EP0587043B1 - 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 device to control and regulate a pressure generator z. B. a variable displacement pump for several in parallel and in temporal overlay, different hydraulic Consumers in machine tools and processing machines with cyclically recurring workflows by the Pressure generator are supplied with pressure medium, whereby the pressure values for the respective consumers and the corresponding pressure setpoints for the pressure generator be specified by an input and arithmetic unit.

DE OS 3 943 357 is a generic one Circuit arrangement with control electronics for the magnetic coils of actuators of a hydraulic circuit known to several consumers. The control of the actuators for consumers is done in conjunction with the Regulation of the variable pump for the flow. Process engineering it happens so that the electronic control only becomes effective when there is an increased power requirement the pump delivery quantity of the connected consumers is no longer sufficient to meet requirements. To the pump flow adapt to the respective need or by the maximum Limit of the possible flow rate not too the flow rate is exceeded with the help of the actuators or metered by the control pump. For that they have Actuators corresponding signal devices (signal pickups and signal generator), which is used as an input signal in the electronic Control go. That means that only after the power requirement of the connected hydraulic consumers by the set flow rate of the pressure generator was exceeded or fallen below, a regulation of respective parameters via the control electronics. This has the disadvantage that with high machine dynamics and changing operating pressures the consumer speed changes experienced, due to switching on or off. This indifferent Changes in speed do not only have negative effects on the even flow of individual functional content of hydraulic consumers, but impair hence the reproducibility of the machine cycle and the quality of what is to be processed or processed Product. This disadvantage is particularly noticeable at high Machine dynamics and long distance of the pressure generator noticeable to the consumer. For machine tools and processing machines, such as B. in an injection molding machine Plastic processing, is compliance with the process engineering given parameters of the machine cycle, however absolutely necessary. So z. B. Speed fluctuations of the plasticizing screw caused by Switching or readjustment processes are caused, adverse effects on the feeding behavior of the plastic material have that are unacceptable. Such Solution is therefore for the control and regulation of the Injection molding process unsuitable for plastics processing.

Furthermore, a so-called "load." sensing "method known in which a purely hydraulic Control and regulation of the volume flow and the pump pressure he follows. However, such a method is only for Control and regulation of slow movements, such as they z. B. occur in mobile systems, suitable. For fast and dynamic movements, in tool and Processing machines with cyclically recurring work processes, such control and regulation is too sluggish and therefore not useful.

The aim of the invention is to control and regulating effort of hydraulic systems connected in parallel and superimposed over time Economically cheaper and in technically with less hydraulic effort To make controls more reliable. The object of the invention is to provide a method and a control and control device for the pressure generator and for the to design parallel connected hydraulic consumers or train that in the operation of the consumer with minimal energy consumption no discontinuities and no indifferent States occur.

According to the task by the characteristics of the characteristic parts of the independent claims 1 and 5 solved, namely that the input and Computing unit after entering the pressure values and the and switch-off times of the individual consumers an envelope calculated for the entire work cycle, which the from Pressure generator to deliver pressure curve over time pretends. This makes the pressure generator to everyone Ensured timing of the need for pressure resulting from the Number and the respective performance requirements of the Operating consumers results.

The method according to the invention enables various designs for control and regulation of parallel connected different hydraulic consumers. So can for a selected process engineering consumer, which is a comparatively high average energy requirement has a regulation of the pressure flow on the basis of pressure values determined by a pressure sensor, while the printing needs for other consumers after the Envelope is regulated. Here, the activation of a Proportional throttle valves a constant adjustment of the current pressure value of the selected consumer at the input value the associated input and arithmetic unit. This pressure control always takes place when the specified pressure values of the other operated in parallel Consumers are lower than the current pressure value for is the selected consumer.

This pressure control can be used with the other consumers but also when these consumers stand still be performed.

According to the invention, even with a cyclically repeating procedural function sequence in the Tool and processing machine on every first cycle the maximum operating pressure as pump pressure for the pressure generator be specified. In this case the actual pressure curve resulting from the respective Machine functions results in predetermined pressure and Time additions as an envelope by the input and arithmetic unit is determined and in the next following cycles is due the similarity of the processes running according to this Envelope controlled by pump pressure.

