EP3734083A1 - Operating button for an industrial truck - Google Patents
Operating button for an industrial truck Download PDFInfo
- Publication number
- EP3734083A1 EP3734083A1 EP20170604.1A EP20170604A EP3734083A1 EP 3734083 A1 EP3734083 A1 EP 3734083A1 EP 20170604 A EP20170604 A EP 20170604A EP 3734083 A1 EP3734083 A1 EP 3734083A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- hydraulic
- valve
- path
- lowering
- hydraulic fluid
- 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.)
- Pending
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
- F15B11/044—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out"
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/305—Directional control characterised by the type of valves
- F15B2211/30505—Non-return valves, i.e. check valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
- F15B2211/31552—Directional control characterised by the connections of the valve or valves in the circuit being connected to an output member and a return line
- F15B2211/31558—Directional control characterised by the connections of the valve or valves in the circuit being connected to an output member and a return line having a single output member
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/35—Directional control combined with flow control
- F15B2211/353—Flow control by regulating means in return line, i.e. meter-out control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/365—Directional control combined with flow control and pressure control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/40—Flow control
- F15B2211/405—Flow control characterised by the type of flow control means or valve
- F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/40—Flow control
- F15B2211/405—Flow control characterised by the type of flow control means or valve
- F15B2211/40576—Assemblies of multiple valves
- F15B2211/40592—Assemblies of multiple valves with multiple valves in parallel flow paths
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/40—Flow control
- F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
- F15B2211/41581—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a return line
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/40—Flow control
- F15B2211/46—Control of flow in the return line, i.e. meter-out control
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/50—Pressure control
- F15B2211/505—Pressure control characterised by the type of pressure control means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/50—Pressure control
- F15B2211/575—Pilot pressure control
- F15B2211/5753—Pilot pressure control for closing a valve
Definitions
- the invention relates to a hydraulic system for an industrial truck, comprising at least one hydraulic lifting cylinder, a hydraulic unit connected to the at least one lifting cylinder via a hydraulic lifting path for supplying hydraulic fluid via the lifting path to the at least one lifting cylinder, and one with the at least one lifting cylinder via a hydraulic lowering path connected lowering valve for discharging hydraulic fluid from the at least one lifting cylinder via the lowering path, a throttle device arranged in the lowering path for regulating the volume flow of the hydraulic fluid in the lowering path.
- the invention also relates to an industrial truck having such a hydraulic system.
- Such a hydraulic arrangement is provided and suitable for an industrial truck, for example for a lifting vehicle such as a forklift truck, and comprises one or more lifting cylinders.
- a load part of the industrial truck can be lifted via the at least one lifting cylinder, in particular by extending a mast of the industrial truck.
- hydraulic fluid is fed from the hydraulic unit to the lifting cylinder.
- the lifting speed can be regulated, for example, via the speed of a motor of the hydraulic unit or via valves in the lifting path.
- the lifting path describes the path that the hydraulic fluid coming from the hydraulic unit travels on its way to the lifting cylinder.
- hydraulic fluid is released from the at least one lifting cylinder and moves back to the hydraulic unit via the so-called lowering path.
- the sink path denotes the path along which the hydraulic fluid flowing from the lifting cylinder back into the hydraulic unit moves.
- throttle devices In order to enable a controlled lowering of the load part, throttle devices, in particular flow control valves, are arranged in the lowering path in hydraulic systems in order to limit the maximum lowering speed. These throttling devices are designed for maximum lowering speed with the rated load on the load part. The consequence of this is that with a low load or without a load on the load part, the flow resistance through the throttle device is so great that the maximum lowering speed cannot be achieved. In particular, this means that with a low load or no load, only a very slow lowering of the load part of the industrial truck is possible, which increases the turnover times.
- WO 2008/151727 A2 a hydraulic control arrangement with a burst pipe safety function has become known.
- a pressure compensator following a lowering valve in the lowering path is intended to throttle the hydraulic flow flowing back from a lifting cylinder to the tank in the event of a pipe break.
- DE 43 24 464 A1 describes a hydraulic lifting device which has a generator in the lowering path for energy recovery from hydraulic fluid flowing back into the tank from the lifting cylinder.
- a volume flow-dependent switching valve picks up a pressure difference across a flow control valve in the sink path and bypasses the generator if the volume flow is too low.
- the invention is based on the object of providing a hydraulic arrangement for an industrial truck which, with a simple structure, enables hydraulic fluid to be drained quickly from the lifting cylinder.
- the hydraulic arrangement according to the invention of the type mentioned at the beginning comprises a bypass valve which is arranged in the sink path to bypass the throttle device and which is adjustable between a blocking position blocking the flow of hydraulic fluid and a flow position releasing the flow of hydraulic fluid, the bypass valve opposing the hydraulic fluid with a lower flow resistance than the throttle device and wherein the bypass valve is designed to tap the load pressure of the hydraulic fluid in the lowering path upstream of the lowering valve as an absolute value via a control line and to switch from the blocking position to the flow position when the load pressure falls below a limit pressure value, so that the throttle device is bypassed.
- the hydraulic system is intended for an industrial truck, in particular for an industrial truck with a load part.
- the at least one hydraulic lifting cylinder can in particular be a mast lifting cylinder for extending a mast belonging to the load part of the industrial truck.
- the truck can lift loads via the load section by extending the lifting cylinder.
- hydraulic fluid is supplied to the hydraulic lifting cylinder from the hydraulic unit, in particular from a tank of the hydraulic unit.
- the hydraulic unit can comprise a hydraulic pump for this purpose.
- the hydraulic fluid is conducted to the at least one lifting cylinder via the lifting path and a piston of the lifting cylinder is thus extended.
- hydraulic fluid can be drawn from the at least one lifting cylinder via the lowering path be drained.
- the hydraulic fluid can be guided back to the hydraulic unit, in particular into the tank of the hydraulic unit, via the sink path.
- a throttle device is arranged in the lowering path following the lowering valve.
- the throttle device forms a local flow resistance, in particular through a cross-sectional constriction in relation to the surrounding hydraulic line.
- the throttle device can, for example, be a permanently set throttle device with constant flow resistance, in particular a constant line cross-section, or a flow control valve for regulating the volume flow of the hydraulic fluid in the sink path.
- the throttle device can be used to limit a maximum lowering speed.
- a bypass valve is also arranged in the sink path to bypass the throttle device, that is to say in particular the flow control valve.
