EP0230884B1 - Hydraulic lifting device - Google Patents

Hydraulic lifting device Download PDF

Info

Publication number
EP0230884B1
EP0230884B1 EP87100211A EP87100211A EP0230884B1 EP 0230884 B1 EP0230884 B1 EP 0230884B1 EP 87100211 A EP87100211 A EP 87100211A EP 87100211 A EP87100211 A EP 87100211A EP 0230884 B1 EP0230884 B1 EP 0230884B1
Authority
EP
European Patent Office
Prior art keywords
hydraulic
lifting
generator
control
load
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
EP87100211A
Other languages
German (de)
French (fr)
Other versions
EP0230884A3 (en
EP0230884A2 (en
Inventor
Martin Schmid
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STEINBOCK BOSS GMBH
Original Assignee
STEINBOCK BOSS GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by STEINBOCK BOSS GmbH filed Critical STEINBOCK BOSS GmbH
Priority to AT87100211T priority Critical patent/ATE94149T1/en
Publication of EP0230884A2 publication Critical patent/EP0230884A2/en
Publication of EP0230884A3 publication Critical patent/EP0230884A3/en
Application granted granted Critical
Publication of EP0230884B1 publication Critical patent/EP0230884B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • 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
    • 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

Definitions

  • the invention relates to a hydraulic hoist for a battery-powered industrial truck with a hydraulic lifting cylinder, with a hydraulic pump operating in the lifting operation as a pump, loading the lifting cylinder with pressure medium and working in the load lowering mode as a motor, driven by the pressure medium pushed out of the lifting cylinder, with a hydraulic unit coupled DC machine working in load lifting mode as an electric motor and in load lowering mode as a generator, with a useful brake circuit fed by the direct current machine in the lowering mode, with a control valve arrangement in the pressure medium path between the hydraulic cylinder and the hydraulic unit and with a hoist control controlling the useful brake circuit and the control valve arrangement.
  • a hydraulic hoist of this type is known from DE-A-20 14 605.
  • the pump charging the hydraulic lifting cylinder with hydraulic fluid for lifting the load is driven by a direct current shunt motor fed from the battery of the vehicle.
  • the pump is a rotary lobe pump, the flow rate of which can be changed continuously from pump operation to motor operation by adjusting a control element.
  • the pump is operated as a hydraulic motor, which drives the shunt motor which works as a generator in the service brake mode.
  • the potential charging energy of the raised load is thus converted into electrical energy that charges the battery when the load is lowered in the service brake mode.
  • the lowering speed of the load is determined by the braking torque generated by the generator. Since the generator does not generate any braking torque when it is at a standstill, a controllable check valve is connected between the hydraulic motor and the hydraulic cylinder, which in the locked state blocks the flow of hydraulic fluid from the hydraulic cylinder to the hydraulic motor locks. When the load is lowered from a standstill, the shut-off valve is opened. In conventional hoists of the type in question, the load then sags under acceleration of the generator until the generator generates a counter torque sufficient to hold the load.
  • a hydraulic hoist is known, the hydraulic pump, which is dimensioned for a constant flow rate, is driven by a cage induction motor.
  • the load lifting operation and the load lowering operation are controlled by separate controllable throttle valves which allow the lifting operation and the lowering operation to be carried out gradually, i.e. start and end smoothly.
  • the induction motor works as a generator and is driven by the pump that acts as a motor.
  • control valve arrangement has a proportional valve that the hoist control opens the proportional valve according to a ramp function during load operation and, depending on the output current of the DC machine operating as a generator, switches the useful brake circuit effectively if the generator output current exceeds a predetermined value, and that the hoist control comprises a speed control device influencing the excitation current of the direct current machine working as a generator, by means of which the speed of the hydraulic unit can be regulated to a specifiable setpoint in load-lowering mode.
  • the load is first throttled down via the proportional valve with increasing pressure medium throughput.
  • the lowering speed is determined by the proportional valve.
  • the hoist control monitors the output current of the DC machine working as a generator and switches on the useful brake circuit for electrical braking of the lowering movement as soon as a sufficient braking torque is exerted on the hydraulic motor due to the generator operation. This type of control prevents the load from initially sagging during the transition to lowering mode.
  • the proportional valve is opened completely.
  • the lowering speed is kept at a desired setpoint by conventional regulation of the excitation of the DC machine.
  • the lowering speed can be selected enlarged, but in particular also compared to the speed value at which the transition to electric braking takes place.
  • the stroke value control can comprise an additional speed control device which keeps the excitation of the DC machine at a predetermined speed setpoint depending on a speed sensor that detects its speed.
  • the lowering speed of the load can be varied within wide limits. By regulating the excitation of the DC machine, the lowering speed can be reduced to almost zero.
  • the proportional valve is closed according to a ramp function when approaching the standstill, so that shutdown shocks are avoided.
  • control valve arrangement arranged between the hydraulic unit and the hydraulic cylinder, this comprises two check valves opening in opposite directions in series with the proportional valve, which are bridged by magnetic check valves.
  • a third check valve that opens in the lifting direction bridges the proportional valve.
  • the lifting cylinder 1 shows a hydraulic lifting cylinder 1, the piston 3 of which is able to raise or lower lifting means (not shown in more detail) of a battery-powered industrial truck, for example a forklift or the like.
  • the lifting cylinder 1 is connected via a control valve arrangement, generally designated 5, to a reversible hydraulic motor 7, which can thus be operated as a pump, for example a gear motor.
  • the hydraulic motor 7 is coupled to a direct current machine 9 which can be operated both as a motor and as a generator, the excitation of which can be regulated both in motor operation and in generator operation by a hoist control generally designated 11.
  • the DC machine 9 is connected to an accumulator or a battery 15 via a thyristor controller 13.
  • the hoist control 11 responds to the excitation of the DC machine by means of a sensor 17 and controls the thyristor circuit 13 operating in chopper mode in such a way that a predetermined value of the excitation, which is selectable via the hoist control 11, and thus a predetermined value of the torque of the DC machine 9 are maintained can.
  • a speed sensor 19 is also coupled to the shaft of the hydraulic motor 7 and outputs a signal corresponding to the speed of the hydraulic motor 7 to the hoist control 11.
  • the hoist control 11 comprises control means which, depending on the determined speed, influence the excitation of the DC machine 9 via the thyristor control 13 in such a way that a predetermined target speed can be maintained both in motor operation and in generator operation. Since the speed of the hydraulic motor is proportional to the pressure medium throughput, the lifting or lowering speed of the piston 3 can be regulated in this way.
  • the DC machine 9 operates as a motor and drives the hydraulic motor 7 in a direction of rotation in which the hydraulic fluid is conveyed from a tank 21 into the hydraulic cylinder 1 via the control valve arrangement 5 becomes.
  • a pressure relief valve 23 connected to the outlet of the hydraulic motor 7 limits the outlet pressure.
  • the hoist control 11 controls the motor excitation so that the speed of the hydraulic motor 7 working as a pump and thus the stroke speed of the piston 3 has a predetermined value.
  • the piston 3 loaded with the load drives the hydraulic fluid back into the tank 21 via the control valve arrangement 5.
  • the hydraulic motor 7 operates in motor mode and drives the DC machine 9, which works as a generator.
  • the armature circuit of the DC machine 9 is connected to the battery 15 via a useful brake switching stage 25.
  • the useful brake switchover stage allows the useful braking of the direct current machine 9 when the generator is in operation, at least part of the current generated by the generator being used to charge the battery 15.
  • the excitation of the DC machine 9 is controlled via the thyristor controller 13 so that the generator exerts a predetermined braking torque on the hydraulic motor 7 and, moreover, the hydraulic motor 7 is kept at a predetermined speed in accordance with a predetermined load lowering speed.
  • the control valve arrangement 5 comprises two solenoid valves 27, 29 which are arranged in series with one another and a proportional valve 31 which is likewise connected in series.
  • the normally closed solenoid valve 27 comprises a check valve 33 which opens in the lowering flow direction of the hydraulic fluid in a shunt path to its closed position.
  • the solenoid valve 29 is normally also closed and has a check valve 35 which opens in the load lifting flow direction of the hydraulic fluid in a shunt path to its closed position.
  • a further check valve 37 is arranged in a bypass line to the proportional valve 31.
  • the solenoid valves 27, 29 and the proportional valve 31 are controlled by the hoist control 11.
  • the hoist control 11 is expediently designed as a microprocessor control and comprises a central arithmetic unit 39 with an input circuit 41, an output circuit 43 and a program and data memory 45 to. At operating level 47, you can switch between lifting and lowering, and the set speed for lifting and lowering can be set.
  • the input circuit 41 is also fed back feedback data from the useful brake switch stage 25 and the thyristor control 13 and data about the state of charge of the battery 15. If the data are in analog form, they are converted into digital data in the input circuit 41.
  • the output circuit 43 controls the chopper operation of the thyristor control 13 and the switching operation of the useful brake switching stage 25.
  • the output circuit 43 also generates control signals for the excitation of the solenoid valves 27, 29 and the proportional valve 31.
  • An error indicator 49 is also connected to the output circuit 43 for Generation of alarm and fault signals.
  • the speed control means can also be omitted, so that the excitation of the DC machine 9 in generator or motor operation is kept at a desired value without taking into account the actual speed.
  • a sensor responding to the motor voltage can also be provided for determining the actual value of the excitation of the DC machine 9.
  • FIG. 2a shows the time course of the control signal M29 output by the hoist control 11 to the solenoid valve 29.
  • the time course of the control signal M31 output to the proportional valve 31 is shown in FIG. 2b.
  • 2c shows the time profile of the excitation current I G of the sliding current machine 9 operating in generator mode.
  • the command for lowering the load is given at operating level 47 at a predetermined lowering speed.
  • the hoist control 11 opens the solenoid valve 29 and generates a ramp signal 51, which opens the proportional valve 31 steadily.
  • the lowering speed is determined by the opening cross section of the proportional valve 31, which increases according to the ramp signal.
  • the useful brake switching stage 25 is deactivated. As soon as the armature current of the direct current machine 9 determined by the hoist control 11 via the sensor 17 is sufficient to hold the load on the piston 3 by the braking torque of the generator, the useful brake operation is switched on via the useful brake switching stage 25 and the proportional valve 31 is completely opened. In Fig. 2c, the switching current I0 is reached at time t1.
  • the speed of the hydraulic motor 7 is regulated via the excitation of the direct current machine 9 to the setpoint set at operating level 47, the setpoint being able to be varied in the course of the lowering speed, as shown in FIG. 2c for the time t 2 .
  • the hoist control 11 not only allows a jerk-free start of the load lowering operation, but also the jerk-free termination. If the setpoint of the lowering speed is set to zero via the operating stage 47 at the time t 3, the lowering speed is first reduced by electrical control of the direct current machine 9 to a value close to standstill.
  • the hoist control 11 generates a proportional valve 31 that closes continuously Ramp signal 53.
  • the solenoid valve 29 is also closed at time t4 when the proportional valve 31 is closed.
  • FIG. 3 shows a preferred exemplary embodiment of a useful brake circuit for a direct current series machine with an armature 63 connected in series with a field winding 61.
  • the field winding 61 is connected via a thyristor 65 to the positive pole of a battery 67.
  • the armature 63 is connected via a current sensor 69 corresponding to the sensor 17 from FIG. 1, for example a shunt resistor, to a control switch 71 which connects the armature 63 to the negative pole of the battery 67.
  • a control circuit 73 which comprises a conventional quenching circuit for the thyristor 65, controls the thyristor 65 in chopper mode and determines the pulse duration and the pulse period of the current flowing through the field winding 61 and the armature 63.
  • the current detected by the sensor 69 is kept at a setpoint which can be predetermined at 75.
  • 77 shows a freewheeling diode connected in parallel with the field winding 61, as is used for conventional thyristor suppressor circuits.
  • the switch 71 In load lifting operation, the switch 71 is closed and the pulsed motor current flows via the thyristor 65, the field winding 61, the armature 63, the sensor 69 and the switch 71.
  • a service brake circuit is activated by opening switch 71.
  • the useful brake circuit comprises a diode 79 connected with its cathode to the positive pole of the battery 67 and with its anode via the sensor 69 to the armature 63.
  • the diode 79 is the series circuit comprising the thyristor 65, the field winding 61, the armature 63 and the sensor 69 connected in parallel.
  • the anode of the diode 79 is connected to the anode of a further diode 81, the cathode of which is connected via a resistor 83 to the negative pole of the battery 67.
  • Resistor 83 is a Capacitor 85 connected in parallel.
  • the switch 71 forms a short-circuit switch to the series circuit comprising the diode 81 and the resistor 83. While the connection point 87 is kept at the potential of the negative pole of the battery 67 via the closed switch 71 in the load-lifting mode, the potential at the point 87 can be opened when the load-lowering mode is in operation Due to the generator voltage generated by the armature 63, the switch 71 increases to a value whose potential is greater than the potential at the positive pole of the battery 67. The diode 79 thereby becomes conductive and a charging current flows into the battery 67. The field winding 61 is excited controllable via thyristor 65 even in this operating state.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Structural Engineering (AREA)
  • Transportation (AREA)
  • Chemical & Material Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Geology (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Civil Engineering (AREA)
  • Analytical Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Forklifts And Lifting Vehicles (AREA)
  • Control Of Direct Current Motors (AREA)
  • Load-Engaging Elements For Cranes (AREA)
  • Lubricants (AREA)
  • Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)

