EP2937307B9 - Hydraulic drive system of an industrial truck - Google Patents

Hydraulic drive system of an industrial truck Download PDF

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Publication number
EP2937307B9
EP2937307B9 EP15163350.0A EP15163350A EP2937307B9 EP 2937307 B9 EP2937307 B9 EP 2937307B9 EP 15163350 A EP15163350 A EP 15163350A EP 2937307 B9 EP2937307 B9 EP 2937307B9
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EP
European Patent Office
Prior art keywords
drive
variable displacement
power
displacement pump
lifting
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EP15163350.0A
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German (de)
French (fr)
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EP2937307B1 (en
EP2937307A1 (en
Inventor
Markus Schwab
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STILL GmbH
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STILL GmbH
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Publication of EP2937307B1 publication Critical patent/EP2937307B1/en
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    • 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

Definitions

  • the invention relates to a hydraulic drive system of a truck, wherein the drive system has a working hydraulics comprising a lifting drive and at least one power take-off, wherein for supplying the lifting drive and the at least one power take-off, a variable in the delivery volume variable displacement pump is provided, which is for driving with an internal combustion engine in Active connection is, wherein the installed hydraulic power of the variable displacement pump is greater than the rated power of the internal combustion engine, wherein the variable displacement pump for adjusting the delivery volume has an adjusting device which is provided with a power limiting device.
  • variable displacement in the variable displacement pump With a pressure regulator and a flow regulator, which are referred to as load-sensing variable displacement pumps.
  • the maximum drive torque to be transmitted to the variable displacement pump by the internal combustion engine is limited by constructional conditions, for example by a clutch arranged between the internal combustion engine and the variable displacement pump or a power takeoff of the internal combustion engine driving the variable displacement pump.
  • the maximum drive torque to be transmitted corresponds to the product of the maximum delivery volume, ie the displacement per revolution, and the maximum system pressure of the variable displacement pump.
  • the maximum system pressure is usually hedged in such drive systems by means of a pressure relief valve.
  • the effect occurs that at cold pressure medium temperatures, for example, after the start of operation of the truck in cold ambient conditions, a lifting operation of the linear actuator with maximum system pressure and maximum delivery occurs.
  • the maximum delivery volume of the variable displacement pump is thus to be interpreted and limited based on the maximum drive torque to be transmitted and the maximum system pressure.
  • the pressure required to lift a load is approx. 15% up to 85% below the maximum system pressure protected by the pressure relief valve. It is disadvantageous that about 15% to 85% of the maximum available drive torque can not be used in the form of delivery volume of the variable.
  • due to the limited displacement of the variable displacement of the engine when lifting a load by means of the lifting drive of the engine must be operated at a high speed to compensate for the limited displacement of the variable.
  • the DE 10 2008 059 181 A1 discloses a generic hydraulic drive system of a truck according to the preamble of claim 1.
  • the present invention is based on the object to provide a hydraulic drive system of the type mentioned with an oversized in the delivery volume variable displacement available, in which the adjustment of the delivery volume of the variable is carried out in a simple manner.
  • the power limiting device of the adjusting device is set such that from a predetermined limit of the lifting drive pending load to be lifted, the power limit of the power limiting device is effective and that an electronic control device is provided, the input side with a recorded load of Hubantriebs detecting sensor device is operatively connected and the output side is in operative connection with a speed setting device of the internal combustion engine, wherein the electronic control device is designed such that above the limit value of the lifting drive to be lifted load the speed of the internal combustion engine is raised to achieve a predetermined lifting speed.
  • a sensor device In conjunction with a sensor device can be determined by an electronic control device in a simple manner, the achievement of the limit of the lifting drive pending load to be lifted, in which the power limit by reducing the delivery volume of the variable starts.
  • the power limiting the variable displacement pump can thus be raised by the electronic control device in a simple way, the speed of the engine to compensate for the reduced displacement of the variable by a speed increase of the engine and to achieve a constant stroke speed over all loads from zero to maximum load.
  • the power limiting device is designed as a power regulator, which changes the delivery volume of the variable displacement pump in dependence on the system pressure of the drive system such that the drive torque of the variable displacement pump is constant.
  • a performance regulator which controls the delivery volume and thus the delivery flow of the variable in dependence on the system pressure so that the product of flow and pressure is kept constant, a power limitation and thus a torque limiter can be achieved in a simple manner.
  • the sensor device is designed as a pressure sensor of the lifting drive detecting pressure sensor.
  • a pressure sensor of the lifting drive detecting pressure sensor can be determined with low construction costs, the load.
  • the adjusting device of the pump further comprises a pressure regulator and a flow regulator.
  • a pressure regulator can be easily achieved a pressure cut.
  • a flow regulator such as a load-sensing controller, allows easy adjustment of the delivery volume to the load.
  • FIG. 1 is a circuit diagram of a hydraulic drive system 1 of the invention illustrated an industrial truck.
  • the drive system 1 has a working hydraulics 2, which comprises a lifting drive 3 and at least one auxiliary drive 4, 5, 6.
  • the lifting drive 3 comprises at least one hydraulic lifting cylinder, which is in communication with a non-illustrated load-receiving means of the truck for lifting and lowering a load L.
  • the working hydraulics 2 comprises, in addition to the lifting drive 3, at least one auxiliary drive 4, 5, for example a tilt drive of a mast and / or a side slide drive for the load receiving means.
  • Another power take-off 6 is formed by a fan drive, such as a hydraulic motor driving a fan, a cooling system 7.
  • the lifting drive 3 and the secondary consumers 4, 5 are controllable by means of control valves, for example, in intermediate positions throttling directional control valves, which are combined in a control valve block 8.
  • a control valve 10 for controlling the lowering movement and the lifting movement of the lifting drive 2 is shown.
  • a control valve 12, 13 is arranged in the control valve block 8 respectively.
  • a control valve 14 may also be provided, which is also preferably arranged in the control valve block 8.
  • variable in the delivery volume adjustment pump 15 is provided which is operatively connected to the drive with an internal combustion engine 16.
  • the variable displacement pump 15 is operated in the open circuit, the pressure medium by means of a suction line 17 from a container 18 sucks and promotes in a feed line 19 which is guided to the control valve block 8 and to the control valves 10-14 of the consumers are connected. From the control valve block 8, a return line 21 leads to the container 18.
  • the cooling system 7 can be used for cooling the internal combustion engine 16 and / or for cooling the pressure medium of the working hydraulics 2.
  • the variable displacement pump 15 has an adjusting device 25 for setting the delivery volume, which is in operative connection with a delivery volume adjusting device 26 of the variable displacement pump 15.
  • the variable displacement pump 15 may be formed as an axial piston machine in swash plate design, in which the winningvolumeneinstellvorides 26 is formed as adjustable in inclination swash plate.
  • the adjusting device 25 of the variable displacement pump 15 has a pressure regulator 30 and a flow regulator 31.
  • the pressure regulator 30 is designed such that the delivery volume of the variable displacement pump 15 is limited or reduced upon reaching a set delivery pressure, so that the pressure regulator 30 limits the maximum delivery pressure of the variable displacement pump.
  • the flow rate controller 31 is configured such that the Delivery volume of the variable displacement pump is controlled in response to the highest load pressure of the driven load, so that the variable displacement pump 15 supplies the requested by the driven loads flow in the delivery line 19 as needed.
  • the adjusting device 25 of the variable displacement pump 15 further comprises a power limiting device 32.
  • the power limiting device 32 is designed as a power controller 33, which is designed such that in dependence on the in the delivery line 19 pending delivery pressure of the variable displacement pump 15 and thus the system pressure of the drive system 1, the delivery volume of the variable displacement pump 15 is controlled such that the drive torque, the corresponds to the product of the delivery volume and the delivery pressure of the variable displacement pump 15, the variable displacement pump 15 is constant.
  • the power limiting device 32 of the adjusting device 25 is set such that, starting from a predetermined limit value of the load L to be lifted on the lifting drive 3, the power limitation and thus the torque limitation of the power limiting device 32 becomes effective.
  • an electronic control device 35 is provided, which is on the input side with a recorded load L of the linear actuator 3 sensing sensor device 36 in operative connection and the output side is in operative connection with a speed control device 37 of the engine 16.
  • the electronic control device 35 is designed such that, above the limit value of the load L to be lifted on the lifting drive 3, the rotational speed of the internal combustion engine 15 is raised in order to achieve a predetermined lifting speed.
  • the sensor device 36 is preferably designed as a pressure sensor 38 detecting the pressure of the lifting drive 3.
  • variable displacement pump 15 with a power limiting device 32 makes it possible for the installed hydraulic power of the variable displacement pump 15 to be greater than Perform rated power of the engine 15, ie over-variable the variable displacement 15.
  • the nominal power of the internal combustion engine 16 adjusts itself at the nominal rotational speed of the internal combustion engine 16.
  • the installed hydraulic power of the variable displacement pump 15 results arithmetically from the product of the maximum delivery flow (delivery volume multiplied by the rated speed) and the maximum system pressure. This makes it possible to select the maximum delivery volume of the variable displacement pump 16 such that at rated speed of the engine 16 of the mathematically calculated from the product of the maximum delivery volume and the nominal speed flow of the variable displacement pump 16 exceeds the maximum required in the working hydraulics 2 flow rate.
  • the over-dimensioned in the maximum delivery volume and oversize variable displacement pump 16 can thus be used to reduce when operating the load of the working hydraulics 2, the speed of the engine 16 relative to the rated speed to save fuel and to achieve a reduced noise level.
  • FIG. 2 is shown by diagrams, the power limit and thus the torque limit of the invention power-limited and oversized in the maximum displacement variable pump 15.
  • the delivery volume Q of the variable displacement pump 15 is shown on the abscissa and the system pressure p is shown on the ordinate.
  • the maximum possible delivery volume Q 1max of the variable displacement pump 15 at a system pressure p 1 for a maximum allowable drive torque M is calculated from the product of the pressure p 1 and the delivery volume Q 1max .
  • the power-controlled variable displacement pump 15 thus makes it possible to increase the delivery volume Q at a low system pressure p - as in the US Pat FIG. 2 is illustrated by the arrows 40, 41 - to take advantage of the maximum permissible drive torque.
  • FIG. 3 is based on a diagram, the speed of the engine 16 with the inventive power-limited and oversized in the maximum flow volume variable displacement pump 15 via the load L of the lifting drive 3 for different constant lifting speeds of the lifting drive 3 shown.
  • the line 50 shows a curve of the speed n of the internal combustion engine 16 using a variable displacement pump of the prior art with a pressure regulator and a delivery rate controller for a constant first stroke speed. To achieve the constant first lifting speed of the engine 16 is to operate at the rated speed n nominal .
  • the line 51 shows a profile of the rotational speed of the internal combustion engine 16 using a power-limited variable displacement pump 15 according to the invention which is oversized in the maximum delivery volume for a constant second lifting speed which is greater than the first stroke speed.
  • a power-limited variable displacement pump 15 which is oversized in the maximum delivery volume for a constant second lifting speed which is greater than the first stroke speed.
  • the line 52 shows a profile of the rotational speed of the internal combustion engine 16 using a power-limited according to the invention and in the maximum delivery volume oversized variable displacement pump 15 for a constant third stroke speed, which is greater than the second stroke speed.
  • the line 53 shows a profile of the rotational speed of the internal combustion engine 16 using a power-limited according to the invention and in the maximum delivery volume oversized variable displacement pump 15 for a constant fourth stroke speed, which is greater than the third stroke speed.
  • the engine 16 is to be operated at the speed n 3 , which is higher than the speed n 2 and lower than the rated speed n nominal .
  • the increase in the rotational speed of the internal combustion engine 16 is effected by means of the electronic control device 35, which determines the reaching of the limit value L limit of the load L on the basis of the sensor device 36 and controls the speed setting device 37 of the internal combustion engine 16 accordingly.
  • variable displacement pump 15 With the power-limited and thus torque-limited variable displacement pump 15 according to the invention, it is also possible to oversize the variable displacement pump 15 so that increased lifting speeds and thus increased handling capacity of the industrial truck are achieved.
  • oversized and in the delivery volume oversized variable displacement pump 15 it is also possible to compensate for a parallel operation of the lifting drive 3 in lifting operation and a PTO 4-6, for example, the fan drive, the power losses, so that a reduction in the lifting speed by the requested performance the auxiliary drive can be avoided.

