Preferably, a closed-loop control valve controls the pressure of each of the plurality of work units. As a result, advantageously an exact and precise pre-control of the setpoint value can be achieved for all the work units even with the work units moving simultaneously, and this contributes to the quality of the injection molded parts to be produced.

For advantageously fast adjustability and precise provision of the flow rates, preferably pre-control of the setpoint value is carried out with time control and/or in real time. For example, pre-control of the setpoint value may be carried out with time control with the work units on the basis of the setpoint values of the volumetric flow of the work units, and/or in real time on the basis of the actual values of the volumetric flow of the closed-loop control valves. In this context, the term “time-coordinated” means that the setpoint value of volumetric flow is made available to the work units at a particular point in time by the setpoint pre-control. For example, setpoint pre-control may advantageously provide an appropriate setpoint pre-control in real time on the basis of the actual values of volumetric flow even if the closed-loop control valves are undergoing closed-loop pressure control and so their volumetric flow is not (only) dependent on the setpoint value of volumetric flow.

In order advantageously to identify leaks at the work units, preferably at least one cyclic integration of the standardized volumetric flow that is controlled by the closed-loop control valves is carried out over at least one work unit cycle. It can then be seen from the integral, for example by comparison with a previous work unit cycle, whether there is a leak.

For advantageous identification of wear to the valve mechanism, for example on control edges or in the event of a leak through a piston, the actual values of volumetric flow of the closed-loop control valves are preferably continuously monitored, evaluated and correlated with the actual values of volumetric flow for at least one cyclic machine operation. For example, by comparison with earlier work unit cycles conclusions can thus be drawn about wear.

For operation that is advantageously energy-optimized, and for an improvement in application to the demands for simultaneity or for greater demands of dynamics and reproducibility, the at least one closed-loop control valve is preferably operated as a switching valve during serial movements of the at least one work unit, and/or the closed-loop control valve is operated as a load-sensing closed-loop control valve during simultaneous movements of the work units. Advantageously, the work units may thus be operated directly by the controller and the central unit during the injection molding cycle. For example, as a switching valve the closed-loop control valves are switched to maximum throughflow or to closed by the controller. Because there are no hydromechanical pressure gages, advantageously approximately the same energy efficiency is thus achieved in serial operation as for purely serial pump systems with a sequence valve for the work unit.

For an advantageous optimum of dynamics and energy consumption per cycle, the derivation of the setpoint pre-control is preferably adapted with self optimization by a cyclically learning observer. For example, the superimposition of pressure in the system circuit may be adapted to optimum dynamics and energy consumption/cycle with self-optimization by the cyclically learning observer, while observing the quality of closed-loop control in the work unit circuits, in particular the overshoots and undershoots of pressure occurring in the work unit circuit.

Preferably, in relation to repeated cyclic movements in uninterrupted operation, the controller may form one or more observers, such as digital observers, in real time in order to carry out condition monitoring of the central drive, the peripheral equipment and the work units, in real time or cyclically. Advantageously, this results in very precise leak identification.

Further advantages are apparent from the subclaims and the description below of a preferred exemplary embodiment. The features that are mentioned individually in the claims are combinable where this is technologically meaningful, and may be supplemented by explanatory factual material from the description and details from the Figures, with further variant embodiments of the disclosure being indicated.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure is explained in more detail below with reference to an exemplary embodiment that is illustrated in the attached Figures, in which:

FIG. 1 shows a hydraulic device having two work units,

FIG. 2 shows the hydraulic device from FIG. 1 with two closed-loop control valves,

FIG. 3 shows the hydraulic device from FIG. 1 with one closed-loop control valve,

FIG. 4a shows a graph of volumetric flow over time, of two work units without pre-control, according to the prior art,

FIG. 4b shows the graph from FIG. 4a, with pre-control, and

FIG. 5 shows a schematic method chart.

DETAILED DESCRIPTION

The disclosure is now explained in more detail by way of example, with reference to the attached drawings. However, the exemplary embodiments are examples, which are not intended to restrict the inventive concept to a particular arrangement. Before the disclosure is described in detail it should be pointed out that it is not restricted to the respective structural parts of the device and the respective method steps, since these structural parts and methods may vary. The terms used here are merely intended to describe particular embodiments and are not used restrictively. Moreover, where the singular or the indefinite article is used in the description or the claims, this also refers to a plurality of these elements unless the overall context unambiguously indicates otherwise.

FIG. 1 shows a hydraulic unit for supplying a plurality of work units, in the exemplary embodiment two work units 3a, 3b, for example an ejector, a nozzle, a core puller or a shut-off nozzle, in particular on a plastics injection molding machine having at least one controller 7, at least one closed-loop valve control and/or open-loop valve control and a central drive 1. The controller 7 may comprise the closed-loop valve control and/or open-loop valve control, and vice versa. A plastics injection molding machine of this kind serves to process plastics and other plasticizable materials, including for example ceramic, metal and/or powder compositions.

As shown in FIG. 1, the central drive 1 may comprise a pump 4 such as a constant pump, a motor 5 such as a servo motor, and a motor controller 6. In principle, however, further work units 3a, 3b may also be provided. In FIG. 1, for each work unit 3a, 3b there is provided a respective switching valve 12a, 12b and a respective closed-loop control valve 2a, 2b. The closed-loop control valves 2a, 2b in the exemplary embodiment of FIG. 1 take the form for example of electronic and/or digital closed-loop flow control valves, p/Q valves with an electric pressure gage function, proportional valves or continuously-adjustable valves which control the volumetric flow to the work units 3a, 3b by closed-loop control.

