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EP0584078B1 - Overload protective device for a drive motor of a hydraulic pressure generator - Google Patents

Overload protective device for a drive motor of a hydraulic pressure generator Download PDF

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Publication number
EP0584078B1
EP0584078B1 EP92905344A EP92905344A EP0584078B1 EP 0584078 B1 EP0584078 B1 EP 0584078B1 EP 92905344 A EP92905344 A EP 92905344A EP 92905344 A EP92905344 A EP 92905344A EP 0584078 B1 EP0584078 B1 EP 0584078B1
Authority
EP
European Patent Office
Prior art keywords
pressure
valve
control chamber
main
consumer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92905344A
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German (de)
French (fr)
Other versions
EP0584078A1 (en
Inventor
Hartmut Benckert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Putzmeister Concrete Pumps GmbH
Original Assignee
Putzmeister Werk Maschinenfabrik GmbH
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Filing date
Publication date
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Publication of EP0584078A1 publication Critical patent/EP0584078A1/en
Application granted granted Critical
Publication of EP0584078B1 publication Critical patent/EP0584078B1/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/002—Hydraulic systems to change the pump delivery
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/10—Other safety measures
    • F04B49/103—Responsive to speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition

Definitions

  • a hydraulically driven thick matter feed pump e.g. a two-cylinder pump for concrete
  • the delivery cylinders of which are driven by means of a hydraulic drive cylinder, by means of which alternating pressurization with the outlet pressure of a pressure supply unit and relief thereof to the tank of the pressure supply unit are intended to achieve continuous concrete delivery, in the event of drastic load fluctuations In the area of the thick matter pump malfunctions a stalling to drive a eg
  • constant volume flow controlled main pump of the pressure supply unit it is known to electronically record the speed of the diesel engine and, if it drops below a threshold value considered critical, the flow rate actuator of the main pump of the pressure supply unit via an electro-hydraulic control device To control the reduction of the volume flow generated by the main pump in order to reduce its torque requirement to such an extent that it can still be covered by the drive motor and the same can be prevented from stalling.
  • the control pressure is generated by means of a pressure adder from the load-dependent pressure in the main line and the constant base pressure tapped before a pressure limiting valve connected downstream of the tapping point of the secondary circuit, whereby a reduction in the pump output is to be achieved when an overload occurs at a low engine speed, while otherwise
  • the delivery rate is also maximized in the underspeed range of the engine.
  • the main disadvantage is that a pressure-variable consumer cannot be switched on in the secondary circuit and that necessary auxiliary functions must therefore be performed by additional units.
  • DE-OS 23 63 480 per se to provide a hydraulic adjusting device for a pump for generating a constant flow rate, the adjusting member of which is regulated with the aid of two adjusting pistons which can be acted upon by a differential pressure derived from the main consumer circuit in such a way that the output volume flow of the pump is reduced with increasing differential pressure and increased with decreasing differential pressure.
  • a three-way flow control valve arranged in the main circuit is provided, which has a connection to a tank via two series-connected throttles, one of the pistons being acted upon by a residual flow branched off between the throttles, while the other is optionally supplied by one Auxiliary pump generated delivery pressure is applied.
  • a protective circuit against overloading the pump drive is not provided.
  • the protective device designed as a purely hydraulic device and using hydraulic regulators and actuators of the main pump, which are already available for their volume flow control, works very reliably and is - thanks to the multiple use of existing hydraulic functional elements - compared to a pressure supply unit without such a protective device Can be realized with comparatively little additional technical effort, which is essentially due to the additional auxiliary pump, a simple pressure-controlled changeover valve and simple flow resistance elements, an effort which, however, is not significant if these functional elements of the protective device are part of the entire pump device, as provided in accordance with claim 2, can be used to fulfill further functions that are necessary anyway and require a secondary consumer group.
  • the consumer fed in the secondary consumer circuit is connected directly to the high-pressure outlet of the auxiliary pump and one for sensing that generated by the auxiliary pump Adjusted flow throttle provided between the consumer and the tank of the pressure supply unit, a simple control valve designed for a low control pressure level is sufficient to control the protective function.
  • the adjustable flow resistance provided for sensing the volume flow generated by the auxiliary pump is connected directly to the pressure output of the auxiliary pump and the e.g. flow resistance formed by a further consumer between the adjusting throttle and the tank of the pressure supply unit, a valve designed for a high control pressure level is required as a protective function control valve, but this can be integrated into the auxiliary pump, which is important both in terms of design and in terms of sensitivity the control is advantageous.
  • control valve according to claim 6 for example as a proportional valve, optionally with the functional positions indicated by the features of claim 7, the response characteristic of the actuating device can be influenced in a simple manner, by means of which the delivery volume of the main pump can be adjusted and thus also a desired application. and discharge characteristics of the pressure supply unit can be achieved overall.
  • control valve provided in accordance with claim 8 can be expedient in order to avoid "oscillation" of the volume flow control in the low speed range of the drive motor.
  • the features of claim 9 indicate a relationship of the flow resistances of the consumer which is favorable from the point of view of a good use of energy and an adjustment throttle of the secondary consumer circuit.
  • the main pump 12 is provided as a swash plate axial piston pump, which can be infinitely adjusted with respect to its delivery volume by swiveling its swash plate represented by the double arrow 14, which values can be changed between a minimum value Q min and a maximum value Q max .
  • the position of the swash plate 14 corresponding to the minimum delivery volume, shown in broken lines, is the one in which its normal runs parallel to the axes of the axial piston pump elements (not shown). In the position of the swash plate 14 corresponding to the maximum delivery volume Q max , its normal runs, for example, at an angle of 30 ° to the central axes of the axial piston pump elements.
  • a throttle 18 with an adjustable flow resistance is connected as a load sensor element, via which a pressure drop ⁇ P occurs during operation of the pressure supply unit 10 and the consumer 11, by which the pressure at the center tap 19 - between the throttle 18 and the high-pressure supply connection 17 of the consumer 11 - the effective supply pressure P V that can be tapped is lower than the outlet pressure P H of the main pump 12 at its high-pressure outlet 16.
  • two linear cylinders 21 and 22 are provided, by means of which oppositely directed torques can be exerted on the swivel plate 14, from their respective equilibrium the respective swivel position of the swivel plate 14 and the associated delivery rate of the main pump 12 result.
  • the drive pressure chamber 29 of the second linear cylinder 22, by means of the pressurization of which a moment urging the control disk 14 in its pivot position associated with its minimum delivery volume can be generated, can alternatively be connected to the - pressure-less - tank 32 of the pressure supply unit 10 or to the pressure-less control valve 31 acting as a pressure compensator High pressure outlet 16 of the main pump 12 can be connected.
  • the prestressed compression spring 28 of the first linear cylinder 21 also acts as a return spring for the second linear cylinder 22, the piston 33 thereof urges into the basic position associated with the minimal volume of its drive pressure chamber 29.
  • the control valve 31 is designed as a 3/2-way valve, which is forced into its illustrated basic position 0 by a valve spring 34, in which the drive pressure chamber 29 of the second linear cylinder 22 is connected to the unpressurized tank 32 of the pressure supply unit and against the high-pressure outlet 16 Main pump 12 is shut off.
  • a first control chamber 36 of the control valve 31 with the high output pressure P H of the main pump 12, the control valve 31 can be controlled into its function position I, which is alternative to the basic position zero, in which the drive pressure chamber 29 of the second linear cylinder is connected to the high pressure output 16 of the main pump 12 and now is blocked against the unpressurized tank 32 of the pressure supply unit 10.
  • control valve 31 By acting on a second control chamber 37 of the control valve 31 with the on the center tap 19 between the Throttle 18 and the consumer 11 pending, compared to the high output pressure P H of the main pump 12 pressure P V , the control valve 31 is pushed into its zero basic position.
  • the control valve 31 is designed as a proportional valve, in which an increasing deflection of its valve piston represented by the switching symbol 38 from its spring-centered end position as the basic position zero initially has a decrease in the flow cross section of the flow path 39 connecting the drive pressure chamber 29 of the second linear cylinder to the tank 32 until this occurs is blocked and a further deflection of the valve piston 38, which leads to the taking of the functional position I, to an increasing, ie cross-section-increasing release of the flow path 41, via which the drive pressure chamber 29 of the second linear cylinder 22 is connected to the high-pressure outlet 16 of the main pump 12 in the functional position I.
  • the pressure supply unit 10 operates when and as long as the center tap 19 between the throttle 18 and the consumer 11 is connected to the second control chamber 37 of the control valve 31, as follows: Before switching on the diesel engine 13 and thus activating the pressure supply unit 10 and starting up the consumer 11, which is connected between the adjustable throttle 18 and the tank 32 of the pressure supply unit 10, the two linear cylinders 21 and 22 are in their illustrated, with maximum delivery volume the main pump 12 linked basic positions, and the piston 38 of the control valve 31 assumes its spring-centered end position linked to the maximum flow cross section of the flow path 39 effective in the basic position 0 of the control valve 31.
  • preliminary activation of the main pump 12 increases to the extent that the flow rate of the oil flow conveyed by the main pump 12 through the throttle 18 and the consumer 11 increases, the pressure P H at the high pressure output of the Main pump and also on the center tap 19 between the throttle 11, the pressure difference ⁇ P - the pressure drop across the throttle 18 - between the high pressure outlet 16 of the main pump 12 and the center tap 19 or the high pressure supply connection 17 of the consumer 11 also according to the amount grows.
  • the difference ⁇ F by which the effective cross-sectional area F2 of the piston 33 of the second linear cylinder 22 is larger than the effective cross-sectional area F1 of the first linear cylinder 21, is dimensioned such that even at relatively low output pressures of the main pump 12 of, for example, 6 to 12 bar, the force deployed by the second linear cylinder 22 is sufficient to to "overpress" the first linear cylinder 21 and to achieve a rotation of the swivel plate 14 into its position linked to the minimum delivery volume of the main pump 12.
  • the control valve 31, the linear cylinders 21 and 22 acting on the swivel plate 14 of the main pump 12 and the throttle 18 connected between the main pump 12 and the consumer 11 provide stabilization of the oil flow flowing via the throttle 18 and the consumer 11 to the tank 32 of the pressure supply unit 10 to an amount which can be predetermined indirectly through the adjustable preload of the valve spring 34 of the control valve 31. It is therefore irrelevant within a wide setting range of the throttle 18 to what amount of its flow resistance the throttle 18 is set.
  • a protective device designated overall by 40 provided that, in cases in which the output torque of the diesel engine 13 is no longer sufficient to drive the main pump 12 in the sense of maintaining a predetermined output volume flow, reliably precludes the diesel engine 13 from stalling, which could lead to considerable malfunctions.
  • a related need situation can arise from a malfunction of the consumer 11, but can also occur in a controlled manner, e.g. characterized in that the throttle 18 is automatically set to increased flow resistance in the final phases of such strokes to achieve a gentle reversal of piston movements of the consumer 11.
  • the protective device 40 comprises an auxiliary pump 42 which, like the main pump 12, is driven by the diesel engine 13 and one which is proportional to the speed of the diesel engine 13 Volume flow generated.
  • auxiliary pump 42 which, like the main pump 12, is driven by the diesel engine 13 and one which is proportional to the speed of the diesel engine 13 Volume flow generated.
  • a hydraulic series circuit consisting of a consumer 44 represented by a fixed throttle and an adjusting throttle 46, via which the outlet pressure P A of the auxiliary pump 42 drops, the one above the components of this series circuit - the consumer 44 and the adjusting throttle 46 - occurring pressure drops .DELTA.P V and .DELTA.P D are proportional to the flow resistances of the consumer 44 and the adjusting throttle 46 and, in total, give the value of the outlet pressure P A of the auxiliary pump 42.
  • the protective device 40 comprises a 3/2-way valve Control valve, which is designed as a pressure-controlled valve, which is urged into its basic position 0 by a prestressed valve spring 48, in which the second control chamber 37 of the pressure-controlled control valve 31 of the pressure supply unit 10 is connected to the tank 32 of the pressure supply unit 10 and this control chamber 37 against the Center tap 19 between the throttle 18 and the consumer 11 is shut off, and this by pressurizing a control chamber 49 with the pressure prevailing between the consumer 44, which is connected to the auxiliary pump 42 and the adjusting throttle 46, the amount of the pressure drop ⁇ P D across the adjusting throttle 46 corresponds to in ne functional position I can be controlled, in which the one used on the center tap 19 between the load sensor element Setting throttle 18 and the pressure prevailing in the consumer 11 is coupled into the second control chamber 37 of the control valve 31 and this control chamber 37 is blocked off
  • the protective device explained so far works as follows: As long as the speed of the diesel engine 13 is higher than a predeterminable threshold value above which a stalling of the diesel engine 13 can be excluded with sufficient certainty, the pressure drop across the adjusting throttle 46 of the protective device 40 and thus the pressure coupled into the control chamber 49 of the control valve 47 is sufficient large to hold the control valve 47 against the action of its valve spring 48 in its functional position I, in which the pressure at the center tap 19 of the main pump circuit is coupled into the second control chamber 37 of the control valve 31 and the pressure supply unit 10 in the normal, load-sensing Control mode works.
  • the speed threshold below which the control valve 47 changes from its functional position I assigned to normal control operation to its basic position 0, which provides protection of the diesel engine 13 against stalling, can be predetermined by setting a specific flow resistance of the adjusting throttle 46.
  • the control pressure from which the control valve 47 is switched to its functional position I is between 4 and 10 bar.
  • the protective device 50 shown in FIG. 2 is functionally equivalent to the protective device 40 according to FIG. 1, but differs from this in terms of circuit technology in that the setting throttle 46, by means of which the speed threshold can be specified as a result, below which the second control chamber 37 of the control valve 31 is depressurized, connected directly to the high-pressure outlet 43 of the auxiliary pump 42 and the consumer 44 is connected between this adjusting throttle 46 and the tank 32 of the pressure supply unit, and in that the control valve 47 ', which is in its basic position 0 and in it Alternative function position I conveys the same functions as the control valve 47 of the protective device 40 according to FIG.
  • a differential valve which is switched from its basic position 0 to its function position I when the pressure difference ⁇ P D between the high-pressure outlet 43 of the auxiliary pump 42 and de r center tap 51 between the adjusting throttle 46 and the consumer 44 exceeds a threshold value, the amount of which can be the same as the control pressure that builds up in the exemplary embodiment according to FIG. 1 via the adjusting throttle 46 connected there between the consumer 44 and the tank 32.
  • control valve 47 'of the protective device 50 according to FIG. 2 in addition to the first control chamber 49', which is acted upon by the output pressure present at the high-pressure outlet 43 of the auxiliary pump 42, whereby the control valve 47 'is forced into its functional position I.
  • control valve 47 ' is acted upon by the pressure present at the center tap 51 between the setting throttle 46 and the consumer 44, whereby the control valve 47 'is pushed into its basic position 0, these control chambers 49' and 52 'being designed such that the forces resulting from their pressurization acting in the opposite direction on the valve piston cancel each other out, so that in the control valve 47 'the pressurization of its second control chamber 52 determines the pressure level against which the pressure coupled into the first control chamber 49' must be higher , so that the control valve 47 'against the action its valve spring 48 can be switched to its functional position I.
  • the control valve 47 ' is also designed so that this pressure difference is only a few bar, e.g. 6 bar.
  • the control chambers 49 'and 52 of the control valve 47' are acted upon by the absolute amount after significantly higher pressures than the control chamber 49 of the control valve 47 Protective device 40 according to FIG. 1, which places increased demands on the tightness of the control chambers 49 and 52.
  • the protective device 50 according to FIG. 2 it is readily possible to structurally combine the control valve 47 'and the adjusting throttle 46 with the auxiliary pump 42 in an integrated construction, since the consumer 44 is hydraulically connected downstream of this hydraulic functional unit.
  • control valve 47 or 47 ' can be designed as a proportional valve, which increases after a transition from one to the other of the possible functional positions 0 and I Opening cross sections of the effective circulation or flow flow paths 53 and 54 releases, whereby particularly gentle and therefore gentle starting and stopping characteristics of the main pump 12 can be achieved in switching situations of the consumer 11 of the main circuit.
  • control valve 47 or 47 ' this is, as not specifically shown, designed as a 3/3-way valve, which between the functional position 0, in which the second control chamber 37 of the control valve 31 against the reference pressure tap 19 of the main consumer circuit 11, 18, but is connected to the tank 32 of the pressure supply unit 10, and the functional position I, in which the second control chamber 37 of the control valve 31 is connected to the comparative pressure tap 19 of the main consumer circuit, but against the tank of the pressure supply unit 10 is locked, a locking position II has, in which the second control chamber 37 of the control valve 31 is shut off both against the reference pressure tap 19 of the main consumer circuit 11, 18 and against the tank 32 of the pressure supply unit 10.
  • the changeover positions in which the control valve changes from its blocking functional position II into its one flow position 0 or the alternative flow position I, seen in the direction of displacement of the valve body can be arranged at a distance from one another , which is between 1/50 and 1/5, preferably around 1/10 of the total stroke that the valve body can carry out between its end positions assigned to the alternative flow function positions 0 and I, respectively.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Control Of Vehicle Engines Or Engines For Specific Uses (AREA)