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Civil Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
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Description

Die Erfindung betrifft ein hydraulisches Antriebssystem eines Flurförderzeugs, wobei das Antriebsystem eine Arbeitshydraulik aufweist, die einen Hubantrieb und zumindest einem Nebenantrieb umfasst, wobei zur Versorgung des Hubantriebs und des zumindest einen Nebenantriebs eine im Fördervolumen verstellbare Verstellpumpe vorgesehen ist, die zum Antrieb mit einem Verbrennungsmotor in Wirkverbindung steht, wobei die installierte hydraulische Leistung der Verstellpumpe größer als die Nennleistung des Verbrennungsmotors ist, wobei die Verstellpumpe zur Einstellung des Fördervolumens eine Stelleinrichtung aufweist, die mit einer Leistungsbegrenzungseinrichtung versehen ist.The invention relates to a hydraulic drive system of a truck, wherein the drive system has a working hydraulics comprising a lifting drive and at least one power take-off, wherein for supplying the lifting drive and the at least one power take-off, a variable in the delivery volume variable displacement pump is provided, which is for driving with an internal combustion engine in Active connection is, wherein the installed hydraulic power of the variable displacement pump is greater than the rated power of the internal combustion engine, wherein the variable displacement pump for adjusting the delivery volume has an adjusting device which is provided with a power limiting device.

