EP0367038B2 - Hydraulic steering system and automotive works-vehicle provided with such a steering system - Google Patents

Hydraulic steering system and automotive works-vehicle provided with such a steering system Download PDF

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Publication number
EP0367038B2
EP0367038B2 EP89119462A EP89119462A EP0367038B2 EP 0367038 B2 EP0367038 B2 EP 0367038B2 EP 89119462 A EP89119462 A EP 89119462A EP 89119462 A EP89119462 A EP 89119462A EP 0367038 B2 EP0367038 B2 EP 0367038B2
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EP
European Patent Office
Prior art keywords
hydraulic
steering
pressure
steering system
valve
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Expired - Lifetime
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EP89119462A
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German (de)
French (fr)
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EP0367038B1 (en
EP0367038A1 (en
Inventor
Douglas Millard Gage
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Deere and Co
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Deere and Co
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Publication of EP0367038A1 publication Critical patent/EP0367038A1/en
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/225—Control of steering, e.g. for hydraulic motors driving the vehicle tracks
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/08—Superstructures; Supports for superstructures
    • E02F9/0841—Articulated frame, i.e. having at least one pivot point between two travelling gear units
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2217—Hydraulic or pneumatic drives with energy recovery arrangements, e.g. using accumulators, flywheels

Definitions

  • Expandable flexible synthetic tubing that is designed to accommodate pressure peaks, or leakage systems through which pressure peaks can be diverted, are not a complete solution to the problem.
  • the unpublished EP-A-306 988 describes a hydraulic steering system of the type mentioned, which contains two hydraulic steering cylinders.
  • the steering cylinders are optionally connected to a hydraulic pressure source or a return line via a separate hydraulic line from a control valve.
  • Cross-pressure relief valves are arranged between the two lines leading to the steering cylinders in order to relieve the pressure in the system.
  • the object to be achieved with the invention is seen in the provision of a hydraulic steering system of the type mentioned at the outset, by means of which pressure peaks can be reduced, so that, for example, the hydraulic steering system of a work vehicle works smoothly.
  • the object is achieved on the basis of a hydraulic steering system according to the generic features of claim 1 according to the invention by the characterizing features of this claim.
  • the hydraulic connections for example with the steering control, are connected via hydraulic supply lines.
  • the hydraulic motors are preferably hydraulic steering cylinders of a steerable vehicle.
  • Pressure swings in the hydraulic cylinders in the direction of the pressure accumulator can be reduced by the exchange check valve arranged between the hydraulic motors. A flow from one hydraulic cylinder to the other is not possible.
  • the loader :
  • the loader 10 shown in Figure 1 is a four wheel driven, articulated loader.
  • the loader 10 comprises a support frame 12 and wheels 14 engaging with the ground.
  • the front part of the loader 10 is provided with a movable boom arrangement 16, at the end of which a pivotable shovel 18 is arranged.
  • the boom is raised by extending a hydraulic boom lift actuator 20.
  • the bucket 18 is pivoted by the hydraulic bucket tilt actuation element 22.
  • the loader 10 is on the vertical axes of rotation 24, 26 articulated and can be steered by a hydraulic control circuit, as shown in Figure 2.
  • the loader 10 is driven by an internal combustion engine housed in the machine housing 30.
  • the internal combustion engine also drives hydraulic pumps, which in turn supply the working groups of the loader 10 and other hydraulic actuation systems.
  • An operator controls the functions of the loader 10 from the cab 32.
  • FIG. 2 The entire hydraulic steering system is shown schematically in Figure 2. It contains an open and a closed hydraulic system.
  • a hydraulic system according to FIG. 2 has already been disclosed by EP 0 306 988 A2 or US Pat. No. 4,809,586 by the applicant. Reference is hereby made to this disclosure.
  • the open center hydraulic system is supplied with hydraulic fluid by a non-adjustable positive displacement pump 100, the hydraulic fluid being passed on from the pump through the hydraulic line 102.
  • the closed hydraulic system (closed center hydraulic system) is supplied with hydraulic fluid by a variable displacement pump 104, the variable displacement pump 104 being provided with a pressure-sensing and pressure-compensating arrangement for maintaining a constant pressure in the hydraulic line 106.
  • the pump 104 is also provided with a hydraulic drainage channel 105, through which hydraulic fluid that runs out is led back to a collecting container 108. Both pumps 100, 104 are operatively connected in a piggyback manner and thus form a compact pump unit.
  • the pumps are driven by the internal combustion engine via suitable mechanical couplings.
  • the pumps 100 and 104 draw the hydraulic fluid through a common suction line 110 from a common reservoir 108.
  • the line 110 is equipped with a filter 112, which removes large particles from the liquid flow that is fed to the pumps 100 and 104.
  • the hydraulic fluid delivered by the pump 100 is directed through the line 102 to a priority valve arrangement 120, which controls the fluid flow between a steering arrangement 200 and a loader arrangement to which the line 302 leads.
  • the priority valve assembly 120 gives priority to the steering assembly 200 by shutting off the hydraulic fluid flow to the loader assembly when there is a fluid request from the steering assembly.
  • the priority valve assembly 120 includes a spring biased 2-position spool 122 that selectively directs fluid to the steering and loader assemblies.
  • the slide 122 lies between hydraulic pressure sensing lines 124 and 125, which have constriction points, and is kept in hydraulic balance.
  • valve 210 When the steering valve 210 is set in a middle, neutral position, the hydraulic flow to the supply line 202 through the valve 210 is interrupted, whereby the hydraulic pressure in the line 202 and in the sensing line 124 increases. In its middle position, valve 210 connects sensing line 125 to header return line 140 via line 126a, thereby reducing the hydraulic pressure in sensing line 125. As a result, the increasing hydraulic pressure in line 124 exceeds the hydraulic pressure in line 125 as well as the biasing force of spring 129, causing the spool 122 to be in a position in which hydraulic fluid is delivered to the leather assembly supply line 302.