Abstract

In a hydraulic pressure generator with a main pump driven by a diesel engine, a main user circuit connected thereto is formed by a setting choke (18) directly connected to the main pump and a user (11) connected in series thereto. By comparing the output pressure PH coupled in a first control chamber of a control valve (31) with the comparison pressure PV which can be detected at the main user (11) and coupled in a second control chamber (37) of the control valve (31), the control valve (31) controls an adjuster (21, 22) in such a way that the flow volume in the main user circuit (16, 11) remains constant. A protective device designed to prevent the diesel engine (13) from stalling under extreme load comprises an auxiliary pump (42) driven with the engine which generates a rotation-speed-proportional output flow volume which passes through a further adjusting choke (46) and a synchronous-revolution user (44) downstream thereof and a pressure-controlled valve (47) via which the second control chamber (37) of the control valve (31) relieves pressure towards the tank (32) and thus sets the main pump (12) to the minimum volume conveyed if the motor speed falls below a threshold.

Description

Um im Betrieb einer hydraulisch angetriebenen Dickstoff-Förderpumpe, z.B. einer Zweizylinder-Pumpe für Beton, deren Förderzylinder mittels je eines hydraulischen Antriebszylinders angetrieben sind, durch deren alternierende Druckbeaufschlagung mit dem Ausgangsdruck eines Druckversorgungsaggregates und Entlastung derselben zum Tank des Druckversorgungsaggregates hin eine kontinuierliche Beton-Förderung erzielt werden soll, im Falle drastischer Last-Schwankung der im Bereich der Dickstoffpumpe auftretenden Störungen ein Abwürgen eines zum Antrieb einer z.B. lastsensierenden, auf konstanten Volumenstrom geregelten Hauptpumpe des Druckversorgungsaggregates zu vermeiden, ist es bekannt, die Drehzahl des Dieselmotors elektronisch zu erfassen und, falls diese unter einen als kritisch erachteten Schwellenwert absinkt, über eine elektrohydraulische Steuereinrichtung das Fördermengen-Stellglied der Hauptpumpe des Druckversorgungsaggregates im Sinne einer Reduzierung des von der Hauptpumpe erzeugten Volumenstromes anzusteuern, um deren Drehmomentbedarf soweit zu reduzieren, daß er von dem Antriebsmotor noch gedeckt und ein Abwürgen desselben vermieden werden kann.In order to operate a hydraulically driven thick matter feed pump, e.g. a two-cylinder pump for concrete, the delivery cylinders of which are driven by means of a hydraulic drive cylinder, by means of which alternating pressurization with the outlet pressure of a pressure supply unit and relief thereof to the tank of the pressure supply unit are intended to achieve continuous concrete delivery, in the event of drastic load fluctuations In the area of the thick matter pump malfunctions a stalling to drive a eg To avoid load-sensing, constant volume flow controlled main pump of the pressure supply unit, it is known to electronically record the speed of the diesel engine and, if it drops below a threshold value considered critical, the flow rate actuator of the main pump of the pressure supply unit via an electro-hydraulic control device To control the reduction of the volume flow generated by the main pump in order to reduce its torque requirement to such an extent that it can still be covered by the drive motor and the same can be prevented from stalling.