In the device for performing the invention Method according to the features in the preamble of claim 5 is the input and arithmetic unit on the one hand with a first Control electronics connected to the pressure of the pressure generator controls and on the other hand with at least one second control electronics connected to the consumer controls. The input and arithmetic unit is after input the pressure values and the on and off times of the individual consumers an envelope for the entire work cycle calculates that from the pressure generator specifies delivering pressure curve over time. By the The pressure generator will be exactly the same at all times Ensured pressure requirement, which is made up of the number and the respective performance requirements of those in operation Consumer results.

According to a further embodiment of the invention, that the pressure generator is a variable displacement pump, whose pressure control device has a proportional pressure control valve is assigned, which is adjusted by the first control electronics becomes.

Another feature of the invention is that one selected consumers with high energy requirements a pressure transducer assigned, on the one hand with the input and computing unit and on the other hand via a proportional throttle valve, a third control electronics and a tachometer generator is connected to the selected consumer and its current pressure values constantly to the input values the input and arithmetic unit are adapted. This is for this consumer a pressure control deviating from the envelope possible if the pressure values of the others are parallel operated consumers are less than that of the pressure sensor measured pressure value.

The advantages of the method and the circuit arrangement according to the invention to control and regulate a pressure generator e.g. B. a variable pump for different hydraulic consumers in machine tools and processing machines are that the equipment needs for the hydraulic circuit by saving valve technology and control elements is significantly reduced, resulting in leads to greater cost savings. Furthermore, the energetic Efficiency of the hydraulic system by the invention Pressure control significantly improved since the hydraulic consumers connected in parallel by the new control and regulation at a lower pressure level can be operated and for the connection of high-performance consumers no special performance reserves are required as long as the flow request the quantity already provided.

Fig. 1

Hydraulische Schaltung für die Verbraucher einer Spritzgießmaschine zur Kunststoffverarbeitung

Fig. 3

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

Fig. 5

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

Fig. 6

Diagramn zum Druckverlauf für vier parallel geschaltete Verbraucher über zwei Zeit zyklen und einer Druckwertvorgabe nach einem Soll-Ist-Vergleich

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. 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. 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

Diagrams 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 control and regulation method according to the invention a pressure generator z. B. a variable pump for several different hydraulic consumers connected in parallel should first use the example for the different Consumer of an injection molding machine for plastics processing to be viewed as. The method according to the invention is however without problems on other processing machines or Machine tools transferable, where parallel operated consumers with different power requirements with pressure medium need to be supplied. In the illustrated in Figure 1 hydraulic circuit are controlled by a pressure Variable pump 1 from the consumer clamping unit 12, Injection unit 13 and the plasticizing drive 15 via a delivery line 1.1 and parallel line branches 1.2 with pressure medium provided.

The pressure p in the delivery line 1.1 is a parallel switched system safety valve 14 limited. The consumers Closing unit 12 and injection unit 13 are over accordingly upstream valve technology 9 and 10, which as Proportional control valves or servo or proportional control valves can be executed, controlled. The performance parameters for consumers 12 and 13 are about an input and computing unit 16, which with the valve technology 9 and 10 and a second control electronics 4.2 linked is specified. According to the power requirements of individual hydraulic consumers connected in parallel is the variable pump 1, by a hydraulic pressure control unit 2 in a parallel line branch 1.3, adjustable. Via a downstream in line branch 1.3 Proportional pressure relief valve 3 is the set point the hydraulic pressure control unit 2 changeable. This variable set point determines the time at which the variable pressure pump 1 automatically should swivel in. The proportional pressure relief valve 3 is with a first control electronics 4.1 for the variable displacement pump 1 linked and controlled by this. The input- and computing unit 16 receives from a pressure sensor 5, the one with the parallel line branch 1.2 for the plasticizing drive 15 is connected to the actual pressure value. In this embodiment the plasticizing drive 15 is selected procedural consumer considered and separately controlled and regulated. This is in parallel Line branch 1.2 in front of the plasticizing drive 15 Proportional throttle valve 8. The pressure transducer 5 is over the proportional throttle valve 8, a third control electronics 7 and a tachometer generator 6 with the selected one Consumer plasticizing drive 15 electrically linked so that the speed of the plasticizing drive 15 on any preselectable value can be kept constant. The third control electronics 7 receives the speed setpoint via an electrical line connection from the input and computing unit 16. With the inventive Method for controlling and regulating a pressure generator for different hydraulic systems connected in parallel Consumers intend to add the sum of all partial flows to choose the individual consumers so that at parallel expiring machine functions the total flow of the Variable pump 1 is not reached and therefore the pressure level can be preselected as high as required.