  • the priority valve assembly 120 is further provided with a filter 126 and a pressure relief valve 128 through which hydraulic fluid can be directed to the reservoir return line 130.
  • the reservoir return line 130 receives hydraulic fluid from the sensing line 125 when a predeterminable pressure is exceeded.
  • Hydraulic fluid that flows from the steering assembly 200 and the leather assembly is directed to the reservoir 108 through the reservoir return line 140.
  • the collecting container return line 140 is equipped with a return filter arrangement 142, which in turn has a filter 144, a hydraulically balanced pressure relief valve 146 and a hydraulically balanced electrical pressure sensor switch 148.
  • the hydraulic fluid is filtered through the filter 144 and then returns to the reservoir 108.
  • the filter 144 collects foreign matter, the hydraulic pressure drop across the filter 144 increases. This leads to the closing of the electrical switch 148.
  • the closing of the electrical switch 148 activates an indicator lamp which is located in the control cabin 32 of the loader 10 and which draws the operator's attention to the fact that the filter 144 should be cleaned or replaced.
  • the pressure limiting valve 146 When the pressure drop across the filter 144 continues to increase due to additional substances accumulating on the filter 144, the pressure limiting valve 146 also opens and enables a hydraulic flow through a bypass past the filter 144.
  • the hydraulic fluid output of the pump 104 is directed to a hydraulic pressure reduction device via a hydraulic supply line 402 and to a brake arrangement via a hydraulic supply line 502.
  • the steering arrangement 200 receives hydraulic fluid from the priority valve arrangement 120 via the hydraulic supply line 202.
  • the hydraulic fluid is directed to a steplessly adjustable steering control valve 210.
  • Hydraulic fluid is routed through the main fluid passage of the valve to steering hydraulic motors or cylinders 220L and 220R to hydraulically assist the steering of the loader.
  • the control valve 210 comprises a metering pump 212 and a valve structure 214, which are coupled to one another by a mechanical return connection 216.
  • Valve structure 214 includes a main flow opening and may also include a damping flow opening.
  • the damping flow opening comprises a number of limited flow channels which serve to dampen pressure peaks in the main flow opening.
  • the steering control valve 210 is described in detail in U.S. Patent No. 4,781,219, which is incorporated herein by reference.
  • the steering arrangement 200 is also equipped with an optionally available additional steering pump 250 which draws hydraulic fluid from the reservoir return line 150 via a hydraulic line 252 and directs the hydraulic fluid to the hydraulic supply line 202 via the hydraulic line 254.
  • the additional pump 250 is electrically powered and alternatively provides hydraulic pressure when the pump 100 is not operating.
  • the valve 256 for the additional steering pump 250 serves to start the pump 250.
  • the control valve 256 comprises a hydraulically balanced, spring-biased piston 258, which is hydraulically balanced between the sensing line 125 and the supply line 202 .
  • a hydraulic sensing line 261 da control valve 256 is fluidly connected to the sensing line 125.
  • the valve piston 258 is coupled to an electrical switch 270, which in the closed state starts the electrical pump 250.
  • the switch 270 is closed when the hydraulic pressure in the sensing line 125 exceeds or is equal to the hydraulic pressure in the line 260, which indicates that the pump 100 has failed,
  • a mechanical damping device 600 which is the subject of the present invention, is hydraulically arranged between the steering cylinders 220L and 220R.
  • the damping device 600 serves to absorb or damp hydraulic pressure peaks which occur in the steering cylinders during the operation of the vehicle. Such pressure peaks can occur through rapid adjustment of the steering, reversing the steering direction, and / or external impacts on the steering system.
  • FIGS. 3a and 3b show an embodiment of the pressure damping device.
  • the first embodiment of a damping device 670 contains a pressure accumulator 672, which is hydraulically located between the supply line 221 and the return line 223 of the control cylinders 220L and 220R via an exchange check valve 674.
  • the shuttle valve 674 includes two inlets 676 and 678 which are hydraulically connected to the control cylinders 220L and 220R, respectively.
  • the valve 674 also includes an outlet 680 which is hydraulically connected to the hydraulic pressure accumulator 672.
  • the ball 682 of the shuttle valve 674 can be located anywhere within the valve 674, as shown in FIG. 3a. However, if one of the control cylinders is subjected to a pressure spike, a pressure difference is generated between the control cylinders, by means of which the ball 682 is displaced from the side of the control cylinder with the higher pressure to the side of the control cylinder with the lower pressure. If the hydraulic pressure peak is applied to the steering cylinder 220L, as shown in FIG. 3b, the pressure in the steering cylinder 220L exceeds the pressure in the steering cylinder 220R, as a result of which the ball 682 is moved away from the steering cylinder 220L and in the direction of the steering cylinder 220R .
  • the shuttle valve 674 connects the steering cylinder 220L to the pressure accumulator 672.
  • the hydraulic pressure peak is absorbed by the pressure accumulator 672.
  • the ball 682 prevents direct flow between the two control cylinders.
  • the pressure accumulator 672 drives hydraulic fluid back through the exchange check valve 674 to the steering cylinder 220L and restores the steering cylinder 220L to equilibrium.
  • the mechanical hydraulic damping device as described here, represents a simple and effective means for damping hydraulic pressure peaks in steering systems of large vehicles.

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Power Steering Mechanism (AREA)
  • Fluid-Pressure Circuits (AREA)

Description

Die Erfindung betrifft ein hydraulisches Lenksystem, insbesondere für ein selbstfahrendes gelenkiges Arbeitsfahrzeug, mit wenigstens zwei Lenkungshydraulikmotoren, die über ein Lenkungsventil mit einer Hydraulikdruckquelle in Verbindung stehen, sowie ein selbstfahrendes Arbeitsfahrzeug mit einem derartigen Lenksystem.The invention relates to a hydraulic steering system, in particular for a self-propelled articulated work vehicle, with at least two steering hydraulic motors, which are connected to a hydraulic pressure source via a steering valve, and a self-propelled work vehicle with such a steering system.

