EP0617758B1 - Initial pressure governor for a variable displacement pump - Google Patents

Abstract

PCT No. PCT/EP92/02880 Sec. 371 Date Jun. 10, 1994 Sec. 102(e) Date Jun. 10, 1994 PCT Filed Dec. 12, 1992 PCT Pub. No. WO93/12342 PCT Pub. Date Jun. 24, 1993A pressure governor for a pump (11) employed as a variable displacement pump for supplying pressurized fluid to a hydraulic power consumer (54) is disclosed. The governor includes a differential pressure regulator (13) connected to the pump for establishing the output flow of the pump. The state of the regulator is controlled by a pressure-regulated valve (21). Valve (21) is, in its initial state, set so as to allow a high volumetric flow out of the pump. A portion of the flow out of the pump returned to the pressure regulated valve to force the valve into a second state. The movement of the valve into the second state resets the valve so that a portion of the output of the pump is applied to the pressure regulator. This flow, in turn, causes the regulator to reduce the output flow from the pump. Thus, the initial output flow of the pump is reduced so as to minimize the possibility that large sustained output flows will damage the components of the hydraulic power consumer to which the flow is applied.

Description

The invention relates to a device for regulating the outlet pressure of a variable displacement pump, in particular a main pump of a pressure supply unit for a hydraulic drive device, which works at a high outlet pressure level, e.g. the / the drive cylinder of a thick matter pump according to the preamble of claim 1. In such a control device, a delivery rate control element is provided which can be actuated by means of a hydraulic servo motor, which by means of alternative pressurization and relief of a drive pressure chamber for executing the actuating movements for the opposing changes in the delivery volume The variable displacement pump can be driven, a pressure-controlled valve being provided to control the relevant pressurization and relief of this drive pressure chamber, which valve, controlled by the output pressure of the pump or a pressure proportional to it, from a minimum pressure determined by a minimum restoring force of a restoring element, e.g. a spring outputs an output pressure which increases with the control pressure coupled into its control chamber and which acts on the drive pressure chamber of the servomotor.

Such control devices are known and comprise a valve which can be controlled with the outlet pressure of the variable pump, for example a valve designed as a proportional valve, and which increases with increasing outlet pressure of the variable pump is increasingly pushed into the functional position mediating the activation of the actuator against the restoring force of a valve spring, the output pressure of the variable pump being determined by the preset preload of the valve spring in the stationary state of the pressure control. This type of control, which can be superimposed on a volume flow control, which - at a lower pressure level than the maximum level determined by the pressure control valve - provides constant control of the volume flow of the high-pressure pump, has the disadvantage, however, that in start-up situations of a consumer who requires a relatively high operating pressure level in the steady state of its motion sequences, strong pressure surges can occur, which are both wear-promoting and associated with considerable noise, since in the start-up situation the control device is set to the greatest possible delivery volume of the variable pump and this is only reduced, when the consumer has started. This is also comparable to the situation in which the consumer or a drive cylinder blocks the same, since even then the output pressure of the variable pump rises very quickly - suddenly - to the value given by the pressure limitation. These problems are particularly serious for consumers who are driven by linear cylinders or hydraulic swivel motors which perform periodic back and forth movements.

The object of the invention is therefore a control device to improve the type mentioned at the outset such that a gentle increase in the operating pressure can be achieved in particular in start-up situations of a hydraulic consumer and / or in the event of load changes in the sense of a sudden increase in the load a correspondingly gentle increase in the operating pressure can be achieved up to a predetermined maximum value.

According to the invention, this object is achieved in that the restoring element is designed for a restoring force which is only a small fraction of e.g. 1/50 to 1/10 of the maximum control force that can be generated by the control pressure and acts on the valve piston of the proportional valve corresponds to the fact that the pressure-controlled valve is provided with a reset chamber as a second control chamber, by the pressurization of which an additional reset force opposite to the control force can be generated, the Maximum amount corresponds at least approximately to that of the control force, and that the pressure coupled into the return chamber is derived from the pressure coupled into the control chamber of the pressure-controlled valve by means of a hydraulic time delay element.

According to this, when the consumer is started up by switching on the pressure supply unit, there is initially an increase in pressure with a high rate of increase in the outlet pressure of the variable displacement pump until it is designed according to a characteristic of the hydraulic time delay element a certain period of time reaches a value which is higher by the pressure equivalent to the restoring force of the restoring element, in practical cases the pretensioning of a valve spring, than the pressure which is coupled into the additional restoring chamber of the pressure-controlled valve via the time delay element. As soon as this is the case and the control force resulting from the coupling of the output pressure of the variable pump into the control chamber of the pressure-controlled valve is greater than the sum of the forces resulting from the spring preload and the coupling of the output pressure of the time delay element into the reset chamber, the pressure-controlled valve becomes one Functional position controlled, in which the actuator acts in the sense of a reduction in the delivery capacity of the variable pump and as a result, the rate of increase of the output pressure of the variable pump is reduced. In the "steady" state of this pressure rise control, there is a reduced rate of increase of the output pressure of the variable displacement pump compared to the unregulated state, such that it increases with a time constant determined by the design of the time delay element - in a good approximation linearly - and from the onset of this Regulation of the output pressure of the variable displacement pump is always greater by the difference due to the predetermined restoring force of the restoring element than the pressure coupled into the restoring chamber of the pressure-controlled valve via the time delay element. This applies mutatis mutandis in the event that during a sudden blockage of the operation of the consumer and thus an increase in the outlet pressure of the variable pump occurs, in which case the control assumes a correspondingly increased outlet pressure level.