Deciding how many consumers with which parameters may be operated, is in the software of the Injection molding machine solved. Do not succeed at the same time Machine functions, the software decides on the Adjustment of what actually occurs when plasticizing Hydraulic pressure on the pressure sensor 5, which pressure level the proportional pressure relief valve 3 should take to thus the variable pump 1 in the required partial load range to be able to operate. Is z. B. the machine function plasticizing in the cooling time (service life of other consumers) not complete, so is a very specific process necessary, the z. B. 2 seconds before, the system pressure at the proportional pressure relief valve 3 adjusted to the maximum value so that the full performance, according to the preselected input values of Input and arithmetic unit for the new ones Consumers of the injection molding machine is guaranteed. The pressure setpoint of the variable pump 1 is not only about regulation by means of tachogenerator 6 and proportional throttle valve 8 kept constant, but takes place simultaneously a pressure-superimposed flow control via the pressure sensor 5 in connection with the proportional throttle valve 8. The required pressure with the partial flow, depending results as required, is by the variable pump 1 on the Lines 1.1 and 1.2 provided. In the following figures 2 to 6 is the pressure curve p on the y-axis in diagrams and the cycle time t on the x-axis for a different one Number of parallel switched consumers labeled a, b, c, d, e and f are for a working or processing machine different performance parameters. In the Explanation of these figures is in each case reference to that in figure 1 circuit arrangement shown with the three in parallel switched consumers 12, 13 and 15 taken, which is analogous for consumers a, b, c, d, e and f in the figures 2 to 6 is valid.

3 shows in an analogous manner for six consumers a, b, c, d, e and f the pressure curve during a cycle evident. The consumer d is the consumer, the one Much of the cycle time is claimed for itself. From the different Area representation of the individual consumers, which overlap in certain time periods can be seen which consumers at what time of the cycle in parallel operate. The power consumption is on the time axis t of the consumer d through the time period t 1 to marked t 2. For the consumer d, the one has special procedural priority According to the invention, a separate regulation using the Pressure transducer 5. Wid through the input and arithmetic unit 16 a constant adjustment of the current pressure value performed. The pressure control always takes place when the Input values of the other consumers operated in parallel c and e are lower than the current pressure value. in the The diagram is the regulated pressure value p reg as a curve in the Period of t 1 and t 2 recognizable that below the The target pressure p target shown as a straight line runs. This Variant has the advantage that over periods of the Overall cycle an energy saving through the adjusted Control pressure p reg is possible.

5 shows an embodiment variant with three consumers for process control and regulation illustrates, in which the specification of the The target pressure value p should be based on a decision table. For this purpose, the first control electronics 4.1 the input values of the input and computing unit 16 and / or the actual pressure values of at least one pressure sensor 5 made a decision. The decision becomes dependent the priority of the current function after a given decision table. That’s it possible that the pump pressure p via the proportional pressure relief valve 3 and the pressure control unit 2 can be predetermined. This adjustment enables an improved economic operation compared to the variants described so far. From Figuar 6 is a control and regulation variant of the Invention removable, the highest from a technical point of view Has comfort. Using the example of four connected in parallel different hydraulic consumers a b, c and d is a cyclically repeating process engineering Functional sequence in a machine tool or processing machine represented in two working cycles. From the graphic Presentation is 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 evident. In every first cycle, the one on the left in FIG Is shown, the maximum operating pressure p max specified as pump pressure. The actual pressure history will then be given as pressure and time allowances Envelope determined by the input and computing unit 16. In the next cycle, shown on the right in Figure 6 is due to the similarity of the repetitive Machining or processing processes according to the determined envelope the pump pressure is controlled. This takes place to the previous one Cycle a target / actual comparison instead of one Correction of the envelope is made. That is a constant self-optimizing process for everyone repetitive Cycle. The embodiments shown in Figures 5 and 6 are two options for an energy economy equivalent procedure. Based on the procedural variants of the Invention is recognizable that it is possible without using it of additional valve technology, e.g. B. arranged in a valve block (pump block) that is regulated by the pressure hydraulic variable pump generated drive power to meet a constantly changing pressure level, causing a significant improvement in energetic Efficiency is achieved.