- the bypass valve is arranged following the lowering valve in the lowering path.
- the bypass valve picks up the absolute pressure of the hydraulic fluid in the lowering path in front of the lowering valve via a control line.
- the bypass valve is arranged in particular in the lowering path behind the lowering valve.
- the bypass valve switches between the flow position and the blocking position, with the bypass valve assuming the flow position when the pressure value tapped via the control line before the lowering valve falls below a limit value.
- bypass valve If the bypass valve is in the flow position, the hydraulic fluid, coming from the lift cylinder, flows along the sink path through the bypass valve instead of through the throttle.
- the throttle device is consequently bypassed.
- the bypass valve has a lower flow resistance than the throttle. If the load pressure of the hydraulic fluid is below the limit pressure value in the Sink path, the hydraulic fluid is consequently drained via the bypass valve as a bypass to the throttle device instead of via the throttle device itself or in addition to it. Due to the lower flow resistance of the bypass valve, a high lowering speed can be achieved even with low load pressure.
- the bypass valve is designed in such a way that a predetermined maximum lowering speed can also be achieved when the load part connected to the lifting cylinder has no load. A rapid lowering of the load part can therefore be achieved even with little or no load.
- the hydraulic arrangement according to the invention only requires a single control line, while in the lifting device from the prior art explained at the beginning, two control lines pick up a differential pressure via the lowering valve.
- the hydraulic system has only one such control line, so the bypass valve can be designed to pick up the load pressure of the hydraulic fluid in the lowering path in front of the lowering valve as an absolute value via only one control line.
- Picking up a differential pressure as in the explained prior art, also has the disadvantage that the switching valve switches depending on the volume flow through the lowering valve, i.e. it is not exclusively load-dependent, but also depends on the position of the lowering valve or the flow resistance of the lowering valve.
- the bypass valve according to the invention controlled only via the absolute load pressure upstream of the lowering valve, enables a reliable bypass of the throttle device regardless of the position of the lowering valve.
- the hydraulic system according to the invention is thus more simply constructed and designed and less prone to errors than the lifting device known from the prior art.
- the throttle device comprises a flow control valve for regulating the volume flow of the hydraulic fluid in the sink path, as already mentioned.
- the throttle device can in particular be formed by such a flow control valve.
- a flow control valve allows, in particular, continuous regulation of the hydraulic flow in the lowering path and can limit the maximum lowering speed.
- the bypass valve is designed to switch from the flow position to the blocking position when the load pressure reaches or exceeds the limit pressure value, so that hydraulic fluid flowing from the lift cylinder through the sink path passes through the throttle device.
- the bypass valve can thus switch back and forth between the flow position and the blocking position depending on the load pressure. If the load pressure of the hydraulic fluid in the lowering path upstream of the lowering valve is at the limit pressure value or above, the hydraulic fluid can be drained via the throttle, i.e. in particular the flow control valve, and the lowering speed can thus be kept at a predetermined maximum value, especially with large loads.
- control line is a hydraulic control line, and the bypass valve can thus be controlled mechanically directly via the hydraulic fluid running in the sink path.
- control line is an electrical control line.
- a pressure sensor can then also be provided which determines the load pressure of the hydraulic fluid present in the lowering path in front of the lowering valve.
- a control unit can be provided which switches the bypass valve as a function of the load pressure determined by the sensor.
- the throttle device and the bypass valve are designed separately from one another. Throttle device and bypass valve can be used as two independent components can be arranged in the sink path. The throttle device and the bypass valve can be arranged in the lowering path following the lowering valve in parallel sections of the lowering path. The throttle device can always be connected to the sink path. If the pressure falls below the limit pressure, bypassing the throttle device is also guaranteed because of the lower flow resistance of the bypass valve.
- the throttle device and the bypass valve are designed as a common component, in particular the throttle device comprises a flow control valve, which is designed as a common valve with the bypass valve. In particular, the flow control valve and bypass valve can be designed as a common 2/2-way valve. Such a structure is particularly simple. It can then be switched between the bypass valve and the throttle device / flow control valve depending on the load pressure applied.
- the bypass valve is connected directly to the hydraulic unit for returning the hydraulic fluid via the sink path.
- Directly connected means that between the bypass valve and the hydraulic unit, i. H. in particular a tank of the hydraulic unit, no further hydraulic elements (apart from a hydraulic line carrying the hydraulic fluid) are arranged.
- no further hydraulic elements are arranged.
- the invention also relates to an industrial truck with a hydraulic system as explained above.
- the at least one lifting cylinder of the hydraulic system can in particular be a mast lifting cylinder that acts on a load part of the industrial truck.
- a mast of the industrial truck can be extended and retracted via the mast lifting cylinder, as already explained.
- FIG. 1 a first hydraulic arrangement 10 according to the invention can be seen.
- the hydraulic arrangement 10 comprises a hydraulic mast lifting cylinder 12, a hydraulic unit connected to the mast lifting cylinder 12 via a hydraulic lifting path 14, comprising a hydraulic motor 16 and a hydraulic tank 18.
- a check valve 20 is arranged in the lifting path.
- the hydraulic system 10 also includes a lowering path 22 with a lowering valve 24 for discharging hydraulic fluid from the lifting cylinder 12, a flow control valve 26 for regulating the volume flow of the hydraulic fluid in the lowering path 22 and a bypass valve 28.
- the flow control valve 26 forms a throttle device in the lowering path.
- a fixedly set throttle device can also be provided tensing the adjustable flow control valve.
- a pressure limiting valve 30 branches off from the lifting path 14 above the hydraulic motor 16.
- the bypass valve 28 can be adjusted between a flow position and a blocking position and, via a control line 32, engages the in the sink path 22 before Lowering valve 24 applied load pressure of the hydraulic fluid as an absolute value.
- the bypass valve 28 also has a lower flow resistance than the flow control valve 26.
- hydraulic fluid is fed from the hydraulic tank 18 via the hydraulic pump 16 and through the check valve 20 along the lifting path 14 to the lifting cylinder 12.
- the lowering valve 24 and also the pressure limiting valve 30 are closed.
- the pressure relief valve 30 opens in a manner known per se, should an unusually high pressure occur in the lifting path 14 and leads to the return of the hydraulic fluid to the tank 18.