Diese Art des Überlastschutzes des Dieselmotors und des Druckversorgungsaggregates insgesamt ist jedoch technisch aufwendig und für die rauhen Betriebsbedingungen, unter denen Dickstoffpumpen oftmals betrieben werden müssen, zu störanfällig.However, this type of overload protection of the diesel engine and of the pressure supply unit as a whole is technically complex and too susceptible to failure for the harsh operating conditions under which thick matter pumps often have to be operated.

Bei einer hydraulischen Steuervorrichtung für eine mittels einer Brennkraftmaschine angetriebene Hauptpumpe mit steuerbarem Hub ist es an sich bekannt (US-4,065,228), einen von einer drehzahlsynchron zur Hauptpumpe angetriebenen Hilfspumpe beaufschlagten Nebenkreis vorzusehen, der eine Abgriffstelle zur Ansteuerung eines einen Steuerdruck an die Hubstelleinrichtung der Hauptpumpe vermittelnden Unterdrehzahlventils aufweist. Der Steuerdruck wird bei der bekannten Steuervorrichtung mittels eines Druckaddierers aus dem lastabhängigen Druck in der Hauptleitung und dem vor einem der Abgriffstelle des Nebenkreises nachgeschalteten Druckbegrenzungsventil abgegriffenen konstanten Basisdruck erzeugt, wodurch bei einer bei geringer Motordrehzahl auftretenden Überlast eine Reduzierung der Pumpenleistung bewirkt werden soll, während ansonsten auch im Unterdrehzahlbereich des Motors die Förderleistung maximiert wird. Neben der fehlenden Möglichkeit zur Regelung auf konstanten, nicht maximalen Förderstrom wird hierbei vor allem als nachteilig empfunden, daß in den Nebenkreis ein druckvariabler Verbraucher nicht einschaltbar ist und damit notwendige Nebenfunktionen durch zusätzliche Aggregate erfüllt werden müssen.In a hydraulic control device for a main pump driven by an internal combustion engine with a controllable stroke, it is known per se (US Pat. No. 4,065,228) to provide an auxiliary circuit which is driven by an auxiliary pump which is driven synchronously with the speed of the main pump and which has a tap point for actuating a control pressure to the stroke adjusting device of the main pump mediating underspeed valve. In the known control device, the control pressure is generated by means of a pressure adder from the load-dependent pressure in the main line and the constant base pressure tapped before a pressure limiting valve connected downstream of the tapping point of the secondary circuit, whereby a reduction in the pump output is to be achieved when an overload occurs at a low engine speed, while otherwise The delivery rate is also maximized in the underspeed range of the engine. In addition to the lack of the possibility of regulating to constant, not maximum, flow rate, the main disadvantage is that a pressure-variable consumer cannot be switched on in the secondary circuit and that necessary auxiliary functions must therefore be performed by additional units.

Weiter ist es aus der DE-OS 23 63 480 an sich bekannt, eine hydraulische Verstelleinrichtung für eine Pumpe zur Erzeugung eines konstanten Förderstroms vorzusehen, deren Verstellglied mit Hilfe zweier mit einem aus dem Haupt-Verbraucherkreis abgeleiteten Differenzdruck beaufschlagbarer Verstellkolben derart geregelt wird, daß der Ausgangs-Volumenstrom der Pumpe mit zunehmendem Differenzdruck reduziert und mit abnehmendem Differenzdruck erhöht wird. Zur Ableitung des Differenzdrucks ist dort ein im Hauptkreis angeordnetes Dreiwege-Stromregelventil vorgesehen, das eine über zwei seriengeschaltete Drosseln geführte Verbindung zu einem Tank aufweist, wobei einer der Kolben mit einem zwischen den Drosseln abgezweigten Reststrom beaufschlagt wird, während der andere mit dem gegebenenfalls von einer Hilfspumpe erzeugten Förderdruck beaufschlagt ist. Bei dieser Verstelleinrichtung ist eine Schutzschaltung gegen eine Überlastung des Pumpenantriebs nicht vorgesehen.Furthermore, it is known from DE-OS 23 63 480 per se to provide a hydraulic adjusting device for a pump for generating a constant flow rate, the adjusting member of which is regulated with the aid of two adjusting pistons which can be acted upon by a differential pressure derived from the main consumer circuit in such a way that the output volume flow of the pump is reduced with increasing differential pressure and increased with decreasing differential pressure. To derive the differential pressure, a three-way flow control valve arranged in the main circuit is provided, which has a connection to a tank via two series-connected throttles, one of the pistons being acted upon by a residual flow branched off between the throttles, while the other is optionally supplied by one Auxiliary pump generated delivery pressure is applied. In this adjustment device, a protective circuit against overloading the pump drive is not provided.

Aufgabe der Erfindung ist es daher, eine Schutzeinrichtung der eingangs genannten Art anzugeben, die bei gleichwohl einfachem Aufbau einen zuverlässigen Überlast-Schutz des Druckversorgungsaggregates vermittelt, insbesondere ein Abwürgen seines Antriebsmotors verhindert.It is therefore an object of the invention to provide a protective device of the type mentioned at the outset which, with a simple construction, provides reliable overload protection of the pressure supply unit, in particular prevents its drive motor from stalling.

Diese Aufgabe wird erfindungsgemäß durch die kennzeichnenden Merkmale des Patentanspruchs 1 gelöst. Die hiernach unter Mitausnutzung hydraulischer Regel- und Stellglieder der Hauptpumpe, die zu deren Volumenstrom-Regelung ohnehin vorhanden sind, als rein hydraulische Einrichtung ausgebildete Schutzeinrichtung arbeitet sehr zuverlässig und ist - dank der Mehrfach-Ausnutzung vorhandener hydraulischer Funktionselemente - gegenüber einem Druckversorgungsaggregat ohne derartige Schutzeinrichtung auch mit vergleichsweise geringem technischem Mehraufwand realisierbar, der im wesentlichen auf die zusätzliche Hilfspumpe, ein einfaches druckgesteuertes Umschaltventil und einfache Strömungswiderstands-Elemente bedingt ist, ein Aufwand, der jedoch dann nicht nennenswert ins Gewicht fällt, wenn diese Funktionselemente der Schutzeinrichtung im Rahmen der gesamten Pumpeinrichtung, wie gemäß Anspruch 2 vorgesehen, zur Erfüllung weiterer ohnehin notwendiger, einen Neben-Verbraucherkreis erfordernder Funktionen ausgenutzt werden.This object is achieved by the characterizing features of claim 1. The protective device, designed as a purely hydraulic device and using hydraulic regulators and actuators of the main pump, which are already available for their volume flow control, works very reliably and is - thanks to the multiple use of existing hydraulic functional elements - compared to a pressure supply unit without such a protective device Can be realized with comparatively little additional technical effort, which is essentially due to the additional auxiliary pump, a simple pressure-controlled changeover valve and simple flow resistance elements, an effort which, however, is not significant if these functional elements of the protective device are part of the entire pump device, as provided in accordance with claim 2, can be used to fulfill further functions that are necessary anyway and require a secondary consumer group.

Ist hierbei, wie gemäß Anspruch 3 vorgesehen, der im Neben-Verbraucherkreis gespeiste Verbraucher unmittelbar an den Hochdruckausgang der Hilfspumpe angeschlossen und eine zur Sensierung des von der Hilfspumpe erzeugten Volumenstromes vorgesehene Einstelldrossel zwischen den Verbraucher und den Tank des Druckversorgungsaggregats geschaltet, so genügt zur Steuerung der Schutzfunktion ein einfaches, auf niedriges Steuerdruckniveau ausgelegtes Steuerventil.Here, as provided in accordance with claim 3, the consumer fed in the secondary consumer circuit is connected directly to the high-pressure outlet of the auxiliary pump and one for sensing that generated by the auxiliary pump Adjusted flow throttle provided between the consumer and the tank of the pressure supply unit, a simple control valve designed for a low control pressure level is sufficient to control the protective function.

Ist andererseits, wie gemäß Anspruch 4 vorgesehen, der zur Sensierung des von der Hilfspumpe erzeugten Volumenstromes vorgesehene einstellbare Strömungswiderstand unmittelbar an den Druckausgang der Hilfspumpe angeschlossen und der z.B. durch einen weiteren Verbraucher gebildete Strömungswiderstand zwischen die Einstelldrossel und den Tank des Druckversorgungsaggregates geschaltet, so wird als Schutzfunktions-Steuerventil zwar ein auf hohes Steuerdruckniveau ausgelegtes Ventil benötigt, das jedoch in die Hilfspumpe integriert sein kann, was sowohl in konstruktiver Hinsicht als auch hinsichtlich der Empfindlichkeit der Steuerung vorteilhaft ist.On the other hand, as provided according to claim 4, the adjustable flow resistance provided for sensing the volume flow generated by the auxiliary pump is connected directly to the pressure output of the auxiliary pump and the e.g. flow resistance formed by a further consumer between the adjusting throttle and the tank of the pressure supply unit, a valve designed for a high control pressure level is required as a protective function control valve, but this can be integrated into the auxiliary pump, which is important both in terms of design and in terms of sensitivity the control is advantageous.

In Kombination hiermit ist durch die Merkmale des Anspruchs 5 eine geeignete Gestaltung des Steuerventils als Differentialventil angegeben.In combination with this, the features of claim 5 indicate a suitable design of the control valve as a differential valve.

Durch eine Gestaltung des Steuerventils gemäß Anspruch 6, z.B. als Proportionalventil, gegebenenfalls mit den durch die Merkmale des Anspruchs 7 angegebenen Funktionsstellungen kann auf einfache Weise die Ansprechcharakteristik der Stelleinrichtung beeinflußt werden, mittels derer das Fördervolumen der Hauptpumpe einstellbar ist und damit auch eine erwünschte An- und Auslaufcharakteristik des Druckversorgungsaggregates insgesamt erzielt werden.By designing the control valve according to claim 6, for example as a proportional valve, optionally with the functional positions indicated by the features of claim 7, the response characteristic of the actuating device can be influenced in a simple manner, by means of which the delivery volume of the main pump can be adjusted and thus also a desired application. and discharge characteristics of the pressure supply unit can be achieved overall.