Abstract

A hydraulic lifting mechanism, particularly suitable for a battery-powered industrial truck, including a hydraulic lifting cylinder, a hydraulic unit, operating as a pump in the load lifting operational mode, and supplying the lifting cylinder with pressure medium, and operating as a motor in the load lowering operational mode during which mode it is actuated by the pressure medium exiting from the lifting cylinder, and a DC generator coupled with the hydraulic unit operating as an electromotor in the load lifting operational mode and as a generator in the load lowering operational mode. A control valve arrangement is provided at the halfway point in the pressure path between the hydraulic cylinder and the hydraulic unit, which is controlled by a lifting mechanism control. In addition, the lifting mechanism control controls a regenerative brake circuit supplied by the DC generator in the load lowering operational mode. The control valve arrangement includes a proportional valve which is opened by the lifting mechanism control in the load lowering operational mode in accordance with a ramp-like function. The regenerative brake circuit is switched on depending on the output current of the DC generator working as a generator, if the generator output current exceeds a predetermined value. Undesirable dropping of the load in the lowering operational mode is hereby prevented during transition to regenerative braking.

Description

Die Erfindung betrifft ein hydraulisches Hubwerk für ein batteriegetriebenes Flurförderzeug mit einem hydraulischen Hubzylinder, mit einer im Lasthebebetrieb als Pumpe arbeitenden, den Hubzylinder mit Druckmittel beschickenden und im Lastsenkbetrieb als Motor arbeitenden, von dem aus dem Hubzylinder ausgeschobenen Druckmittel angetriebenen Hydraulikaggregat, mit einer mit dem Hydraulikaggregat gekuppelten, im Lasthebebetrieb als Elektromotor arbeitenden und im Lastsenkbetrieb als Generator arbeitenden Gleichstrommaschine, mit einer im Lastsenkbetrieb von der Gleichstrommaschine gespeisten Nutzbremsschaltung, mit einer Steuerventilanordnung im Druckmittelweg zwischen dem Hydraulikzylinder und dem Hydraulikaggregat und mit einer die Nutzbremsschaltung und die Steuerventilanordnung steuernden Hubwerksteuerung.The invention relates to a hydraulic hoist for a battery-powered industrial truck with a hydraulic lifting cylinder, with a hydraulic pump operating in the lifting operation as a pump, loading the lifting cylinder with pressure medium and working in the load lowering mode as a motor, driven by the pressure medium pushed out of the lifting cylinder, with a hydraulic unit coupled DC machine working in load lifting mode as an electric motor and in load lowering mode as a generator, with a useful brake circuit fed by the direct current machine in the lowering mode, with a control valve arrangement in the pressure medium path between the hydraulic cylinder and the hydraulic unit and with a hoist control controlling the useful brake circuit and the control valve arrangement.