- the bypass valve 28 is opened or closed depending on the lifting pressure, which is due to the closed lowering valve 24 has no influence on the lifting process.
- the lowering valve 24 is opened to lower the lifting cylinder and thus the load part connected to it. A backflow via the lifting path 14 is prevented due to the check valve 20. As a result of the dead weight of the load part or the load taken up on the load part, the piston of the lifting cylinder 12 is retracted and the hydraulic fluid is returned along the sink path 22 to the hydraulic tank 18. As mentioned, the bypass valve 28 picks up the absolute load pressure upstream of the lowering valve 24 via the control line 32. If the load pressure there exceeds a predetermined limit value, the bypass valve 28 remains in its blocking position or switches to this, whereby hydraulic fluid flowing along the lowering path 22 through the lowering valve 24 to the tank 18 runs via the flow control valve 26.
- the flow control valve 26 can regulate the volume flow of the hydraulic fluid in such a way that a maximum lowering speed is always reached and, in particular, is not exceeded. However, if no or only a very low load is absorbed on the load part, the im The load pressure present in the lowering path 22 is so low that the predetermined maximum possible lowering speed cannot be achieved due to the flow resistance of the flow control valve 26. In this case, the pressure falls below the predetermined limit value, which is determined by the bypass valve 28 via the control line 32. The bypass valve 28 then switches to its flow position, as a result of which the hydraulic fluid flowing out of the lifting cylinder 12 via the lowering path 22 and the lowering valve 24 can be returned directly to the hydraulic tank 18, bypassing the flow control valve 26.
- the maximum possible lowering speed or at least a significantly higher lowering speed than via the flow control valve 26 can thus be achieved even with little or no load.
- the flow control valve 26 can in principle assume any position that the hydraulic fluid in any case predominantly drains through the bypass valve 28 due to the lower flow resistance.
- the hydraulic arrangement 10 'according to the embodiment Figure 2 differs from the design in Figure 1 only that instead of two separate valves for the flow control valve and bypass valve, the flow control valve and the bypass valve are designed as a common 2/2-way valve 34.
- the way it works is ultimately the same as in the first run.
- the common design of the bypass valve and flow control valve due to the common design of the bypass valve and flow control valve, the flow control valve is closed when the bypass valve is opened and vice versa.
- Such a structure is all the simpler since only one valve has to be provided for flow control and bypass.
- the hydraulic systems according to the invention are simple in structure and less prone to failure than hydraulic systems that pick up a pressure difference across the lowering valve.
- only one Control line can be used.
- the switching of the bypass valve takes place more reliably due to the tapping of an absolute pressure and in particular independently of the volume flow running through the lowering valve.
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Forklifts And Lifting Vehicles (AREA)
Abstract
Hydraulikanordnung für ein Flurförderzeug, umfassend mindestens einen hydraulischen Hubzylinder, ein mit dem mindestens einen Hubzylinder über einen hydraulischen Hebenpfad verbundenes Hydraulikaggregat zur Zufuhr von Hydraulikflüssigkeit über den Hebenpfad zu dem mindestens einen Hubzylinder, ein mit dem mindestens einen Hubzylinder über einen hydraulischen Senkenpfad verbundenes Senkventil zum Auslassen von Hydraulikflüssigkeit aus dem mindestens einen Hubzylinder über den Senkenpfad, eine im Senkenpfad angeordnete Drossel, weiter umfassend ein im Senkenpfad zur Umgehung der Drosseleinrichtung angeordnetes Bypassventil, das zwischen einer den Durchfluss von Hydraulikflüssigkeit sperrenden Sperrstellung und einer den Durchfluss von Hydraulikflüssigkeit freigebenden Durchflussstellung verstellbar ist, wobei das Bypassventil der Hydraulikflüssigkeit einen geringeren Strömungswiderstand entgegensetzt als die Drosseleinrichtung und wobei das Bypassventil dazu ausgebildet ist, über eine Steuerleitung den Lastdruck der Hydraulikflüssigkeit im Senkenpfad vor dem Senkventil als Absolutwert abzugreifen und bei Unterschreiten eines Grenzdruckwerts durch den Lastdruck von der Sperrstellung in die Durchflussstellung zu schalten, so dass die Drosseleinrichtung umgangen wird.Hydraulic system for an industrial truck, comprising at least one hydraulic lifting cylinder, a hydraulic unit connected to the at least one lifting cylinder via a hydraulic lifting path for supplying hydraulic fluid via the lifting path to the at least one lifting cylinder, a lowering valve connected to the at least one lifting cylinder via a hydraulic lowering path for exhausting of hydraulic fluid from the at least one lifting cylinder via the sink path, a throttle arranged in the sink path, further comprising a bypass valve arranged in the sink path to bypass the throttle device, which is adjustable between a blocking position that blocks the flow of hydraulic fluid and a flow position that releases the flow of hydraulic fluid, wherein the bypass valve opposes a lower flow resistance to the hydraulic fluid than the throttle device and wherein the bypass valve is designed to be connected to Your line to tap the load pressure of the hydraulic fluid in the lowering path in front of the lowering valve as an absolute value and, if the load pressure falls below a limit pressure value, to switch from the blocking position to the flow position so that the throttle device is bypassed.
Description
Die Erfindung betrifft eine Hydraulikanordnung für ein Flurförderzeug, umfassend mindestens einen hydraulischen Hubzylinder, ein mit dem mindestens einen Hubzylinder über einen hydraulischen Hebenpfad verbundenes Hydraulikaggregat zur Zufuhr von Hydraulikflüssigkeit über den Hebenpfad zu dem mindestens einen Hubzylinder, ein mit dem mindestens einen Hubzylinder über einen hydraulischen Senkenpfad verbundenes Senkventil zum Auslassen von Hydraulikflüssigkeit aus dem mindestens einen Hubzylinder über den Senkenpfad, eine im Senkenpfad angeordnete Drosseleinrichtung zur Regelung des Volumenstroms der Hydraulikflüssigkeit im Senkenpfad. Zudem betrifft die Erfindung ein Flurförderzeug mit einer solchen Hydraulikanordnung.The invention relates to a hydraulic system for an industrial truck, comprising at least one hydraulic lifting cylinder, a hydraulic unit connected to the at least one lifting cylinder via a hydraulic lifting path for supplying hydraulic fluid via the lifting path to the at least one lifting cylinder, and one with the at least one lifting cylinder via a hydraulic lowering path connected lowering valve for discharging hydraulic fluid from the at least one lifting cylinder via the lowering path, a throttle device arranged in the lowering path for regulating the volume flow of the hydraulic fluid in the lowering path. The invention also relates to an industrial truck having such a hydraulic system.