Zur Versorgung der Arbeitshydraulik von Flurförderzeugen, beispielsweise Gabelstaplern, ist es bereits bekannt, eine im Fördervolumen verstellbare Verstellpumpe mit einem Druckregler und einem Förderstromregler einzusetzen, die als Load-Sensing-geregelte Verstellpumpen bezeichnet werden. Das an die Verstellpumpe von dem Verbrennungsmotor zu übertragende maximal Antriebsdrehmoment ist durch bauliche Gegebenheiten begrenzt, beispielsweise durch eine zwischen dem Verbrennungsmotor und der Verstellpumpe angeordnete Kupplung oder einen die Verstellpumpe antreibenden Nebenabtrieb des Verbrennungsmotors. Das zu übertragende maximale Antriebsdrehmoment entspricht dem Produkt aus dem maximalen Fördervolumen, d.h. der Verdrängermenge pro Umdrehung, und dem maximalen Systemdruck der Verstellpumpe. Der maximale Systemdruck wird in der Regel bei derartigen Antriebssystemen mittels eines Druckbegrenzungsventils abgesichert. Bei einem Flurförderzeugen tritt der Effekt auf, dass bei kalten Druckmitteltemperaturen, beispielsweise nach dem Betriebsstart des Flurförderzeugs bei kalten Umgebungsbedingungen, ein Hebenbetrieb des Hubantriebs mit maximalem Systemdruck und maximalem Fördervolumen erfolgt. Das maximale Fördervolumen der Verstellpumpe ist somit anhand des maximal zu übertragenden Antriebsdrehmoments und des maximalen Systemdruckes auszulegen und zu begrenzen. Im betriebswarmen Zustand mit aufgewärmtem Druckmittel bzw. bei Teillast des Hubantriebs liegt der zum Heben einer Last erforderliche Druck ca. 15% bis 85% unterhalb des von dem Druckbegrenzungsventil abgesicherten maximalen Systemdrucks. Hierbei ist nachteilig, dass ca. 15% bis 85% des maximal zur Verfügung stehenden Antriebsdrehmomentes nicht in Form von Fördervolumen der Verstellpumpe genutzt werden. Als Folge hiervon ergibt sich, dass aufgrund des begrenzten Fördervolumens der Verstellpumpe der Verbrennungsmotor beim Heben einer Last mittels des Hubantriebs der Verbrennungsmotor mit einer hohen Drehzahl betrieben werden muss, um das begrenzte Fördervolumen der Verstellpumpe zu kompensieren.To supply the working hydraulics of industrial trucks, such as forklifts, it is already known to use a variable displacement in the variable displacement pump with a pressure regulator and a flow regulator, which are referred to as load-sensing variable displacement pumps. The maximum drive torque to be transmitted to the variable displacement pump by the internal combustion engine is limited by constructional conditions, for example by a clutch arranged between the internal combustion engine and the variable displacement pump or a power takeoff of the internal combustion engine driving the variable displacement pump. The maximum drive torque to be transmitted corresponds to the product of the maximum delivery volume, ie the displacement per revolution, and the maximum system pressure of the variable displacement pump. The maximum system pressure is usually hedged in such drive systems by means of a pressure relief valve. In an industrial truck, the effect occurs that at cold pressure medium temperatures, for example, after the start of operation of the truck in cold ambient conditions, a lifting operation of the linear actuator with maximum system pressure and maximum delivery occurs. The maximum delivery volume of the variable displacement pump is thus to be interpreted and limited based on the maximum drive torque to be transmitted and the maximum system pressure. In the warm operating condition with warmed-up pressure medium or at partial load of the linear actuator the pressure required to lift a load is approx. 15% up to 85% below the maximum system pressure protected by the pressure relief valve. It is disadvantageous that about 15% to 85% of the maximum available drive torque can not be used in the form of delivery volume of the variable. As a result, it follows that due to the limited displacement of the variable displacement of the engine when lifting a load by means of the lifting drive of the engine must be operated at a high speed to compensate for the limited displacement of the variable.

Um diese Nachteile zu vermeiden, ist es bereits aus der DE 10 2007 035 341 A1 bekannt, eine überdimensionierte Verstellpumpe einzusetzen, deren installierte hydraulische Leistung größer als die Nennleistung des Verbrennungsmotors ist. Die überdimensionierte Verstellpumpe ist somit im Fördervolumen übergroß ausgeführt. Bei Verwendung einer überdimensionierten Verstellpumpe ist es erforderlich, bei einem Anstieg des Leistungsbedarfs das Fördervolumen der Verstellpumpe zu verringern.To avoid these disadvantages, it is already out of the DE 10 2007 035 341 A1 known to use an oversized variable displacement whose installed hydraulic power is greater than the rated power of the engine. The oversized variable displacement pump is thus carried out oversized in the delivery volume. When using an oversized variable displacement pump, it is necessary to reduce the delivery volume of the variable with an increase in power consumption.

Die DE 10 2008 059 181 A1 offenbart ein gattungsgemäßes hydraulisches Antriebssystem eines Flurförderzeugs gemäß dem Oberbegriff des Anspruchs 1.The DE 10 2008 059 181 A1 discloses a generic hydraulic drive system of a truck according to the preamble of claim 1.