If, as provided in a preferred design of the control device, the time delay element comprises a throttle and a pressure accumulator which can be charged via the latter, the pressure developing during operation of the consumer at the center tap between the throttle and the pressure accumulator being coupled into the reset chamber of the pressure-controlled valve, so the product of the flow resistance of the throttle and the storage capacity of the pressure accumulator is a measure of the delay time constant of the time delay element, which can thus also be predetermined by specifying these variables, it being particularly advantageous for a targeted variation of the delay time constant of the time delay element, provided that the pressure accumulator has sufficient capacity , if the throttle of the time delay element is designed as a setting throttle.

In order to achieve an expedient limitation of the output pressure of the variable pump to a maximum value of, for example, 400 bar, which is not yet possible with the help of the pressure-controlled valve in its design and function provided for the control device according to the invention, it is advantageous if between the High pressure output of the variable displacement pump and that Time delay element is connected to a pressure reducer, which prevents a higher pressure from being coupled into the time delay element or the reset chamber of the pressure-controlled valve when a threshold value of the output pressure of the variable pump is reached, with the result that, with the cooperation of the control device, the maximum output pressure of the variable pump is limited to one value becomes, which corresponds to the sum of the threshold pressure and the pressure equivalent to the bias of the reset element.

If, as part of a complex hydraulic system, several consumers are supplied with pressure medium by means of the variable pump, e.g. are "switched on" in the course of periodically repeated operating cycles of the system at different times and only short periods of time are available for the activation of individual consumers, it is advantageous if the time delay element can be switched off for the duration of such activation periods, which in the simplest case is due to Shutdown of the pressure accumulator of the time delay element can be reached.

A valve suitable for this purpose is designed in a preferred configuration of the control device as a 3/2-way valve, in the basic position of which the accumulator is connected to the throttle and in the switching position of which the accumulator is shut off against the throttle, but instead on the unpressurized reservoir of the Pressure supply unit is connected. The memory can be discharged in the switch position in order to be rechargeable in a next start-up cycle and to be able to fulfill its deceleration function.

For the purpose of "undamped" control of a consumer, a valve connected between the pump output and the time delay element can also be suitable, which has a basic position 0 in which the pump output is connected to the time delay element and a switching position in which the pump output is blocked against the time delay element , but is directly connected to the second control chamber of the pressure-controlled valve.

In combination with this, it is advantageous if a check valve is connected between the control line, to which the pressure output of the variable displacement pump is connected when the valve is in the switch position, and the pressure accumulator of the time delay element, which acts in the reverse direction due to relatively higher pressure in the control line than in the pressure accumulator is to avoid charging the pressure accumulator in the switching position of the valve.

By means of a valve which is connected between the second control chamber of the pressure-controlled valve and the tapping point of the time delay element, at which the pressure which can be coupled into this control chamber can be tapped, and from a basic position 0, in which the tapping point is connected to the control chamber is switchable to a functional position I, in which the second control chamber of the pressure control valve is shut off from the tap, but is connected to the unpressurized reservoir of the pressure supply unit, the pressure control device can be used to limit the output pressure of the variable pump to the value that the bias of the return spring of the pressure-controlled valve is equivalent.

Both the valve intended to shut off the high-pressure output of the variable pump from the time delay element and, at the same time, direct connection of the pump output to the second control chamber of the pressure-controlled valve, and the valve used to relieve pressure in the control chamber, can be seen as a 3/2-way valve be designed or also be realized by means of a single 4/3-way valve, and it is also understood that these valves, depending on the type of their insertion into a hydraulic system, either as pressure-controlled or as electrically actuable solenoid valves or as combined actuators Valves can be formed.

In order to be able to adapt the pressure regulating device to various operating conditions of possible consumers in a simple manner, it is advantageous if the pretension of the reset valve spring of the pressure-controlled valve can be adjusted.

The control functions explained can be achieved both when the pressure-controlled valve is switched as a pressure control valve, by means of which the variable pump can be regulated to - essentially - constant output pressure, and when the pressure-controlled valve is switched as a volume flow control valve, by means of which the Variable pump is adjustable to - essentially - constant value of its output volume flow.

Fig. 1

ein Hydraulikschema eines Druckversorgungsaggregats mit einer als Verstellpumpe ausgebildeten Hochdruckpumpe und einer erfindungsgemäßen Druckregeleinrichtung zur Dämpfung von Druckstößen am Ausgang der Verstellpumpe,

Fig. 2a

eine halbschematische Längsschnitt-Darstellung eines im Rahmen der Regeleinrichtung gemäß Fig. 1 einsetzbaren Druckregelventils für die Antriebssteuerung eines zur Verstellung des Fördervolumens der Verstellpumpe vorgesehenen Stellzylinders,

Fig. 2b

eine zur Gestaltung des Druckregelventils gemäß Fig. 2a alternative Gestaltung eines Druckregelventils mit einstellbarer Vorspannung der Rückstellfeder,

Fig. 3

ein Diagramm zur Erläuterung der Funktion der Regeleinrichtung gemäß Fig. 1,

Fig. 4

ein hydraulisches Schaltbild eines weiteren Druckversorgungsaggregats mit einer erfindungsgemäßen, lastabhängig arbeitenden Ausgangsdruckregelung für die Hauptpumpe des Druckversorgungsaggregats und Funktions-Steuerventilen zur zeitweisen Abschaltung der Druckregelung und Begrenzung des Pumpen-Ausgangsdruckes unter Mitwirkung der Druck-Regeleinrichtung,

Fig. 4a und b

im Rahmen der Druckregeleinrichtung einsetzbare Gestaltungs-Varianten von Funktionssteuerventilen und

Fig. 5

ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Regelungseinrichtung, bei dem als druckgesteuertes Ventil ein Volumenstrom-Regelventil ausgenutzt ist, mittels dessen die Verstellpumpe auf - im wesentlichen - konstanten Betrag ihres Ausgangs-Volumenstromes regelbar ist, in einer den Fig. 1 und 4 entsprechenden Darstellung.