Eine solche Hydraulikanordnung ist für ein Flurförderzeug vorgesehen und geeignet, beispielsweise für ein Hubfahrzeug wie einen Gabelstapler, und umfasst einen oder mehrere Hubzylinder. Über den mindestens einen Hubzylinder kann ein Lastteil des Flurförderzeugs, insbesondere durch Ausfahren eines Mastes des Flurförderzeugs, gehoben werden. Hierzu wird Hydraulikflüssigkeit von dem Hydraulikaggregat dem Hubzylinder zugeführt. Die Hubgeschwindigkeit kann dabei beispielsweise über die Drehzahl eines Motors des Hydraulikaggregats oder über Ventile im Hebenpfad geregelt werden. Der Hebenpfad bezeichnet den Weg, den die aus dem Hydraulikaggregat kommende Hydraulikflüssigkeit auf dem Weg zum Hubzylinder zurücklegt. Zum Absenken des Lastteils wird Hydraulikflüssigkeit aus dem mindestens einen Hubzylinder ausgelassen und bewegt sich dabei über den sogenannten Senkenpfad zurück zum Hydraulikaggregat. Der Senkenpfad bezeichnet entsprechend den Weg, entlang dessen sich die von dem Hubzylinder zurück in das Hydraulikaggregat fließende Hydraulikflüssigkeit bewegt.Such a hydraulic arrangement is provided and suitable for an industrial truck, for example for a lifting vehicle such as a forklift truck, and comprises one or more lifting cylinders. A load part of the industrial truck can be lifted via the at least one lifting cylinder, in particular by extending a mast of the industrial truck. For this purpose, hydraulic fluid is fed from the hydraulic unit to the lifting cylinder. The lifting speed can be regulated, for example, via the speed of a motor of the hydraulic unit or via valves in the lifting path. The lifting path describes the path that the hydraulic fluid coming from the hydraulic unit travels on its way to the lifting cylinder. To lower the load part, hydraulic fluid is released from the at least one lifting cylinder and moves back to the hydraulic unit via the so-called lowering path. The sink path denotes the path along which the hydraulic fluid flowing from the lifting cylinder back into the hydraulic unit moves.
Um ein kontrolliertes Absenken des Lastteils zu ermöglichen, werden in Hydraulikanordnungen Drosseleinrichtungen, insbesondere Stromregelventile, im Senkenpfad angeordnet, um die maximale Senkgeschwindigkeit zu begrenzen. Diese Drosseleinrichtungen werden dabei auf maximale Senkgeschwindigkeit mit auf dem Lastteil befindlicher Nennlast ausgelegt. Das hat zur Folge, dass bei geringer Last oder ohne Last auf dem Lastteil der Strömungswiderstand durch die Drosseleinrichtung derart groß ist, dass die maximale Senkgeschwindigkeit nicht erreicht werden kann. Insbesondere führt dies dazu, dass bei geringer Last oder ohne Last nur ein sehr langsames Absenken des Lastteils des Flurförderzeugs möglich ist, was die Umschlagszeiten vergrößert.In order to enable a controlled lowering of the load part, throttle devices, in particular flow control valves, are arranged in the lowering path in hydraulic systems in order to limit the maximum lowering speed. These throttling devices are designed for maximum lowering speed with the rated load on the load part. The consequence of this is that with a low load or without a load on the load part, the flow resistance through the throttle device is so great that the maximum lowering speed cannot be achieved. In particular, this means that with a low load or no load, only a very slow lowering of the load part of the industrial truck is possible, which increases the turnover times.
Aus
Ausgehend von dem erläuterten Stand der Technik liegt der Erfindung die Aufgabe zugrunde, eine Hydraulikanordnung für ein Flurförderzeug bereitzustellen, die bei einfachem Aufbau ein schnelles Ablassen von Hydraulikflüssigkeit aus dem Hubzylinder ermöglicht.Proceeding from the explained prior art, the invention is based on the object of providing a hydraulic arrangement for an industrial truck which, with a simple structure, enables hydraulic fluid to be drained quickly from the lifting cylinder.
Die Erfindung löst die Aufgabe durch eine Hydraulikanordnung gemäß Anspruch 1. Vorteilhafte Ausgestaltungen sind Gegenstand der abhängigen Ansprüche, der Beschreibung sowie der Figuren.The invention solves the problem by means of a hydraulic arrangement according to claim 1. Advantageous configurations are the subject matter of the dependent claims, the description and the figures.
Die erfindungsgemäße Hydraulikanordnung der eingangs genannten Art umfasst ein im Senkenpfad zur Umgehung der Drosseleinrichtung angeordnetes Bypassventil, das zwischen einer den Durchfluss von Hydraulikflüssigkeit sperrenden Sperrstellung und einer den Durchfluss von Hydraulikflüssigkeit freigebenden Durchflussstellung verstellbar ist, wobei das Bypassventil der Hydraulikflüssigkeit einen geringeren Strömungswiderstand entgegensetzt als die Drosseleinrichtung und wobei das Bypassventil dazu ausgebildet ist, über eine Steuerleitung den Lastdruck der Hydraulikflüssigkeit im Senkenpfad vor dem Senkventil als Absolutwert abzugreifen und bei Unterschreiten eines Grenzdruckwerts durch den Lastdruck von der Sperrstellung in die Durchflussstellung zu schalten, so dass die Drosseleinrichtung umgangen wird.The hydraulic arrangement according to the invention of the type mentioned at the beginning comprises a bypass valve which is arranged in the sink path to bypass the throttle device and which is adjustable between a blocking position blocking the flow of hydraulic fluid and a flow position releasing the flow of hydraulic fluid, the bypass valve opposing the hydraulic fluid with a lower flow resistance than the throttle device and wherein the bypass valve is designed to tap the load pressure of the hydraulic fluid in the lowering path upstream of the lowering valve as an absolute value via a control line and to switch from the blocking position to the flow position when the load pressure falls below a limit pressure value, so that the throttle device is bypassed.