Der vorliegenden Erfindung liegt die Aufgabe zu Grunde, ein hydraulisches Antriebssystem der eingangs genannten Gattung mit einer im Fördervolumen übergroßen Verstellpumpe zu Verfügung zu stellen, bei dem die Anpassung des Fördervolumens der Verstellpumpe auf einfache Weise erfolgt.The present invention is based on the object to provide a hydraulic drive system of the type mentioned with an oversized in the delivery volume variable displacement available, in which the adjustment of the delivery volume of the variable is carried out in a simple manner.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, dass die Leistungsbegrenzungseinrichtung der Stelleinrichtung derart eingestellt ist, dass ab einem vorgegebenen Grenzwert der am Hubantrieb anstehenden anzuhebenden Last die Leistungsbegrenzung der Leistungsbegrenzungseinrichtung wirksam wird und dass eine elektronische Steuereinrichtung vorgesehen ist, die eingangsseitig mit einer die aufgenommene Last der Hubantriebs erfassenden Sensoreinrichtung in Wirkverbindung steht und ausgangsseitig mit einer Drehzahlstelleinrichtung des Verbrennungsmotors in Wirkverbindung steht, wobei die elektronische Steuereinrichtung derart ausgebildet ist, dass oberhalb des Grenzwerts der am Hubantrieb anstehenden anzuhebenden Last die Drehzahl des Verbrennungsmotors angehoben wird, um eine vorgegebene Hubgeschwindigkeit zu erzielen. Mit einer überdimensionierten und im Fördervolumen übergroßen Verstellpumpe, deren Stelleinrichtung eine Leistungsbegrenzungseinrichtung aufweist, kann mit geringem Bauaufwand erzielt werden, dass im Hebenbetrieb des Hubantriebs eine Drehzahlreduzierung des Verbrennungsmotors bei gleichzeitig erhöhter Hebengeschwindigkeit realisiert werden kann. Hierdurch ist eine Erhöhung der Umschlagsleistung des Flurförderzeugs bei verringerter Drehzahl des Verbrennungsmotors und somit bei verringertem Kraftstoffverbrauch und verringertem Geräuschniveau möglich. Die Anpassung des Fördervolumens der Verstellpumpe an den Leistungsbedarf und somit die Begrenzung der Leistung der Verstellpumpe erfolgt hierbei von der Verstellpumpe selbst mittels der Leistungsbegrenzungseinrichtung. Die Leistungsbegrenzung durch Reduzierung des Fördervolumens der Verstellpumpe setzt somit ab dem vorgegebenen Grenzwert der am Hubantrieb anzuhebenden Last ein. In Verbindung mit einer Sensoreinrichtung kann von einer elektronischen Steuereinrichtung auf einfache Weise das Erreichen des Grenzwertes der am Hubantrieb anstehenden anzuhebenden Last ermittelt werden, bei dem die Leistungsbegrenzung durch Reduzierung des Fördervolumens der Verstellpumpe einsetzt. Bei einsetzender Leistungsbegrenzung der Verstellpumpe kann somit von der elektronischen Steuereinrichtung auf einfache Weise die Drehzahl des Verbrennungsmotors angehoben werden, um das reduzierte Fördervolumen der Verstellpumpe durch eine Drehzahlanhebung des Verbrennungsmotors zu kompensieren und über alle Lasten von Null bis zur Maximallast eine gleichbleibende Hubgeschwindigkeit zu erzielen.This object is achieved in that the power limiting device of the adjusting device is set such that from a predetermined limit of the lifting drive pending load to be lifted, the power limit of the power limiting device is effective and that an electronic control device is provided, the input side with a recorded load of Hubantriebs detecting sensor device is operatively connected and the output side is in operative connection with a speed setting device of the internal combustion engine, wherein the electronic control device is designed such that above the limit value of the lifting drive to be lifted load the speed of the internal combustion engine is raised to achieve a predetermined lifting speed. With an oversized and in the delivery volume oversized variable, whose actuator has a power limiting device can be achieved with low construction costs, that in the lifting operation of the linear actuator speed reduction of the engine can be realized at the same time increased lifting speed. As a result, an increase in the handling capacity of the truck at a reduced speed of the internal combustion engine and thus with reduced fuel consumption and reduced noise level is possible. The adaptation of the delivery volume of the variable displacement pump to the power requirement and thus the limitation of the power of the variable displacement takes place here by the variable displacement pump itself by means of the power limiting device. The power limitation by reducing the delivery volume of the variable displacement thus starts from the predetermined limit of the load to be lifted on the lifting drive. In conjunction with a sensor device can be determined by an electronic control device in a simple manner, the achievement of the limit of the lifting drive pending load to be lifted, in which the power limit by reducing the delivery volume of the variable starts. With the power limiting the variable displacement pump can thus be raised by the electronic control device in a simple way, the speed of the engine to compensate for the reduced displacement of the variable by a speed increase of the engine and to achieve a constant stroke speed over all loads from zero to maximum load.

Vorteilhafterweise ist die Leistungsbegrenzungseinrichtung als Leistungsregler ausgebildet, der in Abhängigkeit von dem Systemdruck des Antriebssystems das Fördervolumen der Verstellpumpe derart verändert, dass das Antriebsdrehmoment der Verstellpumpe konstant ist. Mit einem derartigen Leistungsregler, der in Abhängigkeit vom Systemdruck das Fördervolumen und somit den Förderstrom der Verstellpumpe derart steuert, dass das Produkt aus Förderstrom und Druck konstant gehalten wird, kann auf einfache Weise eine Leistungsbegrenzung und somit eine Drehmomentbegrenzung erzielt werden. Weiterhin wird ermöglicht, mit einer überdimensionierten Verstellpumpe im Teillastbereich das maximal zu übertragenden Antriebsdrehmoment auszunutzen, um eine erhöhte Hubgeschwindigkeit bei gleichzeitig verringerter Drehzahl des Verbrennungsmotors zu erzielen.Advantageously, the power limiting device is designed as a power regulator, which changes the delivery volume of the variable displacement pump in dependence on the system pressure of the drive system such that the drive torque of the variable displacement pump is constant. With such a performance regulator, which controls the delivery volume and thus the delivery flow of the variable in dependence on the system pressure so that the product of flow and pressure is kept constant, a power limitation and thus a torque limiter can be achieved in a simple manner. Furthermore, it is possible to use the maximum drive torque to be transmitted with an oversized variable displacement pump in the partial load range in order to achieve an increased lifting speed while simultaneously reducing the rotational speed of the internal combustion engine.

Zweckmäßigerweise ist die Sensoreinrichtung als ein den Druck des Hubantriebs erfassender Drucksensor ausgebildet. Mit einem den Druck des Hubantriebs erfassenden Drucksensor kann mit geringem Bauaufwand die Last ermittelt werden.Conveniently, the sensor device is designed as a pressure sensor of the lifting drive detecting pressure sensor. With a pressure sensor of the lifting drive detecting pressure sensor can be determined with low construction costs, the load.

Gemäß einer zweckmäßigen Weiterbildung der Erfindung umfasst die Stelleinrichtung der Pumpe weiterhin einen Druckregler und einen Förderstromregler. Mit dem Druckregler kann auf einfache Weise eine Druckabschneidung erzielt werden. Ein Förderstromregler, beispielsweise ein Load-Sensing-Regler, ermöglicht auf einfache Weise eine Anpassung des Fördervolumens an die Last.According to an expedient development of the invention, the adjusting device of the pump further comprises a pressure regulator and a flow regulator. With the pressure regulator can be easily achieved a pressure cut. A flow regulator, such as a load-sensing controller, allows easy adjustment of the delivery volume to the load.

Weitere Vorteile und Einzelheiten der Erfindung werden anhand des in den schematischen Figuren dargestellten Ausführungsbeispiels näher erläutert. Hierbei zeigt

Figur 1
den Schaltplan eines erfindungsgemäßen hydraulischen Antriebssystems,
Figur 2
ein Diagramm des Fördervolumens über den Druck einer leistungsbegrenzten Verstellpumpe des erfindungsgemäßen Antriebssystems und
Figur 3
ein Diagramm der Drehzahl des Verbrennungsmotors über die Last des Hubantriebs eines erfindungsgemäßen Antriebssystems.
Further advantages and details of the invention will be explained in more detail with reference to the embodiment shown in the schematic figures. This shows
FIG. 1
the circuit diagram of a hydraulic drive system according to the invention,
FIG. 2
a diagram of the delivery volume on the pressure of a power-limited variable displacement pump of the drive system according to the invention and
FIG. 3
a diagram of the speed of the internal combustion engine via the load of the linear actuator of a drive system according to the invention.

In der Figur 1 ist ein Schaltplan eines erfindungsgemäßen hydraulischen Antriebssystems 1 eines Flurförderzeugs dargestellt.In the FIG. 1 is a circuit diagram of a hydraulic drive system 1 of the invention illustrated an industrial truck.