Further details and features of the invention result from the following description of special exemplary embodiments with reference to the drawing. Show it:

Fig. 1

1 shows a hydraulic diagram of a pressure supply unit with a high-pressure pump designed as a variable pump and a pressure control device according to the invention for damping pressure surges at the outlet of the variable pump,

Fig. 2a

2 shows a semi-schematic longitudinal sectional illustration of a pressure control valve which can be used in the control device according to FIG. 1 for the drive control of an actuating cylinder provided for adjusting the delivery volume of the variable displacement pump,

Fig. 2b

an alternative to the design of the pressure control valve according to FIG. 2a design of a pressure control valve with adjustable preload of the return spring,

Fig. 3

2 shows a diagram to explain the function of the control device according to FIG. 1,

Fig. 4

a hydraulic circuit diagram of a further pressure supply unit with a load-dependent output pressure control according to the invention for the main pump of the pressure supply unit and function control valves for temporarily switching off the pressure control and limiting the pump output pressure with the help of the pressure control device,

4a and b

Design variants of function control valves and can be used in the context of the pressure control device

Fig. 5

a further embodiment of a control device according to the invention, in which a volume flow control valve is used as a pressure-controlled valve, by means of which the variable pump can be regulated to - essentially - constant amount of its output volume flow, in a representation corresponding to FIGS. 1 and 4.

The pressure supply unit shown in FIG. 1, designated overall by 10, is for one application intended for hydraulic consumers, where, for example, hydraulic motors designed as linear cylinders perform reciprocating movements that should take place at a constant stroke speed, whereby when starting up such drive cylinders and / or reversing the direction of movement, pressure surges of their pistons that occur as rapid pressure increases occur Demand - should be able to be damped to reduce wear and / or noise. These requirements are typical for thick matter pumps in general, especially concrete pumps, whose drive cylinders are operated at high pressures of up to 400 bar.

The central functional element of the pressure supply unit 10 is a variable displacement pump 11 which can be regulated to a constant outlet pressure or also to the constancy of the pressure medium output volume flow, which for the purpose of explanation is assumed to be a rotary-driven swash plate axial piston pump, the delivery volume of which is based on one revolution of its cylinder block (not shown) The angle of attack of the swivel plate represented by the arrow 12 in FIG. 1 can be varied continuously between zero and a maximum value Q _max relative to the direction of the central axes of the axial piston pump elements, the position of the swivel plate 12 shown in dashed lines corresponding to the delivery volume being the one in FIG which is at right angles to the central axes of the - not shown - axial piston pump elements of the pump 11.

In the exemplary embodiment shown, a linear differential cylinder is provided for adjusting the swivel plate 12 as an actuator 13, with the piston 14 of which the swivel plate 12 is coupled in motion via the piston rod 16 emerging from the housing of the differential cylinder on one side. The arrangement of this actuator 13 is such that with the bottom position of its piston 14, the maximum delivery volume of the pump 11 corresponding position of its swash plate 12 is linked, and that the most protruding from the housing of the differential cylinder 13 position of its piston rod 16, the Flow rate zero corresponds to the swivel plate position assigned to the pump. By means of a helical spring 17 of the differential cylinder 13 coaxially surrounding the piston rod, its piston is pushed into its end position near the ground, so that the pump 11 is initially set to the maximum delivery rate when it starts up. The restoring forces developed by the helical spring 17 in the various possible positions of the piston 14 are regarded as negligible compared to the forces acting on the piston 14 by pressurizing the bottom-side drive chamber 18 and / or pressurizing the rod-side drive chamber 19 of the differential cylinder 13.

Within the scope of a device for regulating the outlet pressure of the variable displacement pump 11, designated as 20, a device is designed, for example, as a proportional valve Pressure control valve 21 is provided, for which details of its constructive design are shown in FIG. 2a, to which reference should also be made.

This pressure control valve 21 is designed as a pressure-controlled slide valve, which according to its function is a 3/2-way valve, with a spring-centered basic position 0, in which the bottom-side drive chamber 18 of the actuator cylinder 13 with the unpressurized, i.e. Atmospheric pressure reservoir 23 is connected and blocked against the high pressure outlet 24 of the variable displacement pump 11, and with a function position I alternative to the basic position 0, in which the bottom-side drive chamber 18 of the differential cylinder 13 is blocked against the reservoir 23 of the pressure supply unit 10 and therefore via a flow path 26 of the pressure control valve 21 is connected to the high-pressure outlet 24 of the variable pump 11, to which the rod-side drive chamber 19 of the differential cylinder 13 provided as an actuator is also permanently connected.

The pressure control valve 21 has a first control chamber 27 which is also permanently connected to the high pressure outlet 24 of the variable displacement pump 11. By pressurizing this control chamber 27 with the output pressure of the variable displacement pump 11, a control force K _I , which pushes it into its functional position _{I, is} exerted on the valve piston 28 represented in FIG. 1 by the 3/2-way switching symbol, the amount of which essentially is given by the product P _A (t) · f, with P _A (t) denoting the instantaneous value of the outlet pressure of the variable displacement pump 11 and with f the cross-sectional area of the piston end flange 29 of the axially movable limitation of the first control chamber 27 forming the Valve piston 28 is designated.