Die gemäß Anspruch 8 vorgesehene, spezielle Gestaltung des Steuerventils kann zweckmäßig sein, um im Nieder-Drehzahlbereich des Antriebsmotors ein "Schwingen" der Volumenstrom-Regelung zu vermeiden.The special design of the control valve provided in accordance with claim 8 can be expedient in order to avoid "oscillation" of the volume flow control in the low speed range of the drive motor.

Durch die Merkmale des Anspruchs 9 ist eine unter Gesichtspunkten einer guten Energieausnutzung günstige Relation der Strömungswiderstände des Verbrauchers und einer Einstelldrossel des Neben-Verbraucherkreises angegeben.The features of claim 9 indicate a relationship of the flow resistances of the consumer which is favorable from the point of view of a good use of energy and an adjustment throttle of the secondary consumer circuit.

Weitere Einzelheiten und Merkmale der Erfindung ergeben sich aus der nachfolgenden Beschreibung spezieller Ausführungsbeispiele einer erfindungsgemäßen Schutzeinrichtung anhand der Zeichnung.Further details and features of the invention result from the following description of special exemplary embodiments of a protective device according to the invention with reference to the drawing.

Es zeigen:

Fig. 1
ein erstes Ausführungsbeispiel und
Fig. 2
ein zweites Ausführungsbeispiel einer erfindungsgemäßen Schutzeinrichtung für ein Druckversorgungsaggregat mit von einem Dieselmotor angetriebener Hauptpumpe, in vereinfachter Blockschaltbild-Darstellung.
Show it:
Fig. 1
a first embodiment and
Fig. 2
a second embodiment of a protective device according to the invention for a pressure supply unit with a main pump driven by a diesel engine, in a simplified block diagram representation.

Das in der Fig. 1 dargestellte, insgesamt mit 10 bezeichnete Druckversorgungsaggregat für einen lediglich schematisch angedeuteten Verbraucher 11, z.B. eine Zweizylinder-Dickstoffpumpe für die Betonförderung, umfaßt eine hinsichtlich ihres Fördervolumens pro Hub oder Umdrehung selbsttätig verstellbare Hauptpumpe 12, die mittels eines Dieselmotors 13 antreibbar ist.The pressure supply unit shown in FIG. 1, designated overall by 10, for a consumer 11, which is only indicated schematically, for example a two-cylinder thick matter pump for the conveying of concrete, includes one with regard to its delivery volume per stroke or revolution adjustable main pump 12 which can be driven by means of a diesel engine 13.

Die Hauptpumpe 12 ist als Schwenkscheiben-Axialkolbenpumpe vorausgesetzt, die durch Verschwenken ihrer durch den Doppelpfeil 14 repräsentierten Schwenkscheibe hinsichtlich ihres Fördervolumens stufenlos auf verschiedene Werte einstellbar ist, die zwischen einem Minimalwert Qmin und einem Maximalwert Qmax veränderbar sind. Die minimalem Fördervolumen entsprechende, gestrichelt eingezeichnete Position der Schwenkscheibe 14 ist diejenige, in der ihre Normale parallel zu den Achsen der - nicht dargestellten - Axialkolben-Pumpenelemente verläuft. In der maximalem Fördervolumen Qmax entsprechenden Position der Schwenkscheibe 14 verläuft deren Normale beispielsweise unter einem Winkel von 30° zu den zentralen Achsen der Axialkolben-Pumpenelemente.The main pump 12 is provided as a swash plate axial piston pump, which can be infinitely adjusted with respect to its delivery volume by swiveling its swash plate represented by the double arrow 14, which values can be changed between a minimum value Q min and a maximum value Q max . The position of the swash plate 14 corresponding to the minimum delivery volume, shown in broken lines, is the one in which its normal runs parallel to the axes of the axial piston pump elements (not shown). In the position of the swash plate 14 corresponding to the maximum delivery volume Q max , its normal runs, for example, at an angle of 30 ° to the central axes of the axial piston pump elements.

Zwischen den Hochdruckausgang 16 der Hauptpumpe 12 und den Hochdruck-Versorgungsanschluß 17 ist als Last-Sensor-Glied eine Drossel 18 mit einstellbarem Strömungswiderstand geschaltet, über der im Betrieb des Druckversorgungsaggregates 10 und des Verbrauchers 11 ein Druckabfall ΔP auftritt, um den der an der Mittelanzapfung 19 - zwischen der Drossel 18 und dem Hochdruck-Versorgungsanschluß 17 des Verbrauchers 11 - abgreifbare effektive Versorgungsdruck PV niedriger ist als der Ausgangsdruck PH der Hauptpumpe 12 an deren Hochdruckausgang 16.Between the high-pressure outlet 16 of the main pump 12 and the high-pressure supply connection 17, a throttle 18 with an adjustable flow resistance is connected as a load sensor element, via which a pressure drop ΔP occurs during operation of the pressure supply unit 10 and the consumer 11, by which the pressure at the center tap 19 - between the throttle 18 and the high-pressure supply connection 17 of the consumer 11 - the effective supply pressure P V that can be tapped is lower than the outlet pressure P H of the main pump 12 at its high-pressure outlet 16.

Als Stellantriebe, mittels derer im Zuge einer Fördermengen-Regelung der Hauptpumpe 12 deren Schwenkscheibe 14 auf verschiedene Schwenkpositionen einstellbar ist, sind beim dargestellten, speziellen Ausführungsbeispiel zwei Linearzylinder 21 und 22 vorgesehen, mittels derer entgegengesetzt gerichtete Drehmomente auf die Schwenkscheibe 14 ausübbar sind, aus deren jeweiligem Gleichgewicht die jeweilige Schwenkposition der Schwenkscheibe 14 und die damit verknüpfte Fördermenge der Hauptpumpe 12 resultieren.As actuators, by means of which the swivel plate 14 of the main pump 12 can be adjusted to different swivel positions in the course of a flow control, Special exemplary embodiment, two linear cylinders 21 and 22 are provided, by means of which oppositely directed torques can be exerted on the swivel plate 14, from their respective equilibrium the respective swivel position of the swivel plate 14 and the associated delivery rate of the main pump 12 result.

Der durch einen Kolben 23, welcher über eine Kolbenstange 24 gelenkig mit der Schwenkscheibe 14 verbunden ist, axial beweglich begrenzte Antriebsdruckraum 26 desjenigen Linearzylinders 21, durch dessen Druckbeaufschlagung die Schwenkscheibe 14 im Sinne einer Vergrößerung des Fördervolumens der Hauptpumpe 12 geschwenkt wird, ist über eine Steuerleitung 27 permanent mit dem Hochdruckausgang 16 der Hauptpumpe 12 verbunden. Sowohl durch die hieraus resultierende Druckbeaufschlagung des Antriebsdruckraumes 26 mit dem Ausgangsdruck der Hauptpumpe 12 als auch durch eine vorgespannte Druckfeder 28, entfaltet der Linearzylinder 21 ständig eine Kraft, die zu einem die Schwenkscheibe 14 in deren mit größtmöglichem Fördervolumen verknüpfte Position drängendem Moment führt.The drive pressure chamber 26 of the linear cylinder 21, which is axially movably delimited by a piston 23, which is connected in an articulated manner to the swivel plate 14 by means of a piston rod 24, by the pressurization of which the swivel plate 14 is swiveled in order to increase the delivery volume of the main pump 12, is via a control line 27 permanently connected to the high pressure outlet 16 of the main pump 12. Both by the resulting pressurization of the drive pressure chamber 26 with the outlet pressure of the main pump 12 and by a prestressed compression spring 28, the linear cylinder 21 constantly develops a force which leads to a moment urging the swash plate 14 in its position linked to the greatest possible delivery volume.

Der Antriebsdruckraum 29 des zweiten Linearzylinders 22, durch dessen Druckbeaufschlagung ein die Steuerscheibe 14 in deren mit minimalem Fördervolumen verknüpfte Schwenkposition drängendes Moment erzeugbar ist, ist über ein als Druckwaage wirkendes, druckgesteuertes Regelventil 31 alternativ an den - drucklosen - Tank 32 des Druckversorgungsaggregats 10 oder den Hochdruckausgang 16 der Hauptpumpe 12 anschließbar.The drive pressure chamber 29 of the second linear cylinder 22, by means of the pressurization of which a moment urging the control disk 14 in its pivot position associated with its minimum delivery volume can be generated, can alternatively be connected to the - pressure-less - tank 32 of the pressure supply unit 10 or to the pressure-less control valve 31 acting as a pressure compensator High pressure outlet 16 of the main pump 12 can be connected.

Durch die gelenkige Verbindung der Kolbenstange 35 des die axial bewegliche Begrenzung des Antriebsdruckraumes 29 des zweiten Linearzylinders bildenden Kolbens 33 mit der Schwenkscheibe 14 der Hauptpumpe 12 wirkt die vorgespannte Druckfeder 28 des ersten Linearzylinders 21 auch als Rückstellfeder für den zweiten Linearzylinder 22, die dessen Kolben 33 in die mit minimalem Volumen seines Antriebsdruckraumes 29 verknüpfte Grundstellung drängt.Due to the articulated connection of the piston rod 35 of the piston 33 forming the axially movable delimitation of the drive pressure chamber 29 of the second linear cylinder with the swivel plate 14 of the main pump 12, the prestressed compression spring 28 of the first linear cylinder 21 also acts as a return spring for the second linear cylinder 22, the piston 33 thereof urges into the basic position associated with the minimal volume of its drive pressure chamber 29.

