L2.2 und L2.3 besteht. Ein erster Abschnitt L2.1 der Rückführleitung L2 führt von dem dritten Abschnitt L1.3 der Zuführleitung L1 zu einem zweiten Sitzventil SV2, das zwischen einer Offenstellung, in der eine Strömung in beide Richtungen möglich ist, und einer Sperrstellung verstellbar ist, in der eine Ölströmung in beide Richtungen gesperrt ist. Das zweite Sitzventil SV2 ist mittels einer Feder in die Sperrstellung vorgespannt.In the third section L1.3 of the supply line L1 branches off a return line L2, which also consists of several sections L2.1, L2.2 and L2.3. A first section L2.1 of the return line L2 leads from the third section L1.3 of the supply line L1 to a second seat valve SV2, which is adjustable between an open position in which a flow in both directions is possible and a blocking position Oil flow is blocked in both directions. The second seat valve SV2 is biased by a spring in the blocking position.

Ein zweiter Abschnitt L2.2 der Rückführleitung L2 verläuft von dem zweiten Sitzventil SV2 zu einem proportionalen Druckregelventil PDRV. Von dem zweiten Abschnitt L2.2 der Rückführleitung L2 zweigt stromauf des proportionalen Druckregelventils PDRV eine weitere Druckleitung LDA3 ab, die zu einem dritten Druckaufnehmer DA3 führt, mittels dessen der im zweiten Abschnitt L2.2 der Rückführleitung L2 herrschende Druck erfaßt werden kann. Von dem proportionalen Druckregelventil PDRV führt eine Überbrückungsleitung L5 zu dem zweiten Abschnitt L1.2 der Zuführleitung L1. Die Überbrückungsleitung L5 mündet in den zweiten Abschnitt L1.2 der Zuführleitung L1 zwischen der Druckleitung LDA4 und dem ersten Sitzventil SV1. Darüber hinaus führt ein dritter Abschnitt L2.3 der Rückführleitung L2 von den proportionalen Druckregelventil PDRV zu dem saugseitigen ersten Abschnitt L1.1 der Zuführleitung L1 und mündet in diese zwischen dem Nachsaugventil NSV und der Pumpe P. Nahe der Mündung des dritten Abschnittes L2.3 der Rückführleitung L2 in den ersten Abschnitt L1.1 der Zuführleitung L1 zweigt von dem dritten Abschnitt L2.3 der Rückführleitung L2 eine weitere Druckleitung LDA2 ab, die zu einem zweiten Druckaufnehmer DA2 führt, mittels dessen der in der Nähe des Eingangs der Pumpe P herrschende Druck erfaßt werden kann.A second section L2.2 of the return line L2 extends from the second seat valve SV2 to a proportional pressure control valve PDRV. From the second section L2.2 of the return line L2 branches off upstream of the proportional pressure control valve PDRV another pressure line L DA3 , which leads to a third pressure transducer DA3, by means of which in the second section L2.2 of the return line L2 prevailing pressure can be detected. From the proportional pressure control valve PDRV, a bypass line L5 leads to the second section L1.2 of the supply line L1. The bypass line L5 opens into the second section L1.2 of the supply line L1 between the pressure line L DA4 and the first seat valve SV1. In addition, a third section L2.3 of the return line L2 leads from the proportional pressure control valve PDRV to the suction-side first section L1.1 of the supply line L1 and flows thereinto between the suction valve NSV and the pump P. Near the mouth of the third section L2.3 the return line L2 into the first section L1.1 of the supply line L1 branches off from the third section L2.3 of the return line L2 another pressure line L DA2 , which leads to a second pressure sensor DA2, by means of which in the vicinity of the input of the pump P prevailing pressure can be detected.