The pressure regulating valve 21 also has a second control chamber 31, by the pressurization of which a restoring force K₀ which is permanently exerted by the valve spring 32 of the pressure regulating valve 21 and which is added to the additional restoring force K add can be exerted on the valve piston 28, through which the latter can be applied Functional position 0 of the pressure control valve 21 is pushed towards the corresponding end position.

The amount of this force K₀ is given by the product P _a (t) · f, with P _a (t) the instantaneous value of the pressure coupled into the second control chamber 31 and with f in turn the cross-sectional area of the one-sided axially movable limitation of the second control chamber 31 forming control piston element 33, the effective cross-sectional area f is assumed to be equal to that of the piston end flange 29, which forms the axially movable boundary of the first control chamber 27.

In the context of the pressure control device 20, a pressure accumulator 34 is also provided, which is by means of the variable displacement pump 11 can be charged to a pressure via a volume flow adjusting element, for example an adjusting throttle 36, the maximum value of which Pamax can be set by a pressure reducer or limiter 37 connected between the adjusting throttle 36 and the high-pressure outlet 24 of the adjusting pump 11 in the special exemplary embodiment shown.

The pressure P _a (t) present at a center tap 38 between the setting throttle 36 and the pressure accumulator 34 is coupled via a control line 39 into the second control chamber 31 of the pressure control valve 21.

Between the center tap 38 and the pressure accumulator 34 is a cyclically controllable, designed as a 3/2-way valve delay control valve 41, which has a spring-centered basic position 0, in which the pressure accumulator 34 via a flow path 42 open in this basic position 0 with the Center tap 38 and thus via the setting throttle 36 and the pressure reducer 37 is connected to the high-pressure outlet 24 of the variable displacement pump 11, as well as an alternative function position I, in which the pressure accumulator 34 is shut off against the center tap 38, but via an open flow path in the function position I. 43 is connected to the unpressurized reservoir 23 of the pressure supply unit 10.

“Cyclically controllable” here means that the delay control valve 41 is in one with the various Operating phases of the consumer connected to the pressure supply unit 10 is switched in a suitable, synchronized sequence between its two functional positions 0 and I, in order to be able to set desired low or high pressure rise rates at the pressure outlet 24 of the variable displacement pump 11, which are favorable for the operation of the consumer.

In the embodiment shown in FIG. 1, the delay control valve 41 is designed as a pressure-controlled valve which is switched for the duration of a pressure pulse coupled into its control chamber 44 into its functional position I connecting the memory 34 to the reservoir 23, this pressure pulse of a hydraulic end position transmitter 46 designed as a one-way or non-return valve is generated and used when the drive piston 47 of a hydraulic drive cylinder 48 of the consumer, for example a two-cylinder thick matter pump (not shown) with tube switchover, comes into immediate vicinity of its illustrated end position , in which the delivery stroke of the delivery cylinder of the thick matter pump driven by this drive cylinder 48 is completed, and drops again when ie after switching the pressurization of the drive cylinder 48 from the bottom to the rod-side pressurization Switchover of the feed cylinder driven by this drive cylinder 48 to loading operation, the drive piston 47 is pushed back out of its end position shown and thereby the control input 49 and the reference input 51 of the hydraulic end position transmitter 46 return to the same pressure level that is present in the rod-side drive pressure chamber 52 of the drive cylinder 48, the piston 47 of which moves towards its bottom end position when the pressure-relieved, bottom-side drive pressure chamber 53 is detected a further end position transmitter can be provided, which also generates a pressure output signal when this end position is reached, by means of which the delay control valve 41 can be controlled in an analog manner.

The pressure supply unit 10 explained in terms of its structure operates in typical operating situations of a consumer represented in FIG. 1 by a flow resistance 54 connected between the high pressure outlet 24 of the variable displacement pump 11 and the reservoir 23 of the pressure supply unit 10, for example as follows:

I. Starting operation

As a starting situation, in which the pressure supply unit 10 and the consumer connected to it are put into operation by switching on the variable pump 11, it is assumed that the pressure reducer 37 is set to a defined upper pressure limit value P _amax of, for example, 200 bar, the pressure accumulator 34 to a minimum pressure, for example completely discharged, and the setting throttle 36 is set to a flow resistance which, in combination with the design of the pressure accumulator 34 provided for it, results in a desired delay time τ with which that on the center tap 38 between the setting throttle 36 and the pressure accumulator 34 resulting pressure P _a (t), which is coupled via the control line 39 into the second control chamber 31 of the pressure regulating valve 21, which follows the output pressure P _A (t) developing at the high pressure outlet 34 after the variable pump is switched on. Furthermore, it is a prerequisite that the feed cylinder (s) of a thick matter pump assumed as a consumer are filled, so that the inertia and frictional forces caused by the material to be conveyed are effective when the pump starts up. The pressure control valve 21 is - in the case of pressure-relieved control chambers 27 and 31 - due to the pretensioning of the valve spring 32 - in its basic position 0, this valve spring 32 being designed or its pretensioning being set such that it is equivalent to a control pressure of, for example, 20 bar, ie a small fraction of corresponds to about 1/20 to 1/10 of the maximum outlet pressure P _{A of} the variable displacement pump 11. Via the flow path 56, which is released in the basic position 0 of the pressure control valve 21, the bottom-side drive chamber 18 of the actuator 13 is relieved of pressure, so that the variable displacement pump 11 is prepared for operation with maximum volume flow by the action of the return spring 17 of the actuator 13.