Ein hydraulisches Hubwerk dieser Art ist aus der DE-A-20 14 605 bekannt. Bei diesem Hubwerk eines Staplerfahrzeugs wird die den hydraulischen Hubzylinder zum Heben der Last mit Hydraulikfluid beschickende Pumpe von einem aus der Batterie des Fahrzeugs gespeisten Gleichstrom-Nebenschlußmotor angetrieben. Bei der Pumpe handelt es sich um eine Drehkolbenpumpe, deren Fördermenge durch Verstellen eines Regelorgans stufenlos von Pumpbetrieb auf Motorbetrieb umstellbar ist. Beim Absenken der Last wird die Pumpe als Hydraulikmotor betrieben, der den im Nutzbremsbetrieb als Generator arbeitenden Nebenschlußmotor antreibt. Die potentielle Ladeenergie der angehobenen Last wird damit beim Absenken der Last im Nutzbremsbetrieb in elektrische, die Batterie ladende Energie umgewandelt.A hydraulic hoist of this type is known from DE-A-20 14 605. In this lifting mechanism of a forklift vehicle, the pump charging the hydraulic lifting cylinder with hydraulic fluid for lifting the load is driven by a direct current shunt motor fed from the battery of the vehicle. The pump is a rotary lobe pump, the flow rate of which can be changed continuously from pump operation to motor operation by adjusting a control element. When the load is lowered, the pump is operated as a hydraulic motor, which drives the shunt motor which works as a generator in the service brake mode. The potential charging energy of the raised load is thus converted into electrical energy that charges the battery when the load is lowered in the service brake mode.

Bei Hubwerken der vorstehend erläuterten Art wird die Absenkgeschwindigkeit der Last durch das vom Generator erzeugte Bremsmoment bestimmt. Da der Generator im Stillstand kein Bremsmoment erzeugt, ist zwischen den Hydraulikmotor und den Hydraulikzylinder ein steuerbares Sperrventil geschaltet, welches im gesperrten Zustand den Hydraulikfluidfluß vom Hydraulikzylinder zum Hydraulikmotor sperrt. Beim Absenken der Last aus dem Stillstand heraus wird das Sperrventil geöffnet. Bei herkömmlichen Hubwerken der in Rede stehenden Art sackt hierauf die Last unter Beschleunigung des Generators durch, bis der Generator ein zum Halten der Last ausreichendes Gegendrehmoment erzeugt.In hoists of the type explained above, the lowering speed of the load is determined by the braking torque generated by the generator. Since the generator does not generate any braking torque when it is at a standstill, a controllable check valve is connected between the hydraulic motor and the hydraulic cylinder, which in the locked state blocks the flow of hydraulic fluid from the hydraulic cylinder to the hydraulic motor locks. When the load is lowered from a standstill, the shut-off valve is opened. In conventional hoists of the type in question, the load then sags under acceleration of the generator until the generator generates a counter torque sufficient to hold the load.

Aus der DE-A-30 18 156 ist ein hydraulisches Hubwerk bekannt, dessen für eine konstante Fördermenge bemessene Hydraulikpumpe von einem Käfig-Induktionsmotor angetrieben wird. Der Lasthebebetrieb und der Lastsenkbetrieb werden von gesonderten steuerbaren Drosselventilen gesteuert, die es erlauben, den Hebebetrieb und den Senkbetrieb allmählich, d.h. weich beginnen und enden zu lassen. Im Senkbetrieb arbeitet der Induktionsmotor als Generator und wird von der hierbei als Motor wirkenden Pumpe angetrieben.From DE-A-30 18 156 a hydraulic hoist is known, the hydraulic pump, which is dimensioned for a constant flow rate, is driven by a cage induction motor. The load lifting operation and the load lowering operation are controlled by separate controllable throttle valves which allow the lifting operation and the lowering operation to be carried out gradually, i.e. start and end smoothly. In lowering mode, the induction motor works as a generator and is driven by the pump that acts as a motor.

Es ist Aufgabe der Erfindung, ein hydraulisches Hubwerk der eingangs erläuterten Art anzugeben, bei welchem die Last mit wählbarer Geschwindigkeit im Nutz-Brems-Betrieb abgesenkt werden kann, ohne daß sie zu Beginn des Absenkvorgangs ungewollt absackt.It is an object of the invention to provide a hydraulic hoist of the type described in the introduction, in which the load can be lowered at a selectable speed in the useful braking mode, without sagging unintentionally at the beginning of the lowering process.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß die Steuerventilanordnung ein Proportionalventil aufweist, das die Hubwerksteuerung im Lastbetrieb das Proportionalventil entsprechend einer Rampenfunktion öffnet und abhängig vom Ausgangsstrom der als Generator arbeitenden Gleichstrommaschine die Nutzbremsschaltung wirksam schaltet, wenn der Generatorausgangsstrom hierbei einen vorbestimmten Wert übersteigt, und daß die Hubwerkssteuerung eine den Erregerstrom der als Generator arbeitenden Gleichstrommaschine beeinflussende Drehzahlregeleinrichtung umfaßt, mittels der die Drehzahl des Hydraulikaggregats im Lastsenkbetrieb auf einen vorgebbaren Sollwert regelbar ist.This object is achieved in that the control valve arrangement has a proportional valve that the hoist control opens the proportional valve according to a ramp function during load operation and, depending on the output current of the DC machine operating as a generator, switches the useful brake circuit effectively if the generator output current exceeds a predetermined value, and that the hoist control comprises a speed control device influencing the excitation current of the direct current machine working as a generator, by means of which the speed of the hydraulic unit can be regulated to a specifiable setpoint in load-lowering mode.

Bei einem solchen Hubwerk wird die Last zunächst über das Proportionalventil mit wachsendem Druckmitteldurchsatz gedrosselt abgesenkt. Die Absenkgeschwindigkeit wird hierbei durch das Proportionalventil bestimmt. Die Hubwerksteuerung überwacht den Ausgangsstrom der als Generator arbeitenden Gleichstrommaschine und schaltet die Nutzbremsschaltung zum elektrischen Bremsen der Absenkbewegung ein, sobald aufgrund des Generatorbetriebs ein hinreichend großes Bremsmoment auf den Hydraulikmotor ausübt. Diese Art der Steuerung verhindert anfängliches Absacken der Last beim Übergang in den Absenkbetrieb.In such a hoist, the load is first throttled down via the proportional valve with increasing pressure medium throughput. The lowering speed is determined by the proportional valve. The hoist control monitors the output current of the DC machine working as a generator and switches on the useful brake circuit for electrical braking of the lowering movement as soon as a sufficient braking torque is exerted on the hydraulic motor due to the generator operation. This type of control prevents the load from initially sagging during the transition to lowering mode.

