EP0587043A2 - Method and arrangement for control and regulation of a pressure generator for several different hydraulic consumers connected in parallel - Google Patents

Abstract

The object of the invention, by means of an activating electronic unit for the variable displacement pump, is to effect automatically hydraulically regulated adaptation of the delivery flow of the variable displacement pump as a function of the volumetric flow of the different hydraulic consumers at constantly controlled pump pressure. The method according to the invention, after input of the various pressure values into the input unit (16) for the individual hydraulic consumers (12, 13, 15) connected in parallel, provides for the activating electronic unit (4.1) for the variable displacement pump (1) to determine the maximum operating pressure from the pressure values. The pressure level thus predetermined is signalled to the proportional pressure-relief valve (3) with a larger value predetermined in a defined manner. The hydraulic pressure requirement is then secured by the hydraulic pressure-regulating unit (2) via the variable displacement pump (1). <IMAGE>

Description

The invention relates to a method and a circuit arrangement for controlling and regulating a pressure generator z. B. a variable pump for several different hydraulic consumers connected in parallel in machine tools and processing machines that are supplied with pressure medium via the variable pump. As usual, the pressure of the main flow is limited by a system safety valve. The parameters for the respective consumers are specified by an input unit, which is linked to control electronics and corresponding valve technology. The variable displacement pump can be adjusted with regard to the volume flow and the pump pressure by means of a hydraulic pressure control unit. The setting point of the hydraulic pressure control unit can be changed by means of a proportional pressure relief valve which is controlled by control electronics.

From DEOS 3 943 357 a generic circuit arrangement with control electronics for the solenoid coils of actuators of a hydraulic circuit with several consumers is known. The control of the actuators for the consumers takes place in connection with the control of the variable pump for the flow. In terms of process engineering, this takes place in such a way that the electronic control only becomes effective when the pump delivery volume is no longer sufficient to meet demand due to an increased power requirement of the connected consumers. In order to adapt the pump delivery flow to the respective demand or to not exceed the maximum limit of the possible delivery flow, the delivery flow is controlled using the actuators or metered by the control pump. For this purpose, the actuators have corresponding signal devices (signal pickups and signal transmitters) which go into the electronic control as an input signal. This means that the respective parameters are only controlled via the control electronics after the power requirement of the connected hydraulic consumers has been exceeded or fallen short of by the set flow rate of the variable pump. This has the disadvantage that, with high machine dynamics and changing operating pressures, the consumers experience changes in speed due to connection or disconnection processes.

These indifferent changes in speed not only have a negative impact on the smooth operation of individual functional contents of the hydraulic consumers, they also impair the reproducibility of the machine cycle and the quality of the product to be processed or processed. This disadvantage is particularly noticeable when the machine dynamics are high and the pump is far from the consumer. For machine tools and processing machines, such as. B. in an injection molding machine for plastics processing, compliance with the procedural parameters of the machine cycle is imperative. For example, fluctuations in the speed of the plasticizing screw, which are caused by switching or readjustment processes, can have adverse effects on the feeding behavior of the plastic material, the plasticizing performance and the quality of the end product, which are unacceptable. Such a solution is therefore unsuitable for the control and regulation of the injection molding process in plastics processing.

Furthermore, a so-called "load sensing" method is known from the prior art, in which purely hydraulic control and regulation of the volume flow and the pump pressure takes place. However, such a method is only used to control and regulate slow movement processes, such as they z. B. occur in mobile systems, suitable. Such a control and regulation is too sluggish for fast and dynamic movement processes, as they occur in machine tools and processing machines, and is therefore not sensible.

The aim of the invention is to make the control and regulation outlay of hydraulic consumers connected in parallel economically more cost-effective and technically more reliable with less outlay on hydraulic control elements. The object of the invention is therefore to develop a method and a circuit arrangement for the control and regulation of several hydraulic consumers connected in parallel in machine tools and processing machines in order to use an electronic control unit for the variable pump to independently and hydraulically controlled adjustment of the flow rate of the variable pump depending of the volume flow of the different hydraulic consumers with a constantly controlled pump pressure.