If, in this initial situation, the variable displacement pump 11 is switched on, for example time t₀, then since the pump 11 works with the maximum volume flow, the output pressure is initially not sufficient to start the pump drive cylinders 48, a very rapid increase in pressure which 3 is represented by the first, steeply rising branch 57 of the P _A (t) curve, designated overall by 58, which qualitatively represents the time profile of the pressure P _A (t) at the high pressure outlet 24 of the variable displacement pump 11. This pressure increase is accompanied by a "slower" pressure increase in the pressure P _a (t) which can be tapped at the center tap 38 of the time delay element formed by the adjusting throttle 36 and the pressure accumulator 34, the course of time in the diagram of FIG. 3 qualitatively by the P _a (t ) Curve 59 is reproduced.

As soon as at the time t₁ the difference between the output pressure P _A (t) emitted at the high-pressure outlet 24 of the variable pump, which in the first control chamber 27 of the Pressure control valve 21 is coupled in, and the pressure P _a (t), which rises more slowly compared to this, tapped off at the center tap 38 of the time delay element 36, 34, and which is coupled into the second control chamber 31 of the pressure control valve 21, reaches the value to which the preload of the valve spring 32 of the pressure control valve 21 is equivalent, this is pushed into its function point I, in which the outlet pressure P _a (t) of the variable pump 11 is coupled into the bottom-side drive chamber 18 of the actuator 13 via the flow path 26 and this thereby in the sense of an adjustment of the pump 11 to one reduced volume flow controlled.

By the effective from the time t₁ regulation is in their "steady" - steady - state, the rate of increase ΔP _A (t) / Δt, ie the slope of the P _A (t) curve 58 for the period following the time t₁ reduced to a value which corresponds at most to the rate of increase ΔP _a (t) / Δt of the P _a (t) curve 59 in its initial region 61 between the times t₀ and t₁ and is thus significantly lower than the pressure increase rate of the initial pressure P _A (t) of the variable displacement pump 11 immediately after starting the same, ie in the area represented by the first rising branch 57 of the P _A (t) curve between the times t₀ and t₁, the output pressure P _A (t) of the variable displacement pump 11 always by the pressure difference of 20, for example, corresponding to the preload of the valve spring 32 of the pressure control valve 21 bar is greater than the pressure that can be tapped at the tap 38 of the time delay element 36, 34, which corresponds to the pressure to which the pressure accumulator 34 is charged at the respective time.

By appropriately designing the pressure accumulator 34 and adjusting the flow resistance of the adjusting throttle 36, a desired "gentle" starting of the hydraulic consumer supplied by the pressure supply unit 10 can thus be achieved in a simple manner.

II. Periodic operation of the consumer

Due to the switching of the delay control valve 41 triggered by a pressure pulse output signal from the respective hydraulic end position transmitter 46 in the end positions of the piston 47 of the drive cylinder 48 and the discharge of the pressure accumulator 34 associated therewith, immediately before the direction of movement of the piston 47 of the drive cylinder 48 is reversed achieved essentially the same conditions as in the starting operation described above. In this case, while the pressure accumulator is being discharged, the control device 20, which gently starts the variable-displacement pump 11, is ineffective. This period of time can be used, for example, in a two-cylinder thick matter pump with switchover for switching the drive of a drive cylinder for the switch, since this switchover process takes place very quickly should and therefore a delay of such a switching process, also in the sense of a gentle start-up, is not necessary.

III. Blocking load

Occurs during a stationary operating state of the pressure supply unit 10, ie in an operating phase of the load 54, in which the output pressure of the variable pump 11 is constant, its output volume flow and the pressure to which the pressure accumulator 34 is charged corresponds to the output pressure of the variable pump 11 Sudden increase in load, for example by blocking the thick matter pump or one of its drive cylinders, also leads to this, because the pressure at the high pressure outlet 24 of the variable pump 11 rises faster than at the center tap 38 of the time delay element 36, 34, to a response of the pressure control valve 21 and one Reduction of the delivery volume of the variable displacement pump 11, the output pressure of which, in analogy to the starting situation, increases in a "slowly" controlled manner until the upper limit value thereof is reached, which is higher than the limit value P _amax by which the pressure reducer 37 is _equal to the preload of the valve spring 32 a is posed.

To explain further configurations of the pressure supply unit 10, which are useful in combination with the pressure control device 20 for a versatile use of the pressure supply unit 10, is now with reference to FIG. 4.

As far as components and functional elements of the pressure supply units 10 and 10 'shown in FIGS. 1 and 4' are given the same reference numerals, this is intended to indicate the structural and functional equality or analogy of these elements and with respect to the exemplary embodiment shown in FIG Reference to the description given with reference to FIG. 1 include such designated elements.

In the pressure supply unit 10 'according to FIG. 4, a volume flow control valve 61 is additionally provided in the context of the pressure control device 20', by means of which the output volume flow of the variable pump 11 is reduced to an essentially constant amount required for the operation of the consumer 54 is adjustable, which can be predetermined by setting a setpoint setting element 62.

The setpoint adjustment element 62 is designed as an adjustment throttle, which is connected between the high pressure outlet 24 of the variable displacement pump 11 and the consumer 54 connected to the pressure supply unit 10 '. The pressure difference occurring during operation of the consumer 54 between its operating pressure supply connection 63 and the high pressure outlet 24 of the variable displacement pump 11 is then an exact measure of the volume flow forced through the adjusting throttle 62, which is sensed by detecting this pressure difference.