Große Arbeitsmaschinen, wie beispielsweise selbstfahrende gelenkige Lader mit einem hydraulischen Lenksystem, lassen sich nicht immer so stoßfrei lenken, wie dies wünschenswert ist. Dehnbare flexible Synthetikschläuche, die Druckspitzen aufnehmen sollen, oder Leckagesysteme, durch die Druckspitzen abgeleitet werden können, stellen keine vollständige Lösung des Problems dar.Large machines, such as self-propelled articulated loaders with a hydraulic steering system, cannot always be steered as smoothly as is desirable. Expandable flexible synthetic tubing that is designed to accommodate pressure peaks, or leakage systems through which pressure peaks can be diverted, are not a complete solution to the problem.

Die nicht vorveröffentliche EP-A-306 988 beschreibt ein hydraulisches Lenkungssytem der eingangs genannten Art, welches zwei hydraulische Lenkzylinder enthält. Die Lenkzylinder werden wahlweise jeweils über eine gesonderte Hydraulikleitung von einem Steuerventil mit einer Hydraulikdruckquelle oder einer Rücklaufleitung verbunden. Zwischen den beiden zu den Lenkzylindern führenden Leitungen sind überkreuzliegende Druckentspannungsventile angeordnet, um eine Druckentlastung des Systems herbeizuführen.The unpublished EP-A-306 988 describes a hydraulic steering system of the type mentioned, which contains two hydraulic steering cylinders. The steering cylinders are optionally connected to a hydraulic pressure source or a return line via a separate hydraulic line from a control valve. Cross-pressure relief valves are arranged between the two lines leading to the steering cylinders in order to relieve the pressure in the system.

Ferner wird durch die US-A-4 097 060 ein Dämpfungssystem für Knicklenkerfahrzeuge beschrieben, bei dem ein doppelseitig wirksamer Hydraulikzylinder zwischen die beiden Fahrzeugrahmenteile eingespannt ist. Jedes der beiden Enden des Hydraulikzylinders ist über eine Durchflußdrosselstelle mit einem Hydraulikspeicher verbunden. Hierdurch sollen Rollbewegungen zwischen den beiden Fahrzeugrahmenteilen abgefangen und gedämpft werden.Furthermore, US-A-4 097 060 describes a damping system for articulated vehicles, in which a double-acting hydraulic cylinder is clamped between the two vehicle frame parts. Each of the two ends of the hydraulic cylinder is connected to a hydraulic accumulator via a flow restriction. This is intended to absorb and dampen rolling movements between the two vehicle frame parts.

Die mit der Erfindung zu lösende Aufgabe wird darin gesehen, ein hydraulisches Lenksystem der eingangs genannten Art anzugeben, durch das sich Druckspitzen abbauen lassen, so daß beispielsweise das hydraulische Lenksystem eines Arbeitsfahrzeuges stoßfrei arbeitet.The object to be achieved with the invention is seen in the provision of a hydraulic steering system of the type mentioned at the outset, by means of which pressure peaks can be reduced, so that, for example, the hydraulic steering system of a work vehicle works smoothly.

Die Aufgabe wird ausgehend von einem hydraulischen Lenksystem gemäß den gattungsbildenden Merkmalen des Patentanspruches 1 erfindungsgemäß durch die kennzeichnenden Merkmale dieses Patentanspruches gelöst. Dabei stehen die Hydraulikanschlüsse, beispielsweise mit der Lenksteuerung, über hydraulische Versorgungsleitungen in Verbindung. Bei den Hydraulikmotoren handelt es sich vorzugsweise um hydraulische Lenkzylinder eines lenkbaren Fahrzeuges.The object is achieved on the basis of a hydraulic steering system according to the generic features of claim 1 according to the invention by the characterizing features of this claim. The hydraulic connections, for example with the steering control, are connected via hydraulic supply lines. The hydraulic motors are preferably hydraulic steering cylinders of a steerable vehicle.

Durch das zwischen den Hydraulikmotoren angeordnete Wechselrückschlagventil lassen sich Druckspitzen in den Hydraulikzylindern in Richtung des Druckspeichers abbauen. Ein Durchfluß von einem Hydraulikzylinder zum anderen ist hingegen nicht möglich.Pressure swings in the hydraulic cylinders in the direction of the pressure accumulator can be reduced by the exchange check valve arranged between the hydraulic motors. A flow from one hydraulic cylinder to the other is not possible.

Die Erfindung betrifft ferner ein selbstfahrendes Arbeitsfahrzeug, welches ein erfindungsgemäßes hydraulisches Lenksystem enthält. Dieses Fahrzeug enthält vorzugsweise einen Hydraulikkreis, bei dem eine unverstellbare Verdrängerpumpe in einem offenen Hydrauliksystem ein Prioritätsventil versorgt, welches den Flüssigkeitsstrom zwischen hydraulischen Lenkkreisen und hydraulischen Arbeitskreisen aufteilt. Dabei wird den Lenkkreisen der Vorzug gegeben. Eine mechanische Dämpfungsvorrichtung ist zwischen den hydraulischen Lenkungszylindern angeordnet. Vorzugsweise handelt es sich dabei um die oben beschriebene erfindungsgemäße Dämpfungsvorrichtung.The invention further relates to a self-propelled work vehicle which contains a hydraulic steering system according to the invention. This vehicle preferably contains a hydraulic circuit, in which an adjustable displacement pump in an open hydraulic system supplies a priority valve which divides the fluid flow between hydraulic steering circuits and hydraulic working circuits. The steering circuits are given preference. A mechanical damping device is arranged between the hydraulic steering cylinders. It is preferably the inventive damping device described above.

