DE102015204537A1 - Method for operating a washing machine with improved rinsing phase and this suitable washing machine - Google Patents

Abstract

The invention relates to a method for operating a washing machine 1 with a container 2, a drum 3 for receiving laundry items 4, a drive motor 5 for the drum 3, an impedance sensor 9 in the container 2 for measuring an impedance signal as a function of a composition of an aqueous liquid 7 in the container 2, and a control device 8, wherein subsequent to a washing phase in a rinsing phase, the detergent concentration cten is followed in the rinsing liquid 7 by means of the impedance sensor 9, and wherein the increase in time of the detergent concentration cten is evaluated in view of the further embodiment of the rinsing phase , The invention also relates to a washing machine 1 suitable for carrying out the method.

Description

The invention relates to a method for operating a washing machine with an improved rinsing phase and a washing machine suitable for this purpose. More particularly, the invention relates to a method of operating a washing machine having a container, a drum for receiving laundry, a drive motor for the drum, an impedance sensor (also referred to as an electrochemical impedance sensor) in the container for measuring an impedance signal in response to a composition of an aqueous fluid in the container, and a control device, and a suitable for carrying out this method washing machine.

In a washing machine, laundry is generally treated in a washing phase for cleaning with a detergent containing wash liquor. Detergents contain to form a wash liquor for cleaning laundry in particular surfactants as surface-active substances, which reduce the surface tension of the water in the aqueous solution formed (wash liquor).

Usually, in a washing program following the washing phase, at least one rinsing step is carried out to rinse out the washing liquor enriched with dirt and detergent. In addition to the rinsing time, the rinsing result depends on the amount of water used and the number of rinsing steps, also called rinsing cycles. In order to achieve an acceptable wash result in an acceptable time without undue use of water and energy, an empirically determined number of rinse steps and a rinse duration are generally determined. These can be adjusted by polling a turbidity sensor. If at the end of the washing phase only a very small amount of detergent is present in the items of laundry, it is usually rinsed too long or with too much water. At high residual amounts of detergent in the laundry, which does not cause a significant turbidity of the rinse, they are not completely rinsed from the laundry. Generally, the single rinse step is timed so that the equalization process, i. the concentration balance between irrigation fluid and detergent on the laundry can not be sufficiently considered. So it happens that the rinsing phase is often already finished, although the balancing process is not yet finished. On the other hand, it is often still further flushed, although a compensation process is no longer taking place.

In addition to saving energy and water, a rinsing phase which is optimally matched to a lot of items of laundry also leads in particular to a lower load on the wastewater and a shortened duration of the rinsing phase. The consideration of the actually present in the rinsing liquid detergent concentration or amount in a rinsing phase would therefore be desirable.

The DE 29 17 859 describes a method for monitoring and controlling the program, in particular the water inlet and / or the detergent or detergent addition in automatic washing machines and dishwashers, wherein on the surface tension and / or the water hardness and / or the electrical conductivity of the washing liquid responsive sensors in the Machine are provided, which intervene via an electrical control circuit in the program flow and control the amount of water, the water change and / or the dosage of cleaning or detergent addition.

The DE 100 42 846 A1 describes a method for the qualitative and / or quantitative characterization of polar constituents in liquids by impedance measurement and the application of the method and optionally an electrode arrangement for controlling the surfactant supply due to the characterization of the surfactant content in the washing and / or rinsing water of washing machines.

The DE 42 44 783 C2 describes a method for monitoring and control of the program sequence in a household appliance with several rinses, in which by means of a measuring device, a measured value and its rate of change are determined and adjusted in the amount of water and / or number of rinses in the program flow. In this case, the measured values of two sections in the first rinse are recorded, of which the first is placed at the beginning and the second approximately in the middle of the first rinse, and in the first rinse from the rates of change of the measured values a total rinsing time is derived and in dependence of the determined total rinsing time the subsequent rinses of the program sequence are adjusted accordingly with regard to the amount of water or the number of rinses. In particular, pH value, conductivity turbidity value or temperature may be considered as measured values.

The EP 0 797 761 B1 describes a method for determining the surface tension of a liquid by generating gas bubbles in the liquid, whereafter the surface tension in the liquid is determined by monitoring gas bubbles and wherein the gas bubbles are formed from gas generated in situ.

The EP 2 533 035 A1 describes a device for detecting material properties of a medium, with a measuring device including a sensor device which is in communication with the medium, and a drive device for controlling the sensor device with signals of a predetermined frequency range, and a control device for controlling the operation of the measuring device and specification of predetermined frequency range, wherein the driving means is provided for determining the course of the impedance Z of the medium corresponding to the predetermined frequency range in response to the frequency, and for outputting a detection signal, and the control means is provided for evaluating the detection signal of the drive means, determining a plurality of characteristic Points (P1 to P4) of the course of the impedance Z and generation of a result signal with respect to the properties of the medium. It should thus be possible, for example, to determine whether a wash solution requires a further addition of wax.

