WO2011138122A2

WO2011138122A2 - Dish-washer comprising a concentricity-monitoring unit

Info

Publication number: WO2011138122A2
Application number: PCT/EP2011/055467
Authority: WO
Inventors: Andreas Heidel; Ralf Hochhausen; Bernd KRÄNZLE; Markus Wecker
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2010-05-04
Filing date: 2011-04-08
Publication date: 2011-11-10
Also published as: DE102010028557A1; DE102010028557B4; WO2011138122A3

Abstract

The invention relates to a dishwasher, in particular a domestic dishwasher (1), comprising a control device (2) for carrying out a dish-washing cycle for washing a load, a washing chamber (7) for receiving the load during the washing cycle and a circulation pump (22) for circulating a cleaning fluid (S) which is in the washing chamber (7). Said control device (2) comprises a concentricity-monitoring unit (25) for testing the concentricity of the circulation pump (22), and a power signal (LS) which corresponds to the electric power absorbed by the circulation pump (22) is fed to said concentricity-monitoring unit (25). Said concentricity monitoring unit (25) comprises a filter arrangement (43) with a band pass ratio for generating a filtered power signal (GS) and an evaluation arrangement (44) which is mounted downstream from the filter arrangement (43) for evaluating the filtered power signal (GS).

Description

Dishwasher with a concentricity monitoring unit

The present invention relates to a dishwasher, in particular a domestic dishwasher, with a control device for carrying out a rinse cycle for cleaning items to be washed, with a rinsing chamber for receiving the items to be washed during the rinse cycle and with a circulation pump for circulating a rinsing liquid located in the rinsing chamber, wherein the control device a concentricity monitoring unit for performing a concentricity test in the circulation pump, and wherein the concentricity monitoring unit is supplied with a corresponding to an electrical power consumption of the circulation pump power signal. A known dishwasher has a concentricity monitoring unit to which a power signal corresponding to an electrical power consumption of its circulating pump is supplied. By means of an analysis of the power signal, it is in principle possible to determine, without a separate sensor, whether there is a sufficient amount of washing liquid in the washing chamber for the operation of the dishwasher. Nevertheless, the previously known concentricity monitoring unit is extremely error-prone.

The object of the present invention is to provide a dishwashing machine, in particular a household dishwasher, with an improved concentricity monitoring unit.

The object is achieved in a dishwasher of the type mentioned above in that the concentricity monitoring unit has a filter arrangement with a bandpass behavior for generating a filtered power signal and a downstream of the filter arrangement evaluation arrangement for evaluating the filtered power signal.

The dishwasher according to the invention has a control device for automatically carrying out operating sequences of the dishwasher. For this purpose, the control device can be designed as so-called sequence control, in particular as electronic sequence control.

In the control device, at least one rinse program for performing or controlling a rinsing process, also called rinse cycle, for rinsing items to be washed, in particular for rinsing dishes, deposited. Advantageously, several wash programs are provided, one of which can be selected and started by the operator. This makes it possible to adjust the sequence of a wash cycle, in particular to the load, to the type of loading, to the degree of soiling of the items to be washed and / or to the desired duration of the wash cycle.

The stored rinsing programs can preferably be designed such that the respective rinsing cycle controlled by them in particular at least one pre-rinsing for pre-cleaning items, at least one cleaning operation for thoroughly cleaning items, at least one intermediate rinse for removing soiled rinse liquid from the items to be washed, at least one rinse for avoiding stains on the items to be washed and / or for preparing a drying step, and / or at least one drying course for drying the items to be washed. Rinse cycle, cleaning cycle, intermediate rinse cycle and rinse cycle are hereinafter referred to as water-carrying partial rinses, since during their implementation, the introduced into the rinsing chamber items to be treated with a rinsing liquid. During the drying cycle, a use of rinsing liquid is usually not provided.

The treatment of the items to be washed with rinsing liquid takes place in a substantially complete rinsing chamber, in particular a rinsing container, the dishwasher. In this case, the flushing chamber is associated with an inlet valve, which allows to fill flushing liquid into the washing chamber. In this case, the inlet valve can be opened and closed by the control device so as to influence the inflow of rinsing liquid.

A rinsing liquid is understood here to mean, in particular, a liquid which is intended to be applied to the ware in order to clean it and / or to treat it in another way. Thus, the rinsing liquid can be For example, be provided for heating the dishes, which is common for example during a rinse step.

The rinsing liquid entering the rinsing chamber via the inlet valve is usually fresh water. Depending on the operating phase of the dishwasher, the rinsing liquid in the rinsing chamber can be enriched with cleaning agents, with cleaning aids, such as, for example, rinse aid and / or with dirt which has been removed from the items to be washed. However, cases are also conceivable in which already enriched water is introduced as rinsing liquid via the inlet valve into the rinsing chamber.

Furthermore, the rinsing chamber is assigned a typically electrically driven circulating pump for circulating the filled rinsing liquid, which makes it possible to remove the rinsing liquid in the rinsing chamber, for example, from a collecting device for rinsing liquid and to apply it to the rinsing product via a spraying system assigned to the rinsing chamber. The rotational speed of the circulating pump can be variably controlled and / or regulated by the control device of the dishwasher. The circulation pump may include a brushless electric motor. The brushless electric motor can be designed in particular as a permanent magnet motor. Such a brushless permanent magnet motor may be formed, for example, as a brushless DC motor, also called a BLDC motor, or as a brushless AC motor, also called a BLAC motor. The rotor of the motor comprises at least one permanent magnet, whereas the stator has a plurality of electromagnets. The electromagnets are commutated via a control electronics, in particular via a frequency converter. Compared to other possible engine concepts, this allows both the direction of rotation and the speed of the engine to be controlled in a simple manner. By operating the motor in exactly one direction of rotation, it is possible to optimize the fluid-carrying parts of the circulation pump. This results in a high flow rate with low energy consumption. Furthermore, the brushless permanent magnet motor can be designed as a wet rotor, so that expensive sealing measures are eliminated. The dishwasher further comprises a Rundlaufuberwachungseinheit for performing a concentricity test in the circulation pump. The concentricity monitoring unit can be regarded as a component of the control device, since the results of concentricity tests for influencing operating processes, in particular rinses, of the dishwasher can be used. The power signal supplied to the concentricity monitoring unit can in particular be a signal which corresponds to the current consumption of the circulating pump. In this case, a circulating pump is generally in the concentricity when sufficient rinsing liquid is present in the collecting device of the rinsing chamber in order to prevent suction of air through the circulating pump. Whether air is aspirated or not in an individual case depends, on the one hand, on the amount of rinsing liquid in the rinsing chamber and, on the other hand, on the speed of the circulating pump. The reason for this is that with increasing speed of the circulation pump, an ever smaller part of the total rinsing liquid present in the rinsing chamber is in the collecting device, since it takes a certain time to pass through the line system of the spraying or circulating system and on the washware sprayed rinse liquid passes back into the collection device. This problem arises in particular if the filling quantity of flushing liquid in the collecting device is dimensioned such that at standstill or at a low initial speed of the circulating pump whose passage cross-section is just completely filled with liquid. When speed up the circulation pump to a predetermined target speed then rinsing liquid is conveyed from the collector in the line system of the spray and sprayed on the items to be washed in the washing, so that the liquid level decreases in the collector, whereby the passage cross section of the circulating pump now only partially or temporarily not more of rinsing liquid flows through. This leads to an intermediate air suction of the circulation pump and load fluctuations on the circulation pump.

