EP3268529A1

EP3268529A1 - Method for operating a washing machine having an electrochemical sensor and washing machine suitable therefor

Info

Publication number: EP3268529A1
Application number: EP16704234.0A
Authority: EP
Inventors: Dirk Aurich; Andreas Bischof; Michael Munick; Hartmut Schaub
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2015-03-13
Filing date: 2016-02-15
Publication date: 2018-01-17
Anticipated expiration: 2036-02-15
Also published as: EP3268529B1; DE102015204540A1; WO2016146313A1; CN107407034B; CN107407034A

Abstract

The invention relates to a method for operating a washing machine (1), comprising a container (2), a drum (3) for accommodating laundry items (4), a drive motor (5) for the drum (3), an electrochemical sensor (9) in the container (2) for measuring an electrochemical signal in dependence on a composition of an aqueous liquid (7) in the container (2), and a control device (8), wherein the following steps are performed: (a) providing a detergent-containing aqueous liquid (7) in the container (2); (b) rotating the drum (3) in accordance with a predetermined motion program; (c) ending rotational motion of the drum (3) and allowing the detergent-containing aqueous liquid (7) to rest until a specified calmed state of the detergent-containing aqueous liquid (7) is achieved; and (d) measuring the concentration c_ten of a detergent in the detergent-containing aqueous liquid (7) provided in step (a) by recording and evaluating electrochemical signals of the electrochemical sensor (9) by using a relationship between electrochemical signals and detergent concentrations, which relationship is stored in the control device (8). The invention further relates to a washing machine (1) suitable for performing the method.

Description

Method for operating a washing machine with an electrochemical sensor and suitable for this purpose

Washing machine

The invention relates to a method for operating a washing machine with an electrochemical sensor and a washing machine suitable for this purpose. The invention relates in particular 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 electrochemical sensor in the container for determining an electrochemical signal as a function of a composition of an aqueous liquid 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. In addition, after a rinsing phase with water in which wash liquor and / or soiling present in or on the laundry are removed, a treatment of the laundry with a fabric softener is frequently carried out. For reasons of cost and environmental protection, it makes sense to use an optimum amount of laundry treatment agent (in particular laundry detergent and softener). An overdose but also an underdose should be avoided. In particular, an incorrect dosage of the detergent can lead to effervescence (overdosing) or to a poor washing performance (underdosing). To prevent this from happening, monitoring and optimal adjustment of detergent concentration is desirable.

Therefore, a washing machine has been proposed which has an optimum amount of e.g. Detect detergent and a user of the washing machine on a display display a dosage recommendation with a precise indication of an amount to be used, for example. Can give detergent.

WO 03/029550 A1 describes a process-controlled domestic appliance with a microcomputer and a display for texts, in which a display panel for the Display of the expected in a work process (eg a wash program) required amount of additives (eg detergent) is present. The household appliance has a device by means of which, for example, a washing process additive can be supplied, the dosage must be made by an operator.

To save detergent, it makes sense to dose a quantity of detergent depending on the type and strength of the pollution of the laundry to be washed. A detergent dosage optimally adapted to a lot of items of laundry leads, in addition to a saving of energy and water, in particular also to a lower load on the wastewater.

DE 29 17 859 describes a method for monitoring and controlling the program, in particular the water inlet and / or the cleaning or detergent addition in automatic washing machines and dishwashers, wherein the surface tension and / or the water hardness and / or the electrical conductivity of the Washing liquid responsive sensors are provided in the machine, 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.

EP 2 533 035 A1 describes a device for detecting material properties of a medium, comprising a measuring device including a sensor device, which is in communication with the medium, and a control 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 the 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 generating 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.

EP 2 767 825 A1 describes a method and an apparatus for determining a micelle formation concentration. The process is carried out in a washing device which has a quantity of water required for carrying out a washing process, 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).

For monitoring the concentration of detergent or other additives in the aqueous liquid in a tub, optical or electrochemical sensors are generally employed, e.g. Turbidity sensors, impedance sensors. It should be noted that detergents for forming a wash liquor for cleaning laundry items in particular contain surfactants as surface-active substances, which reduce the surface tension of the water in the aqueous solution formed (wash liquor), since the surfactants preferably on the surface and thus at an interface adsorb. In particular, it is therefore necessary to monitor a surfactant concentration in an aqueous liquid in the tub.