Das Regelventil 31 ist als 3/2-Wege-Ventil ausgebildet, das durch eine Ventilfeder 34 in seine dargestellte Grundstellung 0 gedrängt wird, in welcher der Antriebsdruckraum 29 des zweiten Linearzylinders 22 mit dem drucklosen Tank 32 des Druckversorgungsaggregates verbunden und gegen den Hochdruckausgang 16 der Hauptpumpe 12 abgesperrt ist. Durch Druckbeaufschlagung einer ersten Steuerkammer 36 des Regelventils 31 mit dem hohen Ausgangsdruck PH der Hauptpumpe 12 ist das Regelventil 31 in seine zur Grundstellung Null alternative Funktionsstellung I steuerbar, in welcher der Antriebsdruckraum 29 des zweiten Linearzylinders mit dem Hochdruckausgang 16 der Hauptpumpe 12 verbunden und nunmehr gegen den drucklosen Tank 32 des Druckversorgungsaggregats 10 abgesperrt ist.The control valve 31 is designed as a 3/2-way valve, which is forced into its illustrated basic position 0 by a valve spring 34, in which the drive pressure chamber 29 of the second linear cylinder 22 is connected to the unpressurized tank 32 of the pressure supply unit and against the high-pressure outlet 16 Main pump 12 is shut off. By pressurizing a first control chamber 36 of the control valve 31 with the high output pressure P H of the main pump 12, the control valve 31 can be controlled into its function position I, which is alternative to the basic position zero, in which the drive pressure chamber 29 of the second linear cylinder is connected to the high pressure output 16 of the main pump 12 and now is blocked against the unpressurized tank 32 of the pressure supply unit 10.

Durch Beaufschlagung einer zweiten Steuerkammer 37 des Regelventils 31 mit dem an der Mittelanzapfung 19 zwischen der Drossel 18 und dem Verbraucher 11 anstehenden, gegenüber dem hohen Ausgangsdruck PH der Hauptpumpe 12 etwas abgefallenen Druck PV wird das Regelventil 31 in seine Grundstellung Null gedrängt.By acting on a second control chamber 37 of the control valve 31 with the on the center tap 19 between the Throttle 18 and the consumer 11 pending, compared to the high output pressure P H of the main pump 12 pressure P V , the control valve 31 is pushed into its zero basic position.

Das Regelventil 31 ist als Proportionalventil ausgebildet, bei dem eine zunehmende Auslenkung seines durch das Schaltsymbol 38 repräsentierten Ventilkolbens aus dessen federzentrierter Endstellung als Grundstellung Null zunächst eine Abnahme des Durchflußquerschnittes des den Antriebsdruckraum 29 des zweiten Linearzylinders mit dem Tank 32 verbindenden Durchflußpfades 39 eintritt, bis dieser gesperrt ist und eine weitere Auslenkung des Ventilkolbens 38, die zur Einnahme der Funktionsstellung I führt, zu einer zunehmenden, d.h. querschnittsvergrößernden Freigabe des Durchflußpfades 41 führt, über den in der Funktionsstellung I der Antriebsdruckraum 29 des zweiten Linearzylinders 22 mit dem Hochdruckausgang 16 der Hauptpumpe 12 verbunden ist.The control valve 31 is designed as a proportional valve, in which an increasing deflection of its valve piston represented by the switching symbol 38 from its spring-centered end position as the basic position zero initially has a decrease in the flow cross section of the flow path 39 connecting the drive pressure chamber 29 of the second linear cylinder to the tank 32 until this occurs is blocked and a further deflection of the valve piston 38, which leads to the taking of the functional position I, to an increasing, ie cross-section-increasing release of the flow path 41, via which the drive pressure chamber 29 of the second linear cylinder 22 is connected to the high-pressure outlet 16 of the main pump 12 in the functional position I.

Das insoweit seinem Aufbau nach erläuterte Druckversorgungsaggregat 10 arbeitet, wenn und so lange die Mittelanzapfung 19 zwischen der Drossel 18 und dem Verbraucher 11 mit der zweiten Steuerkammer 37 des Regelventils 31 verbunden ist, wie folgt:
Vor dem Einschalten des Dieselmotors 13 und damit der Aktivierung des Druckversorgungsaggregates 10 und Inbetriebnahme des Verbrauchers 11, der zwischen die einstellbare Drossel 18 und den Tank 32 des Druckversorgungsaggregats 10 geschaltet ist, befinden sich die beiden Linearzylinder 21 und 22 in ihren dargestellten, mit maximalem Fördervolumen der Hauptpumpe 12 verknüpften Grundstellungen, und der Kolben 38 des Regelventils 31 nimmt seine mit maximalem Durchflußquerschnitt des in der Grundstellung 0 des Regelventils 31 wirksamen Durchflußpfades 39 verknüpfte - federzentrierte - Endlage ein.The pressure supply unit 10, as far as its structure is concerned, operates when and as long as the center tap 19 between the throttle 18 and the consumer 11 is connected to the second control chamber 37 of the control valve 31, as follows:
Before switching on the diesel engine 13 and thus activating the pressure supply unit 10 and starting up the consumer 11, which is connected between the adjustable throttle 18 and the tank 32 of the pressure supply unit 10, the two linear cylinders 21 and 22 are in their illustrated, with maximum delivery volume the main pump 12 linked basic positions, and the piston 38 of the control valve 31 assumes its spring-centered end position linked to the maximum flow cross section of the flow path 39 effective in the basic position 0 of the control valve 31.

Mit dem Einschalten des Dieselmotors 13 und der damit verknüpften, einleitenden Aktivierung der Hauptpumpe 12 steigt in dem Maße, wie die Strömungsgeschwindigkeit des von der Hauptpumpe 12 durch die Drossel 18 und den Verbraucher 11 geförderten Ölstromes ansteigt, der Druck PH am Hochdruck-Ausgang der Hauptpumpe und auch an der Mittelanzapfung 19 zwischen der Drossel 11 an, wobei der Druckunterschied ΔP - der Druckabfall über der Drossel 18 - zwischen dem Hochdruckausgang 16 der Hauptpumpe 12 und der Mittelanzapfung 19 bzw. den Hochdruck-Versorgungsanschluß 17 des Verbrauchers 11 dem Betrage nach ebenfalls anwächst.With the switching on of the diesel engine 13 and the associated, preliminary activation of the main pump 12 increases to the extent that the flow rate of the oil flow conveyed by the main pump 12 through the throttle 18 and the consumer 11 increases, the pressure P H at the high pressure output of the Main pump and also on the center tap 19 between the throttle 11, the pressure difference ΔP - the pressure drop across the throttle 18 - between the high pressure outlet 16 of the main pump 12 and the center tap 19 or the high pressure supply connection 17 of the consumer 11 also according to the amount grows.

Durch den am Hochdruckausgang 16 der Hauptpumpe 12 sich aufbauenden Ausgangsdruck PH wird, sobald der Druck in der ersten Steuerkammer 36 des Regelventils 31 ausreichend ist, um dessen Kolben 38 gegen die - relativ geringe - Rückstellkraft der Ventilfeder 34 in seine Funktionsstellung I zu verschieben, ein anwachsender Druck in den Antriebsdruckraum 29 des zweiten zur Verstellung der Schwenkscheibe 14 vorgesehenen Linearzylinders 22 eingekoppelt. Die wirksame Querschnittsfläche F₂ des Kolbens 32 dieses zweiten Linearzylinders 22 ist etwas größer als die wirksame Querschnittsfläche F₁ des ersten Antriebszylinders 21, in dessen Antriebsdruckraum 28 der am Hochdruckausgang 16 der Hauptpumpe 12 anstehende Ausgangsdruck permanent eingekoppelt ist. Der Unterschiedsbetrag ΔF, um den die wirksame Querschnittsfläche F₂ des Kolbens 33 des zweiten Linearzylinders 22 größer ist als die wirksame Querschnittsfläche F₁ des ersten Linearzylinders 21, ist so bemessen, daß schon bei relativ niedrigen Ausgangsdrücken der Hauptpumpe 12 von z.B. 6 bis 12 bar die durch den zweiten Linearzylinder 22 entfaltete Kraft ausreicht, um den ersten Linearzylinder 21 zu "überdrücken" und eine Verdrehung der Schwenkscheibe 14 bis in deren mit minimalem Fördervolumen der Hauptpumpe 12 verknüpfte Position zu erzielen. Dadurch wird - in der einleitenden Phase der Aktivierung des Druckversorgungsaggregats 10 - zunächst eine Reduzierung des Drehmomentbedarfs der Hauptpumpe 12 und damit eine Entlastung des Antriebsmotors 13 erzielt, der dementsprechend rasch auf seine Soll-Drehzahl gebracht werden kann.As a result of the outlet pressure P H building up at the high-pressure outlet 16 of the main pump 12, as soon as the pressure in the first control chamber 36 of the control valve 31 is sufficient to move its piston 38 into its functional position I against the - relatively low - restoring force of the valve spring 34, an increasing pressure is coupled into the drive pressure chamber 29 of the second linear cylinder 22 provided for adjusting the swivel plate 14. The effective cross-sectional area F₂ of the piston 32 of this second linear cylinder 22 is somewhat larger than the effective cross-sectional area F₁ of the first drive cylinder 21, in the drive pressure chamber 28 of which the output pressure pending at the high-pressure outlet 16 of the main pump 12 is permanently coupled. The difference ΔF by which the effective cross-sectional area F₂ of the piston 33 of the second linear cylinder 22 is larger than the effective cross-sectional area F₁ of the first linear cylinder 21, is dimensioned such that even at relatively low output pressures of the main pump 12 of, for example, 6 to 12 bar, the force deployed by the second linear cylinder 22 is sufficient to to "overpress" the first linear cylinder 21 and to achieve a rotation of the swivel plate 14 into its position linked to the minimum delivery volume of the main pump 12. As a result, in the initial phase of the activation of the pressure supply unit 10, a reduction in the torque requirement of the main pump 12 and thus a relief of the drive motor 13 is achieved, which can accordingly be quickly brought up to its target speed.