Parallel zu den ersten Abschnitten der Rückführleitung L2 verläuft eine Umgehungsleitung L3, die an ihrem einen Ende zusammen mit dem ersten Abschnitt L2.1 der Rückführleitung L2 in dem dritten Abschnitt L1.3 der Zuführleitung L1 und mit ihren anderen Ende in dem dritten Abschnitt L2.3 der Rückführleitung L2 mündet. In der Umgehungsleitung L3 ist ein drittes Sitzventil SV3 angeordnet, das zwischen einer Offenstellung, in der eine Strömung in beide Richtungen möglich ist, und einer Sperrstellung verstellbar ist, in der eine Ölströmung in Rückführrichtung, d.h. von dem dritten Abschnitt L1.3 der Zuführleitung L1 zu dem dritten Abschnitt L2.3 der Rückführleitung L2 unterbunden ist. Das dritte Sitzventil SV3 ist mittels einer Feder in die Sperrstellung vorgespannt. Unmittelbar hinter dem dritten Sitzventil SV3 ist ein zweites Rückschlagventil RV2 angeordnet, das eine Strömung in Rückführrichtung, d.h. von dem dritten Abschnitt L1.3 der Zuführleitung L1 zu dem dritten Abschnitt L2.3 der Rückführleitung L2 zuläßt und eine Strömung in Gegenrichtung verhindert.Parallel to the first sections of the return line L2 runs a bypass line L3, which at its one end together with the first section L2.1 of the return line L2 in the third section L1.3 of the feed line L1 and with its other end in the third section L2. 3 of the return line L2 opens. In the bypass line L3, a third seat valve SV3 is arranged, which is adjustable between an open position in which a flow in both directions is possible, and a blocking position in which an oil flow in the return direction, i. from the third section L1.3 of the supply line L1 to the third section L2.3 of the return line L2 is prevented. The third seat valve SV3 is biased by a spring in the blocking position. Immediately behind the third seat valve SV3, a second check valve RV2 is arranged, which has a flow in the return direction, i. from the third section L1.3 of the supply line L1 to the third section L2.3 of the return line L2 permits and prevents flow in the opposite direction.

Das Hydrauliköl kann aus den Hubzylindern 12 über einen in seiner Gesamtheit als Rückströmleitung bezeichneten Weg in den Vorratsbehälter 11 zurückströmen. Die Rückströmleitung umfaßt die Verbindungsleitungen L4.1 und L4.2, einen Teil des dritten Abschnitts L1.3 der Zuführleitung L1, die Rückführleitung L2, die Umgehungsleitung L3, Teile des ersten und des zweiten Abschnitts L1.1 und L1.2 der Zuführleitung L1 einschließlich des Durchströmens der Pumpe P sowie die Zweigleitung L6.The hydraulic oil can from the lifting cylinders 12 via a designated in its entirety as a return flow path in the reservoir 11 flow back. The return line comprises the connection lines L4.1 and L4.2, a part of the third section L1.3 of the supply line L1, the return line L2, the bypass line L3, parts of the first and second sections L1.1 and L1.2 of the supply line L1 including the flow through the pump P and the branch line L6.

Im folgenden werden die unterschiedlichen Betriebsweisen der hydraulischen Hubvorrichtung 10 im einzelnen erläutert.In the following, the different modes of operation of the hydraulic lifting device 10 will be explained in detail.

Im Lasthebebetrieb, d.h. zum Anheben der Hubzylinder 12, muß das Hydrauliköl aus dem Vorratsbehälter 11 durch die Zuführleitung L1 in die entsprechenden Kammern der Hubzylinder 12 gefördert werden. Ausgehend von einem Stillstand der Hubzylinder 12 werden das proportionale Druckbegrenzungsventil PDBV in der Zweigleitung L6 und das erste Sitzventil SV1 in der Zuführleitung L1 geöffnet, während das zweite Sitzventil SV2 und das dritte Sitzventil SV3 geschlossen sind. Der Elektromotor M wird mit der Pumpe P über eine einstellbare Rampenfunktion auf eine Mindestdrehzahl gebracht. Das von der Pumpe P aus dem Vorratsbehälter 11 durch das Nachsaugventil NSV und dem ersten Abschnitt L1.1 der Zuführleitung L1 angesaugte und über den weiterführenden zweiten Abschnitt L1.2 geförderte Hydrauliköl tritt in diesem Zustand, d.h. in der Regel für einige Sekundenbruchteile, aufgrund des vollständig geöffneten proportionalen Druckbegrenzungsventils PDBV vollständig in die Zweigleitung L6 ein und wird drucklos in den Vorratsbehälter 11 abgeleitet.In the lifting operation, i. for lifting the lifting cylinder 12, the hydraulic oil must be conveyed from the reservoir 11 through the supply line L1 into the corresponding chambers of the lifting cylinder 12. Starting from a standstill of the lifting cylinder 12, the proportional pressure relief valve PDBV in the branch line L6 and the first seat valve SV1 in the supply line L1 are opened while the second seat valve SV2 and the third seat valve SV3 are closed. The electric motor M is brought to a minimum speed with the pump P via an adjustable ramp function. The hydraulic oil sucked by the pump P from the reservoir 11 through the sucking valve NSV and the first portion L1.1 of the supply line L1 and conveyed via the continuing second portion L1.2, occurs in this state, i. usually for a few fractions of a second, due to the fully open proportional pressure relief valve PDBV completely in the branch line L6 and is discharged without pressure into the reservoir 11.