The signals of the sensors can be falsified and, if necessary, can only be evaluated poorly or not at all if the aqueous liquid to be measured is present is not sufficiently calm and / or too much foam is present in the aqueous liquid. This can lead, in particular when using impedance sensors as electrochemical sensors, to the fact that no evaluable results are obtained.

EP 0 383 218 B1 describes a method for controlling the rinsing of a program-controlled washing machine, which carries out a plurality of rinse programs following a washing process, wherein the electrical conductivity of the rinse water is measured and the rinse is ended when the difference between the measured conductance and a reference conductance falls below a predetermined level, wherein the conductance measurement is carried out in a section of the drain line, in which after emptying the washing machine room still liquid, and the conductivity measurement is carried out after completion of a rinse on the standing in the section rinse water, and in dependence on the result of conductance measurement It is decided whether another rinsing process is carried out. Preferably, the conductivity measurement is carried out in a calmed pump sump.

Against this background, the object of the present invention was to provide a method for operating a washing machine, which is improved with regard to the measurement of electrochemical signals, in particular of impedance signals of an impedance sensor. The method should preferably allow the simplest possible and / or accurate monitoring of a wash program. 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 laundry, a drive motor for the drum, an electrochemical sensor in the container for measuring a electrochemical signal in dependence on a composition of an aqueous liquid in the container, and a control device, wherein the following steps are carried out:

(a) providing in the container of a detergent-containing aqueous liquid;

(b) rotating the drum according to a predetermined motion program;

(c) terminating a rotary motion of the drum and letting the detergent-containing aqueous liquid stand until a predetermined steady state of the detergent-containing aqueous liquid is achieved; and

(D) Measurement of the concentration c _{th of} a detergent in the provided in step (a) detergent-containing aqueous liquid by recording and evaluation of electrochemical signals of the electrochemical sensor using a stored in the controller relationship between electrochemical signals and detergent concentrations. In this case, the term "detergent-containing aqueous liquid" is to be interpreted broadly as detergent, including its components surfactants, enzymes, bleaching agents, etc., as well as fabric softeners Washing program in which this is incurred, referred to as a wash liquor, such as free liquor, or rinse.

Furthermore, 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. By way of example, the contribution of convection to the transport processes in the aqueous liquid can be used as a measure for a given, calmed state. For the determination of a sufficiently quenched state of the aqueous liquid, the fact that many electrochemical measurement methods in the quiescent state of the aqueous liquid produce electrochemical signals whose faraday proportion is determined by the diffusion of electroactive species in the aqueous liquid can be taken into account. Unless the aqueous fluid is at rest, the transport of electroactive species to the electrode is no longer just diffusion-dependent, but also influenced by convection. This generally results in characteristic changes in the electrochemical signal, the changes being a measure of the contribution of convection. By evaluating the electrochemical signals, it is therefore possible to conclude that convection has contributed as well as an optionally insufficiently soaked state of the aqueous liquid. Suitable electrochemical signals can be measured for example by means of voltammetric methods. Such electrochemical signals can be obtained, for example, by the use of cyclic voltammetry, chronoamperometry or Doppelpulschronoamperometrie, but also by impedance spectroscopy.

In cyclic voltammetry, starting from a starting voltage at a generally constant speed, the voltage at a working electrode of the electrochemical sensor is changed to a so-called reverse voltage υ _λ , which is sufficient for an oxidation or reduction process (so-called "Hinsweep") the direction of the voltage change is reversed and the voltage is changed back to the starting voltage ("reverse sweep"). The resulting current increases in Hinsweep generally up to a peak value l _p , and then drop to the reversal potential υ _λ to a value Ι _λ . The ratio Ι _ρ / Ι _λ is often a characteristic variable l _p / l A ^theorem in diffusion control of the electrode ^processes . If a solution to be tested by voltammetry is in motion, this means the presence of convection, which generally leads to a decrease of Ι _ρ / Ι _λ . As a result, then a measured value Ιρ / Ι _λ ^ΓΘ3 'or the difference ΔΙ = l _p / lA ^theor Ir as a measure of a contribution of convection and thus considered and used as a measure of a calmed state of the aqueous liquid.