Mit stetig zunehmendem Volumenstrom durch die Drossel 18 und den Verbraucher 11 steigt der an der Mittelanzapfung 19 zwischen der Drossel 18 und dem Verbraucher 17 abgegriffene, in die zweite Steuerkammer 37 des Regelventils 31 eingekoppelte Druck PV an, wodurch das Regelventil - mit Unterstützung seiner Ventilfeder 34 - wieder in seine Grundstellung 0 zurückgelangt, in welcher der Antriebsdruckraum 29 des zweiten Linearzylinders 22 in kommunizierende Verbindung mit dem Vorratsbehälter 32 gelangt und als Folge hiervon die Schwenkscheibe 14 im Sinne einer Vergrößerung des Volumenstromes, den die Hauptpumpe 12 fördert, verschwenkt wird. Im "eingeschwungenen" Zustand der Volumenstrom-Regelung vermittelt die das Regelventil 31, die auf die Schwenkscheibe 14 der Hauptpumpe 12 wirkenden Linearzylinder 21 und 22 sowie die zwischen die Hauptpumpe 12 und den Verbraucher 11 geschaltete Drossel 18 umfassende Regeleinrichtung eine Stabilisierung des über die Drossel 18 und den Verbraucher 11 zum Tank 32 des Druckversorgungsaggregats 10 fließenden Ölstromes auf einen Betrag, der - mittelbar - durch die - einstellbare - Vorspannung der Ventilfeder 34 des Regelventils 31 vorgebbar ist. Damit ist es innerhalb eines weiten Einstellbereiches der Drossel 18 unerheblich, auf welchen Betrag ihres Strömungswiderstandes die Drossel 18 eingestellt wird.With a steadily increasing volume flow through the throttle 18 and the consumer 11, the pressure P V tapped at the center tap 19 between the throttle 18 and the consumer 17 and coupled into the second control chamber 37 of the control valve 31 increases, as a result of which the control valve - with the support of its valve spring 34 - returned to its basic position 0, in which the drive pressure chamber 29 of the second linear cylinder 22 comes into communicating connection with the storage container 32 and, as a result, the swivel plate 14 is pivoted in the sense of an increase in the volume flow that the main pump 12 conveys. In the "steady" state of the volume flow control, the control valve 31, the linear cylinders 21 and 22 acting on the swivel plate 14 of the main pump 12 and the throttle 18 connected between the main pump 12 and the consumer 11 provide stabilization of the oil flow flowing via the throttle 18 and the consumer 11 to the tank 32 of the pressure supply unit 10 to an amount which can be predetermined indirectly through the adjustable preload of the valve spring 34 of the control valve 31. It is therefore irrelevant within a wide setting range of the throttle 18 to what amount of its flow resistance the throttle 18 is set.

Zusätzlich zu der im Rahmen des Druckversorgungsaggregats 10 vorgesehenen Regeleinrichtung, die im Ergebnis eine Stabilisierung des von der Hauptpumpe 12 erzeugten Volumenstromes auf einen erwünschten Wert vermittelt, auch wenn die durch den Verbraucher 11 repräsentierte Last erheblichen Schwankungen unterworfen ist, ist eine insgesamt mit 40 bezeichnete Schutzeinrichtung vorgesehen, die in Fällen, in denen das Ausgangsdrehmoment des Dieselmotors 13 nicht mehr ausreicht, die Hauptpumpe 12 im Sinne der Aufrechterhaltung eines vorgegebenen Ausgangs-Volumenstromes anzutreiben, zuverlässig ausschließt, daß der Dieselmotor 13 abgewürgt wird, was zu erheblichen Betriebsstörungen führen könnte.In addition to the control device provided in the context of the pressure supply unit 10, which as a result conveys a stabilization of the volume flow generated by the main pump 12 to a desired value, even if the load represented by the consumer 11 is subject to considerable fluctuations, there is a protective device designated overall by 40 provided that, in cases in which the output torque of the diesel engine 13 is no longer sufficient to drive the main pump 12 in the sense of maintaining a predetermined output volume flow, reliably precludes the diesel engine 13 from stalling, which could lead to considerable malfunctions.

Eine diesbezügliche Bedarfssituation kann durch eine Fehlfunktion des Verbrauchers 11 entstehen, kann aber auch gesteuert eintreten, z.B. dadurch, daß zur Erzielung einer sanften Bewegungsumkehr von Kolben-Bewegungen des Verbrauchers 11 die Drossel 18 in Endphasen solcher Hübe selbsttätig auf erhöhte Strömungswiderstände eingestellt wird.A related need situation can arise from a malfunction of the consumer 11, but can also occur in a controlled manner, e.g. characterized in that the throttle 18 is automatically set to increased flow resistance in the final phases of such strokes to achieve a gentle reversal of piston movements of the consumer 11.

Die Schutzeinrichtung 40 umfaßt eine Hilfspumpe 42, die ebenso wie die Hauptpumpe 12 von dem Dieselmotor 13 angetrieben ist und einen zur Drehzahl des Dieselmotors 13 proportionalen Volumenstrom erzeugt. Zwischen dem Druckausgang 43 und dem Vorratsbehälter 32 des Druckversorgungsaggregates 10 liegt eine aus einem durch eine Festdrossel repräsentierten Verbraucher 44 und einer Einstelldrossel 46 bestehende hydraulische Reihenschaltung, über der der Ausgangsdruck PA der Hilfspumpe 42 abfällt, wobei die über den Komponenten dieser Reihenschaltung - dem Verbraucher 44 und der Einstelldrossel 46 - auftretenden Druckabfälle ΔPV und ΔPD den Strömungswiderständen des Verbrauchers 44 und der Einstelldrossel 46 proportional sind und in der Summe den Wert des Ausgangsdruckes PA der Hilfspumpe 42 ergeben.The protective device 40 comprises an auxiliary pump 42 which, like the main pump 12, is driven by the diesel engine 13 and one which is proportional to the speed of the diesel engine 13 Volume flow generated. Between the pressure outlet 43 and the reservoir 32 of the pressure supply unit 10 there is a hydraulic series circuit consisting of a consumer 44 represented by a fixed throttle and an adjusting throttle 46, via which the outlet pressure P A of the auxiliary pump 42 drops, the one above the components of this series circuit - the consumer 44 and the adjusting throttle 46 - occurring pressure drops .DELTA.P V and .DELTA.P D are proportional to the flow resistances of the consumer 44 and the adjusting throttle 46 and, in total, give the value of the outlet pressure P A of the auxiliary pump 42.

Beim Ausführungsbeispiel gemäß Fig. 1, bei dem der Verbraucher 44 unmittelbar an den Hochdruckausgang 43 der Hilfspumpe 42 angeschlossen und die Einstelldrossel 46 zwischen den Verbraucher 44 und den Tank 32 geschaltet ist, umfaßt die Schutzeinrichtung 40 ein als 3/2-Wege-Ventil ausgebildetes Steuerventil, das als druckgesteuertes Ventil ausgebildet ist, das durch eine vorgespannte Ventilfeder 48 in seine Grundstellung 0 gedrängt wird, in welcher die zweite Steuerkammer 37 des druckgesteuerten Regelventils 31 des Druckversorgungsaggregats 10 mit dem Tank 32 des Druckversorgungsaggregats 10 verbunden ist und diese Steuerkammer 37 gegen die Mittelanzapfung 19 zwischen der Drossel 18 und dem Verbraucher 11 abgesperrt ist, und das durch Druckbeaufschlagung einer Steuerkammer 49 mit dem zwischen dem Verbraucher 44, der an die Hilfspumpe 42 angeschlossen ist und der Einstelldrossel 46 herrschenden Druck, dessen Betrag dem Druckabfall ΔPD über der Einstelldrossel 46 entspricht, in seine Funktionsstellung I steuerbar ist, in welcher der an der Mittelanzapfung 19 zwischen der als Last-Sensorglied ausgenutzten Einstelldrossel 18 und dem Verbraucher 11 herrschende Druck in die zweite Steuerkammer 37 des Regelventils 31 eingekoppelt ist und diese Steuerkammer 37 gegen den Tank 32 des Druckversorgungsaggregats 10 abgesperrt ist.1, in which the consumer 44 is connected directly to the high-pressure outlet 43 of the auxiliary pump 42 and the setting throttle 46 is connected between the consumer 44 and the tank 32, the protective device 40 comprises a 3/2-way valve Control valve, which is designed as a pressure-controlled valve, which is urged into its basic position 0 by a prestressed valve spring 48, in which the second control chamber 37 of the pressure-controlled control valve 31 of the pressure supply unit 10 is connected to the tank 32 of the pressure supply unit 10 and this control chamber 37 against the Center tap 19 between the throttle 18 and the consumer 11 is shut off, and this by pressurizing a control chamber 49 with the pressure prevailing between the consumer 44, which is connected to the auxiliary pump 42 and the adjusting throttle 46, the amount of the pressure drop ΔP D across the adjusting throttle 46 corresponds to in ne functional position I can be controlled, in which the one used on the center tap 19 between the load sensor element Setting throttle 18 and the pressure prevailing in the consumer 11 is coupled into the second control chamber 37 of the control valve 31 and this control chamber 37 is blocked off from the tank 32 of the pressure supply unit 10.

Die insoweit erläuterte Schutzeinrichtung arbeitet wie folgt:
Solange die Drehzahl des Dieselmotors 13 höher ist als ein vorgebbarer Schwellenwert, oberhalb dessen ein Abwürgen des Dieselmotors 13 mit hinreichender Sicherheit ausgeschlossen werden kann, ist der Druckabfall über der Einstelldrossel 46 der Schutzeinrichtung 40 und damit der in die Steuerkammer 49 des Steuerventils 47 eingekoppelte Druck hinreichend groß, um das Steuerventil 47 gegen die Wirkung seiner Ventilfeder 48 in seiner Funktionsstellung I zu halten, in welcher der an der Mittelanzapfung 19 des Hauptpumpenkreises anstehende Druck in die zweite Steuerkammer 37 des Regelventils 31 eingekoppelt ist und das Druckversorgungsaggregat 10 im normalen, Last-sensierenden Regelungsbetrieb arbeitet.The protective device explained so far works as follows:
As long as the speed of the diesel engine 13 is higher than a predeterminable threshold value above which a stalling of the diesel engine 13 can be excluded with sufficient certainty, the pressure drop across the adjusting throttle 46 of the protective device 40 and thus the pressure coupled into the control chamber 49 of the control valve 47 is sufficient large to hold the control valve 47 against the action of its valve spring 48 in its functional position I, in which the pressure at the center tap 19 of the main pump circuit is coupled into the second control chamber 37 of the control valve 31 and the pressure supply unit 10 in the normal, load-sensing Control mode works.