Nach dem Übergang auf elektrisches Bremsen des Absenkens wird das Proportionalventil vollständig geöffnet. Die Absenkgeschwindigkeit wird durch herkömmliches Regeln der Erregung der Gleichstrommaschine auf einem gewünschten Sollwert gehalten. Die Absenkgeschwindigkeit kann wahlweise vergrößert, insbesondere aber auch gegenüber dem Geschwindigkeitswert, bei welchem der Übergang auf elektrische Bremsung erfolgt, verkleinert werden. Zusätzlich zur Steuerung der Erregung der Gleichstrommaschine kann die Hubwertsteuerung eine zusätzliche Drehzahlregeleinrichtung umfassen, die die Erregung der Gleichstrommaschine abhängig von einem deren Drehzahl erfassenden Drehzahlsensor auf einem vorgegebenen Drehzahl-Sollwert hält.After the transition to electrical braking of lowering, the proportional valve is opened completely. The lowering speed is kept at a desired setpoint by conventional regulation of the excitation of the DC machine. The lowering speed can be selected enlarged, but in particular also compared to the speed value at which the transition to electric braking takes place. In addition to controlling the excitation of the DC machine, the stroke value control can comprise an additional speed control device which keeps the excitation of the DC machine at a predetermined speed setpoint depending on a speed sensor that detects its speed.

Nach Wirksamschalten der Nutzbremsschaltung kann die Absenkgeschwindigkeit der Last in weiten Grenzen variiert werden. Durch Regelung der Erregung der Gleichstrommaschine kann die Absenkgeschwindigkeit bis nahezu null abgesenkt werden. In einer bevorzugten Ausführungsform ist vorgesehen, daß bei Annäherung an den Stillstand das Proportionalventil entsprechend einer Rampenfunktion geschlossen wird, so daß Abschaltstöße vermieden werden.After the useful brake circuit has been activated, the lowering speed of the load can be varied within wide limits. By regulating the excitation of the DC machine, the lowering speed can be reduced to almost zero. In a preferred embodiment it is provided that the proportional valve is closed according to a ramp function when approaching the standstill, so that shutdown shocks are avoided.

In einer zweckmäßigen Ausgestaltung der zwischen dem Hydraulikaggregat und dem Hydraulikzylinder angeordneten Steuerventilanordnung umfaßt diese in Serie zu dem Proportionalventil zwei gegensinnig öffnende Rückschlagventile, die durch magnetische Sperrventile überbrückt sind. Ein drittes in Heberichtung öffnendes Rückschlagventil überbrückt das Proportionalventil. Vorteil einer solchen Steuerventilanordnung ist ihr verhältnismäßig geringer ventiltechnischer Aufwand.In an expedient embodiment of the control valve arrangement arranged between the hydraulic unit and the hydraulic cylinder, this comprises two check valves opening in opposite directions in series with the proportional valve, which are bridged by magnetic check valves. A third check valve that opens in the lifting direction bridges the proportional valve. The advantage of such a control valve arrangement is its relatively low expenditure on valves.

Im folgenden soll die Erfindung anhand von Zeichnungen näher erläutert werden. Es zeigt:

Fig. 1
ein schematisches Blockschaltbild eines hydraulischen Hubwerks;
Fig. 2a, b und c
Zeitdiagramme von Steuersignalen des Hinbwerks der Fig. 1 und
Fig. 3
ein Schaltbild einer bei dem Hubwerk der Fig. 1 verwendbaren Nutzbremsschaltung.
The invention will be explained in more detail below with reference to drawings. It shows:
Fig. 1
a schematic block diagram of a hydraulic hoist;
2a, b and c
Timing diagrams of control signals of the implement of FIGS. 1 and
Fig. 3
a circuit diagram of a useful brake circuit usable in the hoist of FIG. 1.

Fig. 1 zeigt einen hydraulischen Hubzylinder 1, dessen Kolben 3 nicht näher dargestellte Hebemittel eines batteriegetriebenen Flurförderzeugs, beispielsweise eines Gabelstaplers oder dergleichen zu heben oder zu senken vermag. Der Hubzylinder 1 ist über eine allgemein mit 5 bezeichnete Steuerventilanordnung an einen reversierbaren und damit als Pumpe betreibbaren Hydraulikmotor 7, beispielsweise einen Zahnradmotor, angeschlossen. Der Hydraulikmotor 7 ist mit einer sowohl als Motor als auch als Generator betreibbaren Gleichstrommaschine 9 gekuppelt, deren Erregung sowohl im Motorbetrieb als auch im Generatorbetrieb von einer allgemein mit 11 bezeichneten Hubwerksteuerung regelbar ist. Die Gleichstrommaschine 9 ist hierzu über eine Thyristorsteuerung 13 an einen Akkumulator oder eine Batterie 15 angeschlossen. Die Hubwerksteuerung 11 spricht mittels eines Sensors 17 auf die Erregung der Gleichstrommaschine an und steuert die im Chopper-Betrieb arbeitende Thyristorschaltung 13 so, daß ein vorbestimmter, über die Hubwerksteuerung 11 wählbarer Wert der Erregung und damit ein vorbestimmter Wert des Drehmoments der Gleichstrommaschine 9 eingehalten werden kann. Mit der Welle des Hydraulikmotors 7 ist ferner ein Drehzahlgeber 19 gekuppelt, der ein der Drehzahl des Hydraulikmotors 7 entsprechendes Signal an die Hubwerksteuerung 11 abgibt. Die Hubwerksteuerung 11 umfaßt Regelmittel, die abhängig von der ermittelten Drehzahl über die Thyristorsteuerung 13 die Erregung der Gleichstrommaschine 9 so beeinflussen, daß sowohl im Motorbetrieb als auch im Generatorbetrieb eine vorbestimmte Solldrehzahl eingehalten werden kann. Da die Drehzahl des Hydraulikmotors dem Druckmitteldurchsatz proportional ist, kann auf diese Weise die Hebe- bzw. Senkgeschwindigkeit des Kolbens 3 geregelt werden.1 shows a hydraulic lifting cylinder 1, the piston 3 of which is able to raise or lower lifting means (not shown in more detail) of a battery-powered industrial truck, for example a forklift or the like. The lifting cylinder 1 is connected via a control valve arrangement, generally designated 5, to a reversible hydraulic motor 7, which can thus be operated as a pump, for example a gear motor. The hydraulic motor 7 is coupled to a direct current machine 9 which can be operated both as a motor and as a generator, the excitation of which can be regulated both in motor operation and in generator operation by a hoist control generally designated 11. For this purpose, the DC machine 9 is connected to an accumulator or a battery 15 via a thyristor controller 13. The hoist control 11 responds to the excitation of the DC machine by means of a sensor 17 and controls the thyristor circuit 13 operating in chopper mode in such a way that a predetermined value of the excitation, which is selectable via the hoist control 11, and thus a predetermined value of the torque of the DC machine 9 are maintained can. A speed sensor 19 is also coupled to the shaft of the hydraulic motor 7 and outputs a signal corresponding to the speed of the hydraulic motor 7 to the hoist control 11. The hoist control 11 comprises control means which, depending on the determined speed, influence the excitation of the DC machine 9 via the thyristor control 13 in such a way that a predetermined target speed can be maintained both in motor operation and in generator operation. Since the speed of the hydraulic motor is proportional to the pressure medium throughput, the lifting or lowering speed of the piston 3 can be regulated in this way.

Im Lasthebebetrieb arbeitet die Gleichstrommaschine 9 als Motor und treibt den Hydraulikmotor 7 in einer Drehrichtung an, in der das Hydraulikfluid aus einem Tank 21 über die Steuerventilanordnung 5 in den Hydraulikzylinder 1 gefördert wird. Ein an den Ausgang des Hydraulikmotors 7 angeschlossenes Überdruckventil 23 begrenzt hierbei den Ausgangsdruck. Die Hubwerksteuerung 11 steuert die Motorerregung so, daß die Drehzahl des als Pumpe arbeitenden Hydraulikmotors 7 und damit die Hubgeschwindigkeit des Kolbens 3 einen vorbestimmten Wert hat.In load lifting operation, the DC machine 9 operates as a motor and drives the hydraulic motor 7 in a direction of rotation in which the hydraulic fluid is conveyed from a tank 21 into the hydraulic cylinder 1 via the control valve arrangement 5 becomes. A pressure relief valve 23 connected to the outlet of the hydraulic motor 7 limits the outlet pressure. The hoist control 11 controls the motor excitation so that the speed of the hydraulic motor 7 working as a pump and thus the stroke speed of the piston 3 has a predetermined value.