• – Zuführen einer Teilmenge eines Waschmittels zu der Wassermenge zur Bildung einer Waschlauge (Schritt 1),
• – Erfassen eines Betrags Z und eines Phasenwinkels φ einer Impedanz der Waschlauge für eine vorbestimmte Anzahl von Frequenzen von Ansteuerungssignalen und Erzeugen einer entsprechenden Anzahl jeweiliger Messwerte (Schritt 2),
• – Ermitteln einer Steigung aus jedem Messwert des Phasenwinkels (Schritt 3),
• – Berechnen eines jeweiligen Mittelwertes aus der Anzahl der Steigungen und den Beträgen der Impedanz (Schritt 4),
• – Ermitteln eines Bestimmungsproduktes MBP aus dem Mittelwert der Steigungen und dem Mittelwert der Beträge der Impedanzen (Schritt 5B),
• – Vergleichen des Bestimmungsproduktes mit einem vorbestimmten Schwellenwert (Schritt 6B), und
• – Wiederholen der Schritte 1 bis 6B, bis das Bestimmungsprodukt gleich oder größer als der Schwellenwert (XB) ist (Schritt 7).

The EP 2 767 825 A1 describes a method for determining a micelle formation concentration in a washing device having an amount of water required for carrying out a washing operation, with the steps

• Feeding a subset of a detergent to the amount of water to form a wash liquor (step 1),
• Detecting an amount Z and a phase angle φ of an impedance of the wash liquor for a predetermined number of frequencies of drive signals and generating a corresponding number of respective measured values (step 2),
• Determining a slope from each measured value of the phase angle (step 3),
• Calculating a respective average of the number of slopes and the amounts of the impedance (step 4),
• Determining a product of determination MBP from the average of the slopes and the mean of the amounts of the impedances (step 5B),
• Comparing the determined product with a predetermined threshold (step 6B), and
• Repeating steps 1 to 6B until the product of determination is equal to or greater than the threshold value (XB) (step 7).

Against this background, the object of the present invention was to provide a method for operating a washing machine, in which a rinsing phase is improved. The method should allow the most efficient and water-saving rinsing of laundry items. The object of the invention was also to provide a suitable for carrying out this method washing machine.

According to the invention, this object is achieved by a method and a washing machine according to the independent patent claims. Preferred embodiments of the invention are listed in the respective dependent claims. Preferred embodiments of the method correspond to preferred embodiments of the washing machine, even if not separately pointed out here in each case.

The invention thus relates to a method for operating a washing machine with a container, a drum for receiving items of laundry, a drive motor for the drum, an impedance sensor in the container for measuring an impedance signal in dependence on a composition of an aqueous liquid in the container, and a control device, wherein subsequent to a washing phase in a rinsing phase, the detergent concentration c _th in the rinsing liquid is followed by means of the impedance sensor, and wherein the increase in time of the detergent concentration c _{th is} evaluated in view of the further embodiment of the rinsing phase.

In addition to one or more surfactants, in particular ionic or nonionic surfactants, a laundry detergent generally also comprises enzymes, bleaches and / or fragrances. In the present case, in particular, the detection of surfactants is concerned, so that a detergent concentration means in particular a surfactant concentration. The term "surfactant" as used herein means a single surfactant as well as a mixture of different surfactants.

In the method according to the invention, the detection of a sharp increase in the detergent concentration indicates greater amounts of detergent still present in the laundry items or the wash liquor passing through them. If, on the other hand, only a small increase is detected or if the increase in concentration is completely absent, this indicates little detergent or already completely rinsed in the laundry items or the wash liquor passing through them. completely washed laundry items. As a result, a further rinsing step can thus be coordinated therewith, for example by adjusting its length to the detergent concentrations found.

Herein, an "aqueous liquid" may mean water, a wash liquor or a rinse liquid.

For the purposes of the invention, a container is understood to mean a suds container, a part of the container or a component in which the aqueous liquid provided during operation of the washing machine is located or flows past. Thus, the impedance sensor in the tub of a washing machine as well as in a measuring container which is communicatively connected to the tub, or in a liquid line through which the aqueous liquid flows during operation of the washing machine may be arranged. The latter could be particularly advantageous if the washing machine has a pumping system, which discharges the aqueous liquid during operation of the washing machine from a tub and feeds again.

• (a) Messung der Waschmittelkonzentration c_ten in einer ersten Spülflüssigkeit mittels des Impedanzsensors solange, bis hinsichtlich der Waschmittelkonzentration c_ten eine vorgegebene maximale Konzentration c_ten ^max oder eine vorgegebene minimale zeitliche Konzentrationsänderung (dc_ten/dt)_min erreicht ist;
• (b) Entfernung der im Schritt (a) vermessenen ersten Spülflüssigkeit;
• (c) Zugabe einer vorbestimmten Wassermenge a₁ und Messung in der dadurch gebildeten zweiten Spülflüssigkeit der Waschmittelkonzentration c_ten in Abhängigkeit von der Zeit t mittels des Impedanzsensors; und
• (d) Auswertung der zeitlichen Zunahme der Waschmittelkonzentration c_ten in Hinblick auf die Ausgestaltung mindestens des nächsten Spülschrittes für die Wäschestücke;

wobei für die Messung ein in der Steuereinrichtung hinterlegter Zusammenhang zwischen Impedanzsignal und Waschmittelkonzentration verwendet wird.In a preferred embodiment of the process according to the invention, the following steps are subsequently carried out on the washing phase:

• (a) measurement of the detergent concentration is c _th in a first rinsing liquid by means of the impedance sensor until terms of detergent concentration c _th a predetermined maximum concentration c _th ^maximum or a predetermined minimum time concentration change (dc _th / dt) _min reached;
• (b) removing the first rinse liquid measured in step (a);
• (c) adding a predetermined amount of water a ₁ and measuring in the second rinsing liquid of the detergent concentration c _th thus formed as a function of the time t by means of the impedance sensor; and
• (d) evaluating the time increase of the detergent concentration c _th with regard to the design of at least the next washing step for the laundry items;

wherein for the measurement a stored in the control device relationship between impedance signal and detergent concentration is used.

During the step (b), a spin may also be performed, or the spin may be performed following the step (b).

• (a1) Messung der Waschmittelkonzentration c_ten in einer ersten Spülflüssigkeit mittels des Impedanzsensors solange, bis hinsichtlich der Waschmittelkonzentration c_ten eine vorgegebene maximale Konzentration c_ten ^max1 oder eine vorgegebene minimale zeitliche Konzentrationsänderung (dc_ten/dt)_min1 erreicht ist;
• (b1) Entfernung der im Schritt (a1) vermessenen ersten Spülflüssigkeit durch Abpumpen;
• (c1) Zugabe einer vorbestimmten Wassermenge a₁;
• (c2) Messung der Waschmittelkonzentration c_ten in der im Schritt (c1) gebildeten zweiten Spülflüssigkeit mittels des Impedanzsensors solange, bis hinsichtlich der Waschmittelkonzentration c_ten eine vorgegebene maximale Konzentration c_ten ^max2 oder eine vorgegebene minimale zeitliche Konzentrationsänderung (dc_ten/dt)_min2 erreicht ist;
• (d1) Ermittlung der zeitlichen Dauer Δt von Schritt (c2); und
• (e1) Auswertung der zeitlichen Dauer Δt von Schritt (c2) in Hinblick auf die Ausgestaltung mindestens des nächsten Spülschrittes;

wobei für die Messung ein in der Steuereinrichtung hinterlegter Zusammenhang zwischen Impedanzsignal und Waschmittelkonzentration verwendet wird.In an even more preferred embodiment of the process according to the invention, the following steps are subsequently carried out on the washing phase:

• (a1) measurement of the detergent concentration c _th in a first rinsing liquid by means of the impedance sensor until terms of detergent concentration c _th a predetermined maximum concentration c _th ^max1 or a predetermined minimum time concentration change (dc _th / dt) is reached _min1;
• (b1) removal of the first flushing liquid measured in step (a1) by pumping;
• (c1) adding a predetermined amount of water a ₁ ;
• (c2) measuring the detergent concentration c _th in the step (c1) formed second rinsing liquid by means of the impedance sensor until terms of detergent concentration c a predetermined maximum concentration c _th ^max2 or a predetermined minimum time concentration change (dc _th / dt) _{min2 th} achieved is;
• (d1) determining the time duration Δt of step (c2); and
• (e1) evaluating the time duration Δt of step (c2) with regard to the configuration of at least the next rinsing step;

wherein for the measurement a stored in the control device relationship between impedance signal and detergent concentration is used.

In this case, the design of at least the next rinsing step generally takes place on the basis of rinsing programs stored in the control device for different time durations Δt of step (c2).

• (a1) Messung der Waschmittelkonzentration c_ten in einer ersten Spülflüssigkeit mittels des Impedanzsensors unter Verwendung eines in der Steuereinrichtung hinterlegten Zusammenhangs zwischen Impedanzsignal und Waschmittelkonzentration solange, bis hinsichtlich der Waschmittelkonzentration c_ten eine vorgegebene maximale Konzentration c_ten ^max oder eine vorgegebene minimale zeitliche Konzentrationsänderung (dc_ten/dt)_min erreicht ist;
• (b1) Entfernung der im Schritt (a1) vermessenen ersten Spülflüssigkeit durch Abpumpen;
• (c1) Zugabe einer vorbestimmten Wassermenge a₁; und
• (c2) Messung der Waschmittelkonzentration c_ten in der im Schritt (c1) gebildeten zweiten Spülflüssigkeit mittels des Impedanzsensors für einen vorgegebenen Zeitraum Δt_set;
• (d2) Registrierung der nach Ablauf von Δt_set gemessenen Waschmittelkonzentration c_ten und/oder der zeitlichen Konzentrationsänderung (dc_ten/dt); und
• (e2) Auswertung der im Schritt (d2) registrierten Waschmittelkonzentration c_ten und/oder der zeitlichen Konzentrationsänderung (dc_ten/dt) in Hinblick auf die Ausgestaltung mindestens des nächsten Spülschrittes unter Verwendung eines in der Steuereinrichtung hinterlegten Zusammenhangs zwischen Impedanzsignal und Waschmittelkonzentration;

wobei für die Messung ein in der Steuereinrichtung hinterlegter Zusammenhang zwischen Impedanzsignal und Waschmittelkonzentration verwendet wird. In a preferred alternative embodiment of the process according to the invention, the following steps are carried out subsequent to the washing phase:

• (a1) measurement of the detergent concentration c _th in a first rinsing liquid by means of the impedance sensor using a stored in the control means the relationship between impedance signal and detergent concentration until terms of detergent concentration c _th a predetermined maximum concentration c _th ^maximum or a predetermined minimum time concentration change (dc _ten / dt) _{min is} reached;
• (b1) removal of the first flushing liquid measured in step (a1) by pumping;
• (c1) adding a predetermined amount of water a ₁ ; and
• (c2) measuring the detergent concentration c _th in the second rinsing liquid formed in step (c1) by means of the impedance sensor for a predetermined period Δt _set ;
• (d2) registration of the detergent concentration c _th measured after expiration of Δt _set and / or the change in the concentration over time (dc _ten / dt); and
• (e2) evaluation of the detergent concentration c _th registered in step (d2) and / or the change in the concentration over time (dc _ten / dt) with regard to the configuration of at least the next rinsing step using a stored in the controller relationship between impedance signal and detergent concentration;

wherein for the measurement a stored in the control device relationship between impedance signal and detergent concentration is used.

Here, the embodiment takes place at least the next rinse step generally based on in the control device for different concentrations c _th and / or temporal gradient of the concentration (dc _th / dt) deposited washing programs.

In both of the aforementioned alternative embodiments of a method according to the invention, the amount of water a ₁ is preferably selected as a function of a load of laundry items, ie a size of a laundry item in the drum. This takes into account the fact that for larger quantities of laundry, based on a certain amount of water used, a larger and more rapid increase in the detergent concentration is to be expected. The addition of the amount of water a ₁ generally indicates the beginning of a next rinse step.

Also in the two aforementioned embodiments, during the step (b1) a spin can be carried out or the spin can be carried out or continued after the step (b1).

The determination of the loading amount can be made by measuring the weight gain of the drum due to loading with laundry or by analyzing the absorbency of water by analyzing the change in hydrostatic pressure during addition of water to dry laundry in a wetting phase. For this purpose, a hydrostatic sensor is preferably present in a washing machine according to the invention. Particularly advantageous is then also a water meter, i. a measuring device for determining the filled amount of water or the amount of filled washing liquor, present. Thus, for example, the hydrostatic pressure p measured with the aid of the hydrostatic sensor can be compared with the filled-in amount of water. The laundry items in the drum absorb water. The absorbed water can not contribute to an increase of the hydrostatic pressure. By comparing the measured hydrostatic pressure p and the accumulated amount of water - the absolute values and their temporal change - with corresponding values stored in the control device of the washing machine for the moistening of laundry, the loading amount of laundry and, if necessary, the degree of moisture penetration (wetting degree) determine.

Wetting phase is understood to mean the phase in a washing program in which items of laundry to be cleaned and in particular to be washed with wash liquor are wetted with a wash liquor to be used, generally up to a saturation of the laundry items with the wash liquor. In this case, the laundry items are generally weak or not at all moved. It is therefore in a wetting phase generally only a small separation of dirt from the laundry to be washed. In particular, a laundry drum in a wetting phase is preferably not rotated at a speed greater than 25 revolutions per minute.

A wash phase generally follows a wetting phase. If a washing program is signaled that sufficient wetting of the laundry is given, for example, by reaching a predetermined threshold value p ₁ for the hydrostatic pressure p and a predetermined threshold value (Δp / Δt) ₁ for the temporal gradient of the hydrostatic pressure p Generally the washing phase.

According to the invention, it is preferred that before the measurement of the detergent concentration by the impedance sensor, a movement program of the drum deposited in the control device is carried out. In this case, it is again preferred that different movement programs of the drum are carried out for different load quantities with laundry items, wherein a relationship between loading amount and movement program of the drum is stored in the control unit.

Moreover, a method is preferred in which a movement program is carried out when _{falling below} a predetermined value c _{set1 of} the detergent _{concentration} or exceeding a predetermined time interval Δt _set for reaching a predetermined value c _{set2 of} the detergent _{concentration} , preferably before the next rinsing step greater load of laundry than in the event that these conditions are not met. As a result, the presence of a comparatively small amount of surfactants is compensated by an increased flow of laundry to support the dilution / leaching of surfactant from the laundry, thus the sensitivity of the inventive method is improved.

A higher laundry load can, for example, by a larger entry mechanical energy or a reinforced flushing mechanism can be achieved. The purging mechanism is herein understood to mean the introduction of mechanical energy into the laundry to be rinsed in the drum. In general, the washing mechanism WM includes a turn-on time [in%], a duration of a reversing cycle [in seconds] and a rotational speed [rpm] of the drum. When _{falling below} a predetermined value c _{set1 of} the detergent _{concentration} or exceeding a predetermined time interval .DELTA.t _set for reaching a predetermined value c _{set2 of} the detergent _{concentration} , preferably the on time [%] and the speed [rpm] of the drum are respectively increased and Duration of a Reversierzyklus [in sec] compared to an otherwise provided rinsing step.