Fällt die Drehzahl des Dieselmotors 13 unter den genannten Schwellenwert, mit der Folge, daß der von der Hilfspumpe 42 erzeugte Volumenstrom nicht mehr ausreicht, um mit dem zwischen dem Verbraucher 44 und der Einstelldrossel 46 der Schutzeinrichtung 40 herrschenden Druck das Steuerventil 47 in seiner Funktionsstellung I halten zu können, so daß dieses durch die Rückstellkraft der Ventilfeder 48 in seine Grundstellung 0 geschaltet wird, so wird die zweite Steuerkammer 37 des Regelventils 31 zum Tank 32 des Druckversorgungsaggregats 10 hin druckentlastet, wodurch die Hauptpumpe 12 in ihren minimalem Fördervolumen und damit auch minimalem Drehmomentbedarf entsprechenden Funktionszustand gesteuert wird, in dem der Dieselmotor 13 nicht abgewürgt werden kann.If the speed of the diesel engine 13 falls below the threshold value mentioned, with the result that the volume flow generated by the auxiliary pump 42 is no longer sufficient to control the control valve 47 in its functional position I with the pressure prevailing between the consumer 44 and the adjusting throttle 46 of the protective device 40 To be able to hold so that this is switched into its basic position 0 by the restoring force of the valve spring 48, the second control chamber 37 of the control valve 31 is relieved of pressure to the tank 32 of the pressure supply unit 10, as a result of which the main pump 12 has its minimum delivery volume and thus also minimal Torque requirement corresponding functional state is controlled in which the diesel engine 13 can not be stalled.

Der Drehzahl-Schwellenwert, bei dessen Unterschreiten das Steuerventil 47 aus seiner dem normalen Regelungsbetrieb zugeordneten Funktionsstellung I in seine den Schutz des Dieselmotors 13 gegen ein Abwürgen vermittelnde Grundstellung 0 übergeht, ist mit Einstellung eines bestimmten Strömungswiderstandes der Einstelldrossel 46 vorgebbar. In einer typischen Auslegung der Schutzeinrichtung 40 beträgt der Steuerdruck, ab welchem das Steuerventil 47 in seine Funktionsstellung I umgeschaltet wird, zwischen 4 und 10 bar.The speed threshold, below which the control valve 47 changes from its functional position I assigned to normal control operation to its basic position 0, which provides protection of the diesel engine 13 against stalling, can be predetermined by setting a specific flow resistance of the adjusting throttle 46. In a typical design of the protective device 40, the control pressure from which the control valve 47 is switched to its functional position I is between 4 and 10 bar.

Die in der Fig. 2 dargestellte Schutzeinrichtung 50 ist mit der Schutzeinrichtung 40 gemäß Fig. 1 funktionsäquivalent, unterscheidet sich von dieser jedoch in schaltungstechnischer Hinsicht dadurch, daß die Einstelldrossel 46, mittels derer im Ergebnis die Drehzahlschwelle vorgebbar ist, unterhalb derer die zweite Steuerkammer 37 des Regelventils 31 druckentlastet wird, unmittelbar an den Hochdruckausgang 43 der Hilfspumpe 42 angeschlossen und der Verbraucher 44 zwischen diese Einstelldrossel 46 und den Tank 32 des Druckversorgungsaggregats geschaltet ist, sowie dadurch, daß das Steuerventil 47', das in seiner Grundstellung 0 und in seiner dazu alternativen Funktionsstellung I dieselben Funktionen vermittelt wie das Steuerventil 47 der Schutzeinrichtung 40 gemäß Fig. 1, hier als Differential-Ventil ausgebildet ist, das aus seiner Grundstellung 0 in seine Funktionsstellung I umgeschaltet wird, wenn die Druckdifferenz ΔPD zwischen dem Hochdruckausgang 43 der Hilfspumpe 42 und der Mittelanzapfung 51 zwischen der Einstelldrossel 46 und dem Verbraucher 44 einen Schwellenwert überschreitet, der dem Betrage nach derselbe sein kann wie der Steuerdruck, der sich beim Ausführungsbeispiel gemäß Fig. 1 über der dort zwischen den Verbraucher 44 und den Tank 32 geschalteten Einstelldrossel 46 aufbaut.The protective device 50 shown in FIG. 2 is functionally equivalent to the protective device 40 according to FIG. 1, but differs from this in terms of circuit technology in that the setting throttle 46, by means of which the speed threshold can be specified as a result, below which the second control chamber 37 of the control valve 31 is depressurized, connected directly to the high-pressure outlet 43 of the auxiliary pump 42 and the consumer 44 is connected between this adjusting throttle 46 and the tank 32 of the pressure supply unit, and in that the control valve 47 ', which is in its basic position 0 and in it Alternative function position I conveys the same functions as the control valve 47 of the protective device 40 according to FIG. 1, here designed as a differential valve, which is switched from its basic position 0 to its function position I when the pressure difference ΔP D between the high-pressure outlet 43 of the auxiliary pump 42 and de r center tap 51 between the adjusting throttle 46 and the consumer 44 exceeds a threshold value, the amount of which can be the same as the control pressure that builds up in the exemplary embodiment according to FIG. 1 via the adjusting throttle 46 connected there between the consumer 44 and the tank 32.

Demgemäß ist bei dem Steuerventil 47' der Schutzeinrichtung 50 gemäß Fig. 2 zusätzlich zu der ersten Steuerkammer 49', die mit dem am Hochdruckausgang 43 der Hilfspumpe 42 anstehenden Ausgangsdruck derselben beaufschlagt ist, wodurch das Steuerventil 47' in seine Funktionsstellung I gedrängt wird, eine zweite Steuerkammer 52 vorgesehen, die mit dem an der Mittelanzapfung 51 zwischen der Einstelldrossel 46 und dem Verbraucher 44 anstehenden Druck beaufschlagt ist, wodurch das Steuerventil 47' in seine Grundstellung 0 gedrängt wird, wobei diese Steuerkammern 49' und 52' so ausgelegt sind, daß die durch ihre Druckbeaufschlagung resultierenden, in entgegengesetzter Richtung auf den Ventilkolben wirkenden Kräfte sich aufheben, so daß bei dem Steuerventil 47' durch die Druckbeaufschlagung seiner zweiten Steuerkammer 52 das Druckniveau bestimmt ist, gegenüber welchem der in die erste Steuerkammer 49' eingekoppelte Druck höher sein muß, damit das Steuerventil 47' gegen die Wirkung seiner Ventilfeder 48 in seine Funktionsstellung I umgeschaltet werden kann. Auch das Steuerventil 47' ist so ausgelegt, daß diese Druckdifferenz nur wenige bar beträgt, z.B. 6 bar.Accordingly, in the control valve 47 'of the protective device 50 according to FIG. 2, in addition to the first control chamber 49', which is acted upon by the output pressure present at the high-pressure outlet 43 of the auxiliary pump 42, whereby the control valve 47 'is forced into its functional position I. second control chamber 52 is provided, which is acted upon by the pressure present at the center tap 51 between the setting throttle 46 and the consumer 44, whereby the control valve 47 'is pushed into its basic position 0, these control chambers 49' and 52 'being designed such that the forces resulting from their pressurization acting in the opposite direction on the valve piston cancel each other out, so that in the control valve 47 'the pressurization of its second control chamber 52 determines the pressure level against which the pressure coupled into the first control chamber 49' must be higher , so that the control valve 47 'against the action its valve spring 48 can be switched to its functional position I. The control valve 47 'is also designed so that this pressure difference is only a few bar, e.g. 6 bar.

Bei dem Ausführungsbeispiel der Schutzeinrichtung 50 gemäß Fig. 2 sind die Steuerkammern 49' und 52 des Steuerventils 47' mit dem Absolutbetrag nach wesentlich höheren Drücken beaufschlagt als die Steuerkammer 49 des Steuerventils 47 der Schutzeinrichtung 40 gemäß Fig. 1, was erhöhte Anforderungen hinsichtlich der Dichtigkeit der Steuerkammern 49 und 52 stellt. Bei der Schutzeinrichtung 50 gemäß Fig. 2 ist es jedoch ohne weiteres möglich, das Steuerventil 47' und die Einstelldrossel 46 baulich mit der Hilfspumpe 42 in einer integrierten Bauweise zusammenzufassen, da der Verbraucher 44 dieser hydraulischen Funktionseinheit hydraulisch nachgeschaltet ist.In the exemplary embodiment of the protective device 50 according to FIG. 2, the control chambers 49 'and 52 of the control valve 47' are acted upon by the absolute amount after significantly higher pressures than the control chamber 49 of the control valve 47 Protective device 40 according to FIG. 1, which places increased demands on the tightness of the control chambers 49 and 52. In the protective device 50 according to FIG. 2, however, it is readily possible to structurally combine the control valve 47 'and the adjusting throttle 46 with the auxiliary pump 42 in an integrated construction, since the consumer 44 is hydraulically connected downstream of this hydraulic functional unit.

Sowohl bei der Schutzeinrichtung 40 gemäß Fig. 1 als auch bei der Schutzeinrichtung 50 gemäß Fig. 2 kann das Steuerventil 47 bzw. 47' als Proportionalventil ausgebildet sein, das nach einem Übergang von der einen in die andere der möglichen Funktionsstellungen 0 und I jeweils zunehmende Öffnungsquerschnitte der wirksamen Umlauf- bzw. Durchflußströmungspfade 53 bzw. 54 freigibt, wodurch sich besonders sanfte und damit schonende An- und Auslaufcharakteristiken der Hauptpumpe 12 in Umschaltsituationen des Verbrauchers 11 des Hauptkreislaufes erzielen lassen.Both in the protective device 40 according to FIG. 1 and in the protective device 50 according to FIG. 2, the control valve 47 or 47 'can be designed as a proportional valve, which increases after a transition from one to the other of the possible functional positions 0 and I Opening cross sections of the effective circulation or flow flow paths 53 and 54 releases, whereby particularly gentle and therefore gentle starting and stopping characteristics of the main pump 12 can be achieved in switching situations of the consumer 11 of the main circuit.