Im Absenkbetrieb treibt der mit der Last belastete Kolben 3 das Hydraulikfluid über die Steuerventilanordnung 5 in den Tank 21 zurück. Der Hydraulikmotor 7 arbeitet im Motorbetrieb und treibt die als Generator arbeitende Gleichstrommaschine 9 an. Der Ankerstromkreis der Gleichstrommaschine 9 ist über eine Nutzbrems-Umschaltstufe 25 mit der Batterie 15 verbunden. Die Nutzbrems-Umschaltstufe erlaubt bei Generatorbetrieb die Nutzbremsung der Gleichstrommaschine 9, wobei zumindest ein Teil des generatorisch erzeugten Stroms zum Laden der Batterie 15 genutzt wird. Auch im Nutzbremsbetrieb wird die Erregung der Gleichstrommaschine 9 über die Thyristorsteuerung 13 so gesteuert, daß der Generator ein vorbestimmtes Bremsdrehmoment auf den Hydraulikmotor 7 ausübt und zudem der Hydraulikmotor 7 auf einer vorbestimmten Drehzahl entsprechend einer vorbestimmten Lastabsenkgeschwindigkeit gehalten wird.In the lowering mode, the piston 3 loaded with the load drives the hydraulic fluid back into the tank 21 via the control valve arrangement 5. The hydraulic motor 7 operates in motor mode and drives the DC machine 9, which works as a generator. The armature circuit of the DC machine 9 is connected to the battery 15 via a useful brake switching stage 25. The useful brake switchover stage allows the useful braking of the direct current machine 9 when the generator is in operation, at least part of the current generated by the generator being used to charge the battery 15. Also in the service brake mode, the excitation of the DC machine 9 is controlled via the thyristor controller 13 so that the generator exerts a predetermined braking torque on the hydraulic motor 7 and, moreover, the hydraulic motor 7 is kept at a predetermined speed in accordance with a predetermined load lowering speed.

Die Steuerventilanordnung 5 umfaßt zwei in Serie zueinander angeordnete Magnetventile 27, 29 und ein ebenfalls in Serie geschaltetes Proportionalventil 31. Das normalerweise geschlossene Magnetventil 27 umfaßt ein in Absenkströmungsrichtung des Hydraulikfluids öffnendes Rückschlagventil 33 in einem Nebenschlußweg zu seiner Schließstellung. Das Magnetventil 29 ist normalerweise ebenfalls geschlossen und hat in einem Nebenschlußweg zu seiner Schließstellung ein in Lasthebeströmungsrichtung des Hydraulikfluids öffnendes Rückschlagventil 35. Ein weiteres Rückschlagventil 37 ist in einer Umwegleitung zu dem Proportionalventil 31 angeordnet.The control valve arrangement 5 comprises two solenoid valves 27, 29 which are arranged in series with one another and a proportional valve 31 which is likewise connected in series. The normally closed solenoid valve 27 comprises a check valve 33 which opens in the lowering flow direction of the hydraulic fluid in a shunt path to its closed position. The solenoid valve 29 is normally also closed and has a check valve 35 which opens in the load lifting flow direction of the hydraulic fluid in a shunt path to its closed position. A further check valve 37 is arranged in a bypass line to the proportional valve 31.

Die Magnetventile 27, 29 und das Proportionalventil 31 werden von der Hubwerksteuerung 11 gesteuert. Die Hubwerksteuerung 11 ist zweckmäßigerweise als Microprozessorsteuerung ausgebildet und umfaßt ein zentrales Rechenwerk 39 mit einer Eingangsschaltung 41, einer Ausgangsschaltung 43 und einem Programm- und Datenspeicher 45. Die Eingangsschaltung 41 führt dem zentralen Rechenwerk 39 Eingangsdaten des Stromsensors 17, des Drehzahlgebers 19 sowie einer Bedienungsstufe 47 zu. An der Bedienungsstufe 47 kann zwischen Hebebetrieb und Senkbetrieb umgeschaltet werden, und es kann die Sollgeschwindigkeit beim Heben und Senken eingestellt werden. Der Eingangsschaltung 41 werden ferner Rückmeldedaten der Nutzbrems-Umschaltstufe 25 und der Thyristorsteuerung 13 sowie Daten über den Ladezustand der Batterie 15 zugeführt. Soweit die Daten in analoger Form vorliegen, werden sie in der Eingangsschaltung 41 in Digitaldaten gewandelt. Die Ausgangsschaltung 43 steuert den Chopper-Betrieb der Thyristorsteuerung 13 und den Umschaltbetrieb der Nutzbrems-Umschaltstufe 25. Die Ausgangsschaltung 43 erzeugt ferner Steuersignale für die Erregung der Magnetventile 27, 29 und des Proportionalventils 31. An die Ausgangsschaltung 43 ist ferner eine Fehleranzeige 49 angeschlossen zur Erzeugung von Alarm- und Störfallsignalen.The solenoid valves 27, 29 and the proportional valve 31 are controlled by the hoist control 11. The hoist control 11 is expediently designed as a microprocessor control and comprises a central arithmetic unit 39 with an input circuit 41, an output circuit 43 and a program and data memory 45 to. At operating level 47, you can switch between lifting and lowering, and the set speed for lifting and lowering can be set. The input circuit 41 is also fed back feedback data from the useful brake switch stage 25 and the thyristor control 13 and data about the state of charge of the battery 15. If the data are in analog form, they are converted into digital data in the input circuit 41. The output circuit 43 controls the chopper operation of the thyristor control 13 and the switching operation of the useful brake switching stage 25. The output circuit 43 also generates control signals for the excitation of the solenoid valves 27, 29 and the proportional valve 31. An error indicator 49 is also connected to the output circuit 43 for Generation of alarm and fault signals.

In einfachen Ausführungsformen der Hubwerksteuerung 11 können die Drehzahlregelungsmittel auch entfallen, so daß die Erregung der Gleichstrommaschine 9 im Generator- bzw. Motorbetrieb ohne Berücksichtigung der Ist-Drehzahl auf einem Sollwert gehalten wird. Statt des auf den Motorstrom ansprechenden Sensors 17 kann auch ein auf die Motorspannung ansprechender Sensor vorgesehen sein zur Ermittlung des Istwerts der Erregung der Gleichstrommaschine 9.In simple embodiments of the hoist control 11, the speed control means can also be omitted, so that the excitation of the DC machine 9 in generator or motor operation is kept at a desired value without taking into account the actual speed. Instead of the sensor 17 responding to the motor current, a sensor responding to the motor voltage can also be provided for determining the actual value of the excitation of the DC machine 9.