Weitere vorteilhafte Ausgestaltungen und Weiterbildungen der Erfindung gehen aus den Unteransprüchen hervor.Further advantageous refinements and developments of the invention emerge from the subclaims.

Anhand der Zeichnung, die ein Ausführungsbeispiel der Erfindung zeigt, sollen die Erfindung sowie weitere Vorteile und vorteilhafte Weiterbildungen und Ausgestaltungen der Erfindung näher beschrieben und erläutert werden.On the basis of the drawing, which shows an exemplary embodiment of the invention, the invention and further advantages and advantageous developments and refinements of the invention are to be described and explained in more detail.

Es zeigt:

  • Figur 1 die Seitenansicht eines vierradangetriebenen, gelenkigen Laders,
  • Figur 2 ein Hydraulikschema des Lenkungssystems gemäß der vorliegenden Erfindung und
  • Figur 3a und 3b Querschnittsansichten einer ersten Ausführungsart der hydraulischen Dämpfungseinrichtung.
It shows:
  • FIG. 1 shows the side view of a four-wheel-drive, articulated loader,
  • Figure 2 is a hydraulic diagram of the steering system according to the present invention and
  • Figures 3a and 3b cross-sectional views of a first embodiment of the hydraulic damping device.

Der Lader:The loader:

Der in Figur 1 dargestellte Lader 10 ist ein vierradangetriebener, gelenkiger Lader. Der Lader 10 umfaßt einen Tragrahmen 12 und mit dem Untergrund in Eingriff stehende Räder 14. Das Vorderteil des Laders 10 ist mit einer bewegbaren Auslegeranordnung 16 versehen, an deren Ende eine verschwenkbare Schaufel 18 angeordnet ist. Der Ausleger wird durch Ausdehnung eines hydraulischen Auslegerhebebetätigungselementes 20 angehoben. Die Schaufel 18 wird durch das hydraulische Schaufelkippbetätigungselement 22 verschwenkt.The loader 10 shown in Figure 1 is a four wheel driven, articulated loader. The loader 10 comprises a support frame 12 and wheels 14 engaging with the ground. The front part of the loader 10 is provided with a movable boom arrangement 16, at the end of which a pivotable shovel 18 is arranged. The boom is raised by extending a hydraulic boom lift actuator 20. The bucket 18 is pivoted by the hydraulic bucket tilt actuation element 22.

Der Lader 10 ist an den vertikalen Drehachsen 24, 26 gelenkig ausgebildet und läßt sich durch einen hydraulischen Steuerkreis, wie er in Figur 2 dargestellt ist, lenken. Der Lader 10 wird durch eine Verbrennungskraftmaschine, die in dem Maschinengehäuse 30 untergebrachtist, angetrieben. Die Verbrennungskraftmaschine treibt auch hydraulische Pumpen an, welche ihrerseits die Arbeitskreise des Laders 10 und andere hydraulische Betätigungssysteme versorgen. Eine Bedienungsperson steuert die Funktionen des Laders 10 von der Kabine 32 aus.The loader 10 is on the vertical axes of rotation 24, 26 articulated and can be steered by a hydraulic control circuit, as shown in Figure 2. The loader 10 is driven by an internal combustion engine housed in the machine housing 30. The internal combustion engine also drives hydraulic pumps, which in turn supply the working groups of the loader 10 and other hydraulic actuation systems. An operator controls the functions of the loader 10 from the cab 32.

Hydraulisches System:Hydraulic system:

Das gesamte hydraulische Lenksystem ist schematisch in Figur 2 dargestellt. Es enthält ein offenes und ein geschlossenes Hydrauliksystem. Ein Hydrauliksystem gemäß Figur 2 wurde bereits durch die EP 0 306 988 A2 beziehungsweise die US-PS 4,809,586 von der Anmelderin offenbart. Auf diese Offenbarung wird hiermit Bezug genommen.The entire hydraulic steering system is shown schematically in Figure 2. It contains an open and a closed hydraulic system. A hydraulic system according to FIG. 2 has already been disclosed by EP 0 306 988 A2 or US Pat. No. 4,809,586 by the applicant. Reference is hereby made to this disclosure.

Das offene Hydrauliksystem (open center hydraulic system) wird durch eine unverstellbare Verdrängerpumpe 100 mit Hydraulikflüssigkeit versorgt, wobei die Hydraulikflüssigkeit von der Pumpe durch die Hydraulikleitung 102 weitergeleitet wird. Das geschlossene Hydrauliksystem (closed center hydraulic system) wird durch eine Verstellpumpe 104 mit Hydraulikflüssigkeit versorgt, wobei die Verstellpumpe 104 mit einer Druckfühlenden und Druck kompensierenden Anordnung zur Aufrechterhaltung eines konstanten Druckes in der Hydraulikleitung 106 versehen ist. Die Pumpe 104 ist ferner mit einem hydraulischen Abflußkanal 105 versehen, durch den auslaufende Hydraulikflüssigkeit zurück zu einem Sammelbehälter 108 geführt wird. Beide Pumpen 100, 104 sind operativ in Huckepack-Weise zusammengeschaltet und bilden so eine kompakte Pumpeneinheit. Die Pumpen werden durch die Verbrennungskraftmaschine über geeignete mechanische Kupplungen angetrieben.The open center hydraulic system is supplied with hydraulic fluid by a non-adjustable positive displacement pump 100, the hydraulic fluid being passed on from the pump through the hydraulic line 102. The closed hydraulic system (closed center hydraulic system) is supplied with hydraulic fluid by a variable displacement pump 104, the variable displacement pump 104 being provided with a pressure-sensing and pressure-compensating arrangement for maintaining a constant pressure in the hydraulic line 106. The pump 104 is also provided with a hydraulic drainage channel 105, through which hydraulic fluid that runs out is led back to a collecting container 108. Both pumps 100, 104 are operatively connected in a piggyback manner and thus form a compact pump unit. The pumps are driven by the internal combustion engine via suitable mechanical couplings.