Das Antriebssystem 1 weist eine Arbeitshydraulik 2 auf, die einen Hubantrieb 3 und zumindest einen Nebenantrieb 4, 5, 6 umfasst. Der Hubantrieb 3 umfasst zumindest einen hydraulischen Hubzylinder, der mit einem nicht näher dargestellten Lastaufnahmemittel der Flurförderzeugs zum Heben und Senken einer Last L in Verbindung steht.The drive system 1 has a working hydraulics 2, which comprises a lifting drive 3 and at least one auxiliary drive 4, 5, 6. The lifting drive 3 comprises at least one hydraulic lifting cylinder, which is in communication with a non-illustrated load-receiving means of the truck for lifting and lowering a load L.

Die Arbeitshydraulik 2 umfasst neben dem Hubantrieb 3 noch mindestens einen Nebenantrieb 4, 5, beispielsweise einen Neigeantrieb eines Hubgerüstes und/oder einen Seitenschieberantrieb für das Lastaufnahmemittel. Ein weiterer Nebenantrieb 6 ist von einem Lüfterantrieb, beispielsweise einem eine Lüfterrad antreibenden Hydraulikmotor, eines Kühlsystems 7 gebildet.The working hydraulics 2 comprises, in addition to the lifting drive 3, at least one auxiliary drive 4, 5, for example a tilt drive of a mast and / or a side slide drive for the load receiving means. Another power take-off 6 is formed by a fan drive, such as a hydraulic motor driving a fan, a cooling system 7.

Der Hubantrieb 3 und die Nebenverbraucher 4, 5 sind mittels Steuerventilen, beispielsweise in Zwischenstellungen drosselnden Wegeventilen, steuerbar, die in einem Steuerventilblock 8 zusammengefasst sind. In dem dargestellten Ausführungsbeispiel ist ein Steuerventil 10 zur Steuerung der Senkenbewegung und der Hebenbewegung des Hubantriebs 2 dargestellt. Zur Steuerung der Nebenverbraucher 4, 5 ist jeweils ein Steuerventil 12, 13 in dem Steuerventilblock 8 angeordnet. Zur Steuerung des Lüfterantriebs 6 kann ebenfalls ein Steuerventil 14 vorgesehen sein, das ebenfalls bevorzugt in dem Steuerventilblock 8 angeordnet ist.The lifting drive 3 and the secondary consumers 4, 5 are controllable by means of control valves, for example, in intermediate positions throttling directional control valves, which are combined in a control valve block 8. In the illustrated embodiment, a control valve 10 for controlling the lowering movement and the lifting movement of the lifting drive 2 is shown. For controlling the secondary consumers 4, 5, a control valve 12, 13 is arranged in the control valve block 8 respectively. To control the fan drive 6, a control valve 14 may also be provided, which is also preferably arranged in the control valve block 8.

Zur Versorgung der Arbeitshydraulik 2 ist eine im Fördervolumen einstellbare Verstellpumpe 15 vorgesehen, die zum Antrieb mit einem Verbrennungsmotor 16 in Wirkverbindung steht. Die Verstellpumpe 15 ist im offenen Kreislauf betrieben, die Druckmittel mittels einer Ansaugleitung 17 aus einem Behälter 18 ansaugt und in eine Förderleitung 19 fördert, die zu dem Steuerventilblock 8 geführt ist und an die Steuerventile 10-14 der Verbraucher angeschlossen sind. Von dem Steuerventilblock 8 führt eine Rücklaufleitung 21 zu dem Behälter 18.To supply the working hydraulics 2, a variable in the delivery volume adjustment pump 15 is provided which is operatively connected to the drive with an internal combustion engine 16. The variable displacement pump 15 is operated in the open circuit, the pressure medium by means of a suction line 17 from a container 18 sucks and promotes in a feed line 19 which is guided to the control valve block 8 and to the control valves 10-14 of the consumers are connected. From the control valve block 8, a return line 21 leads to the container 18.

Das Kühlsystem 7 kann zur Kühlung des Verbrennungsmotors 16 und/oder zur Kühlung des Druckmittels der Arbeitshydraulik 2 dienen.The cooling system 7 can be used for cooling the internal combustion engine 16 and / or for cooling the pressure medium of the working hydraulics 2.

Die Verstellpumpe 15 weist zur Einstellung des Fördervolumens eine Stelleinrichtung 25 auf, die mit einer Fördervolumeneinstellvorrichtung 26 der Verstellpumpe 15 in Wirkverbindung steht. Die Verstellpumpe 15 kann als Axialkolbenmaschine in Schrägscheibenbauweise ausgebildet sein, bei der die Fördervolumeneinstellvorrichtung 26 als in der Neigung verstellbare Schrägscheibe ausgebildet ist.The variable displacement pump 15 has an adjusting device 25 for setting the delivery volume, which is in operative connection with a delivery volume adjusting device 26 of the variable displacement pump 15. The variable displacement pump 15 may be formed as an axial piston machine in swash plate design, in which the Fördervolumeneinstellvorrichtung 26 is formed as adjustable in inclination swash plate.

Die Stelleinrichtung 25 der Verstellpumpe 15 weist einen Druckregler 30 und einen Förderstromregler 31 auf. Der Druckregler 30 ist derart ausgeführt, dass das Fördervolumen der Verstellpumpe 15 bei Erreichen eines eingestellten Förderdrucks begrenzt bzw. verringert wird, so dass der Druckregler 30 den maximalen Förderdruck der Verstellpumpe begrenzt. Der Förderstromregler 31 ist derart ausgeführt, dass das Fördervolumen der Verstellpumpe in Abhängigkeit von dem höchsten Lastdruck der angesteuerten Verbraucher gesteuert ist, so dass die Verstellpumpe 15 bedarfsgerecht den von den angesteuerten Verbrauchern angeforderten Förderstrom in der Förderleitung 19 liefert.The adjusting device 25 of the variable displacement pump 15 has a pressure regulator 30 and a flow regulator 31. The pressure regulator 30 is designed such that the delivery volume of the variable displacement pump 15 is limited or reduced upon reaching a set delivery pressure, so that the pressure regulator 30 limits the maximum delivery pressure of the variable displacement pump. The flow rate controller 31 is configured such that the Delivery volume of the variable displacement pump is controlled in response to the highest load pressure of the driven load, so that the variable displacement pump 15 supplies the requested by the driven loads flow in the delivery line 19 as needed.

Erfindungsgemäß umfasst die Stelleinrichtung 25 der Verstellpumpe 15 weiterhin eine Leistungsbegrenzungseinrichtung 32.According to the invention, the adjusting device 25 of the variable displacement pump 15 further comprises a power limiting device 32.