In chronoamperometry, a voltage jump is generally made to a suitable voltage, which is sufficient for an oxidation or reduction process, and then, depending on the time, a current drop is measured and evaluated. A convective contribution generally leads to a weakening of the current drop. In Doppelpulschronoamperometrie is then jumped back to the starting voltage and at the starting gear voltage in turn, depending on the time a current drop is measured and evaluated.

In a preferred embodiment of the method according to the invention, therefore, a current-voltage curve is recorded as a measure of a calmed state in step (c) and evaluated with regard to a current component not caused by diffusion to the electrochemical sensor.

For this purpose, a cyclic voltammogram is particularly advantageously recorded and the peak current I _p at Hinsweep is evaluated to a reversal potential ΙΙ _λ and the current Ι _λ at the reversal potential υ _λ with respect to the current component not caused by diffusion to the electrochemical sensor.

Alternatively or in addition to this, a potential jump can be performed using the electrochemical sensor and a current-time curve obtained thereby to a non-diffusion-related proportion as a measure of a calmed state, i. a lack of reassurance, the aqueous liquid are evaluated. In this case, the potential jump occurs in particular to a potential at which a component in the aqueous liquid is oxidized or reduced reversibly or irreversibly.

When this is referred to potential changes to the electrochemical sensor, in particular a potential change at the working electrode of the electrochemical sensor forming electrochemical sensor is meant. Accordingly, diffusion and convection with respect to mass transport to the working electrode are meant. In a particularly preferred embodiment of the method according to the invention in step (c), the resting of the detergent-containing aqueous liquid for a predetermined period At _set . Preferably, the amount of which is in this case for determining At _set an amount of the aqueous liquid, a loading amount of laundry and / or in step (b) by guided movement program takes into account, wherein a stored in the control device associated between the period At _se t, aqueous fluid, the amount of laundry items and / or the movement program performed in step (b) is used. The amount of aqueous liquid can be determined, for example, by measuring an amount of water introduced into the container by means of a water meter, taking into account the fraction of water introduced and the so-called free liquor can be determined if, for example, a hydrostatic pressure sensor is arranged in the container is and used to measure the hydrostatic pressure as a measure of the free fleet.

The load of laundry may be adjusted by a user or preferably determined automatically in the washing machine. In this case, the determination of the loading amount by measuring the increase in weight of the drum due to the loading of laundry done or by analyzing the suction behavior of water by the change of hydrostatic pressure is analyzed during an addition of water to dry laundry. For this purpose, a hydrostatic sensor is advantageously present in a washing machine according to the invention. Also particularly advantageous is then a water meter, ie a measuring device for determining the amount of water charged, or the amount of charged wash liquor available. 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, stored in the control device of the washing machine values for the moistening of laundry can be the load of laundry and possibly their Durchfeuchtungsgrad (degree of wetting) determine. In a further preferred embodiment, the resting of the detergent-containing aqueous liquid until a predetermined, soaked state of the detergent-containing aqueous liquid has been reached, takes into account the dependence of the electrochemical signals on an existing amount or concentration of foam. The presence and amount of foam can be determined in different ways.

For example, the detection of foam in a washing machine can take place via a conductance measurement with two electrodes in the lower region of a container. In addition, a foam detection when spinning a drum by means of an evaluation of the target / actual speed difference is possible. In this case, the fact is exploited that foam can brake a rotating drum, whereby there is a difference between the target and the actual speed. Here, the association between a specific foam concentration and the target / actual speed difference is generally stored in the control device of the washing machine. Frequently, the presence of foam (liquid-air mixture) is detected by a pressure build-up during washing or spinning or by a much slower pressure decrease during pumping.