The turn-on time is that time portion of the wash phase during which the drum is rotating. This turn-on time is preferably 60 to 70% in a first flushing step. For example, given a low detergent concentration, the on-time would be increased by at least 20% in a preferred embodiment.

A reversing cycle is generally the period that results from the periods: rotating the drum in one direction, resting the drum, rotating the drum in the opposite direction, resting the drum. If a reversing cycle is carried out in a rinsing step, then this preferably has a duration of 30 to 50 seconds. With a low detergent concentration determined according to the invention, the reversing cycle is thus reduced by, for example, at least 20%.

Alternatively, the higher laundry throughput can be achieved by an improved circulation of the rinsing liquid. In one embodiment of the washing machine with scooping devices, which receives the aqueous liquid, or the rinsing liquid when rotating the drum in the bottom of the tub and transported by the rotation again above the laundry items selbige, also a motion program can be selected in which the speed of the Drum is chosen so that a maximum scooping power is achieved.

In addition, a higher laundry flow in washing machines with a pumping system can be achieved by a movement program is selected in which the drum is rotated at least one speed at which the laundry is applied to the drum shell, and at the same time on the pumping system, the aqueous liquid or the rinsing liquid is sprayed on the adjacent laundry items from the inside. The liquid is conveyed through the laundry by the centripetal force.

In general, in the method according to the invention, the design of the rinsing phase comprises the number of further rinsing steps and / or the amount of water still to be used.

According to the invention, it is preferred that the type and / or amount of soiling of the laundry items to be washed be taken into account in the measurement of the detergent concentration, wherein a relationship between impedance signal and detergent concentration for different types and / or amounts of soiling of the items to be washed is stored in the control device ,

This embodiment advantageously takes into account the effect of small amounts of dirt remaining in the rinsing liquid. For example, when contaminated with oil, nonionic surfactants in particular would be able to dissolve somewhat in the oil and thus be no longer available when determining the detergent concentration and, in particular, a surfactant concentration by means of the impedance sensor. On the other hand, ionic surfactants can be trapped to some extent by ion-containing contaminants, i. are consumed so that they are no longer available for a determination of the surfactant concentration and in particular a surfactant concentration by means of the impedance sensor.

Type and / or amount of contamination can be set by a user of the washing machine or measured by suitable sensors. In particular, the inventively provided impedance sensor is suitable for this purpose. In addition, however, other sensors such as a turbidity sensor can also be used. If a measurement by suitable sensors is to take place in the washing machine, this measurement is generally carried out during the wetting phase before the start of a washing phase or at a predetermined time after the start of the washing phase. Although in a wetting phase, the proportion of detectable in the wash liquor soiling is low, but on the other hand, a possibly interfering effect of surfactants on the measurement is relatively small, since possibly only a small amount of surfactants is rinsed. Depending on the procedure, it may be provided here that initially only water and then further water and / or surfactant-containing detergent are added in a wetting phase.

In the method according to the invention, the measurement of the detergent concentration and in particular the change over time of the Detergent concentration by the impedance sensor generally characterized in that impedance signals are picked up and evaluated by the impedance sensor by the electrical impedance sensor with varying frequencies is applied and the impedance signals are evaluated in terms of the phase angle φ and the amount of impedance, from which the detergent concentration c _th to determine. Phase angle φ and amount of impedance can be evaluated in embodiments of the invention in terms of the type, amount and concentration of surfactants.

For measurement, an impedance spectrum is generally recorded using a suitable electrode system as the impedance sensor. In general, the impedance of an electrochemical system is investigated as a function of the frequency of an alternating voltage. For illustration, various representations are known to those skilled in the art, such as the Nyquist representation, in which the real part or the imaginary part of the impedance is represented as a function of the applied AC voltage frequency. To characterize the impedance spectrum are generally suitable in the investigation of detergent-containing, especially surfactant-containing aqueous liquids such as rinse liquids few characteristic points (see. EP 2 767 825 A1 ), for example at the maximum of the imaginary part in a lower frequency range or at the minimum of the imaginary part in an upper frequency range. From the impedance and frequency values at the characteristic points, characteristic parameters can generally be derived for a surfactant-containing aqueous liquid. For example, the conductivity of the aqueous liquid can be determined from the real part of a point. By evaluating the impedance at this point and the frequency at another point, it is generally possible to determine the capacitance of the so-called conductivity measuring cell formed by the impedance sensor and the aqueous liquid. Another measure, which depends on the properties of the wash liquor, is the flattening of a semicircle in the Nyquist representation, which can be determined by the ratio of height to width of the semicircle. The evaluation is done using formulas known to those skilled in the art.

In a particularly preferred embodiment of the invention, the impedance signals are evaluated in terms of electrical conductivity as a measure of a water hardness.