Die Leistungsbegrenzungseinrichtung 32 ist als Leistungsregler 33 ausgebildet, der derart ausgeführt ist, dass in Abhängigkeit von dem in der Förderleitung 19 anstehenden Förderdruck der Verstellpumpe 15 und somit von dem Systemdruck des Antriebssystems 1 das Fördervolumen der Verstellpumpe 15 derart geregelt ist, dass das Antriebsdrehmoment, das dem Produkt aus dem Fördervolumen und dem Förderdruck der Verstellpumpe 15 entspricht, der Verstellpumpe 15 konstant ist.The power limiting device 32 is designed as a power controller 33, which is designed such that in dependence on the in the delivery line 19 pending delivery pressure of the variable displacement pump 15 and thus the system pressure of the drive system 1, the delivery volume of the variable displacement pump 15 is controlled such that the drive torque, the corresponds to the product of the delivery volume and the delivery pressure of the variable displacement pump 15, the variable displacement pump 15 is constant.

Die Leistungsbegrenzungseinrichtung 32 der Stelleinrichtung 25 ist derart eingestellt ist, dass ab einem vorgegebenen Grenzwert der am Hubantrieb 3 anstehenden anzuhebenden Last L, die Leistungsbegrenzung und somit die Drehmomentbegrenzung der Leistungsbegrenzungseinrichtung 32 wirksam wird.The power limiting device 32 of the adjusting device 25 is set such that, starting from a predetermined limit value of the load L to be lifted on the lifting drive 3, the power limitation and thus the torque limitation of the power limiting device 32 becomes effective.

Bei der Erfindung ist eine elektronische Steuereinrichtung 35 vorgesehen, die eingangsseitig mit einer die aufgenommene Last L der Hubantriebs 3 erfassenden Sensoreinrichtung 36 in Wirkverbindung steht und ausgangsseitig mit einer Drehzahlstelleinrichtung 37 des Verbrennungsmotors 16 in Wirkverbindung steht. Die elektronische Steuereinrichtung 35 ist derart ausgebildet, dass oberhalb des Grenzwerts der am Hubantrieb 3 anstehenden anzuhebenden Last L die Drehzahl des Verbrennungsmotors 15 angehoben wird, um eine vorgegebene Hebengeschwindigkeit zu erzielen.In the invention, an electronic control device 35 is provided, which is on the input side with a recorded load L of the linear actuator 3 sensing sensor device 36 in operative connection and the output side is in operative connection with a speed control device 37 of the engine 16. The electronic control device 35 is designed such that, above the limit value of the load L to be lifted on the lifting drive 3, the rotational speed of the internal combustion engine 15 is raised in order to achieve a predetermined lifting speed.

Die Sensoreinrichtung 36 ist bevorzugt als ein den Druck des Hubantriebs 3 erfassender Drucksensor 38 ausgebildet.The sensor device 36 is preferably designed as a pressure sensor 38 detecting the pressure of the lifting drive 3.

Die Ausführung der Verstellpumpe 15 mit einer Leistungsbegrenzungseinrichtung 32 ermöglicht es, die installierte hydraulische Leistung der Verstellpumpe 15 größer als Nennleistung des Verbrennungsmotors 15 auszuführen, d.h. die Verstellpumpe 15 zu überdimensionieren.The embodiment of the variable displacement pump 15 with a power limiting device 32 makes it possible for the installed hydraulic power of the variable displacement pump 15 to be greater than Perform rated power of the engine 15, ie over-variable the variable displacement 15.

Die Nennleistung des Verbrennungsmotors 16 stellt sich bei Nenndrehzahl des Verbrennungsmotors 16 ein. Die installierte hydraulische Leistung der Verstellpumpe 15 ergibt sich rechnerisch aus dem Produkt des maximalen Förderstroms (Fördervolumen multipliziert mit der Nenndrehzahl) und des maximalen Systemdrucks. Dadurch wird es ermöglicht, das maximale Fördervolumen der Verstellpumpe 16 derart zu wählen, dass bei Nenndrehzahl des Verbrennungsmotors 16 der sich rechnerisch aus dem Produkt des maximalen Fördervolumens und der Nenndrehzahl ergebende Förderstrom der Verstellpumpe 16 den in der Arbeitshydraulik 2 maximal erforderlichen Volumenstrom übersteigt. Die im maximalen Fördervolumen überdimensionierte und übergroße Verstellpumpe 16 kann somit dazu genutzt werden, bei der Betätigung der Verbraucher der Arbeitshydraulik 2 die Drehzahl des Verbrennungsmotors 16 gegenüber der Nenndrehzahl zu reduzieren, um Kraftstoff zu sparen und ein verringertes Geräuschniveau zu erzielen.The nominal power of the internal combustion engine 16 adjusts itself at the nominal rotational speed of the internal combustion engine 16. The installed hydraulic power of the variable displacement pump 15 results arithmetically from the product of the maximum delivery flow (delivery volume multiplied by the rated speed) and the maximum system pressure. This makes it possible to select the maximum delivery volume of the variable displacement pump 16 such that at rated speed of the engine 16 of the mathematically calculated from the product of the maximum delivery volume and the nominal speed flow of the variable displacement pump 16 exceeds the maximum required in the working hydraulics 2 flow rate. The over-dimensioned in the maximum delivery volume and oversize variable displacement pump 16 can thus be used to reduce when operating the load of the working hydraulics 2, the speed of the engine 16 relative to the rated speed to save fuel and to achieve a reduced noise level.

Die Erfindung wird anhand der Figur 2 und der Figur 3 näher erläutert.The invention is based on the FIG. 2 and the FIG. 3 explained in more detail.

In der Figur 2 ist anhand von Diagrammen die Leistungsbegrenzung und somit die Drehmomentbegrenzung der erfindungsgemäßen leistungsbegrenzten und in dem maximalen Fördervolumen überdimensionierten Verstellpumpe 15 dargestellt.In the FIG. 2 is shown by diagrams, the power limit and thus the torque limit of the invention power-limited and oversized in the maximum displacement variable pump 15.

In den Diagrammen der Figur 2 ist hierbei auf der Abszisse jeweils das Fördervolumen Q der Verstellpumpe 15 und auf der Ordinate der Systemdruck p dargestellt.In the diagrams of FIG. 2 in this case the delivery volume Q of the variable displacement pump 15 is shown on the abscissa and the system pressure p is shown on the ordinate.

In der Figur 2 ist mit durchgezogenen Linien das maximale mögliche Fördervolumen Q1max der Verstellpumpe 15 bei einem Systemdruck p1 für ein maximal zulässiges Antriebsdrehmoment M dargestellt. Das maximal zulässige Antriebsdrehmoment M berechnet sich aus dem Produkt des Druckes p1 und dem Fördervolumen Q1max.In the FIG. 2 is shown by solid lines, the maximum possible delivery volume Q 1max of the variable displacement pump 15 at a system pressure p 1 for a maximum allowable drive torque M. The maximum permissible drive torque M is calculated from the product of the pressure p 1 and the delivery volume Q 1max .