The volume flow control valve 61 is constructed in a structural analogy to the pressure control valve 21 as a pressure-controlled 3/2-way proportional valve, which has a first control chamber 64 and a second control chamber 66 through their pressurization in opposite directions to control and restoring forces on the through the 3/2-way valve symbol 67 represented valve piston can be exercised, these control chambers 64 and 66 are in turn designed so that if the two control chambers were subjected to the same pressures, the resulting forces on the valve piston 67 would be balanced.

The first control chamber 64 of the volume flow control valve 61 is connected via a control line 68 to the high-pressure outlet 24 of the variable pump 11. The second control chamber 66 of the volume flow control valve 61 is connected to the supply connection 63 of the consumer 54 via a further control line 69.

A valve spring 71, the pretension of which can be set, and by pressurizing the second control chamber 66 of the volume flow control valve 61, urge it into its basic position 0, while pressurizing the first control chamber 64 with the high output pressure P _A (t) of the variable displacement pump 11 resulting actuating force urges the valve piston 67 of the volume flow control valve 61 into its functional position I.

The volume flow control valve 61 has a flow path 72 which is open in its basic position 0 and via which, when the pressure control valve 21 is in its basic position 0 at the same time, the bottom-side drive chamber 18 of the actuator cylinder 13 is connected to the unpressurized reservoir 23 of the pressure supply unit, and a flow path 73 released in its functional position I, via which, also when the pressure regulating valve 21 is in its basic position 0, the output pressure given at the high pressure outlet 24 of the variable displacement pump 11 can be coupled into the bottom-side drive chamber 18 of the actuating cylinder 13, through which the latter in the sense a reduction in the delivery volume of the variable displacement pump 11 is driven.

Whenever the pressure difference occurring over the setpoint input element 62 becomes greater than a value predetermined by the preload of the valve spring 71 of the volume flow control valve 61, the output volume flow of the variable displacement pump 11 is reduced and, if this pressure difference becomes smaller than that determined by the bias of the valve spring 71, which has a typical value of 20 bar, increased again.

In order to be able to temporarily switch off the very rapid pressure build-up at the high-pressure outlet 24 of the variable displacement pump 11 of the time delay element 36, 34, for example, not yet another 4, a function control valve 74 is provided in the exemplary embodiment according to FIG. 4, which is connected between the pressure reducer 37 and the time delay element 36, 34.

This function control valve 74 is designed as a 3/2-way valve which has a spring-centered basic position 0, in which the pressure outlet 76 of the pressure reducer 37 is connected via a flow path 77 of the function control valve 74 to the setting throttle 36 of the time delay element 36, 34, but against a second one Output port 78 of the function control valve 74 is shut off, which is connected via a bypass line 79 to the control line 39, via which the pressure is coupled into the second control chamber 31 of the pressure control valve 21. This function control valve 74 can be switched hydraulically and / or electrically into a function position I, in which the pressure outlet 76 of the pressure reducer 37 is shut off against the setting throttle 36 of the time delay element 36, 34, but is instead connected to the bypass line 79. A non-return valve 81 is connected between the center tap 38 of the time delay element 36, 34 and the bypass line 79 or the control line 39 leading to the second control chamber 31 of the pressure control valve 21, which check valve 81 has a relatively higher pressure in the bypass line 79 and the control line 39 than at the center tap 38 of the time delay element 36, 34 held in its blocking position and by relatively higher Pressure at the center tap 38 is acted upon in the control line 39 in the opening direction. This check valve 81 prevents pressure medium from the accumulator 34 from being able to be taken up in the functional position I of the function control valve 74, and causes the pressure medium to be passed "directly" to the second control chamber 31 of the pressure regulating valve 21 in order to hold it securely in its basic position 0 , in which the bottom-side drive chamber 18 of the actuating cylinder 13 is relieved of pressure and the adjusting pump 11 is thereby set to the maximum delivery volume.

4, a relief valve 82, shown as a 3/2-way solenoid valve, is provided, which has a spring-centered basic position 0, in which the second control chamber 31 of the pressure control valve 21 either via the check valve 81 or directly control pressure can be coupled in and, as an alternative to this, when actuating its control magnet 83 with a control signal assumed functional position I has a flow position in which the control chamber 31 of the pressure control valve 21 is connected to the - unpressurized - reservoir 23 of the pressure supply unit 10 'against which the check valve 81 or control line 39 connected directly to the center tap 38 of the time delay element 36, 34 is blocked.

In this excited position I of the relief valve 82, the outlet pressure of the variable pump 11 is practically on limited - the - low value to which the optionally adjustable preload of the valve spring 32 of the pressure control valve 21 is equivalent.

The relief valve 82 is particularly suitable for protecting the pressure supply unit 10 ′ against overload when the consumer is blocked.

Instead of the two 3/2-way valves 74 and 82, which are provided in the exemplary embodiment according to FIG. 4 as a function control valve and as a relief valve, a single 4/3-way can be used, as shown in the circuit variants according to FIGS. 4a and 4b Valve 84 (FIG. 4a) or 84 '(FIG. 4b) can be used in the context of the control device 20' as otherwise shown in FIG. 4.

The 4/3-way valve 84 according to Fig. 4a is designed as an exclusively electrically controllable solenoid valve, which by control signals of different control currents I₁ of, for example, 3A and I₂ of, for example, 6A from its spring-centered basic position 0, in which the increase-delay control of the output pressure of the Variable pump 11 is effective, can be switched into a functional position I in which this control is switched off, as well as in a functional position II in which the control line 39 leading to the second control chamber 31 of the pressure control valve 21 is connected to the reservoir 23 and as a result one Limitation of the output pressure of the variable pump 11 at a low, the bias of the valve spring 32 of the pressure control valve 21 equivalent level of 20 bar, for example.