According to the invention, the object is achieved in that, after the various pressure values have been entered into an input unit for the individual hydraulic consumers connected in parallel, the control electronics for the variable displacement pump determine the highest operating pressure of simultaneously operated consumers from the pressure values. This predetermined pressure level is signaled by the control electronics of the variable pump to a proportional pressure relief valve with a defined predetermined larger value, whereby the necessary hydraulic pressure requirement is covered by a hydraulic pressure control unit in connection with the variable pump and the flow rate requirement is secured.

The method according to the invention enables various design variants for the control and regulation of different hydraulic consumers connected in parallel. So for a selected procedural consumer who is comparatively a very high average Energy consumption has to be carried out by means of a pressure control by means of a pressure sensor, a constant adaptation of the current pressure value to the input value of the associated input unit. This pressure control always takes place when the input values of the other consumers operated in parallel are lower than the current pressure value.

According to the invention, it is also possible for the control electronics of the variable displacement pump to be given a differential pressure. The control signal derived from the differential pressure for the specified pump pressure is determined by the control electronics as the sum of the differential pressure plus the highest specified consumer pressure by the input unit.

Another embodiment variant of the invention consists in that the input unit receives the input values via a predetermined decision table and within a certain time interval the pump pressure via the control electronics of the variable pump, the proportional pressure relief valve and the pressure control unit are predetermined to a constant pressure setpoint. In a second time interval with fluctuating actual pressure values, the pump pressure is adapted to a pressure setpoint via the control electronics, the proportional pressure relief valve and the pressure control unit via a pressure sensor on the selected process engineering consumer.

Finally, according to the invention, in the case of a cyclically repeating procedural functional sequence in a machine tool or processing machine, the maximum operating pressure can be specified as the pump pressure for the variable pump in every first cycle. The actual pressure curve, which results from the respective machine functions, is determined via the pressure and time additions to be specified as an envelope by the control electronics of the variable pump. In the next working or processing cycle the pump pressure is controlled based on the similarity of the running processes according to this given envelope.

At the same time, a target / actual comparison is carried out for the previous cycle, by means of which the envelope curve is corrected.

To carry out the method according to the invention, a circuit arrangement is proposed which provides that the proportional pressure relief valve is connected to the input unit via the control electronics of the variable displacement pump and that a technically significant consumer is connected to the input unit via the pressure sensor.

The advantages of the method and the circuit arrangement for controlling and regulating a pressure generator z. B. a variable pump for different hydraulic consumers in machine tools and processing machines consist in the fact that the equipment required for the hydraulic circuit is significantly reduced by the saving of valve technology and control elements, which leads to greater cost savings. Furthermore, the energy efficiency of the hydraulic system is significantly improved by the pressure control according to the invention, since the hydraulic consumers connected in parallel can be operated at a lower pressure level by the new control and regulation, and no special power reserves are required for the connection of powerful consumers, as long as the flow rate requirement ≦ is the quantity provided.

Fig. 1

Hydraulische Schaltung für die Verbraucher einer Spritzgießmaschine zur Kunststoffverarbeitung

Fig. 2

Diagramm zum Druckverlauf über eine Zykluszeit mit Druckvorgabe aus einer Sollwertbestimmung für drei parallel geschaltete Verbraucher

Fig. 3

Diagramm zum Druckverlauf über eine Zykluszeit mit sechs parallel geschalteten Verbrauchern, wovon einer ein verfahrenstechnisch ausgewählter Verbraucher ist.

Fig. 4

Diagramm zum Druckverlauf über eine Zykluszeit für drei parallel geschaltete Verbraucher, die durch Differenzdruck geregelt werden.