In general, to detect the formation of foam by means of a sensor, the hydrostatic pressure in a container is measured. Usually, for this purpose, a pressure sensor, in particular a hydrostatic pressure sensor, is used, which is also suitable for determining the water level in the container as described above. This can lead to measurement errors due to the imbalance of laundry and existing residual water that accumulates during spin, by simulating an apparent pressure increase. By the occurrence of pressure peaks, the presence of foam can be indicated, even if there is no foam. This is due to variations in pressure measurement with a sensor, with the errors in signal acquisition, conversion or processing also depending on whether a digital or analog controller is used. Since negative values are sometimes not detected by a sensor, it is not the true average value which would result if negative proportions were recorded, but an increased pressure of the oscillating water quantity. The signals measured by the pressure sensor increase Moreover, with the speed, so that it comes to a premature exceeding of the pressure threshold value specified for the foam detection. Advantageously, therefore, foam can be detected in a washing machine by a signal S _n measured by a sensor for determining a signal of a liquid contained in the container and possibly containing foam during rotation of the drum at a high speed U _n and at a speed U _n stored in the program control associated value are compared W _n, wherein in the control device for at least two speeds pairs of values U _n, and W are _n (n> 1) are stored, and upon reaching or exceeding the value W _n, that is, when the condition S _n sW _n , the presence of foam is registered. Although the sensor can be an optical measuring system, a conductometric measuring system or a capacitive measuring system. Preference is given to a hydrostatic pressure sensor in which a hydrostatic pressure p and / or a negative time gradient of the hydrostatic pressure (dp / dt), preferably a hydrostatic pressure p, of a liquid-air mixture in the container are measured as a signal. The signal S _n and the associated value W _n are then in particular pressure values.

In a preferred embodiment of the method according to the invention, the presence of foam in the aqueous liquid is therefore determined with a hydrostatic pressure sensor and taken into account for the determination of the calmed state of the aqueous liquid.

Moreover, the presence of foam also manifests itself in electrochemical signals. If foam is in front of the electrode, a measured current will normally drop. The number and duration of such sudden power drops can therefore be taken into account as a measure of existing foam, and the time period At for reassurance (also referred to as "reversing break" or "drum standstill phase") can then be suitably extended until the foam concentration decreases to an acceptable level is. The method used for the detection of foam will generally depend on which phase of a washing program, ie, in particular in a wetting phase, washing phase, rinsing phase or fabric softening phase, a sufficient calming of the aqueous solution is to be ensured so that meaningful electrochemical signals can be recorded. If a pressure sensor, in particular a hydrostatic pressure sensor, is present in the washing machine used, a measured pressure increase during a settling phase, ie drum standstill phase, can be used as a measure for calming the aqueous liquid due to aqueous liquid dripping from the laundry items. The amount of dripping liquid will decrease with increasing time.

Given a predetermined period of time At _{set, it} can advantageously be provided according to the invention that it is checked with the aid of the electrochemical sensor whether there has actually been a sufficient calming of the aqueous liquid. As mentioned above, this can be done by determining a convection-related proportion of mass transport to the working electrode. If this is not the case, the predetermined period of time At _{set can be} adapted and, in particular, extended. It can be advantageously provided that a maximum period At _se t ^{max is} not exceeded. On reaching or exceeding of At _se t ^max , the movement program of the drum is advantageously adapted and in particular the entry of mechanical energy is reduced. This can be achieved that for the rotational breaks of the drum no too long period is needed.

The entry of mechanical energy takes place via a suitable movement program of the drum. The movement program in step (b) of the method according to the invention comprises in particular a switch-on time [in%], a duration of a reversing cycle [in seconds] and a rotational speed [rpm] of the drum. The turn-on time is the temporal portion of a phase of a wash program during which the drum rotates. This switch-on time is preferably 60 to 70%, for example, in a first rinsing step. 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.

For the determination of a sufficient calming and in particular the definition of a predetermined period of time At _set , the type of electrochemical measuring method used in step (d) is advantageously also used, since electrochemical Measurement methods may require different measurement times and quiescent states of the aqueous liquid.

The inclusion of electrochemical signals is particularly accurate when comparatively little dirt and / or foam is present in the aqueous liquid to be examined. This is the case in particular in a wetting phase and in a rinsing phase. In a preferred embodiment of the method according to the invention, therefore, steps (c) and (d) are carried out in a wetting phase and / or in a rinsing phase.

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. Herein, " wash liquor " and " surfactant-containing aqueous liquor " have the same meaning in general. The term "surfactant" as used herein means a single surfactant as well as a mixture of different surfactants.