The dishwashing machine according to the invention is now designed such that the concentricity monitoring unit has a filter arrangement with a bandpass characteristic for generating a filtered power signal. A filter arrangement with bandpass behavior is understood to mean such a filter arrangement, which essentially allows only one predetermined frequency band to pass from an input signal supplied to it, that is to say the frequencies in a predefined passband. The frequency ranges above and below the passband are largely or completely disabled or at least significantly attenuated.

The passband can be given by means of a lower cutoff frequency f _gu and an upper cutoff frequency f _go , the cutoff frequencies, also called transition frequencies, being defined in such a way that the output signal is attenuated there by preferably 3 dB compared to the maximum output signal in the passband , In other words, the cutoff frequencies are preferably where the value of the output signal is 70.7% of the maximum output signal. In many cases, however, the passband is also indicated by specifying two time constants. It corresponds to a first time constant τ-ι the upper limit frequency f _go and a second time constant τ _{2 of} the lower limit frequency f _gu . The time constants τ-ι, τ ₂ and cut-off frequencies f _go , f _gu can generally be calculated according to the formula τ = 1 / (2π ί ₈ ), where π is the circle number and is approximately 3.14. By a suitable choice of the passband of the filter arrangement frequency components of the power signal can be blocked or attenuated, which are not directly related to whether the circulating pump is in the concentricity or not. For example, frequency components which are typically generated by the control and / or regulating action of a speed control device associated with the circulation pump and which are typically located in a low frequency range can be blocked. Also, such high-frequency components can be blocked, which can occur, for example, when commutating an electric motor of the circulation pump. By now the thus filtered power signal through the downstream evaluation arrangement is evaluated, the susceptibility to error of the concentricity monitoring unit is considerably reduced.

The filter arrangement may, in particular if the power signal is a continuous-time and / or continuous-value signal, be designed in particular as an analogue passive filter arrangement comprising one or more components from the group of coils, capacitors and / or resistors. However, it can also be designed as an analog active filter arrangement, which preferably additionally comprises an amplifier, in particular an operational amplifier.

Furthermore, the filter arrangement, in particular if the power signal is a discrete-time and / or discrete-value signal, may advantageously be a digital filter arrangement comprising a digital computer, for example a signal processor or a microprocessor.

Even if the power signal supplied to the filter arrangement is a discrete-time and / or discrete-value signal, in particular if it is a time-discrete and discrete-value digital signal, the advantages of the invention are particularly evident. Thus, in this case, frequency components contained in the power signal can be suppressed, which arise due to the temporal sampling of a signal initially analogous and corresponding to the power and / or the quantization of the values of the initially analog signal. This effect is particularly important when the analog signal is sampled at a constant sampling rate and the circulation pump is operated in a high speed range, since the sampling errors are higher, the less the analog signal is sampled per revolution of the circulation pump. The invention thus ensures a reliable concentricity detection even in the upper speed range of the circulation pump, in particular at its intended maximum speed.

According to an advantageous embodiment of the invention, the filter arrangement comprises a high pass and a low pass, which are connected in series so as to produce the filtered output signal. In this way, the bandpass behavior can be realized in a simple manner. According to an advantageous embodiment of the invention, the filter arrangement comprises a first low-pass filter for generating a first intermediate signal and a second low-pass filter for generating a second intermediate signal, wherein the low pass the power signal is supplied, and wherein the first intermediate signal and the second intermediate signal to a subtractor for generating the filtered Output signal are supplied. Such an arrangement, if the two low-pass filters have different time constants τ-ι, τ ₂ , likewise leads to a bandpass behavior of the filter arrangement, which can be implemented in a simple manner, in particular using a digital computer.

According to an expedient development of the invention, a first time constant of the filter arrangement is at least 50 milliseconds and at most 1200 milliseconds, preferably at least 100 milliseconds and at most 600 milliseconds, more preferably at least 200 milliseconds and at most 300 milliseconds, and a second time constant of the filter arrangement at least 1250 milliseconds and at most 21000 milliseconds, preferably at least 2500 milliseconds and at most 14000 milliseconds, more preferably at least 5000 milliseconds and at most 7000 milliseconds. In the specified ranges, a particularly reliable function of the concentricity monitoring unit results. It goes without saying that the optimum values of the first and the second time constant depend on the concrete individual case, for example on the dynamic behavior of the circulation pump and the components used for its control and / or regulation. The optimum values can be determined, for example, by suitable tests and / or by suitable simulation methods.

According to an advantageous development of the invention, the evaluation arrangement has a squaring member for squaring the filtered power signal or a signal derived therefrom. In this way, a filtered and squared power signal dependent on the power signal is generated, which always has positive values. This simplifies the further processing of the signal since sign changes in the filtered and squared power signal do not occur and therefore do not have to be taken into account. A signal derived from the filtered power signal is understood to mean such a signal, which at least partially has the same information content as the filtered power signal.