Fig. 5

Diagramm zum Druckverlauf für drei parallel geschaltete Verbraucher, bei denen innerhalb der Zykluszeit die Druckwertvorgabe nach einer Entscheidungstabelle erfolgt.

Fig. 6

Diagramm zum Druckverlauf für vier parallel geschaltete Verbraucher über zwei Zeitzyklen und einer Druckwertvorgabe nach einem Soll-Ist-Vergleich

Das erfindungsgemäße Verfahren zur Steuerung und Regelung eines Druckstromerzeugers z. B. einer Verstellpumpe für mehrere parallel geschaltete unterschiedliche hydraulische Verbraucher soll zunächst am Beispiel für die verschiedenen Verbraucher einer Spritzgießmaschine zur Kunststoffverarbeitung betrachtet werden. Das erfindungsgemäße Verfahren ist jedoch problemlos auf andere Verarbeitungsmaschinen oder Werkzeugmaschinen übertragbar, wo parallel betriebene Verbraucher mit unterschiedlichem Leistungsbedarf mit Druckmittel versorgt werden müssen. In der in Figur 1 dargestellten hydraulischen Schaltung werden von einer druckgeregelten Verstellpumpe 1 aus die Verbraucher Schließeinheit 12, Spritzeinheit 13 und der Plastizierantrieb 15 über eine Förderleitung 1.1 und parallele Leitungszweige 1.2 mit Druckmittel bei einem konstanten Systemdruck versorgt.The invention will be explained in more detail below in general exemplary embodiments. In the accompanying drawings is shown

Fig. 1

Hydraulic circuit for the consumers of an injection molding machine for plastics processing

Fig. 2

Diagram of the pressure curve over a cycle time with pressure specification from a setpoint determination for three consumers connected in parallel

Fig. 3

Diagram of the pressure curve over a cycle time with six consumers connected in parallel, one of which is a consumer selected in terms of process technology.

Fig. 4

Diagram of the pressure curve over a cycle time for three consumers connected in parallel, which are regulated by differential pressure.

Fig. 5

Diagram of the pressure curve for three consumers connected in parallel, for which the pressure value is specified according to a decision table within the cycle time.

Fig. 6

Diagram of the pressure curve for four consumers connected in parallel over two time cycles and a pressure value specification based on a target-actual comparison

The inventive method for controlling and regulating a pressure generator z. B. a variable pump for several different hydraulic consumers connected in parallel should first be considered using the example of the various consumers of an injection molding machine for plastics processing. However, the method according to the invention can easily be transferred to other processing machines or machine tools, where consumers operated in parallel with different power requirements have to be supplied with pressure medium. In the hydraulic circuit shown in FIG. 1, the consumer clamping unit 12, injection unit 13 and the plasticizing drive 15 are supplied with pressure medium from a pressure-controlled variable displacement pump 1 via a delivery line 1.1 and parallel line branches 1.2 with a constant system pressure.

The pressure p in the delivery line 1.1 is limited by a system safety valve 14 connected in parallel. The consumer locking unit 12 and injection unit 13 are connected via upstream valve technology 9 and 10, which act as proportional control valves or servo or proportional control valves can be executed, controlled. The performance parameters for consumers 12 and 13 are specified via an input unit 16 which is linked to valve technology 9 and 10 and control electronics 4.2.

Depending on the power requirement of the individual hydraulic consumers connected in parallel, the variable displacement pump 1 can be adjusted by a hydraulic pressure control unit 2 in a parallel line branch 1.3. The setting point of the hydraulic pressure control unit 2 can be changed via a proportional pressure relief valve 3 connected in line branch 1.3. This variable setting point determines the point in time at which predetermined pressure value the variable pump 1 should swing in independently.

The proportional pressure relief valve 3 is linked to control electronics 4.1 for the variable displacement pump 1 and can be controlled by them. The input unit 16 receives the actual pressure value from a pressure sensor 5, which is connected to the parallel line branch 1.2 for the plasticizing drive 15. In this exemplary embodiment, the plasticizing drive 15 is regarded as a selected process engineering consumer and is controlled and regulated separately.