Die Pumpen 100 und 104 ziehen die Hydraulikflüssigkeit durch eine gemeinsame Ansaugleitung 110 aus einem gemeinsamen Sammelbehälter 108 an. Die Leitung 110 ist mit einem Filter 112 ausgerüstet, welcher große Partikel aus dem Flüssigkeitsstrom, der zu den Pumpen 100 und 104 geführt wird, entfernt.The pumps 100 and 104 draw the hydraulic fluid through a common suction line 110 from a common reservoir 108. The line 110 is equipped with a filter 112, which removes large particles from the liquid flow that is fed to the pumps 100 and 104.

Die von der Pumpe 100 geförderte Hydraulikflüssigkeit wird durch die Leitung 102 zu einer Prioritätsventilanordnung 120 gerichtet, welche den Flüssigkeitsstrom zwischen einer Lenkanordnung 200 und einer Laderanordnung, zu welcher die Leitung 302 fuhrt, steuert. Die Proritätsventilanordnung 120 gibt der Lenkanordnung 200 die Priorität, indem der Hydraulikflüssigkeitsstrom zu der Laderanordnung dann geschlossen wird, wenn eine Flüssigkeitsanforderung von der Lenkungsanordnung vorliegt, Die Prioritätsventilanordnung 120 enthält einen federvorgespannten 2-Positionen-Schieber 122, der wahlweise Flüssigkeit zu der Lenkungs- und der Laderanordnung richtet. Der Schieber 122 liegt zwischen hydraulischen Druckfühlleitungen 124 und 125, welche Verengungsstellen aufweisen, und wird in hydraulischem Gleichgewicht gehalten. Wenn das Lenkungsventil 210 in einer mittleren, neutralen Position eingestellt ist, wird der Hydraulikdurchfluß, der Versorgungsleitung 202 durch das Ventil 210 unterbrochen, wodurch der Hydraulikdruck in der Leitung 202 und in der Fühlleitung 124 ansteigt. In seiner mittleren Position verbindet das Ventil 210 die Fühlleitung 125 über die Leitung 126a mit der Sammelbehälterrücklaufleitung 140, wodurch der Hydraulikdruck in der Fühlleitung 125 reduziert wird. Hierdurch übersteigt der anwachsende Hydraulikdruck in der Leitung 124 den Hydraulikdruck in der Leitung 125 sowie die Vorspannungskraft der Feder 129, wodurch der Schieber 122 in eine Position gebracht wird, in der Hydraulikflüssigkeit an die Lederanordnungsversorgungsleitung 302 abgegeben wird.The hydraulic fluid delivered by the pump 100 is directed through the line 102 to a priority valve arrangement 120, which controls the fluid flow between a steering arrangement 200 and a loader arrangement to which the line 302 leads. The priority valve assembly 120 gives priority to the steering assembly 200 by shutting off the hydraulic fluid flow to the loader assembly when there is a fluid request from the steering assembly. The priority valve assembly 120 includes a spring biased 2-position spool 122 that selectively directs fluid to the steering and loader assemblies. The slide 122 lies between hydraulic pressure sensing lines 124 and 125, which have constriction points, and is kept in hydraulic balance. When the steering valve 210 is set in a middle, neutral position, the hydraulic flow to the supply line 202 through the valve 210 is interrupted, whereby the hydraulic pressure in the line 202 and in the sensing line 124 increases. In its middle position, valve 210 connects sensing line 125 to header return line 140 via line 126a, thereby reducing the hydraulic pressure in sensing line 125. As a result, the increasing hydraulic pressure in line 124 exceeds the hydraulic pressure in line 125 as well as the biasing force of spring 129, causing the spool 122 to be in a position in which hydraulic fluid is delivered to the leather assembly supply line 302.

Die Prioritätsventilanordnung 120 ist ferner mit einem Filter 126 und einem Druckbegrenzungsventil 128 versehen, durch welches Hydraulikflüssigkeit zu der Sammelbehälterrücklaufleitung 130 gerichtet werden kann. Die Sammelbehälterrücklaufleitung 130 nimmt Hydraulikflüssigkeit von der Fühlleitung 125 auf, wenn ein vorgebbarer Druck überschritten wird.The priority valve assembly 120 is further provided with a filter 126 and a pressure relief valve 128 through which hydraulic fluid can be directed to the reservoir return line 130. The reservoir return line 130 receives hydraulic fluid from the sensing line 125 when a predeterminable pressure is exceeded.