According to an expedient development of the invention, the evaluation arrangement comprises an integration element for generating an integrated signal which characterizes the course of the filtered power signal or of a signal derived therefrom during an evaluation period with a predetermined duration. The integrated signal makes it possible to reduce the amount of data since it assigns a value combining the course of the filtered power signal or the signal derived therefrom to each evaluation period. At the same time, the effects of noise components in the filtered power signal or in the signal derived therefrom, in particular the effects of random noise components, are reduced by the period-related processing. In this way, the reliability of the concentricity detection can be further improved. In this case, the integrated signal may comprise, for example, the average values of the filtered power signal or of the signal derived therefrom, which are each related to an evaluation period. The evaluation periods may overlap, intersect seamlessly or be spaced apart from each other. In this case, a signal derived from the integrated signal is understood as meaning such a signal which has at least partially the same information content as the integrated signal. This may be, for example, the filtered and squared power signal.

According to an expedient development of the invention, the evaluation arrangement comprises a recognition element for detecting a concentricity of the circulation pump on the basis of the integrated signal or a signal derived therefrom. The detection of a concentricity of the circulating pump based on the integrated signal or a signal derived therefrom allows due to the nature of its generation described above, a simple and reliable detection of a concentricity of the circulation pump. In this case, the recognition element can be embodied such that it generates a recognition signal which can be used directly to control the operating sequences of the dishwasher. For example, an undesired decrease in the level of rinsing liquid in the rinsing chamber during a cleaning phase of a water-carrying partial rinsing leads to a non-circulation of the circulating pump, this information is then provided by means of the detection signal. This can occur, for example, when in the Flushing chamber is a hollow vessel, such as a cup or a pot, the opening facing upward, so that the hollow vessel fills with rinsing liquid, which is then no longer available for circulating. In this case, suitable measures can be taken automatically by the control device. In particular, can be supplemented by a corresponding control of the inlet valve, the missing amount of washing liquid.

According to an advantageous development of the invention, the filtered power signal or the signal derived therefrom is a time-continuous signal, wherein the integrator is designed to integrate the values of the signal during the evaluation period so as to form the integrated signal. Suitable analog integration members are simple, so that in this case the integrated signal can be generated in a simple manner. According to an advantageous embodiment of the invention, the filtered power signal or the signal derived therefrom is a discrete-time signal, wherein the integrator is configured to accumulate the values of the signal during the evaluation period so as to form the integrated signal. In this case, a particularly simple generation of the integrated signal is possible, wherein in particular a digital computer can be used.

According to an expedient development of the invention, the predetermined duration of the evaluation period is at least 2 seconds and at most 20 seconds, preferably at least 3 seconds and at most 15 seconds, more preferably at least 4 seconds and at most 10 seconds. Basically, it applies here that disturbances in the filtered power signal, for example, capacitively or inductively coupled-in interference components in the passband of the filter arrangement, have less effect, the longer the duration of the evaluation periods is fixed. However, this creates a time delay in the concentricity test, in which a change from concentricity to a non-circulation or vice versa is recognized later and later. The specified values for the duration of the evaluation periods are a good compromise for reliable and at the same time fast detection of concentricity of the circulation pump. According to an advantageous development of the invention, the recognition element is a threshold value monitoring element for monitoring a threshold value provided for the integrated signal or for the signal derived therefrom. This results in a particularly simple evaluation of the integrated signal or the signal derived therefrom. For example, it may be provided that a run-out is assumed as long as the threshold value is exceeded, and that a round-trip is assumed as long as the threshold value is undershot. According to an expedient development of the invention, the threshold value monitoring element is designed to compare the intended threshold value with the integrated signal or the signal derived therefrom. In this way, the absolute value of the integrated signal is evaluated, resulting in a particularly simple concentricity detection device.

According to an expedient development of the invention, the threshold value monitoring element is designed to compare the intended threshold value with the difference between the integrated signal or the signal derived therefrom of one of the evaluation periods and from the integrated signal or the signal derived therefrom of the respective subsequent evaluation period. That way, one becomes

Edge, ie a relative change in the integrated signal from one evaluation period to the next evaluation period detected. Such an evaluation of relative changes in the integrated signal can improve the reliability of the concentricity test, as it does not depend on the possibly erroneous absolute value.

According to an expedient development of the invention, the recognition element is a minimum recognition element for recognizing a minimum of the integrated signal or the signal derived therefrom over time. A minimum in the integrated signal can be interpreted as an occurrence of the run-out after a run-out and can be determined with a low computation effort. Therefore, the minimum detection element can be made simple and yet surely detect a transition from run-out to run-out. According to an advantageous development of the invention, the rinse cycle comprises at least one filling sequence, ie in particular at least one filling operation with several partial filling operations, in which an openable by the control device and closable inlet valve for filling rinsing liquid is opened in the rinsing chamber and the circulation pump is operated at a constant filling speed , wherein the control device is designed to close the inlet valve when the concentricity of the circulating pump is detected. In this way, a simple method for filling rinsing liquid is realized in the washing chamber. In particular, it is possible to dispense with a separate fill level sensor, for example a pressure cell, and / or a flow meter for measuring the amount of flushing liquid introduced, for example an impeller counter. In addition, the amount of rinsing liquid filled in can thus be adapted automatically to the actual requirement, which is dependent in particular on the loading of items to be washed. Thus, for example, the proportion of the filled rinsing liquid, which adheres to the items due to the type and amount of items to be washed, automatically taken into account because the filling valve is not closed until the available amount of rinsing liquid for circulation, so the total amount minus the adhering amount sufficient is. This is especially the case when a concentricity of the circulating pump has been detected for a desired filling speed. In this way, the consumption of flushing liquid can be minimized and yet an intended cleaning effect can be ensured.

According to an expedient development of the invention, the filling speed deviates from a cleaning speed of the circulating pump, which is provided for a cleaning sequence following the filling sequence. In this way it is possible to take into account the time difference between the actual entry of the concentricity and the detection of the concentricity, so that the amount introduced can be adapted even more precisely to the actual requirements. As a rule, the detection of the concentricity due to the filtering and the period-related evaluation of the original power signal is temporally after the actual entry of the concentricity, so that without additional measures a not required for the concentricity at the filling speed amount of flushing liquid is filled into the washing chamber , If, however, the filling speed is lowered in a suitable manner compared with the cleaning speed, then it can be achieved that the filled rinsing fluid is just adequate for concentricity at the (higher) cleaning speed. is right. However, cases are also conceivable in which the detection of the concentricity is temporally before the actual entry of the concentricity. In this case, it would be useful to increase the filling speed compared to the cleaning speed. The optimum difference between filling speed and cleaning speed can be determined, for example, by suitable tests and / or simulation methods.