For this purpose, a proportional throttle valve 8 is located in the parallel line branch 1.2 in front of the plasticizing drive 15. The pressure transducer 5 is electrically linked to the selected consumer plasticizing drive 15 via the proportional throttle valve 8, control electronics 7 and a tachometer generator 6 in such a way that the speed of the plasticizing drive 15 is arbitrary preselectable value can be kept constant. For this purpose, the control electronics 7 receives the speed setpoint value via an electrical line connection from the input unit 16. The method according to the invention for the control and regulation of a pressure flow generator for different hydraulic consumers connected in parallel is intended to select the sum of all partial flows to the individual consumers in such a way that that with parallel machine functions the total flow of the Variable pump 1 is not reached and as a result the pressure level can be selected as high as desired. This is done according to the invention in that after the various pressure values for the individual consumers 12, 13 and 15 have been entered by the control electronics 4.1, the highest operating pressure is determined from the individual pressure values. The control electronics 4.1 for the variable displacement pump 1 then forward this detected pressure level to the proportional pressure relief valve 3, with a defined, larger value. As a result, the hydraulic pressure requirement for the variable displacement pump 1 can now be secured via the hydraulic pressure control unit 2. In practice, this means that the system pressure level once selected is always constant. At a constant pressure p, the variable displacement pump 1 automatically adapts to the pressure medium required in each case. The decision of how many consumers can be operated with which parameters is made in the software of the injection molding machine. If no simultaneous machine functions occur, the software decides on the adjustment of the hydraulic pressure actually occurring at the pressure transducer 5, which pressure level the proportional pressure relief valve 3 should assume in order to be able to operate the variable displacement pump 1 in the required part-load range. Is z. B. the machine function plasticizing in the cooling time (standing time of the other consumers) is not completed, a very specific process is necessary, the z. B. 2 seconds beforehand, the system pressure on the proportional pressure relief valve 3 is adjusted to the maximum value, so that the full performance, according to the preselected input values of the input unit, is guaranteed for the newly added consumers of the injection molding machine. The speed of the variable displacement pump 1 is not only kept constant via the control by means of the tachometer generator 6 and proportional throttle valve 8, but at the same time a pressure-superimposed flow control takes place via the Pressure transducer 5 in connection with the proportional throttle valve 8. The required pressure with the partial flow, which results as required, is provided by the variable pump 1 via lines 1.1 and 1.2.

In the following FIGS. 2 to 6, the pressure curve p on the y-axis and the cycle time t on the x-axis are shown in diagrams for a different number of consumers connected in parallel, which are denoted by a, b, c, d, e and f are shown for a machining or processing machine with different performance parameters. In the explanation of these figures, reference is made in each case to the circuit arrangement shown in FIG. 1 with the three consumers 12, 13 and 15 connected in parallel, which correspond mutatis mutandis to consumers a, b, c, d, e and f in FIGS. 2 to 6 Is valid. The diagram in FIG. 2 shows three consumers a, b and c which are operated with different pressure values. The pressure values required for these consumers are input into the input unit 16 (FIG. 1). The control electronics 4.1 for the variable displacement pump 1 then determine the highest operating pressure or setpoint pressure p _setpoint and predefine it on the proportional pressure relief valve 3 with a defined larger value below the maximum system pressure p _max . It can also be seen from FIG. 2 that the consumer b is still operated in parallel with the consumer a for a certain time at the start of switching on, then alone and finally in parallel with the consumer c, who ends the cycle alone as the consumer. With the help of the hydraulic pressure control unit 2, the required volume flow and pressure requirement is secured during this cycle time via the variable pump 1. This embodiment requires the least amount of software to implement the invention.