The extent to which an aqueous fluid is moved by a program of motion and therefore a subsequent drum stoppage phase is required also depends on the presence and shape of laundry drivers in the drum. If the shape of the laundry pickups is asymmetrical, their contribution to the movement of the aqueous liquid at a given rotational speed of the drum will depend on the direction of rotation. Preferably, therefore, in an asymmetrical shape of laundry pickers inserted in the drum, at least the rotational direction of the drum is taken into account before a drum standstill phase.

According to the invention, preferably step (c) and / or step (d) are taken into account taking into account the type and / or amount of soiling of the items of laundry performed, wherein in the control device, a relationship between the electrochemical signals and the detergent concentrations for different types and / or amounts of contaminants of the laundry is deposited. For example, contamination with oil would mean that, in particular, nonionic surfactants could dissolve more or less pronouncedly in the oil and would no longer be detected in a measurement of the detergent concentration. On the other hand, ionic surfactants can be trapped to some extent by ion-containing contaminants, ie consumed, so that they are no longer detected in a measurement of electrochemical signals.

Type and / or amount of contamination can be set by a user of the washing machine or measured by suitable sensors. In particular, the electrochemical sensor provided according to the invention, e.g. Impedance sensor. In addition, however, other sensors such as a turbidity sensor can also be used.

The electrochemical sensor is generally an electrode system of at least two electrodes. When using a three-electrode arrangement, consisting of a working electrode, a counter electrode and a reference electrode, the potential at the working electrode, which is responsible for receiving the electrochemical signals, can be adjusted very precisely.

In any case, according to the invention, a single electrode system can be used for recording different electrochemical signals, that is, for example, for cyclic voltammetry or impedance spectroscopy, in which the electrochemical sensor is also referred to as an impedance sensor. According to the invention, the electrochemical sensor in step (d) is preferably used as an impedance sensor. In this case, the impedance sensor receives as electrochemical signals impedance signals.

In the method according to the invention, the recording and evaluation of the impedance signals is generally carried out by the electrical impedance of the impedance sensor being subjected to varying frequencies and the Impedance signals are evaluated in terms of the phase angle φ and the amount of impedance. Phase angle φ and the amount of impedance can then in turn be evaluated with regard to the type, amount and concentration of detergents, in particular of surfactants and, moreover, of micelle concentrations.

For measurement, an impedance spectrum is generally recorded using a suitable electrode system as the impedance sensor. As a rule, the impedance of an electrochemical system is examined as a function of the frequency of an alternating voltage at the working electrode. 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. For the characterization of the impedance spectrum, only a few characteristic points (see EP 2 767 825 A1) are generally suitable when examining wash liquors, 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, parameters typical for a detergent-containing aqueous liquid can generally be derived. For example, the conductivity of the 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 medium containing detergent. Another measure, which depends on the properties of the aqueous agent-containing aqueous liquid, is the flattening of a semicircle in the Nyquist plot, 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 of the aqueous liquid.

Therefore, according to the invention, impedance signals are recorded with the impedance sensor, the recording and evaluation of the impedance signals being performed is by the electrical impedance sensor with varying frequencies is applied to the impedance sensor and the impedance signals are evaluated in terms of the phase angle φ and the amount of impedance. It is particularly preferred that the recording of the impedance signal is carried out at a predetermined frequency of the AC voltage.

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 p-1 for the hydrostatic pressure p and a predetermined threshold value (Δρ / Δί) -ι for the time gradient of the hydrostatic pressure p, generally starts the washing phase. In particular, in a washing phase, the monitoring of a detergent concentration with an electrochemical sensor makes sense. As a result, the consumption of detergent and thus a possible requirement for a subsequent dosing of detergent can be determined. In addition, a washing program can be optimally adapted to a detected detergent concentration.