While only a valve spring 86 is provided in the 4/3-way valve 84 according to FIG. 4a, against whose increasing restoring force the valve 84 must be controlled into its functional positions I and II, the basic position 0 of this valve being an "edge position" 4b, two oppositely acting valve springs 86 'and 86''are provided in the 4/3-way valve 84' according to FIG. 4b, which center the valve piston of this 4/3-way valve 84 'in a central position, which here is the basic position 0 is provided. Accordingly, two control magnets 87 and 88 are also provided, by means of whose alternative control the 4/3-way solenoid valve 84 'can be controlled into its functional position I or II, which functionally corresponds to the correspondingly designated functional positions I and II of the solenoid valve 84 according to FIG. 4a correspond. In contrast to this, the 4/3-way valve 84 'according to FIG. 4b can be switched "directly" from its basic position 0 to the functional position II without the functional position I having to be "passed over". As an alternative or in addition to the control magnet 87, by the excitation of which the 4/3-way valve 84 'according to FIG. 4b can be switched into its functional position I, a hydraulic control can also be provided for this purpose, as illustrated by a control chamber 89, by the latter for example, simultaneously with the hydraulic control of the deceleration control valve 41 Pressurization of the 4/3-way valve 84 'can be switched into its functional position I.

To the extent that components and functional elements shown in FIGS. 4a and 4b are given the same reference numerals as elements of this figure explained with reference to FIGS. 1 and 4, this is intended to refer to the construction with reference to FIGS. 4a and 4b - And functional equality or analogy of the identically labeled elements and also the reference to the explanation given with reference to FIGS. 1 and 4 mean.

With reference to FIG. 2b, a special design of a pressure control valve 21 that can be used in the context of the pressure control devices 20 or 20 ′ is discussed, in which the preload of the valve spring 32, by the preload of which the minimum value of the output pressure of the variable displacement pump 11 is determined , is adjustable.

The valve spring 32, which urges the valve piston 28, which is only indicated schematically by the 3/2-way valve symbol, into the basic position 0 of the pressure control valve 21, is, seen along the central longitudinal axis 91 of the pressure control valve 21, between a first support plate 92 , which engages axially on a tappet-shaped extension 93 of the valve piston 28 and axially clamps a second support plate 94, which has a control piston extension 96 on its side facing away from the valve spring 32, with which it engages in an axial bore 97 of a control housing part which can be screwed into the valve housing 98 99 is guided so that it can be moved in a pressure-tight manner.

Within this axial bore 97, a control piston element 101 is displaceably guided in a pressure-tight manner, which is axially supported on the control piston extension 96 of the second spring support plate 94 with a slim, plunger-shaped extension 102, the diameter of which is smaller than the diameter of the axial control housing bore 97. The second control chamber 31 is formed axially by the space 104 which extends between the control piston extension 96 of the second support plate 94 and the sealing flange 103 of the control piston element 101 in the axial direction. The preload of the valve spring 32 can be adjusted by means of an adjusting screw 106, which is screwably guided in a threaded section 107 of the control housing part 99 and in turn is supported on the control piston element 101 via an axial, plunger-shaped extension 108.

The axial guide lengths of the control piston extension 96, the control piston element 101 and the threaded portion 107 and the arrangement of the control chamber connection channel 109, to which the control line 39 is connected, are coordinated with one another in such a way that the control chamber connection channel is within the possible strokes of the displaceable elements always opens into the control chamber 31 and the greatest possible variation of the spring tension can be used.

To explain another exemplary embodiment, that corresponds structurally and functionally to the exemplary embodiment according to FIG. 4, reference is now made to FIG. 5.

To the extent that components and functional elements of the pressure supply unit 10 '' shown in FIG. 5 are given the same reference numerals as components and functional elements of the pressure supply unit 10 'according to FIG. 4, this is intended to indicate the structural and functional analogy of such elements and also the Reference to their description given with reference to FIG. 4. The explanation of the pressure supply unit 10 ″ and its pressure control device 20 ″ can therefore be limited to the explanation of the differences compared to the exemplary embodiment according to FIG. 4. These are the following:

The pressure coupled into the time delay element formed by the adjusting throttle 36 and the pressure accumulator 34 in combination with the time delay control valve 44 is applied to the operating pressure supply connection 63, which is the center tap between the consumer 54 and the one between them and the high pressure output 24 of the variable displacement pump 11 as the setpoint value. Tapped setting element 62 switched adjusting throttle, which is provided as a volume flow sensor for the flow control by means of the volume flow control valve 61, which is used in the exemplary embodiment according to FIG. 5 for pressure control, for example in the starting operation of the variable displacement pump 11. Accordingly, the center tap 38 between the adjusting throttle 36 and the pressure accumulator 34 pressure P _a (t) coupled via the control line 39 into the second control chamber 66 of the volume flow control valve 61, so that the restoring force resulting from pressurization of the first control chamber 64 of the volume flow control valve counteracts with the high output pressure P _A (t) of the variable displacement pump, which forces the valve piston 67 of the volumetric flow control valve 61 into its functional position I, the sum of the return force developed by the return spring 71 and the pressure exerted on the second control chamber 66 by the output pressure P _a (t), which lags behind the outlet pressure P _A (t), corresponds to the resulting restoring force.