Gleich nach dem Start der Pumpe P werden das proportionale Druckbegrenzungsventil PDBV und das proportionale Druckregelventil PDRV geschlossen, wodurch der Druck in der Zuführleitung L1 ansteigt. Wenn mittels des Druckaufnehmers DA4 festgestellt wird, daß der Druck in der Zuführleitung L1 den Lastschwebedruck, der mittels des Druckaufnehmers DA1 festgestellt wird, erreicht hat, wird die Drehzahlregelung der Pumpe P freigegeben und das Öl wird durch die Zuführleitung L1 und die Verbindungsleitungen L4.1 und L4.2 zu den Hubzylindern 12 gefördert, so daß diese angehoben werden. Die auf diese Weise ermittelte Drehzahl, bei der die Drehzahlregelung freigegeben wird, wird jedes Mal gespeichert und als minimale Drehzahl Nmin beim Bremsen der Hubbewegung zugelassen.Immediately after the start of the pump P, the proportional pressure relief valve PDBV and the proportional pressure control valve PDRV are closed, whereby the pressure in the supply line L1 increases. If by means of the pressure transducer DA4 is detected that the pressure in the supply line L1 has reached the load floating pressure, which is detected by the pressure transducer DA1, the speed control of the pump P is released and the oil is supplied through the supply line L1 and the connecting lines L4.1 and L4.2 promoted to the lifting cylinders 12 so that they are raised. The speed thus determined, at which the speed control is released, is stored each time and allowed as minimum speed N min for braking the stroke.

Beim Bremsen der Hubbewegung werden die Schritte in umgekehrter Reihenfolge durchgeführt. Die Drehzahl der Pumpe P wird auf den konstanten, minimal zugelassenen Wert Nmin eingestellt, der die Bedingungen p(DA4) = p(DA1) sicherstellen muß, d.h. die Drehzahl muß mindestens so hoch sein, daß sie die Ölverluste abdecken und dabei den Schwebedruck noch erzeugen kann. Auf diese Weise wird sichergestellt, daß die Pumpe nicht in einem Drehzahlbereich betrieben wird, in dem die Schmierung der Pumpe nicht gesichert ist.When braking the lifting movement, the steps are carried out in reverse order. The speed of the pump P is set to the constant, minimum permitted value N min , which must ensure the conditions p (DA4) = p (DA1), ie the speed must be at least so high that they cover the oil losses and thereby the floating pressure can still generate. In this way it is ensured that the pump is not operated in a speed range in which the lubrication of the pump is not secured.

Falls im automatischen Betrieb der Hubvorrichtung die gewünschte Höhenposition verpaßt wurde oder falls ein Benutzer über eine Auswahltaste das sogenannte Schwebeverfahren (= langsame Verstellung) einleitet, wird die Pumpe P mit einer vorgegebenen Mindestdrehzahl Nv (>Nmin) weiterbetrieben, das Sitzventil SV2 der Rückführleitung L2 geöffnet und die Hub- bzw. Senkbewegung über das proportionale Druckregelventil PDRV bestimmt. Wird über die Bestromung dem proportionalen Druckregelventil PDRV der Befehl gegeben, einen größeren Druck als den Schwebedruck zu erzeugen, so wird die Last angehoben. Die Ölzufuhr von der Pumpe P zu den Hubzylindern 12 über die Überbrückungsleitung L5 und das proportionale Druckregelventil PDRV wird geöffnet und die Ableitung des Öls vom Hubzylinder 12 in den dritten Abschnitt L2.3 der Rückführleitung L2 und somit zur Saugseite der Pumpe P wird an dem proportionalen Druckregelventil PDRV geschlossen.If the desired height position has been missed during automatic operation of the lifting device or if a user initiates the so-called levitation method (= slow adjustment) via a selection key, the pump P continues to operate at a predetermined minimum speed N v (> N min ), the seat valve SV 2 of the return line L2 open and determines the lifting or lowering movement via the proportional pressure control valve PDRV. If the order is given to the proportional pressure control valve PDRV via the energization, to generate a greater pressure than the floating pressure, the load is raised. The oil supply from the pump P to the lift cylinders 12 via the bypass line L5 and the proportional pressure control valve PDRV is opened and the discharge of the oil from the lift cylinder 12 in the third section L2.3 of the return line L2 and thus to the suction side of the pump P is closed at the proportional pressure control valve PDRV.