The invention also relates to a washing machine with a container, a drum for receiving laundry, a drive motor for the drum, an electrochemical sensor in the container for measuring an electrochemical signal in response to 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 comprising the following steps:

(a) providing in the container of a detergent-containing aqueous liquid;

(b) rotating the drum according to a predetermined motion program;

(c) terminating the rotary motion of the drum and allowing the detergent-containing aqueous liquid to stand until a predetermined steady state of the detergent-containing aqueous fluid is achieved; and

(D) Measurement of the concentration c _{th of} a detergent in the provided in step (a) detergent-containing aqueous liquid by recording and evaluation of electrochemical signals of the electrochemical sensor using a stored in the controller relationship between electrochemical signals and detergent concentrations. According to the invention, a washing machine is preferred in which a temperature sensor is arranged in the container and a relationship between electrochemical signals, for example impedance signals, and detergent concentrations is stored in the control device for various temperature values measured with the temperature sensor.

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 generally also has a heater and a liquor drain system with a drain pump located at the bottom of a tub. 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 whether a washing phase takes place at an optimum detergent concentration or not. Moreover, it can also be displayed whether the measurements with the electrochemical sensor are carried out in a sufficiently calmed aqueous liquid.

In the case of an underdosing of detergent, a user of the washing machine can be given an indication to nachzudosieren detergent, which in this case can also be a quantity. The dosage recommendation is displayed on the display panel as such or a display panel thereof (collectively referred to as "display display").

The dosage recommendation can be displayed on the display in the form of a text and / or a sign. An appropriate text would be, for example, the direct prompt "please dose" green "", where "green" is an indication of a dispensing aid, other colors may be mentioned or other indications may be given in textual form a color or a symbol may be displayed, for example a circle which may be filled to differentiate individual detergent quantities to varying degrees.

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 for operating a washing machine is provided, in which the monitoring of, for example, the detergent concentration in the wash liquor by means of an electrochemical sensor, in particular an impedance sensor, takes place particularly accurately. This is possible according to the invention by taking into account that an electrochemical measurement and in particular the measurement of an impedance signal with an impedance sensor can be disturbed and thus the measured impedance signal can be corrupted if the solution has not sufficiently calmed down at the time of measurement. In particular, the invention makes it possible to precisely determine the surfactant concentration and the water hardness by means of an electrochemical sensor in a detergent-containing, in particular surfactant-containing aqueous liquid by especially impedance spectroscopy and cyclic voltammetry by adjusting pauses when reversing the drum during wetting, washing and rinsing Incorrect measurements by air bubbles trapped in the aqueous liquid, foam and currents to avoid. By more accurate determination of the actual detergent concentration in a wash program and related measures can be taken in good time on an over or under dosage of detergent. It can be prevented on the one hand, that it comes to a foaming of the washing machine, which may be associated with a water damage in an apartment. On the other hand, an excessive use of rinse water could be avoided, which would be required if excess detergent would have to be removed from the laundry. Also, for example, a more accurate determination of the concentration of ionic surfactants as well as a more accurate adjustment and maintenance of a concentration range for ionic surfactants is made possible.

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

The washing machine 1 of the figure has a tub 2, in which a drum 3 is rotatably mounted and driven by the drive motor 5. For improved ergonomics, the axis of rotation 19 of the drum 3 is directed from the horizontal by a small angle (e.g., 13 °) forwardly upwards so that the user of the washing machine 1 has easier access and insight into the interior of the drum 3. By this arrangement, in cooperation with laundry entrainers 14 and scum means 17 for the aqueous medium containing detergent, e.g. Washing liquor, 7 on the inner surface of the drum shell also achieved an intensification of the flooding of the laundry items 4 with wash liquor 7. The Wäschemitnehmer 14 are asymmetrical in the embodiment shown here, so that the aqueous liquid 7 is brought in the tub 2 at the same rotational speed of the drum 3 for the two possible directions of rotation of the drum 3 to varying degrees in motion. This influence is taken into account in the control device 8, so that a method according to the invention can be carried out even more precisely.

In the dispensing tray 12 is disposed as an electrochemical sensor, an impedance sensor 10, which is generally an electrode system of a plurality of electrodes, for example, two capacitor plates or a three-electrode arrangement. With the aid of impedance sensor 10, an existing in the dispenser 12 detergent or an aqueous liquid containing this detergent can be analyzed to obtain information about the detergent and thus on the design of a washing program.