Preferably, the impedance signals are evaluated with regard to the composition of a detergent, in particular the surfactants contained in it, wherein in the control device for various components and quantities of a detergent impedance signals are stored. This may be an evaluation of the nature and proportions of the components contained in the detergent, e.g. Proportion of nonionic and ionic surfactants, proportion of bleaching agents and / or of enzymes. In this way, the rinsing phase to be performed can be better adapted to the laundry items in the drum and the detergent used surfactant. If the composition of a detergent is to be determined on the basis of the measurement of an impedance, a further impedance sensor can advantageously be arranged in an induction bowl or at another location in the washing machine at which possible contaminations have no or minimal influence on such an analysis.

In the method according to the invention, the rinsing phase is preferably ended when, at the end of a rinsing step, a predetermined minimum detergent _{concentration} c _{tenmin has been} reached. When carrying out the method according to the invention, therefore, the individual steps, in particular rinsing steps, eg the step sequences (a1), (b1), (c1), (c2), (d1), (e1) or (a1), (b1), (c1), (c2), (d2), (e2) are performed several times until a desired rinsing result is achieved.

The embodiment of the rinsing phase preferably comprises a time-optimized and an water-volume-optimized rinse program, the number of rinsing steps being smaller and the individual rinsing water amounts being greater in the time-optimized rinsing program than in the rinsing program optimized in terms of water quantity.

The invention also relates to a washing machine with a container, a drum for receiving laundry, a drive motor for the drum, an impedance sensor in the container for determining an impedance signal in dependence on a composition of an aqueous liquid in the container, and a control device, wherein the control device is set up to carry out a method in which subsequent to a washing phase in a rinsing phase, the detergent concentration c _{th is followed} in the rinsing liquid by means of the impedance sensor, wherein the temporal increase of the detergent concentration c _{th is} evaluated in view of the further embodiment of the rinsing phase.

In a preferred washing machine according to the invention, a temperature sensor is arranged in the container and in the control device there is a relationship between different temperature values measured with the temperature sensor Impedance signals and detergent concentrations deposited.

The washing machine according to the invention makes it possible to dispense with the turbidity sensor often present in a washing machine. However, embodiments of the washing machine according to the invention may also be supplemented by a turbidity sensor.

A washing machine used herein also generally has a heater and a liquor drain system with a drain pump arranged at the bottom of a container. In addition, a washing machine used herein also generally includes laundry drippers and / or scooping devices.

Finally, the washing machine according to the invention may be a washing machine as such or a washer-dryer, ie a device which has the functions of a dryer and a washing machine.

The washing machine according to the invention preferably has an acoustic and / or optical display means for displaying one or more operating states. An optical display means may be, for example, a liquid crystal display on which certain prompts or hints are given. It may also or alternatively light LEDs in one or more colors light up. For example, it can be displayed on the basis of differently colored representations how the rinsing phase is carried out on the basis of the measurements provided according to the invention. These include in particular a length, or the number of rinsing steps still to be performed and / or the amount of water to be used. It can also be displayed, for example, whether a wash program is time-optimized or water-optimized.

In embodiments of the invention, the knowledge of the amount of water flowing into the container or water liquor is important. Preferably, therefore, in the washing machine according to the invention a measuring device for determining the filled amount of water is present, for example, a timing device for determining the opening period of a feed valve for the water or a liquid amount measuring device for measuring the amount of water filled.

The invention has numerous advantages. A method is provided for operating a washing machine, in which a rinsing phase can proceed more efficiently, advantageously also saving water and shortening the entire rinsing time. The method allows a simple and accurate monitoring and control of a rinsing phase. By determining the actual detergent concentration and in particular surfactant concentration in a rinsing phase, the number and design of the individual rinsing steps as well as the total amount of water to be used can be determined particularly accurately. It is possible to consume only as much water as is necessary for a certain amount of laundry and detergent quantity. Unnecessarily long rinsing phases can be reduced to the required number of rinsing steps without worsening the rinsing result. In particular, an individual control of the rinsing phase is possible.

In addition, the invention enables the determination and consideration of the water hardness in a simple manner. The influence of remaining residual amounts of dirt can be taken into account.

Moreover, in embodiments, the invention makes it possible to determine the composition and thus properties of a large number of different detergents, so that the embodiment of the rinsing phase can take into account even better the surfactant-containing detergent used and to be rinsed out in the rinsing phase.

The invention is illustrated below with reference to a non-limiting first embodiment shown in the single figure for a washing machine according to the invention, in which a method according to the invention can be carried out. Shown is a schematic representation of the invention relevant to the parts of the washing machine.

The washing machine 1 the figure has a tub 2 in which a drum 3 rotatably mounted and by the drive motor 5 is drivable. For improved ergonomics is the axis of rotation 19 the drum 3 from the horizontal by a small angle (eg 13 °) directed forward above, allowing the user of the washing machine 1 easier access and insight into the interior of the drum 3 Has. By this arrangement, in cooperation with specially shaped Wäschemitnehmern 14 and scooping devices 17 for the wash liquor 7 on the inner surface of the drum shell also also an intensification of the flood of the laundry items 4 with washing liquor 7 reached.

In the dispenser bowl 12 is an impedance sensor 10 arranged, which is generally an electrode system of a plurality of electrodes, for example, two capacitor plates. With the help of impedance sensor 10 can one in the Einspülschale 12 existing detergent or an aqueous liquid containing this detergent are analyzed, to obtain information about the detergent and thus about the design of a washing program and in particular a rinsing phase.