Wenn dem proportionalen Druckregelventil PDRV der Befehl gegeben wird, einen niedrigeren Druck als den Lastschwebedruck zu erzeugen, wird trotz des anhaltenden Laufs der Pumpe P die Last langsam abgesenkt. Die Ölzufuhr von der Pumpe P zu den Hubzylindern 12 über die Überbrückungsleitung L5 und das proportionale Druckregelventil PDRV wird an diesem geschlossen und die Ableitung des Öls von den Hubzylindern 12 über die Rückführleitung L2 zur Saugseite der Pumpe P wird an dem proportionalen Druckregelventil PDRV geöffnet. Die übrige Ölmenge wird von der Pumpe P über die Zweigleitung L6 und das proportionale Druckbegrenzungsventil PDBV zum Vorratsbehälter 11 geleitet.When the proportional pressure control valve PDRV is commanded to produce a lower pressure than the load floating pressure, the load is slowly lowered despite the continued running of the pump P. The oil supply from the pump P to the lift cylinders 12 via the bypass line L5 and the proportional pressure control valve PDRV is closed thereto and the discharge of the oil from the lift cylinders 12 via the return line L2 to the suction side of the pump P is opened at the proportional pressure control valve PDRV. The remaining amount of oil is passed from the pump P via the branch line L6 and the proportional pressure relief valve PDBV to the reservoir 11.

Wenn der Druck an dem Druckaufnehmer DA3 und der Druck an dem Druckaufnehmer DA1 gleich ist, wird die Last auf Position gehalten. Da man beim Übergang vom Heben auf das Senken und auch umgekehrt den Zustand der Positionshaltung durchläuft, kann diese Bewegung auch mit einem Schwebeverfahren verglichen werden. Anzumerken ist, daß die Druckbegrenzungs- bzw. Druckregelventile an sich kein Volumen regeln können und die maximale Hub- bzw. Senkgeschwindigkeit der Hubzylinder 12 alleine durch die Pumpendrehzahl begrenzt ist.When the pressure at the pressure transducer DA3 and the pressure at the pressure transducer DA1 are equal, the load is held in position. Since one passes through the state of positional posture at the transition from lifting to lowering and vice versa, this movement can also be compared to a levitation method. It should be noted that the pressure relief or pressure control valves can not regulate any volume and the maximum lifting or lowering speed of the lifting cylinder 12 is limited solely by the pump speed.

Beim Lastsenkbetrieb, d.h. dem Absenken der Hubzylinder 12 muß das Hydrauliköl aus den Hubzylindern 12 in den Vorratsbehälter 11 zurückgefördert werden. Zu diesem Zweck werden das proportionale Druckbegrenzungsventil PDBV und das proportionale Druckregelventil PDRV leicht unter dem von dem Druckaufnehmer DA1 erfaßten Lastschwebedruck angeglichen, d.h. p(DA4) ≤ p(DA1) bzw. p(DA3) ≤ p(DA1). Alternativ ist es auch möglich, daß der am proportionalen Druckbegrenzungsventil PDBV eingestellte Druck leicht oberhalb des Lastschwebedrucks liegt. Der Elektromotor M wird auf Null-Drehzahl geregelt gehalten und das Sitzventil SV2 wird geöffnet. Anschließend wird über eine einstellbare Rampe die Bestromung des proportionalen Druckregelventils PDRV reduziert. Dadurch findet in der Rücklaufleitung L2 und auch auf der Eingangsseite der Pumpe P ein Druckanstieg statt, der durch den Druckaufnehmer DA2 erfaßt wird. Durch die Pumpe P hindurch findet ein Druckausgleich soweit statt, daß auch in der Zweigleitung L6 vor dem proportionalen Druckbegrenzungsventil PDBV der voreingestellte Druck herrscht. Sobald der Druckaufnehmer DA2 den vorprogrammierten Wert des Druckanstiegs festgestellt hat, wird die Drehzahlregelung der Pumpe freigeschaltet und das Sitzventil SV3 geöffnet. Da das Öl nur über das auf den Lastschwebedruck voreingestellte proportionale Druckbegrenzungsventil PDBV zum Vorratsbehälter 11 abfließen kann, herrscht an beiden Pumpenanschlüssen in etwa der gleiche Druck. Die Pumpe wird somit wie eine feine Dosiereinrichtung wirken, wobei die innere Leckage Null ist und kleine Senkgeschwindigkeiten der Hubzylinder nunmehr über eine relativ geringe Drehzahl geregelt werden können, da die Gefahr von Kavitationsverschleiß ausgeschlossen ist.When load-lowering operation, ie the lowering of the lifting cylinder 12, the hydraulic oil from the lifting cylinders 12 must be fed back into the reservoir 11. For this purpose, the proportional pressure relief valve PDBV and the proportional pressure control valve PDRV are slightly adjusted below the load floating pressure detected by the pressure sensor DA1, ie p (DA4) ≤p (DA1) or p (DA3) ≤p (DA1). Alternatively, it is also possible that the pressure set on the proportional pressure relief valve PDBV is slightly above the load floating pressure. The electric motor M is kept regulated to zero speed and the seat valve SV2 is opened. Subsequently, the current supply of the proportional pressure control valve PDRV is reduced via an adjustable ramp. Thereby takes place in the return line L2 and also on the input side of the pump P, a pressure increase, which is detected by the pressure sensor DA2. Through the pump P through a pressure equalization takes place so far that prevails in the branch line L6 before the proportional pressure relief valve PDBV the preset pressure. As soon as the pressure transducer DA2 has detected the pre-programmed value of the pressure increase, the pump's speed control is enabled and the seat valve SV3 is opened. Since the oil can only flow to the storage container 11 via the proportional pressure limiting valve PDBV preset on the load floating pressure, the pressure at both pump connections is approximately the same. The pump will thus act as a fine metering device, the inner leakage is zero and small lowering speeds of the lifting cylinder can now be controlled over a relatively low speed, since the risk of cavitation wear is excluded.