The washing machine 1 also has a liquor inlet system, which includes a water connection fitting for the domestic water network 20, an electrically controllable valve 21 and a supply line 13 to the tub 2, which may optionally be performed on the Waschmitteleinspülschale 12, from the incoming water detergent portions in the Lye container 2 can transport. In addition, in the tub 2, a heater 16 for heating water or wash liquor 7. The valve 21 as well as the heater 16 can be controlled by a control device 8 in response to a program flowchart, the time program and / or the achievement of certain Measured values of parameters such as liquor level, liquor temperature, speed of the drum, etc. may be bound within the washing machine 1.

6 means a pressure sensor, ie a sensor for the measurement of the hydrostatic pressure, in the tub 2. The hydrostatic pressure p results from the level of the forming in the tub 2 free fleet 7. In addition, the washing machine 1 comprises a measuring device 15 for determining the filled amount of water, such as a water meter or a flow meter. 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 denotes a drain pump for pumping off the wash liquor 7. In the figure, 9 denotes an electrochemical sensor in the tub 2, with which various electrochemical measurements can be performed, such as voltammetric measurements or impedance measurements. Preferably, the electrochemical sensor is used as an impedance sensor, wherein the structure of electrodes and the implementation and evaluation of the impedance sensor measured impedance signals is not shown here in detail. For carrying out a method according to the invention, the electrochemical signals of the electrochemical sensor 9 and optionally of the impedance sensor 10 and the rotational speed of the drum 2, their loading with laundry items 4, the hydrostatic pressure, etc., and the measured values are fed to the control device 8.

The implementation of the method according to the invention includes the following steps:

(A) provision in the tub 2 of a detergent-containing aqueous liquid 7;

(B) rotation of the drum 3 according to a predetermined movement program, which may include depending on a wetting phase, washing phase or rinsing phase different Reversierschritte, spin steps, etc. at different rotational speeds of the drum 3;

(c) terminating the rotation of the drum 3 and allowing the detergent-containing aqueous liquid 7 to stand until a predetermined steady state of the detergent-containing aqueous liquid 7 is reached; and

(D) Measurement of the concentration c _{th of} a detergent in the provided in step (a) detergent-containing aqueous liquid 7 by recording and evaluation of electrochemical signals of the electrochemical sensor 9 using a stored in the controller 8 relationship between electrochemical signals and detergent concentrations. In step (c), the resting of the detergent-containing liquid 7 is preferably monitored by the electrochemical sensor 9, whereby a measurement by cyclic voltammetry, chronoamperometry or impedance spectroscopy is preferably carried out to determine a predetermined calmed state of the detergent-containing liquid 7.

In step (d), in the embodiment shown here, the measurement of the concentration c _{th of} a detergent in the aqueous liquid 7 containing detergent takes place by recording and evaluating impedance signals of the electrochemical sensor 9 functioning as an impedance sensor 9, wherein a control device 8 in the control device 8 deposited relationship between impedance signals and

Detergent concentrations is used.

1 1 means a display device with which process parameters, in particular a drainage of a washing program with optimal use of detergent (eg represented by a green light-emitting diode) or under non-optimal use of detergent (eg represented by a red light-emitting diode), can be displayed. In particular, a dosage recommendation for a user of the washing machine can also be displayed.

LIST OF REFERENCE NUMBERS

1 washing machine

2 tubs

3 drum

4 pieces of laundry

5 drive motor

6 pressure sensor

7 aqueous liquid, free liquor, wash liquor

8 control device

9 electrochemical sensor in the tub, e.g. Impedance sensor;

Electrode arrangement for measuring the impedance

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

1 1 display device

12 (detergent) Einspülschale

13 Supply line to the tub

14 laundry pickup

15 Measuring device for determining the amount of water filled

16 heating device

17 scooping device

18 pump, drain pump

19 axis of rotation

20 water supply, domestic water supply, water supply

21 (electrically controllable) valve

22 temperature sensor

Claims

Method for operating a washing machine (1) having a container (2), a drum (3) for receiving items of laundry (4), a drive motor (5) for the drum (3), an electrochemical sensor (9) in the container (2 ) for measuring an electrochemical signal in dependence on a composition of an aqueous liquid (7) in the container (2), and a control device (8), characterized in that the following steps are carried out:

(A) provision in the container (2) of a detergent-containing aqueous liquid (7);

(b) rotating the drum (3) in accordance with a predetermined motion program;

(c) terminating a rotational movement of the drum (3) and allowing the detergent-containing aqueous liquid (7) to stand until a predetermined, soaked state of the detergent-containing aqueous liquid (7) has been reached; and

(d) measuring the concentration c _th of a detergent provided in the step (a) detergent-containing aqueous liquid (7) by recording and analysis of electrochemical signals from the electrochemical sensor (9) using an in the control device (8) stored relation between electrochemical Signals and detergent concentrations.