From FIG. 3, the pressure curve during a cycle can be seen in an analogous manner for six consumers a, b, c, d, e, and f. The consumer d is the consumer who takes up a large part of the cycle time. From the Different area representation of the individual consumers, which overlap in certain time ranges, shows which consumers are operated in parallel at which time of the cycle. On the time axis t, the power consumption of the consumer d is characterized by the time period t 1 to t 2. For the consumer d, who has a special procedural priority, according to the invention there is a separate regulation with the aid of the pressure transducer 5. The input unit 16 continuously adjusts the current pressure value.

The pressure control always takes place when the input values of the other consumers c and e operated in parallel are lower than the current pressure value. In the diagram, the regulated pressure value p _{reg can be seen} as a curve in the time period from t 1 to t 2, which runs below the set pressure p _set shown as a straight line. In comparison to the embodiment according to FIG. 2, this variant offers the advantage that an energy saving due to the adjusted regulating pressure p _{reg is achieved} over periods of the entire cycle. is possible.

A further variant of the method according to the invention can be seen in FIG. 4. The control and regulation of the variable pump 1 takes place for three different hydraulic consumers a, b and c connected in parallel, of which the consumers a and b are temporarily operated together.

According to the control electronics 4.1 for the variable pump a differential _pressure p _Diff . e.g. B. of 10 bar, which is determined according to the preselected pressure p _target by the input unit 16. A control signal for the specified pump pressure is derived from the differential pressure. This control signal is determined by the control electronics 4.1 as the sum of the differential pressure plus the highest consumer pressure by the input unit 16, thus ensuring the minimum pressure requirement. The embodiment variant in FIG. 4 enables p _Diff . an energetically more optimal adaptation than the input pressure value p _target shown in FIG.

FIG. 5 illustrates an analogous embodiment variant according to FIG. 4 with three consumers for process control and regulation, in which the target pressure value p _{target is} specified according to a decision table. For this purpose, the control electronics 4.1 make a decision based on the input values of the input unit 16 and / or the actual pressure values of at least one pressure sensor 5. The decision is made depending on the priority of the current function according to a predetermined decision table. This makes it possible for the pump pressure p to be predeterminable via the proportional pressure relief valve 3 and the pressure control unit 2. This adaptation enables improved economic operation compared to the variants described so far.

A control and regulation variant of the invention can be seen from FIG. 6, which has the greatest comfort from a technical point of view. Using the example of four different hydraulic consumers a, b, c and d connected in parallel, a cyclically repeating procedural functional sequence in a machine tool or processing machine is shown in two working cycles. The graphical representation shows the different power requirements of the individual consumers a, b, c and d and the temporary parallel operation of consumers a and b as well as c and d. In every first cycle, which is shown in FIG. 6 in the left image, the maximum operating pressure p _max is specified as the pump pressure. The actual pressure curve is then determined by the control electronics 4 via predetermined pressure and time additions as an envelope. In the next cycle, which is shown on the right in FIG. 6, the pump pressure is controlled on the basis of the similarity of the repetitive machining or processing processes based on the envelope curve determined. A target / actual comparison takes place for the previous cycle, by means of which the envelope curve is corrected. That is a constant self-optimizing process for each repeating cycle. The embodiments shown in FIGS. 5 and 6 are two options for an energy economically equivalent process. Based on the procedural embodiments of the invention it can be seen that it is possible without the use of additional valve technology, for. B. arranged in a valve block (pump block) to provide the drive power generated by the pressure-controlled hydraulic variable pump at a constantly changing pressure level, whereby a significant improvement in energy efficiency is achieved.