Furthermore, the invention relates to a method for operating a dishwasher, in particular according to one of the preceding claims, with a control device for performing a wash cycle for cleaning items to be washed, with a wash chamber for receiving the items to be washed during the wash cycle and with a circulation pump for circulating a in the Flushing liquid located flushing chamber, wherein the control device comprises a concentricity monitoring unit for performing a concentricity test in the circulation pump, wherein the concentricity monitoring unit is supplied to a pump corresponding to an electrical power consumption of the circulation pump power signal.

In the method according to the invention, it is provided that the power signal is fed via a filter arrangement of the concentricity monitoring unit with a bandpass characteristic for generating a filtered power signal, and that the filtered power signal is evaluated by an evaluation arrangement downstream of the filter arrangement for evaluating the filtered power signal.

The inventive method allows a simple, fast and reliable detection of a concentricity of the circulating pump and is characterized by low demands on the structural design of the dishwasher.

Other advantageous embodiments and / or developments of the invention are given in the claims. The reproduced in the dependent claims and / or above advantageous embodiments of the invention may be provided individually or in any combination with each other.

The invention and its developments and their advantages are explained in more detail below with reference to drawings. Show it: 1 shows an embodiment of a domestic dishwasher according to the invention in a schematic side view, Figure 2 shows a further illustration of the dishwasher of Figure 1,

3 shows a signal flow diagram of the control device of the domestic dishwasher of FIGS. 1 and 2, and FIG. 4 shows a diagram for illustrating the function of the inventive device

Dishwasher of Figures 1 to 3.

In the following figures, corresponding parts are provided with the same reference numerals. In this case, only those components of a dishwasher are provided with reference numerals and explained which are necessary for the understanding of the invention. It goes without saying that the dishwasher according to the invention can comprise further parts and assemblies.

FIG. 1 shows an advantageous exemplary embodiment of a household dishwasher 1 according to the invention in a schematic side view. The dishwasher 1 has a control device 2, in which at least one wash program for controlling a wash cycle for washing dishes, in particular dishes, is deposited. Expediently, a plurality of washing programs are stored, so that by selecting a suitable washing program, the sequence of a controlled by the control unit 2 rinse, for example, to the load, to the type of load, to the degree of contamination of the dishes and / or to the desired duration of the wash can be adjusted.

The control device 2 is associated with an operating device 3, which allows an operator of the dishwasher 1 to call one of the washing programs and thereby start. Furthermore, an output device 4 is assigned here in the embodiment of the control device 2, which allows the output of messages to the operator. The output device 4 may comprise indicator lamps, light-emitting diodes, an alpha-numeric display and / or a graphic display for outputting optical messages. Furthermore, the output device 4 additionally or independently thereof be designed for the output of acoustic messages and for example have a buzzer, a speaker and / or the like. The dishwasher 1 further comprises a rinsing container 5, which can be closed by a door 6, so that a closed rinsing chamber 7 is formed for rinsing dishes. If appropriate, the rinsing container 5 can be arranged inside a housing 8 of the dishwasher 1. In built-in dishwashers, the housing 8 is not required and may be omitted altogether at the top. In Figure 1, the door 6 is shown in its closed position. The door 6 is through

Pivoting about an axis perpendicular to the plane arranged axis can be brought into an open position in which it is aligned substantially horizontally and allows the introduction or removal of items to be washed. In the embodiment shown in Figure 1, the operating device 3 is arranged in an easy to use manner at an upper portion of the door 6. The output device 4 is also arranged on the upper portion of the door 6, so that optical messages are clearly visible and / or audible messages are clearly audible. In principle, however, it is possible to arrange the operating device 3 and / or the output device 4 elsewhere.

The control device 2 is accommodated by way of example in a base assembly below the washing container 5. However, it is also possible to arrange the control device 2 at another location of the dishwasher 1. However, the control device 2 could also be configured decentralized, which is understood to include spatially separated components which are connected via communication means such that they can cooperate.

According to an alternative embodiment variant, the control device 2 or at least one of its decentralized components can be positioned in the door 6, so that the required signal connections between the operating device 3, the output device 4 and the control device 2 can be kept short.

The dishwasher 1 has an upper dish rack 9 and a lower dish rack 10 for positioning dishes. The upper dish rack 9 is arranged on extension rails 1 1, which in each case opposite - the, in the depth direction of the washing container extending side walls of the washing compartment 5 are attached. The crockery basket 9 can be moved out of the washing container 5 with the door 6 open by means of the extension rails 1 1, which facilitates the loading and unloading of the upper crockery basket 9. The lower dish rack 10 is arranged on extension rails 12 in an analogous manner.

The one or more washing programs stored in the control device 2 can each provide a plurality of partial wash cycles, for example at least one pre-wash cycle, at least one wash cycle, at least one intermediate wash cycle, at least one rinse cycle and / or at least one drying cycle. Here, pre-wash cycle, cleaning cycle, intermediate rinse cycle and rinse cycle are referred to as water-carrying partial rinses, since during their implementation, the items to be washed positioned in the rinsing chamber 7 are treated with a rinsing liquid S. During the drying cycle, a treatment of the items to be washed with rinsing liquid S is generally not provided.

In the exemplary embodiment, fresh water or feed water ZW, which can preferably be taken up by an external water supply device WH, in particular a drinking water supply network, and filled into the rinsing chamber 7, is used as the rinsing liquid S for the treatment of the items to be washed. Typically, a rinsing liquid S formed from fresh feed water ZW is introduced at the beginning of each water-conducting partial rinse cycle, which rinse liquid is then discharged to the end of the respective rinse cycle to an external sanitation AR as wastewater AW. However, it is also possible to store a rinsing liquid S of a partial rinse cycle in a storage container (not shown) and to refill it into the rinsing chamber 7 in a later partial rinse cycle.

The dishwasher 1 of FIG. 1 comprises a water inlet device 13, which is provided for connection to the external water supply device WH. As in FIG. 1, the external water supply device WH may be a faucet of a building-side water installation which provides pressurized feed water ZW. The water inlet device 13 comprises a connection piece 14, which is provided for connection to the water tap WH. The connection can be made for example via a threaded arrangement, a bayonet arrangement or the like. Downstream- ward of the connecting piece 14 is a connection hose 15 is provided, which is preferably designed to be flexible. The downstream end of the connection tube 15 is connected to a housing-fixed connection piece 16. Downstream of the housing-fixed connecting piece 16, a supply line 17 is provided, which is connected to an input side of a switchable by means of the control device 2 inlet valve 18. An output side of the inlet valve 18 in turn is connected to a liquid inlet 19 of the rinsing chamber 7. In this way it is possible, by means of the water inlet device 13, to feed inlet water ZW as rinsing liquid S into the interior of the rinsing chamber 7 of the dishwasher 1. The inlet valve 18 may be formed as a switchable solenoid valve, which has only an open position and a closed position. In the supply line 17, a water treatment plant, not shown, for example, a water softening system may be provided.