For each closed-loop control valve 2a, 2b, pressure sensors 8 detect at least one pressure upstream and downstream of the corresponding closed-loop control valve 2a, 2b, the load pressures 10a, 10b of the work units 3a, 3b, and the system pressure 9. The pressures may preferably be transmitted to the controller 7 and/or the closed-loop valve control and/or open-loop valve control, preferably by way of a connection 21 such as a bus. In principle, however, other connections 21 are also conceivable, such as a wireless network. The closed-loop control valves 2a, 2b are preferably in contact with the controller 7 and the central drive 1 and/or the closed-loop valve control and/or open-loop valve control by way of the connection 21.

The closed-loop valve control and/or open-loop valve control has knowledge of the control valve geometry of the closed-loop control valves 2a, 2b. The knowledge may take the form for example of a control characteristic, a volumetric flow signal characteristic or the function “cross section of opening=f(stroke)”, or indeed the geometry of the valve slider. In principle, it is conceivable for the knowledge already to be present in the closed-loop valve control and/or open-loop valve control, or to be manually input or automatically made available, for example by way of a network connection. The closed-loop valve control and/or open-loop valve control is configured to derive at least one actual value of volumetric flow for each closed-loop control valve 2a, 2b from a relationship between the control valve geometry and at least one pressure difference that results from the pressures detected upstream and downstream of the at least one closed-loop control valve 2a, 2b.

Typically, as a rule a plurality of closed-loop control valves is provided, even though in FIG. 3 only one p/Q valve is provided as the closed-loop control valve 2a, and one switching valve 12a plus one switching valve 12b in the central drive line for purely serial movement.

Even in this case, in which not all—or in FIG. 3 only one—of the work units is equipped with a closed-loop control valve, the device and the method may advantageously be implemented. One of the work units may for example be supplied by way of a switching valve. For example, this could be the work unit of a shut-off nozzle, of which the switching procedure nonetheless has a systemic effect on the other work units. If this is in pressure-maintenance mode, for example, the pre-control needs a minimum of pressure for this simultaneous actuation.

The closed-loop valve control and/or open-loop valve control knows the exact relationship between pressure and the setting of the closed-loop control valve 2a, 2b, with the result that the closed-loop valve control and/or open-loop valve control knows which pressure results in which setting of the closed-loop control valve and vice versa.

In the exemplary embodiment in FIG. 1, the closed-loop control valves 2a, 2b comprise the closed-loop valve control and/or open-loop valve control and knowledge of the control valve geometry of the closed-loop control valves 2a, 2b, including the geometry of the valve slider, and take the form of electronic and/or digital proportional valves. The closed-loop control valves 2a, 2b derive an actual value of volumetric flow, preferably a standardized actual value of volumetric flow, from the relationship between the control valve geometry and the pressure difference, and transmit this actual value of volumetric flow to the controller 7.

The controller 7 is configured to derive, from the setpoint value of volumetric flow of the work units 3a, 3b and/or the actual values of volumetric flow of the closed-loop control valves 2a, 2b, at least one setpoint pre-control for the central drive 1, such that the system pressure 9 corresponds at least to the maximum load pressure of the work units 3a, 3b. It is thus possible for the system pressure to be equal to or even greater by a certain value than the load pressure.

In this way, the at least one closed-loop control valve 2a, 2b can correct for a physically standardized flow rate, for example in liters/min, at the work unit 3a, 3b, in accordance with the predetermined setpoint value and regardless of the system pressure 9 and load pressure 10a, 10b, and can carry out the pressure maintenance function in a quasi-static condition of the closed-loop pressure control, regardless of fluctuations in the system pressure. It goes without saying that this only applies as long as the hydrodynamic preconditions prevail for compensating losses through the valve by a corresponding delta p between the system pressure 9 and the load pressures 10a, 10b. In this way, the at least one closed-loop control valve 2a, 2b is used to set standardized operation commands and/or standardized flow rates and/or standardized volumetric flows of the work units 3a, 3b independently of the system pressure 9 and/or the load pressure of the at least one work unit.

An example should serve to explain this in more detail.

As an example, two types of valve are used, with the first valve having a nominal maximum volumetric flow of for example 180 liters/min and the second valve having a nominal maximum volumetric flow of for example 140 liters/min. In this example, with linearized characteristics and with a control variable of 50% the first valve would be adjusted to a volumetric flow of 90 liters/min and with a control variable of 50% the second valve would be adjusted to a volumetric flow of 70 liters/min, provided that there is sufficient supply pressure.

In this context the term “standardized,” for a standardized volumetric flow and/or a standardized flow rate, means that the setpoint value for the volumetric flow and/or the flow rate is for example pre-set to 80 liters/min and both valves are adjusted to a volumetric flow of this kind of 80 liters/min, regardless of fluctuations in pressure and regardless of the nominal maximum volumetric flow. The result is thus a flow rate or volumetric flow that is standardized in dependence on a control variable and is independent of load pressure and system pressure. Preferably, the result is thus, for example when using different valves or indeed if other system components are replaced, that no new closed-loop control/open-loop control needs to be implemented.

In principle, it is also possible to standardize to variables other than the volumetric flow or the flow rate provided a correspondingly associated variable is settable in standardized manner and scaled by way of an operation command.