Die Hydraulikanordnung ist vorgesehen für ein Flurförderzeug, insbesondere für ein Flurförderzeug mit einem Lastteil. Der mindestens eine hydraulische Hubzylinder kann insbesondere ein Masthubzylinder sein zum Ausfahren eines zum Lastteil des Flurförderzeugs gehörenden Mastes. Über das Lastteil kann das Flurförderzeug durch Ausfahren des Hubzylinders Lasten heben. Zum Heben wird dem hydraulischen Hubzylinder Hydraulikflüssigkeit aus dem Hydraulikaggregat, insbesondere aus einem Tank des Hydraulikaggregats, zugeführt. Das Hydraulikaggregat kann hierfür eine Hydraulikpumpe umfassen. Über den Hebenpfad wird die Hydraulikflüssigkeit zu dem mindestens einen Hubzylinder geleitet und somit ein Kolben des Hubzylinders ausgefahren. Zum Senken des Kolbens des Hubzylinders, und damit des Lastteils des Flurförderzeugs, kann Hydraulikflüssigkeit aus dem mindestens einen Hubzylinder über den Senkenpfad abgelassen werden. Die Hydraulikflüssigkeit kann über den Senkenpfad zurück zum Hydraulikaggregat, insbesondere in den Tank des Hydraulikaggregats, geführt werden. Zur Regulierung der Senkgeschwindigkeit und insbesondere um lastunabhängig eine möglichst konstante Senkgeschwindigkeit zu erreichen, ist im Senkenpfad nachfolgend auf das Senkventil eine Drosseleinrichtung angeordnet. Die Drosseleinrichtung bildet einen örtlichen Strömungswiderstand, insbesondere durch eine Querschnittsverengung gegenüber der umgebenden Hydraulikleitung. Die Drosseleinrichtung kann beispielsweise eine fest eingestellte Drosseleinrichtung mit konstantem Strömungswiderstand, insbesondere konstantem Leitungsquerschnitt, oder auch um ein Stromregelventil zur Regelung des Volumenstroms der Hydraulikflüssigkeit im Senkenpfad handeln. Insbesondere kann die Drosseleinrichtung, wie eingangs erläutert, zur Begrenzung einer maximalen Senkgeschwindigkeit dienen.The hydraulic system is intended for an industrial truck, in particular for an industrial truck with a load part. The at least one hydraulic lifting cylinder can in particular be a mast lifting cylinder for extending a mast belonging to the load part of the industrial truck. The truck can lift loads via the load section by extending the lifting cylinder. For lifting, hydraulic fluid is supplied to the hydraulic lifting cylinder from the hydraulic unit, in particular from a tank of the hydraulic unit. The hydraulic unit can comprise a hydraulic pump for this purpose. The hydraulic fluid is conducted to the at least one lifting cylinder via the lifting path and a piston of the lifting cylinder is thus extended. To lower the piston of the lifting cylinder, and thus the load part of the industrial truck, hydraulic fluid can be drawn from the at least one lifting cylinder via the lowering path be drained. The hydraulic fluid can be guided back to the hydraulic unit, in particular into the tank of the hydraulic unit, via the sink path. To regulate the lowering speed and in particular to achieve a lowering speed that is as constant as possible regardless of the load, a throttle device is arranged in the lowering path following the lowering valve. The throttle device forms a local flow resistance, in particular through a cross-sectional constriction in relation to the surrounding hydraulic line. The throttle device can, for example, be a permanently set throttle device with constant flow resistance, in particular a constant line cross-section, or a flow control valve for regulating the volume flow of the hydraulic fluid in the sink path. In particular, as explained above, the throttle device can be used to limit a maximum lowering speed.
Erfindungsgemäß ist im Senkenpfad zudem ein Bypassventil angeordnet zur Umgehung der Drosseleinrichtung, also insbesondere des Stromregelventils. Das Bypassventil ist nachfolgend auf das Senkventil im Senkenpfad angeordnet. Das Bypassventil greift über eine Steuerleitung den Absolutdruck der Hydraulikflüssigkeit im Senkenpfad vor dem Senkventil ab. Das Bypassventil ist insbesondere im Senkenpfad hinter dem Senkventil angeordnet. Abhängig von dem über die Steuerleitung gemessenen Druckwert schaltet das Bypassventil zwischen der Durchflussstellung und der Sperrstellung um, wobei das Bypassventil die Durchflussstellung einnimmt, wenn der über die Steuerleitung vor dem Senkventil abgegriffene Druckwert einen Grenzwert unterschreitet. Befindet sich das Bypassventil in der Durchflussstellung, so fließt die Hydraulikflüssigkeit von dem Hubzylinder kommend entlang des Senkenpfads durch das Bypassventil anstatt durch die Drossel. Die Drosseleinrichtung wird folglich umgangen. Das Bypassventil weist einen geringeren Strömungswiderstand auf als die Drossel. Bei unterhalb des Grenzdruckwerts liegendem Lastdruck der Hydraulikflüssigkeit im Senkenpfad, wird die Hydraulikflüssigkeit folglich über das Bypassventil als Bypass zu der Drosseleinrichtung anstatt über die Drosseleinrichtung selbst oder zusätzlich zu dieser abgelassen. Aufgrund des geringeren Strömungswiderstands des Bypassventils kann auch bei geringem Lastdruck eine hohe Senkgeschwindigkeit erreicht werden. Insbesondere ist das Bypassventil derart ausgelegt, dass eine vorbestimmte maximale Senkgeschwindigkeit auch dann erreicht werden kann, wenn das mit dem Hubzylinder verbundene Lastteil keine Last aufweist. Es kann also auch bei geringer oder ohne Last ein schnelles Absenken des Lastteils erreicht werden.According to the invention, a bypass valve is also arranged in the sink path to bypass the throttle device, that is to say in particular the flow control valve. The bypass valve is arranged following the lowering valve in the lowering path. The bypass valve picks up the absolute pressure of the hydraulic fluid in the lowering path in front of the lowering valve via a control line. The bypass valve is arranged in particular in the lowering path behind the lowering valve. Depending on the pressure value measured via the control line, the bypass valve switches between the flow position and the blocking position, with the bypass valve assuming the flow position when the pressure value tapped via the control line before the lowering valve falls below a limit value. If the bypass valve is in the flow position, the hydraulic fluid, coming from the lift cylinder, flows along the sink path through the bypass valve instead of through the throttle. The throttle device is consequently bypassed. The bypass valve has a lower flow resistance than the throttle. If the load pressure of the hydraulic fluid is below the limit pressure value in the Sink path, the hydraulic fluid is consequently drained via the bypass valve as a bypass to the throttle device instead of via the throttle device itself or in addition to it. Due to the lower flow resistance of the bypass valve, a high lowering speed can be achieved even with low load pressure. In particular, the bypass valve is designed in such a way that a predetermined maximum lowering speed can also be achieved when the load part connected to the lifting cylinder has no load. A rapid lowering of the load part can therefore be achieved even with little or no load.