Instead of or in addition to the device-side inlet valve 18 may also be provided between the connector 14 and the faucet WH an external inlet valve, in particular a so-called aqua-stop valve, which is preferably switchable by means of the control device, in particular shut-off and apparently. In other words, if necessary, only an external inlet valve can be coupled directly to the faucet WH as an end piece of the water hose 15 and the internal inlet valve 18 can be omitted.

Due to its weight force, the rinsing liquid S, which has reached the rinsing chamber 7 via the liquid inlet 19, arrives in a collection device formed on a base 20 of the rinsing container 5, which can preferably be designed as a collection pot 21. An input side of a circulation pump 22 is liquid-conducting connected to the collection pot 21. Furthermore, an outlet side of the circulating pump 22 is connected to a spraying device 23, 24, which makes it possible to apply flushing liquid S to the washware introduced into the washing chamber 7.

In the exemplary embodiment, the circulation pump 22 has a brushless AC motor, also called a BLAC motor. In principle, however, other engine concepts would also be conceivable. In the embodiment of Figure 1, the spray means 23, 24 comprises an upper rotatable spray arm and a lower rotatable spray arm. However, alternatively or additionally fixed spray elements could be provided.

The flushing liquid S emerging from the respective spraying device 23, 24 when the circulating pump 22 is switched on is returned to the collecting pot 21 due to its weight within the flushing chamber 21. During the circulation of the flushing liquid S in the flushing chamber 7, the circulation pump 22 is intended to be operated concentrically. The circulating pump 22 is then in the concentricity, if here is such a large amount of flushing fluid S is available that they exclusively excluding flushing liquid S or otherwise expressed promotes no air. By operating the circulating pump 22 in the concentricity, on the one hand, a pump pressure sufficient for an intended cleaning effect can be achieved and, on the other hand, the formation of disturbing snoring noises can be avoided. In order to determine whether the circulation pump 22 is in concentricity or not, a concentricity monitoring unit 25 is provided. This is integrated in the embodiment in the control device 2. However, the concentricity monitoring unit 25 could also be designed as a separate module.

Furthermore, the dishwashing machine 1 here in the exemplary embodiment in a conventional manner to a metering device 26, which makes it possible to offset the rinsing liquid S introduced into the rinsing chamber 7 with cleaning agents and / or cleaning aids to the cleaning effect and / or the drying effect of a rinse cycle improve.

Furthermore, the dishwasher 1 shown in FIG. 1 has a drainage device 27, which serves to pump out rinsing liquid S no longer required as wastewater AW from the rinsing chamber 7 to the outside. The drainage device 27 comprises a drain pump 28 whose inlet side is connected to the collection pot 21. The outlet side of the drain pump 28, however, is connected to a connecting line 29, the downstream end of which is connected to a housing-fixed connection 30 of the dishwasher 1. The drain pump 28 has in the embodiment as well as the circulation pump 22, a brushless AC motor, also called BLAC motor, on. However, other engine concepts would also be conceivable here. Attached to an outlet of the housing-fixed connection 30 is a wastewater hose 31, which is preferably flexible. At the downstream end of the sewage hose 31, a fitting 32 is arranged, which is intended to connect the drainage device 27 with a sanitation AR. The sanitation AR may be a sewer pipe of a building-side water installation. The connection between the connecting piece 32 and the sewage pipe can be designed as a screw connection, as a bayonet connection, as a plug connection or the like.

FIG. 2 shows a block diagram of the household dishwasher 1 of FIG. 1, wherein in particular its control and communication concept is shown. In the exemplary embodiment, a signal line 33 is provided, which connects the operating device 3 to the control device 2 such that operating commands of an operator can be transmitted from the operating device 3 to the control device 2. Furthermore, a signal line 34 is provided, which connects the control device 2 to the output device 4, so that information provided by the control device 2 can be transmitted to the output device 4 and output there to the operator.

Further, a control line 35 is provided, which connects the control device 2 with the switchable inlet valve 18 such that the inlet valve 18 can be closed or opened by the control device 2. In this way, the filling of rinsing liquid S in the rinsing chamber 7 can be controlled by the control device 2. In this case, the control device 2 is embodied such that, in the circuit, in particular in the control of the closing and / or opening times of the inlet valve 18, and possibly also in the control and / or regulation of the filling flow, information generated by the monitoring unit 25 is taken into account can be. A supply line 36 connects the control device 2 to the circulation pump 22. In this way, the circulation pump 22 can also be switched by the control device 2. The control device 2 is designed for switching on and off the circulation pump 22 and in particular for controlling and / or regulating the rotational speed of the circulation pump 22. Further, a supply line 37 is provided, which connects the control device 2 with the drain pump 28, so that the drain pump 28 by the control device 2 switchable, in particular off and on, is. The rotational speed of the drain pump 28 can also be controlled and / or regulated by the control device 2.

FIG. 3 shows a signal flow diagram of the control device 2 of the domestic dishwasher 1 of FIGS. 1 and 2. The control device 2 has a central unit 38 which controls the sequence of a rinse cycle using a selected and activated rinse program. The central unit 38 is connected to the signal line 33 so that its operating commands can be supplied by the operating device 3, for example a command for selecting a washing program. Likewise, the central unit 38 is connected to the signal line 34, so that generated by the central processing unit 38 or forwarded control information and / or other operating information to the output device 4 are transferable to spend them there.

The central unit 38 is further designed to control the circulation pump 22 and the drain pump 28, in particular for switching on and off and for controlling the respective speed. For this purpose, the central unit 38 is designed to generate a speed specification signal DVS as a function of the selected wash program, which is supplied to a speed controller 39 as a setpoint or reference variable. The speed controller 39 is in turn configured to generate a control signal SFU, which is supplied to a frequency converter 40. The frequency converter 40 is designed to supply the circulation pump 22 and the drain pump 28 with electrical energy. For this purpose, the frequency converter 40 for generating a multi-phase, in particular a three-phase, AC voltage is formed, which can be supplied via a supply line 41 of a switching unit 42. The switching unit 42 is designed so that the AC voltage supplied to it can be selectively routed via the supply line 36 to the circulation pump 22 or via the supply line 37 to the drain pump 28 in order to drive one of them. The switching of the switching unit 42 can take place by means of a switching signal SSG, which can be generated by the central unit 38 as a function of the washing program and the switching unit 42 can be fed.