Hydraulikflüssigkeit, die aus der Lenkungsanordnung 200 und der Lederanordnung abfließt, wird durch die Sammelbehälterrücklaufleitung 140 zu dem Sammelbehälter 108 gerichtet. Die Sammelbehälterrücklaufleitung 140 ist mit einer Rücklauffilteranordnung 142 ausgestattet, welche ihrerseits einen Filter 144, ein hydraulisch im Gleichgewicht gehaltenes Druckbegrenzungsventil 146 und einen hydraulisch im Gleichgewicht gehaltenen elektrischen Druckfühlschalter 148 aufweist. Normalerweise wird die Hydraulikflüssigkeit durch den Filter 144 gefiltert und gelangt dann zu dem Sammelbehälter 108 zurück. Sammelt jedoch der Filter 144 Fremdstoffe, so steigt der Hydraulikdruckabfall über dem Filter 144 an. Dies führt zu einem Schließen des elektrischen Schalters 148. Durch das Schließen des elektrischen Schalters 148 wird eine Anzeigelampe angesteuert, die sich in der Bedienungskabine 32 des Laders 10 befindet und die Bedienungsperson darauf aufmerksam macht, daß der Filter 144 gereinigt beziehungsweise ausgewechselt werden sollte. Wenn der Druckabfall über dem Filter 144 durch zusätzliche, sich am Filter 144 ansammelnde Stoffe weiter ansteigt, öffnet sich auch das Druckbegrenzungsventil 146 und ermöglicht einen hydraulischen Durchfluß durch einen Beipaß am Filter 144 vorbei. Die zum Sammelbehälter 108 führende Hydraulikflüssigkeitsrücklaufleitung 150, welche sich stromabwärts der Filteranordnung 142 befindet, ist mit einem Ölkühler 152 ausgestattet, welcher das zum Sammelbehälter 108 zurückströmende Öl kühlt.Hydraulic fluid that flows from the steering assembly 200 and the leather assembly is directed to the reservoir 108 through the reservoir return line 140. The collecting container return line 140 is equipped with a return filter arrangement 142, which in turn has a filter 144, a hydraulically balanced pressure relief valve 146 and a hydraulically balanced electrical pressure sensor switch 148. Typically, the hydraulic fluid is filtered through the filter 144 and then returns to the reservoir 108. However, if the filter 144 collects foreign matter, the hydraulic pressure drop across the filter 144 increases. This leads to the closing of the electrical switch 148. The closing of the electrical switch 148 activates an indicator lamp which is located in the control cabin 32 of the loader 10 and which draws the operator's attention to the fact that the filter 144 should be cleaned or replaced. When the pressure drop across the filter 144 continues to increase due to additional substances accumulating on the filter 144, the pressure limiting valve 146 also opens and enables a hydraulic flow through a bypass past the filter 144. The hydraulic fluid return line 150 leading to the collecting tank 108, which is located downstream of the filter arrangement 142, is equipped with an oil cooler 152, which cools the oil flowing back to the reservoir 108.

Der Ausstoß an Hydraulikflüssigkeit der Pumpe 104 ist über eine hydraulische Versorgungsleitung 402 zu einer Hydraulikdruckverminderungseinrichtung und über eine hydraulische Versorgungsleitung 502 zu einer Bremsanordnung gerichtet.The hydraulic fluid output of the pump 104 is directed to a hydraulic pressure reduction device via a hydraulic supply line 402 and to a brake arrangement via a hydraulic supply line 502.

Die Lenkungsanordnung 200 erhält Hydraulikflüssigkeit über die hydraulische Versorgungsleitung 202 von der Prioritätsventilanordnung 120. Die Hydraulikflüssigkeit ist zu einem stufenlos einstellbaren Lenkungssteuerventil 210 gerichtet. Durch den Hauptflüssigkeitsdurchgang des Ventils wird Hydraulikflüssigkeit zu Lenkungshydraulikmotoren oder -zylindern 220L und 220R geleitet, um die Lenkung des Laders hydraulisch zu unterstützen. Das Steuerventil 210 umfaßt eine Dosierpumpe 212 und eine Ventilstruktur 214, welche miteinander durch eine mechanische Rückführungsverbindung 216 gekoppelt sind. Die Ventilstruktur 214 enthält eine Hauptdurchflußöffnung und kann auch eine Dämpfungsdurchflußöffnung enthalten. Die Dämpfungsdurchflußöffnung umfaßt eine Anzahl begrenzter Durchflußkanäle, welche der Dämpfung von Druckspitzen in der Hauptdurchflußöffnung dienen. Das Lenkungsteuerventil 210 ist im einzelnen in der US-PS 4,781,219 beschrieben, auf die hiermit bezüglich der Offenbarung Bezug genommen wird.The steering arrangement 200 receives hydraulic fluid from the priority valve arrangement 120 via the hydraulic supply line 202. The hydraulic fluid is directed to a steplessly adjustable steering control valve 210. Hydraulic fluid is routed through the main fluid passage of the valve to steering hydraulic motors or cylinders 220L and 220R to hydraulically assist the steering of the loader. The control valve 210 comprises a metering pump 212 and a valve structure 214, which are coupled to one another by a mechanical return connection 216. Valve structure 214 includes a main flow opening and may also include a damping flow opening. The damping flow opening comprises a number of limited flow channels which serve to dampen pressure peaks in the main flow opening. The steering control valve 210 is described in detail in U.S. Patent No. 4,781,219, which is incorporated herein by reference.

Die Lenkungsanordnung 200 ist ferner mit einer wahlweise verfügbaren, zusätzlichen Lenkungspumpe 250 ausgestattet, welche über eine Hydraulikleitung 252 Hydraulikflüssigkeit aus der Sammelbehälterrücklaufleitung 150 zieht und die Hydraulikflüssigkeit zu der hydraulischen Versorgungsleitung 202 über die Hydraulikleitung 254 leitet. Die zusätzliche Pumpe 250 ist elektrisch angetrieben und liefert ersatzweise hydraulischen Druck, wenn die Pumpe 100 nicht arbeitet. Das Ventil 256 für die zusätzliche Lenkungspumpe 250 dient dazu, die Pumpe 250 in Gang zu setzen. Das Steuerventil 256 umfaßt einen hydraulisch im Gleichgewicht gehaltenen, federvorgespannten Kolben 258, welcher zwischen der Fühlleitung 125 und der Versorgungsleitung 202 hydraulisch abgeglichen ist, Eine hydraulische Fühlleitung 260 des Steuerventils 256 ist flüssigkeitsmäßig mit einer Stelle der Versorgungsleitung 202 verbunden,welche stromaufwärts eines Rückschlagventils 264 liegt. Eine hydraulische Fühlleitung 261 da Steuerventils 256 ist flüssigkeitsmäßig mit der Fühlleitung 125 verbunden. Der Ventilkolben 258 ist mit einem elektrischen Schalter 270 gekoppelt, welcher im geschlossenen Zustand die elektrische Pumpe 250 in Gang setzt. Der Schalter 270 ist dann geschlossen, wenn der Hydraulikdruck in der Fühlleitung 125 den Hydraulikdruck in der Leitung 260 übersteigt beziehungsweise mit diesem gleich ist, wodurch angezeigt wird, daß die Pumpe 100 ausgefallen ist,The steering arrangement 200 is also equipped with an optionally available additional steering pump 250 which draws hydraulic fluid from the reservoir return line 150 via a hydraulic line 252 and directs the hydraulic fluid to the hydraulic supply line 202 via the hydraulic line 254. The additional pump 250 is electrically powered and alternatively provides hydraulic pressure when the pump 100 is not operating. The valve 256 for the additional steering pump 250 serves to start the pump 250. The control valve 256 comprises a hydraulically balanced, spring-biased piston 258, which is hydraulically balanced between the sensing line 125 and the supply line 202 . A hydraulic sensing line 261 da control valve 256 is fluidly connected to the sensing line 125. The valve piston 258 is coupled to an electrical switch 270, which in the closed state starts the electrical pump 250. The switch 270 is closed when the hydraulic pressure in the sensing line 125 exceeds or is equal to the hydraulic pressure in the line 260, which indicates that the pump 100 has failed,