Im Lasthebebetrieb ist das Magnetventil 27 geöffnet, und das Hydraulikfluid wird über das Magnetventil 27 und die Rückschlagventile 35, 37 in den Hydraulikzylinder 1 gepumpt. Der Absenkbetrieb wird von der Hubwerksteuerung 11 über das Magnetventil 29 und das ebenfalls normalerweise geschlossene Proportionalventil 31 gesteuert. Fig. 2a zeigt den zeitlichen Verlauf des von der Hubwerksteuerung 11 an das Magnetventil 29 abgegebenen Steuersignals M29. Der zeitliche Verlauf des an das Proportionalventil 31 abgegebenen Steuersignals M31 ist in Fig. 2b dargestellt. Fig. 2c zeigt den zeitlichen Verlauf des Erregerstroms IG der im Generatorbetrieb arbeitenden Gleitstrommaschine 9. Zum Zeitpunkt t₀ wird an der Bedienungsstufe 47 der Befehl zum Absenken der Last mit einer vorbestimmten Absenkgeschwindigkeit gegeben. Die Hubwerksteuerung 11 öffnet hierbei das Magnetventil 29 und erzeugt ein Rampensignal 51, welches das Proportionalventil 31 stetig zunehmend öffnet. Die Absenkgeschwindigkeit wird durch den entsprechend dem Rampensignal sich vergrößernden Öffnungsquerschnitt des Proportionalventils 31 festgelegt. Die Nutzbrems-Umschaltstufe 25 ist unwirksam geschaltet. Sobald der von der Hubwerksteuerung 11 über den Sensor 17 ermittelte Ankerstrom der Gleichstrommaschine 9 ausreicht, um die auf dem Kolben 3 lastende Last durch das Bremsmoment des Generators zu halten, wird der Nutzbremsbetrieb über die NutzbremsUmschaltstufe 25 eingeschaltet und das Proportionalventil 31 vollständig geöffnet. In Fig. 2c wird der Umschaltstrom I₀ zum Zeitpunkt t₁ erreicht. Nach dem Wirksamschalten des Nutzbremsbetriebs wird die Drehzahl des Hydraulikmotors 7 über die Erregung der Gleichstrommaschine 9 auf den an der Bedienungsstufe 47 eingestellten Sollwert geregelt, wobei der Sollwert im Verlauf der Absenkgeschwindigkeit variiert werden kann, wie dies in Fig. 2c für den Zeitpunkt t₂ dargestellt ist. Die Hubwerksteuerung 11 erlaubt nicht nur einen ruckfreien Beginn des Lastabsenkbetriebs, sondern auch die ruckfreie Beendigung. Wird zum Zeitpunkt t₃ über die Bedienungsstufe 47 der Sollwert der Absenkgeschwindigkeit auf null gestellt, so wird zunächst die Absenkgeschwindigkeit durch elektrische Regelung der Gleichstrommaschine 9 bis auf einen Wert nahe dem Stillstand verringert. Die Hubwerksteuerung 11 erzeugt ein das Proportionalventil 31 stetig schließendes Rampensignal 53. Das Magnetventil 29 wird zum Zeitpunkt t₄ bei geschlossenem Proportionalventil 31 ebenfalls geschlossen.In load lifting operation, the solenoid valve 27 is open and the hydraulic fluid is pumped into the hydraulic cylinder 1 via the solenoid valve 27 and the check valves 35, 37. The lowering mode is controlled by the hoist control 11 controlled via the solenoid valve 29 and the normally closed proportional valve 31. FIG. 2a shows the time course of the control signal M29 output by the hoist control 11 to the solenoid valve 29. The time course of the control signal M31 output to the proportional valve 31 is shown in FIG. 2b. 2c shows the time profile of the excitation current I G of the sliding current machine 9 operating in generator mode. At time t₀, the command for lowering the load is given at operating level 47 at a predetermined lowering speed. The hoist control 11 opens the solenoid valve 29 and generates a ramp signal 51, which opens the proportional valve 31 steadily. The lowering speed is determined by the opening cross section of the proportional valve 31, which increases according to the ramp signal. The useful brake switching stage 25 is deactivated. As soon as the armature current of the direct current machine 9 determined by the hoist control 11 via the sensor 17 is sufficient to hold the load on the piston 3 by the braking torque of the generator, the useful brake operation is switched on via the useful brake switching stage 25 and the proportional valve 31 is completely opened. In Fig. 2c, the switching current I₀ is reached at time t₁. After the service brake mode has been activated, the speed of the hydraulic motor 7 is regulated via the excitation of the direct current machine 9 to the setpoint set at operating level 47, the setpoint being able to be varied in the course of the lowering speed, as shown in FIG. 2c for the time t 2 . The hoist control 11 not only allows a jerk-free start of the load lowering operation, but also the jerk-free termination. If the setpoint of the lowering speed is set to zero via the operating stage 47 at the time t 3, the lowering speed is first reduced by electrical control of the direct current machine 9 to a value close to standstill. The hoist control 11 generates a proportional valve 31 that closes continuously Ramp signal 53. The solenoid valve 29 is also closed at time t₄ when the proportional valve 31 is closed.

Fig. 3 zeigt ein bevorzugtes Ausführungsbeispiel einer Nutzbremsschaltung für eine Gleichstrom-Reihenschlußmaschine mit einem in Serie zu einer Feldwicklung 61 geschalteten Anker 63. Die Feldwicklung 61 ist über einen Thyristor 65 an den positiven Pol einer Batterie 67 angeschlossen. Der Anker 63 ist über einen dem Sensor 17 aus Fig. 1 entsprechenden Stromfühler 69, beispielsweise einen Nebenschlußwiderstand, an einen Steuerschalter 71 angeschlossen, der den Anker 63 mit dem negativen Pol der Batterie 67 verbindet. Eine Steuerschaltung 73, welche einen herkömmlichen Löschkreis für den Thyristor 65 umfaßt, steuert den Thyristor 65 im Zerhackerbetrieb und bestimmt die Impulsdauer und die Impulsperiode des durch die Feldwicklung 61 und den Anker 63 fließenden Stroms. Der mittels des Sensors 69 erfaßte Strom wird auf einem bei 75 vorgebbaren Sollwert gehalten. Bei 77 ist eine der Feldwicklung 61 parallel geschaltete Freilaufdiode dargestellt, wie sie für Thyristorlöschkreise herkömmlicher Bauart eingesetzt wird.3 shows a preferred exemplary embodiment of a useful brake circuit for a direct current series machine with an armature 63 connected in series with a field winding 61. The field winding 61 is connected via a thyristor 65 to the positive pole of a battery 67. The armature 63 is connected via a current sensor 69 corresponding to the sensor 17 from FIG. 1, for example a shunt resistor, to a control switch 71 which connects the armature 63 to the negative pole of the battery 67. A control circuit 73, which comprises a conventional quenching circuit for the thyristor 65, controls the thyristor 65 in chopper mode and determines the pulse duration and the pulse period of the current flowing through the field winding 61 and the armature 63. The current detected by the sensor 69 is kept at a setpoint which can be predetermined at 75. 77 shows a freewheeling diode connected in parallel with the field winding 61, as is used for conventional thyristor suppressor circuits.

Im Lasthebebetrieb ist der Schalter 71 geschlossen und der impulsförmige Motorstrom fließt über den Thyristor 65, die Feldwicklung 61, den Anker 63, den Sensor 69 und den Schalter 71.In load lifting operation, the switch 71 is closed and the pulsed motor current flows via the thyristor 65, the field winding 61, the armature 63, the sensor 69 and the switch 71.

Durch Öffnen des Schalters 71 wird eine Nutzbremsschaltung wirksam geschaltet. Die Nutzbremsschaltung umfaßt eine mit ihrer Kathode an den Pluspol der Batterie 67 und mit ihrer Anode über den Sensor 69 an den Anker 63 angeschlossene Diode 79. Die Diode 79 ist der Serienschaltung aus dem Thyristor 65, der Feldwicklung 61, dem Anker 63 und dem Sensor 69 parallel geschaltet. Die Anode der Diode 79 ist mit der Anode einer weiteren Diode 81 verbunden, deren Kathode über einen Widerstand 83 an den negativen Pol der Batterie 67 angeschlossen ist. Dem Widerstand 83 ist ein Kondensator 85 parallel geschaltet. Der Schalter 71 bildet einen Kurzschlußschalter zu der Serienschaltung aus der Diode 81 und dem Widerstand 83. Während im Lasthebebetrieb der Verbindungspunkt 87 über den geschlossenen Schalter 71 auf dem Potential des Minuspols der Batterie 67 gehalten wird, kann das Potential am Punkt 87 bei im Lastabsenkbetrieb geöffnetem Schalter 71 aufgrund der vom Anker 63 erzeugten Generatorspannung auf einen Wert steigen, dessen Potential größer ist als das Potential am Pluspol der Batterie 67. Die Diode 79 wird hierdurch leitend, und es fließt ein Ladestrom in die Batterie 67. Die Erregung der Feldwicklung 61 ist auch in diesem Betriebszustand über den Thyristor 65 steuerbar.A service brake circuit is activated by opening switch 71. The useful brake circuit comprises a diode 79 connected with its cathode to the positive pole of the battery 67 and with its anode via the sensor 69 to the armature 63. The diode 79 is the series circuit comprising the thyristor 65, the field winding 61, the armature 63 and the sensor 69 connected in parallel. The anode of the diode 79 is connected to the anode of a further diode 81, the cathode of which is connected via a resistor 83 to the negative pole of the battery 67. Resistor 83 is a Capacitor 85 connected in parallel. The switch 71 forms a short-circuit switch to the series circuit comprising the diode 81 and the resistor 83. While the connection point 87 is kept at the potential of the negative pole of the battery 67 via the closed switch 71 in the load-lifting mode, the potential at the point 87 can be opened when the load-lowering mode is in operation Due to the generator voltage generated by the armature 63, the switch 71 increases to a value whose potential is greater than the potential at the positive pole of the battery 67. The diode 79 thereby becomes conductive and a charging current flows into the battery 67. The field winding 61 is excited controllable via thyristor 65 even in this operating state.