Aufgrund des Abgreifens eines Absolutdruckwerts benötigt die erfindungsgemäße Hydraulikanordnung lediglich eine einzige Steuerleitung, während bei der eingangs erläuterten Hubvorrichtung aus dem Stand der Technik zwei Steuerleitungen einen Differenzdruck über das Senkventil abgreifen. Insbesondere weist die Hydraulikanordnung lediglich eine solche Steuerleitung auf, das Bypassventil kann also dazu ausgebildet sein, über nur eine Steuerleitung den Lastdruck der Hydraulikflüssigkeit im Senkenpfad vor dem Senkventil als Absolutwert abzugreifen. Das Abgreifen eines Differenzdrucks, wie im erläuterten Stand der Technik, hat zudem den Nachteil, dass das Schaltventil abhängig vom Volumenstrom durch das Senkventil schaltet, also nicht ausschließlich lastabhängig ist, sondern auch von der Stellung des Senkventils oder dem Strömungswiderstand des Senkventils abhängt. Das erfindungsgemäße, lediglich über den Absolutlastdruck vor dem Senkventil gesteuerte Bypassventil, ermöglicht einen sicheren Bypass der Drosseleinrichtung unabhängig von der Stellung des Senkventils. Die erfindungsgemäße Hydraulikanordnung ist somit einfacher aufgebaut und auslegbar sowie weniger fehleranfällig als die aus dem Stand der Technik bekannte Hubvorrichtung.Due to the pick-up of an absolute pressure value, the hydraulic arrangement according to the invention only requires a single control line, while in the lifting device from the prior art explained at the beginning, two control lines pick up a differential pressure via the lowering valve. In particular, the hydraulic system has only one such control line, so the bypass valve can be designed to pick up the load pressure of the hydraulic fluid in the lowering path in front of the lowering valve as an absolute value via only one control line. Picking up a differential pressure, as in the explained prior art, also has the disadvantage that the switching valve switches depending on the volume flow through the lowering valve, i.e. it is not exclusively load-dependent, but also depends on the position of the lowering valve or the flow resistance of the lowering valve. The bypass valve according to the invention, controlled only via the absolute load pressure upstream of the lowering valve, enables a reliable bypass of the throttle device regardless of the position of the lowering valve. The hydraulic system according to the invention is thus more simply constructed and designed and less prone to errors than the lifting device known from the prior art.
Nach einer Ausgestaltung Drosseleinrichtung umfasst die Drosseleinrichtung ein Stromregelventil zur Regelung des Volumenstroms der Hydraulikflüssigkeit im Senkenpfad, wie bereits erwähnt. Die Drosseleinrichtung kann insbesondere durch ein solches Stromregelventil gebildet sein. Ein Stromregelventil erlaubt eine insbesondere stufenlose Regelung des Hydraulikstroms im Senkenpfad und kann die maximale Senkgeschwindigkeit begrenzen.According to one embodiment of the throttle device, the throttle device comprises a flow control valve for regulating the volume flow of the hydraulic fluid in the sink path, as already mentioned. The throttle device can in particular be formed by such a flow control valve. A flow control valve allows, in particular, continuous regulation of the hydraulic flow in the lowering path and can limit the maximum lowering speed.
Nach einer Ausgestaltung ist das Bypassventil dazu ausgebildet, bei Erreichen oder Überschreiten des Grenzdruckwerts durch den Lastdruck von der Durchflussstellung in die Sperrstellung zu schalten, so dass vom Hubzylinder durch den Senkenpfad fließende Hydraulikflüssigkeit die Drosseleinrichtung durchläuft. Das Bypassventil kann somit lastdruckabhängig zwischen Durchflussstellung und Sperrstellung hin und her schalten. Liegt der Lastdruck der Hydraulikflüssigkeit im Senkenpfad vor dem Senkventil beim Grenzdruckwert oder darüber, so kann die Hydraulikflüssigkeit über die Drossel, also insbesondere das Stromregelventil, abgelassen und somit die Senkgeschwindigkeit, insbesondere auch bei großen Lasten, auf einem vorbestimmten Maximalwert gehalten werden.According to one embodiment, the bypass valve is designed to switch from the flow position to the blocking position when the load pressure reaches or exceeds the limit pressure value, so that hydraulic fluid flowing from the lift cylinder through the sink path passes through the throttle device. The bypass valve can thus switch back and forth between the flow position and the blocking position depending on the load pressure. If the load pressure of the hydraulic fluid in the lowering path upstream of the lowering valve is at the limit pressure value or above, the hydraulic fluid can be drained via the throttle, i.e. in particular the flow control valve, and the lowering speed can thus be kept at a predetermined maximum value, especially with large loads.
Nach einer Ausgestaltung ist die Steuerleitung eine hydraulische Steuerleitung, das Bypassventil kann somit mechanisch unmittelbar über die im Senkenpfad verlaufende Hydraulikflüssigkeit gesteuert werden. Nach einer alternativen Ausgestaltung ist die Steuerleitung eine elektrische Steuerleitung. Dann kann zudem ein Drucksensor vorgesehen sein, der den im Senkenpfad vor dem Senkventil anliegenden Lastdruck der Hydraulikflüssigkeit ermittelt. Insbesondere kann eine Steuereinheit vorgesehen sein, die abhängig von dem durch den Sensor ermittelten Lastdruck das Bypassventil schaltet.According to one embodiment, the control line is a hydraulic control line, and the bypass valve can thus be controlled mechanically directly via the hydraulic fluid running in the sink path. According to an alternative embodiment, the control line is an electrical control line. A pressure sensor can then also be provided which determines the load pressure of the hydraulic fluid present in the lowering path in front of the lowering valve. In particular, a control unit can be provided which switches the bypass valve as a function of the load pressure determined by the sensor.