Mechanisch-hydraulische Druckdämpfungsvorrichtung:Mechanical-hydraulic pressure damping device:

Hydraulisch ist zwischen die Lenkzylinder 220L und 220R eine mechanische Dämpfungsvorrchtung 600 angeordnet, welche Gegenstand der vorliegenden Erfindung ist. Die Dämpfungsvorrichtung 600 dient dazu, hydraulische Druckspitzen, die während des Betriebs des Fahrzeuges in den Lenkzylindern auftreten, zu absorbieran beziehungsweise zu dämpfen. Derartige Druckspitzen können durch rasche Verstellung der Lenkung, Umkehr der Lenkrichtung, und/oder externe Stöße auf das Lenksystem auftreten. Durch die Figuren 3a und 3b wird eine Ausführungsart der Druckdämpfungsvorrichtung dargestellt.A mechanical damping device 600, which is the subject of the present invention, is hydraulically arranged between the steering cylinders 220L and 220R. The damping device 600 serves to absorb or damp hydraulic pressure peaks which occur in the steering cylinders during the operation of the vehicle. Such pressure peaks can occur through rapid adjustment of the steering, reversing the steering direction, and / or external impacts on the steering system. FIGS. 3a and 3b show an embodiment of the pressure damping device.

Die erste Ausführungsart einer Dämpfungsvorrichtung 670, wie sie in Figur 3 dargestellt ist, enthält einen Druckspeicher 672, welcher über ein Wechselrückschlagventil 674 hydraulisch zwischen der Versorgungsleitung 221 und der Rückführleitung 223 der Steuerzylinder 220L und 220R liegt.The first embodiment of a damping device 670, as shown in FIG. 3, contains a pressure accumulator 672, which is hydraulically located between the supply line 221 and the return line 223 of the control cylinders 220L and 220R via an exchange check valve 674.

Das Wechselrückschlagventil 674 enthält zwei Einlässe 676 und 678, welche hydraulisch mit den Steuerzylindern 220L beziehungsweise 220R in Verbindung stehen. Das Ventil 674 enthält ferner einen Auslaß 680, welcher hydraulisch mit dem hydraulischen Druckspeicher 672 verbunden ist.The shuttle valve 674 includes two inlets 676 and 678 which are hydraulically connected to the control cylinders 220L and 220R, respectively. The valve 674 also includes an outlet 680 which is hydraulically connected to the hydraulic pressure accumulator 672.

Besteht keine Druckdifferenz zwischen den beiden Steuerzylindern 220L und 220R, so kann sich die Kugel 682 des Wechselrückschlagventils 674 irgendwo innerhalb des Ventils 674 befinden, wie dies Figur 3a zeigt. Ist jedoch einer der Steuerzylinder einer Druckspitze ausgesetzt, so wird eine Druckdifferenz zwischen den Steuerzylindern erzeugt, durch die die Kugel 682 von der Seite des Steuerzylinders mit dem höheren Druck zu du Seite des Steuerzylinders mit dem niedrigeren Druck verschoben wird. Liegt an dem Lenkzylinder 220L die hydraulische Druckspitze an, wie es in Figur 3b dargestellt ist, so übersteigt der Druck in dem Lenkzylinder 220L den Druck in dem Lenkzylinder 220R, wodurch die Kugel 682 von dem Lenkzylinder 220L weg und in Richtung des Lenkzylinders 220R bewegt wird.If there is no pressure difference between the two control cylinders 220L and 220R, the ball 682 of the shuttle valve 674 can be located anywhere within the valve 674, as shown in FIG. 3a. However, if one of the control cylinders is subjected to a pressure spike, a pressure difference is generated between the control cylinders, by means of which the ball 682 is displaced from the side of the control cylinder with the higher pressure to the side of the control cylinder with the lower pressure. If the hydraulic pressure peak is applied to the steering cylinder 220L, as shown in FIG. 3b, the pressure in the steering cylinder 220L exceeds the pressure in the steering cylinder 220R, as a result of which the ball 682 is moved away from the steering cylinder 220L and in the direction of the steering cylinder 220R .