Sobald die Pumpe die vorgegebene Mindestdrehzahl erreicht hat, wird der Druck an dem proportionalen Druckbegrenzungsventil PDBV über eine einstellbare Rampenfunktion bis auf sein Minimum reduziert und der Elektromotor M fängt an im Generator-Betrieb zu arbeiten, in dem er durch die Pumpe angetrieben wird.As soon as the pump has reached the predetermined minimum speed, the pressure at the proportional pressure relief valve PDBV is reduced to its minimum via an adjustable ramp function and the electric motor M starts operating in generator mode in which it is driven by the pump.

Das Bremsen bzw. das Stoppen der Absenkbewegung findet in entsprechend umgekehrter Reihenfolge statt.The braking or stopping the lowering movement takes place in accordance with the reverse order.

Statt einer Druckregelung über das Druckregelventil PDRV kann für das Schwebeverfahren auch eine Geschwindigkeitsregelung mit Hilfe eines Feinproportionalstromreglers für kleine Ölmengen und große Auflösung in Differenzdurchflußverfahren eingesetzt werden. Der Feinproportionalstromregler kann mit seinem einen Anschluß zwischen dem zweiten Sitzventil SV2 und dem proportionalen Druckregelventil PDRV in dem zweiten Abschnitt L2.2 der Rückführleitung L2 münden und mit dem anderen Anschluß an den hinter dem zweiten Rückschlagventil RV2 liegenden und somit der Pumpe P zugewandten Abschnitt der Umgehungsleitung L3 angeschlossen sein. Das Heben, Senken bzw. Schweben der Last kann über die Differenz zwischen der Pumpenfördermenge QP und der Abflußmenge QPSR über den Feinproportionalstromregler bestimmt werden. Wenn die Pumpenfördermenge QP größer als die Abflußmenge QPSR des Feinproportionalstromreglers ist, wird die Last angehoben. Wenn die Pumpenfördermenge QP kleiner als die Abflußmenge QPSR des Feinproportionalstromreglers ist, wird die Last langsam abgesenkt. Wenn die beiden Mengen QP und QPSR gleich sind, wird die Last auf Position gehalten. Die Ölmenge läßt sich entweder über den Feinproportionalstromregler regeln oder über die Pumpendrehzahl entsprechend variieren.Instead of a pressure control via the pressure control valve PDRV can be used for the levitation method, a speed control using a fine proportional flow controller for small amounts of oil and high resolution in Differenzdurchflußverfahren. The fine proportional flow regulator can open with its one connection between the second seat valve SV2 and the proportional pressure control valve PDRV in the second section L2.2 of the return line L2 and with the other terminal to the lying behind the second check valve RV2 and thus the pump P facing portion of the bypass line L3 be connected. The lifting, lowering or floating of the load can be determined by the difference between the pump delivery Q P and the discharge amount Q of PSR over the fine proportional current regulator. When the pump delivery amount Q P is greater than the discharge amount Q PSR of the fine proportional flow controller, the load is raised. When the pump delivery amount Q P is smaller than the discharge amount Q PSR of the fine proportional flow controller, the load is slowly lowered. If the two sets Q P and Q PSR are equal, the load is held in position. The amount of oil can be regulated either via the fine proportional flow controller or vary accordingly over the pump speed.

Figur 2 zeigt eine Abwandlung der hydraulischen Anordnung gemäß Figur 1 und unterscheidet sich von dieser in folgenden Punkten:

  • Die Überbrückungsleitung L5 ist entfallen,
  • statt des proportionalen Druckregelventils PDRV, das ebenfalls entfallen ist, ist eine Düse D1 in dem zweiten Abschnitt L2.2 der Rückführleitung L2 angeordnet. Von dem zweiten Abschnitt L2.2. der Rückführleitung L2 zweigt weiterhin stromauf der Düse D1 die Druckleitung LDA3 ab, die zum dem dritten Druckaufnehmer DA3 führt.
  • Von der zu dem dritten Druckaufnehmer DA3 führenden Druckleitung LDA3 zweigt eine Verbindungsleitung L8 ab, die stromab des proportionalen Druckbegrenzungsventils PDBV in die Zweileitung L6 mündet, die zum Vorratsbehälter 11 führt.
  • In der Verbindungsleitung L8 ist ein Volumenstromregler SR1 angeordnet.
Figure 2 shows a modification of the hydraulic arrangement according to Figure 1 and differs from this in the following points:
  • The bridging line L5 is omitted,
  • instead of the proportional pressure control valve PDRV, which is also omitted, a nozzle D1 in the second Section L2.2 of the return line L2 arranged. From the second section L2.2. the return line L2 further branches upstream of the nozzle D1, the pressure line L DA3 , which leads to the third pressure transducer DA3.
  • From the leading to the third pressure transducer DA3 pressure line L DA3 branches off a connecting line L8, which opens downstream of the proportional pressure relief valve PDBV in the two-line L6, which leads to the reservoir 11.
  • In the connecting line L8, a volumetric flow controller SR1 is arranged.

Im Lastsenkbetrieb erlaubt die Düse D1 den Druckaufbau in der Rücklaufleitung L2 beim Start der normalen Senkbewegung. Das Sitzventil SV2 wird bestromt und geöffnet, so daß in der Rücklaufleitung L2 und auch auf der Eingangsseite der Pumpe P ein Druckanstieg stattfindet. Sobald der zweite Druckaufnehmer DA2 den vorgegebenen Wert des Druckanstieges feststellt, wird das Sitzventil SV3 geöffnet und die Drehzahlregelung der Pumpe freigegeben. Der weitere Ablauf des Senkbetriebes entspricht dem der Ausführung gemäß Figur 1.In the load-lowering mode, the nozzle D1 allows the pressure build-up in the return line L2 at the start of the normal lowering movement. The seat valve SV2 is energized and opened, so that in the return line L2 and also on the input side of the pump P, a pressure increase takes place. As soon as the second pressure sensor DA2 detects the predetermined value of the pressure increase, the seat valve SV3 is opened and the speed control of the pump is released. The further course of the lowering operation corresponds to that of the embodiment according to FIG.

Wenn beim Heben die gewünschte Soll-Position der Hubzylinder 12 überfahren wurde, wird die Soll-Position im sogenannten Schwebezustand angefahren. Dabei wird die Pumpe P auf der minimalen Drehzahl, die die Leckage abdeckt, in Betrieb gehalten, wobei in dem Leitungsabschnitt L1.2 stromab der Pumpe P ein Druck vorhanden sein muß, was durch den vierten Druckaufnehmer DA4 festgestellt wird. Das erste Sitzventil SV1 und das zweite Sitzventil SV2 bleiben bestromt offen. Der Volumenstromregler SR1 wird geöffnet, so daß Hydraulikflüssigkeit über den ersten Abschnitt L2.1 und den zweiten Abschnitt L2.2 der Rückführleitung L2 sowie die Druckleitung LDA3, die Verbindungsleitung L8 und die Zweigleitung L6 in den Vorratsbehälter 11 zurückströmen kann. Der Volumenstromregler SR1 wird soweit geöffnet, bis die gewünschte Senkgeschwindigkeit erreicht ist. Sollte beim Senken die Soll-Position wiederum verpaßt werden, wird die Drehzahl der Pumpe P erhöht, um das Heben einzuleiten. Die Differenz dQ zwischen der von der Pumpe P geförderten Hydraulikölmenge und der von dem Volumenstromregler SR1 abgelassenen Hydraulikölmenge bestimmt die Bewegungsrichtung der Hubzylinder 12. Wenn die Differenzmenge dQ positiv ist (dQ > 0), d.h. die Pumpe P mehr Hydrauliköl fördert als über den Volumenstromregler SR1 abgelassen wird, werden die Hubzylinder 12 angehoben. Entsprechend werden die Hubzylinder 12 abgesenkt, wenn die Differenzmenge negativ ist, d.h. die Pumpe P weniger Hydrauliköl fördert, als durch den Volumenstromregler SR1 abgelassen wird.If during lifting the desired position of the lifting cylinder 12 has been passed over, the target position is approached in the so-called floating state. In this case, the pump P is kept in operation at the minimum speed covering the leakage, wherein in the line section L1.2 downstream of the pump P, a pressure must be present, which is determined by the fourth pressure transducer DA4. The first seat valve SV1 and the second seat valve SV2 remain energized open. The volume flow controller SR1 is opened, so that hydraulic fluid over the first section L2.1 and the second section L2.2 of the return line L2 and the pressure line L DA3 , the connecting line L8 and the branch line L6 can flow back into the reservoir 11. The volume flow controller SR1 is opened until the desired lowering speed is reached. Should the desired position be missed again during lowering, the speed of the pump P is increased to initiate the lifting. The difference dQ between the hydraulic oil amount delivered by the pump P and the amount of hydraulic oil discharged from the volumetric flow controller SR1 determines the direction of movement of the lift cylinders 12. If the difference dQ is positive (dQ> 0), ie, the pump P delivers more hydraulic oil than via the volumetric flow controller SR1 is discharged, the lifting cylinders 12 are raised. Accordingly, the lifting cylinders 12 are lowered when the difference amount is negative, that is, the pump P promotes less hydraulic oil than is discharged through the volumetric flow controller SR1.