Mit gestrichelten Linien ist in der Figur 2 das maximale mögliche Fördervolumen Q2max der Verstellpumpe 15 bei einem Druck p2, der kleiner als der Druck p1 ist, für ein gleichgroßes maximal zulässiges Antriebsdrehmoment M dargestellt.With dashed lines is in the FIG. 2 the maximum possible delivery volume Q 2max of the variable displacement pump 15 at a pressure p 2 , which is smaller than the pressure p 1 , for an equal maximum permissible drive torque M shown.

Mit strichpunktierten Linien ist in der Figur 2 das maximale mögliche Fördervolumen Q3max der Verstellpumpe 15 bei einem Druck p3, der kleiner als der Druck p2 ist, für ein gleichgroßes maximal zulässiges Antriebsdrehmoment M dargestellt.With dotted lines is in the FIG. 2 the maximum possible delivery volume Q 3max of the variable displacement pump 15 at a pressure p 3 , which is smaller than the pressure p 2 , for an equal maximum permissible drive torque M shown.

Die erfindungsgemäße leistungsgeregelte Verstellpumpe 15 ermöglicht es somit, bei einem niedrigen Systemdruck p das Fördervolumen Q zu erhöhen - wie in der Figur 2 durch die Pfeile 40, 41 verdeutlicht ist -, um das maximal zulässige Antriebsdrehmoment auszunutzen.The power-controlled variable displacement pump 15 according to the invention thus makes it possible to increase the delivery volume Q at a low system pressure p - as in the US Pat FIG. 2 is illustrated by the arrows 40, 41 - to take advantage of the maximum permissible drive torque.

In der Figur 3 ist anhand eines Diagrammen die Drehzahl des Verbrennungsmotors 16 mit der erfindungsgemäßen leistungsbegrenzten und in dem maximalen Fördervolumen überdimensionierten Verstellpumpe 15 über die Last L des Hubantriebs 3 für unterschiedliche konstante Hubgeschwindigkeiten des Hubantriebs 3 dargestellt.In the FIG. 3 is based on a diagram, the speed of the engine 16 with the inventive power-limited and oversized in the maximum flow volume variable displacement pump 15 via the load L of the lifting drive 3 for different constant lifting speeds of the lifting drive 3 shown.

In dem Diagramm der Figur 3 ist hierbei auf der Abszisse die Last L des Hubantriebs 3 und auf der Ordinate die Drehzahl n des Verbrennungsmotors 16 dargestellt.In the diagram of FIG. 3 Here, on the abscissa, the load L of the lifting drive 3 and on the ordinate, the speed n of the engine 16 is shown.

Mit der Linie 50 ist ein Verlauf der Drehzahl n des Verbrennungsmotors 16 unter Verwendung einer Verstellpumpe des Standes der Technik mit einem Druckregler und einem Förderstromregler für eine konstante erste Hubgeschwindigkeit dargestellt. Für die Erzielung der konstanten ersten Hubgeschwindigkeit ist der Verbrennungsmotor 16 mit der Nenndrehzahl nNenn zu betreiben.The line 50 shows a curve of the speed n of the internal combustion engine 16 using a variable displacement pump of the prior art with a pressure regulator and a delivery rate controller for a constant first stroke speed. To achieve the constant first lifting speed of the engine 16 is to operate at the rated speed n nominal .

Mit der Linie 51 ist ein Verlauf der Drehzahl des Verbrennungsmotors 16 unter Verwendung einer erfindungsgemäßen leistungsbegrenzten und in dem maximalen Fördervolumen überdimensionierten Verstellpumpe 15 für eine konstante zweite Hubgeschwindigkeit dargestellt, die größer als die erste Hubgeschwindigkeit ist. Für die Erzielung der konstanten zweiten Hubgeschwindigkeit ist der Verbrennungsmotor 16 mit der Drehzahl n1 zu betreiben, die geringer als die Nenndrehzahl nNenn ist. Die Linie 52 zeigt einen Verlauf der Drehzahl des Verbrennungsmotors 16 unter Verwendung einer erfindungsgemäßen leistungsbegrenzten und in dem maximalen Fördervolumen überdimensionierten Verstellpumpe 15 für eine konstante dritte Hubgeschwindigkeit, die größer als die zweite Hubgeschwindigkeit ist. Für die Erzielung der konstanten dritten Hubgeschwindigkeit ist der Verbrennungsmotor 16 mit der Drehzahl n2 zu betreiben, die höher als die Drehzahl n1 und geringer als die Nenndrehzahl nNenn ist. Die Linie 53 zeigt einen Verlauf der Drehzahl des Verbrennungsmotors 16 unter Verwendung einer erfindungsgemäßen leistungsbegrenzten und in dem maximalen Fördervolumen überdimensionierten Verstellpumpe 15 für eine konstante vierte Hubgeschwindigkeit, die größer als die dritte Hubgeschwindigkeit ist. Für die Erzielung der konstanten vierten Hubgeschwindigkeit ist der Verbrennungsmotor 16 mit der Drehzahl n3 zu betreiben, die höher als die Drehzahl n2 und geringer als die Nenndrehzahl nNenn ist.The line 51 shows a profile of the rotational speed of the internal combustion engine 16 using a power-limited variable displacement pump 15 according to the invention which is oversized in the maximum delivery volume for a constant second lifting speed which is greater than the first stroke speed. In order to achieve the constant second lifting speed of the internal combustion engine 16 is to operate at the speed n 1 , which is less than the rated speed n nominal . The line 52 shows a profile of the rotational speed of the internal combustion engine 16 using a power-limited according to the invention and in the maximum delivery volume oversized variable displacement pump 15 for a constant third stroke speed, which is greater than the second stroke speed. To achieve the constant third stroke speed of the internal combustion engine 16 is to operate at the speed n 2 , which is higher than the speed n 1 and less than that Rated speed n nominal . The line 53 shows a profile of the rotational speed of the internal combustion engine 16 using a power-limited according to the invention and in the maximum delivery volume oversized variable displacement pump 15 for a constant fourth stroke speed, which is greater than the third stroke speed. To obtain the constant fourth stroke speed, the engine 16 is to be operated at the speed n 3 , which is higher than the speed n 2 and lower than the rated speed n nominal .