List of the reference symbols used

1

- variable displacement pump

1.1

- conveyor line

1.2

- line branch

1.3

- line branch

2nd

- pressure control unit

3rd

- Proportional pressure relief valve

4.1

- Control electronics for variable pumps

4.2

- Control electronics for the consumer

5

- pressure transducer

6

- tachometer generator

7

- Control electronics for proportional throttle valve

8th

- Proportional throttle valve

9

- valve technology

10th

- valve technology

11

-

12th

- Consumer clamping unit

13

- Consumer injection unit

14

- Plant safety valve

15

- Consumer plasticizing drive

16

- input unit

p

- Delivery pressure in bar

p _max

- maximum system pressure

p _diff

- differential pressure

p _target

- preselected pressure of the input unit

p _Ent.

- Preselected pressure according to the decision table

p _reg.

- regulated pressure

t

- timeline

a

- Consumer

b

- Consumer

c

- Consumer

d

- Consumer

e

- Consumer

f

- Consumer

Claims (6)

Method for controlling and regulating a pressure flow generator, for example a variable displacement pump for several different hydraulic consumers connected in parallel in machine tools and processing machines, which are supplied with pressure medium by the variable displacement pump, the pressure of the main flow being limited by a system safety valve and the parameters for the consumer by a Input unit that is linked to control electronics and corresponding valve technology can be specified, the variable pump can be adjusted with regard to the volume flow and the pump pressure by means of a hydraulic pressure control unit, a proportional pressure relief valve changes the setting point of the hydraulic pressure control unit, the proportional pressure relief valve is controlled by control electronics and the control electronics current value, both via the target values of the input unit and via the current value of a pressure sensor e which is arranged between a proportional throttle valve and a process-technically selected consumer, which via the proportional throttle valve has associated control electronics and a tachogenerator keeps the speed of the selected consumer constant to an arbitrarily preselectable value, characterized in that after the various pressure values have been entered in the input unit ( 16) for the individual hydraulic consumers (12, 13, 15) connected in parallel, the control electronics (4.1) for the variable displacement pump (1) determine the highest operating pressure from the pressure values and the control electronics (4.1) transmit this predetermined pressure level to the proportional pressure relief valve (3) signaled with a defined predetermined larger value, so that the hydraulic pressure control unit (2) ensures the hydraulic pressure requirement via the variable displacement pump (1). Method according to Claim 1, in which a regulation by means of a pressure sensor (5) takes place for a selected procedural consumer (15) with an average high energy requirement, characterized in that the current pressure value is continuously adapted to the input value of the input unit (16) and this pressure control always happens when the input values of the other consumers operated in parallel are lower than the current pressure value. Method according to claim 1, characterized in that the control electronics (4.1) for the variable displacement pump (1) are given a differential pressure and the control signal derived therefrom for the pump pressure to be controlled by the control electronics (4.1) as the sum of differential pressure plus the highest predetermined consumer pressure, is determined by the input unit (16). Method according to Claims 1 to 3, characterized in that the input unit (16) receives the input values via a predetermined decision table and within a certain time interval the pump pressure (p) via the control electronics (4.1) for the variable displacement pump (1) the proportional pressure relief valve (3) and the pressure control unit (2) is set to a constant pressure setpoint (p _setpoint ) and in a second time interval with fluctuating actual pressure values via a pressure sensor (5) at the selected process engineering consumer (15) the pump pressure via the control electronics (4.1), the proportional pressure relief valve (3 ) and the pressure control unit (2) is adapted to a pressure setpoint. Method according to one of claims 1, 2 or 4 with a cyclically repeating procedural functional sequence in the machine tool or processing machine, thereby characterized in that for every first cycle the maximum operating pressure is specified as the pump pressure for the variable displacement pump (1) and the actual pressure curve is determined by the control electronics (4.1) via the pressure and time additions to be specified and in the next cycle due to the similarity of the processes this envelope curve the pump pressure is controlled and a set / actual comparison takes place for the previous cycle, by means of which the envelope curve is corrected. Circuit arrangement for carrying out the method according to claim 1, characterized in that the proportional pressure relief valve (3) is connected to the input unit (16) via the control electronics (4.1) and a consumer (15) which is important in terms of process technology is connected to the input unit (5) 16) is connected.

Images