Nach einer Ausgestaltung sind die Drosseleinrichtung und das Bypassventil separat voneinander ausgebildet. Drosseleinrichtung und Bypassventil können also als zwei voneinander unabhängige Bauteile im Senkenpfad angeordnet sein. Die Drosseleinrichtung und das Bypassventil können hierbei im Senkenpfad auf das Senkventil nachfolgend in parallelen Abschnitten des Senkenpfads angeordnet sein. Die Drosseleinrichtung kann dem Senkenpfad stets zugeschaltet sein. Bei Unterschreiten des Grenzdruckwerts ist eine Umgehung der Drosseleinrichtung aufgrund des geringeren Strömungswiderstands des Bypassventils auch dann gewährleistet. Nach einer alternativen Ausgestaltung sind die Drosseleinrichtung und das Bypassventil als ein gemeinsames Bauteil ausgebildet, insbesondere umfasst die Drosseleinrichtung ein Stromregelventil, welches mit dem Bypassventil als ein gemeinsames Ventil ausgebildet ist. Insbesondere können Stromregelventil und Bypassventil als gemeinsames 2/2-Wege-Ventil ausgebildet sein. Ein solcher Aufbau ist besonders einfach. Es kann dann abhängig vom anliegenden Lastdruck zwischen Bypassventil und Drosseleinrichtung/Stromregelventil umgeschaltet werden.According to one embodiment, the throttle device and the bypass valve are designed separately from one another. Throttle device and bypass valve can be used as two independent components can be arranged in the sink path. The throttle device and the bypass valve can be arranged in the lowering path following the lowering valve in parallel sections of the lowering path. The throttle device can always be connected to the sink path. If the pressure falls below the limit pressure, bypassing the throttle device is also guaranteed because of the lower flow resistance of the bypass valve. According to an alternative embodiment, the throttle device and the bypass valve are designed as a common component, in particular the throttle device comprises a flow control valve, which is designed as a common valve with the bypass valve. In particular, the flow control valve and bypass valve can be designed as a common 2/2-way valve. Such a structure is particularly simple. It can then be switched between the bypass valve and the throttle device / flow control valve depending on the load pressure applied.
Nach einer Ausgestaltung ist das Bypassventil unmittelbar mit dem Hydraulikaggregat verbunden zur Rückführung der Hydraulikflüssigkeit über den Senkenpfad. Unmittelbar verbunden bedeutet, dass zwischen Bypassventil und Hydraulikaggregat, d. h. insbesondere einem Tank des Hydraulikaggregats, keine weiteren hydraulischen Elemente (außer eine die Hydraulikflüssigkeit führende Hydraulikleitung) angeordnet sind. Somit befinden sich im Bypassteil des Senkenpfads keine weiteren Elemente, die den Strömungswiderstand erhöhen und somit das Erreichen einer gewünschten Senkgeschwindigkeit verhindern könnten.According to one embodiment, the bypass valve is connected directly to the hydraulic unit for returning the hydraulic fluid via the sink path. Directly connected means that between the bypass valve and the hydraulic unit, i. H. in particular a tank of the hydraulic unit, no further hydraulic elements (apart from a hydraulic line carrying the hydraulic fluid) are arranged. Thus, there are no further elements in the bypass part of the sink path that could increase the flow resistance and thus prevent a desired lowering speed from being reached.
Die Erfindung betrifft zudem ein Flurförderzeug mit einer wie oben erläuterten Hydraulikanordnung. Der mindestens eine Hubzylinder der Hydraulikanordnung kann insbesondere ein Masthubzylinder sein, der auf ein Lastteil des Flurförderzeugs wirkt. Über den Masthubzylinder kann insbesondere ein Mast des Flurförderzeugs aus- und eingefahren werden, wie bereits erläutert.The invention also relates to an industrial truck with a hydraulic system as explained above. The at least one lifting cylinder of the hydraulic system can in particular be a mast lifting cylinder that acts on a load part of the industrial truck. In particular, a mast of the industrial truck can be extended and retracted via the mast lifting cylinder, as already explained.
Ausgestaltungen der Erfindung werden im Folgenden anhand von Figuren erläutert. Es zeigen:
- Figur 1
- eine erste Ausgestaltung einer erfindungsgemäßen Hydraulikanordnung,
- Figur 2
- eine zweite Ausgestaltung einer erfindungsgemäßen Hydraulikanordnung.
- Figure 1
- a first embodiment of a hydraulic system according to the invention,
- Figure 2
- a second embodiment of a hydraulic system according to the invention.
Soweit nichts anderes angegeben ist, bezeichnen im Folgenden gleiche Bezugszeichen gleiche Gegenstände.Unless stated otherwise, the same reference symbols denote the same items below.