The alternating voltage generated by the frequency converter 40 is variable in frequency, so as to be able to adjust in particular the rotational speed of the circulation pump 22. In order to ensure that the rotational speed of the circulation pump 22 corresponds to the speed specification signal DVS generated by the central unit 38, a closed control loop is provided.

In the exemplary embodiment, a signal RS, LS is generated, which corresponds to a current flowing through a winding of the motor of the circulation pump 22 current, and which is tapped at a arranged in series with the winding shunt resistor. The shunt resistor may be arranged in the frequency converter 40, for example. In this case, the frequency of the signal RS, LS thus generated corresponds to the rotational speed of the circulation pump 22.

The function of the closed loop is based on the return of the thus generated signal RS, LS to the speed controller 39 as a returned signal RS. The speed controller 39 is now designed so that the actual speed contained in the feedback signal RS is compared with the target speed contained in the speed specification signal DVS, wherein in a deviation of the actual speed of the target speed, the control signal SFU is changed as long as until the deviation disappears. This ensures that the actual speed follows the set speed.

The signal RS, LS, which corresponds to a current flowing through a winding of the motor of the circulation pump 22, and which is tapped on a shunt resistor arranged in series with the winding, further corresponds according to the relation P = Rl ² , where P is the Power consumption, R denotes the resistance and I the current, with the electrical power consumption of the circulation pump 2 and is supplied as a power signal LS a filter assembly 43 of the concentricity monitoring unit 25. The filter arrangement 43 has a bandpass characteristic and is designed to generate a filtered power signal GS. In this case, a filter arrangement 43 with bandpass behavior is understood to mean such a filter arrangement 43 which essentially allows only one predetermined frequency band to pass from an input signal LS supplied to it, that is to say the frequencies in a predetermined passband. The frequency ranges above and below the passband are largely blocked or at least significantly attenuated.

By a suitable choice of the passband of the filter assembly 43 frequency components of the power signal LS can be blocked or attenuated, which are not directly related to whether the circulation pump 22 is in the concentricity or not. For example, frequency components which are typically generated by the control and / or regulating action of the speed control device 38, 39, 40 associated with the circulation pump 22 and which are typically located in a low frequency range can be blocked. Likewise, it is possible to block such high-frequency frequency components which can occur, for example, during the commutation of an electric motor of the circulation pump 22. By now the thus filtered power signal GS is evaluated by the downstream evaluation arrangement 44, the error rate of the concentricity monitoring unit 25 is reduced considerably.

In the exemplary embodiment, the filter arrangement 43 comprises a first low-pass filter 45 for generating a first intermediate signal ZS1 and a second low-pass filter 46 for generating a second intermediate signal ZS2, wherein the low-pass filters 45, 46 respectively the power signal LS is supplied, and wherein the first intermediate signal ZS1 and the second Intermediate signal ZS2 are supplied to a subtracter 47 for generating the filtered output signal GS. In this case, the two low-pass filters 45, 46 have different time constants τ- ₁ , τ ₂ . Such an arrangement leads overall to a bandpass behavior of the filter arrangement 43, which is easy to implement, in particular using a digital computer.

Advantageously, the evaluation arrangement 44 has a squaring member 48 for squaring the filtered power signal GS or a signal derived therefrom on. In this way, a filtered and squared power signal QGS dependent on the power signal LS is generated, which always has positive values. This simplifies the further processing of the signal QGS since sign changes in the filtered and squared power signal QGS do not occur and therefore do not have to be taken into account.

Expediently, the evaluation arrangement 44 comprises an integration element 49 for generating an integrated signal IGS, which characterizes the course of the filtered power signal QGS or of a signal derived therefrom during an evaluation period with a predetermined duration. The integrated signal makes it possible to reduce the amount of data since it assigns a value summarizing the course of the filtered power signal QGS or of the signal derived therefrom to each evaluation period. At the same time, the effects of interference components in the filtered power signal GS, in particular the effects of random noise components, are reduced by the period-related processing. The integrated, squared differential signal in particular represents a variance, ie a scattering measure of the intermediate signals ZS1, ZS2 filtered with different time constants or the power signal LS on which they are based. In this way, the reliability of the concentricity monitoring unit 25 can be further improved. In this case, the integrated signal IGS can comprise, for example, the sums of discrete-time samples determined in each evaluation period or the values of values determined in each case in an evaluation period of continuous values. The evaluation arrangement further comprises a recognition element 50 for detecting a concentricity of the circulation pump 22 on the basis of the integrated signal IGS. The detection of a concentricity of the circulation pump 22 on the basis of the integrated signal IGS allows a simple and reliable detection of a concentricity of the circulation pump 22 due to the nature of its above-described generation. The detection element 50 is designed in the exemplary embodiment such that it generates a detection signal ES which can be used directly to control operations of the dishwasher. For this purpose, the detection signal ES is supplied to the central unit 38 in the exemplary embodiment. In the case of an undesirable drop in the level of rinsing liquid S in the rinsing chamber 7 during a cleaning phase of a water-carrying partial rinsing cycle, this may be the case are controlled by the central unit 38 via the control line 35, the inlet valve 18 so that the missing amount of flushing liquid S is added. In addition, the detection signal ES of the concentricity monitoring unit 25 can also be used to control the inlet valve 18 during a filling sequence of a rinse cycle.

FIG. 4 shows a diagram for illustrating a filling sequence FS and a subsequent cleaning sequence RS of the domestic dishwasher 1 explained above. In this case, the operating state Z18 of the inlet valve 18, the speed N22 of the circulating pump 22, the first state generated by the first low-pass filter 45 are on a common time axis t Intermediate signal ZS1, the second intermediate signal ZS2 generated by the second low pass 46, the filtered power signal GS and the integrated filtered signal IGS. At the beginning of the filling sequence FS, the filling valve 18 is opened, which is illustrated by taking the operating state "1", so that rinsing liquid is filled into the rinsing chamber 7. Likewise, the circulation pump 22 is turned on, the circulation pump 22 to a predetermined constant filling speed FD The circulation pump 22 is initially out of circulation because of the small amount of rinsing liquid S in the rinsing chamber 7. However, since the amount of rinsing liquid S in the rinsing chamber 7 increases during the filling sequence FS, the electric power consumption of the circulating pump 22 increases Thus, the values of the intermediate signals ZS1 and ZS2 also increase in the course of the filling sequence FS.