Bei einer derartigen Ausbildung des Steuerventils 47 bzw. 47' ist dieses, wie nicht eigens dargestellt, als 3/3-Wege-Ventil ausgebildet, das zwischen der Funktionsstellung 0, in welcher die zweite Steuerkammer 37 des Regelventils 31 gegen die Vergleichsdruck-Abgriffstelle 19 des Hauptverbraucherkreises 11,18 abgesperrt, dafür aber mit dem Tank 32 des Druckversorgungsaggregats 10 verbunden ist, und der Funktionsstellung I, in welcher die zweite Steuerkammer 37 des Regelventils 31 mit der Vergleichsdruck-Abgriffstelle 19 des Hauptverbraucherkreises verbunden, jedoch gegen den Tank des Druckversorgungsaggregats 10 abgesperrt ist, eine sperrende Funktionsstellung II hat, in der die zweite Steuerkammer 37 des Regelventils 31 sowohl gegen die Vergleichsdruck-Abgriffstelle 19 des Hauptverbraucherkreises 11,18 als auch gegen den Tank 32 des Druckversorgungsaggregats 10 abgesperrt ist.With such a design of the control valve 47 or 47 ', this is, as not specifically shown, designed as a 3/3-way valve, which between the functional position 0, in which the second control chamber 37 of the control valve 31 against the reference pressure tap 19 of the main consumer circuit 11, 18, but is connected to the tank 32 of the pressure supply unit 10, and the functional position I, in which the second control chamber 37 of the control valve 31 is connected to the comparative pressure tap 19 of the main consumer circuit, but against the tank of the pressure supply unit 10 is locked, a locking position II has, in which the second control chamber 37 of the control valve 31 is shut off both against the reference pressure tap 19 of the main consumer circuit 11, 18 and against the tank 32 of the pressure supply unit 10.

In spezieller Gestaltung eines solchen 3/3-Wege-Ventils können die Umschaltpositionen, in denen das Steuerventil aus seiner sperrenden Funktionsstellung II in seine eine Durchflußstellung 0 oder die dazu alternative Durchflußstellung I übergeht, in Verschieberichtung des Ventilkörpers gesehen, in einem Abstand voneinander angeordnet sein, der zwischen 1/50 und 1/5, vorzugsweise um 1/10 des Gesamthubes beträgt, den der Ventilkörper zwischen seinen den alternativen Durchfluß-Funktionsstellungen 0 bzw. I zugeordneten Endpositionen ausführen kann.In a special design of such a 3/3-way valve, the changeover positions in which the control valve changes from its blocking functional position II into its one flow position 0 or the alternative flow position I, seen in the direction of displacement of the valve body, can be arranged at a distance from one another , which is between 1/50 and 1/5, preferably around 1/10 of the total stroke that the valve body can carry out between its end positions assigned to the alternative flow function positions 0 and I, respectively.

Claims (9)

  1. Overload protection device for a drive motor (13), designed as an internal combustion engine, especially a diesel engine, of a main pump (12) of a hydraulic pressure generator (10), adjustable by means of a hydraulic regulating device for constant flow volume in a pressure medium flow connected to the high pressure outlet (16) of the main pump (12), leading from the latter to the tank (32) of the hydraulic pressure generator (10) and flowing through the main consumer circuit completed by the pump (12), for whose monitoring a throttle (18) connected in series with the main consumer (11) is provided, across which throttle (18) a pressure drop (ΔP) characteristic of the actual flow volume through the main consumer (11) appears, the sensing of said pressure drop (ΔP) by means of a regulating valve (31) which, from a comparison between outlet pressure PH of the main pump (12) coupled with a first control chamber (36) of this regulating valve as a reference pressure, and pressure PV prevailing at a tapping point (19) between the throttle (18) and the main consumer (11), and coupled with a second control chamber (37) of the regulating valve (31) as a comparison pressure, regulates a control pressure coupled with a hydraulic positioning device (22) in the main pump (12) in such fashion that when the pressure differential (ΔP) across the throttle (18) increases, the outlet flow volume of the main pump (12) is reduced and the flow volume is increased with a decreasing pressure differential (ΔP) , charaterized by an auxiliary pump (42), likewise driven by drive motor (13) of main pump (12) and rotationally synchronized therewith, being provided and generating a rotational-speed-proportional outlet flow volume conducted through an auxiliary consumer circuit comprising in a hydraulic series circuit an adjustable flow resistance (46) and an additional flow resistance (44) and having a tapping point at which a pressure varying with flow volume appears, to tank (32) of hydraulic pressure generator (10), and by the fact that in order to couple comparison pressure (PV) prevailing at tapping point (19) of main consumer circuit (11, 18) with second control chamber (37) of regulating valve (31), a pressure-controlled valve (47; 47') is provided, urgeable by pretensioned valve spring (48) into a basic position 0 in which second control chamber (37) of regulating valve (31) is relieved of pressure and, by charging of a control chamber (49; 49') with the pressure prevailing at the tapping point of auxiliary consumer circuit (44, 46), is urgeable into a functional position (I) in which comparison pressure (PV) prevailing in main consumer circuit (11, 18) is coupled with second control chamber (37) of regulating valve (31).
  2. Protective device according to Claim 1 characterized in that the additional flow resistance (44) of the auxiliary consumer circuit (46, 44) is designed as a rotational-speed-synchronous consumer, for example as a hydraulically driven mixer.
  3. Protective device according to Claim 1 or Claim 2 characterized by flow resistance (44) of the auxiliary consumer circuit being connected directly to pressure outlet (43) of auxiliary pump (42), and by flow resistance (46), which is adjustable and serves to sense the flow volume, being connected between flow resistance (44) and tank (32) of hydraulic pressure generator (10).
  4. Protective device according to Claim 1 or Claim 2 characterized by adjustable flow resistance (46) of auxiliary consumer circuit (46, 44) being connected directly to pressure outlet (43) of auxiliary pump (42) and by flow resistance (44) or consumer (44) of auxiliary consumer circuit (46, 44) being connected between adjustable flow resistance (46) and tank (32) of hydraulic pressure generator (10).
  5. Protective device according to Claim 4 characterized by pressure-controlled control valve (47') provided for coupling comparison pressure (PV) with second control chamber (37) of regulating valve (31) being designed as a differential valve which, when first control chamber (49') is pressurized with outlet pressure (PH) of main pump (42), is urged into functional position (I), coupling comparison pressure (PV) with second control chamber (37) of regulating valve (31), and when a second control chamber (52) is pressurized, is urgeable into basic position (0) which depressurizes second control chamber (37) of regulating valve (31).
  6. Protective device according to one of Claims 1 to 5 characterized by through flow paths (53 and 54) effective in the alternate functional positions (0 and I) of control valve (47; 47'), undergoing a constant expansion of cross section with increasing deflection of the valve body from the switching range.
  7. Protective device according to one of Claims 1 to 6 characterized by control valve (47; 47') being designed as a 3/3-way valve, which, between functional position (0), in which second control chamber (37) of regulating valve (31) is cut off from comparison pressure tapping point (19) of main consumer circuit (11, 18), and is connected instead with tank (32) of hydraulic pressure generator (10), and functional position (I), in which second control chamber (37) of regulating valve (31) is connected with comparison pressure tapping point (19) of the main consumer circuit but is cut off from tank (32) of hydraulic pressure generator (10), has a blocking functional position (II) in which second control chamber (37) of regulating valve (31) is cut off from both comparison pressure tapping point (19) of main consumer circuit (11, 18) and also from tank (32) of hydraulic pressure generator (10).
  8. Protective device according to Claim 7 characterized by the switching positions in which control valve (47; 47') moves from its blocking functional position (II) to its through flow position (0) or alternate through flow position (I), looking in the displacement direction of the valve body, being arranged at an interval from one another equal to between 1/50 and 1/5, preferably 1/10, of the total stroke which the valve body can execute between the end positions corresponding to alternate through flow functional positions (0 and I).
  9. Protective device according to one of Claims 1 to 8 with the additional flow resistance of the auxiliary consumer circuit being designed as a rotational-speed-synchronous consumer, characterized by the pressure drop across adjustable flow resistance (46) of auxiliary consumer circuit (46, 44) being between 5% and 15%, preferably 10%, of the pressure drop developing across rotational-speed-synchronous consumer (44) of the auxiliary consumer circuit during steady-state operation of main consumer circuit (11, 18).
EP92905344A 1991-05-14 1992-02-27 Overload protective device for a drive motor of a hydraulic pressure generator Expired - Lifetime EP0584078B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4115606A DE4115606A1 (en) 1991-05-14 1991-05-14 OVERLOAD PROTECTION DEVICE FOR A DRIVE ENGINE DESIGNED AS AN INTERNAL COMBUSTION ENGINE OF A MAIN PUMP OF A HYDRAULIC PRESSURE SUPPLY UNIT
DE4115606 1991-05-14
PCT/EP1992/000424 WO1992020921A1 (en) 1991-05-14 1992-02-27 Overload protective device for an internal combustion engine acting as the drive motor of the main pump of a hydraulic pressure generator

Publications (2)

Publication Number Publication Date
EP0584078A1 EP0584078A1 (en) 1994-03-02
EP0584078B1 true EP0584078B1 (en) 1995-01-11

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EP92905344A Expired - Lifetime EP0584078B1 (en) 1991-05-14 1992-02-27 Overload protective device for a drive motor of a hydraulic pressure generator

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US (1) US5421705A (en)
EP (1) EP0584078B1 (en)
JP (1) JP3319753B2 (en)
DE (2) DE4115606A1 (en)
ES (1) ES2068706T3 (en)
WO (1) WO1992020921A1 (en)

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WO1992020921A1 (en) 1992-11-26
JP3319753B2 (en) 2002-09-03
US5421705A (en) 1995-06-06
DE59201202D1 (en) 1995-02-23
DE4115606A1 (en) 1992-11-19
JPH06507219A (en) 1994-08-11
EP0584078A1 (en) 1994-03-02
ES2068706T3 (en) 1995-04-16

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