Claims (5)

  1. Hydraulic lifting device for a battery-operated industrial truck, with a hydraulic lifting cylinder (1), with a hydraulic unit (7) operating as a pump during the lifting operation, supplying the lifting cylinder (1) with pressure medium, operating as a motor in the lowering operation and driven by the pressure medium expelled from the lifting cylinder (1), with a d.c.-machine (9) connected to the hydraulic unit (7), operating as an electric motor in the lifting operation and as a generator in the lowering operation, with a regenerative braking circuit (25; 79) supplied with power by the d.c.-machine (9) in the lowering operation, with a control valve arrangement (5) in the pressure medium line between the hydraulic cylinder (1) and the hydraulic unit (7) and with a lifting device control (11) controlling the regenerative braking circuit (25; 79) and the control valve arrangement (5), characterised in that the control valve arrangement (5) comprises a proportional valve (31), that the lifting device control (11) opens the proportional valve (31) corresponding to a ramp function in the lowering operation and depending on the output current of the d.c.-machine (9) operating as a generator, operates the regenerative braking circuit (25; 79), when the generator output current in this case exceeds a predetermined value and that the lifting device control (11) comprises a speed-regulating device (19, 39) influencing the excitation current of the d.c.-machine (9) operating as a generator, by means of which device (19, 39), the speed of the hydraulic unit (7) can be regulated to a predetermined reference value during the lowering operation.
  2. Hydraulic lifting device according to Claim 1, characterised in that the lifting device control (11) closes the proportional valve (31) corresponding to a ramp function, at the time of transition from the lowering operation to the stopping operation.
  3. Hydraulic lifting device according to Claim 1 or 2, characterised in that the control valve arrangement (5) comprises three non-return valves (33, 35, 37) connected in series with respect to each other between the lifting cylinder (1) and the hydraulic unit (7), whereof the first non-return valve (33) opens in the lowering flow direction of the pressure medium and the second (35) and the third non-return valve (37) open in the lifting flow direction of the pressure medium, that furthermore the control valve arrangement (5) comprises two normally closed solenoid valves (27, 29) to be opened by the lifting unit control (11), whereof the first solenoid valve (27) is in shunt with the first non-return valve (33) and is opened during the lifting operation and the second solenoid valve (29) is in shunt with the second non-return valve (35) and is opened during the lowering operation and that the proportional valve (31) is in shunt with the third non-return valve (37).
  4. Hydraulic lifting device according to one of Claims 1 to 3, characterised in that the hydraulic unit is constructed as a reversible geared motor (7) able to be operated as a pump.
  5. Hydraulic lifting device according to one of Claims 1 to 4, characterised in that the d.c.-machine is constructed as a series-wound motor (61, 63) able to be operated in generator operation.
EP87100211A 1986-01-28 1987-01-09 Hydraulic lifting device Expired - Lifetime EP0230884B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87100211T ATE94149T1 (en) 1986-01-28 1987-01-09 HYDRAULIC LIFT.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863602510 DE3602510A1 (en) 1986-01-28 1986-01-28 HYDRAULIC LIFTING
DE3602510 1986-01-28

Publications (3)

Publication Number Publication Date
EP0230884A2 EP0230884A2 (en) 1987-08-05
EP0230884A3 EP0230884A3 (en) 1990-05-16
EP0230884B1 true EP0230884B1 (en) 1993-09-08

Family

ID=6292792

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87100211A Expired - Lifetime EP0230884B1 (en) 1986-01-28 1987-01-09 Hydraulic lifting device

Country Status (4)

Country Link
US (1) US4723107A (en)
EP (1) EP0230884B1 (en)
AT (1) ATE94149T1 (en)
DE (2) DE3602510A1 (en)