Since the first intermediate signal ZS1 is generated by the first low-pass filter 45, which has a low time constant τ-1 of, for example, 250 milliseconds, this comprises changes in the power consumption of the circulation pump 22 from a low to a medium frequency range. On the other hand, in the first intermediate signal ZS1 high-frequency disturbances are damped or suppressed. Further, since the second intermediate signal ZS2 is generated by the second low-pass filter 46 having a high time constant τ ₂ of, for example, 6000 milliseconds, it includes changes in the power consumption of the circulation pump 22 only in a low frequency range. Thus, in the second intermediate signal ZS2 high-frequency interference ments and changes in power consumption in the mid-frequency range are dampened or suppressed.

The filtered signal GS generated by means of the subtracter 47 corresponds to the difference between the first intermediate signal ZS1 and the second intermediate signal ZS2. As a result, the components contained in both intermediate signals ZS1 and ZS2 cancel each other out in the low frequency range. The filtered signal GS therefore essentially comprises changes in the power consumption of the circulation pump 22 in the middle frequency range, which ultimately means that the filter arrangement 43 has bandpass characteristics.

From the filtered signal GS, a squared filtered power signal QGS (not shown in FIG. 4 for reasons of clarity) is generated by means of the squaring member 48 shown in FIG. 3, from which the integrated signal IGS is formed by means of the integration member 49. The integrated signal IGS has in each of the evaluation periods AP a value which characterizes the course of the squared filtered signal QGS during the preceding evaluation period AP in a comprehensive manner. In the exemplary embodiment, the squared filtered signal QGS is a time-discrete and value-discrete signal QGS whose values are summed up in one of the evaluation periods AP, so as to form the value of the integrated signal IGS for the subsequent evaluation period AP. For example, the integrated signal IGS in the evaluation period AP _{2 has} a value which corresponds to the sum of the values of the filtered signal GS in the evaluation period AP-i. In this case, the integrated, squared difference signal IGS repre- sents, in particular, a variance, ie a scattering measure of the intermediate signals ZS1, ZS2 filtered with different time constants or the power signal LS on which they are based.

In the exemplary embodiment, the integrated signal IGS is examined by means of the recognition element 50 as to whether a threshold value SW predetermined for achieving the pump circulation is exceeded from top to bottom. This is then assessed as the entry of the concentricity of the circulation pump 22, which arrives in FIG. 4 at the end of the evaluation period AP ₅ . Therefore, the inlet valve 18 is closed, which is symbolized by the assumption of the operating state "0", and the filling sequence FS ends. In the method described is generally the detection of the concentricity in terms of time after the actual occurrence of the concentricity of the circulation pump 22. Thus occurs in Figure 4, the actual concentricity already at time t _R. This means that at the end of the filling sequence FS is such an amount of flushing liquid S in the washing chamber, which is above the minimum amount for a concentricity of the circulating pump at filling speed FD. This can now be taken into account so that the filling speed FD of the filling sequence FS is provided below a provided for a subsequent cleaning sequence RS cleaning speed RD. It can be provided, as shown in Figure 4, that at the beginning of the cleaning sequence RS, the rotational speed N22 of the circulating pump is increased. With a suitable tuning of the parameters of the method, in particular the duration of the evaluation period AP, the threshold SW, the time constant of the filter assembly, etc., can be ensured so that the amount of flushing fluid S in the washing chamber 7 just enough for a concentricity of the circulating pump at her Cleaning speed RD is.

In an advantageous embodiment of the invention, the control current LS with different time constants τ-ι, τ _{2 is} filtered. Due to the filtering, a smoothing (averaging) of the signal LS can be achieved. The absorbed current LS is proportional to the filling quantity. If there is enough water in the device 1, the current LS no longer increases. At this time, the concentricity of the circulation pump 22 is ensured. The deviation GS of the currents ZS1 and ZS2 with different time constants τ-ι, τ ₂ falls to a minimum.

The concentricity is detected by first forming the difference GS of the intermediate signals ZS1, ZS2, in particular the controller currents \ - _\ and l _2, which are deeply pass filtered with different time constants TI, τ ₂ . The squaring of the difference GS then prevents compensation due to the sign. Now the squared difference QGS is added up. After the n measured values of a period, the accumulated squared difference QGS can be compared with a threshold SW. It is also possible to detect the negative edge or the minimum of the accumulated squared difference QGS. The integrated, squared difference, ie variance IGS, can be determined in particular for the following mathematical relationship for each evaluation period, eg AP1-AP9:

tn

IGS = Σ (ZS1 (Ti) - ZS2 (T ₂ ) f

to

where T-I is a low time constant for detecting fast changes in the power signal LS;

where τ _{2 is} a higher time constant for averaging the power signal LS;

tn is the integration time or accumulation time;

tO is the respective starting time for the respective accumulation;

IGS is the accumulated quadratic difference of the intermediate signals ZS1, ZS2, which have been low-pass filtered with the different time constant τ ₂ .

There are the following advantages: - true-rotation filling also in the full load range (target speed) possible,

increased measurement dynamics (by squaring the difference GS),

high process reliability based on the evaluation of the characteristic "curvature of the current", that is to say traversing the threshold value SW

- pump variance (tolerances or scattering, winding resistance ...) is not included in the algorithm,

the fill level is adjusted adaptively according to the respective load,

- It may be possible to dispense with a quantity counter (impeller counter).