Aus den Drehzahlverläufen der Linien 51-53 wird deutlich, dass ab dem vorgegebenen Grenzwert LGrenz der am Hubantrieb 3 anstehenden anzuhebenden Last L die Leistungsbegrenzung der Leistungsbegrenzungseinrichtung 32 der erfindungsgemäßen Verstellpumpe 15 wirksam wird und das das Fördervolumen der Verstellpumpe 15 verringert wird. Bis zu dem Grenzwert LGrenz der Last L wird der Verbrennungsmotor 16 mit der für die entsprechende Hubgeschwindigkeit erforderlichen Drehzahl n1 bzw. n2 bzw. n3 betrieben. Oberhalb des Grenzwertes LGrenz der Last L wird die Drehzahl des Verbrennungsmotors 16 ausgehend von der Drehzahl n1 bzw. n2 bzw. n3 angehoben, um bei wirksamer Leistungsbegrenzung der erfindungsgemäßen Verstellpumpe 15 den Effekt der Leitungsbegrenzung (Verringerung des Fördervolumens) auf die Hubgeschwindigkeit zu kompensieren und die entsprechende konstante Hubgeschwindigkeit zu erzielen. Die Anhebung der Drehzahl des Verbrennungsmotors 16 erfolgt mittels der elektronischen Steuereinrichtung 35, die anhand der Sensoreinrichtung 36 das Erreichen des Grenzwertes LGrenz der Last L ermittelt und die Drehzahlstelleinrichtung 37 des Verbrennungsmotors 16 entsprechend ansteuert.From the speed curves of the lines 51-53 it is clear that, starting from the predetermined limit value L limit of the lifting drive 3 to be lifted load L, the power limit of the power limiting device 32 of the variable displacement 15 of the invention is effective and the delivery volume of the variable displacement 15 is reduced. Up to the limit value L limit of the load L, the internal combustion engine 16 is operated at the speed n 1 or n 2 or n 3 required for the corresponding lifting speed. Above the limit L limit of the load L, the speed of the engine 16 is raised from the speed n 1 or n 2 and n 3 , to effectively limiting the power of the variable displacement pump 15 according to the invention the effect of line limitation (reduction of the delivery volume) on the lifting speed compensate and achieve the corresponding constant lifting speed. The increase in the rotational speed of the internal combustion engine 16 is effected by means of the electronic control device 35, which determines the reaching of the limit value L limit of the load L on the basis of the sensor device 36 and controls the speed setting device 37 of the internal combustion engine 16 accordingly.

Mit der erfindungsgemäßen leistungsbegrenzten und somit drehmomentbegrenzten Verstellpumpe 15 wird es ermöglicht, im Hebenbetrieb des Hubantriebs 3 die Drehzahl des Verbrennungsmotors 16 deutlich zu reduzieren - wie in der Figur 3 durch den Pfeil 42 verdeutlicht ist -, wodurch sich eine Reduzierung der Geräusche des Verbrennungsmotors 16 und eine Verringerung des Kraftstoffverbrauchs erzielen lässt.With the inventive power-limited and thus torque-limited variable displacement pump 15, it is possible to significantly reduce the speed of the engine 16 in the lifting operation of the lifting drive 3 - as in the FIG. 3 is illustrated by the arrow 42 -, which can be a reduction in the noise of the engine 16 and a reduction in fuel consumption can be achieved.

Mit der erfindungsgemäßen leistungsbegrenzten und somit drehmomentbegrenzten Verstellpumpe 15 wird es ebenfalls ermöglicht, die Verstellpumpe 15 zu überdimensionieren, so dass erhöhte Hubgeschwindigkeiten und somit eine erhöhte Umschlagsleistung des Flurförderzeugs erzielt werden.With the power-limited and thus torque-limited variable displacement pump 15 according to the invention, it is also possible to oversize the variable displacement pump 15 so that increased lifting speeds and thus increased handling capacity of the industrial truck are achieved.

Mit der überdimensionierten und im Fördervolumen übergroßen erfindungsgemäßen Verstellpumpe 15 wird es ebenfalls ermöglicht, bei einem parallelen Betrieb des Hubantriebs 3 im Hebenbetrieb und eines Nebenantriebs 4-6, beispielsweise des Lüfterantriebs, die Leistungsverluste zu kompensieren, so dass eine Verringerung der Hebengeschwindigkeit durch die abgeforderte Leistung des Nebenantriebs vermieden werden kann.With the oversized and in the delivery volume oversized variable displacement pump 15 according to the invention it is also possible to compensate for a parallel operation of the lifting drive 3 in lifting operation and a PTO 4-6, for example, the fan drive, the power losses, so that a reduction in the lifting speed by the requested performance the auxiliary drive can be avoided.

Claims (5)

  1. Hydraulic drive system (1) of an industrial truck, wherein the drive system (1) has working hydraulics (2) which comprise a lifting drive (3) and at least one secondary drive (4; 5; 6), wherein in order to supply the lifting drive (3) and the at least one secondary drive (4; 5; 6) a variable displacement pump (15) is provided which has an adjustable delivery volume and which is operatively connected to an internal combustion engine (16) for its drive, wherein the installed hydraulic power of the variable displacement pump (15) is greater than the rated power of the internal combustion engine (16), wherein the variable displacement pump (15) has an actuating device (25) for adjusting the delivery volume, which actuating device (25) is provided with a power-limiting device (32), characterized in that the power-limiting device (32) of the actuating device (25) is set in such a way that the power limitation of the power-limiting device (32) becomes effective starting from a predefined limiting value (LGrenz) of a load (L) which is to be lifted and which is located on the lifting drive (3), and in that an electronic control device (35) is provided which is operatively connected on the input side to a sensor device (36) which senses the load (L) taken up by the lifting drive (3), and is operatively connected on the output side to a rotational speed-adjusting device (37) of the internal combustion engine (16), wherein the electronic control device (35) is embodied in such a way that above the limiting value (LGrenz) of the load (L) which is to be lifted and which is located on the lifting drive (3) the rotational speed (n) of the internal combustion engine (16) is raised in order to achieve a predefined lifting speed.
  2. Hydraulic drive system according to Claim 1, characterized in that the power-limiting device (32) is embodied as a power regulator (33) which changes the delivery volume of the variable displacement pump (15) as a function of the system pressure (p) of the drive system (1) in such a way that the drive torque of the variable displacement pump (15) is constant.
  3. Hydraulic drive system according to Claim 1 or 2, characterized in that the sensor device (36) is embodied as a pressure sensor (38) which senses the pressure of the lifting drive.
  4. Hydraulic drive system according to one of Claims 1 to 3, characterized in that the actuating device (25) of the variable displacement pump (15) comprises a pressure regulator (30) and a delivery current regulator (31).
  5. Hydraulic drive system according to one of Claims 1 to 4, characterized in that the secondary drive (6) is embodied as a fan drive of a cooling system (7).
EP15163350.0A 2014-04-22 2015-04-13 Hydraulic drive system of an industrial truck Not-in-force EP2937307B9 (en)

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DE102016000186A1 (en) * 2016-01-11 2017-07-13 Liebherr-Hydraulikbagger Gmbh Device for the controllable hydraulic supply of differently regulated hydraulic consumers as well as hydraulic system and working machine

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DE102007035341A1 (en) 2007-07-27 2009-01-29 Linde Material Handling Gmbh Industrial truck for use as counterbalanced fork-lift truck, has pump arranged in hydrostatic circuit and operating according to displacement principle, where specific delivery volume of pump is adjustable in flow rate-limiting manner
DE102008048054A1 (en) * 2008-09-19 2010-03-25 Still Gmbh Hydrostatic drive system for mobile engine, particularly ground conveyor for operating internal combustion engine, has storage element which is provided for energy recovery in lowering operation of lift drive
DE102008059181A1 (en) * 2008-11-27 2010-06-02 Still Gmbh Mobile work machine, in particular industrial truck, and method for operating the mobile work machine

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