Families Citing this family (44)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63230497A (en) * 1987-03-20 1988-09-26 日産自動車株式会社 Cargo gear for industrial car
SE461391B (en) * 1987-10-28 1990-02-12 Bt Ind Ab HYDRAULIC LIFTING DEVICE
US5117166A (en) * 1991-03-28 1992-05-26 General Electric Company Chopper circuit for dynamic braking in an electric power conversion system
IT1254284B (en) * 1992-03-13 1995-09-14 Guido Palleggi ELECTRIC TRACTION SYSTEM IN FORKLIFTS
DE4317782C2 (en) * 1993-05-28 1996-01-18 Jungheinrich Ag Hydraulic lifting device for battery-powered industrial trucks or the like
DE4333706C1 (en) * 1993-10-02 1995-04-13 Jungheinrich Ag Hydraulic lifting appliance for battery-operated industrial trucks
IT1269440B (en) * 1994-01-19 1997-04-01 Fita Om Carrelli Elevatori S P ELECTRIC MOTORIZED FORKLIFT
DE4402653C2 (en) * 1994-01-29 1997-01-30 Jungheinrich Ag Hydraulic lifting device for battery-powered industrial trucks
GB9422561D0 (en) * 1994-11-09 1995-01-04 Funnell Nicholas J Variable speed electro/hydraulic drive system for animal exercises
AU2070797A (en) * 1996-03-08 1997-09-22 P And S Bolcerek's, Incorporated Efficient energy recapture system
JP3220637B2 (en) * 1996-03-21 2001-10-22 日興電機工業株式会社 Hydraulic power unit device
IT1283752B1 (en) * 1996-04-19 1998-04-30 Fiat Om Carrelli Elevatori LIFTING AND LOWERING SYSTEM OF THE LOAD SUPPORT OF AN ELECTRIC FORKLIFT.
JPH101978A (en) * 1996-06-13 1998-01-06 Yutani Heavy Ind Ltd Battery-driven working machine
US6078855A (en) * 1996-06-19 2000-06-20 Kabushiki Kaisha Kobe Seiko Sho Battery-driven hydraulic excavator
IT1288416B1 (en) * 1996-09-13 1998-09-22 Fidimult Bv COMMAND AND CONTROL DEVICE, IN ENERGY RECOVERY, FOR THE DESCENT PHASE OF LIFTS OPERATING ELECTROHYDRAULIC OPERATION
JPH10152865A (en) * 1996-11-22 1998-06-09 Yutani Heavy Ind Ltd Battery driven working machine
DE19744429A1 (en) * 1997-10-08 1999-04-22 Still Wagner Gmbh & Co Kg Industrial truck with a load suspension device and method for lowering the load suspension device
JP3152200B2 (en) * 1998-02-06 2001-04-03 株式会社豊田自動織機製作所 Solenoid valve control device for industrial vehicles
US6064162A (en) * 1998-04-27 2000-05-16 Square D Company Circuit for automatic operation of a series brake upon power loss during a regenerative braking period
DE19844795A1 (en) * 1998-09-30 2000-04-13 Bosch Gmbh Robert Electro-hydraulic device for speed control of a hydraulic lifting cylinder
JP2000136806A (en) * 1998-11-04 2000-05-16 Komatsu Ltd Pressure oil energy recovery equipment and pressure oil energy recovery/regeneration equipment
JP3782251B2 (en) * 1999-03-31 2006-06-07 株式会社神戸製鋼所 Work machine with battery
JP2001220099A (en) * 2000-02-08 2001-08-14 Mitsubishi Heavy Ind Ltd Vehicle having traveling mechanism and cargo handling mechanism
DE10005779B4 (en) * 2000-02-10 2007-06-14 Robert Bosch Gmbh Method for improving the start-up behavior of a device during the transition from pump to motor operation
DE10010670C2 (en) * 2000-03-04 2003-11-06 Jungheinrich Ag Hydraulic lifting device for battery-operated industrial trucks
US6860068B2 (en) * 2001-06-26 2005-03-01 John J. Halloran Potential energy storage system
DE10342436B3 (en) * 2003-09-11 2005-03-17 Jungheinrich Ag Pump unit for manual fork lift truck has three-stage control valve with three no-return valves and switching valve
US8083499B1 (en) * 2003-12-01 2011-12-27 QuaLift Corporation Regenerative hydraulic lift system
US7249457B2 (en) * 2005-02-18 2007-07-31 Timberjack Inc. Hydraulic gravitational load energy recuperation
JP4727653B2 (en) * 2005-02-25 2011-07-20 三菱重工業株式会社 Cargo handling and regeneration method for battery-powered industrial vehicles and cargo handling and regeneration system
WO2006090709A1 (en) * 2005-02-25 2006-08-31 Mitsubishi Heavy Industries, Ltd. Load handling regeneration system for battery type industrial vehicle
NL1031744C2 (en) * 2006-05-03 2007-11-06 Stertil Bv Lifting system.
DE102006029623A1 (en) * 2006-06-28 2008-01-03 Robert Bosch Gmbh Electrohydraulic system, as well as apparatus and method for actuating such
US7980073B2 (en) * 2008-05-08 2011-07-19 Caterpillar Inc. Hybrid system for a powertrain and hydraulic system
US8362629B2 (en) * 2010-03-23 2013-01-29 Bucyrus International Inc. Energy management system for heavy equipment
DE102010021822B3 (en) * 2010-05-28 2011-07-21 Kapelski, Rainer, 24401 Completely autonomous lashing platform
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
CN102603060B (en) * 2011-01-21 2013-07-03 孙建 Aeration boat
US11305972B1 (en) * 2011-11-11 2022-04-19 Vehcile Service Group, Llc Vehicle lift with locally stored energy source
JP5352663B2 (en) * 2011-12-26 2013-11-27 株式会社豊田自動織機 Hydraulic control device for forklift
EP2844506B1 (en) * 2012-05-01 2021-03-31 Carrier Corporation Transport refrigeration system having electric fans
JP5835249B2 (en) * 2013-02-27 2015-12-24 株式会社豊田自動織機 Hydraulic control device for forklift
CN104141644B (en) * 2013-05-10 2017-12-15 博世力士乐（常州）有限公司 The power unit of hydraulic oil pumping unit and corresponding hydraulic oil pumping unit
US10800275B2 (en) * 2018-01-12 2020-10-13 Ford Global Technologies, Llc Hybrid vehicle system

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3512072A (en) * 1967-11-13 1970-05-12 Allis Chalmers Mfg Co Elevated load potential energy recovery in an electric truck
SE320471B (en) * 1969-03-31 1970-02-09 Asea Ab
US3947744A (en) * 1974-10-21 1976-03-30 Allis-Chalmers Corporation Electric truck having elevated load potential energy recovery with means to adjust rate of carriage descent
DE2724383A1 (en) * 1977-05-28 1978-11-30 Jungheinrich Kg Forklift truck hydraulic lift operating system - uses fluid released on lowering to drive generator for power recovery
JPS56122774A (en) * 1980-02-26 1981-09-26 Oirudoraibu Kogyo Kk Oil pressure elevator
DE3048999A1 (en) * 1980-12-24 1982-07-15 Robert Bosch Gmbh, 7000 Stuttgart CIRCUIT ARRANGEMENT FOR ENERGY RECOVERY IN CHOPPER-CONTROLLED SERIES
DE3104549C2 (en) * 1981-02-10 1986-07-10 Jungheinrich Unternehmensverwaltung Kg, 2000 Hamburg Lifting device

Also Published As

Publication number Publication date
EP0230884A3 (en) 1990-05-16
US4723107A (en) 1988-02-02
DE3787292D1 (en) 1993-10-14
ATE94149T1 (en) 1993-09-15
DE3602510C2 (en) 1989-03-02
DE3602510A1 (en) 1987-07-30
EP0230884A2 (en) 1987-08-05

Similar Documents

Publication Publication Date Title
EP0230884B1 (en) Hydraulic lifting device
DE4317782C2 (en) Hydraulic lifting device for battery-powered industrial trucks or the like
DE4402653C2 (en) Hydraulic lifting device for battery-powered industrial trucks
DE112010002887B4 (en) Control device for hybrid construction machine
DE4440420C2 (en) Method and device for monitoring and / or controlling the speed of an electric drive with frequency converter for hoists
EP1369598B2 (en) Electro-hydraulic lifting control device for industrial use vehicles
DE112007001092T5 (en) lifting system
EP1635070B1 (en) Electro-hydraulic control device
EP0908413B1 (en) Lift truck with a load grasping device
DE3836212A1 (en) METHOD AND DEVICE FOR IMPROVING THE PERFORMANCE OF A MOTOR-CONTROLLED HYDRAULIC ELEVATOR
EP0054614A1 (en) Circuit arrangement for energy regeneration of chopper-controlled series-wound motors
EP1312572B1 (en) Hydraulic elevator with pressure accumulator and control and regulation method for such an elevator
EP0251290B1 (en) Vehicle, especially a maintenance vehicle, with a hydraulic operating device and a hydraulic servo steering device
DE102014108370B4 (en) Hydraulic lifting device for a battery-operated industrial truck
DE4324464C2 (en) Hydraulic lifting device for battery-powered industrial trucks
EP1193211A2 (en) Hydraulic lifting device
DE3629089C3 (en) Forklifts, especially industrial forklifts, with mast
DE19921629A1 (en) Hydraulic lifting device
DE19947372B4 (en) Control circuit for a lifting device
DE2014605A1 (en) Lifting device for forklifts
DE8700431U1 (en) Hydraulic lifting gear
EP1044921A2 (en) Control device for a lifting apparatus, in particular a compact lifting apparatus
EP0184059A1 (en) Driving device for a switch
DE365919C (en) Electric winch, the drum of which is driven by means of a differential gear by two continuously running direct current motors
DE10049829A1 (en) lifting device

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE DE FR GB IT NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): AT BE DE FR GB IT NL SE

17P Request for examination filed

Effective date: 19900911

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: STEINBOCK BOSS GMBH

17Q First examination report despatched

Effective date: 19920507

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE DE FR GB IT NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19930908

Ref country code: NL

Effective date: 19930908

Ref country code: BE

Effective date: 19930908

REF Corresponds to:

Ref document number: 94149

Country of ref document: AT

Date of ref document: 19930915

Kind code of ref document: T

ITF It: translation for a ep patent filed
REF Corresponds to:

Ref document number: 3787292

Country of ref document: DE

Date of ref document: 19931014

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)

Effective date: 19930924

EN Fr: translation not filed
NLV1 Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act
EN Fr: translation not filed

Free format text: BO 94/04 PAGE 197: ANNULATION

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20031027

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 20040102

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20040105

Year of fee payment: 18

REG Reference to a national code

Ref country code: FR

Ref legal event code: CD

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050109

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050109

Ref country code: AT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050109

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20050109

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050930

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20060215

Year of fee payment: 20