The washing machine 1 also has a liquor inlet system, which is a water connection fitting for the domestic water network 20 , an electrically controllable valve 21 and a supply line 13 to the tub 2 optionally, including the Waschmitteleinspülschale 12 can be guided, from the incoming water detergent portions in the tub 2 can transport. It is also in the tub 2 a heating device 16 for heating water or washing liquor 7 , The valve 21 as well as the heater 16 can by a control device 8th in response to a program schedule associated with a timed program and / or the achievement of certain measurements of parameters such as liquor level, liquor temperature, drum speed, etc. within the washing machine 1 can be bound.

6 means a pressure sensor, ie a sensor for measuring the hydrostatic pressure in the tub 2 , The hydrostatic pressure p results from the level of the in the tub 2 training free fleet 7 ie not in the laundry 4 bound aqueous liquid 7 , In addition, the washing machine includes 1 a measuring device 15 for determining the filled amount of water. It can be designed, for example, as a water meter or as a flowmeter. In the case of a flow meter, the amount of water flowed in is calculated in conjunction with a detected filling time. The flow can also be determined by measuring the time to reach a given level height, which corresponds to a certain fixed amount of water. 18 means a drain pump for pumping out the wash liquor 7 ,

Denoted in the figure 9 an impedance sensor in the tub 2 , Whose structure of electrodes is not shown here in detail. For carrying out the method according to the invention and of embodiments thereof, the signals of the impedance sensors 9 and 10 and the rotational speed of the drum 3 their load on laundry items, the hydrostatic pressure, etc., as well as the measured values of the measuring device 15 the control device 8th fed.

11 means a display device, with the process parameters, in particular with respect to the time optimized drainage of a rinsing phase (eg represented by a green light emitting diode) or a non-optimized running (eg represented by a red light emitting diode) are displayed. A user of the invention can also be indicated in particular whether a rinsing phase takes place in a time-optimized or liquid-quantity-optimized manner.

LIST OF REFERENCE NUMBERS

1

 Washing machine

2

tub

3

 drum

4

 laundry

5

 drive motor

6

 pressure sensor

7

 aqueous liquid, free liquor, wash liquor

8th

 control device

9

 Impedance sensor in the tub; Electrode arrangement for measuring the impedance

10

 Impedance sensor in the induction bowl; Electrode arrangement for measuring the impedance

11

 display device

12

 (Detergent) dispensing shell

13

 Supply line to the tub

14

 laundry agitator

15

 Measuring device for determining the amount of water filled

16

 heater

17

 scoop

18

Pump, drain pump

19

axis of rotation

20

Water supply, domestic water network, water supply

21

(electrically controllable) valve

22

 temperature sensor

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 2917859 [0005]
• DE 10042846 A1 [0006]
• DE 4244783 C2 [0007]
• EP 0797761 B1 [0008]
• EP 2533035 A1 [0009]
• EP 2767825 A1 [0010, 0041]

Claims (15)