In the case of the pressure regulating valve 21, only the valve spring 32, the prestress of which is adjustable, is provided as the restoring element which urges it into its basic position 0. In a typical design of the pressure control valve 21, the preload of its valve spring 32 can be set to values that are equivalent to pressures between 50 bar and 400 bar, while in a typical design of the volume flow control valve 61, the preload of its valve spring 71 can be set to values that pressures between 10 bar and 30 bar are equivalent. The function of the pressure supply unit 10 ″ according to FIG. 5 is that of the pressure supply units 10 and 10 ′ according to FIGS. 1 and 4 with regard to the starting operation, the periodic operation of the consumer as well as the behavior when the load is blocked.

In the pressure supply unit 10 ″, a component that is designed specifically for this function and that corresponds to the pressure reducer 37 of the pressure supply units 10 and 10 ′ according to FIGS. 1 and 4 is not required.

Claims (13)

1. Initial pressure governor for a variable displacement pump, in particular of a main pump operating at a high initial pressure level of a compression unit for a hydraulic driving unit, for example, the driving cylinder(s) of a thick matter pump with a pump capacity regulator (12), which is controlled by means of a hydraulic regulating motor, which is driven by alternative pressurization and depressurization of a driving pressure chamber (18) for carrying out the regulating movements for opposite changes of the displaced volume, whereby for the control of the respective pressurization and depressurization of the driving pressure chamber (18) a pressure regulated valve is designed, which, controlled by the initial pressure of the pump or a pressure proportional to it, from a minimum pressure determined by a minimum restoring force of a restoring element, for example, a spring, releases an initial pressure which increases with the control pressure coupled into its control chamber (27), with which the driving pressure chamber of the regulating motor can be regulated, characterized in that the restoring element (32, 71) is regulated by a restoring force which corresponds only to a small fraction of approximately 1/50 to 1/10 of the maximum control force of the pressure regulated valve (28, 61) on the valve piston (28, 67), in that the pressure regulated valve (21, 61) is provided with a restoring chamber (31, 66) as a second control chamber by the pressurization of which an additional restoring force opposite to the control force can be generated, the maximum value of which corresponds at least approximately to that of the control force, and in that the pressure coupled into the restoring chamber (31, 66) is derived by means of a hydraulic retarder (36, 34) by the pressure coupled into the control chamber (27,64) of the pressure regulated valve (21).
2. The pressure governor according to claim 1, characterized in that as a retarder a throttle (36) and a pressure reservoir (34) chargeable by it are designed, at the mid connection (38) of which the second control chamber (31; 66) of the pressure regulated valve (21, 61) is connected.
3. The pressure governor according to claim 2, characterized in that the throttle (36) is formed as a regulating throttle.
4. The pressure governor according to one of the claims 1 to 3, characterized in that a pressure reducer (37) is designed as a pressure limiter which limits the initial pressure of the high pressure pump (11) to an adjustable value.
5. The pressure governor according to one of the claims 1 to 4, characterized in that the retarder (36, 34) can be switched off.
6. The pressure governor according to claim 5 in combination with claim 2, characterized in that the pressure reservoir (34) can be blocked against the throttle (36).
7. The pressure governor according to claim 6, characterized in that a retarding control valve (41) designed for blocking the pressure reservoir (34) is formed as a 3/2-way valve, in the original position of which the pressure reservoir (34) is connected with the pressure reservoir (34) against the throttle (36), but connected to the store tank (23) of the compression unit (10; 10'; 10'').
8. The pressure governor according to one of the claims 5 to 7, characterized in that between the high pressure outlet (24) of the variable displacement pump (11) and the retarder (36, 34) a valve (74; 84; 84') is connected, which has an original position (0), in which the high pressure outlet (24) of the variable displacement pump (11) is connected to the retarder (36, 34) and a regulating position (I), in which the high pressure outlet of the variable displacement pump (11) is blocked against the retarder, but directly connected with the second control chamber (31; 66) of the pressure regulated valve (21, 61).
9. The pressure governor according to claim 8, characterized in that the high pressure outlet (24) of the variable displacement pump (11) is connected between the control line (39) to the switching position (I) of the functional control valve (74; 84; 84'), and a check valve (81) is connected to the pressure reservoir (34) of the retarder (36, 34), which is regulated in blocking direction by a relatively higher pressure in the control line (39) than in the pressure reservoir (34).
10. The pressure governor according to one of the claims 5 to 9, characterized in that between the second control chamber (31; 66) of the pressure regulated valve (21, 61) and the tapping position (38; 38; 81) of the retarder (36, 34) at which the pressure which can be coupled into the second control chamber (31) of the pressure regulating valve (21) can be tapped, a valve (82; 84; 84') is connected which can be switched from an original position (0) in which the tapping position (38, 38; 81) is connected with the control chamber (31; 66) in which the second control chamber (31; 66) is blocked against the tapping position (38), but connected with the depressurized store tank (23) of the compression unit (10; 10').
11. The pressure governor according to one of the claims 1 to 10, characterized in that the initial tension of the valve spring (32, 71) of the pressure regulated valve (21, 61) is controllable.
12. The pressure governor according to one of the claims 1 to 11, characterized in that the pressure regulated valve (21) is connected as a pressure regulating valve, by means of which the variable displacement pump (11) is controllable to a constant initial pressure (Fig. 1 and 4).
13. The pressure governor according to one of the claims 1 to 11, characterized in that the pressure regulated valve (61) is connected as a volume flow control valve, by means of which the variable displacement pump 11 is controllable to a constant initial volume flow.

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