Wenn die von der Pumpe P gefördert Hydraulikölmenge exakt der Hydraulikölmenge entspricht, die durch den Volumenstromregler SR1 abgelassen wird, wird die Position der Hubzylinder gehalten. Die einzelnen Hydraulikölmengen und entsprechend die genannte Differenz zwischen der geförderten und der abgelassenen Hydraulikölmenge kann über eine Änderung der Drehzahl der Pumpe und/oder über die Bestromung und somit den Grad der Öffnung des Volumenstromreglers SR1 beeinflußt werden.When the amount of hydraulic oil pumped by the pump P exactly corresponds to the amount of hydraulic oil discharged through the flow regulator SR1, the position of the lift cylinders is maintained. The individual amounts of hydraulic oil and correspondingly said difference between the delivered and the discharged hydraulic oil quantity can be influenced by a change in the rotational speed of the pump and / or by the current supply and thus the degree of opening of the volumetric flow regulator SR1.

Wenn beim Senken die Soll-Position der Hubzylinder 12 überfahren wurde, wird das dritte Sitzventil SV3 geschlossen und der Druck an dem proportionalen Druckbegrenzungsventil PDBV über den herrschenden Lastdruck, der mittels des ersten Druckaufnehmers DA1 erfaßt wird, eingestellt. Anschließend werden das erste Sitzventil SV1 und das zweite Sitzventil SV2 geöffnet und die Drehzahl der Pumpe P soweit erhöht, bis die gewünschte Hubgeschwindigkeit der Hubzylinder 12 erreicht ist. Von da ab kann das Schwebeverfahren in oben genannter Weise weiter fortgeführt werden.If, when lowering the target position of the lifting cylinder 12 has been run over, the third seat valve SV3 is closed and the pressure at the proportional pressure relief valve PDBV on the prevailing load pressure, which is detected by means of the first pressure transducer DA1, set. Subsequently, the first seat valve SV1 and the second seat valve SV2 opened and the speed of the pump P increased until the desired lifting speed of the lifting cylinder 12 is reached. From then on, the suspension process can be continued in the above-mentioned manner.

Claims (6)