Wenn sich die Kugel 682 von dem Lenkzylinder 220L weg bewegt, verbindet das Wechselrückschlagventil 674 den Lenkzylinder 220L mit dem Druckspeicher 672. Hierbei wird die hydraulische Druckspitze durch den Druckspeicher 672 absorbiert Die Kugel 682 verhindert einen direkten Durchfluß zwischen den beiden Steuerzylindern. Nachdem sich die hydraulische Druckspitze verflüchtigt hat oder abgebaut ist, treibt der Druckspeicher 672 Hydraulikflüssigkeit zurück durch das Wechselrückschlagventil 674 zu dem Lenkzylinder 220L und stellt den Lenkzylinder 220L wieder ins Gleichgewicht ein.When the ball 682 moves away from the steering cylinder 220L, the shuttle valve 674 connects the steering cylinder 220L to the pressure accumulator 672. The hydraulic pressure peak is absorbed by the pressure accumulator 672. The ball 682 prevents direct flow between the two control cylinders. After the hydraulic pressure peak has evaporated or is reduced, the pressure accumulator 672 drives hydraulic fluid back through the exchange check valve 674 to the steering cylinder 220L and restores the steering cylinder 220L to equilibrium.

Die mechanische hydraulische Dämpfungsvorrichtung, wie sie hier beschrieben wurden, stellt ein einfaches und wirkungsvolles Mittel zur Dämpfung hydraulischer Druckspitzen bei Lenksystemen großer Fahrzeuge dar.The mechanical hydraulic damping device, as described here, represents a simple and effective means for damping hydraulic pressure peaks in steering systems of large vehicles.

Claims (3)

  1. Hydraulic steering system, in particular for a self-propelling articulated working vehicle, with at least two hydraulic steering motors (220L, 220R) in communication with a hydraulic pressure source (100) via a steering valve (210), whereby a mechanical damping device (670) for smoothing out hydraulic pressure peaks is arranged between two hydraulic corrections of the hydraulic motors (220L, 220R) characterised in that the damping device (670) comprises a changeover check valve (674) and a hgdraulic pressure reservoir (672), the two inlet connections (676, 678) of the chargeover check valve (674) being in communication with the hydraulic motors (220L, 220R) and the outlet connection (680) of the changeover check valve (674) being in communication with the pressure reservoir (672).
  2. Hydraulic steering system according to claim 1, characterised in that the hydraulic motor is a hydraulic steering cylinder (220L, 220R),
  3. Self-propelling working vehicle with a hydraulic steering system according to one of claims 1 or 2.
EP89119462A 1988-10-25 1989-10-20 Hydraulic steering system and automotive works-vehicle provided with such a steering system Expired - Lifetime EP0367038B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US262399 1988-10-25
US07/262,399 US4915186A (en) 1988-10-25 1988-10-25 Hydraulic steering systems dampening devices

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EP0367038A1 EP0367038A1 (en) 1990-05-09
EP0367038B1 EP0367038B1 (en) 1992-12-30
EP0367038B2 true EP0367038B2 (en) 1995-05-17

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EP89119462A Expired - Lifetime EP0367038B2 (en) 1988-10-25 1989-10-20 Hydraulic steering system and automotive works-vehicle provided with such a steering system

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EP (1) EP0367038B2 (en)
JP (1) JP2937364B2 (en)
CA (1) CA1320980C (en)
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Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5895099A (en) * 1997-10-17 1999-04-20 Deere & Company Hydraulic structure for a brake system
US7597168B2 (en) * 2005-09-23 2009-10-06 Deere & Company Low engine speed steering performance
DE102009032212A1 (en) * 2009-07-03 2011-01-05 Dr. Ing. H.C. F. Porsche Aktiengesellschaft Hydraulic swing motor
DE102020113739A1 (en) * 2020-05-20 2021-11-25 Universität Paderborn Load simulation test bench and capacity element for a load simulation test bench

Family Cites Families (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE17508E (en) * 1926-01-23 1929-11-26 Power steering apparatus
GB1051690A (en) * 1963-08-19
US3333415A (en) * 1965-11-23 1967-08-01 Abex Corp Hydraulic transmission and speed and direction control valve therefor
US3360925A (en) * 1966-02-03 1968-01-02 Int Harvester Co Multiple speed hydraulic control system
DE1915102A1 (en) * 1969-03-25 1970-10-01 Vogel Ignaz Kg Hydropneumatic compression spring
US4097060A (en) * 1977-03-30 1978-06-27 Caterpillar Tractor Co. Roll stiffening and dampening in articulated vehicles
DE2742688A1 (en) * 1977-09-22 1979-04-05 Zahnradfabrik Friedrichshafen HYDRAULIC POWER STEERING WITH POWER SUPPLY DEVICE WITH PRESSURE ACCUMULATOR
US4310062A (en) * 1980-01-22 1982-01-12 International Harvester Company Hydrostatic steering arrangement
DE3006509C2 (en) * 1980-02-21 1984-10-25 Danfoss A/S, Nordborg Hydrostatic steering device
US4405030A (en) * 1981-03-16 1983-09-20 Deere & Company Steering system and compensating valve
US4382483A (en) * 1981-04-09 1983-05-10 Deere & Company Load-responsive steering control valve
US4509409A (en) * 1983-02-07 1985-04-09 Towmotor Corporation Pump arrangement for a linear fluid operated device
JPS6335030U (en) * 1986-08-25 1988-03-07
US4781219A (en) * 1986-10-10 1988-11-01 Eaton Corporation Fluid controller and dampening fluid path
DE3637709C3 (en) * 1986-11-05 1995-09-07 Ahlmann Baumaschinen Gmbh Self-propelled multi-purpose device
US4825748A (en) * 1987-07-02 1989-05-02 Parker-Hannifin Corporation Hydraulic actuator synchronization apparatus and system
US4809586A (en) * 1987-09-11 1989-03-07 Deere & Company Hydraulic system for a work vehicle

Also Published As

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EP0367038B1 (en) 1992-12-30
US4915186A (en) 1990-04-10
CA1320980C (en) 1993-08-03
JP2937364B2 (en) 1999-08-23
EP0367038A1 (en) 1990-05-09
JPH02171387A (en) 1990-07-03
DE58903167D1 (en) 1993-02-11

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