Method for operating a washing machine ( 1 ) with a container ( 2 ), a drum ( 3 ) for receiving laundry items ( 4 ), a drive motor ( 5 ) for the drum ( 3 ), an impedance sensor ( 9 ) in the container ( 2 ) for measuring an impedance signal as a function of a composition of an aqueous liquid ( 7 ) in the container ( 2 ), and a control device ( 8th ), characterized in that following a washing phase in a rinsing phase, the detergent concentration c _th in the rinsing liquid ( 7 ) by means of the impedance sensor ( 9 ), wherein the time increase of the detergent concentration c _{th is} evaluated with regard to the further embodiment of the rinsing phase. A method according to claim 1, characterized in that following the washing phase, the following steps are carried out: (a) Measurement of the detergent concentration c _th in a first rinsing liquid ( 7 ) by means of the impedance sensor ( 9 ) until, with regard to the detergent concentration c _th, a predefined maximum concentration c _th ^max or a predefined minimum change in the temporal concentration (dc _ten / dt) _{min is} reached; (b) removing the first rinse liquid measured in step (a); (c) addition of a predetermined amount of water a ₁ and measurement in the second rinse liquid formed thereby ( 7 ) of the detergent concentration c _th in dependence on the time t by means of the impedance sensor ( 9 ); and (d) evaluating the time increase of the detergent concentration c _th with regard to the configuration of at least the next washing step for the laundry items ( 4 ); wherein for the measurement a in the control device ( 8th ) stored relationship between impedance signal and detergent concentration is used. A method according to claim 1 or 2, characterized in that following the washing phase, the following steps are carried out: (a1) Measurement of the detergent concentration c _th in a first rinsing liquid ( 7 ) by means of the impedance sensor ( 9 ) until, with regard to the detergent concentration c _th, a predefined maximum concentration c _th ^max1 or a predefined minimum temporal concentration change (dc _ten / dt) _{min1 is} reached; (b1) removal of the first flushing liquid measured in step (a1) by pumping; (c1) adding a predetermined amount of water a ₁ ; (c2) Measurement of the detergent concentration c _th in the second rinsing liquid formed in step (c1) ( 7 ) by means of the impedance sensor ( 9 ) until with regard to the detergent concentration c _th a predetermined maximum concentration c _th ^max2 or a predetermined minimum change in the time concentration (dc _ten / dt) _{min2 is} reached; (d1) determining the time duration Δt of step (c2); and (e1) evaluating the time duration Δt of step (c2) with regard to the configuration of at least the next rinsing step; wherein for the measurement a stored in the control device relationship between impedance signal and detergent concentration is used. A method according to claim 1 or 2, characterized in that following the washing phase, the following steps are carried out: (a1) Measurement of the detergent concentration c _th in a first rinsing liquid ( 7 ) by means of the impedance sensor ( 9 ) until with respect to the detergent concentration c _ten ^max a predetermined maximum concentration c _th or a predetermined minimum temporal concentration change (dc _ten / dt) _{min is} reached; (b1) Removal of the first rinsing liquid measured in step (a1) ( 7 ) by pumping; (c1) adding a predetermined amount of water a ₁ ; and (c2) measuring the detergent concentration c _th in the second rinsing liquid formed in step (c1) ( 7 ) by means of the impedance sensor ( 9 ) for a given period Δt _set ; with regard to the detergent concentration c _th and / or a predetermined minimum change in the temporal concentration (dc _ten / dt) _{min is} reached; (d2) registration of the detergent concentration c _th measured after expiration of Δt _set and / or the change in the concentration over time (dc _ten / dt); and (e2) evaluating the detergent concentration c _th registered in step (d2) and / or the temporal concentration change (dc _ten / dt) with regard to the configuration of at least the next rinsing step; wherein for the measurement a in the control device ( 8th ) stored relationship between impedance signal and detergent concentration is used. Method according to one of claims 1 to 4, characterized in that before the measurement of the detergent concentration by the impedance sensor ( 9 ) in the control device ( 8th ) stored movement program of the drum ( 3 ) is carried out. A method according to claim 5, characterized in that for different load amounts with laundry ( 4 ) different movement programs of the drum ( 3 ), wherein in the control device ( 8th ) a relationship between loading amount and movement program of the drum ( 3 ) is deposited. A method according to claim 5 or 6, characterized in that falls below a predetermined value c _{set1 of} the detergent _{concentration} or exceeding a predetermined time interval .DELTA.t _set for achieving a predetermined value c _set2 the detergent _{concentration,} a movement program is performed, preferably before the next rinsing step, which includes a greater laundry throughput than in the case that does not meet these conditions are. Method according to one of claims 1 to 7, characterized in that the embodiment of the rinsing phase comprises the number of further rinsing steps and / or the amount of water still to be used. Method according to one of claims 1 to 8, characterized in that in the measurement of the detergent concentration type and / or amount of contamination of the laundry items to be washed ( 4 ), wherein in the control device ( 8th ) a correlation between impedance signal and detergent concentration for different types and / or quantities of soiling of the laundry items to be washed ( 4 ) is deposited. Method according to one of claims 1 to 9, characterized in that the measurement of the change in time of the detergent concentration by the impedance sensor takes place by impedance signals are recorded and evaluated by the impedance sensor is acted upon by the impedance sensor with alternating electrical voltage with varying frequencies and the impedance signals in With regard to the phase angle φ and the amount of impedance are evaluated in order to determine the detergent concentration c _th . A method according to claim 10, characterized in that the impedance signals are evaluated with regard to the composition of a detergent, in particular the surfactants contained in it, wherein in the control device ( 8th ) for various components and quantities of a detergent impedance signals are deposited. Method according to one of claims 1 to 11, characterized in that the rinsing phase is terminated when in the rinsing liquid ( 7 ) reaches a predetermined minimum detergent _{concentration} c _tenmin at the end of a rinsing step. Method according to one of claims 1 to 12, characterized in that the design of the rinsing phase comprises a time-optimized and a water-volume-optimized wash program, the number of rinsing steps smaller and the individual rinse water quantities are greater than in the water-volume-optimized rinse program in the time-optimized rinse program. Washing machine ( 1 ) with a container ( 2 ), a drum ( 3 ) for receiving laundry items ( 4 ), a drive motor ( 5 ) for the drum ( 3 ), an impedance sensor ( 6 ) in the container ( 2 ) for determining an impedance signal in dependence on a composition of an aqueous liquid ( 7 ) in the container ( 2 ), and a control device ( 8th ), characterized in that the control device ( 8th ) is set up for carrying out a method in which, following a washing phase in a rinsing phase, the detergent concentration c _th in the rinsing liquid ( 7 ) by means of the impedance sensor ( 9 ), wherein the time increase of the detergent concentration c _{th is} evaluated with regard to the further embodiment of the rinsing phase. Washing machine ( 1 ) according to claim 14, characterized in that in the container ( 2 ) a temperature sensor ( 22 ) and in the control device ( 8th ) for different with the temperature sensor ( 22 ) measured temperature values a relationship between impedance signals and detergent concentrations is deposited.

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