LIST OF REFERENCE NUMBERS

1 dishwasher

2 control device

3 control device

4 output device

5 rinse tanks

6 door

7 rinsing chamber

8 housing

9 upper dish rack

10 lower crockery basket

1 1 extension rail

12 extension rail

13 water inlet device

14 connection piece

15 connection hose

16 housing-fixed connection piece

17 Supplies, supply line

18 inlet valve

19 fluid inlet

20 bottom of the washing container

21 collection device, collection pot

22 circulation pump

23 upper spray arm

24 lower spray arm

25 concentricity monitoring unit

26 metering device

27 drainage device

28 drain pump

29 connecting line

30 housing-proof connection

31 sewage hose 32 connection piece

33 signal line

34 signal line

35 control line

36 supply line

37 supply line

38 central unit

39 speed controller

40 frequency inverters

41 supply line

42 switching unit

43 filter arrangement

44 evaluation arrangement

45 first low pass

46 second low pass

47 subtractor

48 squaring member

49 integrator

50 identifier

WH water supply device, faucet

ZW inlet water

S rinsing fluid

AR sanitation facility, sewage pipe AW wastewater

DVS speed specification signal

SFU control signal

SSG switching signal

RS returned signal

LS power signal

GS filtered power signal

ZS1 first intermediate signal

ZS2 second intermediate signal

QGS squared filtered signal IGS integrated signal

ES detection signal

FS filling sequence

RS cleaning sequence

Z18 Operating status of the inlet valve

N22 Speed of the circulating pump

FD filling speed

RD cleaning speed

SW threshold value

AP evaluation period

Claims

claims

1. Dishwasher, in particular domestic dishwasher (1), with a control device (2) for performing a rinse cycle for cleaning items to be washed, with a rinsing chamber (7) for receiving the items to be washed during the rinse cycle and with a circulation pump (22) for circulating a in the flushing chamber (7) located flushing liquid (S), wherein the control device (2) comprises a concentricity monitoring unit (25) for performing a concentricity test in the circulation pump (22), and wherein the Rundlaufüberwacht monitoring unit (25) with an electrical power consumption of the circulation pump (22) corresponding power signal (LS) is supplied, characterized in that the concentricity monitoring unit (25) has a filter arrangement (43) with a bandpass behavior for generating a filtered power signal (GS) and the filter arrangement (43) downstream evaluation arrangement (44) for evaluation of the filtered power signal (GS).

Dishwasher according to the preceding claim, characterized in that the filter arrangement (43) comprises a first low-pass filter (45) for generating a first intermediate signal (ZS1) and a second low-pass filter (46) for generating a second intermediate signal (ZS2), wherein both low-pass filters (45 , 46) the power signal (LS) is supplied, and wherein the first intermediate signal (ZS1) and the second intermediate signal (ZS2) are supplied to a subtractor (47) for generating the filtered power signal (GS).

3. Dishwasher according to the preceding claim, characterized in that a first time constant τ-ι the filter arrangement (43) at least 50 milliseconds and at most 1200 milliseconds, preferably at least 100 milliseconds and at most 600 milliseconds, more preferably at least 200 milliseconds and at most 300 milliseconds , and a second

Time constant τ _{2 of} the filter arrangement (43) at least 1250 milliseconds and at most 21000 milliseconds, preferably at least 2500 milliseconds and at most 14000 milliseconds, more preferably at least 5000 milliseconds and at most 7000 milliseconds. Dishwasher according to one of the preceding claims, characterized in that the evaluation arrangement (44) has a squaring member (48) for squaring the filtered power signal (GS) or a signal derived therefrom.

Dishwasher according to one of the preceding claims, characterized in that the evaluation arrangement (44) an integration member (49) for generating an integrated signal (IGS), which the course of the filtered power signal (GS) or a signal derived therefrom during an evaluation period (P) characterized by a predetermined duration includes.

Dishwasher according to one of the preceding claims, characterized in that the evaluation arrangement (44) comprises a recognition member (50) for detecting a concentricity of the circulation pump (22) based on the integrated signal (IGS) or a signal derived therefrom.

Dishwasher according to claim 5 or 6, characterized in that the filtered power signal (GS) or the signal derived therefrom is a time-continuous signal, wherein the integrating member (49) is designed for integrating the values of the signal (GS) during the evaluation period (AP) to form the integrated signal (IGS).

Dishwasher according to claim 5 or 6, characterized in that the filtered power signal or the signal derived therefrom is a discrete-time signal, wherein the integrating member is adapted to accumulate the values of the signal during the evaluation period, so as to form the integrated signal.

Dishwasher according to one of claims 5 to 8, characterized in that the predetermined duration of the evaluation period (AP) is at least 2 seconds and at most 20 seconds, preferably at least 3 seconds and at most 15 seconds, more preferably at least 4 seconds and at most 10 seconds. Dishwasher according to one of claims 6 to 9, characterized in that the detection member (50) is a threshold monitoring member (50) for monitoring a provided for the integrated signal (IGS) or for the signal derived therefrom threshold (SW).

Dishwasher according to the preceding claim, characterized in that the threshold value monitoring element (50) is designed to compare the intended threshold value (SW) with the integrated signal or the signal derived therefrom.

Dishwasher according to claim 10, characterized in that the threshold value monitoring member (50) for comparing the provided threshold with the difference of the integrated signal (IGS) or the signal derived therefrom one of the evaluation periods (AP) and from the integrated signal (IGS) or the derived therefrom signal of the respective subsequent evaluation period (AP) is formed.

13. Dishwasher according to one of the preceding claims, characterized in that the rinse cycle comprises at least one filling sequence (F), in which by the control device (2) openable and closable inlet valve

(18) for filling rinsing liquid (S) into the rinsing chamber (7) and the circulating pump (22) is operated at a constant filling speed (FD), the control device (2) for closing the inlet valve (18) when the concentricity is detected Circulation pump (22) is formed.

14. Dishwasher according to the preceding claim, characterized in that the filling speed (FD) of a cleaning speed (RD) of the circulating pump (22) deviates, which is provided for one of the filling sequence (FS) subsequent cleaning sequence (RS).

15. A method for operating a dishwasher (1), in particular according to one of the preceding claims, with a control device (2) for performing a rinse cycle for cleaning items to be washed, with a rinsing chamber (7) for receiving the items to be washed during the rinse cycle and with a Circulation pump (22) for circulating a in the washing chamber (7) located Rinsing fluid (S), wherein the control device (2) comprises a Rundlaufüberwacht monitoring unit (25) for performing a concentricity test in the circulation pump (22), wherein the concentricity monitoring unit (25) with an electric power consumption of the circulation pump (22) corresponding to the power signal (LS ), characterized in that the power signal (LS) is passed through a filter arrangement (43) of the concentricity monitoring unit (25) with a bandpass characteristic for generating a filtered power signal (GS), and that the filtered power signal (GS) through one of the filter arrangement (43) downstream evaluation arrangement (44) for evaluating the filtered power signal (GS) is evaluated.