List of the reference symbols used

1 -

Variable pump

1.1 -

Conveyor line

1.2 -

Line branch

1.3 -

Line branch

2 -

Pressure control unit

3 -

Proportional pressure relief valve

4.1 -

first control electronics for variable pump

4.2 -

second control electronics for the consumer

5 -

Pressure transducer

6 -

Tachometer generator

7 -

third control electronics for proportional throttle valve

8th -

Proportional throttle valve

9 -

Valve technology

10 -

Valve technology

11 - 12 -

Consumer clamping unit

13 -

Consumer injection unit

14 -

Plant safety valve

15 -

Consumer plasticizing drive

16 -

Input and arithmetic unit

p -

Delivery pressure in bar

p max -

maximum system pressure

p diff

Differential pressure

p should

preselected pressure of the input unit

p Ent.-

preselected pressure according to decision table

p reg.

regulated pressure

t -

Timeline

a -

consumer

b -

consumer

c -

consumer

d -

consumer

e -

consumer

f -

consumer

Claims (7)

1. Method for controlling and regulating a pressure flow generator (1), for example an adjusting pump, for several hydraulic users (12, 12, 15) in tool and processing machines with cyclic repetitive working processes, said hydraulic users being connected in parallel and operating in a timed overlapping manner and being provided with pressure medium from the pressure generator (1) with the pressure values for the users (12, 13, 15), and the corresponding desired pressure values for the pressure flow generator (1) being set by an input and computing unit (16), characterized in that the input and computing unit (16) calculates an envelope for the entire working cycle upon the input of the pressure values and the on and off switching times of the individual users (12, 13, 15), said envelope defining the time responsive pressure characteristic (P_soll) which is to be generated by the pressure flow generator (1) so that the pressure flow generator (1) maintains at each moment the precise pressure requirement which results from the number and the respective power requests of the users (12, 13, 15) which are operating (Figure 5).
2. Method according to claim 1 wherein the pressure flow is controlled from the pressure values derived from a pressure sensor (5) for a selected process-type user (15) with average high power request whereas the pressure requirement for the other users (12, 13) is controlled by said envelope, characterized in that a continuous adaptation is made of the actual pressure value of the selected user (15) to the input value of the input and computing unit (16) via controlling a proportional throttle valve (18) and that this pressure control is always happening when the predetermined pressure values of the other parallel operating users (12, 13) are lower than the actual pressure value of the selected user (15) (Figure 3).
3. Method according to claim 2,
   characterized in that the control of the selected user (15) is made outside of the envelope.
4. Method according to claim 1 or 3 with a cyclically repeating process-type operation in the tool or processing machine
   characterized in that for each first cycle the maximum operating pressure is set as pump pressure for the pressure flow generator (1) and that the actual pressure curve over predetermined pressure and time requests is derived as envelope by the input and computing unit and that the pump pressure is controlled for the subsequent cycles by this envelope because of the similarity of the processes.
5. Apparatus for controlling and regulating a pressure flow generator (1), for example an adjusting pump, for several hydraulic users (12, 12, 15) in tool and processing machines with cyclic repetitive working processes, said hydraulic users being connected in parallel and operating in a timed overlapping manner and being provided with pressure medium from the pressure generator (1), with an input and computing unit (16) which sets the pressure values for the users (12, 13, 15) and the corresponding desired pressure values for the pressure flow generator (1),
   characterized in that the input and computing unit (16) is connected on the one hand to a first control circuit (4.1) which controls the pressure of the pressure flow generator (1) and on the other hand with at least a second control circuit (4.2, 7) which controls the users (12, 13, 15) with the input and computing unit (16) calculating an envelope for the entire operating cycle upon the input of the pressure values and the on and off switching points of the individual users, said envelope defining the pressure curve over the time which is to be generated by the pressure flow generator (1) so that the pressure flow generator (1) at each time supplies the precise pressure requirement which results from the number of users (12, 13, 15) which are operating and upon their respective power requests.
6. Apparatus according to claim 5,
   characterized in that the pressure flow generator is an adjusting pump (1) with a proportional pressure regulating valve (13) being associated to its pressure control means (2), said valve being adjusted by the first control circuit (4.1).
7. Apparatus according to claim 5 or 6,
   characterized in that a pressure receiver (5) is associated to each selected user (15) having a high power requirement, said receiver being connected on the one hand to the input and computing unit (16) and on the other hand to the third control circuit (7) and to a speed generator (6) via a proportional throttle valve (8) and with the actual pressure values of the user being constantly adapted to the input values of the input and computing unit (16) so that for this user (15) pressure control is possible which deviates from the envelope if the pressure values of the other parallel operating users (12, 13) is lower than the pressure value measured by the pressure sensor (5).

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