  1. Method for controlling a hydraulic lifting device, particularly for battery-powered industrial trucks, which has a pump (P) drivable by an electric motor (M) and by means of which in load lifting operation hydraulic oil is supplied to at least one hydraulic lifting cylinder (12) from a storage tank (11) via a supply line (L1), and in the load lowering operation the hydraulic oil is fed back to storage tank (11) from lifting cylinder (12) via a return flow line (L2, L3, L1.2, L6), accompanied by a flow through the pump (P) driving the electric motor (M) functioning as a generator, characterized in that at the start of the load lowering operation both in the section (L2.3) of the return flow line upstream of pump (P) and in the section (L1.2) of the return flow line downstream of pump (P) substantially the hydraulic pressure prevailing in lifting cylinder (12) is built up, the pump being operated with an actual speed below a speed limit value, and that a proportional pressure relief valve (PDBV) located in the return flow line downstream of pump (P), via a ramp function, is only substantially completely opened when the actual pump speed is above the speed limit value, the electric motor (M) then operating as a generator.
  2. Method according to claim 1, characterized in that the pressure in the return flow line at the start of load lowering operation is brought to the hydraulic pressure prevailing in the lifting cylinder (12) by means of a proportional pressure regulating valve (PDRV), which is located upstream of pump (P), by means of a ramp function.
  3. Method according to claim 1 or 2, characterized in that at the start of the load lifting operation, pump (P) returns hydraulic oil via a branch line (L6) in pressureless manner to storage tank (11) for as long as the actual pump speed is below the speed limit value, and that the branch line (L6) is closed by a valve (PDBV) as soon as the actual speed of pump (P) is above the speed limit value.
  4. Method according to one of the claims 1 to 3, characterized in that the speed limit value corresponds to the minimum speed of pump (P).
  5. Hydraulic lifting device, particularly for performing the method according to one of the claims 1 to 4, having a pump (P) drivable by an electric motor (M) by means of which, in load lifting operation, at least one hydraulic lifting cylinder (12) can be supplied via a supply line (L1) with hydraulic oil from a storage tank (11), whilst in load lowering operation the hydraulic oil is returnable from lifting cylinder (12) via a return flow line (L2, L3, L1.2, L6) and accompanied by a flow through the pump (P) driving the electric motor (M) operating as a generator to the storage tank (11), characterized in that a first pressure sensor (DA1) is provided which detects the hydraulic pressure in lifting cylinder (12), that a proportional pressure regulating valve (PDRV) is placed upstream of pump (P) in the return flow line, that a second pressure sensor (DA2) is provided detecting the inlet-side pressure of pump (P), that a control device is provided by means of which the inlet-side pressure of the pump is matchable by the control of the pressure regulating valve (PDRV) and as a function of the pressure values measured by pressure sensors (DA1, DA2) to the hydraulic pressure in the lifting cylinder (12), and that downstream of pump (P) a proportional pressure relief valve (PDBV) is placed in the return flow line.
  6. Hydraulic lifting device, particularly for performing the method according to one of the claims 1 to 4, having a pump (P) drivable by an electric motor (M) and by means of which, in load lifting operation, to the at least one hydraulic lifting cylinder (12) can be supplied via a supply line (L1) hydraulic oil from a storage tank (11), whereas in load lowering operation the hydraulic oil can be returned to storage tank (11) from lifting cylinder (12) via a return flow line (L2, L3, L1.2, L6), accompanied by a flow through the pump driving the electric motor (M) operating as a generator, characterized in that a first pressure sensor (DA1) is provided and detects the hydraulic pressure in lifting cylinder (12), that a second pressure sensor (DA2) is provided, which detects the inlet-side pressure of pump (P), that upstream of pump (P) a nozzle (D1) is provided in the return flow line and enables the inlet-side pressure of the pump to be matched to the hydraulic pressure in the lifting cylinder (12), and that a proportional pressure relief valve (PDBV) is placed in the return flow line downstream of pump (P).
EP20020024330 2001-11-06 2002-11-02 Hydraulic lifting device in particular for battery-powered industrial trucks and control method therefor Expired - Lifetime EP1308415B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10154449 2001-11-06
DE2001154449 DE10154449A1 (en) 2001-11-06 2001-11-06 Hydraulic lifting device, in particular for battery-powered industrial trucks, and method for controlling it

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EP1308415A2 EP1308415A2 (en) 2003-05-07
EP1308415A3 EP1308415A3 (en) 2005-05-25
EP1308415B1 true EP1308415B1 (en) 2007-02-07

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SE525159C2 (en) * 2002-06-05 2004-12-14 Bt Ind Ab Procedure for controlling the lowering movement of a truck's air cylinder
DE102009053618A1 (en) * 2009-11-17 2011-05-19 Robert Bosch Gmbh Hydraulic drive with energy recovery
US8196464B2 (en) * 2010-01-05 2012-06-12 The Raymond Corporation Apparatus and method for monitoring a hydraulic pump on a material handling vehicle
KR20110127773A (en) 2010-05-20 2011-11-28 두산산업차량 주식회사 Energy reclaiming system for an electric forklift truck
CN102108948B (en) * 2010-12-28 2012-11-28 山河智能装备股份有限公司 Renewable energy power generating system applicable to electrocar for loading, unloading and transporting
DE102012005432A1 (en) * 2012-03-17 2013-09-19 Jungheinrich Aktiengesellschaft Industrial truck for lifting load, has vertical monitoring unit comparing detected pressure values of pressure sensors with each other and generating emergency signal when deviation of pressure values is greater than predetermined value
JP6577336B2 (en) * 2015-11-05 2019-09-18 株式会社豊田自動織機 Industrial vehicle
CN107601391A (en) * 2017-09-22 2018-01-19 太仓市高泰机械有限公司 The automatic sensing and self-locking method of a kind of hydraulic car
CN107458999A (en) * 2017-09-22 2017-12-12 太仓市高泰机械有限公司 A kind of self-adjusting type hydraulic car with damping device
CN107601390A (en) * 2017-09-22 2018-01-19 太仓市高泰机械有限公司 A kind of method of work of the hydraulic car with auto-lock function
CN107352473A (en) * 2017-09-22 2017-11-17 太仓市高泰机械有限公司 A kind of method of work of self-adjusting type hydraulic car
CN112209305A (en) * 2020-10-30 2021-01-12 合力工业车辆（上海）有限公司 Hydraulic system of storage forklift
CN215058526U (en) * 2021-03-19 2021-12-07 湖南星邦智能装备股份有限公司 Control loop of double-acting floating oil cylinder

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DE10048215A1 (en) * 2000-09-28 2002-04-11 Still Wagner Gmbh & Co Kg Hydraulic lifting device

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DE50209428D1 (en) 2007-03-22
EP1308415A3 (en) 2005-05-25
DE10154449A1 (en) 2003-05-15

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