A method according to claim 1, characterized in that as a measure of a calmed state in step (c) with the electrochemical sensor (9) a current voltage curve is recorded and is evaluated in terms of a not by diffusion to the electrochemical sensor (9) conditional current component.

A method according to claim 2, characterized in that a cyclic voltammogram is recorded and the peak current I _p at Hinsweep to a reversal potential ΙΙ _λ and at the reversal potential υ _λ in terms of not due to diffusion to the electrochemical sensor (9) conditional current component is evaluated.

4. The method according to any one of claims 1 to 3, characterized in that using the electrochemical sensor (9), a potential jump is performed and thereby obtained a current-time curve to a non-diffusion-related proportion as a measure of a lack of calming the aqueous liquid is evaluated.

5. The method according to any one of claims 1 to 4, characterized in that in step (c), the resting of the detergent-containing aqueous liquid (7) for a predetermined period At _set .

6. The method according to claim 5, characterized in that for determining At _S et an amount of the aqueous liquid (7), a quantity of laundry items (4) and / or the movement program performed in step (b) is taken into account, wherein a in the control device (8) stored relationship between the period At _se t, the amount of the aqueous liquid (7), the amount of laundry items (4) and / or the movement program performed in step (b) is used.

7. The method according to any one of claims 1 to 6, characterized in that for the resting of the detergent-containing aqueous liquid until a predetermined calmed state of the detergent-containing aqueous liquid (7) is reached, is taken into account as a function of an existing amount or concentration of foam ,

8. The method according to claim 7, characterized in that with a hydrostatic pressure sensor (6) determines the presence of foam in the aqueous liquid (7) and for the determination of the calmed state of the aqueous liquid (7) is taken into account.

9. The method according to any one of claims 1 to 8, characterized in that the steps (c) and (d) are carried out in a wetting phase and / or in a rinsing phase.

10. The method according to any one of claims 1 to 9, that in an asymmetrical shape of in the drum (3) used Wäschemitnehmern (14) at least the direction of rotation of the drum (3) is taken into account before a drum standstill phase.

1 1. Method according to one of claims 1 to 10, characterized in that step (c) and / or step (d) taking into account the type and / or amount of contamination of the laundry items (4) are performed, wherein in the control device (8) Relationship between the electrochemical signals and the detergent concentrations for different types and / or

Amounts of soiling of the laundry items (4) is deposited.

12. The method according to any one of claims 1 to 1 1, characterized in that the electrochemical sensor (9) in step (d) is used as an impedance sensor.

13. The method according to claim 12, characterized in that with the impedance sensor (9) impedance signals have been recorded, wherein the recording and evaluation of the impedance signals is performed by the impedance sensor (9) is acted upon by alternating electrical voltage with varying frequencies and the impedance signals with respect on the

Phase angle φ and the amount of impedance are evaluated.

14. The method according to claim 13, characterized in that the recording of the impedance signal is carried out at a predetermined frequency of the AC voltage.

15. Washing machine (1) with a container (2), a drum (3) for receiving laundry items (4), a drive motor (5) for the drum (3), an electrochemical sensor (6,9) in the container (2 ) for measuring an electrochemical signal in dependence on a composition of an aqueous liquid (7) in the container (2), and a control device (8), characterized in that the control device (8) is arranged to carry out a method which comprises the following steps includes: (A) provision in the container (2) of a detergent-containing aqueous liquid (7);

(b) rotating the drum (3) in accordance with a predetermined motion program;

(c) terminating the rotational movement of the drum (3) and allowing the detergent-containing aqueous liquid (7) to stand still until a predetermined steady state of the detergent-containing aqueous liquid (7) is reached; and