In
Das Bypassventil 28 ist zwischen einer Durchflussstellung und einer Sperrstellung verstellbar und greift über eine Steuerleitung 32 den im Senkenpfad 22 vor dem Senkventil 24 anliegenden Lastdruck der Hydraulikflüssigkeit als Absolutwert ab. Das Bypassventil 28 weist zudem einen geringeren Strömungswiderstand auf als das Stromregelventil 26.The
Zum Ausfahren eines Kolbens des Hubzylinders 12, beispielsweise zum Anheben eines Lastteils des Flurförderzeugs, wird Hydraulikflüssigkeit aus dem Hydrauliktank 18 über die Hydraulikpumpe 16 und durch das Rückschlagventil 20 entlang des Hebenpfads 14 dem Hubzylinder 12 zugeführt. Hierbei ist das Senkventil 24 sowie auch das Druckbegrenzungsventil 30 geschlossen. Das Druckbegrenzungsventil 30 öffnet in an sich bekannter Weise, sollte im Hebenpfad 14 ein ungewöhnlich hoher Druck auftreten und führt zur Rückleitung der Hydraulikflüssigkeit in den Tank 18. Das Bypassventil 28 ist in Abhängigkeit des anstehenden Hubdruckes geöffnet oder geschlossen, was aufgrund des geschlossenen Senkventils 24 jedoch keinen Einfluss auf den Hubvorgang hat.To extend a piston of the lifting
Zum Absenken des Hubzylinders und somit des damit verbundenen Lastteils wird das Senkventil 24 geöffnet. Ein Rückfluss über den Hebenpfad 14 ist aufgrund des Rückschlagventils 20 verhindert. Bedingt durch das Eigengewicht des Lastteils bzw. der auf dem Lastteil aufgenommenen Last wird der Kolben des Hubzylinders 12 eingefahren und die Hydraulikflüssigkeit entlang des Senkenpfads 22 zu dem Hydrauliktank 18 zurückgeführt. Das Bypassventil 28 greift, wie erwähnt, über die Steuerleitung 32 den absoluten Lastdruck vor dem Senkventil 24 ab. Übersteigt der Lastdruck dort einen vorbestimmten Grenzwert, so verbleibt das Bypassventil 28 in seiner Sperrstellung oder schaltet in diese um, wodurch entlang des Senkenpfads 22 durch das Senkventil 24 zum Tank 18 laufende Hydraulikflüssigkeit über das Stromregelventil 26 läuft. Das Stromregelventil 26 kann dabei den Volumenstrom der Hydraulikflüssigkeit derart regeln, dass stets eine maximale Senkgeschwindigkeit erreicht und insbesondere nicht überschritten wird. Ist jedoch auf dem Lastteil keine oder nur eine sehr geringe Last aufgenommen, so ist der im Senkenpfad 22 vorliegende Lastdruck derart gering, dass aufgrund des Strömungswiderstands des Stromregelventils 26 nicht die vorbestimmte maximal mögliche Senkgeschwindigkeit erreicht werden kann. In diesem Fall wird der vorbestimmte Grenzdruckwert unterschritten, was das Bypassventil 28 über die Steuerleitung 32 ermittelt. Das Bypassventil 28 schaltet dann in seine Durchflussstellung, wodurch die aus dem Hubzylinder 12 über den Senkenpfad 22 und das Senkventil 24 ablaufende Hydraulikflüssigkeit, unter Umgehung des Stromregelventils 26 unmittelbar in den Hydrauliktank 18 zurückgeführt werden kann. Aufgrund des sehr geringen Strömungswiderstands des Bypassventils kann somit auch bei geringer oder ohne Last die maximal mögliche Senkgeschwindigkeit oder zumindest eine wesentlich höhere Senkgeschwindigkeit als über das Stromregelventil 26 erreicht werden. Das Stromregelventil 26 kann dabei eine grundsätzlich beliebige Stellung einnehmen, das die Hydraulikflüssigkeit aufgrund des geringeren Strömungswiderstands ohnehin überwiegend durch das Bypassventil 28 abläuft.The lowering
Die Hydraulikanordnung 10' gemäß der Ausgestaltung nach
Die erfindungsgemäßen Hydraulikanordnungen sind einfach im Aufbau und weniger fehleranfällig als Hydraulikanordnungen, die eine Druckdifferenz über das Senkventil abgreifen. So muss bei der Erfindung zum einen nur eine einzige Steuerleitung verwendet werden. Zum anderen erfolgt das Schalten des Bypassventils aufgrund des Abgreifens eines Absolutdrucks zuverlässiger und insbesondere unabhängig von dem durch das Senkventil laufenden Volumenstrom.The hydraulic systems according to the invention are simple in structure and less prone to failure than hydraulic systems that pick up a pressure difference across the lowering valve. In the case of the invention, on the one hand, only one Control line can be used. On the other hand, the switching of the bypass valve takes place more reliably due to the tapping of an absolute pressure and in particular independently of the volume flow running through the lowering valve.
- 10, 10'10, 10 '
- HydraulikanordnungHydraulic arrangement
- 1212
- MasthubzylinderMast lift cylinder
- 1414th
- HebenpfadLifting path
- 1616
- HydraulikmotorHydraulic motor
- 1818th
- HydrauliktankHydraulic tank
- 2020th
- Rückschlagventilcheck valve
- 2222nd
- SenkenpfadSink path
- 2424
- SenkventilLowering valve
- 2626th
- StromregelventilFlow control valve
- 2828
- BypassventilBypass valve
- 3030th
- DruckbegrenzungsventilPressure relief valve
- 3232
- SteuerleitungControl line
- 3434
- gemeinsames Ventilcommon valve
Claims (10)
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DE4324464A1 (en) | 1993-07-21 | 1995-01-26 | Jungheinrich Ag | Hydraulic lifting apparatus for battery-operated industrial trucks |
US20060273270A1 (en) * | 2003-05-16 | 2006-12-07 | Markus Bill | Valve |
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EP2813461A1 (en) * | 2012-02-02 | 2014-12-17 | Kabushiki Kaisha Toyota Jidoshokki | Forklift hydraulic control apparatus |
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DE10031892A1 (en) * | 2000-06-30 | 2002-01-10 | Bosch Gmbh Robert | Controlling speed of electrohydraulic lifting drive involves using range between minimum, maximum revolution rates as proportional working range for controlling electric motor speed |
DE10048215A1 (en) * | 2000-09-28 | 2002-04-11 | Still Wagner Gmbh & Co Kg | Hydraulic lifting device |
DE20208577U1 (en) * | 2002-06-03 | 2003-12-11 | Hawe Hydraulik Gmbh & Co. Kg | Electro-hydraulic lift control device for industrial trucks |
DE10357631B4 (en) * | 2003-01-29 | 2019-05-16 | Buchholz Hydraulik Gmbh | Control device for a lifting and lowering control |
-
2019
- 2019-05-02 DE DE102019111295.8A patent/DE102019111295A1/en active Pending
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Patent Citations (7)
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DE4324464A1 (en) | 1993-07-21 | 1995-01-26 | Jungheinrich Ag | Hydraulic lifting apparatus for battery-operated industrial trucks |
US20060273270A1 (en) * | 2003-05-16 | 2006-12-07 | Markus Bill | Valve |
WO2008151727A2 (en) | 2007-06-15 | 2008-12-18 | Robert Bosch Gmbh | Control arrangement with pipe burst safety function |
DE102007027567A1 (en) * | 2007-06-15 | 2008-12-18 | Robert Bosch Gmbh | Control arrangement with pipe rupture function |
US9771250B2 (en) * | 2011-12-26 | 2017-09-26 | Kabushiki Kaisha Toyota Jidoshokki | Hydraulic control device for forklift |
EP2813461A1 (en) * | 2012-02-02 | 2014-12-17 | Kabushiki Kaisha Toyota Jidoshokki | Forklift hydraulic control apparatus |
DE112016005297T5 (en) * | 2015-11-18 | 2018-08-02 | Kabushiki Kaisha Toyota Jidoshokki | Hydraulic drive device for a freight handling vehicle |
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